JP2019173867A - Hydraulic system of work machine - Google Patents

Abstract

To easily operate a plurality of control valves (hydraulic actuators) in a series circuit.SOLUTION: A hydraulic system of a work machine includes a first control valve 20A controlling a first hydraulic actuator 14, a second control valve 20B disposed at a downstream side of the first control valve and controlling a second hydraulic actuator 17, a discharge oil passage 24b connected to the first control valve, and capable of discharging the hydraulic oil passing through the first control valve, a first oil passage 61 connecting the first control valve and the second control valve, and supplying a return oil as the hydraulic oil returning to the first control valve from the first hydraulic actuator, to the second control valve, a second oil passage 85 connecting the first control valve and the first hydraulic actuator, and supplying a supply oil as the hydraulic oil supplied to the first control valve, to the first hydraulic actuator, a third oil passage 110 connecting the first oil passage and the discharge passage, and a fourth oil passage 120 connected to the first oil passage, and supplying the return oil of the first oil passage to the second oil passage.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a hydraulic system and a control valve for a work machine such as a skid steer loader or a compact truck loader.

  Conventionally, Patent Document 1 is known as a hydraulic system for a working machine. The working machine disclosed in Patent Document 1 includes a boom, a bucket, a boom cylinder that operates the boom, a bucket cylinder that operates the bucket, a spare actuator that operates the spare attachment, and a first control valve that controls expansion and contraction of the boom cylinder. And a second control valve for controlling expansion and contraction of the bucket cylinder, and a third control valve for operating the auxiliary actuator.

JP 2010-270527 A

  In the working machine of Patent Document 1, when the spool of the first control valve is not operated, the hydraulic oil discharged from the pump passes through the inside of the first control valve, and the second control valve and the third control valve. Can be supplied. On the other hand, when the spool of the first control valve is operated, the hydraulic oil (return oil) returned from the boom cylinder to the first control valve can be supplied to the second control valve and the third control valve. . That is, in the hydraulic circuit of the working machine of Patent Document 1, the return oil returned from the upstream control valve (first control valve) is supplied to the downstream control valves (second control valve, third control valve). A series circuit is used. However, in the series circuit, it may be difficult to operate the downstream second control valve, the third control valve, or the like when the upstream control valve is operated.

  The present invention has been made to solve the above-described problems of the prior art, and provides a hydraulic system for a work machine that can easily operate a plurality of control valves (hydraulic actuators) in a series circuit. The purpose is to provide.

The technical means of the present invention for solving this technical problem is as follows.
The hydraulic system of the work machine includes a hydraulic pump that discharges hydraulic oil, a first hydraulic actuator, a second hydraulic actuator, a first control valve that controls the first hydraulic actuator, and a downstream side of the first control valve. And a second control valve that controls the second hydraulic actuator, a discharge oil passage that is connected to the first control valve and that can discharge the hydraulic oil that has passed through the first control valve, A first oil passage for supplying return oil, which is hydraulic oil that returns from the one hydraulic actuator to the first control valve, to the second control valve; and supply oil that is hydraulic oil supplied to the first control valve; A second oil path that supplies the first hydraulic actuator; a third oil path that connects the first oil path and the discharge oil path; and the first oil path that is connected to the first oil path. A fourth oil passage for supplying the return oil to the second oil passage; It is provided.

  A hydraulic pump that discharges hydraulic fluid; a first hydraulic actuator; a second hydraulic actuator; a first control valve that controls the first hydraulic actuator; and a downstream side of the first control valve; and A second control valve for controlling the second hydraulic actuator; a discharge oil passage connected to the first control valve and capable of discharging the hydraulic oil that has passed through the first control valve; the first control valve; and the second control valve. A first oil passage that is connected to a control valve and supplies return oil, which is hydraulic oil that returns from the first hydraulic actuator to the first control valve, to the second control valve; and the first control valve; A second oil passage connected to the first hydraulic actuator and supplying hydraulic oil supplied to the first control valve to the first hydraulic actuator; a first oil passage; A third oil passage connecting the drain oil passage and the front Is connected to the first oil passage, and, a, a fourth oil passage for supplying the return fluid of the first oil passage to the second oil passage.

The hydraulic system of the work machine includes a pressure increase unit that is connected to the discharge oil passage and increases the pressure of the discharge oil passage.
The first oil passage is connected to the first control valve and the first hydraulic actuator, the first connection oil passage through which the return oil flows, and the first control valve provided to the first connection oil passage. A first internal oil passage that communicates; and an external oil passage that communicates with the first internal oil passage and connects the first control valve and the second control valve. A second connection oil passage that connects the first control valve and the first hydraulic actuator and through which the supply oil flows, and a second internal oil passage that is provided in the first control valve and communicates with the second connection oil passage The third oil passage is an oil passage connecting the first internal oil passage and the discharge oil passage.

  The fourth oil path is an oil path different from the first oil path, and connects the external oil path of the first oil path and the first control valve; and the first control A third internal oil passage that is provided in the valve and communicates with the connection oil passage; and hydraulic oil that communicates with the third internal oil passage and passes through the connection oil passage and the third internal oil passage. And a return oil passage returning to the control valve.

  According to the present invention, a plurality of control valves (hydraulic actuators) can be easily operated in a series circuit.

It is a figure which shows the hydraulic system (hydraulic circuit) of a working machine. It is explanatory drawing explaining the flow of hydraulic oil. 1 is an overall view of a skid steer loader exemplified as a working machine.

Hereinafter, a preferred embodiment of a hydraulic system for a working machine according to the present invention will be described with reference to the drawings as appropriate.
First, the working machine will be described.
FIG. 3 shows a side view of the working machine according to the present invention. In FIG. 3, a skid steer loader is shown as an example of a work machine. However, the working machine according to the present invention is not limited to the skid steerer, and may be another type of loader working machine such as a compact truck loader. Moreover, a working machine other than the loader working machine may be used.

The work machine 1 includes a machine body (vehicle body) 2, a cabin 3, a work device 4, and travel devices 5A and 5B.
A cabin 3 is mounted on the body 2. A driver's seat 8 is provided at the rear of the cabin 3. In the embodiment of the present invention, the front side (left side in FIG. 3) of the driver seated on the driver's seat 8 of the work machine 1 is front, the rear side (right side in FIG. 3) is rearward, and the left side of the driver (FIG. 3). 3 on the left side and the driver's right side (the back side in FIG. 3) as the right side. The horizontal direction, which is a direction orthogonal to the front-rear direction, will be described as the body width direction. The direction from the central part of the airframe 2 toward the right part or the left part will be described as the outside of the airframe. In other words, the outward direction of the body is the direction of the body width and away from the body 2. The direction opposite to the outside of the aircraft will be described as the inside of the aircraft. In other words, the in-machine direction is the width direction of the machine body and the direction approaching the machine body 2.

  The cabin 3 is mounted on the airframe 2. The work device 4 is a device that performs work, and is mounted on the machine body 2. The traveling device 5 </ b> A is a device that travels the body 2, and is provided on the left side of the body 2. The traveling device 5 </ b> B is a device that travels the body 2, and is provided on the right side of the body 2. A prime mover 7 is provided at the rear of the machine body 2. The prime mover 7 is a diesel engine (engine). The prime mover 7 is not limited to an engine, and may be an electric motor or the like.

On the left side of the driver's seat 8, a travel lever 9L is provided. A travel lever 9 </ b> R is provided on the right side of the driver seat 8. The left traveling lever 9L operates the left traveling device 5A, and the right traveling lever 9R operates the right traveling device 5B.
The work device 4 includes a boom 10, a bucket 11, a lift link 12, a control link 13, a boom cylinder 14, and a bucket cylinder 17. The boom 10 is provided on the side of the body 2. The bucket 11 is provided at the tip (front end) of the boom 10. The lift link 12 and the control link 13 support the base (rear part) of the boom 10. The boom cylinder 14 drives the boom 10 up or down.

  Specifically, the lift link 12, the control link 13, and the boom cylinder 14 are provided on the side of the machine body 2. The upper part of the lift link 12 is pivotally supported by the upper part of the base part of the boom 10. The lower part of the lift link 12 is pivotally supported on the side part of the rear part of the airframe 2. The control link 13 is disposed in front of the lift link 12. One end of the control link 13 is pivotally supported at the lower part of the base portion of the boom 10, and the other end is pivotally supported by the body 2.

  The boom cylinder 14 is a hydraulic cylinder that raises and lowers the boom 10. The upper part of the boom cylinder 14 is pivotally supported by the front part of the base part of the boom 10. The lower part of the boom cylinder 14 is pivotally supported by the side part of the rear part of the body 2. When the boom cylinder 14 is expanded and contracted, the boom 10 is swung up and down by the lift link 12 and the control link 13. The bucket cylinder 17 is a hydraulic cylinder that swings the bucket 11. The bucket cylinder 17 connects the left part of the bucket 11 and the left boom, and connects the right part of the bucket 11 and the right boom. A spare attachment such as a hydraulic crusher, a hydraulic breaker, an angle bloom, an auger, a pallet fork, a sweeper, a mower, and a snow blower can be attached to the tip (front) of the boom 10 instead of the bucket 11. .

In the present embodiment, wheel type traveling devices 5A and 5B having front wheels 5F and rear wheels 5R are employed as the traveling devices 5A and 5B. Note that crawler type (including semi-crawler type) traveling devices 5A and 5B may be employed as the traveling devices 5A and 5B.
Next, a work system hydraulic circuit (work system hydraulic system) provided in the skid steer loader 1 will be described.

The working system hydraulic system is a system for operating the boom 10, the bucket 11, the preliminary attachment, and the like. As shown in FIG. 1, a plurality of control valves 20 and a working system hydraulic pump (first hydraulic pump) P1 are provided. I have. Further, a second hydraulic pump P2 different from the first hydraulic pump P1 is provided.
The first hydraulic pump P1 is a pump that is operated by the power of the prime mover 7, and is constituted by a constant capacity gear pump. The first hydraulic pump P <b> 1 can discharge the hydraulic oil stored in the tank (hydraulic oil tank) 15. The second hydraulic pump P2 is a pump that is operated by the power of the prime mover 7, and is constituted by a constant capacity gear pump. The second hydraulic pump P <b> 2 can discharge the hydraulic oil stored in the tank (hydraulic oil tank) 15. The second hydraulic pump P2 discharges hydraulic fluid for signal and hydraulic fluid for control in the hydraulic system. The hydraulic fluid for signal and the hydraulic fluid for control are called pilot oil.

The plurality of control valves 20 are valves that control various hydraulic actuators provided in the work machine 1. The hydraulic actuator is a device that operates with hydraulic oil, such as a hydraulic cylinder or a hydraulic motor. In this embodiment, the plurality of control valves 20 are a boom control valve 20A, a bucket control valve 20B, and a preliminary control valve 20C.
The boom control valve 20 </ b> A is a valve that controls a hydraulic actuator (boom cylinder) 14 that operates the boom 10. The boom control valve 20A is a direct acting spool type three-position switching valve. The boom control valve 20A switches to a neutral position 20a3, a first position 20a1 different from the neutral position 20a3, a neutral position 20a3, and a second position 20a2 different from the first position 20a1. In the boom control valve 20A, the neutral position 20a3, the first position 20a1, and the second position 20a2 are switched by moving the spool by operating the operation member. The boom control valve 20A is switched by directly moving the spool by manually operating the operation member. However, the spool is moved by hydraulic operation (hydraulic operation by a pilot valve, hydraulic operation by a proportional valve). Alternatively, it may be moved by an electric operation (electric operation by exciting a solenoid) or may be moved by other methods.

  The boom control valve 20A and the first hydraulic pump P1 are connected by a discharge oil passage 27. A discharge oil passage 24 a connected to the hydraulic oil tank 15 is connected to the section of the discharge oil passage 27 between the boom control valve 20 </ b> A and the first hydraulic pump P <b> 1. A relief valve (main relief valve) 25 is provided in the middle of the discharge oil passage 24a. The hydraulic oil discharged from the first hydraulic pump P1 passes through the discharge oil passage 27 and is supplied to the boom control valve 20A. Further, the boom control valve 20 </ b> A and the boom cylinder 14 are connected by an oil passage 21.

  Specifically, the boom cylinder 14 includes a cylindrical body 14a, a rod 14b provided movably on the cylindrical body 14a, and a piston 14c provided on the rod 14b. A first port 14d through which hydraulic oil is supplied and discharged is provided at the base end of the cylindrical body 14a (the side opposite to the rod 14b side). A second port 14e for supplying and discharging hydraulic oil is provided at the tip (rod 14b side) of the cylindrical body 14a.

The oil passage 21 includes a communication oil passage 21a that connects the first port 31 of the boom control valve 20A and the first port 14d of the boom cylinder 14, a second port 32 of the boom control valve 20A, and a second port of the boom cylinder 14. 14e and an oil passage 21b that connects to 14e.
Therefore, if the boom control valve 20A is set to the first position 20a1, the working oil can be supplied from the communication oil passage 21a to the first port 14d of the boom cylinder 14, and the communication oil is supplied from the second port 14e of the boom cylinder 14. The hydraulic oil can be discharged to the path 21b. As a result, the boom cylinder 14 extends and the boom 10 rises. When the boom control valve 20A is set to the second position 20a2, the hydraulic oil can be supplied from the communication oil passage 21b to the second port 14e of the boom cylinder 14, and the communication oil passage 21a from the first port 14d of the boom cylinder 14. The hydraulic oil can be discharged. As a result, the boom cylinder 14 contracts and the boom 10 descends.

  The bucket control valve 20 </ b> B is a valve that controls a hydraulic cylinder (bucket cylinder) 17 that controls the bucket 11. The bucket control valve 20B is a pilot-type direct acting spool type three-position switching valve. The bucket control valve 20B switches to a neutral position 20b3, a first position 20b1 different from the neutral position 20b3, a neutral position 20b3, and a second position 20b2 different from the first position 20b1. In the bucket control valve 20B, the neutral position 20b3, the first position 20b1, and the second position 20b2 are switched by moving the spool by operating the operation member. The bucket control valve 20B is switched by directly moving the spool by manually operating the operation member. However, the spool is moved by hydraulic operation (hydraulic operation by a pilot valve, hydraulic operation by a proportional valve). Alternatively, it may be moved by an electric operation (electric operation by exciting a solenoid) or may be moved by other methods.

  Bucket control valve 20 </ b> B and bucket cylinder 17 are connected by an oil passage 22. Specifically, the bucket cylinder 17 includes a cylindrical body 17a, a rod 17b that is movably provided on the cylindrical body 17a, and a piston 17c that is provided on the rod 17b. A first port 17d through which hydraulic oil is supplied and discharged is provided at the base end of the cylindrical body 17a (the side opposite to the rod 17b side). A second port 17e through which hydraulic oil is supplied and discharged is provided at the tip (rod 17b side) of the cylindrical body 17a.

The oil passage 22 includes a communication oil passage 22a that connects the first port 35 of the bucket control valve 20B and the second port 17e of the bucket cylinder 17, a second port 36 of the bucket control valve 20B, and a first port of the bucket cylinder 17. And a communication oil passage 22b for connecting 17d.
Therefore, if the bucket control valve 20B is set to the first position 20b1, hydraulic oil can be supplied from the communication oil passage 22a to the second port 17e of the bucket cylinder 17, and communication oil can be supplied from the first port 17d of the bucket cylinder 17. The hydraulic oil can be discharged to the path 22b. As a result, the bucket cylinder 17 contracts and the bucket 11 performs a squeeze operation. If the bucket control valve 20B is set to the second position 20a2, the hydraulic oil can be supplied from the communication oil passage 22b to the first port 17d of the bucket cylinder 17, and the communication oil passage 22a from the second port 17e of the bucket cylinder 17. The hydraulic oil can be discharged. As a result, the bucket cylinder 17 extends and performs a dumping operation.

  The preliminary control valve 20C is a valve that controls the hydraulic actuator (hydraulic cylinder, hydraulic motor, etc.) 16 mounted on the preliminary attachment. The preliminary control valve 20C is a pilot-type direct acting spool type three-position switching valve. The preliminary control valve 20C switches to a neutral position 20c3, a first position 20c1 different from the neutral position 20c3, a neutral position 20c3, and a second position 20c2 different from the first position 20c1. In the preliminary control valve 20C, the neutral position 20c3, the first position 20c1, and the second position 20c2 are switched by moving the spool by the pilot oil pressure. A connecting member 18 is connected to the preliminary control valve 20C via supply / discharge oil passages 83a and 83b. An oil path connected to the hydraulic actuator 16 of the preliminary attachment is connected to the connecting member 18.

  Therefore, if the preliminary control valve 20C is set to the first position 20c1, the hydraulic oil can be supplied from the supply / discharge oil passage 83a to the hydraulic actuator 16 of the preliminary attachment. If the preliminary control valve 20C is set to the second position 20c2, the hydraulic oil can be supplied from the supply / discharge oil passage 83b to the hydraulic actuator 16 of the preliminary attachment. In this way, by supplying hydraulic oil to the hydraulic actuator 16 from the supply / discharge oil passage 83a or the supply / discharge oil passage 83b, the hydraulic actuator 16 (preliminary attachment) can be operated.

  Now, a series circuit (series oil passage) is applied to the hydraulic system. In the series circuit, the hydraulic oil returned from the hydraulic actuator to the upstream control valve can be supplied to the downstream control valve. For example, focusing on the bucket control valve 20B and the spare control valve 20C, the bucket control valve 20B is an upstream control valve, and the spare control valve 20C is a downstream control valve.

Hereinafter, the upstream control valve is referred to as a “first control valve”, and the downstream control valve is referred to as a “second control valve”. A control valve other than the first control valve and the second control valve and provided on the downstream side of the second control valve is referred to as a “third control valve”.
Further, the hydraulic actuator corresponding to the first control valve is referred to as “first hydraulic actuator”, the hydraulic actuator corresponding to the second control valve is referred to as “second hydraulic actuator”, and the hydraulic actuator corresponding to the third control valve is referred to. This is called “third hydraulic actuator”. The oil passage for supplying the return oil, which is the working oil returning from the first hydraulic actuator to the first control valve, to the second control valve is referred to as a “first oil passage”.

In this embodiment, the boom control valve 20A is a “first control valve”, the bucket control valve 20B is a “second control valve”, and the spare control valve 20C is a “third control valve”. Further, the boom cylinder 14 is a “first hydraulic actuator”, the bucket cylinder 17 is a “second hydraulic actuator”, and the hydraulic actuator 16 for the preliminary attachment is a “third hydraulic actuator”.
Hereinafter, the relationship between the first control valve 20A and the second control valve 20B will be described in detail.

  The first control valve 20A and the discharge portion of the first hydraulic pump P1 are connected by a discharge oil passage 27. The discharge oil passage 27 is branched at a midway portion 27a. The oil passage after the branch of the discharge oil passage 27 is connected to the first input port 46a and the second input port 46b of the first control valve 20A. Further, the discharge oil passage 27 is connected to the third input port 46c of the first control valve 20A. Accordingly, the hydraulic oil discharged from the first hydraulic pump P1 can be supplied into the first control valve 20A through the discharge oil passage 27, the first input port 46a, the second input port 46b, and the third input port 46c. It is. The first control valve 20 </ b> A and the second control valve 20 </ b> B are connected by a central oil passage 51. The central oil passage 51 connects the third output port 41c of the first control valve 20A and the third input port 42c of the second control valve 20B.

When the first control valve 20A is set to the neutral position 20a3, it is supplied from the discharge oil passage 27 to the first control valve 20A by the communication of the central oil passage 53c that connects the third input port 46c and the third output port 41c. The supply oil that is the working oil passes through the first control valve 20 </ b> A and is supplied to the central oil passage 51.
The first control valve 20 </ b> A and the second control valve 20 </ b> B are connected by a first oil passage 61 separately from the central oil passage 51. The first oil passage 61 is an oil passage through which the return oil that returns from the first hydraulic actuator 14 to the first control valve 20A passes through the first control valve 20A and is supplied to the second control valve 20B.

The first oil passage 61 includes a communication oil passage (first connection oil passage) 21a, a first internal oil passage 61a, and an external oil passage 61b. The first connection oil passage 21 a is an oil passage that connects the first port 31 of the first control valve 20 A and the first port 14 d of the first hydraulic actuator 14, and the first port 14 d of the first hydraulic actuator 14. This is an oil passage through which return oil discharged from the oil flows.
The first internal oil passage 61a is an oil passage that is provided in the first control valve 20A and communicates with the first connection oil passage 21a. Specifically, the first internal oil passage 61a connects the first port 31 of the first control valve 20A and the first output port 41a of the first control valve 20A when the first control valve 20A is set to the second position 20a2. It is an oil passage to be connected.

  The external oil passage 61b is an oil passage that communicates with the first internal oil passage 61a and is connected to the second control valve 20B. The external oil passage 61b connects the first output port 41a of the first control valve 20A and the first input port 42a of the second control valve 20B, and is connected to the second output port 41b of the first control valve 20A and the second output port 41b. The second input port 42b of the control valve 20B is connected. A midway portion of the external oil passage 61 b is connected to the central oil passage 51. That is, the external oil passage 61b and the central oil passage 51 are joined on the way.

  According to the above, when the first control valve 20A is set to the second position 20a2, which is the lateral position, the supply oil introduced into the second input port 46b passes through the second port 32 and the communication oil passage 21b. The second port 14e of the first hydraulic actuator 14 is entered. When the supply oil is supplied to the second port 14e, for example, the first hydraulic actuator 14 contracts. When the first hydraulic actuator 14 contracts, the return oil discharged from the first port 14d of the first hydraulic actuator 14 passes through the first connection oil passage 21a and flows into the first internal oil passage 61a. The return oil in the oil passage 61a flows toward the second control valve 20B through the external oil passage 61b. Therefore, the return oil of the first hydraulic actuator 14 can be supplied to the second control valve 20B.

Next, the relationship between the second control valve 20B and the third control valve 20C will be described in detail.
The second control valve 20B and the third control valve 20C are connected by a central oil passage 72. The central oil passage 72 connects the third output port 43c of the second control valve 20B and the third input port 44c of the third control valve 20C. Accordingly, when the second control valve 20B is set to the neutral position 20b3, the supply oil that is the hydraulic oil supplied to the second control valve 20B is a central oil passage 73c that connects the third input port 42c and the third output port 43c. And is supplied to the central oil passage 72 connected to the third output port 43c.

The second control valve 20 </ b> B and the third control valve 20 </ b> C are connected by an oil passage 81 separately from the central oil passage 72. The oil passage 81 is an oil passage through which the return oil that returns from the second hydraulic actuator 17 to the second control valve 20B passes through the second control valve 20B and is supplied to the third control valve 20C.
The oil passage 81 includes a communication oil passage 22a, a communication oil passage 81a, and a communication oil passage 81b. The communication oil path 22a is an oil path connecting the first port 35 of the second control valve 20B and the second port 17e of the second hydraulic actuator 17, and the return oil discharged from the second port 17e flows. It is an oil passage.

The communication oil path 81a is an oil path that is provided in the second control valve 20B and communicates with the communication oil path 22a. Specifically, the communication oil passage 81a connects the first port 35 of the second control valve 20B and the first output port 43a of the second control valve 20B when the second control valve 20B is set to the second position 20b2. It is an oil passage.
The communication oil path 81b is an oil path that communicates with the communication oil path 81a and is connected to the third control valve 20C. The communication oil path 81b connects the first output port 43a of the second control valve 20B and the first input port 44a of the third control valve 20C, and connects the second output port 43b of the second control valve 20B to the third output port 43b. The second input port 44b of the control valve 20C is connected. A midway portion of the communication oil passage 81 b joins the central oil passage 72.

  According to the above, when the second control valve 20B is set to the second position 20b2, which is a lateral position, the supply oil introduced into the second input port 42b passes through the second port 36 and the communication oil path 22b. The first port 17d of the second hydraulic actuator 17 is entered. When the supply oil is supplied to the first port 17d, for example, the second hydraulic actuator 17 extends. When the second hydraulic actuator 17 extends, the return oil discharged from the second port 17e of the second hydraulic actuator 17 flows through the communication oil path 22a to the communication oil path 81a, and the return oil of the communication oil path 81a. Flows through the communication oil passage 81b toward the third control valve 20C. Therefore, the return oil of the second hydraulic actuator 17 can be supplied to the third control valve 20C.

  Note that the hydraulic system of the work machine includes a discharge oil passage 24b that can discharge the hydraulic oil to the hydraulic oil tank 15 and the like. The discharge oil passage 24b includes an oil passage 24b1, an oil passage 24b2, and an oil passage 24b3. The oil passage 24b1 is an oil passage connected to the communication oil passage 21b. A relief valve 37 is provided in the middle of the oil passage 24b1. The oil passage 24b2 is an oil passage connected to the first connection oil passage 21a and the first discharge port 33a and the second discharge port 33b of the first control valve 20A. The oil passage 24 b 3 is an oil passage that connects the joining portion of the oil passage 24 b 1 and the oil passage 24 b 2 and the hydraulic oil tank 15.

  Further, the discharged oil passage 24b includes an oil passage 24b4, an oil passage 24b5, an oil passage 24b6, and an oil passage 24b7. The oil passage 24b4 is an oil passage connected to the communication oil passage 22b. A relief valve 38 is provided in the middle of the oil passage 24b1. The oil passage 24b5 is an oil passage connected to the communication oil passage 22a and the first discharge port 34a and the second discharge port 34b of the second control valve 20B. The oil passage 24b6 connects the merging portion of the oil passage 24b1 and the oil passage 24b2, and the oil passage 24b3. The oil passage 24 b 6 communicates with a central oil passage 75 that communicates with the central oil passage 72. The oil passage 24b7 connects the joining portion 76 where the oil passage 24b6 and the central oil passage 75 join, the hydraulic oil tank 15, and the like.

  As shown in FIGS. 1 and 2, the hydraulic system of the working machine includes a third oil passage 110, a fourth oil passage 120, and a pressure increase unit 130. The third oil passage 110 is an oil passage connected to the first oil passage 61. The third oil passage 110 is provided in the first control valve 20A, and connects the first internal oil passage 61a of the first oil passage 61 and the discharge oil passage 24b. Specifically, the third oil passage 110 connects the first internal oil passage 61a and the first discharge port 33a (discharge oil passage 24b) when the first control valve 20 is at the second position 20a2. In addition, you may provide the throttle part 151 which reduces the flow volume of hydraulic fluid in the 3rd oil path 110. FIG.

  The fourth oil passage 120 is an oil passage that is connected to the first oil passage 61 and supplies the return oil of the first oil passage 61 to the second oil passage 85. The second oil passage 85 includes a communication oil passage (second connection oil passage) 21 b and a second internal oil passage 86. The communication oil passage 21b is an oil passage that connects the second port 32 of the first control valve 20A and the second port 14e of the first hydraulic actuator 14, and supplies the supply oil flowing to the second port 32 to the second port. 14e is an oil passage that flows to 14e. The second internal oil passage 86 is an oil passage that is provided in the first control valve 20A and communicates with the communication oil passage 21b. Specifically, the second internal oil passage 86 connects the second input port 46b of the first control valve 20A and the second port 32 of the first control valve 20A when the first control valve 20A is set to the second position 20a2. It is an oil passage to be connected.

  The fourth oil passage 120 includes a connection oil passage 121, a third internal oil passage 122, and a return oil passage 123. The connecting oil passage 121 is an oil passage different from the first oil passage 61 and is an oil passage connecting the external oil passage 61b of the first oil passage 61 and the first control valve 20A. Specifically, the connecting oil passage 121 is a part of the oil passage of the central oil passage 51, and is an oil passage connecting the junction 63 and the third output port 41c of the first control valve 20A. The third internal oil passage 122 connects the third output port 41c of the first control valve 20A and the third input port 46c of the first control valve 20A when the first control valve 20A is at the second position 20a2. It is an oil passage. In addition, you may provide the throttle part 150 which reduces the flow volume of hydraulic fluid in the 3rd internal oil path 122. FIG.

  The return oil passage 123 is a return oil passage that communicates with the third internal oil passage 122 and returns the hydraulic oil that has passed through the connection oil passage 121 and the third internal oil passage 122 to the first control valve 20A. The return oil path 123 is a part of the discharge oil path 27 and includes a section oil path 123 a in the discharge oil path 27 and a section oil path 123 b in the discharge oil path 27. The section oil passage 123a is an oil passage connecting the third output port 41c and the midway portion 27a. The section oil passage 123b is an oil passage that connects the midway portion 27a and the second input port 46b.

  The pressure increase part 130 is a part that is connected to the discharge oil passage 24b and increases the pressure of the discharge oil passage 24b. The pressure increase unit 130 is a check valve 19c, an oil cooler 28, and the like provided in the discharge oil passage 24b. Specifically, the check valve 19c is connected to the middle part of the oil passage 24b7 of the discharge oil passage 24b. The check valve 19 c is a valve that allows the hydraulic oil to flow toward the hydraulic oil tank 15 and prevents the hydraulic oil from flowing toward the central oil passage 75. The check valve 19c has a setting member 19c1 for setting a differential pressure. The setting member 19c1 is configured by a spring or the like, and generates a differential pressure by pushing the valve body with a predetermined urging force from the side opposite to the direction in which the flow of hydraulic oil is allowed (direction to block).

The oil cooler 28 is provided in the middle of the discharged oil passage 24b. The hydraulic oil discharged from the discharge oil passage 24b3 flows into the inflow port 28a of the oil cooler 28. A discharge port 28 b different from the inflow port 28 a of the oil cooler 28 is connected to the hydraulic oil tank 15.
According to the above, when the first control valve 20A is in the second position 20a2, when the pressure of the hydraulic oil in the discharge oil passage 24b is higher than the pressure of the hydraulic oil in the third oil passage 110 by the pressure increase unit 130, As shown by an arrow A1 in FIG. 2, the hydraulic oil in the discharge oil passage 24b flows through the first discharge port 33a and flows into the third oil passage 110. As shown by the arrow A2 in FIG. 2, the working oil (backflow oil) that has flowed back to the third oil passage 110, the return oil that flows through the first internal oil passage 61a that communicates with the third oil passage 110, etc. It passes through the internal oil passage 61a and the first output port 41a and flows to the external oil passage 61b. As shown by the arrow A3 in FIG. 2, a part of the hydraulic oil in the external oil passage 61b passes through the joining portion 63, flows through the connecting oil passage 121 and the third internal oil passage 122, and is discharged from the third input port 46c. Is done. Further, as shown by an arrow A4 in FIG. 2, the hydraulic oil discharged from the third input port 46c passes through the return oil passage 123 and returns to the first control valve 20A again, and the first control valve 20A Two input ports 46b are entered. As shown by an arrow A5 in FIG. 2, the hydraulic oil that has entered the second input port 46b of the first control valve 20A flows through the second internal oil passage 86 of the second oil passage 85 and flows through the second oil passage 85. It will flow to the communication oil passage 21b. That is, as shown to A1-A5 of FIG. 2, the hydraulic fluid of the discharge | emission oil path 24b can be made to flow backward, and the hydraulic fluid etc. which flowed back can be supplied to the communication oil path 21b through which supply oil flows. In other words, the first control valve 20A receives the return oil from the first hydraulic actuator 14 and the working oil (backflow oil) from the discharge oil passage 24, and receives the received working oil (return oil and backflow oil) upstream. The position can be switched between a position (second position) 20a2 for discharging to the side and a position (first position) 20a1 for supplying hydraulic oil to the first hydraulic actuator 14. Further, the first control valve 20 </ b> A can receive the return oil and the backflow oil again at the second position 20 a 2 and return them to the supply side of the first hydraulic actuator 14.

  According to this, for example, when the operation of contracting the first hydraulic actuator 14 or the operation of lowering the boom is performed, in addition to the hydraulic oil discharged by the first hydraulic pump P1, return oil or backflow oil is supplied to the communication oil passage 21b. Can be supplied. As a result, the response to the boom lowering operation becomes faster, and the boom can be lowered smoothly at a quick speed. In other words, since at least the return oil and the backflow oil are added to the hydraulic oil discharged from the first hydraulic pump P1, when the boom lowering operation is performed quickly, the flow rate of the hydraulic oil necessary for temporarily lowering the boom is: It is possible to prevent the flow rate of the hydraulic oil discharged from the first hydraulic pump P1 from being exceeded.

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. The first control valve and the second control valve are not limited to the above-described embodiment, and may be any control valve provided in the work machine. In the above-described embodiment, the hydraulic oil is discharged from the hydraulic oil tank. However, it may be other places. That is, the oil passage for discharging the hydraulic oil may be connected to other than the hydraulic oil tank, for example, may be connected to a suction part (a part for sucking the hydraulic oil) of the hydraulic pump, or other parts. You may connect to.

  In the above-described embodiment, the control valve is a three-position switching valve. However, the number of switching positions is not limited, and other switching is possible regardless of whether it is a two-position switching valve or a four-position switching valve. It may be a valve. In the embodiment described above, the hydraulic pump is a constant displacement pump. However, for example, it may be a variable displacement pump in which the discharge amount is changed by changing the swash plate, or another hydraulic pump.

  Further, the first hydraulic actuator, the second hydraulic actuator, the third hydraulic actuator, the first control valve, the second control valve, and the third control valve are not limited to the above-described embodiment, and are provided in the work machine 1. I just need it.

DESCRIPTION OF SYMBOLS 1 Work implement 10 Boom 11 Bucket 14 Boom cylinder 15 Hydraulic oil tank 16 Hydraulic actuator of spare attachment 17 Bucket cylinder 20 Control valve 20A Boom control valve 20a1 1st position 20a2 2nd position 20a3 Neutral position 20B Bucket control valve 20b1 1st position 20b2 Second position 20b3 Neutral position 20C Preliminary control valve 20c1 First position 20c2 Second position 20c3 Neutral position 21 Oil passage 21a Communication oil passage (first connection oil passage)
21b Communication oil passage (second connection oil passage)
24a Oil discharge passage 24b Oil discharge passage 61 First oil passage 61a First internal oil passage 61b External oil passage 85 Second oil passage 86 Second internal oil passage 110 Third oil passage 120 Fourth oil passage 121 Linked oil passage 122 First 3 Internal oil passage 123 Return oil passage 123a Section oil passage 123b Section oil passage 130 Pressure rise part

Claims (4)

A hydraulic pump that discharges hydraulic oil;
A first hydraulic actuator;
A second hydraulic actuator;
A first control valve for controlling the first hydraulic actuator;
A second control valve provided on the downstream side of the first control valve and controlling the second hydraulic actuator;
A drain oil passage connected to the first control valve and capable of discharging the hydraulic oil that has passed through the first control valve;
A first oil passage for supplying return oil, which is hydraulic oil that returns from the first hydraulic actuator to the first control valve, to the second control valve;
A second oil passage for supplying supply oil, which is hydraulic oil supplied to the first control valve, to the first hydraulic actuator;
A third oil passage connecting the first oil passage and the exhaust oil passage;
A fourth oil passage connected to the first oil passage and supplying the return oil of the first oil passage to the second oil passage;
The working machine's hydraulic system.   2. The hydraulic system for a working machine according to claim 1, further comprising a pressure increase unit that is connected to the discharge oil passage and increases a pressure of the discharge oil passage. The first oil passage is connected to the first control valve and the first hydraulic actuator, the first connection oil passage through which the return oil flows, and the first control valve provided to the first connection oil passage. A first internal oil passage that communicates; and an external oil passage that communicates with the first internal oil passage and connects the first control valve and the second control valve;
The second oil passage is connected to the first control valve and the first hydraulic actuator, and a second connection oil passage through which the supply oil flows, and the second connection oil passage provided in the first control valve. A second internal oil passage communicating with the
3. The hydraulic system for a working machine according to claim 1, wherein the third oil passage is an oil passage connecting the first internal oil passage and the discharge oil passage.   The fourth oil path is an oil path different from the first oil path, and connects the external oil path of the first oil path and the first control valve; and the first control A third internal oil passage that is provided in the valve and communicates with the connection oil passage; and hydraulic oil that communicates with the third internal oil passage and passes through the connection oil passage and the third internal oil passage. The hydraulic system for a working machine according to claim 3, further comprising a return oil passage returning to the control valve.

Images