JPH025976B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a control device for a combustion appliance such as an oil fan heater.

Structure of conventional example and its problems As shown in FIG. 5, a conventional combustion appliance, for example, an oil fan heater, has a fixed tank 3 and a burner unit 4 inside a main body formed of an exterior 1 and a bottom plate 2. Combustion gas A burned in the burner unit 4 is blown out together with room air B from a louver 7 as warm air C by a fan 6 attached to a blower motor 5, and is used to heat the room.

FIG. 3 shows an example of a control circuit for such a combustor. In FIG. 3, a current fuse 9 is connected in series to an AC power source 8, and a combustion control circuit 10 mainly including a microcomputer (hereinafter referred to as microcomputer) 11 is connected between busbars a and b. A series circuit of the heater 13 for vaporizing the kerosene supplied to the burner 4 and the contact 12a of the relay 12, a parallel circuit of the blower motor 5 and the burner motor 14 that sends combustion air into the burner 4, and a contact 15a of the relay 15. A series circuit with the igniter 16, which has a built-in timer element that operates for a certain period of time when power is supplied and is cleared when the power is cut off, supplies kerosene to the vaporization chamber (not shown) in the burner 4. A parallel circuit with the pump circuit 17 and the contact 18a of the relay 18
The series circuits are connected in parallel.
Further, the combustion control circuit 10 is supplied with power by reducing and insulating the effective current voltage applied between the bus lines a and b using a power transformer 19. The secondary side of the power transformer 19 is connected to the AC terminal side of a diode bridge 20, while the base of a transistor 22 is connected to one AC terminal side of the diode bridge 20 via a resistor 21 to form a waveform shaping circuit. It consists of Furthermore, the collector of the transistor 22 is connected to the input terminal Si of the microcomputer 11. The bus C output from the positive terminal side of the diode bridge 20 includes a smoothing capacitor 23, a relay 12 driven by a transistor 24, and a transistor 2.
A relay 15 driven by a transistor 5, a relay 18 driven by a transistor 26, a display circuit 27, and a power failure detection circuit 28 are connected in parallel, and then connected to the input terminal side of a stabilized DC power source 29. The output side of the DC stabilized power supply 29 is connected to the bus d of an auxiliary power supply (hereinafter referred to as a backup power supply) 31 that supplies power to the microcomputer 11 during a power outage via a diode 30 for preventing current backflow during a power outage. There is. A backup power supply 31 connected to one end of the bus d is composed of a series circuit of a current limiting resistor 32 and large capacity capacitors 33, 34, and 35. The switch circuit 36, which is one load connected to the bus d, includes an operation switch 37 that turns the operation ON and OFF, a refueling switch 38 that detects the amount of kerosene remaining in the fixed tank and opens when the amount falls below a certain level, and a fixed The microcomputer 11 inputs the ON/OFF status of the water switch 39, which detects the amount of water accumulated at the bottom of the tank and opens when the amount exceeds a certain level, and the anti-seismic switch 40, which opens when there is vibration such as an earthquake. terminal
It is connected to the microcomputer 11 via signal lines e and f for output to KO and K1. Also, microcontroller 11
A flame rod circuit 41 that detects conditions such as combustion ignition and misfire is connected to the input terminal K2 of the burner, and a flame rod circuit 41 that detects conditions such as combustion ignition and misfire is connected to the input terminal A/D. The connection point between the burner thermistor 42 and the resistor 43 is connected, and the potential at the connection point is input. Reference numeral 44 denotes a clock display, in which the microcomputer 11 counts the number of pulses (clocks) from the waveform shaping circuit input to the input terminal Si of the microcomputer 11 and converts it into a time display.

Next, the operation of the above configuration will be explained. First, when the outlet is inserted and the AC power supply 8 is supplied, the control circuit 10 is energized, and the microcomputer 11 divides the constant frequency determined by the reference oscillator 45 into an appropriate frequency, and presets the frequency according to the divided frequency. The program starts to run one step at a time from the beginning. The operation will be explained based on the flowchart shown in FIG.

First, in step 80, an internal timer of the microcomputer 11, ie, a timer that increases a count value by one each time one command of the program is executed, regardless of the contents of the program, is started. Next, step 81 checks the value of the first counter, and if the value of the first counter indicates a value of 500, the process proceeds to flow A, otherwise branching is performed to proceed to flow B. The first counter is 2m, which will be explained later.
The value is set to increase by 1 every s, and the value of the first counter is 500.
It will move through flow A at a rate of once every second.

Flow A includes a processing group for determining the frequency of the AC power source 8, and step 90 is to check the value of the second counter accumulated as a result of the work in step 85, which will be described later. Depending on whether it is large or small, either step 91, which performs 60Hz processing, or step 92, which performs 50Hz processing, is selected. In step 93, the values of the first and second counters are returned to their initial values. Step 82 following the confluence of flow A and flow B performs the operation of checking the value of the above-mentioned internal timer, and when the value of the above-mentioned internal timer is 2ms.
Step 82 is repeated until the value is shown, and when 2 ms is reached, the process proceeds to step C. That is, step 83 following flow C is processed every 2 ms. Step 83 above
performs the work of incrementing the value of the first counter by one. In step 84, the value of the internal timer is returned to its initial value. Step 85 is microcomputer 11
The pulse (clock) input to the input terminal Si of
In other words, the input signal changes from “H” to “L”
It detects the change from "H" to "H" and increases the value of the second counter by one every pulse (clock). Step 86 is input terminal K3
It detects whether or not there is a power outage based on the input of Check the input status to K3.
Then, in the event of a power outage, the process proceeds to step 2, where operation is stopped at step 87, and operation lamp 2 is turned on at step 88.
7a is turned off, the reset lamp 27b is turned on, and an abnormality operation is performed to prevent automatic restart of operation when the power is restored. If there is no power outage, the flow advances to step 89, where a series of processes executed during normal operation are performed. That is, when the operation switch 37 is turned on, the operation lamp 27a lights up and at the same time the relay 12 is excited and the heater 13 is energized. When the burner thermistor 42 detects that the temperature of the vaporization part within the burner 4 has risen to a predetermined temperature, the relay 15 is energized to turn on the burner motor 14 and the blower motor 15. After a certain period of time, the relay 18 is energized and the pump circuit 17 and igniter 16 are turned on. The igniter 16 discharges electricity for a certain period of time after being energized, and then automatically stops. Here, the ignition state is determined by the flame rod circuit 41.
If there is no ignition, the ignition operation is performed again, or the engine is determined to be abnormal and the operation is stopped.

On the other hand, in the event of a power outage, the power supply from the bus C is cut off, but when a signal is received from the power outage detection circuit 28, power is supplied from the backup power supply 31 to the bus D.
The microcomputer 11 continues to maintain memory and sets the state of each input/output terminal so that the current consumed by the microcomputer 11 and its peripheral circuits is minimized and the backup time is extended as much as possible. Furthermore, if there is a power outage during combustion, and when the power is restored, if you continue the operation that was performed before the power outage, the pump circuit 17 will start operating at the same time as the power is turned on again, so there is a risk of oil leakage, explosion, ignition, etc. is dangerous. Therefore, the power outage detection circuit 28 detects a power outage and provides a power outage signal to the microcomputer 11, thereby working to prevent a dangerous situation when the power is turned on again.

Here, the above-mentioned power failure detection is performed as follows. That is, in this circuit, while current is supplied from the bus C, this current flows through the transistor 28c via the resistor 28b and the Zener diode 28a.
flows into the base of the transistor 28c, turning on the transistor 28c. However, when a power outage occurs and the potential of the bus C supplied from the backup power supply 31 becomes lower than the Zener voltage of the Zener diode 28a, no current flows to the base of the transistor 28c, the transistor 28c is turned off, and the input terminal K3 is set to "H". ” signal is input and step 86
A power outage is detected.

However, since the above circuit judges whether there is a power outage or not based on whether the signal input to the input terminal K3 is "H" or "L", for example, a short circuit between the collector emitter of the transistor 28c or a short circuit between the input terminal K
If there is a disconnection failure in the pull-up resistor 28d of No. 3, there is a problem that even if a power outage occurs, the microcomputer 11 will not detect the power outage and will malfunction.

Purpose of the Invention The present invention was made in view of the above-mentioned problems, and an object of the present invention is to reliably detect the failure of the power failure detection circuit on the open or short circuit side and prevent the microcomputer from malfunctioning. It is.

Structure of the Invention The present invention includes a combustion control circuit, an auxiliary power supply that supplies power to the microcomputer during a power outage, a waveform shaping circuit that generates pulse signals from an AC power supply, and a time measurement circuit that measures time based on at least the number of pulse signals. The microcomputer is equipped with a clock function that counts the number of pulse signals and a power failure judgment function that determines a power outage if the counted value is less than a certain value, and a microcomputer that inputs the pulses for the clock. The configuration shares the input terminal with the input terminal of the microcomputer that inputs pulses for power outage detection, so if the waveform shaping circuit that is the power outage detection circuit fails, the pulse signal from the waveform shaping circuit will disappear, making it reliable. This can be detected.

DESCRIPTION OF EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS. 1 and 2. Parts that are the same as those of the conventional example will be given the same numbers and explanations will be omitted, and only the different parts will be explained.

First, in FIG. 1, a conventional power failure detection circuit 28
is removed, and a diode bridge 20 for clock display, a transistor 22 and a resistor 2 are used to send a pulse (clock) signal to the input terminal Si of the microcomputer 11'.
A waveform shaping circuit consisting of 1 is used as a power outage detection circuit. That is, a power outage is detected using a pulse (clock) signal supplied from a waveform shaping circuit consisting of a transistor 22 and a resistor, and for this purpose, the processing routine of the microcomputer 11' is configured as shown in FIG. There is.

In FIG. 2, a new step 96 is provided between step 81 and step 90, and this step 96
The number of pulses (clocks) counted by step 85 per second is checked and it is determined whether the value is greater than or equal to a predetermined value, for example 10 in this embodiment. If it is less than 10, the process proceeds to step 94 for processing a power outage. I'm starting to be able to do it. A power outage processing step 94 then generates a power outage signal. Reference numeral 86a denotes a power outage detection step which detects the presence or absence of this power outage signal and determines whether or not there is a power outage.When there is a power outage, the process proceeds to an operation stop step 87, and when there is no power outage, the process proceeds to an operation processing step 89.

In the above configuration, normally a pulse (clock) signal is supplied from the transistor 22 to the input terminal Si of the microcomputer 11', and the count value of the second counter counted in step 90 is 10 or more per second, indicating that normal processing is possible. Do a routine.

If a power outage occurs in this state, power is supplied to the microcomputer 11' from the backup power supply 31, but power is not supplied to the transistor 22 of the waveform shaping circuit, which also serves as a power outage detection circuit, and a pulse (clock) signal is supplied to the input terminal Si of the microcomputer 11'. No signal is received. Therefore, naturally, the second counter value counted at step 96 will never exceed 0, that is, 10 per second, and the flow will proceed. In other words, the power outage processing step
94 issues a power outage signal, and in step 86a, the power outage signal is detected and the operation stop routine is entered to stop the operation.

On the other hand, if the power failure detection circuit such as the transistor 22 fails to open or short circuit side although it is not a power outage, the signal inputted from the transistor 22 to the input terminal Si of the microcomputer 11' is only an "H" or "L" signal. Therefore, it is no longer a pulse (clock) signal. Therefore, in this case as well, step 96
When the count value does not exceed 0 per second, that is, 10, it is assumed that there is a power outage and the operation is stopped as in the case described above.

If this transistor 22 etc. breaks down, take steps before the power outage occurs even if there is no actual power outage.
86a determines that there is a power outage and stops operation, but this is because the transistor 22, etc. also works as a clock circuit, and if it fails, the clock displayed by the microcomputer 11' will go awry, so it is assumed that it is a power outage. This is designed to stop the operation and improve reliability.

In addition, in this embodiment, a pulse (clock) signal from a waveform shaping circuit serving as a clock circuit is used to detect a power outage, in other words, a pulse (clock) signal for power outage detection is used.
Since the signal and the pulse (clock) signal for the clock display are shared, the input terminal for the pulse (clock) signal to the microcomputer 11' can also be shared, and the advantage is that the input/output terminals of the microcomputer can be effectively utilized. There is also. In other words, in the control circuit 10 mainly composed of a microcomputer, most of the various signals are sent to the microcomputer 11.
, the number of signal lines input to and output from the microcomputer 11' tends to increase. However, the number of input/output terminals of the microcomputer 11' is limited, and if there is a shortage, a switch circuit 36, etc.
An expensive interface or the like is required to convert signals between the peripheral input/output section and the microcomputer.
Therefore, it is preferable to share input/output signals to the microcomputer 11' as much as possible, and this embodiment has the advantage that the number of input terminals of the microcomputer 11' can be reduced by one.

In the above configuration, the value of the second counter for determining a power outage may be any value from 0 to 50, and in this embodiment, it was experimentally determined to be 10 in consideration of noise tolerance.

Effects of the Invention As is clear from the description of the above embodiments, according to the present invention, the number of pulses (clocks) obtained by half-wave rectification of AC power source is not detected by detecting a voltage drop to detect a power outage. To detect power outages by counting
It is safe because the power failure detection circuit can always detect an abnormality whether it is an open failure or a short circuit failure. Moreover,
Input terminal Si for obtaining a clock as in the embodiment
By using input terminals shared with the microcomputer, the number of input/output terminals used by the microcomputer can be reduced, and the remaining input/output terminals can be used for other functions.

Furthermore, since the input pulse signal for the clock and the input pulse for power outage detection can be shared, the clock will not be delayed in the event of a power outage, and since a power outage is determined by counting the number of pulses within a certain period of time, noise tolerance is increased. Effects can also be obtained.

[Brief explanation of drawings]

FIG. 1 is a control circuit diagram of a combustion appliance according to an embodiment of the present invention, FIG. 2 is a flow chart for explaining the same operation, FIG. 3 is a conventional control circuit diagram, and FIG.
The figure is a flowchart for explaining the operation, and FIG. 5 is a sectional view of a general combustion appliance. 8... AC power supply, 10... Combustion control circuit, 11
...Microcomputer, 20, 21, 22...
...Waveform shaping circuit, 31...Auxiliary (backup)
power supply.

Claims (1)

[Claims] 1. A combustion control circuit, an auxiliary power source that supplies power to the microcomputer during a power outage, a waveform shaping circuit that generates pulse signals from an AC power source, a clock function that measures time based on at least the number of pulse signals, and the above. It is equipped with a microcomputer programmed with a power outage judgment function that counts the number of pulse signals and determines that a power outage has occurred if the counted value is less than a certain value, and an input terminal of the microcomputer that inputs the pulses for the clock, and A control device for a combustion appliance, characterized in that an input terminal of a microcomputer for inputting detection pulses is shared.