JPS6113942Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to an improvement in a temperature sensing plug that senses and measures continuously changing water or oil temperature using a temperature sensing element, for example in an internal combustion engine.

Conventional temperature sensing plugs are equipped with a temperature sensing element near the bottom of a bottomed tubular metal fixture with a threaded part for installation, for example, and this temperature sensing element is connected via two connecting wires. The thermosensing element and the connecting wire are connected to two connection terminals attached to opposite ends of the fixture, and are fixed within the fixture by resin casting. In that case, if there is a sudden temperature change, a failure will occur due to the difference in thermal expansion between the connection wire and the resin, but in order to prevent this, two The connecting wires are twisted together, and a nylon resin, for example, is fixed in the interior space of the fixture by casting. However, this method was not preferable because it was inefficient because it had to be twisted together by hand, and the soldered portions could separate during the work.
In order to solve this problem, it is known that the two connecting wires are given dimensional slack in an arbitrary shape to alleviate the distortion caused by large temperature changes. However, simply adding dimensional slack to the connecting wire makes it difficult for the temperature sensing element and the connecting wire to completely absorb the compressive or tensile force due to the difference in thermal expansion when subjected to thermal history, and this will prevent disconnection of the soldered part. It was still unstable because there was a risk of it happening.

This idea was made to solve this problem.Both the connection wires, including the temperature sensing element, are integrally covered with a single rubber tube made of silicone rubber, and this is installed inside the mounting part. The object of the present invention is to provide a highly reliable temperature sensing plug in which the covered temperature sensing element and the connecting wire are fixed by resin casting, so that the strain caused by large temperature changes is absorbed by the rubber tube. do.

Hereinafter, an embodiment of this invention will be explained based on the drawings. In Fig. 1, a bottomed hollow fitting 1 made of a non-ferrous metal such as brass is screwed and fixed to the cylinder wall of an internal combustion engine, etc., and its cylindrical shape is fixed. The temperature of the cooling water or lubricating oil, which represents the operating state of the internal combustion engine, is detected and measured in the thin wall portion 2 . In order to fix this fixture 1 by screwing, a threaded part 3 is formed next to the thin wall part 2, and a hexagonal head 4 having a hexagonal cross section is formed next to the threaded part 3, and further on the inner wall of the upper edge of the fixture 1, which is connected to the threaded part 3 and a hexagonal head 4 having a hexagonal cross section. An end 6 having an annular groove 5 is formed. This annular groove 5 holds resin injection molded together with elements and connector terminals to be described later so that they do not escape. Furthermore, on the inner surface of the fixture 1,
A bottomed inner cavity 10 having an inner diameter that gradually decreases from the end 6 toward the inner part and terminating near the end surface of the thin wall part 2.
is formed. A chip-type temperature sensing element, such as a thermistor 11, is housed near the bottom. Connecting wires 12 and 13 are soldered to both ends of the temperature sensing element 11, respectively.
Both the connecting wires 12 and 13, including the connecting wires 1, are integrally covered with a single rubber tube 14 made of, for example, heat-shrinkable silicone rubber, which has a heat resistance of about 110° C. or higher and an instantaneous temperature of about 200° C. or higher. After being partially bent as shown, it is soldered to both connecting terminals 8 and 9 that partially protrude from the end 6. Note that this rubber tube 14 may be made of ethylene propylene copolymer rubber (EPR). It is preferable that the material has heat-shrinkable properties such that it shrinks when heated at about 150°C. The hardness is preferably JIS spring type hardness (HS) of 30 to 90. If the inner diameter of the rubber tube 14 is too large, the rubber tube 14 and the connecting wires 12, 13 will be damaged during resin molding, which will be described later.
A small amount of resin may be injected into the space between. This phenomenon can occur especially when resin with good fluidity is used, so this can be avoided by using a heat-shrinkable rubber tube and shrinking it after coating. .
A nylon resin 15 is cast into the space between the bottomed inner cavity 10 and the connecting wires 12, 13 having the slack 7 or their rubber tube 14 together with the soldered portions of the connecting terminals 8, 9. By this casting, the temperature sensing element 11 and both the connecting wires 12, 13 are held and fixed, and the connecting terminals 8, 9 are also fixed.

As detailed above, in the temperature sensing plug of this invention, the connecting wire of the thin part of the temperature sensing element is integrally covered with a rubber tube, typically made of silicone rubber tube and ethylene propylene copolymer rubber, and made of polyamide resin, epoxy resin, etc. Since the resin is cast into the fixture and fixed, the strain caused by the difference in thermal expansion between the thermosensor/connection wire and the resin is completely absorbed by the rubber tube, preventing failures such as disconnection at the soldered part. Therefore, the reliability of the product can be guaranteed. In addition, since only the insertion of the rubber tube requires time and effort, the workability is good, and since a commercially available rubber tube can be used, it can be manufactured at a low cost. Furthermore, in the past, in order to prevent direct contact between the thermosensor and the metal fixture, an insulating tube was inserted and molded in advance to contact the inner cavity of the fixture, but such an insulating tube is unnecessary and provides complete insulation as is. It has many practical effects, such as maintaining the

[Brief explanation of the drawing]

FIG. 1 is a vertical sectional front view showing an embodiment of this invention. 1... Metal fitting, 11... Temperature sensing element, 12,
13... Connection wire, 14... Rubber tube, 15...
...Nylon resin.

Claims (1)

[Scope of utility model registration request] A temperature sensor characterized in that the temperature sensing element and both of its connecting wires are integrally covered with a single rubber tube, and the covered temperature sensing element and the connecting wires are fixed in a tubular fitting by resin casting. Detection plug.