JP2001050154A - Axial piston type hydraulic rotating machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress generation of pressure pulsation and to surely reduce vibration and noise by imparting a non-linear characteristic to rotation displacement of a valve plate. SOLUTION: A rotating lever 15E provided on a valve plate 15 is projected within an actuator case 4. Within the actuator case 4, a valve plate rotating mechanism 17 for the valve plate 15 is provided. The valve plate rotating mechanism 17 is constituted of springs 18, 19 which are disposed between the actuator case 4 and the rotating lever 15E of the valve plate 15 and energizes the rotating lever 15E toward a pressing piston 22 side and a rotating actuator 20 driving the rotating lever 15E against the springs 18, 19 because pressure oil from a discharge port 15B is guided through an oil passage 24.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an axial piston type hydraulic rotary machine mounted on a construction machine such as a hydraulic excavator and suitably used as a hydraulic pump or a hydraulic motor.

[0002]

2. Description of the Related Art In general, a construction machine such as a hydraulic shovel is equipped with a hydraulic pump as a hydraulic source and a traveling or turning hydraulic motor. A plate type or oblique axis type axial piston type hydraulic rotary machine is used.

[0003] An axial piston type hydraulic rotary machine according to this type of prior art is provided with a casing, a rotary shaft rotatably provided in the casing, and a rotary shaft provided in the casing so as to rotate integrally with the rotary shaft. A plurality of cylinders having a plurality of cylinders extending in the axial direction separated from each other in the circumferential direction, a plurality of pistons reciprocally inserted into each cylinder of the cylinder block, and an end face of the cylinder block. It is constituted by a valve plate or the like provided with a pair of supply / discharge ports formed in the casing so as to be in sliding contact with each of the cylinders and intermittently communicating therewith.

[0004] When such an axial piston type hydraulic rotary machine is used as a hydraulic pump, the rotary shaft is driven to rotate by a prime mover such as an engine, so that the cylinder block in the casing is integrated with the rotary shaft. Rotate. As a result, the piston reciprocates in each cylinder of the cylinder block, and while the hydraulic oil is sucked into the cylinder from the suction port on the low pressure side of the pair of supply / discharge ports, the hydraulic oil is pressurized by the piston to increase the pressure on the high pressure side. Pressure oil is supplied from a discharge port to an external hydraulic actuator.

[0005] Further, switching lands are respectively formed on the valve plate between a suction port and a discharge port, which are a pair of supply / discharge ports. The cylinder block in the casing communicates with the discharge port after each cylinder is cut off from the suction port at one switching land, and sucks after each cylinder is cut off from the discharge port at the other switching land. Communicated with port.

Here, the piston in each cylinder enters a suction stroke in which the piston slides from top dead center to bottom dead center while the cylinder is in communication with the suction port, and hydraulic oil is supplied from an external tank to the suction port. Through the cylinder.
In addition, while each cylinder is in communication with the discharge port, the piston is in a discharge stroke in which the piston slides from bottom dead center toward top dead center, and the hydraulic oil sucked into the cylinder is used as high-pressure hydraulic oil as the discharge port. From the outside.

[0007]

In the above-described prior art, the piston slightly slides and displaces in each cylinder while the cylinder passes through the switching land of the valve plate as the cylinder block rotates. Thus, for example, the hydraulic oil sucked into the cylinder during the suction stroke of the piston is pre-compressed before communicating with the discharge port. On the other hand, the pressure in the discharge port is constantly changing due to an external load pressure or the like.

For this reason, when the oil liquid pre-compressed in the cylinder communicates with the discharge port, a pressure difference is generated. For example, the oil liquid flows out as a jet flow into the discharge port. May flow back into the cylinder, which causes pressure pulsation, which causes a problem such as vibration and noise.

On the other hand, an axial piston type hydraulic rotary machine (hereinafter referred to as another prior art) disclosed in Japanese Utility Model Application Laid-Open No. 61-18973 (Japanese Utility Model Application Publication No. 3-13587) is provided between a valve plate and a casing. A valve plate rotating mechanism including a rack-pinion or the like is provided, and the pressure of the oil liquid pre-compressed in the cylinder is adjusted by, for example, rotating and displacing the valve plate with the pressure of pressure oil guided from the discharge port side. It has a configuration.

However, in this case, the valve plate rotating mechanism only rotates and displaces the valve plate in proportion to the pressure in the discharge port. In practice, a differential pressure is often generated between the liquid pressure and the pressure in the discharge port, and there is a problem that it is difficult to reduce the pressure pulsation at this time.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art. It is an object of the present invention to effectively suppress the occurrence of pressure pulsation by giving a non-linear characteristic to the rotational displacement of a valve plate. It is an object of the present invention to provide an axial piston type hydraulic rotary machine capable of reliably reducing vibration, noise and the like.

[0012]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a casing, a rotating shaft rotatably provided in the casing, and a rotating shaft integrally rotatable with the rotating shaft. A cylinder block provided in a casing and provided with a plurality of cylinders extending in an axial direction while being spaced apart in a circumferential direction, a plurality of pistons reciprocally inserted into each cylinder of the cylinder block, and the cylinder The present invention is applied to an axial piston type hydraulic rotary machine comprising a valve plate provided between a block and a casing and having a pair of supply / discharge ports intermittently communicating with the cylinders.

A feature of the structure adopted by the first aspect of the present invention is that the valve plate is disposed between the casing and the valve plate by pressure oil guided from a high pressure port side of the pair of supply / discharge ports. A valve plate rotating mechanism that rotates around a rotation axis is provided, and the valve plate rotating mechanism is configured to give a non-linear characteristic to a rotational displacement of the valve plate with respect to a pressure change of the pressure oil.

With such a configuration, the valve plate rotating mechanism can rotate the valve plate in accordance with a change in the pressure on the high pressure port side, and the rotation displacement of the valve plate changes with the pressure change on the high pressure port side. On the other hand, because of the non-linear displacement characteristics, the pressure of the oil liquid pre-compressed in the cylinder can be made substantially equal to the pressure on the high pressure port side.

According to the second aspect of the present invention, the valve plate turning mechanism is provided with a turning lever provided on the valve plate, and a turning angle of the valve plate provided between the turning lever and the casing. The spring constant increases as the pressure increases, and the pressure oil is provided between the rotating lever and the casing and the pressure oil is guided from the high-pressure port side, thereby opposing the biasing means. And a rotary actuator for rotating the valve plate.

Accordingly, when the pressure on the high pressure port side is low, the valve plate can be urged by the urging means in a direction in which the rotation angle becomes small, and the pressure of the oil liquid precompressed in the cylinder is set to a low pressure state. it can. When the pressure on the high pressure port side rises, the pressure is guided to the rotation actuator to operate the rotation actuator, and the valve plate can be rotated against the urging means, and the valve plate can be rotated. By extending the pre-compression section of the oil liquid, the pressure in the cylinder can be increased to a pressure level substantially matching the pressure on the high pressure port side.

According to the third aspect of the present invention, the biasing means comprises a plurality of springs disposed between the rotating lever and the casing. Thus, the biasing force of the spring can be changed stepwise according to the rotation angle of the valve plate, and a non-linear characteristic can be given to the rotation displacement of the valve plate.

Further, according to the invention of claim 4, the biasing means is constituted by a plurality of coil springs arranged in parallel with different free lengths. Thereby, a plurality of coil springs can be arranged coaxially in parallel with each other, and when the rotation angle of the valve plate is small, the biasing force can be applied to the rotation lever only by the coil spring having a long free length. When the rotation angle of the valve plate becomes large, the biasing force can be applied to the rotation lever by the coil spring having a long free length and the coil spring having a short free length.

[0019]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a hydraulic swash plate type hydraulic pump according to an embodiment of the present invention; FIG. Will be described.

In FIG. 1, reference numeral 1 denotes a casing of a variable displacement swash plate type hydraulic pump. The casing 1 is a casing body 2 formed into a bottomed tubular shape by a tubular portion 2A and a bottom portion 2B.
, A lid 3 covering the opening end side of the cylindrical portion 2A, and an actuator case 4 described later. The lid 3 is provided with a swash plate support member 14 described later.

Also, on the bottom 2B of the casing body 2,
A contact surface 2C for a valve plate 15 described later is provided, and a guide for restricting radial displacement of the valve plate 15 and rotatably guiding the valve plate 15 is provided on an outer peripheral side of the contact surface 2C. The portion 2D is formed in a ring shape, for example, as shown in FIG. Further, an opening 2 </ b> E communicating with the inside of the actuator case 4 is formed in the casing body 2, and the opening 2 </ b> E
A rotating lever 15E described later is inserted into E.

Reference numeral 4 denotes an actuator case attached to the casing body 2. The actuator case 4 is provided so as to protrude radially outward from the casing body 2 at a position between the cylindrical portion 2A and the bottom portion 2B. Which constitute a part of. And the actuator case 4
Is provided with a later-described valve plate rotating mechanism 17.

Reference numeral 5 denotes a rotating shaft rotatably provided on the casing 1 via bearings 6 and 7, and 8 denotes a cylinder block which is rotationally driven by the rotating shaft 5.
Is spline-coupled to the outer peripheral side of the rotating shaft 5 and rotates integrally with the rotating shaft 5 in the cylindrical portion 2A of the casing body 2. The cylinder block 8 has one end face opposed to a swash plate 13 described later, and the other end face slidably in contact with the surface of a valve plate 15 described later.

Reference numerals 9, 9,... Denote a plurality of cylinders drilled in the cylinder block 8. Each of the cylinders 9 is separated from the cylinder block 8 at a certain interval in the circumferential direction of the cylinder block 8 around the rotary shaft 5. 8 in the axial direction. The distal end side of each cylinder 9 is open at one end side end surface of the cylinder block 8, and the proximal end side has cylinder ports 9A, 9A, 9A, 9A,
... are formed.

Are a plurality of pistons slidably inserted into the cylinders 9. Each of the pistons 10
Slides (reciprocates) in the cylinder 9 with the rotation of the cylinder block 8, and at this time, a supply / discharge passage 16
While sucking the oil liquid into the cylinder 9 from the A side through the cylinder port 9A, the sucked oil liquid is discharged as a high-pressure oil to the later-described supply / discharge passage 16B side.

Each of the pistons 10 protruding from each of the cylinders 9 has a projecting end formed with a spherical portion 10A, and a shoe 11 is attached to each of the spherical portions 10A so as to be swingable. Each of these shoes 11 is supported by a shoe retainer 12 or the like so as to always maintain a contact state with the swash plate 13.

Reference numeral 13 denotes a swash plate provided on the side of the lid 3 and provided in the casing 1. The swash plate 13 is supported by a swash plate support member 14 on the side of the lid 3 so as to be tiltable. Shoe 11
Is a smooth surface 13A that makes sliding contact. The shoe 11 slides on the smooth surface 13A of the swash plate 13 in a circular orbit, and reciprocates the piston 10 along the sliding surface of the cylinder 9.

A pair of legs 13B (only one of which is shown) formed of a convex curved surface is formed on the back side of the swash plate 13, and the front side of the swash plate support member 14 corresponds to these legs 13B. A pair of concave curved portions 14A (only one is shown) are formed. The swash plate 13 is tilted and driven in the directions of arrows A and B in FIG. 1 by a tilt actuator (not shown) along the concave curved portion 14A of the swash plate support member 14.

Reference numeral 15 denotes a valve plate provided on the contact surface 2C of the casing body 2 so as to slide on the other end of the cylinder block 8. The valve plate 15 has an eyebrow shape as shown in FIG. A suction port 15A and a discharge port 15B are formed as a pair of supply / discharge ports. A pair of switching lands 15C and 15D are formed between the suction port 15A and the discharge port 15B of the valve plate 15 at positions radially opposite each other with the rotation shaft 5 as a center. And the valve plate 15
Is located on the bottom dead center (BDC) side of the piston 10 displaced in the cylinder 9, and the switching land 15D is located on the top dead center (TDC) of the piston 10. Is what it is.

Thus, when the cylinder block 8 is driven to rotate in the direction of arrow C in FIG. 2 in the casing 1, the cylinder port 9A of each cylinder 9 is connected to one of the switching lands 15a.
At the position C, the cylinder port 9A is disconnected from the suction port 15A and then communicates with the discharge port 15B. At the position of the other switching land 15D, each cylinder port 9A is communicated with the suction port 15A after the cylinder port 9A is cut off from the discharge port 15B. .

Each cylinder 9 has a cylinder port 9A.
The piston 10 slides from the top dead center position to the bottom dead center position while the piston 10 slides from the top dead center position to the tank (not shown) from the later-described supply / discharge passage 16A side while the is communicated with the suction port 15A. ) Is sucked into the cylinder 9.
While the cylinder port 9A is in communication with the discharge port 15B, the piston 10 is slidably displaced from the bottom dead center position to the top dead center position in the cylinder 9 so that the oil liquid is discharged in the cylinder 9. The high-pressure oil is discharged from an after-mentioned supply / discharge passage 16B toward an external hydraulic actuator while being pressurized.

Here, the valve plate 15 is disposed between the contact surface 2C of the casing main body 2 and the end surface of the cylinder block 8 in a state of being sandwiched therebetween. 2 are supported so as to be rotatable in the directions indicated by arrows D and E in FIG. The valve plate 15 is integrally provided with a turning lever 15E that protrudes outward in the radial direction.
Constitutes a part of a valve plate rotating mechanism 17 described later.

A pair of supply / discharge passages 16A and 16B are formed on the bottom 2B side of the casing body 2.
One of the supply and discharge passages 16A and 16B is connected to an external tank via a pipe (not shown), and the other supply and discharge passage 16B is for supplying high-pressure oil to the hydraulic actuator. It is connected to a hydraulic pipe (not shown).

Reference numeral 17 denotes a valve plate rotating mechanism provided in the actuator case 4. The valve plate rotating mechanism 17 is provided between the rotary lever 15 E of the valve plate 15 and the actuator case 4 as shown in FIG. And springs 18 and 19 as urging means for urging the rotary lever 15E in the direction of arrow D toward the push piston 22 described later, and a rotary actuator 20 described later. I have.

Here, the springs 18, 19 are composed of coil springs having different free lengths as shown in FIG.
These are arranged coaxially in parallel with each other. The spring 18 having a long free length is always in contact with the rotating lever 15E as shown in FIG.
In the direction. In this state, the rotating lever 15E is urged only by the spring 18 with a small spring constant (characteristic line portion 26A shown in FIG. 4).

The spring 19 having a short free length moves away from the rotation lever 15E when the displacement of the rotation lever 15E is small as shown in FIG. When the displacement a of the dynamic piston 22 becomes equal to or greater than the displacement a1 shown in FIG. 4), the spring 18 is urged together with the spring 18 in the direction indicated by the arrow D by contacting the pivot lever 15E. .
Then, in this state, the rotating lever 15E is
8 and 19 show a larger spring constant (characteristic line portion 26 in FIG. 4).
B) is activated.

Reference numeral 20 denotes a rotary actuator for driving the rotary lever 15E against the springs 18 and 19. The rotary actuator 20 includes a small-diameter cylinder hole 21 formed in the actuator case 4 and the cylinder hole 21. A push piston 22 slidably inserted into the piston 21 and opposed to the springs 18 and 19 with the rotation lever 15E interposed therebetween, and a hydraulic chamber defined between the push piston 22 and the cylinder hole 21. The pressure on the discharge port 15B side is always introduced into the hydraulic chamber 23 through an oil passage 24 described later.

Then, the pushing piston 22 is pushed in a direction protruding from the cylinder hole 21 by the pressure in the hydraulic chamber 23, and the pushing force pushes the rotating lever 15E against the springs 18, 19 in the direction of arrow E. Drive. When the pressure in the hydraulic chamber 23 decreases to the tank pressure level, the rotating lever 15E is pushed back by the spring 18, and the displacement a of the pushing piston 22 is substantially zero (a = 0).
Is reduced toward the inside of the cylinder hole 21.

At this time, the rotational displacement of the valve plate 15 becomes substantially zero, and the rotational angle θ shown in FIG. 2 also becomes zero (θ = 0). Put in the initial position.
Then, the rotary actuator 20 causes the pushing piston 22 to move into the cylinder hole 2 in response to the increase in the pressure in the hydraulic chamber 23.
1 and extend the rotation lever 15E to the spring 18,
That is, it is rotated and displaced in the direction opposite to the position 19.

Further, reference numeral 24 denotes an oil passage for guiding the pressure oil on the discharge port 15B side to the rotary actuator 20. One end of the oil passage 24 communicates with the discharge port 15B side, and the other end thereof is connected to the rotary actuator 20. The casing body 2 and the actuator case 4 are connected so as to communicate with the hydraulic chamber 23.
Are formed. The oil passage 24 is formed of a small-diameter oil passage, and supplies the pressure oil on the discharge port 15 </ b> B side into the hydraulic chamber 23 of the rotary actuator 20.

The variable displacement type swash plate type hydraulic pump according to the present embodiment has the above-described configuration. Next, the operation thereof will be described.

First, when the rotary shaft 5 is driven to rotate by a prime mover such as a diesel engine, the cylinder block 8 rotates integrally with the rotary shaft 5 in the casing 1.
The piston 10 repeats reciprocating motion in the cylinder 9, and a suction stroke and a discharge stroke are sequentially performed. And the piston 10
In the suction stroke, the oil liquid in the tank is sucked into the cylinder 9 from the supply / discharge passage 16A side, and in the discharge stroke, the oil liquid in the cylinder 9 is pressurized as high pressure oil, and this pressure oil is supplied to the supply / discharge passage 1
Discharge from the 6B side toward an external hydraulic actuator.

Here, as illustrated in FIG.
When the cylinder block 8 rotates in the direction indicated by the arrow C with respect to the valve plate 15, the piston 10 rotates halfway to the left of the Y-Y line, In the suction stroke, the inside of the cylinder 9 is slid from the top dead center to the bottom dead center. This results in a displacing discharge stroke.

When the cylinder port 9A passes through the switching land 15C of the valve plate 15, the oil liquid sucked into the cylinder 9 during the suction stroke of the piston 10 is discharged from the bottom dead center on the line YY to the discharge port. 15B (a range of the rotation angle θ), the cylinder 10 is pre-compressed by the piston 10, and each cylinder port 9A has a discharge port 15 with a pre-compression section of the rotation angle θ.
It will communicate with B.

When the cylinder 9 has a diameter d as shown in FIG. 3, the internal volume of the cylinder 9 when the piston 10 is at the top dead center position L0 is

[0046]

[Number 1] V0 = k × L0 × π × d 2/4 ( where, k is a constant) is set to the minimum volume V0 made.

Then, the piston 10 is moved to the bottom dead center position (L0
+ Ls) is the maximum volume V
If 1,

[0048]

[Number 2] is determined as V1 = V0 + (Ls × π × d 2/4) = (k × L0 + Ls) × π × d 2/4.

On the other hand, the tilt angle α of the swash plate 13 and the piston 10
Separation distance (diameter of piston pitch circle of cylinder block)
Dp, the maximum displacement Ls at which the piston 10 is displaced from top dead center to bottom dead center is:

[0050]

Ls = Dp × (tan α)

Assuming that the displacement amount Lx of the piston 10 in the pre-compression section of the rotation angle θ is this displacement amount L
x is obtained by changing the rotation angle θ within the range of 0 to 180 ° with respect to the maximum displacement Ls.

[0052]

## EQU4 ## The relationship Lx = Ls.times. (1-cos .theta.) / 2 is satisfied.

Therefore, the displacement Lx is calculated according to the equations (3) and (4).

[0054]

Lx = Dp × (tan α) × (1−cos θ) / 2

The volume change ΔVx when the piston 10 is displaced in the cylinder 9 by the displacement Lx is:

[0056]

[6] is a ^{ΔVx = Lx × π × d 2} /4.

Then, the oil liquid in the cylinder 9 is pre-compressed in the rotation angle θ,

[0058]

(Equation 7) (However, β is the compression rate of the oil liquid) Since the pressure is precompressed by the pressure value Px, the pressure value P
x is given by the formulas 2 and 5 to 7,

[0059]

(Equation 8) Becomes

The minimum volume V0 in the cylinder 9 is generally called a dead space. If V0 = 0, L0 = 0.

[0061]

(Equation 9) Thus, the oil liquid in the cylinder 9 is pre-compressed by the pressure value Px according to the equation (9) in the pre-compression section of the rotation angle θ.

On the other hand, the relationship between the rotation angle θ of the valve plate 15 and the displacement a of the pushing piston 22 is from the center of the rotating shaft 5 to the contact point of the pushing piston 22 with respect to the rotating lever 15E as shown in FIG. By the dimension Lp of

[0063]

Tan θ = (a / Lp)

[0064]

## EQU11 ## It is obtained as θ = arctan (a / Lp).

The relationship between the displacement a of the pushing piston 22 and the pressure value Px of the oil liquid pre-compressed in the cylinder 9 is expressed by the characteristic line 25 shown in FIG.
Is required.

Therefore, in the present embodiment, the pushing piston 22 and the valve piston rotating mechanism 17 for rotating and displacing the valve plate 15 with the rotation angle θ in response to the pressure change in the discharge port 15B are provided. Two springs 18 and 19 are coaxially arranged in parallel to face each other, and the spring 18 having a longer free length is used to rotate the spring 18 as shown in FIG.
5E, and always urges the rotating lever 15E toward the initial position in the direction of arrow D (the direction opposite to the pushing piston 22).

The spring 19 having a short free length located radially outside rotates when the displacement of the rotating lever 15E is small, that is, when the displacement a of the pushing piston 22 is smaller than the displacement a1 shown in FIG. When the push piston 22 is separated from the lever 15E and the displacement a of the pushing piston 22 becomes equal to or greater than the displacement a1 shown in FIG.
The rotary lever 15E is urged in the direction of arrow D together with the spring 18.

As a result, the valve plate rotating mechanism 17 rotates the valve plate 1.
4 can be displaced with a non-linear characteristic as indicated by a characteristic line 26 in FIG. 4, and in a state where the rotation angle θ of the valve plate 15 is small (a state in which the displacement a of the pushing piston 22 is less than the displacement a 1), FIG. As shown in the characteristic line portion 26A, the rotating lever 15E can be urged only by the spring 18 with a small spring constant. In a state where the rotation angle θ of the valve plate 15 is large (a state in which the displacement a of the pushing piston 22 is equal to or larger than the displacement a1), the rotation lever 15E is connected to the spring 18 and the characteristic line portion 26B shown in FIG. 19 can be urged with a large spring constant.

Thus, in the present embodiment, the valve plate rotating mechanism 17 that rotates the valve plate 15 in response to a change in the pressure in the discharge port 15B includes the two springs 18, 19 and the pushing piston 22. And a rotation angle θ substantially corresponding to the displacement a of the pushing piston 22.
The pressure value Px of the oil liquid pre-compressed in the cylinder 9 can be made substantially equal to the pressure on the discharge port 15B side by rotating and displacing the valve plate 15 with.

That is, the cylinder port 9A is connected to the switching land 1
The oil liquid pre-compressed in the cylinder 9 while passing through 5C, when there is a pressure difference at the moment when the cylinder port 9A communicates with the discharge port 15B, flows out into the discharge port 15B as a jet, for example, Conversely, the pressure oil in the discharge port 15B may flow back into the cylinder 9, which causes pressure pulsation, which causes vibration, noise, and the like.

However, in the present embodiment, the cylinder port 9A passes through the switching land 15C and the discharge port 15B
Can communicate with the pressure value Px of the oil liquid pre-compressed in the cylinder 9 substantially equal to the pressure on the discharge port 15B side, and the pressure difference between the two can be reliably reduced to reduce the occurrence of pulsation and the like. It can be suppressed well.

When the pressure (load pressure) on the discharge port 15B side is small, the urging force of only the spring 18 is applied to the rotating lever 15E in opposition to the pushing piston 22 to obtain the characteristic shown in FIG. Characteristic line part 26 of line 26
As shown in A, for example, the displacement a of the pushing piston 22 is made equal to or less than the displacement a1 shown in FIG. 4, whereby the pressure value Px of the oil liquid precompressed in the cylinder 9 can be suppressed to the pressure P1 or less.

Further, the pressure on the discharge port 15B side gradually increases, and the displacement a of the pushing piston 22 becomes the displacement a1 shown in FIG.
As described above, the urging forces of the springs 18 and 19 are applied to the rotating lever 15E together with the urging piston 22 so that the characteristic line 26B of the characteristic line 26 is obtained.
For example, the displacement a of the pushing piston 22 can be suppressed from gradually increasing, and the pressure value Px of the oil liquid precompressed in the cylinder 9 is set to be equal to or higher than the pressure P1, and the pressure is controlled so as to correspond to the pressure on the discharge port 15B side. can do.

Therefore, according to the present embodiment, the rotation of the valve plate 15 is controlled by controlling the rotation displacement of the valve plate 15 by using the valve plate rotation mechanism 17 having the two springs 18 and 19. Non-linear characteristics can be given to the dynamic displacement, the generation of pressure pulsation can be effectively reduced, and vibration, noise, and the like can be reliably suppressed.

By arranging the two springs 18 and 19 coaxially and in parallel, these springs 1
8 and 19 can be compactly arranged in the actuator case 4, and the actuator case 4 and the valve plate rotating mechanism 1
7 can be reduced in size.

In the above-described embodiment, the case where the rotational displacement of the valve plate 15 is controlled by using the valve plate rotating mechanism 17 having two springs 18 and 19 has been described as an example. The present invention is not limited to this. For example, as shown in a modification shown in FIG.
The relationship between the displacement a of the pushing piston 22 and the pressure value Px of the oil liquid pre-compressed in the cylinder 9 may be set along the characteristic lines 31A, 31B and 31C.

Further, the number of springs as urging means may be four or more. Further, it is not always necessary to provide the springs coaxially, and it is also possible to adopt a configuration in which springs having different spring constants are spaced apart from each other and arranged in parallel.

In the above-described embodiment, a variable displacement swash plate type hydraulic pump has been described as an example of the hydraulic rotary machine. However, the present invention is not limited to this, and for example, a variable displacement swash plate type hydraulic pump may be used. It may be applied to a hydraulic pump or the like, or may be applied to a fixed displacement hydraulic pump. The present invention is also applicable to a variable displacement or fixed displacement axial piston hydraulic motor.

[0079]

As described above in detail, according to the first aspect of the present invention, the valve is provided between the casing and the valve plate by the pressure oil guided from the high pressure port side of the pair of supply / discharge ports. A valve plate rotating mechanism for rotating the plate around the rotation axis is provided,
Since the valve plate rotating mechanism is configured to give a non-linear characteristic to the rotational displacement of the valve plate with respect to the pressure change of the pressure oil, the valve plate rotating mechanism causes the valve plate to change the pressure on the high pressure port side. Accordingly, the pressure of the oil liquid pre-compressed in the cylinder can be made substantially equal to the pressure of the high pressure port side, thereby effectively reducing the occurrence of pressure pulsation, Vibration, noise, and the like can be reliably suppressed.

According to the second aspect of the present invention, since the valve plate rotating mechanism is constituted by the rotating lever, the urging means and the rotating actuator, the pressure on the high pressure port side increases, and When increasing the rotation angle of the plate, the spring constant of the urging means can be increased to suppress the rotation displacement of the valve plate. The precompression section of the oil liquid in the cylinder can be changed in accordance with the rotation angle of the valve plate, and the pressure in the cylinder can be raised to a pressure level substantially matching the pressure on the high pressure port side.

According to the third aspect of the present invention, since the urging means is constituted by a plurality of springs disposed between the rotary lever and the casing, the urging force of the spring is reduced by the valve plate. Can be changed stepwise in accordance with the amount of rotational displacement of the valve plate, and a non-linear characteristic can be given to the rotational displacement of the valve plate. As a result, the pressure of the oil liquid pre-compressed in the cylinder is made substantially equal to the pressure on the high pressure port side, and the occurrence of pressure pulsation can be effectively reduced, and vibration, noise, and the like can be reliably suppressed.

Further, according to the invention described in claim 4,
The biasing means is constituted by a plurality of coil springs arranged in parallel with different free lengths,
A plurality of coil springs can be arranged coaxially in parallel with each other, and the plurality of coil springs can be arranged compactly.

[Brief description of the drawings]

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

FIG. 2 is an enlarged cross-sectional view of a rotary actuator and the like of a valve plate as viewed from the direction of arrows II-II in FIG.

FIG. 3 is a longitudinal sectional view for explaining a change in volume in a cylinder due to a sliding displacement of a piston.

FIG. 4 is a characteristic diagram showing a relationship between displacement of a pushing piston and a pressure value of an oil liquid pre-compressed in a cylinder.

FIG. 5 is a characteristic diagram showing a relationship between a displacement of a pushing piston and a pressure value of an oil liquid pre-compressed in a cylinder according to a modified example of the present invention.

[Explanation of symbols]

 Reference Signs List 1 casing 5 rotation shaft 8 cylinder block 9 cylinder 10 piston 11 shoe 13 swash plate 15 valve plate 15A suction port (supply / discharge port) 15B discharge port (supply / discharge port) 17 valve plate rotating mechanism 18, 19 spring (biasing means) 20 rotation actuator 21 cylinder hole of rotation actuator 22 pushing piston 23 hydraulic chamber 24 oil passage

 ──────────────────────────────────────────────────の Continued on the front page (72) Haruo Kokubu, Inventor Haruo 650, Kandamachi, Tsuchiura City, Ibaraki Prefecture Inside the Tsuchiura Plant of Hitachi Construction Machinery Co., Ltd. (72) Inventor Kazumasa Yuasa 650, Kandamachi, Tsuchiura City, Ibaraki Prefecture Hitachi Construction Machinery F-term in Tsuchiura Plant (reference) 3H045 AA04 AA10 AA13 AA16 AA24 AA32 BA38 CA03 DA15 DA16 DA25 DA41 3H070 AA01 BB04 BB06 CC03 DD47 DD96 3H084 AA06 AA16 BB01 BB02 CC40 CC42

Claims (4)

[Claims] 1. A casing, a rotating shaft rotatably provided in the casing, and a plurality of shafts provided in the casing so as to rotate integrally with the rotating shaft and extending in an axial direction while being spaced apart in a circumferential direction. Cylinder, a plurality of pistons reciprocally inserted into each cylinder of the cylinder block, and intermittently communicated with each of the cylinders provided between the cylinder block and the casing. An axial piston type hydraulic rotary machine including a valve plate having a pair of supply / discharge ports formed therein, wherein between the casing and the valve plate, the high pressure port side of the pair of supply / discharge ports is guided. A valve plate turning mechanism is provided for turning the valve plate around a rotation axis by pressure oil, and the valve plate turning mechanism has a non-linear characteristic in turning displacement of the valve plate with respect to a pressure change of the pressure oil. Axial piston type hydraulic rotary machine, characterized in that the obtaining configuration. 2. The valve plate turning mechanism according to claim 1, wherein the valve plate turning mechanism is provided between the turning lever and the casing and a turning angle of the valve plate increases. A biasing means for increasing a spring constant, and the valve plate is rotated against the biasing means by guiding hydraulic oil from the high pressure port provided between the rotating lever and the casing. 2. The axial piston type hydraulic rotary machine according to claim 1, further comprising a rotary actuator. 3. An axial piston type hydraulic rotary machine according to claim 2, wherein said urging means comprises a plurality of springs disposed between said rotary lever and said casing. 4. The axial piston type hydraulic rotary machine according to claim 2, wherein said urging means comprises a plurality of coil springs arranged in parallel with different free lengths.