JPS61143975A - Safety device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a circuit for a safety device for a heating element used in an electric heater.

BACKGROUND ART A conventional safety circuit can be found, for example, in Shinkai Publication No. 53-23409. The circuit configuration is shown in FIG. 4. Both ends of the signal line 3 of the heating element are connected, and two series circuit units of a diode and a heating resistor are connected in series so that the diodes have opposite polarities. , the two sets of dividing points and the connection portions at both ends of the signal line 3 were connected.

As shown in Fig. 5, the heating element used here consists of a heating wire 1 spirally wound around a core yarn 4, a heat-sensitive layer 2 coated on top of the heating wire 1, and a signal wire 3 spirally wound on top of the heating wire 1. It was constructed by winding the wire around the wire and sequentially providing an outer insulation layer 6 thereon. In the heating element and circuit configuration of this configuration, when the heat generated by the heating element is overheated to an abnormal temperature due to a failure or misuse of the control circuit A section, the heat sensitive layer 2 melts and the signal The wire 3 and the heating wire 1 are short-circuited, and current flows through the heating resistors R1 and R2 to heat them, and the temperature fuses T and F are fused to maintain safety.

Problems to be Solved by the Invention In such a conventional circuit, if the signal line 3 is disconnected at two or more places, even if abnormal overheating occurs in the heating element, no current flows through the heating resistors R1 and R2. In some cases, the temperature fuses T and F remain unfused, and abnormal overheating of the heating element cannot be suppressed.

For example, at two points (,) and (b) in Figure 4, the signal line a
The signal line 3 was disconnected, and there was an abnormal temperature rise during that time.
Even if the heating wire 1 and the heating wire 1 are short-circuited, no current flows through the heating resistors R1 and R2, and the temperature fuses T and F are not blown out.

This meant that abnormal overheating in that area was progressing and there was a risk of a fire.

The present invention has been made in view of this point, and aims to provide a structure in which, if the signal line is disconnected, the relay that opens and closes the power supply to the heat generating line is immediately closed, and the energization is stopped. It is something that

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention provides a relay control circuit for a relay that opens and closes the power supply to the heat-generating wire, including a first semiconductor element that is controlled in accordance with a temperature signal; It is constructed from a series circuit of second semiconductor elements that detects a break in the signal line and controls the relay to open when the signal line is broken.

According to the present invention, with the above-described configuration, if the signal line is disconnected at even one point, the voltage between the temperature fuse heating circuit unit and the resistor connected in parallel disappears, and therefore the pulse transformer circuit connected in parallel with it is also disconnected. No current flows, and the second
No gate signal is applied to the semiconductor control element, and the relay becomes non-conductive, that is, no current flows through the relay coil circuit, and the relay is in an open state.

On the other hand, if abnormal overheating occurs for some reason, the heat-sensitive layer melts, and the signal line and the heating wire are short-circuited, the heating resistor will not generate heat no matter where on the heating element it overheats. ,
It also has the traditional final safety device of blowing out the temperature fuse.

Embodiment FIG. 1 is a block diagram showing a circuit of a safety device. A
, B, a power supply voltage is applied between them. From A terminal, temperature fuse T, F%! The main current flows to the B terminal via the J relay contact Rs and the heating wire 1. On the other hand, the circuit for driving the relay includes a diode D3, a resistor R6, and a relay coil Ry1.
A series circuit including a transistor Tr and a thyristor S is connected between the power supply voltages.

The temperature fuse heating circuit includes a heating resistor R1, a diode D1, a signal line 3, a diode D2, and a heating resistor R2.
A series circuit with the heating wire 1 is connected in parallel with the heating wire 1. The signal circuit for controlling the thyristor S includes a resistor R7 in parallel with the series circuit of the relay contact Rs, the heat generating resistor R1, and the diode D1, and a resistor R3 in parallel with the series circuit of the diode D2 and the heat generating resistor R2. Furthermore, a resistor R4 and a series circuit of neon lamps N, L and pulse transformers P, T are connected in parallel, and the secondary outputs of the pulse transformers P, T are connected to the thyristor S through the resistor R5. Consists of a circuit connected to the gate. In this circuit, diode D3 and resistor R4
and R5 and R6 are used to ensure stable operation or protection of each element, component, etc.

Resistors R3 and R7 use resistance values that are significantly larger than those of heat generating resistors R1 and R2, so when relay contact R8 is in the closed state and the A terminal is in a positive cycle, the current flows through heat generating resistor R1 and diode. The voltage flows to DI, the signal line 3, and the resistor R3, and the voltage across the resistor R3 has a large value close to the power supply voltage. Also, when relay contact Rs is open, A
When the terminal is in a positive cycle, current flows through resistor R7, signal line 3, and resistor R3, and if resistor R3 is set to a much larger value than R7, the voltage across resistor R3 will still be large. In other words, by choosing constant values for resistors R3 and R7, it is possible to obtain a voltage greater than the predetermined value across resistor R3, whether the relay contact Rs is open or closed. can. Therefore, if you use a neon lamp whose discharge starting voltage value is set to below the predetermined value, the pulse transformer P will always be used.

An output is induced on the secondary side of T, thus allowing the thyristor S to remain conductive. As described above, if the signal line 3 is not disconnected, the thyristor S can always be in a conductive state, but if the signal line 3 is disconnected, a voltage higher than a predetermined value will not be applied to the resistor R3, so the neon lamps N, L does not light up, and the gate signal to the thyristor S is cut off, resulting in a non-conducting state. Here, as mentioned above, the resistances R3 and R7 have very large values, so although a small current flows through the heating resistors R1 and R2, it does not generate heat, so there is no malfunction. On the other hand, when abnormal heating In operation, when the heat-sensitive layer 2 melts and the signal line 3 and the heating line 1 are short-circuited, no matter where the short-circuit occurs, at least one of the heating resistors R1 or R2 generates heat and a temperature fuse is generated. It operates safely by fusing T and F.

Note that during normal temperature control, as mentioned above, the thyristor S is always maintained in a conductive state, so when the processed temperature signal is input to the base terminal C of the transistor Tr, Relay RY becomes conductive, and becomes non-conductive when no input is received. This shows exactly the same operation as the conventional one.

FIG. 2 is a structural diagram of a heating element used in an embodiment of the present invention, in which a signal wire 3 is spirally wound around a core yarn 4, a heat-sensitive layer 2 is formed on the outside, and a heating wire 1 is placed on top of the heat-sensitive layer 2. After winding the material into a spiral shape, the outer insulating layer 6 is formed. Here, the difference from the conventional heating element (Fig. 5) is that the heating wire is an outer winding, and the signal wire 3 is an inner winding, so the inside and outside are configured in the opposite way to the conventional one. . In general, in this type of double-wound heating element, the inner winding has a smaller diameter than the outer winding, so the bending strength is inferior to that of the outer winding. Moreover, since the heating wire 1 is required to have a lower resistance than the signal wire 3, the fresh area of the heating wire becomes larger, which is a further disadvantageous condition for the bending strength of the material. In this way, the reason why conventional heating elements use an inner-wound heating wire even though the inner-wound wire is less convenient for bending is because the signal wire is broken (broken in two or more places). ), there is no failsafe. However, as in this embodiment, a disconnection is detected and
Since it became possible to operate safely, the heating element used in this example had a configuration as shown in FIG. 2. Of course, even if the conventional heating element shown in FIG. 5 is used, the structure of the present invention exhibits the same effect.

FIG. 3 shows the second embodiment, which is composed of two heating elements and has basically the same circuit configuration.
Two signal lines 3 and 3' are connected in series. Further, 1' is a heating wire, and 2' is a heat-sensitive layer.

Effects of the Invention As described above, according to the present invention, the following effects are brought about since the present invention operates safely in the event of a disconnection of the signal line.

(1) A more advanced fail-safe circuit is constructed, improving product safety.

(2) The specification of the heating element can be changed from the inner winding to the outer winding, and the outer winding of the heating wire can improve the bending strength.

(3) Similarly, if the heating wire outer winding method is used, a heating element with excellent rapid heating properties will be obtained.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a circuit in an embodiment of the present invention, FIG.
FIG. 4 is a block diagram showing a circuit in the conventional example, and FIG. 6 is a structural diagram of a conventional heating element. 1... Heat generating wire, 2... Heat sensitive layer, 3...
...Signal line, R1, R2...Heating resistor, T,
F...Temperature fuse, RY...Relay,
Rs...Relay contact, Tr/transistor,
S...Thyristor, N, L...Neon lamp, P, T...Pulse transformer. Name of agent: Patent attorney Toshio Nakao and one other person ÷ 4, 喰Rs - + Lou hat, 1, Hi!... Ryomasu, trench Figure 5 2... , stutter layer

Claims (2)

[Claims] (1) Equipped with a heating element composed of a heating wire, a heat-sensitive layer, and a signal line, a thermal fuse heating circuit, and a relay control circuit,
The relay control circuit includes a first semiconductor element that is controlled according to a temperature signal, and a second semiconductor element that detects a disconnection of the signal line and controls the relay to be in an open state when the signal line is disconnected. A safety device with a series circuit. (2) The thermal fuse heating circuit is constructed by connecting two series circuit units of a diode and a heat generating resistor in series to both ends of the signal line in a direction in which the diodes have opposite polarities, and the unit Claim 1, further comprising a circuit that connects a resistor having a higher resistance than the heat generating resistor in parallel with one of the heat generating resistors, and detects a disconnection of the signal line based on a voltage fluctuation between the resistors. safety equipment.