JPH0842446A - Variable displacement swash plate type hydraulic machine - Google Patents

Abstract

PURPOSE:To reduce power loss of a slide section and prevent metallic contact between a swash plate and a slipper by providing a plurality of mutually independent groove sections in a seal land portion on a bottom surface of a piston slipper and forming a part in the vicinity of radius of a pocket of the slipper into the shape of spherical surface. CONSTITUTION:Pistons 7, 7 are provided in a cylinder bore 6 in a variable capacity type and swash plate type axial piston pump in such a manner that they can reciprocate, and a piston slipper 8 is rotatably provided in a spherical portion at a tip of the piston 7 to press a bottom surface 9 of the slipper 8 against a swash plate 11 by a retainer 10. Grooves 23a-23d whose surface is circular shape and whose cross-section is crescent moon shape are formed mutually independently for a seal land portion 21 on a slide bottom surface 9 of the slipper 8, and a part 24 in the vicinity of radius of a pocket of the slipper 8 is formed into the shape of recessed spherical surface. Consequently, it is possible to reduce torque loss on a slide surface between the swash plate 11 of a hydraulic pump and the piston slipper 8 and the leak amount of hydraulic fluid from the slide surface.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a slipper bearing (static pressure thrust bearing) structure of a variable displacement type swash plate type hydraulic machine capable of operating under a wide range of rotational speed conditions from high speed to low speed.

[0002]

2. Description of the Related Art In a hydraulic system in which a working fluid is used as a power transmission medium, in order to further improve performance, save energy, improve functionality, and increase reliability, the system has a high power density and an electronic system. Is being pursued. In particular, in order to increase the power density of the hydraulic pump / motor, which is the heart of the system components, it is essential to increase the pressure and speed. When the hydraulic pump / motor is operated at a high pressure, it is important to minimize the loss of power due to leakage and friction in each sliding part, which is an important issue for achieving the target. Especially, there are three typical sliding parts in a hydraulic pump / motor ((a) between swash plate and slipper,
(B) between the cylinder block and the valve plate, (c) between the inner wall of the cylinder block and the piston), and the quality of the sliding characteristics at this sliding portion depends on the performance of the pump / motor itself, such as volumetric efficiency and mechanical efficiency. Have a dominant effect on the quality of.

In order to deal with this problem, conventionally, for example,
In the swash plate type axial piston pump / motor, which is one of the variable displacement hydraulic machines, in order to improve the sliding characteristics between the swash plate and the slipper bearing, the bottom surface of the slipper bearing has a bearing load by static pressure and dynamic pressure action. The one provided with a pocket, an annular groove or the like for exhibiting the capacity is put to practical use. Therefore, when classifying these slipper bearings by the bottom shape of the slipper, there is a seal land on the outside, a hydraulic equilibrium chamber in the center, and a pressure guide hole is provided in the center.
Self-discharge pressure is introduced into this pressure guide hole to achieve hydraulic equilibrium, which is a hydraulic equilibrium type (basic type), an external auxiliary surface with an auxiliary bearing surface on the outside of the hydraulic equilibrium type, and both inside and outside the hydraulic equilibrium type. There is an inner and outer auxiliary surface provided with an auxiliary bearing surface, a thin spiral groove facing outward from the hydraulic equilibrium chamber, and a seal land surface lubricated by a pressure drop between them.

[0004]

In the prior art, in the case of the hydraulic equilibrium circular slipper bearing, the shape of the bottom surface of the slipper is simple, so that it is easy to manufacture and inexpensive. However, when disturbances such as force and moment act on the slipper bearing under low-pressure and high-pressure use conditions such as a hydraulic motor, the dynamic pressure effect cannot be expected, and the slipper bearing tilts and the gap between the slipper bearing and the swash plate is reduced. Therefore, it is difficult to form an oil film on the outer seal land.
As a result, the inclination correction function of the slipper bearing itself for maintaining the fluid lubrication state between the swash plate and the slipper is significantly reduced. Further, by applying high pressure, the bottom surface of the slipper is elastically deformed in a convex shape in the out-of-plane direction. As a result, in the sliding portion between the swash plate and the slipper, elastic deformation causes a difference in elastic deformation between the inner and outer diameter portions of the seal land, resulting in partial metal contact. As a result, there is a problem that the power loss between the swash plate and the slippers due to friction increases. Further, due to elastic deformation of the bottom surface of the slipper, the substantial seal length of the slipper seal land is reduced and the leakage flow rate from this surface increases.

Further, when the slipper bearing with the outer auxiliary surface and the inner and outer auxiliary surfaces is used under high speed rotation, there is a problem that the oil film thickness increases due to the dynamic pressure effect and the power loss due to the leakage flow increases. is there. Further, as described above, when the oil film thickness on the sliding surface between the swash plate and the slipper becomes large,
Oil film rigidity decreases. As a result, a disturbance may be applied to the slipper bearing, and an additional problem that the restoring function when the slipper itself is tilted deteriorates is expected. Further, since the bottom surface of the slipper is elastically deformed, the same problem as in the hydraulic balance type described above occurs. Furthermore, the slipper bearing with the inner and outer auxiliary surfaces has a complicated shape of the bottom surface of the slipper, which requires a processing procedure and man-hours. There is a problem that the cost becomes higher than this.

Against this background, the loss power due to friction is mainly reduced by compensating for the influence of the elastic deformation of the bottom surface of the slipper on the sliding characteristics when high pressure is applied, and the oil film thickness is further reduced at high pressure and low speed. It has been desired to develop a slipper bearing that accelerates the formation of the oil, suppresses the increase in the oil film thickness due to the dynamic pressure effect at high pressure and high speed, reduces the power loss due to the leakage flow rate, and is easy to manufacture and inexpensive.

An object of the present invention is to provide a good sliding condition in a wide range of rotational speeds from low speed to high speed at high pressure, that is, a structure that allows sliding with low leakage and low loss torque. Moreover, it is to provide an inexpensive slipper bearing.

[0008]

In order to achieve the above object, the present invention forms a plurality of independent groove portions in a seal land portion of a slipper bottom surface of a hydraulic equilibrium circular slipper bearing to form a slipper pocket radius. The vicinity was formed into a concave spherical shape or a chamfered shape.

Another solution of the present invention is to form a plurality of independent groove portions on the seal land portion on the bottom surface of the slipper of a hydraulic balanced circular slipper bearing, and to form the seal land portion of the slipper into a concave spherical shape. Alternatively, the seal land portion is formed in a tapered shape from the inside to the outside.

Further, in another solution, in order to give a restoring function to the slipper itself when the slipper tilts due to the dynamic behavior based on the rotation and the revolution of the slipper, the surface shape of the groove provided in the seal land portion is The seal land has at least one of a circular shape, a rectangular shape, a triangular shape and a rhombus shape, and the groove has a cross-sectional shape of at least one of a crescent shape, a triangular shape and a rectangular shape. The groove provided in the portion is formed so as to be a combination of at least one set out of the grooves, and at least one set is formed from the shape of the portion near the pocket radius of the slipper or the shape of the seal land portion of the slipper. I tried to combine them.

[0011]

The plurality of grooves, which are provided in the seal land portion of the hydraulic equilibrium circular slipper bearing and have a minute depth independently of each other, act as a plane stop. As a result, the outward radial flow of pressure oil from the hydraulic equilibrium chamber of the slipper bearing forms a liquid pool in the groove. On the other hand, based on the rotation of the slipper itself around the piston ball joint portion and the orbital motion of the slipper bearing with respect to the swash plate, the slipper bearing is tilted due to the load and moment acting on the slipper bearing. However, since the groove functions as a dynamic pressure bearing and a quasi-static pressure bearing, it has a function of correcting the inclination of the slipper bearing. As a result, there is always an oil film thickness having an arbitrary pressure value at the relative sliding portion between the seal land portion of the slipper bearing and the swash plate. Therefore, for example, when it is difficult to form an oil film on the sliding surface, such as when the hydraulic motor is started, the groove described above adapts to the load by the static pressure created, and the hydrostatic effect produces the piston hydraulic pressure of the load. Support the reaction force. As a result, the power loss due to the sliding friction at the start can be reduced. On the other hand, even when the hydraulic pump / motor rotates at high speed at high pressure, the bottom surface of the slipper elastically deforms in the out-of-plane direction, and the slipper itself tilts and rotates and revolves, The concave spherical shape, the chamfered shape, or the taper shape from the inside to the outside of the seal land are preliminarily formed, so that the elastic deformation difference in the out-of-plane direction generated on the bottom surface of the slipper can be absorbed. As a result, metal contact due to elastic deformation does not occur between the swash plate and the slippers. Moreover, since the cross-sectional shape of the plurality of grooves provided in the seal land portion of the slipper is crescent-shaped or triangular, the hydrodynamics based on the above-mentioned dynamic pressure generated in the grooves and the quasi-static based quasi-static pressure are further applied. In addition to the combined action of hydrostatics, a wedge effect based on the geometrical shape of the groove section can be expected. As a result, even if the slipper bearing is subjected to load fluctuation and rotationally tilted in all directions, the tilt of the slipper is quickly corrected. As a result, the oil film thickness formed on the swash plate and the seal land of the slipper bearing can be made uniform. As a result, the torque loss on both sliding surfaces and the leakage flow rate from both sliding surfaces can be reduced. As a result, it is possible to minimize the power loss due to leakage and friction on both sliding surfaces. Further, since the sliding portion between the swash plate and the seal land of the slipper bearing does not come into metal contact with each other, it is possible to prevent galling that occurs on both sliding surfaces.

[0012]

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings, taking a variable displacement type swash plate type axial piston pump as an example.

1 to 3 show a first embodiment of the present invention. FIG. 1 is a vertical sectional view of a rotary portion of a variable displacement swash plate type axial piston pump according to an embodiment of the present invention. In the figure, reference numeral 1 denotes a casing body composed of a casing 1A and a casing 1B, 2 denotes a rotating shaft provided so as to project into the casing 1A, and a male spline 3 is formed in the middle of the rotating shaft 2. The rotary shaft 2 is rotatably supported by rolling bearings 4a and 4b arranged at two places. Reference numeral 5 denotes a cylinder block which is provided in the casing 1 and rotates integrally with the rotary shaft 2. The cylinder block 5 is provided with a plurality of cylinder bores 6, ... 6 bored in the axial direction, and the cylinder bore 6 is provided with a piston 7 and a piston 7, respectively. 7 is provided so as to be able to reciprocate. A piston slipper 8 is rotatably provided on the spherical end of the piston 7.
In addition, the bottom surface 9 of the slipper 8 is attached to the swash plate 11 by the retainer 10.
Pressed to. Reference numeral 12 denotes a valve plate. One end face of the valve plate 12 is in sliding contact with the end face of the cylinder block 5, and the other end face is in contact with the casing 1B. The valve plate 12 is provided with a pair of intake / exhaust ports 13A and 13B that are intermittently communicated with the cylinder bores 6 when the cylinder block 5 rotates.
3A and 13B communicate with a pair of intake / exhaust passages 14A and 14B provided in the casing 1B. Reference numeral 15 is a compression spring for applying a preload to the sliding surface between the cylinder block 5 and the valve plate 12. Reference numeral 16 is a regulator for variably controlling the discharge amount from the pump,
, And is integrally connected to the swash plate 11.

Next, according to the present embodiment, the construction of the bottom surface 9 of the piston slipper 8 for reducing the loss torque at the sliding surface between the swash plate 11 of the hydraulic pump and the piston slipper 8 and the leakage flow rate from the sliding surface. I will describe.

FIG. 2 is a cross-sectional view of the slipper 8 in FIG. 1 as seen from the direction of arrow I, and FIG. 3 is a vertical cross-sectional view of the slipper in FIG. The feature of this embodiment is that a plurality of grooves having a circular surface shape and a crescent-shaped cross section are formed in the seal land portion of the sliding bottom surface 9 of the slipper 8 in the same figure (in the case of four in this embodiment). Independently of each other, the portion near the pocket radius of the slipper 8 is formed in a concave spherical shape. In FIG. 2, 21 is a seal land portion on the sliding surface of the slipper 8, and 23a to 23d are seal land portions 2.
It is a groove formed in 1. Reference numeral 24 is a concave spherical surface portion near the pocket radius of the slipper, 20 is a hydraulic equilibrium chamber in which static pressure exists (hereinafter referred to as pocket portion), and 22 is a fixed throttle portion for supplying static pressure to the pocket portion. Indicates.

Although this embodiment is constructed in this way, the operation when it is used as a hydraulic pump will be described below.

When the rotating shaft 2 is rotated by a drive source such as an engine or an electric motor, the rotating shaft 2 and the cylinder block 5 are integrally connected by a male and female spline or the like, so that the cylinder block 5 is integrated with the rotating shaft 2. Is rotated. As a result, each piston 7 reciprocates in the cylinder bore 6 while the cylinder block 5 is rotating. At this time,
Since the swash plate 11 is tilted in advance from the axis perpendicular to the rotation direction to an arbitrary tilt angle by the regulator 16, a difference occurs in the stroke of each piston 7 while the cylinder block 5 makes one rotation. , While each piston 7 is retracting from the cylinder bore 6, it is a suction process of sucking hydraulic oil from the intake / exhaust passage 14B into the cylinder bore 6 through the intake / exhaust port 13B, and while each piston 7 is entering the cylinder bore 6, 6 is a discharge step of pressurizing the hydraulic oil in 6 and discharging it through the intake / exhaust port 13A and the intake / exhaust passage 14A. At this time, a force (generally referred to as a piston lateral component force) acts on the slipper 8 of the piston 7 located in the discharge step in a direction perpendicular to the axial direction of the piston 8. As a result, a friction moment is generated in the piston 7 and the slipper 8 about the ball joint portion connecting the piston 7 and the slipper 8. As a result, the slipper 8 itself tilts, and a bending moment acts on the piston 7, whereby the sliding state between the swash plate 11 and the bottom surface 9 of the slipper and the sliding state between the inner wall of the cylinder bore 6 and the piston 7 are fluidized. The transition from lubrication to mixed lubrication may partially induce metal contact. In particular, when the hydraulic pump is operated at high speed and high surface pressure, the thermal equilibrium in the sliding portion tends to be lost. As a result, the pV value (here, p: surface pressure, V: peripheral speed), which is a measure of the seizure limit of the sliding member, becomes higher.

On the other hand, in the hydraulic motor, since the rotation speed range used is wide ranging from low speed to high speed, an oil film is formed on the sliding surface of the swash plate 11 and the seal land of the slipper bottom surface 9 especially at low speed and high load. Formation becomes difficult.

At the time of sliding as described above, an increase in loss torque and leakage flow rate due to sliding friction is induced, and loss power resulting from this causes a problem. Therefore, under actual operating conditions, that is, when low to high speeds and high surface pressure (high load) are assumed, the swash plate and slippers should be used to minimize the power loss in the sliding parts even in such operating conditions. Sliding part between,
Especially, the optimization of the structure of the bottom surface 9 of the slipper 8 is indispensable.

The present invention has been invented in order to eliminate such a problem. Since the present invention is constructed as shown in FIGS. 2 and 3, the bottom surface of the slipper is elastically deformed in the out-of-plane direction when a high pressure is applied. However, since the portion of the bottom surface of the slipper near the pocket radius of the slipper having a large elastic deformation difference is previously formed into a concave spherical shape, the elastic deformation difference can be absorbed. Further, even if the slipper 8 is tilted, the four grooves 23a to 23d independently provided in the seal land portion of the bottom surface 9 of the slipper 8 are
It functions to form a hydrodynamic fluid film. As a result, even if the slippers are inclined, the groove portion exerts a positive dynamic pressure bearing effect with a wedge effect, and this inclination can be corrected. That is, in other words, the inclination of the slipper 8 can be corrected by the synergistic effect of the dynamic pressure effect other than the groove portion of the seal land and the quasi-static pressure effect of the dynamic pressure in the groove portion.

As a result, the rotational speed changes from low speed to high speed, and even if the sliding condition between the swash plate and the slipper changes, a small oil film is always formed on both the swash plate 11 and the bottom surface 9 of the slipper 8. The thickness can be maintained in a substantially parallel state of fluid lubrication. This makes it possible to prevent metal contact on both sliding surfaces. Therefore, it is possible to reduce the torque loss due to friction on both sliding surfaces and the leakage flow rate from the sliding surfaces, so that the loss power due to these can be minimized.

FIG. 4 shows a modification of the first embodiment of the present invention, in which a plurality of independent groove portions are formed in the seal land portion on the bottom surface of the hydraulic equilibrium circular slipper, and the pocket radius of the slipper 8 is formed. This is a case where the neighboring portion 26 is formed into a chamfered shape. 5 and 6 show another modification of the first embodiment of the present invention, in which a plurality of independent groove portions are formed in the seal land portion of the bottom surface of the hydraulic equilibrium circular slipper, and the slipper is formed. That is, the seal land portion 28 of No. 8 has a concave spherical shape, or the seal land has a tapered shape 30 from the inside to the outside. FIG.
6 to 6, the basic structure of the slipper 8 except for the pocket radius vicinity portion 26 and the seal land portions 28 and 30 is the same as that of the first embodiment shown in FIGS. 2 and 3.

With such a structure, the same operation and effect as in the case of the first embodiment can be expected. In particular,
When the thickness of the slipper 8 is reduced in order to reduce the weight of the slipper 8, the elastic deformation difference between the inner and outer diameter portions of the seal land increases due to the application of high pressure. In this case, it is possible to absorb the elastic deformation difference generated on the entire surface of the seal land as shown in FIG.
Alternatively, the modified example of FIG. 6 is effective.

On the other hand, in the first embodiment and the modification of the first embodiment of the present invention, the case where the surface shape of the groove provided in the seal land is circular and the sectional shape of the groove is crescent-shaped is described. However, the shape of the groove is not limited to a circular shape, and among geometrical shapes such as a rectangle, a triangle, and a rhombus,
It may have at least one shape.
Further, the cross-sectional shape of the groove may be at least one of geometric shapes such as a triangular shape and a rectangular shape. Furthermore, the shape of the groove or the recess can be modified into an elliptical shape or a polygon with five or more sides in addition to the above typical shape.

Further, the number of grooves is not limited to four, and three grooves may be provided at 120 ° pitch. In addition,
The surface shape and cross-sectional shape of the groove in this case are the same as those in the first embodiment.

On the other hand, by forming a groove having a minute depth in the seal land portion on the bottom surface of the slipper, there is also an effect of absorbing elastic deformation of the bottom surface of the slipper when a high pressure is applied. This prevents the bottom surface of the slipper from deforming in a convex shape. As a result, the oil film thickness formed on the sliding portion between the swash plate 11 and the slipper bottom surface 9 is made uniform, and the power loss at the sliding portion can be reduced.

Therefore, according to the present invention, the synergistic effect of the two effects of dynamic pressure and wedge not only has the function of correcting the inclination of the slipper at low pressure to high speed at high pressure, but also absorbs the elastic deformation of the slipper on the order of micron. Since it can also be demonstrated together, the effect of reducing the loss power of the sliding portion due to friction becomes more reliable.

Further, the present invention is provided with an outer auxiliary surface provided with an auxiliary bearing surface on the outside of a hydraulic balanced type or a hydraulic balanced type, which is a conventional technique relating to a slipper bearing, and further, an auxiliary bearing surface is provided on both inner and outer parts of the hydraulic balanced type. The same effect as the present invention can also be expected when applied to an interior / exterior auxiliary surface.

FIG. 7 shows an embodiment in which the present invention is applied to HST. Although various embodiments can be considered for the basic configuration of the HST drive system, here, the most general case, that is, a closed circuit system including a variable displacement pump and a constant displacement motor will be considered. In the figure, 40 is a drive source electric motor or engine, 42 is a variable displacement pump, 46 is a constant displacement motor, and 44 is a main circuit for hydraulically coupling the pump and the motor. Here, a feature of the present invention is that an HST (hydrostatic transmission) is constituted by 42 pumps and 46 motors in which the groove according to the present invention is formed in the sliding portion between the swash plate and the slippers. With such a configuration, even if the HST is operated in a wide speed range from low speed to high speed, an appropriate fluid lubrication state can be maintained in the sliding portion of the pump / motor, so that a highly efficient and stable HS can be maintained.
A T system can be provided.

In addition to this, it can be applied to the relative sliding portion of a general industrial hydraulic pump / motor. For example, in order to increase the power density of a hydraulic pump / motor for construction machinery, it is essential to increase the speed and pressure of the pump / motor. On the other hand, the biggest problem with the high pressure of the pump / motor is the lack of durability of the rolling bearing for supporting the piston hydraulic reaction load. One solution to this problem has been proposed in which the piston hydraulic reaction force is supported not by rolling bearings but by thrust and radial slipper bearings that use static pressure. The groove of the present invention can be applied to the bottom surface of the slipper bearing that constitutes such a piston hydraulic reaction force support mechanism. As a result, the power loss in the sliding parts of the pump / motor can be reduced, and high pressure and high performance of the hydraulic pump / motor for construction machinery can be realized.

Next, a method of processing the groove formed on the bottom surface of the slipper used in the variable displacement type swash plate type axial piston type hydraulic machine of the present invention will be described. When a groove is formed in the seal land portion on the bottom surface of the slipper, the slipper unit is first cut into a substantially final shape, and then a specific groove is formed in the seal land portion on the bottom surface of the slipper. The method of forming the groove can be roughly classified into (1) plastic working (for example, press working), (2) cutting or grinding, (3) laser processing, (4) precision casting, etc. Can also be molded.

For example, in the case of a so-called bimetal structure slipper in which the seal land portion on the bottom surface of the slipper is formed of an alloy, and the rest is formed of an iron system whose surface is modified by heat treatment, a groove formed in the slipper seal land portion. Among the groove forming means, the method using a plastic working means using a press or the like is simple, has good operability, and is inexpensive, so this method will be described below. That is, a jig having a groove shape formed in the seal land portion is manufactured in advance from a material having high hardness and high toughness (for example, super hard material).
Next, the jig is chucked on, for example, a spindle rotating portion such as a drilling machine, and the bottom surface of the slipper is fixed to a table facing the spindle rotating portion. Then, the main shaft is pushed down to form a specific groove shape on the bottom surface of the slipper.

Although the above-described groove formation is a manual method, the following may be performed in order to improve the efficiency of the groove formation work. That is, the positioning of the spindle in the rotation direction is performed by a stepping motor or the like, and the stroke mechanism below the spindle is driven electrically or hydraulically (air, hydraulic pressure, water pressure), and these movements are programmed in advance. Thus, automation of groove formation can be easily realized.

In the groove processing method, the slipper to be formed with the groove is fixed to the support base, the jig is fixed to the support mechanism that can be positioned in the rotation direction and the vertical direction, and then the support mechanism is set to the groove formation position. An arbitrary groove is formed on the bottom surface of the slipper by the manual or automatic operation. On the other hand, contrary to the above-mentioned processing method, that is, the jig is fixed in advance, the slipper is attached to the support mechanism capable of rotating and linear positioning, and then the support mechanism is positioned at a predetermined position to form the groove. You may make it shape | mold.

[0035]

According to the present invention, the variable displacement type swash plate type hydraulic pump / motor is operated under high surface pressure from low speed to high speed, and the slipper elastically deforms in the out-of-plane direction when a high pressure is applied, and the piston lateral division. Even if tilted due to the influence of force, centrifugal force, friction moment around the piston ball joint, etc., a plurality of independent groove parts are provided in the seal land part on the bottom of the slipper, and the part near the pocket radius of the slipper and the seal land Since the part is formed in a concave spherical shape, chamfered shape and tapered shape from the inside to the outside of the seal land, the inclination of the slipper is corrected by the quasi-static bearing effect due to the dynamic pressure created by this groove, and the bottom of the slipper is also corrected. The shape can absorb the elastic deformation difference in the out-of-plane direction at high pressure. As a result, the loss torque and the starting torque at the sliding portion between the swash plate and the slipper can be minimized, and the leakage flow rate from both sliding surfaces can be reduced. As a result, the loss power based on the loss torque, the starting torque, and the leakage flow rate can be reduced. As a result, it is possible to provide a variable displacement type swash plate type axial piston pump / motor having high performance and good starting characteristics even when the operating conditions of the pump / motor are high and change from low speed to high speed.

Further, both sliding surfaces prevent metal contact,
Moreover, since the fluid lubrication state can be realized, the durability of the slipper sliding surface is improved.

[Brief description of drawings]

FIG. 1 is a sectional view of a rotating portion of a swash plate type axial piston pump / motor showing a first embodiment of the present invention.

FIG. 2 is a sectional view of the slipper in FIG.

3 is a cross-sectional view of the bottom surface of the slipper in FIG. 2 taken along the line AA.

FIG. 4 is an explanatory view showing a modified example of FIG. 2 and showing a chamfered shape in the vicinity of a pocket radius of a slipper.

5 is an explanatory view showing another modified example of FIG. 2 and showing a concave spherical shape of a seal land portion of a slipper.

6 is an explanatory view showing another modified example of FIG. 2 and showing a taper shape from the inside to the outside of the seal land portion of the slipper.

FIG. 7 is an explanatory diagram showing an embodiment when the present invention is applied to HST.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Casing body, 2 ... Rotating shaft, 5 ... Cylinder block, 7 ... Piston, 8 ... Piston slipper, 9 ... Slipper bottom surface, 11 ... Swash plate, 12 ... Valve plate, 13A, 13B ...
Suction / exhaust port, 16 ... Regulator.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Koichi Maezawa 603, Kazunachi-cho, Tsuchiura-shi, Ibaraki Hitate Works Tsuchiura Plant

Claims (1)

[Claims] 1. A cylinder block provided with a rotary shaft projecting into a casing and a plurality of cylinder bores provided in the casing and rotating together with the rotary shaft.
It is movable back and forth in the cylinder bore of the cylinder block, and comprises a piston fixed to a piston slipper,
The piston slipper is slidably attached along a swash plate that is inclined with respect to the rotation axis, and the inclination angle of the swash plate with respect to the rotation axis can be set to an arbitrary angle by a regulator. In the variable displacement type swash plate hydraulic machine described above, a plurality of independent groove portions are provided in the seal land portion of the bottom surface of the slipper, and a portion near the pocket radius of the slipper is formed into a spherical shape. Capacity type swash plate type hydraulic machine.