SWASH PLATE TYPE HYDRAULIC ROTATING MACHINE

Abstract

A swash plate type hydraulic rotating machine includes: a rotating shaft; a valve plate; a swash plate; a cylinder block on the outside of the rotating shaft slidingly contacting the valve plate; cylinders provided in the cylinder block having axially movable pistons therein; shoes on a distal end of respective pistons; an annular keep plate between the swash plate and the cylinder block supporting the shoes having a plain bearing within the inner periphery of the keep plate, the plain bearing supporting the keep plate to push the keep plate toward the swash plate side; and set springs biasing the plain bearing and the cylinder block toward the opposite sides in the axial direction. The swash plate type hydraulic rotating machine is configured such that, when in an assembled state, a gap in the axial direction between the cylinder block and the plain bearing is 0 or a fine gap.

Description

TECHNICAL FIELD

The present invention relates to a swash plate type hydraulic rotating machine suitably serving as, for example, a swash plate type hydraulic pump or swash plate type hydraulic motor.

BACKGROUND ART

Conventionally, there are known swash plate type hydraulic rotating machines such as swash plate type hydraulic pumps and swash plate type hydraulic motors (see Patent Literature 1). FIG. 8 shows a conventional swash plate type hydraulic pump. As shown in FIG. 8, a conventional swash plate type hydraulic pump 100 includes: a cylindrical cylinder block 9 which is spline-fitted to a rotating shaft 3; a plurality of cylinders 11 formed in the cylinder block 9; pistons 13 inserted in the respective cylinders 11, such that the pistons 13 can move in a reciprocating manner; a valve plate 4 being in contact with one end of the cylinder block 9; and a keep plate 17 and a swash plate 15 facing each other, which are provided at the other end of the cylinder block 9. The distal end of each piston 13 is formed as a spherical portion 13a protruding from the respective cylinder 11. Each spherical portion 13a is supported at its spherical surface by a respective one of shoes 14 which are slidingly in contact with a sliding contact surface 15c of the swash plate 15. The shoes 14 are fitted in respective shoe bearing holes 17a. The shoe bearing boles 17a are formed in the keep plate 17, corresponding to the respective cylinders 11. A spherical plain bearing 80 supporting the keep plate 17 is a tubular member spline-fitted to the rotating shaft 3, and is positioned between the cylinder block 9 and the swash plate 15. The diameter of the outer peripheral surface of the spherical plain bearing 80 gradually increases from the swash plate 15 side toward the valve plate 4 side. The outer peripheral surface of the spherical plain bearing 80 is in contact with the inner peripheral surface of the keep plate 17. Set springs 20 are provided between the spherical plain bearing 80 and the cylinder block 9. Due to the spring force of the set springs 20 and hydraulic pressure in the cylinders 11, the cylinder block 9 is pushed against the valve plate 4, so that the cylinder block 9 is in close contact with the valve plate 4, and the shoes 14 are pushed against the sliding contact surface 15c of the swash plate 15.

In the swash plate type hydraulic pump having the above configuration, when the rotating shaft 3 rotates, the pistons 13 reciprocate within the respective cylinders 11 in accordance with the inclination of the swash plate 15. The swash plate type hydraulic pump utilizes the motion of the pistons 13 to suck a required amount of low-pressure working fluid and to discharge the working fluid to the high-pressure side. Swash plate type hydraulic motors are configured such that the rotation of the rotating shaft and the movement of the working fluid are opposite to those of the above swash plate type hydraulic pump.

In the above-described conventional swash plate type hydraulic pump 100, the keep plate 17, which is pushed toward the swash plate 15 side by the spring force of the set springs 20 and the hydraulic pressure in the cylinders 11, causes the shoes 14 to be in close contact with the sliding contact surface 15c of the swash plate 15. However, when the rotating shaft 3 and the cylinder block 9 rotate at high speed, the speed of the reciprocating motion of the pistons 13 within the cylinders 11 increases, which results in that the pistons 13 pull the shoes 14 toward the valve plate 4 side with greater force. In such a high-speed rotation state, if the hydraulic pressure in the cylinders 11 decreases due to, for example, a low-pressure operation, then the force pushing the shoes 14 against the swash plate 15 depends on the spring force of the set springs 20. As a result, the pulling force of the pistons 13 pulling the shoes 14 toward the valve plate 4 side becomes greater than the pushing force pushing the shoes 14, which pushing force is derived from the set springs 20 and the hydraulic pressure. Consequently, as shown in FIG. 9, there is a case where the shoes 14 become lifted from the swash plate 15 or become tipped (become tilted). If the shoes 14 become lifted from the swash plate 15, edge contact occurs between the sliding contact surface 15c of the swash plate 15 and the shoes 14. If the shoes 14 in such an edge-contact state rotate while sliding on the swash plate 15, then torque loss occurs and pump efficiency decreases significantly. In addition, due to the edge contact of the shoes 14, uneven wear, galling, seizing, or the like occurs to the swash plate 15 and the shoes 14. As a result, the life of the shoes 14 and the swash plate 15 is reduced.

In order to prevent the shoes from being lifted as above, the swash plate type hydraulic pump disclosed in Patent Literature 1 is configured such that the peripheral portion of the keep plate 17 pushing the shoes 14 against the swash plate 15 has a tapered structure. Accordingly, the rigidity of the keep plate 17 is improved and deformation of the keep plate 17 is prevented, and thereby the shoes 14 are prevented from being lifted.

Patent Literature 2 discloses an axial plunger type hydraulic system, in which the bearing surface of the shoes, the bearing surface contacting the swash plate, is formed of an aluminum-silicon alloy that is lighter than copper alloys and has excellent abrasion resistance, so that centrifugal force to be exerted on the shoes is reduced. In this manner, the shoes are prevented from being lifted from the swash plate.

CITATION LIST

Patent Literature

• PTL 1: Japanese Laid-Open Patent Application Publication No. 5-164038
• PTL 2: Japanese Laid-Open Patent Application Publication No. 50-146907

SUMMARY OF INVENTION

Technical Problem

Even though deformation of the keep plate 17 is prevented in the conventional swash plate type hydraulic pump 100 as disclosed in Patent Literature 1, if the set springs 20 shrink, then there is a risk that the keep plate 17 moves toward the valve plate 4 side, resulting in that the shoes 14 become lifted from the swash plate 15. Here, one conceivable method of preventing the shoes from being lifted as above is to increase the spring force of the set springs 20 pushing the keep plate 17 toward the swash plate 15 side. However, there is a limit of the spring force of the set springs 20. In addition, if the spring force is increased, then the friction force between the swash plate 15 and the shoes 14 increases, resulting in reduced efficiency and a risk of seizing. For these reasons, the conventional swash plate type hydraulic pump 100 cannot bear a significant increase in the rotational speed of the rotating shaft 3.

In the axial plunger type hydraulic system disclosed in Patent Literature 2, in order to fix the position of the shoes, not a keep plate but a frame is provided at the outer peripheral portion of the swash plate. The frame serves to hold the shoes such that the shoes are kept in contact with the swash plate. When the hydraulic system having this configuration operates, relative slip occurs between the frame of the swash plate and the shoes. Therefore, the axial plunger type hydraulic system disclosed in Patent Literature 2 cannot bear a significant increase in the rotational speed.

In view of the above, an object of the present invention is to provide a technique for preventing the shoes from being lifted from the swash plate in a swash plate type hydraulic rotating machine such as a swash plate type hydraulic pump or swash plate type hydraulic motor, and also to provide a structure capable of bearing further increase in the rotational speed of the swash plate type hydraulic rotating machine.

Solution to Problem

A swash plate type hydraulic rotating machine according to the present invention includes: a rotating shaft; a valve plate and a swash plate facing each other and away from each other in an axial direction of the rotating shaft; a cylinder block fitted to an outside of the rotating shaft between the valve plate and the swash plate, such that the cylinder block is slidingly in contact with the valve plate; a plurality of cylinders provided in the cylinder block; a plurality of pistons inserted in the respective cylinders, such that the pistons are movable in the axial direction in a reciprocating manner; a plurality of shoes each connected to a distal end of a respective one of the pistons such that each shoe is movable in a rocking manner, wherein the distal end of each piston protrudes from a respective one of the cylinders toward the swash plate side; an annular keep plate loosely fitted to the rotating shaft between the swash plate and the cylinder block, the keep plate holding the shoes; a plain bearing provided between the keep plate and the cylinder block, the plain bearing supporting the keep plate; and spring members provided between the plain bearing and the cylinder block, the spring members biasing the plain bearing to cause the plain bearing to push the keep plate toward the swash plate side. A gap in the axial direction between the plain bearing the cylinder block is 0 or a fine gap when the swash plate type hydraulic rotating machine is in an assembled state.

In the above swash plate type hydraulic rotating machine, the gap desirably has a size of 0, or has a size of more than 0 and equal to or less than 1.2 mm.

Alternatively, a swash plate type hydraulic rotating machine according to the present invention includes: a rotating shaft; a valve plate and a swash plate facing each other and away from each other in an axial direction of the rotating shaft; a cylinder block fitted to an outside of the rotating shaft between the valve plate and the swash plate, such that the cylinder block is slidingly in contact with the valve plate; a plurality of cylinders provided in the cylinder block; a plurality of pistons inserted in the respective cylinders, such that the pistons are movable in the axial direction in a reciprocating manner; a plurality of shoes each connected to a distal end of a respective one of the pistons such that each shoe is movable in a rocking manner, wherein the distal end of each piston protrudes from a respective one of the cylinders toward the swash plate side; an annular keep plate loosely fitted to the rotating shaft between the swash plate and the cylinder block, the keep plate holding the shoes; a plain bearing provided between the keep plate and the cylinder block, the plain bearing supporting the keep plate; spring members provided between the plain bearing and the cylinder block, the spring members biasing the plain bearing to cause the plain bearing to push the keep plate toward the swash plate side; and a filling member filling a gap in the axial direction between the plain bearing and the cylinder block.

The filling member may be at least one shim plate. A time-hardening or thermosetting filler may be provided between the filling member and one of the plain bearing and the cylinder block. Alternatively, the filling member may be a press-fit bushing.

According to the swash plate type hydraulic rotating machine having the above configuration, the gap between the cylinder block and the plain bearing is 0 or a fine gap. Accordingly, movement of the plain bearing toward the valve plate side is restricted as a result of the plain bearing contacting the cylinder block. That is, the keep plate, which pushes the shoes against the swash plate, is restricted from moving toward the valve plate side. Therefore, for example, even when the rotational speed of the rotating shaft increases and thereby inertial force that pulls the pistons toward the valve plate side, and centrifugal force moment that causes tipping of the shoes, become greater than the spring force of the set springs, the shoes do not become lifted from the swash plate or become tipped. As described above, in the swash plate type hydraulic rotating machine according to the present invention, the shoes are prevented from being lifted from the swash plate and from tipping. Therefore, the swash plate type hydraulic rotating machine according to the present invention can prevent the occurrence of, for example, decrease in operating efficiency, uneven wear of the swash plate and the shoes, galling phenomenon, and seizing, which are caused when the shoes slidingly rotate on the swash plate in a state where there is edge contact between the swash plate and the shoes. Since, as described above, the shoes do not become lifted from the swash plate even if the rotational speed of the rotating shaft is increased, the rotational speed of the rotating shaft can be further increased in the swash plate type hydraulic rotating machine.

Advantageous Effects of Invention

According to the present invention, even if inertial force that pulls the pistons toward the valve plate side, and centrifugal force moment that causes tipping of the shoes, become greater than the spring force of the set springs, the movement of the keep plate toward the valve plate side is restricted as a result of the plain bearing contacting the cylinder block. This makes it possible to prevent the shoes from being lifted from the swash plate and from tipping.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a longitudinal sectional view showing a schematic configuration of a swash plate type hydraulic pump according to one embodiment of the present invention.

FIG. 2 is an enlarged view of a portion X circled by a two-dot chain line in FIG. 1.

FIG. 3 is an enlarged longitudinal sectional view of part of the swash plate type hydraulic pump, showing Example 1 where a gap in an axial direction is provided between a spherical plain bearing and a cylinder block.

FIG. 4 is an enlarged longitudinal sectional view of part of the swash plate type hydraulic pump, showing Example 2 where a gap in the axial direction is provided between the spherical plain bearing and the cylinder block.

FIG. 5 is an enlarged longitudinal sectional view of part of the swash plate type hydraulic pump, showing Example 2 where space in the axial direction between the spherical plain bearing and the cylinder block is filled.

FIG. 6 is an enlarged longitudinal sectional view of part of the swash plate type hydraulic pump, showing Example 3 where space in the axial direction between the spherical plain bearing and the cylinder block is filled.

FIG. 7 is an enlarged longitudinal sectional view of part of the swash plate type hydraulic pump, showing Example 4 where space in the axial direction between the spherical plain bearing and the cylinder block is filled.

FIG. 8 is a longitudinal sectional view showing a schematic configuration of a conventional swash plate type hydraulic pump.

FIG. 9 shows a shoe being lifted from a swash plate in the conventional swash plate type hydraulic pump.

DESCRIPTION OF EMBODIMENTS

One embodiment of the present invention is described below in detail with reference to the drawings. In the drawings, the same or corresponding components are denoted by the same reference signs, and a repetition of the same description is avoided. Hereinafter, the description is given by taking a swash plate type hydraulic pump as an example of a swash plate type hydraulic rotating machine.

First, a schematic configuration of the swash plate type hydraulic pump is described with reference to FIG. 1. A swash plate type hydraulic pump 10 includes a rotating shaft 3 supported by a casing (not shown). The rotating shaft 3 is connected to a driving source (not shown) such as an engine. A cylinder block 9 having a cylindrical shape and large wall thickness is fitted to the outside of the rotating shaft 3. Specifically, splines formed at the outer periphery of the rotating shaft 3 are engaged with splines 9b formed at the inner periphery of the cylinder block 9. As a result, the cylinder block 9 rotates around the rotating shaft 3 in accordance with the rotation of the rotating shaft 3.

At one side of the cylinder block 9 (right side in FIG. 1), a disc-shaped valve plate 4 is fixed to the casing. The valve plate 4 is slidingly in contact with a valve plate sliding contact surface 97, which is one end surface of the cylinder block 9. A pair of suction/discharge ports 5 and 6 are formed in the valve plate 4. These ports are in communication with a suction/discharge passage (not shown) formed in the casing. At the other side of the cylinder block 9 (left side in FIG. 1), an annular swash plate 15 through which the rotating shaft 3 penetrates is provided facing the valve plate 4. The swash plate 15 and the cylinder block 9 are spaced apart from each other. A surface of the swash plate 15, the surface facing the cylinder block 9, is a sliding contact surface 9c on which shoes 14 slide. The shoes 14 will be described below. The swash plate 15 is inclined relative to a direction that is perpendicular to the axial direction of the rotating shaft 3 (hereinafter, simply referred to as the axial direction L). The swash plate 15 is configured such that the maximum tilting angle thereof can be changed by means of a tilting actuator which is not shown. In the description below, for the sake of convenience, the swash plate 15 side in the axial direction L is referred to as “the first side”, and the valve plate 4 side in the axial direction L is referred to as “the second side”. The first side is the opposite side to the second side.

The cylinder block 9 integrally includes a guide portion 91 and a body 92. The guide portion 91 is inserted in a spherical plain bearing 80 which will be described below. The body 92 is provided with cylinders 11 in which pistons 13 are inserted. The body 92 has a diameter larger than that of the guide portion 91. The guide portion 91 protrudes from the body 92 toward the first side. Accordingly, the cylinder block 9 has two stepped end surfaces facing the first side. The end surface at the first step is a first end surface 95 positioned at the first side of the guide portion 91, and the end surface at the second step is a second end surface 96 positioned at the first side of the body 92. The cylinder block 9 has the aforementioned valve plate sliding contact surface 97 as an end surface facing the second side. A plurality of cylinders 11 (only two cylinders are shown in FIG. 1) are formed in the body 92 of the cylinder block 9, such that the cylinders 11 are arranged on the same circle centered on the rotating shaft 3. Each cylinder 11 is open toward the first side and has cylindrical space therein, the space extending in the axial direction L. The cylinder block 9 is provided with cylinder ports 11a through which the interiors of the cylinders 11 are in communication with the suction/discharge ports 5 and 6. In each cylinder 11, a piston 13 is inserted such that the piston 13 can reciprocate in the axial direction L within the cylinder 11. A spherical portion 13a protruding from the cylinder block 9 toward the first side is formed at the first-side end of each piston 13. The spherical portion 13a of each piston 13 is fitted in a spherical surface support 14a formed at the second side of a respective one of the shoes 14. In this manner, each shoe 14 is connected to the distal end of a respective one of the pistons 13 such that the shoe 14 can move in a rocking manner. The first side of each shoe 14 is slidingly in contact with the sliding contact surface 15c of the swash plate 15. In accordance with the rotation of the rotating shaft 3, each shoe 14 rotates around the rotating shaft 3 while slidingly contacting the sliding contact surface 15c of the swash plate 15.

An annular keep plate 17 is provided between the cylinder block 9 and the swash plate 15. A plurality of shoe bearing holes 17a are formed in the keep plate 17, such that the shoe bearing holes 17a are provided corresponding to the respective cylinders 11. Each shoe 14 is fitted in a respective one of the shoe bearing holes 17a. The outer periphery of the shoe 14 has a smaller diameter portion 14c and a larger diameter portion 14d. The smaller diameter portion 14c can be fitted into the shoe bearing hole 17a. The larger diameter portion 14d is positioned at the first side relative to the smaller diameter portion 14c, and the larger diameter portion 14d has a diameter larger than that of the shoe bearing hole 17a. A stepped surface between the smaller diameter portion 14c and the larger diameter portion 14d of the shoe 14, the stepped surface facing the second side, contacts a peripheral portion around the shoe bearing hole 17a. In this manner, movement of the shoe 14 toward the second side is restricted.

The keep plate 17 is supported by the rotating shaft 3 via the spherical plain bearing 80, such that the keep plate 17 can move in a rocking manner. The diameter of an outer peripheral surface 81 of the spherical plain bearing 80 gradually increases toward the second side. The outer peripheral surface 81 is formed as a smooth curved surface. A flange 82 is formed at the second-side end of the outer peripheral surface 81 of the spherical plain bearing 80. The spherical plain bearing 80 is inserted toward the first side within the inner periphery of the keep plate 17. The outer peripheral surface 81 of the spherical plain bearing 80 is in contact with the inner peripheral surface 17b of the keep plate 17. The keep plate 17 can move in a rocking manner around the rotating shaft 3 as a result that the inner peripheral surface 17b of the keep plate 17 slides on the outer peripheral surface 81 of the spherical plain bearing 80. A fitting portion 83 and a guide hole 84 are formed at the inner periphery of the spherical plain bearing 80. The fitting portion 83 is positioned at the first side relative to the guide hole 84. Splines extending in the axial direction L are formed at the fitting portion 83 of the spherical plain bearing 80. The splines are fitted to the splines formed at the outer periphery of the rotating shaft 3. As a result, the spherical plain bearing 80 can integrally rotate with the rotating shaft 3 and move in the axial direction L. The guide hole 84 of the spherical plain bearing 80 has an opening facing the second side, and is formed as hollow space into which the above-described guide portion 91 of the cylinder block 9 can be inserted toward the first side. In a state where the guide portion 91 of the cylinder block 9 is inserted in the guide hole 84 of the spherical plain bearing 80, the outer periphery of the guide portion 91 of the cylinder block 9 is in contact with the inner periphery of the guide hole 84 of the spherical plain bearing 80. The spherical plain bearing 80 is thus guided by the guide portion 91 of the cylinder block 9, and therefore, the spherical plain bearing 80 can move in the axial direction L without wobbling.

Set springs 20 are provided between the spherical plain bearing 80 and the cylinder block 9. The set springs 20 serve to bias the spherical plain bearing 80 and the cylinder block 9 toward the opposite sides in the axial direction L. Specifically, a plurality of spring accommodating holes 93, which are open facing the first side, are formed in the body 92 of the cylinder block 9. A set spring 20 which is a coil spring is fitted in each spring accommodating hole 93. The first side of the set spring 20 protrudes from the cylinder block 9, and the protruding end of the set spring 20 is in contact with the flange 82 of the spherical plain bearing 80. Due to the spring force of the set springs 20 and hydraulic pressure in the cylinders 11, the valve plate sliding contact surface 97 of the cylinder block 9 is pushed against the valve plate 4, so that the valve plate sliding contact surface 97 is in close contact with the valve plate 4. Also, the spherical plain bearing 80, which is pushed toward the first side by the spring force of the set springs 20 and the hydraulic pressure in the cylinders 11, pushes the keep plate 17 toward the first side. Further, the keep plate 17, which is pushed toward the first side, pushes the shoes 14 against the sliding contact surface 15c of the swash plate 15.

Hereinafter, operations of the swash plate type hydraulic pump 10 having the above configuration are described in relation to a case where, of the suction/discharge ports 5 and 6, one suction/discharge port 5 is used as a suction port and the other suction/discharge port 6 is used as a discharge port. First, when a driving unit such as an engine drives the rotating shaft 3 to rotate, the cylinder block 9 integrally rotates with the rotating shaft 3, and the valve plate sliding contact surface 9a of the cylinder block 9 rotates while slidingly contacting the valve plate 4. Also, the shoes 14 held by the keep plate 17 rotate with the cylinder block 9 and the pistons 13 while slidingly contacting the sliding contact surface 15c of the swash plate 15. As a result, the pistons 13 reciprocate within the respective cylinders 11 at a stroke corresponding to the maximum tilting angle of the swash plate 15. In a suction stroke where each piston 13 moves from the top dead center to the bottom dead center, pressure oil is sucked from the suction/discharge passage into the respective cylinder 11 through the suction port 5. In a discharge stroke where each piston 13 moves back from the bottom dead center to the top dead center, the pressure oil previously sucked into the respective cylinder 11 is discharged as high-pressure oil to the suction/discharge passage through the discharge port 6. When the maximum tilting angle of the swash plate 15 is adjusted by a tilting actuator (not shown), the stroke of the pistons 13 is changed, accordingly. In this manner, the discharge capacity from the cylinders 11 can be variably controlled.

The above swash plate type hydraulic pump 10 is configured such that, when in an assembled state, a gap in the axial direction L between the cylinder block 9 and the spherical plain bearing 80 is 0 or a fine gap. The term “assembled state” herein refers to a fully assembled state of the swash plate type hydraulic pump 10. It should be noted that the term “assembled state” does not exclude an operating state of the swash plate type hydraulic pump 10. The gap in the axial direction L between the cylinder block 9 and the spherical plain bearing 80 may be 0 or a fine gap when the swash plate type hydraulic pump 10 is in an operating state. The above expression, “the gap is 0”, means that the spherical plain bearing 80 and the cylinder block 9 are continuously arranged in the axial direction L and there is no vacant space therebetween. Therefore, the state where the gap in the axial direction L between the cylinder block 9 and the spherical plain bearing 80 is 0 includes: a state where the cylinder block 9 and the spherical plain bearing 80 are in contact with each other in the axial direction L; and a state where there is space G (i.e., a gap) in the axial direction L between the cylinder block 9 and the spherical plain bearing 80 and the space G is filled with a filling member F. In a case where the gap in the axial direction L between the spherical plain bearing 80 and the cylinder block 9 is 0, the spherical plain bearing 80 is unable to move toward the second side in the axial direction L since the spherical plain bearing 80 is in direct or indirect contact with the cylinder block 9.

The above expression, “the gap is a fine gap”, means that there is a fine gap ΔL in the axial direction L between the cylinder block 9 and the spherical plain bearing 80. If there is a fine gap ΔL in the axial direction L between the spherical plain bearing 80 and the cylinder block 9, then the spherical plain bearing 80 can move toward the second side in the axial direction L by the gap ΔL. However, the size of the gap ΔL is sufficiently small. The size of the gap ΔL is such that the amount of movement of the keep plate 17 toward the second side, which is caused when the spherical plain bearing 80 moves toward the second side, is in such a range as not to cause the shoes 14 to lose contact with the sliding contact surface 15c of the swash plate 15. Specifically, the size of the gap ΔL is more than 0 and equal to or less than 1.2 mm, and more desirably, more than 0 and equal to or less than 0.8 mm. For reference, in a conventional general swash plate type hydraulic motor, the gap in the axial direction L between the cylinder block 9 and the spherical plain bearing 80 is designed to be approximately 3 to 5 mm.

In the swash plate type hydraulic pump 10 shown in FIG. 1 and FIG. 2, the space G in the axial direction L is provided between the first end surface 95 of the cylinder block 9 and the hole bottom 85 of the guide hole 84 (i.e., the second-side end surface) of the spherical plain bearing 80. The space G is filled with the filling member F. Accordingly, the cylinder block 9 and the spherical plain bearing 80 are continuously arranged in the axial direction L with no vacant space therebetween, and the size of the gap in the axial direction L is 0. The filling member F is at least one shim plate 30. The thickness and the number of shim plates 30 are suitably selected in accordance with the size of the space G. Since the shim plates 30 are used as the filling member F, even if the size of the space G varies due to dimensional errors of components, the space Gin the axial direction L between the cylinder block 9 and the spherical plain bearing 80 can be filled with high precision by adjusting, i.e., increasing or decreasing, the number of shim plates 30 during the assembling process.

In the swash plate type hydraulic pump 10 having the above configuration, if the rotating shaft 3 rotates at high speed when the hydraulic pressure in the cylinders 11 has decreased due to, for example, a low-pressure operation, then inertial force that pulls the pistons 13 toward the second side, and centrifugal force moment that causes tipping of the shoes 14, may become greater than the spring force of the set springs 20. In this case, if the keep plate 17 is pulled by the pistons 13 and moved toward the second side, then the pushing force of the shoes 14 against the swash plate 15 decreases, which causes tipping of the shoes 14. In this respect, the swash plate type hydraulic pump 10 according to the present embodiment is configured such that when force that causes the keep plate 17 to move toward the second side occurs, the movement of the spherical plain bearing 80 toward the second side is restricted since the spherical plain bearing 80 directly or indirectly contacts the cylinder block 9, and the movement of the keep plate 17 toward the second side is restricted since the keep plate 17 contacts the spherical plain bearing 80. In this manner, the movement of the keep plate 17 toward the second side is restricted in the swash plate type hydraulic pump 10 according to the present embodiment. Therefore, even in the case described above, there is not a risk that the shoes 14 become lifted from the sliding contact surface 15c of the swash plate 15 or become tipped. As a result, the swash plate type hydraulic pump 10 according to the present embodiment prevents the occurrence of for example, pump efficiency decrease, uneven wear of components such as the swash plate 15 and the shoes 14, galling phenomenon, and seizing, which are caused when the shoes 14 slidingly rotate in a state where there is edge contact between the sliding contact surface 15c of the swash plate 15 and the shoes 14. In addition, in the swash plate type hydraulic pump 10 according to the present embodiment, the set springs 20 used therein may have spring force according to conventional specifications. Accordingly, there is not a risk that increased spring force causes an increase in the friction force between the swash plate 15 and the shoes 14, which causes efficiency decrease or seizing. Moreover, the number of components added to prevent the shoes 14 from being lifted from the sliding contact surface 15c of the swash plate 15 and to prevent the shoes 14 from tipping is small, and thus the structure is simple. When the gap G in the axial direction L is filled with the filling member F, the cylinder block 9 and the spherical plain bearing 80 rotate in synchronization with each other. For this reason, relative slip does not occur between the filling member F and the cylinder block 9, and between the filling member F and the spherical plain bearing 80. Accordingly, excessive friction does not occur between the cylinder block 9 and the filling member F, and between the spherical plain bearing 80 and the filling member F. Therefore, these components can bear further increase in the rotational speed of the swash plate type hydraulic pump 10.

Although one preferred embodiment of the present invention is as described above, the present invention is not limited to the above-described embodiment. Various design changes may be made to the above embodiment without departing from the scope of the claims.

For example, although the gap in the axial direction L between the cylinder block 9 and the spherical plain bearing 80 is 0 in the swash plate type hydraulic pump 10 according to the above embodiment, the gap may alternatively be a fine gap. FIG. 3 is an enlarged longitudinal sectional view of part of the swash plate type hydraulic pump, showing an example where a gap in the axial direction is provided between the spherical plain bearing and the cylinder block. The swash plate type hydraulic pump 10 shown in FIG. 3 is in an assembled state where a fine gap ΔL in the axial direction L is provided between the cylinder block 9 and the spherical plain bearing 80. To be more specific, the first end surface 95 of the cylinder block 9 and the hole bottom 85 of the guide hole 84 of the spherical plain bearing 80 are spaced apart from each other in the axial direction L, and there is the gap ΔL in the axial direction L between the first end surface 95 of the cylinder block 9 and the hole bottom 85 of the guide hole 84 of the spherical plain bearing 80. The size of the gap ΔL is designed to be more than 0 and equal to or less than 1.2 mm, and more desirably, more than 0 and equal to or less than 0.8 mm when the swash plate type hydraulic pump 10 is in an assembled state.

It should be noted that the position of the gap ΔL in the axial direction L between the cylinder block 9 and the spherical plain bearing 80 is not limited to the position between the first end surface 95 of the cylinder block 9 and the hole bottom 85 of the guide hole 84 of the spherical plain bearing 80. FIG. 4 is an enlarged longitudinal sectional view of part of the swash plate type hydraulic pump, showing Example 2 where a gap in the axial direction is provided between the spherical plain bearing and the cylinder block. In the example shown in FIG. 4, the second end surface 96 of the cylinder block 9 and the flange 82 of the spherical plain bearing 80 are spaced apart from each other in the axial direction L, and there is a fine gap ΔL in the axial direction L between the second end surface 96 of the cylinder block 9 and the flange 82 of the spherical plain bearing 80. It should be noted that, in this example, the set springs 20 are multiple disc springs provided so as to apply resilient force between the hole bottom 85 of the guide hole 84 of the spherical plain bearing 80 and the first end surface 95 of the cylinder block 9.

As another example, although the shim plates 30 are used as the filling member F in the swash plate type hydraulic pump 10 according to the above embodiment, the filling member F is not limited to the shim plates 30. FIG. 5 is an enlarged longitudinal sectional view of part of the swash plate type hydraulic pump, showing Example 2 where space in the axial direction between the spherical plain bearing and the cylinder block is filled. In the example shown in FIG. 5, space G in the axial direction L is provided between the first end surface 95 of the cylinder block 9 and the hole bottom 85 of the guide hole 84 of the spherical plain bearing 80. The space G is filled with a filling ring 31. Accordingly, the gap in the axial direction L between the cylinder block 9 and the spherical plain bearing 80 is 0. The filling ring 31 serves as an annular filling member F. An accommodating portion 32 in the shape of an annular groove is formed in the hole bottom 85 of the guide hole 84 of the spherical plain bearing 80. The first side of the filling ring 31 is partially embedded in the accommodating portion 32. The second-side end surface of the filling ring 31 is in contact with the first end surface 95 of the cylinder block 9. At the time of assembling the swash plate type hydraulic pump 10, first, a time-hardening or thermosetting filler 33 is injected into the accommodating portion 32 of the spherical plain bearing 80, and then the filling ring 31 is fitted into the accommodating portion 32 toward the first side. Thereafter, the filler 33 is cured in a state where the filling ring 31 and the first end surface 95 of the cylinder block 9 are in contact with each other. When the filler 33 is provided between the spherical plain bearing 80 and the filling ring 31 in the above manner, even if the size of the space G varies due to dimensional errors of components, the space G can be filled with high precision by using the filling ring 31 and the filler 33. It should be noted that the filler 33 desirably has such bonding capability as to fix the filling ring 31 to the accommodating portion 32 of the spherical plain bearing 80. Alternatively, high-strength adhesive may be applied to the outer periphery of the filling ring 31, and the filling ring 31 and the spherical plain bearing 80 may be bonded together at their contacting faces via the adhesive. In such a case, the use of the filler 33 may be eliminated.

Further alternatively, a press-fit bushing may be used as the filling member F. FIG. 6 is an enlarged longitudinal sectional view of part of the swash plate type hydraulic pump, showing Example 3 where space in the axial direction between the spherical plain bearing and the cylinder block is filled. In the example shown in FIG. 6, space G in the axial direction L is provided between the first end surface 95 of the cylinder block 9 and the hole bottom 85 of the guide hole 84 of the spherical plain bearing 80. The space G is filled with a press-fit bushing 41. Accordingly, the gap in the axial direction L between the cylinder block 9 and the spherical plain bearing 80 is 0. The press-fit bushing 41 serves as a tubular filling member F. An annular groove-shaped press-fit portion 42 is formed in the hole bottom 85 of the guide hole 84 of the spherical plain bearing 80. The press-fit bushing 41 is press-fitted into the press-fit portion 42 toward the first side. The press-fit bushing 41 press-fitted into the press-fit portion 42 of the spherical plain bearing 80 cannot be removed from the press-fit portion 42 due to friction. When the swash plate type hydraulic pump 10 is in an assembled state, the second-side end surface of the press-fit bushing 41 is in contact with the first end surface 95 of the cylinder block 9. When the press-fit bushing 41 is used as the filling member F in the above manner, the variation in the size of the space G can be absorbed by adjusting the degree of press-fitting of the press-fit bushing 41. Alternatively, high-strength adhesive may be applied to the outer periphery of the press-fit bushing 41, and the press-fit bushing 41 and the press-fit bushing 41 may be bonded together via the adhesive. In this case, the press-fit bushing 41 need not be press-fitted, but may be loose-fitted.

As yet another example, in the swash plate type hydraulic pump 10 according to the above embodiment, the position of the gap in the axial direction L between the cylinder block 9 and the spherical plain bearing 80, which gap is to be filled with the filling member F, is not limited to the position between the first end surface 95 of the cylinder block 9 and the hole bottom 85 of the guide hole 84 of the spherical plain bearing 80. FIG. 7 is an enlarged longitudinal sectional view of part of the swash plate type hydraulic pump, showing Example 4 where space in the axial direction between the spherical plain bearing and the cylinder block is filled. In the example shown in FIG. 7, space G in the axial direction L is provided between the flange 82 of the spherical plain bearing 80 and the second end surface 96 of the cylinder block 9, at which surface the spring accommodating holes 93 are open. The space G is filled with a filling column 35 which serves as the filling member F. Accordingly, the gap in the axial direction L between the spherical plain bearing 80 and the cylinder block 9 is 0. Similar to the spring accommodating holes 93, the cylinder block 9 is provided with a plurality of filling member accommodating holes 98 opening toward the swash plate 15. The filling column 35 is inserted in each filling member accommodating hole 98. The filling column 35 protrudes toward the first side from each filling member accommodating hole 98 of the cylinder block 9. The end surface of the protruding first side of the filling column 35 is in contact with the flange 82 of the spherical plain bearing 80. At the time of assembling the swash plate type hydraulic pump 10, first, a time-hardening or thermosetting filler 36 is injected into the filling member accommodating holes 98 of the cylinder block 9, and then the filling column 35 is fitted into each filling member accommodating hole 98. Thereafter, the filler 36 is cured in a state where the first-side end surface of the filling column 35 and the flange 82 of the spherical plain bearing 80 are in contact with each other. When the filler 36 is provided between the cylinder block 9 and the filling column 35 in the above manner, even if the size of the space G varies due to dimensional errors of components, the space G can be filled with high precision by using the filling column 35 and the filler 36. It should be noted that the filler 36 desirably has such bonding capability as to fix the filling column 35 into the filling member accommodating hole 98 of the cylinder block 9. Alternatively, high-strength adhesive may be applied to the outer periphery of the filling column 35, and the filling column 35 and the cylinder block 9 may be bonded together via the adhesive. In such a case, the use of the filler 33 may be eliminated.

In the above examples shown in FIGS. 5, 6, and 7, the filling member F (filling ring 31, press-fit bushing 41, filling column 35) is used to fill the space G in the axial direction L between the cylinder block 9 and the spherical plain bearing 80. These filling members F may be provided either at the cylinder block 9 or at the spherical plain bearing 80. The above embodiment has been described by taking the swash plate type hydraulic pump as an example of a swash plate type hydraulic rotating machine. However, the swash plate type hydraulic rotating machine to which the present invention is applicable is not limited to a swash plate type hydraulic pump. The swash plate type hydraulic rotating machine to which the present invention is applied may be a swash plate type hydraulic motor, for example.

INDUSTRIAL APPLICABILITY

The present invention is, when applied to a swash plate type hydraulic rotating machine such as a swash plate type hydraulic pump or swash plate type hydraulic motor, capable of preventing the shoes from being lifted from the swash plate even if the rotational speed of the rotating shaft is increased. Therefore, the present invention is widely applicable to swash plate type hydraulic rotating machines that include a swash plate with a variable maximum tilting angle, regardless of the structural details of such machines.

REFERENCE SIGNS LIST

• • G space
  • F filling member
  • 3 rotating shaft
  • 4 valve plate
  • 5, 6 suction/discharge port
  • 9 cylinder block
  • 11 cylinder
  • 13 piston
  • 14 shoe
  • 15 swash plate
  • 17 keep plate
  • 20 set spring
  • 30 shim plate
  • 31 filling ring
  • 32 accommodating portion
  • 33 filler
  • 35 filling column
  • 36 filler
  • 41 press-fit bushing
  • 80 spherical plain bearing

Claims

1. A swash plate type hydraulic rotating machine comprising:

a rotating shaft;

a valve plate and a swash plate facing each other and away from each other in an axial direction of the rotating shaft;

a cylinder block fitted to an outside of the rotating shaft between the valve plate and the swash plate, such that the cylinder block is slidingly in contact with the valve plate;

a plurality of cylinders provided in the cylinder block;

a plurality of pistons inserted in the respective cylinders, such that the pistons are movable in the axial direction in a reciprocating manner;

a plurality of shoes each connected to a distal end of a respective one of the pistons such that each shoe is movable in a rocking manner, wherein the distal end of each piston protrudes from a respective one of the cylinders toward the swash plate side;

an annular keep plate loosely fitted to the rotating shaft between the swash plate and the cylinder block, the keep plate holding the shoes;

a plain bearing provided between the keep plate and the cylinder block, the plain bearing supporting the keep plate; and

spring members provided between the plain bearing and the cylinder block, the spring members biasing the plain bearing to cause the plain bearing to push the keep plate toward the swash plate side, wherein

a gap in the axial direction between the plain bearing the cylinder block is 0 or a fine gap when the swash plate type hydraulic rotating machine is in an assembled state.

2. The swash plate type hydraulic rotating machine according to claim 1, wherein the gap has a size of 0, or has a size of more than 0 and equal to or less than 1.2 mm.

3. A swash plate type hydraulic rotating machine comprising:

a rotating shaft;

a valve plate and a swash plate facing each other and away from each other in an axial direction of the rotating shaft;

a cylinder block fitted to an outside of the rotating shaft between the valve plate and the swash plate, such that the cylinder block is slidingly in contact with the valve plate;

a plurality of cylinders provided in the cylinder block;

a plurality of pistons inserted in the respective cylinders, such that the pistons are movable in the axial direction in a reciprocating manner;

a plurality of shoes each connected to a distal end of a respective one of the pistons such that each shoe is movable in a rocking manner, wherein the distal end of each piston protrudes from a respective one of the cylinders toward the swash plate side;

an annular keep plate loosely fitted to the rotating shaft between the swash plate and the cylinder block, the keep plate holding the shoes;

a plain bearing provided between the keep plate and the cylinder block, the plain bearing supporting the keep plate;

spring members provided between the plain bearing and the cylinder block, the spring members biasing the plain bearing to cause the plain bearing to push the keep plate toward the swash plate side; and

a filling member filling a gap in the axial direction between the plain bearing and the cylinder block.

4. The swash plate type hydraulic rotating machine according to claim 3, wherein the filling member is at least one shim plate.

5. The swash plate type hydraulic rotating machine according to claim 3, comprising a time-hardening or thermosetting filler between the filling member and one of the plain bearing and the cylinder block.

6. The swash plate type hydraulic rotating machine according to claim 3, wherein the filling member is a press-fit bushing.