JPH03209704A - Liquid-level detecting thermistor - Google Patents

Abstract

PURPOSE:To make the heat dissipation constant of the element of a thermistor in air small so that a current is easy to flow and to eliminate the malfunction of an alarming lamp by machining each lead wire so as to have a curved part such as an S shape, and making the length of each lead wire to the attaching position of to a sensor long. CONSTITUTION:Electrodes 12 are formed on both end parts of an element 11 of a thermistor in a circular cylinder shape or in a prismatic shape. Lead wires 13 which are made of stainless steel having the low thermal expansion coeffi cient and has thermistor holding parts are compressed into the respective electrodes 12 at both ends of the element of the thermistor 11. The entire body other than the parts of the lead wires 13 which are connected to external circuits is covered with a glass material 14. The lead wires are machined so that the S-shaped or Z-shaped curved parts are formed. In this constitution, the lead wires can be machined in the curved shape and attached within a specified size even if the lead wires that are attached to the element of the thermistor are long. Thus, the heat dissipation constant of the element of the thermistor becomes small. Therefore, the resistance value becomes low, and a current is easy to flow.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a thermistor for detecting the level of liquid such as engine oil or gasoline in automobiles or the like.

Conventional technology In devices that detect the level of liquid such as engine oil or gasoline, a voltage within a certain range is applied to a circuit in which a warning light bulb is connected in series to a thermistor for detecting the liquid level. A device is known that turns on or off a light bulb by controlling the amount of current flowing through a circuit based on the difference in heat dissipation constant between the inside and the liquid.

A conventional liquid level detection thermistor will be described below.

As shown in FIG. 2, after attaching three lead wires 3 with thermistor holders to each of the electrodes 2 at both ends of a cylindrical or prismatic thermistor element 1 with electrodes 2 formed at both ends,
The lead wire 3 is covered with a glass material 4 except for the portion connected to the external circuit.

The heat dissipation constant of thermistor element 1 in a liquid such as engine oil or gasoline does not change much even if the length of the lead wire 3 is changed, but the heat dissipation constant of thermistor element 1 in the air does not change much even if the length of the lead wire 3 is changed. The attachment of wire 3 changes as the length to the position changes.

The shorter the length of the thermistor from the element 1 to the mounting position, the more heat can escape through the lead wire 3, and the heat dissipation constant of the thermistor element 1 becomes larger.

Problems to be Solved by the Invention However, in the conventional configuration described above, the length of the lead wire 3 is restricted due to the installation distance, etc., and the heat dissipation constant of the thermistor element 1 in the air increases, making it difficult for the thermistor element 1 to generate heat. Therefore, the resistance value of the thermistor element 1 becomes high. In other words, there was a problem in that the current was difficult to flow, causing a malfunction in which the warning light bulb did not turn on even in the air.

Note that in order to reduce the heat dissipation constant in the air, the length of the lead wire 3 from the thermistor element 1 to the mounting position can be increased, but if the length of the lead wire 3 is increased, the shape of the sensor can be changed. There was a problem in that it was not possible to downsize a large 9.

The present invention solves the above-mentioned conventional problems, and connects a shaped lead wire to the thermistor element to reduce the heat dissipation constant of the thermistor element and lower the resistance value of the thermistor element, thereby allowing current to flow. The purpose of the present invention is to provide a small liquid level detection thermistor that is easy to use and does not malfunction.

Means for Solving the Problems Therefore, in order to solve the above problems, the thermistor for liquid level detection of the present invention has a cylindrical or prismatic thermistor element with electrodes formed at both ends, and the electrodes at both ends are S-shaped or double-shaped. It has a structure in which a lead wire with a thermistor holding part that has been processed to have a curved part is press-fitted and covered with a glass material.

Effect: With this configuration, even if the lead wire to be attached to the thermistor element is long, the shape can be processed and it can be attached within the specified dimensions, so the heat dissipation constant of the thermistor element is reduced, and therefore the resistance value is also lowered, making it easier for current to flow. It happens.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to the drawings.

As shown in FIGS. 1(a) and 1(b), a cylindrical or prismatic thermistor element 11 with electrodes 12 formed at both ends.
A lead wire 13 with a thermistor holder made of stainless steel having a low coefficient of thermal expansion is press-fitted into each of the electrodes 12 at both ends of the
The lead wire 13 except for the portion connected to the external circuit is covered with a glass material 14, and the shape of the lead wire 13 is processed to have a curved portion such as an S-shape or a double-shape.

As an example, for a sample in which a lead wire 13 with a diameter of 0.5 mm and a thermistor holding part made of stainless steel was press-fitted into a thermistor element 11 with a diameter of 1.8 rtan and a length of 4, the lead wire 13 was Table 1 shows the measured values of the heat dissipation constant in the air due to differences in length and shape.

Table 1 Unit: m W/'C Table 1 shows that even if the shape of the lead wire 13 changes, if the length of the lead wire 13 is the same, the heat dissipation constant of the element will hardly change. .

As described above, according to this embodiment, by processing the shape of the lead wire 13 to have an S-shaped or double-shaped curved part, malfunction of the liquid level detection thermistor can be eliminated and the shape can be made smaller. . In the example, lead wire 1
Although the shape of No. 3 is an S-shape or a two-shape, it goes without saying that other shapes may be used.

Effects of the Invention As is clear from the description of the embodiments described above, the present invention involves processing the shape of the lead wire to have a curved part such as an S-shape or a double-shape, and attaching the sensor to the lead wire to the position. By increasing the length, it is possible to reduce the heat dissipation constant of the thermistor element in the air, making it easier for current to flow, and realizing a small and excellent liquid level detection thermistor that eliminates malfunction of the warning light.

[Brief explanation of drawings]

Figure 1 (&) and Figure 1 (b) are cross-sectional views showing the configuration of a liquid level detection thermistor according to an embodiment of the present invention, and Figure 2 is a cross-sectional view showing the configuration of a conventional liquid level detection thermistor. be. DESCRIPTION OF SYMBOLS 11... Thermistor element, 12... Electrode surface, 13... Lead wire with thermistor holding part, 14... Glass material.

Claims (1)

[Claims] A lead wire with a thermistor holding portion is press-fitted into each of the electrodes at both ends of a cylindrical or prismatic thermistor element with electrodes formed at both ends, and the lead wire is entirely covered with a glass material except for a part, and the lead wire is A thermistor for liquid level detection whose wire shape has been processed to have a curved part.