JP6983708B2 - Work machine hydraulic system - Google Patents

Description

The present invention relates to a hydraulic system and a control valve for working machines such as skid steer loaders and compact truck loaders.

Conventionally, Patent Document 1 is known as a hydraulic system for a working machine. The working machine of 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 a spare attachment, and a first control valve that controls expansion and contraction of the boom cylinder. A second control valve that controls expansion and contraction of the bucket cylinder and a third control valve that operates a spare actuator are provided.

Japanese Unexamined Patent Publication No. 2010-270527

In the working machine of Patent Document 1, hydraulic actuators such as a boom cylinder and a bucket cylinder are operated by a plurality of control valves such as a first control valve, a second control valve, and a third control valve. An oil passage (oil supply / drainage passage) connecting a plurality of control valves and a hydraulic actuator, or a discharge oil passage for discharging hydraulic oil is connected to the plurality of control valves. By controlling the hydraulic oil discharged from the oil supply / drainage channel to the drainage oil passage and the hydraulic oil discharged from multiple control valves to the drainage oil passage, the hydraulic actuator can be balanced in various situations. I am trying to operate it.

The present invention has been made to solve the above-mentioned problems of the prior art, and an object of the present invention is to provide a hydraulic system for a working machine capable of operating a control valve (hydraulic actuator) more smoothly. And.

The technical means of the present invention for solving this technical problem is as follows.
The hydraulic system of the work equipment 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. A second control valve that is provided in the above and controls the second hydraulic actuator, a discharge oil passage that connects the hydraulic pump and the first control valve, and the first control valve and the second control valve. A central oil passage connecting the oil, a discharge oil passage for discharging hydraulic oil that has passed through the first control valve, and a pressure rising portion provided in the discharge oil passage and increasing the pressure of the discharge oil passage. A switching valve that can be switched between an allowable position for flowing hydraulic oil toward the pressure rising portion and a suppressing position for suppressing the flow of hydraulic oil toward the pressure rising portion, and the first hydraulic actuator to the first. The first oil passage that supplies the return oil, which is the hydraulic oil returning to the control valve, to the second control valve, and the supply oil, which is the hydraulic oil supplied to the first control valve, are supplied to the first hydraulic actuator. The second oil passage, the third oil passage connecting the first oil passage and the discharge oil passage, and the return oil of the first oil passage connected to the first oil passage are used as the second oil. A fourth oil passage for supplying oil to the oil passage is provided , and the first oil passage connects the first control valve and the first hydraulic actuator, and the return oil flows through the first connecting oil passage. An external oil passage provided in the first control valve and communicating with the first connecting oil passage, and an external one communicating with the first internal oil passage and connecting the first control valve and the second control valve. It has an oil passage, and in the middle of the external oil passage, it has a merging portion that joins in the middle of the central oil passage, and the second oil passage has the first control valve and the first hydraulic actuator. The third oil passage has a second connecting oil passage which is connected to and allows the supply oil to flow, and a second internal oil passage which is provided in the first control valve and communicates with the second connecting oil passage. Is an oil passage provided in the first control valve and connecting the first internal oil passage and the discharge oil passage, and includes a throttle portion, and the fourth oil passage is the first oil passage. A connecting oil passage that is different from the oil passage and connects the external oil passage of the first oil passage and the first control valve, and a connecting oil passage provided in the first control valve and communicating with the connecting oil passage. The third internal oil passage includes a return oil passage that communicates with the third internal oil passage and returns hydraulic oil that has passed through the connecting oil passage and the third internal oil passage to the first control valve. The discharge oil passage is branched into two in the middle part, which is an intermediate part thereof, and is connected to the third internal oil passage of the first control valve from the middle part. The first section oil passage is provided with a second section oil passage connected from the middle portion to the second internal oil passage of the first control valve, and the return oil passage is a hydraulic oil of the external oil passage. Part of the hydraulic oil that has passed through the confluence and flows through the connecting oil passage and the third internal oil passage, and has passed through the connecting oil passage and the third internal oil passage. It is an oil passage that passes through the middle portion and the second section oil passage and returns to the second internal oil passage of the first control valve .

The drainage oil passage has a bypass oil passage that bypasses the upstream side of the pressure rise portion and the downstream side of the pressure rise portion, and the switching valve opens the bypass oil passage when it is in the suppression position. And, when it is in the allowable position, the bypass oil passage is closed.
The hydraulic system of the work machine is connected to the discharge oil passage and includes a branch oil passage leading to a discharge portion for discharging hydraulic oil, and the switching valve is provided in the branch oil passage and is in the allowable position. The branch oil passage is closed, and the branch oil passage is opened when the restraining position is reached.

According to the present invention, the control valve (hydraulic actuator) can be operated more smoothly.

It is a figure which shows the hydraulic system (hydraulic circuit) of a work machine. It is explanatory drawing explaining the flow of hydraulic oil. It is a figure which shows the modification of the switching valve. It is a figure which shows the 1st modification of the hydraulic system of a working machine. It is a figure which shows the 2nd modification of the hydraulic system of a working machine. It is an overall view of the skid steer loader exemplified as a working machine.

Hereinafter, preferred embodiments of the hydraulic system of the 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. 5 shows a side view of the working machine according to the present invention. FIG. 5 shows a skid steer loader as an example of a working machine. However, the working machine according to the present invention is not limited to the skid sterode, and may be, for example, another type of loader working machine such as a compact truck loader. Further, it may be a working machine other than the loader working machine.

The working machine 1 includes a machine body (body) 2, a cabin 3, a working device 4, and traveling devices 5A and 5B.
A cabin 3 is mounted on the aircraft 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 of FIG. 5) of the driver seated in the driver's seat 8 of the work machine 1 is the front, the rear side of the driver (right side of FIG. 5) is the rear, and the left side of the driver (FIG. 5). The front side of 5) will be described as the left side, and the right side of the driver (the back side of FIG. 5) will be described as the right side. Further, 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 center of the machine 2 to the right or left side will be described as the outside of the machine. In other words, the outside of the airframe is the width direction of the airframe and the direction away from the airframe 2. The direction opposite to the outside of the aircraft will be described as the inside of the aircraft. In other words, the inside of the machine is the width direction of the machine and the direction approaching the body 2.

The cabin 3 is mounted on the airframe 2. The work device 4 is a device for performing work and is equipped on the machine body 2. The traveling device 5A is a device for traveling the machine body 2, and is provided on the left side side of the machine body 2. The traveling device 5B is a device for traveling the machine body 2, and is provided on the right side of the machine body 2. A prime mover 7 is provided at the rear part of the machine body 2. The prime mover 7 is a diesel engine (engine). The prime mover 7 is not limited to the engine, but may be an electric motor or the like.

A traveling lever 9L is provided on the left side of the driver's seat 8. A traveling lever 9R is provided on the right side of the driver's seat 8. The traveling lever 9L on the left side operates the traveling device 5A on the left side, and the traveling lever 9R on the right side operates the traveling device 5B on the right side.
The working device 4 has 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 machine 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 on the upper part of the base of the boom 10. The lower part of the lift link 12 is pivotally supported on the rear side of the machine body 2. The control link 13 is arranged in front of the lift link 12. One end of the control link 13 is pivotally supported by the lower part of the base of the boom 10, and the other end is pivotally supported by the machine body 2.

The boom cylinder 14 is a hydraulic cylinder that raises and lowers the boom 10. The upper portion of the boom cylinder 14 is pivotally supported by the front portion of the base of the boom 10. The lower portion of the boom cylinder 14 is pivotally supported on the side portion of the rear portion of the machine body 2. When the boom cylinder 14 is expanded and contracted, the boom 10 swings 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 between the left portion of the bucket 11 and the left boom, and also connects between the right portion and the right boom of the bucket 11. A spare attachment such as a hydraulic crusher, a hydraulic breaker, an angle bloom, an auger, a pallet fork, a sweeper, a mower, or a snow blower can be attached to the tip (front portion) of the boom 10 instead of the bucket 11. ..

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

The working hydraulic system is a system that operates a boom 10, a bucket 11, a spare attachment, etc., and as shown in FIG. 1, a plurality of control valves 20 and a working hydraulic pump (first hydraulic pump) P1 are used. 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 operated by the power of the prime mover 7, and is composed of a constant capacity type gear pump. The first hydraulic pump P1 can discharge the hydraulic oil stored in the tank (hydraulic oil tank) 15. The second hydraulic pump P2 is a pump operated by the power of the prime mover 7, and is composed of a constant capacity type gear pump. The second hydraulic pump P2 can discharge the hydraulic oil stored in the tank (hydraulic oil tank) 15. The second hydraulic pump P2 discharges hydraulic oil for signals and hydraulic oil for control in the hydraulic system. The hydraulic oil for signals and the hydraulic oil for control are called pilot oils.

The plurality of control valves 20 are valves for controlling various hydraulic actuators provided in the working machine 1. A hydraulic actuator is a device operated by hydraulic oil, such as a hydraulic cylinder and 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 20A is a valve that controls the hydraulic actuator (boom cylinder) 14 that operates the boom 10. The boom control valve 20A is a linear motion spool type 3-position switching valve. The boom control valve 20A switches to the neutral position 20a3, the first position 20a1 different from the neutral position 20a3, the neutral position 20a3, and the 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 operating member. The boom control valve 20A is switched by directly moving the spool by manually operating the operating member, but the spool is moved by hydraulic operation (hydraulic operation by the pilot valve, hydraulic operation by the proportional valve). It may be moved by an electric operation (electric operation by exciting a solenoid), or may be moved by another method.

The boom control valve 20A and the first hydraulic pump P1 are connected by a discharge oil passage 27. A discharge oil passage 24a connected to the hydraulic oil tank 15 is connected to the discharge oil passage 27 in the section between the boom control valve 20A and the first hydraulic pump P1. A relief valve (main relief valve) 25 is provided in the middle of the oil discharge 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 20A and the boom cylinder 14 are connected by an oil passage 21.

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

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, and the second port 32 of the boom control valve 20A and the second port of the boom cylinder 14. It has an oil passage 21b that connects to the 14e.
Therefore, if the boom control valve 20A is set to the first position 20a1, the hydraulic oil can be supplied from the communication oil passage 21a to the first port 14d of the boom cylinder 14, and the communication oil can be supplied from the second port 14e of the boom cylinder 14. The hydraulic oil can be discharged to the road 21b. As a result, the boom cylinder 14 is extended and the boom 10 is raised. If the boom control valve 20A is set to the second position 20a2, 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 can be supplied 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 20B 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 3-position switching valve. The bucket control valve 20B switches to the neutral position 20b3, the first position 20b1 different from the neutral position 20b3, the neutral position 20b3, and the 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 operating member. The bucket control valve 20B is switched by directly moving the spool by manually operating the operating member, but the spool is moved by hydraulic operation (hydraulic operation by the pilot valve, hydraulic operation by the proportional valve). It may be moved by an electric operation (electric operation by exciting a solenoid), or may be moved by another method.

The bucket control valve 20B and the bucket cylinder 17 are connected by an oil passage 22. Specifically, the bucket cylinder 17 includes a cylinder 17a, a rod 17b movably provided on the cylinder 17a, and a piston 17c provided on the rod 17b. A first port 17d for supplying and discharging hydraulic oil is provided at the base end portion (the side opposite to the rod 17b side) of the tubular body 17a. A second port 17e for supplying and discharging hydraulic oil is provided at the tip of the cylinder 17a (on the rod 17b side).

The oil passage 22 includes a communication oil passage 22a connecting the first port 35 of the bucket control valve 20B and the second port 17e of the bucket cylinder 17, and the second port 36 of the bucket control valve 20B and the first port of the bucket cylinder 17. It has a communication oil passage 22b that connects to 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 the communication oil can be supplied from the first port 17d of the bucket cylinder 17. The hydraulic oil can be discharged to the road 22b. As a result, the bucket cylinder 17 contracts and the bucket 11 squeezes. If the bucket control valve 20B is set to the second position 20a2, 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 can be supplied from the second port 17e of the bucket cylinder 17. The hydraulic oil can be discharged. As a result, the bucket cylinder 17 expands and dumps.

The spare control valve 20C is a valve that controls a hydraulic actuator (hydraulic cylinder, hydraulic motor, etc.) 16 mounted on the spare attachment. The preliminary control valve 20C is a pilot type direct-acting spool type 3-position switching valve. The preliminary control valve 20C switches to the neutral position 20c3, the first position 20c1 different from the neutral position 20c3, the neutral position 20c3, and the 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 pressure of the pilot oil. A connecting member 18 is connected to the preliminary control valve 20C via oil supply / drainage passages 83a and 83b. An oil passage connected to the hydraulic actuator 16 of the spare attachment is connected to the connecting member 18.

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

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

Hereinafter, the control valve on the upstream side is referred to as a "first control valve", and the control valve on the downstream side is referred to as a "second control valve". A control valve other than the first control valve and the second control valve, which is 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 the "first hydraulic actuator", the hydraulic actuator corresponding to the second control valve is referred to as the "second hydraulic actuator", and the hydraulic actuator corresponding to the third control valve is used. This is called the "third hydraulic actuator". The oil passage that supplies the return oil, which is the hydraulic oil that returns 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 preliminary 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 spare attachment hydraulic actuator 16 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 the middle 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. Therefore, 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. Is. The first control valve 20A and the second control valve 20B 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 connecting the third input port 46c and the third output port 41c. The supplied oil, which is the hydraulic oil, passes through the first control valve 20A and is supplied to the central oil passage 51.
The first control valve 20A and the second control valve 20B are connected by a first oil passage 61 separately from the central oil passage 51. The first oil passage 61 is an oil passage for supplying the return oil returning from the first hydraulic actuator 14 to the first control valve 20A to the second control valve 20B through the first control valve 20A.

The first oil passage 61 has a communication oil passage (first connecting oil passage) 21a, a first internal oil passage 61a, and an external oil passage 61b. The first connecting oil passage 21a is an oil passage connecting the first port 31 of the first control valve 20A and the first port 14d of the first hydraulic actuator 14, and is the first port 14d of the first hydraulic actuator 14. It is an oil passage through which the return oil discharged from the oil flow flows.
The first internal oil passage 61a is an oil passage provided in the first control valve 20A and communicating with the first connecting 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 channel to connect.

The external oil passage 61b is an oil passage that communicates with the first internal oil passage 61a and connects 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 the second output port 41b and the second of the first control valve 20A. It is connected to the second input port 42b of the control valve 20B. The middle part of the external oil passage 61b is connected to the central oil passage 51. That is, the external oil passage 61b and the central oil passage 51 merge in the middle.

According to the above, when the first control valve 20A is set to the second position 20a2 which is a side position, the supply oil introduced into the second input port 46b passes through the second port 32 and the communication oil passage 21b. It will enter the second port 14e of the first hydraulic actuator 14. 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 connecting oil passage 21a and flows into the first internal oil passage 61a, and flows into the first internal oil passage 61a. The return oil in the oil passage 61a flows through the external oil passage 61b toward the second control valve 20B. 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. Therefore, when the second control valve 20B is set to the neutral position 20b3, the supply oil, which is the hydraulic oil supplied to the second control valve 20B, is the central oil passage 73c connecting the third input port 42c and the third output port 43c. It is supplied to the central oil passage 72 connected to the third output port 43c through the oil passage 72.

The second control valve 20B and the third control valve 20C are connected by an oil passage 81 separately from the central oil passage 72. The oil passage 81 is an oil passage for supplying the return oil returning from the second hydraulic actuator 17 to the second control valve 20B to the third control valve 20C through the second control valve 20B.
The oil passage 81 has a communication oil passage 22a, a communication oil passage 81a, and a communication oil passage 81b. The communication oil passage 22a is an oil passage 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 passage 81a is an oil passage provided in the second control valve 20B and communicating with the communication oil passage 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 channel.
The communication oil passage 81b is an oil passage that communicates with the communication oil passage 81a and connects to the third control valve 20C. The communication oil passage 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 the second output port 43b and the third of the second control valve 20B. It is connected to the second input port 44b of the control valve 20C. The middle part of the communication oil passage 81b 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 side position, the supply oil introduced into the second input port 42b passes through the second port 36 and the communication oil passage 22b. It will enter the first port 17d of the second hydraulic actuator 17. 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 is extended, the return oil discharged from the second port 17e of the second hydraulic actuator 17 passes through the communication oil passage 22a and flows into the communication oil passage 81a, and the return oil in the communication oil passage 81a Flows toward the third control valve 20C through the communication oil passage 81b. Therefore, the return oil of the second hydraulic actuator 17 can be supplied to the third control valve 20C.

The hydraulic system of the work equipment includes a drainage channel 24b. The discharge oil passage 24b is connected to the first control valve 20A, and the hydraulic oil that has passed through the first control valve 20A can be discharged to the hydraulic oil tank 15 or 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 connecting oil passage 21a, the first discharge port 33a of the first control valve 20A, and the second discharge port 33b. A relief valve 37 is also provided in the middle of the oil passage 24b2.

The oil passage 24b3 is an oil passage that connects the confluence portion 26a of the oil passage 24b1 and the oil passage 24b2 and the hydraulic oil tank 15.
Further, the discharge oil passage 24 can discharge the hydraulic oil that has passed through the second control valve 20B to the hydraulic oil tank 15 or the like.
Further, the discharge 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, the first discharge port 34a and the second discharge port 34b of the second control valve 20B. A relief valve 38 is also provided in the middle of the oil passage 24b5.

The oil passage 24b6 connects the confluence portion 26b of the oil passage 24b1 and the oil passage 24b2 with the oil passage 24b3. Further, the oil passage 24b6 communicates with the central oil passage 75 communicating with the central oil passage 72. The oil passage 24b7 connects a confluence portion 76 where the oil passage 24b6 and the central oil passage 75 meet, a hydraulic oil tank 15, and the like. The oil passage 24b7 is provided with a throttle portion 113 for reducing the flow rate of the hydraulic oil and an oil cooler 114 for cooling the hydraulic oil. The discharge oil passage 24b includes a bypass oil passage 140, which will be described later.

As shown in FIGS. 1 and 2, the hydraulic system of the working machine includes a third oil passage 110 and a fourth oil passage 120. 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 and the discharge oil passage 24b of the first oil passage 61. 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. The third oil passage 110 may be provided with a throttle portion 151 for reducing the flow rate of hydraulic oil.

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 has a communication oil passage (second connecting oil passage) 21b and a second internal oil passage 86. The communication oil passage 21b is an oil passage connecting the second port 32 of the first control valve 20A and the second port 14e of the first hydraulic actuator 14, and the supply oil flowing to the second port 32 is supplied to the second port. It is an oil passage that flows through 14e. The second internal oil passage 86 is an oil passage provided in the first control valve 20A and communicating 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 channel to connect.

The fourth oil passage 120 has a connecting 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 central oil passage 51, and is an oil passage connecting the merging portion 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 channel. The third internal oil passage 122 may be provided with a throttle portion 150 for reducing the flow rate of hydraulic oil.

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 connecting oil passage 121 and the third internal oil passage 122 to the first control valve 20A. The return oil passage 123 is a part of the oil passage of the discharge oil passage 27, and includes a section oil passage 123a in the discharge oil passage 27 and a section oil passage 123b in the discharge oil passage 27. The section oil passage 123a is an oil passage connecting the third output port 41c and the middle portion 27a. The section oil passage 123b has a middle portion 27a and
It is an oil passage connecting the first input port 46a and the second input port 46b.

The hydraulic system of the working machine includes a pressure riser 130, a bypass oil passage 140, and a switching valve 160. The pressure increasing portion 130 is a portion connected to the exhaust oil passage 24b and increasing the pressure of the exhaust oil passage 24b. The pressure riser 130 is a check valve provided in the oil discharge passage 24b. Specifically, the check valve is provided in the discharge oil passage 24b3 in the section 135 between the confluence portion 26c where the discharge oil passage 24b3 and the discharge oil passage 24a meet and the hydraulic oil tank 15.

The check valve allows the working oil to flow from the merging portion 26a side (merging portion 26c side) toward the hydraulic oil tank 15, and the hydraulic oil is allowed to flow from the hydraulic oil tank 15 side to the merging portion 26a side (merging portion 26c side). ) Is a valve that prevents it from flowing toward. The check valve has a setting member 131 for setting the differential pressure. The setting member 131 is composed of a spring or the like, and a differential pressure is generated by pushing the valve body with a predetermined urging force from the direction opposite to the direction in which the hydraulic oil flows (the direction in which the hydraulic oil flows). In the above-described embodiment, the pressure rising portion 130 is composed of a check valve, but any one can be used as long as it raises the pressure of the drain oil passage 24b, and the oil cooler, the relief valve, and the throttle portion (throttle valve). , May be a choke valve.

The bypass oil passage 140 is an oil passage that constitutes a part of the discharge oil passage 26b, and is an oil passage that bypasses the upstream side of the pressure rising portion 130 and the downstream side of the pressure rising portion 130. Specifically, in the section 135 of the discharge oil passage 24b3, the upstream side of the inflow port 130a of the pressure riser 130 and the downstream side of the discharge port 130b of the pressure riser 130 are connected.
The switching valve 160 is at least a two-position switching valve, and has an allowable position 160a for flowing hydraulic oil toward the pressure riser 130 and a suppression position 160b for suppressing the hydraulic oil from flowing toward the pressure riser 130. It is switchable. Specifically, the switching valve 160 is provided in the bypass oil passage 140, and opens the bypass oil passage 140 when the suppression position 160b is reached, and closes the bypass oil passage 140 when the allowable position is 160a.

In this embodiment, the switching valve 160 is switched by an electric signal. As shown in FIG. 1, a control device 165 composed of a CPU or the like is connected to the switching valve 160. An operating member 166 is connected to the control device 165. The operation member 166 is a switch that can be switched ON / OFF. For example, when the operator turns on the operation member 166, the control device 165 switches the switching valve 160 to the suppression position 160b by outputting a control signal to the switching valve 160. Further, when the operator turns off the operation member 166, the control device 165 switches the switching valve 160 to the allowable position 160a by outputting a control signal to the switching valve 160. In the above-described embodiment, the switching valve 160 is switched manually by the operator operating the operation member 166, but even if the control device 165 determines the state of the working machine and automatically switches the switching valve 160. good.

According to the above, in the state where the switching valve 160 is in the allowable position 160a, the bypass oil passage 140 is closed, so that the operation is performed on the upstream side of the inflow port 130a of the pressure riser 130 in the section 135 of the discharge oil passage 24b3. The flow of oil changes. Cause differential pressure by the throttle portion 151 provided in the third oil passage 110 leading to the oil discharge passage 24b, the pressure in the first internal oil passage 61a is lowered, as indicated by an arrow A1 in FIG. 2 A, the discharge oil passage 24b The hydraulic oil of No. 1 passes through the first discharge port 33a and flows into the third oil passage 110. As shown by the arrow A2 in FIG. 2 A, the return oil and the like flowing through the first inner oil path 61a communicating with the third hydraulic fluid is flowing back to the oil passage 110 (backflow oil) and the third oil passage 110, the first 1 Passes through the internal oil passage 61a and the first output port 41a, and flows into the external oil passage 61b. As indicated by an arrow A3 in FIG. 2 A, part of the hydraulic fluid of an external oil passage 61b flows through the connecting oil path 121 and the third inner oil passage 122 through the confluence section 63, from the third input port 46c It is discharged. Further, as shown in the arrow A4 in FIG. 2 A, the hydraulic fluid discharged from the third input port 46c returns through the oil passage 123, returns to the first control valve 20A again, the first control valve 20A Enter the second input port 46b. As shown by an arrow A5 of FIG. 2 A, hydraulic fluid enters the second input port 46b of the first control valve 20A flows through the second inner oil passage 86 of the second oil passage 85, the second oil passage 85 It will flow into the communication oil passage 21b. That is, as shown in A1 to A5 of FIG. 2A, when the switching valve 160 is set to the allowable position 160a, the hydraulic oil in the discharge oil passage 24b is made to flow back, and the backflowing hydraulic oil or the like is used as the communication oil through which the supply oil flows. It can be supplied to the road 21b.

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

On the other hand, when the switching valve 160 is suppressed position 160 b, since the bypass oil path 140 is opened, as indicated by an arrow A6 in FIG. 2 A, working oil discharge oil passage 24b3 is passed through the bypass oil path 140 Then, it flows toward the hydraulic oil tank 15 and the like. Therefore, since the pressure increasing portion 130 does not act, the pressure of the hydraulic oil in the section 135 of the discharge oil passage 24b3 does not increase. In this case, the hydraulic oil that has passed through the third oil passage 110 of the first control valve 20A can be flowed toward the hydraulic oil tank 15 or the like.

For example, if the bucket 11 or the spare actuator becomes immobile for some reason and the return oil of the first control valve 20A cannot be supplied to the second control valve 20B through the first oil passage 61, there is no place for the return oil. It is conceivable that the first hydraulic actuator 17 becomes difficult to move. In this embodiment, since the third oil passage 110, the discharge oil passage 24b, and the bypass oil passage 140 are provided, the return oil that cannot be supplied from the first control valve 20A to the second control valve 20B can be supplied to the third oil passage. It can be released to the hydraulic oil tank 15 via the 110, the drain oil passage 24b, and the bypass oil passage 140, and as a result, the first hydraulic actuator 17 can be smoothly moved. That is, since the return oil on the rod side of the first hydraulic actuator 17 can be returned to the bottom side of the first hydraulic actuator 17, the speed at which the first hydraulic actuator 17 is extended can be improved.

Further, by switching the switching valve 160, it is possible to efficiently regenerate the hydraulic oil to flow back to the first control valve 20A, and it is possible to improve the fuel efficiency of the working machine.
As shown in FIG. 2B, the check valve 171 may be provided in the switching valve 160. The check valve 171 allows hydraulic oil to flow from the hydraulic oil tank 15 or the like to the confluence portion 26c side when the switching valve 160 is set to the suppression position 160, and flows from the confluence portion 26c side to the hydraulic oil tank 15 side. It is a valve that suppresses this.

FIG. 3 shows a first modification of the hydraulic system of the working machine. The hydraulic system of the working machine of the first modification includes a switching valve 168 different from the switching valve 160 described above.
The switching valve 168 is a valve that can be switched between an allowable position for flowing hydraulic oil toward the pressure rising portion 130 and a suppressing position for suppressing the flow of hydraulic oil toward the pressure rising portion 130. The switching valve 168 is also a valve capable of performing a float operation.

The switching valve 168 is a three-position switching valve, and can be switched between the first position 168a, the second position 168b, and the third position 168c. Further, the switching valve 168 has a first port 231, a second port 232, a third port 233, a fourth port 234, a fifth port 235, and a sixth port 236. An oil passage 169a branched from the communication oil passage 21a is connected to the first port 231, and an oil passage 169b branched from the communication oil passage 21b is connected to the second port 232. Further, the 4th port 234 and the 5th port 235 are connected to the oil passage 169c. The oil passage 169c is an oil passage connecting the fourth port 234 and the fifth port 235 with the inflow port 130a of the pressure increasing portion 130.

The third port 233 and the sixth port 236 are connected to the branch oil passage 280. The branch oil passage 280 is an oil passage leading to a discharge portion for discharging hydraulic oil. The discharge part is a hydraulic oil tank and a suction part (a part for sucking hydraulic oil) of the hydraulic pump. The discharge portion may be any portion as long as it is a portion where the hydraulic oil is discharged, and may be other than the suction portion of the hydraulic oil tank and the hydraulic pump.

It is an oil passage branched from the discharge oil passage 24b, and includes an oil passage 280a and an oil passage 280b. The oil passage 280a is an oil passage that branches from the oil passage 24b2 and connects to the third port 233. The oil passage 280b is an oil passage having one end connected to the sixth port 236 and the other end reaching the hydraulic oil tank 15.
When the switching valve 168 is in the first position 168a, the spool of the switching valve 168 communicates the first port 231 and the fifth port 235, and communicates the second port 232 and the fourth port 234. As a result, when the switching valve 168 is in the first position 168a, the hydraulic oil in the communication oil passage 21a passes through the oil passage 169a and the oil passage 169c, reaches the pressure rise portion 130, and then reaches the pressure rise portion 130. Is discharged to the hydraulic oil tank 15. That is, when the switching valve 168 is in the first position 168a, the hydraulic oil inside the first actuator 14 passes through the first flow passage 281 and is discharged to the hydraulic oil tank 15, and the float operation is performed. Will be.

When the switching valve 168 is in the second position 168b, the spool of the switching valve 168 communicates the third port 233 and the sixth port 236. When the switching valve 168 is in the second position 168b, the spool of the switching valve 168 cuts off the communication between the first port 231 and the fifth port 235, and the second port 232 and the fourth port 234. Block communication. That is, when the switching valve 168 is in the second position 168b, the branch oil passage 280 is opened. As a result, when the switching valve 168 is in the second position 168b, the hydraulic oil discharged from either the first discharge port 33a or the second discharge port 33b of the first control valve 20A is the oil passage 280a and the oil passage 280b. Will be discharged to the hydraulic oil tank 15.

As described above, when the switching valve 168 is in the second position (suppression position) 168b, the hydraulic oil discharged from either the first discharge port 33a or the second discharge port 33b of the first control valve 20A is discharged. , The hydraulic oil can be prevented from flowing toward the pressure rising portion 130.
When the switching valve 168 is in the third position (allowable position) 168c, the spool of the switching valve 168 cuts off the communication between the third port 233 and the sixth port 236. That is, when the switching valve 168 is at the second position 168b, the branch oil passage 280 is closed. Therefore, the hydraulic oil discharged from any of the first discharge port 33a and the second discharge port 33b of the first control valve 20A passes through the oil passages 24b2 and the oil passages 24b3 and reaches the pressure riser 130. Therefore, the pressure of the drainage oil passage 24b can be increased. Even in the first modification, it is preferable that the control device 165 is used for switching the switching valve 168. Further, the switching valve 168 may be manual or automatic as in the above-described embodiment.

Therefore, in the first modification, by switching the switching valve 168 capable of performing the float operation, the pressure of the hydraulic oil in the drainage oil passage 24b can be increased, or the pressure of the hydraulic oil in the discharge oil passage 24b can be increased. It can be in a state where it is not allowed.
FIG. 4 shows a second modification of the hydraulic system of the working machine. The hydraulic system of the working machine of the second modification includes a switching valve 180 different from the switching valve 160 and the switching valve 168 described above. The hydraulic system of the working machine of the second modification is a hydraulic circuit different from the series circuit as in the above-described embodiment.

As shown in FIG. 4, the hydraulic system of the working machine includes a boom control valve 20A, a bucket control valve 20B, and a preliminary control valve 20C. The boom control valve 20A, the bucket control valve 20B, and the preliminary control valve 20C are connected by a central oil passage 500. The boom control valve 20A and the boom cylinder 14 are connected by a communication oil passage 21a and a communication oil passage 21b. The bucket control valve 20B and the bucket cylinder 17 are connected by a communication oil passage 22a and a communication oil passage 22b. The spare control valve 20C and the hydraulic actuator 16 of the spare attachment are connected by an oil supply / drainage passage 83a and an oil supply / drainage passage 83b. A check valve 137 is provided in the oil passage 24b1 and the oil passage 24b2. Further, a check valve 138 is provided in the oil passage 24b4 and the oil passage 24b5. The check valve 137 can suppress the negative pressure generated in the boom cylinder 14 when the boom cylinder 14 is operated. The check valve 138 can suppress the negative pressure generated in the bucket cylinder 17 when the bucket cylinder 17 is operated. A check valve 139 that suppresses the negative pressure of the hydraulic actuator 16 of the spare attachment may be provided. That is, the hydraulic system of the working machine is provided with a check valve (check valve 137, 138, 139) that suppresses the negative pressure of the hydraulic actuator when the hydraulic actuator operates. In other words, the check valve (check valve 137, 138, 139) is a check valve for make-up.

By the way, the oil passage 24b7 of the discharge oil passage 24b is provided with a pressure increasing portion 130. The check valve (check valve 137, 138, 139) operates stably by providing the pressure rising portion 130 to raise the pressure of the drainage oil passage 24b.
The hydraulic system of the working machine of the second modification includes an oil passage 24b8 branched from the oil passage 24b7 of the discharge oil passage 24b. The oil passage 24b8 reaches the hydraulic oil tank 15 and the like from the branch portion 77 branching from the oil passage 24b. The switching valve 180 is at least a two-position switching valve, and has an allowable position 180a for flowing hydraulic oil toward the pressure rising portion 130 and a suppressing position 180b for suppressing the hydraulic oil from flowing toward the pressure rising portion 130. It is switchable. Specifically, the switching valve 180 is provided in the oil passage 24b8, opens the oil passage 24b8 when the suppression position is 180b, and closes the oil passage 24b8 when the allowable position is 180a. The switching valve 180 is switched by the control device 165. The control device 165 is connected to an engine rotation sensor 501 that detects the rotation speed of the prime mover, for example, the engine rotation speed when the prime mover is an engine. Further, the control device 165 is connected to a detection device for detecting the state of the hydraulic actuator such as the boom cylinder 14, the bucket cylinder 17, and the hydraulic actuator 16 of the spare attachment. The detection device is a stroke detection sensor 502, a pilot pressure detection sensor 503, and an operation amount detection sensor 504. The stroke detection sensor 502 is a sensor that detects the stroke of each spool of the plurality of control valves 20, and whether the hydraulic actuator is in an extended state or a contracted state depending on the detected stroke value. Can be detected. The pilot pressure detection sensor 503 is a sensor that detects the pilot pressure acting on the pressure receiving portions of the plurality of control valves 20, and the hydraulic actuator is in an extended state or a contracted state depending on the detected pilot pressure. Can be detected. The operation amount detection sensor 504 is a sensor that detects the operation amount of the operation lever or the like that operates the hydraulic actuator, and the hydraulic actuator is in a state of being extended or contracted depending on the detected operation amount. Can be detected.

For example, when the engine rotation speed detected by the engine rotation sensor 501 is equal to or higher than the threshold value and the boom 10 rises (first condition), the control device 165 sets the switching valve 180 to the suppression position 180b (back pressure decrease). A signal) is output to the switching valve 180 to reduce the pressure in the discharge oil passage 24b (oil passage 24b7). Further, for example, when the engine rotation speed detected by the engine rotation sensor 501 is equal to or higher than the threshold value and the bucket 11 is in a scooping operation (second condition), the control device 165 sends a back pressure drop signal to the switching valve 180. Output and reduce the pressure in the drainage channel 24b.

When the engine is started (third condition), the temperature of the hydraulic oil is below the threshold value (fourth condition), the strokes of the spools of all the control valves 20 are zero (fifth condition), and the like. The control device 165 outputs a back pressure drop signal to the switching valve 180. That is, as shown in the first condition to the fifth condition, the control device 165 reduces the pressure of the drain oil passage 24b by setting the switching valve 180 to the suppression position 180b when make-up is not required.

On the other hand, when the conditions other than the first condition to the fifth condition, that is, when make-up is required, the control device 165 outputs a control signal for setting the switching valve 180 to the allowable position 180a to the switching valve 180. Increase the pressure in the drain oil passage 24b (oil passage 24b7). In other words, by loading a heavy object into the bucket 11, if the boom cylinder 14 moves quickly with a heavy object instead of the hydraulic oil discharged from the first hydraulic pump P1, the switching valve 180 is set to the allowable position 180a. By increasing the pressure in the oil discharge passage 24b, the check valve (check valve 137, 138, 139), that is, the hydraulic actuator corresponding to the check valve can be smoothly operated.

Further, by switching the switching valve 180, unnecessary make-up can be eliminated and the fuel consumption of the working machine can be improved.
It should be noted that the embodiments disclosed this time are exemplary in all respects and are not restrictive. The scope of the present invention is shown by the scope of claims rather than the above description, and is intended to include all modifications within the meaning and scope equivalent to the scope of claims. The first control valve and the second control valve are not limited to the above-described embodiment, and any control valve provided in the working machine may be used. In the above-described embodiment, the hydraulic oil is discharged to the hydraulic oil tank. However, it may be in other places. That is, the oil passage for discharging the hydraulic oil may be connected to other than the hydraulic oil tank, for example, it may be connected to the suction part (the part where the hydraulic oil is sucked) of the hydraulic pump, or at other points. May be connected to.

In the above-described embodiment, the control valve is a 3-position switching valve, but the number of switching positions is not limited, and whether it is a 2-position switching valve or a 4-position switching valve, other switching is possible. It may be a valve. In the above-described embodiment, the hydraulic pump is a constant-capacity pump, but for example, it may be a variable-capacity pump whose discharge amount changes 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 embodiments, but are provided in the working machine 1. All you need is.

1 Work equipment 10 Boom 11 Bucket 14 Boom cylinder 16 Spare attachment hydraulic actuator 17 Bucket cylinder 20A Boom control valve 20a1 First position 20a2 Second position 20a3 Neutral position 20B Bucket control valve 20b1 First position 20b2 Second position 20b3 Neutral position 20C Preliminary control valve 20c1 1st position 20c2 2nd position 20c3 Neutral position 21 Oil passage 28 Oil cooler 28a Inflow port 28b Discharge port 33a 1st discharge port 33b 2nd discharge port 61 1st oil passage 61a 1st internal oil passage 61b External oil Road 86 2nd internal oil passage 110 3rd oil passage 120 4th oil passage 121 Connecting oil passage 122 3rd internal oil passage 123 Return oil passage 123a Section oil passage 123b Section oil passage 130 Pressure riser 130a Inflow port 130b Outlet port 131 Setting member 135 Section 137 Check valve 138 Check valve 139 Check valve 140 Bypass oil passage 160 Switching valve 160a Allowable position 160b Suppression position 165 Control device 166 Operating member 168 Switching valve 168a 1st position 168b 2nd position 168c 3rd position 180 Switching valve 180a Allowable position 180b Suppression position 280 Branch oil passage 280a Oil passage 280b Oil passage 500 Central oil passage

Claims (3)

A hydraulic pump that discharges hydraulic oil and
With the first hydraulic actuator,
With the second hydraulic actuator,
The first control valve that controls the first hydraulic actuator and
A second control valve provided on the downstream side of the first control valve and controlling the second hydraulic actuator,
A discharge oil passage connecting the hydraulic pump and the first control valve,
A central oil passage connecting the first control valve and the second control valve,
An oil discharge passage for discharging hydraulic oil that has passed through the first control valve,
A pressure riser provided in the drainage channel and increasing the pressure of the drainage channel,
A switching valve that can be switched between an allowable position for flowing hydraulic oil toward the pressure rising portion and a restraining position for suppressing the flow of hydraulic oil toward the pressure rising portion.
A first oil passage for supplying return oil, which is hydraulic oil returning from the first hydraulic actuator to the first control valve, to the second control valve.
A second oil passage for supplying the supply oil, which is the hydraulic oil supplied to the first control valve, to the first hydraulic actuator, and
A third oil passage connecting the first oil passage and the discharge oil passage, and
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.
Equipped with
The first oil passage is provided in the first connecting oil passage that connects the first control valve and the first hydraulic actuator and through which the return oil flows, and the first connecting oil passage that is provided in the first control valve. It has a first internal oil passage that communicates with the first internal oil passage 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 middle part of the external oil passage has a merging part that joins in the middle of the central oil passage.
The second oil passage connects the first control valve and the first hydraulic actuator, and is provided in the second connecting oil passage through which the supply oil flows, and the second connecting oil passage provided in the first control valve. Has a second internal oil passage that communicates with
The third oil passage is an oil passage provided in the first control valve and connecting the first internal oil passage and the discharge oil passage, and is provided with a throttle portion.
The fourth oil passage is a connecting oil passage that is different from the first oil passage and connects the external oil passage of the first oil passage and the first control valve, and the first control. The first is the hydraulic oil provided in the valve and communicating with the connecting oil passage and the hydraulic oil communicating with the third internal oil passage and passing through the connecting oil passage and the third internal oil passage. Including the return oil passage to return to the control valve,
The discharge oil passage is branched into two at an intermediate portion, which is an intermediate portion thereof, and a first section oil passage connected from the intermediate portion to the third internal oil passage of the first control valve, and the intermediate portion. A second section oil passage connected to the second internal oil passage of the first control valve is provided.
In the return oil passage, a part of the hydraulic oil of the external oil passage passes through the confluence portion and flows through the connecting oil passage and the third internal oil passage, and passes through the connecting oil passage and the third internal oil passage. A hydraulic system for a working machine, which is an oil passage for passing hydraulic oil through the first section oil passage, the middle portion, and the second section oil passage, and returning it to the second internal oil passage of the first control valve. The drainage oil passage has a bypass oil passage that bypasses the upstream side of the pressure rise portion and the downstream side of the pressure rise portion.
The switching valve is provided in the bypass oil passage, and according to claim 1, the bypass oil passage is opened when the suppression position is reached, and the bypass oil passage is closed when the bypass oil passage is in the allowable position. Work machine hydraulic system. It is provided with a branch oil passage that is connected to the discharge oil passage and leads to a discharge portion that discharges hydraulic oil.
The working machine according to claim 1, wherein the switching valve is provided in the branch oil passage, closes the branch oil passage when it is in the allowable position, and opens the branch oil passage when it is in the restrained position. Hydraulic system.

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