DE4242492A1 - Antitheft prevention system for motor vehicle - Google Patents

Abstract

The theft prevention system has a data unit (2) generating and/or storing a secret code which is activated by an input device (1) within the motor vehicle. A bidirectional line (5) between the input device and the i.c. engine starter motor (6) is used to transmit the secret code to a reception device within the latter which decodes and verifies the code.Pref. the data unit and/or the input device includes a display (4). The data unit may be in the form of a code card.

Description

Means of transportation with internal combustion engines - in particular motor vehicles - are usually by means of me mechanical devices or alarm systems Theft protected, with door contacts, current loops or the interior can be secured.

The invention has for its object a thief steel security system to specify with which thief steels of means of transportation with internal combustion engines Have it prevented in a sustainable manner and with little effort.

This object is achieved by the features solved in the characterizing part of claim 1.

Advantageous further developments of the invention result from the subclaims.

The one in a data unit (e.g. a code card or magnetic card) stored or from the Data unit generated and stored secret code is by means of an input unit (e.g. a plug-in direction or reading device) inside the Means of transportation activated and via a bidirek tional connecting line (preferably the starter line) to inte in the starter of the internal combustion engine grieren (preferably with the start-lock relay  coupled) receive unit. The transfer The secret code is checked in the receiving unit and upon verification, an enable signal via the bidirectional connecting line to the input unit returned. Upon receipt of the release signal the data unit (e.g. the code card) released and starting the starter by actuation conditions of the ignition key.

Optionally can

• - every system compo when activating the system nente (data unit, input unit, bidirection nale connecting line, receiving unit) on your Functionality is checked,
• - after each reading and decoding of a transmitted a new, changed secret code generated and stored in the data unit will,
• - The input unit for diagnostic purposes with a Display device (for example a light diode LED), their display mode depending on the system status or the Transmission mode changes.

The system presented combines several advantages in yourself:

• - compared to existing alarm systems very cheap theft protection can be achieved (few components required, existing connection can be used),
• - There is no change to existing wiring harnesses required,  
• - It is an efficient anti-theft device through Protection of the internal combustion engine against unauthorized use Starting possible with the starter
• - There is a high level of security since there is no back message (internal enable signal) from the starters cannot be started (not even by ex internal manipulation on the starter cable) and thus also the means of transportation cannot be started,
• - The display device is a simple one Diagnostics option via the system status or given the system components.

Furthermore, an exemplary embodiment based on the in the diagram shown with the compo anti-theft system for a Passenger car are discussed.

On the dashboard of the vehicle, an input or plug-in device for a code card 2 is provided as input unit 1 ; the code card 2 contains a secret code stored in a first integrated circuit 3 (for example an EPROM), on the code card 2 a display device 4 (for example an LED) is attached. The receiving device 1 or plug-in device is supplied with power on the one hand via the ignition line 11 and, on the other hand, is connected via the starter line 5 to a second integrated circuit 7 , which is encapsulated in the starter 6 and connected to the start-blocking relay; furthermore, the plug device 1 is connected to the starter 10 via the switch 12 .

The time sequence when starting the motor vehicle is structured as follows:

• - Insert the code card 2 into the plug device 1 and insert the ignition key into the ignition.
• - Switch on the ignition 11 : the anti-theft system receives its supply current, the review of the system components begins.
• - The two integrated circuits (ICs) 3 , 7 are activated (the second IC 7 receives the supply current via the starter line 5 ); after the switch-on signal ("power-on-reset"), the first IC 3 goes to "receive" and the second IC 7 goes to "send".
• - The second IC 7 starts a timer (for example, charging a capacitor), sen det a ready signal via the start terleitung 5 and goes on receipt; the first IC 3 receives the ready signal, goes to transmit and turns on the display device 4 (LED).
• - The first IC 3 sends the secret code to the second IC 7 via the starter line 5 and goes back to reception.
• - The second IC 7 receives the secret code, decodes it and checks it for validity; if the secret code is recognized as correct (verified), the second IC 7 sends an enable signal to the first IC 3 and goes back to reception; At the same time, incoming starter signals for controlling the start-blocking relay 8 are switched through as often as desired via the starter line 5 (until the ignition is switched off).
• - The first IC 3 recognizes the release signal; the display device 4 (LED) goes out, the code card 2 can be removed from the plug-in device 1 .
• - During the starting process, the start signal generated by the ignition lock 10 , 12 is transmitted directly to the second IC 7 via the starter line 5 . If the code was correctly recognized beforehand, the start signal is evaluated, the start / lock relay 8 picks up and the start system 9 is activated.

If decoding is unsuccessful, no enable signal is sent back by the second IC 7 ; after a certain time, the secret code is retransmitted by the first IC 3 . The maximum number of repetitions can be set using a counter; if this is exceeded, each further attempt to start is blocked and the display device 4 flashes. The ignition must be switched off and a certain time must be waited before trying to start again (for example until the capacitor is discharged).

Optionally, the release signal can be coupled to an acoustic message; for example, the horn can be activated if the decoding is unsuccessful. Wei terhin can be prevented by evaluating the generator voltage on the second IC 7 that the start-lock relay B can be activated while the engine is running.

The following diagnostic options are available with the help of the An pointing device (LED) given:

• a) LED always stays off: either defective starter line or defective second IC (second IC does not send ready for operation shaft signal) or defective first IC (first IC  does not recognize a ready signal) or de perfect LED
• b) LED comes on, but no longer goes out: first IC is defective
• c) LED comes on and flashes: either second IC defective (second IC recognizes the Code not) or first IC defective (first IC sen wrong code) or wrong code card or disturbed transmission path
• d) LED comes on briefly and goes out again: valid data transfer.

Claims (11)

1. Theft protection system for a means of transportation with an internal combustion engine, consisting of:

• a) a data unit ( 2 ) for generating and / or storing a secret code,
• b) an input unit ( 1 ) in the interior of the moving means for activating the secret code,
• c) a bidirectional connecting line ( 5 ) between the input unit ( 1 ) and starter ( 6 ) of the internal combustion engine for transmitting the secret code,
• d) in the starter ( 6 ) integrated receiving unit ( 7 ) for decoding and verifying the transmitted NEN code.

2. Anti-theft system according to claim 1, characterized in that the data unit ( 2 ) and / and the input unit ( 1 ) has a display device ( 4 ). 3. Anti-theft system according to claim 1 or 2, characterized in that the data unit ( 2 ) has an integrated circuit ( 3 ). 4. Theft protection system according to claim 3, characterized in that the data unit ( 2 ) is designed as a code card. 5. Theft protection system according to claim 4, characterized in that the input unit ( 1 ) is designed as a plug-in device for a code card. 6. Anti-theft system according to one of claims 1 to 3, characterized in that the data unit ( 2 ) is designed as a magnetic card. 7. Theft protection system according to claim 6, characterized in that the input unit ( 1 ) is designed as a reader device for a magnetic card. 8. Theft protection system according to one of claims 1 to 3, characterized in that data unit ( 2 ) and input unit ( 1 ) are integrated in a keyboard unit. 9. Theft protection system according to one of claims 1 to 8, characterized in that the bidirectional connecting line ( 5 ) is the starter line. 10. Anti-theft system according to one of claims 1 to 9, characterized in that the receiving unit ( 7 ) is designed as an integrated circuit which is connected to the start-blocking relay ( 8 ) or to the start system ( 9 ). 11. Anti-theft system according to one of claims 1 to 10, characterized in that the receiving unit ( 7 ) contains a counter via which the number of allowed verification attempts is determined.