JP6629125B2 - 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.

BACKGROUND ART 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 disclosed in Patent Literature 1 is a swingable operating lever for operating the traveling device forward or backward, and supplies a forward pilot oil to the traveling device when the operating lever is operated in the forward direction. And a reverse operation valve for supplying reverse pilot oil to the traveling device when the operation lever is operated in the reverse direction. In addition, a pressure switch for detecting the pressure of the pilot oil for reverse movement when the reverse operation valve is operated is provided in an oil passage connecting the reverse operation valve and the traveling device.

JP 2013-36276 A

  In the hydraulic system of Patent Document 1, for example, when the operation is stopped from a state in which the forward operation valve is being operated, hydraulic oil in an oil passage connecting the traveling device and the forward operation valve is passed through the forward operation valve. Drained to hydraulic oil tank. At this time, a back pressure is applied to the oil passage for discharging the hydraulic oil from the forward operation valve to the hydraulic oil tank, and the pressure of the hydraulic oil (pressure of the reverse pilot oil) increases in the oil passage on the reverse operation valve side. Sometimes. As a result, there is a possibility that the pressure switch for detecting the reverse movement is operated even though the forward operation valve is operated.

  The present invention has been made in order to solve the above-described problems of the related art, and has an object to provide a hydraulic system of a working machine that can appropriately detect a traveling direction of a traveling device. .

The technical measures taken by the present invention to solve the technical problem are as follows.
The hydraulic system of the work machine includes a traveling device capable of moving forward or backward by hydraulic oil, a forward operation valve capable of supplying hydraulic oil and operating forward movement of the traveling device, and a reverse operation of the traveling device capable of supplying hydraulic oil. A reverse operating valve to be operated, a first oil passage connecting the traveling device and the forward operating valve,
A second oil passage that connects the traveling device and the reverse operation valve, a first measurement device that is connected to the first oil passage, and detects a first pressure that is a pressure of hydraulic oil of the forward operation valve, A second measuring device that is connected to a second oil passage and detects a second pressure that is a pressure of hydraulic oil of the reverse operation valve; and that the traveling device moves forward or backward based on the first pressure and the second pressure. A control device that determines whether there is, and a notification device that notifies that the vehicle is moving backward when the control device determines that the vehicle is moving backward, the traveling device performs the forward movement when the forward operation valve is operated. A forward-side pressure receiving portion that receives a corresponding hydraulic oil, and a reverse-side pressure receiving portion that receives a hydraulic oil corresponding to the reverse when the reverse operation valve is operated, wherein the first oil passage includes: Connecting the pressure receiving portion on the forward side and the forward operation valve, and , And connects the reverse side of the pressure receiving portion and the backward operating valve, the control device, when the first pressure is a predetermined threshold value or more is determined to be the forward rather than the reverse, the If the first pressure is less than the threshold and the second pressure is greater than or equal to the threshold, it is determined that the vehicle is traveling backward.

The hydraulic system of the work machine includes an operation member, wherein the forward operation valve is operated when the operation member is operated on one side, and the reverse operation valve is operated when the operation member is operated on the other side .

  According to the present invention, it is possible to appropriately detect the traveling direction of the traveling device.

It is a figure showing a hydraulic system in a 1st embodiment. It is a figure which shows the 1st pressure and the 2nd pressure at the time of swinging an operation lever to one and the other. FIG. 4 is a diagram illustrating a relationship between a first pressure and a second pressure. It is a figure showing a hydraulic system in a 2nd embodiment. It is a figure showing the side of a truck loader. It is a figure showing the side of a truck loader when a cabin is raised.

Hereinafter, a hydraulic system for a working machine according to an embodiment of the present invention will be described with reference to the drawings.
[First Embodiment]
The overall configuration of the working machine will be described. 4 and 5 show a track loader as an example of the work machine 1. The work 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. Note that, in the present embodiment, the front side (the direction indicated by the arrow F shown in FIG. 4) 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. 4). , The left side of the driver (front side in FIG. 4), and the right side of the driver (back side in FIG. 4).

  As shown in FIGS. 4 and 5, the working machine 1 includes a machine body 2, a working device 3 mounted on the machine body 2, and a traveling device 4 supporting the machine body 2. A cabin 5 is mounted on an upper part of the body 2 and at a front part of the body 2. The 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, the left side) of the driver's seat 13, a traveling operation device 14 for operating the traveling device 4 is arranged. 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 22 </ b> L is arranged on the left of the body 2. The boom 22 </ b> R is arranged on the right side 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 side 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. By simultaneously extending and retracting the lift cylinder 26, the boom 22L and the boom 22R simultaneously swing vertically. A mounting bracket 27 is pivotally connected to the distal ends of the boom 22L and the boom 22R so as to be rotatable around a horizontal axis, and the back side of the bucket 23 is attached to the mounting bracket 27.

Further, a tilt cylinder 28 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 working 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 showing a hydraulic system of a traveling system of a working machine. In the embodiment, the working hydraulic system is omitted.

  As shown in FIG. 1, the hydraulic system has a first hydraulic pump P1 and a second hydraulic pump P2. The first hydraulic pump P1 is used to drive a hydraulic actuator of an 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 used mainly for supplying hydraulic oil pressure as control pressure or signal pressure. Hereinafter, for convenience of explanation, hydraulic oil as control pressure or signal pressure is referred to as “pilot oil”, and pressure of pilot oil is referred to as “pilot pressure”.

As shown in FIG. 1, the traveling device 4 includes a first drive circuit 32A, a second drive circuit 32B, a first traveling unit 21L, and a second traveling unit 21R. The first driving circuit 32A is a circuit for driving the first traveling unit 21L provided on the left, and the second driving circuit 32B is a circuit for driving the second traveling unit 21R provided on the right.
The first drive circuit 32A includes a first traveling hydraulic pump 66A. The first traveling hydraulic pump 66A is connected to a traveling motor (HST motor) 57 of the first traveling section 21L. The second drive circuit 32B includes a second traveling hydraulic pump 66B. The second traveling hydraulic pump 66B is connected to a traveling motor (HST motor) 57 of the second traveling section 21R.

  The traveling hydraulic pumps (the first traveling hydraulic pump 66A and the second traveling hydraulic pump 66B) are swash plate type variable displacement axial pumps driven by the power of the prime mover 29. The first traveling hydraulic pump 66A and the second traveling hydraulic pump 66B each include a pressure receiving portion 66a and a pressure receiving portion 66b on which pilot pressure acts. The angle of the swash plate is 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.

The first traveling unit 21L and the second traveling unit 21R each include a traveling motor 57, a swash plate switching cylinder 58, and a hydraulic switching valve 63. The traveling motor 57 is a swash plate type variable displacement axial motor capable of shifting between high and low speeds. The swash plate switching cylinder 58 is extendable and contractable by hydraulic oil, and is connected to a swash plate of the traveling motor 57.
The hydraulic switching valve 63 is a two-position switching valve according to the pressure of the operating oil (pilot pressure). The hydraulic switching valve 63 moves to the second position 63b when the pilot pressure reaches a predetermined pressure. When the pilot pressure becomes lower than the predetermined pressure, the hydraulic pressure switching valve 63 is returned to the first position 63a by a spring. When the hydraulic pressure switching valve 63 is at the first position 63a, the pilot oil escapes from the swash plate switching cylinder 58 and contracts, and the traveling motor 57 enters the first speed state. When the hydraulic pressure switching valve 63 is at the second position 63b, the pilot oil is supplied to the swash plate switching cylinder 58 to extend, and the traveling motor 57 enters the second speed state.

  As shown in FIG. 1, the discharge port of the second hydraulic pump P2 is connected to a discharge oil passage 100a through which discharge oil (pilot oil) discharged from the second hydraulic pump P2 flows. A first supply path 100b, a second supply path 100c, and a third supply path 100d are branched from the discharge oil path 100a. A traveling hydraulic pump (a first traveling hydraulic pump 66A, a second traveling hydraulic pump 66B) is connected to the first supply path 100b. The traveling operation device 14 is connected to the second supply path 100c. A hydraulic switching valve 63 is connected to the third supply path 100d.

  Further, a direction switching valve 45 formed of a two-position switching valve is connected to a middle part of the third supply path 100d. By switching the direction switching valve 45 to the first position 45a, the hydraulic switching valve 63 is switched to the first position 63a, and by switching the direction switching valve 45 to the second position 45b, the hydraulic switching valve 63 is switched to the second position 63b. Can be switched. Switching of the direction switching valve 45 is performed by a control device 70 described later.

  The traveling operation device 14 includes a forward operation valve 36, a reverse operation valve 37, a right turning operation valve 38, a left turning operation valve 39, a traveling lever 40, first to fourth shuttle valves 41, 42, 43, 44. The operation valves 36, 37, 38, 39 are operated in common, that is, by one traveling lever 40. The operation valves 36, 37, 38, and 39 can change the pressure of the hydraulic oil in accordance with the operation of the traveling lever 40 (operation member). 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 traveling lever is disposed on one side (left side) of the driver's seat 13 and a second traveling lever is disposed on the other side, and the remote control valves 36, 37, 38, 39 may be operated.

  The forward operation valve 36 is a valve for operating the traveling device 4 to advance. The forward operating valve 36 and the traveling hydraulic pumps (first traveling hydraulic pump 66A, second traveling hydraulic pump 66B) of the traveling device 4 are connected by a first oil passage 46. Specifically, the first oil passage 46 includes an oil passage 46a connected to the pressure receiving portion 66a of the first traveling hydraulic pump 66A, an oil passage 46b connected to the pressure receiving portion 66a of the second traveling hydraulic pump 66B, and an oil passage. An oil passage 46c that joins the oil passage 46a and the oil passage 46b is included. The first shuttle valve 41 is provided in the middle of the oil passage 46a, and the second shuttle valve 42 is provided in the middle of the oil passage 46b. The upstream side of the first shuttle valve 41 in the oil passage 46a and the upstream side of the second shuttle valve 42 in the oil passage 46b are connected to an oil passage 46c. The opposite side of the oil passage 46c from the junction side is connected to the forward operation valve 36.

  The reverse operation valve 37 is a valve that operates the reverse of the traveling device 4. The reverse operation valve 37 and the traveling hydraulic pumps (first traveling hydraulic pump 66A, second traveling hydraulic pump 66B) of the traveling device 4 are connected by a second oil passage 47. Specifically, the second oil passage 47 includes an oil passage 47a connected to the pressure receiving portion 66b of the first traveling hydraulic pump 66A, an oil passage 47b connected to the pressure receiving portion 66b of the second traveling hydraulic pump 66B, and an oil passage. An oil passage 47c that joins the oil passage 47a and the oil passage 47b is included. A third shuttle valve 43 is provided in the middle of the oil passage 47a, and a fourth shuttle valve 44 is provided in a middle of the oil passage 47b. The upstream side of the third shuttle valve 43 in the oil passage 47a and the upstream side of the fourth shuttle valve 44 in the oil passage 47b are connected to an oil passage 47c. The opposite side of the joining side of the oil passage 47c is connected to the reverse operation valve 37.

In addition, the first shuttle valve 41 and the fourth shuttle valve 44 are connected to an oil passage 48, and the oil passage 48 is connected to the right turning operation valve 38. The second shuttle valve 42 and the third shuttle valve 43 are connected to an oil passage 49, and the oil passage 49 is connected to the left turning operation valve 39.
When the traveling lever 40 is swung forward (in the direction indicated by the arrow A1 in FIG. 1), the forward operation valve 36 is operated, and the pilot pressure is output from the operation valve 36. This pilot pressure acts on the pressure receiving portion 66a of the first traveling hydraulic pump 66A from the first shuttle valve 41 via the oil passage 46a, and acts on the second traveling hydraulic pump 66B via the oil passage 46b from the second shuttle valve 42. It acts on the pressure receiving part 66a. As a result, the output shaft 57a of the traveling motor 57 rotates forward (rotates forward) at a speed proportional to the swing amount of the traveling lever 40, and the work implement 1 moves straight forward.

  When the traveling lever 40 is swung rearward (in the direction indicated by the arrow A2 in FIG. 1), the reverse operation valve 37 is operated, and the pilot pressure is output from the operation valve 37. This pilot pressure acts on the pressure receiving portion 66b of the first traveling hydraulic pump 66A from the third shuttle valve 43 via the oil passage 47a, and on the second traveling hydraulic pump 66B via the oil passage 47b from the fourth shuttle valve 44. It acts on the pressure receiving part 66b. As a result, the output shaft 57a of the traveling motor 57 reversely rotates (reversely rotates) at a speed proportional to the swing amount of the traveling lever 40, and the work machine 1 moves straight backward.

  When the traveling lever 40 is swung to the right (in the direction of arrow A3 in FIG. 1), the right turn operation valve 38 is operated, and the pilot pressure is output from the operation valve 38. This pilot pressure acts on the pressure receiving portion 66a of the first traveling hydraulic pump 66A from the first shuttle valve 41 via the oil passage 46a and receives the pressure of the second traveling hydraulic pump 66B via the oil passage 47b from the fourth shuttle valve 44. Acts on the part 66b. Accordingly, the output shaft 57a of the first traveling unit 21L rotates forward and the output shaft 57a of the second traveling unit 21R rotates reversely, and the work machine 1 turns rightward.

  When the traveling lever 40 is swung to the left (in the direction of arrow A4 in FIG. 1), the left turning operation valve 39 is operated, and the pilot pressure is output from the operation valve 39. This pilot pressure acts on the pressure receiving portion 66a of the second traveling hydraulic pump 66B from the second shuttle valve 42 via the oil passage 46b, and acts on the pressure receiving portion 66b of the first traveling hydraulic pump 66A from the third shuttle valve 43. As a result, the output shaft 57a of the second traveling unit 21R rotates forward and the output shaft 57a of the first traveling unit 21L rotates reversely, and the truck loader 1 turns leftward.

When the traveling lever 40 is swung in an oblique direction, the rotation direction of the output shaft 57a of the first traveling portion 21L and the second traveling portion 21R is caused by the differential pressure between the pilot pressure acting on the pressure receiving portion 66a and the pressure receiving portion 66b. And the rotation speed are determined, and the working machine 1 turns right or left while moving forward or backward.
That is, when the traveling lever 40 is swung to the front diagonally to the left, the work implement 1 turns left while moving forward at a speed corresponding to the swing angle of the traveling lever 40, and when the traveling lever 40 is swung to the front diagonally right, When the working machine 1 makes a right turn while moving forward at a speed corresponding to the swing angle of the traveling lever 40, and swings the traveling lever 40 to the rear left diagonally, work is performed at a speed corresponding to the swing angle of the traveling lever 40. When the machine 1 makes a left turn while moving backward, and swings the traveling lever 40 to the right rearward, the working machine 1 makes a right turn while moving backward at a speed corresponding to the swing angle of the traveling lever 40.

As shown in FIG. 1, the hydraulic system includes a control device 70, a first measurement device 71, a second measurement device 72, and a notification device 73.
The first measuring device 71 is a device that is connected to the first oil passage 46 and detects the pressure (pilot pressure) of the operating oil of the forward operation valve 36. Specifically, the first measuring device 71 is connected to the oil passage 46c and detects a pilot pressure acting on the forward operation valve 36 and the oil passage 46c. The pilot pressure detected by the first measuring device 71 is called a first pressure. The first pressure is input to the controller 70.

The second measuring device 72 is a device that is connected to the second oil passage 47 and detects the pressure (pilot pressure) of the operating oil of the reverse operation valve 37. Specifically, the second measuring device 72 is connected to the oil passage 47c, and detects the pilot pressure acting on the reverse operation valve 36 and the oil passage 47c. The pilot pressure detected by the second measuring device 72 is called a second pressure. The second pressure is input to the controller 70.
The control device 70 can acquire the first pressure and the second pressure, and determines whether the work implement 1 (the traveling device 4) is moving forward or backward based on the first pressure and the second pressure. In addition, the notification device 73 can acquire the determination result of the control device 70, and notifies that the vehicle is traveling backward when at least the control device 70 determines that the vehicle is traveling backward. The notification device 81 is a device that notifies the outside of the vehicle backward by voice, characters, a light source, and the like. For example, the notification device 81 is a back buzzer.

FIG. 2A is a diagram illustrating a first pressure and a second pressure.
As shown in FIG. 2A, when the traveling lever 40 swings from the neutral position to the forward side (one side), the first pressure F1 increases according to the swing of the traveling lever 40. Further, when the traveling lever 40 is returned to the neutral position while being operated to the front side (referred to as a returning operation), since the pilot oil in the oil passages 46a and 46b escapes to the hydraulic oil tank 31, the first pressure F1 Is lowered according to the swing of the travel lever 40.

When the travel lever 40 swings from the neutral position to the reverse side (the other side), the second pressure F2 increases in accordance with the swing of the travel lever 40. When the traveling lever 40 is returned to the neutral position while being operated to the rear side, the pilot oil in the oil passages 47a and 47b escapes to the hydraulic oil tank 31, so that the second pressure F2 is not applied to the traveling lever. It descends in response to the swing of 40.
As shown in FIG. 1, the first oil passage 46 (oil passage 46a, oil passage 46b, oil passage 46c) and the second oil passage 47 (oil passage 47a, oil passage 47b, oil passage 47c) are traveling pumps. The first traveling hydraulic pump 66A and the second traveling hydraulic pump 66B are connected to pressure receiving portions (pressure receiving portions 66a and 66b) such as servo cylinders. Therefore, for example, when the traveling lever 40 is swung from the neutral position to the forward side, the operation oil of the servo cylinder causes the hydraulic oil to flow into the oil passage 47a and the oil passage 47b from the pressure receiving portion 66b opposite to the pressure receiving portion 66a. Therefore, pressure may be applied to the oil passage 47c. In the conventional hydraulic circuit, since the pressure switch for detecting the backward movement is provided in the oil passage 47c, the pressure switch detects the pressure applied to the oil passage 47c when the traveling lever 40 is operated from the neutral position to the forward position, and the backward movement is performed. there is a possibility.

  Therefore, the control device 70 compares the first pressure F1 with the second pressure F2, and determines that the vehicle is not traveling backward when the first pressure F1 is equal to or higher than the second pressure F2, as shown in FIG. 2B. That is, when the first pressure F1 is equal to or higher than the second pressure F2, the control device 70 determines that the vehicle is moving forward even if the second pressure F2 is applied. The control device 70 compares the first pressure F1 with the second pressure F2, and determines that the vehicle is traveling backward when the second pressure F2 exceeds the first pressure F1.

  That is, even if the second pressure F2 slightly increases in a state where the operation lever 40 is operated, the control device 70 determines that the first pressure F1 corresponding to the forward pressure is equal to or more than the second pressure F2 (F1 ≧ F2). In the case of F2), since it is not determined that the vehicle is traveling backward, the traveling device 4 can be properly detected to be traveling backward without inadvertently determining that the vehicle is traveling backward unlike the related art. On the other hand, in a situation where the operating lever 40 is being operated, when the second pressure F2 exceeds the first pressure F1 (F1 <F2), the control device 70 determines that the vehicle is moving backward. Therefore, it is possible to appropriately detect that the traveling device 4 is moving forward. In particular, when the outside air temperature is low and the viscosity of the hydraulic oil is low, it has conventionally been possible to judge that the vehicle is in reverse. Can be determined to be backward.

  As described above, when the travel lever 40 is operated forward from the neutral position (at the time of forward operation), pressure is applied to the oil passage 47c. Therefore, the pressure applied to the oil passage 47c when the operation lever 40 is operated forward is measured in advance. In addition, a pressure higher than the measured pressure may be set as a determination value (threshold). Alternatively, the minimum pressure when the vehicle is moving forward or backward may be set as the determination value (threshold).

In this case, as shown in FIG. 2B, when first pressure F1 is equal to or greater than a predetermined threshold, control device 70 determines that the vehicle is not traveling backward. When the first pressure F1 is less than the threshold value and the second pressure F2 is equal to or more than the threshold value, the control device 70 determines that the vehicle is traveling backward. Even in such a case, it is possible to appropriately detect that the traveling device 4 is moving forward or backward.
[Second embodiment]
FIG. 3 shows a hydraulic system according to the second embodiment. In the second embodiment, a working hydraulic system is shown. The description of the same configuration as that of the first embodiment is omitted.

As shown in FIG. 3, the hydraulic system is a system for operating the booms 22L and 22R, the bucket 23, the spare attachment, and the like, and includes a plurality of control valves 50 and a first hydraulic pump P1.
The plurality of control valves 50 are valves that control various hydraulic actuators provided in the work machine 1. The hydraulic actuator is a device that operates with hydraulic oil, and is a hydraulic cylinder, a hydraulic motor, or the like. In this embodiment, the plurality of control valves 50 are a first control valve 50A, a second control valve 50B, and a third control valve 50C.

  The first control valve 50A is a valve that controls a hydraulic actuator (lift cylinder) 26 that operates the booms 22L and 22R. The first control valve 50A is a direct-acting spool type three-position switching valve. The first control valve 50A switches to a neutral position 50a3, a first position 50a1, and a second position 50a2. The pressure receiving portion 54a of the first control valve 50A is connected to an operation valve (not shown) via an oil passage 95, and the pressure receiving portion 54b of the first control valve 50A is connected to an operation valve (not shown) via an oil passage 96. Have been. The operation valve is connected to a swingable operation member (operation lever) as in the first embodiment, and the pressure of the hydraulic oil acting on the pressure receiving portions 54a and 54b changes by operating the operation lever. I do. For example, when the operation lever is swung to one side (left), a predetermined pressure acts on the pressure receiving portion 54a, the spool moves, and the first control valve 50A switches to the first position 50a1. When the operation lever is swung to the other side (right), a predetermined pressure acts on the pressure receiving portion 54b, the spool moves, and the first control valve 50A switches to the second position 50a2.

  The first control valve 50A and the first hydraulic pump P1 are connected by a discharge oil passage 56. The hydraulic oil discharged from the first hydraulic pump P1 passes through a discharge oil passage 56 and is supplied to the first control valve 50A. Further, the first control valve 50 </ b> A and the lift cylinder 26 are connected by a third oil passage 53. The third oil passage 53 connects the first port 51 of the first control valve 50A with the bottom side of the lift cylinder 26, the first supply passage 53a, and the second port 52 of the first control valve 50A and the lift cylinder 26. And a second supply path 53b for connecting to the rod side.

  Therefore, when the first control valve 50A is set at the first position 50a1, hydraulic oil can be supplied from the first supply path 53a to the lift cylinder 26, and hydraulic oil can be discharged from the lift cylinder 26 to the second supply path 53b. can do. As a result, the lift cylinder 26 extends, and the booms 22L and 22R rise. By setting the first control valve 50A to the second position 50a2, hydraulic oil can be supplied from the second supply path 53b to the lift cylinder 26, and hydraulic oil can be discharged from the lift cylinder 26 to the first supply path 53a. Can be. As a result, the lift cylinder 26 contracts, and the booms 22L and 22R descend.

As shown in FIG. 3, the hydraulic system has a float unit 90. The float unit 90 has a plurality of float channels 92 and a plurality of switching units 93. The plurality of float flow paths 92 include a first float flow path 92a connecting the first supply path 53a and the discharge oil path 24, and a second float flow path 92b connecting the second supply path 53b and the discharge oil path 24. And
The plurality of switching units 93 include a switching unit 93a connected to an intermediate portion of the first float channel 92a and a switching unit 93b connected to an intermediate portion of the second float channel 92b. The switching unit 93a is a two-position switching valve that can switch between a first position 93a1 and a second position 93a2. The switching unit 93a prevents the hydraulic oil from passing through the first float flow path 92a and being discharged from the first supply path 53a to the discharge oil path 24 when in the first position 93a1. The switching unit 93a allows the hydraulic oil to pass through the first float flow path 92a and to be discharged from the first supply path 53a to the discharge oil path 24 when in the second position 93a2. That is, the switching unit 93a is opened when it is at the second position 93a2.

  The switching portion 93b is a two-position switching valve that can switch between a first position 93b1 and a second position 93b2. The switching unit 93b prevents the hydraulic oil from passing through the second float flow path 92b and being discharged from the second supply path 53b to the discharge oil path 24 when the first position 93b1 is at the first position 93b1. The switching unit 93b allows the hydraulic oil to pass through the second float flow path 92b and to be discharged from the second supply path 53b to the discharge oil path 24 when in the second position 93b2. That is, the switching unit 93b is opened when it is at the second position 93b2. Switching between the switching unit 93a and the switching unit 93b is performed by the control device 70 described later.

  Therefore, when the switching portion 93a is at the second position 93a2 and the switching portion 93b is at the second position 93b2, the hydraulic oil in the first supply passage 53a and the second supply passage 53b is supplied to the first float passage 92a and the second float 93a2. The oil is discharged to the discharge oil passage 24 through the flow path 92b. Therefore, the float operation is turned on. When the switching unit 93a is at the first position 93a1 and the switching unit 93b is at the first position 93b1, the operating oil in the first supply passage 53a and the second supply passage 53b is supplied to the first float passage 92a and the second float 93a1. It is not discharged to the discharge oil passage 24 through the flow path 92b.

  Now, as shown in FIG. 3, the hydraulic system has a control device 70, a first measuring device 81, and a second measuring device 82. The first measuring device 81 is a device that is connected to the oil passage 95 and detects a pressure acting on the pressure receiving portion 54a of the first control valve 50A [the pressure of the hydraulic oil when the boom (boom 22L, 22R) rises]. . The second measuring device 82 is a device that is connected to the oil passage 96 and detects the pressure acting on the pressure receiving portion 54b of the first control valve 50A [the pressure of the hydraulic oil when the boom (boom 22L, 22R) is lowered]. . The pressure of the hydraulic oil detected by the first measuring device 81 is called a third pressure, and the pressure of the hydraulic oil detected by the second measuring device 82 is called a fourth pressure.

  The control device 70 can acquire the third pressure and the fourth pressure, and controls the float operation based on the third pressure and the fourth pressure. More specifically, the control device 70 compares the third pressure with the fourth pressure, and determines that the boom is rising (boom raising) when the third pressure is equal to or higher than the fourth pressure. Further, control device 70 compares the third pressure with the fourth pressure, and determines that the boom is lowering (boom lowering) when the fourth pressure exceeds the third pressure. For convenience of description, the third pressure is “F3” and the fourth pressure is “F4”.

  Even if the fourth pressure F4 slightly increases under the condition where the operation lever is operated, the control device 70 determines that the third pressure F3 corresponding to the boom raising is equal to or higher than the fourth pressure F4 (F3 ≧ F4). Does not judge that the boom should be lowered, so that the boom can be reliably determined. On the other hand, when the fourth pressure F4 exceeds the third pressure F3 (F3 <F4) in a state where the operation lever is operated, the control device 70 determines that the boom is to be lowered.

When the switch 59 is turned on while determining that the boom is to be lowered, the control device 70
The solenoids of the switching units (the switching unit 93a and the switching unit 93b) are excited to switch the switching units (the switching unit 93a and the switching unit 93b) to the second positions 93a2 and 93b2. That is, the control device 70 starts the float operation. When the third pressure is equal to or higher than the fourth pressure during the float operation (the float unit 54 is operating) and the boom is raised, the control device 70 switches the switching units (the switching unit 93a and the switching unit 93b). The switching section (switching section 93a and switching section 93b) is switched to the first position 93a1, 93b1 by demagnetizing the solenoid. That is, the control device 70 releases the float operation (stops the float unit 54).

Note that the control device 70 may determine that the arm is raised when the third pressure F1 is equal to or greater than a predetermined threshold. Further, the control device 70 may determine that the arm is lowered when the third pressure is less than the threshold value and the fourth pressure is equal to or more than the threshold value.
According to this, the float operation can be started while the boom is being lowered. In addition, when raising the boom while performing the float operation, the float operation can be reliably released.

  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. In the above-described embodiment, the control device 70 causes the work implement 1 (the traveling device 4) to move forward or backward based on the pressure of the hydraulic oil in the oil passage connected to the operation valve (the forward operation valve 36, the reverse operation valve 37). The control device 70 determines whether the vehicle is moving backward from the pressure of the hydraulic oil, but the present invention is not limited to this. In addition, the notification device 73 has reported that the vehicle is traveling backward, but the invention is not limited to this. For example, the control device 70 turns right (turn right) and turns left (turn left) based on the pressure of hydraulic oil in an oil passage connected to the operation valves (right turn operation valve 38, left turn operation valve 39). May be determined. The notification device 73 may notify a left turn or a right turn. That is, the control device 70 determines the traveling direction (forward, reverse, right turn, left turn) of the work implement 1 (traveling device 4) based on the pressures (first pressure, second pressure) at at least two or more operation valves. And the notifying device 73 may notify the traveling direction determined by the control device 70. According to this, it is possible to appropriately determine any of forward, reverse, right turn, and left turn.

  In the above-described embodiment, the hydraulic oil is discharged from the hydraulic oil tank, but may be discharged to another location. That is, the oil passage for discharging the hydraulic oil may be connected to a part other than the hydraulic oil tank, for example, may be connected to a suction part (a part for sucking the hydraulic oil) of the hydraulic pump, or may be connected to other parts. May be connected.

REFERENCE SIGNS LIST 1 work machine 4 traveling device 12 support shaft 14 traveling operating device 36 forward operating valve 37 reverse operating valve 38 right turning operating valve 39 left turning operating valve 40 running lever 46 first oil passage 47 second oil passage 63 hydraulic switching valve 70 control device 71 first measuring device 72 second measuring device 73 notification device

Claims (2)

A traveling device capable of moving forward or backward by hydraulic oil,
A forward operation valve that can supply hydraulic oil and operates the forward movement of the traveling device;
A reverse operation valve capable of supplying hydraulic oil and operating the reverse of the traveling device;
A first oil passage connecting the traveling device and the forward operation valve;
A second oil passage connecting the traveling device and the reverse operation valve;
A first measurement device that is connected to the first oil passage and detects a first pressure that is a pressure of hydraulic oil of the forward operation valve;
A second measuring device that is connected to the second oil passage and detects a second pressure that is a pressure of hydraulic oil of the reverse operation valve;
A control device that determines whether the traveling device is moving forward or backward based on the first pressure and the second pressure;
A notification device that notifies that the vehicle is moving backward when the control device determines that the vehicle is moving backward;
With
The traveling device is configured to receive a hydraulic oil corresponding to the reverse when the reverse operation valve is operated, and to receive a hydraulic oil corresponding to the reverse when the reverse operation valve is operated when the forward operation valve is operated. Having a pressure receiving section on the reverse side,
The first oil path connects the forward-side pressure receiving portion and the forward operation valve,
The second oil path connects the reverse-side pressure receiving portion and the reverse operation valve,
When the first pressure is equal to or greater than a predetermined threshold, the control device determines that the vehicle is moving forward instead of the reverse, and the first pressure is less than the threshold and the second pressure is equal to or greater than the threshold. In some cases, the hydraulic system of the work machine that determines that the vehicle is moving backward. With operating members,
The forward operating valve is actuated upon operating the operating member in one direction, the reverse operation valve, the working machine hydraulic system according to claim 1 that operates upon operating the operating member to the other.

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