JPH0510549B2 - - 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. The present invention relates to a possible configuration of an electromagnetic proportional valve control device.

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.
It is required to change the flow rate proportionally to the change in current. However, in the electromagnetic plunger sliding type valve, frictional force is generated in the sliding part of the plunger, so a so-called dead zone occurs in which the flow rate does not change due to static frictional force even if the current is changed, and furthermore, hysteresis occurs. As a result, accurate and highly reproducible flow rate control of the proportional valve coil current cannot be performed. Therefore, the following control devices have conventionally been used to eliminate the dead zone and reduce hysteresis.

The control circuit in this case is shown in FIG. 1. After the AC power source 1 is full-wave rectified by a rectifier 2, a pulsating current flows through a series circuit consisting of a coil 3 of an electromagnetic proportional valve, a transistor amplifier 4, and a resistor 5. A direct current is applied to the plunger, causing 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 above the set level must be increased from the maximum current value (see Figure 2 A) to which full-wave rectified direct current is applied as is. Current control is performed within the range of the desired value obtained by cutting the portion (see Figure 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 conventional method described above, the dither effect weakens, making it difficult to achieve the initial purpose.This drawback is particularly noticeable in the low current range, and the performance of the electromagnetic proportional valve is not fully demonstrated. .

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. As shown in FIG. This outputs output signals with different voltage values x. 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 rise sharply 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 a constant period and constant amplitude as in this conventional method, the period must be made longer, and in this case, the dither effect will be sufficient as in the first conventional example. It becomes impossible to obtain it. In addition, the commercial power supply is rectified, and the direct current, which is not completely smoothed and has pulsating components, is transferred to the coil 3 of the electromagnetic proportional valve.
A method is also known in which the ripple current component is connected in series with the transistor amplifier 4 and the ripple current component is used as a dither effect, but it has not been possible to obtain a sufficient dither effect.

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

Structure of the Invention To achieve this object, the present invention includes a transformer secondary winding that generates a dither signal of the same frequency as a commercial power supply in a DC power supply, a transistor amplifier operated by a coil of an electromagnetic proportional valve, and a current control circuit. are connected in series, a back electromotive force prevention diode is connected in parallel to both ends of the series part of the transformer secondary winding and the coil of the electromagnetic proportional valve, and a capacitor and a resistor are connected in series. Connected.

With this configuration, the coil of the electromagnetic proportional valve has
A commercial frequency sine wave dither signal supplied from the transformer secondary winding and a DC power supply flowing to the transistor amplifier are combined. The direct current flowing through the transistor amplifier can be varied by an electrical control circuit. Due to the dither effect, the current flowing through the coil of the electromagnetic proportional valve has a current waveform with the most preferable constant period and amplitude and gradual rises and falls.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. In Fig. 7, transformer 2 is connected to the DC power supply 10.
The secondary winding 11 of the transformer, the coil 12 of the electromagnetic proportional valve, and the transistor amplifier 14 operated by the current controller 13 are connected in series.
A diode 15 for preventing back electromotive force is connected in parallel to both ends of the series portion of the coil 12 of the electromagnetic proportional valve, and a resistor 16 and a capacitor 17 connected in series are also connected in parallel. 18 is an emitter resistor of the transistor amplifier 14.

In the above configuration, the commercial frequency AC voltage of several volts generated in the secondary winding of the transformer is applied to the circuit formed by the coil 12 of the electromagnetic proportional valve, the diode 15, the resistor 16, and the capacitor 17, and the electromagnetic A dither signal is sent to the proportional valve coil 12, and the eighth
A sinusoidal current flows as shown in the diagram. However, it does not flow to transistor amplifier 14. Then, when a DC current flows into the transistor amplifier 14 due to the signal from the current control circuit 13, the dither signal is combined with the current of the transistor amplifier 14, and the dither signal is superimposed on the DC component as shown in FIG. Then, it flows through the coil 12 of the electromagnetic proportional valve. FIG. 9 shows the emitter current flowing through the emitter resistor 18 at this time. Therefore, the dither signal always has a constant frequency and amplitude regardless of the level of the direct current of the transistor amplifier, has a stable dither effect, and always provides stable flow characteristics. In the embodiment of the present invention, the secondary winding of the transformer that generates the dither signal is obtained from a dedicated transformer, but in general, the DC power source 10 is often obtained by rectifying and smoothing the AC power source. In such a case, a secondary winding for generating a dither signal may be wound over the power transformer of the DC power supply 10 to form one transformer. In this case, since there is no need to provide a separate dither signal transformer, the same dither effect can be obtained in a compact space. In addition, since the core of the power transformer can be used in common, the cost increase is reduced to only the winding cost, and the effect can be obtained at low cost.

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

(1) Since the configuration is such that a dither effect is applied to the electromagnetic proportional valve by the commercial frequency sine wave current supplied from the secondary winding of the transformer, the current in the valve coil has a waveform of 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 system operates with a dither waveform with a constant period and amplitude from low current to high current, no matter where the electromagnetic proportional valve's operating position or flow rate position is, the optimal constant dither effect is always achieved. is obtained, and stable characteristics can always be obtained.

[Brief explanation of the drawing]

Fig. 1 is a basic circuit diagram showing an example of a conventional electromagnetic proportional valve control device, Fig. 2 A, B, and C are current waveform diagrams of the valve coil according to the device shown in Fig. 1, and Fig. 3 is another conventional electromagnetic proportional valve control device. A basic circuit diagram showing an example of an electromagnetic proportional valve control device, Figure 4 D, E, and F are output waveform diagrams of the square wave generation circuit of the device shown in FIG. 3, and FIG. Voltage/current waveform diagram of the valve coil, No. 6
The figure is a flow characteristic diagram of the electromagnetic proportional valve using the device shown in FIG. 3, FIG. 7 is a basic circuit diagram of the electromagnetic proportional valve control device showing an embodiment of the present invention, and FIG. 9 is a current waveform diagram of the coil of the proportional valve; FIG. 9 is a current waveform diagram of the current flowing through the emitter resistor of the device shown in FIG. 7. 10... DC power supply, 11... Transformer secondary winding, 12... Coil of electromagnetic proportional valve, 13... Current control circuit, 14... Transistor amplifier, 15...
... Diode for preventing back electromotive force, 16 ... Resistor, 1
7... Capacitor.

Claims (1)

[Claims] 1 A transformer secondary winding that generates a dither signal with a frequency equal to that of a commercial power supply, a coil of an electromagnetic proportional valve, and a transistor amplifier operated by a current control circuit are connected in series to a DC power supply, and the transformer secondary winding is connected in series to a DC power supply. An electromagnetic proportional valve control device in which a back electromotive voltage prevention diode is connected in parallel to both ends of the series part of the side winding and the electromagnetic proportional valve coil, and a capacitor is also connected in parallel.