CAPACITIVE SENSOR FOR DETECTING THE MOVEMENT OF AN OBJECT

• US 20150341031A1
• Filed: 06/12/2013
• Published: 11/26/2015
• Est. Priority Date: 06/19/2012
• Status: Active Grant

• Current Assignee: Behr-Hella Thermocontrol GmbH (MAHLE-STIFTUNG GmbH)
• Original Assignee: Behr-Hella Thermocontrol GmbH (MAHLE-STIFTUNG GmbH)
• Inventors: Marquas, Karsten, Steinkamp, Michael, Schluter, Dirk
• Granted Patent: US 9,638,587 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G01D 5/2417 by varying separation
• CPC Class Codes: G01L 1/142 using capacitors
• CPC Class Codes: G06F 3/0338 with detection of limited linear or angular displacement of an operating part of the device from a neutral position, e.g. isotonic or isometric joysticks
• CPC Class Codes: H01G 5/013 Dielectrics
• CPC Class Codes: H01G 5/0136 with movable electrodes
• CPC Class Codes: H03K 17/975 using a capacitive movable element

Abstract

The capacitive sensor for detecting the movement of an object, particularly for detecting the actuation of a key of an operating unit, is furnished with a first electrode (30; 32) and a second electrode (34; 36) which is provided for connection or mechanical coupling to or arrangement on the object, the distance of which second electrode from the first electrode changes (30; 32) when the object moves. The two electrodes (30, 34; 32, 36) form a first capacitor (26; 28) with a volume (40) between the electrodes (30, 34; 32, 36), the size of which changes when the object moves. An evaluation unit (38), which is connected to the two electrodes (30, 34; 32, 36) and determines a change of capacitance between the two electrodes (30, 34; 32, 36) resulting from a change of their spacing and volume, is further provided. A deformable, non-gaseous first dielectric (42) is arranged between the two electrodes (30, 34; 32, 36). The first dielectric (42) defines at least one gas volume (44) or, together with at least one of the two electrodes (30, 34; 32, 36) defines a gas volume (44) that is filled by a gaseous second dielectric, wherein at least a part of the second dielectric escapes from the gas volume (44) and from the volume (40) between the two electrodes when the two electrodes (30, 34; 32, 36) approach one another, and, when the two electrodes (30, 34; 32, 36) approach one another, the portion of the volume (40) between the two electrodes (30, 34; 32, 36) occupied by the first dielectric (42) increases and the portion of the volume (40) between the two electrodes (30, 34; 32, 36) occupied by the second dielectric decreases.

Claims

1. A capacitive sensor for detecting the movement of an object, particularly for detecting the actuation of a key of an operating unit, comprising

a first electrode,

a second electrode provided for connection or mechanical coupling to, or for arrangement on, the object, the distance of the second electrode from the first electrode changing when the object moves,

the two electrodes forming a first capacitor with a volume between the electrodes, the size of which changes when the object moves, and

an evaluation unit connected to the two electrodes and operative to determine a change of capacitance between the two electrodes resulting from a change of their spacing and volume,

wherein

a deformable, non-gaseous first dielectric is arranged between the two electrodes,

the first dielectric defines at least one gas volume or, together with at least one of the two electrodes defines a gas volume, said gas volume being filled by a gaseous second dielectric,

at least a part of the second dielectric escaping from the gas volume and from the volume between the two electrodes when the two electrodes approach one another, and,

when the two electrodes approach one another, the portion of the volume between the two electrodes occupied by the first dielectric increases and the portion of the volume between the two electrodes occupied by the second dielectric decreases.

2. The capacitive sensor according to claim 1, wherein the first dielectric comprises an open-celled material.

3. The capacitive sensor according to claim 1, wherein the at least one gas volume is formed by a recess in the first dielectric that is open toward the exterior of the volume between the electrodes, or the like surface profile of the first dielectric.

4. The capacitive sensor according to claim 1, wherein the first dielectric is resilient.

5. The capacitive sensor according to claim 1, wherein the first dielectric is a shaped body formed in the manner of a lens and having two outer sides facing toward the electrodes and that said gas volume is formed between the outer sides and the electrodes.

6. The capacitive sensor according to claim 1, wherein the first dielectric is an elastomer, particularly rubber.

7. The capacitive sensor according to claim 1, wherein the first dielectric has a larger dielectric constant than the second dielectric.

8. The capacitive sensor according to claim 1, comprising a second capacitor which comprises a first electrode and a second electrode provided for connection or mechanical coupling to, or for arrangement on, the object, wherein, in case of a movement of the object, the distances between the electrodes of the two capacitors will change in opposite senses, wherein both capacitors comprise between them a non-gaseous first and a gaseous second dielectric, and wherein the electrodes of both capacitors are connected to the evaluation unit.