Tri-axis accelerometer having a single proof mass and fully differential output signals

• US 7,757,555 B2
• Filed: 08/30/2006
• Issued: 07/20/2010
• Est. Priority Date: 08/30/2006
• Status: Active Grant

• Current Assignee: Robert Bosch GmbH
• Original Assignee: Robert Bosch GmbH
• Inventors: Ulm, Markus, Lang, Christoph, Pan, Zhiyu, Metz, Matthias, Yama, Gary
• Primary Examiner(s): Williams; Hezron
• Assistant Examiner(s): Shah; Samir M
• Application Number:
  US11/513,669
• Publication Number:
  US 20080053228A1
• Time in Patent Office: 1,420 Days
• Field of Search: 735/140.1, 735/142.9, 734/88, 735/041.2, 735/041.3, 735/142.4
• US Class Current: 73/514.24
• CPC Class Codes: G01P 15/0802 Details
• CPC Class Codes: G01P 15/09 by piezoelectric pick-up
• CPC Class Codes: G01P 15/123 by piezo-resistive elements, e.g. semiconductor strain gauges
• CPC Class Codes: G01P 15/18 in two or more dimensions
• CPC Class Codes: G01P 2015/084 the mass being suspended at more than one of its sides, e.g. membrane-type suspension, so as to permit multi-axis movement of the mass
• CPC Class Codes: Y10T 29/42 Piezoelectric device making

Abstract

A tri-axis accelerometer includes a proof mass, at least four anchor points arranged in at least two opposite pairs, a first pair of anchor points being arranged opposite one another along a first axis, a second pair of anchor points being arranged opposite one another along a second axis, the first axis and the second axis being perpendicular to one another, and at least four spring units to connect the proof mass to the at least four anchor points, the spring units each including a pair of identical springs, each spring including a sensing unit.

Claims

1. A tri-axis accelerometer, comprising:

a proof mass;

at least four anchor points arranged in at least two opposite pairs, a first pair of anchor points being arranged opposite one another along a first axis, a second pair of anchor points being arranged opposite one another along a second axis, the first axis and the second axis being perpendicular to one another; and

at least four spring units to connect the proof mass to the at least four anchor points, the spring units each including a pair of identical springs, each spring including a sensing unit;

wherein the at least four spring units extend alongside at least one external edge of, and external to, the proof mass.

2. The tri-axis accelerometer of claim 1, wherein the sensing unit is arranged on the spring.

3. The tri-axis accelerometer of claim 2, wherein the sensing unit includes a piezoelectric layer.

4. The tri-axis accelerometer of claim 2, wherein the sensing unit includes a piezoelectric resistor.

5. The tri-axis accelerometer of claim 1, wherein the pair of identical springs are arranged to detect a fully differential output signal.

6. The tri-axis accelerometer of claim 5, wherein the pair of identical springs are arranged parallel to each other and perpendicular with respect to a longitudinal axis along the connection between the proof mass and a respective anchor point.

7. The tri-axis accelerometer of claim 1, further comprising:

only one pick-up circuit arrangement to detect the fully differential output signal of each pair of identical springs.

8. The tri-axis accelerometer of claim 1, wherein the tri-axis accelerometer is fabricated using one of a Surface MEMS process and a Bulk MEMS process.

9. The tri-axis accelerometer of claim 1, wherein the proof mass, the at least four anchor points, and the at least four springs are arranged on one monolithic microchip.

10. The tri-axis accelerometer of claim 1, wherein each of the at least four spring units extends lengthwise tangentially to a circumference of the proof mass.