Communications: electrical – Selective – Interrogation response
Reexamination Certificate
1998-11-02
2002-05-28
Horabik, Michael (Department: 2735)
Communications: electrical
Selective
Interrogation response
C340S010340, C340S005610, C359S199200
Reexamination Certificate
active
06396390
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to a device for detecting a key which has been inserted into a lock of a motor vehicle, in particular into its ignition lock, and to a correspondingly configured key.
Keys, in particular ignition keys of motor vehicles, are nowadays increasingly equipped with electronic components which permit communication with systems disposed at the lock end, for example control units of electronic ignition systems. The electronic keys are distinguished by an increased level of protection against counterfeiting, so that unauthorized use of the system can be prevented with improved probability.
U.S. Pat. No. 5,808,372 to Schwegler et al. (German patent DE 195 39 852 C1) discloses a system in which an ignition key and a motor vehicle functional unit communicate with one another. The key is equipped with a long-range communications channel for transmitting remote-control commands and with a further, short-range communications channel via which it is in communication with an ignition-lock-end control circuit. The state in which the ignition key is inserted in the ignition lock can be sensed on the basis of a transmission of data information via the short-range communications channel. The key contains a transmitter and a receiver which are connected to a logic control circuit and are controlled thereby.
German patent DE 44 14 734 C2 discloses a circuit arrangement for sensing the switching states of motor vehicle activation means, in particular in the form of a keyless motor vehicle lock system with a transponder that is carried by the user. The circuit contains a generator which intermittently generates pulses for switching on and off a voltage supply main switch, and a microprocessor (logic control unit) for controlling various functions when an activation of the activation means is sensed.
European patent application EP 0 115 747 A1 discloses an immobilizer which can be activated by an electronic key which can be inserted into a fixed receptacle section, signals being transmitted by varying the impedance of inductors. By means of the inductive coupling between the electronic key and the fixed receptacle section it is possible to transmit both data and supply energy to the key. The vehicle-end interrogation device is continuously active and generates an output signal of constant amplitude as long as there is no key introduced into the receptacle section. If the key is inserted, there is, owing to the magnetic coupling, a change in the output signal of the interrogation device by means of which it is possible to check the presence and the correctness of the inserted key.
U.S. Pat. No. 4,486,806 to Mochida et al. (European patent EP 0 065 650 B1) discloses an electronic door locking system for motor vehicles. There, the position of the ignition lock, and thus the position of the ignition key, is interrogated and the door lock system is controlled as a function of the position of the ignition key. Furthermore, Mochida et al. teach how to determine whether the ignition key is still in the ignition lock and, if this is the case, to disable the generation of a door locking signal. In all these cases it is necessary to detect whether or not the key is inserted into the lock.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a device for detecting a key which has been inserted into a motor vehicle lock, which overcomes the above-mentioned disadvantages of the heretofore-known devices and methods of this general type and which permits quick and reliable key detection with little expenditure and provides for a high degree of reliability.
With the foregoing and other objects in view there is provided, in accordance with the invention, a device for detecting a key inserted into a lock of a motor vehicle, wherein, when the key is inserted in the lock, the key communicates via a communications link with a lock-end interrogation device emitting intermittent interrogation pulses, the device which comprises:
a microprocessor, a transmitter connected to the microprocessor, and a receiver connected to the microprocessor; and
a circuit arrangement connected directly between the transmitter and the receiver and bypassing the microprocessor, the receiver activating the circuit arrangement upon receiving an interrogation pulse and actuating the transmitter to transmit a response pulse in response to the interrogation pulse.
The receiver and the transmitter of the key are connected to one another directly via a circuit arrangement which, when the interrogation pulse is received, can activate the transmitter immediately or else with a time delay, in order to generate the response pulse. The outputting of the response pulse is thus implemented purely by means of circuitry so that the reaction time of the key is very short, that is to say the response pulse is generated very quickly, and the current consumption of the key still remains low. The generation of the response pulse thus requires no software support so that the microprocessor in the key can remain in the stand-by mode (power-down mode) during this interrogation “is key inserted?”. The energy requirement is thus minimized.
The interrogation pulses are emitted intermittently, i.e. at regular or irregular time intervals, by the lock-end interrogation device, i.e. the interrogation device in the motor vehicle, and are replied to with short response pulses by the key inserted in the lock, said pulses being preferably transmitted via the communications link, for example an infrared link, a radio link of a remote-control system which may be in the key or of a communications link of inductive design, and being evaluated in the interrogation device, that is to say in the evaluating logic which is in the motor vehicle, as an indication that the key is inserted.
In the embodiment according to the invention there is thus no need for an additional sensor such as a mechanical push button switch, a Reed contact, a Hall sensor, a photoelectric barrier etc. The inserted state of the key is sensed via the functional components which are already provided in the system for other purposes.
The intermittent interrogation may take place cyclically, for example at time intervals of 50 ms or greater, so that there is no appreciable increase in the quiescent current of the interrogation device and the interrogation device can also remain permanently activated even when the ignition is switched off. Since the interrogation takes place very quickly, the insertion of a key into the ignition lock can be detected very rapidly so that no significant system delay times occur.
In accordance with an added feature of the invention, the circuit arrangement is adapted to time an end of the response pulse to lie after a trailing edge of the interrogation pulse. In other words, the end of the response pulse is delayed in relation to the end of the interrogation pulse so that the interrogation device (evaluation logic) can distinguish the response pulse clearly from interference signals which are generated by reflections or other influences of the interrogation pulse, but drop away immediately to zero at the end of the interrogation pulse.
For this purpose, the circuit arrangement may contain a timing element which delays the switching off of the response pulse so that the response pulse persists for a certain time period after the interrogation pulse has already ended.
The key may be provided with a battery, implemented for example as an accumulator, which makes available the energy necessary for outputting the response pulse and also ensures the energy supply for the further components contained in the key, for example the microprocessor. Alternatively, the energy necessary for outputting the response pulse may also be drawn by the key by means of inductive supply from the interrogation device, for example the evaluating control unit. For this purpose, the key then preferably has an LC oscillatory circuit with energy accumulator connected downstream.
In accordance with an additional featu
Achhammer Siegfried
Schweiger Jürgen
Greenberg Laurence A.
Horabik Michael
Locher Ralph E.
Shimizu M
Siemens Aktiengesellschaft
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