Work machine

Abstract

To give an operator with such a feeling that a work machine sufficiently works.SOLUTION: A work machine includes a motor, a travel pump which is operated by power of the motor and discharges hydraulic oil, a travel motor which is rotatable by the hydraulic oil discharged by the travel pump, an operation valve which can change a pilot pressure of pilot oil output to the travel pump according to operation of an operation member, an actuation valve which is actuated by a control signal and can change a primary pressure that is a pilot pressure of pilot oil supplied to the operation valve, a control device for outputting the control signal to the actuation valve, and controlling opening of the actuation valve, and a first detection device for detecting the actual number of rotation of the travel motor. The control device has a change part for changing settings of the control signal so that the opening of the actuation valve increases as the actual number of rotation of the travel motor decreases.SELECTED DRAWING: Figure 4A

Description

Technical Field

[0001] The present invention relates to working machines such as skid steer loaders and compact track loaders.

Background Art

[0002] Conventionally, as a technique for preventing engine stall in working machines such as skid steer loaders and compact track loaders, the technique shown in Patent Document 1 is known. The working machine disclosed in Patent Document 1 includes an engine, an HST pump that operates by the power of the engine, a travel operation device that operates the HST pump, a pressure control valve that controls the travel primary-side pressure which is the pressure on the primary side of the travel operation device, and a control device that controls the pressure control valve. The travel operation device has a travel lever and a pilot valve that outputs a pilot pressure proportional to the operation amount of the travel lever by operating the operation lever.

[0003] The control device performs anti-stall control to prevent engine stall. In the anti-stall control, the pressure control valve is controlled based on the no-load characteristic curve adopted when the engine is unloaded and the droop characteristic curve adopted when a load of a predetermined value or more acts on the engine, thereby preventing engine stall. In other words, when a travel load of a predetermined value or more acts on the working machine, the pressure control valve is controlled to rapidly drop the travel primary-side pressure, thereby minimizing the drop in the engine speed and suppressing engine stall.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the disclosed technology of Patent Document 1, in the medium rotation range of the engine (prime mover), in order to ensure the climbing speed, the output of the pressure control valve is lowered to suppress excessive engine drop, maintain an appropriate engine speed (medium rotation range), and ensure the vehicle speed. However, when the engine speed is in the high rotation range, it is necessary to set the output of the pressure control valve high in order to prevent the phenomenon of the engine speed getting stuck (the phenomenon that the output horsepower of the engine exceeds the consumption horsepower of the HST pump (travel pump) and there is almost no engine drop). When the phenomenon of the engine speed getting stuck occurs, it may give the operator a feeling that the work machine is not working sufficiently (a feeling that the machine is suppressing horsepower against the operator's operation).

[0006] In order to solve the above problems, it is necessary to lower the output of the pressure control valve when the engine speed is in the medium rotation range and set the output of the pressure control valve high when the engine speed is in the high rotation range. However, if the output difference of the pressure control valve is extremely large between the case where the engine speed is in the medium rotation range and the case where the engine speed is in the high rotation range (the slope of the output of the pressure control valve with respect to the engine speed is suddenly set), there is a concern that hunting of the engine speed may occur in control.

[0007] Therefore, in order to prioritize the climbing speed, after setting the output of the pressure control valve according to the case where the engine speed is in the medium rotation range, it is conceivable to set the output of the pressure control valve according to the case where the engine speed is in the high rotation range within a range where hunting does not occur. In this case, the phenomenon of the engine speed getting stuck can be prevented, but the traveling force in the high rotation range tends to decrease. In particular, in work involving the opening of a traveling relief valve such as earth pushing, due to the influence of the swash plate characteristics of the HST pump, the discharge flow rate of the HST pump (the consumption horsepower of the HST pump) decreases, the balanced engine speed increases, and it gives the operator a feeling that the work machine is not working sufficiently.

[0008] An object of the present invention is to provide a work machine that can give the operator a feeling that the machine is working sufficiently.

Means for Solving the Problem

[0009] A working machine according to an aspect of the present invention includes a prime mover, a travel pump that operates by the power of the prime mover and discharges hydraulic oil, a travel motor that can be rotated by the hydraulic oil discharged by the travel pump, an operation valve capable of changing the pilot pressure of the pilot oil output to the travel pump according to the operation of an operation member, an operation valve that operates by a control signal and can change the primary pressure, which is the pilot pressure of the pilot oil supplied to the operation valve, a first detection device that detects the actual rotational speed of the travel motor, a rotational speed operating tool for operating the target rotational speed of the prime mover, a second detection device for detecting the actual rotational speed of the prime mover, when the difference between the target rotational speed and the actual rotational speed of the prime mover is greater than or equal to a first threshold value, outputting the control signal based on the first line to the actuating valve, and when the difference between the target rotational speed and the actual rotational speed of the prime mover is less than the first threshold value, based on the second line, larger than the first line a control device that outputs the control signal to the operation valve and controls the opening degree of the operation valve and and includes, when the difference between the target rotational speed and the actual rotational speed of the prime mover is greater than or equal to the first threshold value a changing unit that changes the setting of the control signal so that the opening degree of the operation valve increases as the actual rotational speed of the travel motor decreases.

[0010] Further, the working machine the first line and the second line stores in a memory part and the changing unit may change the first line by changing the control signal shown in the first line so that the opening degree of the operation valve increases as the actual rotational speed of the travel motor decreases.

[0011] Further, the changing unit may change the control signal shown in the first line based on a first correction coefficient defined corresponding to the actual rotational speed of the travel motor. Further, the storage unit stores a first function defining the relationship between the actual rotational speed of the travel motor and the first correction coefficient, and the changing unit may calculate the first correction coefficient by substituting the actual rotational speed of the travel motor detected by the first detection device into the first function.

[0012] Further, the first function may be defined with the first correction coefficient being a value of 1 or more, and the first correction coefficient corresponding to a second rotation speed that is the actual rotation speed of the traveling motor and is smaller than the first rotation speed may be defined to be larger than the first correction coefficient corresponding to the first rotation speed which is the actual rotation speed of the traveling motor. Further, the first function may have different slopes based on a second threshold value of the actual rotation speed of the traveling motor, and the slope when the actual rotation speed of the traveling motor is less than or equal to the second threshold value may be defined to be larger than the slope when the actual rotation speed of the traveling motor is greater than or equal to the second threshold value.

[0013] Further, the control device may be switchable between a plurality of modes, the storage unit may store a plurality of the first functions having at least partially different slopes corresponding to the plurality of modes, and the changing unit may calculate the first correction coefficient based on the first function corresponding to the mode of the control device. Further, in addition to the first correction coefficient, the changing unit may change the control signal indicated on the first line based on a second correction coefficient defined corresponding to the actual rotation speed of the prime mover.

[0014] Further, the storage unit may store a second function defining the relationship between the actual rotation speed of the prime mover and the second correction coefficient, and the changing unit may calculate the second correction coefficient by substituting the actual rotation speed of the prime mover detected by the second detection device into the second function. Further, the second function may define the second correction coefficient as 1 when the actual rotation speed of the prime mover is greater than or equal to a third threshold value, and may define the second correction coefficient as a value less than 1 when the actual rotation speed of the prime mover is less than the third threshold value.

[0015] Further, the control device may be switchable between a plurality of modes, the storage unit may store a plurality of the second functions having at least partially different slopes corresponding to the plurality of modes, and the changing unit may calculate the second correction coefficient based on the second function corresponding to the mode of the control device. Further, the modification unit calculates a third correction coefficient based on the product of the first correction coefficient and the second correction coefficient, and changes the control signal shown in the first line when the third correction coefficient exceeds 1, and when the third correction coefficient is 1 or less, it may not change the control signal shown in the first line.

Advantages of the Invention

[0016] According to the present invention, it is possible to give the operator a feeling that the working machine is working sufficiently. This can be achieved.

Brief Description of the Drawings

[0017]

Figure 1

Figure 2

Figure 3

Figure 4A

Figure 4B

Figure 4C

Figure 4D

Figure 5A

Figure 5B

Figure 5C

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

MODE FOR CARRYING OUT THE INVENTION

[0018] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 10 is a side view showing a track loader which is an example of the working machine 1. In FIG. 10, a compact track loader is shown as an example of the working machine 1. However, the working machine 1 according to the present invention is not limited to a compact track loader, and may be another type of loader working machine such as a skid steer loader. Further, the working machine 1 may be a working machine other than a loader working machine.

[0019] As shown in FIG. 10, the working machine 1 includes a machine body 2, a cabin 3, a working device 4, and a traveling device 5. In the embodiment of the present invention, the direction in which the driver sitting on the driver's seat 8 of the working machine 1 faces (the left side in FIG. 10) is referred to as the front, and the opposite direction (the right side in FIG. 10) is referred to as the rear. Also, the left side of the driver (the front side in FIG. 10) is referred to as the left, and the right side of the driver (the back side in FIG. 10) is referred to as the right. Note that the horizontal direction, which is a direction orthogonal to the front-rear direction, is referred to as the machine body width direction.

[0020] The cab 3 is mounted on the airframe 2. A driver's seat 8 is provided in the cab 3. The working device 4 is attached to the airframe 2. A prime mover 6 is mounted at the rear part inside the airframe 2. The traveling device 5 is provided outside the airframe 2. The traveling device 5 includes a first traveling device 5L provided on the left side of the airframe 2 and a second traveling device 5R provided on the right side of the airframe 2.

[0021] Hereinafter, with reference to FIG. 10, the working device 4 will be described in detail. The working device 4 has a boom 10, a working tool 11, a lift link 12, a control link 13, a boom cylinder 14, and a bucket cylinder 15. The booms 10 are respectively provided on the left and right sides of the cab 3 so as to be swingable up and down. The working tool 11 is, for example, a bucket, and the working tool 11 is provided on the first end portion (front end portion) 10a of the boom 10 so as to be swingable up and down. The lift link 12 and the control link 13 support the second end portion (rear end portion) 10b, which is the opposite end of the first end portion 10a of the boom 10, so as to be swingable up and down. The boom cylinder 14 raises and lowers the boom 10 by expanding and contracting. The bucket cylinder 15 swings the working tool 11 by expanding and contracting.

[0022] The first end portions (front end portions) 10a of the left boom 10 and the right boom 10 are connected by a deformed connecting pipe (not shown). The second end portions (rear end portions) 10b of the left boom 10 and the right boom 10 are connected by a circular connecting pipe. The lift link 12, the control link 13, and the boom cylinder 14 are respectively provided on the left and right sides of the airframe 2 corresponding to the left boom 10 and the right boom 10.

[0023] The lift link 12 is vertically provided on the rear side of the second end portion 10b of the boom 10. The first end portion (upper end portion) 12a of the lift link 12 is pivotally supported via a pivot shaft 16 rotatably about a horizontal axis near the rear side of the second end portion 10b of the boom 10. Also, the second end portion (lower end portion) 12b, which is the end portion opposite to the first end portion 12a of the lift link 12, is pivotally supported via a pivot shaft 17 rotatably about a horizontal axis near the rear side of the machine body 2.

[0024] The first end portion (upper end portion) 14a of the boom cylinder 14 is pivotally supported via a pivot shaft 18 rotatably about a horizontal axis. The pivot shaft 18 is provided near the front side of the second end portion 10b of the boom 10. The second end portion (lower end portion) 14b, which is the end portion opposite to the first end portion 14a of the boom cylinder 14, is pivotally supported via a pivot shaft 19 rotatably about a horizontal axis. The pivot shaft 19 is provided below the rear portion of the machine body 2.

[0025] The control link 13 is provided in front of the lift link 12. The first end portion (front end portion) 13a of this control link 13 is pivotally supported via a pivot shaft 20 rotatably about a horizontal axis. The pivot shaft 20 is provided on the machine body 2 in front of the lift link 12. The second end portion (rear end portion) 13b, which is the end portion opposite to the first end portion 13a of the control link 13, is pivotally supported via a pivot shaft 21 rotatably about a horizontal axis. The pivot shaft 21 is provided on the boom 10 in front of and above the pivot shaft 17.

[0026] Therefore, the boom 10 is supported at the second end portion 10b by the lift link 12 and the control link 13, and by extending and retracting the boom cylinder 14, it swings up and down about the pivot shaft 16. Thereby, the first end portion 10a of the boom 10 moves up and down. Also, the control link 13 swings up and down about the pivot shaft 20 as the boom 10 swings up and down. The lift link 12 swings back and forth about the pivot shaft 17 as the control link 13 swings up and down.

[0027] In addition, in Fig. 10, although a bucket is attached to the first end portion 10a of the boom 10 as the working tool 11, another working tool 11 can be attached to the first end portion 10a of the boom 10 instead of the bucket. Another working tool 11 that can be attached to the first end portion 10a of the boom 10 is, for example, an attachment (spare attachment) 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. The spare attachment has a hydraulic device such as a hydraulic motor and a hydraulic cylinder, and is operated by the supplied hydraulic oil.

[0028] A connecting member 25 is provided at the first end portion 10a of the left boom 10. The connecting member 25 is a member that connects a first pipe material (not shown) connected to the spare attachment and a second pipe material (not shown) such as a pipe provided on the boom 10. Specifically, a first pipe material connected to the spare attachment is connected to the first end portion (front end portion) 25a of the connecting member 25. On the other hand, a second pipe material is connected to the second end portion (rear end portion) 25b which is the end portion opposite to the first end portion 25a. Thereby, the hydraulic oil flowing through the second pipe material passes through the first pipe material and is supplied to the spare attachment.

[0029] The bucket cylinders 15 are respectively arranged on the side of the first end portion 10a of the boom 10. The first end portion (upper end portion) 15a of the bucket cylinder 15 is pivotally supported via a pivot shaft 22 so as to be rotatable about a horizontal axis. The pivot shaft 22 is provided closer to the rear side of the first end portion 10a of the boom 10. The second end portion (lower end portion) 15b which is the end portion opposite to the first end portion 15a of the bucket cylinder 15 is pivotally supported via a pivot shaft 23 so as to be rotatable about a horizontal axis. The pivot shaft 32 is provided above the rear portion of the working tool 11. Thereby, the bucket cylinder 15 expands and contracts to swing the working tool 11.

[0030] The left traveling device 5 (first traveling device 5L) and the right traveling device 5 (second traveling device 5R) employ crawler-type traveling devices 5 in this embodiment. Note that the traveling device 5 is not limited to the crawler type as shown in FIG. 10, and may be a semi-crawler type or a wheel-type traveling device 5 having front and rear wheels. The prime mover 6 is an internal combustion engine (engine) such as a diesel engine or a gasoline engine, an electric motor, or the like. In this embodiment, the prime mover 6 is a diesel engine, but is not limited thereto.

[0031] Hereinafter, the hydraulic system of the traveling system will be described with reference to FIG. 1. FIG. 1 is a diagram showing the hydraulic circuit of the traveling system among the hydraulic systems (hydraulic circuits) of the work machine 1. The hydraulic system of the traveling system of the work machine 1 is a system for operating the traveling device 5. As shown in FIG. 1, the work machine 1 includes a control device 100, a first hydraulic pump P1, a second hydraulic pump P2, a traveling pump 50, and a traveling motor 51. The control device 100 is a device composed of an electric / electronic circuit, a program stored in a CPU, an MPU, or the like. The control device 100 controls various devices of the work machine 1. Further, the control device 100 has a storage unit 100a. The storage unit 100a is a non-volatile memory or the like, and stores various information related to the control of the control device 100.

[0032] The first hydraulic pump P1 is operated by the power of the prime mover 6 and discharges hydraulic oil. Further, the first hydraulic pump P1 is composed of a fixed-displacement gear pump. Specifically, the first hydraulic pump P1 is connected between the hydraulic oil tank T and the discharge oil passage 40, and can discharge the hydraulic oil stored in the hydraulic oil tank T to the discharge oil passage 40. In particular, the first hydraulic pump P1 mainly discharges the hydraulic oil used for controlling the work machine 1.

[0033] In the following description, among the hydraulic oil discharged from the first hydraulic pump P1, the hydraulic oil used for control may be described as pilot oil, and the pressure of the pilot oil may be described as pilot pressure. The second hydraulic pump P2 is operated by the power of the prime mover 6 and discharges hydraulic oil. Further, the second hydraulic pump P2 is constituted by a fixed displacement gear pump. The second hydraulic pump P2 is connected between the hydraulic oil tank T and the main oil passage 45, and can discharge the hydraulic oil stored in the hydraulic oil tank T to the main oil passage 45. In particular, the second hydraulic pump P2 supplies hydraulic oil to a hydraulic system of a work system different from the traveling system.

[0034] The traveling pump 50 and the traveling motor 51 are devices operated by hydraulic oil. In the following description, the traveling pump 50 and the traveling motor 51 may be referred to as the hydraulic device S. The traveling pump 50 is a pump operated by the power of the prime mover 6. In the present embodiment, the traveling pump 50 includes a first traveling pump 50L and a second traveling pump 50R. Specifically, the traveling pump 50 is an inclined plate type variable displacement axial piston pump operated by the power of the prime mover 6. The traveling pump 50 has a forward pressure receiving portion 50a and a reverse pressure receiving portion 50b on which a pilot pressure acts. The traveling pump 50 changes the angle of the swash plate according to the pilot pressure acting on the forward pressure receiving portion 50a and the reverse pressure receiving portion 50b. By changing the angle of the swash plate, the traveling pump 50 can change the discharge amount (output) of the hydraulic oil supplied from the discharge oil passage 40 and the discharge direction of the hydraulic oil.

[0035] The traveling motor 51 is a motor that is operated by the hydraulic oil discharged from the traveling pump 50 and transmits power to the drive shaft of the traveling device 5. In the present embodiment, the traveling motor 51 includes a first traveling motor 51L and a second traveling motor 51R. The first traveling motor 51L is a motor that transmits power to the drive shaft of the traveling device 5 (first traveling device 5L) provided on the left side of the machine body 2. The first traveling motor 51L can be operated by the hydraulic oil discharged by the first traveling pump 50L. Specifically, the first traveling motor 51L is connected to the first traveling pump 50L by a circulation oil passage 53a. Therefore, the first traveling pump 50L can supply hydraulic oil to the first traveling motor 51L via the circulation oil passage 53a.

[0036] The first traveling motor 51L can change its rotational speed (number of revolutions) based on the flow rate of the hydraulic oil supplied from the first traveling pump 50L. In addition, the first traveling motor 51L can change its rotational speed between a first speed (a predetermined low speed range) on the low speed side and a second speed (a predetermined high speed range) on the high speed side relative to the first speed. In this embodiment, the first traveling motor 51L can change its rotational speed (number of revolutions) by expanding and contracting the swash plate switching cylinder 52L. Specifically, as shown in FIG. 1, the swash plate switching cylinder 52L is connected to the first traveling motor 51L. When the swash plate switching cylinder 52L contracts, the rotational speed of the first traveling motor 51L is set to the first speed. On the other hand, when the swash plate switching cylinder 52L extends, the rotational speed of the first traveling motor 51L is set to the second speed.

[0037] The second traveling motor 51R is a motor that transmits power to the drive shaft of the traveling device 5 (the second traveling device 5R) provided on the right side of the machine body 2. The second traveling motor 51R can be operated by the hydraulic oil discharged from the second traveling pump 50R. Specifically, the second traveling motor 51R is connected to the second traveling pump 50R through the circulation oil passage 53b. Therefore, the second traveling pump 50R can supply hydraulic oil to the second traveling motor 51R through the circulation oil passage 53b.

[0038] The second traveling motor 51R can change its rotational speed (number of revolutions) based on the flow rate of the hydraulic oil supplied from the second traveling pump 50R. Further, the second traveling motor 51R can change its rotational speed between a first speed (a predetermined low speed range) on the low speed side and a second speed (a predetermined high speed range) on the high speed side relative to the first speed. In the present embodiment, the second traveling motor 51R can change the rotational speed (number of revolutions) by expanding and contracting a swash plate switching cylinder 52R. Specifically, as shown in FIG. 1, a swash plate switching cylinder 52R is connected to the second traveling motor 51R. When the swash plate switching cylinder 52R contracts, the rotational speed of the second traveling motor 51R is set to the first speed. On the other hand, when the swash plate switching cylinder 52R extends, the rotational speed of the second traveling motor 51R is set to the second speed.

[0039] As shown in FIG. 1, a traveling relief valve 71 is provided in a circulation oil passage 53a connecting the first traveling pump 50L and the first traveling motor 51L, and a traveling relief valve 71 is also provided in a circulation oil passage 53b connecting the second traveling pump 50R and the second traveling motor 51R. When the work implement 1 performs operations such as earth pushing with the bucket, the traveling relief valve 71 discharges the hydraulic oil flowing through the circulation oil passages 53a and 53b to the hydraulic oil tank T, respectively.

[0040] Hereinafter, operations related to the traveling of the work implement 1, that is, operations of the traveling device 5 (traveling operations) will be described in detail. As shown in FIG. 1, the work implement 1 includes a traveling operation device (operation device) 54. The operation device 54 is a device for operating the traveling pumps 50 (the first traveling pump 50L and the second traveling pump 50R). The operation device 54 can change the angle of the swash plate (swash plate angle) of the traveling pump 50 by changing the pilot pressure acting on the forward pressure receiving portion 50a and the reverse pressure receiving portion 50b. The operation device 54 includes an operation member (traveling lever) 55 and a plurality of operation valves (traveling operation valves) 56.

[0041] The operating member 55 is an operating lever that swings in the left-right direction (machine body width direction) or the front-rear direction. The operating member 55 is supported by the operating valve 56. The operating member 55 can be operated forward (in the direction of arrow A1 in FIG. 1) and backward (in the direction of arrow A2 in FIG. 1) from the neutral position N, and can also be operated leftward (in the direction of arrow A3 in FIG. 1) and rightward (in the direction of arrow A4 in FIG. 1) from the neutral position N.

[0042] In other words, the operating member 55 can swing in at least four directions with respect to the neutral position N. Hereinafter, for convenience of explanation, in the description of the operating member 55, the two-way direction of forward and backward, that is, the front-rear direction, is referred to as the first direction. Also, the two-way direction of left and right, that is, the left-right direction (machine body width direction), may be referred to as the second direction. The plurality of operating valves 56 are valves that are actuated by the operation of the operating member 55. Specifically, the plurality of operating valves 56 are connected to the discharge oil passage 40, and the pressure (pilot pressure) of the pilot oil, which is the hydraulic oil supplied from the discharge oil passage 40, can be changed. The plurality of operating valves 56 are operated by a common operating member 55, that is, one operating lever. The plurality of operating valves 56 are a first pilot valve 56A, a second pilot valve 56B, a third pilot valve 56C, and a fourth pilot valve 56D.

[0043] When the operating member 55 swings forward (one side) in the front-rear direction (the first direction), that is, when the operating member 55 is operated forward, the first pilot valve 56A changes the pressure of the pilot oil output according to the operation amount (operation) of the forward operation. When the operating member 55 swings backward (the other side) in the front-rear direction (the first direction), that is, when the operating member 55 is operated backward, the second pilot valve 56B changes the pressure of the pilot oil output according to the operation amount (operation) of the backward operation.

[0044] When the third pilot valve 56C swings the operating member 55 to the left (one side) in the left - right direction (second direction), that is, when the operating member 55 is operated to the left, the pressure of the hydraulic oil output according to the operation amount (operation) of the left operation changes. When the fourth pilot valve 56D swings the operating member 55 to the right (the other side) in the left - right direction (second direction), that is, when the operating member 55 is operated to the right, the pressure of the pilot oil output according to the operation amount (operation) of the right operation changes.

[0045] As shown in FIG. 1, the plurality of operation valves 56 are connected to the travel pump 50 by the travel oil passage 42. That is, the travel pump 50 is a hydraulic device operable by the pilot oil output from the operation valves 56 (the first pilot valve 56A, the second pilot valve 56B, the third pilot valve 56C, and the fourth pilot valve 56D). As shown in FIG. 1, the travel oil passage 42 is an oil passage connecting the plurality of operation valves 56 and the travel pump 50. The travel oil passage 42 has a first travel oil passage 42a, a second travel oil passage 42b, a third travel oil passage 42c, a fourth travel oil passage 42d, and a fifth travel oil passage 42e.

[0046] The first travel oil passage 42a is an oil passage connected to the forward pressure receiving portion 50a of the first travel pump 50L. The second travel oil passage 42b is an oil passage connected to the reverse pressure receiving portion 50b of the first travel pump 50L. The third travel oil passage 42c is an oil passage connected to the forward pressure receiving portion 50a of the second travel pump 50R. The fourth travel oil passage 42d is an oil passage connected to the reverse pressure receiving portion 50b of the second travel pump 50R. The fifth travel oil passage 42e is an oil passage connecting the operation valve 56 and each of the first travel oil passage 42a, the second travel oil passage 42b, the third travel oil passage 42c, and the fourth travel oil passage 42d. Specifically, the fifth travel oil passage 42e includes a bridge portion 42e1 that is connected to the first travel oil passage 42a, the second travel oil passage 42b, the third travel oil passage 42c, and the fourth travel oil passage 42d and has a plurality of shuttle valves 43, and a connecting path 45e2 that connects the confluence portion of the bridge portion 42e1 and the plurality of operation valves 56.

[0047] When the operation member 55 swings forward (in the direction of arrow A1 in Fig. 1), the first pilot valve 56A is operated, and the first pilot valve 56A outputs pilot oil. The pressure of the pilot oil (pilot pressure) output from the first pilot valve 56A acts on the forward pressure receiving portion 50a of the first travel pump 50L via the fifth travel oil passage 42e and the first travel oil passage 42a. Also, the pressure of the pilot oil (pilot pressure) output from the first pilot valve 56A acts on the forward pressure receiving portion 50a of the second travel pump 50R via the fifth travel oil passage 42e and the third travel oil passage 42c. As a result, the swash plate angles of the first travel pump 50L and the second travel pump 50R are changed, and the first travel motor 51L and the second travel motor 51R operate on the forward rotation (forward movement) side, causing the work machine 1 to move straight forward.

[0048] Also, when the operation member 55 swings backward (in the direction of arrow A2 in Fig. 1), the second pilot valve 56B is operated, and the second pilot valve 56B outputs pilot oil. The pressure of the pilot oil (pilot pressure) output from the second pilot valve 56B acts on the reverse pressure receiving portion 50b of the first travel pump 50L via the fifth travel oil passage 42e and the second travel oil passage 42b. Also, the pressure of the pilot oil (pilot pressure) output from the second pilot valve 56B acts on the reverse pressure receiving portion 50b of the second travel pump 50R via the fifth travel oil passage 42e and the fourth travel oil passage 42d. As a result, the swash plate angles of the first travel pump 50L and the second travel pump 50R are changed, and the first travel motor 51L and the second travel motor 51R operate on the reverse rotation (reverse movement) side, causing the work machine 1 to move straight backward.

[0049] Further, when the operation member 55 is swung leftward (in the direction of arrow A3 in FIG. 1), the third pilot valve 56C is operated, and the third pilot valve 56C outputs pilot oil. The pressure of the pilot oil (pilot pressure) output from the third pilot valve 56C acts on the forward pressure receiving portion 50a of the second travel pump 50R via the fifth travel oil passage 42e and the third travel oil passage 42c. Also, the pressure of the pilot oil (pilot pressure) output from the third pilot valve 56C acts on the reverse pressure receiving portion 50b of the first travel pump 50L via the fifth travel oil passage 42e and the second travel oil passage 42b. As a result, the swash plate angles of the first travel pump 50L and the second travel pump 50R are changed, the first travel motor 51L operates on the reverse side, and the second travel motor 51R operates on the forward side, and the work machine 1 turns left.

[0050] Also, when the operation member 55 is swung rightward (in the direction of arrow A4 in FIG. 1), the fourth pilot valve 56D is operated, and the fourth pilot valve 56D outputs pilot oil. The pressure of the pilot oil (pilot pressure) output from the fourth pilot valve 56D acts on the forward pressure receiving portion 50a of the first travel pump 50L via the fifth travel oil passage 42e and the first travel oil passage 42a. Also, the pressure of the pilot oil (pilot pressure) output from the fourth pilot valve 56D acts on the reverse pressure receiving portion 50b of the second travel pump 50R via the fifth travel oil passage 42e and the fourth travel oil passage 42d. As a result, the swash plate angles of the first travel pump 50L and the second travel pump 50R are changed, the first travel motor 51L operates on the forward side, and the second travel motor 51R operates on the reverse side, and the work machine 1 turns right.

[0051] Furthermore, when the operation member 55 is swung obliquely, the rotational direction and rotational speed of the first travel motor 51L and the second travel motor 51R are determined by the differential pressure of the pilot pressure acting on the forward pressure receiving portion 50a and the reverse pressure receiving portion 50b, and the work machine 1 turns right or left while moving forward or backward. Specifically, when the operation member 55 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 operation member 55. When the operation member 55 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 operation member 55. When the operation member 55 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 operation member 55. And when the operation member 55 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 operation member 55.

[0052] As shown in FIG. 1, the work machine 1 includes a travel switching valve 57. The travel switching valve 57 is switchable between a first state in which the rotational speed (number of revolutions) of the travel motor 51 is set to a first speed and a second state in which the rotational speed is set to a second speed. The travel switching valve 57 includes first switching valves 58L and 58R and a second switching valve 59. The first switching valve 58L is a two-position switching valve that switches between a first position 58L1 and a second position 58L2. The first switching valve 58L is connected to the swash plate switching cylinder 52L via an oil passage. When the first switching valve 58L is in the first position 58L1, the supply of hydraulic oil to the swash plate switching cylinder 52L is stopped, and the swash plate switching cylinder 52L is contracted. On the other hand, when the first switching valve 58L is in the second position 58L2, hydraulic oil is supplied to the swash plate switching cylinder 52L, and the swash plate switching cylinder 52L is extended.

[0053] The first switching valve 58R is a two-position switching valve that switches between a first position 58R1 and a second position 58R2. The first switching valve 58R is connected to the swash plate switching cylinder 52R via an oil passage. When the first switching valve 58R is in the first position 58R1, the supply of hydraulic oil to the swash plate switching cylinder 52R is stopped, and the swash plate switching cylinder 52R is contracted. On the other hand, when the first switching valve 58R is in the second position 58R2, hydraulic oil is supplied to the swash plate switching cylinder 52R, and the swash plate switching cylinder 52R is extended.

[0054] The second switching valve 59 is a solenoid valve that switches the switching positions of the first switching valve 58L and the first switching valve 58R. Specifically, the second switching valve 59 is a two-position switching valve that can be switched between a first position 59a and a second position 59b by excitation. As shown in FIG. 1, the second switching valve 59 is connected to the first switching valve 58L and the first switching valve 58R by an oil passage 41. When the second switching valve 59 is in the first position 59a, it supplies hydraulic oil to the pressure-receiving portions of the first switching valve 58L and the first switching valve 58R, switches the first switching valve 58L to the first position 58L1, and switches the first switching valve 58R to the first position 58R1. On the other hand, when the second switching valve 59 is in the second position 59b, it stops the supply of hydraulic oil to the pressure-receiving portions of the first switching valve 58L and the first switching valve 58R, switches the first switching valve 58L to the second position 58L2, and switches the first switching valve 58R to the second position 58R2. That is, when the second switching valve 59 is in the first position 59a, the traveling switching valve 57 is in the first state, the swash plate switching cylinders 52L and 52R contract, and the rotational speed of the traveling motor 51 (the first traveling motor 51L and the second traveling motor 51R) switches to the first speed. On the other hand, when the second switching valve 59 is in the second position 59b, the traveling switching valve 57 is in the second state, the swash plate switching cylinders 52L and 52R extend, and the rotational speed of the traveling motor 51 (the first traveling motor 51L and the second traveling motor 51R) is set to the second speed.

[0055] Therefore, the traveling switching valve 57 can switch the traveling motor 51 (the first traveling motor 51L and the second traveling motor 51R) between the first speed and the second speed.

[0056] As shown in FIG. 1, the working machine 1 is provided with a switching device (speed operating device) 101 that can be operated by an operator or the like. The switching device 101 is a changeover switch that performs a switching operation between a first speed and a second speed in the traveling motor 51 (first traveling motor 51L and second traveling motor 51R). The switching device 101 is connected to the control device 100, is operated by an operator or the like, and inputs the operation signal to the control device 100. The control device 100 outputs a control signal (for example, voltage, current, etc.) to the traveling changeover valve 57 based on the switching operation of the switching device 101, and switches the traveling changeover valve 57 between a first state and a second state.

[0057] Thereby, the switching device (changeover switch) 101 can perform a switching operation of the traveling changeover valve 57 from the first state to the second state and a switching operation of the traveling changeover valve 57 from the second state to the first state. That is, the switching device 101 can operate a speed increase for switching the traveling motor 51 (first traveling motor 51L and second traveling motor 51R) from the first speed to the second speed and a speed decrease for switching the traveling motor 51 (first traveling motor 51L and second traveling motor 51R) from the second speed (second state) to the first speed (first state).

[0058] The working machine 1 of the present invention can reduce the output of the hydraulic equipment S (traveling pump 50 and traveling motor 51) and suppress engine stall. Specifically, the working machine 1 suppresses engine stall by changing the pilot pressure (primary pressure) of the pilot oil supplied to the operation valve 56 and reducing the output of the hydraulic equipment S. Anti-stall control will be described in detail below.

[0059] As shown in Fig. 1, the working machine 1 includes a rotational speed operating tool (accelerator) 102 and a second detection device 103. The rotational speed operating tool 102 is a member that operates the target rotational speed of the prime mover 6. The rotational speed operating tool 102 is connected to the control device 100 and inputs an operation signal to the control device 100. The rotational speed operating tool 102 is provided near the driver's seat 8. The rotational speed operating tool 102 is an accelerator lever supported swingably, an accelerator pedal supported swingably, an accelerator volume supported rotatably, an accelerator slider supported slidably, and the like. Note that the rotational speed operating tool 102 only needs to be able to operate the target rotational speed of the prime mover 6 and is not limited to the above-described examples.

[0060] The second detection device 103 is a sensor or the like that detects the actual rotational speed of the prime mover 6. The second detection device 103 is connected to the control device 100 and inputs the detected signal (detection signal) to the control device 100. Based on the difference (drop rotational speed) between the target rotational speed of the prime mover 6 operated by the rotational speed operating tool 102 and the actual rotational speed of the prime mover 6 detected by the second detection device 103, the control device 100 performs control to suppress the stop of the prime mover 6, that is, control to suppress engine stall (anti-stall control). In the present embodiment, in the anti-stall control, when the drop rotational speed is equal to or higher than the first threshold value, the control device 100 suppresses engine stall by reducing the output of the travel pump 50.

[0061] As shown in Fig. 1, the working machine 1 includes a control valve 70. The control valve 70 is a valve capable of changing the pilot pressure of the pilot oil that operates the travel pump 50. The control valve 70 is provided in the discharge oil passage 40 and changes the pilot pressure (primary pressure) of the pilot oil supplied from the discharge oil passage 40 to the operating device 54 (a plurality of control valves 56). The operation valve 70 operates according to a control signal (e.g., voltage, current, etc.) from the control device 100, and by changing the opening degree, changes the pilot pressure (primary pressure) of the pilot oil supplied from the discharge oil passage 40 to the operating device 54. Hereinafter, the case where the control signal of the control device 100 is current will be described, and the current value output as the control signal of the control device 100 is referred to as the "indicated current value". The electromagnetic proportional valve constituting the operation valve 70 can increase the opening degree in proportion to the magnitude of the indicated current value.

[0062] That is, the primary pressure is changed according to the control signal output from the control device 100 to the operation valve 70. In the case of this embodiment, since the control device 100 outputs the indicated current value to the operation valve 70, the primary pressure is changed according to the magnitude of the indicated current value output from the control device 100 to the operation valve 70. Specifically, when the indicated current value output from the control device 100 to the operation valve 70 increases, the opening degree of the operation valve 70 becomes larger and the primary pressure increases. On the other hand, when the indicated current value output from the control device 100 to the operation valve 70 decreases, the opening degree of the operation valve 70 becomes smaller and the primary pressure decreases.

[0063] Figure 2 is a diagram showing an example of the relationship between the control signal (indicated current value) and the primary pressure. As shown in Figure 2, there is a proportional relationship or a correspondence relationship (correlation relationship) close to the proportional relationship between the indicated current value and the primary pressure. Therefore, the control device 100 can change the target pressure of the pilot pressure (primary pressure) of the pilot oil supplied to the plurality of operation valves 56 by changing the indicated current value, which is the control signal output to the operation valve 70.

[0064] As shown in Figure 1, the control device 100 has an arithmetic unit 100b. The arithmetic unit 100b is composed of an electric / electronic circuit provided in the control device 100, a program stored in a CPU, etc. The arithmetic unit 100b calculates the drop rotational speed by subtracting the actual rotational speed of the prime mover 6 detected by the second detection device 103 from the target rotational speed of the prime mover 6 operated by the rotational speed operating tool 102. Further, the arithmetic unit 100b defines a control signal (command current value) output to the operation valve 70 based on the actual rotational speed of the prime mover 6 detected by the second detection device 103 and the calculated drop rotational speed. The arithmetic unit 100b acquires a control map pre-stored in the storage unit 100a and refers to a setting line L defined in the control map.

[0065] The storage unit 100a stores a control map including the setting line L. FIG. 3 is a diagram showing an example of the setting line L for setting a control signal (target pressure of the primary pressure) based on the actual rotational speed of the prime mover 6. The setting line L is a function that defines a control signal based on the actual rotational speed of the prime mover 6 detected by the arithmetic unit 100b (control device 100) using the second detection device 103. The setting line L is defined based on the relationship between the actual rotational speed of the prime mover 6 when the opening degree of the operation valve 56 is fully open and the magnitude of the command current value. The example shown in FIG. 3 is a control map (anti-stall map) showing an example of the setting line L. The setting line L includes a first line La and a second line Lb.

[0066] As described above, the magnitude of the command current value, which is the control signal output by the control device 100 to the operation valve 70, and the target pressure of the primary pressure have a corresponding relationship such as a proportional relationship (see FIG. 2). That is, the setting line L (first line La and second line Lb) shown in FIG. 3 can be rephrased as a setting line L that defines the target pressure of the primary pressure corresponding to the control signal (command current value) based on the actual rotational speed of the prime mover 6. Therefore, in FIG. 3, the vertical axis can be referred to as "control signal (command current value)" or "primary pressure (target pressure)".

[0067] When the drop rotation speed calculated by the arithmetic unit 100b is equal to or higher than the first threshold, the first line La is a line for setting a control signal (command current value) corresponding to the target pressure of the primary pressure based on the actual rotation speed. That is, the first line La is a droop characteristic line adopted when a driving load equal to or higher than a predetermined value occurs on the prime mover 6. When the drop rotation speed calculated by the arithmetic unit 100b is less than the first threshold, the second line Lb is a line for setting a control signal (command current value) corresponding to the target pressure of the primary pressure based on the actual rotation speed. The second line Lb sets the control signal (command current value) to be larger than that of the first line La. That is, the second line Lb is a no-load characteristic line adopted when the load on the prime mover 6 is less than a predetermined value.

[0068] As shown in FIG. 1, the control device 100 has a changing unit 100c. The changing unit 100c is composed of an electric / electronic circuit provided in the control device 100, a program stored in a CPU, etc. When the drop rotation speed calculated by the arithmetic unit 100b is equal to or higher than the first threshold, the changing unit 100c changes (corrects) the control signal (command current value) calculated from the first line La so that the opening degree of the operation valve 70 increases as the actual rotation speed of the traveling motor 51 decreases. In addition, the changing unit 100c may change the control signal based on the actual rotation speed of the prime mover 6 in addition to the actual rotation speed of the traveling motor 51. Specifically, the changing unit 100c changes the control signal when the target rotation speed of the prime mover 6 operated by the rotation speed operating tool 102 is equal to or higher than a predetermined fourth threshold and the actual rotation speed of the prime mover 6 is equal to or higher than a fifth threshold. The fourth threshold and the fifth threshold are preset values. The fourth threshold is defined between the medium rotation range and the high rotation range of the target rotation speed of the prime mover 6. In addition, the fifth threshold is defined as a value corresponding to, for example, the minimum value of the actual rotation speed of the prime mover 6 required when the work implement 1 travels. Note that the fourth threshold and the fifth threshold may be appropriately changeable by operating an operation switch, a terminal, etc. connected to the control device 100.

[0069] In addition, in this embodiment, the changing unit 100c changes the control signal based on both the actual rotation speed of the traveling motor 51 and the target rotation speed of the prime mover 6. However, when the changing unit 100c changes the control signal based only on the actual rotation speed of the traveling motor 51, the changing unit 100c may change the control signal regardless of the target rotation speed of the prime mover 6 when the target rotation speed of the prime mover 6 operated by the rotation speed operating tool 102 is equal to or higher than a predetermined fourth threshold value. Hereinafter, the change of the indicated current value by the changing unit 100c will be described in detail.

[0070] As shown in FIG. 1, the work machine 1 includes a first detection device 104. The first detection device 104 is a sensor or the like that detects the actual rotation speed (actual motor rotation speed) of the traveling motor 51. The first detection device 104 is connected to the control device 100 and inputs the detected signal (detection signal) to the control device 100. When a plurality of traveling motors 51 are provided in the work machine 1, the actual rotation speed of each can be detected. In the present embodiment, since the traveling motor 51 includes a first traveling motor 51L and a second traveling motor 51R, the first detection device 104 is attached to the first traveling motor 51L and the second traveling motor 51R, respectively. The first detection device (first rotation sensor) 104 attached to the first traveling motor 51L detects the actual rotation speed of the first traveling motor 51L, and the first detection device (second rotation sensor) 104 attached to the second traveling motor 51R detects the actual rotation speed of the second traveling motor 51R.

[0071] The changing unit 100c calculates the actual rotation speed of the first traveling motor 51L and the actual rotation speed of the second traveling motor 51R based on the detection signals input from the control device 100 from the first detection device (first rotation sensor, second rotation sensor) 104. In the present embodiment, the changing unit 100c calculates the actual rotation speed of the traveling motor 51 without distinguishing between the rotation speed during forward rotation and the rotation speed during reverse rotation. For example, when the actual rotation speed when the traveling motor 51 rotates forward is set as positive and the actual rotation speed when it rotates in reverse is set as negative, the changing unit 100c calculates the absolute value of the actual rotation speed as the actual rotation speed of the traveling motor 51.

[0072] Further, the changing unit 100c calculates the moving average of the same number (n) of data among the actually measured rotational speeds of the first traveling motor 51L and the actually measured rotational speed of the second traveling motor 51R, thereby calculating the moving average of the actually measured rotational speed of the first traveling motor 51L and the moving average of the actually measured rotational speed of the second traveling motor 51R, respectively. The changing unit 100c adopts the smaller one of the moving average of the actually measured rotational speed of the first traveling motor 51L and the moving average of the actually measured rotational speed of the second traveling motor 51R as the actually measured rotational speed of the traveling motor 51. Thereby, the changing unit 100c changes the control signal based on the smaller one of the moving average of the actually measured rotational speed of the first traveling motor 51L and the moving average of the actually measured rotational speed of the second traveling motor 51R (the actually measured rotational speed of the traveling motor 51).

[0073] In the following, the smaller one of the moving average of the actually measured rotational speed of the first traveling motor 51L and the moving average of the actually measured rotational speed of the second traveling motor 51R adopted by the changing unit 100c will be simply described as the "actually measured rotational speed of the traveling motor 51". Also, in the present embodiment, the changing unit 100c may change the control signal based on the actually measured rotational speed of the traveling motor 51. In the present embodiment, the changing unit 100c may, for example, not calculate the moving average of the actually measured rotational speed of the first traveling motor 51L and the actually measured rotational speed of the second traveling motor 51R, and adopt the smaller one of the actually measured rotational speed of the first traveling motor 51L and the actually measured rotational speed of the second traveling motor 51R as the actually measured rotational speed of the traveling motor 51.

[0074] The changing unit 100c changes the control signal shown on the first line La based on a first correction coefficient (gain value) defined corresponding to the actual rotation speed of the traveling motor 51. Specifically, the storage unit 100a stores a first function M1 that defines the relationship between the actual rotation speed of the traveling motor 51 and the first correction coefficient, and the changing unit 100c calculates the first correction coefficient by substituting the actual rotation speed of the traveling motor 51 detected by the first detection device 104 into the first function M1. In the present embodiment, the changing unit 100c calculates the first correction coefficient by substituting the actual rotation speed of the traveling motor 51 adopted from the moving average of the actual rotation speed of the first traveling motor 51L and the moving average of the actual rotation speed of the second traveling motor 51R into the first function M1. FIG. 4A is a diagram showing an example of the first function M1 that defines the relationship between the actual rotation speed of the traveling motor 51 and the first correction coefficient.

[0075] As shown in FIG. 4A, the first function M1 defines the first correction coefficient with a value of 1 or more, and the first correction coefficient corresponding to the second rotation speed, which is the actual rotation speed of the traveling motor 51 and is smaller than the first rotation speed, is larger than the first correction coefficient corresponding to the first rotation speed, which is the actual rotation speed of the traveling motor 51. The first rotation speed and the second rotation speed are arbitrary rotation speeds within the range defined by the first function M1, and the first rotation speed is greater than the second rotation speed. In other words, as shown in the first function M1, the first correction coefficient is 1 or more, and decreases as the actual rotation speed of the traveling motor 51 increases, and increases as the actual rotation speed of the traveling motor 51 decreases. That is, since the first correction coefficient is 1 or more and not less than 1, it is a coefficient that can greatly correct the control signal (command current value) of the first line La. Therefore, according to the first function M1, the changing unit 100c can increase the opening degree of the operation valve 70 by changing the command current value to increase as the actual rotation speed of the traveling motor 51 decreases. That is, the changing unit 100c can increase the consumption horsepower of the traveling pump 50 by increasing the primary pressure as the actual rotation speed of the traveling motor 51 decreases.

[0076] Also, as shown in FIG. 4A, the first function M1 has different slopes based on the second threshold value Rm2 of the actual rotational speed of the traveling motor 51, and the slope when the actual rotational speed of the traveling motor 51 is less than the second threshold value Rm2 is defined to be larger than the slope when the actual rotational speed of the traveling motor 51 is equal to or greater than the second threshold value Rm2. In other words, the first function M1 is defined such that the slope when the actual rotational speed of the traveling motor 51 is less than the second threshold value Rm2 is larger than the slope when the actual rotational speed of the traveling motor 51 exceeds the second threshold value Rm2.

[0077] That is, in the first function M1, the first correction coefficient decreases significantly more when the actual rotational speed of the traveling motor 51 increases from zero toward the second threshold value Rm2 than when the actual rotational speed of the traveling motor 51 increases from the second threshold value Rm2. On the other hand, in the first function M1, the first correction coefficient increases significantly more when the actual rotational speed of the traveling motor 51 decreases from the second threshold value Rm2 toward zero than when the actual rotational speed of the traveling motor 51 decreases to the second threshold value Rm2.

[0078] In the present embodiment, the first function M1 is defined in the range where the actual rotational speed of the traveling motor 51 is equal to or greater than the first lower limit value Rm1 and equal to or less than the first upper limit value Rm3, and the second threshold value Rm2 is defined as a value between the first lower limit value Rm1 and the first upper limit value Rm3. That is, the portion where the actual rotational speed of the traveling motor 51 is equal to or less than the second threshold value Rm2 (the first portion) is the section (the first section m1) of the first function M1 where the actual rotational speed of the traveling motor 51 is equal to or greater than the first lower limit value Rm1 and equal to or less than the second threshold value Rm2. On the other hand, the portion where the actual rotational speed of the traveling motor 51 is equal to or greater than the second threshold value Rm2 (the second portion) is the section (the second section m2) of the first function M1 where the actual rotational speed of the traveling motor 51 is equal to or greater than the second threshold value Rm2 and equal to or less than the first upper limit value Rm3.

[0079] The first lower limit value Rm1 corresponds to the minimum value of the actual rotational speed of the traveling motor 51, and in the present embodiment it is zero. On the other hand, the first upper limit value Rm3 corresponds to the maximum value of the actual rotational speed of the traveling motor 51, and corresponds to, for example, the maximum rotational speed that the traveling motor 51 can output. Note that the second threshold value Rm2 is a preset value, and the first section m1 is defined as a section where the actual rotational speed of the travel motor 51 is in a relatively low rotational speed range, such as when the working machine 1 performs operations such as earth pushing with the bucket. In the present embodiment, the first section m1 corresponds to the speed range (low speed range) when the travel motor 51 is at the first speed, and the second threshold value Rm2 is a value corresponding to any of the actual rotational speeds in the speed range when the travel motor 51 is at the first speed. Further, the second threshold value Rm2 may be one that can be appropriately changed by operating an operation switch connected to the control device 100, a terminal, or the like.

[0080] In both the first section m1 and the second section m2, the first correction coefficient is in a proportional relationship with the actual rotational speed of the travel motor 51. As shown in FIG. 4A, in the first function M1, when the actual rotational speed of the travel motor 51 is the first lower limit value Rm1, the first correction coefficient is 1.6 (160%). Also, in the first function M1, when the actual rotational speed of the travel motor 51 is the second threshold value Rm2, the first correction coefficient is 1.2 (120%). And in the first function M1, when the actual rotational speed of the travel motor 51 is the first upper limit value Rm3, the first correction coefficient is 1.0 (100%).

[0081] That is, in the first section m1 of the first function M1 shown in FIG. 4A, the first correction coefficient decreases substantially linearly from 1.6 (160%) to 1.2 (120%) as the actual rotational speed of the travel motor 51 increases, and increases substantially linearly from 1.2 (120%) to 1.6 (160%) as the actual rotational speed of the travel motor 51 decreases. On the other hand, in the second section m2 of the first function M1 shown in FIG. 4A, the first correction coefficient decreases substantially linearly from 1.2 (120%) to 1.0 (100%) as the actual rotational speed of the travel motor 51 increases, and increases substantially linearly from 1.0 (100%) to 1.2 (120%) as the actual rotational speed of the travel motor 51 decreases.

[0082] Therefore, when the actual rotational speed of the travel motor 51 is relatively low, such as in an operation like earth pushing, the modified section 100c can increase the output of the travel pump 50, thereby increasing the discharge flow rate (consumed horsepower of the travel pump 50) of the travel pump 50. That is, by increasing the consumed horsepower of the travel pump 50, the actual rotational speed of the prime mover 6 that balances with the discharge flow rate of the travel pump 50 can be lowered. As a result, in an operation involving the opening of the travel relief valve 71 such as earth pushing, due to the influence of the swash plate characteristics of the travel pump 50, the phenomenon that the consumed horsepower of the travel pump 50 decreases and the actual rotational speed of the prime mover 6 that balances with the discharge flow rate increases can be prevented. As a result, in earth pushing operations and the like, a feeling can be given to the operator that the work implement 1 is working sufficiently, and even when the travel load increases, the operation can be continued by increasing the discharge flow rate of the travel pump 50.

[0083] In the description of the first correction coefficient, examples of the magnitude of each value were described, but the value is merely an illustration and may be one that can be appropriately changed by operating an operation switch, a terminal, etc. connected to the control device 100. Also, in the present embodiment, the case where the first correction coefficient is in a proportional relationship with the actual rotational speed of the travel motor 51 in both the first section m1 and the second section m2 was described as an example, but the first function M1 only needs to have a different slope based on the second threshold value Rm2 of the actual rotational speed of the travel motor 51. That is, the first function M1 may be a function that draws a substantially curved line.

[0084] In addition to the first correction coefficient, the modified section 100c changes the control signal shown on the first line La based on a second correction coefficient (gain value) defined corresponding to the actual rotational speed of the prime mover 6. Specifically, the storage unit 100a stores a second function M2 that defines the relationship between the actual rotational speed of the prime mover 6 and the second correction coefficient, and the modified section 100c calculates the second correction coefficient by substituting the actual rotational speed of the prime mover 6 detected by the second detection device 103 into the second function M2. FIG. 4B is a diagram showing an example of the second function M2 that defines the relationship between the actual rotational speed of the prime mover 6 and the second correction coefficient.

[0085] As shown in FIG. 4B, when the actual rotational speed of the prime mover 6 is equal to or higher than the third threshold value Re2, the second function M2 defines the second correction coefficient as 1, and when the actual rotational speed of the prime mover 6 is less than the third threshold value Re2 the second correction coefficient is defined as a value less than 1. Therefore, according to the second function M2, the changing unit 100c does not change the command current value so that at least the opening degree of the operation valve 70 increases, and when the actual rotational speed of the prime mover 6 is less than the third threshold value Re2, as the actual rotational speed of the prime mover 6 decreases, the command current value is changed to decrease, so that the opening degree of the operation valve 70 can be decreased. That is, when the actual rotational speed of the prime mover 6 is less than the third threshold value Re2, the changing unit 100c can decrease the power consumption of the travel pump 50 by decreasing the primary pressure as the actual rotational speed of the prime mover 6 decreases.

[0086] In the present embodiment, the second function M2 is defined in the range where the actual rotational speed of the prime mover 6 is equal to or higher than the second lower limit value Re1 and equal to or lower than the second upper limit value Re3, and the third threshold value Re2 is defined as a value between the second lower limit value Re1 and the second upper limit value Re3. That is, the portion where the actual rotational speed of the prime mover 6 is less than the third threshold value Re2 (the third portion) is the section (the third section m3) of the second function M2 where the actual rotational speed of the prime mover 6 is equal to or higher than the second lower limit value Re1 and less than the third threshold value Re2. On the other hand, the portion where the actual rotational speed of the prime mover 6 is equal to or higher than the third threshold value Re2 (the fourth portion) is the section (the fourth section m4) of the second function M2 where the actual rotational speed of the prime mover 6 is equal to or higher than the third threshold value Re2 and equal to or lower than the second upper limit value Re3.

[0087] The second lower limit value Re1 is defined to be the same as the fifth threshold value. That is, in the present embodiment, the second lower limit value Re1 corresponds to, for example, the minimum value of the actual rotational speed of the prime mover 6 required when the work machine 1 travels. On the other hand, the second upper limit value Re3 corresponds to the maximum value of the actual rotational speed of the prime mover 6, and corresponds to, for example, the maximum rotational speed that the prime mover 6 can output. The third threshold value Re2 is a preset value, and the third section m3 is defined as a section where the actual rotational speed of the prime mover 6 is in the medium rotational speed range or lower, such as when the work machine 1 travels uphill. In the present embodiment, the third threshold value Re2 is defined to be smaller than the fourth threshold value. Further, the third threshold value Re2 may be one that can be appropriately changed by operating an operation switch, a terminal, or the like connected to the control device 100.

[0088] In the third section m3 where the actual rotational speed of the prime mover 6 is less than the third threshold value Re2, the second correction coefficient is less than 1 and is in a proportional relationship with the actual rotational speed of the prime mover 6. Specifically, in the third section m3, the second correction coefficient increases as the actual rotational speed of the prime mover 6 increases, and decreases as the actual rotational speed of the travel motor 51 decreases. For example, in the third section m3 of the second function M2, the second correction coefficient is defined as a value in the range from 0.9 (90%) to 1.0 (100%).

[0089] Also, in the fourth section m4 where the actual rotational speed of the prime mover 6 is greater than or equal to the third threshold value Re2, the second correction coefficient is 1. That is, in the fourth section m4 where the actual rotational speed of the prime mover 6 is greater than or equal to the third threshold value Re2, the changing unit 100c does not change the control signal according to the second correction coefficient. That is, in the third section m3 of the second function M2 shown in FIG. 4B, the second correction coefficient increases substantially linearly from 0.9 (90%) to 1.0 (100%) as the actual rotational speed of the prime mover 6 increases, and increases substantially linearly from 1.0 (100%) to 0.9 (90%) as the actual rotational speed of the prime mover 6 decreases.

[0090] On the other hand, in the fourth section m4 of the second function M2 shown in FIG. 4B, the second correction coefficient is constant at 1.0 (100%). Therefore, when the rotational speed of the prime mover 6 is less than the third threshold value Re2 and is relatively low, the changing unit 100c can change the first line La in a direction in which the primary pressure output from the operation valve 70 decreases. Thereby, the output of the traveling pump 50 can be reduced, and engine stalling can be prevented.

[0091] In addition, in the description of the second correction coefficient, examples of the magnitude of the values are described, but the values are merely illustrative and may be appropriately changed by operating an operation switch, a terminal, etc. connected to the control device 100. The changing unit 100c changes the control signal indicated on the first line La according to a third correction coefficient based on the first correction coefficient and the second correction coefficient. Specifically, the changing unit 100c calculates the third correction coefficient based on the product of the first correction coefficient and the second correction coefficient. That is, when the third correction coefficient calculated by the changing unit 100c exceeds 1 (100%), when the changing unit 100c multiplies the indicated current value by the third correction coefficient, the changed indicated current value is larger than the indicated current value before the change. Thus, when the third correction coefficient acquired by the changing unit 100c exceeds 1, the operation valve 70 that outputs the changed indicated current value is changed in a direction in which the primary pressure output becomes larger than before the change. When the third correction coefficient calculated by the changing unit 100c is 1 (100%), the changed indicated current value is not changed even if the changing unit 100c multiplies the indicated current value by the third correction coefficient.

[0092] Also, when the third correction coefficient exceeds 1, the changing unit 100c changes the control signal indicated on the first line La, and when the third correction coefficient is 1 or less, the changing unit 100c does not change the control signal indicated on the first line La. Thereby, it is possible to suppress the changing unit 100c from changing the first line La too much in a direction in which the primary pressure output from the operation valve 70 decreases. That is, when the actual rotational speed of the prime mover 6 is less than the third threshold value Re2, it is possible to suppress the traveling force of the traveling motor 51 from decreasing too much by the changing unit 100c changing the first line La.

[0093] In addition, in the present embodiment, when the third correction coefficient is 1 or less, the change unit 100c does not change the control signal shown in the first line La. However, when suppressing engine stall is prioritized, when the third correction coefficient is less than 1, the control signal shown in the first line La may be changed by multiplying the indicated current value by the third correction coefficient. In such a case, when the third correction coefficient acquired by the change unit 100c is less than 1 (100%), when the change unit 100c multiplies the indicated current value by the third correction coefficient, the changed indicated current value becomes smaller than the indicated current value before the change. Therefore, when the third correction coefficient acquired by the change unit 100c is less than 1, the operation valve 70 that outputs the changed indicated current value is changed in a direction in which the primary pressure output is smaller than before the change.

[0094] Figure 5A is an operation flow showing the flow of the operation of the control device 100 for changing the control signal (indicated current value). Hereinafter, a series of flows in which the control device 100 changes the control signal will be described with reference to Figure 5A. First, the arithmetic unit 100b calculates the drop rotation speed based on the target rotation speed of the prime mover 6 operated by the rotation speed operating tool 102 and the actual rotation speed of the prime mover 6 detected by the second detection device 103 (S1). Specifically, the arithmetic unit 100b acquires the target rotation speed of the prime mover 6 operated by the rotation speed operating tool 102 and the actual rotation speed of the prime mover 6 detected by the second detection device 103, and calculates the drop rotation speed by subtracting the actual rotation speed of the prime mover 6 from the target rotation speed of the prime mover 6.

[0095] When the arithmetic unit 100b calculates the drop rotation speed (S1), it checks whether the drop rotation speed is less than the first threshold value (S2). When the arithmetic unit 100b confirms that the drop rotation speed is less than the first threshold value (S2, Yes), it acquires the second line Lb from the storage unit 100a (S3). When the arithmetic unit 100b acquires the second line Lb from the storage unit 100a (S3), it acquires the indicated current value corresponding to the actual rotation speed detected by the second detection device 103 based on the acquired second line Lb (S4).

[0096] When the calculation unit 100b obtains the command current value corresponding to the actual rotation speed (S4), it defines the command current value as the control signal output by the control device 100 to the operation valve 70 (S5). On the other hand, when the calculation unit 100b confirms that the drop rotation speed is not less than the first threshold value, that is, the drop rotation speed is equal to or greater than the first threshold value (S2, No), it acquires the first line La from the storage unit 100a (S6). When the calculation unit 100b acquires the first line La from the storage unit 100a (S6), based on the acquired first line La, it acquires the command current value corresponding to the actual rotation speed detected by the second detection device 103 (S7).

[0097] When the calculation unit 100b acquires the command current value corresponding to the actual rotation speed (S7), the modification unit 100c acquires the first function M1 from the storage unit 100a (S8). When the modification unit 100c acquires the first function M1 from the storage unit 100a (S8), based on the detection signal detected by the first detection device 104, it calculates the actual rotation speed of the traveling motor 51 (S9). When the modification unit 100c calculates the actual rotation speed of the traveling motor 51 (S9), it calculates the first correction coefficient by substituting the actual rotation speed of the traveling motor 51 into the first function M1 (S10) When the modification unit 100c calculates the first correction coefficient (S10), it acquires the second function M2 from the storage unit 100a (S11). When the modification unit 100c acquires the second function M2 from the storage unit 100a (S11), it calculates the second correction coefficient by substituting the actual rotation speed of the prime mover 6 into the second function M2 (S12). When the modification unit 100c calculates the second correction coefficient (S12), it calculates the third correction coefficient based on the product of the first correction coefficient and the second correction coefficient (S13). When the modification unit 100c calculates the third correction coefficient (S13), it checks whether the calculated third correction coefficient exceeds 1 (S14).

[0098] When the modification unit 100c calculates the second correction coefficient (S12), it calculates the third correction coefficient based on the product of the first correction coefficient and the second correction coefficient (S13). When the modification unit 100c calculates the third correction coefficient (S13), it checks whether the calculated third correction coefficient exceeds 1 (S14). When it is confirmed that the third correction coefficient exceeds 1 (S14, Yes), the change unit 100c multiplies the indicated current value obtained by the calculation unit 100b by the third correction coefficient to change the control signal shown in the first line La (S15). When the change unit 100c changes the control signal (S15), the calculation unit 100b defines the changed indicated current value (control signal) as the control signal output from the control device 100 to the operating valve 70 (S16).

[0099] On the other hand, when it is confirmed that the third correction coefficient does not exceed 1, that is, the third correction coefficient is 1 or less (S14, No), the change unit 100c does not change the control signal shown in the first line La (S17). That is, the calculation unit 100b defines the indicated current value (control signal) shown in the first line La as the control signal output from the control device 100 to the operating valve 70 (S18).

[0100] In the modification example where the change unit 100c changes the control signal shown in the first line La when the third correction coefficient is less than 1, the flow of the operation of the control device 100 for correcting the control signal is as shown in FIG. 5B. FIG. 5B is an operation flow showing the flow of the operation of the control device 100 for changing the control signal in the first modification example. Specifically, as shown in FIG. 5B, the flow of the operation of the control device 100 in this modification example is different from the operation flow shown in FIG. 5A in that S19 to S23 are used instead of S14 to S18. Specifically, in the modification example shown in FIG. 5B, when the change unit 100c calculates the third correction coefficient (S13), it checks whether the calculated third correction coefficient is 1 (S19).

[0101] When it is confirmed that the third correction coefficient is 1 (S19, Yes), the change unit 100c does not change the control signal shown in the first line La by the third correction coefficient (S20). That is, the calculation unit 100b defines the indicated current value shown in the first line La as the control signal output from the control device 100 to the operating valve 70 (S21). On the other hand, when it is confirmed that the third correction coefficient is not 1 (S19, No), the changing unit 100c multiplies the third correction coefficient by the command current value to change the control signal shown in the first line La (S22). When the changing unit 100c changes the control signal (S22), the arithmetic unit 100b defines the changed command current value as the control signal output from the control device 100 to the operating valve 70 (S23).

[0102] Further, the control device 100 can be switched between a plurality of modes, and the storage unit 100a may store a plurality of first functions M1 and a plurality of second functions M2 corresponding to the plurality of modes. FIG. 4C is a diagram showing an example of the first function M1 in a modified example in which the control device 100 can be switched between a plurality of modes for each of the plurality of modes. Further, FIG. 4D is a diagram showing an example of the second function M2 in the modified example for each of the plurality of modes. As shown in FIG. 4C, at least a part of the slopes of the plurality of first functions M1 are different from each other, and as shown in FIG. 4D, at least a part of the slopes of the plurality of second functions M2 are different from each other. The changing unit 100c calculates the first correction coefficient based on the first function M1 corresponding to the mode of the control device 100. Further, the changing unit 100c calculates the second correction coefficient based on the second function M2 corresponding to the mode of the control device 100.

[0103] That is, by switching the control device 100 between a plurality of modes, the changing unit 100c can change the control signal differently according to the mode. Hereinafter, a case where both the first function M1 and the second function M2 correspond to a plurality of modes and the storage unit 100a stores a plurality of first functions M1 and a plurality of second functions M2 will be described as an example. Note that only one of the first function M1 and the second function M2 may correspond to a plurality of modes. In such a case, the storage unit 100a stores a plurality of first functions M1 corresponding to a plurality of modes and a single second function M2 Alternatively, the storage unit 100a may store a single first function M1 and a plurality of second functions M2 corresponding to a plurality of modes. Further, the control device 100 may be able to separately switch each mode between a mode corresponding to a plurality of first functions M1 and a mode corresponding to a plurality of second functions M2. Also, the number of the plurality of first functions M1 and the number of the plurality of second functions M2 do not have to correspond, and their combination is not particularly limited, either.

[0104] As shown in FIG. 1, the work machine 1 includes a switching member (operating tool) 105. The switching member 105 is an operation switch that can be operated by an operator or the like and performs a mode switching operation of the control device 100. The switching member 105 is connected to the control device 100, is operated by an operator or the like, and inputs the operation signal to the control device 100. In the present embodiment, the switching member 105 is a display image displayed on the display device 110. The display device 110 is communicably connected to the control device 100 and is a device that displays various information related to the work machine 1 to assist in the traveling and work of the work machine 1. The display device 110 is, for example, a driving support device provided near the driver's seat 8. Also, the display device 110 is communicably connected to the devices included in the work machine 1 by wire or wirelessly and can transmit and receive information to and from each other.

[0105] FIG. 6 is a diagram showing an example of the switching screen D1 displayed by the display device 110 and the display unit 111 in a modified example. As shown in FIG. 6, the display device 110 has a display unit 111. The display unit 111 is composed of any one of a liquid crystal panel, a touch panel, and other panels, and can display various information for assisting in the traveling and work of the work machine 1. When an operator performs a predetermined operation, the display unit 111 displays a switching screen D1. The switching screen D1 displays a switching member 105. The switching member 105 has a plurality of selection buttons 105a and accepts operations by the operator. In the present embodiment, the operator touches and selects one selection button 105a among the plurality of selection buttons 105a displayed on the switching screen D1. When one selection button 105a is selected by the operator, the display device 110 outputs the operation information to the control device 100. In the present embodiment, the switching member 105 is the plurality of selection buttons 105a displayed on the display unit 111. However, the switching member 105 may be connected to the control device 100 and may be capable of switching modes. For example, it may be a dial connected to the control device 100 and having a plurality of switching positions, or a plurality of buttons.

[0106] Also, the display unit 111 can display which mode the control device 100 is in. FIG. 7 is a diagram for explaining the display device 110 in a modified example and the mode display unit 111a displayed on the display unit 111. For example, as shown in FIG. 7, in the screen D2 displayed by the display unit 111, a mode display unit 111a is displayed in the upper region d1. The mode display unit 111a displays the current mode of the control device 100 as a character string. In the example of FIG. 7, the current mode of the control device 100 is displayed as a character string. However, the display form is not limited to a character string. The display unit 111 may display the current mode of the control device 100 by an arbitrary graphic such as an icon.

[0107] In this embodiment, the control device 100 has a first mode, a second mode, and a third mode as a plurality of modes, and can switch between these modes. The first mode is a mode in which the feeling of the work machine 1 is enhanced when the actual rotational speed of the traveling motor 51 is relatively low. That is, the first mode is a mode in which when the actual rotational speed of the traveling motor 51 is relatively low, the horsepower consumption of the traveling pump 50 is further increased, and the engine rotational speed balanced with the discharge flow rate of the traveling pump 50 is made even lower. Further, the third mode is a mode that prioritizes suppression of engine stall over the feeling of the work machine 1. Note that the second mode is a mode positioned between the first mode and the third mode. Hereinafter, the first function M1 in a plurality of modes (the first to third modes) will be described.

[0108] FIG. 4C is a diagram showing an example of the first function M1 in a modification for each of a plurality of modes. As shown in FIG. 4C, in the plurality of first functions M1, as a part of the slope for each of the plurality of modes, the slope of the first section m1 is different. In FIG. 4C, the first section m1a of the first function M1 in the first mode is described by a solid line, the first section m1b of the first function M1 in the second mode is described by a one-dot chain line, and the first section m1c of the first function M1 in the third mode is described by a two-dot chain line. Also, in the plurality of first functions M1, the first correction coefficient when the actual rotational speed of the traveling motor 51 is the second threshold value Rm2 is the same value. In the plurality of first functions M1, the first correction coefficient when the actual rotational speed of the traveling motor 51 is the second threshold value Rm2 is the same value.

[0109] As shown in FIG. 4C, among the slopes of the first intervals m1 of the plurality of modes, the slope of the first mode is the largest and the slope of the third mode is the smallest. That is, the first correction coefficient of the first mode corrects the command current value so that the amount of change with respect to the actual rotation speed of the traveling motor 51 is the largest compared to the first correction coefficients of other modes, and the primary pressure of the operation valve 70 is relatively large compared to other modes. On the other hand, the first correction coefficient of the third mode corrects the command current value so that the amount of change with respect to the actual rotation speed of the traveling motor 51 is the smallest compared to the first correction coefficients of other modes, and the primary pressure of the operation valve 70 is relatively small compared to other modes. That is, in the present embodiment, when the actual rotation speed of the traveling motor 51 is the same, the first correction coefficient increases in the order of the third mode, the second mode, and the first mode.

[0110] In an example of the first function M1 corresponding to the first mode shown in FIG. 4C, the first correction coefficient when the actual rotation speed of the traveling motor 51 is the first lower limit value Rm1 is 1.6 (160%). Therefore, the first correction coefficient of the first interval m1a in the first mode decreases substantially linearly from 1.6 (160%) to 1.2 (120%) as the actual rotation speed of the traveling motor 51 increases, and increases substantially linearly from 1.2 (120%) to 1.6 (160%) as the actual rotation speed of the traveling motor 51 decreases.

[0111] Also, in an example of the first function M1 corresponding to the second mode shown in FIG. 4C, the first correction coefficient when the actual rotation speed of the traveling motor 51 is the first lower limit value Rm1 is 1.5 (150%). Therefore, the first correction coefficient of the first interval m1b in the third mode decreases substantially linearly from 1.5 (150%) to 1.2 (120%) as the actual rotation speed of the traveling motor 51 increases, and increases substantially linearly from 1.2 (120%) to 1.5 (150%) as the actual rotation speed of the traveling motor 51 decreases.

[0112] Then, in an example of the first function M1 corresponding to the third mode shown in FIG. 4C, when the actual rotational speed of the traveling motor 51 is the first lower limit value Rm1, the first correction coefficient is 1.4 (140%). Therefore, the first correction coefficient in the first section m1c in the third mode decreases substantially linearly from 1.4 (140%) to 1.2 (120%) as the actual rotational speed of the traveling motor 51 increases, and increases substantially linearly from 1.2 (120%) to 1.4 (140%) as the actual rotational speed of the traveling motor 51 decreases.

[0113] In the description of the plurality of modes, examples of the magnitudes of the values of the first correction coefficients are described respectively. However, the values are merely illustrative, and it is sufficient that the first correction coefficient is larger in at least the order of the third mode, the second mode, and the first mode. It may be such that it can be appropriately changed by operating an operation switch, a terminal, etc. connected to the control device 100. FIG. 4D is a diagram showing an example of the second function M2 in a modified example for each of a plurality of modes. As shown in FIG. 4D, for the plurality of second functions M2, as partial slopes for each of the plurality of modes, the slopes of the third section m3 are different. In FIG. 4D, the third section m3a of the second function M2 in the first mode is described by a solid line, the third section m3b of the second function M2 in the second mode is described by a one-dot chain line, and the third section m3c of the second function M2 in the third mode is described by a two-dot chain line. Also, in the plurality of second functions M2, the second correction coefficients are the same when the actual rotational speed of the prime mover 6 is the third threshold value Re2.

[0114] As shown in FIG. 4D, among the slopes of the third intervals m3 of the plurality of modes, the slope of the first mode is the smallest and the slope of the third mode is the largest. That is, the second correction coefficient of the first mode corrects the command current value so that the amount of change with respect to the actual rotational speed of the prime mover 6 is the smallest compared to the second correction coefficients of other modes, and the primary pressure of the operation valve 70 becomes relatively large compared to other modes. On the other hand, the second correction coefficient of the third mode corrects the command current value so that the amount of change with respect to the actual rotational speed of the prime mover 6 is the largest compared to the second correction coefficients of other modes, and the primary pressure of the operation valve 70 becomes relatively small compared to other modes. That is, in the present embodiment, when the actual rotational speed of the prime mover 6 is the same, the second correction coefficient becomes smaller in the order of the first mode, the second mode, and the third mode.

[0115] In an example of the second function M2 corresponding to the first mode shown in FIG. 4D, the second correction coefficient when the actual rotational speed of the prime mover 6 is the second lower limit value Re1 is 0.9 (90%). Therefore, the second correction coefficient of the third interval m3a in the first mode increases substantially linearly from 0.9 (90%) to 1.0 (100%) as the actual rotational speed of the prime mover 6 increases, and decreases substantially linearly from 1.0 (100%) to 0.9 (90%) as the actual rotational speed of the prime mover 6 decreases.

[0116] Further, in an example of the second function M2 corresponding to the second mode shown in FIG. 4D, the second correction coefficient when the actual rotational speed of the prime mover 6 is the second lower limit value Re1 is 0.8 (80%). Therefore, the second correction coefficient of the third interval m3b in the second mode increases substantially linearly from 0.8 (80%) to 1.0 (100%) as the actual rotational speed of the prime mover 6 increases, and decreases substantially linearly from 1.0 (100%) to 0.8 (70%) as the actual rotational speed of the prime mover 6 decreases.

[0117] Then, in an example of the second function M2 corresponding to the third mode shown in FIG. 4D, when the actual rotational speed of the prime mover 6 is the second lower limit value Re1, the second correction coefficient is 0.5 (50%). Therefore, the second correction coefficient in the third section m3c in the third mode increases substantially linearly from 0.5 (50%) to 1.0 (100%) as the actual rotational speed of the prime mover 6 increases, and decreases substantially linearly from 1.0 (100%) to 0.5 (50%) as the actual rotational speed of the prime mover 6 decreases.

[0118] In the description of a plurality of modes, examples of the magnitudes of the values of the second correction coefficient are described respectively. However, the values are merely illustrative, and it is only necessary that the first correction coefficient be smaller in the order of at least the first mode, the second mode, and the third mode. It may also be such that it can be appropriately changed by operating an operation switch, a terminal, etc. connected to the control device 100. FIG. 5C is an operation flow showing the flow of the operation in which the control device 100 in the second modification changes the control signal. Hereinafter, with reference to FIG. 5C, a series of flows for changing the control signal (command current value) when the control device 100 can switch between a plurality of modes will be described. In such a case, the flow of the operation in which the control device 100 corrects the control signal is different from the operation flow shown in FIG. 5A in that, as shown in FIG. 5C, S30 and S31 are performed instead of S8, and S32 is performed instead of S11. In the following description, the explanation will be centered on S30 to S31 and S32, and the explanation of the other steps will be omitted.

[0119] When the arithmetic unit 100b acquires the command current value corresponding to the actual rotational speed (S7), the changing unit 100c checks the current mode of the control device 100 (S30). Specifically, the changing unit 100c checks the current mode of the control device 100 based on the operation information of the switching member 105. When the changing unit 100c checks the current mode of the control device 100 (S30), it acquires the first function M1 corresponding to the current mode from the storage unit 100a (S31).

[0120] When the change unit 100c acquires the first function M1 from the storage unit 100a (S31), it calculates the actual rotational speed of the traveling motor 51 based on the detection signal detected by the first detection device 104 (S9). Also, when the change unit 100c calculates the first correction coefficient (S10), it acquires the second function M2 corresponding to the current mode from the storage unit 100a (S32).

[0121] When the change unit 100c acquires the second function M2 from the storage unit 100a (S32), it calculates the second correction coefficient by substituting the actual rotational speed of the prime mover 6 into the second function M2 (S12). In the above-described embodiment, the operation valve 70 was provided on the upstream side (discharge oil passage 40) of the control valve 56. Instead, the operation valve 70 may be provided, for example, in the middle of the fifth traveling oil passage 42e.

[0122] Alternatively, as shown in FIG. 8, the operation valve 70 may be provided in the traveling oil passage 42 connected to the traveling pump 50 (first traveling pump 50L, second traveling pump 50R). Specifically, an oil passage 44 is branched from each of the first traveling oil passage 42a, the second traveling oil passage 42b, the third traveling oil passage 42c, and the fourth traveling oil passage 42d, and an operation valve 70 such as a variable relief valve or an electromagnetic proportional valve is provided in the oil passage 44, and the opening degree of the operation valve 70 may be controlled by the first control signal and the second control signal.

[0123] Also, in the above-described embodiment, the operating device 54 was a hydraulic type that changes the pilot pressure acting on the traveling pump 50 (first traveling pump 50L, second traveling pump 50R) by the control valve 56. However, as shown in FIG. 9, the operating device 54 may be an electrically operated device. As shown in FIG. 9, the operation device 54 includes an operation member 55 that swings in the left - right direction (machine body width direction) or the front - rear direction, and an operation valve 56 (a first pilot valve 56a, a second pilot valve 56b, a third pilot valve 56c, a fourth pilot valve 56d) composed of electromagnetic proportional valves. A control device 100 is connected to an operation detection sensor that detects the operation amount and operation direction of the operation member 55. The control device 100 controls the operation valve 56 (the first pilot valve 56a, the second pilot valve 56b, the third pilot valve 56c, the fourth pilot valve 56d) based on the operation amount and operation direction detected by the operation detection sensor.

[0124] When the operation member 55 is operated forward (in the A1 direction, see FIG. 1), the control device 100 outputs a control signal to the first pilot valve 56a and the third pilot valve 56c, and swings the swash plates of the first travel pump 50L and the second travel pump 50R in the forward rotation (forward movement) direction. When the operation member 55 is operated rearward (in the A2 direction, see FIG. 1), the control device 100 outputs a control signal to the second pilot valve 56b and the fourth pilot valve 56d, and swings the swash plates of the first travel pump 50L and the second travel pump 50R in the reverse rotation (backward movement) direction.

[0125] When the operation member 55 is operated leftward (in the A3 direction, see FIG. 1), the control device 100 outputs a control signal to the second pilot valve 56b and the third pilot valve 56c, swings the swash plate of the first travel pump 50L in the reverse rotation direction, and swings the swash plate of the second travel pump 50R in the forward rotation direction. When the operation member 55 is operated rightward (in the A4 direction, see FIG. 1), the control device 100 outputs a control signal to the first pilot valve 56a and the fourth pilot valve 56d, swings the swash plate of the first travel pump 50L in the forward rotation direction, and swings the swash plate of the second travel pump 50R in the reverse rotation direction.

[0126] The above-described work machine 1 includes a prime mover 6, a travel pump 50 that is operated by the power of the prime mover 6 and discharges hydraulic oil, a travel motor 51 that is rotatable by the hydraulic oil discharged by the travel pump 50, an operation valve 56 that can change the pilot pressure of the pilot oil output to the travel pump 50 according to the operation of an operation member 55, an operation valve 70 that is operated by a control signal and can change the primary pressure, which is the pilot pressure of the pilot oil supplied to the operation valve 56, a control device 100 that outputs a control signal to the operation valve 70 to control the opening degree of the operation valve 70, and a first detection device 104 that detects the actual rotational speed of the travel motor 51. The control device 100 has a changing unit 100c that changes the setting of the control signal so that the opening degree of the operation valve 70 increases as the actual rotational speed of the travel motor 51 decreases. According to the above configuration, the control device 100 can change the setting of the control signal output to the operation valve 70 based on the actual rotational speed of the travel motor 51 by the changing unit 100c. Therefore, the control device 100 can change the primary pressure, which is the pilot pressure of the pilot oil supplied by the operation valve 70 to the operation valve 56, based on the actual rotational speed of the travel motor 51. As a result, the work machine 1 can give the operator a feeling that the work machine 1 is working sufficiently according to the actual rotational speed of the travel motor 51.

[0127] The working machine 1 also includes a rotational speed operating tool 102 for operating the target rotational speed of the prime mover 6, a second detection device 103 for detecting the actual rotational speed of the prime mover 6, a first line La that defines a control signal based on the actual rotational speed of the prime mover 6 when the difference between the target rotational speed and the actual rotational speed of the prime mover 6 is equal to or greater than a first threshold value, and a second line Lb that defines a control signal to be greater than the first line La when the difference between the target rotational speed and the actual rotational speed of the prime mover 6 is less than the first threshold value. The storage unit 100a stores these. The changing unit 100c changes the first line La by changing the control signal indicated by the first line La such that the opening degree of the operation valve 70 increases as the actual rotational speed of the traveling motor 51 decreases. According to the above configuration, the changing unit 100c can appropriately change the setting of the control signal output to the operation valve 70 based on the actual rotational speed of the traveling motor 51 in two cases: when the load on the prime mover 6 is a low load (the difference between the target rotational speed and the actual rotational speed is less than the first threshold value), and when the load on the prime mover 6 is a high load (the difference between the target rotational speed and the actual rotational speed is equal to or greater than the first threshold value).

[0128] Further, the changing unit 100c changes the control signal indicated by the first line La based on a first correction coefficient defined corresponding to the actual rotational speed of the traveling motor 51. According to the above configuration, the changing unit 100c can use the first correction coefficient defined corresponding to the actual rotational speed of the traveling motor 51 to change the setting of the control signal output to the operation valve 70, so that the control signal can be changed easily and appropriately.

[0129] The storage unit 100a stores a first function M1 that defines the relationship between the actual rotational speed of the traveling motor 51 and the first correction coefficient. The changing unit 100c calculates the first correction coefficient by substituting the actual rotational speed of the traveling motor 51 detected by the first detection device 104 into the first function M1. According to the above configuration, the changing unit 100c can easily and accurately calculate the correction coefficient by using the function that defines the relationship between the actual rotational speed of the traveling motor 51 and the first correction coefficient.

[0130] Further, the first function M1 defines the first correction coefficient with a value of 1 or more, and the first correction coefficient corresponding to the second rotation speed, which is the actual rotation speed of the travel motor 51 and is smaller than the first rotation speed, is larger than the first correction coefficient corresponding to the first rotation speed, which is the actual rotation speed of the travel motor 51. According to the above configuration, since the first correction coefficient is defined with a value of 1 or more, the changing unit 100c can increase the power consumption of the travel pump 50 by changing the first line La in the direction of increasing the primary pressure output from the operation valve 70. In particular, when the actual rotation speed of the travel motor 51 is relatively low, the changing unit 100c can increase the power consumption of the travel pump 50 and can lower the engine rotation speed that balances with the discharge flow rate of the travel pump 50. Thereby, the control device 100 can prevent the phenomenon of the engine 6 stalling in terms of rotation speed, prevent the decrease in the traveling force in the high rotation range, and give the operator a feeling that the work implement 1 is working sufficiently. Also, even when the traveling load increases, the work can be continued by increasing the discharge flow rate of the travel pump 50.

[0131] Further, the first function M1 has different slopes based on the second threshold value Rm2 of the actual rotation speed of the travel motor 51, and the slope when the actual rotation speed of the travel motor 51 is equal to or less than the second threshold value Rm2 is defined to be larger than the slope when the actual rotation speed of the travel motor 51 is equal to or higher than the second threshold value Rm2. According to the above configuration, when the actual rotation speed of the travel motor 51 is relatively low, such as in an operation like earth pushing, the changing unit 100c can increase the output of the travel pump 50, thereby increasing the power consumption of the travel pump 50. Therefore, the balanced engine rotation speed can be lowered, and the operator can be given a feeling that the work implement 1 is working sufficiently.

[0132] Further, the control device 100 is switchable between a plurality of modes. The storage unit 100a stores a plurality of first functions M1 with at least some slopes different corresponding to the plurality of modes. The modification unit 100c calculates a first correction coefficient based on the first function M1 corresponding to the mode of the control device 100. According to the above configuration, the control device 100 can change the mode according to the priorities such as suppression of engine stall, feeling, and running force.

[0133] Further, in addition to the first correction coefficient, the modification unit 100c changes the control signal shown in the first line La based on a second correction coefficient defined corresponding to the actual rotational speed of the prime mover 6. According to the above configuration, the modification unit 100c can change the setting of the control signal output to the operation valve 70 using the second correction coefficient defined corresponding to the actual rotational speed of the prime mover 6, and can change the control signal easily and appropriately.

[0134] Further, the storage unit 100a stores a second function M2 that defines the relationship between the actual rotational speed of the prime mover 6 and the second correction coefficient. The modification unit 100c calculates the second correction coefficient by substituting the actual rotational speed of the prime mover 6 detected by the second detection device 103 into the second function M2. According to the above configuration, the modification unit 100c can calculate the correction coefficient easily and accurately by using the function that defines the relationship between the actual rotational speed of the prime mover 6 and the second correction coefficient.

[0135] Further, when the actual rotational speed of the prime mover 6 is equal to or higher than the third threshold value Re2, the second function M2 defines the second correction coefficient as 1, and when the actual rotational speed of the prime mover 6 is less than the third threshold value Re2, the second correction coefficient is defined as a value less than 1. According to the above configuration, when the rotational speed of the prime mover 6 is less than the third threshold value Re2 and is relatively low, the modification unit 100c can change the first line La in the direction in which the primary pressure output from the operation valve 70 decreases. Thereby, the output of the travel pump 50 can be reduced, and engine stall can be prevented.

[0136] In addition, the control device 100 can be switched among a plurality of modes, and the storage unit 100a stores a plurality of second functions M2 with at least some slopes being different corresponding to the plurality of modes. The changing unit 100c calculates a second correction coefficient based on the second function M2 corresponding to the mode of the control device 100. According to the above configuration, the control device 100 can change the mode according to the priorities such as suppression of engine stall, feeling, and driving force.

[0137] In addition, the changing unit 100c calculates a third correction coefficient based on the product of the first correction coefficient and the second correction coefficient, and changes the control signal indicated by the first line La when the third correction coefficient exceeds 1, and does not change the control signal indicated by the first line La when the third correction coefficient is 1 or less. According to the above configuration, it is possible to prevent the changing unit 100c from excessively changing the first line La in the direction in which the primary pressure output from the operating valve 70 decreases. That is, when the actual rotational speed of the prime mover 6 is less than the third threshold value Re2, it is possible to prevent the driving force of the traveling motor 51 from decreasing excessively by the changing unit 100c changing the first line La.

[0138] As described above, the present invention has been described, but 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 Signs

[0139] 1 Working machine 6 Prime mover 50 Traveling pump 51 Traveling motor 55 Operating member 56 Operating valve 70 Operating valve 100 Control device 100a Storage unit 100c Changing unit 103 Second detection device 104 First detection device La First line Lb Second line M1 First function M2 Second function Re2 Third threshold value Rm2 Second threshold value

Claims

1. A prime mover, a traveling pump that is operated by the power of the prime mover and discharges hydraulic oil, a traveling motor that is rotatable by the hydraulic oil discharged by the traveling pump, an operation valve capable of changing the pilot pressure of the pilot oil output to the traveling pump in response to the operation of an operation member, an operation valve that is operated by a control signal and is capable of changing a primary pressure that is the pilot pressure of the pilot oil supplied to the operation valve, a first detection device that detects the actual rotational speed of the traveling motor, a rotational speed operation tool that operates the target rotational speed of the prime mover, a second detection device that detects the actual rotational speed of the prime mover, a control device that, when the difference between the target rotational speed and the actual rotational speed of the prime mover is equal to or greater than a first threshold value, outputs the control signal based on a first line to the operation valve, and when the difference between the target rotational speed and the actual rotational speed of the prime mover is less than the first threshold value, outputs the control signal greater than the first line to the operation valve based on a second line to control the opening degree of the operation valve, and comprising, the control device has a changing unit that changes the setting of the control signal so that the opening degree of the operation valve increases as the actual rotational speed of the traveling motor decreases when the difference between the target rotational speed and the actual rotational speed of the prime mover is equal to or greater than the first threshold value. A working machine.

2. The working machine according to claim 1, further comprising a storage unit that stores the first line and the second line, wherein the changing unit changes the first line by changing the control signal indicated by the first line so that the opening degree of the operation valve increases as the actual rotational speed of the traveling motor decreases.

3. The working machine according to claim 2, wherein the changing unit changes the control signal indicated by the first line based on a first correction coefficient defined corresponding to the actual rotational speed of the traveling motor.

4. The storage unit stores a first function that defines the relationship between the actual rotational speed of the traveling motor and the first correction coefficient, The working machine according to claim 3, wherein the changing unit calculates the first correction coefficient by substituting the actual rotational speed of the traveling motor detected by the first detection device into the first function.

5. The first function defines the first correction coefficient with a value of 1 or more, and the first correction coefficient corresponding to a second rotation speed that is the actual rotation speed of the traveling motor and is smaller than the first rotation speed is larger than the first correction coefficient corresponding to the first rotation speed which is the actual rotation speed of the traveling motor. The work machine according to claim 4.

6. The first function has different slopes based on a second threshold value of the actual rotation speed of the traveling motor, and the slope below the second threshold value is defined to be larger than the slope when the actual rotation speed of the traveling motor is equal to or higher than the second threshold value. The work machine according to claim 5.

7. The control device is switchable between a plurality of modes, The storage unit stores a plurality of the first functions with at least partially different slopes corresponding to the plurality of modes, The changing unit calculates the first correction coefficient based on the first function corresponding to the mode of the control device. The work machine according to any one of claims 4 to 6.

8. In addition to the first correction coefficient, the changing unit Changes the control signal shown in the first line based on a second correction coefficient defined corresponding to the actual rotation speed of the prime mover. The work machine according to any one of claims 3 to 7.

9. The storage unit stores a second function defining the relationship between the actual rotation speed of the prime mover and the second correction coefficient, The changing unit calculates the second correction coefficient by substituting the actual rotation speed of the prime mover detected by the second detection device into the second function. The work machine according to claim 8.

10. When the actual rotation speed of the prime mover is equal to or higher than a third threshold value, the second function defines the second correction coefficient as 1, and when the actual rotation speed of the prime mover is less than the third threshold value, the second correction coefficient is defined with a value less than 1. The work machine according to claim 9.

11. The control device is switchable between a plurality of modes, The storage unit stores a plurality of the second functions with at least partially different slopes corresponding to the plurality of modes, The changing unit calculates the second correction coefficient based on the second function corresponding to the mode of the control device. The work machine according to claim 9 or 10.

12. The modification unit calculates a third correction coefficient based on the product of the first correction coefficient and the second correction coefficient, and when the third correction coefficient exceeds 1, changes the control signal shown in the first line, and when the third correction coefficient is 1 or less, does not change the control signal shown in the first line. The working machine according to any one of claims 8 to 11.

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