Pressure sensor with a thermal pressure detecting element

• US 6,393,919 B1
• Filed: 08/24/2000
• Issued: 05/28/2002
• Est. Priority Date: 12/24/1998
• Status: Expired due to Term

• Current Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Original Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Inventors: Yutani, Naoki, Sakai, Yuichi, Tsutsumi, Kazuhiko, Ohji, Hiroshi
• Primary Examiner(s): OEN, WILLIAM L
• Application Number:
  US09/644,693
• Time in Patent Office: 642 Days
• Field of Search: 73/706,708,715-728 338/2,3,4,42 361/283.1-283.4
• US Class Current: 73/708
• CPC Class Codes: G01L 11/002 by thermal means, e.g. hypsometer

Abstract

A pressure sensor of the present invention comprises a diaphragm 6 having a first surface which receives pressure and a thermal detecting portion 3 with a heat sensitive portion disposed as to oppose the diaphragm through a spacer, wherein displacement values of the diaphragm owing to variations in pressure are detected at the thermal detecting portion as variation values of thermal equilibrium state. With this arrangement, a surface of the diaphragm which directly receives pressure from measuring fluid does not need to undergo film forming or photolithographic processes whereby main portions of thermal pressure detecting elements might be formed onto a silicon substrate by large quantities in a lump sum through simple manufacturing processes so that it is possible to improve accuracy and reliability of the thermal pressure detecting elements and to obtain a pressure sensor of low cost.

Claims

1. A pressure sensor comprising:

a first diaphragm including,

a first surface configured to receive pressure, and

a thermal detecting portion disposed opposite a second surface of the first diaphragm,

wherein displacement values of the first diaphragm owing to variations in pressure are thermally detected by the thermal detecting portion due to changes in heat flow from the thermal detecting portion to the first diaphragm.

2. The pressure sensor of claim 1, wherein the thermal detecting portion includes a heating mechanism configured to heat, and displacement values of the first diaphragm are measured by variations in resistance values of the thermal detecting portion.

3. The pressure sensor of claim 1, wherein the thermal detecting portion includes a heating mechanism configured to heat to a specified temperature, and displacement values of the first diaphragm are measured by variations in current values of the thermal detecting portion.

4. The pressure sensor of claim 1, wherein the thermal detecting portion is smaller in size than the first diaphragm.

5. The pressure sensor of claim 1, wherein the thermal detecting potion includes a heating mechanism configured to heat, and further includes a temperature detecting portion adjacent to the heating mechanism, and displacement values of the first diaphragm are measured by variations in temperature of the temperature detecting portion.

6. The pressure sensor of claim 1, further comprising:

a temperature compensating mechanism configured to measure and compensate an ambient temperature.

7. The pressure sensor of claim 6, further comprising:

a second temperature compensating mechanism configured to measure and compensate a temperature of the diaphragm.

8. The pressure sensor of claim 1, further comprising:

a second thermal detecting portion disposed opposite an end portion of the second surface of the first diaphragm.

9. The pressure sensor of claim 8, wherein the first thermal detecting portion and the second thermal detecting portion comprise a bridge circuit.

10. The pressure sensor of claim 1, wherein the thermal detecting portion is formed in a concave portion of the substrate, and the diaphragm and the thermal detecting portion are disposed opposite each other through the concave portion of the substrate.

11. The pressure sensor of claim 1, further comprising:

spacers configured to regulate an opposing distance between the thermal detecting portion and the first diaphragm, provided on a substrate on which the thermal detector portion is formed.

12. The pressure sensor of claim 1, further comprising:

a second diaphragm at least a part of which is supported on a first surface of a silicon substrate,

wherein the thermal detecting portion is arranged on the second diaphragm.

13. The pressure sensor of claim 12, wherein the second diaphragm forms a bridge arrangement with respect to the silicon substrate.

14. The pressure sensor of claim 12, wherein the silicon substrate includes a void formed on a side of a second surface of said substrate, and a length of the void from a second diaphragm surface in a normal direction is set larger than a distance between the second diaphragm and the first diaphragm.

15. The pressure sensor of claim 13, wherein a void is formed on a side of the second surface of the silicon substrate, and a length of the void from a second diaphragm surface in a normal direction is set larger than a distance between the second diaphragm and the first diaphragm.

16. The pressure sensor of claim 1, further comprising:

a protecting portion covering the thermal detecting portion.

17. The pressure sensor of claim 16, wherein a pressure of an interior of the protecting portion is set at atmospheric pressure or higher than atmospheric pressure.