A hydrostatic transaxle for use as a drive apparatus of a vehicle is provided. The hydrostatic transaxle includes a main housing joined to a gear housing to enclose a hydrostatic transmission and a reduction gear set. The hydrostatic transmission includes an axial piston pump assembly and an axial p
A hydrostatic transaxle for use as a drive apparatus of a vehicle is provided. The hydrostatic transaxle includes a main housing joined to a gear housing to enclose a hydrostatic transmission and a reduction gear set. The hydrostatic transmission includes an axial piston pump assembly and an axial piston motor assembly arranged in a parallel configuration on one side of a center section. A charge pump is contained within a pocket on an opposing side of the center section. A charge pump cover assembly secures the charge pump in the pocket and has a charge relief assembly that extends into a void volume defined by a ring gear of the gear reduction set. The gear reduction set drives an axle extending from the gear housing.
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1. A transaxle comprising: a main housing having disposed therein an axial piston pump driven by a pump input shaft, an axial piston motor with a motor output shaft, and a center section assembly, said center section assembly comprising: a center section having a pump running surface and a motor run
1. A transaxle comprising: a main housing having disposed therein an axial piston pump driven by a pump input shaft, an axial piston motor with a motor output shaft, and a center section assembly, said center section assembly comprising: a center section having a pump running surface and a motor running surface on a first side, a pocket formed on a second side opposite the first side and porting formed therein to connect the pump running surface to the motor running surface;a charge pump disposed in the pocket and driven by the pump input shaft;a charge pump cover disposed over said pocket, said charge pump cover having an external surface, an internal surface defining a charge gallery and a charge relief passage through said charge pump cover; anda charge relief tower extending from the external surface of the charge pump cover and communicating with the charge relief passage, said charge relief tower having a charge relief assembly fixed thereto;a gear housing fastened to said main housing; anda reduction gear set disposed in the gear housing and comprising a pinion gear driven by the motor output shaft and driving a ring gear, said reduction gear set driving an axle, wherein said charge relief tower extends into a void volume defined by the circumference of said ring gear. 2. The transaxle of claim 1, further comprising a second pocket formed in the second side of the center section to support an end of the axle in the second side of the center section. 3. The transaxle of claim 2, wherein the charge pump cover further comprises a clearance pocket to allow clearance of the pump input shaft with respect to the charge pump cover. 4. The transaxle of claim 1, wherein the charge gallery is comprised of two internal volumes disposed between the charge pump cover and the second side of the center section, and a center passage extending between the two internal volumes, wherein the center passage extends in a direction that is generally perpendicular to a plane formed by the axes of rotation of the pump input shaft and the motor output shaft. 5. The transaxle of claim 4, further comprising a first check valve and a second check valve extending into the center section from the second side thereof to permit hydraulic fluid to enter the porting, wherein the first check valve is disposed adjacent one of the two internal volumes and the second check valve is disposed adjacent the other of the two internal volumes. 6. The transaxle of claim 4, wherein the charge relief passage is disposed in the center passage. 7. The transaxle of claim 4, wherein the gear housing and the main housing form a common sump for the pump, the motor and the reduction gear set, and the charge pump cover further comprises a charge pump inlet extending through the charge pump cover to permit hydraulic fluid to flow from the common sump to the charge pump. 8. The transaxle of claim 7, wherein the charge pump cover further comprises a clearance pocket to allow clearance of the pump input shaft with respect to the charge pump cover, and the charge pump inlet is disposed on one side of the clearance pocket and the center passage is disposed on a second side of the clearance pocket opposite the first side. 9. A center section assembly for a hydrostatic transmission having a pump driven by a pump input shaft and a motor driving a motor output shaft, the center section assembly comprising: a center section having a pump running surface and a motor running surface formed on a first side thereof, and a pocket for a charge pump formed on a second side thereof, opposite the first side;a charge pump cover engaged to the center section and disposed over said pocket, said charge pump cover having an internal surface defining a charge gallery;a charge relief passage in communication with the charge gallery and extending through said charge pump cover; anda charge relief tower extending from an external surface of said charge pump cover and communicating with the charge relief passage, said charge relief tower having a charge relief valve disposed therein to permit hydraulic fluid to discharge from the charge relief passage into a sump. 10. The center section assembly of claim 9, further comprising a second pocket to support an end of an axle in the second side of the center section. 11. The center section assembly of claim 9, wherein the charge pump cover further comprises a clearance pocket to allow clearance of the pump input shaft with respect to the charge pump cover. 12. The center section assembly of claim 11, wherein the charge gallery is comprised of two internal volumes disposed between the charge pump cover and the second side of the center section, and a center passage extending between the two internal volumes, wherein the center passage extends in a direction that is generally perpendicular to a plane formed by the axes of rotation of the pump input shaft and the motor output shaft. 13. The center section assembly of claim 12, further comprising a first check valve and a second check valve extending into the center section from the second side thereof to permit hydraulic fluid to enter the porting, wherein the first check valve is disposed adjacent one of the two internal volumes and the second check valve is disposed adjacent the other of the two internal volumes. 14. A drive apparatus, comprising: a first housing member joined to a second housing member to form an internal sump;a transmission disposed in the internal sump and comprising a pump driven by a pump input shaft, a motor driving a motor output shaft, and a center section having a pump running surface on which the pump is rotatably disposed and a motor running surface on which the motor is rotatably disposed, wherein the pump running surface and the motor running surface are located on a first side of the center section and are connected by means of hydraulic porting formed in the center section;a first check valve and a second check valve disposed in the center section on a second side thereof, opposite the first side;a charge pump is disposed on the second side of the center section and driven by the pump input shaft;a charge pump cover mounted to the second side of the center section and disposed over the charge pump, the charge pump cover having an external surface and an internal surface defining a charge gallery comprising a first internal volume located adjacent the first check valve, a second internal volume adjacent the second check valve, a center passage connecting the first internal volume with the second internal volume, and a charge relief passage through said charge pump cover at the center passage to permit hydraulic fluid to be exhausted from the charge gallery to the internal sump; anda reduction gear set disposed in the internal sump and comprising a pinion gear driven by the motor output shaft and driving a ring gear,an axle disposed in the second housing member and driven by the reduction gear set, one end of the axle extending out of the second housing member. 15. The drive apparatus of claim 14, further comprising a charge relief tower extending from the external surface of the charge pump cover and communicating with the charge relief passage, said charge relief tower having a charge relief assembly fixed thereto, wherein said charge relief tower extends into a void volume defined by the circumference of said ring gear. 16. The drive apparatus of claim 15, wherein the charge relief tower extends in an axial direction that is parallel to an axis of rotation of the pump input shaft. 17. The drive apparatus of claim 14, wherein the charge pump comprises a gerotor disposed in a pocket formed on the second side of the center section. 18. The drive apparatus of claim 14, wherein a second end of the axle is supported in the second side of the center section. 19. The drive apparatus of claim 14, wherein the charge pump cover further comprises a clearance pocket to allow clearance of the pump input shaft with respect to the charge pump cover. 20. The drive apparatus of claim 14, wherein the center passage extends in a direction that is generally perpendicular to a plane formed by the axes of rotation of the pump input shaft and the motor output shaft.
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이 특허에 인용된 특허 (15)
Hauser Ray (Decatur IL) Smothers Daryl (Sullivan IL) Schreier John (Villa Grove IL), Auxiliary pumps for axle driving apparatus including hydrostatic transmission.
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