FUNCTION DISPLAY FOR SELECTIVELY DISPLAYING SEVERAL SYMBOLS THAT RESPECTIVELY REPRESENT A SWITCHING FUNCTION AND/OR SEVERAL SWITCHING STATES, WITH AN ALIGNMENT FUNCTION OF THE LIGHT SOURCES, AND ASSOCIATED ASSEMBLY METHOD

Abstract

The invention relates to a function display (1) for selectively displaying several symbols representing one switching function, respectively, and/or at least two switching states, respectively, comprising: a light guide stack which, given an attachment of the function display (1) as intended, forms a display surface (8) facing towards the observer (B); wherein the light guide stack is formed from at least two transparent or translucent, planar light guides (2, 3) arranged in an overlaid manner in a stacking direction, which are arranged so as to be spaced apart by a transparent or translucent layer consisting of a material that is optically thinner compared to the adjacent light guides (2, 3), preferably an air gap (14), so that the light guides (2, 3) each have a main surface (H) facing towards the observer (B) and a main surface (H′) facing away from the observer (B), and, in at least one light guide (2), the main surface (H′) facing away from the observer (B) faces towards a light guide (3) which is most closely adjacent in the opposite direction to the stacking direction;

at least one light source (5, 5′) per light guide (2, 3), which is arranged such that in each case, its light (L, L′), via an end face (11) of an associated light guide (2, 3) facing towards the light source (5, 5′), is coupled into the respective light guide (2, 3); wherein, further, at least one microstructured symbol area (12a, 12b) provided in or on the light guide (2, 3) is provided for each light guide (2, 3), which is configured, if the light source (5, 5′) is respectively activated, to be visible, illuminated by the light (L, L′) coupled into the light guide (2, 3), to the observer (B); a circuit board (7) on which the several light sources (5, 5′) are arranged and fixed; a panel (6) fixed to the light guide stack by substance-to-substance connection and/or non-positively and/or positively, to which the circuit board (7) is fixed while resting against a mounting surface (15), wherein two light sources (5′) of the circuit board serve as an alignment aid in attaching the circuit board (7) and the panel (6); and an associated assembly method.

Claims

1. A function display (1) for selectively displaying several symbols representing one switching function, respectively, and/or at least two switching states, respectively, in particular for a motor vehicle, comprising: a light guide stack which, given an attachment of the function display (1) as intended, forms a display surface (8) facing towards the observer (B); wherein the light guide stack is formed from at least two transparent or translucent, planar light guides (2, 3) arranged in an overlaid manner in a stacking direction, which are arranged so as to be spaced apart by a transparent or translucent layer consisting of a material that is optically thinner compared to the adjacent light guides (2, 3), preferably an air gap (14), so that the light guides (2, 3) each have a main surface (H) facing towards the observer (B) and a main surface (H′) facing away from the observer (B), and, in at least one light guide (2), the main surface (H′) facing away from the observer (B) faces towards a light guide (3) which is most closely adjacent in the opposite direction to the stacking direction; at least one light source (5, 5′) per light guide (2, 3), which is arranged such that in each case, its light (L, L′), via an end face (11) of an associated light guide (2, 3) facing towards the light source (5, 5′), is coupled into the respective light guide (2, 3); wherein, further, at least one microstructured symbol area (12a, 12b) provided in or on the light guide (2, 3) is provided for each light guide (2, 3), which includes several light-refractive and/or light-scattering microstructures (4) and is configured, if the light source (5, 5′) is respectively activated, to be visible, illuminated by the light (L, L′) coupled into the light guide (2, 3), to the observer (B), in order to display to the observer (B) a symbol composed of one or several microstructured symbol areas (12a, 12b); a circuit board (7) on which the several light sources (5, 5′) are arranged and fixed; a panel (6) fixed to the light guide stack by substance-to-substance connection and/or non-positively and/or positively, to which the circuit board (7) is fixed while resting against a mounting surface (15), wherein the panel (6) has several light shafts (8, 8′) that are open on both sides and respectively accommodate at least one of the light sources (5, 5′) of the circuit board (7), so that at least one light source (5, 5′) is situated opposite an associated end face (11) in order to couple light (L, L′) into the associated end face (11), wherein the first clearance (21′), which is present in the stacking direction (S), between two light shafts (8′) spaced apart transversely to the stacking direction (S) and the associated light source (5′) accommodated in the respective light shaft (8′) is smaller than each second clearance (21), which is present in the stacking direction (S), between the remaining light shafts (8) and the associated light source (5) accommodated in the respective light shaft (8).

2. The function display (1) according to claim 1, wherein the light sources (5, 5′) are light-emitting diodes configured with an SMD design.

3. The function display (1) according to any one of the preceding claims, wherein the microstructured symbol area (12a, 12b) has in each case several, preferably singular, microstructures (4) configured in an identically shaped manner.

4. The function display (1) according to any one of the preceding claims, wherein the panel (6) has a number of grooves (20) corresponding to the number of the light guides (2, 3), for the positive accommodation of, respectively, that end of the light guide (2, 3) that forms the end face (11) facing towards the light source (5, 5′).

5. The function display (1) according to any one of the preceding claims, wherein, for fixing the circuit board (7) to the panel (6), the panel (6) forms a pin (10), which extends through a recess or through-hole (9) of the circuit board (7) and whose free end is heat-staked.

6. The function display (1) according to any one of the preceding claims, wherein at least the outer light guides (2, 3) of the light guide stack each have a cranked portion (23) at the end that forms the end face (11) facing towards the light source (5, 5′).

7. The function display (1) according to any one of the preceding claims, further comprising a cover layer (18) consisting of a transparent material, which is disposed between the light guide stack and the observer (B).

8. The function display (1) according to any one of the preceding claims, further comprising a transparent electrode array (19) disposed between the observer (B) and the light guide stack, and an associated electronic evaluation unit for capacitive, preferably spatially resolved capacitive, touch detection.

9. The function display (1) according to any one of the preceding claims, wherein the circuit board (7) has a circuit board surface (16) carrying the light sources (5, 5′) and the stacking direction (S) is parallel to the circuit board surface (16).

10. The function display (1) according to any one of the preceding claims, further comprising a housing (17), wherein the circuit board (7) is supported, not in a direct manner, or exclusively elastically, on the housing (17).

11. An assembly method for a function display (1) for selectively displaying symbols representing switching functions and/or switching states, in particular for a motor vehicle, comprising the following steps: providing a light guide stack which, given an attachment of the function display (1) as intended, forms a display surface (8) facing towards the observer (B); wherein the light guide stack is formed from at least two transparent or translucent, planar light guides (2, 3) arranged in an overlaid manner in a stacking direction, which are arranged so as to be spaced apart by a transparent or translucent layer consisting of a material that is optically thinner compared to the adjacent light guides, preferably an air gap (14), so that the light guides (2, 3) each have a main surface (H) facing towards the observer (B) and a main surface (H′) facing away from the observer (B), and, in at least one light guide (2), the main surface (H′) facing away from the observer (B) faces towards a light guide (3) which is most closely adjacent in the opposite direction to the stacking direction, and wherein, further, at least one microstructured symbol area (12a, 12b) provided in or on the light guide (2, 3) is provided for each light guide (2, 3), which includes several light-refractive and/or light-scattering microstructures (4); providing a circuit board (7) with a number of several light sources (5, 5′) arranged on the circuit board (7) that corresponds to at least the number of the light guides (2, 3); providing a panel (6) which has a mounting surface (15) for the circuit board (7) to rest against, and several light shafts (8, 8′) that are open on both sides, wherein the light shafts (8, 8′) are configured to accommodate in each case at least one of the light sources (5, 5′) of the circuit board (7); fixing the light guide stack to the panel (6) by substance-to-substance and/or non-positive and/or positive connection; aligning the circuit board (7) while it rests against the mounting surface (15), such that in each case at least one light source (5, 5′) is situated opposite an end face (11) of one of the light guides (2, 3) in order to couple in light through one of the light shafts (8, 8′), and the light sources (5, 5′) are each accommodated in one of the light shafts (8, 8′); and wherein the first clearance (21′), which is present in the stacking direction (S), between two light shafts (8′) spaced apart transversely to the stacking direction (S) and the associated light source (5′) accommodated in the respective light shaft (8′) is smaller than each second clearance (21), which is present in the stacking direction (S), between the remaining light shafts (8) and the associated light source (5) accommodated in the respective light shaft (8); fixing the circuit board to the panel in such a way that in each case the light of the light sources, via an end face (S) of an associated light guide (13, 14, 15) facing towards the light source, is coupled into the respective light guide (13, 14, 15), and the microstructured symbol area, if the light source (12, 12′) is respectively activated, becomes visible, illuminated by the light coupled into the light guide (13, 14, 15), to the observer (B), in order to display to the observer (B) a symbol (18) composed of one or several microstructured symbol areas.

12. The assembly method according to the preceding claim, wherein, for fixing the circuit board (7) to the panel (6), the panel (6) forms a pin (10), which extends through a recess or through-hole (9) of the circuit board (7), and which extends through the recess or the through-hole (9) with a third clearance (22) present in the stacking direction (S) that is at least greater than the first clearance (21′); and the fixing comprises a final heat-staking of the pin (10) in order to fix the circuit board (7) to the panel (6).

13. The assembly method according to any one of the two preceding claims, wherein the light sources (5, 5′) are light-emitting diodes configured with an SMD design, and are soldered to the circuit board (7) in a soldering step preceding the providing of the circuit board (7).

Description

[0037] The invention as well as the technical environment will be explained in more detail below with reference to the Figures. It must be remarked that the Figures depict a particularly preferred embodiment of the invention, but that the latter is not limited thereto. The Figures schematically show:

[0038] FIG. 1 a schematic cross-sectional view of a first embodiment of a function display 1 according to the invention;

[0039] FIG. 2 a perspective view of a panel 6 of the first embodiment from FIG. 1;

[0040] FIG. 3 a perspective view of a circuit board 7 of the first embodiment from FIG. 1,

[0041] FIG. 4 an enlarged depiction of a part of FIG. 1;

[0042] FIG. 5 a schematic cross-sectional view of a second embodiment of the function display 1 according to the invention.

[0043] FIG. 1 schematically shows a first embodiment according to the invention of the function display 1. The function display 1 comprises an outer transparent or translucent cover layer 18, which is not absolutely required and is only optionally provided, and which, given an arrangement of the function display 1 as intended, defines a surface facing towards the observer B. For example, this is a layer consisting of a plastic, preferably a thermoplastic material, such as polyethylene (PE), polycarbonate (PC), polystyrene (PS), polyvinyl chloride (PVC), polyamide (PA), acrylonitrile butadiene styrene (ABS) or polymethyl methacrylate (PMMA), or a glass material. The cover layer 18 may also be part of a layer structure consisting of several layers. A transparent, conductive coating, which forms an electrode array and which serves for spatially resolved touch detection and is connected in an electrically conductive manner by means of several flexible conductors to an evaluation unit that is not shown, is applied, adjacent to the cover layer 18, to the surface of the cover layer 18 facing away from the observer B.

[0044] The function display 1 further comprises a light guide stack consisting of at least two transparent or translucent, planar light guides 2, 3 arranged in an overlaid manner. The latter are also formed from a plastic, preferably a thermoplastic material, such as polyethylene (PE), polycarbonate (PC), polystyrene (PS), polyvinyl chloride (PVC), polyamide (PA), acrylonitrile butadiene styrene (ABS) or polymethyl methacrylate (PMMA), or a glass material. Preferably, this is a thermoplastic plastic layer or a thermoplastic plastic film in each case. The light guides 2, 3 are separated from each other by a layer 14 provided between the light guides 2, 3, in this case an air gap, consisting of a material, in this case air, with a refractive index lower than that of the adjacent light guides 2, 3. An air layer, which is not defined herein in more detail, is also provided between the cover layer 18 and the most closely adjacent uppermost light guide 2. The light guides 2, 3 each form at least one main surface H facing towards the observer B and a main surface H′ facing away from the observer B, while the upper light guide 2 that is closer to the observer B has a main surface H′ which faces away from the observer and faces towards the light guide 14 which is most closely adjacent in the opposite direction to the stacking direction S.

[0045] At least one light source 5 or 5′, i.e. a light-emitting diode with an SMD design in each case, which are arranged in such a way that the light produced by them is coupled into the assigned light guide 2, 3 via an end face 11 situated towards the side with regard to the stacking direction S, is assigned to the light guides 2, 3. In order to avoid, among other things, unwanted light scattering or light emission into the adjacent light guides 2, 3 in each case, a panel 6 consisting of an opaque material, particularly of an opaque thermoplastic material, is provided. The panel 6 forms protruding ribs 13 which are positively accommodated and fixed between the grooves for accommodating the light guides 2, 3, specifically the ends thereof with the end faces 11 provided for coupling in light.

[0046] A frame-shaped housing 17 is provided at the opposite end face. A reflection-reducing coating, which is not shown, can be applied to the end faces of the light guides 2, 3 facing away from the light sources 5, 5′ in order to minimize a reflection back into the respective light guide 2, 3. Several singular microstructures 4 are incorporated by embossing or molding into at least one of the main surfaces of the light guide 2, in this case into the main surface H facing towards the observer B, which ensure that the light L′ coupled into the light guide 2 is coupled out from the respective light guide 2 by light refraction and/or light scattering and define a microstructured symbol area 12a comprising the microstructures 4. On its own or by optical cooperation with other symbol areas, the latter reproduces the shape of a symbol which becomes visible to the observer B in an illuminated manner if the associated light source 5′ is activated accordingly.

[0047] The microstructures 4 are configured so as to be shaped identically to one another and have a maximum diameter in the range from 1 to 25 μm. The light guide 3 distant from the observer B, in its main surface H facing towards the observer B, also has microstructures 4 that are also configured to be singular and shaped identically to one another. They are also incorporated into the associated main surface H of the light guide 3, which in this case faces towards the observer B, by embossing or molding. They also couple the light L coupled into the light guide 3 in the direction of the observer B in order to visualize the symbol area 12b to the observer in this case.

[0048] By selectively activating the light sources 5, 5′, different switching states or switching functions can be visualized in a comparatively simple manner. The function display 1 is simple and cost-effective to realize and provides the designer with a large degree of designing leeway, which also pertains to the placement of the function display 1. The function display exhibits almost no ageing effects caused by light emission and is comparatively energy-saving. Acting on its own or in cooperation with others, the microstructured symbol area 12, 12b, for example, represents the symbol in a positive manner as an image, as the inverse representation thereof, or as its outline. A certain depth effect is the result of, among other things, the distance between the light guides 2, 3, e.g. the air gap thickness. For example, the distance is in the range of 1 to 3 mm.

[0049] Outside the microstructured symbol area 12a, 12b, all the light guides 2, 3 are transparent. Thus, a large part of the display surface 8 remains optically transmissive, so that, for example, the possibility of looking through the function display 1 is ensured in order to provide the observer B with the possibility of following other displays or the course of the road through the function display 1. For example, placing the function display 1 on a steering wheel is possible, e.g. in the area between the steering wheel hub and the steering wheel rim, without impeding the view onto the dashboard. Looking vertically at the display surface 8, the microstructured symbol areas 12a, 12b of the individual light guides 2, 3 do not overlap in order not to affect the quality of the depiction of the symbols.

[0050] A circuit board 7 is provided on which the several light sources 5, 5′ are arranged and fixed. Here, they are fixed by soldering them to a metallic contact pad of the circuit board 7. The above-described panel 6 forms, on the side thereof facing away from the light guides 2, 3, a mounting surface 15 that serves for the contact of the surface of the circuit board 7 provided with the light sources 5, 5′. This surface is orientated parallel to the stacking direction S. The circuit board 7 has a through-hole 9 through which a pin 10, which is formed by the panel 6, extends and whose free end is deformed by heat staking so as to reach behind and fix the circuit board 7. The panel 6 has several light shafts 8, 8′ that are open on both sides and respectively accommodate at least one of the light sources 5, 5′ of the circuit board 7, so that at least one light source 5, 5′ is situated in each case opposite an end face 11 in order to couple light into the respectively associated end face 11, and in order to ensure, if possible, the exclusive light transition from the light source 5, 5′ to the associated light guide 2, 3, which, due to the arrangement of its end face 11 opposite to the respective light 5, 5′ source, is associated therewith. Consequently, the light shafts 8, 8′ are configured in such a way that an unwanted light transition towards the observer B, towards other layers or light guides 2, 3 next to the associated light guide 2, 3 is suppressed. FIG. 2 shows the panel 6 in detail with a view into the groove 20, which is formed between the ribs 13 and provided for positively accommodating and fixing the light guides 2, 3. Here, it becomes clear that the light shafts 8 and 8′ differ with regard to their dimensions in the stacking direction S.

[0051] FIG. 4 shows the circuit board 7 in a top view onto the surface 16 equipped with the light sources 5, 5′. In each case, the light sources 5, 5′ are identically shaped SMD light-emitting diodes soldered to the contact pads of the circuit board 7. Two light sources 5′ spaced apart in a direction transverse to the stacking direction, due to a special dimensioning of the light shafts assigned to them, qualify as so-called alignment light sources, as will be explained below:

[0052] If the dimensions of all light sources 5, 5′ in the stacking direction S match, this results in the scenario depicted in FIG. 3. The first clearance 21′, which is present in the stacking direction S, between two light shafts 8′ spaced apart transversely to the stacking direction S and the associated light source 5′ accommodated in the respective light shaft 8′ is smaller than the second clearance 21, which is present in the stacking direction S, between the remaining light shafts 8 and the associated light source accommodated in the respective light shaft 8. The first or second clearances 21, 21′ are understood to denote the clear overall distance between the respective light source 5, 5′ and the light shaft 8, 8′ in the stacking direction S, to which the movability of the respective light source 5, 5′ in the light shaft 8, 8′ associated therewith is limited in the stacking direction S. Thus, two light sources 5′ spaced apart transversely to the stacking direction S and almost positively accommodated light sources 5′, in cooperation with the light shaft 8′ respectively associated therewith, serve for the mechanical alignment between the panel 6 and the circuit board 7, while the circuit board 7 is brought to rest against the mounting surface 15 of the panel 6. Due to the greater second play 21, the remaining light sources 5 or light shafts 8 remain unaffected thereby. Due to the danger of damage to the light sources 5, 5′ or their electrical contacting, such as the loss of the soldered contact or a detachment of the contact pad of the circuit board 7 by shearing forces, particularly in the case of the light source 5, 5′ being configured as light-emitting diodes with an SMD design, such a mechanical intervention was generally omitted in the known solutions, with the drawback that a misalignment of the light sources 5, 5′ had to be tolerated. Tolerating the danger of damage to at most two light sources 5′, the present embodiment uses them as a mechanical positioning aid for the connection between the circuit board 7 and the panel 6, with the advantage that a sufficiently precise alignment of all light sources 5, 5′ with the associated end faces 11, and thus an optimal illumination of the associated light guide 2, 3, is now ensured.

[0053] In order to strengthen, for example, the mechanical connection to the circuit board 7 of the two light sources 5′ provided for mechanical alignment, previously referred to as alignment light sources, various measures may be taken, for example, e.g. an enlarged contact pad on the circuit board 7, a solder that is more mechanically durable, a different alignment of the alignment light source, e.g. compared to the remaining light sources 5 of the circuit board 7. In the embodiment shown, a further light source 5, which does not act as an alignment light source, and which thus has a greater second clearance 21 when arranged in the associated light shaft 8, may be assigned as a redundant light source to the light guide 2 associated with the alignment light source.

[0054] As FIG. 4 also shows, the pin 10 provided on the panel 6 for fixing the circuit board 7, at least prior to heat staking, extends through the through-hole 9 provided in the circuit board 7 with a third clearance 22 to be determined in the stacking direction S, which is at least greater than the first clearance 21′, in order not to impede the alignment of the circuit board 7, during its placement on the mounting surface 15 and the insertion of the light sources 5, 5′ into the associated light shafts prior to heat staking, by a displacement or twisting of the circuit board 7 relative to the panel 6 or the mounting surface 15 that is made possible to at least a limited extent.

[0055] FIG. 5 shows a second embodiment of the function display 1 according to the invention. The latter differs from the first embodiment substantially due to the shaping of the light guides 2, 3. In order to avoid the risk of mutual light crosstalk in the adjacent light guides 2, 3, at least the outer light guides 2, 3 of the light guide stack each have a cranked portion 23 at the end that forms the end face 11 facing towards the light source 5, 5′. Here, the cranked portion 23 is formed so as to increase the distance between the light guides 2, 3 in the direction of the panel 6 with respect to the region of the light guides 2, 3 in which the microstructured symbol area 12a, 12b is arranged, in order to improve the fixation of the light guides 2, 3 and improve the mutual optical insulation due to the panel 6. Moreover, in contrast to the first embodiment, the housing 17 is configured to be frame-shaped, wherein a direct contact between the housing 17 and the circuit board 7 is excluded.