EP3152532A1

EP3152532A1 - Magnetically passive position sensor, in particular for motor vehicle fuel tanks

Info

Publication number: EP3152532A1
Application number: EP15717910.2A
Authority: EP
Inventors: Petr Tesar
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2014-06-05
Filing date: 2015-04-24
Publication date: 2017-04-12
Also published as: WO2015185270A1; DE102014210737A1

Abstract

Proposed is a magnetically passive position sensor (1) comprising a movable magnet, a plurality of contact spring elements (4) arranged in a motion region of the magnet and a resistance device (2). The contact spring elements (4) are spaced opposite the resistance device (2) and can be moved by the magnet to the resistance device (2). The resistance device (2) comprises a plurality of electrical contact surfaces (3) arranged opposite the contact spring elements (4) and arranged separately from each other. Each contact surface (3) is, for example, designed in a U-shape, comprising two limbs (11, 13) made of electrically conductive material, a gap (15) arranged between the limbs (11, 13) without electrically conductive material and a base region (17) made of electrically conductive material, said base region joining the limbs (11, 13). Owing to the U-shaped design of the contact surfaces (3), a potentially expensive electrically conductive material can be saved. In addition, dirt particles can preferably accumulate in the gap (15), where same scarcely affect the function of the position sensor.

Description

description

Magnetically passive position sensor, in particular for motor vehicle fuel tanks

Field of the invention

The present invention relates to a magnetically passive position sensor, in particular as a level sensor in a fuel tank of a

Motor vehicle can be used.

State of the art

Fill level sensors are used e.g. used to measure an amount of fuel in a fuel tank of a motor vehicle. For this purpose, for example, a float, which floats on the fuel, a mechanism be connected, by means of which a current position of the float can be measured in the fuel tank. From this position can then be deduced the level in the tank.

In EP 0 844 549 A1 a magnetically passive position sensor is described by means of which, for example, the position of the float can be determined. On a substrate while a resistor network is applied. Opposite this substrate and spaced from this substrate, a contact structure is arranged, which under the action of a

Magnetic device can be deflected such that a mechanical and thus an electrical contact can be established between tongues of the contact structure and parts of the resistor network. The magnetic device can in this case be coupled to the float, so that the position sensor can finally determine an electrical signal which indicates information about the position of the float and thus the filling level. In DE 10 2004 004 102 B3 is a further development of this

Position sensor described. To be sensitive to

To reduce dirt particles are assigned to a single contact of a resistance device at least two tongues of contact spring elements.

Disclosure of the invention

Embodiments of the present invention may include one

Fill level sensor used to describe magnetically passive position sensor, which is less expensive to produce and / or less sensitive to dirt than conventional magnetically passive

Position sensors.

According to a first aspect of the invention, there is provided a magnetically passive position sensor comprising a movable magnet, a plurality of magnets arranged in a range of movement of the magnet

Contact spring elements and a resistance device. The

Contact spring elements are the resistance device spaced

arranged opposite and from the magnet to the

Resistance device formed movable. The resistance device has a plurality of separately arranged, the contact spring elements opposite arranged electrical contact surfaces. Optionally, at least two tongues each of the contact spring elements can be assigned to a single contact surface of the resistance device and designed to be movable toward it. The position sensor is characterized in that each contact surface is formed with two legs of electrically conductive material, a gap arranged between the legs without electrically conductive material and a leg connecting the legs

Base area made of electrically conductive material.

Ideas for embodiments of the present invention may be considered, inter alia, as being based on the thoughts and findings described below: As described in the introduction, in the position sensor described in DE 10 2004 004 102 B3, two tongues of a contact spring element can contact one another when they are attracted by a magnet and bent towards the contact. The contact had at each position to be detected on a single, usually rectangular, area-related contact surface.

It has now been recognized that such a position sensor can advantageously be further developed by replacing the areal contiguous contact area with a U-shaped contact area. In this U-shaped contact surface is no longer as before a whole, for example, rectangular area on one

Carrier substrate covered with an electrically conductive material to form a contact, with which the two tongues can come into contact.

Instead, the U-shaped contact surface has two laterally spaced limbs of electrically conductive material, which are preferably connected at one of their ends to one another by a base region, which is likewise formed from electrically conductive material. The two legs are spaced apart by an intermediate gap. Preferably, the two elongated legs may be arranged parallel to each other.

The U-shaped configuration of the contact surfaces can inter alia on the one hand lead to the fact that the formation of the contact generally requires less surface of a carrier substrate to be coated with electrically conductive material. This can in particular for the case that the contact surfaces are formed by metal, in particular by noble metal, to a

Save money.

Contact surfaces of a position sensor can be particularly advantageously printed by means of a metal-containing paste, for example by screen printing, onto a carrier substrate. The paste may be e.g. Contain particles of precious metal such as gold, platinum, silver or the like. Accordingly, the paste can be expensive, so that by a possible savings of paste due to the design of the contact surfaces as a U-shaped with

Intermediate unprinted gap a significant cost reduction is possible. On the other hand, by means of the U-shaped configuration of the contact surfaces, it can be achieved that a risk of a contact closure between a tongue of a contact spring element and a contact surface due to intervening dirt particles being prevented can be reduced. A U-shaped contact surface can in the region of the legs to a

Difference in height further from a carrier substrate to the

Abut contact spring elements than in the area of the gap. Of the

Height difference, for example, be at least 4 μηι. Between the legs can thus be formed in the region of the gap a recess in which any dirt particles can preferably attach, where they do not interfere with a contact closure between a tongue of a contact spring element and a leg of the contact surface.

The gap may, for example, be wider than 75 μm. Thus, the gap can be dimensioned so that dirt particles can accumulate well therein.

It should be noted that possible features and benefits of

Position sensors are described herein with respect to different embodiments. One skilled in the art will recognize that the features may be suitably combined or replaced to provide additional ones

To arrive embodiments of the invention.

Brief description of the drawings

Embodiments of the invention will now be described with reference to the accompanying drawings, in which neither the drawings nor the description are to be construed as limiting the invention.

Fig. 1 shows a perspective partial view of contact surfaces and these contacting tongues in a conventional magnetically passive

Position sensor.

2 shows a perspective partial view of contact surfaces and these contacting tongues in a magnetically passive position sensor according to an embodiment of the present invention. FIG. 3 shows a sectional view along the line AA from FIG. 2.

The figures are only schematic and not to scale. Like reference numerals in the figures designate the same or equivalent

Characteristics.

Embodiments of the invention

FIG. 1 shows a perspective partial view of contact surfaces 3 and tongues 5 which contact these contact surfaces 3 in a conventional manner

Position sensor 1. The tongues 5 are part of a contact spring element 4 (only partially shown in FIG. 1), which is arranged at a distance from a carrier substrate 7. The contact surfaces 3 are part of a resistance device 2 (only partially shown in Fig. 1) of the position sensor 1, which on the

Carrier substrate 7 is provided. The resistance device 2 can

For example, a web 6 of material having a significant electrical resistance, so that the total resistance of the web 6 along the length of the web 6 successively changed. The web 6 is produced, for example, by means of a thick-film technique, in particular imprinted. The contact surfaces 3 are electrically connected to the track 6 of the resistance device 2. Between the tongues 5 and the contact surfaces 3 in the operation of the position sensor 1, an electrical contact is caused position-dependent, for example, a position with a float in one

Vehicle tank connected magnet 8 (see Fig. 3), which attracts the tongues 5, to be able to determine.

The position sensor 1 may in many respects correspond to a position sensor, as e.g. in EP 0 844 459 A1 or DE 10 2004 004 102 B3.

The contact surfaces 3 are areas on a carrier substrate 7, on which a metal layer is applied. For example, metal can be applied by printing a metal-containing paste. The contact surfaces 3 are elongated and rectangular. Adjacent contact surfaces 3 are via gaps 9

spaced apart and electrically separated. The contact surfaces 3 are dimensioned in their width B _K so that in each case two spaced-apart tongues 5 of a contact spring element can contact an associated contact surface 3. Each of the tongues 5 has a width b of, for example, between 150 and 180 μηη, which is substantially smaller than the width B _K of, for example, between 300 and 550 μηη of the associated contact surface. 3

Furthermore, the two tongues 5 are arranged sufficiently close to each other, so that both tongues 5, when they are bent under the action of a magnet toward the carrier substrate 7, come into contact with the associated contact surface 3 and can make electrical contact therewith. This results in a redundancy in the contact formation, since it can be sufficient in principle that only one of the tongues 5 closes the contact, so that any dirt that can block a single tongue 5, not necessarily prevents a contact closure.

FIG. 2 shows a perspective partial view of contact surfaces 3 and tongues 5 of a position sensor 1 according to an embodiment of the invention. The contact surfaces 3 are formed in the example shown U-shaped and have two mutually parallel legs 11, 13, which include a gap 15 between them. In end regions, the two legs 11, 13 are connected to each other via base regions 17. Both the legs 11, 13 and the base portions 17 have electrically conductive material and can be produced for example by printing a noble metal-containing paste.

Instead of the illustrated U-shape, the contact surfaces 3 may also have other geometries, for example an H-shape, in which legs 11, 13 are connected to each other.

As illustrated in FIGS. 2 and 3, the contact surfaces 3 protrude further in the region of a limb 11, 13 by a height difference h from the carrier substrate 7 towards the tongues 5 than in the area of the tongue

intermediate gap 15. The height difference may typically be between 4 and 20μηη. The width B _{s of} a leg may correspond approximately to the width b of an associated tongue 5 and thus be significantly smaller than half the width B _{K of} the entire contact surface 3 and, for example, in the range of 100 to 550 μηη.

The width B _{G of} the gap 15 may correspond approximately to a lateral distance between adjacent tongues 5 and, for example, be in the range of 75 to 200 μm.

Any dirt particles can thus advantageously either in one of the interspaces 9 between laterally adjacent contact surfaces 3 or alternatively in one of the gaps 15 between the legs 11, 13 within a

Contact surface 3 are included. There they do not disturb a movement of an associated tongue 5 and in particular do not prevent the tongue

5 attracted e.g. by a magnet 8 in mechanical contact with one of the legs 11, 13 of the contact surface 3 comes.

Claims

claims

1 . Magnetically passive position sensor (1) comprising:

a movable magnet;

a plurality of contact spring elements (4) arranged in a range of movement of the magnet;

a resistance device (2);

wherein the contact spring elements (4) of the resistance means (2) spaced from each other and from the magnet towards the

Resistance device (2) are movable;

wherein the resistance means (2) a plurality of separately arranged, the contact spring elements (4) opposite

having arranged electrical contact surfaces (3);

characterized in that

each contact surface (3) is formed with two legs (1 1, 13) made of electrically conductive material, a between the legs (1 1, 13) arranged gap (15) without electrically conductive material and a leg (1 1, 13) connecting base region (17) made of electrically conductive material.

2. Position sensor according to claim 1, wherein a contact surface (3) in the region of the legs (1 1, 13) by a height difference (h) further from a carrier substrate (7) towards the Kontaktfederlementen (4) protrudes than in a region of the gap (15).

3. Position sensor according to claim 2, wherein the height difference (h)

is at least 4 μηι.

4. Position sensor according to one of claims 1 to 3, wherein the electrically conductive material of the contact surfaces (3) contains precious metal.

5. Position sensor according to one of claims 1 to 4, wherein the electrically conductive material of the contact surfaces (3) is a printed metal-containing paste.

6. Position sensor according to one of claims 1 to 5, wherein the gap (15) is wider than 75 μηι.

7. Position sensor according to one of claims 1 to 6, wherein at least two tongues (5) of the contact spring elements (4) are associated with a single contact surface (3) of the resistance device (2) and are formed towards this movable.

8. Position sensor according to one of claims 1 to 7, wherein the two

Legs (1 1, 13) are arranged parallel to each other.