JP6682496B2 - Hydraulic system of work equipment - Google Patents

Description

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

BACKGROUND ART Conventionally, Patent Document 1 is known as a hydraulic system for working machines such as skid steer loaders and compact truck loaders.
The hydraulic system of the traveling system of Patent Document 1 includes a plurality of HST motors capable of switching between low speed (1st speed) and high speed (2nd speed), a hydraulic switching valve capable of switching the HST motors to 1st speed or 2nd speed. And a directional valve that can be placed in position. In Patent Document 1, by switching the directional 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.

  Further, in the 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 hydraulic system of the traveling system of Patent Document 1, since the direction switching valve only switches to a plurality of predetermined positions, the pressure of the hydraulic oil acting on the hydraulic switching valve is set to, for example, the traveling hydraulic pressure of the traveling pump or the like. It cannot be changed according to the state of the equipment or the state of the prime mover. That is, according to Patent Document 1, the characteristics of the switching pressure when switching the hydraulic switching valve cannot be changed according to the running state or the state of the prime mover.

  Now, in the hydraulic system of the traveling system of Patent Document 1, it has been attempted to control the pressure of the hydraulic oil acting on the hydraulic switching valve by changing the directional switching valve to a proportional valve. For example, the pressure of the hydraulic oil is applied to the hydraulic pressure switching valve in advance, that is, the pressure is applied, by opening the proportional valve slightly. By thus applying the pressure, the response of the hydraulic switching valve can be improved and the hydraulic switching valve can be warmed up.

  The present invention has been made to solve the above-mentioned problems of the prior art, and can apply a pressurizing force (applying pressure), and can change the pressurizing force according to various situations. It is an object of the present invention to provide a hydraulic system for a work machine capable of

The technical means taken by the present invention to solve the above technical problems are as follows.
The hydraulic system of the working machine is capable of switching to a plurality of switching positions according to the pressure of the hydraulic oil, a hydraulic pump that discharges hydraulic oil, a hydraulic actuator that operates with the hydraulic oil, and outputs to the hydraulic actuator by the switching. The hydraulic pressure switching valve capable of changing the operating oil, the oil supply and discharge passage provided between the hydraulic switching valve and the hydraulic actuator, and the pressure lower than the switching pressure of the hydraulic oil switching to the switching position. A proportional valve that can apply a given pressure that is a predetermined pressure to the hydraulic pressure switching valve,
A switching valve capable of switching between an open state in which the supply / drain oil passage is opened and a shut-off state in which the supply / drain oil passage is shut off; and the proportional valve is provided when the switching valve is in a shut-off state. Increase the pressure above a certain level.

The hydraulic system of the working machine includes a first measuring device capable of detecting the temperature of the hydraulic oil, and the proportional valve controls 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. Be above a certain level.
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 sets the applied pressure to a predetermined value when the temperature of the outside air measured by the second measuring device is a predetermined value or less. More than that.

  According to the present invention, a pressurizing force (applying pressure) can be applied, and the pressurizing force 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 work system in 1st Embodiment. It is a figure which shows the relationship between the position of a hydraulic pressure switching valve, and pilot pressure. It is the figure which showed the example which gives a pressure to the hydraulic pressure switching valve at the time of deceleration. It is the figure which showed the example which gives deceleration setting pressure different from 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 another modification showing the relation between the position of a hydraulic pressure switching valve and pilot pressure. It is a figure which shows the hydraulic system of the work system in 3rd Embodiment. It is a figure which shows the relationship between the pilot pressure which acts on the pressure receiving part of a preliminary control valve, and a position. 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 and pilot pressure in 5th Embodiment. It is a figure which shows the modification of a traveling hydraulic system and a hydraulic switching valve. It is a figure which shows the relationship between the position of the hydraulic switching valve and a pilot pressure in a modification. It is a figure which shows the hydraulic system of a traveling system when a memory | storage part is provided in a control apparatus. FIG. 6 is a diagram showing a hydraulic system in which an exhaust oil passage, a throttle unit, and a measuring device common to the hydraulic pressure switching valve are provided. It is a figure when an operating valve is connected to a servo cylinder of a traveling motor. It is another figure in the case of connecting the actuation valve to the servo cylinder of the traveling motor. It is a side view showing a truck loader which is an example of a working machine concerning the present invention. It is a side view which shows a part of truck loader in the state which raised the cabin.

Hereinafter, preferred embodiments of a hydraulic system for a working machine and a working machine including the hydraulic system according to the present invention will be described with reference to the drawings as appropriate.
[First Embodiment]
First, the overall configuration of the working machine will be described.
The overall configuration of the working machine will be described. 18 and 19 show a truck loader as an example of the working machine 1. The work machine is not limited to the 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 (the direction indicated by the arrow F shown in FIG. 18) of the driver sitting in the driver's seat of the work machine 1 is the front side, and the rear side of the driver (the direction indicated by the arrow R shown in FIG. 18). Will be referred to as "back", the driver's left side (front side as viewed in FIG. 18) will be left, and the driver's right side (back side as viewed in FIG. 18) as right.

  As shown in FIGS. 18 and 19, the work machine 1 includes a machine body 2, a work device 3 mounted on the machine body 2, and a traveling device 4 that supports the machine body 2. A cabin 5 is mounted on the upper part of the machine body 2 and on the front part of the machine body 2. The rear portion of the cabin 5 is supported by the support bracket 11 of the machine body 2 and can swing around the support shaft 12. The front portion of the cabin 5 can be supported by the front portion of the machine body 2.

A driver's seat 13 is provided in the cabin 5. On one side (for example, the left side) of the driver's seat 13, a traveling operation device 14 for operating the traveling device 4 is arranged.
The traveling device 4 is composed of a crawler type traveling hydraulic device. The traveling device 4 is provided below the left side of the machine body 2 and below the right side of the machine body 2. The traveling device 4 can travel by the driving force of a hydraulically driven traveling hydraulic device 44 described later.

  The work device 3 includes a boom 22L, a boom 22R, and a bucket 23 (work implement) attached to the tips of the boom 22L and the boom 22R. The boom 22L is arranged on the left of the machine body 2. The boom 22R is arranged on the right of the machine 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. A lift cylinder 26, which is a double-acting hydraulic cylinder, is provided between the bases of the booms 22L and 22R and the lower rear portion of the machine body 2 so as to correspond to the booms 22L and 22R. By simultaneously expanding and contracting 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 tip ends of the boom 22L and the boom 22R so as to be rotatable around a horizontal axis, and the back side of the bucket 23 is attached to the mounting bracket 27.

Further, a tilt cylinder 28, which is a double-acting hydraulic cylinder, is interposed between the mounting bracket 27 and the middle portions of the boom 22L and the boom 22R on the tip end side so as to correspond to the boom 22L and the boom 22R. As the tilt cylinder 28 expands and contracts, the bucket 23 swings (squeeze / dump).
The bucket 23 is detachable from the mounting bracket 27. The mounting bracket 27 is configured such that various attachments (hydraulic drive type working tools having hydraulic actuators) can be attached by removing the bucket 23, and various work other than excavation (or other excavation work) can be performed. Has been done.

A prime mover 29 is provided on the rear side of the bottom wall of the machine 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 of the bottom wall of the machine body 2.
Next, the hydraulic system of the working machine will be described.
FIG. 1 is a diagram showing a hydraulic system of a traveling system of a work machine. FIG. 2 shows a hydraulic system of a 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 P1 and the second hydraulic pump P2 are constant capacity type gear pumps 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 P1 (main pump) is used to drive a hydraulic actuator of an attachment attached to the tip end side of the lift cylinder 26, the tilt cylinder 28, or the boom 22. The second hydraulic pump P2 (pilot pump, charge pump) is mainly used to supply the pressure of the hydraulic oil as a control pressure or a signal pressure. Hereinafter, for convenience of description, the hydraulic oil as the control pressure or the signal pressure is referred to as “pilot oil”, and the pressure of the pilot oil is referred to as “pilot pressure”.

  The hydraulic system includes a traveling hydraulic device 44, an operating valve 45, and a hydraulic pressure switching valve 90. The traveling hydraulic device 44 is a device that can change the speed with hydraulic oil. That is, in the traveling hydraulic device 44, the rotational speed (rotational speed) of the traveling motor described later is changed. In other words, the traveling hydraulic device 44 is a device that can change the propulsive force when the traveling device 4 travels. The traveling hydraulic device 44 has a first traveling hydraulic pump 66A, a second traveling hydraulic pump 66B, a first traveling motor 80A, and a second traveling motor 80B. The hydraulic pressure switching valve 90 has a hydraulic pressure switching valve 90A and a second hydraulic pressure switching valve 90B.

  The first traveling hydraulic pump 66A and the first traveling motor 80A are connected by a first circulation oil passage 101 capable of circulating hydraulic oil. The second traveling hydraulic pump 66B and the second traveling motor 80B are connected by a second circulation oil passage 102 capable of circulating hydraulic oil. The first hydraulic pressure 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 90A, the second hydraulic pressure switching valve 90B, and the operation valve 45 are connected by an oil passage (first oil passage) 105. The discharge oil passage 108 is connected to the pressure receiving portion 91 of the hydraulic pressure switching valve (first hydraulic pressure switching valve 90A, second hydraulic pressure switching valve 90B). The discharge oil passage 108 is an oil passage for discharging the working oil of the first oil passage 105 (the working oil acting on the pressure receiving portion 91) to the outside, and, for example, one end thereof 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 the suction portion of the hydraulic pump or another portion. The discharge oil passage 108 is provided with a first throttle portion (for example, an orifice) 109a. A second throttle portion (for example, an orifice) 109b is provided in the section of the first oil passage 105 between the connection portion 180 between the first oil passage 105 and the discharge oil passage 108 and the hydraulic oil 45. It is provided. The inner diameters (throttle diameters) of the first throttle portion 109a and the second throttle portion 109b are set to be substantially the same. The diameters of the first throttle portion 109a and the second throttle portion 109b are not limited to the above-mentioned diameters.

The operation valve 45 and the second hydraulic pump P2 are connected by the oil passage 106. The first traveling hydraulic pump 66A and the second traveling hydraulic pump 66B are connected to the second hydraulic pump P2 by an oil passage (not shown), and the hydraulic oil discharged from the second hydraulic pump P2 is used for the first traveling hydraulic pump P2. It can be supplied to the hydraulic pump 66A and the second traveling hydraulic pump 66B.
The first traveling hydraulic pump 66A is a swash plate type variable displacement axial pump driven by the power of the prime mover 29. Further, 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 changes, the discharge direction and discharge amount of the hydraulic oil also change, which changes the rotation output of the first traveling 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 discharge amount of the hydraulic oil are changed, which changes the rotation output of the second traveling motor 80B.
The first traveling motor 80A is composed of a cam motor (radial piston motor). The first traveling motor 80A is a variable capacity type that can change the size of the capacity (motor capacity) during operation, and the rotation and torque of the output shaft can be changed by changing the motor capacity. Specifically, the first traveling motor 80A has a first motor 81 and a second motor 82. By supplying the hydraulic oil to both the first motor 81 and the second motor 82, the motor capacity is increased and the first traveling motor 80A becomes the first speed. Further, by supplying the hydraulic oil to either the first motor 81 or the second motor 82, the motor capacity becomes smaller and the first traveling motor 80 becomes 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 pressure switching valve 90A is a hydraulic pressure switching valve that can switch to a plurality of switching positions according to the pilot pressure that is the pressure of pilot oil, and can switch the first traveling motor 80A to the first speed or the second speed. Is. The first hydraulic pressure switching valve 90A is, for example, a three-position switching valve capable of switching among three switching positions of 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 does not reach the switching pressure that is a predetermined pressure set in advance, the hydraulic switching valve 90 is moved to the first position 90a by the 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 becomes 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, the hydraulic oil is supplied only to the first motor 81, and the first traveling motor 80A becomes 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 operating valve 45 is a valve capable of changing the pressure (flow rate) of the operating oil acting on the hydraulic pressure switching valve (the first hydraulic pressure switching valve 90A, the second hydraulic pressure switching valve 90B), and the hydraulic switching valve is a predetermined switching valve. It is a valve that can apply the pressure of hydraulic fluid to the extent that it does not switch to the position. The opening of the actuating valve 45 can be changed by a control signal output from the control device 110 described later. In this embodiment, the actuation 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 (supplied) to the hydraulic pressure switching valve changes.

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

  As shown by the shift pressure L1 in FIG. 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 the 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 pressure switching valve is in the first position 90a, the traveling motors (first traveling motor 80A, second traveling motor 80B) are in the first speed. 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 pressure switching valve, as shown in FIG. In other words, the proportional valve 45 applies the preset applied pressure F1 to the pressure receiving portion 91 of the hydraulic pressure 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 portions 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 pressure switching valve 90B are in the neutral position 90c. 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 exceeded. The switching valve 90A and the second hydraulic pressure switching valve 90B are in the second position 90b. When the hydraulic pressure switching valve is in the second position 90b, the travel motor is in second speed. That is, there is a proportional relationship between the opening of the proportional valve 45 and the pilot pressure acting on the hydraulic pressure switching valve, and the travel motor can be switched to the first speed or the second speed according to the opening of the proportional valve 45.

  As described above, the proportional valve 45 has a structure capable of exerting a pressurizing force on the hydraulic pressure switching valve. In particular, the first oil passage 105 is provided with the discharge oil passage 108 and then the second throttle portion. Since the pressure change valve 109b is provided, it is possible to accurately pressurize the hydraulic pressure switching valve. By providing the first throttle portion 109a and the second throttle portion 109b, the pressure width when the proportional valve 45 operates can be increased by these throttle portions. That is, it is possible to allow the proportional valve 45 a margin in the control pressure range during pressurization.

  Now, as shown in FIG. 1, the oil passage 106 is branched on the upstream side of the proportional valve 45, and the oil passage 107 after the branch is connected to the traveling operation device 14. The traveling operation device 14 has 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, and a travel lever 40. Further, the traveling operation device 14 has first to fourth shuttle valves 51, 52, 53, 54. The remote control valves 36, 37, 38, 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 traveling lever 40 (operation member) and supply the changed hydraulic oil to the traveling hydraulic device 14. In this embodiment, the remote control valves 36, 37, 38, 39 are operated by one traveling lever 40, but a plurality of traveling levers 40 may be used. For example, the first traveling lever is arranged on one side (left side) of the driver's seat 13 and the second traveling lever is arranged on the other side, and the remote control valves 36, 37, 38, and You may operate 39.

  The traveling lever 40 is tiltable 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, pilot pressure proportional to the operation amount from the neutral position of the traveling 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 to the front side (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 via the oil passage 61, and also from the second shuttle valve 52 via the oil passage 62 to the second traveling hydraulic pump 66B. 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 (rotate forward) at a speed proportional to the tilt amount of the traveling lever 40, and the working machine 1 travels straight forward.

When the traveling lever 40 is tilted rearward (direction of arrow A2 in FIG. 1), the reverse drive remote control valve 37 is operated and the 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 also from the fourth shuttle valve 54 via the oil passage 63 to the second traveling hydraulic pump 66B. 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 (reverse rotation) at a speed proportional to the tilt amount of the traveling lever 40, and the working machine 1
Goes straight backwards.

  When the traveling lever 40 is tilted to the right (direction A3 in FIG. 1), the right turning remote control valve 38 is operated and the 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 via the oil passage 61, and also from the fourth shuttle valve 54 via the oil passage 63 to the second traveling hydraulic pump 66B. Acting on the pressure receiving portion 66b. As a result, the output shaft of the first traveling motor 80A rotates in the forward direction and the output shaft of the second traveling motor 80B rotates in the reverse direction, so that the working machine 1 turns to the right.

  When the traveling lever 40 is tilted to the left (direction A4 in FIG. 1), the left turning 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 also from the third shuttle valve 53 via the oil passage 64 to the first traveling hydraulic pump 66A. Acting on the pressure receiving portion 66b. As a result, the output shaft of the first traveling motor 80A rotates in the reverse direction, the output shaft of the second traveling motor 80B rotates in the forward direction, and the working machine 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 80A and the second traveling motor 80A and the second traveling hydraulic pump 66B are driven by the differential pressure of the pilot pressure acting on the pressure receiving portions 66a and 66b of the second traveling hydraulic pump 66B. The rotation direction and rotation speed of the output shaft of the traveling motor 80B are determined, and the track loader 1 turns right or left while moving forward or backward.
That is, when the traveling lever 40 is tilted forward to the left, the working machine 1 turns left while moving forward at a speed corresponding to the tilt angle of the traveling lever 40. When the traveling lever 40 is tilted forward to the right, the working machine 1 turns right while moving forward at a speed corresponding to the tilt angle of the traveling lever 40. When the traveling lever 40 is tilted to the left rearward, the working machine 1 turns left while moving backward at a speed corresponding to the tilting angle of the traveling lever 40. When the traveling lever 40 is tilted rearward to the right, the working machine 1 turns right while moving backward at a speed corresponding to the tilting angle of the traveling lever 40.

Next, the hydraulic system of the working 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 70B 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 the neutral position,
The operation of the boom 22 and the bucket 23 can be performed by the operation member 71 provided around the driver's seat 13. The operation member 71 is supported so as to be tiltable in the front-rear direction, the width direction orthogonal to the front-rear direction, and the diagonal direction from the neutral position. By tilting the operation member 71, the remote control valves 72A, 72B, 72C, 72D provided below the operation member 71 can be operated.

When the operating member 71 is tilted forward, the remote control valve 72A is operated and the pilot pressure is output from the remote control valve 72A. This pilot pressure acts on the pressure receiving portion of the boom control valve 70A and supplies the hydraulic oil that has entered the boom control valve 70A to the rod side of the lift cylinder 26, so that the boom (boom 22L, boom 22R) descends. .
When the operation member 71 is tilted rearward, the remote control valve 72B is operated and the pilot pressure is output from the remote control valve 72B. This pilot pressure acts on the pressure receiving portion of the boom control valve 70A, and the working oil that has entered the boom control valve 70A is supplied to the bottom side of the lift cylinder 26, whereby the boom rises.

That is, the boom control valve 70A is connected to the lift cylinder 26 according to the pressure of the hydraulic oil set by the operation of the operation member 71 (the pilot pressure set by the remote control valve 72A, the pilot pressure set by the remote control valve 72B). It is possible to control the flow rate of flowing hydraulic oil.
When the operating 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 the direction in which the tilt cylinder 28 is extended, and the bucket 23 dumps at a speed proportional to the tilt amount of the operating member 71.

When the operating 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 makes a squeezing operation at a speed proportional to the tilt amount of the operation member 71.
That is, the bucket control valve 70B causes the tilt cylinder 28 to move according to the pressure of the hydraulic oil set by the operation of the operating member 71 (the pilot pressure set by the remote control valve 72C, the pilot pressure set by the remote control valve 72D). It is possible to control the flow rate of flowing hydraulic oil. That is, the remote control valves 72A, 72B, 72C, 72D change the pressure of the hydraulic oil according to the operation of the operating member 71 and supply the changed hydraulic oil to the boom control valve 70A and the bucket control valve 70B.

  A supply / drain oil passage 74 is connected to the preliminary control valve 70C. The oil supply / drain 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 supply / discharge oil passage 74 (oil passage 74a and oil passage 74b) is connected to a connecting member 75, and the connecting member 75 can be connected to a hydraulic actuator 76 of a preliminary attachment. 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 can be changed according to the pressure of the hydraulic oil. The proportional valve 73 has a first proportional valve 73A connected to the pressure receiving portion 70C1 of the preliminary control valve 70C via an oil passage 77a and a second proportional valve 73A connected to the pressure receiving portion 70C2 of the preliminary control valve 70C via an oil passage 77b. And a proportional valve 73B. When the first proportional valve 73A opens, the pilot oil acts on the pressure receiving portion 70C1 via the oil passage 77a. Further, when the second proportional valve 73B is opened, pilot oil acts on the pressure receiving portion 70C2 via the oil passage 77b. Therefore, when pilot oil acts on the pressure receiving portion 70C1 or the 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 control device 110 operates the first proportional valve 73A and the second proportional valve 73B. An operation member 78 provided around the driver's seat 13 is connected to the control device 110. The operation member 78 is configured by, for example, a rocking seesaw type switch, a slidable slide type switch, or a pushable push type switch. 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) according to the operation amount of the operation member 78 to the first proportional valve 73A or the second proportional valve 73B. The proportional valve 73 (first proportional valve 73A, second proportional valve 73B) is opened and closed by a control signal output from the control device 110. Therefore, when the hydraulic oil output to the proportional valve 73 (the first proportional valve 73A, the second proportional valve 73B) reaches a predetermined value or more, the preliminary control valve 70C causes the first position 79a, the second position 79b, and the third position. The hydraulic attachment 76 can be operated by switching to 79c.

  Now, as shown in FIG. 1, the hydraulic system includes a control device 110 and a measuring device 118. The measurement device 118 is a device that detects the pressure of the hydraulic oil that acts on the hydraulic pressure switching valves (the first hydraulic pressure switching valve 90A and the second hydraulic pressure switching valve 90B), and is the device of the first hydraulic pressure switching valve 90A or the second hydraulic pressure switching valve 90B. It is provided in the pressure receiving portion 91 or the oil passage 105. In this embodiment, the measuring device 118 is provided in the oil passage 105 between the second throttle portion 109b and the pressure receiving portion 91. 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 sets the traveling motors (the first traveling motor 80A and the second traveling motor 80B) to the first speed or the second speed. The operation member 115 is composed of, for example, a swingable seesaw type switch, a slidable slide type switch, or a pushable push type switch.

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-type switch is pressed, the speed is switched between the first speed and the second speed.
The control device 110 sets either the applied pressure F1 lower than the switching pressure CP1, the opening of the proportional valve 45 corresponding to the applied pressure F1 (the applied opening), or the current value corresponding to the applied opening (the applied current value). I remember. In this embodiment, the description will proceed assuming that the applied current value corresponding to the applied pressure F1 is stored. When the application pressure F1 or the application opening is stored, the control device 110 converts the application pressure F1 or the application opening into a control signal (application current) to control the proportional valve 45. You can

When the first speed is set by the operating member 115, the control device 110 outputs the applied current to the proportional valve 45, for example. 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 pressure switching valve, as indicated by the shift pressure L1 in FIG.
Here, after outputting the applied current to the proportional valve 45, that is, in the applying period, the control device 110 monitors the detected pressure F2 of the hydraulic oil detected by the measuring device 118, that is, the actual applied pressure F2. Specifically, as shown in FIG. 3, under the condition that the control device 110 controls the hydraulic pressure switching valve to apply the applied pressure F1 (at the first speed), the control device 110 causes the actual applied pressure to increase. It is determined whether 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 preset 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 and becomes equal to or higher than the warning pressure F3 under some circumstances (for example, load fluctuations during work etc.). If so, the control device 110 stops controlling the applied pressure to the proportional valve 45. That is, when the actual applied pressure F2 becomes equal to or higher than the warning pressure F3, the control device 110 stops the output of the applied 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 application of the hydraulic oil to the hydraulic pressure switching valve.

  Therefore, even when the actual applied pressure F2 applied to the hydraulic pressure switching valve rises for some reason while the hydraulic oil is being applied to the hydraulic pressure switching valve, the hydraulic pressure switching valve moves to the neutral position 90c and the second position 90b. It is possible to prevent switching. That is, in the hydraulic pressure switching valve that switches to a plurality of switching positions, it is possible to reliably perform the pressurization while preventing the hydraulic pressure switching valve from being carelessly switched by the applied pressure F1.

  When the hydraulic switch valve is in the first position, that is, in the first speed, and is set to the second speed by the operation member 115, the control device 110 causes the hydraulic switch valve to apply the hydraulic oil, or the hydraulic pressure. Regardless of stopping the application of 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 equal to or higher than the switching pressure CP2. When the pressure (actual application 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 preset set pressure Q3, the control device 110 sets the actual application pressure F2 and the set pressure Q3. The opening degree of the proportional valve 45 is controlled so that

  When the hydraulic switching valve is in the second position 90b, that is, in the second speed, when the operating member 115 is set to the first 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 switches from the second position 90b to the first position 90a, and after deceleration from the second speed to the first speed, the applied pressure F1 is applied to the hydraulic switching valve. To be done.

  In the above-described embodiment, the proportional valve 45 applies the applied pressure F1 to the hydraulic pressure switching valve when decelerating from the second speed to the first speed, but stops applying the applied pressure F1 to the hydraulic pressure switching valve. 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 shown by the shift pressure L1a in FIG. That is, when decelerating from the 2nd speed to the 1st speed to the 1st speed, the proportional valve 45 does not apply the applied pressure F1 to the hydraulic pressure switching valve.

  Further, after deceleration from the 2nd speed to the 1st speed (after the control device 110 demagnetizes the solenoid of the proportional valve 45), when a predetermined time T1 set in the 1st speed has elapsed, the control device 110 is restarted. The applied current is output to the proportional valve 45. As a result, as shown by the shift pressure L1b in FIG. 4, the pressure acting (applied) on the hydraulic pressure switching valve increases to the applied pressure F1. That is, the proportional valve 45 makes the pressure of the hydraulic oil acting (applying) on the hydraulic pressure switching valve substantially zero for a predetermined time T1 after deceleration.

  In this way, since the application of the applied pressure F1 by the proportional valve 45 is stopped when decelerating from the second speed to the first speed, the hydraulic oil can be stably applied to the hydraulic 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 (applied pressure) of the hydraulic oil applied to the hydraulic pressure switching valve constant. For example, when the proportional valve 45 has a relatively large hysteresis, the applied pressure at the first speed and the applied pressure at the time of deceleration from the second speed to the first speed are different due to the influence of the hysteresis. In the above-described embodiment, since the proportional valve 45 is fully closed once 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 that acts (applies) to the hydraulic pressure switching valve is set to substantially zero, but instead of this, as shown in FIG. The valve 45 may apply the deceleration set pressure F4, which is a pressure less than the applied pressure, to the hydraulic pressure switching valve. The control device 110 stores the deceleration setting pressure F4 lower than the applied pressure F1, the opening of the proportional valve 45 (deceleration opening) corresponding to the deceleration setting pressure F4, and the current value (deceleration current) corresponding to the deceleration opening. ing. The control device 110 outputs the deceleration current corresponding to the deceleration opening degree to the proportional valve 45 when the deceleration from the second speed to the first speed is performed. Then, the proportional valve 45 opens according to the deceleration opening degree. As a result, as shown by the shift pressure L1c in FIG. 5, immediately after deceleration, the pressure acting on the hydraulic pressure switching valve (oil passage 105) becomes the deceleration set pressure F4.

  Further, after decelerating from the 2nd speed to the 1st speed and the predetermined time T1 has elapsed in the state where the 1st speed is set, the control device 110 outputs the applied current to the proportional valve 45. Then, as shown by the shift pressure L1d in FIG. 5, the pressure applied (acting) to the hydraulic pressure switching valve increases to the applied pressure F1. That is, the proportional valve 45 sets the pressure of the hydraulic oil acting on the hydraulic pressure switching valve to the deceleration set pressure F4 for the predetermined time T1 after deceleration. 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 the first speed to the second speed. change.

Thus, when decelerating from the 2nd speed to the 1st speed, the deceleration setting pressure F4, which is a pressure lower than the applied pressure F1, is applied to the hydraulic pressure switching valve instead of applying the applied pressure F1 by the proportional valve 45. Therefore, it is possible to apply a little pressure to the hydraulic pressure 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 is applicable 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 in which the traveling device 4, that is, the traveling hydraulic device 44 is braked, and a released state in which the braking state is released. The braking device 130 brakes the traveling motors (first traveling motor 80A, second traveling motor 80B). The braking device 130 includes a first disc provided on the output shaft of the first traveling motor 80A, a movable second disc, and a spring that urges the second disc to contact the first disc. There is. In addition, the braking device 130 includes an accommodating portion (accommodation case) 130a that accommodates the first disc, the second disc, and the spring. An oil passage 132 is connected to a storage portion in which the second disk is stored in the storage portion 130a. The 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 operation valve 133 is composed of a switching valve (hydraulic switching valve) that can switch between a braking position that brings the braking device 130 into a braking state and a releasing position that brings the braking device 130 into a released state. When the operation valve 133 is switched to the release position (first position 133a), the operation oil is supplied to the storage section of the storage section 130a. When the pressure of the hydraulic oil in the storage portion becomes equal to or higher than a predetermined value, the second disk moves to the side opposite to the braking (the side opposite to the spring urging 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 part of the storage part 130a. When the pressure of the hydraulic oil in the storage portion becomes equal to or lower than a predetermined value, the second disc moves to the side in contact with the first disc, and braking by the braking device 130 can be performed. The 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. Further, the control device 131 switches the operating valve 133 to the second position 133b by demagnetizing the operating valve 133. Further, 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 pressurizing 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 made by the operating 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, pressurize the hydraulic oil to the hydraulic switching valve, and the like. I do.
The control device 131 sets the applied pressure F1 to be high when applying the pressurizing force to the hydraulic pressure switching valve when the first speed is set and the braking device 130 is braking. For convenience of explanation, the applied pressure F1 set when releasing the braking is referred to as "first applied pressure F1", and the applied pressure F6 different from this applied pressure F1 is referred to as "second applied pressure F6 (not shown)". .

The control device 131 stores one of the second applied pressure F6, the opening of the proportional valve 45 corresponding to the second applied pressure F6 (the applied opening), and the current value corresponding to the applied opening (the applied current value). 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. The second applied pressure F6 may be larger than the switching pressure CP1.
The control device 131 sets the pressure of the hydraulic oil to be applied to the hydraulic pressure switching valve to the second applied pressure F6 on condition that it is in the first speed and the braking device 130 is controlled to perform braking. 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 operation valve 133, the control device 131 corresponds to the second applied pressure F6. And outputs the applied current value 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 the braking by the braking device 130 is released, the second applied pressure F6 operates. Oil application is stopped.

  Therefore, when the operating valve 133 is in the braking position 133b, the proportional valve 45 sets the applied pressure for applying the hydraulic oil to the hydraulic pressure switching valve to a predetermined value or more, that is, the second applied pressure F6. As a result, the hydraulic oil that acts on the pressure receiving portion 91 of the hydraulic pressure switching valve becomes large, and the hydraulic fluid between the proportional valve 45 and the pressure receiving portion 91 of the hydraulic pressure switching valve can be efficiently circulated through the discharge oil passage 108. .

  In the above-described embodiment, the pilot pressure acting on the pressure receiving portion 91 of the hydraulic pressure switching valve is gradually increased during shifting (during acceleration from the first speed to the second speed and during deceleration from the second speed to the first speed). In other words, the section from the pre-shift to the post-shift in the shift pressure L1 is inclined, but as shown in FIG. 7, during the shift, the shift pressure L2 is changed halfway as shown in FIG. It may be raised or lowered.

  Specifically, when shifting from the first speed to the second speed, as shown by the shift pressure L2a in FIG. 7, from the state in which the applied pressure F1 is applied to the hydraulic pressure switching valve by the proportional valve 45, the neutral position is changed. The shift pressure is increased all at once until the first set pressure Q1 determined corresponding to (1st stage). When the pressure acting on the pressure receiving portion 91 of the hydraulic pressure switching valve reaches the first set pressure Q1, as shown by the shift pressure L2b, from the time when the first set pressure Q1 is reached, the second position determined corresponding to the second position is established. 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 pressure switching valve reaches the second set pressure Q2, as shown by the shift pressure L2c, the shift pressure is changed all at once until the third set pressure Q3 set at the second position is reached. Is increased (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, in the case of shifting from the 2nd speed to the 1st speed, as shown by the shift 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 reduced all at once until the fourth set pressure Q4 is reached (first stage). When the pressure acting on the pressure receiving portion 91 of the hydraulic pressure switching valve reaches the fourth set pressure Q4, as shown by the shift pressure L2e, from the time when the fourth set pressure Q4 is reached, the first position determined corresponding to the first position is established. 5 The shift pressure is gradually decreased until the set pressure Q5 is reached (second stage). Then, when the pressure acting on the pressure receiving portion 91 of the hydraulic pressure switching valve reaches the fifth set pressure Q5, the shift pressure is reduced all at once until it reaches the applied pressure F1 (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 decreased in three stages.

In the hydraulic system, the first oil passage 105 is provided with the second throttle portion 109b, and the measuring device 118 is provided between the second throttle portion 109b and the pressure receiving portion 91 of the hydraulic pressure switching valve. Therefore, as described above, it is easy to set (control) the pressure of the hydraulic oil that acts on the pressure receiving portion 91 of the hydraulic pressure switching valve by controlling the proportional valve 45, and it is possible to switch the hydraulic pressure switching valve 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 degree of the proportional valve 45 and the pressure of the hydraulic oil acting on the pressure receiving portion 91 of the hydraulic pressure switching valve. In addition, in addition to this, 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. Note that the description of the same configuration as the first embodiment or the second embodiment will be omitted.

As shown in FIG. 8, a shutoff valve (switching valve) 140 and a control device 141 are provided.
The shutoff 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 with a shutoff valve 140 in the middle of the oil supply and discharge passage 74, that is, in the middle of the oil passages 74a and 74b. The shutoff valve 140 is a switching valve that can be switched between a first position 140a that opens the oil supply and drainage passage 74 and a second position 140b that puts the oil supply and drainage passage 74 in a shutoff state. Therefore, when the shutoff valve 140 is set to the first position 140a, the midway portions of both the oil passage 74a and the oil passage 74b are connected, and when it is set to the second position 140b, both the oil passage 74a and the oil passage 74b are connected. Shut off.

  The discharge 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 discharge oil passage 85 is provided with a throttle 86 that reduces the flow rate of the hydraulic oil flowing through the discharge 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) according to the operation amount of the operation member 78 to the first proportional valve 73A or the second proportional valve 73B. The proportional valve 73 (first proportional valve 73A, second proportional valve 73B) is 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.

  The controller 141 also 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 the pressure at the boundary 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 less than the switching pressure CP3.

When the shutoff valve 140 is in the first position 140a and is in the 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 controller 141 outputs the applied current to the proportional valve 73 (first proportional valve 73A, second proportional valve 73B). Therefore, as shown by the shift 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 condition that the shutoff valve 140 is in the second position 140b and is in the shutoff state, and the operation member 78 is not operated, the control device 141 controls the amount of hydraulic oil to act on the preliminary control valve 70C. The pressure is made higher than the preset applied pressure F7. For example, the pressure of the hydraulic oil applied to 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 to the switching pressure CP3 or higher. Good. In other words, when the cutoff valve 140 is in the cutoff state, the pressure of the hydraulic oil (applied pressure) applied to the preliminary control valve 70C is set to the warning pressure F8 or the switching pressure CP3 or higher, and the cutoff 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 equal to the applied pressure F7.

Further, 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 causes the proportional valve 73 to change the current corresponding to the operation amount of the operation member 78. Output to. Therefore, when the operation member 78 is operated with the shutoff valve 140 open, the preliminary control valve 70C can be switched according to the operation of the operation member 78.
The pressure (applying 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, a measuring device (first measuring device) 150 capable of detecting the temperature of the hydraulic oil is connected to the control device 141. When the operation member 78 is not operated, and the shutoff valve 140 is in the shutoff state and the temperature of the hydraulic oil detected by the measurement device 150 is lower than or equal to the predetermined value, the control device 141 causes the preliminary control valve 70C to act. The pressure (applied pressure) of the hydraulic oil is set to the warning pressure F8 or the switching pressure CP3 or higher. For example, when the temperature of the hydraulic oil is low and the viscosity is high, the control device 141 sets the pressure (applied pressure) of the hydraulic oil 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, the control device 141 is connected to a measuring device (second measuring device) 151 capable of detecting the temperature of the outside air. When the operation member 78 is not operated and the shutoff valve 140 is shut off and the temperature of the outside air detected by the measurement device 151 is lower than or equal to a predetermined value, the control device 141 causes the preliminary control valve 70C to operate. 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 is applicable to the hydraulic systems of the first to third embodiments described above. It should be noted that description of the same configurations as those of the first to third embodiments will be omitted.

  In the above-described embodiment, the first traveling hydraulic pump 66A and the second traveling hydraulic pump 66B operate on the remote control valves 36, 37, 38, 39, but in the fourth embodiment, the first traveling hydraulic pump 66A and 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 can be supplied to the working valves 210A and 210B from the second hydraulic pump P2 through an oil passage (not shown). The pressure (pilot pressure) of the hydraulic oil acting on the traveling hydraulic pumps (the first traveling hydraulic pump 66A and the second traveling hydraulic pump 66B) is changed by changing the opening degrees of the operating valves 210A and 210B. The angle of the swash plate can be changed by the pressure acting on the traveling hydraulic pump. Hereinafter, for convenience of explanation, the actuating valve 210A and the actuating 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 similar to 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. Further, 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 210A and the proportional valve 210B based on the operation member 161 connected to the control device 160. That is, the control device 160 controls the traveling hydraulic pumps (the first traveling hydraulic pump 66A and the second traveling hydraulic pump 66B).

  When the 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 braking is released, the control device 160 causes the proportional valve 210A and the proportional valve 210A to be proportional to the swing amount (operation amount). A control signal (for example, current) is output to 210B. The control signal increases the opening of the proportional valve 210A and the proportional valve 210B, and the angle of the swash plate of the traveling hydraulic pump (the first traveling hydraulic pump 66A, the second traveling hydraulic pump 66B) increases according to the opening. . As the traveling hydraulic pumps (the first traveling hydraulic pump 66A and the second traveling 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 the state where the braking is released, the control device 160 determines the swing amount (operation amount). Then, a control signal (for example, current) is output to the proportional valve 210A and the proportional valve 210B. The control signal reduces the opening of the proportional valve 210A and the proportional valve 210B, and the angle of the swash plate of the traveling hydraulic pump (the first traveling hydraulic pump 66A, the second traveling hydraulic pump 66B) decreases according to the opening. . As the traveling hydraulic pumps (the first traveling hydraulic pump 66A and the second traveling hydraulic pump 66B) decrease, the discharge amount of hydraulic oil decreases. When the operation member 161 is not operated while the braking is released, the control device 160 controls the opening of the proportional valve 210A and the proportional valve 210B to discharge the traveling hydraulic pump. The applied pressure (first applied pressure) F8 is applied to the travel hydraulic pump to such an extent that the travel motor is not rotated by the hydraulic oil.

  The control device 160 sets the applied pressure to a high value when applying the applied pressure to the traveling hydraulic pump when the braking device 130 is braking. That is, the control device 160 controls the second application pressure F9 (not shown), the opening (application opening) of the proportional valve 210A and the proportional valve 210B corresponding to the second application pressure F9, and the current value corresponding to the application opening (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, provided that the operation member 161 is not operated and the braking device 130 is controlled to perform braking. To do. On the other hand, the control device 160 does not operate the operation member 161 when the condition other than the above-mentioned conditions is satisfied, for example, when the operation member 161 is operated, or when the braking by the braking device 130 is released. If the braking by the braking device 130 is released, the application of the hydraulic oil having the second application pressure F9 is stopped.
[Fifth Embodiment]
FIG. 11 shows a hydraulic system of the fifth embodiment. The hydraulic system for the traveling system shown in the fifth embodiment is applicable to the hydraulic systems of the above-described first to fourth embodiments. Note that description of the same configurations as those of the first to fourth embodiments will be 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 is composed of a CPU and the like. The control device 170 controls the proportional valve 45 based on the setting by the operating member 115 and the pressure (detection pressure) of the hydraulic oil detected by the measuring device 118.
The control device 170 stores either the applied pressure F1, the opening of the proportional valve 45 corresponding to the applied pressure F1 (applied opening), or the current value (applied current value) corresponding to the applied opening. 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 the applied current to the proportional valve 45, for example. The control device 170 also monitors the detected pressure F2 during the application period. As shown in FIG. 12, in the application period, when the detected pressure F2 is larger than the application pressure F1, the control device 170 controls the proportional valve 45 to operate the hydraulic oil that acts on the pressure receiving portion 91 of the hydraulic pressure switching valve. Feedback control is performed so that the applied pressure F1 is equal to the detected pressure F2. Further, when the detected pressure F2 is lower 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 pressure switching valve to increase the applied pressure F1. The feedback control is performed so that the detected pressure and the detected pressure match. As described above, the control device 170 can match the pressure of the hydraulic oil acting on the pressure receiving portion 91 of the hydraulic pressure switching valve with the applied pressure F1 by monitoring the detected pressure F2 and performing the feedback control.

  Further, when the hydraulic switch 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 to cause the hydraulic switch valve to operate. The pressure of the working oil is set to the switching pressure CP2 or more. When the pressure of the hydraulic oil acting on the hydraulic pressure switching valve (applied pressure F1) is equal to or higher than the switching pressure CP2 and reaches the preset set pressure Q3, the control device 170 causes the applied pressure F1 and the set pressure Q3 to coincide with each other. The opening of the proportional valve 45 is controlled so that

  Further, 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 to the applied current value. Then, the switching pressure L1 gradually decreases, the hydraulic switching valve switches from the second position 90b to the first position 90a, and after deceleration from the second speed to the first speed, the applied pressure F1 is applied to the hydraulic switching valve. To be done.

As described above, the control device 170 can control the proportional valve 45 so that the detected pressure F2 detected by the measuring device 118 and the applied pressure F1 match.
The embodiments disclosed this time are to be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description but by the scope of claims for patent, and it is intended that all modifications within the scope and meaning equivalent to the scope of claims for patent are included.

  FIG. 13 shows a modification of the hydraulic pressure switching valve and the traveling motor. As shown in FIG. 13, the hydraulic pressure switching valve includes 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 are movable between a first position 200a and a second position 200b according to pilot pressure. As shown by the shift 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 traveling motor has a first traveling motor 201A and a second traveling motor 201B. The first traveling motor 201A and the second traveling motor 201B are swash plate type variable displacement axial motors capable of shifting to high and low second speeds. Each of the first traveling motor 201A and the second traveling 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 traveling 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 traveling 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 traveling motor 201A and the second traveling motor 201B are in the first position 200a, the swash plate switching cylinder 202 contracts to change the angle of the swash plate of the first traveling motor 201A and the second traveling motor 201B. change. As a result, the first traveling motor 201A and the second traveling motor 201B become the first speed. When the first traveling motor 201A and the second traveling motor 201B are in the second position 200b, the swash plate switching cylinder 202 extends to change the angle of the swash plate of the first traveling motor 201A and the second traveling motor 201B. . As a result, the first traveling motor 201A and the second traveling motor 201B become the second speed. Even if the proportional valve 45 is a hydraulic switching valve that does not include the neutral position, the shift pressure L4 can be changed according to the traveling state, the traveling load, the load of 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 pressure of the hydraulic oil detected by the measuring device 118. Preferably. The control device 110 is provided with a setting mode. The setting mode can be switched to valid or invalid by an operation member such as a switch (not shown). When the setting mode is effective, 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 ends when the pressure of the hydraulic oil acting on the pressure receiving portion 91 of the hydraulic switching valve (the detection pressure detected by the measuring device 118) reaches the applied pressure F1. In the setting mode, the detection pressure until the pressure of the hydraulic oil acting on the pressure receiving portion 91 of the hydraulic pressure switching valve gradually increases from zero to reach the applied pressure F1 and the control signal output to the proportional valve 45 by the control device 110 ( Current) 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 pressure of the hydraulic oil until reaching the applied pressure F1 is acquired. Then, the control device 110 performs normal control when the setting mode is invalid. That is, when the applied pressure is applied 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. 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 discharge 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 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 the hydraulic system that pressurizes the hydraulic pressure switching valve, the discharge 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 discharge oil passage 108, the first throttle portion 109a, and the second throttle portion 109b may be omitted.

  Further, as shown in FIGS. 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 valve 45 causes the traveling motor (first traveling motor 201A, The second traveling motor 201B) may be switched to the first speed or the second speed. The control device 110 is different from the above-described embodiment in that the control target is the swash plate switching cylinder 202, and other operations are the same as those in the above-described embodiment. That is, the hydraulic pressure switching valve may be read as a swash plate switching cylinder.

  For example, when the first speed is set, the control device 110 makes the pressure acting on the swash plate switching cylinder 202 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, when the pressure acting on the swash plate switching cylinder 202 is less than the predetermined pressure CP3, the traveling motor is in the second speed, and when it is equal to or higher than the predetermined pressure CP3, the traveling motor is in the first speed. The swash plate switching cylinder (servo cylinder) 202 may be performed by a control device other than the control device 110.

  Further, in the above-described embodiment, when the proportional valve 45 is controlled by the control device 110, the pressure (detection pressure) of the hydraulic oil detected by the measuring device 118 is fed back to the control device 110 to feedback control the proportional valve 45. You may. For example, when the detected pressure is higher 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 pressure switching valve, The applied pressure F1 and the detected pressure are matched. When the detected pressure is lower than the predetermined applied pressure F1, the control device 110 controls the proportional valve 45 to increase the pressure of the hydraulic oil acting on the pressure receiving portion 91 of the hydraulic pressure switching valve, The applied pressure F1 and the detected pressure are matched.

1 Working Machine 4 Traveling Device 44 Traveling Hydraulic Device 45 Proportional Valve 73 Proportional Valve 74 Supply / Drain Oil Path 76 Hydraulic Actuator 78 Operating Member 90 Hydraulic Switching Valve 110 Control Device 115 Operating Member 130 Braking Device 131 Control Device 133 Actuating Valve 140 Shutoff 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 part

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;
A supply / drain oil passage provided between the hydraulic pressure switching valve and the hydraulic actuator,
A proportional valve capable of applying an applied pressure, which is a predetermined pressure and is lower than the switching pressure of the hydraulic oil switched to the switching position, to the hydraulic switching valve;
A switching valve capable of switching between an open state in which the oil supply / drain passage is opened and a shutoff state in which the oil supply / drain passage is shut off;
Equipped with
The proportional valve is a hydraulic system for a working machine that applies a predetermined pressure or more when the switching valve is in a shut-off state. Equipped with a first measuring device that can detect the temperature of hydraulic oil,
The hydraulic system for a working machine according to claim 1, wherein the proportional valve sets the applied pressure to a predetermined value or more when the temperature of the hydraulic oil measured by the first measuring device is a predetermined value or lower. With a second measuring device that can detect the temperature of the outside air,
The hydraulic system for a working machine according to claim 1, wherein the proportional valve sets the applied pressure to a predetermined value or more when the temperature of the outside air measured by the second measuring device is a predetermined value or lower.

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