Variable speed transaxle - Patent Review 4979583

Claims

What is claimed is:

1. An axle assembly comprising a housing for an internally disposed hydrostatic transmission and forming an integral part of said hydrostatic transmission; axle shafts rotatably supported in said housing; said housing being defined by at least two separable elements of said axle assembly, wherein at least two of said elements are separable at a parting plane generally containing the longitudinal axes of said axle shafts; and differential gearing means supported by said housing drivingly connected between said hydrostatic transmission and said axle shafts.

2. An axle assembly according to claim 1 wherein said hydrostatic transmission includes at least one power transmission shaft and wherein said elements locate said power transmission shafts.

3. An axle assembly according to claim 1 wherein a gear train is internally disposed within said housing.

4. An axle assembly according to claim 1 wherein said hydrostatic transmission includes a pump and a motor mounted to respective sides of a central member.

5. An axle assembly comprising two main housing elements together defining an internal cavity in which a hydraulic hydrostatic transmission is encapsulated, said hydrostatic transmission comprising pintle support means dividing said cavity into first and second chambers; a pintle fixedly and non-rotatably mounted in said pintle support means, said pintle having first and second ends extending into said first and second chambers, respectively, and internal first and second hydraulic fluid passages terminating in ports; a rotary cylinder barrel rotatably mounted on each end of said first and second extending pintle ends, each said barrel comprising a plurality of radially arranged cylinders and a plurality of pistons disposed in said cylinders, said cylinders successively communicating with said ports during rotation of said barrels; an annular cam track surrounding each said barrel, said pistons operatively connected to the respective cam track; first and second rotary shafts, each said rotary shaft being rotatably mounted in one said housing element, respectively, said rotary shafts extending into said first and second chambers, respectively; and means coupling said rotary shafts to said barrels.

6. An axle assembly according to claim 5 wherein the said internal cavity is formed when the said two housing elements are assembled and located together.

7. An axle assembly according to claim 5, wherein said pintle support means is secured between the said two housing elements.

8. An axle assembly according to claim 5, wherein said hydrostatic transmission includes a gear train disposed within the said two housing elements.

9. An axle assembly according to claim 5, including axle shafts rotatably supported in said housing elements and means drivingly connecting one of said first and second rotary shafts to said axle shafts, and where said housing elements are separable at a parting plane generally containing the longitudinal axes of the axle shafts.

10. An axle assembly according to claim 5, wherein the said hydrostatic transmission includes an oil expansion tank disposed within the said two housing elements.

11. An axle assembly comprising two main housing elements encapsulating a separate dished housing supporting a hydraulic hydrostatic transmission, said dished housing serving to segregate a gear compartment of the axle assembly from an oil compartment of the hydrostatic transmission, said hydrostatic transmission comprising pintle support means dividing said oil compartment into first and second chambers; a pintle fixedly and non-rotatably mounted in said pintle support means, said pintle having first and second ends extending into said first and second chambers, respectively, and internal first and second hydraulic fluid passages terminating in ports; a rotary cylinder barrel rotatably mounted on each of said first and second extending pintle ends, each said barrel comprising a plurality of radially arranged cylinders and a plurality of pistons disposed in said cylinders, said cylinders successively communicating with said ports during rotation of said barrels; an annular cam track surrounding each said barrel, said pistons operatively connected to the respective cam track; first and second rotary shafts, said first rotary shaft being rotatably mounted in one housing element, said second rotary shaft being rotatably mounted in said dished housing, said first and second rotary shafts extending into said first and second chambers, respectively; and means coupling said first and second rotary shafts to said barrels.

12. An axle assembly according to claim 11 wherein the said pintle support means is secured between the said dished housing and one of the said main housing elements.

13. An axle assembly comprising two main housing elements of which one defines a recessed chamber in which a hydraulic hydrostatic transmission is located, said hydrostatic transmission comprising pintle support means dividing said recessed chamber into first and second compartments; a pintle fixedly and non-rotatably mounted in said pintle support means, said pintle having first and second ends extending into said first and second compartments, respectively, and internal first and second hydraulic fluid passages terminating in ports; a rotary cylinder barrel rotatably mounted on each of said first and second extending pintle ends, each said barrel comprising a plurality of radially arranged cylinders and a plurality of pistons disposed in said cylinders, said cylinders successively communicating with said ports during rotation of said barrels; an annular cam track surrounding each said barrel, said pistons operatively connected to the respective cam track; an auxiliary housing providing enclosure means to said recessed chamber; a first rotary shaft rotatably mounted in said auxiliary housing, and a second rotary shaft rotatably mounted in one said housing element, said rotary shafts extending into said first and second compartments, respectively; and means coupling said rotary shafts to said barrels.

14. An axle assembly according to claim 13 wherein the said pintle support means is secured between the said auxiliary housing and one of the said main housing elements.

15. An axle according to claim 13 wherein the transmission includes a gear train disposed within the said main housings elements.

16. An axle assembly according to claim 13 including axle shafts rotatably supported in said housing elements and means drivingly connecting one of said first and second rotary shafts to said axle shafts, and where said housing elements are separable at a parting plane generally containing the longitudinal axes of the axle shafts.

17. An axle assembly comprising two housing elements providing two internal chambers in which a hydraulic hydrostatic transmission is encapsulated, said hydrostatic transmission comprising a pintle fixedly and non-rotatably mounted between two said housing elements, said pintle having first and second ends extending into said first and second chambers, respectively, and internal first and second hydraulic fluid passages terminating in ports; a rotary cylinder barrel rotatably mounted on each of said first and second extending pintle ends, each said barrel comprising a plurality of radially arranged cylinders and a plurality of pistons disposed in said cylinders, said cylinders successively communicating with said ports during rotation of said barrels; and annular cam track surrounding each said barrel, said pistons operatively connected to the respective cam track; first and second rotary shafts rotatably mounted between the two housing elements, said rotary shafts extending into said first and second chambers, respectively; and means coupling said rotary shafts to said barrels.

18. An axle assembly according to claim 17 wherein the said two housing elements act to provide a partition wall between the said cylinder barrels, said partition wall being formed as an integral part of the said two housing elements.

19. An axle assembly according to claim 17 wherein the said hydrostatic transmission includes a gear train disposed within the said housing elements, said gear train being located and supported between said housing elements.

20. An axle assembly according to claim 16 including axle shafts rotatably supported in said housing elements and means drivingly connecting one of said first and second rotary shafts to said axle shafts, and where said housing elements are separable at a parting plane generally transverse to the longitudinal axes of the axle shafts.

21. An axle assembly comprising:

a housing including two main housing elements defining an internal cavity;

a hydraulic hydrostatic transmission encapsulated in said cavity, said hydrostatic transmission comprising means dividing said cavity into first and second chambers, a hydrostatic pump in one chamber and a hydrostatic motor operatively coupled to said pump and being disposed in the other chamber;

axle shafts rotatably supported in said housing;

said housing elements being separable at a parting plane generally containing the longitudinal axes of said axle shafts; and

differential gearing means within said housing drivingly connected between said hydrostatic motor and said axle shafts.

22. The axle assembly of claim 21 wherein said dividing means is secured between said main housing elements.

23. The axle assembly of claim 21 wherein said axle shafts are coaxial and said parting plane is generally coincident with the axis of said axle shafts.

24. The axle assembly of claim 22 including a pintle mounted in said dividing means, said pintle having first and second ends extending into said first and second chambers, respectively, and internal first and second hydraulic fluid passages, and wherein said hydrostatic pump and said hydrostatic motor are fluidly connected by means of said passages.

25. The axle assembly of claim 15 wherein said pintle is fixedly and non-rotatably connected to said dividing means, and wherein said hydrostatic pump and motor each comprises a rotary cylinder barrel rotatably mounted on said first and second ends, respectively, of said pintle and including cylinders in fluid communication with said fluid passages as said barrels rotate, said hydrostatic pump and motor including radially oriented pistons in said cylinders.

26. The axle assembly of claim 16 including a vertically oriented input shaft rotatably mounted in one housing element and connected to said hydrostatic pump, and a vertically oriented output shaft rotatably mounted in the other housing element and connected to said hydrostatic motor.

27. The axle assembly of claim 16 wherein said dividing means is secured between said main housing elements.

28. The axle assembly of claim 12 including a vertically oriented input shaft rotatably mounted in one housing element and connected to said hydrostatic pump, and a vertically oriented output shaft rotatably mounted in the other housing element and connected to said hydrostatic motor.

29. The axle assembly of claim 19 wherein said dividing means is secured between said main housing elements.

30. The axle assembly of claim 12 wherein said housing includes a gearing compartment containing said differential gearing, said housing segregating said differential gearing compartment from said internal cavity.

31. The axle assembly of claim 21 wherein said dividing means is secured between said main housing elements.

32. The axle assembly of claim 22 including a pintle mounted in said dividing means, said pintle having first and second ends extending into said first and second chambers, respectively, and internal first and second hydraulic fluid passages, and wherein said hydrostatic pump and said hydrostatic motor are fluidly connected by means of said passages, and including a pair of check valve means in said first and second pintle passages, respectively, both said check valve means being disposed at either or both ends of said pintle.

33. The axle assembly of claim 22 wherein said dividing means comprises an intermediary member between said hydrostatic pump and hydrostatic motor, and a dish element forming a wall of one of said chambers and being in engagement with said intermediary member and at least one of said housing elements.

34. The axle assembly of claim 24 wherein said dividing means is secured between said main housing elements.

35. The axle assembly of claim 25 wherein said axle shafts are coaxial and said main housing elements are connected together along a parting plane that is generally coincident with the axis of said axle shafts.

36. The axle assembly of claim 24 wherein said housing includes a gearing compartment containing said differential gearing, and said dish element segregates said gearing compartment from said hydrostatic transmission cavity.

37. The axle assembly of claim 24 wherein said dish element is connected to an upper ne of said main housing elements.

38. An axle assembly comprising:

a housing including two main housing elements and a hydrostatic transmission cover element, said housing defining a hydrostatic transmission cavity between said cover element and one of said main housing elements and defining a gearing compartment between said main housing elements,

a hydraulic hydrostatic transmission encapsulated in said cavity, said hydrostatic transmission including means dividing said cavity into first and second chambers, a hydrostatic pump disposed in said first chamber and a hydrostatic motor operatively coupled to said pump and being disposed in said second chamber,

coaxial axle shafts rotatably supported in said housing,

said housing elements being separable at a parting plane parallel to the longitudinal axes of said coaxial axle shafts, and

differential gearing means within said housing drivingly connected between said hydrostatic motor and said coaxial axle shafts.

39. The axle assembly of claim 29 including a pintle mounted in said dividing means, said pintle having first and second ends extending into said first and second chamber, respectively, and internal first and second hydraulic fluid passages, and wherein said hydrostatic pump and said hydrostatic motor are fluidly connected by means of said passages.

40. An axle assembly comprising:

a housing including two main housing elements connected together along a parting plane and defining an internal cavity,

a hydrostatic transmission encapsulated in said cavity and including first and second chambers, a hydrostatic pump in one chamber and a hydrostatic motor fluidly coupled to the hydrostatic pump and being disposed in the other chamber,

coaxial axle shafts rotatably supported in said housing,

said housing elements being separable at said parting plane that is generally parallel to the longitudinal axes of said coaxial axle shafts, and

gearing means in said housing drivingly connected between said hydrostatic motor and said coaxial axle shafts.

41. The axle assembly of claim 31 wherein said hydrostatic transmission includes:

means dividing said cavity into said chambers and a fixed pintle mounted in said dividing means, said pintle including internal passages for providing fluid communication between said hydrostatic pump and motor.

42. The axle assembly of claim 32 wherein said hydrostatic pump and motor each includes a cylinder barrel rotatably mounted on opposite ends of said pintle.

43. The axle assembly of claim 33 wherein said dividing means is secured is clamped between said main housing elements.

44. The axle assembly of claim 31 including a gearing compartment in said housing containing said gearing means, said housing including a wall separating said gearing means from said hydrostatic transmission first and second chambers.

45. An axle assembly according to claim 4 wherein said central member forms a component part of said hydrostatic transmission and is held between said separable elements.

46. An axle assembly according to claim 4 wherein said central member is formed as a component part of at least one of said separable elements comprising said housing.

47. An axle assembly according to claim 5, including axle shafts rotatably supported in said housing elements and means drivingly connected one of said first and second rotary shafts to said axle shafts, and where said housing elements are separable at a parting plane generally transverse to the longitudinal axes of the axle shafts.

48. An axle assembly according to claim 11, including axle shafts rotatably supported in said housing elements and means drivingly connecting one of said first and second rotary shafts to said axle shafts, and where said housing elements are separable at a parting plane generally containing the longitudinal axes of the axle shafts.

49. An axle assembly according to claim 11, including axle shafts rotatably supported in said housing elements and means drivingly connecting one of said first and second rotary shafts to said axle shafts, and where said housing elements are separable at a parting plane generally transverse to the longitudinal axes of the axle shafts.

50. An axle assembly according to claim 13, including axle shafts rotatably supported in said housing elements and means drivingly connecting one of said first and second rotary shafts to said axle shafts, and where said housing elements are separable at a parting plane generally transverse to the longitudinal axes of the axle shafts.

51. An axle assembly according to claim 17, including axle shafts rotatably supported in said housing elements and means drivingly connecting one of said first and second rotary shafts to said axle shafts, and where said housing elements are separable at a parting plane generally containing the longitudinal axes of the axle shafts.

52. The axle 1 assembly of claim 12 wherein said housing includes a gearing compartment containing said differential gearing, said housing segregating said differential gearing compartment from said internal cavity.

53. The axle assembly of claim 29 wherein said housing includes a gearing compartment containing said differential gearing, and said housing elements segregates said gearing compartment from said hydrostatic transmission cavity.

54. The axle assembly of claim 32 wherein the said dividing means forms part of said main housing elements.

55. An axle assembly comprising:

a housing including two main housing elements connected together along a parting plane and defining first and second internal cavities separated from each other,

a hydrostatic transmission encapsulated in said first cavity, and means dividing said first cavity into first and second chambers, a hydrostatic pump in one chamber and a hydrostatic motor fluidly coupled to the hydrostatic pump and being disposed in the other chamber,

axle shafts rotatably supported in said housing, and

gearing means located in said second cavity and drivingly connected between said hydrostatic motor and said axle shafts.

56. The axle assembly of claim 46 wherein said main housing elements are separable at a plane generally parallel to the longitudinal axes of the axle shafts.

57. The axle of assembly of claim 46 wherein said main housing elements are separable at a plane generally containing the longitudinal axes of the axle shafts.

58. An axle assembly of claim 46 wherein said housing includes a wall separating said second cavity from said hydrostatic transmission first and second chambers.

59. An axle assembly of claim 49 wherein said wall acts to prevent hydraulic fluid contained within said first and second chambers of said hydrostatic transmission from entering said second cavity containing said gearing means.

60. An axle assemble comprising:

a housing including two main housing elements connected together along a parting plane and defining at least two internal cavities,

a hydrostatic transmission, comprising a hydrostatic pump and a hydrostatic motor, at least partly disposed in one or more cavities;

gearing means disposed in at least one other cavity; said gearing means drivingly connecting said hydrostatic motor to axle shafts, and said cavities associated with said hydrostatic transmission and said cavities associated with said gearing means of the axle shafts being segregated.

61. The axle assembly of claim 51 wherein said axle shafts are rotatably supported in said housing, and said main housing elements are separable at a plane generally transverse to the longitudinal axes of the shafts.

62. The axle assembly of claim 51 wherein said axle shafts are rotatably supported in said housing, and said main housing elements are separable at a plane generally containing the longitudinal axes of the axle shafts.

63. An axle assembly according to claim 3 wherein said gear train and said hydrostatic transmission are supported and positioned in pockets that are formed between said separable elements of said housing, and wherein said separable elements form partition means between said gear train and said hydrostatic transmission.

64. An axle assembly comprising a housing having a first cavity for an internally disposed hydrostatic transmission, said first cavity forming an integral part of said hydrostatic transmission; axle shafts rotatably supported in said housing; said housing being defined by at least two separable elements of said axle, wherein at least two of said elements are separable at a parting plane generally transverse to the longitudinal axes of said axle shafts; and differential gearing means within a second cavity of and supported by said housing drivingly connected between said hydrostatic transmission and said axle shafts, said first and second cavities being segregated from each other.

65. An axle assembly according to claim 64 wherein a gear train is internally disposed within said housing.

66. An axle assembly according to claim 65 wherein said gear train and said hydrostatic transmission are supported and positioned in pockets that are formed between said separable elements of said housing, and where said separable elements form partition means between said gear train and said hydrostatic transmission.

This invention relates to axles and in particular but not exclusively to an improved Lawn tractor axle built with two segregated internal chambers, one in which houses the gear and differential assembly, the other housing to the hydrostatic transmission, and in particular a hydrostatic transmission of the type where both pump and motor are mounted back to back either side of a central plate.

Existing hydrostatic transmissions of the back to back type currently fitted to such vehicles require a separate axle containing the necessary reduction gearing and differential. Such hydrostatic transmissions are obtained as self contained units including their own end housings, and where the hydrostatic transmission is attached to an external face of the axle by bolts.

The prohibiting factor which at present prevents such hydrostatic machines gaining a larger market share in such vehicles, is that the combined cost of the hydrostatic transmission and the axle amounts to over double the price when compared to a conventional mechanical shift transmission.

A further disadvantage of all current hydrostatic transmission is that the combined height dimension when the hydrostatic transmission is mounted onto the axle is too great to allow for its application to the mass produced lower horsepower tractors where the vertical engine shaft and drive wheels of 18 inches diameter or less, are becoming by far the most common vehicle configuration. This is due to the limited space available between the ground and the underside of the tractor chassis, and therefore the height dimension of the axle is of critical importance.

As it is these lower horsepower tractors which are produced in far larger number then the higher horsepower tractors, a unconventional approach is required to satisfy both cost and dimensional requirements if a new hydrostatic transmission is to make a breakthrough in this market area, and it is therefore the aim of the invention to provide solutions which will largely overcome these existing problems.

Thus one object of the invention is to provide an axle into which a hydrostatic transmission can be assembled as one component part, without regarding the usual and expensive two end housings of the hydrostatic transmission.

The invention, in one form thereof, relates to a hydrostatic transmission including a radial piston pump coupled to a radial piston hydrostatic motor, the pump and motor each comprising a rotary cylinder barrel provided generally radial cylinders which accommodate pistons co-operating with a surrounding annular cam track, both cylinder barrels being mounted on a common fixed pintle provided with internal fluid flow and return passages which form a closed hydraulic circuit. Preferably the pintle is provided with check valves communicating with the machine chamber and arranged to open automatically to admit make-up fluid to the circuit. The pintle is fixedly and non-rotatably mounted in a sandwich plate which acts as a partitioning wall between the pump and motor. Transmission means are provided for coupling the rotary cylinder barrel members to their respective drive shafts, one or preferably both drive shafts being supported and positioned in the main axle housings.

The hydrostatic transmission is totally incapsulated inside an inbetween the two main axle housings elements. The two main axle housing when bolted together lock and locate both the hydrostatic transmission as well as the gear reduction and differential assembly. The two main chambers inside the axle containing the hydrostatic transmission and the gearing are purposely segregated so avoiding metal material worn away from the gears from finding its way into the closed oil circuit of the hydrostatic transmission.

According to the preferred embodiment of the invention the central sandwich plate of the hydrostatic transmission is intentionally wedged into a locked position between the two housings of the axle, and where the mating faces of the axle housing elements are on a plane generally containing the longitudinal axis of the axle.

According to the invention in another aspect, the sandwich plate/pintle assembly and rotary cylinder elements of the hydrostatic transmission are mounted onto a dished member which is then intentionally wedged into a locked position between the two main axle housings.

According to the invention in another aspect, the sandwich plate/pintle assembly and rotary cylinder elements of the hydrostatic transmission are mounted into a recess formed into one of the axle housings, and where a separate domed member is attached over the recess to lock and locate the elements of the hydrostatic transmission in place.

According to the invention in another aspect, the axle comprises two main housings where the plane of the mating face is generally transverse to the longitudinal axis of the axle, and where the rotary cylinder elements guided on the pintle valve are positioned either side of a portion wall which forms part of the axle housing.

According to one preferred feature of the invention, the axle containing the hydrostatic transmission is preferably mounted to the underside of the vehicle chassis so that the drive shafts of the hydrostatic transmission are in alinement with the engine shaft of the vehicle.

According to another preferred feature of the invention the axle can be installed in both the vertical and horizontal plane, thereby allowing application to both inline horizontal and vertical crankshaft engined vehicles.

The invention may be performed in various ways and will now be described by way of example with reference to the accompanying drawings, in which:

FIG. 1 is a side view of a typical grass cutting lawn or garden tractor vehicle,

FIG. 2 is an underneath view of the vehicle in FIG. 1,

FIG. 3 is a side view of the axle according to the invention, viewed from the position of the drive wheel, with partial cross-section through the elements of the hydrostatic transmission,

FIG. 4 is a sectional plan view downwards of an axle on line I--I on FIG. 3,

FIG. 5 is a frontal view of the axle, with partial cross-sectional through the drive shaft axis line II--II on FIG. 4,

FIG. 6 is a partial view of the underside of the axle on line III--III on FIG. 5,

FIG. 7 is a plan view in partial section of the hydrostatic transmission according to the invention on line IV--IV on FIG. 4,

FIG. 8 is a sectional side elevation of the hydrostatic transmission viewed on line V--V on FIG. 7,

FIG. 9 is a sectional frontal view illustrating a modified form of axle prior to the assembly of the two main housing elements around the hydrostatic transmission,

FIG. 10 is a sectional frontal view illustrating a further modified form of axle with the hydrostatic transmission located into a recess in one of the main housing elements prior to assembly between the other main housing element and a domed member,

FIG. 11 is a sectional side elevation of an axle with internal hydrostatic transmission illustrating a further possible modification,

FIG. 12 is a sectional plan view through the axle on the line VI--VI in FIG. 11,

FIG. 13 is a partial view of the pintle clamping means on line VII--VII in FIG. 11.

Almost all manufacturers of light duty lawn tractor grass mowers prefer to install vertical crankshaft internal combustion engines to such vehicles, thereby enabling them to fit simple belt drives from the engine to the mower deck and transmission.

The engine can be mounted on the chassis of the vehicle either over the front or the rear wheels, whereas the transmission is almost always mounted in a position close to or directly over the rear drive wheels.

This installation allows for a simple Vee belt operating in the horizontal plane to transfer engine power from the engine pulley to a drive pulley keyed to the input shaft of the axle.

The tractor vehicle illustrated in FIGS. 1 and 2 comprises a vertically installed internal combustion engine 1 with the crank shaft 2 pointing down to the ground. The engine 1 is shown mounted at the front end of the tractor chassis 3 and the axle 5 containing the internal hydrostatic transmission is mounted towards the rear of the tractor chassis 3 and connected to the rear drive wheels 6. A simple V belt 10 operating in the horizontal plane connects the engine pulley 11 with the input drive pulley 12 of the axle 5, with a simple jockey pulley 17 acting as tensioning means for the V belt as shown in FIG. 2.

In FIG. 1, a grass mower deck 15 is shown located beneath the vehicle chassis 3 in a position between the rear two drive wheels 6 and the front two steering wheels 7 of the tractor. The mower deck 15 is attached to the tractor chassis 3 by way of height-adjusting supports 8 and is driven from the engine 1 by means of a short Vee belt 16.

Up to now very few hydrostatic transmissions have been installed in such vehicles due to the higher cost price of such transmissions over standard mechanical shift gearbox transmissions. Therefore in order to reduce the cost of manufacture and thereby increase the number of hydrostatic transmissions used in such applications, it becomes necessary to simplify the construction by using fewer component parts, and according to at least one embodiment of the invention this can now be done by incorporating the hydrostatic transmission inside the axle such that the two end housings normally fitted to all existing hydrostatic transmissions of this general type now become obsolete, and where preferably the two halves of the axle form the required end housings of the said hydrostatic transmission.

The upper axle housing 20 as shown in FIG. 3 contains the necessary bearing support 21 for the axle pulley 12 and drive shaft 22, and positions the hydrostatic transmission speed varying control shaft 23.

The upper axle housing 20 abuts directly against the lower axle housing 25, and the two halves forming the complete axle are tightened together by a number of screws 26 as shown in FIG. 4.

As the screws are tightened, the `O` ring type seal 27 placed between the sandwich plate 28 and the two ax