Accelerometer

• US 20040244485A1
• Filed: 06/03/2003
• Published: 12/09/2004
• Est. Priority Date: 06/03/2003
• Status: Active Grant

• Current Assignee: ZF Friedrichshafen AG (Zeppelin - Stiftung der Stadt Friedrichshafen)
• Original Assignee: Cherry Corporation (ZF Electronics Corp.)
• Inventors: Joseph, Peter D., Albrecht, Kenneth A., Linske, Erik W.
• Granted Patent: US 6,904,805 B2
• Time in Patent Office: Days
• US Class Current: 73/514.26
• CPC Class Codes: G01P 15/08 with conversion into electric or magnetic values
• CPC Class Codes: G01P 15/0802 Details
• CPC Class Codes: G01P 15/093 by photoelectric pick-up

Abstract

An accelerometer is limited to a very small displacement range, and within that range, is useful for detecting motion and change of rate of motion by optical, magnetic, or electrical means. A unique spring suspends a planar mass that is very sensitive to motion of an object in which the accelerometer is held. In one embodiment, an optical detector detects the motion of the mass by the intensity of reflected radiation. In another embodiment, a Hall-effect sensor detects the motion of the mass by a current generated by the motion of the mass in an electric field. The accelerometer may be used in a variety of automotive, appliance, and industrial applications.

Claims

1. An accelerometer, comprising:

a housing;

a spring comprising a planar area separated from a periphery of the spring by at least one path;

a detector for detecting motion of the planar area; and

a conversion circuit for converting the motion into electrical signals, wherein the planar area is supported by at least one land with a width that varies linearly.

2. The accelerometer of claim 1, wherein the detector is selected from the group consisting of an optical detector, a magnetic detector, and an electrical detector.

3. The accelerometer of claim 1, wherein the detector is an optical detector comprising an optical emitter and an optical receiver.

4. The accelerometer of claim 3, wherein the optical detector uses light in a portion of the electromagnetic spectrum selected from the group consisting of visible, ultraviolet, and infrared light.

5. The accelerometer of claim 1, wherein the detector is a magnetic detector comprising a Hall-effect sensor.

6. The accelerometer of claim 1, wherein the detector is a capacitance detector.

7. The accelerometer of claim 1, wherein the at least one path describes from one to two complete paths between the planar area and the periphery.

8. The accelerometer of claim 1, wherein the planar area is a square or a rectangle separated on four sides with paths between the planar area and the periphery.

9. The accelerometer of claim 1, wherein the spring is nonmetallic.

10. The accelerometer of claim 1, wherein the width decreases by one-third over at least a portion of the land.

11. A method of detecting movement, the method comprising:

suspending a planar spring by at least one land having a width that varies linearly;

vibrating the planar spring in response to motion;

detecting vibration of the spring; and

generating a signal indicative of the vibration.

12. The method of claim 11, further comprising generating a second signal if the vibration exceeds a threshold level.

13. The method of claim 11 wherein the steps of vibrating and detecting are accomplished by a method selected from the group consisting of an optical method, a magnetic method, and an electrical method.

14. The method of claim 11, wherein the planar spring comprises a central planar area separated from a periphery of the spring by at least one path.

15. The method of claim 11, wherein the spring is nonmetallic.

16. An accelerometer, comprising:

a housing;

a spring comprising a planar area separated from a periphery of the spring by one to two complete paths between the central planar area and the periphery;

a detector for detecting motion of the planar area; and

a conversion circuit for converting the motion into electrical signals.

17. The accelerometer of claim 16, wherein the central planar area comprises a form selected from the group consisting of an irregular form, a polygon, an ellipse, and a circular form.

18. The accelerometer of claim 16, wherein the planar area is supported by at least one land having a width that varies.

19. The accelerometer of claim 16, wherein the detector comprises an infrared transmitter and an infrared receiver.

20. The accelerometer of claim 16, wherein the detector comprises a Hall-effect sensor and a magnet on the spring.

21. A motion detector, comprising:

a housing;

a non-metallic spring comprising a planar area separated from a periphery of the spring by at least one path; and

a detector for detecting motion of the planar area.

22. The detector of claim 21, further comprising a conversion circuit for converting the motion of the planar area Into an electrical signal.

23. The detector of claim 21, wherein the width of the at least one path varies linearly.

24. The detector of claim 21, wherein the planar area is supported by at least one land with a width that varies linearly.

25. The detector of claim 21, wherein the at least one path describes from one to two complete paths between the planar area and the periphery.