JPH0459469B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an axial piston machine, and more particularly to a fully hydrostatic bearing supported oblique axis type axial piston machine suitable for high pressure and high durability. [Background of the Invention] As described in Japanese Patent Application Laid-Open No. 59-131776, in a conventional device, the operation input shaft of an axial piston machine and a drive flange supporting a plurality of piston rod members are directly connected by screw connection or metal bearing. has been done. On the other hand, the reaction force of the piston rod acting on the drive flange is diffused into an axial component force and a radial component force and acts on the drive flange. However, in such a structure, the point of action of the resultant force of the axial component of the piston rod reaction force and the resultant force of the opening force generated by the pressure chambers of the slide shoe arranged radially with respect to the axial direction of the drive flange. Since the points of action do not match perfectly, a moment load component is generated on the drive flange, and the moment load acts directly on the joint between the operation input shaft and the drive flange, promoting fretting wear. Cause. In particular, when the total number of pistons is 7 and the number of pistons involved in discharge is 3, this kind of fretting wear becomes noticeable, and the radial Since the amount of displacement due to the directional force is added, the fretting wear increases. Additionally, increased fretting wear is expected to increase mechanical losses in axial piston machines. As mentioned above, in JP-A-59-131776, no consideration was given to preventing fretting wear. [Object of the Invention] An object of the present invention is to provide a fully hydrostatic bearing supported oblique shaft type axial piston machine having high pressure and high durability. [Summary of the Invention] The present invention connects the drive flange and the operation input shaft with a spline shaft in order to eliminate the fretting wear that occurs at the joint between the drive flange and the operation input shaft of an axial piston machine. In addition, by optimizing the radial clearance at the spline shaft portion, metal contact does not occur at the spline shaft coupling portion. This can prevent fretting wear. [Embodiment of the Invention] An embodiment of the present invention will be described below with reference to FIGS. 1 and 2. Axial piston machine housing cover 1
The cylinder block 3 includes a cylinder block 3 having a plurality of cylinder holes 2, and a piston 5 which is movable back and forth within the cylinder holes 2 and is fixed to a piston rod 4. The piston rod 4 is pivotally mounted within the drive disk 6B of a drive shaft body 6 consisting of a shaft 6A and a drive disk 6B, which are connected to an operation input shaft (not shown) of the axial piston machine. Further, as shown in FIG. 2, when no input is applied to the shaft 6A of the axial piston machine, the shaft 6A of the axial piston machine and the drive disk 6B are fixed to each other in the radial direction by the spline shaft joint 7. They fit together with a gap between them. Furthermore, shaft 6
A bearing 9 for rotatably supporting the shaft 6A is disposed between the outer periphery of the shaft 6A and the bearing sleeve 8. Further, the cylinder block 3 is rotatably provided via a spherical universal joint or a center rod (both not shown), and a valve plate 11 having a suction port 11A and a discharge port 11B for the working medium is connected by the center shaft 10. It is supported on the head cover 12 via the head cover 12 . Head cover 12
is provided with a suction port 12A and a discharge port 12B, and these ports communicate with a suction port 11A and a discharge port 11B on the valve plate 11 , respectively. The spherical universal joint also includes a spherical bearing (not shown) and is pivotally mounted within the drive disk 6B. An adjusting device (not shown) for changing the angle of inclination of the cylinder block 3 acts on a yoke (not shown). By changing the inclination angle, the stroke of the piston 5 in the cylinder hole 2 is changed. The drive disk 6B and the shaft 6A are connected by a splined shaft 7, the shaft 6A acting as an input shaft according to the operating method of the axial piston machine. Further, the bearing sleeve 8 includes a chamber 13, and the chamber 1
The rod portion 16a of the hydrostatic bearing pad 16 , which is composed of the constricted portion 14 and the pressure chamber 15, is inserted into the flange portion 1 of the hydrostatic bearing pad 16.
6b is an end surface 1 perpendicular to the axial direction of the bearing sleeve 8;
7 and the end 18 of the drive disk 6B, the end surfaces 17 and 18 are in contact with each other. As mentioned above, the hydrostatic bearing pad 16
4 and pressure chambers 15, at least four or more,
Hydrostatic bearing pads 16 for the number of pistons at most
are arranged radially with respect to the bearing sleeve 8 at a certain distance. Furthermore, on the end surface 16C of the rod portion 16b of the hydrostatic bearing pad 16,
A working medium having a direct discharge pressure Pb is introduced and communicates with the pressure chamber 15 via the constriction part 14 . On the other hand, the drive disk 6B is supported on the outer circumferential surface of a bearing sleeve 19 disposed within the housing 1 as a radial slide bearing. Around the piston 5, at least four or more pressure chambers 20, corresponding to the number of pistons 5 at most, are provided on the inner circumferential surface of the bearing sleeve 19 at a pitch of at least four. Discharge pressure is applied to the outer peripheral surface of the bearing sleeve 19.
A Pd supply port 21 is provided corresponding to the pressure chamber 20, and the supply port 21 and the pressure chamber 20 are connected to each other via a constriction part 22 for controlling the static pressure of the pressure chamber 20 in accordance with the load. It's communicating. Next, the operation of the fully static pressure bearing supported oblique shaft type axial piston machine constructed as described above will be explained. In axial piston machines, the discharge pressure
Number of pressurizing pistons to generate Pd and discharge pressure (for example, if the total number of pistons is 7, the maximum number of pressurizing pistons is 4, the minimum number of pressurizing pistons is 3, the average number of pressurizing pistons is 4, 5), the piston reaction force load changes and this fluctuating load acts on the drive disk 6B. The load acting on the drive disk 6B is diffused into an axial component force and a radial component force on the drive disk 6B on the support surface of the piston rod 4.
The load spread in two directions in this way is caused by static pressure in the pressure chambers 15 and 20 provided on the inner peripheral surfaces of the static pressure bearing pad 16 and the bearing sleeve 19, respectively.
It is supported by hydrostatically and hydrodynamically acting sliding bearings. Thereby, the loaded drive disk 6B is supported axially and radially within the machine housing 1 with hydrostatic and hydrodynamic slide bearings by means of the hydrostatic bearing pad 16 and the bearing sleeve 19. Here, the support form of the load acting on the drive disk 6B will be discussed in detail. First, consider the axial component of load. The resultant force in the axial direction of the load, that is, the axial component of the reaction force of the piston rod 4 (the point of application to the drive disk 6B, and the static pressure created by the pressure chambers 15 of the hydrostatic bearing pads 16 corresponding to the number of piston rods 4). Since the point of application of the resultant force does not completely match, not only a thrust load but also a moment load component based on the difference in the point of application of the force acts on the drive disk 6B. In addition to the axial translational displacement,
Rotational displacement also occurs. Further, the radial component force of the load also acts on the drive disk 6B at the same time as the axial component force, and in response to this radial component force, the working fluid supplied into the pressure chamber 20 of the bearing disk 19 is A hydrodynamic lubricating film corresponding to the directional force is directly formed, and the drive disk 6B
Metallic contact between the outer circumferential surface of the bearing sleeve 19 and the inner circumferential surface of the bearing sleeve 19 can be prevented. In this way, when a load acts on the drive disk 6B, a radial displacement and an out-of-plane displacement with respect to the plane of the paper act on the drive disk 6B at the same time.
The central axis of the drive disk 6B is inclined in the in-plane and out-of-plane directions with respect to the plane of the paper. This phenomenon occurs when the number of pressurizing pistons is minimal (for example,
When the total number of pistons is seven, this corresponds to the case where the number of pressurizing pistons is three. ) is noticeable. However, in the present invention, the drive disk 6B and the shaft 6A for operation input are separately formed and connected by the spline shaft portion 7, and the radial direction at the spline shaft fitting portion of both is formed separately. The gap δ is larger than the amount of displacement based on the load described above (radial displacement δθ at the spline shaft due to the inclination of the central axis of the drive disk + radial displacement δr at the spline shaft due to the eccentricity of the drive disk in the radial direction). Since it is configured to
Even if the load acting on the drive disk 6B fluctuates in synchronization with the rotation speed of the axial piston machine, fretting wear may occur in the spline shaft fitting portion 7 due to metal-to-metal contact between the shaft 6A and the drive disk 6B. There is no. Further, according to the present invention, the gap in the spline shaft fitting portion 7 can be lubricated with the leakage flow from the hydrostatic bearing pad 16 , so that fretting wear can be more reliably prevented. [Effects of the Invention] According to the present invention, it is possible to prevent fretting wear at the shaft coupling portion between the drive disk and the shaft, so that it is possible to prevent long-term use of a high-pressure and small-sized fully hydrostatic bearing supported oblique shaft type axial piston machine. This has the effect of increasing durability and reducing mechanical loss in axial piston machines.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view of a fully hydrostatic bearing supported oblique shaft type axial piston machine representing an embodiment of the present invention, and FIG. 2 is a cross-sectional view taken along the line -- in FIG. 1
...Housing cover, 3...Cylinder block, 4...Piston rod, 5...Piston, 6
... Drive shaft, 6A ... Shaft, 6B ... Drive disk, 7 ... Spline shaft joint, 8 ... Bearing sleeve, 11 ... Valve plate, 12 ... Head cover, 16 ... Hydrostatic bearing pad, 19 ... Bearing sleeve, 15, 20 ... Pressure chamber, 14, 22 ... Throttle section.

Claims (1)

[Scope of Claims] 1. A housing cover, a cylinder block having a plurality of cylinder holes, a piston that is movable in the longitudinal direction within the cylinder holes and is fixed to a piston rod, and the piston rod is used to operate an axial piston machine. A fully hydrostatic bearing supported diagonal shaft type that is pivotally mounted on the drive shaft, and the drive shaft is hydrostatically and hydrodynamically supported in the axial and radial directions of the drive shaft by a plurality of hydrostatic bearings. In the axial piston machine, the operation drive shaft is divided into two members consisting of a shaft that connects the operation input shaft and a drive disk that supports the piston rod, and a specific gap is provided between the shaft and the drive disk in the radial direction. A fully hydrostatic bearing supported oblique shaft type axial piston machine characterized by being integrally connected by a spline shaft. 2. In the fully hydrostatic bearing supported oblique shaft type axial piston machine as set forth in claim 1, the radial clearance in the spline shaft coupling portion is set to δ,
In addition, when the amount of radial displacement at the spline shaft due to the inclination of the central axis of the drive disk is δθ, and the amount of radial displacement at the spline shaft due to eccentricity in the radial direction of the drive disk is δr, the gap δ and the amount of displacement δθ 1. A fully hydrostatic bearing supported oblique shaft type axial piston machine, characterized in that a spline shaft coupling part is configured such that δ>δθ+δr holds between the two.