Motor vehicle anti-theft device and method

The invention relates to an anti-theft device For motor vehicles and on a Anti-theft method according to the preamble Of the claims 1 and 5.

It becomes a personal transponder And on the vehicle side an immobilizer was used to convert the Operation of an internal combustion engine as a function of Of the access authorization of the transponder owner influence. This is done by intervening in the function Of a motor control unit (applies to ottomotors As well as for controls on diesel engines). procedures And devices of this type are known.

DE-A-43 20 776 includes statements A device in which the encoded signal of a Transponders to an immobilizer becomes. Will be this transponder identification code Is recognized by the immobilizer as correct (permissible) The immobilizer has a frequency code (or a Permission signal as in DE-A-195 14 074) to the Engine control unit, where a comparison with a stored Frequency code. comparison-dependent Then the motor function is enabled or disabled. At the The transmission of the transponder identification code To the immobilizer and the transmission of the frequency code To the engine control unit still exist Certain intervention possibilities, the commissioning Of the motor vehicle by unauthorized persons.

For other anti-theft devices Here attempts are made to provide a remedy so that, for example, Also a "transponder" identification code Is not suitable for the later unauthorized Commissioning of the motor vehicle. For example Are different exchange code methods known.

Between transponder and immobilizer No constant and thus copiable and durable Usable codes For example, to the engine control unit transmitted. This can be encrypted Be, however, at least a one-time Commissioning of the motor vehicle possible. Of the Desire for a multiple use of the motor vehicle Is then only with great effort Can be fulfilled.

EP-A-0 683 293 discloses a process for the preparation of a process according to claim 1 Theft stamping described in a transponder An encrypted information of an immobilizer (Reading device). By secret Linking with transponder hardcodes is then a Secret code generated to the immobilizer too Is transmitted. There will then be in a similar way An immobilizer secret text is determined and with the Transponder secret. On agreement Of the secret texts are the control devices to be secured Which can be coded. The Security of information exchange between transponders And immobilizer is high. It can, however, again Unauthorized intervention by determining the release information, Which is sent to the control unit, Respectively. Even if the immobilizer, as indicated, As a component of the control device, Must be a (manipulatable) interface. The System security is high, but comparable As in the case of interchange code methods.

It is an object of the invention to provide an anti-theft device To create with the help of a As little effort as possible and reliable In operation. Furthermore, a method for Theft protection is developed, which does not Sensible manipulation from the outside and only by Very complex replacement of the entire system To theft protection.

In order to solve these problems, the Anti-theft device according to the preamble Of patent claim 1 by the characterizing clause Features of Patent Claim 1. The inventive The anti - theft system is protected by the As described in claim 6. Details of the invention result from The patent claims 2 to 5 and 7 to 11.

A transponder in a known construction Is combined with an ignition key and Includes a transmitting and receiving antenna as well as An electronic computing unit and a storage unit. For theft protection of a particular motor vehicle Several transponders can be suitable. For example Are three transponders in one family Or a plurality of transponders exist In a vehicle park, there for a motor vehicle Are required. Preferably, the transponders Battery-free, thus passive.

An immobilizer associated with the motor vehicle Is composed of a transmitting and receiving antenna, Which is arranged in the region of the ignition lock Is. The transponder is connected to the antenna when the antenna is plugged in Ignition key can be excited, and it is data Between transponder and immobilizer interchangeable.

The immobilizer is provided with a plant-relevant Control device of the motor vehicle, in particular With a function of a combustion engine (Petrol or diesel engine), electrically controlled connected. Proper operation of this control unit And thus the combustion engine is only After proof of the access authorization of the Transponder owner.

The function of the immobilizer is opposite Known anti-theft devices Has been changed. He has the sole task, The connection between transponder and Motor control unit in the initialization phase And thus the data exchange between them Devices. Verification of access authorization Is no longer carried out by the immobilizer, But directly in the control unit, which is an error source And a manipulation possibility has been. The exact proof of the access authorization Has therefore by communication between transponders And engine control unit, wherein the Immobilizer just has the task of doing this communication And possibly less Relevant functions. For example, From the immobilizer still depending on the presence Of a known transponder (one of the Vehicle belonging to the vehicle) an anti-theft alarm system Turn it on or off Can be customized vehicle settings Via the immobilizer.

The thus designed anti-theft device Preferably operates according to the following method:

A certain number of transponders will To the motor vehicle by storing storage units Of the transponders receive a specific coding. The stored information consists of A security code and a transponder identification code. The vehicles belonging to the motor vehicle Transponder identification codes are also stored in memory Of the immobilizer and, if appropriate, of the In the engine control unit Also the security code is filed.

After inserting the ignition key into the The ignition key of the motor vehicle becomes the transponder From the immobilizer via the respective antennas And the transponder identification code is sent to the Immobilizer. There is a first check Where it is determined whether one of the Vehicle, the communication Has been recorded. If so, the communication To the engine control unit Otherwise used input of the engine control unit Is switched accordingly.

Turn the engine on with the ignition key , The engine control unit signals via Output signal (for example, the motor control light output) The beginning of communication with the Transponders. An information, especially one not Constant, arbitrarily formed in the engine control unit Random information is transmitted to the transponder. There, the random information, the transponder identification code And the secret information with help A secret calculation operation to a code, Which is transmitted to the engine control unit. In the engine control unit the same secret Calculating operation to form a reference code. Of the The required transponder identification code of the Currently in communication Transponders can be transferred from the immobilizer to the Engine control unit. On the other hand Can be used in the engine control unit with all individual permissible Transponder identification codes several reference codes be calculated. The one in the transponder Computed code has then with at least one of the Reference codes. Is that the case, The engine operation is properly controlled by the engine control unit Controlled. Otherwise, the motor function is too high lock.

A more detailed description of the invention Is carried out by means of an exemplary embodiment, wherein the FIG Theft device.

The anti-theft device comprises At least one with an ignition key 1 Passive (battery-free) transponder 2. An immobilizer 3 is in close proximity to a Ignition lock 4 of the motor vehicle. Furthermore Is, in the figure, a motor control unit 5 and a diagnostic tester 6 are shown.

The transponder 2 and the immobilizer 3 Each have a transmitting and receiving antenna 7, 8 , Via which the transponder 2 supplies power And data are exchanged. The transponder 2 further includes an electronic storage unit 9 and a computing unit 10. The immobilizer 3 also includes a storage unit 11 and a storage unit 11 Computing unit 12, an interface 13 and one here Which is controlled by a switching device 14 (Shown in a position during the initialization phase). The engine control unit 5 in general Known design includes an interface 16, a microprocessor 17, and a memory unit 18 other components which are not of interest here.

The anti-theft device operates In the following manner, thus also the procedure for the Theft protection is explained:

After inserting the ignition key 1 into the Ignition key 4, the antenna 7 of the transponder 2 becomes From the antenna 8 of the immobilizer 3. It Results in the transmission of a frequency- or amplitude-modulatable Electrical voltage. One in memory 9 stored transponder identification code Via the computing unit 10 and the antennas 7, 8 Processing unit 12 of the immobilizer 3. In Of the storage unit 11 of the immobilizer 3 are identification codes Of the vehicle belonging to the motor vehicle Transponder 2. These are compared with the Transponder 2. Is one of the allowed transponders 2 in the range Of the ignition lock 4 are detected by the (12) of the immobilizer has several functions But the operation of the motor vehicle is controlled Not yet approved. On the other hand Outputs 19, 20 of the interface 13 external functions To be controlled. For example, a Theft alarm system or another Switching function. At this time Can also connect to the engine control unit 5 can be produced via the change-over switch 15 But can only be done later Below. The change-over switch 15 is normal In one the engine control unit 5 with the diagnostic tester 6, so that here Corresponding data are interchangeable. In the initialization phase This connection becomes the input / output Of the engine control unit 5 as is known in the art Transmission of other data.

If the ignition is activated by the ignition key 1 , The starting program runs in the engine control unit 5 The immobilizer 3 ultimately also has a Indicator light output 22 of the engine control unit 5 Is signaled. At the latest after the request of this The change-over switch 15 disconnects the diagnostic tester 6 from the engine control unit 5 and connects the interfaces 13 and 16 with each other. This is done either After detection of a permissible transponder 2 or After a given start command by a signal of the Computing unit 12.

The immobilizer 3 now operates exclusively As a transit station. The ability to communicate Between transponder 2 and engine control unit 5 is produced. The final identification process Is carried out by exchanging data between the Motor control unit 5 and the transponder 2:

The engine control unit 5 transmits via the connection 21 as well as the antennas 8, 7 are based on a Random function in the processor 17 To the transponder 2. There is a memory in the memory 9 Secret algorithm, using one Linking the random information to the transponder identification code And a transponder internal Secret code. The computed code will be sent to the Engine control unit 5. The memory there 18 (in addition to extensive data and programs) For the motor control) also the secret information And, where appropriate, all approved transponder identification codes As well as the computing algorithm. With the help of the random information, the secret information And a transponder identification code Reference codes are determined. However, it is also The transponder identification code of the Current transponder 2 to the engine control unit 5 And thus only a reference code Is determined. Finally, the data transmitted by the transponder 2 Transmitted code with at least one reference code In the engine control unit 5. On agreement The motor function is enabled. Otherwise The engine control unit 5 is disabled And the engine is turned off if it has already started Is.

After completion of the initialization phase, The change-over switch 15 in the immobilizer 3 is actuated again And the connection 21 to the diagnosis tester 6. *** " placed. Is the engine for a certain time except Operation, the anti-theft device becomes automatic "Sharpened", ie the identification process To repeat the functionality of the engine control unit Respectively.

The anti-theft device thus formed Is particularly simple, since the existing Components of the engine control unit 5 be used. The immobilizer 3 is only added to the Establishing connection between transponder 2 And the engine control unit 5, but has none Function more in the actual release of the Engine control unit 5. There will be no constant "Interceptible" data between transponders 2 and 4 Engine control unit 5, by means of which the method Would be comprehensible. The random information, the From the engine control unit 5 to the transponder 2 Is only valid once. The arithmetic algorithm and The secret information is stored in internal memories 9, 18 And can not be read from there by unauthorized persons. A transfer of this information takes place not at all. Because the access authorization in the engine control unit 5 itself, is also not enabling information More to the engine control unit 5 Which also allows this possibility of intervention Is eliminated.