JP3514631B2 - Axial piston pump / motor - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotating axial piston pump / motor for a cylinder block.

[0002]

2. Description of the Related Art This type of axial piston pump
As an example of the motor, there is one as shown in FIG. 20 (in this example, an opposed swash plate type motor is shown). This axial piston pump / motor is slidable in a housing 2 having an end cover 1, a cylinder block 3 rotatably supported in the housing 2 by bearings 7A and 7B, and cylinder holes 4 of the cylinder block 3. A piston 5 provided and a swash plate that converts the reciprocal motion of the piston 5 into the rotational motion of the cylinder block 3 when used as a motor, and converts the rotational motion of the cylinder block 3 into the reciprocal motion of the piston 5 when used as a pump. Mechanism (motion conversion mechanism)
20 and two main ports 6A, 6B formed in the end cover 1 and the cylinders which are arranged between the end covers 1 and the end faces of the cylinder block 3 so as not to rotate and to be able to move in the axial direction minutely. The block plate 3 is provided with a valve plate 8 for switching the connection oil passage with each cylinder hole 4.

Further, as also shown in FIGS. 21 to 23, a cylinder port 9 communicating with each cylinder hole 4 is opened on the sliding surface of the cylinder block 3 on the valve plate 8 side. A pair of supply / discharge ports 11A and 11B are provided on the sliding surface of the valve plate 8 on the cylinder block 3 side.
Is provided. The supply / discharge ports 11A and 11B selectively communicate with the cylinder port 9 by leaving the closing portion 10 that closes the cylinder port 9 as a boundary portion. On the surface of the valve plate 8 on the end cover 1 side, corresponding parts of the supply / discharge ports 11A, 11B and the main ports 6A, 6B communicate with each other in a liquid-tight manner, and the oil acting on the supply / discharge ports 11A, 11B A sleeve 12 is provided which is axially slid by pressure and thereby presses the valve plate 8 against the cylinder block 3.
Here, both ends of the sleeve 12 are slidably and liquid-tightly fitted into circular sleeve holes 13 and 14 formed on the opposing surfaces of the valve plate 8 and the end cover 1, and the sleeve hole 13 on the valve plate 8 side is formed. 15 between the sleeve and the sleeve 12
Is installed.

In this structure, during operation, the valve plate 8 is forced to press the valve plate 8 against the end surface of the cylinder block 3 (hereinafter referred to as "pressing force").
Then, a force to pull them apart (hereinafter referred to as "repulsion force") acts. The pressing force is generated from the main ports 6A, 6B or the supply / discharge ports 11A, 11B by the hydraulic pressure acting on the end surface of the sleeve 12 and the force of the spring 15. Also,
The separating force is the pressure acting on the cylinder port 9 of the cylinder block 3 and the valve plate 8 and the cylinder block 3.
It is generated by the pressure of the oil film on the sliding surface of. The ratio of the pressing force to the separating force (= separating force / pressing force) is called the hydraulic balance ratio.

When the separating force becomes larger than the pressing force (hydraulic balance ratio> 1), the valve plate 8 separates from the end surface of the cylinder block 3 and the oil leakage increases remarkably, resulting in a decrease in volumetric efficiency and inability to rotate. Causes the problem. If the pressing force is greater than the separating force (hydraulic balance ratio <
1) Oil leakage is eliminated, but if it is too large, friction loss increases and torque efficiency decreases.

Normally, the pressing force generated by the sleeve 12 is constant and does not change, but the separating force is the separating force.
Changes with the rotation of. That is, when the cylinder port 9 switches between high pressure and low pressure, the two supply / discharge ports 11A,
Although passing through the closed portion (top dead center, bottom dead center) 10 between 11B, when passing through the closed portion 10, high pressure is contained in the cylinder hole 4 of the rotating cylinder block 3. Therefore, a large separating force acts on the sliding surface (valve surface) between the cylinder block 3 and the valve plate 8. Therefore, the separation force, that is, the hydraulic balance ratio, changes greatly by changing the overlapping area of the cylinder port 9 with respect to the closing portion 10 according to the rotational angle position of the cylinder block 3.

Therefore, to give priority to reducing the amount of oil leakage, the place where the separating force is the largest, that is, the closing portion 10 is used.
It is necessary to increase the pressing force of the sleeve 12 in order to reduce the oil pressure balance ratio at the time of passing through.
However, if the pressing force by the sleeve 12 is set on the basis of the place where the separating force is the largest, the hydraulic balance ratio becomes too small in the place where the separating force is small (the place other than the closing portion 10), and the friction loss becomes large. Therefore, the torque efficiency becomes low. Further, there is a possibility that a sliding surface of the cylinder block 3 and the valve plate 8 may have a problem such as seizure.

On the other hand, in order to prioritize improvement of torque efficiency,
If the pressing force by the sleeve 12 is set to be weak, oil leakage will increase in a place where the separating force is large, and there is a strong possibility that problems such as a decrease in volumetric efficiency and inability to rotate occur.

As described above, it has been a difficult problem to achieve both improvement of torque efficiency and reduction of oil leakage.

Therefore, in the above-described pump / motor, the small oil hole 25 and the small oil hole 25 are formed on the center line of the closing portion 10 of the valve plate 8 (the center line of the closing portion 10 in the circumferential direction of the valve plate 8). Only one set of the piston hole 27 and the small piston 28 is provided, and the pressure in the cylinder hole 4 is guided to the small piston hole 27 through the small oil hole 25.
The valve plate 8 at the closing portion 10 by sliding the valve plate 8 in the axial direction by the pressure.
It is designed to increase the force that is pressed against the end face of.

According to this structure, the contact state of the sliding surface (valve surface) between the cylinder block 3 and the valve plate 8 can be stabilized by the action of the small piston 28, and at the same time, the closing portion (top dead center, It is possible to prevent a sudden pressure change at (bottom dead center) 10.

Incidentally, the small oil hole 25 and the small piston hole 2
7 and the technique of providing the small piston 28 are described in Sumitomo Heavy Industries Technical Report “Vol. 21 No. 60 April 1973”.
P80- ", British Patent No. 1222232, Utility Model Registration Publication No. 2502901, and the like.

[0013]

By the way, in the conventional pump / motor in which the closing portion 10 of the valve plate 8 has the small piston 28, only one small piston 28 is provided for each closing portion 10. Not yet, and
Only one small oil hole 25 is provided on the center line of the small piston hole 27.

Therefore, the distance from when the cylinder port 9 starts overlapping with the closing portion 10 of the valve plate 8 to the small oil hole 27 on the center line of the closing portion 10 is long, and during that time, the small piston 28 moves. The effect of the small piston 28 appears when the cylinder port 9 reaches the small oil hole 27 after the pressure of the cylinder hole 4 acts on the overlapping portion and the separating force greatly increases without any effect. , The pressing force will increase. In particular, when the cylinder port 9 has an elongated elliptical shape or an eyebrow shape, the distance (time) until the pressure is introduced to the small piston 28 becomes extremely long.

In such a case, although the improvement is certainly made as compared with the case where the small piston 28 does not exist, the fluctuation of the hydraulic balance ratio is still large. Therefore, there is a possibility that oil leakage or torque fluctuation may increase during low-speed operation or at startup, etc., and it has not been sufficient to cope with operating conditions that dislike them. An object of the present invention is to provide an axial piston pump / motor that prevents oil leakage from the valve plate and obtains high torque efficiency (that is, low friction loss) at any rotation angle position.

[0016]

An axial piston pump / motor according to the invention of claim 1 is rotatably provided in a housing having an end cover, and has a plurality of cylinder holes spaced at a circumferential direction. Block and
A piston slidably provided in each cylinder hole of the cylinder block, and reciprocating motion of the piston is converted into rotational motion of the cylinder block when used as a motor, and rotational motion of the cylinder block when used as a pump. To a reciprocating motion of the piston, and two non-rotatable main ports formed in the end cover, which are non-rotatably arranged between the end cover and the end surface of the cylinder block, and the cylinder. And a valve plate for switching connection oil passages with each cylinder hole of the block, and a cylinder port communicating with each cylinder hole is opened on a sliding surface on the valve plate side of the cylinder block, Cylinder port is closed on the sliding surface of the valve plate on the cylinder block side. Closed portion by leaving a border portion of that pair of arcuate sheet discharge port is provided to selectively communicate with the cylinder port, further, the surface of the cylinder block side of the closed portion of the valve plate,
When a small oil hole that can communicate with the cylinder port is provided, and a small piston hole that communicates with the small oil hole is provided on the opposite surface, and the small oil hole communicates with the cylinder port. Is slid in the axial direction by the hydraulic pressure trapped in the cylinder hole,
In an axial piston pump / motor provided with a small piston that presses the valve plate against the cylinder block, a plurality of sets of the small piston hole and the small piston and the small oil hole are provided for each closing portion. The above problems are solved by arranging them side by side in the circumferential direction.

According to the present invention, since a plurality of small pistons are arranged in the closing direction (top dead center, bottom dead center) of the valve plate in the circumferential direction, the small pistons are arranged depending on the degree of overlap between the cylinder port and the closing section. The force for pressing the valve plate against the cylinder block (pressing force) can be finely adjusted in synchronism with the separating force due to the stacking so as to obtain the intended characteristics.

That is, according to the rotation angle of the cylinder block (= the degree of overlapping of the cylinder port and the closed portion),
It is possible to reduce the fluctuation of the ratio (hydraulic balance) of the pressing force and the separating force acting on the valve plate. Therefore, it is possible to reduce the friction loss of the sliding surface (valve surface) between the cylinder block and the valve plate and the oil leakage from the sliding surface (valve surface) at the same time, thereby improving the operating efficiency. it can.

According to a second aspect of the invention, the axial piston pump / motor according to the first aspect is arranged such that the small oil hole communicating with the small piston hole is displaced from the center line of the small piston hole in the circumferential direction of the valve plate. It is characterized by having done.

In the present invention, since the position of the small oil hole is displaced from the center line, in at least one rotation direction,
The timing of communication between the cylinder port and the small oil hole can be advanced (compared to the case where the small oil hole is arranged on the center line). Therefore, the hydraulic pressure of the cylinder port can be introduced into the small piston hole at an early timing, and the effect of improving the hydraulic balance by the small piston can be effectively exhibited.

An axial piston pump / motor according to a third aspect of the present invention is the axial piston pump / motor according to the first aspect, wherein the small piston hole 1 is provided.
The number of the small oil holes per piece is plural, and the small oil holes are arranged on both sides of the center line of the small piston hole in the circumferential direction of the valve plate as a boundary.

In the present invention, since the small oil holes are arranged on both sides of the center line of the small piston hole, the oil pressure of the cylinder port can be introduced into the small piston hole at an early timing regardless of the rotation direction of the pump / motor. Therefore, the effect of improving the hydraulic balance by the small piston can be effectively exerted.

According to the axial piston pump / motor of the invention of claim 4, in claim 3, a plurality of small oil holes communicating with the one small piston hole are arranged at positions where they do not communicate with another cylinder port at the same time. It is characterized by having done.

According to the present invention, since the plurality of small oil holes communicating with one small piston hole do not communicate with another cylinder port at the same time, internal leakage is prevented and the volumetric efficiency is improved.

According to a fifth aspect of the present invention, in the axial piston pump / motor according to the third aspect, a plurality of small oil holes communicating with the one small piston hole are located at positions where they can simultaneously communicate with another cylinder port. It is characterized by having been placed.

In the present invention, since a plurality of small oil holes communicating with one small piston hole may simultaneously communicate with another cylinder port, it is possible to obtain the characteristics of particularly enhancing the noise prevention and pulsation prevention effects.

The axial piston pump / motor according to a sixth aspect of the present invention is the axial piston pump / motor according to any one of the first to fifth aspects, wherein V is continuous with the opening of the small oil hole on the cylinder block side and extends in the direction in which the cylinder port approaches. It is characterized in that a notch groove such as a notch or a U notch is provided.

In the present invention, V is provided at the inlet (opening) of the small oil hole.
Since the notch groove such as the notch and the U notch is provided, the internal pressure of the cylinder hole can be smoothly guided to the small piston hole.
As a result, noise prevention and pulsation prevention effects are enhanced.

According to a seventh aspect of the invention, in any one of the first to sixth aspects, the end surface of the sleeve disposed on the end cover side surface of the valve plate is formed by the force of the spring and the hydraulic pressure acting on the sleeve. It is characterized in that the flat surface formed on the side of the end cover is pressed in liquid-tight contact.

According to the present invention, since only the flat portion for receiving the end face of the sleeve in a liquid-tight manner needs to be formed on the valve plate side, the processing amount on the end cover side can be reduced and the main port inside the end cover can be reduced. The freedom of layout is increased.

An axial piston pump / motor according to an eighth aspect of the present invention is the axial piston pump / motor according to any one of the first to seventh aspects, wherein at least one pair of end portions of all the small pistons is positioned by a positioning pin for restraining rotation of the valve plate. Also, it is slidably fitted in the fitting hole on the end cover side.

In the present invention, at least one pair of all the small pistons is also fitted to the valve plate side, so that the valve plate can be stopped at a fixed position.

According to a ninth aspect of the present invention, in any one of the first to eighth aspects, an O-ring for sealing a gap with the small piston hole is fitted on the outer circumference of the small piston.

According to the present invention, it is possible to prevent oil leakage from the gap between the small piston and the valve plate, prevent a pressure drop in the small piston hole, and maintain the pressing force.

[0035]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a side cross section of the swash plate type axial piston pump / motor of the embodiment. For convenience, the left side is the front end side and the right side is the rear end side in the figure. The pump / motor housing 51 includes a housing body 52,
It is divided into an end cover 53. The housing main body 52 integrally includes a cylindrical peripheral wall 52A that secures an internal space of the housing 51 and a front end wall 52B that closes a front end opening thereof. In addition, the end cover 53 is the peripheral wall 5
It is configured as a rear end wall that closes the rear end opening of 2A, and is fixed to the rear end portion of the housing main body 52 with bolts 100 while being fitted to the rear end portion. Housing body 5
A rotating shaft (an output shaft when used as a motor and an input shaft when used as a pump) is provided on the front end wall 52B of No. 2.
A through hole 52C for projecting the tip of 56 to the outside is formed, and a swash plate 60 is integrally formed on the inner surface. Reference numeral 61 denotes a thrust plate, which is arranged on the surface of the swash plate 60.

A cylinder block 54 having a structure in which a cylinder barrel 55 and a rotary shaft 56 are integrated is housed inside the housing 51. The rotating shaft 56 is provided in the front part of the cylinder block 54, and the cylinder barrel 55 is provided in the outer periphery of the rear part of the cylinder block 54. The cylinder block 54 is rotatably supported by bearings 57 and 58 mounted on the front and rear portions of the housing 51, and the front end of the rotary shaft 56 is exposed to the outside from the through hole 52C of the front end wall 52B. There is. The front bearing 57 is arranged on the inner periphery of the through hole 52C of the front end wall 52B, and the rear bearing 58 is formed on the inner surface of the end cover 53.
It is located on the outer periphery of. On the rear end surface of the cylinder block 54, a concave portion 55 that fits into the convex portion 59 of the end cover 53.
b is bored, and the inner circumference of the concave portion 55b and the convex portion 59 are formed.
The bearing 58 on the rear side is fitted between the outer circumferences of the.

The cylinder barrel 55 is located between the end cover 53 and the swash plate 60 provided on the inner surface of the front end wall 52B of the housing 51. In the cylinder barrel 55,
A plurality of cylinder holes 55a are formed at equal intervals on the circumference, and pistons 62 projecting and retracting toward the swash plate 60 are slidably inserted into the respective cylinder holes 55a. A slipper 63, which slidably contacts the sliding surface of the swash plate 60, is rotatably fitted to the spherical front end head portion 62a of each piston 62. The slipper 63 is held by a single ring-shaped retainer plate 64. Here, the swash plate 60, the thrust plate 61, the slipper 6
3, the retainer plate 64, etc. constitute a swash plate type motion conversion mechanism.

Further, between the rear end surface of the cylinder barrel 55 and the end cover 53, a ring-shaped valve plate 70 with which the rear end surface of the cylinder barrel 55 contacts while rotating is disposed. The valve plate 70 is formed in the end cover 53 as the cylinder barrel 55 rotates.
One main port 75A, 75B and cylinder barrel 5
5 plays a role of switching the connection state with each cylinder hole 55a, and is fitted into the outer periphery of the convex portion 59 provided on the end cover 53. A sleeve 73 and a disc spring 72 are arranged between the valve plate 70 and the end cover 53. The sleeve 73 and the disc spring 72 slidably and liquid-tightly press-contact the valve plate 70 with the rear end surface of the cylinder barrel 55, and the valve plate 7
It corresponds to a seal mechanism that fluid-tightly communicates between 0 and the main port 75.

FIG. 2 is a view showing the rear end face of the cylinder block 54 (cylinder barrel 55), and FIG. 3 is the valve plate 7.
0 is a front end surface of the valve plate 70, and FIG. 4 is a rear end surface of the valve plate 70. The structure around the valve plate 70 will be described in detail with reference to FIG. 1 and these drawings.

As shown in FIG. 2, on the rear end surface of the cylinder barrel 55 (sliding surface with the valve plate 70 = valve surface),
Cylinder ports 55c, which are long holes in the circumferential direction and communicate with the respective cylinder holes 55a, are opened.

Further, as shown in FIG. 3, the front end surface of the valve plate 70 (sliding surface with the cylinder barrel 55 = valve surface).
Includes a closing portion 80 for closing the cylinder port 55c.
Is left as a boundary, each cylinder port 5
Two bottomed supply / discharge ports 71 selectively communicating with 5c
A and 71B are formed. When used as a motor, one of these two supply / discharge ports 71A, 71B is the oil supply side (suction side in the case of a pump) and the other is the discharge side (discharge side in the case of a pump). It is formed as an arc-shaped elongated hole along the circumferential direction of the cylinder barrel 54. Each of the supply / discharge ports 71A and 71B has a circumferential length that communicates with half of the plurality of cylinder ports 55c.

As shown in FIG. 4, on the rear end surface of the valve plate 70, front side supply / discharge ports 71A and 71B are provided.
A plurality of (6 in this example) bottomed circular holes 82 are formed at regular intervals in the circumferential direction. Of these, half (3) of the circular holes 82 are the one of the supply / discharge ports 71.
The remaining half (three) circular holes 82 communicate with A and communicate with the other supply / discharge port 71B. The closing part 8
No circular hole 82 is formed at 0.

On the other hand, as shown in FIG. 1, the end cover 53
Two main ports 75A and 75B are provided in the. The valve plate 7 is provided on the inner surface of the end cover 53.
Corresponding to the circular hole 82 of 0, each main port 75A,
An opening of 75B is formed. In this case, the opening of the one main port 75A communicates with the one supply / discharge port 71A through the corresponding circular hole 82, and the opening of the other main port 75B through the corresponding circular hole 82. It communicates with the discharge port 71B.

In order to maintain such correspondence, the valve plate 70 has the pin 7 with respect to the end cover 53.
8 (also used as a long small piston 94 described later)
The rotation is stopped by. The pin 78 is arranged at a position avoiding the circular hole 82, and is provided in the end cover 53 and has a bottomed hole 79.
Both ends are fitted in a small piston hole 92 provided in the rear end surface of the valve plate 70.

The sleeve 73 is made of a cylindrical body and is slidably fitted in the inner circumference of each circular hole 82 of the valve plate 70, and the liquid tightness is secured between the outer circumference of the sleeve 73 and the inner circumference of the circular hole 82. Is fitted with an O-ring 74. The sleeve 73 is for communicating the openings of the main ports 75A and 75B with the circular hole 82 of the valve plate 70, and the end cover is accommodated by the disc spring 72 housed between the bottom surface of the circular hole 82 and the front end surface of the sleeve 73. It is urged toward the 53 side, and the rear end surface thereof is pressed into liquid-tight contact with the flat surface 81 formed on the peripheral edges of the openings of the main ports 75A and 75B. Further, as a result, the disc spring 72 presses the valve plate 70 against the rear end surface of the cylinder barrel 55 in a liquid-tight manner.

Further, the closing portion 8 of the valve plate 70
As shown in FIG. 3, the cylinder port 55
A small oil hole 91 that can communicate with c is provided, and a small piston hole 92 that communicates with the small oil hole 91 is provided on the opposite rear end surface as shown in FIG. Then, as shown in FIG. 1, the small piston 9 is inserted into each small piston hole 92.
3, 94 (94 is the pin 78 described above) are accommodated slidably in a liquid-tight manner in the axial direction of the cylinder block 54.

In this embodiment, three sets of the small piston holes 92, the small pistons 93 and 94, and the small oil holes 91 are arranged for each closed portion 80. Two of them are arranged side by side in the circumferential direction of the valve plate 70 on the outer peripheral side, and the other one is arranged on the inner peripheral side of them in the closed portion 8.
It is located on the center line of 0 (center line in the circumferential direction of the valve plate 70). Two small oil holes 91 communicate with each small piston hole 92, and these two small oil holes 91 are bordered by the center line of the small piston hole 92 in the circumferential direction of the valve plate 70. , Are arranged symmetrically on both sides. Also, the small piston hole 9
The set of 2, the small oil hole 91, and the small pistons 93 and 94 are arranged symmetrically with respect to the center line of each closing portion 80. Therefore, the two small piston holes 92 and the small oil holes 91 on the outer peripheral side are not located on the center line of the closing portion 80, but are located at positions displaced toward the supply / discharge ports 71A and 71B.

As can be seen at a glance in FIG. 4, three small piston holes 92 are distributed over the entire closing portion 80 at substantially equal intervals. Then, as will be described later, the cylinder hole 55C and the small oil hole 91 communicating with another small piston hole 92 one after another for each predetermined rotation angle θ of the cylinder block 54 according to the rotation angle position of the cylinder block 54. They are distributed so that they can correspond to each other.

Further, as shown in FIG. 1, the small piston 93 housed in the small piston hole 92 on the outer peripheral side has a short length, and its end face is in direct pressure contact with the inner face of the end cover 53. However, the small piston 94 housed in the small piston hole 92 on the inner peripheral side has a long length, and its end portion slides into the bottomed hole 79 formed on the inner surface of the end cover 53. It is freely inserted and hits the bottom of the bottomed hole 79.

In this way, one of the three small pistons 93, 94 of the pair of closing portions 80 is one small piston 94.
Since the end cover 53 and the valve plate 70 are engaged with each other (two pieces including both the closing portions 80), the small piston 94 serves as a positioning pin in the rotation direction of the valve plate 70 described above. It will play the role of 78. Therefore, it is not necessary to separately provide another positioning pin, and it is not necessary to fit the sleeve 73 into the hole on the end cover 53 side for positioning.

It should be noted that oil is prevented from leaking from the gap between the small pistons 93, 94 and the small piston holes 92 on the outer circumference of each of the small pistons 93, 94, and the pressure drop in the small piston holes 92 is prevented. An O-ring 95 is fitted to maintain the pressing force.

Next, the operation will be described.

When used as a motor, when high-pressure oil flows in from one main port 75A (or 75B), the high-pressure oil enters the cylinder hole 55a of the cylinder barrel 55 through the valve plate 70 and reaches the end surface of the piston 62. By acting, the piston 62 is moved in the axial direction, and the slipper 63 is pressed against the swash plate 60. And slippers 6
3 is pressed against the slope 60, the piston 6
A component force in a direction orthogonal to the movement direction of 2 is generated, and this component force becomes a rotational force to rotate the cylinder block 54,
The rotating shaft 56 integral therewith is rotated. During this operation, the high-pressure side piston 62 should move from top dead center (retraction limit) to bottom dead center (projection limit), and the low pressure side piston 62 should move from bottom dead center to top dead center. Accordingly, the low-pressure oil that has been operated flows out from the other main port 75B (or 75A) through the valve plate 70.

When used as a pump, the rotary shaft 56
The rotation of the cylinder block 54 rotates, and the rotation of the cylinder block 54 causes the piston 62 to reciprocate.
By the reciprocating movement of the piston 62, the suction stroke and the discharge stroke are sequentially executed. At the same time, the oil passage is automatically switched by the valve plate 70, and the hydraulic oil is sucked from one main port 75A (or 75B) and discharged from the other main port 75B (or 75B).

In the above operation, the valve plate 70 is constantly brought into pressure-contact with the rear end surface of the cylinder barrel 55 in a liquid-tight manner by the action of the hydraulic pressure acting on the disc spring 72 and the circular hole 82, and the valve plate 70 and the valve plate 70. The sleeve 73 is always fluid-tightly connected to the opening of the main port 75. Therefore, it is possible to switch the connection state between the main ports 75A and 75B and the cylinder hole 55a while surely preventing oil leakage.

Further, the small pistons 93, 94 slide in accordance with the rotational angular position of the cylinder block 54, and generate a pressing force against the separating force increasing at the closing portion 80. The details of the operation will be described below.

FIG. 5 is a diagram showing the relationship between the rotation angle of the cylinder block 54 and the hydraulic pressure balance ratio.
6 to 10 show the relationship among the cylinder port 55c, the closing portion 80, the small piston hole 92, and the small oil hole 91 at each stage of (e) to (e). The arrows in FIGS. 6 to 10 indicate the rotation direction of the cylinder block 54. Here, the operation will be described in order taking the case where the supply / discharge port 71A is on the high pressure side and the supply / discharge port 71B is on the low pressure side as an example.

(1) When the cylinder block 54 rotates in the direction of the arrow, the cylinder port 55c overlaps with the closing portion 80 of the valve plate 70 with the rotation [see FIG. 6]. Step (a) of FIG. 5]. The overlapping part is code 1
Shown by 20. The pressure of the overlapping portion 120 increases the separating force.

(2) Eventually, when the cylinder port 55c rotates by the predetermined rotation angle θ and reaches the small oil hole 91 leading to the first small piston hole 92, the pressure in the cylinder hole 55a is increased to the first small piston hole 92. , The small piston 93 slides to push the end plate 53, and the pressing force of the valve plate 70 increases as a reaction force thereof (see FIG. 7). Step (b) of FIG. 5].

(3) When the cylinder block 54 further rotates, the overlapping portion 120 increases and the separating force increases again. When the cylinder port 55c eventually reaches the small oil hole 91 leading to the next small piston hole 92, the cylinder hole 5
The pressure in 5a is guided to the next small piston hole 92, whereby the small piston 94 slides to push the end plate 53, and the pressing force of the valve plate 70 increases as a reaction force thereof (see FIG. 8). Step (c) of FIG. 5].

(4) When the cylinder block 54 further rotates, the overlapping portion 120 increases and the separating force increases again. Eventually, when the cylinder port 55c reaches the small oil hole 91 leading to the next (last) small piston hole 92,
The pressure in the cylinder hole 55a is guided to the next small piston hole 92, whereby the small piston 93 slides to press the end plate 53, and the pressing force of the valve plate 70 increases as a reaction force thereof (see FIG. 9). . Step (d) of FIG. 5].

(5) The cylinder block 54 further rotates, and the cylinder port 55c becomes the low pressure side supply / discharge port 71.
When it reaches B, the internal pressure of the cylinder hole 55a decreases, and at the same time, the pressure of the small piston hole 92 also decreases [see FIG. 10]. Step (e) of FIG. 5].

As described above, since the pressing force also gradually increases in synchronization with the increase in the separating force due to the rotation of the cylinder block 54, the fluctuation of the hydraulic balance ratio as shown in FIG. It is smaller than the one shown by the dotted line).

FIG. 11, FIG. 12 and FIG. 13 are diagrams showing, for comparison, the difference in fluctuation of the hydraulic balance ratio. Figure 11
12 shows the case where there is no small piston, FIG. 12 shows that there is only one small piston (small piston hole 92) on the center line of the closing portion 80 (corresponding to the conventional example), and FIG.
The case where there are a plurality of small pistons (small piston holes 92) (the case of the present embodiment) is shown. As can be seen from these drawings, in the present embodiment, three small pistons are arranged, and the cylinder holes 55c are sequentially separated for each predetermined rotation angle θ of the cylinder block 54 according to the rotation angle position of the cylinder block 54. Small piston holes 92a, 92
The small pistons of the small piston holes 92 connected to the small oil holes 91a, 91b, 91c of b and 92c exert the pressing force increasing action one after another, so that the fluctuation of the hydraulic balance ratio is significantly suppressed as compared with other cases. can do. Therefore, regardless of the rotational angle position of the cylinder block 54, the hydraulic balance ratio can be balanced, and the low leak amount and the high torque efficiency can both be achieved, and high overall performance can be exhibited. Also, the small piston 9
Since the pressing force of 3, 94 and the separating force of the overlapping portion act almost at the same position, the moments acting on the valve plate 70 can be easily balanced.

Further, in the present embodiment, as shown in an enlarged view in FIG. 14, the small oil hole 91 is provided with the center line of the small piston hole 92 (the center line in the circumferential direction of the cylinder block 54) C.
Since it is intentionally removed from the top and symmetrically arranged on both sides of the center line, when looking at each small piston hole 92, one small oil hole 91 shifts to one supply / discharge port 71A side, and the other small oil hole 91A shifts. The hole 91 is displaced toward the other supply / discharge port 71B. Therefore, whichever direction the cylinder block 54 rotates, the cylinder port 55c is faster than when the small oil hole 91 is arranged on the center line of the small piston hole 92.
And the small oil hole 91 can be brought out together, the pressure can be quickly introduced to the small piston hole 92, and the hydraulic pressure balance can be easily balanced.

As another function and effect, this pump
In the case of a motor, the end surface of the sleeve 73 is made to press-contact with the flat surface 81 formed on the end cover 53 side in a liquid-tight manner by the force of the disc spring 72 and the hydraulic pressure acting on the sleeve 73. It is not necessary to perform precise hole processing for accommodating the sleeve 73 on the cover 53 side, the amount of processing on the end cover side can be reduced, and the flexibility of layout of the main ports 75A and 75B inside the end cover 53 can be reduced. There is also an advantage that the manufacturing cost of the end cover 53 can be reduced as a result.

Further, since at least one pair of small pistons 94 out of the plurality of small pistons 93, 94 are used as the positioning pins 78 for restraining the rotation of the valve plate 70, it is not necessary to separately provide the positioning pins. The structure can be simplified. Further, when the sleeve is used for positioning as in the conventional case, it is necessary to improve the positional accuracy of the sleeve hole, but the small piston 94 is not used as an oil passage, but is simply used for positioning, and the end cover 53 is used. Therefore, the precision of the bottomed hole 79 on the end cover 53 side does not have to be so high.

In the above embodiment, as shown in FIG. 14, since it is necessary to operate in either rotation direction when the motor is operating, the small oil hole 91 is provided for each small piston hole 92. Two are provided and are arranged symmetrically, but when the rotation direction is constant such as when operating as a pump, as shown in FIG. 15, one small oil hole 91 per one small piston hole 92. Alternatively, the number may be one, and they may be arranged so as to be offset in the direction in which the cylinder port 55c approaches. Also in this case, the cylinder port 55c may be connected to the different small oil holes 91a, 91b, 91c at every predetermined rotation angle of the cylinder block 54 (or the cylinder port 55c).

Of course, it is not prohibited to provide the small oil hole 91 on the center line C.

When it is important to prevent internal leakage and to improve volumetric efficiency, as shown in FIG. 16, two small oil holes 9 communicating with one small piston hole 92 are provided.
1 are arranged so that they do not communicate with another cylinder port 55c at the same time.

In addition, when importance is attached to noise prevention, pulsation prevention, etc., as shown in FIG. 17, a plurality of small oil holes 91 communicating with one small piston hole 92 are intentionally provided at the same time in different cylinder ports. It is arranged so as to communicate with 55c.

Further, as shown in FIG. 18, a cutout groove 99 such as a V notch or a U notch extending in the approaching direction of the cylinder port 55c is provided continuously to the opening of the small oil hole 91 on the cylinder block 54 side. For example, the internal pressure of the cylinder hole 55a can be smoothly guided to the small piston hole 92, and as a result, noise prevention and pulsation prevention effects can be enhanced.

Further, in order to prevent noise and pulsation, FIG.
As shown in FIG. 9, the supply / discharge port 71 of the valve plate 70.
Oil grooves 71 such as V notches and U notches at the ends of A and 71B
c may be provided.

In the above embodiment, the case where the present invention is applied to the swash plate type axial piston pump / motor has been shown. It can be applied to all types of pump motors with floating valve plate type valve plates with supply / discharge ports, regardless of the type of motor.

If the floating valve plate type is used, this structure can be applied whether the sleeve is installed in the valve plate or in the end cover.

Further, in the above-described embodiment, the sleeve 73 is pressed into contact with the flat surface 81 on the end cover 53 side, but a sleeve hole is formed in the end cover 53 as in the conventional example of FIG. The end of the sleeve 73 may be slidably fitted in the hole. If you do,
Since the sleeve 73 can also serve as a positioning pin, it is not necessary to fit the small piston 94 into the bottomed hole 79 on the end cover 53 side.

Further, the number of the small piston holes 92 and the number of the small oil holes 91 per one small piston hole 92 are not particularly limited as long as they match the gist of the present invention.

[0079]

As described above, according to the present invention,
Since a plurality of small pistons are arranged side by side in the circumferential direction in the closing part of the valve plate, the pressing force acting on the valve plate is finely adjusted in multiple stages in synchronization with the separating force due to the overlapping of the cylinder port and the closing part. be able to.
Therefore, it is possible to suppress the fluctuation of the hydraulic balance ratio regardless of the rotational angle position of the cylinder block, improve the torque efficiency by reducing the friction loss of the sliding surface of the cylinder block and the valve plate, and improve the torque efficiency from the sliding surface. It is possible to improve volumetric efficiency by reducing oil leakage.

[Brief description of drawings]

FIG. 1 is a sectional view of an axial piston pump / motor according to an embodiment of the present invention.

FIG. 2 is a view showing a main part (a rear end surface of a cylinder block) of a cross section taken along line II-II of FIG.

FIG. 3 is a view showing a main part (a front end surface of a valve plate) of a cross section taken along the line III-III in FIG.

FIG. 4 is a diagram showing a main part (rear end surface of the valve plate) of a cross section taken along the line IV-IV in FIG.

FIG. 5 is a characteristic diagram showing a relationship between a cylinder block rotation angle and an oil pressure balance ratio of the axial piston pump / motor according to the embodiment.

FIG. 6 is a diagram showing the relationship between the valve plate and the cylinder port at the stage of FIG. 5 (a).

FIG. 7 is a diagram showing the relationship between the valve plate and the cylinder port at the stage of FIG. 5 (b).

8 is a diagram showing the relationship between the valve plate and the cylinder port at the stage of FIG. 5 (c).

9 is a diagram showing the relationship between the valve plate and the cylinder port at the stage of FIG. 5 (d).

10 is a diagram showing the relationship between the valve plate and the cylinder port at the stage of FIG. 5 (e).

FIG. 11 is a diagram showing a configuration of a conventional example having no small piston and a relationship between a cylinder block rotation angle and a hydraulic balance ratio.

FIG. 12 is a diagram showing a configuration of a conventional example in which one small piston and one small oil hole are located on a center line of a closed portion, and a relationship between a cylinder block rotation angle and a hydraulic balance ratio.

FIG. 13 is a diagram showing the relationship between the cylinder block rotation angle and the hydraulic balance ratio in the case of the present embodiment in which a plurality of small pistons and small oil holes are provided on the center line of the closed portion and on both sides thereof.

FIG. 14 is an enlarged view of a main part of this embodiment.

FIG. 15 is a diagram showing a modification thereof.

FIG. 16 is an enlarged view of a main part of another embodiment.

FIG. 17 is an enlarged view of a main part of still another embodiment.

FIG. 18 is an enlarged view of a main part of still another embodiment.

FIG. 19 is a view of a front end face of a valve plate according to still another embodiment.

FIG. 20 is a side sectional view showing an example of a conventional axial piston pump / motor.

21 is a view showing a main part (rear end surface of a cylinder block) of a cross section taken along the arrow XXI-XXI in FIG.

22 is a view showing a main part (front end face of valve plate) of a cross section taken along the line XXII-XII in FIG.

23 is a view showing a main part (rear end surface of the valve plate) of a cross section taken along the line XXIII-XXIII in FIG.

[Explanation of symbols]

53 ... End cover 51 ... Housing 54 ... Cylinder block 55a ... Cylinder hole 55c ... Cylinder port 60 ... Swash plate (motion conversion mechanism) 62 ... piston 70 ... Valve plate 71A, 71B ... Supply / discharge port 73 ... Sleeve 75A, 75B ... Main port 78 ... pin 80 ... Closed part 81 ... Flat surface 91 ... Small oil hole 92 ... Small piston hole 93, 94 ... Small piston 95 ... O-ring 99 ... Notch groove

Continuation of front page (56) Reference JP-A-10-131846 (JP, A) JP-A-2-227565 (JP, A) Actually open 4-27177 (JP, U) Actually open 58-169172 (JP , U) Utsukushihei 4-69679 (JP, U) Utsukushikai 51-26501 (JP, U) Utility model registration 2502901 (JP, Y2) British patent application publication 1222382 (GB, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) F04B 1/20-1/24 F04B 21/00 F01B 3/02 F03C 1/06

Claims (9)

(57) [Claims] 1. A cylinder block rotatably provided in a housing having an end cover and having a plurality of cylinder holes at circumferential intervals, and a cylinder block slidably provided in each cylinder hole of the cylinder block. A piston, and a motion conversion mechanism that converts the reciprocating motion of the piston into a rotary motion of the cylinder block when used as a motor, and converts the rotary motion of the cylinder block into a reciprocating motion of the piston when used as a pump, Non-rotatably arranged between the end cover and the end surface of the cylinder block, the connection oil passage is switched between the two main ports formed in the end cover and each cylinder hole of the cylinder block as the cylinder block rotates. A valve plate, and a sliding surface on the valve plate side of the cylinder block. To
A cylinder port that communicates with each of the cylinder holes is opened, and a sliding surface on the cylinder block side of the valve plate,
By leaving the closing portion for closing the cylinder port as a boundary portion, a pair of arc-shaped supply / discharge ports selectively communicating with the cylinder port is provided, and further, the cylinder block side of the closing portion of the valve plate. Is provided with a small oil hole that can communicate with the cylinder port, and the opposite surface is provided with a small piston hole that communicates with the small oil hole, and the small oil hole is provided with the small oil hole. In an axial piston pump / motor provided with a small piston that is axially slid by the hydraulic pressure trapped in the cylinder hole when communicating with the cylinder hole, thereby pressing the valve plate against the cylinder block. , A plurality of sets of the small piston hole and the small piston and small oil hole per one closing portion, in the circumferential direction of the valve plate Axial piston pump motor, characterized in that side by side arranged with. 2. The axial piston pump according to claim 1, wherein the small oil hole communicating with the small piston hole is arranged offset from the center line of the small piston hole in the circumferential direction of the valve plate.
motor. 3. The small oil hole according to claim 1, wherein the number of the small oil holes per one of the small piston holes is plural, and the small piston holes are arranged on both sides of the center line of the small piston hole in the circumferential direction of the valve plate. Axial piston pump / motor with small oil holes. 4. The axial piston pump / motor according to claim 3, wherein a plurality of small oil holes communicating with the one small piston hole are arranged at positions that do not simultaneously communicate with another cylinder port. .. 5. The axial piston pump according to claim 3, wherein a plurality of small oil holes communicating with the one small piston hole are arranged at positions where they can simultaneously communicate with another cylinder port. motor. 6. The cylinder according to claim 1, wherein the small oil hole is connected to the opening on the cylinder block side,
An axial piston pump / motor having a notch groove extending in the direction in which the cylinder port approaches. 7. The end surface of the sleeve arranged on the end cover side surface of the valve plate is moved to the end cover side by the force of the spring and the hydraulic pressure acting on the sleeve. An axial piston pump / motor, characterized in that the formed flat surface is pressed in liquid-tight contact. 8. The method according to claim 1, wherein at least one pair of ends of all the small pistons also serves as a positioning pin for restraining rotation of the valve plate,
An axial piston pump / motor that is slidably fitted in a fitting hole on the end cover side. 9. The axial piston pump / motor according to claim 1, wherein an O-ring for sealing a gap between the small piston and the small piston hole is fitted on the outer circumference of the small piston.