JPH0226132B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention has a proportional control valve that controls the flow rate of fluid according to an electrical signal, and also has a flow rate sensor in a flow path, and a flow rate sensor and a desired setting. The present invention relates to a gas combustion amount control device that controls a proportional control valve according to a signal deviation signal.

Structure of a conventional example and its problems A conventional gas combustion amount control device of this type is shown in FIG. In FIG. 1, 1 is a valve device, 2 is a drive device for driving the valve device 1, 3 is a flow rate sensor connected in series on the outlet side of the valve device 1, and 4 is a control circuit.

The valve device 1 includes a fluid inlet 5 and a fluid outlet 6, a valve seat 7 formed on a partition wall between the fluid inlet 5 and the fluid outlet 6,
and a valve body 8 and a spring 9 that biases the valve body 8 in the valve closing direction.
has.

The drive device 2 includes a plunger 1 that operates together with a valve body 8.
0, bearings 11 that support both ends of the plunger 10;
It is composed of a coil 12 provided on the outer periphery of the plunger 10 and a yoke 13. By energizing the coil 12, an electromagnetic force Fm acts on the plunger 10, pushing down the valve body 8 and opening the valve.

The flow rate sensor 3 includes a tubular housing 14 communicating with the fluid outlet 6, a blade wheel 15 housed in the housing 14 and rotated by fluid flow, a permanent magnet 16 provided at the edge of the blade wheel 15, and a permanent magnet 16 provided at the edge of the blade wheel 15. magnet 1
6 and a Hall element 17 that detects pulse-like changes in magnetic flux.

The control circuit 4 includes a detection circuit 18 that converts the output of the Hall element 17 into a pulse signal, an integration circuit 19 that amplifies and outputs a voltage signal proportional to the generation of the pulse signal, and a desired setting signal and the integration circuit 19. Comparator 20 that compares signals and outputs a deviation signal
and a drive circuit 21 that supplies power to the coil 12 using this deviation signal.

When a setting signal is supplied in the above configuration,
The comparator 20 outputs a deviation signal between the integrator 19 and the setting signal to the drive circuit 21, and power is supplied to the coil 12. When the coil 12 is energized, the plunger 10
receives the downward electromagnetic force Fm, opens against the spring 9, and the fluid flows out through the fluid outlet 6 and the rotor 15. When the fluid passes, the rotor blade 15 rotates, the Hall element 17 detects a change in the pulse-like magnetic flux caused by the permanent magnet 16, and the detection circuit 18 outputs a pulse signal. This pulse signal is proportional to the flow rate of fluid passing through the flow sensor 3. Therefore, the flow rate is always monitored by the flow rate sensor 3 and the valve opening degree is controlled so that the flow rate is the one set by the setting signal. Furthermore, by varying the setting signal, the flow rate can be controlled with high precision in proportion to the signal.

However, when this conventional example is applied to gas combustion equipment, the flow rate sensor is required to have a wide measurement range. As shown in Figure 2, even in gas appliances with the same combustion rate, city gas may have a smaller calorific value depending on the type of gas used as fuel.
3,500kcal/m ³ is 7 times different from LP gas's 24,500kcal/m ³ , so the gas flow rate for the rated combustion amount of LP gas is set to 1.
In this case, city gas would flow seven times as much. Moreover, the gas combustion amount can be adjusted within the range of 1/3 of the rated combustion amount.
Since the flow rate is changed by up to 1/5, the ratio of the minimum detection value to the maximum detection value of the flow sensor becomes 1:35, necessitating a flow sensor with an extremely wide measurement range.

Furthermore, since the flow rate is measured by the rotation speed of the impeller, the flow rate varies depending on the type of gas, so naturally the rotation speed also varies. Therefore, since the electrical signal of the flow rate sensor varies depending on the type of gas, it is necessary to adjust the setting signal of the control circuit depending on the type of gas.

Furthermore, in the case of LP gas, which has a small flow rate, detection accuracy tends to deteriorate because the rotational speed is low.
Therefore, in order to improve the detection accuracy of LP gas, a flow sensor with a high rotation speed at a low flow rate is used, but as shown in Figure 3, in the case of city gas with a large flow rate, the pressure loss of the flow sensor becomes large. It was hot.

Therefore, countermeasures such as replacing the flow rate sensor depending on the type of gas were required.

Purpose of the Invention The present invention solves such conventional problems by expanding the detection range of a flow rate sensor with a narrow detection range, and
The purpose is to handle all gas types with the same flow rate sensor and to simplify gas type changes when users move or gas companies switch gases.

Structure of the Invention In order to achieve this object, the present invention includes a valve seat provided between a fluid inlet and a fluid outlet, a valve body facing the valve seat, and a valve body that is displaceable with respect to the valve seat to allow fluid flow. A drive device that varies a passage area, a flow rate sensor that exchanges a passing gas flow rate into an electric signal, a bypass passage provided in parallel with the flow rate sensor, a bypass amount variable part that changes fluid resistance of the bypass passage, and the electric signal. and the desired setting signal,
and a control circuit that controls the drive device using the deviation signal.

With this configuration, the ratio of the gas flow rate flowing through the flow rate sensor to the gas flow rate flowing through the bypass passage is changed by changing the resistance of the bypass passage, so that different gas flow rates depending on the gas type can be detected with the same flow rate sensor.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. Note that the same members as in the conventional example shown in FIG. 1 are given the same numbers.

A bypass passage 22 is provided in parallel with the flow rate sensor 3, and a variable throttle 24 is provided in the bypass passage 22 as a bypass amount variable section 23. 2
5 is a ring for sealing.

In the above configuration, when using LP gas as the fuel gas, the variable throttle 2 of the bypass amount variable section 23
4 is held in the fully closed position. The flow rate sensor 3 has a flow rate range suitable for LP gas. FIG. 5 shows the flow rate of the proportional control valve and the rotation speed of the impeller. When using LP gas, the variable throttle 24 is fully closed, so all the gas flow flows through the flow rate sensor 3. In the case of city gas, it also flows through the bypass passage 22, and by adjusting the variable throttle 24 of the bypass amount variable section 23, the rotation speed of the impeller 15 is made to be the same as that of LP gas. By adjusting the variable throttle according to the gas type in this manner, it becomes possible to use the same flow rate sensor 3 to handle all gas types. Furthermore, even in the small flow rate range of LP gas, the flow rate detection accuracy can be improved because the portion with a high rotational speed is used. On top of that,
In high-flow areas of city gas, bypass passage 2
2 is bypassed, which has the effect of reducing pressure loss.

Next, another embodiment of the present invention will be described using FIG. 6. FIG. 6 shows another embodiment of the bypass amount variable section. Note that the same members as in FIG. 4 are given the same numbers. A fixed throttle 26 is provided in the bypass amount variable portion 23 of the bypass passage 22. According to this configuration, the fixed throttle 26 corresponding to the gas type is prepared in advance and replaced depending on the gas type. Since it is a fixed aperture, there is no need for adjustment, and the amount of bypass is stabilized, which is effective in stabilizing detection accuracy.

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

(1) A bypass passage is provided in parallel to the flow rate sensor, so the measurement range can be expanded and all gas types can be handled.

(2) Since the electric signal of the flow sensor is the same for LP gas with a low flow rate and city gas with a high flow rate, there is no need to change the control circuit depending on the gas type, making it easy to switch gas types.

[Brief explanation of drawings]

Figure 1 is a configuration diagram of a conventional gas combustion amount control device.
Fig. 2 is a graph showing the relationship between the flow rate and rotation speed of the flow sensor of the same device, Fig. 3 is a graph showing the relationship between the flow rate and pressure loss of the flow sensor of the same device, and Fig. 4 is the gas combustion control of the present invention. A configuration diagram showing one embodiment of the device, FIG. 5 is a graph showing the relationship between the flow rate and rotation speed of the same device of the present invention, and FIG. 6 is a diagram showing another embodiment of the bypass amount variable part of the same device of the present invention. FIG. 2... Drive device, 3... Flow rate sensor, 4... Control circuit, 5... Fluid inlet, 6... Fluid outlet, 7...
... Valve seat, 8 ... Valve body, 22 ... Bypass passage, 2
3...Bypass amount variable section.

Claims (1)

[Claims] 1. A valve seat provided between a fluid inlet and a fluid outlet;
a valve body facing the valve seat; a drive device that changes the fluid passage area by displacing the valve body with respect to the valve seat; a flow rate sensor that converts a passing gas flow rate into an electrical signal; It has a bypass passage provided in parallel, a bypass amount variable part that changes the fluid resistance of the bypass passage, and a control circuit that compares the electric signal with a desired setting signal and controls the drive device based on the deviation signal. Gas combustion amount control device. 2. The gas combustion amount control device according to claim 1, wherein the bypass amount variable section uses a variable throttle. 3. The gas combustion amount control device according to claim 1, which uses a fixed throttle in the bypass amount variable section.