GB2280499A

GB2280499A - Reflector for headlight of automobile

Info

Publication number: GB2280499A
Application number: GB9415341A
Authority: GB
Inventors: Norikazu Saitoh
Original assignee: Koito Manufacturing Co Ltd
Current assignee: Koito Manufacturing Co Ltd
Priority date: 1993-07-30
Filing date: 1994-07-29
Publication date: 1995-02-01
Anticipated expiration: 2014-07-29
Also published as: GB9415341D0; JP2753942B2; DE4426998B4; JPH0745101A; GB2280499B; DE4426998A1

Description

2280499 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 formed of reflecting segments for forming a portion in the vicinity of an slant cut line of a luminance pattern of a low beam without a gap portion at a boundary of the reflecting segments so as to prevent dazzling light from taking place.

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 form ng 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 multireflector. In the multi -reflector, - the reflecting surface is formed of reflecting segments. The luminance of the reflecting surface Is controlled so as to fo= a luminance pattern of a low beam, or a similar pattewn.

Fig. 8 is a schematic diagram showing an example of 1 such a reflector.

In Fig. 8, reference letter a is a reflector that is formed of a large number of reflecting segments b, b,... on a base 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 thereof is defined. By composing patterns projected from the reflecting regions, a predetermined luminance pattern or a similar pattern thereto can be formed. Thus, the luminance pattern can be controlled while being less affected by the.lens steps of the outer lens than in the conventional reflector.

The left portion of Fig. 9 is an enlarged view showing segments 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. These segments are a portion denoted by a one-point dashed line in Fig. 8.

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 or a paraboloid of revolution.

A reflecting region d disposed just above the reflecting segment a 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 2 reflecting segments b_d, b_d,... that are shaped In elliptic paraboloids.

In Fig. 8, reference letter f 15 a filament for irradiating a low beam. The center axis of the filament ú extends in vertical direction of the drawing. When a low beam is irradiated, rays of light that travel from the filament f toward a predetermined region (denoted by A in Fig. 8) of the reflecting surface are blocked with a shade g. In other words, the reflecting region denoted by B of Fig. 8 f oraLs a luminance pattern of a low beam.

However, in the reflector a, gap portions h, h, are formed at boundaries between the reflecting segments b_c, b_c,..., which form a portion in the vicinity of the slant cut line, and the reflecting segments b-d, b_d,... (see Figs. 8 and 9). Thus, rays of light are dif fusely reflected at the gap portions and thereby dazzling light takes place.

In other words, as shown in the right drawing of Fig. 9, which is a sectional view taken along line A-A of the right drawing, when reflected rays i, i,... that travel toward the gap portions h, h,... are rereflected, they travel In an upper direction of the slant cut line. These rays sometimes become dazzling light.

When a reflector is produced, an undercoat layer j Is formed. Thereafter, a reflecting surface is formed by evaporating aluminum or the like thereon. Since the undercoat layer j Is formed of a paint, if the film thickness of the undercoat layer j at the gap portions h, h,... is irregular, dIffused reflection tends to take place, resulting in dazzling light.

3 According to the present invention, a reflector for forming a luminance pattern of a low beam for a headlight of an automobile comprises a plurality of reflecting regions including the third and sixth regions which are adapted for forming a portion in the vicinity of an inclined cut line and are formed of a plurality of reflecting segments, wherein a reflecting surface of each reflecting segment of the sixth region is a surf ace where the lower side of a corresponding reflecting segment of the third region that forms a boundary line with a respective reflecting segment of the sixth region is revolved about an axis that extends parallel to and in the vicinity of the main optical axis of the reflector.

Thus, no gap portions are formed between the elliptic paraboloid and a curved surface continuous to the lower surface thereof. Thus, dazzling light caused by diffused reflection at the gap portions can be prevented.

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 a schematic diagram showing principal portions of the present invention; Fig. 4 is a perspective view showing the shape of an elliptic paraboloid; Fig. 5 is a schematic diagram for explaining the formation of a curved surface of reflecting segments of reflecting regions 2(3), 2(6); Fig. 6 is a schematic diagram showing patterns projected from the reflecting regions 2(3) and 2(6); Fig. 7 is a schematic diagram for explaining the formation of a curved surface of a reflecting segment; Fig. 8 is a front view showing a conventional reflector; and Fig. 9 is a schematic diagram for explaining a disadvantage involved in a related art reference.

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

Fig. 1 is a front view showing luminance control regions of a reflector 1. The reflector 1 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 - 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 (1) is formed of a large number of reflecting segments SEG(l), SEG(1),... that are shaped in hyperbolic paraboloids. Referring to Fig. 2, the reflecting segments are formed in 6 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(3) is formed of reflecting segments SEG(3). In the fourth quadrant of the y-z plane, a reflecting 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 adjacent to the right of the reflecting region 2 (1). 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. The curvatures of the reflecting regions 2(6) and 2(3) are designed so that no gap portions are formed at the boundary portions therebetween.

Fig. 3 is an enlarged top view of Fig. 2, Fig. 3 shows the reflecting segments SEG(3), SEG(3),...' which 7 form the ref lecting region 2 (3), and the ref lecting segments SEG(6), SEG(6),..., which form the reflecting region 2(6). The reflecting segments SEG(6), SEG(6),... are connected to the reflecting segments SEG(3), SEL7(3), 5... in the drawing, a dotted line 5 that extends horizontally represents a boundary line of the reflecting segments SEG(3) and SEG(6). However, since the reflecting segments SEG(3) and SEG(6) are continuously formed, this boundary line is an expedient line.

As descried above, the reflecting segments SEG(3), SEG(3),... disposed above the dotted line 5 are shaped In elliptic paraboloids. 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 abovedescribed 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 20 is defined as z axis, the parabolas on the horizontal and vertical sections are U-letter shaped in the plus direction of the x axis.

The reflecting regions SEG(6), SEG(6),... have curved shapes where parabolas that are boundary lines with the reflecting segments SEG(3), SEG(3), are revolved about the center axes of revolution of the reflecting regions SEG(6), SEG(6),,.. .

Now, the reflecting segments SEG(3), SEG(3),... are defined as SEG(3a), SEG(3b), SEG(3c),... where the reflecting segment SEG(3) that is the closest to the a is main optical axis (x axis) of the reflector I is SEG(3a), the reflecting segment SEG(3) that is the second closest to the main optical axis is SEG(3b), and so forth. Likewise, the reflecting segments SEG(6), SEG(6),.. ., which are disposed adjacent to the reflecting segments SEG(3a), SEG(3b), SEG(3c) are defined as SEG(6a), SEG(6b), SEG(6c), and so forth, respectively. In this condition, the reflecting segment SEG(6a) is a surface of revolution where a parabola PARA_a that is a boundary line with the reflecting segment SEG(3a) is revolved about a center axis of revolution (denoted by A). The center axis A is disposed in a region in the vicinity of the x axis (this region is denoted by a two-dashed line of Fig. 3) and extends along the x axis.

Likewise, the reflecting segments SEG(6b) and SEG(6c) are surfaces of revolution where parabolas PARA-b and PARA_c that are boundary lines with the reflecting segments SEG(3b) and SEG(3c) are revolved about their center axes of revolutions (denoted by B and C), respectively.

Fig. 5 is a conceptional view showing the reflecting regions SEG(6a), SEG(6b), SEG(6c) that are formed by such revolving operations.

Since the reflecting segments SEG(6a), SEG(6b), and SEG(6c) are formed by revolving parabolas that are lower end boundaries of the reflecting segments SEG(3a), SEG(3b), and SEG(3c) about the center axes of revolution A, B, and C, respectively, no gap portions take place on the dotted 11ne 5 of Fig. 3. Thus, it Is possible that the reflecting segments SEG(3a) and SEG(6a) are treated as a small reflecting surface. This applies to the relation between 9 is the reflecting segments SEG(3b) and SEG(6b) and the relation between the reflecting segments SEG(3c) and SEG(6c). Although the center axes of revolution A, B, and C sometimes accord with the x axis, they are generally defined for each reflecting segment in the vicinity of the x axis.

Fig. 6 is a schematic diagram showing a pattern 6 projected from the reflecting segment SEG(3) and a pattern 7 projected from the reflecting segment SEG(6). The patterns 6 and 7 are projected on a screen spaced apart from the reflector 1 disposed in front of the reflector 1. In Fig. 6, "H-H" and "V-V" represent a horizontal line and a vertical line, respectively.

The patterns 6 and 7 are disposed on the left of the vertical line V-V. in addition, the pattern 6 is disposed Just below the horizontal line H-H. The projection pattern 7 is disposed above the pattern 6 so that the pattern 7 extends in an upper left direction.

If the boundary between the reflecting regions SEG(3) and SEG(6) is discontinuous, rays of light that are reflected at the gap portion and that travel toward an upper portion of the slant cut line become dazzling light for the opposed automobiles. However, since the boundary between the reflecting segments SEG(3) and SEG(6) is continuous, such a disadvantage does not arise.

The reflecting segment SEG(3) and the reflecting segment SEG(6) that Is connected thereto are substantially treated as a small reflecting surface. In the small reflecting surface, the degree of diffusion In horizontal direction denoted by arrow I and the degree of diffusion in the slant out line direction denoted by arrow J can be totally controlled.

In the above-described embodiment, the center axis of revolution is defined for each reflecting segment. However, each reflecting segment may be divided into several regions and local center axes of revolution may be defined so as to more precisely perform luminance control.

In other words, as shown in Fig. 7, the parabola PARA_a that is the lower end boundary line of the reflecting segment SEG(3a) is revolved about the center axis of revolution Al by an angle of el. In addition, the parabola PAPA_a is revolved about the center axis of revolution A2 by a predetermine angle 82. In such a manner, different center axes of revolution are defined at individual portions so as to form the reflecting segment SEG(6a). In this case, the center axes of revolution Al, A2, and so forth extend in the vicinity of the x axis therealong.

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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 plurality of reflecting regions including the third and sixth regions which are adapted f or forming a portion in the vicinity of an inclined cut line and are formed of a plurality of reflecting segments, wherein a reflecting surface of each reflecting segment of the sixth region is a surface where the lower side of a corresponding reflecting segment of the third region that forms a boundary line with a respective reflecting segment of the sixth region is revolved about an axis that extends parallel to and in the vicinity of the main optical axis (x) of the reflector.

2. A reflector according to claim 1, wherein the reflecting segments of the first region are formed in an elliptic paraboloid shape and the lower side is formed in a parabola shape.

3. A reflector according to claim 1 or claim 2, wherein the reflecting regions are formed of six portions that are first to sixth reflecting regions respectively.

4. A reflector according to claim 3, wherein the first reflecting region is formed of a plurality of reflecting segments that are sectioned in a grid pattern and formed in a hyperbolic paraboloid shape.

5. A reflector according to claim 3 or claim 4, wherein the sixth reflecting region is formed as an approximate fan-shape; and the reflecting segments of the sixth region are arranged radially.

6. A reflector according to any one of claims 3 to 5, wherein the second reflecting region, the third reflecting 121 region, the fourth reflecting region, and the fifth reflecting region are formed of reflecting segments, respectively, that have an elliptic paraboloid shape.

7. A reflector according to claim 3, wherein the f irst reflecting region is disposed at upper and lower positions of a lamp mounting hole and disposed at most portions in first and second quadrants of a vertical plane (y-z) viewed f rom the f ront of said ref lector and a portion close to said lamp mounting hole in third and f ourth quadrants thereof; the second ref lecting region is disposed at a portion adjacent to one side of the first reflecting region in the second and third quadrants of said vertical plane (y-z); the third reflecting region is disposed at a portion adjacent to the other side of the first reflecting region in the first quadrant in the vertical plane (y-z); the fourth reflecting region is disposed at a portion adjacent to the lamp mounting hole and just below a horizontal plane (x-y) in the fourth quadrant of the vertical plane (y-z); fifth reflecting region is disposed at a portion adjacent to the other side of the f irst reflecting region in the fourth quadrant of the vertical plane (y-z); and the sixth reflecting region is disposed at a portion just below the horizontal plane (x-y) in the fourth quadrant in the vertical plane (y-z).

8. A reflector substantially as described with reference to Figs. 1 to 7 of the accompanying drawings.

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