JP6656989B2 - Working machine hydraulic system - 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.

Conventionally, as a hydraulic system of a working machine such as a skid steer loader and a compact truck loader, Patent Document 1 is known.
The hydraulic system of the traveling system disclosed in Patent Document 1 includes an HST motor capable of switching between low speed (first speed) and high speed (second speed), a hydraulic switching valve capable of switching the HST motor between first speed and second speed, and a plurality of hydraulic switching valves. A directional switching valve that can be 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 is moved to the first position corresponding to the first speed. The vehicle 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 first speed or 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-system hydraulic system of Patent Document 1, the direction switching valve only switches to a plurality of predetermined positions. Therefore, the pressure of the working oil acting on the hydraulic switching valve is changed, for example, by the traveling hydraulic pressure of a traveling pump or the like. It cannot be changed according to the state of the device or the state of the prime mover. That is, in Patent Document 1, it is a fact that the characteristics of the switching pressure when the hydraulic switching valve is switched cannot be changed according to the running state or the state of the prime mover.

  Now, in the traveling hydraulic system of Patent Literature 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 pressure of the hydraulic oil is previously applied to the hydraulic switching valve, that is, pressurization is performed. As described above, by performing the pressurization, the responsiveness of the hydraulic switching valve can be improved, and the hydraulic switching valve can be warmed up.

  The present invention has been made in order to solve the above-described problems of the related art, and can apply a pressurization (applying pressure), and can change the pressurizing according to various situations. It is an object of the present invention to provide a hydraulic system of a working machine that can perform the operation.

The technical measures taken by the present invention to solve the above technical problem are as follows.
The hydraulic system of the work machine includes a hydraulic pump that discharges hydraulic oil, a hydraulic switching valve that can be switched to a plurality of switching positions according to the pressure of the hydraulic oil, and a switching pressure that is lower than a switching pressure of the hydraulic oil that switches to the switching position. A proportional valve capable of applying a given pressure, which is a predetermined pressure, to the hydraulic switching valve; a traveling hydraulic device capable of changing a speed in accordance with a switching position of the hydraulic switching valve; A measuring device capable of detecting the pressure of the operating oil, wherein the pressure of the operating oil detected by the measuring device is determined by the proportional valve when the applied pressure is equal to or higher than a predetermined value. Stop pressurizing.
The hydraulic system of the work machine includes a hydraulic pump that discharges hydraulic oil, a hydraulic switching valve that can be switched to a plurality of switching positions in accordance with the pressure of the hydraulic oil, and a hydraulic pressure switching valve that switches to the switching position. A proportional valve capable of applying a given pressure, which is a low pressure and a predetermined pressure, to the hydraulic switching valve; and a traveling hydraulic device capable of changing a speed in accordance with a switching position of the hydraulic switching valve; The valve applies the applied pressure to the hydraulic switching valve before increasing the speed of the traveling hydraulic device, and applies the applied pressure after reducing the speed of the traveling hydraulic device, thereby increasing the speed of the traveling hydraulic device. When the speed is decelerated, the proportional valve sets the applied pressure applied after the deceleration to an applied pressure smaller than the applied pressure applied before increasing the speed and larger than zero.
The proportional valve keeps the pressure of the hydraulic oil acting on the hydraulic switching valve at less than the applied pressure for a predetermined time.

Hydraulic system working machine, a hydraulic pump that discharges hydraulic oil, a switchable hydraulic switching valve in a plurality of switching positions according to the pressure of the hydraulic oil, than switching pressure of the hydraulic fluid switched to the switching position A proportional valve that can apply a given pressure that is a low pressure and a predetermined pressure to the hydraulic switching valve, a traveling hydraulic device that can change the speed in accordance with a switching position of the hydraulic switching valve, and a hydraulic switching valve. A measuring device capable of detecting the pressure of the applied hydraulic oil, and a control device that controls the proportional valve, the control device is configured to control the pressure of the hydraulic oil detected by the measuring device and the applied pressure. The proportional valve is controlled to match.

  The proportional valve is a valve that operates based on a control signal, and the control device has a storage unit that stores a relationship between a control signal output to the proportional valve and a pressure of hydraulic oil detected by the measuring device. are doing.

  ADVANTAGE OF THE INVENTION According to this invention, pressurization (application pressure) can be applied and pressurization can be changed according to various situations.

It is a figure showing the hydraulic system of the run system in a 1st embodiment. It is a figure which shows the hydraulic system of the working system in 1st Embodiment. FIG. 3 is a diagram illustrating a relationship between a position of a hydraulic switching valve and a pilot pressure. FIG. 4 is a diagram illustrating an example in which pressure is applied to a hydraulic switching valve during deceleration. FIG. 5 is a diagram illustrating an example in which a deceleration setting pressure different from the applied pressure is applied during deceleration. It is a figure showing the hydraulic system of the run system in a 2nd embodiment. FIG. 11 is a diagram of another modified example showing the relationship between the position of the hydraulic switching valve and the pilot pressure. It is a figure showing the hydraulic system of the work system in a 3rd embodiment. It is a figure showing the relation between pilot pressure which acts on the pressure receiving part of a preliminary control valve, and a position. It is a figure showing the hydraulic system of the run system in a 4th embodiment. It is a figure showing the hydraulic system of the run system in a 5th embodiment. It is a figure showing the relation between the position of a hydraulic switching valve and pilot pressure in a 5th embodiment. It is a figure which shows the modification of a traveling hydraulic device and a hydraulic switching valve. It is a figure which shows the relationship between the position of a hydraulic switching valve and a pilot pressure in a modification. It is a figure which shows the hydraulic system of the driving | running system at the time of providing a memory | storage part in a control apparatus. It is a figure which shows the hydraulic system in the case of providing the discharge oil path common to a hydraulic switching valve, a throttle part, and a measuring device. FIG. 4 is a diagram when an operation valve is connected to a servo cylinder of a traveling motor. FIG. 5 is another view when the operation valve is connected to a servo cylinder of a traveling motor. FIG. 1 is a side view showing a track loader as an example of a working machine according to the present invention. FIG. 3 is a side view showing a part of the track loader in a state where a cabin is raised.

Hereinafter, preferred embodiments of a hydraulic system of a working machine according to the present invention and a working machine including the hydraulic system 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. FIGS. 18 and 19 show a track 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 (the direction indicated by the arrow F shown in FIG. 18) of the driver sitting on the driver's seat of the work machine 1 is forward, and the rear side of the driver (the direction indicated by the arrow R shown in FIG. 18). , The left side of the driver (front side as viewed in FIG. 18) is the left side, and the right side of the driver (back side as viewed in FIG. 18) is the right side.

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

A driver's seat 13 is provided in the cabin 5. On one side (for example, 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 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 hydraulically driven traveling hydraulic device 44 described later.

  The working device 3 includes a boom 22L, a boom 22R, and a bucket 23 (work implement) attached to a tip of the boom 22L and the boom 22R. The boom 22L is arranged on the left of the body 2. The boom 22 </ b> R is arranged on the right of the body 2. The boom 22L and the boom 22R are interconnected by a connector (not shown) provided between the boom 22L and the boom 22R. The boom 22L and the boom 22R are supported by a first lift link 24 and a second lift link 25, respectively. A lift cylinder 26 composed of a double-acting hydraulic cylinder is provided between the base of the boom 22L and the boom 22R and the rear lower part of the body 2 so as to correspond to the boom 22L and the boom 22R. The boom 22L and the boom 22R simultaneously swing vertically by extending and retracting the lift cylinder 26 simultaneously. A mounting bracket 27 is pivotally connected to the distal ends of the booms 22L and 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 composed of a double-acting hydraulic cylinder is interposed between the mounting bracket 27 and the middle part on the distal end side of the boom 22L and the boom 22R corresponding to the boom 22L and the boom 22R. The bucket 23 swings (squeezes and dumps) by the expansion and contraction of the tilt cylinder 28.
The bucket 23 is detachable from the mounting bracket 27. When the mounting bracket 27 is detached from the bucket 23, various attachments (a hydraulically driven work tool having a hydraulic actuator) can be attached, and various operations other than excavation (or other excavation operations) can be performed. Have been.

A prime mover 29 is provided on the rear side of the bottom wall of the body (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 body 2.
Next, the hydraulic system of the working machine will be described.
FIG. 1 is a diagram illustrating a hydraulic system of a traveling system of a working machine. FIG. 2 shows a working hydraulic system of the working machine.

  As shown in FIGS. 1 and 2, the hydraulic system (a traveling hydraulic system and a 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 displacement 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 for driving a hydraulic actuator of a lift cylinder 26, a tilt cylinder 28, or an attachment attached to the distal end side of the boom 22. The second hydraulic pump P2 (pilot pump, charge pump) is mainly used to supply hydraulic oil pressure as a control pressure or a signal pressure. Hereinafter, for convenience of explanation, hydraulic oil as control pressure or signal pressure is referred to as “pilot oil”, and pressure of pilot oil is referred to as “pilot pressure”.

  The hydraulic system includes a traveling hydraulic device 44, an operating valve 45, and a hydraulic 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 rotation speed (rotation speed) of the traveling motor described later is changed. In other words, the traveling hydraulic device 44 is a device that can change the propulsion force when the traveling device 4 travels. The traveling hydraulic device 44 includes 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 switching valve 90 has 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 circulation 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 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. The first hydraulic switching valve 90A, the second hydraulic switching valve 90B, 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 each of the hydraulic switching valves (the first hydraulic switching valve 90A and the second hydraulic switching valve 90B). The discharge oil passage 108 is an oil passage that discharges the working oil (the working oil acting on the pressure receiving portion 91) of the first oil passage 105 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 part of a hydraulic pump or another part. The discharge oil passage 108 is provided with a first throttle portion (for example, an orifice) 109a. A second throttle (for example, an orifice) 109b is provided in a section of the first oil passage 105 between the hydraulic oil 45 and the connection portion 180 between the first oil passage 105 and the discharge oil passage 108. Is provided. The inner diameter (diaphragm diameter) of the first diaphragm 109a and the second diaphragm 109b is 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-described diameters.

The operating valve 45 and the second hydraulic pump P2 are connected by an oil passage 106. Note that 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 change, thereby changing 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 the discharge amount of the working oil are changed, thereby changing the rotation output of the second traveling motor 80B.
The first traveling motor 80A is configured by a cam motor (radial piston motor). The first traveling motor 80A is a variable displacement type that can change the magnitude of the displacement (motor displacement) during operation, and can change the rotation and torque of the output shaft by changing the displacement of the motor. More 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 is in the first speed. Further, by supplying the 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 first speed or second speed.

The first hydraulic switching valve 90A is a hydraulic switching valve that can switch to a plurality of switching positions in accordance with a pilot pressure, which is a pressure of pilot oil, and is a valve that can switch the first traveling motor 80A to first speed or second speed. It is. The first hydraulic switching valve 90A is, for example, a three-position switching valve that can be switched to 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 switching valve 90A is less than the switching pressure that is a predetermined pressure, the hydraulic switching valve 90 is moved to the first position 90a by a spring. Will be retained. When the first hydraulic switching valve 90A is at 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 switching valve 90A is equal to or higher than the switching pressure, the first hydraulic switching valve 90A is switched to the second position 90b via the neutral position 90c. When the first hydraulic switching valve 90A is at the second position 90b, the operating oil is supplied only to the first motor 81, and the first traveling motor 80A is in the second speed.

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

  FIG. 3 is a diagram showing a relationship between the positions of the hydraulic switching valves (the first hydraulic switching valve and the second hydraulic switching valve) and the hydraulic oil pressure (pilot pressure) when the operating valve is operated. Shift pressure L1 shown in FIG. 3 is a pilot pressure acting on the pressure receiving portion of the hydraulic switching valve. Hereinafter, the operating valve 45 is referred to as a proportional valve 45 for convenience of description. Further, the first hydraulic switching valve 90A and the second hydraulic switching valve 90B may be referred to as a hydraulic switching valve, and the first traveling motor 80A and the second traveling motor 80B may be referred to as a traveling motor.

  As shown by the shift pressure L1 in FIG. 3, the pilot pressure acting on the pressure receiving portion 91 of the first hydraulic switching valve 90A and the second hydraulic switching valve 90B becomes the boundary pressure (switching pressure) between the first position 90a and the neutral position 90c. If the pressure is less than CP1, the hydraulic switching valves (the first hydraulic switching valve 90A and the second hydraulic switching valve 90B) are at the first position 90a. When the hydraulic switching valve is at the first position 90a, the traveling motors (the first traveling motor 80A and the second traveling motor 80B) are in the first speed. The proportional valve 45 applies a pressure to the hydraulic switching valve while the hydraulic switching valve maintains the first position 90a. That is, as shown in FIG. 3, the proportional valve 45 can apply the applied pressure F1 to the pressure receiving portion 91 of the hydraulic switching valve. In other words, when the traveling motor is in the first speed, the proportional valve 45 applies the preset application pressure F1 to the pressure receiving portion 91 of the hydraulic switching valve.

  Here, the opening degree of the proportional valve 45 is gradually increased, and when the pilot pressure acting on the pressure receiving portion 91 of the first hydraulic switching valve 90A and the second hydraulic switching valve 90B exceeds the switching pressure CP1, the first hydraulic pressure The switching valve 90A and the second hydraulic switching valve 90B are at the neutral position 90c. When the pilot pressure acting on the pressure receiving portion 91 of the first hydraulic switching valve 90A and the second hydraulic switching valve 90B exceeds the boundary pressure (switching pressure) CP2 between the neutral position 90c and the second position 90b, the first hydraulic pressure changes. The switching valve 90A and the second hydraulic switching valve 90B are at the second position 90b. When the hydraulic switching valve is at 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 in accordance with the opening degree of the proportional valve 45.

  As described above, the proportional valve 45 is configured to be able to apply a preload to the hydraulic switching valve. In particular, the proportional valve 45 is provided with the discharge oil passage 108 in the first oil passage 105 and the second throttle portion. Since the pressure switch 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 at the time of the operation of the proportional valve 45 can be increased by these throttle portions. That is, the control valve width at the time of pressurization can have a margin with respect to the proportional valve 45.

  As shown in FIG. 1, the oil passage 106 branches upstream of the proportional valve 45, and the branched oil passage 107 is connected to the travel operating device 14. The travel operating device 14 includes a remote control valve 36 for forward travel, a remote control valve 37 for reverse travel, a remote control valve 38 for right turn, a remote control valve 39 for left turn, and a travel lever 40. The traveling operation device 14 has first to fourth shuttle valves 51, 52, 53, and 54. The remote control valves 36, 37, 38, and 39 are commonly operated, that is, operated by one traveling lever 40. The remote control valves 36, 37, 38, 39 change the pressure of the hydraulic oil in accordance with 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 used. For example, a first travel lever is disposed on one side (left side) of the driver's seat 13 and a second travel lever is disposed on the other side, and the remote control valves 36, 37, 38, 39 may be operated.

  The traveling lever 40 can be tilted 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 traveling lever 40, the remote control valves 36, 37, 38, and 39 of the traveling operation device 14 are operated. Then, a pilot pressure proportional to the operation amount from the neutral position of the traveling lever 40 is output from the secondary ports of the remote control valves 36, 37, 38, and 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 via the oil passage 61, and the second traveling hydraulic pump 66B via the oil passage 62 from the second shuttle valve 52. 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 amount of tilt of the traveling lever 40, and the work implement 1 moves straight forward.

  When the traveling lever 40 is tilted rearward (in the direction indicated by the 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 the second traveling hydraulic pump 66B via the oil passage 63 from the fourth shuttle valve 54. On the pressure receiving portion 66b. As a result, the output shafts of the first traveling motor 80A and the second traveling motor 80B reversely rotate (reversely rotate) at a speed proportional to the amount of tilt of the traveling lever 40, and the work implement 1 moves straight backward.

  When the traveling lever 40 is tilted to the right (in the direction indicated by the 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 via the oil passage 61 and the second traveling hydraulic pump 66B via the oil passage 63 from the fourth shuttle valve 54. On the pressure receiving portion 66b. As a result, the output shaft of the first traveling motor 80A rotates forward and the output shaft of the second traveling motor 80B rotates reversely, and the work implement 1 turns to the right.

  When the traveling lever 40 is tilted to the left (in the direction of arrow A4 in FIG. 1), the remote control valve 39 for turning left is operated, and the 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 the first traveling hydraulic pump 66A via the oil passage 64 from the third shuttle valve 53. On the pressure receiving portion 66b. Thereby, the output shaft of the first traveling motor 80A rotates in the reverse direction, and the output shaft of the second traveling motor 80B rotates in the forward direction, so that the work implement 1 turns left.

Further, when the traveling lever 40 is tilted in an oblique direction, the first traveling motor 80A and the second traveling motor 80A and the second traveling hydraulic pump 66B are caused 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 truck loader 1 turns right or left while moving forward or backward.
That is, when the traveling lever 40 is tilted forward and left diagonally, the work implement 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 and obliquely to the right, the work implement 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 leftward and rearward, the work implement 1 turns left while moving backward at a speed corresponding to the tilt angle of the traveling lever 40. When the traveling lever 40 is tilted to the right rear side, the work implement 1 turns right while moving backward at a speed corresponding to the tilt angle of the traveling 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 70 </ b> A is a pilot direct-acting spool-type three-position switching valve, and controls the lift cylinder 26. The bucket control valve 70 </ b> B is a pilot-operated 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 a first position 79a, a second position 79b, and a third position 79c by the pilot pressure. Note that the third position 79c is a neutral position.
The operation of the boom 22 and the bucket 23 can be performed 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, the width direction orthogonal to the front-rear direction, and the oblique direction. 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 the hydraulic oil that has entered the boom control valve 70A is supplied to the rod side of the lift cylinder 26, whereby the booms (the booms 22L and 22R) descend. .
When the operating 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 hydraulic 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 causes the lift cylinder 26 to respond to the hydraulic oil pressure set by the operation of the operation member 71 (the pilot pressure set by the remote control valve 72A and the pilot pressure set by the remote control valve 72B). The flow rate of the flowing hydraulic oil can be controlled.
When the operating member 71 is tilted rightward, 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 to extend the tilt cylinder 28, and the bucket 23 performs a dump operation at a speed proportional to the amount of tilt 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 the squeezing operation at a speed proportional to the amount of tilt of the operation member 71.
That is, the bucket control valve 70B controls the tilt cylinder 28 in accordance with the hydraulic oil pressure set by the operation of the operation member 71 (the pilot pressure set by the remote control valve 72C and the pilot pressure set by the remote control valve 72D). 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 in accordance with 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 supply / discharge oil 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 (the oil passage 74a and the oil passage 74b) is connected to a connection member 75, and the connection member 75 can be connected to a hydraulic actuator 76 of a spare attachment. Therefore, 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 a proportional valve 73 whose opening can be changed in accordance with 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, pilot oil acts on the pressure receiving portion 70C1 via the oil passage 77a. Further, when the second proportional valve 73B is opened, the 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 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 constituted by, for example, a swingable seesaw switch, a slide switch that can slide, or a push 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) according 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 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 moves to the first position 79a, the second position 79b, and the third position. Switching to 79c, the hydraulic attachment 76 can be operated.

  Now, 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 for detecting the pressure of the hydraulic oil acting on the hydraulic switching valve (the first hydraulic switching valve 90A, the second hydraulic switching valve 90B), and detects the pressure of the first hydraulic switching valve 90A or the second hydraulic switching valve 90B. The pressure receiving portion 91 or the oil passage 105 is provided. 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 includes 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 constituted by, for example, a swingable seesaw switch, a slideable slide switch, or a pushable push switch.

In a seesaw switch, the first speed can be set by swinging to one side, and the second speed can be set by swinging to the other side. In the slide switch, the first speed can be set by sliding to one side, and the second speed can be set by sliding to the other side. In the case of a push-type switch, the gear switches in the order of first speed and second speed each time the switch is pressed.
The control device 110 determines any one of the applied pressure F1 lower than the switching pressure CP1, the opening of the proportional valve 45 (the applied opening) corresponding to the applied pressure F1, and the current value (the applied current value) corresponding to the applied opening. I remember. In this embodiment, the description will be made on the assumption 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 proportional valve 45 is controlled by converting the application pressure F1 or the application opening into a control signal (application current). Can be.

When the first speed is set by the operation member 115, the control device 110 outputs, for example, the applied current to the proportional valve 45. The proportional valve 45 opens according to the applied current. As a result, as shown by the shift pressure L1 in FIG. 3, the applied pressure F1 is applied to the pressure receiving portion 91 of the hydraulic switching valve.
Here, after outputting the applied current to the proportional valve 45, that is, during the application 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, in a situation where the control device 110 is performing control to apply the applied pressure F1 to the hydraulic pressure switching valve (at the first speed), the control device 110 controls the actual applied pressure It is determined whether or not F2 is equal to or higher than a predetermined alert pressure F3. The warning pressure F3 is a pressure set between the applied pressure F1 preset in the control device 110 and the switching pressure CP1. When the actual applied pressure F2 becomes higher than the alarm pressure F3, that is, the actual applied pressure F2 rises above the applied pressure F1 and becomes higher than the alarm pressure F3 for some reason (for example, a load change during work or the like). In this case, 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 alert pressure F3, the control device 110 stops outputting the applied current to the proportional valve 45 (deactivates the solenoid of the proportional valve 45). That is, when the actual applied pressure F2 becomes equal to or higher than the alert pressure F3, the proportional valve 45 is fully closed to stop applying hydraulic oil to the hydraulic switching valve.

  Therefore, even if the actual applied pressure F2 applied to the hydraulic switching valve is increased for some reason under the condition that the hydraulic oil is applied to the hydraulic switching valve, the hydraulic 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, the pressurization can be reliably performed 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 state where the hydraulic switching valve is in the first position, that is, in the first speed, the control device 110 determines whether the hydraulic oil is being applied to the hydraulic switching valve, or Regardless of the stop of the supply 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 equal to or higher than the switching pressure CP2. When the pressure of the hydraulic oil (actual applied pressure F2) 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 switches the actual applied pressure F2 and the set pressure Q3. Is controlled so as to match.

  Further, when the hydraulic switching valve is set to the first speed by the operating member 115 in the second position 90b, that is, in the state of 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 switches from the second position 90b to the first position 90a, and after the second speed is reduced to the first speed, the applied pressure F1 is applied to the hydraulic switching valve. Is done.

  In the above-described embodiment, 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. Is also good. As shown in FIG. 4, when deceleration from the second speed to the first speed is set by operating member 115, control device 110 demagnetizes the solenoid of 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 the first speed is set in the deceleration from the second speed to the first speed, the proportional valve 45 does not apply the applied pressure F1 to the hydraulic pressure switching valve.

  After the deceleration from the second speed to the first speed (after the control device 110 demagnetizes the solenoid of the proportional valve 45), when a predetermined time T1 elapses in the state where the first speed is set, the control device 110 restarts. 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 (applying) on the hydraulic switching valve increases to the applied pressure F1. That is, the proportional valve 45 sets the pressure of the hydraulic oil acting (applied) to the hydraulic switching valve to approximately zero for the predetermined time T1 after deceleration.

  As described above, when decelerating from the second speed to the first speed, the application of the applied pressure F1 by the proportional valve 45 is stopped, so that 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 the fully closed state, it is easy to make the pressure (applied pressure) of the hydraulic oil applied to the hydraulic 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 effect of the hysteresis. In the above-described embodiment, since the proportional valve 45 is fully closed once during deceleration, the difference in the applied pressure can be reduced.

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

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

Thus, when decelerating from the second speed to the first speed, instead of applying the applied pressure F1 by the proportional valve 45, the deceleration set pressure F4, which is a pressure lower than the applied pressure F1, is applied to the hydraulic switching valve. Therefore, it is possible to apply a small pressure 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 hydraulic system of the traveling 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 traveling state, that is, a braking state for braking the traveling hydraulic device 44 and a release state for releasing the braking state. The braking device 130 brakes the traveling motors (the first traveling motor 80A and the second traveling motor 80B). The braking device 130 includes a first disk provided on an output shaft of the first traveling motor 80A, a movable second disk, and a spring that biases the second disk toward a side where the second disk contacts the first disk. I have. In addition, the braking device 130 includes an accommodating portion (accommodating case) 130a that accommodates the first disk, the second disk, and the spring. In the storage section 130a, an oil passage 132 is connected to a storage section in which the second disk is stored. The oil passage 106 is connected to the oil passage 132 so that hydraulic oil can be supplied to the storage section of the storage section 130a. An openable / closable operating valve 133 is connected to the oil passage 132. The operating 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 operating valve 133 is switched to the release position (first position 133a), the operating 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 opposite side to the braking (opposite to the biasing direction of the spring), and the braking by the braking device 130 can be released. On the other hand, when the operating valve 133 switches to the braking position (the second position 133b), the pressure of the pilot oil in the storage section of the storage section 130a decreases. When the pressure of the hydraulic oil in the storage section becomes equal to or lower than a predetermined value, the second disk moves to the side in contact with the first disk, 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 operating valve 133 is a solenoid-operated two-position switching valve, the control device 131 switches the operating valve 133 to the first position 133a by exciting the operating valve 133. Further, the control device 131 switches the operating valve 133 to the second position 133b by demagnetizing the operating valve 133. 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 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, pressurize the hydraulic switching valve with hydraulic oil, and the like. I do.
The control device 131 sets the applied pressure F1 higher when applying the pressurized pressure to the hydraulic pressure switching valve when the first speed is set and the braking device 130 is performing braking. For convenience of explanation, the applied pressure F1 set when the braking 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 any one of the second applied pressure F6, the opening of the proportional valve 45 (the applied opening) corresponding to the second applied pressure F6, and the current value (the applied current value) corresponding to the applied opening. 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 alert pressure F3. Further, the second applied pressure F6 may be higher than the switching pressure CP1.
The control device 131 sets the pressure of the hydraulic oil applied to the hydraulic switching valve to the second applied pressure F6 on condition that the first speed is set and the braking device 130 is controlled to perform braking. That is, when the setting of the first speed is input to the control device 131 by the operation member 115 and the control device 131 degausses the operating valve 133, the control device 131 responds 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 enters a state other than the above conditions, for example, when the second speed is set, when the braking by the braking device 130 is released, or the like, the control device 131 operates the second applied pressure F6. Oil application stops.

  Therefore, when the operating valve 133 is at the braking position 133b, the proportional valve 45 sets the applied pressure for applying the hydraulic oil to the hydraulic switching valve to a predetermined value or more, that is, the second applied pressure F6. As a result, the amount of 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 above-described embodiment, the pilot pressure acting on the pressure receiving portion 91 of the hydraulic switching valve is gradually increased during shifting (when increasing the speed from the first speed to the second speed, and when reducing the speed from the second speed to the first speed). In other words, the section from before the shift to after the shift is inclined at the shift pressure L1, but as shown in FIG. 7, during the shift, 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, the state in which the applied pressure F1 is applied to the hydraulic switching valve by the proportional valve 45 is changed to the neutral position. The shift pressure is raised at a stroke until the pressure reaches the first set pressure Q1 determined in correspondence with the above (first stage). When the pressure acting on the pressure receiving portion 91 of the hydraulic pressure changeover valve reaches the first set pressure Q1, as shown by the shift pressure L2b, the second pressure determined corresponding to the second position from the time when the first set pressure Q1 is reached. The shift pressure is gradually increased until the second set pressure Q2 is reached (second stage). Then, 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 changed all at once until the third set pressure Q3 set 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 second speed to the first 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 the predetermined position, and is determined corresponding to the neutral position. The shift pressure is reduced 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 indicated by the shift pressure L2e, the fourth position determined from the time when the fourth set pressure Q4 is reached, corresponding to the first position. The shift pressure is gradually decreased until the set pressure Q5 reaches 5 (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 at a stroke until it reaches the applied pressure F1 (third stage). That is, as shown in FIG. 7, when shifting from the second speed to the first speed, the change of the shift pressure is decreased 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 it is possible to switch the hydraulic 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 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 reduced. The setting accuracy can be improved.
[Third embodiment]
FIG. 8 shows a hydraulic system according to the third embodiment. The working hydraulic system shown in the third embodiment is applicable to the hydraulic system of the first embodiment or the second embodiment described above.
The description of the same configuration as that of the first embodiment or the second embodiment is 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 an oil passage between the control valve 70 and the hydraulic actuator. Specifically, the shut-off valve 140 is provided in a middle part of the supply / discharge oil passage 74, that is, in a middle part 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 for opening the oil supply / discharge passage 74 and a second position 140b for closing the oil supply / discharge passage 74. Therefore, when the shut-off valve 140 is in the first position 140a, the middle portions of both the oil passages 74a and 74b are connected, and when the shut-off valve 140 is in the second position 140b, both the oil passages 74a and 74b are both connected. Cut off.

  The discharge passage 83 is connected to the 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 for reducing the flow rate of the working oil flowing through the discharge oil passage 83. A discharge oil passage 85 is connected to the oil passage 77b. The discharge oil passage 85 is connected to the hydraulic oil tank 31. The discharge oil passage 85 is provided with a throttle portion 86 for reducing the flow rate of the working 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 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 preliminary 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 a relationship between pilot pressure acting on the pressure receiving portions 70C1 and 70C2 of the preliminary control valve 70C and switching of the preliminary control valve 70C. The switching pressure CP3 shown in FIG. 9 is a pressure at a boundary where 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 the open state, and the operation of the operation member 78 is not performed [when the preliminary control valve 70C is in the third position (the neutral position 79c)], the control device 141 outputs an 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 shut-off valve 140 is open and the operation of the operation member 78 is not performed, 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 of the operation member 78 is not performed, the control device 141 controls the operating oil of the preliminary control valve 70C. The pressure is set to be 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 be equal to or higher than the switching pressure CP3. Good. In other words, when the shut-off valve 140 is in the shut-off 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 higher, and the shut-off 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 match the applied pressure F7.

When the shut-off valve 140 is in the first position 140a and is in the open state, and the operation of the operation member 78 is performed, the control device 141 transmits the current corresponding to the operation amount of the operation member 78 to the proportional valve 73. Output to Therefore, when the operation of the operation member 78 is performed while the shutoff valve 140 is open, the preliminary control valve 70C can be switched according to the operation of the operation member 78.
The pressure (application 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 capable of detecting the temperature of the hydraulic oil. When the operation of the operation member 78 is not performed and the shutoff valve 140 is in the shutoff 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 causes the preliminary control valve 70C to act. The hydraulic oil pressure (applied pressure) is set to be higher than the warning pressure F8 or the switching pressure CP3. For example, when the temperature of the hydraulic oil is low and the viscosity becomes high, the control device 141 causes the pressure of the hydraulic oil to act on the preliminary control valve 70C (
Applied pressure) is set to be equal to or higher than the warning pressure F8 or the switching pressure CP3.

Further, the pressure (application 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 of the operation member 78 is not performed and the shutoff valve 140 is in the 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 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 is applicable to the hydraulic systems of the first to third embodiments described above. Note that a description of the same configuration as in 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 the remote control valves 36, 37, 38, and 39, but in the fourth embodiment, the first traveling hydraulic pump 66A and the The second traveling hydraulic pump 66B is operated by an operation valve 210A and an 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 operating oil can be supplied to the operating valve 210A and the operating valve 210B from the second hydraulic pump P2 via an oil passage (not shown). By changing the opening of the operating valve 210A and the operating valve 210B, the pressure (pilot pressure) of the operating oil acting on the traveling hydraulic pumps (the first traveling hydraulic pump 66A and the second traveling hydraulic pump 66B) changes. The angle of the swash plate can be changed by the pressure acting on the traveling hydraulic pump. Hereinafter, for convenience of description, the actuation valve 210A and the actuation valve 210B will be 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 in 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 determines the proportional valve 210A and the proportional valve 210A according to the amount of swing (operation amount). A control signal (for example, current) is output to 210B. The opening of the proportional valves 210A and 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, the second traveling hydraulic pump 66B) is increased according to the degree of opening. . As the traveling hydraulic pumps (the first traveling hydraulic pump 66A and the second traveling hydraulic pump 66B) increase, the discharge amount of the working oil increases.

  When the operation member 161 is swung from the position in one direction or the position in the other direction to the neutral position in a state where the braking is released, the control device 160 determines the amount of the operation (operation amount). Thus, a control signal (for example, current) is output to the proportional valve 210A and the proportional valve 210B. The opening of the proportional valves 210A and 210B is reduced by the control signal, and the angles of the swash plates of the traveling hydraulic pumps (the first traveling hydraulic pump 66A and the second traveling hydraulic pump 66B) are reduced according to the degrees of opening. . As the traveling hydraulic pumps (the first traveling hydraulic pump 66A and the second traveling hydraulic pump 66B) decrease, the discharge amount of the hydraulic oil decreases. Note that when the operation of the operation member 161 is not performed in a state where the braking is released, the control device 160 controls the opening of the proportional valve 210A and the proportional valve 210B to discharge from the traveling hydraulic pump. The applied pressure (first applied pressure) F8 is applied to the traveling hydraulic pump to such an extent that the traveling motor is not rotated by the hydraulic oil.

The control device 160 sets the applied pressure higher when applying pressure to the traveling hydraulic pump when the braking is performed by the braking device 130. That is, the control device 160 includes a second applied pressure F9 (not shown), the proportional valve 210A and the proportional valve 21 corresponding to the second applied pressure F9.
Either an opening degree of 0B (giving opening degree) or a current value (giving current value) corresponding to the opening degree is stored. Here, the second applied pressure F9 is larger than at least 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 operating oil applied to the traveling hydraulic pump to the applied pressure F9 on the condition that the operation of the operation member 161 is not performed and the control of performing braking on the braking device 130 is performed. I do. On the other hand, when the control device 160 enters a state other than the above-described conditions, for example, when the operation of the operation member 161 is performed, when the braking by the brake device 130 is released, the operation of the operation member 161 is not performed. For example, 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 of a fifth embodiment. The traveling hydraulic system shown in the fifth embodiment is applicable to the hydraulic systems of the above-described first to fourth embodiments. The description of the same configuration as in the first to fourth embodiments will be omitted. The hydraulic system shown in FIG. 11 does not include the discharge oil passage 108, the first throttle unit 109a, and the second throttle unit 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 (detection pressure) of the hydraulic oil detected by the measurement device 118.
The control device 170 stores one of the applied pressure F1, the opening of the proportional valve 45 corresponding to the applied pressure F1 (applied opening), and the current value corresponding to the applied opening (applied current value). In this embodiment, the description will be made on the assumption that the applied current value corresponding to the applied pressure F1 is stored.

  When the first speed is set by the operating member 115, the control device 170 outputs, for example, the applied current to the proportional valve 45. The control device 170 monitors the detected pressure F2 during the application period. As shown in FIG. 12, during the application period, when the detected pressure F2 is higher than the application pressure F1, the control device 170 controls the proportional valve 45 to operate the hydraulic oil acting on the pressure receiving portion 91 of the hydraulic switching valve. Is performed, and feedback control is performed to make the applied pressure F1 and the detected pressure F2 coincide with each other. 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 working oil acting on the pressure receiving portion 91 of the hydraulic switching valve, thereby increasing the applied pressure F1. And the detected pressure are made to coincide with each other. As described above, the control device 170 monitors the detection pressure F2 and performs feedback control, whereby the pressure of the hydraulic oil acting on the pressure receiving portion 91 of the hydraulic pressure switching valve can be made equal to the applied pressure F1.

  When the second position is set by the operating member 115 in a state where the hydraulic pressure switching valve is in the first position (first speed), the control device 170 outputs a control signal to the proportional valve 45 and causes the hydraulic pressure switching valve to output the control signal. The pressure of the working oil that acts is set to the switching pressure CP2 or more. When the pressure of the hydraulic oil (applied pressure F1) acting on the hydraulic 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 with the set pressure Q3. The opening degree of the proportional valve 45 is controlled so that

  Further, when the operating member 115 sets the first speed in the state where the hydraulic pressure switching valve is in the second position 90b (second speed), the control device 170 outputs a control signal to the proportional valve 45 to an 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 the second speed is reduced 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 such that the detected pressure F2 detected by the measuring device 118 matches the applied pressure F1.
The embodiments disclosed this time are to be considered in all respects as illustrative 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 traveling motor. As shown in FIG. 13, the hydraulic switching valve has a first hydraulic switching valve 200A and a second hydraulic switching valve 200B. The first hydraulic switching valve 200A and the second hydraulic switching valve 200B are two-position switching valves that can move 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 switching valve 200A and the second hydraulic switching valve 200B are in the first position 200a when the pilot pressure applied to the pressure receiving portion is lower than the switching pressure CP4, When the pilot pressure becomes equal to or higher than the switching pressure CP4, the second position 200b is set.

  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 between high and low 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 switching valve 200A, and expands and contracts with hydraulic oil from the first hydraulic switching valve 200A. The swash plate switching cylinder 202 of the second traveling motor 201B is connected to the second hydraulic switching valve 200B, and expands and contracts with hydraulic oil from the second hydraulic switching valve 200B.

  Therefore, when the first traveling motor 201A and the second traveling motor 201B are at the first position 200a, the swash plate switching cylinder 202 contracts, and the angle of the swash plate of the first traveling motor 201A and the second traveling motor 201B is reduced. 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 at the second position 200b, the swash plate switching cylinder 202 is extended 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 enter 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. Is preferred. The control device 110 is provided with a setting mode. The setting mode can be switched between enabled and disabled by operating members such as switches (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 working 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 working oil (the detection 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 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 (the control signal output from the control device 110 to the proportional valve 45) Current) are sequentially obtained, 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 the applied pressure F1 is reached is acquired. Then, when the setting mode is invalid, control device 110 performs normal control. That is, when applying the applied pressure to the hydraulic switching valve by the normal control, the control device 110 controls the proportional valve 45 using the relationship (the control signal and the pressure stored in the storage unit 240) obtained by the setting mode. I do. The storage unit 240 and the setting mode may be provided in a control device other than the control device 110.

  In the above-described embodiment, each of the first hydraulic switching valve 90A and the second hydraulic switching valve 90B is provided with the discharge oil passage 108, the first throttle portion 109a, the second throttle portion 109b, and the measuring device 118. 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 common to the first hydraulic switching valve 90A and the second hydraulic switching valve 90B may be provided. In a hydraulic system that pressurizes the hydraulic 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 systems 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 not be provided.

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 traveling motor (the first traveling motor 201A, The second traveling motor 201B) may be switched to first speed or second speed. The control device 110 differs from the above-described embodiment only in that the control target is a swash plate switching cylinder 202, and the other operations are the same as those in the above-described embodiment. That is, the hydraulic switching valve may be replaced with a swash plate switching cylinder.

  For example, when the first speed is set, the control device 110 reduces the pressure acting on the swash plate switching cylinder 202 to less than the predetermined pressure CP3. When the second speed is set, the control device 110 sets the pressure acting on the swash plate switching cylinder 202 to a predetermined pressure CP3 or more. In the case of FIG. 16B, when the pressure acting on the swash plate switching cylinder 202 is lower than the predetermined pressure CP3, the traveling motor is in the second speed, and when the pressure is equal to or higher than the predetermined pressure CP3, the traveling motor is in the first speed. Note that 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 (detected pressure) of the hydraulic oil detected by the measuring device 118 is fed back to the control device 110 to perform feedback control of the proportional valve 45. May be. 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 switching valve, The applied pressure F1 is made to match the detected pressure. Further, 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 acting on the pressure receiving portion 91 of the hydraulic switching valve, The applied pressure F1 is made to match the detected pressure.

1 Work Machine 4 Traveling Device 44 Traveling Hydraulic Device 45 Proportional Valve 73 Proportional Valve 74 Oil Supply / Drainage Channel 76 Hydraulic Actuator 78 Operating Member 90 Hydraulic Switching Valve 110 Control Device 115 Operating Member 130 Braking Device 131 Control Device 133 Operating 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 section

Claims (3)

A hydraulic pump that discharges hydraulic oil,
A hydraulic switching valve capable of switching to a plurality of switching positions according to the pressure of the hydraulic oil,
A proportional valve capable of applying a given pressure, which is a pressure lower than the switching pressure of the hydraulic oil switched to the switching position and a predetermined pressure, to the hydraulic switching valve,
A traveling hydraulic device whose speed can be changed according to the switching position of the hydraulic switching valve,
A measuring device capable of detecting the pressure of the hydraulic oil applied to the hydraulic switching valve,
With
The hydraulic system for a working machine, wherein the proportional valve stops pressurizing by the proportional valve when the pressure of the hydraulic oil detected by the measuring device is equal to or higher than a predetermined pressure. A hydraulic pump that discharges hydraulic oil,
A hydraulic switching valve switchable to a plurality of switching positions according to the pressure of the hydraulic oil,
A proportional valve capable of applying a given pressure, which is a pressure lower than the switching pressure of the hydraulic oil switched to the switching position and a predetermined pressure, to the hydraulic switching valve,
A traveling hydraulic device whose speed can be changed according to the switching position of the hydraulic switching valve,
With
The proportional valve applies an applied pressure to the hydraulic switching valve before increasing the speed of the traveling hydraulic device, and applies the applied pressure after reducing the speed of the traveling hydraulic device,
When the speed of the traveling hydraulic device is reduced, the proportional valve reduces the applied pressure applied after the deceleration to an applied pressure smaller than the applied pressure applied before increasing the speed, and to an applied pressure larger than zero. Hydraulic system of the working machine to set .   The hydraulic system for a working machine according to claim 1, wherein the proportional valve holds the pressure of the hydraulic oil acting on the hydraulic switching valve at a pressure lower than the applied pressure for a predetermined time.

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