JP6716927B2 - Combustion equipment - Google Patents

Description

The present invention relates to a combustion device such as a gas stove or a gas water heater provided with an electromagnetic valve such as an electromagnetic safety valve or a source gas electromagnetic valve.

In a combustion device such as a gas stove or a gas water heater, a microcomputer is generally used as a control center of a control controller that controls combustion. The microcomputer operates with a clock generated by an internal or external oscillator circuit, and the clock is also used to measure flame detection confirmation time and other various timers, and to detect by dynamic scanning of various operation switches. Since the stability of combustion is ensured and the avoidance of gas leakage and high temperature hot water is performed by the control based on, the accuracy and stability of the clock frequency are required at a high level.

For example, when the clock frequency becomes higher, the flame detection confirmation time becomes shorter and the thermocouple voltage is not confirmed to rise sufficiently, so there is a concern that misfire errors may occur frequently. On the other hand, when the clock frequency becomes low, the reception sensitivity of the switch for performing the combustion stop operation becomes poor, and it is difficult for the user operation to stop the combustion accurately and promptly. It is also assumed that the actual time becomes longer, for example, the time until the safe operation starts becomes longer.

As a method of ensuring the accuracy and stability of the clock frequency, there is a method of mounting two or more oscillation circuits and mutually monitoring or compensating with the clocks generated by the respective oscillation circuits (see, for example, Patent Document 1). It becomes a factor of cost increase.

Further, as disclosed in Patent Document 2 below, for example, in a combustion device such as a battery-powered gas stove, a microcomputer is used to watchdog the computer so that the electromagnetic valve is automatically closed when the microcomputer that performs combustion control runs out of control. The pulse is output to the solenoid valve drive circuit. The drive circuit outputs the watchdog pulse to the control terminal (base in the case of a bipolar transistor) of the semiconductor switching element via the RC series differentiating circuit, so that the electromagnetic wave is generated only when the watchdog pulse is normally output. The valve is electrically connected to the power source battery, and when the watchdog pulse becomes High fixed or Low fixed due to the runaway of the microcomputer, the solenoid valve is cut off from the power source.

The watchdog pulse is also generated based on the clock generated by the oscillator circuit. However, if an abnormality occurs in the clock frequency, the cycle of the watchdog pulse also becomes abnormal, and the time constant of the RC series differentiating circuit Depending on the relationship, the power supply to the solenoid valve may become unstable even though the watchdog pulse is being output.

In addition, by adopting a microcomputer with a built-in on-chip oscillator (clock generation circuit) as the control center of the control unit and not providing a crystal oscillation circuit outside the microcomputer using a crystal oscillator, parts of the control unit of the combustion equipment Although it is possible to reduce the size and cost by reducing the number of points and the mounting area, frequency abnormalities are present in an environment where combustion equipment is rarely used and is placed near a high-heat combustion section and performs daily combustion operation. It is necessary to take further measures against

Japanese Patent No. 5171379 JP-A-8-270822

The present invention has been made in view of the above circumstances, and an object thereof is to take measures against clock frequency abnormality in a control unit of a combustion device.

The present invention has taken the following technical means in order to achieve the above object.

That is, the present invention includes a combustion unit, a control unit that controls a combustion operation of the combustion unit, and a capacitor, and the control unit is driven by a clock generated by a clock oscillation circuit and is based on the clock. In a combustion device in which a pulse signal is generated and output to the capacitor and the capacitor is charged by the pulse signal, the control unit controls the clock based on the relationship between the output pulse number of the pulse signal and the charging voltage of the capacitor. Is configured to be able to perform a clock frequency diagnostic process for determining whether the frequency of the clock is normal, and when the clock frequency diagnostic process determines that the frequency of the clock is not normal, It is characterized in that the combustion operation is prohibited or a predetermined abnormality notification process is performed (Claims 1 and 5 ).

According to such a combustion device of the present invention, when the control unit such as a microcomputer generates a pulse signal based on the driving clock and outputs the pulse signal to the capacitor to charge the capacitor, the number of output pulses of the pulse signal and the capacitor are increased. The charging unit has a certain correlation with the charging voltage of, and the charging voltage of the capacitor also fluctuates according to the fluctuation of the pulse width (pulse period) of the pulse signal, and the control unit is controlled to output the pulse signal. By configuring the clock frequency diagnostic processing to determine whether the frequency of the clock is normal based on the relationship between the number of pulses and the charging voltage of the capacitor, the pulse width and pulse period of the pulse signal The occurrence of an abnormality in the underlying clock frequency can be detected. If it is determined that the combustion operation of the combustion unit is prohibited when the clock frequency is determined to be abnormal, unstable combustion operation can be avoided in advance, and a predetermined abnormality notification process can be performed. By doing so, it can be notified that the clock frequency is not normal. The abnormality notification process may be, for example, a buzzer or display device built into the combustion device itself, or an error signal sent to a remote control or other external display device connected to the combustion device. The processing may be performed.

In the above-described combustion device of the present invention, the control unit may be configured to execute the clock frequency diagnosis processing at the start of combustion operation control (claims 2 and 6 ). According to this, when the clock frequency is diagnosed to be abnormal by the clock frequency diagnosis processing, the combustion operation can be stopped, and the unstable combustion operation due to the clock frequency abnormality is prevented in advance. it can.

Further, the control unit may be configured to execute the clock frequency diagnosis process at the end of combustion operation control (claims 3 and 7 ). According to this, it is possible to diagnose whether or not the clock frequency is normal in the state where the temperature is raised by the heat generation of the control unit itself due to the continuous operation or the heat transferred from the combustion unit during the combustion operation. Appropriate post-processing can be performed, such as detecting a clock frequency abnormality when the temperature rises that cannot be detected by the diagnosis at the start of control, and prohibiting the start of combustion operation after such abnormality occurs (safe stop mode). ..

The control unit further includes a forced discharge circuit that discharges the capacitor when a discharge command signal is input, and the control unit outputs the discharge command signal to the forced discharge circuit before execution of the clock frequency diagnosis process. It can be configured as follows (claims 4 and 8 ). According to this, by forcibly discharging the capacitor before executing the clock frequency diagnosis process, it is possible to avoid erroneous diagnosis due to the voltage already charged in the capacitor.

Further, the clock frequency diagnosis processing may be to determine whether or not the frequency of the clock is normal based on the charging voltage of the capacitor when the pulse signal of a predetermined number of pulses is output ( Claims 1, 9 ). According to this, it can be determined whether or not the charging voltage exceeds a predetermined threshold value, and for example, the control unit can be configured to determine based on the output signal of the comparator that compares the charging voltage and the threshold value.

In addition, the clock frequency diagnosis processing determines whether the frequency of the clock is normal based on the number of output pulses of the pulse signal when the pulse signal is output until the charging voltage of the capacitor reaches a predetermined voltage. It may be determined (claim 10 ). According to this, it can be determined that the clock frequency is higher than the normal value when the number of output pulses is higher than the normal range, while the clock frequency is the normal value when the number of output pulses is lower than the normal range. It can be determined that it is lower than.

Also, a solenoid valve that opens and closes a fuel supply path to the combustion unit, a switching circuit that can be turned on so as to connect the solenoid valve to a power source, and that shuts off the solenoid valve from the power source during an off operation, and the pulse signal. And a differentiating circuit for differentiating and supplying the pulse signal to the capacitor, wherein the switching circuit continuously outputs the pulse signal based on the clock having a frequency within a normal range to the capacitor used for the clock frequency diagnostic processing. The capacitor may be configured to be turned on by the charging voltage of the capacitor supplied to the capacitor (Claim 5 ). According to this, when the circuit that performs the clock frequency diagnosis process and the control unit runaway and the pulse signal becomes fixed at High or Low, the electromagnetic valve is forcibly closed by shutting off the power supply to the electromagnetic valve. It is possible to share a part of the circuit configuration with the safety circuit for the purpose of reducing the number of components, the board mounting area, and the cost while mounting these functions.

As described above, according to the present invention, even if only one clock oscillation circuit is mounted, the combustion operation is performed in a state where the combustion is unstable due to the clock frequency abnormality. It can be avoided.

It is a circuit diagram which shows the main circuit parts of the control part of the combustion equipment which concerns on one Embodiment of this invention. It is a voltage waveform diagram of a circuit predetermined portion at the time of clock frequency diagnosis processing when the clock frequency is normal (cycle 10 ms). It is a voltage waveform diagram of a circuit predetermined portion at the time of clock frequency diagnosis processing when the clock frequency is abnormal (cycle 20 ms). It is a voltage waveform diagram of a circuit predetermined portion at the time of clock frequency diagnosis processing when the clock frequency is abnormal (cycle 5 ms).

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows a schematic configuration of a drive circuit for a solenoid valve such as a source gas solenoid valve or a safety valve in a gas combustion device such as a gas stove or a gas water heater.

The combustion device includes a combustion unit 1 mainly composed of a gas burner, a solenoid valve 3 for opening and closing a fuel supply path 2 to the combustion unit 1, and a combustion operation of the combustion unit 1 by controlling an opening/closing operation of the solenoid valve 3. The microcomputer 4 as a control unit for controlling, a drive circuit 5 for outputting a drive voltage to the solenoid valve 3 when the solenoid valve drive command signal and the watchdog pulse signal output from the microcomputer 4 are input, the microcomputer 4 and the solenoid valve 3 The power supply circuit serves as the power supply 6. As the power supply circuit, for example, a DC/DC converter that outputs a predetermined voltage (for example, 5 V) based on the battery voltage can be used.

As the microcomputer 4, for example, one having an on-chip oscillator (clock oscillation circuit) built therein may be adopted, or a clock oscillation circuit having an external crystal oscillator may be separately provided. The microcomputer 4 is driven by the clock generated by the internal or external clock oscillator circuit. In the gas combustion equipment, a clock frequency of several MHz to several tens of MHz is generally used.

Further, the microcomputer 4 has a WD signal output terminal capable of outputting a watchdog pulse signal, which is a rectangular wave pulse signal generated based on a drive clock, and a solenoid valve drive command output terminal capable of outputting a solenoid valve drive command. A forced-off output terminal for forcibly stopping the solenoid valve 3, a reference voltage switching signal output terminal, and a comparison input terminal are provided.

The drive circuit 5 includes first and second switching circuits S1 and S2 that can be turned on so that the solenoid valve 3 is electrically connected to the power source 6 and that shuts off the solenoid valve 3 from the power source 6 when the solenoid valve 3 is turned off. The first and second switching circuits S1 and S2 are connected in series between the power source 6 and the solenoid valve 3, and the solenoid valve 3 is conducted to the power source 6 only when both switching circuits S1 and S2 are turned on. Drive voltage based on the power supply voltage is supplied to the solenoid valve 3, and when either of the switching circuits S1 and S2 is in the off operation, the solenoid valve 3 is cut off from the power supply 6 and the drive voltage is not output to the solenoid valve 3. Is configured.

The first switching circuit S1 is mainly composed of two semiconductor switching elements Q1 and Q2, and one switching element Q1 is a pnp-type transistor provided in the middle of a power supply path from the power supply 6 to the solenoid valve 3. It is configured. The emitter of the switching element Q1 is connected to the power source 6 side, and the collector is connected to the solenoid valve 3 side.

Another switching element Q2 is composed of an npn-type transistor whose collector is connected to the base of the switching element Q1 via a base resistor R1. The emitter (ground terminal) of the switching element Q2 is grounded to the ground (negative electrode of the power supply 6 in the illustrated example). The base of the switching element Q2 becomes the control terminal of the first switching circuit S1.

A smoothing capacitor C1 capable of holding a control voltage for turning on the switching element Q2 is connected to a control terminal of the first switching element S1 via a base resistor R2, and a negative terminal of the smoothing capacitor C1. Is grounded to ground. The smoothing capacitor C1 and the WD signal output terminal of the microcomputer 4 are connected via an RC series differentiating circuit 7. As a result, when the watchdog pulse signal is continuously output from the WD signal output terminal, the smoothing capacitor C1 is supplied with a pulse-like current through the differentiating circuit 7, and the smoothing capacitor C1 becomes equal to or higher than the control voltage. When charged, the switching elements Q2 and Q1 are sequentially turned on. On the other hand, when a DC signal that is not a pulse signal is output from the WD signal output terminal, the differentiating circuit 7 cuts off the current supply from the WD signal output terminal to the smoothing capacitor C1 and discharges from the smoothing capacitor C1 to cause a switching element. Q2 and Q1 are turned off.

The control terminal of the switching circuit S1 is connected to the forced off output terminal of the microcomputer 4. In the present embodiment, the forced-off output terminal is composed of an open collector output terminal, the smoothing capacitor C1 is charged at the time of open output, and a Low signal is output as a forced-off command signal so that the smoothed capacitor C1 is charged. It is possible to forcibly discharge the smoothing capacitor C1 by sucking it into the forced off output terminal via the resistor R2.

A diode D1 that cuts a negative voltage is provided between the output of the differentiating circuit 7 and the ground, and a backflow prevention diode D2 is provided between the output of the differentiating circuit 7 and the smoothing capacitor C1. ..

Further, the capacity of the smoothing capacitor C1 is designed with a certain margin with respect to the control voltage. For example, when 2V is required as the charging voltage of the capacitor C1 to turn on the switching element Q2, When fully charged, the charging voltage is set to about 3V. This is because in the clock frequency diagnosis process described later, when the clock frequency and the frequency of the watchdog pulse signal become long, the voltage can be charged to a voltage higher than that in the normal state.

The second switching circuit S2 is mainly composed of one semiconductor switching element Q3. The switching element Q3 is composed of a pnp type transistor, and is connected in series with the switching element Q1 between the power source 6 and the solenoid valve 3. That is, the emitter of the switching element Q3 is connected to the collector of the switching element Q1, and the collector of the switching element Q3 is connected to the solenoid valve 3 side. The base of the switching element Q3 is connected to the solenoid valve ON output terminal of the microcomputer 4 via the base resistor R3. The solenoid valve drive command output terminal is configured by an open collector output terminal in the illustrated example, the switching element Q3 is turned off at the time of open output, and a Low signal output is output as a solenoid valve drive command signal when the solenoid valve 3 is opened. By doing so, the switching element Q3 is turned on.

When both the first and second switching circuits S1 and S2 are turned on, the solenoid valve 3 is electrically connected to the power source 6 through the switching elements Q1 and Q3, and the solenoid valve 3 is driven from the collector output of the switching element Q3. The voltage is output. In order to cut back electromotive force due to switching of the switching element Q3, a diode D3 for cutting negative voltage is connected to the collector output of the switching element Q3.

Further, in the drive circuit 5 of the present embodiment, the frequency of the clock generated by the clock oscillation circuit based on the charging voltage of the smoothing capacitor C1 when the watchdog pulse signal is output by a predetermined number of pulses (for example, only 10 pulses). The microcomputer 4 performs a clock frequency diagnostic process for determining whether the operation is normal when the combustion operation control starts (immediately before the opening operation control of the solenoid valve 3) and when the combustion operation control ends (immediately after the closing operation control of the solenoid valve 3). Is configured to be executable.

In order to enable such clock frequency diagnosis processing, the drive circuit 5 includes a reference voltage generation circuit 8 that generates a reference voltage for comparison with the charging voltage of the smoothing capacitor C1, and the reference voltage generation circuit 8. A comparator 9 for comparing the output reference voltage with the charging voltage of the smoothing capacitor C1 is provided. The output signal of the comparator 9 is input to the comparison input terminal of the microcomputer 4.

The reference voltage generation circuit 8 is configured to be able to change the reference voltage generated by the reference voltage switching signal output from the reference voltage switching output terminal of the microcomputer 4. Specifically, the reference voltage generation circuit 8 is composed of a voltage dividing circuit including three resistors R4, R5, and R6 connected in series, and by dividing the power supply voltage by the voltage dividing circuit, two of the three voltages are generated. The voltage between the two resistors R4 and R5 is output as a reference voltage. Any one of the resistors R5 can be bypassed by a bypass circuit whose electric path is opened and closed by the switching element Q4, and when the microcomputer 4 outputs a HIGH signal (ON signal) as a reference voltage switching signal, the two resistors R4. , R6, the divided reference voltage is output, and when the LOW signal (OFF signal) is output as the reference voltage switching signal, the divided reference voltage is output by the three resistors R4, R5, R6.

FIG. 2 shows measurement points a, b, c, d shown in FIG. 1 when a watchdog pulse signal of 10 pulses is output when the pulse width of the watchdog pulse signal is normal, for example, 10 ms. , E of the voltage waveforms. FIG. 3 shows a similar voltage waveform when the pulse width of the watchdog pulse signal becomes 20 ms due to an abnormality in the clock frequency. FIG. 4 shows a similar voltage waveform when the pulse width of the watchdog pulse signal becomes 5 ms due to an abnormality in the clock frequency.

The charging voltage V(c) of the capacitor C1 immediately after outputting the watchdog pulse signal for 10 pulses is about 2.3 V when the pulse width is 10 ms (see FIG. 2), but the pulse width is 20 ms. Then, the voltage rises to about 2.6 V (see FIG. 3), and drops to about 1.7 V when the pulse width reaches 5 ms (see FIG. 4).

Therefore, for example, the normal range of the charging voltage of the capacitor C1 immediately after outputting the watchdog pulse signal for 10 pulses is set to 2.2V to 2.4V, and the upper limit threshold of this normal range is 2.4V and the lower limit threshold. After the resistance values of the three resistors R4 to R6 are selected so that the output reference voltage can be switched to 2.2 V, the smoothing capacitor C1 is discharged by outputting the forced off output command signal in advance, First, either the upper limit threshold value or the lower limit threshold value is generated by the reference voltage generating circuit 8 and compared with the charging voltage of the smoothing capacitor C1 immediately after outputting the watchdog pulse signal for 10 pulses, and then the smoothing capacitor C1 is discharged again. Then, the reference voltage generation circuit 8 is caused to generate the other threshold value, the watchdog pulse signal for 10 pulses is again output, and the clock frequency is lowered by comparing with the charging voltage of the smoothing capacitor C1 immediately after that. Therefore, even if the pulse width is longer than the upper limit threshold value, or if the pulse width is shorter than the lower limit threshold value due to the higher clock frequency, any abnormality can be detected by the microcomputer 4.

Then, when the microcomputer 4 determines that the clock frequency is abnormal, it is possible to perform appropriate processing such as prohibition of the subsequent combustion operation and error notification, whereby only one clock oscillation circuit is installed. Even when the combustion is not performed, it is possible to prevent the combustion operation from being performed in a state where the combustion is unstable due to the clock frequency abnormality.

The present invention is not limited to the above embodiment, and the design can be changed as appropriate.

For example, in the above-described embodiment, an example in which the comparison determination with both the upper limit threshold and the lower limit threshold is performed has been shown, but only the abnormality that the clock frequency becomes high is compared with only one of the upper limit threshold and the lower limit threshold. Alternatively, the microcomputer 4 may be configured to detect only an abnormality in which the clock frequency becomes low.

Further, in the above-described clock frequency diagnostic processing, an example has been shown in which whether or not the clock frequency is normal is determined based on the charging voltage of the smoothing capacitor C1 when a predetermined number of watchdog pulse signals are output. It is also possible to determine whether or not the clock frequency is normal based on the output pulse number of the pulse signal when the watchdog pulse signal is output until the charging voltage of the smoothing capacitor C1 reaches the predetermined voltage. For example, referring to FIGS. 2 to 4, if the watchdog signal is output until the charging voltage of the smoothing capacitor C1 exceeds 2V, 8 pulses are output when the pulse width is 10 ms and 20 pulses when the pulse width is 20 ms. It is understood that 5 pulses are output, and 10 pulses are output when the pulse width is 5 ms. Therefore, by determining whether or not the number of output pulses is normal by setting the normal range to 7 to 9 pulses, it is possible to determine abnormality by one clock frequency diagnosis process regardless of whether the pulse width is large or small. It can be carried out.

Further, in the above embodiment, the watchdog pulse signal is charged by directly supplying it to the smoothing capacitor C1, but the capacitor is connected to the power supply via an appropriate switching circuit, and this switching circuit is turned on by the watchdog pulse signal. It is also possible to charge by turning on/off the drive by supplying a current from the power supply to the capacitor in a pulse form by the watchdog pulse signal. In this case, the capacitor may be provided only for clock frequency diagnosis.

1 Combustion part 3 Solenoid valve 4 Control part (microcomputer)
5 Solenoid valve drive circuit 6 Power supply 7 Differentiation circuit C1 Capacitor S1 Switching circuit

Claims (10)

A combustion unit, a control unit that controls the combustion operation of the combustion unit, and a capacitor are provided, and the control unit is driven by a clock generated by a clock oscillation circuit, and a pulse signal based on the clock is applied to the capacitor. In a combustion device that produces and outputs, the capacitor is charged by the pulse signal,
The control unit is configured to be able to execute a clock frequency diagnostic process for determining whether or not the frequency of the clock is normal based on the relationship between the number of output pulses of the pulse signal and the charging voltage of the capacitor. Together with the clock frequency diagnosis process, when it is determined that the frequency of the clock is not normal, the combustion operation of the combustion unit is prohibited or a predetermined abnormality notification process is performed ,
The clock frequency diagnostic processing is characterized by determining whether or not the frequency of the clock is normal based on the charging voltage of the capacitor when the pulse signal of a predetermined number of pulses is output. Combustion equipment. The combustion apparatus according to claim 1, wherein the control unit is configured to execute the clock frequency diagnosis processing at the start of combustion operation control. The combustion equipment according to claim 1 or 2, wherein the control unit is configured to execute the clock frequency diagnosis processing at the end of combustion operation control. The combustion device according to claim 1, 2 or 3, further comprising a forced discharge circuit that discharges the capacitor when a discharge command signal is input from the control unit, the control unit before executing the clock frequency diagnosis process. A combustion device, which is configured to output the discharge command signal to the forced discharge circuit. A combustion unit, a control unit that controls the combustion operation of the combustion unit, and a capacitor are provided, and the control unit is driven by a clock generated by a clock oscillation circuit, and a pulse signal based on the clock is applied to the capacitor. In a combustion device that produces and outputs, the capacitor is charged by the pulse signal,
The control unit is configured to be able to execute a clock frequency diagnostic process for determining whether or not the frequency of the clock is normal based on the relationship between the number of output pulses of the pulse signal and the charging voltage of the capacitor. Together with the clock frequency diagnosis process, when it is determined that the frequency of the clock is not normal, the combustion operation of the combustion unit is prohibited or a predetermined abnormality notification process is performed ,
A solenoid valve that opens and closes a fuel supply path to the combustion section, a switching circuit that can be turned on to connect the solenoid valve to a power source, and that shuts off the solenoid valve from the power source during an off operation, and the pulse signal is differentiated. The switching circuit continuously supplies the pulse signal based on the clock having a frequency within a normal range to the capacitor used for the clock frequency diagnosis processing. The combustion device is configured to be turned on by the charging voltage of the capacitor due to the above . The combustion equipment according to claim 5, wherein the control unit is configured to execute the clock frequency diagnosis processing at the start of combustion operation control . The combustion equipment according to claim 5 or 6, wherein the control unit is configured to execute the clock frequency diagnosis processing at the end of combustion operation control . The combustion device according to claim 5, 6 or 7, further comprising: a forced discharge circuit that discharges the capacitor when a discharge command signal is input from the control unit, the control unit before executing the clock frequency diagnosis process. A combustion device, which is configured to output the discharge command signal to the forced discharge circuit. In the combustion equipment according to any one of claims 5 to 8, in the clock frequency diagnostic processing, the frequency of the clock is determined based on a charging voltage of the capacitor when the pulse signal of a predetermined number of pulses is output. Combustion equipment characterized by determining whether or not it is normal. The combustion device according to any one of claims 5 to 8, wherein the clock frequency diagnostic process outputs the number of pulses of the pulse signal when the pulse signal is output until the charging voltage of the capacitor reaches a predetermined voltage. A combustion device for determining whether or not the frequency of the clock is normal based on the above.

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