MICROMECHANICAL ACCELERATION SENSOR HAVING AN OPEN SEISMIC MASS

• US 20090314085A1
• Filed: 05/19/2009
• Published: 12/24/2009
• Est. Priority Date: 06/24/2008
• Status: Active Grant

• Current Assignee: Robert Bosch GmbH
• Original Assignee: Robert Bosch GmbH
• Inventors: Tebje, Lars, Schubert, Dietrich, Stahl, Heiko
• Granted Patent: US 8,393,215 B2
• Time in Patent Office: Days
• US Class Current: 73/514.320
• CPC Class Codes: G01P 15/125 by capacitive pick-up
• CPC Class Codes: G01P 2015/0814 for translational movement of the mass, e.g. shuttle type

Abstract

A micromechanical acceleration sensor having a substrate, a suspension, a seismic mass, and stationary capacitive electrodes, in which the seismic mass is suspended over the substrate with the help of the suspension, the seismic mass has a mass center of gravity, the suspension has at least two anchors on the substrate, the two anchors are situated on opposite sides of the mass center of gravity, the distance between the two anchors being small compared to a horizontal extension of the seismic mass, the two anchors determine a central axis, the seismic mass have recesses which are situated on opposite sides of the central axis and are laterally open outward on the sides facing away from the central axis, and the stationary electrodes at least engage in the recesses of the seismic mass.

Claims

1. A micromechanical acceleration sensor, comprising:

a substrate;

a suspension having at least two anchors on the substrate, wherein the two anchors determine a central axis;

a seismic mass, wherein the seismic mass is suspended over the substrate with the aid of the suspension, and wherein the seismic mass has a mass center of gravity; and

stationary capacitive electrodes;

wherein the two anchors are situated on opposite sides of the mass center of gravity, a distance between the two anchors being small compared to a horizontal extension of the seismic mass along the central axis,

wherein the seismic mass has recesses which are situated on opposite sides of the central axis and which are laterally open outward on sides facing away from the central axis, and

wherein the stationary electrodes at least engage in the recesses of the seismic mass.

2. The acceleration sensor of claim 1, wherein the seismic mass has two bars on opposite sides of the central axis, and wherein one comb structure has recesses formed on each of the two bars.

3. The acceleration sensor of claim 2, wherein the seismic mass has a ground bar, which passes through the mass center of gravity and is situated between the two anchors, the ground bar connecting the two bars.

4. The acceleration sensor of claim 1, wherein a connecting beam, which is situated along the central axis, is formed with each anchor, a spring element connected to the seismic mass and being situated on the connecting beams on sections situated opposite the anchors.

5. The acceleration sensor of claim 1, wherein the suspension has one of an S-shaped spring element, a U-shaped spring element, and a folded spring element.

6. The acceleration sensor of claim 3, wherein the two bars 14) are connected to each other at the ends via a first and second additional ground bar.

7. The acceleration sensor of claim 6, wherein the first and second additional ground bars surround the respective spring elements.

8. The acceleration sensor of claim 1, wherein the stationary electrodes are attached to the substrate in the area near the central axis.

9. The acceleration sensor of claim 8, wherein the stationary electrodes are in the shape of individual bars, the bars being attached to the substrate in end areas which are associated with the central axis.

10. The acceleration sensor of claim 8, wherein the stationary electrodes are connected on both sides to a third and fourth additional connecting beam, which are oriented parallel to the central axis and are situated in the lateral edge area of the seismic mass, the third and fourth additional connecting beams running in a direction of the central axis in a recess of the seismic mass via a first and second additional connecting beam, the first and second additional connecting beam being connected to the substrate in an area of one end associated with the central axis.

11. The acceleration sensor of claim 1, wherein the seismic mass surrounds the suspension.