Abstract:
A device with a key-operated lock cylinder acts on a switching device as a function of the turning of a key. In addition to the key channel for holding the associated key and the tumblers, the cylinder core has a permanent magnet on its periphery. Similarly, in addition to a locking channel for the tumblers, the cylinder housing has at least one sensor which, when the cylinder core is actuated by the key, responds to the permanent magnet and activates the switching device via an evaluator. In order to secure the device against theft as a result of an unauthorized person replacing the cylinder core in the lock cylinder, an entire group of different cylinder cores is associated with the cylinder housing. They differ from one another with respect to at least one of their permanent magnets. In the device a given pair of cylinder core and cylinder housing is used as the lock cylinder which then has a given magnet code. When the lock cylinder is actuated by the key, the sensor detects the differences in the magnets. If the evaluator is programmed to a given magnet code, the evaluator responds only when the correct cylinder core corresponding to its magnet code is located in the lock cylinder when the lock Ls actuated by the key. If an unauthorized person replaces the cylinder core, the lock cylinder would have a different magnet code which cannot activate the device evaluator.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention pertains to a device wherein in the area of lock cylinders, both mechanical and electrical components are used, which, when a key is used to operate the lock, activate or deactivate electrical functions by way of the electrical switching device. The lock cylinder consists of a stationary cylinder housing with a rotatable cylinder core inside, which can be rotated by a properly fitting key. The mechanical components comprise a key channel which accepts the key, tumblers in the cylinder core, and a locking channel for the tumblers in the cylinder housing. The electrical components include at least one permanent magnet on the circumference of the cylinder core and a sensor in the cylinder housing, which, when the key is used to operate the cylinder core, responds to the permanent magnet. The sensor is connected to an evaluator, which activates the electrical switching device when the key operates the lock. The lock cylinder of a device such as this is preferably installed as a steering lock in the area of the steering column of a motor vehicle, and the electrical switching device contains the electronics of the engine. Devices of this type are used to protect the motor vehicle against theft. The device is then referred to as an “electronic device for preventing a vehicle from being driven away”. 
     2. Description of the Related Art 
     A device such as this is known from U.S. Pat. No. 5,186,031. In this device, the vehicle is protected from theft even after the thief has pulled the cylinder core of the lock cylinder axially out of the cylinder housing in order to manipulate the interior of the cylinder housing. In this known device, the cylinder core has a radially spring-loaded retaining element, which, when the cylinder core is installed, snaps behind a shoulder on the housing. It is thus easy to install the cylinder core axially in the cylinder housing. When the cylinder core is torn out axially by the thief, the retaining element destroys the electrical connections of the sensor in the cylinder housing and thus makes the device inoperable. This anti-theft protection fails, however, when it is possible to use a break-in tool to move the spring-loaded retaining element into its release position with respect to the cylinder housing. In the case of devices in which the cylinder core is not connected to the cylinder housing by means of a snap-in attachment such as this, however, no anti-theft protection is present at all. The reason for this is as follows. 
     The anti-theft protection of vehicles equipped with these types of lock cylinders consists in that there are a large number of different lock cylinders, each of which has a different set of tumblers in the cylinder core. The cylinder core can thus be rotated only by a certain key which fits this cylinder core. Whereas the cylinder housing has a uniform design, there are many different keys, and each key fits only the corresponding, individual arrangement of tumblers in the cylinder core. To break open a lock equipped with a lock cylinder for which the proper key is not available, it is sufficient for the thief to tear out the cylinder core and replace it with a new cylinder core, for which he has the proper key. It makes no difference to the cylinder housing that the original cylinder core has been replaced by a new one for which the thief has the proper key. This theft strategy also functions in the case of the known device in which the cylinder core has a permanent magnet and the cylinder housing has a sensor, because the new cylinder core bought with the key also has a permanent magnet, which is then able to perform the same functions in the interior of the cylinder housing as the permanent magnet of the torn-out cylinder core. The known device thus does not offer adequate protection. 
     SUMMARY OF THE INVENTION 
     The invention is based on the task of developing a reliable device of the aforementioned kind, which is characterized by a high level of protection against manipulations of the lock cylinder by unauthorized persons. This is accomplished according to the invention by means of the following features: 
     a group of different cylinder cores is assigned to the cylinder housing with a sensor in a predetermined, fixed location; 
     where, although the cores have the same tumblers and can be actuated by the same key, they differ from each other magnetically with respect to one at least one of the permanent magnets; 
     in that, for each application of the device, one cylinder core is selected from this group and paired with the cylinder housing to form a magnet-specific lock cylinder; 
     which, because of the selected cylinder core, forms a lock cylinder with a specific magnetic code; 
     in that the sensor detects the magnetic differences in the magnetic code upon operation of the cylinder core by the key; 
     in that the evaluator can be set or programmed for the specific magnetic code of the lock cylinder used in the device; and 
     in that, after this setting or programming, the evaluator will respond by actuating the switching device upon operation of the key only when the selected cylinder core upon which the magnetic code is based is in the lock cylinder. 
     The invention introduces a new variant of a lock cylinder for the known device. What is available now is a family of cylinder cores which differ from each other not only with respect to the arrangements of their tumblers, these cores requiring different keys, of course, but still being capable of working together with the same cylinder housing, but also with respect to their magnetic properties, which still allows them to be installed in the same cylinder housing. According to the invention, therefore, there are lock cylinders with identical housings which differ not only mechanically from each other on the basis of their key code but also electrically as a result of a “magnetic code”. When, in the case of the device according to the invention, a thief tears out the cylinder core with its permanent magnet and replaces it with a new cylinder core also having a permanent magnet, he cannot circumvent the device according to the invention even though he has the right key. Because of the differences according to the invention between the permanent magnets of the various cylinder cores, the new lock cylinder assembled in this way will usually have a different magnetic code. This is detected by the sensor, which therefore will not actuate the evaluator when the key is used to operate the newly installed cylinder core. The evaluator in the invention is still set or programmed for the old code. The replacement of the cylinder core does not benefit the thief in any way when the device according to the invention is present; the sensor is able to tell that the cylinder core is “wrong”. The electrical switching device is therefore not activated, and the attempted theft fails. 
     If it is possible not only to use the same number of permanent magnets but also to mount them at the same point on the individual cylinder cores, the device will be especially simple in its design and also inexpensive to manufacture, provided that the cylinder cores to be installed in a standard cylinder housing can still be made magnetically different from each other. In turns out that, to make them magnetically different from each other, it is sufficient to vary their field direction. This can be easily done at the time the permanent magnets are installed in the individual cylinders. Permanent magnets with a specific orientation of their north pole-south pole axis are used, and sensors which are able to detect the orientation of the magnetic field are provided. The number of different magnetic codes available depends only on the accuracy with which these sensors can distinguish between different magnetic field orientations. The selected rotational position of the permanent magnet at the time it is installed in the cylinder core determines the magnetic code. This is very easy to accomplish. As a result, the devices according to the invention can be manufactured at very low cost. In addition, the sensor is able to determine the orientation of a magnetic field with a surprisingly high degree of accuracy, and it is thus possible to differentiate a large number of magnetic codes effectively and reliably. 
     It is also advantageous to incorporate a locking bar such as that already familiar from the state of the art into the cylinder core of the device according to the invention by designing the locking bar itself as a permanent magnet. This bar thus no longer serves to provide only mechanical protection. The advantages which result from this measure are described further below. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     Additional measures can be derived from the drawings, and the following text. The invention is directed to all of the new features and combinations of features which can be derived from the claims, drawings, and text, even if they are not stated explicitly in the claims. An exemplary embodiment of the invention is illustrated schematically in the drawings: 
     FIG. 1 shows a cross section through a lock cylinder of the device according to the invention along line I—I of FIG. 2; 
     FIG. 2 shows a plan view of an axial section of the lock cylinder in the viewing direction of arrow II of FIG. 1 in a partial, longitudinal cross section; 
     FIG. 3 shows a functional block diagram of the basic design of the evaluator according to the invention, which is connected to the sensor; and 
     FIG. 4 shows a performance diagram of the sequence of magnetic field changes detected by the sensor and the resulting voltage input values sent to the evaluator when the key is inserted and the cylinder core is turned. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Only the most essential parts of the device are shown in the drawings and are to be supplemented by additional standard components. A lock cylinder  10  is shown, which has a cylinder housing  11 . The housing is installed permanently in, for example, a motor vehicle in the area of the steering column lock. The housing can be designed as a sleeve, the interior of which serves to hold the cylinder core  12 , which is able to turn in the housing. Cylinder core  12  is the other part of lock cylinder  10 , and it has a key channel  13  for a key  20 . In addition, a family of tumblers  14  is integrated into cylinder core  12 , these tumblers being pushed by springs toward key channel  13 . This is illustrated by a force arrow  15  in FIG.  1 . The elastic force proceeds from springs  16 , indicated schematically. As long as key  20  is absent, tumblers  14  project into a locking channel  53  in cylinder housing  11 . Key  20  has a suitable adjusting means  21 , e.g., cutaway areas which create a certain profile. When the key is inserted, these means cooperate with complementary control surfaces  17  of the various tumblers  14 . Thus tumblers  14  are disengaged from locking channel  53 , as shown in FIG.  1 . 
     A locking bar  31 , which is able to move essentially in the radial direction, is provided in an axial recess in cylinder core  12 . This bar is spring-loaded, as illustrated by force arrow  33  in FIG.  1 . Spring loading  33  tries to the keep locking bar in its extended, lowered position shown in FIG. 1, but normally it is prevented from doing this by tumblers  14 . If, for example, a properly fitting key  20  has not been fully inserted in key channel  13 , tumblers  14  will assume a disordered configuration in cylinder core  12  because of their spring loading  15 , and the inner end of locking bar  31  will be held back at various points along the longitudinal edges  18  of individual tumblers  14 . As a result, the outer area of the locking bar projects radially beyond the circumference  19  of the cylinder, thus assuming position  31 ′ illustrated in dash-dot line in FIG.  1 . In this dash-dot position  31 ′, the locking bar engages in a groove  22  in housing  11  and thus prevents the cylinder from turning, as illustrated by rotation arrow  23  in FIG.  1 . Thus dash-dot position  31 ′ of the bar represents its “locking position”. 
     But when a properly fitting key  20  is inserted fully into cylinder core  12 , the various tumblers  14  are then positioned in the interior of the cylinder core  12  by key faces  21  in such a way that lateral recesses  24  provided in the sides of the tumblers are all aligned with the inner edge of locking bar  31 . In this situation, therefore, spring loading  33  can move the locking bar into aligned lateral recesses  24 , the bar thus assumes its lowered, pulled-out position  31  shown in FIG. 1, in which its outer edge no longer projects beyond the circumference  19  of the cylinder. In this pulled-out position  31 , therefore, locking bar  31  is no longer engaged in housing groove  22 , for which reason this position  31  of the bar turns out to be its “release position”. Now cylinder core  12  can be turned by inserted key  20  in the direction of arrow  23 . Turning stops (not shown) prevent cylinder core  12  from being turned in a direction opposite that of rotation arrow  23 . 
     In addition, pulse springs (not shown) or the like ensure that cylinder core  12  is always held in the starting rotational position as shown in FIG. 1 until key rotation  23  occurs. In this starting rotational position, the outer edge of the locking bar, which is normally in locking position  31 ′, is aligned with a sensor  35 , which responds to magnetic fields, this sensor being installed in cylinder housing  11 . 
     This sensor can consist of a Hall-efffect device. It is recommended, however, that a so-called magneto-resistive element be used, which also responds to changes in direction of the magnetic field. This is described in greater detail below. Sensor  35  is lodged in an opening in housing  11  and is located in the space above housing groove  22 , which cooperates in creating locking position  31 ′. In the present case, locking bar  31  is itself a permanent magnet. As an alternative, it would be possible for locking bar  31  to be made of a ferromagnetic material, which is acted upon by the magnetic field of a permanent magnet located at some other point in the cylinder core, as a result of which the bar itself can act as a magnet. As FIG. 2 shows, the axis of locking bar  31  is parallel to the axis of cylinder  12 . 
     If it is desired to do without the monitoring function, described in greater detail below, which occurs when key  20  is inserted, it is also possible for locking bar  31  in a modification of the exemplary embodiment to be nonmagnetic. Thus, at least one additional permanent magnet  32  is provided in cylinder core  12 , but this one, in contrast to magnetic locking bar  31 , remains stationary on cylinder core  12 . 
     In FIGS. 1 and 2, permanent magnet  32 , shown shaded with dots, is located at a certain point on the circumference of cylinder core  12 , which is offset with respect to locking bar  31 . The orientation of the magnetic field of permanent magnet  32  is defined by its north pole N and its south pole S and is indicated by an arrow  30  in FIG.  2 . Permanent magnet  32  is mounted in a hole  52  let into circumferential surface  19  of cylinder core  12 . As suggested with dots, permanent magnet  32  could also be mounted in the same hole in cylinder core  12  so that its magnetic field assumes various other orientations  30 ′,  30 ″, etc., illustrated in dotted line. Sensor  35  is in a position where it can detect the orientation of the magnetic field, which will be explained in greater detail on the basis of FIG.  4 . 
     Sensor  32 , however, can also determine the field strength of a permanent magnet  32 . As an alternative to the exemplary embodiment of FIGS. 1 and 2, it would therefore be possible to provide a bar of magnetizable material instead of permanent magnet  32 . As in the case of locking bar  31  described above, this bar is acted upon by a magnet mounted a certain distance away in cylinder core  12 . Like object  32  of the exemplary embodiment, this bar is mounted in a stationary manner in cylinder core  12 ; it therefore represents a fixed bar. In this alternative embodiment, differences in the magnetic behavior of a fixed bar such as this can be easily produced by varying its axial position, which is determined by sensor  35  when cylinder core  12  is subjected to rotation  23 . 
     Distinctions between permanent magnets  32  as described above can therefore be achieved by changing their magnetic field strength instead of by changing the orientation of their magnetic fields. These changes, too, can be detected by sensor  35 . Another method of creating differences between them could be to mount permanent magnet or magnets  32  on different parts of cylinder core  12 , differences which sensor  35  would obviously be able to detect immediately. It would also be possible to provide more than one sensor  35  and to connect these sensors to a common electronic evaluator  40 . 
     An exemplary embodiment of an evaluator  40  is explained in greater detail in FIGS. 3 and 4. Sensor  35  is connected by an electric power line  43 , in which a series resistor  39  is inserted, and by a ground lead  42  to a voltage source (not shown) and has two signal lines  51 ,  51 ′ for sending its measurement values. Sensor  35  can determine the exact orientation  30  of the magnetic field by measuring two field components which are perpendicular to each other, namely, Bx and By, as will be explained in greater detail on the basis of FIG.  4 . An inverter (not shown) can be connected downline from the sensor if desired. Electrical voltages in the form of an analog signal are obtained first. These are converted in an A/D converter  26  to digital signals  36 , which is indicated in FIG.  3 . It would also be possible to use a comparator instead of this converter  26 . Because of the Bx and By measurement of the magnetic field by way of the two signal lines  51 ,  51 ′, two digital signals  36  are obtained in the present case. These signals  36  arrive as “input values” at a computer  27  (microcomputer), which is provided with a memory unit  28 . This connection between  26  and  27  can also consist of a 4-bit or 8-bit parallel connection, as indicated by dashes in FIG.  3 . In addition, sensor  35  is also connected directly by a wake-up line  25  to the microcomputer. 
     Memory  28  is an EEPROM (electrical erasable programmable read-only memory). Computer  27  and memory  28  have a clock  29 . At the output from evaluator  40  [Note  6 ], a corresponding alternating-current signal is obtained, which is smoothed by a filter, illustrated by a resistor  37  and a capacitor  38 . A certain direct-current signal is therefore obtained on line  41  leaving evaluator  40 . In memory  28 , evaluator  40  can be programmed for certain individual digital signals  36  of the two measurement components Bx and By. Evaluator  40  will then respond only when sensor  35  has identified these predetermined signals. Only in this case does evaluator  40  transmit a control signal on output line  41 , which is connected to an electrical switching device (not shown), e.g., the electronics of the engine of a motor vehicle. 
     FIG. 4 illustrates the way in which the device according to the invention operates. Time is shown on the horizontal axis, and the values of the magnetic field strength Bx and By determined on-site by sensor  35  and also the voltage signals  36  obtained in evaluator  40  are shown on the vertical axis. Because of the two measurement components Bx and By, two voltages Ux and Uy, which are illustrated in FIG. 4 by lines of different thickness, are obtained in the present case in the evaluator. These are processed by computer  27  in the following way. 
     Initial segments  44 ,  44 ′ of the two curves Ux, Uy shown in dashed line in FIG. 4 represent the original state of the device according to the invention, i.e., before the insertion of key  20 . In the original rotational position of FIG. 1, sensor  35  detects the magnetic field generated by the locking bar in locking position  31 ′, but this does not lead to the activation of evaluator  40 . Sensor  35 , as indicated by dash-dot lines in the cross-sectional view of FIG. 2, is at the point in cylinder housing  11  where locking bar  31  is located when cylinder core  12  is in its starting position. In this case, evaluator  40  is in an off or stand-by position. The motor vehicle equipped with the device according to the invention on the steering column lock is at a standstill. This changes, however, as soon as a properly fitting key  20  is inserted in cylinder core  12 . 
     When the motor vehicle is to be started, key  20  must, of course, first be inserted into cylinder core  12 . This happens at time t 1  of the performance diagram of FIG.  4 . As a result of the previously mentioned drop of the locking bar from its locking position  31 ′ of FIG. 1 into its release position  31 , the magnetic field detected by sensor  35  also decreases. This is illustrated in FIG. 4 by vertical curve segments  45 ,  45 ′ for Ux and Uy. The evaluator  40  awakens only when change  45 ,  45 ′ is within certain limiting values, which are programmed into memory unit  28 . For this purpose, the previously mentioned wake-up line  25  is used, which connects sensor  35  directly to computer  27 . A magnetic field change at  45 ,  45 ′ lying outside these limiting values is not noticed by evaluator  40 . If the rotation of key  20  does not begin immediately, more-or-less long horizontal curve segments  46 ,  46 ′ for Ux and Uy follow. 
     Starting at time t 2  in FIG. 4, cylinder core  12  is turned in direction  23 . Magnetic locking bar  31  thus first moves away from sensor  35 , for which reason the two curves have falling, curved segments  47 ,  47 ′. Then, however, permanent magnet  32  comes increasingly into the measuring range of sensor  35 , which has the effect of making the two curves rise again at  48 ,  48 ′. When permanent magnet  32  reaches its closest position, the two curves Ux and Uy reach their corresponding maxima  50 ,  50 ′. This happens, according to FIG. 4, at time t 3 . Then, as cylinder core  12  continues to turn in direction  23 , the curves again have falling segments  49 ,  49 ′, because permanent magnet  32  is now moving farther away from sensor  35 . 
     The criterion for the activation of evaluator  40  can be the difference ΔU, which is the difference between the two curves Ux and Uy at or near the two maxima  50 ,  50 ′, for example. If a different cylinder core  12  is inserted into cylinder housing  11 , the magnetic field orientation  30  of which is different, e.g., with orientation  30 ′ or  30 ″ of FIG. 2, from that of the magnetic field of permanent magnet  32  located at the same point, then the heights of the two maxima  50 ,  50 ′ of FIG. 4 are changed to different values upon turning the key in direction  23 . This has the result of producing a different voltage difference ΔU. Memory unit  28  in evaluator  40 , however, is programmed for certain values of ΔU, for which reason, when cylinder cores  12  are exchanged, evaluator  40  is no longer activated. As a result, therefore, it is no longer possible to steal the motor vehicle. In addition to the mechanical coding between key  20  and cylinder core  12  in conjunction with locking bar  31 , there is also, according to the invention, a magnetic coding. This magnetic code is determined in the exemplary embodiment by orientation  30 ,  30 ′, or  30 ″, etc., of the magnetic field of only a single permanent magnet  32 , located at the same point on the cylinder core  12 . Through the combination of a large number of such magnetically different cylinder cores  12  with a cylinder housing  11  of the same type, a correspondingly large number of lock cylinders  10  with different magnetic codes is obtained. 
     As already mentioned, locking bar  31  itself is designed as a permanent magnet in the exemplary embodiment, which can also be used to differentiate one magnetic code from another. The lengths of vertical curve segments  45 ,  45 ′ which result when key  20  is inserted into cylinder core  12 , or the difference between them, can be stored in memory unit  28  of evaluator  40 . This itself can be used to turn on evaluator  40  as previously described. Specific magnetic codes can thus be obtained simply by providing the various locking bars  31  in a group of cylinder cores  12 , which can be combined with a standard cylinder housing  11 , with different magnetic properties. This magnetic code of locking bar  31  can be combined with the additional magnetic code resulting from the use of permanent magnet or magnets  32 . As a result, a correspondingly large number of lock cylinders  10  which differ from each other magnetically is obtained.