FR2538544A1 - TUBULAR LEVEL SENSOR FOR MOTOR VEHICLE - Google Patents

Abstract

This tubular sensor comprises two insulating substrates made of glass or enamelled sheet on which superimposed layers of conductive and insulating inks are deposited by screen printing, to form a resistance and a conduction path. These two substrates are held against each other, screen-printed faces outwards, by gluing or clamping on a metal plate of suitable shape ensuring the guidance of a float provided with 2 sliders moving along this strip in function of the liquid level, so as to obtain a resistance whose value varies in proportion to the level. This assembly is placed inside a tube having a calibrated orifice at its lower part. (CF DRAWING IN BOPI)

Description

The principle of this type of sensor is well known and the

  wanderer has already taken patents on the subject They describe a float

  carrying two sliders moving inside a hollow tube which

  door in its lower part a filling hole.

  The sliders move according to the fluid level

  along a resistance disposed parallel to the walls of the tube.

  The main advantages of this system lie in the fact that this particular structure allows easy mounting in the tank while reserving a space with little disturbance and having a strong constant

  time with respect to rapid fluctuations in the level within the

  service, due to turns, braking, acceleration, etc. b The more the di-

  the filling hole is large and the time constant is weak. However, the classical techniques of obtaining the law

  resistive are not very flexible, especially if strong non-linear

  In addition, in the case of mass production, adjustments must be made quickly in order to reduce

cost price.

  Known solutions use coiled wire or circuit

  printed on which is deposited a resistive layer of cupronickel (constant

  tan) for example This particular realization does not make it possible to obtain

  various laws of nonlinearity; this is due to the fact that the metal laminate

  The deposited electrode has a unique resistivity, thus limiting the possibilities.

  -The error on the thickness of the laminate can reach + 10%.

  The adjustment methods to obtain an accuracy of 1% are

  limited (milling, sanding, etc.) We find a device of this kind -

described in the patent 82 05 977

  As for the wound wire, it offers even fewer possibilities.

  The error on the section of the wire is important (i 15%) and it is not possible to obtain two different laws on the same rule.

  Adjustment methods are very limited.

  The process according to the invention is to use the techniques

  thick layers deposited on insulating laminates inert in fuels with added alcohol (glass or enamelled sheet) The invention will be better understood from the accompanying drawings in which

  Fig 1 shows the prior art.

  FIG. 2 represents a float with articulated lever arm,

  still in the prior art.

  FIG. 3 shows a method of assembling the laminates as well as the

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  diagram of'different layers' deposited on the substrate.

  FIGS. 4 a and b show another way of assembling the subsystems

  especially when they are fragile (glass by

example).

  FIGS. 5 ab, c represent an embodiment of the cursor,

  and its location on the ruler.

  Fig 6 gives an example of assembly of two enamelled sheet metal substrates.

  FIG. 1 shows a sensor immersed in a liquid 6 containing

  naked in a reservoir 7 This sensor comprises a tube 2 inside which moves a float 1 driving 2 contacts 3 which slide on a

  coil resistor 4 The tube has a calibrated orifice 5 of communication

  with the inside of the tank The 2 contacts are electrically

  same potential and joined to a flexible wire 9 coming out of the sensor.

  mite 8 of the resistor 4 is also available outside When the level changes, the float moves along the resistance and between the wires 8 and 9, there is a change in the resistance, depending on the resistance.

liquid level.

  The wire 9 connected to the float, poses big problems because it

  must be of sufficient length not to prevent the float from

  dye the lower part of the sensor and must not disturb its rise in -

  for example, attaching to the internal projections of the sensor.

  A clear progress is made in fig 2 which represents a cir-

  printed epoxy-glass baking pan 10, on which was deposited by gluing a

  laminate (constantan for example) 40 and a semi-circular track 50.

  A float 30 drives, via an arm of

  lever 20 whose length is determined according to the height of the car-

  gauge to gauge, 2 sliders joined electrically which rub on the tracks 40 and 50 The arm 2 pivots about the axis 80 As in the previous case, the variation of resistance taken between the son 60 and 70 is a function of the height of liquid in the tank But the cursor being recalled throughout its run by the track 50, the wire 70 can

  to be very short and not disturbing.

  The disadvantage of this device is that the error on the thick-

  metal laminate is important- (107) and the reduced width

  of the resistive strip imposes a law of limited nonlinearity.

  The short length of it does not facilitate the

quick settings at 1%.

  One of the structures produced according to the invention is de-

  it contains 2 substrates lia and llb maintained by gluing

  12 on a plate 13, sheet steel for example This assembly is very simple

  ply and inexpensive lia and 1 lb are made from iso-

  lants for baking conductive and resistive inks high temperature sufficiently inert and stable in fuels with added alcohol The assembly mode, according to the invention, shown in this figure is more particularly suitable for fragile substrates, such as the glass Indeed, the glass is very cheap, it is an inert material and usable in large or small series with a very simple manufacturing tooling Unlike the enamelled sheet which requires, him, a particular tooling and expensive of cutting But its purchase price is also little

  elevated The following is a more specific assembly structure

  adapted to this type of substrate (fig 6).

  On the glass plate 11a, of fig 3, one deposits succes-

  by serigraphy and in superimposed layers the motifs 14, 15, 16

  and 17 The layer 14 on which moves one of the two sliders is real-

  The layer 15 is platinum-Ag on it, is

  silk screened the actual resistance 16 The whole is then covered

  green of an insulator 17, leaving only the slip path uncovered

cursor.

  The glass plate 11b has only one conductive track

  trice, in palladium-Ag, for example, facing the layer 14, intended to recall the cursor throughout its course, as described above

(50 fig 2).

  On the steel plate 13 are welded parts 18a and 18b

  intended to serve as a guide to the float carrying the two sliders together elec-

geometrically.

  Another structure according to the invention which can

  also to fragile substrates, such as glass', is described in

fig 4 a and in fig 4 b.

  Fig 4a is a section of fig 4b She shows how

  are assembled the different elements.

  The metal part 25 having tenons is inserted into the sheet 24 provided with appropriate holes and then into the U-shaped part 23a which holds the two plates via a rubber seal 22a.

  of glass 11a and 11b in compression on the piece 25.

  To avoid the direct contact of glass-and steel,

  insulating mylar sheets 26 are interposed between the two.

  To provide lateral compression, another U-shaped part, 23b, and another rubber seal 22b are used to hold the two plates, the tightening of the assembly being ensured by a crimping of the

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room 25 on the runway 23 b.

  Fig 5a shows a ruler view-in section The notations

  used are the same as in figs 4a and 4b. The float 90 represents

  5b in elevation comprises two notches 91 inside the

  which slides the ends A of the parts 24 and 25 2 bosses 93 abut on the part 23 b in the marked places B (Fig 5 a) Two sliders 92 are fixed in the float 90 A cut in C (Fig 5 c) shows

  their implementation in a more precise way.

  A simple way of mounting a ruler using two enamelled sheet metal plates is indicated in FIG. 6. The two plates 31a and 31b, after serigraphy, are placed against each other, with their faces towards

  outside, and held in place by 2 flanks (32), having openings

  half-masked tails comprising tongues in which are inserted the corresponding tabs of the plates On these, a weld deposit 33 has been made, which allows after reflow

  of tin to obtain a simple and inexpensive fixation of serigraphic

  phiées. The guidance of the float is provided by the flanks themselves, in D. In general, the invention should not be considered conne limited to the embodiments described and shown which have been given only as examples non-restrictive and which are likely to

  various variants within the framework and spirit of the invention.

tion.

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Claims (3)

R E V E N D I C A T IO N S   1 probe for measuring a liquid level, comprising a float provided with sliders sliding along two insulating substrates   Characterized by the fact that each of said substrates   carries a resistivated track made by serigraphy in thick layers su-   placed on ordinary glass, and that these are glued back to back on a metal plate ensuring the rigidity of the assembly and of such shape   that it serves as a guide to the movement of the float.   2 probe according to claim 1, characterized by the use of enamelled sheet substrates 3 probe according to claim 2, characterized by a particular assembly of substrates coupled back to back, screen-printed side outward, said assembly being made by two plates serving as a guide to the float, and comprising   holes with tongues in which are inserted pins   covered with tin in both substrates, so that the fixation   the plate and substrates assembly is effected by simple pressure.   4 probe according to claim 1, characterized by a pressure resistance of the 2 substrates on   a metal plate 25, by 2 metal U 23 and 2 rubber tabs   rubber 22, maintaining the lateral compression being provided by torsion   legs of the piece 25 after inserter in the piece 23 b.