Heatable touch sensor and steering wheel having such a touch sensor

Abstract

The invention relates to a heatable touch sensor and a steering wheel. It has an optical waveguide which is connected to an electrical heat conductor. The optical waveguide changes its transmission behavior, which is determined, with a change in position or bending. The heat conductor is a resistance heater which emits heat by applying an electrical voltage and by the associated current flow. The touch sensor operates by means of optical interferometry, which enables a very high sensing accuracy.

Claims

1. A steering wheel comprising: a metallic core; a support structure, made of thermoplastic material, contacting an exterior surface of the metallic core and disposed around the metallic core; a heat insulating foam matrix disposed around the support structure; a thermally conductive film disposed around the heat insulating foam matrix; a cover disposed around the thermally conductive film; a heatable touch sensor embedded within the heat insulating foam matrix, and substantially having a thickness extending from the support structure to the thermally conductive film, the heatable touch sensor comprising: an optical waveguide; an electrical heat conductor disposed around the optical waveguide; wherein touch sensing by the heatable touch sensor is carried out via optical interferometry.

2. The steering wheel according to claim 1, wherein the heatable touch sensor further comprises a carbon layer disposed between the optical waveguide and the electrical heat conductor.

3. The steering wheel according to claim 2, wherein the heatable touch sensor further comprises an insulating varnish coated directly on the electrical heat conductor, the insulating varnish comprising polyamide, silicone, polytetrafluoroethylene, polyether ether ketone, polyether ketone, polypropylene, or polyethylene.

4. The steering wheel according to claim 2, wherein the heatable touch sensor further comprises a plastic sheath disposed between the optical waveguide and the carbon layer.

5. The steering wheel according to claim 1, wherein the optical waveguide is a single mode fiber.

6. The steering wheel according to claim 1, wherein the electrical heat conductor is spirally wound around the optical waveguide.

7. The steering wheel according to claim 6, wherein the electrical heat conductor is spirally wound around the optical waveguide with different lay lengths.

8. The steering wheel according to claim 1, wherein the steering wheel is divided into circle segments, each circle segment having at least one heatable touch sensor.

9. The steering wheel according to claim 8, wherein a plurality of detection zones are defined for each circle segment over a cross section of the steering wheel rim, each detection zone having at least one heatable touch sensor.

10. The steering wheel according to claim 8, wherein at least one heatable touch sensor is disposed in a region of spokes of the steering wheel.

11. The steering wheel according to claim 1, wherein the heatable touch sensor is arranged in a meandering manner, so that the heatable touch sensor has a planar extent.

12. The steering wheel according to claim 1, wherein the steering wheel is a steering wheel of a motor vehicle.

13. The steering wheel according to claim 1, further comprising a thermally activatable lamination layer connecting the cover to the thermally conductive film.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus, are not limitive of the present invention, and wherein:

(2) FIG. 1 shows the structure of a heatable, fiber-optic touch sensor of the invention;

(3) FIG. 2 shows a variant of the integration of a heatable, fiber-optic touch sensor into a steering wheel;

(4) FIG. 3 shows an alternative variant of the integration of a heatable, fiber-optic touch sensor into a steering wheel;

(5) FIG. 4 shows a division of a steering wheel into circle segments as detection zones;

(6) FIG. 5 shows the representation of the cross section of a steering wheel rim with detection zones;

(7) FIG. 6 shows a segmented steering wheel cover with heatable, fiber-optic touch sensors of the invention;

(8) FIG. 7 is a diagram of the results of touch sensing with turned-off heating; and

(9) FIG. 8 is a diagram of the results of the contact sensing with turned-on heating; and

(10) FIGS. 9 and 10 show further embodiment variants of a touch sensor.

DETAILED DESCRIPTION

(11) FIG. 1 shows the structure of a heatable, fiber-optic touch sensor 1 of the invention. It has an optical waveguide 11 in the core, in the form of a single mode fiber with a diameter of 4 to 10 μm. The single mode fiber is enclosed by a sheath 12 having a diameter of 50 to 125 μm.

(12) A carbon layer 13 is disposed on core sheath 12. A heat conductor 14, in this exemplary embodiment in the form of a copper layer with a diameter of 165 μm, is disposed on carbon layer 13. An insulating varnish 15 is applied as the outermost layer.

(13) FIG. 2 shows a sectional view of a steering wheel rim 2. Steering wheel rim 2 has a cover 21, made of leather, on the outside. The inside of cover 21 is connected by means of a thermally activatable lamination 26 to a thermally conductive film 22 made of aluminum, copper, or another good thermally conductive material. Thermally conductive film 22 is connected to a heat-insulating film 23, wherein heatable touch sensor 1 of the invention is embedded between thermally conductive film 22 and heat-insulating film 23. The embedding occurs in a meandering manner between the two films 22 and 23, so as to enable planar touch sensing and heating.

(14) Heat-insulating film 23 is glued to steering wheel rim support structure 24 made of, for example, PUR material or other thermoplastic materials and adhesives. A homogeneous heat distribution on the contact surface with low heat losses is ensured by embedding the heatable, fiber-optic touch sensor 1 in a thermally conductive film 22, which is directed to the outside of steering wheel rim 2 (contact surface), and a heat-insulating film 23, which is directed to the support structure of steering wheel rim 2.

(15) FIG. 3 likewise shows a sectional view of a steering wheel rim 2 with an alternative integration of the heatable, fiber-optic touch sensor 1 of the invention. It is introduced here into a foamable, adhesive matrix 25, which is also made of PUR. Matrix 25 is glued to the steering wheel rim support structure 24. Directed to the outside of steering wheel rim 2, matrix 25 is glued to a thermally conductive film 22. Thermally conductive film 22 is again connected by means of a thermally activatable lamination 26 to the inside of cover 21 of steering wheel rim 2. Here as well, heatable touch sensor 1 is introduced in a meandering manner into matrix 25, so as to enable planar touch sensing and heating.

(16) The integration of touch sensing and heating in a steering wheel, very simple in terms of manufacturing technology, is readily recognizable, because an additional layer in the form of heatable touch sensor 1, placed between two films 22 and 23, needs to be introduced under cover 21 merely by means of lamination 26.

(17) FIG. 4 shows the division of a steering wheel 3, having a steering wheel rim 2 and steering wheel spokes 35, into circle segments for defining detection zones of the steering wheel contact. Steering wheel 3 was divided into four circle segments 31, 32, 33, and 34 on the basis of steering wheel spokes 35.

(18) FIG. 5 shows the cross section of circle segment 31 in the sectional plane A of steering wheel rim 2, shown in FIG. 4, with support structure 24 and metallic support 241. Four detection zones 41, 42, 43, and 44 were also defined over the circumference of steering wheel rim 2. Detection zone 41 faces the driver; detection zone 42 designates the area directed towards the steering wheel center (steering wheel hub), detection zone 43 designates the area facing away from the driver (therefore toward the instrument panel), and detection zone 44 designates the area facing away from the center of the steering wheel (thus facing away from the steering wheel hub).

(19) Four sensor elements distributed over the four zones 41, 42, 43, and 44 are arranged in each of the four segments 31, 32, 33, and 34. As a result of this distribution of the sensor elements, it is possible to determine firstly whether the driver has one or two hands on steering wheel rim 2 and in which circle segment 31, 32, 33, or 34 they are located. In addition, it can be determined whether the driver places his hands only on steering wheel rim 2, for example, by detection only in zone 41, or grips the entire steering wheel rim 2 with the hand, by detection in all four detection zones.

(20) FIG. 6 shows an element of a cover 21 of a steering wheel rim 2, on the inside of which there are sensor elements 5, formed of thermally conductive film 22, heat-insulating film 23, and heatable, fiber-optic touch sensor 1 arranged therebetween and covering the surface in a meandering manner (see FIG. 2). The element shown of cover 21 covers detection zone 41 of steering wheel rim 2 over segments 31, 32, and 33 and has a sensor element 5 for each segment 31, 32, 33. Thus, a segmented touch sensing of detection zone 41 is made possible with little assembly effort. The element of cover 21 is then glued to further cover elements 21 in order to cover the entire steering wheel rim 2.

(21) FIG. 7 shows the diagram of the touch sensing with the heating turned off. Two interference raw signals PD1 (solid line) and PD2 (broken line) can be seen. In the left part of the diagram, the system is in standby; that is, there is no contact. At about 4 s, there is contact of the steering wheel (hands on), which is detected by a brief noise of both signals. After that, the system is in a quasistatic state. At about 6 s, the steering wheel is released again (hands off), which is also recognizable by a noise of both signals. After that, the system is again in standby. A different signal behavior during hands on compared to hands off is also clearly evident.

(22) FIG. 8 shows the diagram from FIG. 7 with the heating turned on. Here as well, the events of hands on at about 2.7 s and hands off at about 7.3 s are easily recognizable by the noise. Thus, the touch sensing is independent of the heating function.

(23) Hereinafter, further embodiment variants will be explained with reference to FIGS. 9 and 10, in which the heat conductor as an electrical conductor (wire) and an optical waveguide are wound.

(24) FIG. 9 shows different variants a) to d) of a conductor bundle 50. In variant a), an electrical conductor 51 is wound around a straight optical waveguide 52 with a constant lay length.

(25) In variant b), electrical conductor 51 is also wound around a straight optical waveguide 52, but with two different lay lengths. Regions 53 with a short lay length L1 alternate with regions 54 with a longer lay length L2.

(26) Variant c) shows a conductor bundle 50 in which optical waveguide 52 is wound together with the electrical conductor 51, wherein optical waveguide 52 is not made straight here.

(27) Variant d) shows a straight optical waveguide 52, which is wound with two different electrical conductors 51 and 55 with a constant lay length.

(28) FIG. 10 shows a heatable touch sensor 1 for installation in a steering wheel under the steering wheel cover. Here, optical waveguide 52 is a touch sensor which detects changes in position or bending and thus touches by the user by means of interferometry through the steering wheel cover. An electrical conductor 51, which acts as a resistance heater, is wound around optical waveguide 52. For installation in the steering wheel, the heatable touch sensor is applied in a meandering manner to a carrier film, to enable planar sensing and heating. The carrier film is made of aluminum and thus has a very good thermal conductivity, so that the steering wheel heating responds quickly. It is understood that electrical conductor 51 is provided with an insulating varnish to prevent an electrical short circuit.

(29) The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are to be included within the scope of the following claims.