EP3688729A1

EP3688729A1 - Sensor device with a capacitive sensor for motor vehicles

Info

Publication number: EP3688729A1
Application number: EP18765826.5A
Authority: EP
Inventors: Peter Van Gastel; Michael Elßner; Andreas Gornik; Michael Kalesse
Original assignee: Huf Huelsbeck and Fuerst GmbH and Co KG
Current assignee: Huf Huelsbeck and Fuerst GmbH and Co KG
Priority date: 2017-12-18
Filing date: 2018-08-30
Publication date: 2020-08-05
Also published as: WO2019120644A1; US20210072046A1

Abstract

A sensor device for a motor vehicle for detecting an operation by a user, comprising at least one capacitive sensor which has a sensor electrode (5, 11, 12, 13), which is coupled to a control and evaluation circuit (4). The sensor electrode has a primary detection section which extends adjacent to a detection region into which a body part of a user is moved for operation purposes. The sensor electrode is accommodated in a housing (2) which runs, in sections, between the sensor electrode and the detection region (7). The sensor electrode (11, 12) is provided, in the region of the primary detection section, for increasing the electrical field in sections, with recesses and/or openings which are delimited by edges (11a, 12a), so that a length at the limiting edges, which length is increased in relation to a continuous electrode area, is present in the primary detection section.

Description

Sensor device with capacitive sensor for motor vehicles

The invention relates to a sensor device with at least one capacitive sensor. Sensor devices of this type are used at various points in motor vehicles,

For example, in the field of door handles, tailgates or the instruments in the interior.

The capacitive sensor electrode of such a sensor arrangement is coupled to a control and evaluation circuit. The

Sensor electrode has at least one primary

Detection section adjacent to a

Extending detection range. In a detection area body parts are detected, which brings a user to operate in this detection area. For this purpose, the sensor electrode is accommodated in a housing which extends at least in sections between the sensor electrode and the detection area and thus removes the sensor electrode from direct access and contact by the user and also protects against other environmental influences.

Such sensor devices with integrated capacitive sensors are known in the art, in particular their application is widespread in door outer handles of motor vehicles. For example, DE 196 17 038 A1 discloses a door handle with capacitive sensors to detect an approach of a potential operator. The one with the at least one

Sensor electrode coupled control and evaluation circuit measures a capacitance of the sensor electrode to ground. By

Approach of the hand or other part of the body of an operator from outside the detection area in the

Detection area into the capacitance of the electrode is changed to ground and this is detected by the control and evaluation circuit. Depending on the detected signal, a function can be triggered in the vehicle. The function of a capacitive sensor and a control and evaluation circuit are not explained in the context of this application, since they are well known. In particular, circuits for frequent reloading of the sensor electrode are known, wherein charge durations or charge quantities are detected, from which the capacitance of a sensor electrode

can be concluded.

The sensor electrodes are classical

Considering the capacitance of the plate capacitor in its sensitivity primarily dependent on the detection surface and the distance of the detection surface from the detection area.

It is always an objective of the capacitive sensor technology to provide the highest possible sensitivity with the smallest possible and lightest sensor electrodes.

The invention is therefore based on the object, the

Sensitivity of sensor electrodes to improve without affecting the electrode size.

This object is achieved by a sensor device having the features of patent claim 1 and a sensor device having the features of patent claim 7.

According to claim 1, a sensor device of the type mentioned in the area of its primary

Detection section recesses and / or openings, which are bounded by edges. These recesses and / or

Accordingly, openings are arranged such that their delimiting edges lie in the primary detection section and thus one opposite to a continuous electrode surface in the latter

primary detection section enlarged number or length of edges is formed.

The primary detection section is the extension area of the sensor electrode, which is designed to form the sensed user-adjustable electric field in the detection area. In addition, the sensor electrode can, for example, feed cables and shielded surfaces although they are conductively connected, but do not contribute to the detection capability to a technically relevant extent. Thus, the definition of the primary detection section depends on the expert design of the sensor arrangement and is also dependent on the applied voltage and the housing geometry and other components. At least the section of

The electrode that is closest to the detection area is part of the primary detection section.

It is known in physics that when conducting

Objects that lie at a predetermined potential, a field line cant or - takes place _V fabrication of edges, points and corners. The smaller the radius of curvature of such an edge, point or corner, the stronger the falls

Field elevation off. This effect is for example at

Used corona discharges. It has been found that the selective arrangement of edges, points or corners in the primary detection section of a sensor electrode acts favorably with respect to the sensitivity of the sensor electrode. If such edges, corners or points are located in the primary detection section, then a smaller electrode area is sufficient in order to be able to provide identical sensitivities in comparison with through electrodes.

In order to achieve the corresponding field enhancement effects, radii of curvature are to be selected which have the effect of

Field elevation favor clearly. These are regular

Curvature radii of well below 1 mm, regularly the radii of curvature should be less than 100 ym and can, for. B. in the formation of peaks, ridges, corners or roughnesses, be significantly smaller than 10 ym and lie in the range of nanometers.

It is therefore within the scope of the invention to form edged, in particular sharp-edged boundaries of the electrode or corresponding contours of the surface of the electrode in the primary detection section of the electrode. On In these places there is a field increase, which favors the sensitivity of the electrode.

The edges, corners and points are to be aligned in such a way that the field elevation is directed in the direction of the detection area, ie in particular on the detection area

facing side of the sensor electrode.

The edges may be outer boundaries of the electrode, it may also be edges that define openings in the electrode, such as holes, punches, embossments or the like.

It is essential that in the field of primary

Detecting portion of the sensor electrode targeted by the

Geometry and surface design of the sensor electrode

Field overshoots are effected. This seems the

to contradict fundamental efforts to design components as possible without sharp edges and without burrs. According to this invention, however, properly placed edges, burrs and

Roughness in appropriate form favorable for the

Field elevation and sensitivity improvement.

As far as it is mentioned that an increased length is formed at the limiting edges in the primary detection section, a continuous electrode surface is used as a comparison, the area of which is the area of the primary

Covering section covers and envelops, wherein the

Recesses and / or openings according to the invention are spanned by the continuous electrode. For example, such an electrode according to the invention with enlarged

Edge length by punching, cutting out or

Drill out of parts of the electrode surface are formed, wherein the edges of the respective recesses and / or openings are arranged in the primary detection section.

In one embodiment of the invention, the sum of the length of all the primary detection section bounding edges at least 25% larger than the edge length of a rectangle enclosing the primary detection area.

According to this embodiment, an electrode surface is enlarged by cuts, notches or holes in terms of their edge length so that this edge length is at least 25% longer than a rectangular electrode covering the primary detection portion.

In a further embodiment of the invention is the

Sensor electrode formed in the primary detection portion of a metallic sheet.

Metallic flat materials are in terms of

Possibility of forming openings and recesses particularly easy to edit and also to bring in a desired shape for adaptation to a sensor arrangement. Such flat materials may in particular be sheets, flat cast bodies, metallic layers on guide plates or the like.

The production of such sensor electrodes is particularly simple and, in addition to a blank for the formation of edges, upstands and profilings can also be made, which further improves the field superelevation in these areas.

In a particularly preferred embodiment of the invention, the sensor electrode is formed in the primary detection section with two conductor structures, which are spaced apart from each other and each bounded by edges. The spaced

Conductor structures may be formed, for example, as parallel fingers or adjacent conductive structures.

It is particularly preferred if the spaced

Ladder structures forked by a common

Base portion of the sensor electrode are connected, wherein the base portion extends at least partially outside of the primary detection portion.

Such a fork-like structure provides in particular for mechanically independent sensor electrodes, ie in particular Sensor electrodes without underlying carrier material, a mechanically stable and at any time in terms of

Ladder structures aligned design for

Available. Such a sensor electrode is easy to arrange and the conductors are always properly aligned with each other. The primary detection section is formed in these electrodes from portions of the two parallel conductor structures. The sensor electrode is thus arranged, for example, so that an operator places a finger on a region of the housing, so that the finger spans the gap between the conductor structures and the edges bounding the gap are under fingers. With regard to the concrete design of the edges, the person skilled in the art can select a method of production which is based on the electrode material and the

Processing options is tuned. However, it is

It is particularly preferred if the radius of curvature in the region of the edges is less than 0.5 mm, preferably less than 0.1 mm and in particular less than 50 μm. smaller

Radii of curvature, e.g. in the nanometer range are also possible with suitable methods.

Since the manifestation of field elevation in this area depends strongly on the radius of curvature, it should be strived for

The radius of curvature as low as possible to choose and design, as far as this with the technically accessible possibilities

is reachable. A radius of curvature of a few micrometers or even in the sub-micrometer range is basically desirable, but not attainable in many electrode materials in view of their production or softness and the available processing steps. However, burrs reached during cutting operations or punching processes can be quite appropriate

Reach radii of curvature, which burrs can then be selectively left to provide additional field peaks. According to a second aspect of the invention, the sensor device of the type mentioned in the region of the primary detection section for the sectional elevation of the electric field on the detection area side facing peaks and / or corners. Peaks and / or corners are to be understood as structures which are designed specifically for the elevation of the electric field. In particular, the tips and / or corners are characterized by radii of curvature, which are realized as small as possible, depending on electrode material and available means of production.

In a preferred embodiment of the invention, the sensor electrode is formed in the region of the primary detection section of a metallic sheet material, which for

Formation of tips and / or corners was at least partially roughened mechanically and / or thermally and / or by applying material.

To form the tips and / or corners in the primary

Detecting section can be used mechanical means, in particular embossing means, cutting means or machining processes that lift or deform material from the sensor electrode in the primary detection section to form tips and / or corners. Alternatively or additionally, thermal methods can be used, for example, an electrode surface can be melted to then through

Press and lift off tools to pull threads or tips of the electrode material before the material recovers

catches .

Finally, it is also possible to selectively provide the electrode surface with material application to apply corners, tips or a generally larger roughness by this additional material. The applied material may be identical to the material of the electrode or another material.

For example, metal colloids with a conductive

Adhesive to be sprayed on the surface to get through form the colloid tips or corners on the surface of the electrode.

Again, the radius of curvature of the tips or corners in this area should be minimized, but consideration should be given to available manufacturing tools and materials. The peaks or corners should be at most a few tens of microns, preferably a few microns, to sub-micrometer radii of curvature.

If, in addition to or instead of the corners and peaks, the roughness of the sensor electrode is purposefully increased, the sensitivity is likewise increased. For the definition of roughness reference is made to DIN EN ISO 4287 (Edition 07-2010). The roughness of the electrode surface is increased according to this embodiment compared to conventional production methods and electrodes targeted. If e.g. a sensor electrode in one

If wet-chemical methods are produced on a circuit board, it can be assumed that surface chemical topographies with Ra = 0.2-0.5ym and Rz = 2.5-5ym occur (depending on the etch rate) in commercial chemical microetching (for the definition of the parameters see below and definition of the mentioned DIN EN ISO 4287). According to the preferred embodiment, portions or regions of the sensing portion of the sensor electrode are already provided with larger values of the roughness depth or the average roughness value than these values during production or by post-processing. This increases the surface area of the sensor electrode and increases the density of deformations with peaks or corners on the surface, resulting in improved sensitivity.

The invention will now be explained in more detail with reference to the accompanying drawings.

Figure 1 shows schematically the arrangement of a

Sensor device in a vehicle door handle according to the prior art; FIG. 2 shows schematically the effect of field elevation on an electrode tip;

Figure 3a shows schematically the arrangement of a

Sensor electrode according to the prior art in the door handle;

Figure 3b shows schematically the arrangement of a

Sensor electrode according to a first embodiment of the

Invention in a door handle;

Figure 3c shows schematically the arrangement of a

Sensor electrode according to a second embodiment of the invention in a door handle; and

FIG. 3d schematically shows the arrangement of a

Sensor electrode according to a third embodiment of the invention in a door handle;

Figure 4a shows schematically the definitions of some

Roughness parameters according to DIN EN ISO 4287;

FIG. 4b schematically shows the definitions of a

Roughness characteristic according to DIN EN ISO 4287;

FIG. 1 shows a motor vehicle door handle 1 which has a housing 2 on which mechanical coupling elements 2a and 2b are arranged. The mechanical coupling elements 2a and 2b protrude through a door panel into the interior of a door and provide a mechanical operative connection of the door handle with an actuating assembly (not shown) disposed in the door.

The housing 2 receives in the region of the handle of the door handle a circuit board 3, on which a control and evaluation circuit 4 and a sensor electrode 5 are mounted. The electronics on the board 3 can be coupled by a line or a harness 6 with a central control device in the vehicle.

The control and evaluation circuit 4 controls the

Sensor electrode 5 and supplies them with voltage. This causes an electric field to be built up by the sensor electrode 5, which passes through a detection area 7, which is outside the housing 2 and accessible to a user is arranged in the room. If a user moves his hand or his finger in the detection area 7, thereby changing the capacitance of the sensor electrode 5, which is detected by the control and evaluation circuit 4.

As described above, various control and evaluation circuits for capacitive sensing electrodes are known and described in the prior art. In particular, the area of the sensor electrode 5 and its orientation as well as the applied voltage and the associated measuring method of the control and evaluation circuit 4 have an influence on the size and extent of the detection area 7.

In the sensor electrode in Figure 1 is a flat

Sensor electrode according to the prior art shown.

The invention makes use of the effect of field elevation on edges, points and corners in electric fields. FIG. 2 schematically shows a tip of a sensor electrode 10 to which a voltage has been applied. A counter electrode is not shown in this illustration, since it is not necessary for understanding. When a voltage is applied to a conductive electrode 10, the surface of the electrode is an equipotential surface. In the area of peaks, corners, edges and general areas with a small radius of curvature, there is a so-called field elevation, represented by more closely spaced field lines. This effect is well known and studied physically, and is used in various ways

Exploited applications.

Now, the orientation of the electrode of Figure 2 is chosen so that the range of field elevation for

Aligned detection range, an increase in the sensitivity of the sensor electrode can be achieved without requiring a significant increase in the total electrode area.

Figure 3a shows an example of the arrangement of

Sensor electrode 5 of Figure 1 according to the prior art in the Door handle 2 in a detail enlargement. The electrode is arranged flat, wherein the perspective in the figures 3a to 3d indicates that the electrode is oriented with its planar extent perpendicular to the detection area 7.

This type of planar electrode, as in FIG. 3a, has various rectangular or even round dimensions in the state of the art in numerous capacitive sensor devices. It defines a reference to which the invention is delimited. According to the invention structures are created at the electrode, which lead to a field elevation.

Figure 3b shows a first embodiment of the

Improvement of sensitivity with reduction of

Electrode surface.

In Figure 3b is a U-shaped electrode in the door handle

arranged, whereby here also the areal extent of the

Electrode is perpendicular to the detection area.

In contrast to the electrode of FIG. 3 a, the edge length in the electrode region is increased according to the invention in that two electrode legs are guided at a distance from one another. At these edges, which are formed with the smallest possible radius of curvature, it comes to Feldüberhöhung and to increase the sensitivity in this electrode area. Although the area of the electrode is reduced with respect to the electrode of FIG. 3a, measurements have shown that increased sensitivity is found when the identical object is approached identically. In a test setup, grounded metal cuboids were placed at an identical distance both in planar electrodes as in FIG. 3 a and in fork-type electrodes as in FIG. 3 b. The corresponding signal response and capacitive change was reproducibly higher in the electrode arrangement of Figure 3b, although less electrode material

is set. The detection area extends above the two limbs of the electrode but in particular also over the gap therebetween. A field swell at the edges 11a overcompensates the effect of the missing electrode surface. The effect of field elevation is initially dependent on the edges, so the gap can be very narrow.

On the other hand, electrode material is saved by the gap formation. In simple measurements, the ratio can be

Electrode surface, edge length and gap masses are optimized to ensure the desired sensitivity.

FIG. 3 c shows a second embodiment of the invention, wherein there the enlargement of the edge length is realized by milling or bores in the surface of the electrode 12. These can be through openings through the entire electrode material which are delimited by edges 12a; alternatively, blind openings can also be introduced into the surface of the electrode 12 to form edges. It is quite possible to form the boundaries of the respective openings, milling or holes in such a way that burrs in

Direction of detection remain. For example, electrode sheets can be punched or drilled from the back so that burrs protrude in the direction of detection at the edges of the holes. Such ridges and edges improve the

Sensitivity of the electrode significantly, as attached to them

form significant field peaks, while simultaneously

Electrode material is saved.

FIG. 3d shows a sensor electrode 13 according to a third exemplary embodiment of the invention. On the

Electrode surface 13 are targeted surface roughness, tips and corners applied. This can be achieved by a machining process, for example a targeted roughening of the

Surface can be done by roughing or by combined thermal, mechanical treatment. Finally, such surface roughnesses can also be followed by applying conductive and curable dry materials or colloidal solutions. It is essential that the surface compared to a usual Surface is roughened targeted or made with appropriate edges, corners or tips.

It is possible the different designs of the

to combine different embodiments in order to increase the effect even more. For example, the electrode 11 of the first embodiment or the electrode 12 of the second embodiment with corresponding

Surface roughness are provided.

Figures 4a and 4b illustrate the roughness characteristics to which reference is made in the claims and which correspond to the definitions of DIN EN ISO 4287.

A measuring section ln can be subdivided into several individual measuring sections lr. The lines shown in FIGS. 4a and 4b show a surface profile along the measuring path ln.

FIG. 4 a shows that an average roughness depth Rz can be determined for the measuring section ln, which results as an average value from the Rz values of the individual sections contained.

The characteristic value Ra shown in FIG. 4b designates the arithmetic mean roughness, which results as the average deviation of the profile values from the center line ml.

Reference is made to DIN EN ISO 4287 for further definition and description Measurement of the parameters.

When referring to the roughness of the electrode surface in the foregoing, this refers to a structural design of the electrode surface which presents a greater roughness according to said parameters than that of conventional ones

Manufacturing method of eg printed conductors is provided. The roughness is thus selectively increased, compared to conventional manufacturing processes. As described above, commercially available chemical microetching methods have surface topographies with Ra = 0.2-0.5ym and Rz = 2.5-5ym. According to the invention, portions or regions of the sensing portion of the sensor electrode may already be opposite these values at the time of manufacture or by post-processing with larger values of the roughness depth or Center roughness. This increases the surface area of the sensor electrode and increases the density of deformations with peaks or corners on the surface, resulting in improved sensitivity.

Claims

ZENZ Patent Attorneys Ruettenscheider Str. 2 D-45128 Essen H 1193 WO PL Claims

A sensor device for a motor vehicle for detecting an actuation by a user, comprising at least one capacitive sensor having a sensor electrode (5, 11, 12, 13),

wherein the sensor electrode (5, 11, 12, 13) with a

Control and evaluation circuit (4) is coupled,

wherein the sensor electrode is at least one primary

Detecting portion extending adjacent to a detection area in which a body part of a user is made to operate,

wherein the sensor electrode is accommodated in a housing (2) which runs in sections between the sensor electrode and the detection area (7),

characterized,

that the sensor electrode (11, 12) in the region of the primary detection section for the sectional elevation of the electric field with recesses and / or openings

which are delimited by edges (11a, 12a), so that in the primary detection section an enlarged length compared to a continuous electrode surface

limiting edges is present.

2. Sensor device according to claim 1, wherein the sum of the lengths of all the primary detection portion bounding edges (11a, 12a) by at least 25% greater than that

Edge length of a rectangle enclosing the primary detection area.

3. Sensor device according to claim 1 or 2, wherein the sensor electrode (11, 12, 13) is formed in the primary detection portion of a metallic sheet.

4. Sensor device according to one of the preceding

Claims, wherein the sensor electrode (11) in the primary 2

Detection portion has two or more edge-defined, spaced conductor structures.

5. Sensor device according to claim 4, wherein the

spaced ladder structures forked by one

common base portion of the sensor electrode (11) are connected, wherein the base portion extends at least partially outside of the primary detection portion.

6. Sensor device according to one of the preceding

Claims wherein the radius of curvature of the electrode material in the region of at least a portion of the edges in the primary sensing portion and in the cross-edge direction is less than 0.5 mm, preferably less than 0.1 mm, more preferably less than 50 mm.

7. A sensor device for a motor vehicle for detecting an actuation by a user, comprising at least one capacitive sensor having a sensor electrode (11, 12, 13),

wherein the sensor electrode (11, 12, 13) is coupled to a control and evaluation circuit,

wherein the sensor electrode is at least one primary

Has detection section, which extends along a

Detection area (7) extends, in which a body part of a user is brought to actuation,

wherein the sensor electrode is accommodated in a housing which runs in sections between the sensor electrode and the detection area,

wherein a primary detection area is determined by a projection of the primary detection section in the direction of the detection area,

characterized,

in that the sensor electrode (13), in the area of the primary detection section, faces the detection area for the sectional elevation of the electric field 3

Surface deformations in the form of tips (13 a) and / or corners and / or roughness is formed.

8. Sensor device according to claim 7, wherein the

Sensor electrode is formed in the primary detection section of a metallic sheet material which has been roughened at least partially mechanically and / or thermally and / or by the application of material to form tips (13a) and / or corners.

9. Sensor device according to one of the preceding

Claims, wherein the radius of curvature of the electrode material in the region of the tips and / or corners is less than 0.5 mm, preferably less than 0.1 mm, particularly preferably less than 50 mm.

10. Sensor device according to claim 7, wherein the primary detection section in the region of the tips and / or corners has a roughness, with an average roughness M3> 0.5mih and / or an average roughness Rz> 5mm according to DIN ISO 4287th

11. Sensor device according to claim 10, wherein the primary detection section in the region of the tips and / or corners has a roughness, with a mean roughness Ra> ^ m and / or an average surface roughness Rz> 10mm according to DIN ISO 4287th