Title of Invention	"A MANGNETICALLY PASSIVE POSITION SENSOR"
Abstract	The invention relates to a magnetically passive position sensor for filling level sensors in fuel tanks of motor vehicles, comprising a movable magnet (2), a plurality of contact spring elements (5,6) arranged along the movement range of the magnet (2), the contact spring elements (5,6) disposed opposite a resistance device (4) and is moveable by the magnet (2) against the resistance device (4), the resistance device (4) having a multiplicity of individual electrical contacts (7), arranged opposite the contact spring elements (5,6), characterized in that an individual contact (7) of the resistance device (4) is assigned at least two tongues (10, 11) of the contact spring elements (5, 6) such that at least one of the two tongues (10,11) is enabled to establish a connection with the contact (7) in an event the dust particles sticking to the contacts prevent electrical connection between one of the at least two tongues (10,11) and the contacts (7).

Title of Invention

"A MANGNETICALLY PASSIVE POSITION SENSOR"

Abstract

The invention relates to a magnetically passive position sensor for filling level sensors in fuel tanks of motor vehicles, comprising a movable magnet (2), a plurality of contact spring elements (5,6) arranged along the movement range of the magnet (2), the contact spring elements (5,6) disposed opposite a resistance device (4) and is moveable by the magnet (2) against the resistance device (4), the resistance device (4) having a multiplicity of individual electrical contacts (7), arranged opposite the contact spring elements (5,6), characterized in that an individual contact (7) of the resistance device (4) is assigned at least two tongues (10, 11) of the contact spring elements (5, 6) such that at least one of the two tongues (10,11) is enabled to establish a connection with the contact (7) in an event the dust particles sticking to the contacts prevent electrical connection between one of the at least two tongues (10,11) and the contacts (7).

Full Text	FIELD OF INVENTION The invention relates to a magnetically passive position sensor with a movable magnet, with a multiplicity of contact spring elements arranged in the range of movement of the magnet, the contact spring elements lying opposite a resistance device and being able to be moved by the magnet against the resistance device, the resistance device having a number of individual electrical contacts, lying opposite the contact spring elements. BACKGROUND OF THE INVENTION Such a position sensor is often used for filling level sensors in fuel tanks of modern motor vehicles and is known for example from DE 196 48 539 Al. The position sensor generates electrical signals in dependence on the position of the magnet. The contact spring elements are formed as a row of resilient tongues electrically connected to one another. One of the tongues in each case lies opposite one of the contacts of the resistance device. If the magnet is moved over the resistance device, the contact spring elements come up against the contacts of the resistance device. A disadvantage of the known position sensor is that soiling of the contacts or of the contact spring elements prevents electrical connection. In this case, the position sensor cannot generate any electrical signals. Therefore, usually a number of contact spring elements, for example three, are moved against three contacts that are adjacent one another. However, here, too, the failure of one of the contact elements leads to falsification of the electrical signals of the position sensor. OBJECT OF THE INVENTION The invention is based on the problem of designing a position sensor of the type mentioned at the beginning in such a way that a reduction in the accuracy of the signals in dependence on the position of the magnet as a result of individual dirt particles is largely avoided. SUMMARY OF THE INVENTION This problem is solved according to the invention by an individual contact of the resistance device being assigned at least two tongues of the contact spring elements, As a result of this design, if there is a dirt particle sticking to the contact, only the electrical connection of one of the tongues to the contact is prevented. The second tongue can establish the connection with the contact. This contact can therefore generate signals of the position sensor. Consequently, the number of tongues assigned to an individual contact provides redundancy. Therefore, individual dirt particles do not lead to a reduction in the accuracy of the position sensor according to the invention. The position sensor according to the invention is of a particularly simple structural design if the tongues are each formed as an individual contact spring element. BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS The invention allows numerous embodiments. To illustrate its basic principle further, one of these is described below and is represented in the accompanying drawings, in which: FIG. 1 shows a sectional representation through a position sensor according to the invention, FIG. 2 shows a sectional representation through the position sensor according to the invention from FIG. 1 along the line II-II. DETAIL DESCRIPTION OF THE INVENTION Figure 1 shows a position sensor with a magnet 2 arranged on a pivoting arm 1. The pivoting arm 1 is fastened on a pivot pin 3. The pivot pin 3 can be connected for example to a float (not represented) of a level sensor of a fuel tank. By means of the pivot pin 3, the magnet 2 is pivoted over a resistance device 4. On the side of the resistance device 4 that is facing away from the magnet 2, magnetic contact spring elements 5, 6 are arranged. The contact spring elements 5, 6 can be attracted by the magnet 2 and pressed against the resistance device 4. The resistance device 4 has a number of contacts 7 lying opposite the contact spring elements 5, 6. The contacts 7 are connected to one another by means of a resistor track 8. As an alternative to this, the contacts could also be arranged on a thick-film network. The resistance device 4 is connected by means of electrical lines 9 to an electronic system (not represented), which senses the position of the magnet 2 by means of the contact spring elements 5, 6 lying against the resistance device 4. This position sensor is described in detail in DE 196 48 539 A1, for which reason reference is expressly made to this document for the disclosure of the structure and function. Figure 2 shows a sectional representation through the position sensor from Figure 1, the contact spring elements each having two tongues 10, 11 lying opposite an individual contact. The magnet 2 contacts altogether three contacts 7 with the contact spring elements 5. Soiling 12, which prevents contacting with one of the tongues 10 of the contact spring element 5, is represented on one of the contacts 7 by way of example. The contact 7 is contacted by the second tongue 10 of the contact spring element 5 lying opposite this contact 7. WE CLAIM 1. A magnetically passive position sensor for filling level sensors in fuel tanks of motor vehicles, comprising a movable magnet (2), a plurality of contact spring elements (5,6) arranged along the movement range of the magnet (2), the contact spring elements (5,6) disposed opposite a resistance device (4) and is moveable by the magnet (2) against the resistance device (4), the resistance device (4) having a multiplicity of individual electrical contacts (7), arranged opposite the contact spring elements (5,6), characterized in that an individual contact (7) of the resistance device (4) is assigned at least two tongues (10, 11) of the contact spring elements (5, 6) such that at least one of the two tongues (10,11) is enabled to establish a connection with the contact (7) in an event the dust particles sticking to the contacts prevent electrical connection between one of the at least two tongues (10,11) and the contacts (7). 2. The magnetically passive position sensor as claimed in claim 1, wherein the tongues (10, 11) are each formed as an individual contact spring element (5, 6). ABSTRACT TITLE : "A MAGNETICALLY PASSIVE POSITION SENSOR" The invention relates to a magnetically passive position sensor for filling level sensors in fuel tanks of motor vehicles, comprising a movable magnet (2), a plurality of contact spring elements (5,6) arranged along the movement range of the magnet (2), the contact spring elements (5,6) disposed opposite a resistance device (4) and is moveable by the magnet (2) against the resistance device (4), the resistance device (4) having a multiplicity of individual electrical contacts (7), arranged opposite the contact spring elements (5,6), characterized in that an individual contact (7) of the resistance device (4) is assigned at least two tongues (10, 11) of the contact spring elements (5, 6) such that at least one of the two tongues (10,11) is enabled to establish a connection with the contact (7) in an event the dust particles sticking to the contacts prevent electrical connection between one of the at least two tongues (10,11) and the contacts (7).

Full Text

FIELD OF INVENTION
The invention relates to a magnetically passive position sensor with a movable
magnet, with a multiplicity of contact spring elements arranged in the range of
movement of the magnet, the contact spring elements lying opposite a
resistance device and being able to be moved by the magnet against the
resistance device, the resistance device having a number of individual electrical
contacts, lying opposite the contact spring elements.
BACKGROUND OF THE INVENTION
Such a position sensor is often used for filling level sensors in fuel tanks of
modern motor vehicles and is known for example from DE 196 48 539 Al. The
position sensor generates electrical signals in dependence on the position of the
magnet. The contact spring elements are formed as a row of resilient tongues
electrically connected to one another. One of the tongues in each case lies
opposite one of the contacts of the resistance device. If the magnet is moved
over the resistance device, the contact spring elements come up against the
contacts of the resistance device. A disadvantage of the known position sensor is
that soiling of the contacts or of the contact spring elements prevents electrical
connection. In this case, the position sensor cannot generate any electrical
signals. Therefore, usually a number of contact spring elements, for example
three, are moved against three contacts that are adjacent one another. However,
here, too, the failure of one of the contact elements leads to falsification of the
electrical signals of the position sensor.

OBJECT OF THE INVENTION
The invention is based on the problem of designing a position sensor of the type
mentioned at the beginning in such a way that a reduction in the accuracy of the
signals in dependence on the position of the magnet as a result of individual dirt
particles is largely avoided.
SUMMARY OF THE INVENTION
This problem is solved according to the invention by an individual contact of the
resistance device being assigned at least two tongues of the contact spring
elements,
As a result of this design, if there is a dirt particle sticking to the contact, only
the electrical connection of one of the tongues to the contact is prevented. The
second tongue can establish the connection with the contact. This contact can
therefore generate signals of the position sensor. Consequently, the number of
tongues assigned to an individual contact provides redundancy. Therefore,
individual dirt particles do not lead to a reduction in the accuracy of the position
sensor according to the invention.
The position sensor according to the invention is of a particularly simple
structural design if the tongues are each formed as an individual contact spring
element.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The invention allows numerous embodiments. To illustrate its basic principle
further, one of these is described below and is represented in the accompanying
drawings, in which:
FIG. 1 shows a sectional representation through a position sensor according to
the invention,
FIG. 2 shows a sectional representation through the position sensor according to
the invention from FIG. 1 along the line II-II.
DETAIL DESCRIPTION OF THE INVENTION
Figure 1 shows a position sensor with a magnet 2 arranged on a pivoting arm 1.
The pivoting arm 1 is fastened on a pivot pin 3. The pivot pin 3 can be
connected for example to a float (not represented) of a level sensor of a fuel
tank. By means of the pivot pin 3, the magnet 2 is pivoted over a resistance
device 4. On the side of the resistance device 4 that is facing away from the
magnet 2, magnetic contact spring elements 5, 6 are arranged. The contact
spring elements 5, 6 can be attracted by the magnet 2 and pressed against the
resistance device 4. The resistance device 4 has a number of contacts 7 lying
opposite the contact spring elements 5, 6. The contacts 7 are connected to one
another by means of a resistor track 8. As an alternative to this, the contacts

could also be arranged on a thick-film network. The resistance device 4 is
connected by means of electrical lines 9 to an electronic system (not
represented), which senses the position of the magnet 2 by means of the contact
spring elements 5, 6 lying against the resistance device 4. This position sensor is
described in detail in DE 196 48 539 A1, for which reason reference is expressly
made to this document for the disclosure of the structure and function.
Figure 2 shows a sectional representation through the position sensor from
Figure 1, the contact spring elements each having two tongues 10, 11 lying
opposite an individual contact. The magnet 2 contacts altogether three contacts
7 with the contact spring elements 5. Soiling 12, which prevents contacting with
one of the tongues 10 of the contact spring element 5, is represented on one of
the contacts 7 by way of example. The contact 7 is contacted by the second
tongue 10 of the contact spring element 5 lying opposite this contact 7.

WE CLAIM
1. A magnetically passive position sensor for filling level sensors in fuel tanks
of motor vehicles, comprising a movable magnet (2), a plurality of contact
spring elements (5,6) arranged along the movement range of the magnet
(2), the contact spring elements (5,6) disposed opposite a resistance
device (4) and is moveable by the magnet (2) against the resistance
device (4), the resistance device (4) having a multiplicity of individual
electrical contacts (7), arranged opposite the contact spring elements
(5,6), characterized in that an individual contact (7) of the resistance
device (4) is assigned at least two tongues (10, 11) of the contact spring
elements (5, 6) such that at least one of the two tongues (10,11) is
enabled to establish a connection with the contact (7) in an event the dust
particles sticking to the contacts prevent electrical connection between
one of the at least two tongues (10,11) and the contacts (7).
2. The magnetically passive position sensor as claimed in claim 1, wherein
the tongues (10, 11) are each formed as an individual contact spring
element (5, 6).

ABSTRACT

TITLE : "A MAGNETICALLY PASSIVE POSITION SENSOR"
The invention relates to a magnetically passive position sensor for filling level
sensors in fuel tanks of motor vehicles, comprising a movable magnet (2), a
plurality of contact spring elements (5,6) arranged along the movement range of
the magnet (2), the contact spring elements (5,6) disposed opposite a resistance
device (4) and is moveable by the magnet (2) against the resistance device (4),
the resistance device (4) having a multiplicity of individual electrical contacts (7),
arranged opposite the contact spring elements (5,6), characterized in that an
individual contact (7) of the resistance device (4) is assigned at least two
tongues (10, 11) of the contact spring elements (5, 6) such that at least one of
the two tongues (10,11) is enabled to establish a connection with the contact (7)
in an event the dust particles sticking to the contacts prevent electrical
connection between one of the at least two tongues (10,11) and the contacts
(7).

"A MANGNETICALLY PASSIVE POSITION SENSOR"

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