JPH10122129A - Axial piston type hydraulic pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain pulsation, and effectively prevent vibration and a noise by setting a length of a notch groove extending in the circumferential direction toward the directional control valve part side from the starting end of a delivery port arranged in a valve plate, to a length corresponding to an angle formed by the notch groove to the center of a rotary shaft. SOLUTION: A length L1 of a notch 19 corresponds to an angle θ1 (θ1=π/N) when the number of pistons is denoted by N and the ratio of the circumference of a circle to its diameter is denoted by π, to the center of a rotary shaft 6. When cylinders reach the starting end side of a delivery port 17, the pistons reduce, and since pressure oil in the cylinders flows out toward the delivery port 17 side, a flow rate of the pressure oil delivered from a delivery port 17 increases. Here, when the length L1 of the notch 19 is set to an angle θ1 corresponding to an angle of about a half of an angle θ2 between respective cylinder ports 9A, in a half of time necessary every time when the respective cylinder ports 9A communicate with the delivery port 17, the respective cylinders and the delivery port 17 can communicate with each other through the notch 19.

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 pump used as, for example, a swash plate type pump, an oblique type pump and the like.

[0002]

2. Description of the Related Art In general, a hydraulic cylinder for working equipment such as a hydraulic shovel and a hydraulic pump for supplying hydraulic oil to a hydraulic motor for turning and traveling are provided with a casing and a rotary pump rotatably provided in the casing. A shaft, provided to rotate integrally with the rotating shaft located in the casing,
A cylinder block in which a plurality of cylinders extending in the axial direction and separated in the circumferential direction is formed, and the cylinder block is slidably inserted into each cylinder of the cylinder block. Move to inhale hydraulic oil,
2. Description of the Related Art An axial piston hydraulic pump including a plurality of pistons to be discharged and a valve plate provided between the casing and an end surface of a cylinder block and formed with a suction port and a discharge port communicating with each of the cylinders is widely known. Have been.

In this type of conventional hydraulic pump, when the rotary shaft is driven to rotate by a drive source such as an engine, the cylinder block rotates together with the rotary shaft in the casing. As a result, the piston is reciprocated in each cylinder of the cylinder block, and the operating oil sucked into the cylinder from the suction port is pressurized by the piston and discharged as pressure oil to the discharge port.

The operation of the cylinder block, the piston, and the valve plate will now be described. When the cylinder port of each cylinder communicates with the suction port of the valve plate, the direction in which the piston projects from the cylinder from the beginning to the end of the suction port. And a suction stroke for sucking hydraulic oil into the cylinder from the suction port. On the other hand, when the cylinder port of each of the cylinders communicates with the discharge port, a discharge stroke in which the piston moves in a direction in which the piston enters the cylinder from the start end to the end of the discharge port to discharge the hydraulic oil in the cylinder into the discharge port. Become. Then, by rotating the cylinder block to repeat this operation (stroke), the hydraulic oil sucked into the cylinder from the suction port in the suction stroke is pressurized in the discharge stroke and discharged to the discharge port, and this pressure oil is They are supplied to cylinders and hydraulic motors.

As another prior art, for example, in a hydraulic pump described in Japanese Utility Model Application Laid-Open No. 4-95767, a notch groove is provided at the starting end of a suction port or a discharge port, and a cylinder port is connected to the suction port or the discharge port. The configuration is such that sudden pressure fluctuations of the pressure oil generated at the time of communication are alleviated.

Further, as another prior art, for example, in a hydraulic pump described in Japanese Utility Model Laid-Open No. 6-18465, a side branch as a pulsation absorber is provided by branching into a discharge pipe connected to a discharge port. The pulsation of the pressure oil in the discharge pipe is reduced.

[0007]

By the way, in the above-mentioned axial piston type hydraulic pump according to the prior art, the pressure in the cylinder which sucks the hydraulic oil through the suction port of the valve plate during the suction stroke is reduced to the pressure in the discharge port. The pressure becomes lower than that. When the cylinder port of each cylinder starts to communicate with the discharge port, high-pressure oil in the discharge port rapidly flows (backflow) into the low-pressure cylinder through the cylinder port, causing a large pressure fluctuation. Due to this pressure fluctuation, pulsation occurs in the discharge flow rate of the pressure oil discharged from the discharge port, and the pulsation of the pressure oil is transmitted to other structures through a discharge pipe or the like connected to the discharge port, generating noise and vibration. There is a problem.

Therefore, as a countermeasure for preventing the generation of pulsation, in the above-mentioned other prior art, a notch groove is provided at the start end side of the suction port and the discharge port, and the cylinder port is connected to the suction port through the notch groove. And a discharge port. However, in this case, although the pressure fluctuation in the discharge port can be reduced, the pulsation of the pressure oil cannot be prevented, and there is a problem that vibration and noise from the discharge pipe or the like cannot always be sufficiently reduced.

In another conventional technique, in which a pulsation absorber such as a side branch is provided branching from a discharge pipe, pulsation generally has a plurality of frequency components.
Since the pulsation that can be reduced by the pulsation absorber is limited to a part of the frequency components, there is a problem that the pulsation including the frequency components that cannot be reduced causes vibration and noise.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and has as its object to provide an axial piston type hydraulic pump capable of suppressing pulsation and effectively preventing vibration, noise, and the like. .

[0011]

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 the casing so as to rotate integrally with the rotating shaft. A cylinder block provided with a plurality of cylinders formed therein, and a plurality of pistons reciprocating in the respective cylinders with the rotation of the cylinder block being slidably inserted into the respective cylinders of the cylinder block. An axial piston type hydraulic comprising a valve plate provided between the casing and the cylinder block and having a pair of switching valve portions formed between a suction port and a discharge port so as to face each other with the rotary shaft interposed therebetween. Applies to pumps.

A feature of the structure adopted by the invention of claim 1 is that the valve plate is provided with a cutout groove extending in a circumferential direction from the start end of the discharge port toward the switching valve portion with a length L1. Assuming that the angle formed by the notch groove with respect to the axis of the rotating shaft is substantially π / N, the length L1 of the notch groove is set to a length corresponding to this angle π / N.

With this configuration, the cylinder which has reached the switching valve after completing the suction stroke is filled with low-pressure hydraulic oil. Then, when this cylinder communicates with the discharge port, high-pressure hydraulic oil flows (backflow) toward the cylinder. However, at this time, since the cylinder communicates with the discharge port through the cutout groove over a length L1 corresponding to the angle π / N, the pressure oil in the discharge port gradually flows into the cylinder, Abrupt pressure fluctuation can be prevented.

In the invention described in claim 2, the valve plate is provided with a notched groove extending in the circumferential direction from the start end of the discharge port toward the switching valve portion with a length L2, and the shaft of the rotary shaft is provided. The angle formed by the notch groove with respect to the center is approximately 2π /
Assuming 3N, the length L2 of the notch groove is equal to this angle 2π /
That is, the length is set to correspond to 3N.

With this configuration, the cylinder that has reached the switching valve after completing the suction stroke is filled with low-pressure hydraulic oil. Then, when this cylinder communicates with the discharge port, high-pressure hydraulic oil flows (backflow) toward the cylinder. However, at this time, the cylinder has an angle of 2π / 3.
By communicating with the discharge port through the notch groove over the length L2 corresponding to N, the pressure oil in the discharge port gradually flows into the cylinder and prevents sudden pressure fluctuations in the cylinder. it can.

Further, according to the third aspect of the present invention, a discharge pipe for discharging pressure oil from the discharge port is connected to the discharge port, and a pulsation absorber for reducing pulsation of the pressure oil is connected to the discharge pipe. Is provided.

With such a configuration, the pressure fluctuation of the pressure oil can be reduced by the cutout groove, and the pulsation of the pressure oil can be absorbed by the pulsation absorber, so that the pulsation of the pressure oil can be reduced efficiently.

In the invention described in claim 4, a discharge pipe for discharging pressure oil from the discharge port is connected to the discharge port, and a pulsation absorber for reducing pulsation of the pressure oil is connected to the discharge pipe. This pulsation absorber is constituted by a cylinder whose one end is closed, and the length S1 of this cylinder is approximately equal to the sound velocity V in pressurized oil, the number of revolutions M of the rotating shaft, and the number N of pistons. It is set to an odd multiple of 15 V / (M × N).

With this configuration, the pulsation of the pressure oil that has reached the cylinder from the discharge pipe is reflected at the closed end through the cylinder and returns to the discharge pipe again. At this time,
The pulsation of the pressure oil in the discharge pipe is reduced by interfering with the pulsation reflected in the cylinder, and pressure oil with less pulsation can be supplied from the discharge pipe.

Further, in the invention according to claim 5, a discharge pipe for discharging pressure oil from the discharge port is connected to the discharge port, and a pulsation absorber for reducing pulsation of the pressure oil is connected to the discharge pipe. The pulsation absorber is constituted by a cylinder having one end closed, and the length S2 of the cylinder is substantially longer than the sound velocity V in pressurized oil, the number of rotations M of the rotating shaft, and the number N of pistons. It is set to an odd multiple of 10 V / (M × N).

With this configuration, the pulsation of the pressure oil that has reached the cylinder from the discharge pipe is reflected at the closed end through the cylinder and returns to the discharge pipe again. At this time,
The pulsation of the pressure oil in the discharge pipe is reduced by interfering with the pulsation reflected in the cylinder, and pressure oil with less pulsation can be supplied from the discharge pipe.

[0022]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

FIGS. 1 to 7 show a first embodiment of the present invention. In the figure, reference numeral 1 denotes an axial piston type hydraulic pump driven by a drive source (not shown) such as an engine. The hydraulic pump 1 is constituted by a variable displacement swash plate type hydraulic pump. The hydraulic pump 1 discharges high-pressure oil while sucking hydraulic oil from a tank 20 described later.

Reference numeral 2 denotes a casing which forms an outer shell of the hydraulic pump 1, and the casing 2 comprises a cylindrical casing body 3;
The front casing 4 includes a front casing 4 that closes an opening at one end of the casing main body 3 and a rear casing 5 that closes an opening at the other end of the casing main body 3. In the front casing 4, an insertion hole 4A through which a rotating shaft 6 described later is inserted is formed in the axial direction.

Reference numeral 6 denotes a rotary shaft rotatably supported by the casing 2 via a bearing 7. The rotary shaft 6 projects outside through, for example, an insertion hole 4A of the front casing 4, and is driven by a drive source (such as an engine) shown in FIG. (Not shown).

Reference numeral 8 denotes a cylinder block which is provided in the casing 2 and is provided so as to rotate integrally with the rotary shaft 6 by spline connection. The cylinder block 8 has a plurality of cylinders (in this example, spaced apart in the circumferential direction). 9) are bored in the axial direction, and each cylinder 9
A cylinder port 9A is formed on the sliding surface 8A side of the cylinder block 8 and opens in an oval shape.

Here, the cylinder block 8 has a sliding surface 8A.
Slides in the direction of arrow A shown in FIG. 3 with respect to a valve plate 15 to be described later, and at this time, each of the cylinder ports 9A sequentially communicates with and shuts off a suction port 16 and a discharge port 17 to be described later.

Reference numerals 10, 10,... Denote a plurality of pistons slidably inserted in the respective cylinders 9.
Reciprocates in each cylinder 9 as the cylinder block 8 rotates, and repeats a suction stroke and a discharge stroke in each cylinder 9. Further, a spherical portion 10A is formed at the tip end of each piston 10 protruding from the cylinder block 8.

Are a plurality of shoes provided on the outer peripheral side of the spherical portion 10A of each piston 10, respectively.
Each shoe 11 is swingably mounted on the spherical portion 10A, and slides on a swash plate 12, which will be described later, as the cylinder block 8 rotates.

Reference numeral 12 denotes a swash plate provided between the front casing 4 and the cylinder block 8, and a front surface side (cylinder block 8 side) of the swash plate 12 is a sliding surface 12A on which each shoe 11 rotates while sliding. The rear side is a semi-cylindrical tilting sliding portion 12B which is slidably fitted in a concave curved guide groove 13 formed in the front casing 4.

Further, the swash plate 12 has an insertion hole 12C which is formed in the center portion and has a diameter increased from the front side to the rear side, and is formed on a side surface of the tilting sliding portion 12B, A tilting mechanism insertion hole 12D into which a part of the rotation driving mechanism is inserted is formed. When the tilt angle of the swash plate 12 is changed by the tilt drive mechanism, the stroke amount of each piston 10 is appropriately adjusted to change the displacement (discharge amount) of the hydraulic pump.
Is variably controlled.

Reference numeral 14 denotes an annular shoe retainer fixed to the sliding surface 12A of the swash plate 12 while engaging with the outer peripheral side of each shoe 11, and the shoe retainer 14 is a sliding surface 12A of the swash plate 12.
The above allows each shoe to perform a circular motion, and compensates for each piston 10 reciprocating in each cylinder 9 as the cylinder block 8 rotates.

Reference numeral 15 denotes a valve plate fixed to the rear casing 5 of the casing 2 and having one side surface serving as a sliding surface 15A.
The valve plate 15 has an eyebrow-shaped suction port 16 and a discharge port 1.
7 extend in the circumferential direction so as to be substantially symmetrical.

A switching valve portion 15B is provided between the suction port 16 and the discharge port 17 of the valve plate 15 at the top dead center side where each piston 10 switches from the discharge stroke to the suction stroke. A switching valve portion 15C on the other side is provided at the bottom dead center side where the switching valve portion 15B on one side is opposed to the rotary shaft 6 with the piston 10 switching from the suction stroke to the discharge stroke. When the cylinders 9 sliding on the valve plate 15 reach the switching valve portion 15B on one side, the communication with the discharge port 17 is cut off, and the cylinders 9 slide on the switching valve portion 15C on the other side. The communication with the suction port 16 is cut off.

In the suction stroke in which the piston 10 strokes from the top dead center position to the bottom dead center position, each cylinder port 9A communicates with the suction port 16,
Hydraulic oil is sucked into the cylinder 9 via. On the other hand, in the discharge stroke in which the piston 10 strokes from the bottom dead center position to the top dead center position, each cylinder port 9 </ b> A communicates with the discharge port 17, and discharges the hydraulic oil in the cylinder 9 via the discharge port 17.

Reference numeral 18 denotes a notch extending in the circumferential direction from the suction port 16 to the switching valve portion 15B on one side.
Numeral 8 is formed in a substantially triangular shape so that the cylinder port 9A of each cylinder 9 and the suction port 16 gradually communicate with each other. The notch 18 alleviates the rapid flow of high-pressure oil from each cylinder 9 after the discharge stroke toward the suction port 16.

Reference numeral 19 denotes a notch as a notch groove extending with a length L1 from the discharge port 17 toward the switching valve portion 15C on the other side. The notch 19 gradually connects the cylinder port 9A of each cylinder 9 and the discharge port 17 to each other. It is formed in a substantially triangular shape so as to communicate with. And the discharge port 1
The notch 19 at 7 alleviates the rapid flow of high-pressure oil from the discharge port 17 into each cylinder 9 after the suction stroke.

Here, the notch 19 is substantially at an angle θ 1 (θ 1 = π / N) when the number N of the pistons 10 (9 in this example) and the π are set with respect to the center of the rotation shaft 6. It is formed over. The length L1 of the notch 19 is the angle θ
Corresponding to 1,

[0039]

## EQU1 ## The length is set so that L1∝θ1. The angle .theta.1 formed by the notch 19 is set to be approximately half the angle .theta.2 (.theta.1 = .theta.2 / 2) formed by the starting ends of the adjacent cylinder ports 9A.

Reference numeral 20 denotes an oil tank which communicates with the suction port 16, and this tank 20 contains hydraulic oil. In the tank 20, each cylinder port 9A of the hydraulic pump 1 communicates with the suction port 16 so that hydraulic oil is sucked into the cylinder 9 during the suction stroke through the suction port 16 and discharged from the actuator 23 and the like described later. Return oil (hydraulic oil) is collected.

Reference numeral 21 denotes a discharge pipe as a discharge pipe having one end connected to the discharge port 17. The discharge pipe 21 has the other end connected to an actuator 23 such as a hydraulic cylinder via a control valve 22. The pressure oil discharged from the pump is circulated toward the actuator 23 side.

Numeral 24 designates a side branch as a cylindrical body branched from one end of the discharge pipe 21. The side branch 24 is formed as a bottomed cylindrical body having a length S1, and the inside thereof is a resonance chamber. And communicates with the discharge port 17 to operate as a pulsation absorber.

Here, the pulsation frequency F of the pressure oil that can be absorbed by the side branch 24 is the sound velocity V (m / m
s) and the length S1 of the side branch 24, the pulsation frequency F, the sound velocity V in the oil, the side branch 24
Between the natural number n and the length S1

[0044]

(Equation 2) Have a relationship

[0045]

(Equation 3) Is established. Further, since the pulsation of the pressure oil caused by the operation of the hydraulic pump 1 is generated each time each of the cylinder ports 9A communicates with the discharge port 17, the basic frequency F0 of the pulsation of the pressure oil is determined by the rotation speed M of the hydraulic pump 1 ( rpm),
For the number N of pistons 10,

[0046]

(Equation 4) There is a relationship. For this reason, the length S of the side branch 24
1 is when n = 1,

[0047]

(Equation 5) Is set to

The hydraulic pump according to this embodiment has the above-described configuration. First, when the rotating shaft 6 is rotated by the motor, the cylinder block 8 spline-coupled to the rotating shaft 6 is integrally rotated. As a result, the piston 10 inserted into each cylinder 9 rotates together with the cylinder block 8, and the spherical portion 10A is guided by the shoe retainer 14 via the shoe 11 while the sliding surface 1 of the swash plate 12 is
Rotate on 2A. At this time, since the sliding surface 12A of the swash plate 12 has a predetermined tilt angle, while the cylinder block 8 makes one rotation, the top dead center of the piston 10 that has entered (reduced) the most in the cylinder 9 is obtained. The stroke is made between the position and the bottom dead center position most extended from the cylinder 9.

Here, during the half rotation in which each piston 10 strokes from the top dead center position to the bottom dead center position, while the cylinder port 9A communicates with the suction port 16, the suction passage (via the suction port 16) is provided. (Not shown), the suction stroke of sucking the oil liquid into the cylinder 9 is performed. On the other hand, during the half rotation of the piston 10 from the bottom dead center position to the top dead center position, while the cylinder port 9A communicates with the discharge port 17, the discharge port 17 is compressed while the oil liquid sucked into the cylinder 9 is compressed. This is a discharge process of discharging from a discharge passage (not shown) through the discharge passage. As described above, by rotating the rotating shaft 6 to reciprocate the piston 10 in the cylinder 9, the suction stroke and the discharge stroke are repeated, and the pumping action is performed.

To variably control the discharge capacity of the pump, the displacement capacity in the cylinder 9 is changed by appropriately tilting the swash plate 12 along the guide groove 13 by the tilt drive mechanism. It is supposed to.

Next, the operation of the notch 19 on the discharge port 17 side and the operation of the side branch 24 will be described in detail with reference to FIGS.

First, each cylinder 9 is connected to the cylinder block 8.
At the same time, the cylinder 9 rotates in the direction indicated by the arrow A, and the cylinder port 9A of the cylinder 9 which has completed the suction stroke is blocked from the suction port 16 and reaches the switching valve portion 15C on the other side. At this time, the pressure in the cylinder 9 on the switching valve portion 15C is
It becomes a low pressure almost equal to the internal pressure.

Next, when the cylinder 9 communicates with the discharge port 17 through the notch 19, the high-pressure hydraulic oil in the discharge port 17 flows into the cylinder 9 through the notch 19 and the like (backflow). Then, the flow rate of the pressure oil discharged from the discharge port 17 decreases.

On the other hand, when the cylinder block 8 further rotates and the cylinder 9 reaches the start end of the discharge port 17, the pressure in the cylinder 9 substantially matches the pressure in the discharge port 17. Then, the piston 10 in the cylinder 9 contracts, and the pressure oil in the cylinder 9 flows out toward the discharge port 17 side, so that the flow rate of the pressure oil discharged from the discharge port 17 increases.

Here, the length L1 of the notch 19 is such that the angle θ1 formed by the notch 19 is the angle θ between the cylinder ports 9A.
2, half of the time required for each cylinder port 9 </ b> A to communicate with the discharge port 17 is connected to each cylinder 9 and the discharge port 17 via the notch 19. Communicate.

Therefore, the pressure oil discharged from the discharge port 17 has a period T1 as shown by a characteristic line 25 in FIG.
(T1 = 1 / F0) pulsation occurs, and each cylinder port 9
A communicates with the discharge port 17 every time period T1.
Also, half the time T2 (T2 = T1 //) of the period T1.
In 2), since each cylinder 9 communicates with the discharge port 17 via the notch 19, the flow rate of the pressure oil decreases. on the other hand,
At other times (T1 -T2), the pressure oil is supplied from each cylinder 9 to the discharge port 17, so that the flow rate of the pressure oil increases.

Since the amount of pressure oil flowing from the discharge port 17 into each cylinder 9 increases and decreases in proportion to the flow path cross-sectional area of the notch 19, each cylinder 9 and the suction port 1
6. The pulsation waveform can be adjusted by arbitrarily adjusting the shapes of the discharge port 17 and the notch 19.

As described above, the pressure oil discharged from the discharge port 17 generates a substantially rectangular wave pulsation having a duty ratio of about 50% at substantially the cycle T1. For this reason, as shown in FIG. 5, the pressure oil from the discharge port 17 has a large variation in the flow rate (pulsation) with respect to the frequency which is an odd multiple of the basic frequency F0, and an even number which is not an odd multiple of the basic frequency F0. Ripple at twice the frequency is very small.

Next, the pressure oil discharged from the discharge port 17 is supplied into the discharge pipe 21 and also reaches the side branch 24. Here, the pulsation of the pressure oil that has reached the inside of the side branch 24 passes through the inside of the side branch 24,
The light is reflected at the closed end and returns to the inside of the discharge pipe 21 again. At this time, the pulsation of the pressure oil in the discharge pipe 21 is caused by the side branch 2
The pressure oil, which is reduced by interfering with the pulsation reflected inside 4 and has little pulsation, is supplied to the actuator 23 and the like via the discharge pipe 21.

Here, as shown in FIG. 6, the side branch 24 has a large pulsation reduction rate characteristic with respect to an odd multiple of the fundamental frequency F0. Further, the pulsation of a frequency such as an even multiple of the fundamental frequency F0 is very small due to the notch 19. For this reason, as shown in FIG. 7, the pressure oil supplied from the discharge pipe 21 reduces the pulsation of a frequency such as an even multiple of the fundamental frequency F0 by the notch 19, and the odd oil of the fundamental frequency F0 by the side branch 24. The pulsation of the frequency is reduced, and the pulsation of the pressure oil is greatly reduced.

Thus, in this embodiment, the notch 19 extending from the start end of the discharge port 17 toward the switching valve portion 15C is provided, and the length L1 of the notch 19 is set to each cylinder port 9
A is set so as to correspond to half the angle θ1 of the angle θ2 between A. Therefore, it is possible to alleviate the rapid flow of the pressure oil from the discharge port 17 into each cylinder 9 and to set the discharge port 17
The pulsation of the pressure oil discharged from the pump can be made into a substantially rectangular waveform with a duty ratio of about 50%, and the fundamental frequency F0
In contrast, pulsation at frequencies such as even multiples other than odd multiples can be made very small.

The discharge pipe 21 has a side branch 2
4, the pulsation of a frequency which is an odd number multiple of the fundamental frequency F0 can be efficiently absorbed by one side branch 24, and the pulsation of the pressure oil can be greatly reduced. Is a control valve 22 through a discharge pipe 21 or the like,
Noise and vibration generated by transmitting to the actuator 23 and a structure such as a building can be reliably prevented.

FIGS. 8 to 13 show a second embodiment of the present invention. In this embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof will be omitted. It shall be. However, the feature of this embodiment is that the length L2 of the notch 31 provided on the discharge port 17 side is set to correspond to the angle .theta.3 of 1/3 of the angle .theta.2 between the cylinder ports 9A.

The notch 31 as the notch groove has a length L from the discharge port 17 toward the switching valve portion 15C on the other side.
2 and is formed in a substantially triangular shape so that the cylinder port 9A of each cylinder 9 and the discharge port 17 are gradually communicated. Then, the notch 31 alleviates the sudden flow of high-pressure oil from the discharge port 17 into each cylinder 9 that has completed the suction stroke.

Here, the notch 31 extends over an angle θ 3 (θ 3 = 2π / 3N) when the number of the pistons 10 is nine (in this example, nine) with respect to the axis center of the rotating shaft 6 and the pi is π. It is formed. The length L2 of the notch 31 corresponds to the angle θ3,

[0066]

## EQU6 ## The length is set so that L2∝θ3. The angle θ3 formed by the notch 31 is about 1/3 of the angle θ2 formed between the starting ends of the adjacent cylinder ports 9A (θ3 = θ2 / 3).
Is set to

At one end of the discharge pipe 21, a side branch 32 as a cylindrical body is provided in a branched manner. The side branch 32 is formed as a bottomed cylindrical body having a length S2, and the inside thereof is a resonance chamber. And is configured to communicate with the discharge port 17.

Here, the side branch 32 is a pulsation absorber, and the length S2 of the side branch 32 is set so that the pulsation reduction amount is maximized at a frequency 1.5 times the basic frequency F0 of the pressure oil. With respect to the number of rotations M (rpm) of 1 and the number N of pistons 10,

[0069]

(Equation 7) Is set to

Next, the operation of the notch 31 and the side branch 32 on the discharge port 17 side will be described in detail with reference to FIGS.

First, each cylinder 9 is connected to the cylinder block 8
At the same time, the cylinder 9 rotates in the direction indicated by the arrow A, and the cylinder port 9A of the cylinder 9 which has completed the suction stroke is blocked from the suction port 16 and reaches the switching valve portion 15C on the other side. At this time, the pressure in the cylinder 9 on the switching valve portion 15C is
It becomes a low pressure almost equal to the internal pressure.

Next, when the cylinder 9 communicates with the discharge port 17 through the notch 31, the high-pressure hydraulic oil in the discharge port 17 flows into the cylinder 9 (reverse flow) through the notch 31 and the like. The discharge flow rate of the pressure oil discharged from 17 decreases.

When the cylinder block 8 further rotates and the cylinder 9 reaches the start end of the discharge port 17,
The pressure in the cylinder 9 substantially matches the pressure in the discharge port 17. When the piston 10 in the cylinder 9 contracts, the pressure oil in the cylinder 9 is discharged from the discharge port 17.
The discharge flow rate of the pressure oil discharged toward the side and discharged from the discharge port 17 increases.

Here, the length L2 of the notch 31 is determined by setting the angle θ3 formed by the notch 31 to the angle θ between the cylinder ports 9A.
2 is set to correspond to about 1/3 of the angle, so that 1/3 of the time required for each cylinder port 9A to communicate with the discharge port 17 is connected to each cylinder 9 via the notch 31. The discharge port 17 communicates with the discharge port 17.

For this reason, the pressure oil discharged from the discharge port 17 has a period T1 as shown by a characteristic line 33 in FIG.
(T1 = 1 / F0) pulsation occurs, and each cylinder port 9
A communicates with the discharge port 17 every time period T1.
Also, a time T3 (T3 = T1 //), which is one third of the period T1
In 3), since each cylinder 9 communicates with the discharge port 17 via the notch 31, the flow rate of the pressure oil decreases. on the other hand,
At other times (T1 -T3), the pressure oil is supplied from each cylinder 9 to the discharge port 17, so that the flow rate of the pressure oil increases.

As described above, the pressure oil discharged from the discharge port 17 generates a substantially rectangular wave pulsation having a duty ratio of about 67% at a period T1. For this reason, as shown in FIG.
The pulsation of the frequency 2F0, twice the fundamental frequency F0, the frequency 4F0, four times the fundamental frequency F0, the frequency 5F0, five times the fundamental frequency F0, becomes larger, and the natural frequency n becomes (3 × The pulsation of the frequency which is n) times is very small.

The pressure oil discharged from the discharge port 17 is supplied into the discharge pipe 21 and also reaches the side branch 32. Here, the pulsation of the pressure oil that has reached the inside of the side branch 32 passes through the inside of the side branch 32,
The light is reflected at the closed end and returns to the inside of the discharge pipe 21 again. At this time, the pulsation of the pressure oil in the discharge pipe 21 is caused by the side branch 3
The pressure oil which is reduced by interfering with the pulsation reflected in the inside 2 and has a small pulsation is supplied to the actuator 23 and the like via the discharge pipe 21.

Here, as shown in FIG. 12, the side branch 32 has a maximum pulsation reduction rate with respect to a frequency F1 which is 1.5 times the fundamental frequency F0 and has a maximum pulsation reduction rate with respect to a frequency component which is an odd multiple of the frequency F1. However, it has a characteristic that the pulsation reduction rate is large. The pressure oil discharged from the discharge port 17 includes a basic frequency F0, a frequency 2F0, a frequency 4F0, a frequency 5F0,
.. And the like, but the pulsations at these frequencies are close to odd multiples of the frequency F1 and are therefore absorbed by the side branch 32. Further, the pulsation at a frequency that is (3 × n) times the fundamental frequency F0 that cannot be reduced by the side branch 32 is extremely reduced by the notch 31.

For this reason, as shown in FIG. 13, the pulsation of the pressure oil supplied from the discharge pipe 21 is reduced by a notch 31 at a frequency of (3 × n) times the fundamental frequency F0, and the side branch 32 reduces the pulsation. Pulsations such as the fundamental frequency F0 and the frequency 2F0 are reduced, and the pulsation of the pressure oil is greatly reduced.

Thus, in this embodiment constructed as described above, the same operation and effect as those of the first embodiment can be obtained. In this embodiment, particularly, in the present embodiment, the switching valve is provided from the start end side of the discharge port 17. A notch 31 extending toward the portion 15C is provided.
A is set so as to correspond to the angle θ3 which is ３ of the angle θ2 between A. Therefore, it is possible to alleviate the rapid flow of the pressure oil from the discharge port 17 into each cylinder 9 and to reduce the pressure port 1.
7 has a duty ratio of about 67%
, And a fundamental frequency F
Pulsation at a frequency that is (3 × n) times as large as 0 can be extremely reduced.

The discharge pipe 21 has a side branch 3
2, the pulsations such as the fundamental frequency F0 and the frequency 2F0 can be efficiently absorbed by one side branch 32, and the pulsation of the pressure oil can be greatly reduced. Vibration can be reliably prevented.

In each of the above embodiments, a case where a variable displacement swash plate type hydraulic pump is used as an axial piston type pump has been described as an example. However, the present invention is not limited to this, and the present invention is not limited to this. It may be applied to a swash plate type hydraulic pump,
The present invention may be applied to a variable displacement or fixed displacement oblique shaft type hydraulic pump or the like.

In each of the above embodiments, the case where nine cylinders 9 and cylinder ports 9A are formed in the cylinder block 8 is shown as an example. However, the present invention is not limited to this, and may be eight or less. Alternatively, ten or more cylinders may be formed in the cylinder block.

Further, in each of the above embodiments, each cylinder 9
Although the case where the cylinder port 9A is formed in an elliptical shape is shown as an example, the shape of the cylinder port 9A may be elliptical or circular.

[0085]

As described above in detail, according to the first aspect of the present invention, the length L1 from the discharge port toward the switching valve portion is provided on the valve plate.
The length L1 of the notch groove is set to a length corresponding to the angle π / N formed by the notch groove, so that the pressure oil rapidly flows into each cylinder from the discharge port. And the pulsation of the pressure oil discharged from the discharge port can be made into a substantially rectangular waveform having a duty ratio of about 50%. Can be very small.

According to the second aspect of the present invention, the valve plate is provided with a notch groove extending from the discharge port toward the switching valve portion with a length L2, and the length L2 of the notch groove is equal to the angle 2π formed by the notch groove. Since the length is set to correspond to / 3N, it is possible to alleviate the rapid flow of pressure oil from the discharge port into each cylinder, and to reduce the pulsation of the pressure oil discharged from the discharge port by the duty ratio. A substantially rectangular waveform of about 67% can be obtained, and the natural frequency n is (3 × n) of the fundamental frequency.
The pulsation of the doubled frequency can be made very small.

Further, according to the third aspect of the present invention, the discharge pipe is connected to the discharge port, and the discharge pipe is provided with the pulsation absorber for reducing the pulsation of the pressure oil. Can be efficiently absorbed by a single pulsation absorber, and it is not necessary to provide a plurality of pulsation absorbers, and the manufacturing cost can be reduced. Further, since the pulsation of the pressure oil can be greatly reduced, the reliability of hydraulic equipment such as a control valve and a cylinder can be improved, and noise and vibration due to the pulsation of the pressure oil can be reliably prevented.

According to the fourth aspect of the present invention, the pulsation absorber provided at the discharge port is constituted by a cylinder whose one end is closed, and the length S1 of the cylinder is determined by the sound velocity V in the pressure oil. Since the rotation number M is set to be an odd multiple of 15 V / (M × N) with respect to the number of rotations M of the rotating shaft and the number N of pistons, the pulsation of a frequency which is an odd multiple of the fundamental frequency which cannot be reduced by the cutout groove is 1 It can be efficiently absorbed by the individual cylinders, and the pulsation of the pressure oil can be greatly reduced.

According to the fifth aspect of the present invention, the pulsation absorber provided at the discharge port is constituted by a cylindrical body having one end closed, and the length S1 of the cylindrical body is determined by the sonic velocity V in the pressure oil. Since the rotation number is set to an odd multiple of about 10 V / (M × N) with respect to the rotation number M of the rotating shaft and the number N of pistons, pulsation of a frequency that cannot be reduced by the cutout groove can be efficiently performed by one cylinder. It can be absorbed, and the pulsation of the pressure oil can be greatly reduced.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram showing a hydraulic pump and the like according to a first embodiment of the present invention.

FIG. 2 is a longitudinal sectional view showing the hydraulic pump according to the first embodiment of the present invention.

FIG. 3 is an enlarged cross-sectional view in the direction of arrows III-III in FIG. 2 showing a valve plate and the like having a suction port and a discharge port.

FIG. 4 is a characteristic diagram showing a relationship between a flow rate of pressure oil discharged from a discharge port in FIG. 3 and time.

FIG. 5 is an explanatory diagram illustrating a relationship between a flow rate and a frequency of pressure oil discharged from a discharge port in FIG. 3;

FIG. 6 is an explanatory diagram illustrating a relationship between a pulsation reduction rate and a frequency by a side branch in FIG. 1;

FIG. 7 is an explanatory diagram for explaining a relationship between a flow rate of pressure oil supplied from a discharge pipe in FIG. 1 and a frequency.

FIG. 8 is an overall configuration diagram showing a hydraulic pump and the like according to a second embodiment of the present invention.

FIG. 9 is a sectional view similar to FIG. 3, showing a valve plate and the like of a hydraulic pump according to a second embodiment of the present invention.

FIG. 10 is a characteristic diagram showing a relationship between a flow rate of pressure oil discharged from a discharge port in FIG. 9 and time.

FIG. 11 is an explanatory diagram illustrating a relationship between a flow rate and a frequency of pressure oil discharged from a discharge port in FIG. 9;

FIG. 12 is an explanatory diagram illustrating a relationship between a pulsation reduction rate and a frequency by a side branch in FIG. 8;

FIG. 13 is an explanatory diagram illustrating a relationship between a flow rate of pressure oil supplied from a discharge pipe in FIG. 8 and a frequency.

[Explanation of symbols]

 2 Casing 6 Rotating shaft 8 Cylinder block 9 Cylinder 9A Cylinder port 10 Piston 15 Valve plate 15B, 15C Switching valve section 16 Intake port 17 Discharge port 19, 31 Notch (notched groove) 21 Discharge pipe 24, 32 Side branch (pulsation absorber) )

Claims (5)

[Claims] A casing, a rotating shaft rotatably provided in the casing, a cylinder block provided in the casing so as to rotate integrally with the rotating shaft, and having a plurality of cylinders formed therein; N pistons slidably inserted into the cylinders of the cylinder block and reciprocating in the respective cylinders as the cylinder block rotates, and a suction port provided between the casing and the cylinder block. An axial piston type hydraulic pump comprising a pair of switching valve portions formed so as to face each other with the rotation axis interposed between the discharge port and the discharge plate, wherein the valve plate is switched from a start end of the discharge port. A notch groove extending in the circumferential direction with a length L1 toward the valve portion side is provided, and the angle formed by the notch groove with respect to the axis center of the rotating shaft is substantially π.
/ N, the length L1 of the notch groove is equal to this angle π / N
Axial piston type hydraulic pump characterized in that it is set to a length corresponding to. 2. A casing, a rotating shaft rotatably provided in the casing, a cylinder block provided in the casing so as to rotate integrally with the rotating shaft, and having a plurality of cylinders formed therein. A plurality of pistons which are slidably inserted into the respective cylinders of the cylinder block and reciprocate in the respective cylinders as the cylinder block rotates; and a suction port and a discharge port provided between the casing and the cylinder block. An axial piston type hydraulic pump comprising: a valve plate having a pair of switching valve portions formed so as to face each other with the rotary shaft interposed between the port and a port. A notch groove extending in the circumferential direction with a length L2 toward the portion side is provided, and the angle formed by the notch groove with respect to the axis center of the rotating shaft is approximately 2 °.
Assuming π / 3N, the length L2 of the notched groove is equal to this angle 2
An axial piston type hydraulic pump characterized in that the length is set to correspond to π / 3N. 3. A discharge pipe for discharging pressure oil from the discharge port is connected to the discharge port, and the discharge pipe is provided with a pulsation absorber for reducing pulsation of the pressure oil. The axial piston type hydraulic pump according to [1]. 4. A discharge pipe for discharging pressure oil from the discharge port is connected to the discharge port, and the discharge pipe is provided with a pulsation absorber for reducing pulsation of the pressure oil, and the pulsation absorber has one end. The length S1 of the cylinder is an odd number of approximately 15V / (M × N) with respect to the sound velocity V in the pressurized oil, the number of rotations M of the rotating shaft, and the number N of pistons. The axial piston type hydraulic pump according to claim 1, wherein the axial piston type hydraulic pump is configured to be set to double. 5. A discharge pipe for discharging pressure oil from the discharge port is connected to the discharge port, and the discharge pipe is provided with a pulsation absorber for reducing pulsation of the pressure oil, and the pulsation absorber has one end. Is closed, and the length S2 of the cylinder is approximately 10 V / (M × N) with respect to the speed of sound V in pressurized oil, the number of rotations M of the rotating shaft, and the number N of pistons. 3. The axial piston hydraulic pump according to claim 2, wherein the hydraulic pump is set to an odd multiple.