JPH11269941A - Hydraulic controller for construction machine and its hydraulic control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control the flow rate supplied to an actuator according to the control input of a control means, based on the will of an operator to control the control means. SOLUTION: A hydraulic controller for a construction machine has a pressure compensating valve 5A having either a first pressure receiving part which receives pressure downstream of a flow control valve and second pressure receiving part which receives the maximum load pressure of an actuator, or first pressure receiving part which receives hydraulic pump pressure at one end and a second pressure receiving part which receives the maximum load pressure of the actuator at the other end. The area ratio of the first pressure receiving part to the second pressure receiving part of the pressure compensating valve 5A is controlled to become variable depending on a control input detected by a control input detection means 25a.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic control device for controlling a working machine of a construction machine such as a hydraulic shovel and an actuator of a turning device for turning an upper turning body.
In particular, the present invention relates to a hydraulic control device for a construction machine and a hydraulic control method for a hydraulic pressure control device, in which an opening area ratio of a pressure compensation valve is made variable and a required flow rate is supplied to an actuator.

[0002]

2. Description of the Related Art Conventional construction machines such as hydraulic excavators include:
In order to drive a working machine such as a boom, an arm, and a bucket (not shown), a closed, center, load sensing system (hereinafter, referred to as a hydraulic control device) as shown in FIG. 8 is employed. Although the driving circuit of the arm actuator 55 and the boom actuator 56 is shown in the drawing, the same circuit is used for driving the boom actuator 56 and a turning actuator (not shown). A conventional hydraulic control device will be described using a drive circuit for an arm actuator 55 and a boom actuator 56 as an example. As shown in FIG. 8, the pressure oil discharged from the variable displacement hydraulic pump 50 (hereinafter, referred to as the hydraulic pump 50) is supplied to the arm flow control valve 51 and the boom flow control valve 52 from the respective pipelines 51a and 51b. Through the pressure compensating valves 53 and 54 to flow into the arm actuator 55 and the boom actuator 56. The arm actuator 55 and the boom actuator 56 are configured as a so-called parallel circuit.

An operation signal corresponding to the operation amount (stroke) of the arm operation means 63 is output to the arm flow control valve 51 of the arm actuator drive circuit, and the opening area of the valve 51 is adjusted. Thus, when the arm is operated alone, the pressure oil discharged from the hydraulic pump 50 flows into the arm actuator 55 from the first pressure compensation valve 53 on the arm side through the arm flow control valve 51 whose opening area is adjusted. In the first pressure compensating valve 53, an upstream pressure (a downstream pressure of the flow control valve) acts on one end side via a pilot pipe, and a downstream arm actuator 55 pipe on the other end side (spring side). Is acting from the pilot line via a check valve 59. For this reason, the first pressure compensating valve 53 is provided with an upstream pressure (a downstream pressure of the flow control valve).
Is adjusted to a predetermined opening area (aperture amount) by a pressure difference between the pressure and the downstream pressure (load pressure).

An operation signal corresponding to the operation amount (stroke) of the boom operation means 64 is output to the boom flow control valve 52 of the boom actuator drive circuit, and the opening area of the valve 52 is adjusted. Thus, when the boom is operated alone, the pressure oil discharged from the hydraulic pump 90 flows into the boom actuator 56 from the boom-side second pressure compensating valve 54 through the boom flow control valve 52 whose opening area is adjusted. In the second pressure compensating valve 54, an upstream pressure (a downstream pressure of the flow control valve) acts on one end through a pilot pipe, and a downstream boom actuator pipe is provided on the other end (spring side). The generated load pressure P2 acts via the pilot line. For this reason, the second pressure compensating valve 54 has an upstream pressure (flow control valve downstream pressure) and a downstream pressure (load pressure).
Is adjusted to a predetermined opening area (aperture amount) by a pressure difference between the opening and the opening.

Next, a description will be given of the operation of a combined operation for simultaneously operating the arm actuator 55 and the boom actuator 56. When simultaneously operating the arm operating means 63 and the boom operating means 64 to perform a combined operation of the arm and the boom (not shown), the pressure oil discharged from the hydraulic pump 50 passes through the respective pipelines 51a and 51b to the arm flow control valve 51 and Through the boom flow control valve 52, it flows into the arm actuator 55 and the boom actuator 56 via the respective pressure compensating valves 53 and 54. At this time, the load W applied to the arm actuator 55
1 and the load W2 applied to the boom actuator 56,
When W1 <W2, the load pressure P1 generated in the arm actuator 55 line and the load pressure P2 generated in the boom actuator 56 line are P1 <P2, and the higher load pressure P2 is transmitted through the pilot line 61. Regulator 50
a. At this time, the discharge pressure P3 of the hydraulic pump 50 is acting on the other side of the regulator 50a via the pilot line 62. Thus, the swash plate angle of the pump is controlled by the pressure difference ΔPA between the load pressure P2 and the discharge pressure P3 of the pump, and the load sensing control is performed.

Each of the pressure compensating valves 53 and 54 provided in the pressure oil supply line of the conventional arm actuator 55 and the boom actuator 56 has a pressure receiving portion which receives an upstream pressure (a downstream pressure of the flow control valve) at one end. The opening area ratio between the other end (spring side) and the pressure receiving portion that receives the downstream pressure (load pressure) is set to 1: 1. Therefore, during the combined operation of the arm actuator 55 and the boom actuator 56, as described above, when the load W1 applied to the arm actuator 55 and the load W2 applied to the boom actuator 56 satisfy W1 <W2, the arm on the low load pressure side The load pressure of the boom actuator 56 acts on the other end of the pressure compensating valve 53 provided in the pressure oil supply line of the actuator 55. As a result, the pressure compensation valve 53 of the low load pressure side arm actuator 55 receives the load pressure P2 of the high load side boom actuator 56, and the opening area is reduced. At this time, the flow supplied to the arm actuator 55 can be increased or decreased only in accordance with the opening area of the arm flow control valve 51.

In the hydraulic control device shown in FIG. 8, the pressure compensating valves 53 and 54 are used to control the maximum load pressure when the boom and the arm actuators 55 and 56 are operated in combination.
The opening amount (throttle amount) is adjusted by a balance with each upstream pressure (flow control valve downstream pressure). For example,
When the load pressure of the boom actuator 56 shown in FIG.
If kg / cm ² , the pressure compensating valve 53 on the arm actuator 55 side has an upstream pressure (downstream pressure of the flow control valve) of 100.
The opening amount is adjusted to be kg / cm ² . At this time, the upstream pressure (downstream pressure of the flow control valve) of the pressure compensating valve 54 on the boom actuator 56 side at the maximum load pressure is adjusted to 100 kg / cm ² . Therefore, since the upstream pressure of each flow control valve 51, 52 is the pump discharge pressure, the differential pressure between the upstream pressure and the downstream pressure of each flow control valve 51, 52 becomes equal in all the flow control valves 51, 52. . The flow rate Q passing through the spools of the flow control valves 51 and 52 is represented by Q = C · A · ΔP ^1/2 when the coefficient is C, the spool opening area is A, and the differential pressure across the flow control valve is ΔP. Desired. Therefore, if ΔP is constant, the flow rate passing through the spool of the flow control valve is determined only by the opening area of the spool regardless of the magnitude of the load. For example, if the opening areas of the flow rate control valve spools on the boom and arm sides are equal, the flow rates are equal even if the magnitude of the load is different. That is, the flow rate discharged from the pump is 1:
1 is distributed to the arm actuator 55 and the boom actuator 56.

Further, when the flow rate discharged from one hydraulic pump is supplied to an arm actuator and a boom actuator constituted by a parallel circuit, when the loads acting on the respective actuators are different, if the pressure is not compensated, it is light. It becomes easier for pressure oil to flow to the actuator on the load side. For this reason, if it is equally distributed to both the light load side actuator and the high load side actuator, the operation feeling of the operation lever changes greatly. Further, when a plurality of actuators are simultaneously operated and one of the actuators is relieved by a high load, the downstream pressure of the flow control valve of the lightly loaded actuator becomes the same as the relief pressure of the one of the actuators. The pressure oil hardly flows to the actuator on the load side, and much oil is discarded from the relief valve to the tank. In the hydraulic control device having such a configuration, the composite operability is poor. Therefore, in the hydraulic control device shown in FIG. 8, when the arm flow control valve 51 has the maximum opening area, the arm flow control valve 51 is supplied via the pressure compensating valve 53 whose opening area is controlled by the load pressure of the boom actuator 56 on the high load side. However, there is a problem in that the flow rate cannot supply the flow rate necessary for driving the arm actuator 55 and the speed is reduced.

In order to solve such a problem, the present applicant has filed Japanese Patent No. 2556998. The contents of this application will be described with reference to FIG. The present invention provides a plurality of operation valves 75 in a discharge path 70a of a hydraulic pump 70,
A pressure compensating valve 78 is provided in a connection circuit between each operation valve 75 and each hydraulic actuator 76, and each pressure compensating valve 78 is pushed in a large opening area direction by the pressure of the first pressure receiving portion 79, and the pressure of the second pressure receiving portion 80 is increased. Is pressed in the small opening area direction.
The operation valve outlet side pressure is supplied to the first pressure receiving portion 79 of each pressure compensating valve 78, and the highest load pressure among the load pressures of the hydraulic actuators 76 is supplied to the second pressure receiving portion 80 of each pressure compensating valve 78. In the hydraulic circuit, the pressure compensating valve 78 provided in the connection circuit of the hydraulic actuator 76 on the low load side
The pressure receiving area of the first pressure receiving portion 79 is larger than the pressure receiving area of the second pressure receiving portion 80 in FIG.

[0010]

The above-mentioned patent No. 25569
In the technique disclosed in Japanese Patent No. 98, the area ratio of the pressure compensating valve is set to a value smaller than 1 to facilitate the flow of the pressure oil to the actuator on the light load side. However, the pressure receiving area ratio of the pressure receiving portion of the pressure compensating valve is a fixed value that gives a difference between the pressure receiving area between the upstream pressure (pump pressure) and the maximum load pressure (actuator load pressure). It is not easy to tune and manufacture according to the specifications, and in construction machines such as hydraulic excavators that work under various working conditions, it is not always necessary to accurately control the shunting to the high-load side and light-load side actuators. Difficult to do.

The present invention pays attention to the above-mentioned conventional problems, and provides hydraulic oil to a plurality of actuators for driving a working machine such as a boom, an arm, and a bucket of a construction machine such as a hydraulic shovel, and a turning device for turning a vehicle body. By changing the area ratio between the pressure receiving part on one side of the pressure compensating valve and the pressure receiving part on the other side according to the operation amount (stroke) of the operating lever,
The required flow rate is also supplied to the actuator on the light load side, and the actuator is driven in accordance with the operation amount of the operating means to improve the combined operability, and the construction of the hydraulic control device is simple and easy to manufacture. It is an object to provide a hydraulic control device and a hydraulic control method thereof.

[0012]

In order to achieve the above object, a first invention of a hydraulic control device for a construction machine according to the present invention comprises a hydraulic pump, a working machine such as a boom, an arm, and a bucket. And a plurality of actuators for driving a turning device for turning the vehicle body, respective flow control valves for supplying pressure oil discharged from a hydraulic pump to the plurality of actuators, and respective operating means for controlling an opening area of each flow control valve And a pipeline between the plurality of actuators and the respective flow control valves, or a pipeline between the hydraulic pump and the respective flow control valves, and is connected to the actuator according to the highest pressure of the plurality of actuators. In a hydraulic control device for a construction machine having a pressure compensating valve for controlling a flow rate, an operation amount detection means for detecting an operation amount of the operation means, and a pressure control valve downstream pressure received at one end. A second pressure receiving part receiving the maximum load pressure of the actuator at the other end, or a first pressure receiving part receiving the hydraulic pump pressure at one end and a second pressure receiving part receiving the maximum load pressure of the actuator at the other end. A pressure compensating valve having a pressure receiving portion, and variably controlling the area ratio between the first pressure receiving portion and the second pressure receiving portion of the pressure compensating valve in accordance with the operation amount detected by the operation amount detecting means. It was done. According to the above configuration, in the case where the area ratio between the first pressure receiving portion and the second pressure receiving portion of one of the pressure compensating valves decreases (weakens the pressure compensation) as the operation amount of the operating means increases, In order to drive the actuators on the high load side and the light load side, when the operating means on the light load side is changed from the half stroke (1/2 operation amount) to the full stroke (maximum operation amount) from the state of both strokes, At the same time as the spool opening amount of the flow control valve on the load side increases, the area ratio of the pressure compensating valve further decreases, and more is applied to the actuator on the light load side as compared with the conventional one in which the area ratio is fixed. Can be diverted. Further, when the area ratio between the first pressure receiving portion and the second pressure receiving portion of the other pressure compensating valve is increased (the pressure compensation is strengthened) as the operation amount of the operating means increases, the high load side and the In order to drive the actuator on the light load side, the operating means on both sides are changed from full stroke (maximum operation amount) to half stroke (1/2 operation amount) on the high load side.
In this case, the area ratio of the pressure compensating valve on the light load side is further reduced at the same time as the spool opening amount of the flow control valve on the high load side is reduced, and the area ratio of the pressure compensating valve is fixed as in the conventional case. Can be further diverted to the actuator on the light load side.

The ratio of the pressure receiving area of the pressure compensating valve (the pressure receiving area of the highest load pressure / the pressure receiving area of the downstream pressure (pump discharge pressure) of the flow control valve) is called an area ratio of the pressure compensating valve.
Different for each actuator. For example, assuming that the area ratio of the light load side pressure compensating valve is 0.9, the downstream pressure of the light load side flow control valve is 90 kg / cm ² and the pump discharge pressure is 120 kg / cm ² .
In the case of kg / cm ^2, the differential pressure across the flow control valve spool on the light load side is ΔPA = 30 kg / cm ² . On the other hand, if the area ratio of the pressure compensating valve on the high load side is 1, the downstream pressure of the flow control valve on the high load side is 100 kg / cm ² , and if the discharge pressure of the pump is 120 kg / cm ² , The differential pressure across the flow control valve spool on the side is ΔPB = 20 kg / cm ² . Therefore, when the actuators on the high load side and the light load side are operated at the same time, the pressure oil easily flows to the actuator on the light load side. As a result, when the spool opening areas of the flow control valves on the high load side and the light load side are equal, the split ratio of the discharge amount of the hydraulic pump between the high load side actuator and the light load side actuator is C as a coefficient and A is flow control. The flow rate Q when the pressure difference between the spool opening area of the valve and the spool of the flow rate control valve is ΔP can be obtained by Q = C · A · ΔP ^1/2. When the actuator is B, A: B = CA301 ^{/ 2} : CA2
0 ^1/2 ≒ 1.2: 1. Therefore, by making the area ratio between the pressure receiving part on one side of the pressure compensating valve and the pressure receiving part on the other side variable according to the operation amount (stroke) of the operating means, the actuators on the light load side and the high load side can be used. The required flow rate can be supplied. Further, since the load can be detected at the time of operation, workability is improved, and the structure of the hydraulic control device is simple and easy to manufacture.

According to a second aspect of the present invention, there are provided a hydraulic pump, a plurality of actuators for driving a working machine such as a boom, an arm, and a bucket, and a plurality of actuators for driving a turning device for turning the vehicle body, and a plurality of actuators for supplying hydraulic oil discharged from the hydraulic pump. Each flow control valve to be supplied to the flow control valve, and each operating means for controlling an opening area of each flow control valve, a pipeline between a plurality of actuators and each flow control valve, or a hydraulic pump and each flow control In a hydraulic control device for a construction machine, the pressure control valve includes a pressure compensating valve that controls a flow rate to the actuator in accordance with the highest pressure of the plurality of actuators.
An operation amount detection means for detecting an operation amount of the operation means, a first pressure receiving portion that receives a pressure downstream of the flow control valve at one end and a second pressure receiving portion that receives the maximum load pressure of the actuator at the other end;
Alternatively, a pressure compensating valve having a first pressure receiving portion receiving the hydraulic pump pressure on one end side and a second pressure receiving portion receiving the maximum load pressure of the actuator on the other end side, and a first pressure receiving portion and a second pressure receiving portion of the pressure compensating valve. An electromagnetic control valve for variably controlling the area ratio of the pressure receiving section,
Receiving a signal from the operation amount detecting means, the operation amount is calculated by a function of a previously stored operation amount of the operation means and an area ratio of the first pressure receiving portion and the second pressure receiving portion of the pressure compensating valve. A control means for outputting a command signal to the electromagnetic control valve so as to variably control the area ratio between the first pressure receiving portion and the second pressure receiving portion of the pressure compensating valve based on the control signal is provided. According to the above configuration, the function of the operation amount (stroke) of the operation means and the ratio of the opening area of the pressure compensation valve is stored in the control means in advance. The control means outputs a command signal for varying the area ratio of the pressure compensating valve to the electromagnetic control valve based on the result of the operation based on the input operation amount signal of the operation means. If the area ratio between the first pressure receiving portion and the second pressure receiving portion of one pressure compensating valve decreases (weakens the pressure compensation) as the operation amount increases, the actuators on the high load side and the light load side When the operating means on the light load side is changed from the half stroke (1/2 operation amount) to the full stroke (maximum operation amount) to drive the spool, the spool opening of the flow control valve on the light load side is opened. At the same time as the amount increases, the area ratio of the pressure compensating valve further decreases, and more shunts to the light-load side actuator than in the conventional case where the area ratio of the pressure compensating valve is fixed. It can be. Therefore, even when a plurality of actuators such as a working machine of a construction machine are operated at the same time, a required flow rate can be supplied to the high-load side and light-load side actuators, thereby improving workability.

A third aspect of the present invention relates to a hydraulic pump, a plurality of actuators for driving a working machine such as a boom, an arm, and a bucket, and a plurality of actuators for driving a turning device for turning a vehicle body, and a plurality of actuators for supplying hydraulic oil discharged from the hydraulic pump. Each flow control valve to be supplied to the flow control valve, and each operating means for controlling an opening area of each flow control valve, a pipeline between a plurality of actuators and each flow control valve, or a hydraulic pump and each flow control In a hydraulic control device for a construction machine, the pressure control valve includes a pressure compensating valve that controls a flow rate to the actuator in accordance with the highest pressure of the plurality of actuators.
An operation amount detection means for detecting an operation amount of the operation means, a first pressure receiving portion that receives the downstream pressure of the flow control valve at one end and a second pressure receiving portion that receives the maximum load pressure of the actuator at the other end;
Alternatively, one end has a first pressure receiving portion that receives a hydraulic pump pressure, and the other end has a second pressure receiving portion that receives a maximum load pressure of an actuator, and the electromagnetic operating portion is arranged in parallel with the first pressure receiving portion. And a function of receiving a signal from the operation amount detection means and receiving a signal from the operation amount detection means, the operation amount of the operation means being stored in advance, and the area ratio between the first pressure receiving portion and the second pressure receiving portion of the pressure compensation valve. And the first of the pressure compensating valves is calculated based on the calculation result.
A control unit for outputting a command signal to the electromagnetic operation unit so as to variably control the area ratio between the pressure receiving unit and the second pressure receiving unit is provided. According to the above configuration, the function of the operation amount (stroke) of the operation means and the ratio of the opening area of the pressure compensation valve is stored in the control means in advance. This control means
A command signal for varying the area ratio of the pressure compensating valve is output to the operating section of the pressure compensating valve based on the operation result based on the input operation amount signal of the operating means. When the area ratio between the first pressure receiving portion and the second pressure receiving portion of one of the pressure compensating valves decreases (weakens the pressure compensation) as the pressure increases, the actuators on the high load side and the light load side are driven. When the operation means on the light load side is changed to the full stroke (maximum operation amount) from the state of the half stroke (1/2 operation amount), the spool opening amount of the flow control valve on the light load side is increased. Simultaneously with the increase, the area ratio of the pressure compensating valve is further reduced, so that the pressure compensating valve can be further diverted to the light-load side actuator as compared with the conventional pressure compensating valve having the fixed area ratio. Can. Therefore, even when a plurality of actuators such as working machines of a construction machine are operated at the same time, the required flow rate can be supplied to the high-load side and the light-load side actuators, so that the workability is improved and the second invention is improved. The electromagnetic control valve is not required for the hydraulic control device, and the structure is simplified.

According to a fourth aspect of the present invention, in the configuration according to any one of the first to third aspects, the operating means uses pressure oil from a pilot hydraulic pressure source with a pilot pressure corresponding to an operation amount of the operating means. Alternatively, a voltage signal of the potentiometer according to the operation amount is output. According to the above configuration, since the operating means can be of a pilot hydraulic type or an electric type, it is useful because it can be appropriately selected according to the specifications of construction machines such as small to large hydraulic excavators.

According to a fifth aspect of the present invention, there is provided a hydraulic control method for a construction machine according to the present invention, comprising a hydraulic pump, a working machine such as a boom, an arm and a bucket, and a plurality of actuators for driving a turning device for turning the vehicle body. And each flow control valve for supplying the pressure oil discharged from the hydraulic pump to the plurality of actuators, each operating means for controlling the opening area of each flow control valve, and the plurality of actuators and each flow control valve A pressure compensating valve interposed in the pipeline or the pipeline between the hydraulic pump and each flow control valve, and controlling a flow rate to the actuator according to the highest pressure of the plurality of actuators; And a hydraulic control method for a construction machine in which a required flow rate is distributed to an actuator on a light load side, wherein an operation amount detected by an operation amount detection unit that detects an operation amount of an operation unit is reduced. Accordingly, the first pressure receiving portion receiving the downstream pressure of the flow control valve and the second pressure receiving portion receiving the actuator load pressure on the downstream side thereof, or the first pressure receiving portion receiving the hydraulic pump pressure and the other end of the actuator have the highest pressure receiving portion. The area ratio of the second pressure receiving portion receiving the load pressure is variably controlled. According to the above-described hydraulic control method, the opening area ratio of the pressure compensating valve can be made variable according to the operation amount of the operating means, so that various work conditions (excavation work, leveling work, etc.) vary depending on the work site of the construction machine. Even if different, the required flow rate can be supplied to the actuators on the high load side and the light load side, and the load detection at the time of operation becomes easy, so that the workability is improved.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A hydraulic control apparatus for a construction machine and a hydraulic control method according to the present invention will be described below with reference to FIGS. First, a first embodiment of the present invention will be described with reference to FIGS. The variable displacement hydraulic pump 1 (hereinafter, referred to as the hydraulic pump 1) shown in FIG. 1 is driven by an engine (not shown). The hydraulic pump 1 is connected to an arm flow control valve 4 (hereinafter, referred to as a first flow control valve 4) via a branch pipe 3 branched from a pipe 2. The first flow control valve 4 supplies pressure oil to a position a for supplying pressure oil to the bottom chamber b of the arm actuator 10 (hereinafter, referred to as the first actuator 10), and supplies pressure oil to the head chamber a of the first actuator 10. b position. The operation unit 4 a and the operation unit 4 b of the valve 4 are connected to the control unit 40. The switching of the valve 4 is performed by an electric lever 25 (hereinafter, referred to as operation means 25), and a potentiometer 25a (hereinafter, referred to as operation amount detection means 25a) corresponds to the operation amount (operation displacement) of the operation means 25. The voltage signal is input to the control means 40.

The first flow control valve 4 is connected to a first actuator 10 via a first pressure compensating valve 5A interposed in a pipe 3a.
Is connected to the bottom chamber b. Further, the valve 4 is connected to the first actuator 10 via the line 3b through the second pressure compensating valve 5B.
Is connected to the head chamber a. The first pressure compensating valve 5A interposed in the pipe line 3a includes a first pressure receiving portion that receives the discharge pressure of the hydraulic pump 1 generated downstream of the first flow control valve 4 via a pilot conduit 3c. The same valve 5A
The pilot conduit 5b, which will be described in detail later,
And a second pressure receiving portion that receives a higher load pressure of the first actuator 10 or the second actuator 11 through the second pressure receiving portion. The second pressure compensating valve 5B interposed in the pipe 3b is
There is provided a first pressure receiving portion that receives the discharge pressure of the hydraulic pump 1 generated downstream of the first flow control valve 4 via the pilot conduit 3d. Further, the valve 5B is connected to the first actuator 10 or the other boom actuator 11 (hereinafter, referred to as a “boom actuator 11”) via a pilot conduit 5c described later in detail on the spring 5e side.
This is referred to as a second actuator 11. ) Is provided with a second pressure receiving portion for receiving a higher load pressure. The first pressure compensating valve 5
The A and the second pressure compensating valve 5B variably control the opening area ratio between the first pressure receiving portion and the second pressure receiving portion in accordance with the operation amount (stroke) of the operation means 25 described later in detail. I have.

The first pressure receiving portion of the first pressure compensating valve 5A is
It is connected to the electromagnetic control valve 12 via a pilot line 16a. The electromagnetic control valve 12 is connected to the control means 40 and is switched between a communication position a and a blocking position b. The valve 12 is connected to a pilot line 16
To the pilot hydraulic power source 14. The second
The first pressure receiving portion of the pressure compensating valve 5B is connected to the pilot line 15a.
Is connected to the solenoid-operated control valve 13. The electromagnetic control valve 13 is connected to the control means 40 and switches between a communication position a and a cutoff position b. The valve 13 is connected to a pilot hydraulic pressure source 14 via a pilot line 15.

The hydraulic pump 1 is connected to a boom flow control valve 7 (hereinafter, referred to as a second flow control valve 7) via a branch pipe 63 branched from the pipe line 2. The second flow control valve 7 has a position a for supplying pressure oil to the bottom chamber b of the second actuator 11 and a head chamber a of the second actuator 11.
B position for supplying pressure oil to the The operation unit 7 a and the operation unit 7 b of the valve 7 are connected to the control unit 40. Switching of the valve 7 is performed by an electric lever 35 (hereinafter, referred to as operating means 35) and a potentiometer 35a.
(Hereinafter, referred to as the operation amount detection means 35a.)
A voltage signal corresponding to the operation amount (operation displacement) of No. 5 is input to the control means 40.

The second flow control valve 7 is connected to a second actuator 11 via a third pressure compensating valve 8A interposed in the line 6a.
Is connected to the bottom chamber b. The valve 7 is connected to the second actuator 11 from the pipe 6b through a fourth pressure compensating valve 8B.
Is connected to the head chamber a. The third pressure compensating valve 8A interposed in the pipe line 6a includes a first pressure receiving portion that receives a discharge pressure of the hydraulic pump 1 generated downstream of the second flow control valve 7 via a pilot conduit 6c. The same valve 8A
The pilot conduit 8b, which will be described in detail later,
And a second pressure receiving portion that receives a higher load pressure of the first actuator 10 or the second actuator 11 through the second pressure receiving portion. The fourth pressure compensating valve 8B interposed in the conduit 6b is
There is provided a first pressure receiving portion that receives a discharge pressure of the hydraulic pump 1 generated downstream of the second flow control valve 7 via a pilot conduit 6d. Further, the valve 8B includes a second pressure receiving portion that receives a higher load pressure of the first actuator 10 or the second actuator 11 via a pilot conduit 8c described later in detail on the spring 8e side. The third pressure compensating valve 8A and the fourth pressure compensating valve 8B vary the opening area ratio between the first pressure receiving portion and the second pressure receiving portion in accordance with the operation amount (stroke) of the operation means 35 described later in detail. Control.

The first pressure receiving portion of the third pressure compensating valve 8A
It is connected to the electromagnetic control valve 17 via a pilot line 21a. The electromagnetic control valve 17 is connected to the control means 40 and is switched between two positions: a communication position a and a cutoff position b. The valve 17 is connected to the pilot line 21.
Is connected to the pilot hydraulic pressure source 19 via the. The fourth
The first pressure receiving portion of the pressure compensating valve 8B is connected to the pilot line 20a.
Is connected to the electromagnetic control valve 18 via the. The electromagnetic control valve 18 is connected to the control means 40 and is switched between two positions: a communication position a and a cutoff position b. The valve 18 is connected to a pilot hydraulic pressure source 19 via a pilot line 20.

The load pressure P of one of the first actuators 10
1 joins the shuttle valve 9 from the conduit 9b. The load pressure P2 of the other second actuator 11 is applied to the shuttle valve 9 from the conduit 9b. The higher of the load pressure P1 and the load pressure P2 at the shuttle valve 9 acts on one end of the regulator 1a via a conduit 9a.
The discharge pressure P3 of the hydraulic pump 1 acts on the other end of the regulator 1a via a conduit 2a. Thus, the swash plate angle of the pump is controlled by the pressure difference ΔPA between the load pressure P1 and the higher load pressure of the load pressure P2 and the discharge pressure P3 of the hydraulic pump, and the load sensing control is performed. The control means 40 transmits the command signals i1, i2, i3, i4 to the respective electromagnetic control valves 12, 13, 17 for variably controlling the area ratio of the first to fourth pressure compensating valves 5A, 5B, 8A, 8B. , 1
8 is output. As a result, the respective electromagnetic control valves 12, 13, 17, 18 are switched to the position a, and the control pressure from the pilot hydraulic pressure sources 14, 19 is applied to the first pressure receiving valves 5A, 5B, 8A, 8B. By acting on the portion, the area ratio can be variably controlled.

The function map stored in the control means 40 will be described with reference to FIG. 1 and FIGS. First, FIG. 5 shows a first function map of a lever stroke (which is an operation amount of the operation means 25 and 35 shown in FIG. 1) and an area ratio. The area ratio is an area ratio between the first pressure receiving portion and the second pressure receiving portion of each of the first to fourth pressure compensating valves 5A, 5B, 8A, 8B shown in FIG. As shown in FIG. 5, the lever stroke and the area ratio have a functional relationship shown by a line a. The area ratio between the lever stroke and the area ratio is such that when the lever stroke from the point a1 of the line a is small, the area ratio is large, and in the area from the point a1 to the point a2, the area ratio is sequentially increased as the lever stroke increases. Is designed to be smaller. After the point a2, there is a functional relationship indicated by a line substantially parallel to the right side. FIG. 5,
The lever strokes on the horizontal axis shown in FIGS. 6 and 7 are detected by the operation amount detecting means 25a and 35a (potentiometers 25a and 35a) when the operating means 25 and 35 (electric levers 25 and 35) shown in FIG. 1 are used. Is converted into a lever stroke and used.

FIG. 6 shows a second function map of the lever stroke (the operation amount of the operation means 25, 35 shown in FIG. 1) and the area ratio. As shown in FIG. 6, the lever stroke and the area ratio have a functional relationship shown by a line b.
The lever stroke and the area ratio are, as shown by the line b, when the lever stroke is small, the area ratio is large,
There is a functional relationship in which the area ratio sequentially decreases as the lever stroke increases. FIG. 7 shows a third function map of the lever stroke (the amount of operation of the operation means 25 and 35 shown in FIG. 1) and the area ratio. As shown in FIG. 7, the lever stroke and the area ratio have a functional relationship shown by a line c. The ratio between the lever stroke and the area ratio is such that when the lever stroke from the point c1 of the line c is small, the area ratio is reduced, and in the region from the point c1 to the point c2, as the lever stroke increases, the area ratio decreases. Is to be increased. After the point c2, there is a functional relationship indicated by a line substantially parallel to the right side. FIG. 5 above
Any one of the first to third function maps shown in FIG. 7 to FIG. Thus, the control means 40 variably controls the area ratio of the first to fourth pressure compensating valves 5A, 5B, 8A, 8B according to the operation amounts (strokes) of the operating means 25, 35 shown in FIG. Has become.

A second embodiment of the construction machine hydraulic control apparatus according to the present invention will be described with reference to FIG. FIG. 1 of the first embodiment.
Since the components denoted by the same reference numerals have the same functions, the description is omitted here. In the second embodiment, the first and second flow control valves 4A and 7A can be switched by a hydraulic pilot type. The operation lever 26 for switching the first flow control valve 4A is linked to a pilot valve 26a connected to a pilot hydraulic pressure source (not shown). An operating means comprising an operating lever 26 and a pilot valve 26a is provided. By operating the operating lever 26 to the F side, an operating signal (pilot pressure) is transmitted to the first flow control valve via a pilot line 27a. 4A operation unit 4
Acting on c, the valve 4A is switched to position a. By operating the operation lever 26 to the R side, the operation signal acts on the operation part 4d of the first flow control valve 4A via the pilot line 27b, and switches the valve 4A to the position b. I have. The pilot line 27
Hydraulic sensors 28a and 28b (hereinafter referred to as operation amount detecting means 28a and 28b) are connected to a and 27b, respectively. The signals from the operation amount detection means 28a and 28b are input to the control means 40. This control means 40
Outputs a command signal to each of the electromagnetic control valves 12, 13 in accordance with the operation amount of the operation means, and switches the valves 12, 13 to the position a. As a result, the control pressure from the hydraulic pressure source 14 acts on the first pressure receiving portions of the first and second pressure compensating valves 5A and 5B, and variably controls the area ratio between the first pressure receiving portion and the second pressure receiving portion. It is supposed to.

The operating lever 36 for switching the second flow control valve 7A is interlocked with a pilot valve 36a connected to a pilot hydraulic pressure source (not shown). An operating means comprising an operating lever 36 and a pilot valve 36a is provided. By operating the operating lever 36 to the F side, an operating signal (pilot pressure) is transmitted to a pilot line 37.
acting on the operating part 7c of the second flow control valve 7A through
The valve 7A is switched to the position a. Also,
By operating the operation lever 36 to the R side, the operation signal acts on the operation portion 7d of the second flow control valve 7A via the pilot line 37b, and switches the valve 7A to the position b. Oil pressure sensors 38a, 38b (hereinafter referred to as operation amount detecting means 38a, 38b) are connected to the pilot pipes 37a, 37b, respectively. The signals from the operation amount detection means 38a and 38b are input to the control means 40. The control means 40 outputs a command signal to each of the electromagnetic control valves 17 and 18 according to the operation amount of the operation means, and switches the valves 17 and 18 to the ab position.
As a result, the control pressure from the hydraulic pressure source 19 becomes the third pressure.
And the first pressure receiving portion of each of the fourth pressure compensating valves 8A and 8B, and variably controls the area ratio between the first pressure receiving portion and the second pressure receiving portion. In the second embodiment, as in the first embodiment, any one of the first to third function maps shown in FIGS. 5 to 7 is stored in the control means 40 in advance.

Next, a third embodiment of the construction machine hydraulic control apparatus according to the present invention will be described with reference to FIG. FIG.
Since the components denoted by the same reference numerals as those of the second embodiment have the same functions, the description is omitted here. The third embodiment is different from the electromagnetic control valve 12, 1 of the second embodiment.
3, 17 and 18 are abolished and the first to fourth pressure compensating valves 5
A, 5B, 8A, and 8B each have an electromagnetic operation unit 50.
d, 51d, 80d, and 81d. The upstream pressure (hydraulic pressure) is supplied to the first pressure receiving portions 50b, 51b, 80b, 81b of the first to fourth pressure compensating valves 5A, 5B, 8A, 8B via conduits 3c, 3d, 6c, 6d, respectively. Pump discharge pressure). The second pressure receiving portions 50c, 51c, 80c, 81c of the pressure compensating valves 5A, 5B, 8A, 8B are respectively connected to the first actuator 10 and the second actuator 11 via conduits 5b, 5c, 8b, 8c. The higher load pressure acts. Also in the third embodiment, the control means 40B is similar to the second embodiment of FIG.
Stores any one of the first function map to the third function map shown in FIGS. 5 to 7, and a command signal i from the control unit 40B which is calculated according to the operation amount of the operation unit.
1, i2, i3, i4 are the pressure compensating valves 50A, 51A, 80
A, 81A electromagnetic operation units 50d, 51d, 80d, 8
Output to 1d. As a result, the pressure compensating valves 50A, 51A, 80A, and 81A act on the first pressure receiving portions, and variably control the area ratio between the first pressure receiving portion and the second pressure receiving portion.

Next, a fourth embodiment of the hydraulic control device for construction machines according to the present invention will be described with reference to FIG. The components having the same reference numerals as those in the second embodiment shown in FIG. 2 have the same functions, and a description thereof will be omitted. In the fourth embodiment, as shown in FIG. 4, the control means is eliminated from the second embodiment of FIG. 2, and the operation levers 26 and 36 and the pilot valve 26 are removed.
a, 36a directly from the first and fourth pressure compensating valves 5A, 5B,
The first pressure receiving portions 8A and 8B act on the first pressure receiving portions.
Thereby, the area ratio between the first pressure receiving portion and the second pressure receiving portion of each of the pressure compensating valves 5A, 5B, 8A, 8B can be variably controlled.

According to the first to fourth embodiments of the hydraulic control apparatus for a construction machine according to the present invention described above, as the operation amount of the operating means increases, the first pressure receiving portion of one of the pressure compensating valves and the first (2) When the area ratio of the pressure receiving section is reduced (weakened the pressure compensation), both operating means are half-stroke (1/2 operation amount) to drive the actuators on the high load side and the light load side. When the operation means on the light load side is set to the full stroke (maximum operation amount) from the state of
At the same time as the spool opening of the light load side flow control valve increases, the area ratio of the pressure compensating valve further decreases. Many can be diverted. As the operation amount of this operation means increases,
When the area ratio between the first pressure receiving portion and the second pressure receiving portion of the other pressure compensating valve is increased (strengthening the pressure compensation), each operation is performed to drive the actuators on the high load side and the light load side. When the operation means on the high load side is changed to the half stroke (1/2 operation amount) from the state of the full stroke (maximum operation amount), the spool opening amount of the flow control valve on the high load side decreases and at the same time the light load side The area ratio of the pressure compensating valve is further reduced, and the flow can be further diverted to the light load side actuator as compared with the conventional pressure compensating valve in which the area ratio of the pressure compensating valve is fixed.

The ratio of the pressure receiving area of the pressure compensating valve (the pressure receiving area of the highest load pressure / the pressure receiving area of the downstream pressure (pump discharge pressure) of the flow control valve) is referred to as the area ratio of the pressure compensating valve.
Different for each actuator. For example, assuming that the area ratio of the light load side pressure compensating valve is 0.9, the downstream pressure of the light load side flow control valve is 90 kg / cm ² and the pump discharge pressure is 120 kg / cm ² .
In the case of kg / cm ^2, the differential pressure across the flow control valve spool on the light load side is ΔPA = 30 kg / cm ² . On the other hand, if the area ratio of the pressure compensating valve on the high load side is 1, the downstream pressure of the flow control valve on the high load side is 100 kg / cm ² , and if the discharge pressure of the pump is 120 kg / cm ² , The differential pressure across the flow control valve spool on the side is ΔPB = 20 kg / cm ² . Therefore, when the actuators on the high load side and the light load side are operated at the same time, the pressure oil easily flows to the actuator on the light load side. As a result, when the spool opening areas of the flow control valves on the high load side and the light load side are equal, the split ratio of the discharge amount of the hydraulic pump between the high load side actuator and the light load side actuator is C as a coefficient and A is flow control. The flow rate Q when the pressure difference between the spool opening area of the valve and the spool of the flow rate control valve is ΔP can be obtained by Q = C · A · ΔP ^1/2. When the actuator is B, A: B = CA301 ^{/ 2} : CA2
0 ^1/2 ≒ 1.2: 1. Therefore, by making the area ratio between the pressure receiving part on one side of the pressure compensating valve and the pressure receiving part on the other side variable according to the operation amount (stroke) of the operating means, the actuators on the high load side and the light load side can be used. The required flow rate can be supplied. Further, since the load can be detected at the time of operation, workability is improved, and the structure of the hydraulic control device is simple and easy to manufacture.

Further, a function of the operation amount (stroke) of the operation means and the ratio of the opening area of the pressure compensating valve is stored in the control means in advance. The control means outputs a command signal for varying the area ratio of the pressure compensating valve to the electromagnetic control valve based on the result of the operation based on the input operation amount signal of the operation means. If the area ratio between the first pressure receiving portion and the second pressure receiving portion of one of the pressure compensating valves decreases (weakens the pressure compensation) as the operation amount increases, the actuators on the high load side and the light load side When the operating means on the light load side is changed from the half stroke (1/2 operation amount) to the full stroke (maximum operation amount) to drive the spool, the spool opening of the flow control valve on the light load side is opened. At the same time as the amount increases, the area ratio of the pressure compensating valve further decreases, and more shunts to the light-load side actuator than in the conventional case where the area ratio of the pressure compensating valve is fixed. It can be.
Therefore, even when a plurality of actuators such as working machines of a construction machine are operated at the same time, the required flow rate can be supplied to the high-load side and light-load side actuators, so that the workability is improved.

Further, a function of the operation amount (stroke) of the operation means and the ratio of the opening area of the pressure compensating valve is stored in the control means in advance. The control means outputs a command signal for changing the area ratio of the pressure compensating valve to the electromagnetic operation section of the pressure compensating valve based on the result of the operation based on the input operation amount signal of the operating means. Therefore, if the area ratio between the first pressure receiving portion and the second pressure receiving portion of one of the pressure compensating valves is reduced (weakened the pressure compensation) as the operation amount of the operating means increases, the high load side and When the operating means on the light load side is changed from a half stroke (1/2 operation amount) to the full stroke (maximum operation amount) for driving the actuator on the light load side,
At the same time as the spool opening of the flow control valve on the light load side increases, the area ratio of the pressure compensating valve further decreases. To more actuators. Therefore, even when a plurality of actuators such as a working machine of a construction machine are operated at the same time, a required flow rate can be supplied to the high-load side and the light-load side actuators. No valve is required and the structure is simplified.

Furthermore, since the operating means can be a pilot hydraulic type or an electric type, it is useful because it can be appropriately selected according to the specifications of construction machines such as small to large hydraulic excavators.

The required flow rate is distributed to the high load side and light load side actuators by using the hydraulic control device of the construction machine according to any one of the first to fourth embodiments according to the present invention. According to the hydraulic pressure control method for a construction machine, the first pressure receiving portion that receives the pump pressure on the upstream side of the pressure compensating valve and the first pressure receiving portion corresponding to the operation amount detected by the operation amount detection unit that detects the operation amount of the operation unit, Since the area ratio of the second pressure receiving portion that receives the load pressure of the actuator on the downstream side is variably controlled, even if various work conditions (excavation work, leveling work, etc.) differ depending on the work site of the construction machine, the high load side and The required flow rate can be supplied to the actuator on the light load side, and the load can be easily detected at the time of operation, thereby improving workability.

The hydraulic control apparatus and the hydraulic control method for a construction machine according to the present invention have been described with respect to an actuator for driving a boom and an arm of a construction machine such as a hydraulic shovel.
Other combinations of buckets and actuators of the turning device that turns the vehicle body (for example, boom + turning)
It is needless to say that the present invention can also be applied to an industrial vehicle having a plurality of actuators other than a construction machine. In the above embodiment, the pressure compensation valve is disposed between the flow control valve and the actuator,
Although connected to the first pressure receiving portion that receives the downstream pressure of the flow control valve and the second pressure receiving portion that receives the maximum load pressure of the actuator,
A pressure compensation valve is disposed between the hydraulic pump and the flow control valve,
One end may be connected to a first pressure receiving portion receiving the hydraulic pump pressure and the other end may be connected to a second pressure receiving portion receiving the maximum load pressure of the actuator.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a first embodiment of a hydraulic control device for a construction machine according to the present invention.

FIG. 2 is a diagram illustrating a hydraulic control device for a construction machine according to a second embodiment.

FIG. 3 is a diagram illustrating a third embodiment of the hydraulic control device for the construction machine.

FIG. 4 is a diagram illustrating a fourth embodiment of the hydraulic control device for the construction machine.

FIG. 5 is a first function map stored in the control unit.

FIG. 6 is a second function map stored in the control unit.

FIG. 7 is a third function map stored in the control unit.

FIG. 8 is a diagram illustrating an example of a conventional hydraulic control device for a construction machine.

FIG. 9 is a diagram illustrating two examples of a conventional hydraulic control device for a construction machine.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Variable displacement hydraulic pump 1a Regulator 4, 4A First flow control valve 7, 7A Second flow control valve 5A, 50A First pressure compensation valve 5B, 51A Second pressure compensation valve 8A, 80A Third pressure compensation valve 8B, 81A Fourth pressure compensating valve 9 Shuttle valve 10 First actuator 11 Second actuator 12 First electromagnetic control valve 13 Second electromagnetic control valve 17 Third electromagnetic control valve 18 Fourth electromagnetic control valve 25, 35 Electric Operation levers 25a, 35a Operation amount detection means of electric operation levers 26, 36 Operation levers 28a, 28b, 38a, 38b Operation amount detection means of operation levers 40, 40A, 40B Control means 50d, 51d, 80d, 81d Electromagnetic operation Department

Claims (5)

[Claims] 1. A hydraulic pump, a plurality of working machines such as a boom, an arm, and a bucket, and a plurality of actuators for driving a turning device for turning a vehicle body, and pressure oil discharged from the hydraulic pump is supplied to the plurality of actuators. Each flow control valve, each operation means for controlling the opening area of each flow control valve, a pipe between a plurality of actuators and each flow control valve, or a pipe between a hydraulic pump and each flow control valve Road,
A pressure compensating valve for controlling the flow rate to the actuator in accordance with the highest pressure of the plurality of actuators interposed in the hydraulic control device of the construction machine, the operating means (25, 35, 26, 26a, 36, 36a), an operation amount detecting means (25a, 35a, 28a, 28b, 38a, 38b) for detecting the operation amount of the first pressure receiving portion which receives the downstream pressure of the flow control valve at one end and the maximum pressure of the actuator at the other end. A second pressure receiving portion that receives the load pressure, or a first pressure receiving portion that receives the hydraulic pump pressure at one end and a second pressure receiving portion that receives the maximum load pressure of the actuator at the other end.
Pressure compensating valve (5A, 5B, 8A, 8B, 50A, 51A, 8
0A, 81A), and corresponding to the operation amount detected by the operation amount detection means (25a, 35a, 28a, 28b, 38a, 38b), the pressure compensating valves (5A, 5B, 8A, 8B, 50A, 51
A, 80A, 81A), wherein the area ratio between the first pressure receiving portion and the second pressure receiving portion is variably controlled. 2. A hydraulic pump, a plurality of working machines such as a boom, an arm, and a bucket, and a plurality of actuators for driving a turning device for turning a vehicle body, and pressure oil discharged from the hydraulic pump is supplied to the plurality of actuators. Each flow control valve, and each operating means for controlling the opening area of each flow control valve, a pipeline between a plurality of actuators and each flow control valve, or a hydraulic pump and each flow control valve A pressure compensating valve for controlling the flow rate to the actuators in accordance with the highest pressure of the plurality of actuators interposed between the pipelines, and the operating device (25, 35, 26 , 26a, 36, 36a), an operation amount detecting means (25a, 35a, 28a, 28b, 38a, 38b) for detecting the operation amount of the first pressure receiving portion receiving the downstream pressure of the flow control valve at one end and the other end Receiving the maximum load pressure of the actuator on the side Parts, or the second receiving the maximum load pressure of the actuator to the first pressure receiving portion and the other end side for receiving the hydraulic pump pressure on one end
A pressure compensating valve (5A, 5B, 8A, 8B) having a pressure receiving portion; and an electromagnetic valve for variably controlling the area ratio between the first pressure receiving portion and the second pressure receiving portion of the pressure compensating valve (5A, 5B, 8A, 8B). In response to signals from the type control valves (12, 13, 17, 18) and the operation amount detecting means (25a, 35a, 28a, 28b, 38a, 38b), operating means (25, 35 , 26,
26a, 36,36a) and the first pressure receiving part and the second
The first pressure receiving part and the second pressure receiving part of the pressure compensating valve (5A, 5B, 8A, 8B) are calculated based on the calculation result based on the function of the area ratio of the pressure receiving part.
An electromagnetic control valve (12,
13,17,18) and a control means (40,40A) for outputting a command signal. 3. A hydraulic pump, a plurality of actuators for driving a working machine such as a boom, an arm, and a bucket, and a turning device for turning a vehicle body, and supplying hydraulic oil discharged from the hydraulic pump to the plurality of actuators. Each flow control valve, and each operating means for controlling the opening area of each flow control valve, a pipeline between a plurality of actuators and each flow control valve, or a hydraulic pump and each flow control valve A pressure compensating valve for controlling the flow rate to the actuator in accordance with the highest pressure of the plurality of actuators interposed between the pipelines, and the hydraulic control device for the construction machine, wherein the operating means (26, 26a, 36 , 36a), and a first pressure receiving section (50) which receives the downstream pressure of the flow control valve at one end.
b, 51b, 80b, 81b) and a second pressure receiving part (50c, 51c, 80c, 81c) receiving the maximum load pressure of the actuator at the other end, or a first pressure receiving part receiving the hydraulic pump pressure at one end. A second pressure receiving portion that receives the maximum load pressure of the actuator on the end side, and an electromagnetic operating portion (50d, 51d, 80d, 80d, 80b, 81b) in parallel with the first pressure receiving portion (50b, 51b, 80b, 81b). 81d) with pressure compensating valve (50
A, 51A, 80A, 81A) and the operation amount of the operation means (26, 26a, 36, 36a) stored in advance in response to a signal from the operation amount detection means (28a, 28b, 38a, 38b). And the area ratio between the first pressure receiving portion and the second pressure receiving portion of the pressure compensating valve (50A, 51A, 80A, 81A), and based on the calculation result, the pressure compensating valve (50A, 51A, 80A, 81A) is calculated. And a control means (40B) for outputting a command signal to the electromagnetic operation sections (50d, 51d, 80d, 81d) so as to variably control the area ratio between the first pressure receiving section and the second pressure receiving section. A hydraulic control device for a construction machine. 4. The hydraulic control device for a construction machine according to claim 1, wherein the operating means (25,
35, 26, 26a, 36, 36a) is to control the hydraulic oil from the pilot hydraulic pressure source with pilot pressure according to the operation amount of the operating means, or
A hydraulic control device for a construction machine, wherein a voltage signal of a potentiometer according to an operation amount is output. 5. A hydraulic pump, a plurality of actuators for driving a working machine such as a boom, an arm, and a bucket, and a turning device for turning a vehicle body, and supplying hydraulic oil discharged from the hydraulic pump to the plurality of actuators. Each flow control valve, each operation means for controlling the opening area of each flow control valve, a pipe between a plurality of actuators and each flow control valve, or a pipe between a hydraulic pump and each flow control valve Road,
And a pressure compensating valve for controlling the flow rate to the actuator in accordance with the highest pressure of the plurality of actuators, and distributing the required flow rate to the high load side and light load side actuators. In the control method, a first pressure receiving portion that receives a downstream pressure of a flow control valve and a second pressure receiving portion that receives an actuator load pressure downstream thereof correspond to an operation amount detected by an operation amount detection unit that detects an operation amount of an operation unit. 2 pressure receiving part or first receiving hydraulic pump pressure
A hydraulic control method for a construction machine, wherein an area ratio between a pressure receiving portion and a second pressure receiving portion receiving the maximum load pressure of an actuator at the other end is variably controlled.