U.S. patent application number 13/440746 was filed with the patent office on 2012-08-02 for suspension architecture for a snowmobile.
This patent application is currently assigned to Polaris Industries Inc.. Invention is credited to Timothy J. Giese.
Application Number | 20120193158 13/440746 |
Document ID | / |
Family ID | 43333362 |
Filed Date | 2012-08-02 |
United States Patent
Application |
20120193158 |
Kind Code |
A1 |
Giese; Timothy J. |
August 2, 2012 |
SUSPENSION ARCHITECTURE FOR A SNOWMOBILE
Abstract
A rear suspension architecture is provided for coupled rear
suspension systems.
Inventors: |
Giese; Timothy J.; (Roseau,
MN) |
Assignee: |
Polaris Industries Inc.
Medina
MN
|
Family ID: |
43333362 |
Appl. No.: |
13/440746 |
Filed: |
April 5, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12968749 |
Dec 15, 2010 |
8151923 |
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13440746 |
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11709421 |
Feb 22, 2007 |
7854285 |
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12968749 |
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60775997 |
Feb 24, 2006 |
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Current U.S.
Class: |
180/193 |
Current CPC
Class: |
B62M 2027/026 20130101;
B62M 27/02 20130101 |
Class at
Publication: |
180/193 |
International
Class: |
B62M 27/02 20060101
B62M027/02 |
Claims
1. A snowmobile having a coupled suspension, the snowmobile
comprising: a chassis having a front and rear end; a lower rail; a
front control arm positioned adjacent to the chassis front end, the
front control arm pivotally interconnecting the chassis and the
lower rail; a rear inverted control link interconnected to the
lower rail; a rear control arm positioned adjacent to the chassis
rear end and pivotally interconnected to the chassis and the rear
inverted control link, the rear control arm interconnected to the
rear inverted control link at a position below the interconnection
between the rear inverted control arm and the lower rail; and a
coupling member providing a controlled degree of freedom of
movement between the coupling member and the rear control arm,
until coupling between the rear control arm and the lower rail
occurs.
2. The snowmobile of claim 1, wherein the snowmobile includes a
pair of spaced-apart lower rails.
3. The snowmobile of claim 2, wherein the snowmobile includes
another front and rear control arm and another rear inverted
control link to define a pair of front and rear control arms and a
pair of rear inverted control links.
4. The snowmobile of claim 3, wherein the coupling member is
positioned between the spaced-apart lower rails.
5. The snowmobile of claim 1 wherein the coupling member includes a
housing including an opening extending between a front and rear
bump stop, the bump stops configured to limit the degree of freedom
of movement of the rear control arm and the lower rail.
6. The snowmobile of claim 5, further comprising a cross shaft
supported by the rear control arm, the cross shaft adapted to be
positioned and move within the opening in the housing of the
coupling member.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional of U.S. patent application
Ser. No. 12/968,749 filed Dec. 15, 2010, which is a divisional of
U.S. application Ser. No. 11/709,421, filed on Feb. 22, 2007, which
claims the benefit of U.S. Provisional Application Ser. No.
60/775,997 filed Feb. 24, 2006, the disclosures of which are fully
incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The invention relates generally to the architecture for a
snowmobile suspension system.
BACKGROUND AND SUMMARY
[0003] Most snowmobiles include a chassis, an engine, a
transmission, and endless belt assembly designed to contact the
ground and propel the snowmobile. Typical snowmobiles also include
a pair of front skis support by a front suspension system. The
endless belt assembly generally includes a rear suspension system
designed to help the belt assembly maintain contact with the ground
when riding over uneven terrain and provide the rider with a
comfortable ride.
[0004] Generally, there are two types of snowmobile rear
suspensions in the snowmobile industry: coupled and uncoupled. The
term "coupled" is generally given to suspensions that have
dependant kinematics front-to-rear and/or rear-to-front relative to
the lower rails of the rear suspension. A suspension is coupled
rear-to-front when the front portion of the lower rails is
deflected vertically and the rear portion of the lower rails is
forced to move vertically to some degree. A suspension is coupled
rear-to-front when the rear portion of the lower rails is deflected
vertically and the front portion of the lower rails is forced to
move vertically to some degree. An uncoupled rear suspension is
generally independent front-to-rear and rear-to-front relative to
the lower rails of the rear suspension. A vertical deflection of
the front portion of the suspension causes little to no vertical
deflection of the rear portion of the suspension and vice
versa.
[0005] Coupled suspensions differ from uncoupled suspension in at
least two areas. There is a distinct stiffness or rate of
deflection of the rear suspension per pound of force applied to the
rear suspension for both the front and rear portion of the rear
suspension. A coupled suspension combines the rates of both the
front and rear portions of the rear suspension so the overall rate
becomes higher than rate that may be achieved with an uncoupled
rear suspension. Second, a coupled rear suspension may be used to
control weight transfer to the rear suspension during acceleration
of the snowmobile.
[0006] One embodiment of the present invention includes a
snowmobile comprising a chassis, a motor supported by the chassis,
and an endless belt assembly including a belt and a coupled
suspension, the coupled suspension including a lower rail, a front
and rear control arm, a first and second bump stop, and a coupling
member positioned between the first and second bump stops, the
front control arm adapted to operably connect the lower rail to the
chassis, the rear control arm adapted to operably connect the
coupling member to the chassis, the first bump stop supported by
the lower rail at a first position, the second bump stop supported
by the lower rail at a second position, the coupling member
pivotally supported to the lower rail, the coupling member being
moveable between the first bump stop and the second bump stop, the
coupling member configured to exert a horizontal and vertical force
on the second bump stop, the vertical force being greater than the
horizontal force.
[0007] Another embodiment of the present invention includes a
snowmobile having a coupled suspension, the snowmobile comprising a
chassis having a front and rear end, a lower rail, a front control
arm positioned adjacent to the chassis front end, the front control
arm pivotally interconnecting the chassis and the lower rail, a
rear inverted control link interconnected to the lower rail, a rear
control arm positioned adjacent to the chassis rear end and
pivotally interconnected to the chassis and the rear inverted
control link, the rear control arm interconnected to the rear
inverted control link at a position below the interconnection
between the rear inverted control arm and the lower rail, and a
coupling member providing a controlled degree of freedom of
movement between the coupling member and the rear control arm,
until coupling between the rear control arm and the lower rail
occurs.
[0008] Another embodiment of the present invention includes a
snowmobile comprising a chassis having a front and rear end, a
lower rail, a front control arm defining a first length extending
between first and second spaced-apart ends, the front control arm
positioned adjacent to the chassis front end, the front control arm
pivotally coupled to the chassis on the first end and pivotally
coupled to the lower rail on the second end, a rear control arm
positioned adjacent to the chassis rear end and pivotally
interconnected to the chassis and lower rail, a linkage assembly
supported by the front control arm at a first position between the
first and second ends of the front control arm, the first position
being spaced-apart from the second end of the front control arm by
at least a first distance, the first distance being defined by
one-quarter of the length of the front control arm, and a shock
absorber and pull rod each including first and second spaced-apart
ends, the first ends interconnected to the rear control arm, the
second ends operably coupled to the linkage assembly.
[0009] Another embodiment of the present invention includes a
snowmobile comprising a chassis having a front and rear end, a
lower rail having front and rear ends, and an endless belt assembly
including a belt, a front control arm, a rear control arm, a
coupling member, and a belt tensioning system, the front control
arm positioned adjacent to the chassis front end and adapted to
pivotally interconnect the chassis and the lower rail, the rear
control arm positioned adjacent to the chassis rear end and adapted
to pivotally interconnect the chassis and one of the coupling
member and the lower rail, the coupling member providing a
controlled degree of freedom of movement between the coupling
member and the rear control arm, the belt tensioning system
configured to maintain an appropriate belt tension during movement
between the chassis and lower rail.
[0010] In yet another embodiment, a snowmobile having a coupled
suspension comprises a chassis, at least one lower rail, at least
one front control arm pivotally coupled to the chassis at a first
end and pivotally coupled to the lower rail on a second end, a rear
control arm positioned adjacent to the chassis rear end and
pivotally interconnected to the chassis and lower rail, a front
linkage assembly supported by the front control arm, a rear linkage
assembly supported by the rear control arm; a tension rod extending
between the front and rear linkage, an LFE operatively connected
between the front linkage assembly and the rear linkage assembly,
and extending along a longitudinal line of action (LOA), where the
LFE front pivot point and a front pivot point of the tension rod
being substantially along the LOA, and being spaced apart from each
other.
[0011] The above mentioned and other features of this invention,
and the manner of attaining them, will become more apparent and the
invention itself will be better understood by reference to the
following description of embodiments of the invention taken in
conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is a profile view of one embodiment of a
snowmobile;
[0013] FIG. 2 is a profile view of the endless belt assembly of the
snowmobile shown in FIG. 1;
[0014] FIG. 3 is a top view of the coupled rear suspension system
of the endless belt assembly shown in FIG. 2;
[0015] FIG. 4 is an elevated, perspective view of the coupled rear
suspension system shown in FIG. 3;
[0016] FIG. 5 is a cross-sectional view of the coupled rear
suspension system shown in FIG. 4;
[0017] FIG. 6 is a partial, exploded view of the front portion of
the coupled rear suspension system shown in FIGS. 3-5;
[0018] FIG. 7 is a perspective view of the rear portion of the
coupled rear suspension system shown in FIGS. 3-6;
[0019] FIG. 8 is a perspective view of components of the rear
portion of the coupled rear suspension system shown in FIG. 7;
[0020] FIG. 9 is a partial, exploded view of the rear portion of
the coupled rear suspension system shown in FIGS. 3-8;
[0021] FIG. 10 is a profile view of the rear portion of the coupled
rear suspension system shown in FIG. 9, the rear suspension is
shown in a first position in solid lines and a second position
shown in phantom;
[0022] FIG. 11 is a profile view of another embodiment of a
snowmobile having a coupled rear suspension;
[0023] FIG. 12 is a profile view of the endless belt assembly of
the snowmobile shown in FIG. 11;
[0024] FIG. 13 is a top view of the coupled rear suspension system
of the endless belt assembly shown in FIG. 12;
[0025] FIG. 14 is an elevated, perspective view of the coupled rear
suspension system shown in FIG. 13;
[0026] FIG. 15 is a cross-sectional view of the of coupled rear
suspension system shown in FIG. 14;
[0027] FIG. 16 is a partial, exploded view of the front portion of
the coupled rear suspension system shown in FIGS. 13-15;
[0028] FIG. 17 is a perspective view of the rear portion of the
coupled rear suspension system shown in FIGS. 13-16;
[0029] FIG. 18 is a perspective view of components of the rear
portion of the coupled rear suspension system shown in FIG. 17;
[0030] FIG. 19 is a partial exploded view of the rear portion of
the coupled rear suspension system shown in FIGS. 13-18;
[0031] FIG. 20 is a profile view of the rear portion of the coupled
rear suspension system shown in FIG. 19, the rear suspension is
shown in a first position in solid lines and a second position
shown in phantom;
[0032] FIG. 21 is a partial, perspective view of the belt
tensioning assembly of the coupled rear suspension system shown in
FIGS. 11-20;
[0033] FIG. 22 is a partial, exploded view of the belt tensioning
assembly shown in FIG. 21;
[0034] FIG. 23 is a cross-sectional view of the belt tensioning
assembly shown in FIGS. 21 and 22;
[0035] FIG. 24 shows an alternative front shock mount assembly;
[0036] FIG. 25 is an enlarged view of the mount shown in FIG.
24;
[0037] FIG. 26 is an exploded view of the shock mount assembly of
FIG. 24;
[0038] FIG. 27 is a side view of the shock mount assembly of FIG.
25 at full rebound;
[0039] FIG. 28 is a side view similar to that of FIG. 27 at full
jounce;
[0040] FIG. 29 shows the front load case curve for three
comparative suspensions; and
[0041] FIG. 30 shows the rear load case curve for three comparative
suspensions.
[0042] Corresponding reference characters indicate corresponding
parts throughout the several views. Although the drawings represent
embodiments of the present invention, the drawings are not
necessarily to scale and certain features may be exaggerated in
order to better illustrate and explain the present invention.
DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION
[0043] The embodiments disclosed below are not intended to be
exhaustive or to limit the invention to the precise forms disclosed
in the following detailed description. Rather, the embodiments are
chosen and described so that others skilled in the art may utilize
their teachings. For example, while the following description
refers primarily to a rear suspension system for a snowmobile, it
should be understood that the principles of the invention apply
equally to other suspension systems. While the present invention
primarily involves a snowmobile, it should be understood, however,
that the invention may have application to other types of vehicles
such as all-terrain vehicles, motorcycles, watercraft, utility
vehicles, scooters, and mopeds.
[0044] Referring to FIG. 1, one embodiment of a snowmobile 10 is
shown. Snowmobile 10 includes a chassis 12, an endless belt
assembly 14, and a pair of front skis 20. Snowmobile 10 also
includes a front-end 16 and a rear-end 18.\
[0045] Referring now to FIGS. 2-4, endless belt assembly 14
includes a coupled rear suspension system 22 and a belt 24. Belt 24
extends around powered roller 25 and idler rollers 26 which are
mounted at various locations on suspension system 22. Roller 25 is
powered by an engine (not shown) and transmission (not shown) of
snowmobile 10. In operation roller 25 rotates about its central
axis to move belt 24 around endless belt assembly 14 to propel
snowmobile 10. Coupled rear suspension system 22 includes a pair of
spaced-apart lower rails 28, a pair of front control arms 30, a
pair of rear control arms 32, a coupling member 34, and a belt
tensioning assembly 36. Front control arms 30 are coupled together
on an upper end by cross shaft 42. Cross shaft 42 couples to
chassis 12 of snowmobile 10. Similarly, rear control arms 32 are
coupled together by cross shaft 44 which is coupled to chassis 12
of snowmobile 10. Together, chassis 12, front control arms 30, rear
control arms 32, and lower rails 28 form a four-bar linkage. Front
control arms 30 are pivotally coupled to lower rails 28 at pivot
points 43. Rear links 32 are coupled on their lower end to cross
shaft 35 (FIG. 4). Cross shaft 35 is pivotally coupled to coupling
member 34 by fastener 39. Coupling member 34 is pivotally coupled
to lower rails 28 by fastener 79 (FIG. 2). Coupling member 34 is
described in more detail below.
[0046] Coupled suspension system 22 also includes a shock absorber
38 and pull rods 40 which are coupled between front control arms 30
and cross shaft 44. The upper end of shock absorber 38 and pull
rods 40 is coupled to a pair of plates 46 which are coupled to
cross shafts 44 and 45. Plates 46 are rigidly coupled to cross
shafts 44 and 45 to interconnect shock absorber 38 and pulls rods
40 with rear control arms 32. The lower ends of shock absorber 38
and pull rods 40 are coupled to a linkage assembly 47 including
link 48. Pull rods 40 accelerate the stroke of shock absorber 38
when coupled suspension system 22 is compressed. Link 42 behaves as
a bell crank.
[0047] Referring now to FIGS. 5 and 6, coupling link 48 is
pivotally coupled on an upper end to bracket 50 which is mounted on
cross shaft 52. Cross shaft 52 extends between front control arms
30 to provide strength and maintain front control arms 30 in a
parallel relationship. Link 48 is pivotally coupled to bracket 50
at upper end 54 of link 48. Shock absorber 38 is coupled to link 48
at lower end 56 of link 48. Pull rods 40 are coupled to link 48 at
pivot point 58, which is positioned between upper end 54 and lower
end 56 of link 48. Shock absorber 38 and pull rods 40 are
operatively coupled to front links 30 by link 48 and bracket 50. In
this embodiment, bracket 50 is positioned about two-thirds of the
length of front links 30 away from lower pivot point 43. In other
embodiments, bracket 50 may be coupled to front links 30 at any
position between lower pivot point 43 and cross shaft 42. However,
in the preferred embodiment, bracket 50 is preferably coupled to
front links 30 at a position spaced-apart from lower pivot points
43 by at least one-quarter of the length of front links 30.
[0048] Referring now to FIGS. 5-10, coupling member 34 is
described. Rear control arms 32 are coupled together on their lower
end by cross shaft 35. Cross shaft 35 is pivotally coupled between
vertical plates 61 of coupling member 34 by bushing 37 and fastener
39. Vertical plates 61 of coupling member 34 are rigidly coupled
together by cross shafts 66 and 68. In this embodiment, vertical
plates 61 are substantially triangularly shaped, however any
suitable shape may be used. Bushing 78 and fastener 79 extend
through cross shaft 68 and apertures in lower rails 28 to pivotally
couple coupling member 34 between lower rails 28. Vertical plates
61 of coupling member 34 each include a back plate 62 and a lower
plate 64.
[0049] Suspension system 22 also includes a pair of bump stops 72
positioned on cross shaft 70 (FIG. 7) which is coupled between
lower rails 28. Cross shaft 70 is coupled to lower rails 28 by
fasteners 71. A second pair of bump stops 76 (FIG. 10) is
positioned on cross shaft 74. Cross shaft 74 is coupled between
lower rails 28 by fasteners 77 (FIG. 9). In this embodiment, second
pair of bump stops 76 is positioned substantially below first pair
of bump stops 72, as will be described further herein.
[0050] As shown in FIG. 10, coupling member 34 rotates about an
axis defined by fastener 79. The range of motion or degrees of
freedom of movement of coupling member 34 is limited by bump stops
72 and 76. When endless belt assembly encounters a bump or sudden
change in elevation, coupling member 34 rotates about fastener 79
and moves from a first position (shown in solid lines) in which
lower plates 64 abut bump stops 76 to a second position (shown in
phantom) in which back plates 62 abut bump stops 72. When coupling
member 34 is in the first position, lower plates 64 exert both a
horizontal and vertical force on bump stops 76, however the
vertical force is greater than the horizontal force. It should be
understood that lower plates 64 may be constructed to any suitable
length, however lengthening lower plates 64 and moving bump stops
76 away from the axis defined by fastener 79 effectively lengthens
a moment arm defined by lower plates 64 and reduces the contact
force between lower plates 64 and bump stops 76.
[0051] During movement of coupling member 34 from the first
position to the second position, the angle between rear control
arms 32 and lower rails 28 decreases and the effective length of
lower rails 28 is lengthened relative to the four-bar orientation
of chassis 12, lower rails 28, front control arms 30, and rear
control arms 32. The effect of lengthening the lower rails 28
during a sudden change in elevation or jounce stiffens suspension
system 22 and helps endless belt assembly 14 maintain contact with
the ground during jounce and weight transfer caused by
acceleration.
[0052] Referring back to FIGS. 8 and 9, belt tensioning assembly 36
includes a pair of extendable links 84 including first ends 86 and
second ends 88. Links 84 may be extended or retracted to adjust the
tension of belt 24. First ends 86 are pivotally coupled to coupling
member 34. Coupling member 34 includes a cross shaft 66 coupled
between vertical plates 61. Bushing 80 extends through cross shaft
66 and apertures 82 in lower rails 28. In this embodiment,
apertures 82 are profiled as slightly elongated slots, however any
suitably shaped aperture may be used. First ends 86 of links 84 are
coupled to the ends of bushing 88 by fasteners 87.
[0053] Referring now to FIG. 3, the second ends 88 of links 84 are
coupled to cross shaft 91. Cross shaft 91 extends through apertures
90 in lower rails 28 and supports idler rollers 26 (FIG. 4). Idler
rollers 26 support belt 24 and rotate about cross shaft 91. Links
84 translate the movement of coupling member 34 to cross shaft 91
to adjust the tension of belt 24 during movement of suspension
system 22. As coupling member 34 moves between the first and second
positions, as discussed above, links 84 move cross shaft 91 and
idler rollers 26 frontward or rearward to maintain the appropriate
tension of belt 24.
[0054] Referring now to FIG. 11, another embodiment of a snowmobile
110 is shown. Snowmobile 110 includes a chassis 112, an endless
belt assembly 114, and a pair of front skis 120. Snowmobile 110
also includes a front-end 116 and a rear-end 118. Snowmobile 110 is
similar to snowmobile 10 shown in FIG. 1 with the exception of
endless belt assembly 114, which is explained below.
[0055] Referring now to FIGS. 12-14, endless belt assembly 114
includes a coupled rear suspension system 122 and a belt 124. Belt
124 extends around powered roller 125 and idler rollers 126 which
are mounted at various locations on suspension system 122. Similar
to roller 25, discussed above, roller 125 is powered by an engine
(not shown) and transmission (not shown) of snowmobile 110. In
operation roller 125 rotates about its central axis to move belt
124 around endless belt assembly 114 to propel snowmobile 110.
[0056] Suspension system 122 includes a pair of spaced part lower
rails 128, a pair of front control arms 130, a pair of rear control
arms 132, a coupling member 134, and a belt tensioning assembly
136. In this embodiment, front control arms 130 include upper and
lower portions 129 and 131, respectively. Each upper portion 129 is
interconnected with each lower portion 131 by cross shaft 152 (FIG.
14). Each front control arm 130 also includes a bracing member 133
extending between upper portion 129 and lower portion 131 to
provide added strength. Front control arms 130 are coupled together
on an upper end by cross shaft 142. Cross shaft 142 couples to
chassis 112 of snowmobile 110. Similarly rear control arms 132 are
coupled together by cross shaft 144 which is coupled to chassis 112
of snowmobile 110. Rear control arms 132 include bracing members
127 which couple to rear control arms 132 on a lower end and couple
to cross shaft 144 on an upper end. When suspension system 122 is
in the coupled state, chassis 112, front control arms 130, rear
control arms 132, and lower rails 128 form a four-bar linkage.
Front control arms 130 are pivotally coupled to lower rails 128 at
lower pivot points 143. Rear control arms 132 are coupled to cross
shaft 135 (FIG. 15). Cross shaft 135 is coupled to inverted links
160 by bushing 178 and fastener 180. Coupling member 134 is
pivotally coupled to lower rails 128 by bushing 174 and fastener
176 which extend through cross shaft 168. Coupling member 134 is
described in more detail below.
[0057] Referring now to FIGS. 15 and 16, coupled rear suspension
system 122 also includes a shock absorber 138 and pull rods 140
which are coupled between front control arms 130 and cross shaft
144. The upper end of shock absorber 138 and pull rods 140 is
coupled to a pair of plates 146 which are coupled to cross shaft
144. Plates 146 are rigidly coupled to cross shaft 144 to
interconnect shock absorber 138 and pulls rods 140 with rear
control arms 132. The lower ends of shock absorber 138 and pull
rods 140 are coupled to linkage 147 which includes link 150. Pull
rods 140 increase the rate of compression of shock absorber 138
when coupled rear suspension system 122 is compressed. Pull rods
140 and shock absorber 138 function in the same manner discussed
above in the first embodiment, however, in this embodiment the
lower ends of pull rods 140 and the lower end of shock absorber 138
are mounted coaxially on link 150.
[0058] Link 150 is pivotally coupled on an upper end to cross shaft
152. Cross shaft 152 is coupled to front control arms 130. Bushing
157 extends through cross shaft 152 and link 150 and receives
fasteners 159 to pivotally couple link 150 to front control arms
132. Cross shaft 152 also provides strength and maintains front
control arms 130 in a parallel relationship. In this embodiment,
link 150 is spaced-apart from lower pivot points 143 by a distance
equal to about one-half of the distance between cross shaft 144 and
lower pivot points 143. In other embodiments, link 150 may be
coupled to front links 130 at any position between lower pivot
points 143 and cross shaft 142. However, in the preferred
embodiment, link 150 is preferably coupled to front links 130 at a
position at least one-quarter of the distance between cross shaft
142 and lower pivot points 143 above lower pivot points 143.
[0059] Referring now to FIGS. 15 and 17-20, coupling member 134 is
described. Rear control arms 132 are coupled together on their
lower end by cross shaft 135. Cross shaft 135 is pivotally coupled
between inverted links 160 of coupling member 134 by bushing 178
and fastener 180. Coupling plates 161 of coupling member 134 are
coupled together by cross shaft 168 and fasteners 177. In this
embodiment coupling plates 161 have a semi-circular top profile,
however any suitable shape may be used. Coupling plates 161 each
include a slot 171 positioned coaxial to one another. Stops 162 and
164 are positioned between coupling plates 161 and are secured by
fasteners 177. As discussed above, bushing 174 and fastener 176
extend through cross shaft 168 and apertures in lower rails 128 to
pivotally couple coupling member 134 between lower rails 128. Stops
162 and 164 may be constructed of metal, rubber, plastic, or any
suitable substance.
[0060] As discussed above, the lower end of rear control arms 132
is couple to cross shaft 135. Fastener 180 extends though apertures
in the lower end of inverted links 160 and bushing 178, which is
positioned in cross shaft 135, to operably couple rear control arms
132 to coupling member 134. Cross shaft 166 is coupled between rear
control arms 132 and extends through slots 171 in inverted links
160 in coupling member 134.
[0061] As shown in FIG. 20, rear control arms 132 rotate about an
axis defined by fastener 180. In this embodiment, the position of
the pivot point of rear control arms 132, the axis defined by
fastener 180, is located below the location of the coupling point,
cross shaft 166, of rear control arms 132. The range of motion or
degrees of freedom of movement of rear control arms 132 is limited
by stops 162 and 164 and/or slots 171 of coupling member 134. When
endless belt assembly 114 encounters a bump or sudden change in
elevation, rear control arms 132 rotate about an axis defined by
fastener 180 and moves from a first position (shown in solid lines)
in which cross shaft 166 abuts stop 162 to a second position (shown
in phantom) in which cross shaft 166 abuts stop 164. During this
movement, rear suspension 122 is in an "uncoupled" state.
[0062] When cross shaft 166 abuts stop 162 and rear control arms
132 continue to move toward lower rails 128, coupling member 134 is
forced to rotate downward about an axis defined by fastener 176.
When this occurs, suspension 122 returns to a "coupled" state.
Similarly, when cross shaft 166 abuts stop 166 and rear control
arms 132 continues to move away from lower rails 128, coupling
member 134 is forced to rotate upward about an axis defined by
faster 176. When this occurs, suspension system 122 once again
returns to a "coupled" state. The inverted pivot orientation of
coupling member 134 and rear control arms 132 decreases and the
effective length of rear control arms 132 relative to the four-bar
orientation of chassis 112, lower rails 128, front control arms
130, and rear control arms 132. The effect of shortening rear
control arms 130 during a sudden change in elevation or jounce
stiffens suspension system 122 and helps endless belt assembly 114
maintain contact with the ground during jounce and/or weight
transfer caused by acceleration. In other embodiments (not shown),
coupling member 134 may include multiple bump stops or may be
constructed to form a slotted link to limit the degree of freedom
between coupling member 134 and rear control arms 132.
[0063] Referring now to FIGS. 18-23, belt tensioning assembly 136
is shown. Belt tensioning assembly 136 is similar to belt
tensioning assembly 36 described above and shown in FIGS. 1-10.
Belt tensioning assembly 136 includes a pair of extendable links
184 including first ends 186 and second ends 188. Links 184 may be
extended or refracted to adjust the tension of belt 124. First ends
186 are pivotally coupled to inverted links 160 of coupling member
134 by cross shaft 170. Cross shaft 170 extends through slots 172
in lower rails 128, apertures in inverted links 160, and first ends
186 of links 184. Fasteners 173 are received in cross shaft 170 to
secure it in slots 172. In this embodiment, slots 172 are elongated
semi-circular slots, however any suitably shaped aperture may be
used.
[0064] Second ends 188 of links 184 are supported by cross shafts
191. Cross shaft 191 extends into bushings 198. Bushings 198
interact with apertures 190 in lower rails 28 and slide blocks 194.
Slide blocks 194 are coupled to lower rails 128 and are positioned
in apertures 190. Spacers 200 and bushings 202 are positioned
between slide blocks 194 and idler rollers 126. Bushing 196 extends
through idler wheels 126, bushings 202, spacers 200, slide blocks
194, bushings 198, crossbar 191, and second ends 188 of links 184.
Fasteners 204 are received by bushing 196 to secure the assembly.
Idler rollers 126 support belt 124 and rotate about bushing 196.
Links 184 translate the movement of coupling member 134 to bushing
196 to adjust the tension of belt 124 during movement of suspension
system 122. As coupling member 134 moves between the first and
second positions, as discussed above, links 184 move bushing 196
and idler rollers 126 fore and aft along a longitudinal axis
defined by lower rails 128 to maintain the appropriate tension of
belt 124.
[0065] Referring now to FIGS. 24-26, a snowmobile suspension is
described with a coupling member 234 similar in nature to coupling
member 134 (FIG. 14), yet with a different mounting system at the
front end of shock absorber 238. This system generally includes
shock absorber or LFE 238 and pull rods 240 which are coupled
between front control arms 230 and cross shaft 244 (FIG. 26). The
upper end of shock absorber 238 and pull rods 240 are coupled to a
pair of plates 246 which are coupled to cross shaft 244. Plates 246
are rigidly coupled to cross shaft 244 to interconnect shock
absorber 238 and pulls rods 240 with rear links 227. As best shown
in FIG. 25, the lower end of shock absorber 238 and pull rods 240
are coupled to linkage 247 which, includes links 250. Linkage 247
in turn is pivotally attached to cross shaft 252 by way of pivot
bracket 300. Pull rods 240 increase the rate of compression of
shock absorber 238 when coupled rear suspension system is
compressed. Pull rods 240 and shock absorber 238 function in the
same manner discussed above in the first embodiment, however, in
this embodiment the lower ends of pull rods 240 and the lower end
of shock absorber 238 are mounted in line.
[0066] With respect to FIG. 26, link 250 is pivotally coupled on an
upper end to bracket 300. Cross shaft 252 is coupled to front
control arms 230. Bushing 257 extends through link 250 and receives
a fastener 259 to pivotally couple link 250 to front control arms
230. Cross shaft 252 also provides strength and maintains front
control arms 230 in a parallel relationship. In this embodiment,
lower end of shock absorber 238 is attached to link 250 by way of a
C-shaped link 320. Lower end of shock absorber 238 includes a
mounting arm 322 having mounting apertures. C-shaped link includes
spaced apart C-shaped plates 324, where fasteners 326 may be
received therethrough for fastening the C-shaped link to the
mounting arm 322. Link 320 has an opening 330 with a pivot opening
332 opposite thereto.
[0067] Link 250 is somewhat triangular, and acts as a bell-crank,
having a pivot stub shaft 336 at one corner and apertures 338 at
another. Opening 330 can "wrap around" stub shaft 336, intermediate
links 250 (see FIGS. 2-5) with opening 332 aligned with opening
338. Thus a fastener 340 can be received through opening 338;
through sleeve 342 and opening 332, and through the opposite side
of the link 250.
[0068] With the above described geometry, a progressive rate
suspension is achieved that has the best behaviors of both the
coaxial (FIG. 16 embodiment) and an offset design (FIG. 5
embodiment). At full rebound, the system acts similar to a coaxial
design because the tension rod pivot is on or near the shock
absorber line of action (LOA), as best shown in FIG. 27. As shown,
the pivot point of the tension rod 240 (left end as viewed in FIG.
27) is approximately 0.26 inches from the LOA, and would preferably
be within 0.75 inches, and more preferably within 0.50 inches. At
full jounce, the bell crank, formed by plates 246, rotates so that
the tension rod pivot is above the pivot of the shock absorber, as
best shown in FIG. 28.
[0069] As also shown in the attached curves of FIGS. 29, 30, one
can see that the suspension of FIGS. 24-26 is optimized. The
front/rear bias is improved by lowering the front rate, but yet the
front rate is maintained with the same basic shape. With respect to
the rear loadcase, a progressive rate is created.
[0070] While this invention has been described as having an
exemplary design, the present invention may be further modified
within the spirit and scope of this disclosure. This application is
therefore intended to cover any variations, uses, or adaptations of
the invention using its general principles. Further, this
application is intended to cover such departures from the present
disclosure as come within known or customary practice in the art to
which this invention pertains.
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