JPH0429174Y2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to an improvement in the control circuit of a current-controlled proportional valve, which is an electromagnetic valve used in water heaters and the like to control the amount of fuel supplied to a combustion section.

<Conventional technology> When supplying fuel such as raw gas to the combustion part of a water heater, etc., the supply amount is controlled according to the required combustion amount. A current-controlled proportional valve that adjusts the valve opening is a component that must be used.
The control of this proportional valve itself is often performed based on a pulse signal output from a microcomputer in water heaters etc. developed recently, and the valve opening degree is in particular determined by the frequency of the pulse signal. It is becoming more and more common.

In such a case, a control circuit configuration as shown in Fig. 2 is adopted between the microcomputer and the proportional valve. The frequency of the pulse signal P ₁ applied to the integrating circuit 3 from the output port 2 of the microcomputer 3 increases, thereby increasing the output voltage of the integrating circuit 3.

After passing through a suitable impedance converter 4, this voltage signal is applied to the positive phase input of a voltage comparator 5 for automatically controlling the proportional valve 1 so that a drive current corresponding to the voltage signal flows through the proportional valve 1.

On the other hand, the proportional valve 1 has a current control transistor 6
It is supplied with power supply current through the circuit, and indicates the degree of opening according to the current value at that time, but the current value that gives the degree of opening at that time is converted into a voltage value and detected. Since the voltage across the detection resistor 7 is given to the negative phase input of the comparator 5, now,
When the voltage value on the positive phase input side increases as shown above,
The output potential of the comparator 5 becomes high level, the drive transistor 8 continues to be turned on, and the current control transistor 6 also continues to be turned on, and the amount of current supplied to the proportional valve 1 increases and the valve opening of the proportional valve changes. changes in the opening direction.

However, as a matter of course, the current increasing process is converted into a voltage value across the current detection resistor 7 and detected, and this is fed back to the negative phase input of the comparator 5, so that the current value supplied to the proportional valve 1 increases. is not unlimited, and eventually stabilizes when the negative-sequence input voltage catches up with the current positive-sequence input voltage.

In other words, if the negative phase input voltage slightly fluctuates in a state close to the positive phase input voltage of the comparator 5, the output of the comparator 5 will be at a low level when the voltage value on the negative phase input side is high. Then, the drive transistor 8 is turned off, and the current control transistor 6 is also temporarily turned off to cut off the supply current, and while waiting for the proportional valve 1 to close, the reverse phase input is turned off. When the side becomes low, the drive transistor 7 and current control transistor 6 are turned on by the high level output of the comparator 5, and current is continued to be supplied to the proportional valve 1 until the negative phase input side becomes high again.
The valve opening is widened.

In this way, in the conventional example shown in the second figure, the valve opening is adjusted to a predetermined degree according to the frequency signal _P1 emitted from the microcomputer.
The current supplied to the proportional valve 1 is automatically controlled.

<Problems to be Solved by the Invention> As is obvious, in the above conventional example, a frequency-to-voltage converter called an integral circuit is inserted between the microcomputer and the proportional valve.

Therefore, it is necessary to be prepared for a certain amount of signal propagation time delay, and in practice, when such a control circuit is adopted, it has been pointed out that the response is slow.

In addition, the number of parts required is large,
It cannot be said that it is a very rational structure.

The present invention has been developed based on these viewpoints, and it is an object of the present invention to provide a proportional valve control circuit that is easy to configure and has high speed.

<Means for Solving the Problems> In order to achieve the above object, the present invention includes a current control transistor that is inserted in series in the power supply current line supplied to the current control proportional valve and controls the supply current. , and a drive transistor that controls the current control transistor, the control circuit for the current control proportional valve has a microcomputer that controls the drive transistor according to the valve opening required for the proportional valve at any given time. We propose a control circuit that directly supplies a pulse signal train while making the duty ratio variable, and turns on and off the driving transistor in accordance with the duty ratio of the pulse train signal.

<Operations and Effects> According to the above configuration of the present invention, instead of expressing the valve opening command signal required from time to time by a proportional valve as a frequency as in the conventional case, the duty ratio of a pulse signal train emitted from a microcomputer is used. It is expressed as a ratio.

Therefore, if the duty ratio changes, the on/off time rate of the drive transistor receiving it will also change, and the on/off time rate of the current control transistor will also change correspondingly, so the duty ratio at that time will change accordingly. A power supply current corresponding to the ratio is applied to the proportional valve, and a corresponding desired valve opening degree is obtained.

As described above, the present invention eliminates the need to use an integrating circuit between the microcomputer and the proportional valve, which causes signal propagation delay and complicates the configuration, and is extremely simple. Therefore, it is possible to realize an extremely high-speed proportional valve control system.

<Embodiment> FIG. 1 shows a control circuit for a current-controlled proportional valve constructed according to the present invention.

The current control proportional valve 1 has a power supply current _I0 supplied thereto controlled by a current control transistor 6,
Achieve a valve opening degree that corresponds to this.

Current control transistor 6 is drive transistor 8
The drive transistor 8 is directly controlled by the pulse train signal P ₀ appearing on the proportional valve control port 12 of the microcomputer 10.

This pulse train signal _P0 is designed to represent the valve opening degree that should be obtained depending on the duty ratio.

That is, when increasing the valve opening degree from the current one, the microcomputer 10 issues a pulse train signal P ₀ with a relatively large duty ratio so that the high level period becomes longer. Therefore, the period in which the drive transistor 8 is turned on within a certain period of time becomes longer, so the current control transistor 6 also becomes the same, and the amount of current supplied to the proportional valve 1 increases within a certain period of time. , the valve opening also increases.

Of course, on the contrary, when it is desired to throttle the valve more than it currently is, a pulse train signal P ₀ with a smaller duty ratio is issued from the microcomputer 10, and in response to this, the drive transistor 8 and, by extension, the current control transistor 6 are activated within a certain period of time. The period during which the proportional valve 1 is turned on becomes shorter, and the amount of current applied to the proportional valve 1 eventually decreases, settling down to the desired narrowed valve opening.

In the case of this embodiment, a resistor 7 in series with the proportional valve is also shown in correspondence with the conventional example shown in the second figure, but as is clear from the above, when the present invention is adopted, This resistance has no other meaning other than for controlling the maximum current value supplied to the proportional valve 1. Therefore, this resistor 7 may be omitted depending on the case.

In any case, according to the present invention, the necessary valve opening degree is expressed by the duty ratio of the pulse signal train. Furthermore, since the drive transistor (and by extension the current control transistor) is directly controlled by this pulse train signal, there is no delay element unlike the conventional one, and extremely high-speed response characteristics can be exhibited.

As a result, the configuration has also become extremely convenient, and in practice, the degree of simplification of the circuitry external to the microcomputer has become extremely large.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram of a current-controlled proportional valve control circuit as a preferred embodiment constructed according to the present invention, and FIG. 2 is a schematic configuration diagram of a typical control circuit of a conventional current-controlled proportional valve. It is. In the figure, 1 is a current control proportional valve, 6 is a transistor for power supply current control, 8 is a drive transistor, and 10 is a current control proportional valve.
12 is a microcomputer, and 12 is a microcomputer output port that outputs a pulse signal train with a variable duty ratio in accordance with a desired valve opening degree.

Claims (1)

[Claims for Utility Model Registration] A current control transistor that is inserted in series in a power supply current line supplied to the current control proportional valve and controls the supply current; A drive transistor that controls the current control transistor; A drive transistor that controls the current control transistor; A pulse signal train is directly supplied to the transistor while changing the duty ratio according to the valve opening required for the proportional valve at each time.
A microcontroller that operates the drive transistor on and off according to the duty ratio of the pulse train signal.
A control circuit for a current-controlled proportional valve, comprising: a computer;