JP2022033083A - Work machine - Google Patents

Abstract

To give a worker such a feeling that a work machine sufficiently works by preventing reduction in the travel force in a high rotation area while preventing a phenomenon in which an engine speed stops at a high level.SOLUTION: A work machine comprises: an engine; a travel pump which actuates with the power of the engine and discharges hydraulic oil; a travel motor which can rotate with the hydraulic oil discharged by the travel pump; an operation valve which can change the pilot pressure of pilot oil output to the travel pump according to the operation of the operation member; an actuation valve which can actuate with a control signal and change the primary pressure being the pilot pressure of the pilot oil supplied to the operation valve; a control device which sets the control signal output to the actuation valve; a circulation oil passage which connects the travel pump with the travel motor; and a pressure detection device which detects the travel pressure being the pressure of the hydraulic oil of the circulation oil passage. The control device includes a setting change part which changes the setting of the control signal output to the actuation valve on the basis of the travel pressure.SELECTED DRAWING: Figure 5

Description

The present invention relates to working machines such as skid steer loaders and compact truck loaders.

Conventionally, the technique shown in Patent Document 1 is known as a technique for preventing an engine stall in a working machine such as a skid steer loader or a compact truck loader.
The working machine disclosed in Patent Document 1 controls an engine, an HST pump driven by the power of the engine, a traveling operation device for operating the HST pump, and a traveling primary side pressure which is the pressure on the primary side of the traveling operation device. It is equipped with a pressure control valve and a control device for controlling the pressure control valve.

In the control device, the engine stall is performed by controlling the pressure control valve based on the no-load characteristic line adopted when the load is no load and the drop characteristic line adopted when a load exceeding a predetermined value is applied to the engine. It is preventing. In other words, when a traveling load exceeding a predetermined value is applied to the work equipment, the pressure control valve is controlled to sharply reduce the pressure on the primary traveling side to minimize the drop in engine speed, thereby causing engine stall. We are trying to prevent it.

Japanese Unexamined Patent Publication No. 2013-36274

In the disclosed technology of Patent Document 1, excessive engine drop is suppressed by lowering the output of the pressure control valve in order to secure the climbing speed in the medium rotation speed range of the engine, and an appropriate engine rotation speed (medium rotation speed range). The vehicle speed is secured by maintaining. However, in the high engine speed range, the output of the pressure control valve is set high in order to prevent the high engine speed stop phenomenon (the phenomenon that the output horsepower of the engine exceeds the horsepower consumed by the HST pump and the engine hardly drops). There is a need. When the phenomenon of high engine speed staying occurs, the worker is given a feeling that the work machine is not working sufficiently (the machine suppresses the horsepower against the operation of the worker).

In order to solve the above problem, it is necessary to lower the output of the pressure control valve in the middle rotation range of the engine and set the output of the pressure control valve high in the high rotation range of the engine. However, if the output difference of the pressure control valve is made extremely large (the slope of the output of the pressure control valve is suddenly set with respect to the engine speed) in the medium and high speed regions of the engine, the engine speed will be controlled. There is a concern that hunting will occur.

Therefore, it is conceivable to set the output in the middle rpm range of the engine in order to prioritize the climbing speed, and then set the high rpm range within the range where hunting does not occur. In this case, the phenomenon that the engine speed remains high can be prevented, but the running force in the high speed range tends to decrease. In particular, in work involving the opening of the traveling relief valve such as earth pushing, the discharge flow rate of the HST pump (horsepower consumed by the HST pump) decreases due to the influence of the swash plate characteristics of the HST pump, and the balanced engine speed increases. Give the worker the feeling that the work machine is not doing enough work.

INDUSTRIAL APPLICABILITY The present invention can prevent a decrease in running force in a high rotation speed range while preventing a phenomenon that the engine speed remains high, and can give an operator a feeling that the work machine is working sufficiently. The purpose is to provide a working machine.

The technical means taken by the present invention to solve the above technical problems is characterized by the following points.
The working machine according to one aspect of the present invention includes a prime mover, a traveling pump that is operated by the power of the prime mover and discharges hydraulic oil, a traveling motor that can be rotated by the hydraulic oil discharged by the traveling pump, and an operating member. An operation valve that can change the pilot pressure of the pilot oil output to the traveling pump according to the operation, and an operation that can change the primary pressure that is the pilot pressure of the pilot oil that is operated by the control signal and supplied to the operation valve. A valve, a control device for setting the control signal to be output to the operating valve, a circulating oil passage connecting the traveling pump and the traveling motor, and a traveling pressure which is the pressure of the hydraulic oil in the circulating oil passage are detected. The control device includes a pressure detecting device for changing the setting of a control signal output to the operating valve based on the traveling pressure.

Further, when the accelerator for setting the target rotation speed of the prime mover, the rotation detection device for detecting the actual rotation speed of the prime mover, and the difference between the target rotation speed and the actual rotation speed is equal to or more than the first threshold value, the said. When the difference between the first line for setting the control signal based on the actual rotation speed and the target rotation speed and the actual rotation speed is less than the first threshold value, the control signal is set larger than the first line. The setting changing unit includes a second line and a storage unit for storing the first line, and the setting changing unit changes the control signal shown in the first line based on the traveling pressure to change the first line. change.

Further, the operating valve is an electromagnetic proportional valve that increases the opening degree in proportion to the magnitude of the current value, and the setting changing unit is the operating valve when the traveling pressure becomes the second threshold value or more. The first line is changed in the direction in which the primary pressure output from is increased.
Further, the operating valve is an electromagnetic proportional valve that increases the opening degree in proportion to the magnitude of the current value, and the setting changing unit is the operating valve when the traveling pressure becomes the second threshold value or more. The first line is changed so that the primary pressure output from is smaller.

The setting change unit ends the change of the first line when the running pressure becomes equal to or less than the third threshold value smaller than the second threshold value.
When the setting change unit finishes the change of the first line, the setting change unit gradually returns the control signal to the value before the change of the first line.
Further, the setting changing unit changes the setting of the control signal output to the operating valve based on the correction coefficient set corresponding to the value of the traveling pressure.

Further, the storage unit stores a function that defines the relationship between the traveling pressure and the correction coefficient, and the setting changing unit corrects the traveling pressure by substituting the traveling pressure detected by the pressure detecting device into the function. Calculate the coefficient.

According to the present invention, it is possible to prevent a decrease in running force in a high rotation speed range while preventing a phenomenon that the engine speed remains high, and to give a worker a feeling that the work machine is working sufficiently. Can be done.

It is a figure which shows the hydraulic system (hydraulic circuit) of a work machine. It is a figure which showed an example of the correspondence relation between a control signal (indicating current value) and a primary pressure. It is a figure which showed an example of the setting line which sets the control signal (primary pressure) output to the operation valve based on the actual rotation speed of a prime mover. This is an operation flow for changing the first line in the control device. It is a figure which showed an example of the correction function which defined the relationship between a running pressure and a correction coefficient. It is a figure which shows an example of the case where the operation valve is provided on the secondary side of the operation valve. It is a figure which shows the modification which changed the operation device into the operation device which operates electrically, such as a joystick. It is a side view which shows the truck loader which is an example of a working machine.

Hereinafter, suitable embodiments of the working machine according to the present invention will be described with reference to the drawings as appropriate.
FIG. 8 shows a side view of the working machine according to the present invention. FIG. 8 shows a compact truck loader as an example of a working machine. However, the working machine according to the present invention is not limited to the compact truck loader, and may be, for example, another type of loader working machine such as a skid steer loader. Further, it may be a working machine other than the loader working machine.

As shown in FIG. 8, 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 front side (left side of FIG. 8) of the driver seated in the driver's seat 8 of the work machine 1 is the front, the rear side of the driver (right side of FIG. 8) is the rear, and the left side of the driver (FIG. 8). The front side of No. 8) will be described as the left side, and the right side of the driver (the back side of FIG. 8) will be described as the right side. Further, the horizontal direction, which is a direction orthogonal to the front-rear direction, will be described as the body width direction.

The cabin 3 is mounted on the airframe 2. The cabin 3 is provided with a driver's seat 8. The working device 4 is attached to the machine body 2. A motor 32 is mounted on the rear portion of the machine body 2. The traveling device 5 is provided on the outside of the machine body 2. The traveling device 5 includes a first traveling device 5L provided on the left side of the machine body 2 and a second traveling device 5R provided on the right side of the machine body 2.

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 boom 10 is provided on the right side and the left side of the cabin 3 so as to be vertically swingable. The work tool 11 is, for example, a bucket, and the bucket 11 is provided at the tip end portion (front end portion) of the boom 10 so as to be vertically swingable. The lift link 12 and the control link 13 support the base (rear portion) of the boom 10 so that the boom 10 can swing up and down. The boom cylinder 14 expands and contracts to raise and lower the boom 10. The bucket cylinder 15 swings the bucket 11 by expanding and contracting.

The front parts of the left and right booms 10 are connected to each other by a deformed connecting pipe. The bases (rear parts) of the booms 10 are connected to each other by a circular connecting pipe.
The lift link 12, the control link 13, and the boom cylinder 14 are provided on the left side and the right side of the machine body 2, respectively, corresponding to the left and right booms 10.
The lift link 12 is provided vertically at the rear of the base of each boom 10. The upper part (one end side) of the lift link 12 is rotatably and rotatably supported around the horizontal axis via the pivot shaft 16 (the pivot shaft) toward the rear portion of the base of each boom 10. Further, the lower portion (the other end side) of the lift link 12 is rotatably supported around the horizontal axis via the pivot shaft 17 (the pivot shaft) toward the rear portion of the machine body 2. The pivot shaft 17 is provided below the pivot shaft 16.

The upper portion of the boom cylinder 14 is rotatably supported around the horizontal axis via the pivot shaft 18 (the pivot shaft). The pivot shaft 18 is the base of each boom 10 and is provided at the front of the base. The lower portion of the boom cylinder 14 is rotatably supported around a horizontal axis via a pivot shaft 19 (a pivot shaft). The pivot shaft 19 is provided near the lower part of the rear part of the machine body 2 and below the pivot shaft 18.

The control link 13 is provided in front of the lift link 12. One end of the control link 13 is rotatably supported around the horizontal axis via the pivot shaft 20 (the pivot shaft). The pivot shaft 20 is the airframe 2, and is provided at a position corresponding to the front of the lift link 12. The other end of the control link 13 is rotatably supported around the horizontal axis via the pivot shaft 21 (the pivot shaft). The pivot shaft 21 is a boom 10 and is provided in front of the pivot shaft 17 and above the pivot shaft 17.

By expanding and contracting the boom cylinder 14, each boom 10 swings up and down around the pivot shaft 16 while the base of each boom 10 is supported by the lift link 12 and the control link 13, and the tip of each boom 10 moves up and down. do. The control link 13 swings up and down around the pivot shaft 20 as each boom 10 swings up and down. The lift link 12 swings back and forth around the pivot shaft 17 as the control link 13 swings up and down.

Another work tool can be attached to the front of the boom 10 instead of the bucket 11. Another working tool is, for example, an attachment (spare attachment) such as a hydraulic crusher, a hydraulic breaker, an angle bloom, an earth auger, a pallet fork, a sweeper, a mower, or a snow blower.
A connecting member 50 is provided at the front of the boom 10 on the left side. The connecting member 50 is a device for connecting the hydraulic device equipped in the spare attachment and the first pipe material such as a pipe provided in the boom 10. Specifically, the first pipe material can be connected to one end of the connecting member 50.
A second pipe material connected to the hydraulic equipment of the spare attachment can be connected to the other end. As a result, the hydraulic oil flowing through the first pipe material passes through the second pipe material and is supplied to the hydraulic equipment.

The bucket cylinder 15 is arranged near the front of each boom 10. By expanding and contracting the bucket cylinder 15, the bucket 11 is swung.
As each of the left and right traveling devices 5 (first traveling device 5L, second traveling device 5R), a crawler type (including a semi-crawler type) traveling device is adopted in the present embodiment. A wheel-type traveling device having front wheels and rear wheels may be adopted.

The prime mover 32 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 32 is, but is not limited to, a diesel engine.
Next, the hydraulic system of the working machine 1 will be described.
The hydraulic system of the working machine 1 shown in FIG. 1 can drive the traveling device 5. The hydraulic system of the working machine 1 includes a first traveling pump 53L, a second traveling pump 53R, a first traveling motor 36L, and a second traveling motor 36R.

The first traveling pump 53L and the second traveling pump 53R are pumps driven by the power of the prime mover 32. Specifically, the first traveling pump 53L and the second traveling pump 53R are swash plate type variable displacement axial pumps driven by the power of the prime mover 32. The first traveling pump 53L and the second traveling pump 53R have a forward pressure receiving portion 53a on which a pilot pressure acts and a reverse pressure receiving portion 53b, and the swash plate is subjected to the pilot pressure acting on the pressure receiving portions 53a and 53b. The angle is changed. By changing the angle of the slab, the output (discharge amount of hydraulic oil) and the discharge direction of the hydraulic oil of the first traveling pump 53L and the second traveling pump 53R can be changed.

The first traveling pump 53L and the first traveling motor 36L are connected by a circulating oil passage 57h, and the hydraulic oil discharged by the first traveling pump 53L is supplied to the first traveling motor 36L. The second traveling pump 53R and the second traveling motor 36R are connected by a circulating oil passage 57i, and the hydraulic oil discharged by the second traveling pump 53R is supplied to the second traveling motor 36R.
The first traveling motor 36L is a motor that transmits power to the drive shaft of the traveling device 5 provided on the left side of the machine body 2. The first traveling motor 36L can be rotated by the hydraulic oil discharged from the first traveling pump 53L, and the rotation speed (rotational speed) can be changed by the flow rate of the hydraulic oil. A swash plate switching cylinder 37L is connected to the first traveling motor 36L, and the rotation speed (rotation speed) of the first traveling motor 36L can be changed by expanding and contracting the swash plate switching cylinder 37L to one side or the other side. Can be done. That is, when the swash plate switching cylinder 37L is contracted, the rotation speed of the first traveling motor 36L is set to a low speed (first speed), and when the swash plate switching cylinder 37L is extended, the first traveling motor 36L is set. The rotation speed of is set to high speed (second speed). That is, the rotation speed of the first traveling motor 36L can be changed between the first speed on the low speed side and the second speed on the high speed side.

The second traveling motor 36R is a motor that transmits power to the drive shaft of the traveling device 5 provided on the right side of the machine body 2. The second traveling motor 36R can be rotated by the hydraulic oil discharged from the second traveling pump 53R, and the rotation speed (rotational speed) can be changed by the flow rate of the hydraulic oil. A swash plate switching cylinder 37R is connected to the second traveling motor 36R, and the rotation speed (rotation speed) of the second traveling motor 36R can be changed by expanding and contracting the swash plate switching cylinder 37R to one side or the other side. Can be done. That is, when the swash plate switching cylinder 37R is contracted, the rotation speed of the second traveling motor 36R is set to a low speed (first speed), and when the swash plate switching cylinder 37R is extended, the second traveling motor 36R is set. The rotation speed of is set to high speed (second speed). That is, the rotation speed of the second traveling motor 36R can be changed between the first speed on the low speed side and the second speed on the high speed side.

As shown in FIG. 1, the hydraulic system of the working machine includes a traveling switching valve 34. The travel switching valve 34 switches between a first state in which the rotation speed (rotation speed) of the travel motors (first travel motor 36L, second travel motor 36R) is set to the first speed and a second state in which the travel speed is set to the second speed. It is possible. The traveling switching valve 34 has a first switching valve 71L, 71R and a second switching valve 72.
The first switching valve 71L is a two-position switching valve that is connected to the swash plate switching cylinder 37L of the first traveling motor 36L via an oil passage and switches between the first position 71L1 and the second position 71L2. The first switching valve 71L contracts the swash plate switching cylinder 37L when it is in the first position 71L1, and expands the swash plate switching cylinder 37L when it is in the second position 71L2.

The first switching valve 71R is a two-position switching valve that is connected to the swash plate switching cylinder 37R of the second traveling motor 36R via an oil passage and switches to the first position 71R1 and the second position 71R2. The first switching valve 71R contracts the swash plate switching cylinder 37R at the first position 71R1 and expands the swash plate switching cylinder 37R at the second position 71R2.
The second switching valve 72 is a solenoid valve that switches between the first switching valve 71L and the first switching valve 71R, and is a two-position switching valve that can be switched between the first position 72a and the second position 72b by excitation. The second switching valve 72, the first switching valve 71L, and the first switching valve 71R are connected by an oil passage 41. The second switching valve 72 switches the first switching valve 71L and the first switching valve 71R to the first positions 71L1 and 71R1 when it is in the first position 72a, and the first switching valve 71L and when it is in the second position 72b. The first switching valve 71R is switched to the second positions 71L2 and 71R2.

That is, when the second switching valve 72 is in the first position 72a, the first switching valve 71L is in the first position 71L1, and the first switching valve 71R is in the first position 71R1, the traveling switching valve 34 is in the first state. The rotation speed of the traveling motors (first traveling motor 36L, second traveling motor 36R) is set to the first speed. When the second switching valve 72 is in the second position 72b, the first switching valve 71L is in the second position 71L2, and the first switching valve 71R is in the second position 71R2, the traveling switching valve 34 is in the second state and the traveling motor. The rotation speed of (first traveling motor 36L, second traveling motor 36R) is set to the second speed.

Therefore, the traveling switching valve 34 can switch the traveling motor (first traveling motor 36L, second traveling motor 36R) between the first speed on the low speed side and the second speed on the high speed side.
The hydraulic system of the working machine includes a first hydraulic pump P1, a second hydraulic pump P2, and an operating device 54. The first hydraulic pump P1 is a pump driven by the power of the prime mover 32, and is composed of a constant capacity type gear pump. The first hydraulic pump P1 can discharge the hydraulic oil stored in the tank 22. In particular, the first hydraulic pump P1 discharges hydraulic oil mainly used for control. For convenience of explanation, the tank 22 for storing the hydraulic oil may be referred to as a hydraulic oil tank. Further, among the hydraulic oil discharged from the first hydraulic pump P1, the hydraulic oil used for control may be referred to as pilot oil, and the pressure of the pilot oil may be referred to as pilot pressure.

The second hydraulic pump P2 is a pump driven by the power of the prime mover 32, and is composed of a constant capacity type gear pump. The second hydraulic pump P2 can discharge the hydraulic oil stored in the tank 22, and supplies the hydraulic oil to, for example, the oil passage of the working system. For example, the second hydraulic pump P2 supplies hydraulic oil to the boom cylinder 14 that operates the boom 10, the bucket cylinder 15 that operates the bucket, and the control valve (flow control valve) that controls the preliminary hydraulic actuator that operates the preliminary hydraulic actuator. do.

The operating device 54 is a device for operating the traveling pump (first traveling pump 53L, second traveling pump 53R), and the angle of the swash plate of the traveling pump (swash plate angle) can be changed. The operating device 54 includes an operating member 59 and a plurality of operating valves 55.
The operating member 59 is an operating lever 59 that is supported by the operating valve 55 and swings in the left-right direction (body width direction) or in the front-rear direction. The operating lever 59 can be operated to the right and left from the neutral position N and can be operated forward and backward from the neutral position N with respect to the neutral position N. In other words, the operating lever 59 can swing in at least four directions with respect to the neutral position N. For convenience of explanation, the front and rear directions, that is, the front-back direction is referred to as the first direction. Further, the bidirectional direction between the right side and the left side, that is, the left-right direction (airframe width direction) may be referred to as the second direction.

Further, the plurality of operating valves 55 are commonly operated, that is, operated by one operating lever 59. The plurality of operating valves 55 operate based on the swing of the operating lever 59. A discharge oil passage 40 is connected to the plurality of operation valves 55, and hydraulic oil (pilot oil) from the first hydraulic pump P1 can be supplied via the discharge oil passage 40. The discharge oil passage 40 is an oil passage connecting the operation valve 55 and the operation valve 67.

The plurality of operating valves 55 are an operating valve 55A, an operating valve 55B, an operating valve 55C, and an operating valve 55D. The operation valve 55A is operated to output according to the operation amount (operation) of the previous operation when the operation lever 59 is swung forward (one side) in the front-rear direction (first direction) (when the operation lever 59 is operated forward). The pressure of the oil changes. The operation valve 55B is operated to output according to the operation amount (operation) of the rear operation when the operation lever 59 is swung backward (the other) in the front-rear direction (first direction) (when the operation lever 59 is rear-operated). The pressure of the oil changes. In the left-right direction (second direction), the operation valve 55C outputs when the operation lever 59 swings to the right (one side) (when the operation lever 59 is operated to the right) according to the operation amount (operation) of the right operation. The pressure of the hydraulic oil changes. The operation valve 55D outputs according to the operation amount (operation) of the left operation when the operation lever 59 is swung to the left (the other) in the left-right direction (second direction) (when the operation lever 59 is operated to the left). The pressure of the hydraulic fluid changes.

The operation valve 55 can change the pilot pressure of the pilot oil to be output to the traveling pumps (first traveling pump 53L, second traveling pump 53R) according to the operation of the operating lever (operating member) 59. The plurality of operating valves 55 and the traveling pumps (first traveling pump 53L, second traveling pump 53R) are connected by a traveling oil passage 45. In other words, the traveling pump (first traveling pump 53L, second traveling pump 53R) is hydraulic pressure that can be operated by the hydraulic oil output from the operating valve 55 (operating valve 55A, operating valve 55B, operating valve 55C, operating valve 55D). It is a device. The traveling oil passage 45 is an oil passage connecting the operation valve 55 and the traveling pump (first traveling pump 53L, second traveling pump 53R).

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

When the operating lever 59 is swung forward (in the direction of arrow A1 in FIG. 1), the operating valve 55A is operated and the pilot pressure is output from the operating valve 55A. This pilot pressure acts on the pressure receiving portion 53a of the first traveling pump 53L via the first traveling oil passage 45a and acts on the pressure receiving portion 53a of the second traveling pump 53R via the third traveling oil passage 45c. As a result, the swash plate angles of the first traveling pump 53L and the second traveling pump 53R are changed, the first traveling motor 36L and the second traveling motor 36R rotate forward (forward rotation), and the work machine 1 moves straight forward. ..

Further, when the operating lever 59 is swung backward (in the direction of arrow A2 in FIG. 1), the operating valve 55B is operated and the pilot pressure is output from the operating valve 55B. This pilot pressure acts on the pressure receiving portion 53b of the first traveling pump 53L via the second traveling oil passage 45b and also acts on the pressure receiving portion 53b of the second traveling pump 53R via the fourth traveling oil passage 45d. As a result, the swash plate angles of the first traveling pump 53L and the second traveling pump 53R are changed, the first traveling motor 36L and the second traveling motor 36R are reversed (reverse rotation), and the working machine 1 moves straight backward.

Further, when the operation lever 59 is swung to the right (in the direction of arrow A3 in FIG. 1), the operation valve 55C is operated and the pilot pressure is output from the operation valve 55C. This pilot pressure acts on the pressure receiving portion 53a of the first traveling pump 53L via the first traveling oil passage 45a and acts on the pressure receiving portion 53b of the second traveling pump 53R via the fourth traveling oil passage 45d. As a result, the swash plate angles of the first traveling pump 53L and the second traveling pump 53R are changed, the first traveling motor 36L rotates forward and the second traveling motor 36R reverses, and the working machine 1 turns to the right.

Further, when the operating lever 59 is swung to the left (in the direction of arrow A4 in FIG. 1), the operating valve 55D is operated and the pilot pressure is output from the operating valve 55D. This pilot pressure acts on the pressure receiving portion 53a of the second traveling pump 53R via the third traveling oil passage 45c and also acts on the pressure receiving portion 53b of the first traveling pump 53L via the second traveling oil passage 45b. As a result, the swash plate angles of the first traveling pump 53L and the second traveling pump 53R are changed, the first traveling motor 36L reverses, the second traveling motor 36R rotates forward, and the working machine 1 turns to the left.

Further, when the operating lever 59 is swung in an oblique direction, the rotation direction and rotation speed of the first traveling motor 36L and the second traveling motor 36R are increased by the differential pressure of the pilot pressure acting on the pressure receiving portion 53a and the pressure receiving portion 53b. Determined, the working machine 1 makes a right turn or a left turn while moving forward or backward.
That is, when the operation lever 59 is swung diagonally forward to the left, the work machine 1 turns left while advancing at a speed corresponding to the swing angle of the operating lever 59, and when the operating lever 59 is swung diagonally forward to the right. When the working machine 1 turns to the right while moving forward at a speed corresponding to the swing angle of the operating lever 59, and when the operating lever 59 is swung diagonally backward to the left, the working machine 1 is swung at a speed corresponding to the swing angle of the operating lever 59. 1 turns left while moving backward, and when the operating lever 59 is swung diagonally backward to the right, the working machine 1 turns right while moving backward at a speed corresponding to the swing angle of the operating lever 59.

Switching between the first speed and the second speed in the traveling motor (first traveling motor 36L, second traveling motor 36R) can be performed by the switching unit. The switching unit is, for example, a changeover switch 61 connected to the control device 60, and can be operated by an operator or the like. The switching unit (changeover switch 61) changes the speed from the first speed (first state) to the second speed (second state) and from the second speed (second state) to the first speed (first state). It can be switched to either deceleration or deceleration.

The control device 60 is composed of a CPU, a semiconductor such as an MPU, an electric / electronic circuit, and the like. The control device 60 switches the traveling switching valve 34 between the first state and the second state based on the switching operation of the changeover switch 61.
As shown in FIG. 1, the accelerator 65 and the rotation detection device 66 are connected to the control device 60. The accelerator 65 is a member that sets a target rotation speed of the prime mover 32. The accelerator 65 is provided in the vicinity of the driver's seat 8. The accelerator 65 includes an accelerator lever that is swingably supported, an accelerator pedal that is swingably supported, an accelerator volume that is rotatably supported, an accelerator slider that is slidably supported, and the like. The accelerator 65 is not limited to the above-mentioned example. The rotation detection device 66 is a sensor or the like that detects the actual rotation speed (actual motor rotation speed) of the prime mover 32.

The control device 60 performs control for preventing the motor 32 from stopping, that is, control for preventing engine stall (anti-stall control). For example, in the control device 60, in the anti-stall control, the difference (drop rotation speed) between the target rotation speed set by the accelerator 65 and the actual rotation speed detected by the rotation detection device 66 is a threshold value (hereinafter, "first threshold value"). When the above is the case, the engine stall is prevented by reducing the output of the traveling pumps (first traveling pump 53L, second traveling pump 53R).

Hereinafter, anti-stall control will be described in detail.
As shown in FIG. 1, the hydraulic system of the working machine 1 includes a working valve 67.
The actuating valve 67 is a valve capable of changing the pilot pressure of the pilot oil that operates the traveling pumps (first traveling pump 53L, second traveling pump 53R). The operating valve 67 is provided in the discharge oil passage 40 through which the pilot oil flows, and the pilot pressure (pressure receiving pressure) of the pilot oil that operates the traveling pumps (first traveling pump 53L, second traveling pump 53R) by changing the opening degree is provided. The operating pilot pressure acting on the portions 53a and 53b) is changed.

The actuating valve 67 is operated by a control signal (for example, voltage, current, etc.) of the control device 60. Hereinafter, a case where the control signal of the control device 60 is a current will be described, and the current value output as the control signal of the control device 60 is referred to as an “instructed current value”. The actuating valve 67 is an electromagnetic proportional valve whose opening degree can be changed based on the control signal of the control device 60. The electromagnetic proportional valve constituting the operating valve 67 can increase the opening degree in proportion to the magnitude of the indicated current value.

The control device 60 changes the pilot pressure (primary pressure) from the operating valve 67 to the operating device 54 by outputting a control signal to excite the solenoid 67a of the operating valve 67. As a result, the pilot pressure (primary pressure) for operating the traveling pumps (first traveling pump 53L, second traveling pump 53R) is changed.
As described above, the control device 60 outputs a control signal to change the pilot pressure (primary pressure) output to the operation valve 55. In other words, the primary pressure is determined according to the control signal output from the control device 60. In the case of the present embodiment, the opening degree of the operating valve 67 is determined according to the indicated current value which is a control signal output from the control device 60, and the primary pressure is determined according to the opening degree of the operating valve 67. More specifically, when the indicated current value increases, the opening degree of the operating valve 67 increases and the primary pressure increases, and when the indicated current value decreases, the opening degree of the operating valve 67 decreases and the primary pressure decreases. That is, there is a proportional relationship or a corresponding relationship (correlation) close to a proportional relationship between the indicated current value and the primary pressure (see FIG. 2). Therefore, the control device 60 can determine the primary pressure output to the operating valve 55 by determining the indicated current value which is a control signal output to the operating valve 67.

As shown in FIG. 1, a pressure detection device 68 for detecting a pilot pressure (secondary pressure) output by the operation valve 55 is connected to the control device 60. The pressure detection device 68 is a pressure sensor or the like, and is a pilot pressure (second oil passage) 45 of the traveling oil passage (second oil passage) 45 connecting the operation valve 55 and the traveling pump (first traveling pump 53L, second traveling pump 53R). Secondary pressure) is detected. That is, the pressure detection device 68 detects the pilot pressure of the traveling oil passage (second oil passage) 45 as the secondary pressure.

As shown in FIG. 1, the control device 60 includes a storage unit 160A, a calculation unit 160B, and a setting change unit 160C.
The storage unit 160A is a non-volatile memory. The calculation unit 160B and the setting change unit 160C are an electric circuit / electronic circuit provided in the control device 60, a program stored in the control device 60, and the like.

The storage unit 160A stores the correspondence relationship (see FIG. 2) between the control signal (indicated current value) output by the control device 60 to the operating valve 67 and the primary pressure. Based on this correspondence, the primary pressure is determined according to the control signal (instructed current value).
The storage unit 160A stores a setting line 80 for setting the primary pressure based on the actual rotation speed of the prime mover 32. The setting line 80 is set based on the relationship between the actual rotation speed and the primary pressure when the operation valve 55 is in a fixed position (for example, a fully open position). FIG. 3 is a map (anti-stall map) showing an example of the setting line 80. The setting line 80 includes a first line 80A and a second line 80B.

As described above, the magnitude of the indicated current value, which is a control signal output by the control device 60 to the operating valve 67, and the primary pressure have a corresponding relationship such as a proportional relationship (see FIG. 2). Therefore, the setting line (first line 80A and second line 80B) shown in FIG. 3 can be paraphrased as a setting line for setting a control signal (indicated current value) corresponding to the primary pressure based on the actual rotation speed of the prime mover 32. Can be done. Therefore, in FIG. 3, the vertical axis can be referred to as a “primary pressure” or a “control signal (indicated current value)”.

The first line 80A sets a control signal (indicated current value) based on the actual rotation speed when the difference (drop rotation speed) between the target rotation speed and the actual rotation speed of the prime mover 32 is equal to or higher than the first threshold value. It is a line.
The second line 80B sets a control signal (indicated current value) based on the actual rotation speed when the difference (drop rotation speed) between the target rotation speed and the actual rotation speed of the prime mover 32 is less than the first threshold value. It is a line. The second line 80B is a line for setting the control signal (indicated current value) to be larger than that of the first line 80A.

The setting change unit 160C changes the setting of the control signal output to the operating valve 67 based on the traveling pressure. Hereinafter, the running pressure will be described.
As shown in FIG. 1, the circulation oil passages 57h and 57i connecting the traveling pump (first traveling pump 53L, second traveling pump 53R) and the traveling motor (first traveling motor 36L, second traveling motor 36R) , A pressure detection device 69 (hereinafter referred to as "second pressure detection device 69") is provided. The second pressure detection device 69 detects the pressure of the hydraulic oil in the circulating oil passages 57h and 57i as the running pressure. The second pressure detection device 69 is a pressure sensor or the like. The detection signal indicating the value of the running pressure detected by the second pressure detection device 69 is transmitted to the control device 60.

The second pressure detection device 69 includes a pressure detection device 80a, a pressure detection device 80b, and a pressure detection device 8.
Includes 0c, pressure detector 80d. The pressure detection device 80a is provided on the first port P11 side of the left traveling motor 36L in the circulating oil passage 57h, and detects the traveling pump pressure on the first port P11 side as the first traveling pressure V1. The pressure detection device 80b is provided on the second port P12 side of the left traveling motor 36L in the circulating oil passage 57h, and detects the traveling pump pressure on the second port P12 side as the second traveling pressure V2. The pressure detection device 80c is provided on the third port P13 side of the right traveling motor 36R in the circulating oil passage 57i, and detects the traveling pump pressure on the third port P13 side as the third traveling pressure V3. The pressure detection device 80d is provided on the fourth port P14 side of the right traveling motor 36R in the circulating oil passage 57i, and detects the traveling pump pressure on the fourth port P14 side as the fourth traveling pressure V4.

The setting change unit 160C is set to, for example, the first running pressure to the fourth running pressure (V1 to V4), which is the running pump pressure detected by the plurality of second pressure detecting devices 69 provided in the circulating oil passages 57h and 57i. Based on this, the setting of the control signal output to the actuating valve 67 is changed. For example, the setting changing unit 160C has a first differential pressure obtained by subtracting the second traveling pressure V2 from the first traveling pressure V1, a second differential pressure obtained by subtracting the first traveling pressure V1 from the second traveling pressure V2, and a third traveling pressure. Of the third differential pressure obtained by subtracting the fourth running pressure V4 from V3 and the fourth differential pressure obtained by subtracting the third running pressure V3 from the fourth running pressure V4, the highest differential pressure is adopted as the "running pressure". The setting of the control signal output to the operating valve 67 is changed based on the traveling pressure (maximum value of the traveling pressure). The setting changing unit 160C may adopt the average value of the first running pressure to the fourth running pressure (V1 to V4) as the running pressure. Further, among a plurality of running pressures (first running pressure V1, second running pressure V2, third running pressure V3, fourth running pressure V4), the average of two running pressures is adopted as the running pressure used for anti-stall control. Alternatively, the average of the three running pressures may be used as the running pressure for anti-stall control, and the running pressure is not limited. In the anti-stall control, the difference between at least two running pressures among a plurality of running pressures (first running pressure V1, second running pressure V2, third running pressure V3, fourth running pressure V4) is used for anti-stall control. It may be adopted as a running pressure to be used. That is, in the anti-stall control, the differential pressure may be adopted as the traveling pressure, the traveling pressure itself may be adopted, or the absolute value of the differential pressure may be adopted.

The setting change unit 160C changes the first line 80A by changing the control signal shown in the first line 80A based on the traveling pressure when the correction mode is set. Specifically, when the setting change unit 160C is not in the correction mode, when the traveling pressure becomes equal to or higher than the second threshold value, the setting change unit 160C enters the correction mode and changes (corrects) the first line 80A. When the setting change unit 160C is not in the correction mode and the traveling pressure is less than the second threshold value, the setting change unit 160C does not change the first line 80A. After entering the correction mode, the setting change unit 160C ends the correction mode when the condition for canceling the correction mode is satisfied, and stops the change of the first line 80A. For example, the setting changing unit 160C ends the correction mode when the traveling pressure becomes equal to or less than the third threshold value in the correction mode. Hereinafter, the second threshold value may also be referred to as a “running pressure threshold value”. Further, the third threshold value for terminating the correction mode is a value smaller than the second threshold value.

The change of the first line 80A by the setting change unit 160C is performed by changing the control signal shown in the first line 80A. For example, by increasing the indicated current value I10, which is a control signal set based on the actual rotation speed M10, the first line 80A is changed to move upward (see arrow D1 in FIG. 3). Alternatively, the first line 80A is moved downward by reducing the indicated current value I10, which is a control signal set based on the actual rotation speed M10 (see arrow D2 in FIG. 3).

In the case of the present embodiment, the setting changing unit 160C has a direction in which the primary pressure output from the operating valve 67 increases (a direction in which the indicated current value increases) when the traveling pressure becomes equal to or higher than the second threshold value (traveling pressure threshold value). ) Is changed to the first line 80A.
In FIG. 3, the first line 80A after changing in the direction in which the primary pressure increases is shown by the alternate long and short dash line 80A1. That is, when the running pressure becomes equal to or higher than the second threshold value (running pressure threshold value), the setting changing unit 160C changes the initial first line 80A shown by the solid line to the first line 80A1 shown by the alternate long and short dash line.

As described above, when the setting change unit 160C is in the correction mode and the running pressure becomes equal to or higher than the second threshold value (running pressure threshold value), the primary pressure increases as the running pressure increases. The first line 80A is changed to. As a result, the horsepower consumed by the traveling pumps 53L and 53R can be increased. By increasing the horsepower consumed by the traveling pumps 53L and 53R, the engine speed that is balanced with the discharge flow rate of the traveling pump can be lowered.

As a result, in work involving opening of the traveling relief valve 73 such as earth pushing, the discharge flow rate (horsepower consumed by the traveling pump) of the traveling pumps 53L and 53R decreases due to the influence of the swash plate characteristics of the traveling pumps 53L and 53R. It is possible to prevent the occurrence of the phenomenon that the engine speed that balances with the discharge flow rate becomes high. As a result, it is possible to prevent a decrease in the running force in a high rotation speed range while preventing a phenomenon that the engine speed remains high, and to give the operator a feeling that the work machine is working sufficiently.

FIG. 4 is an operation flow for changing the first line 80A in the control device 60. The calculation unit 160B calculates the drop rotation speed by subtracting the actual rotation speed from the target rotation speed based on the target rotation speed set by the accelerator 65 and the actual rotation speed detected by the rotation detection device 66, and the drop rotation speed is calculated. When is less than the first threshold value, the setting change unit 160C sets a control signal (indicated current value) based on the second line 80B. When the drop rotation speed is equal to or higher than the first threshold value, the setting change unit 160C sets a control signal (indicated current value) based on the first line 80A.

As shown in FIG. 4, the setting change unit 160C determines whether or not the target rotation speed of the prime mover is equal to or higher than the threshold value (S1). When the target rotation speed of the prime mover is equal to or higher than the threshold value, that is, when the target rotation speed of the prime mover is set to a certain high level, the setting change unit 160C refers to the running pressure and the referred running pressure. Is determined to be equal to or higher than the second threshold value (running pressure threshold value) (S2). When the running pressure is equal to or higher than the second threshold value (running pressure threshold value), the setting changing unit 160C enters the correction mode (S3). In the correction mode, the setting change unit 160C is in the direction in which the primary pressure increases (arrow in FIG. 3) based on the traveling pressure and the correction coefficient shown in FIG. 5, for example, with reference to the first line (initial first line) 80A. By changing to the D1 direction), the first line 80A1 is set, and the control signal (indicated current value) is set based on the set (changed) first line 80A1.

The setting change unit 160C determines whether or not the mode is the correction mode (S4). When the setting change unit 160C is in the correction mode (S4, Yes), the setting change unit 160C determines whether or not the traveling pressure is equal to or less than the third threshold value (S5). When the traveling pressure is equal to or less than the third threshold value (S5, Yes), the setting changing unit 160C ends the correction mode (S6). Further, the setting changing unit 160C determines whether or not the actual rotation speed is equal to or less than the threshold value (S7), and if the actual rotation speed is equal to or less than the threshold value (S7, Yes), the correction mode is terminated (S6). After the correction mode ends, the setting change unit 160C slowly returns the control signal to the value corresponding to the first line 80A or the second line 80B by gradually returning the correction coefficient (gain) to 1.0. go. As shown in FIG. 4, when the actual rotation speed is not equal to or less than the threshold value (S7, No), the setting change unit 160C returns the process to S3 and continues the correction mode. In other words, if the traveling pressure is not equal to or less than the third threshold value, the setting changing unit 160C can return the process to S3 and continue the correction mode.

That is, the setting changing unit 160C enters the correction mode when the running pressure is equal to or higher than the second threshold value (running pressure threshold value), and in the correction mode, the second line 80B is based on the correction coefficient corresponding to the running pressure. When the setting (change) is continued and the running pressure becomes equal to or less than the third threshold value, the correction mode can be terminated and the control signal is gradually returned to the state before the correction.
Hereinafter, a specific example of a change method when the setting change unit 160C changes the setting of the control signal output to the operating valve 67 will be described.

The setting change unit 160C can change the setting of the control signal output to the operating valve 67 based on the correction coefficient (gain) set corresponding to the value of the traveling pressure. The storage unit 160A stores a function that defines the relationship between the running pressure and the correction coefficient.
FIG. 5 shows an example of the correction function stored in the storage unit 160A. As shown in FIG. 5, the correction coefficient increases with increasing running pressure. In FIG. 5, the running pressure shown on the horizontal axis is the maximum value of the running pressure (the maximum value among the first running pressure to the fourth running pressure (V1 to V4)).

The setting change unit 160C calculates the correction coefficient by substituting the running pressure detected by the second pressure detection device 69 into the correction function. For example, when the correction function shown in FIG. 5 is used and the running pressure detected by the second pressure detection device 69 is +36 MPa (corresponding to the scale of +3600 on the horizontal axis), the correction coefficient is calculated as 1.2. Will be done.
As shown in FIG. 5, the correction coefficient is set to a value exceeding 1. Specifically, the correction coefficient is set to a value exceeding 1 when the traveling pressure is equal to or higher than a predetermined pressure. The correction coefficient is not set when the running pressure is less than the predetermined pressure. In the example shown in FIG. 5, the correction coefficient is set to a value exceeding 1 when the traveling pressure is 30 MPa or more, and is not set when the traveling pressure is less than 30 MPa.

The predetermined pressure of the running pressure for which the correction coefficient is set can be, for example, the same as the second threshold value (running pressure threshold value). Therefore, the correction coefficient can be set to a value exceeding 1 when the running pressure is equal to or higher than the second threshold value (running pressure threshold value).
The setting change unit 160C changes the setting of the control signal output to the operating valve 67 based on the calculated correction coefficient. Specifically, by multiplying the calculated correction coefficient by the indicated current value of the control signal shown on the first line 80A, the indicated current value which is the control signal output to the operating valve 67 is changed. As a result, the first line 80A is changed.

Since the correction coefficient is a value exceeding 1, the indicated current value increases when the correction coefficient is multiplied, and the first line 80A is changed in the direction in which the primary pressure output from the operating valve 67 increases. That is, in FIG. 3, the first line 80A is changed in the direction indicated by the arrow D1. In this way, when the rotation speed of the prime mover is high and the running pressure is high (when the pressure is equal to or higher than the predetermined pressure), the setting of the control signal output to the operating valve 67 is changed using a correction coefficient exceeding 1. By doing so, the setting of the control signal output to the operating valve 67 is changed in the direction in which the primary pressure output from the operating valve 67 increases.

The change method when the setting change unit 160C changes the setting of the control signal output to the actuating valve 67 is not limited to the method using the correction coefficient described above. For example, the setting changing unit 160C may be configured to change the set value of the control signal (instructed current value) output to the operating valve 67 by changing the anti-stall map according to the traveling pressure. Specifically, a plurality of different anti-stall maps (anti-stall maps in which the first line 80A is different) corresponding to a plurality of different running pressures are stored in the storage unit 160A in advance, and the setting changing unit 160C responds to the running pressure. The anti-stall map corresponding to the generated differential pressure is selected, and the set value of the control signal (indicated current value) output to the operating valve 67 is changed based on the first line 80A shown in the anti-stall map. It may be configured as follows.

In the above-described embodiment, when the setting change unit 160C is in the correction mode and the running pressure becomes equal to or higher than the second threshold value (running pressure threshold value), the first line 80A is changed in the direction in which the primary pressure increases. However, as shown in FIG. 3, the first line 80A may be changed in the direction in which the primary pressure becomes smaller. That is, the setting changing unit 160C can reduce the output of the traveling pumps 53L and 53R by lowering the first line 80A to the first line 80A2 as the traveling pressure increases, thereby preventing engine stall. Can be done.

In the above-described embodiment, the operating valve 67 is provided on the upstream side (discharge oil passage 40) of the operating valve 55, but instead of this, the operating valve 67 is installed in the middle of the fifth traveling oil passage 45e, for example. The actuating valve 67 may be provided.
Alternatively, as shown in FIG. 6, the operating valve 67 may be provided in the traveling oil passage 45 connected to the traveling pump (left traveling pump 53L, right traveling pump 53R). Specifically, the oil passage 51 is branched from each of the first traveling oil passage 45a, the second traveling oil passage 45b, the third traveling oil passage 45c, and the fourth traveling oil passage 45d, and the variable relief valve is connected to the oil passage 51. An operating valve 67 such as an electromagnetic proportional valve may be provided, and the opening degree of the operating valve 67 may be controlled by the first control signal and the second control signal.

In the above-described embodiment, the traveling operation device 54 is a hydraulic type in which the pilot pressure acting on the traveling pumps (first traveling pump 53L, second traveling pump 53R) is changed by the operation valve 55, which is shown in FIG. 7. As described above, the traveling operation device 54 may be an electrically operated device.
As shown in FIG. 7, the traveling operation device 54 is an operation valve 55 (operation valves 55A, 55B, 55C) composed of an operation member 59 that swings in the left-right direction (machine width direction) or the front-rear direction and an electromagnetic proportional valve. , 55D). The control device 60 is connected to an operation detection sensor that detects the operation amount and operation direction of the operation member 59. The control device 60 controls the operation valves 55 (operation valves 55A, 55B, 55C, 55D) based on the operation amount and the operation direction detected by the operation detection sensor.

When the operating member 59 is operated forward (in the A1 direction, see FIG. 1), the control device 60 outputs a control signal to the operating valve 55A and the operating valve 55C, and the first traveling pump 53L and the second traveling pump 53R. Swing the swash plate in the direction of forward rotation (forward).
When the operating member 59 is operated rearward (A2 direction, see FIG. 1), the control device 60 outputs a control signal to the operating valve 55B and the operating valve 55D, and the first traveling pump 53L and the second traveling pump 53R. Swing the swash plate in the reverse (reverse) direction.

When the operation member 59 is operated to the right (A3 direction, see FIG. 1), the control device 60 outputs a control signal to the operation valve 55A and the operation valve 55D, and rotates the swash plate of the first traveling pump 53L in the normal direction. The swash plate of the second traveling pump 53R is swung in the reverse direction.
When the operation member 59 is operated to the left (A4 direction, see FIG. 1), the control device 60 outputs a control signal to the operation valve 55B and the operation valve 55C, and reverses the swash plate of the first traveling pump 53L. Swing in the direction, and swing the swash plate of the second traveling pump 53R in the direction of forward rotation.

The working machine 1 includes a prime mover 32, traveling pumps 53L and 53R that are operated by the power of the prime mover 32 and discharge hydraulic oil, and traveling motors 36L and 36R that can be rotated by the hydraulic oil discharged by the traveling pumps 53L and 53R. The operation valve 55 that can change the pilot pressure of the pilot oil output to the traveling pumps 53L and 53R according to the operation of the operation member 59, and the pilot pressure of the pilot oil that is operated by the control signal and supplied to the operation valve 55. An operating valve 67 capable of changing the primary pressure, a control device 60 for setting a control signal to be output to the operating valve 67, and circulation oil passages 57h and 57i connecting the traveling pumps 53L and 53R and the traveling motors 36L and 36R. A pressure detecting device (second pressure detecting device) 69 for detecting the running pressure which is the pressure of the hydraulic oil in the circulating oil passages 57h and 57i is provided, and the control device 60 is output to the operating valve 67 based on the running pressure. It has a setting change unit 160C for changing the setting of the control signal.

According to this, the control device 60 can change the setting of the control signal output to the operating valve 67 based on the traveling pressure by the setting changing unit 160C. Therefore, it is possible to change the primary pressure, which is the pilot pressure of the pilot oil supplied by the operating valve 67 to the operating valve 55, based on the traveling pressure. By making this change, it is possible to prevent the engine speed from stopping at a high speed, prevent the running force from decreasing in the high speed range, and give the worker the feeling that the work machine 1 is working sufficiently. It will be possible to give.

Further, in the working machine 1, the accelerator 65 for setting the target rotation speed of the prime mover 32, the rotation detection device 66 for detecting the actual rotation speed of the prime mover 32, and the difference between the target rotation speed and the actual rotation speed are equal to or larger than the first threshold value. When the difference between the first line 80A, which sets the control signal based on the actual rotation speed, and the target rotation speed and the actual rotation speed is less than the first threshold value, the control signal is set larger than the first line. The second line 80B and the storage unit 160A for storing the second line 80B are provided, and the setting changing unit 160C changes the control signal shown in the first line 80A based on the traveling pressure to change the control signal shown in the first line 80A. To change.

According to this, the load applied to the prime mover 32 is a low load (the difference between the target rotation speed and the actual rotation speed is less than the first threshold value), and the load applied to the prime mover 32 is a high load (the target rotation speed and the actual rotation speed). The setting of the control signal output to the operating valve 67 can be appropriately changed based on the traveling pressure according to the two cases where the difference from the number is equal to or greater than the first threshold value.
Further, the operating valve 67 is an electromagnetic proportional valve that increases the opening degree in proportion to the magnitude of the current value, and the setting changing unit 160C is referred to from the operating valve 67 when the traveling pressure becomes the second threshold value or more. The first line 80A is changed in the direction in which the output primary pressure increases.

According to this, when the traveling pressure becomes equal to or higher than the second threshold value, the horsepower consumed by the traveling pumps 53L and 53R is reduced by changing the first line in the direction in which the primary pressure output from the operating valve 67 increases. Can be increased. By increasing the horsepower consumed by the traveling pumps 53L and 53R, the engine speed balanced with the discharge flow rate of the traveling pumps 53L and 53R can be lowered. As a result, it is possible to prevent a decrease in the running force in a high rotation speed range while preventing a phenomenon that the engine speed remains high, and to give the operator a feeling that the work machine 1 is working sufficiently. Will be.

Further, the operating valve 67 is an electromagnetic proportional valve that increases the opening degree in proportion to the magnitude of the current value, and the setting changing unit 160C is referred to from the operating valve 67 when the traveling pressure becomes the second threshold value or more. The first line is changed so that the primary pressure to be output decreases. According to this, the output of the traveling pumps 53L and 53R can be reduced, and the engine stall can be prevented.
The setting change unit 160C ends the change of the first line when the running pressure becomes equal to or less than the third threshold value smaller than the second threshold value. According to this, the change of the first line 80A can be continued until the running pressure becomes the third threshold value smaller than the second threshold value.

When the setting change unit 160C finishes the change of the first line, the setting change unit 160C gradually returns the control signal to the value before the change of the first line. According to this, the control signal output to the operating valve 67 can be gradually returned from the control signal set by the change of the first line 80A to the first line 80A before the change, and the change of the first line 80A is completed. It is possible to suppress abrupt pressure fluctuations of the secondary pressure (primary pressure) at times.

Further, the setting changing unit 160C changes the setting of the control signal output to the operating valve 67 based on the correction coefficient set corresponding to the value of the traveling pressure.
According to this, since the setting of the control signal output to the operating valve 67 can be changed by using the correction coefficient set corresponding to the running pressure value, the operation is performed according to the running pressure value. The setting of the control signal output to the valve 67 can be easily and appropriately changed.

Further, the storage unit 160A stores a function that defines the relationship between the traveling pressure and the correction coefficient, and the setting changing unit 160C substitutes the traveling pressure detected by the pressure detection device (second pressure detection device) 69 into the function. By doing so, the correction coefficient is calculated.
According to this, the correction coefficient can be calculated easily and accurately by using the function that defines the relationship between the running pressure and the correction coefficient.

Although the embodiments of the present invention have been described above, it should be considered that the embodiments disclosed this time are exemplary in all respects and are not restrictive. The scope of the present invention is shown not by the above description but by the scope of claims, and is intended to include all modifications within the meaning and scope equivalent to the scope of claims.

1 Work machine 32 Motor 36L, 36R Travel motor 53L, 53R Travel pump 55 Operation valve 57h, 57i Circulation oil passage 59 Operation member 60 Control device 160A Storage unit 160B Calculation unit 160C Setting change unit 65 Accelerator 66 Rotation detection device 67 Operation valve 69 Pressure detector (second pressure detector)
80A 1st line 80B 2nd line

Claims (8)

The prime mover and
A traveling pump that is operated by the power of the prime mover and discharges hydraulic oil,
A traveling motor that can be rotated by the hydraulic oil discharged by the traveling pump,
An operating valve that can change the pilot pressure of the pilot oil output to the traveling pump according to the operation of the operating member,
An operating 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 operating valve.
A control device that sets the control signal to be output to the operating valve, and
A circulating oil passage connecting the traveling pump and the traveling motor,
A pressure detection device that detects the running pressure, which is the pressure of the hydraulic oil in the circulating oil passage, and
Equipped with
The control device is a working machine having a setting changing unit for changing the setting of a control signal output to the operating valve based on the traveling pressure. The accelerator that sets the target rotation speed of the prime mover and
A rotation detection device that detects the actual rotation speed of the prime mover, and
The first line for setting the control signal based on the actual rotation speed when the difference between the target rotation speed and the actual rotation speed is equal to or more than the first threshold value, and the target rotation speed and the actual rotation speed. A storage unit that stores a second line that sets the control signal larger than the first line when the difference is less than the first threshold value.
Equipped with
The working machine according to claim 1, wherein the setting changing unit changes the first line by changing the control signal shown in the first line based on the traveling pressure. The actuated valve is an electromagnetic proportional valve that increases the opening degree in proportion to the magnitude of the current value.
The setting change part is
The working machine according to claim 2, wherein the first line is changed in a direction in which the primary pressure output from the operating valve increases when the traveling pressure becomes equal to or higher than the second threshold value. The actuated valve is an electromagnetic proportional valve that increases the opening degree in proportion to the magnitude of the current value.
The setting change part is
The working machine according to claim 2, wherein the first line is changed in a direction in which the primary pressure output from the operating valve becomes smaller when the traveling pressure becomes equal to or higher than the second threshold value. The working machine according to claim 3 or 4, wherein the setting changing unit ends the change of the first line when the traveling pressure becomes equal to or less than the third threshold value smaller than the second threshold value. The working machine according to claim 5, wherein the setting changing unit gradually returns the control signal to the value before the change of the first line when the change of the first line is completed. 13. Working machine. The storage unit stores a function that defines the relationship between the traveling pressure and the correction coefficient.
The working machine according to claim 7, wherein the setting changing unit calculates the correction coefficient by substituting the running pressure detected by the pressure detection device into the function.

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