JPH10331759A - Hydraulic machine of swash plate type - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain high efficiency and low noise upon low tilting, high pressure, and high rotational speed operation by providing a swash type hydraulic machine piston comprising a hollow cylindrical piston shaft whose inner part is removed, and filler material which has a narrow hole penetrating axially and is inserted in a rear inner diameter part of the shaft. SOLUTION: A piston 7, which reciprocates in a cylinder bore 6 according to the ratation of a cylinder block 5 since it is pressed against a swash plate 17, comprises a hollow cylindrical piston shaft 7a sliding on the bore 6, a spherical part 73 formed at a fore end of the shaft 7a, and a filler 9 inserted into a rear end a hole 8 in the shaft 7a. Namely, the piston 7 is made hollow to be lightweight by removing the axial part of the shaft 7 so that a chamber 11 may be formed between the filler 9 and the spherical part 7j. A narrow hole 10 is formed in the axial part of the filler 9 while a lubrication hole 7h in the axial part of the spherical part 7j, and they 10, 7 are communicated with the chamber 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable displacement or fixed displacement swash plate type hydraulic machine, and more particularly to a small displacement, high pressure,
The present invention relates to a swash plate type hydraulic machine having a piston suitable for operating under high rotation conditions.

[0002]

2. Description of the Related Art A hydraulic system using a working fluid as a medium for power transmission has a higher power density (per weight) in order to achieve higher performance, energy saving, higher functionality and higher reliability. (Increase in output) and computerization. In particular, in order to increase the power density of a hydraulic pump / motor, which is the heart of system components, it is essential to increase the pressure and speed.

For example, in a system using oil as a working fluid, in order to realize high power density by increasing the pressure and rotation of a hydraulic pump / motor, it is essential to reduce power loss due to leakage and friction at each sliding portion. Becomes

As a prior art, a piston device of a variable displacement type or fixed displacement type swash plate type hydraulic machine is disclosed in, for example,
No. 42446. In the piston device disclosed in this publication, as shown in FIG.
The movable part is reduced in weight by removing the excess thickness from the center of the piston 7 to form a hollow cylindrical shape. The structure of the swash plate type hydraulic machine using this type of piston will be described with reference to FIGS.

[0005] By making the piston hollow, it is possible to minimize the piston inertia generated when the pump rotates at high speed. Therefore, during the suction stroke of the piston, the piston slipper 13 is
The preload spring force that is indispensable to prevent the preload spring 7 from being separated from the sliding surface can be realized with a minimum necessary magnitude.

Accordingly, the initial surface pressure value between the swash plate and the slipper due to the preload spring force can be suppressed, so that the friction loss at the time of initial sliding can be reduced.

[0007]

In order to increase the power density of a swash plate type axial piston pump, which represents a swash plate type hydraulic machine, high efficiency and low noise are obtained even when the pump is rotated at a small tilt, high pressure and high speed. It needs to be realized. On the other hand, since the piston 7 of the piston pump / motor according to the prior art has a hollow shape in which the rear end in the discharge direction is open, the space formed between the end face of the piston 7 and the cylinder port 6A in the cylinder bore 6. Not only the inside but also the hollow part of the piston 7 is filled with the fluid.

On the other hand, fluids are compressible, sometimes high pressure,
When used under high speed rotation, the volume change due to compression cannot be ignored. In particular, when a large amount of liquid is retained in the opened hollow portion of the piston 7 as in the case of the piston device according to the related art, the fluid in the cylinder behaves integrally, and thus the volume change due to compression occurs. The amount increases.

In the piston pump / motor, high pressure and low pressure are alternately switched every time the cylinder block 5 makes one rotation. Therefore, at the bottom dead center of the suction stroke in which the piston 7 retreats most from the cylinder block 5, the internal volume of the cylinder 6 becomes the largest including the volume of the hollow portion of the piston 7. When the cylinder block 5 further rotates and passes through the bottom dead center, the cylinder port 6A and the discharge port 25A are in communication. At this time, since the internal pressure of the cylinder 6 has not been sufficiently increased, the high-pressure fluid upstream of the discharge port 25A flows back into the cylinder port through the notch (see FIG. 2) of the closing portion of the valve plate 24. At this time, cylinder 6
A large surge pressure is generated due to the compressibility of the internal volume, and the pressure and flow pulsation of the discharged fluid are increased.

As a result, the noise of the pump / motor increases, and vibrations caused by the noise occur, which is a major obstacle in realizing a low noise of the pump / motor.

Further, the backflow from the high-pressure port 25A becomes a leak from the pump itself, and thus the volume efficiency is reduced. The leakage caused by the backflow becomes remarkable at the time when the inclination angle of the swash plate 17 of the pump is small, that is, when the inclination is small.

On the other hand, at the moment when the piston 7 switches from the top dead center of the high pressure discharge stroke into the cylinder block 5 to the low pressure suction port, the compressed high pressure fluid is discharged to the low pressure side. This results in energy loss and reduced volumetric efficiency due to leakage. As a result, the overall efficiency, which is a measure of the performance of the pump itself, is reduced.

Accordingly, the present invention will simultaneously solve (1) weight reduction of the piston, (2) reduction of fluid dead volume in the cylinder, and (3) suppression of a sharp change in the cylinder pressure near the bottom dead center. It is assumed that.

On the other hand, in the above-described prior art piston apparatus, consideration is given to minimizing the inertia of the piston by reducing the weight of the piston, but the influence of compressibility due to dead volume in the hollow portion of the piston is minimized. Further, no consideration has been given to the provision of a damping mechanism for suppressing a steep change in the cylinder internal pressure due to the backflow near the bottom dead center of the pressure switching point.

An object of the present invention is to provide a swash plate type hydraulic machine which realizes high efficiency and low noise even during small tilting, high pressure, and high speed operation.

[0016]

In order to achieve the above object, a first swash plate type hydraulic machine of the present invention is provided with a rotating shaft supported on an axis of a casing, and mounted around the rotating shaft,
A cylinder block having a plurality of cylinder bores opening parallel and equidistant to the axis of the rotating shaft and forwardly, and a piston slipper slidably fitted into the cylinder bore and a ball-socket joint at the front end. The attached piston, the swash plate provided in contact with the front surface of the piston slipper and inclined with respect to the rotation axis, the cylinder port penetrating the bottom of the rear end of each cylinder bore, and the cylinder port in contact with the rear surface of the cylinder block A corresponding valve plate having a liquid suction / discharge port, wherein the piston is a hollow cylindrical piston shaft formed with the ball part of the ball-socket joint as the front end and having a hollow inside. And a filler which is fitted and fixed to the rear inner diameter of the shaft and has pores penetrating in the axial direction.

In the first swash plate type hydraulic machine, the piston is formed in a conical shape with an annular groove formed on the outer periphery of the filler, and the piston is formed from the outer periphery of the piston shaft corresponding to the annular groove of the filler. It is preferable that the filler and the piston shaft be integrated by swaging from the outer periphery of the rear end of the piston shaft. Alternatively, the piston is made into a drum shape having a convex circular outer circumference and a concave cylindrical shape at the rear end of the piston shaft, and after inserting the filler into the internal diameter at the rear end of the piston shaft, the piston By swaging the vicinity of the rear end of the shaft from the outer periphery, the piston shaft and the filler may be integrated.
Alternatively, the piston is formed into a straight rod piece shape in which a plurality of annular grooves are provided on the outer periphery of the filling material, and a stepped hole is provided through the inner diameter of the rear end of the piston shaft. The piston shaft and the filler may be integrated by inserting a material and caulking the rear end of the piston shaft.

In order to achieve the above object, the second aspect of the present invention
The swash plate type hydraulic machine of the first embodiment is different from the first swash plate type hydraulic machine in the structure of the piston and the piston slipper.
Similarly to the swash plate type hydraulic machine, a rotating shaft supported on the axis of the casing, a cylinder block mounted around the rotating shaft and having a plurality of cylinder bores, and a piston slipper attached via a ball-socket joint are attached. Piston
A hydraulic machine including a swash plate provided to be inclined with respect to the rotation axis, a cylinder port penetrating the bottom of the rear end of each cylinder bore, and a valve plate having a liquid suction / discharge port. The front end is a socket part of a ball-socket joint, the rear end is a bottom plate with a small hole penetrated, and the middle part is constituted by a hollow cylindrical piston shaft with extra hollow inside, and the piston slipper is: The socket joint has a spherical portion at its rear end, and the piston and the piston slipper are integrated by caulking the socket portion from the outer periphery so as to enclose the spherical portion.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION

<First Embodiment> A first embodiment of the present invention will be described below with reference to FIG. FIG. 1 is a longitudinal sectional view of a rotating part of a variable displacement swash plate type axial piston pump according to Embodiment 1 of the present invention. In the following description, this swash plate type axial piston pump has a movement direction when the piston discharges a fluid as the rear (FIG. 1 right) and a movement direction when the fluid is sucked as the front (FIG. 1 left). The structure will be described.

This swash plate type axial piston pump has:
A hollow casing body 1 composed of a cylindrical casing 1A having an open rear end and a plate-shaped casing 1B joined to the rear end of the casing 1A, and a spline portion 3 provided at the axis of the casing main body 1 and being intermediate therebetween. A rotating shaft 2 formed and having a front end protruding from the casing main body 1, and a rolling bearing 4a and a cylindrical casing 1A provided in a plate-like casing 1B for rotatably supporting the rotating shaft 2 respectively.
And a cylinder block 5 having a center hole through which the rotating shaft 2 is inserted, and fitted with the spline portion 3 of the rotating shaft 2 and integrally rotating with the rotating shaft 2.
The cylinder block 5 is fixed to the inner surface of the casing 1B.
And a plurality of cylinder bores having a cylinder port 6A at the rear end and an open front end, the valve plate 24 being in contact with the rear end face, and the cylinder block 5 being bored in the cylinder direction at an equal distance from the axis and equidistant from each other. 6, each piston 7 having a spherical portion at its front end, which is reciprocally fitted into each cylinder bore 6, and which is characterized by the present invention as described later, and a socket portion 13s which engages with the spherical portion of each piston 7 so as to be rotatable. A connected piston slipper 13, a swash plate 17 disposed in the casing 1A, and having a central hole inserted through the rotary shaft 2 to be in contact with the front surface of each piston slipper 13;
Is fitted to the slipper retainer 15 for supporting the front surface of the piston slipper 13 so as to contact the swash plate 17 and the spline portion 3 of the rotary shaft 2 at the front end of the cylinder block 5;
A retainer guide 16 for supporting the slipper retainer 15 in contact with the center hole at the semicircular ball seat, and a boss at the front of the cylinder block 5 so as to press the piston slipper 13 against the swash plate 17 via the retainer guide 16 and the slipper retainer 15. A plurality of push pins 18 arranged through the portion 5a
In order to press the push pins 18, a cylindrical storage chamber 19 formed concentrically with the rotation shaft 2 on the inner surface of the rear portion of the center hole of the cylinder block 5 is sequentially arranged from the front to the rear. , An intermediate member 20, a plurality of disc springs 21, an annular locking member 22, and a retaining ring 23.

The piston 7 which characterizes the present invention is a hollow cylindrical piston shaft 7a which slides with respect to the cylinder bore 6.
A spherical portion 7j formed at the front end of the piston shaft 7a;
A chamber chamber 11 is formed between the filler 9 and the spherical portion 7j, and is formed of a continuous filler 9 inserted into the rear end of the hole 8 in the piston shaft 7a. By removing the excess thickness from the shaft center, it is hollow and lightweight. A pore 10 is provided in the axis of the filler 9 and a lubrication hole 7h is provided in the axis of the spherical portion 7j.
0 and 7h are connected to the chamber chamber 11. Further, the concave portion (near the minimum cross-sectional area) of the conical filler 9 is caulked from the outer peripheral side 12 of the piston shaft 7a to form the piston shaft 7a and the filler 9 integrally.

The rear locking member 22 serves to prevent the retaining ring from coming out when the retaining ring 23 is bent.
The plurality of disc springs 21 urge the intermediate member 20 toward the boss 6A. Also, the bottom surface 14 of the piston slipper 13
The push pin 18, the retainer guide 16 and the slipper retainer 15 are moved by the intermediate member 20 urged by the disc spring 21.
Through the swash plate 17. The swash plate 17 is supported by a well-known method (for example, a cradle method) not shown, and the inclination angle and the axial position of the swash plate 17 with respect to the rotating shaft 2 change even when a pressing force is applied by the bottom surface 14 of the piston slipper 13. Never.

On the other hand, the cylinder block 5 includes a disc spring 21
The rear locking member 2
2 and the retaining ring 23 are pressed and urged toward the valve plate 24 side,
The cylinder block 5 rotates while sliding on the valve plate 24. The valve plate 24 is formed with a pair of suction / discharge ports 25A, 25B which are intermittently communicated with the respective cylinder bores 6 by the rotation of the cylinder block 5;
25B is a pair of suction and discharge passages 26 provided in the casing 1B.
A, 26B. A regulator 27 for variably controlling the discharge amount from the pump is connected to the swash plate 17 at a connecting portion 28, and controls an angle formed by the swash plate 17 with the rotating shaft 2.

FIG. 2 is a view taken in the direction of arrows II-II in FIG. 1 and shows arc-shaped discharge ports 25A formed on the annular valve plate 24, respectively.
(High pressure side) and a drawing showing the suction port 25B (low pressure side) in plan view. A discharge port 25A and a suction port 25B formed point-symmetrically with respect to a center point of the annular valve plate 24, and a discharge port 25A and a suction port 25B
Each notch extending from one end of the circular arc and similarly formed in a point symmetry and a plane portion formed in the same point symmetry so as to correspond to the cross section of the cylinder port 6A are connected to form a circle. Each notch is a groove formed on the inner surface side of the valve plate 24.

The present embodiment is configured as described above.
Next, the operation when used as a hydraulic pump is shown in FIG.
2 will be described.

Drive source (not shown) for engine, electric motor, etc.
When the rotary shaft 2 is rotated by the rotation of the rotary shaft 2 and the cylinder block 5, the rotary shaft 2 and the cylinder block 5 are integrally connected by the spline portion 3 so as to restrict the relative movement in the circumferential direction. Rotate. The spherical portion 7j at the front end of each piston 7 is rotatably fitted to the socket portion 13s of the piston slipper 13, and the piston slipper 13 is pressed against the swash plate 17, so that each piston 7 is rotated by the rotation of the cylinder block 5, It reciprocates in the cylinder bore 6.

At this time, since the swash plate 17 is previously tilted by the regulator 27 so as to have an arbitrary tilt angle from a plane perpendicular to the rotation shaft 2, each swash plate 17 is rotated while the cylinder block 5 makes one rotation. A difference occurs in the strokes of the pistons 7, and while each piston 7 retreats from the cylinder bore 6 (while moving to the left in the drawing), the cylinder bores pass from the suction / discharge passage 26 B of the casing 1 B via the suction / discharge port 25 B of the valve plate 24. During the suction stroke of sucking the hydraulic oil into the cylinder bore 6, on the other hand, while each piston 7 enters the cylinder bore 6 (while moving to the right in the drawing), the hydraulic oil in each cylinder bore 6 is pressurized and the valve plate is pressed. 24 suction / discharge ports 25
A, a discharge stroke for discharging through the suction / discharge passage 26A of the casing 1B.

Here, the rotation angle of the cylinder block 5 slightly advances from the bottom dead center of the suction stroke (the position where the piston 7 retreats most from the cylinder bore 6), and the cylinder port 6A connected to the cylinder bore 6 and the high pressure discharge port 25A
Are in communication with each other through the notch in the closed section, the high-pressure oil in the discharge port 25A is supplied to the low-pressure cylinder bore 6.
A so-called backflow phenomenon occurs. This backflow phenomenon occurs due to the compressibility of the dead volume in the cylinder bore 6 including the volume of the fluid that always exists in the hollow piston.

When this backflow phenomenon occurs, the working fluid in the high-pressure discharge port 25A flows into the low-pressure cylinder bore 6, thereby substantially reducing the discharge flow rate. This reduces the volumetric efficiency of the pump. The effect of this decrease in volumetric efficiency becomes more significant as the inclination angle of the swash plate of the pump is smaller. Further, since the pressure inside the cylinder 6 changes sharply due to the backflow, the pulsation amplitude of the pressure and flow rate of the fluid discharged from the high-pressure port 25A increases. This has a direct effect on the pump noise increase.

Incidentally, in order to increase the power density of the pump, it is indispensable to use a high-pressure, high-speed pump. Further, it is strongly required that the pump not only have a high power density but also have high efficiency and low noise even under high pressure and high rotation. However, when the pump is driven to rotate at high speed, the piston slipper 13 is moved to the swash plate 1.
7, the spring force required to press the pressure increases in proportion to the piston weight. On the other hand, by increasing the power density of the pump to reduce the diameter of the pitch circle in which the cylinder ports 6A are arranged, the space 1 for accommodating the spring 21 is reduced.
9 is also constrained, and, consequently, the magnitude of the spring force for applying an appropriate pressure to the piston slipper 13 within the limited space is also constrained.

Therefore, in order to reduce the spring force, in the above-mentioned prior art, the piston 7 has a hollow shape with one end open. The weight reduction by hollowing the piston 7 is effective for reducing the piston inertia force which directly affects the magnitude of the spring force. However, increasing the dead volume in the cylinder bore 6 makes it difficult to suppress a decrease in volumetric efficiency and a steep change in the cylinder internal pressure due to compressibility during the backflow. This sharp change in the cylinder internal pressure promotes a pulsating change in the pressure and flow discharged from the high-pressure port 25A, and thus becomes a major bottleneck in realizing a low noise pump.

In order to increase the power density of the pump, and at the same time to achieve high efficiency and low noise, it is indispensable to optimize a piston capable of simultaneously solving the above-mentioned conflicting problems.
The present invention has been devised in order to solve such a problem. As shown in FIG. 1, the piston 7 has a spherical portion 7j at the front end, and the piston shaft 7a is formed by removing excess thickness. A hollow filler 9 having a pore 10 with a large length / diameter ratio is inserted into the hollow 8 at the rear end thereof, and a chamber is provided between the filler 9 and the spherical portion 7j. The chamber 11 is formed, and the vicinity of the minimum sectional area of the filler 9 is caulked from the outer peripheral side of the piston shaft 7a to form the piston shaft 7a and the filler 9 integrally. A hole 10h provided in the spherical portion 7j of the piston 7 in the axial direction of the piston.
Are used for lubrication, and guide the hydraulic oil that has entered the chamber 11 of the piston 7 to the piston slipper 13 as lubricating oil.

When the present invention and the conventional example are compared relatively with respect to the piston, the present invention takes advantage of the lightening of the piston 7 due to the hollow piston shape of the conventional example.
And the dead volume in the cylinder bore 6 can be reduced. This reduces the piston inertia,
In addition, the spring pressing mechanism against the swash plate of the piston slipper 13 and the valve plate 24 of the cylinder block 5 can be optimized. Further, since the flow rate flowing into the low-pressure cylinder bore 6 from the high-pressure port 25A at the time of backflow can be reduced, a decrease in volumetric efficiency due to compressibility can be suppressed to a minimum, and power loss due to leakage can be reduced. Therefore, high efficiency of the pump can be realized.

Further, in the present invention, the restriction by the pores 10 provided in the filler 9 and the volume of the chamber 11
A damping structure is provided. This allows
When a backflow occurs near the bottom dead center of the piston 7, a steep change in the cylinder pressure caused by the fluid flowing into the low-pressure cylinder bore 6 from the high-pressure discharge port 25A can be suppressed. Therefore, the discharge port 25A
Pulsating components related to the pressure and the flow rate of the fluid flowing out of the apparatus can be attenuated. Thus, a small, lightweight, high-efficiency, low-noise swash plate type axial piston pump can be realized.

In the above-mentioned embodiment of the present invention, a variable displacement swash plate type axial piston pump is taken as an example, but the number of pistons 7 is generally adopted.
The number may be other than nine or nine. Further, a fixed displacement piston pump or a variable displacement or fixed displacement swash plate type axial piston motor may be used. Furthermore, even if it is a variable displacement type or fixed displacement type swash plate type axial piston pump / motor having a pressing mechanism different from the present invention,
It is obvious that the piston according to the invention can likewise be employed.

The weight of the piston can be reduced by forming the filler 9 from any one of aluminum alloy, titanium alloy, and engineering plastic, which are light materials. As a result, the weight of the movable part of the piston can be reduced, so that the inertia force of the piston can be reduced.

<Second Embodiment> FIG. 3 is a partial longitudinal sectional view of a main part of a piston employed in a swash plate type axial piston pump according to a second embodiment of the present invention. The difference between the piston 30 used in the present embodiment and the piston (7) used in the first embodiment is that a hollow cylindrical piston shaft 30 is used.
The filler 30c is inserted into the inner diameter portion 30b of FIG. 3A, and the vicinity of the minimum cross-sectional area of the filler 30c is caulked in the same manner as in the first embodiment, and the piston 3 of the filler 30c is further fitted.
0a is caulked from the outer peripheral side 30e of the piston shaft 30a to the piston shaft 30a and the filler 3
0c is integrally formed. The other components of the swash plate type axial piston pump according to the second embodiment than the piston are the same as those of the first embodiment, and therefore, description thereof is omitted.

By configuring the piston in this manner, the inertia force of the piston can be reduced, and at the time of small tilting, the reduction in volumetric efficiency caused by the backflow generated near the bottom dead center of the suction stroke under high pressure and high speed rotation is prevented. It is possible to prevent sharp changes in the cylinder internal pressure. Furthermore, according to the present embodiment, in addition to the effects of the first embodiment, even when an impact pressure is applied to the filler 30c, the filling is performed by caulking the end 30f near the end face side of the piston 30c. The reliability of preventing the material 30c from coming off the piston 30c can be improved.

<Third Embodiment> FIG. 4 is a partial longitudinal sectional view of a main part of a piston employed in a swash plate type axial piston pump according to a third embodiment of the present invention. The piston 40 used in the present embodiment has a hollow cylindrical surface shape at the rear end side inner diameter portion 40b of the piston shaft 40a from which the excess thickness has been removed, and further has a convex cylindrical outer periphery with respect to the concave cylindrical portion,
A filler 40c having 0d is mounted, and the vicinity of the rear end 40e of the outer periphery of the piston shaft is caulked to form the piston shaft 40a and the filler 40c in an integrated manner.
The other configuration of the swash plate type axial piston pump of the third embodiment than the piston is the same as that of the first embodiment, and therefore, the description is omitted.

By adopting such a configuration, the piston itself can be simplified in addition to the same effects as in the first and second embodiments. Thereby, the piston can be easily manufactured, and the cost can be reduced. Therefore, even under high-pressure and high-speed conditions, not only the efficiency of the pump can be improved and the noise can be reduced, but also the manufacturing cost can be reduced.

<Fourth Embodiment> FIG. 5 shows a fourth embodiment of the present invention.
It is a principal part longitudinal cross-sectional view of the principal part of the piston used for the swash plate type axial piston pump of the embodiment. The piston 50 used in the present embodiment is a
a while forming the rear end side inner diameter portion 50b into a stepped shape,
A filler 50c having fine holes 50d and having a plurality of grooves formed in the outer peripheral portion is fitted into the stepped portion on the rear end side of the piston 50a on the rear end side, and the rear end portion 50e of the piston shaft 50a is caulked to form the piston shaft. 50a and the filler 50c are integrally formed. In the swash plate type axial piston pump of the present embodiment, the configuration other than the piston is the same as that of the first embodiment, and the description is omitted.

With such a configuration, in addition to the same effects as in the third embodiment, in manufacturing the piston according to the present invention, a jig for caulking the end face 50e of the piston 50a in advance is used. It is sufficient if they are prepared, and the cost can be reduced by mass production.

<Fifth Embodiment> FIG. 6 shows a fifth embodiment of the present invention.
It is a principal part longitudinal cross-sectional view of the principal part of the piston used for the swash plate type axial piston pump of the embodiment. The piston 60 used in the present embodiment is a
A part of the filler 60c having the pores 60d extends toward the opposite end face side of the piston shaft 60a with respect to the stepped inner diameter portion 60b of (a), and the extended portion 60f is fitted to the piston inner diameter portion 60e. The thickness of the extending portion 60f of the filler 60c is set in the axial direction of the piston shaft 60a.
a, by gradually increasing the thickness toward the rear end side, the extended portion 60f is formed in a concave shape, and the end face portion 60g of the piston 60a is further caulked to separate the piston shaft 60a and the filler 60c. It is formed integrally. Fifth Embodiment In the swash plate type axial piston pump, the configuration other than the piston is the same as that of the first embodiment.

With such a configuration, in addition to the same effect as in the fourth embodiment, the cylinder internal pressure is applied to the concave portion of the extending portion of the filler 60c,
Since the extending portion is elastically deformed, the degree of fitting of the filler 60c to the inner diameter portion 60e of the piston shaft 60a is increased. Thereby, the filling material 60 with respect to the piston shaft 60a is
The removal strength of c can be improved.

<Sixth Embodiment> FIG. 7 shows a sixth embodiment of the present invention.
It is a principal part longitudinal cross-sectional view of the principal part of the piston used for the swash plate type axial piston pump of the embodiment. The piston 70 used in the present embodiment is a
A spherical filler 70c having fine pores 70d is fitted into the rear end of the inner diameter portion 70b of FIG.
The outer peripheral portion 70e of FIG.
The rear end side of Oc and the inner diameter portion of the piston rear end are formed integrally by welding 70f. In the swash plate type axial piston pump according to the sixth embodiment, the configuration other than the piston is the same as that of the first embodiment.

With such a configuration, in addition to the same effect as in the fifth embodiment, the combined use of caulking and welding makes the integral type of the piston 70a and the filler 70c stronger. Can be something. Thereby, the filler 7
Since the removal strength of 0c can be improved, high reliability can be imparted even when the piston of the present invention is used under high pressure and high speed rotation.

<Seventh Embodiment> FIG. 8 shows a seventh embodiment of the present invention.
FIG. 4 is a partial longitudinal sectional view of a main part of a piston used in the swash plate type axial piston pump according to the embodiment. The piston 80 used in the present embodiment is a piston shaft 80 with a reduced thickness.
A spherical filler 80c having pores 80d having a restricting function is fitted to the rear end side of the inner diameter portion 80b of Fig. a, and the fillers 80c are formed by caulking both sides 80e and 80f near both end surfaces of the filler 80c. And the piston 80a are integrally formed. The configuration of the swash plate type axial piston pump of the seventh embodiment is the same as that of the swash plate axial piston pump in the other embodiments, and therefore, the description thereof is omitted.

With such a configuration, in addition to the same effect as in the sixth embodiment, the jig for simultaneous caulking at two places is prepared in advance, so that the piston of the present invention can be used in a short time. In addition, since the pump can be easily manufactured, the cost of the pump itself can be reduced.

<Eighth Embodiment> FIG. 9 shows an eighth embodiment of the present invention.
It is a principal part longitudinal cross-sectional view of the principal part of the piston used for the swash plate type axial piston pump of the embodiment. The piston 90 used in the present embodiment is a
A bottom plate 90b is provided on the rear end side of the piston shaft 90a, a small hole 90c is formed in the bottom plate 90b, and the outer peripheral portion on the front end side of the piston shaft 90a is caulked to form a socket portion 90f.
A ball-socket joint is formed by f and the ball portion 90e formed on the piston slipper 90d, and the piston and the piston slipper are formed integrally.

The swash plate type axial piston pump according to the eighth embodiment is the same as the first embodiment except for the piston and the piston slipper. With such a configuration, in addition to the same effects as in the above embodiment, the structure of the piston itself can be simplified since no filler is used in the embodiment of the present invention.

<Ninth Embodiment> FIG. 10 shows a ninth embodiment of the present invention, in which the present invention is applied to a hydrostatic transmission. Various embodiments are conceivable for the basic configuration of the present hydrostatic transmission, but the example shown in the figure shows a most general case, that is, a closed circuit system including a variable displacement pump and a constant displacement motor. . The illustrated hydrostatic transmission includes a variable displacement pump 110 and an electric motor or engine 10 as a drive source for driving the variable displacement pump 110.
0, a constant displacement motor 120, and a main circuit 1 fluidly coupling the variable displacement pump 110 and the constant displacement motor 120.
30.

Variable displacement pump 110, constant displacement motor 12
No. 0 uses a pump / motor employing the piston according to the present invention.

With such a configuration, even if the hydrostatic transmission is operated under high pressure, high rotation, and light load conditions, the pump / motor can operate at the bottom dead center of the suction and discharge strokes, The leak amount near the top dead center can be reduced, and a steep change in the cylinder internal pressure can be suppressed. This makes it possible to provide a small, lightweight, highly efficient, and low-noise hydrostatic transmission. The present invention can be applied to any energy conversion element or power transmission element as long as it is a swash plate type axial piston pump motor using a compressible medium.

[0054]

According to the present invention, even if the variable displacement type swash plate type axial piston pump / motor is operated under the condition of small tilt, high pressure and high rotation, the piston of the pump / motor is constituted as described above. Therefore, a decrease in the leakage flow rate due to a backflow from the high pressure discharge port generated near the bottom dead center of the suction stroke into the low pressure cylinder bore can be minimized, and a sharp change in the cylinder internal pressure can be suppressed.

As a result, the power loss based on the leakage flow rate can be minimized, and the pressure and flow rate pulsation of the discharged fluid can be reduced. As a result, it is possible to provide a small-sized, light-weight, high-efficiency, low-noise, variable displacement axial piston pump / motor.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a rotating part of a swash plate type axial piston pump according to a first embodiment of the present invention.

FIG. 2 is a plan view of the valve plate of the swash plate type axial piston pump, taken along the line II-II of FIG. 1;

FIG. 3 is a partial longitudinal sectional view of a main part of a piston of a swash plate type axial piston pump according to a second embodiment of the present invention.

FIG. 4 is a partial vertical sectional view of a main part of a piston of a swash plate type axial piston pump according to a third embodiment of the present invention.

FIG. 5 is a partial longitudinal sectional view of a main part of a piston of a swash plate type axial piston pump according to a fourth embodiment of the present invention.

FIG. 6 is a partial longitudinal sectional view of a main part of a piston of a swash plate type axial piston pump according to a fifth embodiment of the present invention.

FIG. 7 is a partial longitudinal sectional view of a main part of a piston of a swash plate type axial piston pump according to a sixth embodiment of the present invention.

FIG. 8 is a partial vertical sectional view of a main part of a piston of a swash plate type axial piston pump according to a seventh embodiment of the present invention.

FIG. 9 is a partial vertical sectional view of a main part of a piston of an swash plate type axial piston pump according to an eighth embodiment of the present invention.

FIG. 10 is a system diagram showing a hydrostatic transmission according to a ninth embodiment of the present invention.

FIG. 11 is a partial vertical sectional view of a main part of a piston of a swash plate type axial piston pump showing an example of the prior art.

[Explanation of symbols]

1 Casing body 1A, 1B
Casing 2 Rotating shaft 3 Spline part 4a, 4b Rolling bearing 5 Cylinder block 5a Boss part 6 Cylinder bore 6A Cylinder port 7 Piston 7a Piston shaft 7j Piston ball part 8 Piston inner diameter part 9 Filling material 10 Pores 11 Chamber chamber 12 Piston outer peripheral caulking part Reference Signs List 13 piston slipper 13s socket 15 slipper retainer 16 retainer guide 17 swash plate 18 push pin 19 storage chamber 20 intermediate member 21 disc spring 22 rear locking member 23 retaining ring 24 valve plate 25A, 25
B suction / discharge port 26A, 26B suction / discharge passage 27 regulator 30 piston 30a extra-thin piston shaft 30c filler 30d pore 40 piston 40a extra-thick piston shaft 40c filler 40d pore 50 piston 50a extra-thick Piston 50c Filler 50d Pores 60 Piston 60a Extra-thick piston shaft 60c Filler 60d Pores 70 Piston 70a Extra-thick piston shaft 70c Filler 70d Pores 80 Piston 80a Extra-thick piston shaft 80c Filler 80d Pores 90 Piston 90a Extra-thinned piston shaft 90c Pores 90d Piston slipper 90e Ball joint 100 Electric motor or engine 110 Variable displacement pump 120 Constant displacement motor 130 Main circuit

Claims (5)

[Claims] 1. A cylinder having a rotating shaft supported by an axis of a casing, and a plurality of cylinder bores mounted around the rotating axis and opened at equal distances parallel to the axis of the rotating shaft and forwardly. A block, a piston slidably fitted into the cylinder bore, a piston having a piston slipper attached to a front end thereof via a ball-socket joint, and a front surface of the piston slipper being brought into contact with the piston to be inclined with respect to the rotation axis. Swash plate type hydraulic machine, comprising: a swash plate, a cylinder port penetrating through the bottom of the rear end of each of the cylinder bores, and a valve plate in contact with the rear surface of the cylinder block and having a liquid suction / discharge port corresponding to the cylinder port. In the above, the piston is formed as a front end portion of the ball portion of the ball-socket joint, a hollow cylindrical piston shaft having a hollow portion, and a rear inner diameter of the piston shaft A swash plate type hydraulic machine characterized by comprising a filler having a pore penetrating in the axial direction, which is fitted and fixed in the swash plate. 2. The piston, wherein the filler is formed in a conical shape having an annular groove formed on an outer periphery thereof, and the piston is formed from an outer periphery of the piston shaft corresponding to the annular groove of the filler.
2. The swash plate type hydraulic machine according to claim 1, wherein said filler and said piston shaft are integrally formed by caulking from the outer periphery of said piston shaft rear end. 3. The piston has a drum shape in which the outer periphery of the filler is convex and the inner diameter of the rear end of the piston shaft is a concave cylindrical surface, and the inner diameter of the rear end of the piston shaft is the filler. 2. The swash plate type hydraulic machine according to claim 1, wherein the piston shaft and the filler are integrally formed by caulking the vicinity of the rear end of the piston shaft from an outer periphery after the piston shaft is inserted into the swash plate. 4. The piston has a shape of a straight bar with a plurality of annular grooves formed on the outer periphery of the filler, and a stepped hole is formed through the inside diameter of a rear end of the piston shaft. 2. The oblique shape according to claim 1, wherein the piston shaft and the filler are integrally formed by inserting a filler in a shape of a straight rod and crimping a rear end of the piston shaft. Plate type hydraulic machine. 5. A cylinder having a rotating shaft supported by an axis of a casing, and a plurality of cylinder bores mounted around the rotating axis and opened at equal distances parallel to the axis of the rotating shaft and forwardly. A block, a piston slidably fitted into the cylinder bore, a piston having a piston slipper attached to a front end thereof via a ball-socket joint, and a front surface of the piston slipper being brought into contact with the piston to be inclined with respect to the rotation axis. Swash plate type hydraulic machine, comprising: a swash plate, a cylinder port penetrating through the bottom of the rear end of each of the cylinder bores, and a valve plate in contact with the rear surface of the cylinder block and having a liquid suction / discharge port corresponding to the cylinder port. In the piston, the front end portion is a socket portion of the ball-socket joint, the rear end portion is a bottom plate having a small hole penetrated therein, and the middle portion is formed by removing the extra thickness. The piston slipper is formed by an empty cylindrical piston shaft, and the piston slipper is configured to have a spherical portion at the rear end of the socket joint, and caulks the socket portion from the outer periphery so as to include the spherical portion. A swash plate type hydraulic machine, wherein the piston and the piston slipper are integrated.