Magnetostrictive stress wave sensor

• US 20050194240A1
• Filed: 03/05/2004
• Published: 09/08/2005
• Est. Priority Date: 03/05/2004
• Status: Active Grant

• Current Assignee: Littelfuse Incorporated
• Original Assignee: Key Safety Systems, Inc. (Ningbo Junsheng Investment Group Co., Ltd.)
• Inventors: Stuve, Steven R.
• Granted Patent: US 7,081,801 B2
• Time in Patent Office: Days
• US Class Current: 200/61.45M
• CPC Class Codes: B60R 21/0136 responsive to actual contact with an obstacle , e.g. to vehicle deformation, bumper displacement or bumper velocity relative to the vehicle monitoring crash strength in combination with passenger seat detection B60R21/01558
• CPC Class Codes: G01H 11/04 using magnetostrictive devices
• CPC Class Codes: G01P 15/0885 by magnetostrictive pick-up
• CPC Class Codes: G01P 15/0891 with indication of predetermined acceleration values G01P15/135 takes precedence

Abstract

A shock sensor has a housing with a Terfenol-D type sensing element positioned inside a sensing coil. A permanent biasing magnet is positioned in engagement with the Terfenol-D sensing element, and a spacer engages the Terfenol-D sensing element and extends from the housing. The housing has a beam with one or two mounting holes through which fasteners extend to mount the shock sensor to a structural member. The housing places the spacer in compression against the structural member. In an alternative embodiment a DC current can be supplied to the sensing coil to provide the biasing magnetic field. A high frequency filter separates the shock sensing signal from the applied DC biasing current.

Claims

1. A shock sensor in an automobile comprising:

a housing;

a biasing magnet mounted to the housing and positioned to provide a biasing magnetic field to a giant magnetostrictive sensing element also mounted to the housing;

a coil mounted to the housing and surrounding the giant magnetostrictive sensing element, for sensing a change in magnetic field produced by a shock wave in the giant magnetostrictive sensing element;

a portion of the housing providing a mounting surface;

a fastener extending between the housing and an automobile structural element to hold the mounting surface of the housing against the automobile structural element, wherein the giant magnetostrictive sensing element is directly, or through a spacer, loaded against the automobile structural element when the portion of the housing providing a mounting surface is held by the fastener against the automobile structural element; and

wherein the housing has a portion that extends between the mounting surface and the giant magnetostrictive sensing element, that resiliently biases the giant magnetostrictive sensing element or the spacer, against the automobile structural element.

2. The shock sensor of claim 1 wherein the biasing magnet is in direct contact with the giant magnetostrictive sensing element and the giant magnetostrictive sensing element is bonded to the spacer.

3. The shock sensor of claim 1 wherein the giant magnetostrictive sensing element is composed of Terfenol-D.

4. The shock sensor of claim 1 wherein the housing has two mounting surfaces, and wherein the giant magnetostrictive sensing element is located between the mounting surfaces, and wherein the housing has a portion between each mounting surface and the giant magnetostrictive sensing element that resiliently biases the giant magnetostrictive sensing element or the spacer against the automobile structural element.

5. The shock sensor of claim 1 wherein the biasing magnet is a high-strength type containing a rare earth metal.

6. A shock sensor in an automobile comprising:

a housing;

a giant magnetostrictive sensing element mounted to the housing;

a coil mounted to the housing;

a DC power source connected to the coil to form a biasing magnet, the coil being positioned to provide a biasing magnetic field to the giant magnetostrictive sensing;

an electronic filter connected across the coil for sensing a change in magnetic field produced by a shock wave in the giant magnetostrictive sensing element;

a portion of the housing providing a mounting surface;

a fastener extending between the housing and an automobile structural element to hold the mounting surface of the housing against the automobile structural element, wherein the giant magnetostrictive sensing element is directly, or through a spacer, loaded against the automobile structural element when the portion of the housing providing a mounting surface is held by the fastener against the automobile structural element; and

wherein the housing has a portion that extends between the mounting surface and the giant magnetostrictive sensing element, that resiliently biases the giant magnetostrictive sensing element or the spacer against the automobile structural element.

7. The shock sensor of claim 6 wherein the giant magnetostrictive sensing element is bonded to the spacer.

8. The shock sensor of claim 6 wherein the giant magnetostrictive sensing element is composed of Terfenol-D.

9. The shock sensor of claim 6 wherein the housing has two mounting surfaces, and wherein the giant magnetostrictive sensing element is located between the mounting surfaces, and wherein the housing has a portion between each mounting surface and the giant magnetostrictive sensing element that resiliently biases the giant magnetostrictive sensing element or the spacer against the automobile structural element.

10. A shock sensor comprising:

a housing having a beam extending between portions forming two mounting apertures and two mounting surfaces, and having portions defining a cavity between the mounting apertures;

mounted to the housing in the mounting cavity a biasing magnet, a giant magnetostrictive sensing element;

a biasing magnet mounted to the housing in the mounting cavity;

a giant magnetostrictive sensing element or a giant magnetostrictive sensing element and a spacer mounted to the housing in the mounting cavity to engage the biasing magnet, wherein portions of the giant magnetostrictive sensing element or the spacer protrude from the mounting cavity;

a coil mounted to the housing and surrounding the mounting aperture and the giant magnetostrictive sensing element therein, the coil for sensing a change in magnetic field produced by a shock wave in the giant magnetostrictive sensing element;

a portion of the housing providing a mounting surface;

a fastener extending through each mounting aperture holding the mounting surface of the housing against a structure;

wherein the giant magnetostrictive sensing element is directly, or through a spacer, loaded against the structure when the portion of the housing providing a mounting surface is held by the fastener against the structure; and

wherein the housing has a portion between each mounting surface and the giant magnetostrictive sensing element that resiliently biases the giant magnetostrictive sensing element or the spacer, against the automobile structural element.

11. The shock sensor of claim 10 wherein the biasing magnet is in direct contact with the giant magnetostrictive sensing element and the giant magnetostrictive sensing element is bonded to the spacer.

12. The shock sensor of claim 10 wherein the giant magnetostrictive sensing element is composed of Terfenol-D.

13. The shock sensor of claim 10 wherein the biasing magnet is a high-strength type containing a rare earth metal.

14. A shock sensor comprising:

a housing;

portions of the housing defining a mounting aperture;

portions of the housing defining a cavity spaced from the mounting aperture;

portions of the housing defining a beam extending between the mounting aperture and the cavity;

a biasing magnet mounted to the housing in the mounting cavity;

a sensing assembly having a giant magnetostrictive sensing element therein, the sensing assembly mounted within the mounting cavity and having portions which extend from the housing;

a coil mounted to the housing and surrounding the mounting aperture and the giant magnetostrictive sensing element therein, the coil for sensing a change in magnetic field produced by a shock wave in the giant magnetostrictive sensing element;

a portion of the housing providing a mounting surface;

a fastener extending through the mounting aperture to hold the mounting surface of the housing against a structure, wherein the sensing assembly is loaded against the structure when the portion of the housing providing a mounting surface is held by the fastener against the structure; and

a portion of the housing that extends between the mounting surface and sensing assembly, that resiliently biases the sensing assembly against the structure.

15. The shock sensor of claim 14 wherein the sensing assembly comprises a giant magnetostrictive sensing element and a spacer, and wherein the portions of the sensing element which extend from the housing are defined by the spacer.

16. The shock sensor of claim 15 wherein the biasing magnet is in direct contact with the giant magnetostrictive sensing element and the giant magnetostrictive sensing element is bonded to the spacer.

17. The shock sensor of claim 14 wherein the giant magnetostrictive sensing element is composed of Terfenol-D.

18. The shock sensor of claim 14 wherein the biasing magnet is a high-strength type containing a rare earth metal.