JP2010261504A - Hydraulic device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To miniaturize a hydraulic device and reduce portions where oil is leaked, in the hydraulic device elongating and contracting a reciprocating hydraulic cylinder 16 by an axial piston hydraulic pump 31. <P>SOLUTION: When the hydraulic cylinder is connected to the hydraulic pump through a first hydraulic pipe 32 and a second hydraulic pipe 33, charge relief circuits 62, 63 with respect to the first and second hydraulic pipes 32, 33 are built in a housing body 34 in the hydraulic pump 31. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a hydraulic apparatus using a variable displacement type axial piston hydraulic pump as a hydraulic pump for operating a backward-acting hydraulic cylinder.

  In a backward-acting hydraulic cylinder that drives a movable part (such as a boom) of a work machine such as a backhoe, it is patented to use a variable displacement axial piston hydraulic pump as a hydraulic pump that operates the hydraulic cylinder. Documents 1, 2, etc.

  As is well known in the art, this axial piston hydraulic pump includes a cylinder block that rotates integrally with a rotating shaft of a housing body, and a valve plate that has at least a first hydraulic port and a second hydraulic port. In conjunction with rotation in one direction, the pistons in the plurality of cylinder chambers formed in the cylinder block are reciprocated to discharge and suck hydraulic pressure from the first hydraulic port and the second hydraulic port. Is.

  The axial piston hydraulic pump is communicated with the return-acting hydraulic cylinder via a first hydraulic pipe in which the first hydraulic port of the hydraulic pump is flexible. By connecting the second hydraulic port of the hydraulic pump to the other cylinder chamber of the hydraulic cylinder via a flexible second hydraulic pipe, and forming a closed loop hydraulic circuit therebetween. The hydraulic cylinder is configured to reciprocate so as to expand and contract.

  That is, when the axial piston hydraulic pump discharges hydraulic pressure from its first hydraulic port, this hydraulic pressure is sent to one cylinder chamber in the hydraulic cylinder via the first hydraulic piping, while the other cylinder chamber in the hydraulic cylinder. When the hydraulic pressure in is sucked into the second hydraulic port via the second hydraulic pipe, the hydraulic cylinder is extended or contracted.

  When the axial piston hydraulic pump discharges hydraulic pressure from the second hydraulic port, the hydraulic pressure is sent to the other cylinder chamber of the hydraulic cylinder via the second hydraulic piping, while one cylinder chamber of the hydraulic cylinder is supplied. When the hydraulic pressure in is sucked into the first hydraulic port via the first hydraulic pipe, the hydraulic cylinder is contracted or extended.

  By the way, in the hydraulic device, the first hydraulic pipe and the second hydraulic pipe may be caused by a difference in pressure receiving area between the cylinder chambers of the hydraulic cylinder or a hydraulic leak or the like. Thus, an excess or deficiency in the amount of oil occurs. Therefore, an adjustment hydraulic pump for adjusting the axial piston hydraulic pump is connected to the first hydraulic pipe via a first charge relief circuit, and the second By connecting to the hydraulic piping via a second charge relief circuit, it is configured to correct the excess or deficiency of the oil amount between the two hydraulic piping (see, for example, Patent Document 3).

JP-A-10-169547 JP-A-11-107926 Japanese Patent Laid-Open No. 04-219568

  However, conventionally, the first charge relief circuit for the first hydraulic piping and the second charge relief circuit for the second hydraulic piping are separated from the axial piston hydraulic pump, and the first hydraulic piping and the second hydraulic piping are separated. It is configured to be provided in the middle of the hydraulic piping.

  For this purpose, a space for providing the first charge relief circuit and the second charge relief circuit must be secured separately from the axial piston hydraulic pump, the hydraulic cylinder, and the like. In addition, there is a problem that not only the structure of both the hydraulic pipes is complicated, but also the number of places where hydraulic leakage occurs is increased.

  Further, in the conventional hydraulic device, the hydraulic cylinder is provided by providing a holding valve for stopping the flow of hydraulic pressure to both cylinder chambers in the hydraulic cylinder in both the first hydraulic pipe and the second hydraulic pipe. , It is configured to lock inoperable at any operating position.

  In this case, conventionally, the holding valve is configured to be provided at a location where the first hydraulic pipe and the second hydraulic pipe are connected to the hydraulic cylinder, that is, a location adjacent to the hydraulic cylinder. As described, there was a problem that a time delay occurred in the operation of the hydraulic cylinder by the hydraulic pump.

  That is, the operation of the hydraulic cylinder is started by supply of hydraulic pressure from a hydraulic pump, but when the holding valve is provided at a location adjacent to the hydraulic cylinder, the inside of the first hydraulic pipe and the second hydraulic pipe is The hydraulic pressure is lowered by closing the holding valve until the hydraulic pressure is supplied from the hydraulic pump. After the hydraulic pressure is increased to a predetermined value by the hydraulic pressure supplied from the hydraulic pump, the hydraulic pressure is reduced. Since the hydraulic cylinder starts to operate, the operation start of the hydraulic cylinder is delayed by the time required for the pressure to increase.

  The present invention has a technical problem to solve these problems.

In order to achieve this technical problem, claim 1
“A variable displacement axial piston hydraulic pump having at least a first hydraulic port and a second hydraulic port, and a return hydraulic cylinder, wherein the first hydraulic port and one cylinder chamber of the hydraulic cylinder A hydraulic device in which the second hydraulic port and the other cylinder chamber of the hydraulic cylinder are connected via a second hydraulic pipe, while the first hydraulic pipe is connected to the other cylinder chamber;
A charge relief port communicating with both the first hydraulic port and the second hydraulic port is provided in the housing main body of the axial piston hydraulic pump, and the charge relief port is used for adjustment with respect to the axial piston hydraulic pump. A hydraulic pump is connected, and a first charge relief circuit is provided between the first hydraulic port and the charge relief port inside the housing body, and between the second hydraulic port and the charge relief port. A second charge relief circuit is provided for each. "
It is characterized by that.

Claim 2
“A check valve according to claim 1, wherein both the first charge relief circuit and the second charge relief circuit open only in the direction from the charge relief port to the first hydraulic port and the second hydraulic port; The first hydraulic port and the relief valve that opens when the hydraulic pressure increases in the second hydraulic port are arranged in parallel. "
It is characterized by that.

Claim 3
“In claim 2, the first charge relief circuit and the second charge relief circuit are configured such that the check valve in the charge relief circuit includes the relief valve in the charge relief circuit.”
It is characterized by that.

Claim 4
“In any one of the first to third aspects of the present invention, the flow of hydraulic pressure is not present in a portion of the first hydraulic port and the second hydraulic port that is downstream of the first charge relief circuit and the second charge relief circuit. Each of the holding valves is provided so that the first hydraulic pipe and the second hydraulic pipe to the hydraulic cylinder are connected.
It is characterized by that.

  According to claim 1, both the first charge relief circuit for correcting the oil amount for the first hydraulic piping and the second charge relief circuit for correcting the oil amount for the second hydraulic piping. However, since it is built in the housing body of the axial piston hydraulic pump, it is not necessary to secure a separate space for providing the first and second charge relief circuits, and the hydraulic device can be greatly reduced in size. In addition to simplifying the structure of both the hydraulic pipes, the number of occurrences of hydraulic leakage can be reduced.

  In this case, according to the second aspect, each of the first charge relief circuit and the second charge relief circuit can be realized with a simple configuration by arranging a check valve and a relief valve in parallel.

  In particular, in the second aspect, as described in the third aspect, the charge relief circuit can be downsized by incorporating the relief valve into the check valve. , A further reduction in size and weight of the axial piston hydraulic pump can be achieved.

  According to claim 4, when each holding valve is closed, the hydraulic pressure in the first hydraulic pipe and the second hydraulic pipe can be maintained in a high pressure state. When the actuator is operated by supplying hydraulic pressure from an axial piston hydraulic pump, it is possible to reliably avoid a delay in starting the operation.

It is a side view of a backhoe. It is a circuit diagram of the hydraulic device in a backhoe. It is a vertical front view of an axial piston hydraulic pump. It is a figure which shows a valve plate by the IV-IV sectional view of FIG. FIG. 5 is a sectional view taken along line VV in FIG. 3. It is a principal part enlarged view of FIG.

  Hereinafter, an embodiment in which the present invention is employed in a backhoe as an example of a work machine will be described with reference to the drawings (FIGS. 1 to 6).

  FIG. 1 is a side view of the backhoe, and FIG. 2 is a circuit diagram of a hydraulic device for the backhoe.

  The backhoe 1 includes a crawler type traveling device 2 having a pair of left and right traveling crawlers 3 (shown only on the left side in FIG. 1), and a swivel base 4 (airframe) provided on the traveling device 2 so as to be horizontally rotatable. ing. A soil discharge plate 5 is mounted on the front portion of the traveling device 2 so as to be rotatable up and down.

  The swivel 4 is equipped with a cabin 6 as a control unit and an engine 7 as a drive source. A working unit 10 having a boom 11, an arm 12, and a bucket 13 for excavation work is provided at the front of the swivel 4. Although details are not shown, a control seat on which an operator sits and a group of levers for various operations on the backhoe 1 are arranged inside the cabin 6.

  The boom 11, which is a component of the working unit 10, is formed in a shape that protrudes forward at the distal end side and is bent in a letter shape in side view. The base end portion of the boom 11 is pivotally attached to a boom bracket 14 attached to the front portion of the swivel base 4 so as to be swingable up and down about a horizontal boom shaft 15. On the inner surface (front surface) side of the boom 11, a one-rod double-acting hydraulic cylinder 16 for a boom for swinging it up and down is disposed.

  The cylinder side end of the boom hydraulic cylinder 16 is pivotally supported by the front end of the boom bracket 14, while the rod side end of the hydraulic cylinder 16 is on the front side of the bent portion of the boom 11. It is pivotally supported by the front bracket 17 fixed to the (dent side).

  A base end portion of a long rectangular tube-like arm 12 is pivotally attached to the distal end portion of the boom 11 so as to be swingable about a lateral arm shaft 19.

  A one-rod double-acting hydraulic cylinder 20 for swinging and swinging the arm 12 is disposed on the front side of the upper surface of the boom 11.

  The cylinder side end of the hydraulic cylinder 20 is pivotally supported by a rear bracket 18 fixed to the back side (protrusion side) of the bent portion of the boom 11, while the rod side end of the hydraulic cylinder 20 is supported. The portion is pivotally supported by an arm bracket 21 fixed to an outer surface (front surface) of the base end side of the arm 12 so as to be rotatable.

  A bucket 13 as an excavation attachment is pivotally attached to the distal end portion of the arm 12 so as to be swiveled around a lateral bucket shaft 22. Further, on the outer surface (front surface) side of the arm 12, a single rod double acting bucket hydraulic cylinder 23 for scrambling and rotating the bucket 13 is disposed.

  The cylinder side end of the bucket hydraulic cylinder 23 is pivotally supported by the arm bracket 21, while the rod side end of the bucket hydraulic cylinder 23 is connected via a connecting link 24 and a relay rod 25. And pivotally supported by the bucket 13.

  Next, the hydraulic device of the backhoe 1 will be described with reference to FIG.

  The hydraulic device 30 of the backhoe 1 shown in FIG. 2 includes the boom hydraulic cylinder 16 described above and a variable displacement axial piston hydraulic pump / motor for supplying hydraulic pressure to the hydraulic cylinder 16 to operate it. 31 (hereinafter referred to as an axial piston hydraulic pump 31).

  Both of them, that is, the hydraulic cylinder 16 and the axial piston hydraulic pump 31, are a flexible first hydraulic pipe 32 such as a pressure-resistant and oil-resistant rubber hose, and a pressure-resistant and oil-resistant rubber hose. The second hydraulic pipe 33 having flexibility is connected in a closed loop shape.

  As described above, the boom hydraulic cylinder 16 is a single-rod double-acting type with one piston rod 16 ', and of the cylinder chambers 16a and 16b, the bottom cylinder chamber 16a in which the piston rod 16' does not exist. The pressure receiving area (cross-sectional area) in the cylinder rod 16 'is larger than the pressure receiving area in the rod cylinder chamber 16b in which the piston rod 16' exists among the cylinder chambers 16a and 16b by the cross-sectional area of the piston rod 16 '. ing.

  As shown in FIGS. 3 to 5, the housing main body 34 of the axial piston hydraulic pump 31 is composed of a pump casing 34a and an end face plate 34b detachably attached to one end thereof. Inside, there are three hydraulic ports including a first hydraulic port 35, a second hydraulic port 36, and a third hydraulic port 37. The first hydraulic port 35 includes a bottom cylinder of the boom hydraulic cylinder 16. 16a is connected via the first hydraulic pipe 32, and the rod cylinder 16b of the boom hydraulic cylinder 16 is connected to the second hydraulic port 36 via the second hydraulic pipe 33. A hydraulic oil tank 38 is connected to the port 37.

  The axial piston hydraulic pump 31 is of a so-called swash plate type (see FIG. 3), and is configured to rotationally drive the rotating shaft 39 by the power of the engine 7. By adjusting the tilt angle of the movable swash plate 42 in the axial piston hydraulic pump 31 via the controller 41 according to the operation amount of the operation lever 40 disposed in the cabin 6 of the backhoe 1, , The discharge direction and discharge amount of the hydraulic pressure from the hydraulic pump 31 are adjusted.

  The rotary shaft 39 in the hydraulic pump 31 drives an adjusting hydraulic pump 43 that is a separate pump, and supplies the hydraulic pressure from the adjusting hydraulic pump 43 to the hydraulic servo mechanism 44 for the movable swash plate 42. Thus, the movable swash plate 42 is configured to change and adjust the inclination angle.

  The hydraulic servo mechanism 44 changes and adjusts the inclination angle of the movable swash plate 42 via solenoid valves 45a and 45b in accordance with the operation from the neutral position of the operation lever 40 to up or down.

  Further, a charge relief port 45 is provided in a portion between the first hydraulic port 35 and the second hydraulic port 36 inside the end face plate 34b of the housing main body 34 in the axial piston hydraulic pump 31, The charge relief port 45 is connected to a hydraulic charge pipe 46 from the adjustment hydraulic pump 43.

  Next, the structure of the axial piston hydraulic pump 31 will be described.

  As shown in FIG. 3, the hydraulic pump 31 is configured to rotate integrally with a rotary shaft 39 rotatably supported by bearings 47 and 48 in a hollow box-shaped housing body 34. And a valve plate 54 having communication ports 50, 51, 53 connected to the first to third hydraulic ports 35-37, respectively. In the cylinder block 49, a plurality of cylinder chambers 55 extending in parallel with the rotation shaft 39 are formed on the same circumference around the rotation shaft 39. In each cylinder chamber 55, a piston 56 is fitted and slidable.

  A movable swash plate 42 whose inclination angle can be changed by the action of the hydraulic servo mechanism 44 is disposed on the bearing 48 side in the housing body 34. A piston shoe 57 provided at the tip of the piston 56 is in contact with the piston sliding surface of the movable swash plate 42 facing the cylinder block 49. The convex spherical surface portion of the movable swash plate 42 opposite to the piston sliding surface is slidably in contact with the concave spherical surface portion of the swash plate holder 58 provided inside the pump casing 34 a of the housing body 34. Yes.

  A compression spring 60 is disposed in the storage chamber 59 in the cylinder block 49 so as to be fitted on the rotary shaft 39. The piston shoe 57 is pressed against the piston sliding surface of the movable swash plate 42 by the action (pressing biasing force) of the compression spring 60.

  Between the end face plate 34 b constituting the housing body 39 and the cylinder block 49, the valve plate 54 is disposed in a state of being fitted on the rotary shaft 39. The compression spring 60 described above also plays a role of pressing the cylinder block 49 against the valve plate 54 by the pressing biasing force. Therefore, the cylinder block 49 rotates integrally with the rotary shaft 39 in a state of surface contact with the valve plate 54.

  In the valve plate 54, three communication ports 50, 51, 52 penetrating in the thickness direction are formed in an arc shape extending along the same circumference centering on the rotation shaft 39 with an appropriate interval. (See FIG. 4).

  In the embodiment, the opening section S1 in the communication port 50 with respect to the first hydraulic port 35 has an opening section S3 in the communication port 52 with respect to the third hydraulic port 37, as compared with the opening section S2 in the communication port 50 with respect to the second hydraulic port 36. It is bigger by That is, the sum of the opening sections S2 and S3 of the second communication port 51 and the third communication port 52 is set to be the same as the opening section S1 of the first communication port 50 (the relationship of S1 = S2 + S3 holds). ing).

  The ratio of the opening section S2 of the second communication port 51 to the opening section S1 of the first communication port 50 is set to be the same as the ratio of the pressure receiving area R of the rod cylinder chamber 16b to the pressure receiving area B of the bottom cylinder chamber 16a. Has been. That is, the relationship S2 / S1 = R / B is established. As shown in FIG. 4, the opening area a3 of the third communication port 52 is set larger than the difference between the opening areas a1 and a2 of the first communication port 50 and the second communication port 51. That is, the relationship of a3> a1-a2 is established.

  On the other hand, a communication hole 61 communicating with each cylinder chamber 55 is formed on the end face of the cylinder block 49 on the side contacting the valve plate 54. Each communication hole 61 is configured to selectively communicate with each communication port 50 to 52 of the valve plate 54 as the cylinder block 49 rotates.

  The rotating shaft 39 of the hydraulic pump 31 is configured to rotate only in one direction (counterclockwise direction (arrow b direction) in FIG. 4) with the power of the engine 7. For this reason, the cylinder block 49 rotates only in the direction of arrow b in FIG. Each cylinder chamber 56 of the cylinder block 49 communicates in the order of the first communication port 50, the third communication port 52, and the second communication port 51 from the upstream side of the rotation as the cylinder block 49 rotates in one direction. It is configured as follows.

  When the rotating shaft 39 is rotated about the axis by the power of the engine 7, the cylinder block 49 rotates integrally with the rotating shaft 39, and the piston shoe 57 slides on the piston sliding surface of the movable swash plate 42. Based on the inclination angle of the movable swash plate 42 (piston sliding surface) at this time, each piston 56 slides back and forth in the cylinder chamber 55 to change the volume of each cylinder chamber 55.

  For this reason, in each cylinder chamber 55, the suction stroke and the discharge stroke are sequentially executed, and the switching of the communication ports 50 to 52 with respect to each cylinder chamber 55 is also performed from the upstream side of the rotation as the cylinder block 49 rotates. The first communication port 50, the third communication port 52, and the second communication port 51 are automatically executed in this order.

  As a result, the hydraulic oil is sucked from the first hydraulic port 35 and discharged from the second and third hydraulic ports 36 and 37, so that the hydraulic cylinder 16 is contracted.

  Further, when the tilt angle of the movable swash plate 42 is operated in the reverse direction by the action of the hydraulic servo mechanism 44, the hydraulic oil is sucked from the second hydraulic port 36 and discharged from the first and third hydraulic ports 35 and 37. As a result, the hydraulic cylinder 16 is extended.

  In this case, if the inclination angle of the movable swash plate 42 is changed, the stroke stroke of each piston 56 changes. By changing the stroke, the amount of hydraulic oil discharged from the hydraulic pump 31 is adjusted, and consequently the speed of expansion / contraction operation in the hydraulic cylinder 16 can be adjusted.

  As shown in FIG. 5, a first charge relief circuit is provided between the first hydraulic port 35 and the charge relief port 45 inside the end face plate 34 b of the housing main body 34 in the axial piston hydraulic pump 31. 62, by providing a second charge relief circuit 63 between the second hydraulic port 36 and the charge relief port 45, respectively, the adjustment hydraulic pressure is applied to the first hydraulic port 35 and the second hydraulic port 36. Replenishment (charging) of the hydraulic pressure from the pump 43 and relief from the first and second hydraulic ports 35 and 36 are performed, thereby reducing the excess or deficiency of the oil amount between the hydraulic pipes 32 and 33. It is configured to correct.

  As shown in FIG. 6, the first charge relief circuit 62 is a relief valve in which the valve body 62a ′ opens against the spring 62a ″ when the hydraulic pressure of the first hydraulic port 35 becomes higher than a predetermined value. 62a and a check valve 62b that opens only in the direction from the charge relief port 45 to the first hydraulic port 35 when the hydraulic pressure of the first hydraulic port 35 drops, is provided in parallel. The check valve 62b is composed of a valve body 62b 'and a spring 62b "that presses and biases the valve body 62b normally closed. The check valve 62b has a hollow valve body 62b' inside the relief valve 62a. The relief valve 62a is built in the check valve 62b such that a valve body 62a 'is provided.

  On the other hand, as shown in FIG. 6, the second charge relief circuit 63 causes the valve body 63a ′ to open against the spring 63a ″ when the hydraulic pressure of the second hydraulic port 36 becomes higher than a predetermined value. A relief valve 63a, and a check valve 63b that opens only in the direction from the charge relief port 45 to the second hydraulic port 36 when the hydraulic pressure of the second hydraulic port 36 decreases, are provided in parallel. In this case, the check valve 63b is composed of a valve body 63b 'and a spring 63b "that normally presses and biases the valve body 63b'. The relief valve 63a is built in the check valve 63b so that a valve body 63a is provided in the valve 63a.

  Further, the end plate 34 b of the axial piston hydraulic pump 31 is provided with a first holding valve 64 at a portion where the first hydraulic pipe 32 is connected to the first hydraulic port 35, and to the second hydraulic port 36. The second holding valve 65 is detachably attached to the portion connecting the second hydraulic pipe 33, and the first hydraulic pipe 32 is connected to the first holding valve 64 of the holding valves 64, 65, and the second The second hydraulic pipes 33 are connected to the holding valves 65, respectively.

  Each of the holding valves 64 and 65 interlocks with the operation lever 40 when the operation lever 40 is returned to the neutral position, thereby completely closing the oil passage. It is configured to lock inoperable in the operating position.

  In this case, each of the holding valves 64 and 65 includes check valves 64 a and 65 a that are opened only in the direction from the axial piston hydraulic pump 31 to the hydraulic cylinder 16.

  In the present invention, as described above, the first charge relief circuit 62 for correcting the oil amount for the first hydraulic pipe 32 and the oil amount for the second hydraulic pipe 33 are corrected. Since both the second charge relief circuit 63 is built in the housing main body 34 of the axial piston hydraulic pump 31, it is not necessary to secure a separate space for providing the first and second charge relief circuits 62, 63. The hydraulic device can be greatly reduced in size, the structure of the hydraulic pipes 32 and 33 can be simplified, and the occurrence of hydraulic leakage can be reduced.

  Further, in the present invention, the first hydraulic port 35 provided in the housing main body 34 of the axial piston hydraulic pump 31 with the holding valve 64 for the first hydraulic pipe 32 and the holding valve 65 for the second hydraulic pipe 33. When the holding valves 64 and 65 are closed by providing them at the downstream side of the first charge relief circuit 62 and the second charge relief circuit 63 in the second hydraulic port 36, both hydraulic pipes Since the hydraulic pressure in the pressure chambers 32 and 33 can be maintained at a high pressure, the operation is started when the hydraulic cylinder 16 is operated by supplying hydraulic pressure from the axial piston hydraulic pump 31. It is possible to reliably avoid the occurrence of the delay.

  The present invention is not limited to the above-described embodiment, and can be embodied in various forms. For example, the present invention can be applied not only to a backhoe but also to a farm work machine such as a combine machine or a special work vehicle such as a wheel loader. Further, the axial piston hydraulic pump is not limited to the swash plate type, but may be an oblique axis type or a radial type. A simple axial piston hydraulic pump may be used. In addition, the configuration of each unit is not limited to the illustrated embodiment, and various modifications can be made without departing from the spirit of the present invention.

16 Hydraulic cylinder 16a Bottom cylinder chamber 16b Rod cylinder chamber 30 Hydraulic device 31 Axial piston hydraulic pump 32 First hydraulic piping 33 Second hydraulic piping 34 Housing body 35 First hydraulic port 36 Second hydraulic port 43 Adjustment hydraulic pump 45 Charge relief Port 62 First charge relief circuit 63 Second charge relief circuit 62a, 63a Relief valve 62b, 63b Check valve 64, 65 Holding valve

Claims (4)

A variable displacement axial piston hydraulic pump having at least a first hydraulic port and a second hydraulic port; and a return hydraulic cylinder; and between the first hydraulic port and one cylinder chamber of the hydraulic cylinder. Is connected via a first hydraulic pipe, while the second hydraulic port and the other cylinder chamber of the hydraulic cylinder are connected via a second hydraulic pipe,
A charge relief port communicating with both the first hydraulic port and the second hydraulic port is provided in the housing main body of the axial piston hydraulic pump, and the charge relief port is used for adjustment with respect to the axial piston hydraulic pump. A hydraulic pump is connected, and a first charge relief circuit is provided between the first hydraulic port and the charge relief port inside the housing body, and between the second hydraulic port and the charge relief port. And a second charge relief circuit is provided in each.   The check valve according to claim 1, wherein both the first charge relief circuit and the second charge relief circuit open only in a direction from the charge relief port to the first hydraulic port and the second hydraulic port, A hydraulic apparatus comprising a relief valve that opens in parallel with an increase in oil pressure at a first hydraulic port and a second hydraulic port.   3. The structure according to claim 2, wherein the first charge relief circuit and the second charge relief circuit are configured such that the check valve in the charge relief circuit includes the relief valve in the charge relief circuit. Hydraulic system to play.   In any one of the said Claims 1-3, the flow of hydraulic pressure is carried out to the site | part of the said 1st hydraulic port and a 2nd hydraulic port downstream from the said 1st charge relief circuit and a 2nd charge relief circuit. A hydraulic apparatus comprising: a holding valve configured to be stopped; and each of the first hydraulic pipe and the second hydraulic pipe connected to the hydraulic cylinder connected to the holding valve.

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