JPS5828498B2 - Temperature control device for heating equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for checking disconnection of a negative characteristic thermistor for temperature measurement in a heating device.

Especially regarding those measuring high temperatures. For example, it involves evaporating liquid fuel in a high-temperature evaporator and burning the vaporized fuel with blue flame in a combustor.

The evaporator is heated to a predetermined temperature using an electric heater or the like.

Electric heaters are controlled by a temperature control circuit that uses a negative thermistor as a detection element.The negative thermistor has a large resistance at low temperatures, so if the negative thermistor is disconnected or forgotten, the resistance will become infinite. As a result, the electric heater continues to be energized, which is extremely dangerous.

For this reason, it is possible to check for disconnection of the negative characteristic thermistor.

Compared to the resistance of a negative characteristic thermistor at room temperature, if the resistance is a dog, it is determined that the wire is disconnected.

However, the temperature suitable for evaporation of liquid fuel kerosene is approximately 25
It is about 0'C.

Therefore, the resistance value of the negative characteristic thermistor at room temperature is extremely large, and it is difficult to distinguish it from the resistance value caused by a disconnection.

The present invention has been made to improve this problem.

That is, first, electricity is applied to a heating device such as an electric heater to heat the evaporator, and after a predetermined period of time, that is, after the temperature has risen to a temperature that makes it easy to compare resistance values, the resistance value is measured and judged. This is what I did.

The present invention will be explained below with reference to an embodiment shown in the drawings.

The example is a case where the present invention is applied to the above-mentioned combustion device.

1 is a DC power supply, 2 is an operation switch, 4 is a combustion control circuit,
For example, it is made up of highly integrated circuits.

The combustion control circuit 4 inputs a liquid fuel evaporator temperature signal 5, a load temperature signal, a combustor flame signal, a clock signal, an abnormal state detection signal, etc. from each input terminal, and inputs a blower drive signal, a fuel supply signal, etc. Combustion control is performed by outputting a device drive signal, an ignition device drive signal, an alarm output signal in an emergency state, etc. from each output terminal.

11 is a negative characteristic thermistor for detecting the temperature of the evaporator; 12
is a resistor, and 13 is a capacitor.

14 is a circuit that detects the temperature of the evaporator and controls the combustion control circuit, and includes a comparator 15 and resistors 16, 17, and 18.
, 19, and a diode 20.

21 is a heater control circuit, which includes a comparator 22, a transistor 23, a relay 24, and a resistor 25°26.27.2
8.29.30, diode 31゜32, capacitor 3
It consists of 3,34.

Relay 24 controls the electric heater.

40 is a disconnection check circuit; a temperature detection circuit 41;
It is composed of a timer 42 and a determination circuit 42.

The temperature detection circuit 41 includes a comparator 44 and a resistor 45.4.
6, 47, and a capacitor 48.

When the negative characteristic thermistor 11 is normal, the comparator 44 outputs the "L" level before the predetermined time set by the timer 42 has elapsed.

The circuit 41 is configured to detect the temperature expected by heating by the electric heater for the predetermined time.

The timer 42 has a comparator 50 and a resistor 51゜52.5.
3.54.55.56, a capacitor 57.58, and a diode 59.

A resistor 51 and a diode 57 constitute a timer of the comparator 50.

The comparator 50 outputs the "H" level after a predetermined time.

Diode 59 is for discharging capacitor 57.

The determination circuit 43 includes a transistor 61, a resistor 62, 63,
It is composed of a diode 64.

Note that the comparators 15, 22, 44, and 50 are quat comparators.

The capacitors other than capacitor 57 are mainly for noise prevention.

70 is a set coil of a keep relay, which has contacts 71.

72 is a reset coil of the keep relay.

73 is a reset switch. 74 is a diode.

75 is a warning lamp. The operation of such a configuration will be explained.

When operation switch 2 is turned on and the evaporator temperature is low,
The output of the comparator 15 is L1 lebel, and is inputted to the combustion control circuit 4 from the input terminal 5.

The combustion control circuit 4 does not start operating until the evaporator reaches a predetermined temperature.

The output of the comparator 22 of the heater control circuit 21 is "H1"
Since it is a power supply, transistor 23 and relay 24 are OFF.
N and energize the electric heater to heat the evaporator.

When the evaporator is heated to a predetermined temperature (for example, about 30° C.), the output of the comparator 44 of the disconnection check circuit becomes “I,”
It becomes 2 rubels.

After a predetermined time (for example, about 3 minutes, although it varies depending on the heat capacity of the evaporator and the determination temperature) after turning on the operation switch 2, that is,
After the comparator 44 is inverted, the CR timers 51, 52, 5
7 inverts the output of comparator 1/-50 to et H1 level.

Therefore, the transistor 61 continues to be OFF, the keep relay does not operate, and the electric heater continues to be energized.

When the temperature is suitable for liquid fuel evaporation, comparator 1
5 becomes H level, and the combustion control circuit 4 starts operating.

When the temperature of the evaporator becomes high, the output of the comparator 22 becomes L'' level, and the power supply to the electric heater is stopped.

If the negative characteristic thermistor 11 has a disconnection or the like, the output of the comparator 44 is "H9 level".

After a predetermined period of time, the output of the comparator 50 also reaches the nHu level, so the transistor 61 is ONL, the set coil 70 is activated, and the relay 24 etc. are turned off by the contact 71 to ensure safety.

Transistor 61 is self-supported by contact 71b.

If a wire breakage or the like occurs during combustion, the output of the comparator 44 is reversed to the "Hn" level, so that the energization of the heater can be stopped.

The diode 59 will be explained.

After the timer tj is activated, the output of the comparator continues to be at the 'H' level.

Even if the operation switch is turned off, it is for long time measurement.
Discharging of capacitor 57 is slow.

Therefore, when the operation switch is turned ON again after being turned OFF, if the evaporator is not discharged and the temperature of the evaporator is low, the transistor 61 is turned ON.

The purpose of the diode 59 is to prevent this, and allows the discharge to occur faster through another location with lower impedance than from the resistor 52.

In this way, since the check is performed after a predetermined period of time from the start of heating, that is, when the temperature has risen slightly, the check can be easily performed.

Furthermore, since the timer is composed of a comparator, the configuration of the determination circuit can be simplified.

[Brief explanation of drawings]

The figure is a circuit diagram of a temperature control device for a heating device according to an embodiment of the present invention. 4... Combustion control circuit, 11... Negative characteristic thermistor, 21... Heater control circuit, 24...
... Relay, 40 ... Disconnection check circuit, 41 ... Temperature detection circuit, 42 ... Timer, 43 ... Judgment circuit, 70 ... ...Keep relay set coil.

Claims (1)

[Scope of Claims] 1. Temperature control means for driving the heating device, a negative characteristic thermistor for temperature detection of the temperature control means, timer means that operates after a predetermined time from the start of operation, and driving the heating device according to the predetermined time. temperature detection means for detecting a resistance value of the negative characteristic thermistor corresponding to the temperature that should be generated by the temperature detection means; and a temperature detection means for detecting a resistance value of the negative characteristic thermistor corresponding to the temperature that should be generated by the temperature detection means; A temperature control device for a heating device, comprising means for determining whether the resistance value is the same or not, and means for stopping the heating device based on the output of the determination circuit. 2. In claim 1, the temperature detection means is constituted by a comparator, the timer means is constituted by a comparator whose one input is a voltage generated by a CR timer, and the judgment circuit is configured such that the surface outputs are at the same level. Temperature control device for heating equipment consisting of transistors that operate at. 3. In claim 2, the output of the comparator of the temperature detecting means is set at the resistance value "J, 1 level, and the output of the comparator of the timer means is set at the level "H1" after the predetermined time. , a temperature control device for a heating device in which the surface output is used as the base voltage of the transistor.