Method of making an acceleration sensor

• US 5,628,100 A
• Filed: 05/09/1995
• Issued: 05/13/1997
• Est. Priority Date: 11/04/1993
• Status: Expired due to Term

• Current Assignee: Sensata Technologies Incorporated (Sensata Technologies Holding Plc)
• Original Assignee: Texas Instruments, Inc.
• Inventors: Johnson, Larry K., Silva, William, Gouin, Michael D., Amatruda, Andrew A. Jr., Reidemeister, Eric P., Southworth, Robert O.
• Primary Examiner(s): Hall, Carl E.
• Application Number:
  US08/437,687
• Time in Patent Office: 735 Days
• Field of Search: 29/25.41, 29/837-839, 361/280, 361/283.3, 73/514.32, 73/514.36
• US Class Current: 29/25.41
• CPC Class Codes: G01P 1/023 for acceleration measuring devices
• CPC Class Codes: G01P 15/125 by capacitive pick-up
• CPC Class Codes: G01P 2015/0828 the mass being of the paddle type being suspended at one of its longitudinal ends
• CPC Class Codes: Y10T 29/43 Electric condenser making
• CPC Class Codes: Y10T 29/49139 by inserting component lead or terminal into base aperture

Abstract

An acceleration sensor is shown having a substrate (16, 16'"'"', 16", 16'"'"'") on which a capacitor detect plate (24) and source plate mounting portion (28c) are disposed. An electrically conductive blade member (40, 44) having an attachment portion (40a, 44h), a source plate portion (40i, 44a) and integrally attached beams (40b, 40c; 44b) extending along opposite sides of the blade member is mounted on the substrate by welding the attachment portion to a mounting element (36, 36'"'"', 36", 36'"'"'") which is closely received in a bore (32, 32'"'"', 32", 32'"'"'") formed through the substrate at the source plate mounting portion. The mounting element or the bore is formed with a surface suitable for forming an interference fit and for making electrical engagement with a conductive layer received in the bore. The mounting element has one end (36b, 36b'"'"', 36b") which extends above the top surface (26, 26") an adjustable selected amount(s) to provide desired spacing between the source plate portion and the detect plate. A single mounting element of a pair of mounting elements can be used and may be in the form of a solid (36, 36", 36'"'"'") or a hollow (36'"'"') pin.

Claims

1. A method for making an acceleration sensor comprising the steps of:

forming a substrate having an electrically insulative top surface and a bottom surface and with a bore extending into the substrate through the top surface at a mounting portion formed on the top surface,

placing an electrically conductive detect plate on the top surface and providing electrical circuit paths on the substrate in connection with the detect plate and the mounting portion,

forming a movable blade assembly comprising an electrically conductive, flexible metal blade member having an attachment portion, a source plate portion and integral, resilient beams connecting the attachment portion to the source plate portion, and an electrically conductive mounting element having first and second ends,

inserting the electrically conductive mounting element into the bore in electrical engagement with a respective circuit path and with the first end extending above the top surface a selected distance and with the source plate portion overlying the detect plate in selected spaced relation to form a capacitor.

2. A method for making an acceleration sensor according to claim 1 including the step of welding the attachment portion to the first end of the electrically conductive mounting element prior to inserting the element into the bore.

3. A method for making an acceleration sensor according to claim 2 including the steps of connecting the detect plate and the metal blade member to an electrical source and monitoring the capacitance level as the mounting element is inserted into the bore, the selected distance the mounting element extends above the top surface being determined when the selected capacitance level is obtained.

4. A method for making an acceleration sensor according to claim 1 including the step of welding the attachment portion to the first end of the electrically conductive mounting element after inserting the element into the bore.

5. A method for making an acceleration sensor according to claim 4 in which the bore extends between the top and bottom surfaces and the mounting element extends above the top surface a distance less than the selected distance and including the step, after the step of welding the attachment portion to the first end of the mounting element, of connecting the detect plate and the metal blade member to an electrical source, and monitoring the capacitance level while applying a force to the second end of the mounting element through the bore from the bottom surface to move the mounting element until a selected capacitance level is obtained.

6. A method for making an acceleration sensor according to claim 4 in which the mounting element extends above the top surface a distance greater than the selected distance and including the step, after the step of welding the attachment portion to the first end of the mounting element, of connecting the detect plate and the metal blade member to an electrical source, and monitoring the capacitance level while applying a force through the blade member to move the mounting element until a selected capacitance level is obtained.

7. A method for making an acceleration sensor according to claim 1 in which the attachment portion of the flexible metal blade member is centralized relative to the plate.

8. A method for making an acceleration sensor according to claim 1 in which the mounting element is a solid pin.

9. A method for making an acceleration sensor according to claim 1 in which the mounting element is a hollow pin in which the said first end is a closed end.

10. A method for making an acceleration sensor according to claim 1 in which the substrate is composed of 94 percent alumina ceramic and the flexible metal blade member and mounting element are each composed of metal having a nominal composition of 42 percent nickel and the balance iron.

11. A method for making an acceleration sensor according to claim 1 including the step of forming a knurled surface on the outer periphery of the mounting element.

12. A method for making an acceleration sensor according to claim 1 in which the mounting element is generally cylindrical and has a longitudinal axis extending between the opposite ends of the element including the step of forming a plurality of longitudinally extending ribs on the outer peripheral surface of the element.

13. A method for making an acceleration sensor according to claim 12 in which the ribs are formed with a curved outer surface.

14. A method for making an acceleration sensor according to claim 12 in which the outer peripheral surface of the three ribs comprise approximately 90°

of the outer peripheral surface of the element.

15. A method for making an acceleration sensor according to claim 1 including the step of inserting the mounting element in the bore using a force between a minimum of approximately 10 pounds and a maximum of approximately 200 pounds.

16. A method for making an acceleration sensor according to claim 14 including the step of inserting the mounting element into the bore using a force between a minimum of approximately 10 pounds and a maximum of approximately 200 pounds.

17. A method for making an acceleration sensor according to claim 14 including the step of inserting the mounting element into the bore using a force between a minimum of approximately 50 pounds and a maximum of approximately 100 pounds.