Head-up display for a motor vehicle and method for manufacturing a cover for a head-up display

Description

[0001] The invention relates to a head-up display for a motor vehicle of the type specified in the preamble of claim 1. The invention further relates to a method for manufacturing a cover for such a head-up display.

[0002] Head-up displays are generally divided into two different types. On the one hand, there are head-up displays that project an image onto a windshield. On the other hand, there are also head-up displays that project an image onto a separate, so-called combiner screen. For head-up displays that project the image onto a vehicle's windshield, a transparent cover is typically used to protect the display from dust or other contaminants. This cover protects the opening of the display housing from the top.

[0003] The cover is transparent so that light from an imaging unit can pass through the cover, via a magnifying mirror, and be projected onto the windshield. These transparent covers are typically made of polycarbonate and often feature a scratch-resistant and anti-reflective coating. Laminates made of polycarbonate and polarizers are also available. In both cases, a scratch-resistant layer, often called a hardcoat, is required to achieve a hardness of 3H or higher.

[0004] Furthermore, there is a trend towards head-up displays with increasingly larger display areas, for example, to implement so-called contact-analog reality head-up displays. With such head-up displays, the entire windshield is often used to display augmented content superimposed on reality. For these types of head-up displays, it is necessary that the corresponding opening in the housing of the head-up display is also correspondingly large, or rather, increasingly larger.

[0005] Studies show that it is becoming increasingly difficult to shift the resonant frequencies of such large, transparent plastic covers sufficiently into a range where they do not produce audible vibrations during normal driving. To achieve this, transparent plastic covers must be made very thick. Exciting the transparent cover at its resonant frequency can cause a so-called drumming sound, which is perceived negatively by vehicle occupants.

[0006] German patent DE 10 2009 032 141 A1 discloses a head-up display for a motor vehicle. The head-up display comprises a housing with an opening that serves as a light emission aperture. A transparent glass cover is inserted into the opening. The head-up display also includes an image transmitter located within the housing, by means of which an image can be projected through the cover onto the windshield of the motor vehicle.

[0007] WO 2017 / 022568 A1 also describes a cover for a light emission aperture of a head-up display, the cover consisting of a multitude of laminated polarizing filters.

[0008] Dle WO2017036582A1 reveals a head-up display with a glass cover.

[0009] The object of the present invention is to provide a solution by which transparent covers for head-up displays can be prevented from being excited to acoustically perceptible vibrations during operation.

[0010] This problem is solved by a head-up display for a motor vehicle and by a method for manufacturing a cover for a head-up display with the features of the independent claims. Advantageous embodiments with expedient and non-trivial further developments of the invention are specified in the dependent claims.

[0011] The head-up display according to the invention for a motor vehicle comprises a housing with an opening. This opening is a light emission aperture. Furthermore, the head-up display includes a transparent cover inserted into the opening. The head-up display also includes an image transmitter arranged in the housing, by means of which an image can be projected through the display onto a windshield of the motor vehicle. The image transmitter can, for example, be a TFT display which is backlit by a suitable light source, for example by means of LEDs. The head-up display according to the invention is characterized in that the cover has a glass pane with a thickness of less than 500 µm.

[0012] The invention therefore provides that the cover is not made of a plastic, such as polycarbonate. The invention is based on the understanding that plastic covers typically require additional scratch protection and are also relatively limited in their operating temperature range. Furthermore, plastic covers for such head-up displays usually have to be relatively thick, especially when they are intended to cover very large openings in such head-up display housings that serve as light emission points. In addition, plastic covers unintentionally affect the polarization, particularly due to birefringence of light. This unwanted birefringence can originate, among other things, from material stresses within the plastic.Furthermore, plastic covers also undesirably affect the color of the image projected onto the windshield by the image sensor.

[0013] The head-up display according to the invention comprises the cover, which has a glass pane with a thickness of less than 500 µm. In other words, the glass pane is so-called ultra-thin glass. Preferably, the glass pane has a thickness of 25 µm to 210 µm. Particularly in this thickness range, the glass pane can be bent without heating. Such ultra-thin glass can be easily deformed in one dimension when cold, which is ideal for head-up displays that project images onto the windshield. Preferably, the glass pane has a radius of curvature of 200 to 400 millimeters. Such radii of curvature can be easily achieved without heating the glass pane if it has the aforementioned thickness of less than 500 µm, and particularly less than 210 µm.

[0014] Furthermore, even without a scratch-resistant coating, the glass panel offers significantly better scratch protection than plastics with a so-called hardcoat. Additionally, the glass panel prevents UV light from penetrating the head-up display housing through the opening that serves as the light exit aperture, as the UV light is absorbed by the glass.

[0015] Especially when the head-up display is intended to project particularly large images onto the windshield, for example, because it is a contact-analog head-up display as mentioned earlier, it is possible to prevent unwanted, acoustically perceptible vibrations from being excited by the glass pane during driving or other vehicle use, despite its large dimensions. This is because glass has a significantly higher modulus of elasticity compared to plastic, meaning that the first resonant frequency is shifted to considerably higher frequencies than would be the case with a plastic cover. As a result, the glass pane can be made much thinner than plastic panes, and particularly large-format dimensions can be installed without excitation and with standard glass thicknesses.In the head-up display according to the invention, the cover according to the invention reliably prevents it from being excited to unwanted and acoustically perceptible resonance vibrations.

[0016] An advantageous embodiment of the invention provides that the glass pane is chemically tempered. The tempering, and thus the breakage resistance of the glass pane, can be further increased by chemical tempering. However, other tempering methods are also possible.

[0017] In a further embodiment of the invention, the glass pane is provided with a decorative print, in particular with a black border. The glass pane can easily be provided with such a decorative print. This black border need not only serve as a decorative print, but can also, for example, contain ceramic particles that give the edge area a rough and adhesive surface.

[0018] Another advantageous embodiment of the invention provides that the cover is a laminate, wherein the glass pane forms the outermost layer of the laminate and is bonded to at least one underlying layer. This means that the cover has a layered structure, with the glass pane positioned at the outermost point of the cover, facing the windshield, in the intended installation position of the head-up display. In other words, the glass pane, as the outermost layer, faces the windshield when the head-up display is installed. In particular, the laminated structure of the cover prevents it from shattering, and the at least one additional layer of glass pane provides greater stability.

[0019] In a further advantageous embodiment of the invention, it is provided that the glass pane is bonded to the at least one layer by means of an optical adhesive.

[0020] Optical adhesives have the particular advantage of being transparent.

[0021] This does not affect the image display via the head-up display.

[0022] According to a further advantageous embodiment of the invention, the glass pane is at least indirectly bonded to a polarizing film. It is possible, for example, for the glass pane to be bonded directly to the polarizing film. The polarizing film improves the optical display characteristics of the head-up display.

[0023] In a further advantageous embodiment of the invention, the glass pane is at least indirectly bonded to an anti-reflective film. The glass pane can either be bonded directly to the anti-reflective film, or, for example, the anti-reflective film can be bonded to the aforementioned polarizing film. The anti-reflective film prevents unwanted reflections in the head-up display.

[0024] According to a further advantageous embodiment of the invention, the anti-reflective film has a three-dimensional nanostructure with protrusions and / or an anti-reflective layer. In both cases, unwanted reflections from the head-up display can be reliably prevented.

[0025] In a further advantageous embodiment of the invention, the cover comprises another glass pane, which forms the innermost layer of the laminate. For example, it is possible that only the optical adhesive is arranged between the two glass panes. However, other configurations are also possible, such that, for example, one or more of the aforementioned films are arranged between the two glass panes. The two glass panes can have the same thickness or different thicknesses. For example, if the opening in the housing serving as the light exit aperture is particularly large, it is conceivable that it is advantageous to use two of the glass panes bonded together.

[0026] In the inventive method for producing a cover for the inventive head-up display or an advantageous embodiment of the inventive head-up display, a glass material with a thickness of less than 500 µm is bonded to at least one further layer in the form of the laminate.

[0027] Preferably, the glass material is supplied as roll stock on a first roll, and the at least one further layer is also supplied as roll stock on a second roll. The two rolls are automatically unwound onto each other to produce the laminated cover, bonding them together in the process. The cover is then separated from the bonded roll stock. In other words, the laminated cover can be produced first as a continuous material in the manner described and then separated. This allows for the efficient and reliable production of a large number of laminated covers.

[0028] Alternatively, the glass material and at least one layer can be pre-cut to a predetermined cover dimension and bonded together to create the laminated cover. In other words, the glass material and at least one layer can be supplied as individual sheets, already cut to the desired cover dimensions. Furthermore, the glass material and at least one layer can be pre-bent to a predetermined cover curvature before bonding. This offers the advantage of eliminating the need to bend the laminate after production. This prevents unnecessary and undesirable stresses from developing after the individual layers have been laminated.For the laminated cover, special attention must be paid to so-called stress-free lamination in order to avoid delamination in the installed state and under the influence of temperature.

[0029] The invention further relates to a motor vehicle with the head-up display according to the invention or an advantageous embodiment of the head-up display according to the invention.

[0030] Further features of the invention are evident from the claims, the figures, and the description of the figures. The features and combinations of features mentioned above in the description, as well as those subsequently mentioned in the description of the figures and / or shown in the figures alone, are not only usable in the combinations specified but also in other combinations without departing from the scope of the invention. Thus, embodiments of the invention that are not explicitly shown and explained in the figures but can be derived and generated from separate combinations of features in the explained embodiments are also to be considered as encompassed and disclosed. Embodiments of the combinations of features that do not exhibit all the features of an originally formulated independent claim are also to be considered disclosed.Furthermore, embodiments and combinations of features, in particular those set out above, are to be considered disclosed which go beyond or deviate from the combinations of features set out in the cross-references of the claims.

[0031] The drawing shows in: Fig. 1 a schematic side view of a motor vehicle with a head-up display; Fig. 2 a schematic perspective view of the head-up display, which has an opening in a housing serving as a light emission aperture, which is closed by a cover shown in exploded view; Fig. 3 a highly schematic representation of a method for manufacturing the transparent cover in the form of a laminate; Fig. 4 a schematic representation of one embodiment of the laminate-like transparent cover; Fig. 5 a schematic representation of another embodiment of the laminate-like transparent cover; Fig. 6 a schematic representation of another embodiment of the laminate-like transparent cover; Fig. 7 a schematic representation of another embodiment of the laminate-like transparent cover; and in Fig.8A schematic representation of another embodiment of the transparent cover, wherein this has only one glass pane.

[0032] In the figures, identical or functionally equivalent elements have been provided with the same reference symbols.

[0033] A motor vehicle 1 is shown in a schematic side view in Fig. 1 shown. A head-up display 3 is arranged in front of a driver 2 of the motor vehicle 1, by means of which an image can be projected onto a windshield 4 of the motor vehicle 1.

[0034] In Fig. 2 The head-up display 3 is shown in a schematic perspective view. The head-up display 3 comprises a housing 4 with an opening 6 serving as a light inlet. The opening 6 is covered by a transparent cover 7, which is shown here in an exploded view. Furthermore, a schematically indicated image transmitter 8 is arranged in the housing 5 of the head-up display 3, by means of which an image can be projected through the transparent cover 7 onto the windshield 4 of the vehicle 1.

[0035] The image sensor 8 can, for example, have a TFT display and LED-based backlighting of the TFT display. Furthermore, optical elements, such as folding mirrors and concave mirrors, can be arranged in the housing 5 to direct and scale the beam path of the image sensor 8 onto the windshield 4 as desired.

[0036] In the present case, the cover 7 is constructed as a laminate, i.e., it comprises several layers. The uppermost layer is formed by a glass sheet 9, which has a thickness of less than 500 µm. In other words, the glass sheet 9 is so-called ultrathin glass. Preferably, the glass sheet 9 has a thickness between 25 µm and 210 µm. Furthermore, the glass sheet 9 preferably has a radius of curvature of 200 to 400 millimeters.

[0037] The glass pane 9 can also be chemically tempered to make it particularly durable and, above all, scratch-resistant. This can also increase the breakage resistance of the glass pane 9. Furthermore, the glass pane 9 can also be provided with a decorative print (not shown in detail here), for example, in the form of a black border or similar.

[0038] The glass pane 9 is bonded to a polarizing film 11 or an anti-reflective film 12 using an optical adhesive 10. Other layered structures are also possible.

[0039] In Fig. 3 A process for manufacturing the cover 7 is schematically illustrated. The process shown here is a continuous manufacturing process. A glass material is provided as roll stock 13 wound onto a first roll 14. Furthermore, at least one additional layer 11, 12 is also provided as roll stock 15 wound onto a second roll 16. The two rolls 14, 16 are automatically unwound onto each other to produce the laminated cover 7 and are bonded together in the process. The cover 7 is then separated from the bonded roll stock. This separation can be achieved, for example, using a laser or other cutting techniques. This continuous manufacturing process makes it possible to produce a large number of laminated covers 7 in a particularly reliable and cost-effective manner.

[0040] Alternatively, the glass material and at least one layer 11, 12 can be pre-cut to a predetermined dimension of the cover 7 to be manufactured and then bonded together. Furthermore, in this case, the glass material and at least one layer 11, 12 can also be pre-bent to a predetermined curvature of the cover 7 before bonding.

[0041] In Fig. 4 Another embodiment of the laminate-like cover 7 is shown schematically. In the embodiment shown here, the outer glass pane 9 has been bonded to another glass pane 17 by means of the optical adhesive 10.

[0042] In Fig. 5 Another embodiment of the cover 7 is shown schematically. In the embodiment shown here, the outer glass pane 9 has been bonded to the previously mentioned polarizing film 11 by means of the optical adhesive 10.

[0043] In Fig. 6 Another embodiment of the cover 7 is shown schematically. In this embodiment, the outer glass pane 9 is bonded to the previously mentioned anti-reflective film 12 by means of the optical adhesive 10.

[0044] In Fig. 7 Finally, another embodiment of the cover 7 is shown schematically. In the embodiment shown here, the cover 7 again comprises the two glass panes 9, 17, which are bonded to the polarizing film 11 via the respective optical adhesive 10.

[0045] The optical adhesive 10 can, for example, have a thickness of 10 µm in all embodiments. The two glass panes 9, 17 can, for example, each have a thickness of 150 µm. It is also possible, for example, that the glass pane 9 has a thickness of 200 µm. The polarizing film 11 can, for example, have a thickness of 50 µm, while the anti-reflective film 12 can, for example, have a thickness of 250 µm. The anti-reflective film 12 can, for example, be a polycarbonate film provided with a three-dimensional nanostructure with raised areas and / or with an anti-reflective coating.

[0046] The laminated cover 7 with the ultra-thin cover glass 9 has the advantage in all embodiments that, due to the significantly higher modulus of elasticity of the glass 9 compared to plastic, the first resonance frequency is shifted to significantly higher frequencies, as a result of which the cover 7 cannot be subjected to undesirable, audible vibrations during driving or use of the motor vehicle 1.

[0047] The illustrated embodiments of the cover 7 are particularly well-suited when the head-up display 3 is a so-called contact-analog head-up display, which, for example, projects various information across the entire windshield 4 to enhance or augment reality. In this case, the opening 7 in the housing 5 of the head-up display 3 is correspondingly large. Despite the relatively large dimensions of the opening and the associated large size of the cover 7, its design allows it to be used in the motor vehicle 1 without any vibration, i.e., without generating unwanted noise.

[0048] Finally, in Fig. 8 Another embodiment of the cover 7 is shown. In contrast to the other embodiments shown, this one is not constructed as a laminate. Instead, the cover 7 comprises only the single glass pane 9. This can be attached, for example, to the housing 5 of the head-up display 3 using suitable adhesives (see Figure 1). Fig. 2 ) be attached.

Claims

1. Head-up display (3) for a motor vehicle (1), comprising - a housing (5) with an opening (6) serving as a light exit opening; - a transparent cover (7) inserted into the opening (6); - an image generator (8) arranged in the housing (5), by means of which an image can be projected through the cover (7) onto a windshield (4) of the motor vehicle (1); - optical elements arranged in the housing (5) to direct and scale the beam path of the image generator (8) onto the windshield (4) of the motor vehicle (1); characterized in that the cover (7) has a glass pane (9) with a thickness less than 500 µm and the cover (7) is a laminate, wherein the glass pane (9) forms the outermost layer of the laminate and is bonded to at least one layer (11, 12, 17) arranged underneath.

2. Head-up display (3) according to claim 1, characterized in that the glass pane (9) has a thickness between 25 µm and 210 µm.

3. Head-up display (3) according to claim 1 or 2, characterized in that the glass pane (9) has a radius of curvature of 200 to 400 mm.

4. Head-up display (3) according to any one of the preceding claims, characterized in that the glass pane (9) is chemically hardened.

5. Head-up display (3) according to any one of the preceding claims, characterized in that the glass pane (9) is provided with a decorative print, in particular with a black border.

6. Head-up display (3) according to claim 1, characterized in that the glass pane (9) is bonded to the at least one layer (11, 12, 17) by means of an optical adhesive.

7. Head-up display (3) according to claim 6, characterized in that the glass pane (9) is at least indirectly bonded to a polarization film (11).

8. Head-up display (3) according to claim 6 or 7, characterized in that the glass pane (9) is at least indirectly bonded to an anti-reflection film (12).

9. Head-up display (3) according to claim 8, characterized in that the anti-reflection film (12) has a three-dimensional nanostructure with elevations and / or an anti-reflection layer.

10. Head-up display (3) according to any one of claims 1 to 9, characterized in that the cover (7) has a further glass pane (17) which forms the innermost layer of the laminate.

11. Method for producing a cover (7) for a head-up display (3) according to any one of claims 1 to 10, in which a glass material with a thickness less than 500 µm is bonded with the at least one further layer (11, 12, 17) in the form of the laminate.