JP2022033071A - Work machine - Google Patents

Abstract

To reduce shift shock while securing responsiveness in deceleration.SOLUTION: A work machine includes: a motor; a travel pump capable of changing a flow rate of a hydraulic fluid discharged according to an angle of a swash plate; a travel motor rotatable by the hydraulic fluid discharged by the travel pump, and capable of switching a rotating speed between a first speed and a second speed higher than the first speed; a travel switch valve capable of switching a first state in which the rotating speed of the travel motor is a first speed, and a second state in which the rotating speed of the travel motor is a second speed; an operation device; an operation valve capable of changing the angle of the swash plate of the travel pump according to the operation of the operation device; a working valve disposed at an upstream side or a downstream side of the operation valve; and a control device for making a control signal to control the operation valve, return after being lowered to a reduction valve lower than a set value in switching from the second state to the first state. The control device makes a first reduction speed of the control signal from a starting point of a reduction section to the middle of the reduction section, higher than a second reduction speed of the control signal from the middle to a terminal point of the reduction section, in the reduction section to reach the reduction value from the set value.SELECTED DRAWING: Figure 2A

Description

The present invention relates to working machines such as skid steer loaders, compact truck loaders, and backhoes, for example.

Conventionally, there is a technique shown in Patent Document 1 as a technique for decelerating and increasing the speed of a working machine. The hydraulic system of the working machine of Patent Document 1 includes a hydraulic pump that discharges hydraulic oil, a hydraulic switching valve that can switch to a plurality of switching positions according to the pressure of the hydraulic oil, and a speed according to the switching position of the hydraulic switching valve. Is equipped with a variable traveling hydraulic system.

JP-A-2017-179922

In the working machine of Patent Document 1, since the bleed oil passage is provided in the pressure receiving portion of the hydraulic pressure switching valve, it is possible to reduce the shift shock when the working machine is accelerated or decelerated. However, in Patent Document 1, a bleed oil passage must be provided in order to reduce shift shock, and the number of parts increases. Further, in a traveling motor having no neutrality, it is required to further sufficiently reduce the shift shock.

The present invention has been made to solve the above-mentioned problems of the prior art, and an object of the present invention is to provide a working machine capable of reducing shift shock while ensuring responsiveness during deceleration. And.

The technical measures taken by the present invention to solve the technical problems are as follows.
The work equipment can be rotated by a traveling pump capable of changing the flow rate of the hydraulic oil discharged according to the angle of the swash plate and the hydraulic oil discharged by the traveling pump, and the rotation speeds are the first speed and the first speed. A traveling motor that can be switched to a second speed higher than the speed, a first state in which the rotation speed of the traveling motor is set to the first speed, and a second state in which the rotation speed of the traveling motor is set to the second speed. A traveling switching valve that can be switched to, an operating device, an operating valve that can change the angle of the swash plate of the traveling pump according to the operation of the operating device, and the operation valve on the upstream side or the downstream side of the operating valve. An operating valve connected to the operating valve, and a control device that reduces the control signal for controlling the operating valve to a reduction value lower than the set value and then returns when switching from the second state to the first state. In the reduction section from the set value to the reduction value, the control device sets the first reduction speed of the control signal from the start point of the reduction section to the middle of the reduction section in the middle of the reduction section. It is made larger than the second lowering speed of the control signal from to the end point.

In the control device, the first line in which the first reduction amount per unit time is constant and the first reduction rate from the start point to the middle of the unit time is shown, and the second reduction amount per unit time is the first reduction amount. Based on the setting unit that is smaller and constant and sets the second line indicating the second reduction speed from the middle to the end point, and the first line and the second line set by the setting unit. It has a control unit for controlling the first reduction speed and the second reduction speed.

When the traveling load is equal to or higher than a predetermined threshold value, the control unit controls the first reduction speed and the second reduction speed based on the first line and the second line.
The setting unit sets the value of the control signal of the inflection point which is the boundary between the first line and the second line based on the traveling load when switching from the second state to the first state. change.

The setting unit adopts the highest hydraulic oil pressure among the hydraulic oil pressures discharged from the traveling pump as the traveling load.
The setting unit shifts the value of the control signal of the inflection point to the set value side when the traveling load is large, and shifts the value of the control signal of the inflection point to the setting value side when the traveling load is small. Shift to the reduced value side.

When the control signal is restored after the control signal reaches the reduction angle, the control device sets the amount of restoration per unit time at the time of restoration to the second reduction rate per unit time. Make it larger than the amount of decrease.
The working machine can be rotated by the prime mover, a traveling pump capable of changing the flow rate of the hydraulic oil discharged according to the angle of the swash plate, and the hydraulic oil discharged by the traveling pump, and the rotation speed is the first speed. A traveling motor that can be switched to a second speed higher than the first speed, a first state in which the rotation speed of the traveling motor is set to the first speed, and a rotation speed of the traveling motor to be set to the second speed. A traveling switching valve that can be switched to the second state, an operating device, an operating valve that can change the angle of the swash plate of the traveling pump according to the operation of the operating device, and an upstream side or a downstream side of the operating valve. An actuated valve arranged in the above, and a control device that increases the control signal for controlling the actuated valve to an increase value higher than the set value and then returns when switching from the second state to the first state. In the increasing section from the set value to the increase value, the control device sets the first increase speed of the control signal from the start point of the increase section to the middle of the increase section from the middle to the end point of the increase section. It is made larger than the second increase speed of the control signal up to.

In the control device, the first line in which the first increase amount per unit time is constant and the first increase rate from the start point to the middle of the unit time is shown, and the second increase amount per unit time is the first increase amount. Based on the setting unit that is smaller and constant and sets the second line indicating the second increasing speed from the middle to the end point, and the first line and the second line set by the setting unit. It has a control unit for controlling the first increasing speed and the second increasing speed.

When the traveling load is equal to or higher than a predetermined threshold value, the control unit controls the first increasing speed and the second increasing speed based on the first line and the second line.
The setting unit sets the value of the control signal of the inflection point which is the boundary between the first line and the second line based on the traveling load when switching from the second state to the first state. change.

The setting unit shifts the value of the control signal of the inflection point to the set value side when the traveling load is large, and shifts the value of the control signal of the inflection point to the setting value side when the traveling load is small. Shift to the increase value side.
When the control signal is restored after the control signal reaches the increase value, the control device sets the amount of restoration per unit time at the time of restoration to the second increase rate per unit time. Make it larger than the amount of increase.

According to the present invention, shift shock can be reduced while ensuring responsiveness during deceleration.

It is a figure which shows the hydraulic system (hydraulic circuit) of a work machine. It is a figure which showed the relationship between the control signal and the switching of a traveling motor when the traveling motor is accelerated. It is a figure which shows the state which reduces the control signal output to the actuating valve by the deceleration line which consists of the 1st line and the 2nd line when the traveling motor is decelerated. It is a figure which shows the state which reduces the control signal output to the actuating valve by the arc-shaped deceleration line which does not have an inflection point when the traveling motor is decelerated. It is a figure which shows the deformation example when the operation valve is provided in the traveling oil passage. It is a side view which shows the truck loader which is an example of a working machine.

Hereinafter, a hydraulic system for a working machine according to the present invention and a preferred embodiment of the working machine provided with the hydraulic system will be described with reference to the drawings as appropriate.
FIG. 4 shows a side view of the working machine according to the present invention. FIG. 4 shows a compact truck loader as an example of a working machine. However, the working machine according to the present invention is not limited to the compact truck loader, and may be, for example, another type of loader working machine such as a skid steer loader. Further, it may be a working machine other than the loader working machine.

As shown in FIG. 4, the working machine 1 includes a machine body 2, a cabin 3, a working device 4, and a traveling device 5. In the embodiment of the present invention, the front side (left side of FIG. 4) of the driver seated in the driver's seat 8 of the work machine 1 is the front, the rear side of the driver (right side of FIG. 4) is the rear, and the left side of the driver (FIG. 4). The front side of No. 4) will be described as the left side, and the right side of the driver (the back side of FIG. 4) will be described as the right side. Further, the horizontal direction, which is a direction orthogonal to the front-rear direction, will be described as the body width direction. The direction from the center of the machine 2 to the right or left side will be described as the outside of the machine. In other words, the outside of the airframe is the width direction of the airframe and the direction away from the airframe 2. The direction opposite to the outside of the aircraft will be described as the inside of the aircraft. In other words, the inside of the machine is the width direction of the machine and the direction approaching the body 2.

The cabin 3 is mounted on the airframe 2. The cabin 3 is provided with a driver's seat 8. The working device 4 is attached to the machine body 2. The traveling device 5 is provided on the outside of the machine body 2. A motor 32 is mounted on the rear portion of the machine body 2.
The working device 4 has a boom 10, a working tool 11, a lift link 12, a control link 13, a boom cylinder 14, and a bucket cylinder 15.

The boom 10 is provided on the right side and the left side of the cabin 3 so as to be vertically swingable. The work tool 11 is, for example, a bucket, and the bucket 11 is provided at the tip end portion (front end portion) of the boom 10 so as to be vertically swingable. The lift link 12 and the control link 13 support the base (rear portion) of the boom 10 so that the boom 10 can swing up and down. The boom cylinder 14 expands and contracts to raise and lower the boom 10. The bucket cylinder 15 swings the bucket 11 by expanding and contracting.

The front parts of the left and right booms 10 are connected to each other by a deformed connecting pipe. The bases (rear parts) of the booms 10 are connected to each other by a circular connecting pipe.
The lift link 12, the control link 13, and the boom cylinder 14 are provided on the left side and the right side of the machine body 2, respectively, corresponding to the left and right booms 10.
The lift link 12 is provided vertically at the rear of the base of each boom 10. The upper portion (one end side) of the lift link 12 is rotatably supported around the horizontal axis via the pivot shaft 16 (first pivot shaft) toward the rear portion of the base of each boom 10. Further, the lower portion (the other end side) of the lift link 12 is rotatably and rotatably supported around the horizontal axis via the pivot shaft 17 (second pivot shaft) toward the rear portion of the machine body 2. The second pivot shaft 17 is provided below the first pivot shaft 16.

The upper portion of the boom cylinder 14 is rotatably supported around a horizontal axis via a pivot shaft 18 (third pivot shaft). The third pivot shaft 18 is the base of each boom 10 and is provided at the front of the base. The lower portion of the boom cylinder 14 is rotatably supported around a horizontal axis via a pivot shaft 19 (fourth pivot shaft). The fourth pivot shaft 19 is provided near the lower part of the rear part of the machine body 2 and below the third pivot shaft 18.

The control link 13 is provided in front of the lift link 12. One end of the control link 13 is rotatably supported around a horizontal axis via a pivot shaft 20 (fifth pivot shaft). The fifth pivot shaft 20 is the airframe 2, and is provided at a position corresponding to the front of the lift link 12. The other end of the control link 13 is rotatably supported around a horizontal axis via a pivot shaft 21 (sixth pivot shaft). The sixth pivot shaft 21 is a boom 10 and is provided in front of the second pivot shaft 17 and above the second pivot shaft 17.

By expanding and contracting the boom cylinder 14, each boom 10 swings up and down around the first pivot shaft 16 while the base of each boom 10 is supported by the lift link 12 and the control link 13, and the tip of each boom 10 Goes up and down. The control link 13 swings up and down around the fifth pivot shaft 20 as each boom 10 swings up and down. The lift link 12 swings back and forth around the second pivot shaft 17 as the control link 13 swings up and down.

Another work tool can be attached to the front of the boom 10 instead of the bucket 11. Another working tool is, for example, an attachment (spare attachment) such as a hydraulic crusher, a hydraulic breaker, an angle bloom, an earth auger, a pallet fork, a sweeper, a mower, or a snow blower.
A connecting member 50 is provided at the front of the boom 10 on the left side. The connecting member 50 is a device for connecting the hydraulic device equipped in the spare attachment and the first pipe material such as a pipe provided in the boom 10. Specifically, the first pipe material can be connected to one end of the connecting member 50, and the second pipe material connected to the hydraulic device of the spare attachment can be connected to the other end. As a result, the hydraulic oil flowing through the first pipe material passes through the second pipe material and is supplied to the hydraulic equipment.

The bucket cylinder 15 is arranged near the front of each boom 10. By expanding and contracting the bucket cylinder 15, the bucket 11 is swung.
As each of the left and right traveling devices (first traveling device, second traveling device) 5, a crawler type (including semi-crawler type) traveling device is adopted in the present embodiment. A wheel-type traveling device having front wheels and rear wheels may be adopted.

The prime mover 32 is an internal combustion engine such as a diesel engine or a gasoline engine, an electric motor, or the like. In this embodiment, the prime mover 32 is, but is not limited to, a diesel engine.
Next, the hydraulic system of the working machine will be described.
As shown in FIG. 1, the hydraulic system of the working machine can drive the traveling device 5. The hydraulic system of the working machine includes a first traveling pump 53L, a second traveling pump 53R, a first traveling motor 36L, and a second traveling motor 36R.

The first traveling pump 53L and the second traveling pump 53R are pumps driven by the power of the prime mover 32. Specifically, the first traveling pump 53L and the second traveling pump 53R are swash plate type variable displacement axial pumps driven by the power of the prime mover 32. The first traveling pump 53L and the second traveling pump 53R are inclined by the pilot pressure acting on the pressure receiving portions 53a and 53b having the forward pressure receiving portion 53a on which the pilot pressure acts and the reverse pressure receiving portion 53b. The angle of the board is changed. By changing the angle of the slab, the output (discharge amount of hydraulic oil) and the discharge direction of the hydraulic oil of the first traveling pump 53L and the second traveling pump 53R can be changed.

The first traveling pump 53L and the first traveling motor 36L are connected by a circulating oil passage 57h, and the hydraulic oil discharged by the first traveling pump 53L is supplied to the first traveling motor 36L. The second traveling pump 53R and the second traveling motor 36R are connected by a circulating oil passage 57i, and the hydraulic oil discharged by the second traveling pump 53R is supplied to the second traveling motor 36R.
The first traveling motor 36L is a motor that transmits power to the drive shaft of the traveling device 5 provided on the left side of the machine body 2. The first traveling motor 36L can be rotated by the hydraulic oil discharged from the first traveling pump 53L, and the rotation speed (rotational speed) can be changed by the flow rate of the hydraulic oil. A swash plate switching cylinder 37L is connected to the first traveling motor 36L, and the rotation speed (rotation speed) of the first traveling motor 36L is also changed by expanding and contracting the swash plate switching cylinder 37L to one side or the other side. be able to. That is, when the swash plate switching cylinder 37L is contracted, the rotation speed of the first traveling motor 36L is set to a low speed (first speed), and when the swash plate switching cylinder 37L is extended, the first traveling motor 36L is set. The rotation speed of is set to high speed (second speed). That is, the rotation speed of the first traveling motor 36L can be changed between the first speed on the low speed side and the second speed on the high speed side.

The second traveling motor 36R is a motor that transmits power to the drive shaft of the traveling device 5 provided on the right side of the machine body 2. The second traveling motor 36R can be rotated by the hydraulic oil discharged from the second traveling pump 53R, and the rotation speed (rotational speed) can be changed by the flow rate of the hydraulic oil. A swash plate switching cylinder 37R is connected to the second traveling motor 36R, and the rotation speed (rotation speed) of the second traveling motor 36R is also changed by expanding and contracting the swash plate switching cylinder 37R to one side or the other side. be able to. That is, when the swash plate switching cylinder 37R is contracted, the rotation speed of the second traveling motor 36R is set to a low speed (first speed), and when the swash plate switching cylinder 37R is extended, the second traveling motor 36R is set. The rotation speed of is set to high speed (second speed). That is, the rotation speed of the second traveling motor 36R can be changed between the first speed on the low speed side and the second speed on the high speed side.

As shown in FIG. 1, the hydraulic system of the working machine includes a traveling switching valve 34. The travel switching valve 34 switches between a first state in which the rotation speed (rotation speed) of the travel motors (first travel motor 36L, second travel motor 36R) is set to the first speed and a second state in which the travel speed is set to the second speed. It is possible. The traveling switching valve 34 has a first switching valve 71L, 71R and a second switching valve 72.
The first switching valve 71L is a two-position switching valve that is connected to the swash plate switching cylinder 37L of the first traveling motor 36L via an oil passage and switches between the first position 71L1 and the second position 71L2. The first switching valve 71L contracts the swash plate switching cylinder 37L when it is in the first position 71L1, and expands the swash plate switching cylinder 37L when it is in the second position 71L2.

The second switching valve 71R is a two-position switching valve that is connected to the swash plate switching cylinder 37R of the second traveling motor 36R via an oil passage and switches to the first position 71R1 and the second position 71R2. The second switching valve 71R contracts the swash plate switching cylinder 37R when it is in the first position 71R1, and expands the swash plate switching cylinder 37R when it is in the second position 71R2.
The second switching valve 72 is a solenoid valve that switches between the first switching valve 71L and the second switching valve 71R, and is a two-position switching valve that can be switched between the first position 72a and the second position 72b by excitation. The second switching valve 72, the first switching valve 71L, and the second switching valve 71R are connected by an oil passage 41. The second switching valve 72 switches the first switching valve 71L and the second switching valve 71R to the first positions 71L1 and 71R1 when it is in the first position 72a, and the first switching valve 71L and when it is in the second position 72b. The second switching valve 71R is switched to the second positions 71L2 and 71R2.

That is, when the second switching valve 72 is in the first position 72a, the first switching valve 71L is in the first position 71L1, and the second switching valve 71R is in the first position 71R1, the traveling switching valve 34 is in the first state. The rotation speed of the traveling motors (first traveling motor 36L, second traveling motor 36R) is set to the first speed. When the second switching valve 72 is in the second position 72b, the first switching valve 71L is in the second position 71L2, and the second switching valve 71R is in the second position 71R2, the traveling switching valve 34 is in the second state and the traveling motor. The rotation speed of (first traveling motor 36L, second traveling motor 36R) is set to the second speed.

Therefore, the traveling switching valve 34 can switch the traveling motor (first traveling motor 36L, second traveling motor 36R) between the first speed on the low speed side and the second speed on the high speed side.
Switching between the first speed and the second speed in the traveling motor can be performed by the switching unit. The switching unit is, for example, a changeover switch 61 connected to the control device 60, and can be operated by an operator or the like. The switching unit (changeover switch 61) changes the speed from the first speed (first state) to the second speed (second state) and from the second speed (second state) to the first speed (first state). It can be switched to either deceleration or deceleration.

The control device 60 is composed of a CPU, a semiconductor such as an MPU, an electric / electronic circuit, and the like. The control device 60 switches the traveling switching valve 34 based on the switching operation of the changeover switch 61. The changeover switch 61 is a push switch. For example, when the traveling motor is pressed in the first speed state, the changeover switch 61 outputs a command to set the traveling motor to the second speed (a command to set the traveling switching valve 34 to the second speed) to the control device 60. Will be done. Further, when the traveling motor is pressed in the second speed state, the changeover switch 61 outputs a command to set the traveling motor to the first speed (a command to set the traveling switching valve 34 to the first state) to the control device 60. .. The changeover switch 61 may be a push switch that can be held ON / OFF, and when it is OFF, a command for holding the traveling motor at the first speed is output to the control device 60 and is ON. In this case, a command for holding the traveling motor at the second speed is output to the control device 60.

When the control device 60 obtains a command to put the traveling switching valve 34 into the first state, the control device 60 degausses the solenoid of the second switching valve 72 to put the traveling switching valve 34 into the first state. Further, when the control device 60 acquires a command to put the traveling switching valve 34 into the second state, the control device 60 excites the solenoid of the second switching valve 72 to put the traveling switching valve 34 into the second state.
The hydraulic system of the working machine includes a first hydraulic pump P1, a second hydraulic pump P2, and an operating device 54. The first hydraulic pump P1 is a pump driven by the power of the prime mover 32, and is composed of a constant capacity type gear pump. The first hydraulic pump P1 can discharge the hydraulic oil stored in the tank 22. In particular, the first hydraulic pump P1 discharges hydraulic oil mainly used for control. For convenience of explanation, the tank 22 for storing the hydraulic oil may be referred to as a hydraulic oil tank. Further, among the hydraulic oil discharged from the first hydraulic pump P1, the hydraulic oil used for control may be referred to as pilot oil, and the pressure of the pilot oil may be referred to as pilot pressure.

The second hydraulic pump P2 is a pump driven by the power of the prime mover 32, and is composed of a constant capacity type gear pump. The second hydraulic pump P2 can discharge the hydraulic oil stored in the tank 22, and supplies the hydraulic oil to, for example, the oil passage of the working system. For example, the second hydraulic pump P2 supplies hydraulic oil to the boom cylinder 14 that operates the boom 10, the bucket cylinder 15 that operates the bucket, and the control valve (flow control valve) that controls the preliminary hydraulic actuator that operates the preliminary hydraulic actuator. do.

The operating device 54 is a device for operating the traveling pump (first traveling pump 53L, second traveling pump 53R), and the angle of the swash plate of the traveling pump (swash plate angle) can be changed. The operating device 54 includes an operating lever 59 and a plurality of operating valves 55.
The operating lever 59 is an operating lever that is supported by the operating valve 55 and swings in the left-right direction (body width direction) or in the front-rear direction. That is, the operating lever 59 can be operated to the right and left from the neutral position N and forward and backward from the neutral position N with reference to the neutral position N. In other words, the operating lever 59 can swing in at least four directions with respect to the neutral position N. For convenience of explanation, the front and rear directions, that is, the front-back direction is referred to as the first direction. Further, the bidirectional direction between the right side and the left side, that is, the left-right direction (airframe width direction) may be referred to as the second direction.

Further, the plurality of operating valves 55 are commonly operated, that is, operated by one operating lever 59. The plurality of operating valves 55 operate based on the swing of the operating lever 59. A discharge oil passage 40 is connected to the plurality of operation valves 55, and hydraulic oil (pilot oil) from the first hydraulic pump P1 can be supplied via the discharge oil passage 40. The plurality of operating valves 55 are an operating valve 55A, an operating valve 55B, an operating valve 55C, and an operating valve 55D.

The operation valve 55A is operated to output according to the operation amount (operation) of the previous operation when the operation lever 59 is swung forward (one side) in the front-rear direction (first direction) (when the operation lever 59 is operated forward). The pressure of the oil changes. The operation valve 55B is operated to output according to the operation amount (operation) of the rear operation when the operation lever 59 is swung backward (the other) in the front-rear direction (first direction) (when the operation lever 59 is rear-operated). The pressure of the oil changes. In the left-right direction (second direction), the operation valve 55C outputs when the operation lever 59 swings to the right (one side) (when the operation lever 59 is operated to the right) according to the operation amount (operation) of the right operation. The pressure of the hydraulic oil changes. The operation valve 55D outputs according to the operation amount (operation) of the left operation when the operation lever 59 is swung to the left (the other) in the left-right direction (second direction) (when the operation lever 59 is operated to the left). The pressure of the hydraulic fluid changes.

The plurality of operating valves 55 and the traveling pumps (first traveling pump 53L, second traveling pump 53R) are connected by a traveling oil passage 45. In other words, the traveling pump (first traveling pump 53L, second traveling pump 53R) is hydraulic pressure that can be operated by the hydraulic oil output from the operation valve 55 (operation valve 55A, operation valve 55B, operation valve 55C, operation valve 55D). It is a device.
The traveling oil passage 45 has a first traveling oil passage 45a, a second traveling oil passage 45b, a third traveling oil passage 45c, a fourth traveling oil passage 45d, and a fifth traveling oil passage 45e. The first traveling oil passage 45a is an oil passage connected to the advancing pressure receiving portion 53a of the traveling pump 53L. The second traveling oil passage 45b is an oil passage connected to the reverse pressure receiving portion 53b of the traveling pump 53L. The third traveling oil passage 45c is an oil passage connected to the advancing pressure receiving portion 53a of the traveling pump 53R. The fourth traveling oil passage 45d is an oil passage connected to the reverse pressure receiving portion 53b of the traveling pump 53R. The fifth traveling oil passage 45e is an oil passage connecting the operation valve 55, the first traveling oil passage 45a, the second traveling oil passage 45b, the third traveling oil passage 45c, and the fourth traveling oil passage 45d.

When the operating lever 59 is swung forward (in the direction of arrow A1 in FIG. 1), the operating valve 55A is operated and the pilot pressure is output from the operating valve 55A. This pilot pressure acts on the pressure receiving portion 53a of the first traveling pump 53L via the first traveling oil passage 45a and acts on the pressure receiving portion 53a of the second traveling pump 53R via the third traveling oil passage 45c. As a result, the swash plate angles of the first traveling pump 53L and the second traveling pump 53R are changed, the first traveling motor 36L and the second traveling motor 36R rotate forward (forward rotation), and the work machine 1 moves straight forward. ..

Further, when the operating lever 59 is swung backward (in the direction of arrow A2 in FIG. 1), the operating valve 55B is operated and the pilot pressure is output from the operating valve 55B. This pilot pressure acts on the pressure receiving portion 53b of the first traveling pump 53L via the second traveling oil passage 45b and also acts on the pressure receiving portion 53b of the second traveling pump 53R via the fourth traveling oil passage 45d. As a result, the swash plate angles of the first traveling pump 53L and the second traveling pump 53R are changed, the first traveling motor 36L and the second traveling motor 36R are reversed (reverse rotation), and the working machine 1 moves straight backward.

Further, when the operation lever 59 is swung to the right (in the direction of arrow A3 in FIG. 1), the operation valve 55C is operated and the pilot pressure is output from the operation valve 55C. This pilot pressure acts on the pressure receiving portion 53a of the first traveling pump 53L via the first traveling oil passage 45a and acts on the pressure receiving portion 53b of the second traveling pump 53R via the fourth traveling oil passage 45d. As a result, the swash plate angles of the first traveling pump 53L and the second traveling pump 53R are changed, the first traveling motor 36L rotates forward and the second traveling motor 36R reverses, and the working machine 1 turns to the right.

Further, when the operating lever 59 is swung to the left (in the direction of arrow A4 in FIG. 1), the operating valve 55D is operated and the pilot pressure is output from the operating valve 55D. This pilot pressure acts on the pressure receiving portion 53a of the second traveling pump 53R via the third traveling oil passage 45c and also acts on the pressure receiving portion 53b of the first traveling pump 53L via the second traveling oil passage 45b. As a result, the swash plate angles of the first traveling pump 53L and the second traveling pump 53R are changed, the first traveling motor 36L reverses, the second traveling motor 36R rotates forward, and the working machine 1 turns to the left.

Further, when the operating lever 59 is swung in an oblique direction, the rotation direction and rotation speed of the first traveling motor 36L and the second traveling motor 36R are increased by the differential pressure of the pilot pressure acting on the pressure receiving portion 53a and the pressure receiving portion 53b. Determined, the working machine 1 makes a right turn or a left turn while moving forward or backward.
That is, when the operation lever 59 is swung diagonally forward to the left, the work machine 1 turns left while advancing at a speed corresponding to the swing angle of the operating lever 59, and when the operating lever 59 is swung diagonally forward to the right. When the working machine 1 turns to the right while moving forward at a speed corresponding to the swing angle of the operating lever 59, and when the operating lever 59 is swung diagonally backward to the left, the working machine 1 is swung at a speed corresponding to the swing angle of the operating lever 59. 1 turns left while moving backward, and when the operating lever 59 is swung diagonally backward to the right, the working machine 1 turns right while moving backward at a speed corresponding to the swing angle of the operating lever 59.

By the way, the accelerator 65 for setting the motor rotation speed is connected to the control device 60. The accelerator 65 is provided in the vicinity of the driver's seat 8. The accelerator 65 includes an accelerator lever that is swingably supported, an accelerator pedal that is swingably supported, an accelerator volume that is rotatably supported, an accelerator slider that is slidably supported, and the like. The accelerator 65 is not limited to the above-mentioned example. Further, a rotation detection device 66 for detecting the rotation speed of the prime mover is connected to the control device 60. The rotation detection device 66 allows the control device 60 to grasp the actual motor rotation speed (actual rotation speed) of the prime mover 32. The control device 60 sets a target prime mover rotation speed (target rotation speed) based on the operation amount of the accelerator 65, and controls the actual rotation speed so as to reach the set target rotation speed.

By the way, as shown in FIG. 1, the discharge oil passage 40 is branched in the middle portion, and is a section 40a which is the discharge oil passage 40 after the branch and reaches the operation device 54, that is, on the upstream side of the operation valve 55. , The actuating valve 69 is connected. The operating valve 69 is an electromagnetic proportional valve (proportional valve), and its opening degree can be changed by the control of the control device 60. The opening degree of the actuating valve 69 increases as the control signal output from the control device 60 increases, and the opening degree decreases as the control signal decreases. Hereinafter, for convenience of explanation, the operating valve 69 will be referred to as a proportional valve 69.

The proportional valve 69 increases the rotation speed of the traveling motor from the first speed to the second speed when the traveling switching valve 34 is switched from the first state (first speed) to the second state (second speed). In this case, the pressure of the hydraulic oil supplied to the operating device 54 (the pressure of the hydraulic oil on the primary side in the operating valve 55) is changed. Further, the proportional valve 69 changes the rotation speed of the traveling motor from the second speed to the first speed when the traveling switching valve 34 is switched from the second state (second speed) to the first state (first speed). When decelerating, the pressure of the hydraulic oil supplied to the operating device 54 (the pressure of the hydraulic oil on the primary side in the operating valve 55) is changed.

The control device 60 reduces the control signals such as the current and voltage output to the proportional valve 69 to a reduction value (second set value) lower than the set value (first set value) at both the speed increase and the deceleration. After lowering to, it is restored.
FIG. 2A is a diagram showing the relationship between the set value and the reduction value of the control signal when the traveling motor is accelerated from the first speed to the second speed and the switching of the traveling motor. On the vertical axis showing the control signal of FIG. 2A, the value is low on the origin side and increases as the distance from the origin increases.

As shown in FIG. 2A, in the control device 60, the changeover switch (switching valve) 61 is operated at the time point Q21, and the control device 60 is in the first state (first speed) to the second state (second speed). It is assumed that the command to be set (2-speed command) is acquired. When the control device 60 acquires the second speed command, the output value W11 of the control signal output to the proportional valve 69 is reduced to a predetermined value (reduction value) W13 lower than the set value W12. The predetermined value (reduction value) W13 is a value for reducing the shift shock when switching from the first speed to the second speed, and is a value obtained by subtracting the reduction amount ΔD2 from the set value W12. For example, the set value W12 of the control signal of the proportional valve 69 is set by the vehicle speed of the working machine and the actual rotation speed of the prime mover rotation speed. More specifically, when the control device 60 does not acquire the second speed command (when switching is not performed), the control device 60 sets a control signal (current value) at which the proportional valve 69 is fully opened. .. On the other hand, when the control device 60 acquires the second speed command, the control device 60 changes the set value W12 of the control signal according to the vehicle speed of the working machine or the actual rotation speed of the prime mover rotation speed.

When the output value W11 reaches a predetermined value (reduced value) W13 at the time point Q22, the control device 60 returns the output value W11 to the set value W12 by increasing the control signal to the proportional valve 69. Alternatively, the control device 60 increases the control signal to the proportional valve 69 during the reduction time T21 for reducing the output value W11 to the predetermined value (reduction value) W13, so that the output value W11 is set to the set value W12 on the way. Return. Here, the control device 60 sets the return time T22 for returning the output value W11 from the predetermined value (reduction value) W13 to the set value W12 longer than the reduction time T21. That is, the control device 60 makes the reduction speed at which the output value W11 is reduced to the predetermined value (reduction value) W13 faster than the return speed at which the output value W11 is returned from the predetermined value (reduction value) W13 to the set value W12.

Further, the control device 60 excites the solenoid of the traveling switching valve 34 at least during the reduction time T21, that is, before starting the control for returning the output value W11 from the predetermined value (reduction value) W13 to the set value W12. Is output to switch the traveling switching valve (switching valve) 34 from the first state (first speed) to the second state (second speed). In other words, the control device 60 returns the output value W11 to the set value W12 after switching the traveling switching valve 34 to the second state.

FIG. 2B is a diagram showing the relationship between the set value and the reduction value of the control signal when the traveling motor is decelerated from the second speed to the first speed, and the switching of the traveling motor. On the vertical axis showing the control signal of FIG. 2B, the value is low on the origin side and increases as the distance from the origin increases.
As shown in FIG. 2B, in the control device 60, the changeover switch (changeover SW) 61 is operated at the time point Q31, and the control device 60 is in the second state (second speed) to the first state (first speed). It is assumed that the command to be set (1st speed command) is acquired. When the control device 60 acquires the first speed command, the output value W11 of the control signal output to the proportional valve 69 is reduced to a predetermined value (reduction value) W14 lower than the set value W12.

Specifically, as shown in FIG. 2B, in the reduction section T31 from the set value W12 to reaching the predetermined value (reduction value) W14, the control device 60 adjusts the control signal to the proportional valve 69 by adjusting the control signal to the proportional valve 69. The section from the start point (time point Q31) of the reduction section T31 to the middle of the reduction section T31 (first section) The first reduction speed of the output value W11 of T31a is the section from the middle of the reduction section T31 to the end point (Q32) (first section). 2 sections) The output value of T31b is made larger than the second decrease rate of W11. That is, when the traveling motor is decelerated, the control device 60 steeply lowers the output value W11 toward the reduction value W14, and then gradually lowers the output value W14 toward the reduction value W14.

The decrease in the output value W11 due to the control device 60 will be described in more detail.
As shown in FIG. 1, the control device 60 has a setting unit 60A and a control unit 60B. The setting unit 60A and the control unit 60B are composed of an electric / electronic circuit provided in the control device 60, a program stored in the control device 60, and the like.
When the setting unit 60A is fixed to the second speed command, the setting value W12 is set according to the vehicle speed of the working machine and the actual rotation speed of the prime mover rotation speed.

Further, when the setting unit 60A is switched from the 2nd speed command to the 1st speed command, the setting unit 60A has a first line L1 indicating the first reduction speed of the output value W11 and a second line L2 indicating the second reduction speed of the output value W11. And call. That is, when the setting unit 60A is switched from the 2nd speed command to the 1st speed command, it shifts to the process of reducing the output value W11, and in the process, when the output value W11 is reduced in the reduction section T31, the first Control is executed so that the inflection point P25 is formed on the line (reduction line) L10 composed of the first line L1 and the second line L2.

Further, the setting unit 60A sets the inclination of the first line L1 so that the first reduction rate is constant, that is, the reduction amount per unit time (first reduction amount) is constant. Further, the setting unit 60A sets the inclination of the second line L2 so that the second reduction rate is constant, that is, the reduction amount per unit time (second reduction amount) is constant. That is, the setting unit 60A makes the inclination of the first line L1 (first decrease amount) larger than the inclination of the second line L2 (second decrease amount). In other words, the setting unit 60A makes the inclination of the second line L2 (the second decrease amount) smaller than the inclination of the first line L1 (the first decrease amount).

The control unit 60B controls the first reduction speed and the second reduction speed of the control signal (output value W11) based on the first line L1 and the second line L2 set by the setting unit 60A. That is, when the first speed command is acquired, the control unit 60B outputs a control signal to the proportional valve 69 so that the output value W11 decreases corresponding to the first line L1. Further, the control unit 60B outputs a control signal to the proportional valve 69 so that the output value W11 decreases corresponding to the second line L2.

The setting unit 60A may change either the first reduction amount or the second reduction amount based on the traveling load when switching from the second state to the first state.
As shown in FIG. 1, the traveling load can be detected by, for example, the traveling pump pressure V detected by the traveling pump pressure detecting device 80 provided in the circulating oil passages 57h and 57i. Specifically, the traveling pump pressure detecting device 80 includes a first pressure detecting device 80a, a second pressure detecting device 80b, a third pressure detecting device 80c, and a fourth pressure detecting device 80d. The first pressure detecting device 80a is provided on the first port P11 side of the left traveling motor 36L in the circulating oil passage 57h, and detects the traveling pump pressure V on the first port P11 side as the first traveling pump pressure V1. The second pressure detecting device 80b is provided on the second port P12 side of the left traveling motor 36L in the circulating oil passage 57h, and detects the traveling pump pressure V on the second port P12 side as the second traveling pump pressure V2. The third pressure detection device 80c is provided on the third port P13 side of the right traveling motor 36R in the circulation oil passage 57i, and detects the traveling pump pressure V on the third port P13 side as the third traveling pump pressure V3. The fourth pressure detecting device 80d is provided on the fourth port P14 side of the right traveling motor 36R in the circulating oil passage 57i, and detects the traveling pump pressure V on the fourth port P14 side as the fourth traveling pump pressure V4.

The setting unit 60A adopts the pressure of the hydraulic oil discharged from the traveling pump, that is, the pressure of the highest hydraulic oil among the traveling pump pressures V (V1 to V4) as the traveling load. As shown in FIG. 2B, when the traveling load is large, the setting unit 60A shifts the control signal value (inflection value) W25 of the inflection point P25 to the set value W12 side, and raises the inflection point P25. Increase the height. When the traveling load is small, the setting unit 60A shifts the inflection value W25 of the control signal of the inflection point P25 to the reduction value W14 side to lower the height of the inflection point P25.

In other words, when the traveling load is large, the setting unit 60A reduces the difference (deviation) between the set value W12 and the inflection value W25 without changing the inclinations of the first line L1 and the second line L2. .. Further, when the traveling load is small, the setting unit 60A increases the difference between the set value W12 and the inflection value W25 without changing the inclinations of the first line L1 and the second line L2.
For example, when the traveling load is larger than the reference, the setting unit 60A increases the shift amount (decreasing the deviation) for shifting the inflection value W25 toward the set value W12 as the traveling load becomes larger than the reference. .. Further, when the traveling load is smaller than the reference, the setting unit 60A reduces the shift amount (increasing the deviation) for shifting the inflection value W25 to the reduction value W14 side as the traveling load becomes smaller than the reference. ..

When the inflection value W25 of the inflection point P25 is changed by the setting unit 60A, the control unit 60B outputs a control signal to the proportional valve 69 corresponding to the changed inflection value W25.
In the above-described embodiment, the output value W11 is lowered by the first line L1 and the second line L2. However, in performing the control for lowering the output value W11 (shock reduction control), the traveling load is referred to. When the traveling load is equal to or higher than a predetermined threshold value, the control unit 60B may control the first reduction speed and the second reduction speed based on the first line L1 and the second line L2. That is, when switching for decelerating the traveling motor from the second speed to the first speed is performed, the control device 60 refers to the traveling load and sets it when it is determined that the traveling load is larger than the threshold value. After setting and changing the first lowering speed and the second lowering speed by the unit 60A, the proportional valve 69 is controlled.

In the above-described embodiment, the setting unit 60A changes the inflection value W25 at the inflection point P25 based on the traveling load, but changes it based on the load of the prime mover 32 and the rotation speed of the prime mover. May be good.
As shown in FIG. 2B, when the output value W11 reaches a predetermined value (reduced value) W14 at the time point Q32, the control device 60 (control unit 60B) returns the output value W11 to the set value W12. When returning the output value W11 to the set value W12, the control device 60 (control unit 60B) makes the return amount per unit time at the time of return larger than the second reduction amount per unit time of the second reduction speed. .. In other words, the slope of the return line L3 in the return section T32 for returning the output value W11 to the set value W12 is made gentler than the slope of the second line L2 indicating the second reduction speed.

In the above-described embodiment, when the output value W11 is lowered, the inflection point P25 is provided by the first line L1 and the second line L2, but as shown in FIG. 2C, the line L10 of the reduction section T31 is provided. It is not necessary to form the inflection point P25 by making the curve shape. In the vertical axis showing the control signal of FIG. 2C, the value is low on the origin side and increases as the distance from the origin increases.

The work machine 1 is rotatable and has a rotational speed by the prime mover 34, the traveling pumps 53L and 53R capable of changing the flow rate of the hydraulic oil discharged according to the angle of the swash plate, and the hydraulic oil discharged by the traveling pumps 53L and 53R. Is a traveling motor (first traveling motor 36L, second traveling motor 36R) capable of switching between a first speed and a second speed higher than the first speed, and a traveling motor (first traveling motor 36L, second traveling motor 36R). ) Is switched between the first state in which the rotation speed is set to the first speed and the second state in which the rotation speed of the traveling motors (first traveling motor 36L, second traveling motor 36R) is set to the second speed. The operation device 54, the operation valve 55 that can change the angle of the swash plate of the traveling pumps 53L and 53R according to the operation of the operation device 54, and the operation valve 55 on the upstream side or the downstream side of the operation valve 55. An actuating valve 69 to be connected, and a control device 60 that reduces the control signal for controlling the actuating valve 69 to a reduction value W14 lower than the set value W12 when switching from the second state to the first state, and then returns. In the reduction section T31 from the set value W12 to the reduction value W14, the control device 60 sets the first reduction speed of the control signal from the start point of the reduction section T31 to the middle of the reduction section T31 in the reduction section T31. It is made larger than the second lowering speed of the control signal from the middle to the end point. According to this, when switching from the second state to the first state (during deceleration), the shift shock can be reduced while ensuring the responsiveness of operating the traveling pumps 53L and 53R.

In the control device 60, the first line L1 in which the first reduction amount per unit time is constant and the first reduction speed from the start point to the middle is shown, and the second reduction amount per unit time is smaller than the first reduction amount. The first line is based on the setting unit 60A that sets the second line L2 that is constant and indicates the second reduction speed from the middle to the end point, and the first line L1 and the second line L2 that are set by the setting unit 60A. It has a control unit 60B for controlling the reduction speed and the second reduction speed. According to this, the first lowering speed and the second lowering speed can be easily controlled by the first line L1 and the second line L2, and the portion where the first line L1 and the second line L2 are continuous becomes an inflection point. The shift shock can be reduced smoothly.

When the traveling load is equal to or higher than a predetermined threshold value, the control unit 60B controls the first reduction speed and the second reduction speed based on the first line L1 and the second line L2. According to this, it is possible to further reduce the shift shock when decelerating in a state where the traveling load is high.
The setting unit 60A changes the value W25 of the control signal at the inflection point P25, which is the boundary between the first line L1 and the second line L2, based on the traveling load when switching from the second state to the first state. do. According to this, by changing the value W25 of the control signal according to the traveling load, it is possible to reduce the shift shock without deteriorating the responsiveness at the time of shifting (during deceleration).

The setting unit 60A adopts the highest hydraulic oil pressure among the hydraulic oil pressures discharged from the traveling pumps 53L and 53R as the traveling load. According to this, the traveling load can be easily detected.
The setting unit 60A shifts the control signal value W25 of the inflection point P25 to the set value W12 side when the traveling load is large, and reduces the control signal value W25 of the inflection point P25 when the traveling load is small. Shift to the value W14 side. According to this, it is possible to reduce the shift shock while ensuring the responsiveness of operating the traveling pumps 53L and 53R at the time of shifting (during deceleration).

When the output value W11 reaches the reduction value W14 and then the output value W11 is restored, the control device 60 sets the amount of restoration per unit time at the time of restoration to the second decrease per unit time of the second reduction rate. Make it larger than the amount. According to this, deceleration can be performed quickly while reducing the shift shock.
In the above-described embodiment, the operating valve 69 is provided on the upstream side (discharge oil passage 40) of the operating valve 55, but instead of this, it may be provided on the downstream side (running oil passage 45) of the operating valve 55. .. For example, a working valve 69 may be provided in the middle of the fifth traveling oil passage 45e, or as shown in FIG. 3, the first traveling oil passage 45a, the second traveling oil passage 45b, the third traveling oil passage 45c, An oil passage 51 may be branched from each of the fourth traveling oil passages 45d, and an operating valve 69 such as a variable relief valve or an electromagnetic proportional valve may be provided in the oil passage 51.

In the above-described embodiment, the operating valve 69 is a valve in which the opening degree increases as the value of the control signal increases and the opening degree decreases as the value of the control signal decreases. The valve may have a valve in which the opening degree decreases as the value of the control signal increases and the opening degree increases as the value of the control signal decreases. In the case of such a working valve 69 (in the case of a modified example), in FIGS. 2A to 2C, on the vertical axis showing the control signal, the value is high on the origin side and decreases as the distance from the origin increases. That is, in the case of the modified example, since the high and low of the control signal are reversed in the above-described embodiment, if the contents related to the high and low are read in reverse, the modified example will be explained. More specifically, in the above-described embodiment, "decrease" is "increase", "low" is "high", "reduction section" is "increase section", "decrease rate" is "increase rate", and "decrease amount". Can be read as "increase amount", "decrease value" as "increase value", and "decrease" as "increase" to explain the modified example.

In summary, when switching from the second state to the first state, the control device 60 increases the control signal for controlling the actuating valve 69 to an increase value W14 higher than the set value W12, and then returns. In the increase section T31 from the set value W12 to the increase value, the control device 60 sets the first increase speed of the control signal from the start point of the increase section T31 to the middle of the increase section T31 from the middle to the end point of the increase section. It is made larger than the second increasing speed of the control signal.

In the control device 60, the first line L1 in which the first increase amount per unit time is constant and the first increase rate from the start point to the middle is shown, and the second increase amount per unit time is smaller than the first increase amount. The first line is based on the setting unit 60A that sets the second line L2 that is constant and indicates the second increasing speed from the middle to the end point, and the first line L1 and the second line L2 that are set by the setting unit 60A. It has a control unit 60B that controls the increasing speed and the second increasing speed.

When the traveling load is equal to or higher than a predetermined threshold value, the control unit 60B controls the first increasing speed and the second increasing speed based on the first line L1 and the second line L2.
The setting unit 60A changes the value of the control signal at the inflection point P25, which is the boundary between the first line L1 and the second line L2, based on the traveling load when switching from the second state to the first state. ..
The setting unit 60A shifts the value of the control signal of the inflection point P25 to the set value W12 side when the traveling load is large, and increases the value of the control signal of the inflection point P25 when the traveling load is small. Shift to the side.

When the control signal returns the control signal after the control signal reaches the increase value, the control device 60 sets the return amount per unit time at the time of return to be larger than the second increase amount per unit time of the second increase rate. Enlarge.
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.

In the above-described embodiment, the switching unit is configured by the changeover switch 61 that can be manually operated by an operator or the like, but it may be built in the control device 60. When built in the control device 60, the switching unit is composed of a program, electrical, and electronic components (electronic / electronic circuits) stored in the control device 60. In this case, the switching unit of the control device 60 determines whether to switch between the first speed state and the second speed state based on the detection information from various detection devices provided in the work machine 1, for example, the sensor, and based on the judgment result. Then, a control signal is output to the traveling switching valve 34. The traveling switching valve 34 switches to the 1st speed state when the control signal in the 1st speed state is acquired, and switches to the 2nd speed state when the control signal in the 2nd speed state is acquired.

The traveling switching valve 34 is a valve that can switch between the first state in which the traveling motor (first traveling motor 36L, second traveling motor 36R) is set to the first speed and the second state in which the traveling motor is set to the second speed. Often, it may be a proportional valve different from the directional control valve.
The traveling motor may be a motor having neutrality between the first speed and the second speed.

The traveling motor (first traveling motor 36L, second traveling motor 36R) may be an axial piston motor or a radial piston motor. When the traveling motor is a radial piston motor, it is possible to switch to the first speed by increasing the motor capacity, and it is possible to switch to the second speed by reducing the motor capacity.
As described above, since the second speed (second state) may be faster than the first speed (first state), the work machine 1 is not limited to two speeds, and has multiple speeds (multiple stages). However, it can be applied.

1: Working machine 34: Travel switching valve 36L: Left travel motor (first travel motor)
36R: Right traveling motor (second traveling motor)
53L: 1st traveling pump (traveling pump)
53R: 2nd traveling pump (traveling pump)
60: Control device 60A: Setting unit 60B: Control unit 69: Proportional valve (actuated valve)
L1: 1st line L10: Reduction line L2: 2nd line L3: Return line

Claims (14)

A traveling pump that can change the flow rate of hydraulic oil to be discharged according to the angle of the swash plate,
A traveling motor that can rotate by the hydraulic oil discharged by the traveling pump and can switch between a first speed and a second speed whose rotation speed is higher than the first speed.
A traveling switching valve capable of switching between a first state in which the rotation speed of the traveling motor is set to the first speed and a second state in which the rotation speed of the traveling motor is set to the second speed.
With the operating device
An operating valve that can change the angle of the swash plate of the traveling pump according to the operation of the operating device.
An operating valve connected to the operating valve on the upstream side or the downstream side of the operating valve,
When switching from the second state to the first state, a control device that reduces the control signal for controlling the operating valve to a reduction value lower than the set value and then returns the control signal.
Equipped with
In the reduction section from the set value to the reduction value, the control device sets the first reduction speed of the control signal from the start point of the reduction section to the middle of the reduction section from the middle to the end point of the reduction section. A work machine whose control signal is made larger than the second reduction speed. The control device is
The first decrease amount per unit time is constant and the first line showing the first decrease rate from the start point to the middle, and the second decrease amount per unit time is smaller and constant than the first decrease amount. In addition, a setting unit for setting the second line indicating the second reduction speed from the middle to the end point, and
A control unit that controls the first reduction speed and the second reduction speed based on the first line and the second line set by the setting unit.
The working machine according to claim 1. 2. The control unit controls the first reduction speed and the second reduction speed based on the first line and the second line when the traveling load is equal to or higher than a predetermined threshold value. The working machine described in. The setting unit sets the value of the control signal of the inflection point which is the boundary between the first line and the second line based on the traveling load when switching from the second state to the first state. The working machine according to claim 3 to be changed. The working machine according to claim 3 or 4, wherein the setting unit adopts the pressure of the highest hydraulic oil among the pressures of the hydraulic oil discharged from the traveling pump as the traveling load. The setting unit shifts the value of the control signal of the inflection point to the set value side when the traveling load is large, and shifts the value of the control signal of the inflection point to the setting value side when the traveling load is small. The working machine according to claim 4, which shifts to the reduced value side. When the control signal is restored after the control signal reaches the reduction value, the control device sets the amount of restoration per unit time at the time of restoration to the second reduction rate per unit time. The working machine according to any one of claims 1 to 6, wherein the amount of reduction is larger than the amount of reduction. The prime mover and
A traveling pump that can change the flow rate of hydraulic oil to be discharged according to the angle of the swash plate,
A traveling motor that can rotate by the hydraulic oil discharged by the traveling pump and can switch between a first speed and a second speed whose rotation speed is higher than the first speed.
A traveling switching valve capable of switching between a first state in which the rotation speed of the traveling motor is set to the first speed and a second state in which the rotation speed of the traveling motor is set to the second speed.
With the operating device
An operating valve that can change the angle of the swash plate of the traveling pump according to the operation of the operating device.
An actuating valve arranged on the upstream side or the downstream side of the operation valve,
When switching from the second state to the first state, a control device that increases the control signal for controlling the actuated valve to an increase value higher than the set value and then returns the control signal.
Equipped with
In the increase section from the set value to the increase value, the control device sets the first increase speed of the control signal from the start point of the increase section to the middle of the increase section from the middle to the end point of the increase section. A working machine that makes the control signal larger than the second increasing speed. The control device is
The first line showing the first increase rate from the start point to the middle, and the second increase amount per unit time are smaller and constant than the first increase amount per unit time. In addition, a setting unit for setting the second line indicating the second increasing speed from the middle to the end point, and
A control unit that controls the first increasing speed and the second increasing speed based on the first line and the second line set by the setting unit.
The working machine according to claim 8. 9. The control unit controls the first increasing speed and the second increasing speed based on the first line and the second line when the traveling load is equal to or higher than a predetermined threshold value. The working machine described in. The setting unit sets the value of the control signal of the inflection point which is the boundary between the first line and the second line based on the traveling load when switching from the second state to the first state. The working machine according to claim 10. The working machine according to claim 10 or 11, wherein the setting unit adopts the pressure of the highest hydraulic oil among the pressures of the hydraulic oil discharged from the traveling pump as the traveling load. The setting unit shifts the value of the control signal of the inflection point to the set value side when the traveling load is large, and shifts the value of the control signal of the inflection point to the setting value side when the traveling load is small. The working machine according to claim 11, which shifts to the increasing value side. When the control signal is restored after the control signal reaches the increase value, the control device sets the amount of restoration per unit time at the time of restoration to the second increase rate per unit time. The working machine according to any one of claims 8 to 13, which is made larger than the increased amount.

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