JPH08159012A - Hydraulic pump/motor - Google Patents

Abstract

PURPOSE: To reduce noise and carry out downsizing by providing a communicating part for communicating a hollow part for accumulating high pressrue fluid and each cylinder with each other on a position near a confining part where a piston attains from a suction port to a bottom dead point. CONSTITUTION: When each piston 20 attains a bottom dead point and becomes in a confining condition, a high pressure fluid which is packed in a hollow part 13 is supplied from a communicating part 16 into a cylinder 12 corresponding to the piston 20, and pressure is applied on inner pressure of a cylinder 12. At this time, since a small hole 18 is provided in the vicinity of one piston 20 which precedes the other piston 20 in a confining condition, the small hole 18 is communicated with a notch, and thereby, the high pressure fluid is supplied from the notch of a discharging port 10 into the hollow part 13 through the small hole 18, and the high pressure fluid which is discharged for pressurization in the confining part is replenished. When the piston 20 is rotated, an intake/ exhaust passage 17 is communicated gradually, discharging pressure is increased smoothly following with pressurization effect. It is thus possible to prevent generation of reverse flow in the confining part.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a swash plate type or swash shaft type axial hydraulic pump / motor.

[0002]

2. Description of the Related Art Generally, an axial hydraulic pump / motor has a casing as a main body and a rotor rotatably provided in the casing and having a plurality of cylinders.
A rotary shaft that engages with the rotor, a piston slidably provided in the cylinder, and a valve plate that slidably faces the rotor are provided. By rotating the rotor in conjunction with each other, the piston reciprocates, whereby the low-pressure fluid sucked into the cylinder is pressurized and discharged by the piston.In the case of a hydraulic motor, high-pressure fluid is stored in the cylinder. The inflow causes the piston to reciprocate, thereby rotationally driving the rotor and the rotary shaft. It has been conventionally known that, in such a hydraulic pump / motor, suppressing the fluctuation of the discharge pressure is effective in reducing noise, and an example thereof is disclosed in Japanese Utility Model Laid-Open No. 14475/1990. . The noise reduction means described in the publication has an opening on a sliding surface from a suction port to a discharge port of a valve plate, and a pressure accumulator is connected to the opening through a passage so that a piston is connected to the suction port. At the closing part reaching the bottom dead center, the high pressure fluid discharged from the opening gives a pre-pressure in the cylinder and the discharged pressure is charged from the pressure accumulator. Since the backflow in the closed portion is prevented by the amount of the increase, it is possible to suppress the fluctuation of the discharge pressure.

[0003]

However, in the conventional example configured as described above, the volume of the high pressure fluid supplied into the cylinder is determined by the size of the opening. It is practically difficult to form a large opening on the sliding surface of the valve plate from the suction port to the discharge port due to the space constraints, and therefore the volume of the high pressure fluid supplied to the cylinder decreases and the preload However, there is a problem that the noise reduction effect is low. In particular, in the state of the maximum tilt angle where the discharge pressure fluctuates greatly, or in the hydraulic pump / motor operated at a constant tilt angle, the noise becomes remarkable when the preload is insufficient. Further, although a pressure accumulator is connected to the opening to maintain pressure discharge and charge, there is a problem that the structure is complicated by the pressure accumulator and the passage, and miniaturization is hindered.

The present invention has been made in view of the above-mentioned circumstances of the prior art, and an object thereof is to provide a low-noise hydraulic pump / motor having a high noise reduction effect and suitable for downsizing. .

[0005]

SUMMARY OF THE INVENTION The above-mentioned object of the present invention includes a casing, a rotor rotatably provided in the casing and having a plurality of cylinders, and a rotating shaft engaging with the rotor. In a hydraulic pump / motor comprising a piston slidably provided in the cylinder and a valve plate slidably opposed to the rotor, a cavity for accumulating high-pressure fluid is provided inside the rotor. A plurality of small holes communicating with the hollow portion are provided on a sliding surface of the rotor with the valve plate, and notches for intermittently communicating the small holes with the discharge port are provided in the valve plate, and the piston is a suction port. This is achieved by providing a communication portion that communicates the hollow portion and each of the cylinders at a position near the closed portion that reaches from the bottom dead center to the bottom dead center.

[0006]

When the piston reaches the bottom dead center and enters the closed state, the high-pressure fluid in the cavity provided inside the rotor is supplied from the communicating portion into the cylinder, and a preload is applied to the internal pressure of the cylinder. . At that time, in the portion preceding the piston in the closed state, the small hole provided in the rotor communicates with the notch of the discharge port, so that high-pressure fluid is supplied from the notch to the cavity through the small hole, and the closed portion is closed. The high-pressure fluid released for precompression is replenished at the inlet.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. 1 is a sectional view of a swash plate type hydraulic pump according to an embodiment of the present invention, FIG. 2 is a sectional view of a rotor included in the hydraulic pump, and FIG. 3 is a plan view of a valve plate included in the hydraulic pump. In these drawings, reference numeral 1 denotes a main case, 2 denotes a sub plate fixed to the lower surface of the main case 1, and the main case 1 and the sub plate 2 form a casing that forms a main body. 3 are bearings 4, 5 in the casing
The rotary shaft 6 is supported by the valve plate 6, and the valve plate 6 is fixed on the sub-plate 2. The valve plate 6 communicates with the suction port 9 and the discharge passage 8 which communicate with the suction passage 7 provided in the sub-plate 2. The discharge port 10 is bored. As shown in FIG. 3, a suction port 9 and a discharge port 10 of the valve plate 6 are shown.
Notches 9a and 10a are formed at one end of the discharge port 10, respectively, and a plurality of notches 10b are formed at the outer peripheral edge of the discharge port 10 at predetermined intervals.

Reference numeral 11 is a cylinder block made of a metal material such as steel or aluminum, and 12 is the cylinder block 11.
A plurality of cylinders formed inside the cylinder, 13 a cavity formed around each cylinder 12, 14 a sliding member fixed to the lower end of the cylinder block 11, and the cylinder block 11 and the sliding member 14 And constitute the rotor 15. A communication part 16 is provided on the wall surface of each cylinder 12.
Is formed, and the inside of each cylinder 12 is communicated with the hollow portion 13 by this communicating portion 16. Further, the sliding member 14 is provided with a continuous suction / discharge passage 17 inside each cylinder 12, and the connecting portion between the cylinder block 11 and the sliding member 14 including each cylinder 12 is sealed. . Further, the sliding member 14 is provided with a plurality of small holes 18 communicating with the hollow portion 13, and as shown in FIG. 2, one end of each of the small holes 18 is located between the cylinders 12. . On the other hand, as shown in FIG. 3, the other end of each small hole 18 faces the valve plate 6 and slides on each of the notches 10b described above. Therefore, the rotor 1
When 5 slides on the valve plate 6 while rotating, each small hole 1
8 communicates intermittently with the cutouts 10b, so that the high-pressure fluid is allowed to flow from the discharge port 10 through the small holes 18 into the cavity 13
Is supplied to.

The rotor 15 is connected to the rotary shaft 3 via a spline, and is pressed against the valve plate 6 by receiving a preload from a spring 19 wound around the rotary shaft 3.
Reference numeral 20 denotes a piston arranged in each cylinder 12 so as to be capable of reciprocating, and a spherical tip end of each piston 20 is engaged with a piston shoe 21 so as to be swingable. Reference numeral 22 is a shoe retainer that holds the piston shoe 21, and the shoe retainer 22 is a spherical seat 2 of the rotating shaft.
Guided by 3. Reference numeral 24 denotes a swash plate, and the piston shoe 21 rotates and slides on the swash plate 24.

Next, the operation of the hydraulic pump thus constructed will be described. FIG. 1 shows a state in which the tilt angle of the swash plate 24 is maximum. When the rotating shaft 3 is rotated in this state, the rotational force is transmitted to the cylinder block 11 via the spline, and the rotor 15 as a whole rotates. It rotates in conjunction with shaft 3. The rotation of the rotor 15 causes the piston shoe 21 that engages with the tip end portion of the piston 20 to rotationally slide on the swash plate 24, and the swash plate 24 is provided so as to be inclined with respect to the axis of the rotating shaft 3. , Each piston 20 reciprocates in the cylinder 12 while the rotor 15 is rotating. Also, the rotor 1
When 5 rotates, the intake / exhaust passage 17 of the sliding member 14 intermittently communicates with the intake port 9 and the discharge port 10 of the valve plate 6, and in the suction process in which the piston 20 extends from the cylinder 12,
In the discharge process in which the intake / exhaust passage 17 communicates with the intake port 9 to suck the low-pressure fluid into the cylinder 12, and the piston 20 enters the cylinder 12, the intake / exhaust passage 17 communicates with the discharge port 10 and pressurizes with the piston 20. The discharged high pressure fluid is discharged.

FIG. 4 is an explanatory view showing the positional relationship between the pistons 20 and the cylinders 12 at this time.
(D) is a suction process, (e) is bottom dead center, (f) to (i)
Indicates the discharging step. As shown in the figure, the communication portion 16 formed on the wall surface of each cylinder 12 has a piston 20
Is closed in the suction process of (a) to (d),
When the piston 20 reaches the bottom dead center of (e) and is in the closed state, the piston 20 is opened in the section Δ, and the piston 20 (f)-
It is closed in the discharge step (i). Therefore, when the piston 20 reaches the bottom dead center and enters the closed state, the high-pressure fluid filled in the cavity 13 is released from the communicating portion 16 opened in the very limited section Δ to the cylinder 12 corresponding to the piston 20. Is supplied into the cylinder 12, and a preload is applied to the internal pressure of the cylinder 12. At that time, as shown in FIG. 3, another piston 2 preceding the piston 20 in the closed state
Since small holes 18 are also provided in the vicinity of 0, the small holes 18 communicate with the cutouts 10b, whereby high-pressure fluid is supplied from the cutouts 10b of the discharge port 10 to the hollow portion 13 through the small holes 18, The high pressure fluid released for precompression is replenished at the closure. And the piston 20
3 rotates in the direction of the arrow in FIG.
0a, the discharge pressure smoothly rises in combination with the above-mentioned preload effect, and backflow at the closed portion is prevented.

According to the above-described embodiment, since the cavity portion 13 provided in the rotor 15 having a spatial allowance is used as the preload applying means for increasing the cylinder internal pressure in the closed portion, the maximum tilt angle is obtained. Even in a hydraulic pump / motor that operates in a state or at a constant tilt angle, the capacity of the high pressure fluid for preload supplied to the cylinder 12 increases, and the noise reduction effect can be enhanced. Further, since such a preloading action is performed at the closed portion, the high pressure fluid required for this preloading is charged at another place, that is, by utilizing the notch 10b provided in the discharge port 10 of the valve plate 6. Since the preload effect can be further enhanced and the pressure accumulator and its passage can be omitted, the size can be reduced. Furthermore, since it is not necessary to provide an opening on the sliding surface of the valve plate 6 from the suction port 9 to the discharge port 10 unlike the conventional example, the degree of freedom in forming the notch 10a on the sliding surface is improved. Can also increase the preload effect.

In the above embodiment, the sliding member 14 is attached to the cylinder block 11 having the cylinder 12 and the cavity 13.
The case where the rotors are joined to form the rotor 15 has been described.
The rotor may be manufactured by carving out the cylinder 12, the cavity 13 and the like from one metal block, or the portion corresponding to the cylinder may be composed of a plurality of pipes.

[0014]

As described above, according to the present invention,
A cavity for accumulating high-pressure fluid is provided inside the rotor, and the cavity is communicated with the inside of each cylinder at a position near the closing part where the piston reaches the bottom dead center. In addition, the high pressure fluid can be discharged and charged into the cavity in the casing without using a pressure accumulator, and thus the noise reduction effect is high and the low noise suitable for downsizing is achieved. It is possible to provide the hydraulic pump / motor of

[Brief description of drawings]

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

FIG. 2 is a cross-sectional view of a rotor included in the hydraulic pump of FIG.

FIG. 3 is a plan view of a valve plate included in the hydraulic pump of FIG.

FIG. 4 is an explanatory diagram showing a positional relationship between each piston and a cylinder provided in the hydraulic pump of FIG.

[Explanation of symbols]

 1 Main Case 2 Sub Plate 3 Rotating Shaft 6 Valve Plate 9 Intake Port 10 Exhaust Port 9a, 10a Notch 10b Notch 11 Cylinder Block 12 Cylinder 13 Cavity 14 Sliding Member 15 Rotor 16 Communicating Part 17 Intake / Exhaust Channel 18 Small Hole 20 Piston

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kenichi Hirano, 2424, Kamishodo, Ayase-shi, Kanagawa Yuken Industry Co., Ltd. Sagami Plant

Claims (2)

[Claims] 1. A casing, and a rotor rotatably provided in the casing and having a plurality of cylinders,
A hydraulic pump / motor comprising: a rotary shaft that engages with the rotor; a piston that is slidably provided in the cylinder; and a valve plate that slidably faces the rotor. A cavity for accumulating high-pressure fluid is provided, a plurality of small holes communicating with the cavity are provided on a sliding surface of the rotor with the valve plate, and the valve plate intermittently communicates the small hole with a discharge port. A hydraulic pump-motor, characterized in that a notch is provided, and a communicating portion that communicates the hollow portion and each of the cylinders is provided at a position near a closing portion where the piston reaches a bottom dead center from an intake port. 2. The hydraulic pump / motor according to claim 1, wherein a plurality of the notches are provided.