JPH0243316B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a DC power supply heater overheat detection device for heating a car seat, bed, etc.

A conventional heater overheat detection device for a direct current power supply of this type was constructed as shown in FIG. This example shows a car seat heater that heats the seats of a car. That is, in FIG. 1, 1 is a seat sheet, 2 is a back sheet, 3 is a heater wire that heats the seat and back sheets 1 and 2, and 4 is a wire between the seat and back sheets 1 and 2. A thermostat 5 which is embedded and controls the temperature of the heater wire 3 is embedded in the same place as the thermostat 4, and which detects overheating of the heater wire 3 and stops energization of the heater wire 3. circuit breaker, 6
is a lead wire, and 7 is a connector that connects to the car's battery. However, in the above-described conventional configuration, the overheat circuit breaker 5 is activated by detecting overheating at one point, and therefore cannot detect local overheating in other parts, for example, if the thermostat 4 is welded. If the cushion comes off the overheat circuit breaker 5 and covers the seat sheet 1 while the heater wire 3 is continuously energized, only the space between the cushion and the seat sheet 1 will overheat. become,
As a result, there was a risk that the overheat circuit breaker 5 would not operate, leading to a fire.

The present invention solves the above-mentioned conventional drawbacks, and aims to detect overheating in all parts of the heater wire and stop energization of the heater wire.

To achieve the above object, the present invention provides a tubing heater configured in a tube shape by winding a heater wire and a conductive wire through an insulator that melts at high temperatures; A resistor that generates a small voltage drop due to the flowing current.
It is provided with a voltage generator such as a diode, a potential change detection means for detecting a potential change in the conductive wire, and an energization stopping means for stopping energization of the heater wire based on the output of the potential change detection means. be.

With the above configuration, when the heater wire overheats due to a welding failure of the thermostat, the insulator melts due to the overheating, and the heater wire and the conductive wire come into contact with each other. The potential of the conductive wire moves and changes to the potential of the contact portion with the heater wire. For example, the conductive wire is normally set at ground potential, and the voltage generator is connected between the heater wire and the ground potential, so that when the heater wire and the conductive wire come into contact, the contact point, That is, no matter where the overheating point is, the potential of the conductive wire increases from the ground potential to a value higher than the potential generated by the voltage generator. The potential change detecting means detects the potential change and energizes the energization stopping means to stop energizing the heater wire, thereby making it possible to prevent a fire from occurring.

In other words, the above action makes it possible to reliably detect overheating at all points where the heater wires are installed and stop energizing the heater wires, dramatically increasing safety in terms of fire prevention. It has the excellent feature of improving performance.

An embodiment of the present invention will be described below with reference to FIGS. 2 to 4.

FIG. 2 shows a structural diagram of the tubing heater used in the present invention, in which 8 is a core thread, 9 is a conductive wire wound on the core thread 8, and 10 is a conductive wire 9 that covers the entire surface thereof. This insulating material 10 is made of a material such as nylon that melts when heated to high temperatures. Reference numeral 11 denotes a heater wire wound on the insulator 10, and this heater wire 11 is wound with a certain stress. Reference numeral 12 denotes an insulating coating that covers the entire surface of the heater wire 11.

In the above configuration, when the heater wire 11 is overheated, the insulator 10 melts, and the stress of the heater wire 11 causes the heater wire 11 to contract toward the center and come into contact with the conductive wire 9. Note that, depending on the structure of the tubing heater, the conductive wire 9 and the heater wire 11 may be interchanged, or the inner wire may not be wound but may be straight and serve as a core thread. There are many examples, and the invention is not limited to the example shown in FIG.

FIG. 3 shows an electrical circuit diagram of the present invention.
13 is a DC power source, which in this case is a car battery. 14 is the ground potential of the DC power supply, 1
5 is a heating switch; 16 is a resistor that generates a slight voltage drop due to the current flowing through the heater wire 11; and 17 is a resistor that fixes the conductive wire 9 to the ground potential 14; A wire having a much higher resistance value (several tens of kilohms or more) than the heater wire 11 or the conductive wire 9 is used. 1
Reference numeral 8 denotes a potential change detecting means for detecting a change in the potential of the conductive wire 9. This potential change detecting means 18 is composed of resistors 19 and 20 that generate a reference potential, and a comparator 21 (open collector type comparator). There is. Reference numeral 22 denotes energization stopping means for stopping energization of the heater wire 11 based on the output of the potential detecting means 18. Resistor 25 that suddenly heats up due to
and a temperature fuse 26 that is blown by the heat generated by this resistor 25.

In the circuit configuration shown in FIG. 3 above, during normal temperature adjustment after turning on the heating switch 15,
Since the heater wire 11 does not overheat, there is no contact between the conductive wire 9 and the heater wire 11, and therefore the potential of the conductive wire 9 is fixed to the ground potential 14 by the resistor 17. Therefore, the positive input terminal potential of the comparator 21 is lower than the negative input terminal potential, and its output is OFF, so that the transistor 24 remains OFF.
However, if part or all of the insulator 10 melts due to welding or local heating of the thermostat 4, and the conductive wire 9 and the heater wire 11 come into contact, the potential of the conductive wire 9 will change to the previous one. The potential increases from the ground potential to the potential of the contact portion of the heater wire 11. At this time, the heater wire 11 is raised from the ground potential by the potential generated at both ends of the resistor 16, that is, the potential is biased, so if the heater wire 11 comes into contact with the part closest to the ground. Even if it is, a rise in potential generated across the resistor 16 appears on the conductive line 9. Therefore, by setting the reference potential obtained by the resistors 19 and 20 to a value approximately intermediate between the potential across the resistor 16 and the ground potential, the change in the potential of the conductive wire 9 can cause the The potential at the + side input terminal of the comparator 21 rises higher than the potential at the - side input terminal, and its output becomes ON. Thereby said transistor 2
4 is turned ON, and the heating resistor 25 is made to generate heat to blow out the temperature fuse 26 and the heater wire 1 is turned on.
1 is stopped. This can prevent a fire from occurring.

FIG. 4 shows an electric circuit diagram in another embodiment of the present invention, and the only difference from FIG. 3 is that a diode 27 is connected instead of the resistor 16 as a voltage generator. The operation is similar to that shown in FIG.

As described above, the DC power supply heater overheat detection device of the present invention has the following excellent features.

(1) A tubing heater configured in a tube shape by winding a heater wire and a conductive wire through an insulator that melts in a high temperature state, and a tubing heater that is connected in series with the heater wire and that when the heater wire is energized, A voltage generating body such as a resistor or diode that generates a minute voltage drop due to the current flowing through the wire, a potential change detecting means for detecting a change in the potential of the conductive wire, and an output of the potential change detecting means. It is equipped with an energization stopping means that stops the energization of the heater wire, and is equipped with a energization stopping means to stop the energization of the heater wire.
When overheating of the heater wire occurs, the insulator melts due to the overheating, and the heater wire and the conductive wire come into contact and the potential of the conductive wire changes, so that the heater wire Since the heater wire is configured to detect overheating and then stop the power supply to the heater wire, overheating status can be monitored over a wide range, resulting in a highly safe system that can prevent fires from occurring. A heater overheat detection device can be provided.

(2) Since the overall potential of the heater wire can be biased by the voltage generator, no matter where the conductive wire and the heater wire come into contact, the potential is at least equal to the potential bias. appears as a change in the potential of the conductive wire, and as a result, the heater wire has a configuration in which there is no blind spot at all in its ability to detect local overheating, so the reliability of overheat detection is extremely high.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram of a conventional DC power supply heater overheat detection device, Fig. 2 is a perspective view showing the structure of a tubing heater used in the DC power supply heater overheat detection device of the present invention, and Fig. 3 is the same detection device. Electrical circuit diagram of the device. FIG. 4 is an electrical circuit diagram showing another embodiment of the present invention. 9... Conductive wire, 10... Insulator, 11... Heater wire, 13... DC power supply, 16... Resistor, 18...
... Potential change detection means, 22 ... Energization stopping means, 2
7...Diode.

Claims (1)

[Claims] 1. A tubing heater configured in a tube shape by winding a heater wire and a conductive wire through an insulator that melts in a high temperature state, a DC power source for energizing the heater, and a negative side of the heater wire and the DC power source. A voltage generator such as a resistor or diode that is connected between the heater wire and generates a slight voltage drop due to the current flowing through the heater wire when the heater wire is energized; Therefore, there is a potential change detection means for detecting a potential change in the conductive wire caused by contact between the heater wire and the conductive wire, and an energization stop for stopping energization of the heater wire based on the output of the potential change detection means. A DC power supply heater overheat detection device comprising: