Abstract:
An apparatus for preventing the replacement of a control unit, present in a motor vehicle, by an unauthorized person. The apparatus includes a function-inhibiting device, associated with a connection between the control unit and the connector element of an electrical supply lead, which immobilizes the control unit and the connection element in a predetermined connected position with respect to one another. Disconnection from this connected position without damage is possible only after delivery of an unlocking code to the control unit. If an attempt at forcible disconnection is made, the function-inhibiting device causes an irreversible interruption in the associated connection.

Description:
FIELD OF THE INVENTION 
     The present invention relates to an electronic drive lock. 
     BACKGROUND INFORMATION 
     A conventional electronic drive lock is described in German publication “mot”, February 1995, pages 102-106. Such a conventional drive lock is based on an access device in the form of an ignition key, a handheld transmitter (or a chip card), a control unit containing the drive lock, and an engine management control unit for controlling a gasoline or diesel engine. Other functional elements present in the vehicle can also be connected to the drive lock control unit, for example the electric fuel pump or the starter. A prerequisite for providing a vehicle equipped with the drive lock as described is that a prescribed unlocking code should be delivered to the drive lock control unit. Because the vehicle cannot, for this reason, readily be started up by an unauthorized person, the conventional drive lock offers at least some protection against theft, i.e. the vehicle being driven away. Given the increasing professionalism of vehicle thieves, however, it is foreseeable that vehicles will be misappropriated by replacing the original, locked drive lock control unit with an unlocked but otherwise functionally identical replacement control unit. 
     Accordingly, it is the object of the invention to indicate a possibility for preventing the theft of vehicles by replacing a control unit. 
     SUMMARY OF THE INVENTION 
     This object is achieved with a device according to the present invention. A replacement protector according to the present invention considerably increases the effort required to steal a vehicle by replacing a protected control unit. In the event of forcible severing of a connection, secured according to the present invention, between the electrical supply lead and control unit, the electrical supply lead must be properly equipped with a connector element. For a vehicle thief, the effort to remove such replacement protector is cost-intensive and most of all time-consuming. For a legitimate user, on the other hand, the replacement protector according to the invention involves no additional effort when removing a protected control unit. It is advantageous, according to the present invention to provide a supply lead and a control unit with respect to one another in such a way that even when connected, a slight relative movement is possible. This makes it possible to eliminate any contact problems between supply lead and control unit by gently jiggling the connection, with no need to unlock the control unit for the purpose. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows a drive lock according to the present invention. 
     FIG. 2 shows a control unit of the drive lock illustrated in FIG. 1 with connected electrical supply leads. 
     FIG. 3 shows a combination of the contact spring, connector pin, and lever with retaining pin for the control unit illustrated in FIG.  2 . 
     FIG. 4 schematically illustrates exemplary parts of a control unit and a connector element according to the present invention including a fuse, a circuit breaker and a battery. 
     FIG. 5 schematically illustrates an exemplary electrical transmitter circuit  52  according to the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 shows, exemplary, a drive lock for motor vehicles which is locked and unlocked using of a magnetic card  33 . The code stored on magnetic card  33  is read by a card reader  32  which is connected via an electrical connection  21  to a drive lock control unit  30 . Connected downstream from this via a further electrical connection  21  is an engine control unit  31  which controls, among other things, ignition system  34  and fuel injection system  35 . Also connected to drive lock control unit  30  is starter  36  and, if necessary, other control units present in the vehicle. Control units  31  and  36  are enabled, thus making it possible to start up the vehicle, only if a correct unlocking code has been delivered to drive lock control unit  30  by the use of an authorized magnetic card  33 . The use of a magnetic card as the code carrier is exemplary only; any other conventional code delivery system can of course also be used. Other such systems may also include the common systems which operate in non-contact fashion. A more detailed diagram of the general layout of a conventional drive unit is provided in the publication ‘mot’. 
     FIG. 2 shows the layout of a connection between one or more electrical connections  21  and a control unit  40 . The control unit  40  can be drive lock control unit  30 , card reader  32 , engine control unit  31 , or starter  36 . The control unit includes a housing  10  in which an electronic circuit  14  is arranged. An exemplary illustration of electronic circuit  14  is shown in FIG. 2 having the form of a circuit board. Located on one side of housing  10  is a connector receptacle  15  in which one or more electrical connector pins  16  are arranged, which lead inside housing  10  to circuit  14 . Also located in control unit housing  10  is an actuator  11  which can be actuated using an electrical signal delivered externally. Actuator  11  may be advantageously configured as part of electronic circuit  14 . Actuator  11  moves one end of a lever  12  that is rotatable about a bearing shaft  17 , the other end of Lever  12  being arranged outside housing  10  and inside connector receptacle  15 . At the external end, lever  12  has a retaining pin  13 . Bearing shaft  17  is in turn mounted in connector receptacle  15  or in housing  10 . 
     Engaging with a precise fit into the connecting device mounted on the control unit, constituted by connector receptacle  15  with connector pins  16  as well as levers  12  with retaining pins  13  located therein, is a connector element  20  to which are guided all the electrical supply leads  21  to be connected to electronic circuit  14  arranged in the control unit. Connector element  20  is made up of a housing which encloses an interior space  25  in which electrical supply leads  21  end. One connector side  24  of the housing of connector element  20  is configured to fit precisely onto the contour of connector receptacle  15  mounted on the control unit. Located in connector side  24  of connector element  20  are recesses in which contact springs  22  are arranged, matched in terms of physical position to connector pins  16  on the control unit side. When a connection is made between connector element  20  and control unit  40 , these springs coact with connector pins  16 . Inside cavity  25 , contact springs  22  extend into connector lugs  26 , to each of which, as a rule, one electrical supply lead is guided. A defined break point  23  is configured in each case between connector lug  26  and the internal end of a contact spring  22 . This break point can be implemented, for example, by reducing the cross section of connector lug  26  at one point, or by using a brittle, easily breakable material. At least some of contact springs  22  also have, in connector region  24 , an opening  27  (shown in FIG. 3) whose axis lies substantially perpendicular to the direction along which contact spring  22  and connector pin  16  coact. Opening  27  is arranged so that when connector element  20  and control unit  40  assume a predetermined position with respect to one another, lever  12  with retaining pin  13  can be pivoted at its tip into opening. In one example embodiment of the present invention, an electrical transmitter circuit  52  (FIG. 5) generates an acknowledgment signal when the predetermined connected position is established. 
     It is also advantageous that, opening  27  has the shape of a hole elongated along the effective direction of the connection between connector element  20  and control unit  40 . Control unit  40  (with housing  10 ) can, as a result, be moved slightly with respect to one another even if lever  12  with retaining pin  13  is engaged in opening  27 . Thus, if there is no electrical contact between a spring contact  22  and a connector pin  16 , an attempt can first be made, by gently jiggling the connection at connector element  20  of control unit  40 , to re-establish contact. 
     The arrangement described above can be is utilized as follows. At each termination of a vehicle operation that took place after prior authorized startup, a signal is generated from card reader  32  or drive lock control unit  30  which authorizes actuator  11  to pivot lever  12  with retaining pin  13  into opening  27  in contact spring  22  or connector pin  16 . The coaction of retaining pin  13 , lever  12 , and the contact springs is illustrated in FIG.  3 . If, in this state, connector element  20  and control unit  40  are forcibly disconnected, defined break point  23  in connector element  20  breaks, causing contact springs  22  to be torn out of their mount in connector element  20 , and the associated electrical connection  21  to be interrupted. A different control unit can no longer be connected to the vehicle by way of connector element  20  that has been damaged in this fashion. 
     If, however, a control unit is to be removed or replaced with the consent of the legitimate owner, for example in the event of a defect or in the context of maintenance, a defined unlocking code signal is to be delivered for this purpose to the relevant control unit. This code signal can be generated only by a legitimate user who is in possession of the correct magnetic card  33 . The code can be generated in various ways; in simple fashion, for example, the code is already located on magnetic card  33  and can be read out with an additional appropriate card reader. On the basis of the code signal, actuator  11 , even in the shut-down state, pivots lever  12  with retaining pin  13  out of opening  27 , or causes the lever not to pivot into the opening into the first place, whereupon connector element  20  can be disconnected from control unit  10  without damage. 
     Retaining the basic conception of securing the connection between the connector element of an electrical supply lead and a control unit by means of a mechanical catch which acts perpendicular to the connection direction and can be actuated without damage only with the aid of a code signal, a plurality of embodiments of the arrangement whose principle is set forth in FIGS. 2 and 3 is possible. This applies, for example, to the nature and arrangement of actuator  11 , the configuration of lever  12  with retaining pin  13 , the nature and configuration of defined break point  23 , or the number of catch devices. Interchanging of functions is also possible, the actuator being arranged in connector element  20  and defined break point  23  in control unit  40 . 
     It is also possible to provide electrical retention instead of mechanical retention using retaining pin  13 . For example, as illustrated in FIG. 4, a circuit breaker  44  and a battery  46  to power it can be provided in control unit  40 , and a safety fuse  42  in connector element  20 . If an unauthorized person attempts forcibly to sever the connection between the connector element and control unit  40 , the circuit breaker feeds a high current into one of electrical connections  16 ,  21  in the connector element, which causes the safety fuse to be destroyed. Provision can also be made for the high current fed in by the circuit breaker to control unit  40  to cause destruction of the accessory powered by the relevant electrical connection  16 ,  21 , for example an engine speed sensor.