AU677988B2 - Safety device for vehicles - Google Patents

Description

1 Vehicle security device Prior art The invention is based on a device of the generic type of the main claim.

In order to protect vehicles against unauthorized use, it is known to use security devices which only permit the vehicle to be activated if a code :ignal generated by means of a signal generator corresponds to a reference code signal present in the vehicle. Known devices usually comprise the door locking devices and control elements for monitoring the functioning of vehicle components which are essential for operation, such as for example the starter, the petrol pump, the fuel injection system or the central engine control unit.

A vehicle which is protected in such a way cannot be activated even if an unauthorized user has been able to enter the passenger compartment of the vehicle and has short-circuited the ignition. The security devices are activated in many cases using a remote control which outputs for example encoded high-frequency signals or infrared signals.

Many modern vehicles have a device, designated below as an engine management system, for controlling the power output by the engine, rotational speed signals being fed to the said device from a rotational speed sensor arranged on the engine. The rotational speed sensor is frequently arranged on the flywheel of the engine. The rotational speed information is used to set suitable engine parameters for the starting process and for the different operating states in order to achieve the highest possible level of efficiency.

The object of the invention is to disclose a security device for a vehicle equipped in such a way, which security device only permits signals to be exchanged between the rotational speed sensor and the engina management system if the security device has been deactivated in a prescribed manner by an authorized person.

i This object is achieved by means of a device with

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U r Ip 2 the characterizing features of the main claim.

According to the invention, a protection device which only permits a regular exchange of data betweeA the rotational speed sensor and the engine management system if it has been deactivated correctly is connected into the signal path between the rotational speed sensor and the engine management system. Normally, the engine management system is initiated by the first signals coming from the rotational speed sensor when the engine is started. In response it sets suitable engine parameters in order to support the starting of the engine. If the unlocking of the security device did not take place in a correct manner, the protection device prevents the signals output by the rotational speed sensor from being passed on to the engine management system. As a result it is not possible to start up the engine. Thus, it is ensured in an advantageous manner that an unauthorized user cannot start the engine even if he activates the starter by short-circuiting the ignition. According to the invention, the protection device changes the signal received from the rotational speed sensor as it is passed on to the engine management system. This has the advantage that unauthorized starting of the engine is not possible even if an unauthorized user both short-circuits the ignition and additionally bridges the protection device. Therefore, considerable technical and methodical outlay is required to bypass the security device according to the invention. Thus, it forms a good protection against unauthorized use of the protected vehicle, The proposed security device is suitable for application in conjunction with virtually any desired activation system, for example with a mechanical key or a remote control which operates in a contactless manner.

Expedient embodiments of the security devices can be found in the subclaims.

An exemplary embodiment of the security device is explained in greater detail with reference to the drawing.

AL /N> Td -3- Drawing Figure 1 shows a block diagram of the proposed security device, Figure 2 shows a second embodiment.

Figure 1 shows the essential components of a proposed security device. It 4s activated and deactivated by means of a remote-control key 8. It is composed of a grip housing 10 and a key blade 12 which emerges therefrom. However, the latter can also be missing or be realized for example in a separate key. A signal iU generating device for generating signals for activating and deactivating the security device and an aerial for emitting the unlocking signals are arranged in the grip housing 10. In the vehicle to be protected there is an evaluation unit 4 which is assigned an aerial 6 for receiving the signals emitted by the remote-control key 8. On the output side, the said aerial 6 is connected to the door locking device system 24 and to a protection device 30. Furthermore, it can also be connected to other devices which are elementary for the functioning of the vehicle, such as for example the starter, the petrol pump and/or the injection system. A rotational speed sensor 28 is connected to the protection device 30 on the input side and an engine management system 26 is connected to the said protection device 30 on the output side.

In customary engine control systems, the signals supplied by the rotational speed sensor 28 are fed directly to the engine management system 26 which, in addition, also receives signals from various other sources (not illustrated here). On the basis of all the signals fed to the engine management system, the said engine management system identifies at least scne of the engine parameters which are to be set for optimized engine operation, such as for example the ignitio time or the fuel mixing ratio. During the starting process, the engine management system 26 evaluates in particular the signals supplied by the rotational speed sensor 28.

The said engine management system 26 begins to operate as soon as it receives signals from the rotational speed sensor 28, which signals indicate the start of the Lu: i M 4 starting process by the starter. In such a case it then initially sets the engine parameters in such a way that reliable starting of the engine is achieved.

According to the invention, the protection device 30 is connected between the rotational speed sensor 28 and the engine management system 26. It operates in such a way that it only passes on signals from the rotational speed sensor 281 to the engine management system 26 if the evaluation unit 4 has been activated in a prescribed manner by an authorized signal from the remote-control key 8, and has subsequently enabled the protection device For the exemplary embodiment indicated in Figure 1 it is assumed that the rotation speed sensor 28 outputs a binary square wave signal 32 with an amplitude of for example 0.5 volts as soon as the starter has been activated. The signal 32 is fed to the protection device The latter generates a binary sequence signal 34 to the signal 32, the said binary sequence signal 34 also being square wave-shaped, but its amplitude differing from that of the signal 32 significantly and being for example volts. The sequence signal 34 is fed to the engine management system 26. The input of the engine management system 26 at which the sequence signal 34 is present has a voltage threshold value stage. It only allows signals to pass whose amplitude is above a threshold value which sequence signals 34 have when correct unlocking takes place. If the latter is for example usually 5 volts, the engine managerient system 26 would not react to signals with an amplitude of 0.5 volts. Therefore, it is not possible to activate the engine management system 26 by simply short-circuiting the protection device 30 in that the signal supplied by the rotational speed sensor 28 is fed directly to the engine management system 26.

According to further expedient embodiments of the security device, the rotational speed sensor 28 generates a square wave signal 32 with a prescribed frequency or, alternatively, with a binary coding. The protection iAL w device 30 is configured in such a way that in the first eNT uf~ a

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K 1 0~cC I 5 case it generates from the said square wave signal 32 a sequence signal 34 with another frequency or, in the second case, generates a sequence signal 34 with changed coding, and passes on the said sequence signal 34 to the management system 26.

Figure 2 shows a further embodiment of the security devic:e according to the invention. It corresponds with respect to the elements used to the security device illustrated in Figure i. However, in this case the protection device 30 itself generates an encoded square wave signal 36 which is fed to the rotational speed sensor 28. The latter waits for the signal supplied by the protection device 30. The rotational speed sensor 28 does not generate a sequence signal 34 which is accepted by the engine management system until the signal 36 is received. Since the arrangement illustrated in Figure 2 cannot be bypassed in particular by the rotational speed sensor simply being supplied with voltage, it also provides a high degree of protection against the security arrangement being bypassed.

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Claims (4)

1. Security device for a vehicle which is equipped with an engine management system and a rotational speed sensor, characterized in that a protection device (30) is arranged between the engine management system (26) and the rotational speed sensor to which protection device (30) the signals (32) generated when the rotational speed sensor (28) starts are fed and which generates from the said signals (32) sequence signals (34) which are different from the signals (32) and which are fed to the engine management system the protection device (30) only transferring signals (34) to the engine management system (26) if it has been unlocked by means of an unlocking device in a prescribed manner.

2. Security device according to Claim 1, charac- terized in that the sequence signal (34) has a different amplitude from the signals [*aEj (32) output by the rotational speed sensor (28)

3. Security device according to Claim 1, charac- terized in that the sequence signal (34) has a different frequency from the signal output by the rotational speed sensor (28)

4. Security device according to Claim i, charac- terized in that the sequence signal (34) has a different coding from the signal output by the rotational speed sensor (28) Security device for a vehicle which is equipped with an engine management system and a rotational speed sensor, characterized in that a protection device which transfers a prescribed signal (36) to the rotational speed sensor (28) when the engine is started is connected upstream of the rotational speed sensor and in that the rotational speed sensor (28) only transfers a signal to the engine management system (26) if the protection device (30) has been unlocked by means of an-activation device in a prescribed manner. I 7 Abstract A security device is proposed for a vehicle which is equipped with an engine management system and a rotational speed sensor. According to the invention, a protection device (30) to which the signals (32) generated when the rotational speed sensor (28) starts is arranged between the engine management system (26) and the rotational speed sensor The protection device generates from the said signals (32) sequence signals (34) which are different from the said signals The sequence signals (34' are fed to the engine management system However, this only happeris if the protection device (30) has been unlocked by means of an unlocking device in a prescribed manner. The sequence signal (34) expediently has a different amplitude from the signal output by the rotational speed sensor (28). (Figure 1) i, c- I r