JP2017106485A - Hydraulic system for work machine and work machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydraulic system for a work machine capable of performing float movement and horizontal movement, which can suitably perform both of the float movement and the horizontal movement, and a work machine.SOLUTION: A hydraulic system for a work machine includes a first hydraulic actuator 14, a second hydraulic actuator 17 different from the first hydraulic actuator, a first control valve 20A having a float portion 40 performing float movement of the first hydraulic actuator and controlling the first hydraulic actuator, a second control valve 20B for controlling the second hydraulic actuator, a first oil passage 21 connected to the first hydraulic actuator, a second oil passage 22 connected to the second hydraulic actuator, a horizontal control section 41 connected with the first oil passage and the second oil passage and performing the horizontal movement of the second hydraulic actuator, and a control device 42 for stopping the horizontal movement during the float movement.SELECTED DRAWING: Figure 1

Description

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

  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 moves the boom, a bucket cylinder that moves the bucket, a first control valve that controls expansion and contraction of the boom cylinder, and a second that controls expansion and contraction of the bucket cylinder. And a control valve. The hydraulic oil discharged from the pump is supplied to the first control valve and the second control valve. In addition, since the hydraulic system of Patent Document 1 includes a float control device, the boom can be floated.

JP 2010-84784 A

  Now, hydraulic systems that perform horizontal movement of buckets are known. In order to perform the horizontal movement of the bucket, the bucket can be horizontally operated by supplying hydraulic oil (return oil) that returns to the first control valve when the boom is raised to the bucket cylinder. In a hydraulic system having both the horizontal movement of the bucket and the floating movement of the boom, it has been difficult to operate both properly.

  The present invention has been made to solve the above-described problems of the prior art, and in a hydraulic system capable of a float operation and a horizontal operation, a hydraulic system for a working machine capable of operating both properly. And to provide a working machine.

The technical means of the present invention for solving this technical problem is as follows.
A hydraulic system for a working machine according to the present invention includes a first hydraulic actuator, a second hydraulic actuator different from the first hydraulic actuator, a float unit that performs a floating operation of the first hydraulic actuator, and the first hydraulic actuator, A first control valve for controlling one hydraulic actuator, a second control valve for controlling the second hydraulic actuator, a first oil passage connected to the first hydraulic actuator, and a second hydraulic actuator connected to the second hydraulic actuator A second oil path, a horizontal control unit that is connected to the first oil path and the second oil path and that performs a horizontal operation of the second hydraulic actuator, and a control device that stops the horizontal operation during the float operation It has.

In the hydraulic system for a work machine, the horizontal control unit includes a first switching unit that turns on or off the horizontal operation, and the control device turns off the first switching unit during the float operation.
In the hydraulic system for a work machine, the first oil path includes a first supply path connected to a first port of the first hydraulic actuator and a second supply path connected to a second port of the first hydraulic actuator. And the switching unit is connected to the second supply path.

In the hydraulic system for a work machine, the float unit includes a second switching unit that turns on or off the float unit, and the control device turns off the first switching unit when the second switching unit is turned on. To do.
In the hydraulic system of the work machine, the first hydraulic actuator is a boom cylinder, and the second hydraulic actuator is a bucket cylinder.

In the hydraulic system of the work machine, the first oil path connects the first control valve and the first hydraulic actuator, and the second oil path connects the second control valve and the second hydraulic actuator. Connected.
The work machine includes the hydraulic system described above.

  According to the present invention, in a hydraulic system capable of a float operation and a horizontal operation, both can be appropriately operated.

It is a figure which shows the hydraulic system (hydraulic circuit) in 1st Embodiment. It is a figure which shows the hydraulic system (hydraulic circuit) in 2nd Embodiment. 1 is an overall view of a skid steer loader exemplified as a working machine.

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

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

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

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

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

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

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

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

The plurality of control valves 20 are valves that control various hydraulic actuators provided in the work machine 1. The hydraulic actuator is a device that operates with hydraulic oil, such as a hydraulic cylinder or a hydraulic motor. In this embodiment, the plurality of control valves 20 are a first control valve 20A, a second control valve 20B, and a third control valve 20C.
The first control valve 20 </ b> A is a valve that controls a hydraulic actuator (boom cylinder) 14 that operates the boom 10. The first control valve 20A is a direct acting spool type four position switching valve. The first control valve 20A switches to a neutral position 20a3, a first position 20a1 that is different from the neutral position 20a3, a second position 20a2 that is different from the neutral position 20a3, and the first position 20a1, and a third position 20a4. In the first control valve 20A, the neutral position 20a3, the first position 20a1, the second position 20a2, and the third position 20a4 are switched by moving the spool by operating the operation member. The first control valve 20A is switched by directly moving the spool by manually operating the operating member. However, the spool is moved by hydraulic operation (hydraulic operation by a pilot valve, hydraulic operation by a proportional valve). It may be moved by electric operation (electric operation by exciting a solenoid) or may be moved by other methods. For convenience of explanation, the hydraulic actuator (boom cylinder) 14 may be referred to as a first hydraulic actuator 14.

The first control valve 20A and the first hydraulic pump P1 are connected by a discharge oil passage 27. The hydraulic oil discharged from the first hydraulic pump P1 passes through the discharge oil passage 27 and is supplied to the first control valve 20A. The first control valve 20 </ b> A and the first hydraulic actuator 14 are connected by a first oil passage 21.
Specifically, the first hydraulic actuator (boom cylinder) 14 includes a cylindrical body 14a, a rod 14b that is movably provided on the cylindrical body 14a, and a piston 14c that is provided on the rod 14. A first port 14d through which hydraulic oil is supplied and discharged is provided at the base end of the cylindrical body 14a (the side opposite to the rod 14b side). A second port 14e for supplying and discharging hydraulic oil is provided at the tip (rod 14b side) of the cylindrical body 14a.

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

  Further, the first control valve 20A has a float portion 40 that causes the boom cylinder 14 to float. The float unit 40 is provided on the spool of the first control valve 20A. The float unit 40 includes a passage 40 a that communicates the first port 31 and the first discharge port 33, and a passage 40 b that communicates the second port 32 and the second discharge port 34. The first discharge port 33 and the second discharge port 34 are connected to a discharge oil passage 24 connected to the hydraulic oil tank 15.

  Therefore, if the first control valve 20A is set to the third position 20a4, the first port 31 and the first discharge port 33 communicate with each other, and the second port 32 and the second discharge port 34 communicate with each other. The hydraulic oil in the cylinder body 14a of the boom cylinder 14 is discharged through the first oil passage 21, the first port 31, the second port 32, the passage 40a, the passage 40b, the first discharge port 33, and the second discharge port 34. 24 is discharged. Therefore, the boom cylinder 14 performs a float operation.

The float operation of the boom cylinder 14, that is, the switching of the third position 20a4 of the first control valve 20A can be performed by, for example, a switch 50 provided around the driver's seat 8. When the switch 50 is turned on, the first control valve 20A is switched to the third position 20a4, and the float operation can be started.
The second control valve 20 </ b> B is a valve that controls a hydraulic cylinder (bucket cylinder) 17 that controls the bucket 11. The second control valve 20B is a pilot type direct acting spool type three-position switching valve. The second control valve 20B switches to a neutral position 20b3, a first position 20b1 different from the neutral position 20b3, a neutral position 20b3, and a second position 20b2 different from the first position 20b1. In the second control valve 20B, the neutral position 20b3, the first position 20b1, and the second position 20b2 are switched by moving the spool by operating the operation member. The second control valve 20B is switched by directly moving the spool by manually operating the operating member. However, the spool is moved by hydraulic operation (hydraulic operation by a pilot valve, hydraulic operation by a proportional valve). It may be moved by electric operation (electric operation by exciting a solenoid) or may be moved by other methods. For convenience of explanation, the hydraulic actuator (bucket cylinder) 17 may be referred to as a second hydraulic actuator 17.

  The second control valve 20B and the first control valve 20A are connected by a first supply / discharge oil passage 28a and a second supply / discharge oil passage 28b. When the first control valve 20A is in the neutral position 20a3 or the third position 20a4, the hydraulic oil is supplied to the second control valve 20B through the first supply / discharge oil passage 28a. Further, when the first control valve 20A is at the first position 20a1 or the second position 20a2, hydraulic oil is supplied to the second control valve 20B via the second supply / discharge oil passage 28b.

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

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

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

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

Now, the hydraulic system has a horizontal control unit 41 and a control device 42. The horizontal control unit 41 is a horizontal control valve that performs a horizontal operation of the second hydraulic actuator (bucket cylinder) 17. The horizontal control unit 41 includes a first switching unit 43, a first control unit 44, and a second control unit 45.
The first switching unit 43 is a valve (on-off valve) that switches a horizontal operation, and is, for example, a two-position switching valve that can be switched between a first position 43a and a second position 43b. The 1st switching part 43 is provided in the middle part of the 1st oil path 21 (2nd supply path 21b). When the first switching unit 43 is in the first position 43a, the flow of hydraulic oil returning from the first hydraulic actuator 14 toward the first control valve 20A is allowed in the first oil passage 21 (second supply passage 21b). In addition, the flow of hydraulic oil flowing from the first control valve 20A toward the first hydraulic actuator 14 is allowed. That is, the 1st switching part 43 opens the middle part of the 1st oil path 21 (2nd supply path 21b), when it is the 1st position 43a. When the first switching unit 43 is at the first position 43a, the horizontal operation is not performed.

  When the first switching unit 43 is in the second position 43b, the hydraulic oil (return) returns from the first hydraulic actuator 14 toward the first control valve 20A in the first oil passage 21 (second supply passage 21b). The flow of hydraulic oil that flows from the first control valve 20 </ b> A toward the first hydraulic actuator 14 is allowed. When the first switching unit 43 is at the second position 43b, the horizontal operation is on.

  The first control unit 44 is a two-position switching valve that can be switched between a first position 44a and a second position 44b. The first control unit 44 and the downstream side of the first switching unit 43 (the first hydraulic actuator 14 side) and the first control unit 44 are connected by a first flow path 46, and the operation of the first flow path 46 is performed. The oil pressure acts on the pressure receiving portion 44 c of the first control portion 44. The 2nd control part 45 is a 3 position switching valve which can be switched to the 1st position 45a, the 2nd position 45b, and the 3rd position 45c. The first control unit 44 and the second control unit 45 are connected by the second flow path 47, and the pressure of the hydraulic oil in the second flow path 47 acts on the pressure receiving part 45 d of the second control unit 45. The second flow path 47 is the first oil path 21 (second supply path 21b), and is connected to the upstream side (first control valve 20A side) of the first switching unit 43. The second control unit 45 and the second oil passage 22 (first supply passage 22a) are connected by a third flow passage 48.

  Therefore, in the case of the first position 43a (when the horizontal operation is off), the first hydraulic actuator (boom cylinder) 14 can be expanded and contracted by switching the first control valve 20A, and the second control valve 20B By switching, the second hydraulic actuator (bucket cylinder) 17 can be expanded and contracted. In the case of the second position 43b (when horizontal operation is on), the return from the first hydraulic actuator (boom cylinder) 14 when the first hydraulic actuator (boom cylinder) 14 is extended, that is, when the boom 10 is raised. Oil (referred to as boom return oil) is blocked by the first switching unit 43. The boom return oil acts on the pressure receiving part 44 c of the first control unit 44 and also acts on the pressure receiving part 45 d of the second control unit 45. Then, by switching between the first control unit 44 and the second control unit 45, the boom return oil acts on the second oil path 22 (first supply path 22 a) via the third flow path 48. As a result, the second hydraulic actuator (bucket cylinder) 17 dumps, that is, performs a horizontal operation by the boom return oil.

  The control device 42 is composed of a CPU or the like, and issues a horizontal control command to the horizontal control unit 41. The control device 42 outputs a command to stop the horizontal operation at least during the float operation to the horizontal control unit 41. Specifically, the switch 50 is connected to the control device 42, and a signal indicating whether or not to perform a float operation (ON or OFF of the switch 50) is input. Further, an operation member such as a switch 51 is connected to the control device 42, and a signal indicating whether or not to perform a horizontal operation (ON or OFF of the switch 51) is input.

  When the switch 50 is off (when the float operation is not performed), when the switch 51 is turned on (an operation command for a horizontal operation) is input to the control device 42, the control device 42 receives the first switching unit. 43 solenoid 43c is excited. When the solenoid 43c of the first switching unit 43 is excited, the first switching unit 43 is switched to the second position 43b. When the switch 50 is turned off and the switch 51 is turned off (horizontal operation stop command) is input to the control device 42, the control device 42 demagnetizes the solenoid 43c of the first switching unit 43. When the solenoid 43c of the first switching unit 43 is demagnetized, the first switching unit 43 is switched to the first position 43a.

  In addition, when the switch 50 is on (when the float operation is performed), the control device 42 receives the first switch 51 on (horizontal motion operation command) and inputs the first control device 42. The solenoid 43c of the switching unit 43 is not excited (the first switching unit 43 is turned off). That is, when the float operation and the horizontal operation are set to ON by the switches 50 and 51, the control device 42 does not operate the horizontal operation and stops the horizontal operation (excites the solenoid 43c of the first switching unit 43). . In other words, the control device 42 prohibits execution of the horizontal operation when the float operation is set on by the switches 50 and 51 and the horizontal operation is set on.

  For example, when the float operation is being performed and the switch 51 for setting the horizontal operation is switched from OFF to ON, the control device 42 does not issue a horizontal operation start command to the horizontal control unit 41. Further, when the horizontal operation is performed in a state where the switch 51 for setting the horizontal operation is on and the switch 50 for setting the float operation is set from off to on, the control device 42 performs the horizontal operation. Is commanded to the horizontal control unit 41 (the solenoid 43c of the first switching unit 43 is excited).

According to the above, in a state where the setting of the float operation by the switch 50 is turned off, the bucket 11 can be kept horizontal while raising the boom 10 by turning on the setting of the horizontal operation by the switch 51. . That is, the horizontal operation can be appropriately performed. Even if the setting of the float operation by the switch 50 is ON and the setting of the horizontal operation by the switch 51 is ON, the first switching unit 43 is not set to the second position 43b by the control device 42. Therefore, since the return oil from the boom cylinder 14 can be discharged to the hydraulic oil tank 15, the float operation can be performed appropriately.
[Second Embodiment]
The second embodiment is a modification of the hydraulic system. FIG. 2 shows a deformed portion of the hydraulic system in the second embodiment. Other configurations are the same as those of the first embodiment. In the second embodiment, a structure different from the first embodiment will be described.

  As shown in FIG. 2, the first control valve 20 </ b> A of the second embodiment has a float portion 50 provided in addition to the spool. The first control valve 20 </ b> A includes a float unit 50 and a pilot type direct acting spool type three-position switching valve (switching valve) 51. The switching valve 51 can be switched to the first position 20a1, the second position 20a2, and the neutral position 20a3. Since the switching valve 51 is the same as the above-described first control valve 20A except for the above-described float portion 40, the description is given with reference numerals (the description of the above-described first control valve 20A is referred to the switching valve 50). Just replace it). The float unit 50 includes a plurality of float channels 52 and a plurality of second switching units 53.

The plurality of float flow paths 52 include a first float flow path 52a that connects the first supply path 21a and the discharge oil path 24, and a second float flow path 52b that connects the second supply path 21b and the discharge oil path 24. Including.
The plurality of second switching parts 53 include a second switching part 53a connected to the middle part of the first float channel 52a and a second switching part 53b connected to the middle part of the second float channel 52b. . The second switching unit 53a is a two-position switching valve that can be switched between the first position 53a1 and the second position 53a2. When the second switching unit 53a is at the first position 53a1, the second switching unit 53a prevents the hydraulic oil from passing through the first float flow path 52a and discharging the hydraulic oil from the first supply path 21a to the discharge oil path 24. . When the second switching portion 53a is at the second position 53a2, the hydraulic oil passes through the first float flow path 52a and allows the hydraulic oil to be discharged from the first supply path 21a to the discharge oil path 24. . That is, the second switching unit 53a is opened when the second position 53a2 is reached.

  The second switching unit 53b is a two-position switching valve that can be switched between the first position 53b1 and the second position 53b2. When the second switching unit 53b is in the first position 53b1, the hydraulic oil passes through the second float channel 52b and prevents the hydraulic oil from being discharged from the second supply channel 21b to the discharge oil channel 24. . When the second switching portion 53b is in the second position 53b2, the hydraulic oil passes through the second float flow path 52b and allows the hydraulic oil to be discharged from the second supply path 21b to the discharge oil path 24. . That is, the second switching unit 53b opens when the second position 53b2.

  Therefore, when the second switching portion 53a is at the second position 53a2 and the second switching portion 53b is at the second position 53b2, the hydraulic fluid in the first supply passage 21a and the second supply passage 21b is in the first float passage 52a. And it is discharged | emitted to the discharge oil path 24 through the 2nd float flow path 52b. Therefore, the float operation is turned on. When the second switching unit 53a is at the first position 53a1 and the second switching unit 53b is at the first position 53b1, the hydraulic fluid in the first supply path 21a and the second supply path 21b is in the first float path 52a. In addition, the oil is not discharged to the oil discharge passage 24 through the second float passage 52b. Therefore, the float operation is turned off.

  The control device 42 switches the second switching unit 53 (53a, 53b). When the switch 50 is set to ON, the control device 42 excites the solenoid 53a3 of the second switching unit 53a and the solenoid 53b3 of the second switching unit 53b. When the switch 50 is set to OFF, the control device 42 demagnetizes the solenoid 53a3 of the second switching unit 53a and the solenoid 53b3 of the second switching unit 53b.

Therefore, the control device 42 demagnetizes the solenoid 43c of the first switching unit 43 in a state where the solenoid 53a3 of the second switching unit 53a and the solenoid 53b3 of the second switching unit 53b are excited.
According to the above, even if the setting of the float operation by the switch 50 is on and the setting of the horizontal operation by the switch 51 is on, the control device 42 does not set the first switching unit 43 to the second position 43b. Therefore, since the return oil from the boom cylinder 14 can be discharged to the hydraulic oil tank 15, the float operation can be performed appropriately.

In the above-described embodiment, the plurality of float channels 52 are connected by the plurality of second switching units 53, but the number of the second switching units 53 may be one. For example, a plurality of float flow paths 52 may be joined on the way, and the float flow paths after joining may be connected by one second switching unit 53.
The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims. In the above-described embodiment, the hydraulic oil is discharged to the hydraulic oil tank, but may be other places. That is, the oil passage for discharging the hydraulic oil may be connected to other than the hydraulic oil tank, for example, may be connected to a suction part (a part for sucking the hydraulic oil) of the hydraulic pump, or other parts. You may connect to.

DESCRIPTION OF SYMBOLS 1 Work implement 20 Control valve 20A 1st control valve 20B 2nd control valve 21 1st oil path 21a 1st supply path 21b 2nd supply path 22 2nd oil path 22a 1st supply path 22b 2nd supply path 24 Exhaust oil path 27 Discharge oil passage 28a First supply / discharge oil passage 28b Second supply / discharge oil passage 31 First port 32 Second port 35 First port 36 Second port 40 Float section 41 Horizontal control section 42 Control device 43 First switching section 50 Float part 51 Switching valve 52 Float flow path 52a First float flow path 52b Second float flow path 53 Second switch part 53a Second switch part 53b Second switch part P1 First hydraulic pump P2 Second hydraulic pump

Claims (7)

A first hydraulic actuator;
A second hydraulic actuator different from the first hydraulic actuator;
A first control valve having a float part for performing a float operation of the first hydraulic actuator, and controlling the first hydraulic actuator;
A second control valve for controlling the second hydraulic actuator;
A first oil passage connected to the first hydraulic actuator;
A second oil passage connected to the second hydraulic actuator;
A horizontal control unit connected to the first oil path and the second oil path and performing a horizontal operation of the second hydraulic actuator;
A control device that stops the horizontal operation during the float operation;
The working machine's hydraulic system. The horizontal control unit has a first switching unit for turning on or off the horizontal operation,
The hydraulic system for a working machine according to claim 1, wherein the control device turns off the first switching unit during the float operation.   The first oil passage has a first supply passage connected to a first port of the first hydraulic actuator and a second supply passage connected to a second port of the first hydraulic actuator, and the first switching passage. The working unit hydraulic system according to claim 2, wherein the unit is connected to the second supply path. The float unit has a second switching unit that turns on or off the float unit,
4. The hydraulic system for a working machine according to claim 2, wherein the control device turns off the first switching unit when the second switching unit is turned on. 5.   The hydraulic system for a working machine according to any one of claims 1 to 4, wherein the first hydraulic actuator is a boom cylinder, and the second hydraulic actuator is a bucket cylinder.   2. The first oil passage connects the first control valve and the first hydraulic actuator, and the second oil passage connects the second control valve and the second hydraulic actuator. The hydraulic system of the working machine according to any one of?   The working machine provided with the hydraulic system of the working machine in any one of Claims 1-6.

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