JP2018084335A - Hydraulic system of working machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydraulic system of a working machine capable of applying pressurization (application pressure), and changing the pressurization according to various situations.SOLUTION: A hydraulic system of a working machine includes a hydraulic pump P1 discharging a working fluid, a hydraulic actuator 76 operated by the working fluid, a hydraulic switch valve 70C capable of being switched to a plurality of switch positions according to a pressure of the working fluid, and changing the working fluid outputted to the hydraulic actuator by switching, a supply/discharge oil passage 74 disposed between the hydraulic switch valve and the hydraulic actuator, a proportional valve 73 capable of applying an application pressure as a prescribed pressure lower than a switching pressure of the working fluid switched to the switch position, to the hydraulic switch valve, and a switch valve 140 capable of switching an opening state for opening the supply/discharge oil passage and a blocking state for blocking the supply/discharge oil passage. The proportional valve determines the application pressure of a prescribed pressure or more when the switch valve is in the blocking state.SELECTED DRAWING: Figure 8

Description

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

Conventionally, Patent Document 1 is known as a hydraulic system for working machines such as a skid steer loader and a compact truck loader.
The traveling hydraulic system of Patent Document 1 includes an HST motor that can be switched between a low speed (first speed) and a high speed (second speed), a hydraulic switching valve that can switch the HST motor to first speed or second speed, And a directional switching valve capable of being positioned. In Patent Document 1, by switching the direction switching valve to a predetermined position, the pressure of the hydraulic oil acting on the pressure receiving portion of the hydraulic switching valve changes, and as a result, the hydraulic switching valve moves to the first position corresponding to the first speed. It was switched to the second position corresponding to the second speed. That is, in the traveling hydraulic system, the hydraulic switching valve (HST motor) is switched to the first speed or the second speed by switching the direction switching valve to a predetermined position.

  In a working hydraulic system, the hydraulic actuator is operated by switching a control valve (hydraulic switching valve) connected to the hydraulic actuator via an oil passage.

JP 2013-36276 A

  In the traveling hydraulic system of Patent Document 1, since the direction switching valve only switches to a plurality of predetermined positions, the hydraulic oil pressure acting on the hydraulic switching valve is set to, for example, traveling hydraulic pressure such as a traveling pump. It cannot be changed according to the state of the device or the state of the prime mover. That is, in Patent Document 1, the actual condition is that the characteristics of the switching pressure when the hydraulic switching valve is switched cannot be changed according to the traveling state or the state of the prime mover.

  Now, in the traveling hydraulic system of Patent Document 1, an attempt has been made to control the pressure of hydraulic oil acting on the hydraulic switching valve by changing the direction switching valve to a proportional valve. For example, by slightly opening the proportional valve, the hydraulic pressure is preliminarily applied to the hydraulic switching valve, that is, pressurization is performed. Thus, by applying pressure, the responsiveness of the hydraulic switching valve can be improved or the hydraulic switching valve can be warmed up.

  The present invention has been made to solve the above-described problems of the prior art, and can apply a pressure (applied pressure), and can change the pressure according to various situations. An object of the present invention is to provide a hydraulic system for a working machine capable of performing the above.

The technical means taken by the present invention to solve the technical problem is as follows.
The hydraulic system of the work machine includes a hydraulic pump that discharges hydraulic oil, a hydraulic actuator that is operated by hydraulic oil, and can be switched to a plurality of switching positions according to the pressure of the hydraulic oil, and output to the hydraulic actuator by the switching. A hydraulic switching valve capable of changing the operating oil to be changed, a supply / discharge oil passage provided between the hydraulic switching valve and the hydraulic actuator, and a pressure lower than the switching pressure of the hydraulic oil that switches to the switching position. A proportional valve capable of applying an applied pressure that is a predetermined pressure to the hydraulic pressure switching valve;
A switching valve that can be switched between an open state that opens the oil supply / drain passage and a shut-off state that shuts off the oil supply / discharge passage, and the proportional valve is provided when the switching valve is in a cutoff state. Set the pressure to a predetermined level or higher.

The hydraulic system of the work machine includes a first measuring device capable of detecting the temperature of the hydraulic oil, and the proportional valve applies the applied pressure when the temperature of the hydraulic oil measured by the first measuring device is equal to or lower than a predetermined value. Make it more than predetermined.
The hydraulic system of the working machine includes a second measuring device capable of detecting the temperature of the outside air, and the proportional valve determines the applied pressure when the temperature of the outside air measured by the second measuring device is equal to or lower than a predetermined value. That's it.

  According to the present invention, a pressurization (applied pressure) can be applied, and the pressurization can be changed according to various situations.

It is a figure which shows the hydraulic system of the traveling system in 1st Embodiment. It is a figure which shows the hydraulic system of the working system in 1st Embodiment. It is a figure which shows the relationship between the position of a hydraulic switching valve, and pilot pressure. It is the figure which showed the example which provides a pressure with respect to the hydraulic switching valve at the time of deceleration. It is the figure which showed the example which provides the deceleration setting pressure different from an application pressure at the time of deceleration. It is a figure which shows the hydraulic system of the traveling system in 2nd Embodiment. It is a figure of the other modification which shows the relationship between the position of a hydraulic switching valve, and pilot pressure. It is a figure which shows the hydraulic system of the working system in 3rd Embodiment. It is a figure which shows the relationship between the pilot pressure and the position which act on the pressure receiving part of a preliminary | backup control valve. It is a figure which shows the hydraulic system of the traveling system in 4th Embodiment. It is a figure which shows the hydraulic system of the traveling system in 5th Embodiment. It is a figure which shows the relationship between the position of the hydraulic switching valve in 5th Embodiment, and pilot pressure. It is a figure which shows the modification of a traveling hydraulic apparatus and a hydraulic switching valve. It is a figure which shows the relationship between the position of the hydraulic switching valve in a modification, and pilot pressure. It is a figure which shows the hydraulic system of a traveling system at the time of providing a memory | storage part in the control apparatus. It is a figure which shows the hydraulic system at the time of providing the discharge oil path, throttle part, and measuring apparatus which are common in a hydraulic switching valve. It is a figure at the time of connecting an operating valve to the servo cylinder of a traveling motor. It is another figure at the time of connecting an operating valve to the servo cylinder of a traveling motor. It is a side view which shows the track loader which is an example of the working machine which concerns on this invention. 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.
The overall configuration of the work machine will be described. 18 and 19 show a truck loader as an example of the work machine 1. The working machine is not limited to a truck loader, and may be, for example, a tractor, a skid steer loader, a compact truck loader, a backhoe, or the like. In the present embodiment, the front side (direction indicated by the arrow F shown in FIG. 18) of the driver seated on the driver's seat of the work machine 1 is forward, and the rear side of the driver (direction indicated by the arrow R shown in FIG. 18). Will be described as the rear, the left side of the driver (front side toward the paper surface of FIG. 18) as the left side, and the right side of the driver (back side toward the paper surface of FIG. 18) as the right side.

  As shown in FIGS. 18 and 19, the work machine 1 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. A cabin 5 is mounted on the upper portion of the airframe 2 and 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 and can swing around the support shaft 12. The front part of the cabin 5 can be supported by 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 configured by a crawler traveling hydraulic 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 can travel by the driving force of a hydraulic drive traveling hydraulic device 44 described later.

  The work device 3 includes a boom 22L, a boom 22R, and a boom 23L and a bucket 23 (work implement) attached to the tip of the boom 22R. 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 (not shown) provided between the boom 22L and the boom 22R. The boom 22L and the boom 22R are supported by the first lift link 24 and the second lift link 25, respectively. Between the base side of the boom 22L and the boom 22R and the rear lower part of the body 2, a lift cylinder 26 composed of a double-acting hydraulic cylinder is provided corresponding to the boom 22L and the boom 22R. By simultaneously extending and retracting the lift cylinder 26, the boom 22L and the boom 22R simultaneously swing up and down. A mounting bracket 27 is pivotally connected to the distal ends of the boom 22L and the boom 22R so as to be rotatable about a horizontal axis, and the back side of the bucket 23 is attached to the mounting bracket 27.

Further, a tilt cylinder 28 composed of a double-acting hydraulic cylinder is interposed between the mounting bracket 27 and the middle portion of the boom 22L and the boom 22R in correspondence with the boom 22L and 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. The mounting bracket 27 is configured such that if the bucket 23 is removed, various attachments (hydraulic drive working tools having a hydraulic actuator) can be attached, and various operations other than excavation (or other excavation operations) can be performed. Has been.

A prime mover 29 is provided on the rear side of the bottom wall of the body (vehicle body) 2. The prime mover 29 is a diesel engine, a motor generator, or the like. A fuel tank 30 and a hydraulic oil tank 31 are provided on the front side on the bottom wall of the machine body 2.
Next, the hydraulic system of the work machine will be described.
FIG. 1 is a diagram illustrating a traveling hydraulic system of a work machine. FIG. 2 shows a hydraulic system of the work system of the work machine.

  As shown in FIGS. 1 and 2, the hydraulic system (traveling hydraulic system, working hydraulic system) includes a first hydraulic pump P1 and a second hydraulic pump P2. The first hydraulic pump P <b> 1 and the second hydraulic pump P <b> 2 are constant capacity type gear pumps that are driven by the power of the prime mover 29. The first hydraulic pump P1 and the second hydraulic pump P2 may be swash plate type variable displacement pumps driven by the prime mover 29, or may be other pumps.

  The first hydraulic pump P <b> 1 (main pump) is used to drive a hydraulic actuator of an attachment attached to the lift cylinder 26, the tilt cylinder 28 or the tip side of the boom 22. The second hydraulic pump P2 (pilot pump, charge pump) is mainly used for supplying hydraulic oil pressure as control pressure or signal pressure. Hereinafter, for convenience of explanation, hydraulic oil as control pressure or signal pressure is referred to as “pilot oil”, and pilot oil pressure is referred to as “pilot pressure”.

  The hydraulic system includes a traveling hydraulic device 44, an operation valve 45, and a hydraulic pressure switching valve 90. The traveling hydraulic device 44 is a device capable of changing the speed with hydraulic oil. In other words, the traveling hydraulic device 44 changes the rotational speed (rotational speed) of a traveling motor, which will be described later. In other words, the traveling hydraulic device 44 is a device that can change the propulsive force when the traveling device 4 travels. The travel hydraulic device 44 includes a first travel hydraulic pump 66A, a second travel hydraulic pump 66B, a first travel motor 80A, and a second travel motor 80B. The hydraulic switching valve 90 includes a hydraulic switching valve 90A and a second hydraulic switching valve 90B.

  The first traveling hydraulic pump 66A and the first traveling motor 80A are connected by a first circulating oil passage 101 that can circulate hydraulic oil. The second traveling hydraulic pump 66B and the second traveling motor 80B are connected by a second circulating oil passage 102 that can circulate the hydraulic oil. The first hydraulic switching valve 90A and the first traveling motor 80A are connected by an oil passage 103, and the second hydraulic switching valve 90B and the second traveling motor 80B are connected by an oil passage 104. Further, the first hydraulic pressure switching valve 90 </ b> A, the second hydraulic pressure switching valve 90 </ b> B, and the operating valve 45 are connected by an oil passage (first oil passage) 105. A discharge oil passage 108 is connected to the pressure receiving portion 91 of the hydraulic switching valve (first hydraulic switching valve 90A, second hydraulic switching valve 90B). The discharge oil passage 108 is an oil passage that discharges the hydraulic oil of the first oil passage 105 (the hydraulic oil acting on the pressure receiving portion 91) to the outside. For example, one end is connected to the first oil passage 105, The other end is connected to the hydraulic oil tank 31. The connection destination of the discharge oil passage 108 is not limited to the hydraulic oil tank 31 and may be a suction portion of the hydraulic pump or other portion. The drain oil passage 108 is provided with a first throttle portion (for example, an orifice) 109a. Further, in the first oil passage 105, a section between the connecting portion 180 between the first oil passage 105 and the discharge oil passage 108 and the hydraulic oil 45, a second throttle portion (for example, an orifice) 109b is provided. Is provided. The inner diameters (diaphragm diameters) of the first diaphragm portion 109a and the second diaphragm portion 109b are set to be substantially the same. In addition, the diameter of the 1st aperture part 109a and the 2nd aperture part 109b is not limited to the diameter mentioned above.

The operating valve 45 and the second hydraulic pump P2 are connected by an oil passage 106. The first traveling hydraulic pump 66A, the second traveling hydraulic pump 66B, and the second hydraulic pump P2 are connected by an oil passage (not shown), and the hydraulic oil discharged from the second hydraulic pump P2 is the first traveling hydraulic pump. The hydraulic pump 66A and the second traveling hydraulic pump 66B can be supplied.
The first traveling hydraulic pump 66 </ b> A is a swash plate type variable displacement axial pump driven by the power of the prime mover 29. The first traveling hydraulic pump 66A includes a pressure receiving portion 66a and a pressure receiving portion 66b on which pilot pressure acts. The angle of the swash plate can be changed by the pilot pressure acting on the pressure receiving portions 66a and 66b. When the angle of the swash plate is changed, the discharge direction and the discharge amount of the hydraulic oil change, thereby changing the rotation output of the first travel motor 80A.

The second traveling hydraulic pump 66B has the same configuration as the first traveling hydraulic pump 66A. When the angle of the swash plate of the second traveling hydraulic pump 66B is changed, the discharge direction and the discharge amount of the hydraulic oil change, thereby changing the rotation output of the second traveling motor 80B.
The first travel motor 80A is constituted by a cam motor (radial piston motor). The first travel motor 80A is a variable capacity type that can change the capacity (motor capacity) during operation, and can change the rotation and torque of the output shaft by changing the motor capacity. Specifically, the first travel motor 80 </ b> A includes a first motor 81 and a second motor 82. By supplying hydraulic oil to both the first motor 81 and the second motor 82, the motor capacity increases, and the first traveling motor 80A becomes the first speed. Further, by supplying hydraulic oil to either the first motor 81 or the second motor 82, the motor capacity is reduced and the first traveling motor 80 is set to the second speed. The second traveling motor 80B has the same configuration as the first traveling motor 80A and can be changed to the first speed or the second speed.

The first hydraulic switching valve 90A is a hydraulic switching valve that can be switched to a plurality of switching positions in accordance with the pilot pressure that is the pressure of the pilot oil, and that can switch the first traveling motor 80A to the first speed or the second speed. It is. The first hydraulic pressure switching valve 90A is a three-position switching valve that can be switched to three switching positions, for example, a first position 90a, a second position 90b, and a neutral position 90c.
Specifically, when the pressure of the pilot oil acting on the pressure receiving portion 91 of the first hydraulic pressure switching valve 90A is less than the switching pressure that is a predetermined pressure, the hydraulic pressure switching valve 90 is moved to the first position 90a by a spring. Retained. When the first hydraulic pressure switching valve 90A is in the first position 90a, hydraulic oil is supplied to both the first motor 81 and the second motor 82, and the first traveling motor 80A is in the first speed. When the pressure of the pilot oil acting on the pressure receiving portion 91 of the first hydraulic pressure switching valve 90A is equal to or higher than the switching pressure, the first hydraulic pressure switching valve 90A is switched to the second position 90b via the neutral position 90c. When the first hydraulic pressure switching valve 90A is in the second position 90b, hydraulic oil is supplied only to the first motor 81, and the first traveling motor 80A is in the second speed.

The second hydraulic pressure switching valve 90B has the same configuration as the first hydraulic pressure switching valve 90A. The second hydraulic pressure switching valve 90B can switch the second traveling motor 80B to the first speed or the second speed.
The operation valve 45 is a valve capable of changing the pressure (flow rate) of the hydraulic oil acting on the hydraulic pressure switching valve (the first hydraulic pressure switching valve 90A and the second hydraulic pressure switching valve 90B). It is a valve capable of applying hydraulic oil pressure to such an extent that it does not switch to a position. The opening degree of the operating valve 45 can be changed by a control signal output from the control device 110 described later. In this embodiment, the operation valve 45 is an electromagnetic proportional valve (proportional valve), and the opening degree is changed by a control signal. By changing the opening degree of the operating valve 45, the pressure of the operating oil acting (supplying) on the hydraulic pressure switching valve changes.

  FIG. 3 is a diagram showing the relationship between the position of the hydraulic pressure switching valve (first hydraulic pressure switching valve, second hydraulic pressure switching valve) and hydraulic oil pressure (pilot pressure) when the operation valve is operated. The transmission pressure L1 shown in FIG. 3 is a pilot pressure that acts on the pressure receiving portion of the hydraulic switching valve. Hereinafter, for convenience of explanation, the operation valve 45 is referred to as a proportional valve 45. The first hydraulic pressure switching valve 90A and the second hydraulic pressure switching valve 90B may be referred to as a hydraulic pressure switching valve, and the first traveling motor 80A and the second traveling motor 80B may be referred to as a traveling motor.

  3, the pilot pressure acting on the pressure receiving portion 91 of the first hydraulic pressure switching valve 90A and the second hydraulic pressure switching valve 90B is a boundary pressure (switching pressure) between the first position 90a and the neutral position 90c. ) When it is less than CP1, the hydraulic pressure switching valves (the first hydraulic pressure switching valve 90A and the second hydraulic pressure switching valve 90B) are in the first position 90a. When the hydraulic switching valve is in the first position 90a, the travel motors (first travel motor 80A, second travel motor 80B) are first gear. The proportional valve 45 applies pressure to the hydraulic pressure switching valve in a state where the hydraulic pressure switching valve maintains the first position 90a. That is, the proportional valve 45 can apply the applied pressure F1 to the pressure receiving portion 91 of the hydraulic switching valve, as shown in FIG. In other words, the proportional valve 45 applies a preset applied pressure F1 to the pressure receiving portion 91 of the hydraulic switching valve when the traveling motor is in the first speed.

  Here, when the opening degree of the proportional valve 45 is gradually increased and the pilot pressure acting on the pressure receiving portion 91 of the first hydraulic pressure switching valve 90A and the second hydraulic pressure switching valve 90B exceeds the switching pressure CP1, the first hydraulic pressure is increased. The switching valve 90A and the second hydraulic switching valve 90B are in the neutral position 90c. Further, when the pilot pressure acting on the pressure receiving portion 91 of the first hydraulic pressure switching valve 90A and the second hydraulic pressure switching valve 90B exceeds the boundary pressure (switching pressure) CP2 between the neutral position 90c and the second position 90b, the first hydraulic pressure is changed. The switching valve 90A and the second hydraulic switching valve 90B are in the second position 90b. When the hydraulic switching valve is in the second position 90b, the traveling motor is in the second speed. That is, the opening degree of the proportional valve 45 and the pilot pressure acting on the hydraulic pressure switching valve are in a proportional relationship, and the traveling motor can be switched to the first speed or the second speed according to the opening degree of the proportional valve 45.

  As described above, the proportional valve 45 is configured to be able to apply a pressure to the hydraulic pressure switching valve. In particular, after the discharge oil passage 108 is provided in the first oil passage 105, the second throttle portion is provided. Since 109b is provided, it is possible to accurately pressurize the hydraulic switching valve. By providing the first throttle portion 109a and the second throttle portion 109b, the pressure width when the proportional valve 45 is operated can be increased by these throttle portions. In other words, the proportional pressure valve 45 can be given a margin in the control pressure range during pressurization.

  As shown in FIG. 1, the oil passage 106 is branched on the upstream side of the proportional valve 45, and the branched oil passage 107 is connected to the traveling operation device 14. The traveling operation device 14 includes a remote control valve 36 for forward movement, a remote control valve 37 for backward movement, a remote control valve 38 for turning right, a remote control valve 39 for turning left, and a traveling lever 40. The traveling operation device 14 includes first to fourth shuttle valves 51, 52, 53, and 54. The remote control valves 36, 37, 38 and 39 are operated in common, that is, by one traveling lever 40. The remote control valves 36, 37, 38, 39 change the pressure of the hydraulic oil according to the operation of the travel lever 40 (operation member) and supply the changed hydraulic oil to the travel hydraulic device 14. In this embodiment, the remote control valves 36, 37, 38, and 39 are operated by one traveling lever 40, but a plurality of traveling levers 40 may be provided. For example, a first traveling lever is disposed on one side (left side) of the driver's seat 13 and a second traveling lever is disposed on the other side, and these two traveling levers allow remote control valves 36, 37, 38, 39 may be operated.

  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, the remote control valves 36, 37, 38, 39 of the travel operation device 14 are 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.

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. This pilot pressure acts on the pressure receiving portion 66a of the first traveling hydraulic pump 66A from the first shuttle valve 51 through the oil passage 61, and at the same time, the second traveling hydraulic pump 66B from the second shuttle valve 52 through the oil passage 62. Acting on the pressure receiving portion 66a. As a result, the output shafts of the first traveling motor 80A and the second traveling motor 80B rotate forward (forward rotation) at a speed proportional to the tilting amount of the traveling lever 40, and the work implement 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 pressure receiving portion 66b of the first traveling hydraulic pump 66A from the third shuttle valve 53 via the oil passage 64, and at the same time, the second traveling hydraulic pump 66B from the fourth shuttle valve 54 via the oil passage 63. Acting on the pressure receiving portion 66b. As a result, the output shafts of the first traveling motor 80A and the second traveling motor 80B are reversely rotated (reversely rotated) at a speed proportional to the tilting amount of the traveling lever 40, and the work machine 1
Go straight backwards.

  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 pressure receiving portion 66a of the first traveling hydraulic pump 66A from the first shuttle valve 51 through the oil passage 61, and at the same time, the second traveling hydraulic pump 66B from the fourth shuttle valve 54 through the oil passage 63. Acting on the pressure receiving portion 66b. As a result, the output shaft of the first travel motor 80A rotates in the forward direction and the output shaft of the second travel motor 80B rotates in the reverse direction, and the work implement 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 pressure receiving portion 66a of the second traveling hydraulic pump 66B from the second shuttle valve 52 via the oil passage 62, and at the same time, the first traveling hydraulic pump 66A from the third shuttle valve 53 via the oil passage 64. Acting on the pressure receiving portion 66b. As a result, the output shaft of the first travel motor 80A reverses and the output shaft of the second travel motor 80B rotates in the forward direction so that the work implement 1 turns to the left.

Further, when the traveling lever 40 is tilted in the oblique direction, the first traveling motor 80A and the second traveling motor 40A and the second traveling motor 40A are driven by the differential pressure between the pilot pressures acting on the pressure receiving portions 66a and 66b of the first traveling hydraulic pump 66A and the second traveling hydraulic pump 66B. The rotation direction and rotation speed of the output shaft of the travel motor 80B are determined, and the track loader 1 turns right or left while moving forward or backward.
That is, when the travel lever 40 is tilted to the left front side, the work implement 1 turns left while moving forward at a speed corresponding to the tilt angle of the travel lever 40. When the travel lever 40 is tilted to the right front side, the work machine 1 turns right while moving forward at a speed corresponding to the tilt angle of the travel lever 40. When the travel lever 40 is tilted to the left rear side, the work implement 1 turns left while moving backward at a speed corresponding to the tilt angle of the travel lever 40. When the travel lever 40 is tilted to the right rear side, the work machine 1 turns right while moving backward at a speed corresponding to the tilt angle of the travel lever 40.

Next, a working hydraulic system will be described.
As shown in FIG. 2, an oil passage 108 is connected to the first hydraulic pump P1. A plurality of control valves 70 are connected to the oil passage 108. The plurality of control valves 70 are a boom control valve 70A, a bucket control valve 70B, and a preliminary control valve 70C. The boom control valve 70A is a pilot-type direct acting spool type three-position switching valve, and controls the lift cylinder 26. The bucket control valve 70 </ b> B is a pilot-type direct acting spool type three-position switching valve, and controls the tilt cylinder 28. The preliminary control valve 70C is a pilot-type direct acting spool type three-position switching valve, and controls the hydraulic actuator 76 of the preliminary attachment. The preliminary control valve 70C can be switched to the first position 79a, the second position 79b, and the third position 79c by the pilot pressure. The third position 79c is a neutral position.
The boom 22 and the bucket 23 can be operated by an operation member 71 provided around the driver's seat 13. The operation member 71 is supported so as to be tiltable from the neutral position in the front-rear direction and the width direction and the oblique direction orthogonal to the front-rear direction. By operating the operation member 71 to tilt, the remote control valves 72A, 72B, 72C, 72D provided at the lower part of the operation member 71 can be operated.

When the operation member 71 is tilted forward, the remote control valve 72A is operated and pilot pressure is output from the remote control valve 72A. The pilot pressure acts on the pressure receiving portion of the boom control valve 70A, and the boom (the boom 22L and the boom 22R) is lowered by supplying the hydraulic oil that has entered the boom control valve 70A to the rod side of the lift cylinder 26. .
When the operation member 71 is tilted rearward, the remote control valve 72B is operated and pilot pressure is output from the remote control valve 72B. The pilot pressure acts on the pressure receiving portion of the boom control valve 70A, and the boom is raised by supplying the hydraulic oil that has entered the boom control valve 70A to the bottom side of the lift cylinder 26.

That is, the boom control valve 70A is applied to the lift cylinder 26 in accordance with the hydraulic oil pressure (the pilot pressure set by the remote control valve 72A and the pilot pressure set by the remote control valve 72B) set by operating the operation member 71. The flow rate of the flowing hydraulic oil can be controlled.
When the operation member 71 is tilted to the right, the remote control valve 72C is operated, and the pilot oil acts on the pressure receiving portion of the bucket control valve 70B. As a result, the bucket control valve 70B operates in a direction in which the tilt cylinder 28 is extended, and the bucket 23 performs a dumping operation at a speed proportional to the tilting amount of the operation member 71.

When the operation member 71 is tilted to the left, the remote control valve 72D is operated, and the pilot oil acts on the pressure receiving portion of the bucket control valve 70B. As a result, the bucket control valve 70B operates in a direction to reduce the tilt cylinder 28, and the bucket 23 performs a squeeze operation at a speed proportional to the tilting amount of the operation member 71.
That is, the bucket control valve 70B is applied to the tilt cylinder 28 in accordance with the hydraulic oil pressure (the pilot pressure set by the remote control valve 72C, the pilot pressure set by the remote control valve 72D) set by operating the operation member 71. The flow rate of the flowing hydraulic oil can be controlled. That is, the remote control valves 72A, 72B, 72C, 72D change the pressure of the hydraulic oil according to the operation of the operation member 71 and supply the changed hydraulic oil to the boom control valve 70A and the bucket control valve 70B.

  A supply / discharge oil passage 74 is connected to the preliminary control valve 70C. The oil supply / discharge passage 74 has an oil passage 74a connected to one of the two ports of the preliminary control valve 70C, and an oil passage 74b connected to the other port. The oil supply / discharge passage 74 (the oil passage 74 a and the oil passage 74 b) is connected to a connection member 75, and a hydraulic actuator 76 of a preliminary attachment can be connected to the connection member 75. Therefore, the hydraulic oil can be supplied from the preliminary control valve 70c to the hydraulic actuator 76 of the preliminary attachment. The operation of the preliminary control valve 70C is performed by the proportional valve 73 whose opening degree can be changed according to the pressure of the hydraulic oil. The proportional valve 73 includes a first proportional valve 73A connected to the pressure receiving portion 70C1 of the preliminary control valve 70C via the oil passage 77a, and a second proportional valve 73A connected to the pressure receiving portion 70C2 of the preliminary control valve 70C via the oil passage 77b. And a proportional valve 73B. When the first proportional valve 73A is opened, the pilot oil acts on the pressure receiving portion 70C1 through the oil passage 77a. When the second proportional valve 73B is opened, the pilot oil acts on the pressure receiving portion 70C2 via the oil passage 77b. Accordingly, when pilot oil acts on the pressure receiving portion 70C1 or pressure receiving portion 70C2 of the preliminary control valve 70C, the preliminary control valve 70C is switched, and the hydraulic actuator 76 of the preliminary attachment is operated by the hydraulic oil supplied from the preliminary control valve 70C. The operation of the first proportional valve 73A and the second proportional valve 73B is performed by the control device 110. An operation member 78 provided around the driver's seat 13 is connected to the control device 110. The operation member 78 is composed of, for example, a swingable seesaw type switch, a slide type switch that can slide, or a push type switch that can be pressed. The operation amount of the operation member 78 is input to the control device 110. The control device 110 outputs a control signal (for example, current) corresponding to the operation amount of the operation member 78 to the first proportional valve 73A or the second proportional valve 73B. The proportional valves 73 (the first proportional valve 73A and the second proportional valve 73B) are opened and closed by a control signal output from the control device 110. Therefore, when the hydraulic fluid output to the proportional valves 73 (the first proportional valve 73A and the second proportional valve 73B) reaches a predetermined level or more, the preliminary control valve 70C has the first position 79a, the second position 79b, and the third position. Switching to 79c, the hydraulic attachment 76 can be operated.

  As shown in FIG. 1, the hydraulic system includes a control device 110 and a measurement device 118. The measuring device 118 is a device that detects the pressure of the hydraulic oil acting on the hydraulic pressure switching valves (the first hydraulic pressure switching valve 90A and the second hydraulic pressure switching valve 90B), and the first hydraulic pressure switching valve 90A or the second hydraulic pressure switching valve 90B. The pressure receiving portion 91 or the oil passage 105 is provided. In this embodiment, the measuring device 118 is provided between the second throttle portion 109 b and the pressure receiving portion 91 in the oil passage 105. The hydraulic oil pressure (pilot pressure) detected by the measuring device 118 is input to the control device 110.

  The control device 110 is composed of a CPU and the like. The control device 110 and the proportional valve 45 are connected. The control device 110 controls the proportional valve 45 based on the operation member 115 connected to the control device 110. The operation member 115 is a member that makes the travel motor (the first travel motor 80A and the second travel motor 80B) 1st speed or 2nd speed. The operation member 115 is composed of, for example, a swingable seesaw type switch, a slide type switch that can slide, or a push type switch that can be pressed.

The seesaw type switch can be set to the first speed by swinging to one side and to the second speed by swinging to the other side. The slide type switch can be set to the first speed by sliding to one side and to the second speed by sliding to the other side. In the push type switch, every time the push switch is pressed, the first speed and the second speed are switched.
The control device 110 selects one of an applied pressure F1 lower than the switching pressure CP1, an opening degree of the proportional valve 45 corresponding to the applied pressure F1 (applied opening degree), and a current value corresponding to the applied opening degree (applied current value). I remember it. In this embodiment, the description will proceed assuming that the applied current value corresponding to the applied pressure F1 is stored. When the applied pressure F1 or the applied opening is stored, the controller 110 controls the proportional valve 45 by converting the applied pressure F1 or the applied opening into a control signal (applied current). Can do.

When the first speed is set by the operation member 115, the control device 110 outputs, for example, an applied current to the proportional valve 45. The proportional valve 45 opens according to the applied current. As a result, the applied pressure F1 is applied to the pressure receiving portion 91 of the hydraulic switching valve, as indicated by the transmission pressure L1 in FIG.
Here, after outputting the application current to the proportional valve 45, that is, during the application period, the control device 110 monitors the hydraulic oil detection pressure F2 detected by the measuring device 118, that is, the actual application pressure F2. Specifically, as shown in FIG. 3, in a situation where the control device 110 performs control to apply the applied pressure F <b> 1 to the hydraulic switching valve (at the first speed), the control device 110 performs the actual applied pressure. It is determined whether or not F2 is equal to or higher than a predetermined warning pressure F3. The warning pressure F3 is a pressure set between the applied pressure F1 and the switching pressure CP1 set in advance in the control device 110. When the actual applied pressure F2 becomes equal to or higher than the warning pressure F3, that is, the actual applied pressure F2 rises higher than the applied pressure F1 due to some circumstances (for example, load fluctuation at the time of work, etc.) and becomes equal to or higher than the warning pressure F3. In this case, the control device 110 stops the control of the applied pressure with respect to the proportional valve 45. That is, when the actual application pressure F2 becomes equal to or higher than the warning pressure F3, the control device 110 stops outputting the application current to the proportional valve 45 (demagnetizes the solenoid of the proportional valve 45). That is, when the actual application pressure F2 becomes equal to or higher than the warning pressure F3, the proportional valve 45 is fully closed to stop the application of the hydraulic oil to the hydraulic pressure switching valve.

  Therefore, even when the actual application pressure F2 applied to the hydraulic pressure switching valve rises due to some circumstances under the situation where hydraulic oil is applied to the hydraulic pressure switching valve, the hydraulic pressure switching valve is moved to the neutral position 90c and the second position 90b. Switching can be prevented. That is, in the hydraulic switching valve that switches to a plurality of switching positions, it is possible to reliably apply pressure while preventing the hydraulic switching valve from being inadvertently switched by the applied pressure F1.

  Further, when the hydraulic switching valve is set to the second position by the operating member 115 in the first position, that is, in the first speed, the control device 110 is applying the hydraulic oil to the hydraulic switching valve or hydraulic pressure is set. Regardless of stopping the application of the hydraulic oil to the switching valve, a control signal is output to the proportional valve 45 so that the pressure of the hydraulic oil acting on the hydraulic switching valve becomes the switching pressure CP2 or more. When the pressure (actually applied pressure F2) of the hydraulic oil acting on the hydraulic pressure switching valve is equal to or higher than the switching pressure CP2 and reaches a predetermined set pressure Q3, the control device 110 sets the actual applied pressure F2 and the set pressure Q3. Are controlled to control the opening of the proportional valve 45.

  Further, when the hydraulic switching valve is set to the first position by the operation member 115 in the second position 90b, that is, in the second speed, the control device 110 outputs a control signal to the proportional valve 45 to the applied current value. . Then, the switching pressure L1 gradually decreases, the hydraulic switching valve is switched from the second position 90b to the first position 90a, and after decelerating from the second speed to the first speed, the applied pressure F1 is applied to the hydraulic switching valve. Is done.

  In the embodiment described above, the proportional valve 45 applies the applied pressure F1 to the hydraulic switching valve when decelerating from the second speed to the first speed, but stops applying the applied pressure F1 to the hydraulic switching valve. Also good. As shown in FIG. 4, when deceleration from the second speed to the first speed is set by the operation member 115, the control device 110 demagnetizes the solenoid of the proportional valve 45. Therefore, the proportional valve 45 is fully closed, and the pressure acting on the hydraulic pressure switching valve becomes substantially zero as indicated by the transmission pressure L1a in FIG. That is, when the speed is reduced from the second speed to the first speed, the proportional valve 45 does not apply the applied pressure F1 to the hydraulic switching valve.

  Further, after decelerating from the second speed to the first speed (after the control device 110 demagnetizes the solenoid of the proportional valve 45), when the predetermined time T1 elapses in the state set to the first speed, the control device 110 again The applied current is output to the proportional valve 45. As a result, as shown by the transmission pressure L1b in FIG. 4, the pressure acting (applying) on the hydraulic switching valve increases to the applied pressure F1. In other words, the proportional valve 45 reduces the pressure of the hydraulic oil acting (applied) to the hydraulic pressure switching valve after deceleration for substantially the predetermined time T1.

  As described above, when the speed is reduced from the second speed to the first speed, the application of the application pressure F1 by the proportional valve 45 is stopped, so that the hydraulic oil can be stably applied to the hydraulic pressure switching valve. In other words, since the operation of the proportional valve 45 is once returned to the initial position such as fully closed, it is easy to make the pressure of the hydraulic oil (applied pressure) applied to the hydraulic switching valve constant. For example, when the proportional valve 45 is a valve having a relatively large hysteresis, the applied pressure at the first speed is different from the applied pressure when the speed is reduced from the second speed to the first speed due to the influence of the hysteresis. In the embodiment described above, since the proportional valve 45 is once fully closed during deceleration, the difference in applied pressure can be reduced.

  Further, in FIG. 4, when the speed is reduced from the 2nd speed to the 1st speed, the pressure of the hydraulic oil acting (applying) to the hydraulic pressure switching valve is made substantially zero, but instead, as shown in FIG. The valve 45 may apply a deceleration set pressure F4, which is a pressure lower than the applied pressure, to the hydraulic switching valve. The control device 110 stores a deceleration setting pressure F4 lower than the applied pressure F1, an opening degree of the proportional valve 45 (deceleration opening degree) corresponding to the deceleration setting pressure F4, and a current value (deceleration current) corresponding to the deceleration opening degree. ing. When the control device 110 decelerates from the second speed to the first speed, it outputs a deceleration current corresponding to the deceleration opening degree to the proportional valve 45. And the proportional valve 45 opens according to the deceleration opening degree. As a result, as shown by the transmission pressure L1c in FIG. 5, immediately after deceleration, the pressure acting on the hydraulic switching valve (oil passage 105) becomes the deceleration setting pressure F4.

  When the predetermined time T1 elapses after the vehicle is decelerated from the second speed to the first speed and set to the first speed, the control device 110 outputs an applied current to the proportional valve 45. Then, as indicated by the transmission pressure L1d in FIG. 5, the pressure applied (acted) to the hydraulic pressure switching valve increases to the applied pressure F1. That is, after the deceleration, the proportional valve 45 sets the hydraulic oil pressure acting on the hydraulic pressure switching valve to the deceleration setting pressure F4 for a predetermined time T1. In the above-described embodiment, when the first speed is set to the second speed within the predetermined time T1, the control device 110 outputs a predetermined control signal to the proportional valve 45 to change from the first speed to the second speed. change.

Thus, when decelerating from the 2nd speed to the 1st speed, instead of applying the applied pressure F1 by the proportional valve 45, the deceleration setting pressure F4 that is lower than the applied pressure F1 is applied to the hydraulic pressure switching valve. Therefore, a slight pressure can be applied to the hydraulic switching valve while returning the proportional valve 45 to the initial position as much as possible.
[Second Embodiment]
FIG. 6 shows a hydraulic system according to the second embodiment. The traveling hydraulic system shown in the second embodiment can be applied to the hydraulic system of the first embodiment described above. The description of the same configuration as that of the first embodiment is omitted.

  As shown in FIG. 6, the hydraulic system includes a braking device 130 and a control device 131. The braking device 130 is a device that can be switched between a braking state that brakes the traveling device 4, that is, the traveling hydraulic device 44, and a release state that releases the braking state. The braking device 130 brakes the traveling motor (the first traveling motor 80A and the second traveling motor 80B). The braking device 130 includes a first disk provided on the output shaft of the first traveling motor 80A, a movable second disk, and a spring that biases the second disk to a side in contact with the first disk. Yes. Further, the braking device 130 includes an accommodating portion (accommodating case) 130a that accommodates the first disk, the second disk, and the spring. In the housing portion 130a, an oil passage 132 is connected to the storage portion in which the second disk is stored. An oil passage 106 is connected to the oil passage 132, and hydraulic oil can be supplied to the storage portion of the housing portion 130a. An operating valve 133 that can be opened and closed is connected to the oil passage 132. The actuating valve 133 is configured by a switching valve (hydraulic switching valve) that can be switched between a braking position where the braking device 130 is in a braking state and a release position where the braking device 130 is in a releasing state. When the operation valve 133 is switched to the release position (first position 133a), hydraulic oil is supplied to the storage portion of the storage portion 130a. When the pressure of the hydraulic oil in the storage unit exceeds a predetermined value, the second disk moves to the side opposite to the braking (the side opposite to the spring biasing direction), and the braking by the braking device 130 can be released. On the other hand, when the operation valve 133 is switched to the braking position (second position 133b), the pressure of the pilot oil decreases in the storage portion of the storage portion 130a. When the pressure of the hydraulic oil in the storage unit becomes a predetermined value or less, the second disk moves to the side in contact with the first disk, and braking by the braking device 130 can be performed. Switching of the operation valve 133 can be performed by the control device 131. When the operation valve 133 is a solenoid valve type two-position switching valve, the control device 131 switches the operation valve 133 to the first position 133a by exciting the operation valve 133. In addition, the control device 131 switches the operating valve 133 to the second position 133b by demagnetizing the operating valve 133. In addition, the control device 131 has the functions of the control device shown in the first embodiment. That is, the control device 131 can control the proportional valve 45, and the proportional valve 45 can apply a pressure to the hydraulic pressure switching valve.

When the braking is released by the braking device 130, the control device 131 controls the proportional valve 45 according to the setting by the operation member 115. That is, as shown in FIGS. 3 to 5 of the first embodiment, the control device 131 controls the proportional valve 45 to switch between the first speed and the second speed, pressurization of hydraulic oil to the hydraulic switching valve, and the like. I do.
In the case where the control device 131 is set to the first speed and braking is being performed by the braking device 130, the applied pressure F1 is set higher when the applied pressure is applied to the hydraulic pressure switching valve. For convenience of explanation, the applied pressure F1 set when the brake is released is referred to as “first applied pressure F1”, and the applied pressure F6 different from the applied pressure F1 is referred to as “second applied pressure F6 (not shown)”. .

The control device 131 stores either the second applied pressure F6, the opening degree of the proportional valve 45 (applied opening degree) corresponding to the second applied pressure F6, or the current value (applied current value) corresponding to the applied opening degree. ing. Here, the second applied pressure F6 is at least larger than the first applied pressure F1, and is, for example, the same as the warning pressure F3. Further, the second application pressure F6 may be greater than the switching pressure CP1.
The control device 131 sets the hydraulic pressure applied to the hydraulic pressure switching valve to the second applied pressure F6 on condition that the speed is the first speed and that the brake device 130 is controlled to be braked. That is, when the first speed setting is input to the control device 131 by the operation member 115 and the control device 131 demagnetizes the operating valve 133, the control device 131 corresponds to the second applied pressure F6. The applied current value is output to the proportional valve 45. On the other hand, when the control device 131 is in a state other than the above-described conditions, for example, when the second speed is set, or when braking by the braking device 130 is released, the operation of the second applied pressure F6 is performed. Oil application stops.

  Accordingly, the proportional valve 45 sets the applied pressure for applying the hydraulic oil to the hydraulic pressure switching valve at a predetermined value or higher, that is, the second applied pressure F6 when the operating valve 133 is at the braking position 133b. As a result, the hydraulic oil acting on the pressure receiving portion 91 of the hydraulic switching valve increases, and the hydraulic oil between the proportional valve 45 and the pressure receiving portion 91 of the hydraulic switching valve can be efficiently circulated through the discharge oil passage 108. .

  In the embodiment described above, the pressure of the pilot acting on the pressure receiving portion 91 of the hydraulic switching valve is gradually increased during a shift (when the speed is increased from the first speed to the second speed, and when the speed is decreased from the second speed to the first speed). In other words, as shown in FIG. 7, when shifting, the transmission pressure L2 is increased halfway as shown in FIG. May be raised or lowered.

  Specifically, when shifting from the 1st speed to the 2nd speed, as shown by the shift pressure L2a in FIG. 7, from the state where the applied pressure F1 is applied to the hydraulic switching valve by the proportional valve 45, the neutral position is reached. The shift pressure is increased at a stroke until the first set pressure Q1 determined corresponding to (step 1) is reached. When the pressure acting on the pressure receiving portion 91 of the hydraulic switching valve reaches the first set pressure Q1, as indicated by the transmission pressure L2b, the first value determined corresponding to the second position from the time when the first set pressure Q1 is reached. 2. The shift pressure is gradually increased until the set pressure Q2 is reached (second stage). When the pressure acting on the pressure receiving portion 91 of the hydraulic switching valve reaches the second set pressure Q2, as shown by the shift pressure L2c, the shift pressure is increased all at once until the third set pressure Q3 determined at the second position is reached. Is raised (third stage). That is, as shown in FIG. 7, when shifting from the first speed to the second speed, the change in the shift pressure is increased in three stages.

  On the other hand, when shifting from the 2nd speed to the 1st speed, as shown by the transmission pressure L2d in FIG. 7, the proportional valve 45 is closed from the state where it is maintained at a predetermined position, and is determined corresponding to the neutral position. The shift pressure is lowered at a stroke until the fourth set pressure Q4 is reached (first stage). When the pressure acting on the pressure receiving portion 91 of the hydraulic switching valve reaches the fourth set pressure Q4, as indicated by the transmission pressure L2e, the first position determined corresponding to the first position from the time when the fourth set pressure Q4 is reached. The transmission pressure is gradually lowered until the set pressure Q5 is reached (second stage). When the pressure acting on the pressure receiving portion 91 of the hydraulic switching valve reaches the fifth set pressure Q5, the shift pressure is lowered at a stroke until the applied pressure F1 is reached (third stage). That is, as shown in FIG. 7, when shifting from the 2nd speed to the 1st speed, the change in the shift pressure is lowered in three stages.

In the hydraulic system, a second throttle portion 109b is provided in the first oil passage 105, and a measuring device 118 is provided between the second throttle portion 109b and the pressure receiving portion 91 of the hydraulic switching valve. Therefore, as described above, it is easy to set (control) the pressure of the hydraulic oil acting on the pressure receiving portion 91 of the hydraulic switching valve by controlling the proportional valve 45, and the hydraulic switching valve can be switched with high accuracy. . In other words, by providing the second throttle portion 109b in the first oil passage 105, it is easy to stabilize the relationship between the opening of the proportional valve 45 and the pressure of the hydraulic oil acting on the pressure receiving portion 91 of the hydraulic switching valve. In addition, since the proportional valve 45 is controlled by the measuring device 118 provided between the second throttle portion 109b and the pressure receiving portion 91, the pressure of the hydraulic oil acting on the pressure receiving portion 91 of the hydraulic switching valve is controlled. The setting accuracy can be improved.
[Third Embodiment]
FIG. 8 shows a hydraulic system according to the third embodiment. The hydraulic system of the working system shown in the third embodiment can be applied to the hydraulic system of the first embodiment or the second embodiment described above. In addition, description of the same structure as 1st Embodiment or 2nd Embodiment is abbreviate | omitted.

As shown in FIG. 8, a shutoff valve (switching valve) 140 and a control device 141 are provided.
The shut-off valve (shut valve) 140 is a valve that opens or shuts off the oil passage between the control valve 70 and the hydraulic actuator. Specifically, the shutoff valve 140 is provided in the middle of the oil supply / discharge oil passage 74, that is, in the middle of the oil passage 74a and the oil passage 74b. The shutoff valve 140 is a switching valve that can be switched between a first position 140a that opens the oil supply / discharge passage 74 and a second position 140b that closes the supply / discharge oil passage 74. Therefore, when the shutoff valve 140 is set to the first position 140a, the middle portions of both the oil passage 74a and the oil passage 74b are connected, and when the cutoff valve 140 is set to the second position 140b, both the oil passage 74a and the oil passage 74b are connected. Shut off.

  A drain oil passage 83 is connected to the oil passage 77a. The hydraulic oil tank 31 is connected to the discharge oil passage 83. The discharge oil passage 83 is provided with a throttle portion 84 that reduces the flow rate of the hydraulic oil flowing through the discharge oil passage 83. A discharge oil passage 85 is connected to the oil passage 77b. The hydraulic oil tank 31 is connected to the discharge oil passage 85. The exhaust oil passage 85 is provided with a throttle portion 86 that reduces the flow rate of the working oil flowing through the exhaust oil passage 85.

  The control device 141 controls the proportional valve 73. An operation member 78 is connected to the control device 141. The operation amount of the operation member 78 is input to the control device 141. The control device 141 outputs a control signal (for example, current) corresponding to the operation amount of the operation member 78 to the first proportional valve 73A or the second proportional valve 73B. The proportional valves 73 (the first proportional valve 73A and the second proportional valve 73B) are opened and closed by a control signal output from the control device 141. Therefore, the auxiliary actuator can be operated under the control of the control device 141.

  Further, the control device 141 controls the proportional valve 73 based on the state of the shutoff valve 140. FIG. 9 is a diagram showing the relationship between the pilot pressure acting on the pressure receiving portions 70C1 and 70C2 of the preliminary control valve 70C and the switching of the preliminary control valve 70C. The switching pressure CP3 shown in FIG. 9 is a boundary pressure at which the preliminary control valve 70C switches from the neutral position 79c to the first position 79a or the second position 79c. The applied pressure F7 shown in FIG. 9 is a pressure lower than the switching pressure CP3.

When the shutoff valve 140 is in the first position 140a and is in an open state, and the operation member 78 is not operated [when the preliminary control valve 70C is in the third position (neutral position 79c)],
The control device 141 outputs the applied current to the proportional valve 73 (first proportional valve 73A, second proportional valve 73B). Therefore, as shown by the transmission pressure L3 in FIG. 9, when the shutoff valve 140 is in the open state and the operation member 78 is not operated, the applied pressure F7 can be applied to the preliminary control valve 70C.

  Further, on the condition that the shutoff valve 140 is in the shutoff state at the second position 140b and the operation member 78 is not operated, the control device 141 supplies the hydraulic oil that acts on the preliminary control valve 70C. The pressure is set to be larger than a preset application pressure F7. For example, the pressure of the hydraulic oil that acts on the preliminary control valve 70C may be substantially the same as the warning pressure F8 set between the applied pressure F7 and the switching pressure CP3, or may be set higher than the switching pressure CP3. Good. In other words, when the shutoff valve 140 is in the shutoff state, the pressure (applied pressure) of the hydraulic oil applied to the preliminary control valve 70C is set to the warning pressure F8 or the switching pressure CP3 or more, and the shutoff valve 140 is in the open state. In this case, the pressure of the hydraulic oil applied to the preliminary control valve 70C is made to coincide with the applied pressure F7.

When the shutoff valve 140 is in the first position 140a and is in the open state, and the operation member 78 is operated, the control device 141 supplies a current corresponding to the operation amount of the operation member 78 to the proportional valve 73. Output to. Therefore, when the operation member 78 is operated while the shutoff valve 140 is open, the preliminary control valve 70 </ b> C can be switched according to the operation of the operation member 78.
Note that the pressure (applied pressure) of the hydraulic oil applied to the preliminary control valve 70C may be set based on the temperature of the hydraulic oil. As shown in FIG. 8, the control device 141 is connected to a measuring device (first measuring device) 150 that can detect the temperature of the hydraulic oil. When the operation member 78 is not operated and the shut-off valve 140 is in the shut-off state and the temperature of the hydraulic oil detected by the measuring device 150 is equal to or lower than a predetermined value, the control device 141 acts on the preliminary control valve 70C. The hydraulic oil pressure (applied pressure) is set to a warning pressure F8 or a switching pressure CP3 or higher. For example, when the temperature of the hydraulic oil is low and the viscosity becomes high, the control device 141 sets the pressure (applied pressure) of the hydraulic oil to be applied to the preliminary control valve 70C to the warning pressure F8 or the switching pressure CP3 or higher.

Further, the pressure (applied pressure) of the hydraulic oil applied to the preliminary control valve 70C may be set based on the temperature of the outside air. As shown in FIG. 8, a measuring device (second measuring device) 151 capable of detecting the temperature of the outside air is connected to the control device 141. When the operation member 78 is not operated and the shutoff valve 140 is in a shutoff state and the temperature of the outside air detected by the measuring device 151 is equal to or lower than a predetermined value, the control device 141 operates to act on the preliminary control valve 70C. The oil pressure (applied pressure) is set to the warning pressure F8 or the switching pressure CP3 or higher.
[Fourth Embodiment]
FIG. 10 shows a hydraulic system according to the fourth embodiment. The traveling hydraulic system shown in the fourth embodiment can be applied to the hydraulic systems of the first to third embodiments described above. In addition, description of the structure similar to 1st Embodiment-3rd Embodiment is abbreviate | omitted.

  In the above-described embodiment, the first traveling hydraulic pump 66A and the second traveling hydraulic pump 66B are operated to the remote control valves 36, 37, 38, 39. In the fourth embodiment, the first traveling hydraulic pump 66A and the second traveling hydraulic pump 66B are operated. The second traveling hydraulic pump 66B is operated by the operation valve 210A and the operation valve 210B. The operation valve 210A and the operation valve 210B are electromagnetic proportional valves (proportional valves) whose opening degree is changed by a control signal. The working oil 210A and the working valve 210B can be supplied with working oil from the second hydraulic pump P2 through an oil passage (not shown). By changing the opening degree of the working valve 210A and the working valve 210B, the pressure (pilot pressure) of the working oil acting on the traveling hydraulic pump (the first traveling hydraulic pump 66A and the second traveling hydraulic pump 66B) is changed. The angle of the swash plate can be changed by the pressure acting on the traveling hydraulic pump. Hereinafter, for convenience of explanation, the operation valve 210A and the operation valve 210B are referred to as a proportional valve 210A and a proportional valve 210B, respectively.

The hydraulic system includes a braking device 130 and a control device 160. The braking device 130 is the same as that of the fourth embodiment. The control device 160 switches the operating valve 133 to the first position 133a by exciting the operating valve 133. In addition, the control device 160 switches the operating valve 133 to the second position 133b by demagnetizing the operating valve 133.
Further, the control device 160 controls the proportional valve 210 </ b> A and the proportional valve 210 </ b> B based on the operation member 161 connected to the control device 160. That is, the control device 160 controls the traveling hydraulic pumps (first traveling hydraulic pump 66A, second traveling hydraulic pump 66B).

  When braking is released by the braking device 130, the control device 160 controls the proportional valve 210A and the proportional valve 210B according to the setting by the operation member 161. When the operation member 161 is swung in one direction or the other direction from the neutral position in the state where the brake is released, the control device 160 determines that the proportional valve 210A and the proportional valve according to the swing amount (operation amount). A control signal (for example, current) is output to 210B. The opening of the proportional valve 210A and the proportional valve 210B is increased by the control signal, and the angle of the swash plate of the traveling hydraulic pump (the first traveling hydraulic pump 66A and the second traveling hydraulic pump 66B) is increased according to the opening. . As the travel hydraulic pumps (first travel hydraulic pump 66A, second travel hydraulic pump 66B) increase, the discharge amount of hydraulic oil increases.

  Further, when the operation member 161 is swung from the position in one direction or the position in the other direction toward the neutral position in a state where the braking is released, the control device 160 responds to the swing amount (operation amount). The control signal (for example, current) is output to the proportional valve 210A and the proportional valve 210B. The opening of the proportional valve 210A and the proportional valve 210B is reduced by the control signal, and the angle of the swash plate of the traveling hydraulic pump (the first traveling hydraulic pump 66A, the second traveling hydraulic pump 66B) is decreased according to the opening. . As the travel hydraulic pump (first travel hydraulic pump 66A, second travel hydraulic pump 66B) decreases, the discharge amount of hydraulic oil decreases. When the operation member 161 is not operated in a state where the braking is released, the control device 160 discharges from the traveling hydraulic pump by controlling the opening degree of the proportional valve 210A and the proportional valve 210B. An applied pressure (first applied pressure) F8 is applied to the traveling hydraulic pump to such an extent that the traveling motor does not rotate due to the hydraulic oil.

  When braking is performed by the braking device 130, the control device 160 sets the applied pressure higher when applying the applied pressure to the traveling hydraulic pump. That is, the control device 160 opens the second application pressure F9 (not shown), the opening degree (applying opening degree) of the proportional valve 210A and the proportional valve 210B corresponding to the second applying pressure F9, and the current value (applying application). One of the current values) is stored. Here, the second applied pressure F9 is at least larger than the first applied pressure F8 and smaller than the minimum pressure of the traveling hydraulic pump at which the traveling motor starts rotating by the traveling hydraulic pump.

The control device 160 sets the pressure of the hydraulic oil to be applied to the traveling hydraulic pump to the applied pressure F9 on condition that the operation member 161 is not operated and the brake device 130 is controlled to be braked. To do. On the other hand, when the control device 160 is in a state other than the above-described conditions, for example, when the operation member 161 is operated, when braking by the braking device 130 is released, the operation member 161 is not operated. When the braking by the braking device 130 is released, the application of the hydraulic oil at the second applied pressure F9 is stopped.
[Fifth Embodiment]
FIG. 11 shows a hydraulic system according to a fifth embodiment. The traveling hydraulic system shown in the fifth embodiment can be applied to the hydraulic systems of the first to fourth embodiments described above. In addition, description of the same structure as 1st Embodiment-4th Embodiment is abbreviate | omitted. The hydraulic system shown in FIG. 11 is not provided with the discharge oil passage 108, the first throttle portion 109a, and the second throttle portion 109b.

In the traveling hydraulic system, the control device 170 includes a CPU and the like. The control device 170 controls the proportional valve 45 based on the setting by the operation member 115 and the pressure (detected pressure) of the hydraulic oil detected by the measuring device 118.
The control device 170 stores any one of the applied pressure F1, the opening degree of the proportional valve 45 (applied opening degree) corresponding to the applied pressure F1, and the current value (applied current value) corresponding to the applied opening degree. In this embodiment, the description will proceed assuming that the applied current value corresponding to the applied pressure F1 is stored.

  When the first speed is set by the operation member 115, the control device 170 outputs, for example, an applied current to the proportional valve 45. Further, the control device 170 monitors the detected pressure F2 during the application period. As shown in FIG. 12, during the application period, the control device 170 controls the proportional valve 45 when the detected pressure F2 is greater than the application pressure F1, thereby operating the hydraulic oil acting on the pressure receiving portion 91 of the hydraulic switching valve. The feedback control is performed so that the applied pressure F1 and the detected pressure F2 coincide with each other. Further, when the detected pressure F2 is smaller than the applied pressure F1, the control device 170 controls the proportional valve 45 to increase the pressure of the hydraulic oil that acts on the pressure receiving portion 91 of the hydraulic switching valve, thereby providing the applied pressure F1. And feedback control to match the detected pressure. Thus, the control device 170 can match the pressure of the hydraulic oil acting on the pressure receiving portion 91 of the hydraulic switching valve with the applied pressure F1 by monitoring the detected pressure F2 and performing feedback control.

  Also, when the hydraulic switching valve is in the first position (first speed) and is set to the second speed by the operation member 115, the control device 170 outputs a control signal to the proportional valve 45, and the hydraulic switching valve is turned on. The pressure of the working hydraulic fluid is set to the switching pressure CP2 or more. When the pressure of the hydraulic oil (applied pressure F1) acting on the hydraulic pressure switching valve is equal to or higher than the switching pressure CP2 and reaches a predetermined set pressure Q3, the control device 170 matches the applied pressure F1 and the set pressure Q3. Thus, the opening degree of the proportional valve 45 is controlled.

  In addition, when the hydraulic switching valve is in the second position 90b (second speed) and is set to the first speed by the operation member 115, the control device 170 outputs a control signal to the proportional valve 45 as an applied current value. Then, the switching pressure L1 gradually decreases, the hydraulic switching valve is switched from the second position 90b to the first position 90a, and after decelerating from the second speed to the first speed, the applied pressure F1 is applied to the hydraulic switching valve. Is done.

As described above, the proportional valve 45 can be controlled by the control device 170 so that the detected pressure F2 detected by the measuring device 118 matches the applied pressure F1.
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.

  FIG. 13 shows a modification of the hydraulic switching valve and the travel motor. As shown in FIG. 13, the hydraulic pressure switching valve has a first hydraulic pressure switching valve 200A and a second hydraulic pressure switching valve 200B. The first hydraulic pressure switching valve 200A and the second hydraulic pressure switching valve 200B are two-position switching valves that can move to the first position 200a and the second position 200b in accordance with the pilot pressure. As shown by the transmission pressure L4 in FIG. 14, the first hydraulic pressure switching valve 200A and the second hydraulic pressure switching valve 200B are in the first position 200a when the pilot pressure acting on the pressure receiving portion is less than the switching pressure CP4. When the pilot pressure becomes equal to or higher than the switching pressure CP4, the second position 200b is reached.

  The travel motor includes a first travel motor 201A and a second travel motor 201B. The first traveling motor 201A and the second traveling motor 201B are swash plate type variable displacement axial motors that can change speed between high and low speeds. Each of the first travel motor 201A and the second travel motor 201B includes a swash plate switching cylinder 202 that switches the angle of the swash plate. The swash plate switching cylinder 202 of the first travel motor 201A is connected to the first hydraulic pressure switching valve 200A and expands and contracts by the hydraulic oil from the first hydraulic pressure switching valve 200A. The swash plate switching cylinder 202 of the second travel motor 201B is connected to the second hydraulic pressure switching valve 200B and expands and contracts by the hydraulic oil from the second hydraulic pressure switching valve 200B.

  Therefore, when the first travel motor 201A and the second travel motor 201B are at the first position 200a, the swash plate switching cylinder 202 contracts, and the swash plate angles of the first travel motor 201A and the second travel motor 201B are reduced. change. Thereby, the first traveling motor 201A and the second traveling motor 201B are set to the first speed. When the first travel motor 201A and the second travel motor 201B are at the second position 200b, the swash plate switching cylinder 202 extends to change the angles of the swash plates of the first travel motor 201A and the second travel motor 201B. . As a result, the first traveling motor 201A and the second traveling motor 201B are in the second speed. Even if the proportional valve 45 is a hydraulic switching valve that does not include a neutral position, the transmission pressure L4 can be changed according to the traveling state, the traveling load, the load on the prime mover, and the state of the prime mover.

  As shown in FIG. 13, the control device 110 has a storage unit 240 that stores the relationship between the control signal (current value) output to the proportional valve 45 and the hydraulic oil pressure detected by the measurement device 118. It is preferable. A setting mode is provided in the control device 110. The setting mode can be switched between valid and invalid by an operation member such as a switch (not shown). When the setting mode is valid, for example, by gradually opening the proportional valve 45 from the fully closed state, the pressure of the hydraulic oil acting on the pressure receiving portion 91 of the hydraulic switching valve is gradually increased from zero. . In the setting mode, the setting mode is terminated when the hydraulic oil pressure (detected pressure detected by the measuring device 118) acting on the pressure receiving portion 91 of the hydraulic switching valve reaches the applied pressure F1. In the setting mode, the detected pressure until the hydraulic oil pressure acting on the pressure receiving portion 91 of the hydraulic pressure switching valve gradually increases from zero and reaches the applied pressure F1, and the control signal (the control device 110 outputs to the proportional valve 45). Current) is sequentially acquired, and the relationship between the detected pressure and the control signal is stored in the storage unit 240. That is, in the setting mode, the relationship between the control signal output from the control device 110 to the proportional valve 45 and the hydraulic oil pressure until the applied pressure F1 is reached is acquired. Then, the control device 110 performs normal control when the setting mode is invalid. That is, when applying pressure to the hydraulic pressure switching valve by normal control, the control device 110 controls the proportional valve 45 using the relationship (control signal and pressure stored in the storage unit 240) obtained by the setting mode. To do. Note that the storage unit 240 and the setting mode may be provided in a control device other than the control device 110.

  In the embodiment described above, the drain oil passage 108, the first throttle portion 109a, the second throttle portion 109b, and the measuring device 118 are provided in each of the first hydraulic pressure switching valve 90A and the second hydraulic pressure switching valve 90B. As shown in FIG. 15, a discharge oil passage 108, a first throttle portion 109a, a second throttle portion 109b, and a measuring device 118 that are common to the first hydraulic pressure switching valve 90A and the second hydraulic pressure switching valve 90B may be provided. Further, in a hydraulic system that applies pressure to the hydraulic switching valve, the drain oil passage 108, the first throttle portion 109a, and the second throttle portion 109b may or may not be provided. For example, in the hydraulic system of FIGS. 1, 10, 13, 15, and 17, the drain oil passage 108, the first throttle portion 109a, and the second throttle portion 109b may be omitted.

  16A and 16B, the proportional valve 45 is connected to the swash plate switching cylinder (servo cylinder) 202 via the oil passage 105, and the proportional motor 45 (the first traveling motor 201A, The second traveling motor 201B) may be switched to the first speed or the second speed. The control device 110 differs from the above-described embodiment only in that the control target is the swash plate switching cylinder 202, and other operations are the same as those of the above-described embodiment. That is, the hydraulic switching valve may be read as a swash plate switching cylinder.

  For example, when the first speed is set, the control device 110 causes the pressure acting on the swash plate switching cylinder 202 to be less than the predetermined pressure CP3. When the second speed is set, control device 110 sets the pressure acting on swash plate switching cylinder 202 to a predetermined pressure CP3 or higher. In the case of FIG. 16B, the traveling motor is in the second speed when the pressure acting on the swash plate switching cylinder 202 is less than the predetermined pressure CP3, and the traveling motor is in the first speed if the pressure is greater than or equal to the predetermined pressure CP3. The swash plate switching cylinder (servo cylinder) 202 may be performed by a control device other than the control device 110.

  In the above-described embodiment, when the proportional valve 45 is controlled by the control device 110, the hydraulic oil pressure (detected pressure) detected by the measuring device 118 is fed back to the control device 110, and the proportional valve 45 is feedback-controlled. May be. For example, when the detected pressure is greater than the predetermined applied pressure F1, the control device 110 controls the proportional valve 45 to reduce the pressure of the hydraulic oil acting on the pressure receiving portion 91 of the hydraulic switching valve, The applied pressure F1 and the detected pressure are matched. In addition, when the detected pressure is smaller than the predetermined applied pressure F1, the control device 110 controls the proportional valve 45 to increase the pressure of the hydraulic oil that acts on the pressure receiving portion 91 of the hydraulic switching valve, The applied pressure F1 and the detected pressure are matched.

DESCRIPTION OF SYMBOLS 1 Work machine 4 Traveling apparatus 44 Traveling hydraulic apparatus 45 Proportional valve 73 Proportional valve 74 Supply / discharge oil path 76 Hydraulic actuator 78 Operation member 90 Hydraulic switching valve 110 Control apparatus 115 Operation member 130 Braking apparatus 131 Control apparatus 133 Actuation valve 140 Shut-off valve 141 Control device 150 Measuring device (first measuring device)
151 measuring device (second measuring device)
160 Control Device 161 Operation Member 170 Control Device 180 Connection Portion

Claims (3)

A hydraulic pump that discharges hydraulic oil;
A hydraulic actuator that operates with hydraulic oil;
A hydraulic switching valve capable of switching to a plurality of switching positions according to the pressure of the hydraulic oil and capable of changing the hydraulic oil output to the hydraulic actuator by the switching;
An oil supply / discharge passage provided between the hydraulic switching valve and the hydraulic actuator;
A proportional valve that is lower than the switching pressure of the hydraulic oil that switches to the switching position and is capable of applying an applied pressure that is a predetermined pressure to the hydraulic switching valve;
A switching valve that can be switched between an open state for opening the oil supply / discharge passage and a shut-off state for blocking the oil supply / discharge passage;
With
The proportional valve is a hydraulic system for a working machine that makes an applied pressure equal to or higher than a predetermined pressure when the switching valve is in a shut-off state. A first measuring device capable of detecting the temperature of the hydraulic oil;
2. The hydraulic system for a working machine according to claim 1, wherein when the temperature of the hydraulic oil measured by the first measuring device is equal to or lower than a predetermined value, the proportional valve increases the applied pressure to a predetermined value or higher. A second measuring device capable of detecting the temperature of the outside air;
3. The hydraulic system for a working machine according to claim 1, wherein the proportional valve increases the applied pressure to a predetermined level or higher when the temperature of the outside air measured by the second measuring device is equal to or lower than a predetermined level.

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