JPH05142013A - Thermistor liquid level detector - Google Patents

Abstract

(57) [Abstract] [Purpose] In the thermistor liquid level detector used for vehicle fuel level warning lights, etc., the lead side wire breakage or terminal due to electrolytic corrosion that occurs when used in alcohol fuel. Provided is a thermistor liquid level detector having excellent durability that solves the problem of deterioration due to corrosion of aluminum. [Structure] By suppressing the leakage current flowing from the positive side lead wire 8 to the metal case 2 through the fuel by covering the surface of the positive side lead wire 8 drawn out from the thermistor element 7 with an insulating tube 15. Because you can
Even when used in alcohol fuel, electrolytic corrosion is less likely to occur, and breakage of the positive side lead wire 8 and corrosion of the terminal 4 can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermistor liquid level detector used in a liquid having a low electric resistance such as alcohol.

[0002]

2. Description of the Related Art In recent years, a thermistor liquid level detector has been used as a liquid level detector for gasoline, light oil, a mixed fuel of alcohol and gasoline, kerosene, etc., as a vehicle fuel remaining amount warning light and a household fuel remaining amount warning device. Is used for.

A conventional thermistor liquid level detector will be described below with reference to the drawings. FIG. 4 is a sectional view showing the structure of a conventional thermistor liquid level detector 1. In FIG.
Reference numeral 2 is a metal case having a liquid outflow hole 3 at the bottom.
A terminal plate 6 having a cylindrical terminal 4 fixed by caulking and a liquid outflow hole 5 is fixed to the metal case 2 at its opening by caulking or the like. The metal case 2 accommodates a thermistor element 7 coated with an insulating paint and the like, plus side lead wire 8 and minus side lead wire 9 connected thereto, and the plus side lead wire 8 is soldered by a solder 10. Negative side lead wires 9 are soldered to the terminals 4 to the bottom of the metal case 2 with solder 11. Further, an external lead wire 12 is soldered to the terminal 4 with a solder 10 and electrically connected to the plus side lead wire 8.

Next, FIG. 5 shows a circuit diagram of this thermistor liquid level detector. In the figure, 13 is a DC power source, 1
Reference numeral 4 denotes a display lamp, which is connected in series with the thermistor liquid level detector 1. Here, the external lead wire 12 shown in FIG. 4 is connected to the plus side of the DC power source 13, and the metal case 2 is connected to the minus side.

The operation of the thermistor liquid level detector 1 constructed as above will be described below. First, when the thermistor liquid level detector 1 is arranged at a predetermined position in the fuel tank, when the fuel is sufficient, the thermistor element 7 is located in the fuel and it is difficult for the thermistor element 7 to self-heat due to the heat radiation effect to the fuel. Therefore, the resistance value becomes high, and the display lamp 14 does not light. On the other hand, when the fuel is reduced to a predetermined amount or less, the thermistor element 7 is exposed to the air. However, since the thermal conductivity of air is lower than that of the fuel, the thermistor element 7 rapidly generates heat, and the resistance value decreases, resulting in a large current. And the display lamp 14 lights up.

[0006]

However, in the above conventional structure, when used in a fuel having a low electric resistance such as alcohol, when a voltage is applied with the fuel in the metal case, a current flows to the positive side. In addition to flowing from the lead wire to the minus side lead wire, leakage current also flows to the metal case via the fuel, so that the positive side lead wire is disconnected due to electrolytic corrosion. Further, there is a problem that the terminals are corroded and deteriorated.

The present invention solves the above-mentioned conventional problems, and an object of the present invention is to provide a thermistor liquid level detector which has a significantly improved durability when used in a fuel having a low electric resistance. ..

[0008]

In order to achieve this object, the present invention is a conventional thermistor liquid level detector in which at least the positive lead wire is covered with an insulating tube or a heat shrinkable tube. ..

[0009]

With this structure, since the plus side lead wire is covered with the insulating tube or the heat shrinkable tube, the leakage current flowing from the plus side lead wire through the fuel is suppressed. Therefore, electrolytic corrosion of the positive lead wire is less likely to occur, the durability of the positive lead wire can be significantly improved, and deterioration due to corrosion of the terminal can be prevented.

[0010]

【Example】

(Embodiment 1) An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view showing the structure of a thermistor liquid level detector according to the first embodiment of the present invention.
1 is different from the conventional configuration of FIG. 4 in that the plus side lead wire 8 is covered with an insulating tube 15.

With respect to the thermistor liquid level detector constructed as described above, a durability evaluation test by energizing in alcohol was carried out while comparing with a conventional thermistor liquid level detector. 1 time of disconnection
It was confirmed that the wire did not break even after a time of 0 times or more.

As described above, according to this embodiment, by covering the plus side lead wire 8 with the insulating tube 15, the current flowing from the plus side lead wire 8 to the metal case 2 through the fuel can be suppressed. The disconnection of the positive side lead wire 8 can be prevented.

(Embodiment 2) Next, a second embodiment of the present invention will be described with reference to the drawings. FIG. 2 is a sectional view of a thermistor liquid level detector according to the second embodiment of the present invention. 2 is different from the conventional configuration of FIG. 4 in that the positive side lead wire 8 is covered with the heat shrinkable tube 16 so as to be in close contact with the surface of the positive side lead wire 8.

An evaluation test similar to that of Example 1 was carried out on the thermistor liquid level detector having the above-mentioned structure while comparing it with the conventional product, and the result of this Example product was the same as that of Example 1. Therefore, it was confirmed that the disconnection of the positive side lead wire 8 can be prevented.

As described above, by covering the surface of the plus side lead wire 8 with the heat-shrinkable tube 16 so as to be in close contact therewith, no leakage current flows from the plus side lead wire 8 to the metal case 2 through the fuel, and the plus side. It is possible to prevent disconnection of the lead wire 8.

(Embodiment 3) Next, a third embodiment of the present invention will be described with reference to the drawings. FIG. 3 is a sectional view of a thermistor liquid level detector showing a third embodiment of the present invention. 3 is different from the conventional configuration of FIG. 4 in that the positive side lead wire 8 is covered with an insulating tube 15, the insulating cylinder 17 is inserted into the inner wall surface of the metal case 2, and the outer surface of the terminal 4 is thermally contracted. This is the point covered with the tube 18.

The thermistor liquid level detector constructed as described above was subjected to the same evaluation test as in Example 1 while comparing it with a conventional product, and when a brass material generally used for the terminal 4 was used. However, it was confirmed that the deterioration of the terminal 4 due to corrosion was prevented.

As described above, by covering the outer surface of the terminal 4 with the heat shrinkable tube 18, the durability of the terminal 4 can be improved.

In the first to third embodiments, only the plus side lead wire 8 is insulated tube 15 or heat shrinkable tube 1.
Although it is covered with 6, it goes without saying that the minus side lead wire 9 may be covered with these tubes.

[0020]

As described above, according to the present invention, at least the positive lead wire is covered with the insulating tube or the heat-shrinkable tube to suppress the leakage current flowing from the positive lead wire to the metal case through the fuel. Because you can
This is a thermistor liquid level detector that can significantly improve the durability of the positive side lead wire and can prevent deterioration due to corrosion of the terminals.

[Brief description of drawings]

FIG. 1 is a sectional view of a thermistor liquid level detector according to a first embodiment of the present invention.

FIG. 2 is a sectional view of a thermistor liquid level detector according to a second embodiment of the present invention.

FIG. 3 is a sectional view of a thermistor liquid level detector according to a third embodiment of the present invention.

FIG. 4 is a sectional view of a conventional thermistor liquid level detector.

[Figure 5] Circuit diagram of the thermistor liquid level detector

[Explanation of symbols]

 2 Metal case 3,5 Outflow hole 4 Terminal 6 Terminal plate 7 Thermistor element 8 Positive lead wire 9 Negative lead wire 12 External lead wire 15 Insulation tube 16,18 Heat shrink tube

Claims (2)

[Claims] 1. A terminal plate having a liquid outflow hole is connected to an opening of a metal case having one end opening having a liquid outflow hole at the bottom, and the terminal connected to the terminal plate and the bottom surface of the metal case. In the thermistor liquid level detector that connects the positive side and negative side lead wires drawn from both ends of the thermistor element, respectively, and uses the metal case at a negative potential, at least the positive side lead wire is an insulating tube or a heat shrink tube. Covered thermistor liquid level detector. 2. The thermistor liquid level detector according to claim 1, wherein the outer surface of the terminal is covered with a heat-shrinkable tube.