JP6377520B2 - Work system hydraulic system and work machine equipped with the hydraulic system - Google Patents

Description

  The present invention relates to a hydraulic system for a working machine such as a skid steer loader or a compact truck loader, and a working machine equipped with the hydraulic system.

Conventionally, it is known that a working system such as a skid steer loader or a compact truck loader is equipped with a system for increasing the amount of hydraulic oil supplied to a hydraulic actuator using two pumps (see Patent Document 1).
The hydraulic system of Patent Literature 1 includes a first pump that discharges hydraulic oil, a second pump that discharges hydraulic oil, a first control valve, a second control valve, and a hydraulic actuator. The hydraulic oil discharged from one of the two hydraulic pumps is input to the first control valve. The first control valve controls hydraulic oil supplied to the hydraulic actuator. The hydraulic oil discharged from the other hydraulic pump of the two hydraulic pumps is input to the second hydraulic actuator. The second control valve also controls the hydraulic oil supplied to the hydraulic actuator.

  By operating both the first control valve and the second control valve, the amount of hydraulic oil supplied to the hydraulic actuator can be increased.

JP 2009-293631 A

  In the hydraulic system of Patent Document 1, the hydraulic oil supplied to the hydraulic actuator can be increased by operating both the first control valve and the second control valve, but the pressure of the hydraulic oil is high. In this system, the flow rate can be increased more than necessary. Therefore, in the hydraulic system of Patent Document 1, there is a possibility that the horsepower consumed by the pump (referred to as consumed horsepower) becomes too large.

  The present invention has been made to solve the above-described problems of the prior art, and is capable of supplying proper hydraulic oil to the hydraulic actuator and suppressing the horsepower consumed by the pump. It is an object of the present invention to provide a system and a working machine equipped with the hydraulic system.

The technical means of the present invention for solving the technical problem is as follows.
A hydraulic system for a work machine according to a first aspect of the present invention includes a hydraulic actuator, a connecting portion that connects the hydraulic actuator, a constant capacity pump, a first hydraulic pump that discharges hydraulic oil, and a constant capacity type A second hydraulic pump that discharges hydraulic oil and is different from the first hydraulic pump; a first oil passage that connects the connecting portion and the first hydraulic pump; and a middle of the first oil passage One end is connected between the first control valve provided in the section, the hydraulic actuator in the first oil passage and the first control valve, and the other end is connected to the second hydraulic pump . wherein the second oil passage, and the second is provided in the oil passage and the second control valve capable of setting the flow rate of the hydraulic oil flowing through the second oil passage, and the first hydraulic pump definitive in the first oil passage first a first relief valve connected between the first control valve, the second It has one end that definitive the road and a second relief valve connected between said second control valve.

In the hydraulic system for a work machine according to a second aspect , the set pressure of the second relief valve is set lower than the set pressure of the set pressure of the first relief valve.

The hydraulic system for a work machine according to a third aspect allows a flow of hydraulic oil in a direction from the second oil passage to the first oil passage, and from the first oil passage to the second oil passage. A check valve is provided to block the flow of hydraulic fluid in the direction of travel.
A work machine according to claim 4 is a hydraulic system for a work machine according to any one of claims 1 to 5, a machine body, a work device provided in the machine body, and a traveling device disposed on a right side and a left side of the machine body. And.

  ADVANTAGE OF THE INVENTION According to this invention, while being able to supply an appropriate hydraulic fluid to a hydraulic actuator, the horsepower consumption of a pump can be suppressed.

1 is a hydraulic circuit showing a hydraulic system according to the present invention. It is a figure which shows the example which connected the 2nd relief valve to the 1st area of the 2nd flow path. It is a figure which shows the example which connected the 2nd relief valve to the 2nd area of the 2nd flow path. It is a figure which shows the example which connected the 2nd control valve to the 2nd flow path. It is a figure which shows the relationship of the pressure-flow volume of the conventional 1st pump and 2nd pump. It is a figure which shows the pressure-flow rate relationship of the 1st pump of this invention, and a 2nd pump. It is a figure which shows the pressure-flow rate relationship of the variable displacement pump with a horsepower control. It is a side view which shows the skid steer loader which is an example of the working machine which concerns on this invention.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of a hydraulic system for a working machine and a working machine provided with the hydraulic system according to the invention will be described with reference to the drawings as appropriate.
In FIG. 4, a skid steer loader is shown as an example of the work machine 1. However, the working machine 1 according to the present invention is not limited to the skid steer loader, and may be another type of working machine such as a compact truck loader or a backhoe.

The work machine 1 includes a machine body 2, a cabin 3, a work device 4, and a traveling device 5.
The cabin 3 is mounted on the machine body 2, and the work device 4 is mounted on the machine body 2. The traveling device 5 is provided on each of the right outer side and the left outer side of the body 2.
A prime mover 6 is mounted at the rear of the machine body 2. The prime mover 6 is an engine, a motor, or the like. In the embodiment, an engine is employed. A driver's seat 8 is provided at the rear of the cabin 3.

In all the embodiments of the present invention, the front side (left side in FIG. 4) of the driver seated on the driver's seat 8 of the work machine 1 is the front side, the rear side of the driver (right side in FIG. 4) is the back side, and the driver The left side (front side in FIG. 4) is the left side, and the right side of the driver (back side in FIG. 4) is the right side. The horizontal direction which is the direction orthogonal to the front and rear will be described as the body width direction.
The work device 4 includes a boom 10, a work tool 11, a lift link 12, a control link 13, a boom cylinder 14, and a bucket cylinder 15.

  The boom 10 is provided on the right and left sides of the cabin 3 so as to be swingable up and down. The work tool 11 is, for example, a bucket, and the bucket 11 is provided at the tip (front end) of the boom 10 so as to be swingable up and down. The lift link 12 and the control link 13 support the base part (rear part) of the boom 10 so that the boom 10 can swing up and down. The boom cylinder 14 raises and lowers the boom 10 by expanding and contracting. The bucket cylinder 15 swings the bucket 11 by expanding and contracting.

The front portions of the left and right booms 10 are connected to each other by a deformed connection pipe (front connection pipe). The bases (rear parts) of the booms 10 are connected by a circular connection pipe (rear connection pipe).
The lift link 12, the control link 13, and the boom cylinder 14 are respectively provided on the left side and the right side of the body 2 corresponding to the left and right booms 10.

  The lift link 12 is provided in the longitudinal direction at the rear of the base of each boom 10. The upper portion (one end side) of the lift link 12 is pivotally supported around the horizontal axis via a pivot shaft 16 (first pivot shaft) near the rear portion of the base of each boom 10. Further, the lower portion (the other end side) of the lift link 12 is pivotally supported around the horizontal axis via a pivot shaft 17 (second pivot shaft) near the rear portion of the machine body 2. The second pivot shaft 17 is provided below the first pivot shaft 16.

  The upper part (one end side) of the boom cylinder 14 is pivotally supported about a horizontal axis via a pivot shaft 18 (third pivot shaft). The third pivot shaft 18 is the base of each boom 10 and is provided in front of the first pivot shaft 16. The lower part (the other end side) of the boom cylinder 14 is pivotally supported about a horizontal axis via a pivot shaft 19 (fourth pivot shaft). The fourth pivot shaft 19 is provided near the lower part of the rear part of the machine body 2 and below the third pivot shaft 18.

  The control link 13 is provided in front of the lift link 12. One end of the control link 13 is pivotally supported about a horizontal axis via a pivot shaft 20 (fifth pivot shaft). The fifth pivot shaft 20 is provided on the body 2. The other end of the control link 13 is pivotally supported about a horizontal axis via a pivot shaft 21 (sixth pivot shaft). The sixth pivot shaft 21 is the boom 10 and is provided in front of the second pivot shaft 17 and above the second pivot shaft 17.

  By extending and retracting the boom cylinder 14, each boom 10 is moved around the first pivot shaft 16 so that the base of each boom 10 is supported by the lift link 12 and the control link 13 and the tip of each boom 10 is raised and lowered. Swings up and down. The control link 13 swings up and down around the fifth pivot shaft 20 as each boom 10 swings up and down. The lift link 12 swings back and forth around the second pivot shaft 17 as the control link 13 swings up and down.

  The bucket 11 can be attached to and detached from the mounting device 24 pivotally supported on the front portion (tip portion) of each boom 10. Instead of the bucket 11, another work tool can be mounted on the mounting device 24. Another working tool is an attachment (preliminary attachment) such as a hydraulic crusher, a hydraulic breaker, an angle bloom, an earth auger, a pallet fork, a sweeper, a mower, and a snow blower.

The bucket cylinder 15 is arranged near the front part of each boom 10. By expanding and contracting the bucket cylinder 15, the bucket 11 is swung.
In the present embodiment, the left and right traveling devices 5 are wheel-type traveling devices having front wheels 5F and rear wheels 5R. Note that a crawler type (including a semi-crawler type) traveling device may be employed as the traveling device 5.

FIG. 1 is a schematic diagram of a hydraulic system provided in a work machine.
As shown in FIG. 1, the hydraulic system 30 is a system that can move a spare actuator (hydraulic actuator) 31 that can actuate a spare attachment. The hydraulic system 30 includes a first hydraulic pump P1, a second hydraulic pump P2, a third pump P3, a first control valve 32, a connection portion 33, a first operation valve 34, and a second operation valve 35. It has.

  The first hydraulic pump P1 is a pump that is driven by the power of the prime mover 6, and is a constant capacity gear pump. The first hydraulic pump P <b> 1 can discharge the hydraulic oil stored in the hydraulic oil tank 22. A first oil passage 40 is provided at a discharge port (discharge port) that discharges hydraulic oil in the first hydraulic pump P1. Specifically, the first oil passage 40 is constituted by a pipe such as a steel pipe, and one end of the first oil passage 40 is connected to the discharge port and the other end is connected to the connection portion 33.

  The second hydraulic pump P2 is a pump that is driven by the power of the prime mover 6, and is a pump installed at a position different from the first hydraulic pump P1. The second hydraulic pump P2 is also a constant capacity type gear pump. The second hydraulic pump P <b> 2 can discharge the hydraulic oil stored in the hydraulic oil tank 22. A second oil passage 41 is provided at a discharge port (discharge port) that discharges hydraulic oil in the second hydraulic pump P2. Specifically, the second oil passage 41 is constituted by a pipe such as a steel pipe, one end of the second oil passage 41 is connected to the discharge port of the second hydraulic pump P2, and the other end is the first oil passage. 40.

  The third hydraulic pump P3 is a pump that is driven by the power of the prime mover 6, and is a pump installed at a position different from the first hydraulic pump P1 and the second hydraulic pump P2. The third hydraulic pump P3 is also a constant capacity type gear pump. The third hydraulic pump P3 can discharge the hydraulic oil stored in the hydraulic oil tank 22. A third oil passage 43 is provided at a discharge port (discharge port) that discharges hydraulic oil in the third pump. In particular, the third hydraulic pump P3 discharges hydraulic oil mainly used for control. For convenience of explanation, the hydraulic oil discharged from the third hydraulic pump P3 is called pilot oil, and the pressure of the pilot oil is called pilot pressure.

  The first control valve 32 is a valve that controls the preliminary actuator 31, and is constituted by a direct-acting spool type three-position switching valve. Specifically, the first control valve 32 can be switched between a neutral position 32a, a first position 32b, and a second position 32c according to the pilot pressure. The first control valve 32 has a structure that is switched to the neutral position 32a by a spring when a predetermined pilot pressure is not applied.

  The connecting portion 33 is constituted by a joint that connects the auxiliary actuator 31. The connection part 33 has the 1st pipe line 33a, the 2nd pipe line 33b, and the non-return valve 33c connected to the 1st pipe line 33a and the 2nd pipe line 33b. A connection port 33d to which a hydraulic hose or the like connected to the preliminary actuator 31 is connected is formed at one end of the first pipeline 33a and the second pipeline 33b. Two connection ports 33e and 33f to which the first oil passage 40 is connected are formed at the other ends of the first conduit 33a and the second conduit 33b, respectively. For convenience of explanation, at the other ends of the first pipeline 33a and the second pipeline 33b, one connection port is referred to as a first connection port 33e, and the other connection port is referred to as a second connection port 33f.

A first control valve 32 is connected to the middle portion of the first oil passage 40. In the first oil passage 40, the first control valve 32 is connected between the first hydraulic pump P <b> 1 and the connecting portion 44.
In addition, the connection part 44 is a part which connects the 1st oil path 40 and the 2nd oil path 41, Comprising: It is comprised from the joint.
Specifically, with respect to the first oil passage 40, the first section 40 a from the first hydraulic pump P 1 to the first control valve 32 is connected to the input port of the first control valve 32. Regarding the first oil passage 40, a second section 40 b extending from the first control valve 32 to the first connection port 33 e is connected to the first output port of the first control valve 32. Regarding the first oil passage 40, a third section 40c extending from the first control valve 32 to the second connection port 33f is connected to the second output port.

  A first relief oil passage 50 is connected to the second section 40 b, and a relief valve 51 is connected to the first relief oil passage 50. A second relief oil passage 52 is connected to the third section 40 c, and a relief valve 53 is connected to the second relief oil passage 52. Further, a bypass oil passage 54 that branches from the first section 40 a and communicates with the connection port of the first control valve 32 is provided. A first escape oil passage 50 and a second escape oil passage 52 are connected to the bypass oil passage 54. The bypass oil passage 54 is also connected to a discharge oil passage 56 that returns the hydraulic oil to the hydraulic oil tank 22.

  A first relief valve 57 is provided in the first section 40 a of the first oil passage 40. Specifically, the first relief valve 57 is connected to the bypass oil passage 54 connected to the first section 40a. In addition, by providing the first relief valve 57 in the bypass oil passage 54, the first relief valve 57 is connected to the first section 40a, but the first relief valve 57 is directly connected to the first section 40a. You may connect.

The first relief valve 57 is a valve that lowers the pressure in the first section 40a when the hydraulic oil pressure in the first section 40a becomes equal to or higher than a predetermined value. When the first relief valve 57 is operated, the hydraulic oil flows through the bypass oil passage 54 and flows into the discharge oil passage 56.
The first operation valve 34 is a valve that switches the position of the first control valve 32, and is composed of a proportional solenoid valve. The input port of the first operation valve 34 is connected to the third oil passage 43. The output port of the first operation valve 34 is connected to the first pilot oil passage 45. The first pilot oil passage 45 is connected to the first pressure receiving portion 32 d of the first control valve 32.

The second operation valve 35 is a valve that switches the position of the first control valve 32, and is composed of a proportional solenoid valve. The input port of the second operation valve 35 is connected to the third oil passage 43. The output port of the second operation valve 35 is connected to the second pilot oil passage 46. The second pilot oil passage 46 is connected to the second pressure receiving portion 33 e of the first control valve 32.
The operation of the first operation valve 34 and the second operation valve 35 is performed by a control unit (controller) 60 composed of a CPU or the like. An operation member 61 is connected to the control unit 60. The operation member 61 is configured by a switch such as a swingable seesaw type switch, a slidable slide type switch, or a pushable push type switch.

  An operation signal corresponding to the operation amount of the switch is input to the control unit 60. When the switch is operated to one side, the control unit 60 outputs a first command signal corresponding to the operation amount when operated to one side to the first operation valve 34. Then, the solenoid 34 a of the first operation valve 34 is excited by the first command signal, and a pilot pressure proportional to the operation amount of the switch flows through the first pilot oil passage 45. The pilot pressure acts on the first pressure receiving portion 32d of the first control valve 32, and the first control valve 32 can be operated to the first position 32b in proportion to the operation amount of the switch.

  When the switch is operated to the other side, the control unit 60 outputs a second command signal corresponding to the operation amount when operated to the other side to the second operation valve 35. Then, the solenoid 35a of the second operation valve 35 is excited by the second command signal, and a pilot pressure proportional to the operation amount of the switch is applied to the second pilot oil passage 46. The pilot pressure acts on the second pressure receiving portion 32e of the first control valve 32, and the first control valve 32 can be operated to the second position 32c in proportion to the operation amount of the switch.

As described above, according to the hydraulic system 30, by switching the first control valve 32 to the first position 32b or the second position 32c, hydraulic oil is supplied to the spare actuator 31 connected to the connecting portion 33, and the spare actuator 31 is Can be operated.
Now, in the hydraulic system 30, the amount of hydraulic oil supplied to the reserve actuator 31 can be increased. That is, the hydraulic oil discharged from the first hydraulic pump P1 and the hydraulic oil discharged from the second hydraulic pump P2 can be combined and supplied to the preliminary actuator 31.

  The hydraulic system 30 includes a second control valve (high flow valve) 65 and a switching valve (high flow switching valve) 66. The second control valve 65 is a valve that can set the flow rate of the hydraulic oil flowing in the second oil passage 41, and is a two-position switching valve that operates with a pilot pressure. The second control valve 65 can be switched to two switching positions (first position 65a and second position 65b) by pilot pressure. The second control valve 65 is connected to the middle part of the second oil passage 41. The second control valve 65 is closed at the first position 65a, and the flow rate of the hydraulic oil flowing in the second oil passage 41 is made zero. The second control valve 65 is opened at the second position 65b, and the flow rate of the hydraulic oil flowing through the second oil passage 41 is changed from zero to a predetermined flow rate. In other words, the second control valve 65 blocks the second oil passage 41 when it is in the first position 65a, and allows the second oil passage 41 to communicate when it is in the second position 65b.

  The switching valve 66 is a valve that operates the second control valve 65 by switching, and is constituted by an electromagnetic two-position switching valve 66. The switching valve 66 can be switched between a first position 66a and a second position 66b. The switching valve 66 is connected to the third oil passage 43. When the switching valve 66 is in the first position 66a, the pilot pressure is not applied to the pressure receiving portion 65c of the second control valve 65, and the second control valve 65 is set to the first position 66a. When the switching valve 66 is in the second position 66b, the pilot pressure is applied to the pressure receiving portion 66c of the second control valve 65, and the second control valve 65 is set to the first position 65b.

  Switching between the first position 66 a and the second position 66 b in the switching valve 66 is performed by the control unit 60. When the switch is operated to the maximum position, the control unit 60 continuously excites the solenoid 66c of the switching valve 66. Then, the switching valve 66 is switched to the second position 66b. When the switch is not at the maximum position, the control unit 60 demagnetizes the solenoid 66c of the switching valve 66. Then, the switching valve 66 is switched to the first position 66a.

  According to the hydraulic system 30 described above, when the pilot pressure is applied to the pressure receiving portion of the second control valve 65 by moving the switching valve 66 to the second position 66b, the second control valve 65 becomes the second position 65b. As a result, the hydraulic oil discharged from the second hydraulic pump P2 passes through the second control valve 65, and the hydraulic oil flows to the connecting portion 44 that is the end of the second oil passage 41. And in the connection part 44, the hydraulic oil which flowed from the 2nd oil path 41, and the hydraulic oil which flows through the 2nd area 40b in the 1st oil path 40 flow, and flow toward the connection part 33, and hydraulic oil flows. Increase the amount. On the other hand, when the pilot pressure is not applied to the pressure receiving portion of the second control valve 65 by setting the switching valve 66 to the first position 66a, the second control valve 65 becomes the first position 65a. As a result, the hydraulic oil discharged from the second hydraulic pump P2 is blocked by the second control valve 65, and the hydraulic oil that cannot pass through the second control valve 65 returns to the hydraulic oil tank 22. As a result, only the hydraulic oil flowing through the second section 40 b of the first oil passage 40 flows toward the connection portion 33.

  A second relief valve 70 is provided in the middle of the second oil passage 41. Specifically, the second relief valve 70 is connected to the second oil passage 41 between the second control valve 65 and the connecting portion 44 (sometimes referred to as the first section 41a). That is, in the second oil passage 41, the second relief valve 70 is connected to the downstream side of the second control valve 65. More specifically, the second oil passage 41 branches off in the first section 41 a and communicates with the hydraulic oil tank 22. A second relief valve 70 is connected to a communication oil passage 74 that communicates from the branch portion to the hydraulic oil tank 22.

In this embodiment, as described above, the second oil passage 41 is branched and the second relief valve 70 is provided in the communication oil passage 74 that connects the branch portion and the hydraulic oil tank 22. As shown, the second relief valve 70 may be directly connected to the first section 41a without branching the second oil passage 41.
The second relief valve 70 is a valve that lowers the pressure in the first section 41a when the pressure of the hydraulic oil in the first section 41a becomes equal to or higher than a predetermined value. The set pressure of the second relief valve 70 is equal to or higher than the pressure necessary for operating the auxiliary actuator. The set pressure of the second relief valve 70 is set lower than the set pressure of the set pressure of the first relief valve 57. That is, the set pressure of the second relief valve is set to be equal to or higher than the pressure necessary for operating the auxiliary actuator (required set pressure) and lower than the set pressure of the first relief valve 57. For example, the set pressure of the first relief valve 57 is set to 24.5 MPa, and the set pressure of the second relief valve 70 is set to 20 MPa. In addition, the numerical value of the setting pressure of the 1st relief valve 57 is not limited.

  In the first section 41 a of the second oil passage 41, a check valve 72 is provided on the upstream side of the second relief valve 70, that is, between the second relief valve 70 and the connecting portion 44. The check valve 72 allows the flow of hydraulic oil in the direction from the second oil passage 41 to the first oil passage 40. On the other hand, it is a valve that blocks the flow of hydraulic oil in the direction from the first oil passage 40 to the second oil passage 41. Since the check valve 72 is provided in this way, in a state where the amount of hydraulic oil is not increased (a state where the second control valve 65 is switched to the first position 65a), Backflow can be prevented. That is, it is possible to prevent the pressure of the hydraulic oil supplied to the reserve actuator 31 from being lowered as a result of the second relief valve 70 being actuated by the hydraulic oil flowing backward from the first oil passage 40 to the second oil passage 41. it can.

FIG. 3A is a diagram showing the relationship between the hydraulic oil pressure and the flow rate in a conventional example (comparative example) in which the second relief valve 70 or the like is not provided in the second oil passage 41. FIG. 3B is a diagram illustrating the relationship between the hydraulic oil pressure and the flow rate in the embodiment in which the second relief valve 70 and the like are provided in the second oil passage 41.
As shown in FIG. 3A, in the comparative example, both the first hydraulic pump P1 and the second hydraulic pump P2 can ensure the flow rate of the hydraulic oil even when the hydraulic oil pressure is high. That is, the hydraulic oil can be discharged by both pumps even in the high pressure-high flow rate region. However, although there are many types of spare attachments, if a high pressure is required, the hydraulic fluid can be operated sufficiently even if the flow rate of the hydraulic oil is relatively small. In other words, in the high pressure-high flow rate region, the actual situation is that the horsepower consumed increases.

  On the other hand, as shown in FIG. 3B, in the embodiment, since the flow rate in the high pressure-high flow rate region can be cut by the second relief valve 70, the consumed horsepower of the pump can be suppressed. That is, although the first hydraulic pump P1 and the second hydraulic pump P2 are constant displacement pumps, as shown in FIG. 3C, the pressure-flow rate characteristic can be made substantially the same as the variable displacement pump with horsepower control. .

In the second pump, the relationship between the pressure and the flow rate (the slope of the first line L1) can be set based on the override characteristic of the second relief valve 70. It is possible to employ the second relief valve 70 in which the relationship between the pressure and the flow rate (inclination of the second line L2) in the first line L1 in FIG. 3B and the variable displacement pump with horsepower control shown in FIG. preferable.
The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  Note that the second relief valve 70 may be provided not in the first section 41a of the second oil passage 41 but in the fifth section 41b from the second hydraulic pump P2 to the second control valve 65 as shown in FIG. 2B. . That is, the second relief valve 70 may be connected upstream of the second control valve 65 in the second oil passage 41. More specifically, in the second oil passage 41, the second relief valve 70 may be provided in a communication oil passage 75 that branches in the fifth section 41 b and communicates the branch portion and the hydraulic oil tank 22.

  In the embodiment described above, the opening degree of the first operation valve 34 and the second operation valve 35 is changed based on the operation of the operation member 61, and thereby the first control valve 32 is controlled. The method of operating the valve 32 is not limited to the embodiment described above. For example, the operation member 61 may be configured with a joystick or the like, and the first control valve 32 may be operated with the joystick. The operation of the second control valve (high flow valve) may also be performed with a joystick.

  In the embodiment described above, the second control valve 65 is a two-position switching valve capable of communicating or blocking the second oil passage 41, but may be other valves. For example, as shown in FIG. 2C, an oil passage 80 branched from the second oil passage 41 may be provided, and a second control valve 65 constituted by a two-position switching valve may be connected to the middle portion of the oil passage 80. The oil passage 80 is preferably connected to the hydraulic oil tank 22.

  In this case, when the second control valve 65 is switched to one position 65e, the input port and the output port of the second control valve 65 are connected, and the hydraulic oil in the second oil passage 41 passes through the oil passage 80. It flows to the hydraulic oil tank 22. When the second control valve 65 is switched to the other position 65f, the input port and the output port of the second control valve 65 are shut off, and the hydraulic oil in the second oil passage 41 does not flow to the hydraulic oil tank 22. That is, by providing the second control valve 65 constituted by a two-position switching valve in the oil passage 80 branched from the second oil passage 41, the amount of hydraulic oil can be increased or decreased. The second control valve 65 may not be a two-position switching valve but may be an electromagnetic proportional valve.

DESCRIPTION OF SYMBOLS 1 Working machine 2 Airframe 4 Working device 5 Traveling device 22 Hydraulic oil tank 30 Hydraulic system 31 Preliminary actuator (hydraulic actuator)
33 connecting portion 40 first oil passage 41 second oil passage 43 third oil passage 44 connecting portion 57 first relief valve 65 second control valve (high flow valve)
66 Switching valve (High flow switching valve)
70 Second relief valve 72 Check valve 74 Communicating oil passage L1 First line L2 Second line

Claims (4)

A hydraulic actuator;
A connection for connecting the hydraulic actuator;
A constant displacement pump, a first hydraulic pump for discharging hydraulic oil;
A constant displacement pump that discharges hydraulic oil and is different from the first hydraulic pump;
A first oil passage connecting the connecting portion and the first hydraulic pump;
A first control valve provided in the middle of the first oil passage;
A second oil path having one end connected between the hydraulic actuator and the first control valve in the first oil path, and the other end connected to the second hydraulic pump ;
A second control valve provided in the second oil passage and capable of setting a flow rate of hydraulic oil flowing through the second oil passage;
A first relief valve connected between the first hydraulic pump definitive in the first oil passage and said first control valve,
A second relief valve connected between said one end definitive in the second oil passage and the second control valve,
The working machine's hydraulic system. 2. The hydraulic system for a working machine according to claim 1, wherein a set pressure of the second relief valve is set lower than a set pressure of the first relief valve. A check that allows the flow of hydraulic oil in the direction from the second oil path to the first oil path and prevents the flow of hydraulic oil in the direction from the first oil path to the second oil path. The hydraulic system for a working machine according to claim 1 or 2 , further comprising a valve. A working machine comprising the hydraulic system for a working machine according to any one of claims 1 to 3 ,
The aircraft,
A working device provided on the airframe;
Traveling devices arranged on the right and left sides of the aircraft;
Work machine equipped with.

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