JP2019060485A - Hydraulic system of working machine - Google Patents

Abstract

To enable a plurality of control valves (hydraulic actuators) to be easily operated in a series circuit.SOLUTION: A hydraulic system of a working machine comprises: a hydraulic pump discharging hydraulic oil; a first hydraulic actuator; a second hydraulic actuator; a first control valve that has an input port into which the hydraulic oil to be supplied to the first hydraulic actuator is introduced, and controls the first hydraulic actuator by the supplied hydraulic oil; a second control valve that is provided on a downstream side of the first control valve and controls the second hydraulic actuator; a first oil passage that connects the first control valve to the second control valve and supplies return oil, which is the hydraulic oil returning from the first hydraulic actuator to the first control valve, to the second control valve; a second oil passage that, separately from the first oil passage, connects the first control valve to the second control valve; and a third oil passage that returns the return oil of the first oil passage to the input port.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a hydraulic system of a working machine such as a skid steer loader and a compact truck loader.

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

JP, 2010-270527, A

  In the work machine of Patent Document 1, when the spool of the first control valve is not operated, the hydraulic fluid discharged from the pump passes through the inside of the first control valve and the second control valve and the third control valve It is possible to supply On the other hand, when the spool of the first control valve is operated, the hydraulic oil (return oil) that has 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 valve (second control valve, third control valve) Use a series circuit. However, in the series circuit, it may be difficult to operate the downstream second control valve, the third control valve, and the like at the time of operation of the upstream control valve or the like.

  The present invention was made to solve the problems of the prior art as described above, and is a hydraulic system of a working machine capable of easily operating a plurality of control valves (hydraulic actuators) in a series circuit. Intended to be provided.

The technical means of the present invention for solving this technical problem are as follows.
The hydraulic system of the work machine has a hydraulic pump for discharging hydraulic fluid, a first hydraulic actuator, a second hydraulic actuator, and an input port into which hydraulic fluid to be supplied to the first hydraulic actuator is introduced. A first control valve for controlling the first hydraulic actuator by the supplied hydraulic oil, a second control valve provided downstream of the first control valve and for controlling the second hydraulic actuator, and the first control valve A first oil passage connecting the first control valve and the second control valve, and supplying the second control valve with a return oil, which is a hydraulic oil returning from the first hydraulic actuator to the first control valve; A second oil passage connecting the first control valve and the second control valve separately from the first oil passage and in communication with the second oil passage communicating with the first oil passage; And the input of the return oil of the first oil passage It includes a third oil passage that returns to over preparative, a.

The first control valve has a neutral position for supplying the supply oil, which is the hydraulic oil supplied to the first control valve, to the second oil passage by passing the first control valve, and the first hydraulic actuator The supply oil is supplied to the first oil passage, and the return oil is allowed to flow to the first oil passage, and is further switchable to a side position connecting the third oil passage and the second oil passage.
The first hydraulic actuator is an expanding and contracting hydraulic cylinder, which can discharge hydraulic oil as the return oil at the time of contraction and extension, and the first control valve has a first output connected to the second oil passage And a second output port connected to the first oil passage, and the three oil passages include the input port and the first output port when the first control valve is in the side position. Connect

  The first hydraulic actuator has a first port capable of discharging hydraulic oil as the return oil at the time of contraction, and a second port capable of discharging hydraulic oil as the return oil at the time of extension, and the first oil A passage connects the first control valve and the second port of the first hydraulic actuator, and an oil passage through which return oil discharged from the second port flows, and is provided in the first control valve and the oil A first internal oil passage communicating with the passage and the second output port; and an external oil passage communicating with the first internal oil passage and the second port and connected to the second control valve .

  The hydraulic system of the work machine connects a third hydraulic actuator, a third control valve for controlling the third hydraulic actuator, the first control valve and the third control valve, and the third hydraulic actuator The fourth oil passage for supplying the first control valve with the return oil, which is the hydraulic oil returning from the third control valve to the third control valve, and the return oil, which is the hydraulic oil returning from the third hydraulic actuator , And an exhaust oil passage to be discharged.

The hydraulic system of the work machine includes a bucket and a work tool provided on the boom separately from the bucket, and the first hydraulic actuator is a bucket cylinder for operating the bucket, and the second hydraulic actuator Is a hydraulic device that operates the work tool.
The hydraulic system of the working machine includes a boom, a bucket provided to the boom, and a work tool provided to the boom separately from the bucket, and the first hydraulic actuator operates a bucket cylinder for operating the bucket The second hydraulic actuator is a hydraulic device that operates the work tool, and the third hydraulic actuator is a boom cylinder that operates the boom.

The hydraulic system of the working machine includes a boom and a bucket provided to the boom, the first hydraulic actuator is a boom cylinder for operating the boom, and the second hydraulic actuator operates the bucket. Boom cylinder.
The hydraulic system of the work machine includes a pressure raising portion that raises the pressure of the hydraulic fluid in the first oil passage.

  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 a figure which shows the hydraulic system of the working machine provided with the pressure rise part. It is a figure which shows the modification of the hydraulic system of a working machine. It is a general view of a skid steer loader illustrated as a work machine.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a hydraulic system for a working machine according to the present invention and a preferred embodiment of a working machine provided with the hydraulic system will be described with reference to the drawings.
First, the working machine will be described.
FIG. 4 shows a side view of a working machine according to the present invention. In FIG. 4, a skid steer loader is shown as an example of the work machine. However, the working machine according to the present invention is not limited to the skid steerer, and may be, for example, another type of loader working machine such as a compact track loader. In addition, a working machine other than the loader working machine may be used.

The work implement 1 includes an airframe (vehicle body) 2, a cabin 3, a work device 4, and travel devices 5A and 5B.
A cabin 3 is mounted on the fuselage 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. 4) of the driver sitting on the driver's seat 8 of the work machine 1 is forward, the rear side (right side in FIG. 4) of the driver is rear, and the left side 4) will be described as the left, and the driver's right side (the far side in FIG. 4) as the right. Moreover, the horizontal direction which is a direction orthogonal to the front-back direction is demonstrated as a body width direction. The direction from the central part of the airframe 2 to the right or left will be described as the direction outside the airframe. In other words, the extracorporeal direction is the width direction of the vehicle and is the direction away from the vehicle 2. The direction opposite to the direction outside the aircraft will be described as the direction inside the aircraft. In other words, the inside of the vehicle is the width direction of the vehicle and is the direction approaching the vehicle 2.

  The cabin 3 is mounted on the airframe 2. The work device 4 is a device that performs work and is equipped on the machine body 2. The traveling device 5 </ b> A is a device for causing the vehicle 2 to travel, and is provided on the left side of the vehicle 2. The traveling device 5 </ b> B is a device for causing the vehicle 2 to travel, and is provided on the right side of the vehicle 2. At the rear of the fuselage 2, a motor 7 is provided. The prime mover 7 is a diesel engine (engine). The motor 7 is not limited to the 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. On the right side of the driver's seat 8, a travel lever 9R is provided. The left traveling lever 9L operates the left traveling device 5A, and the right traveling lever 9R operates the right traveling device 5B.
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 2. The bucket 11 is provided at the front end (front end) of the boom 10. The lift link 12 and the control link 13 support the base (rear) 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 portion of the lift link 12 is pivotally supported at the upper portion of the base of the boom 10. The lower part of the lift link 12 is pivotally supported on the rear side 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 by the lower portion of the base of the boom 10 and the other end is pivotally supported by the airframe 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 at the front of the base of the boom 10. The lower part of the boom cylinder 14 is pivotally supported on the rear side of the airframe 2. When the boom cylinder 14 is expanded and contracted, the boom 10 pivots 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 connects between the right portion of the bucket 11 and the right boom. In addition, in place 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, a snow blower or the like can be attached to the tip (front) of the boom 10. .

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

The working hydraulic system is a system for operating the boom 10, the bucket 11, the spare attachment, etc., and as shown in FIG. 1, a plurality of control valves 20 and a hydraulic pump (first hydraulic pump) P1 of the working system. Have. In addition, 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 constituted by a fixed displacement 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 constituted by a fixed displacement 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 fluid for signals and hydraulic fluid for control in a 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 operated by hydraulic fluid, such as a hydraulic cylinder, a hydraulic motor or the like. 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 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 and 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 the operation of the operation member. The boom control valve 20A is switched by directly moving the spool by manually operating the operation member, but the spool is moved by hydraulic operation (hydraulic operation by a pilot valve, hydraulic operation by a proportional valve) It may be moved by electrical operation (electrical 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 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 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. 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 14 a, a rod 14 b provided movably on the cylinder 14 a, and a piston 14 c provided on the rod 14 b. A first port 14d for supplying and discharging the hydraulic oil is provided at the base end of the cylinder 14a (opposite to the rod 14b). A second port 14e for supplying and discharging the hydraulic oil is provided at the tip (rod 14b side) of the cylindrical body 14a.

The oil passage 21 includes a first connection oil passage 21a connecting 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 And a second connection oil passage 21b connecting the two ports 14e.
Therefore, when the boom control valve 20A is set to the first position 20a1, the hydraulic fluid can be supplied from the first connection oil passage 21a to the first port 14d of the boom cylinder 14, and the second port 14e of the boom cylinder 14 The hydraulic oil can be discharged to the second connection oil passage 21b. Thereby, the boom cylinder 14 is extended and the boom 10 is raised. By setting the boom control valve 20A to the second position 20a2, the hydraulic fluid can be supplied from the second connection oil passage 21b to the second port 14e of the boom cylinder 14, and the first port 14d of the boom cylinder 14 can be used. The hydraulic oil can be discharged to the connection oil passage 21a. Thereby, the boom cylinder 14 is contracted and the boom 10 is lowered.

  The bucket control valve 20 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 and a first position 20b1 different from the neutral position 20b3, to a second position 20b2 different from the neutral position 20b3 and the first position 20b1. In the bucket control valve 20B, switching between the neutral position 20b3, the first position 20b1 and the second position 20b2 is performed by moving the spool by the operation of the operation member. Although switching of the bucket control valve 20B is performed by moving the spool directly by manually operating the operation member, the spool is moved by hydraulic operation (hydraulic operation by a pilot valve, hydraulic operation by a proportional valve) It may be moved by electrical operation (electrical operation by exciting a solenoid) or may be moved by other methods.

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

The oil passage 22 includes a first connection oil passage 22a connecting 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 connection of the bucket cylinder 17. And a second supply passage 22b connecting the one port 17d.
Therefore, when the bucket control valve 20B is set to the first position 20b1, the hydraulic oil can be supplied from the first connection oil passage 22a to the second port 17e of the bucket cylinder 17, and the first port 17d of the bucket cylinder 17 The hydraulic oil can be discharged to the second supply passage 22b. As a result, the bucket cylinder 17 contracts and the bucket 11 squeezes. By setting the bucket control valve 20B to the second position 20a2, the hydraulic fluid can be supplied from the second supply passage 22b to the first port 17d of the bucket cylinder 17, and the first connection from the second port 17e of the bucket cylinder 17 The hydraulic oil can be discharged to the oil passage 22a. By this, the bucket cylinder 17 is expanded and dumped.

A discharge oil passage 24c is connected to the first connection oil passage 22a and the second connection oil passage 22b, and a relief valve 38 is provided in the discharge oil passage 24c. The set pressure of the relief valve 38 is set to be higher than, for example, the set pressure of the main relief valve 25.
The preliminary control valve 20C is a valve that controls a 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 and a first position 20c1 different from the neutral position 20c3, and a second position 20c2 different from the neutral position 20c3 and the first position 20c1. In the preliminary control valve 20C, switching between the neutral position 20c3, the first position 20c1 and the second position 20c2 is performed by moving the spool by the pressure of the pilot oil. The connection member 18 is connected to the preparatory control valve 20C via the oil supply and discharge oil passages 83a and 83b. An oil passage connected to the hydraulic actuator 16 of the preliminary attachment is connected to the connection member 18.

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

  Now, in a hydraulic system, a series circuit (series oil passage) is applied. 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 preliminary control valve 20C, the bucket control valve 20B is an upstream control valve, and the preliminary control valve 20C is a downstream control valve.

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". The control valve other than the first control valve and the second control valve and provided on the upstream side of the second control valve is referred to as a "third control valve".
Also, a hydraulic actuator corresponding to the first control valve is referred to as "first hydraulic actuator", a hydraulic actuator corresponding to the second control valve is referred to as "second hydraulic actuator", and a hydraulic actuator corresponding to the third control valve. The thing is called "the third hydraulic actuator". The oil passage for supplying the second control valve with the return oil, which is the hydraulic oil returning from the first hydraulic actuator to the first control valve, is referred to as the "first oil passage".

In this embodiment, the bucket control valve 20B is a "first control valve", the preparatory control valve 20C is a "second control valve", and the boom control valve 20A is a "third control valve". Further, the bucket cylinder 17 is a “first hydraulic actuator”, the hydraulic actuator 16 of the backup attachment is a “second hydraulic actuator”, and the boom cylinder 14 is a “third hydraulic actuator”.
The first control valve, the second control valve, and the third control valve will be described in detail below.

  The third 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 47a. The branched oil passage of the discharge oil passage 27 is connected to the first input port 46a and the second input port 46b of the third control valve 20A. Further, the discharge oil passage 27 is connected to the third input port 46c of the third control valve 20A. Therefore, the hydraulic oil discharged from the first hydraulic pump P1 can be supplied into the third control valve 20A through the discharge oil path 27, the first input port 46a, the second input port 46b, and the third input port 46c. It is. The third control valve 20A and the first control valve 20B are connected by a central oil passage 51. The central oil passage 51 connects the third output port 41c of the third control valve 20A and the third input port 42c of the first control valve 20B.

Now, when the third control valve 20A is set to the neutral position 20a3, the discharge oil passage 27 is supplied to the third 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 a hydraulic oil, is supplied to the central oil passage 51 through the third control valve 20A.
The third control valve 20A and the first control valve 20B are connected by a return oil passage 61 separately from the central oil passage 51. The return oil passage 61 is an oil passage for supplying the return oil from the third hydraulic actuator 14 back to the third control valve 20A to the first control valve 20B through the third control valve 20A. For convenience of explanation, the return oil passage 61 may be referred to as a "fourth oil passage".

The return oil passage 61 has a second connection oil passage 21b, an internal oil passage 61a, and an external oil passage 61b. The second connection oil passage 21 b is an oil passage connecting the second port 32 of the third control valve 20 A and the second port 14 e of the third hydraulic actuator 14, and the second connection oil passage 21 b is a second port 14 e of the third hydraulic actuator 14. It is an oil passage through which the return oil discharged from the
The second connection oil passage 21b is connected to the discharge oil passage 24b. The discharge oil passage 24b includes an oil passage 24b1 connected to the second connection oil passage 21b, an oil passage 24b2 connected to the first discharge port 33a and the second discharge port 33b of the third control valve 20A, an oil passage 24b1 and an oil An oil passage 24b3 connecting the junction of the passage 24b2 and the hydraulic oil tank 15 is provided. A relief valve 37 is provided in the middle of the oil passage 24b1. The set pressure of the relief valve 37 is set to be higher than, for example, the set pressure of the main relief valve 25.

The internal oil passage 61a is an oil passage provided in the third control valve 20A and in communication with the second connection oil passage 21b. Specifically, when the third control valve 20A is set to the second position 20a2, the internal oil passage 61a connects the second port 32 of the third control valve 20A and the first output port 41a of the third control valve 20A. It is an oil passage.
The external oil passage 61b is an oil passage that communicates with the internal oil passage 61a and is connected to the first control valve 20B. The external oil passage 61b connects the first output port 41a of the third control valve 20A and the first input port 42a of the first control valve 20B, and the second output port 41b of the third control valve 20A and the first It is connected to the second input port 42b of the control valve 20B. The middle part of the external oil passage 61 b is connected to the central oil passage 51. In other words, the external oil passage 61 b and the central oil passage 51 merge on the way. In the external oil passage 61b, a check valve 29a is provided between the first control valve 20B and a joining portion 63 where the external oil passage 61b and the central oil passage 51 join together. The check valve 29 a allows hydraulic fluid to flow from the merging portion 63 to the first control valve 20 B, and prevents hydraulic fluid from flowing from the first control valve 20 B to the merging portion 63.

Further, in the external oil passage 61b, a check valve 64 is provided between the junction portion 63 and the third control valve 20A. The check valve 64 allows hydraulic fluid to flow from the third control valve 20A to the merging portion 63, and prevents hydraulic fluid from flowing from the merging portion 63 to the third control valve 20A.
The first control valve 20 B and the second control valve 20 C are connected by a central oil passage (second oil passage) 72. The central oil passage 72 connects the third output port 43c of the first control valve 20B and the third input port 44c of the second control valve 20C. Therefore, when the first control valve 20B is in the neutral position 20b3, the supply oil, which is the hydraulic oil supplied to the first control valve 20B, is a central oil passage 73c connecting 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 first control valve 20 B and the second control valve 20 C are connected by a first oil passage 81 separately from the central oil passage 72. The first oil passage 81 is an oil passage that supplies the return oil, which is returned from the first hydraulic actuator 17 to the first control valve 20B, to the second control valve 20C through the first control valve 20B.
The first oil passage 81 includes an oil passage (first connection oil passage) 22a, an internal oil passage 81a, and an external oil passage 81b. The first connection oil passage 22a is an oil passage connecting the first port 35 of the first control valve 20B and the second port 17e of the first hydraulic actuator 17, and is a return oil discharged from the second port 17e. Flow through the

The oil passage (second connection oil passage) 22b is connected to the discharge oil passage 24b. The discharge oil passage 24b includes an oil passage 24b4 connected to the second connection oil passage 22b, an oil passage 24b5 connected to the first discharge port 34a and the second discharge port 34b of the first control valve 20B, an oil passage 24b4 and an oil An oil passage 24b3 connecting the junction of the passage 24b5 and the hydraulic oil tank 15 is provided.
The internal oil passage 81a is an oil passage provided in the first control valve 20B and in communication with the first connection oil passage 22a. Specifically, the internal oil passage 81a connects the second port 36 of the first control valve 20B and the first output port 43a of the first control valve 20B when the first control valve 20B is at the second position 20b2. It is an oil passage.

  The external oil passage 81b is an oil passage that communicates with the internal oil passage 81a and is connected to the second control valve 20C. The external oil passage 81b connects the first output port 43a of the first control valve 20B and the first input port 44a of the second control valve 20C, and the second output port 43b of the first control valve 20B and the second The second input port 44b of the control valve 20C is connected. The middle part of the external oil passage 81b is connected to the central oil passage 73c. In other words, the external oil passage 81b and the central oil passage 73c merge on the way. In the external oil passage 81b, a check valve 29b is provided between the second control valve 20C and a joining portion 93 where the external oil passage 81b and the central oil passage 73c join together. The check valve 29 b allows hydraulic fluid to flow from the merging portion 93 to the second control valve 20 C, and prevents hydraulic fluid from flowing from the second control valve 20 C to the merging portion 93.

Further, in the external oil passage 81b, a check valve 94 is provided between the merging portion 93 and the first control valve 20B. The check valve 94 allows hydraulic fluid to flow from the first control valve 20B to the merging portion 93, and prevents hydraulic fluid from flowing from the merging portion 93 to the first control valve 20B.
According to the above, when the first control valve 20B is set to the second position 20b2 which is the side position, the supply oil is supplied to the second input port 42b, and the supply oil passes through the second connection oil passage 22b. (1) The hydraulic actuator 17 is supplied. On the other hand, when the first control valve 20B is set to the second position 20b2, the return oil discharged from the second port 17e of the first hydraulic actuator 17 is the first oil passage 81, that is, the first connection oil passage 22a, the inside It flows toward the second control valve 20C through the oil passage 81a and the external oil passage 81b.

  The hydraulic system of the working machine is provided with a third oil passage 90. The third oil passage 90 is an oil passage that returns the return oil flowing from the first control valve 20B toward the second control valve 20C through the first oil passage 81 back to the first control valve 20B. Specifically, the third oil passage 90 is a return oil that is discharged from the first output port 43a of the first control valve 20B and flows through the external oil passage 81b as an input port of the first control valve 20B (a first input port It is an oil passage returned to 42a and the 2nd input port 42b).

  For example, when the first control valve 20B is at the second position 20b2 which is one of the side positions, the third oil passage 90 has the third output port 43c of the first control valve 20B and the first control valve 20B. It is an oil passage which connects with the 3rd input port 42c. In other words, in the case of the second position 20b2 of the first control valve 20B, the third oil passage 90 and the second oil passage 72 are connected. The third oil passage 90 is preferably provided with a throttling portion 91 that reduces the flow rate of the hydraulic oil.

  According to the above, when the first control valve 20B is set to the second position 20b2 which is the side position, the supply oil is supplied to the second input port 42b, and the supply oil passes through the second connection oil passage 22b. (1) The hydraulic actuator 17 is supplied. On the other hand, when the first control valve 20B is set to the second position 20b2, the return oil discharged from the second port 17e of the first hydraulic actuator 17 passes through the inner oil passage 81a and the outer oil passage 81b to perform the second control. It flows toward the valve 20C.

  With the return oil passing through the first oil passage 81 and the preparatory control valve 20C switching to the first position 20c1 or the second position 20c2, the hydraulic pressure 16 of the preparatory attachment is operating, and the hydraulic pressure Consider a case where the actuator 16 is stopped by external force, or in the case where the hydraulic actuator 16 is a hydraulic cylinder, it reaches the end (end) and stops moving, or the hydraulic oil is not supplied. In other words, consider the case where the return oil passes through the first oil passage 81 and no hydraulic oil is introduced to the first input port 44a and the second input port 44b of the preparatory control valve 20C.

  Under such circumstances, when the third oil passage 90 is not provided in the first control valve 20B, the return oil of the first oil passage 81 has no place to go, so the first oil passage 81 is communicated with the first oil passage 81. The pressure on the bottom side of the hydraulic actuator 17 rises. When the pressure on the bottom side of the first hydraulic actuator 17 increases, the pressure on the rod side of the first hydraulic actuator 17 also increases. When the cross-sectional area of the bottom side and the rod side is compared inside the first hydraulic actuator 17, the cross-sectional area on the bottom side is larger than the cross-sectional area on the rod side. As a result, when the first hydraulic actuator 17 is extended by the pressure increase on the bottom side of the first hydraulic actuator 17, the pressure increase on the rod side becomes relatively large. For example, when the first hydraulic actuator 17 and the third hydraulic actuator 14 are combinedly operated, the operation of the first hydraulic actuator 17 may be delayed if the above-described situation occurs.

  On the other hand, when hydraulic oil is not introduced to the first input port 44a and the second input port 44b of the preparatory control valve 20C when there is the third oil passage 90, the return oil of the first oil passage 81 is a merging portion It flows to the second oil passage 72 through 93. The return oil that has flowed to the second oil passage 72 returns to the input port (the first input port 42 a, the second input port 42 b) through the merging portion 63. As a result, the return oil of the first oil passage 81 returns to the first control valve 20B again via the second oil passage 72 and the third oil passage 90, so that the first hydraulic actuator 17 operates smoothly. Can.

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 the time of extension of the first hydraulic actuator 17 can be improved.
In particular, when the first hydraulic actuator (bucket cylinder) 17 and the third hydraulic actuator (boom cylinder) 14 are combinedly operated, for example, when the boom cylinder 17 is extended and the bucket cylinder 14 is extended (the boom 14 is lifted) (When the bucket cylinder 14 is dumped), the bucket 11 can be dumped quickly.

  As shown in FIG. 1, the hydraulic system of the working machine may be provided with a discharge oil passage 70 branched from the internal oil passage 61 c. The internal oil passage 61c is an oil passage connecting the first port 31 and the second output port 41b when the third control valve 20A is in the first position 20a1. The discharge oil passage 70 is an oil passage that communicates with the first discharge port 33a when the first control valve 20A is in the first position 20a1. The discharge oil passage 70 is provided with a throttle portion 71 for reducing the flow rate of the hydraulic oil. The throttling portion 71 is configured, for example, by making a part of the discharge oil passage 70 thinner than the other part. In other words, it is configured by making the cross-sectional area of the portion through which the hydraulic oil flows in the discharge oil passage 70 smaller than the other portions.

Therefore, since a part of the return oil is discharged by the discharge oil passage 70, the third hydraulic actuator 14 can be operated smoothly. The configuration of the diaphragm unit 71 is not limited to the example described above.
Further, as shown in FIG. 2, the hydraulic system of the working machine may be provided with a pressure rising portion 130. The pressure raising portion 130 is a portion that raises the pressure of the first oil passage 81. In other words, the pressure in the first oil passage 81 is raised by raising the pressure in the oil passages (the center oil passage 75, the center oil passage 72, the oil passage 24b3, the oil passage 24b7) connected to the first oil passage 81. The central oil passage 75 is an oil passage connected to the second control valve 20C and in communication with the central oil passage 72. The central oil passage 75 and the oil passage 24b3 join at a joining portion 76. The oil passage 24b7 connects the merging portion 76 and the hydraulic oil tank 15 and the like.

The pressure raising portion 130 is the check valve 19c, the oil cooler 28, and the like. The pressure raising portion 130 may be anything that raises the pressure in the discharge oil passage 24b, and may be a relief valve, a throttling portion (throttling valve), or a choke valve.
Specifically, the check valve 19c is connected to the middle of the oil passage 24b7 of the discharge oil passage 24b. The check valve 19 c is a valve that allows hydraulic fluid to flow toward the hydraulic fluid tank 15 and prevents hydraulic fluid from flowing toward the central fluid passage 75. The check valve 19c has a setting member 19c1 for setting the differential pressure. The setting member 19c1 is constituted by a spring or the like, and generates a differential pressure by pushing the valve body with a predetermined biasing force from the opposite side (the blocking direction) to the direction allowing the flow of the hydraulic oil. According to the check valve 19c, in the oil passage 24b7, it is possible to increase the pressure of the hydraulic fluid on the upstream side from the inlet side of the check valve 19c to the merging portion 76.

  Therefore, when the first control valve 20B is set to the second position 20b2, the pressure of the hydraulic fluid in the central oil passage 75 and the central oil passage 72 can be increased by the check valve 19c. Thus, the pressure of the entire first oil passage 81 connected to the central oil passage 72 can be increased. That is, since the pressure of the first oil passage 81 through which the return oil flows can be increased, the return oil acting on the central oil passage 72 through the merging portion 93 can easily flow to the third oil passage 90. .

  The oil cooler 28 is provided in the middle of the discharge 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. Therefore, when the first control valve 20B is set to the second position 20b2, the pressure of the working oil of the central oil passage 75 and the central oil passage 72 can be increased also in the case of the oil cooler 28 similarly to the check valve 19c. . As a result, the return oil that acts on the central oil passage 72 via the merging portion 93 can easily flow to the third oil passage 90. The return oil that has passed through the third oil passage 90 passes through the third input port 42c, passes through the merging portion 63, and is introduced into the first input port 42a and the second input port 42b.

  FIG. 3 shows a modification of the hydraulic system of the working machine described above. In this modification, the boom control valve 20A is the "first control valve", the bucket control valve 20B is the "second control valve", and the preparatory control valve 20C is the "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 of the backup attachment is a “third hydraulic actuator”. Further, in the modification, the first oil passage is the return oil passage 61. That is, in the case of the modification, the return oil (first oil passage) 61 has a second connection oil passage 21b, an internal oil passage 61c, and an external oil passage 61b. The second oil passage is the central oil passage 51. The third oil passage is an oil passage 190.

  The oil passage (third oil passage) 190 passes the return oil (first oil passage) 61 and flows from the first control valve 20A toward the second control valve 20B to the first control valve 20A again. It is an oil passage to return. Specifically, the oil passage 190 is discharged from the second output port 41b of the first control valve 20A and flows through the external oil passage 61b as the input port (first input port 46a) of the first control valve 20A. It is an oil path to return to

  For example, when the first control valve 20A is at the first position 20a1 which is one of the side positions, the oil passage 190 has the third output port 41c of the first control valve 20A and the third of the first control valve 20A. This is an oil passage connecting the three input port 46c. In other words, when the first control valve 20A is at the first position 20a1, the oil passage 190 and the central oil passage (second oil passage) 51 are connected. Preferably, the oil passage 190 is provided with a throttle portion 191 which reduces the flow rate of the hydraulic oil.

  According to the above, when the first control valve 20A is set to the first position 20a1 which is the side position, the supply oil is supplied to the first input port 46a, and the supply oil passes through the first connection oil passage 21a. 1 supplied to the hydraulic actuator 14 In addition, when the first control valve 20A is set to the first position 20a1, the return oil discharged from the second port 14e of the first hydraulic actuator 14 is returned oil path (first oil path) 61, that is, the second connection It flows toward the second control valve 20B through the oil passage 21b, the internal oil passage 61c and the external oil passage 61b. The return oil that has flowed to the external oil passage 61b passes through the merging portion 63, then flows to the central oil passage (second oil passage) 51, and is introduced to the third input port 41c. The return oil introduced to the third input port 41c flows to the oil path (third oil path) 190 and returns to the input port (first input port 46a). The return oil returned to the input port (first input port 46a) is introduced into the first input port 46a and the second input port 46b via the discharge oil passage 27. As a result, the return oil of the return oil passage (first oil passage) 61 passes through the central oil passage (second oil passage) 51 and the oil passage (third oil passage) 190 to the first control valve 20A again. Since it returns, the 1st hydraulic actuator 14 can be operated smoothly.

It should be understood that the embodiments disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is indicated not by the above description but by claims, and is intended to include all modifications within the meaning and scope equivalent to claims. The first control valve and the second control valve are not limited to the above-described embodiment, and any control valve may be used as long as it is a control valve provided in the work machine. In the above-described embodiment, the hydraulic oil is discharged to the hydraulic oil tank But may be elsewhere. 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 portion (portion which sucks in the hydraulic oil) of the hydraulic pump, or other places You may connect to

  In the embodiment described above, the control valve is a three-position switching valve, but the number of switching positions is not limited, and even if it is a two-position switching valve or a four-position switching valve, other switchings It may be a valve. In the embodiment described above, the hydraulic pump is a constant displacement pump, but may be, for example, a variable displacement pump whose discharge amount is changed by changing the swash plate, or any other hydraulic pump.

In addition, 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 embodiment described above, and are provided in the work machine 1. I hope there is.
Further, as described above, in the hydraulic system (hydraulic circuit) provided with the pressure raising portion 130, the third oil passages 90, 190 may be provided to the control valve on the most downstream side among the plurality of control valves 20. Good.

DESCRIPTION OF SYMBOLS 1 work machine 14 boom cylinder 16 hydraulic actuator of spare attachment 17 bucket cylinder 17d 1st port 17e 2nd port 20 control valve 20A boom control valve 20B bucket control valve 20C spare control valve 61 return oil passage 61a internal oil passage 61b external oil passage 61c internal oil passage 72 central oil passage (second oil passage)
81 first oil passage 81a internal oil passage 81b external oil passage 83a supply and discharge oil passage 83b supply and discharge oil passage 90 third oil passage P1 first hydraulic pump P2 second hydraulic pump

Claims (9)

A hydraulic pump that discharges hydraulic oil,
A first hydraulic actuator,
A second hydraulic actuator,
A first control valve having an input port into which hydraulic fluid to be supplied to the first hydraulic actuator is introduced, and controlling the first hydraulic actuator by the supplied hydraulic fluid;
A second control valve provided downstream of the first control valve and controlling the second hydraulic actuator;
A first oil that connects the first control valve and the second 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 Road,
A second oil passage connecting the first control valve and the second control valve separately from the first oil passage and communicating with the first oil passage;
A third oil passage in communication with the second oil passage and returning return oil of the first oil passage to the input port;
The hydraulic system of the working machine that is equipped with. The first control valve is
A neutral position for supplying a supply oil, which is a hydraulic oil supplied to the first control valve, to the second oil passage through the first control valve;
It is possible to supply the supply oil to the first hydraulic actuator, flow the return oil to the first oil passage, and switch it to a side position connecting the third oil passage and the second oil passage. The hydraulic system of the working machine according to claim 1, wherein The first hydraulic actuator is a hydraulic cylinder that expands and contracts, and can discharge hydraulic oil as the return oil during contraction and expansion,
The first control valve includes a first output port connected to the first oil passage, the second output port, and a third output port connected to the second oil passage.
The hydraulic system according to claim 2, wherein the third oil passage connects the input port and the third output port when the first control valve is in the side position. The first hydraulic actuator has a first port capable of discharging hydraulic oil as the return oil at the time of contraction, and a second port capable of discharging hydraulic oil as the return oil at the time of extension.
The first oil passage is
An oil passage connecting the first control valve and the second port of the first hydraulic actuator and through which return oil discharged from the second port flows;
A first internal oil passage provided in the first control valve and in communication with the oil passage and the first output port;
An external oil passage communicating with the first internal oil passage and the second port and connected to the second control valve;
The hydraulic system of the working machine according to claim 3, comprising A third hydraulic actuator,
A third control valve for controlling the third hydraulic actuator;
Fourth oil that connects the first control valve and the third control valve and supplies return oil, which is hydraulic oil that returns from the third hydraulic actuator to the third control valve, to the first control valve Road,
An exhaust oil passage for discharging a return oil, which is a hydraulic oil returning from the third hydraulic actuator to the third control valve;
The hydraulic system of the working machine according to any one of claims 1 to 4, comprising: With the bucket,
A work tool provided on the boom separately from the bucket;
Equipped with
The hydraulic system according to any one of claims 1 to 5, wherein the first hydraulic actuator is a bucket cylinder for operating the bucket, and the second hydraulic actuator is a hydraulic device for operating the work tool. . With the boom,
A bucket provided to the boom;
A work tool provided on the boom separately from the bucket;
Equipped with
The first hydraulic actuator is a bucket cylinder that operates the bucket,
The second hydraulic actuator is a hydraulic device that operates the work tool,
The hydraulic system of a working machine according to any one of claims 1 to 5, wherein the third hydraulic actuator is a boom cylinder for operating the boom. With the boom,
A bucket provided to the boom;
Equipped with
The hydraulic system of a working machine according to any one of claims 1 to 5, wherein the first hydraulic actuator is a boom cylinder for operating the boom, and the second hydraulic actuator is a boom cylinder for operating the bucket.   The hydraulic system of the working machine according to any one of claims 1 to 8, further comprising a pressure raising portion that raises the pressure of the hydraulic fluid of the first oil passage.

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