JPH08213151A - Deterioration judgement method for heater wire and electrical equipment using the wire - Google Patents

Abstract

PURPOSE: To properly identify the service life of a resistance heat generating coil heater wire in an easy and inexpensive way for preventive maintenance by superposing a high frequency on the wire, and making judgement about the deterioration of the wire on the basis of a change in the impedance thereof. CONSTITUTION: Regarding a heater device 1 using a heater wire 2 formed in coil out of a resistance heat generating material such as a nichrome wire, the commercial AC or DC power supply is used as a heating power source 3. Furthermore, a high frequency is superposed on the wire 2 from a high frequency power supply 4. In this case, a superposition circuit 5 is provided with a high-pass filter A6, and a heater circuit is provided with a low-pass filter B7, respectively to prevent the interference of both power currents. Thereafter, a change in the impedance of the wire 2 is detected with an ammeter as a high frequency current change. The change so detected is used for identifying the deterioration of the wire 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention mainly relates to a method for determining the deterioration state of a heating wire of an electric device having a heating wire, and an electric device to which the method is applied.

[0002]

2. Description of the Related Art Deterioration of a heating wire is not constant even if the heating wire has the same specifications due to the usage environment of the heating wire and variations in products. Therefore, in the past, emphasis was placed on detecting wire breakage, and the presence or absence of current flowing in the heating wire was monitored, and a new wire was replaced with a wire break, or periodic replacement based on the period of use based on the track record of wire breakage. It is being carried out.

Further, a method of grasping the deterioration state of the heating wire by the change of the voltage and current of the heating power source is not practical in terms of sensitivity. In other words, the method according to the prior art is the most primitive BM (post-maintenance) in terms of maintenance technology,
Depending on the use of the electric equipment having the heating wire, there is a problem that the heating wire deteriorates or breaks, causing a serious failure, and the maintenance cost becomes large in the case of regular replacement.

[0004]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems, accurately grasps the life of the heating wire, and replaces a new one before the heating wire is broken, that is, it is possible to determine deterioration of the heating wire that enables preventive maintenance. An object of the present invention is to provide a method and an electric device to which the method is applied.

[0005]

DISCLOSURE OF THE INVENTION The present invention is characterized in that a high frequency is superposed on a heating wire which is a resistance heating element and is formed in a coil shape, and an impedance change of the heating wire is used for deterioration determination. In the present invention, it is preferable that the present invention detect a change in impedance of the heating wire as a change in high frequency current, and the present invention is a resistance heating element and has a heating wire formed in a coil shape. In electric equipment, heating power supply / control circuit, high frequency power supply /
An electric device having a detection circuit and a superposition circuit.

The present invention uses incandescent bulbs made of Nichrome wire and Kanthal wire, quartz heaters, tube heaters, electric heaters,
It is preferably applied to a cartridge heater, and further to an electric device equipped with them. Further, in the present invention, in order to prevent the heating power source current and the high frequency power source current from interfering with the high frequency power source and the heating power source, respectively, a low pass filter (low pass filter) is provided in the heating power source circuit. High-pass filter (high-pass filter) in the circuit
Is preferably arranged.

As the heating power source in the present invention, either an AC power source or a DC power source can be used.

[0008]

[Operation] The characteristics of the deterioration of the heating wire are: Reduction of conductor cross-sectional area due to surface oxidation of heating wire body → local heating disconnection 2. Deformation of the heating wire shape due to the heat atmosphere around the heating wire body → melting 3. There is an accidental disconnection due to product variations.

The inventors of the present invention have paid attention to the fact that the wire diameter change or deformation due to surface oxidation of the heating wire at the time of deterioration of 1 and 2 appears as a change of impedance in the case of the heating wire formed into a coil. Invented. The inventor
As a parameter for continuously monitoring the deterioration of the heating wire, a parameter satisfying the following conditions was considered.

[0010] 1. It must be a parameter that sensitively reflects the shape change of the heating wire. 2. It must be a parameter that does not affect the actual heating control. In order to satisfy the above conditions, the detection system must have a high frequency voltage /
We decided to use electric current. The advantages in this case are: A change or deformation of the wire diameter of the heating wire can be detected as an impedance change, and the impedance change has a larger change amount than the pure resistance change.

2. Weak high frequencies do not affect the heating and control of commercial AC power supplies and DC power supplies. Is mentioned. The high frequency power supply circuit in the present invention can be inexpensively configured by a simple oscillation device circuit.

[0012]

Embodiments of the present invention will be specifically described with reference to FIGS. FIG. 1 shows an example of a circuit configuration used in the method and apparatus of the present invention, and FIG. 2 shows an example of detecting an impedance change of a heating wire as a change of high frequency current according to the present invention. In FIG. 1, reference numeral 1 is a resistance heating element, and a heating device (1 kW, 50 kW) containing a heating wire 2 formed in a coil shape.
HZ / 60HZ AC), 3 is a heating power supply and its control circuit, 4 is a high frequency power supply and detection circuit, 5 is a superposition circuit, 6
Indicates a filter A which is a high pass filter, and 7 indicates a filter B which is a low pass filter.

As the simple oscillation device circuit, a crystal oscillation circuit (for example, Pierce circuit) or an LC oscillation circuit (for example, Hartley circuit, Colpitts circuit) is generally adopted. The detection circuit 4 has a built-in ammeter for measuring high frequency current in series with the circuit. The filter A, which is a high-pass filter, has an impedance of 1 MΩ or more for a current having a frequency of about 1 kHz or less, and the filter B, which is a low-pass filter, also has an impedance of 1 MΩ or more for a current having a frequency of about 1 kHz or more. Has impedance.

Therefore, it is possible to prevent the heating power source current and the high frequency power source current from interfering with the high frequency power source and the heating power source, respectively. In the above circuit configuration, when the impedance viewed from the high frequency power source side is Z, Z changes by ΔZ due to the shape change of the heating wire. The amount of change ΔZ is detected by the change in the high-frequency current I, and it can be determined that the deterioration occurs when I becomes equal to or less than the set value.

High-frequency current value I measured by the method of the present invention
2 shows the relationship between the heating time and the elapsed time after the start of use of the heating wire.
The high-frequency current value I at the start of use of the heating wire was 150 mA, and the heating wire was exchanged when it reached 50 mA five years after the start of use. The surface of the exchanged heating wire was oxidized, the cross-sectional diameter was reduced, and the overall shape was also deformed.

It should be noted that the set values in FIG. 2 for judging deterioration are theoretical when the deformation / deterioration state is unique, and when the deformation / deterioration state is not, the data is accumulated while monitoring the state periodically. Can be corrected.

[0017]

According to the present invention, by superposing a high frequency wave on the heating wire which is a resistance heating element and is formed in a coil shape, and using the impedance change of the heating wire for the deterioration determination of the heating wire,
It has an industrially excellent effect that it is possible to avoid serious troubles due to deterioration and disconnection of the heating wire in advance, and the maintenance cost can be reduced as compared with the conventional regular replacement method.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of a circuit configuration used in the method and apparatus of the present invention.

FIG. 2 is a graph showing an example of detecting a change in impedance of a heating wire according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Heating device 2 Heating wire 3 Heating power supply and its control circuit 4 High frequency power supply and detection circuit 5 Superposition circuit 6 Filter A 7 Filter B

Claims (3)

[Claims] 1. A method for determining deterioration of a heating wire, comprising: superposing a high frequency wave on a heating wire formed of a resistance heating element and having a coil shape, and using a change in impedance of the heating wire for deterioration determination. 2. The heating wire deterioration determination method according to claim 1, wherein a change in impedance of the heating wire is detected as a change in a high frequency current. 3. An electric device, which is a resistance heating element and has a heating wire formed in a coil shape, comprising a heating power supply / control circuit, a high frequency power supply / detection circuit, and a superposition circuit.