Variable displacement hydrualic piston machine saddle bearing

#The present invention is directed to variable displacement hydraulic piston machines (pumps and motors), and more particularly to an improved saddle bearing for mounting the piston displacement-control yoke to the machine housing.

#Variable displacement hydraulic piston pumps and motors conventionally include a plurality of pistons slidable in a cylinder block coupled to a shaft that is rotatable within the machine housing. The pistons engage a yoke that is pivotally mounted to the housing by laterally spaced saddle bearings and engaged by a hydraulic piston or other suitable means for controlling displacement of the pistons within the cylinder block as the cylinder block rotates about the axis of the shaft. The cylinder block cavities in which the pistons are disposed are coupled by a valve plate or other suitable means to fluid inlet and outlet ports in the housing. The present invention deals with construction of the saddle bearings, which are lubricated by hydraulic fluid at case pressure within the machine housing.

#The saddle bearings may be of non-rolling element construction as disclosed in U.S. Pat. No. 4,862,789, or of rolling element (roller or needle bearing) construction as in the present application. When a rolling element saddle bearing is employed, the roller retainer or cage is free during assembly to travel outside of the boundary of the inner and outer bearing races. It would be advantageous to provide facility to time the three arcuate bearing components (the cage and the inner and outer races) during assembly to prevent the cage from being positioned incorrectly. It is therefore a general object of the present invention to provide a rolling element saddle bearing of the described character having such facility for positioning and retaining the bearing elements with respect to each other during the assembly process.

#The invention, together with additional objects, features and advantages thereof, will be best understood from the following description, the appended claims and the accompanying drawings in which:

#FIG. 1 is a fragmentary sectional view of a variable displacement hydraulic piston machine embodying the present invention;

#FIG. 2 is a sectional view that illustrates a saddle bearing mounting the displacement control yoke to the housing in the machine of FIG. 1;

#FIG. 1 illustrates a variable displacement hydraulic in-line piston machine 10 as comprising a housing 12 that includes a case 14 mounted to a valve block 16. A shaft 18 is mounted by bearings 20 for rotation within housing 12. A cylinder block 22 is coupled to shaft-18 for co-rotation therewith, and has a circumferential array of cylinder cavities surrounding shaft 18. A plurality of pistons 24 are axially slidably disposed in associated cavities of cylinder block 22. The axial end of each piston 24 is fastened to a shoe 26 that slidably engages the face of a swash plate or yoke 28. Yoke 28 is mounted to housing 12 by a pair of saddle bearings 30 disposed on opposed sides of shaft 18, and is engaged on opposed sides of shaft 18 by a spring-biased piston 32 and a displacement control valve 34 for controlling pivotal position of yoke 28 with respect to housing 12 and shaft 18. The cylinder cavities of cylinder block 22 are connected through a valve plate 36 and suitable passages in valve block 26 to machine inlet and outlet ports for feeding fluid to and from the cylinder block.

#In operation as a pump, rotary motion is applied to shaft 18 from an external source (not shown) for rotating cylinder block 22 within housing 12. Pivotal position of yoke 28 is controlled by spring-biased piston 32 and control valve 34 to vary displacement of pistons 24 within cylinder block 22 from a zero displacement position in which yoke 28 is perpendicular to the axis of shaft 18, to a maximum displacement position as shown in FIG. 1. Displacement of pistons 24 within cylinder block 22 as the cylinder block rotates draws hydraulic fluid from a sump and pumps the fluid under pressure through suitable valving and outlet ports in valve block 16. In operation as a motor, the hydraulic fluid is pumped under pressure to the cavities of cylinder block 22, and positive displacement of pistons 24 within the cylinder block causes rotation of the cylinder block and corresponding rotation of shaft 18 as an output from the motor.

#Saddle bearing 30 in accordance with one presently preferred embodiment of the invention is illustrated in FIGS. 2 and 3 as comprising an arcuate inner bearing race 40 and an arcuate outer bearing race 42 respectively mounted (by screws or pins not shown) to yoke 28 and base 44 on housing 12. Outer bearing race 42 has a central arcuate slot 46 and a pair of axially spaced radially extending end ribs 48. A plurality of rollers 50 are rotatably captured in corresponding pockets of an arcuate cage 52, which is slidably disposed in bearing channel 46 such that rollers 50 are axially captured between ribs 48. In accordance with the present invention, a timing lever 54 has a central portion 56 with an aperture 58 pivotally mounted to a leg 60 that projects laterally from cage 52 between spaced rollers 50. A pair of arms 62 integrally and oppositely extend from central lever portion 56, and terminate in respective part-spherical lever end portions 64. Each arm 62 extends through a corresponding slot 66, 68 in beating races 40, 42 so that the respective end portions 64 are slidably disposed in cylindrical openings 70, 72 in saddle 28 and housing base 44 respectively. Thus, timing lever 54 functions to locate the bearing elements with respect to each other and with respect to the opposed mounting structure 28, 44, and to limit bearing motion during assembly and operation of the pump. The length of lever 54 is determined by the physical size of the bearing. The lever will position the bearing correctly during assembly and maintain proper position during use. In the particular embodiment illustrated, saddle 28 can rotate approximately 10.degree. in either direction, resulting in rotation at cage 52 of approximately 5.degree. in either direction.