JP2546242Y2 - Hydraulic circuit of construction machinery - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic circuit of a construction machine, and more particularly to a hydraulic circuit of a construction machine provided with a negative regulator to limit a maximum flow rate of a variable displacement pump.

[0002]

2. Description of the Related Art FIG. 3 shows a hydraulic circuit of a conventional construction machine of this type. The pressure oil discharged from the variable displacement pump 1 is sent to each actuator (not shown) by the direction switching valves 2, 2,... When the direction switching valves 2, 2,.
A part of the oil passes through the center bypass line 3 and returns to the tank 5 through the throttle valve 4, and the remaining pressure oil is led out from the pilot line 6 to the negative regulator 7.

When the negative regulator 7 is operated, the maximum flow rate of the variable displacement pump 1 is limited, and when the directional control valves 2, 2,... Are in the neutral position, the discharge amount of the variable displacement pump 1 is minimized. If the directional control valves 2, 2,... Are operated to operate the actuator, the pressure applied to the negative regulator 7 from the center bypass line 3 through the pilot line 6 decreases, and the flow rate of the variable displacement pump 1 is restricted. Is released, and the discharge amount increases.

[0004]

The hydraulic circuit of the above-mentioned conventional construction machine is provided with a negative regulator 7, and when the directional control valves 2, 2,... Are in the neutral position, the flow rate is restricted to reduce energy consumption. When the actuator is actuated, the operation of the negative regulator 7 is stopped, and the discharge amount of the variable displacement pump 1 is increased. However, when the actuator is operated, the direction switching valves 2, 2
Are rapidly operated, the pressure oil flowing from the bypass line 3 to the pilot line 6 decreases, the operation of the negative regulator 7 stops suddenly, and the discharge amount of the variable displacement pump 1 sharply increases. Therefore, there is a defect that the driving pressure to the actuator also changes suddenly, and the construction machine main body shakes and a shock to an operator becomes large.

[0005] Therefore, when an actuator of a construction machine having a negative regulator in a hydraulic circuit is suddenly operated, there arises a technical problem to be solved in order to reduce the shaking of the body and the shock to the operator.
The purpose of the present invention is to solve this problem.

[0006]

DISCLOSURE OF THE INVENTION The present invention has been proposed to achieve the above object, and is a variable displacement pump.
An actuator and an actuator from the variable displacement pump.
Direction switching valve that switches the direction of pressure oil sent to the heater
If, by controlling the discharge flow rate of the variable capacitance pump, when the direction switching valve of the activator <br/> Yueta the neutral position, and a negative regulator for limiting the maximum flow rate by bypassing the discharge pressure of the variable displacement pump in a hydraulic circuit for a construction machine comprising providing a sensor for detecting the discharge pressure of the variable displacement pump to a downstream position of the direction switching valve is provided, and, actuates a negative regulator by the secondary pressure of the electromagnetic proportional pressure reducing valves A hydraulic circuit for a construction machine, comprising: a control device that changes a secondary pressure of an electromagnetic proportional pressure reducing valve based on a detection value of the sensor to generate a time difference in a response of a negative regulator. is there.

[0007]

According to the present invention, a sensor provided at a position downstream of the direction switching valve detects a discharge pressure of a variable displacement pump passing through a center bypass line, and the detected value is transmitted to a control device by an electric signal.
Output as The controller changes the secondary pressure of the electromagnetic proportional pressure reducing valve based on the detection value of this sensor. Therefore,
When the directional control valve is suddenly operated from the neutral position, the output value of the sensor changes abruptly. The discharge amount of the variable displacement pump is returned to the original state, and the vibration to the construction machine and the shock to the operator are reduced.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below in detail with reference to FIGS. Note that, for convenience of explanation, the same components as those in the related art will be described at the same time. FIG. 1 shows a hydraulic circuit of a construction machine. Pressure oil discharged from a variable displacement pump 11 is sent to each actuator (not shown) by a directional control valve 12, 12,. And buckets and the like. When the direction switching valves 12, 12,... Are in the illustrated neutral position, the pressure oil discharged from the variable displacement pump 11 passes through the throttle valve 14 through the center bypass line 13, and returns to the tank 15.

The pressure oil passing through the center bypass line 13 is increased by a throttle valve 14, and the oil pressure is detected by a sensor 16. That is, when the actuators are operating, the pressure flowing from the direction switching valves 12, 12,... To the center bypass line 13 decreases, and when the actuators stop and the direction switching valves 12, 12,. The pressure flowing into the center bypass line 13 increases. The pressure of the bypass line 13 detected by the sensor 16 is sent to the control device 17 as an electric signal.

Here, reference numeral 18 denotes an electromagnetic proportional pressure reducing valve. When a solenoid 19 is energized, a spool of the electromagnetic proportional pressure reducing valve 18 moves, and pressure oil flows from a hydraulic source 20 to a pilot line 21. At this time, the secondary pressure of the electromagnetic proportional pressure reducing valve 18 is reduced and flows into the pilot line 21. Then, the negative pressure of the negative regulator 2 is controlled by the secondary pressure of the electromagnetic proportional pressure reducing valve 18 flowing into the pilot line 21.
2 to limit the maximum flow rate of the variable displacement pump 11.

When the detected value of the sensor 16 becomes a certain value or more, that is, when the directional control valves 12, 12,... Reach the neutral position, a constant voltage is applied from the control device 17 to the solenoid 19. Then, the spool of the electromagnetic proportional pressure reducing valve 18 switches, and the secondary pressure flows into the pilot line 21. In such a case, the negative regulator 22 operates to limit the discharge amount of the variable displacement pump 11 to a minimum. Therefore, energy consumption when the actuator is not operating can be reduced.

On the other hand, when the direction switching valves 12, 12,... Are switched to operate the actuator, the hydraulic pressure in the center bypass line 13 decreases, and the detection value of the sensor 16 becomes equal to or less than a predetermined pressure. At that time, the control device 17 stops energizing the solenoid 19 of the electromagnetic proportional pressure reducing valve 18, the spool of the electromagnetic proportional pressure reducing valve 18 returns to the original position, and the pressure oil of the pilot line 21 returns to the tank 15.

Here, the operator operates the directional control valve 12,1.
When the switching operation of 2... Is performed rapidly, the detection value of the sensor 16 rapidly decreases as shown in FIG.
However, if the power supply from the control device 17 to the solenoid 19 is not stopped instantaneously but is stopped after a time lag, the return of the pressure oil in the pilot line 21 to the tank 15 is delayed, and as shown in FIG. , the secondary pressure of the electromagnetic proportional pressure reducing valve 18 is reduced with a delay time t _1. Accordingly, occurs a time difference in the response of the negative regulator 22, the hydraulic pressure of the pressure fluid starts to flow to the actuator is suppressed to a minimum, the discharge pressure of the variable displacement pump 11 is normal state after a lapse of time t _1. That is, when the actuator is suddenly activated, a time difference occurs in the response, and the vibration of the body of the construction machine and the shock of the operator are reduced.

[0014] Further, the operator operates the directional control valves 12, 12 ...
When the switching operation is rapidly performed, if the energizing voltage from the control device 17 to the solenoid 19 is gradually reduced, the pressure oil in the pilot line 21 gradually returns to the tank 15, and as shown in FIG. , the secondary pressure of the electromagnetic proportional pressure reducing valve 18 is reduced gradually during the time t _2. Accordingly, it occurs a time difference in the response of the negative regulator 22, the hydraulic pressure of the pressure fluid starts to flow through the actuator gradually increases from the minimum oil pressure, the discharge pressure of the variable displacement pump 11 is returned to its normal state after a lapse of time t _2. That is, when the actuator is suddenly activated, the actuator is gradually activated, so that the vibration of the body of the construction machine and the shock of the operator are reduced.

According to the characteristics of the actuator,
The hydraulic circuit of the construction machine is controlled by selectively using or combining the above two types of control of the electromagnetic proportional pressure reducing valve. still,
The present invention can be variously modified without departing from the spirit of the present invention, and it goes without saying that the present invention extends to the modified one.

[0016]

According to the present invention, as described in detail in the above-described embodiment, the sensor provided at the downstream position of the directional control valve is located at the center.
Check the discharge pressure of the variable displacement pump passing through the bypass line.
And outputs the detected value to the control device as an electric signal.
The control device changes the secondary pressure of the electromagnetic proportional pressure reducing valve based on the detection value of this sensor . Therefore, the directional control valve is neutral.
When suddenly operating from the position, the sensor output
To varying, second solenoid proportional pressure reducing valve by the control device
Change the secondary pressure to allow time for negative regulator response
Difference occurs and the actuator can be driven to some extent.
Return the displacement of the variable displacement pump to its original state.

[0017] Depending on, suddenly the construction machine of the actuator
Even if the start operation is performed at the
The pressure oil pressure does not rise rapidly, but
Since a normal hydraulic state is reached, the vibration of the construction machine and the shock to the operator can be reduced. Furthermore,
When the actuator of the construction machine is not used, the flow rate of the variable displacement pump can be limited to reduce energy consumption.

[Brief description of the drawings]

FIG. 1 is a hydraulic circuit diagram of a construction machine according to an embodiment of the present invention.

2A is a graph showing a relationship between a change in a detection value of a sensor and time, and FIGS. 2B and 2C are graphs showing a relationship between a change in a secondary pressure of an electromagnetic proportional pressure reducing valve and time.

FIG. 3 is a hydraulic circuit diagram of a conventional construction machine.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Variable displacement pump 12 Directional switching valve 16 Sensor 17 Control device 18 Electromagnetic proportional pressure reducing valve 22 Negative regulator

Claims (1)

(57) [Scope of request for utility model registration] 1. A variable displacement pump, an actuator,
Pressure oil sent from the variable displacement pump to the actuator
Direction switching valve for switching the direction of
Controlling the discharge flow rate, when the direction switching valve is in the neutral position of the actuator, in the hydraulic circuit for a construction machine comprising providing a negative regulator for limiting the maximum flow rate by bypassing the discharge pressure of the variable displacement pump, A sensor for detecting the discharge pressure of the variable displacement pump is provided at a position downstream of the direction switching valve, and a negative regulator is operated by the secondary pressure of the electromagnetic proportional pressure reducing valve, and the electromagnetic proportional pressure reducing valve is operated based on the detection value of the sensor. A hydraulic circuit for a construction machine, comprising: a control device that changes the secondary pressure of the negative pressure to generate a time difference in response of the negative regulator.