JPH0770350B2 - Temperature control device for heating equipment - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a temperature control device for a heating tool using a sheet heater.

[0002]

2. Description of the Related Art As disclosed in Japanese Utility Model Publication No. 52-40447, a conventional temperature control device for a heating tool having a planar heater has a heat-sensitive layer whose resistance value changes with temperature change. A temperature detection electrode is provided via the heat-sensitive layer, and a short-circuit detection electrode plate (conductive sheet) is provided on the planar heater via the heat-sensitive layer.

The control means measures the resistance value of the heat-sensitive layer by using the temperature detecting electrode to detect the temperature in the vicinity of the sheet heater, and compares and controls the temperature in the sheet heater and the set temperature. The temperature of the planar heater is maintained at the set temperature.

The short-circuit detection electrode plate (conductive sheet) detects a short-circuit current when a pin or the like is stabbed to prevent electric shock, and is usually provided in a warming tool using a planar heater. It is a thing.

[0005]

However, in the case of the above-mentioned conventional apparatus, the body of the heat collecting tool must be provided with a heat sensitive layer and a temperature sensing electrode for performing normal temperature control in addition to the short circuit sensing electrode plate. In addition, the structure of the body of the warming tool is complicated, and in the temperature control method using the heat-sensitive layer and the temperature detection electrode, when used at a high temperature of, for example, about 60 ° C., the heat-sensitive layer deteriorates severely and the heat Since the temperature characteristic of the layer changes, there is a problem that an error in the detected temperature occurs.

The present invention has been made in view of the above points, and the structure of the heating tool can be simplified to reduce the number of manufacturing steps, and even if the heating tool is used at a high temperature, an error in the detected temperature due to deterioration does not occur. An object of the present invention is to provide a temperature control device for a tool.

[0007]

In order to solve the above-mentioned problems, the present invention relates to a sheet heater connected to a power source via an energization control means, and the sheet heater via an insulating member to the sheet heater. A conductive sheet provided so as to have a capacitance between, a rectifier circuit provided in parallel with the planar heater, and a variable resistor connected to the rectifier circuit for varying the detection level, And the other end is composed of a leakage current detection means connected to the conductive sheet, and a control means connected to the leakage current detection means and the energization control means, the control means from the leakage current detection means. The energization control means is controlled based on the detection signal to maintain the temperature near the planar heater at a desired temperature.

[0008]

[Operation] The variable resistance is operated to determine the set temperature, and the operation is performed.

At this time, the rectifier circuit generates a DC voltage for generating a leakage current between the conductive sheet and the planar heater,
Apply to the conductive sheet side.

First, when the temperature in the vicinity of the sheet heater is lower than the set temperature, a small leakage current flows between the sheet heater and the conductive sheet, so that the leakage current detecting means controls without detecting the leakage current. No detection signal is input to the means. Therefore, the control means determines that the temperature near the planar heater has not reached the set temperature, and sends a signal to the energization control means to energize the planar heater.

Next, when the temperature in the vicinity of the sheet heater is higher than the set temperature, a large leakage current flows between the sheet heater and the conductive sheet. Therefore, the leakage current detecting means detects the leakage current. A detection signal is input to the control means. Therefore, the control means determines that the temperature in the vicinity of the planar heater has reached the set temperature, does not send a signal to the energization control means, and energizes the planar heater.

As described above, the leak current detecting means detects the leak current between the sheet heater and the conductive sheet to maintain the temperature near the sheet heater at a desired temperature.

Further, since an insulating member is provided between the sheet heater and the conductive sheet and the leak current is detected, deterioration due to temperature does not occur, and the temperature can be detected to such an extent that the insulating member does not melt. is there.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

First, in FIG. 1, 1 is a commercial AC power supply,
A sheet heater H is connected to the commercial AC power source 1 via a power switch S1, an emergency switch S2, and a bidirectional three-terminal thyristor SCR which is an energization control means.

Then, diodes D1 and D2 whose cathodes face each other in parallel with the planar heater H, and resistors R2 and R for voltage drop between the diodes D1 and D2.
The rectifier circuit 2 formed by connecting 3 is connected. The output of the rectifier circuit 2 is the light emitting diode side (input) of the photocoupler P which is the leakage current detecting means and the photocoupler P.
Is connected in parallel to the conductive sheet ES via a variable resistor VR for varying the detection level and a current limiting resistor R4.
It is connected to the.

Although not shown, the heater 3 has a quadrangular sheet heater H, which is located above the sheet heater H and has the same shape and substantially the same area as the sheet heater H, for example, aluminum. A conductive sheet ES made of foil,
The planar heater H and the conductive sheet ES are each wrapped with vinyl chloride 3a which is an insulating member, and are bonded to each other in an electrically separated state. The lower surface of the planar heater H may be covered with a heat insulating material.

Reference numeral 4 denotes a control means, which is a port P5 and a port P.
6 is connected to the transistor (output) side of the photocoupler P. Further, the port P4 of the control means 4 is connected to the trigger terminal of the bidirectional three-terminal thyristor SCR, and the port P3 is connected to the resistor R1 which is a voltage detection means having one end connected to the output of the rectifier circuit. The ports P7 and P8 are connected to the relay coil RC, and the relay coil RC is configured to open the emergency switch S2 by the output signals from the ports P7 and P8.

Reference numeral 5 denotes a power supply circuit for the control means 4, which is connected between the power switch S1 and the emergency switch S2, and the output of the power supply circuit 5 is connected to the ports P1 and P2 of the control means 4. ing.

By the way, the sheet heater H and the conductive sheet E
S has substantially the same shape, and is insulated by vinyl chloride 5 during this period. Therefore, the structure is equivalent to that of a capacitor having a capacitance. That is, although a leakage current is generated between the planar heater H and the conductive sheet ES, the values of the leakage current are 30 ° C.-about 0.1 mA and 60 ° C.-about 0.2 mA as shown in FIG. It has the temperature characteristic of. In contrast to this characteristic, the photocoupler P has a characteristic of starting operation from 0.1 mA-0.9 V as shown in FIG.

Therefore, the variable resistor VR has a structure in which the resistance value can be set within a range in which the photocoupler P can operate between the normal operating temperature of 30 ° C. to 65 ° C.

The operation of the above structure will be described.

First, in normal operation, the power switch S1
Is closed, the shunt ratio is adjusted by the variable resistor VR, and the current flowing through the photocoupler P is set to 0.1 mA at 40 ° C., for example. The rectifier circuit 2 is a supply source that generates a leakage current between the planar heater H and the conductive sheet ES via the resistor R4.

Here, the temperature near the planar heater H is 10 ° C.
In the case of a certain degree, the control means 4 does not input a signal to the port P5 and the port P6, so that the port 4 causes a trigger output to the bidirectional three-terminal thyristor SCR to energize the planar heater H.

The temperature near the planar heater H is 40.degree.
When the photocoupler P operates and the signals are input to the ports P5 and P6 of the control means 4, the control means 4 receives the bidirectional three-terminal thyristor SCR from the port 4.
To stop the energization of the planar heater H.

Since such energization control is performed, the temperature of the heating tool 3 can be set by variable resistance VR from 30 ° C to 65 ° C.
The desired temperature between can be obtained.

Therefore, even if the heat collecting tool 3 is constituted only by the planar heater H, the conductive sheet ES, and the insulating member 3a that electrically insulates and covers these, the temperature control can be performed in the same manner as in the conventional case.

Next, the abnormal state will be described.

For example, during the above-mentioned normal operation, the pin or the like penetrates the conductive sheet ES and the planar heater H.
In the case of touching, a large current with respect to the leakage current flows between the conductive sheet ES and the planar heater H.

At this time, the trigger output from the control means 4 is stopped and the bidirectional three-terminal thyristor SCR is deenergized, but the diode D2 → resistor R3 → photocoupler P → resistor R4 → conductive sheet ES → planar. An electric current flows through the path of the heater H. Here, the control means 4 detects the voltage of the photocoupler P portion from the port P4 via the resistor R1, and the current of the above path causes the voltage of the photocoupler P portion to drop from 100V to, for example, 70V. Then, the control means 4 detects that the short-circuit current has been generated by the comparison means, outputs a signal from the port P7 and the port P8 to the relay coil RC, and opens the emergency switch S2.

Further, when the bidirectional three-terminal thyristor SCR fails and the planar heater H becomes conductive despite the absence of a trigger signal from the control means, as shown in FIG. A leakage current of about 4 mA will be generated, and by setting the set values of the resistor R1 and the comparison means (not shown) inside the control means 4 so that the voltage drop due to the leakage current can be detected, even with respect to an abnormal temperature. This can be dealt with by opening the emergency switch S2.

Therefore, since the voltage drop is detected by the resistor R1, not only the temperature control but also the abnormality detection can be performed, the function is the same as the conventional one, and the temperature of the heating tool 3a does not become complicated. A control device can be provided.

The present invention is not limited to the above-mentioned embodiment, the control means may be an electronic circuit or a microcomputer, and the leakage current detection means is not limited to the photocoupler but has a function capable of switching at a low current. What is necessary is that the sheet heater has a meandering wiring, and if it forms a capacitance that produces a leak current that can be detected between the conductive sheet and the sheet heater. The present invention can be appropriately modified and implemented without departing from the above.

[0034]

EFFECTS OF THE INVENTION In a heat collecting tool having a conductive sheet provided on a planar heater via an insulating member, a heat sensitive layer and a temperature detecting electrode are eliminated, and a leak current is detected by connecting to the conductive sheet to detect a leak current. Means and a variable resistor for varying the detection current are provided, and the control means cuts off the control signal to the energization control means in response to the detection of the leakage current to maintain the desired temperature. It is possible to provide a temperature control device for a heating tool in which the structure of the heating tool can be simplified, the number of manufacturing steps can be reduced, and an error in the detected temperature due to deterioration does not occur even when used at a high temperature.

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram of the present invention.

FIG. 2 is a characteristic diagram of leakage current with respect to temperature change of the heating tool of the present invention.

FIG. 3 is an operational characteristic diagram of the photocoupler according to the present invention.

[Explanation of symbols]

 SCR energization control means H planar heater 3a insulating member ES conductive sheet 2 rectifier circuit VR variable resistance P leakage current detection means 4 control means

Claims (1)

[Claims] 1. A conductive sheet provided so as to have a capacitance between a planar heater connected to a power source via an energization control means and the planar heater via an insulating member so as to have a capacitance. And a rectifier circuit provided in parallel with the planar heater and a variable resistor connected to the rectifier circuit for varying the detection level and having the other end connected to the conductive sheet for detecting leakage current. And a control means connected to the leakage current detection means and the energization control means, the control means controlling the energization control means based on a detection signal from the leakage current detection means to control the surface condition. A temperature control device for a heat collecting tool, characterized in that the temperature around the heater is maintained at a desired temperature.