JPH04258508A - Hydraulic driving device for construction machine - Google Patents

Abstract

PURPOSE:To enable supply of respective required flow rates to a plurality of flow rate control valves 4 regardless of the magnitude of inlet pressures (load pressure) of a plurality of actuators 5 and to correct the total of the required flow rates so that it accords with the maximum discharge flow rate when the total of the required flow rates exceeds the maximum flow rate in a hydraulic circuit for driving a construction machine such as a power shovel. CONSTITUTION:The magnitude of inlet pressures of actuators 5a and 5b is judged by a control device 8 so that an opening area of a flow rate control valve on the larger side becomes maximum, and a pump discharge pressure is calculated by the opening area of the flow rate control valve on the large inlet pressure side and a required flow rate, while the opening area of the flow rate control valve on the smaller inlet pressure side is calculated by the discharge pressure of the pump and the required flow rate. A control command is generated according to the results and when the total of the required flow rates exceeds the maximum flow rate of the pump, correction is made so that the total of the required flow rates becomes the maximum discharge flow rate of the pump.

Description

Description: FIELD OF INDUSTRIAL APPLICATION This invention relates to a hydraulic drive system for construction machinery such as an excavator. 2. Description of the Related Art FIG. 9 shows an example of a circuit of a conventionally known general hydraulic drive device. This hydraulic drive device consists of an engine 1, a variable displacement hydraulic pump 2 driven by the engine 1, a regulator 3 that controls the displacement volume or tilt angle of the variable displacement hydraulic pump 2, and a variable displacement hydraulic pump 2. an actuator 5a driven by pressure oil;
5b, and the actuator 5a from the variable displacement hydraulic pump 2.
, 5b, the flow rate control valves 4a, 4 control the pressure oil supplied to the
b, operating levers 7a and 7b that command the drive of the regulator 3 of the variable displacement hydraulic pump 2 and the actuators 5a and 5b, and a control device 6 that controls the drive of the regulator 3 and the flow rate control valves 4a and 4b. is provided. In this hydraulic drive device, a variable displacement hydraulic pump 2 is operated by the drive of an engine 1, and an operating lever 7a is operated.
, 7b, pressure oil discharged from the variable displacement hydraulic pump 2 is supplied to the actuators 5a, 5b. The regulator 3 is a positive control system that controls the discharge amount of the variable displacement hydraulic pump 2 based on commands from the operating levers 7a and 7b. The relationship between the operating lever stroke and pump discharge amount in the hydraulic drive system shown in FIG. 9 is shown in FIG. 10 (a).
), and the relationship between the operating lever stroke and the flow rate to the actuator is shown in FIG. 10(b). As can be seen from the characteristic lines in FIG. 10, the flow rate discharged from the variable displacement hydraulic pump 2 in response to commands from the operating levers 7a and 7b, and the flow rate supplied to the actuators 5a and 5b from the flow rate control valves 4a and 4b. are the same, and excellent operability can be obtained when operated alone. However, when operating an actuator with a large load and an actuator with a small load at the same time,
There is a problem in that a large amount of flow flows to the actuator with a small load, and a small amount flows to the actuator with a large load. In addition, when the discharge amount of the pump is insufficient for the required flow rate of the operating lever due to multiple operations, etc., the metering area, which is the area that controls the actuator, becomes narrow (s in Figure 10), resulting in poor operability. There is also the problem that fine manipulation becomes difficult. [0007] The present invention has been made with the aim of solving the above problems, and includes:
The required flow rate is supplied to each of the plurality of flow control valves 4a, 4b regardless of the magnitude of the inlet pressure (load pressure) of the actuators 5a, 5b, and the total required flow rate exceeds the maximum discharge amount of the pump. In this case, the purpose is to correct the total required flow rate to match the maximum discharge amount, thereby lowering the flow rate supplied to the actuator relative to the operation lever stroke, and ensuring a metering area. Means for Solving the Problems: A variable displacement hydraulic pump 2 driven by an engine 1, a regulator 3 that controls the tilt angle of the variable displacement hydraulic pump 2, and a pressure output from the variable displacement hydraulic pump 2. A plurality of actuators 5a, 5b driven by oil, a plurality of flow control valves 4a, 4b that control the pressure oil supplied from the variable displacement hydraulic pump 2 to the actuators 5a, 5b, and the drive of the regulator 3 and the actuator 5a. , 5b, the electromagnetic valve 9a controls the stroke of the flow control valves 4a, 4b.
, 9b, 9c, 9d, and pressure sensors 10a, 10b, 10c, which detect the inlet pressure of the actuators 5a, 5b.
10d, and control levers 7a, 7 on the input side.
b and pressure sensors 10a, 10b, 10c, and 10d are connected to it, and a control device 8 is connected to the output side of the drive unit of the electromagnetic valves 9a, 9b, 9c, and 9d, and the drive unit of the regulator 3, respectively. The device 8 is the actuator 5
The opening area of the flow control valve on the larger side is maximized by determining the magnitude of the inlet pressures a and 5b, and the pump discharge pressure is calculated from the opening area of the flow control valve on the larger inlet pressure side and the required flow rate, and the pump Calculate the opening area of the flow control valve on the side where the inlet pressure is smaller than the discharge pressure and the required flow rate, issue a control command according to the result, and if the total required flow rate exceeds the maximum discharge rate of the pump, the required flow rate The present invention is characterized by comprising means for distributing the pump maximum discharge amount according to the ratio of each required flow rate so that the sum of the pump discharge amounts becomes the pump maximum discharge amount. Embodiment FIG. 1 shows a control circuit according to an embodiment of the present invention. Components that are the same as those in the conventional example shown in FIG. 9 are designated by the same reference numerals, and description thereof will be omitted. Variable displacement hydraulic pump 2 driven by engine 1, flow rate control valves 4a, 4b, operating levers 7a, 7
Regarding b, it is the same as the conventional example shown in FIG.
d, pressure sensors 10a, 10b, 10c, and 10d that detect the inlet pressures of the actuators 5a and 5b, and a hydraulic pump 11 that serves as a drive source for the flow rate control valves 4a and 4b. The control device 8 has memory, arithmetic and logical judgment functions, and includes a setting means, a calculation means, a judgment means and an output means. Levers 7a, 7b and pressure sensor 10a
, 10b, 10c, and 10d are connected, and on the output side, the drive part of the solenoid valves 9a, 9b, 9c, and 9d, and the regulator 3 are connected.
drive parts are connected to each other. The setting means of the control device 8 is "the relationship between the operating lever stroke θ and the electric signal Eθ" (FIG. 2).
, "Relationship between the operating lever electrical signal Eθ and the required flow rate Q of the flow rate control valve" (Fig. 3), "The electrical signal E to the regulator
P and the pump discharge amount QP" (FIG. 4) and "the relationship between the opening area A of the flow rate control valve and the electrical signal EC to the solenoid valve" (FIG. 5). Similarly, the calculating means includes a means for calculating the total required flow rate of the flow rate control valve, and a means for calculating the pump discharge pressure from the inlet pressure from the pressure sensor and the required flow rate of the flow rate control valve (larger inlet pressure side). ``Means for calculating the opening area of the flow control valve from the pump discharge pressure and required flow rate (lower inlet pressure side)'' and ``If the total required flow rate exceeds the maximum discharge flow rate of the variable displacement pump, "means for performing a correction calculation so that the sum of the required flow rates becomes the pump maximum discharge flow rate." Similarly, the determining means includes ``a means for determining the magnitude of the inlet pressure of the actuator'' and ``a means for determining the magnitude of the total required flow rate and the maximum discharge flow rate of the pump.'' The output means includes an "output section that outputs an electrical signal EP to the regulator" and an "output section that outputs an electrical signal EC to the solenoid valve." [Operation] Referring to the control flow shown in FIG.
To explain the operation of the operation levers 7a and 7b, first
operating strokes θ1, θ2 and actuator 5
Read the inlet pressures P1 and P2 of the flow control valves 4a and 5b, calculate the total Q of the required flow rates Q1 and Q2 of the flow control valves 4a and 4b, and compare it with the maximum discharge amount QPmax of the variable displacement hydraulic pump 2 to determine its magnitude. . As a result, when the total required flow rate Q is less than or equal to the pump maximum discharge rate QPmax, the pump discharge rate QP is made to match the total required flow rate Q. (QP = Q) 00
18] Also, the total required flow rate Q is the pump maximum discharge amount QP
When it exceeds max, the pump maximum discharge rate QPm is adjusted so that the total required flow rate Q becomes the pump maximum discharge rate QPmax.
ax is corrected and distributed according to the ratio of each required flow rate. Q1'=Q1 ×QPmax/Q Q2'=Q2 ×QPmax/Q (Q
=Q1 +Q2)QP =Q1'+Q2'=QPmax
1. When the inlet pressure of the actuator is P1 > P2 (2) Set the opening area A1 of the P1 side flow control valve 4a to the maximum opening area A1max. ■ P1 side required flow rate Q1 (or corrected Q1') and inlet pressure P1
The pump discharge pressure is calculated from Equation 1 shown in FIG. 8 from A1max and A1max. P=(Q1/C/A1max)2・r/2g+P1
Or P=(Q1'/C/A1max)2・r/2
g+P1 ■ From the pump discharge pressure P, the P2 side required flow rate Q2 (or corrected Q2'), and the inlet pressure P2, calculate the P2 side opening area A2 using Equation 2 shown in FIG. [0020] The pump discharge amount QP is the total required flow rate Q(
or the corrected total required flow rate i.e. QPmax)
An electrical signal EP is output to the regulator 3 so that. (See Figure 4) [0021] The electric signal EC to the solenoid valve is on the P1 side:
EC1max...See FIG. 5(a) P2 side: EC2 corresponding to the opening area A2...See FIG. 5(b) is output. 2. The inlet pressure of the actuator is P1 <
In the case of P2, the suffixes (1) and (2) are exchanged and the procedure is the same as above. [0023] According to the present invention, the variable displacement hydraulic pump 2
discharges the total required flow rate of the plurality of flow rate control valves 4a, 4b, and each required flow rate is supplied to the plurality of flow rate control valves regardless of the magnitude of the inlet pressure (load pressure) of the actuators 5a, 5b. Composite operability is improved. Furthermore, if the total required flow rate exceeds the maximum discharge rate of the pump, the total required flow rate is corrected to match the maximum discharge rate, so the flow rate supplied to the actuator in response to the operation lever stroke decreases. , metering area can be secured. (See Figures 6 and 7)

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of an embodiment of the present invention.

FIG. 2 is a diagram showing the relationship between the operating lever stroke θ and the electric signal Eθ.

[Figure 3] Electrical signal E corresponding to operating lever stroke θ
FIG. 3 is a diagram showing the relationship between θ and the required flow rate Q of the flow rate control valve.

FIG. 4 is a diagram showing the relationship between the electric signal EP to the regulator and the pump discharge amount QP.

FIG. 5 is a diagram showing the relationship between the opening area A of the flow control valve and the electric signal EC to the electromagnetic valve.

FIG. 6 is a diagram showing the relationship between the operating lever stroke θ1 and the flow rate flowing into the actuator.

FIG. 7 is a diagram showing the relationship between the operating lever stroke θ2 and the flow rate flowing into the actuator.

FIG. 8 is a flowchart showing a calculation processing procedure.

FIG. 9 is a circuit diagram of a conventional example.

FIG. 10 is a diagram showing the relationship (a) between the operating lever stroke and pump discharge amount and the relationship (b) between the flow rate to the actuator in a conventional example.

[Explanation of symbols]

1 Engine 2 Variable displacement hydraulic pump 3 Regulator 4a, 4b Flow rate control valve 5a, 5b Actuator 6 Control device (conventional example) 7a, 7b Operation lever 8 Control device 9a, 9b, 9c, 9d Solenoid valve 10a, 10b, 10c, 10d Pressure sensor 11
Hydraulic pump θ Operation lever stroke A Opening area of the flow control valve Eθ Electric signal EC to the control device Electric signal EP to the solenoid valve Electric signal QP to the regulator Pump discharge amount Q Requested flow rate of the flow control valve

Claims (1)

[Claims] Claim 1: A variable displacement hydraulic pump (2) driven by an engine (1), a regulator (3) for controlling the tilt angle of the variable displacement hydraulic pump (2), and a variable displacement hydraulic pump (2). a plurality of actuators (5a, 5b) driven by pressure oil from the variable displacement hydraulic pump (2);
b) a plurality of flow control valves (
4a, 4b) and an operating lever (7a, 7b) for instructing the drive of the regulator (3) and the actuator (5a, 5b). It is equipped with a solenoid valve (9a, 9b, 9c, 9d) that controls the stroke, a pressure sensor (10a, 10b, 10c, 10d) that detects the inlet pressure of the actuator (5a, 5b), and an operating lever on the input side. (7a, 7b) and pressure sensors (10a, 10b, 10c, 10d) are connected, and the drive part of the solenoid valve (9a, 9b, 9c, 9d) and the drive part of the regulator (3) are connected to the output side, respectively. a control device (8);
determines the magnitude of the inlet pressure of the actuator (5a, 5b), maximizes the opening area of the flow control valve on the larger side, and determines the pump discharge pressure from the opening area of the flow control valve on the larger inlet pressure side and the required flow rate. calculate the opening area of the flow control valve on the side where the inlet pressure is lower than the pump discharge pressure and the required flow rate, issue a control command according to the results, and if the sum of the required flow rates exceeds the maximum discharge amount of the pump A hydraulic drive device for construction machinery, comprising means for distributing the maximum discharge amount of the pump according to the ratio of each required flow rate so that the sum of the required flow rates becomes the maximum discharge amount of the pump.