Light diffusion preventing structure

1. Field of the Invention

This invention relates to a light diffusion preventing structure, and more particularly to a light diffusion preventing structure used in conducting light from a light source into a enclosed space that is defined by a structure having an interior finished with a structural member, while the light source is located outside of the enclosed space.

2. Description of the Related Art

FIG. 3 depicts a relation between a light source and a conventional structure provided with a hole for allowing the light to pass from the light source through structure. FIG. 4 shows a spatial relationship between a grille used as a conventional structure and a light source for providing a spotlight on a shift lever or gear lever.

In FIGS. 3 and 4, a lamp 20 comprises an incandescent lamp or other light source fitted into a lamp holder 21 . The grille 22 is an ornamental panel attached as a part of the interior trim of a vehicle. The grille 22 also includes a hole 23 for allowing the light from lamp 20 to spotlight a shift lever 30 .

In the conventional structure, the light from lamp 20 spotlights the shift lever 30 with light having an irradiation angle θ. The direction of the spotlight illumination is determined by the relationship between the light source 20 and the opening that is located at a lower surface and defined by a lower edge of the hole 23 of the grille 22 .

However, the light of the lamp 20 irradiates a first thickness surface 23 a or an inner peripheral surface of the hole 23 at one side of the grille 22 as well as a second thickness surface 23 b or an inner peripheral surface of the hole 22 at the other side of the grille 22 . The brightness at the first thickness surface 23 a and the second thickness surface 23 b is inversely proportional to square of the distance from the lamp 20 to the surfaces 23 a, 23 b. The surfaces 23 a, 23 b are located near the lamp 20 . Moreover, the first thickness surface 23 a is a surface facing the light source or the lamp 20 , while the second thickness surface 23 b is a surface more parallel to a radiating direction of the light. Consequently, the first thickness surface 23 a has an increased brightness when compared with the second thickness surface 23 b. As a result, the first thickness surface 23 a tends to be brighter than its surroundings. If such light is located at a position in which light from first thickness surface 23 a shines directly into the eyes of a driver at a position where the light from the first thickness surface 23 a can be reflected by an inside rear view mirror into the eyes of the driver, it may cause the driver to be distracted.

An object of the present invention is to provide a light diffusion preventing structure by which the light passing through a hole is not diffused by the sidewalls of the hole.

According to a first aspect of the invention, there is provided a light diffusion preventing structure comprising a light source and a structural member. The structural member has a hole that passes a light from the light source. The hole has a three-dimensional shape that has a first opening located near the light source and a second opening located away from the light source. Further, the area of the first opening is smaller than the area of the second opening. Indeed, the circumferential edge of the second opening is located completely outside of a zone defined between imaginary straight lines connecting the point light source and the circumferential edge of the first opening provided that the light source is the point light source. This configuration ensures that the imaginary straight lines never touch any of the inner peripheral surface of the structural member between the first and second opening.

According to a second aspect of the invention, there is provided a light diffusion preventing structure comprising a light source and a structural member. The structural member has a hole that allows light from the light source to pass through the member and into an interior space. The hole has a three-dimensional shape that includes a first opening located near the light source and a second opening located away from the light source. The first and second openings are configured so that the area of the first opening is smaller than an area of the second opening. Imaginary straight lines connecting the circumferential edge of the first opening and the opposite circumferential edge of the second opening have a crossing angle of not more than 160 degrees and more preferably not more than 150 degrees.

According to a third aspect of the invention, there is provided a light diffusion preventing structure comprising a light source and a structural member.

The structural member has a hole that allows light from the light source to pass through the member and into an interior space. The hole has a three-dimensional shape that includes a first opening located near the light source and a second opening located away from the light source. The first and second openings are configured so that the area of the first opening is smaller than an area of the second opening. The holes are also configured so that the circumferential edge of the second opening is located outside a zone defined between first imaginary straight lines connecting a point light source and the circumferential edge of the first opening provided that the light source is the point light source. The first imaginary straight lines are never touch any of the inner peripheral surface of the structural member between the first and second opening. Second imaginary straight lines connecting the circumferential edge of the first opening and the opposite circumferential edge of the second opening have a crossing angle of not more than 160 degrees and more preferably not more than 150 degrees.

Further objects and advantages of the invention will be apparent from the following description, reference being had to the accompanying drawings, wherein preferred embodiments of the invention are clearly shown.

FIG. 1 is an explanatory drawing of a light diffusion preventing structure according to a first embodiment of the invention.

FIG. 2 is an explanatory drawing depicting a basic principle of the light diffusion preventing structure according to the first embodiment of the invention.

FIG. 3 is an explanatory drawing showing a relation between a light source and a structural member having a hole that permits the light to go through in prior art.

FIG. 4 is an explanatory drawing showing a relationship between the structural member and the light source intended to spotlight a shift lever from an overhead grille in prior art.

Several embodiments of the invention are described below with reference to the attached drawings. The same reference characters are used to identify the corresponding elements in each of the figures with FIGS. 1 and 2 illustrating an embodiment of the invention and FIGS. 3 and 4 showing prior art structures.

FIG. 1 illustrates a light diffusion preventing structure according to a first embodiment of the invention.

Referring to FIG. 1, a lamp 10 comprising a incandescent lamp, a light emitting diode (LED), a fluorescent lamp or the like is provided as a light source. The light source is not limited to the one that is used for spot illumination. However, as described later, the light diffusion preventing structure according to the present invention is particularly useful for use in conjunction with light sources adapted for spot illumination. The lamp 10 is inserted in a lamp holder 11 that both supplies electric power and positions the lamp. A grille 12 is an ornamental panel mounted for a decoration of an interior of a vehicle and provides an ornamental design for the interior of the vehicle.

The grille 12 has a through hole 13 formed therein. The through hole 13 permits light from lamp 10 to pass through the grille and into the interior of the vehicle. Thus, light passing through hole 13 can illuminate a shift lever (not shown) or the other interior feature as in the prior art.

The through hole 13 includes a stepped hole 13 a adjacent the lower (i.e., interior) surface of the grille 12 . The stepped hole 13 a opens downwardly and includes a shoulder, thereby defining the lower opening at the lower surface of the grille 12 . The diameter A of the lower end of through hole 13 (the lower opening of the stepped hole 13 a ) is larger than a diameter B of the upper opening that is formed by through hole 13 at the upper surface of the grille 12 . As illustrated in FIG. 1, the lower opening with the diameter A is defined by the shoulder at the lower side of the through hole 13 in the stepped hole 13 a in FIG. 1 . However, a stepped hole having a shoulder is not always necessary to produce a light diffusion preventing structure according to the present invention. FIG. 2, for example, shows a modified embodiment without a stepped hole.

In the embodiment illustrated in FIG. 2, the through hole 13 lacks the stepped hole 13 a found at the lower surface of the grille 12 as in the embodiment illustrated in FIG. 1 . Specifically, the lower end portion of the through hole 13 has a substantially upwardly tapered shape that defines a lower end opening having a larger diameter at the lower surface of the grille 12 . The embodiment illustrated in FIG. 2 is similar in other structural elements to the embodiment illustrated in FIG. 1 . Given this similarity, the description of the common elements will be addressed with reference to the embodiment illustrated in FIG. 1 but should be understood to apply equally to the embodiment illustrated in FIG. 2 .

The through hole has a height H between the lower opening having a diameter A and the upper opening having a diameter B. The height H may be equal to a thickness of the grille 12 , but as illustrated, the height H may be larger than the thickness of the adjacent portions of the grille 12 . Specifically, an upper part of the through hole 13 is defined by an upwardly protruded portion formed on the upper side of the grille 12 corresponding to the through hole 13 . The upper part of the through hole 13 is substantially tapered upwardly so that the lower part of the through hole 13 (stepped hole 13 a ) is both continuous with the upper part of the through hole 13 but provides a diameter A that is larger than the diameter B.

The lower opening with the diameter A and the upper opening with the diameter B of the through hole 13 is formed as follows. Specifically, the through hole 13 is configured with a three-dimensional shape so that the area of the upper opening (diameter A) located near the lamp 10 is smaller than the area of the lower opening (diameter B) located at the other end of the through hole 13 . Provided that the lamp 10 is essentially a point light source, if the point light source and the upper opening are connected with imaginary straight lines a and b, the lower opening is located entirely outside of a zone defined between the lines a and b. This means that the front end of the lower opening is located forward of the light projected from lamp 10 through the upper opening as illustrated by the front imaginary line b. Similarly, the back end of the lower opening is located behind the light projected from lamp 10 through the upper opening as illustrated by the back imaginary line a.

Moreover, the three-dimensional shape of the through hole 13 is configured so that lines a and b do not intersect any portion of the inner peripheral surface of the through hole 13 .

Although lines a and b intersect the uppermost edge of the upper opening (diameter B), the inner peripheral surface 13 b is configured to be at least substantially parallel to lines a and b it is inclined slightly away. With this configuration, the illumination of the inner peripheral surface 13 b is very low compared with the illumination of a vertical surface or a surface on which the light is radiated in a perpendicular direction. Thus, even if the driver can directly see a portion of the inner peripheral surface 13 b, it is not reflecting sufficient light, i.e., is not bright, and will not distract or annoy the driver. That is, the illumination of the inner peripheral surface 13 b never becomes higher than the illumination of the interior of the vehicle. Consequently, there is no light reflection surface (reflected light source) that is highly illuminated on the inner peripheral surface 13 b of the through hole 13 or at the lower surface of the grille 13 . As a result, no light will be reflected from peripheral surface 13 b into the driver's eyes either directly or via an interior rear view mirror. Thus, the driver will not be distracted by such reflected light. Thus, it is possible to obtain a structure that ensures that light passing through the grille 12 is never diffused at the through hole 13 .

In the present embodiment, an imaginary straight line X and an imaginary straight line Y are defined by connecting a rear edge and a front edge of the upper opening (diameter B) with a front edge and a rear edge of the lower end opening (diameter A), respectively. A crossing angle θ between the line X and the line Y is set at a predetermined small value. Consequently, when the line a and the line b contact part of the edge of the upper opening, even if the edge part has a rough finished surface (e.g. a fibrous state) and becomes an irregular reflection surface, the reflected light never comes into the view of the driver either directly or via the interior rear view mirror.

Particularly, according to an experiment of the inventors, it has been confirmed that, if the crossing angle δ between the line X and the line Y is 160 degrees or less, there is very small probability that the reflected light will come into the view of the driver either directly or via the interior rear view mirror. Moreover, it has been also confirmed that even if the crossing angle δ between the line X and the line Y is 150 degrees or less, the influence of the reflected light can be almost completely disregarded.

Consequently, if the spotlight is radiated on the shift lever or the like at an irradiation angle θ as shown in the prior art, the direction of the spot illumination is determined solely by the orientation and configuration of the through hole 13 in the grille 12 . Then, it is possible to eliminate substantially all diffusion of light by the through hole 13 .

Each of the upper opening (diameter B) and the lower opening (diameter A) preferably is formed into a circular shape in the present embodiment. However, it is possible to form them into another shape such as a square shape or a rectangular shape.

While the through hole 13 is formed on the grille 12 in the present embodiment, it may be formed on any structural member comprising an interior ornamental member.

Although a light diffusion preventing structure according to the present invention may satisfy only one of the preferred relations of the lines a and b and the relation of the lines X and Y described above. If both the relations are satisfied, it is possible to increase reliability and improve performance.

The through hole 13 of the structural member is not limited to a simple through hole. It may be partially or completely filled with a transparent material such as glass or a transparent plastic. The term thickness surface of the structural member is used to describe a surface that has a dimensional change in a linear direction from the light source by the thickness thereof or an additional portion that has been worked thereon.

The preferred embodiments described herein are illustrative and not restrictive, the scope of the invention being indicated in the appended claims and all variations which come within the meaning of the claims are intended to be embraced therein.