Transmission and engine configuration

A drive train configuration is disclosed. The drive train configuration has a transmission or transaxle assembly which may be directly mounted to a vehicle frame. The drive train configuration also comprises an engine that may be attached to a housing of the transmission or transaxle portion. The drive train configuration may also have a power take off mechanism.

BACKGROUND OF THE INVENTION

This invention relates to drive train configurations; in particular, drive train configurations that include a prime mover or engine and a transmission or transaxle assembly.

SUMMARY OF THE INVENTION

An engine and transmission assembly is disclosed herein. The transmission assembly may include gearing and axles. The engine is physically supported by the transmission assembly, forming a drive train assembly. The details of the invention are set forth below in connection with the detailed description of the embodiments.

A better understanding of the invention will be obtained from the following detailed descriptions and accompanying drawings, which set forth illustrative embodiments that are indicative of the various ways in which the principals of the invention may be employed.

DETAILED DESCRIPTION OF THE DRAWINGS

Turning now to the figures, there is illustrated inFIG. 1an embodiment of the invention. Drive train assembly10comprises a prime mover in the form of engine12, which is mounted on a transmission or transaxle assembly14. Additional details of transaxle assembly14may be seen inFIGS. 2 and 3. Engine12has an output shaft16that engages input member18of transaxle assembly14. As shown inFIG. 1, output shaft16drives input member18which in turn drives first gear20. First gear20then drives second gear22and third gear24. Input member18is also selectively engageable to power take off26, as shown inFIG. 8and as discussed in detail below. When power take off26is engaged, output shaft16is coupled to power take off shaft28, which may then be used to drive an implement such as a mowing deck (not shown) or have a pulley mounted thereon for the purpose of connecting power take off shaft28by means of a belt to a driven device such as an auxiliary pump (not shown).

Power take off mechanisms, such as power take off26, are well known in the art. Moreover, it will be appreciated by those in the art that any number of power take off mechanisms will be covered by the scope of the present invention. In the embodiment shown, output shaft16is coupled to input member18. Input member18is the coupling rotor of power take off26. Input member18is splined (or otherwise engaged), as shown inFIGS. 8 and 10, to first gear20so that output shaft16drives both power take off input member18and first gear20.

A brake assembly58may be located on each of the motor output shafts37and49. The disc-style brake assembly58shown is well known in the art and is not illustrated in detail. Additional elements that may house and actuate brake pads59are not shown but are well known in the art.

As shown inFIGS. 8,9and10, first gear20rotates in gear chamber21on pressure plate19, which is seated in central housing66. Pressure plate19serves as a gear pump running surface for gear20. Second gear22rotates in second gear chamber23on gear pump running surface98and third gear24rotates in third gear chamber25on gear pump running surface99. In the embodiment shown, gear pump running surfaces98and99are integrally formed in housing66. In an alternative embodiment (not shown) pressure plates similar to pressure plate19may be added to gear chambers98and99to prevent excessive wear to housing66.

The configuration and operation of hydraulic pumps, motors, shafts and gearing such as that shown inFIGS. 3 and 8is well known in the art and will only briefly be explained herein. Details of such hydraulic components can be found, for example, in U.S. Pat. No. 6,705,840, which is incorporated herein by reference in its entirety. Second gear22is coupled to a first pump shaft30that then drives first pump32. First pump32may be mounted on a first center section34, on which may be mounted a first motor36. First motor36may then drive a first gear train38that then drives a first axle shaft40. Axle shaft40may drive a vehicle tire (not shown) or other mechanism. First motor36may also directly drive axle shaft40rather than driving a gear train.

Third gear24is similarly coupled to second pump shaft42that then drives second pump44. Second pump44may be mounted on a second center section46, on which may be mounted a second motor48. It will be understood that center sections34and46will include hydraulic porting (not shown) to connect the respective pumps and motors. Second motor48may then drive a second gear train50that then drives a second axle shaft52. Second axle shaft52may drive a vehicle tire (not shown) or other mechanism. Second motor48may also directly drive second axle shaft52rather than driving a gear train.

In combination, gears20and22or gears20and24may form a gear pump that may be used to provide replenishment fluid to first pump32and first motor36and second pump44and second motor48as well as hydraulic pressure to actuate power take off26. Generally, using input gears as gear pumps is generally known in the art, an example of which is disclosed in, for example, U.S. Pat. No. 7,225,617, which is incorporated herein by reference in its entirety.

Drive train assembly10and transaxle assembly14may further comprise actuator arms54to modify the position of swash plates56, and thus the displacements of first pump32and second pump44. First motor36and second motor48may also be adjustable in displacement.

The housings of transaxle assembly14may provide multiple functions. By way of example, the housings may provide containment for the internal elements of transaxle assembly14previously described. As shown inFIGS. 2 and 7, the housings may also provide attachment points60to aid in attachment of drive train assembly10to a vehicle frame62. Central housing66shown in, among others,FIGS. 2,4,5,6and7, also provides engine support pads64for attachment of engine12. Thus, attachment of engine12to transaxle assembly14creates drive train assembly10and allows an equipment manufacturer to simplify installation of the engine and transaxle assembly by forming a unitary assembly prior to installation in a vehicle. Three-point attachment of assembly10to frame62is illustrated inFIG. 7, but additional attachment points may be added to housing members of transaxle14, if needed. This may be done to reduce and control stresses imparted to transaxle14when frame62flexes.

Central housing66may also provide locations for numerous elements of drive train assembly10. For example, accumulator chamber68may be provided to help operate power take off26and to function as a charge fluid gallery to provide replenishment fluid to first center section34and second center section46. Additionally, central housing66may comprise passages77, which connect chamber68to center sections34and46as shown inFIGS. 5 and 6. There are two passages77connecting chamber68with each of the center sections34and46. Check valves79, located in center sections34and46between each passage77and pumps32and34, may additionally be provided. Accumulators such as accumulator chamber68are well known in the art and will not be described in detail herein. Moreover, it will be appreciated by those of skill in the art that any number of accumulators will be covered by the scope of the present invention. As such, the elements of the accumulator chamber68will only be generally described.

In the depicted embodiment as shown inFIGS. 9 and 10, piston87interfaces with the wall of piston chamber69in central housing66such that it divides accumulator piston chamber69into a lower portion69aand upper portion69b. Pressurized fluid may flow into accumulator piston chamber69from accumulator chamber68. The pressure in the lower portion of accumulator piston chamber69is equal to the pressure in the hydraulic circuit formed in drive transaxle assembly14. Under normal operating conditions, the force from the fluid pressure is greater than the force provided by spring88and thus spring88is compressed. If for any reason, such as the engagement of power take off26, there is a pressure drop across the transaxle assembly14, the force in spring88will be greater than the force from the fluid pressure and piston87driven by spring88will descend into lower portion69aof accumulator piston chamber69, pushing the accumulated lower pressure fluid into chamber68through passage89thus repressurizing the hydraulic circuit in transaxle assembly14for a short period of time.

As shown in, e.g.,FIG. 6, a pocket70may be provided in central housing66to locate a power take off clutch assembly and optional brake (not shown) of power take off26. The brake which may be located in pocket70facilitates deceleration of power take off shaft28and then prevents shaft28from moving when the power take off26is in a non-actuated condition.

A valve80may also be provided in central housing66to control power take off26. Valve80may be manually actuated or may be remotely hydraulically or electrically actuated. The details of such manual or remote actuation are not shown, but such manual and remotely actuated valves are well known in the art. Valve80may reside in a port82formed in central housing66. Pressurized fluid flows from accumulator chamber68into valve80by way of opening72. Valve80then directs pressurized fluid through opening73to annular region74, which is accessible to internal passages75formed in power take off shaft28.

Pressurized fluid in internal passages75may cause power take off26to be actuated. For example, pressurized fluid flowing from internal passages75may move a clutch piston, which in turn compresses clutch stators and clutch rotors, engaging a power take off clutch assembly and coupling input member18with power take off shaft28. Similarly, valve80may release pressure by way of passage76to reservoir78to permit power take off26to be deactivated. Valve80may also provide a pathway to release pressure from any passageways associated with a brake or a power take off clutch assembly.

Additionally, fluid filter90may also be provided inside central housing66as shown inFIGS. 9 and 10. The details of fluid filter90are not shown because fluid filters are well known in the art. Those of ordinary skill in the art will also understand that fluid filter90may be located at a multitude of locations along the hydraulic circuit formed in central housing66which drives transaxle assembly14. In the depicted embodiment, pump kidneys67aand67bare formed in running surface99of housing66to serve as fluid passages to provide pressurized fluid (resulting from the interface of gears20and24) to filter chamber91. Pressurized fluid flows through filter90into chamber68by way of passage92.

Certain optional elements may be provided. For example, an expansion tank, expansion volume or expansion volumes may be present. An internal expansion volume may be formed when gear train housing elements95aand96aare assembled together to form gear train housing assembly94aon one side of housing66and a separate volume may be formed when gear train housing elements95band96bare assembled together to form gear train housing assembly94bon the opposite side of housing66. Expansion tubes84aand84bas shown inFIGS. 2,7and8(or equivalent internal passages not shown) connect reservoir78of housing66with the fluid expansion volume in gear train housing assemblies94aand94b, respectively. Housing assemblies94aand94binclude overflow tubes85in the event fluid expands to a volume greater than the expansion volume available in gear train housing assemblies94aand94b. Note that it may be possible to use only one of the housing assemblies94aor94bas an expansion volume and therefore, only one of the expansion tubes84aor84bmay be needed, but both housing assemblies94aand94bmay still require overflow tubes85or other known venting elements.

In order for gear train housing assemblies94aand94bto function as expansion tanks, they must be sealed from housing66so that the fluid volumes contained in housing assemblies94aand94bare separated from the housing66fluid volume in a manner which permits fluid transfer (discharge and siphoning) through each of tubes84aand84b. If they are not sealed from housing66in a manner that allows them to be used as internal fluid expansion compartments, then an external expansion tank may be required.

In an alternate embodiment (not shown), output shaft16of engine12may rotate in the opposite direction. In that case, the positions of filter90and accumulator piston assembly86may be switched due to the resultant switch between pressure sides related to forward and reverse of a vehicle. As shown, the configuration of chambers69and91may be equivalent to enable easy switching of these elements and therefore, flexibility in manufacturing. Note that pump kidneys67aand67bwould be formed in running surface98instead of running surface99to accommodate opposite rotation of shaft16.