Capacitive linear encoder
First Claim
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1. A capacitive linear encoder for determining positions along a feed direction comprising:
- a read head having a multiplicity of first coupling electrodes arranged along the feed direction,a scale having a multiplicity of second coupling electrodes arranged along the feed direction, anda control and evaluation unit, wherein;
read head and scale are displaceable relative to one another in the feed direction,the width of the first coupling electrodes and the width of the second coupling electrodes are coordinated with one another,the first coupling electrodes have at least three coupling signal phases offset with respect to one another, wherein the sequence of the coupling signal phases is defined by a phase permutation, such that in each case a series of adjacent first coupling electrodes form a P-interval,upon control by the control and evaluation unit temporally changing coupling signals are exchanged by capacitive coupling between the first and second coupling electrodes,the positions are determinable by the control and evaluation unit by a signal evaluation of the coupling signals exchanged between the first and second coupling electrodes, wherein the second coupling electrodes are divided into at least two mutually reciprocal types for a differential evaluation of the coupling signals, andthe scaleis passive, for which purpose the linear encoder comprises capacitive, signal transfer means for transferring the coupling signals between scale and read head, andhas at least one position reference marker which is formed by means of the signal transfer means, for which purpose signal transfer means are modified at a location of the scale that defines a position reference,for position reference marker identification the position reference marker is identifiable by means of identification signals controlled by the control and evaluation unit.
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Abstract
Some embodiments of the invention include a capacitive linear encoder for determining positions comprising a scale and a read head for capacitively scanning the scale, wherein scale and read head are movable relative to one another. The scale has at least one, preferably capacitive, position reference marker. On the basis of the position references provided by the capacitive position reference marker, the positions are locatable in absolute terms and verifiable.
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Citations
20 Claims
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1. A capacitive linear encoder for determining positions along a feed direction comprising:
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a read head having a multiplicity of first coupling electrodes arranged along the feed direction, a scale having a multiplicity of second coupling electrodes arranged along the feed direction, and a control and evaluation unit, wherein; read head and scale are displaceable relative to one another in the feed direction, the width of the first coupling electrodes and the width of the second coupling electrodes are coordinated with one another, the first coupling electrodes have at least three coupling signal phases offset with respect to one another, wherein the sequence of the coupling signal phases is defined by a phase permutation, such that in each case a series of adjacent first coupling electrodes form a P-interval, upon control by the control and evaluation unit temporally changing coupling signals are exchanged by capacitive coupling between the first and second coupling electrodes, the positions are determinable by the control and evaluation unit by a signal evaluation of the coupling signals exchanged between the first and second coupling electrodes, wherein the second coupling electrodes are divided into at least two mutually reciprocal types for a differential evaluation of the coupling signals, and the scale is passive, for which purpose the linear encoder comprises capacitive, signal transfer means for transferring the coupling signals between scale and read head, and has at least one position reference marker which is formed by means of the signal transfer means, for which purpose signal transfer means are modified at a location of the scale that defines a position reference, for position reference marker identification the position reference marker is identifiable by means of identification signals controlled by the control and evaluation unit. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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17. A capacitive linear encoder for determining positions along a feed direction comprising:
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a read head having a multiplicity of first coupling electrodes arranged along the feed direction, a scale having a multiplicity of second coupling electrodes arranged along the feed direction, and a control and evaluation unit, wherein; read head and scale are displaceable relative to one another in the feed direction, the width of the first coupling electrodes and the width of the second coupling electrodes are coordinated with one another, the first coupling electrodes have at least three coupling signal phases offset with respect to one another, wherein the sequence of the coupling signal phases is defined by a phase permutation, such that in each case a series of adjacent first coupling electrodes form a P-interval, upon control by the control and evaluation unit temporally changing coupling signals are exchanged by capacitive coupling between the first and second coupling electrodes, the positions are determinable by the control and evaluation unit by a signal evaluation of the coupling signals exchanged between the first and second coupling electrodes, wherein the second coupling electrodes are divided into at least two mutually reciprocal types for a differential evaluation of the coupling signals, the scale is passive, for which purpose the linear encoder comprises transfer electrodes as signal transfer means for transmitting the coupling signals from the scale to the read head, wherein the scale has a plurality of second transfer electrodes per type of the second coupling electrodes, and the read head has at least one first transfer electrode per type of the second coupling electrodes, each of the second transfer electrodes is electrically conductively connected to one or a plurality of second coupling electrodes of the same type, second transfer electrodes couple capacitively to the at least one first transfer electrode of the same type, the read head has shielding electrodes for electrically shielding the first transfer electrodes, whereby disturbances of the coupling signals caused by external or internal sources are at least reduced, wherein the shielding electrodes are fitted in a manner disposed upstream and/or downstream of the first transfer electrodes in the feed direction, wherein in relation to a respective first transfer electrode at least one respective shielding electrode is fitted in a manner disposed upstream in the feed direction and one respective shielding electrode is fitted in a manner disposed downstream in the feed direction, and the extent in the feed direction of the arrangement of the first coupling electrodes is greater than the extent of the first transfer electrodes, such that a portion of the first coupling electrodes extends beyond the first transfer electrode in the feed direction, wherein the extent in the feed direction of the arrangement of the first coupling electrodes is at least approximately of the same magnitude as the extent in the feed direction of the respective first transfer electrodes and of the respective shielding electrodes together.
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18. A method for determining positions for a linear encoder, the method comprising:
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displacing the read head relative to the scale along the feed direction proceeding from a first relative position of read head with respect to scale, capacitively scanning the scale by means of the read head by means of exchanging coupling signals between the first and second coupling electrodes, wherein the exchanging is dependent on the respective relative position, transmitting the coupling signals by means of the signal transfer means between scale and read head, determining with a control and evaluation unit a relative position as distance between the first relative position and a second relative position of read head with respect to scale by means of differential signal evaluation of the exchanged coupling signals. - View Dependent Claims (19, 20)
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Specification