Pressure switch for monitoring tire pressure, particularly of motor vehicle tires

• US 4,894,639 A
• Filed: 03/24/1989
• Issued: 01/16/1990
• Est. Priority Date: 03/30/1988
• Status: Expired due to Fees

• Current Assignee: Dr Ing hc F Porsche AG (Volkswagen AG)
• Original Assignee: Dr Ing hc F Porsche AG (Volkswagen AG)
• Inventors: Schmierer, Wolfgang
• Primary Examiner(s): Crosland, Donnie L.
• Application Number:
  US07/328,541
• Time in Patent Office: 298 Days
• Field of Search: 340/444, 340/442, 73/146.5, 73/146, 116/34 R, 116/34 A, 116/34 B, 200/61.22, 200/61.25, 200/61.45 R, 200/80 R, 200/83 R, 200/83 B, 200/83 N
• US Class Current: 340/444
• CPC Class Codes: B60C 23/0408 transmitting the signals by non-mechanical means from the wheel or tyre to a vehicle body mounted receiver

Abstract

A pressure switch for monitoring a tire pressure of a motor vehicle tire is fastened to a wheel rim and is actuated by the inflating pressure in the tire. The pressure switch comprises a reference pressure chamber which is sealed off by an electrically conductive switching diaphragm in the direction of the tire, and carries a contact pin interacting with this diaphragm. The switching diaphragm has a mass which is controlled as a function of centrifugal force in response to tire rotation such that the switching point of the pressure switch can be changed automatically as a function of vehicle speed.

Claims

1. A pressure switch for monitoring tire pressure of motor vehicle tires, which is fastened at a wheel rim of the tire and is actuated by inflating pressure in the tire, comprising:

a reference pressure chamber which faces in the direction of the tire and is sealed off from the tire by an electrically conductive switching diaphragm;

the chamber supports a contact pin which interacts with this switching diaphragm to close an electric circuit between the pin and diaphragm; and

the switching diaphragm has applied to it a force responsive to the tire pressure and a mass which is controlled as a function of centrifugal force indicative of tire rotational speed so that closing points of the pressure switch are determined by tire pressure that varies automatically with tire rotational speed.

2. A pressure switch according to claim 1, wherein closing points of the pressure switch, as a result of the rotational speed of the tire and hence speed of the vehicle, follow a desired characteristic speed curve which provides a warning threshold for an excessively low tire pressure that increases as vehicle speed increases.

3. A pressure switch according to claim 1, wherein the switching diaphragm of the pressure switch is arranged in a vertical transverse plane which extends approximately at a right angle with respect to a direction of force of the centrifugal force.

4. A pressure switch according to claim 2, wherein the switching diaphragm of the pressure switch is arranged in a vertical transverse plane which extends approximately at a right angle with respect to the direction of force of the centrifugal force.

5. A pressure switch according to claim 1, wherein the switching diaphragm has a centric accumulation of mass opposite the switching pin.

6. A pressure switch according to claim 2, wherein the switching diaphragm has a centric accumulation of mass opposite the switching pin.

7. A pressure switch according to claim 3, wherein the switching diaphragm has a centric accumulation of mass opposite the switching pin.

8. A pressure switch according to claim 4, wherein the switching diaphragm has a centric accumulation of mass opposite the switching pin.

9. A pressure switch according to claim 1, wherein the switching diaphragm has an accumulation of mass distributed uniformly over the circumference thereof.

10. A pressure switch according to claim 2, wherein the switching diaphragm has an accumulation of mass distributed uniformly over the circumference thereof.

11. A pressure switch according to claim 3, wherein the switching diaphragm has an accumulation of mass distributed uniformly over the circumference thereof.

12. A pressure switch according to claim 4, wherein the switching diaphragm has an accumulation of mass distributed uniformly over the circumference thereof.

13. A pressure switch according to claim 1, wherein the switching diaphragm has an accumulation of mass which consists of a thickened wall of the switching diaphragm which thickness is set to produce a desired vehicle speed-tire pressure relationship.

14. A pressure switch according to claim 2, wherein the switching diaphragm has an accumulation of mass which consists of a thickened wall of the switching diaphragm which thickness is set to produce a desired vehicle speed-tire pressure relationship.

15. A pressure switch according to claim 3, wherein the switching diaphragm has an accumulation of mass which consists of a thickened wall of the switching diaphragm which thickness is set to produce a desired vehicle speed-tire pressure relationship.

16. A pressure switch according to claim 4, wherein the switching diaphragm has an accumulation of mass which consists of a thickened wall of the switching diaphragm which thickness is set to produce a desired vehicle speed-tire pressure relationship.

17. A pressure switch according to claim 1, wherein the switching diaphragm has an accumulation of mass provided by a centrically arranged sleeve which is connected with the switching diaphragm and surrounds a free end of the contact pin.

18. A pressure switch according to claim 2, wherein the switching diaphragm has an accumulation of mass provided by a centrically arranged sleeve which is connected with the switching diaphragm and surrounds a free end of the contact pin.

19. A pressure switch according to claim 3, wherein the switching diaphragm has an accumulation of mass provided by a centrically arranged sleeve which is connected with the switching diaphragm and surrounds a free end of the contact pin.

20. A pressure switch according to claim 4, wherein the switching diaphragm has an accumulation of mass provided by a centrically arranged sleeve which is connected with the switching diaphragm and surrounds a free end of the contact pin.