GB2280739A

GB2280739A - Reflector for headlight of automobile

Info

Publication number: GB2280739A
Application number: GB9415872A
Authority: GB
Inventors: Norikazu Saitoh
Original assignee: Koito Manufacturing Co Ltd
Current assignee: Koito Manufacturing Co Ltd
Priority date: 1993-08-06
Filing date: 1994-08-05
Publication date: 1995-02-08
Anticipated expiration: 2014-08-05
Also published as: JPH0757505A; GB2280739B; JP2753943B2; DE4427702A1; GB9415872D0; DE4427702B4

Description

2280739 Reflector for Headlight of Automobile The present Invention

relates to a reflector for a headlight of an automobile, in particular, to a reflector having a reflecting region whose luminance can be precisely controlled.

As automobiles have been streamlined due to needs for aerodynamical characteristics and attractive shapes, headlights corresponding to narrow front portions (namely, slant-nose) of automobiles should be designed.

However, in the conventional reflectors, since lens steps of an outer lens are important for forming a luminance pattern with a cut line peculiar to a low beam, the angle of the outer lens against the optical axis cannot be unlimitedly increased. Thus, such reflectors cannot be adequately applied to slant-type lamps.

To solve such a problem, a reflector that can be provided with a front lens that has no or a few lens steps has been desired.

An example of such a reflector is a so called multiref lector. in the multi-ref lector, the ref lecting surf ace is formed of reflecting segments. The luminance of the reflecting surface is controlled so as to form a luminance pattern of a low beam or a similar pattern.

Fig. 12 is a schematic diagram showing an example "a" of such a reflector.

In Fig. 12(a), reference letter a is a reflector that is formed of a large number of reflecting segments b, b, 1 is .. on a bass surface that is a paraboloid of revolution. The base shape of each reflecting segment is a hyperbolic paraboloid, an elliptic paraboloid, a hyperboloid of two sheets, or the like.

The reflecting surface is decomposed into several regions so as to control the luminance. In consideration of diffusion and Concentration of light for each reflecting region, the shape of reflecting segments b, b,.. . is defined. By composing patterns projected from the reflecting regions, a predetermined luminance pattern or a similar pattern thereto can be forSwML Thus, the luminance pattern can be controlled while being less affected by lens steps of the outer lens.

Fig. 12(b) is an enlarged view showing a region for obtaining a beam that travels toward a slant cut line with a predetermined angle against horizontal line of a luminance pattern of a low beam. This region is a portion denoted by a circle of Fig. 12A.

A fan-shaped reflecting region c is a portion for forming a slant cut line. The reflecting region c is formed of reflecting segments b_c, b_c,.. .. that are shaped in hyperboloids of two sheets.

A reflecting region d disposed just above the reflecting segment c is a portion for forming a pattern disposed below the slant cut line and diffused in the horizontal direction. The reflecting region d is formed of reflecting segments b_d, b_d,... that are shaped in elliptic paraboloids.

In Fig. 12(a), reference letter f is a filament for irradiating a low beam. The center axis of the filament f 2 c is extends in vertical direction of the drawing. When a low beam is irradiated, rays of light that travel from the filament f toward a lower region of the reflecting surface are blocked with a shade g disposed below the filament f.

However, the degree of freedom of the disposition of the reflecting segments b, b,... of the reflector a is low. In addition, as shown in Fig. 12(a), the reflecting segments other than reflecting region c are shaped in a grid pattern. Moreover, the reflecting region c is decomposed of reflecting segments that are formed as concentric circles with the center of the optical axis. Thus, the luminance of a portion in the vicinity of the slant cut line with a predetermined angle to the horizontal line "HHI" cannot be adequately controlled corresponding to luminance standard.

In other words, as shown in Fig. 13(a), a pattern h projected from the reflecting region c forms a slant cut line disposed on the right of the vertical line (denoted by V-V). However, as is clear fTom. the shape of reflecting segments b_c, b_c,... that form the reflecting region c, the pattern extends radially from an intersection j disposed between the slant cut line and the horizontal cut line (this direction is denoted by arrows i, i, ---)Thus, since the pattern h at the intersection j is thin, the center intensity of the luminance pattern cannot be obtained.

As shown in Fig. 13(b), since a pattern k projected from a reflecting region d is disposed below the slant cut line, on the right of the vertical line V-V, and along and just below the horizontal line H-H, there is a gap 2 3 is (numly, dirk portion) between the pattern k and h. For example, In the European luminance standards, a detecting point P (so-called 75M in defined on a horizontal cut line denoted by a dotted line a. However, since the pattern k In not present at the detecting point P, It In difficult to obtain a predetermined amount of luminance at the detecting point P.

An object of the present invention Is to provide a reflector for a headlight of an automobile, the reflector having a reflecting region whose luminance can be precisely controlled.

The present Invention is a reflector for forming a luminance pattern of a low beam for a headlight of an automobile, comprising a reflecting region for forming a luminance pattern in the vicirLity of a horizontal line below an Inclined cut line inclined with a predetermined cut line angle against the horizontal lino, the reflecting region being formed of a plurality of reflecting segments shaped in an elliptic paraboloid, each of the reflecting segments being formed of a surface where the elliptic paraboloid is rotated with the cut line angle or less about main optical axle of the reflector.

According to the present Invention, a portion in the vicinity of a slant cut line of a luminance pattern of a low beam and a portion below the slant cut line and In the vicinity of horizontal line are formed by revolving reflecting segments shaped In an elliptic paraboloid about a main optical axis of a reflector, the dispositions of patterns projected from the reflecting segments can be 4 precisely controlled.

According to the first aspect of the present invention, a reflecting region for forming a portion In the vicinity of a slant cut line is formed of a set of reflecting segments shaped in an elliptic paraboloid. The reflecting segments are formed of a surface of revolution of the elliptic paraboloid revolved about the main optical axis of the reflector with a predetermined angle. A patte= projected from the reflecting region extends with an angle against the horizontal line. The direction in which the pattern spreads out is in parallel with the slant direction thereof. Since one end portion of the pattern is not narrow at the intersection between the horizontal cut line and the slat cut line, this portion can be used as rays of light for forming the center portion of the luminance pattern.

According to the second aspect of the present invention, a reflecting region for forming a portion below a slant cut line and in the vicinity of the horizontal line is formed of a set of reflecting segments shaped in an elliptic paraboloid. The reflecting segments are formed as surfaces revolved with any angles lose than a cut line angle about the main optical axis of the reflector. A pattern projected from the reflecting region extends with an angle against the horizontal line. The pattern is disposed just below and adjacent to the slant cut line. Thus, no gap is disposed between the pattern and the portion in the vicinity of the slant cut line.

These and other objects, features and advantages of the present invention will become more apparent in light of is the following detailed description of a bent mode ediment thereof, as illustrated In the accompanying drawings.

In the accompanying drawings:- Fig. 1 is a front view schematically showing luminance control regions of a reflector according to the present invention; Fig. 2 is a front view showing the reflector according to the present invention; Fig. 3 is an enlarged view for explaining constructions of reflecting regions 2(3) and 2(6); Fig. 4 is a perspective view showing the shape of an elliptic paraboloid; Fig. 5 is a schematic diagram for explaining a revolving operation of a reflecting segment SEG(6) about an optical axis of the reflector; Figs. 6(a) and 6(b) are schematic diagrams for explaining the formation of a curved surface of a reflecting segment forming the reflecting region 2(6), Fig. 6(a) is a schematic diagram showing the relation between the reflecting segment and a pattern projected therefrom in the case that the reflecting segment is not revolved about the z axis, Fig. 6(b) is a schematic diagram showing the relation between the reflecting segment and the pattern, projected therefrom in the case that the reflecting segment is revolved about the z axis; Fig. 7 is a schematic diagram showing a pattern projected from the reflecting region 2(6); Fig. 8 Is a schematic diagram for explaining a revolving operation of a reflecting segment SEG(3) about 6 the optical axis of the reflector; Figs. 9(a) and 9(b) are schematic diagrams for explaining the formation of a curved surface of a reflecting segment forming the reflecting region 2(3), Fig. 9 (a) is a schematic diagram showing the relation between the reflecting segment and a pattern projected therefrom in the case that the reflecting segment is not revolved about the x axis, Fig. 9(b) is a schematic diagram showing the relation between the reflecting segment and the pattern projected therefrom in the case that the reflecting segment is revolved about the x axis; Fig. 10 is a schematic diagram for explaining the value of angle of revolution 8 of the reflecting segment SEGM; Fig. 11 is a schematic diagram showing a pattern projected from the reflecting region 2(3); Figs. 12(a) and 12(b) are schematic diagram showing a conventional reflector, Fig. 12(a) is a front view thereof, Fig. 12(b) is an enlarge front view of principal portions thereof; and Figs. 13(a) and 13(b) are schematic diagrams for explaining a problem in the related art reference, Fig. 13(a) is a schematic diagram showing a pattern projected from a reflecting region c, Fig. 13(b) is a schematic diagram showing a pattern projected from a reflecting region d.

Next, with reference to the accompanying drawings, a reflector for a headlight of an automobile will Ixab 7 described. In the embodiment, the present invention is applied to a nearly circular reflector.

Fig. I is a front view showing luminance control regions of a reflector 1. The reflector I has a reflecting surface 2 that has a total of six reflecting regions that are denoted by 2(1) where i is an identification number representing each region (i u 1 to 6, integer number).

The reflector 1 employs orthogonal coordinate system. The axis that passes through the center of the reflecting surface 2 and extends perpendicular to the drawing is defined as x axis. The axis that is perpendicular to the x axis and that extends horizontally is defined as y axis. The axis that is perpendicular to the x axis and that extends vertically is defined as z axis. The center of the reflecting surface 2 is defined as the origin of the orthogonal coordinate system. A lamp mounting hole 2a is formed at the center of the reflecting surface 2 (namely, at the origin 0 of the orthogonal coordinate system).

In Fig. 1, reference numeral 3 is a filament for irradiating a low beam. The filament 3 is mounted on the lamp mounting hole 2a. The center axis of the filament 3 extends along the x axis. About the lower half portion of the filament 3 is covered by a shade 4.

Two reflecting regions 2(l) are disposed above and below the lamp mounting hole 2a. The reflecting regions 2(l) take most portions of the first and second quadrants of the y-z plane and portions along the z axis of the third and fourth quadrants thereof.

As shown in Fig. 2, the reflecting region 2(l) is formed of a large number of reflecting segments SEG(l), 8 1 X7 9 SEG(l).... that are shaped in hyperbolic paraboloids. Referring to Fig. 2, the reflecting segments are formed in a grid shape.

In the second and third quadrants of the y-z plane, a reflecting region 2 (2) is disposed adjacent to the left of the ref lecting region 2 (1). The ref lecting region 2 (2) is formed of reflecting segments SEG(2). In the first quadrant of the y-z plane, the reflecting region 2 (3) is disposed adjacent to the right of the reflecting region 2(l). The reflecting region 2(1) is formed of reflecting segments SEG(1). In the fourth quadrant of the y-z plane, a ref lecting region 2 (4) is disposed just below the x-y plane and adjacent to the right of the reflecting region 2(l). The reflecting region 2(4) is formed of reflecting segments SEG(4). A reflecting region 2(5) is disposed in the fourth quadrant to the right of the reflecting region 2(l). The reflecting region 2(5) is formed of reflecting segments SEG(5). Each of the reflecting segments SEG(i) (where i = 2, 3, 4 and 5) is shaped in a hyperbolic paraboloid.

In the fourth quadrant of the y-z plane, a reflecting region 2 (6) is disposed just below the x-y plane. As shown in Fig. 2, the reflecting region 2(6) is formed of reflecting segments SEG(6), SEG(6),... that are radially disposed with the center of the origin 0.

The reflecting region 2(6) forms a slant cut line of a luminance pattern of a low beam. A portion that is a part of the reflecting region 2(3) and that is adjacent to the reflecting region 2(6) reflects light corresponding to a lower part of the slant cut line.

Fig. 3 is an enlarged top view of Fig. 2. Fig. 3 shows the reflecting segments SEG(3), SEG(3),...' which form the reflecting region 2(3), and the reflecting segments SEGM, SEGM,..., which form the reflecting region 2(6). The reflecting segments SEGM, SEG(6),... are connected to the reflecting segments SEG(3), SEG(3), The reflecting segments SEG(3), SEG(3),... and the reflecting segments SEGM, SEGM,... have a shape where an elliptic paraboloid is revolved about the optical axis (x axis) of the reflector with a predetermined angle of revolution.

As shown in Fig. 4, the horizontal and vertical cross sections of the reflecting segments SEG(3), SEG(3),... are shaped in parabolas. In the above-desoribed coordinate system, where the axis that extends from the origin in the normal direction is defined as x axis, the axis that is perpendicular to the x axis and extends horizontally is defined as y axis, and the axis that is perpendicular to the x axis and extends vertically is def ined as z axis, the parabolas on the horizontal and vertical sections are Uletter shaped in the plus direction of the x axis.

When the reflecting segments SEG(6), SEG(6),... are disposed on a paraboloid of revolution that is a base surface, elliptic paraboloids are disposed an the bass surface in such a way that they are revolved with an angle of cut line as shown in Fig. S. The angle of cut line is denoted by ecl.

Fig. 6 is a schematic diagram showing the relation between a revolving operation of the reflecting segment SEGM about the x axis of the reflector with respect to the elliptic paraboloid and the position of a pattern projected therefrom. Fig. 6(a) shows the relation between is V a reflecting segment shaped in an elliptic paraboloid and a pattern projected therefrom on a screen SCN disposed in front of the reflecting segment in the case that no revolving operation is performed. Fig. 6(b) shows the relation between a reflecting segment shaped in an elliptic paraboloid and a projection pattern projected therefrom on the screen disposed in front of the reflecting segment in the case that the revolving operation is performed.

As shown in Fig. 6(a), the front view of the reflecting segment 5 is square. in addition, the reflecting segment 5 is disposed on the bass surface so that the axes Y and Z of the coordinate system shown in Fig. 4 are in parallel with the axes y and z of the reflector 1, respectively. Thus, the pattern 6 extends horizontally.

on the other hand, the reflecting segment 7 where the elliptic paraboloid is revolved counterclockwise about the optical axis (x axis) of the reflector 1 with an angle of cut line ecl projects a pattern 8 whose center axis is inclined with the angle of cut line 6cl.

In other words, since the revolving operation of the elliptic paraboloid about the x axis includes a revolving operation at the center point of the reflecting segment 7 and a moving operation on the y-z plane, these operations affect the position of the pattern S.

Fig. 7 is a schematic diagram showing a pattern 9 projected from the reflecting region 2(6).

The pattern 9 extends in a lower left direction beyond vertical line V-V. The portion that extrudes from the vertical line V-V is rays of light that form the center 11 portion of the luminance pattern of the low beam. Although the horizontal line on the screen SCH of Fig. 6(b) does not accord with the horizontal line H-H of Fig. 7, they can be finally matched by an aiming adjustment of the headlight.

Unlike with the reflecting regions 2(2), 2(3), 2(4), and 2(5) where the boundary lines of the adjacent reflecting segments extend along the y axis or the z axis, the boundary lines of the adjacent reflecting segments of the reflecting region 2(6) extend with an angle against the y axis or the z axis (see Fig. 3).

Next, the shapes of the reflecting segments SEG(3), SEG(3),... that form the reflecting region 2(3) will be described.

The reflecting segments SEG(3), SEG(3),... are shaped in elliptic paraboloids. When the reflecting segments SEG(3), SEG(3),... are disposed on a paraboloid of revolution that is a base surface, as shown in Fig. 8, they are revolved about the optical axis (x axis) of the reflector by an angle of revolution G (where 0 < 0 s ecl).

Fig. 9 is a schematic diagram showing the relation between a revolving operation of the reflecting segment SEG(3) about the x axis of the reflector with respect to the elliptic paraboloid and the position of a pattern projected therefrom. Fig. 9(a) shows the relation between a reflecting segment shaped in an elliptic paraboloid and a pattern projected therefrom on a screen SCN disposed in front of the reflecting segment in the case that no revolving operation is performed. Fig. 9(b) shows the relation between a reflecting segment shaped in an elliptic paraboloid and a projection pattern projected therefrom on 12 the screen disposed in front of the reflecting segment in the case that the revolving operation is preformed.

As shown in Fig. 9(a), the front view of the reflecting segment 10 is square. In addition, the reflecting segment 10 is disposed on the base surface so that the axes Y and Z of the coordinate system shown in Fig. 4 are in parallel with the axes y and z of the reflector 1, respectively. Thus, the pattern 11 extends horizontally.

On the other hand, the reflecting segment 12 where the elliptic paraboloid is revolved counterclockwise about the optical axis (x axis) of the reflector I with an angle of revolution e projects a pattern 13 whose center axis Is inclined with the angle of revolution 6.

The angle of revolution e for each reflecting segment is proportional to the distance to the x axis.

In other words, as shown in Fig. 10, the reflecting segment SEG(3) that is the ARmt closest to the x axis is defined as SEG(3a). The reflecting segment SEG(3) that is the second closest to the x axis is defined as SEG(3b). The angles of revolution for the reflecting segments SEG(3a), SEG(3b), SEG(3c), and so forth are defined as Ga, eb, and 6c, and so forth, respectively, where the relation of ea < eb < ec <... is satisfied. Arrow I in Fig. 10 represents the direction where angle of revolution 8 increases.

Fig. 11 is a schematic diagram showing a pattern 14 projected from a reflecting segment SEG(3).

The pattern 14 extends in an upper right direction beyond a vertical line V-V. In addition, the pattern 14 is 13 is present just below the pattern 9 of the reflecting region 2(6). Thus, a gap (dark portion) does not take place between the pattern 9 and the pattern 14. The position of the pattern 14 can be adjusted with an angle of revolution e for each reflecting segment so that the pattern 14 is present at a predetermined detecting point concerning European luminance (namely, 75R).

An Is clear from the curved surfaces of the reflecting segments SE0(3), SEG(3),... of the reflecting region 2(3), the boundary lines of the adjacent reflecting segments have an angle against the y axle or the z axis (see Fig. 3).

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Claims

1. A reflector for forming a luminance pattern of a low beam for a headlight of an automobile, the reflector comprising: a reflecting surface having a plurality of reflecting regions; the reflecting regions including first and second reflecting segments for forming a luminance pattern in the vicinity of a horizontal line below an inclined cut line inclined with a predetermined cut line angle (Ocl) with respect to the horizontal line; and a plurality of reflecting segments in each of the first and second reflecting segments and each shaped as elliptic paraboloids; wherein at least one of the reflecting segments is formed of a surface where the elliptic paraboloid is rotated with an angle about a main optical axis (x) of the reflector; and the angle is equal to or less than the cut line angle.

2. A reflector according to claim 1, wherein the second reflecting region is adapted for forming a luminance pattern of a portion in the vicinity of the horizontal line, and the angle is equal to the cut line angle.

3. A reflector according to claim 1 or claim 2, wherein the first reflecting region is adapted for forming a luminance pattern of a portion that is below the inclined cut line and in the vicinity of the horizontal line, the first region is formed of a plurality of reflecting segments, the segments are a surf ace where an elliptic paraboloid is rotated with any angle equal to less than the cut line angle, respectively.

4. A reflector according to claim 3, where the angle is proportional to the distance to the main optical axis of each of the reflecting segments.

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5. A reflector according to claim 2, wherein the second ref lecting region is substantially f an-shaped, and the reflecting segments are radially spaced.

6. A reflector for forming a luminance pattern of a low beam f or a headlight of an automobile substantially as described with reference to Figs. 1 to 11 of the accompanying drawings.