Abstract:
A pointer needle for an indication device of a motor vehicle has a transparent optical waveguide that receives light propagating along a direction of propagation at a light-entry side, and emits the light in an emission direction at a light-exit side. The optical waveguide has a scattering side opposite to the light-exit side, the scattering side having steps arranged offset to one another across the propagation direction. When the steps are irradiated by light, the pointer needle provided in the indication device can clearly be perceived in the dark.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a U.S. national stage of International Application No. PCT/EP2015/001391, filed on Jul. 7, 2015. The International Application claims the priority benefit of German Application No. 10 2014 010 310.2 filed on Jul. 11, 2014. Both the International Application and German Application are incorporated by reference herein in their entirety. 
     
    
     BACKGROUND 
       [0002]    Described herein is a display device for a motor vehicle. The display device is configured as a pointer instrument and has a pointer with a pointer needle in which a transparent lightguide emits light in a propagation direction toward a viewer. 
         [0003]    Such pointer needles are typically used in display instruments in which a specific value is to be marked within a circular scale. In particular in the case of combination instruments, this involves, for example, a speed display (tachometer) or rotational speed display. In order to obtain a pointer needle of transparent lightguide, the pointer needle can be fabricated, for example, from PMMA or a polycarbonate (PC) and can have on an underside a hot stamping foil, by which light which is propagated in the lightguide is scattered in the emission direction. 
         [0004]    Since the lightguide is transparent, in the dark, for example when traveling at night, generally only the scattering hot stamping foil is seen, which foil is perceived only as a diffuse bar, i.e. as a result of its scattering property. Therefore, a driver can undesirably take a long time to focus on the pointer needle when moving his gaze from the events on the road to the combination instrument. 
         [0005]    German Patent Application No. 10 2008 011 062 A1 describes a multi-colored pointer for a measuring element which can generate at least two colors of light from a light source with a single color. The light is colored by using a film. 
         [0006]    German Patent Application No. 36 28 540 A1 describes a pointer for a display instrument whose cross section is in the shape of an equilateral triangle, with the result that a colored layer can be seen on the underside from various directions of viewing the pointer, as a result of refraction and total reflection of the beam entry in the pointer. 
         [0007]    Japan Patent Application No. 6-281751 A describes a pointer for a display instrument, into the transparent material of which a fluorescent substance is mixed. A curved groove scatters the fluorescent light into the surroundings. 
       SUMMARY 
       [0008]    Described herein is a pointer needle for a display device of a motor vehicle such that the pointer needle can be perceived clearly in the dark. 
         [0009]    The pointer needle and a motor vehicle having a display device with the pointer needle is described herein. Advantageous developments are further described herein. 
         [0010]    A display device for a motor vehicle includes a pointer needle with a transparent lightguide which is configured to receive, on a light entry side, light which propagates along a propagation direction from a light input device, and to emit the light in a predetermined emission direction on a light-exit side, that is to say toward a viewer. In other words, the pointer needle has a lightguide which is, in particular shaped in an elongate fashion and extends in the direction of longitudinal extent thereof along the pointer needle from a pointer foot to a pointer tip. Light is input into the lightguide at a light-entry side by the light input device, and the lightguide deflects the light toward the light emission direction, with the result that the light exits again on the light-exit side thereof. 
         [0011]    For the deflection or scattering of the light there is provision that the lightguide described herein has a scattering side which lies opposite the light-exit side and has a plurality of steps. The steps are arranged offset in relation to one another, transversely or perpendicularly with respect to the propagation direction of the light, with the result that each step is irradiated independently of every other step, by the light which enters the lightguide on the light-entry side. 
         [0012]    The display device described herein provides the advantage that now a diffusely lit bar cannot be seen as the pointer needle in the display device but instead an object which is lit in a three-dimensional fashion and is formed from illuminated steps which are arranged offset in relation to one another. A driver can therefore focus on the pointer needle with much less effort. 
         [0013]    The steps may also be arranged one behind the other along the propagation direction, with the result that the steps together form a cascade or staircase as a result of their transverse offset with respect to the propagation direction and their arrangement one behind the other along the propagation direction. This results in a particularly pronounced depth effect when observing the pointer needle. 
         [0014]    One advantageous development provides that the steps have a rough surface structure and/or scattering bodies which are integrated into a material of the lightguide and/or have a reflective, opaque surface coating and/or a fluorescent material. This results in the advantage that the steps appear particularly bright, since they divert a particularly large amount of light in the emission direction. A rough surface structure can be achieved for example by grinding the lightguide or by using a correspondingly rough tool mold when generating the lightguide, for example by injection molding or stamping the lightguide. For example a granulate made of reflective bodies, for example mother of pearl, can be provided as the scattering bodies. A reflective surface coating may be made available, for example, on the basis of chromium or a surface coating agent, e.g. with a white color. The fluorescent material can be integrated into the material of the lightguide or applied to the surface of the lightguide. 
         [0015]    The steps may have an oblique position with respect to the propagation direction of the light, on the one hand, and the emission direction, on the other. In other words, a surface normal of the steps may enclose, with a vector of the propagation direction, an angle which lies in a range from 5° to 85°, or in a range from 5° to 45°. As a result, the steps appear as countersunk, wide, lit steps in the pointer needle. 
         [0016]    With respect to the position of the light-entry side and the orientation of the steps there are two basic configurations in the display device described herein, for example, a lateral illumination, on the one hand, and a longitudinally directed illumination, on the other. 
         [0017]    In the case of the lateral illumination there is provision that the light-entry side extends along a direction of longitudinal extent of the pointer needle from a pointer foot to a pointer tip. At the pointer foot, the pointer needle can be arranged on a rotatably mounted pointer shaft. The pointer tip can be moved by rotating the pointer shaft over a scale. The light input device therefore also extends from the pointer foot to the pointer tip on this longitudinal side of the pointer needle. The light input device has here a light-tight mount element into which a propagation region, e.g. with a lightguide fiber, is integrated. The propagation region is opened toward the light-entry side. The light is therefore distributed along the direction of longitudinal extent of the pointer needle in the propagation region and enters the lightguide laterally, that is to say perpendicularly with respect to the direction of longitudinal extent. The propagation direction along which the light enters the lightguide is therefore perpendicular with respect to the direction of longitudinal extent. Correspondingly, the steps extend along the direction of longitudinal extent from the pointer foot to the pointer tip. This provides the advantage that light can be distributed particularly homogenously in the lightguide and as a result the pointer needle is illuminated particularly homogenously. 
         [0018]    In order to distribute the light in the propagation region within the mount element, one development provides that a lightguide fiber is arranged in the propagation region, and/or a wall of the mount element has a reflective or light-scattering coating and/or a fluorescent material. The reflective coating of the inside of the mount element can be achieved, for example, by using chromium or a mirrored foil. Light-scattering coatings can be achieved, for example, by using a surface coating, for example white paint, or by roughening the surface. The developments make it possible to transport the light from a light source into the lightguide of the pointer needle with particularly low loss. 
         [0019]    Given lateral illumination, there is an example embodiment in which not only is the light input from a light-entry side but also the lightguide is configured to receive, on a further light-entry side lying opposite the light-entry side, light which propagates along a further propagation direction from a further light input device. In other words, light can therefore penetrate the lightguide from both of its longitudinal sides. On the scattering side, that is to say the underside of the lightguide facing the scale, further steps which are mirror-symmetrical with respect to the steps are made available, which also scatter the light which enters through the further light-entry side toward the propagation direction. The light can be transported or guided to the further light-entry side by a further mount element. In other words, in this embodiment the pointer needle is configured in such a way that a lightguide on each of its two longitudinal sides has a mount element for directing light into the longitudinal sides of the lightguide. 
         [0020]    In the second illumination technique, of longitudinally directed illumination, there is provision that the light-entry side is formed on the pointer foot and the propagation direction of the entering light points along the longitudinal extent of the pointer from the pointer foot to the pointer tip. Correspondingly, the steps then extend perpendicularly with respect to the direction of longitudinal extent, that is to say transversely with respect to the pointer needle. This embodiment has the advantage that the pointer needle can be illuminated in its entire width since there is no need for a light-tight mount element to guide the light. 
         [0021]    With respect to the generation of light, an embodiment of the display device provides that the pointer is arranged so as to be rotatable with respect to a light source for the light in that the light source is arranged next to the pointer shaft of the pointer, that is to say for example on a printed circuit board or circuit board which can also have a motor for rotating the pointer shaft. The light source is configured here to emit the light along the pointer shaft, e.g. into a pointer cap. The light input device can start in the pointer cap, the light input device then guiding the light toward the light-entry side of the lightguide. The light source can include, for example, one or more light emitting diodes. An alternative embodiment provides for the light source to be arranged in the pointer cap itself. 
         [0022]    The display device described herein may be configured as a combination instrument. It can also have more than one of the described pointer needles. Each pointer needle is then associated, in particular, with one pointer instrument of the display device. 
         [0023]    Also described herein is a motor vehicle (for example, a motor car, such as a passenger car). The motor vehicle may include at least one display device which constitutes in each case an embodiment of the display device described herein. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0024]    These and other aspects and advantages will become more apparent and more readily appreciated from the following description of the exemplary embodiments, taken in conjunction with the accompanying drawings of which: 
           [0025]      FIG. 1  is a schematic illustration of an embodiment of the motor vehicle as described herein, 
           [0026]      FIG. 2  is a schematic illustration of a perspective view of a pointer of a display device of the motor vehicle from  FIG. 1 , 
           [0027]      FIG. 3  is a schematic illustration of a further perspective view of the pointer from  FIG. 2 , 
           [0028]      FIG. 4  is a schematic illustration of a cross section through the pointer in  FIG. 2 , 
           [0029]      FIG. 5  is a schematic illustration of a further cross section of the pointer from  FIG. 2 , and 
           [0030]      FIG. 6  is a schematic illustration of a longitudinal section of a pointer of an alternative embodiment to the display device as described herein. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0031]    Reference will now be made in detail to the preferred embodiments, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. 
         [0032]    Exemplary embodiments are explained below with reference to the drawings. In the exemplary embodiments the described components of the embodiments each constitute individual features which can be considered independently of one another and each also develop the disclosure independently of one another and can therefore be considered either individually or in a combination other than that shown. Furthermore, the described embodiments can also be supplemented by further features which have already been described. 
         [0033]      FIG. 1  illustrates a motor vehicle  10  which can be, for example, a motor car, such as a passenger car. The motor vehicle  10  can have a display device  12  which can be configured, for example, as a combination instrument or as a display device of a dashboard of the motor vehicle  10 . The display device  12  can have a pointer instrument  14 . The pointer instrument  14  can be, for example, a tachometer or a rotational speed display. The pointer instrument  14  displays here a current value, to be displayed, on a scale (not illustrated) by using a pointer  16 . The pointer  16  can have a pointer needle  18  and a pointer cap  20  and a pointer shaft  22 . The pointer shaft  22  can be connected in a rotationally fixed fashion to a shaft  24  of an electric motor  28 , for example plugged onto the shaft  24 . By rotating the shaft  24  by using the motor  28 , the pointer shaft  22  and also the entire pointer  16  can be rotated and as a result a pointer tip  30  of the pointer needle  18  can be oriented as a value of the scale. A pointer foot  32  of the pointer needle  18  can be arranged in the pointer cap  20 . The motor  28  can be located on a printed circuit board  34 . The pointer cap  20  can be embodied with a glossy injection-molded finish or surface coated and can be configured to cover a deflection of illumination for the pointer needle  18 . The illumination can be effected by using various possibilities, and for example may be effected by an illumination using one or more light emitting diodes  36  which are arranged on an upper side of the printed circuit board  34 , that is to say toward the pointer  16 . The light emitting diodes  36  then emit their light  38  toward the pointer cap  20 , where it is then input into the pointer needle  18  and as a result the pointer needle  18  is irradiated in an emission direction  40  away from the scale and toward a viewer by using deflection and/or reflection of the light  38 . 
         [0034]    The distribution of the light  38  in the pointer needle  18  can be effected by using lateral illumination as is explained in relation to  FIGS. 2 through 5 . An alternative constitutes a longitudinally directed illumination which will be explained in relation to  FIG. 6 . 
         [0035]    The lateral illumination provides, as illustrated in  FIG. 2 , that the pointer needle  18  has a transparent lightguide  42  and a light-tight pointer sheath  44  which surrounds the lightguide  42  laterally, transversely with respect to the propagation direction  40 . The lightguide  42  can be manufactured, for example, from PMMA or from a polycarbonate. The pointer sheath  44  can be provided with a first mount element  46  on one side and a second mount element  48  on the opposite side of the lightguide  42 . 
         [0036]    In  FIG. 3 , the pointer  16  is illustrated from a perspective from the circuit board  34 , that is to say the light emitting diodes  36 . The pointer foot  32  is defined toward the pointer tip  30 . The mount elements  46 ,  48  also extend in the direction  50  of longitudinal extent from the pointer foot  32  to the pointer tip  30  and are arranged on opposite sides of the lightguide  42 , that is to say enclose the lightguide  42  and therefore form a sandwich arrangement together with the lightguide  42 . The light  38  which is emitted by the light emitting diodes  36  can penetrate a respective propagation region  52 ,  54  of the mount elements  46 ,  48  in the region of the pointer foot  32 . The propagation regions  52 ,  54  extend along the direction  52  of longitudinal extent in the interior of the mount elements  46 ,  48  as illustrated by using the cross section in  FIG. 4 . A possible position along the cross section along the pointer needle  18  is illustrated in  FIG. 3  and  FIG. 4 . 
         [0037]    In the cross section in  FIG. 4  it is shown that the propagation regions  52 ,  54  can be configured, for example, as chambers in which a lightguide fiber  56 ,  58  (illustrated in  FIG. 4  as a vector pointing into the plane of the drawing) can be arranged along the direction  50  of the longitudinal extent. The light which has penetrated the propagation regions  52 ,  54  at the pointer foot  32  propagates in the lightguide fibers  56 ,  58  along the direction  50  of longitudinal extent and in doing so exits through passage openings  60 ,  62  in the propagation regions  52 ,  54  toward the lightguide  42 . The lightguide  42  has in each of the regions of the passage openings  60 ,  62  a light-entry side  64 ,  66  through which the light  38  which enters the lightguide  42  along the respective propagation direction  68 ,  70 . 
         [0038]    The lightguide  42  has, on a scattering side  74  lying opposite the light-exit side  72 , two stepped cascade-shaped regions  76 ,  78  within the pointer needle  18 . The stepped regions  76 ,  78  can be embodied in such a way that they become visible to the respective viewer by using a structure  84  which is located on edges or steps  80 ,  82  as soon as the steps  84  are irradiated by using the light  38 . The effect which occurs here generates a three-dimensional image for the viewer and gives rise to a depth effect within the pointer needle  18 . The depth effect is generated here, on the one hand, by the structuring  84  and, on the other hand, by a slightly oblique positioning of the end regions of the cascades  76 ,  78 , that is to say the steps  80 ,  82 . The steps  80 ,  82  are offset one next to the other transversely with respect to the propagation direction  68 ,  70  of the light  38  which is irradiating them, that is to say offset one over the other in  FIG. 4 . The steps  80 ,  82  are also arranged one behind the other along the respective propagation direction  68 ,  70 , that is to say laterally with respect to one another in  FIG. 4 . The steps  80 ,  82  each form a staircase which leads in the propagation direction  40 . 
         [0039]    The oblique positioning is explained once more in relation to  FIG. 5 .  FIG. 5  shows the normal vector  86  of the plane of the step for a step  80 . The step vector  86  intersects with the associated propagation direction  68  at an angle  88  which is greater than 0°. 
         [0040]    The illumination by using the lightguide fibers  56 ,  58  or generally the propagation regions  52 ,  54  which are located laterally on the lightguide  42 , the light  38  is distributed in the direction  50  of the longitudinal extent along the lightguide  42  and can therefore penetrate the lightguide  42  and illuminate it homogenously with light. In order to cover the lightguide fibers  56 ,  58 , they are covered by the light-tight pointer sheath  44 . Here it is possible even to dispense with a pointer cap  20  or to integrate the pointer cap  20  into the component of the pointer sheath  44 . 
         [0041]    In  FIG. 6 , the longitudinally directed illumination is illustrated. In  FIG. 6 , the same reference signs are used for functionally identical elements as in the preceding figures.  FIG. 6  shows that the light entry face  64  is arranged on the pointer foot  32  of the pointer needle  42  and the light  38  passes, for example via a pointer cap  20  which in this case constitutes a lightguide device, toward the light entry face  64  and penetrates the material of the pointer needle along the direction  50  of longitudinal extent of the pointer needle  42 . At steps  80  which can also have the described structure  84 , the light can be refracted at the scattering side  74  of the pointer needle  42  in the direction of the emission direction  40 , with the result that the light  38  exits the lightguide  42  at the light-exit side  72  in the direction of the viewer. In the case of the pointer illustrated in  FIG. 6 , there is no need for a pointer enclosure (sheath)  44  for distributing the light. The inputting of light is carried out underneath the pointer cap. 
         [0042]    According to one or more embodiments described herein there is provided a 3-dimensional display of pointer instruments in the combination instrument by using gradation or cascades and structuring within the pointer needle. 
         [0043]    A description has been provided with particular reference to preferred embodiments thereof and examples, but it will be understood that variations and modifications can be effected within the spirit and scope of the claims which may include the phrase “at least one of A, B and C” as an alternative expression that means one or more of A, B and C may be used, contrary to the holding in  Superguide  v.  DIRECTV,  358 F3d 870, 69 USPQ2d 1865 (Fed. Cir. 2004).