Security system to prevent unauthorized starting of the engine of a vehicle

• US 6,489,886 B2
• Filed: 04/17/2001
• Issued: 12/03/2002
• Est. Priority Date: 04/19/2000
• Status: Expired due to Term

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments Deutschland Gesellschaft Mit Beschrã¤Nkter Haftung (Texas Instruments, Inc.)
• Inventors: Meier, Herbert
• Primary Examiner(s): TRIEU, VAN THANH
• Application Number:
  US09/835,927
• Publication Number:
  US 20010035813A1
• Time in Patent Office: 595 Days
• Field of Search: 340/425.5, 340/426, 340/438, 340/461, 340/468, 340/825.69, 340/825.72, 340/539, 180/287, 307/10.2, 307/10.3
• US Class Current: 340/426.1
• CPC Class Codes: B60R 25/04 operating on the propulsion system, e.g. engine or drive motor
• CPC Class Codes: B60R 25/24 using electronic identifiers containing a code not memorised by the user

Abstract

A security system to prevent unauthorized starting of the engine of a vehicle has a remote control unit (18) equipped with a transponder which, on reception of an interrogation signal using at least one reception aerial (20), transmits an identification code group using a transmitter unit (40). Located in the vehicle is a control unit (12), which on actuation of a starter button (26) within the vehicle, transmits the interrogation signal, and subsequently checks the identification code group transmitted by the remote control unit. Starting of the engine will only be possible when the identification code group coincides with the code group expected by it. Connected to the reception aerial (20) is a signal detector (28), which has a reaction threshold level that can be toggled between a high value and a low value. This signal detector will relay the interrogation signal to further processing stages only when the interrogation signal level exceeds the set reaction threshold.

Claims

1. A security system to prevent unauthorized operation of a vehicle comprising:

a vehicle control unit comprising a transmitter and a receiver and being responsive to a control signal to transmit an interrogation signal;

a remote transponder comprising a receiver for receiving the interrogation signal and for generating a DC voltage to operate the transponder and a coded signal therefrom, a signal strength detector having a plurality of threshold levels receiving the coded signal and a code checking circuit receiving an output of the signal strength detector to determine if a code in the coded signal matches a stored code, the code checking circuit, on determining a match, changing the threshold level of the signal strength detector from a first to a second level which permits only signals of a predetermined strength to be received, whereby the predetermined signal strength is indicative of the transponder being at a chosen location within the vehicle; and

a transmitter in the transponder transmitting an authorization signal to the vehicle control unit to authorize the operation of the vehicle if a properly coded interrogation signal is received at the second threshold level.

2. Security system of claim 1 wherein the receiver has three antennas for receiving the interrogation signal, the antennas being spatially arranged so that each has a main reception direction along one of three mutually perpendicular axes, each said antenna being coupled to a separate signal strength detector.

3. Security system of claim 1 wherein the control signal is generated by closing a switch.

4. Security system of claim 2 wherein the control signal is generated by closing a switch.

6. Security system of claim 3 wherein the receiver has three antennas for receiving the interrogation signal, the antennas being spatially arranged so that each has a main reception direction along one of three mutually perpendicular axes, each said antenna being coupled to a separate signal strength detector.

7. Security system of claim 6 wherein the control signal is generated by closing a switch.

5. In a security system for a vehicle having a control unit in the vehicle and a transponder, the improvement comprising:

a signal strength detector having a plurality of threshold levels, a properly coded signal received at a first threshold level operative to change the threshold level to a second threshold level, the second threshold level being indicative of the transponder being at a chosen location within the vehicle.

8. Security system of claim 5 wherein the control signal is generated by closing a switch.