JP6657329B2 - Working machine hydraulic system - Google Patents

Description

The present invention relates to a skid steer loader, the hydraulic system of the working machine such as a compact track loaders.

BACKGROUND ART Conventionally, it is known that a working machine such as a skid steer loader and 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 Document 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. 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 one 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, 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, but a region where the pressure of the hydraulic oil is high is high. In this system, the flow rate can be increased more than necessary. Therefore, in the hydraulic system of Patent Literature 1, the horsepower consumed by the pump (referred to as consumed horsepower) may be too large.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems of the related art, and is capable of supplying a proper hydraulic oil to a hydraulic actuator and suppressing a hydraulic power consumption of a working machine capable of suppressing horsepower consumption of a pump. an object of the present invention is to provide a system.

The technical means of the present invention for solving the technical problem is as follows.
Hydraulic system working machine is a fixed displacement pump, a first hydraulic pump that discharges hydraulic oil, a fixed displacement pump, and and the first hydraulic pump discharges the hydraulic oil A different second hydraulic pump, a first oil passage connected to the first hydraulic pump, a first control valve provided at an intermediate portion of the first oil passage, and a first control in the first oil passage. A connecting portion provided downstream of the valve, a first relief valve connected upstream of the first control valve in the first oil passage, and a second connecting the second hydraulic pump and the connecting portion. A second oil passage, a second control valve provided in a middle part of the second oil passage, and a second relief provided in a communication oil passage branched from an upstream side of the second control valve in the second oil passage. And a valve .

Hydraulic system working machine, prior Symbol an oil passage relief capable of discharging the connected and the hydraulic oil in the first oil passage to the first oil passage, and a third relief valve provided in the relief oil passage, the Have.
Hydraulic system working machine is provided with a connecting portion for connecting the hydraulic actuator, said first oil passage includes a first section extending from said first hydraulic pump to the first control valve, said from the first control valve A second section extending to the connection section; and a third section extending from the first control valve to the connection section separately from the second section, wherein the relief oil passage is connected to the second section and the second section is connected to the second section. It includes a first relief oil passage provided with a three relief valve, and a second relief oil passage connected to the third section and provided with the third relief valve.

The hydraulic actuator is a preliminary actuator that operates a preliminary attachment attached to a tip of a boom, and the first control valve is a valve that controls hydraulic oil supplied to the preliminary actuator.
The set pressure of the second relief valve is set lower than the set pressure of the first relief valve.

  ADVANTAGE OF THE INVENTION According to this invention, while being able to supply a suitable hydraulic oil 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 showing the example which connected the 2nd relief valve to the 1st section of the 2nd channel. It is a figure showing the example which connected the 2nd relief valve to the 2nd section of the 2nd channel. It is a figure showing the example which connected the 2nd control valve to the 2nd channel. It is a figure which shows the pressure-flow rate relationship of the conventional 1st pump and 2nd pump. FIG. 3 is a diagram showing a pressure-flow rate relationship of a first pump and a second pump of the present invention. 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 showing the skid steer loader which is an example of the work machine concerning the present invention.

Hereinafter, preferred embodiments of a hydraulic system of a working machine according to the present invention and a working machine including the hydraulic system will be described with reference to the drawings as appropriate.
FIG. 4 shows a skid steer loader 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 and a backhoe.

The work machine 1 includes a body 2, a cabin 3, a work device 4, and a traveling device 5.
The cabin 3 is mounted on the body 2, and the working device 4 is mounted on the body 2. The traveling devices 5 are respectively provided on the right outside and the left outside of the body 2.
A prime mover 6 is mounted on a rear portion of the 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 a rear portion in the cabin 3.

In all the embodiments of the present invention, the front (left side in FIG. 4) of the driver sitting on the driver's seat 8 of the work machine 1 is forward, the rear side of the driver (right side in FIG. 4) is rear, and the driver is The left side (the front side in FIG. 4) is described as the left side, and the right side (the rear side in FIG. 4) of the driver is the right side. A horizontal direction that is a direction orthogonal to the front and rear will be described as a body width direction.
The working device 4 includes a boom 10, a work implement 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 vertically swingable. The work implement 11 is, for example, a bucket, and the bucket 11 is a tip (a front end) of the boom 10.
Are provided to be able to swing up and down. The lift link 12 and the control link 13 support a base (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 an odd-shaped connecting pipe (front connecting pipe). The bases (rear portions) of the booms 10 are connected by a circular connecting pipe (rear connecting pipe).
The lift link 12, the control link 13, and the boom cylinder 14 are provided on the left and right sides of the body 2 corresponding to the left and right booms 10, respectively.

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

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

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

  By expanding and contracting the boom cylinder 14, each boom 10 rotates around the first pivot shaft 16 so that the tip of each boom 10 moves up and down while the base of each boom 10 is supported by the lift link 12 and the control link 13. Rocks up and down. The control link 13 swings up and down around the fifth pivot 20 as each boom 10 swings up and down. The lift link 12 swings back and forth around the second pivot 17 with the vertical swing of the control link 13.

  The bucket 11 can be attached to and detached from a mounting device 24 pivotally supported at the front part (tip part) of each boom 10. Another work tool can be mounted on the mounting device 24 instead of the bucket 11. Another working tool is, for example, 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 cylinders 15 are respectively arranged near the front of each boom 10. By expanding and contracting the bucket cylinder 15, the bucket 11 is swung.
In the present embodiment, a wheel-type traveling device having a front wheel 5F and a rear wheel 5R is adopted as each of the left and right traveling devices 5. The traveling device 5 may be a crawler type (including a semi-crawler type) traveling device.

FIG. 1 is a schematic diagram of a hydraulic system provided in a working machine.
As shown in FIG. 1, the hydraulic system 30 is a system that can move a preliminary actuator (hydraulic actuator) 31 that can operate a preliminary 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 unit 33, a first operation valve 34, a second operation valve 35, It has.

  The first hydraulic pump P1 is a pump driven by the power of the prime mover 6, and is constituted by a constant displacement gear pump. The first hydraulic pump P1 can discharge hydraulic oil stored in the hydraulic oil tank 22. A first oil passage 40 is provided at a discharge port (discharge port) for discharging hydraulic oil in the first hydraulic pump P1. Specifically, the first oil passage 40 is formed of 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 driven by the power of the prime mover 6, and is a pump installed at a different position from the first hydraulic pump P1. The second hydraulic pump P2 is also constituted by a constant displacement gear pump. The second hydraulic pump P2 is capable of discharging the hydraulic oil stored in the hydraulic oil tank 22. A second oil passage 41 is provided at a discharge port (discharge port) for discharging hydraulic oil in the second hydraulic pump P2. Specifically, the second oil passage 41 is formed of a pipe such as a steel pipe, and one end of the second oil passage 41 is connected to a discharge port of the second hydraulic pump P2, and the other end is connected to the first oil passage. 40.

  The third hydraulic pump P3 is a pump driven by the power of the prime mover 6, and is a pump installed at a different position from the first hydraulic pump P1 and the second hydraulic pump P2. The third hydraulic pump P3 is also constituted by a constant displacement 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) for discharging 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 referred to as pilot oil, and the pressure of the pilot oil is referred to as pilot pressure.

  The first control valve 32 is a valve for controlling the preliminary actuator 31 and is constituted by a direct-acting spool type three-position switching valve. Specifically, the first control valve 32 is switchable between a neutral position 32a, a first position 32b, and a second position 32c according to the pilot pressure. The first control valve 32 is configured to switch to the neutral position 32a by a spring when a predetermined pilot pressure is not applied.

  The connection part 33 is formed of a joint for connecting the spare actuator 31. The connection part 33 has a first pipeline 33a, a second pipeline 33b, and a check valve 33c connected to the first pipeline 33a and the second pipeline 33b. At one end of the first pipeline 33a and the second pipeline 33b, a connection port 33d to which a hydraulic hose or the like connected to the preliminary actuator 31 is connected is formed. Two connection ports 33e and 33f to which the first oil passage 40 is connected are formed at the other end of the first pipeline 33a and the second pipeline 33b, respectively. For convenience of explanation, at the other end of the first conduit 33a and the second conduit 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.

The first control valve 32 is connected to a middle part of the first oil passage 40. In the first oil passage 40, the first control valve 32 is connected between the first hydraulic pump P1 and the connecting portion 44. The connecting portion 44 connects the first oil passage 40 and the second oil passage 41, and is formed of a joint or the like.
Specifically, with respect to the first oil passage 40, a first section 40a from the first hydraulic pump P1 to the first control valve 32 is connected to an input port of the first control valve 32. Regarding the first oil passage 40, a second section 40b from the first control valve 32 to the first connection port 33e is connected to a first output port of the first control valve 32. Further, in the first oil passage 40, a third section 40c 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 40b, 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 40c, and a relief valve 53 is connected to the second relief oil passage 52. In addition, a bypass oil passage 54 that branches off from the first section 40a and communicates with a connection port of the first control valve 32 is provided. A first relief oil passage 50 and a second relief 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 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, a first relief valve 57 is connected to the bypass oil passage 54 connected to the first section 40a. 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 pressure of the hydraulic oil in the first section 40a becomes equal to or higher than a predetermined value. The hydraulic oil when the first relief valve 57 is operated flows through the bypass oil passage 54 to the discharge oil passage 56.
The first operation valve 34 is a valve for switching the position of the first control valve 32, and is constituted by 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 32d of the first control valve 32.

The second operation valve 35 is a valve for switching the position of the first control valve 32, and is constituted by 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 33e 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 including a CPU and 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 switch, a slideable slide switch, or a pushable push 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 the switch is operated to one side to the first operation valve 34. Then, the solenoid 34a 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. Then, 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 the other side is operated 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. Then, 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, the operating oil is supplied to the preliminary actuator 31 connected to the connection portion 33, and the preliminary actuator 31 is Can operate.
Now, in the hydraulic system 30, the amount of hydraulic oil supplied to the preliminary 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 supplied to the spare actuator 31 together.

  The hydraulic system 30 includes a second control valve (high flow switching 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 hydraulic oil flowing through the second oil passage 41, and is a two-position switching valve that operates with pilot pressure. The second control valve 65 can be switched between two switching positions (first position 65a and second position 65b) by pilot pressure. The second control valve 65 is connected to a middle part of the second oil passage 41. The second control valve 65 is closed at the first position 65a, and reduces the flow rate of the hydraulic oil flowing through the second oil passage 41 to zero. Further, the second control valve 65 is opened at the second position 65b, and changes the flow rate of the working oil flowing through the second oil passage 41 from zero to a predetermined flow rate. In other words, the second control valve 65 shuts off the second oil passage 41 when in the first position 65a, and connects the second oil passage 41 when in the second position 65b.

  The switching valve 66 is a valve that operates the second control valve 65 by switching, and is configured by an electromagnetic two-position switching valve 66. The switching valve 66 is switchable 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 at 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 at 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 66a and the second position 66b 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 switches 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 switches to the first position 66a.

  According to the above hydraulic system 30, when the pilot pressure is applied to the pressure receiving portion of the second control valve 65 by setting the switching valve 66 to the second position 66b, the second control valve 65 is set to 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 flows into the connecting portion 44, which is the end of the second oil passage 41. Then, at the connecting portion 44, the operating oil flowing from the second oil passage 41 and the operating oil flowing through the second section 40 b of the first oil passage 40 are combined and flow toward the connecting portion 33, and the operating 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 is set to the first position 65a. As a result, the hydraulic oil discharged from the second hydraulic pump P2 is shut off 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 40b 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, a 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 a first section 41a). That is, the second relief valve 70 is connected downstream of the second control valve 65 in the second oil passage 41. 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 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 connecting 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 required to operate the preliminary 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 (required set pressure) required to operate the preliminary actuator and equal to or 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. The numerical value of the set pressure of the first relief valve 57 is not limited.

  In the first section 41a of the second oil passage 41, a check valve 72 is provided upstream 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 a 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 from the first oil passage 40 to the second oil passage 41. Since the check valve 72 is provided in this manner, in a state in which the amount of hydraulic oil is not increased (a state in which the second control valve 65 is switched to the first position 65a), the amount of hydraulic oil from the first oil passage 40 is reduced. Backflow can be prevented. In other words, it is possible to prevent the second relief valve 70 from being operated by the hydraulic oil flowing backward from the first oil passage 40 to the second oil passage 41, thereby preventing the pressure of the hydraulic oil supplied to the spare actuator 31 from decreasing. it can.

FIG. 3A is a diagram showing the relationship between the pressure and the flow rate of hydraulic oil in a conventional example (comparative example) in which the second relief valve 70 and the like are not provided in the second oil passage 41. FIG. 3B is a diagram illustrating a relationship between the pressure and the flow rate of the working oil 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 working oil even when the pressure of the working oil is high. That is, both pumps can discharge the hydraulic oil even in a high pressure-high flow rate region. However, although there are many types of the pre-attachment, when a high pressure is required, the operation is sufficient even if the flow rate of the hydraulic oil is relatively small. That is, in the high pressure-high flow rate region, the horsepower consumed is actually large.

  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 horsepower consumption 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 characteristics 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 inclination 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 first line L1 in FIG. 3B and the relationship between the pressure and the flow rate (the inclination of the second line L2) in the variable displacement pump with horsepower control shown in FIG. preferable.
The embodiments disclosed this time are to be considered in all respects as illustrative 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 in the fifth section 41b from the second hydraulic pump P2 to the second control valve 65, as shown in FIG. 2B, instead of the first section 41a of the second oil passage 41. . That is, a second relief valve 70 may be connected upstream of the second control valve 65 in the second oil passage 41. More specifically, a second relief valve 70 may be provided in a communication oil passage 75 that branches off in the fifth section 41 b in the second oil passage 41 and connects the branch portion to the hydraulic oil tank 22.

  In the above-described embodiment, the opening degrees of the first operation valve 34 and the second operation valve 35 are changed based on the operation of the operation member 61, whereby 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 by a joystick or the like, and the first control valve 32 may be operated by the joystick. Also, the operation of the second control valve (high flow valve) may be performed with a joystick.

  In the above-described embodiment, the second control valve 65 is a two-position switching valve capable of communicating or blocking the second oil passage 41, but may be another valve. 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 an intermediate portion of the oil passage 80. The oil passage 80 is desirably connected to the hydraulic oil tank 22.

  In this case, when the second control valve 65 is switched to the one position 65e, the input port and the output port of the second control valve 65 are connected, and the operating 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 into 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 need not be a two-position switching valve, but may be an electromagnetic proportional valve.

DESCRIPTION OF SYMBOLS 1 Working machine 2 Body 4 Working device 5 Traveling device 22 Hydraulic oil tank 30 Hydraulic system 31 Spare actuator (hydraulic actuator)
33 connection part 40 first oil passage 41 second oil passage 43 third oil passage 44 connecting part 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 communication oil passage L1 first line L2 second line

Claims (5)

A first hydraulic pump for discharging hydraulic oil, which is a constant displacement pump;
A second hydraulic pump that discharges hydraulic oil and is different from the first hydraulic pump;
A first oil passage connected to the first hydraulic pump,
A first control valve provided in the middle of the first oil passage;
A connecting portion provided in the first oil passage downstream of the first control valve;
A first relief valve connected to the first oil passage upstream of the first control valve;
A second oil passage connecting the second hydraulic pump and the connecting portion,
A second control valve provided in the middle of the second oil passage;
A second relief valve provided in a communication oil path branched from an upstream side of the second control valve in the second oil path;
The working machine is equipped with hydraulic system. A relief oil passage connected to the first oil passage and capable of discharging hydraulic oil in the first oil passage;
A third relief valve provided in the relief oil passage;
Working machine hydraulic system according to claim 1 which comprises a. It has a connection part for connecting the hydraulic actuator,
The first oil passage includes a first section from the first hydraulic pump to the first control valve, a second section from the first control valve to the connection section, and the second section separately from the second section. A third section from one control valve to the connection part,
The relief oil passage is connected to the second section and provided with a third relief valve. The first relief oil passage is connected to the third section and provided with a third relief valve. The hydraulic system for a working machine according to claim 2, further comprising an oil passage . The hydraulic actuator is a preliminary actuator that operates a preliminary attachment attached to the end of the boom,
The hydraulic system for a working machine according to claim 3, wherein the first control valve is a valve that controls hydraulic oil supplied to the preliminary actuator . The hydraulic system for a working machine according to any one of claims 1 to 3 , wherein a set pressure of the second relief valve is set lower than a set pressure of the first relief valve .

Images