KR100540772B1 - Hydraulic driving unit for working machine, and method of hydraulic drive - Google Patents

Abstract

The fuel injection control apparatus (electronic governor 12 and controller 13) of the engine 1 can control the governor region with isochronous characteristics. The work machine controller 18 inputs the discharge pressure signal P so that when the discharge pressure of the hydraulic pump exceeds a predetermined pressure, the regulator does not exceed the value determined by the preset pump absorption torque curve 20 when the discharge pressure of the hydraulic pump exceeds a predetermined pressure. The control unit 16 controls the regulator 16 so that the discharge amount of the hydraulic pump increases as the discharge pressure of the hydraulic pump is lowered from the predetermined pressure when the discharge pressure of the hydraulic pump 2 is lower than or equal to the predetermined pressure. As a result, even if the governor region is controlled with isochronous characteristics, the discharge flow rate of the hydraulic pump can be increased as the engine load becomes lighter.

Description

HYDRAULIC DRIVING UNIT FOR WORKING MACHINE, AND METHOD OF HYDRAULIC DRIVE}

The present invention relates to an engine having a fuel injection control device installed in a work machine such as a hydraulic excavator and capable of controlling the governor area with isochronous or reversed loop characteristics, and a hydraulic pressure of a work machine having a variable displacement hydraulic pump driven by the engine. It relates to a drive device and a hydraulic drive method.

Conventionally, as shown in Japanese Unexamined Patent Publication No. 7-83084, there is a hydraulic drive device for a work machine provided with a mechanical governor engine.

BACKGROUND OF THE INVENTION The prior art having a mechanical governor engine of this kind generally includes a variable displacement hydraulic pump driven by the engine, a regulator for controlling displacement of the hydraulic pump, and a hydraulic oil discharged from the hydraulic pump. A plurality of hydraulic actuators to be driven, a pressure detector for detecting a discharge pressure of the hydraulic pump and outputting a discharge pressure signal, and a discharge pressure signal output from the pressure detector to control the displacement of the hydraulic pump to the regulator. It is equipped with the controller which outputs a signal.

In the prior art having this mechanical governor type engine, the engine output characteristic is a droop characteristic in which the engine speed increases as the engine output torque (engine load) decreases in the governor region where the mechanical governor is controlled. Have Such droop characteristics are caused by the inertia of the flywheel included in the mechanical governor.

Therefore, in the case of a hydraulic excavator, for example, in the case of a hydraulic excavator, the discharge pressure of the hydraulic pump is lowered during the no-load operation (unloading operation) after unloading the soil with a bucket. Since the weight is lighter and the engine speed is increased, the discharge flow rate of the hydraulic pump increases, and the flow rate supplied to the hydraulic actuator is increased, so that a relatively fast hydraulic actuator speed is obtained. As a result, the work speed in the unloading operation is faster and the work efficiency can be improved.

Unlike conventional Japanese Patent Application Laid-Open Publication Nos. 10-89111, 10-159599, and the mechanical governor type engine as described above, the governor area can be controlled by isochronous or reversed-loop characteristics. There has also been proposed a hydraulic drive device for a work machine equipped with an engine having a fuel injection control device (hereinafter, referred to as an engine for appropriately isochronous control or reverse droop control). The isochronous characteristic of engine control is a characteristic in which the engine speed is kept constant in the governor area irrespective of the light load of the engine, that is, the engine output torque is lowered, and the reverse droop characteristic is an engine output torque (engine load). The engine speed decreases as) decreases.

In such a prior art, it is possible to eliminate the influence of inertia of a flywheel, such as a mechanical governor, thereby realizing low fuel consumption and low noise as compared to a work machine equipped with an engine having a mechanical governor.

As described above, a work machine equipped with an engine for isochronous control or reverse droop control has an advantage of realizing low fuel consumption and low noise. However, even when the engine is lightly loaded, the engine speed does not increase. There is a thing. For example, as described above, when the work machine is a hydraulic excavator, the engine rotation speed does not increase even when the engine load is light and the engine load is light. Therefore, the discharge flow rate of the hydraulic pump does not increase, and the flow rate supplied to the hydraulic actuator is increased. Can not expect to improve the work efficiency.

When working with a work machine equipped with an engine that performs isochronous control or reverse droop control, even if the operator is accustomed to operating a work machine equipped with a mechanical governor type engine, the engine load is light, As the hydraulic actuator speed does not increase like a curl governor type engine work machine, there is a feeling of discomfort in operation.

SUMMARY OF THE INVENTION An object of the present invention is a hydraulic drive apparatus having an engine having a fuel injection control device capable of controlling at least a portion of the governor region with any one of isochronous and reversed-loop characteristics, and as the engine load becomes light even in the governor region An object of the present invention is to provide a hydraulic drive device and a hydraulic drive method of a work machine capable of increasing the discharge flow rate of a hydraulic pump.

(1) In order to achieve the above object, the present invention provides an engine having a fuel injection control device capable of controlling at least a part of the governor region to any one of isochronous characteristics, reversed loop characteristics, and combinations of isochronous characteristics and reversed loop characteristics. And a variable displacement hydraulic pump driven by the engine and a plurality of hydraulic actuators driven by the hydraulic oil discharged from the hydraulic pump, wherein the discharge pressure of the hydraulic pump is set to zero. 1, if the predetermined pressure is exceeded, pump absorption torque control means for controlling the displacement of the hydraulic pump so that the displacement of the hydraulic pump does not exceed a value determined by a preset pump absorption torque curve, and the discharge pressure of the hydraulic pump is 1 When the pressure is below the predetermined pressure, the discharge pressure of the hydraulic pump is lowered from the second predetermined pressure so that the hydraulic pump The flow rate correction control means for controlling so that the displacement of the gas is increased.

In the present invention configured as described above, when the engine load at the time of operation is heavy and the discharge pressure of the hydraulic pump is higher than the first predetermined pressure, the output horsepower of the engine by the pump absorption torque control (pump absorption horsepower control) Effective use becomes possible. In addition, when the engine load shifts from the heavy load to the light load at the time of operation, and the discharge pressure of the hydraulic pump is equal to or less than the second predetermined pressure, the displacement of the hydraulic pump increases due to the decrease in the pump discharge pressure by the flow correction control means. The discharge flow rate of the hydraulic pump can be increased without increasing the engine speed due to isochronous characteristics or reversed-loop characteristics in the governor region, thereby increasing the hydraulic actuator speed at the engine light load.

(2) In order to achieve the above object, the present invention provides an engine having a fuel injection control device capable of controlling at least a part of the governor region by any one of isochronous characteristics, reversed loop characteristics, and combinations of isochronous characteristics and reversed loop characteristics. And a variable displacement type hydraulic pump driven by the engine and a plurality of hydraulic actuators driven by pressure oil discharged from the hydraulic pump, the hydraulic drive of the work machine controlling the displacement of the hydraulic pump. A regulator, a pressure detector for detecting a discharge pressure of the hydraulic pump, and a discharge amount of the hydraulic pump in a preset pump absorption torque curve when the discharge pressure of the hydraulic pump detected by the pressure detector exceeds a first predetermined pressure. Pump absorption torque control means for controlling the regulator so as not to exceed a value determined by And a flow rate correction control means for controlling the regulator so that the displacement of the hydraulic pump increases as the discharge pressure of the hydraulic pump is lowered from the second predetermined pressure when the discharge pressure of the hydraulic pump is below the first predetermined pressure. Shall be.

In the present invention configured as described above, as described in the above (1), the effective use of the output horsepower of the engine by the pump absorption torque control (pump absorption horsepower control) and the increase control of the pump discharge flow rate at light engine loads are enabled. At light engine loads, the hydraulic actuator speed can be increased.

(3) In the above (1) or (2), preferably, the second predetermined pressure coincides with the first predetermined pressure.

As a result, when the discharge pressure of the hydraulic pump is equal to or less than the first predetermined pressure, the flow rate correction control means may immediately function to increase the displacement of the hydraulic pump.

(4) Further, in the above (1) or (2), further comprising control release means for invalidating the increase control of the displacement of the hydraulic pump by the flow rate correction control means.

Thereby, the control by the flow rate correction control means can be canceled as needed, and the flow rate control according to the work content is attained.

(5) In the above (4), preferably, the fuel injection control device is capable of controlling at least a part of the governor area with isochronous characteristics, and the control releasing means includes a travel mode switch, a load lift mode switch, and a stop ( At least one of the mode switch.

Accordingly, in operations or operations that do not want to increase or decrease the discharge flow rate of the hydraulic pump, such as driving, lifting or stopping operations, the hydraulic actuator speed is maintained at the same speed regardless of the increase or decrease of the engine load. Work and stop work can be carried out.

(6) In the above (1) or (2), preferably, the flow rate correction control means is configured such that the discharge flow rate of the hydraulic pump increases as the discharge pressure of the hydraulic pump is lowered from the second predetermined pressure. The displacement of the hydraulic pump is controlled.

As a result, as described in (1), the discharge flow rate of the hydraulic pump can be increased even when the engine speed is not increased due to the isochronous characteristic or the reversed loop characteristic.

(7) In the above (1) or (2), the fuel injection control device is capable of controlling at least a part of the governor area with reversed loop characteristics, and the flow rate correction control means has a discharge pressure of the hydraulic pump set to the first. A first means for controlling the displacement of the hydraulic pump so that the discharge flow rate of the hydraulic pump increases as it is lowered from a predetermined pressure; and the discharge of the hydraulic pump when the discharge pressure of the hydraulic pump is lowered from the second predetermined pressure And second means for controlling the displacement of the hydraulic pump so that the flow rate is kept constant, and selecting means for selecting one of the first means and the second means.

Thus, irrespective of the characteristics of the governor area, when the first means is selected, the discharge flow rate of the hydraulic pump is controlled to increase, and when the second means is selected, the discharge flow rate of the hydraulic pump is controlled to be kept constant so that According to the flow control is possible.

(8) In the above (7), preferably, the flow rate correction control means further has a third means for invalidating the increase control of the displacement of the hydraulic pump, wherein the selection means comprises the first means and the second means. One of the means and the third means is selected.

As a result, when the third means is selected, the increase control of the displacement of the hydraulic pump becomes invalid, and the flow rate control according to the work content is possible.

(9) Further, in the above (1) or (2), preferably, the pump absorption torque control means calculates a target displacement for pump absorption torque control from the discharge pressure of the hydraulic pump and the pump absorption torque curve. And means for maintaining the target exhaust amount at a constant value when the discharge pressure of the hydraulic pump is below the first predetermined pressure, wherein the flow rate correction control means lowers the discharge pressure of the hydraulic pump from the second predetermined pressure. Means for calculating an amount of displacement correction value increased according to the second displacement amount; and means for calculating a second displacement amount corrected by adding the displacement amount correction value to the target displacement amount, and controlling the displacement amount of the hydraulic pump by the corrected target displacement amount. do.

Thereby, the pump absorption torque control means and the flow rate correction control means can be computerized.

(10) In the above (1) or (2), preferably, the pump absorption torque control means is a means for limiting the maximum value of the displacement of the hydraulic pump to a value determined by the pump absorption torque curve or less. The flow rate correction control means is means for controlling the maximum value of the displacement of the hydraulic pump as the discharge pressure of the hydraulic pump is lowered from the second predetermined pressure.

As a result, as described in (1) above, the effective use of the output horsepower of the engine by the pump absorption torque control (pump absorption horsepower control) and the increase of the pump discharge flow rate at light load of the engine are enabled. When the required flow rate is small, the displacement of the hydraulic pump can be controlled accordingly to obtain a desired actuator speed.

(11) Further, in the above (1) or (2), further comprising a first calculating means for calculating a first target displacement according to the required flow rate of the plurality of hydraulic actuators, wherein the pump absorption torque control means The second target displacement for pump absorption torque control is calculated from the discharge pressure of the pump and the pump absorption torque curve, and the target displacement is maintained at a constant value when the discharge pressure of the hydraulic pump is below the first predetermined pressure. And a second calculating means, wherein the flow rate correction control means comprises: means for calculating a displacement correction value that increases as the discharge pressure of the hydraulic pump is lowered from the second predetermined pressure, and the displacement correction to the second target displacement; Means for calculating the corrected second target displacement by adding a value, wherein the first target displacement and the corrected second target displacement The smaller one is selected as the target displacement for control and the displacement of the hydraulic pump is controlled.

As a result, when the first target displacement according to the required flow rates of the plurality of hydraulic actuators is larger than the corrected second target displacement, the corrected second target displacement is a target displacement for control, so the displacement of the hydraulic pump is corrected to the second target. As described above in (1), it is possible to effectively use the output horsepower of the engine and control the increase of the pump discharge flow rate at light engine load by the pump absorption torque control (pump absorption horsepower control). On the other hand, when the first target displacement is smaller than the corrected second target displacement, since the first target displacement is the control target displacement, the displacement of the hydraulic pump is controlled in accordance with the required flow rate on the basis of the first target displacement, and thus the desired actuator speed. Can be obtained.

(12) In order to achieve the above object, the present invention has a fuel injection control device capable of controlling at least a portion of the governor region to any one of isochronous characteristics, reversed loop characteristics, and combinations of isochronous characteristics and reversed loop characteristics. In a hydraulic drive method of a work machine, comprising: an engine, a variable displacement hydraulic pump driven by the engine, and a plurality of hydraulic actuators driven by pressure oil discharged from the hydraulic pump, wherein the discharge pressure of the hydraulic pump When the first predetermined pressure is exceeded, the displacement of the hydraulic pump is controlled so that the displacement of the hydraulic pump does not exceed a value determined by a preset pump absorption torque curve, and the discharge pressure of the hydraulic pump is equal to or less than the first predetermined pressure. , The displacement of the hydraulic pump increases as the discharge pressure of the hydraulic pump is lowered from the second predetermined pressure. It is to control so that.

As a result, as described in (1) above, it is possible to effectively use the output horsepower of the engine by the pump absorption torque control (pump absorption horsepower control) and to increase the pump discharge flow rate at the engine light load. You can increase the speed.

(13) In the above (12), preferably, when the discharge pressure of the hydraulic pump is below the first predetermined pressure, the displacement of the hydraulic pump is increased as the discharge pressure of the hydraulic pump is lowered from the second predetermined pressure. Either of the control and the control of keeping the displacement of the hydraulic pump constant can be selected.

As a result, the increase control of the displacement can be canceled as necessary, thereby enabling the flow rate control according to the work content.

(14) Further, in (12), preferably, when the discharge pressure of the hydraulic pump is below the first predetermined pressure, the discharge flow rate of the hydraulic pump is lowered as the discharge pressure of the hydraulic pump is lowered from the second predetermined pressure. The displacement of the hydraulic pump is controlled to increase this.

As a result, as described in (1), the discharge flow rate of the hydraulic pump can be increased even when the engine speed is not increased due to the isochronous characteristic or the reversed loop characteristic.

(15) In the above (12), preferably, the fuel injection control device is capable of controlling at least a part of the governor area with the reverse droop characteristic, and when the discharge pressure of the hydraulic pump is below the first predetermined pressure, Control to increase the displacement of the hydraulic pump so that the discharge flow rate of the hydraulic pump increases as the discharge pressure of the hydraulic pump is lowered from the second predetermined pressure, and the discharge pressure of the hydraulic pump is lowered from the second predetermined pressure In accordance with this it is possible to select any one of the control to increase the displacement of the hydraulic pump so that the discharge flow rate of the hydraulic pump is kept constant.

This makes it possible to control the flow rate according to the work contents regardless of the characteristics of the governor area.

BRIEF DESCRIPTION OF THE DRAWINGS The figure which shows the whole system containing the hydraulic circuit of the hydraulic drive of the working machine which concerns on 1st Embodiment of this invention.

2 is a view showing an appearance of a hydraulic excavator on which a hydraulic drive device according to the present embodiment is mounted;

3 is a characteristic diagram showing the relationship between the rotational speed and the output torque of an engine having an electronic governor for isochronous control;

4 is a diagram showing details of a structure of a regulator;

5 is a view showing a relationship between a control current signal given to an electromagnetic proportional pressure reducing valve of a regulator and a tilt angle of a hydraulic pump;

6 is a functional block diagram showing an arithmetic function of a work machine controller;

FIG. 7 is a diagram showing a relationship between a pump discharge pressure and a second target script used in the second target tilt angle calculating unit of the work machine controller; FIG.

8 is a diagram showing a relationship between a pump discharge pressure and a pump tilt angle correction value used in the tilt angle correction value calculating unit of the work machine controller;

9 is a view showing a relationship between the pump discharge pressure corrected in the adder and the second target pump script;

FIG. 10A is a view showing a relationship between a pump discharge pressure P and a pump stiffness θ according to the prior art having a mechanical governor type engine which controls the governor area with a droop characteristic. FIG.

10B is a diagram showing a relationship between a pump discharge pressure and a pump discharge flow rate according to the prior art;

Fig. 11A is a diagram showing a relationship between a pump discharge pressure P and a pump tilt? According to the prior art having an engine for controlling the governor area with isochronous characteristics, and this embodiment.

11B is a diagram showing a relationship between the pump discharge pressure and the pump discharge flow rate according to the prior art and the present embodiment;

Fig. 12 is a characteristic diagram showing the relationship between the rotational speed and output torque of an engine having an electronic governor for controlling the reverse droop characteristic according to the second embodiment of the present invention;

Fig. 13 is a functional block diagram showing the arithmetic function of the work machine controller according to the second embodiment;

14 is a diagram showing a relationship between a pump discharge pressure and a pump tilt angle correction value used in the tilt angle correction value calculating unit of the work machine controller;

15 is a diagram showing a relationship between the discharge pressure signal corrected in the adder and the second target scripture;

Fig. 16A is a diagram showing a relationship between a pump discharge pressure P and a pump warp [theta] according to the prior art having an engine for controlling the governor area with reverse looping characteristic;

Fig. 16B is a diagram showing the relationship between the pump discharge pressure and the pump discharge flow rate according to the prior art;

FIG. 17A is a diagram showing the relationship between the pump discharge pressure P and the pump tilt? In the second embodiment; FIG.

17B is a diagram showing a relationship between a pump discharge pressure and a pump discharge flow rate according to the second embodiment;

Fig. 18 is a characteristic diagram showing the relationship between the rotational speed and the output torque of an engine having an electronic governor which performs control combining a isochronous characteristic and a reversed loop characteristic according to the third embodiment of the present invention;

19 is a diagram showing a relationship between a pump discharge pressure and a pump tilt angle correction value used in the tilt angle correction value calculating unit of the work machine controller;

20 is a diagram showing a relationship between the discharge pressure signal corrected in the adder and the second target script.

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of this invention is described using drawing.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows the whole system containing the hydraulic circuit of the hydraulic drive of the working machine which concerns on one Embodiment of this invention.                 

The hydraulic drive device according to the present embodiment is provided in a work machine, for example, a hydraulic excavator, and as shown in FIG. 1, an electronic governor 12 constituting the engine 1 and the fuel injection control device of the engine 1. ) And an engine controller 13. The electronic governor 12 and the engine controller 13 are capable of controlling the governor region with isochronous characteristics, that is, isochronous to maintain the rotational speed of the engine 1 at the rated rotational speed regardless of the increase or decrease of the engine load in the governor region. The electronic governor 12 is controlled by the engine controller 13 to inject fuel into the engine 1. A fuel injection control device of this kind is known from, for example, Japanese Patent Laid-Open No. 10-159599.

Moreover, the hydraulic drive apparatus which concerns on this embodiment is the swash plate type variable displacement type hydraulic pump 2 driven by the engine 1, as shown in FIG. 1, the displacement of this hydraulic pump 2, That is, the regulator 16 for controlling the displacement adjusted by controlling the tilt angle of the swash plate, the hydraulic cylinder 3 driven by the hydraulic oil discharged from the hydraulic pump 2, the hydraulic motor 4, the hydraulic cylinder 5, 6) A plurality of hydraulic actuators such as the above, the direction control valves 7 to 10 for controlling the flow of the hydraulic oil supplied to these hydraulic actuators, the main relief valve 11 and the direction control valves 7 to 10 are switched. Operation lever devices 50, ... (only one shown) for generating a pilot pressure for operation, a pressure detector 14 for detecting the discharge pressure of the hydraulic pump 2 and outputting a discharge pressure signal P; Slope angle sword which detects the inclination angle of the swash plate of the hydraulic pump 2 and outputs the inclination angle signal θ. 15, the mode selection switch 17 capable of outputting the control release signal F, and the shuttle for inputting the pilot pressure from the operating lever device 50, ... to select and output one of the pilot pressures. A signal control valve 53 having a combination of valves, a pressure detector 55 for detecting a pilot pressure output from the signal control valve 53 and outputting a pilot pressure signal D, and an output from the pressure detector 14. The discharge pressure signal P to be output, the tilt angle signal θ output from the tilt angle detector 15, the control release signal F output from the mode selection switch 17, and the pilot pressure output from the pressure detector 55. The work machine controller 18 which inputs the signal D and outputs the control current signal R which controls the displacement amount to the regulator 16 is provided.

2, the external appearance of the hydraulic excavator in which the hydraulic drive apparatus which concerns on this embodiment is mounted is shown.

The hydraulic excavator has a lower traveling body 102, an upper swinging body 103, and a front work machine 104, and the upper swinging body 103 is rotatably mounted on an upper portion of the lower traveling body 102, and the front work machine ( 104 is provided in the front part of the upper pivot 103 so that it can move up and down.

The upper swing body 103 is provided with an engine room 105 and a cab 106. The front work machine 104 is a multi-joint structure having a pour 108, an arm 109, and a bucket 110. The lower traveling body 102, the upper swinging body 103, and the front work machine 104 are the actuators of the left and right traveling motors 111 (only one side), the swinging motor 112, the buoyant cylinder 113, and the arm cylinder, respectively. 114, the bucket cylinder 115, the lower traveling body 102 travels by the rotation of the left and right traveling motors 111, and the upper swinging body 103 turns by the rotation of the swinging motor 112. In addition, the buoy 108 of the front work machine 104 is rotated in the vertical direction by the expansion and contraction of the buoy cylinder 113, the arm 109 is rotated in the vertical, front and rear directions by the expansion and contraction of the arm cylinder 114, The bucket 110 rotates vertically and vertically by the expansion and contraction of the bucket cylinder 115.

The hydraulic cylinders 3, 5, 6 and the hydraulic motor 4 shown in FIG. 1 are representative of the actuators. For example, the hydraulic cylinders 3, 5, 6 are the swell cylinder 113, the arm cylinder 114. ), The bucket cylinder 115, the hydraulic motor 4 is the swing motor (112).

Moreover, the operating lever device 50, ..., and the mode selection switch 17 are arranged in the cab 106, and the engine 1 and the hydraulic pump 2 are provided in the engine room 105. Hydraulic devices and electronic devices such as the directional control valves 7 to 10, the engine controller 13, the work machine controller 18, and the like are provided at appropriate positions of the upper swing body 103.

3 shows the relationship between the rotation speed N and the output torque Te of the engine 1 by the fuel injection control apparatus (electronic governor 12 and engine controller 13) performing isochronous control.

As shown in FIG. 3, the output torque characteristic of the engine 1 is divided into the characteristic (isochronous characteristic) of the governor area | region 33 shown by the straight line 32, and the characteristic of the full load area | region shown by the curve 30. As shown in FIG. The governor area 33 is an output area in which the governor opening degree is 100% or less, and the full load area is an output area in which the governor opening degree is 100%. In the figure, the broken line 31 shows the characteristic (droupe characteristic) in the governor area of the conventional mechanical governor type engine for comparison. Since the mechanical governor adjusts the fuel injection amount by the balance of the flywheel and the spring, the governor area of the mechanical governor type engine is reduced in engine output torque (engine load) Te like the broken line 31. As a result, the engine speed N increases. On the other hand, in the engine 1 according to the present embodiment, the engine speed N is set at the rated speed regardless of the decrease in the engine output torque Te by the electronic governor 12 in the governor area as in the straight line 32. It has the isochronous characteristic which performs isochronous control which keeps it constant at (N0). By this isochronous control, low fuel consumption and low noise can be realized as compared with a work machine equipped with a mechanical governor engine.

The detail of the regulator 16 is shown in FIG. The regulator 16 controls the tilt angle of the hydraulic pump 2 to match the target pump tilt angle indicated by the control current signal R by the control current signal R output from the work machine controller 18. The proportional pressure reducing valve 60, the servo valve 61, and the servo piston 62 are provided. The electromagnetic proportional pressure reducing valve 60 inputs a control current signal R from the work machine controller 18, outputs a control pressure proportional to the control current signal R, and the servo valve 61 is applied to the control pressure. It operates by controlling the position of the servo piston 62, the servo piston 62 drives the swash plate 2a of the hydraulic pump 2 to control the tilt angle.

The discharge pressure of the hydraulic pump 2 is guided to the input port of the servovalve 61 via the check valve 63 and always acts on the small diameter chamber 62a of the servo piston 62 via the passage 54. Doing. The discharge pressure of the pilot pump 66 is guided to the input port of the electromagnetic proportional pressure reducing valve 60, and the electromagnetic proportional pressure reducing valve 60 is decompressed to become the control pressure. This control pressure acts on the pilot piston 61a of the servovalve 61 via the passage 67. When the discharge pressure of the hydraulic pump 2 is lower than the discharge pressure of the pilot pump 66, the discharge pressure of the pilot pump 66 passes through the check valve 69 as the servo assist pressure to the input port of the servo valve 61. Induced.

5 is a tilt angle of the control current signal R given to the electromagnetic proportional pressure reducing valve 60 and the swash plate 2a of the hydraulic pump 2 (hereinafter referred to simply as a tilt angle or a pump tilt of the hydraulic pump 2). ].

When the control current signal R is equal to or less than R1, the electromagnetic proportional pressure reducing valve 60 does not operate and the control pressure from the electromagnetic proportional pressure reducing valve 60 is zero. For this reason, the spool 61b of the servovalve 61 is pressed to the left by the spring 61c, and the discharge pressure (or discharge pressure of the pilot pump 66) of the hydraulic pump 2 is a check valve 63, It acts on the large diameter chamber 62b of the servo piston 62 via the sleeve 61d and the spool 61b. Although the discharge pressure of the hydraulic pump 2 also acts on the small diameter chamber 62a of the servo piston 62 through the passage 54, the servo piston 62 moves to the right side due to the area difference.

When the servo piston 62 moves to the right of the illustration, the feedback lever 71 rotates counterclockwise in the illustration with the pin 72 as the support point. Since the tip of the feedback lever 71 is connected to the sleeve 61d by the pin 73, the sleeve 61d moves to the left in the illustration. The movement of the servo piston 62 is performed until the notch of the opening of the sleeve 61d and the spool 61b is closed, and when it is completely closed, the servo piston 62 stops.

By these operations, the tilt angle of the hydraulic pump 2 becomes the minimum position, and the discharge flow rate of the hydraulic pump 2 becomes minimum.

When the control current signal R becomes larger than R1 and the electromagnetic proportional pressure reducing valve 60 is operated, the control pressure according to the actuation amount of the electromagnetic proportional pressure reducing valve 60 passes through the passage 67 to the pilot piston of the servo valve 61. Acting on 61a, the spool 61b is moved to the right of the illustration to a position that is balanced with the force of the spring 61c. When the spool 61b moves, the large diameter chamber 62b of the servo piston 62 is connected to the tank 75 via a passage inside the spool 61b. Since the discharge pressure of the hydraulic pump 2 (or the discharge pressure of the pilot pump 66) always acts on the small diameter chamber 62a of the servo piston 62 through the passage 54, the servo piston 62 Moving to the left of the illustration, the working oil of the large diameter chamber 62b returns to the tank 75.

When the servo piston 62 moves to the left side of the figure, the feedback lever 71 rotates clockwise in the city with the pin 72 as a support point, and the sleeve 61d of the servovalve 61 moves to the right side of the figure. The movement of the servo piston 62 is performed until the notch of the opening of the sleeve 61d and the spool 61b is closed, and when it is completely closed, the servo piston 62 stops.

By these operations, the tilt angle of the hydraulic pump 2 increases, so that the discharge flow rate of the hydraulic pump 2 increases. Incidentally, the increase amount of the discharge flow rate of the hydraulic pump 2 is proportional to the increase amount of the control pressure, that is, the increase amount of the control current signal R.

When the control current signal R is lowered and the control pressure from the electromagnetic proportional pressure reducing valve 60 is lowered, the spool 61b of the servovalve 61 is returned to the left in the figure to a position that is balanced with the force of the spring 61c. Then, the discharge pressure of the hydraulic pump 2 (or the discharge pressure of the pilot pump 66) is the large diameter chamber 62b of the servo piston 62 through the sleeve 61d of the servo valve 61 and the spool 61b. Servo piston 62 moves to the right in the drawing due to the area difference with the small diameter chamber 62a.

When the servo piston 62 moves to the right of the illustration, the feedback lever 71 rotates counterclockwise as shown by the pin 72 as a supporting point, and the sleeve 61d of the servo valve 61 moves to the left of the illustration. The movement of the servo piston 62 is performed until the notch of the opening of the sleeve 61d and the spool 61b is closed, and when it is completely closed, the servo piston 62 stops.

By these operations, the tilt angle of the pump 2 is reduced, and the discharge flow rate of the hydraulic pump 2 is reduced. The amount of reduction in the discharge flow rate of the hydraulic pump 2 is proportional to the amount of decrease in the control pressure, that is, the amount of decrease in the control current signal R.

6 shows the details of the mode selection switch 17 and the arithmetic function of the work machine controller 18 in a functional block diagram.

The mode selection switch 17 includes, for example, a driving mode switch 17A, a load lifting mode switch 17B, and a stop mode switch 17C, and any one of these switches 17A to 17C is operated by an operator. When the control is operated, the control release signal F is output.

The work machine controller 18 includes a first target pump tilt angle calculation unit 81, a second target pump tilt angle calculation unit 82, a tilt angle correction value calculation unit 83, a switching unit 84, and an adder ( 85, the minimum value selecting section 86, the subtracting section 87, and the control current calculating section 88, respectively.

The first target pump tilt angle calculation unit 81 inputs the pilot pressure signal D from the pressure detector 55, refers to the table stored in the memory, and the pilot pressure indicated by the signal D at that time. Compute the first target light (θD) of the hydraulic pump (2) corresponding to. This first target script θD is the target script of positive control according to the lever operation amount (required flow rate) of the operating lever device 50,... (See FIG. 1), and the table of the memory has a first target script as the pilot pressure increases. The relationship between the two is set so that the target script θD is also increased.

The second target pump tilt angle calculating unit 82 inputs the discharge pressure signal P of the hydraulic pump 2 from the pressure detector 14, refers to the table stored in the memory, and then the signal P at that time. The second target light bulb θT of the hydraulic pump 2 corresponding to the pump discharge pressure (hereinafter, denoted by the same symbol P as the signal for convenience) is calculated. The second target light θT is a limit value for performing torque control of the hydraulic pump 2, and the pump discharge pressure P based on the pump absorption torque curve is shown in the memory table as shown in FIG. A relationship with the second target light bulb θT (limit value) of the hydraulic pump 2 is set.

In FIG. 7, 20 is a pump absorption torque curve, and the curve 21 of the output torque Te (refer FIG. 3) at the predetermined rotation speed (for example, the rated rotation speed N0) of the engine 1 is shown. It is set to match. When the pump discharge pressure P is in the range of P1 or more, the second target pump drop θT changes according to the pump absorption torque curve 20, and the pump discharge pressure P increases, thereby increasing the second target pump drop θT. Decreases.

When the pump discharge pressure P is P1, the second target pump drop θT is the first maximum drop θmax1, and in the range where the discharge pressure P is lower than P1, like the characteristic line 19, the second target pump The script θT is held in the first maximum script θmax1. The first maximum warp θmax1 is a design specification of the hydraulic excavator, for example, the swing motor 112, the pour cylinder 113, the arm cylinder 114, and the bucket cylinder 115 (hydraulic cylinders 3 and 5). , 6) and hydraulic motor (4)] are determined by design specifications such as operating speed. That is, the first maximum warp? Max1 is set such that the pump discharge flow rate obtained thereby applies the desired operating speed of those actuators.

Pmin is the minimum discharge pressure of the hydraulic pump 2, Pmax is the maximum discharge pressure of the hydraulic pump (2). The maximum discharge pressure Pmax corresponds to the set pressure of the main relief valve 11 (see FIG. 1).

The range 23 between the minimum discharge pressure Pmin and the pressure P1 is an area corresponding to the governor area 33 described above.

The absorption torque of the hydraulic pump 2 is represented by the product of the discharge pressure of the hydraulic pump 2 and the displacement (light angle) of the hydraulic pump 2. Accordingly, the second target light bulb θT corresponding to the pump discharge pressure P is calculated from the pump absorption torque curve 20, and the tilt angle of the hydraulic pump 2 is controlled to be the second target pump light bulb θT. The hydraulic pump 2 is constructed such that the product of the pump discharge pressure P and the second target pump stirrer θT (absorption torque of the hydraulic pump 2) is maintained at the pump absorption torque (constant value) indicated by the curve 20. Means to control the scriptures.

The tilt angle correction value calculating unit 83 inputs the discharge pressure signal P of the hydraulic pump 2 from the pressure detector 14, refers to the table stored in the memory, and the signal P at that time is The correction value S of the second target light θT of the hydraulic pump 2 corresponding to the pump discharge pressure (hereinafter, denoted by the same symbol P as the signal) is calculated. This correction value S increases the tilt angle of the hydraulic pump 2 as the engine load decreases even if the engine speed in the governor region 33 (FIG. 3) is constant by isochronous control. It is for correcting the tilt angle of the hydraulic pump 2 so as to increase. As shown in FIG. When smaller, the relationship between the discharge pressure P and the correction value S is set so that the correction value S increases linearly proportionally as the discharge pressure P decreases.

The switching unit 84 is opened when the control release signal F is output from the mode selection switch 17 to invalidate the correction value S of the target pump script.

The adder 85 is a correction value of the target pump warp calculated by the warp angle correction value calculation unit 83 to the second target warp θT of the hydraulic pump 2 calculated by the second target pump warp angle calculator 82. (S) is added to calculate the corrected second target script θT.

9 shows a relationship between the discharge pressure P corrected by the adder 85 and the second target light bulb θT.

By adding the correction value S to the second target script θT, the characteristic line 19 shown in FIG. 7 is corrected like the characteristic line 22 and corrected as the pump discharge pressure P decreases from P1 to Pmin. The second target script θT increases linearly from the first maximum script θmax1 to the second maximum script θmax2 (= first maximum script θmax1 + Smax). For example, it is set corresponding to the structural maximum light drop (pump performance limit) of the hydraulic pump 2.                 

The minimum value selector 86 is configured to calculate the first target light θD of the hydraulic pump 2 calculated by the first target pump light angle calculator 81 and the second target light θT corrected by the adder 85. The smaller one is selected to be the target light bulb θc for the control of the hydraulic pump 2. Accordingly, when the first target script θD of the hydraulic pump 2 calculated by the first target pump tilt angle calculation unit 81 is large by the corrected second target script θT, the second target script θT corrected. ) Is output as the control target pump script θc so that the control target pump script θc is limited to the corrected second target script θT or less.

The subtraction unit 87 calculates the deviation Δθ between the control target pump script θc and the tilt angle signal θ output from the tilt angle detector 15 so that the control current calculation unit 88 performs, for example, an integral control operation. The control current signal R is calculated from the deviation?. Thereby, the inclination-angle signal (theta) is controlled so that it may correspond with the control target pump inclination (theta) c.

The operation in the present embodiment configured as described above is as follows.

First, when none of the switches 17A to 17C of the mode selection switch 17 is operated and the release signal F is not output, that is, the switching unit 84 of the work machine controller 18 is turned off. It demonstrates.

When the engine 1 is started to drive the hydraulic pump 2, and any one of the operating lever devices 50, ... is operated, the pressure oil discharged from the hydraulic pump 2 is applied to the direction control valves 7 to 10. Through this, it is supplied to the hydraulic cylinders 3, 5, 6, the hydraulic motor 4, etc., for example, the front work machine 104 of the hydraulic excavator shown in FIG. 2 is driven, and earth excavation work etc. are performed.                 

In the work machine controller 18, in the first target pump tilt angle calculator 81, the first target tilt θD of the hydraulic pump 2 corresponding to the pilot pressure signal D output from the pressure detector 55 is received. The second target drop of the hydraulic pump 2 corresponding to the discharge pressure signal P of the hydraulic pump 2 calculated by the second target pump tilt angle calculation unit 82 and output from the pressure detector 14 ( θT) is calculated and the corrected value of the target drop of the hydraulic pump 2 corresponding to the discharge pressure signal P of the hydraulic pump 2 output from the pressure detector 14 by the tilt angle correction value calculating unit 83 ( S) is calculated.

At this time, if the lever operation amount of the operating lever device is small, θD <θc (= θT), the minimum target selector 86 in the first target pump tilt angle calculation unit 81 calculates the first target tilt θD of the hydraulic pump 2. Selected as the control target script θc, and the control current signal R for matching the script angle θ to the target script θc is calculated by the subtractor 87 and the control current calculator 88. This control current signal R is output to the electromagnetic proportional pressure reducing valve 60 of the regulator 16. Thereby, the tilt angle of the hydraulic pump 2 is controlled to correspond to the control target tilt (θc (= θD)), and the hydraulic pump 2 rotates the target tilt (θc) and the number of revolutions of the engine 1 at that time ( Discharge the flow rate proportional to the product of N). This discharge flow rate is the flow rate according to the lever operation amount of the operation lever device, and this discharge flow rate is supplied to the corresponding of the hydraulic cylinders 3, 5, 6 or the hydraulic motor 4, and the corresponding actuator is operated according to the operation amount of the operation lever device. Driven at speed.

On the other hand, for example, if the operating lever of the operating lever device is fully operated and θD> θc (= θT), the minimum value selector 86 performs the first operation of the hydraulic pump 2 calculated by the second target pump tilt angle calculation unit 82. 2 The target script θT is selected as the control target script θc so that the control current signal R calculated from the target script θc and the tilt angle signal θ is the electronic proportional pressure reducing valve 60 of the regulator 16. )

At this time, if the pump discharge pressure indicated by the signal P output from the pressure detector 14, for example, heavy excavation or the like is P2 higher than P1 shown in FIG. 9, the tilt angle correction value calculating unit 83 The correction value S = 0 is calculated, and the second target pump tilt angle calculating unit 82 calculates the second target tilt (θT = θ2), and the θ2 is the second target tilt (θT) as it is. For this reason, the tilt angle of the hydraulic pump 2 is limited to θ2, and the discharge flow rate of the hydraulic pump 2 is also limited to the following flow rate Q1.

Q1 = aθ2N

(a is an integer)

As a result, the discharge flow rate of the hydraulic pump 2 is limited, so that the horsepower of the hydraulic pump 2 represented by the product of the discharge flow rate of the hydraulic pump 2 and the discharge pressure is also limited. Thereby, the effective use of the output horsepower of the engine 1 can be performed in the range which prevents overload of the engine 1 and does not produce an engine stall.

The control of the tilt angle of the hydraulic pump 2 based on the pump absorption torque curve 20 is called pump absorption torque control, and the control of the discharge flow rate of the hydraulic pump 2 is called pump absorption horsepower control.

From the above-described state, for example, when the soil is discarded from the bucket 110 and the air is released, the discharge pressure P of the hydraulic pump 2 decreases from P2. When this pump discharge pressure P falls to P3 smaller than P1, for example, correction value S = S1 is computed by the tilt angle correction value calculation part 83, and the 2nd target by the 2nd target pump tilt angle calculation part 82 is calculated. The script θT = θmax1 is calculated, and the value obtained by adding the correction value S1 to θmax1 becomes the corrected second target script θT. For this reason, the tilt angle of the hydraulic pump 2 is controlled to be θmax1 + S1, and the discharge flow rate of the hydraulic pump 2 is also controlled to be the following flow rate Q3.

Q3 = a (θmax1 + S1) N

That is, the warp angle of the hydraulic pump 2 is increased by the amount of the correction value S1 compared to the first maximum warp θmax1 which is the warp angle when the discharge pressure of the hydraulic pump 2 is at P1, and thus the hydraulic pressure is increased. The discharge flow rate of the pump 2 also increases.

Here, the correction value S is set to increase linearly proportionally as the discharge pressure P becomes lower than P1, and the corrected second target script θT is the pump discharge pressure P as the characteristic line 22. ) Increases linearly proportionally from the first maximum script θmn1 to the second maximum script θmax2 (= first maximum script θmax1 + Smax). For this reason, even if the rotation speed of the engine 1 is constant in the range 23 corresponding to the governor area 33 (FIG. 3) by isochronous control, the discharge flow volume of the hydraulic pump 2 becomes lighter as the engine load becomes lighter. It is controlled to increase, and accordingly, the operation speed of hydraulic actuators, such as the hydraulic cylinders 3, 5, 6, and the hydraulic motor 4, can be made faster. The characteristic shown by this characteristic line 22 is substantially identical with the droop characteristic line 31 in the mechanical governor shown in FIG.                 

10A and 10B show the relationship between the pump discharge pressure P and the pump warp θ and the pump discharge pressure and the pump discharge flow rate according to the prior art having a mechanical governor type engine which controls the governor area with a droop characteristic. The relationship with

In the prior art which does not include the warp angle correction value calculating part 83, the switching part 84, and the adder 85 shown in FIG. 6 in the calculation function of a work machine controller, it corresponds to the governor area | region 33 (FIG. 3). In the range 23 between Pmin and P1, as shown by the straight line 25, the pump tilt θ is constant. On the other hand, in the governor region 33 of the mechanical governor type engine, as shown by the broken line 31 of FIG. 3, the droop characteristic in which the engine speed N increases as the engine output torque (engine load) Te decreases. Obtained. For this reason, in the range 23 between Pmin and P1, the engine speed N increases as the pump discharge pressure P decreases from P1, so that the engine speed N is constant even if the pump warp θ is constant. The pump discharge flow rate Q increases as indicated by the broken line 26 by the increase of. As a result, the flow rate supplied to the hydraulic actuator is increased, so that the working speed in the unloading operation is increased, thereby improving work efficiency.

11A and 11B show the relationship between the pump discharge pressure P and the pump slewing?, The pump discharge pressure and the pump discharge flow rate according to the prior art having an engine for controlling the governor area with isochronous characteristics, Indicates a relationship.

In the governor region 33 of the engine which controls the governor region with isochronous characteristics, the engine speed N is equal to the rated rotation speed N0 regardless of the decrease in the engine output torque Te as shown in the straight line 32 of FIG. 3. Is constant. For this reason, as shown by the dashed-dotted line 27 in the range 23 between Pmin and P1 which correspond to the governor area | region 33, when pump stiffness (theta) is constant, the pump discharge flow rate Q is also one point in FIG. As shown by the dashed line 28, it is constant. In contrast, in the present embodiment, in the range 23 between Pmin and P1 corresponding to the governor region 33, the pump tilt θ changes as the straight line 35 corresponding to the characteristic line 22 of FIG. 9. The pump discharge flow rate Q changes as indicated by the straight line 36 due to the increase in the pump tilt θ. That is, even if the engine speed N is constant, the pump discharge flow rate Q increases linearly proportionally as the pump discharge pressure P decreases from P1. As a result, the flow rate supplied to the hydraulic actuator increases in the same manner as in the prior art shown in FIGS. 10A and 10B, thereby increasing the working speed in the unloading operation and improving work efficiency.

As described above, there are a traveling operation, a load lifting operation, and a stopping operation as an operation or operation for which the increase in discharge flow rate of the hydraulic pump 2 is not desired under light engine load. When such an operation or operation is performed, the operator operates the switch 17A to 17C of the mode selection switch 17 corresponding thereto. Thereby, the control release signal F is output from the mode selection switch 17 to the work machine controller 18, and the switching part 84 is turned on, and the correction value S of the target pump warp becomes invalid. As a result, the increase control of the discharge flow volume of the hydraulic pump 2 by the correction value S of the tilt angle correction value calculation part 83 is not performed.

For example, the driving mode switch 17A of the mode selection switch 17 described above may be configured to operate when a signal from the detection means for detecting the operation of the driving operation lever is input to the work machine controller 18. . The same applies to the other mode switches 17B and 17C.

According to this embodiment configured as described above, in the case where the engine 1 to which isochronous control is applied is provided, the pump discharge flow rate Q can be gradually increased as the engine load becomes light even in the governor region 33. In other words, it is possible to increase the pump discharge flow rate which is approximately equivalent to the increase in the flow rate due to the droop characteristic in the mechanical governor. As a result, the speed of the hydraulic actuator at light engine speed can be increased, and the work efficiency at light load such as unloading work can be improved. In addition, a good feeling of operation can be given to an operator who has become accustomed to the operation of a work machine provided with a mechanical governor type engine.

When the running operation, the lifting operation or the stopping operation is performed, the correction value S by the tilt angle correction value calculating unit 83 is invalidated and isochronous control is performed according to the isochronous characteristic line 32 shown in FIG. By discharging, the discharge flow rate of the hydraulic pump 2 becomes constant regardless of the engine load, and it is possible to perform good driving operation, lifting operation and stopping operation by maintaining the hydraulic actuator speed at the constant speed regardless of the increase or decrease of the engine load. .

A second embodiment of the present invention will be described with reference to Figs. 12 to 17B. In this embodiment, the present invention is applied to a hydraulic driving apparatus including an engine having a fuel injection control apparatus capable of controlling the governor region with reverse droop characteristics.

The overall configuration of the hydraulic drive apparatus according to the present embodiment is substantially the same as the first embodiment shown in FIG. 1 except for the following points.                 

In the present embodiment, the fuel injection control device including the electronic governor 12 and the engine controller 13 shown in FIG. 1 is capable of controlling the governor region with the reversed loop characteristic, whereby the engine 1 is located in the governor region. As the engine output torque Te (engine load) becomes lighter, the rotation speed of the engine 1 is controlled to decrease.

12 shows the relationship between the rotation speed N and the output torque Te of the engine 1 controlled by the reverse droop characteristic. In FIG. 12, the governor region 33 has a reverse droop characteristic in which the engine speed N decreases as the engine output torque Te (engine load) decreases as in the straight line 34. This reverse droop characteristic further lowers the engine speed at light load as compared with the droop characteristic and isochronous characteristic, thereby further achieving low fuel consumption and low noise.

13 shows a calculation function of the work machine controller 18 according to the present embodiment.

The work machine controller 18 includes a first target pump tilt angle calculation unit 81, a second target pump tilt angle calculation unit 82, a first tilt angle correction value calculation unit 83A, and a second tilt angle correction value calculation unit ( 83B), 0 setting unit 83C, switching unit 84A, adding unit 85, minimum value selecting unit 86, subtracting unit 87, and control current calculating unit 88 Have

The first and second tilt angle correction value calculation units 83A and 83B input the discharge pressure signal P of the hydraulic pump 2 from the pressure detector 14, respectively, and refer to the table stored in the memory. The correction value S of the second target light bulb θT of the hydraulic pump 2 is calculated.

The first tilt angle correction value calculation unit 83A uses a hydraulic pump so that the discharge flow rate of the hydraulic pump 2 increases as the engine load decreases even when the engine speed in the governor region 33 decreases due to the reverse droop characteristic. 2) To correct the warp angle of 2), the memory table shows a correction value Sa = O when the pump discharge pressure P is equal to or greater than P1, and the discharge pressure when the discharge pressure P becomes smaller than P1. As (P) decreases, the relationship between the discharge pressure P and the correction value Sa is set so that the correction value Sa increases linearly in proportion.

Also, the second tilt angle correction value calculating unit 83B uses the hydraulic pump so that the discharge flow rate of the hydraulic pump 2 is constant regardless of the engine load even when the engine speed decreases in the governor region 33 due to the reverse droop characteristic. 2). To correct the warp angle of 2), as shown in FIG. 14, when the pump discharge pressure P is equal to or greater than P1, the correction value Sb = 0, and when the discharge pressure P becomes smaller than P1, 1 As the discharge pressure P decreases at a rate smaller than the correction value Sa calculated by the tilt angle correction value calculation unit 83A, the discharge pressure P and the correction value are increased so as to increase the correction value Sb linearly. The relationship of (Sb) is set.

The zero setting unit 83C outputs zero as the correction value S. FIG.

The mode selection switch 17A is dial type and has three switching positions of the first, second, and third.

When the mode selection switch 17A is in the first position shown, the switching unit 84A selects the correction value Sa calculated by the first tilt angle correction value calculating unit 83A as shown, and the mode selection switch When 17A is switched to the second position, the correction value Sb calculated by the second tilt angle correction value calculation unit 83B is selected, and when the mode selection switch 17A is switched to the third position, the 0 setting unit 83C is selected. The correction value S (= 0) outputted from &quot; 1 &quot; is selected and output as the correction value S, respectively.

In the adder 85, similarly to the first embodiment, the correction value S selected by the second target light θT of the hydraulic pump 2 calculated by the second target pump light angle calculation unit 82 and the switching unit 84A is obtained. ) Is calculated to calculate the corrected second target script θT.

15 shows a relationship between the pump discharge pressure P corrected by the adder 85 and the second target light bulb θT.

The characteristic line 19 in the range 23 corresponding to the governor area 33 when the correction value Sa calculated by the 1st tilt angle correction value calculation part 83A in the switching part 84A is selected. Is corrected like the characteristic line 40, and the second target script θT corrected as the pump discharge pressure P decreases from P1 to Pmin is from the first maximum script θmax1 to the fourth maximum script θmax4. It linearly increases up to (= 1st largest scripture (theta) max1 + Samax). This fourth maximum warp θmax4 is set in correspondence with the structural maximum warp (pump performance limit) of the hydraulic pump 2, for example.

Characteristic line 19 in the range 23 corresponding to the governor area 33 when the correction value Sb calculated by the second tilt angle correction value calculation unit 83B is selected in the switching unit 84A. Is corrected like the characteristic line 41, and the second target script θT corrected as the pump discharge pressure P decreases from P1 to Pmin is from the first maximum script θmax1 to the third maximum script θmax3. It increases linearly to (= 1st largest script | script) (theta) max1 + Sbmax).

When the correction value S = 0 of the 0 setting section 83C is selected in the switching section 84A, the characteristic line 19 in the range 23 corresponding to the governor region 33 is not corrected. , The second target tilting angle θT calculated by the second target pump tilting angle calculating unit 82 is output as it is.

The characteristic represented by the characteristic line 40 is almost identical in appearance to the droop characteristic line 31 in the mechanical governor shown in FIG. 12, and the characteristic represented by the characteristic line 41 is characteristic of isochronous control shown in FIG. 3. It is almost coincident with the line 32 in appearance.

In the operation in the present embodiment configured as described above, the engine 1 is controlled by the reversed-loop characteristic so that the discharge flow increase control of the hydraulic pump 2 is controlled to either the correction value Sa or the correction value Sb. It is substantially the same as 1st Embodiment except the point which consists of.

That is, for example, when a heavy excavation or the like is performed, the operation lever of the operating lever device is fully operated, and when the mode> θD> θc (= θT) is P> P1, the mode switching switch 17A is switched to the first position, When the correction value Sa calculated by the first tilt angle correction value calculating unit 83A is selected, increase control of tilt angle of the hydraulic pump 2 by the characteristic line 40 shown in FIG. 15 (increase control of discharge flow rate) When the correction value Sb calculated by the second tilt angle correction value calculation unit 83B is selected by switching the mode switching switch 17A to the second position, the characteristic line 41 shown in FIG. Increase control of the tilt angle of the hydraulic pump 2 (maintenance control of the discharge flow rate) is performed.

16A and 16B show the relationship between the pump discharge pressure P and the pump warp [theta] and the relationship between the pump discharge pressure and the pump discharge flow rate according to the prior art having an engine for controlling the governor area with reverse dloop characteristics. .                 

As described above, when the arithmetic function of the work machine controller does not include the warp angle correction value calculation unit 83, the switching unit 84, and the adding unit 85 shown in Fig. 6, it corresponds to the governor area 33. In the range 23 between Pmin and P1, as shown by the straight line 25, the pump tilt θ is constant. On the other hand, in the reversed loop characteristic, as the engine output torque (engine load) Te decreases as shown by the straight line 34 of FIG. 12, the engine speed N decreases. For this reason, in the range 23 between Pmin and P1, the engine speed N decreases as the pump discharge pressure P decreases from P1, so that the engine speed N even if the pump warp θ is constant. As a result, the pump discharge flow rate Q decreases as indicated by the broken line 44. As a result, there is a problem that the flow rate supplied to the hydraulic actuator decreases and the working speed in the idle operation becomes longer later than in the case of isochronous control.

17A and 17B show the relationship between the pump discharge pressure P and the pump drop θ according to the present embodiment, and the relationship between the pump discharge pressure and the pump discharge flow rate.

In this embodiment, when the correction value Sa calculated by the 1st tilt angle correction value calculation part 83A is selected, and the characteristic line 19 shown in FIG. 15 is correct | amended by the characteristic line 40, the governor area | region 33 In the range 23 between Pmin and P1 corresponding to), the pump tilt (θ) changes like the straight line 45 corresponding to the characteristic line 40 of FIG. 15 so that the pump discharge flow rate Q By the increase of θ), it is changed as indicated by the straight line 46. That is, even if the engine speed N decreases due to the reverse droop characteristic, the pump discharge flow rate Q increases linearly as the pump discharge pressure P decreases from P1. As a result, as in the prior art shown in FIGS. 10A and 10B, the flow rate supplied to the hydraulic actuator is increased, so that the working speed in the unloading operation is increased, thereby improving work efficiency.

Moreover, when the correction value Sb calculated by the 2nd tilt angle correction value calculation part 83B is selected, and the characteristic line 19 shown in FIG. 15 is correct | amended by the characteristic line 41, it corresponds to the governor area | region 33. FIG. In the range 23 between Pmin and P1, the pump tilt? Is changed like the straight line 47 corresponding to the characteristic line 41 in FIG. 15, and the pump discharge flow rate Q is the pump tilt? It becomes as shown by the straight line 48 by increase of (). In other words, even if the engine speed N decreases due to the reverse droop characteristic, the decrease in the pump discharge flow rate Q is canceled by the increase in the pump warp so that the pump discharge flow rate Q is kept constant. As a result, in an operation or operation that does not require an increase control of the discharge flow rate of the hydraulic pump 2 such as a running operation, a lifting operation, or a stopping operation, the hydraulic actuator speed is set at the constant speed regardless of the increase or decrease of the engine load. Lift, stop and carry out loads.

When the correction value (S = 0) of the zero setting part 83C is selected and the characteristic line 19 shown in FIG. 15 is not corrected, the range 23 between Pmin and P1 corresponding to the governor area 33 is obtained. In FIG. 15, the pump warp θ becomes constant like the straight line 49 corresponding to the characteristic line 19 of FIG. 15, and the pump discharge flow rate Q is the engine speed N due to the reversed loop characteristic as shown in FIG. 16B. As a result, the pump discharge flow rate Q decreases like the straight line 50. Thereby, fuel economy can be further improved.

According to the present embodiment configured as described above, in the hydraulic drive apparatus including the engine controlled by the reverse droop characteristic, the same effect as in the first embodiment can be obtained. In other words, by switching the mode changeover switch 17A to the first position and selecting the correction value Sa calculated by the first tilt angle correction value calculating unit 83A, the engine load becomes lighter even if it is in the governor region 33. The pump discharge flow rate Q can be gradually increased to increase the pump discharge flow rate approximately equal to the increase in the flow rate due to the droop characteristic in the mechanical governor. As a result, the hydraulic actuator speed at the engine light load can be increased, and the work efficiency at the light load such as unloading work can be improved. Moreover, even the operator who became accustomed to the operation of the work machine provided with the mechanical governor type engine 1 can provide a favorable feeling of operation.

When the driving operation, the load lifting operation or the stopping operation is performed, the engine is switched by selecting the correction value Sb calculated by the second tilt angle correction value calculation unit 83B by switching the mode switching switch 17A to the second position. Irrespective of the load, the discharge flow rate of the hydraulic pump 2 becomes constant, and it is possible to perform good running operation, lifting operation, and stopping operation by setting the hydraulic actuator speed at the constant speed regardless of the increase or decrease of the engine load.

Moreover, according to this embodiment, since the hydraulic pump 2 is driven using an engine controlled by the reverse droop characteristic, the engine speed at light load is further increased as compared with the first embodiment using the engine controlled by the isochronous characteristic. By lowering, it is possible to further realize low fuel consumption and low noise.

In addition, in the case of light excavation, if the fuel economy is to be prioritized, the hydraulic pressure pump (1) is switched to the third position and the set value (S = 0) of the 0 setting section 83C is selected. The discharge flow rate of 2) can be reduced to further improve fuel economy.                 

A third embodiment of the present invention will be described with reference to FIGS. 18 to 20.

In the above embodiment, the present invention is applied to a hydraulic drive apparatus having an engine for controlling the governor region with isochronous or reversed loop characteristics, but the characteristics of the governor region are not limited thereto. In this embodiment, the present invention is applied to an example in which the governor region is provided with an engine controlled by a combination of isochronous characteristics and reversed loop characteristics.

FIG. 18 shows the relationship between the engine speed N and the output torque Te controlled by the combination of the isochronous and reverse looping characteristics. In the governor area 33 in FIG. 18, the engine speed N is maintained at a constant value of the rated rotation speed N0 regardless of the decrease in the engine output torque Te (engine load) as in the straight line 90a. It has the characteristic 90 which combined the isochronous characteristic and the reverse droop characteristic which reduces the engine speed N as the engine output torque Te falls like the straight line 90b. According to this characteristic (90), the engine speed is kept constant according to the isochronous characteristic at heavy loads, to secure a certain actuator speed, and also to improve the noise and fuel economy. The characteristic enables further improvement of noise and fuel economy.

FIG. 19: is a figure which shows the characteristic of the pump tilt correction value S in the tilt angle correction value calculating part 83 (refer FIG. 6) when an engine has such a characteristic 90. In FIG. The characteristic of the pump drop correction value S is set to the line bent in correspondence with the characteristic of the straight line 90a and the straight line 90b shown in FIG.                 

FIG. 20 is the same characteristic diagram as FIG. 9 in the case where the correction value S of the tilt angle correction value calculating part 83 has the characteristic as shown in FIG. By adding the correction value S to the second target script θT, the characteristic line 19 is corrected to the characteristics of the same broken line as the broken line of the correction value S like the characteristic line 91. As a result, in the operation in which the tilt angle of the hydraulic pump 2 is limited to the second target tilt θT, such as heavy excavation, in the range 23 between Pmin and P1 corresponding to the governor region 33, the pump tilt ( θ) is changed like the characteristic line 91, whereby the discharge flow rate of the hydraulic pump is changed as shown by the straight line 36 in Fig. 11B, so that the same increase control of the pump discharge flow rate as in the first embodiment can be performed.

Further, in the above-described embodiment, as a characteristic of the correction value S for increasing the pump discharge flow rate at the engine light load at which the pump discharge pressure P is equal to or lower than P1, roughly the droop characteristics of the mechanical governor. Although it is set that the increase control of the pump discharge flow volume can be matched, the present invention is not limited to setting such discharge flow rate characteristics. For example, the inclination of the characteristic line of the pump drop correction value S shown in FIG. 8 may be made larger, and the pump discharge flow rate may increase more than the increase in the pump discharge flow rate due to the droop characteristics, or vice versa. In addition, even when the characteristic of the governor region is not a combination of the isochronous characteristic and the reversed loop characteristic, the characteristic line of the pump drop correction value S shown in FIG. 8 may be a broken line. In addition, the characteristic line of the pump value correction value S may be a curve rather than a straight line.

In addition, in the said embodiment, although the pump discharge pressure which makes correction | amendment value S zero was made into P1 which is a starting pressure of control by the pump absorption torque curve 20, the pressure lower than that may be sufficient.

In the above embodiment, one characteristic corresponding to the droop characteristic is set as the characteristic of the correction value S for increasing the pump discharge flow rate at the engine light load at which the pump discharge pressure P is equal to or lower than P1. One or more characteristics may be set and the operator may select one of them by switching the mode selection switch. Further, the mode selection switch may be a dial type for continuously changing the output, and the characteristics of the correction value S may be changed continuously. As a result, the operator can select a desired operating speed of the operator while maintaining the effects of low fuel consumption and low noise, which are advantages of the isochronous characteristic or the reverse droop characteristic, to the work machine.

In the above embodiment, the actuator portion of the fuel injection control device which can be controlled by the isochronous characteristic or the reverse droop characteristic is used as the electronic governor 12. However, the present invention is not limited thereto, and the injection amount is controlled regardless of the engine rotation speed. A common rail fuel injection control device or a unit ejector fuel injection control device may be provided.

Further, in the above embodiment, the control of the tilt angle of the hydraulic pump 2 according to the required flow rate, the absorption torque control of the hydraulic pump 2 (absorption horsepower control), and the increase of the tilt angle control of the hydraulic pump under light load, which is a feature of the present invention, are performed. All of the calculation of the command value was performed by the work machine controller 18 and the control current signal was sent to the regulator 16 to control the tilt angle of the hydraulic pump. However, some of them (for example, the hydraulic pump according to the required flow rate) Control of the tilt angle 2) and absorption torque control (absorption horsepower control) of the hydraulic pump 2 may be hydraulically performed by a regulator. Further, in the above embodiment, the tilt angle of the hydraulic pump 2 is detected by the tilt angle detector 15, and the tilt angle is controlled by a feedback loop so that the tilt angle matches the target tilt angle, but the tilt angle detector 15 is provided. Alternatively, the tilt angle of the hydraulic pump may be controlled as an open loop.

According to the present invention, in a hydraulic drive apparatus having an engine which can control at least a part of the governor region by any one of isochronous characteristics, reverse droop characteristics, and a combination of isochronous characteristics and reverse droop characteristics, the engine even in the governor region. As the load becomes lighter, the discharge flow rate of the hydraulic pump can be increased, and the hydraulic actuator speed at the engine light load can be increased as with the mechanical governor type engine, thereby improving the working efficiency at the light load.

In addition, a good feeling of operation can be given to an operator who has become accustomed to operating a work machine provided with a mechanical governor type engine.

Further, according to the present invention, it is possible to selectively control the discharge flow rate of the hydraulic pump so that the hydraulic actuator speed is maintained at the same speed irrespective of the increase or decrease of the engine load, so that the operation or work desired by the operator can be satisfactorily performed.

Claims (22)

delete delete An engine 1; In at least a part of the governor region 33 which is a control region of the fuel injection amount of the engine, the output torque characteristic of the engine is any one of a combination of isochronous characteristics, reversed loop characteristics, isochronous characteristics and reversed loop characteristics. Fuel injection control devices 12 and 13 for controlling the fuel injection amount; A variable displacement hydraulic pump (2) driven by the engine; In the hydraulic drive of the work machine having a plurality of hydraulic actuators (3-6) driven by the pressure oil discharged from the hydraulic pump, A pump for controlling the displacement of the hydraulic pump so that the absorption torque of the hydraulic pump does not exceed the maximum output torque of the engine in the governor area 33 when the discharge pressure of the hydraulic pump 2 exceeds the first predetermined pressure; Absorption torque control means (82); When the discharge pressure of the hydraulic pump is below the first predetermined pressure and the output torque of the engine is within the range of the governor area 33, the discharge pressure of the hydraulic pump is lowered from the second predetermined pressure and the engine output torque is lowered. Flow rate correction control means (83, 85; 17A, 83A, 83B, 84A, 85) for controlling the displacement of the hydraulic pump to increase as the pressure decreases, wherein the second predetermined pressure is equal to the first predetermined pressure. Hydraulic drive device of the work machine, characterized in that. An engine 1; In at least a part of the governor region 33 which is a control region of the fuel injection amount of the engine, the output torque characteristic of the engine is any one of a combination of isochronous characteristics, reversed loop characteristics, isochronous characteristics and reversed loop characteristics. Fuel injection control devices 12 and 13 for controlling the fuel injection amount; A variable displacement hydraulic pump (2) driven by the engine; In the hydraulic drive of the work machine having a plurality of hydraulic actuators (3-6) driven by the pressure oil discharged from the hydraulic pump, A pump for controlling the displacement of the hydraulic pump so that the absorption torque of the hydraulic pump does not exceed the maximum output torque of the engine in the governor area 33 when the discharge pressure of the hydraulic pump 2 exceeds the first predetermined pressure; Absorption torque control means (82); When the discharge pressure of the hydraulic pump is below the first predetermined pressure and the output torque of the engine is within the range of the governor area 33, the discharge pressure of the hydraulic pump is lowered from the second predetermined pressure and the engine output torque is lowered. Flow rate correction control means (83, 85; 17A, 83A, 83B, 84A, 85) for controlling the displacement of the hydraulic pump to increase as it decreases, and the flow rate correction control means (83, 85; 17A, 83A, 83B). And a control releasing means (17, 84; 17A, 83C) for invalidating the increase control of the displacement of said hydraulic pump by 84A, 85. The method of claim 4, wherein The fuel injection control devices 12 and 13 control the fuel injection amount so that the output torque characteristic of the engine becomes isochronous in at least a part of the governor region 33, And said control releasing means (17, 84) comprises at least one of a travel mode switch (17a), a load lift mode switch (17B), and a stop mode switch (17C). An engine 1; In at least a part of the governor region 33 which is a control region of the fuel injection amount of the engine, the output torque characteristic of the engine is any one of a combination of isochronous characteristics, reversed loop characteristics, isochronous characteristics and reversed loop characteristics. Fuel injection control devices 12 and 13 for controlling the fuel injection amount; A variable displacement hydraulic pump (2) driven by the engine; In the hydraulic drive of the work machine having a plurality of hydraulic actuators (3-6) driven by the pressure oil discharged from the hydraulic pump, A pump for controlling the displacement of the hydraulic pump so that the absorption torque of the hydraulic pump does not exceed the maximum output torque of the engine in the governor area 33 when the discharge pressure of the hydraulic pump 2 exceeds the first predetermined pressure; Absorption torque control means (82); When the discharge pressure of the hydraulic pump is below the first predetermined pressure and the output torque of the engine is within the range of the governor area 33, the discharge pressure of the hydraulic pump is lowered from the second predetermined pressure and the engine output torque is lowered. Flow rate correction control means (83, 85; 17A, 83A, 83B, 84A, 85) for controlling the displacement of the hydraulic pump to increase as it decreases, and the flow rate correction control means (83, 85: 17A, 83A, 84A) And (85) control the displacement of the hydraulic pump so that the discharge flow rate of the hydraulic pump increases as the discharge pressure of the hydraulic pump (2) is lowered from the second predetermined pressure. An engine 1; In at least a part of the governor region 33 which is a control region of the fuel injection amount of the engine, the output torque characteristic of the engine is any one of a combination of isochronous characteristics, reversed loop characteristics, isochronous characteristics and reversed loop characteristics. Fuel injection control devices 12 and 13 for controlling the fuel injection amount; A variable displacement hydraulic pump (2) driven by the engine; In the hydraulic drive of the work machine having a plurality of hydraulic actuators (3-6) driven by the pressure oil discharged from the hydraulic pump, A pump for controlling the displacement of the hydraulic pump so that the absorption torque of the hydraulic pump does not exceed the maximum output torque of the engine in the governor area 33 when the discharge pressure of the hydraulic pump 2 exceeds the first predetermined pressure; Absorption torque control means (82); When the discharge pressure of the hydraulic pump is below the first predetermined pressure and the output torque of the engine is within the range of the governor area 33, the discharge pressure of the hydraulic pump is lowered from the second predetermined pressure and the engine output torque is lowered. Flow rate correction control means (83, 85; 17A, 83A, 83B, 84A, 85) for controlling the displacement of the hydraulic pump to increase as it decreases, and the fuel injection control device (12, 13) is the governor area ( 33. The fuel injection amount according to at least a part of 33) is controlled so that the output torque characteristic of the engine becomes a reverse droop characteristic. The flow rate correction control means 17A, 83A, 83B, 84A, 85 discharges the hydraulic pump so that the discharge flow rate of the hydraulic pump increases as the discharge pressure of the hydraulic pump 2 is lowered from the second predetermined pressure. First means (83A, 85) for controlling the; Second means (83B, 85) for controlling the displacement of said hydraulic pump so that the discharge flow rate of said hydraulic pump is kept constant when the discharge pressure of said hydraulic pump is lowered from said second predetermined pressure; And a selection means (17A, 84A) for selecting one of the first means and the second means. The method of claim 7, wherein The flow rate correction control means 17A, 83A, 83B, 84A, 85 further have third means 83C for invalidating the increase control of the displacement of the hydraulic pump 2, and the selection means 17A, 84A. ) Selects any one of the first means, the second means and the third means. An engine 1; In at least a part of the governor region 33 which is a control region of the fuel injection amount of the engine, the output torque characteristic of the engine is any one of a combination of isochronous characteristics, reversed loop characteristics, isochronous characteristics and reversed loop characteristics. Fuel injection control devices 12 and 13 for controlling the fuel injection amount; A variable displacement hydraulic pump (2) driven by the engine; In the hydraulic drive of the work machine having a plurality of hydraulic actuators (3-6) driven by the pressure oil discharged from the hydraulic pump, A pump for controlling the displacement of the hydraulic pump so that the absorption torque of the hydraulic pump does not exceed the maximum output torque of the engine in the governor area 33 when the discharge pressure of the hydraulic pump 2 exceeds the first predetermined pressure; Absorption torque control means (82); When the discharge pressure of the hydraulic pump is below the first predetermined pressure and the output torque of the engine is within the range of the governor area 33, the discharge pressure of the hydraulic pump is lowered from the second predetermined pressure and the engine output torque is lowered. Flow rate correction control means (83, 85; 17A, 83A, 83B, 84A, 85) for controlling the displacement of the hydraulic pump to increase as it decreases, wherein the pump absorption torque control means (82) is the hydraulic pump (2) A target exhaust amount θT for controlling the absorption torque of the hydraulic pump is calculated from the discharge pressure of the pump and the preset pump absorption torque curve 20, and the discharge pressure of the hydraulic pump is set to the first predetermined value. Means 82 for maintaining the target displacement at a constant value? Max1 when the pressure is below the pressure, The flow rate correction control means 83, 85; 17A, 83A, 83B, 84A, 85 are means for calculating the displacement correction value S which increases as the discharge pressure of the hydraulic pump is lowered from the second predetermined pressure ( 83; 83A, 83B, and means for calculating the second displacement θT corrected by adding the displacement correction value S to the target displacement, and the displacement of the hydraulic pump is adjusted by the corrected target displacement. Hydraulic drive device of the work machine, characterized in that for controlling. An engine 1; In at least a part of the governor region 33 which is a control region of the fuel injection amount of the engine, the output torque characteristic of the engine is any one of a combination of isochronous characteristics, reversed loop characteristics, isochronous characteristics and reversed loop characteristics. Fuel injection control devices 12 and 13 for controlling the fuel injection amount; A variable displacement hydraulic pump (2) driven by the engine; In the hydraulic drive of the work machine having a plurality of hydraulic actuators (3-6) driven by the pressure oil discharged from the hydraulic pump, A pump for controlling the displacement of the hydraulic pump so that the absorption torque of the hydraulic pump does not exceed the maximum output torque of the engine in the governor area 33 when the discharge pressure of the hydraulic pump 2 exceeds the first predetermined pressure; Absorption torque control means (82); When the discharge pressure of the hydraulic pump is below the first predetermined pressure and the output torque of the engine is within the range of the governor area 33, the discharge pressure of the hydraulic pump is lowered from the second predetermined pressure and the engine output torque is lowered. Flow rate correction control means (83, 85; 17A, 83A, 83B, 84A, 85) for controlling the displacement of the hydraulic pump to increase as it decreases, wherein the pump absorption torque control means (82) is the hydraulic pump (2) Means for limiting the maximum displacement of the engine to below the maximum output torque of the engine in the governor area 33, The flow rate correction control means 83, 85; 17A, 83A, 83B, 84A, 85 are means for controlling the maximum value of the displacement of the hydraulic pump as the discharge pressure of the hydraulic pump is lowered from the second predetermined pressure. Hydraulic drive device of the work machine, characterized in that. An engine 1; In at least a part of the governor region 33 which is a control region of the fuel injection amount of the engine, the output torque characteristic of the engine is any one of a combination of isochronous characteristics, reversed loop characteristics, isochronous characteristics and reversed loop characteristics. Fuel injection control devices 12 and 13 for controlling the fuel injection amount; A variable displacement hydraulic pump (2) driven by the engine; In the hydraulic drive of the work machine having a plurality of hydraulic actuators (3-6) driven by the pressure oil discharged from the hydraulic pump, A pump for controlling the displacement of the hydraulic pump so that the absorption torque of the hydraulic pump does not exceed the maximum output torque of the engine in the governor area 33 when the discharge pressure of the hydraulic pump 2 exceeds the first predetermined pressure; Absorption torque control means (82); When the discharge pressure of the hydraulic pump is below the first predetermined pressure and the output torque of the engine is within the range of the governor area 33, the discharge pressure of the hydraulic pump is lowered from the second predetermined pressure and the engine output torque is lowered. Flow rate correction control means (83, 85; 17A, 83A, 83B, 84A, 85) for controlling the displacement of the hydraulic pump to increase as it decreases, and according to the required flow rates of the plurality of hydraulic actuators (3-6) Further comprising first calculating means 81 for calculating the first target displacement θD, The pump absorption torque control means 82 has a second target displacement θT for controlling absorption torque of the hydraulic pump from the discharge pressure of the hydraulic pump 2 and the preset pump absorption torque curve 20. And second calculating means 82 for maintaining the target displacement at a constant value θmax1 when the discharge pressure of the hydraulic pump is below the first predetermined pressure, The flow rate correction control means 83, 85; 17A, 83A, 83B, 84A, 85 are means for calculating the displacement correction value S which increases as the discharge pressure of the hydraulic pump is lowered from the second predetermined pressure ( 83; 83A, 83B, and means 85 for calculating the corrected second target displacement θT by adding the displacement correction value to the second target displacement, The hydraulic driving apparatus of the work machine characterized by selecting the smaller one of the said 1st target displacement and the corrected 2nd target displacement as a target displacement for control, and control the displacement of the said hydraulic pump. An engine 1; In at least a part of the governor region 33 which is a control region of the fuel injection amount of the engine, the output torque characteristic of the engine is any one of a combination of isochronous characteristics, reversed loop characteristics, isochronous characteristics and reversed loop characteristics. A fuel injection control device (12, 13) for controlling the fuel injection amount; A variable displacement hydraulic pump (2) driven by the engine; In the hydraulic drive method of the work machine having a plurality of hydraulic actuator (3-6) driven by the pressure oil discharged from the hydraulic pump, When the discharge pressure of the hydraulic pump 2 exceeds the first predetermined pressure, the displacement of the hydraulic pump is controlled so that the absorption torque of the hydraulic pump does not exceed the maximum output torque of the engine in the governor area 33. , When the discharge pressure of the hydraulic pump is below the first predetermined pressure and the output torque of the engine is within the range of the governor region 33, the discharge pressure of the hydraulic pump is lowered from the second predetermined pressure and the engine output torque is lowered. Hydraulic drive method of the work machine, characterized in that for controlling to increase the displacement of the hydraulic pump. The method of claim 12, When the discharge pressure of the hydraulic pump is less than or equal to the first predetermined pressure, control to increase the displacement of the hydraulic pump as the discharge pressure of the hydraulic pump is lowered from the second predetermined pressure, and control to keep the displacement of the hydraulic pump constant Hydraulic drive method of the work machine, characterized in that any one can be selected. The method of claim 12, When the discharge pressure of the hydraulic pump is below the first predetermined pressure, the discharge amount of the hydraulic pump is controlled to increase the discharge flow rate of the hydraulic pump as the discharge pressure of the hydraulic pump is lowered from the second predetermined pressure Hydraulic driving method of work machine. The method of claim 12, The fuel injection control devices 12 and 13 control the fuel injection amount in at least a part of the governor region 33 so that the output torque characteristic of the engine becomes a reverse droop characteristic, When the discharge pressure of the hydraulic pump is below the first predetermined pressure, the discharge amount of the hydraulic pump is increased so that the discharge flow rate of the hydraulic pump increases as the discharge pressure of the hydraulic pump 2 is lowered from the second predetermined pressure. It is possible to select either one of a control for increasing and a control for increasing the displacement of the hydraulic pump so that the discharge flow rate of the hydraulic pump is kept constant as the discharge pressure of the hydraulic pump is lowered from the second predetermined pressure. Hydraulic drive method of working machine. An engine 1; In at least a part of the governor region 33 which is a control region of the fuel injection amount of the engine, the output torque characteristic of the engine is any one of a combination of isochronous characteristics, reversed loop characteristics, isochronous characteristics and reversed loop characteristics. Fuel injection control devices 12 and 13 for controlling the fuel injection amount; A variable displacement hydraulic pump (2) driven by the engine; In the hydraulic drive of the work machine having a plurality of hydraulic actuators (3-6) driven by the pressure oil discharged from the hydraulic pump, A pump for controlling the displacement of the hydraulic pump so that the absorption torque of the hydraulic pump does not exceed the maximum output torque of the engine in the governor area 33 when the discharge pressure of the hydraulic pump 2 exceeds the first predetermined pressure; Absorption torque control means (82); When the discharge pressure of the hydraulic pump is below the first predetermined pressure and the output torque of the engine is within the range of the governor area 33, the discharge pressure of the hydraulic pump is lowered from the second predetermined pressure and the engine output torque is lowered. And flow rate correction control means (83, 85; 17A, 83A, 83B, 84A, 85) for controlling the displacement of the hydraulic pump to increase as it decreases, The first predetermined pressure is the maximum of the hydraulic pump determined by the design specifications of the plurality of actuators 3 to 6 in the characteristic diagram in which the relationship between the discharge pressure of the hydraulic pump 2 and the target exhaust amount θT is determined. It is a pressure value corresponding to the intersection of the characteristic line 19 which shows the displacement (theta) max1, and the pump absorption torque curve 20 preset in correspondence with the maximum output torque of the engine in the governor area 33. It is characterized by the above-mentioned. Hydraulic drive system of working machine. An engine 1; In at least a part of the governor region 33 which is a control region of the fuel injection amount of the engine, the output torque characteristic of the engine is any one of a combination of isochronous characteristics, reversed loop characteristics, isochronous characteristics and reversed loop characteristics. Fuel injection control devices 12 and 13 for controlling the fuel injection amount; A variable displacement hydraulic pump (2) driven by the engine; In the hydraulic drive of the work machine having a plurality of hydraulic actuators (3-6) driven by the pressure oil discharged from the hydraulic pump, A pump for controlling the displacement of the hydraulic pump so that the absorption torque of the hydraulic pump does not exceed the maximum output torque of the engine in the governor area 33 when the discharge pressure of the hydraulic pump 2 exceeds the first predetermined pressure; Absorption torque control means (82); When the discharge pressure of the hydraulic pump is below the first predetermined pressure and the output torque of the engine is within the range of the governor area 33, the discharge pressure of the hydraulic pump is lowered from the second predetermined pressure and the engine output torque is lowered. And flow rate correction control means (83, 85; 17A, 83A, 83B, 84A, 85) for controlling the displacement of the hydraulic pump to increase as it decreases, And said first predetermined pressure is a value corresponding to a maximum pressure of a discharge pressure range (23) of said hydraulic pump (2) corresponding to said governor area (33). delete The method of claim 12, The first predetermined pressure is the maximum of the hydraulic pump determined by the design specifications of the plurality of actuators 3 to 6 in the characteristic diagram in which the relationship between the discharge pressure of the hydraulic pump 2 and the target exhaust amount θT is determined. It is a pressure value corresponding to the intersection of the characteristic line 19 which shows the displacement (theta) max1, and the pump absorption torque curve 20 preset in correspondence with the maximum output torque of the engine in the governor area 33. It is characterized by the above-mentioned. Hydraulic drive method of working machine. The method of claim 12, And said first predetermined pressure is a value corresponding to a maximum pressure of a discharge pressure range (23) of said hydraulic pump (2) corresponding to said governor area (33). delete An engine 1; In at least a part of the governor region 33 which is a control region of the fuel injection amount supplied to the engine, the output torque characteristic of the engine is any one of isochronous characteristics, reversed loop characteristics, a combination of isochronous characteristics and reversed loop characteristics. A fuel injection control device (12, 13) for controlling the fuel injection amount to be one; A variable displacement hydraulic pump (2) driven by the engine; In the hydraulic drive of the work machine having a plurality of hydraulic actuators (3-6) driven by the pressure oil discharged from the hydraulic pump, Pump absorption torque control means for controlling the displacement of the hydraulic pump so that the absorption torque of the hydraulic pump does not exceed the maximum output torque of the engine in the governor area 33 when the discharge pressure of the hydraulic pump 2 rises ( 82); When the absorption torque of the hydraulic pump is within the range of the governor region 33, flow rate correction control means 83, 85; 17A, 83A, for controlling the discharge amount of the hydraulic pump to increase as the discharge pressure of the hydraulic pump is lowered. And 83B, 84A, 85).

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