Work equipment

Abstract

To enable a work machine to be automatically accelerated easily according to a state of the work machine.SOLUTION: A work machine comprises: a machine body; an engine provided on the machine body; a left travel device provided on a left side of the machine body; a right travel device provided on a right side of the machine body; a left travel motor that can transmit power to the left travel device and switch between a first speed and a second speed faster than the first speed; a right travel motor that can transmit the power to the right travel device and switch between the first speed and the second speed faster than the first speed; and a control device that can automatically accelerate from the first speed to the second speed when the left travel motor and the right travel motor are at the first speed and can change and set an acceleration threshold for determining whether or not automatically accelerating.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, or a backhoe. [Background technology]

[0002] A conventional technique for decelerating and accelerating a work machine is disclosed in Patent Document 1. The work machine in Patent Document 1 includes a prime mover including an engine, a hydraulic pump that is operated by power from the prime mover and discharges hydraulic oil, a traveling hydraulic device that can change the speed between a first speed and a second speed that is faster than the first speed depending on the pressure of the hydraulic oil, an actuated valve that can change the pressure of the hydraulic oil acting on the traveling hydraulic device, and a measuring device that can detect the pressure of the hydraulic oil, and when the detected pressure, which is the pressure of the hydraulic oil detected by the measuring device, drops from a set pressure corresponding to the second speed to a predetermined pressure or below, the actuated valve reduces the pressure of the hydraulic oil acting on the traveling hydraulic device to decelerate the traveling hydraulic device to the first speed. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-179923 Summary of the Invention [Problem to be solved by the invention]

[0004] The work machine of Patent Document 1 can automatically decelerate from the second speed to the first speed when the pressure of the hydraulic oil supplied to the traveling device is equal to or higher than a predetermined value while traveling. However, in reality, it is difficult to automatically increase the speed appropriately depending on the condition of the work machine.

[0005] The present invention has been made to solve the problems of the prior art as described above, and has an object to provide a work machine that can easily automatically increase speed depending on the condition of the work machine. [Means for solving the problem]

[0006] The technical means adopted by the present invention to solve the technical problems are as follows.

[0007] The work machine includes a body, a prime mover provided on the body, a left traveling device provided on the left side of the body, a right traveling device provided on the right side of the body, a left traveling motor capable of transmitting power to the left traveling device and switchable between a first speed and a second speed faster than the first speed, and a right traveling motor capable of transmitting power to the right traveling device and switchable between a first speed and a second speed faster than the first speed. a left traveling pump driven by the prime mover and supplying hydraulic oil to the left traveling motor; and a right traveling pump driven by the prime mover and supplying hydraulic oil to the right traveling motor. The left traveling motor and the right traveling motor Automatic deceleration is performed to automatically decelerate from the second speed to the first speed. The first speed After that, from the first speed to the second speed automatically To decide whether to switch Recovery Threshold and a control device that can change and set the

[0008] the return threshold is determined according to the rotation speed of the prime mover, The control device The rotation speed of the prime mover Based on the above return Change the threshold.

[0010] The work equipment is a travel operation member that can change the rotation direction of the left travel motor and the right travel motor, The control device When the speed is automatically switched from the first speed to the second speed, the rotation speed of the prime mover is the same, and the operation of the travel operating member is for straight travel, the return threshold value is set to: When the operation of the travel operating member is a turning operation, return Threshold Make it higher than that.

[0011] The control device adjusts the degree of straight traveling based on the operation of the travel operating member. return Change the threshold.

[0012] The work machine includes a first circulation oil passage connected to a first port and a second port of the left traveling pump and connected to the left traveling motor, a second circulation oil passage connected to a third port and a fourth port of the right traveling pump and connected to the right traveling motor, a first pressure detection device provided on the first port side of the left traveling motor and detecting the pressure of hydraulic oil acting on the first circulation oil passage when the left traveling motor is rotating as a first traveling pressure, and a second pressure detection device provided on the second port side of the left traveling motor and detecting the pressure of hydraulic oil acting on the first circulation oil passage when the left traveling motor is rotating as a first traveling pressure. a second pressure detection device that detects the pressure of hydraulic oil acting on the oil passage as a second traveling pressure; a third pressure detection device that is provided on a third port side of the right traveling motor and that detects the pressure of hydraulic oil acting on the second circulation oil passage when the right traveling motor is rotating as a third traveling pressure; and a fourth pressure detection device that is provided on a fourth port side of the right traveling motor and that detects the pressure of hydraulic oil acting on the second circulation oil passage when the right traveling motor is rotating as a fourth traveling pressure, and the control device is In a situation where the automatic deceleration is being performed, The first travelling pressure, the second travelling pressure, the third travelling pressure, and the fourth travelling pressure When the speed becomes equal to or less than the return threshold, the speed is automatically switched from the first speed to the second speed. . [Effects of the Invention]

[0013] According to the present invention, automatic speed increase can be easily performed according to the condition of the work machine. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 2 is a diagram showing a hydraulic system (hydraulic circuit) of the work machine. [Figure 2] 4A and 4B are diagrams showing the operation direction of a travel operation member, etc.; [Figure 3] FIG. 10 is a diagram showing an example of the relationship between the traveling state of the work machine and a correction coefficient η. [Figure 4] 5 is a diagram showing an example of the travel state of the work machine, the prime mover rotation speed, and the correction coefficient η (rpm). FIG. [Figure 5] FIG. 4 is a diagram showing an example of a traveling state of a work machine, a first correction coefficient ηa, and a second correction coefficient ηb. [Figure 6]FIG. 10 is a diagram showing an example of a correction coefficient η (deceleration threshold ST (rpm)). [Figure 7] FIG. 10 is a diagram showing an example of a correction coefficient η (deceleration threshold ST (rpm)) based on a difference in motor rotation speed. [Figure 8] FIG. 4 is a diagram showing another hydraulic system (hydraulic circuit) of the work machine. [Figure 9] 1 is a side view showing a track loader as an example of a work machine. DETAILED DESCRIPTION OF THE INVENTION

[0015] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a hydraulic system for a work machine according to the present invention and a work machine equipped with this hydraulic system will be described below with reference to the accompanying drawings.

[0016] Figure 9 shows a side view of a work machine according to the present invention. In Figure 9, a compact track loader is shown as an example of a work machine. However, the work machine according to the present invention is not limited to a compact track loader, and may be, for example, another type of loader work machine, such as a skid steer loader. Also, work machines other than loader work machines may be used.

[0017] As shown in FIG. 9 , the work machine 1 includes a body 2, a cabin 3, a work device 4, and a pair of traveling devices 5L and 5R. In the embodiment of the present invention, the front side of the driver seated in the driver's seat 8 of the work machine 1 (the left side in FIG. 9 ) will be referred to as the front, the rear side of the driver (the right side in FIG. 9 ) as the rear, the left side of the driver (the near side in FIG. 9 ) as the left side, and the right side of the driver (the far side in FIG. 9 ) as the right side. In addition, the horizontal direction that is perpendicular to the front-to-rear direction will be referred to as the width direction of the machine body. The direction from the center of the machine body 2 toward the right or left side will be referred to as the outward direction of the machine body. In other words, the outward direction of the machine body is the width direction of the machine body, and is the direction away from the machine body 2. The direction opposite to the outward direction of the machine body will be referred to as the inward direction of the machine body. In other words, the inward direction of the machine body is the width direction of the machine body, and is the direction approaching the machine body 2.

[0018] The cabin 3 is mounted on the machine body 2. A driver's seat 8 is provided in the cabin 3. The work device 4 is attached to the machine body 2. A pair of traveling devices 5L, 5R are provided on the outside of the machine body 2. A prime mover 32 is mounted at the rear inside the machine body 2.

[0019] The work device 4 includes a boom 10 , a work implement 11 , a lift link 12 , a control link 13 , a boom cylinder 14 , and a bucket cylinder 15 .

[0020] The booms 10 are mounted on the right and left sides of the cabin 3 so as to be able to swing up and down. The work implement 11 is, for example, a bucket, and the bucket 11 is mounted 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. A boom cylinder 14 extends and retracts to raise and lower the boom 10. A bucket cylinder 15 extends and retracts to swing the bucket 11.

[0021] The front portions of the left and right booms 10 are connected to each other by a connecting pipe with an irregular shape, and the bases (rear portions) of the booms 10 are connected to each other by a circular connecting pipe.

[0022] 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.

[0023] The lift link 12 is provided vertically at the rear of the base of each boom 10. The upper part (one end) of this lift link 12 is pivoted rotatably about a horizontal axis via a pivot shaft 16 (first pivot shaft) near the rear of the base of each boom 10. The lower part (other end) of the lift link 12 is pivoted rotatably about a horizontal axis via a pivot shaft 17 (second pivot shaft) near the rear of the aircraft body 2. The second pivot shaft 17 is provided below the first pivot shaft 16.

[0024] An upper portion of the boom cylinder 14 is pivotally supported about a horizontal axis via a pivot shaft 18 (third pivot shaft). The third pivot shaft 18 is the base of each boom 10 and is provided at the front of the base. A lower portion of the boom cylinder 14 is pivotally supported about a horizontal axis via a pivot shaft 19 (fourth pivot shaft). The fourth pivot shaft 19 is provided below the third pivot shaft 18, near the lower rear of the machine body 2.

[0025] The control link 13 is provided in front of the lift link 12. One end of this control link 13 is pivoted rotatably about a horizontal axis via a pivot shaft 20 (fifth pivot shaft). 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 rotatably about a horizontal axis via a pivot shaft 21 (sixth pivot shaft). The sixth pivot shaft 21 is provided on the boom 10 in front of and above the second pivot shaft 17.

[0026] 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 moves up and down. 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.

[0027] Instead of the bucket 11, another work implement can be attached to the front of the boom 10. The other work implement 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.

[0028] A connecting member 50 is provided at the front of the left boom 10. The connecting member 50 is a device that connects hydraulic equipment equipped 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 connecting member 50, and a 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.

[0029] 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.

[0030] Of the pair of traveling devices 5L, 5R, the traveling device 5L is provided on the left side of the machine body 2, and the traveling device 5R is provided on the right side of the machine body 2. In this embodiment, the pair of traveling devices 5L, 5R are crawler-type (including semi-crawler-type) traveling devices. Note that wheel-type traveling devices having front and rear wheels may also be used. Hereinafter, for convenience of explanation, the traveling device 5L may be referred to as the left traveling device 5L, and the traveling device 5R may be referred to as the right traveling device 5R.

[0031] 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.

[0032] Next, the hydraulic system of the work machine will be described.

[0033] As shown in FIG. 1, the hydraulic system of the work machine includes a first hydraulic pump P1 and a second hydraulic pump P2. The first hydraulic pump P1 is a pump driven by the power of a prime mover 32 and is configured as a fixed displacement gear pump. The first hydraulic pump P1 is capable of discharging hydraulic oil stored in a tank 22. In particular, the first hydraulic pump P1 discharges hydraulic oil that is mainly used for control. For ease of explanation, the tank 22 that stores 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.

[0034] The second hydraulic pump P2 is a pump driven by the power of the prime mover 32 and is configured as a fixed displacement gear pump. The second hydraulic pump P2 is capable of discharging hydraulic oil stored in the tank 22 and supplies the hydraulic oil to oil passages of the work system, for example. For example, the second hydraulic pump P2 supplies the 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.

[0035] The hydraulic system of the work machine also includes a pair of travel motors 36L, 36R and a pair of travel pumps 53L, 53R. The pair of travel motors 36L, 36R are motors that transmit power to the pair of travel devices 5L, 5R. Of the pair of travel motors 36L, 36R, one travel motor 36L transmits rotational power to the travel device (left travel device) 5L, and the other travel motor 36R transmits rotational power to the travel device (right travel device) 5R.

[0036] The pair of travel pumps 53L, 53R are pumps driven by the power of the prime mover 32, and are, for example, swash plate-type variable displacement axial pumps. When driven, the pair of travel pumps 53L, 53R supply hydraulic oil to the pair of travel motors 36L, 36R, respectively. Of the pair of travel pumps 53L, 53R, one travel pump 53L supplies hydraulic oil to the travel pump 53L, and the other travel pump 53R supplies hydraulic oil to the travel pump 53R.

[0037] Hereinafter, for convenience of explanation, the travel pump 53L may be referred to as the left travel pump 53L, the travel pump 53R may be referred to as the right travel pump 53R, the travel motor 36L may be referred to as the left travel motor 36L, and the travel motor 36R may be referred to as the right travel motor 36R.

[0038] The left travel pump 53L and the right travel pump 53R have pressure receiving portions 53a and 53b on which the pressure (pilot pressure) of hydraulic oil (pilot oil) from the first hydraulic pump P1 acts, and the angle of the swash plate is changed by the pilot pressure acting on the pressure receiving portions 53a and 53b. By changing the angle of the swash plate, the output (amount of hydraulic oil discharged) and the discharge direction of hydraulic oil of the left travel pump 53L and the right travel pump 53R can be changed. The left travel pump 53L has a first port 82a that discharges hydraulic oil during forward rotation and a second port 82b that discharges hydraulic oil during reverse rotation. The right travel pump 53R has a third port 82c that discharges hydraulic oil during forward rotation and a fourth port 82d that discharges hydraulic oil during reverse rotation.

[0039] The first port 82a and second port 82b of the left travel pump 53L are connected to the left travel motor 36L by a connecting oil passage (first circulation oil passage) 57h, and the hydraulic oil discharged by the left travel pump 53L is supplied to the left travel motor 36L. The third port 82c and fourth port 82d of the right travel pump 53R are connected to the right travel motor 36R by a connecting oil passage (second circulation oil passage) 57i, and the hydraulic oil discharged by the right travel pump 53R is supplied to the right travel motor 36R.

[0040] A first relief valve 81a is connected to the connecting oil passage 57h on the side of the first port 82a of the left travel pump 53L, and a second relief valve 81b is connected to the oil passage on the side of the second port 82b of the left travel pump 53L. For example, the first relief valve 81a is likely to operate when the pressure acting on the connecting oil passage 57h increases due to forward rotation of the left travel pump 53L, and the second relief valve 81b is likely to operate when the pressure acting on the connecting oil passage 57h increases due to reverse rotation of the left travel pump 53L.

[0041] A third relief valve 81c is connected to the connecting oil passage 57i on the side of the third port 82c of the right travel pump 53R, and a fourth relief valve 81d is connected to the oil passage on the side of the fourth port 82d of the right travel pump 53R. For example, the third relief valve 81c is likely to operate when the pressure acting on the connecting oil passage 57i increases due to forward rotation of the right travel pump 53R, and the fourth relief valve 81d is likely to operate when the pressure acting on the connecting oil passage 57i increases due to reverse rotation of the right travel pump 53R.

[0042] The left travel motor 36L is rotated by hydraulic oil discharged from the left travel pump 53L, and its rotation speed (number of rotations) can be changed by adjusting the flow rate of the hydraulic oil. A swash plate switching cylinder 37L is connected to the left travel motor 36L, and the rotation speed (number of rotations) of the left travel motor 36L can be changed by extending or retracting the swash plate switching cylinder 37L. That is, when the swash plate switching cylinder 37L is retracted, the rotation speed of the left travel motor 36L is set to a low speed (first speed), and when the swash plate switching cylinder 37L is extended, the rotation speed of the left travel motor 36L is set to a high speed (second speed). That is, the rotation speed of the left travel motor 36L can be changed between a low speed (first speed) and a high speed (second speed).

[0043] The right travel motor 36R is rotated by hydraulic oil discharged from the right travel pump 53R, and its rotation speed (number of rotations) can be changed by adjusting the flow rate of the hydraulic oil. A swash plate switching cylinder 37R is connected to the right travel motor 36R, and the rotation speed (number of rotations) of the right travel motor 36R can be changed by extending or retracting the swash plate switching cylinder 37R to one side or the other. That is, when the swash plate switching cylinder 37R is retracted, the rotation speed of the right travel motor 36R is set to a low speed (first speed), and when the swash plate switching cylinder 37R is extended, the rotation speed of the right travel motor 36R is set to a high speed (second speed). That is, the rotation speed of the right travel motor 36R can be changed between a first speed, which is a low speed, and a second speed, which is a high speed.

[0044] 1, the hydraulic system of the work machine includes a travel switching valve 34. The travel switching valve 34 is switchable between a first state in which the rotation speed (number of rotations) of the travel motors (left travel motor 36L, right travel motor 36R) is set to a first speed, and a second state in which the rotation speed (number of rotations) is set to a second speed. The travel switching valve 34 includes first switching valves 71L, 71R and a second switching valve 72.

[0045] The first switching valve 71L is connected to the swash plate switching cylinder 37L of the left 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, it contracts the swash plate switching cylinder 37L, and when the first switching valve 71L is in the second position 71L2, it extends the swash plate switching cylinder 37L.

[0046] The first switching valve 71R is connected to the swash plate switching cylinder 37R of the right traveling motor 36R via an oil passage and is a two-position switching valve that can be switched between a first position 71R1 and a second position 71R2. When the first switching valve 71R is in the first position 71R1, it contracts the swash plate switching cylinder 37R, and when the first switching valve 71R is in the second position 71R2, it extends the swash plate switching cylinder 37R.

[0047] 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 when excited. 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 first positions 71L1 and 71R1, and when the second position 72b, the second switching valve 72 switches the first switching valve 71L and the first switching valve 71R to second positions 71L2 and 71R2.

[0048] In other words, when the second selector valve 72 is in the first position 72a, the first selector valve 71L is in the first position 71L1, and the first selector valve 71R is in the first position 71R1, the travel selector valve 34 is in the first state, and the rotation speed of the travel motors (left travel motor 36L, right travel motor 36R) is set to the first speed. When the second selector valve 72 is in the second position 72b, the first selector valve 71L is in the second position 71L2, and the first selector valve 71R is in the second position 71R2, the travel selector valve 34 is in the second state, and the rotation speed of the travel motors (left travel motor 36L, right travel motor 36R) is set to the second speed.

[0049] Therefore, the travel switching valve 34 can switch the travel motors (left travel motor 36L, right travel motor 36R) between a first speed, which is on the low speed side, and a second speed, which is on the high speed side.

[0050] The operating device (travel operating device) 54 is a device that applies hydraulic oil to the pressure receiving portions 53a, 53b of the travel pumps (left travel pump 53L, right travel pump 53R) when the travel operating member 59 is operated, and can change the angle of the swash plate (swash plate angle) of the travel pump. The operating device 54 includes the travel operating member 59 and multiple operating valves 55.

[0051] The travel operation member 59 is an operation lever supported by the operation valve 55 and swings left and right (machine width direction) or forward and backward. That is, with a neutral position N as a reference, the travel operation member 59 can be operated to the right and left from the neutral position N, and can also be operated forward and backward from the neutral position N. In other words, the travel operation member 59 can swing in at least four directions from the neutral position N. For ease of explanation, both forward and backward directions, i.e., the forward and backward direction, will be referred to as the first direction. Furthermore, both right and left directions, i.e., the left and right direction (machine width direction), will sometimes be referred to as the second direction.

[0052] The multiple operation valves 55 are operated in common, that is, by a single travel operation member 59. The multiple operation valves 55 operate based on the swing of the travel operation member 59. A discharge oil passage 40 is connected to the multiple operation valves 55, and hydraulic oil (pilot oil) from the first hydraulic pump P1 can be supplied via the discharge oil passage 40. The multiple operation valves 55 are operation valve 55A, operation valve 55B, operation valve 55C, and operation valve 55D.

[0053] When the travel operating member 59 is swung forward (one side) in the front-rear direction (first direction) (when operated forward), the pressure of the hydraulic oil output by the operating valve 55A changes in accordance with the operation amount (operation) of the forward operation. When the travel operating member 59 is swung backward (the other side) in the front-rear direction (first direction) (when operated backward), the pressure of the hydraulic oil output by the operating valve 55B changes in accordance with the operation amount (operation) of the backward operation. When the travel operating member 59 is swung right (one side) in the left-right direction (second direction), the pressure of the hydraulic oil output by the operating valve 55C changes in accordance with the operation amount (operation) of the right operation. When the travel operating member 59 is swung left (the other side) in the left-right direction (second direction), the pressure of the hydraulic oil output by the operating valve 55D changes in accordance with the operation amount (operation) of the left operation.

[0054] The multiple operating valves 55 and the travel pumps (left traveling pump 53L, right traveling pump 53R) are connected by the travel oil passage 45. In other words, the travel pumps (left traveling pump 53L, right traveling pump 53R) are hydraulic devices that can be operated by hydraulic oil output from the operating valves 55 (operating valve 55A, operating valve 55B, operating valve 55C, operating valve 55D).

[0055] 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 pressure receiving portion (first pressure receiving portion) 53a of the left travel pump 53L, and is an oil passage through which hydraulic oil acts on the pressure receiving portion (first pressure receiving portion) 53a when the travel operating member 59 is operated. The second travel oil passage 45b is an oil passage connected to the pressure receiving portion (second pressure receiving portion) 53b of the left travel pump 53L, and is an oil passage through which hydraulic oil acts on the pressure receiving portion (second pressure receiving portion) 53b when the travel operating member 59 is operated. The third travel oil passage 45c is an oil passage connected to the pressure receiving portion (third pressure receiving portion) 53a of the right travel pump 53R, and is an oil passage through which hydraulic oil acts on the pressure receiving portion (third pressure receiving portion) 53a when the travel operating member 59 is operated. The fourth travel oil passage 45d is an oil passage connected to the pressure receiving portion (fourth pressure receiving portion) 53b of the right travel pump 53R, and is an oil passage through which hydraulic oil acts on the pressure receiving portion (fourth pressure receiving portion) 53b when the travel operating member 59 is operated. The fifth travel oil passage 45e is an oil passage that connects 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.

[0056] When the travel operating member 59 is swung forward (in the direction of arrow A1 in FIGS. 1 and 2), the operating valve 55A is operated and pilot pressure is output from the operating valve 55A. This pilot pressure acts on the pressure receiving portion 53a of the left travel pump 53L via the first travel oil passage 45a and also acts on the pressure receiving portion 53a of the right travel pump 53R via the third travel oil passage 45c. This changes the swash plate angles of the left travel pump 53L and the right travel pump 53R, causing the left travel motor 36L and the right travel motor 36R to rotate forward (forward rotation), and the work machine 1 moves straight forward.

[0057] Furthermore, when the travel operating member 59 is swung rearward (in the direction of arrow A2 in FIGS. 1 and 2), the operation valve 55B is operated and pilot pressure is output from the operation valve 55B. This pilot pressure acts on the pressure receiving portion 53b of the left travel pump 53L via the second travel oil passage 45b, and also acts on the pressure receiving portion 53b of the right travel pump 53R via the fourth travel oil passage 45d. This changes the swash plate angles of the left travel pump 53L and the right travel pump 53R, causing the left travel motor 36L and the right travel motor 36R to rotate in the reverse direction (reverse rotation), causing the work machine 1 to travel straight backward.

[0058] Furthermore, when the travel operating member 59 is swung to the right (in the direction of arrow A3 in FIGS. 1 and 2), the operation valve 55C is operated and pilot pressure is output from the operation valve 55C. This pilot pressure acts on the pressure receiving portion 53a of the left travel pump 53L via the first travel oil passage 45a and also acts on the pressure receiving portion 53b of the right travel pump 53R via the fourth travel oil passage 45d. This changes the swash plate angles of the left travel pump 53L and the right travel pump 53R, causing the left travel motor 36L to rotate forward and the right travel motor 36R to rotate reverse, causing the work machine 1 to perform a spin turn (pilot turn) to the right.

[0059] Furthermore, when the travel operating member 59 is swung to the left (the direction of arrow A4 in FIGS. 1 and 2), the operating valve 55D is operated and pilot pressure is output from the operating valve 55D. This pilot pressure acts on the pressure receiving portion 53a of the right travel pump 53R via the third travel oil passage 45c, and also acts on the pressure receiving portion 53b of the left travel pump 53L via the second travel oil passage 45b. This changes the swash plate angles of the left travel pump 53L and the right travel pump 53R, causing the left travel motor 36L to rotate in the reverse direction and the right travel motor 36R to rotate in the forward direction, causing the work machine 1 to perform a spin turn (pilot turn) to the left.

[0060] In addition, when the travel operating member 59 is swung diagonally (in the direction of arrow A5 in Figure 2), the rotation direction and rotation speed of the left travel motor 36L and the right travel motor 36R are determined by the differential pressure of the pilot pressure acting on the pressure receiving portion 53a and the pressure receiving portion 53b, and the work machine 1 makes a right or left pivot turn while moving forward or backward.

[0061] That is, when the travel operating member 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 travel operating member 59, when the travel operating member 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 travel operating member 59, when the travel operating member 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 travel operating member 59, and when the travel operating member 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 travel operating member 59.

[0062] As shown in Fig. 1, the work machine 1 is equipped with a control device 60. The control device 60 performs various controls on the work machine 1 and is composed of semiconductors such as a CPU and an MPU, electric and electronic circuits, etc. An accelerator 65, a mode switch 66, a speed change switch 67, and a rotation speed detection device 68 are connected to the control device 60.

[0063] The mode switch 66 is a switch that switches between enabling and disabling automatic deceleration. For example, the mode switch 66 is a switch that can be switched between ON and OFF, and switches automatic deceleration to enabled when it is ON, and switches automatic deceleration to disabled when it is OFF.

[0064] The speed change switch 67 is provided near the driver's seat 8 and can be operated by the driver (operator). The speed change switch 67 is a switch that can manually switch the travel motors (left travel motor 36L, right travel motor 36R) between a first speed and a second speed. For example, the speed change switch 67 is a seesaw switch that switches between the first speed side and the second speed side, and can perform an accelerating operation to switch from the first speed side to the second speed side and a decelerating operation to switch from the second speed to the first speed.

[0065] The rotation speed detection device 68 is composed of a sensor or the like that detects the rotation speed, and is capable of detecting the prime mover rotation speed, which is the rotation speed of the prime mover 32.

[0066] The control device 60 includes an automatic deceleration unit 61. The automatic deceleration unit 61 is an electric / electronic circuit or the like provided in the control device 60, a program or the like stored in the control device 60, or the like.

[0067] The automatic deceleration unit 61 performs automatic deceleration control when the vehicle is in the driving mode and automatic deceleration is enabled, but does not perform automatic deceleration control when the vehicle is in the driving mode and automatic deceleration is disabled.Furthermore, the automatic deceleration unit 61 does not perform automatic deceleration control even in the acquisition mode.

[0068] In the automatic deceleration control, when the travel motors (left travel motor 36L, right travel motor 36R) are at the second speed and a predetermined condition (automatic deceleration condition) is met, the travel motors (left travel motor 36L, right travel motor 36R) are automatically switched from the second speed to the first speed. In the automatic deceleration control, when the automatic deceleration condition is met while at least the travel motors (left travel motor 36L, right travel motor 36R) are at the second speed, the control device 60 deenergizes the solenoid of the second selector valve 72, thereby switching the second selector valve 72 from the second position 72b to the first position 72a, thereby decelerating the travel motors (left travel motor 36L, right travel motor 36R) from the second speed to the first speed. In other words, when performing automatic deceleration in the automatic deceleration control, the control device 60 decelerates both the left travel motor 36L and the right travel motor 36R from the second speed to the first speed.

[0069] Note that, after performing automatic deceleration, if the return condition is satisfied, the automatic deceleration unit 61 excites the solenoid of the second switching valve 72, thereby switching the second switching valve 72 from the first position 72a to the second position 72b, thereby increasing the speed of the travel motors (left travel motor 36L, right travel motor 36R) from the first speed to the second speed, i.e., restoring the speed of the travel motors. In other words, when restoring from the first speed to the second speed, the control device 60 increases the speed of both the left travel motor 36L and the right travel motor 36R from the first speed to the second speed.

[0070] When automatic deceleration is disabled, the control device 60 performs manual switching control to switch the travel motors (left travel motor 36L, right travel motor 36R) to either a first speed or a second speed in accordance with the operation of the speed selector switch 67. In manual switching control, when the speed selector switch 67 is switched to the first speed side, the solenoid of the second selector valve 72 is de-energized to set the travel motors (left travel motor 36L, right travel motor 36R) to the first speed. In manual switching control, when the speed selector switch 67 is switched to the second speed side, the solenoid of the second selector valve 72 is de-energized to set the travel motors (left travel motor 36L, right travel motor 36R) to the second speed.

[0071] The control device 60 automatically decelerates based on the pressure in the circulation oil passages 57h and 57i. A plurality of pressure detection devices 80 are connected to the circulation oil passages 57h and 57i. The plurality of pressure detection devices 80 includes a first pressure detection device 80a, a second pressure detection device 80b, a third pressure detection device 80c, and a fourth pressure detection device 80d. The first pressure detection device 80a is provided in the circulation oil passage 57h on the side of the first port P11 of the left traveling motor 36L and detects the pressure on the first port P11 side as a first traveling pressure LF(t). The second pressure detection device 80b is provided in the circulation oil passage 57h on the side of the second port P12 of the left traveling motor 36L and detects the pressure on the second port P12 side as a second traveling pressure LB(t). The third pressure detection device 80c is provided in the circulation oil passage 57i on the third port P13 side of the right traveling motor 36R and detects the pressure on the third port P13 side as a third traveling pressure RF(t). The fourth pressure detection device 80d is provided in the circulation oil passage 57i on the fourth port P14 side of the right traveling motor 36R and detects the pressure on the fourth port P14 side as a fourth traveling pressure RB(t).

[0072] The control device 60 (automatic deceleration unit 61) performs automatic deceleration based on the first running pressure LF(t, rpm) detected by the first pressure detection device 80a, the second running pressure LB(t, rpm) detected by the second pressure detection device 80b, the third running pressure RF(t, rpm) detected by the third pressure detection device 80c, and the fourth running pressure RB(t, rpm) detected by the fourth pressure detection device 80d.

[0073] Note that (t, rpm) indicated by the first running pressure LF(t, rpm), second running pressure LB(t, rpm), third running pressure RF(t, rpm), and fourth running pressure RB(t, rpm) is a notation indicating that the value is linked to the actual rotation speed (rpm) of the prime mover at a certain time (t). Therefore, each of the first running pressure LF(t, rpm) to fourth running pressure RB(t, rpm) is a running pressure obtained at the actual rotation speed (rpm) of the prime mover at time (t).

[0074] Specifically, as shown in equation (1), the automatic deceleration unit 61 performs automatic deceleration when any one of the first running pressure LF(t, rpm), the second running pressure LB(t, rpm), the third running pressure RF(t, rpm), and the fourth running pressure RB(t, rpm) becomes equal to or greater than the deceleration threshold ST(rpm), which is a pressure value determined according to the rotation speed of the prime mover.

[0075] In addition, in equation (1), the first traveling pressure LF(t, rpm) may be replaced by a traveling pressure difference LF-LB(t, rpm) which is the difference between the first traveling pressure LF(t, rpm) and the second traveling pressure LB(t, rpm), the second traveling pressure LB(t, rpm) may be replaced by a traveling pressure difference LB-LF(t, rpm) which is the difference between the second traveling pressure LB(t, rpm) and the first traveling pressure LF(t, rpm), the third traveling pressure RF(t, rpm) may be replaced by a traveling pressure difference RF-RB(t, rpm) which is the difference between the third traveling pressure RF(t, rpm) and the fourth traveling pressure RB(t, rpm), and the fourth traveling pressure RB(t, rpm) may be replaced by a traveling pressure difference RB-RF(t, rpm) which is the difference between the fourth traveling pressure RB(t, rpm) and the third traveling pressure RF(t, rpm).

[0076]

number

[0077] When the work machine 1 is traveling, the control device 60 (automatic deceleration unit 61) sets the deceleration threshold ST (rpm) to a value that corresponds to the state of the work machine 1. That is, the control device 60 (automatic deceleration unit 61) sets the deceleration threshold ST (rpm) by changing the correction coefficient η according to the state of the work machine 1, as shown in equation (2). The pressure values ​​A1 (rpm), A2 (rpm), A3 (rpm), and A4 (rpm) in equation (2) are values ​​determined for each rotation speed (rpm) of the prime mover, and are, for example, the pressure when four relief valves provided in the circulation oil passage begin to operate, or the pressure when the relief valves operate and the pressure in the circulation oil passage stabilizes. Note that the pressure values ​​A1 (rpm), A2 (rpm), A3 (rpm), and A4 (rpm) are merely examples and are not limited thereto.

[0078]

number

[0079] The control device 60 (automatic deceleration unit 61) sets the deceleration threshold ST (rpm) in accordance with the operation of the travel operating member 59. Fig. 3 shows a correction curve that represents the relationship between the travel state of the work machine 1 and the correction coefficient η.

[0080] As shown in Fig. 3, when the travel operation member 59 is operated in a forward direction or the like to cause the work machine 1 to travel straight (forward), the automatic deceleration unit 61 sets the correction coefficient η to η1. When the travel operation member 59 is operated diagonally to the right or diagonally to the left from the forward direction to cause the work machine 1 to make a pivot turn from straight travel, the automatic deceleration unit 61 sets the correction coefficient η to η2, which is lower than η1. Furthermore, when the travel operation member 59 is operated diagonally to the right or diagonally to the left from the neutral position to cause the work machine 1 to make a pivot turn from a stopped position, the automatic deceleration unit 61 sets the correction coefficient η to η3, which is lower than η2. Furthermore, when the travel operation member 59 is operated diagonally to the right or left from the neutral position to cause the work machine 1 to make a pivot turn from a stopped position, the automatic deceleration unit 61 sets the correction coefficient η to η4, which is lower than η3.

[0081] That is, as shown in Fig. 3, the automatic deceleration unit 61 continuously changes the correction coefficient η (rpm) when the travel control member 59 is operated in a "straight direction," "straight direction to a pivot turn," "stop to a pivot turn," or "stop to a pivot turn." As shown in Fig. 3, a correction curve indicating the relationship between the operation pattern of the travel control member 59 (straight direction, stop, pivot turn, pivot turn) and the correction coefficient η is stored in the storage device 63, and the control device 60 can extract the correction coefficient η from the storage device 63 in accordance with the operation of the travel control member 69. Whether the work machine 1 is traveling straight, pivoting, stopping, or pivot turn may be determined, for example, by detecting the operation direction of the travel control member 59 with a sensor or the like, or by the first travel pressure LF(t, rpm), the second travel pressure LB(t, rpm), the third travel pressure RF(t, rpm), and the fourth travel pressure RB(t, rpm), but is not limited thereto.

[0082] As described above, the control device 60 (automatic deceleration unit 61) can change the deceleration threshold ST (rpm) depending on the operation of the travel operation member 59, that is, the state in which the travel operation member 59 is operated.

[0083] The control device 60 (automatic deceleration unit 61) may change the deceleration threshold ST (rpm) by setting the turning correction coefficient (turning correction coefficient) η corresponding to turning (spin turn, pin turn) to a fixed value (default value), and switching to the straight-line correction coefficient (straight-line correction coefficient) η corresponding to straight-line traveling only when the operation of the travel operating member 59 is straight-line traveling.

[0084] Now, when focusing on turning (spin turn, pivot turn) and straight-ahead driving, when the rotation speed of the prime mover 32 is the same, the control device 60 (automatic deceleration unit 61) sets the deceleration threshold ST (rpm) when the vehicle 2 is driving straight ahead higher than the deceleration threshold ST (rpm) when the vehicle 2 is turning. In other words, when the rotation speed of the prime mover 32 is a predetermined rotation speed, the straight-ahead correction coefficient η is larger than the turning correction coefficient η, making it more difficult to perform automatic deceleration when driving straight ahead than when turning. In other words, when the rotation speed of the prime mover 32 is a predetermined rotation speed, the control device 60 (automatic deceleration unit 61) sets the turning correction coefficient η smaller than the straight-ahead correction coefficient η, and the deceleration threshold ST (rpm) when turning is lower than when driving straight ahead, making it easier to perform automatic deceleration when turning.

[0085] Note that, when automatic deceleration is being performed, the control device 60 stops (restores) automatic deceleration by switching from the first speed to the second speed if the first running pressure LF(t, rpm), second running pressure LB(t, rpm), third running pressure RF(t, rpm), and fourth running pressure RB(t, rpm) fall below a return threshold SE (rpm) determined according to the rotation speed of the prime mover. Even when automatic deceleration is restored, if the rotation speed of the prime mover 32 is the same, the control device 60 (automatic deceleration unit 61) sets the return threshold SE (rpm) when the vehicle 2 is traveling straight higher than the return threshold SE (rpm) when the vehicle 2 is turning, thereby making it easier to restore automatic deceleration when traveling straight than when turning. In other words, if the rotation speed of the prime mover 32 is the same, the control device 60 (automatic deceleration unit 61) sets the return threshold SE (rpm) when turning lower than when traveling straight, making it more difficult to restore automatic deceleration when turning. The straight running correction coefficient η may be changed according to the degree of straight running. The degree of straight running may be calculated based on the pilot pressure or operation information obtained from the electrically operated travel operation device 54, and the correction coefficient η may be increased based on the calculation results. For example, if the center (neutral position) of the travel operation member 59 is set as the origin and the angle when tilted completely forward is 90 degrees (deg), the correction coefficient η is changed according to the tilt angle, such as 0.9 at 80 degrees (deg) and 0.8 at 70 degrees (deg).

[0086] In the above-described embodiment, the control device 60 (automatic deceleration unit 61) set the deceleration threshold ST (rpm) by changing the correction coefficient η based on the operation of the travel operation member 59, but the deceleration threshold ST (rpm) may also be set by changing the correction coefficient η according to the prime mover rotation speed.

[0087] The automatic deceleration unit 61 sets the deceleration threshold ST (rpm) based on the formula (3). The correction coefficient η (rpm) in the formula (3) is a value corresponding to the motor rotation speed.

[0088]

number

[0089] FIG. 4 shows an example of the travel state of the work machine 1, the prime mover rotation speed, and the correction coefficient η (rpm). Line L1 in FIG. 4 represents the correction coefficient η (rpm) when the prime mover rotation speed is 2400 rpm, and line L2 represents the correction coefficient η (rpm) when the prime mover rotation speed is 1200 rpm. The automatic deceleration unit 61 increases the correction coefficient η (rpm) as the prime mover rotation speed increases, and decreases the correction coefficient η (rpm) as the prime mover rotation speed decreases. As shown in FIG. 4, correction information indicating the relationship between the prime mover rotation speed and the correction coefficient η is stored in the storage device 63, and the control device 60 can extract the correction coefficient η from the storage device 63 in accordance with the prime mover rotation speed.

[0090] In the above-described embodiment, the deceleration threshold ST (rpm) is calculated by multiplying by the correction coefficient η. However, instead of this, the deceleration threshold ST (rpm) may be calculated by multiplying A1 (rpm), A2 (rpm), A3 (rpm), and A4 (rpm) determined according to the rotation speed of the prime mover by the correction coefficient η and then multiplying the result by the reference value α. (rpm) The deceleration threshold ST (rpm) may be set by adding or subtracting the reference value α. Specifically, the control device 60 (automatic deceleration unit 61) sets the deceleration threshold ST (rpm) based on the following equation (4). (rpm) is a value determined in accordance with the motor rotation speed and is stored in advance in the storage device 63.

[0091]

number

[0092] The control device 60 (automatic deceleration unit 61) may set the deceleration threshold ST (rpm) based on multiple correction coefficients η. Specifically, the control device 60 (automatic deceleration unit 61) sets the deceleration threshold ST (rpm) by multiplying the first traveling pressure LF(t, rpm), the second traveling pressure LR(t, rpm), the third traveling pressure RF(t, rpm), and the fourth traveling pressure RR(t, rpm) by the first correction coefficient ηa and the second correction coefficient ηb, respectively, as shown in equation (5).

[0093]

number

[0094] Fig. 5 is a diagram showing an example of the traveling state, first correction coefficient ηa, and second correction coefficient ηb of the work machine 1. As shown in Fig. 5, the first correction coefficient ηa and the second correction coefficient ηb are largest when traveling straight, and are smallest when making a pivot turn, and the first correction coefficient ηa and the second correction coefficient ηb are smaller when making a pivot turn than when traveling straight and larger than when making a pivot turn. In this way, by setting the deceleration threshold ST (rpm) based on multiple correction coefficients η, it is possible to automatically decelerate precisely according to the traveling state.

[0095] The work machine 1 includes a body 2, a prime mover 32 provided on the body 2, a left traveling device 5L provided on the left side of the body 2, a right traveling device 5R provided on the right side of the body 2, a left traveling motor 36L capable of transmitting power to the left traveling device 5L and switchable between a first speed and a second speed faster than the first speed, a right traveling motor 36R capable of transmitting power to the right traveling device 5R and switchable between the first speed and a second speed faster than the first speed, and a control device 60 capable of automatic deceleration, in which the left traveling motor 36L and the right traveling motor 36R are automatically decelerated from the second speed to the first speed when they are at the second speed, and capable of changing a deceleration threshold ST (rpm) for determining whether to perform automatic deceleration. This allows the automatic deceleration to be changed according to various conditions of the work machine 1.

[0096] The work machine 1 is equipped with a travel operation member 59 that can change the rotation direction of the left travel motor 36L and the right travel motor 36R, and the control device 60 changes the deceleration threshold ST (rpm) based on the operation of the travel operation member 59. This makes it possible to change the automatic deceleration in response to the operation of the travel operation member 59.

[0097] The control device 60 can acquire either a turning correction coefficient for setting the deceleration threshold ST (rpm) when the travel operating member 59 is operated for turning, or a straight running correction coefficient for setting the deceleration threshold ST (rpm) when the travel operating member 59 is operated for straight running, and switches from the turning correction coefficient to the straight running correction coefficient when the travel operating member 59 is operated for straight running. This allows the work machine 1 to perform automatic deceleration differently when turning and when traveling straight.

[0098] The control device 60 changes the deceleration threshold ST (rpm) in accordance with the rotation speed of the prime mover 32. This makes it possible to easily change whether or not to perform automatic deceleration in accordance with the rotation speed of the prime mover 32.

[0099] The work machine 1 includes a first circulation oil passage 57h connected to a first port and a second port of the left travel pump 53L and connected to the left travel motor 36L, a second circulation oil passage 57i connected to a third port and a fourth port of the right travel pump 53R and connected to the right travel motor 36R, a first pressure detection device 80a provided on the first port side of the left travel motor 36L and detecting, as a first travel pressure, the pressure of hydraulic oil acting on the first circulation oil passage 57h when the left travel motor 36L is rotating, and a second pressure detection device 80b provided on the second port side of the left travel motor 36L and detecting, as a second travel pressure, the pressure of hydraulic oil acting on the first circulation oil passage 57h when the left travel motor 36L is rotating. a third pressure detection device 80b provided on the third port side of the right travel motor 36R and detecting the pressure of hydraulic oil acting on the second circulation oil passage 57i when the right travel motor 36R is rotating as a third travel pressure; and a fourth pressure detection device 80d provided on the fourth port side of the right travel motor 36R and detecting the pressure of hydraulic oil acting on the second circulation oil passage 57i when the right travel motor 36R is rotating as a fourth travel pressure, and when the left travel motor 36L and the right travel motor 36R are at the second speed, the control device 60 performs automatic deceleration based on any of the first travel pressure, the second travel pressure, the third travel pressure, and the fourth travel pressure and the set deceleration threshold value. This allows automatic deceleration to be easily performed using the travel pressures (first travel pressure, second travel pressure, third travel pressure, fourth travel pressure) and the deceleration threshold value.

[0100] The control device 60 can change the deceleration threshold when the operation of the travel operation member 59 is a turning operation. This makes it possible to more smoothly determine whether to execute automatic deceleration or the like in accordance with the turning operation of the travel operation member 59.

[0101] As described above, the second speed only needs to be faster than the first speed, so the work machine 1 is not limited to having two speed stages, and can be applied to a multi-stage (multiple stages) work machine.

[0102] In the above-described embodiment, the left traveling motor 36L and the right traveling motor 36R are configured to switch between the first speed and the second speed at the same time, and automatic deceleration is also performed simultaneously for the left traveling motor 36L and the right traveling motor 36R, but automatic deceleration may also be performed in a state where at least one of the left traveling motor 36L and the right traveling motor 36R is switched between the first speed and the second speed, and at least one of the left traveling motor 36L and the right traveling motor 36R is at the second speed.

[0103] The travel motors (left travel motor 36L, right travel motor 36R) may be either axial piston motors or radial piston motors. Whether the travel motor is a radial piston motor or a radial piston motor, the first speed can be shifted by increasing the motor capacity, and the second speed can be shifted by decreasing the motor capacity.

[0104] In the above-described embodiment, the correction coefficient η is a correction coefficient multiplied by the pressure value A1 (rpm), pressure value A2 (rpm), pressure value A3 (rpm), and pressure value A4 (rpm), which are values ​​determined by the rotation speed of the prime mover, but the correction coefficient η may also be the pressure (its value itself) used to determine the deceleration threshold ST (rpm).

[0105] For example, as shown in Fig. 6, the correction coefficient η (deceleration threshold ST (rpm)), which changes depending on the operation of the operating member 59 and the rotation speed of the prime mover, is obtained by lines L11 and L12. The correction coefficient η (deceleration threshold ST (rpm)) increases as the rotation speed of the prime mover increases, and decreases as the rotation speed of the prime mover decreases.

[0106] In the above-described embodiment, as shown in Figures 4 and 6, the correction coefficient η is increased as the actual motor rotation speed (referred to as actual motor rotation speed) increases, thereby increasing the deceleration threshold ST (rpm) obtained by equations (2) to (5).

[0107] However, another method may be used as shown in Fig. 7. Fig. 7 is a diagram showing an example of a correction coefficient η (rpm) based on the difference in motor rotation speed.

[0108] As shown in Fig. 7, the correction coefficient η may be changed by lines L13 and L14 based on the difference between the target rotation speed of the prime mover based on a command such as operation of accelerator 65 (referred to as prime mover target rotation speed) and the actual prime mover rotation speed (prime mover rotation speed difference). The prime mover target rotation speed is a predetermined rotation speed (i.e., prime mover rotation speed) that is determined in advance in accordance with the opening of accelerator 65, etc. As shown in Fig. 7, when the prime mover rotation speed difference is large, the correction coefficient η is made small, and when the prime mover rotation speed difference is small, the correction coefficient η is made large. In this way, the correction coefficient η is made larger as the prime mover rotation speed difference becomes smaller, and the deceleration threshold ST (rpm) obtained by equations (2) to (5) may be made larger.

[0109] In the above-described embodiment, the deceleration threshold ST (rpm) is a value calculated using equations (2) to (5) using the correction coefficient η. Therefore, the deceleration threshold ST (rpm) also changes in response to changes in the traveling state of the work machine 1 in the same manner as lines L11 and L12 shown in Fig. 6 and lines L13 and L14 shown in Fig. 7. Therefore, by plotting the change in the deceleration threshold ST (rpm) in response to changes in the traveling state of the work machine 1, lines corresponding to lines L11 and L12 shown in Fig. 6 and lines L13 and L14 shown in Fig. 7 can be obtained as the change in the deceleration threshold ST (rpm).

[0110] In other words, if the vertical axis of the graphs shown in Figures 6 and 7 is changed from the correction coefficient η to the deceleration threshold ST (rpm), a graph showing the change in the deceleration threshold ST (rpm) in response to changes in the running state of the work machine 1, that is, a graph showing the characteristics of the deceleration threshold ST (rpm), can be obtained.

[0111] The control device 60 may store in advance a map showing the change in the deceleration threshold ST (rpm) in response to the change in the running state of the work machine 1, which corresponds to this graph.

[0112] Finally, in the above-described embodiment, the operating device 54 was a hydraulic type that changed the pilot pressure acting on the travel pumps (travel pumps 53L, 53R) using the operating operating member 59 and the operating valve 55. However, the operations performed by the operating device 54 in the above-described embodiment can be realized by employing an electrically operated joystick, a control device 60, and a hydraulic regulator that changes the angle of the swash plate of the travel pump. Even with this configuration using a joystick, smooth automatic deceleration can be performed using the deceleration threshold ST (rpm) described above. The configuration using a joystick will be described below.

[0113] The joystick, which replaces the operating lever 59, is an operating lever that swings left and right (widthwise of the aircraft body) or forward and backward. The joystick has a sensor (operation detection sensor) that detects the amount of operation (amount of swing) and the direction of operation (swing direction). This operation detection sensor is connected to the control device 60.

[0114] Hydraulic regulators that operate the swash plates of the travel pumps (travel pumps 53L, 53R) are connected to the control device 60. One hydraulic regulator is connected to each of the swash plates of the travel pump 53L and the travel pump 53R. Therefore, the swash plates of the travel pump 53L and the travel pump 53R can be controlled independently.

[0115] When the joystick is operated forward, the control device 60 outputs a control signal corresponding to the amount of operation of the joystick to the hydraulic regulator. In response to this control signal, the hydraulic regulator swings the swash plates of the travel pumps 53L and 53R in the forward rotation (forward movement) direction, thereby moving the work machine 1 forward.

[0116] When the joystick is operated backward, the control device 60 outputs a control signal corresponding to the amount of operation of the joystick to the hydraulic regulator. In response to this control signal, the hydraulic regulator swings the swash plates of the traveling pumps 53L and 53R in the reverse (reverse) direction. This causes the work machine 1 to move backward.

[0117] Furthermore, when the joystick is operated to the right, the control device 60 outputs a control signal corresponding to the amount of joystick operation to the hydraulic regulator. In response to this control signal, the hydraulic regulator swings the swash plate of the travel pump 53L in the forward rotation direction and swings the swash plate of the travel pump 53R in the reverse rotation direction. This causes the work implement to turn right.

[0118] When the joystick is operated to the left, the control device 60 outputs a control signal corresponding to the amount of joystick operation to the hydraulic regulator. In response to this control signal, the hydraulic regulator swings the swash plate of the travel pump 53L in the reverse direction and swings the swash plate of the travel pump 53R in the forward direction. The work implement turns left.

[0119] Instead of a hydraulic system that changes the pilot pressure, a configuration in which the swash plate of the travel pump is oscillated using a control signal from a joystick can also detect the traveling state of the work machine 1. If the correction coefficient η is changed in accordance with the state of the work machine 1 detected using a configuration that uses a joystick, the deceleration threshold ST (rpm) can be set in the configuration described in the above embodiment.

[0120] Furthermore, control valves 155L, 155R and hydraulic regulators 156L, 156R shown in Fig. 8 may be employed. The switching position and opening 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. The control valves 155L, 155R are each configured as electromagnetic proportional valves. The control device 60 can operate the hydraulic regulators 156L, 156R by controlling the control valves 155L, 155R.

[0121] As shown in Fig. 8, the hydraulic regulators 156L, 156R are connected to the swash plates of the travel pumps (travel pump 53L, travel pump 53R), respectively. Each of the hydraulic regulators 156L, 156R is capable of changing the angle (swash plate angle) of the swash plates of the travel pumps (travel pump 53L, 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 as the piston rod 158 moves (i.e., expands and contracts), thereby changing the swash plate angle.

[0122] The operating valve 155L is a valve that directly operates the hydraulic regulator 156L and controls the amount of hydraulic oil output by the travel pump 53L through the operation of the hydraulic regulator 156L. The operating valve 155L is configured as an electromagnetic proportional valve having a solenoid, and a spool of the operating valve 155L moves based on a control signal output from the control device 60 to the solenoid. This movement of the spool changes the opening degree of the operating valve 155L. Here, 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.

[0123] 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 145a. 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 145b.

[0124] The control valve 155R is a valve that directly operates the hydraulic regulator 156R and controls the amount of hydraulic oil output by the second travel pump 53R through the operation of the hydraulic regulator 156R. The control valve 155R is configured as an electromagnetic proportional valve having a solenoid, and a spool of the control valve 155R moves based on a control signal applied to the solenoid from the control device 60. This movement of the spool changes the opening degree of the control valve 155R. Here, the control 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.

[0125] A first port of the operation valve 155R and a supply chamber 157 of the hydraulic regulator 156R are connected by a third travel oil passage 145c. A second port of the operation valve 155R and a supply chamber 157 of the hydraulic regulator 156R are connected by a fourth travel oil passage 145d.

[0126] When the control valves 155L and 155R are switched to the first position 159a, the hydraulic regulators 156L and 156R are activated, the swash plates of the travel pumps (travel pump 53L, travel pump 53R) are swung, and the travel pumps are rotated 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 activated, the swash plates of the travel pumps (first travel pump 53L, second travel pump 53R) are swung, and the travel pumps are rotated in the reverse direction.

[0127] When the operation valve 155L is switched to the first position 159a and the operation valve 155R is switched to the second position 159b, the travel pump 53L rotates forward and the travel pump 53R rotates reverse. When the operation valve 155L is switched to the second position 159b and the operation valve 155R is switched to the first position 159a, the travel pump 53L rotates reverse and the travel pump 53R rotates forward.

[0128] In a configuration in which the swash plate of the travel pump is oscillated using a control signal from a joystick, even if the configuration is such that the swash plate of the travel pump is oscillated using the control valves 155L, 155R and the hydraulic regulators 156L, 156R, it is possible to detect the traveling state of the work machine 1. In this way, by changing the correction coefficient η in accordance with the traveling state of the work machine 1 detected using the configuration using the joystick, it is possible to determine the deceleration threshold ST (rpm) with the configuration described in the above embodiment.

[0129] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0130] 1 Work equipment 2 aircraft 5L left running device 5R Right running gear 32 Prime Mover 36L Left drive motor 36R Right travel motor 53L left travel pump 53R Right Travel Pump 57h Connection oil path (1st circulation oil path) 57i Connection oil path (2nd circulation oil path) 60 Control device 80a First pressure detection device 80b Second pressure detection device 80c Third pressure detection device 80d Fourth pressure detection device

Claims

1. The aircraft and a prime mover provided on the airframe; a left running device provided on the left side of the machine body; a right running device provided on the right side of the machine body; a left traveling motor capable of transmitting power to the left traveling device and switchable between a first speed and a second speed faster than the first speed; a right traveling motor capable of transmitting power to the right traveling device and switchable between a first speed and a second speed faster than the first speed; a left traveling pump that is driven by the prime mover and supplies hydraulic oil to the left traveling motor; a right traveling pump that is driven by the prime mover and supplies hydraulic oil to the right traveling motor; a control device that is capable of changing and setting a return threshold value for determining whether to automatically switch from the first speed to the second speed after the left traveling motor and the right traveling motor have automatically decelerated from the second speed to the first speed and have reached the first speed; and A work machine equipped with the above.

2. The recovery threshold is determined according to the rotation speed of the prime mover, The work machine according to claim 1 , wherein the control device changes the return threshold value based on the rotation speed of the prime mover.

3. A travel operating member that can change the rotation direction of the left travel motor and the right travel motor, The work machine according to claim 1, wherein when the control device automatically switches from the first speed to the second speed, and when the rotation speed of the prime mover is the same, the control device sets the return threshold value when the operation of the travel operating member is for straight travel higher than the return threshold value when the operation of the travel operating member is for turning.

4. The control device adjusts the return threshold in accordance with the degree of straight traveling based on the operation of the travel operating member. The work implement according to claim 3, wherein the value is changed.

5. a first circulation oil passage connected to a first port and a second port of the left traveling pump and connected to the left traveling motor; a second circulation oil passage connected to the third port and the fourth port of the right traveling pump and connected to the right traveling motor; a first pressure detection device that is provided on a first port side of the left traveling motor and detects, as a first traveling pressure, a pressure of hydraulic oil acting on the first circulation oil passage when the left traveling motor is rotating; a second pressure detection device that is provided on a second port side of the left traveling motor and detects, as a second traveling pressure, the pressure of hydraulic oil acting on the first circulation oil passage when the left traveling motor is rotating; a third pressure detection device that is provided on a third port side of the right traveling motor and detects, as a third traveling pressure, the pressure of hydraulic oil acting on the second circulation oil passage when the right traveling motor is rotating; a fourth pressure detection device that is provided on a fourth port side of the right traveling motor and detects, as a fourth traveling pressure, the pressure of hydraulic oil acting on the second circulation oil passage when the right traveling motor is rotating; Equipped with The control device is configured to automatically switch from the first speed to the second speed when the first traveling pressure, the second traveling pressure, the third traveling pressure, and the fourth traveling pressure become equal to or lower than the return threshold value while the left traveling motor and the right traveling motor are performing the automatic deceleration.

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