JPS6131343B2 - - Google Patents

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention eliminates the fluid sticking phenomenon that often occurs when the spool of a control valve is in the neutral position or offset position, and provides an electric/hydraulic system with excellent reliability and responsiveness. The present invention relates to the configuration of a conversion device.

(Prior art) Many spool-type electric/hydraulic proportional control valves have a non-energized state as their normal state, and in this state, for example, the spool neutral position or offset position, they are affected by the pressure of the hydraulic circuit. It is often observed that a fluid sticking phenomenon occurs.

In this type of proportional control valve, it is necessary to control the solenoid from a de-energized neutral position state where the current value is 0 to a stepless variable opening degree by energizing. Fluid sticking phenomena occur most frequently in the position state, and fluid phenomena also naturally occur when the valve is fixed at an offset position other than the neutral position, so it is necessary to eliminate such fluid sticking phenomena. Without it, there was a problem that not only smooth startup but also good proportional control could not be performed.

Normally, as a means to solve the problem of the fluid sticking phenomenon described above, it has been widely practiced to apply a dither wave to the applied current. A typical example is a device in which a pulsating direct current is passed through a circuit consisting of a solenoid and a transistor amplifier in series, and the current is controlled while slightly vibrating a spool valve.

In this case, in order to change the average value of the current, current control is performed using an arbitrary current value in the shape of a truncated pulsating flow, which is obtained by cutting off the wave height portion above the set level from the maximum current value to which the pulsating flow is applied as is. Normally, this control is performed steplessly.

(Problem to be Solved by the Invention) However, with this method, in the low current range where the valve opening is small, the peak value of the pulsating flow is low, so the dither effect is weakened, and the dither effect is weakened, making it impossible to achieve the intended purpose. There was a problem in that it was difficult to achieve this, and the control performance of the electromagnetic proportional valve was not fully demonstrated.

Furthermore, since the conventional method only exerts a dither effect when electricity is applied, it is impossible to eliminate the fluid sticking phenomenon at the neutral position mentioned above, so it is necessary to control the valve opening to a small degree from this neutral position. In this case, the problem was that control could not be performed because the operating force to overcome this fluid sticking force (static friction) could not be obtained.

In view of this fact, the present invention has invented a new device that can reliably eliminate the fluid sticking phenomenon that occurs not only at the offset position but also at the neutral position, thereby achieving reliable startup and high control responsiveness. It is an attempt to achieve a purpose.

(Means for Solving the Problems) As is clear from the subsequent explanation of the embodiments, the present invention includes a sawtooth wave generation circuit 5 that generates a sawtooth wave signal, and a sawtooth wave generation circuit 5 that adjusts the level of the signal. The setting input S to be obtained and the sawtooth wave outputted by the sawtooth wave generation circuit 5 are converted into a square wave with a high peak value and constant.
a switching circuit 6 that controls the on/off time ratio of the square wave according to the level of the square wave; an output amplifier circuit 3 that amplifies the power of the square wave output from the switching circuit 6; an electro-hydraulic conversion device comprising a solenoid 1 of a spool-type electro-hydraulic proportional control valve to which an output is applied, and a comparator 7 which operates upon receiving the setting input S and generates a pulse signal when energization starts; The comparator 7 operates in response to the pulse signal, and generates an impulse having a higher peak value than the sawtooth wave signal generated by the sawtooth wave generation circuit 5.
This configuration includes an impulse generating circuit 8 that generates impulses only once and outputs them to the switching circuit 6.

(Function) The present invention having such a configuration supplies the solenoid with an impulse sufficient to impact the spool, which is difficult to move due to the fluid sticking phenomenon, at the start of energization, thereby causing the valve body to move due to the influence of the pressure of the hydraulic circuit. Furthermore, it is possible to eliminate the fluid sticking phenomenon by providing a strong dither effect even at an offset position in a low current range where the valve opening is small.

(Example) Hereinafter, an example of the present invention will be described in detail based on the accompanying drawings.

FIG. 1 is a block diagram showing the main parts of the electric circuit related to the electro-hydraulic converter of the present invention. 1 is a solenoid of an electro-hydraulic proportional control valve (hereinafter referred to as a proportional valve); It is connected to the constant voltage DC power supply 2 through the power supply 2, and is supplied with a pulsed DC voltage whose pulse width can be controlled and which has a predetermined frequency and is transformed from a smoothed DC voltage.

In this way, by applying a pulsed DC voltage to the solenoid 1, the proportional valve can be controlled to exhibit a dither effect.

The output amplifier circuit 3 has a transistor as an element, and the output side of the transistor is connected in series with the solenoid 1, and this series circuit is connected to the DC constant voltage power supply 2. A dither oscillation circuit 4, a comparator 7 and an impulse generation circuit 8 are connected to the input setting line connected to
A signal processing device is disposed with the main component as the main component.

The dither oscillation circuit 4 consists of a sawtooth wave generation circuit 5 and a switching circuit 6. The dither oscillation circuit 4 converts the sawtooth wave of a constant frequency generated in the sawtooth wave generation circuit 5 into a wave having a high peak value and a constant square shape by the operation of the switching circuit 6. After converting the square wave into a wave, this square wave is applied to the output amplification circuit 3, and the on/off time ratio of the switching circuit 6 is changed to large or small by adjusting the setting input S that can adjust the signal level. The width is controlled and the average current value flowing through the solenoid 1 is controlled steplessly from approximately 0 to the maximum value, with the peak value of the square wave being kept constant at a high state.

On the other hand, the comparator 7 and the impulse generation circuit 8
What is the transmission terminal of setting input S and switching circuit 6?
A series circuit is formed and interposed between the input terminal of the comparator 7 and the input terminal of the comparator 7. The functions of both circuits 7 and 8 will be explained below. On the other hand, the impulse generating circuit 8 operates in response to the pulse output signal of the comparator 7 and generates a pulse signal compared to the sawtooth wave signal generated by the sawtooth wave generating circuit 5. An impulse with a high wave height value is generated only once,
It operates to provide the impulse to the output amplification circuit 3 via the switching circuit 6 in a priority state that can substantially nullify the output of the sawtooth signal.

With the above circuit configuration, when the solenoid 1 enters the control state from the non-energized normal state, only one impulse is applied to the solenoid 1 to apply sufficient driving force to the spool. becomes possible.

The energization state at this time is a solid line current diagram in FIG. 2, which is clearly different from the conventional energization state (broken line) in which no impulse is applied.

The strength of the impulse, that is, the energy determined by the maximum peak value (Io) and time (to) may be set in advance at an optimal value depending on the shape and dimensions of the spool.

For example, Io is the maximum rated current value for the proportional valve,
to should be selected to be approximately 0.02 seconds.

Furthermore, if there is a dead zone (all port block) when the valve is in the neutral position, it is only necessary to change Io and to appropriately according to the valve response time and the amount of overlap.
In either case, it is necessary to produce an impulse effect that retains enough energy to prevent overshoot from occurring in the valve output amount.

Thus, fluid sticking phenomena when initiating valve control are eliminated by applying an impulse to the solenoid.

(Effects of the Invention) As is clear from the above, the present invention has the following advantages:
In an electric/hydraulic conversion device that operates a spool-type electric/hydraulic proportional control valve that is prone to fluid sticking, an impulse that has an amount of energy that does not cause an overshoot in the output hydraulic pressure of the proportional control valve at the start of energization. Since this occurs only once and is applied to the solenoid 1, it is possible to reliably eliminate the fluid sticking phenomenon that has the greatest effect when the valve is stationary, and it has excellent accuracy and responsiveness in the entire control range. It is possible to provide an electric/hydraulic conversion device.

Further, the present invention can eliminate the fluid sticking phenomenon at the offset position, and can fully exhibit the dither effect by providing a pulsating flow with a high wave height value even in a region where the valve opening is small.

Thus, the present invention provides better electrical and
A hydraulic conversion device can be obtained, which is extremely useful in simplifying the pressure control circuit and improving accuracy.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a main part of an electric circuit according to an example of the device of the present invention, and FIG. 2 is a current-time characteristic diagram comparing the characteristics of the device of the present invention with a conventional device. 1... Solenoid, 3... Output amplification circuit, 5...
...Sawtooth wave generation circuit, 6...Switching circuit, 7...Comparator, 8...Impulse generation circuit, S...Setting input.

Claims (1)

[Claims] 1 A sawtooth wave generation circuit 5 that generates a sawtooth wave signal, a setting input S that can adjust the level of the signal, and a circuit that receives the sawtooth wave signal and the setting input S so that the peak value is high and constant. A switching circuit 6 that converts and outputs a square wave whose on/off time ratio is controlled in magnitude depending on the level of the setting input S, and an output amplification circuit 3 that amplifies the power of the square wave outputted by the switching circuit 6. , and a solenoid 1 of a spool type electric/hydraulic proportional control valve to which the output of the output amplification circuit 3 is applied, and is activated when the setting input S is received and the energization is started. A comparator 7 generates a pulse signal, and the comparator 7 operates in response to the pulse signal to generate an impulse having a higher peak value than the sawtooth wave signal generated by the sawtooth wave generation circuit 5 only once. , and an impulse circuit 8 that outputs an output to the switching circuit 6.