JPH0629792B2 - Thermistor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a small thermistor having a high response speed, capable of measuring the temperature of a narrow portion and high reliability, and more specifically, in a high temperature atmosphere. Alternatively, the present invention relates to a structure of a small thermistor which can be inserted into water, a living body or the like for use.

[Prior art]

The thermistor is a semiconductor temperature sensitive resistor, and its stability has been improved by various improvements in recent years, and it has come to be widely used as a temperature sensor for industrial measurement. Currently, it has a wide range of applications, and is used in various fields such as industrial temperature measurement, and medical field such as electronic thermometer and in-vivo temperature measurement.

The thermistor element is mainly composed of Mn, Co, Ni, Fe, etc. 2
An NTC (Negative Tem-perature Goefficient) type thermistor, which consists of a sintered body of at least one kind of transition metal oxide, and whose resistance decreases as the measurement temperature increases is mainly used for ordinary industrial applications. Further, the thermistor element has various shapes such as a bead shape, a disk shape, a rod shape, a thick film shape, and a peritoneal shape, depending on the manufacturing method and shape thereof.
Are used by many people. An example of the structure of a thermistor that has been conventionally used is shown in FIG. 2, in which an insulating glass coat layer 3 is generally provided on the thermistor element 1, and two layers from the thermistor element 1 are provided. The dumet wire 2 is led out and further connected to a lead wire 4 for connection with an external device. In some cases, a resin coating layer 6 may be further provided on the resin coating layer 6 in order to improve the insulation.
Most of the conventional thermistor elements have a diameter of 1 mm or more.

On the other hand, as a recent application, in a high humidity atmosphere, and even 1mm
There is an increasing need for temperature measurement in narrow parts having the following dimensions. In particular, temperature measurement in a living body is a field in which miniaturization of a thermistor and high reliability are required. Further, in many cases, whether for industrial or medical purposes, a high response speed is required for temperature measurement, and the conventional thermistor having a diameter of 1 mm or more has an insufficient response speed.

Conventionally, a thermistor having a diameter of 1 mm or less has been studied, and as shown in FIG. 2, various measures have been taken to enhance the insulating property of the Dumet wire 2, or the joint 8 between the Dumet wire 2 and the lead wire 4. It has been done. A resin coat is used as an example, but in this case, a dip coat of the resin is required 3 to 5 times or more to obtain sufficient insulation, and nevertheless the Dumet wire 2 or the Dumet wire 2 is used. There is a high possibility that insulation failure will occur at the joint portion 8 between the lead wire 4 and the lead wire 4.

In addition to the above, a method of encapsulating the whole in resin or a method of covering the resin tube and filling the resin as shown in FIG. 3 has been performed, but in either method, the insulating property is sufficient. On the other hand, there is a drawback in that the heat capacity of the thermistor temperature-sensing portion increases, and therefore a large decrease in response speed cannot be avoided.

[Object of the Invention]

The present invention was conducted as a result of researching a small thermistor having a diameter of 1 mm or less, which has a high degree of reliability and a fast response speed, which could not be achieved in the past. As a result, a joint between a Dumet wire and an external lead wire was combined with a resin tube and a filling resin. The present inventors have obtained the knowledge that the insulating property can be improved by coating with a coating, and based on this knowledge, various researches have been advanced to complete the present invention. It is an object of the present invention to provide a thermistor capable of imparting high reliability without impairing the response speed in a narrow portion in water or in a living body in a high humidity atmosphere.

[Structure of Invention]

That is, the present invention is a thermistor comprising a glass-coated thermistor element having an outer diameter of 1 mm or less, and two dumet wires derived from the thermistor element, wherein the glass coat layer on the surface of the thermistor element and the dumet wire are insulated from each other. The distance between the resin-coated external lead wire and the junction is 1
Within 0 mm, the Dumet wire led out from the thermistor element, the joint portion, and the vicinity of the joint portion at the end of the external lead wire are covered with a resin tube having an inner diameter smaller than that of the thermistor element portion. , At least one selected from the group consisting of polyester resins, epoxy resins and polyurethane resins,
A non-solvent type liquid resin having a viscosity in the range of 100,000 cps is filled, and the liquid resin is further coated and cured on the surface of the thermistor element and at least a portion of the resin tube in contact with the thermistor element. It is a thermistor.

Hereinafter, the present invention will be described in detail with reference to FIG.

The thermistor of the present invention is basically composed of a thermistor element 1 and two dumet wires 2, and after joining an external lead wire 4 to which a resin coating 9 is applied in advance to the dumet wire 2,
The resin tube 7 is mounted so as to cover the Dumet wire, the joint portion 8, and the vicinity of the joint portion at the end of the external lead wire, and the insulating resin is filled in the resin tube 7. At this time, it is desirable to coat the surface of the thermistor element and the contact portion between the resin tube and the thermistor element with an insulating resin to provide the resin coating layer 6.

The outer shape of the thermistor element may be a bead type, a disc type, a rod type, or the like, but is not particularly limited.
As the external lead wire 4 which is joined to the Dumet wire 2 and connected to the equipment, it is possible to use one coated with vinyl chloride resin, fluororesin or the like, but the thermistor is downsized. , To reduce the size,
It is more preferable to use one coated with an insulating resin varnish such as an enamel wire. When joining the Dumet wire 2 and the external lead wire 4, the resin coating 9 at the terminal end of the external raid wire 4 is peeled off by a mechanical method or a chemical solution, and a precision resistance welding machine is generally used for the joining. It is not limited to.

The distance between the glass coat layer 3 on the surface of the thermistor element 1 and the joint portion 8 is preferably within 10 mm, and when the distance exceeds 10 mm, the size of the thermistor becomes large and two dumet wires 2 come into contact with each other. This is not preferable because the risk of causing a short circuit increases.

Along with this, the length of the resin tube 7 varies depending on the position of the joint portion 8, but it is desirable to position the joint portion 8 at the center of the resin tube 7. Therefore, the glass coat layer of the thermistor element 1 is usually used. Dumet wire 2 exposed from 3
If the length is 1 to 10 mm, the length of the resin tube 7 is preferably in the range of 2 to 20 mm. The resin tube 7 is
Any material can be used as long as it has an inner diameter smaller than that of the thermistor element 1 and can easily cover the joint portion 8, but the wall thickness is as thin as possible without being easily collapsed.
A wall thickness in the range of 02 mm to 0.1 mm is suitable. Also,
The material of the resin tube 7 is polyester resin,
Examples thereof include polyimide-based resins and fluorine-based resins, but are not particularly limited to these.

The insulating resin filled in the voids 5 in the resin tube 7 includes at least one selected from the group consisting of polyimide resins, polyester resins, epoxy resins and polyurethane resins, and is a solventless liquid. It must be a resin. That is, when a resin solution containing a solvent is used, a cavity is formed in the resin filled portion in the resin tube during the process of filling the resin solution and removing the solvent, and as a result, the insulating property is extremely lowered, and therefore the resin solution cannot be used. The method of filling the liquid resin into the resin tube is usually a reduced pressure method. That is, the tube is set in the tip of the thermistor, immersed in a resin solution, further depressurized by a vacuum pump or the like and left for a predetermined time, and then taken out from the resin solution to cure the resin. Therefore, the viscosity of the liquid resin is 500 to 10
50,000 cps, preferably 5,000 to 50,000 cps
It should be s. When the viscosity is 500 cps or less, it is convenient for filling because of low viscosity, but liquid resin is apt to flow out from the resin tube during curing after filling, which is unsuitable. On the other hand, when it exceeds 100,000 cps, it is not suitable because it is difficult to flow and it takes too much time to fill the resin tube, resulting in poor filling. The viscosity of the above liquid resin is the viscosity at the time of filling, and therefore it is possible to fill the liquid resin while keeping the viscosity within a predetermined range by controlling the temperature as necessary.

As the resin for forming the resin coat layer 6, the above-mentioned insulating resin, polyimide resin, polyester resin,
In addition to a solventless liquid resin such as an epoxy resin or a polyurethane resin, a solvent type polyimide resin, a polyester resin solution or the like can be used. Also, the type of resin is not particularly limited as long as it satisfies the characteristics required for use of the thermistor such as film forming property, insulation property, moisture resistance, heat resistance, etc. There is no problem even if the above is used in combination, but from the viewpoint of adhesiveness, it is preferable to use the same resin as the filling resin in the resin tube. Therefore, in this case, since the resin coat layer 6 is also obtained at the same time when the space 5 is filled with the resin by a method such as immersing the thermistor in the resin liquid, it is not necessary to coat the resin again. It can be created in the process, and this is extremely advantageous in terms of cost. It is also effective to apply a filling resin for reinforcement or a resin used for the resin coat layer 6 to the boundary between the resin tube 7 and the resin coat layer 6 to further enhance safety.

〔The invention's effect〕

According to the present invention, the formation of the resin portion in the vicinity of the joint between the external lead wire and the Dumet wire of the thermistor is reliable, the insulating property is excellent, and the response speed is improved in a narrow portion such as in a high temperature atmosphere, water or in a living body. A small thermistor having high reliability can be obtained without damaging it. Therefore, it is suitable as a temperature sensor applicable not only for industrial use but also for medical fields requiring extremely high safety.

Example 1 Two dumet wires having a diameter of 0.02 mmφ were derived and glass-coated, and a thermistor element having an outer diameter of 0.9 mmφ was used. Joining was performed with a welding machine. The bonding position was 2 mm from the thermistor element. Next, let the lead wire flow from the end side 5 mm and the inner diameter 0.4.
Insert into a polyimide tube with a diameter of 0.5 mm and an outer diameter of 0.5 mm,
Coated around the joint.

Next, a predetermined amount of the epoxy resin main agent and the curing agent were mixed and stirred. The viscosity of the obtained resin liquid at room temperature is 10,
It was 000 cps. In a bell jar, the thermistor element portion was dipped in an epoxy resin solution, and a vacuum pump was used to reduce the pressure at 750 mmHg for 10 minutes. The epoxy resin was cured at room temperature to obtain a thermistor as shown in FIG.

A total of 10 thermistors were prepared, and as an insulation test of the coat layer, copper was used as a counter electrode in water and the thermistor was immersed in a position 20 mm from this, and the resistance value was measured when a direct current of 20 V was applied between them. did. Also, as a response speed test,
The thermistor was immersed in warm water of 50 ° C. from the air at room temperature of 25 ° C., and the time to reach 63.2% of the change in thermistor resistance value, that is, the time constant was measured. As a result, the thermistor obtained in this example has an insulation property of 10 × in water.
The value was as high as 10 ¹² Ω or more, and the time constant was 0.3 seconds or less, which was an extremely fast response speed. In the following Examples and Comparative Examples, the same procedure as in Example 1 is performed unless otherwise specified.

Comparative Example 1 In Example 1, the thermistor element was directly immersed in an epoxy resin solution without using a tube, and pulled up and cured.
The obtained thermistor was 10 ⁴ in the underwater insulation test.
The resistance was as low as Ω or less, and the insulation of the Dumet wire portion was insufficient.

Example 2 A polyester resin tube having a flow rate of 5 mm, an inner diameter of 0.35 mmφ and an outer diameter of 0.43 mmφ was used as a coated tube, and a two-component urethane resin solution having a viscosity of 95,000 cps was filled in the tube under reduced pressure. As a result, the insulating properties of the obtained thermistors in water all showed a resistance value of 10 ¹² Ω or more, and the time constant was as short as 0.5 seconds or less.

Comparative Examples 2 and 3 In Example 1, the resin liquid viscosity was 400 cps and 110,
000 cps and Comparative Examples 2 and 3, respectively. In the underwater insulation test of the obtained thermistor, the insulation was poor at 10 ⁴ Ω or less in all cases. In Comparative Example 2, since the viscosity of the resin liquid is too low, the resin flows down from the tube. On the other hand, in Comparative Example 3, since the viscosity is too high, the resin is not sufficiently filled in the tube even when the pressure is reduced. Also in the comparative example, as a result, insulation failure was caused by insufficient filling in the tube.

[Brief description of drawings]

FIG. 1 is a view showing a sectional structure of a thermistor element portion in the present invention. Further, FIGS. 2 and 3 are views showing a sectional structure of a conventional thermistor element portion.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-61-10019 (JP, A) JP-A-49-46015 (JP, A) Actually open Sho-49-119743 (JP, U) Actual-open Sho-61- 117202 (JP, U)

Claims (1)

[Claims] 1. A thermistor comprising a glass-coated thermistor element having an outer diameter of 1 mm or less and two dumet wires derived from the thermistor element, the glass coat layer on the surface of the thermistor element being insulated from the dumet wire. The distance between the resin coated outer lead wire and the joint is 10
Within the mm, the Dumet wire led from the thermistor element, the joint, and the vicinity of the joint at the end of the external lead wire are covered with a resin tube having an inner diameter smaller than that of the thermistor element,
The void in the resin tube contains at least one selected from the group consisting of a polyimide resin, a polyester resin, an epoxy resin and a polyurethane resin, and 500
A non-solvent type liquid resin having a viscosity in the range of 100,000 cps is filled, and the liquid resin is further coated and cured on the surface of the thermistor element and at least a portion of the resin tube in contact with the thermistor element. Thermistor.