JP2004101078A - Gas flow control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem of complicating circuit constitution due to the necessity of separate power sources for amplifying positive and negative voltage respectively to amplify voltage variable in polarity in the case the output voltage is changed to the positive side or negative side by the characteristic dispersion of individual pressure sensors, a temperature change around the pressure sensor, or the like in a secondary pressure detecting means in a conventional gas flow control device. <P>SOLUTION: A resistance value changing means R3 is provided for changing the resistance value of at least one resistance out of resistances R1, R2, R3 constituting a bridge circuit 8 including the pressure sensor 7. In the case of correcting the output voltage in the atmospheric pressure state of pressure in a gas passage by the resistance value changing means, the output voltage is corrected offset to the polarity side increased with the increase of pressure in the gas passage, to prevent the reversal of polarity of the voltage outputted to an amplifying means. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a gas flow control device used for a gas cooking appliance such as a gas stove.
[0002]
[Prior art]
This type of gas flow control device has a gas passage connected to a gas injection nozzle connected to a mixing pipe of a gas burner, and the gas passage is driven by, for example, a geared motor to change the opening degree of the gas passage. Means are provided.
[0003]
A pressure sensor, which is secondary pressure detecting means for detecting a secondary pressure of the fuel gas, is provided in a gas passage upstream of the flow rate adjusting means and downstream of the gas injection nozzle. When this gas flow control device is provided on a gas stove, for example, to adjust the set heating power of a gas burner, the secondary pressure detected by the pressure sensor by the microcomputer provided on the gas stove matches the target secondary pressure stored in the microcomputer in advance. The opening degree of the flow rate adjusting means is adjusted by feedback-controlling the motor in such a manner (see Patent Document 1).
[0004]
The pressure sensor changes its resistance value according to, for example, the pressure of the fuel gas in the gas passage, and the change in the resistance value of the pressure sensor is taken out as a voltage via a bridge circuit. Further, in order to amplify the output voltage from the bridge circuit, for example, an amplifying means such as an OP amplifier is connected to the bridge circuit. The pressure sensor and each resistor are set so that the output voltage is 0 V even when a predetermined voltage is input when the pressure in the gas passage is atmospheric pressure.
[0005]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 2001-56118 (for example, Claim 1)
[0006]
[Problems to be solved by the invention]
However, when such a pressure sensor is provided in each gas flow control device and the output voltage of the pressure sensor is detected when the pressure in the gas passage is the atmospheric pressure, variations in the characteristics of the individual pressure sensors and the peripheral In some cases, the output voltage changes to the plus side or the minus side, respectively, due to a temperature change or the like.
[0007]
For example, when the output voltage changes to the minus side, the polarity of the output voltage changes to the plus side with the change in the pressure in the gas passage. In order to amplify such a change in polarity, separate power supplies for amplifying the positive or negative voltages are required, and there has been a problem that the circuit configuration becomes complicated and the cost increases.
[0008]
In view of the above problems, an object of the present invention is to provide a gas flow control device having a simple circuit configuration and low-cost pressure detecting means.
[0009]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, a gas flow control device according to the present invention includes a pressure sensor provided in a gas passage communicating with a gas injection nozzle and having a resistance value that changes according to a pressure of fuel gas in the gas passage. A bridge circuit that converts a change in the resistance value of the sensor into a voltage, and amplifying means for amplifying an output voltage from the bridge circuit, provided in the gas passage based on the output voltage amplified by the amplifying means, In a gas flow rate control device for controlling a gas flow rate adjusting means for adjusting a gas flow rate by changing a passage area of a gas passage, a resistance value changer for changing a resistance value of at least one of resistors constituting the bridge circuit. Means for correcting the output voltage in a state in which the pressure in the gas passage is at atmospheric pressure by the resistance changing means, and increasing the pole as the pressure in the gas passage increases. The output voltage on the side corrected by the offset, the polarity of the voltage to be output to the amplifying means is characterized in that so as not inverted.
[0010]
According to the present invention, the output voltage is corrected when the pressure in the gas passage provided with the pressure sensor is at the atmospheric pressure. In this case, for example, in anticipation of the amount of change in the output voltage that can change due to a temperature change in the gas passage provided with the pressure sensor, the output voltage is offset to the polarity side that increases as the pressure in the gas passage increases. To correct. Thus, the polarity of the voltage output to the amplifying means is not inverted, and there is no need to provide a separate power supply for amplifying the positive or negative voltage.
[0011]
The resistance changing means may be, for example, a variable resistor.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Referring to FIGS. 1 and 2, reference numeral 1 denotes a gas flow control device of the present invention provided in, for example, a gas stove. The gas flow control device 1 has a device main body 12 having a gas passage 11 connected to a gas injection nozzle (not shown) connected to a mixing pipe of a gas burner provided on a gas stove. A gas valve 2 which is a flow rate adjusting means for adjusting a gas flow rate of a fuel gas to a gas injection nozzle is provided on a lower surface of one end of the apparatus main body 12.
[0013]
The gas valve 2 has a valve casing 22 provided with an internal passage 21 communicating with the gas passage 11, and a gas inlet 23 communicating with the internal passage 21 is opened on an upper surface of the valve casing 22.
[0014]
A stepping motor 3 having a rotation angle detecting means 31 is connected to the lower surface of the valve casing 22, and one end of a rotation shaft 32 of the motor 3 projects into the internal passage 21 via a seal member 33.
[0015]
In the internal passage 21, the rotating disk 4 located upstream of the gas outlet 23 and connected to one end of the rotating shaft 32, and a fixed member located above the rotating disk 4 and fitted to the valve casing 22. A disk 5 is provided. The opening degree of the passage area of the internal passage 21 is changed by the rotating disk 4 and the fixed disk 5 to adjust the gas flow rate.
[0016]
As shown in FIG. 2, four holes 51, 52, 53, and 54, which are first communication holes, are formed on the same circumference with different opening areas from each other in the fixed disk 5. Holes 52, 53, and 54 other than the first hole 51 that determine the minimum gas flow rate are formed continuously.
[0017]
When the rotating shaft 32 rotates by a predetermined angle, the rotary disk 4 has one ellipse that matches the holes 51, 52, 53, and 54 of the first communication hole and allows communication between the internal passage 21 and the gas passage 11. A second communication hole 41 is formed.
[0018]
Here, the minimum gas flow rate at which the flame of the gas burner does not extinguish differs depending on the type of fuel gas used and the capacity of the gas burner. For this reason, it is preferable that the minimum gas flow rate can be set for each different gas appliance such as the type of fuel gas used.
[0019]
In the present embodiment, a bypass passage 13 that connects the first hole 51 of the first communication hole to the gas passage 11 is provided in the apparatus main body 12, and an orifice 14 that sets a minimum gas flow rate is inserted into the bypass passage 13. . Therefore, by replacing the orifice 14, the minimum gas flow rate corresponding to the type of the fuel gas and the capacity of the gas burner can be set.
[0020]
If the second communication hole 41 does not match any one of the first communication holes 51, 52, 53, 54, the internal passage 21 is closed and the supply of the fuel gas to the gas passage 11 is stopped (FIG. 2 (a)).
[0021]
On the other hand, the motor 3 is driven to rotate the rotating disk 4, and the opening is changed by matching the second communication hole 41 with one of the first communication holes 51, 52, 53, 53, 54. The gas flow to the gas burner is adjusted. In consideration of safety and the like, an electromagnetic safety valve 6 as an on-off valve is provided upstream of the gas inlet 23 (see FIG. 1).
[0022]
The gas passage 11 is provided with a pressure sensor 7 for detecting a secondary pressure in the gas passage 11. The pressure sensor 7 has an introduction tube 72 inserted through a sealing member 71 into a branch passage 11 a provided in a vertical direction from the gas passage 11, and a sealed empty space 73 communicated through the introduction tube 72. A resin thin plate (not shown) is incorporated therein.
[0023]
When the fuel gas flows through the gas passage 11, the thin plate is deformed by the secondary pressure of the fuel gas introduced into the empty space 73 through the introduction tube 72, and the amount of distortion of the thin plate 11 at that time is detected. In this case, in order to convert the amount of strain into a resistance value and convert the change in the resistance value into a voltage, a bridge circuit 8 as pressure detecting means including a pressure sensor 7 is provided as shown in FIG. 3 (FIG. 3). reference).
[0024]
The voltage output from the bridge circuit 8 is amplified by the OP amplifier 81 and input to a microcomputer that controls the operation of the gas stove, and the secondary pressure in the gas passage 11 is calculated from the voltage. When the pressure in the gas passage 11 is the atmospheric pressure, the output voltage Vo becomes 0 V even when the predetermined voltage E is input, and the resistance value changes by flowing the fuel gas through the gas passage 11 and deforming the thin plate. Then, the pressure sensor 7 and the resistors R1, R2, and R3 were set so that the output voltage Vo increased.
[0025]
In the present embodiment, for example, the gas valve 2 is controlled by a light touch switch provided on the operation panel of the gas stove so that the heat of the gas burner can be set in four stages from the heat 1 to the heat 4.
[0026]
Here, in the initial state, the secondary pressures respectively corresponding to the thermal power 1, the thermal power 2, the thermal power 3 and the thermal power 4 are set as follows. That is, as shown in FIG. 2B, the motor is rotated to make the second communication hole 41 coincide with the first hole 51 of the first communication hole, and the pressure sensor 7 detects the secondary pressure at that time. Next, the second communication hole 41 is matched with the third hole 53 and the fourth hole 54 of the first communication hole (see FIG. 2E), and the secondary pressure at that time is detected by the pressure sensor 7.
[0027]
Next, by dividing the parallel roots of these secondary pressures into three equal parts and squaring them, the secondary pressures corresponding to thermal power 2 and thermal power 3 are calculated, and the secondary pressures of each thermal power from thermal power 1 to thermal power 4 are calculated. It is set as an initial value and stored in the microcomputer. When the heating power is changed by pressing the light touch switch, the secondary pressure is detected by the pressure sensor 7 and the motor 3 is controlled so that the detected secondary pressure matches the set secondary pressure set as the initial value.
[0028]
In this case, with the thermal power 1, the second communication hole 41 and the first hole 51 of the first communication hole coincide with each other, and a minimum gas flow rate that does not extinguish the flame of the gas burner flows (see FIG. 2B). In the thermal power 2, the second communication hole 41 matches the first hole 51 and the second hole 52 of the first communication hole (see FIG. 2 (c)), and the flow rate of the fuel gas for reducing the thermal power of the gas burner is reduced. It flows to the gas passage 11. With the thermal power 3, the second communication hole 41 matches the second hole 52 and the third hole 53 of the first communication hole (see FIG. 2D), and with the thermal power 4, the second communication hole 41 and the first communication hole are used. The third hole 53 and the fourth hole 54 coincide with each other (see FIG. 2E), and the fuel gas flows into the gas passage 11 at a flow rate that makes the heat of the gas burner medium and high, respectively.
[0029]
Referring to FIG. 4, even if the output voltage Vo to the microcomputer is set to 0 V when the pressure in the gas passage 11 is atmospheric pressure, variations in characteristics of the individual pressure sensors 7 and changes in temperature around the pressure sensors 7 may occur. Depending on the situation, the position may change to the plus side (line a) or the minus side (line b).
[0030]
Here, for example, when the voltage Vo changes to the minus side as shown by the line b in FIG. 4, the polarity of the voltage Vo output according to the pressure change in the gas passage 11 changes to the plus side. In order to amplify such a change in polarity, a separate power supply for amplifying the positive or negative voltage is required, which complicates the circuit configuration and increases the cost.
[0031]
Referring to FIGS. 3 and 5, in the present embodiment, one of the resistors constituting bridge circuit 8 is made a variable resistor and a volume switch (not shown) for changing the resistance value of variable resistor R3. Zu) was provided.
[0032]
Then, after the gas flow control device 1 is assembled into the gas stove, the output voltage Vo to the microcomputer is increased via the volume switch while the pressure in the gas passage 11 is at the atmospheric pressure. The resistance value of the variable resistor R3 is offset and corrected so that the polarity increases along with the increase (from line c to line d) so that the polarity of the output voltage Vi to the OP amplifier 81 is not inverted. Note that the amount of the resistance value to be offset to the plus side may be set in consideration of, for example, variations in the characteristics of the pressure sensor 7 used.
[0033]
Thus, even if the output voltage Vo from the bridge circuit 8 changes in the negative direction due to the influence of the individual characteristics of the pressure sensor 7, the ambient temperature, and the like, the output voltage Vo is constantly maintained when adjusting the heating power of the gas burner. Since it is on the positive side (line e), only one power supply is required to amplify the output voltage Vi, and the circuit configuration can be simplified. Further, the pressure sensor 7 whose output voltage largely fluctuates to the plus and minus sides due to the characteristics can be used.
[0034]
【The invention's effect】
As described above, the gas flow control device of the present invention has an effect that the pressure detecting means can have a simple circuit configuration and can be manufactured at low cost.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view illustrating a gas flow control device according to the present invention. FIGS. 2A to 2E are diagrams illustrating flow rate adjustment by a gas valve. FIG. 3 is a diagram illustrating a pressure detection circuit. 4) A graph for explaining a change in the characteristic of the pressure sensor due to a change in the characteristic or the ambient temperature.
DESCRIPTION OF SYMBOLS 1 Gas flow control device 11 Gas passage 7 Pressure sensor 8 Bridge circuit R1, R2, R3 Resistance

Claims (2)

A pressure sensor provided in a gas passage communicating with the gas injection nozzle and having a resistance value that changes according to the pressure of the fuel gas in the gas passage; and a bridge circuit that converts a change in the resistance value of the pressure sensor into a voltage. Amplifying means for amplifying the output voltage from the bridge circuit, and a flow control provided in the gas passage based on the output voltage amplified by the amplifying means, for changing a passage area of the gas passage and adjusting a gas flow rate. In the gas flow control device for controlling the means,
Resistance value changing means for changing a resistance value of at least one of the resistors constituting the bridge circuit, and the resistance value changing means corrects the output voltage in a state where the pressure in the gas passage is atmospheric pressure; In this case, the output voltage is offset and corrected to the polarity side that increases as the pressure in the gas passage increases, so that the polarity of the voltage output to the amplifying unit is not inverted. Gas flow control device. 2. The gas flow control device according to claim 1, wherein said resistance value changing means is a variable resistance.

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