FR2753155A1 - DRIVING BLOCK DEVICE FOR MOTOR VEHICLE - Google Patents

Abstract

The device comprises a portable coded transmitter (1) of information coded in the form of a modulated oscillation (3), and a fixed coded receiver (2), which receives the modulated oscillation by means of an antenna (7) , analyzes and demodulates it, in order to recover the coded information, which is then compared with an expected setpoint coded information. According to the invention, the receiver (2) comprises: - an adder (4), adding a DC voltage part to the modulated oscillation (3), - a holding element (5) for analyzing the modulated oscillation (3) which sends the analyzed values, to an evaluation unit, and - a generator (22) of pulses, by means of which the element (5) is controlled at such a rate, with regard to its instants d analysis, that each moment of analysis of the modulated oscillation, within each period, is maintained at a constant value.

Description

The present invention relates to a pipe locking device, for

  motor vehicle, by means of which the use of the vehicle is only possible

  demonstrating an authorization.

  In such channel blocking devices (DE 44 30 360 C1, DE 44 38 286 C1 or DE 195 44 722 C1), modulated binary coded information is transmitted from a portable coded transmitter to a coded receiver arranged from

fixed way.

  In the receiver, the oscillation received by an antenna is analyzed and is then demodulated to recover the coded information. Then, the retrieved coded information is compared to a coded setpoint information, expected, stored in memory. In case of coincidence of the two coded information at least in

  to a large extent, a release signal is produced.

  If such a pipe blocking device is used in a motor vehicle, the coded information is then transmitted by means of the inductive coupling of two coils located on the one hand in the coded transmitter and on the other hand in the coded receiver. Since the coded transmitter has no power supply, the energy required for its operation

  is taken from the voltage induced in its coil.

  Thus, due to a poor magnetic coupling factor between the two coils that is due to the embodiment, the encoded receiver must form a field

  magnetic drive to power the encoded transmitter.

  As a result, the encoded receiver coil operates at a voltage of approximately 150 VDC (voltage

peak to peak).

  Although the binary coded information leaves the coded transmitter with a modulation rate of 1 (modulation depth 100%), the voltage read by the coded receiver coil is only a few hundred millivolts (mV) peak-to-peak, since the coupling factor is so bad. This means that the envelope curve of the modulated oscillation, envelope curve which is formed in the coil of the coded receiver, presents, in the different logical levels, differences of amplitude which are only a few hundred millivolts, it is ie an amplitude of

modulation of some 100 mV.

  In order for the modulated oscillation to be processed by conventional digital components, it must be reduced, by division, in the range of approximately 5 to 3 V. Thus, the modulation amplitude is also lowered, by division, by several times, so that there is then a modulation amplitude of only a few millivolts. In any case, such small voltage differences can only be detected

  in a very difficult and imprecise way.

  In other known line blocking devices (DE 44 18 069 Cl or DE 44 22 296 A1), coded signals are transmitted from a portable coded transmitter to a coded receiver located in the motor vehicle. There, the transmitted coded signal is checked with regard to its authorization. If authorized, a pipe lock is triggered. In all known pipe blocking devices, it is essential that the coded signal be picked up correctly, since otherwise the

  Driving blockage can not be triggered.

  It is an object of the invention to provide a conduit lock device in which binary coded information can be picked up in a fast and secure manner.

  in the receiver from a modulated oscillation.

  To this end, the subject of the invention is a driving blocking device for a motor vehicle comprising: a portable coded transmitter, which transmits coded information in the form of a modulated oscillation, and a coded receiver arranged in a manner fixed, which receives the oscillation modulated by means of an antenna, the analysis and the demodule, to recover the coded information, which is then compared to an expected coded setpoint information, characterized in that the coded receiver comprises an adder, by means of which a portion of DC voltage is added to the modulated oscillation; an analysis holding element, which analyzes the modulated oscillation and sends the analyzed, unmodified values to a unit of evaluation, and - a pulse generator, which generates pulses by means of which the analysis holding element is controlled at such a rate, as regards its instants of analysis, that each moment of a analysis of the modulated oscillation, within

  each period is maintained at a constant value.

  Thus, a DC voltage is first applied to the modulated oscillation, so that all oscillation amplitudes are greater than 0 V. Next, the modulated oscillation is analyzed and the analyzed values are sent to a demodulator. An analysis phase element, which is synchronized with the modulated oscillation, produces pulses presenting

  the same period duration as the modulated oscillation.

  The analysis phase element controls the analysis hold element so that the modulated oscillation is always analyzed with the same phase angle at

inside a period.

  The pipe blocking device according to the invention may advantageously also include one or more of the following features: the adder is formed as a locking circuit comprising a series coupling capacitor, which isolates the antenna from the analytic holding member with respect to the direct current, and a latching diode connected to a DC voltage, by means of which the value of the DC voltage portion is set; a damping element, by means of which the modulated oscillation is damped with respect to its amplitude, is arranged before the adder; a low-pass filter, by means of which troublesome parts of the modulated oscillation are filtered, is arranged between the damping element and the adder; the analysis holding element comprises a field effect transistor whose gate is connected to a locking circuit comprising a locking capacitor and a discharge resistor and whose gate is controlled by the pulses of the generator;

pulse.

  Thus, the adder may be embodied as a simple latch circuit which includes a coupling capacitor which is charged and discharged by a latching diode. The modulated oscillation, as received by the antenna, may first be damped by means of a damping element having a relatively small damping factor. In any case, the depreciation should not be set too high, since in the case of

  contrary, the amplitude of modulation is too weak.

  In addition, a low-pass filter can filter out troublesome frequency

modulated oscillation.

  Examples of implementation of the invention are described below in detail with reference to the schematic drawings. FIG. 1 shows a circuit of the access control system according to the invention, in FIGS. 2a to 2d: variations in the time of signals present in the circuit of FIG. 1 and in FIG. : a circuit of an analysis phase element of the access control system according to the invention. In an access control system according to the invention, a portable coded transmitter 1 (FIG. 1) sends a binary coded information, in the form of amplitude-modulated oscillation, to a coded receiver 2 arranged in a fixed manner. The coded receiver 2 receives this modulated oscillation 3 (see FIG. 2a), formats it by means of an adder 4 for further processing, analyzes the oscillation 3 by means of a holding element for analysis 5 and demodulates as well

  the coded information from the oscillation 3.

  The analysis holding element 5 is then controlled in a constant phase rhythmic manner, that is to say controlled in a manner synchronized with the modulated oscillation 3 at a constant analysis instant having an angle of

constant phase.

  In this way, the coded information is retrieved from the modulated oscillation 3. The coded information thus recovered is compared, in a not shown evaluation unit, with an expected coded setpoint information. When the two coded information coincide at least to a large extent, the user is then authorized and a release signal is generated, by means of which a security assembly, such as for example an electronic locking device

  driving or closing device, is controlled.

  The coded generator 1 produces a high frequency carrier oscillation which is modified with respect to

  its amplitude by means of the binary coded information.

  There is thus a modulated oscillation in

  amplitude that has a low level and a high level.

  By means of a not shown coil located in the coded generator 1, the modulated oscillation is transmitted inductively (by means of a magnetic field)

to the coded receiver 2.

  The coded receiver 2 comprises a reception antenna (hereinafter called antenna 7) in the form of a coil. The antenna 7 forms with an oscillation capacitor 8 an oscillating circuit which is oscillated by means of the magnetic field produced by

  the coded transmitter 1 and comprising the modulated oscillation 3.

  As a result, there is in the coded receiver 2 the same modulated oscillation 3 (FIG. 2a). The binary coded information is then contained in the curve

  envelope of modulated oscillation 3.

  In the case of inductive data transmission, peak values of the modulated oscillation 3 are produced in the antenna 7 by an order of magnitude.

  which is in part much larger than 50 VDC.

  The amplitude of modulation, that is to say the difference of the amplitudes at the high level and the low level is relatively small. In the present examples of implementation, the modulation amplitude is in the range of less than 150 mV. The coded receiver 2 must capture and exploit this modulation amplitude of a

  unambiguous manner.

  Once the modulated oscillation 3 received by the antenna 7, it is first lowered, by division, by a factor 2 with respect to its peak value, from about 60 Vdc to about 30 Vdc, by means of a damping element 9 in the form of an ohmic resistor. As a result, the modulation amplitude is also divided by this factor. Although this damping of the modulated oscillation 3 is advantageous for the continuation of the treatment, it must not

  however, not take place unconditionally.

  Indeed, if a damping element 9 is present, the amplitude of modulation must not become too small, since, in the opposite case, there is again the risk that the coded information

  binary is not captured exactly.

  A low-pass filter 10, subsequently connected and in the form of a grounded filtering capacitor, eliminates modulated oscillation 3, by

  filtering, troublesome frequency domains.

  The adder 4 connected thereafter adds a DC voltage portion to the modulated oscillation 3, so that - independently of the DC voltage portion transmitted by the coded transmitter 1 - the modulated oscillation 3 can be better subjected to following the treatment. For this purpose, the adder 4 is advantageously implemented in the form of a locking circuit, as it is known for example by the

television technique.

  The locking circuit is constituted by a coupling capacitor 12 which isolates the antenna 7, with respect to the direct current, from the analysis holding circuit 5 arranged subsequently. A locking diode 13 is arranged next to the ground between the signal path and the ground and, in parallel thereto, a locking resistor 14. This locking circuit makes it possible to raise the DC voltage portion. modulated oscillation 3 by about its maximum amplitude, which means that it is "locked" (fixed), by its lowest value, to about 0 V. Thus, the modulated oscillation 3 is located above the OV line, as shown in FIG. 2b (in this respect, for the sake of clarity, the on-state voltage is not taken into account,

  about 0.7 V, of the latching diode 13).

  If the locking diode 13 is connected, by its anode, not to ground (which is equivalent to OV), but to a bias voltage higher or lower than 0 V, the DC voltage portion of the modulated oscillation 3 can be changed according to this

bias voltage.

  The peak-to-peak value of the modulated oscillation 3 is not modified by the locking circuit and

is worth about 30 VDC.

  Depending on the phase position of the analysis instants, it is possible to analyze small analysis values as well as large analysis values. If such an oscillation is analyzed with an analysis element having a fixed working point, the analysis values can then be deformed in an inadmissible manner, since such an analysis element

  involves only a limited area of work.

  Therefore, what is known as a "floating" analysis element is used in accordance with the invention. As an analysis element, in the example of implementation of FIG. 1, a JFET (JFET = Junction Field Effect Transistor = junction or isolated field effect transistor) is used which is connected by its input (drain or source) to the adder 4 and its output (respectively source or drain) to a holding element 16. A locking circuit is also connected to its control input (gate), this locking circuit comprising a The latching capacitor 17 then forms the latching circuit with the gate diode of JFET 15, which is anyway and serves as a diode. locking. Using the locking circuit, the JFET work area

  is automatically adapted to the analysis values.

  The analysis phase element 6 produces, at the rate of the carrier oscillation, intermittent analysis pulses 21 as shown in FIG. 2c. For this purpose, the analysis phase element 6 comprises an oscillating circuit 22 which is controlled by a rectangular signal, as shown in FIG. 2d. Due to the permanent switching on and off of the oscillating circuit 22, there is a high amplitude oscillation, for example here 30 V. The negative half-wave of the oscillation is eliminated by means of a diode 24 which is connected to the oscillating circuit 22. As a result, there are analysis pulses 21 with an amplitude of 30 V and a repetition frequency equal to the carrier frequency of

the modulated oscillation 3.

  These analysis pulses 21 are applied to the gate of the JFET 15, which forces the JFET 15 to transmit, as analysis value at its output, the amplitude of the modulated oscillation 3 which occurs at its input. at the moment of analysis. The locking circuit 17, 18 provided on the grid gives the assurance that the working point is adapted to the analysis value and the result is that the value

  analysis is transmitted without loss to the output.

  Thanks to the locking circuit arranged on the gate, the JFET 15 adapts automatically or "in a floating manner" to the moment analysis value. The difference in voltage between the input analysis value and the amplitude of the analysis pulse 21 is used to charge the locking capacitor 17. When a smaller analysis value is analyzed, the difference is then larger and the lock capacitor 17 is more heavily loaded. If, on the other hand, the analysis value is large, then the difference is small and the locking capacitor 17 is only lightly charged. As a result, no current flows through the gate in the

JFET release 15.

  After each analysis at a determined analysis time, the locking capacitor 17 is discharged by the high resistance resistor 18. The time constant T = R * C of the locking capacitor 17 and the discharge resistor 18 must be chosen to be in the range of the oscillation time of the carrier oscillation. The locking capacitor 17 must therefore be discharged again to some extent at the next analysis time so that, during the following analysis operation - with an optionally modified input voltage, the JFET 15 can be switched on in a safe way in order to be able to

  transmit the analysis value to its output.

  The analysis values are applied to the holding element 16 through a resistor 25. The holding element 16 is designed as a holding capacitor. The analysis value is maintained for a prefixed duration and can then be submitted as a result of the processing. The analysis phase element 6 and the analysis holding element 5 are used so that the modulated oscillation 3 is always analyzed at the same analysis time within the duration of a period. As a result, each instant of analysis depends on the voltage, and this as soon as the analysis pulse 21 has crossed a prefixed threshold value. However, since the modulated oscillation 3 at a time of constant analysis over time is not constant with respect to its

  amplitude and its phase, it must be demodulated.

  The latch capacitor 17 and the discharge resistor 18 form, together with the gate diode of the JFET, a latching circuit which is floatingly tuned to the modulated oscillation 3. The analysis phase element 6 serves the modulated oscillation 3 is always analyzed at the same phase. The latch circuit 17, 18 imposes a transmission of the analysis values substantially one by one from the input to the output. The amplitudes in the two low and high logic states of the modulated oscillation 3 differ only by about 100 mVcc. The analysis holding element 5 does not have an adverse influence on this voltage difference. A final amplifier, not shown, receives, via the analysis holding element, analysis values which differ by approximately 50 mV depending on the coded information and transfers them to the unit. devaluation. With such a difference in voltage, the evaluation unit can clearly make the

  distinction between the low level and the high level.

  Thus, the binary coded information can be retrieved in a fast and safe manner from the oscillation

modulated 3.

  In place of the JFET 15, it is also possible to use an insulated gate FET (MOSFET 26) (see FIG. 3). However, when a MOSFET 26 is used, two diodes 29 must be provided, namely one in parallel with the drain-gate path of the MOSFET 26 and one in parallel with the sourcegrid path. With the locking capacitor 17 and the discharge resistor 18, these two diodes form the locking circuit by means of which the working point of the MOSFET 26 is regulated in a floating manner.

to the analysis values.

  An analysis pulse 21 with a sufficiently large slope and amplitude is necessary for controlling and blocking a field effect transistor. Each analysis pulse 21 is constituted - as already indicated above - by a half wave which is produced by the oscillating circuit 22. Since the gate of the field effect transistor is controlled in a sinusoidal manner, in the case of transistors with a large blocking voltage, this can result in a period of switching on of an unwanted length. The rise of the analysis pulse 21 can become steeper if a variable capacitance diode 27 is connected

  to the oscillating circuit 22 in parallel with the diode 24.

  With the coded receiver 2, it is not only possible to receive data from the coded transmitter 1, but also to send coded data or energy thereto. For this purpose, as the transmitter stage, a suitable generator or modulator can be connected to the antenna 7 via a

  symmetrical amplifier 28 (push-pull) (see Figure 1).

  Data or energy can then be sent via the antenna 7 to the coded generator 1 which then responds with its coded information. However, such a transmitter stage does not affect the analysis of the oscillation received, but it has one against the amplitudes, since these are increased in comparison with the simple operation of emission of

the coded transmitter.

  The modulated oscillation 3 is transmitted by means of a carrier oscillation oscillating at a frequency of about 125 kHz. In a manner corresponding to this frequency, the analysis phase element 6 is controlled by a rectangular signal 23 having a period duration T1 of about 8 bs. The pulse duration t1 of the rectangular signal 23 is about 3 gs. As a result, the analysis phase element 6 allows the generation of analysis pulses 21 having a pulse duration t2 of about 1.9 Us and a period duration.

T2 = T1 also about 8 gs.

  The binary coded information contains user-specific data that is compared in the unit

  from exploitation to information stored in memory.

  When there is coincidence, a release signal is produced. If such an access control system is used in the case of a motor vehicle, the encoded receiver 2 is then placed in the vehicle. The release signal then enables the engine control, fuel supply or ignition current to be activated, as well as to lock or unlock

door locks.

  Likewise, other applications outside a motor vehicle, in which a coded signal is transmitted from a portable coded generator 1 to a coded receiver 2, are also possible. The coded receiver 2 is arranged in a fixed manner in an object to which a user wishes to have access. The user proves his authorization by means of the transmitted coded information. The coded information is exploited in the coded receiver 2. Correspondingly, the access control system can be used for access and authorization to a computer, access to

rooms or closed areas, etc.

  In the present invention, the peak voltage value of the oscillation between the maximum positive amplitude and the negative amplitude is referred to as the peak value.

  maximum if the DC voltage portion is zero.

  As a unit in this respect, the VCC is used. The difference of the amplitudes at the low level and at the high level of the amplitude-modulated oscillation 3 is

  qualified modulation amplitude.

Claims (5)

  A driving blocking device for a motor vehicle, comprising - a portable coded transmitter (1), which transmits coded information in the form of a modulated oscillation (3), and - a coded receiver (2) arranged in a manner fixed, which receives the modulated oscillation by means of an antenna (7), the analysis and the demodule, to recover the coded information, which is then compared with an expected coded setpoint information, characterized in that the coded receiver (2) comprises: - an adder (4), by means of which a DC voltage portion is added to the modulated oscillation (3),   an analysis holding element (5), which analyzes the modulated oscillation (3) and sends the analyzed, unmodified values to an evaluation unit, and - a pulse generator (22), which produces pulses by means of which the analysis holding element (5) is controlled at such a rate, with respect to its analysis instants, that each instant of analysis of the modulated oscillation, within   each period is maintained at a constant value.   Pipe locking device according to Claim 1, characterized in that the adder (4) is constructed as a latching circuit having a series coupling capacitor (12) which isolates the antenna (7). of the analysis holding element (5) with respect to the direct current, and a locking diode (13) connected to a DC voltage, by means of which the value of the voltage portion continuous is fixed.   Conducting device according to Claim 1, characterized in that a damping element (9) by means of which the modulated oscillation (3) is damped in respect of its   amplitude, is arranged before the adder (4).   4. Line locking device according to claim 3, characterized in that a low-pass filter (10), by means of which disturbing parts of the modulated oscillation are filtered, is arranged between   the damping element (9) and the adder (4).   Pipe lock device according to Claim 1, characterized in that the analysis holding element (5) comprises a field effect transistor (15, 26) whose gate is connected to a locking circuit comprising a locking capacitor (17) and a discharge resistor (18) and whose gate is controlled by the pulses of the generator pulses (22).