En este apartado voy a ir recopilando
todas las patentes que pueda sobre sistemas de suspensiones.
A diferencia de los anuncios publicitarios las patentes suelen
ser documentos bastante serios que explican el funcionamiento
real de los sistemas. En el Trabajo de Ken Sasaki por ejemplo
se habla bastante de la patente del sistema VPP asi que creo
que reunirlas todas juntas puede ser una buena idea.
De momento voy a ir colgando
los textos en Ingles, si en un futuro pudiese dedicarle mas
tiempo intentaría traducir algo.
DW-Link
United States Patent Application 20050067810
Kind Code A1
Weagle, David March 31, 2005
Bicycle suspension systems
Abstract
A bicycle rear wheel suspension system in which plural interconnections
are provided of rear wheel-supporting components, at which interconnections
there occurs pivotal traverses contributing to urging the axle
of the rear wheel along a path providing positions of movement
therealong to achieve a desired extent of pressure feedback
to the pedals, an easing of suspension reaction to bumps, and
multiple chainstay lengths, all parameters to better suit the
bicycle to its end uses and the terrain on which it is used.
Inventors: Weagle, David; (Edgartown, MA)
Correspondence Name and Address:
PERKINS COIE LLP
P.O. BOX 2168
MENLO PARK
CA
94026
US
Serial No.: 669412
Series Code: 10
Filed: September 25, 2003
U.S. Current Class: 280/284
U.S. Class at Publication: 280/284
Intern'l Class: B62K 001/00
Claims
1. A compressible linkage suspension system for a rear axle
of a bicycle rear wheel comprising controlled axle path, said
path allowing for a range of anti-squat curves, and said anti-squat
curves beginning within a range of 50 percent of a theoretical
100 percent value, transitioning towards a lower range of anti-squat
curves at a higher end of said path.
2. The linkage suspension system according to claim 1, further
comprising a frame member which supports a bicycle seat and
a spring damper unit supported by said frame member.
3. The linkage suspension system according to claim 2, further
comprising a support braket to facilitate the support of the
damper unit by the frame member and an interconnection that
facilitates a multitude of pivotal traverses.
4. A compressible linkage suspension system for a bicycle rear
wheel comprising means for achieving an anti-squat response.
5. The linkage suspension system according to claim 4, wherein
said anti-squat response is higher in the beginning of the suspension
travel and lesser thereafter.
6. A compressible linkage suspension system for a bicycle rear
wheel comprising means for easing of suspension reaction to
bumps.
7. The linkage suspension system according to claim 6, wherein
said means comprise interconnections that enable a multitude
of pivotal traverses.
8. The linkage suspension system according to claim 7, wherein
said means are placed to minimize the effect of braking force
on rear wheel movement.
9. A compressible linkage suspension system for a bicycle rear
wheel comprising a spring damper unit, a frame member which
supports a bicycle seat and which further supports said spring
damper unit, and a pair of triangular brackets supporting said
spring damper unit, wherein said spring damper unit partakes
in pivotal traverses to achieve an anti-squat response.
10. The linkage suspension system according to claim 9, wherein
said anti-squat response is higher in the beginning of the suspension
travel and lesser thereafter.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of the U.S. Provisional
Patent Application No. 60/412,669 filed on Sep. 28, 2002, the
contents of which are incorporated herein by reference thereto.
[0002] The present invention relates generally to improvements
for bicycles, the improvements more particularly residing in
a link suspension system that can more effectively be tuned
to balance forces in the rear suspension of the bicycle, all
as will be better understood as the description proceeds.
EXAMPLE OF THE PRIOR ART
[0003] Take into consideration the system described by U.S.
Pat. No. 6,206,397 B1. This link suspension system claims linkage
arrangement and a defined range of rear wheel axle paths for
a suspension bicycle. The axle path claimed and shown in the
patent art can be manipulated into an S shape, or a converging
C shape. The theory behind this is that during the lower part
of the suspension travel, the wheel axle will travel at an increasing
rate, away from the bottom bracket center. By achieving this,
the designers hope to increase the resistance to rear suspension
compression during the beginning of the travel. This resistance
to suspension compression is called anti-squat in popular engineering
text. As the '397 patent is examined, it becomes obvious that
the inventors overlooked several key factors that must be evaluated
in order to obtain a clear understanding of anti-squat and how
it pertains to a suspension system. The system as described
in the '397 patent feature pro-squat in the beginning of the
suspension travel, and a rising rate of anti-squat as the suspension
cycles through the end of its travel. In practice bicycles designed
using the system described in the '397 patent feature inefficient
acceleration in the beginning of the suspension travel, where
efficient acceleration is needed most.
[0004] As background to understanding the present invention
it is to be noted that a link bicycle suspension system is a
defined specific range of kinematical linkages which can be
used to produce a tactical rear axle path. Each combination
of linkages can be tuned to balance forces in the rear suspension
of the bicycle in ways that no previous system has been able
to. Variations of the linkage layout can shift the balance of
forces to give distinct advantages for suspension systems used
for differing applications. The suspension system allows a designer
to manipulate the rear axle path in relation to the bicycle
frame. Manipulating axle paths has a huge impact on the performance
of the rear suspension, since axle path governs several key
aspects of suspension performance.
[0005] It is an object of the present invention to achieve
a desired variable amount of anti-squat as the rear suspension
cycles through its travel. Manipulating rear axle path in a
tactical manner using a linkage system allows the designer to
obtain a desired range of anti-squat curves. A preferred anti-squat
curve is one that features a higher amount of anti-squat in
the beginning of the suspension travel, and a lesser amount
as the suspension cycles compressively through its travel. This
anti-squat amount lessens with regard to the amount of spring
force provided by a spring damper unit. In addition to this
lessening anti-squat amount as the suspension compresses, the
linkage arrangement is also designed to impart a minimal amount
of feedback to the pedals as the suspension cycles. The preferred
linkage arrangement also can be optimized so that a spring damper
unit can be driven at a strategic leverage rate, furthermore
reducing inefficient rear wheel movement. Also the linkage arrangement
can be strategically placed so that the effect of braking force
on rear wheel movement is minimized.
[0006] The description of the invention which follows, together
with the accompanying drawings should not be construed as limiting
the invention to the example shown and described, because those
skilled in the art to which this invention appertains will be
able to devise other forms thereof within the ambit of the appended
claims.
[0007] FIG. 1 is a diagrammatic view of a mode of adjusting
bicycle rear wheel suspension according to the present invention;
[0008] FIG. 2 is a partial perspective view of a bicycle component
providing the rear wheel suspension; and
[0009] FIG. 3 is a view similar to FIG. 2 on an enlarged scale.
[0010] A link suspension system according to the present invention
is embodied in a bicycle 10 having a body frame member 12 which
extends from a handlebar 14 rearwardly downward at an angular
orientation to a pedal mechanism 16 and is integral at juncture
18 to a vertically oriented frame member 20 which supports a
bicycle seat 22. At the junction 18, a cylindrical configuration
24 is provided for journaling in rotation the rotor 26 of the
pedal mechanism 16.
[0011] Mounted to extend rearwardly of the frame members 12,
20 are an upper angularly oriented pair of supports 28 and 30
and lower horizontally pair of supports 32 and 34 which at respective
ends 36 and 38 are attached to a rear wheel 40 for rotatably
mounting of the rear wheel 40 to the bicycle.
[0012] Just above the juncture 18 are spaced apart brackets
42 and 44 welded as at 46 to frame member 12 having aligned
openings 48 for receiving therethrough bolt means 50 connecting
thereto the bottom end 52 of a housing 54 of an internally mounted
damper spring 56, the upper housing end 58 being connected to
a pair of triangular brackets 60 and 62, in turn connected,
as at 64, to cooperating openings 66 provided in rear wheel
supports 32 and 34, the remaining bracket opening 72 being bolted
to support bracket 74 and 76 welded, as at 78, to the seat support
frame 20.
[0013] Completing the link suspension system are brackets 80
and 82 connected at opposite ends 84 to cooperating openings
86 provided in the rear wheel supports 32 and 34 and at ends
88 to the cylindrical configuration 24.
[0014] Referring to the diagrammatic illustration of FIG. 1,
it will be understood that the interconnections at 48, 72, 76
enable the interconnected components to partake of a multitude
of pivotal traverses, of which a significant pivotal traverse
90 implements axle path changes in a rear sprocket 92 of the
rear wheel 40 contributing to a range 94 of rear wheel positions,
all to the end of achieving a selected (1) extent of pressure
feedback to the pedals, (2) an easing of suspension reaction
to bumps, and (3) as known in the parlance of the art, multiple
chainstay lengths. Thus, one well versed in the art is able
by selection to tune the described combination of linkages to
balance forces in the rear suspension of the bicycle as desired
and as dictated by the end use of the bicycle and the terrain
on which it is used.
[0015] While the apparatus herein shown and disclosed in detail
is fully capable of attaining the objects and providing the
advantages hereinbefore stated, it is to be understood that
it is merely illustrative of the presently preferred embodiment
of the invention and that no limitations are intended to the
detail of construction or design herein shown other than as
defined in the appended claims.
United States Patent Application 20050067806
Kind Code A1
Weagle, David March 31, 2005
Vehicle suspension systems
Abstract
A wheel suspension system having under powered acceleration
a squat response that begins in the realm of anti squat and
passes through a point of lessened anti squat at a further point
in the travel.
Inventors: Weagle, David; (Edgartown, MA)
Correspondence Name and Address:
PERKINS COIE LLP
P.O. BOX 2168
MENLO PARK
CA
94026
US
Serial No.: 949264
Series Code: 10
Filed: September 24, 2004
U.S. Current Class: 280/124.1
U.S. Class at Publication: 280/124.1
Intern'l Class: B60G 003/02
Claims
What is claimed is:
1. A suspension system for a rear wheel suspension comprising
a damper unit, a pivot, and a suspended wheel, wherein said
suspension system is designed to result in a squat curve with
a negative slope in the beginning of suspension travel, in the
interim of suspension travel and in the end of suspension travel,
and wherein the slope in the beginning of suspension travel
and in the end of suspension travel are more negative than the
slope in the interim of suspension travel.
Description
[0001] This application is a continuation in part of U.S. application
Ser. No. 10/669,412, filed Sep. 25, 2003, which is incorporated
herein by reference in its entirety.
BACKGROUND
[0002] This invention relates to suspension systems capable
of reducing or eliminating a squat response.
[0003] Automobiles, bicycles, motorcycles, all terrain vehicles,
and other wheel driven vehicles are used for various purposes,
including transportation and leisure. These vehicles are designed
to use a power source to drive through a power transmission
system to a wheel or wheels, which transfers rotary motion to
the ground via tractive force between a wheel or wheels and
the ground. Vehicles are also used to traverse even terrain
like paved streets, and uneven terrain like off-road dirt trails.
Off road trails are generally bumpier and allow for less wheel
traction than paved roads. A bumpier terrain is best navigated
with a vehicle that has a suspension system. A suspension system
in a vehicle is aimed to provide a smoother ride for an operator
or rider, and increase wheel traction over varied terrain. Vehicle
suspension systems for the front wheel and for the back wheel
are available.
[0004] One undesirable effect of suspension systems is the
loss of energy in the way of suspension compression or extension
during powered acceleration. Such energy loss is particularly
notable in vehicles that are driven by low energy power sources,
for example, bicycles and solar vehicles. For example, the average
rider of a bicycle can exert only a limited amount of power
or energy for a short period of time and an even lesser amount
for an extended period of time. Therefore, even a very small
power loss can have a significant effect on rider performance
and comfort. Suspension travel is the distance a suspended wheel
travels when the suspension is moved from a fully extended state
to a fully compressed state. In bicycles, suspension travel
has been increased for many designs and with these increases
in suspension travel; the aforementioned energy loss has become
even more apparent to riders. But even for a vehicle with a
high power energy source, any loss in energy reduces the vehicle's
efficiency, for example its fuel efficiency. Where vehicles
are used in a manner that requires frequent accelerations, including
positive and negative accelerations, the efficiency of the vehicle
is particularly affected by any loss of energy resulting from
the vehicles geometry, including the geometry and design of
its suspension systems.
[0005] Thus, by minimizing energy loss resulting from the design
of a vehicle's suspension system, the efficiency of the vehicle
is improved and thereby its environmental impact. The need for
a suspension system that can better preserve a vehicles efficiency
and energy has therefore become more pressing. The present invention
provides suspension system designs for vehicles that reduce
these energy losses.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] FIG. 1a is a side view of a chain driven vehicle using
a driven wheel suspension system that achieves a squat curve
according to certain embodiments of the current invention. The
vehicle is shown with the driven wheel suspension system in
an uncompressed state.
[0007] FIG. 1b is a side view of a chain driven vehicle as
shown in FIG. 1a with the driven wheel suspension system in
a completely compressed state.
[0008] FIG. 1c is an enlarged section of the side view of the
chain driven vehicle shown in FIGS. 1a and 1b with the driven
wheel suspension system in a completely uncompressed state.
[0009] FIG. 1d is an enlarged section of the side view of the
chain driven vehicle shown in FIGS. 1a, 1b, and 1c with the
driven wheel suspension system in a completely compressed state.
[0010] FIG. 2a is a side view of a shaft driven vehicle using
a driven wheel suspension system that achieves a squat curve
according to certain embodiments of the current invention. The
vehicle is shown with the driven wheel suspension system in
an uncompressed state.
[0011] FIG. 2b is a side view of a shaft driven vehicle as
shown in FIG. 2a with the driven wheel suspension system in
a completely compressed state.
[0012] FIG. 2c is an enlarged section of the side view of the
shaft driven vehicle shown in FIGS. 2a and 2b with the driven
wheel suspension system in a completely uncompressed state.
[0013] FIG. 2d is an enlarged section of the side view of the
shaft driven vehicle shown in FIGS. 2a, 2b, and 2c with the
driven wheel suspension system in a completely compressed state.
[0014] FIGS. 3 and 4 show squat curves for suspension systems
according to certain embodiments of the invention graphed on
a squat curve graph as disclosed herein.
[0015] FIGS. 5-13 show alternative embodiments of suspension
systems comprising a squat curve of the invention. Each embodiment
shown includes a spring/damper unit (small irregular box) and
different frame members (thicker lines) interconnected through
pivots (small circles).
SUMMARY OF THE INVENTION
[0016] The current invention relates to new suspension systems
for vehicles, for example, bicycles, motorcycles, cars, SUVs,
trucks, two wheel vehicles, four wheel vehicles, front wheel
suspension vehicles, driven wheel suspension vehicles, and any
other kind of vehicle with a suspension system. In certain embodiments
of the invention, a suspension system of the invention is capable
of facilitating a squat response that lowers the energy loss
resulting from squat. In certain preferred embodiments, a suspension
system of the invention is capable of lowering energy loss resulting
from squat by producing an anti-squat response. An anti-squat
response of a suspension system of the invention, in certain
embodiments, varies along suspension travel of the vehicle and
preferably is higher at the beginning of suspension travel and
less thereafter.
[0017] Certain embodiments of the invention comprise a wheel
suspension design that uses a tuned squat response to reduce
powered acceleration induced suspension movement at tactical
points during the driven wheel suspension travel. A vehicle
designed to use the preferred embodiment of the invention can
accelerate under power with a lower amount of energy loss and
a more stable vehicle chassis than known systems.
[0018] Suspension systems of the invention are useful for a
variety of vehicles and preferably in human powered vehicles.
The average rider of a bicycle or other human powered vehicle
can exert only a limited amount of power or energy for a short
period of time and an even lesser amount for an extended period
of time. Therefore, even a very small power loss can have a
significant detrimental effect on rider performance and comfort.
The need for a suspension system that can better preserve the
rider's energy has therefore become more pressing. The present
invention provides suspension system designs for vehicles that
reduce energy loss during powered acceleration.
[0019] In certain embodiments of the invention, a wheel suspension
system comprises a wheel connected to a wheel carrier unit and
said wheel carrier unit connected to spring damper means; and
isolating said wheel from a frame structure with the wheel suspension
system having an squat curve with said squat curve having a
decreasing rate of squat as the suspension system moves from
a beginning point in the wheel travel to an ending point in
the wheel travel.
[0020] In certain embodiments of the invention, a compressible
wheel suspension system comprises a wheel connected to a wheel
carrier unit and said wheel carrier unit connected to spring
damper means; and isolating said wheel from a frame structure
with the wheel suspension system having a squat curve with said
squat curve having a decreasing squat amount and without said
squat amount increasing as the suspension system moves from
a beginning point in the wheel travel towards an ending point
in the wheel travel increase.
[0021] In certain embodiments of the invention, a compressible
vehicle suspension system comprises a defined squat curve, with
said squat curve having a maximum value at the lowest amount
of suspension compression, and a minimum value at a further
point in the travel, and a continuously decreasing amount of
squat throughout the wheel travel.
[0022] In certain embodiments of the invention, a vehicle suspension
system comprises a defined squat curve, with said squat curve
having a slope that is generally negative at an earlier point
in the suspension travel, and a slope that is less negative
at a interim point in the suspension travel, and a slope that
is then more negative at a latter point in the suspension travel.
[0023] In certain embodiments of the invention, a compressible
wheel suspension system comprises a wheel connected to a wheel
carrier unit and said wheel carrier unit connected to a top
link and a bottom link, with a top link connected to spring
damper means; With said top and bottom links rotating together
in a clockwise direction, and said top and bottom links connecting
said wheel carrier to a frame structure, isolating said wheel
from the frame structure. Said top link and said bottom link
having projected link force lines and said top link projected
force line intersecting said lower link projected force line
at a point in the beginning of the suspension travel and said
top link projected force line intersecting said lower link at
a point later in the travel.
[0024] In certain embodiments of the invention, a compressible
wheel suspension system comprises a wheel connected to a wheel
carrier unit and said wheel carrier unit connected to a top
link and a bottom link, with said wheel carrier connected to
spring damper means; with said top and bottom links rotating
together in a clockwise direction, and said top and bottom links
connecting said wheel carrier to a frame structure, isolating
said wheel from the frame structure. Said top link and said
bottom link having projected link force lines and said top link
projected force line intersecting said lower link projected
force line at a point in the beginning of the suspension travel
and said top link projected force line intersecting said lower
link at a point later in the travel.
[0025] In certain embodiments of the invention, a compressible
wheel suspension system comprises a wheel connected to a wheel
carrier unit and said wheel carrier unit connected to a top
link and a bottom link, with said bottom link connected to spring
damper means; with said top and bottom links rotating together
in a clockwise direction, and said top and bottom links connecting
said wheel carrier to a frame structure, isolating said wheel
from the frame structure, said top link and said bottom link
having projected link force lines and said top link projected
force line intersecting said lower link projected force line
at a point in the beginning of the suspension travel and said
top link projected force line intersecting said lower link at
a point later in the travel.
[0026] In certain embodiments of the invention, a compressible
wheel suspension system comprises a wheel connected to a wheel
carrier unit and said wheel carrier unit connected to a top
link and a bottom link, with said top and bottom links connected
to spring damper means; with said top and bottom links rotating
together in a clockwise direction, and said top and bottom links
connecting said wheel carrier to a frame structure, isolating
said wheel from the frame structure. Said top link and said
bottom link having projected link force lines and said top link
projected force line intersecting said lower link projected
force line at a point in the beginning of the suspension travel
and said top link projected force line intersecting said lower
link at a point later in the travel.
[0027] In practice, precisely controlling squat in a suspension
system can allow for very little suspension movement during
powered acceleration with favorable bump compliance. The further
a vehicle suspension is compressed, the higher the spring force
at the wheel rotational axis. Most powered acceleration happens
within the first 40 percent of the suspension travel. Because
spring force is lowest in the beginning of a suspension travel,
a suspension is more susceptible to manipulation due to squat
forces at that time. If enough anti squat force is not present
to inhibit mass transfer in the beginning of the suspension
travel, the suspension will compress, and when it rebounds,
energy will be lost through the damper. The low spring force
in the beginning of the suspension travel allows for higher
levels of movement than at later points in the suspension travel.
Minimizing suspension movement due to mass transfer during powered
acceleration reduces the amount of damper movement that occurs
at that time. With lower amounts of damper movement comes a
lower amount of energy that the damper must dissipate, and therefore
more of the acceleration force provided by a power source can
be used to accelerate the vehicle. The amount of energy consumed
to produce enough anti-squat force to reduce movement earlier
in the suspension travel is less than the amount of energy that
would be lost in the damper during suspension movement. As a
driven wheel suspension system is compressed through its travel,
spring force increases, and therefore driven wheel resistance
to movement increases. At this later point in the suspension
travel, because of the increased spring force, squat force has
less of manipulating effect on a wheel suspension. A lower amount
of anti squat can be used so that more energy can be transferred
to forward movement.
DETAILED DESCRIPTION
[0028] Vehicles must be accelerated against their environment
to propel an operator or rider across terrain. In order to accelerate
these vehicles, a certain amount of energy must be exerted and
transformed into rotary motion at a wheel or plurality of wheels.
Suspended wheeled vehicle energy conversion types are widely
varied. Some vehicles like bicycles, tricycles, and pedal cars
use converted human energy as the drive unit. Other vehicles
use electric motors or combustion engines, as their drive unit.
These electric motors and combustion engines extract rotary
motion through the controlled release of chemically stored energy.
[0029] Almost all vehicle types use some sort of rotary motion
transmission system to transfer rotational force from a drive
unit to a wheel or plurality of wheels. A simple bicycle or
motorcycle or all terrain vehicle uses a chain or belt to transfer
power from a drive unit to a wheel. These chain or belt drive
transmissions typically use one sprocket in the front which
is coupled to a drive system and one sprocket in the rear which
is coupled to a wheel.
[0030] More complex bicycles, motorcycles, all terrain vehicles,
and automobiles use a shaft drive system to transfer power from
a drive system to a driven wheel or wheels. These shaft drive
systems transfer power through a rotating shaft that is usually
reasonably perpendicular to the driven wheel spinning axis,
with power transferred to the driven wheel via a bevel, spiral
bevel, hypoid, worm gear drivetrain, or some other means. These
single sprocket chain and belt, and shaft driven vehicles can
use a direct driven single speed arrangement, where drive unit
output shaft speed and torque is transferred to the driven wheel
at a constant unchanging ratio. These single sprocket chain
and belt, and shaft driven vehicles can also use a commonly
found multi speed arrangement, where drive unit output shaft
speed and torque is transferred to the driven wheel at a variable
ratio through operator selected or automatically selected ratio
changing mechanisms.
[0031] A bicycle with a more advanced design includes gear
changing systems that have clusters of selectable front chainrings
and rear sprockets. These gear changing systems give the bicycle
rider a selectable mechanical advantage for use during powered
acceleration. The mechanical advantage selection, allows a rider
spinning a front sprocket cluster via crank arms, to attain
lower revolution speed and higher torque values, or conversely,
higher revolution speed and lower torque values at a driven
wheel.
[0032] The current invention, in certain embodiments, is directed
at suspension systems that can maintain low energy loss under
powered acceleration of the vehicle, for example, a bicycle,
a motorcycle, a car, an SUV, a truck, or any other kind of vehicle.
Suspension systems of the current invention are useful for a
large variety of vehicles, including, but not limited to, human
powered vehicles, off road use vehicles with long displacement
suspension, high efficiency road going vehicles, and other vehicles.
[0033] A vehicle suspension system isolates a vehicle chassis
from forces imparted on the vehicle when traversing terrain
by allowing the vehicle's ground contact points to move away
from impacts at the terrain level and in relation to the vehicle
chassis by a compressible suspension movement. The compressible
suspension movement that isolates a chassis from these impacts
is called suspension displacement or suspension travel. Compressible
suspension travel has a beginning point where the suspension
is in a completely uncompressed state, and an ending point of
displacement, where the suspension is in a completely compressed
state. Suspension travel displacement is measured in a direction
parallel to and against gravity. In certain preferred embodiments,
a suspension system of the invention uses a tuned squat curve
to provide an amount of squat closer to or higher in the range
of the squat condition known as anti squat in the beginning
of a suspension travel displacement, and an amount of squat
closer to the range of the squat condition known as anti squat
than the initial measurement at a later point in the suspension
travel displacement. As a suspension system of the invention
is compressed, a spring or damper unit is compressed. As this
spring or damper unit is compressed, the force output from the
unit rises. As the suspended wheel moves through its axle path,
spring force at the wheel rises. A suspended wheel has a compressible
wheel suspension travel distance that features a beginning travel
point where the suspension is completely uncompressed to a point
where no further suspension extension can take place, and an
end travel point where a suspension is completely compressed
to a point where no further suspension compression can take
place. At the beginning of the wheel suspension travel distance,
when the suspension is in a completely uncompressed state, the
spring is in a state of least compression, and the suspension
is easily compressed. In certain preferred embodiments, a higher
amount of anti squat in the beginning of the suspension travel
is needed to keep the suspension from compressing due to mass
transfer under acceleration. As the suspension compresses, spring
force at the wheel rises. When spring force rises to levels
present in the middle of the suspension travel, mass transfer
due to acceleration has a much smaller effect on vehicle traction
or chassis attitude because the mass transfer is not capable
of significantly compressing the suspension system. At this
point, in certain preferred embodiments, the present invention
decreases anti squat amount so that a greater amount of mass
transfer towards the wheel can occur. This mass transfer allows
increased wheel traction while transferring more energy towards
forward propulsion.
[0034] FIG. 1a shows certain embodiments of the invention and
it presents a graphical method useful to attain a squat point
measurement, and a graphical method to attain suspension geometry
kinematical layout from an existing desired measured squat point.
Shown in FIG. 1a are the following: driven wheel (1); swinging
wheel carrier link (2); upper carrier manipulation link (3);
lower carrier manipulation link (4); chain force vector (5);
driving force vector (6); squat force vector (7); upper carrier
manipulation link force vector (8); lower carrier manipulation
link force vector (9); squat definition point (10); squat layout
line (11); lower squat measurement definition line (12); measured
squat distance (13); driven wheel axle path (14); driven wheel
suspension travel distance (15); vehicle chassis (16); center
of the driven wheel tire to ground contact patch (31).
[0035] FIG. 1a exemplifies that as the driven wheel 1 suspension
system is completely uncompressed in its driven wheel suspension
travel distance 15, its squat force vector 7 is shown in relation
to the vehicle chassis 16. The squat force vector's 7 measured
squat distance 13 which is measured as the perpendicular distance
between the lower squat measurement definition line 12 and the
squat definition point 10, is also shown in FIG. 1a. As the
suspension system is compressed through its driven wheel suspension
travel distance 15, change in measured squat distance 13 over
the driven wheel suspension travel distance 15 is used to create
a squat curve 17. FIG. 1b shows a side view of a chain driven
vehicle as shown in FIG. 1a with the driven wheel suspension
system in a completely compressed state. Certain embodiments
are further exemplified, for example, vectors useful to a graphical
method to attain a squat point measurement are shown. Also exemplified
is a graphical method useful to attain suspension geometry kinematical
layout from an existing desired measured squat point. Shown
in FIG. 1b in addition to what is presented in FIG. 1a, are
the following: upper link fixed pivot (20); lower link fixed
pivot (21); upper link floating pivot (22); lower link floating
pivot (23); instant force center (24); driven wheel rotation
axis (25); chain force vector and driving force vector intersection
point (26); driving cog (27); driven cog (28); driving cog rotation
axis (29).
[0036] FIG. 1b exemplifies that as the driven wheel 1 suspension
system is completely compressed through its driven wheel suspension
travel distance 15, its squat force vector 7 moves in relation
to the vehicle chassis 16. The squat force vector's 7 measured
squat distance 13, which is measured as the perpendicular distance
between the lower squat measurement definition line 12 and the
squat definition point 10, decreases in relation to the measured
squat distance 13 shown in FIG. 1a. This change in measured
squat distance 13 over the driven wheel suspension travel distance
15, in certain preferred embodiments, is used to create a squat
curve 17. FIG. 1b shows the graphical method used to obtain
a squat curve 17 from chain driven vehicle geometry, or chain
driven vehicle geometry from a squat curve 17. In the vehicle
shown in FIG. 1b, a driven wheel 1 is attached to a swinging
wheel carrier link 2, which pivots at one end of an upper carrier
manipulation link 3. The upper carrier manipulation link 3 is
pivotally attached to the vehicle chassis 16 at the upper link
fixed pivot 20. A lower carrier manipulation link 4 is also
attached to the swinging wheel carrier link 2. This lower carrier
manipulation link 4 is attached to the vehicle chassis 16 at
a lower link fixed pivot 21. An upper carrier manipulation link
force vector 8 is graphed coincident to the swinging wheel carrier
link 2 upper pivot and the upper link fixed pivot 20. The upper
carrier manipulation link force vector 8 is graphed so that
it intersects a lower carrier manipulation link force vector
9, which is graphed coincident to the swinging wheel carrier
link 2 lower pivot and the lower link fixed pivot 21. The intersection
point of the upper carrier manipulation link force vector 8,
and the lower carrier manipulation link force vector 9 is called
the instant force center 24. A driving force vector 6 is graphed
beginning at the driven wheel rotation axis 25, and passes through
the instant force center 24. A chain force vector 5 is drawn
tangent to the tops of the driving cog 27 and driven cog 28,
and intersects the driving force vector 6 at a chain force vector
and driving force vector intersection point 26. The squat force
vector 7 is graphed from a beginning point at the center of
the driven wheel tire to ground contact patch 31, and passes
through the chain force vector and driving force vector intersection
point 26, before it terminates on a squat layout line 11. The
intersection of the squat force vector 7 and the squat layout
line is called the squat layout point 10. The squat layout line
11 is graphed at a perpendicular angle to gravitational force.
A lower squat measurement definition line 12 is graphed beginning
at the center of the driven wheel tire to ground contact patch
31 and terminating perpendicular and coincident to the squat
layout line 11. The perpendicular measurement from the lower
squat measurement definition line 12 to the squat layout point
10 is called the measured squat distance 13. This measured squat
distance 13 changes as driven wheel suspension travel distance
15 compresses, and is used to create a squat curve 17 in a squat
curve graph as shown in FIGS. 3 and 4.
[0037] FIG. 1c shows an enlarged section of the side view of
the chain driven vehicle shown in FIGS. 1a and 1b with the driven
wheel suspension system in a completely uncompressed state.
[0038] FIG. 1d shows an enlarged section of the side view of
the chain driven vehicle shown in FIGS. 1a , 1b, and 1c with
the driven wheel suspension system in a completely compressed
state. FIGS. 1c and 1d further exemplify certain embodiments,
for example, points and vectors useful for a graphical method
used to attain a squat point measurement, and a graphical method
to attain suspension geometry kinematical layout from an existing
desired measured squat point.
[0039] FIG. 2a shows certain embodiments of the invention and
it presents a graphical method useful to attain a squat point
measurement, and a graphical method to attain suspension geometry
kinematical layout from an existing desired measured squat point.
Shown in FIG. 2a are the following: driven wheel (1); swinging
wheel carrier link (2); upper carrier manipulation link (3);
lower carrier manipulation link (4); squat force vector (7);
upper carrier manipulation link force vector (8); lower carrier
manipulation link force vector (9); squat definition point (10);
squat layout line (11); lower squat measurement definition line
(12); measured squat distance (13); driven wheel axle path (14);
driven wheel suspension travel distance (15); vehicle chassis
(16); center of the driven wheel tire to ground contact patch
(31).
[0040] FIG. 2a exemplifies that as the driven wheel 1 suspension
system is completely uncompressed in its driven wheel suspension
travel distance 15, its defined squat force vector 7 is shown
in relation to the vehicle chassis 16. The squat force vector's
7 measured squat distance 13, which is measured as the perpendicular
distance between the lower squat measurement definition line
12 and the squat definition point 10, is shown in FIG. 2a. As
the suspension system is compressed through its driven wheel
suspension travel distance 15, change in measured squat distance
13 over the driven wheel suspension travel distance 15 is used
to create a squat curve 17.
[0041] FIG. 2b shows a side view of a shaft driven vehicle
as shown in FIG. 2a with the driven wheel suspension system
in a completely compressed state. Certain embodiments are further
exemplified, for example, vectors useful to a graphical method
to attain a squat point measurement are shown. Also exemplified
is a graphical method useful to attain suspension geometry kinematical
layout from an existing desired measured squat point. Shown
in FIG. 2b in addition to what is presented in FIG. 2a, are
the following: upper link fixed pivot (20); lower link fixed
pivot (21); upper link floating pivot (22); lower link floating
pivot (23); instant force center (24); driven wheel rotation
axis (25); chain force vector and driving force vector intersection
point (26); driving cog (27); driven cog (28); driving cog rotation
axis (29).
[0042] FIG. 2b exemplifies that as the driven wheel 1 suspension
system is completely compressed through its driven wheel suspension
travel distance 15, its defined squat force vector 7 moves in
relation to the vehicle chassis 16. The squat force vector's
7 measured squat distance 13 which is measured as the perpendicular
distance between the lower squat measurement definition line
12 and the squat definition point 10, decreases in relation
to the measured squat distance 13 shown in FIG. 2a. This change
in measured squat distance 13 over the driven wheel suspension
travel distance 15 is used to create a squat curve 17. FIG.
2b shows the graphical method used to obtain a squat curve 17
from shaft driven vehicle geometry, or shaft driven vehicle
geometry from a squat curve 17. In the vehicle shown in FIG.
2b, a driven wheel 1 is attached to a swinging wheel carrier
link 2, which pivots at one end of an upper carrier manipulation
link 3. The upper carrier manipulation link 3 is pivotally attached
to the vehicle chassis 16 at the upper link fixed pivot 20.
A lower carrier manipulation link 4 is also attached to the
swinging wheel carrier link 2. This lower carrier manipulation
link 4 is attached to the vehicle chassis 16 at a lower link
fixed pivot 21. An upper carrier manipulation link force vector
8 is graphed coincident to the swinging wheel carrier link 2
upper pivot and the upper link fixed pivot 20. The upper carrier
manipulation link force vector 8 is graphed so that it intersects
a lower carrier manipulation link force vector 9, which is graphed
coincident to the swinging wheel carrier link 2 lower pivot
and the lower link fixed pivot 21. The intersection point of
the upper carrier manipulation link force vector 8, and the
lower carrier manipulation link force vector 9 is called the
instant force center 24. The squat force vector 7 is graphed
from a beginning point at the center of the driven wheel tire
to ground contact patch 31, and passes through the instant force
center 24, before it terminates on a squat layout line 11. The
intersection of the squat force vector 7 and the squat layout
line is called the squat layout point 10. The squat layout line
11 is graphed at a perpendicular angle to gravitational force.
A lower squat measurement definition line 12 is graphed beginning
at the center of the driven wheel tire to ground contact patch
31 and terminating perpendicular and coincident to the squat
layout line 11. The perpendicular measurement from the lower
squat measurement definition line 12 to the squat layout point
10 is called the measured squat distance 13. This measured squat
distance 13 changes as driven wheel suspension travel distance
15 compresses, and is used to create a squat curve 17 in a squat
curve graph as shown in FIGS. 3 and 4.
[0043] FIG. 2c shows an enlarged section of the side view of
the shaft driven vehicle shown in FIGS. 2a and 2b with the driven
wheel suspension system in a completely uncompressed state.
[0044] FIG. 2d shows an enlarged section of the side view of
the shaft driven vehicle shown in FIGS. 2a, 2b, and 2c with
the driven wheel suspension system in a completely compressed
state. FIGS. 2c and 2d further exemplify certain embodiments,
for example, points and vectors useful for a graphical method
used to attain a squat point measurement, and a graphical method
to attain suspension geometry kinematical layout from an existing
desired measured squat point.
[0045] FIG. 3 shows a squat curve for suspension systems according
to certain embodiments of the invention graphed on a squat curve
graph as disclosed herein. The percent of total suspension travel
is shown on the x-axis, and the percent of total squat is shown
on the y-axis. FIG. 3 exemplifies a squat curve (17). The slope
and shape of the squat curve shown in FIG. 3 exemplifies a squat
curve produced by suspension systems of the invention, for example,
suspension systems including features as illustrated in FIGS.
1a-1d and FIGS. 2a-2d. FIG. 3 also exemplifies a graphical method
useful to obtain a squat curve graph.
[0046] FIG. 4 shows a squat curve for suspension systems according
to certain embodiments of the invention. The percent of total
suspension travel is shown on the x-axis, and the percent of
total squat is shown on the y-axis. FIG. 4 exemplifies a squat
curve 17 with tangent lines depicting a slope of the curve at
certain points along the squat curve. The slopes exemplified
by the tangent lines are the first squat curve slope 18, the
second squat curve slope 19, and the third squat curve slope
30. FIG. 4 exemplifies a slope of the squat curve 17 as produced
by a suspension system of certain embodiments of the current
invention, for example, a suspension system including features
as illustrated in FIGS. 1a-1d and FIGS. 2a-2d, and that the
slope varies as the vehicle suspension travel distance increases.
The squat curve 17 produced has a first squat curve slope 18
that has a negative value at the beginning point in the suspension
travel, and a second squat curve slope 19 at an interim point
that is higher, or less negative, than the first squat curve
slope 18 in the suspension travel, and a third squat curve slope
30 at the ending point in the suspension travel that has a lower,
or more negative, value than the second squat curve slope 19.
[0047] FIGS. 5-13 show alternative embodiments of suspension
systems comprising a squat curve of the invention. Each embodiment
shown includes a spring/damper unit (small irregular box) and
different frame members (thicker lines) interconnected through
pivots (small circles).
[0048] Mass transfer is discussed. All vehicles have mass.
The mass of a suspended static vehicle system can be modeled
as shown in the FIG. 1. Mass in all vehicles with a suspension
system can be divided into sprung and unsprung mass. Unsprung
mass is comprised of the sum of all vehicle parts that move
with a suspended wheel. Sprung mass is comprised of the sum
of vehicle parts that can remain stationary as a suspended wheel
is moved. The dynamic center of the sprung mass as shown in
FIG. 2 is a combination of rider and/or passenger mass and the
vehicle mass.
[0049] The combination of a rider's mass and the sprung mass
of the bicycle are always supported fully by the combination
of the vehicle's tires. Powered forward acceleration transfers
mass from the vehicle's front wheel(s) to the vehicle's driven
wheel(s), braking transfers mass from the vehicle's front wheel(s)
to the vehicle's driven wheel(s). Riding on the driven wheel(s)
only transfers all of the mass to the driven wheel(s), and riding
on the front wheel(s) only transfers all of the mass to the
front wheel(s).
[0050] Due to their combination of short wheelbase (WB) and
high center of gravity (CG), motorcycles and bicycles experience
the affects of load transfer to a much greater extent than other
vehicles in existence. The ratio of the distance from the ground
to the CG and the distance between the points where the wheels
touch the ground (WB) illustrates this point. For example, a
common bicycle will exhibit a center of gravity to wheelbase
ratio of nearly 100%, motorcycles are typically near 50%, and
passenger cars are typically near 25%. Mass transfer is sometimes
also referred to as load transfer.
[0051] Energy loss through mass transfer is discussed. One
undesirable effect of driven wheel suspension systems is the
loss of energy in the way of extreme suspension compression
or extension during powered acceleration. This suspension compression
or extension is categorized as squat.
[0052] A suspension system's geometry and positional relationships
between the vehicle drive system components can greatly affect
the internal distribution of forces within the vehicle chassis.
As a suspension system cycles through its suspension travel,
the positional relationships between the suspension system and
the vehicle drive system can change, and at the same time, the
suspension geometry itself will change. These fluctuations of
internal forces are what govern suspension response to powered
acceleration and braking. Vehicle attitude in relation to gravity,
and sprung weight center of mass change will also govern suspension
response to powered acceleration and braking. These external
forces are considered stationary and equal when comparing like
vehicles in order to determine squat characteristics.
[0053] Squat is the result of internal chassis forces that
can cause a rear suspension to extend or compress during powered
acceleration. Squat is an instantaneous condition that can vary
throughout the suspension travel. Instantaneous squat response
is governed by sprung mass CG placement, suspension geometry,
powertrain component location, and grade in relation to gravity
that the vehicle is traveling on. Sprung mass CG placement only
defines the amount of squat present in a suspension, and does
not change the squat conditions. The squat conditions define
the direction of squat force in relation to gravity.
[0054] There are three squat conditions that must be considered.
The first condition is pro-squat, and describes the condition
present when a rear suspension is forced to compress by internal
suspension forces under powered acceleration. The second condition
is anti-squat. Anti-squat describes the condition present when
a rear suspension compression is counteracted by internal suspension
forces under powered acceleration. The third condition is zero-squat.
Zero-squat occurs only at the instant in between pro-squat and
anti-squat, where no suspension manipulating forces are present
under powered acceleration. A vehicle suspension operating at
the point of zero-squat will not use acceleration forces to
manipulate suspension reaction in any way.
[0055] Squat force works independent of the spring force that
supports a suspended vehicle. Because the squat force is independent
of the vehicle spring force, when under acceleration, a vehicle
suspension is acted upon by its spring and the squat force together.
Suspended vehicles use springs to support the vehicle chassis
and dampers to dissipate impact energy when the suspension system
is compressed and extended while the vehicle travels over rough
terrain. Springs can be in the form of compressive gas springs,
leaf springs, or coil springs, and dampers can use fluid or
friction to dissipate energy. When a vehicle is at rest, suspended
wheels are compressed a certain amount so that the suspended
wheel can follow irregular road surfaces with both bumps and
dips. The spring that supports a wheel suspension acts as an
energy storage device. Vehicle suspensions use the damper units
to dissipate energy stored in a spring after the spring is compressed.
The further a spring is compressed, the more energy is stored,
and the more energy will be dissipated by the damper when the
spring rebounds. Because spring force increases as a wheel is
compressed into its suspension travel, force at the suspended
wheel also increases.
[0056] Squat curve graphing is discussed. A squat curve graph
is a representation of the squat produced by a compressible
suspension system under powered acceleration. The squat curve
graph is laid out so that the percentage of suspension travel
is graphed on the X axis, and escalating in a positive direction.
The minimum suspension travel, which is zero percent suspension
compression, is shown at the far left of the x-axis, and the
maximum suspension travel, which is represented by 100 percent
suspension compression, is shown at the far right of the x-axis.
Percent suspension compression is measured and graphed in minimum
increments of 5 percent total suspension compression; measured
Percent total squat is graphed on the y-axis in an escalating
amount. The highest amount of squat is defined as 100 percent,
and is represented at the top of the y-axis. These values are
taken directly from the squat points which are measured from
graphed squat points on the squat layout line. Measurement is
taken at a perpendicular distance from the lower squat measurement
definition line. Zero percent squat is always measured at the
point of zero squat condition. This zero squat condition is
measured when the squat point lies directly on the lower squat
measurement definition line. At this point, the squat measurement
has no value. Any measurement of a squat point that lies below
the lower squat definition line is equal to a pro squat amount,
and must be graphed as a negative percentage of the 100 percent
squat value. The amount of squat closer to or highest in the
range of the squat condition known as anti squat is listed as
the highest positive squat value, and lower amounts of anti
squat, zero squat, and pro-squat are listed as lower percentages
of the highest anti squat value. Zero squat is shown when the
squat curve crosses or terminates at zero value on the y-axis,
and pro squat is graphed as a negative y-axis percentage below
the x-axis. For example, if a squat curve begins with a measurement
that is measured 100 millimeters above the lower squat measurement
definition line, at a point of zero suspension compression,
this point will be graphed at a value of 1 on the y-axis, and
0 on the x-axis. If a later point is measured 100 millimeters
below the lower squat measurement definition line, at a point
of 100 percent suspension compression, this point will be graphed
at a value of -1 on the y-axis, and 1 on the x-axis. In the
squat curve graph, the distance set to equal 100 percent suspension
travel and the distance set to equal 100 percent squat should
be set as equal distances. Therefore, the distance between zero
value for squat to maximum value for squat will be equal to
the graphed distance between zero value for suspension compression
to maximum value for suspension compression. When desired squat
point values are known and graphed versus their corresponding
percent measured suspension compression values, the points can
be connected from point to point using typical graphing method
A curve can then be fit to the point to point graph so that
the curve represents a smoothed best fit version of the point
to point graph. The most efficient method to obtain such a curve
is to use a computer program such as Microsoft Excel, available
from Microsoft Corporation, One Microsoft Way, Redmond, Wash.
98052-6399, USA. Using Microsoft Excel, a user can input the
escalating suspension travel measurements beginning with the
zero percent measurement and ending with the 100 percent measurement,
and can input the measured or preferred squat point measurements
that coincide with their percent suspension travel measurements.
Microsoft Excel then can be used to create a graph of the points
with a curve fit to the graphed points. This graphed curve is
the discussed squat curve.
[0057] Slope of a squat curve between two points on a curve
is defined by the standard coordinate geometry equation: slope=rise/run.
A squat curve that has a squat amount at zero suspension travel,
with 20 percent less squat at a point 10 percent into the wheel
suspension travel compression will have a slope of -2, because
per the equation slope=rise/run, -0.2/0.1=-2. A squat curve
that has a pro squat amount at zero suspension travel, with
20 percent more pro squat at a point 10 percent into the wheel
suspension travel compression will have a slope of -2, because
per the equation slope=rise/run, -0.2/0.1=-2. A squat curve
can be produced for any wheel suspension system by graphing
the percent of squat throughout the suspension travel.
[0058] In certain embodiments, a suspension system according
to the invention has a squat curve with a negative, or decreasing,
slope. In certain preferred embodiments, the slope of the squat
curve is more negative at the beginning of suspension travel
than in the interim, or mid range, of suspension travel. In
certain other preferred embodiments, the slope of the squat
curve is more negative at the end of suspension travel than
in the interim, or mid range, of suspension travel. In certain
other preferred embodiments, the slope of the squat curve is
more negative at the beginning of suspension travel than at
the end of suspension travel.
[0059] In certain embodiments, the beginning of the suspension
travel is 0 to 50 percent, or about 0 to about 50 percent, of
suspension travel; or 0 to 40 percent, or about 0 to about 40
percent, of suspension travel; or 0 to 30 percent, or about
0 to about 30 percent, of suspension travel; or 0 to 20 percent,
or about 0 to about 20 percent, of suspension travel; or 0 to
10 percent, or about 0 to about 10 percent, of suspension travel;
or 0 to 5 percent, or about 0 to about 5 percent, of suspension
travel; or 0 or about 0 percent of suspension travel. In certain
embodiments, the interim, or mid range, of the suspension travel
is 25 to 75 percent, or about 25 to about 75 percent, of suspension
travel; or 30 to 70 percent, or about 30 to about 70 percent,
of suspension travel; or 35 to 65 percent, or about 35 to about
65 percent, of suspension travel; or 40 to 60 percent, or about
40 to about 60 percent, of suspension travel; or 45 to 55 percent,
or about 45 to about 55 percent, of suspension travel; or 50
percent or about 50 percent, of suspension travel; or 60 to
80 percent, or about 60 to about 80 percent, of suspension travel;
or 65 to 75 percent, or about 65 to about 75 percent, of suspension
travel; or 70 percent or about 70 of suspension travel; or 50
to 60 percent, or about 50 to about 60 percent, of suspension
travel. In certain embodiments, the end of the suspension travel
is 70 to 100 percent, or about 70 to about 100 percent, of suspension
travel; or 75 to 100 percent, or about 75 to about 100 percent,
of suspension travel; or 80 to 100 percent, or about 80 to about
100 percent, of suspension travel; or 85 to 100 percent, or
about 85 to about 100 percent, of suspension travel; or 90 to
100 percent, or about 90 to about 100 percent, of suspension
travel; or 95 to 100 percent, or about 95 to about 100 percent,
of suspension travel; or 100 or about 100 percent of suspension
travel.
[0060] In certain embodiments, a suspension system of the invention
has a squat curve with a slope in the beginning of suspension
travel of -0.2 to -5, or about -0.2 to about -5; of -0.5 to
-4.5, or about -0.5 to about -4.5; of -0.75 to -4.0, or about
-0.75 to about -4.0; of -1.0 to -3.5, or about -1.0 to about
-3.5; of -1.5 to -3.0, or about -1.5 to about -3.0; of -2.0
to -2.5, or about -2.0 to about -2.5. In certain embodiments,
a suspension system of the invention has a squat curve with
a slope in the interim, or mid range, of suspension travel of
-0.0001 to -5, or about -0.0001 to about -5; of -0.01 to -4.0,
or about -0.01 to about -4.0; of -0.1 to -3.0, or about -0.1
to about -3.0; of -0.2 to -2.0, or about -0.2 to about -2.0;
of -0.3 to -1.2, or about -0.3 to about -1.2; of -0.4 to -0.8,
or about -0.4 to about -0.8. In certain embodiments, a suspension
system of the invention has a squat curve with a slope in the
end of suspension travel of -0.0002 to -1000, or about -0.0002
to about -1000; of -0.1 to -500, or about -0.1 to about -500;
of -0.2 to -50, or about -0.2 to about -50; of -0.3 to -10,
or about -0.3 to about -10; of -0.4 to -5.0, or about -0.4 to
about -5.0; of -0.6 to -2.0, or about -0.6 to about -2.0.
[0061] Graphical kinematical squat curves are discussed. Graphical
methods can be used to determine suspension kinematical layout
used to attain a desired squat curve for a suspension. For shaft
drive and chain drive vehicles, graphical layout is identical
until factoring in the unique features of each powertrain. Any
suspended wheel in a vehicle has an axle path that a wheel follows
when a suspension is moved through suspension travel. The curvature
of this axle path and its layout in relation to specific powertrain
components define a squat curve. A squat curve is a measurement
of the changing magnitude and direction of squat developed under
powered acceleration as suspension system is cycled through
suspension travel from its beginning uncompressed point to its
ending fully compressed point. Every instantaneous point in
a suspension travel has a corresponding instantaneous amount
of squat present. These instantaneous squat points can be measured
or graphed as a point on the squat layout line at a perpendicular
distance from the lower squat layout line. When the desired
instantaneous amounts of squat at instantaneous points in the
suspension travel are known, squat definition points can be
graphed in conjunction with each other, beginning when a suspension
is in its uncompressed state and ending in its fully compressed
state, and in relation to the vehicle geometry to obtain a suspension
kinematical layout which will attain the desired squat curve.
The squat curve beginning value is measured at the point where
the suspension system is in its completely uncompressed state.
As the suspension is cycled further through suspension travel
towards complete compression pausing at a minimum of 5 percent
total suspension travel increments, further squat points are
measured and graphed versus their correlating escalating percent
total suspension travel increments. Suspension travel displacement
is measured in a direction parallel to and against gravity,
and parallel to the instantaneous squat point measurements.
Critical and known preexisting defining points such as vehicle
wheelbase, powertrain location, and center of mass are graphed
alongside the squat definition points to obtain a clear picture
of vehicle squat performance. Vehicle graphs for obtaining and
defining squat performance are always laid out with the vehicle
viewed in the side elevational view.
[0062] A squat layout line is drawn parallel to and against
gravitational force through center of the front wheel contact
patch between the tire and the ground and terminating at further
points. A squat definition point, which is taken directly from
the aforementioned squat curve will be graphed on this squat
layout line. A squat lower measurement definition line is drawn
from the center of the driven wheel tire to ground contact patch
perpendicular to and terminating on the squat layout line. Squat
definition points are drawn on the squat definition line in
relation to one another, and in relation to the squat lower
measurement definition line. A squat definition point drawn
above the squat lower measurement definition line will correlate
with a squat amount. A squat definition point drawn coincident
with the squat lower measurement definition line will correlate
with a zero squat amount. A squat definition point drawn below
the squat lower measurement definition line will correlate with
a pro squat amount. A squat force vector is drawn from the center
of the driven wheel tire to ground contact patch to the squat
point on the squat layout line. As the suspension is moved through
instantaneous measured points through suspension travel, the
squat force vector is drawn with a beginning point at the center
of the rear tire to ground contact patch, and an ending point
at its corresponding measured instantaneous squat point graphed
on the squat layout line.
[0063] Diversion in graphical method to obtain specific suspension
system kinematical layouts from a desired squat curve must occur
when factoring in specifics for different types of power transfer
systems such as shaft drive or chain drive.
[0064] A shaft drive system generally uses a power transmission
system that can transmit power via rotary motion from a power
unit output shaft to a wheel shaft. The two shafts are generally
fixed at close to a perpendicular angle in one plane. Power
transmission systems can vary from gears to cogs to friction
wheels and other types of systems, all herein referred to universally
as cogs. These shaft drive systems feature a driving cog which
is rotatably attached to the power unit output, a first intermediate
cog, which transfers rotational motion from the driving cog
to a relatively perpendicular shaft, a second intermediate cog,
which transfers rotational motion from the shaft to a driven
cog which is rotatably attached to the rotation axis of a wheel.
[0065] Shaft drive vehicle powertrains and suspensions typically
take one of two forms. These are, a single pivot system, or
a multi link system. A simple single pivot system features a
driven cog that is fixed to and housed within a swinging wheel
carrier link which pivots around a single pivot. In this arrangement,
there is only one pivot connecting the swinging wheel carrier
link to the vehicle frame structure. The rotating drive torque
is acted against by the driven cog housing, which is part of
the swinging wheel carrier link. Action against the drive torque
in the swinging wheel carrier link causes a torque about the
ling single frame pivot. The addition of this torque plus the
driving force imparted through the wheel tire combination to
the ground through a tire to ground contact patch totals a squat
response. An instantaneous pivot location for a single pivot
shaft drive system can be found at any point on a drawn squat
force vector that correlates with the desired instantaneous
squat response. These single pivot systems produce a linear
squat curve.
[0066] A multi pivot linkage can be used to alter squat characteristics
and obtain a variable squat curve in a shaft driven wheel suspension
system. A multi link shaft drive suspension system isolates
the torque passed through the driven cog in the system from
the swinging link system. In a 4-bar variation, the driven cog
is attached to a swinging wheel carrier link, which pivots at
one end of a first swinging link. The first carrier manipulation
link is pivotally attached to the vehicle chassis at the end
opposite of the swinging wheel carrier link pivot. A torque
reaction, like the one discussed in the single pivot shaft drive
system works to rotate the swinging wheel carrier link against
the first carrier manipulation link. A second carrier manipulation
link is also attached to the swinging wheel carrier link. This
second carrier manipulation link is attached to the vehicle
chassis at a different location from the first swinging carrier
manipulation link. The second carrier manipulation link works
to inhibit free rotation of the swinging wheel carrier link
against the first carrier manipulation link. To find instantaneous
carrier manipulation link pivot points which will give a desired
instantaneous squat amount, its correlating desired squat force
vector must be graphed. The two swinging wheel carrier link
pivots are next defined. Carrier manipulation link force lines
are drawn so that a force line passes directly through the center
of the rearward pivots which are coincident with the pivots
on the swinging wheel carrier link. The carrier manipulation
link force lines are drawn so that they intersect on the desired
squat force vector. The first and second vehicle chassis pivots
can be positioned upon the corresponding first and second carrier
manipulation link force lines to attain the desired instantaneous
squat response. Graphing the carrier manipulation link force
lines and desired squat force vectors together overlaid at multiple
points in the suspension travel will allow the designer to choose
pivot point locations and kinematical suspension layout that
can attain a desired variable squat curve.
[0067] A chain drive powertrain system uses a chain or belt
to transmit power between two reasonably parallel shafts. Chain
drive systems are very common in motorcycle, ATV, and bicycle
applications because of their light weight, robustness, and
simplicity in both manufacturing and use. The chain drive systems
feature a driving cog and a driven cog, with the driving cog
attached to a power source, and a driven cog rotatably attached
to the rotation axis of a wheel. The driven wheel or wheels
is/are attached to a swinging link or linkage system via a bearing
or bushing system, which allows rotational motion of the driven
wheel or wheels in relation to the swinging link or linkage
system.
[0068] Chain drive suspensions typically take one of several
forms. These include single pivot systems, multi link systems,
cam/track type systems, and flexure type systems. The suspensions
can also feature variable chainline type designs, which manipulate
a chain force vector line through the use of a pulley system
that moves with the suspension. A single pivot system uses a
single pivoting suspension link to transmit force between a
suspended wheel and a chassis. A multi link system uses an arrangement
of pivoting suspension links to transmit force between a suspended
wheel and a chassis. A cam/track type system that uses sliding
elements but does not use links to attain force transfer from
a wheel axle to a chassis is also possible but uncommon in practice.
Flexure type systems use flexing elements to transmit power
from a suspended wheel to a chassis structure. In all types
of the chain driven wheel suspension system mentioned above,
the driving force can be represented as a vector drawn perpendicular
to the driven wheel axle path. In a chain driven suspension,
driving force is always the major force component when compared
to chain pull.
[0069] There are two internal forces present within a chain
driven vehicle chassis that together create a squat response.
These two forces are driving force, and chain pull force.
[0070] When a chain driven vehicle is accelerated, force is
transferred from a power source to a driving cog. This driving
cog transmits its force through a chain to a driven cog. The
force direction and magnitude present in the tensioned chain
are referred to as chain pull force. Fixed chainline type designs
are present where at any instantaneous point, a single driving
cog is fixed rotationally on a chassis structure, and a driven
cog is attached to a suspension member, and force is transmitted
from the driving cog to the driven cog through a chain. In this
fixed chainline type design, the chainline force vector is always
located at one end by the tensioned chainline tangent point
where the chain is fixed in relation to the vehicle chassis
structure, and by the tensioned chainline tangent point of the
moving pulley at the opposite end.
[0071] In variable chainline type designs, which manipulate
a chain force vector line through the use of a pulley system
that moves with the suspension, the chainline force vector is
always located at one end by the tensioned chainline tangent
point where the chain is fixed in relation to the vehicle chassis
structure, and by the tensioned chainline tangent point of the
moving pulley at the opposite end. Sliding elements can also
be substituted for pulleys in this application.
[0072] In the chain drive powertrain, the driven cog is rotatably
attached to a wheel/tire combination. The wheel pushes against
the ground resulting in friction. As the wheel rotates a driving
force transmitted from the contact patch through the wheel structure
and a force is imparted at the rear hub axle. This pushing force
can be transferred to the chassis via a wheel suspension system,
ultimately pushes the vehicle forward. This pushing force is
referred to as driving force. The driving force direction is
measured and represented graphically as a driving force vector
drawn from the driven wheel rotation axis, perpendicular to
the driven axle path, where the axle path is defined as a line
that a suspended wheel rotational axis travels as a suspension
is moved through suspension travel. This axle path can be a
constant curvature or changing curvature line depending on suspension
layout.
[0073] A simple single pivot system features a driven cog that
is rotatably attached to a wheel, which is rotatably attached
to a swinging wheel carrier link which pivots around a singular
pivot. In this arrangement, the suspended wheel travels in a
constant radius arc. To find the instantaneous swinging link
pivot point for a single pivot chain drive system, which will
give a desired instantaneous squat amount, its correlating desired
squat force vector must be graphed. Because there is only one
link in the single pivot suspension, the swinging link pivot
will lie coincident with the driving force line. Desired vehicle
geometry is graphed in a side view. This vehicle geometry will
include the size, location, and center points of vehicle tires,
powertrain component layout, and the direction of gravitational
force. A squat layout line is graphed first. A desired squat
force vector is drawn from the center of a rear wheel contact
patch to the desired squat layout point on a squat layout line
as described previously. Next, the chain force vector is graphed
in relation to the powertrain components as described previously.
The chain force vector is drawn so that it intersects the squat
force vector. Finally, the driving force vector is drawn from
the center of the rear wheel axis to the intersection point
of the squat force vector and chain pull force vector. The pivot
point for the single pivot swinging link suspension arm will
lie at any point along the driving force vector to achieve the
desired instantaneous squat amount. Graphing the chain pull
force vector, and squat force vectors together overlaid at multiple
points in the suspension travel will allow the designer to find
driving force vectors at multiple points through the suspension
travel. The crossing point of the overlaid driving force vectors
for different points in the suspension travel define the single
pivot point location and kinematical suspension layout that
can attain the desired squat curve.
[0074] Multi link systems, cam/track (sliding link) type systems,
and flexure type systems feature a driven cog that is rotatably
attached to a wheel, which is rotatably attached to a swinging
wheel carrier link which moves the wheel along an axle path
that is defined by a multi element system. To aid the analysis
of multi-element systems, it is simplest to define or measure
an axle path which will guide a wheel, and then define the elements
that will give the desired axle path later, as opposed to trying
to define elements first and measure axle path as a byproduct
later to attain a desired result. Multi element systems do not
have a single hardware defined pivot point like a single fixed
pivot system does. The multi element systems use combinations
of links or cams to project a virtual or instantaneous pivot
point. This pivot point can always be found at a point along
a driving force vector, which is drawn perpendicular to a driven
wheel axle path as previously described.
[0075] To find the axle path which will give a desired instantaneous
squat amount, its correlating desired squat force vectors must
be graphed. Desired vehicle geometry is graphed in a side view.
This vehicle geometry will include the size, location, and center
points of vehicle tires, vehicle ground plane, powertrain component
layout, and the direction of gravitational force. A vehicle
wheel suspension system always has a minimum suspension travel
point, where the suspended wheel is at its zero compressed suspension
travel point, and a maximum suspension travel point, where the
suspended wheel is at its 100 percent compressed suspension
travel point. Several overlaid graphs must be made to obtain
a squat curve. The minimum increment in suspension compression
displacement that can be used to graph an accurate squat curve
from the graphical method using squat force vectors as presented
has been found to be 5 percent of total suspension compression
displacement between graphed squat force vectors. A squat layout
line is graphed first. A desired squat force vector is drawn
from the center of a driven wheel contact patch to the desired
squat layout point on a squat layout line as described previously.
Next, the chain force vector is graphed in relation to the powertrain
components as described previously. The chain force vector is
drawn so that it intersects the squat force vector. Finally,
the driving force vector is drawn from the center of the driven
wheel axis to the intersection point of the squat force vector
and chain pull force vector. The instantaneous pivot point for
the single pivot swinging link suspension arm will lie at any
point along the driving force vector to achieve the desired
instantaneous squat amount. Graphing the chain pull force vector,
and squat force vectors together overlaid at multiple points
in the suspension travel will allow the designer to find driving
force vectors at multiple points through the suspension travel.
The crossing point of the overlaid driving force vectors for
different points in the suspension travel define the instantaneous
pivot point movement through the suspension travel, and kinematical
suspension layout that can attain the desired squat curve. For
multi element systems, there are several methods that can define
element layout based on a desired axle path, for example, by
using kinematical analysis computer software. Software that
can perform this specific function is marketed under the names
SyMech, which is available from SyMech Inc, 600 Townsend Street,
San Francisco, Calif., 94107, USA, and SAM, which is available
from ARTAS--Engineering Software, Het Puyven 162, NL-5672 RJ
Nuenen, The Netherlands. This software allows a user to define
an axle path, and set parameters such as mechanical element
type, number of mechanical elements, and desired location of
anchor components. The software will then suggest multiple link
layout choices that will meet all of the set forth parameters.
Graphical analysis can also be performed by hand. In a hand
graphical analysis, the mechanical components of a multi element
system are measured at multiple points through the suspension
travel. At each point in the suspension travel, the instant
center of the link system is graphed. A common 4-bar linkage
suspension system features a driven cog that is rotatably attached
to a driven wheel, which is rotatably attached to a swinging
wheel carrier link which is pivotably attached to two separate
carrier manipulation links. The swinging links are pivotably
attached to a vehicle chassis at their other ends. The instant
center in a 4 bar pivoting linkage system such as shown in FIG.
1a, is found by projecting individual link force lines through
both pivots of each of the two carrier manipulation links that
support the swinging wheel carrier. The two carrier manipulation
link force lines are projected so that they intersect each other.
This intersection point is commonly known at the instant force
center. A driving force line can be drawn directly from the
rotation axis of the driven wheel to this instant force center.
As the carrier manipulation links rotate on their pivots, the
instant center position changes in relation to the driven wheel
rotation axis and the vehicle chassis. This causes the driving
force line to move in relation to the chain force line. Because
the squat force line is defined in part by the location of the
driven wheel contact patch, and the intersection between the
driving force vector and the chain force vector, a change in
squat vector direction can occur. The perpendicular distance
from the lower squat definition line to the point at which this
squat direction vector intersects the drawn squat layout line
to is measured and recorded.
[0076] Four bar sliding link suspension systems are analyzed
identically to 4 bar pivoting systems, but the identification
of the instant center is performed in a slightly different manner
due to the constraints of the sliding link system. Four bar
sliding link systems feature a driven cog that is rotatably
attached to a driven wheel, which is rotatably attached to a
swinging wheel carrier link which is pivotably attached to two
separate sliding carrier manipulation sliding blocks. The individual
carrier manipulation sliding blocks move on individual sliding
rails. The instant center in a 4 bar sliding linkage system
is found by projecting individual sliding link force lines centered
at the pivots of each of the two carrier manipulation sliding
block that support the swinging wheel carrier. The carrier manipulation
sliding block force lines are projected perpendicular to the
sliding rail so that the two carrier manipulation sliding black
force lines intersect each other. This intersection can be referred
to as the instant force center. A driving force line can be
drawn directly from the rotation axis of the driven wheel to
this instant force center. As the carrier manipulation sliding
blocks slide on their respective sliding rails, the instant
center position changes in relation to the driven wheel rotation
axis and the vehicle chassis. This causes the driving force
line to move in relation to the chain force line. Because the
squat force line is defined in part by the location of the driven
wheel contact patch, and the intersection between the driving
force vector and the chain force vector, a change in squat vector
direction can occur. The perpendicular distance from the the
lower squat definition line to the point at which this squat
direction vector intersects the drawn squat layout line to is
measured and recorded.
[0077] Measurement of multi element systems to determine axle
path can be done graphically, or by using measurement equipment.
Using measurement equipment, the vehicle can be rigidly mounted
and oriented so that the suspended wheel can be moved freely
through measured points in its suspension travel while the chassis
stays stationary. In a side view orientation, the horizontal
and vertical distance from the suspended wheel rotation axis
to a fixed point on the vehicle frame at multiple points in
the suspension travel is taken. As the suspension is cycled
through suspension travel, the corresponding measurements of
horizontal and vertical distance form a wheel rotation axis
travel path in relation to the vehicle chassis. This path is
referred to as the axle path.
[0078] Analysis has shown that a vehicle with a compressible
suspension system using a chain driven suspended wheel achieves
the squat curve 17 of the current invention by having a layout
that features a driven cog that is rotatably attached to a driven
wheel, which is rotatably attached to a swinging wheel carrier
link which is pivotably attached to separate upper and lower
carrier manipulation links. The upper and lower carrier manipulation
links are pivotably attached to a vehicle chassis at their other
ends. The upper and lower carrier manipulation links rotate
in the same rotational direction about their respective fixed
axis at the vehicle chassis. The upper carrier manipulation
link is arranged in relation to the lower carrier manipulation
link so that the instant center projected by the two carrier
manipulation links, when measured at zero percent suspension
compression, is at a point that is beyond the outer limits of
the two pivots of the lower carrier manipulation link. This
condition is shown in FIGS. 1a and 1c. As the suspension is
compressed towards a point of full compression, the rotation
of the upper and lower carrier manipulation links in relation
to each other causes the instant center of the linkage system
to lie at points on the lower carrier manipulation link in between
the lower carrier manipulation link fixed vehicle chassis pivot,
and moving pivot attached to the swinging wheel carrier link.
This condition is shown in FIGS. 1b and 1d.
[0079] Analysis has shown that a vehicle with a compressible
suspension system using a shaft driven suspended wheel achieves
the squat curve 17 of the current invention by having a layout
that features a driven cog that is rotatably attached to a driven
wheel, which is rotatably attached to a swinging wheel carrier
link which is pivotably attached to separate upper and lower
carrier manipulation links. The upper and lower carrier manipulation
links are pivotably attached to a vehicle chassis at their other
ends. The upper and lower carrier manipulation links rotate
in a contra rotational direction about their fixed axes at the
vehicle chassis. The upper carrier manipulation link is arranged
in relation to the lower carrier manipulation link so that the
instant center projected by the two carrier manipulation links,
when measured at zero percent suspension compression, lies at
a point on the lower carrier manipulation link in between the
lower carrier manipulation link fixed vehicle chassis pivot,
and moving pivot attached to the swinging wheel carrier link.
This condition is shown in FIGS. 2a and 2c. As the suspension
is compressed towards a point of full compression, the rotation
of the upper and lower carrier manipulation links in relation
to each other causes the instant center of the linkage system
to lie at a point that is beyond the outer limits of the two
pivots of the lower carrier manipulation link. This condition
is shown in FIGS. 2a and 2d.
[0080] The present invention is not to be limited in scope
by the specific embodiments described herein, which are intended
as single illustrations of individual aspects of the invention,
and functionally equivalent methods and components are within
the scope of the invention. Indeed, various modifications of
the invention, in addition to those shown and described herein,
will become apparent to those skilled in the art from the foregoing
description. Such modifications are intended to fall within
the scope of the appended claims. All cited publications, patents,
and patent applications are herein incorporated by reference
in their entirety.
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Bueno pues ahí queda eso :o) Las imagenes no las he
podido colgar todavía porque el visor de la página
no es compatible con mi navegador, ya las iré incorporado
en cuanto las consiga...