JPS6040678B2 - sheet heating element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a sheet heating element used in carpets, roof heaters, and the like.

What is shown in FIG. 1 is a cross section of a conventional sheet heating element, in which an insulating layer 4 is polymerized on both the upper and lower surfaces of a film heater 1.
On top of this, a heating element 2 made of sheet-like semiconductor plastic such as nylon resin and having negative impedance characteristics with respect to temperature is sandwiched between a pair of heat-sensitive electrodes 3a and 3b formed of metal foil such as aluminum foil. It has a structure in which detecting sections 5 are stacked, and the temperature detecting section 5 detects a change in a signal applied between both heat-sensitive electrodes 3a and 3b due to a change in impedance of the heat-sensitive element 2.

In this case, the temperature detection signal that is released uses the same commercial frequency as the commercial power supply that is supplied to the heater, simplifying the detection and control circuits. However, since the structure of this sheet heating element is complicated, the manufacturing cost of the sheet heating element accounts for the majority of the total cost including the control circuit and the like. In contrast, a configuration as shown in FIG. 2 has been proposed. This is done by arranging the pattern of the heater 1 on the insulating layer 4,
On top of this, a sheet-like heat-sensitive element 2, a sheet-like heat-sensitive electrode 3, and an insulating layer 4 are sequentially layered, and a temperature control signal is applied between the heat-sensitive electrode 3 and the heater 1. . In this case, the heat generating part and the temperature detecting part are integrated, so the manufacturing cost is low, and the heater and sensor V
Since it is in contact with the thermal element, the temperature of the heater can be detected accurately. However, in this case, if the temperature detection signal uses the same frequency as the commercial power supply applied to the heater, the following problem will occur. That is, since the heat-sensitive electrodes are coupled via the heat-sensitive element, the heat-sensitive electrodes receive a certain alternating current voltage (approximately 50 V) due to the commercial power supply voltage applied to the heater. On the other hand, temperature is detected by detecting changes in the signal applied between the heat-sensitive electrode and the heater, such as voltage changes due to changes in the impedance of the heat-sensitive element. The sensitive electrode is affected by the commercial power supply voltage applied to the heater, making accurate temperature detection inaccurate. If the heater at the same potential is short-circuited with the heat-sensitive electrode, it may not be possible to detect a change in the signal. Therefore, in this planar heating element, the temperature detection signal is transmitted at a frequency different from the commercial frequency, for example, 50
It is necessary to reduce the influence of commercial power supply by using 0Hz or IKHz. For this reason, an oscillation circuit, an insulating transformer, etc. are also required in the control circuit, but the increased cost of the control circuit can be fully eliminated by reducing the cost of the sheet heating element. A planar heating element in which the two are integrated can be provided at a lower cost.
However, the planar heating element which has such advantages also has the following problems. In other words, as shown in Figure 2,
When the pin 11 is inserted into this planar heating element, if it is disconnected from the heater 1, which is arranged only in a certain pattern, an AC potential of about 50V is applied by the commercial power supply voltage applied to the heater 1 as described above. Heat sensitive electrode 3
This causes pin 11 to be charged. Of course, if the pin 11 were inserted through the heat-sensitive electrode 3 and the heater 1, the impedance between the heat-sensitive electrode 3 and the heater 1 would change, so this could be detected and the power to the heater 1 cut off. However, if this heater is removed and becomes dirty, there is a risk of electric shock due to the pin 11 unless a leakage detection function is added to the control circuit. The purpose of the present invention is to provide a planar heating element with this integrated structure that does not require the above-mentioned electric shock countermeasures, and as shown in FIG. A sheet-like heat-sensitive element 2 is arranged on a heater 1 which has a pattern and a heat-sensitive electrode 3 having the same pattern as the heater 1. They are placed opposite each other.

As a result, the pin 11 passing through the heat-sensitive electrode 3 necessarily passes through the heater as well, and the control circuit is activated to cut off power to the heater, thereby preventing electric shock. Figure 4 and below shows this control circuit, where 6 is a commercial power supply, 7 is a power supply circuit, 8 is an oscillation circuit, 9 is a coupling circuit, and 10 is a switching circuit.The operation of each part will be briefly explained. , the oscillation circuit 8 is activated by the DC voltage supplied from the power supply circuit 7, and oscillates a signal at a frequency different from the commercial frequency. FIG. 7 shows an example of this oscillation circuit 8, and shows a Colpitts oscillation circuit. This oscillated signal is supplied between the heat-sensitive electrode 3 and the heater 1 by the coupling circuit 9. FIG. 5 shows an example of the coupling circuit 9. When a signal is input in a state insulated by the transformer T, the signal is connected to the heat-sensitive electrode 3 and the heater 1 via the primary winding of the transformer T2 and the coupling capacitor C. applied in between. The secondary side of transformer T2 is capacitor C3
A parallel resonant circuit is constructed and resonates with the frequency component of the signal. The voltage of the signal applied between the heat-sensitive electrode 3 and the heater 1 changes as the impedance of the heat-sensitive element 2 changes. In other words, the impedance of the value obtained by converting the resonance impedance of the secondary side of the transformer L to the primary side and the heat-sensitive element 2
A signal voltage determined by the ratio of the impedance of C2 is a coupling capacitor. 8th
The figure shows an example of the switching circuit 10. When a rectified signal voltage is input to the comparator 13, the comparator 13 switches the output level according to the height of the signal voltage with respect to the temperature of the heater 1, By operating the line Ry, control contacts 12, 12 inserted between the commercial power source 6 and both ends of the heater 1, respectively, are opened and closed. FIG. 6 shows another coupling circuit 9, in which the transformer L
When a signal is input from the oscillation circuit 8 via the temperature setting variable resistor VR and the coupling capacitor C4, this signal is transmitted to the heat-sensitive electrode 3 and the heater 1 through the variable resistor VR and the impedance of the heat-sensitive element 2. It is applied at a voltage ratio determined by the voltage division ratio of . The change in impedance due to the temperature of the heat-sensitive element 2 is inputted to the switching circuit 1 via the transformer t as a change in signal voltage. Similar to the transformer T2, the transformer T4 forms a parallel resonant circuit with the capacitor C8, and exhibits a sufficiently higher impedance than the impedance of the heat-sensitive element 2 at the signal frequency. C5 is a coupling capacitor. In this case, since the signal voltage input to the switching circuit becomes opposite to that shown in FIG. 5 with respect to temperature changes, the voltage operation of the comparator 13 of the switching circuit 10 also becomes opposite. Therefore, if the temperature of the heater 1 is not higher than the set value, the control contact 12 is turned off, and if the temperature is lower than the set value, the control contact 12 is turned on, and the heater 1 temperature is controlled within the set range. . A short circuit between the heat-sensitive electrode 3 and the heater 1 is similarly detected, and the control contact 12 is turned off. This prevents electric shocks caused by short-circuited pins. As mentioned above, in the present invention, the heat-sensitive electrode, which is AC-charged by the commercial power applied externally, is always facing the heater arranged in the same pattern. The pin inserted into the body either passes through both the heater and the heat-sensitive electrode, or it does not pass through it at all; in the former case, the current to the heater can be controlled by shorting with this pin; in the latter case, has the advantage that there is no danger and there is no need to take special measures against electric shock.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a conventional example, FIG. 2 is a sectional view of another subordinate example, FIG. 3 is a sectional view of an embodiment of the present invention, FIG. 4 is a block diagram of the same control circuit, and FIG. 6 and 6 are respectively coupling circuit diagrams in the control circuit, FIG. 7 is an oscillation circuit diagram, and FIG. 8 is a switching circuit diagram. , 3 indicates a heat-sensitive electrode. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8

Claims (1)

[Claims] 1 In a planar heating element, a temperature detection signal of a frequency different from the commercial frequency is applied between the heater and the heat-sensitive electrode, which face each other across a heat-sensitive element whose impedance changes depending on the temperature. A planar heating element characterized in that the heating elements are arranged in the same pattern and facing each other.