Work equipment

Abstract

To easily grasp a traveling state.SOLUTION: A work machine comprises: a first pressure detection device to detect a pressure of a hydraulic fluid acting on a first port side of a left travel motor as a first travel pressure; a second pressure detection device to detect a pressure of a hydraulic fluid acting on a second port side of the left travel motor as a second travel pressure; a third pressure detection device to detect a pressure of a hydraulic fluid acting on a third port side of a right travel motor as a third travel pressure; a fourth detection device to detect a pressure of a hydraulic fluid acting on a fourth port side of the right travel motor as a fourth travel pressure; and a control device to determine a traveling state of a machine body based on a first right / left differential pressure obtained by subtracting the third travel pressure from the first travel pressure, a second right / left differential pressure obtained by subtracting the first travel pressure from the third travel pressure, a third right / left differential pressure obtained by subtracting the fourth travel pressure from the second travel pressure, a fourth right / left differential pressure obtained by subtracting the second travel pressure from the fourth travel pressure, and a first threshold.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 while traveling is equal to or higher than a predetermined value. However, it is difficult to grasp the traveling state of the work machine, such as turning or traveling straight, and it is difficult to set the timing for automatic deceleration. 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 whose traveling state can be easily grasped. [Means for solving the problem]

[0005] The technical means adopted by the present invention to solve the above technical problems are as follows. The work machine includes a machine body, a prime mover provided on the machine body, a left traveling device provided on the left side of the machine body, a right traveling device provided on the right side of the machine body, a left traveling motor capable of transmitting power to the left traveling device, a right traveling motor capable of transmitting power to the right traveling device, a left traveling pump that supplies hydraulic oil to the left traveling motor, a right traveling pump that supplies hydraulic oil to the right traveling motor, 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, and a first pressure detector that is provided on the first port side of the left traveling motor in the first circulation oil passage and detects the pressure of the hydraulic oil acting on the first port side of the left traveling motor as a first traveling pressure. a second pressure detection device provided on a second port side of the left travel motor in the first circulation oil passage and detecting, as a second traveling pressure, the pressure of hydraulic oil acting on the second port side of the left travel motor; a third pressure detection device provided on a third port side of the right travel motor in the second circulation oil passage and detecting, as a third traveling pressure, the pressure of hydraulic oil acting on the third port side of the right travel motor; a fourth pressure detection device provided on a fourth port side of the right travel motor in the second circulation oil passage and detecting, as a fourth traveling pressure, the pressure of hydraulic oil acting on the fourth port side of the right travel motor; a first left-right differential pressure obtained by subtracting the third traveling pressure from the first traveling pressure; a second left-right differential pressure obtained by subtracting the first traveling pressure from the third traveling pressure; a third left-right differential pressure obtained by subtracting the fourth traveling pressure from the second traveling pressure; and a fourth left-right differential pressure obtained by subtracting the second traveling pressure from the fourth traveling pressure; Calculate and a control device for The control device determines whether the aircraft is turning or whether the aircraft is moving straight based on a result of comparing each of the first left-right differential pressure, the second left-right differential pressure, the third left-right differential pressure, and the fourth left-right differential pressure with a predetermined first threshold value. do.

[0006] The control device is configured to: and The fourth left-right differential pressure Each of , the first threshold The result of comparison withBased on this, it is determined whether the aircraft is turning or flying straight. The control device is configured to: and The fourth left-right differential pressure Each of , the first threshold The result of comparison with Based on this, it is determined whether the aircraft is moving forward or backward.

[0007] The control device is configured to: and The fourth left-right differential pressure Each of , the first threshold The result of comparison with Based on this, it is determined whether the aircraft is turning and the turning direction of the aircraft. The control device is configured to: and The fourth left-right differential pressure Each of , the first threshold The result of comparison with Based on this, the aircraft Nobuchi Making a turn thing Determine the following.

[0008] The control device determines that the aircraft is turning when any one of the first left-right differential pressure, the second left-right differential pressure, the third left-right differential pressure, and the fourth left-right differential pressure is greater than the first threshold value, and determines that the aircraft is not turning when the first left-right differential pressure, the second left-right differential pressure, the third left-right differential pressure, and the fourth left-right differential pressure are equal to or less than the first threshold value. After determining that the aircraft is turning, the control device adjusts the first left-right differential pressure, the second left-right differential pressure, the third left-right differential pressure, and The fourth left-right differential pressure Each of , predetermined Second Threshold The result of comparison with Based on this, it is determined whether the turning of the aircraft has ended.

[0009] The control device determines that the aircraft is traveling in a straight line when the first left-right differential pressure, the second left-right differential pressure, the third left-right differential pressure, and the fourth left-right differential pressure are less than or equal to the first threshold value, and determines that the aircraft is not traveling in a straight line when any of the first left-right differential pressure, the second left-right differential pressure, the third left-right differential pressure, and the fourth left-right differential pressure is greater than the first threshold value. The control device determines, based on the first left-right differential pressure, the second left-right differential pressure, the third left-right differential pressure, the fourth left-right differential pressure, and the first threshold value, that the aircraft is not traveling straight and is turning, and then calculates the first left-right differential pressure, the second left-right differential pressure, the third left-right differential pressure, and The fourth left-right differential pressure Each of , predetermined Second Threshold The result of comparison with Based on this, it is determined whether the aircraft has started to move straight ahead.

[0010] The rotation speeds of the left traveling motor and the right traveling motor are switchable between a first speed, which is a low speed range, and a second speed, which is a high speed range faster than the first speed, and when the rotation speeds of the left traveling motor and the right traveling motor are switched to the second speed, the control device performs automatic deceleration to automatically decelerate the rotation speeds of the left traveling motor and the right traveling motor from the second speed to the first speed based on the first traveling pressure, the second traveling pressure, the third traveling pressure, or the fourth traveling pressure. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide a work machine that allows the traveling state of the machine body, such as turning or moving straight, to be easily grasped. [Brief explanation of the drawings]

[0012] [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. 4 is a diagram showing the relationship between traveling relief pressure and motor rotation speed. [Figure 4]1 is a side view showing a track loader as an example of a work machine. DETAILED DESCRIPTION OF THE INVENTION

[0013] 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. Fig. 4 shows a side view of a work machine according to the present invention. Fig. 4 shows a compact track loader 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.

[0014] As shown in FIG. 4, 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. 4) will be referred to as the front, the rear side of the driver (the right side in FIG. 4) as the rear, the left side of the driver (the near side in FIG. 4) as the left side, and the right side of the driver (the far side in FIG. 4) 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.

[0015] 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. 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 .

[0016] 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.

[0017] 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. 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. 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.

[0018] 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.

[0019] The control link 13 is provided in front of the lift link 12. One end of this control link 13 is pivotally supported via a pivot shaft 20 (fifth pivot shaft) so as to be rotatable about a horizontal axis. The fifth pivot shaft 20 is provided on the fuselage 2 at a position corresponding to the front of the lift link 12. The other end of the control link 13 is pivotally supported via a pivot shaft 21 (sixth pivot shaft) so as to be rotatable about a horizontal axis. The sixth pivot shaft 21 is on the boom 10 and is provided in front of and above the second pivot shaft 17.

[0020] 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.

[0021] 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. 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.

[0022] 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. 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. 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.

[0023] Next, the hydraulic system of the work machine will be described. 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.

[0024] 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.

[0025] The hydraulic system of the work machine is equipped with 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.

[0026] 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 motor 36L, and the other travel pump 53R supplies hydraulic oil to the travel motor 36R.

[0027] 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. 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. 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] The left travel motor 36L is rotated by hydraulic oil discharged from the left travel pump 53L. The rotational speed of the left travel motor 36L can be changed by changing the flow rate of hydraulic oil to the left travel motor 36L. A swash plate switching cylinder 37L is connected to the left travel motor 36L, and the rotational speed of the left travel motor 36L can also be changed by extending or retracting the swash plate switching cylinder 37L. That is, when the swash plate switching cylinder 37L is retracted, the rotational speed of the left travel motor 36L is set to a first speed (predetermined low-speed range), which is a low speed. On the other hand, when the swash plate switching cylinder 37L is extended, the rotational speed of the left travel motor 36L is set to a second speed (predetermined high-speed range), which is a high-speed. That is, the rotational speed of the left travel motor 36L can be changed between the first speed and the second speed.

[0032] The right travel motor 36R is rotated by hydraulic oil discharged from the right travel pump 53R. The rotation speed of the right travel motor 36R can be changed by changing the flow rate of hydraulic oil to the right travel motor 36R. A swash plate switching cylinder 37R is connected to the right travel motor 36R, and the rotation speed of the right travel motor 36R can also 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 first speed (predetermined low-speed range), which is a low speed. On the other hand, when the swash plate switching cylinder 37R is extended, the rotation speed of the right travel motor 36R is set to a second speed (predetermined high-speed range), which is a high-speed. That is, the rotation speed of the right travel motor 36R can be changed between the first speed and the second speed.

[0033] 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 rotational speed (number of rotations) of the travel motors 36L, 36R is set to a first speed, and a second state in which the rotational 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. 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.

[0034] 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. 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.

[0035] 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, contracting the swash plate switching cylinders 37L and 37R to set the rotation speed of the travel motors 36L and 36R to a 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, expanding the swash plate switching cylinders 37L and 37R to set the rotation speed of the travel motors 36L and 36R to a second speed. Therefore, the travel selector valve 34 can switch the travel motors 36L and 36R between the first speed and the second speed.

[0036] 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 53L, 53R (left travel pump 53L, right travel pump 53R) when the travel operating member 59 is operated, and can change the angle of the swash plates (swash plate angle) of the travel pumps 53L, 53R. The operating device 54 includes the travel operating member 59 and multiple operating valves 55.

[0037] The travel operation member 59 is an operation lever that is supported by the operation valve 55 and swings left and right (machine body width direction) or forward and backward. The travel operating member 59 can be operated to the right and left from the standing position N, and can also be operated forward and backward from the neutral position N. In other words, the travel operating member 59 can be swung in at least four directions based on the neutral position N. For ease of explanation, both the forward and backward directions, i.e., the front-to-rear direction, will be referred to as the first direction. Also, both the right and left directions, i.e., the left-to-right direction (machine body width direction), will sometimes be referred to as the second direction.

[0038] 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.

[0039] 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.

[0040] The multiple operation valves 55 and the travel pumps 53L, 53R are connected by the travel oil passage 45. In other words, the travel pumps 53L, 53R are hydraulic devices that can be operated by hydraulic oil output from the operation valves 55 (operation valve 55A, operation valve 55B, operation valve 55C, operation valve 55D). 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.

[0041] 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.

[0042] When the travel operating member 59 is swung rearward (in the direction of arrow A2 in FIGS. 1 and 2), the operating valve 55B is operated and pilot pressure is output from the operating 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 second travel oil passage 45b. The pressure 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 move straight backward.

[0043] Furthermore, when the travel operating member 59 is swung to the right (the direction of arrow A4 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.

[0044] Furthermore, when the travel operating member 59 is swung to the left (in the direction of arrow A3 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.

[0045] 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. 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.

[0046] 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. 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.

[0047] 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 rotation speed of the traveling motors 36L, 36R (left traveling motor 36L, right traveling motor 36R) between a first speed and a second speed. For example, the speed change switch 67 is a seesaw switch that can perform an accelerating operation to switch the rotation speed of the traveling motors 36L, 36R from the first speed to the second speed, and a decelerating operation to switch from the second speed to the first speed.

[0048] The rotation speed detection device 68 is composed of a sensor or the like, and is capable of detecting the rotation speed of the prime mover 32, that is, the prime mover rotation speed. The control device 60 includes an automatic deceleration unit 61. The automatic deceleration unit 61 is provided in the control device 60. The control device 60 includes an electric and electronic circuit, a program, etc. stored in the control device 60. The automatic deceleration unit 61 performs automatic deceleration control when the vehicle is in the traveling mode and automatic deceleration is enabled, and does not perform automatic deceleration control when the vehicle is in the traveling mode and automatic deceleration is disabled.

[0049] In the automatic deceleration control, when the rotation speeds of the travel motors 36L, 36R are set to the second speed, the rotation speeds of the travel motors 36L, 36R are automatically switched from the second speed to the first speed when a predetermined condition (automatic deceleration condition) is met. 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 the rotation speeds of both the left travel motor 36L and the right travel motor 36R from the second speed to the first speed.

[0050] 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 rotation speed of the travel motors 36L, 36R from the first speed to the second speed. That is, the rotation speed of the travel motors 36L, 36R is returned to the second speed. In other words, when returning from the first speed to the second speed, the control device 60 increases the rotation speed of both the left travel motor 36L and the right travel motor 36R from the first speed to the second speed.

[0051] When automatic deceleration is disabled, the control device 60 performs manual switching control to switch the rotation speed of the traveling motors 36L, 36R to either a first speed or a second speed in accordance with the operation of the speed change switch 67. In manual switching control, when the speed change switch 67 is switched to the first speed side, the solenoid of the second switching valve 72 is de-energized to set the rotation speed of the traveling motors 36L, 36R to the first speed. In manual switching control, when the speed change switch 67 is switched to the second speed side, the solenoid of the second switching valve 72 is de-energized to set the rotation speed of the traveling motors 36L, 36R to the second speed.

[0052] The control device 60 performs automatic deceleration (control processing to automatically switch the rotation speed of the travel motors 36L, 36R from the second speed to the first speed) based on the pressure in the circulation oil passages 57h, 57i. A plurality of pressure detection devices 80 are connected to the circulation oil passages 57h, 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.

[0053] The first pressure detecting device 80a is provided in the circulation oil passage 57h on the first port P11 side of the left travel motor 36L and detects the pressure on the first port P11 side as a first travel pressure LF(t). The second pressure detecting device 80b is provided in the circulation oil passage 57h on the second port P12 side of the left travel motor 36L and detects the pressure on the second port P12 side as a second travel pressure LB(t). The third pressure detecting device 80c is provided in the circulation oil passage 57i on the third port P13 side of the right travel motor 36R and detects the pressure on the third port P13 side as a third travel pressure RF(t). The fourth pressure detecting device 80d is provided in the circulation oil passage 57i on the fourth port P14 side of the right travel motor 36R and detects the pressure on the fourth port P14 side as a fourth travel pressure RB(t).

[0054] The automatic deceleration unit 61 of the control device 60 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. The (t, rpm) values ​​shown in LB(t, rpm), third running pressure RF(t, rpm), and fourth running pressure RB(t, rpm) indicate that they are values ​​linked to the actual rotation speed of the prime mover at a certain time t.

[0055] Specifically, as shown in equation (1), the automatic deceleration unit 61 performs automatic deceleration (processing to automatically switch the rotation speed of the traveling motors 36L, 36R from a second speed, which is a high speed range, to a first speed, which is a low speed range) when at least one of the first traveling pressure LF(t, rpm), the second traveling pressure LB(t, rpm), the third traveling pressure RF(t, rpm), and the fourth traveling pressure RB(t, rpm) becomes equal to or greater than a turning threshold (first threshold) Z1 (rpm).Equation (1) is an example of an automatic deceleration condition.

[0056]

number

[0057] As another example, the automatic deceleration unit 61 may perform automatic deceleration based on the results of comparing at least two 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). Now, the control device 60 determines whether the work machine 1 is turning based on the first traveling pressure LF (t, rpm), the second traveling pressure LB (t, rpm), the third traveling pressure RF (t, rpm), the fourth traveling pressure RB (t, rpm), and the turning threshold Z1 (rpm).

[0058] The control device 60 refers to the first traveling pressure LF(t, rpm), the second traveling pressure LB(t, rpm), the third traveling pressure RF(t, rpm), and the fourth traveling pressure RB(t, rpm) while the work machine 1 is traveling. Then, as shown in equation (2), the control device 60 calculates a first left-right differential pressure ΔZa obtained by subtracting the third traveling pressure RF(t, rpm) from the first traveling pressure LF(t, rpm), a second left-right differential pressure ΔZb obtained by subtracting the first traveling pressure LF(t, rpm) from the third traveling pressure RF(t, rpm), a third left-right differential pressure ΔZc obtained by subtracting the fourth traveling pressure RB(t, rpm) from the second traveling pressure LB(t, rpm), and a fourth left-right differential pressure ΔZd obtained by subtracting the second traveling pressure LB(t, rpm) from the fourth traveling pressure RB(t, rpm).

[0059]

number

[0060] The control device 60 quantifies the balance during forward rotation of the left traveling motor 36L and the right traveling motor 36R based on a first left-right differential pressure ΔZa obtained by subtracting the third traveling pressure RF(t, rpm) from the first traveling pressure LF(t, rpm) and a second left-right differential pressure ΔZb obtained by subtracting the first traveling pressure LF(t, rpm) from the third traveling pressure RF(t, rpm). The control device 60 also quantifies the balance during reverse rotation of the left traveling motor 36L and the right traveling motor 36R based on a third left-right differential pressure ΔZc obtained by subtracting the fourth traveling pressure RB(t, rpm) from the second traveling pressure LB(t, rpm) and a fourth left-right differential pressure ΔZd obtained by subtracting the second traveling pressure LB(t, rpm) from the fourth traveling pressure RB(t, rpm).

[0061] The control device 60 also determines whether the machine body 2 (work machine 1) is turning based on the first left-right differential pressure ΔZa, the second left-right differential pressure ΔZb, the third left-right differential pressure ΔZc, and the fourth left-right differential pressure ΔZd. For example, if the first left / right differential pressure ΔZa is higher than a predetermined turning threshold Z1 (rpm), the control device 60 determines that the pressure on the forward rotation side of the left traveling motor 36L is high and determines that the work machine 1 (machine body 2) is making a pivot turn while moving forward to the right. Also, if the second left / right differential pressure ΔZb is higher than the turning threshold Z1 (rpm), the control device 60 determines that the pressure on the forward rotation side of the right traveling motor 36R is high and determines that the work machine 1 (machine body 2) is making a pivot turn while moving forward to the left.

[0062] Furthermore, if the third left / right differential pressure ΔZc is higher than a predetermined turning threshold Z1 (rpm), the control device 60 determines that the pressure on the reverse side of the left traveling motor 36L is high and determines that the work machine 1 (machine body 2) is making a pivot turn while traveling backward to the right. Furthermore, if the fourth left / right differential pressure ΔZd is higher than the turning threshold Z1 (rpm), the control device 60 determines that the pressure on the reverse side of the right traveling motor 36R is high and determines that the work machine 1 (machine body 2) is making a pivot turn while traveling backward to the left.

[0063] The control device 60 may determine the degree of the work machine 1 (machine body 2) based on the magnitudes of the first left-right differential pressure ΔZa, the second left-right differential pressure ΔZb, the third left-right differential pressure ΔZc, and the fourth left-right differential pressure ΔZd. For example, the control device 60 determines that the degree of turning in which the work machine 1 (machine body 2) is making a pivot turn while moving forward to the right increases as the first left-right differential pressure ΔZa increases. Also, the control device 60 determines that the degree of turning in which the work machine 1 (machine body 2) is making a pivot turn while moving forward to the left increases as the second left-right differential pressure ΔZb increases.

[0064] In this way, the control device 60 can determine whether the work machine 1 (machine body 2) is turning based on the first left-right differential pressure ΔZa, the second left-right differential pressure ΔZb, the third left-right differential pressure ΔZc, and the fourth left-right differential pressure ΔZd obtained by equation (2). The control device 60 uses the result of the determination as to whether the work machine 1 (machine body 2) is turning to set a deceleration threshold for automatic deceleration. The control device 60 may also display the result of the determination as to whether the work machine 1 is turning on a display device mounted on the work machine 1, or may notify the user that the work machine 1 is turning by a buzzer, lamp, or the like.

[0065] The control device 60 sets the turning threshold Z1 (rpm) based on the first traveling relief pressure w1 of the first relief valve 81a, the second traveling relief pressure w2 of the second relief valve 81b, the third traveling relief pressure w3 of the third relief valve 81c, and the fourth traveling relief pressure w4 of the fourth relief valve 81d. For example, the control device 60 sets the turning threshold Z1 (rpm) based on each of the first traveling relief pressure w1, the second traveling relief pressure w2, the third traveling relief pressure w3, and the fourth traveling relief pressure w4 and the correction coefficient α1.

[0066] The traveling relief pressure is the pressure of the hydraulic oil when the first relief valve 81a, the second relief valve 81b, the third relief valve 81c, and the fourth relief valve 81d are activated, or the pressure of the hydraulic oil when the first relief valve 81a, the second relief valve 81b, the third relief valve 81c, and the fourth relief valve 81d have stabilized after being activated. The control device 60 is set to an acquisition mode by a predetermined operation. When the control device 60 is set to the acquisition mode, first, while changing the prime mover rotation speed, the control device 60 acquires the first traveling relief pressure w1, the second traveling relief pressure w2, the third traveling relief pressure w3, and the fourth traveling relief pressure w4 when the prime mover rotation speed is a predetermined rotation speed. Then, the control device 60 sets the turning threshold Z1 (rpm) according to the traveling relief pressures w1 to w4 determined corresponding to the prime mover rotation speed.

[0067] For ease of explanation, the first traveling relief pressure w1 will be referred to as the first traveling relief pressure w1 (rpm), the second traveling relief pressure w2 will be referred to as the second traveling relief pressure w2 (rpm), the third traveling relief pressure w3 will be referred to as the third traveling relief pressure w3 (rpm), and the fourth traveling relief pressure w4 will be referred to as the fourth traveling relief pressure w4 (rpm). When setting the turning threshold Z1 (rpm), the control device 60 calculates the first traveling relief pressure w1 (rpm), the second traveling relief pressure w2 (rpm), and the third traveling relief pressure w3 (rpm) as shown in the formula (3). ), and the fourth traveling relief pressure w4 (rpm). Also, α1 in equation (3) is a correction coefficient. As shown in equation (3), the control device 60 sets the turning threshold Z1 (rpm) by multiplying the differential pressures of the first traveling relief pressure w1 (rpm), the second traveling relief pressure w2 (rpm), the third traveling relief pressure w3 (rpm), and the fourth traveling relief pressure w4 (rpm) by the correction coefficient α1.

[0068]

number

[0069] More specifically, in the acquisition mode of the work machine 1, the control device 60 sets the prime mover rotation speed to a predetermined rotation speed. The measurement device 69 (see FIG. 1) measures the first traveling relief pressure w1 (rpm), the second traveling relief pressure w2 (rpm), the third traveling relief pressure w3 (rpm), and the fourth traveling relief pressure w4 (rpm) when the prime mover rotation speed is the predetermined rotation speed. In addition, the control device 60 may set the turning threshold Z1 (rpm) using the reference value β1, the first traveling relief pressure w1 (rpm), the second traveling relief pressure w2 (rpm), the third traveling relief pressure w3 (rpm), the fourth traveling relief pressure w4 (rpm), and the correction coefficient α2, as shown in equation (4).

[0070]

number

[0071] In the acquisition mode of the work implement 1, the control device 60 controls the drive of the prime mover 32 to change the rotation speed of the prime mover 32 within a range from a prime mover rotation speed corresponding to at least idling to the maximum prime mover rotation speed that can be output by the prime mover 32. Then, each time the control device 60 changes the prime mover rotation speed, it acquires the first traveling relief pressure w1 (rpm), the second traveling relief pressure w2 (rpm), the third traveling relief pressure w3 (rpm), and the fourth traveling relief pressure w4 (rpm).

[0072] More specifically, a storage unit (not shown), such as a nonvolatile memory, provided inside the control device 60 stores in advance table data showing the correspondence between the prime mover rotation speed and each traveling relief pressure w1 (rpm), w2 (rpm), w3 (rpm), and w4 (rpm), as shown in FIG. 3. The correspondence between the prime mover rotation speed and each traveling relief pressure w1 (rpm), w2 (rpm), w3 (rpm), and w4 (rpm) is determined in advance based on the event and design. When the control device 60 detects the prime mover rotation speed using the rotation speed detection device 68 (FIG. 1), it reads out from the internal storage the first traveling relief pressure w1 (rpm), second traveling relief pressure w2 (rpm), third traveling relief pressure w3 (rpm), and fourth traveling relief pressure w4 (rpm) that correspond to that prime mover rotation speed.

[0073] In the above-described embodiment, it is determined that a turn is occurring when the first left-right differential pressure ΔZa, the second left-right differential pressure ΔZb, the third left-right differential pressure ΔZc, or the fourth left-right differential pressure ΔZd becomes higher than the turning threshold Z1 (rpm), but the end of the turn, i.e., the aircraft 2 is no longer in a turning state, is determined by the turn cancellation threshold (second threshold) Z2 (rpm). When the rotational speed drops below the threshold value Z2 (rpm), it is determined that the turning has ended, i.e., the aircraft 2 is no longer in a turning state. Like the turning threshold value Z1 (rpm), this turning cancellation threshold value Z2 (rpm) is set based on the rotational speed of the prime mover 32 and is set by a correction coefficient.

[0074] Specifically, as shown in equation (5), the control device 60 sets the turning release threshold Z2 (rpm) by multiplying the differential pressures of the first traveling relief pressure w1 (rpm), the second traveling relief pressure w2 (rpm), the third traveling relief pressure w3 (rpm), and the fourth traveling relief pressure w4 (rpm) by a correction coefficient γ1.

[0075]

number

[0076] As shown in equation (6), the control device 60 may calculate the turning release threshold Z2 (rpm) using the reference value β2, the first traveling relief pressure w1 (rpm), the second traveling relief pressure w2 (rpm), the third traveling relief pressure w3 (rpm), the fourth traveling relief pressure w4 (rpm), and the correction coefficient γ2.

[0077]

number

[0078] Now, the control device 60 can also determine whether the work machine 1 (machine body 2) is in a straight-line state based on the first running pressure LF (t, rpm), the second running pressure LB (t, rpm), the third running pressure RF (t, rpm), the fourth running pressure RB (t, rpm), and the turning threshold Z1 (rpm). In detail, when the work machine 1 is in a traveling state, the control device 60 determines that the machine body 2 is moving straight if the first left / right differential pressure ΔZa obtained by subtracting the third traveling pressure RF(t, rpm) from the first traveling pressure LF(t, rpm), the second left / right differential pressure ΔZb obtained by subtracting the first traveling pressure LF(t, rpm) from the third traveling pressure RF(t, rpm), the third left / right differential pressure ΔZc obtained by subtracting the fourth traveling pressure RB(t, rpm) from the second traveling pressure LB(t, rpm), and the fourth left / right differential pressure ΔZd obtained by subtracting the second traveling pressure LB(t, rpm) from the fourth traveling pressure RB(t, rpm) are below the turning threshold Z1 (rpm).

[0079] Furthermore, when at least one of the first left-right differential pressure ΔZa, the second left-right differential pressure ΔZb, the third left-right differential pressure ΔZc, and the fourth left-right differential pressure ΔZd is higher than the turning threshold Z1 (rpm), the control device 60 determines that the aircraft 2 is not traveling straight. In this case, as described above, the control device 60 determines that the aircraft 2 is turning. Furthermore, after determining that the aircraft 2 is turning, if at least one of the first left-right differential pressure ΔZa, the second left-right differential pressure ΔZb, the third left-right differential pressure ΔZc, and the fourth left-right differential pressure ΔZd becomes equal to or less than the turning release threshold Z2 (rpm), the control device 60 determines that the turning of the aircraft 2 has ended and the aircraft 2 has started moving straight.

[0080] The turning cancellation threshold Z2 (rpm) may be set to a value lower than the turning threshold Z1 (rpm). In this case, the control device 60 calculates the first left-right differential pressure ΔZa, the second left-right differential pressure ΔZb, the third left-right differential pressure ΔZc, and the third left-right differential pressure ΔZc. The control device 60 may determine that the aircraft 2 is moving straight when the fourth left-right differential pressure ΔZd is higher than the turn cancellation threshold Z2 (rpm) and equal to or lower than the turn threshold Z1 (rpm). The control device 60 may also determine that the aircraft 2 is turning when the first left-right differential pressure ΔZa, the second left-right differential pressure ΔZb, the third left-right differential pressure ΔZc, and the fourth left-right differential pressure ΔZd are higher than the turn cancellation threshold Z2 (rpm) and the turn threshold Z1 (rpm).

[0081] The control device 60 may also perform automatic deceleration when the vehicle 2 is traveling straight. In this case, for example, the control device 60 performs automatic deceleration when at least one of the first traveling pressure LF(t, rpm), the second traveling pressure LB(t, rpm), the third traveling pressure RF(t, rpm), and the fourth traveling pressure RB(t, rpm) becomes equal to or greater than a predetermined straight traveling threshold (third threshold). The straight traveling threshold may also be set by the control device 60 based on the first traveling relief pressure w1, the second traveling relief pressure w2, the third traveling relief pressure w3, and the fourth traveling relief pressure w4. Furthermore, after automatically decelerating the vehicle body 2 when it is traveling straight, the control device 60 may automatically increase the rotation speed of the travel motors 36L, 36R from a first speed to a second speed when a predetermined return condition is met.

[0082] According to the above embodiment, the work machine 1 has the following configuration and provides the following effects. The work machine 1 includes a machine body 2, a prime mover 32 provided on the machine body 2, a left traveling device 5L provided on the left side of the machine body 2, a right traveling device 5R provided on the right side of the machine body 2, a left traveling motor 36L capable of transmitting power to the left traveling device 5L and capable of switching the rotation speed between a first speed and a second speed that is faster than the first speed, a right traveling motor 36R capable of transmitting power to the right traveling device 5R and capable of switching the rotation speed between the first speed and the second speed, and a hydraulic oil supply to the left traveling motor 36L. a left traveling pump 53L that supplies hydraulic oil to the right traveling motor 36R; a first circulation oil passage 57h that is connected to a first port and a second port of the left traveling pump 53L and is connected to the left traveling motor 36L; a second circulation oil passage 57i that is connected to a third port and a fourth port of the right traveling pump 53R and is connected to the right traveling motor 36R; and a first circulation oil passage 57i that is provided on the first port side of the left traveling motor 36L and that is connected to the first port side of the left traveling motor 36L when the left traveling motor 36L is rotating. A first pressure detection device 80a detects the pressure of the hydraulic oil acting on the circulation oil passage 57h as a first traveling pressure, a second pressure detection device 80b is provided on the second port side of the left traveling motor 36L and detects the pressure of the hydraulic oil acting on the first circulation oil passage 57h when the left traveling motor 36L is rotating as a second traveling pressure, and a third pressure detection device 80c is provided on the third port side of the right traveling motor 36R and detects the pressure of the hydraulic oil acting on the second circulation oil passage 57i when the right traveling motor 36R is rotating as a third traveling pressure. a third pressure detection device 80c that outputs a fourth pressure detection signal; a fourth pressure detection device 80d that is provided on the fourth port side of the right traveling motor 36R and that detects the pressure of the hydraulic oil acting on the second circulation oil passage 57i when the right traveling motor 36R is rotating as a fourth traveling pressure; and a control device 60 that is capable of determining whether the machine body 2 is turning based on the first traveling pressure, the second traveling pressure, the third traveling pressure, the fourth traveling pressure, and a first threshold value (turning threshold value) and that is capable of changing the first threshold value.

[0083] As described above, while the work machine 1 (machine body 2) is traveling, it is possible to grasp the balance between the left traveling motor 36L and the right traveling motor 36R when rotating forward, and the balance between the left traveling motor 36L and the right traveling motor 36R when rotating reverse. Therefore, it is possible to easily grasp whether the machine body 2 is in a swing state without detecting the input of the operating member 59 with a sensor or the like. Moreover, because the control device 60 can change the first threshold value, it is possible to appropriately determine whether the work machine 1 is in a swing state based on the first threshold value according to various situations of the work machine 1 and the above-mentioned traveling pressures. The control device 60 can then appropriately set the timing for automatic deceleration in accordance with the swing state of the work machine 1, making it possible to perform automatic deceleration during a swing at the set timing. In addition, when the work machine 1 is traveling (not stopped), if the work machine 1 is in a turning state, it can be considered that the work machine 1 is not in a straight-ahead state. Therefore, whether the machine body 2 is in a straight-ahead state can also be determined from the result of determining whether the machine body 2 is in a turning state. It is possible.

[0084] Furthermore, the control device 60 determines whether the machine body 2 is turning based on a first left-right differential pressure obtained by subtracting the third traveling pressure from the first traveling pressure, a second left-right differential pressure obtained by subtracting the first traveling pressure from the third traveling pressure, a third left-right differential pressure obtained by subtracting the fourth traveling pressure from the second traveling pressure, a fourth left-right differential pressure obtained by subtracting the second traveling pressure from the fourth traveling pressure, and a first threshold value (turning threshold value). This makes it possible to easily determine whether the machine body 2 is turning while the work machine 1 is traveling, based on the balance between the left traveling motor 36L and the right traveling motor 36R when rotating forward and the balance between the left traveling motor 36L and the right traveling motor 36R when rotating reverse. Furthermore, after determining that the machine body 2 is turning, the control device 60 determines whether the turning of the machine body 2 has ended based on the first traveling pressure, the second traveling pressure, the third traveling pressure, the fourth traveling pressure, and the second threshold value (turn release threshold value). This makes it possible to easily determine whether the turning of the work machine 1 (machine body 2) has ended properly after the work machine 1 (machine body 2) has turned.

[0085] The work machine 1 includes a machine body 2, a prime mover 32 provided on the machine body 2, a left traveling device 5L provided on the left side of the machine body 2, a right traveling device 5R provided on the right side of the machine body 2, a left traveling motor 36L capable of transmitting power to the left traveling device 5L and capable of switching the rotation speed between a first speed and a second speed that is faster than the first speed, a right traveling motor 36R capable of transmitting power to the right traveling device 5R and capable of switching the rotation speed between the first speed and the second speed, and a hydraulic oil supply to the left traveling motor 36L. a left traveling pump 53L that supplies hydraulic oil to the right traveling motor 36R; a first circulation oil passage 57h that is connected to a first port and a second port of the left traveling pump 53L and is connected to the left traveling motor 36L; a second circulation oil passage 57i that is connected to a third port and a fourth port of the right traveling pump 53R and is connected to the right traveling motor 36R; and a first circulation oil passage 57i that is provided on the first port side of the left traveling motor 36L and that is connected to the first port side of the left traveling motor 36L when the left traveling motor 36L is rotating. A first pressure detection device 80a detects the pressure of the hydraulic oil acting on the circulation oil passage 57h as a first traveling pressure, a second pressure detection device 80b is provided on the second port side of the left traveling motor 36L and detects the pressure of the hydraulic oil acting on the first circulation oil passage 57h when the left traveling motor 36L is rotating as a second traveling pressure, and a third pressure detection device 80c is provided on the third port side of the right traveling motor 36R and detects the pressure of the hydraulic oil acting on the second circulation oil passage 57i when the right traveling motor 36R is rotating as a third traveling pressure. a third pressure detection device 80c that outputs a fourth pressure detection signal; a fourth pressure detection device 80d that is provided on the fourth port side of the right traveling motor 36R and that detects the pressure of the hydraulic oil acting on the second circulation oil passage 57i when the right traveling motor 36R is rotating as a fourth traveling pressure; and a control device 60 that is capable of determining whether the machine body 2 is turning based on the first traveling pressure, the second traveling pressure, the third traveling pressure, the fourth traveling pressure, and a first threshold value (turning threshold value) and that is capable of changing the first threshold value.

[0086] As described above, while the work machine 1 is traveling, it is possible to grasp the balance between the left traveling motor 36L and the right traveling motor 36R when rotating forward, and the balance between the left traveling motor 36L and the right traveling motor 36R when rotating reversely. Therefore, it is possible to easily grasp whether the machine body 2 is traveling straight, without detecting the input of the operating member 59 with a sensor or the like. Moreover, because the control device 60 can change the first threshold value, it is possible to appropriately determine whether the work machine 1 is turning, based on the first threshold value according to various situations of the work machine 1 and the above-mentioned traveling pressures. The control device 60 can then appropriately set the timing for automatic deceleration in accordance with the straight-travel state of the work machine 1, and it becomes possible to perform automatic deceleration when traveling straight at the set timing. When the work machine 1 is traveling and in a straight-ahead state, it can be considered that the work machine 1 is not in a turning state. Therefore, it is possible to determine whether the machine body 2 is in a turning state from the result of determining whether the machine body 2 is in a straight-ahead state.

[0087] The control device 60 also calculates a first left-right differential pressure by subtracting the third traveling pressure from the first traveling pressure, a second left-right differential pressure by subtracting the first traveling pressure from the third traveling pressure, and a third left-right differential pressure by subtracting the fourth traveling pressure from the second traveling pressure. Whether the machine body 2 is traveling straight or not is determined based on the right differential pressure, the fourth left / right differential pressure obtained by subtracting the second traveling pressure from the fourth traveling pressure, and the first threshold value (turning threshold value). This makes it possible to easily determine whether the machine body 2 is traveling straight or not based on the balance between the left traveling motor 36L and the right traveling motor 36R when rotating forward and the balance between the left traveling motor 36L and the right traveling motor 36R when rotating reverse while the work machine 1 is traveling.

[0088] Furthermore, after determining that the machine body 2 is turning based on the first traveling pressure, the second traveling pressure, the third traveling pressure, the fourth traveling pressure, and the first threshold value, the control device 60 determines whether the machine body 2 has started to move straight based on the first traveling pressure, the second traveling pressure, the third traveling pressure, the fourth traveling pressure, and the second threshold value (turn cancellation threshold value). This makes it easy to know that the work machine 1 has finished turning and started to move straight. Furthermore, the control device 60 changes the first threshold value (swing threshold value) based on the first traveling pressure, the second traveling pressure, the third traveling pressure, or the fourth traveling pressure. This allows the first threshold value to be set in accordance with various changes in the conditions of the work machine 1, making it possible to more appropriately determine the turning state or straight traveling state of the work machine 1.

[0089] The work machine 1 also includes a first relief valve 81a connected to the first circulation oil passage 57h on the first port 82a side, a second relief valve 81b connected to the first circulation oil passage 57h on the second port 82b side, a third relief valve 81c connected to the second circulation oil passage 57i on the third port 82c side, and a fourth relief valve 81d connected to the second circulation oil passage 57i on the fourth port 82d side, and the control device 60 sets a first threshold value (swing threshold value) based on the first traveling relief pressure of the first relief valve 31a, the second traveling relief pressure of the second relief valve 31b, the third traveling relief pressure of the third relief valve 31c, and the fourth traveling relief pressure of the fourth relief valve 31d, which correspond to the rotation speed of the prime mover 32. This allows the first threshold value to be appropriately set according to the first traveling relief pressure, second traveling relief pressure, third traveling relief pressure, and fourth traveling relief pressure in the work machine 1, i.e., according to the state of the relief valve installed in the work machine 1.

[0090] Furthermore, the control device 60 sets the second threshold value (swing release threshold value) based on the first traveling relief pressure, the second traveling relief pressure, the third traveling relief pressure 31c, and the fourth traveling relief pressure 31d. This allows the second threshold value to be set appropriately based on the traveling relief pressures of the relief valves 31a to 31d that operate in accordance with various conditions of the work machine 1.

[0091] Furthermore, when the rotation speeds of the left traveling motor 36L and the right traveling motor 36R are switched to a second speed, which is a high speed range, the control device 60 automatically decelerates the rotation speeds of the left traveling motor 36L and the right traveling motor 36R from the second speed to the first speed, which is a low speed range, based on the first traveling pressure, the second traveling pressure, the third traveling pressure, or the fourth traveling pressure. This allows the work machine 1 to determine whether it is in a turning state, whether it is in a straight traveling state, and whether automatic deceleration is appropriate, based on the same parameter, such as the first traveling pressure, the second traveling pressure, the third traveling pressure, or the fourth traveling pressure. As a result, automatic deceleration can be appropriately performed when the work machine 1 is turning or traveling straight, thereby improving the safety of the machine body 2 when traveling and the convenience achieved by automation.

[0092] In the above-described embodiment, the first threshold value (swing threshold value) was set and changed based on the travel relief pressures (first to fourth travel relief pressures) of the relief valves 31a to 31d, but the first threshold value may also be changed based on the temperature of the hydraulic oil (oil temperature) or the rotation speed of the prime mover 32 (prime mover rotation speed). For example, the control device 60 sets and changes the first threshold value based on the prime mover rotation speed detected by the rotation speed detection device 68. Alternatively, the control device 60 detects the temperature of the hydraulic oil (oil temperature) flowing to the travel motors 36L, 36R or the travel pumps 53L, 53R using an oil temperature detection device, and sets and changes the first threshold value based on the detected oil temperature.

[0093] 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]

[0094] 1 Work equipment 2 aircraft 5L left running device 5R Right running gear 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) 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; a right traveling motor capable of transmitting power to the right traveling device; a left traveling pump that supplies hydraulic oil to the left traveling motor; a right travel pump that supplies hydraulic oil to the right travel motor; 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 that is provided on a first port side of the left traveling motor in the first circulation oil passage and detects, as a first traveling pressure, a pressure of hydraulic oil acting on the first port side of the left traveling motor; a second pressure detection device that is provided on a second port side of the left traveling motor in the first circulation oil passage and detects the pressure of hydraulic oil acting on the second port side of the left traveling motor as a second traveling pressure; a third pressure detection device that is provided in the second circulation oil passage on a third port side of the right traveling motor and detects the pressure of hydraulic oil acting on the third port side of the right traveling motor as a third traveling pressure; a fourth pressure detection device that is provided on a fourth port side of the right traveling motor in the second circulation oil passage and detects the pressure of hydraulic oil acting on the fourth port side of the right traveling motor as a fourth traveling pressure; a control device that calculates a first left-right differential pressure obtained by subtracting the third travel pressure from the first travel pressure, a second left-right differential pressure obtained by subtracting the first travel pressure from the third travel pressure, a third left-right differential pressure obtained by subtracting the fourth travel pressure from the second travel pressure, and a fourth left-right differential pressure obtained by subtracting the second travel pressure from the fourth travel pressure, The control device is a work machine that determines whether the machine is turning or moving straight based on the results of comparing each of the first left-right differential pressure, the second left-right differential pressure, the third left-right differential pressure, and the fourth left-right differential pressure with a predetermined first threshold value.

2. The work machine according to claim 1, wherein the control device determines whether the machine is turning or moving straight based on the results of comparing each of the first left-right differential pressure, the second left-right differential pressure, the third left-right differential pressure, and the fourth left-right differential pressure with the first threshold value.

3. The work machine according to claim 1 or 2, wherein the control device determines whether the machine is moving forward or backward based on a result of comparing each of the first left-right differential pressure, the second left-right differential pressure, the third left-right differential pressure, and the fourth left-right differential pressure with the first threshold value.

4. The control device determines whether the machine is turning and determines the turning direction of the machine based on the results of comparing each of the first left-right differential pressure, the second left-right differential pressure, the third left-right differential pressure, and the fourth left-right differential pressure with the first threshold value.

5. The work machine according to any one of claims 1 to 4, wherein the control device determines that the machine is performing a pivot turn based on the results of comparing each of the first left-right differential pressure, the second left-right differential pressure, the third left-right differential pressure, and the fourth left-right differential pressure with the first threshold value.

6. The control device determines that the machine is turning when any one of the first left-right differential pressure, the second left-right differential pressure, the third left-right differential pressure, and the fourth left-right differential pressure is greater than the first threshold value, and determines that the machine is not turning when the first left-right differential pressure, the second left-right differential pressure, the third left-right differential pressure, and the fourth left-right differential pressure are equal to or less than the first threshold value.

7. The work machine described in claim 6, wherein the control device determines whether the machine is turning or not based on the results of comparing each of the first left-right differential pressure, the second left-right differential pressure, the third left-right differential pressure, and the fourth left-right differential pressure with a predetermined second threshold value after determining that the machine is turning.

8. The control device determines that the machine is moving in a straight line when the first left-right differential pressure, the second left-right differential pressure, the third left-right differential pressure, and the fourth left-right differential pressure are equal to or less than the first threshold value, and determines that the machine is not moving in a straight line when any of the first left-right differential pressure, the second left-right differential pressure, the third left-right differential pressure, and the fourth left-right differential pressure is greater than the first threshold value.

9. The control device determines whether the vehicle is not traveling in a straight line but is turning based on the first left-right differential pressure, the second left-right differential pressure, the third left-right differential pressure, the fourth left-right differential pressure, and the first threshold value, and then determines whether the vehicle has started traveling in a straight line or not based on a result of comparing each of the first left-right differential pressure, the second left-right differential pressure, the third left-right differential pressure, and the fourth left-right differential pressure with a predetermined second threshold value.

10. the rotation speeds of the left traveling motor and the right traveling motor are switchable between a first speed which is a low speed range and a second speed which is a high speed range faster than the first speed, The work machine according to any one of claims 1 to 9, wherein when the rotation speeds of the left traveling motor and the right traveling motor are switched to the second speed, the control device performs automatic deceleration to automatically decelerate the rotation speeds of the left traveling motor and the right traveling motor from the second speed to the first speed based on the first traveling pressure, the second traveling pressure, the third traveling pressure, or the fourth traveling pressure.

Images