Pressure sensor having thin pressure sensing membrane

• US 20060219020A1
• Filed: 06/05/2006
• Published: 10/05/2006
• Est. Priority Date: 10/18/2004
• Status: Active Grant

• Current Assignee: Precision Mechatronics Pty Ltd
• Original Assignee: Silverbrook Research Pty Limited
• Inventors: Silverbrook, Kia, Mallinson, Samuel George
• Granted Patent: US 7,260,995 B2
• Time in Patent Office: Days
• US Class Current: 73/729.200
• CPC Class Codes: B60C 23/0408 transmitting the signals by non-mechanical means from the wheel or tyre to a vehicle body mounted receiver
• CPC Class Codes: G01L 9/0042 Constructional details associated with semiconductive diaphragm sensors, e.g. etching, or constructional details of non-semiconductive diaphragms details about the integration or bonding of piezoresistor in or on the diaphragm G01L9/0052 and G01L9/0057 respectively
• CPC Class Codes: G01L 9/0072 using variations in capacitance
• CPC Class Codes: G01L 9/0075 using a ceramic diaphragm, e.g. alumina, fused quartz, glass
• CPC Class Codes: G01L 9/125 with temperature compensating means non electric temperature compensating means G01L19/04

Abstract

A pressure sensor is provided having a chamber partially defined by a flexible membrane which is less than three microns thick, exposed to fluid pressure and is configured to deflect from a reference position due to changes in the fluid pressure, and associated circuitry for converting the deflection of the flexible membrane into an output signal indicative of the fluid pressure.

Claims

1. A pressure sensor comprising:

a chamber partially defined by a flexible membrane which is less than three microns thick and is exposed to fluid pressure, the flexible membrane being configured to deflect from a reference position due to changes in said fluid pressure; and

associated circuitry for converting the deflection of the flexible membrane into an output signal indicative of the fluid pressure.

2. A pressure sensor according to claim 1, wherein the flexible membrane is a laminate having at least two layers of different metal ceramics.

3. A pressure sensor according to claim 2, wherein one or more of the layers of the laminate is metal.

4. A pressure sensor according to claim 1, wherein the pressure sensor is adapted to sense the air pressure within a pneumatic tire.

5. A pressure sensor according to claim 1, wherein the flexible membrane is non-planar.

6. A pressure sensor according to claim 5, wherein the flexible membrane is corrugated.

7. A pressure sensor according to claim 6, wherein the corrugations have a period of between five microns and 15 microns.

8. A pressure sensor according to claim 6, wherein the flexible membrane is substantially circular and the corrugations are annular.

9. A pressure sensor according to claim 6, wherein the corrugations have a substantially square-shaped cross-sectional profile.

10. A pressure sensor according to claim 6, wherein the flexible corrugated membrane has a corrugation factor of eight.

11. A pressure sensor according to claim 1 having a linear response up to about 1 MPa.

12. A pressure sensor according to claim 1, wherein the flexible membrane is approximately 0.5 μ

m thick.

13. A pressure sensor according to claim 1, further comprising a laminated apertured guard arranged to protect the sensor from damaging contact.

14. A pressure sensor according to claim 1, wherein the flexible membrane is circular with a diameter less than 500 microns.

15. A pressure sensor according to claim 14, wherein the flexible membrane diameter is less than 300 microns.

16. A pressure sensor according to claim 15, wherein the flexible membrane diameter is 100 microns.

17. A pressure sensor according to claim 1, wherein:

the sensor is a capacitive sensor having a first capacitor electrode provided as a conductive layer in the chamber, and a second capacitor electrode provided as a conductive material of the flexible membrane;

the associated circuitry is configured to convert capacitance changes due to the deflection of the flexible membrane to the output signal; and

the conductive layer is arranged such that deflection of the flexible membrane towards the conductive layer displaces fluid from between the flexible membrane and the conductive layer.

18. A pressure sensor according to claim 17, wherein the conductive layer is less than 50 microns from the flexible membrane at its reference position.

19. A pressure sensor according to claim 17, wherein the conductive layer is apertured to allow fluid to flow from between the flexible membrane and the conductive layer.