JPS6382322A - Preparation of liquid level detector - Google Patents

Abstract

PURPOSE:To enhance detection accuracy by enhancing the positional accuracy of a heat-sensitive element, by forming an electric circuit by electrically connecting the heat-sensitive element to a conductive member constituted by mutually and integrally forming the upper ends of a plurality of connection parts electrically connecting the heat-sensitive element. CONSTITUTION:Two longitudinal grooves 8 are formed to a plate-shaped conductor 3 made of a metal such as Cu also used as the holding member of temp. compensating PTC by cutting so as to leave the upper end connection part 4 of said conductor 3 to form three connection segments 5a-5c and holes 6 are provided to the upper ends of said connection segments 5a-5c. Further, one connection segment 5c among the connection segments 5a-5c is made shorter as compared with two other segments. PTC 2a is arranged across the lower ends of the connection segments 5a, 5b and PTC 2b is arranged across the lower end of the connection segment 5c and the intermediate part of the connection segment 5b corresponding thereto, and both electrode surfaces of PTC 2a, 2b are soldered to the connection segments 5a, 5b and the connection segments 5b, 5c. The connection segments 5a-5c are molded using a synthetic resin 11 so as to expose PTC 2a, 2b and the connection part 4 is subsequently cut.

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 the fuel tank of an automobile, the oil level in the 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 additional heating or mechanical parts was published in Japanese Patent Publication No. 55-688. It existed as indicated in the official gazette.

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 groove 04 is formed in the short cylindrical PTC.
Lead wire 05. on both sides of Ol. With Of3 connected in parallel, this PTCOl is loaded once into the circular hole 03, the lead wire 05 is inserted into the groove 04, and the heat insulating holder 0 is inserted.
A heat insulating cover plate 08 was integrally bonded to the other side surface 07 of 2.

In the liquid level detector described above, it is necessary to perform soldering in order to connect the lead wires 05.06 to both sides of the PTCOI, and also to keep the interval between the PTCOI constant and to connect the lead wires 05.06 to both sides of the PTCOI. It is difficult to solder 06 to both sides of PTCOl, and when inserting lead wire 05 into full 04, it is difficult to hook the lead wire 05 and separate the connection, or to connect the lead wire 05 with a wire. there were.

There was a case in which a metal i9 plate was used as a band-shaped conductor of PTC instead of the lead wire in Japanese Patent No. 51-291323.

In addition, a patent application was filed in 1986-12 for using the end of a band-shaped conductor protruding from the detector body as a connecting terminal of a connector.
There is No. 8130.

1 However, it is difficult to keep the distribution relationship between one pole of the conductor, the heat-sensitive element, and the other type of conductor constant, electrically connect them, and form a liquid level detection circuit. In addition, when the end of the strip-shaped conductor of the liquid level detector is used as the connection terminal of the connector, the arrangement of the end of the strip-shaped conductor must be kept constant. When integrally forming a liquid level detector using a synthetic resin or the like, it was necessary to fix the strip-shaped conductor with a jig and perform connection and molding operations between the heat-sensitive element and the strip-shaped conductor.

11　r　to ``1'' h.

The present invention relates to an improvement in a method for manufacturing a liquid level detector that overcomes these difficulties, and includes a method for manufacturing a liquid level detector that is immersed in a liquid and detects the height of the liquid level. After forming an electric circuit by electrically connecting the heat-sensitive element to a conductive member formed by integrally forming the upper ends of a plurality of connecting portions that are connected to each other, the upper ends of the conductive member are cut and By using the upper parts of the multiple connection parts as connection terminals, the electrical circuit of the liquid level detector can be constructed while the conductive members are held in a relatively integral positional relationship without the need for any jigs. A liquid level detector can be manufactured.

Point JLJ Hereinafter, one embodiment of the present invention illustrated in FIGS. 2 to 6 will be described.

In the liquid level detector 1 of this embodiment, a PTC2 is used as a heat-sensitive element that generates heat by itself and has a property that its electrical resistance value changes with temperature changes.
TC>, a temperature-sensitive semiconductor such as a CRT, or a platinum resistance temperature sensor may be used.

In addition, the plate-shaped conductor 3 made of gold such as copper, which also serves as a holding member for the PTC 2, has two parts below it, leaving the upper end connecting part 4.
The longitudinal groove 8 of the book is cut out to form three connecting pieces 5, each of which has a hole 6 at its upper end.

Furthermore, one of the three connecting pieces 5, 5C, is shorter than the other two connecting pieces 5a, 5b.

Furthermore, as shown in FIG.
The PTC 2a is placed astride the lower end, and the PTC 2b is placed astride the lower end of the connecting piece 5C and the corresponding middle part of the connecting piece 5b, and both electrode surfaces of the PTC 2a, 2b and the connecting part are placed. The pieces 5a, 5b and the connecting pieces 5b, 5c are each soldered 9 to form an electric circuit 10 of the liquid level detector 1 (see FIG. 2).

Next, the connecting piece 5 is molded with heat insulating synthetic resin 11 so that the PTCs 2a and 2b are exposed (see FIG. 3), and the upper end connecting portion 4 of the plate-shaped conductor 3 is cut (see FIG. 4) and the liquid level detector 1).

The connection terminals 7a, 7 of the liquid level detector 1 configured in this way
c are connected to the terminal 13 of the power source via indicator lamps 12a and 12b, respectively, and the connecting terminal 7b is grounded 14.

In the actual dust examples shown in FIGS. 2 to 6, the connection piece 5a
, 5b, PTC2a at the bottom of 5c.

2b, and are also integrally connected to the upper end connecting part 4 at the upper part of the connecting pieces 5a, 5b, 5C, so that when molding, the plate-shaped conductor No matter which part of 3 is supported, the connection piece 5a
, 5b, and 5c can be maintained parallel to each other, and when the upper end connecting portion 4 is cut after molding, the upper portions of the connecting pieces 5a, 5b, and 5c are placed on one plane. The connection terminals 7a, 7b, and 7c can be positioned parallel to each other along the line, and as a result, the connection terminals 7a, 7b, and 7c can be formed without the need for a jig.

Also, the connecting pieces 5a, 5b, 5c are connected at both endsfg
Since the liquid level detector 1 can be molded, there is no variation in accuracy of the liquid level detector 1.

Since the plate-shaped conductor 3 is obtained by press molding, it is suitable for 8 production.

In this way, since no jigs or the like are required, the number of man-hours is small, and it is suitable for mass production, it is possible to significantly reduce costs.

In the embodiment shown in FIGS. 2 to 6, the liquid level detector 1
When the PTC2a is immersed in the fuel in the fuel tank 15,
, 2b are in direct contact with the fuel tank, the height of the liquid level LS in the fuel tank is detected step by step by selectively lighting the indicator lamps 12a and 12b, but it is difficult to continuously detect this. , the liquid level detector 20 may be configured as shown in FIGS. 7 to 12.

The plate-shaped conductor 21 made of copper (aluminum or the like may be used) is composed of a heat conductive plate 22 that also serves as one electrode plate, a correction electrode 28, the other electrode plate 33, and an upper end connecting portion 38. As shown in FIG. 7, one plate is manufactured by punching and press molding.

Also, one side end of the heat conduction plate 22 has a shell-like heat dissipation surface 23.
The other side end has two heating parts 24 at the top and bottom.
is arranged, and the other side end surface is formed in a tapered shape so that it approaches the heat radiation surface 23 as it goes up and down from this heating section 24, and a liquid surface elongated in the up and down direction is formed on one side of this heating section 24. One side of the detection PTC 2 is joined together.

Furthermore, in the part sandwiched between the heat radiation surface 23 and the heating part 24,
Three circular heat insulating holes 25 are provided in each of the upper and lower two locations to increase the thermal resistance between the portion of the heating section 24 facing the heat dissipating surface 23 and the heat dissipating surface 23. It is formed so that the thermal resistance between each of the heat dissipation sections, which are considered to be divided into n sections in the vertical direction between the width portions 26 and the heating section 24, is approximately equal.

Furthermore, a correction electrode 28 is disposed at a location above the heat dissipation surface 23 of the heat conduction plate 22 on the opposite side of the heat dissipation surface 23 at a predetermined interval, and the side remote from the heat dissipation surface 23 is tapered and has an area A narrow heat dissipation surface 29 is formed, and one side surface of a vertically elongated temperature correction PTC 32 is integrally joined to one side surface of the heating section 30 located at the base of the correction electrode 28 .

Moreover, in the electrode plate 33 constituting the other ground plate of the liquid level detection PTC 2 and the temperature correction PTC 32, the joint portion 35 in contact with the liquid level detection PTC 2 is shaped and shaped along the longitudinal direction of the electrode plate 33. The joint portion 36, which is bent into an L-shape and comes into contact with the temperature correction PTC 32, has its negative side in the width direction bent at a right angle, and then its end portion is further bent at a right angle in the opposite direction.

Moreover, after the joint portions 35 and 36 are bent, the upper part of the electrode plate 33 is bent so that the joint portions 36 and 35 can contact the temperature correction PTCs 32, PTC2, and PTC2. A bent portion 34 is formed at.

Also, a PTC 2 for liquid level detection, a PTC 32 for temperature correction, and a heat conduction plate 22. Correction electrode 28. The electrode plate 33 is bonded to the electrode plate 33 by low-humidity soldering or other suitable bonding means.

In this way, the heat conductive plate 22. The liquid level detector is constructed by closing the assembly in which the PTC 2 for liquid level detection and the PTC 32 for temperature correction are joined to the correction voltage t'4! 28 and the electrode plate 33 with three foamed resin insulation materials without any gaps. be done.

In addition, the connection terminal 27 of the heat conduction plate 22, the correction connection terminal 31 of the correction electrode 28, and the connection terminal 37 of the electric plate 33 are the 12th
As shown in the figure, it is connected to an ammeter 40 that displays changes in the liquid level and a battery 41.

Since the embodiments shown in FIGS. 7 to 012 are configured as described above, when the liquid level Is of the fuel tank is low and is located below the lowest part of the heat radiation surface 23, the heat radiation surface 23
3 is not cooled by fuel, so PT for liquid level detection
C2 is maintained at a high temperature, the electrical resistance of the PTC 2 for liquid level detection is large, and the deflection of the pointer of the ammeter 40 is small.

As the liquid level LS of the fuel tank increases, the cooling portion by the fuel tank increases from the bottom of the heat dissipation surface 23 upwards.
The temperature of PTC2 for liquid level detection gradually decreases, and the temperature of PTC2 for liquid level detection decreases.
The electrical resistance of C2 decreases, and the deflection of the pointer of the ammeter 40 increases.

In addition, the change in electrical resistance of the liquid level detection PTC 2 due to the influence of the ambient temperature is corrected by the temperature correction PTC 32, so the deflection of the pointer of the ammeter 40 is not affected by the ambient temperature, and the change in the electrical resistance due to the influence of the ambient temperature It is possible to accurately indicate the level of the surface LS.

Furthermore, by using only two relatively small PTC2 for liquid level detection, it is possible to detect level fluctuations in the fuel level LS, which is many times the length of this PTC2 for liquid level detection. .

11 Suction Plate According to the present invention, since the conductive member is integrally formed, the position and connection accuracy of the heat-sensitive element in the liquid level detection circuit are improved, the reliability of the liquid level detector is increased, and the connection Since the terminal spacing is always constant, assembly work efficiency is improved.

Furthermore, a jig for positioning the conductive member is no longer necessary, and the number of man-hours can be reduced, making it possible to manufacture a high-precision liquid level detector at low cost.

[Brief explanation of the drawing]

FIG. 1 is an exploded perspective view of a conventional liquid level detector, FIGS. 2 to 4 are perspective views illustrating the working steps of an embodiment of the method for manufacturing a liquid level detector according to the present invention, and FIG. The figure is a circuit diagram of a liquid level detector equipped according to this embodiment, FIG. 6 is a side view showing a state in which this liquid level detector is attached to a fuel tank, and FIGS. 7 to 10 are in accordance with the present invention. FIG. 9 is a view taken along the TX-IX arrow in FIG. 8, FIG. 10 is a perspective view thereof, and FIG. 11 is a diagram showing the liquid level produced in this example. A longitudinal sectional view of the detector and FIG. 12 are its circuit diagrams. DESCRIPTION OF SYMBOLS 1... Liquid level detector, 2... PTC, 3... Plate-shaped conductor, 4... Upper end connection part, 5... Connection piece, 6...
- Hole, 7... Connection terminal, 8... Groove, 9... Soldering, 10... Electric circuit, 11... Synthetic resin, 12.
... Indication lamp, 13... Child terminal, 14... Earth terminal, 15... Fuel tank, 20... Liquid level detector,
21... Plate-shaped conductor, 22... Heat conductive plate, 23...
- Heat radiation surface, 24... Heating part, 25... Heat insulation hole, 26
...Minimum width portion, 27... Connection terminal, 28... Correction electrode, 29... Heat dissipation surface, 30... Heating part, 31...
...Correction connection terminal, 32...PTC133 for temperature correction
...Electrode plate, 34...Bending part, 35...Joining part, 36...Joining part, 37...Connection terminal, 38...
...Top end connection part, 39...Insulating material, 40...Ammeter, 41...Battery, L...Fuel r1゜

Claims (1)

[Claims] In a method for manufacturing a liquid level detector that is immersed in a liquid and detects the height of the liquid level, the upper ends of a plurality of connection parts that electrically connect heat-sensitive elements are formed integrally with each other. After forming an electric circuit by electrically connecting the heat-sensitive element to a conductive member made of Method of manufacturing a liquid level detector.