Abstract:
A small vehicle features a drive system that directs power from an engine unit to at least one driven wheel. The driven wheel is connected to a half shaft. The half shaft is driven by a ring gear. The ring gear is driven by a pinion gear. The pinion gear is connected to a longtinudinally extending drive shaft. The pinion gear is axially adjustable along the rotational axis of the drive shaft relative to the ring gear. The pinion gear is not substantially axially adjustable relative to a cover member the partially defines a gear housing. The cover member is adjustably secured to the balance of the gear housing through a shim. The shim can be exchanged for varied shim sizes to effect proper meshing between the pinion gear and

Description:
RELATED APPLICATIONS  
         [0001]    This application is related to Japanese Patent Application No. 2001-109,380, filed Apr. 9, 2001, which application is hereby incorporated by reference in its entirety.  
         BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    The present invention generally relates to drive systems for small vehicles. More particularly, the present invention relates to such a drive system featuring a construction that facilitates backlash adjustment between a pinion gear and a ring gear.  
           [0004]    2. Description of the Related Art  
           [0005]    All terrain vehicles are but one example of smaller vehicles that are powered by internal combustion engines. These smaller vehicles typically transfer the power from the engine to a set of wheels or other similar members. In some arrangements, a longitudinally-extending drive shaft carries the power from the engine to a pair of rear wheels through a pinion gear and a ring gear. As the drive shaft rotates the pinion gear, the pinion gear rotates the ring gear and any axles that are connected to the ring gear. The end of the drive shaft carrying the pinion gear typically is fixed to a gear case that contains the ring gear.  
           [0006]    These smaller vehicles also generally comprise a simplified braking system. In one arrangement, such as that shown in U.S. Pat. No. 4,667,760, issued to Takimoto on May 26, 1987, the braking system generally comprises a brake disc that is mounted to the drive shaft and a brake caliper that is mounted to the gear case. To slow or stop the vehicle, the brake caliper is actuated to clamp a set of brake pads to the brake disc. By slowing or stopping the rotation of the drive shaft, the vehicle itself can be slowed or stopped.  
         SUMMARY OF THE INVENTION  
         [0007]    While these constructions have proven generally satisfactory for quite some time, improvements to the manufacturability of the vehicles and the drive lines have been desired. One such improvement relates to achieving the proper degree of meshing between the pinion gear and the ring gear. As discussed above, both the pinion gear and the brake system are rigidly fixed to the gear housing that contains the ring gear. It has been found that proper meshing is best achieved when the placement of the pinion gear relative to the ring gear can be slightly adjusted. The rigid connections between the pinion gear and the housing and the between the brake system and the housing thwart such adjustments.  
           [0008]    Accordingly, one aspect of the present invention involves a drive system for a small vehicle. The system comprises an engine crankshaft with a drive shaft driven by the crankshaft. The drive shaft extends in a generally longitudinal direction. A gear housing is disposed proximate a distal end of the drive shaft. The gear housing comprises an opening that is substantially closed by a first cover. The drive shaft is coupled to a drive sleeve with the drive sleeve extending through an aperture defined in the first cover. A stub shaft is rotationally secured to the drive sleeve and couples a pinion gear to the drive sleeve. The pinion gear is disposed within the gear housing and meshes with a ring gear. The pinion gear is axially fixed relative to the first cover and is axially adjustable relative to the ring gear.  
           [0009]    Another aspect of the present invention involves a drive system for a small vehicle. The drive system comprises a longitudinally extending drive shaft with a pinion gear driven by the drive shaft. The pinion gear meshes with a ring gear. The pinion gear and the ring gear are disposed within a chamber defined by a gear housing. The gear housing comprises a first cover with the pinion being connected to the first cover and the pinion and first cover being axially adjustable relative to the ring gear.  
           [0010]    A further aspect of the present invention involves a drive system for a small vehicle that comprises a longitudinally extending drive shaft, a gear housing, a pinion gear driven by the drive shaft and disposed within the gear housing, a ring gear meshing with the pinion gear and disposed within the gear housing, at least one axle coupled to the ring gear and extending from the gear housing, and means for adjusting an axial position of the pinion gear relative to the drive shaft. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]    These and other features, aspects and advantages of the present invention will now be described with reference to the drawings of a preferred embodiment, which preferred embodiment is intended to illustrate and not to limit the invention. The drawings comprise five figures.  
         [0012]    [0012]FIG. 1 is a side elevation view of a vehicle having a drive system arranged and configured in accordance with certain features, aspects and advantages of the present invention.  
         [0013]    [0013]FIG. 2 is a top plan view of the vehicle of FIG. 1 showing a portion of the drive system with hidden lines.  
         [0014]    [0014]FIG. 3 is an enlarged side elevation view of a portion of the vehicle and drive system of FIG. 1.  
         [0015]    [0015]FIG. 4 is an enlarged top plan view of the portion of the vehicle and drive system shown in FIG. 3.  
         [0016]    [0016]FIG. 5 is an enlarged cross-sectioned view the portion of the drive system shown in FIGS. 3 and 4. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0017]    With initial reference to FIGS. 1 and 2, a vehicle  10  that comprises a drive system arranged and configured in accordance with certain features, aspects and advantages of the present invention will be described. The illustrated vehicle  10  is a four-wheeled utilitarian or recreational vehicle. More particularly, the illustrated vehicle  10  is a four-wheeled all terrain vehicle. In some applications, the vehicle  10  can have other numbers of wheels. For instance, the vehicle can have as few as one wheel or more than four wheels, depending upon the desired application. In addition, certain features, aspects and advantages of the present invention can be used with tracked vehicles, such as snowmobiles, for instance. Accordingly, the illustrated vehicle  10  simply provides one environment in which certain features, aspects and advantages of the present invention can be used.  
         [0018]    The illustrated vehicle  10  generally comprises a welded-up frame assembly  12  (see FIGS. 3 and 4). Any suitable frame assembly  12  can be used. The illustrated frame assembly  12  generally comprises a pair of substantially parallel subassemblies that are laterally spaced from each other and secured together with a number of cross members  13 .  
         [0019]    The subassemblies each generally comprise a main tube  14  that extends rearward from a head tube (not shown). The main tubes  14  in the illustrated arrangement extend rearward and are supported by pillar tubes  16  proximate a rear portion of the main tubes  14  and down tubes  18  at a location forward of the pillar tubes  16 . Suitable bracing members  20  can be provided in strategic locations to reinforce the subassemblies. Bottom rails  22  extend a majority of the length of each subassembly and are connected to a lower portion of the respective pillar tubes  16  and down tubes  18 .  
         [0020]    The frame assembly  12  is supported by ground engaging elements, such as a group of wheels in the illustrated arrangement. The ground engaging elements also can comprise runners, skis, drive belts and the like, depending upon the application. The illustrated vehicle comprises a pair of front wheels  24  and a pair of rear wheels  26  that support the frame assembly  12  in a known manner. In general, the wheels  24 ,  26  are connected to the frame assembly  12  using any suitable suspension system.  
         [0021]    A body assemblage is supported by the frame assembly  12 . The body assemblage comprises a number of components that are generally known to those of ordinary skill in the art. These components are attached to the frame assembly  12  in any suitable manner, including those generally known to those of ordinary skill in the art.  
         [0022]    The body assemblage comprises a front fender assembly  28  and a rear fender assembly  30 . The fender assemblies  28 ,  30  generally comprise members that extend over the respective wheels  24 ,  26  and, in some arrangements, intermediate members that span the distance between the wheel covering members. These members can be integrated into a single component or can be formed of distinct components.  
         [0023]    The body assemblage also comprises a front carrying rack  32  and a rear carrying rack  34 . These racks  32 ,  34  are supported above a portion of the respective fender assemblies  28 ,  30  in any suitable manner. In some configurations, the racks  32 ,  34  are supported by the respective fender assemblies  28 ,  30 .  
         [0024]    Rearward of the front fender assembly  28 , the body assemblage also comprises a gauge cluster  36 . The gauge cluster  36  comprises a number of vehicle operating condition indicators, such as are known in the art. The gauge cluster  36  can be integrated into the front fender assembly  28  in some configurations.  
         [0025]    Rearward of the illustrated gauge cluster, the body assemblage preferably comprises a fuel tank  38  and a seat  40 . The fuel tank  38  can be an actual fuel tank or can be a hollowed shell component that is designed to resemble a fuel tank while providing a recess into which an air intake can extend. In such arrangements, the actual fuel tank  38  can be positioned below the seat  40 .  
         [0026]    Forward of the fuel tank  38  and rearward of the gauge cluster in the illustrated arrangement, the vehicle  10  comprises a handlebar assembly  42 . The handlebar assembly  42  preferably comprises a pair of handgrips  44  that are mounted in a manner to allow an operator holding the grips  44  to pivot a steering column  46 . The steering column  46  effects steering movement of the front wheels  24  through any suitable linkage.  
         [0027]    In the illustrated arrangement, a pair of foot boards  48  are mounted to the frame assembly  12 , with one foot board  48  being positioned on each lateral side of the frame assembly  12 . In some arrangements, the foot boards  48  can be replaced by foot pegs, nerf bars. Other suitable foot support arrangements also can be used.  
         [0028]    With reference to FIG. 1, an engine unit  50  is mounted to the frame assembly  12  at a location generally below the fuel tank  38  and the seat  40 . The engine unit  50  can be of any suitable construction. In a preferred arrangement, the engine unit  50  comprises an internal combustion engine and a transmission that are combined into a single member. The engine unit  50  can have any desired orientation. In the illustrated arrangement, as shown in the simplified view of FIG. 2, the engine unit  50  comprises a transversely extending crankshaft  52 . The crankshaft  52  comprises a single throw, which is defined by a pin that extends between a pair of webs of the crankshaft  52 . Thus, the illustrated engine unit  50  is a single cylinder construction; however, more than one cylinder can be used in other arrangements.  
         [0029]    The crankshaft  52  preferably drives a suitable continuously variable transmission (CVT)  54 . More preferably, the crankshaft drives a belt-type CVT  54 , such as that shown in the illustrated arrangement. Other suitable CVT constructions also can be used. In addition, arrangements not using a CVT can be implemented.  
         [0030]    The CVT  54  drives a change speed transmission  56  in the illustrated arrangement. The change speed transmission  56  preferably provides a low, high, neutral and reverse gearing. In some configurations, the change speed transmission also features a park lock position such that movement of the vehicle can be precluded by a construction positioned within the change speed transmission  56 . As the operator operates the vehicle  10 , the operator can shift gears among low, high, neutral and reverse depending upon the desired operating characteristics.  
         [0031]    The illustrated change speed transmission  56  features an output shaft that drives a bevel gear  58  that can be disposed within a transfer case. (not shown). In some arrangements, the transfer case can be integrated into the engine unit  50 , which also includes a gear box that contains the change speed transmission  56 .  
         [0032]    The bevel gear  58  is connected to a front drive shaft  60  and a rear drive shaft  62 . Preferably, the front drive shaft  60  can be selectively coupled and decoupled from the drive train to switch operation between four wheel drive and two wheel drive. The front drive shaft  60  is connected to a pair of front half shafts  64  and the rear drive shaft is connected to a pair of rear half shafts  66 . Preferably, the half shafts  64 ,  66  are connected to the respective drive shafts  60 ,  62  with suitable constant velocity joints (CV joints). The half shafts  64 ,  66  drive the respective wheels  24 ,  24 .  
         [0033]    With reference now to FIGS. 3 and 4, an integrated brake and rear gear housing  70  is illustrated therein. The housing  70  comprises a brake portion  72  and a gearing portion  74 . The gearing portion  74  contains gears to transfer power from the rear drive shaft  62  to the two rear half shafts  66 . In some arrangements, the brake portion  72  and the gearing portion  74  can be separately provided and spaced from each other; however, the illustrated arrangement provides a compact and simple construction that facilitates assembly and improves manufacturability in manners that will be described.  
         [0034]    The housing  70  preferably is mounted rearward of the engine unit  50  and within the frame assembly  12 . In the illustrated arrangement, the housing  70  is mounted below the rear fender assembly  34 , generally rearward of the seat  40 , and centrally between the two rear wheels  26 . In the illustrated arrangement, the housing  70  also is mounted to a pair of cross members  13  in a suitable manner. Other suitable mounting arrangements also can be used.  
         [0035]    With reference now to FIG. 5, the housing  70  and the components disposed within the housing  70  will be described. The housing  70  generally comprises a main case  76  that comprises three openings. When the housing  70  is installed on the vehicle  10 , one of the three openings extends through a forward portion of the main case  76  while the other two openings extend through the two lateral portions of the main case  76 . The forward-facing opening receives a first cover  78  that contains an opening sized and configured to accommodate the rear drive shaft  62 . One of the lateral-facing openings is sized and configured to accommodate a first axle sleeve  80 . The other of the lateral-facing openings receives a second cover  82  that contains an opening sized and configured to accommodate a second axle sleeve  80 . Together, the main case  76  and the two covers  78 ,  82  define a chamber  84  in which the rear drive shaft  62  is coupled to the two rear half shafts  66 .  
         [0036]    In the illustrated arrangement, the actual rear drive shaft  62  terminates just forward of the chamber  84 . The rear drive shaft  62  has a distal or rear portion  86  that comprises splines or other suitable keyways formed about its circumference. A collar  88  that features both an internally splined surface and an externally splined surface is fixed for rotation along the rear portion  86  of the rear drive shaft  62 . The splines can be any suitable keyway or the like that allows two rotary members to be coupled for rotation. Preferably, the interlocking structure also allows relative axial movement between the members once the members are joined together. The illustrated collar  88  is secured in position along the distal portion of the rear drive shaft  62  with a pair of snap rings or the like.  
         [0037]    A drive sleeve  90  extends over the collar  88  and the rear portion  86  of the rear drive shaft  62 . The drive sleeve preferably contains a structure the interlocks with the outer surface of the collar. For instance, in the illustrated arrangement, the drive sleeve  90  comprises an internally splined surface that interlocks with external splines on the collar  88 . In this manner, the drive sleeve  90  is connected to the drive shaft  62  through the intermediate collar  88 . In one arrangement, the drive sleeve  90  can be directly connected to the drive shaft  62  without an intervening member; however, the collar  88  facilitates assembly of the illustrated components due to the relative diameters reflected by each of the illustrated components.  
         [0038]    The drive sleeve  90  comprises a number of mounting lugs  92  (one shown) that extend radially outward from a cylindrical portion of the drive sleeve  90 . The lugs  92  receive fasteners  94 , such as bolts, threaded fasteners or the like. The fasteners attach a brake disc  96  to the drive sleeve  90 . In addition, a brake caliper  98  is attached to the first cover  78  with a threaded fastener  100 . Other methods of attaching the brake caliper  98  to the first cover  78  also can be used. The brake caliper  98  extends around a portion of the periphery of the brake disc and can be actuated to clamp onto the brake disc in any suitable manner. The illustrated arrangement features a cable construction; however, other suitable actuating arrangements, such as hydraulic actuation, can be used.  
         [0039]    The drive sleeve  90  extends through the opening in the first cover  78 . A seal  102  is provided between the drive sleeve  90  and the opening in the first cover  78 . A bearing  104  is mounted within the first cover proximate the opening and proximate a distal end of the drive sleeve  90 . The bearing  104 , preferably a ball bearing, journals a stub shaft  106  that is secured to the drive sleeve  90 . The stub shaft  106  preferably is connected to the drive sleeve in a manner that locks the two components together for rotation. In addition, as shown in FIG. 5, the stub shaft can be secured within the drive sleeve  90  against axial movement away from the rear drive shaft  62  through a nut and washer combination  108 . In the illustrated arrangement, the bearing  104  is sandwiched between a step formed on the stub shaft  106  and the end of the drive sleeve  90  for reasons that will become apparent.  
         [0040]    The end of the stub shaft  106  comprises a pinion gear  110  and a portion journaled relative to the main case  76  by a set of needle bearings  111 . The pinion gear  110  meshes with a ring gear  112 . The meshing of the pinion gear and the ring gear  112  is accompanied by a slight amount of backlash. Adjusting the degree of backlash in the system can be accomplished by adjusting the mating positions of the pinion gear  110  and the ring gear  112 , thus achieving proper meshing and improved performance.  
         [0041]    The illustrated construction fixes the position of the pinion gear  110  relative to the first cover  78 . Thus, by placing one or more appropriately sized shims between the main case  76  and the first cover  78 , the position of the pinion gear  110  relative to the ring gear  112  can be more easily controlled. During assembly, the placement of the pinion gear  110  relative to the ring gear  112  can be incrementally adjusted by altering the shim size or the number of shims used. Thus, the pinion gear  110  can be moved axially away from the circumference of the ring gear  112  by inserting more shims or by inserting larger shims and the pinion gear  110  can be moved axially toward the circumference of the ring gear  112  by removing shims or by inserting smaller shims.  
         [0042]    Furthermore, in the illustrated construction, at least the following components can be moved relative to the ring gear  112  as a single unit: the pinion gear  110 , the stub shaft  106 , the bearing  104 , the drive sleeve  90 , the first cover  78  and the brake components. Thus, the housing  70  can be thought of as having two portions that are adjustable relative to each other in an axial direction of the drive shaft. These two portions respectively comprise the pinion gear  110  and the ring gear  112 .  
         [0043]    The illustrated ring gear  112  is journaled relative to the second cover  82  with a bearing, such as the ball bearing  115 . The ring gear  112  also is mounted to a coupling member  116 . The coupling member joins the ring gear  112  and the two axle sleeves  80 . The coupling member  116  is suitably journaled relative to the main case  76  with a set of bearings, preferably needle bearings  118 . The two axle sleeves  80  preferably are fixed for rotation with the coupling member  116 . In the illustrated arrangement, the three components are fixed with the use of splines. Keyways or the like also can be used to secure the three components for rotation. Moreover, suitable seals  120  are used to seal gap between the rotating sleeves  80  and the stationary second lid  82  and the stationary main case  76 , respectively.  
         [0044]    In one arrangement, the CV joints and the bevel gear, can be constructed similar to the manner disclosed in U.S. Pat. No.  6 , 250 , 415 , issued on Jun. 26, 2001 and hereby incorporated by reference in its entirety. Such a construction can decrease the lateral dimension of the coupling between the half shafts and the drive shafts while increasing the length of the half shafts to provide more suspension travel.  
         [0045]    Although the present invention has been described in terms of a certain embodiment, other embodiments apparent to those of ordinary skill in the art also are within the scope of this invention. Thus, various changes and modifications may be made without departing from the spirit and scope of the invention. For instance, various components may be repositioned as desired. Moreover, not all of the features, aspects and advantages are necessarily required to practice the present invention. Accordingly, the scope of the present invention is intended to be defined only by the claims that follow.