JPH022028B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an electromagnetic proportional valve control device that controls fluid flow rate according to current, and in particular can be operated to have small and good hysteresis and stable flow characteristics. Concerning possible control device configurations.

Conventional structure and its problems Electromagnetic proportional valves are used in gas water heaters, gas heaters, gas cookers, etc. to control the amount of gas supplied to the burner in response to the temperature load to be controlled. In the case of the electromagnetic plunger sliding type valve,
When the valve body starts to move, it does not move until a force is generated that overcomes the static friction force, and when the valve body stops, it stops when the dynamic friction force and the driving force match, and there is an error that is commensurate with the friction force, and the plunger and yoke Due to hysteresis caused by residual magnetism, accurate and highly reproducible flow rate control of the proportional valve coil current cannot be performed. Conventionally, the following control device is known in order to improve the hysteresis characteristics and the like.

The control circuit in this case is shown in Fig. 1, in which the AC power source 1 is full-wave rectified by a rectifier 2, and a pulsating DC current is passed through a series circuit consisting of a coil 3 of an electromagnetic proportional valve, a transistor amplifier 4, and a resistor 5. A current is passed through the plunger to cause the plunger to vibrate in a predetermined manner.

In order to change the average value of the current flowing through the proportional valve coil 3, as shown in Figure 2, the wave height part above the set level is calculated from the maximum current value (see Figure 2 A) where full-wave rectified direct current is applied as is. The current is controlled within the range of the desired value obtained by cutting the current (see FIG. 2 B and C), and this control is performed steplessly by the current adjustment circuit 6.

In addition, there is also a type in which current is controlled by a phase control method using a thyristor.

However, with the above conventional method, there is a problem that the dither (output current waveform) effect becomes weak and it is difficult to achieve the initial purpose.This drawback is especially noticeable in the low current range, so the performance of the electromagnetic proportional valve is affected. I wasn't able to perform to my full potential.

In order to compensate for the above drawbacks, the following control device is known as another conventional example.

As shown in FIG. 3, the control circuit in this case has a configuration in which a transistor amplifier 4 and a coil 3 of an electromagnetic proportional valve are connected in series to a DC power supply 7, and a square wave signal generating circuit 8 is connected to the base terminal of the transistor amplifier 4. The square wave signal generating circuit 8, as shown in FIG. It outputs output signals with different voltage values. The reason why a resistor 5 and a diode 9 are connected in series in parallel with the electromagnetic proportional valve 3 is to absorb the surge voltage of the valve coil 3.

In the above conventional example, an intermittent square wave voltage is applied to the coil 3 of the electromagnetic proportional valve, and the voltage and current waveforms of the valve coil 3 have a sudden rise and rise as shown in FIG.
This causes irregular vibrations in the plunger and valve body of the electromagnetic proportional valve, causing the flow rate to deviate from the normal flow rate as shown in Figure 6, and become turbulent as shown in Figure 6. However, there was a problem in that so-called characteristic disturbances were likely to occur. If you try to make the rise and fall gradual under the conditions of constant period and constant amplitude as in this conventional method, the period must be made longer, and then, as in the first conventional example, a sufficient dither effect cannot be achieved. It becomes impossible to obtain it. There is also a method in which the commercial power source is rectified and a DC voltage that is not completely smoothed, leaving a pulsating component, is applied to the series circuit of the electromagnetic proportional valve's coil 3 and the transistor amplifier 4, and the pulsating component is used as a dither effect. Although this is known, the frequency of the pulsating flow is limited to 50 Hz or 60 Hz, and a sufficient dither effect cannot be obtained.

Purpose of the invention The present invention solves such conventional problems,
It is an object of the present invention to provide an electromagnetic proportional valve control device that can obtain a sufficient dither effect, is less likely to cause irregular valve vibrations, and operates so as to have stable flow characteristics with good hysteresis.

Structure of the Invention In order to achieve this object, the present invention connects a valve coil and a transistor amplifier in series to a DC power supply,
a current control circuit that varies a DC voltage level; a dither generation circuit that generates a voltage waveform with a constant period and amplitude from a low current to a high current output from the current control circuit; and the dither generation circuit and the current control circuit. The output signal of the adder circuit is connected to the base terminal of the transistor amplifier, and a capacitor is connected in parallel with the collector-emitter direction of the transistor amplifier. With this configuration, when the average current level flowing through the electromagnetic proportional valve coil is changed, the current in the valve coil changes due to the dither effect.
It acts to provide a current waveform with the most preferable constant period and amplitude and gradual rise and fall.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. In FIG. 7, a DC power supply 10 includes a coil 11 of an electromagnetic proportional valve, a transistor amplifier 12, and a resistor 13.
are connected in series, a diode 14 is connected in parallel with the valve coil 11, and a capacitor 1 is connected in parallel with the transistor 12.
5 are connected to each other, and a dither generating circuit 16 is connected to the
and the output of the current control circuit 17 are connected to be input to an adder circuit 18, and the output terminal of the adder circuit 18 is connected to the base terminal of the transistor 12.

In the above configuration, the voltage waveform generated by the dither generating circuit 16 is set to an optimal constant period constant amplitude that can reduce hysteresis for the electromagnetic proportional valve and does not cause undesirable valve vibration, and the voltage waveform of the dither generating circuit 16 is and the DC voltage signal of the current control circuit 17 are added in the adder circuit 18, and the base current waveform of the transistor 12 becomes a large average current as shown in FIG.
When I _BH , when the average current I _BL is small, and when the period
It acts so that the amplitude does not change and remains constant. At this time, the current waveform of the coil 11 of the electromagnetic proportional valve acts in a substantially trapezoidal waveform as shown in FIG. To explain the reason, first, when the base current of transistor 12 suddenly falls, it can be thought of as if the electric resistance between the collector and emitter of transistor 12 suddenly increased, and the collector current of transistor 12 suddenly decreased. Decrease. However, since the capacitor 15 is connected in parallel with the transistor 12, the capacitor 15 is charged and this charging current flows through the valve coil 11. At this time, capacitor 15
The charging current gradually decreases as the battery is charged. From the above, when the base current suddenly falls, the current in the valve coil 11 will gradually decrease. Conversely, when the base current rises, the charge stored in the capacitor 15 is discharged via the transistor 12, so that the valve coil 1
The current of 1 will increase as the capacitor discharge current decreases, and will increase gradually. Therefore, the current in the coil 11 of the electromagnetic proportional valve changes in a substantially trapezoidal waveform as shown in FIG. The effect is that stable proportional flow characteristics with small hysteresis can be obtained.

Effects of the Invention As described above, the electromagnetic proportional valve control device of the present invention provides the following effects.

(1) The signals from the dither generation circuit that generates a waveform with a constant period and amplitude and the current control circuit are added by an adder circuit, and the result is input to the transistor base terminal, and a capacitor is connected in parallel with the transistor. The current in the valve coil acts in a roughly trapezoidal waveform with gradual rises and falls.
Since no undesirable valve vibration is induced while exhibiting an effective dither effect, the electromagnetic proportional valve can be operated with small and good hysteresis and stable flow characteristics.

(2) Since the dither signal from the dither generation circuit and the DC signal from the current control circuit are added together and input to the transistor base terminal connected in series with the valve coil, the dither waveform, period, and amplitude can be set arbitrarily and optimally. It can be set to various types of solenoid proportional valves. Moving parts of electromagnetic proportional valves
Depending on the shape and weight of the valve body, etc., the conditions for the waveform, period, and amplitude that can best exhibit the dither effect are often different, and the same is true for the conditions that cause undesirable valve vibration. According to this, it is possible to operate them under optimal conditions.

(3) Since the method operates with a dither waveform with a constant periodic amplitude from low current to high current,
No matter where the operating position and flow rate position of the electromagnetic proportional valve are, a certain optimum dither effect can always be obtained, and stable characteristics can always be obtained.

[Brief explanation of drawings]

Fig. 1 is a basic circuit diagram showing an example of a conventional electromagnetic proportional valve control device, Fig. 2 A to C are current waveform diagrams of the valve coil by the device shown in Fig. 1, and Fig. 3 is a basic circuit diagram showing an example of a conventional electromagnetic proportional valve control device. A basic circuit diagram showing an example of a proportional valve control device, Figures 4(d) to 4(f) are output waveform diagrams of the square wave generation circuit of the device shown in FIG. 3, and FIG. 5 is a diagram of the valve coil of the device shown in FIG. Voltage/current waveform diagram, Fig. 6 is a flow rate characteristic diagram of the electromagnetic proportional valve according to the device shown in Fig. 3, Fig. 7 is a basic circuit diagram showing an embodiment of the electromagnetic proportional valve control device of the present invention, Fig. 8 is a transistor base current waveform diagram of the device shown in FIG. 7, and FIG. 9 is a valve coil current waveform diagram of the device shown in FIG. 10...DC power supply, 11...Valve coil, 12...
...Transistor amplifier, 15...Capacitor, 1
6... dither generation circuit, 17... current control circuit,
18...Addition circuit.

Claims (1)

[Claims] 1. A valve coil and a transistor amplifier are connected in series to a DC power supply, and a current control circuit that varies the DC voltage level, and the output of the current control circuit generates a voltage waveform with a constant period and amplitude from low current to high current. and an adder circuit that adds signals from the dither generator and current control circuit, the output signal of the adder being connected to the base terminal of the transistor amplifier, and the collector of the transistor amplifier being connected to the base terminal of the transistor amplifier. - An electromagnetic proportional valve control device consisting of a capacitor connected in parallel with the emitter direction.