Tire pressure monitor

• US 4,300,120 A
• Filed: 11/13/1978
• Issued: 11/10/1981
• Est. Priority Date: 11/13/1978
• Status: Expired due to Term

• Current Assignee: Eaton Corp. (Wisconsin) (Eaton Corporation PLC.)
• Original Assignee: Eaton Corp. (Wisconsin) (Eaton Corporation PLC.)
• Inventors: Surman, James J.
• Primary Examiner(s): Trafton, David L.
• Application Number:
  US05/959,553
• Time in Patent Office: 1,093 Days
• Field of Search: 340/58, 340/693, 340/539, 325/117, 325/185, 73/146.2, 73/146.5, 310/75 A, 310/67 R, 310/67 A
• US Class Current: 340/447
• CPC Class Codes: B60C 23/041 Means for supplying power to the signal- transmitting means on the wheel

Abstract

Tire pressure monitors are incorporated in vehicles having pneumatic tires to continuously or periodically measure the air pressure in the tires and to alert the driver should the pressure in one of the tires fall below a predetermined value. A self-contained generator-transmitter unit is affixed to each wheel, each unit monitoring the air pressure in the tire associated therewith and generating an RF signal when the pressure falls below a predetermined value. A receiver, located in the passenger compartment of the vehicle, receives the signal(s) from the generator-transmitter units to indicate a low tire condition to the vehicle operator. The generators operate only during rotation of the wheels which effect relative rotation between two members in each generator, one member carrying a permanent magnet and the other carrying an inductor. The member carrying the inductor is mounted to a wheel and the second member is mounted for rotation proximate the first member, having a mass center which is displaced from the axis of the first member, resulting in a pendulum or vertical position seeking affect.

Claims

1. In a vehicle having a plurality of pneumatic tires, a tire pressure monitor comprising:

generator means associated with each tire, each said generator means including first and second members, said first member mounted for rotation with an associated wheel and defining an axis of rotation, said second member mounted for rotation relative to said first member about said axis and including a center of gravity displaced from said axis, said generator means further including an inductor carried by said first member and a permanent magnet carried by said second member, said inductor and magnet being coextensively displaced from said axis to effect periodic alignment therebetween and a resulting electrical potential within said inductor during said relative rotation;

transmitter means associated with each generator means, each transmitter means operative to receive the electrical potential from the generator means associated therewith, each said transmitter means being further operative to generate a low tire condition signal when the fluid pressure within the tire associated therewith falls below a predetermined value; and

receiver means disposed remotely from said transmitter means and operative to receive said low tire condition signals and to generate an alarm signal as a function thereof.

2. The tire pressure monitor of claim 1 wherein said second member is elongated, having a first end rotatively mounted to said first member through an intermediate bearing, and a second end distal said first end, carrying said magnet.