KR101913309B1 - Hydraulic drive device of working machine - Google Patents

Abstract

A hydraulic drive device for a work machine capable of realizing good operability during normal operation and fine operation and reducing energy loss during fine operation.
The present invention is characterized in that when the controller (31) is an operating mode in which the operation mode of the operating element operating device is regarded as a fine operation, the displacement volume of the variable displacement hydraulic pump (10) is made smaller than the displacement volume corresponding to the normal operation A pump discharge amount control section (40) for performing a control process of outputting a control signal to the control section of the proportional pressure reducing valve (21); and a control section A center bypass valve control section 50 for performing control processing for outputting a control signal for making the opening amount relatively large to the control section of the proportional solenoid valve 23 while the bypass valve 22 is in the switching state between the deployed position and the full- As shown in Fig.

Description

HYDRAULIC DRIVE DEVICE OF WORKING MACHINE [0001]

The present invention relates to a hydraulic shovel which includes a working element such as a boom and an arm and which has a normal operation and a fine operation which can be performed at a small operation amount, The present invention relates to a hydraulic driving apparatus for a work machine having a direction control valve of an open center type and positively controlling a variable displacement hydraulic pump.

As a conventional technique of this type of open center positive control system, there is one disclosed in Patent Document 1. In this prior art, an open center type directional control valve for a boom and a directional control valve for an arm are arranged on a center bypass line connecting the variable displacement hydraulic pump and the tank, and the displacement of the variable displacement hydraulic pump And the volume is variably controlled in accordance with the operation amount of the operation device for switching operation of the directional control valve for boom and the directional control valve for arm.

Japanese Patent Application Laid-Open No. 11-82416

In the above-described conventional technique, when the system is set in consideration of securing good operability during normal operations such as excavation work, the operation amount of the operation device is reduced or the operation speed is made slow to perform the fine operation As a result, the extra pump flow can easily flow into the tank through the directional control valve and the center bypass line. That is, the energy that is not utilized for the work is increased, and it is easy to cause energy loss. In addition, when the system is set in consideration of reducing the excess flow rate flowing through the tank during the fine operation, the operability during normal operation deteriorates. As described above, in the prior art, it is difficult to achieve both reduction of energy loss during fine operation and securing good operability during normal operation.

Further, in general, even when the work is performed by a fine operation, a work such as a crane operation performed in a hydraulic excavator, in which a load pressure becomes high and becomes a heavy load, There is a work in which the load pressure is low and the load is light. Conventionally, consideration has not been given to control of other operations of the load in such a fine operation. Therefore, energy loss accompanied with high or low load of the fine operation and deterioration of operability are likely to occur.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described prior art, and its object is to provide a method for securing good operability during normal operation and fine operation and reducing energy loss during fine operation And to provide a hydraulic drive apparatus for a working machine having the hydraulic pump.

In order to achieve this object, the present invention provides a working machine equipped with a working device capable of performing a normal operation and a fine operation performed with a smaller operation amount and a slower operation speed than the normal operation, comprising a variable displacement hydraulic pump, An actuator for a working element which is operated by a pressure oil discharged from the variable displacement hydraulic pump and drives a working element contained in the working device; An open center-type working element direction control valve for controlling the flow of pressure oil supplied from the variable displacement hydraulic pump to the actuator for the working element, and a working element operating device for switching operation of the working element direction control valve A displacement control unit for controlling a displacement amount of the variable displacement hydraulic pump, A center bypass valve provided at a portion of the center bypass line positioned downstream of the directional control valve for the working element and capable of controlling a flow rate returned to the tank via the center bypass line; A center bypass valve control device for controlling the center bypass valve, a displacement volume control device, and a controller for controlling the center bypass valve control device, wherein the controller controls the operation of the operation element operating device Wherein the displacement volume control device outputs a control signal to the displacement volume control device to set the displacement volume of the variable displacement hydraulic pump to a displacement volume corresponding to the normal operation when the operation mode of the variable displacement hydraulic pump is regarded as the normal operation, When the operating mode of the operating device for the working element is an operating mode considered as the fine operation, A pump discharge amount control section for performing control processing for outputting to the displacement volume control device a control signal for making the displacement volume of the hydraulic oil pump smaller than the displacement volume corresponding to the normal operation; A control signal for controlling opening and closing of the center bypass valve when the operating mode is regarded as an operation and a control signal for operating the operating element for the working element when the operation mode of the operating element operating device is regarded as the fine operation, To a state of switching between a fully open position and a fully closed position to the center bypass valve control device, As the operation mode considered as the fine operation, the load pressure of the actuator for the working element is high A control signal for reducing the opening amount of the center bypass valve in the switching state between the deployed position and the full closing position and a control signal for reducing the opening amount of the center bypass valve when the operation mode of the working element operating apparatus is regarded as the fine operation A control process for outputting to the center bypass valve control device a control signal for setting the center bypass valve as an opening larger than the opening amount when the load pressure of the actuator for the working element is low as the sun And a center bypass valve control unit.

According to the present invention configured as described above, when the operation element operating device is operated in a normal operation, the displacement amount control device of the controller controls the displacement volume of the variable displacement hydraulic pump to a relatively large displacement volume Is output. As a result, a large flow rate is supplied from the variable displacement hydraulic pump to the actuator for the working element through the directional control valve for the working element. During this time, a control signal for controlling opening and closing of the center bypass valve is outputted from the center bypass valve control section of the controller to the center bypass valve control device. As a result, a large flow rate can be returned from the actuator for the working element to the tank via the center bypass line and the center bypass valve. By these operations, it is possible to ensure good normal operability that enables the work element to be driven at a high operating speed.

Further, in the present invention, when the operation element operating device is operated with a small operation amount or a slow operation speed in a work performed by fine operation, the displacement amount control device of the controller causes the displacement amount control device to change the displacement of the variable displacement hydraulic pump A control signal is output which makes the volume smaller than the displacement volume corresponding to the normal operation. As a result, a small flow rate is supplied to the actuator for the work element from the variable displacement hydraulic pump through the directional control valve for the work element, as compared with a normal operation. During this time, a control signal is outputted from the center bypass valve control unit of the controller to the center bypass valve control unit to control the center bypass valve to the switching state between the unfolding position and the full closing position. This makes it possible to suppress the amount of flow back from the actuator for the working element to the tank via the center bypass line and the center bypass valve. By these operations, it is possible to secure good micro operability which enables the work element to be driven at a slow operating speed. At this time, the output of the variable displacement hydraulic pump can be suppressed, and the energy loss can be reduced.

Further, in the fine operation of the working element actuator, the center bypass valve control unit of the controller is connected to the center bypass valve control unit when the load pressure of the actuator for the working element is high, A control signal for further reducing the opening amount of the center bypass valve is output. As a result, the discharge pressure of the variable displacement hydraulic pump becomes high, so that good operability in this fine operation and heavy load operation can be ensured.

Further, even in the minute operation of the present invention, when the load pressure of the actuator for the working element is low, the center bypass valve control unit of the controller transmits the center bypass valve to the deployment position, A control signal for increasing the opening amount of the center bypass valve in comparison with the opening amount in the above-described heavy load is output. As a result, the discharge pressure of the variable displacement hydraulic pump is suppressed to be low, and good operability can be secured in this fine operation and light load work. At this time, the output of the variable displacement hydraulic pump can be suppressed, and the energy loss can be reduced.

Further, according to the present invention, in the above-described invention, based on the manipulated variable, the manipulated speed, or the manipulated acceleration of the working element manipulating device, the controller is a manipulation mode in which the manipulating mode of the working element manipulating device is regarded as a fine manipulation And a process for calculating the value of the product is executed.

Further, according to the present invention, in the above invention, it is preferable that the working machine is a hydraulic excavator, the working element includes a boom and an arm, the actuator for the working element comprises a boom cylinder for operating the boom, Wherein the directional control valve for the working element includes a directional control valve for a boom for controlling the boom cylinder and an arm directional control valve for controlling the arm cylinder, , A boom operation device for switching operation of the boom directional control valve, and an arm operation device for switching the arm directional control valve.

According to the present invention, in the above-described invention, the discharge pressure sensor for detecting the discharge pressure of the variable displacement hydraulic pump, or the bottom pressure sensor for detecting the bottom pressure of the boom cylinder, And the center bypass valve control section of the controller controls at least one of an operation amount of the operation amount of the boom operation device and an operation amount of the arm operation device, Or the operation amount of the operation device for the arm and the operation amount of at least one of the bob pressure detected by the bottom pressure sensor and the load pressure detected by the load pressure sensor , And a load pressure of the actuator for the working element is set to be smaller than a load pressure of the working element When there is the state, and wherein the performing a control process of outputting a control signal to the center by-pass valve with a relatively large opening amount.

The present invention is characterized in that the controller is provided with a pump discharge amount control section for outputting a control signal made to have a different displacement volume in accordance with normal operation and fine operation to a displacement displacement control device for controlling displacement volume of the variable displacement hydraulic pump, And outputs a control signal to the center bypass valve control device for controlling the center bypass valve in accordance with the normal operation and the fine operation to be different from each other by a different center bypass opening amount, And a center bypass valve control section for outputting control signals to the control section of the proportional electromagnetic valve described above, the control signals being different from each other depending on the level of the center bypass valve opening. With this configuration, it is possible to secure good operability at the time of normal operation and to secure a good operability in accordance with the load pressure of the actuator for the working element at the time of fine operation, and at the same time, The reduction of the energy loss can be realized. Therefore, it is possible to realize a highly reliable hydraulic drive apparatus which can realize an operability that is higher than that of the prior art, and which is economical and practical.

1 is a side view showing a hydraulic excavator as an example of a working machine.
Fig. 2 is an electric / hydraulic circuit diagram showing the hydraulic drive apparatus according to the first embodiment provided in the hydraulic excavator shown in Fig. 1. Fig.
3 is a block diagram showing a configuration of a pump discharge amount control unit included in a controller included in the hydraulic drive apparatus according to the first embodiment shown in Fig.
4 is a block diagram showing the configuration of the center bypass valve control section included in the controller included in the hydraulic drive apparatus according to the first embodiment shown in Fig.
5 is a diagram showing control performed in the hydraulic drive apparatus according to the first embodiment.
Fig. 6 is a diagram showing control performed in the hydraulic drive apparatus according to the second embodiment of the present invention. Fig.
7 is a block diagram showing the configuration of the main parts of the pump discharge amount control unit included in the controller included in the hydraulic drive apparatus according to the third embodiment of the present invention.
8 is a block diagram showing a configuration of a main portion of a center bypass valve control section included in a controller included in the hydraulic drive apparatus according to the third embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of a hydraulic drive apparatus for a working machine according to the present invention will be described with reference to the drawings.

1 is a side view showing a hydraulic excavator as an example of a working machine.

The hydraulic drive apparatus according to the first embodiment is provided in, for example, a hydraulic excavator and includes a traveling body 1, a swivel body 2 disposed on the traveling body 1, And a work device (3) mounted on the body (2) so as to be vertically rotatable. The working device 3 includes a boom cylinder 7 for actuating a working element actuator such as a boom 4 together with a boom 4, an arm 5 and a bucket 6 constituting a working element, An arm cylinder 8 for actuating the bucket 6, and a bucket cylinder 9 for operating the bucket 6.

Fig. 2 is an electric / hydraulic circuit diagram showing the hydraulic drive apparatus according to the first embodiment provided in the hydraulic excavator shown in Fig. 1, Fig. 3 is included in a controller included in the hydraulic drive apparatus according to the first embodiment shown in Fig. 2 Fig. 4 is a block diagram showing the configuration of the center bypass valve control section included in the controller included in the hydraulic drive apparatus according to the first embodiment shown in Fig. 2; Fig.

2, the hydraulic drive apparatus according to the first embodiment includes a variable displacement hydraulic pump 10, a servo valve 20 and a control actuator 20a included in a regulator of the variable displacement hydraulic pump 10, And a displacement displacement control device for controlling the displacement of the variable displacement hydraulic pump 10, for example, the proportional pressure reducing valve 21, which controls the servo valve 20.

In addition to the above-described boom cylinder 7 and arm cylinder 8 which are operated by the hydraulic fluid discharged from the variable displacement hydraulic pump 10 and constitute the actuator for the working element, the variable displacement hydraulic pump 10 For controlling the flow of the pressure oil supplied from the variable displacement hydraulic pump 10 to the boom cylinder 7 and the arm cylinder 8 is provided in the center bypass line 60 connecting the tank 34 to the boom cylinder 7, A direction control valve for a boom, and a direction control valve 15 for an arm. The boom operating device 12 and the arm operating device 13 are provided with operating elements for operating elements for switching operation of the boom directional control valve 14 and the arm directional control valve 15.

The first embodiment is provided in the portion of the center bypass line 60 located downstream of the directional control valve 14 for the boom and the flow rate returned to the tank 34 via the center bypass line 60 And a center bypass valve control device for controlling the center bypass valve 22, for example, a proportional solenoid valve 23. The center bypass valve 22 controls the center bypass valve 22, The first embodiment further includes a controller 31 that controls the electron proportional pressure reducing valve 21 via the signal line 32 and the proportional solenoid valve 23 via the signal line 33. [

The controller 31 controls the displacement volume of the variable displacement hydraulic pump 10 to correspond to a normal operation when the operation mode of the boom operation device 12 and the arm operation device 13 is regarded as a normal operation. To the control unit of the proportional-pressure reducing valve 21 via the signal line 32 and the operation mode of the boom operation device 12 and the arm operation device 13 is controlled by the micro- , A control signal for making the displacement volume of the variable displacement hydraulic pump 10 smaller than the displacement volume corresponding to the normal operation is outputted to the control section of the proportional pressure reducing valve 21 via the signal line 32 And a pump discharge amount control section 40 to be described later for performing a control process for controlling the pump discharge amount.

The controller 31 controls the control valve 32 to open and close the center bypass valve 22 when the operation mode of the boom operation device 12 and the arm operation device 13 is an ordinary operation, When the operation mode of the boom operation device 12 and the arm operation device 13 is regarded as a fine operation, the center bypass valve 22 is switched between a deployed position and a fully closed position in a predetermined switching state (The state in which the center bypass line 60 is limited by the bypass valve 22) to the control unit of the proportional solenoid valve 23 through the signal line 33 And a center bypass valve control unit 50. [ The center bypass valve control unit 50 is an operation mode in which the operation mode of the boom operation device 12 and the arm operation device 13 is regarded as a microoperation, and the boom cylinder 7, the arm cylinder 8 When the load pressure is high, a control signal for switching the center bypass valve 22 between a deployed position and a full-closed position in a predetermined switching state and for reducing the opening amount is also transmitted to the boom control device 12, When the load pressure of the boom cylinder 7 and the arm cylinder 8 is low as an operation mode in which the operating mode of the operating device 13 is regarded as a fine operation, the center bypass valve 22 is opened and closed And outputs a control signal to the control section of the proportional solenoid valve 23 through the signal line 33 to make the opening amount larger than the opening amount when the above-mentioned load pressure is high, Processing is performed.

The first embodiment is different from the first embodiment in that the pilot pump 11 for supplying the pilot pressure to the boom operation device 12 and the arm operation device 13 and the discharge pressure for detecting the discharge pressure of the variable displacement hydraulic pump 10 And a sensor 24 are provided. A boom-raising pressure sensor 25 for detecting a pilot pressure generated by the boom raising operation by the boom control device 12 and a pilot signal generator 25 for generating a boom by the boom- An arm dump pressure sensor 27 for detecting a pilot pressure generated in accordance with the arm dump operation by the arm operating device 13, And an arm crowd pressure sensor 28 for detecting a pilot pressure generated by an arm crowding operation by the arm 13.

The first embodiment is provided with a bottom pressure sensor 29 for detecting the bottom pressure of the boom cylinder 7 and a load pressure sensor 30 for detecting the load pressure of the arm cylinder 8.

3, the pump discharge amount control unit 40 of the controller 31 described above controls the pump discharge amount control unit 40 of the boom up pressure sensor 25 according to the boom up operation amount of the boom operation device 12, A boom-raising function generating section 40a1 for calculating a displacement volume of the displacement hydraulic pump 10 and a boom-raising function generating section 40a2 for calculating a displacement volume of the boom- And a boom function generating unit 40a2 for calculating the displacement volume of the variable displacement hydraulic pump 10, as shown in Fig. The boom function generating unit 40a is configured to generate a displacement volume which becomes a larger value as the lever operation amount of the boom operation device 12 becomes larger.

The pump discharge amount control section 40 calculates the displacement volume of the variable displacement hydraulic pump 10 in accordance with the signal output from the arm crowd pressure sensor 28 in accordance with the arm crowd operation amount of the arm operation device 13 And the displacement amount of the variable displacement hydraulic pump 10 according to the signal outputted from the arm dump pressure sensor 27 in accordance with the arm dump manipulated variable of the arm manipulating device 13, And an arm function generating unit 40b2 for arithmetic operation of the arm function generating unit 40b. The arm function generating section 40b also has such a constitution as to generate a displacement volume which becomes a large value as the lever operation amount of the arm operating device 13 increases.

The pump discharge amount control section 40 also controls the displacement amount output from the boom rising function generating section 40a1 in the boom function generating section 40a and the maximum displacement amount outputted from the boom down function generating section 40a2 And a maximum value selection unit 40c for selecting a value. The pump discharge amount control unit 40 also controls the displacement amount output from the arm crow function generating unit 40b1 and the displacement amount output from the arm dump function generating unit 40b2 in the arm function generating unit 40b And a maximum value selection unit 40d for selecting a maximum value.

The pump discharge amount control unit 40 includes an addition unit 40e for adding the displacement volume output from the maximum value selection unit 40c and the displacement volume output from the maximum value selection unit 40d, And a control function generating unit 40f for outputting a control signal corresponding to the displacement volume output from the control unit 40e to the control unit of the proportional pressure reducing valve 21. [ The control function generating unit 40f is configured to output a control signal of a small value to the control unit of the proportional-pressure reducing valve 21 as the displacement volume output from the adding unit 40e becomes larger.

4, the center bypass valve control unit 50 of the above-described controller 31 controls the boom up operation of the boom control device 12 so that the differential pressure difference (differential pressure) between the pump discharge pressure and the boom bottom pressure And a first differential pressure generation unit 50a for outputting a target differential pressure that is a target value of the pressure. The first differential pressure generating portion 50a is configured to output a large target differential pressure as the pressure output from the boom up pressure sensor 25 increases.

The center bypass valve control section 50 subtracts the pressure output by the bottom pressure sensor 29 of the boom cylinder 7 from the pressure output by the discharge pressure sensor 24 to calculate the actual pump discharge pressure A first subtractor 50b for calculating an actual differential pressure that is a differential pressure between actual boom bottom pressure and an actual actual differential pressure outputted from the first subtractor 50b from a target differential pressure outputted by the first differential pressure generator 50a; And a second subtractor 50c for subtracting the differential pressure.

The center bypass valve control unit 50 also includes a second differential pressure generating unit (not shown) for outputting a target differential pressure that is a target value of the differential pressure between the pump discharge pressure and the arm load pressure in accordance with the arm dump operation of the arm operating device 13 50d. The second differential pressure generating portion 50d is also configured to output a large target differential pressure as the pressure output from the arm dump pressure sensor 27 increases.

The center bypass valve control unit 50 subtracts the pressure output by the load pressure sensor 30 of the arm cylinder 8 from the pressure output by the discharge pressure sensor 24 to calculate the actual pump discharge pressure A third subtractor 50e for calculating an actual differential pressure which is a differential pressure between the actual armload pressure and the actual armload pressure and an actual actual output from the third subtractor 50e from the target differential pressure outputted by the second differential pressure generator 50d, And a fourth subtractor 50f for subtracting the differential pressure.

The center bypass valve control unit 50 also calculates the difference between the target differential pressure and the actual differential pressure output from the second subtractor 50c and the difference between the target differential pressure and the actual differential pressure output from the fourth subtractor 50f A control signal operating section 50h for converting the difference output from the maximum value selecting section 50g into a control signal and a control signal operating section 50h for selecting a current value And an adder 50i for adding a control signal to the previous control value to generate a new control signal. Further, the control signal operating section 50 performs arithmetic processing for outputting a control signal of a small value as the difference output from the maximum value selecting section 50g increases, for example. With such a configuration, the pump discharge pressure is controlled to be higher than the load pressure of the actuator by only the difference between the target differential pressure selected by the maximum value selection part 50g and the actual differential pressure.

In the first embodiment having such a configuration, for example, the boom operation device 12 and the arm operation device 13 are operated with a large operation amount in the digging operation of the earth and sand, 3, a large operation amount of the boom operation device 12 is detected by the boom-up pressure sensor 25 and the pump discharge amount control section 40 (see FIG. 3) of the controller 31 ) For the boom-rising function generating unit 40a1. The large operation amount of the arm operating device 13 is detected by the arm dump pressure sensor 27 and input to the arm dump function generating section 40b2 included in the pump discharge amount control section 40. [ Therefore, a displacement volume having a large value is output to each of the maximum value selection units 40c and 40d from each of the boom rising function generating unit 40a1 and the arm dumping function generating unit 40b2, 40e, and output to the control function generating unit 40f. The control function generating unit 40f outputs a control signal of a small value to the electron proportional pressure reducing valve 21 shown in Fig. 2 in accordance with the displacement volume of a large value.

Therefore, the electromagnetic proportional pressure reducing valve 21 tends to be switched to the upper end side in Fig. 2 in accordance with the force of the spring, so that the control port of the servo valve 20 is controlled via the electromagnetic proportional pressure reducing valve 21, And the servo valve 20 is connected to the apparatus 12 and the arm operating device 13 according to the pilot pressure output in accordance with the operation amount of the boom operation device 12 and the arm operation device 13, As shown in Fig. Thereby, the pilot pressure from the pilot pump 11 is supplied to the small-diameter chamber of the control piston 20a via the servo valve 20, and the large-diameter chamber is supplied to the tank 34 , And the control piston 20a moves in the leftward direction of Fig. As a result, the displacement volume of the variable displacement hydraulic pump 10 is controlled to be large, and a large flow rate is discharged from the variable displacement hydraulic pump 10.

During this time, the boom directional control valve 14 is switched to the left position in Fig. 2 in accordance with the boom raising operation of the boom operation device 12, and in accordance with the arm dump operation of the arm operating device 13, The valve 15 is switched to the right position in Fig. Therefore, a large flow rate of hydraulic fluid discharged from the hydraulic pump 10 is supplied to the rod chamber of the arm cylinder 8 via the directional control valve 15 for the arm, and the directional control valve 14 for the boom And is supplied to the bottom chamber (chamber) of the boom cylinder 7. As a result, the boom cylinder 7 is extended to perform the boom raising operation, and the arm cylinder 8 is contracted to perform the arm dump operation.

From each of the bottom pressure sensor 29 for detecting the bottom pressure of the boom cylinder 7 and the load pressure sensor 30 for detecting the rod pressure of the arm cylinder 8 in accordance with these operations, Pressure is detected. Therefore, in the subtracting section 50b included in the center bypass valve control section 50 of the controller 31 shown in Fig. 4, the pressure detected by the bottom pressure sensor 29 from the pressure detected by the discharge pressure sensor 24 The pressure is subtracted to calculate a small actual differential pressure of the pump discharge pressure and the boom bottom pressure, and the small actual differential pressure is output to the subtractor 50c. On the other hand, the first differential pressure generating portion 50a outputs a large target differential pressure to the subtracting portion 50c in accordance with the large boom up operation amount output from the boom up pressure sensor 25. [ The subtracting unit 50c subtracts the actual differential pressure output by the subtracting unit 50b from the target differential pressure output by the first differential pressure generating unit 50a to calculate a difference between the target differential pressure and the actual differential pressure, And outputs it to the maximum value selection unit 50g.

Similarly, in the subtraction unit 50e included in the center bypass valve control unit 50, the pressure detected by the load pressure sensor 30 is subtracted from the pressure detected by the discharge pressure sensor 24, The actual actual differential pressure of the load pressure is calculated, and the small actual differential pressure is outputted to the subtraction portion 50f. On the other hand, the second differential pressure generating section 50d outputs a large target differential pressure to the subtracting section 50f in accordance with the large arm dump manipulated variable outputted from the arm dump pressure sensor 27. [ The subtracting unit 50f subtracts the actual differential pressure outputted by the subtracting unit 50e from the target differential pressure outputted by the second differential pressure generating unit 50d to select the difference between the relatively large target differential pressure and the actual differential pressure as the maximum value And outputs it to the unit 50g.

The maximum value selection unit 50g selects the difference between the difference between the target differential pressure and the actual differential pressure output from the subtraction unit 50c and the difference between the target differential pressure and the actual differential pressure output from the subtraction unit 50f, And the selected relatively large difference is outputted to the control signal calculating section 50h. The control signal operating section 50h converts the control signal to a comparatively small control signal having a value corresponding to a relatively large difference output from the maximum value selecting section 50g, and outputs the control signal to the adding section 50i. The adding unit 50i adds the converted control signal to the previous control value to perform a correction calculation for generating a new control signal, and outputs the calculated value to the control unit of the proportional solenoid valve 23 shown in Fig. 2 .

As described above, the proportional solenoid valve 23 tends to be switched to the lower end of the same Fig. 2 due to the force of the spring as the control signal given to the control portion of the proportional solenoid valve 23 is small, The pilot pump 11 and the control port of the center bypass valve 22 are connected. Thereby, the pilot pressure of the pilot pump 11 is given to the control port of the center bypass valve 22 via the proportional solenoid valve 23, and the center bypass valve 22, To be in a predetermined switching state. As a result, the amount of pressure loss from the center bypass line 60 to the tank 34 is reduced, and a boom-up / arm-dump combination operation is performed by normal operation at a high operating speed. It is possible to carry out a desired excavation work of the soil through the combined operation of the arm dump.

In addition, unlike the excavation work of the above-mentioned gravel, for example, in a crane operation carried out by suspending a load on a portion of the bucket 6 by a combined operation of boom ascending and arm dumping, 3, when a small operation amount of the boom operation device 12 is set to a low boom operation amount as shown in Fig. 3, when the operation device 13 is operated with a small operation amount and the operation load is slow and the actuator load pressure is high, Is input to the boom rising function generating section 40a1 included in the pump discharge amount control section 40 of the controller 31 and is detected by the rising pressure sensor 25 and the small manipulated variable of the arm operating device 13 Is detected by the arm dump pressure sensor 27 and input to the arm dump function generating unit 40b2 included in the pump discharge amount control unit 40. [

Therefore, the displacement volume smaller than that at the excavation work of the gypsum is outputted from each of the boom-raising function generating section 40a1 and the arm-dumping function generating section 40b2 to the maximum value selecting sections 40c and 40d These values are added by the adder 40e and output to the control function generator 40f. The control function generating unit 40f outputs a control signal of a large value to the electron proportional pressure reducing valve 21 shown in Fig. 2 in accordance with the displacement volume of a small value.

2, the control port of the servo valve 20 tends to communicate with the tank 34, and the servo- valve 20 is connected to the servo- The valve 20 tends to be switched to the right side position in Fig. 2 by the force of the spring. As a result, the pilot pressure from the pilot pump 11 is supplied to the large-diameter chamber of the control piston 20a, and the control piston 20a is moved in the rightward direction of Fig. 2 by the difference in area between the large- do. As a result, the displacement volume of the variable displacement hydraulic pump 10 is controlled to be small, and a small flow rate is discharged from the variable displacement hydraulic pump 10.

During this time, the boom directional control valve 14 is slightly shifted to the left side position in the same figure 2 in accordance with the boom raising operation in which the operation amount of the boom operation device 12 is small and the operation amount of the arm operation device 13 is small, The direction control valve 15 for the arm is slightly switched to the right side position in Fig. 2 in accordance with the operation. Therefore, a small flow rate of hydraulic fluid discharged from the hydraulic pump 10 is supplied to the rod chamber of the arm cylinder 8 through the direction control valve 15 for the arm, and is supplied to the load chamber of the boom cylinder 8 via the boom direction control valve 14. [ (7).

At this time, in accordance with the crane operation in which the load is increased, the bottom pressure sensor 29 for detecting the bottom pressure of the boom cylinder 7 and the load pressure sensor 30 for detecting the load pressure of the arm cylinder 8 And is output to the controller 31. The controller 31 detects the high pressure in the pressure sensor 31, Therefore, in the subtracting section 50b included in the center bypass valve control section 50 of the controller 31 shown in Fig. 4, the pressure detected by the bottom pressure sensor 29 from the pressure detected by the discharge pressure sensor 24 The high pressure is subtracted to calculate a small actual differential pressure, and the small actual differential pressure is output to the subtractor 50c. On the other hand, the first differential pressure generating portion 50a outputs a small target differential pressure to the subtracting portion 50c in accordance with the small boom up operation amount output from the boom up pressure sensor 25. [ The subtracting unit 50c subtracts the actual differential pressure output by the subtracting unit 50b from the target differential pressure output by the first differential pressure generating unit 50a to calculate a difference between the target differential pressure and the actual differential pressure, And outputs it to the maximum value selection unit 50g.

Similarly, in the subtraction section 50e of the center bypass valve control section 50, the high pressure detected by the load pressure sensor 30 is subtracted from the pressure detected by the discharge pressure sensor 24 to calculate a small actual differential pressure , The small actual differential pressure is outputted to the decompression portion 50f. On the other hand, the second differential pressure generating section 50d outputs a small target differential pressure to the subtracting section 50f in accordance with the small arm dump manipulated variable outputted from the arm dump pressure sensor 27. [ The subtracting unit 50f subtracts the actual differential pressure outputted by the subtracting unit 50e from the target differential pressure outputted by the second differential pressure generating unit 50d to calculate a difference between the target differential pressure and the actual differential pressure, And outputs it to the maximum value selection unit 50g.

The maximum value selection unit 50g selects the difference between the difference between the target differential pressure and the actual differential pressure output from the subtraction unit 50c and the difference between the target differential pressure and the actual differential pressure output from the subtraction unit 50f, And the selected relatively large difference is outputted to the control signal calculating section 50h. The control signal operating section 50h converts the control signal to a control signal having a small value corresponding to a relatively large difference output from the maximum value selecting section 50g, and outputs the control signal to the adding section 50i. The adder 50i adds a current control signal converted to the previous control value to generate a new control signal, and outputs the calculated value to the control unit of the proportional solenoid valve 23 shown in Fig. 2 .

As described above, the proportional solenoid valve 23 tends to be switched to the lower end side of Fig. 2 by the force of the spring in accordance with the small control value given to the control part of the proportional solenoid valve 23, The pilot pump 11 and the control port of the center bypass valve 22 are connected. Thus, the pilot pressure of the pilot pump 11 is given to the control port of the center bypass valve 22, and the center bypass valve 22 is further opened in the predetermined switching state between the deployed position and the full- The center bypass line 60 tends to close. As a result, the boom elevation / arm dump combined operation in which the actuator load pressure is increased is performed as a fine operation with a slow operation speed, and a desired crane operation can be performed.

The first embodiment differs from the above-described crane operation in that, for example, in the soil-sanding operation performed through the combined operation of the boom elevation and arm dump, the boom operation device 12 and the arm operation device 13 In order to reduce the operating speed and to lower the actuator load pressure. At this time, the control of the pump discharge amount control unit 40 of the controller 31 is the same as that of the crane operation described above, but the center bypass valve control unit 50 performs control different from that at the time of crane operation.

That is, a small flow rate is supplied to the rod chambers of the arm cylinder 8 and the bottom chambers of the boom cylinder 7, respectively. With the sanding work for lowering the actuator load pressure at this time, A low pressure is detected at each of the bottom pressure sensor 29 for detecting the pressure and the load pressure sensor 30 for detecting the load pressure of the arm cylinder 8 and outputted to the controller 31. [ Therefore, in the subtracting section 50b included in the center bypass valve control section 50 of the controller 31 shown in Fig. 4, the pressure detected by the bottom pressure sensor 29 from the pressure detected by the discharge pressure sensor 24 The low pressure is subtracted to calculate a large actual differential pressure, and the large actual differential pressure is output to the subtractor 50c. On the other hand, the first differential pressure generating portion 50a outputs a small target differential pressure to the subtracting portion 50c in accordance with the small boom up operation amount output from the boom up pressure sensor 25. [ The subtracting unit 50c subtracts the actual differential pressure outputted by the subtracting unit 50b from the target differential pressure outputted by the first differential pressure generating unit 50a to calculate a difference between the target differential pressure and the actual differential pressure which is a relatively small value And outputs it to the maximum value selection unit 50g.

Likewise, in the subtraction section 50e of the center bypass valve control section 50, the low pressure detected by the load pressure sensor 30 is subtracted from the pressure detected by the discharge pressure sensor 24 to calculate a large actual differential pressure , And the large actual differential pressure is outputted to the subtraction section 50f. On the other hand, the second differential pressure generating portion 50d outputs a small target differential pressure to the subtracting portion 50f in accordance with the small boom up operation amount output from the arm dump pressure sensor 27. [ The subtracting unit 50f subtracts the actual differential pressure output by the subtracting unit 50e from the target differential pressure output by the second differential pressure generating unit 50d to calculate the difference between the target differential pressure and the actual differential pressure, And outputs it to the maximum value selection unit 50g.

The maximum value selection unit 50g selects the difference between the target difference pressure and the actual difference pressure output from the subtraction unit 50c and the smaller difference between the difference between the target differential pressure and the actual differential pressure output from the subtraction unit 50f , And the selected difference is outputted to the control signal operating section 50h. The control signal operating section 50h converts the small difference output from the maximum value selecting section 50g into a control signal and outputs it to the adding section 50i. The adding unit 50i adds a selected control signal to the previous control value to perform a correction calculation that generates a control signal slightly larger in value than the previous control value and outputs the calculated value to the control unit of the proportional solenoid valve 23 .

As described above, the proportional solenoid valve 23 tends to be switched to the upper side of the same Fig. 2 against the force of the spring in accordance with a larger value of the control signal given to the control section of the proportional solenoid valve 23 The control port of the center bypass valve 22 tends to be disconnected from the control port of the center bypass valve 22 while the control port of the center bypass valve 22 tends to be connected to the tank 34 . Thus, the center bypass line 22 has a slightly larger opening amount in the switching state between the deployed position and the fully closed position due to the force of the spring, and accordingly, the center bypass line 60 is fine It tends to be open more than the operation / heavy load. As a result, the flow rate of the water flowing through the tank 34 through the center bypass line 60 is increased, and the combined operation of the boom ascending and the arm damping, in which the actuator load pressure is lowered, It is possible to carry out the selection of soil.

5 is a diagram showing control performed in the hydraulic drive apparatus according to the first embodiment.

5, the abscissa indicates the amount of lever manipulation, for example, the lever manipulation amount of the boom manipulation device 12 and the lever manipulation amount of the arm manipulation device 13, and the axis of abscissa indicates the boom And the load pressure of the actuator such as the cylinder 7 and the arm cylinder 8 is shown.

As shown in Fig. 5, in the first embodiment, when the operation amount of the boom operation device 12 and the operation amount of the arm operation device are increased, the control of the normal operation area A in which the discharge amount of the hydraulic pump 10 is increased For example, as described above, it is possible to carry out a normal operation such as excavation of soil. In the above description, the case where the bottom pressure of the boom cylinder 7 and the rod pressure of the arm cylinder 8 are increased is described. However, in the normal operation area A, the actuator load pressure There is no restriction on the difference.

In addition, when the operation amount of the boom operation device 12 and the operation amount of the arm operation device 13 are made small, the discharge amount of the hydraulic pump 10 is made small, and the speed of the actuator is slowed down. In this case, fine operation in which the load pressure of the actuator is high. In the operation area B under the heavy load, for example, a crane work or the like can be performed as described above. In addition, in the operation area C under the fine operation and light load where the load pressure of the actuator is lowered, the sanding work can be performed as described above.

According to the first embodiment configured as described above, by increasing the operation amount of the boom operation device 12 and the arm operation device 13, the work elements such as the boom 4 and the arm 5 can be driven at a high operation speed It is possible to secure a good normal operability as far as possible. In addition, by reducing the operation amounts of the boom operation device 12 and the arm operation device 13, it is possible to secure a good micro operability capable of driving the work elements such as the boom 4 and the arm 5 at a slow operation speed . At this time, the output of the variable displacement hydraulic pump 10 can be suppressed, and the energy loss can be reduced. In addition, in the first embodiment, at the time of heavy load where the load pressure of the boom cylinder 7 and the arm cylinder 8 becomes high even in the minute operation, the discharge pressure of the variable displacement hydraulic pump 10 is made high, It is possible to secure good operability in the operation of the operation and the heavy load. When the load is applied to the boom cylinder 7 and the arm cylinder 8 at the time of a light load, the discharge pressure of the variable displacement hydraulic pump 10 is lowered even during fine operation, It is possible to secure a good operability in a work to be performed. At this time, the output of the variable displacement hydraulic pump 10 can be suppressed and the energy loss can be reduced. Therefore, according to the present embodiment, it is possible to realize a highly reliable hydraulic drive apparatus that can achieve high precision and high operability, and is economical and practical.

In the above embodiment, only the configuration related to the combined operation of the boom rising and the arm dump is shown. However, the same configuration as that in the above embodiment related to the boom lowering operation and the arm crowd operation may be provided. If necessary, the same structure as that in the above embodiment related to the operation of the turning, the operation of the bucket 6, and the attachment attached in place of the bucket 6 may be provided.

The first embodiment can be implemented not only in a combined operation of the boom 4 and the arm 5 but also in a single operation of the boom 4 and in a single operation of the arm 5 .

In the first embodiment, the control is performed in accordance with the operation amount of the boom operation device 12 and the operation amount of the arm operation device 13. However, for example, in the boom cylinder 7, On the basis of a signal outputted from the pressure sensor 29 or a signal outputted from the load pressure sensor 30 provided on the arm cylinder 8, the controller 31 controls the lever of the boom control device 12 The operation speed or the operation speed of the lever of the arm operating device may be calculated and the control may be performed in accordance with the calculated operation speed.

Fig. 6 shows the case of the second embodiment in which the control is performed at the above-described operation speed. In Fig. 6, A1 denotes a normal operation region, B1 denotes a fine operation / heavy operation region, and C1 denotes a fine operation / light operation region. Normally, when the micro-operation is performed, the operation speed of the levers of the boom operation device 12 and the arm operation device 13 is made slow by the operator. Therefore, by performing control based on the operation speed in this manner instead of the operation amount, it is possible to realize the control with higher accuracy in accordance with the actual operation state. Further, instead of the control based on the operating speed, the controller 31 may calculate an operation acceleration, and perform the control according to the calculated operation acceleration.

FIG. 7 is a block diagram showing a main part of the pump discharge amount control unit included in the controller provided in the hydraulic drive apparatus according to the third embodiment of the present invention. FIG. FIG. 2 is a block diagram showing the configuration of a main portion of a center bypass valve control unit included in a controller provided in the control apparatus of FIG.

The third embodiment related to the present invention detects the load pressure of the arm cylinder 8 and the bottom pressure sensor 29 that detects the signal output from the discharge pressure sensor 24 or the bottom pressure of the boom cylinder 7 It is determined whether the work performed by the work device 3 is a heavy load operation or a light load operation by means of a signal outputted from the load pressure sensor 30. When it is determined as a heavy load operation, The pump discharge amount control unit 40 and the center bypass valve control unit 70 of the controller 31 which are shown in FIG. 7, the pump discharge amount control section 40 of the third embodiment is connected to the addition section 40e, and the signal output from the discharge pressure sensor 24 is supplied to the boom cylinder 7 The signal output from the bottom pressure sensor 29 for detecting the bottom pressure and the load pressure sensor 30 for detecting the load pressure of the arm cylinder 8 are turned ON when the signal is corresponding to the light load, And a switch unit 40g which is turned off at the time of switching. When the switch portion 40g is turned on, the addition value of the addition portion 40e is converted into a control signal to control the electron proportional pressure reducing valve 21 for adjusting the displacement volume of the variable displacement hydraulic pump 10 And is output to the function generating unit 40f.

In the third embodiment, the configuration of the center bypass valve control section 70 of the controller 31 is different from that of the first embodiment. The center bypass valve control unit 70 of the third embodiment is provided with a boom function generating unit 70a for outputting the opening area of the center bypass valve 22 in accordance with the operation amount of the boom operation device 12, And an arm function generating section 70b for outputting the opening area of the center bypass valve 22 in accordance with the operation amount of the operating device 13. [

The boom function generating section 70a includes a boom up function generating section 70a1 for outputting the opening amount of the large center bypass valve 22 in accordance with the decrease in the boom up operation amount, And a boom-lowering function generating section 70a2 for outputting an opening amount of the large center bypass valve 22 accompanied by a smaller boom-down operation amount, that is, under the light load of the micro-operation. The relationship between the boom up operation amount of the boom up function generating portion 70a1 and the opening amount of the center bypass valve 22 and the relationship between the boom down operation amount of the boom down function generating portion 70a2 and the center bypass valve The relationship of the aperture amount of the lens 22 is set in advance. Further, since the boom tends to have a smaller load pressure due to the influence of its own weight in the descending direction, it is possible to reduce the load on the boom up function generating portion 70a1 , It is possible to set such that the opening amount in the same micro-operation area set in the boom-down function generating section 70a2 becomes larger.

Similarly, the arm function generating section 70b includes an arm crow function generating section (for example, a function generating section for arm crowd) for outputting the opening amount of the large center bypass valve 22 with the arm crowd manipulated variable becoming small, And an arm dump function generating section 70b2 for outputting an opening amount of the large center bypass valve 22 accompanied with a decrease in the arm dump manipulated variable, that is, under the light load of the fine manipulation. The relationship between the arm crowd operation amount in the arm crow function generating portion 70b1 and the opening amount of the center bypass valve 22 and the relationship between the arm dump manipulated amount in the arm dump function generating portion 70b2 and the center bypass valve The relationship of the aperture amount of the lens 22 is set in advance.

The center bypass valve control unit 70 calculates the center bypass valve 22 based on the opening amount of the center bypass valve 22 output from the boom up function generating unit 70a1 and the center bypass valve 22 output from the boom down function generating unit 70a2, The maximum value selecting section 70c for selecting the larger one of the opening amounts of the path valve 22 and the arm bypass valve 22 and the opening amount of the center bypass valve 22 outputted from the arm crow function generating section 70b1, And a maximum value selecting unit 70d for selecting a larger one of the opening amounts of the center bypass valve 22 output from the function generating unit 70b2.

The center bypass valve control section 70 is configured to control the opening amount of the center bypass valve 22 outputted from the maximum value selection section 70c and the opening amount of the center bypass valve And an adding unit 70e for adding the opening amount of each of the light receiving units 22a and 22a.

The center bypass valve control section 70 is connected to the adder section 70e and receives a signal output from the discharge pressure sensor 24 or a bottom pressure sensor 29 for detecting the bottom pressure of the boom cylinder 7 And the load pressure sensor 30 for detecting the load pressure of the arm cylinder 8 are turned ON when the signal corresponding to the light load is a signal corresponding to the light load and the switch portion 70f Respectively.

The center bypass valve control unit 70 converts the addition value related to the opening amount of the center bypass valve 22 of the addition unit 70e into a control signal when the switch unit 70f is turned ON And a proportional solenoid valve 23 for controlling the center bypass valve 22, as shown in Fig. In this control function generating section 70g, the relationship of the control signal value that increases as the addition value of the adding section 70e increases is set in advance. The other configurations in the third embodiment are equivalent to those in the first embodiment described above.

In the third embodiment configured as described above, when a fine operation is performed by operating the boom operation device 12 and the arm operation device 13, the fine operation is performed by the boom function generator 40a, The small value output from the boom function generating unit 40a and the small value output from the arm function generating unit 40b are detected by the maximum value selecting unit 40c and 40d, And is output to the switch unit 40g. At this time, when it is detected that the pressure value detected by the discharge pressure sensor 24 (or the bottom pressure sensor 29 or the load pressure sensor 30) is high and the state is a heavy load operation while being finely operated, And the output of the addition value added by the addition section 40e to the control function generation section 40f is cut off. In this state, the processing operation corresponding to the heavy load operation in the normal fine operation state is performed.

When the pressure value detected by the discharge pressure sensor 24 (or the bottom-pressure sensor 29 or the load-pressure sensor 30) is low during fine operation and it is detected that the valve is in a state of light operation under fine- The switch unit 40g is turned on, and the added value added by the adder 40e is output to the control function generator 40f. The control function generating section 40f outputs a large control signal value corresponding to a relatively small value added by the adding section 40e to the proportional-pressure reducing valve 21. Therefore, the proportional solenoid valve 21 tends to be switched to the lower end position of Fig. 2, whereby the displacement volume of the variable displacement hydraulic pump 10 is controlled to be small as described above, 10).

In the center bypass valve control section 70 of the third embodiment, the discharge pressure is detected by the discharge pressure sensor 24 (or the bottom pressure sensor 29 and the load pressure sensor 30) during fine operation When it is detected that the pressure value is high and the micro-operation is in the middle, the switch portion 70f is turned off and the output of the addition value added by the addition portion 70e to the control function generating portion 70g is cut off. In this state, the processing operation corresponding to the heavy load operation in the normal fine operation state is performed. At this time, the proportional solenoid valve 23 tends to be held at the lower end position of FIG. 2 so as to guide the pilot pressure of the pilot pump 11 to the control port of the center bypass valve 22. The center bypass valve 22 is controlled so that the opening amount becomes relatively small in a predetermined switching state between the deployed position and the full closing position. As a result, a pressure is generated in the center bypass line 60, and a desired fine operation / heavy load operation can be performed.

In the center bypass valve control section 70, the pressure value detected by the discharge pressure sensor 24 (or the bottom pressure sensor 29 and the load pressure sensor 30) is low during fine operation, When the micro-operation is detected under the light load state, the switch portion 70f is turned on, and the added value added by the addition portion 70e is output to the control function generating portion 70g. The control function generating section 70g outputs a large control signal value to the proportional solenoid valve 23 according to a large addition value. Therefore, the proportional solenoid valve 23 tends to be switched to the upper position side in Fig. Accordingly, the center bypass valve 22 is controlled so that the opening amount becomes larger in the predetermined switching state between the deployed position and the fully closed position, as compared with the above-mentioned minute operation and heavy load. As a result, the flow rate to the tank 34 through the center bypass line 60 is increased, so that the desired fine operation and light load operation can be performed.

According to the third embodiment constructed as described above, the same effect as that of the first embodiment can be obtained. In addition, the pressure sensor for detecting the load pressure of the actuator is provided with the discharge pressure sensor 24 or the bottom pressure sensor 29, And the load-pressure sensor 30, so that the number of pressure sensors can be reduced compared with the first embodiment, and the device configuration can be simplified.

3: Work device 4: Boom (work element)
5: arm (work element)
7: Boom cylinder (Actuator for work element)
8: Arm cylinder (Actuator for working element)
10: Variable displacement hydraulic pump 11: Pilot pump
12: Operation device for boom (operation device for work)
13: Operation device for arm (operation device for work)
14: directional control valve for boom (directional control valve for working element)
15: Directional control valve for arm (Directional control valve for working element)
20: Servo valve 20a: Control piston
21: Electronic proportional pressure reducing valve (displacement displacement control device)
22: Center bypass valve
23: proportional solenoid valve (center bypass valve control unit)
24: Discharge pressure sensor 25: Boom rising pressure sensor
27: arm dump pressure sensor 29: bottom pressure sensor
30: load pressure sensor 31: controller
34: tank 40: pump discharge amount control section
40a: boom function generating unit 40b: arm function generating unit
40c: maximum value selection unit 40d: maximum value selection unit
40e: adder 40f: control function generator
40g: Switch part 50: Center bypass valve control part
50a: first differential pressure generating section 50b: first calculating section
50c: second calculating section 50d: second differential pressure generating section
50e: third arithmetic section 50f: fourth arithmetic section
50g: maximum value selection unit 50h: control signal calculation unit
50i: adder 60: center bypass line
70: Center bypass valve control unit 70a: Boom function generating unit
70b: arm function generating unit 70c: maximum value selecting unit
70d: maximum value selector 70e:
70f: switch section 70g: control function generating section
A: Normal control B: Fine operation / heavy load control
C: Micro-operation / light-load control A1: Normal control
B1: Micro / heavy load control C1: Micro / light load control

Claims (4)

A work machine provided with a normal operation and a working device capable of fine operation performed with a smaller operation amount and a slower operation speed than the normal operation,
A variable-capacity hydraulic pump; an actuator for working elements that is operated by pressure oil discharged from the variable-displacement hydraulic pump to drive a working element included in the working device; and a center bypass And a control unit for controlling the flow of the pressurized oil supplied from the variable displacement hydraulic pump to the actuator for the working element, and an operation element for switching operation of the directional control valve for the working element 1. A hydraulic drive apparatus for a work machine having an operation device,
A displacement volume control device for controlling the displacement volume of the variable displacement hydraulic pump and a bypass valve provided in the center bypass line portion located downstream of the working element directional control valve and returned to the tank via the center bypass line A center bypass valve control device for controlling the center bypass valve, a displacement volume control device, and a controller for controlling the center bypass valve control device,
The controller comprising:
A control signal for increasing the displacement volume of the variable displacement hydraulic pump to the displacement volume corresponding to the normal operation when the operating mode of the operating element for the working element is regarded as the normal operation is transmitted to the displacement volume control device A control signal for making the displacement volume of the variable displacement hydraulic pump smaller than the displacement volume corresponding to the normal operation when the operation mode of the operating device for the working element is regarded as the fine operation, A pump discharge amount control unit for performing a control process of outputting to a displacement displacement control device,
A control signal for controlling the center bypass valve to an opening amount according to a normal operation when the operating mode of the operating element operating device is regarded as the normal operation, A control process for outputting to the center bypass valve control device a control signal for controlling the center bypass valve to a small opening amount in comparison with the opening amount at the time of normal operation is performed And when the load pressure of the actuator for the working element is in a high state as an operation mode in which the operating mode of the operating element operating device is regarded as the fine operation, A control signal for controlling the opening amount to be smaller for a small opening amount, When the load pressure of the actuator for the working element is in a low state as an operation mode in which the operation mode of the small operation device is regarded as the fine operation, the center bypass valve is larger than the opening amount when the load pressure of the actuator is high And a center bypass valve control section for performing control processing for outputting a control signal having an opening amount to the center bypass valve control device,
The controller executes a process of calculating that the operating mode of the operating element for a working element is an operating mode considered as a fine operation on the basis of the manipulated variable, the manipulated speed, or the manipulated acceleration of the manipulating device for the working element,
Wherein said work machine is a hydraulic excavator,
Wherein the work element comprises a boom and an arm,
Wherein the actuator for the working element includes a boom cylinder for operating the boom and an arm cylinder for actuating the arm,
Wherein the directional control valve for the working element includes a boom directional control valve for controlling the boom cylinder and an arm directional control valve for controlling the arm cylinder,
Wherein the operation element operating device includes a boom operation device for switching operation of the boom directional control valve and an arm operation device for switching the arm directional control valve,
A load pressure sensor for detecting the discharge pressure of the variable displacement hydraulic pump or a bottom pressure sensor for detecting the bottom pressure of the boom cylinder and a load pressure sensor for detecting the load pressure of the arm cylinder,
The center bypass valve control unit of the controller,
The operation amount of at least one of the operation amount of the boom operation device and the operation amount of the arm operation device and the discharge pressure detected by the discharge pressure sensor or the operation amount of the boom operation device and the operation amount of the arm operation device As an operation mode in which the operation mode of the operating element operating apparatus is regarded as the fine operation in accordance with at least one manipulated variable, a bottom pressure detected by the bottom pressure sensor, and a load pressure detected by the load pressure sensor, And when the load pressure of the actuator for the element is low, a control signal for outputting a control signal for increasing the opening amount of the center bypass valve is executed.

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