JPS6035184Y2 - Temperature control circuit for heat generating equipment - Google Patents

Description

[Detailed description of the invention] The present invention relates to a temperature control circuit for heat generating devices such as carpets and roof heaters. We have improved the circuit that prevents the heater from rising to an abnormal temperature due to a continuity failure when there is a continuity failure in the circuit using the semiconductor element connected to the contact drive relay, and the circuit works more reliably to prevent abnormal temperature rises. To provide a temperature control circuit that can

Conventionally, as shown in FIGS. 1a to 1, the heater 1 has a heat-sensitive element 2 having a temperature impedance characteristic and a heat-sensitive electrode 3 in combination to enable temperature detection. Applying a high frequency signal voltage between 1 and the heat-sensitive electrode 3, detecting a change in the signal voltage due to a change in impedance of the heat-sensitive element 2, and activating a switching circuit,
A temperature control circuit that turns on and off the power supply line to the heater 1 has been considered.

FIG. 2 shows details of the switching circuit in the temperature control circuit, and the Schmitt configuration switching circuit S1 includes a heat-sensitive element 2 that decreases as the heater temperature rises.
When the input voltage level decreases due to the impedance and the input becomes 1/2 of the power supply voltage VDD of the inverter gates G□ and G2, a switching operation is performed and the output of the inverter gate G2 becomes L level.

Therefore, thyristor 5CR1 is turned off and relay R
y turns off the switching contacts r and r to cut off the power supply to the heater 1.

When the switching contacts r and r are turned off, a voltage is generated across the resistor R1 connected to the inverter gate G2 on the output side, which causes the switching circuit S2 for preventing abnormal temperature rise consisting of the inverter gate G3 to pass through the diode D□. The input level becomes H, and the output side becomes L level, turning off the thyristor 5CR2.

Therefore, no current flows through the resistor B2 connected to the AC power supply V, and normal temperature control is performed.

And if the opening/closing contacts r and r are welded, the thyristor 5
If an accident occurs such as CR1 becoming disconnected, relay Ry will not operate properly, so switching circuit S□
Regardless of inverter gate G2 being at L level, heater 1
Continuous current is applied to the resistor R1, and since the switching contacts r and r are on at both ends of the resistor R1, no voltage is generated, and the input of the inverter G3 is H on the L1 output side, and the thyristor 5CR2 is on and the resistor R2 is turned on. Heat is generated and the AC power source (■) is disconnected by the heater 1 using the temperature fuse F.

In the conventional temperature control circuit that prevents abnormal temperature rise, when the inverter gate of the switching circuit S fails, the output of gate G2 becomes H level regardless of the input to gate G□. In this case, since the relay Ry is driven by the ON of the thyristor SCR and turns on the switching contacts r and r, the second switching circuit monitors the output of the inverter gate G2 and the voltage between the switching contacts r and r. Since the voltage across the resistor R1 is not applied to S2, the output is at L level and the thyristor 5CR2 is off, so the temperature fuse F is not cut off, which is dangerous.

This invention was developed in view of the above reasons.

The temperature control circuit of the heat generating device of the present invention will be explained below with reference to FIG.
and a first switching circuit S1 consisting of Schmitt-configured inverter gates G, , G2 which are activated by the temperature detection signal of the heater 1, and the switching contacts r, r are turned on and off by the first switching circuit S1. an output circuit consisting of a relay Ry and a thyristor 5CR1; a second switching circuit S2 connected to the input side of the first switching circuit S1 and operating at a higher level than the operating level of the switching circuit S1; A heating device comprising a circuit consisting of a resistor R2 and a thyristor 5CR2 connected in series to the AC power source V and the temperature fuse F at the output of the switching circuit S2, the temperature fuse F being cut off by the heat generated by the resistor R2. This is a circuit to prevent abnormal temperature rise.

According to the present invention, when the temperature detection signal is at the H level, the output of the first switching circuit S is at the L level and the thyristor SCR is turned off, and the relay Ry turns off the switching contacts r and r. Cut off the heater circuit.

When the temperature detection signal becomes L level, the output of the first switching circuit S1 becomes H level, driving relay Ry and turning on switching contacts r and r.

In the process of temperature control, when the opening/closing contacts r and r are welded, the temperature of the heater 1 rises abnormally.As a result, the level of the temperature detection signal rises, and the second switching circuit S2 inputs the signal. The temperature fuse F is cut off by detecting the signal and turning on the thyristor 5CR2 to generate heat in the resistor R2.

This is true even if the thyristor SCR□ is non-conducting, the relay Ry is not driven, and the switching contacts r and r are on.

Next, even if the output of the inverter gate G2 becomes L level due to a failure in the inverter gates G□ and G2 of the first switching circuit S□, it is activated by the input side temperature detection signal, and the temperature increases due to the heat generated by the resistor R2. Cut off fuse F and disconnect heater 1.

As mentioned above, according to the abnormal temperature rise prevention circuit of the heating device of the present invention, the temperature fuse F and the switching contact re are connected to the AC power supply ■.
A heater 1 connected through r and a first switching circuit S1 activated by the temperature detection signal of the heater 1.
and a relay Ry that turns on and off the switching contacts r and r by the first switching circuit S1, and a thyristor SCR, and an output circuit that is connected to the input side of the first switching circuit S1. A second switching circuit S2 activated by the abnormal temperature detection signal is provided, and its output connects the AC power supply V and the temperature fuse F.
Temperature fuse F
Since the temperature detection input to the first switching circuit S is detected, the switching contacts r,
It is possible to cut off the temperature fuse F even in the event of welding of the relay R, poor conduction of the driving thyristor SCR of the relay Ry, or a failure of the first switching circuit S1, thereby providing a reliable circuit for preventing abnormal temperature rises. It will be done.

[Brief explanation of the drawing]

1A and 1B show a heat generating device, FIG. 1A is a cross-sectional front view in which a heater and a heat-sensitive electrode are configured separately, and FIG. 1 is a cross-sectional front view in which the heater and a heat-sensitive electrode are integrated. FIG. 2 is a diagram showing a conventional example of a temperature control circuit for a heating element. FIG. 3 is a diagram showing the temperature control circuit of the heat generating device of the present invention. ■...AC power supply, F...temperature fuse, Ry...relay r...opening/closing contact, S□. S2...Switching circuit, G1. G2. G3... Inverter gate, 1... Heater, 2... Heat sensitive element, 3... Heat sensitive electrode.

Claims (1)

[Scope of utility model registration request] A heater connected to an AC power supply through a temperature fuse and a switching contact, and a first heater that is activated by the temperature detection signal of the heater.
a switching circuit, an output circuit consisting of a relay and a thyristor that turn on and off the opening/closing contact by the first switching circuit, and an output circuit connected to the input side of the first switching circuit and whose operating level is higher than that of the switching circuit. a second switching circuit that operates at a level, and a circuit consisting of a resistor and a thyristor that connects the output of the second switching circuit in series to the AC power source and the temperature fuse, and shuts off the temperature fuse by heat generated by the resistor. A temperature control circuit for a heat generating device.