JPS5840090B2 - Safety check method and device for heating equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heating device having a negative characteristic thermistor as a temperature sensor of a temperature control means, and to a method and apparatus for checking for disconnection of the negative characteristic thermistor.

Negative characteristic thermistors (hereinafter referred to as thermistors) have a high resistance at low temperatures and a low resistance at high temperatures, so if a wire breakage or lead wire connection failure occurs, the resistance between the thermistor's connecting terminals will be high and the resistance will be the same as at low temperatures. condition, and heating continues, which is dangerous.

As a check for disconnection of the servo star, etc., it is conceivable to enter steady operation if the check is normal when the heating device starts operating.

For example, the resistance value is measured at the start of operation, and if it is larger than the assumed low-temperature resistance value at the start of operation, it is determined that the wire is disconnected.

However, in the case of a thermistor whose operating temperature is high to control the heating source, the resistance value at low temperature at the start of operation is very large, and there is not much difference from the resistance value at the time of disconnection. Checking the value is difficult.

For example, if a thermistor is used as a temperature sensor for a kerosene vaporizer in a burner that heats kerosene and turns it into a gas, the temperature at the start of operation will be below 0°C in winter, and -
The operating temperature is approximately 250°C or higher.

The present invention has been made based on the above points, and an object of the present invention is to check a thermistor for high-temperature operation with a simple configuration.

The present invention first starts heating at the start of operation, and then checks the thermistor after a predetermined period of time.The temperature is raised to lower the resistance value of the thermistor, making it easier to compare it with the resistance value at the time of disconnection. be.

An embodiment in which the present invention is applied to a vaporizer for a kerosene vaporizing blue sky combustion burner will be described below with reference to the drawings.

In this type of burner, the vaporizing chamber of the vaporizing device is heated by an electric heater, and a thermistor detects when the temperature reaches a predetermined temperature (250°C or higher), starts supplying kerosene, and then stops energizing the heater. The combustion heat is then recovered from the combustion flame into the vaporization chamber to continue vaporization.

In the figure, 1 is the commercial power supply, 2 is the normally open contact of the relay, and 3 is the normally open contact of the relay.
is a heater, 4 is a relay coil, 5 is a diode, 6 is a transistor, 7, 8 is a trx resistor, 9 is a transistor, 1
0. '1L12 is a resistor, 13 is a voltage comparator for temperature control of the vaporization section, 14, 15° 16t17 is a resistor, 18 is a capacitor, 19 is a Zener diode, 20, 2iu transistor, 22.21r is a resistor, 24 is a thermistor Voltage comparator for checking, 25 is a resistor, 26 is a thermistor,
27.28u resistor, 29 a circuit for detecting the temperature at which the supply of kerosene is started, 30 a combustion control circuit, 31 an operation switch 32, and a DC power source.

Incidentally, the operating value of the comparator 24 is, for example, 160°C.

The operation of this configuration will be explained.

When the operation switch 31 is turned on, the voltage divided by the resistors 27 and 28 is applied to the negative input terminal of the voltage comparator 24, and the voltage divided by the resistor 25 and thermistor 26 is applied to the positive input terminal. Ru.

At this time, since the resistance value of the thermistor 26 is large, the output of the voltage comparator 24 becomes It 1 jj, and the transistor 21 becomes conductive.

At the same time, charge is stored in the capacitor 18 through the resistor 17, and the terminal voltage of the capacitor begins to rise.

In this state, the transistor 20U is OFF.

Also, the voltage divided by the resistors 15 and 16 is applied to the voltage comparator 1.
3, resistor 25 and thermistor 2
The voltage divided by 6 is applied to the negative input terminal.

At this time, since the resistance value of the servo star is large, the output of the voltage comparator 13 is u ``o'''', and the transistor 9H
The transistor 6U is turned OFF, the relay coil 4 is energized, the relay normally open contact 2 is closed, the heater 3 is energized, and the vaporization chamber begins to be heated.

Next, after a certain period of time, a base current flows into the transistor 20 through the Zener diode 19, turning it on.

At this time, if the thermistor 26 has a resistance value greater than a certain value, including disconnection, the transistor 21U remains ON.
The base voltage of the transistor 6 becomes tt O'', the transistor 6 becomes OFF'F, and no current flows through the relay coil 4, so the relay contact 2 opens and 1. The heater 3 stops energizing.

Therefore, the temperature in the vaporization chamber does not rise to 1 to gasify kerosene,
Combustion will not start.

Conversely, if the thermistor 6 is normal, the resistance value LrJ of the thermistor 26 increases during the time until the transistor 20 becomes conductive.
, is smaller than a certain value, so the output of the voltage comparison number 24 becomes 0, the transistor 21 is turned off, the transistor 6 is turned on, and the heater 3 continues to be energized.

When the temperature in the vaporization chamber reaches a temperature sufficient to gasify the kerosene, circuit 29 is activated, and circuit 30 is activated to start combustion.

After that, when the temperature of the vaporization chamber rises to the temperature at which the heater 3 is turned off, the voltage divided by the resistor 25 and the resistor 26 becomes lower than the voltage divided by the resistor 15.16. The output of the voltage comparator 13 becomes po, tt l n, the transistor 9 turns on, and the transistor 6fl
It becomes OFF, and the heater 3 stops energizing.

Next, if the circuit 26 is disconnected in this state, the transistor 9UOF'F becomes the transistor 21UOF'F.
Since transistor 20 is already turned on, transistor 6 remains off and heater 3VC is turned on.
There is no need to turn on electricity, and the temperature of the vaporization chamber does not rise abnormally, making it safe.

In this way, for a certain period of time after turning on the operation switch, first the heater 3 is turned on.
is driven to raise the temperature of the object to be heated to a certain extent, and in this state, if the thermistor 26 is normal, the heater 3 continues to be energized, and the resistance value of the thermistor 26, which should rise in temperature within this time, increases. If it is abnormally large, it is considered as a disconnection.
Turn off the heater.

Therefore, the high temperature servo starter 26 can be easily checked and safety can be ensured.

Furthermore, if the wire breaks during operation, immediately turn off the heater 26.
FF" configuration, it is safe.

As explained above, in the present invention, when the operation is started, heating is first started, and after a predetermined time, the resistance value of the thermistor is measured.
Since the quality of the thermistor is determined, the difference between the resistance value at the time of disconnection and the resistance value at the time of measurement becomes large, making it possible to easily check the thermistor.

[Brief explanation of drawings]

The figure is a circuit diagram of an embodiment of the present invention. 3... Heater, 4... Relay, 26... Negative characteristic thermistor, 31... Operation switch.

Claims (1)

[Scope of Claims] 1. A negative characteristic thermistor is provided as a temperature sensor of the heating control means, heating is started in response to an operation start signal, and after a predetermined time, the negative characteristic thermistor reaches a predetermined temperature that should be reached within the predetermined time. 1. A method for checking the safety of a heating device, comprising: measuring whether the temperature of the heating device is below a predetermined resistance value, and determining whether or not the heating should be continued. 2. The heating device safety check method according to claim 1, wherein the predetermined time for performing the measurement is shorter than the time required for the object to be heated to reach the predetermined control temperature. 3. A safety check method for a heating device according to claim 1, wherein the negative characteristic thermistor is provided as a temperature sensor of a vaporization chamber that gasifies kerosene to a temperature that allows green combustion. 4. A first device having a negative characteristic thermistor as a temperature sensor of the heating source control means, which becomes non-conductive and stops the operation of the heating source when the negative characteristic thermistor becomes equal to or less than a predetermined resistance value.
The first transistor is provided to conduct when the operation start signal is applied to drive the heating source, and the second transistor is conductive when the negative characteristic resistor has a predetermined resistance value or more. and a third transistor that becomes conductive after a predetermined time from the start of operation of the heat source are connected in series, and when the second and third transistors become conductive, the first transistor becomes non-conductive. A safety check device for a heating device, which is characterized by: 5. A safety check device for a heating device according to claim 4, wherein the predetermined period of time during which the transistor of @drug distribution 3 conducts is shorter than the time required for the object to be heated to reach a predetermined control temperature. 6. Claim 5, wherein a fourth transistor that becomes conductive when the negative characteristic thermistor reaches the control temperature is connected so as to make the first transistor non-conductive at that time.
Safety check device for heating equipment as described in section. 7. A safety check device for a heating device according to claim 4, wherein the negative characteristic thermistor is provided as a temperature sensor of an air chamber in which kerosene is gasified to a temperature that allows combustion.