JPH0763203A - Hydraulic drive device of hydraulic machine - Google Patents

Abstract

PURPOSE:To secure high work accuracy by calculating an opening area element based on the operational signals of respective actuators, and the opening characteristic of a bleed-off valve and calculating the target opening area of the bleed- off valve based thereon, so as to calculate a drive signal. CONSTITUTION:Calculation is carried out to obtain the opening area elements a1, a2 of a bleed-off valve 38 based on operational signals S1, S2 and preliminarily set by means of the first and second opening characteristics at a first calculation means of a controller 40, when the operational signal S1 of a boom directional changeover valve and a second operational signal S2 of an arm directional changeover valve 2 are outputted from an operational device 50a to the controller 40. The target opening area of the bleed-off valve 3(0) is calculated by a second calculation means based on the opening area elements a1, a2. A drive signal I0 matching the target opening area is calculated by a third calculation means, and the bleed-off valve is varied by the then boom and arms cylinders 11, 12 are placed in complex drive. In this way, the opening area of the bleed-off valve is varied by the complex operation, and thereby operational speed can be quickened, and high drive control can be released even in a single operation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is provided in a hydraulic machine such as a hydraulic excavator and has a bleed-off valve which operates according to an operation signal output from an operating device and controls a flow rate from a hydraulic pump to a tank. The present invention relates to a hydraulic drive device.

[0002]

2. Description of the Related Art FIG. 3 is a circuit diagram showing a conventional hydraulic drive device of this type, which is provided, for example, in a hydraulic excavator. This conventional technique includes a hydraulic pump 20, a plurality of actuators driven by pressure oil discharged from the hydraulic pump 20, for example, a boom cylinder 11 which is a first actuator, an arm cylinder 12 which is a second actuator, and a closed cylinder. It is formed in a center type and includes a hydraulic cylinder 20, a boom cylinder 11, and an arm cylinder 12.
And a boom directional control valve 1 which is a first directional control valve and a second directional control valve 2 for an arm which is a second directional control valve for controlling the flow of pressure oil supplied to each of the above. Also,
An operation signal for driving the bleed-off valve 31 arranged between the hydraulic hoop 20 and the tank, the boom directional switching valve 1, the arm directional switching valve 2 and the bleed-off valve 31, that is, the pilot pressure P. ₁ , P ₁ ′, P ₂ , P ₂
Operation device 51a, 5 for outputting the corresponding one of
1b and.

The relationship between the spool stroke of the bleed-off valve 31 and the opening area is such that as the spool stroke increases, the opening area decreases and the flow rate to the tank decreases as shown in FIG. 4 (a). It is set. The relationship between the spool stroke and the opening area of the boom directional control valve 1 and the arm directional control valve 2 is as shown in FIG.
The opening area increases as the spool stroke increases, and the boom cylinder 11 or the arm cylinder 1 increases.
2 is set so as to increase the flow rate supplied to No. 2.

In the prior art having such a configuration,
For example, a pilot pressure P ₁ that is a first operation signal for driving the boom cylinder 11 is generated by half-operating the operating lever of the operating device 51a, and the boom directional control valve 1 is switched by this pilot pressure P ₁ , and further operation is performed. For example, the arm cylinder 12 is operated by half-operating the operation lever of the device 51b.
A composite operation of generating a pilot pressure P ₂ which is a second operation signal for driving the arm and switching the arm directional control valve 2 by the pilot pressure P ₂ will be described below.

[0005] generating a pilot pressure P ₁ by half the operation lever of the operating device 51a, the pilot pressure P ₁ is applied to the left driving unit of FIG. 3 of the boom directional control valve 1, FIG. 4 ( In accordance with the characteristic of b), the boom directional control valve 1 tends to be switched to the left position, and the pressure oil of the hydraulic pump 20 is supplied to the bottom side of the boom cylinder 11 via the boom directional control valve 1 and the boom cylinder 11 is closed. It can be driven in the extending direction. At this time, at the same time, the pilot pressure P ₁ which is an operation signal for driving the bleed-off valve 31 is given to the drive unit of the bleed-off valve 31 via the shuttle valve, and the spool is adjusted according to the magnitude of the pilot pressure P _1. Is changed, and the opening area is changed according to the spool stroke in FIG. 4A, and the flow rate through the bleed-off valve 31 to the tank is controlled to be reduced.

When the operating lever of the operating device 51b is half-operated to generate the pilot pressure P ₂ from such a state, the operating amount of the operating lever of the operating device 51b is temporarily changed to the operating amount of the operating lever of the operating device 51a. If it is less than the above, since P ₁ > P ₂ , P ₁ is detected by the shuttle valve, and the spool stroke of the bleed-off valve 31 does not change. On the other hand, the arm directional control valve 2 has a pilot pressure P.
₂ tends to be switched to the left position in FIG. 3 according to the characteristic shown in FIG. 4B, and the passage communicating from the hydraulic pump 20 to the arm cylinder 12 is opened. At this time, the holding pressure of the arm cylinder 12 is increased by the bleed-off valve 3
If the generated pressure is higher than 1, the arm cylinder 12 does not move. On the contrary, if the holding pressure of the arm cylinder 12 is lower than the pressure generated by the bleed-off valve 31, the arm cylinder 1
2 also starts to move. When the arm cylinder 12 begins to move, the flow rate is taken there and the bleed flow rate decreases.
Thus, when the bleed flow rate decreases and the generated pressure reaches the holding pressure of the arm cylinder 12, the arm cylinder 1
2 does not move.

[0007]

In the above-mentioned prior art, the combined operation of the boom cylinder 11 and the arm cylinder 12 when the operating levers of the operating devices 51a and 51b are both half-operated can be realized for the time being. However,
In the combined operation when both of these operation levers are half-operated, the operation amount of the operation lever of the operation device 51b that drives the arm cylinder 12 is the boom cylinder 11
In the above case, which is smaller than the operation amount of the operating lever of the operating device 51a for driving the lever, in the case of P ₁ > P ₂ , the opening area of the bleed-off valve 31 is the operating lever of the operating device 51a for driving the boom cylinder 11. Of the bleed-off valve 3 depending on the operating amount of the operating lever of the operating device 51b that drives the arm cylinder 12.
The opening area of No. 1 cannot be changed, and accordingly, the operating speed of the arm cylinder 12 cannot be increased by a certain value or more, and the efficiency of work performed via an arm (not shown) driven by the arm cylinder 12 is improved. There is an unpredictable problem.

Further, in the above-mentioned prior art, the operating device 5
Operate each operation lever of 1a, 51b individually,
Even when the boom cylinder 11 and the arm cylinder 12 are driven independently of each other, the bleed-off valve 31 is set to the unique opening characteristic shown in FIG. Since it is not possible to drive each of the arm cylinders 12 with unique operating characteristics, it is difficult to realize more accurate actuator drive control, and it is also difficult to obtain high working accuracy.

In the above description, in order to simplify the explanation,
Although the boom cylinder 11 and the arm cylinder 12 are given as examples of the actuator, the same applies when the actuator is another hydraulic cylinder such as a bucket cylinder or a hydraulic motor such as a swing motor.

The present invention has been made in view of the above-mentioned circumstances in the prior art, and an object thereof is to drive respective actuators in a combined operation of a first actuator and a second actuator among a plurality of actuators. The opening area of the bleed-off valve can be changed in association with the above, and the opening characteristics of the bleed-off valve unique to each actuator can be secured when the first actuator and the second actuator are individually operated. An object is to provide a hydraulic drive system for a hydraulic machine.

[0011]

In order to achieve this object, the present invention provides a hydraulic pump, a plurality of actuators driven by pressure oil discharged from the hydraulic pump,
A closed center type directional control valve for controlling the flow of pressure oil supplied from the hydraulic pump to each of the actuators; a bleed-off valve arranged between the hydraulic hoop and the tank; A hydraulic drive system for a hydraulic machine, comprising: a switching valve and an operating device that outputs an operating signal for driving the bleed-off valve,
A first operation signal for driving a first directional control valve of the directional control valves that controls the flow of pressure oil supplied to the first actuator, and a preset value related to the first actuator in advance. Calculating a first opening area element of the bleed-off valve based on the first operation signal and a first opening characteristic which is a functional relationship of the first opening area element of the bleed-off valve. A second operation signal for driving a second directional control valve of the directional control valves that controls the flow of pressure oil supplied to the second actuator,
A second opening of the bleed-off valve based on a second operation signal that is set in advance in relation to the second actuator and a second opening characteristic that is a functional relationship between the second opening area element.
And a first calculation means for calculating the opening area element of
Second calculating means for calculating the target opening area of the bleed-off valve based on the first opening area element and the second opening area element calculated by the second calculating means, and the second calculating means. And a third calculation means for calculating a drive signal for driving the bleed-off valve based on the target opening area.

[0012]

Since the present invention has the above-described structure, for example, when the operating device is operated to perform a combined operation of the first actuator and the second actuator, the first directional switching valve is operated from the operating device. A first operation signal for driving and a second operation signal for driving the second directional control valve are output. The first directional switching valve and the second directional switching valve are switched according to each of these first and second operation signals, and the pressure oil discharged from the hydraulic pump is the first actuator and the second actuator. Is supplied to each.

At this time, at the same time, the first computing means is
Calculating the first opening area element of the bleed-off valve on the basis of the above-mentioned first operation signal for driving the directional control valve and the preset first opening characteristic, and the second directional control valve The second opening area element of the bleed-off valve is calculated based on the above-described second operation signal for driving the valve and the preset second opening characteristic. Then, the second calculation means calculates the target opening area of the bleed-off valve based on the first opening area element and the second opening area element obtained as described above. Further, the third calculation means calculates a drive signal corresponding to the above-mentioned target opening area. This drive signal is given to the drive unit of the bleed-off valve, the bleed-off valve is switched so as to have the target opening area obtained by the second calculating means, and the flow rate from the bleed-off valve to the tank is reduced. The pressure generated by the bleed-off valve is first
When the holding pressures of the actuator and the second actuator become higher, the flow rate discharged from the hydraulic pump becomes the first
Of the first actuator and the second actuator, and the combined operation of the first actuator and the second actuator can be performed.

The target opening area of the bleed-off valve obtained by the above-mentioned second computing means is the first operation signal output from the operating device for operating the first actuator, and the operation for operating the second actuator. Since it is calculated in accordance with both the second operation signal output from the device, the target opening area of the bleed-off valve is changed in association with the driving of each of the first actuator and the second actuator. be able to. Thus, for example, the first
Even when the operation amount of the second actuator is smaller than the operation amount of the actuator of, the first actuator,
The bleed-off valve can be driven so that the target opening area depends on the operation amounts of both the second actuators, and the first opening characteristic of the first actuator and the second opening characteristic of the second actuator are set in advance. By appropriately setting, the operating speed of the second actuator can be set to a relatively high speed that is not restricted by the operation amount of the first actuator.

Further, for example, when the operating device is operated to drive the first actuator alone, the first calculating means obtains the first opening area element according to the first opening characteristic, and the second calculating means. Is the target opening area of the bleed-off valve based on the first opening area element, and the third calculating means calculates a drive signal in accordance with the target opening area thus obtained, and by the drive signal. The bleed-off valve is switched. Similarly, when the operating device is operated to drive the second actuator alone, the second computing means obtains the second aperture area element according to the second aperture characteristic, and the second computing means produces the second aperture area element. The target opening area of the bleed-off valve is obtained based on the opening area element of, the third calculating means calculates a drive signal according to the target opening area, and the bleed-off valve is switched by the drive signal.

Here, a first opening characteristic which is a functional relationship between the first operation signal set in relation to the above-mentioned first actuator and the opening area element of the bleed-off valve, and the second opening characteristic.
Is a functional relationship between a second operation signal set in relation to the actuator of FIG.
The opening characteristic can be set in advance as a unique characteristic. With this setting, the opening characteristic of the bleed-off valve unique to each actuator can be secured, and highly accurate drive control of each actuator can be realized.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a hydraulic drive system for a hydraulic machine according to the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram showing an embodiment of a hydraulic drive system for a hydraulic machine according to the present invention, and FIG.
3 is a block diagram showing the configuration of a controller provided in the embodiment shown in FIG.

The embodiment of the present invention shown in FIG. 1 is also provided, for example, in a hydraulic excavator, and has the same hydraulic pump 20 as the hydraulic drive system shown in FIG. 3 and the pressure discharged from this hydraulic pump 20. A plurality of actuators driven by oil, for example, a boom cylinder 11 which is a first actuator, an arm cylinder 12 which is a second actuator, a hydraulic cylinder 1i which is another actuator such as a bucket cylinder, and a closed center type, With the boom directional control valve 1 and the second directional control valve that are the first directional control valves that control the flow of the pressure oil supplied from the hydraulic pump 20 to the boom cylinder 11, the arm cylinder 12, and the hydraulic cylinder 1i, respectively. A certain direction switching valve 2 for the arm, and another direction switching valve i for the hydraulic cylinder 1i. It is provided.

Further, between the hydraulic pump 20 and the tank,
A bleed-off valve 30 including a solenoid valve is provided, and a first operation signal S ₁ for driving the boom directional control valve 1 and the bleed-off valve 30, the arm directional control valve 2 and the bleed-off valve 30 are provided. For operating the operating device 50a capable of outputting the second operation signal S ₂ for driving individually or in combination, and for driving the directional switching valve i and the like which are other directional switching valves and the bleed-off valve 30. An operation device 50b capable of outputting an operation signal Si, and an operation signal S output from the operation devices 50a and 50b having a calculation / storage function.
Drive signals I ₁ , I ₁ ′ for driving the directional control valve 1 for booms, drive signals I ₂ , I ₂ ′ for driving directional control valve 2 for arms, for hydraulic cylinders by processing ₁ , S ₂ , Si. The control means, that is, the controller 40, which can output the drive signals Ii and Ii ′ for driving the direction switching valve i and the drive signal I ₀ for driving the bleed-off valve 30, respectively, is provided.

The controller 40, as shown in FIG. 2, includes a first computing means 60, a second computing means 70, and
The third calculating means 80 and the fourth calculating means 81 are incorporated. Of these, the first calculation means 60 is set (stored) in consideration of the first operation signal S ₁ for driving the boom direction switching valve 1 and the desired operation mode of the boom cylinder 11. operation signal based on the first and the opening characteristic which is a function relationship of S ₁ and the first opening surface elements a ₁ bleed off valve 30, calculates a first opening area element a ₁ of bleed-off valve 30. In addition, the second operation signal S ₂ for driving the arm directional control valve ₂ and the arm cylinder 12 in advance
The second that is set (stored) in consideration of the desired operation mode of
Based on the second opening characteristic which is a second functional relationship of an opening area of the element a ₂ of the operation signal S ₂ and the bleed-off valve 30, and calculates a second opening area element a ₂ bleed off valve 30 . Hereinafter, similarly, an operation signal Si for driving the directional control valve i for the hydraulic cylinder and an operation signal S preset (stored) in consideration of a desirable operation mode of the hydraulic cylinder 1i.
The opening area element ai of the bleed-off valve 30 is calculated based on i and the opening characteristic which is the functional relationship of the opening area element ai of the bleed-off valve 30. In addition, although the above-mentioned respective opening characteristics are made different depending on, for example, each actuator, the opening area elements gradually decrease from the maximum opening as the operation signal increases.

Further, the above-mentioned second calculating means 70 is based on the first opening area element a ₁ , the second opening area element a ₂ , the opening area element ai, etc. which are obtained by the first calculating means 60. The target opening area A of the bleed-off valve 30 is calculated. In this case, for example, as shown in FIG. 2, the first opening area element a ₁ , the second opening area element a ₂ , the opening area element a
The target opening area A is calculated by dividing the product of i and the like by the square root of the sum of squares of the first opening area element a ₁ , the second opening area element a ₂ and the opening area element ai.

Further, the above-mentioned third computing means 80 has the target opening area A obtained by the second computing means 70, the preset (stored) target opening area A and the drive current I of the bleed-off valve 30. Based on the functional relationship between and, the drive current I is calculated, and the drive current I ₀ is calculated. In addition,
The above-mentioned functional relationship is such that the drive current I takes a maximum value when the target opening area A is 0, and the value of the drive current I decreases as the target opening area A increases.

Further, the above-mentioned fourth computing means 81 has the first operation signal S ₁ for driving the boom directional control valve ₁ and
Based on the preset first operation signal S ₁ and the functional relationship between the drive signal I ₁ (I ₁ ′) of the first directional control valve 1, the corresponding drive signal I of the first directional control valve 1 ₁ (I ₁ ′) is calculated. Further, a second operation signal S ₂ for driving the arm directional control valve 2, the second operation signal S ₂ and the drive signal I ₂ of the second directional control valve 2 which is set in advance of (I ₂ ') Based on the functional relationship, the drive signal I of the corresponding second directional control valve 2
₂ (I ₂ ′) is calculated. Hereinafter, similarly, an operation signal Si for driving the directional switching valve i for the hydraulic cylinder, a preset operation signal Si, and a drive signal Ii (Ii for the directional switching valve i
The drive signal Ii (Ii ′) of the corresponding directional control valve i is calculated based on the functional relationship of ′). The functional relationship described above is such that the drive current takes a minimum value when the operation signal is 0, and the value of the drive current increases as the operation signal increases.

The operation of the embodiment thus configured is as follows. For example, in order to perform a combined operation of the boom cylinder 11 and the arm cylinder 12, the operating device 50
Operating the a, a first operation signals S ₁ for driving the boom directional control valve 1 from the operation unit 50a, a second operational signal S ₂ for driving the arm directional control valve 2 is output to the controller 40. These first, fourth calculating means 81, for example, driving signals I _1, I ₂ of the controller 40 is determined depending on the respective second operation signals S _1, S _2, these drive signals I _1, I ₂ is provided to each of the drive parts located on the left side of FIG. 1 of the boom directional control valve 1 and the arm directional control valve 2. As a result, each of the boom direction switching valve 1 and the arm direction switching valve 2 is switched to the left position in FIG.

Further, as described above, the first operation signal S for driving the boom direction switching valve 1 from the operation device 50a.
_{When 1} and the second operation signal S ₂ for driving the arm directional control valve 2 are output to the controller 40, at the same time,
The first computing means 60 of the controller 40 operates the bleed-off valve 30 based on the first operation signal S ₁ for driving the boom directional control valve ₁ and the preset first opening characteristic.
The addition to the first operation the opening area elements a _1, a second operational signal S ₂ for driving the arm directional control valve 2, the bleed-off valve 30 on the basis of the second opening characteristic set in advance A calculation for obtaining the second opening area element a ₂ is performed.

Then, the second calculating means 70, based on the first opening area element a ₁ and the second opening area element a ₂ obtained as described above, the target opening area of the bleed-off valve 30. The calculation of the following formula (1) for obtaining A is performed. A = a ₁ · a ₂ / √ (a ₁ ² + a ₂ ² ) By modifying the above equation, A = a ₁ / √ {1+ (a ₁ / a ₂ ) ² } (1) Furthermore, the third The calculation means 80 calculates the drive current I corresponding to the above-mentioned target opening area A, and performs the calculation using this drive current I as the drive signal I ₀ . This drive signal I ₀ is applied to the drive section of the bleed-off valve 30 and the bleed-off valve 3
0 is switched so as to become the target opening area A obtained by the second calculating means 70, and the flow rate of the fluid flowing from the bleed-off valve 30 to the tank is reduced.

When the pressure generated by the bleed-off valve 30 becomes higher than the holding pressure of the boom cylinder 11 and the arm cylinder 12, the pressure oil discharged from the hydraulic pump 20 is applied to the respective rod sides of the boom cylinder 11 and the arm cylinder 12. The boom cylinder 11 and the arm cylinder 12 that are supplied are compositely driven in the extending direction. Along with this, a boom and an arm (not shown) are driven, and desired work is performed.

In this case, the target opening area A of the bleed-off valve 30 is determined by both the first opening area element a ₁ and the second opening area element a ₂ as shown in the above equation (1). This is a value based on both the first operation signal S ₁ for driving the boom cylinder 11 and the second operation signal S ₂ for driving the arm cylinder 12. Therefore, for example, the operation amount of the operation lever of the operation device 50a for driving the boom cylinder 11 is relatively large, and accordingly, the value of the first operation signal S ₁ is relatively large. The value of the opening area element a ₁ is relatively small even if it does not take the minimum value, while the operation amount of the operating lever of the operating device 50 a for driving the arm cylinder 12 is equal to that of the operating lever for driving the boom cylinder 12. When the value of the second opening area element a ₂ is slightly smaller than the operation amount, the operation amount of the operation lever of the operation device 50 a for driving the boom cylinder 11 is conventionally limited to only the operation amount. Although the opening amount of the bleed-off valve is determined depending on this, in the present embodiment, the operating device 5 for driving the arm cylinder 12 is used.
The bleed-off valve 3 depending on the operation amount of the operation lever 0a.
The opening area of 0 can be changed. That is, when the operation amount of the operating lever of the operating device 50a for driving the arm cylinder 12 is gradually increased, the value of the second opening area element a ₂ becomes smaller, and {1+
Since the value of (a ₁ / a ₂ ) ² } becomes large, the value of the target opening area A gradually decreases from a ₁ , that is, the bleed-off valve 30 is switched to a direction in which it is more closed. The flow rate flowing into the tank via the valve 30 is further reduced, and accordingly, a larger flow rate can be supplied to the arm cylinder 12, and the operating speed of the arm cylinder 12 is adjusted by the operation amount of the operation lever of the operation device 50a. Can be faster depending on.

Further, for example, when the operating device 50a is operated to drive the boom cylinder 11 alone, the first calculating means 60 of the controller 40 obtains the first opening area element a ₁ according to the first opening characteristic. , Second computing means 70
Is a bleed-off valve 3 based on the first opening area element a _1.
A calculation for obtaining the target opening area A of 0 is performed.

In the case of such a single drive, the second opening area element a ₂ related to the arm cylinder 12 not operated is
Performs infinity processing. As a result, the above equation (1) is {1+ (a ₁ / a ₂ ) ² } = 1, and thus A = a ₁ . The third calculating means 80 calculates a drive signal according to the target opening area A (= a ₁ ) thus obtained, and the bleed-off valve 30 is switched by the drive signal.

The same applies when the operating device 50a is operated to drive the arm cylinder 12 independently, and the first opening area element a relating to the boom cylinder 11 that is not operated is the same.
_{Since 1} is infinite, the above equation (1) is {1+ (a ₁ / a ₂ ) ² } = 1, so A = a ₂ and the third operation The means 80 calculates a drive signal according to the target opening area A (= a ₂ ) thus obtained, and the bleed-off valve 30 is switched by the drive signal.

A first opening characteristic which is a functional relationship between the first operation signal S ₁ set in relation to the boom cylinder 11 and the first opening area element a ₁ of the bleed-off valve 30, and the arm cylinder. The second opening characteristic, which is a functional relationship between the second operation signal S ₂ set in relation to 12 and the second opening area element a ₂ of the bleed-off valve 30, is set in advance as a unique characteristic. Because there is a boom cylinder 1
1. The opening characteristic of the bleed-off valve 30 unique to each of the arm cylinders 12 and 12 can be secured, and highly accurate drive control of these cylinders 11 and 12 can be realized.

In the embodiment thus constructed, in the combined operation of the boom cylinder 11 and the arm cylinder 12 as described above, the speed increase of the boom cylinder 11 and the arm cylinder 12 is realized according to the operation of both cylinders. Yes, these boom cylinder 11 and arm cylinder 12
The efficiency of the work performed through the operation of can be improved.

When the boom cylinder 11 and the arm cylinder 12 are individually operated, the opening characteristic of the bleed-off valve 30 unique to each of them can be secured as described above.
As a result, more accurate boom cylinder 11 drive control and arm cylinder 12 drive control can be realized, and as a result, high work precision can be obtained as work performed through the operation of the boom cylinder 11 and arm cylinder 12.

Although the hydraulic cylinders such as the boom cylinder 11 and the arm cylinder 12 are mentioned as the actuators in the above-described embodiments, the present invention is not limited to these hydraulic cylinders, and may be hydraulic motors such as a swing motor. Good.

[0036]

Since the present invention is configured as described above, in the combined operation of the first actuator and the second actuator of the plurality of actuators, the bleed-off valve of the bleed-off valve is associated with the driving of each actuator. The opening area can be changed, whereby the operating speed of the first actuator and the second actuator can be made faster than in the past, and the efficiency of the work performed through the operation of these actuators can be improved. In addition, when the first actuator and the second actuator are individually operated, the opening characteristic of the bleed-off valve unique to each actuator can be secured, and high drive control peculiar to these actuators can be realized. Along with this, it is possible to obtain higher working accuracy than in the past.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of a hydraulic drive system for a hydraulic machine according to the present invention.

FIG. 2 is a block diagram showing a configuration of a controller provided in the embodiment shown in FIG.

FIG. 3 is a circuit diagram showing a conventional hydraulic drive system for a hydraulic machine.

4 is a diagram showing characteristics of a bleed-off valve and characteristics of a direction switching valve provided in the hydraulic drive system shown in FIG.

[Explanation of symbols]

1 Boom Directional Changeover Valve (First Directional Changeover Valve) 2 Arm Directional Changeover Valve (Second Directional Changeover Valve) 11 Boom Cylinder (First Actuator) 12 Arm Cylinder (Second Actuator) 20 Hydraulic Pump 30 bleed-off valve 40 controller 50a operating device 60 first calculating means 70 second calculating means 80 third calculating means 81 fourth computing means S ₁ first operational signal S ₂ the second operation signal a ₁ first Opening area element a ₂ Second opening area element A Target opening area

Claims (2)

[Claims] 1. A hydraulic pump, and a plurality of actuators driven by pressure oil discharged from the hydraulic pump,
A closed center type directional control valve for controlling the flow of pressure oil supplied from the hydraulic pump to each of the actuators; a bleed-off valve arranged between the hydraulic hoop and the tank; A hydraulic drive system for a hydraulic machine, comprising: a switching valve and an operating device for outputting an operating signal for driving the bleed-off valve, wherein a hydraulic oil supplied to a first actuator of the directional switching valve is used. A first operation signal for driving a first directional control valve for controlling a flow, the first operation signal preset in relation to the first actuator, and a first opening area of the bleed-off valve. A first opening area element of the bleed-off valve is calculated based on a first opening characteristic that is a functional relationship of the elements, and a second actuation valve of the directional control valve is operated. A second operation signal for driving a second directional control valve for controlling the flow of pressure oil supplied to the motor;
A second opening of the bleed-off valve based on the second operation signal preset in relation to the second actuator and a second opening characteristic that is a functional relationship of the second opening area element. A first calculation means for calculating the area element; a first opening area element obtained by the first calculation means; and a second opening area element
Second computing means for computing a target opening area of the bleed-off valve based on the opening area element of the bleed-off valve, and driving for driving the bleed-off valve based on the target opening area obtained by the second computing means. A hydraulic drive system for a hydraulic machine, comprising: a third calculation means for calculating a signal. 2. The target opening area of the bleed-off valve is
The product of the first opening area element and the second opening area element obtained by the first calculating means is calculated as the square root of the sum of squares of the first opening area element and the second opening area element. The hydraulic drive system for a hydraulic machine according to claim 1, wherein the hydraulic drive system is substantially equal to the divided value.