JPS63234122A - Thermistor - Google Patents

Abstract

PURPOSE:To obtain a thermistor which has high reliability which maintains its response speed in water or at a narrow part in a living body, etc., by coating the connection parts between Dumet wires and external lead wires with a resin tube and charged resin in combination. CONSTITUTION:This thermistor consists of a glass-coated thermistor element 1 or <=1mm in external diameter and two Dumet wires 2. The external lead wires 4 which are coated 9 with resin previously are connected to the Dumet wires 2, the resin tube 7 is mounted covering the Dumet wires 2, connection parts 8, and the parts of the external lead wires terminals nearby the connection parts, and the resin for insulation is charged in the resin tube 7. At this time, the surface of the thermistor element 1 and the contact part between the resin tube 7 and thermistor element 1 are coated with resin for insulation to provide a resin coat layer 6 preferably. Further, the connection part between the Dumet wires 2 and the external lead wires 4 which are coated with the insulating resin are set at an interval of <=10mum.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a small thermistor that has a fast response speed, can measure temperature in narrow areas, and has high reliability. , or the structure of a small thermistor that can be inserted into water, a living body, etc.

C. Prior Art] A thermistor is a semiconductor temperature-sensitive resistor, and its stability has been improved through various improvements in recent years, and it has come to be widely used as a temperature sensor for industrial measurement. Currently, the range of applications is wide-ranging, and they are used in all kinds of fields, including industrial temperature measurement and medical use, such as electronic thermometers and measurement of internal body temperature.

Thermistor elements are mainly made of Mn, Go, and Ni.

Consisting of a sintered body of Fe and two or more transition metal oxides,
For typical industrial applications, NTC (Negative Temp-p) is used, where the resistance decreases as the measurement temperature increases.
Therature GOeffiCient) type thermistors are mainly used. In addition, the manufacturing method of the thermistor element,
There are various shapes depending on the shape, such as a bead shape, a disk shape, a rod shape, a thick film shape, and a thin film shape, among which the former two types are currently used most often. An example of the structure of a conventionally used thermistor is shown in Fig. 2, in which an insulating glass coat layer 3 is generally provided on the thermistor element 1, and two layers are formed from the thermistor element 1. A dumet wire 2 is led out and further connected to a lead wire 4 for connection with external equipment. In some cases, a resin coat layer 6 is further provided thereon to improve insulation.

Most conventional thermistor elements have a diameter of 1M4 or more.

On the other hand, recent applications include
There is an increasing need for temperature measurement in narrow areas with dimensions of s or less. In particular, temperature measurement within a living body is a field that requires miniaturization and high reliability of thermistors. Furthermore, whether for industrial or medical purposes, temperature measurement often requires a high response speed, and conventional thermistors having a diameter of 1 mm or more have insufficient response speed.

Conventionally 11! Thermistors having a diameter of Ill or less have been studied, and various efforts have been made to improve the insulation of the Dumet wire 2 or the joint 8 between the Dumet wire 2 and the lead wire 4, as shown in FIG. . A resin coat is used as the second side, but in this case, 3 to 5 or more resin dip coats are required to obtain sufficient insulation. is the joint 8 between the dumet wire 2 and the lead wire 4
There is a high possibility that insulation failure will occur.

Other methods include encapsulating the entire body in resin, or covering a resin tube and filling it with resin as shown in Figure 3, but either method has sufficient insulation properties. On the other hand, the heat capacity of the thermistor temperature-sensing portion increases, which inevitably leads to a large drop in response speed.

[Purpose of the invention]

The present invention has a diameter III that combines a high degree of reliability and a fast response speed that could not previously be achieved! As a result of research aimed at creating a small thermistor with r1 or less, we found that insulation could be improved by covering the joint between the Dumet wire and the external lead wire with a combination of a resin tube and filled resin. Based on this knowledge, various studies have been carried out and the present invention has been completed. The purpose of this is to perform the
It is an object of the present invention to provide a thermistor that can be provided with high reliability without impairing response speed.

, [Structure of the Invention] That is, the present invention provides a thermistor consisting of a glass-coated thermistor element having an outer diameter of 1 s or less, and two Dumet wires derived from the thermistor element, the glass coat layer on the surface of the thermistor element. The distance between the Dumet wire and the joint of the end of the external lead wire coated with insulating resin is 1.
0MIII or less, cover the Dumet wire led out from the thermistor element, the joint, and the vicinity of the joint at the end of the external lead wire with a resin tube whose inner diameter is smaller than the thermistor element, and fill the gap in the resin tube with insulating resin. This thermistor is characterized in that the surface of the thermistor element and at least the portion of the resin tube in contact with the thermistor element are coated with an insulating resin.

Hereinafter, the present invention will be explained in detail using FIG. 1.

The thermistor of the present invention basically consists of a thermistor element 1 and two Dumet wires 2. After joining the Dumet wire 2 with an external lead wire 4 coated with a resin coating 9 in advance, a resin tube 7 is attached to the Dumet wire. , the joint part 8 and the vicinity of the joint part at the end of the external and negative wires, and the resin tube 7 is filled with an insulating resin. 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 a resin coat layer 6.

The external shape of the thermistor element includes a beat shape, a disk shape, a rond shape, etc., but is not particularly limited. In addition, as the external lead wire 4 that is joined to the dumet wire 2 and connected to equipment, it is acceptable to use one coated with vinyl chloride resin, fluorine resin, etc., but the thermistor can be made smaller. In order to form a mold, it is more preferable to use a wire coated with an insulating resin varnish such as an enameled wire. When joining the dumet wire 2 and the external lead wire 4, the resin coating 9 at the end of the external lead wire 4 is peeled off mechanically or with a chemical solution, and a precision resistance welder is generally used for joining. It is not limited to.

Bonding portion 8 with the glass coat layer 3 on the surface of the thermistor element 1
The distance between the two dumet wires 2 is preferably within 10 m; if it exceeds 10 m, the dimensions of the thermistor body will increase, and there will be a greater risk that the two dumet wires 2 will come into contact and cause a short circuit, which is not preferable.

Along with this, the length of the resin tube 7 varies depending on the position of the joint part 8, but since it is desirable that the joint part 8 is located at the center of the resin tube 7, the length of the resin tube 7 is usually Dumet wire 2 exposed from 3
If the length of the resin tube 7 is 1 to 10 m, the length of the resin tube 7 is preferably in the range of 2 to 20 m. The resin tube 7 is
It is acceptable as long as the inner diameter is smaller than the diameter of the thermistor element 1 and can easily cover the joint part 8, but the wall thickness is as thin as possible without being easily crushed, for example 0.
Wall thicknesses ranging from 0.2 mm to 0.1 #1111 are preferred. Furthermore, examples of the material for the resin tube 7 include polyester resins, polyimide resins, fluorine resins, etc., but are not particularly limited to these.

The insulating resin to be filled in the cavity 5 in the resin tube 7 includes at least one type selected from the group consisting of polyimide resin, polyester resin, epoxy resin, and polyurethane resin, and is a solvent-free liquid resin. It needs to be resin.

That is, when a resin solution containing a solvent is used, a cavity is formed in the resin-filled portion of the resin tube during the process of filling the resin solution and removing the solvent, and as a result, the insulation properties are extremely reduced, making it unusable. The liquid resin is normally filled into the resin tube using a reduced pressure method. That is, the tube is set at the tip of the thermistor and then immersed in the resin liquid, the pressure is further reduced by a vacuum pump, etc., and the tube is left for a predetermined period of time, and then taken out from the resin liquid and the resin is cured. Therefore, the viscosity of the liquid resin is preferably 500 to 100,000 cps, preferably 5,000 to 50,000 cps. If the viscosity is 500 cps or less, it is convenient for filling due to its low viscosity, but it is unsuitable because there is a high possibility that the liquid resin will flow out from the resin tube during curing after filling. On the other hand, if it exceeds 100,000 cus, it is not suitable because it is difficult to flow and it takes too much time to fill the resin tube, and there are many cases where filling is incomplete. Note that the viscosity of the liquid resin described above is the viscosity at the time of filling, and therefore, by controlling the temperature as necessary, it is possible to fill while keeping the viscosity within a predetermined range.

As the resin for forming the resin coat layer 6, the above-mentioned insulating resins, polyimide resins, polyester resins,
In addition to solvent-free liquid resins such as epoxy resins or polyurethane resins, solvent-type polyimide resins and polyester resin solutions can be used. Also, film forming properties and insulation properties.

The type of resin is not particularly limited as long as it satisfies the characteristics required for use of the thermistor, such as moisture resistance and heat resistance, and two or more of these resins may be used in combination. However, 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, when filling the void 5 with resin by immersing the thermistor in a resin liquid, the resin coating layer 6 is also obtained at the same time, so there is no need to coat it again, and it is a one-time operation. It can be produced in a process, and is therefore extremely advantageous in terms of cost. It is also effective to apply a filling resin or the resin used for the resin coat layer 6 for reinforcement to the boundary between the resin tube 7 and the resin coat layer 6 to further increase safety. .

〔Effect of the invention〕

According to the present invention, the resin part is reliably formed near the joint between the external lead wire and the dumet wire of the thermistor, has excellent insulation properties, and has a high response speed in a narrow space such as in a high temperature atmosphere, underwater, or inside a living body. A compact thermistor with high reliability can be obtained without any damage, and therefore it is suitable as a temperature sensor that can be applied not only to industrial use but also to the medical field where extremely high safety is required.

Example 1 Two dumet wires with a diameter of 0.02 mφ were drawn out and coated with glass to have an outer diameter of 0.02 mφ. Using a thermistor element with a diameter of 9 mφ, this dumet wire and a polyester-coated Ni lead wire with a diameter of 0.1 a++φ were joined using a precision resistance welding machine. The bonding position was 2 m from the thermistor element. Next, connect the lead wire from the end side with a length of 5# and an inner diameter of 0.
．． It was inserted into a polyimide tube with a diameter of 48φ and an outer diameter of 0.5#φ, and the joint was covered with the center.

Next, predetermined amounts of the epoxy resin base and curing agent were mixed and stirred. The viscosity of the obtained resin liquid at room temperature was 10.
It was ooocps. Put this in Pelger,
The thermistor element portion was immersed in the epoxy resin liquid, and the pressure was reduced to 750 mt1g for 10 minutes using a vacuum pump. The epoxy resin was cured at room temperature to obtain a thermistor as shown in FIG.

A total of 10 thermistors were made, and to test the insulation of the coating layer, the thermistor was immersed in water at a distance of 20 m from copper as a counter electrode, and the resistance value was measured when 20 V DC was applied between the two. did. In addition, as a test of response speed,
The hethermistor was immersed in warm water at 50°C from air at room temperature 25°C, and the time required to reach 63.2% of the thermistor resistance change, that is, the time constant, was measured. As a result, the thermistor obtained in this example had an insulation property of 10X in water.
It showed a high value of 1012Ω or more, and the time constant was 0.3 seconds or less, which was an extremely fast response speed. In addition, in the following Examples and Comparative Examples, unless otherwise specified, the same procedures as in Example 1 were carried out.

Comparative Example 1 In Example 1, the thermistor element was directly immersed in an epoxy resin solution without using a tube, and then pulled up and cured.

The obtained thermistor achieved a rating of 104 in an underwater insulation test.
The resistance value was low, less than Ω, and the insulation of the dumet wire portion was insufficient.

A two-component urethane resin liquid having a viscosity of 95,000 cps was filled into the tube under reduced pressure. As a result, the insulation properties of the obtained thermistors in water all showed resistance values of 1012Ω or more, and the time constants were as fast as 0.5 seconds or less.

Comparative Example 2.3 In Example 1, the resin liquid viscosity was set to 400C and 110C.
,000 cps, and were used as Comparative Examples 2 and 3, respectively.

The resin flowed down from the underwater insulation test tube of the obtained thermistor, whereas in Comparative Example 3, the viscosity was too high, so the resin was not sufficiently filled into the tube even by reducing the pressure, and therefore none of the comparisons In this example as well, the result was poor insulation due to insufficient filling in the tube.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a cross-sectional structure of a thermistor element portion in the present invention. Further, FIGS. 2 and 3 are diagrams showing the cross-sectional structure of a conventional thermistor element section.

Claims (2)

[Claims] (1) A thermistor consisting of a glass-coated thermistor element with 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, the dumet wire and the insulating resin coat. The distance between the end of the external lead wire and the joint is 10 mm.
Cover the dumet wire led out from the thermistor element, the joint, and the vicinity of the joint at the end of the external lead wire with a resin tube whose inner diameter is smaller than that of the thermistor element, and fill the void inside the resin tube with insulating resin. And furthermore,
A thermistor characterized in that the surface of the thermistor element and at least the portion of the resin tube in contact with the thermistor element are coated with an insulating resin. (2) The insulating resin that fills the void inside the resin tube is
It is characterized by being a solvent-free liquid resin containing at least one selected from the group consisting of polyimide resin, polyester resin, epoxy resin, and polyurethane resin, and having a viscosity in the range of 500 to 100,000 cps. A thermistor according to claim 1, wherein: