JPH0313463B2 - - Google Patents

Description

[Detailed description of the invention] Industrial application field The present invention is installed in a gas combustion appliance, etc., and is used to control the temperature of hot water,
The present invention relates to a gas flow rate control device using a proportional control valve that continuously controls the gas flow rate according to a combustion load signal such as room temperature, and operates so as to obtain a desired hot water temperature and room temperature.

Structure of a conventional example and its problems A conventional gas flow rate control device of this type is shown in FIG. 1 is integrally provided with a valve seat 4 provided between a fluid inlet 2 and a fluid outlet 3, a valve body 5 provided opposite to the valve seat 4, and operates in response to fluid pressure. It is a gas governor part having a diaphragm 6, has a well-known governor function, and has a valve seat 4.
An elastic body 7 is provided at the contact portion of the valve body 5 and the valve body 5.
By providing a closing spring 8 that biases the valve in the valve-closing direction, it has a valve-closing function that blocks the gas flow path.

Reference numeral 9 denotes an electromagnetic drive unit having a coil 10, a yoke 11, and a plunger 14 supported at both ends by leaf springs 13. By energizing the coil 10, electromagnetic force acts on the valve body 5 to continuously control the flow rate. can do. In other words, if a load signal S _F such as hot water temperature is detected and an amount of current is supplied to the coil 10 according to the deviation signal from the setting signal S _S , the necessary gas flow rate is automatically controlled and the desired hot water temperature is achieved. is obtained.

This type of gas flow control device has a flow rate proportional control function, a gas governor function, and a valve closing function.
Although the gas control block can be made more compact and lower in cost, it has the following problems. That is, in order to provide the valve closing function, the closing spring 8
It is necessary to increase the valve closing force. FIG. 2 shows the coil current I supplied to the coil 10 and the electromagnetic force _Fe ,
In other words, it shows the relationship between the forces that displace the valve body 5 downward.If the force of the closing spring is _Fs , and the force that produces a fully open flow rate is _Fn , the range of coil current required for flow rate control is Is _to I. becomes _n . The force (F _n ~ _{F s} ) required for flow rate control is determined by the diameter of the valve seat 4 and the pressure at the fluid outlet 3, but it may be less than 1/3 of the valve closing force F _s , and this type of electromagnetic In the drive section 9, 2 of the current I
Since an electromagnetic force F _e proportional to the power is generated, the flow rate control current width becomes narrower. Therefore, as shown in Figure 3, the gain of the flow rate control characteristics becomes large, and even if a small current change ΔI occurs, a large flow rate change ΔQ occurs, which deteriorates flow rate control accuracy and causes hunting. Become. Therefore, special measures are required on the electrical control circuit side, which is a factor in increasing costs.

In addition, in order to ensure control accuracy, it was necessary to weaken the valve closing force _Fs , which raised concerns about the closing performance.

Purpose of the Invention The present invention solves these conventional problems, and provides a gas flow control device that improves flow control accuracy by reducing the gain of flow control characteristics and provides sufficient valve closing force. The purpose is to

Configuration of the Invention In order to achieve this object, the present invention includes a coil,
an electromagnetic drive unit having a yoke and a plunger that is movable in the axial direction of the coil, a valve seat;
a valve body provided opposite to the valve seat and connected to the plunger, an elastic body provided at a position where the valve seat and the valve body abut, and biasing the valve body in a direction to close it. a gas governor section having a valve closing spring and a diaphragm fixed to the valve body, a control circuit for controlling the electromagnetic drive section by superimposing a dither signal on a DC signal, and a magnetic circuit for the electromagnetic drive section; A narrow portion is provided in at least one of the yoke and the plunger forming the yoke and the plunger.

With this configuration, it is possible to adjust the coil current that causes magnetic saturation in the narrow part provided in at least one of the yoke and the plunger in the magnetic circuit of the electromagnetic drive unit, which corresponds to the force of the closing spring that does not change the gas flow rate. It is possible to generate an electromagnetic force in proportion to the square of the current without magnetically saturating the magnetic circuit of the electromagnetic drive unit up to a current that generates an electromagnetic force. In the flow rate control current range where the gas flow rate changes, it is possible to cause magnetic saturation in the electromagnetic drive section, so the electromagnetic force is directly proportional to the current. Therefore, the gain in the proportional control region of the proportional control valve can be reduced.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG.

Figure 4 shows the flow rate control device, with the gas governor 15
and a proportional control valve 17 consisting of an electromagnetic drive section 16.
and a control circuit 18 that controls the electromagnetic drive unit 16, and a comparator 19 that compares a detection signal of a load such as hot water temperature with a setting signal S _S and provides a deviation signal thereof to the control circuit 18.

The gas governor section 15 has a fluid inlet 20 and a fluid outlet 2.
1, a valve body 23 provided opposite to the valve seat 22, and a closing spring 24 that biases the valve body 23 in the valve closing direction. The diaphragm 25, which operates in response to pressure on the fluid inlet 20 side, connects the pin 27 to the retaining ring 2 through the membrane plate 26.
7a, and is press-fitted and airtightly mounted.

Reference numeral 28 denotes a locking ring for the valve seat 22 made of an elastic body, and is airtightly fixed in the valve body 29 by press fitting.

Reference numeral 30 denotes a base cap, which is airtightly attached to the valve body 29 via a packing 31.

A diaphragm bracket 32 forms a back pressure chamber 25a of the diaphragm 25 and presses the outer peripheral bead of the diaphragm 25 to maintain it airtight.

The electromagnetic drive unit 16 includes a coil 33, a yoke 34, a yoke plate 35, a sliding pipe 36 penetrating through the center of the coil 33, a plunger 37 provided to be movable up and down within the sliding pipe 36, and the plunger 37 and a pin. Spacer 3 made of non-magnetic material provided between 27
It has 8. The plunger 37 is provided with a notch 39 for reducing the cross-sectional area and achieving magnetic saturation.

Diaphragm bracket 32 and sliding pipe 36
A sealing material 40 is provided between them, and a cap 42 with a vent 41 that acts as a damper to prevent valve vibration is press-fitted into the upper part of the sliding pipe, and the back pressure chamber of the diaphragm 25 is 25
a communicates with the atmosphere only through a vent 41.

The control circuit 18 receives combustion load signals such as hot water temperature and room temperature.
S _F is compared with the desired setting signal _S
3, and a circuit that superimposes a dither signal on the DC signal.

In the above configuration, when no current is applied, the valve body 23 is pressed against the valve seat 22 made of an elastic body with sufficient closing force due to the action of the closing spring 24, and even if gas pressure acts on the fluid inlet 20 side, the valve body 23 is pressed against the valve seat 22 made of an elastic body. The valve is closed without any leakage.

When energized, the setting signal S _S and the combustion load signal are compared in the comparator 19, and the difference signal is sent to the control circuit 18.
Then, the dither signal is superimposed on the DC current, which is then supplied to the coil 33.

The dither signal is sent to the sliding pipe 3 of the electromagnetic drive unit 16.
This is to reduce the static friction and sliding friction that occur in the sliding portion between the plunger 6 and the plunger 37, and to operate the plunger 37 smoothly in response to changes in drive current. In the embodiment of the present invention, a sine wave alternating current of 50 Hz or 60 Hz, which is the same as the power supply frequency, is used as the dither signal. Note that the frequency and current value of the dither signal are determined through experiments in consideration of the responsiveness of the plunger 37 to the dither signal.

When the coil 33 is energized from the control circuit 18,
The plunger 37 generates a downward force by electromagnetic force and attempts to open the valve body 23 against the force of the closing spring 24. When the current is further applied, the electromagnetic force overcomes the closing force of the closing spring 24 and opens the valve body 23.
The gas passes through the fluid outlet 21 to a burner (not shown).
leaks to. Here, the coil current I and electromagnetic force of the electromagnetic drive section 16 when no dither signal is superimposed.
The relationship of Fe is shown in Figure 5. As is clear from the figure, the notch 39 is provided in a part of the plunger 37 to be narrower than the other part to reduce the cross-sectional area, so when the current exceeds a certain level, the notch 39 becomes magnetically saturated. will arise. As is clear from the so-called B-H characteristic, which is the magnetic property of the magnetic material, when magnetic saturation occurs, the magnetic hysteresis increases, and the magnetic hysteresis of the electromagnetic drive unit 16 increases.

FIG. 6a shows the relationship between the coil current I and the electromagnetic force Fe when a dither signal is superimposed on a DC signal.
As is clear from this figure, by superimposing the dither signal, it is possible to reduce the magnetic hysteresis that has become large due to magnetic saturation. Next, the effect of the dither signal will be explained using FIG. 6b. In the figure, the characteristic when the dither signal is not superimposed is characteristic A shown by the solid line, and different trajectories are drawn depending on the magnetic hysteresis when the coil current I is increased and when it is decreased. If, for example, the coil current I is decreased in the middle of increasing the coil current I when it reaches point A, and then returned to its original value, a small loop-shaped trajectory will be created, similar to the so-called minor loop of magnetic materials. draw. Even when the coil current I is applied to the maximum current and then decreased, a similar loop-like locus is drawn as shown in the figure. In other words,
Coil current I while increasing and lowering the current with a constant amplitude
When , is continuously changed, the average value becomes the midpoint of the loop-like trajectory, and becomes the characteristic A shown by the broken line.

In other words, the operation of increasing and lowering the current with a constant amplitude corresponds to a dither signal, and is continuously superimposed at a frequency of several tens of Hz, which is thought to have the effect of reducing magnetic hysteresis.

Similarly, in FIG. 6a, if the valve opening force of the closing spring 24 is F _s and the force for fully opening the flow rate is F _n , the range of coil current required for flow rate control is I _s to I _n . In the embodiment of the present invention, the cross-sectional area of the notch 39 is set so that the current value at which magnetic saturation occurs in the plunger 37 of the electromagnetic drive unit 16 is near the electromagnetic force F _s corresponding to the valve closing force of the closing spring 24. ing. Therefore, the notch 39 of the plunger 37 is not yet magnetically saturated up to the current range in which the electromagnetic force F _s corresponding to the valve closing force of the closing spring 24 is generated. Therefore,
In this range, the electromagnetic force increases as the square of the coil current, and in the flow rate control area, magnetic saturation occurs, so that an electromagnetic force characteristic proportional to the coil current is obtained.

FIG. 7 shows the flow rate control characteristics of the gas flow rate control device according to this embodiment. The figure shows coil current I and gas flow rate.
If _ΔQ is the change in gas flow rate for a unit change in coil current ΔI, then the gain is ΔQ/
It can be expressed as ΔI. The smaller this gain is, the less affected by variations in the control circuit and temperature characteristics, and more accurate flow rate control can be performed.

As described above, according to this embodiment, the valve seat 22 is made of an elastic body, and the closing spring 24 provides sufficient valve closing force to improve valve closing reliability. Further, since the dither signal is superimposed on the DC signal, it is possible to reduce the hysteresis in the flow control characteristics caused by the sliding friction of the plunger 37 and the magnetic hysteresis of the magnetic material comprising the plunger 37, yoke 34, and yoke plate 35. In this embodiment, a notch 39 is provided in a portion of the plunger 37 to form a narrow portion, but a narrow portion may be provided in a portion of the yoke 34 and yoke plate 35 made of other materials that constitute the electromagnetic drive portion 16. A similar effect can be obtained. Furthermore, since the diaphragm 25 is provided and has a governor function, the three functions of a proportional control valve, a shutoff valve, and a gas governor can be integrated, and the entire flow control device can be made more compact and lower in cost.

Effects of the Invention As described above, the gas flow rate control device of the present invention provides the following effects.

An elastic body is provided at the contact area between the valve seat and the valve body, and a closing spring provides sufficient valve closing force to improve valve closing reliability, and a dither signal is superimposed on the DC signal to control the electromagnetic drive unit. A control circuit is provided, and the electromagnetic drive section has a flow rate ratio control range of the proportional control valve.
Since a narrow portion is provided in a part of the material constituting the electromagnetic drive unit so as to be in the magnetic saturation range of the electromagnetic drive unit, the relationship between the coil current and the electromagnetic force is a proportional relationship in the proportional control range, The gain of flow rate control characteristics can be reduced. In addition, while maintaining sufficient valve closing reliability,
Highly accurate flow control is possible regardless of temperature characteristics. Furthermore, since the dither signal is superimposed, it is possible to reduce the sliding resistance of the electromagnetic drive unit and the hysteresis in the flow control characteristics due to magnetic hysteresis due to magnetic saturation.

[Brief explanation of drawings]

Fig. 1 is a sectional view of a conventional gas flow rate control device, Fig. 2 is an electromagnetic force characteristic diagram of the same device, Fig. 3 is a flow rate control characteristic diagram of the same, and Fig. 4 is an embodiment of the present invention. The configuration diagram of the gas flow rate control device, Fig. 5 is the electromagnetic force characteristic diagram of the same device, Fig. 6 a is the electromagnetic force characteristic diagram when the dither signal of the same device is superimposed, and Fig. 6 b is the hysteresis due to the dither signal. An electromagnetic force characteristic diagram for explaining the reduction effect, and FIG. 7 is a flow rate control characteristic diagram in an embodiment of the present invention. 15... Gas governor section, 16... Electromagnetic drive section,
17... Proportional control valve, 18... Control circuit, 22...
... Valve seat (elastic body), 23 ... Valve body, 24 ... Closing spring.

Claims (1)

[Claims] 1. An electromagnetic drive unit having a coil, a yoke, and a plunger movable in the axial direction of the coil,
a valve seat, a valve body provided opposite to the valve seat and connected to the plunger, an elastic body provided at a position where the valve seat and the valve body abut, and a direction for closing the valve body. a gas governor section having a valve-closing spring that biases the valve, and a diaphragm fixed to the valve body; and a control circuit that controls the electromagnetic drive section by superimposing a dither signal on a DC signal. A gas flow control device comprising a narrow portion in at least one of the yoke and the plunger forming a magnetic circuit.