JPH03240202A - Thermistor - Google Patents

Abstract

PURPOSE:To avoid the occurrence of any swell and pinholes as well as the deterioration in insulation during the dry-printing process by a method wherein the surfaces of a thermoelectronic element and electrode wires thereof are coated with a metallic alkoxide base paint and then hydrolyzed or thermal- cracked to form an insulation coated layer of a metallic oxide. CONSTITUTION:Within the title thermistor T, both sides of a heat-sensitive element 1 comprising a transition metallic oxide, etc., baked and processed into a bar type pellet as well as the slug lead heads 2a of dumet wires 2 comprising the slug lead heads 2a and lead wires 2b are respectively connected to each other so as to output the variable resistances of the heat-sensitive element 1 through the intermediary of the dumet wires 2. Next, the heads 2a connected to both sides of the element 1 are inserted into a glass tube 3 sealed with nitrogen gas. Next, the surfaces of thermistor 1, an insulating base 4 and metallic struts 5 are coated with alikoxide base coating agent so as to form an insulation coating film 6 comprising the metallic oxide by hydrolysis or thermal cracking of the metallic alkoxide constituent. Finally, as for the coating agent, e.g. Si-O-Ti base compound alkoxide is applicable.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a thermistor used in electric ovens, microwave ovens, electromagnetic cookers, and the like.

[Conventional technology]

Generally, thermistors used in microwave ovens and electronic cookers are installed inside the grill or in the hood of the exhaust vent, and have the function of detecting air temperatures ranging from room temperature to about 300°C.

Since it has the property that the resistance value changes with good reproducibility due to temperature change, this property is used as a temperature sensor for detecting temperature, controlling the power amount of the heating element, etc.

However, thermistors installed in cooking appliances are not only exposed to high temperature and humidity due to moisture generated from food, but also exposed to salt mist contained in that moisture, and are exposed to extremely harsh environments. , the range of temperature changes is wide from room temperature to high temperatures of about 300° C., and the temperature changes in a short time, which can easily cause electrical corrosion, high-temperature oxidation phenomena, and disconnection due to thermal fatigue, resulting in measurement errors and failures.

Conventionally, thermistors used in such harsh environments have been coated with a heat-resistant paint such as polyimide or polyamide on their surfaces to prevent electrolytic corrosion and high-temperature oxidation caused by moisture and salt ξst. Measures have been taken to prevent heat fatigue.

Furthermore, in JP-A No. 63-317730, a double coating technology consisting of a base layer containing a fluorine resin and a top layer made of a tetrafluoroethylene perfluoroalkoxylene copolymer was used to overcome the harsh conditions described above. Techniques for protecting thermistors from the environment are disclosed.

[Problem to be solved by the invention]

However, with conventional surface protection treatment methods, when a coating film is formed using the dipping method or spray method, if the thickness differs locally, blisters or pinholes may be formed in those areas due to baking drying, or long coatings may be formed. Due to long-term use, the protective coating layer undergoes thermal deterioration and cracks, which causes insulation to deteriorate, resulting in malfunctions and conductors breaking due to electrolytic corrosion.Production Management 2 Quality Control Problems was there.

In addition, as shown in Japanese Patent Application Laid-open No. 63-317730, in order to improve reliability by double coating, two
The process of painting and drying each type of paint separately is not only time-consuming, but also increases equipment costs.
There is a problem in that the production cost increases as the number of steps increases.

Therefore, the present invention prevents the occurrence of blisters and pinholes during dry baking by performing surface treatment with a ceramic insulating layer.
Preventing insulation deterioration and malfunctions due to thermal deterioration and improving production management 2
The goal is to solve quality control problems, improve heat resistance and reliability, and reduce equipment and production costs.

[Means to accomplish the task]

In order to achieve this object, the present invention coats the surface of the heat-sensitive element and its electrode wire with a metal alkoxide paint, and forms an insulating coating layer of the metal oxide by hydrolysis or thermal decomposition of the metal alkoxide component. It is characterized by the presence of

[Action of the invention]

Since the thermistor of the present invention has a structure in which the surface is protected by a metal oxide, insulation is ensured, malfunctions are suppressed, and the thermistor can sufficiently withstand long-term use in harsh environments.

In the present invention, the hydrolysis and thermal decomposition of the alkoxide M(OR) applied to the surface of the thermistor generally forms a metal oxide through the following reaction.

(Hydrolysis) M (OR)n + n Hz O -4M(OH)II + n R(OH)M(OH)
+1- MO*zz + 1)/2 HzO (thermal decomposition) M(OR),,= MO,/□ +-/z R(OH
) + Olefin In the thermal decomposition reaction, most of the hydroxyl groups are converted to O by heating at 200° C. for one hour or more, forming a metal oxide.

〔Example〕

Examples of the present invention will be described below.

FIG. 1 is a sectional view showing an example of the thermistor of the present invention.

The thermistor T includes a heat-sensitive element 1 which is processed into a bar-shaped verleft after firing a transition metal oxide, for example, and a slug lead of a Dumet wire 2 consisting of a slag lead head 2a and a lead wire 2b on both sides of the heat-sensitive element 1. The heads 2a are connected to each other and are forced to output the resistance change of the heat sensitive element 1 via the Dumet wires 2 and 2.

Note that the heat-sensitive element 1 of the thermistor T and the slug lead heads 2a and 2a connected to both sides thereof are inserted into a glass tube 3 and sealed with glass in a nitrogen gas (N2) atmosphere.

Then, the Dumet! 2 and 2 are spot welded, the thermistor T is mounted and supported, and a thermistor unit is formed.

Note that the other end side 5b of the metal support S is protruded to the back side of the insulating base 4 as a connection terminal.

A thermistor T is exposed to the heated side when the insulating base 4 is attached to a wall of a microwave oven or the like.

A metal alkoxy coating agent is applied to the surfaces of the insulating base 4 and the metal supports 5 and 5, and an insulating coating layer 6 made of a metal oxide layer is formed by hydrolysis or thermal decomposition of the metal alkoxide component.

Examples of metal alkoxide coating agents include:
A 5i-0-Ti complex alkoxide is used.

This is the Si-based alkoxide St(○CzHs)4,
Methanol CH30H and acetic acid ethyl ester CH.

After adding COOC2Hs, stir well, add an acidic aqueous solution that does not cause sufficient hydrolysis, and stir vigorously to cause partial hydrolysis, so that ○H groups and OCH3 groups coexist on Si. Partially hydrolyzed Sin makes a sol, and this is further mixed with Ti-based alkoxide Ti while stirring.
It is made by dropping (OC3HY)4.

Then, the thermistor T attached to the insulating base 4 was immersed in a 10% aqueous solution of caustic soda NaOH for 2 minutes, subjected to alkaline degreasing treatment, washed with water, and dried.

Next, it was immersed in a solution obtained by adding 10 parts of 5iOz powder and 10 parts of alumina A to 70 parts of the Si-〇-Ti-based composite alkoxide coating solution, taken out, and heated at 100 to 150°C for 10 minutes. Heated. Repeat this dipping and heating several times to achieve a thickness of 250~5.
A film of 00 μm was formed.

Further, the film was dried at 180° C. for 10 minutes, and as a result of the hydrolysis and thermal decomposition reactions that progressed during that time, an insulating coating layer 6 of a metal oxide having high dielectric strength and high heat resistance was formed. Manufactured a thermistor unit.

The thermistor Uni-71 manufactured in this way is
The characteristics of the insulating coating layer 6 are that the dielectric strength voltage is 10 kV or more, the volume resistivity is 10"Ω.0 or more, and the hardness (pencil hardness) is 5H or more, and even if heated at a high temperature of 500°C, the insulating coating layer will not change. Excellent properties such as no peeling, no blistering or pinholes during heat drying, and no deterioration of dielectric strength were obtained.

In addition, A 12 z○! is added to the metal alkoxide coating agent as a filler. + Z r 02+ Cr
z Metal oxides such as O31Cab, 5nO1, BN,
When at least one type of fine particles, fine fibers, or fine powder such as B4C2SiC or Si3N4 is mixed in an appropriate proportion, the dielectric strength voltage is further improved.

In addition, as the composite alkoxide used in the coating agent, alkoxides such as Al, Ba, La, Sn, Sr, etc., or composite alkoxides of these and the above-mentioned Si or Ti, can be used to improve adhesion, dielectric strength, An insulating coating layer with excellent heat resistance and atmosphere resistance can be obtained.

Furthermore, Si and T1. B+ Alr P+ Polymer having skeletons of one or more of Qe, As, or Sb, oxygen, and carbon; for example, organometallic polymer 10 such as borosiloxane resin
Even if a mixture consisting of ~200 parts and 100 parts of an inorganic fine powder that does not melt at the decomposition temperature of the polymer is used as a coating agent, an insulating coating layer with superior dielectric strength and heat resistance equivalent to or higher than that of the above example is formed. be able to.

〔Effect of the invention〕

As described above, according to the present invention, even at high temperatures of 500°C or higher, the insulation coating layer does not crack and dielectric strength voltage deteriorates, and corrosion resistance and electrolytic corrosion resistance are significantly improved. It has the excellent effect of being able to provide a thermistor with extremely little change in characteristics even under harsh environments, and with high reliability and quality.

Furthermore, since the insulating coating layer can be easily formed in a relatively simple process, there is an effect that equipment costs and production costs can be reduced.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an example of the thermistor of the present invention. Explanation of symbols T--Thermistor, 1... Heat-sensitive element, 2--Dumet wire, 6--Insulating coating layer

Claims (1)

[Scope of Claims] [1] The surface of the heat-sensitive element (1) and its electrode wires (2, 2) is coated with a metal alkoxide paint, and the metal alkoxide component is hydrolyzed or thermally decomposed. A thermistor characterized in that an insulating coating layer (6) of metal oxide is formed. [2] The metal alkoxide paint contains Si, Ti, B
, Al, P, Ge, As, or Sb and a polymer having an oxygen skeleton, or a mixture of one or more of the above substances, a polymer having oxygen and carbon skeletons, and an inorganic fine powder. A thermistor according to claim 1.