JPH04225723A - Shuttdown control device - Google Patents

Abstract

PURPOSE:To prevent excess current from flowing to a switching device which prohibits the output of a shutdown signal and drives a drive coil when the drive coil of the shutdown valve is short-circuited with regards to a shutdown control device which automatically shutdowns gas when any operational failure, such as gas flow rate installed to an automatic shutdown function-equipped gas meter. CONSTITUTION:The shutdown control device comprises a control means 14 which outputs a shutdown signal which decides an operational failure of a gas flow rate or the like and actuates a switching device 17 for driving a drive coil 7 during failure detection, shutdown signal control means 24 and 24 which trigger a shutdown signal output from the control means 14, actuates a switching device 17 momentarily, decides a short circuit of the drive coil 7 and prohibit the application of the shutdown signal to the switching device 17 when the short circuit of the aforesaid drive coil is detected.

Description

[Detailed description of the invention]

[Object of the invention]

0002

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shutoff control device that is installed in a gas meter with an automatic shutoff function and automatically shuts off gas when an abnormality such as a gas flow rate is detected.

0003

2. Description of the Related Art FIG. 4 shows an example of the configuration and basic functions of a conventional gas meter with an automatic shutoff function.

A gas meter with an automatic cutoff function includes a gas meter body 1, a seismic sensor 2 for detecting earthquakes, a pressure sensor 4 for detecting a drop in gas pressure, a cutoff valve 6 for cutting off gas, A control unit 16 having a shutoff valve return device 8, a flow rate sensor 9 for detecting a gas flow rate, a display device 13, a one-chip microcomputer 14 as a control means, a battery 15, and the like are incorporated.

[0005] Then, the one-chip microcomputer 14 of the control unit 16 determines whether there is an abnormality in the flow rate data detected by the flow rate sensor 9, and thereby operates the shut-off valve 6 via a shut-off valve drive circuit, which will be described later, to shut off the gas. It has the function of Furthermore, in order to prevent gas accidents from occurring, the gas meter with automatic shutoff function has the following five basic functions (abnormality judgment program) programmed into the one-chip microcomputer 14 in the control unit 16.

[0006] ② Determine an abnormality in the gas flow rate and shut off the gas.

[0007] ■ Cutting off the gas after determining that the gas equipment has been used for an abnormally long time.

[0008] Gas is shut off in the event of a large earthquake based on the signal from the seismic sensor 2.

(2) Cut off the gas when an abnormal drop in the gas supply pressure is detected.

■ Gas is cut off by external signals from city gas alarms (gas leak alarms), incomplete combustion alarms, etc.

These five basic functions are operated by programs of the one-chip microcomputer 14 within the control unit 16.

FIG. 5 shows an example of a shutoff valve drive circuit. The shutoff valve 6 is driven by the I/O port P1 of the one-chip microcomputer 14. When the one-chip microcomputer 14 detects an abnormality in the gas flow rate, it turns on the I/O port P1 (low level) for a certain period of time, turns on the transistor 17 as a switching element, and sends the signal to the drive coil 7 of the cutoff valve 6. Voltage is supplied from a battery 15 to operate the shutoff valve 6.

[0013]

[Problems to be Solved by the Invention] Conventionally, when the drive coil 7 of the cutoff valve 6 is short-circuited, when an attempt is made to operate the cutoff valve 6, the resistance of the drive coil 7 of the cutoff valve 6 is not present. An overcurrent will flow. In addition, if the shutoff valve drive signal remains in the ON state due to runaway of the one-chip microcomputer 14, etc., the transistor 17
The overcurrent continues to flow. Therefore, in the worst case, there is a problem that the transistor 17 may be burnt out due to heat generation.

[0014] Therefore, the present invention detects a short circuit in the drive coil of the shut-off valve when the shut-off valve is driven, and if a short circuit is detected, the output of a shut-off signal is prohibited to prevent overcurrent from flowing to the switching element. The purpose of the present invention is to provide a shutoff control device that can

[Configuration of the invention]

[0016]

[Means for Solving the Problems] In order to solve the above problems, the present invention provides a cutoff control device that is installed in a gas meter and operates a cutoff valve to cut off gas when an abnormality such as a gas flow rate is detected. , a switching element that drives a drive coil of the shutoff valve; a control means that determines an abnormality in the gas flow rate or the like and outputs a shutoff signal that turns on the switching element when an abnormality is detected; and a shutoff signal output from the control means. a cutoff signal control means that instantaneously turns on the switching element using the trigger as a trigger to determine a short circuit in the drive coil, and prohibits application of the cutoff signal to the switching element when a short circuit in the drive coil is detected. The main point is to have the following.

[0017]

[Operation] The control means determines whether there is an abnormality in the gas flow rate or the like, and when an abnormality is detected, a cutoff signal is output to turn on the switching element. In the cutoff signal control means, a voltage is applied to the drive coil of the cutoff valve for a short time using the cutoff signal as a trigger, and a short circuit of the cutoff valve drive coil is detected by the voltage generated at both ends of the cutoff valve drive coil. If there is a short circuit, the cutoff signal output from the control means is inhibited to prevent overcurrent from flowing through the switching element.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the present invention will be described below with reference to FIGS. 1 to 3.

1 to 3 that are the same or equivalent to the equipment, circuit elements, etc. in FIGS. 4 and 5 are designated by the same reference numerals, and redundant explanation will be omitted.

FIG. 1 shows a shutoff control device (shutoff valve drive circuit)
This figure shows the overall configuration of a gas meter with automatic shutoff function. A display device 18 centered around a one-chip microcomputer 14 as a control means to display the reason for shutoff, a test switch 19 to perform a shutoff function test, and a pressure sensor input circuit 5 to input a detection signal from the pressure sensor 4. , a seismic sensor input circuit 3 for inputting the detection signal from the seismic sensor 2, a reed switch 11 for detecting the flow rate pulse in the flow rate sensor 9, and a flow rate pulse input for inputting the detected flow rate pulse. A circuit 12, a gas leak alarm input circuit 22 for detecting a signal from an alarm 21 installed outside the gas meter, and a voltage drop determination circuit 23 for detecting a voltage drop in the battery 15 are incorporated. A short-circuit determination circuit 24 for detecting a short circuit in the drive coil 7 and a cut-off signal control circuit 25 for controlling and driving the cut-off valve 6 based on a cut-off signal from the one-chip microcomputer 14 are incorporated.

FIG. 2 shows a portion of the cutoff valve drive circuit including the above-mentioned short circuit determination circuit 24 and cutoff signal control circuit 25. The shutoff valve drive circuit is one-chip microcomputer 1.
The shutoff valve 6 is activated for a short period of time triggered by the shutoff signal from the shutoff valve 6.
A voltage is applied to the drive coil 7 of the short circuit determination circuit 24.
A voltage generated across the cutoff valve drive coil 7 is introduced to determine whether the cutoff valve drive coil 7 is short-circuited. If a short circuit is detected, the one-chip microcomputer 14
The cut-off signal output from the transistor 17 is inhibited by the cut-off signal control circuit 25 to prevent overcurrent from flowing through the transistor 17. Therefore, the short judgment circuit 2
4 and the cutoff signal control circuit 25 constitute a cutoff signal control means that prohibits the application of the cutoff signal to the transistor 17 when a short circuit in the drive coil 7 is detected.

Next, a specific circuit configuration example of the above-mentioned shutoff valve drive circuit and its operation will be described using FIG.

The cutoff valve drive circuit includes a one-chip microcomputer 14 that detects an abnormality in the gas flow rate and outputs a cutoff signal;
A transistor 17 that drives the drive coil 7 of the cutoff valve, a capacitor C2 that turns on the transistor 17 instantaneously when the cutoff signal outputted from the one-chip microcomputer 14 rises, and a cutoff signal outputted from the one-chip microcomputer 14. An inverter 26 and a NAND gate 2 for prohibiting the operation when determining a short circuit in the cutoff valve drive coil 7.
It is composed of 7 mag.

Next, its operation will be explained.

First, the operation in a normal case where the drive coil 7 of the cutoff valve 6 is not short-circuited will be explained.

The one-chip microcomputer 14 operates the I/O to operate the shutoff valve 6 when detecting an abnormality in the gas flow rate or the like.
A cutoff signal (low active) with a constant pulse width is output from port P1. The cutoff signal (low active) output from the one-chip microcomputer 14 is connected to the capacitor C.
2, the shutoff valve driving transistor 17 is momentarily turned to O.
A voltage is momentarily applied to the drive coil 7 of the shutoff valve 6. At this time, if the drive coil 7 is not short-circuited, a voltage will be generated across the drive coil 7. In other words, point A in FIG. 3 is at H level. The signal at point A is N
It is input to the input IN1 of the AND gate 27, and when the A point becomes H level, the input IN1 of the NAND gate 27 also becomes H level.
level.

On the other hand, the cutoff signal output from the one-chip microcomputer 14 is input to the input IN2 of the NAND gate 27 via the inverter 26. therefore,
When the input IN1 of the NAND gate 27 is at H level, the cutoff signal output from the one-chip microcomputer 14 is input to the base of the transistor 17 via the inverter 26 and the NAND gate 27, and the cutoff signal ( ON only for the duration of the pulse width (low/active)
I will let you do it.

Next, the operation when the drive coil 7 of the cutoff valve 6 is short-circuited will be explained.

Similarly to the above, when the one-chip microcomputer 14 detects an abnormality in the gas flow rate, etc., and outputs a cutoff signal (low active) with a constant pulse width from the I/O port P1, the transistor 17 is activated via the capacitor C2. momentarily O
N, and voltage is momentarily applied to the shutoff valve drive coil 7. At this time, if the cutoff valve drive coil 7 is short-circuited, no voltage is generated across the cutoff valve drive coil 7. Therefore, the voltage level at point A remains at L level. When the voltage level at point A is at the L level, the input IN1 of the NAND gate 27 also goes to the L level, and the cutoff signal output from the one-chip microcomputer 14 is prohibited from being output by the NAND gate 27, so the transistor 17 is not turned on. It turns out. That is, the transistor 17 is momentarily turned on by the capacitor C2 when the cutoff signal (low active) is output, but is not turned on thereafter even if the cutoff signal is output.

As described above, according to the cutoff control device of this embodiment, if the drive coil 7 of the cutoff valve 6 is not short-circuited, the cutoff signal outputted from the one-chip microcomputer 14 causes the cutoff valve drive transistor 17 to be activated. By turning on the shutoff valve 6, the shutoff valve 6 can be reliably operated.

On the other hand, when the drive coil 7 of the cutoff valve 6 is short-circuited, the transistor 17 is activated when the cutoff signal (low active) is output from the one-chip microcomputer 14 (at the rising edge of the cutoff signal). It is only turned on momentarily, and the time during which overcurrent flows to the transistor 17 can be made very short. The ON time of the transistor 17 is determined by the time constants of the capacitor C2 and the resistors R1 and R2, so by setting the ON time so that it is less than the maximum rating of the transistor 17, the transistor 17 can be turned on even if the cutoff valve driving coil 7 is short-circuited. 17 can be minimized. In addition, in the unlikely event that the one-chip microcomputer 14 malfunctions, the cutoff signal may be
Even if the output continues to be output from port P1, if the cutoff valve drive coil 7 is short-circuited, the transistor 17 will not turn on, resulting in the problem of heat generation and burnout due to overcurrent. Must not be.

[0032]

[Effects of the Invention] As explained above, according to the present invention, a short-circuit in the drive coil is determined by instantaneously turning on the switching element using a cutoff signal output from the control means as a trigger when an abnormality such as a gas flow rate is detected. When a short circuit in the drive coil is detected, the application of a cutoff signal to the switching element is prohibited, which prevents overcurrent from flowing to the switching element and prevents thermal damage. I can do it.

[Brief explanation of the drawing]

FIG. 1 is a block configuration diagram showing the overall configuration of a gas meter with an automatic shutoff function incorporating an embodiment of a shutoff control device according to the present invention.

FIG. 2 is a block diagram showing an embodiment of a shutoff control device according to the present invention.

FIG. 3 is a circuit diagram showing a specific example of the circuit configuration of the embodiment of FIG. 2;

FIG. 4 is a block configuration diagram showing a conventional gas meter with an automatic shutoff function.

FIG. 5 is a circuit diagram showing a cutoff valve drive circuit in the conventional example of FIG. 4;

[Explanation of symbols]

6 Shutoff valve 7 Drive coil 14 One-chip microcomputer (control means) 17 Transistor (switching element) 24 Short-circuit determination circuit 25 Shut-off signal control circuit that constitutes shut-off signal control means together with the short-circuit determination circuit

Claims (1)

[Claims] 1. A cutoff control device that is installed in a gas meter and operates a cutoff valve to cut off gas when an abnormality in the gas flow rate or the like is detected, the control device comprising: a switching element that drives a drive coil of the cutoff valve; a control means that determines an abnormality in the flow rate, etc., and outputs a cutoff signal that turns on the switching element when the abnormality is detected; and a control means that instantly turns on the switching element using the cutoff signal output from the control means as a trigger, and controls the drive coil. and a cutoff signal control means for determining a short circuit in the drive coil and prohibiting application of the cutoff signal to the switching element when a short circuit in the drive coil is detected.