JPH0517401B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electromagnetic proportional control valve that causes dither oscillation.

For electromagnetic proportional control valves that linearly control the valve opening in response to the excitation current to the electromagnetic solenoid, a dither signal may be combined with the control signal to cause slight vibrations in order to reduce operating hysteresis. In this case, the dither oscillation is continued even in the neutral position to ensure a stable neutral position even when the amount of lapping is small.

However, if the plunger of this proportional control valve has a seal such as an O-ring, such as one in which a portion of the plunger protrudes outward from the valve housing, the vibration of the plunger associated with dither oscillation may cause long-term During use, the sealing O-ring wore out, causing oil leakage.

The present invention has been made with attention to such problems, and in an electromagnetic proportional control valve to which dither oscillation is added, the reliability of the control valve is improved by preventing wear of the seals fitted to the spool and plunger. The purpose is to increase durability.

In order to achieve such an objective, the present invention
A plunger or spool is provided that is directly or indirectly displaced in any direction from a neutral position based on the driving force of an electromagnetic proportional solenoid, and the amount of displacement of the plunger or spool from the neutral position is controlled proportionally in accordance with the solenoid excitation current. A dither oscillation circuit that supplies a dither signal to be synthesized with the control current of the electromagnetic proportional solenoid, and a dither oscillation circuit that supplies this oscillation signal to the neutral of the plunger or spool. Equipped with a switch circuit that shuts off at certain positions.

Based on the above configuration, dither oscillation can prevent hysteresis during normal operation, while dither oscillation is cut off at the neutral position of the plunger or spool, reducing seal wear on the plunger or spool caused by dither vibration, improving its durability and Improved reliability.

Embodiments of the present invention will be described below based on the drawings.

FIG. 1 shows a specific structure of an electromagnetic proportional control valve to which the present invention is applied. Pressure chambers 26 and 27 inside a double-acting cylinder 25 partitioned by a double-acting piston 24 contain pilot hydraulic pressure. supply passage 28,
Pilot hydraulic pressure is introduced through orifices 29, 30, etc.

And the outlets 26a, 2 of each pressure chamber 26, 27
The cross-sectional area of 7a is the electromagnetic proportional solenoid 17, 18
It can be freely increased or decreased by poppets 17a and 18a that interlock with each other.

For example, when a current flows through the electromagnetic proportional solenoid 17 and the poppet 17a moves downward, the cross-sectional area of the outlet 26a becomes relatively smaller than that of the outlet 27a, creating a pressure difference between the pressure chambers 26 and 27.

As a result, the double-acting piston 24 moves rightward and stops at a position where this moving force and the elastic force of the spring 31 are balanced.

The amount of movement at this time, that is, the amount of stroke of the double-acting piston 24 increases in proportion to the current flowing through the electromagnetic proportional solenoid 17.

Conversely, when current flows through the electromagnetic proportional solenoid 18 and the poppet 18a moves downward, the double-acting piston 2
4 moves to the left.

In this way, the double-acting piston 24 moves left and right with a stroke amount that corresponds to the current flowing through the electromagnetic proportional solenoids 17 and 18.

By the way, high-pressure hydraulic oil flows from the pump P according to the displacement of the spool 32, bypassing the hydraulic cylinder and passing through the passage 33, passage 41, and passage 42 to the tank T.
The quantitative proportion of the amount that returns to the hydraulic cylinder via passage 43 - passage 43' - supply port A and returns to tank T from return port B via passage 35 - passage 42 is regulated. .

This spool 32 is adapted to be displaced in accordance with the movement of a plunger 36 that moves integrally with the above-mentioned double-acting piston 24.

Specifically, the taper portion 36a of the plunger 36
As a result, a variable orifice 34a is formed in the middle of the passage 43 and the passage 43', and the pressure before and after this variable orifice 34a is applied to the branch passages 34b and 34.
Pressure chambers 32 on both end faces of the spool 32 via c
For example, when the plunger 36 moves to the left from the state shown in this figure and the differential pressure across the orifice 34a increases, the spool 32
is displaced to the right against the spring 37, and as a result, the flow rate of hydraulic oil to the hydraulic cylinder via the passage 34 is throttled by the variable orifice 44, and at the same time the passage 3
The amount of bypass from 3 is increased by the variable orifice 45.

As a result of the operation of the electromagnetic proportional control valve 19 as described above, for example, the flow rate of hydraulic oil from the A port to the hydraulic cylinder increases or decreases depending on the current flowing to the electromagnetic proportional solenoid 17, and conversely, the current flowing to the electromagnetic proportional solenoid 18 increases or decreases. The flow rate of hydraulic oil decreases accordingly.

The control current supplied to the electromagnetic proportional solenoids 17 and 18 is controlled by the control circuit shown in FIG.

In FIG. 2, 1 and 2 are sliding resistors connected to a control lever (not shown), 3 and 4 are amplifier circuits, and 17 and 18 are electromagnetic proportional solenoids installed in the electromagnetic proportional control valve of FIG.

The sliding resistors 1 and 2 are connected to the control lever so as to exhibit resistance changes independently of each other. For example, when the control lever is tilted to the right from the neutral position, the amplifying circuit 4 causes the sliding resistance to change depending on the tilting angle of the control lever. Only the current to the electromagnetic proportional solenoid 17 increases gradually from zero. FIG. 3 shows this in terms of the relationship between the tilt angle of the control lever and the voltage at point A in FIG. In the circuit shown in FIG. 2, the voltage at point A increases in the negative direction.

Conversely, when tilting to the left from the neutral position, only the current flowing to the electromagnetic proportional solenoid 18 gradually increases from zero.

Since the amplifier circuits 3 and 4 are constructed in the same way, only the amplifier circuit 4 will be shown in detail in the drawings and will be specifically explained.

The sliding terminal voltage signal A of the sliding resistor 2, which changes proportionally according to the tilting angle of the control lever, is amplified by the amplifier 5 and transistors 6 and 7, and then supplied to the electromagnetic proportional solenoid 17 as a current signal. Ru.

In this embodiment, after the tilt angle of the control lever reaches a predetermined value, the comparator 8 adjusts the sliding resistance based on the magnitude relationship between the sliding terminal voltage signal A and the predetermined reference voltage signal B. In addition to the input voltage from the electromagnetic proportional solenoid 17, a predetermined additional voltage is supplied to the amplifier 5, and the output current to the electromagnetic proportional solenoid 17 is forcibly added and corrected by a predetermined current (see Fig. 5). .

After the neutral dead zone of the plunger 36 is exceeded, the rate of change of the current supplied to the electromagnetic proportional solenoid 17 is adjusted to adjust the amplification factor so that the plunger 36 strokes at an appropriate rate relative to the tilting of the control lever. It is set to a predetermined value by variable resistor VR-1.

In addition, if it is necessary to provide a dead band width for the control lever in order to prevent valve operation due to inadvertent contact, etc., by increasing or decreasing the value of reference voltage signal B via variable resistor VR-2, It is possible to freely adjust its width.

Furthermore, if the neutral dead zone of the spool 32 with respect to the stroke of the plunger 36 is large, the additional voltage can be correspondingly increased by the variable resistor VR-3 to further increase the additional current to the electromagnetic proportional solenoid 17. Bye.

In this way, the control current is amplified according to the tilt angle of the control lever, but at the same time, dither oscillation is added to this control current, so
A dither signal C from a dither oscillation circuit 10 is input to an amplifier 5 via an analog switch 11.

Here, analog switch 11 is comparator 1
2 constitutes the switch circuit of the present invention, that is, the analog switch 11 is turned on and off by the output of the comparator 12, and the comparator 12 is connected to the sliding resistor 2 connected to the control lever.
The analog switch 11 is turned on by outputting a high level signal only when the output of the analog switch 11 is above a predetermined level (see FIG. 4).

In other words, when the control lever is in the neutral position, the comparator 12 is switched to low level and the analog switch 11 is turned off.

FIG. 6 is a current characteristic diagram showing the relationship between the current value finally supplied to the electromagnetic proportional solenoid 17 or 18 by the above circuit, the tilt angle of the control lever, and the relationship between the area where the dither oscillation signal is cut off. It is.

Based on the above configuration, when the control lever is in the neutral position, the oscillation signal from the dither oscillation circuit 10 is not combined with the output of the sliding resistor 2, and therefore the dither oscillation is superimposed on the electromagnetic solenoid control current to be amplified. do not.

As a result, when the electromagnetic proportional control valve 19 is in the neutral position, the plunger 3 is
6 does not cause minute vibrations hydraulically, and therefore, the sealing material such as the O-ring 40 fitted to the part of the plunger 36 that protrudes from the housing 39 to the outside is not subject to minute vibrations and is therefore less likely to wear out. It can be prevented.

On the other hand, when the control lever is switched in either direction, the analog switch 11 is turned on when the set value of the comparator 12 is exceeded based on the output of the sliding resistor 1 or 2.

As a result, the oscillation signal of the dither oscillation circuit 10 is input to the amplifier 5 together with the outputs of the sliding resistors 2 and 1, and this combined input is amplified.

As a result, the control currents of the electromagnetic proportional solenoids 17 and 18 increase or decrease according to the tilt angle of the control lever while oscillating with minute amplitude, and based on this, the double-acting piston 24 and furthermore the plunger 36 hydraulically vibrate slightly. This prevents the sticking phenomenon and avoids hysteresis in operation.

Note that the present invention is not limited to the electromagnetic proportional control valve of the illustrated embodiment, but can be applied to any type having a seal such as an O-ring fitted to the spool or plunger (therefore, a part of the spool or plunger protrudes outside the valve housing). (type that can be manually switched), it can be applied to any type of equipment.

As described above, according to the present invention, the dither oscillation is stopped at the control valve neutral position (the position where the spool and plunger are controlled to the neutral position), which is generally frequently used. At the same time, it is possible to improve the durability and reliability of the control valve by reducing the wear caused by minute vibrations of the seals fitted to the spool and plunger.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a control valve showing an embodiment of the present invention;
FIG. 2 is a circuit diagram of the control circuit. Third
The figure is a voltage characteristic diagram showing the relationship between the tilt angle of the control lever and the voltage at point A in figure 2. Figure 4 is a voltage characteristic diagram showing the relationship between the tilt angle of the control lever and the voltage at point A in figure 2. A control characteristic diagram showing the prohibited area, Figure 5 is a voltage characteristic diagram showing the relationship between the additional voltage set by VR-2 in Figure 2 and the voltage at point A, and Figure 6 is a diagram showing the control lever angle and the final result. FIG. 3 is a current characteristic diagram showing the relationship between the current value outputted to the electromagnetic proportional solenoid and the area where the dither oscillation signal is cut off. 1, 2...Sliding resistance, 3, 4...Amplification circuit, 5
...Amplifier, 8...Comparator, 10...Dither oscillation circuit, 11...Analog switch, 12
... Comparator, 17, 18 ... Electromagnetic proportional solenoid, 24 ... Double-acting piston, 32 ... Spool, 36 ... Plunger.

Claims (1)

[Claims] 1. A plunger or spool that is directly or indirectly displaced in any direction from a neutral position based on the driving force of an electromagnetic proportional solenoid, and proportionally controls the amount of displacement of the plunger or spool from the neutral position in accordance with the solenoid excitation current. In this electromagnetic proportional control valve, the valve opening is linearly controlled by a dither oscillation circuit that supplies a dither signal to be synthesized with the control current of the electromagnetic proportional solenoid, and a dither oscillation circuit that supplies this oscillation signal to the neutral position of the plunger or spool. An electromagnetic proportional control valve characterized by being equipped with a switch circuit that shuts off at