TEMPERATURE COMPENSATED MINIATURE PRESSURE SENSOR

• US 20090044630A1
• Filed: 09/21/2008
• Published: 02/19/2009
• Est. Priority Date: 10/18/2004
• Status: Active Grant

• Current Assignee: Precision Mechatronics Pty Ltd
• Original Assignee: Silverbrook Research Pty Limited
• Inventors: Lapstun, Paul, Walmsley, Simon Robert, Silverbrook, Kia
• Granted Patent: US 7,854,171 B2
• Time in Patent Office: Days
• US Class Current: 73/708
• 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: B81B 2201/0264 Pressure sensors
• CPC Class Codes: B81B 7/0029 Protection against environmental influences not provided for in groups B81B7/0012 - B81B7/0025
• CPC Class Codes: G01L 15/00 Devices or apparatus for measuring two or more fluid pressure values simultaneously
• CPC Class Codes: G01L 19/0636 using particle filters
• CPC Class Codes: G01L 9/0047 Diaphragm with non uniform thickness, e.g. with grooves, bosses or continuously varying thickness
• CPC Class Codes: G01L 9/0073 using a semiconductive diaphragm
• CPC Class Codes: G01L 9/125 with temperature compensating means non electric temperature compensating means G01L19/04

Abstract

The present invention relates to a temperature-compensated pressure sensor assembly for fitting within the valve stem of a vehicle tire. The assembly includes a substrate assembly defining a plurality of holes. A pressure sensor is mounted to the substrate assembly. The pressure sensor includes a first deflectable membrane defining a first chamber and a first cap mounted to the membrane to form a second chamber. A temperature compensation sensor is mounted to the substrate assembly. The temperature compensation sensor includes a second deflectable membrane mounted to the substrate assembly to define a third chamber and a second cap mounted to the other membrane to form a fourth chamber.

Claims

1. A pressure sensor assembly for fitting within the valve stem of a vehicle tire, the assembly comprising:

a substrate assembly defining a plurality of holes;

a pressure sensor mounted to the substrate assembly, the pressure sensor including a first deflectable membrane defining a first chamber and a first cap mounted to the membrane to form a second chamber; and

a temperature compensation sensor mounted to the substrate assembly, the temperature compensation sensor including a second deflectable membrane mounted to the substrate assembly to define a third chamber and a second cap mounted to the other membrane to form a fourth chamber.

2. A pressure sensor assembly as claimed in claim 1, wherein the sensors are mounted adjacently on the same side of the substrate assembly.

3. A pressure sensor assembly as claimed in claim 1, wherein the first chamber is a sealed chamber and the first cap defines a plurality of holes so that the second chamber is an unsealed chamber.

4. A pressure sensor assembly as claimed in claim 3, wherein the second membrane defines a plurality of holes through which the third and fourth chambers are interconnected.

5. A pressure sensor assembly as claimed in claim 1, wherein the pressure sensor assembly is a micro-electromechanical system (MEMS) formed using integration circuit fabrication techniques.

6. A pressure sensor assembly as claimed in claim 5, wherein the substrate assembly includes:

a silicon substrate layer;

a CMOS layer deposited on the silicon substrate layer;

a conductive layer deposited on the CMOS layer; and

a passivation layer deposited on the conductive layer;

wherein said plurality of holes pass through each layer.

7. A pressure sensor assembly as claimed in claim 6, wherein each membrane is conductive and the conductive layer and conductive membrane together form a pair of electrodes which can develop a capacitance between them.

8. A pressure sensor assembly as claimed in claim 1, wherein each membrane is formed from non-conductive material which is in contact with a piezo-electric material.