JP6766030B2 - Work machine hydraulic system - Google Patents

Description

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

Conventionally, Patent Document 1 is known as a hydraulic system for working machines such as skid steer loaders and compact truck loaders.
The traveling hydraulic system of Patent Document 1 includes a plurality of HST motors capable of switching between low speed (1st speed) and high speed (2nd speed), hydraulic switching valves capable of switching the HST motor to 1st speed or 2nd speed, and a plurality of hydraulic systems. It is equipped with a possible direction switching valve at the position. In Patent Document 1, by switching the direction switching valve to a predetermined position, the pressure of the hydraulic oil acting on the pressure receiving portion of the hydraulic switching valve changes, and as a result, the hydraulic switching valve moves to the first position corresponding to the first speed. It was switched or switched to the second position corresponding to the 2nd speed. That is, in the hydraulic system of the traveling system, the hydraulic switching valve (HST motor) is switched to the 1st speed or the 2nd speed by switching the direction switching valve to a predetermined position.

Further, in the hydraulic system of the work system, the hydraulic actuator is operated by switching the control valve (hydraulic switching valve) connected to the hydraulic actuator via the oil passage.

Japanese Unexamined Patent Publication No. 2013-36276

In the traveling hydraulic 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, for example, 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, the actual situation is that the characteristic of the switching pressure when switching the hydraulic switching valve cannot be changed according to the traveling state or the state of the prime mover.

By the way, in the hydraulic system of the traveling system of Patent Document 1, an attempt is 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 opening the proportional valve slightly, the hydraulic oil pressure is applied to the hydraulic switching valve in advance, that is, pressurization is performed. By pressurizing in this way, 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 to solve the above-mentioned problems of the prior art, and can apply a pressurization (pressurization), and can change the pressurization according to various situations. It is intended to provide a hydraulic system for working machines capable of.

The technical measures taken by the present invention to solve the above technical problems are as shown below.
The hydraulic system of the work machine is more than the hydraulic pump that discharges the hydraulic oil, the hydraulic switching valve that can switch to a plurality of switching positions according to the pressure of the hydraulic oil, and the switching pressure of the hydraulic oil that switches to the switching position. lower pressurization and the hydraulic switching valve in grantable proportional valve with a pressure which is a predetermined pressure, a travel hydraulic device capable of changing the speed in accordance with the switching position of the hydraulic switching valve, the hydraulic switching valve A first oil passage connecting the and the proportional valve, and a discharge oil passage connected to the pressure receiving portion of the hydraulic switching valve or the first oil passage and capable of discharging the hydraulic oil of the first oil passage. The proportional valve is a working machine that applies an applied pressure to the hydraulic switching valve before increasing the speed of the traveling hydraulic device, and applies the applied pressure after decelerating the speed of the traveling hydraulic device. In the hydraulic system of the above, the first throttle portion is provided in the discharge oil passage, and the first oil passage is proportional to the connection portion in which the first oil passage and the discharge oil passage are connected. A second throttle is provided on the valve side .

The hydraulic system of the working machine includes a pressure receiving portion of the hydraulic switching valve, or a measuring device capable of detecting the pressure of hydraulic oil between the second throttle portion and the pressure receiving portion in the first oil passage. It includes a control device that controls the proportional valve based on the pressure of the hydraulic oil measured by the measuring device.
The control device controls the proportional valve so that the pressure of the hydraulic oil detected by the measuring device becomes a pressure corresponding to the applied pressure .

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 hydraulic oil pressure detected by the measuring device. are doing.

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

It is a figure which shows the hydraulic system of the traveling system in 1st Embodiment. It is a figure which shows the hydraulic system of the work system in 1st Embodiment. It is a figure which shows the relationship between the position of a hydraulic switching valve and a pilot pressure. It is a figure which showed the example which applies pressure to the hydraulic pressure switching valve at the time of deceleration. It is a figure which showed the example which applies the deceleration set pressure different from the applied 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 which shows the relationship between the position of a hydraulic switching valve and a 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 position and the pilot pressure acting on the pressure receiving part of a preliminary control valve. It is a figure which shows the hydraulic system of the traveling system in 4th Embodiment. It is a figure which shows the hydraulic system of the traveling system in 5th Embodiment. It is a figure which shows the relationship between the position of the hydraulic switching valve and the pilot pressure in 5th Embodiment. It is a figure which shows the modification of the traveling hydraulic system and the 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 traveling system when the storage part is provided in the control device. It is a figure which shows the hydraulic system when the exhaust oil passage, the throttle part, and the measuring device common to a hydraulic switching valve are provided. It is a figure when the operation valve is connected to the servo cylinder of a traveling motor. It is another figure when the operation valve is connected to the servo cylinder of the traveling motor. It is a side view which shows the truck loader which is an example of the working machine which concerns on this invention. It is a side view which shows a part of the truck loader in the state where the cabin is raised.

Hereinafter, a hydraulic system for a working machine according to the present invention and a preferred embodiment of a working machine provided with this 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. 18 and 19 show a truck loader as an example of the working machine 1. The working machine is not limited to the truck loader, and may be, for example, a tractor, a skid steering loader, a compact truck loader, a backhoe, or the like. In the present embodiment, the front side of the driver seated in the driver's seat of the work machine 1 (the direction indicated by the arrow F shown in FIG. 18) is forward, and the rear side of the driver (the direction indicated by the arrow R shown in FIG. 18). Will be described as the rear, the left side of the driver (front side toward the paper in FIG. 18) as the left side, and the right side of the driver (back side toward the paper in FIG. 18) as the right side.

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

A driver's seat 13 is provided in the cabin 5. 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 body 2 and below the right side of the body 2. The traveling device 4 can travel by the driving force of the hydraulically driven traveling hydraulic device 44 described later.

The working device 3 includes a boom 22L, a boom 22R, and a bucket 23 (working tool) attached to the tips of the boom 22L and the boom 22R. The boom 22L is arranged on the left side of the machine body 2. The boom 22R is arranged on the right side 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 made of a double-acting hydraulic cylinder is provided between the base side of the boom 22L and the boom 22R and the rear lower portion of the machine body 2 corresponding to the boom 22L and the boom 22R. By simultaneously expanding and contracting the lift cylinder 26, the boom 22L and the boom 22R swing up and down at the same time. Mounting brackets 27 are pivotally connected to the tip sides of the boom 22L and the boom 22R so as to be rotatable around the horizontal axis, and the back side of the bucket 23 is attached to the mounting bracket 27.

Further, a tilt cylinder 28 made of a double-acting hydraulic cylinder is interposed between the mounting bracket 27 and the boom 22L and the tip end side halfway portion of the boom 22R corresponding to the boom 22L and the boom 22R. The bucket 23 swings (squeeze dump operation) due to the expansion and contraction of the tilt cylinder 28.
The bucket 23 is removable from the mounting bracket 27. The mounting bracket 27 is configured so that various attachments (hydraulic-driven work tools having a hydraulic actuator) can be attached by removing the bucket 23, and various work (or other excavation work) other than excavation can be performed. Has been done.

A prime mover 29 is provided on the rear side of the bottom wall of the machine 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 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 working machine. FIG. 2 shows the hydraulic system of the working system of the working machine.

As shown in FIGS. 1 and 2, the hydraulic system (driving system hydraulic system, working system hydraulic system) has 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 gear pumps driven by the power of the prime mover 29. The first hydraulic pump P1 and the second hydraulic pump P2 may be a swash plate type variable displacement pump driven by the prime mover 29, or may be other pumps.

The first hydraulic pump P1 (main pump) is used to drive the hydraulic actuator of the attachment attached to the tip 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 explanation, 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 switching valve 90. The traveling hydraulic device 44 is a device whose speed can be changed by hydraulic oil. That is, in the traveling hydraulic device 44, the rotation speed (rotation speed) of the traveling motor, which will be described later, is changed. In other words, the traveling hydraulic device 44 is a device capable of changing the propulsive 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 circulating 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 circulating oil passage 102 capable of circulating hydraulic oil. The first hydraulic switching valve 90A and the first traveling motor 80A are connected by an oil passage 103, and the second hydraulic switching valve 90B and the second traveling motor 80B are connected by an oil passage 104. Further, the first hydraulic switching valve 90A, the second hydraulic switching valve 90B and the operating valve 45 are connected by an oil passage (first oil passage) 105. An oil discharge passage 108 is connected to the pressure receiving portion 91 of the hydraulic switching valve (first hydraulic switching valve 90A, second hydraulic switching valve 90B). The discharge oil passage 108 is an oil passage for discharging the hydraulic oil of the first oil passage 105 (the hydraulic oil acting on the pressure receiving portion 91) to the outside. For example, one end 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 a suction portion of the hydraulic pump or another portion. The drainage channel 108 is provided with a first throttle portion (for example, an orifice) 109a. Further, in the first oil passage 105, a second throttle portion (for example, an orifice) 109b is provided in a section 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 diameter of the first throttle portion 109a and the second throttle portion 109b is not limited to the above-mentioned diameter.

The operating valve 45 and the second hydraulic pump P2 are connected by an oil passage 106. The first traveling hydraulic pump 66A and the second traveling hydraulic pump 66B and the second hydraulic pump P2 are connected by an oil passage (not shown), and the hydraulic oil discharged from the second hydraulic pump P2 is used for the first traveling. 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 the pilot pressure acts. The angle of the swash plate can be changed by the pilot pressure acting on the pressure receiving portions 66a and 66b. When the angle of the swash plate is changed, the discharge direction and the discharge amount of the hydraulic oil are changed, thereby changing the rotational 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 hydraulic oil are changed, thereby changing the rotational 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 capable of changing 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 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 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 switching valve 90A is a hydraulic switching valve that can switch to a plurality of switching positions according to the pilot pressure, which is the pressure of the pilot oil, and is a valve that can switch the first traveling motor 80A to the first speed or the second speed. Is. The first hydraulic switching valve 90A is, for example, a three-position switching valve capable of switching 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 which is a predetermined predetermined pressure, the hydraulic switching valve 90 is moved to the first position 90a by a spring. Be retained. When the first hydraulic 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 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 in the second position 90b, hydraulic oil is supplied only to the first motor 81, and the first traveling motor 80A becomes 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 the first speed or the second speed.
The operating valve 45 is a valve capable of changing the pressure (flow rate) of the hydraulic oil acting on the hydraulic switching valve (first hydraulic switching valve 90A, second hydraulic switching valve 90B), and the hydraulic switching valve is a predetermined switching. It is a valve that can apply hydraulic oil pressure to the extent that it does not switch to a position. The opening degree of the operating valve 45 can be changed by a control signal output from the control device 110 described later. In this embodiment, the operating 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 hydraulic oil acting (supplying) on the hydraulic switching valve changes.

FIG. 3 is a diagram showing the relationship between the positions of the hydraulic switching valves (first hydraulic switching valve, second hydraulic switching valve) and the hydraulic oil pressure (pilot pressure) when the operating valve is operated. The shift pressure L1 shown in FIG. 3 is a pilot pressure acting on the pressure receiving portion of the hydraulic switching valve. Hereinafter, for convenience of explanation, the operating valve 45 is referred to as a proportional valve 45. 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 in the speed change pressure L1 of 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 is the boundary pressure (switching pressure) between the first position 90a and the neutral position 90c. ) When it is less than CP1, the hydraulic switching valve (first hydraulic switching valve 90A and second hydraulic switching valve 90B) is at the first position 90a. When the hydraulic 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 pressurization 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, the proportional valve 45 applies a preset applied pressure F1 to the pressure receiving portion 91 of the hydraulic switching valve when the traveling motor is in the first speed.

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

As described above, the proportional valve 45 has a configuration in which pressurization can be applied to the hydraulic switching valve. In particular, the second throttle portion is provided with the discharge oil passage 108 in the first oil passage 105. Since 109b is provided, pressurization to the hydraulic switching valve can be performed with high accuracy. By providing the first throttle portion 109a and the second throttle portion 109b, the pressure width at the time of operation of the proportional valve 45 can be increased by these throttle portions. That is, the proportional valve 45 can have a margin in the control pressure width at the time of pressurization.

By the way, 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 includes a forward remote control valve 36, a reverse remote control valve 37, a right turn remote control valve 38, a left turn remote control valve 39, 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 (operating 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, a first traveling lever is arranged on one side (left side) of the driver's seat 13, a second traveling lever is arranged on the other side, and the remote control valves 36, 37, 38, are provided by these two traveling levers. 39 may be operated.

The traveling lever 40 can be tilted from the neutral position in the width direction and the diagonal direction orthogonal to the front-rear direction and the front-back direction. By tilting the traveling lever 40, the remote control valves 36, 37, 38, 39 of the traveling operating device 14 are operated. Then, the pilot pressure proportional to the amount of operation from the neutral position of the traveling lever 40 is output from the secondary port of the remote control valves 36, 37, 38, 39.

When the traveling lever 40 is tilted to the front side (in the direction of arrow A1 in FIG. 1), the forward remote control valve 36 is operated and the 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 from the second shuttle valve 52 via the oil passage 62. Acts on the pressure receiving portion 66a of. 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 machine 1 moves straight forward.

Further, when the traveling lever 40 is tilted to the rear side (in the direction of arrow A2 in FIG. 1), the reverse 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. Acts on the pressure receiving portion 66b of. As a result, the output shafts of the first traveling motor 80A and the second traveling motor 80B are reversed (reverse rotation) at a speed proportional to the amount of tilt of the traveling lever 40, and the work machine 1
Goes straight backwards.

Further, when the traveling lever 40 is tilted to the right side (in the direction of arrow 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. Acts on the pressure receiving portion 66b of. As a result, the output shaft of the first traveling motor 80A rotates in the normal direction, the output shaft of the second traveling motor 80B rotates in the reverse direction, and the work machine 1 turns to the right.

Further, when the traveling lever 40 is tilted to the left side (in the direction of arrow A4 in FIG. 1), the left turning remote control valve 39 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 from the third shuttle valve 53 via the oil passage 64. Acts on the pressure receiving portion 66b of. As a result, the output shaft of the first traveling motor 80A reverses, the output shaft of the second traveling motor 80B rotates in the normal direction, and the work machine 1 turns to the 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 motor 80A and the second traveling hydraulic pump 66A and the second traveling hydraulic pump 66B are subjected to the differential pressure of the pilot pressure acting on the pressure receiving portions 66a and 66b of the first traveling hydraulic pump 66A and the second traveling hydraulic pump 66B. The rotation direction and rotation speed of the output shaft of the 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 diagonally forward to the left, the work machine 1 turns left while advancing at a speed corresponding to the tilting angle of the traveling lever 40. When the traveling lever 40 is tilted diagonally forward to the right, the work machine 1 turns to the right while advancing at a speed corresponding to the tilting angle of the traveling lever 40. When the traveling lever 40 is tilted diagonally to the left and rearward, the work machine 1 turns to the left while moving backward at a speed corresponding to the tilting angle of the traveling lever 40. When the traveling lever 40 is tilted diagonally rearward to the right, the work machine 1 turns to the 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 that controls the lift cylinder 26. The bucket control valve 70B is a pilot-type linear motion spool type three-position switching valve that controls the tilt cylinder 28. The spare control valve 70C is a pilot-type direct-acting spool type three-position switching valve that controls the hydraulic actuator 76 of the spare attachment. The preliminary control valve 70C can be switched to the first position 79a, the second position 79b, and the third position 79c by the pilot pressure. The third position 79c is a neutral position.
The 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 operating member 71 is supported so as to be tiltable from the neutral position in the width direction and the oblique direction orthogonal to the front-rear direction and the front-rear direction. By tilting the operating member 71, the remote control valves 72A, 72B, 72C, and 72D provided at the lower part of the operating 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 operating member 71 is tilted to the rear side, 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 supplies the hydraulic oil that has entered the boom control valve 70A to the bottom side of the lift cylinder 26, so that the boom rises.

That is, the boom control valve 70A is attached to the lift cylinder 26 according to the hydraulic oil pressure set by the operation of the operating 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 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 of extending the tilt cylinder 28, and the bucket 23 dumps at a speed proportional to the amount of tilt of the operating member 71.

When the operating member 71 is tilted to the left, the remote control valve 72D is operated, and 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 of reducing the tilt cylinder 28, and the bucket 23 squeezes at a speed proportional to the amount of tilt of the operating member 71.
That is, the bucket control valve 70B is attached to the tilt cylinder 28 according to the hydraulic oil pressure set by the operation of the operating 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, and 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.

An oil supply / drainage passage 74 is connected to the preliminary control valve 70C. The supply / drainage 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 / drainage oil passage 74 (oil passage 74a and oil passage 74b) is connected to the connecting member 75, and the hydraulic actuator 76 of the spare attachment can be connected to the connecting member 75. Therefore, hydraulic oil can be supplied from the spare control valve 70c to the hydraulic actuator 76 of the spare attachment. The operation of the preliminary control valve 70C is performed by the proportional valve 73 whose opening degree can be changed according to the pressure of the hydraulic oil. The proportional valve 73 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 73 connected to the pressure receiving portion 70C2 of the preliminary control valve 70C via an oil passage 77b. Includes a proportional valve 73B. When the first proportional valve 73A is opened, 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 the 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 spare 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 operating member 78 provided around the driver's seat 13 is connected to the control device 110. The operating member 78 is composed of, for example, a swingable 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, an electric current) according to the operation amount of the operating 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 (first proportional valve 73A, 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. It switches to 79c and the hydraulic attachment 76 can be operated.

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

The control device 110 is composed of a CPU and the like. The control device 110 and the proportional valve 45 are connected. The control device 110 controls the proportional valve 45 based on the operating member 115 connected to the control device 110. The operation member 115 is a member that sets the traveling motors (first traveling motor 80A and second traveling motor 80B) to first speed or second speed. The operating member 115 is composed of, for example, a swingable seesaw type switch, a slidable slide type switch, or a pushable push type switch.

In the seesaw type switch, it is possible to set the first speed by swinging to one side and the second speed by swinging to the other side. In the slide type switch, it can be set to 1st speed by sliding to one side and 2nd speed by sliding to the other side. In the push type switch, each time the switch is pressed, the switch is switched in the order of 1st speed and 2nd speed.
The control device 110 determines one of an applied pressure F1 lower than the switching pressure CP1, an opening degree of the proportional valve 45 corresponding to the applied pressure F1 (applied opening degree), and a current value corresponding to the applied opening degree (applied current value). I remember. In this embodiment, the description will proceed assuming that the applied current value corresponding to the applied pressure F1 is stored. When the applied pressure F1 or the applied opening degree is stored, the proportional valve 45 is controlled by converting the applied pressure F1 or the applied opening degree into a control signal (applied current) by the control device 110. Can be done.

When the control device 110 is set to the first speed by the operating member 115, for example, the applied current is output to the proportional valve 45. The proportional valve 45 opens according to the applied current. As a result, as shown in the speed change pressure L1 of FIG. 3, the applied pressure F1 is applied to the pressure receiving portion 91 of the hydraulic switching valve.
Here, the control device 110 monitors the detection pressure F2 of the hydraulic oil detected by the measuring device 118, that is, the actual applied pressure F2, after the applied current is output to the proportional valve 45, that is, during the applied period. Specifically, as shown in FIG. 3, the control device 110 controls the hydraulic switching valve to apply the applied pressure F1 to the hydraulic switching valve (at the first speed), and the control device 110 actually applies the pressure. It is determined whether or not F2 is equal to or higher than a predetermined warning pressure F3. The warning pressure F3 is a pressure set between the applied pressure F1 preset in the control device 110 and the switching pressure CP1. When the actual applied pressure F2 becomes the warning pressure F3 or higher, that is, for some reason (for example, load fluctuation during work, etc.), the actual applied pressure F2 rises above the applied pressure F1 and becomes the warning pressure F3 or higher. If so, the control device 110 stops the control of the applied pressure to the proportional valve 45. That is, when the actual applied pressure F2 becomes the warning pressure F3 or more, the control device 110 stops the output of the applied current to the proportional valve 45 (degausses the solenoid of the proportional valve 45). That is, when the actual applied pressure F2 becomes the warning pressure F3 or higher, the proportional valve 45 is fully closed to stop the application of hydraulic oil to the hydraulic switching valve.

Therefore, even if the actual applied pressure F2 applied to the hydraulic switching valve rises 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. It is possible to prevent switching. 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 2nd speed by the operating member 115 in the 1st position, that is, in the 1st speed, the control device 110 is applying hydraulic oil to the hydraulic switching valve or hydraulic pressure. Regardless of whether the application of hydraulic oil to the switching valve is stopped, a control signal is output to the proportional valve 45 to set the pressure of the hydraulic oil acting on the hydraulic switching valve to the switching pressure CP2 or higher. In the control device 110, when the pressure of the hydraulic oil (actual applied pressure F2) acting on the hydraulic switching valve is equal to or higher than the switching pressure CP2 and reaches a predetermined set pressure Q3, the actual applied pressure F2 and the set pressure Q3 are obtained. The opening degree of the proportional valve 45 is controlled so that

Further, when the hydraulic switching valve is set to the first speed by the operating member 115 in the state of the second position 90b, that is, 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 decelerating from the second speed to the first speed, the applied pressure F1 is applied to the hydraulic switching valve. Will be 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. May be good. As shown in FIG. 4, when the deceleration from the second speed to the first speed is set by the operating member 115, the control device 110 degausses the solenoid of the proportional valve 45. Therefore, the proportional valve 45 is fully closed, and as shown in the speed change pressure L1a of FIG. 4, the pressure acting on the hydraulic switching valve becomes substantially zero. That is, when the speed is reduced 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 switching valve.

Further, after decelerating from the 2nd speed to the 1st speed (after the control device 110 degausses the solenoid of the proportional valve 45), when a predetermined predetermined time T1 elapses in the state set to the 1st speed, the control device 110 returns. The applied current is output to the proportional valve 45. As a result, as shown in the shift pressure L1b of FIG. 4, the pressure acting (applied) to the hydraulic switching valve increases to the applied pressure F1. That is, after deceleration, the proportional valve 45 reduces the pressure of the hydraulic oil acting (applied) to the hydraulic switching valve to substantially zero for a predetermined time T1.

In this way, when decelerating from the 2nd speed to the 1st 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 fully closed, it is easy to keep the pressure (applied pressure) of the hydraulic oil applied to the hydraulic switching valve constant. For example, in the proportional valve 45, when the valve has a relatively large hysteresis, the applied pressure at the first speed and the applied pressure at the time of decelerating 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 once fully closed during deceleration, the difference in applied pressure can be reduced.

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

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

In this way, when decelerating from the 2nd speed to the 1st speed, instead of applying the applied pressure F1 by the proportional valve 45, a 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 amount of 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 the hydraulic system of the second embodiment. The hydraulic system of the traveling system shown in the second embodiment can be applied to the hydraulic system of the first embodiment described above. The description of the configuration similar to that of the first embodiment will be 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 traveling device 4, that is, a device capable of switching between 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 (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 come into contact with the first disc. There is. Further, the braking device 130 includes a first disc, a second disc, and a housing portion (storage case) 130a for accommodating the spring. In the accommodating portion 130a, an oil passage 132 is connected to the accommodating portion in which the second disk is housed. An oil passage 106 is connected to the oil passage 132, and hydraulic oil can be supplied to the storage portion of the accommodating portion 130a. An openable / closable actuating valve 133 is connected to the oil passage 132. The operating valve 133 is composed of a switching valve (hydraulic switching valve) that can switch between a braking position that puts the braking device 130 in the braking state and a release position that puts the braking device 130 in the release state. When the operating valve 133 is switched to the release position (first position 133a), hydraulic oil is supplied to the accommodating portion of the accommodating portion 130a. When the pressure of the hydraulic oil in the storage portion becomes equal to or higher than a predetermined value, the second disc moves to the side opposite to the braking direction (the side opposite to the urging direction of the spring), and the braking by the braking device 130 can be released. On the other hand, when the operating valve 133 is switched to the braking position (second position 133b), the pressure of the pilot oil decreases in the accommodating portion of the accommodating portion 130a. When the pressure of the hydraulic oil in the storage portion becomes equal to or less than a predetermined value, the second disc moves to the side in contact with the first disc, and the braking device 130 can perform braking. The switching of the operation valve 133 can be performed by the control device 131. When the operating valve 133 is a solenoid valve type 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 degaussing 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 pressurization 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 operating member 115. That is, as shown in FIGS. 3 to 5 of the first embodiment, the control device 131 switches between the first speed and the second speed, pressurizes the hydraulic oil to the hydraulic switching valve, and the like by controlling the proportional valve 45. I do.
When the control device 131 is set to the first speed and braking is performed by the braking device 130, the applied pressure F1 is set higher when applying the pressurization to the hydraulic switching valve. For convenience of explanation, the applied pressure F1 set at the time of releasing 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 opening degree (giving opening degree) of the proportional valve 45 corresponding to the second applying pressure F6 and the second applying pressure F6, and the current value (giving current value) corresponding to the giving opening degree. ing. Here, the second applied pressure F6 is at least larger than the first applied pressure F1, and is the same as, for example, the warning pressure F3. Further, the second applied pressure F6 may be larger than the switching pressure CP1.
The control device 131 sets the pressure of the hydraulic oil acting on the hydraulic switching valve to the second applied pressure F6 on condition that the speed is 1st and the braking device 130 is controlled to brake. That is, when the setting of the first speed is input to the control device 131 by the operating member 115 and the control device 131 degausses the operation valve 133, the control device 131 corresponds to the second applied pressure F6. The applied current value to be applied is output to the proportional valve 45. On the other hand, when the control device 131 is in a state other than the above-mentioned conditions, for example, when the second speed is set, when the braking by the braking device 130 is released, or the like, the second applied pressure F6 is operated. Oiling will stop.

Therefore, 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 when the operating valve 133 is at the braking position 133b. As a result, the hydraulic oil acting on the pressure receiving portion 91 of the hydraulic switching valve becomes large, 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 applied during shifting (when increasing the speed from the first speed to the second speed and when decelerating from the second speed to the first speed). In other words, the section from before the shift to after the shift was tilted at the shift pressure L1, but as shown in FIG. 7, at the time of the shift, the shift pressure L2 was raised halfway at once as shown in FIG. May be raised or lowered.

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

On the other hand, when shifting from the 2nd speed to the 1st speed, as shown in the speed change pressure L2d in FIG. 7, the proportional valve 45 is closed from the state of being maintained at a predetermined position, and is determined corresponding to the neutral position. The shift pressure is lowered 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 switching valve reaches the fourth set pressure Q4, as shown in the speed change pressure L2e, the first position corresponding to the first position is determined from the time when the fourth set pressure Q4 is reached. 5 The shift pressure is gradually lowered until the set pressure Q5 is reached (second stage). Then, when the pressure acting on the pressure receiving portion 91 of the hydraulic switching valve reaches the fifth set pressure Q5, the shifting pressure is lowered at once until the applied pressure becomes F1 (third stage). That is, as shown in FIG. 7, when shifting from the second speed to the first speed, the change in the shifting pressure is lowered in three stages.

In the hydraulic system, a second throttle portion 109b is provided in the first oil passage 105, and a measuring device 118 is provided between the second throttle portion 109b and the pressure receiving portion 91 of the hydraulic switching valve. Therefore, as described above, the pressure of the hydraulic oil acting on the pressure receiving portion 91 of the hydraulic switching valve can be easily set (controlled) by controlling the proportional valve 45, and the hydraulic switching valve can be switched with high accuracy. .. In other words, by providing the second throttle portion 109b in the first oil passage 105, it is easy to stabilize the relationship between the opening 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 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 increased. The accuracy of setting can be improved.
[Third Embodiment]
FIG. 8 shows the hydraulic system of the third embodiment. The hydraulic system of the working 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 configuration similar to that of 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 / drainage passage 74, that is, in the middle of the oil passage 74a and the oil passage 74b. The shutoff valve 140 is a switching valve that can be switched between a first position 140a that opens the oil supply / drainage passage 74 and a second position 140b that makes the oil supply / drainage passage 74 shut off. Therefore, when the shutoff valve 140 is set to the first position 140a, the middle portions of both the oil passage 74a and the oil passage 74b are connected, and when the shutoff valve 140 is set to the second position 140b, both the oil passage 74a and the oil passage 74b are connected. To shut off.

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

The control device 141 controls the proportional valve 73. An operating 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, an electric current) according to the amount of operation of the operating 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) opens and closes according to a control signal output from the control device 141. Therefore, the spare actuator can be operated by the control of the control device 141.

Further, the control device 141 controls the proportional valve 73 based on the state of the shutoff valve 140. FIG. 9 is a diagram showing the relationship between the pilot pressure acting on the pressure receiving portions 70C1 and 70C2 of the preliminary control valve 70C and the switching of the preliminary control valve 70C. The switching pressure CP3 shown in FIG. 9 is the pressure at the 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 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 operating member 78 is not operated [when the preliminary control valve 70C is in the third position (neutral position 79c)],
The control device 141 outputs the applied current to the proportional valve 73 (first proportional valve 73A, second proportional valve 73B). Therefore, as shown in the speed change pressure L3 of FIG. 9, when the shutoff valve 140 is in the open state and the operation member 78 is not operated, the applied pressure F7 can be applied to the preliminary control valve 70C.

Further, on the condition that the shutoff valve 140 is in the second position 140b and is in the shutoff state, and the operation member 78 is not operated, the control device 141 is a hydraulic oil that acts on the preliminary control valve 70C. The pressure is increased above the preset applied pressure F7. For example, the pressure of the hydraulic oil acting on the preliminary control valve 70C may be substantially the same as the warning pressure F8 set between the applied pressure F7 and the switching pressure CP3, or may be set to the switching pressure CP3 or higher. Good. In other words, when the shutoff valve 140 is in the shutoff state, the hydraulic oil pressure (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 shutoff valve 140 is in the open state. In this case, the pressure of the hydraulic oil applied to the preliminary control valve 70C is made to match 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 applies a current corresponding to the operation amount of the operation member 78 to the proportional valve 73. Output to. Therefore, when the operation member 78 is operated 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 of the hydraulic oil (applied pressure) 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 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 measuring device 150 is equal to or lower than a predetermined value, the control device 141 acts on the preliminary control valve 70C. The hydraulic oil pressure (applied pressure) is set to 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 becomes high, the control device 141 sets the pressure (applied pressure) of the hydraulic oil acting on the preliminary control valve 70C to the warning pressure F8 or the switching pressure CP3 or higher.

Further, the pressure (applied pressure) of the hydraulic oil applied to the preliminary control valve 70C may be set based on the temperature of the outside air. As shown in FIG. 8, a measuring device (second measuring device) 151 capable of detecting the temperature of the outside air is connected to the control device 141. When the operation member 78 is not operated and the shutoff valve 140 is in 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 the hydraulic system of the fourth embodiment. The hydraulic system of the traveling system shown in the fourth embodiment can be applied to the hydraulic systems of the first to third embodiments described above. The description of the configuration similar to that 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 are operating 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 operating valve 210A and the operating valve 210B. The operating valve 210A and the operating valve 210B are electromagnetic proportional valves (proportional valves) whose opening degree is changed by a control signal. Hydraulic 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 degree of the operating valve 210A and the operating valve 210B, 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. The angle of the swash plate can be changed by the pressure acting on the traveling hydraulic pump. Hereinafter, for convenience of explanation, the operating valve 210A and the operating 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 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 degaussing the operating valve 133.
Further, the control device 160 controls the proportional valve 210A and the proportional valve 210B based on the operating member 161 connected to the control device 160. That is, the control device 160 controls the traveling hydraulic pumps (first traveling hydraulic pump 66A, second traveling hydraulic pump 66B).

When 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 operating member 161. When the operating member 161 is swung in one direction or the other direction from the neutral position while the braking is released, the control device 160 controls the proportional valve 210A and the proportional valve according to the swing amount (operation amount). A control signal (for example, current) is output to 210B. The control signal increases the opening degree of the proportional valve 210A and the proportional valve 210B, and the angle of the swash plate of the traveling hydraulic pumps (first traveling hydraulic pump 66A, second traveling hydraulic pump 66B) increases according to the opening degree. .. As the number of traveling hydraulic pumps (first traveling hydraulic pump 66A, second traveling hydraulic pump 66B) increases, the discharge amount of hydraulic oil increases.

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

When braking is performed by the braking device 130, the control device 160 sets the applied pressure higher when applying the pressurization to the traveling hydraulic pump. That is, the control device 160 has the opening degree (giving opening degree) of the proportional valve 210A and the proportional valve 210B corresponding to the second applying pressure F9 and the second applying pressure F9 (not shown), and the current value corresponding to the giving opening degree (giving opening degree). 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 in which the traveling motor starts rotating by the traveling hydraulic pump.

The control device 160 sets the pressure of the hydraulic oil acting on the traveling hydraulic pump to the applied pressure F9 on condition that the operating member 161 is not operated and the braking device 130 is controlled to brake. To do. On the other hand, when the control device 160 is in a state other than the above-mentioned conditions, for example, when the operation member 161 is operated, when the braking by the braking device 130 is released, the operation member 161 is operated. If the braking by the braking device 130 is released, the application of the hydraulic oil of the second application pressure F9 is stopped.
[Fifth Embodiment]
FIG. 11 shows the hydraulic system of the fifth embodiment. The hydraulic system of the traveling system shown in the fifth embodiment can be applied to the hydraulic systems of the first to fourth embodiments described above. The description of the same configuration as that of the first to fourth embodiments will be omitted. The hydraulic system shown in FIG. 11 is not provided with the drainage passage 108, the first throttle portion 109a, and the second throttle portion 109b.

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

When the control device 170 is set to the first speed by the operating member 115, for example, the applied current is output to the proportional valve 45. Further, the control device 170 monitors the detection pressure F2 during the application period. As shown in FIG. 12, during the application period, when the detection pressure F2 is larger than the application pressure F1, the control device 170 controls the proportional valve 45 to act on the pressure receiving portion 91 of the hydraulic switching valve. The feedback control is performed so that the applied pressure F1 and the detected pressure F2 are matched with each other. When the detection pressure F2 is smaller than the applied pressure F1, the control device 170 controls the proportional valve 45 to increase the pressure of the hydraulic oil acting on the pressure receiving portion 91 of the hydraulic switching valve, and the applied pressure F1. Feedback control is performed to match the detection pressure with the detection pressure. In this way, the control device 170 can match the pressure of the hydraulic oil acting on the pressure receiving portion 91 of the hydraulic switching valve with the applied pressure F1 by monitoring the detected pressure F2 and performing feedback control.

Further, when the hydraulic switching valve is in the first position (1st speed) and is set to the 2nd speed by the operating member 115, the control device 170 outputs a control signal to the proportional valve 45 to the hydraulic switching valve. The pressure of the hydraulic oil that acts is set to the switching pressure CP2 or higher. In the control device 170, 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 applied pressure F1 and the set pressure Q3 match. The opening degree of the proportional valve 45 is controlled so as to do so.

Further, when the hydraulic switching valve is set to the 1st speed by the operating member 115 in the state where the 2nd position 90b (2nd speed) is set, 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 decelerating from the second speed to the first speed, the applied pressure F1 is applied to the hydraulic switching valve. Will be done.

As described above, the control device 170 can control the proportional valve 45 so that the detection pressure F2 detected by the measurement device 118 and the applied pressure F1 match.
It should be considered that the embodiments disclosed this time are exemplary in all respects and not restrictive. The scope of the present invention is shown not by the above description but by the scope of claims, and is intended to include all modifications within the meaning and scope equivalent to the scope of claims.

FIG. 13 shows a modified example of the hydraulic switching valve and the traveling motor. As shown in FIG. 13, the hydraulic switching valve includes 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 to the first position 200a and the second position 200b according to the pilot pressure. As shown in the speed change pressure L4 of 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 acting on the pressure receiving portion is less than the switching pressure CP4. When the pilot pressure becomes the switching pressure CP4 or more, the second position 200b is reached.

The traveling motor includes 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 capacitance 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 for switching 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 the 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 the hydraulic oil from the second hydraulic 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 reduce 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 is extended to change the angles of the swash plates 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. The proportional valve 45 can change the shifting pressure L4 according to the traveling state, the traveling load, the load of the prime mover, and the state of the prime mover even if the hydraulic switching valve does not include the neutral position.

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 preferable. A setting mode is provided in the control device 110. The setting mode can be switched between valid and invalid by an operating member such as a switch (not shown). When the setting mode is valid, for example, the pressure of the hydraulic oil acting on the pressure receiving portion 91 of the hydraulic switching valve is gradually increased from zero by gradually opening the proportional valve 45 from the fully closed state. .. In the setting mode, the setting mode ends when the pressure of the hydraulic oil (detected pressure detected by the measuring device 118) acting on the pressure receiving portion 91 of the hydraulic switching valve reaches the applied pressure F1. In the setting mode, the detection pressure until the pressure of the hydraulic oil acting on the pressure receiving portion 91 of the hydraulic switching valve gradually increases from zero to reach the applied pressure F1 and the control signal output by the control device 110 to the proportional valve 45 ( The current) is sequentially acquired, and the relationship between the detected pressure and the control signal is stored in the storage unit 240. That is, in the setting mode, the relationship between the control signal output from the control device 110 to the proportional valve 45 and the pressure of the hydraulic oil until the applied pressure F1 is reached is acquired. Then, the control device 110 performs normal control when the setting mode is invalid. That is, when an applied pressure is applied to the hydraulic 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 above-described embodiment, the drain oil passage 108, the first throttle portion 109a, the second throttle portion 109b, and the measuring device 118 are provided in each of the first hydraulic switching valve 90A and the second hydraulic switching valve 90B. As shown in 15, the discharge oil passage 108, the first throttle portion 109a, the second throttle portion 109b, and the measuring device 118 common to the first hydraulic switching valve 90A and the second hydraulic switching valve 90B may be provided. Further, in the 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 system of FIGS. 1, 10, 13, 15, and 17, the drainage 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 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 only in that the control target is the swash plate switching cylinder 202, and other operations are the same as those of the above-described embodiment. That is, the hydraulic switching valve may be read as a swash plate switching cylinder.

For example, when the control device 110 is set to the first speed, the pressure acting on the swash plate switching cylinder 202 is set to less than the predetermined pressure CP3. When the control device 110 is set to the second speed, the pressure acting on the swash plate switching cylinder 202 is set 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 less 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. 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 hydraulic oil pressure (detection pressure) 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 larger than the predetermined applied pressure F1, the control device 110 controls the proportional valve 45 to reduce the pressure of the hydraulic oil acting on the pressure receiving portion 91 of the hydraulic switching valve. The applied pressure F1 and the detected pressure are matched. 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 and the detected pressure are matched.

1 Work equipment 4 Traveling device 44 Traveling hydraulic device 45 Proportional valve 73 Proportional valve 74 Oil supply / drainage passage 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

Claims (4)

A hydraulic pump that discharges hydraulic oil and
A hydraulic switching valve that can switch to multiple switching positions according to the pressure of the hydraulic oil,
A proportional valve capable of applying an applied pressure, which is a predetermined pressure lower than the switching pressure of the hydraulic oil that switches to the switching position, to the hydraulic switching valve.
A traveling hydraulic device speed can be changed depending on the switching position of the hydraulic switching valve,
A first oil passage connecting the hydraulic switching valve and the proportional valve,
A discharge oil passage that is connected to the pressure receiving portion of the hydraulic switching valve or the first oil passage and is capable of discharging hydraulic oil from the first oil passage.
With
The proportional valve is a hydraulic system of a working machine in which an applied pressure is applied to the hydraulic switching valve before increasing the speed of the traveling hydraulic device, and the applied pressure is applied after decelerating the speed of the traveling hydraulic device. And
A first throttle portion is provided in the discharge oil passage, and a second throttle portion is provided on the proportional valve side of the first oil passage where the first oil passage and the discharge oil passage are connected. The hydraulic system of the working machine provided . A measuring device capable of detecting the pressure of hydraulic oil between the pressure receiving portion of the hydraulic switching valve or the pressure receiving portion of the first oil passage and the second throttle portion and the pressure receiving portion.
A control device that controls the proportional valve based on the pressure of the hydraulic oil measured by the measuring device, and
The hydraulic system of the working machine according to claim 1. The hydraulic system of a working machine according to claim 2, wherein the control device controls the proportional valve so that the pressure of the hydraulic oil detected by the measuring device becomes a pressure corresponding to the applied pressure . The proportional valve is a valve that operates based on a control signal.
The control device
The hydraulic system for a working machine according to claim 2 or 3, further comprising a storage unit that stores a relationship between a control signal output to the proportional valve and the pressure of hydraulic oil detected by the measuring device.

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