JPH0330031B2 - - 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. After the AC power source 1 is full-wave rectified by a rectifier 2, a pulsating current is sent to 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 passed through 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 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 FIGS. 2b and 2c), 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 generation circuit 8 is shown in FIG. 4a, b,
As shown in c, the peak value (amplitude) and period of the square wave are constant, and the time ratio between on and off (duty) is constant.
is changed to produce output signals with different average 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 characteristic a as shown in Figure 6, and become a disordered flow rate characteristic as shown in b. 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. In addition, the direct current that is not completely smoothed by rectifying the commercial power supply and has a pulsating component is removed from the coil 3 of the electromagnetic proportional valve.
A method is also known in which the ripple current component is connected in series to the transistor amplifier 4 and used as a dither effect, but the ripple frequency is limited to 50 Hz or 60 Hz, and it is still not possible to obtain a sufficient dither effect. Ta.

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 is operated 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 dither generation circuit that generates a voltage waveform of a substantially triangular wave or a substantially sine wave with a constant period and amplitude, a current control circuit that varies the DC voltage level, and an adder circuit that adds signals from the dither generation circuit and the current control circuit. It is composed of.

With this configuration, when the average current level flowing through the electromagnetic proportional valve coil is changed, the current in the valve coil has a current waveform with a constant period, amplitude, and gradual rises and falls that is most preferable due to the dither effect. act.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. 7 to 9. In FIG. 7, a DC power supply 10 includes a solenoid proportional valve coil 11 and 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 the outputs of a dither generating circuit 15 and a current control circuit 16, which generate a voltage waveform of a substantially triangular wave or a substantially sine wave with a constant period and amplitude, are connected in series. It is connected to be input to an adder circuit 17, and the output terminal of the adder circuit 17 is connected to the base terminal of the transistor 12.

Among the above configurations, one circuit example of the dither generating circuit 15 is shown in FIG. This figure shows a dither circuit that generates a triangular voltage waveform, in which resistors 20 and 21 are connected in series between the output terminal of an operational amplifier 18 and the negative terminal of an operational amplifier 19, and the connecting point 23 of the resistors 20 and 21 and the operational amplifier 18 are connected in series. Resistor 2 between the positive terminals
4, a resistor 25 is connected between the output terminal of the operational amplifier 19 and the positive terminal of the operational amplifier 18, and the negative terminal of the operational amplifier 18 and the positive terminal of the operational amplifier 19 are respectively grounded. Connect Sienar diodes 26 and 27 to and ground the other end, and connect the operational amplifier 1
Connect capacitor 2 between the negative terminal of 9 and the output terminal.
8 is connected. In this circuit, a square wave appears at the connection point 23, and a triangular wave is generated at the output terminal of the operational amplifier 19, but the saturation voltage at the connection point 23 is set to V
1. The resistance values of resistors 24 and 25 are R ₂₄ and
Assuming R ₂₅ , the peak voltage V _p of the triangular wave is V _p = R ₂₅ /R ₂₅ · V1, and the amplitude of the triangular wave can be controlled by the resistor 24, and from the voltage V1 at the connection point 23 via the resistor 21,
Since the capacitor 28 is charged linearly, the cycle of the triangular wave can be controlled by the resistor 21.

In the configuration shown in FIGS. 7 and 8 above, the voltage waveform generated by the dither generation circuit 15 is a square wave voltage as in the conventional example, and does not cause problems such as valve vibration due to sudden rises and falls of the voltage. The signal of the dither generation circuit 15 and the current control circuit 16 are set to have a triangular voltage waveform with a gradual rise and fall, and a constant period and constant amplitude, which is optimal for the electromagnetic proportional valve and can reduce hysteresis. The DC voltage signals of are added in the adding circuit 17, and the base current waveform of the transistor 12 has a constant period and amplitude when the average current I _H is large and when the average current I _L is small, as shown in Figure 9. It acts so that At this time, the current waveform of the coil 11 of the electromagnetic proportional valve also changes in period when the average current I _H is large and when the average current I _L is small, similar to the base current waveform in FIG.
The current waveform is approximately a triangular wave with a constant amplitude that does not change and rises and falls slowly, so there is no valve vibration and the excellent dither effect provides stable flow characteristics with low hysteresis. .

The dither generation circuit 15 has been explained using a triangular wave generation circuit as an example in FIG. 8, but if the waveform is not a sharp rise and fall waveform like a square wave, but a gradual rise and fall waveform, it can be a substantially triangular waveform like a sawtooth wave. Any dither generating circuit that generates a voltage waveform such as a waveform, a substantially triangular waveform such as a trapezoid, a sine wave, or a slightly distorted substantially sine waveform can achieve the same effect as the triangular wave generating circuit described above. It will be done.

In addition, electromagnetic proportional valves are not limited to the plunger sliding type.
Similar effects can also be obtained with moving magnet type or moving coil type electromagnetic proportional valves that are commonly used in gas water heaters.

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 and the current control circuit, which generate a voltage waveform with a constant period and amplitude that slowly rises and falls, are added together in an adder circuit, and the signals are added to the base terminal of the transistor amplifier connected in series with the valve coil and the DC power supply. Since the input is configured so that the current in the valve coil acts as a dither current with a waveform of gentle rise and fall and a constant period and amplitude, it produces an effective dither effect while suppressing undesirable valve vibration. Since no induction occurs, 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 adjusted arbitrarily and optimally. It can be set to various types of electromagnetic proportional valves. Depending on the shape and weight of the movable parts and valve body of the electromagnetic proportional valve, the conditions for the waveform, period, and amplitude that can best exhibit the dither effect often vary. The same applies to conditions that cause undesirable valve vibration.
According to the configuration of the present invention described above, it becomes 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 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, FIG. 4 a, b, and c are output waveform diagrams of the square wave generation circuit of the device shown in FIG. 3, and FIG. 5 is an output waveform diagram of the device shown in FIG. 3. Voltage/current waveform diagram of the valve coil, No. 6
The figure is a flow characteristic diagram of an electromagnetic proportional valve using the device shown in Fig. 3, Fig. 7 is a basic circuit diagram of an electromagnetic proportional control device showing an embodiment of the present invention, and Fig. 8 is an example of the dither generation circuit shown in Fig. 7. FIG. 9 is a transistor base current waveform diagram and a valve coil current waveform diagram of the device shown in FIG. 7. 10...DC power supply, 11...Valve coil, 12...
...Transistor amplifier, 15...Dither generation circuit, 16...Current control circuit, 17...Addition circuit.

Claims (1)

[Claims] 1. A dither generation circuit that connects a valve coil and a transistor amplifier in series to a DC power source and generates a voltage waveform of a substantially triangular wave or a substantially sine wave with a constant period and amplification, and a current control circuit that varies the DC voltage level.
An electromagnetic proportional valve control device comprising an addition circuit that adds signals from the dither generation circuit and the current control circuit.