JPH054761B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a lens for a vehicle lamp having a Fresnel lens in which a Fresnel step consisting of a refractive prism and a reflective prism is formed on a non-planar plate. .

[Conventional technology]

Conventionally, a Fresnel step consisting of a refractive prism and a reflective prism formed on the lens plate of a Fresnel lens is either flat as shown in Figure 7, or even if it is a surface, it is spherical. In addition, as shown in a when the lens plate material is a flat plate, or b in the case of a spherical plate with a curvature R, in both cases, the rotation axis CL perpendicular to the center C of the surface is the optical axis of the lens. It is limited to those that coincide with L and form a rotation shape with this as the center of rotation. With such a structure, not only can the light distribution of each Fresnel step be easily achieved by two-dimensional design in the radial direction, but also machining and molding can be carried out easily.

[Problem to be solved by the invention]

However, in recent years, for the purpose of reducing the aerodynamic drag of the exterior of the vehicle body, in order to reduce the aerodynamic drag of the exterior of the vehicle, those with complex shapes that follow the exterior of the vehicle are being used for automobile taillights and other vehicle lights. Of course, it goes without saying that the lens plate material has a quadratic curved surface with curvatures in different directions, but even for a lens member that has a quadratic curved surface with an axis that is the center of rotation, the optical axis L of the lens is the same as the plate material. If the rotation axis CL is tilted relative to the dotted line (see the two-dot chain line), the rotation axis CL cannot be used for light distribution design and processing and molding, making normal two-dimensional design impossible. Therefore, correction steps are generally formed outside of each Fresnel step of the lens, resulting in disadvantages due to decreased productivity and increased costs associated with the processing of the correction steps.

In addition, the configuration of the correction step described above cannot be used when machining a quadratic curved surface that has different curvatures in two directions, so a lattice Fresnel step (square direct step) is used as shown in Figure 8. However, with this structure, the number of processing steps increases, which directly increases costs, and not only does it have an economic disadvantage, but since it is processed by a milling machine, if it is made into a mold as it is, it will not be possible due to the structure of joining the plates. The problem was that mold cooling performance was poor and molding defects were likely to occur.

The present invention was devised in view of the above-mentioned problems, and is directed to a lens surface that is a so-called quadratic curved surface, in which the optical axis is tilted with respect to the lens surface or has different curvatures in the radial direction and the circumferential direction. Therefore, it is an object of the present invention to provide a lens for a vehicle lamp having a Fresnel lens having a Fresnel step structure.

[Means to solve the problem]

In order to achieve the above object, the lens for a vehicle lamp having a Fresnel lens according to the present invention draws a concentric pitch base line with an appropriate pitch on a lens member surface curved into a quadratic curved surface, etc. , in a large number of arcuate Fresnel step design sections defined by a number of radiation section lines passing through the center of the pitch baseline across the pitch baseline, the transmitted light from the focal point on the back side of the lens is reflected by the refractive system prism or reflected light. so as to form a nearly parallel beam of light through the system prism,
The gist is that the chevron-shaped Fresnel steps are cut by changing the slope angle and the inclination of the ridge line in the direction of the pitch base line, and the respective chevron-shaped Fresnel steps are arranged in parallel in the circumferential direction along the pitch base line. be.

[Effect]

The Fresnel lens configured in the above-mentioned lens for a vehicle lamp has Fresnel steps arranged in parallel along the pitch base line C of the lens surface divided into each arcuate Fresnel step design section, so the pitch P of the pitch base line C is made small. (P=0.3 to 1.5 mm), each Fresnel step can be formed with a reduced height H.

In addition, since each Fresnel step is constructed discontinuously, in the arc-shaped Fresnel step design section divided into the radial direction and the circular direction on the lens member, the direction in which the light beam crosses the Fresnel step and the tangential direction are respectively determined. By dividing the beam into two-dimensional designs and constructing a three-dimensional Fresnel step, the refraction of the light beam can be easily controlled.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the specific principle of engraving Fresnel steps on a vehicle lamp lens having a Fresnel lens according to the present invention will be explained with reference to the drawings.

On a lens member 1 which is curved in two directions, with one curvature r1 and the curvature perpendicular to it r2, the lens member 1 is placed at equal pitches (pitch width P) from the center O of the lens as shown in FIG. A concentric base line C is drawn, and a large number of arcuate Fresnel step design sections 2 are defined by a large number of radial section lines R that are equally divided in the circumferential direction passing through the center O.

FIG. 2 is an enlarged view of one of the arcuate Fresnel step design sections 2, and the arcuate Fresnel step design section 2 has pitch baselines C1 and C1.
2 and radiation division lines R1 and R2. The Fresnel step 3 designed in the arcuate Fresnel step design section 2 will be explained with reference to FIGS. 3 to 5.

First, as shown in FIG. 3, the light ray l1 from the focal point F on the light ray L of the lens member 1 is transmitted through the center of the Fresnel step 3 and becomes parallel to the optical axis L within the radiation section SR. In order to construct a refractive prism and a reflective prism that control the light ray l2 to be such that the light ray l2 is, the apex angle of the Fresnel step 3 is determined by designing the inclination angle α of the inner slope 4 and the inclination angle β of the outer slope 5, respectively. Determine γ.

Next, as shown in FIG. 4, while maintaining this apex angle γ, the top ridge line 6 is aligned with the lens so that the transmitted light ray l2 becomes parallel to the optical axis L within the tangential plane CS in the direction of the pitch base line C. An inclination angle (θ) is designed for the member 1.

At this time, a flat lens portion 8 that gradually expands toward one side can be formed between the outer valley line 7 formed at the valley position of the outer slope 5 and the pitch base line C2. .

Since the above inclination angles α and β are the inclination angles with respect to the orthographic projection line, the apex angle γ is γ = α + β, and since α, β and γ are fixed, it is not possible to cut with a 3-axis milling machine. It becomes possible.

Hereinafter, the structure of the Fresnel step formed in the Fresnel step design section will be explained with reference to FIGS. 5 and 6.

As shown in FIG. 5, a so-called multi-axis milling machine is used to sequentially cut and form the Fresnel steps 3 in each arc-shaped Fresnel step design section, and the inclination angle α of the inner slope 4 and the slope angle α of the outer slope 5 are determined. In order to obtain the inclination angle β, move the cutting tool B in a scanning manner in three-dimensional directions based on the design of the Fresnel step, and align the circular section lines C1, C2 and the radial section lines R1, R.
A Fresnel step 3 is cut and formed within the arcuate Fresnel step design section surrounded by 2. This scanning cutting is sequentially performed on adjacent arcuate Fresnel step design sections 2, resulting in a continuous Fresnel step stripe in the circumferential direction.

When using a multi-spindle milling machine that can tilt the axis of the cutting tool B (arrow φ) during the above-mentioned cutting, as shown in FIG. Alternatively, the Fresnel step may be constructed by cutting any surface of the outer slope 5 and cutting the adjacent surface by scanning movement of the cutting tool shaft.

〔Effect of the invention〕

Since the lens for a vehicle lamp having a Fresnel lens according to the present invention is constructed as described above, even if the optical axis of the lens is a curved surface inclined, desired transmission control can be easily achieved by designing the lens on a quadratic curve. In addition to being able to obtain light, the Fresnel step can be easily cut with a multi-axis milling machine, reducing processing costs.Furthermore, when it is used as a mold as it is, mold cooling performance is reduced. Since it does not have a structure that causes damage, it has excellent features such as no problems such as molding defects.

[Brief explanation of the drawing]

Fig. 1 is a partially cutaway front view a of a lens member showing the Fresnel step design section in a lens for a vehicle lamp having a Fresnel lens according to the present invention, and an enlarged view b thereof, and Fig. 2 is an enlarged perspective view showing the Fresnel step. , Figure 3 is an explanatory diagram a showing the radial design direction of the Fresnel step, its enlarged sectional view b, and the fourth
The figures are an explanatory diagram a showing the circumferential design direction of the Fresnel step and an enlarged sectional view b thereof, Fig. 5 is an explanatory diagram showing the cutting process using a multi-axis milling machine, and Fig. 6 is an explanatory diagram showing the relationship between the Fresnel step and the cutting tool. , FIG. 7 is an explanatory diagram of a conventional Fresnel lens in the case of a flat plate (a) and in the case of a spherical plate (b), and FIG. 8 is a perspective view of the main part showing the conventional structure. DESCRIPTION OF SYMBOLS 1... Lens member, 2... Arc-shaped Fresnel step design section, 3... Fresnel step, 4...
Inner slope, 5...Outer slope, 6...Top ridgeline, 7
...Outer valley line, 8...Plane lens part, B...Bite.

Claims (1)

[Scope of Claims] 1. A concentric pitch base line is drawn at an appropriate pitch on the surface of a lens member curved into a quadratic curved surface, etc., and a large number of radial division lines passing through the center of the pitch base line are drawn. In a large number of arcuate Fresnel step design sections that cross the pitch baseline, the peak angle and the pitch baseline are adjusted so that the transmitted light from the focal point on the back side of each lens forms a substantially parallel beam of light through a refractive prism or a reflective prism. A lens for a vehicle lamp having a Fresnel lens in which chevron-shaped Fresnel steps are cut by changing the inclination of a ridge line in a direction, and each of the chevron-shaped Fresnel steps are arranged in succession in a circumferential direction along the pitch base line. 2. The lens according to claim 1, further comprising a flat lens portion that gradually widens toward one side along the pitch baseline between the outer valley line formed at the valley position of the outer slope and the pitch base line. Lens for vehicle lights with Fresnel lens.