JPS5868620A - Fuel level sensor for automobile - Google Patents

Abstract

PURPOSE:To obtain a highly reliable titled sensor, by providing a conductive wiper which is connected to a float that is floated in a fuel tank through an arm, rotating the wiper in association with the up and down movement of the float, and sliding the contact point of the tip part of the wiper on a thick film resistor. CONSTITUTION:One end of the arm 1 is supported between a bottom surface part 11a of a bracket 11 and a cut and raised part 11b, and the other end is linked to the float 13 floated on a liquid level 12 in the fuel tank. The arm 1 is rotated in the direction of the movement of the float 13 shown by an arrow A with a rotary supporting point 1a as a center. A wiper base 5 and the wiper 4 are fixed to the arm 1. The contact point 4a of the wiper 4 is slidden on the surface of the thick film resistor 6 in association with the movement of the arm 1, and rotated in the direction of an arrow B. A spring 14 is provided so as to contact the wiper 4. The spring 4 is fixed to an insulating adjusting plate 15 that is fixed to the bottom surface part 11a of the bracket 11.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fuel level sensor for an automobile using a thick film resistor, and more particularly to a structure of an output signal extraction section including a wiper that slides on the thick film resistor.

This type of automotive fuel level sensor detects the movement of a float that moves up and down in response to changes in the fuel level by converting it into an electrical signal using a variable resistor made of thick film resistors. Since the wiper slides on the wiper, a spring wiper made of phosphor bronze or the like is generally provided with a contact made of a hard material such as tungsten. Therefore, in order to prevent the accuracy of the output characteristics from decreasing due to the contact resistance of the contact portions and the electrical resistance of the paths, it is necessary to suppress the polarity of the current flowing through these paths and extract only the potential. In this case, the bracket supporting the movable arm is generally made of metal and is connected to the vehicle body, which in turn is connected to the ground terminal of the power source. Therefore, the output extraction part including the wiper must be electrically insulated from the bracket.

Conventionally, a structure as shown in FIG. 1 has not been considered as one that satisfies these conditions. In the figure, reference numeral 1 denotes an arm connected to a float in the fuel tank and rotates according to the vertical movement of the float. Wiper pace 5 is continuous. Here, the wiper 4 and the wiper paste 5 are fixed to each other by press-fitting the protruding part of the wiper paste 5 into a hole formed in the wiper 4. The wiper base 5 and the wiper 4 are fixed to the arm 1, and as the arm 1 rotates, the contact 4a provided at the tip of the wiper 4 is connected to the thick film resistor 6. Slide on the ll. The protrusions of the wiper pace 5 and the wiper 4 are fitted into the holes of the spring 3, but the two are not fixed, and the wiper 4 rotates with its bottom surface in contact with the top surface of the spring 3.

Further, the output signal lead line T is connected to the spring 3 by solder 8.

However, such an h output signal extraction mechanism has a large number of parts that must be set through the arm 1, and the workability is poor, resulting in high costs, and it is difficult to fix the spring 3 and the insulating plate 2 to the bracket. Because of this, play in the rotational direction occurs, resulting in poor durability; and output signal output via the spring 3 is done by soldering the output wire 1 directly to the spring 3, resulting in poor durability against vibrations and workability. It had disadvantages such as being inferior to

The present invention has been made in view of the above circumstances, and its purpose is to simplify the structure of the output signal extraction section,
An object of the present invention is to provide a fuel level sensor for an automobile that can improve workability, reliability, and economical efficiency.

In order to achieve such an object, the present invention provides a thick film resistor constituting a variable resistor and a thick film conductor as an output signal lead line on the surface of an insulating substrate fixed to a bracket, and a wiper As the wiper rotates, a contact point of the vehicle crest wiper slides on the thick film resistor, and a pneumatic connection between the thick film conductor and the wiper is maintained. Hereinafter, the present invention will be explained in detail using Examples.

FIG. 2 is a schematic diagram showing the overall configuration of an embodiment of the present invention.

In the same figure, the arm 1 has a bracket 11 at one end.
The float 1 is supported between the bottom part 11m and the cut-and-raised part 11b, and the other end is supported by the float 1 floating on the liquid level 12 in the fuel tank.
According to the movement of the float 13 connected to 3 and indicated by arrow A,
It rotates around the rotational fulcrum 1a. In addition, 11C is
An arm stopper is provided to prevent the arm 1 from moving beyond its proper range due to external impact or the like. A wiper base 5 and a wiper 4 are fixed to the arm 1, and the wiper 4 slides on the surface of the thick film resistor 6 with its contact 4a in conjunction with the movement of the arm 10, and moves along the arrow BK.
Rotate as shown. Further, a spring 14 is provided in contact with Wino<4. The spring 14 is fixed to an insulating adjustment plate 15 fixed to the bottom surface 111 of the bracket 11, and one end of the spring 14 is attached to the surface of an insulating substrate 16 together with the thick film resistor 6. It is soldered to a thick film conductor for output signal extraction (not shown). Note that the round tooth shape ISm formed at the end of the adjusting plate 15 (V-) 15, as described later,
This is used for positioning when fixing the platen to the platen 11. ′! Furthermore, a base 1T for mounting the fuel tank is fixed to the lower end of the bracket 11, and this base I
It is formed by drawing a Tt-1 plate member,
An amplifier circuit section as described later is molded into the inner space of the protrusion 17m. Note that 1Tb is a hole for attaching a fuel tank. The details will be explained below.

FIG. 3 shows an output signal extraction section of the automobile fuel level sensor shown in FIG. 2. In the same figure, arm 1 has
Wiper 4. The wiper base 5 and the spring 14 are passed through. Among these, the wiper 4 and the wiper base 5 are fixed to each other by press-fitting the protruding part of the wiper base 5 into a hole provided with a cut-out part of the wiper 4, and the wiper pace 5 and the arm 1 are fixed to each other by They are fixed to each other by being press-fitted into the center hole of the two. Therefore, the wiper base 5 fixes the wiper 4 to the arm 1 and electrically isolates the two from each other.

Further, the spring 14 is fixed to the shear adjust plate 1 with rivets or the like at the fixing portion 14a, and
One end thereof is connected by solder 19 to a thick film conductor 18 formed on the surface of the substrate 16 for taking out an output signal.

The cut and raised portion of the wiper 4 is fitted into the hole of the spring 14, but the two are not fixed, and the wiper 4 rotates with its bottom surface in contact with the top surface of the spring 14. Although not shown in the figure, both ends of the thick film resistor 6 formed on the insulating substrate 16 are also connected to thick film conductors for power connection, which are also formed on the substrate 16.

In this way, by using the adjustment plate 15 as an insulating member for electrically insulating the output signal extraction section including the wiper 4 from the bracket 11, the insulating plate 2 as shown in FIG. 1 is unnecessary. The number of parts can be reduced. Further, since the spring 14 is fixed to the adjustment plate 15, there is no play in the rotation direction.

Furthermore, for drawing out the output signal, a thick film conductor 18, which was formed on the surface of the substrate 1 fixed to the adjustment plate 15, was used instead of a conductor, and a spring, which was also fixed to the adjustment plate 15, was used to draw out the output signal. By soldering to 14, vibration resistance and workability are significantly improved.

Here, when assembling the various components mentioned above, the adjustment plate 15 adjusts the level of the float 13 and the thick film resistor 6 of (the contact point 4m of) the wiper 4 which is interlocked with it via the arm 1.
This is provided to appropriately correspond to the relative position of the That is, the deviation that occurs between a specific level of the float 13 and the position of the contact point 4a on the thick film resistor 6, which should originally correspond to that level, depends on the dimensional accuracy and assembly accuracy of each of the above component parts. However, these combined error-generating factors often result in a significant drop in accuracy in the output characteristics. For this reason, the front V thick film resistor 6 is fixedly formed on the adjustment plate 15 via the substrate 1B, and the adjustment plate itself is initially supported at only one point on the bottom surface 11 & of the bracket, and It is configured to be rotatable about a point as a fulcrum. In this case, this fulcrum is coaxial with the rotation fulcrum 11L of the arm 1.

That is, as shown in FIG. 4, the tip of the arm 1 is caulked after penetrating the adjustment plate 15 and the bottom surface 11a of the bracket to form a stopper 1b to prevent it from coming off upward. A grommet 20 is fitted into the through hole, and the inner wall of the grommet 20 supports the arm 1. As a result, the adjustment plate 15, together with the thick film resistor 6 thereon, rotates relative to the bracket 11 about the same axis as the wiper 4. In this case, the adjustment plate 15 can be rotated with a jig, and the degree of caulking of the eyelet 2G is adjusted to such an extent that it will not rotate freely when left unused, so that the adjustment plate 15 makes contact with the bracket 11. Adjust intensity. In addition, one to seven tooth profiles 15& are provided at the end of the adjustment plate 15 so that rotation with less mold can be performed using a jig. Therefore, if the float 13 is positioned at a predetermined level and the adjustment plate 15 is rotated and adjusted so that the output at that time becomes a predetermined value, the adjustment brake 15 is fixed to the bracket 11 by adhesive. Errors in output characteristics due to variations in parts and assembly precision can be eliminated. In this case, since the rotation center of the adjustment plate 15 is coaxial with the rotation center of the wiper 4, it is possible to properly draw the original sliding line by adjusting only one point (the level of the float 13). .

On the other hand, if the rotation centers are different, as shown in FIG. 5, distortion will occur at each point other than the adjustment point P. A discrepancy will occur between the two.

By providing the adjustment plate 15 in this way, variations in parts and assembly can be absorbed using a simple jig, and highly accurate output characteristics can be obtained.
Since parts and assembly accuracy can be made rough, the overall cost can be significantly reduced even if the adjustment plate 15 itself and jigs are added.

Furthermore, a base 17 having an amplification circuit section is fixed to the bracket 11 in advance, and this PACE IT is formed by drawing into a shape having a protrusion 17jk as shown in FIG. It is constructed by incorporating an amplifier circuit 21 as shown in FIG. In FIG. 6, (b) is a perspective view showing the main body of the base IT, and (b) is a cross-sectional view thereof.

As mentioned above, this base 1T is provided with a hole lrb for attachment to a fuel tank, as well as protrusions 17 &
A notch Ire for a terminal is provided in the terminal. On the other hand, the amplifier circuit 21 includes necessary circuit elements such as active elements such as transistors, as shown in FIG.
A is provided with a terminal 21@ for connection within the fuel tank embedded in a rubber bush 21b, and this is assembled into the internal space of the protrusion 17& of the base 1T as shown in FIG. That is, the terminal notch 171 provided at the top of the protrusion 17 &
Insert the Pushi xl 1b into the set, and take it out!
1122 is soldered and resin molded.

By integrating the circuit having the active element into the base part in this manner, there is no need to provide one circuit part as an independent assembly, and the circuit part can be incorporated without using the external dimensions of the level sensor main body. Moreover, by resin molding, not only can vibration resistance be improved, but also a sealing effect to prevent fuel leakage can be obtained.

FIG. 9 is a perspective view showing an output signal extraction section in another embodiment of the present invention, and FIG. 10 is a sectional view thereof. In this embodiment, the wiper 4 has a double contact structure, and one contact 4a slides on the surface of a thick film resistor 6 provided on an insulating substrate 16 as in the case of FIG. , the other contact 4b slides on the surface of the metal piece 23 provided on the substrate 16.

The metal piece 23 is a thick film conductor 2 deposited on 1% of the substrate.
It is fixed to the board 16 by soldering ffK via 4.

Additionally, the substrate 16 is fixed to the bottom surface 11 of the bracket 11 with an adhesive 25. That is, in the case of Figure 3, Mori,
An electrical signal from a wiper 4 that is linked to the arm 1 is taken out through a spring 14 that is in sliding contact with the wiper 4, and the spring 14 is fixed to an insulating adjustment plate 15 and a signal provided on a substrate 16. In this embodiment, the electrical signal input from the contact 4a of the wiper 4 is connected to the thick film conductor for takeout, whereas the contact 4b, which forms part of the wiper 4 itself, is connected to the substrate 1B.
It is output by K slidingly contacting the metal piece 23 provided on the top of the K. Although not shown in the figure, the thick film resistor 6 and the metal piece 23 are connected to thick film conductors for power supply connection and output signal extraction, which are formed on the substrate 16. Therefore, in this embodiment, there is no need for a spring or an insulating adjustment plate as in the case of FIG. This has the advantages of improved workability, reduced costs, and improved reliability.

As explained above, according to the present invention, the structure of the output signal extraction section is simplified and workability is improved, so that it has the excellent effect of reducing costs and improving reliability. .

[Brief explanation of the drawing]

Figure 1 is an exploded perspective view showing the output signal extraction part of a conventional automobile fuel level sensor, Figure 2 is an explanatory diagram showing the overall configuration of an embodiment of the present invention, and Figure 3 is the output signal extraction part. Fig. 4 is a sectional view showing the support part of the arm, Fig. 5 is an explanatory drawing showing the sliding line on the thick film resistor, Fig. 6 (&) and (b) is a perspective view showing the ti base. 7 is a perspective view showing an amplifier circuit, FIG. 8 is a sectional view showing a base with a built-in amplifier circuit, and FIG. 9 is a perspective view showing an output signal extraction section in another embodiment of the present invention. FIG. 10 is a sectional view of 10. 1...Arm, 1m...Rotation fulcrum, 4...-
Wiper, 4IL, 4b... Contact, 5... Wafer head, 6... Thick film resistor, 11... Bracket, 12... Liquid level, 13... Float, 14・・・・・・
Spring, 15...Adjust plate, 16...
...Substrate, 18...Thick film conductor, 1s...Solder,
23...Gold fat piece, 25...Adhesive. Patent Applicant Koito Manufacturing Co., Ltd. Agent Masaki Yamakawa (and 1 other person) Figure 1 Figure 2 Figure 3 Portion A Fifth Seal Figure 6 (01(b) Figure 9

Claims (1)

[Claims] A float floating on the liquid surface in a fuel tank, a conductive wiper connected to the float via an arm, a bracket supporting the arm with a bearing, an insulating substrate fixed to this bracket, and a covering on the insulating substrate. The wiper comprises a thick film resistor constituting a variable resistor formed by depositing and a thick film conductor for taking out an output signal also formed by depositing on a vehicle crest insulating substrate, and the wiper includes:
The wiper rotates in conjunction with the vertical movement of the float while maintaining electrical connection with the thick film conductor, and the contact provided at the rotating tip of the wiper slides on the thick film resistor. An automobile fuel level sensor characterized by comprising: