Micromechanical pressure sensor element and method for using a pressure sensor element of this type

• US 20060288789A1
• Filed: 06/20/2006
• Published: 12/28/2006
• Est. Priority Date: 06/23/2005
• Status: Active Grant

• Current Assignee: Robert Bosch GmbH
• Original Assignee: Robert Bosch GmbH
• Inventors: Ullmann, Dirk
• Granted Patent: US 7,305,874 B2
• Time in Patent Office: Days
• US Class Current: 73/705
• 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: G01P 13/00 Indicating or recording presence, absence, or direction, of movement electric switches H01H; counting moving objects G06M7/00

Abstract

A micromechanical pressure sensor element, in particular for tire pressure measurement. The device has at least: a layer system having a diaphragm underneath which a cavity is formed, which is separated from an external space outside the pressure sensor element; a measuring device for measuring a deflection of the diaphragm; and a seismic mass formed on, underneath, or in the diaphragm. Furthermore, in a method for using such a pressure sensor element, the pressure sensor element is operatable in a sleep mode having lower power consumption and in an operating mode having higher power consumption; in the sleep mode a change in the measuring signals of the measuring device over time is checked, and if a relevant change in the measuring signals is detected, a position change is inferred and a switchover to the operating mode is performed, in which the measuring signals of the measuring device or the analysis signals formed from the measuring signals are transmitted via a transmitter, for example, an antenna.

Claims

1. A micromechanical pressure sensor element comprising:

a structure including a diaphragm, underneath which a cavity is formed, which is separated from an external space outside the pressure sensor -element;

a measuring device for measuring a deflection of the diaphragm; and

a seismic mass situated one of on, under, and in the diaphragm.

2. The pressure sensor element according to claim 1, wherein the structure includes a layer system.

3. The pressure sensor element according to claim 1, wherein the measuring device includes at least one of a piezoelectric resistor situated in the diaphragm and a piezoelectric element situated in the diaphragm for measuring the deflection of the diaphragm.

4. The pressure sensor element according to claim 3, wherein the at least one of the piezoelectric resistor and piezoelectric element is formed by local doping of the diaphragm.

5. The pressure sensor element according to claim 4, wherein the at least one of the piezoelectric resistor and piezoelectric element is contacted over semiconductor regions having the same doping and higher doping concentration.

6. The pressure sensor element according to claim 1, wherein the seismic mass includes a solder bump applied to the diaphragm.

7. The pressure sensor element according to claim 1, wherein the seismic mass is formed micromechanically one of in, on, and underneath the diaphragm.

8. The pressure sensor element according to claim 2, wherein the layer system has at least one upper layer having the cavity and the diaphragm, and a lower layer secured underneath the at least one upper layer and covering the cavity.

9. The pressure sensor element according to claim 8, wherein the cavity is etched by bulk micromechanical methods, including a wet chemical process.

10. The pressure sensor element according to claim 1, further comprising a dedicated power source.

11. The pressure sensor element according to claim 1, wherein the pressure sensor element is connected to a dedicated power source.

12. A method for using a pressure sensor element comprising:

operating the pressure sensor element in a sleep mode having lower power consumption and in an operating mode having higher power consumption;

checking, in the sleep mode, a change over time in at least one measuring signal of a measuring device; and

if a relevant change in the measuring signal is detected, inferring a position change and performing a switchover to the operating mode, in which one of (a) the measuring signal of the measuring device and (b) at least one analysis signal formed from the measuring signal is transmitted by a transmitting device.

13. The method according to claim 12, wherein the transmitting device includes an antenna.

14. The method according to claim 12, further comprising, in the sleep mode, analyzing changes in the measuring signal in a low-frequency range of less than 10 Hz, and recognizing changes in the measuring signal in the low-frequency range as a position change of the sensor element.

15. The method according to claim 12, further comprising, in the sleep mode, recognizing changes in the measuring signal of the measuring device over a limiting value as a position change of the sensor element.

16. The method according to claim 12, wherein the pressure sensor element is used for measuring an internal tire pressure.