JPS6340321B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a motor vehicle headlamp reflector made of synthetic material.

BACKGROUND OF THE INVENTION In the manufacture of motor vehicle headlights, it has been previously proposed to replace stamped sheets with reflectors made of synthetic material, the optical surfaces of which are formed by vacuum deposition, in particular by aluminum deposition.

The essential problem in this case is that the synthetic materials most suitable for forming the optical surfaces by vacuum deposition after forming into the shape of the reflector are generally It is a lack of tolerance.

In other words, as shown by experiments on the structure of large reflectors for automobile headlamps, the heat generated during headlamp operation is strictly defined on the optical surface, which is generally a paraboloid. This is incompatible with the constancy of the inner surface (vacuum deposited surface).

In order to eliminate this defect, the following various proposals have been made so far.

Use synthetic materials with good heat resistance. Although such synthetic materials exist, their high cost prevents them from being used in the manufacture of headlights.

A commercially available synthetic material is used that incorporates stiffening components to strengthen the reflector.

The reflector is fabricated with non-uniform thickness, particularly thin sections that tend to limit thermal deformation in non-active portions of the reflector.

None of these solutions are fully satisfactory.

The present invention provides a reflector of a novel construction in which a reflector structure free from deformation effects due to heat generation during operation can be obtained by simple molding of the most readily available synthetic materials.

According to the invention, a portion of the inner surface shape which is far from the desired optical shape at ambient temperature, but is brought to the desired optical shape by deformation of the reflector in the exothermic state corresponding to the operation of the headlamp. is structurally formed in the upper region of the reflector made of synthetic material.

In other words, the "cold" inner surface shape of the reflector is imperfect, but after deformation due to an increase in temperature, this inner surface shape becomes suitable for the light source combined with the reflector to obtain a predetermined luminous flux. This provides an ideal optical shape for cooperation.

The reflector according to a preferred embodiment is of the type having a paraboloid of revolution over its entire width closed at the top and bottom respectively by a generally flat top and bottom plate, the profile of the aperture of the reflector being Defined by edges forming rigid ribs or ridges.

In this type of reflector, according to the invention:
The selected region of the paraboloid has a flattened shape by being slightly bent from above to below around a base line preferably formed by a cutting line of the paraboloid by a virtual horizontal plane.

This bent-shaped area is always located in contact with the top plate. The total width of this region is within the range of a fraction of the total width of the reflector, and the total height is within the range of 1/10 to 3/4 of the half height of the reflector. Bending or flattening about the baseline is included in the range 0.2-6% (in radians).

The exact selection of the dimensions and angle of this flattening will depend on the exact characteristics of the reflector, its dimensions and thickness, the characteristics of the cooperating light source and the synthetic material from which the reflector is made, and will depend on theoretical considerations and Those skilled in the art can appropriately conduct experiments.

In particular, by iterative modification of the mold, a series of reflectors with progressively larger bending zones, both in terms of spread and bending shape, have been experimentally obtained;
This allows the optimum shape to be determined.

According to another embodiment of the invention, a series of flattened areas arranged in a stepped manner are shaped into the reflector. A small region with the most strongly bent shape is formed inside a medium-sized region with less bending, which itself is formed inside a larger region with even less bending. be done. All these areas are positioned as before against the top plate of the reflector.

Next, preferred embodiments of the present invention shown in the drawings will be described in detail.

The reflector of FIGS. 1 and 2 is a reflector with a rectangular profile and a parabolic working optical surface and is made of molded plastic, more precisely molded PBT (polybutylene terephthalate). The reflector has a uniform thickness of 2 mm. The reflector has a paraboloid P with an optical axis 00 extending over its entire width and is provided with a generally flat top plate J1 and a bottom plate J2 at the top and bottom, respectively. The paraboloid P plays an optical role and forms the reflective surface of the reflector, but the upper plate J1 and the lower plate J2 only serve as mechanical connections without optical effects. The edge R delimits the reflector aperture and forms a stiffening rib or ridge. The focal length of the paraboloid is 26.5 mm, the aperture width is 190 mm, and the height is 120 mm.
When in use, a mirror (not shown) closes the front of the reflector, and a light bulb (not shown) is attached to the rear part S of the opening.

In a reflector with this structure, when a headlight is used with the specified light bulb (CRE type or H4 type),
Generates considerable heat. The temperature at point B on the upper plate J1 is on the order of 106°C, the temperature at the extreme point A on the paraboloid P is on the order of 100°C, and the temperature at the central region C of the paraboloid P is on the order of 80°C. Become an order (second
(see figure).

According to the invention, the reflector is adapted to adapt to temperature changes between a cold inactive state and an active state.
A shape bent by about 2% around the base line Z1-Z1 is given to the upper rectangular region Z1 of the paraboloid P.

Base line Z1-Z1 is formed by a cutting line of paraboloid P by a virtual horizontal plane. The region P1 extends to the upper plate J1 and has a height of 1/10 of the height of the paraboloid P, that is,
12mm, length is about 2/3 of the width of paraboloid P, or about 130mm
It is. Region Z1 is centered with respect to a vertical plane passing through optical axis 0-0. 2% bending around the base line means that the cross section of paraboloid P along the - line (see Figure 2) and all cross sections parallel to this (all vertical cross sections parallel to each other) are shown in Figure 2. Baseline Z1
- This means that the shape is bent by 2% around Z1. The cross-sectional shape similar to that in Fig. 2 is the area Z
It can also be obtained for the cut planes along all the cross-sectional lines parallel to the - line included in 1.

In Figure 2, the solid line indicates the true shape after bending,
The broken line indicates the exact parabolic shape (unbent shape).

In this configuration, the use of the reflector, i.e. its cooperation with a suitable bulb and the subsequent heat generation, is manifested in the upward tilting of the top plate J1 and the rectangular area Z1.
After this tilt, the inner surface of the rectangular area Z1 is aligned with the optical axis 0.
It perfectly matches the paraboloid of revolution around -0. That is, heat generation has an effect opposite to the structural bending shape for the rectangular area.

The examples described above are of course not limiting, and other embodiments are also possible.

As shown in FIGS. 1 and 2, the rectangular area Z1 can be limited only to the center area of the reflector, but it may be extended in a band shape over the entire width of the upper part of the reflector below the upper plate J1.

FIG. 3 shows a second embodiment of the invention which is very similar to the embodiment described above. In this figure, parts or members that are the same as in the previous embodiment are designated by the same reference numerals as in FIGS. 1 and 2.

The reflector according to this implementation has three step-shaped bent-shaped regions Z1, Z2, Z3, region Z2 is located inside region Z1, and region Z2 is located inside region Z3, Three areas Z1
~Z3 is in contact with the upper plate J1 as in the previous embodiment.

FIG. 3 represents the actual size in the sense that the top plates J1, J2 have the dimensions and relative positions shown. Region Z1 has a shape bent by 2% around the horizontal baseline Z1-Z1, similar to the previous example. Similarly, the area Z2 is located on the horizontal base line Z2-
Although it is bent around Z2, the magnitude of the bend is 1%. In addition, the area Z3 is a horizontal base line Z3-Z
It is bent by 0.5% around 3.

A temperature-compensating flattened shape of at least one of the reflectors according to the invention has been provided in some types of reflectors in the prior art to modify the optical properties of the reflected light beam. It has nothing to do with irregular or receding shapes. In fact, with this known technique, the shape of the entire area of the reflector is considered to remain unchanged;
The luminous flux is the same whether the headlight is at room temperature or at operating temperature. According to the basic idea of the invention, on the contrary, the properties of thermally deformable synthetic materials in relatively small thicknesses are exploited to a large extent, and the properties of the composite materials can be used without any attempt to suppress thermal deformation when the temperature rises. Sometimes the deformation is compensated a priori by an optical shape that is far from the required optical shape.

Furthermore, although this technology has been known for some time, no attempt has been made to apply it to synthetic material reflectors for automobile headlamps.

[Brief explanation of drawings]

FIG. 1 is a perspective view of a parabolic reflector with a rectangular aperture profile according to a first embodiment of the present invention, and FIG.
Sectional view taken along the - line in the figure, No. 3
1 is a perspective view similar to FIG. 1 of a parabolic reflector according to a second embodiment of the present invention. Explanation of symbols, P...paraboloid. R... Edge. J1
...Upper board. J2...Lower board. Z1...Rectangular area.

Claims (1)

[Scope of Claims] 1. A reflector for an automobile headlamp that cooperates with a light source to obtain a predetermined reflected luminous flux, comprising:
The construction has an inner surface profile in the upper region which is subjected to at least a large heating, which substantially deviates from the optical shape required for this effect, and which inner surface profile corresponds to the normal operation of the headlamp. 1. A reflector characterized in that the reflector is deformed by thermal expansion in a heated state to reach an optical surface necessary to produce the predetermined reflected light beam. 2 At least in the upper area that receives the greatest heating,
2. A reflector as claimed in claim 1, characterized in that it comprises at least one region of flattened shape around the base line. 3. A reflector according to claim 1 of the type having a rectangular opening shape with a paraboloid at the center, an upper plate, and a lower plate, which is approximately horizontal from below to above around a base line. A reflector characterized in that it has at least one flattened rectangular area in contact with the top plate. 4 The rectangular area is 1/10 to 3/4 of the half height of the paraboloid.
The height is extended from 1/10 of the width of the paraboloid to the full width of the paraboloid, and the degree of flattening is 0.2 to 6%.
A reflector according to claim 3, characterized in that: 5. The reflector according to claim 3 or 4, which has a plurality of flattened regions.