Work Machine

Abstract

To enable appropriate reduction of gear-changing shock of work machines.SOLUTION: A work machine comprises: a machine body 2; a driving pump 53; a travel changeover valve 34 which can change the revolution speed of a driving motor 36 to a first state that is capable of increasing to a first maximum speed and to a second state that is capable of increasing to a second maximum speed that is greater than the first maximum speed; and a control unit 60 which reduces the volume of the hydraulic oil supplied from the driving pump 53 to the driving motor 36 according to a travel condition of the machine body 2 when a changeover switch 61 gives an order to increase or reduce the speed. The control unit 60, when it is in speed-increase processing, switches the travel changeover valve 34 from the first state to the second sate during a prior period before reduction of the supply volume to the driving motor 36, during a recovery period in which the supply volume to the driving motor 36, upon having been reduced, is being recovered, or after the recovery.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a work machine such as a skid steer loader, a compact track loader, a backhoe, or the like. [Background technology]

[0002] Conventionally, a technology for decelerating and accelerating a working machine is disclosed in Patent Document 1. The working machine disclosed in Patent Document 1 includes a prime mover, a hydraulic pump that is operated by the operation of the prime mover and discharges hydraulic oil, a hydraulic switch valve that can be switched to a plurality of switch positions depending on the pressure of the hydraulic oil, a proportional valve that can change the hydraulic oil acting on the hydraulic switch valve, a traveling hydraulic device that can change the speed depending on the switch position of the hydraulic switch valve, and a control device that controls the proportional valve depending on the traveling state of the working machine or the state of the prime mover. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2017-179922 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the work machine of Patent Document 1, the pressure characteristics of the hydraulic switching valve are changed when the work machine is decelerated, thereby reducing shift shock (impact, discomfort). However, in a work machine in which shift timing is shifted due to variations in response delay of the rotation of the hydraulic equipment or prime mover, the shift shock may not be reduced. The present invention has been made to solve the problems of the conventional technology as described above, and has an object to provide a work machine capable of appropriately reducing gear change shock. [Means for solving the problem]

[0005] The technical means adopted by the present invention to solve the technical problems are as follows. A work machine according to one aspect of the present invention comprises a prime mover, a travel pump operated by the power of the prime mover and discharging hydraulic oil, a travel motor that can be rotated by the hydraulic oil discharged by the travel pump, a machine body provided with the prime mover, the travel pump, and the travel motor, a travel switch valve that can switch between a first state in which the rotation speed of the travel motor can be increased to a first maximum speed and a second state in which the rotation speed of the travel motor can be increased to a second maximum speed that is higher than the first maximum speed, a travel operation device having an operation valve that can change the pressure of hydraulic oil acting on the travel pump in response to operation of an operation member, and a control device that reduces the amount of hydraulic oil supplied from the travel pump to the travel motor based on the travel state of the machine body when performing either an acceleration process for switching from the first state to the second state or a deceleration process for switching from the second state to the first state, and the control device reduces the amount of hydraulic oil supplied from the travel pump to the travel motor based on the travel state of the machine body when performing the acceleration process. ,before The travel switching valve is switched from the first state to the second state during a middle recovery period or a post recovery period in which the supply amount to the travel motor is restored after being reduced.

[0006] Moreover, a work machine according to one aspect of the present invention includes a prime mover, a travel pump operated by power of the prime mover and discharging hydraulic oil, a travel motor that can be rotated by hydraulic oil discharged by the travel pump, a machine body provided with the prime mover, the travel pump, and the travel motor, a travel switch valve that can switch between a first state in which the rotation speed of the travel motor can be increased to a first maximum speed and a second state in which the rotation speed of the travel motor can be increased to a second maximum speed that is higher than the first maximum speed, a travel operation device having an operation valve that can change the pressure of hydraulic oil acting on the travel pump in response to operation of an operation member, and a control device that reduces the amount of hydraulic oil supplied from the travel pump to the travel motor based on the travel state of the machine body when performing either an acceleration process for switching from the first state to the second state or a deceleration process for switching from the second state to the first state, and the control device reduces the amount of hydraulic oil supplied from the travel pump to the travel motor based on the travel state of the machine body when performing the deceleration process. ,beforeThe travel changeover valve is switched from the second state to the first state during a middle decrease period or a late return period in which the amount of power supplied to the travel motor is decreased.

[0007] In the work machine according to one aspect of the present invention, when the control device performs the deceleration process, ,before The travel changeover valve is switched from the second state to the first state during a middle decrease period or a late return period in which the amount of power supplied to the travel motor is decreased. In addition, in one embodiment of the work machine of the present invention, a travel detection device is provided that can detect the travel speed of the machine body as the travel state, and when performing the speed increase processing, the control device determines an amount of reduction in the supply amount to the travel motor that corresponds to the travel speed detected by the travel detection device, and reduces the supply amount to the travel motor in accordance with the determined amount of reduction. In addition, in one embodiment of the work machine of the present invention, a travel detection device is provided that can detect the travel speed of the machine body as the travel state, and when performing the deceleration processing, the control device determines an amount of reduction in the supply amount to the travel motor that corresponds to the travel speed detected by the travel detection device, and reduces the supply amount to the travel motor in accordance with the determined amount of reduction.

[0008] In addition, a working machine according to one aspect of the present invention includes a switching unit that issues a speed change command to either increase or decrease speed, and an accelerator that operates the rotation speed of the prime mover, and the control device reduces the amount of hydraulic oil supplied from the travel pump to the travel motor by reducing the rotation speed of the prime mover, and when the control device receives the speed change command to increase speed from the switching unit, ,before During a middle or post-return period in which the rotation speed of the prime mover is restored after being reduced below a target rotation speed, which is the rotation speed of the prime mover operated by the accelerator, the travel changeover valve is switched from the first state to the second state in response to the shift command.

[0009] In addition, a working machine according to one aspect of the present invention includes a switching unit that issues a speed change command to either increase or decrease speed, and an accelerator that operates the rotation speed of the prime mover, and the control device reduces the amount of hydraulic oil supplied from the travel pump to the travel motor by reducing the rotation speed of the prime mover, and when the control device receives the speed change command to decrease speed from the switching unit, ,before During a middle period of reduction or a late period of recovery in which the rotation speed of the prime mover is reduced below a target rotation speed, which is the rotation speed of the prime mover operated by the accelerator, the travel changeover valve is switched from the second state to the first state in response to the shift command.

[0010] In the working machine according to one aspect of the present invention, when the control device receives the speed change command for deceleration from the switching unit, ,before During a middle period of decrease or a post-return period in which the rotation speed of the prime mover is decreased below the target rotation speed operated by the accelerator, the travel changeover valve is switched from the second state to the first state in response to the shift command.

[0011] Moreover, a work machine according to one embodiment of the present invention includes a switching unit that issues a speed change command to either increase or decrease speed, and an operating valve that is connected to the operating valve on the upstream or downstream side of the operating valve and is capable of controlling hydraulic oil flowing through the operating valve, and when the control device issues a speed change command to increase speed to the switching unit, the control device switches the travel switching valve from the first state to the second state in response to the speed change command during a preliminary period until the operating valve starts to decrease in opening degree, a middle recovery period or a post recovery period in which the opening degree of the operating valve is restored after being decreased.

[0012] In addition, a work machine of one embodiment of the present invention includes a switching unit that issues a speed change command to either increase or decrease speed, and an operating valve that is connected to the operating valve on the upstream or downstream side of the operating valve and is capable of controlling the hydraulic oil flowing through the operating valve, and when the switching unit receives the speed change command to decrease speed, the control device switches the travel switching valve from the second state to the first state in response to the speed change command during a preliminary period until the opening of the operating valve starts to decrease, a reduction period during which the opening of the operating valve is reduced, or a post-return period. Furthermore, in the work machine of one aspect of the present invention, when the switching unit receives a speed change command to decelerate, the control device switches the travel switching valve from the second state to the first state in response to the speed change command during a preliminary period until the reduction in the opening degree of the actuating valve begins, a reduction period in which the opening degree of the actuating valve is reduced, or a post-return period.

[0013] In addition, a work machine of one aspect of the present invention includes a switching unit that issues a speed change command to either increase or decrease speed, an accelerator that operates the rotation speed of the prime mover, and an operating valve that is connected to the operating valve on the upstream or downstream side of the operating valve and is capable of controlling hydraulic oil flowing through the operating valve, and when the switching unit receives the speed change command to increase speed, the control device switches the traveling switch valve from the first state to the second state in response to the speed change command during an advance period until a decrease in an opening degree of the operating valve starts, and during a middle or post-return period in which the opening degree of the operating valve is restored after the decrease in the opening degree of the operating valve is restored, and when the switching unit receives the speed change command to decrease speed, the control device switches the traveling switch valve from the second state to the first state in response to the speed change command during an advance period until a decrease in the rotation speed of the prime mover starts, and during a middle or post-return period in which the rotation speed of the prime mover is decreased below a target rotation speed, which is the rotation speed of the prime mover operated by the accelerator.

[0014] In the work machine according to one aspect of the present invention, the changeover unit is a changeover switch that outputs the speed change command to the control device. In the work machine according to one aspect of the present invention, when the speed increasing process is performed, the control device Reduce the supply to the drive motor The absolute value of the gradient of the supply amount to the operating valve is set smaller than that in the middle period of decrease. In the work machine according to one aspect of the present invention, the control device is configured to perform the deceleration process in the lowering intermediate period. To restore the supply amount to the traveling motor after the supply amount has been reduced The absolute value of the gradient of the supply amount to the operating valve is set smaller than that in the intermediate return period. Effect of the Invention

[0015] According to the present invention, it is possible to appropriately reduce the speed change shock of the work machine. [Brief description of the drawings]

[0016] [Figure 1] FIG. 1 is a diagram showing a hydraulic system (hydraulic circuit) of a work machine in a first embodiment. [Figure 2A] 11 is a diagram showing the relationship between the rotation speed of the prime mover and switching of the traveling motor when the traveling motor is accelerated. FIG. [Figure 2B] 11 is a diagram showing the relationship between the rotation speed of the prime mover and switching of the traveling motor when the traveling motor is decelerated. FIG. [Figure 2C] FIG. 13 illustrates an example of a storage table. [Figure 2D] FIG. 13 is a diagram showing how the delay period is changed based on the forward traveling pressure and the reverse traveling pressure. [Figure 2E] 11 is a diagram showing the relationship between the rotation speed of the prime mover and switching of the traveling motor when the traveling motor is accelerated. FIG. [Figure 2F] 11 is a diagram showing the relationship between the rotation speed of the prime mover and switching of the traveling motor when the traveling motor is decelerated. FIG. [Figure 2G] 11 is a diagram showing the relationship between the rotation speed of the prime mover and switching of the traveling motor when the traveling motor is accelerated. FIG. [Figure 2H] 11 is a diagram showing the relationship between the rotation speed of the prime mover and switching of the traveling motor when the traveling motor is decelerated. FIG. [Figure 3A] 4 is a flowchart of a first operation of the control device when the speed of the traveling motor is increased. [Figure 3B] 6 is a flowchart of a second operation of the control device when the traveling motor is decelerated. [Figure 3C] FIG. 13 is a flowchart showing a process of changing the gear shift switching delay period by the control device when accelerating forward. [Figure 3D] FIG. 13 is a flowchart showing a process of changing the gear shift switching delay period by the control device when decelerating forward. [Figure 3E]FIG. 11 is a flowchart showing a process of changing the gear shift switching delay period of the control device when accelerating forward in the second embodiment. [Figure 3F] FIG. 11 is a flowchart showing a process of changing the gear shift switching delay period by the control device during forward deceleration in the second embodiment. [Figure 4A] 13 is a diagram showing the relationship between the swash plate angle of the travel pump and switching of the travel motor when the speed of the travel motor is increased. FIG. [Figure 4B] 11 is a diagram showing the relationship between the swash plate angle of the travel pump and switching of the travel motor when the travel motor is decelerated. FIG. [Figure 4C] 13 is a diagram showing the relationship between the swash plate angle of the travel pump and switching of the travel motor when the speed of the travel motor is increased. FIG. [Figure 4D] 11 is a diagram showing the relationship between the swash plate angle of the travel pump and switching of the travel motor when the travel motor is decelerated. FIG. [Figure 4E] 13 is a diagram showing the relationship between the swash plate angle of the travel pump and switching of the travel motor when the speed of the travel motor is increased. FIG. [Figure 4F] 11 is a diagram showing the relationship between the swash plate angle of the travel pump and switching of the travel motor when the travel motor is decelerated. FIG. [Figure 5A] 10 is a flowchart of a third operation of the control device when the speed of the traveling motor is increased. [Figure 5B] 13 is a flowchart of a fourth operation of the control device when the traveling motor is decelerated. [Figure 6A] FIG. 11 is a diagram showing a hydraulic system (hydraulic circuit) of a work machine in a third embodiment. [Figure 6B] FIG. 13 is a diagram showing a part of a hydraulic system (hydraulic circuit) of a work machine in a fourth modified example. [Figure 6C] FIG. 13 is a diagram showing a part of a hydraulic system (hydraulic circuit) of a work machine in a fifth modified example. [Figure 7A] FIG. 11 is a diagram showing a hydraulic system (hydraulic circuit) of a work machine in a fourth embodiment. [Figure 7B] FIG. 13 is a diagram showing a hydraulic system (hydraulic circuit) of a work machine in a fifth embodiment. [Figure 8A] 1 is a table showing the relationship between the actual rotation speed W1 of the prime mover, the traveling pilot pressure, and the reduction amount ΔD1 of the prime mover rotation speed. [Figure 8B] This is the graph of Figure 8A. [Figure 9A] 11 is a table showing the relationship between the travel pilot pressure and the reduction amount (reduction amount ΔD2) of the travel pilot pressure. [Figure 9B] This is the graph of Figure 9A. [Figure 10] FIG. 1 is a side view showing a track loader as an example of a work machine. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of a hydraulic system for a work machine and a work machine equipped with this hydraulic system according to the present invention will be described with reference to the drawings as appropriate. [First embodiment] Fig. 10 shows a side view of a working machine 1 according to the present invention. Fig. 10 shows a compact track loader as an example of the working machine 1. However, the working machine according to the present invention is not limited to a compact track loader, and may be, for example, another type of loader working machine, such as a skid steer loader. Also, the working machine may be a working machine other than a loader working machine.

[0018] As shown in FIG. 10, the working machine 1 includes a machine body 2, a cabin 3, a working device 4, and a traveling device 5. In the first embodiment of the present invention, the direction in which the driver seated in the driver's seat 8 of the working machine 1 faces (the left side of FIG. 10) is referred to as the front, and the opposite direction (the right side of FIG. 10) is referred to as the rear. The left side of the driver (the near side of FIG. 10) is referred to as the left side, and the right side of the driver (the far side of FIG. 10) is referred to as the right side. The horizontal direction perpendicular to the front-rear direction is referred to as the machine body width direction, and the direction from the center of the machine body 2 to the right or left side is referred to as the machine body outside. In other words, the machine body outside is the machine body width direction, and is the direction away from the machine body 2. The opposite direction to the machine body outside is referred to as the machine body inside. In other words, the machine body inside is the machine body width direction, and is the direction approaching the machine body 2.

[0019] The cabin 3 is mounted on the machine body 2. A driver's seat 8 is provided in the cabin 3. 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 prime mover 32 is mounted at the rear inside the machine body 2. The working device 4 has a boom 10, a bucket 11 which is an example of a working tool, a lift link 12, a control link 13, a boom cylinder 14, and a bucket cylinder 15.

[0020] The boom 10 is provided on the right and left sides of the cabin 3 so as to be able to swing up and down. The bucket 11 is provided on the tip (front end) of the boom 10 so as to be able to swing up and down. A lift link 12 and a control link 13 support the base (rear) of the boom 10 so that the boom 10 can swing up and down. The boom cylinder 14 raises and lowers the boom 10 by extending and retracting. The bucket cylinder 15 swings the bucket 11 by extending and retracting. The front portions of the left and right booms 10 are connected to each other by a connecting pipe having an irregular shape, and the base portions (rear portions) of the booms 10 are connected to each other by a circular connecting pipe.

[0021] The lift link 12, the control link 13 and the boom cylinder 14 are provided on the left and right sides of the machine body 2 corresponding to the left and right booms 10, respectively. The lift link 12 is provided vertically at the rear of the base of each boom 10. An upper portion (one end side) of this lift link 12 is pivoted rotatably about a horizontal axis via a pivot shaft (e.g., a first pivot shaft 16) near the rear of the base of each boom 10. A lower portion (the other end side) of the lift link 12 is pivoted rotatably about a horizontal axis via a pivot shaft (e.g., a second pivot shaft 17) near the rear of the aircraft body 2. The second pivot shaft 17 is provided below the first pivot shaft 16.

[0022] An upper portion of the boom cylinder 14 is pivoted to be rotatable about a horizontal axis via a pivot shaft (e.g., a third pivot shaft 18). The third pivot shaft 18 is the base of each boom 10 and is provided at the front of the base. A lower portion of the boom cylinder 14 is pivoted to be rotatable about a horizontal axis via a pivot shaft (e.g., a fourth pivot shaft 19). The fourth pivot shaft 19 is provided below the third pivot shaft 18, toward the lower rear portion of the machine body 2.

[0023] The control link 13 is provided in front of the lift link 12. One end of the control link 13 is pivoted to be rotatable about a horizontal axis via a pivot shaft (e.g., the fifth pivot shaft 20). The fifth pivot shaft 20 is provided on the aircraft body 2 at a position corresponding to the front of the lift link 12. The other end of the control link 13 is pivoted to be rotatable about a horizontal axis via a pivot shaft (e.g., the sixth pivot shaft 21). The sixth pivot shaft 21 is provided on the boom 10, in front of and above the second pivot shaft 17.

[0024] By extending and retracting the boom cylinder 14, the base of each boom 10 is supported by the lift link 12 and the control link 13, while each boom 10 swings up and down about the first pivot shaft 16, and the tip of each boom 10 rises and falls. The control link 13 swings up and down about the fifth pivot shaft 20 in conjunction with the up and down swing of each boom 10. The lift link 12 swings back and forth about the second pivot shaft 17 in conjunction with the up and down swing of the control link 13.

[0025] Instead of the bucket 11, another working tool can be attached to the front of the boom 10. The other working tool can be, for example, an attachment (spare attachment) such as a hydraulic crusher, a hydraulic breaker, an angle broom, an earth auger, a pallet fork, a sweeper, a mower, or a snow blower. A connection member 50 is provided at the front of the left boom 10. The connection member 50 is a device that connects hydraulic equipment provided on the spare attachment to a first tubular member such as a pipe provided on the boom 10. Specifically, the first tubular member can be connected to one end of the connection member 50, and the second tubular member connected to the hydraulic equipment of the spare attachment can be connected to the other end. This allows the hydraulic oil flowing through the first tubular member to pass through the second tubular member and be supplied to the hydraulic equipment.

[0026] The bucket cylinders 15 are disposed near the front of each boom 10. By extending and contracting the bucket cylinders 15, the bucket 11 is swung. In this embodiment, crawler type (including semi-crawler type) traveling devices are used as the left and right traveling devices (first traveling device, second traveling device) 5. Note that wheel-type traveling devices having front and rear wheels may also be used.

[0027] The prime mover 32 is an internal combustion engine such as a diesel engine or a gasoline engine, an electric motor, etc. In this embodiment, the prime mover 32 is a diesel engine, but is not limited to this. Next, the hydraulic system of the work machine 1 will be described. 1, the hydraulic system of the work machine 1 is capable of driving the traveling device 5. The hydraulic system of the work machine 1 includes a first traveling pump 53L, a second traveling pump 53R, a first traveling motor 36L, and a second traveling motor 36R.

[0028] The first travel pump 53L and the second travel pump 53R are pumps driven by the power of the prime mover 32. Specifically, the first travel pump 53L and the second travel pump 53R are swash plate type variable displacement axial pumps driven by the power of the prime mover 32. The first travel pump 53L and the second travel pump 53R have a forward pressure receiving portion 53a and a reverse pressure receiving portion 53b on which a pilot pressure acts. The angle of the swash plate of the first travel pump 53L and the second travel pump 53R is changed by the pilot pressure acting on the forward pressure receiving portion 53a and the reverse pressure receiving portion 53b. By changing the angle of the swash plate, the output (discharge amount of hydraulic oil) and the discharge direction of the hydraulic oil of the first travel pump 53L and the second travel pump 53R can be changed. The first travel pump 53L and the first travel motor 36L are connected by a circulation oil passage 57h, and the hydraulic oil discharged by the first travel pump 53L is supplied to the first travel motor 36L. The second travel pump 53R and the second travel motor 36R are connected by a circulation oil passage 57i, and the hydraulic oil discharged by the second travel pump 53R is supplied to the second travel motor 36R.

[0029] 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 hydraulic oil discharged from the first traveling pump 53L, and the rotation speed (number of rotations) 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 (number of rotations) of the first traveling motor 36L can also be changed by extending or retracting the swash plate switching cylinder 37L to one side or the other side. 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 (a first speed range up to a first maximum speed: hereinafter, appropriately abbreviated as "first speed"), and when the swash plate switching cylinder 37L is extended, the rotation speed of the first traveling motor 36L is set to a high speed (a second speed range up to a second maximum speed higher than the first maximum speed: hereinafter, appropriately abbreviated as "second speed"). That is, the rotation speed of the first traction motor 36L can be changed between a first speed, which is a low speed, and a second speed, which is a high speed.

[0030] 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 hydraulic oil discharged from the second traveling pump 53R, and the rotation speed (number of rotations) 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 (number of rotations) of the second traveling motor 36R can also be changed by expanding or contracting the swash plate switching cylinder 37R to one side or the other side. 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 expanded, the rotation speed of the second traveling motor 36R is set to a high speed (second speed). That is, the rotation speed of the second traveling motor 36R can be changed between a first speed, which is a low speed, and a second speed, which is a high speed.

[0031] 1, the hydraulic system of the work machine 1 includes a travel switching valve 34. The travel switching valve 34 is switchable between a first state in which the rotation speed (revolutions) of the travel motors 36 (first travel motor 36L, second travel motor 36R) can be increased to a first maximum speed, and a second state in which the rotation speed (revolutions) can be increased to a second maximum speed that is higher than the first maximum speed. The travel switching valve 34 includes first switching valves 71L, 71R and a second switching valve 72. The first switching valve 71L is connected to the swash plate switching cylinder 37L of the first traveling motor 36L via an oil passage and is a two-position switching valve that can be switched between a first position 71L1 and a second position 71L2. When the first switching valve 71L is in the first position 71L1, the swash plate switching cylinder 37L is contracted, and when the first switching valve 71L is in the second position 71L2, the swash plate switching cylinder 37L is extended.

[0032] The first switching valve 71R is connected to the swash plate switching cylinder 37R of the second traveling motor 36R through an oil passage. The first switching valve 71R is a two-position switching valve that is connected to the first position 71R1 and is switchable between a first position 71R1 and a second position 71R2. When the first switching valve 71R is in the first position 71R1, the swash plate switching cylinder 37R is contracted, and when the first switching valve 71R is in the second position 71R2, the swash plate switching cylinder 37R is extended. The second switching valve 72 is a solenoid valve that switches the first switching valve 71L and the first switching valve 71R, and is a two-position switching valve that can be switched between a first position 72a and a second position 72b by excitation. The second switching valve 72, the first switching valve 71L, and the first switching valve 71R are connected by an oil passage 41. When the second switching valve 72 is in the first position 72a, the second switching valve 72 switches the first switching valve 71L and the first switching valve 71R to the first positions 71L1 and 71R1, and when the second position 72b, the first switching valve 71L and the first switching valve 71R to the second positions 71L2 and 71R2.

[0033] In other words, 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 first switching valve 71R is in the first position 71R1, the travel switching valve 34 is in the first state, and the rotation speed of the travel motor 36 (first travel motor 36L, second travel 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 first switching valve 71R is in the second position 71R2, the travel switching valve 34 is in the second state, and the rotation speed of the travel motor 36 (first travel motor 36L, second travel motor 36R) is set to the second speed. Therefore, the travel switching valve 34 can switch the travel motor 36 (first travel motor 36L, second travel motor 36R) between a first speed, which is the low speed side, and a second speed, which is the high speed side.

[0034] The travel motor 36 can be switched between the first speed and the second speed by a switching unit (changeover switch 61). The changeover switch 61 is connected to, for example, the control device 60, and issues a speed change command to either increase or decrease speed in response to an operation by an operator or the like. The changeover switch 61 can be switched to either increase speed by switching from the first speed (first state) to the second speed (second state), or decrease speed by switching from the second speed (second state) to the first speed (first state). In other words, the changeover switch 61 outputs an increase speed command (second speed command) or a decrease speed command (first speed command) to the control device 60.

[0035] The control device 60 is composed of semiconductors such as a CPU and an MPU, and electric and electronic circuits. The control device 60 switches the traveling switching valve 34 based on the switching operation of a change-over switch 61. The change-over switch 61 is a push switch. For example, when the change-over switch 61 is pressed while the traveling motor 36 is at a first speed, the change-over switch 61 outputs an increase in speed command to the control device 60. The increase in speed command is a command to change the traveling motor 36 to a second speed (a command to change the traveling switching valve 34 to the second state). In addition, when the change-over switch 61 is pressed while the traveling motor 36 is at the second speed, the change-over switch 61 outputs a deceleration command to the control device 60. The deceleration command is a command to change the traveling motor 36 to the first speed (a command to change the traveling switching valve 34 to the first state). In addition, the change-over switch 61 may be a push switch that can be held ON / OFF, and when it is OFF, a command to hold the traveling motor 36 at a first speed is output to the control device 60, and when it is ON, a command to hold the traveling motor 36 at a second speed is output to the control device 60.

[0036] When the control device 60 receives a deceleration command, it de-energizes the solenoid of the second switching valve 72, thereby putting the traveling switching valve 34 in the first state. When the control device 60 receives a speed increase command, it excites the solenoid of the second switching valve 72, thereby putting the traveling switching valve 34 in the second state. The hydraulic system of the work machine 1 includes a first hydraulic pump P1, a second hydraulic pump P2, and a traveling operation device 54. The first hydraulic pump P1 is a pump driven by the power of the prime mover 32, and is configured by a fixed displacement gear pump. The first hydraulic pump P1 is capable of discharging 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 that stores the hydraulic oil may be referred to as a hydraulic oil tank. Furthermore, of 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.

[0037] The second hydraulic pump P2 is a pump driven by the power of the prime mover 32 and is a fixed displacement type. The second hydraulic pump P2 is configured by a gear pump. The second hydraulic pump P2 is capable of discharging hydraulic oil stored in the tank 22, and supplies hydraulic oil to, for example, an oil passage of a work system. For example, the second hydraulic pump P2 supplies hydraulic oil to a boom cylinder 14 that operates the boom 10, a bucket cylinder 15 that operates the bucket, and a control valve (flow control valve) that controls a standby hydraulic actuator that operates a standby hydraulic actuator.

[0038] The travel operation device 54 is a device that operates the travel pumps 53 (first travel pump 53L, second travel pump 53R) and is capable of changing the angle of the swash plate (swash plate angle) of the travel pumps 53. The travel operation device 54 includes an operation lever 59 (operation member) and a plurality of operation valves 55. The operating lever 59 is supported by the operating valve 55 and is an operating lever that swings left and right (aircraft width direction) or front and rear. That is, with the neutral position N as a reference, the operating lever 59 can be operated to the right and left from the neutral position N, and can also be operated forward and rearward from the neutral position N. In other words, the operating lever 59 can swing in at least four directions with the neutral position N as a reference. For ease of explanation, both the forward and rearward directions, i.e., the front and rear directions, are referred to as the first direction. Also, both the right and left directions, i.e., the left and right directions (aircraft width direction), are sometimes referred to as the second direction.

[0039] Further, the multiple control valves 55 are commonly operated, that is, by a single control lever 59. The multiple control valves 55 operate based on the swinging of the control lever 59. A discharge oil passage 40 is connected to the multiple control valves 55, and hydraulic oil (pilot oil) can be supplied from the first hydraulic pump P1 via the discharge oil passage 40. The multiple control valves 55 are control valve 55A, control valve 55B, control valve 55C, and control valve 55D.

[0040] In the front-rear direction (first direction), when the operating lever 59 is swung forward (one side) (when operated forward), the pressure of the hydraulic oil output by the operating valve 55A changes according to the operation amount (operation) of the forward operation. In the front-rear direction (first direction), when the operating lever 59 is swung backward (the other side) (when operated backward), the pressure of the hydraulic oil output by the operating valve 55B changes according to the operation amount (operation) of the backward operation. In the left-right direction (second direction), when the operating lever 59 is swung right (one side) (when operated right), the pressure of the hydraulic oil output by the operating valve 55C changes according to the operation amount (operation) of the right operation. In the left-right direction (second direction), when the operating lever 59 is swung left (the other side) (when operated left), the pressure of the hydraulic oil output by the operating valve 55D changes according to the operation amount (operation) of the left operation.

[0041] The multiple operating valves 55 and the travel pumps 53 (first travel pump 53L, second travel pump 53R) are connected by the travel oil passage 45. In other words, the travel pumps 53 (first travel pump 53L, second travel pump 53R) are hydraulic devices that can be operated by hydraulic oil output from the operating valves 55 (operation valve 55A, operation valve 55B, operation valve 55C, operation valve 55D).

[0042] The travel oil passage 45 has a first travel oil passage 45a, a second travel oil passage 45b, a third travel oil passage 45c, a fourth travel oil passage 45d, and a fifth travel oil passage 45e. The first travel oil passage 45a is an oil passage connected to the forward pressure receiving portion 53a of the first travel pump 53L. The second travel oil passage 45b is an oil passage connected to the reverse pressure receiving portion 53b of the first travel pump 53L. The third travel oil passage 45c is an oil passage connected to the forward pressure receiving portion 53a of the second travel pump 53R. The fourth travel oil passage 45d is an oil passage connected to the reverse pressure receiving portion 53b of the second travel pump 53R. The fifth travel oil passage 45e is an oil passage connecting the operation valve 55, the first travel oil passage 45a, the second travel oil passage 45b, the third travel oil passage 45c, and the fourth travel oil passage 45d.

[0043] When the operating lever 59 is swung forward (in the direction of arrow A1 in FIG. 1), the operating valve 55A is operated and pilot pressure is output from the operating valve 55A. This pilot pressure acts on the forward pressure receiving portion 53a of the first traveling pump 53L via the first traveling oil passage 45a and also acts on the forward pressure receiving portion 53a of the second traveling pump 53R via the third traveling oil passage 45c. This changes the swash plate angle of the first traveling pump 53L and the second traveling pump 53R, and the first traveling motor 36L and the second traveling motor 36R rotate forward (forward rotation), causing the work machine 1 to move straight forward.

[0044] When the operating lever 59 is swung backward (in the direction of the arrow A2 in FIG. 1), the operating valve 55B is operated, and pilot pressure is output from the operating valve 55B. This pilot pressure acts on the reverse pressure receiving portion 53b of the first travel pump 53L via the second travel oil passage 45b, and also acts on the reverse pressure receiving portion 53b of the second travel pump 53R via the fourth travel oil passage 45d. This changes the swash plate angles of the first travel pump 53L and the second travel pump 53R, causing the first travel motor 36L and the second travel motor 36R to rotate in the reverse direction (reverse rotation), causing the work machine 1 to move straight backward.

[0045] Furthermore, when the operating lever 59 is swung to the right (the direction of arrow A3 in FIG. 1), the operating valve 55C is operated and pilot pressure is output from the operating valve 55C. This pilot pressure acts on the forward pressure receiving portion 53a of the first traveling pump 53L via the first traveling oil passage 45a, and also acts on the reverse pressure receiving portion 53b of the second traveling pump 53R via the fourth traveling oil passage 45d. This changes the swash plate angles of the first traveling pump 53L and the second traveling pump 53R, causing the first traveling motor 36L to rotate forward and the second traveling motor 36R to rotate reversely, causing the work machine 1 to swing to the right.

[0046] Furthermore, when the operating lever 59 is swung to the left (the direction of arrow A4 in FIG. 1), the operating valve 55D is operated and pilot pressure is output from the operating valve 55D. This pilot pressure acts on the forward pressure receiving portion 53a of the second traveling pump 53R via the third traveling oil passage 45c, and also acts on the reverse pressure receiving portion 53b of the first traveling pump 53L via the second traveling oil passage 45b. This changes the swash plate angles of the first traveling pump 53L and the second traveling pump 53R, causing the first traveling motor 36L to rotate in the reverse direction and the second traveling motor 36R to rotate in the forward direction, causing the work machine 1 to swing to the left.

[0047] In addition, when the operating lever 59 is swung diagonally, the rotation direction and rotation speed of the first traveling motor 36L and the second traveling motor 36R are determined by the differential pressure acting on the forward pressure receiving portion 53a and the reverse pressure receiving portion 53b, and the work machine 1 turns right or left while moving forward or backward. In other words, when the operating lever 59 is swung diagonally forward to the left, the work machine 1 turns left while moving forward at a speed corresponding to the swing angle of the operating lever 59, when the operating lever 59 is swung diagonally forward to the right, the work machine 1 turns right while moving forward at a speed corresponding to the swing angle of the operating lever 59, when the operating lever 59 is swung diagonally backward to the left, the work machine 1 turns left while moving backward 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 right, the work machine 1 turns right while moving backward at a speed corresponding to the swing angle of the operating lever 59.

[0048] An accelerator 65 that sets the prime mover rotation speed is connected to the control device 60. The accelerator 65 is provided near the driver's seat 8. The accelerator 65 may be an accelerator lever supported so as to be able to swing, an accelerator pedal supported so as to be able to swing, an accelerator volume supported so as to be able to rotate, an accelerator slider supported so as to be able to slide, or the like. It should be noted that the accelerator 65 is not limited to the above-mentioned example. A rotation detection device 66 that detects the rotation speed of the prime mover 32 is also connected to the control device 60. The rotation detection device 66 enables the control device 60 to grasp the actual rotation speed (real rotation speed) of the prime mover 32. The control device 60 sets a target prime mover rotation speed (target rotation speed) based on the amount of operation of the accelerator 65, and controls the actual rotation speed so that it becomes the set target rotation speed.

[0049] A rotation detection sensor 64 that detects the rotation speed and rotation direction of the travel motors 36 (first travel motor 36L and second travel motor 36R) is also connected to the control device 60. The rotation detection sensor 64 enables the control device 60 to grasp the rotation speed and rotation direction of the travel motors 36. Now, when the travel switching valve 34 is switched from the first state to the second state and when it is switched from the second state to the first state, i.e., when the rotational speed of the travel motor 36 is increased from the first speed to the second speed and when it is decreased from the second speed to the first speed, the control device 60 performs control to reduce gear shift shock by reducing the amount of hydraulic oil supplied from the travel pump 53 to the travel motor 36 in accordance with the travel state of the vehicle 2, by reducing the rotational speed of the prime mover 32.

[0050] In addition, when a gear shift command is issued while the working machine (machine body 2) is traveling, the control device 60 reduces the rotation speed of the prime mover 32. However, when a gear shift command is issued while the working machine (machine body 2) is stopped, the control device 60 However, the rotation speed of the prime mover 32 is not reduced. FIG. 2A is a diagram showing the relationship between the rotation speed (target rotation speed, actual rotation speed) of the prime mover 32 and switching of the traveling motor 36 when the traveling motor 36 is increased from a first speed to a second speed. As shown in Fig. 2A, at time Q1, the changeover switch (changeover SW) 61 is operated, and the control device 60 acquires an increase in speed command (second speed command) to change from the first state (first speed) to the second state (second speed). When the control device 60 acquires the second speed command, it reduces the actual rotation speed W1 to a predetermined rotation speed W3 that is lower than the target rotation speed W2 set by the accelerator 65. The predetermined rotation speed W3 is a rotation speed that reduces a shift shock when switching from the first speed to the second speed, and is, for example, a value obtained by subtracting a reduction amount ΔD1 from the actual rotation speed W1.

[0051] The control device 60 sets the reduction amount ΔD1 according to the travel speed of the working machine (machine body 2), which is one of the travel states. Specifically, the control device 60 is connected to a travel detection device 67 that detects the travel speed as a travel state. The travel detection device 67 is, for example, a device that detects the pressure (pilot pressure) of the hydraulic oil (pilot oil) output from the operation valve 55 (operation valve 55A, operation valve 55B, operation valve 55C, operation valve 55D) and converts the detected pilot pressure into a travel speed. For example, when the pilot pressure of the travel oil passage 45 is high, the travel speed is detected as high, and when the pilot pressure is low, the travel speed is detected as low. Note that the travel detection device 67 detects the travel speed from the pilot pressure of the travel oil passage 45, but instead of this, it may be a device that detects the rotation speed of the rotating shaft of the travel motor 36 and converts the detected rotation speed into a travel speed, and any device that can detect the travel speed may be used.

[0052] That is, when switching to increasing the speed, the control device 60 sets a decrease amount ΔD1 corresponding to the traveling speed detected by the traveling detection device 67, and reduces the prime mover rotation speed in accordance with the set decrease amount ΔD1. As shown in Fig. 8A, the control device 60 stores reduction amount calculation data showing the relationship between the actual rotation speed W1, the pilot pressure (travel pilot pressure) of the travel oil passage 45, and the reduction amount ΔD1. Fig. 8B is a graph of Fig. 8A. Note that the reduction amount calculation data in Figs. 8A and 8B is an example, and is not limited thereto.

[0053] For example, as shown in Fig. 8A, when the control device 60 acquires a second speed command, the actual rotation speed W1 is 3000 rpm, and the traveling pilot pressure is 1.5 MPa, the control device 60 sets the reduction amount ΔD1 to 500 rpm. Note that, as shown in Fig. 8A, when reducing the prime mover rotation speed, the control device 60 sets a lower limit value for the prime mover rotation speed so that it does not become smaller than the minimum prime mover rotation speed. Furthermore, when reducing the prime mover rotation speed, the control device 60 keeps the gradient K1 (gradient of reduction time T1) of reducing the prime mover rotation speed constant even when the reduction amount ΔD1 is different.

[0054] As shown in Fig. 2A, when the actual rotation speed W1 reaches the predetermined rotation speed W3 at time point Q2, the control device 60 returns the actual rotation speed W1 to the target rotation speed W2. Alternatively, the control device 60 returns the actual rotation speed W1 to the target rotation speed W2 midway during the reduction time T1 during which the actual rotation speed W1 is reduced to the predetermined rotation speed W3. Here, the control device 60 makes the recovery time T2 during which the actual rotation speed W1 is restored from the predetermined rotation speed W3 to the target rotation speed W2 longer than the reduction time T1. That is, the control device 60 makes the reduction speed at which the actual rotation speed W1 is reduced to the predetermined rotation speed W3 faster than the recovery speed at which the actual rotation speed W1 is restored from the predetermined rotation speed W3 to the target rotation speed W2.

[0055] Furthermore, the control device 60 outputs a signal to excite the solenoid of the travel switching valve 34 at the timing when a predetermined delay period has elapsed from time Q1, that is, at the switching timing (timing during the return time T2 in FIG. 2A), to switch the travel switching valve (switching valve) 34 from the first state (first speed) to the second state (second speed). In other words, the control device 60 switches the travel switching valve 34 to the second state during the return time T2.

[0056] The period of the return time T2 is a return period indicating a period from time Q2 when the actual rotation speed of the prime mover 32 is reduced to a rotation speed (e.g., a predetermined rotation speed W3) lower than the target rotation speed W2 to when the actual rotation speed of the prime mover 32 is restored to the target rotation speed W2. In other words, the period of the return time T2 can be said to be a return period during which the supply amount to the traveling motor 36 is restored after the supply amount is reduced. 3A is a flowchart of a first operation of the control device 60 when changing the rotation speed of the traveling motor 36 from a first speed to a second speed. Note that the work machine 1 is not in a stopped state but in a traveling state.

[0057] The control device 60 judges whether the changeover switch 61 has been switched from the first speed to the second speed (S1). If the changeover switch 61 has not been switched to the second speed, that is, if the changeover switch 61 is maintained at the first speed (NO in S1), the control device 60 sets the actual rotation speed W1 to the target rotation speed W2 based on the operation of the accelerator 65 (S2). If the changeover switch 61 has been switched from the first speed to the second speed (YES in S1), the control device 60 judges whether it is a switching timing when a predetermined delay period has elapsed from the time point Q1 (S3). If it is not the switching timing (NO in S3), the control device 60 proceeds to S5. On the other hand, if it is the switching timing (YES in S3), the control device 60 switches the traveling switching valve 34 from the first state (first speed) to the second state (second speed) (S4). If the answer is NO in S3 or after S4, the control device 60 reduces the actual rotation speed W1 toward a predetermined rotation speed W3 that is lower than the target rotation speed W2 (S5).

[0058] The control device 60 judges whether the actual rotation speed W1 has reached the predetermined rotation speed W3 (S6), and returns to S3 if the actual rotation speed W1 has not reached the predetermined rotation speed W3 (NO in S6). On the other hand, when the actual rotation speed W1 reaches the predetermined rotation speed W3 (YES in S6), the control device 60 judges whether it is time to switch (S7). If it is time to switch (YES in S7), the control device 60 switches the travel switching valve 34 from the first state (first speed) to the second state (second speed) (S8). On the other hand, if it is not time to switch (NO in S7) or after S8, the control device 60 returns the actual rotation speed W1 to the target rotation speed W2 (S9). The control device 60 judges whether the actual rotation speed W1 has returned to the target rotation speed W2 (S10), and returns to S7 if it is not time to switch (NO in S10). When the control device 60 determines that the actual rotation speed W1 has returned to the target rotation speed W2 (YES in S10), the control device 60 ends this process.

[0059] FIG. 2B is a diagram showing the relationship between the rotation speed (target rotation speed, actual rotation speed) of the prime mover 32 and the switching of the traveling motor 36 when the traveling motor 36 is decelerated from a first speed to a second speed. As shown in FIG. 2B, at time Q11, the changeover switch (changeover SW) 61 is operated, and the control device 60 acquires a deceleration command (first speed command) to change from the second state (second speed) to the first state (first speed). When the control device 60 acquires the first speed command, it reduces the actual rotation speed W1 to a predetermined rotation speed W4 that is lower than the target rotation speed W2 set by the accelerator 65. The predetermined rotation speed W4 is a rotation speed that reduces a shift shock when switching from the second speed to the first speed, and is set, for example, by a reduction amount ΔD1 from the target rotation speed W2. The setting of the reduction amount ΔD1 is the same as in the above-mentioned embodiment, and when switching to deceleration, the control device 60 sets the reduction amount ΔD1 corresponding to the traveling speed detected by the traveling detection device 67, and reduces the prime mover rotation speed corresponding to the set reduction amount ΔD1. Furthermore, when reducing the prime mover rotation speed, the control device 60 keeps the gradient K2 of the reduction in the prime mover rotation speed (the gradient of the reduction time T11) constant even when the reduction amount ΔD1 varies.

[0060] As shown in Fig. 2B, when the actual rotation speed W1 reaches the predetermined rotation speed W4 at time point Q12, the control device 60 returns the actual rotation speed W1 to the target rotation speed W2. Alternatively, the control device 60 returns the actual rotation speed W1 to the target rotation speed W2 midway during the reduction time T11 during which the actual rotation speed W1 is reduced to the predetermined rotation speed W4. Here, the control device 60 makes the recovery time T12 during which the actual rotation speed W1 is restored from the predetermined rotation speed W4 to the target rotation speed W2 shorter than the reduction time T11. That is, the control device 60 makes the reduction speed at which the actual rotation speed W1 is reduced to the predetermined rotation speed W3 slower than the recovery speed at which the actual rotation speed W1 is restored from the predetermined rotation speed W3 to the target rotation speed W2.

[0061] Furthermore, the control device 60 outputs a signal to demagnetize the solenoid of the travel switching valve 34 at a switching timing when a predetermined delay period has elapsed from the time point Q11 (for example, during the drop time T11), and switches the travel switching valve (switching valve) 34 from the second state (second speed) to the first state (first speed). In other words, the control device 60 restores the actual rotation speed W1 to the target rotation speed W2 after switching the travel switching valve 34 to the first state during the drop time T11.

[0062] The period of reduction time T11 is a reduction period from the start of the reduction in the actual rotation speed of the prime mover 32 (e.g., time point Q11) until the actual rotation speed of the prime mover 32 is reduced to a rotation speed (e.g., predetermined rotation speed W3) lower than the target rotation speed W2. In other words, the period of reduction time T11 can be said to be a reduction period during which the supply amount to the traveling motor 36 is reduced. 3B is a flowchart of a second operation of the control device 60 when changing the rotation speed of the traveling motor from the second speed to the first speed. Note that the work machine is not in a stopped state but in a traveling state.

[0063] The control device 60 judges whether the changeover switch 61 has been switched from the second speed to the first speed (S11). If the changeover switch 61 has not been switched to the first speed, that is, if the changeover switch 61 is maintained at the second speed (NO in S11), the control device 60 sets the actual rotation speed W1 to the target rotation speed W2 based on the operation of the accelerator 65 (S12). If the changeover switch 61 has been switched from the second speed to the first speed (YES in S11), the control device 60 judges whether it is time to switch (S13). If it is not time to switch (NO in S13), the control device 60 proceeds to S15. On the other hand, if it is time to switch (YES in S13), the control device 60 switches the travel switching valve 34 from the second state (second speed) to the first state (first speed) (S14). If NO in S13 or after S14, the control device 60 reduces the actual rotation speed W1 to a predetermined rotation speed W4 lower than the target rotation speed W2 (S15). The control device 60 judges whether the actual rotation speed W1 has reached the predetermined rotation speed W4 (S16), and returns to S13 if the actual rotation speed W1 has not reached the predetermined rotation speed W4 (NO in S16). On the other hand, when the actual rotation speed W1 reaches the predetermined rotation speed W4 (YES in S16), the control device 60 judges whether it is time to switch (S17). If it is time to switch (YES in S17), the control device 60 switches the travel switching valve 34 from the second state (second speed) to the first state (first speed) (S18). On the other hand, if it is not time to switch (NO in S17) or after S18, the control device 60 returns the actual rotation speed W1 to the target rotation speed W2 (S19). The control device 60 determines whether the actual rotation speed W1 has returned to the target rotation speed W2 (S20), and if it determines that the actual rotation speed W1 has not returned (NO in S20), the process returns to S17. Note that if the control device 60 determines that the actual rotation speed W1 has returned to the target rotation speed W2 (YES in S20), the process ends.

[0064] A plurality of pressure detecting devices 80 (traveling pressure detecting devices) are connected to the circulation oil passage 57h. The plurality of pressure detecting devices 80 include a first pressure detecting device 80a and a second pressure detecting device 80b. A plurality of pressure detecting devices 80 are connected to the circulation oil passage 57i. The plurality of pressure detecting devices 80 include a third pressure detecting device 80c and a fourth pressure detecting device 80d. The first pressure detecting device 80a to the fourth pressure detecting device 80d are each connected to the control device 60.

[0065] Specifically, the first pressure detection device 80a is provided in the circulation oil passage 57h on the first port P11 side of the first traveling motor 36L, and detects the pressure on the first port P11 side as the first traveling pressure V1. The second pressure detection device 80b is provided in the circulation oil passage 57h on the second port P12 side of the first traveling motor 36L, and detects the pressure on the second port P12 side as the second traveling pressure V2. The third pressure detection device 80c is provided in the circulation oil passage 57i on the third port P13 side of the second traveling motor 36R, and detects the pressure on the third port P13 side as the third traveling pressure V3. The fourth pressure detection device 80d is provided in the circulation oil passage 57i on the fourth port P14 side of the second traveling motor 36R, and detects the pressure on the fourth port P14 side as the fourth traveling pressure V4.

[0066] The first port P11 is an intake port when the first traveling motor 36L rotates forward, and the second port P12 is a discharge port when the first traveling motor 36L rotates forward. The third port P13 is an intake port when the second traveling motor 36R rotates forward, and the fourth port P14 is a discharge port when the second traveling motor 36R rotates forward. When a gear change occurs while the machine body 2 (work machine 1) is moving forward (i.e., the first traveling motor 36L and the second traveling motor 36R are rotating forward), the first traveling pressure V1 detected by the first pressure detection device 80a and the third traveling pressure V3 detected by the third pressure detection device 80c are the forward traveling pressure V1 and the forward traveling pressure V3, respectively. The second traveling pressure V2 detected by the second pressure detecting device 80b and the fourth traveling pressure V4 detected by the fourth pressure detecting device 80d are called reverse traveling pressures.

[0067] Furthermore, when a gear change occurs while the machine body 2 (work machine 1) is reversing (i.e., the first traveling motor 36L and the second traveling motor 36R are rotating in the reverse direction), the first traveling pressure V1 detected by the first pressure detection device 80a and the third traveling pressure V3 detected by the third pressure detection device 80c are called the reverse traveling pressures, and the second traveling pressure V2 detected by the second pressure detection device 80b and the fourth traveling pressure V4 detected by the fourth pressure detection device 80d are called the forward traveling pressures, conversely to the above. Now, the control device 60 changes the delay period from the output timing of the shift command of the switching unit (change-over switch 61) to the switching timing of the traveling switching valve 34, depending on the traveling pressure detected by the pressure detection device 80 (traveling pressure detection device) at the time of a shift command.

[0068] The pressure detection device 80 detects the pressure of the hydraulic oil supplied from the travel pump 53 to the travel motor 36 during forward rotation as the forward travel pressure. Specifically, the first pressure detection device 80a detects the first travel pressure V1 as the forward travel pressure, and the third pressure detection device 80c detects the third travel pressure V3 as the forward travel pressure. At least one of the first pressure detection device 80a and the third pressure detection device 80c corresponds to the first travel pressure detection device. When issuing a speed change command to increase or decrease speed, the control device 60 changes the delay period according to the forward travel pressures detected by the first pressure detection device 80a and the third pressure detection device 80c (i.e., the first travel pressure V1 and the third travel pressure V3). In the first embodiment, the control device 60 determines the larger of the first travel pressure V1 and the third travel pressure V3 as the forward travel pressure, but may determine the smaller of them. In addition, the control device 60 may set both the first traveling pressure V1 and the third traveling pressure V3 as the forward traveling pressure, or may set the average value of the first traveling pressure V1 and the third traveling pressure V3 as the forward traveling pressure.

[0069] Specifically, the control device 60 shortens the delay period when a second gear command is received while the vehicle 2 is moving forward (forward acceleration) and the forward running pressure exceeds a threshold value (e.g., a first threshold value for acceleration).In addition, the control device 60 shortens the delay period when a first gear command is received while the vehicle 2 is moving forward (forward deceleration) and the forward running pressure exceeds a threshold value (e.g., a second threshold value for deceleration).

[0070] The control device 60 includes a storage device 60a having a storage table TB (see FIG. 2C). The storage table TB stores thresholds (e.g., a first threshold for accelerating and a second threshold for decelerating), a median value indicating a predetermined period from the output timing of the shift command of the changeover switch 61, a first value indicating a first period shorter than the period indicated by the median value, and a second value indicating a second period longer than the period indicated by the median value. FIG. 2C shows data when the rotation speed of the prime mover 32 is a certain rotation speed RTn (e.g., n=1500 to 3000 rpm, etc.). When the control lever 59 is operated forward to move the machine body 2 forward and an acceleration or deceleration process is performed (i.e., when an acceleration command (second gear command) or a deceleration command (first gear command) is issued by the changeover switch 61), the control device 60 determines whether the forward traveling pressure (here, the larger of the first traveling pressure V1 and the third traveling pressure V3) detected by the first pressure detection device 80a and the third pressure detection device 80c exceeds a threshold value (for example, a first threshold value for acceleration when accelerating, and a second threshold value for deceleration when decelerating). If the control device 60 determines that the threshold value is not exceeded, it sets the median value as the delay period, and if it determines that the threshold value is exceeded, it sets the first value as the delay period.

[0071] In addition, in the case of forward deceleration, in addition to detecting the forward traveling pressure described above, the pressure detection device 80 detects the pressure of the hydraulic oil discharged from the traveling motor 36 to the traveling pump 53 during forward rotation as the reverse traveling pressure. Specifically, the second pressure detection device 80b detects the second traveling pressure V2 as the reverse traveling pressure, and the fourth pressure detection device 80d detects the fourth traveling pressure V4 as the reverse traveling pressure. At least one of the second pressure detection device 80b and the fourth pressure detection device 80d corresponds to the second traveling pressure detection device. When issuing a speed change command for deceleration, the control device 60 changes the delay period according to the reverse traveling pressures (i.e., the second traveling pressure V2 and the fourth traveling pressure V4) detected by the second pressure detection device 80b and the fourth pressure detection device 80d. In the first embodiment, the control device 60 sets the larger of the second traveling pressure V2 and the fourth traveling pressure V4 as the reverse traveling pressure, but it may set the smaller one as the reverse traveling pressure. The control device 60 also controls the second travel pressure V2 and the fourth travel pressure V3. Alternatively, the average value of the second traveling pressure V2 and the fourth traveling pressure V4 may be set as the traveling pressure on the reverse side.

[0072] Specifically, when a first gear command is issued while the vehicle 2 is moving forward (forward deceleration), if the forward traveling pressure does not exceed the second threshold for deceleration and the reverse traveling pressure exceeds the second threshold for deceleration, the control device 60 lengthens the delay period. For example, when the operation lever 59 is operated forward to move the vehicle 2 forward and deceleration processing is performed (that is, when a deceleration command (first gear command) is issued by the changeover switch 61), the control device 60 determines whether or not the reverse traveling pressure (here, the larger of the second traveling pressure V2 and the fourth traveling pressure V4) detected by the second pressure detection device 80b and the fourth pressure detection device 80d exceeds the second threshold for deceleration. If the control device 60 determines that the second threshold for deceleration is not exceeded, the control device 60 sets the median value as the delay period, and if the second threshold for deceleration is exceeded, the control device 60 sets the second value as the delay period.

[0073] The storage device 60a stores a threshold value (a first threshold value for accelerating, a second threshold value for decelerating), a median value, a first value, and a second value for each rotation speed of the prime mover 32. The control device 60 uses the threshold value, the median value, the first value, and the second value corresponding to the rotation speed of the prime mover 32 detected by the rotation detection device 66. Note that the threshold value when performing the acceleration process (the first threshold value for accelerating) and the threshold value when performing the deceleration process (the second threshold value for deceleration) are different values, but may be the same value.

[0074] Furthermore, the control device 60 can switch from the normal mode to a setting mode that sets the gear shift switching timing based on the operation of the operator, and in the setting mode, the machine body 2 (work machine 1) is made to actually run (a state in which it is actually running) or to idle (a state in which it is not actually running), and changes the delay period if the threshold value is exceeded. Note that the control device 60 may change the delay period in the normal mode if the threshold value is exceeded. When changing the delay period in the normal mode, the changed delay period is used the next time a gear shift command is issued.

[0075] Here, the process of changing the gear shift switching delay period by the control device 60 when accelerating forward will be described with reference to FIG. 3C. When the control lever 59 is operated to move forward and the machine body 2 is moving forward (that is, when the rotation detection sensor 64 indicates that the rotation directions of the first and second traveling motors 36L, 36R are normal), the control device 60 judges whether or not there is a speed increase command (second speed command) from the changeover switch 61 (S51). When the control device 60 has not received a second speed command (NO in S51), it returns to S51 and waits until it receives a second speed command. On the other hand, when the control device 60 receives a second speed command from the changeover switch 61, it judges that there is speed increase during forward movement (YES in S51) and obtains the rotation speed of the prime mover 32 by the rotation detection device 66 (S52). The control device 60 obtains a threshold value corresponding to the rotation speed of the prime mover 32 (first threshold value for speed increase) from the memory table TB (S53).

[0076] The control device 60 acquires the forward traveling pressure (here, the larger of the first traveling pressure V1 and the third traveling pressure V3) detected by the first pressure detection device 80a and the third pressure detection device 80c (S54). The control device 60 judges whether the forward traveling pressure (here, the larger of the first traveling pressure V1 and the third traveling pressure V3) exceeds a threshold value (for example, a first threshold value for accelerating) (S55). When the forward traveling pressure exceeds the first threshold value for accelerating (YES in S55), the control device 60 selects a first value shorter than the median value as the delay period (S56). That is, the control device 60 changes the delay period from the median value (60 milliseconds) to the first value (40 milliseconds) as shown in FIG. 2C and FIG. 2D. As shown in FIG. 2A, the delay period Z10 when it is the median value (60 milliseconds) is changed to a delay period Z10A shorter than the median value.

[0077] On the other hand, when the forward traveling pressure does not exceed the first threshold value for accelerating (NO in S55), the control device 60 keeps the delay period at the median value (60 milliseconds) (S57) as shown in Figures 2C and 2D. As shown in Figure 2A, the delay period Z10 is kept at the median value (60 milliseconds). Next, the process of changing the gear shift switching delay period by the control device 60 during forward deceleration will be described with reference to FIG. 3D.

[0078] When the control lever 59 is operated to move forward and the machine body 2 is moving forward (that is, when the rotation direction of the first and second traveling motors 36L, 36R detected by the rotation detection sensor 64 is forward), the control device 60 judges whether or not there is a deceleration command (first speed command) from the changeover switch 61 (S61). When the control device 60 has not received the first speed command (NO in S61), it returns to S61 and waits until it receives the first speed command. On the other hand, when the control device 60 receives the first speed command from the changeover switch 61, it judges that there is deceleration during forward movement (YES in S61) and obtains the rotation speed of the prime mover 32 by the rotation detection device 66 (S62). The control device 60 obtains a threshold value corresponding to the rotation speed of the prime mover 32 (a second threshold value for deceleration) from the memory table TB (S63).

[0079] The control device 60 acquires the forward running pressure (here, the larger of the first running pressure V1 and the third running pressure V3) detected by the first pressure detection device 80a and the third pressure detection device 80c (S64). The control device 60 determines whether the forward running pressure (here, the larger of the first running pressure V1 and the third running pressure V3) exceeds a threshold value (for example, a second threshold value for deceleration) (S65). When the forward running pressure exceeds the second threshold value for deceleration (YES in S65), the control device 60 selects a first value shorter than the median value as the delay period (S66). That is, as shown in FIG. 2C and FIG. 2D, the control device 60 changes the delay period from the median value (680 milliseconds) to the first value (660 milliseconds). As shown in FIG. 2B, the delay period Z11 when it is the median value (680 milliseconds) is changed to a shorter delay period Z11B.

[0080] On the other hand, when the forward traveling pressure does not exceed the second threshold value for deceleration (NO in S65), the control device 60 acquires the reverse traveling pressure (here, the larger of the second traveling pressure V2 and the fourth traveling pressure V4) detected by the second pressure detection device 80b and the fourth pressure detection device 80d (S67). The control device 60 determines whether the reverse traveling pressure (here, the larger of the second traveling pressure V2 and the fourth traveling pressure V4) exceeds a threshold value (for example, the second threshold value for deceleration) (S68). When the reverse traveling pressure does not exceed the second threshold value for deceleration (NO in S68), the control device 60 maintains the delay period at the median value (680 milliseconds) (S69). As shown in FIG. 2B, the delay period Z11 is maintained at the median value (680 milliseconds).

[0081] On the other hand, when the traveling pressure on the reverse side exceeds the second threshold value for deceleration (YES in S68), the control device 60 selects a second value longer than the median value as the delay period (S70). That is, the control device 60 changes the delay period from the median value (680 milliseconds) to the second value (700 milliseconds) as shown in Fig. 2C and Fig. 2D. As shown in Fig. 2B, the delay period Z11 when it is the median value (680 milliseconds) is changed to a longer delay period Z11A.

[0082] The work machine 1 of the first embodiment described above includes a prime mover 32, a travel pump 53 that is operated by the power of the prime mover 32 and discharges hydraulic oil, a travel motor 36 that can be rotated by the hydraulic oil discharged by the travel pump 53, a machine body 2 in which the prime mover 32, the travel pump 53, and the travel motor 36 are provided, a travel switching valve 34 that can be switched between a first state in which the rotation speed of the travel motor 36 can be increased to a first maximum speed and a second state in which the rotation speed of the travel motor 36 can be increased to a second maximum speed that is greater than the first maximum speed, a travel operation device 54 having an operation valve that can change the pressure of the hydraulic oil acting on the travel pump 53 in response to the operation of an operation lever 59 (operation member), and a travel operation device 55 that can be switched from the first state to the second state. The vehicle is equipped with a control device 60 that reduces the amount of hydraulic oil supplied from the travel pump 53 to the travel motor 36 based on the travel state of the vehicle body 2 when performing either an acceleration process to switch to the first state or a deceleration process to switch from the second state to the first state, a change-over switch 61 (switching unit) that issues a speed change command to either increase or decrease the speed, and a pressure detection device 80 (travel pressure detection device) that detects the pressure of the hydraulic oil discharged by the travel pump 53 to the travel motor 36 as travel pressure when a speed change command is issued, and the control device 60 changes the delay period from the output timing of the speed change command of the change-over switch 61 to the switching timing of the travel switching valve 34 depending on the travel pressure detected by the pressure detection device 80 when a speed change command is issued.

[0083] According to this configuration, the control device 60 changes the delay period from the output timing of the shift command from the changeover switch 61 to the switching timing of the travel switching valve 34, depending on the traveling pressure at the time of the shift command. Therefore, for a work machine 1 in which a deviation in the shift timing occurs due to variation in the response delay of the rotation of the hydraulic device or the prime mover 32, an adjustment can be made to reduce the shift shock.

[0084] The pressure detection device 80 includes a first traveling pressure detection device (first pressure detection device 80a and third pressure detection device 80c) that detects the pressure of the hydraulic oil supplied from the travel pump 53 to the travel motor 36 during forward rotation as the forward traveling pressure, and the control device 60 changes the delay period according to the forward traveling pressure (first traveling pressure V1 and third traveling pressure V3) detected by the first pressure detection device 80a and the third pressure detection device 80c when a speed change command for speed increase or deceleration is issued. With this configuration, the control device 60 changes the delay period from the output timing of the speed increase or deceleration command during forward travel to the switching timing of the travel switching valve 34 according to the forward traveling pressure when the work machine 1 moves forward and performs the speed increase or deceleration process. For this reason, for the work machine 1 in which a shift in speed change timing occurs due to variations in the response delay of the rotation of the hydraulic device or the prime mover 32, adjustments can be made to reduce the speed change shock when the work machine 1 increases or decreases speed during forward travel.

[0085] Furthermore, the control device 60 shortens the delay period when the forward traveling pressure (first traveling pressure V1 and third traveling pressure V3) detected by the first traveling pressure detection device (first pressure detection device 80a and third pressure detection device 80c) exceeds the threshold value at the time of a speed increase shift command. According to this configuration, when the forward traveling pressure exceeds the threshold value when the work machine 1 moves forward and performs the speed increase process, the control device 60 shortens the delay period from the output timing of the speed increase shift command when moving forward to the switching timing of the travel switching valve 34. Therefore, for a work machine 1 in which a deviation in the speed change timing occurs due to variations in the response delay of the hydraulic equipment or the rotation of the prime mover 32, it is possible to reduce the speed change shock when the work machine 1 increases its speed while moving forward.

[0086] Furthermore, the control device 60 shortens the delay period when the forward traveling pressure (first traveling pressure V1 and third traveling pressure V3) detected by the first traveling pressure detection device (first pressure detection device 80a and third pressure detection device 80c) exceeds the threshold value at the time of a deceleration gear shift command. According to this configuration, when the forward traveling pressure exceeds the threshold value when the work machine 1 moves forward and decelerates, the control device 60 shortens the delay period from the output timing of the deceleration gear shift command during forward travel to the switching timing of the travel switching valve 34. For this reason, for a work machine 1 in which a deviation in gear shift timing occurs due to variations in response delays in the rotation of the hydraulic equipment or prime mover 32, it is possible to reduce gear shift shock during deceleration during forward travel of the work machine 1.

[0087] The pressure detection device 80 also includes a second traveling pressure detection device (second pressure detection device 80b and fourth pressure detection device 80d) that detects the pressure of the hydraulic oil discharged from the traveling motor 36 to the traveling pump 53 during forward rotation as the traveling pressure on the reverse side, and the control device 60 lengthens the delay period when the traveling pressure on the reverse side (the second traveling pressure V2 and the fourth traveling pressure V4) detected by the second pressure detection device 80b and the fourth pressure detection device 80d at the time of a gear shift command for deceleration exceeds a threshold value. According to this configuration, the control device 60 lengthens the delay period from the output timing of the gear shift command for deceleration during forward movement to the switching timing of the traveling switching valve 34 when the traveling pressure on the reverse side when the working machine 1 is moving forward and decelerating exceeds a threshold value. Therefore, for the working machine 1 in which a shift timing deviation occurs due to a variation in the response delay of the rotation of the hydraulic device or the prime mover 32, the gear shift shock during deceleration during forward movement of the working machine 1 can be appropriately reduced. Furthermore, the control device 60 changes the delay period when in a setting mode for setting the gear shift switching timing. With this configuration, when in a setting mode for setting the gear shift switching timing, adjustments can be made to reduce gear shift shock.

[0088] The control device 60 includes a storage device 60a having a storage table TB that stores at least a threshold value, a median value indicating a predetermined period from the output timing of the shift command of the changeover switch 61, and a first value indicating a first period shorter than the period indicated by the median value. When the operation of the operating lever 59 is a forward operation and an acceleration process or deceleration process is performed, the control device 60 judges whether the forward side traveling pressure (first traveling pressure V1 and third traveling pressure V3) detected by the first traveling pressure detection device (first pressure detection device 80a and third pressure detection device 80c) exceeds the threshold value. If it is determined that the threshold value is not exceeded, the control device 60 sets the median value as the delay period, and if it is determined that the threshold value is exceeded, the control device 60 sets the first value as the delay period. According to this configuration, when the control device 60 determines that the forward side traveling pressure exceeds the threshold value when the working machine 1 moves forward and performs the acceleration process or deceleration process, the control device 60 changes the delay period from the output timing of the acceleration or deceleration shift command for forward travel to the switching timing of the travel switching valve 34 to the first value, which is a period shorter than the period indicated by the median value. Therefore, for a work machine 1 in which there is a deviation in the timing of gear shifting due to variations in the response delay of the rotation of the hydraulic equipment or the prime mover 32, if the median value does not sufficiently reduce the gear shift shock, the delay period can be changed to a first value that is shorter than the median value, thereby making it possible to appropriately reduce the gear shift shock when the work machine 1 accelerates or decelerates while moving forward.

[0089] The control device 60 includes a storage device 60a having a storage table TB that stores at least a threshold value, a median value indicating a predetermined period from the output timing of the shift command of the changeover switch 61, and a second value indicating a second period longer than the period indicated by the median value. When the operation of the operating lever 59 is a forward operation and deceleration is performed, the control device 60 determines whether the reverse side traveling pressure (second traveling pressure V2 and fourth traveling pressure V4) detected by the second traveling pressure detection device (second pressure detection device 80b and fourth pressure detection device 80d) exceeds the threshold value. If it is determined that the threshold value is not exceeded, the median value is set as the delay period, and if it is determined that the threshold value is exceeded, the second value is set as the delay period instead of the median value. According to this configuration, when the control device 60 determines that the reverse side traveling pressure when the working machine 1 is moving forward and decelerating exceeds the threshold value, the control device 60 changes the delay period from the output timing of the shift command for deceleration in forward to the switching timing of the traveling switching valve 34 to the second value, which is a period longer than the period indicated by the median value. Therefore, for a work machine 1 in which there is a deviation in the timing of gear shifting due to variations in the response delay of the rotation of the hydraulic equipment or the prime mover 32, if the median value does not sufficiently reduce the gear shift shock, the delay period can be changed to a second value longer than the median value, thereby making it possible to appropriately reduce the gear shift shock during deceleration while moving forward.

[0090] The control device 60 uses the threshold value, median value, and first value corresponding to the rotation speed of the prime mover 32 detected by the rotation detection device 66. According to this configuration, the storage device 60a stores the threshold value, median value, and first value corresponding to the rotation speed of the prime mover 32, so that the gear shift shock can be appropriately reduced in accordance with the rotation speed of the prime mover 32.

[0091] The control device 60 uses the threshold value, median value, and second value corresponding to the rotation speed of the prime mover 32 detected by the rotation detection device 66. According to this configuration, the storage device 60a stores the threshold value, median value, and second value corresponding to the rotation speed of the prime mover 32, so that the gear shift shock can be appropriately reduced in accordance with the rotation speed of the prime mover 32. In addition, the threshold value when performing the speed increase process (first threshold value for speed increase) is different from the threshold value when performing the speed decrease process (second threshold value for speed decrease). According to this configuration, since different threshold values ​​are used when performing the speed increase process and when performing the speed decrease process, it is possible to appropriately set the delay period when performing the speed increase process and when performing the speed decrease process.

[0092] In addition, in the work machine 1 of the first embodiment described above, when performing the speed increase process, the control device 60 switches the traveling switching valve 34 from the first state to the second state during a recovery period (for example, the period of recovery time T2 shown in FIG. 2A) during which the rotation speed of the prime mover 32 is restored after the rotation speed of the prime mover 32 is reduced below the target rotation speed W2, which is the rotation speed of the prime mover 32 operated by the accelerator 65. That is, the control device 60 switches the traveling switching valve 34 from the first state to the second state during a recovery period during which the supply amount to the traveling motor 36 is restored after the supply amount is reduced. Therefore, for the work machine 1 in which a shift in the timing of the shift occurs due to the variation in the response delay of the hydraulic device or the rotation of the prime mover 32, the shock of the shift can be appropriately reduced when the speed increase process is performed. Therefore, for the work machine 1 in which a shift in the timing of the shift occurs when the speed increase occurs, the shock of the shift can be appropriately reduced.

[0093] Furthermore, the control device 60 switches the traveling switching valve 34 from the second state to the first state during a decrease period (for example, a period of decrease time T11 shown in FIG. 2B) in which the rotation speed of the prime mover 32 is decreased below the target rotation speed W2 operated by the accelerator 65. When performing deceleration processing, the control device 60 switches the traveling switching valve 34 from the second state to the first state during a decrease period until the decrease in the supply amount to the traveling motor 36 starts. is switched from the second state to the first state. Therefore, for a work machine 1 in which a shift timing occurs due to a variation in response delay of the rotation of the hydraulic device or the prime mover 32, the shift shock when decelerating can be appropriately reduced. Therefore, for a work machine 1 in which a shift timing occurs during deceleration, the shift shock can be appropriately reduced.

[0094] As described above, the control device 60 can change the delay period from the output timing of the shift command of the changeover switch 61 to the switching timing of the travel switching valve 34, depending on the travel pressure detected by the pressure detection device 80 (travel pressure detection device) at the time of the shift command. Therefore, the control device 60 can change the delay period to the advance period shown in Figures 2G and 2H, or the post-return period shown in Figures 2E and 2F.

[0095] Here, a case will be described where the delay periods Z10B and Z11C are set to the advance periods shown in Figs. 2G and 2H. When performing the speed increase process, the control device 60 may switch the travel switching valve 34 from the first state to the second state during the advance period until the supply amount to the travel motor 36 starts to decrease (for example, as shown in Fig. 2G, the advance period T1A until the rotation speed of the prime mover 32 starts to decrease). When the delay period Z10B is set within the advance period T1A, the control device 60 switches the travel switching valve 34 from the second state to the first state in S4 shown in Fig. 3A. In this case, for a work machine 1 in which a shift in the timing of the speed change occurs due to a variation in the response delay of the hydraulic device or the rotation of the prime mover 32, the shock of the speed change when performing the speed increase process can be appropriately reduced. Furthermore, when performing deceleration processing, the control device 60 may switch the travel switching valve 34 from the second state to the first state during a preliminary period until the supply amount to the travel motor 36 starts to decrease (for example, as shown in FIG. 2H, a preliminary period T1A until the rotation speed of the prime mover 32 starts to decrease). When the control device 60 sets the delay period Z11C within the preliminary period T11A, the control device 60 switches the travel switching valve 34 from the second state to the first state in S14 shown in FIG. 3B. In this case, for a work machine 1 in which deviations in the timing of gear shifting occur due to variations in response delays in the rotation of the hydraulic device or the prime mover 32, it is possible to appropriately reduce shocks caused by gear shifting when performing deceleration processing.

[0096] Next, a case where the delay periods Z14 and Z15 are set to extend to the post-return period shown in Fig. 2E and Fig. 2F will be described. When performing the speed increase process, the control device 60 may switch the traveling switching valve 34 from the first state to the second state during the post-return period (for example, as shown in Fig. 2E, the post-return period T3, which is a period from the time when the rotation speed of the prime mover 32 returns to the target rotation speed W2 to a predetermined period). When the end point of the delay period Z14 is set within the post-return period T3, the control device 60 provides the same processes as S7 and S8 after S10 shown in Fig. 3A, and switches the traveling switching valve 34 from the first state to the second state in the same process as S8. In this case, for the work machine 1 in which a shift in the timing of the speed change occurs due to the variation in the response delay of the rotation of the hydraulic device or the prime mover 32, the shock of the speed change when performing the speed increase process can be appropriately reduced. Furthermore, when performing the deceleration process, the control device 60 may switch the traveling switching valve 34 from the second state to the first state during a post-return period (for example, as shown in FIG. 2F, a post-return period T13 that is a period from the time when the rotation speed of the prime mover 32 returns to the target rotation speed W2 to a predetermined period). When the control device 60 sets the end point of the delay period Z15 within the post-return period T13, the control device 60 provides the same processes as S17 and S18 after S20 shown in FIG. 3B, and switches the traveling switching valve 34 from the second state to the first state in the same process as S18. In this case, for a work machine 1 in which a shift in the timing of the shift occurs due to a variation in the response delay of the rotation of the hydraulic device or the prime mover 32, it is possible to appropriately reduce the shock of the shift when performing the deceleration process.

[0097] The control device 60 also includes a travel detection device 67 capable of detecting the travel speed of the machine body 2 as a travel state, and when performing speed increase processing or deceleration processing, the control device 60 determines the amount of reduction in the supply amount to the travel motor 36 corresponding to the travel speed detected by the travel detection device 67, and reduces the supply amount to the travel motor 36 corresponding to the determined reduction amount. According to this configuration, when performing speed increase processing or deceleration processing of the work machine 1, the supply amount to the travel motor 36 is reduced according to the travel speed, so that the shock of gear change is reduced regardless of the state of the travel speed. It can be reduced. The switching unit is a change-over switch 61 that outputs a gear shift command to the control device 60. With this configuration, even when an operator or the like operates the change-over switch 61 to output a gear shift command for increasing speed or decreasing speed to the control device 60, a gear shift shock can be appropriately applied to a work machine in which a deviation in gear shift timing occurs.

[0098] <When shifting gears while moving in reverse> In the first embodiment, a case where a gear shift command is issued while the machine body 2 is moving forward has been described, but the delay period can also be changed in the same way when a gear shift command is issued while the machine body 2 is moving backward. First, in S51 shown in FIG. 3C and S61 shown in FIG. 3D, when the operation lever 59 is operated to move backward and the machine body 2 is moving backward (that is, when the rotation detection sensor 64 detects that the rotation directions of the first and second traveling motors 36L and 36R are reversed), the control device 60 determines whether or not there is a speed increase command (second speed command) from the changeover switch 61 (S51) and whether or not there is a deceleration command (first speed command) (S61). Furthermore, the pressures (first traveling pressure V1 and third traveling pressure V3) detected by the first traveling pressure detection device (first pressure detection device 80a and third pressure detection device 80c) detect the pressure of the hydraulic oil supplied from the traveling pump 53 to the traveling motor 36 during reverse rotation as the traveling pressure on the reverse side. That is, when the working machine 1 is moving backward, the pressures detected by the first pressure detection device 80a and the third pressure detection device 80c (the first traveling pressure V1 and the third traveling pressure V3) are the traveling pressures on the reverse side, not the traveling pressures on the forward side, and the pressures detected by the second pressure detection device 80b and the fourth pressure detection device 80d (the second traveling pressure V2 and the fourth traveling pressure V4) are the traveling pressures on the forward side, not the traveling pressures on the reverse side. According to this configuration, the control device 60 changes the delay period from the timing of outputting a speed change command for increasing or decreasing the speed during moving backward to the timing of switching the travel switching valve 34, depending on the traveling pressure on the reverse side when the working machine 1 is moving backward and performing an increasing or decreasing speed process. Therefore, for the working machine 1 in which a shift in the speed change timing occurs due to a variation in the response delay of the rotation of the hydraulic device or the prime mover 32, it is possible to adjust the speed change shock when the working machine 1 is increasing or decreasing the speed during moving backward.

[0099] Also, in a user switching mode in which the user sets the shift change timing, when the operation of the operating lever 59 (operating member) is a reverse operation and deceleration is performed, the control device 60 may determine whether or not the reverse side traveling pressure detected by the first traveling pressure detection device exceeds a threshold value, and if it determines that it does not exceed the threshold value, set the median value as the delay period, and if it determines that it exceeds the threshold value, set the first value instead of the median value as the delay period. According to this configuration, in a user switching mode in which the user sets the shift change timing, when it determines that the traveling pressure when the work machine 1 is reversed and decelerating exceeds the threshold value, the control device 60 changes the delay period from the output timing of a shift command for deceleration in reverse to the switching timing of the travel switching valve 34 to the first value, which is a period shorter than the period indicated by the median value. Therefore, in the user switching mode, for a work machine 1 in which there is a deviation in the timing of gear shifting due to variations in the response delay of the rotation of the hydraulic equipment or the prime mover 32, if the median value does not sufficiently reduce the gear shift shock, the delay period can be changed to a first value that is shorter than the median value, thereby making it possible to appropriately reduce the gear shift shock when the work machine 1 is reversing.

[0100] In the case of speed increase, the control device 60 sets the return time T2 for restoring the prime mover rotation speed longer than the reduction time T1 for reducing the prime mover rotation speed, and in the case of speed decrease, sets the return time T12 shorter than the reduction time T11. This makes it possible to reduce the gear shift shock as much as possible in a situation where the prime mover rotation speed is returned to the level before the gear shift as quickly as possible after the gear shift shock has been reduced.

[0101] [Second embodiment] The second embodiment is different from the first embodiment in that the control device 60 changes the delay period in accordance with the difference between the forward traveling pressure and the reverse traveling pressure. When the vehicle 2 is moving forward and a speed change command is issued to increase or decrease the speed, the control device 60 detects the forward traveling pressure (first traveling pressure V1 and third traveling pressure V3) detected by the first traveling pressure detection device (first pressure detection device 80a and third pressure detection device 80c) and the reverse traveling pressure (second traveling pressure V The delay period is changed depending on the difference between the second and fourth travel pressures V2 and V4.

[0102] Specifically, in the case of forward acceleration or deceleration, if this difference is a positive value and the absolute value of the difference exceeds the judgment value, the control device 60 shortens the delay period. Also, in the case of forward deceleration, if this difference is a negative value and the absolute value of the difference exceeds the judgment value, the control device 60 lengthens the delay period. In the second embodiment, the storage table TB stores the judgment value, a median value indicating a predetermined period from the output timing of the shift command of the change-over switch 61, a first value indicating a first period shorter than the period indicated by the median value, and a second value indicating a second period longer than the period indicated by the median value. Here, the process of changing the gear shift switching delay period by the control device 60 when accelerating forward in the second embodiment will be described with reference to FIG. 3E.

[0103] When the control lever 59 is operated to move forward and the machine body 2 is moving forward (i.e., when the rotation detection sensor 64 indicates that the rotation directions of the first and second traveling motors 36L, 36R are normal), the control device 60 judges whether or not there is a speed increase command (second speed command) from the changeover switch 61 (S71). When the control device 60 has not received a second speed command (NO in S71), it returns to S71 and waits until it receives a second speed command. On the other hand, when the control device 60 receives a second speed command from the changeover switch 61, it judges that there is speed increase during forward movement (YES in S71) and obtains the rotation speed of the prime mover 32 from the rotation detection device 66 (S72). The control device 60 obtains a judgment value corresponding to the rotation speed of the prime mover 32 from the memory table TB (S73).

[0104] The control device 60 obtains the forward traveling pressure (here, the larger of the first traveling pressure V1 and the third traveling pressure V3) detected by the first pressure detection device 80a and the third pressure detection device 80c, and the reverse traveling pressure (here, the larger of the second traveling pressure V2 and the fourth traveling pressure V4) detected by the second pressure detection device 80b and the fourth pressure detection device 80d, and calculates the difference therebetween (S74). The control device 60 determines whether this difference is positive and the absolute value of this difference exceeds the determination value (S75). When this difference is positive and the absolute value of this difference exceeds the determination value (YES in S75), the control device 60 selects a first value shorter than the median value as the delay period (S76). For example, the control device 60 changes the delay period from the median value (60 milliseconds) to the first value (40 milliseconds) as shown in FIG. 2C and FIG. 2D. On the other hand, if this difference is positive and the absolute value of this difference does not exceed the judgment value (NO in S75), the control device 60 leaves the delay period at the median value (60 milliseconds) (S77).

[0105] Next, the process of changing the gear shift switching delay period by the control device 60 during forward deceleration in the second embodiment will be described with reference to FIG. 3F. When the control lever 59 is operated to move forward and the machine body 2 is moving forward (i.e., when the rotation detection sensor 64 indicates that the rotation directions of the first and second traveling motors 36L, 36R are normal), the control device 60 judges whether or not there is a deceleration command (first speed command) from the changeover switch 61 (S81). When the control device 60 has not received a first speed command (NO in S81), it returns to S81 and waits until it receives a first speed command. On the other hand, when the control device 60 receives a first speed command from the changeover switch 61, it judges that there is deceleration during forward movement (YES in S81) and obtains the rotation speed of the prime mover 32 from the rotation detection device 66 (S82). The control device 60 obtains a judgment value corresponding to the rotation speed of the prime mover 32 from the memory table TB (S83).

[0106] The control device 60 obtains the forward traveling pressure (here, the larger of the first traveling pressure V1 and the third traveling pressure V3) detected by the first pressure detection device 80a and the third pressure detection device 80c, and the reverse traveling pressure (here, the larger of the second traveling pressure V2 and the fourth traveling pressure V4) detected by the second pressure detection device 80b and the fourth pressure detection device 80d, and calculates the difference therebetween (S84). The control device 60 determines whether this difference is positive and whether the absolute value of this difference exceeds the determination value (S85). When this difference is positive and the absolute value of this difference exceeds the determination value (YES in S85), the control device 60 selects a first value that is shorter than the median value as the delay period (S86). For example, the control device 60 changes the delay period from the median value (680 milliseconds) to the first value (660 milliseconds) as shown in FIG. 2C and FIG. 2D. As shown in FIG. 2B, the delay period Z11, which was the median value (680 ms), is changed to a shorter delay period Z11B.

[0107] On the other hand, if the difference is negative, or if the difference is positive and the absolute value of the difference does not exceed the judgment value (NO in S85), the control device 60 judges whether the difference is negative and the absolute value of the difference exceeds the judgment value (S87). If the difference is negative and the absolute value of the difference does not exceed the judgment value, or if the difference is positive and the absolute value of the difference does not exceed the judgment value (NO in S87), the control device 60 leaves the delay period at the median value (680 milliseconds) (S69). As shown in FIG. 2B, the delay period Z11 is left at the median value (680 milliseconds).

[0108] On the other hand, when the difference is negative and the absolute value of the difference exceeds the judgment value (YES in S87), the control device 60 selects a second value longer than the median as the delay period (S70). That is, the control device 60 changes the delay period from the median (680 milliseconds) to the second value (700 milliseconds) as shown in Figures 2C and 2D. As shown in Figure 2B, the delay period Z11 that would have been the median (680 milliseconds) is changed to a longer delay period Z11A.

[0109] In the work machine 1 of the second embodiment described above, the control device 60 changes the delay period from the output timing of a speed increase or deceleration command when moving forward to the switching timing of the travel switching valve 34, depending on the difference between the forward traveling pressure and the reverse traveling pressure when the work machine 1 moves forward and performs speed increase or deceleration processing. Therefore, for a work machine 1 in which a deviation in the speed change timing occurs due to variations in the response delay of the hydraulic equipment or the rotation of the prime mover 32, adjustment can be made to reduce the speed change shock when the work machine 1 increases or decreases speed when moving forward.

[0110] Furthermore, when the difference between the forward traveling pressure and the reverse traveling pressure when the work machine 1 moves forward and performs speed-up processing is a positive value and the absolute value of the difference exceeds a judgment value, the control device 60 shortens the delay period from the output timing of a speed-up command when moving forward to the switching timing of the travel switching valve 34. Therefore, for a work machine 1 in which a deviation in the speed-up timing occurs due to variations in the response delay of the hydraulic equipment or the rotation of the prime mover 32, it is possible to appropriately reduce the speed-up shock when the work machine 1 is speeding up when moving forward.

[0111] Furthermore, when the difference between the forward travel pressure and the reverse travel pressure when the work machine 1 is moving forward and decelerating is a positive value and the absolute value of the difference exceeds a judgment value, the control device 60 shortens the delay period from the timing of outputting a speed change command for deceleration when moving forward to the timing of switching the travel switching valve 34. Therefore, for a work machine 1 in which a deviation in the speed change timing occurs due to variations in the response delay of the hydraulic equipment or the rotation of the prime mover 32, it is possible to appropriately reduce the speed change shock when the work machine 1 decelerates when moving forward.

[0112] Furthermore, when the difference between the forward travel pressure and the reverse travel pressure when the work machine 1 is moving forward and decelerating is a negative value and the absolute value of the difference exceeds a judgment value, the control device 60 lengthens the delay period from the timing of outputting a speed change command for deceleration when moving forward to the timing of switching the travel switching valve 34. Therefore, for a work machine 1 in which a deviation in the speed change timing occurs due to variations in the response delay of the hydraulic equipment or the rotation of the prime mover 32, it is possible to appropriately reduce the speed change shock when the work machine 1 decelerates when moving forward.

[0113] [Third embodiment] 6A shows the hydraulic system of the work machine 1 in the third embodiment. In the third embodiment, not only can the operating device 154 change the swash plate angle of the travel pumps 53 (first travel pump 53L, second travel pump 53R), but the control device 60 can also change the swash plate angle of the travel pumps. Note that while FIG. 6A shows the travel pumps 53 (first travel pump 53L, second travel pump 53R), the operating device 154, and the control device 60, the other parts are similar to FIG. 1.

[0114] The operation device 154 is a joystick-type device that electrically changes the swash plate angle of the travel pump 53, and has an operation lever 59 and an operation detection device (sensor) 82 that converts the operation amount and operation direction of the operation lever 59 into an electric signal. When the operation lever 59 is operated to the right, left, forward, or backward, the operation detection device 82 detects the operation amount and operation direction, and the detected operation amount and operation direction are input to the control device 60. The control device 60 changes the swash plate angle of the travel pump 53 based on the operation amount and operation direction detected by the operation detection device 82. Specifically, the travel pumps 53 (first travel pump 53L, second travel pump 53R) have a regulator 155 that changes the swash plate angle, and the control device 60 controls the regulator 155 to change the swash plate angle. The travel pumps 53 (first travel pump 53L, second travel pump 53R) discharge a larger flow rate of hydraulic oil as the swash plate angle increases, and discharge a smaller flow rate of hydraulic oil as the swash plate angle decreases. In addition, an angle detection device 68 that detects the swash plate angle is connected to the control device 60. The angle detection device 68 allows the control device 60 to grasp the actual swash plate angle (actual angle) of the travel pump 53.

[0115] The control device 60 reduces the swash plate angle of the travel pump 53 (first travel pump 53L, second travel pump 53R) when switching the travel switching valve 34 from the first state to the second state (when increasing the rotational speed of the travel motor 36 from the first speed to the second speed). FIG. 4A is a diagram showing the relationship between the swash plate angle (target angle, actual angle) and switching of the traveling motor when the traveling motor is increased from a first speed to a second speed.

[0116] As shown in FIG. 4A, the control device 60 assumes that the changeover switch (changeover valve) 61 is operated at time Q21, and the control device 60 acquires a speed increase command (second speed command) to change from the first state (first speed) to the second state (second speed). When the control device 60 acquires the second speed command, the control device 60 reduces the actual angle W11 of the travel pump 53 (first travel pump 53L, second travel pump 53R) to a predetermined angle W13 that is lower than the target angle (target angle) W12 of the swash plate angle set based on the operation amount of the operation device 154. The predetermined angle W13 is an angle that reduces 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 actual angle W11.

[0117] As shown in Fig. 9A, the control device 60 stores reduction amount calculation data showing the relationship between the traveling pilot pressure and the reduction amount (reduction amount ΔD2) of the traveling pilot pressure. Fig. 9B is a graph of Fig. 9A. The reduction amount calculation data of Figs. 9A and 9B are examples and are not limited. In addition, the traveling speed (vehicle speed) shown in Fig. 9A is a value shown for convenience of explanation, and is a value at a predetermined prime mover rotation speed, and is not limited.

[0118] 9A and 9B show the amount of reduction in the traveling pilot pressure, and there is a correlation between the amount of reduction in the traveling pilot pressure and the amount of reduction in the swash plate angle ΔD2. That is, since the swash plate angle is controlled by the traveling pilot pressure, the higher the traveling pilot pressure, the larger the swash plate angle, and the lower the traveling pilot pressure, the smaller the swash plate angle. For example, as shown in Fig. 9A, when the control device 60 acquires a second speed command and the traveling speed is 5.0 km / h (traveling pilot pressure: 1.5 MPa), it sets the reduction amount of the traveling pilot pressure to 0.50 MPa. Note that, as shown in Fig. 9A, when reducing the prime mover rotation speed, the control device 60 sets a lower limit value of the swash plate angle (traveling pilot pressure) so that the swash plate angle, i.e., the traveling pilot pressure, does not become smaller than the minimum pilot pressure.

[0119] When the actual angle W11 reaches the predetermined angle W13 at time point Q22, the control device 60 returns the actual angle W11 to the target angle W12. Alternatively, the control device 60 returns the actual angle W11 to the target angle W12 midway during a reduction time T21 during which the actual angle W11 is reduced to the predetermined angle W13. Here, the control device 60 makes the return time T22 during which the actual angle W11 is returned from the predetermined angle W13 to the target angle W12 longer than the reduction time T21. That is, the control device 60 makes the reduction speed at which the actual angle W11 is reduced to the predetermined angle W13 faster than the return speed at which the actual angle W11 is returned from the predetermined angle W13 to the target angle W12.

[0120] Furthermore, the control device 60 outputs a signal to excite the solenoid of the travel switching valve 34 at a predetermined switching timing (timing during the return time T22 in FIG. 4A) from time Q21 to switch the travel switching valve (switching valve) 34 from the first state (first speed) to the second state (second speed). In other words, the control device 60 switches the travel switching valve 34 to the second state during the return time T22, and then returns the actual angle W11 to the target angle W12. 5A is a flowchart of a third operation of the control device 60 when changing the rotation speed of the traveling motor from a first speed to a second speed in the third embodiment. Note that the work machine 1 is not in a stopped state but in a traveling state.

[0121] The control device 60 judges whether the changeover switch 61 has been switched from the first speed to the second speed (S21). If the changeover switch 61 has not been switched to the second speed, that is, if the changeover switch 61 is maintained at the first speed (NO in S21), the control device 60 sets the actual angle W11 to the target angle W12 based on the operation of the operating device 154 (S22). If the changeover switch 61 has been switched from the first speed to the second speed (YES in S21), the control device 60 judges whether it is a predetermined switching timing from the time point Q21 (S23). If it is not the switching timing (NO in S23), the control device 60 proceeds to S5. On the other hand, if it is the switching timing (YES in S23), the control device 60 switches the travel switching valve 34 from the first state (first speed) to the second state (second speed) (S24). If the result is NO in S23 or after S24, the control device 60 reduces the actual angle W11 toward a predetermined angle W13 that is lower than the target angle W12 (S25).

[0122] The control device 60 judges whether the actual angle W11 has reached the predetermined angle W13 (S26), and returns to S23 if the actual angle W11 has not reached the predetermined angle W13 (NO in S26). On the other hand, when the actual angle W11 has reached the predetermined angle W13 (YES in S26), the control device 60 judges whether it is time to switch (S27). If it is time to switch (YES in S27), the control device 60 switches the travel switching valve 34 from the first state (first speed) to the second state (second speed) (S28). On the other hand, if it is not time to switch (NO in S27) or after S28, the control device 60 returns the actual angle W11 to the target angle W12 (S29). The control device 60 judges whether the actual angle W11 has returned to the target angle W12 (S30), and returns to S27 if it is not time to switch (NO in S30). When the control device 60 determines that the actual angle W11 has returned to the target angle W12 (YES in S30), the control device 60 ends this process.

[0123] FIG. 4B is a diagram showing the relationship between the swash plate angle (target angle, actual angle) and switching of the traveling motor when the traveling motor is decelerated from the second speed to the first speed. 4B, it is assumed that at time Q31, the changeover switch (changeover SW) 61 is operated and the control device 60 acquires a deceleration command (first speed command) to change from the second state (second speed) to the first state (first speed). When the control device 60 acquires the first speed command, it reduces the actual angle W11 of the travel pump 53 (first travel pump 53L, second travel pump 53R) to a predetermined angle W14 that is lower than the target angle W12 of the swash plate angle that is set based on the operation amount of the operating device 154.

[0124] When the actual angle W11 reaches the predetermined angle W14 at time point Q32, the control device 60 returns the actual angle W11 to the target angle W12. Alternatively, the control device 60 returns the actual angle W11 to the target angle W12 midway through a reduction time T31 during which the actual angle W11 is reduced to the predetermined angle W14. Here, the control device 60 sets the return time T32 during which the actual angle W11 is returned from the predetermined angle W14 to the target angle W12 to be shorter than the reduction time T31. That is, the control device 60 sets the reduction speed at which the actual angle W11 is reduced to the predetermined angle W14 to be slower than the return speed at which the actual angle W11 is returned from the predetermined angle W14 to the target angle W12.

[0125] Furthermore, the control device 60 outputs a signal to demagnetize the solenoid of the travel switching valve 34 at a predetermined switching timing (for example, a timing during the drop time T31) from the time point Q31, thereby switching the travel switching valve 34 from the second state (second speed) to the first state (first speed). In other words, the control device 60 returns the actual angle W11 to the target angle W12 during the drop time T31. 5B is a flowchart of a fourth operation of the control device 60 when changing the rotation speed of the traveling motor from the second speed to the first speed in the third embodiment. Note that the work machine 1 is not in a stopped state but in a traveling state.

[0126] The control device 60 judges whether the changeover switch 61 has been switched from the second speed to the first speed (S31). If the changeover switch 61 has not been switched to the second speed, i.e., if the second speed is maintained (NO in S31), the control device 60 sets the actual angle W11 to the target angle W12 based on the operation of the operating device 154 (S32). If the changeover switch 61 has been switched from the second speed to the first speed (YES in S31), the control device 60 From Q31, it is determined whether or not it is a predetermined switching timing (S33). If it is not the switching timing (NO in S33), the control device 60 proceeds to S35. On the other hand, if it is the switching timing (YES in S33), the control device 60 switches the traveling switching valve 34 from the second state (second speed) to the first state (first speed) (S34). If NO in S33 or after S34, the control device 60 reduces the actual angle W11 to a predetermined angle W14 lower than the target angle W12 (S35). The control device 60 determines whether or not the actual angle W11 has reached the predetermined angle W14 (S36), and returns to S33 if the actual angle W11 has not reached the predetermined angle W14 (NO in S36). On the other hand, when the actual angle W11 reaches the predetermined angle W14 (YES in S36), the control device 60 determines whether or not it is the switching timing (S37). If it is the switching timing (YES in S37), the control device 60 switches the travel switching valve 34 from the second state (second speed) to the first state (first speed) (S38). On the other hand, if it is not the switching timing (NO in S37) or after S38, the control device 60 returns the actual angle W11 to the target angle W12 (S39). The control device 60 determines whether the actual angle W11 has returned to the target angle W12 (S40), and if it is determined that the actual angle W11 has not returned (NO in S40), the control device 60 returns to S37. Note that if the control device 60 determines that the actual angle W11 has returned to the target angle W12 (YES in S40), this process ends.

[0127] Now, in the work machine 1 of the third embodiment as well, the control device 60 changes the delay period from the output timing of the shift command of the switching unit (changeover switch 61) to the switching timing of the travel switching valve 34, depending on the traveling pressure detected by the pressure detection device 80 (traveling pressure detection device) when a shift command is issued. The change in the delay period is the same as in the first and second embodiments described above, and therefore will not be described here.

[0128] For example, in the case shown in FIG. 3C of the first embodiment, when the forward traveling pressure exceeds the first threshold value for accelerating (YES in S55), the control device 60 selects a first value shorter than the median value as the delay period (S56). That is, the control device 60 changes the delay period from the median value (60 milliseconds) to the first value (40 milliseconds) as shown in FIG. 2C and FIG. 2D. As shown in FIG. 4A, the delay period Z12 in the case of the median value (60 milliseconds) is changed to a shorter delay period Z12A. On the other hand, when the forward traveling pressure does not exceed the first threshold value for accelerating (NO in S55), the control device 60 keeps the delay period at the median value (60 milliseconds) as shown in FIG. 2C and FIG. 2D (S57). As shown in FIG. 4A, the delay period Z12 is kept at the median value (60 milliseconds).

[0129] In the case shown in Fig. 3D of the first embodiment, when the reverse traveling pressure exceeds the second threshold value for deceleration (YES in S68), the control device 60 selects a second value longer than the median value as the delay period (S70). That is, the control device 60 changes the delay period from the median value (680 milliseconds) to the second value (700 milliseconds) as shown in Fig. 2C and Fig. 2D. As shown in Fig. 4B, the delay period Z13 when it is the median value (680 milliseconds) is changed to a longer delay period Z13A. The work machine 1 of the third embodiment can also provide the same effects as those of the work machines 1 of the first and second embodiments described above.

[0130] [Fourth embodiment] In the embodiment described above, the swash plate angle is changed by regulator 155, but the swash plate angle may be changed by other methods. For example, as shown in Fig. 7A, discharge oil passage 40 branches off midway, and proportional valve 69 is connected to section 40a of discharge oil passage 40 after the branch that leads to travel operation device 54. Proportional valve 69 is an electromagnetic proportional valve, and the opening degree of proportional valve 69 can be changed by control of control device 60.

[0131] When the control lever 59 of the travel operation device 54 is at full stroke, i.e., when the control valves 55 (55A, 55B, 55C, 55D) are substantially fully open, the control device 60, upon receiving a command from the changeover switch 61 to change from the first gear state to the second gear state, reduces the opening of the proportional valve 69 to a value smaller than the opening when the changeover switch 61 is operated, thereby lowering the primary pressure of the hydraulic oil directed toward the control valve 55, and reduces the swash plate angle of the travel pump 53 (first travel pump 53L, second travel pump 53R) from the current value, as in FIG. 4A. After the swash plate angle of the travel pump 53 (first travel pump 53L, second travel pump 53R) is reduced, the control device 60 switches the travel switching valve 34 to the second state, and after switching to the second state, restores the opening of the proportional valve 69.

[0132] In addition, when the control lever 59 of the travel operation device 54 is at full stroke, if the control device 60 receives a command to change from second gear to first gear by the changeover switch 61, the control device 60 reduces the opening of the proportional valve 69 to a value smaller than the opening when the changeover switch 61 is operated, thereby lowering the primary pressure of the hydraulic oil directed to the operation valve 55, and lowers the swash plate angle of the travel pump 53 (first travel pump 53L, second travel pump 53R) from the current value, as in FIG. 4B. After the swash plate angle of the travel pump 53 (first travel pump 53L, second travel pump 53R) is lowered, the control device 60 switches the travel switching valve 34 to the first state, and after switching to the first state, restores the opening of the proportional valve 69. Whether the operation lever 59 is at full stroke or not can be determined from the amount of operation detected by the operation detection device (sensor) 82.

[0133] That is, as shown in FIG. 7A, the proportional valve 69 provided in the discharge oil passage 40 (40a) can also reduce the swash plate angle of the travel pump 53 (first travel pump 53L, second travel pump 53R) when speeding up or slowing down. Now, in the work machine 1 of the fourth embodiment as well, the control device 60 changes the delay period from the output timing of the shift command of the switching unit (changeover switch 61) to the switching timing of the travel switching valve 34, depending on the traveling pressure detected by the pressure detection device 80 (traveling pressure detection device) when a shift command is issued. The change in the delay period is the same as in the first and second embodiments described above, and therefore will not be described here. The work machine 1 of the fourth embodiment can also provide the same effects as those of the work machines 1 of the first and second embodiments described above.

[0134] Furthermore, when a speed-up command is issued to the changeover switch 61 (switching unit), the control device 60 switches the traveling switching valve 34 from the first state to the second state in response to the speed-up command, for example, during a recovery period (for example, a period of recovery time T22 shown in FIG. 4A) in which the opening of the proportional valve 69 (operating valve) is reduced and then the opening is restored. Therefore, when performing the speed-up process, the switching timing of the traveling switching valve 34 during the control of reducing the opening of the proportional valve 69 can be appropriately set. Therefore, for a work machine 1 in which a deviation in the speed-up timing occurs due to variations in the response delay of the rotation of the hydraulic device or the prime mover 32, the shock of the speed-up can be appropriately reduced when the speed of the work machine 1 is increased.

[0135] Furthermore, when a speed change command for deceleration is given to the change-over switch 61 (switching unit), the control device 60 switches the traveling switching valve 34 from the second state to the first state while the opening of the proportional valve 69 (operating valve) is being reduced. Therefore, when performing deceleration processing, it is possible to appropriately set the switching timing of the traveling switching valve 34 while the opening of the proportional valve 69 is being controlled to be reduced. Therefore, for a work machine 1 in which a deviation in the speed change timing occurs due to variations in the response delay of the rotation of the hydraulic equipment or the prime mover 32, it is possible to appropriately reduce the shock of the speed change when the speed of the work machine 1 is decelerated.

[0136] As described above, the control device 60 can change the delay period from the output timing of the shift command of the changeover switch 61 to the switching timing of the travel switching valve 34, depending on the travel pressure detected by the pressure detection device 80 (travel pressure detection device) at the time of the shift command. Therefore, the control device 60 can change the delay period to the advance period shown in Figures 4E and 4F, or the post-return period shown in Figures 4C and 4D.

[0137] Here, a case will be described where the delay periods Z16A, Z17A are set to the advance periods shown in Figs. 4E and 4F. When performing the speed increase process, the control device 60 may switch the travel switching valve 34 from the first state to the second state during the advance period until the supply amount to the travel motor 36 starts to decrease (for example, as shown in Fig. 4E, advance period T21A until the opening degree of the proportional valve 69 (operating valve) starts to decrease). When the delay period Z16A is set within the advance period T21A, the control device 60 switches the travel switching valve 34 from the second state to the first state in S24 shown in Fig. 5A. In this case, for a work machine 1 in which a shift in the timing of the speed change occurs due to variations in the response delay of the rotation of the hydraulic device or the prime mover 32, it is possible to appropriately reduce the shock of the speed change when performing the speed increase process. In addition, the control device 60 When performing deceleration processing, the travel switching valve 34 may be switched from the second state to the first state during a preliminary period until the supply amount to the travel motor 36 starts to decrease (for example, as shown in FIG. 4F, preliminary period T31A until the opening degree of the proportional valve 69 (operating valve) starts to decrease). When the control device 60 sets the delay period Z17A within the preliminary period T31A, the control device 60 switches the travel switching valve 34 from the second state to the first state in S34 shown in FIG. 5B. In this case, for a work machine 1 in which a deviation in the timing of gear shifting occurs due to variations in the response delay of the rotation of the hydraulic device or the prime mover 32, it is possible to appropriately reduce the shock of gear shifting when performing deceleration processing.

[0138] Next, a case where the delay periods Z16 and Z17 are set to extend to the post-return period shown in Fig. 4C and Fig. 4D will be described. When performing the speed-up process, the control device 60 may switch the traveling switching valve 34 from the first state to the second state during the post-return period (for example, as shown in Fig. 4C, the post-return period T23, which is a period from the time when the opening degree of the proportional valve 69 (operating valve) is restored to a predetermined period). When the end point of the delay period Z16 is set within the post-return period T23, the control device 60 provides the same processes as S27 and S28 after S30 shown in Fig. 5A, and switches the traveling switching valve 34 from the first state to the second state in the same process as S28. In this case, for the work machine 1 in which a shift in the timing of the speed-up process occurs due to the variation in the response delay of the rotation of the hydraulic device or the prime mover 32, the shock of the speed-up process can be appropriately reduced. Furthermore, when performing the deceleration process, the control device 60 may switch the traveling switching valve 34 from the second state to the first state during a post-return period (for example, as shown in FIG. 4D, a post-return period T33 that is a period from the time when the opening degree of the proportional valve 69 (operating valve) is restored to a predetermined period). When the control device 60 sets the end point of the delay period Z17 within the post-return period T33, the control device 60 provides the same processes as S37 and S38 after S40 shown in FIG. 5B, and switches the traveling switching valve 34 from the second state to the first state in the same process as S38. In this case, for a work machine 1 in which a shift in the timing of the shift occurs due to a variation in the response delay of the rotation of the hydraulic device or the prime mover 32, it is possible to appropriately reduce the shock of the shift when performing the deceleration process.

[0139] Furthermore, when performing the speed increase process, the control device 60 makes the absolute value of the slope of the supply amount to the operation valve 55 smaller during the return period (e.g., the period of return time T22 shown in FIG. 4A) than during the decrease period (e.g., the period of decrease time T21 shown in FIG. 4A). This configuration makes it possible to reduce the shock of the gear shift while shortening the period for reducing the shock of the gear shift. Specifically, when performing the speed increase process, the absolute value of the slope of the supply amount to the operation valve 55 is smaller during the return period than during the decrease period. In other words, since the decrease period is made shorter than the return period, the period for reducing the shock of the gear shift can be shortened accordingly.

[0140] Furthermore, when performing deceleration processing, the control device 60 makes the absolute value of the slope of the supply amount to the operation valve 55 smaller in the decrease intermediate period (e.g., the period of decrease time T31 shown in FIG. 4B) than in the return intermediate period (e.g., the period of return time T32 shown in FIG. 4B). With this configuration, it is possible to reduce the shock of the gear shift while shortening the period for reducing the shock of the gear shift. Specifically, when performing deceleration processing, the absolute value of the slope of the supply amount to the operation valve 55 is smaller in the decrease intermediate period than in the return intermediate period. In other words, since the return intermediate period is made shorter than the decrease intermediate period, it is possible to shorten the period for reducing the shock of the gear shift by the shortened period.

[0141] [Fifth embodiment] The work machine 1 of the fifth embodiment shown in Fig. 7 is equipped with a tilt detection device 63 (e.g., an acceleration sensor, an inertial measurement sensor, etc.) that detects the pitch angle of the machine body 2. When the machine body 2 moves forward or backward in a normal mode that is not a setting mode in which a gear shift switching timing is set, if the pitch angle detected by the tilt detection device 63 is a positive value, the control device 60 corrects the delay period so as to shorten the delay period according to the magnitude of the pitch angle, and if the pitch angle detected by the tilt detection device 63 is a negative value, the control device 60 corrects the delay period so as to lengthen the delay period according to the magnitude of the pitch angle. According to this configuration, the delay period is corrected according to the pitch angle, so that it is possible to appropriately reduce gear shift shock when the work machine 1 moves forward or backward on an upward or downward slope in the normal mode.

[0142] Furthermore, when the vehicle 2 moves forward or backward in the setting mode, if the pitch angle detected by the tilt detection device 63 is a positive value, the control device 60 may correct the threshold value to be larger according to the magnitude of the pitch angle, and if the pitch angle detected by the tilt detection device 63 is a negative value, the control device 60 may correct the threshold value to be smaller according to the magnitude of the pitch angle. According to this configuration, since the running pressure increases on an upward slope, by increasing the threshold value accordingly, the delay period can be appropriately set even when the setting mode for setting the gear shift switching timing is performed under an upward slope. Furthermore, since the running pressure decreases on a downward slope, by decreasing the threshold value accordingly, the delay period can be appropriately set even when the setting mode for setting the gear shift switching timing is performed under a downward slope.

[0143] [First Modification] In the user switching mode in which the user sets the shift change timing, when the operation lever 59 (operation member) is operated for forward travel and the speed increase or decrease process is performed, the control device 60 determines whether the forward travel pressure (i.e., the first travel pressure V1 and the third travel pressure V3) detected by the first travel pressure detection device (the first pressure detection device 80a and the third pressure detection device 80c) exceeds a threshold value, and when it is determined that the threshold value is not exceeded, the control device 60 may set the delay period to the median value, and when it is determined that the threshold value is exceeded, the control device 60 may set the delay period to the first value instead of the median value. According to this configuration, in the user switching mode in which the user sets the shift change timing, when it is determined that the forward travel pressure exceeds the threshold value when the work machine 1 moves forward and performs the speed increase or decrease process, the control device 60 changes the delay period from the output timing of the speed increase or decrease command for forward travel to the switching timing of the travel switching valve 34 to the first value, which is a period shorter than the period indicated by the median value. Therefore, in the user switching mode, for a work machine 1 in which there is a deviation in the timing of gear shifting due to variations in the response delay of the rotation of the hydraulic equipment or the prime mover 32, if the median value does not sufficiently reduce the gear shift shock, the delay period can be changed to a first value that is shorter than the median value, thereby making it possible to appropriately reduce the gear shift shock when the work machine 1 moves forward.

[0144] In addition, in FIG. 2C and FIG. 2D, the first value (for example, 40 milliseconds) and the second value (for example, 80 milliseconds) in the case of accelerating are each one, and the first value (for example, 660 milliseconds) and the second value (for example, 700 milliseconds) in the case of decelerating are each one, but this is not limited to this. For example, the first value in the case of accelerating may be a plurality of values ​​such as 50 milliseconds, 40 milliseconds, 30 milliseconds, etc., and the second value in the case of accelerating may be a plurality of values ​​such as 70 milliseconds, 80 milliseconds, 90 milliseconds, etc., and the control device 60 may select the first value in a stepwise decreasing order and the second value in a stepwise increasing order until the traveling pressure detected by the pressure detection device 80 does not exceed the threshold value. In addition, the first value (for example, 660 milliseconds) and the second value (for example, 700 milliseconds) in the case of decelerating may also be a plurality of values. For example, the first value in the case of speed increase may be multiple, such as 670 milliseconds, 660 milliseconds, 650 milliseconds, etc., and the second value in the case of speed increase may be multiple, such as 690 milliseconds, 700 milliseconds, 710 milliseconds, etc., and the control device 60 may select the first value in an order of gradually decreasing values ​​and the second value in an order of gradually increasing values ​​until the running pressure detected by the pressure detection device 80 no longer exceeds the threshold value.

[0145] [Second modified example] In the second modified example, the delay period during forward travel is internally changed based on the operational record. Specifically, in a normal mode that is not a setting mode for setting the shift change timing, when the operation of the operating lever 59 (operating member) is a forward travel operation and a speed increase process or a speed decrease process is performed, the control device 60 determines whether the forward travel pressure detected by the first travel pressure detection device exceeds a threshold value, and if it is determined that the threshold value is exceeded, stores the determination result that the threshold value is exceeded in the storage device 60a, and when the number of determination results reaches a predetermined number of actual results, the first value may be used as the delay period instead of the median value.

[0146] According to this configuration, in a normal mode that is not a setting mode, when the determination result that the forward traveling pressure exceeds the threshold when the work machine 1 moves forward and performs an acceleration process or deceleration process reaches a predetermined number of actual results, the delay period is changed to the first value instead of the median value. Therefore, for a work machine 1 in which a shift timing is shifted due to variations in the response delay of the rotation of the hydraulic device or the prime mover 32, the delay period can be changed to the first value that is shorter than the median value based on the actual results that the median value does not sufficiently reduce the shift shock. Therefore, the shift shock when the work machine 1 moves forward can be appropriately reduced based on the actual results.

[0147] Furthermore, the delay period during reverse travel may be internally changed based on the operation record. Specifically, in a normal mode that is not a setting mode for setting the shift change timing, when the operation lever 59 (operation member) is a reverse operation and deceleration is performed, the control device 60 may determine whether or not the reverse travel pressure detected by the first travel pressure detection device exceeds a threshold value, and if it is determined that the threshold value is exceeded, store the determination result that the threshold value is exceeded in the storage device 60a, and if the number of determination results has not reached a predetermined number of results, set the median value as the delay period, and if the number of determination results has reached the predetermined number of results, set the first value as the delay period.

[0148] According to this configuration, when the determination result that the traveling pressure on the reverse side exceeds the threshold when the work machine 1 is reversed and decelerating in the normal mode, which is not the setting mode, reaches a predetermined number of actual results, the delay period is changed to the first value instead of the median value. Therefore, for a work machine 1 in which a shift timing deviation occurs due to variation in the response delay of the rotation of the hydraulic device or the prime mover 32, the delay period can be changed to the first value which is shorter than the median value based on the actual result that the median value does not sufficiently reduce the shift shock. Therefore, the shift shock when the work machine 1 is reversed can be appropriately reduced based on the actual result.

[0149] [Third Modification] In the work machine 1 of the third modified example, when a speed-change command to increase speed is given to the change-over switch 61, the control device 60 switches the traveling change-over valve 34 from the first state to the second state in response to the speed-change command during the advance period until the opening of the proportional valve 69 (operating valve) starts to decrease, and during the return period or post-return period in which the opening of the proportional valve 69 is restored after being decreased, and when a speed-change command to decrease speed is given to the change-over switch 61, the control device 60 switches the traveling change-over valve 34 from the second state to the first state in response to the speed-change command during the advance period until the rotational speed of the prime mover 32 starts to decrease, and during the reduction period or post-return period in which the rotational speed of the prime mover 32 is reduced below the target rotational speed operated by the accelerator 65.

[0150] According to this configuration, when performing the speed increase process, the control device 60 switches the travel switching valve 34 from the first state to the second state in the advance period until the proportional valve 69 starts to decrease in opening degree, during the return period or the post-return period of the opening degree of the proportional valve 69. Therefore, when performing the speed increase process, the switching timing of the travel switching valve 34 during the control of decreasing the opening degree of the proportional valve 69 can be appropriately set. Therefore, for the work machine 1 in which a shift in the timing of the speed change occurs due to the variation in the response delay of the hydraulic device or the rotation of the prime mover 32, the shock of the speed change when increasing the speed of the work machine 1 can be appropriately reduced. Furthermore, when performing the deceleration process, the control device 60 switches the travel switching valve from the second state to the first state in the advance period until the rotation speed of the prime mover 32 starts to decrease, during the decrease period or the post-return period of the rotation speed of the prime mover 32. Therefore, when performing the deceleration process, the switching timing of the travel switching valve 34 during the control of decreasing the rotation speed of the prime mover 32 can be appropriately set. Therefore, for a work machine 1 in which deviations in the timing of gear shifting occur due to variations in the response delay of the rotation of the hydraulic equipment or the prime mover 32, the gear shift shock when the speed of the work machine 1 is decelerated can be appropriately reduced.

[0151] [Fourth Variation] In the first and fourth embodiments described above, the travel operation device 54 is of a hydraulic type that changes the pilot pressure acting on the travel pumps (first travel pump 53L, second travel pump 53R) using the operating valve 55, but in the work machine of the fourth modified example, the travel operation device 54 shown in FIG. 6B may be an electrically operated device.

[0152] As shown in Fig. 6B, the traveling operation device 54 includes an operation lever 59 that swings left and right (machine body width direction) or front and rear, and operation valves 55 (operation valves 55A, 55B, 55C, 55D) configured from electromagnetic proportional valves. An operation detection sensor that detects the operation amount and operation direction of the operation lever 59 is connected to the control device 60. The control device 60 controls the operation valves 55 (operation valves 55A, 55B, 55C, 55D) based on the operation amount and operation direction detected by the operation detection sensor.

[0153] When the operating lever 59 is operated forward (in the A1 direction, see FIG. 1), the control device 60 outputs a control signal to the operating valve 55A and the operating valve 55C, causing the swash plates of the first traveling pump 53L and the second traveling pump 53R to swing in the normal (forward) direction. When the operating lever 59 is operated rearward (A2 direction, see Figure 1), the control device 60 outputs a control signal to the operating valve 55B and the operating valve 55D, causing the swash plates of the first traveling pump 53L and the second traveling pump 53R to swing in the reverse (reverse) direction. When the operating lever 59 is operated to the right (A3 direction, see Figure 1), the control device 60 outputs a control signal to the operating valve 55A and the operating valve 55D, causing the swash plate of the first traveling pump 53L to swing in the forward rotation direction and the swash plate of the second traveling pump 53R to swing in the reverse rotation direction.

[0154] When the operating lever 59 is operated to the left (A4 direction, see Figure 1), the control device 60 outputs a control signal to the operating valve 55B and the operating valve 55C, causing the swash plate of the first traveling pump 53L to oscillate in the reverse direction and the swash plate of the second traveling pump 53R to oscillate in the forward direction. 6B, the control device 60 may change the delay period from the output timing of the shift command from the change-over switch 61 to the switching timing of the travel switching valve 34. This makes it possible to perform adjustments to reduce shift shock for a work machine 1 in which deviations in the shift timing occur due to variations in the response delays of the rotation of the hydraulic equipment or the prime mover 32.

[0155] [Fifth Modification] Fig. 6C is a diagram showing a part of a hydraulic system (hydraulic circuit) of a work machine in the fifth modified example. As in Fig. 6B, the fifth modified example employs an operating lever 59 configured as an electrically operated joystick and a control device 60. In this embodiment, instead of the operating valve 55 (operating valves 55a, 55b, 55c, 55d) shown in Fig. 6B, operating valves (operating valves) 155L, 155R and hydraulic regulators 156L, 156R configured as solenoid proportional valves shown in Fig. 6C are employed.

[0156] As in the fourth modified example, the operation lever 59 is an operation lever that swings left and right (body width direction) or front and rear. The operation lever 59 has a sensor (operation detection sensor) that detects the operation amount (swing amount) and operation direction (swing direction). This operation detection sensor is connected to the control device 60. The control valves (operating valves) 155L, 155R, which are constituted by electromagnetic proportional valves, are electrically connected to the control device 60. As with the control valves 55 (control valves 55a, 55b, 55c, 55d) according to the fifth modified example, the switching positions and openings of the control valves 155L, 155R are also controlled by control signals from the control device 60 in response to the operation of the control lever 59.

[0157] As shown in Fig. 6C, the hydraulic regulators 156L, 156R are connected to the swash plates of the travel pumps (first travel pump 53L, second travel pump 53R). Each of the hydraulic regulators 156L, 156R can change the angle of the swash plate (swash plate angle) of the travel pumps 53L, 53R (first travel pump 53L, second travel pump 53R), and includes a supply chamber 157 to which hydraulic oil is supplied, and a piston rod 158 provided in the supply chamber 157. The piston rod 158 is connected to the swash plate, and the swash plate swings due to the movement (i.e., extension and contraction) of the piston rod 158, and the swash plate angle can be changed.

[0158] Here, the supply chamber 157 of the hydraulic regulator 156L connected to the swash plate of the first travel pump 53L is referred to as a first pressure receiving portion, and the supply chamber 157 of the hydraulic regulator 156R connected to the swash plate of the second travel pump 53R is referred to as a second pressure receiving portion. The operating valve 155L is a valve that operates the hydraulic regulator 156L, and controls the amount of hydraulic oil output by the first travel pump 53L by operating the hydraulic regulator 156L. The operating valve 155L is configured as an electromagnetic proportional valve having a solenoid 160L, and a spool of the operating valve 155L moves based on a control signal output from the control device 60 to the solenoid 160L. This movement of the spool changes the opening degree of the operating valve 155L. The operating valve 155L has a first position 159a, a second position 159b, and a neutral position 159c, and can be switched to any of these positions.

[0159] A first port of the operation valve 155L and a supply chamber 157 of the hydraulic regulator 156L are connected by a first travel oil passage 45a. A second port of the operation valve 155L and a supply chamber 157 of the hydraulic regulator 156L are connected by a second travel oil passage 45b. The operating valve 155R is a valve that operates the hydraulic regulator 156R, and controls the amount of hydraulic oil output by the second travel pump 53R by operating the hydraulic regulator 156R. The operating valve 155R is configured as an electromagnetic proportional valve having a solenoid 160R, and a spool of the operating valve 155R moves based on a control signal applied to the solenoid 160R from the control device 60. This movement of the spool changes the opening degree of the operating valve 155R. The operating valve 155R has a first position 159a, a second position 159b, and a neutral position 159c, and can be switched to any of these positions.

[0160] A first port of the operation valve 155R and a supply chamber 157 of the hydraulic regulator 156R are connected by a third traveling oil passage 45c. A second port of the operation valve 155R and a supply chamber 157 of the hydraulic regulator 156R are connected by a fourth traveling oil passage 45d. When the control valves 155L and 155R are switched to the first position 159a, the hydraulic regulators 156L and 156R are operated to swing the swash plates of the first travel pump 53L and the second travel pump 53R, and the travel pumps rotate in the forward direction. When the control valves 155L and 155R are switched to the second position 159b, the hydraulic regulators 156L and 156R are operated to swing the swash plates of the first travel pump 53L and the second travel pump 53R, and the travel pumps rotate in the reverse direction.

[0161] When the control valve 155L is switched to the first position 159a and the control valve 155R is switched to the second position 159b, the first travel pump 53L rotates forward and the second travel pump 53R rotates reverse. When the control valve 155L is switched to the second position 159b and the control valve 155R is switched to the first position 159a, the first travel pump 53L rotates reverse and the second travel pump 53R rotates forward. In this embodiment, the hydraulic regulators 156L, 156R are operated by operating the operating valves 155L, 155R using the operating lever 59 and the control device 60, thereby oscillating the swash plates of the first traveling pump 53L and the second traveling pump 53R, as in the second embodiment.

[0162] 6C, the control device 60 may change the delay period from the output timing of the shift command from the change-over switch 61 to the switching timing of the travel switching valve 34. This makes it possible to perform adjustments to reduce shift shock for a work machine 1 in which deviations in shift timing occur due to variations in response delays in the rotation of the hydraulic equipment or the prime mover 32. The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present invention is defined by the claims, not the above description, and is intended to include all modifications within the meaning and scope of the claims.

[0163] In the above-described embodiment, the switching unit (switch 61) is configured as a switch 61 that can be operated manually by an operator or the like, but it may be built into the control device 60. When built into the control device 60, the switching unit is configured with a program and electric and electronic components (electric and electronic circuits) stored in the control device 60. In this case, the switching unit of the control device 60 judges whether to switch between the first speed state and the second speed state based on detection information from various detection devices, for example, sensors, provided in the work machine 1, and outputs a control signal to the traveling switching valve 34 based on the judgment result. When the traveling switching valve 34 receives a control signal for the first speed state, it switches to the first speed state, and when the traveling switching valve 34 receives a control signal for the second speed state, it switches to the second speed state.

[0164] The travel switching valve 34 may be any valve that can be switched between a first state in which the travel motors 36 (first travel motor 36L, second travel motor 36R) are at a first speed, and a second state in which they are at a second speed, and may be a proportional valve different from a directional control valve. The travel motor 36 is a motor having a neutral position between the first speed and the second speed. may be also possible.

[0165] The travel motors 36 (first travel motor 36L, second travel motor 36R) may be axial piston motors or radial piston motors. When the travel motors are radial piston motors, the motor capacity is increased to allow switching to first speed, and the motor capacity is decreased to allow switching to second speed. Since the traveling speed changes depending on the operation of the operating lever 59, the traveling detection device 67 may be a device that detects the traveling speed based on the operation amount (operation angle) and operation position of the operating lever 59. As described above, since the second speed (second state) only needs to be faster than the first speed (first state), the working machine is not limited to having two gears, and can also be applied to a multi-gear (multiple gears) working machine. [Explanation of symbols]

[0166] 1 Work equipment 2. Aircraft 32 Prime Mover 34 Travel changeover valve 36 Travel motor 53 Travel pump 54 Travel control device 60 Control device 60a Storage device 61 Changeover switch (changeover part) 65 Axel 67 Travel detection device 80 Pressure detection device (travel pressure detection device) 80a: First pressure detection device (first travel pressure detection device) 80b Second pressure detection device (second travel pressure detection device) 80c Third pressure detection device (first travel pressure detection device) 80d Fourth pressure detection device (second travel pressure detection device)

Claims

1. The prime mover, a travel pump that is operated by the power of the prime mover and discharges hydraulic oil; a travel motor that can be rotated by the hydraulic oil discharged by the travel pump; a machine body provided with the prime mover, the travel pump, and the travel motor; a travel switching valve switchable between a first state in which the rotation speed of the travel motor can be increased up to a first maximum speed and a second state in which the rotation speed of the travel motor can be increased up to a second maximum speed that is higher than the first maximum speed; a travel operation device having an operation valve capable of changing a pressure of hydraulic oil acting on the travel pump in response to an operation of an operation member; a control device that reduces the amount of hydraulic oil supplied from the travel pump to the travel motor based on a travel state of the vehicle when performing either an acceleration process for switching from the first state to the second state or a deceleration process for switching from the second state to the first state; and Equipped with When performing the speed increase process, the control device switches the travel switching valve from the first state to the second state during a middle recovery period or a post recovery period in which the supply amount to the travel motor is restored after being reduced.

2. The prime mover, a travel pump that is operated by the power of the prime mover and discharges hydraulic oil; a travel motor that can be rotated by the hydraulic oil discharged by the travel pump; a machine body provided with the prime mover, the travel pump, and the travel motor; a travel switching valve switchable between a first state in which the rotation speed of the travel motor can be increased up to a first maximum speed and a second state in which the rotation speed of the travel motor can be increased up to a second maximum speed that is higher than the first maximum speed; a travel operation device having an operation valve capable of changing a pressure of hydraulic oil acting on the travel pump in response to an operation of an operation member; a control device that reduces the amount of hydraulic oil supplied from the travel pump to the travel motor based on a travel state of the vehicle when performing either an acceleration process for switching from the first state to the second state or a deceleration process for switching from the second state to the first state; and Equipped with When performing the deceleration process, the control device switches the travel switching valve from the second state to the first state during a middle decrease period or a post return period in which the supply amount to the travel motor is reduced.

3. The work machine according to claim 1 , wherein, when the deceleration process is performed, the control device switches the travel switching valve from the second state to the first state during a middle decrease period or a post-return period in which the supply amount to the travel motor is reduced.

4. a travel detection device capable of detecting a travel speed of the vehicle as the travel state, The work machine according to claim 1 or 3, wherein when performing the speed increase process, the control device determines an amount of reduction in the supply amount to the traveling motor corresponding to the traveling speed detected by the traveling detection device, and reduces the supply amount to the traveling motor in accordance with the determined amount of reduction.

5. a travel detection device capable of detecting a travel speed of the vehicle as the travel state, The work machine according to claim 2 or 3, wherein when performing the deceleration process, the control device determines an amount of reduction in the supply amount to the traveling motor corresponding to the traveling speed detected by the traveling detection device, and reduces the supply amount to the traveling motor in accordance with the determined amount of reduction.

6. A switching unit that issues a speed change command to either increase or decrease speed; An accelerator for controlling the rotation speed of the prime mover; Equipped with the control device reduces an amount of hydraulic oil supplied from the travel pump to the travel motor by reducing a rotation speed of the prime mover, 4. The work machine according to claim 1 or 3, wherein when a speed change command to increase the speed is given to the switching unit, the control device switches the travel switching valve from the first state to the second state in response to the speed change command during a middle recovery period or a post recovery period in which the rotation speed of the prime mover is restored to a target rotation speed, which is the rotation speed of the prime mover operated by the accelerator, after the rotation speed of the prime mover has been reduced.

7. A switching unit that issues a speed change command to either increase or decrease speed; An accelerator for controlling the rotation speed of the prime mover; Equipped with the control device reduces an amount of hydraulic oil supplied from the travel pump to the travel motor by reducing a rotation speed of the prime mover, 4. The work machine according to claim 2 or 3, wherein when a speed change command for deceleration is given to the switching unit, the control device switches the travel switching valve from the second state to the first state in response to the speed change command during a middle period of reduction or a post-return period in which the rotation speed of the prime mover is reduced below a target rotation speed, which is the rotation speed of the prime mover operated by the accelerator.

8. The work machine according to claim 6, wherein when a speed change command for deceleration is given to the switching unit, the control device switches the travel switching valve from the second state to the first state in response to the speed change command during a middle period of reduction or a post-return period in which the rotation speed of the prime mover is reduced to be lower than the target rotation speed operated by the accelerator.

9. A switching unit that issues a speed change command to either increase or decrease speed; an actuation valve connected to the operation valve on the upstream or downstream side of the operation valve and capable of controlling hydraulic oil flowing through the operation valve; Equipped with 4. The work machine according to claim 1 or 3, wherein when a speed change command to increase the speed is given to the switching unit, the control device switches the travel switching valve from the first state to the second state in response to the speed change command during a preliminary period until a reduction in the opening degree of the operating valve starts, a middle recovery period or a post recovery period in which the opening degree of the operating valve is restored after the reduction in the opening degree of the operating valve is restored.

10. A switching unit that issues a speed change command to either increase or decrease speed; an actuation valve connected to the operation valve on the upstream or downstream side of the operation valve and capable of controlling hydraulic oil flowing through the operation valve; Equipped with 4. The work machine according to claim 2 or 3, wherein when a speed change command for deceleration is given to the switching unit, the control device switches the travel switching valve from the second state to the first state in response to the speed change command during a preliminary period until a reduction in the opening degree of the operating valve starts, a reduction period in which the opening degree of the operating valve is reduced, or a post-return period.

11. The work machine according to claim 9, wherein, when a speed change command for deceleration is given to the switching unit, the control device switches the travel switching valve from the second state to the first state in response to the speed change command during a preliminary period until a reduction in the opening degree of the operating valve starts, a reduction period in which the opening degree of the operating valve is reduced, or a post-return period.

12. A switching unit that issues a speed change command to either increase or decrease speed; An accelerator for controlling the rotation speed of the prime mover; an actuation valve connected to the operation valve on the upstream or downstream side of the operation valve and capable of controlling hydraulic oil flowing through the operation valve; Equipped with The control device includes: When a speed-change command to increase the speed is given to the switching unit, the travel switching valve is switched from the first state to the second state in response to the speed-change command during a pre-period until the reduction in the opening degree of the operating valve starts, during a recovery period or a post-recovery period in which the opening degree of the operating valve is restored after the reduction in the opening degree of the operating valve is restored, 4. The work machine according to claim 3, wherein when a speed change command for deceleration is given to the switching unit, the travel switching valve is switched from the second state to the first state in response to the speed change command during a preliminary period until a decrease in the rotation speed of the prime mover begins, a decrease period during which the rotation speed of the prime mover is decreased below a target rotation speed that is the rotation speed of the prime mover operated by the accelerator, or a post-return period.

13. The work machine according to any one of claims 6 to 12, wherein the switching unit is a change-over switch that outputs the speed change command to the control device.

14. The work machine according to claim 1, 4, 6 or 9, wherein, when performing the speed-up process, the control device makes the absolute value of the slope of the supply amount to the operating valve smaller during the return period than during the decrease period in which the supply amount to the travel motor is decreased.

15. The work machine according to claim 2, 5, 7 or 10, wherein when the control device performs the deceleration process, the absolute value of the slope of the supply amount to the operating valve is smaller during the decrease intermediate period than during the return intermediate period in which the supply amount to the travel motor is restored after being reduced.

Images