JP2008169742A - Variable displacement piston pump motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a low cost piston pump motor by reducing the weight of a main body corresponding to a swash plate support part. <P>SOLUTION: A variable displacement piston pump motor 10 is provided with the main body 13 comprising a body 11 and a case 12. A plurality of pistons 21 moving in axial directions are provided in a cylinder block 18 coupled with a shaft 16 pivotally supported by the main body by spline 17 and rotating with synchronizing with the shaft 16. A semicircular plain bearing 25 mounted on the case 12 butts on a swash plate 24 obliquely moved, having a fulcrum on a cylinder center by a control piston 31 slidably inserted in the case 12. The semicircular body 11 has a plurality of plain bearings 25 having angle range B (B>A) fixed in a specific angle range A by an oval counter-sunk screw, a parallel pin, a spring pin or the like. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a variable displacement piston pump and motor, and more particularly to a cradle swash plate support mechanism for a cradle swash plate type axial piston pump and motor used as a hydraulic power source for construction machinery and general industrial machinery.

Conventionally, a variable displacement swash plate type piston pump / motor tilts a swash plate to change a discharge amount per one rotation. In addition, because of the structure of the swash plate type variable displacement piston pump / motor, a load corresponding to the product of the pump (or motor) pressure and the piston cross-sectional area acts on the tilting support portion of the swash plate. It is necessary to withstand a high surface pressure and reduce the amount of wear. Furthermore, it is necessary to reduce the sliding resistance so that the swash plate can act smoothly, and it can be said that this is the largest bottleneck item in the swash plate type variable displacement piston pump and motor.
Therefore, a large and small pocket that guides the pressure to float and support the swash plate is attached to the hydrostatic bearing in the circumferential direction, and the large pocket is formed closer to the point of action of the piston concentrated load than the small pocket. Dividing into two different port areas, a pressure introducing passage for communicating a large pocket in the second port area with a second port in the same port area, and a small pocket in the second port area as the first port A swash plate type piston pump / motor having a pressure introduction path communicating with a first port in a region has been proposed (for example, see Patent Document 1).
JP 2000-205119 A

However, the support portion of the swash plate disclosed in Patent Document 1 is provided with a plurality of pressure oil grooves for the swash plate, but the processing for introducing oil into the pressure oil grooves is complicated, resulting in high costs. There was a problem. Further, when the pressure oil groove is extended in the circumferential direction in order to increase the reaction force due to the pressure oil groove, there is a problem that the main body portion supporting the semi-cylindrical slide bearing becomes large in order to secure the seal width.
The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a variable displacement piston pump / motor that is lightweight, inexpensive and highly durable.

In order to solve the above-mentioned problem, the invention according to claim 1 is a cylinder block coupled with a shaft member by a spline and rotating in synchronization with the shaft member;
A plurality of pistons fitted in the cylinder block in the axial direction;
A swash plate that makes the discharge capacity per rotation variable;
In a piston pump motor having
In order to fix the bearing member to the main body having a semi-cylindrical bearing member as a supporting member that is a fulcrum for tilting the swash plate, and one end of which is extended from the main body supporting the bearing member. In addition, at least one countersunk machine screw, a parallel pin, or a spring pin is used.
According to the present invention, since the main body does not need to support the entire area of the bush, the weight of the main body can be reduced.

    According to the present invention, the mass of the main body corresponding to the swash plate support can be reduced without deteriorating the life, so that it is possible to provide a lighter and less expensive piston pump / motor. Furthermore, machining is easy because the cutting range of the cylindrical portion is reduced.

Preferred embodiments of the variable displacement piston pump / motor according to the present invention will be described below in detail with reference to the accompanying drawings.
FIG. 1 is a longitudinal sectional view showing a schematic configuration of a variable displacement piston pump / motor 10 according to the present invention. As shown in FIG. 1, a variable displacement piston pump / motor 10 has a body 11 and a case 12 formed by a screw member (not shown), and a body 13 formed by a ball bearing 14 and a needle bearing 15. A shaft (shaft member) 16 that is rotatably supported is mounted. A spline 17 is formed on the shaft 16 and is coupled to a spline groove 19 formed on the inner peripheral surface of the cylinder block 18 so that the cylinder block 18 rotates together with the shaft 16.

A plurality of bores 20 are formed on the same circumference around the rotation axis of the cylinder block 18, and a plurality of pistons 21 are slidably inserted into the bore 20. A head portion 22 which is one end portion of the piston 21 protrudes from the opening of the bore 20 and is slidably abutted on the surface of the swash plate 24 via a shoe 23.
The swash plate 24 is in contact with a slide bearing (bearing member) 25 coupled to the body 11. The elastic force of the spring member 26 acts on the swash plate 24 via a needle bearing 27, a cylinder holder 28, and a shoe holder 29. The inclination angle θ of the swash plate 24 changes as the sliding bearing 25 slides. The swash plate 24 is normally biased at its rear end so that the inclination angle θ is maximized by the elastic force of the spring member 30, and the control piston 31 disposed on the opposite side of the spring member 30 has a control piston 31. The swash plate 24 is controlled to the minimum inclination angle θ against the urging force of the spring member 30. The slide bearing 25 is formed of a resin system and a metal system (including a copper alloy).

  The control piston 31 is slidably fitted into a cylinder chamber 32 formed in the case 12, and one end portion (right end in FIG. 1) of the control piston 31 is formed in a spherical shape and engaged with the swash plate 24. The other end (the left end in FIG. 1) is in contact with a guide 38 that is movably fitted in a hole 37 formed in communication with the cylinder chamber 32. The guide 38 is moved in the axial direction by an adjusting bolt 39 that is moved by a screw mechanism formed in the case 12. Accordingly, the control piston 31 moves in the direction of the arrow X or Y through the guide 38 when the adjustment bolt 39 enters and exits, and functions to adjust the pump discharge amount by changing the inclination angle of the swash plate 14. Reference numeral 40 denotes a nut, and the guide 38 is positioned by adjusting the entrance and exit of the adjustment bolt 39.

In the variable displacement piston pump / motor 10 shown in FIG. 1, a semi-cylindrical body 11 having a specific angular range A as shown in FIG. 2 has a plurality of angular ranges B (where B> A). The center portion of the slide bearing 25 is fixed by a flat head screw, a parallel pin, a spring pin or the like. In this case, the position of the countersunk machine screw, the parallel pin or the spring pin is not limited to the center part, and may be the periphery or one side of the center part, and the position of the countersunk machine screw, the parallel pin or the spring pin may be one place or a plurality of places. .
Further, although the plain bearing 25 is formed in a semi-cylindrical shape in advance, the cylinder inner diameter after assembly is made larger than the cylindrical radius of the swash plate so that oil clearance is secured at both ends of the bearing member. The main body provided at an angle equal to or greater than the angle A is not necessary, and the weight of the pump / motor can be reduced.
FIG. 2 is a cross-sectional view of the main part showing a schematic structure relating to the engagement state of the body, the swash plate, and the slide bearing of FIG. FIG. 3 is an enlarged view of a portion C in FIG.

The variable displacement piston pump / motor 10 of the embodiment of the present invention is basically constructed as described above. Next, its operation and effects will be described.
The variable displacement piston pump / motor 10 is configured such that when the shaft 16 is rotated by a prime mover such as an internal combustion engine (not shown) and the cylinder block 18 is rotated, the stroke of the piston 21 is controlled by the swash plate 24 inside the cylinder block 18. The pressure fluid enters and exits the bore 20, and alternately discharges the pressure fluid from the bore 20 to the discharge port 35 or 36, and supplies the pressure fluid to a hydraulic device (not shown).
According to the variable displacement piston pump / motor having such a configuration, the cylindrical inner diameter of the bearing member 25 after being assembled to the body 11 is larger than the cylindrical radius of the swash plate 24 and oil clearance is provided at both ends of the portion where the load acts. Is forming. The actual contact range is limited to the load center portion, and the main body that supports the bearing member 25 does not need to support the entire surface.
Therefore, the weight of the main body corresponding to the swash plate support portion can be reduced without reducing the life, so that it is possible to provide a lighter and less expensive piston pump / motor. Furthermore, since the cutting range of a cylindrical part becomes small, a process becomes easy.

1 is a schematic longitudinal sectional view showing a schematic structure of a variable displacement piston pump / motor according to an embodiment of the present invention. It is principal part sectional drawing which shows the schematic structure which concerns on the engagement state with the body of FIG. 1, a swash plate, and a slide bearing. It is an enlarged view of the C section of FIG.

Explanation of symbols

10. Variable displacement piston pump / motor
11 Body 12 Case 13 Body 14 Swash plate 25 Slide bearing

Claims (1)

A cylinder block coupled with a shaft member by a spline and rotating in synchronization with the shaft member;
A plurality of pistons fitted in the cylinder block in the axial direction;
A swash plate that makes the discharge capacity per rotation variable;
In a piston pump motor having
In order to have a semi-cylindrical bearing member as a supporting member that is a fulcrum for tilting the swash plate, and one end thereof is extended from the main body supporting the bearing member, and the bearing member is fixed to the main body. A variable displacement piston pump motor using at least one countersunk machine screw, a parallel pin, or a spring pin.

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