Steerable axles transaxle assembly

A transaxle assembly is provided which is configured to be mounted to a frame of a vehicle. The transaxle assembly includes a transmission that has two separately attached pivotable knuckle assemblies. Each pivotable knuckle assembly can be independently steered and includes an axle driven by the transmission. Each axle drives a wheel of the vehicle. In another configuration, the two pivotable knuckle assemblies are joined by an integrally formed crossmember.

RELATED APPLICATIONS

This application is a non-provisional of U.S. Patent Application No. 61/446,095, filed on Feb. 24, 2011. The contents of this application are incorporated by reference herein in its entirety.

BACKGROUND OF THE INVENTION

This application relates to transaxles generally and, in particular, to transaxles having steerable axles.

SUMMARY OF THE INVENTION

An improved steerable axles transaxle assembly is disclosed herein, as described in more detail below. One or more of the disclosed transaxle assemblies can be mounted to the frame of a vehicle, such as a lawn mower or utility vehicle, for example, to enable two-steered-wheel-drive, four-steered-wheel-drive, etc.

Unique pivotable knuckle assemblies, each including a pivot bearing support that is integrally formed with a specialized mounting flange, are pre-assembled and then attached to a transmission via the specialized mounting flange using a first set of fasteners. The resultant steerable axles transaxle assembly can then be attached directly to the vehicle frame via the specialized mounting flange using a second set of fasteners.

The pivot bearing supports of two pivotable knuckle assemblies can be joined together by an integral structural crossmember to form a dual pivotable knuckles assembly that can be attached to a transmission to reinforce the vehicle frame and protect the transmission from flexural and/or impact damage. Certain configurations of the pivot bearing supports described herein are designed to facilitate easy removal of the transmission from a vehicle for servicing, without removing the pivotable knuckle assemblies (or dual pivotable knuckles assembly) from the vehicle frame.

The pivotable knuckle(s) assemblies disclosed herein are suitable for conversion of a variety of transmission types, such as mechanical, electro-mechanical, hydrostatic, etc., to steerable axles transaxle assemblies. Different types of steerable axles transaxle assemblies having similar pivotable knuckle(s) assemblies and therefore, similar mounting features, can be used in a single vehicle configuration such as, for example, in a hybrid vehicle having both a hydrostatic transmission and an electrically driven transmission that are both converted to steerable axles transaxle assemblies in accordance with the present invention.

A complete, pre-tested steerable axles transaxle assembly that is ready to install onto a vehicle frame can improve assembly efficiency and reduce assembly tooling and labor costs for a vehicle manufacturer while improving assembly accuracy and product quality.

The modular nature of the steerable axles transaxle assemblies disclosed herein enables versatility for designing across product platforms.

A better understanding of the objects, advantages, features, properties and relationships of the invention will be obtained from the following detailed description and accompanying drawings which set forth illustrative embodiments that are indicative of the various ways in which the principles of the invention may be employed.

DETAILED DESCRIPTION OF THE DRAWINGS

It should be noted that in the description and drawings, like or substantially similar elements may be labeled with the same reference numerals. However, sometimes these elements may be labeled with differing numbers, such as, for example, in cases where such labeling facilitates a more clear description. Additionally, the drawings set forth herein are not necessarily drawn to scale, and in some instances proportions may have been exaggerated to more clearly depict certain features. As stated above, the present specification is intended to be taken as a whole and interpreted in accordance with the principles of the present invention as taught herein and understood by one of ordinary skill in the art.

Referring toFIGS. 1-4, a first embodiment of a steerable axles transaxle assembly14, referred to herein as simply “transaxle14,” includes a transmission20having a housing22having a first end22aand a second end22b. A first driven shaft24extends out the first end22aand a second driven shaft25extends out the second end22b. A first pinion gear26ais disposed on an external end of the first driven shaft24and a second pinion gear26bis disposed on an external end of the second driven shaft25. A first pivotable knuckle assembly38is attached to the housing first end22aand a second pivotable knuckle assembly39is attached to the housing second end22b. The first pivotable knuckle assembly38includes a first pivot bearing support30and the second pivotable knuckle assembly39includes a second pivot bearing support31. Each pivot bearing support30,31includes a cylindrical opening30c, into which a pivot bearing33may be installed.

A first axle42is rotatably supported in and extends through a first steerable axle support40of pivotable knuckle assembly38and a second axle43is rotatably supported in and extends through a second steerable axle support41of pivotable knuckle assembly39. One end of each of the first and second axles42,43is gear-driven, as will be described in more detail herein, while a second end of each axle42,43drives a wheel16of a vehicle10.

As shown, knuckle assembly39can be a mirror image of knuckle assembly38. Notably, the only difference between pivot bearing supports30and31, as illustrated, is the mirrored positioning of grease accommodation features described herein that are formed in pivot bearing supports30and31for grease fittings86. Optionally, grease fittings86can be positioned such that two identical bearing supports (not shown) can be used in place of bearing supports30,31. Furthermore, grease fittings86are not required if, for example, certain known composite bearing materials are used to form the pivot bearings.

Dependent upon load parameters applied when designing and engineering vehicle10and upon the material characteristics of pivot bearing supports30,31, a pivot bearing33may not be required in opening30cfor some lighter duty applications, i.e., the cylindrical surface of opening30ccan serve as a bearing surface. Pivot bearing supports30,31can be formed from a variety of materials, such as cast iron, hardened steel, forged steel, alloy steel, aluminum, composites, etc., based upon vehicle configuration and load parameters.

As shown, a grease fitting86can be installed in a passage30fthat connects to a grease groove30gto allow periodic lubrication of the pivot bearing33. Pivot bearing33can be a simple, single, cylindrical bearing, as shown, or a more complex bearing, a pair of bushings, etc. Many different types of bearings are well known, their utilization is dependent upon loading and operational environment considerations, and they will not be described in detail herein.

Pivot bearing supports30,31each have a plurality of openings30afor attachment of pivotable knuckle assembly38to housing end22aby means of a plurality of fasteners, such as screws70, along with a corresponding first set of nuts70athat is installed into recesses30eformed in each of the pivot bearing supports30,31. Recesses30ecan be round counterbore-style recesses, as shown, or could be hexagonal, for example, so that nuts70acannot rotate, thereby facilitating ease of assembly and disassembly, including removal of transmission20without removal of the pivotable knuckle assemblies38,39from vehicle frame12, as will be further described.

As shown inFIG. 1, screws70are long enough to extend through vehicle frame12during the installation of transaxle14onto frame12so that a corresponding second set of nuts70bcan be used in conjunction with screws70to attach transaxle14, including housing first end22aand housing second end22b, to frame12. In addition to screws70, a second plurality of fasteners, such as screws71, is installed through openings30bformed in each pivot bearing support30,31in order to separately attach transaxle14to frame12via nuts71awithout further attaching housing first end22aand housing second end22bto frame12. Then, if nuts71aare captured so that they cannot rotate, as described previously, transmission20can be removed from frame12for servicing by simply removing nuts70band screws70without removing the pivotable knuckle assemblies38,39(and associated wheels16of vehicle10) from frame12.

Alternatively, a shorter variant of screws70may be used so that they do not extend through vehicle frame12or, as another alternative, frame12may comprise clearance openings that allow screws70to extend through frame12without attachment thereto. In a manner similar to that described previously herein, these two alternatives also facilitate removal of transmission20without removing the pivotable knuckle assemblies38,39from frame12. Both of these alternatives are accomplished by attaching transaxle14to frame12via a separate plurality of screws71and nuts71ainstalled through openings30bformed in pivot bearing supports30,31. Particularly with these two alternatives, considering that screws70are not used to attach transmission20directly to frame12, it may be desirable to increase the size of the mounting flange30h, as indicated by phantom lines30ishown onFIG. 3, so that additional openings30b, along with additional screws71and nuts71a, can be added to ensure appropriate structural attachment of transaxle14to frame12, depending upon the operating parameters of vehicle10and resultant stresses imparted to frame12.

Furthermore, numerous variations of the mounting flange30hof bearing supports30,31are possible while maintaining interchangeability with the bearing supports30,31shown assembled in knuckle assemblies38,39. This simple variation of the mounting flange30hpermits adaptation to a variety of transmissions and vehicle frames, thereby facilitating modularity.

As described previously herein, fasteners, such as plurality of screws71and nuts71a, can be used to attach transaxle14to vehicle frame12. Alternatively, other fastening methods, such as riveting, for example, could be used to attach pivot bearing supports30,31of transaxle14to frame12.

If needed, screws72can be used to further strengthen and stabilize the assembly of transaxle14to vehicle frame12. Screws72engage openings30d, which may be tapped openings, formed in pivot bearing supports30,31.

In order to further strengthen vehicle frame12and protect transaxle14from flexural damage, frame reinforcing members such as gussets, C-channel crossmembers, I-beam crossmembers, etc. (not shown), can be added where needed, as is known. In order to protect transmission20from flexural and/or impact damage, a vehicle frame reinforcement member such as plate13can be added to frame12.

Referring primarily toFIGS. 1 and 2, the first and second pivotable knuckle assemblies38,39include a first and second steerable axle support40,41, respectively. Each of the knuckle assemblies38,39has a shaft support tube34that is pivotably supported by and extends through each of the pivot bearings33so that both ends of each shaft support tube34extend into mating openings40a,40band41a,41bformed in each of the first and second steerable axle supports40and41, respectively.

Referring again toFIGS. 1-4, steerable axle supports40,41are pivoted about the rotational axes of a third driven shaft50and a fourth driven shaft51, respectively, by means of steering arms40c,41c, respectively. Steering arms40cand41ccan be integrally formed, as shown, on axle supports40,41or, alternatively, with minor modifications, can be attached thereto. If attachment accommodations (not shown) for attachable versions of arms40c,41care formed in axle supports40,41and are located symmetrically fore and aft of the rotational axes of axles42,43, then axle supports40,41can be identical components. Furthermore, if such attachment accommodations are provided, then interchangeable variations of steering arms40c,41c, such as steering arms having various lengths and/or angles of attachment relative to axle supports40,41, is facilitated, thereby introducing a further degree of modularity.

Referring again primarily toFIGS. 1 and 2, the first axle42and the second axle43, that are oriented perpendicularly to the driven shafts50,51, are each supported by one or more bearings45that are mounted in the first and second steerable axle supports40,41, respectively, and retained in position by retaining rings49or the like in conjunction with features such as bearing lands40dshown inFIG. 2. Bearings45are illustrated as ball bearings but could be tapered roller bearings, needle bearings, etc., depending upon the vehicle configuration, load requirements, etc. A driven axle gear44ais fixed on one end of the first axle42and a driven axle gear44bis fixed on one end of the second axle43. Steps or shoulders, such as shoulders42a, can be formed on axles42and43to control positioning of axles42,43and limit axial loading on bearings45while allowing appropriate clearance for axle rotation. Other steps or shoulders (not shown) can be formed on axles42,43to control positioning of gears and hubs, for example, to prevent binding when nuts47aand47bare installed.

As described previously herein, transmission20includes a first driven shaft24having a first pinion gear26adisposed on an external end and a second driven shaft25having a second pinion gear26bdisposed on an external end. The third driven shaft50and the fourth driven shaft51, that are oriented perpendicularly to the first and second driven shafts24,25, are each rotatably mounted in and extend through one of the shaft support tubes34of knuckle assemblies38,39. Each of the driven shafts50,51has a driven gear52fixed on one end and a driving gear53fixed on a second end, wherein each of the driven gears52is engaged to and driven by one of the first pinion gear26aor the second pinion gear26band each of the driving gears53is engaged to and drives one of the driven axle gears44aor44b.

The pinion gears26a,26b, driven gears52, driving gears53and driven axle gears44a,44bcan all be the same size and type of spiral bevel gear, as shown, or optionally they can be different sizes and/or types of gears, as needed, for various gear reductions, working parameters, etc.

As shown most clearly inFIG. 2, each of the driven shafts50and51is supported by one or more bearings54. The driven shafts50and51can be retained in shaft support tubes34by means of retaining rings56or the like that also retain gears52and53on shafts50and51. As is known in the art, shoulders or steps (not shown) are formed on shafts50and51to control positioning of shafts50and51, while allowing appropriate clearance for shaft rotation. Thrust washers57can be employed to provide running surfaces for gears52and53and prevent excessive wear of mating components.

Axles42and43can each be retained in an axle support40and41, respectively, by means of nuts47aand47b. Nuts47aretain gears44aand44bthat are fixed on one end of each axle42and43, respectively, while nuts47bretain wheel hubs48that are rotatably fixed on a second end of each axle42and43. Wheel hubs48facilitate attachment of each axle42,43to a wheel16of vehicle10. Thrust washers58can be employed to provide running surfaces for gears44aand44b, while thrust washers59can be employed to provide running surfaces for hubs48.

Additional thrust washers or spacers, such as spacers64shown inFIG. 2, can be added between hubs48and thrust washers58, as needed, to properly locate and/or provide appropriate clearance between components. Additional thrust washers or spacers, such as spacers65,66and67, can be added between various gears and thrust washers, as needed, to properly locate components and achieve proper gear mesh.

Referring now toFIGS. 1 and 2, sumps60aand60bprovide lubrication for gears44aand44b, respectively, and for gears53, bearings45and bearings54. Each sump60a,60bis sealed at an outer end of each axle42,43by a seal46and at an upper end of each shaft50,51by a seal55. Each sump60a,60bcan be filled with oil by means of fluid passages82and83having removable plugs80and81installed therein, respectively. A fluid passage82is formed in each axle support40and41and a T-shaped fluid passage83having a vertical passage83aintersected by a horizontal passage83bis formed in each of the driven shafts50and51. Passages83acan remain unfilled when sumps60aand60bare filled so that the fluid in sumps60aand60bcan expand during operation of transaxle14without forcing leakage through various seals as the sump fluid temperature rises.

Sump covers61a,61b, depicted using phantom lines to reveal details that would otherwise be hidden, are attached to the axle supports40,41, respectively, to enclose sumps60aand60b, respectively. Each sump cover61aand61bis attached by means of screws63or the like and is sealed by means of sealant or a perimeter seal or gasket62, depicted using dashed lines. The quantity, style and placement of screws63shown inFIG. 2is illustrative only, and screws63or the like can be employed as needed to ensure durable sealing of sump covers61a,61b.

Thrust washers57and58can have holes or openings (not shown) formed therein to allow flow of fluid throughout the volume contained between seals46and55, the flow of fluid particularly needed when filling sumps60a,60b.

Gear covers68aand68b, depicted generically in phantom lines to reveal details that would otherwise be hidden, can be provided to shield and protect gears52,26aand26bfrom contact with foreign objects, contamination, etc. Grease or other suitable lubricant can be applied to gears52,26aand26b. Optionally, gear covers68aand68bcould be attached to brackets (not shown) attached to vehicle frame12.

Referring now toFIG. 4, a generic vehicle10, having a vehicle frame12to which two transaxles14are attached, is depicted generically because it can be any of a variety of vehicle types including, but not limited to, lawn mowers, utility vehicles, etc. Furthermore, although transaxles14are illustrated as having variable-speed electro-mechanical transmissions20having integrated electric motors21, a variety of other transmission types that are not electrically driven could be used in place of transmissions20.

Vehicle10is illustrated as a four-steered-wheel-drive vehicle wherein one transaxle14has been rotated 180 degrees in relation to the other. In this configuration, due to the 180 degree rotation of one transaxle14in relation to the other, one motor21is electrically driven in one direction of rotation and the other motor21is electrically driven in the opposite direction of rotation so that the wheels16of vehicle10will all be rotationally driven in the same direction. Generically depicted linkages17that are connected to each of the steering arms40c,41ccan be mechanical linkages, electric actuators, hydraulic cylinders, etc, that are controlled by a steering control mechanism or device18. Steering control mechanism or device18can be any known electronic, mechanical, electro-mechanical, hydraulic, etc., device employed to control the steering linkages17. Depiction of four linkages17is not meant to imply that all four wheels must be steered independently (although they can be, if desired), as tie rods may be used to connect steering arms, as is well known.

Referring toFIGS. 5 and 6, a second embodiment of a transaxle114is essentially the same as the first embodiment transaxle14, except as will be described herein. Whereas transaxle14includes a first pivotable knuckle assembly38and a second pivotable knuckle assembly39separately mounted to transmission housing22, transaxle114includes a dual pivotable knuckles assembly136having both of the steerable axle supports40,41attached thereto such that the dual pivotable knuckles assembly136can be pre-assembled and then attached to transmission20to form transaxle114.

In transaxle114, a first pivot bearing support128jis connected to a second pivot bearing support128kby an integrally formed crossmember128mdisposed under the housing22to form a pivot bearings support128. Pivot bearing supports128jand128kof pivot bearings support128correspond to pivot bearing supports30and31, respectively, of transaxle14of the first embodiment. Crossmember128mprotects portions of transaxle114, and particularly transmission20of transaxle114, from flexural and/or impact damage.

Each of the pivot bearing supports128jand128kincludes openings128aand128b, corresponding to similar openings30aand30b, respectively, shown in the first embodiment. In like manner to the first embodiment, openings128aand128breceive fasteners170and171that are similar to fasteners70and71, respectively, and serve the same function. Each of the pivot bearing supports128jand128kalso includes cylindrical openings128c, openings128dand recesses128ethat correspond to the same or similar openings30c, openings30dand recesses30e, respectively. A pivot bearing133is installed in each of the cylindrical openings128c. Each pivot bearing133is illustrated as a composite bearing that does not require lubrication.

The integrally formed crossmember128mmay have a simple rectangular cross-section. Optionally, as shown inFIGS. 7 and 8, an integrally formed crossmember129mof a pivot bearings support129of a dual pivotable knuckles assembly137has an I-beam cross-section for greater strength and flexural resistance. All other features of pivot bearings support129, i.e.,129a,129b,129c,129d,129e,129jand129kare substantially the same as previously-described features128a,128b,128c,128d,128e,128jand128k, respectively, of pivot bearings support128such that pivot bearings support129is interchangeable with pivot bearings support128.

Referring toFIG. 11, a generic vehicle210that is similar to generic vehicle10, but having just one transaxle14attached to a vehicle frame212, is depicted. Vehicle210is a four-steered-wheel, two-wheel-drive vehicle. To enable this configuration, the gear sets and certain other components shown inFIG. 2have been removed from pivotable knuckle assembles38and39to form pivotable knuckle assemblies238and239, respectively. Pivotable knuckle assembly238is illustrated inFIGS. 9 and 10and pivotable knuckle assembly239can be a mirror image of pivotable knuckle assembly238, as shown inFIG. 11. Thus, the basic structural components of pivotable knuckle assemblies238and239can be the same as those used in pivotable knuckle assemblies38and39, respectively, thereby further facilitating modularity. As shown inFIG. 10, a shorter axle242is used in pivotable knuckle assembly238in lieu of axle42used in pivotable knuckle assembly38shown inFIG. 2. Alternatively, axle42can be used in pivotable knuckle assembly238by adding a spacer in place of the removed gear44a. In yet another alternative configuration, a pivot bearings support128or129can be used in lieu of the bearing supports30,31shown inFIG. 11, in the same manner as illustrated inFIGS. 6-8.