JPH037801B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to pressure control in a hydraulic circuit, and more particularly to a pressure control method capable of controlling the pressure to be varied in multiple stages using an electromagnetic proportional pressure control valve with a quick response.

Conventionally, control to change pressure in multiple stages using an electromagnetic proportional pressure control valve is based on a pressure change switching signal.
The amount of electricity (current value) input to the electromagnetic proportional pressure control valve is changed, thereby moving the spool inside the pressure control valve to the position required for predetermined pressure control.

Therefore, it takes time from when the pressure change control signal is issued until the pressure change is completed.
In the case of changing the pressure up to MAX, a time of 50 to 300 msec was required, depending on the size of the pressure control valve. Therefore, when it is necessary to increase the response speed in control of changing pressure in multiple stages, a servo valve is used instead of an electromagnetic proportional pressure control valve. However, servo valves have the disadvantage of high cost.

The present invention eliminates such drawbacks, and its purpose is to provide a multi-stage pressure control method for a hydraulic circuit that is low in cost and has a high response speed. Using an electromagnetic proportional pressure control valve, while one control valve A is controlling pressure, the amount of electricity input to the other control valve B is changed to the amount of electricity required for the next stage of pressure control, and the inside of control valve B is changed. By providing a pressure control method that eliminates the drawback of slow response by switching the pressure control circuit from the control valve A circuit to the control valve B circuit using an electromagnetic directional control valve after the time for completion of spool movement. be.

Next, referring to FIGS. 1 and 2, one embodiment of the present invention is shown in FIG. 2, P ₁₁₁ , P ₂₂₁ , P ₁₁₂ , P ₂₂₂ .
An example of a hydraulic control circuit that performs multistage pressure control in eight stages of P _11n and P _22o will be explained.

A pump 101 pressurizes the oil in the tank 102 and sends it to the actuator 103. 104 is a relief valve provided on the discharge side of the pump 101. A pair of electromagnetic proportional pressure control valves (hereinafter referred to as electromagnetic relief valves) 106 and 107 are provided in the vent circuit 104A of the relief valve 104 via an electromagnetic directional control valve 105. Either one of the pair of electromagnetic relief valves 106 and 107 controls the pressure of the vent circuit 104A. The electromagnetic relief valves 106 and 107 are connected to the second pressure setting devices 114 and 115, respectively.
Pressures P ₁₁₁ , P ₁₁₂ , P ₁₁₃ , P _11n as shown in FIG. 2 and P ₂₂₁ , P ₂₂₂ , P ₂₂₃ as shown in FIG.
P _22o , the electromagnetic relief valves 106 and 107 are alternately switched by switching the electromagnetic directional control valve 105, and the actuator 103 is operated as shown in FIG.
Pressures P ₁₁₁ , P ₂₂₁ , P ₁₁₂ , P ₂₂₂ ,... as shown in
It is designed to perform pressure control in 8 stages of P _11n and P _{22o ,} and as shown in FIG. It's about to start.

The time Δt ₁₀₁ is a time that takes into consideration the travel time of the spool of the electromagnetic relief valve 106, and at the same time as the timeout signal, the electromagnetic directional control valve 10
5, that is, at the same time as the pressure program shown in FIG. 2 is started, the first set pressure P ₁₁₁ set in the program is set, and as shown in FIG. 107 is also activated in advance for the next switching so that the second set pressure P ₂₂₁ of the pressure program shown in FIG. The same process is performed after the third set pressure _P112 , and each time the electromagnetic directional control valve 105 is switched, when the - side of the pair of electromagnetic relief valves 106, 107 is selected, the other side is also selected in advance. When switching, the valve is operated at a predetermined pressure to avoid a delay in the response of the electromagnetic relief valve.

Since the multi-stage pressure control method of the present invention is configured as described above, when the electromagnetic directional switching valve 105 is switched and any electromagnetic relief valve is selected, the pressure of the valve has already been changed to the specified pressure.
The switching time of the electromagnetic directional control valve 105 is usually about 20 m.
sec, a much faster response speed can be obtained compared to the conventional method of adjusting the amount of electricity of an electromagnetic relief valve.

In the above-mentioned embodiment, the set pressure of each electromagnetic relief valve is set to 4 stages, and an 8-stage pressure program is used, but of course, the pressure program is not limited to this, and any number of multi-stage pressure control is possible.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an embodiment of the present invention. FIG. 2 is an explanatory diagram showing the pressure control situation in the embodiment shown in FIG. 104... Relief valve, 104A... Vent circuit, 105... Solenoid directional control valve, 106, 107
...Electromagnetic proportional pressure control valve, 111...Signal switch B, 112...Signal switch C, 113...Signal switch D, 114, 115...Pressure setting device.

Claims (1)

[Claims] 1. A relief valve that controls the pressure of the hydraulic circuit, a pair of electromagnetic proportional pressure control valves that control the pressure of the vent circuit of the relief valve, and a pressure of the vent circuit of the relief valve that controls the pressure of the vent circuit of the relief valve. an electromagnetic directional control valve for controlling each of the two, a pressure setting device in which a large number of pressure values are set for controlling each of the pair of electromagnetic proportional pressure control valves in a multi-stage program, and settings set in the pressure setting device. A signal switch C and D connected to each solenoid of the pair of electromagnetic proportional pressure control valves, and a set value switching signal for performing desired pressure program control. After receiving the
A pressure control device of a hydraulic circuit consisting of a signal switch B that alternately switches the switch signals C and D causes the - of the pair of electromagnetic proportional pressure control valves to be switched on at a predetermined time before the start of the desired pressure program control.
side is operated at a predetermined pressure, and after the elapse of the predetermined time, the program control is started at the predetermined pressure of the - side electromagnetic proportional pressure control valve, and when switching the set pressure after starting the pressure program control, - A multi-stage pressure control method characterized in that when an electromagnetic proportional pressure control valve on one side is selected, the electromagnetic proportional pressure control valve on the other side is simultaneously operated in advance at the next set pressure value.