JPH06330849A - Variable displacement swash plate type hydraulic machine - Google Patents

Abstract

PURPOSE:To compensate the inclination of a slipper after forming a fluid film as well as to reduce the extent of loss power by forming a lot of grooves on a seal land on this bottom face, in this slipper of a piston attached free of slide motion along a swash plate tilting to a turning shaft. CONSTITUTION:When a turning shaft 2 is rotated, a cylinder block 5 is also rotated as one body, therefore two pistons 7 reciprocate in the inner part of a cylinder bore 6. Incidentally, a swash plate 11 is tilted by a regulator 16 in advance, so that there is a difference happening in strokes of these pistons. In consequence, hydraulic operating fluid is made into suction or discharge with each retractable motion of these pistons. At this time, since a lateral component force acts on each slipper of these pistons 7, a friction moment is produced in these connecting parts, while metal-to-metal contact is produced in a sliding part or the like between the swash plate 11 and a slipper bottom face 9. In order to cope with it, a lot of grooves 23a to 23d are formed in a seal land 21 of this slipper bottom face 9, through which a dynamic hydromechanical fluid film is formed up.

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 which can be operated under a wide range of rotation speed conditions from high speed to low speed and its manufacture. Regarding the method.

[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 pressure of the hydraulic pump / motor is increased, it is important to minimize the power loss due to leakage and friction in each sliding part as a subject for realizing the above-mentioned target. Especially hydraulic pumps /
There are three typical sliding parts on the motor ((a) swash plate-
Between slippers, (b) between cylinder block and valve plate, (c)
(Between the inner wall of the cylinder block and the piston), and the quality of the sliding characteristics at this sliding part has a dominant effect on the performance of the pump / motor itself, for example, the volume efficiency and mechanical efficiency. .

In order to address this problem, in the prior art, for example, in one swash plate type axial piston pump / motor of a variable displacement hydraulic machine, in order to improve the sliding characteristics between the swash plate and the slipper bearing, The bottom surface of the slipper bearing is practically provided with a pocket, an annular groove, or the like for exerting bearing load capacity by static pressure and dynamic pressure.
Therefore, when classifying these slipper bearings according to 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, and a self discharge pressure is introduced into this pressure guide hole. A hydraulic balance type (basic type) that achieves hydraulic balance, an outer auxiliary surface with an auxiliary bearing surface on the outside of the hydraulic balance type, and an inner and outer auxiliary surface with auxiliary bearing surfaces on both the inside and outside of the hydraulic balance type There is one in which a thin spiral groove facing outward from the hydraulic equilibrium chamber is provided and the seal land surface is lubricated by the 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 a disturbance such as force or moment acts on the slipper bearing under low-pressure and high-pressure use conditions such as a hydraulic motor, the dynamic pressure effect cannot be expected. Since the parallelism between the swash plate and the swash plate is impaired, it becomes 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. As a result, in the sliding portion between the swash plate and the slipper, there is a problem that the power loss due to friction increases.

Further, when the slipper bearing with the outer auxiliary surface and the inner and outer auxiliary surfaces is used under high speed rotation, the oil film thickness increases due to the dynamic pressure effect, and the power loss due to the leakage flow rate increases. Have In addition, as described above, when the oil film thickness on the sliding surface between the swash plate and the slipper becomes large, the oil film rigidity becomes small. 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. Also,
In the slipper bearing with the inner and outer auxiliary surfaces, the shape of the bottom surface of the slipper is complicated, which requires a processing procedure and man-hours. There is a problem that the cost becomes higher than this.

Against this background, the formation of oil film thickness is promoted at high pressure and low speed, mainly the reduction of loss power due to friction is suppressed, and the increase of oil film thickness due to dynamic pressure effect is suppressed at high pressure and high speed, It has been desired to develop a slipper bearing that can reduce power loss due to the leakage flow rate and is easy to manufacture and inexpensive.

In view of the problems of the prior art, therefore, the object of the present invention is to eliminate these problems, and at the time of high pressure, in a wide sliding speed range from low speed to high speed, in a good sliding condition, that is, with low leakage. It is an object of the present invention to provide a slipper bearing that has a simple structure, is easy to manufacture, and is inexpensive, and that enables low-loss torque sliding.

[0008]

In order to achieve the above object, one of the means for solving the problems of the present invention is to provide a plurality of independent groove portions or recesses in a seal land portion of the bottom surface of a slipper of a hydraulic balanced circular slipper bearing. Is formed.

Further, another solution is to provide a surface of a groove provided in the seal land portion in order to impart a restoring function to the slipper itself when the slipper is tilted due to a dynamic behavior based on the rotation and revolution of the slipper. The shape has a shape of at least one of a circle, a rectangle, a triangle and a rhombus, and the cross-sectional shape of the groove has a shape of at least one of a crescent, a triangle and a rectangle, and The groove provided in the seal land portion is formed so as to be a combination of at least one of the grooves.

[0010]

The plurality of grooves, which are provided in the seal land portion of the hydraulic equilibrium circular slipper bearing and are independent of each other and have a minute depth, act as a plane stop. As a result, the outward radial flow of the 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 and the orbital motion of the slipper bearing with respect to the swash plate, the slipper bearing is tilted by the load acting on the slipper bearing and the load consisting of moments.

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 and the swash plate of the slipper bearing. 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 above-mentioned groove adapts to the load due to the static pressure produced, and the load is applied by the hydrostatic effect. It supports the piston hydraulic 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 pressure at a high speed, and the slipper itself tilts and rotates and revolves, the cross-sectional shape of the plurality of grooves provided in the seal land of the slipper is a crescent moon. In addition to the combined action of the dynamic fluid dynamics based on the dynamic pressure and the quasi-static hydrodynamics based on the quasi-static pressure, which are formed in a groove or a triangular shape,
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 fluctuations and tilts in all directions, the tilt of the slipper is
It will be corrected quickly. As a result, the oil film thickness formed on the seal land of the swash plate and the slipper bearing can be made uniform, so that the torque loss on both the sliding surfaces and the leakage flow rate from the 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. Therefore, the problems in the prior art do not occur.

[0013]

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 main body composed of a casing 1A and a casing 1B, and 2 denotes a rotating shaft provided so as to project into the casing 1A. Has a male spline 3. The rotating shaft 2 is rotatably supported by rolling bearings 4a and 4b arranged at two places.

A cylinder block 5 is provided in the casing 1 and rotates integrally with the rotary shaft 2. The cylinder block 5 has a plurality of cylinder bores 6 bored in the axial direction.
6 are provided, and pistons 7, 7 are provided in the cylinder bore 6 so as to be reciprocally movable. A piston slipper 8 is rotatably provided on the spherical end of the piston 7, and a bottom surface 9 of the slipper 8 is pressed against a swash plate 11 by a retainer 10. 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, 13B which communicate with each cylinder bore 6 by the rotation of the cylinder block 5, and the intake / exhaust ports are formed. 13A and 13B communicate with a pair of suction and discharge 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 a connecting portion 17 which is integrally connected to the swash plate 11.

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

FIG. 2 is a horizontal cross-sectional view of the slipper 8 in FIG. 1 as seen in the direction of arrow I, and FIG. 3 is a vertical cross-sectional view of a portion AA of a groove provided in the seal land portion of the slipper in FIG. The feature of this embodiment is that a plurality of grooves (concave portions in this embodiment) having a circular surface shape and a crescent-shaped cross section are formed on the seal land portion of the sliding bottom surface 9 of the slipper 8 in FIG. (Indicated in the case of individual pieces). In FIG. 2, 21 is a seal land portion on the sliding surface of the slipper 8, and 23a to 23d are grooves formed in the seal land portion 21. Reference numeral 20 denotes a hydraulic equilibrium chamber (hereinafter referred to as a pocket portion) in which static pressure exists, and 22 denotes a fixed throttle portion for supplying static pressure to the pocket portion.

The present embodiment is constructed in this way, and next, the operation when used as a hydraulic pump will be explained.

Drive source (not shown) for the engine, electric motor, etc.
When the rotary shaft 2 is rotated by, the rotary 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 rotated integrally with the rotary shaft 2. 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 by the regulator 16 from the axis perpendicular to the rotation direction to an arbitrary tilt angle, each of the above-mentioned respective ones during one rotation of the cylinder block 5. While the strokes of the pistons 7 are different and each piston 7 retreats from the cylinder bore 6,
During the intake stroke, in which the working oil is sucked into the cylinder bore 6 from the suction / discharge passage 14B through the suction / discharge port 13B, the working oil in each cylinder bore 6 is pressurized and sucked while each piston 7 enters the cylinder bore 6. The discharge process is to discharge through the port 13A and the suction / discharge passage 14A.

At this time, the piston 7 located in the discharge stroke
A force (generally called a piston lateral force) in the direction perpendicular to the axial direction of the piston 8 acts on the slipper 8. As a result, the piston 7 and the slipper 8 have a friction mode centered on the ball joint portion where the piston 7 and the slipper 8 are connected.
Ment occurs. As a result, the slipper 8 itself tilts, and the bending moment acts on the piston 7, whereby the sliding portion between the swash plate 11 and the bottom surface 9 of the slipper and the sliding portion between the inner wall of the cylinder bore 6 and the piston 7 are lubricated. Can transition from fluid lubrication to mixed lubrication and, in part, 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 rotational speed range used is wide ranging from low speed to high speed, the sliding surface of the swash plate 11 and the seal land portion of the bottom 9 of the slipper is particularly effective at low speed and high load. It becomes difficult to form an oil film.

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, when the actual use conditions, that is, low speed to high speed and high surface pressure (high load) are assumed, in order to minimize the power loss in the sliding portion even in such an operating state, the swash plate to the slipper should be used. 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 devised in order to eliminate such a problem. Since the present invention has the structure shown in FIGS. 2 and 3, even if the slipper 8 is tilted, the bottom surface 9 of the slipper 8 is inclined. Four grooves 2 provided in the seal land independently of each other
3a to 23d function to form a hydrodynamic fluid film. From this, even if the slippers are tilted, the groove portion exhibits a positive dynamic pressure bearing effect with a wedge effect,
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 sliding surfaces of 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 can prevent metal contact between the two 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 the surface shape of the groove provided in the seal land portion of the bottom surface 9 of the slipper 8 is a rectangle (here, a square is shown). Is. Further, FIGS. 5 and 6 show cases where the surface shapes of the grooves are triangular and rhombic, respectively. 4 and 5
Further, in FIG. 6, 25a to 25d, 27a to 27d and 29a to 29d indicate the grooves formed in the seal land portion 21. The groove has a triangular cross section taken along the line A-A, as shown in FIG.

FIG. 8 shows a modification of the number of grooves of the first embodiment of the present invention, which is the seal land portion 2 of the bottom surface 9 of the slipper 8.
The case where the number of the grooves provided in 1 is 3 is shown. The feature of this embodiment is that the grooves 31a to 31c are provided at a pitch of approximately 120 °. The surface shape and cross-sectional shape of the groove portions 31a to 31c are the same as those in the first embodiment.

With such a structure, even if the slipper 8 is rotated in any direction, the grooves at two or more locations simultaneously have dynamic pressure with wedge effect as in the case of the first embodiment. In order to exert the quasi-static pressure bearing effect by the action, it has a function of correcting the inclination of the slipper.

FIG. 9 shows a modification of the groove sectional shape shown in FIG. 3 or 7, and is a partial vertical sectional view showing a case where the groove portion has a rectangular sectional shape.

This modification is intended to secure the oil film thickness formed in both sliding portions between the swash plate and the slipper by increasing the fluid intervening in the groove portion by making the groove sectional shape rectangular. As a result, the starting characteristic can be improved even under a low speed and high load condition as in the case of a hydraulic motor.
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.

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 can be made uniform, and the power loss at the sliding portion can be reduced.

Therefore, according to the present invention, by 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 high pressure and low speed to high speed, but also absorbs the elastic deformation of the micron order of the slipper. Since the action can be exhibited together, the effect of reducing the loss power of the sliding portion due to friction becomes more reliable.

Next, an embodiment in which the present invention is applied to a portion other than slippers of a variable displacement type swash plate type hydraulic machine will be described.

FIG. 10 shows the case where the groove according to the present invention is formed on the slipper sliding surface of the swash plate 11. In the figure, swash plate 1
1, the slipper sliding surface 11a of FIG.
A plurality of the above-mentioned grooves having the surface and cross-sectional shapes shown in 4, 5, 6, 7, and 9 are provided independently of each other. Here, of the hydraulic machines, not only the swash plate type axial piston pump but also the forward and reverse directions of the piston motor are taken into consideration, and the case where the number of pistons is 9 is assumed, for example, 4
The case where a total of nine groups of one group of grooves 33a to 33d are provided.

On the other hand, in the case of the pump, since the rotation direction is one direction, the number of groove groups provided on the swash plate sliding surface 11a depends on the total number of pistons Za. For example, when Za is 9 and 7, the number of groove groups located in the high pressure region is 5 and 4 groups, respectively. In order to effectively dispose the predetermined groove group on the sliding surface 11a of the swash plate 11, it is only necessary to first consider the mounting positional relationship between adjacent pistons and to form it in the discharge area.

By configuring the groove as described above, it is possible to expect the same operation and effect as in the case where the groove is formed in the seal land portion of the bottom surface 9 of the slipper 8.

FIG. 11 shows the case where the groove according to the present invention is formed in the scallop portion 58 of the sliding surface 12a of the valve plate 12 having the auxiliary pressure receiving surface. In the figure, if the direction of rotation of the cylinder block is assumed to be the arrow direction, 13A is an eyebrow suction port, 13B is an eyebrow discharge port, 54 is an inner seal land, 56 is an outer seal land, and 58. Indicates a scallop as an auxiliary pressure receiving surface provided on the outermost side of the valve plate 12, and is expected to generate an oil film pressure by rotation. Reference numerals 51a to 51d denote the grooves according to the present invention provided in the scallop portion 58.

With such a structure, dynamic pressure generated by rotation on the sliding surfaces of the scallops other than the grooves 51a to 51d and the grooves 51a to 51d of the scallop 58 are generated.
A quasi-static bearing effect due to the dynamic pressure at 51d and a synergistic effect such as a wedge effect of the oil film pressure can be expected. As a result, even if the cylinder block 5 tilts due to, for example, dynamic fluctuation of the resultant force of the piston lateral force component and the piston hydraulic reaction force, the scallop 58 including the grooves 51a to 51d corrects the tilt of the cylinder block 5. Function. As a result, it is possible to prevent fatal troubles such as one-sided contact between the two sliding surfaces and metal contact, and reduce power loss due to friction and leakage. In the figure, the number of the grooves formed in the scallop 58 is one per scallop, but the present invention is not limited to this. For example, a plurality of grooves may be formed per scallop.

On the other hand, when the static pressure bearing guide surface shape of the valve plate 12 is formed on the sliding surface side of the cylinder block 5, the groove according to the present invention is formed on the sliding surface side of the cylinder block 5. And similarly formed.

FIG. 12 shows a modification of FIG.
This is a case where the grooves 53a to 53b according to the present invention are provided at two locations near the bottom dead center (BDC) and the top dead center (TDC) of the valve plate 12. In the figure, when the rotation direction of the cylinder block 5 of the hydraulic machine is in the direction of the arrow, the pressure in the cylinder block rapidly changes from low pressure to high pressure near BDC and from high pressure to low pressure near TDC. As a result, the BD
The oil film thickness changes rapidly near C and TDC. Therefore, when the rotation speed of the machine is low and the discharge pressure is high, it is difficult to form an oil film in the BDC and TDC regions, and it is expected that a mixed lubrication state will result. In such a state, loss torque due to friction on the sliding surface of the valve plate increases. As a result, the stability of low-speed operation is impaired and the power loss is increased, which is not preferable. However, in the present invention, in order to solve the above-mentioned problems, B
The grooves 53a, 53 according to the present invention are provided at DC and TDC locations.
b is formed. As a result, the oil film thickness formed by the dynamic pressure action in the groove portion has the function of relaxing the mixed lubrication state and changing it to the fluid lubrication state, so that loss power can be reduced even at low speed and high pressure sliding.

FIG. 13 shows another modification of FIG. 11, in which the sliding surface 12 of the valve plate 12 having an auxiliary pressure receiving surface is shown.
The case where the scalloped portion 58 of a is provided with grooves 55a to 55d having a rectangular surface and an asymmetrical slope in cross section as shown in FIG. Other than this, it is similar to FIG.

The feature in this figure is that the cross-sectional shape of the groove is formed so that the groove depth gradually becomes shallower in the sliding direction of the cylinder block 5. The relationship of the groove inclination is
Let α> β. With such a configuration, the groove can exert not only a quasi-static pressure bearing effect due to a dynamic pressure action but also a wedge effect based on the taper groove shape against the inclination of the cylinder block 5. As a result, the inclination of the cylinder block 5 with respect to any direction can be quickly corrected, and the sliding surface between the cylinder block and the valve plate can be brought into a fluid lubrication state.

As a result, the power loss on the sliding surface can be minimized. In addition, the cylinder block 5 and the valve plate 12
Since it is possible to prevent metal contact with the sliding surface 12a of the
The wear resistance of the valve plate sliding surface 12a can be improved.

FIG. 15 shows a modification of FIG.
This is a case where the grooves 57a and 57b according to the present invention are provided at two locations near the bottom dead center (BDC) and the top dead center (TDC) of the valve plate 12. With the configuration shown in this figure, the same operation and effect as in the case of FIG. 12 can be expected.

FIG. 16 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, the most general case, that is, a closed circuit system including a variable displacement pump and a constant displacement motor will be considered here. In the figure, 70 is a driving source electric motor or engine, 72 is a variable displacement pump, 76 is a constant displacement motor, and 74 is a main circuit for fluidly coupling the pump and the motor. is there. Here, an HST (hydrostatic transmission) is constituted by 72 pumps and 76 motors in which the groove according to the present invention is formed in a sliding portion between a swash plate and a slipper and between a cylinder block and a valve plate. It is characterized by that. With such a configuration, the HS
Even if T is operated in a wide speed range from low speed to high speed, a proper fluid lubrication state can be maintained in the sliding portion of the pump / motor, so that a highly efficient and stable HST system can be provided.

Besides this, a slant shaft type hydraulic pump for general industry /
It can also be applied to relative sliding parts such as motors. 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 increasing the pressure of the pump / motor is insufficient durability of the rolling bearing for supporting the piston hydraulic reaction load. One solution to this problem is
A method has been proposed in which the piston hydraulic reaction force is supported by thrust and radial slipper bearings using static pressure, instead of rolling bearings. 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 pump
The power loss in the sliding parts of the motor can be reduced, and the hydraulic pump and motor for construction machinery can be operated at higher pressure and higher performance.

Next, a method of processing the groove formed on the bottom surface of the slipper used in the variable displacement 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 for forming the groove is roughly classified into (1) plastic working (for example,
Press processing), (2) cutting or grinding, (3) lathe
The machining, (4) precision casting, (5) electric discharge machining and the like are considered, and molding can be performed by any means.

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 such as LBC or PBC, and other than this, which is formed of an iron system whose surface is modified by heat treatment, the slipper slipper is used. -For the groove formed in the luland portion, among the groove forming means, the method of using the plastic working means using a press or the like is simple, good in operability, and 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 a high hardness and a high toughness (for example, a super hard material). Next, the jig is chucked on, for example, a spindle rotating portion of a ball board or the like, and the slipper bottom surface is fixed to a table facing the spindle rotating portion. Then, the main shaft is pushed downward to form a specific groove shape on the bottom surface of the slipper.

The above-mentioned groove formation is a manual method, but in order to improve the efficiency of the groove formation work, it may be carried out as follows. That is, the positioning of the spindle in the rotating 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. By doing so, automation of groove formation can be easily realized.

In the above-described groove processing method, the slipper to be formed with the groove is fixed to the support base, the jig is fixed to a support mechanism that can be positioned in the rotational direction and the vertical direction, and then the support mechanism is inserted into the groove. An arbitrary groove is formed on the bottom surface of the slipper by manual or automatic operation according to the formation position. On the other hand, contrary to the above-mentioned processing method, that is, by fixing the jig in advance, further attaching the slipper to the support mechanism capable of rotating and linearly positioning, and then positioning the support mechanism at a predetermined position. Groove formation may be performed.

Further, in the cutting process, a predetermined portion of the seal land is cut with a cutting tool or end mill adapted to the groove shape, and in the grinding process, a grinding wheel suitable for the groove shape is rotated or ultrasonic waves are applied thereto. The seal land can be ground while applying vibration such as vibration. Also,
In laser processing, a groove having a predetermined shape is formed by using laser light, in precision casting, casting is performed using a precision mold such as die casting, and in electric discharge machining, a discharge voltage is applied to an electrode having a groove shape. It can be applied to perform processing.

[0053]

According to the present invention, the variable displacement type swash plate type hydraulic pump / motor is operated at a high surface pressure from low speed to high speed, and the slipper is provided with a lateral piston force, a centrifugal force and a piston ball joint. Even if the slipper is tilted due to the influence of friction moments, etc., a plurality of independent grooves are provided in the seal land on the bottom of the slipper. The inclination of can be corrected. 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. Thus, there is provided a variable displacement 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 pressure and change from low speed to high speed. be able to.

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

[Brief description of drawings]

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

2 is a cross-sectional view of the slipper in FIG. 1 taken along the line I-arrow.

3 is a vertical cross-sectional view taken along the line AA of a groove portion provided in a seal land portion of the slipper shown in FIG.

FIG. 4 is a view showing a modification of FIG. 2 and showing a case where the surface shape of the groove is rectangular.

FIG. 5 is a diagram showing another modification of FIG. 2 in which the surface shape of the groove is triangular.

FIG. 6 is a view showing another modification of FIG. 2 and showing a case where the surface shape of the groove is a rhombus.

FIG. 7 is a partial vertical cross-sectional view showing a groove portion of a modified example of the present invention shown in FIGS. 4, 5 and 6.

FIG. 8 is a modification of the number of grooves of the first embodiment of the present invention, showing a case where the number of grooves provided on the slipper bottom seal land is three.

FIG. 9 is a partial vertical cross-sectional view showing a modification of FIG. 7, showing a case where the groove has a rectangular cross-sectional shape.

FIG. 10 is a view showing a case where a groove according to the present invention is formed on a sliding surface of a swash plate.

FIG. 11 is a view showing a case where the groove according to the present invention is formed in a scallop portion of a sliding surface of a valve plate having an auxiliary pressure receiving surface.

FIG. 12 is a view showing a modified example of FIG. 11, showing a case where the groove according to the present invention is provided at two positions near the top dead center and the bottom dead center of the valve plate.

FIG. 13 is a diagram showing a surface shape of a groove when the groove showing a modification of FIG. 11 is formed in a scallop portion of a valve plate sliding surface.

FIG. 14 is a vertical sectional view of a groove portion when a groove showing a modification of FIG. 11 is formed in a scallop portion of a sliding surface of a valve plate.

FIG. 15 is a view showing a modified example of FIG. 13, showing a case where the groove is provided at two positions near the bottom dead center and the top dead center of the valve plate.

FIG. 16 is a diagram showing an example where 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 ...
Intake / exhaust port, 16 ... Regulator, 20 ... Hydraulic balance chamber,
21 ... Seal land, 22 ... Fixed throttle part, 23a-23
d, 25a to 25d, 27a to 27d, 29a to 29
d, 31a to 31c, 33a to 33d, 35a to 35
d, 37a to 37d, 39a to 39d, 41a to 41
d, 43a to 43d, 45a to 45d, 47a to 47
d, 49a to 49d, 51a to 51d, 53a to 53
b, 55a to 55d, 57a to 57b ... Groove, 54 ... Inner seal land, 56 ... Outer seal land, 58 ... Scallop, 60 ... Electric motor or engine, 62 ... Variable displacement pump, 66 ... Constant displacement motor, 64 ... Main circuit

 ─────────────────────────────────────────────────── --- Continuation of the front page (72) Inventor Takeshi Yokomori 603 Kitsudachi Town, Tsuchiura City, Ibaraki Prefecture Hitate Factory, Tsuchiura Plant (72) Yoshiaki Yamada 603 Kandachi Town, Tsuchiura City, Ibaraki Prefecture Hitate Co., Ltd. Inside the Tsuchiura Plant of the Works (72) Inventor Koichi Maezawa 603 Kintate-cho, Tsuchiura City, Ibaraki Prefecture Inside the Hitachi Co., Ltd. Tsuchiura Plant

Claims (13)

[Claims] 1. A cylinder block comprising a rotary shaft rotatably provided in a casing, and a plurality of cylinder bores provided in the casing and rotating together with the rotary shaft.
It can move back and forth in the cylinder bore of the cylinder block.
A piston fixed to a piston slipper, the piston slipper being slidably attached along a swash plate inclined with respect to the rotation axis, and the inclination angle of the swash plate with respect to the rotation axis. In a variable displacement type swash plate hydraulic machine configured so that it can be set to an arbitrary angle by a regulator, a plurality of independent groove portions are provided in a seal land portion of the bottom surface of the slipper. Variable capacity swash plate type hydraulic machine. 2. The variable displacement swash plate hydraulic machine according to claim 1, wherein the plurality of grooves provided in the seal land portion are independent of each other, and the surface shape of the grooves is circular, rectangular, triangular or rhombic. A variable displacement swash plate type hydraulic machine characterized in that it has at least one of the above geometrical shapes. 3. The variable displacement swash plate hydraulic machine according to claim 1, wherein the groove cross sections provided in the seal land independently of each other include geometric shapes such as a crescent shape, a triangular shape, and a rectangular shape. A variable displacement swash plate type hydraulic machine characterized by being formed to have at least one shape. 4. The variable displacement swash plate hydraulic machine according to claim 1, wherein the number of grooves formed in the seal land portion is at least 3 or 4. machine. 5. The variable displacement type swash plate hydraulic machine according to claim 1, wherein the groove is formed on a swash plate side sliding surface between the swash plate and the slippers. Swash plate type hydraulic machine. 6. The variable displacement swash plate hydraulic machine according to claim 1, wherein the groove is formed by at least one of the cylinder block sliding surface and the valve plate sliding surface of the hydraulic machine. A variable displacement swash plate type hydraulic machine characterized in that it is formed on the outer sliding surface of the outer seal land. 7. The variable displacement swash plate hydraulic machine according to claim 1, wherein the groove is an outer sliding surface of an outer seal land of the valve plate sliding surface of the hydraulic machine. A variable displacement swash plate type hydraulic machine characterized in that it is formed near the top dead center and the bottom dead center of the valve plate. 8. The variable displacement swash plate hydraulic machine according to claim 1, wherein a surface shape is provided on an outer sliding surface of at least one of the cylinder block sliding surface and the valve plate sliding surface. Is a rectangular strip, and a variable capacity swash plate type hydraulic machine is characterized in that a triangular groove having asymmetrical inclination is formed so that the cross-sectional shape gradually becomes shallower in the sliding direction. 9. The variable displacement swash plate type hydraulic machine according to claim 8, wherein the groove is formed on the outer sliding surface of an outer seal land of the valve plate sliding surface of the hydraulic machine. A variable displacement swash plate type hydraulic machine characterized in that it is formed near the top dead center and the bottom dead center. 10. A hydraulic pump for a hydrostatic continuously variable transmission, comprising the variable displacement swash plate type hydraulic machine according to claim 1.
A hydrostatic continuously variable transmission characterized by comprising a motor. 11. The variable capacity swash plate hydraulic machine according to claim 1, wherein the groove is formed by press working by a die, cutting, precision casting, or laser working. A method for forming a groove, which is characterized in that it is formed by the above method. 12. The variable displacement swash plate hydraulic machine according to claim 1, wherein when forming the groove in the slipper by pressing with a mold, a groove-shaped mold to be formed is first formed. Made of high hardness wear resistant member, and then either one of the mold or the slipper,
After fixing to a rotating member having a means capable of positioning the rotation angle, one of the bottom surface of the slipper to be grooved or the mold is fixed to the opposite side, and the metal mold is formed by pressure molding means. A method of forming a groove, characterized in that one of a mold and a slipper is pressed against one of a bottom surface of a slipper and a mold. 13. The method for forming a groove according to claim 12, wherein the mold is positioned in the forming position in the rotating direction and in the vertical straight line direction by either electric driving means or hydraulic driving means. A method for forming a groove, characterized in that one side is formed.