Acceleration sensor method for operating an acceleration sensor

• US 8,752,431 B2
• Filed: 12/11/2009
• Issued: 06/17/2014
• Est. Priority Date: 02/04/2009
• Status: Active Grant

• Current Assignee: Robert Bosch GmbH
• Original Assignee: Robert Bosch GmbH
• Inventors: Reinmuth, Jochen, Emmerich, Harald
• Primary Examiner(s): KWOK, HELEN C
• Application Number:
  US13/148,038
• Publication Number:
  US 20120017681A1
• Time in Patent Office: 1,649 Days
• Field of Search: 735/143.2, 735/143.8, 735/143.6
• US Class Current: 73/514.32
• CPC Class Codes: G01P 15/125 by capacitive pick-up
• CPC Class Codes: G01P 2015/0831 the mass being of the paddle type having the pivot axis between the longitudinal ends of the mass, e.g. see-saw configuration

Abstract

An acceleration sensor includes a housing, a first seismic mass which is formed as a first asymmetrical rocker and is disposed in the housing via at least one first spring, a second seismic mass which is formed as a second asymmetrical rocker and is disposed in the housing via at least one second spring, and a sensor and evaluation unit which is designed to ascertain information regarding corresponding rotational movements of the first seismic mass and the second seismic mass in relation to the housing and to determine acceleration information with respect to an acceleration of the acceleration sensor, taking the ascertained information into account. In addition, a method for operating an acceleration sensor is disclosed. The rockers execute opposite rotational movements in response to the presence of an acceleration. A differential evaluation of the signals makes it possible to free the measuring signal of any existing interference signals.

Claims

1. An acceleration sensor comprising:

a housing;

a first seismic mass which is in the form of a first antisymmetric rocker and is supported in the housing via at least one first spring in such a way that the first seismic mass is adjustable around a torsion axis of the at least one first spring in relation to the housing;

a second seismic mass which is in the form of a second antisymmetric rocker and is supported in the housing via at least one second spring in such a way that the second seismic mass is adjustable around a torsion axis of the at least one second spring in relation to the housing; and

a sensor and evaluation unit configured to (a) ascertain information regarding corresponding rotational movements of the first seismic mass and the second seismic mass in relation to the housing, and (b) determine acceleration information with respect to an acceleration of the acceleration sensor, taking the ascertained information into account;

wherein the first seismic mass and the second seismic mass are formed in such a way and, in at least one position, are positioned relative to each other such that at least one end section of the first seismic mass directed away from the torsion axis of the at least one first spring extends into at least one interspace defined by the second seismic mass; and

wherein a maximum width of the at least one end section of the first seismic mass extending into the at least one interspace defined by the second seismic mass is less than a maximum width of the second seismic mass defining the at least one interspace, the respective maximum widths being defined in a direction perpendicular to the torsion axes of the first and second springs and being measured from the respective torsion axes.

2. The acceleration sensor as recited in claim 1, wherein:

the torsion axis of the at least one first spring subdivides the first seismic mass into (a) a first partial mass on a first side of the torsion axis of the at least one first spring and (b) a second partial mass on a second side of the torsion axis of the at least one first spring, the second partial mass being lighter than the first partial mass; and

the torsion axis of the second spring subdivides the second seismic mass into (a) a third partial mass on a first side of the torsion axis of the at least one second spring and (b) a fourth partial mass on a second side of the torsion axis of the at least one second spring, the fourth partial mass being heavier than the third partial mass.

3. The acceleration sensor as recited in claim 2, wherein:

the first seismic mass includes a first electrode situated on the first side of the torsion axis of the at least one first spring and a second electrode situated on the second side of the torsion axis of the at least one first spring;

the second seismic mass includes a third electrode situated on the first side of the torsion axis of the at least one second spring and a fourth electrode situated on the second side of the torsion axis of the at least one second spring; and

the sensor and evaluation unit includes four counter-electrodes fixedly disposed in relation to the housing.

4. The acceleration sensor as recited in claim 3, wherein the sensor and evaluation unit is configured such that (a) a first capacitance between the first electrode and an associated first counter-electrode of the four counter-electrodes and a fourth capacitance between the fourth electrode and an associated fourth counter-electrode of the four counter-electrodes are interconnected to form a first sum, and (b) a second capacitance between the second electrode and an associated second counter-electrode of the four counter-electrodes and a third capacitance between the third electrode and an associated third counter-electrode of the four counter-electrodes are interconnected to form a second sum.

5. The acceleration sensor as recited in claim 4, wherein the sensor and evaluation unit is configured to (a) ascertain a difference between the first sum and the second sum, and (b) determine the acceleration information regarding the acceleration of the acceleration sensor based on the difference ascertained.

6. The acceleration sensor as recited in claim 1, wherein the torsion axis of the at least one first spring lies on the torsion axis of the at least one second spring.

7. The acceleration sensor as recited in claim 1, wherein:

the first seismic mass includes a first comb-like section having at least one tooth;

the second seismic mass includes a second comb-like section having at least two teeth; and

the first seismic mass in at least one position is disposed relative to the second seismic mass in such a way that the at least one tooth of the first comb-like section extends into the at least one interspace between the at least two teeth of the second comb-like section.

8. The acceleration sensor as recited in claim 7, wherein:

the first seismic mass includes at least one third comb-like section; and

the second seismic mass includes at least one fourth comb-like section.

9. A method for operating an acceleration sensor having a housing, a first seismic mass which is formed as a first antisymmetric rocker and is supported in the housing via at least one first spring in such a way that the first seismic mass is adjustable about a torsion axis of the at least one first spring in relation to the housing, and a second seismic mass which is formed as a second antisymmetric rocker and is supported in the housing via at least one second spring in such a way that the second seismic mass is adjustable about a torsion axis of the at least one second spring in relation to the housing, the method comprising:

ascertaining information regarding corresponding rotational movements of the first seismic mass and the second seismic mass in relation to the housing; and

determining acceleration information with respect to an acceleration of the acceleration sensor, taking the ascertained information into account;

wherein the first seismic mass and the second seismic mass are formed in such a way and, in at least one position, are positioned relative to each other such that at least one end section of the first seismic mass directed away from the torsion axis of the at least one first spring extends into at least one interspace defined by the second seismic mass; and

wherein a maximum width of the at least one end section of the first seismic mass extending into the at least one interspace defined by the second seismic mass is less than a maximum width of the second seismic mass defining the at least one interspace, the respective maximum widths being defined in a direction perpendicular to the torsion axes of the first and second springs and being measured from the respective torsion axes.