JP2018062848A - Hydraulic system of work machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydraulic system of work machine capable of ensuring to give a driver a feeling of engine-drop while preventing engine stall when a load acts on an engine.SOLUTION: A hydraulic system work machine includes: an engine; a setting member for setting target rotation speed of the engine; a hydraulic pump which is operable being driven by the engine to discharge hydraulic fluid; an operation valve to which the hydraulic fluid discharged from the hydraulic pump is supplied; a hydraulic device which is operable by means of the hydraulic fluid from the operation valve; a storage part that stores plural different first control characteristics of an inclination which is determined corresponding to a target rotation speed, which are characteristics representing a relationship between the pressure of the hydraulic fluid of the operation valve when the load on the engine is a predetermined value or more and the actual rotation speed of the engine; and a control unit that, when the load on the engine is a predetermined value or more, controls the operation valve based on the different first control characteristics of the inclination which is determined depending on the target rotation speed.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a hydraulic system for a work machine such as a skid steer loader or a compact truck loader.

Conventionally, a technique shown in Patent Document 1 is known as a technique for preventing engine stall in working machines such as a skid steer loader and a compact truck loader.
In the working machine of Patent Document 1, an engine, an HST pump that is driven by power of the engine, a travel operation device that operates the HST pump, and a pressure control that controls a travel primary side pressure that is a primary pressure of the travel operation device. And a control device for controlling the pressure control valve.

  The control device controls the engine stall by controlling the pressure control valve based on a no-load characteristic line that is used when the load is unloaded and a drop characteristic line that is adopted when a load greater than a predetermined level is applied to the engine. It is preventing. In other words, by controlling the pressure control valve when the working load exceeds a predetermined level on the work equipment and drastically reducing the traveling primary side pressure, the decrease in the engine speed is reduced as much as possible. I'm trying to prevent it.

JP2013-78115A

The operator of the work implement senses that the engine is operating sufficiently by lowering the engine speed when a traveling load is applied to the work implement. Accordingly, if the engine speed does not decrease even though a load is applied to the work machine, the driver may be suspicious that the engine is not operating sufficiently.
On the other hand, if the engine speed is greatly reduced due to the load acting on the work implement, if the engine speed is not reduced, engine stall will occur.

  An object of the present invention is to provide a hydraulic system for a working machine that can achieve both a feeling of a driver when a load is applied to a prime mover and prevention of engine stall.

The technical means taken by the present invention to solve the technical problems are characterized by the following points.
The working machine hydraulic system includes a prime mover, a setting member for setting a target rotational speed of the prime mover, a hydraulic pump operable by driving the prime mover and discharging hydraulic oil, and hydraulic oil discharged from the hydraulic pump. A characteristic indicating a relationship between a supplied operating valve, a hydraulic device operable by the operating oil of the operating valve, and a pressure of the operating oil of the operating valve and an actual rotational speed of the prime mover when a load of the prime mover is not less than a predetermined value In the case where the storage unit stores a plurality of first control characteristics having different inclinations determined in accordance with the target rotational speed, and the load on the prime mover is equal to or greater than a predetermined value, And a control unit that controls the operation valve based on the first control characteristics having different predetermined inclinations.

The control unit controls the operation valve using a first control characteristic in which the inclination is set to be small as the target rotational speed is increased.
The hydraulic system of the work machine includes a switch that can change the first control characteristic.
The hydraulic system of the work machine includes a switch that can change the determination value.
The working machine hydraulic system includes a prime mover, a setting member for setting a target rotational speed of the prime mover, a hydraulic pump operable by driving the prime mover and discharging hydraulic oil, and hydraulic oil discharged from the hydraulic pump. A characteristic indicating a relationship between a supplied operating valve, a hydraulic device operable by the operating oil of the operating valve, and a pressure of the operating oil of the operating valve and an actual rotational speed of the prime mover when a load of the prime mover is not less than a predetermined value A plurality of first control characteristics whose inclinations corresponding to the target rotational speed are parallel or different from each other, and the pressure of the hydraulic fluid of the operating valve and the actuality of the prime mover when the load of the prime mover is less than a predetermined value. A storage unit that stores a second control characteristic indicating a relationship with the rotational speed, and the second control characteristic when the amount of decrease in the actual rotational speed from the target rotational speed is less than a predetermined determination value Control of the actuating valve based on A controller that controls the operating valve based on the first control characteristic determined according to the target rotational speed when the amount of decrease is equal to or greater than a determination value of the actual rotational speed; I have.

  The working machine hydraulic system includes a prime mover, a setting member for setting a target rotational speed of the prime mover, a hydraulic pump operable by driving the prime mover and discharging hydraulic oil, and hydraulic oil discharged from the hydraulic pump. A characteristic indicating the relationship between the supplied operating valve, the hydraulic equipment operable by the operating oil of the operating valve, and the pressure of the operating oil of the operating valve and the actual rotational speed of the prime mover, corresponding to the target rotational speed A storage unit that stores a plurality of first control characteristics having different inclinations, and a reduction amount of the actual rotational speed from the target rotational speed is equal to or greater than a predetermined determination value. And a control unit that controls the operation valve based on the first control characteristics having different inclinations determined according to the number of rotations.

  The working machine hydraulic system includes a prime mover, a setting member for setting a target rotational speed of the prime mover, a hydraulic pump operable by driving the prime mover and discharging hydraulic oil, and hydraulic oil discharged from the hydraulic pump. A characteristic indicating the relationship between the supplied operating valve, the hydraulic equipment operable by the operating oil of the operating valve, and the pressure of the operating oil of the operating valve and the actual rotational speed of the prime mover, corresponding to the target rotational speed A plurality of first control characteristics that are parallel to each other or different from each other, and a storage section that stores a second control characteristic that indicates a relationship between the pressure of the hydraulic oil of the operating valve and the actual rotational speed of the prime mover; When the decrease amount of the actual rotation number from the target rotation number is less than a predetermined determination value, the operation valve is controlled based on the second control characteristic, and the decrease amount is the actual rotation If the number is more than the judgment value And and a control unit for controlling said actuating valves based on said first control characteristic determined in accordance with the serial target speed.

  According to the present invention, it is possible to achieve both the feeling of the driver when the load is applied to the prime mover and the prevention of engine stall.

It is a figure which shows the hydraulic system (hydraulic circuit) of the traveling system of a working machine. It is a figure which shows the hydraulic system (hydraulic circuit) of the working system of a working machine. It is a figure which shows the relationship between an engine speed and driving | running | working primary pressure, Comprising: It is a characteristic view which shows 1st Embodiment of anti-stall control. It is a figure which shows the relationship between an engine speed and driving | running | working primary pressure, Comprising: It is a characteristic view which shows 2nd Example of anti-stall control. It is a side view which shows the track loader which is an example of a working machine. It is a side view which shows a part of track loader of the state which raised the cabin.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of a hydraulic system for a working machine and a working machine provided with the hydraulic system according to the invention will be described with reference to the drawings as appropriate.
[First embodiment]
First, the overall configuration of the work machine will be described.
As shown in FIGS. 5 and 6, the work machine 1 according to the present invention includes a machine body frame 2, a work device 3 attached to the machine body frame 2, and a traveling device 4 that supports the machine body frame 2. . 5 and 6 show a truck loader as an example of a working machine, the working machine according to the present invention is not limited to a truck loader. For example, a tractor, a skid steer loader, a compact truck loader, and a wheel loader are used. , Backhoe or the like. In the present invention, the front side (left side in FIG. 5) of the driver seated on the driver's seat 13 of the work machine 1 is front, the rear side (right side in FIG. 5) is rearward, and the left side of the driver (FIG. 5). The front side) will be described as the left side, and the right side of the driver (the back side in FIG. 5) will be described as the right side.

A cabin 5 is mounted on the upper part of the body frame 2 and in the front part. The rear portion of the cabin 5 is supported by the support bracket 11 of the body frame 2 so as to be swingable around the support shaft 12. The front part of the cabin 5 can be placed on the front part of the body frame 2.
A driver's seat 13 is provided in the cabin 5. A travel operation device 14 for operating the travel device 4 is disposed on one side (for example, the left side) of the driver seat 13.

The traveling device 4 is a crawler traveling device. The traveling device 4 is provided below the left side of the body frame 2 and below the right side of the body frame 2. The traveling device 4 includes a first traveling unit 21L that operates by hydraulic driving and a second traveling unit 21R that operates by hydraulic driving. The work machine 1 can travel by the first traveling unit 21L and the second traveling unit 21R.
The work device 3 includes a boom 22L, a boom 22R, and a bucket 23 (work tool). The boom 22L is disposed on the left side of the body frame 2. The boom 22R is disposed on the right side of the body frame 2. The boom 22L and the boom 22R are connected to each other by a connecting body. The boom 22L and the boom 22R are supported by the first lift link 24 and the second lift link 25. A lift cylinder 26 composed of a double-acting pressure cylinder is provided between the base side of the boom 22L and the boom 22R and the rear lower part of the body frame 2. By simultaneously expanding and contracting the lift cylinder 26, the boom 22L and the boom 22R swing up and down.

The bucket 23 is mounted on the tip side of the boom 22L and the boom 22R. A mounting bracket 27 is pivotally supported on the distal ends of the boom 22L and the boom 22R so as to be rotatable about the horizontal axis, and the back side of the bucket 23 is attached to the mounting brackets 27 provided on the left and right.
Further, a tilt cylinder 28 composed of a double-acting hydraulic cylinder is interposed between the mounting bracket 27 and the middle part of the boom 22L and the front end side of the boom 22R. The bucket 23 swings (squeeze operation and dump operation) by the expansion and contraction of the tilt cylinder 28.

The bucket 23 is detachable from the mounting bracket 27. By removing the bucket 23 and attaching various attachments (hydraulic drive work tools having a hydraulic actuator described later) to the mounting bracket 27, various work other than excavation (or other excavation work) can be performed. ing.
A prime mover 29 is provided on the rear side on the bottom wall of the body frame 2, and a fuel tank and a hydraulic oil tank 31 are provided on the front side on the bottom wall of the body frame 2. The prime mover 29 is, for example, a diesel engine. The prime mover 29 may be an electric motor, or a diesel engine and an electric motor. A diesel engine is sometimes simply called an engine.

Next, a hydraulic system for a working machine according to the present invention will be described.
FIG. 1 shows an overall view of a traveling hydraulic system. FIG. 2 shows an overall view of a working hydraulic system.
First, a traveling hydraulic system will be described.
As shown in FIGS. 1 and 2, the hydraulic system (hydraulic circuit) includes a first hydraulic pump P1 and a second hydraulic pump P2. The first hydraulic pump P <b> 1 and the second hydraulic pump P <b> 2 are hydraulic pumps that can be operated by driving the prime mover 29. Further, the first hydraulic pump P1 and the second hydraulic pump P2 are driven by the power of the prime mover 29 to discharge hydraulic oil. The first hydraulic pump P1 and the second hydraulic pump P2 are configured by, for example, constant displacement gear pumps.

  The first hydraulic pump P <b> 1 (main pump) is used to drive a hydraulic actuator of an attachment attached to the lift cylinder 26, the tilt cylinder 28 or the tip side of the boom 22. The second hydraulic pump P2 (pilot pump, charge pump) is mainly used for supplying a control signal (pilot pressure). Hereinafter, for convenience of explanation, the hydraulic oil discharged from the second hydraulic pump P2 and the hydraulic fluid for the control signal may be referred to as pilot oil, and the pressure of the pilot oil may be referred to as pilot pressure.

  As shown in FIG. 1, a discharge oil passage 100a is connected to the second hydraulic pump P2. A first supply / discharge passage 100b and a second supply / discharge passage 100c are connected to the discharge oil passage 100a. A first drive circuit 32A and a second drive circuit 32B are connected to the first supply / discharge path 100b. A travel operation device 14 is connected to the second oil supply / discharge passage 100c. An operation valve 45 is connected to the middle portion of the second supply / discharge oil passage 100c. Therefore, the working oil discharged from the second hydraulic pump P2 is supplied to the working valve 45. In this embodiment, the operation valve 45 is constituted by an electromagnetic proportional valve.

  The first drive circuit 32A is a circuit that drives the first traveling unit 21L provided on the left side. The first drive circuit 32A and the first traveling unit 21L constitute an HST (hydrostatic transmission). The second drive circuit 32B is a circuit for driving the second traveling unit 21R provided on the right. The second drive circuit 32B and the second traveling unit 21R constitute an HST (hydrostatic transmission).

The first drive circuit 32 </ b> A includes a travel pump (HST pump) 66. The traveling pump 66 is a hydraulic device that can be operated by pilot oil (operating oil) output from the operating valve 45. The traveling pump 66 is connected to a traveling motor (HST motor) 57 of the corresponding first traveling portion 21L by a transmission oil passage 100h and a transmission oil passage 100i.
Note that the second drive circuit 32B has the same structure as the first drive circuit 32A, and a description thereof will be omitted.

The traveling pump 66 is a swash plate type variable displacement axial pump driven by the power of the prime mover 29 and a pilot-type hydraulic pump (swash plate type variable displacement hydraulic pump) in which the angle of the swash plate is changed by the pilot pressure. . Specifically, the traveling pump 66 includes a forward pressure receiving portion 66a and a reverse pressure receiving portion 66b on which pilot pressure acts.
The angle of the swash plate is changed by the pilot pressure acting on the pressure receiving portions 66a and 66b. When the angle of the swash plate is changed, the discharge direction and the discharge amount of the hydraulic oil are changed, thereby changing the rotation outputs of the first traveling unit 21L and the second traveling unit 21R.

The first traveling unit 21L includes a traveling motor 57 (traveling hydraulic motor), a swash plate switching cylinder 58, a first hydraulic switching valve 63, a brake mechanism 59, a flushing valve 60, and a flushing relief valve 61. Have
The traveling motor 57 is a hydraulic device that is operated by pilot oil (hydraulic oil). The traveling motor 57 is, for example, a swash plate type variable displacement axial motor that can shift to high and low speeds. The swash plate of the traveling motor 57 is provided with a telescopic swash plate switching cylinder 58. By the expansion and contraction of the swash plate switching cylinder 58, the angle of the swash plate of the traveling motor 57 can be changed. By changing the angle of the swash plate of the travel motor 57, the travel motor 57 is shifted to the first speed or the second speed.

  The first hydraulic pressure switching valve 63 is a two-position switching valve having a spool that can move between a first position 63a and a second position 63b in accordance with the pressure of the pilot oil (pilot pressure). When the pilot pressure reaches a predetermined pressure, the spool of the first hydraulic pressure switching valve 63 moves to the second position 63b, and the operating state changes. Further, the spool of the first hydraulic pressure switching valve 63 is returned to the first position 63a by the spring when the pilot pressure becomes less than a predetermined pressure, and the operating state is changed. When the spool of the first hydraulic pressure switching valve 63 is in the operating state moved to the first position 63a, the pilot oil is removed from the swash plate switching cylinder 58 and contracts, and the traveling motor 57 enters the first speed state. When the spool of the first hydraulic pressure switching valve 63 is in the operating state moved to the second position 63b, the pilot oil is supplied to the swash plate switching cylinder 58 and extends, and the traveling motor 57 enters the second speed state.

  The first hydraulic pressure switching valve 63 is switched by the second hydraulic pressure switching valve 62. The first hydraulic pressure switching valve 63 and the second hydraulic pressure switching valve 62 are connected by a third supply / discharge path 100d. The second hydraulic pressure switching valve 62 is a two-position switching valve having a spool that can move between a first position and a second position in accordance with the pressure of the pilot oil (pilot pressure). When the second hydraulic pressure switching valve 62 is in the first position, the first hydraulic pressure switching valve 63 is in the first position 63a. When the second hydraulic pressure switching valve 62 is in the second position, the first hydraulic pressure switching valve 63 is in the second position 63b. The switching of the second hydraulic pressure switching valve 62 can be performed by an electric signal, a pilot pressure, a machine operation, or the like. Therefore, the traveling motor 57 can be switched to the first speed or the second speed by switching the second hydraulic pressure switching valve 62 to the first position or the second position.

  The travel pump 66 and the travel motor 57 are operated by the travel operation device 14. The travel operation device 14 includes a plurality of remote control valves, a travel lever 40, and first to fourth shuttle valves 41, 42, 43, 44. The plurality of remote control valves include a remote control valve 36, a remote control valve 37, a remote control valve 38, and a remote control valve 39. The remote control valves 36, 37, 38 and 39 are operated in common, that is, by one traveling lever 40. The remote control valves 36, 37, 38, 39 change the pressure of the hydraulic oil according to the operation of the travel lever 40 (operation member).

  The travel lever 40 can tilt from the neutral position in the front-rear direction, the width direction orthogonal to the front-rear direction, and the oblique direction. By tilting the traveling lever 40, the remote control valves 36, 37, 38, 39 of the traveling operation device 14 are operated. Then, a pilot pressure proportional to the operation amount from the neutral position of the travel lever 40 is output from the secondary side ports of the remote control valves 36, 37, 38, 39.

When the traveling lever 40 is tilted forward (in the direction of arrow A1 in FIG. 1), the remote control valve 36 is operated and pilot pressure is output from the remote control valve 36. The pilot pressure acts on the forward pressure receiving portion 66a of the first drive circuit 32A from the first shuttle valve 41 via the first flow path 46 and is second from the second shuttle valve 42 via the second flow path 47. It acts on the forward pressure receiver 66a of the drive circuit 32B. As a result, the output shafts 57a of the first traveling unit 21L and the second traveling unit 21R rotate forward (forward rotation) at a speed proportional to the tilting amount of the traveling lever 40, and the track loader 1 moves straight forward.

  When the travel lever 40 is tilted rearward (in the direction of arrow A2 in FIG. 1), the remote control valve 37 is operated and pilot pressure is output from the remote control valve 37. The pilot pressure acts on the backward pressure receiving portion 66b from the third shuttle valve 43 via the third flow path 48 and the second drive pressure 32b from the fourth shuttle valve 44 via the fourth flow path 49. The drive circuit 32B acts on the reverse pressure receiving portion 66b. As a result, the output shafts 57a of the first traveling unit 21L and the second traveling unit 21R are reversely rotated (reversely rotated) at a speed proportional to the tilting amount of the traveling lever 40, and the track loader 1 moves straight backward.

  Further, when the traveling lever 40 is tilted to the right (in the direction of arrow A3 in FIG. 1), the remote control valve 38 is operated and pilot pressure is output from the remote control valve 38. This pilot pressure acts on the forward pressure receiving portion 66a of the first drive circuit 32A from the first shuttle valve 41 via the first flow path 46, and from the fourth shuttle valve 44 via the fourth flow path 49 to the second drive. The circuit 32B acts on the backward pressure receiving portion 66b. As a result, the output shaft 57a of the first traveling unit 21L rotates in the forward direction and the output shaft 57a of the second traveling unit 21R rotates in the reverse direction, so that the track loader 1 turns to the right.

  Further, when the traveling lever 40 is tilted to the left (in the direction of arrow A4 in FIG. 1), the remote control valve 39 is operated and pilot pressure is output from the remote control valve 39. This pilot pressure acts on the forward pressure receiving portion 66a of the second drive circuit 32B from the second shuttle valve 42 via the second flow path 47, and also from the third shuttle valve 43 via the third flow path 48 for the first drive. The circuit 32A acts on the reverse pressure receiving portion 66b. As a result, the output shaft 57a of the second traveling unit 21R rotates in the forward direction and the output shaft 57a of the first traveling unit 21L rotates in the reverse direction, so that the track loader 1 turns to the left.

Further, when the traveling lever 40 is tilted in the oblique direction, the first traveling portion 21L and the first traveling portion 21L and the differential pressure between the forward pressure receiving portion 66a and the reverse pressure receiving portion 66b of each of the first drive circuits 32A and 32B are caused. The rotation direction and rotation speed of the output shaft 57a of the second traveling unit 21R are determined, and the truck loader 1 turns right or left while moving forward or backward.
That is, when the travel lever 40 is tilted to the left front side, the track loader 1 turns left while moving forward at a speed corresponding to the tilt angle of the travel lever 40. When the traveling lever 40 is tilted to the right front side, the track loader 1 turns right while moving forward at a speed corresponding to the tilting angle of the traveling lever 40. Further, when the traveling lever 40 is tilted to the left rear side, the track loader 1 turns left while moving backward at a speed corresponding to the tilting angle of the traveling lever 40. Further, when the travel lever 40 is tilted to the right rear side, the truck loader 1 turns right while moving backward at a speed corresponding to the tilt angle of the travel lever 40.

Next, a working hydraulic system will be described.
As shown in FIG. 2, a discharge oil passage 100e is connected to the first hydraulic pump P1. A plurality of control valves 70 are connected to the discharge oil passage 100e. The plurality of control valves 70 are a boom control valve 70A, a bucket control valve 70B, and a preliminary control valve 70C. The boom control valve 70A is a valve that controls the lift cylinder 26, the bucket control valve 70B is a valve that controls the tilt cylinder 28, and the preliminary control valve 70C is a valve that controls the hydraulic actuator of the preliminary attachment. is there. In the working hydraulic system, the lift cylinder 26, the tilt cylinder 28, the hydraulic actuator for the spare attachment, and the like are hydraulic devices.

  The boom 22 and the bucket 23 can be operated by an operation member 71 provided around the driver's seat 13. The operation member 71 is supported so as to be tiltable from the neutral position in the front-rear direction, the width direction orthogonal to the front-rear direction, and the oblique direction. By operating the operation member 71 to tilt, the remote control valves 72A, 72B, 72C, 72D provided at the lower part of the operation member 71 can be operated.

When the operation member 71 is tilted forward, the remote control valve 72A is operated and pilot pressure is output from the remote control valve 72A. The pilot pressure acts on the pressure receiving portion of the boom control valve 70A, and the boom 22 is lowered by supplying the hydraulic oil that has entered the boom control valve 70A to the rod side of the lift cylinder 26.
When the operation member 71 is tilted rearward, the remote control valve 72B is operated and pilot pressure is output from the remote control valve 72B. The pilot pressure acts on the pressure receiving portion of the boom control valve 70A, and the boom 22 is raised by supplying the hydraulic oil that has entered the boom control valve 70A to the bottom side of the lift cylinder 26.

That is, the boom control valve 70A is applied to the lift cylinder 26 in accordance with the hydraulic oil pressure (the pilot pressure set by the remote control valve 72A and the pilot pressure set by the remote control valve 72B) set by operating the operation member 71. The flow rate of the flowing hydraulic oil can be controlled.
When the operation member 71 is tilted to the right, the remote control valve 72C is operated, and the pilot oil acts on the pressure receiving portion of the bucket control valve 70B. As a result, the bucket control valve 70B operates in a direction in which the tilt cylinder 28 is extended, and the bucket 23 performs a dumping operation at a speed proportional to the tilting amount of the operation member 71.

When the operation member 71 is tilted to the left, the remote control valve 72D is operated, and the pilot oil acts on the pressure receiving portion of the bucket control valve 70B. As a result, the bucket control valve 70B operates in a direction to reduce the tilt cylinder 28, and the bucket 23 performs a squeeze operation at a speed proportional to the tilting amount of the operation member 71.
That is, the bucket control valve 70B is applied to the tilt cylinder 28 in accordance with the hydraulic oil pressure (the pilot pressure set by the remote control valve 72C, the pilot pressure set by the remote control valve 72D) set by operating the operation member 71. The flow rate of the flowing hydraulic oil can be controlled. That is, the remote control valves 72A, 72B, 72C, 72D change the pressure of the hydraulic oil according to the operation of the operation member 71 and supply the changed hydraulic oil to the boom control valve 70A and the bucket control valve 70B.

  The operation of the preliminary control valve 70C is performed by the first electromagnetic valve 73A and the second electromagnetic valve 73B. When the first electromagnetic valve 73A is opened, the pilot oil acts on one pressure receiving portion of the preliminary control valve 70C. When the second electromagnetic valve 73B is opened, pilot oil acts on the other pressure receiving portion of the preliminary control valve 70C. Therefore, when pilot oil acts on one pressure receiving portion or the other pressure receiving portion of the preliminary control valve 70C, the preliminary control valve 70C is switched, and the preliminary actuator of the preliminary attachment is operated by the hydraulic oil supplied from the preliminary control valve 70C. . The operation of the first electromagnetic valve 73A and the second electromagnetic valve 73B is performed by a second control device 82 described later.

As shown in FIGS. 1 and 2, the track loader (work machine) 1 includes a control device that performs control related to the work machine. The control device includes a first control device 81 and a second control device 82. Although the second control device 82 is shown in FIGS. 1 and 2, the second control device 82 shown in FIG. 1 is the same as the second control device 82 shown in FIG.
The first control device 81 is a control device that controls the prime mover 29. When the prime mover 29 is an engine, the first control device 81 is an engine control device. For convenience of explanation, it is assumed that the prime mover 29 is an engine.

  A setting member 83 is connected to the first control device 81. The setting member 83 is a device that sets (commands) a target rotational speed (target engine rotational speed) of the engine (prime motor) 29. The setting member 83 includes a pedal portion 83a and a sensor 83b that detects an operation amount of the pedal portion 83a. The pedal portion 83a is an accelerator lever supported in a swingable manner or an accelerator pedal supported in a swingable manner. The operation amount detected by the sensor 83 b is input to the first control device 81. The engine speed corresponding to the operation amount detected by the sensor 83b is the target engine speed. In other words, the target engine speed is set (determined) based on the operation amount of the setting member 83. The engine 29 is controlled by the first control device 81 so as to achieve the determined target engine speed. The first control device 81 is connected to a sensor 84 that detects an actual engine speed (referred to as an actual engine speed), and the actual engine speed is input.

  The engine control of the first control device 81 is general. For example, a control signal indicating the fuel injection amount, the injection timing, and the fuel injection rate is output to the injector. The first control device 81 outputs a signal indicating the fuel injection pressure and the like to the supply pump and the common rail. That is, the first control device 81 controls the injector, the supply pump, and the common rail so that the actual engine speed becomes the target engine speed set by the setting member 83.

  The second control device 82 is a control device that controls the hydraulic system. For example, the second control device 82 controls the first electromagnetic valve 73A and the second electromagnetic valve 73B. A switch 74 (see FIG. 2) provided around the driver's seat 13 is connected to the second control device 82. The switch 74 is configured by, for example, a swingable seesaw type switch, a slide type switch that can slide, or a push type switch that can be pressed. The operation of the switch 74 is input to the second control device 82. By the operation of the switch 74, the first electromagnetic valve 73A or the second electromagnetic valve 73B is opened and closed. Therefore, the auxiliary actuator can be operated under the control of the second control device 82.

  Moreover, the 2nd control apparatus 82 has the calculating part 82a, the memory | storage part 82b, and the control part 82c. The calculation unit 82a, the storage unit 82b, and the control unit 82c are configured by a program, an electric / electronic circuit, an electric / electronic component, and the like incorporated in the second control device 82. The second control device 82 can acquire the actual engine speed and the target engine speed from the first control device 81.

  When a load is applied to the engine 29, the actual engine speed decreases from the target engine speed. The amount of decrease in the actual rotational speed from the target rotational speed when a load is applied to the engine 29 (the difference between the target rotational speed of the engine and the actual rotational speed of the engine) is referred to as the engine drop amount. The engine drop amount is calculated by the calculation unit 82 a based on the target engine speed determined by the setting member 83 and the actual engine speed detected by the sensor 84. In the present embodiment, when the actual engine speed decreases (drops) from the target engine speed, the controller 82c determines that a load is applied to the engine 29.

  In addition, the operation valve 45 is connected to the second control device 82. The operating valve 45 can be controlled (the opening degree can be changed) by the control unit 82c. Specifically, the opening degree of the operating valve 45 is changed by a command signal output from the control unit 82c to the solenoid of the operating valve 45, and thereby the pressure of the hydraulic oil (pilot pressure) output from the operating valve 45 is changed. It can be changed. The storage unit 82b stores control characteristics (a first control characteristic L1 and a second control characteristic L2 described later) for controlling the operation valve 45. The control unit 82b controls the operation valve 45 based on the control characteristics stored in the storage unit 82b.

By the way, the driver of the work machine 1 feels that the engine 29 is operating sufficiently by lowering the engine speed when a load is applied to the work machine 1. Therefore, if the engine speed does not decrease even though a load is applied to the work machine 1, the driver may be suspicious that the engine 29 is not operating sufficiently.
On the other hand, when the engine drop amount is large, engine stall occurs.

  The second control device 82 performs control (anti-stall control) to prevent engine stall while making the driver feel a drop in the engine speed (a driver's feeling that the engine speed is decreasing). . Further, the second control device 82 performs anti-stall control (prevents engine stall) by changing the opening of the operation valve 45 based on the drop amount of the engine.

The anti-stall control will be described below with reference to FIGS.
FIG. 3 is a characteristic diagram showing the first embodiment of the anti-stall control. FIG. 4 is a characteristic diagram showing a second embodiment of the anti-stall control. 3 and 4 show the relationship between the engine speed, the traveling primary pressure, the plurality of first control characteristics L1, and the second control characteristics L2. 3 and 4, the horizontal axis indicates the engine speed (the actual engine speed), and the engine speed increases toward the right. The vertical axis indicates the primary traveling pressure, and the pressure increases as it goes upward.

The traveling primary pressure is the pressure of hydraulic oil in the oil passage from the operation valve 45 to the remote control valve (remote control valves 36, 37, 38, 39) in the second supply / discharge oil passage 100c. That is, it is the pressure (pilot pressure) of the hydraulic oil output from the hydraulic valve 45, and is the primary pressure of the hydraulic oil that enters the remote control valves 36 to 39 provided in the traveling lever 40 that performs the traveling operation.
First, a first embodiment of anti-stall control will be described with reference to FIG.

The plurality of first control characteristics L1 are characteristics that indicate the relationship between the traveling primary pressure and the actual engine speed when the load on the engine 29 is greater than or equal to a predetermined value (when the engine drop amount is greater than or equal to a predetermined engine speed). is there. The first control characteristic L1 is provided corresponding to the target engine speed. That is, the first control characteristic L1 exists for each target engine speed.
The second control characteristic L2 is a characteristic indicating the relationship between the traveling primary pressure and the actual engine speed when the load on the engine 29 is less than a predetermined value (when the engine drop amount is less than the predetermined engine speed). The second control characteristic L2 is a common characteristic line for all target rotational speeds. Therefore, the second control characteristic L2 is one.

The plurality of first control characteristics L1 and second control characteristics L2 are stored in the storage unit 82a of the second control device 82 (data indicating the first control characteristics L1 and the second control characteristics L2, or functions, etc. The control parameter and the like are stored in the storage unit 82a).
The controller 82c of the second control device 82 has a determination value for determining an engine drop amount (amount of decrease in the actual rotational speed from the target rotational speed) for each target rotational speed. When the engine drop amount is less than a predetermined determination value, the control unit 82c controls the operation valve 45 based on the second control characteristic L2. That is, when the engine drop amount is less than the predetermined amount, the opening degree of the proportional valve 45 is adjusted by the control unit 82c so that the relationship between the actual engine speed and the traveling primary pressure matches the second control characteristic L2. (The opening degree of the operating valve 45 is adjusted by the control unit 82c so that the traveling primary pressure corresponding to the actual rotational speed determined by the second control characteristic L2 is output from the operating valve 45).

  Further, when the engine drop amount is equal to or larger than a predetermined determination value, the control unit 82c is based on the first control characteristic L1 corresponding to the target rotational speed set by the setting member 83 (second). The control valve 45 is controlled by switching from the control characteristic L2 to the first control characteristic L1. That is, when the engine drop amount is greater than or equal to the predetermined amount, the opening degree of the proportional valve 45 is adjusted by the control unit 82c so that the relationship between the actual engine speed and the traveling primary pressure matches the first control characteristic L1. (The opening degree of the operating valve 45 is adjusted by the control unit 82c so that the traveling primary pressure corresponding to the actual rotational speed determined by the first control characteristic L1 is output from the operating valve 45).

  In FIG. 3 (first embodiment), as the plurality of first control characteristics L1, four control characteristics, that is, the first control characteristic L1a, the first control characteristic L1b, the first control characteristic L1c, and the first control characteristic L1d are represented. Illustrated. The first control characteristic L1a is a characteristic when the target rotational speed is M1 rpm. The first control characteristic L1b is a characteristic when the target rotational speed is M2 rpm lower than M1 rpm. The first control characteristic L1c is a characteristic when the target rotation speed is M3 rpm lower than M2 rpm. The first control characteristic L1d is a characteristic when the target rotation speed is M4 rpm lower than M3 rpm.

Next, the first control characteristic L1a, the first control characteristic L1b, the first control characteristic L1c, and the first control characteristic L1d will be described in detail.
In the present embodiment, the first control characteristic L1a, the first control characteristic L1b, the first control characteristic L1c, and the first control characteristic L1d are linear and have the same inclination.
The first control characteristic L1a is a characteristic line in which the traveling primary pressure decreases as the engine speed decreases from the point A1a on the second control characteristic L2. Point A1a is a point where the actual engine speed has decreased by a drop amount X1a from the target speed M1rpm (a point on the second control characteristic L2 when the drop quantity from the target speed M1rpm is X1a). The first control characteristic L1b is a characteristic line in which the traveling primary pressure decreases as the engine speed decreases from the point A1b on the second control characteristic L2. Point A1b is a point where the actual engine speed has decreased by a drop amount X1b from the target engine speed M2rpm. The first control characteristic L1c is a characteristic line in which the traveling primary pressure decreases as the engine speed decreases from the point A1c on the second control characteristic L2. Point A1c is a point where the actual engine speed has decreased by a drop amount X1c from the target engine speed M3rpm. The first control characteristic L1d is a characteristic line in which the traveling primary pressure decreases as the engine speed decreases from the point A1d on the second control characteristic L2. Point A1d is a point where the actual engine speed has decreased by a drop amount X1d from the target engine speed M4 rpm.

  The drop amount X1b is smaller than the drop amount X1a. The drop amount X1c is smaller than the drop amount X1b. The drop amount X1d is smaller than the drop amount X1c. For example, when the target engine speed is 2800 rpm, the determination value of the drop amount X1 until the switch from the second control characteristic L2 to the first control characteristic L1 is 300 rpm. When the target engine speed is 2600 rpm, the determination value is 200 rpm. When the engine target speed is 2400 rpm, the determination value is 100 rpm. When the engine speed is 2300 rpm or less, the determination value is 50 rpm. When a plurality of determination values are set, the smallest determination value may be zero.

  Therefore, the drop amount X1 until switching from the second control characteristic L2 to the first control characteristic L1 is set so that the value increases as the target engine speed increases. In other words, the control unit 82c has a determination value that is set to increase as the target rotational speed increases. The control unit 82c controls the operation valve 45 using a determination value that is set to a larger value as the target rotational speed increases.

  The first control characteristic L1a, the first control characteristic L1b, the first control characteristic L1c, and the first control characteristic L1d follow the third characteristic L3. The third characteristic L3 is a characteristic line in which the traveling primary pressure decreases as the engine speed decreases, and is a linear characteristic line. The inclination of the third characteristic L3 is smaller than the first control characteristic line L1 (first control characteristic L1a, first control characteristic L1b, first control characteristic L1c, and first control characteristic L1d).

Next, the relationship between the first control characteristic L1 and the third characteristic L3 will be described.
The first control characteristic L1a is connected to the third characteristic L3 at the first rotational speed D1 at which the actual rotational speed of the engine is a predetermined value. The first control characteristic L1b is connected to the third characteristic L3 at the second rotational speed D2 in which the actual rotational speed of the engine is lower than the first rotational speed D1. The first control characteristic L1c is connected to the third characteristic L3 at a third rotational speed D3 in which the actual rotational speed of the engine is lower than the second rotational speed D2. The first control characteristic L1d is connected to the third characteristic L3 at a fourth rotational speed D4 in which the actual rotational speed of the engine is lower than the third rotational speed D3. The first control characteristic L1a, the first control characteristic L1b, the first control characteristic L1c, and the first control characteristic L1d follow the common third characteristic L3.

Next, control by the control unit 82c will be described.
As shown in FIG. 3, when the load of the engine 29 is less than a predetermined value, that is, when the actual engine speed does not exceed a predetermined drop amount from the target engine speed, the control unit 82c has the second control characteristic L2. The opening degree of the operating valve 45 is controlled so that the actual engine speed shown in the figure matches the pressure output from the operating valve 45 (the pressure of the operating oil entering the remote control valves 36 to 39).
Here, when the target engine speed of the engine is M1 and the actual engine speed decreases from the target engine speed M1 by the drop amount X1a or more (below the point A1a), the control unit 82c determines from the second control characteristic L2 Switch to 1 control characteristic L1a. The control unit 82c controls the opening degree of the working valve 45 so that the actual engine speed indicated by the first control characteristic L1a matches the pressure output from the working valve 45. In addition, when the operating valve 45 is controlled with the first control characteristic L1a, the operating valve 45 is controlled according to the third control characteristic L3 when the actual engine speed becomes equal to or lower than the first engine speed D1.

  When the target engine speed is M2 and the actual engine speed drops from the target engine speed M2 by the drop amount X1b or more (below the point A1b), the controller 82c starts from the second control characteristic L2 to the first control characteristic. Switch to L1b. And the control part 82c controls the opening degree of the operating valve 45 so that the actual engine speed shown by the 1st control characteristic L1b and the pressure output from the operating valve 45 may correspond. Further, when the operating valve 45 is controlled with the first control characteristic L1b, the operating valve 45 is controlled according to the third control characteristic L3 when the actual engine speed becomes equal to or lower than the second engine speed D2.

  When the target engine speed is M3 and the actual engine speed drops from the target engine speed M3 by the drop amount X1c or more (below the point A1c), the controller 82c starts from the second control characteristic L2 to the first control characteristic. Switch to L1c. Then, the control unit 82c controls the opening degree of the working valve 45 so that the actual engine speed indicated by the first control characteristic L1c matches the pressure output from the working valve 45. Further, when the operating valve 45 is controlled with the first control characteristic L1c, the operating valve 45 is controlled according to the third control characteristic L3 when the actual engine speed becomes the third engine speed D3 or less.

  When the target engine speed is M4 and the actual engine speed drops from the target engine speed M4 by the drop amount X1d or more (below the point A1d), the controller 82c starts from the second control characteristic L2 to the first control characteristic. Switch to L1d. The control unit 82c controls the opening degree of the working valve 45 so that the actual engine speed indicated by the first control characteristic L1d matches the pressure output from the working valve 45. Further, when the operating valve 45 is controlled with the first control characteristic L1d, the operating valve 45 is controlled according to the third control characteristic L3 when the actual engine speed becomes the fourth rotational speed D4 or less.

  As described above, in the second control characteristic L2, the degree of decrease in the traveling primary pressure accompanying the decrease in the actual engine speed is more gradual than in the first control characteristic L1. Therefore, in the second control characteristic L2, the suppression force against the decrease in the actual engine speed when the engine 29 is loaded is small (the actual engine speed decreases in accordance with the load). As a result, when a load is applied to the engine 29, it is possible to make the driver feel a drop in the engine speed (that the engine 29 is operating sufficiently).

  In the first control characteristic L1, the traveling primary pressure for a predetermined engine speed is lower than the traveling primary pressure of the second control characteristic L2. That is, when focusing on the same engine speed, the traveling primary pressure of the first control characteristic L1 is lower than the traveling primary pressure of the second control characteristic L2. Therefore, the pressure (pilot pressure) of the hydraulic oil entering the remote control valve is suppressed to be lower than the control based on the second control characteristic L2 by the control based on the first control characteristic L1. By adjusting the swash plate angle of the traveling pump (traveling hydraulic pump) 66 by the hydraulic oil suppressed to a low level, the load acting on the engine 29 is effectively reduced, and the engine speed is effectively reduced. (The engine speed can be kept high as compared with the control based on the second control characteristic L2). As a result, engine stall can be effectively prevented when the load on the engine 29 becomes larger than a predetermined value and the decrease in the engine speed increases.

As described above, it is possible to achieve both the feeling of the driver when the load is applied to the engine 29 and the prevention of the engine stall.
In addition, when the drop amount until switching from the second control characteristic L2 to the first control characteristic L1 is the same for all target rotational speeds, the target rotational speed can be obtained by adjusting the drop amount to a high target rotational speed. The smaller the value, the higher the possibility of causing an engine stall accompanying a decrease in the engine speed. On the other hand, in the first embodiment, the drop amount X1 until switching from the second control characteristic L2 to the first control characteristic L1 is smaller when the target rotational speed is low than when the target rotational speed is high. I am doing so. Thereby, both the feeling of the driver and the prevention of the engine stall can be achieved according to the target engine speed.

  The relationship between the target engine speed and the drop amount X1 may be a proportional relationship in which the drop amount X1 increases proportionally as the target engine speed increases continuously or stepwise. The relationship between the target engine speed and the drop amount X1 may be such that a threshold value is provided for the target engine speed and the drop amount is switched at this threshold value (the drop amount varies before and after the threshold value).

On the other hand, when the actual rotational speed of the engine decreases beyond the first rotational speed D1 to the fourth rotational speed D4, the pressure of the hydraulic oil entering the remote control valves 36 to 39 is controlled by the control based on the third control characteristic L3. .
For example, when the working machine 1 is advanced and the bucket 23 is thrust into piled earth and sand, the actual engine speed drops greatly, but when the engine speed drops greatly, When the slope of the first control characteristic L1 is large (when the amount of decrease in the traveling primary pressure with respect to the drop amount is large), the torque of the engine 29 is insufficient, and the actual engine speed returns slowly. Therefore, the slope of the third control characteristic L3, which is an area where the drop amount is excessive in the first control characteristic L1, is made gentler than the slope of the first control characteristic L1 (decreasing the travel primary pressure drop relative to the drop amount). This makes it easier for the actual engine speed to recover after the engine speed drops to an extremely large level. When the bucket 23 is pushed into the piled earth and sand, etc. can do.

  Further, the drop amount X1 may be switched by a driver's operation. That is, it is a first control characteristic of another pattern different from the first control characteristic L1 of the pattern illustrated in FIG. 3, and the drop amount X1 is made different (a numerical value larger than the drop amount X1 shown in FIG. 3 or The other pattern of the first control characteristic is stored in the storage unit 82b. Further, as shown in FIG. 1, a switch (referred to as a changeover switch) 110 connected to the second control device 82 is provided, and the changeover switch 110 is disposed where the driver can operate (for example, around the driver's seat 13). To do. The changeover switch 110 is used to switch between the first control characteristic of the pattern shown in FIG. 3 and the first control characteristic of another pattern. Thereby, the 1st control characteristic of the pattern according to the work situation etc. can be selected. The pattern of the first control characteristic to be switched may be two patterns or three or more patterns.

Note that another switch (referred to as a setting switch) 111 connected to the second control device 82 is provided, and this setting switch 111 is disposed around the driver's seat 13. This setting switch 111 can arbitrarily set the determination value.
Further, the switching of the pattern of the first control characteristic may be automatically performed by switching the shifting (traveling speed) of the traveling motor 57 (switching between the first speed and the second speed). For example, the changeover switch 110 is constituted by a changeover valve that is switched by a pilot pressure that switches the first hydraulic pressure changeover valve 63. Then, the pattern of the first control characteristic is automatically switched in conjunction with the switching of the first hydraulic pressure switching valve 63. Alternatively, the pattern of the first control characteristic may be automatically switched by switching the shift of the traveling motor 57 provided with the shift pattern of the third speed or higher.

  Further, the switching of the pattern of the first control characteristic may be automatically switched according to the type of attachment mounted (mounted). The attachment to be attached may be automatically identified by a sensor when attached to the work machine 1. In addition, the driver may select and switch the pattern of the first control characteristic corresponding to the attached attachment.

[Second Embodiment]
FIG. 4 is a diagram illustrating a relationship between the engine speed and the traveling primary pressure in the second embodiment.
About this 2nd Example, the difference with 1st Embodiment is demonstrated and description of the part of the same structure is abbreviate | omitted.
First, the outline of the second embodiment will be described.

  In the second embodiment, there are a plurality of first control characteristics L1 having different inclinations determined corresponding to the target engine speed. The storage unit 82b stores a plurality of first control characteristics L1 having different inclinations. When the load of the engine 29 is equal to or greater than a predetermined value, the control unit 82c controls the operation valve 45 based on a plurality of first control characteristics L1 having different inclinations determined according to the target engine speed. The inclination of the first control characteristic L1 is set to become smaller as the target engine speed increases. The operation valve 45 is controlled using the first control characteristic L1 having a smaller inclination as the target engine speed of the engine increases.

Next, the first control characteristic L1 of the second embodiment will be described in detail.
As shown in FIG. 4, the first control characteristic L1a is a characteristic line in which the traveling primary pressure decreases as the engine speed decreases from the point B1a on the second control characteristic L2. Point B1a is a point on the second control characteristic L2 and corresponds to the target rotational speed M1. The first control characteristic L1b is a characteristic line in which the traveling primary pressure decreases as the engine speed decreases from the point B1b on the second control characteristic L2. Point B1b is a point on the second control characteristic L2 and corresponds to the target rotational speed M2. The first control characteristic L1c is a characteristic line in which the traveling primary pressure decreases as the engine speed decreases from the point B1c on the second control characteristic L2. Point B1c is a point on the second control characteristic L2 and corresponds to the target rotational speed M3. The first control characteristic L1d is a characteristic line in which the traveling primary pressure decreases as the engine speed decreases from the point B1d on the second control characteristic L2. Point B1d is a point on the second control characteristic L2, and corresponds to the target rotational speed M4.

  The engine stall due to a decrease in the actual engine speed occurs with a smaller drop amount as the target engine speed decreases (the area with a lower target speed has a smaller drop quantity than the area with a higher target engine speed). An engine stall occurs. When the slope of the first control characteristic provided for each target engine speed is the same as in the prior art, the slope of the first control characteristic is given to the driver in a region where the target speed is high. If the inclination is such that engine stall can be prevented, it may be difficult to prevent engine stall in a region where the target rotational speed is low. On the other hand, if it is difficult to give the driver a drop feeling in the high target speed range if the inclination is such that it gives the driver a drop feeling in the low target speed range and can prevent engine stall. Occurs.

  Therefore, the inclination of the first control characteristic L1 is set so that the inclination becomes smaller (relaxed) as the target engine speed increases. The operating valve 45 is controlled using the first control characteristic L1 whose inclination is set to be smaller as the target engine speed of the engine increases. Thereby, it is possible to achieve both the feeling of the driver when the load is applied to the engine 29 and the prevention of the engine stall.

  The relationship between the target engine speed and the slope of the first control characteristic L1 is that the slope of the first control characteristic L1 increases proportionally as the target engine speed increases continuously or stepwise. It may be a proportional relationship. In addition, the relationship between the target engine speed and the slope of the first control characteristic L1 is that a threshold value is set for the target engine speed, and the slope of the first control characteristic L1 is switched at this threshold value (first and second before and after the threshold value). The slope of the control characteristic L1 may be different).

  Further, the slope of the first control characteristic L1 may be switched by the operation of the driver. That is, it is the first control characteristic of another pattern different from the first control characteristic L1 of the pattern illustrated in FIG. 4, and the slope of the first control characteristic L1 is made different (larger than the slope shown in FIG. 4 or The other pattern of the first control characteristic is stored in the storage unit 82b. Then, the changeover switch 110 switches between the first control characteristic of the pattern shown in FIG. 4 and the first control characteristic of another pattern. Thereby, the 1st control characteristic of the pattern according to the work situation etc. can be selected. The pattern of the first control characteristic to be switched may be two patterns or three or more patterns.

Further, the switching of the pattern of the first control characteristic may be automatically performed by switching the shift of the traveling motor 57 as in the first embodiment.
Also, the switching of the pattern of the first control characteristic may be automatically switched according to the type of attachment mounted (mounted), as in the first embodiment.
The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

In the embodiment described above, the traveling pump 66 is exemplified as the hydraulic device. However, any hydraulic device that can be operated by the hydraulic oil output from the operating valve 45 may be used.
Further, the control may be performed by combining the first control characteristic having the same plurality of inclinations shown in FIG. 3 and the first control characteristic having the different inclinations shown in FIG. The storage unit 82b has a first control characteristic (first control characteristic shown in FIG. 3) having the same inclination and parallel to each other, and a first control characteristic (first control characteristic shown in FIG. 4) having a different inclination with respect to the parallel first control characteristic. 1 control characteristic). That is, the storage unit 82b stores both the first control characteristic shown in FIG. 3 and the first control characteristic shown in FIG. The controller 82c controls the operation valve 45 based on the second control characteristic when the amount of decrease in the actual rotational speed from the target rotational speed is less than a predetermined determination value. In addition, when the amount of decrease is equal to or greater than the determination value of the actual rotational speed, the control unit 82c determines the first control characteristic determined according to the target rotational speed (the first control characteristic or the parallel parallel slope is the same and the slope is different The operation valve 45 is controlled based on the first control characteristic. The control of the operation valve 45 in the control unit 82c is the same as that in the above-described embodiment.

  In addition, the operating valve 45 is a valve that supplies the traveling primary pressure to the traveling operation device 14 that operates the traveling pump 66, but is not limited thereto. For example, an electromagnetic proportional valve that supplies hydraulic oil (servo pressure) for control to a servo regulator that controls the swash plate of the traveling pump 66 may be used as the operating valve. In this case, the operation valve (electromagnetic proportional valve) operates in conjunction with the operation of the travel lever 40 of the travel operation device 14. For example, when the travel lever 40 is not operated and is in the neutral position, the output of the actuating valve is zero. When the travel lever 40 is operated to the maximum (maximum operation), a pressure corresponding to the travel primary pressure is output as shown in FIGS. The actuating valve outputs a pressure corresponding to the traveling primary pressure and the operation amount of the traveling lever. For example, when the traveling primary pressure is 2.5 MPa, the operating valve outputs a value obtained by equally assigning 2.5 MPa to the operation amount (0% to 100%) of the traveling lever 40. In this case, when the operation amount of the travel lever 40 is the maximum operation (100%), the operating valve outputs 2.5 MPa corresponding to the maximum operation, and when the operation amount is half (50%). 1.25 MPa corresponding to half is output. When the traveling primary pressure is 1.0 MPa, the operating valve outputs a value obtained by assigning 1.0 MPa to the operation amount (0% to 100%) of the traveling lever 40. Moreover, after setting the primary travel pressure corresponding to the maximum operation amount of the travel lever 40 in advance, the primary travel pressure is assigned to the range from the maximum operation amount to the minimum operation amount (relationship between the operation amount and the primary travel pressure). Is constant slope). If the travel primary pressure obtained by the operation amount of the operation lever 40 does not exceed the travel primary pressure corresponding to the actual engine speed when the travel lever 40 is operated, the travel lever 40 can be obtained by the operation amount of the operation lever 40. Apply traveling primary pressure. On the other hand, when the traveling primary pressure obtained by the operation amount of the operation lever 40 exceeds the traveling primary pressure corresponding to the actual engine speed, the traveling primary pressure corresponding to the actual engine speed is adopted. That is, the relationship between the operation amount of the travel lever 40 and the travel primary pressure is set, and control is performed so as not to exceed the travel primary pressure based on the operation amount.

  When the primary travel pressure is assigned to the operation amount of the travel lever 40, it may be assigned in consideration of play of the travel lever 40. Moreover, the allocation of the travel primary pressure to the operation amount of the travel lever 40 may not be evenly allocated. Further, the relationship between the traveling primary pressure and the traveling lever 40 may not be a proportional relationship.

1 Working machine (truck loader)
29 prime mover (engine)
45 Actuating valve 57 Traveling motor (hydraulic equipment)
66 Traveling pump (hydraulic equipment)
82b Storage unit 82c Control unit 83 Setting member P2 Second hydraulic pump

Claims (7)

Prime mover,
A setting member for setting a target rotational speed of the prime mover;
A hydraulic pump operable by driving the prime mover and discharging hydraulic oil;
An operating valve to which hydraulic oil discharged from the hydraulic pump is supplied;
Hydraulic equipment operable by hydraulic fluid of the operating valve;
A plurality of first characteristics having a relationship between a pressure of hydraulic oil of the working valve and an actual rotational speed of the prime mover when a load of the prime mover is equal to or greater than a predetermined value and having different inclinations determined according to the target rotational speed A storage unit for storing control characteristics;
When the load of the prime mover is equal to or greater than a predetermined value, a control unit that controls the operating valve based on the first control characteristic having a different slope determined according to the target rotational speed;
The working machine's hydraulic system.   2. The hydraulic system for a working machine according to claim 1, wherein the control unit controls the operation valve using a first control characteristic in which an inclination is set to be small as the target rotational speed is increased.   The working machine hydraulic system according to claim 1, further comprising a switch capable of changing the first control characteristic.   The hydraulic system for a working machine according to any one of claims 1 to 3, further comprising a switch capable of changing the determination value. Prime mover,
A setting member for setting a target rotational speed of the prime mover;
A hydraulic pump operable by driving the prime mover and discharging hydraulic oil;
An operating valve to which hydraulic oil discharged from the hydraulic pump is supplied;
Hydraulic equipment operable by hydraulic fluid of the operating valve;
The characteristic indicating the relationship between the hydraulic oil pressure of the operating valve and the actual rotational speed of the prime mover when the load on the prime mover is greater than or equal to a predetermined value, and the slopes corresponding to the target rotational speed are parallel or different A storage unit that stores a plurality of first control characteristics, and a second control characteristic that indicates a relationship between a pressure of hydraulic fluid of the working valve and an actual rotational speed of the prime mover when a load of the prime mover is less than a predetermined value;
When the decrease amount of the actual rotation number from the target rotation number is less than a predetermined determination value, the operation valve is controlled based on the second control characteristic, and the decrease amount is the actual rotation number. A control unit that controls the operating valve based on the first control characteristic determined according to the target rotational speed when the determination value is equal to or greater than
The working machine's hydraulic system. Prime mover,
A setting member for setting a target rotational speed of the prime mover;
A hydraulic pump operable by driving the prime mover and discharging hydraulic oil;
An operating valve to which hydraulic oil discharged from the hydraulic pump is supplied;
Hydraulic equipment operable by hydraulic fluid of the operating valve;
A storage unit for storing a plurality of first control characteristics having different inclinations corresponding to the target rotational speed, which are characteristics indicating a relationship between the pressure of the hydraulic oil of the hydraulic valve and the actual rotational speed of the prime mover;
When the amount of decrease in the actual rotational speed from the target rotational speed is equal to or greater than a predetermined determination value, the operation is performed based on the first control characteristic having a different slope determined according to the target rotational speed. A control unit for controlling the valve;
The working machine's hydraulic system. Prime mover,
A setting member for setting a target rotational speed of the prime mover;
A hydraulic pump operable by driving the prime mover and discharging hydraulic oil;
An operating valve to which hydraulic oil discharged from the hydraulic pump is supplied;
Hydraulic equipment operable by hydraulic fluid of the operating valve;
A plurality of first control characteristics indicating a relationship between the pressure of the hydraulic oil of the operating valve and the actual rotational speed of the prime mover, wherein the slopes corresponding to the target rotational speed are parallel or different from each other; and A storage unit for storing a second control characteristic indicating a relationship between the pressure of the hydraulic oil of the working valve and the actual rotational speed of the prime mover;
When the decrease amount of the actual rotation number from the target rotation number is less than a predetermined determination value, the operation valve is controlled based on the second control characteristic, and the decrease amount is the actual rotation number. A control unit that controls the operating valve based on the first control characteristic determined according to the target rotational speed when the determination value is equal to or greater than
The working machine's hydraulic system.

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