JP2903909B2 - Construction machine control circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a control circuit called negative control (hereinafter referred to as "negative control") in a hydraulic circuit of a construction machine such as a power shovel.

[0002]

2. Description of the Related Art FIG. 2 shows a conventionally known general negative control circuit. When the negative displacement control of the variable displacement hydraulic pump 1 is performed, the direction switching valve 3 that controls the movement of the actuator 2
Has a passage called a center bypass through which the discharge oil from the pump 1 passes when in a neutral state. Aperture 5
Is provided.

When the negative control pressure is led to a regulator section 7 having characteristics as shown in FIG. 3 through a negative control signal line 6, the pump flow rate is small during operation neutral (standby flow rate) and the actuator 2 is operated. When the directional control valve 3 is operated to supply a part of the pump flow rate to the actuator 2, the flow rate passing through the center bypass 4 decreases, and the negative control pressure generated in the negative control throttle 5 also decreases. The pump flow rate increases according to the characteristics shown in (1). In this way, the required pump flow is obtained during operation,
When neutral, the pump flow is reduced to save energy.

[0004] As shown in FIG. 2, when a plurality of actuators 2 and 2 'are driven by a plurality of hydraulic pumps 1 and 1', for example, A For the hydraulic system that drives the actuator 2 on the side, the secondary pressure of the operating hydraulic pilot valve 8 is provided downstream of the direction switching valve 3 ′ of the center bypass 4 ′ of the B-side hydraulic system and upstream of the negative control throttle 5 ′. A throttle valve 9 'having a characteristic as shown in FIG. 4 which operates at Pi is provided, and A is supplied through a check valve 10 from upstream of the throttle valve 9'.
A bypass passage 12 communicating with the pressure oil supply line 11 of the side direction switching valve 3 is provided so that the pump flow rate of the plurality of hydraulic pumps 1 and 1 'can be supplied. In order to improve the operation speed of the B-side actuator 2 ', the configuration is similarly reversed.

If the pump discharge pressure until the pump flow rate is supplied to the actuator is P, the standby flow rate is Q, and the center bypass opening area of the directional control valve (or throttle valve) is A, P, A and Q There is the following relationship between P∝Q ² / A ²

Here, in order to supply a pump flow rate to the actuator, the pump discharge pressure must be higher than the load pressure. That is, since the center bypass opening area A decreases in accordance with the operation amount while the standby flow rate Q is kept constant (in an inverse proportional relationship), it is necessary to set the pump discharge pressure higher than the load pressure as compared with the low load pressure. At high load pressures, the amount of operation must be increased. That is, the point at which the actuator starts to move with respect to the operation amount is different depending on the magnitude of the load pressure, and there is a problem that the operation feeling is adversely affected.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems, and to minimize the change in operability caused by the load pressure of an actuator in a negative control circuit. It is intended to improve operability.

[0008]

SUMMARY OF THE INVENTION The present invention provides a means for solving the above-mentioned problems. In order to drive a plurality of actuators 2 and 2 'by a plurality of hydraulic pumps 1 and 1', a direction switching is performed. Negative control throttles 5 and 5 'are provided at the most downstream of the center bypass passages 4 and 4' of the valves 3 and 3 ', and the regulators 7 and 6 are connected via negative control signal lines 6 and 6'.
A pressure sensor for detecting a negative control pressure in a hydraulic circuit in which throttle valves 9, 9 'controlled by pilot pressures of hydraulic pilot valves 8, 8' are inserted into the center bypass passages 4, 4 'while controlling 7'. 5a, 5a '
And pressure sensors 2a and 2a 'for detecting the load pressures of the actuators 2 and 2', respectively.
3 ′ to control the secondary pressure of the electromagnetic proportional pressure reducing valves 13, 13 ′ through the shuttle valves 14, 14 ′.
A gist is a control circuit for a construction machine, which is connected to a 9 'pilot line.

[0009]

According to the present invention, the electromagnetic proportional pressure-reducing valves 13, 2 'are detected by the pressure sensors 2a, 2a' for detecting the load pressure of the actuators 2, 2 'via the controller 12.
13 ′, and controls the secondary pressures of the electromagnetic proportional pressure reducing valves 13 and 13 ′ via the shuttle valves 14 and 14 ′.
By connecting to the pilot line 9 ', the opening area of the center bypass passage can be changed according to the change of the load pressure. For example, the pump discharge pressure is set to P _L + α with respect to the load pressure P _L. As described above, since the required pump discharge pressure can be obtained by controlling the opening area of the center bypass passage, the movement start point of the actuators 2 and 2 'is determined by the load pressure with respect to the operation amount of the directional control valves 3 and 3'. The problem that a difference is made depending on the size is eliminated.

After the actuators 2, 2 'have started to move, the pressure sensors 5a, 5a' sense a decrease in the negative control pressure with an increase in the operation amount, and actuate the electromagnetic proportional pressure reducing valves 13, 13 'according to the degree. If the opening areas of the throttle valves 9 and 9 'are increased via this, the influence of the throttle valves 9 and 9' is reduced, and the subsequent operation feeling is the same as in the past.

[0011]

FIG. 1 is a circuit diagram showing an embodiment of the present invention. The same parts as those of the conventional example shown in FIG. 2 are denoted by the same reference numerals, and the description thereof will be omitted. The new parts will be described.
5a 'is a pressure sensor for detecting a negative control pressure,
The input side is connected to the center bypass passages 4 and 4 ′ in front of the negative control diaphragms 5 and 5 ′, and the output side is connected to the controller 12.

Reference numerals 2a and 2a 'denote pressure sensors for detecting the load pressure of the actuators 2 and 2', the input side of which is connected to the load-side operating hydraulic line of the actuators 2 and 2 ', and the output side of which is a controller 12a. It is connected to the.

Reference numeral 12 denotes a controller, the input side of which is connected to the pressure sensors 5a, 5a 'and 2a, 2a', and the output side of which is connected to electromagnetic proportional pressure reducing valves 13, 13 '. The controller 12 controls the electromagnetic proportional pressure reducing valves 13 and 13 ′ based on the electric signals from the two pressure sensors.
Is controlled.

The primary side of the electromagnetic proportional pressure reducing valves 13 and 13 'is connected to a pilot hydraulic pump, and the secondary side is a shuttle valve 1
4, 14 'through the center bypass passage 4,
It is connected to the pilot circuit of the throttle valves 9, 9 'inserted in 4'.

The operation of this embodiment will be described. For example, when the cylinder of the actuator 2 on the A side in FIG. 1 is extended against the load W, the pump 2 is operated in the neutral state of the directional control valves 3 and 3 '. the discharge flow rate of 2 'are both standby flow Q _S by the negative control control.

Here, the pressure sensor 2a and the controller 1
The controller 12 controls the discharge pressure P of the pump 1 with respect to the load pressure P _L on the A side input to the controller 2 via the electromagnetic proportional pressure reducing valve 13 based on the equation (1) so that P = P _L + α. by controlling the opening area a _i of the throttle valve 9, a minimum discharge pressure of the pump 1 the a side is compensated as P _L + alpha. _{A i = Q S / √ (} P L + α) ‥‥‥ (1)

The same applies to the case where the cylinder of the actuator 2 'on the B side is extended. Also, when the actuators 2 and 2' on both sides A and B are simultaneously operated, A and B
The opening areas of both throttle valves 9, 9 'may be controlled by simultaneously operating the electromagnetic proportional pressure reducing valves 13, 13' on both sides.

As described above, when starting up from the operation neutral state, the discharge pressure P of the pumps 1 and 1 'can be increased by the load pressure P _L. Therefore, the starting point of the actuator with respect to the operation amount differs depending on the magnitude of the load pressure. The problem that appears is eliminated.

Here, after the actuators 2, 2 'start moving, a decrease in the negative control pressure accompanying an increase in the operation amount is sensed by the pressure sensors 5a, 5a', and only the A side or A, B is detected depending on the degree. Electromagnetic proportional pressure reducing valve on both sides 13, 13 '
If the opening areas of the throttle valves 9, 9 'are increased through the above, the influence of the throttle valves 9, 9' is reduced, and the subsequent operation feeling is the same as in the past. The electromagnetic proportional pressure reducing valve 1
Hydraulic pilot valve 8, 8 '2 from the secondary pressure of 3, 13'
It goes without saying that if the next pressure increases, the opening areas of the throttle valves 9, 9 'are controlled by the latter.

[0020]

According to the present invention, the electromagnetic pressure is reduced via the controller 12 by the detection values of the pressure sensors 5a, 5a 'for detecting the negative control pressure and the pressure sensors 2a, 2a' for detecting the load pressure of the actuators 2, 2 '. Valve 13, 13 '
And the secondary pressure of the electromagnetic proportional pressure reducing valves 13 and 13 'is connected to the pilot lines of the throttle valves 9 and 9' via the shuttle valves 14 and 14 '. Therefore, the opening area of the center bypass passage is controlled so that the pump discharge pressure becomes P _L + α with respect to the load pressure P _L , for example, and the required area can be changed. Since the pump discharge pressure can be obtained, it is possible to solve the problem that the movement start point of the actuators 2 and 2 'differs depending on the magnitude of the load pressure with respect to the operation amount of the directional control valves 3 and 3'. The operability change caused by the load pressure of the actuator can be minimized, and the operability of the construction machine can be improved.

[Brief description of the drawings]

FIG. 1 is a hydraulic circuit diagram according to the present invention.

FIG. 2 is a circuit diagram of a conventional example.

FIG. 3 is a characteristic diagram showing a relationship between a negative control pressure and a pump discharge amount.

FIG. 4 is a relationship diagram between pilot valve secondary pressure and throttle valve opening area.

[Explanation of symbols]

 1, 1 'Variable displacement pump 2, 2' Actuator 2a, 2a 'Pressure sensor 3, 3' Directional switching valve 4, 4 'Center bypass passage 5, 5' Negative control throttle 5a, 5a 'Pressure sensor 6, 6' Negative control Signal line 7, 7 'Regulator 8, 8' Hydraulic pilot valve 9, 9 'Throttle valve 10, 10' Check valve 11, 11 'Pressure oil supply line 12 Controller 13, 13' Electromagnetic proportional pressure reducing valve 14, 14 'Shuttle valve

Claims (2)

(57) [Claims] A direction switching valve for driving a plurality of actuators (2, 2 ') by a plurality of hydraulic pumps (1.1').
A negative control throttle (5, 5 ') is provided at the most downstream of the center bypass passage (4, 4') of (3, 3 '), and a regulator (7, 7') is provided via a negative control signal line (6, 6 '). And a throttle valve controlled by the pilot pressure of the hydraulic pilot valve (8, 8 ')
In the hydraulic circuit in which (9, 9 ') is inserted into the center bypass passage (4, 4'), a pressure sensor (2a, 2a ') for detecting the load pressure of the actuator (2, 2') is provided. Sensor (2a, 2
a ') controls the electromagnetic proportional pressure reducing valve (13, 13') via the controller (12) by the detected value, and the electromagnetic proportional pressure reducing valve (13, 13 ')
The secondary pressure of the throttle valve via the shuttle valve (14, 14 ')
A control circuit for a construction machine, wherein the control circuit is connected to a pilot line (9, 9 '). 2. A directional control valve for driving a plurality of actuators (2, 2 ') by a plurality of hydraulic pumps (1.1').
A negative control throttle (5, 5 ') is provided at the most downstream of the center bypass passage (4, 4') of (3, 3 '), and a regulator (7, 7') is provided via a negative control signal line (6, 6 '). And a throttle valve controlled by the pilot pressure of the hydraulic pilot valve (8, 8 ')
In the hydraulic circuit in which (9, 9 ') is inserted into the center bypass passage (4, 4'), a pressure sensor (5
a, 5a ') and a pressure sensor (2a, 2a') that detects the load pressure of the actuator (2, 2 '), and the controller (2a, 2a' and 5a, 5a ') detects the load pressure of both controllers. 12) to control the electromagnetic proportional pressure reducing valve (13, 13 '), the electromagnetic proportional pressure reducing valve (1
A control circuit for a construction machine, wherein the secondary pressure of (3, 13 ') is connected to a pilot line of the throttle valve (9, 9') via a shuttle valve (14, 14 ').