JP2681284B2 - Control circuit for hot air heater - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control circuit for a hot air heater that prevents abnormal overheating.

Conventional technology As a conventional technology of this kind, there is a temperature sensor inside the warm air heater to detect an abnormal temperature rise, dust adheres to the convection fan to reduce the air flow, and the temperature inside the vessel becomes abnormal. In some cases, when the temperature rises, the sensor detects the temperature and shuts off the circuit, stopping the operation. (For example,
54-43160) Also, as an alarm device for a warm air heater, a voltage comparator between a flame level and a first level, a voltage comparator between a flame level and a second level, and a light emitting element that receives them and is turned on. A combustion control unit for controlling is provided, the flame level is detected after a lapse of a certain time after starting the combustion, and the temperature inside the vessel rises due to the dust clogging of the convection fan and the flame level does not reach the first level. In some cases, the light emitting element is blinked to warn of dust clogging of the convection fan, and when the flame level does not reach the second level, the light emitting element is turned on to give an alarm for another purpose.
(For example, Japanese Utility Model Laid-Open No. 62-81856) Problems to be Solved by the Invention In the case where the operation is stopped when the abnormal temperature rise inside the warm air heater is detected by the temperature sensor, the convection fan is notified of dust clogging. If it operates without doing so, it will be inconvenient because it will be stopped. When a thermistor is used as the temperature sensor, if an open or short circuit failure occurs, the abnormal temperature prevention function does not work even if the temperature inside the body rises, the operation does not stop, and the body overheats. There was a risk of becoming a danger mode of ignition.

Also, it is convenient to use a light emitting element to compare the flame levels and to warn if the convection fan is clogged with dust because it alerts you to dust clogs, but if the flame level detection means has an open failure, convection will occur regardless of flame level. If an alarm is output as a dust clogging of the fan and the flame level detection means has a short circuit failure, the alarm does not sound even if the temperature inside the body abnormally rises due to the dust clogging of the convection fan. There was a risk of overheating and ignition.

Means for Solving the Problems The present invention has been made to solve the above problems, and a temperature detection circuit is configured by a thermistor that is a temperature sensor and a required number of voltage comparators, and an operation stop temperature detection is performed. For superimposing the pulse output of the pump driving output port by the software of the microcomputer on the reference voltage side input of the voltage comparator for
The output of this voltage comparator compares with the thermistor voltage to operate the driver for pump drive, and the pulse output of the above output port is also superimposed on the reference voltage input of the voltage comparator for alarm temperature detection. The output of the voltage comparator compared with the voltage is input to the alarm input port of the microcomputer.

Action With the above configuration, the pulse output for pump drive by the software of the microcomputer that is input to the reference voltage side input of the voltage comparator for detecting the shutdown temperature will start when the thermistor detects the shutdown temperature. When the thermistor has an open or short circuit failure, it stops the output of the temperature detection circuit from being a pulse signal, determines that the thermistor has a failure, and stops the operation. The pulse output input to the reference voltage side input of the voltage comparator for detection has a function of issuing an alarm when the thermistor detects the alarm temperature.

Embodiment FIG. 1 is a schematic view of the structure of a hot air heater, FIG. 2 is a control circuit diagram of the hot air heater showing an embodiment of the present invention, and FIG. 3 is a waveform diagram at a specific point thereof.

In the figure, 1 is a cabinet of a warm air heater, 2 is a combustion chamber, 3 is a convection fan for warm air provided on the back of the cabinet 1 above the combustion chamber 2, and 4 is a hot air blower provided on the front of the cabinet 1. The outlets 5 are provided in the cabinet 1,
The thermistor 6 for detecting the internal temperature of the body is a filter provided at the suction port of the convection fan 3 to prevent dust from entering the expected interior. Reference numeral 7 is a commercial power source, and 8 is a controller for a hot air heater such as a vaporizer preheater and an igniter (not shown). Reference numeral 9 is a pulse-driving pump for supplying liquid fuel. 10 pumps the signal from the electronic circuit 9
It is a photo coupler to tell. Reference numeral 11 is a relay for driving the convection fan 3, 11-a is its contact point, and 11-b is its coil portion. Reference numeral 12 is a step-down transformer for an electronic circuit, 13 is a rectifying bridge diode, 14 is a smoothing capacitor, and 15 is a 5V constant-voltage regulator for an electronic circuit. 12V, 5V and 0V lines are shown. 16 is a microcomputer in which the control sequence of the warm air heater is programmed. Reference numeral 17 is a temperature detection circuit inside the body, which is composed of a thermistor 5 which is a temperature sensor, resistors 18 to 24, voltage comparators (comparators) 25 and 26, and the like. The pulse output from the output port 34 for driving the pump by the software of the microcomputer 16 is input to the comparators 25 and 26.
22 is superimposed on the reference voltage side input A section of the voltage comparator 26 for detecting the operation stop temperature and the reference voltage side input B section of the voltage comparator 25 for detecting the alarm temperature, and the output of the voltage comparator 26 is a microcomputer. It is input to the operation stop temperature input port 35 of 16 and the driver 27 for driving the pump, and the output of the voltage comparator 25 is input to the alarm temperature input port 36 of the microcomputer 16. The driver 27 operates the pump 9 via the photocoupler 10. 28 is a driver that receives the input of the relay driving port 38 of the microcomputer 16 and drives the relay 11, 29 is a driver that receives the output of the alarm port 38 of the microcomputer 16 and turns on the lamp 30 for the abnormal body overheat alarm, 31 is Receiving the output of the operation stop port 39 of the microcomputer 16, it is a driver for the abnormal body overheat operation stop lamp 32, and 33 is an operation switch connected to the input 40 of the microcomputer 16.

 The operation of the present embodiment having the above configuration will be described.

When the operation switch 33 is turned on, the operation is started by the control sequence programmed in the microcomputer 16, and the vaporization part preheating heater, the igniter and the like of the control part 8 are operated. Microcomputer 16
The pulse output D section by the microcomputer software from the port 34 is superposed on the reference voltage side input of the voltage comparator 26 via the resistor 22. The resistors 19, 20, and 21 serve as reference voltages for detecting the temperature of the thermistor 5, the voltage of the A section is set to the abnormal body overheat operation stop level, and the voltage of the B section is set to the abnormal body overheat alarm level. If the temperature inside the body is normal, thermistor 5
The voltage of the C section due to is higher than the A section voltage and the B section voltage, and the output of the comparator 26 outputs a pulse waveform like the E section waveform,
The pump driving driver 27 is operated and the pump 9 is operated via the photocoupler 10 by the pulse shown in the lower part to perform combustion operation. In addition, the port 38 of the microcomputer 16 turns on the driver 28 to excite the relay 11 to close the contact 11-a,
The convection fan 3 is operated to send hot air into the room for combustion heating.

When the filter 6 is clogged with dust during operation, the air volume of the convection fan 3 decreases. Therefore, the temperature of the thermistor 5 increases and the resistance value decreases, so that the voltage at the C portion decreases and B
When the voltage becomes lower than the pulse voltage of the section, the output of the voltage comparator 25 changes from pulse output to DC output. The DC output is input to the port 36 of the microcomputer 16 so that the microcomputer 16 can
Turn on the driver 29 at 38, and turn the abnormal lamp overheat alarm lamp
30 is turned on and the user is warned of an abnormality such as clogging of the filter 6. Further, the clogging of the filter 6 progresses,
When the internal temperature of the body rises, the voltage of the C section drops, and when it becomes lower than the voltage of the A section, the output of the voltage comparator 26 changes from pulse output to DC output. This DC output is input to the driver 27, the pump 9 is stopped, and the combustion is stopped. This DC output is also input to the port 35 of the microcomputer 16 as a device abnormal overheat stop signal. The microcomputer 16 uses the driver 31 at port 39
It is turned on, the abnormal body overheat lamp 32 is turned on, and the user is notified that combustion has stopped due to clogging of the filter 6 or the like.

Further, when the thermistor 5 is in the open or short failure mode, the voltage at the input A of the voltage comparator 26 becomes 5V or 0V, the output of the voltage comparator 26 becomes only 0V or 5V DC output, and the pump 9 Remains stopped, and the abnormal body overheat lamp 32 also remains lit.

As described above, according to the present invention, the pulse output by the software of the microcomputer is superimposed on the reference voltage side input of the voltage comparator for detecting the alarm temperature which constitutes the thermistor temperature detecting circuit, and the output of this voltage comparator is used. Since the alarm is issued, the user can know the filter clogging of the convection fan, and the pulse output is also superimposed on the reference voltage side input of the voltage comparator for detecting the operation stop temperature. Since the pump drive is stopped by the output, abnormal overheating of the body due to clogging of the convection fan filter can be prevented, and even if the thermistor opens or shorts, the comparator output will Only the abnormal mode output will be output, and the danger mode such as overheating and ignition of the body can be set in advance without stopping the combustion operation during abnormal overheating due to a temperature detection circuit failure. Has the effect of preventing.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of the structure of an oil warm air heater, FIG. 2 is a control circuit diagram of the warm air heater showing an embodiment of the present invention, and FIG. 3 is a waveform diagram at a specific point thereof. 5 ... Thermistor, 16 ... Microcomputer, 17 ... Temperature detection circuit, 25, 26 ... Voltage comparator, 27 ... Driver, 34, 36 ... Port.

Claims (2)

(57) [Claims] 1. A thermistor (5) provided inside a body
And a temperature detection circuit (17) having the required number of voltage comparators (25) and (26), and the operation is stopped when the thermistor (5) detects an abnormal temperature rise inside the body. In the control circuit of the controller, the reference voltage input (A) of the voltage comparator (26) for detecting the operation stop temperature of the temperature detection circuit (17)
Part), the pulse output (part D) of the pump driving output port (34) by the software of the microcomputer (16) is superimposed, and the output (part E) of this voltage comparator (26) is applied to the pump driving driver (27). ) Is a control circuit of the warm air heater. 2. A pulse output (D section) of the output port (34) is superimposed on a reference voltage side input (B section) of a voltage comparator (25) for detecting an alarm temperature of the temperature detection circuit (17). The control circuit for the warm air heater according to claim 1, wherein the output of the voltage comparator (25) is input to the alarm input port (36) of the microcomputer (16).