JP2000230867A - Thermoelectric converter element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To raise the obtained thermoelectromotive force to expand the usable range. SOLUTION: A Cu wire 1 of 2.0 mm diameter is utilized and cut into Cu wires 1-1, 1-2, Cu suboxide 1-3 is formed at the contact between the Cu wires 1-1, 1-2 owing to the hot zone phenomenon and cut into two Cu wires 1-1', 1-2', and the Cu wire 1-1' is used as a second electrode the end face 1-1'a of which is polished. Similarly to the second electrode 1-1', a first electrode 2 (Cu wire of 2.0 mm diameter) the end face 2a of which is polished is prepared, and the end face 2a of the first electrode 2 and the end face 1-1' of the second electrode 1-1' are butted and bonded mutually.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermoelectric conversion element used for temperature measurement and the like.

[0002]

2. Description of the Related Art Conventionally, as this type of thermoelectric conversion element, an Armel-Chromel thermocouple (hereinafter referred to as a K thermocouple) has been often used. This K thermocouple has a first electrode (+ side) mainly composed of nickel and chromium, and a second electrode (− side) mainly composed of nickel, and has an end face of the first electrode. The end face of the second electrode is butted and joined. The junction between the first electrode and the second electrode is set at a temperature measurement point. Then, a thermoelectromotive force corresponding to the temperature at the temperature measurement point is generated at the junction between the first electrode and the second electrode.

[0003]

However, in the conventional thermoelectric conversion element such as a K thermocouple, the magnitude of the obtained thermoelectromotive force is small, so that its use is limited.

The present invention has been made in order to solve such a problem, and an object of the present invention is to provide a thermoelectric conversion element capable of increasing the obtained thermoelectromotive force and expanding its use. It is in.

[0005]

In order to achieve such an object, a thermoelectric conversion element according to the present invention has a first electrode composed mainly of copper (Cu) and a second electrode composed of sub-electrode. The electrode is mainly composed of copper oxide (Cu ₂ O).
According to the present invention, a thermoelectromotive force is generated at the junction between the first electrode mainly composed of copper and the second electrode mainly composed of cuprous oxide. Note that the second electrode is an integrally formed electrode mainly containing cuprous oxide. That is, instead of using powder or particles of cuprous oxide, a bulk electrode mainly containing cuprous oxide is used. The bulk electrode mainly composed of cuprous oxide is formed by a hot zone phenomenon using a material mainly composed of copper as a starting material.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on embodiments. FIG. 1 is a view showing a process of manufacturing a thermoelectric conversion element according to an embodiment of the present invention. In the present embodiment, for example, a copper wire 1 having a diameter of 2.0 mm shown as a conductor of a two-core cable in JISC3342 (see FIG. 1)
Using (a)), this copper wire 1 is cut into two to obtain copper wires 1-1 and 1-2 (FIG. 1 (b)). The cable used for the actual measurement was Nishi Nippon Electric Cable Co., Ltd.
This is a V flat vinyl insulated vinyl sheath cable (VVF).

The end of the copper wire 1-1 and the copper wire 1-
The end faces of the copper wire 1-1 and the end face of the copper wire 1-2 are repeatedly opened and closed during the energization. When the opening and closing are repeated, cuprous oxide 1-3 is generated at the contact portion due to the heat of the opening and closing arc (FIG. 1C). Since the cuprous oxide 1-3 near room temperature has a large resistance, when the copper wire 1-1 and the copper wire 1-2 come into contact with each other with the cuprous oxide 1-3 interposed therebetween, almost no current flows.

In this state, as one of means for increasing the temperature of the contact portion, a small amount of water drops is dropped on the cuprous oxide 1-3. Then, it is heated by the current flowing in the water, and the resistance decreases. If you continue to drop water, it will be heated further,
Hot zones shining orange are generated. The hot zone immediately after the occurrence is very small. If this state is left as it is, the length of the hot zone increases, the resistance value also increases, and the generation region of the cuprous oxide 1-3 expands (FIG. 1D). Eventually, the growth of the hot zone slows down and stops. This also stops the production of cuprous oxide 1-3.

In this way, the copper wire 1-1 and the copper wire 1-2
After a cuprous oxide 1-3 is generated at the contact portion with the copper wire, it is cut into two to obtain copper wires 1-1 ′ and 1-2 ′ (FIG. 1).
(E)). Then, one of the copper wires 1-1 ′ and 1-2 ′, here, the copper wire 1-1 ′ is used as a second electrode, and the second electrode
Polish the end face 1-1′a of the electrode 1-1 ′ of FIG.
(F)). Here, for example, abrasive paper No. 150 → 400
Polishing is performed in the order of No. 800 to No. 1000, and finally a mirror finish is performed using a metal abrasive.

Then, as shown in FIG. 1 (g), a first electrode (a copper wire having a diameter of 2.0 mm) 2 whose end face 2a is mirror-finished in the same manner as the second electrode 1-1 'is prepared. Then, the end face 2a of the first electrode 2 and the end face 1-1'a of the second electrode 1-1 'are abutted and joined (using a fine movement device 7 shown in FIG. 2 described later) to form the present embodiment. Is obtained.

The thermoelectric conversion element 3 can obtain a thermoelectromotive force 6 to 8 times that of the conventional K thermocouple. Thus, according to the thermoelectric conversion element 3 of the present embodiment, the thermoelectric conversion element is not only used as a temperature sensor, but also applied to a new field as a thermoelectric conversion element such as a gas appliance, a relatively simple direct control, and a thermal battery. Is possible, and the use of the device is expanded.

Until now, cuprous oxide has been mainly used only as a paint for preventing shellfish from adhering to the bottom of a ship, and only a powdery substance obtained by reducing copper oxide has been manufactured. In recent years, industrial applications of cuprous oxide have practically disappeared due to the development of high-performance anti-shellfish paint. For this reason, a technique for integrally forming cuprous oxide, that is, a technique for manufacturing cuprous oxide in a bulk (integral mass) has not been established. In the present embodiment, the second electrode 1-1 ′
It is necessary to use a bulky cuprous oxide for the joint with the first electrode 2 of the above. In order to realize this, reference 1 (“Hot zone growth phenomenon at the conductor connecting portion”: Transactions of the Institute of Electrical Engineers of Japan,
61-A63, Showa 61-11) and Reference 2 (“DC 12
Hot zone of conductor connection in V circuit ": T.IEE Ja
pan, Vol. 117-A, NO. 2, '97), etc., so as to generate cuprous oxide using a hot zone phenomenon. At present, no other manufacturing method is known.

In this embodiment, the diameter is 2.0 mm.
Was used as a first electrode 2, and a copper wire having a diameter of 2.0 mm as a starting material and a cuprous oxide formed by a hot zone phenomenon was used as a second electrode 1-1 ′. It is not limited to a copper wire having a diameter of 2.0 mm. Also, of course, the first electrode 2 cannot be completely pure copper,
What is necessary is just to use copper as a main component. The copper wire having a diameter of 2.0 mm contains impurities that are unavoidable industrially and economically. Also, the cuprous oxide in the second electrode 1-1 ′ cannot be completely pure cuprous oxide, and it is sufficient that cuprous oxide is the main component.

[Comparison of thermoelectromotive force between conventional K thermocouple and thermoelectric conversion element 3 of this embodiment] FIG. 2 shows the thermoelectromotive force of conventional K thermocouple and thermoelectric conversion element 3 of this embodiment. FIG. 3 is a diagram showing an outline of a sample holding device for comparing. In the figure, 4 is a base, 5 is a fixed support, 6 is a movable support, and 7 is a fine movement device. The fixed support 5 and the movable support 6 are made of brass having a diameter of 20 mm, and have a sufficiently large heat capacity. The fine movement device 7 is provided with a knob 7-1. By turning the knob 7-1, the movable column 6 can be moved in the directions indicated by arrows A and B.

The thermoelectric conversion element 3 of this embodiment is set as a sample in the sample holding device. That is, the first electrode 2 side of the thermoelectric conversion element 3 is fixed to the fixed column 5 with the screw 5-1 and the second electrode 1-1 'side is fixed to the movable column 6 with the screw 6.
Fix by -1. At this time, the junction between the first electrode 2 and the second electrode 1-1 'of the thermoelectric conversion element 3 is connected to the K thermocouple 8
Are thermally bonded, wrapped in a mylar 9, and covered with an iron plate sheath 10. Further, the K thermocouple 11 is set on the base 4.

Then, an alligator clip 12-1 is attached to an end of the first electrode 2 of the thermoelectric conversion element 3, and an alligator clip 12-2 is attached to an end of the second electrode 1-1 '. Then, as shown in FIG. 3, the thermoelectromotive force generated between the lead wires from the alligator clips 12-1 and 12-2 (the thermoelectromotive force generated at the junction of the thermoelectric conversion elements 3) is converted to the amplifier 13-1, It is provided to the computer 15 via the A / D converter 14-1. The thermoelectromotive force generated in the K thermocouple 8 is transmitted to the amplifier 13-3 and the A / D converter 14-2 via the amplifier 13-2 and the A / D converter 14-2. -3 to the computer 15.

In such a setting situation, a sheath 10 is provided by using a hand-held gas (butane gas) burner 16.
The junction between the first electrode 2 and the second electrode 1-1 'of the thermoelectric conversion element 3 covered with is heated. Since the flame of the gas burner 16 is unstable and the heat capacity of the thermoelectric conversion element 3 is small, it is difficult to maintain a constant temperature. For this reason, heating is performed from a 360 ° direction while appropriately adjusting the way of the flame.

It is difficult to measure the thermoelectromotive force by following the temperature fluctuation with a normal voltmeter. Therefore, simultaneous measurement is performed using the computer 15. The temperature difference at the junction between the first electrode 2 and the second electrode 1-1 'of the thermoelectric conversion element 3 is the temperature of the sample holder (measured by the K thermocouple 11).
It is measured by a temperature difference between the temperature of the sample junction and the temperature of the sample joint (measured by the K thermocouple 8).

In FIG. 3, the gain of the amplifier 13-1 is "5", and the gains of the amplifiers 13-2 and 13-3 are "7".
0 ", and the A / D converters 14-1 to 14-3 use 8-bit A / D converters. In addition, a program is given to the computer 15 so that the temperature range is from room temperature to 800 ° C. and at 50 ° C. intervals.

The data obtained at this time is random with respect to the temperature. By sorting the collected data, the K-thermocouple 8 and the temperature-electromotive force characteristics of the thermoelectric conversion element 3 of the present embodiment are sorted out. Can be compared. FIG. 4 shows the temperature-electromotive force characteristics of the K thermocouple 8 and the thermoelectric conversion element 3 of the present embodiment based on the measurement result of the computer 15 at this time. Characteristic I is a temperature-electromotive force characteristic of the K thermocouple 8, and characteristic II is a temperature-electromotive force characteristic of the thermoelectric conversion element 3 of the present embodiment. As can be seen from these characteristics I and II, the thermoelectric conversion element 3 of the present embodiment can obtain a thermoelectromotive force 6 to 8 times that of the conventional K thermocouple 8.

The characteristics I and II in FIG. 4 are obtained by plotting simple averages of ten data for each of the thermoelectromotive forces at 50 ° C. intervals, and connecting these by lines. In the characteristic II of the thermoelectric conversion element 3 of the present embodiment, linearity appears up to around 500 ° C. Up to this area, it can be used as a temperature sensor. In this case, it is advantageous that the thermoelectromotive force is large, and the measurement accuracy can be improved.

When the temperature exceeds about 500 ° C., the linearity is lost. At a temperature near the point where the linearity is lost, this is an initial temperature at which the cuprous oxide exhibits red heat, and is also a temperature range where softening starts. It is also considered that this is related to the region where the conductivity is rapidly reduced. On the other hand, 800 ° C
Is where the Fermi rank of cuprous oxide as a P-type semiconductor is almost saturated. Although it is a short time, at 1200 ° C. in a temperature range considered to be in a softened state, 8
A thermoelectromotive force of 00 mV was recorded.

[0023]

As is apparent from the above description, according to the thermoelectric conversion element of the present invention, the first electrode mainly composed of copper and the second electrode mainly composed of cuprous oxide are used. Provided,
Since the first electrode and the second electrode are joined,
By increasing the thermoelectromotive force at the junction, the usage can be expanded.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a manufacturing process of a thermoelectric conversion element according to an embodiment of the present invention.

FIG. 2 is a diagram showing an outline of a sample holding device for comparing the thermoelectromotive force between a conventional K thermocouple and the thermoelectric conversion element of the present embodiment.

FIG. 3 is a diagram showing a measurement system for comparing the thermoelectromotive force between a conventional K thermocouple and the thermoelectric conversion element of the present embodiment.

FIG. 4 is a diagram showing temperature-electromotive force characteristics of a K thermocouple based on a measurement result of a computer in the measurement system and a thermoelectric conversion element of the present embodiment.

[Explanation of symbols]

1: Copper wire, 1-1 ': Second electrode, 1-1'a: End face,
2 1st electrode, 2a ... end face, 1-3 ... cuprous oxide, 3 ...
Thermoelectric conversion element.

Claims (3)

[Claims] A first electrode mainly composed of copper and a second electrode mainly composed of cuprous oxide, wherein the first electrode and the second electrode are joined to each other. A thermoelectric conversion element. 2. The thermoelectric conversion element according to claim 1, wherein the second electrode is an integrally formed electrode mainly composed of cuprous oxide. 3. The thermoelectric conversion element according to claim 2, wherein the second electrode is formed by a hot zone phenomenon using a material mainly composed of copper as a starting material.