JPS63204120A - Liquid level detector - Google Patents

Abstract

PURPOSE:To enhance workability to a large extent while holding the accuracy of a product to a constant level, by constituting an electric circuit by electrically connecting a heat-sensitive element and applying the molding of a resin to the outer periphery of said electric circuit. CONSTITUTION:The leading end of a heat conductive plate 2 and that of the min. width part 6 are respectively formed into connection terminals 7, 12 and holes 8, 13 are formed to said connection terminals 7, 12. Then, the heat conductive plate 2 and the min. width part 6 are connected to both surfaces of PTC 1 by soldering to constitute an electric circuit 14 which is, in turn, integrally molded by a heat insulating synthetic resin 15 so that only the radiation surface of the heat conductive plate 2 is exposed but all of other parts are hermetically closed. The connection terminals 7, 12 of the electric circuit 14 are connected to an ammeter 16 displaying the conversion of a liquid level and a battery 17 being a power source. In this case, since PTC 1 is strongly held by the heat conductive plate 2 and a strip like conductor 9, when the outer periphery of the electric circuit 14 is integrally molded by the heat insulating resin 15, the handling work thereof can be rapidly performed and molding work can be efficiently performed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a liquid level detector for detecting the fuel level in an automobile fuel tank, the oil level in an engine, etc.

A liquid level detector using a positive temperature coefficient thermistor (hereinafter referred to as PTC) as a small and highly reliable liquid level detector without mechanical moving parts was published in Japanese Patent Publication No. 1988-688. It existed as shown.

In this liquid level detector, as shown in FIG. 1, circular holes 03 are provided at regular intervals in the longitudinal direction in a vertically long thermally insulating holder 02, and the circular holes 03 are made to communicate with each other. A short cylindrical PTC is formed.
With the lead wires 05 and 06 connected in parallel to both sides of the PTCOI, this PTCOI is fitted into the circular hole 03, and the lead wire 05 is inserted into the hole 04, and the other side 07 of the thermally insulating holder 02 is thermally insulated. The cover plate 08 was glued together.

In the liquid level detector described above, it is necessary to solder to connect the lead wires 05.06 to both sides of the PTCOl, and the spacing between the PTCOIs is kept constant and the thin lead wires 05.0G are connected to the PTCOl. It was difficult to solder both sides of the board. When roughly inserting the lead wire 05 into the groove 04, the lead wire 05 is caught and the connection part is separated.
Or, there was a fear that the lead wire 05 would be disconnected.

In order to improve this problem, as shown in Fig. 2, PTCOl is supported and fixed on a metal holding plate 02 which also serves as a heat conduction plate by soldering or the like. , a liquid level detector can be considered in which the lead wire 03 is connected to the other surface of PTCOl by soldering to form an electric circuit, and the outer periphery is integrally molded with synthetic resin 04, but the lead wire 03 can be connected manually. It had to be done manually, resulting in poor work efficiency and lack of reliability.

■- and (fJFJfi) The present invention relates to an improvement of a liquid level detector that overcomes such difficulties, and includes a liquid level detector that is immersed in a liquid and detects the height of the liquid level. In the device, one flat connecting member having a heat-sensitive element fixed to its flat surface and the other connecting member connected to the heat-sensitive element are arranged so as to be oriented substantially at right angles, and the heat-sensitive element is electrically connected. Since the electric circuit is drawn using a resin mold and the outer periphery of the electric circuit is molded with resin, there is no risk of separation or derailment of the connections between the heat-sensitive element and each connecting member, which reduces the defective rate and eliminates the need for rough handling. The heat-sensitive element and the other connecting member can be automatically and simultaneously connected without any work.

In addition, in the present invention, the force acting on the other connecting member of the tS1 finger mold when attempting to peel off the connecting portion of the heat-sensitive element is released.
1 heat sensitive end and the other connection part (A's bald head can be made into a defense 1).

An Example of Practical Effects The embodiment shown in FIGS. 3 to 6 will be described below.

In this example, PTol is used as a heat-sensitive element that generates heat by itself and has the characteristic that the electrical resistance value changes due to temperature changes.
-C is used, but in addition to that, a thermistor (NTC), C
A temperature-sensitive semiconductor such as RT or a platinum resistance temperature sensor may also be used.

J. The side end face of the copper heat conductive plate 2 (aluminum is also acceptable) which is the connection member for the power is formed into a flat heat dissipation surface 3, and the other side end has heating parts at two places above and below. 4 is arranged, and the other side end surface is formed in a tapered shape so that it approaches the heat radiation surface 3 as it advances from this heating part 4 in the vertical direction.
One side of the TCI is integrally joined by soldering.

Further, in a portion sandwiched between the heat dissipation surface 3 and the heating section 4, circular heat insulating holes 5 are provided at the top and bottom in order to increase the thermal resistance between the heat dissipation surface 3 and the portion of the heating section 4 that faces the heat dissipation surface 3. Three pieces are provided at each of two locations, and one in the vertical direction between the minimum width part 6 of the heat conduction plate 2 - (between each heat dissipation section and the heating section 4, which are considered to be separated into n sections). are formed so that their thermal resistances are approximately equal.

Furthermore, the copper strip-shaped conductor 9, which is the other connecting member, has
A large number of heat insulating holes 10 are provided along the longitudinal direction, and contact protrusions 11 are formed on the negative side at intervals equal to the arrangement interval of PTCl. It is soldered on the side.

Furthermore, the tips of the heat conductive plate 2 and the minimum 11 portion 6 are formed into connection terminals 7 and 12, respectively, and holes 8 and 13 are formed in the connection terminals 7 and 12, respectively.

Heat conductive plate 2 and minimum 11] part 6 on both sides of PTC1
are connected by soldering to form an electric circuit 14, and integrally molded with a heat insulating synthetic resin 15 so that only the heat dissipation surface 3 of the heat conduction plate 2 is exposed but everything else is sealed.

The connecting terminals 7, 12 of the electric circuit 14 are connected to a current side 16 for indicating changes in the liquid level and to a power source fluctuation 17, as shown in FIG.

Since the embodiment shown in FIGS. 3 to 6 is constructed as described above, the liquid level 1-8 of the fuel tank is high, and the heat dissipating surface 3 is entirely in contact with the fuel 1-8 for cooling. In the wide-area state, PTCl is cooled to a low temperature and becomes P T' C1
The electrical resistance of the ammeter 16 is small, and the pointer of the ammeter 16 swings large.

As the fuel is consumed and the liquid level LS of the fuel 1- becomes low, the cooling portion of the heat radiation surface 3 by the fuel decreases, and P
The temperature of TCI gradually rises, the electrical resistance of PTCl increases, and the swing of the finger of the ammeter 16 decreases.

In addition, since PTCl is firmly held by the heat conductive plate 2 and the band-shaped conductor 9, it can be handled quickly and efficiently molded when integrally molding the outer periphery of the electric circuit 14 on the heat insulating synthetic resin 15. Able to perform work.

Roughly, PTCl is fixed to the heating parts 4 of the heat conduction plate 2 which are arranged at a constant interval, and the band-shaped conductor 9 has high rigidity and its contact protrusions 11 can maintain a constant interval. The PTCI can be positioned reliably to improve product accuracy, and the soldering process between the PTCI and the contact protrusion 11 can be easily automated.

Furthermore, since the ends of the heat conductive plate 2 and the band-shaped conductor 9 can be formed into a connecting terminal 7.12 with a fixed relative position,
The electric circuit 14 can be easily connected to external wiring.

Moreover, since a large number of insulation holes 10 are opened in the band-shaped conductor 9,
It is possible to improve the heat insulation properties of the band-shaped conductor 9, avoid stress acting perpendicularly to the flat part of the band-shaped conductor 9 during resin molding, and further strengthen the band-shaped conductor 9 and the heat-insulating synthetic resin 15. be combined.

In the embodiment shown in FIGS. 3 to 6, the strip conductor 9
The contact protrusions 11 are formed by punching and press forming into a shape that protrudes in the width direction of the band-shaped conductor 9. However, as shown in FIGS. A protruding piece 20 parallel to one side of the conductor 18 may be formed by stamping and press forming, and this may be bent at right angles to form the contact piece 21, or alternatively, as shown in FIGS. 9 to 10.
The strip-shaped conductor 22 may be configured as shown in the figure.

In the present invention, the heat-sensitive element and the other connecting part can be connected automatically and at the same time without manual work, so the accuracy of the product can be maintained at a certain level. Work efficiency can be greatly improved.

Further, in the present invention, it is possible to prevent the heat-sensitive element from peeling off from the other connecting member during resin molding, so that the defective rate of products can be reduced.

Roughly speaking, in the present invention, since both sides of the heat-sensitive element are supported by one flat connecting member and the other connecting member, the resin molding operation can be carried out without any trouble.

[Brief explanation of the drawing]

FIG. 1 is an exploded perspective view of a conventional liquid level detector, FIG. 2 is a schematic perspective view of another conventional liquid level detector, and FIG. 3 is an implementation of a liquid level detector according to the present invention. An exploded perspective view of the example, FIG. 4 is a cross-sectional view thereof, and FIG. 5 is a schematic transparent perspective view of the same example.
FIG. 6 is a circuit diagram thereof, FIG. 7 is a side view of another embodiment of the present invention, FIG. 8 is a perspective view of the protruding piece in a bent state, and FIG.
The figure is a perspective view of still another embodiment of the present invention, and FIG. 10 is a side view thereof. 1... PTC, 2... Heat conduction plate, 3... Heat radiation surface,
4... Heating part, 5... Heat insulation hole, 6... Minimum width part,
7... Connection terminal, 8... Hole, 9... Band-shaped conductor,
DESCRIPTION OF SYMBOLS 10... Heat insulation hole, 11... Contact protrusion, 12... Connection terminal, 13... Hole, 14... Electric circuit, 15...
・Insulating synthetic resin, 1G... Current tear, 17... Battery, 18... Band-shaped conductor, 19... Insulating hole, 20
... Protruding piece, 21... Contact piece, 22... Band-shaped conductor, 23... Heat insulation hole, 24... Protruding piece, 25... Contact piece, L... Fuel, LS...Liquid level.

Claims (1)

[Claims] A liquid level detector that is immersed in a liquid to detect the height of the liquid level, comprising: one flat connecting member having a heat-sensitive element fixed to its flat surface; and a flat connecting member connected to the heat-sensitive element. The heat-sensitive element is arranged so as to be oriented substantially perpendicularly to the other connecting member, the heat-sensitive element is electrically connected to form an electric circuit, and the outer periphery of the electric circuit is molded with resin. surface detector.