WO2012048770A1

WO2012048770A1 - Electrode, especially for the construction of a proximity detector

Info

Publication number: WO2012048770A1
Application number: PCT/EP2011/004170
Authority: WO
Inventors: Stephan Baudru; Xavier Hourne; Alain Fontanet
Original assignee: Continental Automotive France; Continental Automotive Gmbh
Priority date: 2010-10-13
Filing date: 2011-08-18
Publication date: 2012-04-19
Also published as: FR2966280A1; FR2966280B1

Abstract

The invention relates to an electrode (300) and to the electrical screen thereof. Such an electrode (300) is used in particular for producing a proximity or contact detector, more particularly in a door handle (120) of a motor vehicle (100). The electrode (300) according to the invention comprises: an insulating support (350) extending mainly along a longitudinal direction (360); a first face (301), called electrode, consisting of a conducting circuit (310) printed on one face of the insulating support (350), said face being able to constitute an electrode; a second face (302), called screen, consisting of a conducting circuit (330) printed on a second face (302) of the insulating support (350), on the opposite side from the first face (301), this second face (302) being capable of constituting an electrical screen for the electrode of the first face (301); the two conducting circuits (310, 330) being printed in the form of a plurality of parallel bands extending along the longitudinal direction (360) and separated from one another by an insulating band (320, 340).

Description

Electrode in particular for constituting a proximity detection sensor

The invention relates to an electrode and its electrical shielding screen. Such an electrode is used in particular for producing a proximity and / or contact detection sensor, more particularly in a door handle of a motor vehicle. The invention is more particularly adapted to the realization of a device for access and passive passive boot or "passive start and entry" in English, in particular for a vehicle.

Figure 1, according to the prior art, a vehicle (100) comprising such a device comprises a cockpit calculator (1 10), commonly referred to by the acronym BCM for "Body Control Module" in English. This computer is connected to electronic components located in particular in the door handles (120). These handles include means for detecting the approach and / or contact of a hand on the door handle (120) and means for emitting an electromagnetic field to a badge (130). Thus, when a person wearing this badge (130), for example the owner of the vehicle, is in an area (140) near the vehicle and his hand approaches and / or comes into contact with the door handle (120). ), in particular when approaching or coming into contact with a specific and determined unlocking zone, this approach and / or this contact is detected and the BCM (1 10) is informed and generates an electromagnetic field by means of an antenna also located in the handle. The badge (130) then detects the emission of the electromagnetic field of the vehicle and transmits a code. The code received by the vehicle is transferred to the BCM (1 0) which confirms the validity of the code and unlocks the doors of the vehicle when the wearer of the badge puts his hand on the door handle (120). This method of unlocking the doors (120) of the vehicle (100) is known from the state of the art. The method of locking the doors (120) of the vehicle (100) operates identically on a specific and determined locking zone.

Figure 2, in a detail view in section relative to the prior art, a door handle (120) of such a vehicle comprises an antenna (221) for transmitting at a specific frequency and activate the badge. It also includes an electrode (223) for detecting the approach and / or contact of a hand on the door handle (120). For security reasons, when the presence of the badge (130) is detected near the vehicle (100) by the antenna (221), the doors thereof are unlocked only if the contact, in this case with a hand is detected by the electrode (223) on the inside of the door handle (120). This detection is generally of the capacitive type. A screen shield (222) prevents detection on the outer face of the handle.

For this device to work, and in particular for the detection of the low-power emission of the antenna (221) is detected and allows activation of the circuit of the badge (130), the antenna transmission frequency spectrum (221) must be perfectly controlled. However, if it is easy to define this spectrum according to the characteristics of the antenna (221), it is modified by the environment of this antenna, in particular by the presence of the electrode (223) and its screen (221). Indeed currents induced by the electrode circulate in the antenna and disrupt its emission. To counteract these effects, one of the solutions of the prior art consists in placing a thick electrically insulating layer between the antenna (221) and the screen (222). However, this solution to the problem is at the expense of compactness, the device then being difficult to integrate into a door handle (120). Alternatively, the transmitting circuit of the antenna (221) can be calibrated once the antenna mounted in the handle. This solution, which preserves the compactness, implies that for each type of vehicle (100), door handle (120), electrode (223) and screen shield (221), the circuit is calibrated differently , even if the antenna (223) is the same. This situation is economically unfavorable, particularly for very large-scale applications such as in the automotive sector.

The invention aims at solving the disadvantages of the prior art by proposing an electrode, in particular for constituting a capacitive proximity sensor, characterized in that it comprises:

An insulating support extending mainly in a longitudinal direction;

A first face, called an electrode, consisting of a conductive circuit printed on one side of the insulating support, said face being able to constitute an electrode;

A second face, called a screen, consisting of a conductive circuit printed on one side of the insulating support opposite to the first, this face being able to constitute an electrical shielding screen for the electrode of the first face;

The two conductive circuits being printed in the form of a plurality of parallel strips extending longitudinally and separated from each other by an insulating strip.

The realization of the electrode and shielding screen by printed circuit technology allows, by the presence of the insulating strips between the conductive strips, to prevent the creation of currents induced by the antenna in the electrode and in the the shielding screen, they can not form any circulation loops except inside the bands themselves; induced currents which, according to the prior art, resulted in a decrease of the electrical characteristics such as the inductance and the resistance of the circuit resignation. Thus, the characteristics of the antenna as it has been designed are retained and the calibration of the transmission circuit is no longer indispensable.

The invention can be implemented according to the advantageous modes described below, which can be considered individually or in any technically operative combination.

Advantageously, the width of the conductive strips is greater than the width of the insulating strips separating them on the electrode face and the width of the conductive strips is less than the width of the insulating strips separating them on the screen face. This characteristic, by increasing the distance between the conducting strips of the part in the immediate vicinity of the antenna and reducing the width of these conductive strips, confines any circulation of induced currents in very narrow bands, the width of which is nevertheless sufficient to create the shield shield of the electrode. On the electrode side, on the first face where a larger conducting surface is required to perform the detection function, the insulating strips nevertheless prevent the creation of induced current circulation loops on the surface of the electrode.

For a device placed in a door handle and an antenna emitting at 125 kHz, which constitutes a standard for this type of application, optimal results are obtained for a width of the conductive strips equal to 1 mm and a width of the insulating strips 0.3 mm on the electrode side and vice versa on the screen side. These dimensions are also easy to respect with printed circuit technology.

The invention also relates to a device for transmitting and detecting proximity, characterized in that it comprises an electrode according to one of the preceding embodiments and an antenna in contact with the screen face of this electrode. Such a device is particularly compact because it does not require the interposition of an insulator between the electrode and the antenna.

This device can be advantageously implemented in a door handle, the electrode being able to detect the contact and / or the approach of a hand on this handle.

Finally, the invention also relates to a vehicle, in particular an automobile, comprising such a door handle. Thus this vehicle can offer a function of access and passive startup competitive in terms of cost.

The invention will now be more specifically described in the context of its preferred embodiments, which are in no way limiting, and FIGS. 1 to 4 in which:

FIG. 1, relating to the prior art, schematically represents a motor vehicle in top view;

FIG. 2, also relating to the prior art, illustrates in plan view and in cutting a door handle comprising an antenna and an electrode for detecting contact with the handle;

FIG. 3 shows a front view of an electrode according to an exemplary embodiment of the invention, FIG. 3A according to the electrode face, FIG. 3B according to the screen face;

And FIG. 4 is a comparative table showing an example of modification of the characteristics of the antenna when it is placed close to an electrode according to the prior art and close to an electrode according to the invention.

3, an electrode 300 according to the invention consists of a "comb" printed circuit on each of its faces, separated by an insulating support (350), extending mainly in a longitudinal direction 360. FIG. the electrode side 301 the conductive strips 310 are separated by insulating strips 320 narrower than the conductive strips, these strips are oriented in the longitudinal direction 360 of the electrode 300. The conductive strips 310 are connected to one of their ends 31 1 to an electronic circuit. At their other end 312, they are disjoint and separated by an insulating strip 320. According to an advantageous embodiment, the conductive strips 310 have a width of 1 mm and are separated by insulating strips 320 of 0.3 mm. Thus the electrode side face 301 behaves vis-à-vis the technical function of contact detection as an electrode whose conductive surface covers the entire surface of this face. In contrast, the conductive strips 310 being disjoint at one of their ends 312, this discontinuity prevents the creation of induced currents on the entire surface of the electrode 301.

3B, on the shielding screen side 302, the conductive strips 330 are of smaller width than the insulating strips 340 separating them. According to an advantageous embodiment, the conductive strips 330 have a width of 0.3 mm and the insulating strips 340 a width of 1 mm. The conductive strips 330 are connected to ground at one of their ends 31 1 'and are disjoint, separated by insulating strips 340 at their other end 312'. The conductive surface on this face 302 is sufficient to ensure the shielding screen technical function vis-à-vis the electrode side face 301, but the discontinuities between the conductive strips 330 at their end 312 'prevent the creation of induced currents on the surface of this face.

4, the array 400 gives the value of the inductance 41 1 (Ls) and the resistor 412 (Rs) of a sinusoidal antenna set at a supply voltage of 1 volt peak at 125 kHz.

Column 421 gives the nominal values of the antenna in micro-Henry (μΗ) for the inductance and in Ohms for the resistance. Column 422 gives the values modified inductance 41 1 and resistance 412 when the antenna 221 is placed on an electrode 300 according to the prior art, consisting of a continuous surface copper plate. Column 423 shows the modification of the nominal values (411 and 412) when this antenna 221 is placed in contact with the electrode 301 with an electrode according to an exemplary embodiment of the invention, and the column 424 gives the modified characteristic values 411 and 412. when the antenna 221 is placed in contact with an electrode 300 according to the invention shielding screen side 302.

The above description clearly illustrates that by its different features and advantages, the present invention achieves the objectives it intended. In particular, the electrode according to the invention has very little influence on the characteristics of the antenna and eliminates the need for calibration of the power supply circuit thereof.

Claims

A capacitive proximity transmission and detection device comprising an electrode (300) and an antenna (221), said device being characterized in that the antenna (221) comprises:

An insulating support (350) extending mainly in a longitudinal direction (360);

A first face (301), called an electrode, consisting of a conductive circuit (310) printed on one side of the insulating support (350), said face being able to constitute an electrode;

A second face (302), called a screen, consisting of a conductive circuit (330) printed on one side of the insulating support (350) opposite to the first, this second face (302) being able to constitute an electrical shielding screen for the electrode of the first face (301);

The two conductive circuits (310, 330) being "combed" in the form of a plurality of parallel conductive strips (310, 330) extending in the longitudinal direction (360) and separated from one another other by an insulating strip (320, 340),

and in that the antenna (221) is in contact with the shield face (302) of the electrode (300).

2. Device according to claim 1, characterized in that the width of the conductive strips (310) is greater than the width of the insulating strips (320) separating them on the electrode face (301) and the width of the conductive strips (330) is less than the width of the insulating strips (340) separating them on the screen face (302).

3. Device according to claim 2, characterized in that the width of the conductive strips (310) is equal to 1 mm and the width of the insulating strips (320) to 0.3 mm on the electrode face (301) and vice versa on the screen face (302).

4. Device according to claim 3, characterized in that the transmission frequency of the antenna is 125 kHz.

5. door handle (20) characterized in that it comprises a device according to claim 1, the electrode (300) being adapted to detect the contact and / or the approach of a hand on this handle.

6. Vehicle (100), particularly automobile, characterized in that it comprises a door handle (120) according to claim 5.