JPS6041433B2 - Temperature control circuit for sheet heating element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a temperature control circuit for a planar heating element used in carpets, roof heaters, etc., and its purpose is to connect a heater and a heat-sensitive electrode facing each other, and to provide a heat-sensitive element having a temperature impedance characteristic between them. In a planar heating element having a heat-sensitive electrode, when temperature control is performed by applying a high-frequency control signal voltage between the heater and the heat-sensitive electrode, the circuit configuration of the oscillation part that generates the control signal voltage is simple. The purpose of this invention is to provide a temperature control circuit that will become a reality.

Figures 1a and 1b show conventionally used carpets, in which a heater and a heat-sensitive electrode 2 are opposed to each other, and a heat-sensitive element 3 made of polyamide resin is interposed between them as a planar heating element, which is electrically insulated by an insulating layer 4. , furthermore, a front surface material 6 and a back surface material 6 are polymerized.

In FIG. 1a, the heater 1 has a fixed pattern having conductive parts meandering in a planar shape, and the heat-sensitive electrode 2 has a planar shape that is not patterned. In FIG. 1b, the heater 1 and the heat-sensitive electrode 2 are each formed in a meandering plane. 2), the temperature control circuit for the planar heating element supplies power to the heater 1 from a commercial frequency AC power source 7 via switching contacts 8, 8, and is connected to the AC power source 7. A control circuit power supply section 9 is provided, and by operating an oscillation section 10, a synthesis section 11, and a switching section 12 in the power supply section 9, a control signal voltage from the oscillation section 10 is connected to the heater 1 via a coupling section 11. A coupling section 11 detects a change in the signal voltage applied between the heat-sensitive electrodes 2 due to a change in impedance of the heat-sensitive element 3, and drives a switching section 12 to turn on or off the switching contacts 8, 8.

In this case, the heat-sensitive electrode 2 is normally charged to the same potential as the heater 1 by the induced voltage from the heater 1, although the value differs depending on whether there is a person on the carpet surface or not, that is, whether it is insulated or not. Therefore, if a person rides on that part, resulting in a locally insulated state, or if a metal pin is inserted into the part, a dead zone will be created, causing problems in the operation of the control circuit.

Therefore, the frequency of the signal voltage used for temperature control is set to a frequency different from the commercial frequency by the oscillator 10, but in this case, the coil L is set as shown in FIG.
and capacitor C. , C2, and the oscillation section 10 is generally constructed of a Colpitt type LC oscillation circuit using a sine wave. However, in such an oscillation circuit using a sine wave, when oscillating a control signal around IKHZ,
It is determined by f = 1'2 no LC, but taking into account the oscillation conditions and miniaturization, the value of capacitor C cannot be very large, and the value of inductance L is around 10 hH. This makes the shape larger. In addition, a capacitor C is used as a means to adjust the frequency of the control signal voltage.
It is difficult to finely adjust the value of (usually due to the inductance L). Therefore, it becomes larger and more expensive.

The present invention was developed in view of the above-mentioned circumstances, and utilizes a signal whose control frequency is a distorted wave containing harmonic components. 4 to 7, the case where a square wave is used as the oscillation waveform will be explained as an example. Control circuit power supply unit 9 connected to power supply 7
, the temperature control circuit is the same as the conventional example shown in FIG. 2, and includes an oscillating section 10, a coupling section 11, and a switching section 12.However, as shown in FIG. , an inverter gate ICAA is used to output the square wave shown in FIG.

The oscillation frequency can be easily adjusted by adjusting the resistor R, and since no inductance component is used, the device can be made compact and can be oscillated at low cost. In the case where a square wave is used in this way, the next-stage coupling section 11 uses coupling transformers on the transmitting side and the receiving side, respectively, as shown in Fig. 5, and the square wave is applied between the heater and the heat-sensitive electrode 2 on the transmitting side. At the same time, on the receiving side, a filter circuit B made of LC is provided in the coupling section 11 to extract the fundamental harmonic components of the square wave, cut odd harmonic components, and pass the fundamental harmonic components to the next stage switching circuit 12. It is used to drive the

The switching circuit 12 is a Schmitt switching circuit D using an inverter IC as shown in FIG. 6, which can be used in common with the inverter IC of the oscillation section 10, thereby reducing the size of the entire circuit configuration. Although a square wave is used in the embodiment of the oscillation unit 10 described above, it is of course possible to use other distorted AC waveforms having harmonic components, such as a triangular wave.

As explained above, according to the temperature control circuit for the sheet heating element of the present invention, the heater 1 is connected to the commercial frequency AC power source 7 via the switching contacts 8, 8, and the control circuit power source is connected to the AC power source 7. 9, an oscillation section 10, a coupling section 11, and a switching section 12. In addition, a heat-sensitive element 3 is interposed between the heater 1 of the planar heating element and the heat-sensitive electrode 2, and a change in impedance of the heat-sensitive element 3 is detected via the coupling part 11 to drive the switching part 12. Therefore, instead of the Colpitts oscillation circuit using a coil L and capacitors C, C2 as in the past, an oscillation circuit using a resistor R, a capacitor C, and an inverter gate IC can be used, which makes it much smaller than before. The oscillation section 10 and the switching section 1 can be constructed at low cost, and in order to extract the fundamental harmonic component from the distorted wave containing the harmonic component and drive the switching section 12.
The inverter IC can be shared with 2 and 2, and the amplitude VD in FIG.

/2 square wave can be easily oscillated and the fundamental harmonic amplitude is VDo
Since a large waveform of /m can be obtained, the value of the voltage VDD of the control circuit power supply section 9 may be a small value, and the circuit-related parts of the isotemperature control circuit can be made smaller so that the power supply section can also be made smaller.

[Brief explanation of drawings]

1 to 3 show a conventional temperature control circuit for a planar heating element, FIG. 1a is a cross-sectional front view showing the configuration of the planar heating element, and FIG. 1b shows another configuration. It is a cross-sectional front view. FIG. 2 is a diagram showing the temperature control circuit, and FIG. 3 is a circuit diagram of the oscillation section. 4 to 7 show an embodiment of the temperature control circuit for the planar heating element of the present invention, FIG. 4 is a circuit diagram of the oscillating section, FIG. 5 is a circuit diagram of the coupling section, and FIG. 6 is the oscillating section. Output waveform diagram of
FIG. 7 is a circuit diagram of the switching section. 1... Heater, 2... Heat-sensitive electrode, 3... Heat-sensitive element, 7... AC power supply, 8... Switching contact, 9...
... Control circuit power supply section, 10 ... Oscillation section, 1
1...Coupling section, 12...Switching section, R...Resistor, C...Capacitor, A...
...Inverter IC, B...Filter section. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7

Claims (1)

[Claims] 1 A heater connected to a commercial frequency AC power source via a switching contact, and a control circuit connected to the AC power source A temperature control circuit comprising a power supply section, an oscillation section, a coupling section, and a switching section, and the output of the oscillation section A distorted wave containing harmonic components is applied as a signal voltage at a control frequency between the heater of the planar heating element with a heat-sensitive element interposed therebetween and the heat-sensitive electrode via the coupling part, and a signal voltage is generated as the impedance of the heat-sensitive element changes. A temperature control circuit for a planar heating element configured to detect a change in temperature through a coupling part and drive a switching part.