JP2017105434A - Hydraulic system of work machine and work machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to suppress a shock in the case that an operation state of hydraulic equipment is changed.SOLUTION: A hydraulic system of a work machine comprises: a hydraulic pump for discharging hydraulic oil; first hydraulic equipment which is operated in the case that a pressure of the hydraulic oil is equal to or more than a prescribed value; a first oil passage which is connected to the first hydraulic equipment and can supply the hydraulic oil to the first hydraulic equipment; a second oil passage which is connected to the first oil passage and can discharge the hydraulic oil in the first oil passage; and a pilot check valve which has a pressure reception part which receives a pressure of the hydraulic oil, blocks discharge of the hydraulic oil in the second oil passage when the pressure reception part receives the pressure of the hydraulic oil, and permits discharge of the hydraulic oil in the second oil passage when the pressure reception part receives no pressure of the hydraulic oil.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.

2. Description of the Related Art Conventionally, a hydraulic system that performs a shift using a variable displacement hydraulic motor in a working machine such as a skid steer loader or a compact truck loader is known (see Patent Document 1).
The hydraulic system disclosed in Patent Document 1 is a system that performs a shift using a swash plate type variable displacement axial motor (HST motor). The hydraulic system has a speed changing mechanism that can change the speed of the HST motor. The speed changing mechanism includes a direction switching valve, a hydraulic switching valve whose position is switched by the direction switching valve, and a swash plate switching cylinder connected to the hydraulic switching valve and the HST motor. In the speed changing mechanism, first, the swash plate switching cylinder is expanded and contracted by changing the position of the hydraulic switching valve using the direction switching valve. When the swash plate switching cylinder expands and contracts, the angle of the swash plate of the HST motor changes, and the HST motor switches to the first speed or the second speed.

JP 2013-36276 A

In the hydraulic system of Patent Document 1, the HST motor is switched to the first speed or the second speed using a hydraulic pressure switching valve of the speed transmission mechanism. For this reason, it is difficult to suppress a shock when shifting is performed by the hydraulic switching valve (when the traveling state is changed). In other words, the feeling when the shift state is changed may be reduced.
The present invention has been made to solve the above-described problems of the prior art, and provides a hydraulic system for a working machine and a working machine that can suppress a shock when changing the operating state of a hydraulic device. The purpose is to provide.

The technical measures taken by the present invention to solve the technical problem are as follows.
The hydraulic system of the work machine includes a hydraulic pump that discharges hydraulic oil, a first hydraulic device that changes an operating state when the pressure of the hydraulic oil exceeds a predetermined level, and the first hydraulic device that is connected to the first hydraulic device. A first oil passage capable of supplying hydraulic oil to one hydraulic device, a second oil passage connected to the first oil passage and capable of discharging the hydraulic oil in the first oil passage, and a pressure receiving pressure for receiving the hydraulic oil The hydraulic oil in the second oil passage when the hydraulic oil is received by the pressure receiving portion and the hydraulic oil is prevented from being discharged from the second oil passage. And a pilot check valve that allows discharge of the gas.

The hydraulic system of the work machine includes a third oil passage connected to the pressure receiving portion, and a first operation portion capable of changing the flow rate of the hydraulic oil to the third oil passage.
A hydraulic system for a work machine includes: a second hydraulic device whose operating state changes when the pressure of the hydraulic oil exceeds a predetermined level; a fourth oil passage connected to the second hydraulic device; and the fourth oil passage And a second operating part that can change the flow rate of the hydraulic oil to the fourth oil passage, and the first oil passage is connected to the fourth oil passage.

The first oil passage is connected to the hydraulic pump.
The first hydraulic device is a traveling motor whose speed can be changed by the pressure of hydraulic oil.
The first hydraulic device is a travel motor whose speed can be changed by the pressure of hydraulic oil, and the second hydraulic device is a brake mechanism that brakes the travel motor and releases the brake by the pressure of hydraulic oil. is there.

The third oil passage is connected to the fourth oil passage and is connected to the first passage capable of discharging the hydraulic oil of the fourth oil passage, and the first passage and the first operation portion are connected to each other. 2 flow paths, and the 3rd flow path which connects the said 2nd flow path and the said pressure receiving part are included.
In the hydraulic system of the work machine, the third oil passage connected to the pressure receiving portion, the first operation portion capable of changing the flow rate of the hydraulic oil to the third oil passage, and the pressure of the hydraulic oil become a predetermined level or more. And a fifth hydraulic passage that connects the first hydraulic section, the second hydraulic equipment, and the third hydraulic passage.

The first operating part is a remote control valve that changes the pressure of the hydraulic oil according to the operation of the operating member, and the second hydraulic device operates according to the pressure of the hydraulic oil output from the remote control valve.
The hydraulic system of the working machine includes a travel motor, the first hydraulic device is a brake mechanism that performs braking and release of the travel motor by pressure of hydraulic oil, and the second hydraulic device A traveling pump that operates according to the pressure of hydraulic oil output from a remote control valve and supplies hydraulic fluid to the traveling motor.

  The hydraulic system of the work machine includes a sixth oil passage connected to the third oil passage and capable of discharging the hydraulic oil in the third oil passage, and a first switching valve connected to the sixth oil passage and switchable. And the first hydraulic device is a brake mechanism that brakes the traveling motor and releases the braking by the pressure of the hydraulic oil, and the second hydraulic device has a hydraulic oil output from the remote control valve. A traveling pump that operates in response to pressure.

  In the hydraulic system of the work machine, the third oil passage connected to the pressure receiving portion, the first operation portion capable of changing the flow rate of the hydraulic oil to the third oil passage, and the pressure of the hydraulic oil become a predetermined level or more. And a remote control valve that changes the pressure of the hydraulic oil in accordance with the operation of the operating member, wherein the first hydraulic equipment is configured to drive the travel motor by the pressure of the hydraulic oil. The second hydraulic device is driven by engine power and operates according to the pressure of hydraulic oil output from the remote control valve and operates on the travel motor. It is a traveling pump that supplies oil, and the first operating part is an anti-stall control valve that prevents the engine from stalling.

  The hydraulic system of the work machine includes a hydraulic pump that discharges hydraulic oil, a first hydraulic device that changes an operating state when the pressure of the hydraulic oil exceeds a predetermined level, and the first hydraulic device that is connected to the first hydraulic device. A first oil passage capable of supplying hydraulic oil to one hydraulic device, a second oil passage connected to the first oil passage and capable of discharging the hydraulic oil in the first oil passage, and a pressure receiving pressure for receiving the hydraulic oil And when the hydraulic pressure is not received by the pressure receiving part, the hydraulic oil is prevented from being discharged from the second oil path, and when the hydraulic oil is received by the pressure receiving part, the hydraulic oil of the second oil path And a pilot check valve that allows discharge of the gas.

The hydraulic system of the work machine includes a third oil passage connected to the pressure receiving portion, and a first operation portion capable of changing the flow rate of the hydraulic oil to the third oil passage.
The hydraulic system of the work machine includes a hydraulic actuator, the first hydraulic device is a work control valve that controls operation of the hydraulic actuator, and the first operating unit is a float switching that performs a float operation of the hydraulic actuator It is a valve.

The working machine hydraulic system includes a relief valve provided in the second oil passage, and the first hydraulic device is a brake mechanism that brakes the traveling motor and releases the braking by the pressure of hydraulic oil, The first operating portion is a second switching valve that is the first oil passage, is connected to the upstream side of the brake mechanism, and is connected to the third oil passage.
A hydraulic system for a working machine includes the remote control valve that is the first oil passage, is connected upstream of the first hydraulic device, and changes the pressure of hydraulic oil in response to an operation of an operation member. 1 hydraulic device is a traveling pump whose traveling state changes depending on the pressure of the hydraulic oil, and the first operating portion acts on the pressure receiving portion of the pilot check valve so as to be the first oil passage, and It is the 3rd switching valve which reduces the pressure of the hydraulic fluid of the area between a remote control valve and the said traveling pump.

The hydraulic system of the work machine includes a hydraulic actuator, a remote control valve that is connected to the first oil passage and upstream of the first hydraulic device, and changes the pressure of the hydraulic oil according to the operation of the operation member, The first hydraulic device is a work control valve that controls the operation of the hydraulic actuator, and the first operating portion acts on the pressure receiving portion of the pilot check valve, whereby the first oil passage And it is a 4th switching valve which reduces the pressure of the hydraulic fluid of the area between the said remote control valve and the said traveling pump.

  The hydraulic system of the work machine includes a third oil passage connected to the pressure receiving portion, a first operation portion capable of changing a flow rate of hydraulic oil to the third oil passage, a hydraulic actuator, and an operation of the hydraulic actuator The first hydraulic device is a ride control device that suppresses a vibration suppression operation that suppresses pressure fluctuations of the hydraulic actuator when the pressure of the hydraulic oil is applied. The first operating valve is a remote control valve that is connected to the work control valve and changes the pressure of the hydraulic oil in accordance with the operation of the operating member.

  The work machine includes the hydraulic system described above.

  ADVANTAGE OF THE INVENTION According to this invention, the shock at the time of changing the operating state of hydraulic equipment can be suppressed.

It is a figure which shows the hydraulic system (hydraulic circuit) in 1st Embodiment. It is a figure which shows the modification of the hydraulic system (hydraulic circuit) in 1st Embodiment. It is a figure which shows the hydraulic system (hydraulic circuit) in 2nd Embodiment. It is a figure which shows the hydraulic system (hydraulic circuit) in 3rd Embodiment. It is a figure which shows the hydraulic system (hydraulic circuit) in 4th Embodiment. It is a figure explaining anti-stall, Comprising: It is a figure which shows the relationship between a primary pressure and an engine speed. It is a figure which shows the hydraulic system (hydraulic circuit) in 5th Embodiment. It is a figure which shows the hydraulic system (hydraulic circuit) in 6th Embodiment. It is a figure which shows the hydraulic system (hydraulic circuit) in 7th Embodiment. It is a figure which shows the hydraulic system (hydraulic circuit) in 8th Embodiment. It is a figure which shows the hydraulic system (hydraulic circuit) in 9th Embodiment. It is a side view which shows the track loader which is an example of a working machine. It is a side view which shows a part of track loader of the state which raised the cabin.

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 overall configuration of the work machine will be described.
As shown in FIGS. 12 and 13, the work machine 1 according to the present invention includes a machine body 2, a work device 3 attached to the machine body 2, and a traveling device 4 that supports the machine body 2. 12 and 13, a truck loader is shown as an example of a working machine. However, the working machine according to the present invention is not limited to a truck loader. For example, a tractor, a skid steer loader, a compact truck loader, a backhoe, etc. It may be. In the present invention, the front side (left side in FIG. 12) of the driver seated in the driver's seat of the work machine is front, the rear side (right side in FIG. 12) is rearward, and the left side of the driver (front side in FIG. 12). Side) is the left side, and the right side of the driver (the back side in FIG. 12) is the right side.

A cabin 5 is mounted on the front portion of the airframe 2. The rear portion of the cabin 5 is supported by the support bracket 11 of the airframe 2 so as to be swingable around the support shaft 12. The front part of the cabin 5 can be placed on the front part of the airframe 2.
A driver's seat 13 is provided in the cabin 5. A travel operation device 14 for operating the travel device 4 is disposed on one side (for example, the left side) of the driver seat 13.

The traveling device 4 is a crawler traveling device. The traveling device 4 is provided below the left side of the body 2 and below the right side of the body 2. The traveling device 4 includes a first traveling unit 21L and a second traveling unit 21R that operate by hydraulic drive, and can travel by the first traveling unit 21L and the second traveling unit 21R.
The work device 3 includes a boom 22L, a boom 22R, and a bucket 23 (work tool). The boom 22L is disposed on the left side of the body 2. The boom 22R is disposed on the right side of the body 2. The boom 22L and the boom 22R are connected to each other by a connecting body. The boom 22L and the boom 22R are supported by the first lift link 24 and the second lift link 25. Between the base side of the boom 22L and the boom 22R and the rear lower part of the machine body 2, a lift cylinder 26 composed of a double-acting pressure cylinder is provided. By simultaneously expanding and contracting the lift cylinder 26, the boom 22L and the boom 22R swing up and down. A mounting bracket 27 is pivotally supported around the horizontal axis on the front ends of the boom 22L and the boom 22R, and the back side of the bucket 23 is attached to the mounting brackets 27 provided on the left and right.

Further, a tilt cylinder 28 composed of a double-acting hydraulic cylinder is interposed between the mounting bracket 27 and the middle part of the boom 22L and the front end side of the boom 22R. The bucket 23 swings (squeeze / dump operation) by the expansion and contraction of the tilt cylinder 28.
The bucket 23 is detachable from the mounting bracket 27. By removing the bucket 23 and attaching various attachments (hydraulic drive work tools having a hydraulic actuator described later) to the mounting bracket 27, various work other than excavation (or other excavation work) can be performed. ing. A prime mover 29 is provided on the rear side of the machine body. The former prime mover 29 is an engine. The prime mover 29 may be an electric motor or may have both an engine and an electric motor. The airframe 2 is provided with a tank (hydraulic oil tank) 31 for storing hydraulic oil.

Next, a hydraulic system for a working machine according to the present invention will be described.
FIG. 1 shows an overall view of a traveling hydraulic system.
As shown in FIG. 1, the hydraulic system (hydraulic circuit) includes a first hydraulic pump P1. The first hydraulic pump P1 is a hydraulic pump that is driven by the power of the engine 29 and discharges hydraulic oil, and is configured by, for example, a constant capacity type gear pump. The first hydraulic pump P1 is mainly used for supplying a control signal (pilot pressure). Hereinafter, for convenience of explanation, the hydraulic fluid discharged from the first hydraulic pump P1 and the hydraulic fluid for the control signal may be referred to as pilot oil, and the pressure of the pilot oil may be referred to as pilot pressure. The hydraulic system has a second hydraulic pump (not shown). The second hydraulic pump is a pump that mainly supplies hydraulic oil to a working hydraulic system. The lift cylinder 26, the tilt cylinder 28, and the like are operated by the hydraulic oil discharged from the second hydraulic pump.

The hydraulic system (hydraulic circuit) includes a first drive circuit 32A and a second drive circuit 32B. The first drive circuit 32A is a circuit that drives the first travel unit 21L provided on the left, and the second drive circuit 32B is a circuit that drives the second travel unit 21R provided on the right.
The first drive circuit 32 </ b> A and the second drive circuit 32 </ b> B include an HST pump (travel pump) 50. The HST pump 50 is connected to the traveling motor 51 of the corresponding first traveling portion 21L, 21R by a pair of speed change oil passages 71h, 71i. Note that the second drive circuit 32B has the same structure as the first drive circuit 32A, and a description thereof will be omitted.

The HST pump 50 is a swash plate type variable displacement axial pump driven by the power of the engine 29 and a pilot-type hydraulic pump (swash plate type variable displacement hydraulic pump) in which the angle of the swash plate is changed by the pilot pressure. . Specifically, the HST pump 50 includes a forward pressure receiving portion 50a and a reverse pressure receiving portion 50b on which pilot pressure acts.
The angle of the swash plate is changed by the pilot pressure acting on the pressure receiving portions 50a and 50b. When the angle of the swash plate is changed, the discharge direction and the discharge amount of the hydraulic oil are changed, thereby changing the rotation output of the first traveling units 21L and 21R. When the rotation speed of the HST pump 50 increases, the discharge amount of the HST pump 50 increases and the traveling speed increases. The rotation speed of the HST pump 50, that is, the discharge amount of the HST pump 50 varies with the output of the engine 29.

Now, the hydraulic system has a first hydraulic device that can change its operating state when the pressure of the hydraulic oil becomes a predetermined pressure or higher. In this embodiment, the first hydraulic device is a travel motor (travel hydraulic motor) 51 provided in the first travel unit 21L and the second travel unit 21R. The travel motor 51 is a travel motor (HST motor) whose speed can be changed by the pressure of the hydraulic oil, and is operated by the hydraulic oil discharged from the HST pump 50. The traveling motor 51 is, for example, a swash plate type variable displacement axial motor that can change speed between high and low speeds.

  The travel motor 51 can be operated by the travel operation device 14. The travel operation device 14 includes a forward remote control valve 36, a reverse remote control valve 37, a right turn remote control valve 38, a left turn remote control valve 39, a travel lever 40 as an operation member, First to fourth shuttle valves 41, 42, 43, and 44 are provided. Each remote control valve 36, 37, 38, 39 is operated in common, that is, by one traveling lever 40. The operating oil discharged from the first pump P1 is supplied to the remote control valves 36, 37, 38, and 39. In the remote control valves 36, 37, 38, and 39, the pressure of the hydraulic oil changes according to the operation of the travel lever (operation member) 40.

  The travel lever 40 can tilt from the neutral position in the front-rear direction, the width direction orthogonal to the front-rear direction, and the oblique direction. By tilting the travel lever 40, each remote control valve 36, 37, 38, 39 of the travel operation device 14 is operated. Then, a pilot pressure proportional to the operation amount from the neutral position of the travel lever 40 is output from the secondary side ports of the remote control valves 36, 37, 38, 39. That is, the remote control valves 36, 37, 38, 39 are constituted by proportional valves. The remote control valve may not be a proportional valve as long as the hydraulic oil pressure changes according to the operation of the travel lever (operation member) 40.

  When the traveling lever 40 is tilted forward (in the direction of arrow A1 in FIG. 1), the forward remote control valve 36 is operated and pilot pressure is output from the remote control valve 36. The pilot pressure acts on the forward pressure receiving portion 50a of the first drive circuit 32A from the first shuttle valve 41 via the first operation oil passage 75a and from the second shuttle valve 42 via the second operation oil passage 75b. It acts on the forward pressure receiver 50a of the second drive circuit 32B. As a result, the output shaft 51a of the first traveling unit 21L and the second traveling unit 21R rotates forward (forward rotation) at a speed proportional to the tilting amount of the traveling lever 40, and the track loader 1 moves straight forward.

  When the traveling lever 40 is tilted rearward (in the direction of arrow A2 in FIG. 1), the reverse remote control valve 37 is operated and pilot pressure is output from the remote control valve 37. This pilot pressure acts on the reverse pressure receiving portion 50b for the first drive circuit 32A from the third shuttle valve 43 via the third operation oil passage 75c, and from the fourth shuttle valve 44 via the fourth operation oil passage 75d. The second drive circuit 32B acts on the reverse pressure receiver 50b. As a result, the output shafts 51a of the first traveling unit 21L and the second traveling unit 21R are reversely rotated (reversely rotated) at a speed proportional to the tilting amount of the traveling lever 40, and the track loader 1 moves straight backward.

  When the traveling lever 40 is tilted to the right (in the direction of arrow A3 in FIG. 1), the right turn remote control valve 38 is operated, and pilot pressure is output from the remote control valve 38. This pilot pressure acts on the forward pressure receiving portion 50a of the first drive circuit 32A from the first shuttle valve 41 via the first operation oil passage 75a, and from the fourth shuttle valve 44 via the fourth operation oil passage 75d. The second drive circuit 32B acts on the reverse pressure receiving portion 50b. As a result, the output shaft 51a of the first traveling unit 21L rotates in the forward direction and the output shaft 51a of the second traveling unit 21R rotates in the reverse direction so that the track loader 1 turns to the right.

  When the travel lever 40 is tilted to the left (in the direction of arrow A4 in FIG. 1), the left turn remote control valve 39 is operated and pilot pressure is output from the remote control valve 39. This pilot pressure acts on the forward pressure receiving portion 50a of the second drive circuit 32B from the second shuttle valve 42 via the second operation oil passage 75b, and from the third shuttle valve 43 via the third operation oil passage 75c. The first drive circuit 32A acts on the reverse pressure receiver 50b. As a result, the output shaft 51a of the second traveling unit 21R rotates in the forward direction and the output shaft 51a of the first traveling unit 21L rotates in the reverse direction so that the track loader 1 turns to the left.

Further, when the traveling lever 40 is tilted in the oblique direction, the first traveling portion 21L and the first traveling portion 21L and the differential pressure between the forward pressure receiving portion 50a and the reverse pressure receiving portion 50b of each of the first drive circuits 32A and 32B are caused. The rotation direction and rotation speed of the output shaft 51a of the second traveling unit 21R are determined, and the truck loader 1 turns right or left while moving forward or backward.
In other words, when the travel lever 40 is tilted to the left and forward, the track loader 1 turns left at a speed corresponding to the tilt angle of the travel lever 40, and when the travel lever 40 is tilted to the right and forward, the travel lever 40 is moved. When the track loader 1 turns right while moving forward at a speed corresponding to the tilt angle, and the travel lever 40 is tilted to the left rear side, the track loader 1 moves backward at a speed corresponding to the tilt angle of the travel lever 40. When turning left and tilting the traveling lever 40 to the right rear side, the truck loader 1 turns right while moving backward at a speed corresponding to the tilting angle of the traveling lever 40.

Hereinafter, a circuit (structure) around the first traveling unit 21L will be described. The circuit (structure) of the second traveling unit 21R is the same as that of the first traveling unit 21L.
Now, the traveling motor (first hydraulic device) 51 of the first traveling unit 21 </ b> L includes a swash plate switching cylinder 53. The swash plate of the travel motor 51 is connected to a swash plate switching cylinder 53. By supplying the hydraulic oil to the swash plate switching cylinder 53 composed of a hydraulic cylinder or the like, the speed of the traveling motor 51 changes. That is, the swash plate switching cylinder 53 is expanded and contracted to switch the swash plate angle of the travel motor 51. As a result, the traveling motor 51 shifts to the first speed or the second speed.

A travel oil 51, that is, a swash plate switching cylinder 53 is connected to a first oil passage (discharge oil passage) 71. A first hydraulic pump P <b> 1 is connected to the first oil passage 71. Therefore, the operating oil discharged from the first hydraulic pump P1 can be supplied to the traveling motor 51 (swash plate switching cylinder 53). Reference numerals X1, X2, and X3 in FIG. 1 indicate connection destinations of the oil passages.
Specifically, the first oil passage 71 includes a first supply passage 71a, a second supply passage 71b, a third supply passage 71c, and a fourth supply passage 71d. A first drive circuit 32A and a second drive circuit 32B are connected to the first supply path 71a, and pilot oil which is the discharge oil of the first hydraulic pump P1 is supplied to the first drive circuit 32A and the second drive circuit 32B. It can be supplied. The travel operation device 14 is connected to the second supply path 71b, and the pilot oil of the first hydraulic pump P1 is supplied to the travel operation device 14 through the second supply path 71b. A first operating part 61 and a second operating part 62 are connected to the third supply path 71c. The first operating part 61 and the second operating part 62 are supplied with pilot oil from the first hydraulic pump P1. The fourth supply path 71d connects the first hydraulic pump P1 and the swash plate switching cylinder 53.

  A second oil passage 72 is connected to the first oil passage 71. The second oil passage 72 is connected to the middle portion of the fourth supply passage 71d. In the fourth supply path 71d, a throttle (throttle part) 80 that reduces hydraulic oil is provided upstream of the connection part that connects the fourth supply path 71d and the second oil path 72. The second oil passage 72 is an oil passage through which the hydraulic oil in the first oil passage 71 can be discharged. The hydraulic oil tank 31 is connected to the second oil passage 72. A pilot check valve 65 is provided in the middle of the second oil passage 72. The pilot check valve 65 has a pressure receiving portion 65a that receives the hydraulic oil. When the pressure of the hydraulic oil applied to the pressure receiving portion 65a is equal to or higher than a predetermined value, the pilot check valve 65 is closed. That is, the pilot check valve 65 prevents the hydraulic oil from being discharged from the second oil passage 72 when the hydraulic oil is received by the pressure receiving portion 65a. On the other hand, if the pressure of the hydraulic oil applied to the pressure receiving portion 65a is less than a predetermined value, the pilot check valve 65 can be opened. That is, the pilot check valve 65 allows the hydraulic oil to be discharged from the second oil passage 72 when the hydraulic oil is not received by the pressure receiving portion 65a.

  Therefore, when the pilot check valve 65 prevents the hydraulic oil from being discharged from the second oil passage 72, the pressure in the first oil passage 71 (fourth supply passage 71d) increases. Therefore, the swash plate switching cylinder 53 can be extended from the first speed to the second speed side. In other words, the pilot check valve 65 prevents the hydraulic oil from being discharged from the second oil passage 72, whereby the travel motor (first hydraulic device) 51 can be shifted from the first speed to the second speed. Since the pilot check valve 65 is used to extend the swash plate switching cylinder 53 (switching the speed), it is possible to suppress the shock of the speed switching (during gear shift switching). A shock in the case of changing the operating state of the traveling motor (first hydraulic device) 51 can be suppressed. Moreover, the operational feeling at the time of speed switching of the traveling motor 51 can be improved.

The operation of the hydraulic oil to the pressure receiving portion 65 a of the pilot check valve 65 is performed by the first operating portion 61. The pressure receiving portion 65 a of the pilot check valve 65 and the first operating portion 61 are connected by a third oil passage 73.
The first operating part 61 is a two-position switching valve whose position can be changed between the first position 61a and the second position 61b. Switching of the 1st operation part 61 is performed by control device 64, for example. An operation member 66 is connected to the control device 64. The operation member 66, a swingable seesaw type switch, a slidable slide type switch, a pushable push type switch, or a lever are configured.

  The control device 64 demagnetizes the solenoid of the first operating portion (two-position switching valve) 61 when the first speed command is given by the operation member 66. In a state where the solenoid of the first operating part 61 is demagnetized, the one operating part is in the first position 61a, so that the pressure of the hydraulic oil (pilot oil) does not act on the pressure receiving part 65a of the pilot check valve 65. The control device 64 excites the solenoid of the first operating part (two-position switching valve) 61 when the second speed command is given by the operation member 66. In a state where the solenoid of the first operating part 61 is excited, the first operating part 61 is in the second position 61b, and therefore the pressure of the hydraulic oil (pilot oil) acts on the pressure receiving part 65a of the pilot check valve 65.

Now, the hydraulic system has a second hydraulic device that can change the operating state when the pressure of the hydraulic oil exceeds a predetermined value, in addition to the traveling motor (first hydraulic device) 51. In this embodiment, the first hydraulic device is a brake mechanism 52 that brakes the traveling motor 51.
The brake mechanism 52 changes to a state in which the traveling motor 51 is braked or released from the brake by the pilot oil (hydraulic oil) discharged from the first hydraulic pump P1. For example, the brake mechanism 52 includes a first disk provided on the output shaft 51a of the travel motor 51, a movable second disk, and a spring that biases the second disk to a side in contact with the first disk. ing. The brake mechanism 52 includes an accommodating portion (accommodating case) 52a that accommodates the first disc, the second disc, and the spring. A fourth oil passage 74 is connected to a portion of the housing portion 52a in which the second disk is accommodated. That is, the brake mechanism 52 is connected. A throttle (throttle part) 81 is provided in the middle of the fourth oil passage 74. A second operating part 62 is connected to the upstream side of the throttle part 81 of the fourth oil passage 74.

The brake mechanism 52 is braked or released by the second operating unit 62. The second operating part 62 is a two-position switching valve whose position can be changed between the first position 62a and the second position 62b. Switching of the 2nd operation part 62 is performed by control device 64, for example.
The control device 64 demagnetizes the solenoid of the second operating part (two-position switching valve) 62, thereby setting the second operating part 62 to the first position 62a. When the 2nd operation part 62 is the 1st position 62a, the operation oil of the 4th oil way 74 flows into operation oil tank 31. Therefore, in the storage part of the storage part 52a, the pressure of the pilot oil becomes equal to or lower than a predetermined value, so that the second disk moves to the side in contact with the first disk. The travel motor 51 is braked by the brake mechanism 52. The control device 64 brings the second operating part 62 into the second position 62b by exciting the solenoid of the second operating part (two-position switching valve) 64. When the 2nd action | operation part 62 is the 2nd position 62b, the working oil discharged from the 1st hydraulic pump P1 flows into the 4th oil path 74. FIG. Therefore, in the storage part of the storage part 52a, the inside of the storage part becomes a predetermined pressure, and the second disk moves to the side opposite to the braking (the side opposite to the biasing direction of the spring). The travel motor 51 is released from braking by the brake mechanism 52.

  In this embodiment, the third oil passage 73 and the fourth oil passage 74 are connected. The third oil path 73 includes a first flow path 73a, a second flow path 73b, and a third flow path 73c. The first flow path 73 a is an oil path that is connected to the fourth oil path 74 and can discharge the hydraulic oil in the fourth oil path 74. A throttle (throttle part) 82 is provided in the middle of the first flow path 73a, and the hydraulic oil tank 31 is connected to the first flow path 73a.

The second flow path 73 b is a flow path that connects the first flow path 73 a and the first operating unit 61. One end of the second flow path 73b is connected to a section between the throttle section 82 of the first flow path 73a and the hydraulic oil tank 31 in the first flow path 73a. A throttle (throttle part) 83 is provided in the middle of the second flow path 73b, and a check valve (check valve) 84 is provided upstream of the throttle part 83 (on the first operating part 61 side). Yes. The check valve 84 allows the hydraulic oil flowing downstream from the first operating portion 61 and blocks the hydraulic oil flowing from the downstream to the first operating portion 61.

The third flow path 73c is a flow path that connects the second flow path 73b and the pressure receiving portion 65a. One end of the third flow path 73c is connected to a section between the throttle portion 83 and the check valve 84 in the second flow path 73b.
According to the above, hydraulic oil (pilot oil) is supplied to the pressure receiving portion 65a through the first flow path 73a and the third flow path 73c in a state where the braking of the traveling motor 51 is released by the brake mechanism 52. Can do. If the first operating portion 61 is set to the second position 61b in a state where the braking of the traveling motor 51 is released, the traveling motor 51 can be switched from the first speed to the second speed.

In the above-described embodiment, the first oil passage 71 is connected to the travel motor (first hydraulic device) 51. Instead, as shown in FIG. 1 hydraulic equipment) 51. Specifically, the fourth oil passage 74 includes a first flow path 74a that connects the second operating portion 62 and the brake mechanism (second hydraulic device) 52, a second operating portion 62, and a travel motor (first hydraulic device). 2 and a second flow path 74b that connects the first flow path 51 and the second flow path 74b. The second flow path 74b is provided with a throttle portion 80, a second oil path 72, and a swash plate switching cylinder 53. Therefore, the hydraulic oil can be supplied to the travel motor (first hydraulic device) 51 in a state where the second operating portion 62 is set to the second position 62b and braking is released by the brake mechanism 52. That is, in the hydraulic system of FIG. 2, the speed of the travel motor 51 can be changed when the braking is released and the vehicle can travel.
[Second Embodiment]
The second embodiment is a modification of the hydraulic system. FIG. 3 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. 3, the first hydraulic device is a brake mechanism 52, and the second hydraulic device is a travel pump 50. The first oil passage 71 includes a first supply passage 71a, a second supply passage 71b, a fifth supply passage 71e, and a sixth supply passage 71f. The fifth supply path 71e connects the first hydraulic pump P1 and the accommodating portion (accommodating case) 52a of the brake mechanism 52. The sixth supply path 71f is connected to the fifth supply path 71e. The sixth supply path 71f is an oil path that can discharge the hydraulic oil in the fifth supply path 71e. The hydraulic oil tank 31 is connected to the sixth supply path 71f.

A pilot check valve 65 having a pressure receiving portion 65a is provided in the middle of the sixth supply path 71f.
The first operating part is a remote control valve (remote control valves 36, 37, 38, 39) that changes the pressure of the hydraulic oil according to the operation of the travel lever 40. For convenience of explanation, the explanation will be given by taking the remote control valve 36 and the remote control valve 37 as an example. The remote control valve is not limited to that shown in the embodiment. The first operating part (remote control valve) and the traveling pump (second hydraulic device) 50 are connected by a fifth oil passage 75. The fifth oil passage 75 connects the second operation oil passage 75b that connects the remote control valve 36 and the forward pressure receiving portion 50a of the traveling pump 50, and the second oil passage 75b that connects the remote control valve 37 and the backward pressure receiving portion 50b of the traveling pump 50. 4 operation oil passage 75d.

  Further, the fifth oil passage 75 and the third oil passage 73 are connected. The third oil path 73 has a fourth flow path 73d connected to the second operation oil path 75b and a fifth flow path 73e connected to the fourth operation oil path 75d. A check valve 85 is connected to the middle part of the fourth flow path 73d and the fifth flow path 73e. The fourth flow path 73d and the fifth flow path 73e are merged, and the merge side is connected to the pressure receiving portion 65. Instead of the check valve 85, a high pressure selection valve that selects a higher pressure may be used. A bleed-off circuit (bleed-off oil path) 88 for discharging hydraulic oil, that is, a sixth oil path 88 is provided in the oil path after the fourth flow path 73d and the fifth flow path 73e merge.

According to the above, when the first operating part (remote control valve) is operated, the traveling pump (second hydraulic device) 50 operates according to the pressure output from the remote control valve. At this time, the pressure of the hydraulic oil increases not only in the fifth oil passage 75 but also in the third oil passage 73 (the fourth passage 73d and the fifth passage 73e). If the pressure of the hydraulic oil in the third oil passage 73 rises, the pilot check valve 65 closes (blocks the hydraulic oil in the sixth supply passage 71f from flowing into the hydraulic oil tank 31). As a result, the sixth supply path 7
When the pressure of 1f increases, the brake mechanism 52 releases the brake. That is, according to the second embodiment, when the traveling operation is performed by the traveling lever 40, the braking can be automatically released.

  When the operation of the first operating part (remote control valve) is stopped, the hydraulic oil in the third oil passage 73 (fourth flow passage 73d, fifth flow passage 73e) passes through the bleed-off circuit (bleed-off oil passage) 88. As a result, the pressure in the third oil passage 73 decreases. The brake mechanism 52 brakes. That is, when the traveling operation of the traveling lever 40 is stopped, the braking can be automatically performed.

In addition, although the 1st action | operation part which can change the flow volume of the hydraulic fluid to a 3rd oil path is comprised by the remote control valve (remote control valve 36, 37, 38, 39), a remote control valve is a travel member (travel lever). 40) may not be directly connected. Further, the hydraulic system may have a structure in which the swash plate of the traveling motor 50 is directly operated by the pressure of the hydraulic oil discharged from the remote control valve.
Further, although the first hydraulic device is the brake mechanism 52 and the second hydraulic device is the travel pump 50, it is not limited to the brake mechanism 52 and the travel pump 50 instead. That is, the second hydraulic device may be a hydraulic device that operates according to the pressure of the hydraulic oil output from the remote control valve. If it does in this way, when the operation member (remote control valve) which operates the 2nd hydraulic equipment is operated, the 1st hydraulic equipment can be operated. That is, the first hydraulic device and the second hydraulic device can be operated in conjunction with the operation of the operation member.
[Third Embodiment]
The third embodiment is a modification of the hydraulic system. FIG. 4 shows a deformed portion of the hydraulic system in the second embodiment. Other configurations are the same as those in the first embodiment or the second embodiment.

  As shown in FIG. 4, the first hydraulic device is a brake mechanism 52, and the second hydraulic device is a travel pump 50. The remote control valves (remote control valves 36 and 37) are electromagnetic proportional valves whose opening degree is changed based on a control signal output from the control device 64. That is, in the second embodiment described above, the operation of the travel lever 40 directly acts on the remote control valve to change the pressure of the hydraulic oil, but the remote control valve of the third embodiment acts electrically. It is a valve. 4 shows the remote control valves 36 and 37 for convenience of explanation, it can be applied to other remote control valves 38 and 39 and hydraulic devices corresponding to the remote control valves 38 and 39.

  An operation member 101 is connected to the control device 64. The operation member 101 is a swingable travel lever. When the travel lever 101 is operated, the operation amount and / or the swinging direction is input to the control device 64. The control device 64 outputs a control signal corresponding to the swing amount output from the travel lever 101 to the remote control valve. The opening of the remote control valve is changed according to the control signal output from the control device 64. Therefore, by operating the travel lever 101, the travel pump 50 can be rotated forward or reverse as in the above-described embodiment.

  As shown in FIG. 4, the first switching valve 102 is connected to the bleed-off circuit (sixth oil passage) 88. The switching valve 102 is a two-position switching valve whose position can be changed between the first position 102a and the second position 102b, and is a hydraulic lock valve that performs hydraulic locking. Switching of the hydraulic lock valve 102 is performed by the control device 64, for example. A switch 103 is connected to the control device 64. When the switch 103 is on, the control device 64 demagnetizes the solenoid of the hydraulic lock valve 102. The hydraulic lock valve 102 is in the first position 102a when the solenoid is demagnetized. Therefore, the hydraulic oil in the third oil path 73 (the fourth flow path 73d and the fifth flow path 73e) passes through the sixth oil path 88 and is discharged to the hydraulic oil tank 31. As a result, the pressure in the third oil passage 73 decreases, and the brake mechanism 52 brakes. That is, if the switch 103 for performing hydraulic lock is turned on, braking can be performed in conjunction with the hydraulic lock.

When the switch 103 is off, the control device 64 excites the solenoid of the hydraulic lock valve 102. The hydraulic lock valve 102 is in the second position 102b when the solenoid is excited. Therefore, since the hydraulic oil in the third oil passage 73 does not flow through the sixth oil passage 88, the pressure in the third oil passage 73 rises and the braking by the brake mechanism 52 is released. That is, if the switch 103 is turned off, braking can be released in conjunction with the hydraulic lock.
[Fourth Embodiment]
The fourth embodiment is a modification of the hydraulic system. FIG. 5 shows a deformed portion of the hydraulic system in the second embodiment. Other configurations are the same as those in the first embodiment or the second embodiment.

  As shown in FIG. 5, the first hydraulic device is a brake mechanism 52, and the second hydraulic device is a travel pump 50. The first operating part is an electromagnetic proportional valve 105 provided on the upstream side of the remote control valves (remote control valves 36 and 37). In the fourth embodiment, for convenience of explanation, the remote control valves 36 and 37 are shown as shown in FIG. 5, but the other remote control valves 38 and 39 and the hydraulic equipment corresponding to the remote control valves 38 and 39 are used. Is also applicable.

The electromagnetic proportional valve 105 is, for example, a control valve (anti-stall control valve) that prevents engine stall. The opening degree of the electromagnetic proportional valve 105 is performed by the control device 64. The anti-stall control performed by the control device 64 and the electromagnetic proportional valve 105 will be described.
The control device 64 prevents engine stall by changing the opening of the electromagnetic proportional valve 105 based on the amount of engine drop that is the difference between the target engine speed and the actual engine speed. The control device 64 can acquire the actual engine speed and the target engine speed.

FIG. 6 shows the relationship between the engine speed, the traveling primary pressure, and the control lines L1 and L2.
The traveling primary pressure is the hydraulic oil pressure (pilot pressure) in the second supply passage 71b from the electromagnetic proportional valve 105 to the remote control valve. That is, it is the primary pressure of the hydraulic oil that enters the remote control valve provided in the traveling lever 40 that performs the traveling operation. The control line L1 shows the relationship between the engine speed and the traveling primary pressure when the drop amount is less than a predetermined amount. The control line L2 shows the relationship between the engine speed and the traveling primary pressure when the drop amount is greater than or equal to a predetermined amount.

  When the drop amount is less than the predetermined value, the control device 64 adjusts the opening degree of the electromagnetic proportional valve 105 so that the relationship between the actual engine speed and the traveling primary pressure matches the control line L1. Further, when the drop amount is equal to or greater than a predetermined value, the control device 64 adjusts the opening degree of the electromagnetic proportional valve 105 so that the relationship between the actual engine speed and the traveling primary pressure matches the control line L2. In the control line L2, the traveling primary pressure for a predetermined engine speed is lower than the traveling primary pressure of the control line L1. That is, when attention is paid to the same engine speed, the traveling primary pressure of the control line L2 is lower than the traveling primary pressure of the control line L1. Therefore, the pressure (pilot pressure) of the hydraulic oil entering the remote control valve is kept low by the control based on the control line L2. As a result, the swash plate angle of the HST pump 50 is adjusted, the load acting on the engine 29 is reduced, and stalling of the engine 29 can be prevented. In FIG. 6, one control line L2 is shown, but a plurality of control lines L2 may be provided. For example, the control line L2 may be set for each engine speed.

The control device 64 preferably has data indicating the control lines L1 and L2, or control parameters such as functions.
In the second supply path 71b, a third oil path 73 is connected to a section 71b1 between the electromagnetic proportional valve 105 and the remote control valve. Therefore, when the electromagnetic proportional valve 105 is operated, the pressure in the third oil passage 73 increases, so that the braking can be released in conjunction with the anti-stall control. In this embodiment, the electromagnetic proportional valve 105 has been described by taking an anti-stall control valve as an example. However, the electromagnetic proportional valve 105 may not be an anti-stall control valve.
[Fifth Embodiment]
As shown in FIG. 7, the fifth embodiment is an embodiment in which the pilot check valve 65 described above is changed to the pilot check valve 110.

The pilot check valve 110 has a pressure receiving part 110a that receives hydraulic oil. When the pressure of the hydraulic oil applied to the pressure receiving part 110a is equal to or higher than a predetermined value, the pilot check valve 110 opens. That is, the pilot check valve 110 allows the hydraulic oil to be discharged from the second oil passage when the hydraulic oil is received by the pressure receiving portion 110a. On the other hand, if the pressure of the hydraulic oil applied to the pressure receiving portion 110a is less than a predetermined value, the pilot check valve 110 is closed. That is, the pilot check valve 110 prevents the hydraulic oil from being discharged from the second oil passage when the hydraulic oil is not received by the pressure receiving portion 110a. In this embodiment, the sixth supply path 71f shown in the first embodiment is the second oil path.

  As shown in FIG. 7, a pilot check valve 110 is provided in the middle of the second oil passage (sixth supply passage 71f). A relief valve 111 is provided on the downstream side of the pilot check valve 110. The first hydraulic device is a brake mechanism 52. The first oil passage 71 includes a fifth supply passage 71e that connects the first hydraulic pump P1 and the accommodating portion (accommodating case) 52a of the brake mechanism 52, and a second supply passage 71b that is connected to the fifth supply passage 71e. have. A brake valve 62 that brakes or releases the brake mechanism 52 is provided in the middle of the fifth supply path 71e. The brake valve 62 is the same as the second operating part in the first embodiment.

In the fifth supply path 71 e, the upstream side of the brake valve 62 is branched, and a switching valve (second switching valve) 113 is connected to the branch oil path 112. The third oil passage 73 connected to the pilot check valve 110 is connected to the switching valve 113. The switching valve 113 is a two-position switching valve that can be changed between a first position and a second position.
Switching of the switching valve 113 can be performed by the control device 64 or the like. For example, when a switch or the like is connected to the control device 64 and the switch is turned on, the control device 64 excites the solenoid of the switching valve 113 to switch to the second position. When the switch is turned off, the control device 64 demagnetizes the solenoid of the switching valve 113 and switches it to the first position. Therefore, by operating the switch connected to the control device 64, the pressure of the hydraulic oil acting on the pilot check valve 110 (the flow rate of the hydraulic oil flowing through the third oil passage 73) can be changed. As a result, the primary pressure of the hydraulic oil that acts on the remote control valves (remote control valves 36 and 37) of the travel operation device 14 can be changed. In the fifth embodiment, for convenience of explanation, the remote control valves 36 and 37 are shown as shown in FIG. 7, but the other remote control valves 38 and 39 and the hydraulic equipment corresponding to the remote control valves 38 and 39 are used. Is also applicable.
[Sixth Embodiment]
The sixth embodiment is a modification of the hydraulic system. FIG. 8 shows a case where the pilot check valve 110 is applied to a working hydraulic system. First, a working hydraulic system will be described. The working hydraulic system is not limited to the following configuration.

As shown in FIG. 8, the work system hydraulic system is a system for operating the boom 22L, the boom 22R, the bucket 23 (work implement), and the like, and includes a plurality of work control valves 115, a work system hydraulic pump ( A second hydraulic pump P2 is provided.
The second hydraulic pump P2 is a pump installed at a position different from the first hydraulic pump P1, and is constituted by a constant capacity type gear pump. The second hydraulic pump P <b> 2 can discharge the hydraulic oil stored in the hydraulic oil tank 22. In particular, the second hydraulic pump P2 mainly discharges hydraulic oil that operates the hydraulic actuator.

A main oil passage (oil passage) 116 is provided on the discharge side of the second hydraulic pump P2. A plurality of work control valves 115 are connected to the main oil passage 116. The work control valve 115 is a valve capable of switching the flow direction of the working oil by the pilot pressure of the pilot oil.
The plurality of work control valves 115 include a first work control valve 115A and a second work control valve 115B. The first work control valve 115 </ b> A is a valve that controls the lift cylinder 26. The second work control valve 115 </ b> B is a valve that controls the tilt cylinder 28.

Each of the first work control valve 115A and the second work control valve 115B is a pilot-type direct acting spool type three-position switching valve. The first work control valve 115A and the second work control valve 115B are switched to the first position, the neutral position, and the second position by the pilot pressure.
A lift cylinder 26 is connected to the first work control valve 115A via oil passages 151 and 152, and a tilt cylinder 28 is connected to the second work control valve 115B via an oil passage.

The operation of the boom 22L, the boom 22R, and the bucket 23 can be performed by a work operation device 119 provided around the driver's seat 13. The work operation device 119 includes an operation member 120 and a plurality of remote control valves 121, 122, 123, and 124. The operation member 120 is an operation lever that is supported so as to be tiltable in the front-rear, left-right, and diagonal directions from the neutral position. By tilting the operation lever 120, a plurality of remote control valves 121, 122, 123, and 124 provided below the operation lever 120 can be operated. The remote control valves 121, 122, 123, 124 and the first hydraulic pump P1 are connected by a discharge oil passage 71.

  The plurality of remote control valves 121, 122, 123, 124 and the plurality of work control valves 115 are connected to each other by a plurality of oil passages 125a, 125b, 125c, 125d. Specifically, the remote control valve 121 is connected to the first work control valve 115A via the first operation oil passage 125a. The remote control valve 122 is connected to the first work control valve 115A via the second operation oil passage 125b. The remote control valve 123 is connected to the first work control valve 115B via the third operation oil passage 125c. The remote control valve 124 is connected to the first work control valve 115B via the fourth operation oil passage 125d. The remote control valves 121, 122, 123, and 124 can set the hydraulic oil pressure that is output in accordance with the operation of the operation lever 120.

Specifically, when the operation lever 120 is tilted forward, the lowering remote control valve 121 is operated and the pilot pressure of the pilot oil output from the lowering remote control valve 121 is set. This pilot pressure acts on the pressure receiving portion of the first work control valve 115A, the lift cylinder 26 contracts, and the booms 22L and 22R descend.
When the operation lever 120 is tilted rearward, the ascending remote control valve 122 is operated, and the pilot pressure of the pilot oil output from the ascending remote control valve 122 is set. This pilot pressure acts on the pressure receiving portion of the first work control valve 115A, the lift cylinder 26 extends, and the booms 22L and 22R rise.

When the operation lever 120 is tilted to the right, the bucket dump remote control valve 123 is operated, and the pilot pressure of the pilot oil output from the remote control valve 123 is set. This pilot pressure acts on the pressure receiving portion of the second work control valve 115B, the tilt cylinder 28 extends, and the bucket 23 performs a dumping operation.
When the operation lever 120 is tilted to the left, the bucket squeeze remote control valve 124 is operated and the pilot pressure of the pilot oil output from the remote control valve 124 is set. This pilot pressure acts on the pressure receiving portion of the second work control valve 115B, the tilt cylinder 28 contracts, and the bucket 23 performs a squeeze operation.

As shown in FIG. 8, a float control device 130 capable of bringing the lift cylinder 26 into a float state is provided. The float control device 130 includes a first float control valve 131, a second float control valve 132, and a float switching valve 133.
The first float control valve 131 and the second float control valve 132 are two-position switching valves that can be changed in position between a first position where the flow of hydraulic oil is blocked and a second position where the flow of hydraulic oil is allowed. .
The first float control valve 131 and the second float control valve 132 are connected to the float switching valve 133 via the oil passage 141. The first float control valve 131 is connected to an oil passage 151 that connects the bottom side of the lift cylinder 26 and the first work control valve 115A. The first float control valve 131 is connected to an oil passage 153 that discharges hydraulic oil. When the first float control valve 131 is in the second position, the oil passage 151 and the oil passage 153 are communicated with each other, and when the first float control valve 131 is in the first position, the communication between the oil passage 151 and the oil passage 153 is interrupted. To do.

  The second float control valve 132 is connected to an oil passage 152 that connects the rod side of the lift cylinder 26 and the first work control valve 115A. Further, the second float control valve 132 is connected to the oil passage 153. When the second float control valve 132 is in the second position, the oil path 152 and the oil path 153 are communicated with each other, and when the second float control valve 132 is in the first position, the communication between the oil path 152 and the oil path 153 is blocked. To do.

  Therefore, by setting the first float control valve 131 and the second float control valve 132 to the second position, the bottom side and the rod side of the lift cylinder 26 are connected to the oil passage (discharge oil passage) 153. The cylinder 26 can be floated. By setting the first float control valve 131 and the second float control valve 132 to the first position, the lift cylinder 26 is not in the float state, and the lift cylinder 26 can be moved up and down by the first work control valve 115A. it can.

  The first float control valve 131 and the second float control valve 132 can be switched by the float switching valve 133 and the control device 64. The float switching valve 133 is a two-position switching valve whose position can be changed between the first position and the second position. For example, when a switch or the like is connected to the control device 64 and the switch is turned on, the control device 64 excites the solenoid of the float switching valve 133 to switch to the second position and discharges from the first hydraulic pump P1. The oil pressure is set to the oil passage 141. Thereby, the 1st float control valve 131 and the 2nd float control valve 132 can be switched to the 2nd position. On the other hand, when the switch is turned off, the control device 64 demagnetizes the solenoid of the float switching valve 133 to switch to the first position, and discharges the hydraulic oil in the oil passage 141 to the hydraulic oil tank 31 and the like. Thereby, the 1st float control valve 131 and the 2nd float control valve 132 can be switched to the 1st position.

Now, as shown in FIG. 8, the first operating part that causes the working oil to act on the pressure receiving part 110 a of the pilot check valve 110 is a float switching valve 133. The first hydraulic device is a first work control valve 115A for operating the lift cylinder 26, and the first oil passage includes a discharge oil passage 71 and a first operation oil passage 125a.
The second oil passage 72 is connected to a first operation oil passage 125a that connects the remote control valve 121 and the first work control valve 115A. That is, the second oil passage 72 is connected to a first operation oil passage (lower operation oil passage) 125a for instructing the operation control valve 115A to lower the lift cylinder 26. A pilot check valve 110 is provided in the second oil passage 72. The third oil passage 73 connected to the pressure receiving portion 110 a of the pilot check valve 110 is connected to the oil passage 141.

Therefore, when the float operation is performed, the hydraulic oil acts on the pressure receiving portion 110a of the pilot check valve 110. That is, when the booms 22L and 22R are operated to be lowered in a state where the float operation is being performed, the work control valve 115A can be prevented from being operated, so that waste of hydraulic oil can be eliminated.
The first hydraulic device may be the second work control valve 115B that controls a hydraulic actuator such as the tilt cylinder 28 or another work control valve. Further, the first oil passage can be applied to any of the second operation oil passage 125b, the third operation oil passage 125c, and the fourth operation oil passage 125d in addition to the first operation oil passage 125a. In that case, the second oil passage 72 can also be applied to any of the second operation oil passage 125b, the third operation oil passage 125c, and the fourth operation oil passage 125d.
[Seventh Embodiment]
The seventh embodiment is a modification of the hydraulic system. FIG. 9 shows a deformed portion of the hydraulic system in the sixth embodiment. Other configurations are the same as those of the sixth embodiment.

As shown in FIG. 9, a plurality of second oil passages 72 are connected to the first oil passage (first operation oil passage) 125a. In this embodiment, two second oil passages 72 are connected to the first operation oil passage 125a.
Of the two second oil passages 72, the pilot check valve 110 is connected to one second oil passage 72a, and the pilot check valve 110 is also connected to the other second oil passage 72b. A check valve 160 capable of changing a set pressure (differential pressure) is provided in the first oil passage 72a.

  For convenience of explanation, the pilot check valve 110 connected to the second oil passage 72a is referred to as a first pilot check valve 110A, and the pilot check valve 110 connected to the second oil passage 72b is referred to as a second pilot. It is called check valve 110B. The third oil passage 73 connected to the first pilot check valve 110A is referred to as an oil passage 73a, and the third oil passage 73 connected to the second pilot check valve 110B is referred to as an oil passage 73b.

A switching valve 161 is connected to the oil passage 73a, and a switching valve 162 is connected to the oil passage 73b. The fourth switching valve (switching valve 161, switching valve 162) is connected to the discharge oil passage 71 connected to the first hydraulic pump P1. The switching valve 161 and the switching valve 162 are two-position switching valves capable of changing the position between the first position and the second position. Therefore, by switching the switching valve 161 and the switching valve 162, the pressure of the hydraulic oil acting on the first pilot check valve 110A and the second pilot check valve 110B (the flow rate of the hydraulic oil flowing through the third oil passage 73) is changed. be able to. That is, the switching valve 161 and the switching valve 162 are the pilot check valve 11.
It is the 1st operation part which can change the pressure of the operation oil which acts on 0.

  Switching of the first operating part (switching valve 161, switching valve 162) can be performed by the control device 64 or the like. For example, a switch or the like that can switch between three positions is connected to the control device 64. When the switch is set to the first position, the control device 64 excites the solenoid of the switching valve 161 and demagnetizes the solenoid of the switching valve 162. Accordingly, since the switching valve 161 is in the second position and the switching valve 162 is in the first position, a part of the hydraulic fluid in the first operating oil passage 125a can be discharged by the first pilot check valve 110A. When the switch is set to the second position, the control device 64 excites the solenoid of the switching valve 162 and demagnetizes the solenoid of the switching valve 161. Accordingly, since the switching valve 161 is in the first position and the switching valve 162 is in the second position, a part of the hydraulic fluid in the first operation oil passage 125a can be discharged by the second pilot check valve 110B. When the switch is in the third position, the switching valve 161 and the switching valve 162 are in the first position.

Therefore, the pressure of the hydraulic oil acting on the first operation oil passage 125a (the flow rate of the hydraulic oil flowing through the third oil passage 73) is changed by the first pilot check valve 110A, the second pilot check valve 110B, and the check valve 160. be able to. The numbers of pilot check valve 110, check valve 160, and switching valves 161 and 162 are not limited to those in the embodiment. Moreover, although the some 2nd oil path 72 is provided in the 1st operation oil path 125a, you may provide the 2nd oil path 72 in another oil path.
[Eighth Embodiment]
The eighth embodiment is a modification of the hydraulic system. FIG. 10 shows a deformed portion of the hydraulic system in the sixth embodiment. Other configurations are the same as those of the sixth embodiment.

  As shown in FIG. 10, the first oil passage 71 includes a seventh supply passage 71g that connects the ride control device 170 and the first hydraulic pump P1. The ride control device 170 is a device that performs a vibration suppression operation that suppresses pressure fluctuations of the hydraulic actuator. In this embodiment, the ride control device 170 is a device that performs a vibration control operation of the lift cylinder 26 (the boom 22L and the boom 22R). The ride control device 170 includes a vibration control switching valve 171 and a braking unit 172 that performs a vibration control operation. The vibration suppression switching valve 171 is a two-position switching valve capable of changing the position between the first position and the second position. The vibration control switching valve 171 can be switched by the control device 64 or the like. For example, when a switch or the like is connected to the control device 64 and the switch is turned on, the control device 64 excites the solenoid of the vibration suppression switching valve 171 and switches it to the second position. When the switch is turned off, the control device 64 demagnetizes the solenoid of the vibration control switching valve 171 and switches it to the first position. Therefore, when the vibration suppression switching valve 171 is set to the second position, the hydraulic oil acts on the braking portion 172 and the braking portion 172 operates to brake the lift cylinder 26. When the vibration suppression switching valve 171 is set to the first position, the hydraulic oil does not act on the braking portion 172, and therefore the braking of the lift cylinder 26 by the braking portion 172 stops.

  A second oil passage 72 is connected to the seventh supply passage 71g. A pilot check valve 110 is connected to the middle part of the second oil passage 72. A third oil passage 73 is connected to the pilot check valve 110. The third oil path 73 has a sixth flow path 73f connected to the first operation oil path 125a and a seventh flow path 73g connected to the second operation oil path 125b. A check valve 173 is connected to the middle part of the sixth flow path 73f and the seventh flow path 73g. The sixth flow path 73f and the seventh flow path 73g merge, and the merge side is connected to the pressure receiving part 110a. Instead of the check valve 173, a high pressure selection valve that selects a higher pressure may be used.

In the eighth embodiment, the first hydraulic device is the ride control device 170, and the first operation valves are the remote control valves 121 and 122. Therefore, the vibration damping operation of the lift cylinder 26 can be performed by switching the vibration damping switching valve 171, while the vibration damping operation can be canceled when the operation lever 120 is operated.
[Ninth Embodiment]
The ninth embodiment is a modification of the hydraulic system. FIG. 11 shows a deformed portion of the hydraulic system in the ninth embodiment. Other configurations are the same as those of the above-described embodiment.

As shown in FIG. 11, the hydraulic system includes an operation device 181 that can perform both a traveling operation and a work operation with a single operation member 180. The operating device 181 includes a forward remote control valve 36, a reverse remote control valve 37, a descending remote control valve 121, and an ascending remote control valve 122. The remote control valve 36 and the remote control valve 37 are connected to the HST pump 50, and the remote control valve 121 and the remote control valve 122 are connected to the first work control valve 115.

  Specifically, the remote control valve 36 is connected to the HST pump 50 via the first operation oil passage 75a. The remote control valve 37 is connected to the HST pump 50 via the third operation oil passage 75c. The remote control valve 121 is connected to the first operation control valve 115A via the first operation oil passage 125a. The remote control valve 122 is connected to the first operation control valve 115A via the second operation oil passage 125b. For convenience of explanation, the operating oil passages (the first operating oil passage 75a and the third operating oil passage 75c) of the traveling system are referred to as a first traveling oil passage 75a and a second traveling oil passage 75c.

A second oil passage 72 is connected to the first traveling oil passage 75a and the second traveling oil passage 75c. The second oil passage 72 is an oil passage that joins the oil passage 72c connected to the first traveling oil passage 75a, the oil passage 72d connected to the second traveling oil passage 75c, and the oil passage 72c and the oil passage 72d. 72e. A check valve 183 is provided in the oil passage 72c and the oil passage 72d.
A pilot check valve 110 is connected to the oil passage 72e. A switching valve (third switching valve) 182 is connected to the third oil passage 73 connected to the pilot check valve 110a. The switching valve 182 is a two-position switching valve capable of changing the position between the first position and the second position. Therefore, by switching the switching valve 182, the pressure of the hydraulic fluid acting on the pilot check valve 110 can be changed. The switching valve 182 is a first operating part.

  Switching of the switching valve 182 can be performed by the control device 64 or the like. For example, a switch or the like is connected to the control device 64. When the switch is turned on, the control device 64 excites the solenoid of the switching valve 182. Accordingly, since the switching valve 182 is in the second position, the first pilot check valve 110 causes a part of the hydraulic oil in the operating oil passages (the first operating oil passage 75a and the third operating oil passage 75c) of the traveling system. Can be discharged. When the switch is turned off, the control device 64 demagnetizes the solenoid of the switching valve 182. Accordingly, the HST pump 50 can be operated as usual by operating the operation member 180.

  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 embodiment described above, the first operating valve 61 and the second operating valve 62 are two-position switching valves, but may be proportional valves instead. In the above-described embodiment, the traveling motor 51 and the brake mechanism 52 have been described as the hydraulic equipment. However, the hydraulic equipment may be anything as long as it operates with the pressure of hydraulic oil. The traveling motor is a motor that switches to the first speed or the second speed (the traveling state changes), but the number of switching stages of the traveling motor is not limited to the first speed and the second speed. 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 Working machine 51 Traveling motor 52 Brake mechanism 65 Pilot check valve 65a Pressure receiving part 71 1st oil path 72 2nd oil path 73 3rd oil path 73a 1st flow path 73b 2nd flow path 73c 3rd flow path 74 4th oil Passage 75 fifth oil passage 84 check valve 85 check valve

Claims (20)

A hydraulic pump that discharges hydraulic oil;
A first hydraulic device whose operating state changes when the pressure of the hydraulic oil exceeds a predetermined level;
A first oil passage connected to the first hydraulic device and capable of supplying hydraulic oil to the first hydraulic device;
A second oil passage connected to the first oil passage and capable of discharging the hydraulic oil of the first oil passage;
A pressure receiving portion that receives the hydraulic oil, and prevents the hydraulic oil from being discharged from the second oil passage when the hydraulic oil is received by the pressure receiving portion; and when the hydraulic oil is not received by the pressure receiving portion, A pilot check valve that allows the hydraulic oil to be discharged from the second oil passage;
The working machine's hydraulic system. A third oil passage connected to the pressure receiving portion;
A first working part capable of changing a flow rate of the working oil to the third oil passage;
A hydraulic system for a working machine according to claim 1, comprising: A second hydraulic device whose operating state changes when the pressure of the hydraulic oil exceeds a predetermined level;
A fourth oil passage connected to the second hydraulic device;
A second operating portion connected to the fourth oil passage and capable of changing a flow rate of the hydraulic oil to the fourth oil passage;
With
The work system hydraulic system according to claim 2, wherein the first oil passage is connected to the fourth oil passage.   The work system hydraulic system according to claim 2, wherein the first oil passage is connected to the hydraulic pump.   The hydraulic system for a working machine according to any one of claims 1 to 4, wherein the first hydraulic device is a traveling motor whose speed can be changed by the pressure of hydraulic oil. The first hydraulic device is a travel motor whose speed can be changed by the pressure of hydraulic oil,
5. The hydraulic system for a working machine according to claim 3, wherein the second hydraulic device is a brake mechanism that brakes the traveling motor and releases the braking by a hydraulic oil pressure.   The third oil passage is connected to the fourth oil passage and is connected to the first passage capable of discharging the hydraulic oil of the fourth oil passage, and the first passage and the first operation portion are connected to each other. The hydraulic system for a working machine according to any one of claims 2 to 4, further comprising a second flow path and a third flow path that connects the second flow path and the pressure receiving portion. A third oil passage connected to the pressure receiving portion;
A first working part capable of changing a flow rate of the working oil to the third oil passage;
A second hydraulic device whose operating state changes when the pressure of the hydraulic oil exceeds a predetermined level;
A fifth oil passage connecting the first operating portion, the second hydraulic device, and the third oil passage;
A hydraulic system for a working machine according to claim 1, comprising: The first operating part is a remote control valve that changes the pressure of the hydraulic oil according to the operation of the operating member,
9. The hydraulic system for a working machine according to claim 8, wherein the second hydraulic device operates in accordance with a pressure of hydraulic oil output from the remote control valve. With a travel motor,
The first hydraulic device is a brake mechanism that performs braking of the traveling motor and release of the braking by pressure of hydraulic oil,
10. The hydraulic system for a working machine according to claim 9, wherein the second hydraulic device is a travel pump that operates according to the pressure of the hydraulic oil output from the remote control valve and supplies the hydraulic oil to the travel motor. A sixth oil passage connected to the third oil passage and capable of discharging the hydraulic oil of the third oil passage;
A first switching valve connected to the sixth oil passage and switchable;
With
The first hydraulic device is a brake mechanism that performs braking of the traveling motor and release of the braking by the pressure of hydraulic oil,
10. The hydraulic system for a working machine according to claim 9, wherein the second hydraulic device is a traveling pump that operates according to a pressure of hydraulic oil output from the remote control valve. A third oil passage connected to the pressure receiving portion;
A first working part capable of changing a flow rate of the working oil to the third oil passage;
A second hydraulic device whose operating state changes when the pressure of the hydraulic oil exceeds a predetermined level;
A remote control valve that changes the pressure of the hydraulic oil according to the operation of the operation member;
With
The first hydraulic device is a brake mechanism that performs braking of the traveling motor and release of the braking by pressure of hydraulic oil,
The second hydraulic device is a travel pump that is driven by engine power and operates according to the pressure of the hydraulic oil output from the remote control valve and supplies the hydraulic oil to the travel motor;
2. The hydraulic system for a working machine according to claim 1, wherein the first operating unit is an anti-stall control valve that prevents the engine from stalling. A hydraulic pump that discharges hydraulic oil;
A first hydraulic device whose operating state changes when the pressure of the hydraulic oil exceeds a predetermined level;
A first oil passage connected to the first hydraulic device and capable of supplying hydraulic oil to the first hydraulic device;
A second oil passage connected to the first oil passage and capable of discharging the hydraulic oil of the first oil passage;
A pressure receiving portion that receives the hydraulic oil, and prevents the hydraulic oil from being discharged from the second oil passage when the hydraulic oil is not received by the pressure receiving portion; and when the hydraulic oil is received by the pressure receiving portion, A pilot check valve that allows the hydraulic oil to be discharged from the second oil passage;
The working machine's hydraulic system. A third oil passage connected to the pressure receiving portion;
A first working part capable of changing a flow rate of the working oil to the third oil passage;
The hydraulic system for a working machine according to claim 13, comprising: With hydraulic actuators,
The first hydraulic device is a work control valve that controls operation of the hydraulic actuator,
The hydraulic system for a working machine according to claim 14, wherein the first operating unit is a float switching valve that performs a float operation of the hydraulic actuator. A relief valve provided in the second oil passage;
The first hydraulic device is a brake mechanism that performs braking of the traveling motor and release of the braking by pressure of hydraulic oil,
The hydraulic pressure of the working machine according to claim 14, wherein the first operating part is a second switching valve that is the first oil passage, is connected to the upstream side of the brake mechanism, and is connected to the third oil passage. system. The first oil path, connected to the upstream side of the first hydraulic device, and provided with a remote control valve for changing the pressure of the hydraulic oil according to the operation of the operation member;
The first hydraulic device is a traveling pump whose traveling state changes depending on the pressure of hydraulic oil,
The first actuating part acts on the pressure receiving part of the pilot check valve to reduce the pressure of the working oil in the section of the first oil path between the remote control valve and the traveling pump. The hydraulic system for a working machine according to claim 14, which is a three-way valve. A hydraulic actuator;
A remote control valve that is connected to the first oil passage and upstream of the first hydraulic device, and that changes the pressure of the hydraulic oil according to the operation of the operation member;
With
The first hydraulic device is a work control valve that controls operation of the hydraulic actuator,
The first actuating part acts on the pressure receiving part of the pilot check valve to reduce the pressure of the working oil in the section of the first oil path between the remote control valve and the traveling pump. The hydraulic system for a working machine according to claim 14, wherein the hydraulic system is a four-way valve. A third oil passage connected to the pressure receiving portion;
A first working part capable of changing a flow rate of the working oil to the third oil passage;
A hydraulic actuator;
A work control valve for controlling the operation of the hydraulic actuator;
With
The first hydraulic device is a ride control device that suppresses a vibration suppression operation that suppresses pressure fluctuations of the hydraulic actuator when a pressure of the hydraulic oil is applied, and the first hydraulic valve is configured to control the work control. The hydraulic system for a working machine according to claim 13, wherein the hydraulic system is a remote control valve that is connected to the valve and changes the pressure of the hydraulic oil according to the operation of the operation member.   A working machine comprising the working machine hydraulic system according to claim 1.

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