CA1332623C - Snowmobile ski suspension - Google Patents
Snowmobile ski suspensionInfo
- Publication number
- CA1332623C CA1332623C CA000612079A CA612079A CA1332623C CA 1332623 C CA1332623 C CA 1332623C CA 000612079 A CA000612079 A CA 000612079A CA 612079 A CA612079 A CA 612079A CA 1332623 C CA1332623 C CA 1332623C
- Authority
- CA
- Canada
- Prior art keywords
- ski
- leg
- snowmobile
- bearing
- ski leg
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
- B62B—HAND-PROPELLED VEHICLES, e.g. HAND CARTS OR PERAMBULATORS; SLEDGES
- B62B17/00—Accessories or details of sledges
- B62B17/02—Runners
- B62B17/04—Runners resiliently suspended
Landscapes
- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Combustion & Propulsion (AREA)
- Transportation (AREA)
- Mechanical Engineering (AREA)
- Vibration Prevention Devices (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
In a snowmobile ski suspension the ski is carried upon a generally upright ski leg which is attached directly to the suspension arms by spherically curved bearings. This arrangement requires a reduced number of parts compared with prior art ski suspensions, and also offers improved reliability and service life.
In a snowmobile ski suspension the ski is carried upon a generally upright ski leg which is attached directly to the suspension arms by spherically curved bearings. This arrangement requires a reduced number of parts compared with prior art ski suspensions, and also offers improved reliability and service life.
Description
~` 133~2~
SNOWMOBILE SKI SUSPENSION
~ACKGROUND OF TH~ IN ENTION
(a) FIELD OE THE INVENTION
This inventlon relates to lmprovements in snowmobile ski suspensions.
~b) DESCRIPTION OF THE PRIOR AR~
In a commonly used snowmoblle suspenslon, the ~ki ls pivotally attached to the lower end of a skl leg that 1B arranged in a generally upright manner and rotatable withln a tubular housing to effect steering movement of the skl, the skl leg typlcally pro~ecting above the upper end of the houslng and havlng a spllned end to whlch ls connected a radlally pro~ectlng arm that ls coupled to the steerlng llnkage. Tubular bushings would be provided between the tubular houslng and the ski leg to allow the steering movement, and the tubular houslng would be connected to the snowmobile frame through suspension arms attached to the tubular houslng by bushings or ball ~oints to per~it rotation between the houslng and the suspension arms to permlt the deslred vertical travel of the ski.
The prior art configuration discussed in the foregoing requires a relatively large number of bu~hings and/or ball ~oints to accommodate the required movement. This involves substantial -~
cost since each bushing requlres to have an exact fit so that lt will function properly, and this in turn lnvolves precision machinlng of the components. The complexlty of the suspension arrangement also involves a slgniflcan~ cost ln terms of maintenance. Furthermore slnce wlth such arrangement lt is not possible to arrange all of the bushlngs on the tubular housing of 133262~ -66283-g50 the skl leg on the same axls, the resultlng load path ls non-llnear. ~he non-llnear load results in a bending moment belng transmltted to the su~penslon arms through the bushlngs whlch accordlngly have to support not ~ust purely radlal loads but also bendlng loads, a condltlon referred $o as "edge loading" whlch signlflcantly lncreases the wear experlenced in such plaln bearlngs and glves rlse to the development of play ln the bearlngs.
As explalned, steerlng of the skl ls effected from the steerlng llnkage through a steerlng arm attached to the spllned upper end of the skl leg, thls arrangement belng complex and costly ln the manufacture. Furthermore, the strength of the skl leg must be high slnce it must transmlt the steerlng torque applied from the steerlng llnkage to the skl.
SUMMARY OF TH~ INVENTION
The present lnventlon provldes a snowmoblle comprlslng a frame havlng a forward portlon that is supported on a palr of laterally spaced steerable skls through a suspenslon system, each sald skl belng carrled at the lower end of a generally uprlght skl leg, sald suspenslon system lncludlng for each skl~ suspenslon arm means plvotally connected at one end to sald frame and at the other end to sald skl leg to permlt generally vertlcally dlrected deflectlon of said skl leg and skl ln response to the forces that act thereon ln use, sald 3kl leg belng mounted to be angularly rotatable about the longltudlnal axls thereof wlth respect to sald suspenslon arm means to accommodate steerlng movement of sald skl, steerlng llnkage means belng coupled to effect control of such .
332~23 -~
steerlng movement, sald skl leg havlng at axlally spaced locatlons thereon two spherlcally curved bearlng surfaces the center of curvature of each of whlch lles on sald axls, each sald bearlng surface belng ln slldlng engagement wlth a respectlve bearlng element that ls carrled by sald suspenslon arm means.
Preferably the two spherlcally curved bearlng surfaces are lntegral wlth the skl leg, each belng ln slldlng contect wlth a bearing element ln the form of a bearing shell of low frlctlon ~;~
materlal such as nylon or Teflon (Trademark) that ls carrled ln the outboard end of a suspenslon arm. - -Preferably the skl ls plvotally attached on a horlzontal axls transverse to lts length on a block connected at the lower end of the skl leg, the steerlng llnkage belng coupled to an arm pro~ectlng from thls block, 80 that the steerlng forces are not transmltted through the skl leg. Convenlently the block may be provlded wlth a cyllndrlcal socket ln whlch the lower end of the skl leg ls recelved, the socket havlng a radlally extendlng slot openlng from one slde to the outer surface of the block, and fastener means belng provlded to act between the opposlte sldes of the slot to produce a clamplng ef~ect between the socket and the skl leg. The fasteners are arranged to be posltloned ln transverse grooves ln the skl leg so that even lf the fasteners become loosened, the block wlll stlll remaln flxed to the skl leg and cannot become separated.
In thls arrangement, wlth the centre of curvature of the spherlcal bearlng surfaces lylng on the axls of the skl leg, the latter does not generate any bendlng moments ln lts connectlon to the suspenslon arms. By vlrtue of the spherlcally curved bearlng ~ 332~2~
surfaces, rotation of the skl leg shaft for steerlng purposes and rotation of the suspension arms relative to the ski leg for suspension travel purposes are combined lnto the same bearlngs.
Thus ln place of the slx cyllndrlcal bushings reguired ln the above discussed prlor art arrangement, the suspenslon arrangement enclosed herewith requlres only two spherlcal bearlngs, and thus offers a considerable cost advantage. Furthermore, these two spherlcal bearings can accommodate a signlflcant amount of mlsallgnment wh~ch could arlse as a result of manufacturlng tolerances in the suspension arms, and thus reduce the possibility oS undesirable stresses in the system belng generated upon assembly.
Slnce the steering torque is no longer transmitted through the skl leg, the stresses ln the latter are lower, and furthermore the upper end of the ski leg does not requlre to have a spllned configuratlon, whlch therefore reduces fabrication cost and complexity.
A further advantage of the spherlcal bearlng arrangement ls that by vlrtue of the spherlcal conflguration the contact loads are unlformly distributed so that the "edge loadlng" condltlon commonly found in tubular bushlngs ls ellmlnated. Also due to their slze, lt ls posslble to lncrease the contact surface area of the spherlcal bearings slgniflcantly ln comparison to the previously used tubular bushlngs so that the surface pressure ls slgnlflcantly reduced whlch ln turn dramatlcally reduces wear and the development of play during the service llfe of the vehlcle. t~#
BRIEF DESCRIPTION OF THE DRAWINGS
The lnventlon wlll further be described, by way of ,~.; .. , ,, . . . -,,,;' ~ '- . ' ' . : -:
133~3 example only, wlth reference to the accompanying drawings wherein:
Figure 1 is a somewhat schematic side view of a snowmobile;
Figure 2 is a front elevation showlng element~ of the ~kl suspension arrangement of the snowmoblle o Flgure 1, drawn to a larger scale;
Pigure 3 is a front elevatlon of one slde of the skl suspension shown partly sectloned and to an enlarged scale;
Plgure 4 ls a fragmentary perspective vlew from above and to the right of the view shown in Flgure 3;
Flgure 5 is a section view taken on the line V-V in Flgure 3 and drawn to a larger scale;
Flgure 6 ls an exploded view showlng the components of the suspension assembly; and Figure 7 ls an exploded vlew showlng for comparison purpo6es the components of a prlor art ski assembly.
DESCRIPTION OF THE PREFERRSD ~MBODIHENTS
As seen in Figure 1, a snowmoblle 10 has a frame 11 the rear end of whlch lc supported on a driven endlesq track 12 and the front end of which i~ supported upon a pair of spaced skis 13, the skl~ being steerable under control of the operator by nean~ of handlebars 14 and a steering linXage 15.
As seen in Plgure 2, the skis 13 are supported in a suspension system 16 which for each ski includes an upper 2 suspen310n arm 17 and a lower suspension arm 18. -~
The lower suspenslon arm 18 as is best seen in Pigure 4 is of wishbone shape having horizontally spaced tubular limbs 18a the inboard ends of which are plvoted coaxially on a pivotal S
- ~ 1332~3 mounting 19 in the frame 11, by means of rubber filled bushlngs (not shown). The angular movement is provided by deforma~ion of the rubber inRtead of a traditional sliding contact. This reduces the development of play during ~he service llfe and damp~ the structural vibrations and noise whlch reduces road harshness and thus improves comfort. The outboard ends of the llmbs 18a are ~olned to a bearlng assembly 20 connected to the skl leg ~tructure 21.
Each upper suspenslon arm 1~ of trlangular conflguratlon havlng a pair of horlzon~ally spaced tubular member~ 17a the inboard ends are coaxlally supported on a pivotal mountlng 22 on the frame 11. A third tubular member 17b extends upwardly between the members 17a, and is connected thereto by means of a gusset plate 17c near the lnboard ends of the tubes 17a and 17b and arranged generally radially thereof, and further gusset plates 17d of trlangular shape arranged transversely to the tubular members 17a and 17b and supportlng between them an apertured mounting plate 17e. The varlous components of the su~penslon arms are connected together by any 6uitable manner, e.g. as by welding. At the outboard end of the upper suspension arm 17, the tubular members 17a and 17b converge and are connected to a bearing a~sembly 23 which receive~ the upper end of the ski leg ~tructure 21.
The inboard end of the upper tubular member 17b of the suspenslon arm 17 forms a pivotal connection 24 to one end of a hydraullc damper and shock absorber assembly 25 angularly arranged ln a generally transverse plane and having an lnner end pivotally attached to a mounting 26 in the snowmoblle frame by ~ean6 of the .. . . .
, . . . .
133~
rubber bushings discussed earlier.
A torsion bar stabllizer 27 has a generally stralght transverse central section that is carried in bearings 23 on the snowmobile frame 11, and at each end thereof has a generally rearwardly directed arm 29 that passes through and ls received by a rubber grommet fixed in the hole 30 in the mountlng plate 17e that is carrled ln the upper suspenslon arm 17.
From a consideratlon of Figure 3 it will be evldent that as the ski 13 is moved upwardly relative to the snowmobile frame, whether as a result of loading lmposed on the vehicle or in response to dynamic conditions encountered by the ~kl in operation, the movement is accommodated by swinging of the upper and lower suspension arms about their pivotal mountings 22 and 19 respectively on the snowmobile frame. The arms 17 and 18 form an approxlmately parallelogram llnkage so that as the skl moves vertically, it maintains an essentially upright orlentatlon, as lllustrated ln broken lines ln Flgure 3. It wlll be noted that as the upper suspenslon arms swings about the plvotal mounting 22, ~ -the plvotal connection 2g will apply a compresslve loading to the hydraulic damper and shock absorber assembly 25 which will accordingly resist upwards deflection of the ski.
The upper and lower suspension arm arrangements provide independent suspension for each of the skis 13 so that they can respond lndlvidually to the dynamlc condltlons encountered.
Furthermore, this arrangement also permlts posltlonlng of the plvot polnts of the suspenslon arms ln con~unctlon with the length of the said arms and skl leg so that the contact point between the ski base and the ground describes a vertical line in space durlng 3 2 ~
j the upward dlsplacement of the ski. This feature lmprove~ the ride quality and the handllng precislon of the vehicle. However lt will be appreciated that by means of the mounting plate 17e cooperating with the arm 29 of the stabllizer bar 27, when one skl ls deflected relative to the other, the stablllzer bar wlll be twisted and thereby transmit a force urglng d~flectlon of the other ~kl ln the ~ame dlrection a~ the flr~t ski.
The B~i leg structure 21 is more clearly illustrated ln Figure 5 as comprising a cylindrical steel skl leg shaft 35 having at lts upper end a first enlarged spherlcally curved bearlng surface 36 and at an lntermediate point ln lts length a slmilar enlarged spherlcally curved bearlng portlon 37.
The upper bearing assembly 23 connecting the upper suspenslon arm 17 to the skl leg structure 21 comprlses a generally cyllndrical cup 38 wèlded to the end of the arm 17 and definlng a cyllndrical seat $n which is received the cylindrical outer surface of an annular bearing shell 39 carried on the upper bearing portion 36. The bearing shell 39 has a cylindrically curved inner surface that is ln slldlng contact wlth the bearing portlon 36, and ls retained ln poæition within the cup 38 by means of a spring retainer rlng 40 seated ln a groove near the ~outh of the cup.
The lower bearing assembly 20 compri~es a cyllndrlcal houslng 41 havlng a radlal flange 42 at its lower end provldlng a seat for an annular bearlng shell 43 that has a spherlcally curved inner surface in sliding contact with the lower bearlng portlon 37 : of the s~l leg shaft 35, the bearlng shell 43 belng retalned ln po~ltlon relative to the housing 41 by a sprlng retaining ring 44 ~ ` 1332~
recelved in a groove near the upper end of the housing 41.
The bottom end of the ski leg shaft 35 is attached to a block 4S whlch in turn ls plvotally attached ~o the ski 13 by means of a bolt 46 passing through aligned bores ln a bracket 47 formed on the upper slde of the ski and in the lower end of the block 45, the axis of the bolt being tran~verse to the length o~
the ski.
The lower end of the ski leg shaft 35 is received within a cylindrical socket 50, there being a slot 51 arranged radially of an opening from the socket 50 to the front exterior surface of the block 45. The socket 50 is of a dlameter to closely receive the lower end of the shaft 35, the latter being formed with a pair of axially spaced transversely extendlng mllled grooves 52 therein. Pairs of aligned bores 53 are provided in the block 45 on opposite sides of the slot 51, and designed to receive threaded fasteners 54. Thus when the lower end of the skl leg shaft 35 is lnæerted in the socket 50 as illustrated in Figure 5, the mllled grooves 52 are aligned with the bores 53. In this position the fasteners 54 can be passed through the aligned bores and the milled grooves and tightened to narrow the slot slightly and deform the block 45 to clamp the socket 50 lnto rlgid engagement wlth the ski leg shaft 35, relative axial or angular movement being further inhiblted by the presence of the fasteners 54 passing through the grooves 52.
Aæ best seen in Figures 2 and 3, the ski leg shaft 35 is : :~
enclosed above and below the lower bearing assembly 20 by a flexible, bellows-type rubber boot 55, 56 to inhibit extraneous material from reaching the bearing parts.
~ . ~ ' . ~.,' ' ' ~ 3~262~
The steering mechanl~m 15 is coupled to the skis 13 not through the skl leg shaft~ 35, but rather through the ~X1 leg blocks 45. As ~hown ln Eigure 4~ a tie rod 60 of the steering mechanlsm has a swivel joint connectlon 61 to an upwardly pro~ecting steering arm 62 that i~ lntegrally formed with the block 45. In this way, steering forces acting between the steering linkage 15 and the skl 13 are not directed through the ski leg shaft 35.
The upper and lower bearing shells 39, 43 are preferably formed of a sultable low friction material sùch a~ nylon or Teflon and are preferably prea6sembled to the ski leg shaft 35 before the latter is attached in the suspension assembly. Thus, as shown, the diameter of the annular interior wall of each bearing shell 39, 43 ls at a maximum ~equal to the diameter of the bearing portlons 36, 37) in the midpolnt of the length thereof, and tapers spherically from there towards lts opposlte end~, i.e. in the direction of the opposite poles of the sphere. As seen ln Flgure 6, each bearing shell 39, 43 læ formed wlth an angularly spaced serles of radial slits opening from one end thereof to permit deformation of that end when the bearlng shell ls belng moved lnto position on the associated bearlng section 36, 37. However once the bearing shells 39, 43 are asæembled, and the ~kl leg assembly moùnted ln the upper and lower bearlng a6semblies 23 and 20, the bearing shells are effectively axially fixed with respect to the ski leg ~haft 35, since the surroundlng cup 38 or cylindrical houslng 41 closely surrounds the outer perlphery of the bearing shell so that the latter cannot pass over the associated cylindrically curved bearlng section of the shaft 35.
13~2~23 ~ The reduction in the number of parts and the associated :~, assembly and maintenance work can perhaps best be appreclated by a comparlson of the exploded vlews of Figure 6 ghowing one slde of a ~kl suspension ln accordance wlth the present lnvention, and Flgure 7 ~howing an exploded view of one slde of a prlor art skl suspension. The latter lncludes a ski leg 80 that ls rotatably mounted ln a tubular housing 81 by means of two bushlngs 82 and a pair of thrust washers 83, belng secured ln place by a snap ring 84 and a steerlng arm 85 attached to the spllned upper end of the ski leg. The upper and lower suspension arms 86, 87 are each attached to brackets on the tubular houslng 81 by a palr of flanged bushlngs 88 inserted ln the ends of the suspenslon arms and retalned by threaded fasteners 89.
Apart from the reduced complexity and cost of the suspenslon arrangement as shown ln Flgures 1 to 6, lt also achieves superlor performance and servlce llfe ln the reduced wear experlenced by the spherlcal bearlng parts as contrasted with the tubular bearlng shell~ of the prlor art arrangement.
SNOWMOBILE SKI SUSPENSION
~ACKGROUND OF TH~ IN ENTION
(a) FIELD OE THE INVENTION
This inventlon relates to lmprovements in snowmobile ski suspensions.
~b) DESCRIPTION OF THE PRIOR AR~
In a commonly used snowmoblle suspenslon, the ~ki ls pivotally attached to the lower end of a skl leg that 1B arranged in a generally upright manner and rotatable withln a tubular housing to effect steering movement of the skl, the skl leg typlcally pro~ecting above the upper end of the houslng and havlng a spllned end to whlch ls connected a radlally pro~ectlng arm that ls coupled to the steerlng llnkage. Tubular bushings would be provided between the tubular houslng and the ski leg to allow the steering movement, and the tubular houslng would be connected to the snowmobile frame through suspension arms attached to the tubular houslng by bushings or ball ~oints to per~it rotation between the houslng and the suspension arms to permlt the deslred vertical travel of the ski.
The prior art configuration discussed in the foregoing requires a relatively large number of bu~hings and/or ball ~oints to accommodate the required movement. This involves substantial -~
cost since each bushing requlres to have an exact fit so that lt will function properly, and this in turn lnvolves precision machinlng of the components. The complexlty of the suspension arrangement also involves a slgniflcan~ cost ln terms of maintenance. Furthermore slnce wlth such arrangement lt is not possible to arrange all of the bushlngs on the tubular housing of 133262~ -66283-g50 the skl leg on the same axls, the resultlng load path ls non-llnear. ~he non-llnear load results in a bending moment belng transmltted to the su~penslon arms through the bushlngs whlch accordlngly have to support not ~ust purely radlal loads but also bendlng loads, a condltlon referred $o as "edge loading" whlch signlflcantly lncreases the wear experlenced in such plaln bearlngs and glves rlse to the development of play ln the bearlngs.
As explalned, steerlng of the skl ls effected from the steerlng llnkage through a steerlng arm attached to the spllned upper end of the skl leg, thls arrangement belng complex and costly ln the manufacture. Furthermore, the strength of the skl leg must be high slnce it must transmlt the steerlng torque applied from the steerlng llnkage to the skl.
SUMMARY OF TH~ INVENTION
The present lnventlon provldes a snowmoblle comprlslng a frame havlng a forward portlon that is supported on a palr of laterally spaced steerable skls through a suspenslon system, each sald skl belng carrled at the lower end of a generally uprlght skl leg, sald suspenslon system lncludlng for each skl~ suspenslon arm means plvotally connected at one end to sald frame and at the other end to sald skl leg to permlt generally vertlcally dlrected deflectlon of said skl leg and skl ln response to the forces that act thereon ln use, sald 3kl leg belng mounted to be angularly rotatable about the longltudlnal axls thereof wlth respect to sald suspenslon arm means to accommodate steerlng movement of sald skl, steerlng llnkage means belng coupled to effect control of such .
332~23 -~
steerlng movement, sald skl leg havlng at axlally spaced locatlons thereon two spherlcally curved bearlng surfaces the center of curvature of each of whlch lles on sald axls, each sald bearlng surface belng ln slldlng engagement wlth a respectlve bearlng element that ls carrled by sald suspenslon arm means.
Preferably the two spherlcally curved bearlng surfaces are lntegral wlth the skl leg, each belng ln slldlng contect wlth a bearing element ln the form of a bearing shell of low frlctlon ~;~
materlal such as nylon or Teflon (Trademark) that ls carrled ln the outboard end of a suspenslon arm. - -Preferably the skl ls plvotally attached on a horlzontal axls transverse to lts length on a block connected at the lower end of the skl leg, the steerlng llnkage belng coupled to an arm pro~ectlng from thls block, 80 that the steerlng forces are not transmltted through the skl leg. Convenlently the block may be provlded wlth a cyllndrlcal socket ln whlch the lower end of the skl leg ls recelved, the socket havlng a radlally extendlng slot openlng from one slde to the outer surface of the block, and fastener means belng provlded to act between the opposlte sldes of the slot to produce a clamplng ef~ect between the socket and the skl leg. The fasteners are arranged to be posltloned ln transverse grooves ln the skl leg so that even lf the fasteners become loosened, the block wlll stlll remaln flxed to the skl leg and cannot become separated.
In thls arrangement, wlth the centre of curvature of the spherlcal bearlng surfaces lylng on the axls of the skl leg, the latter does not generate any bendlng moments ln lts connectlon to the suspenslon arms. By vlrtue of the spherlcally curved bearlng ~ 332~2~
surfaces, rotation of the skl leg shaft for steerlng purposes and rotation of the suspension arms relative to the ski leg for suspension travel purposes are combined lnto the same bearlngs.
Thus ln place of the slx cyllndrlcal bushings reguired ln the above discussed prlor art arrangement, the suspenslon arrangement enclosed herewith requlres only two spherlcal bearlngs, and thus offers a considerable cost advantage. Furthermore, these two spherlcal bearings can accommodate a signlflcant amount of mlsallgnment wh~ch could arlse as a result of manufacturlng tolerances in the suspension arms, and thus reduce the possibility oS undesirable stresses in the system belng generated upon assembly.
Slnce the steering torque is no longer transmitted through the skl leg, the stresses ln the latter are lower, and furthermore the upper end of the ski leg does not requlre to have a spllned configuratlon, whlch therefore reduces fabrication cost and complexity.
A further advantage of the spherlcal bearlng arrangement ls that by vlrtue of the spherlcal conflguration the contact loads are unlformly distributed so that the "edge loadlng" condltlon commonly found in tubular bushlngs ls ellmlnated. Also due to their slze, lt ls posslble to lncrease the contact surface area of the spherlcal bearings slgniflcantly ln comparison to the previously used tubular bushlngs so that the surface pressure ls slgnlflcantly reduced whlch ln turn dramatlcally reduces wear and the development of play during the service llfe of the vehlcle. t~#
BRIEF DESCRIPTION OF THE DRAWINGS
The lnventlon wlll further be described, by way of ,~.; .. , ,, . . . -,,,;' ~ '- . ' ' . : -:
133~3 example only, wlth reference to the accompanying drawings wherein:
Figure 1 is a somewhat schematic side view of a snowmobile;
Figure 2 is a front elevation showlng element~ of the ~kl suspension arrangement of the snowmoblle o Flgure 1, drawn to a larger scale;
Pigure 3 is a front elevatlon of one slde of the skl suspension shown partly sectloned and to an enlarged scale;
Plgure 4 ls a fragmentary perspective vlew from above and to the right of the view shown in Flgure 3;
Flgure 5 is a section view taken on the line V-V in Flgure 3 and drawn to a larger scale;
Flgure 6 ls an exploded view showlng the components of the suspension assembly; and Figure 7 ls an exploded vlew showlng for comparison purpo6es the components of a prlor art ski assembly.
DESCRIPTION OF THE PREFERRSD ~MBODIHENTS
As seen in Figure 1, a snowmoblle 10 has a frame 11 the rear end of whlch lc supported on a driven endlesq track 12 and the front end of which i~ supported upon a pair of spaced skis 13, the skl~ being steerable under control of the operator by nean~ of handlebars 14 and a steering linXage 15.
As seen in Plgure 2, the skis 13 are supported in a suspension system 16 which for each ski includes an upper 2 suspen310n arm 17 and a lower suspension arm 18. -~
The lower suspenslon arm 18 as is best seen in Pigure 4 is of wishbone shape having horizontally spaced tubular limbs 18a the inboard ends of which are plvoted coaxially on a pivotal S
- ~ 1332~3 mounting 19 in the frame 11, by means of rubber filled bushlngs (not shown). The angular movement is provided by deforma~ion of the rubber inRtead of a traditional sliding contact. This reduces the development of play during ~he service llfe and damp~ the structural vibrations and noise whlch reduces road harshness and thus improves comfort. The outboard ends of the llmbs 18a are ~olned to a bearlng assembly 20 connected to the skl leg ~tructure 21.
Each upper suspenslon arm 1~ of trlangular conflguratlon havlng a pair of horlzon~ally spaced tubular member~ 17a the inboard ends are coaxlally supported on a pivotal mountlng 22 on the frame 11. A third tubular member 17b extends upwardly between the members 17a, and is connected thereto by means of a gusset plate 17c near the lnboard ends of the tubes 17a and 17b and arranged generally radially thereof, and further gusset plates 17d of trlangular shape arranged transversely to the tubular members 17a and 17b and supportlng between them an apertured mounting plate 17e. The varlous components of the su~penslon arms are connected together by any 6uitable manner, e.g. as by welding. At the outboard end of the upper suspension arm 17, the tubular members 17a and 17b converge and are connected to a bearing a~sembly 23 which receive~ the upper end of the ski leg ~tructure 21.
The inboard end of the upper tubular member 17b of the suspenslon arm 17 forms a pivotal connection 24 to one end of a hydraullc damper and shock absorber assembly 25 angularly arranged ln a generally transverse plane and having an lnner end pivotally attached to a mounting 26 in the snowmoblle frame by ~ean6 of the .. . . .
, . . . .
133~
rubber bushings discussed earlier.
A torsion bar stabllizer 27 has a generally stralght transverse central section that is carried in bearings 23 on the snowmobile frame 11, and at each end thereof has a generally rearwardly directed arm 29 that passes through and ls received by a rubber grommet fixed in the hole 30 in the mountlng plate 17e that is carrled ln the upper suspenslon arm 17.
From a consideratlon of Figure 3 it will be evldent that as the ski 13 is moved upwardly relative to the snowmobile frame, whether as a result of loading lmposed on the vehicle or in response to dynamic conditions encountered by the ~kl in operation, the movement is accommodated by swinging of the upper and lower suspension arms about their pivotal mountings 22 and 19 respectively on the snowmobile frame. The arms 17 and 18 form an approxlmately parallelogram llnkage so that as the skl moves vertically, it maintains an essentially upright orlentatlon, as lllustrated ln broken lines ln Flgure 3. It wlll be noted that as the upper suspenslon arms swings about the plvotal mounting 22, ~ -the plvotal connection 2g will apply a compresslve loading to the hydraulic damper and shock absorber assembly 25 which will accordingly resist upwards deflection of the ski.
The upper and lower suspension arm arrangements provide independent suspension for each of the skis 13 so that they can respond lndlvidually to the dynamlc condltlons encountered.
Furthermore, this arrangement also permlts posltlonlng of the plvot polnts of the suspenslon arms ln con~unctlon with the length of the said arms and skl leg so that the contact point between the ski base and the ground describes a vertical line in space durlng 3 2 ~
j the upward dlsplacement of the ski. This feature lmprove~ the ride quality and the handllng precislon of the vehicle. However lt will be appreciated that by means of the mounting plate 17e cooperating with the arm 29 of the stabllizer bar 27, when one skl ls deflected relative to the other, the stablllzer bar wlll be twisted and thereby transmit a force urglng d~flectlon of the other ~kl ln the ~ame dlrection a~ the flr~t ski.
The B~i leg structure 21 is more clearly illustrated ln Figure 5 as comprising a cylindrical steel skl leg shaft 35 having at lts upper end a first enlarged spherlcally curved bearlng surface 36 and at an lntermediate point ln lts length a slmilar enlarged spherlcally curved bearlng portlon 37.
The upper bearing assembly 23 connecting the upper suspenslon arm 17 to the skl leg structure 21 comprlses a generally cyllndrical cup 38 wèlded to the end of the arm 17 and definlng a cyllndrical seat $n which is received the cylindrical outer surface of an annular bearing shell 39 carried on the upper bearing portion 36. The bearing shell 39 has a cylindrically curved inner surface that is ln slldlng contact wlth the bearing portlon 36, and ls retained ln poæition within the cup 38 by means of a spring retainer rlng 40 seated ln a groove near the ~outh of the cup.
The lower bearing assembly 20 compri~es a cyllndrlcal houslng 41 havlng a radlal flange 42 at its lower end provldlng a seat for an annular bearlng shell 43 that has a spherlcally curved inner surface in sliding contact with the lower bearlng portlon 37 : of the s~l leg shaft 35, the bearlng shell 43 belng retalned ln po~ltlon relative to the housing 41 by a sprlng retaining ring 44 ~ ` 1332~
recelved in a groove near the upper end of the housing 41.
The bottom end of the ski leg shaft 35 is attached to a block 4S whlch in turn ls plvotally attached ~o the ski 13 by means of a bolt 46 passing through aligned bores ln a bracket 47 formed on the upper slde of the ski and in the lower end of the block 45, the axis of the bolt being tran~verse to the length o~
the ski.
The lower end of the ski leg shaft 35 is received within a cylindrical socket 50, there being a slot 51 arranged radially of an opening from the socket 50 to the front exterior surface of the block 45. The socket 50 is of a dlameter to closely receive the lower end of the shaft 35, the latter being formed with a pair of axially spaced transversely extendlng mllled grooves 52 therein. Pairs of aligned bores 53 are provided in the block 45 on opposite sides of the slot 51, and designed to receive threaded fasteners 54. Thus when the lower end of the skl leg shaft 35 is lnæerted in the socket 50 as illustrated in Figure 5, the mllled grooves 52 are aligned with the bores 53. In this position the fasteners 54 can be passed through the aligned bores and the milled grooves and tightened to narrow the slot slightly and deform the block 45 to clamp the socket 50 lnto rlgid engagement wlth the ski leg shaft 35, relative axial or angular movement being further inhiblted by the presence of the fasteners 54 passing through the grooves 52.
Aæ best seen in Figures 2 and 3, the ski leg shaft 35 is : :~
enclosed above and below the lower bearing assembly 20 by a flexible, bellows-type rubber boot 55, 56 to inhibit extraneous material from reaching the bearing parts.
~ . ~ ' . ~.,' ' ' ~ 3~262~
The steering mechanl~m 15 is coupled to the skis 13 not through the skl leg shaft~ 35, but rather through the ~X1 leg blocks 45. As ~hown ln Eigure 4~ a tie rod 60 of the steering mechanlsm has a swivel joint connectlon 61 to an upwardly pro~ecting steering arm 62 that i~ lntegrally formed with the block 45. In this way, steering forces acting between the steering linkage 15 and the skl 13 are not directed through the ski leg shaft 35.
The upper and lower bearing shells 39, 43 are preferably formed of a sultable low friction material sùch a~ nylon or Teflon and are preferably prea6sembled to the ski leg shaft 35 before the latter is attached in the suspension assembly. Thus, as shown, the diameter of the annular interior wall of each bearing shell 39, 43 ls at a maximum ~equal to the diameter of the bearing portlons 36, 37) in the midpolnt of the length thereof, and tapers spherically from there towards lts opposlte end~, i.e. in the direction of the opposite poles of the sphere. As seen ln Flgure 6, each bearing shell 39, 43 læ formed wlth an angularly spaced serles of radial slits opening from one end thereof to permit deformation of that end when the bearlng shell ls belng moved lnto position on the associated bearlng section 36, 37. However once the bearing shells 39, 43 are asæembled, and the ~kl leg assembly moùnted ln the upper and lower bearlng a6semblies 23 and 20, the bearing shells are effectively axially fixed with respect to the ski leg ~haft 35, since the surroundlng cup 38 or cylindrical houslng 41 closely surrounds the outer perlphery of the bearing shell so that the latter cannot pass over the associated cylindrically curved bearlng section of the shaft 35.
13~2~23 ~ The reduction in the number of parts and the associated :~, assembly and maintenance work can perhaps best be appreclated by a comparlson of the exploded vlews of Figure 6 ghowing one slde of a ~kl suspension ln accordance wlth the present lnvention, and Flgure 7 ~howing an exploded view of one slde of a prlor art skl suspension. The latter lncludes a ski leg 80 that ls rotatably mounted ln a tubular housing 81 by means of two bushlngs 82 and a pair of thrust washers 83, belng secured ln place by a snap ring 84 and a steerlng arm 85 attached to the spllned upper end of the ski leg. The upper and lower suspension arms 86, 87 are each attached to brackets on the tubular houslng 81 by a palr of flanged bushlngs 88 inserted ln the ends of the suspenslon arms and retalned by threaded fasteners 89.
Apart from the reduced complexity and cost of the suspenslon arrangement as shown ln Flgures 1 to 6, lt also achieves superlor performance and servlce llfe ln the reduced wear experlenced by the spherlcal bearlng parts as contrasted with the tubular bearlng shell~ of the prlor art arrangement.
Claims (6)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A snowmobile comprising a frame having a forward portion that is supported on a pair of laterally spaced steerable skis through a suspension system, each said ski being carried at the lower end of a generally upright ski leg, said suspension system including for each ski: suspension arm means pivotally connected at one end to said frame and at the other end to said ski leg to permit generally vertically directed deflection of said ski leg and ski in response to the forces that act thereon in use, said ski leg being mounted to be angularly rotatable about the longitudinal axis thereof with respect to said suspension arm means to accommodate steering movement of said ski, steering linkage means being coupled to effect control of such steering movement, said ski leg having at axially spaced locations thereon two spherically curved bearing surfaces the center of curvature of each of which lies on said axis, each said bearing surface being in sliding engagement with a respective bearing element that is carried by said suspension arm means.
2. A snowmobile as claimed in claim 1 wherein said suspension arm means includes two generally transversely oriented and vertically spaced suspension arms each having an inboard end pivotally mounted on said frame and an outboard end carrying a said bearing element in sliding engagement with a respective one of said bearing surfaces.
3. A snowmobile as claimed in claim 1 or 2 wherein each said bearing surface is formed integrally with said ski leg.
4. A snowmobile as claimed in claim 2 wherein said bearing surfaces are formed integrally with said ski leg, and each said bearing element comprising a bearing shell formed of low friction material and having a spherically curved surface in contact with the bearing surface on the ski leg.
5. A snowmobile as claimed in claim 1, 2 or 4 wherein the lower end of said ski leg is formed as a block which provides a pivotal attachment to said ski, said steering linkage being attached to said block.
6. A snowmobile as claimed in claim 1, 2 or 4 wherein at the lower end of said ski leg there is a block which provide a pivotal attachment to said ski, and to which said steering linkage is connected, said block defining a cylindrical socket in which said ski leg is received, there being a narrow slot extending radially of said socket to the exterior surface of said block, fastener means being provided acting between portions of said block on opposite sides of said slot to effect clamping of the lower end of said ski leg in said socket.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000612079A CA1332623C (en) | 1989-09-20 | 1989-09-20 | Snowmobile ski suspension |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000612079A CA1332623C (en) | 1989-09-20 | 1989-09-20 | Snowmobile ski suspension |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1332623C true CA1332623C (en) | 1994-10-18 |
Family
ID=4140630
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000612079A Expired - Lifetime CA1332623C (en) | 1989-09-20 | 1989-09-20 | Snowmobile ski suspension |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1332623C (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US8336660B2 (en) | 2008-12-05 | 2012-12-25 | Yamaha Hatsudoki Kabushiki Kaisha | Snowmobile |
-
1989
- 1989-09-20 CA CA000612079A patent/CA1332623C/en not_active Expired - Lifetime
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US8336660B2 (en) | 2008-12-05 | 2012-12-25 | Yamaha Hatsudoki Kabushiki Kaisha | Snowmobile |
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| MKEX | Expiry | ||
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