Locking system for motor vehicles detecting approach of the user

The present invention relates to a motor vehicle equipped with a system for detecting the approach of a user.

Such detection systems are already used in certain motor vehicles to automatically trigger the unlocking of a door lock or an authorization to open the door, as soon as the user approaches, without the latter needing to use a key or remote control. To perform this automatic unlocking before opening the door, a system generally called "hands-free access system" is used, which system consists in activating a remote exchange of information between an identifier on the vehicle and an identifier carried by the 'user. When the identifier has been recognized as correct by the identifier, the lock will be unlocked, thus allowing the user to open the door by simply pulling on the door pallet.

However, it is not possible to leave the identifier and / or the identifier constantly activated since their electrical consumption is too high. On the other hand, the identifier and the identifier must be able to be activated at all times because the approach of the vehicle by the user is unpredictable. Therefore, it has already been proposed to use an approach detection system or pallet entry by the user, to activate the vehicle identifier only when the user is preparing to open the door.

It has thus been proposed to equip the door pallets with an electrical contactor for detecting the start of the actuating stroke of the pallet for opening the door. However, this solution has the disadvantage of carrying out a detection of the user approach that is too late, since the time necessary for the identifier to correctly recognize the identifier of the user and to order unlocking of the lock is generally much longer than the time required for the user to complete the pallet actuation stroke. In other words, the door is generally not yet unlocked when the user has completed the actuating stroke of the pallet and it is sometimes necessary for him to actuate the pallet several times before obtaining the opening of the door.

It is also known to use optical or ultrasonic detection systems, but their cost is generally too high.

The document <patcit id="pcit0001" dnum="EP0735219A"><text>EP-A-0735219</text></patcit> describes a system for detecting the approach of the user in order to activate the on-board interrogation device, using an antenna connected to a Doppler type, volumetric, or infrared sensor.

The document <patcit id="pcit0002" dnum="DE19617038"><text>FROM n ° 196 17 038</text></patcit> describes a motor vehicle comprising a first electrode integrated into a door handle, a second electrode on the surface of the door, a capacitive sensor integrated into the door handle, the capacitive sensor being connected by an electrical connection to the unit centralized control, a voltage of opposite poles being applied to the two electrodes and, to produce an electric field, between the handle and the door, the insertion of the user's hand between the two electrodes modifying the electric field, this modification being measured by the capacitive detector which can thus trigger the interrogation with a view to identifying the user. However, such a system requires detecting a change in the electric field generated between two electrodes, and inserting the hand between the two electrodes, which delays detection.

In addition, all currently known solutions require additional electrical connections between the pallet and another element of the door.

The object of the invention is to eliminate the aforementioned drawbacks and to propose a motor vehicle equipped with a new approach detection system for a user, allowing detection, which is anticipated with respect to that of a contactor of pallet and whose cost price is lower than that of an optical or ultrasonic detector, without requiring connection by connectors or additional electrical harness with the pallet.

To this end, the subject of the invention is a motor vehicle equipped with a system for detecting the approach of a user, as defined in claim 1.

This detection of variation in capacity could be processed by an electronic module, for example, previously integrated in the lock of a vehicle door, to control various functions, such as unlocking the door lock, as well as transferring the information on the state of a lock to other locks.

According to the invention, the aforementioned surface forms part of an opening pallet of a vehicle opening, for example, a door, a fuel door, a trunk, said pallet being connected to a door lock by a mechanical link which is electrically conductive and isolated from the mass of the vehicle to serve as an electrical connection between - said surface and the aforementioned generator. In this case, the aforementioned dipole is formed, on the one hand, by the mass of the vehicle and, on the other hand, by the whole of said surface and the mechanical connection, which can be constituted, for example, by sheathed cable or a control rod actuating a lever for opening the door lock.

According to the invention, the detector is arranged to activate an identifier on the vehicle, which identifier, firstly, checks, when activated, if the user has an authorized identifier and, secondly, if the verification shows that the identifier is recognized as correct, ordered at least one function of the vehicle, for example unlocking of a door lock.

The threshold value Cs is advantageously obtained by the following formula:<maths id="math0001" num=""><math display="block"><mi>Cs</mi><mo>=</mo><mfrac><mrow><mi>Cmin</mi><mo>+</mo><mi>at Cmax</mi></mrow><mrow><mn>1</mn><mo>+</mo><mi mathvariant="normal">at</mi></mrow></mfrac></math><img file="EP0918309B2_D0001.tif" /></maths> a being a dimensionless coefficient between 0 and 1.

In a particular embodiment, the device comprises a system for performing automatic recalibration of the above-mentioned threshold value. For example, when the detected capacity value remains stably greater than the threshold value Cs for a predetermined period, for example of the order of 30 s, the minimum capacity value Cmin then takes this new capacity value detected. Conversely, when the detected capacity value remains stably lower than the minimum capacity value Cmin for a predetermined duration, for example, of the order of 2 s, Cmin then takes this new detected capacity value. In the case of automatic recalibration, when the minimum capacity value Cmin is modified, the maximum capacity value Cmax is also modified so as to keep the ratio Cmax / Cmin constant.

According to yet another characteristic of the invention, the device comprises a system for performing a series of elementary capacitance detections, each corresponding to different generated frequencies, said elementary capacitance values ​​detected from the same series then being averaged, by removing possibly the discordant values, said mean value then being compared with the predetermined threshold value Cs to activate, if necessary, the identifier. If all the frequencies generated in the same series result in discordant elementary detections, the system is arranged not to activate the identifier, in order to maintain the security of locking.

In an advantageous embodiment, the detector is arranged to detect the imaginary part alone of the admittance of the dipole for a fixed frequency delivered by a stable oscillator serving as a generator of high frequency waves, in order to make the detection insensitive to the presence more or less conductive liquid, for example, salt water in contact with the pallet. In this case, one can even envisage a correct functioning of the system in total immersion of the pallet.

Advantageously, an inductance can be provided in parallel to the equivalent impedance of the dipole and determined to eliminate from the value of the detected capacity, the value of the residual capacity of the dipole in the absence of the user.

According to yet another characteristic, the metal surface can be covered with an insulating overmold to protect it from external aggressions.

Of course, we could also alternatively measure the capacity of the dipole according to other methods: for example, by inserting the capacitor in an oscillator circuit whose frequency is measured, by measuring the impulse response of the capacitor to an emission of pulses. high frequency, or by measuring the module of the capacitor admittance for a fixed frequency delivered by a stable oscillator.

The stable frequency generator can be obtained from a signal linked to the clock of a microcontroller or from the microcontroller itself, this microcontroller possibly being part of an electronic module integrated into the lock.

To better understand the object of the invention, there will now be described by way of purely illustrative and nonlimiting example, an embodiment shown in the accompanying drawing.

On this drawing :<ul id="ul0001" list-style="dash" compact="compact"><li>the <figref idref="f0001">figure 1</figref> is a functional block diagram of a motor vehicle according to the invention;</li><li>the <figref idref="f0001">figure 2</figref> is a schematic view of a door of a vehicle according to the invention;</li><li>the <figref idref="f0002">figure 3</figref> is a block diagram of the detection system of a vehicle according to the invention;</li><li>the <figref idref="f0002">figure 4</figref> is an electrical diagram illustrating in more detail the detection system of a vehicle according to the invention;</li><li>the <figref idref="f0001">figure 5</figref> represents the simplified electrical diagram of a variant of the <figref idref="f0002">figure 3</figref>.</li></ul>

According to the embodiment shown in the drawing, it has been indicated by broken lines on the <figref idref="f0001">figure 1</figref>, a door 1 of a motor vehicle which comprises a detector 2, an identifier 3 and a lock 4. The detector 2 is intended to detect the approach of a user 5 of the door 1, as indicated by the arrow 6. When the user 5 will have been detected close enough to door 1, detector 2 will send a signal via a line 7 to identifier 3 to activate it. When the identifier 3 is activated, it exchanges information signals with an identifier carried by the user 5, as represented by the two opposing arrows 8, 9. As soon as the identifier 3 recognizes the identifier of the user 5 as correct, it sends a control signal via line 10 to lock 4 to cause it to be unlocked. The detector 2 will have been arranged so as to detect the approach of the user 5 sufficiently early to allow unlocking of the lock 4 before the user 5 actuates this same lock 4 by a pallet to open the door 1, according to an action indicated by arrow 11.

However, if the unlocking has not been completed by the time the user finishes lifting the pallet, provision may also be made for using a lock making double action on the door handle unnecessary, for example the lock described in the request for <patcit id="pcit0003" dnum="FR2767348"><text>French patent n ° FR2767348</text></patcit>. In this case, the door will be opened at the same time as it is unlocked.

To open the door 1, the user 5 must grasp a door opening pallet 12 and exert a tensile force on it to cause the opening of the lock 4, by means of a sheathed cable 13 or a control rod connecting the pallet 12 to an opening lever 14 linked to the lock 4. As visible on the <figref idref="f0001">figure 2</figref>, the pallet 12 comprises a metal surface portion 15, which is electrically connected to the detector 2 via the cable 13 and the lever 14 which are electrically conductive and isolated from the mass of the vehicle. The surface portion 15 can also be covered with an overmolding to protect it from external aggressions. As a variant, the whole of the pallet 12 can constitute said metallic surface. By using the mechanical connection 13 between the pallet 12 and the detection module 2, additional connection is avoided in the door.

Referring now to the <figref idref="f0002">figure 3</figref>, it can be seen that this surface 15 is supplied with current by a high-frequency wave generator 16, which generator 16 may already be present in an electronic module M integrated into the lock 4. Under these conditions, the torque formed by, d on the one hand, the vehicle V which is grounded, and on the other hand, the whole of the surface 15 and of the cable 13, defines a radiating dipole whose equivalent impedance Z₁ is represented on the <figref idref="f0002">figure 3</figref>. This impedance Z₁ is generally constant and made up of a low capacity C₁ resulting from the residual capacity of the cable 13 and a parallel conductance g₁, whose value represents the resistive leaks between the assembly (pallet-cable-lock) and the mass of the vehicle, this conductance being able to vary according to untimely leaks to the mass, for example, in the presence of water in the door. The dipole admittance value should be minimized to limit the radiation effect around the vehicle. In other words, this dipole is determined so that it behaves like an antenna which is not tuned and undersized with respect to the wavelength emitted by the generator 16. The dipole also comprises in parallel a capacitor C with variable capacity which is defined between the aforementioned surface 15 and the hand of the user 5. This variable capacitance C increases as the hand approaches surface 15. When the user's hand comes into contact with the surface 15, the capacity becoming infinite, the capacitor C disappears and the user then acts as a radiating strand of antenna, which has the effect of lengthening the antenna and to transmit more high-frequency waves. On the other hand, if an insulating overmolding is provided on the surface 15, there can never be direct contact between the surface 15 and the hand of the user 5. The aforementioned dipole further comprises, in series with the capacitor C, an impedance Z₂ equivalent to the user / mass pair, this impedance Z₂ being generally weak compared to C and consisting of a capacitor C₂ in parallel to a conductance g₂.

We will now refer to the <figref idref="f0002">figure 4</figref>, which represents an electronic circuit to measure the imaginary part alone of the admittance of the dipole. Measuring the imaginary part of the admittance alone has the advantage of only detecting the capacitive part of the dipole and avoiding the value of the resistance of the dipole, which resistance can vary in the presence of liquid more or less conductor and therefore may distort the measurement to be made. As the frequency used is constant, we can model the radiating dipole by the simplified equivalent electrical diagram referenced Z. On the <figref idref="f0002">figure 4</figref>, we see that the equivalent impedance Z of the dipole has a conductance g equivalent to the set of conductances g₁ and g₂ and, in parallel, a variable capacity C 'equivalent to all of the capacities C₁, VS₂ and C of the <figref idref="f0002">figure 3</figref>.

The generator 16 is a stable oscillator delivering a sinusoidal signal of voltage U (t), with U (t) = Ucos (2πf₀.t). This voltage signal generates in the dipole Z a current, which is converted into a voltage U₂(t) by an amplifier A1 connected to the terminals of a resistor R_m, R_m being connected on the one hand, to the generator 16 and on the other hand, to the dipole Z.

The voltage U (t) is also applied to the positive input of a comparator A₀ whose negative input is at the mean value of the signal, therefore at zero, thanks to the capacitor 25, which connects said negative input to ground, a resistor 26 being, moreover, disposed between the two inputs of comparator A₀. This comparator A₀ detects the zero crossings of the voltage U (t) and emits a slot at each of these passages. A monostable flip-flop T detects the rising or falling edges of the output signal from A₀ as the case may be, and generates pulses sent to a capture circuit Cp. These pulses control an electronic switch I which receives the output signal U₂(t) of operational amplifier A₁. A capture of the voltage U is thus carried out by sampling / blocking.₂(t) and a voltage is obtained which provides via an operational amplifier A₂, a usable output U_S which allows to obtain the instantaneous captured value of the current i (to) at the instant t_O such that U (t_O) = 0. We have (to) = 2.π.fo.C'.U, where C 'is the capacitance of the equivalent capacitor, U the peak amplitude of U (t) and f₀ the frequency of U (t); the current value i (to) is independent of the conductance g.

The electronic circuit of the <figref idref="f0002">figure 4</figref> and its operation for obtaining the imaginary part alone of the admittance of the dipole Z will not be described here in more detail and reference will be made, to this effect, to the request of <patcit id="pcit0004" dnum="FR2768508"><text>French patent n ° FR2768508</text></patcit> on behalf of the plaintiff.

As a variant, instead of capturing the instantaneous value of the current when the voltage signal passes through 0, one could measure the phase shift between the voltage and the current as well as the amplitude of the current, to obtain the value of the desired capacity independently of resistance, although in this case a calculation unit is necessary.

The interest of the <figref idref="f0002">figure 4</figref> is that it can be used in conjunction with the microcontroller present in the electronic module integrated into the door lock, by simply using a current acquisition interface.

Furthermore, a high frequency signal can be generated outside and come to be superimposed on the measurement signals detected for different reasons, for example, by antenna effect, parasitic capacitive coupling, induction, etc. It can result amplitude and phase beats on the measured current, as well as random errors on current measurements, for high frequency disturbances modulated by the generator. Of course, the measurements carried out are not sensitive to untimely phenomena known as “high frequency envelope detection” present in non-modulated disturbances because here the measurement does not take account of the continuous components.

To overcome measurement errors caused by a radiated field type disturbance, it is possible to carry out a series of n elementary detections, n being a predetermined integer, each detection corresponding to a different frequency fi, with i ranging between 0 and n . From these n measurements, we will take the average value, having previously discarded all measurements having too great a discrepancy with respect to the other measurements. Then this average value will be compared with the threshold capacity value Cs for activating or not the vehicle identifier.

If the totality of the frequencies results in discordant detections, in the case of an extreme disturbance and with very broad spectrum or a deterioration of a part of the system, an average value cannot be obtained, in a reliable way, and the system will be arranged to place itself "by default" in a state maintaining the locking of the lock.

The threshold capacity value Cs is acquired during mounting of the system on the vehicle, by self-learning the minimum capacity values ​​Cmin and maximum Cmax which correspond respectively to a state of non-approach and maximum approach to the surface 15 by the user.

The threshold value Cs will be obtained by the following formula:<maths id="math0002" num=""><math display="block"><mi>Cs</mi><mo>=</mo><mfrac><mrow><mi>Cmin</mi><mo>+</mo><mi mathvariant="normal">α Cmax</mi></mrow><mrow><mn>1</mn><mo>+</mo><mi mathvariant="normal">α</mi></mrow></mfrac><mspace width="1em" /><mi>with</mi><mspace width="1em" /><mn>0</mn><mfenced open="|" close="|"><mi mathvariant="normal">α</mi></mfenced><mo>⁢</mo><mn>1</mn></math><img file="EP0918309B2_D0002.tif" /></maths>

The value of the coefficient α is preferably taken to be less than 1 because the capacitance capacity curve as a function of the distance between the surface and the hand is of the exponential type. Therefore, in order to have a detection of the approach of the hand when the latter is still sufficiently distant from the pallet, to allow unlocking of the lock before the user has completed the actuation stroke of the pallet, it is better to weight the value of the minimum capacity Cmin more than that of the maximum capacity Cmax. For example, the threshold capacity value Cs will be determined so that it corresponds to a distance of approximately 10 cm between the hand and the pallet.

In the case of <figref idref="f0002">figure 3</figref>, Cmin will be equal to C₁ and Cmax will be at most equal to C₂ + C₁. However, if the value of C₁ is too high compared to C₂ to obtain a reliable detection of the variation in capacitance, an additional inductance L can be used in parallel with the impedance Z of the dipole (see <figref idref="f0001">figure 5</figref>) to eliminate detection of C₁. For example, we choose LC₁. (2 π fo)² equivalent to 1 to eliminate C₁ of the value detected by the module M and C 'then becomes a function only of C and C₂, C 'varying between 0 and C₂.

Throughout the life of the system, the automatic recalibration of Cs can be kept operational, to prevent the detection system from being blocked for a prolonged period in a state leading to permanent activation of the identifier, this which could cause the vehicle battery to discharge. For example, if the vehicle is parked close enough to a wall or pole, the detected capacity may increase accordingly and cause the identifier to be activated. Consequently, it can be provided that, if the detected capacity value remains stably greater for a determined period than the threshold value Cs, the minimum capacity value Cmin is replaced by this new value, to shift the value by as much of the threshold capacity Cs and thus deactivate the identifier. Then, when this disturbance is removed, the detected capacity value again becomes less than Cmin, and after a predetermined period of time, the system is arranged to replace Cmin with this new detected value when the latter remains stable during this period. . Thus, the minimum capacity value Cmin returns to its usual reference value after a determined period.

It is also preferable to modify the maximum capacity value Cmax accordingly, so as to maintain the same Cmax / Cmin ratio.

Although the invention has been described in connection with a particular embodiment, it is obvious that it is in no way limited thereto and that it includes all the technical equivalents of the means described as well as their combinations, if these these fall within the scope of the invention defined by the claims.