Work machine

Abstract

To enable a work machine to be smoothly decelerated according to traveling of the work machine.SOLUTION: A work machine has a control device that automatically decelerates a first revolving speed of a left travel motor capable of transmitting power to a left travel device provided on a left side of a machine body and a second revolving speed of a right travel motor capable of transmitting the power to a right travel device provided on a right side of the machine body from a second speed in a prescribed high speed range to a first speed in a prescribed low speed range. The control device does not automatically decelerate when either one of the first revolving speed or the second revolving speed is equal to or higher than a prescribed revolving speed.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a working machine such as a skid steer loader, a compact track loader, a backhoe, etc.

Background Art

[0002] Conventionally, as a technique for decelerating and accelerating in a working machine, there is one shown in Patent Document 1. The working machine of Patent Document 1 includes a prime mover including an engine, a hydraulic pump that operates by the power of the prime mover and discharges hydraulic oil, a traveling hydraulic device whose speed can be changed between a first speed and a second speed higher than the first speed according to the pressure of the hydraulic oil, a control 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. The control valve reduces the pressure of the hydraulic oil acting on the traveling hydraulic device when the detected pressure, which is the pressure of the hydraulic oil detected by the measuring device, drops below a predetermined pressure from the set pressure corresponding to the second speed, and decelerates the traveling hydraulic device to the first speed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the working machine of Patent Document 1, when the pressure of the hydraulic oil supplied to the traveling device during traveling is equal to or higher than a predetermined pressure, it can automatically decelerate from the second speed to the first speed. However, depending on the traveling state (ultra-sharp turning, turning in place, straight traveling) of the working machine (traveling device), it may decelerate inadvertently.

[0005] The present invention has been made to solve the problems of the prior art as described above, and an object thereof is to provide a working machine that can decelerate smoothly according to the traveling of the working machine.

Means for Solving the Problem

[0006] The technical means taken by the present invention to solve the above technical problems are as follows. The working machine includes a 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 first rotation detection device for detecting the first rotation speed of the left traveling motor, a second rotation detection device for detecting the second rotation speed of the right traveling motor, a left traveling pump for supplying hydraulic oil to the left traveling motor, a right traveling pump for supplying hydraulic oil to the right traveling motor, and a control device for automatically decelerating the first rotation speed and the second rotation speed from the second speed on the high-speed side to the first speed on the low-speed side when the first rotation speed and the second rotation speed are the second speed on the high-speed side. The control device does not perform the automatic deceleration when either the first rotation speed or the second rotation speed is equal to or higher than a predetermined rotation speed.

[0007] The working machine includes a traveling operation device for operating at least one of the left traveling pump and the right traveling pump. The control device does not perform the automatic deceleration when the traveling operation device is operated in the direction of advancing the machine body and the left traveling motor and the right traveling motor are rotating in the direction corresponding to the reverse movement of the machine body.

[0008] The working machine includes a hydraulic pump for discharging pilot oil and a plurality of traveling oil paths connected to a plurality of pressure receiving portions respectively provided in the left traveling pump and the right traveling pump. The traveling operation device is operated to change the angle of the swash plate respectively provided in the left traveling pump and the right traveling pump, and changes the pilot pressure, which is the pressure of the pilot oil output to the plurality of traveling oil paths respectively according to the operation. The control device determines the operation direction of the traveling operation device based on the pilot pressure of each of the plurality of traveling oil paths, and performs the automatic deceleration when it is determined that the operation direction corresponds to the direction of in-place turning of the machine body to the left or right direction. Further, when the control device determines that the operation direction of the traveling operation device corresponds to the direction of skidding to the left or right of the aircraft, the automatic deceleration is performed.

[0009] The traveling operation device includes a traveling operation member that is swing-operated, and a plurality of operation valves that operate according to the operation state of the traveling operation member and change the pilot pressure, which is the pressure of the pilot oil output to each of the plurality of traveling oil passages. When the pilot pressure acting on each of the plurality of pressure receiving portions of the left traveling pump and the right traveling pump changes from the plurality of traveling oil passages, the angles of the swash plates respectively included in the left traveling pump and the right traveling pump are changed, and the rotation directions and rotation speeds of the left traveling motor and the right traveling motor are changed.

[0010] The traveling operation device has a plurality of high-pressure selection valves respectively connected to the plurality of traveling oil passages and respectively connected to any two of the plurality of operation valves. The plurality of high-pressure selection valves output the higher pilot pressure among the pilot pressures output from the two connected operation valves to the connected traveling oil passage.

[0011] The work machine includes a pressure detection device that detects the pressure of the hydraulic oil supplied to the left traveling motor and the right traveling motor. The control device determines whether to perform the automatic deceleration based on the pressure of the hydraulic oil detected by the pressure detection device and a predetermined threshold value. The control device sets the threshold value based on the first rotation speed and the second rotation speed. The control device sets the threshold value lower as the first rotation speed and the second rotation speed increase.

Advantages of the Invention

[0012] According to the present invention, deceleration can be smoothly performed according to the traveling of the work machine.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6A

Figure 6B

Figure 7

Figure 8A

Figure 8B

Figure 9

Embodiments for Carrying Out the Invention

[0014] Hereinafter, a hydraulic system of a work machine according to the present invention and a preferred embodiment of a work machine equipped with this hydraulic system will be described with appropriate reference to the drawings. Figure 9 shows a side view of a work machine according to the present invention. In Figure 9, as an example of a work machine, a compact track loader is shown. 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, it may be a work machine other than a loader work machine.

[0015] As shown in FIG. 9, the work machine 1 includes a machine body 2, a cabin 3, a working device 4, and a pair of traveling devices 5L and 5R. In the embodiment of the present invention, the front side (the left side in FIG. 9) of the driver sitting on the driver's seat 8 of the work machine 1 is defined as the front, the rear side (the right side in FIG. 9) of the driver is defined as the rear, the left side (the front side in FIG. 9) of the driver is defined as the left, and the right side (the back side in FIG. 9) of the driver is defined as the right for explanation. Also, the horizontal direction, which is perpendicular to the front-rear direction, is defined as the machine body width direction for explanation. The direction from the central part of the machine body 2 toward the right part or the left part is defined as the outside of the machine body for explanation. In other words, the outside of the machine body is the direction in the machine body width direction and away from the machine body 2. The direction opposite to the outside of the machine body is defined as the inside of the machine body for explanation. In other words, the inside of the machine body is the direction in the machine body width direction and approaching the machine body 2.

[0016] The cabin 3 is mounted on the machine body 2. A driver's seat 8 is provided in this cabin 3. The working device 4 is attached to the machine body 2. The pair of traveling devices 5L and 5R are provided outside the machine body 2. A prime mover 32 is mounted at the rear part inside the machine body 2. The working device 4 includes a boom 10, a working tool 11, a lift link 12, a control link 13, a boom cylinder 14, and a bucket cylinder 15.

[0017] The boom 10 is provided on the right side and the left side of the cabin 3 so as to be swingable up and down. The working tool 11 is, for example, a bucket. The bucket 11 is provided at the tip (front end) of the boom 10 so as to be swingable up and down. The lift link 12 and the control link 13 support the base (rear part) of the boom 10 so that the boom 10 can swing up and down. The boom cylinder 14 raises and lowers the boom 10 by expanding and contracting. The bucket cylinder 15 swings the bucket 11 by expanding and contracting.

[0018] The front parts of the left and right booms 10 are connected by a deformed connecting pipe. The base parts (rear parts) of the booms 10 are connected by a circular connecting pipe. The lift link 12, control link 13, and boom cylinder 14 are respectively provided on the left and right sides of the airframe 2 corresponding to the left and right booms 10. The lift link 12 is provided vertically at the rear of the base of each boom 10. The upper part (one end side) of the lift link 12 is pivotally supported around a horizontal axis via a pivot shaft 16 (first pivot shaft) near the rear of the base of each boom 10. Also, the lower part (the other end side) of the lift link 12 is pivotally supported around a horizontal axis via a pivot shaft 17 (second pivot shaft) near the rear of the airframe 2. The second pivot shaft 17 is provided below the first pivot shaft 16.

[0019] The upper part of the boom cylinder 14 is pivotally supported around a horizontal axis via a pivot shaft 18 (third pivot shaft). The third pivot shaft 18 is provided at the base of each boom 10 and at the front of the base. The lower part of the boom cylinder 14 is pivotally supported around a horizontal axis via a pivot shaft 19 (fourth pivot shaft). The fourth pivot shaft 19 is provided near the lower part of the rear of the airframe 2 and below the third pivot shaft 18.

[0020] The control link 13 is provided in front of the lift link 12. One end of this control link 13 is pivotally supported around a horizontal axis via a pivot shaft 20 (fifth pivot shaft). The fifth pivot shaft 20 is provided on the airframe 2 at a position corresponding to the front of the lift link 12. The other end of the control link 13 is pivotally supported around 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.

[0021] By extending and retracting the boom cylinder 14, while the base of each boom 10 is supported by the lift link 12 and the control link 13, each boom 10 swings up and down around the first pivot shaft 16, and the tip of each boom 10 moves up and down. The control link 13 swings up and down around the fifth pivot shaft 20 as each boom 10 swings up and down. The lift link 12 swings back and forth around the second pivot shaft 17 as the control link 13 swings up and down.

[0022] Another working tool can be attached to the front part of the boom 10 instead of the bucket 11. Examples of the other working tools include attachments (optional attachments) such as a hydraulic crusher, a hydraulic breaker, an angle boom, an earth auger, a pallet fork, a sweeper, a mower, a snow blower, etc. A connecting member 50 is provided at the front part of the left boom 10. The connecting member 50 is a device that connects the hydraulic equipment equipped on the optional attachment and the first pipe material such as a pipe provided on the boom 10. Specifically, one end of the connecting member 50 can be connected to the first pipe material, and the other end can be connected to the second pipe material connected to the hydraulic equipment of the optional attachment. Thereby, the hydraulic oil flowing through the first pipe material passes through the second pipe material and is supplied to the hydraulic equipment.

[0023] The bucket cylinders 15 are respectively arranged near the front parts of the respective booms 10. By expanding and contracting the bucket cylinders 15, the bucket 11 is swung. Among the pair of traveling devices 5L and 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 and 5R adopt crawler-type (including semi-crawler type) traveling devices. Note that a wheel-type traveling device having front wheels and rear wheels may be adopted. 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 it is not limited thereto.

[0024] Next, the hydraulic system of the working machine 1 will be described. As shown in FIG. 1, the hydraulic system of the work machine 1 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 the prime mover 32 (FIG. 9) and is composed of a fixed-displacement gear pump. The first hydraulic pump P1 can discharge the hydraulic oil stored in the tank 22. In particular, the first hydraulic pump P1 mainly discharges the hydraulic oil used for control. For the sake of convenience in explanation, the tank 22 that stores the hydraulic oil may be referred to as the hydraulic oil tank. Also, among the hydraulic oil discharged from the first hydraulic pump P1, the hydraulic oil used for control may be referred to as pilot oil, and the pressure of the pilot oil may be referred to as pilot pressure.

[0025] The second hydraulic pump P2 is a pump driven by the power of the prime mover 32 and is composed of a fixed-displacement gear pump. The second hydraulic pump P2 can discharge the hydraulic oil stored in the tank 22 and supplies the hydraulic oil to, for example, the oil circuit of the working system. For example, the second hydraulic pump P2 supplies the hydraulic oil to the boom cylinder 14 that operates the boom 10, the bucket cylinder 15 that operates the bucket, and a control valve (flow control valve) that controls a standby hydraulic actuator to operate the standby hydraulic actuator.

[0026] Also, the hydraulic system of the work machine 1 includes a pair of travel motors 36L and 36R and a pair of travel pumps 53L and 53R. The pair of travel motors 36L and 36R are motors that transmit power to a pair of travel devices 5L and 5R. Among the pair of travel motors 36L and 36R, one travel motor 36L transmits the rotational power to the travel device (left travel device) 5L, and the other travel motor 36R transmits the rotational power to the travel device (right travel device) 5R.

[0027] The pair of travel pumps 53L and 53R are pumps driven by the power of the prime mover 32, and are, for example, swash plate type variable displacement axial pumps. The pair of travel pumps 53L and 53R supply hydraulic oil to each of the pair of travel motors 36L and 36R by driving. Among the pair of travel pumps 53L and 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.

[0028] 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 a pressure receiving portion 53a and a pressure receiving portion 53b on which the pressure (pilot pressure) of the 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 (discharge amount of hydraulic oil) and the discharge direction of the hydraulic oil of the left travel pump 53L and the right travel pump 53R can be changed.

[0029] The left travel pump 53L and the left travel motor 36L are connected by a connection 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 right travel pump 53R and the right travel motor 36R are connected by a connection 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.

[0030] The left travel motor 36L can be rotated by the hydraulic oil discharged from the left travel pump 53L. By changing the flow rate of the hydraulic oil to the left travel motor 36L, the rotation speed (rotational speed) of the left travel motor 36L can be changed. A swash plate switching cylinder 37L is connected to the left travel motor 36L. By extending or contracting the swash plate switching cylinder 37L to one side or the other side, the rotation speed of the left travel motor 36L can also be changed. That is, when the swash plate switching cylinder 37L is contracted, the rotation speed of the left travel motor 36L is set to the first speed (predetermined low speed range) on the low speed side. Also, when the swash plate switching cylinder 37L is extended, the rotation speed of the left travel motor 36L is set to the second speed (predetermined high speed range) on the high speed side. That is, the rotation speed of the left travel motor 36L can be changed between the first speed and the second speed.

[0031] The right travel motor 36R can be rotated by the hydraulic oil discharged from the right travel pump 53R. By changing the flow rate of the hydraulic oil to the right travel motor 36R, the rotation speed of the right travel motor 36R can be changed. A swash plate switching cylinder 37R is connected to the right travel motor 36R. By extending or contracting the swash plate switching cylinder 37R to one side or the other side, the rotation speed of the right travel motor 36R can also be changed. That is, when the swash plate switching cylinder 37R is contracted, the rotation speed of the right travel motor 36R is set to the first speed (predetermined low speed range) on the low speed side. Also, when the swash plate switching cylinder 37R is extended, the rotation speed of the right travel motor 36R is set to the second speed (predetermined high speed range) on the high speed side. That is, the rotation speed of the right travel motor 36R can be changed between the first speed and the second speed.

[0032] As shown in FIG. 1, the hydraulic system of the work machine 1 includes a travel switching valve 34. The travel switching valve 34 can be switched between a first state in which the rotation speeds of the travel motors 36L and 36R (left travel motor 36L and right travel motor 36R) are set to the first speed and a second state in which the rotation speeds are set to the second speed. The travel switching valve 34 has first switching valves 71L and 71R and a second switching valve 72. The first switching valve 71L is a two-position switching valve that is connected to the swash plate switching cylinder 37L of the left traveling motor 36L via an oil passage and switches 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 it is in the second position 71L2, it extends the swash plate switching cylinder 37L.

[0033] The first switching valve 71R is a two-position switching valve that is connected to the swash plate switching cylinder 37R of the right traveling motor 36R via an oil passage and switches 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 it 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 by excitation. The second switching valve 72, the first switching valve 71L, and the first switching valve 71R are connected by an oil passage 41. When the second switching valve 72 is in the first position 72a, it switches the first switching valve 71L and the first switching valve 71R to the first positions 71L1 and 71R1, and when it is in the second position 72b, it switches the first switching valve 71L and the first switching valve 71R to the second positions 71L2 and 71R2.

[0034] That is, when the second switching valve 72 is in the first position 72a, the first switching valve 71L is in the first position 71L1, and the first switching valve 71R is in the first position 71R1, the traveling switching valve 34 is in the first state, the swash plate switching cylinders 37L and 37R are contracted, and the rotational speeds of the traveling motors 36L and 36R are set to the first speed. When the second switching valve 72 is in the second position 72b, the first switching valve 71L is in the second position 71L2, and the first switching valve 71R is in the second position 71R2, the traveling switching valve 34 is in the second state, the swash plate switching cylinders 37L and 37R are extended, and the rotational speeds of the traveling motors 36L and 36R are set to the second speed. Therefore, the traveling motors 36L and 36R can be switched between the first speed and the second speed by the traveling switching valve 34.

[0035] The operating device (traveling operating device) 54 is a device that causes hydraulic oil to act on the pressure receiving parts 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 a travel operating member 59 and a plurality of operation valves 55.

[0036] The travel operating member 59 is an operating lever that is supported by the operation valve 55 and swings in the left - right direction (machine width direction) or the front - rear direction. That is, with the neutral position N as a reference, the travel operating member 59 can be operated to the right and left from the neutral position N, and can also be operated to the front and rear from the neutral position N. In other words, the travel operating member 59 can swing in at least four directions with the neutral position N as a reference. For the sake of convenience of explanation, the two - way direction of the front and the rear, that is, the front - rear direction is referred to as the first direction. Also, the two - way direction of the right and the left, that is, the left - right direction (machine width direction) may be referred to as the second direction.

[0037] Also, the plurality of operation valves 55 are common, that is, they are operated by a single travel operating member 59. The plurality of operation valves 55 operate based on the swing of the travel operating member 59. A discharge oil passage 40 is connected to the plurality of operation valves 55, and hydraulic oil (pilot oil) from the first hydraulic pump P1 can be supplied through the discharge oil passage 40. The plurality of operation valves 55 are an operation valve 55A, an operation valve 55B, an operation valve 55C, and an operation valve 55D.

[0038] The operation valve 55A changes the pressure of the hydraulic oil output according to the operation amount (operation) of the forward operation when the traveling operation member 59 is swung forward (one side) in the front-rear direction (first direction) (when performing a forward operation). The operation valve 55B changes the pressure of the hydraulic oil output according to the operation amount (operation) of the rear operation when the traveling operation member 59 is swung rearward (the other side) in the front-rear direction (first direction) (when performing a rear operation). Among the left-right direction (second direction), the operation valve 55C changes the pressure of the hydraulic oil output according to the operation amount (operation) of the right operation when the traveling operation member 59 is swung to the right (one side) (when performing a right operation). The operation valve 55D changes the pressure of the hydraulic oil output according to the operation amount (operation) of the left operation when the traveling operation member 59 is swung to the left (the other side) in the left-right direction (second direction) (when performing a left operation).

[0039] The plurality of operation valves 55 and the traveling pumps 53L and 53R are connected by a traveling oil passage 45. In other words, the traveling pumps 53L and 53R are hydraulic devices that can be operated by the hydraulic oil output from the operation valves 55 (operation valve 55A, operation valve 55B, operation valve 55C, operation valve 55D). The traveling oil passage 45 has a first traveling oil passage 45a, a second traveling oil passage 45b, a third traveling oil passage 45c, a fourth traveling oil passage 45d, and a fifth traveling oil passage 45e. The first traveling oil passage 45a is an oil passage connected to the pressure receiving portion (first pressure receiving portion) 53a of the left traveling pump 53L, and is an oil passage that allows the hydraulic oil acting on the pressure receiving portion (first pressure receiving portion) 53a when the traveling operation member 59 is operated to pass through. The second traveling oil passage 45b is an oil passage connected to the pressure receiving portion (second pressure receiving portion) 53b of the left traveling pump 53L, and is an oil passage that allows the hydraulic oil acting on the pressure receiving portion (second pressure receiving portion) 53b when the traveling operation member 59 is operated to pass through. The third traveling oil passage 45c is an oil passage connected to the pressure receiving portion (third pressure receiving portion) 53a of the right traveling pump 53R, and is an oil passage that allows the hydraulic oil acting on the pressure receiving portion (third pressure receiving portion) 53a when the traveling operation member 59 is operated to pass through. The fourth traveling oil passage 45d is an oil passage connected to the pressure receiving portion (fourth pressure receiving portion) 53b of the right traveling pump 53R, and is an oil passage that allows the hydraulic oil acting on the pressure receiving portion (fourth pressure receiving portion) 53b when the traveling operation member 59 is operated to pass through. The fifth traveling oil passage 45e is an oil passage that connects the operation valve 55, the first traveling oil passage 45a, the second traveling oil passage 45b, the third traveling oil passage 45c, and the fourth traveling oil passage 45d.

[0040] A plurality of high-pressure selection valves 47a, 47b, 47c, 47d are provided in the fifth traveling oil passage 45e. The plurality of high-pressure selection valves 47a, 47b, 47c, 47d are connected to the first traveling oil passage 45a, the second traveling oil passage 45b, the third traveling oil passage 45c, and the fourth traveling oil passage 45d, and allow the hydraulic oil to flow to the one with the higher pressure (pilot pressure) of the hydraulic oil. When the traveling operation member 59 is swung forward (in the direction of arrow A1 in FIGS. 1 and 2), the operation valve 55A is operated and a pilot pressure is output from the operation valve 55A. This pilot pressure acts on the pressure receiving portion 53a of the left traveling pump 53L via the first traveling oil passage 45a and acts on the pressure receiving portion 53a of the right traveling pump 53R via the third traveling oil passage 45c. As a result, the swash plate angles of the left traveling pump 53L and the right traveling pump 53R are changed, and the left traveling motor 36L and the right traveling motor 36R rotate forward (rotate forward), and the work machine 1 travels straight forward.

[0041] Further, when the traveling operation member 59 is swung rearward (in the direction of arrow A2 in FIGS. 1 and 2), the operation valve 55B is operated and a pilot pressure is output from the operation valve 55B. This pilot pressure acts on the pressure receiving portion 53b of the left traveling pump 53L via the second traveling oil passage 45b and also acts on the pressure receiving portion 53b of the right traveling pump 53R via the fourth traveling oil passage 45d. As a result, the swash plate angles of the left traveling pump 53L and the right traveling pump 53R are changed, and the left traveling motor 36L and the right traveling motor 36R rotate reversely (rotate backward), causing the work machine 1 to go straight backward.

[0042] Further, when the traveling operation member 59 is swung rightward (in the direction of arrow A4 in FIGS. 1 and 2), the operation valve 55C is operated and a pilot pressure is output from the operation valve 55C. This pilot pressure acts on the pressure receiving portion 53a of the left traveling pump 53L via the first traveling oil passage 45a and also acts on the pressure receiving portion 53b of the right traveling pump 53R via the fourth traveling oil passage 45d. As a result, the swash plate angles of the left traveling pump 53L and the right traveling pump 53R are changed, and the left traveling motor 36L rotates forward and the right traveling motor 36R rotates reversely, causing the work machine 1 to perform a spin turn (ultra-close turning) to the right.

[0043] Further, when the traveling operation member 59 is swung leftward (in the direction of arrow A3 in FIGS. 1 and 2), the operation valve 55D is operated and a pilot pressure is output from the operation valve 55D. This pilot pressure acts on the pressure receiving portion 53a of the right traveling pump 53R via the third traveling oil passage 45c and also acts on the pressure receiving portion 53b of the left traveling pump 53L via the second traveling oil passage 45b. As a result, the swash plate angles of the left traveling pump 53L and the right traveling pump 53R are changed, and the left traveling motor 36L rotates reversely and the right traveling motor 36R rotates forward, causing the work machine 1 to perform a spin turn (ultra-close turning) to the left.

[0044] Further, when the traveling operation member 59 is swung in an oblique direction (in the direction of arrow A5 in FIG. 2), the rotational directions and rotational speeds of the left traveling motor 36L and the right traveling 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 performs a crab turn to the right or left while moving forward or backward. That is, when the traveling operation member 59 is swung obliquely forward to the left, the work machine 1 turns left while moving forward at a speed corresponding to the swing angle of the traveling operation member 59. Further, when the traveling operation member 59 is swung obliquely forward to the right, the work machine 1 turns right while moving forward at a speed corresponding to the swing angle of the traveling operation member 59. Further, when the traveling operation member 59 is swung obliquely backward to the left, the work machine 1 turns left while moving backward at a speed corresponding to the swing angle of the traveling operation member 59. Furthermore, when the traveling operation member 59 is swung obliquely backward to the right, the work machine 1 turns right while moving backward at a speed corresponding to the swing angle of the traveling operation member 59.

[0045] As shown in FIG. 1, the work machine 1 includes a control device 60. The control device 60 performs various controls of the work machine 1 and is composed of semiconductors such as a CPU and an MPU, and electric and electronic circuits. A mode switch 66, a speed change switch 67, and a plurality of rotation detection devices 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 to enable automatic deceleration when it is ON, and switches to disable automatic deceleration when it is OFF.

[0046] 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 speeds of the traveling motors 36L and 36R (left traveling motor 36L and right traveling motor 36R) to either the first speed or the second speed. For example, the speed change switch 67 is a toggle switch, and can perform a speed increase operation for switching the rotation speeds of the traveling motors 36L and 36R from the first speed to the second speed, and a speed decrease operation for switching from the second speed to the first speed.

[0047] The plurality of rotation detection devices 68 are composed of sensors and the like, and detect the rotation speeds (motor rotation speeds) of the current traveling motors 36L and 36R. The rotation detection device 68 includes a first rotation detection device 68a that detects the motor rotation speed (first rotation speed) of the left traveling motor 36L, and a second rotation detection device 68b that detects the motor rotation speed (second rotation speed) of the right traveling motor 36R. The control device 60 includes an automatic deceleration unit 61. The automatic deceleration unit 61 is an electric and electronic circuit provided in the control device 60, a program stored in the control device 60, and the like. The automatic deceleration unit 61 performs automatic deceleration control when automatic deceleration is effective, and does not perform automatic deceleration control when automatic deceleration is ineffective.

[0048] In the automatic deceleration control, when the rotation speeds of the traveling motors 36L and 36R are set to the second speed and a predetermined condition (automatic deceleration condition) is satisfied, the rotation speeds of the traveling motors 36L and 36R are automatically switched from the second speed to the first speed. Specifically, in the automatic deceleration control, at least in a situation where the traveling motors 36L and 36R are at the second speed, when the automatic deceleration condition is satisfied, the control device 60 demagnetizes the solenoid of the second switching valve 72, thereby switching the second switching valve 72 from the second position 72b to the first position 72a, and decelerating the rotation speeds of the traveling motors 36L and 36R from the second speed to the first speed. That is, in the automatic deceleration control, when performing automatic deceleration, the control device 60 decelerates the rotation speeds of both the left traveling motor 36L and the right traveling motor 36R from the second speed to the first speed.

[0049] Note that after performing automatic deceleration, when the automatic deceleration unit 61 satisfies a predetermined return condition, it 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, and increasing the rotation speeds of the traveling motors 36L and 36R from the first speed to the second speed. That is, the rotation speeds of the traveling motors 36L and 36R are restored to the second speed. That is, the control device 60 increases the rotation speeds of both the left traveling motor 36L and the right traveling motor 36R from the first speed to the second speed.

[0050] When the automatic deceleration is invalid, the control device 60 performs manual switching control to switch the rotational speeds of the traveling motors 36L and 36R to either the first speed or the second speed according to the operation of the speed change switch 67. In the 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 demagnetized to set the rotational speeds of the traveling motors 36L and 36R to the first speed. Also, in the 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 excited to set the rotational speeds of the traveling motors 36L and 36R to the second speed. Note that even when the automatic deceleration is valid, the control device 60 may switch the rotational speeds of the traveling motors 36L and 36R to either the first speed or the second speed by manual switching control when the speed change switch 67 is operated.

[0051] Now, an accelerator 65 for setting the target rotational speed of the prime mover 32 is connected to the control device 60. The accelerator 65 is provided near the driver's seat 8. The accelerator 65 is an accelerator lever supported so as to be swingable, an accelerator pedal supported so as to be swingable, an accelerator volume supported so as to be rotatable, an accelerator slider supported so as to be slidable, or the like. Note that the accelerator 65 is not limited to the above-described example. Also, a third rotation detection device 69 for detecting the actual rotational speed of the prime mover 32 is connected to the control device 60. The control device 60 can grasp the actual rotational speed of the prime mover 32 by the third rotation detection device 69. The control device 60 sets a target rotational speed based on the operation amount of the accelerator 65 and controls the actual rotational speed so as to reach the set target rotational speed.

[0052] Further, the control device 60 performs automatic deceleration based on the pressures 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 on the first port P11 side of the left travel motor 36L in the circulation oil passage 57h, and detects the pressure on the first port P11 side as the first travel pressure V1. The second pressure detection device 80b is provided on the second port P12 side of the left travel motor 36L in the circulation oil passage 57h, and detects the pressure on the second port P12 side as the second travel pressure V2. The third pressure detection device 80c is provided on the third port P13 side of the right travel motor 36R in the circulation oil passage 57i, and detects the pressure on the third port P13 side as the third travel pressure V3. The fourth pressure detection device 80d is provided on the fourth port P14 side of the right travel motor 36R in the circulation oil passage 57i, and detects the pressure on the fourth port P14 side as the fourth travel pressure V4. Note that the installation positions of the first pressure detection device 80a, the second pressure detection device 80b, the third pressure detection device 80c, and the fourth pressure detection device 80d are not limited, and they may be provided on the port side of the left travel pump 53L or the port side of the right travel pump 53R.

[0053] The control device 60 (automatic deceleration unit 61) performs automatic deceleration (control process of switching the rotation speeds of the travel motors 36L and 36R from the second speed to the first speed) based on the first travel pressure V1 detected by the first pressure detection device 80a, the second travel pressure V2 detected by the second pressure detection device 80b, the third travel pressure V3 detected by the third pressure detection device 80c, and the fourth travel pressure V4 detected by the fourth pressure detection device 80d.

[0054] When the rotation speeds of the travel motors 36L and 36R are set to the second speed and the machine body 2 (or the left travel device 5L and the right travel device 5R) performs on-site turning to the left, the control device 60 refers to the third travel pressure V3 and the fourth travel pressure V4 corresponding to the right travel motor 36R on the right side, and when the third travel pressure V3 or the fourth travel pressure V4 is the first left threshold ST1 LIf the above conditions are met, automatic deceleration is performed. Further, when the rotational speeds of the traveling motors 36L and 36R are set to the second speed and the aircraft body 2 is making a ground turn to the right, the control device 60 refers to the first traveling pressure V1 and the second traveling pressure V2 corresponding to the left traveling motor 36L, and if the first traveling pressure V1 or the second traveling pressure V2 is the first right threshold value ST1 R If the above conditions are met, automatic deceleration is performed.

[0055] Here, the case of making a ground turn means when the traveling operation member 59 is operated in a direction corresponding to a ground turn, or when the aircraft body 2 shows a behavior of making a ground turn. In order to detect the operation direction of the traveling operation member 59 shown in FIG. 2, a sensor may be provided. Alternatively, a pressure detection device for detecting the pilot pressure of the traveling oil passages 45 (the first traveling oil passage 45a, the second traveling oil passage 45b, the third traveling oil passage 45c, the fourth traveling oil passage 45d) in which the pressure (pilot pressure) of the hydraulic oil changes due to the operation of the traveling operation member 59 is provided, and based on the change in the pilot pressure detected by the pressure detection device, the control device 60 may detect the operation direction of the traveling operation member 59. Further, the detection of the operation direction of the operation member 59 is not limited to the above, and other configurations and methods may be used.

[0056] When the traveling operation member 59 or the aircraft body 2 is moving forward and making a ground turn to the left, moving forward and making a ground turn to the right, moving backward and making a ground turn to the left, and moving backward and making a ground turn to the right, the control device 60 performs automatic deceleration based on the traveling pressures V1 to V4 as described above. In the above-described embodiment, when the operation of the traveling operation member 59 or the behavior of the aircraft body 2 is a ground turn to the left, the third traveling pressure V3 or the fourth traveling pressure V4 is the first left threshold value ST1 L If the above conditions are met, it is determined whether to perform automatic deceleration. When the operation of the traveling operation member 59 or the behavior of the aircraft body 2 is a ground turn to the right, if the first traveling pressure V1 or the second traveling pressure V2 is the first right threshold value ST1 R If the above conditions are met, it is determined whether to perform automatic deceleration. In addition to this, it may be determined whether to perform automatic deceleration based on the effective differential pressure of the traveling pressures V1 to V4 as follows.

[0057] For example, when the rotational speeds of the traveling motors 36L and 36R are set to the second speed and the vehicle body 2 is making a skid turn to the left, the control device 60 calculates an effective third differential pressure (the value obtained by subtracting the fourth traveling pressure V4 from the third traveling pressure V3) ΔV3 corresponding to the right traveling motor 36R on the right side, and an effective fourth differential pressure (the value obtained by subtracting the third traveling pressure V3 from the fourth traveling pressure V4) ΔV4 corresponding to the right traveling motor 36R. Then, when the third differential pressure ΔV3 or the fourth differential pressure ΔV4 is greater than or equal to the second left threshold value ST2 L If the above condition is met, the control device 60 performs automatic deceleration.

[0058] Further, when the rotational speeds of the traveling motors 36L and 36R are set to the second speed and the vehicle body 2 is making a skid turn to the right, the control device 60 calculates an effective first differential pressure (the value obtained by subtracting the second traveling pressure V2 from the first traveling pressure V1) ΔV1 corresponding to the left traveling motor 36L on the left side, and an effective second differential pressure (the value obtained by subtracting the first traveling pressure V1 from the second traveling pressure V2) ΔV2 corresponding to the left traveling motor 36L. Then, when the first differential pressure ΔV1 or the second differential pressure ΔV2 is greater than or equal to the second right threshold value ST2 R If the above condition is met, the control device 60 performs automatic deceleration.

[0059] Now, the control device 60 sets a left threshold value (the first left threshold value ST1 L、 the second left threshold value ST2 L ) used during a skid turn to the left and a right threshold value (the first right threshold value ST1 R、 the second right threshold value ST2 Rと ) used during a skid turn to the right based on the rotational speeds of the traveling motors 36L and 36R. That is, the control device 60 sets the left threshold value and the right threshold value as deceleration threshold values for determining deceleration during automatic deceleration based on the rotational speeds of the traveling motors 36L and 36R. Hereinafter, for convenience of explanation, the rotational speed of the left traveling motor 36L is referred to as "the first rotational speed LM RPM ", and the rotational speed of the right traveling motor 36R is referred to as "the second rotational speed RM RPM ".

[0060] FIG. 3 shows the left threshold value (the first left threshold value ST1 L、 the second left threshold value ST2 L ) and the second rotational speed RM RPMshows the relationship with. Note that for the sake of explanation, in FIG. 3, the second rotational speed RM RPM with respect to, the first left threshold ST1 L and the second left threshold ST2 L are shown. However, the control device 60 may set either the first left threshold ST1 L or the second left threshold ST2 L . As shown in FIG. 3, as the second rotational speed RM RPM decreases, the control device 60 lowers the left threshold (the first left threshold ST1 L、 the second left threshold ST2 L ), and as the second rotational speed RM RPM increases, the control device 60 raises the left threshold. Also, the control device 60 applies the second rotational speed RM RPM detected by the second rotation detection device 68b to the lines L1 and L2 showing the relationship between the second rotational speed RM L、 and the left threshold (the first left threshold ST1 L the second left threshold ST2 RPM ) to set the left threshold (the first left threshold ST1 L、 the second left threshold ST2 L ). Alternatively, control data such as an expression (a linear function expression representing the lines L1 and L2 in FIG. 3) or a table showing the relationship between the second rotational speed RM RPM and each left threshold ST1 L、 ST2 L is stored in the storage unit 63 in advance, and the control device 60 extracts the first left threshold ST1 RPM corresponding to the second rotational speed RM L、 detected by the second rotation detection device 68b from the control data to set the left threshold (the first left threshold ST1 L the second left threshold ST2 L、 ). L )

[0061] Also, FIG. 4 shows the relationship between the right threshold (the first right threshold ST1 R、 the second right threshold ST2 R ) and the first rotational speed LM RPM . Note that for the sake of explanation, in FIG. 3, for the first rotational speed LM RPM with respect to, the first right threshold ST1R and the second right threshold ST2 R Although two right thresholds are shown, the control device 60 may set either the first right threshold ST1 R or the second right threshold ST2 R . As shown in FIG. 4, as the first rotational speed LM RPM decreases, the control device 60 lowers the right threshold (the first right threshold ST1 R、 the second right threshold ST2 R ), and as the first rotational speed LM RPM increases, the control device 60 raises the right threshold. The control device 60 applies the first rotational speed LM RPM detected by the first rotation detection device 68a to the lines L3 and L4 showing the relationship between the first rotational speed LM R、 and the right threshold (the first right threshold ST1 R the second right threshold ST2 RPM ) shown in FIG. 4, thereby setting the right threshold (the first right threshold ST1 R、 the second right threshold ST2 R ). Alternatively, the relationship between the first rotational speed LM RPM and the first right threshold ST1 R、 the second right threshold ST2 R is stored in advance in the storage unit 63 as control data such as an expression (a linear function expression representing the lines L3 and L4 in FIG. 4) or a table, and the control device 60 extracts the first right threshold ST1 RPM corresponding to the first rotational speed LM R、 detected by the first rotation detection device 68a from the control data, and the second right threshold ST2 R thereby setting the right threshold (the first right threshold ST1 R、 the second right threshold ST2 R ).

[0062] During left-hand turning in place, the control device 60 automatically decelerates based on the left threshold (the first left threshold ST1 RPM the second left threshold ST2 L、 ) set according to the second rotational speed RM L of the right traveling motor 36R on the side opposite to the left traveling motor 36L. Further, during right-hand turning in place, the control device 60 uses the first rotational speed LMRPM The right threshold value (the first right threshold value ST1) set according to R、 the second left threshold value ST2 L is used to perform automatic deceleration.

[0063] Specifically, when the vehicle is making a skid turn to the left, the control device 60 refers to the second rotational speed RM RPM to set the first left threshold value ST1 L . After setting the first left threshold value ST1 L , if the third running pressure V3 or the fourth running pressure V4 is greater than or equal to the first left threshold value ST1 L , the control device 60 performs automatic deceleration. Alternatively, when the vehicle is making a skid turn to the left, the control device 60 refers to the second rotational speed RM RPM to set the second left threshold value ST2 L . After setting the second left threshold value ST2 L , if the third differential pressure ΔV3 or the fourth differential pressure ΔV4 is greater than or equal to the second left threshold value ST2 L , the control device 60 performs automatic deceleration.

[0064] Also, when the vehicle is making a skid turn to the right, the control device 60 refers to the first rotational speed LM RPM to set the first right threshold value ST1 R . After setting the first right threshold value ST1 R , if the first running pressure V1 or the second running pressure V2 is greater than or equal to the first right threshold value ST1 R , the control device 60 performs automatic deceleration. Alternatively, when the vehicle is making a skid turn to the right, the control device 60 refers to the first rotational speed LM RPM to set the second right threshold value ST2 R . After setting the second right threshold value ST2 R , if the first differential pressure ΔV1 or the second differential pressure ΔV2 is greater than or equal to the second right threshold value ST2 R , the control device 60 performs automatic deceleration.

[0065] Note that the control device 60 may change the left threshold values (the first left threshold value ST1 L、 the second left threshold value ST2 L ) and the right threshold values (the first right threshold value ST1 R、 the second right threshold value ST2 R ) according to the rotational speed of the prime mover 32. Also, in the above-described embodiment, as shown in FIGS. 3 and 4, the rotational speeds LM RPM , RM RPM are used to set the left and right threshold values (the first left threshold value ST1 L、 the second left threshold value ST2 L , the first right threshold value ST1 R、 the second right threshold value ST2 R ). However, when each of the rotational speeds LM RPM , RM RPM is equal to or greater than a predetermined threshold value M30, that is, when the rotational speeds of the traveling motors 36L and 36R are in the speed range from the maximum rotational speed to the threshold value M30, automatic deceleration may not be performed. For convenience of explanation, the left threshold values (the first left threshold value ST1 RPM and the second left threshold value ST2 RPM ) and the right threshold values (the first right threshold value ST1 L、 the second right threshold value ST2 L ) at the first rotational speed LM R、 and the second rotational speed RM R ) are set below the threshold value M30 (lines L1 and L2 reach the threshold value M30), but there is no problem in performing the calculation of the left and right threshold values even when they are set above the threshold value M30.

[0066] Now, when the aircraft body 2 performs a super-accurate turn, the control device 60 sets the super-accurate threshold value (the first super-accurate threshold value ST1 P , the second super-accurate threshold value ST2 P ), which is the deceleration threshold value, to a value lower than the left and right threshold values in the case of the above-described accurate turn. Also, the control device 60 sets the super-accurate threshold value according to the higher (faster) rotational speed among the first rotational speed LM RPM of the left traveling motor 36L and the second rotational speed RM RPM of the right traveling motor 36R.

[0067] Then, when the rotational speeds of the traveling motors 36L and 36R are set to the second speed and the aircraft body 2 (or the left traveling device 5L and the right traveling device 5R) performs a super-accurate turn in the left or right direction, if any of the first traveling pressure V1, the second traveling pressure V2, the third traveling pressure V3, and the fourth traveling pressure V4 is equal to or greater than the first super-accurate threshold value ST1 P , automatic deceleration is performed. Alternatively, when the rotation speeds of the traveling motors 36L and 36R are set to the second speed and the aircraft body 2 makes an extremely sharp turn to the left or right, if any of the first differential pressure ΔV1, the second differential pressure ΔV2, the third differential pressure ΔV3, and the fourth differential pressure ΔV4 is equal to or greater than the second extremely sharp turn threshold ST2 P the control device 60 performs automatic deceleration.

[0068] Further, when the rotation speeds of the traveling motors 36L and 36R are set to the second speed and the aircraft body 2 travels straight forward (advances), if either the first traveling pressure V1 or the third traveling pressure V3 is equal to or greater than the first straight-ahead threshold SF1 S the control device 60 performs automatic deceleration. Alternatively, when the rotation speeds of the traveling motors 36L and 36R are set to the second speed and the aircraft body 2 travels straight forward, if either the first differential pressure ΔV1 or the third differential pressure ΔV3 is equal to or greater than the second straight-ahead threshold SF2 S the control device 60 performs automatic deceleration.

[0069] Here, the case where the aircraft body 2 travels straight means when the traveling operation member 59 is operated in a direction corresponding to straight-ahead travel forward or backward, or when the aircraft body 2 shows a behavior of traveling straight forward or backward. Note that the operation of the traveling operation member 59 for straight-ahead travel forward or backward can be detected by a sensor, a pressure detection device, or the like, similar to the extremely sharp turn described above. Further, when the operation of the traveling operation member 59 changes from the extremely sharp turn side to the straight-ahead side, the control device 60 also determines whether to perform automatic deceleration based on the straight-ahead threshold values described later. In addition, the straight-ahead operation of the traveling operation member 59 is when the traveling operation member 59 is tilted forward and backward as shown in FIG. 2. Even if the operation direction of the traveling operation member 59 is oblique, as long as it is within a predetermined range allowed as straight-ahead travel, it is included in the straight-ahead operation.

[0070] Based on the rotation difference ΔMP between the first rotation speed LM detected by the first rotation detection device 68a RPM and the second rotation speed RM detected by the second rotation detection device RPM the control device 60 determines the straight-ahead threshold values (the first straight-ahead threshold SF1 S and the second straight-ahead threshold SF2 SSet it. Note that the rotational difference ΔMP is the first rotational speed LM RPM minus the second rotational speed RM RPM and may be the value obtained by subtraction, or may be the value obtained by subtracting the first rotational speed LM RPM from the second rotational speed RM RPM . Also, when the rotational difference ΔMP is a negative value, it is taken as the absolute value.

[0071] FIG. 5 shows the relationship between the straight - ahead threshold values (the first straight - ahead threshold value SF1 S , the second straight - ahead threshold value SF2 S ) and the rotational difference ΔMP. Note that for the sake of convenience of explanation, FIG. 5 shows two straight - ahead threshold values, the first straight - ahead threshold value SF1 S and the second straight - ahead threshold value SF2 S , but the control device 60 may set either one of the first straight - ahead threshold value SF1 S and the second straight - ahead threshold value SF2 S . As shown in FIG. 5, the control device 60 sets the straight - ahead threshold value (the first straight - ahead threshold value SF1 S , the second straight - ahead threshold value SF2 S ) higher as the rotational difference ΔMP increases, and sets the straight - ahead threshold value lower as the rotational difference ΔMP decreases. As shown in FIG. 5, the control device 60 applies the calculated rotational difference ΔMP to the lines L5, L6 showing the relationship between each straight - ahead threshold value SF1 S , SF2 S and the rotational difference ΔMP, and may set the first straight - ahead threshold value SF1 S and the second straight - ahead threshold value SF2 S . Alternatively, control data such as an expression (a linear function expression representing the lines L5, L6 in FIG. 5) or a table showing the relationship between the rotational difference ΔMP and each straight - ahead threshold value SF1 S , SF2 S is stored in the storage unit 63 in advance, and the control device 60 extracts the first straight - ahead threshold value SF1 S and the second straight - ahead threshold value SF2 S corresponding to the calculated rotational difference ΔMP from the control data, and may set the first straight - ahead threshold value SF1 S and the second straight - ahead threshold value SF2 S .

[0072] That is, when the control device 60 goes straight ahead, i.e., moves forward, it uses the rotational speed difference ΔMP between the first rotational speed LM RPM and the second rotational speed RM RPM to perform automatic deceleration based on the straight-ahead threshold values (the first straight-ahead threshold value SF1 S , the second straight-ahead threshold value SF2 S ) set thereby. Specifically, when moving forward, the control device 60 refers to the first rotational speed LM RPM and the second rotational speed RM RPM to calculate the rotational speed difference ΔMP, and based on the calculated rotational speed difference ΔMP, it sets the first straight-ahead threshold value SF1 S . After setting the first straight-ahead threshold value SF1 S , if the first traveling pressure V1 or the third traveling pressure V3 is equal to or greater than the first straight-ahead threshold value SF1 S , the control device 60 performs automatic deceleration. Alternatively, when moving forward, the control device 60 calculates the rotational speed difference ΔMP, and based on the calculated rotational speed difference ΔMP, it sets the second straight-ahead threshold value SF2 S . After setting the second straight-ahead threshold value SF2 S , if the first differential pressure ΔV1 or the third differential pressure ΔV3 is equal to or greater than the second straight-ahead threshold value SF2 S , the control device 60 performs automatic deceleration.

[0073] In the above-described embodiment, the first straight-ahead threshold value SF1 S and the second straight-ahead threshold value SF2 S were obtained based on the rotational speed difference ΔMP. Instead of this, the first straight-ahead threshold value SF1 S and the second straight-ahead threshold value SF2 S may be obtained based on the rotational ratio difference ΔDP. The rotational ratio difference ΔDP is the difference between the first ratio obtained by dividing the first rotational speed LM RPM by the second rotational speed RM RPM , and the second ratio obtained by dividing the second rotational speed RM RPM by the first rotational speed LM RPM . When the rotational ratio difference ΔDP becomes a negative value, the absolute value is applied.

[0074] The control device 60 refers to the first rotational speed LM RPM and the second rotational speed RM RPMUsing the above, the rotation ratio difference ΔDP is obtained, and based on the rotation ratio difference ΔDP, the straight - ahead threshold values (the first straight - ahead threshold value SF1 S , the second straight - ahead threshold value SF2 S ) are set. FIG. 6A shows the relationship between the straight - ahead threshold values (the first straight - ahead threshold value SF1 S , the second straight - ahead threshold value SF2 S ) and the rotation ratio difference ΔDP. Note that for the sake of explanation, FIG. 6 shows two straight - ahead threshold values, the first straight - ahead threshold value SF1 S and the second straight - ahead threshold value SF2 S with respect to the rotation ratio difference ΔDP. However, the control device 60 may set either one of the first straight - ahead threshold value SF1 S and the second straight - ahead threshold value SF2 S .

[0075] As shown in FIG. 6A, the control device 60 sets the straight - ahead threshold values (the first straight - ahead threshold value SF1 S , the second straight - ahead threshold value SF2 S ) higher as the rotation ratio difference ΔDP increases, and sets the straight - ahead threshold values lower as the ratio difference ΔDP decreases. As shown in FIG. 6A, the control device 60 applies the calculated rotation ratio difference ΔDP to the lines L7, L8 showing the relationship between each straight - ahead threshold value SF1 S , SF2 S and the rotation ratio difference ΔDP, thereby setting the first straight - ahead threshold value SF1 S and the second straight - ahead threshold value SF2 S . Alternatively, control data such as an expression (a linear function expression representing the lines L7, L8 in FIG. 6A) or a table showing the relationship between the rotation ratio difference ΔDP and each straight - ahead threshold value SF1 S , SF2 S is stored in the storage unit 63 in advance, and the control device 60 extracts the first straight - ahead threshold value SF1 S and the second straight - ahead threshold value SF2 S corresponding to the calculated rotation ratio difference ΔDP from the control data, thereby setting the first straight - ahead threshold value SF1 S and the second straight - ahead threshold value SF2 S .

[0076] That is, when moving forward, the control device 60 uses the first rotational speed LM RPM and the second rotational speed RMRPM The straight-ahead threshold value (first straight-ahead threshold value SF1 S , second straight-ahead threshold value SF2 S ) set based on the rotation ratio difference ΔDP with respect to is used to perform automatic deceleration. Specifically, when moving forward, the control device 60 refers to the first rotational speed LM RPM and the second rotational speed RM RPM to calculate the rotation ratio difference ΔDP, and sets the first straight-ahead threshold value SF1 S based on the calculated rotation ratio difference ΔDP. After setting the first straight-ahead threshold value SF1 S , if the first traveling pressure V1 or the third traveling pressure V3 is greater than or equal to the first straight-ahead threshold value SF1 S , the control device 60 performs automatic deceleration. Alternatively, when moving forward, the control device 60 calculates the rotation ratio difference ΔDP and sets the second straight-ahead threshold value SF2 S based on the calculated rotation ratio difference ΔDP. After setting the second straight-ahead threshold value SF2 S , if the first differential pressure ΔV1 or the third differential pressure ΔV3 is greater than or equal to the second straight-ahead threshold value SF2 S , the control device 60 performs automatic deceleration.

[0077] In the above-described embodiment, the straight-ahead threshold value (first straight-ahead threshold value SF1 S , second straight-ahead threshold value SF2 S ) is set based on the rotation ratio difference ΔDP. However, the straight-ahead threshold value (first straight-ahead threshold value SF1 RPM and the second straight-ahead threshold value SF2 RPM ) may be obtained based on the ratio (rotation ratio) ΔDQ between the first rotational speed LM S and the second rotational speed RM S . As shown in FIG. 6B, the control device 60 increases the straight-ahead threshold value (first straight-ahead threshold value SF1 S , second straight-ahead threshold value SF2 S ) as the rotation ratio ΔDQ decreases, and decreases the straight-ahead threshold value as the rotation ratio ΔDQ increases. As shown in FIG. 6B, the control device 60 applies the calculated rotation ratio ΔDQ to the lines L9 and L10 showing the relationship between each straight-ahead threshold value SF1 S , SF2 S and the rotation ratio ΔDQ, thereby obtaining the first straight-ahead threshold value SF1 Sand the second straight-ahead threshold SF2 S may be set. Alternatively, the rotation ratio ΔDQ and each straight-ahead threshold SF1 S , SF2 S The control data such as the expression showing the relationship with (the linear function expressions representing lines L9 and L10 in FIG. 6B) or a table is stored in the storage unit 63 in advance, and the control device 60 calculates from the control data the first straight-ahead threshold SF1 corresponding to the calculated rotation ratio ΔDQ S and the second straight-ahead threshold SF2 S By extracting, the first straight-ahead threshold SF1 S and the second straight-ahead threshold SF2 S may be set.

[0078] That is, when moving forward, the control device 60 uses the first rotation speed LM RPM and the second rotation speed RM RPM The straight-ahead threshold set by the rotation ratio ΔDQ (the first straight-ahead threshold SF1 S , the second straight-ahead threshold SF2 S ) to perform automatic deceleration. Specifically, when moving forward, the control device 60 refers to the first rotation speed LM RPM and the second rotation speed RM RPM to calculate the rotation ratio ΔDQ, and based on the calculated rotation ratio ΔDQ, set the first straight-ahead threshold SF1 S . After setting the first straight-ahead threshold SF1 S , if the first traveling pressure V1 or the third traveling pressure V3 is equal to or higher than the first straight-ahead threshold SF1 S , automatic deceleration is performed. Alternatively, when moving forward, the control device 60 calculates the rotation ratio ΔDQ and sets the second straight-ahead threshold SF2 based on the calculated rotation ratio ΔDQ S . After setting the second straight-ahead threshold SF2 S , if the first differential pressure ΔV1 or the third differential pressure ΔV3 is equal to or higher than the second straight-ahead threshold SF2 S , automatic deceleration is performed.

[0079] In the above-described embodiment, the first straight-ahead threshold SF1 is based on the rotation difference ΔMP or the rotation ratio difference ΔDP S and the second straight-ahead threshold SF2 S were set, but instead of this, the first rotation speed LMRPM and the second rotational speed RM RPM Based on this, the first straight-ahead threshold value SF1 S and the second straight-ahead threshold value SF2 S may be set. As shown in FIG. 7, the control device 60 sets the straight-ahead threshold value (the first straight-ahead threshold value SF1 RPM and the second rotational speed RM RPM to decrease as the first rotational speed LM S and the second straight-ahead threshold value SF2 S ) decreases, and sets the straight-ahead threshold value to increase as the first rotational speed LM RPM and the second rotational speed RM RPM decreases. As shown in FIG. 7, the control device 60 applies the first rotational speed LM S detected by the first rotation detection device 68a and the second rotational speed RM S detected by the second rotation detection device 68b to the lines L11 and L12 indicating the relationship between the straight-ahead threshold values SF1 RPM , SF2 RPM and the rotational speeds LM RPM , RM RPM to set the first straight-ahead threshold value SF1 S and the second straight-ahead threshold value SF2 S . Alternatively, control data such as an expression (a linear function expression representing the lines L11 and L12 in FIG. 7) or a table indicating the relationship between each rotational speed LM RPM , RM RPM and each straight-ahead threshold value SF1 S , SF2 S is stored in advance in the storage unit 63, and the control device 60 extracts the first straight-ahead threshold value SF1 RPM and the second straight-ahead threshold value SF2 RPM corresponding to the first rotational speed LM S and the second rotational speed RM S from the control data to set the first straight-ahead threshold value SF1 S and the second straight-ahead threshold value SF2 S .

[0080] That is, when moving forward, the control device 60 uses the straight-ahead threshold value (the first straight-ahead threshold value SF1 RPM and the second rotational speed RM RPM ) set by the first rotational speed LM S and the second straight-ahead threshold value SF2S Performs automatic deceleration based on Specifically, when moving forward, the control device 60 uses the first rotational speed LM RPM and the second rotational speed RM RPM to refer to, and sets the first straight - ahead threshold value SF1 RPM from the first rotational speed LM RPM and the second rotational speed RM S . After setting the first straight - ahead threshold value SF1 S , when both the first traveling pressure V1 and the third traveling pressure V3 continuously exceed the first straight - ahead threshold value SF1 S , automatic deceleration is performed. More specifically, when the length of the time (elapsed time) during which both the first traveling pressure V1 and the third traveling pressure V3 exceed the first straight - ahead threshold value SF1 S is equal to or greater than the first determination time, automatic deceleration is performed. The control device 60 shortens the first determination time as the first rotational speed LM RPM or the second rotational speed RM RPM increases, and lengthens the first determination time as the first rotational speed LM RPM or the second rotational speed RM RPM decreases.

[0081] Alternatively, when moving forward, the control device 60 uses the first rotational speed LM RPM and the second rotational speed RM RPM to refer to, and sets the second straight - ahead threshold value SF2 RPM from the first rotational speed LM RPM and the second rotational speed RM S . After setting the second straight - ahead threshold value SF2 S , when both the first differential pressure ΔV1 and the third differential pressure ΔV3 continuously exceed the second straight - ahead threshold value SF2 S , automatic deceleration is performed. More specifically, when the length of the time (elapsed time) during which both the first differential pressure ΔV1 and the third differential pressure ΔV3 exceed the second straight - ahead threshold value SF2 S is equal to or greater than the second determination time, automatic deceleration is performed. The control device 60 shortens the second determination time as the first rotational speed LM RPM or the second rotational speed RM RPM increases, and lengthens the second determination time as the first rotational speed LM RPM or the second rotational speed RM RPMAs it becomes smaller, the second determination time is set longer.

[0082] In the above-described embodiment, when the operation of the travel operation member 59 is operated in the direction to move the aircraft 2 forward and the left travel motor 36L and the right travel motor 36R are rotating in the direction corresponding to the reverse movement of the aircraft 2, that is, when they are rotating in reverse, automatic deceleration is not performed. The control device 60 is the first rotation speed LM of the left travel motor 36L RPM is equal to or higher than a predetermined rotation speed, or the second rotation speed RM of the right travel motor 36R RPM is equal to or higher than a predetermined rotation speed, automatic deceleration is not performed. For example, the control device 60 is the first rotation speed LM of the left travel motor 36L RPM is equal to or higher than the first maximum rotation speed at which it rotates by the power of the left travel motor 36L, automatic deceleration is not performed. The control device 60 is the second rotation speed RM of the right travel motor 36R RPM is equal to or higher than the second maximum rotation speed at which it rotates by the power of the right travel motor 36R, automatic deceleration is not performed. According to this, when the first rotation speed LM RPM and the second rotation speed RM RPM are in a high region, workability can be improved by not performing automatic deceleration.

[0083] In the above-described embodiment, the hydraulic travel operation device 54 that changes the pilot pressure acting on the travel pumps (the first travel pump 53L and the second travel pump 53R) by the operation valve 55 is used. Instead of this, for example, as shown in FIGS. 8A and 8B, an electrically operated travel operation device 54 may be used. In this case, the travel operation member 59 may be composed of an electrically operated operation member such as a joystick.

[0084] The traveling operation device 54 shown in Fig. 8A includes operation valves 55a, 55b, 55c, and 55d each constituted by an electromagnetic proportional valve. An operation detection sensor 161 for detecting the operation amount and operation direction of an operation member 59 that swings in the left-right direction (machine width direction) or the front-rear direction is connected to a control device 60. The control device 60 controls the operation valves 55a, 55b, 55c, and 55d based on the operation amount and operation direction of the operation member 59 detected by the operation detection sensor 161.

[0085] When the operation member 59 is operated forward (in the A1 direction in Fig. 2), the control device 60 outputs a control signal to the operation valves 55a and 55c to swing the swash plates of the first traveling pump 53L and the second traveling pump 53R in the forward rotation (forward movement) direction. Thereby, the first traveling pump 53L and the second traveling pump 53R can rotate forward. Further, when the operation member 59 is operated rearward (in the A2 direction in Fig. 2), the control device 60 outputs a control signal to the operation valves 55b and 55d to swing the swash plates of the first traveling pump 53L and the second traveling pump 53R in the reverse rotation (rearward movement) direction. Thereby, the first traveling pump 53L and the second traveling pump 53R can rotate in reverse.

[0086] Also, when the operation member 59 is operated rightward (in the A4 direction in Fig. 2), the control device 60 outputs a control signal to the operation valves 55a and 55d to swing the swash plate of the first traveling pump 53L in the forward rotation direction and swing the swash plate of the second traveling pump 53R in the reverse rotation direction. Thereby, the first traveling pump 53L can rotate forward and the second traveling pump 53R can rotate in reverse. Furthermore, when the operation member 59 is operated leftward (in the A3 direction in Fig. 2), the control device 60 outputs a control signal to the operation valves 55b and 55c to swing the swash plate of the first traveling pump 53L in the reverse rotation direction and swing the swash plate of the second traveling pump 53R in the forward rotation direction. Thereby, the first traveling pump 53L can rotate in reverse and the second traveling pump 53R can rotate forward.

[0087] The traveling operation device 54 shown in FIG. 8B includes operation valves 155L and 155R and hydraulic regulators 156L and 156R. The hydraulic regulators 156L and 156R have a supply chamber 157 to which hydraulic oil can be supplied and a piston rod 158 provided in the supply chamber 157. The piston rod 158 of the hydraulic regulator 156L is connected to the swash plate of the first traveling pump 53L. The piston rod 158 of the hydraulic regulator 156R is connected to the swash plate of the second traveling pump 53R. By the operation (linear movement) of the piston rods 158 of the hydraulic regulators 156L and 156R, the angles of the swash plates of the traveling pumps 53L and 53R are changed.

[0088] The operation valve 155L is an electromagnetic proportional valve that operates the hydraulic regulator 156L and can be switched between a first position 159a, a second position 159b, and a neutral position 159c. The position of the operation valve 155L is changed by the movement of the spool of the operation valve 155L based on a control signal output from the control device 60. The first port of the operation valve 155L and the supply chamber 157 of the hydraulic regulator 156L are connected by a first traveling oil passage 145a. The second port of the operation valve 155L and the supply chamber 157 of the hydraulic regulator 156L are connected by a second traveling oil passage 145b.

[0089] The operation valve 155R is an electromagnetic proportional valve that operates the hydraulic regulator 156R and can be switched between a first position 159a, a second position 159b, and a neutral position 159c. The position of the operation valve 155R is changed by the movement of the spool of the operation valve 155R based on a control signal output from the control device 60. The first port of the operation valve 155R and the supply chamber 157 of the hydraulic regulator 156R are connected by a third traveling oil passage 145c. The second port of the operation valve 155R and the supply chamber 157 of the hydraulic regulator 156R are connected by a fourth traveling oil passage 145d.

[0090] The control device 60 outputs control signals to the operation valves 155L and 155R to switch the operation valves 155L and 155R to the first position 159a. As a result, the swash plates of the first travel pump 53L and the second operation pump 53R swing in the forward rotation direction, and the first travel pump 53L and the second travel pump 53R can rotate forward. Also, the control device 60 outputs control signals to the operation valves 155L and 155R to switch the operation valves 155L and 155R to the second position 159b. As a result, the swash plates of the first travel pump 53L and the second operation pump 53R swing in the reverse rotation direction, and the first travel pump 53L and the second travel pump 53R can rotate in reverse.

[0091] Also, the control device 60 outputs control signals to the operation valves 155L and 155R to switch the operation valve 155L to the first position 159a and the operation valve 155R to the second position 159b. As a result, the swash plate of the first travel pump 53L swings in the forward rotation direction, and the first travel pump 53L can rotate forward, and the swash plate of the second operation pump 53R swings in the reverse rotation direction, and the second travel pump 53R can rotate in reverse.

[0092] Furthermore, the control device 60 outputs control signals to the operation valves 155L and 155R to switch the operation valve 155L to the second position 159b and the operation valve 155R to the first position 159a. As a result, the swash plate of the first travel pump 53L swings in the reverse rotation direction, and the first travel pump 53L can rotate in reverse, and the swash plate of the second operation pump 53R swings in the forward rotation direction, and the second travel pump 53R can rotate forward. The angle of the swash plate of the travel motors 36L and 36R may be changed using electric actuators such as the electromagnetic proportional valves 155a to 155d, 155L, and 155R described above.

[0093] According to the above embodiments, the work machine 1 has the following configuration and effects. The working machine 1 includes a 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, a right traveling motor 36R capable of transmitting power to the right traveling device 5R, and a first rotational speed LM of the left traveling motor 36L RPM A first rotation detection device 68a for detecting, a second rotational speed RM of the right traveling motor 36R RPM A second rotation detection device 68b for detecting, a left traveling pump 53L for supplying hydraulic oil to the left traveling motor 36L, a right traveling pump 53R for supplying hydraulic oil to the right traveling motor 36R, a traveling operation device 54 for operating at least one of the left traveling pump 53L and the right traveling pump 53R, and the first rotational speed LM RPM And the second rotational speed RM RPM A control device 60 for performing automatic deceleration to automatically decelerate from the second speed on the high-speed side to the first speed on the low-speed side when the second speed is reached. The control device 60 determines whether to perform automatic deceleration when the machine body 2 makes a ground-engaging turn to the left. A left threshold value (first left threshold value ST1 L、 Second left threshold value ST2 L ) is set based on the second rotational speed RM RPM , and a right threshold value (first right threshold value ST1 R、 Second right threshold value ST2 R ) for determining whether to perform automatic deceleration when the machine body 2 makes a ground-engaging turn to the right is set based on the first rotational speed LM RPM .

[0094] According to the above, for example, when making a ground-engaging turn to the left, the second rotational speed RM of the right traveling motor 36R becomes faster than the first rotational speed LM of the left traveling motor 36L RPM , and when making a ground-engaging turn to the right, the first rotational speed LM of the left traveling motor 36L becomes faster than the second rotational speed RM of the right traveling motor 36R RPM . When making a ground-engaging turn to the right, the second rotational speed RM of the right traveling motor 36R RPM Compared to, the first rotational speed LM of the left traveling motor 36L RPMIt speeds up. That is, since the rotational speed of the traveling motor on the opposite side with respect to the turning direction speeds up, by setting deceleration thresholds (left threshold, right threshold) for automatic deceleration based on the rotational speed of the traveling motor, automatic deceleration corresponding to turning in place to the left or turning in place to the right can be smoothly performed. In other words, it is possible to prevent accidentally performing automatic deceleration during turning in place to the left or turning in place to the right, and automatic deceleration can be performed only when necessary.

[0095] The control device 60 has a second rotational speed RM RPM As it becomes lower, the left threshold (first left threshold ST1 L、 second left threshold ST2 L ) is set lower, and as the second rotational speed RM RPM becomes higher, the left threshold (first left threshold ST1 L、 second left threshold ST2 L ) is set higher. As the first rotational speed LM RPM becomes lower, the right threshold (first right threshold ST1 R、 second right threshold ST2 R ) is set lower, and as the first rotational speed LM RPM becomes higher, the right threshold (first right threshold ST1 R、 second right threshold ST2 R ) is set higher. According to this, automatic deceleration corresponding to turning in place to the left or turning in place to the right can be smoothly performed. In other words, it is possible to suppress accidentally performing automatic deceleration during turning in place to the left or turning in place to the right, and automatic deceleration can be performed only when necessary.

[0096] The working machine 1 includes a first circulation oil passage 57h that connects the left traveling pump 53L and the left traveling motor 36L, a second circulation oil passage 57i that connects the right traveling pump 53R and the right traveling motor 36R, a first pressure detection device 80a that is provided on the first port P11 side of the left traveling motor 36L and detects the pressure of the hydraulic oil acting on the first circulation oil passage 57h during the rotation of the left traveling motor 36L as the first traveling pressure V1, a second pressure detection device 80b that is provided on the second port P12 side of the left traveling motor 36L and detects the pressure of the hydraulic oil acting on the first circulation oil passage 57h during the rotation of the left traveling motor 36L as the second traveling pressure V2, a third pressure detection device 80c that is provided on the third port P13 side of the right traveling motor 36R and detects the pressure of the hydraulic oil acting on the second circulation oil passage 57i during the rotation of the right traveling motor 36R as the third traveling pressure V3, and a fourth pressure detection device 80d that is provided on the fourth port P14 side of the right traveling motor 36R and detects the pressure of the hydraulic oil acting on the second circulation oil passage 57i during the rotation of the right traveling motor 36R as the fourth traveling pressure V4.

[0097] In the above configuration, when the machine body 2 makes a skid turn to the left, the control device 60 automatically decelerates when the third traveling pressure V3 or the fourth traveling pressure V4 is equal to or higher than a left threshold value (the first left threshold value ST1 L ). When the machine body 2 makes a skid turn to the right, the control device 60 automatically decelerates when the first traveling pressure V1 or the second traveling pressure V2 is equal to or higher than a right threshold value (the first right threshold value ST1 R ). According to this, when the machine body 2 makes a skid turn to the left, automatic deceleration can be performed when the traveling pressure (the third traveling pressure V3, the fourth traveling pressure V4) corresponding to the right traveling motor 36R is equal to or higher than the left threshold value (the first left threshold value ST1 L ). When the machine body 2 makes a skid turn to the right, automatic deceleration can be performed when the traveling pressure (the first traveling pressure V1, the second traveling pressure V2) corresponding to the left traveling motor 36L is equal to or higher than the left threshold value (the first right threshold value ST1 R ).

[0098] As another example, when the machine body 2 makes a skid turn to the left, the control device 60 determines that a third differential pressure ΔV3 obtained by subtracting the fourth traveling pressure V4 from the third traveling pressure V3, or a fourth differential pressure ΔV4 obtained by subtracting the third traveling pressure V3 from the fourth traveling pressure V4 is equal to or higher than a left threshold value (the second left threshold value ST2L ) When automatic deceleration is performed when the above is satisfied and the aircraft 2 makes a coordinated turn to the right, the first differential pressure ΔV1 obtained by subtracting the second travel pressure V2 from the first travel pressure V1, or the second differential pressure ΔV2 obtained by subtracting the first travel pressure V1 from the second travel pressure V2 is the right threshold value (the second right threshold value ST2 R ) When the above is satisfied, automatic deceleration is performed. According to this, when the aircraft 2 makes a coordinated turn to the left, the effective travel pressures (the third differential pressure ΔV3, the fourth differential pressure ΔV4) corresponding to the right travel motor 36R are the left threshold values (the second left threshold value ST2 L ) When the above is satisfied, automatic deceleration can be performed. Further, when the aircraft 2 makes a coordinated turn to the right, the effective travel pressures (the first differential pressure ΔV1, the second differential pressure ΔV2) corresponding to the left travel motor 36L are the left threshold values (the second right threshold value ST2 R ) When the above is satisfied, automatic deceleration can be performed.

[0099] The control device 60 adjusts the left threshold values (the first left threshold value ST1 L、 the second left threshold value ST2 L ) and the right threshold values (the first right threshold value ST1 R、 the second right threshold value ST2 R ) according to the rotational speed of the prime mover 32. According to this, since the left and right threshold values can be adjusted according to the rotational speed of the prime mover 32 that changes according to the load of the prime mover, automatic deceleration corresponding to the load can be performed. When the aircraft 2 makes a coordinated turn to the left, the control device 60 sets the left threshold values (the first left threshold value ST1 L、 the second left threshold value ST2 L ) when the operation of the travel operation device 54 is operated in a direction corresponding to a coordinated turn to the left. When the aircraft 2 makes a coordinated turn to the right, the control device 60 sets the right threshold values (the first right threshold value ST1 R、 the second right threshold value ST2 R ) when the operation of the travel operation device 54 is operated in a direction corresponding to a coordinated turn to the right. According to this, the left and right threshold values are set according to the rotational speeds LM RPM , RM RPM of the left and right travel motors 36L and 36R immediately before the aircraft 2 makes a coordinated turn, and automatic deceleration can be performed.

[0100] The control device 60 sets a skid threshold (a first skid threshold ST1 P , a second skid threshold ST2 P ) according to the higher rotational speed of the first rotational speed LM RPM and the second rotational speed RM RPM to determine whether to perform automatic deceleration when the aircraft 2 performs a skid turn. According to this, when performing a skid turn, when a rotational speed difference occurs between the rotational speeds LM RPM and RM RPM of the traveling motors 36L and 36R, automatic deceleration can be performed when necessary.

[0101] The control device 60 sets a skid threshold for determining whether to perform automatic deceleration when the aircraft 2 performs a skid turn to be lower than the left threshold (a first left threshold ST1 L、 , a second left threshold ST2 L ) and the right threshold (a first right threshold ST1 R、 , a second right threshold ST2 R ). According to this, when the aircraft 2 performs a skid turn, automatic deceleration can be smoothly performed when necessary. When the aircraft 2 performs a skid turn, the control device 60 performs automatic deceleration when any one of the first traveling pressure V1, the second traveling pressure V2, the third traveling pressure V3, and the fourth traveling pressure V4 is equal to or higher than the skid threshold (the first skid threshold ST1 P ). According to this, it is possible to determine whether to perform automatic deceleration during a skid turn according to the pressures of the first traveling pressure V1, the second traveling pressure V2, the third traveling pressure V3, and the fourth traveling pressure V4, and automatic deceleration can be performed only when any one of the first traveling pressure V1, the second traveling pressure V2, the third traveling pressure V3, and the fourth traveling pressure V4 is equal to or higher than the skid threshold (the first skid threshold ST1 P ).

[0102] The control device 60 performs automatic deceleration when the operation of the traveling operation device 54 is operated in a direction corresponding to a skid turn and any one of the first traveling pressure V1, the second traveling pressure V2, the third traveling pressure V3, and the fourth traveling pressure V4 is equal to or higher than the skid threshold, assuming that the aircraft 2 performs a skid turn. According to this, automatic deceleration can be performed according to the traveling pressures V1 to V4 immediately before the aircraft 2 performs a skid turn.

[0103] When the aircraft 2 performs a super-stable turn, the control device 60 calculates the first differential pressure ΔV1 obtained by subtracting the second travel pressure V2 from the first travel pressure V1, the second differential pressure ΔV2 obtained by subtracting the first travel pressure V1 from the second travel pressure V2, the third differential pressure ΔV3 obtained by subtracting the fourth travel pressure V4 from the third travel pressure V3, and the fourth differential pressure ΔV4 obtained by subtracting the third travel pressure V3 from the fourth travel pressure V4. If any of these differential pressures is greater than or equal to the super-stable threshold (the second super-stable threshold ST2 P ), automatic deceleration is performed. According to this, it is possible to determine whether to perform automatic deceleration during a super-stable turn according to the pressures of the first differential pressure ΔV1, the second differential pressure ΔV2, the third differential pressure ΔV3, and the fourth differential pressure ΔV4. Automatic deceleration can be performed only when any of the first differential pressure ΔV1, the second differential pressure ΔV2, the third differential pressure ΔV3, and the fourth differential pressure ΔV4 is greater than or equal to the super-stable threshold (the second super-stable threshold ST2 P ).

[0104] The control device 60 determines whether to perform automatic deceleration when the aircraft 2 is moving straight ahead, based on a straight-ahead threshold (the first straight-ahead threshold SF1 S , the second straight-ahead threshold SF2 S ) set based on the rotational difference ΔMP or the rotational ratio difference ΔDP between the first rotational speed LM RPM and the second rotational speed RM RPM . For example, when the aircraft 2 transitions from a stable turn state to a straight-ahead state, a difference occurs between the first rotational speed LM RPM of the left travel motor 36L and the second rotational speed RM RPM of the right travel motor 36R. In such a case, by setting the straight-ahead threshold (the first straight-ahead threshold SF1 RPM , the second straight-ahead threshold SF2 RPM ) based on the rotational difference ΔMP or the rotational ratio difference ΔDP between the first rotational speed LM S and the second rotational speed RM S , the travel speed of the aircraft 2 can be maintained. That is, when the aircraft 2 transitions from a stable turn state to a straight-ahead state, automatic deceleration is not performed, and when the straight-ahead state of the aircraft 2 is stable, automatic deceleration can be performed as necessary.

[0105] The control device 60 increases the straight - ahead threshold values (the first straight - ahead threshold value SF1 S , the second straight - ahead threshold value SF2 S ) as the rotational difference ΔMP increases, and decreases the straight - ahead threshold values (the first straight - ahead threshold value SF1 S , the second straight - ahead threshold value SF2 S ) as the rotational difference ΔMP decreases. According to this, when the state of the aircraft 2 is close to the turning - in - place state (when the rotational difference ΔMP is large), it becomes difficult to perform automatic deceleration, and when it is close to the straight - ahead state (when the rotational difference ΔMP is small), it becomes easier to perform automatic deceleration.

[0106] The control device 60 increases the straight - ahead threshold values (the first straight - ahead threshold value SF1 S , the second straight - ahead threshold value SF2 S ) as the rotational ratio difference ΔDP increases, and decreases the straight - ahead threshold values (the first straight - ahead threshold value SF1 S , the second straight - ahead threshold value SF2 S ) as the rotational ratio difference ΔDP decreases. According to this, when the state of the aircraft 2 is close to the turning - in - place state (when the ratio difference ΔDP is large), it becomes difficult to perform automatic deceleration, and when it is close to the straight - ahead state (when the ratio difference ΔDP is small), it becomes easier to perform automatic deceleration.

[0107] When the aircraft 2 moves straight ahead, the control device 60 performs automatic deceleration when either the first travel pressure V1 or the third travel pressure V3 is greater than or equal to the straight - ahead threshold value (the first straight - ahead threshold value SF1 S ). According to this, when the aircraft 2 moves forward, automatic deceleration can be performed based on the travel pressure (the first travel pressure V1) corresponding to the left travel motor 36L and the travel pressure (the third travel pressure V3) corresponding to the right travel motor 36R.

[0108] When the aircraft 2 moves straight ahead, the control device 60 performs automatic deceleration when either the first differential pressure ΔV1 obtained by subtracting the second travel pressure V2 from the first travel pressure V1 or the third differential pressure ΔV3 obtained by subtracting the fourth travel pressure V4 from the third travel pressure V3 is greater than or equal to the straight - ahead threshold value (the second straight - ahead threshold value SF2 SWhen the above conditions are met, automatic deceleration is performed. According to this, when the aircraft 2 moves forward, automatic deceleration can be performed based on the effective differential pressure corresponding to the left travel motor 36L (the first differential pressure ΔV1) and the effective differential pressure corresponding to the right travel motor 36R (the third differential pressure ΔV3).

[0109] The control device 60 determines the first rotation speed LM detected by the first rotation detection device 68a RPM and the second rotation speed RM detected by the second rotation detection device 68b RPM Based on this, a straight-ahead threshold value (the first straight-ahead threshold value SF1 S , the second straight-ahead threshold value SF2 S ) is set. For example, when the vehicle speed of the aircraft 2 accelerates from a low state or when it accelerates from a stopped state, the first rotation speed LM of the left travel motor 36L RPM and the second rotation speed RM of the right travel motor 36R RPM increase (become higher). In such cases, while suppressing the occurrence of automatic deceleration, automatic deceleration can be performed when the straight-ahead movement of the aircraft 2 is stable.

[0110] The control device 60, when the first rotation speed LM RPM or the second rotation speed RM RPM is small, sets the straight-ahead threshold value (the first straight-ahead threshold value SF1 S , the second straight-ahead threshold value SF2 S ) low, and when the first rotation speed LM RPM or the second rotation speed RM RPM is large, sets the straight-ahead threshold value (the first straight-ahead threshold value SF1 S , the second straight-ahead threshold value SF2 S ) high. According to this, when the aircraft 2 accelerates from a low vehicle speed state or when it accelerates from a stopped state, while suppressing the occurrence of automatic deceleration, automatic deceleration can be performed when the straight-ahead movement of the aircraft 2 is stable.

[0111] When the aircraft 2 moves straight ahead, the control device 60 determines that when both the first travel pressure V1 and the third travel pressure V3 are the straight-ahead threshold value (the first straight-ahead threshold value SF1 SWhen the elapsed time when the above time is equal to or greater than the first determination time, automatic deceleration is performed. According to this, when the aircraft 2 moves straight forward, the travel pressure corresponding to the left travel motor 36L (the first travel pressure V1) and the travel pressure corresponding to the right travel motor 36R (the third travel pressure V3) are the straight-ahead threshold values (the first straight-ahead threshold value SF1 S ) When the elapsed time when it is equal to or greater than the first determination time, automatic deceleration can be performed. That is, when the first travel pressure V1 and the third travel pressure V3 are equal to or greater than the straight-ahead threshold values (the first straight-ahead threshold value SF1 S ) for a certain period of time, automatic deceleration can be performed.

[0112] The control device 60 sets the first determination time shorter as the first rotation speed LM RPM or the second rotation speed RM RPM increases, and sets the first determination time longer as the first rotation speed LM RPM or the second rotation speed RM RPM decreases. According to this, when the first rotation speed LM RPM or the second rotation speed RM RPM is small and the vehicle speed (travel speed) is slow (low), the first determination time becomes longer, so automatic deceleration can be performed only when the state of low vehicle speed continues for a long time. On the other hand, when the first rotation speed LM RPM or the second rotation speed RM RPM is large and the vehicle speed (travel speed) is fast, automatic deceleration can be performed quickly when necessary.

[0113] When the aircraft 2 moves straight forward, the control device 60 performs automatic deceleration when the elapsed time when both the first differential pressure ΔV1 obtained by subtracting the second travel pressure V2 from the first travel pressure V1 and the third differential pressure ΔV3 obtained by subtracting the fourth travel pressure V4 from the third travel pressure V3 are equal to or greater than the straight-ahead threshold value (the second straight-ahead threshold value SF2 S ) is equal to or greater than the second determination time. According to this, when the aircraft 2 moves forward, the effective travel pressure corresponding to the left travel motor 36L (the first differential pressure ΔV1) and the effective travel pressure corresponding to the right travel motor 36R (the third differential pressure ΔV3) are the straight-ahead threshold values (the second straight-ahead threshold value SF2 SWhen the elapsed time when the above is satisfied is equal to or longer than the second determination time, automatic deceleration can be performed. That is, when the effective traveling pressure (first differential pressure ΔV1) and the effective traveling pressure (third differential pressure ΔV3) have been equal to or higher than the straight-ahead threshold value (second straight-ahead threshold value SF2 S ) for a certain period of time, automatic deceleration can be performed.

[0114] The control device 60 sets the second determination time shorter as the first rotational speed LM RPM or the second rotational speed RM RPM increases, and sets it longer as the first rotational speed LM RPM or the second rotational speed RM RPM decreases. According to this, when the first rotational speed LM RPM or the second rotational speed RM RPM is low and the vehicle speed (traveling speed) is slow, the first determination time becomes long, so automatic deceleration can be performed only when the low vehicle speed state continues for a long time. On the other hand, when the first rotational speed LM RPM or the second rotational speed RM RPM is high and the vehicle speed (traveling speed) is fast (high), automatic deceleration can be quickly performed when necessary.

[0115] When the operation of the traveling operation member 59 is operated in the direction of advancing the airframe 2 and the left traveling motor 36L and the right traveling motor 36R are rotating in the direction corresponding to the reverse of the airframe 2, the control device 60 does not perform automatic deceleration. According to this, when the traveling operation member 59 is instantaneously operated to the forward side from the state where the airframe 2 is moving backward, the reverse of the work machine 1 can be stabilized by not performing automatic deceleration.

[0116] When the first rotational speed LM RPM of the left traveling motor 36L is equal to or higher than a predetermined rotational speed, or when the second rotational speed RM RPM of the right traveling motor 36R is equal to or higher than a predetermined rotation, the control device 60 does not perform automatic deceleration. According to this, workability can be improved by not performing automatic deceleration when the first rotational speed LM RPM and the second rotational speed RM RPM are in a high region. The control device 60 is configured such that when the first rotational speed LM of the left traveling motor 36L is equal to or higher than the first maximum rotational speed at which the left traveling motor 36L rotates by the power of the left traveling motor 36L, or when the second rotational speed RM of the right traveling motor 36R is equal to or higher than the second maximum rotational speed at which the left traveling motor 36L rotates by the power of the left traveling motor 36L, automatic deceleration is not performed. For example, in a situation where the aircraft body 2 is climbing a slope in the state of the second speed, even if the rotational speed of the left traveling motor 36L exceeds the first maximum rotational speed when in the first speed state or the rotational speed of the right traveling motor 36R exceeds the second maximum rotational speed when in the first speed state, the aircraft body 2 can be made to travel without degrading the traveling performance by not performing automatic deceleration. RPM In the above-described embodiments, the left traveling motor 36L and the right traveling motor 36R are simultaneously switched to the first speed or the second speed, and automatic deceleration is also simultaneously performed on the left traveling motor 36L and the right traveling motor 36R. However, at least one of the left traveling motor 36L and the right traveling motor 36R may be switched to the first speed or the second speed, and automatic deceleration may be performed even when at least one of the left traveling motor 36L and the right traveling motor 36R is in the second speed state. RPM In the above-described embodiments, the left traveling motor 36L and the right traveling motor 36R are simultaneously switched to the first speed or the second speed, and automatic deceleration is also simultaneously performed on the left traveling motor 36L and the right traveling motor 36R. However, at least one of the left traveling motor 36L and the right traveling motor 36R may be switched to the first speed or the second speed, and automatic deceleration may be performed even when at least one of the left traveling motor 36L and the right traveling motor 36R is in the second speed state.

[0117] In the above-described embodiments, the left traveling motor 36L and the right traveling motor 36R are simultaneously switched to the first speed or the second speed, and automatic deceleration is also simultaneously performed on the left traveling motor 36L and the right traveling motor 36R. However, at least one of the left traveling motor 36L and the right traveling motor 36R may be switched to the first speed or the second speed, and automatic deceleration may be performed even when at least one of the left traveling motor 36L and the right traveling motor 36R is in the second speed state.

[0118] Also, the traveling motors 36L and 36R may be axial piston motors or radial piston motors. Regardless of whether the traveling motors 36L and 36R are radial piston motors or axial piston motors, the rotational speed of the traveling motor can be switched to the first speed by increasing the pressure of the hydraulic oil supplied to the motor, and the rotational speed of the traveling motor can be switched to the second speed by decreasing the pressure of the hydraulic oil.

[0119] It should be considered that the embodiments disclosed this time are illustrative in all respects and not restrictive. The scope of the present invention is shown not by the above description but by the claims, and it is intended that all modifications within the meaning and scope equivalent to the claims are included.

Explanation of Reference Numerals

[0120] 1: Working machine 2: Machine body 5L: Left traveling device 5R: Right traveling device 36L: Left traveling motor 36R: Right traveling motor 53L: Left traveling pump 53R: Right traveling pump 54: Operating device (traveling operating device) 57h: Circulation oil path (first circulation oil path) 57i: Circulation oil path (second circulation oil path) 60: Control device 68a: First rotation detection device 68b: Second rotation detection 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 left running device provided on the left side of the aircraft body; A right running device provided on the right side of the aircraft 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 first rotation detection device that detects a first rotation speed of the left traveling motor; a second rotation detection device that detects a second rotation speed of the right traveling motor; a left traveling pump for supplying hydraulic oil to the left traveling motor; a right traveling pump for supplying hydraulic oil to the right traveling motor; a control device that performs automatic deceleration to automatically decelerate the first rotation speed and the second rotation speed from the second speed to a first speed on a lower speed side when the first rotation speed and the second rotation speed are a second speed on a higher speed side, The control device does not perform the automatic deceleration when either the first rotation speed or the second rotation speed is equal to or higher than a predetermined rotation speed.

2. A travel operation device that operates at least one of the left travel pump and the right travel pump, The work machine according to claim 1, wherein the control device does not perform the automatic deceleration when the travel operation device is operated in a direction to move the machine forward and the left travel motor and the right travel motor are rotating in a direction corresponding to moving the machine backward.

3. A hydraulic pump that discharges pilot oil; A plurality of travel oil passages connected to a plurality of pressure receiving portions included in the left travel pump and the right travel pump, respectively; A travel operation device that operates at least one of the left travel pump and the right travel pump, The travel operation device is operated to change the angle of a swash plate that each of the left travel pump and the right travel pump has, and changes a pilot pressure, which is the pressure of the pilot oil output to each of the multiple travel oil passages, in response to the operation, The control device determines the operation direction of the traveling operation device based on the pilot pressure of each of the multiple traveling oil paths, and performs the automatic deceleration when it determines that the operation direction corresponds to a pivot turn to the left or right of the vehicle body.

4. A hydraulic pump that discharges pilot oil; A plurality of travel oil passages connected to a plurality of pressure receiving portions included in the left travel pump and the right travel pump, respectively; A travel operation device that operates at least one of the left travel pump and the right travel pump, The work machine according to any one of claims 1 to 3, wherein the control device performs the automatic deceleration when it determines that the operation direction of the travel operation device is a direction corresponding to a left or right pivot turn of the machine body.

5. A hydraulic pump that discharges pilot oil; A plurality of travel oil passages connected to a plurality of pressure receiving portions included in the left travel pump and the right travel pump, respectively; A travel operation device that operates at least one of the left travel pump and the right travel pump, The traveling operation device is A travel operating member that is swung; and a plurality of operation valves that operate in response to an operation state of the travel operation member to change a pilot pressure, which is the pressure of the pilot oil output to each of the plurality of travel oil passages; The work machine according to any one of claims 1 to 4, wherein the pilot pressures acting on the multiple pressure receiving portions of the left traveling pump and the right traveling pump from the multiple traveling oil passages change, thereby changing the angles of the swash plates of the left traveling pump and the right traveling pump, and thereby changing the direction and speed of rotation of the left traveling motor and the right traveling motor.

6. The traveling operation device has a plurality of high-pressure selection valves each connected to a plurality of the traveling oil passages and each connected to any two of the plurality of operation valves, The work machine according to claim 5 , wherein the plurality of high-pressure selection valves output a higher pilot pressure of the pilot pressures output from the two connected operation valves to the connected travel oil line.

7. a pressure detection device that detects the pressure of the hydraulic oil supplied to the left traveling motor and the right traveling motor; 7. The work machine according to claim 1, wherein the control device determines whether or not to perform the automatic deceleration based on the pressure of the hydraulic oil detected by the pressure detection device and a predetermined threshold value.

8. The work machine according to claim 7 , wherein the control device sets the threshold value based on the first rotation speed and the second rotation speed.

9. The work machine according to claim 8 , wherein the control device sets the threshold value lower as the first rotation speed and the second rotation speed increase.

Images