DE202008018075U1 - Curved vehicle windscreen made of laminated glass - Google Patents

Abstract

Curved vehicle windshield made of laminated glass, the outer and inner surfaces of which form a wedge angle with one another, at least in preferred areas, in order to avoid or reduce double images disturbing the view, characterized in that the two glass surfaces have a depending on the respective angle of incidence φ and on the respective local bending radius R have continuously changing wedge angle δ.

Description

The invention relates to a curved vehicle windshield made of laminated glass, the outer and inner surfaces of which form a wedge angle with each other at least in preferred areas to avoid or to reduce in the review disturbing double images.

The occurrence of double vision when looking through the windshield can be very disturbing for the driver of the vehicle. Double images appear to the driver's eye, in particular in the case of curved windshields under certain contrast conditions, namely usually during night driving over the headlight images of oncoming vehicles or other bright light sources. They arise as a result of multiple reflections on the surfaces of the windshield when a portion of the incident light rays, the so-called secondary beam, exits the windshield at an angle to the primary beam. The angle between the primary beam and the secondary beam is called a double-angle image. Since the intensity of the secondary beam is very low and is usually less than 1% of the intensity of the primary beam, it is only visible if it can stand out from the dark environment, ie at night or when passing through an unlit tunnel.

Double images occur in glass panes with so-called wedge defects and bent glass panes. Since today's float glass panes, which are used for the production of windshields, in contrast to the previously used glass panes have virtually no more wedge errors, disturbing double images are observed essentially only in curved glass panes. Depending on the shape and the respective inclination of the windshield but they can take on very disturbing proportions.

wobei

η

den Doppelbildwinkel,

n

den Brechungsindex des Glases,

d

die Dicke der Glasscheibe

R

den Biegeradius der Glasscheibe am Ort des einfallenden Lichtstrahls, und

φ

den Einfallswinkel des Lichtstrahls zur Normalen auf die Tangente zur Scheibe bedeuten.

To JP Aclocque "Double images as a disturbing optical error of the windshield" in Z. Glastechn. Ber. 193 (1970) pp. 193-198 can be calculated as a function of the bending radius and the angle of incidence of the light beam, the double image angle according to the following relationship:

in which

η

the double angle,

n

the refractive index of the glass,

d

the thickness of the glass pane

R

the bending radius of the glass pane at the location of the incident light beam, and

φ

Mean the angle of incidence of the light beam to the normal to the tangent to the disc.

von dem durch die Glasoberflächen gebildeten Keilwinkel δ abhängig ist, lässt sich durch Gleichsetzung der beiden genannten Gleichungen der Keilwinkel δ, der bei gegebenem Biegeradius R und gegebenem Einfallswinkel φ für die Eliminierung des Doppelbildes erforderlich ist, nach der Formel

berechnen.As with flat glass panes the double angle η according to the formula

is dependent on the formed by the glass surfaces wedge angle δ, can be by equating the two equations of the wedge angle δ, which is required for a given bending radius R and given angle of incidence φ for the elimination of the double image, according to the formula

to calculate.

From the DE 19535053 A1 and the DE 19611483 A1 It is known to use the physical relationships to reduce the annoying double images of bent glass panels by using a wedge-shaped cross-section bonding film to produce a laminated glass windshield. For the calculation of the wedge angle while a mean angle of incidence and a mean bending radius of the windshield are used. It should be reduced by at least 20%, and in particular by at least 60% by the measures proposed in this document, the amount of the double angle with respect to the entire windscreen. The thicker area of the bonding film should be at the top, and with increasing curvature of the windshield a connecting film with a larger wedge angle should be used.

In windshields with relatively simple bending can be achieved with this known method, ie with a connecting film with a constant wedge angle, satisfactory results. In so-called panoramic windshields, however, which are bent at the top and possibly also in the lateral areas, the double images can not be sufficiently reduced in this way. Therefore, at least in complex bent glass panes still double images are visible, which can significantly disturb the driver.

The invention is based on the object bent windshields, in which the outer glass surfaces include a wedge angle to reduce the double images, to further develop that even with strongly and / or irregularly curved windshields and flat mounting angles, the double images largely compensated by the shape of the windshields become.

This object is achieved by a windshield having the features of claim 1.

Preferably, the windshield according to the invention between the outer glass surfaces on a wedge angle curve, which varies steadily from the lower edge of the windshield to the upper edge of the windshield.

Since ultimately only the course of the wedge angle enclosed by the glass surfaces is responsible for the double image angles and their compensation, it is fundamentally possible to incorporate the required wedge angle profile into one of the individual glass panes used in composite glass production or into both glass panes. However, the invention can be realized more economically if the required continuously changing wedge angle is incorporated in the thermoplastic intermediate film used for the production of the windshield.

Stronger bends of the glass sheets are often associated with slight changes in thickness due to the areal stretching of the glass. An expedient development of the invention is therefore distinguished by the fact that, in determining the continuously changing wedge angle, the changes in thickness caused by the deformation of the individual glass panes are taken into account.

Windshields, which also have larger bends in the horizontal direction, for example in the lateral end regions, are characterized in an expedient development of the invention in that the surfaces of the windshield in these areas also have a continuously changing wedge angle in the horizontal direction. For such windshields intermediate films are required with a complex thickness profile, which can be achieved for example by superimposing two crossed wedge films, or by subsequent superficial removal of the intermediate film.

However, in the case of complex geometries of the glass panes, which have a greater bending in both the vertical and the horizontal direction, one must take into account when calculating the course of the compensation wedge angle that the beam path no longer lies in a plane, but runs three-dimensionally.

Conveniently, the calculation of the required compensation wedge angle is based on the shape and the inclination of the windshield along the vertical center line of the windshield. Along this line, starting at the lower edge of the windshield, at intervals of, for example, a few centimeters, the compensation wedge angles δ are determined with the aid of the abovementioned equation [3], which are respectively required at these locations. These calculations continue to the top edge of the windshield. The intermediate values between these calculated values are obtained by interpolation. In this way, the complete course of the wedge angle δ over the entire wheel height is determined. The thickness profile of the thermoplastic intermediate film is then calculated from the required wedge angle curve determined in this way, with which the individual glass panes are connected to one another using heat and pressure. This thickness profile is transferred to the finished laminated glass pane after the glass sheets have been joined.

The required wedge angle profile and the resulting thickness profile of the intermediate foil must be calculated separately for each disc shape. The thickness profile according to the invention can be achieved by using a corresponding slot nozzle in the extrusion of the film, or by targeted stretching of the heated film with a corresponding temperature profile. However, it is also possible to produce by subsequent removal of the film, the desired thickness profile. These methods can also be combined by, for example, producing the thickness profile in one direction through a corresponding slot die during extrusion, and in the other direction by subsequently correspondingly stretching the film.

For the calculation of the double image angle η and the corresponding local compensation wedge angle δ, one can choose the arrangement as described in the test specification ECE R43 Annex 3 for the determination of the double angle is recommended. With this arrangement, the double image angles are detected when the driver's head moves from a lower position in the vertical direction to an upper end position. That is, the driver's line of sight always remains horizontal. Preferably, however, an arrangement is selected in which the double image angle is calculated from an average steady position of the driver (eye point), wherein the driver's angle of vision changes through the windshield. It has been found that this arrangement is more practical than the arrangement provided for in the test specification.

In the following the invention with reference to an embodiment and the drawings will be explained in more detail. From the drawings shows

1 a simplified schematic representation of the beam path, which leads to the formation of the double images;

2 FIG. 3 is a graph illustrating the profile of the double-angle η versus the height of the windshield for a particular model of windshield viewed from the point of view; FIG.

3 a diagram showing the course of the calculated Kompensationskeilwinkels δ over the height of the windshield, and

4 the course of the Kompensationskeilwinkel corresponding thickness profile of the intermediate foil.

In 1 is the fundamental beam path shown, as he beam passing through a curved glass 1 in the eye 2 the driver leads to the formation of double images. From the light source 3 the primary light beam P goes out after two deflections on the two surfaces of the glass pane 1 as primary beam P 'in the eye 2 the driver falls. The eye sees the bright light source 3 however, as a primary image 3 ' in extension of the primary beam P '. Inside the glass pane 1 a small part of the primary beam P is reflected twice on the glass surfaces and exits as a secondary beam S from the glass pane. The eye 2 the driver sees the double picture 3 '' in extension of the secondary beam S. In the area where the of the light source 3 outgoing primary jet on the glass pane 1 hits, has the glass pane 1 a curvature with the bending radius R on. The angle enclosed by the primary beam P 'and the secondary beam S is the so-called double image angle η.

In the following, the calculations for the determination of the wedge angle profile according to the invention are carried out for a specific windscreen model designed for a vehicle to be newly developed.

In the calculation, it is done so that along a vertical section in the middle of the windshield, taking into account the real installation angle and a mean eye position at intervals of about 10 cm each resulting in the driver's eye double angle η according to the formula given above [1] be calculated. Since the driver's downside view is normally limited by the edge of the bonnet, it suffices if the calculation of the double image angle begins at this point, which is referred to as MK in the table below. To the top, the view through the windshield is normally not limited, so that the calculation is expediently carried out up to the upper edge of the pane.

In the following table, the points on the vertical center line of the windshield where each calculation of the double-angle was made are defined by their distance in mm from the hood edge MK. At each of these measuring points, on the one hand, the inclination angle φ determined by the normal to the tangent to the bent glass pane is determined, and on the other hand, in each case, the bending radius R of the glass pane is determined. From these data, using the above equation [1], first the double image angle η, and then, with the aid of the equation [3], the wedge angle δ, which is required at this point for the compensation of the double image. In calculation formulas, the refractive index of the glass is assumed to be 1.52, and the thickness d of the windscreen is 4.96 mm. Distance MK φ R η δ film thickness (Mm) (°) (Mm) ( ') (Mrad) (Mm) 1531 68.17 3464 2,484 0.228 1,399 1429 59,95 3481 3,418 0,300 1.375 1327 53.18 3482 4,201 0,350 1.345 1225 47.75 3468 4,850 0,383 1,309 1123 43.43 3439 5,392 0.404 1,270 1021 40.02 3397 5,855 0,417 1,229 919 37.34 3343 6,259 0.426 1,186 817 35.24 3279 6.625 0.434 1.143 714 33.61 3207 6,964 0.441 1,098 612 32.37 3127 7,286 0.449 1,053 510 31.45 3042 7,602 0.459 1,008 408 30,80 2952 7,911 0,470 0,961 306 30.38 2859 8,220 0,483 0.913 204 30.17 2765 8,529 0.499 0,864 102 30.14 2670 8,836 0.516 0.813 0 30.12 2575 9,165 0.535 0,760

Since the usual standard films, the thickness of the films for reasons of puncture resistance of the windshield is 0.76 mm, the thickness of the film also at the intermediate layer according to the invention at its thinnest point also has the value of 0.76 mm. The thickness increases continuously up to the upper edge of the windscreen up to 1.399 mm.

The values calculated in this way for the double angle η, the compensating wedge angle δ and the film thickness are in the 2 to 4 represented in the form of corresponding diagrams. While 2 shows the course of the double image angle η (in arc minutes) with increasing distance from the hood edge 3 the course of the compensation wedge angle δ in mrad, also with increasing distance from the motor edge MK. 4 Finally, the thickness profile of the intermediate foil represents the required ever-changing wedge angle between the surfaces of the glass sheet when the individual glass sheets are bonded together with such an intermediate sheet by application of heat and pressure.

In the 4 the solid curve represents the inventive thickness profile of the intermediate film corresponding to the table. In contrast, the dashed line curve shows the state of the art corresponding linear thickness profile of the intermediate film with the same wedge angle. It can be clearly seen that the thickness profile according to the invention differs significantly from the linearly extending thickness profile.

During the bending process of the glass panes, that is to say in the transition from the two-dimensional to the three-dimensional form, depending on the extent of the bending, the glass panes are partially stretched slightly, which is inevitably associated with changes in thickness. These changes in thickness can be quite a few microns in spherically curved glass in the areas that were heated locally stronger. These inevitably occurring changes in thickness which, depending on the shape of the windshield, influence the wedge-angle course in one or the other direction must, of course, be taken into account accordingly for the final determination of the wedge-angle course. Also, the minimum elongation of the intermediate film, which takes place during the joining process, namely when the two-dimensional shape changes to a three-dimensional shape, must be taken into account when determining the wedge angle profile.

Even small geometric deviations can have a significant influence on the double images. However, during the prototype phase in vehicle construction, it is usually possible to tailor the wedge angle profile once again to the given situation.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 19535053 A1 [0006]
• DE 19611483 A1 [0006]

Cited non-patent literature

• JP Aclocque "Double images as a disturbing optical error of the windshield" in Z. Glastechn. Ber. 193 (1970) pp. 193-198 [0004]
• ECE R43 Annex 3 [0017]

Claims (6)

Curved vehicle windshield made of laminated glass, the outer and inner surfaces of which form a wedge angle with each other, at least in preferred areas to avoid or reduce in the review double-spaced, characterized in that the two glass surfaces a depending on the respective angle of incidence φ and the respective local bending radius R have continuously changing wedge angle δ. Vehicle windshield according to claim 1, characterized in that the wedge angle δ between the outer and the inner surface of a vertically curved windshield continuously changes from the lower edge to the upper edge of the windshield. Vehicle windshield according to claim 2, characterized in that the wedge angle is continuously reduced from the lower edge to the upper edge of the windshield. Vehicle windshield according to one of claims 1 to 3, characterized in that the wedge angle δ between the outer and the inner surface of the windshield in areas of strong horizontal bending continuously changes in these areas in the horizontal direction. Vehicle windscreen according to one of claims 1 to 4, characterized in that the continuously changing wedge angle δ is incorporated in the intermediate film used for the production of the windscreen of laminated glass. Vehicle windshield according to one of claims 1 to 5, characterized in that in the determination of the continuously changing wedge angle δ due to the deformation of the individual glass panes thickness changes are taken into account.

Images