SENSOR DEVICE WITH A CAPACITIVE SENSOR FOR MOTOR VEHICLES

Abstract

A sensor device for a motor vehicle for detecting an operation by a user, including at least one capacitive sensor which has a sensor electrode, which is coupled to a control and evaluation circuit. 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 which runs, in sections, between the sensor electrode and the detection region. The sensor electrode 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, 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.

Claims

1. Sensor device for a motor vehicle for detecting an operation by a user, comprising at least one capacitive sensor which has a sensor electrode, the sensor electrode being coupled to a control and evaluation circuit, wherein 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, wherein the sensor electrode is accommodated in a housing which runs, in sections, between the sensor electrode and the detection region, wherein the sensor electrode 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, 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.

2. Sensor device according to claim 1, wherein the sum of the lengths of all edges delimiting the primary detection section is at least 25% greater than the edge length of a rectangle enveloping the primary detection area.

3. Sensor device according to claim 1, wherein the sensor electrode is made of a metallic flat material in the primary detection section.

4. Sensor device according to claim 1, wherein the sensor electrode has two or more spaced-apart conductor structures delimited by edges in the primary detection section.

5. Sensor device according to claim 4, wherein the spaced conductor structures are connected in a fork-like manner by a common base section of the sensor electrode, wherein the base section extends at least partially outside the primary detection section.

6. Sensor device according to claim 1, wherein a radius of curvature of the electrode material in the region of at least part of the edges in the primary detection section and in a direction transverse to the edge is less than 0.5 mm.

7. Sensor device for a motor vehicle for detecting an operation by a user, with at least one capacitive sensor having a sensor electrode, wherein the sensor electrode is coupled to a control and evaluation circuit, wherein the sensor electrode has at least one primary detection section which extends along a detection region into which a body part of a user is moved for operation purposes, wherein the sensor electrode is accommodated in a housing which runs, in sections, between the sensor electrode and the detection region, wherein a primary detection area is determined by a projection of the primary detection section in the direction of the detection region, wherein the sensor electrode is formed in the region of the primary detection section for increasing the electrical field in sections having surface deformations facing the detection region in the form of tips and/or corners and/or roughness.

8. Sensor device according to claim 7, wherein the sensor electrode is made of a metallic flat material in the primary detection section, which has been roughened mechanically and/or thermally and/or by material application at least in regions to form tips and/or corners.

9. Sensor device according to claim 1, wherein a radius of curvature of the electrode material in the region of the tips and/or corners is less than 0.5 mm.

10. Sensor device according to claim 7, wherein the primary detection section has a roughness in the region of the tips and/or corners, having a mean roughness value Ra>0.5 m and/or an average roughness depth Rz>5 m according to DIN ISO 4287.

11. Sensor device according to claim 10, wherein the primary detection section has a roughness in the region of the tips and/or corners, having a mean roughness value Ra>1 m and/or an average roughness depth Rz>10 m according to DIN ISO 4287.

12. Sensor device according to claim 6, wherein the radius of curvature is less than 0.1 mm.

13. Sensor device according to claim 6, wherein the radius of curvature is less than 50 m.

14. Sensor device according to claim 9, wherein the radius of curvature is less than 0.1 mm.

15. Sensor device according to claim 9, wherein the radius of curvature is less than 50 m.

Description

[0033] The invention will now be explained in more detail with reference to the accompanying drawings.

[0034] FIG. 1 shows schematically the arrangement of a sensor device in a vehicle door handle according to the prior art;

[0035] FIG. 2 shows schematically the effect of the field increase at an electrode tip;

[0036] FIG. 3a shows schematically the arrangement of a sensor electrode according to the prior art in the door handle;

[0037] FIG. 3b shows schematically the arrangement of a sensor electrode according to a first exemplary embodiment of the invention in a door handle;

[0038] FIG. 3c shows schematically the arrangement of a sensor electrode according to a second exemplary embodiment of the invention in a door handle; and

[0039] FIG. 3d shows schematically the arrangement of a sensor electrode according to a third exemplary embodiment of the invention in a door handle;

[0040] FIG. 4a shows schematically the definitions of some roughness parameters according to DIN EN ISO 4287;

[0041] FIG. 4b shows schematically the definitions of a roughness parameter according to DIN EN ISO 4287;

[0042] 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 ensure a mechanical operative connection of the door handle having an operational structure arranged in the door (not shown).

[0043] The housing 2 accommodates a circuit board 3 in the region of the handle of the door handle, on which a control and evaluation circuit 4, and a sensor electrode 5 are mounted. The electronics on the circuit board 3 can be coupled to a central control device in the vehicle by means of a line or a cable harness 6.

[0044] The control and evaluation circuit 4 controls the sensor electrode 5 and supplies it with voltage. This has the effect that an electrical field is built up by the sensor electrode 5, which extends through a detection region 7, which is arranged outside the housing 2 and is accessible to a user in the room. If a user moves his hand or his finger in the detection region 7, the capacitance of the sensor electrode 5 changes as a result, which is detected by the control and evaluation circuit 4.

[0045] As described above, various control and evaluation circuits for capacitive sensor electrodes are known and described in the prior art. The size and extent of the detection region 7 are influenced, in particular, by the area of the sensor electrode 5 and its orientation, as well as the voltage applied and the associated measuring method of the control and evaluation circuit 4.

[0046] A flat sensor electrode according to the prior art is shown in the sensor electrode in FIG. 1.

[0047] The invention makes use of the effect of a field increase at edges, tips, and corners in electrical 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 area. In the region of tips, corners, edges, and general areas having a small radius of curvature, there is a so-called field increase, represented by field lines that are closer together. This effect is well known and studied physically and is used in various applications.

[0048] If the orientation of the electrode from FIG. 2 is chosen such that the region of the field increase is aligned with the detection region, an increase in the sensitivity of the sensor electrode can be achieved without requiring a significant increase in the entire electrode area.

[0049] FIG. 3a shows an example of the arrangement of the sensor electrode 5 from FIG. 1 according to the prior art in the door handle 2 in a detail enlargement. The electrode is arranged flat, the perspective in FIGS. 3a to 3d indicating that the flat surface of the electrode is oriented perpendicular to the detection region 7.

[0050] This type of flat electrode as in FIG. 3a occurs in various rectangular or round dimensions in the prior art in numerous capacitive sensor devices. It defines a reference variable against which the invention is distinguished. According to the invention, structures are created on the electrode which lead to a field increase.

[0051] FIG. 3b shows a first exemplary embodiment for improving the sensitivity while reducing the electrode area.

[0052] In FIG. 3b, a U-shaped electrode is arranged in the door handle, wherein the areal extension of the electrode is here also perpendicular to the detection region.

[0053] Compared to the electrode from FIG. 3a, 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 designed with the smallest possible radius of curvature, the field increase occurs, and the sensitivity in this electrode region is increased. Although the area of the electrode is reduced compared to the electrode from FIG. 3a, measurements have shown that an increased sensitivity can be determined when an identical object is approached identically. For this purpose, in a test setup, grounded metal cuboids were placed at identical distances both with flat electrodes as in FIG. 3a and with fork-like electrodes as in FIG. 3b. The corresponding signal response and capacitive change was reproducibly higher in the electrode arrangement from FIG. 3b, although less electrode material is used. The detection region extends above the two legs of the electrode, but in particular also extends over the gap in between. A field increase at the edges 11a overcompensates for the effect of the missing electrode area. The effect of the field increase is initially dependent on the edges, so the gap can be chosen to be very narrow. On the other hand, electrode material is saved due to the gap formation. The ratio of electrode area, edge length, and gap dimensions can be optimized in simple measurements to ensure the desired sensitivity.

[0054] FIG. 3c shows a second embodiment of the invention, in which the edge length is increased by milling or drilling 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 made in the surface of the electrode 12 to form edges. It is entirely possible to design the delimitations of the respective openings, millings, or bores in such a way that burrs remain in the direction of the detection. For example, electrode sheets can be punched or drilled from the rear, such that burrs protrude from the edges of the holes in the direction of detection. Such burrs and edges significantly improve the sensitivity of the electrode, since significant field increases are formed on them, at the same time saving electrode material.

[0055] FIG. 3d shows a sensor electrode 13 according to a third exemplary embodiment of the invention. Surface roughness, tips, and corners are applied in a targeted manner to the electrode area 13. This can be done by a cutting method, for example a targeted roughening of the surface by roughing or by combined thermal, mechanical treatment. Finally, such surface roughness can also follow by applying conductive and curable dry materials or colloid solutions. It is substantial that the surface is roughened in a targeted manner compared to a conventional surface or is manufactured with corresponding edges, corners, or tips.

[0056] It is possible to combine the different designs of the different exemplary embodiments in order to further increase the effect. For example, the electrode 11 from the first exemplary embodiment or the electrode 12 from the second exemplary embodiment can be provided with a corresponding surface roughness.

[0057] FIGS. 4a and 4b explain the roughness parameters to which reference is made in the claims and which correspond to the definitions of DIN EN ISO 4287.

[0058] A measuring section In can be divided into several individual measuring sections Ir. The lines shown in FIGS. 4a and 4b show a surface profile along the measuring section In.

[0059] FIG. 4a shows that an average roughness depth Rz can be determined for the measuring section In, which is obtained as the mean value from the Rz values of the individual sections contained.

[0060] The characteristic variable Ra shown in FIG. 4b denotes the arithmetic mean roughness value, which is the average deviation of the profile values from the center line ml.

[0061] For further definition and description of measurement of the parameters, reference is made to DIN EN ISO 4287.

[0062] If the roughness of the electrode area is mentioned in the foregoing, this refers to a structural design of the electrode area which represents a greater roughness according to the parameters mentioned than is provided in the usual manufacturing methods of, for example, conductor tracks. The roughness is therefore increased in a targeted manner compared to conventional manufacturing processes. As described above, standard chemical micro-etching methods have surface topographies with Ra 0.2-0.5 m and Rz=2.5-5 m. According to the invention, sections or regions of the detection section of the sensor electrode can be equipped with larger values of the roughness depth or the mean roughness value during manufacture or by post-processing. This increases the surface region of the sensor electrode and increases the density of the deformations with tips or corners on the surface, which leads to an improved sensitivity.