Abstract:
A head lamp for a vehicle includes a light source configured to emit a light and a reflective mirror configured to reflect the light. A reflective mirror extended portion extends toward a front of the head lamp from the reflective mirror. An upper shield protrudes radially toward an inner side of the head lamp and shields the light. A lower shield extends toward the front of the head lamp, such that a part of the light transmitted from the light source is indirectly transmitted to the front of the head lamp. A light developing hole is formed between the upper and lower shields to allow another part of the transmitted and reflected light to pass therethrough. A lens mounted to one end of the reflective mirror extended portion allows the light passing through the light developing hole to penetrate the lens and emit the penetrated light toward a front view of the vehicle.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of priority to Korean Patent Application No. 10-2013-0129331 filed in the Korean Intellectual Property Office on Oct. 29, 2013, the entire contents of which are incorporated herein by reference. 
     TECHNICAL FIELD 
     The present disclosure relates to a head lamp for a vehicle. More particularly, the present disclosure relates to a head lamp for a vehicle of which luminous efficiency is improved. 
     BACKGROUND 
     Generally, a head lamp of a vehicle, also called a head light, lights a front view for safe driving of the vehicle at night or in a dark area. 
     The head lamp produces a light beam which can be shifted in up/down directions to not dazzle a driver of an oncoming vehicle from an opposite direction. According to safety standards, the high beam is required to identify an obstacle existing at 100 m ahead of the vehicle, and a low beam is required to identify an obstacle at 40 m ahead of the vehicle. 
     In order to implement such light beam, a shield is disposed between a light source and a lens. The shield shields a portion of a light incident on the lens from the light source or a reflective mirror. According to a shape and movement of the shield, the high beam or the low beam can be selectively implemented. 
     Because the light shielded by the shield is not used to illuminate, the efficiency of head lamp is limited. In addition, if luminance efficiency of the light passing through the shield is low, the head lamp efficiency may deteriorate in comparison to that of the light source. Thereby further the head lamp efficiency. Particularly, when the low beam is used, the amount of the effective light emitted from the head lamp may be deteriorated as the amount of the light shielded by the shield is increased. 
     The above information disclosed in this Background section is only for enhancement of understanding of the background of the disclosure, and therefore, it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art. 
     SUMMARY 
     The present disclosure has been made in an effort to provide a head lamp for a vehicle having advantages of improving luminous efficiency. 
     In addition, the present disclosure has been made in an effort to provide a head lamp for a vehicle having further advantages of improving the performance of the low beam by a simple configuration without increasing the production cost. 
     A head lamp for a vehicle according to an exemplary embodiment of the present inventive concept may include a light source configured to emit a light. A reflective mirror surrounds the light source configured to reflect the light. A reflective mirror extended portion extends toward a front of the head lamp from an upper part of the reflective mirror. An upper shield protrudes from the reflective mirror extended portion toward an inner side of the head lamp along a radial direction and shields the light such that a part of the light transmitted from the light source toward the front of the head lamp is indirectly transmitted toward the front of the head lamp. A lower shield extends toward the front of the head lamp from a lower part of the reflective mirror and shields light such that the part of the light transmitted from the light source toward the front of the head lamp is indirectly transmitted toward the front of the head lamp. A light developing hole is formed between the upper shield and the lower shield and allows another part of the light transmitted from the light source toward the front of the head lamp and the light reflected by the reflective mirror to pass therethrough toward the front of the head lamp. A lens mounted to one end of the reflective mirror extended portion, allows the light passing through the light developing hole to penetrate the lens, and emits the penetrated light toward a front view of the vehicle. 
     A shield reflective surface may be formed at the lower shield and reflects the light transmitted from the light source toward the reflective mirror. 
     The reflective mirror may reflect the light transmitted from the light source and the light transmitted from the shield reflective surface and allows all the light reflected by the reflective mirror to pass through the light developing hole. 
     A surface reflecting the light of the reflective mirror may be disposed to correspond with a surface of an ellipsoidal solid in which a center of the light source and one point adjacent the lower shield in the light developing hole are two focal points. 
     The lower shield may extend from the one end of the reflective mirror such that the shield reflective surface is adjacent the one point in the light developing hole. 
     The shield reflective surface may be disposed to correspond with a surface of a sphere in which the center of the light source is a center of the sphere. 
     The light reflected by the shield reflective surface may be reflected by the reflective mirror and passes through the light developing hole. 
     The reflective mirror may be integrally formed with the lower shield. The surface reflecting the light of the reflective mirror may correspond with a surface of an ellipsoidal solid in which a center of the light source and one point adjacent the lower shield in the light developing hole are two focal points. The shield reflective surface may correspond with a surface of a sphere in which the center of the light source is a center of the sphere. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       The FIGURE is a schematic diagram of a head lamp for a vehicle according to an exemplary embodiment of the present inventive concept. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     An exemplary embodiment of the present disclosure will hereinafter be described in detail with reference to the accompanying drawing. 
     The figure is a schematic diagram of a head lamp for a vehicle according to an exemplary embodiment of the present inventive concept. 
     As shown in the figure, a head lamp  1  for a vehicle according to an exemplary embodiment of the present disclosure includes a light source  12 , an upper reflective mirror  20 , an upper shield  24 , a lower reflective mirror  30 , a lower shield  34 , a reflective mirror extended portion  26 , and a lens  40 . 
     The light source  12  is connected with and receives electric power from a power supply  10 , and emits a light by transferring electrical energy to light energy. 
     The upper reflective mirror  20  surrounds the light source  12  and extends toward a front side of the head lamp  1 . In addition, the upper reflective mirror  30  forms an upper reflective surface  22 . Further, the upper reflective surface  22  reflects the light transmitted from the light source  12 . The upper shield  24  is formed at one end of the extended upper reflective mirror  20 . 
     The lower reflective mirror  30  surrounds the light source  12  and extends toward the front side of the head lamp  1 . In addition, the lower reflective mirror  30  forms a lower reflective surface  32 . Further, the lower reflective surface  32  reflects the light transmitted from the light source  12 . The lower shield  34  is formed at one end of the extended lower reflective mirror  30 . 
     The upper reflective mirror  20 , the lower reflective mirror  30 , the upper shield  24 , and the lower shield  34  are integrally or respectively formed and then assembled as one body. The upper reflective mirror  20  and the lower reflective mirror  30  together have a hollow cylindrical shape. One surface of the hollow cylindrical shape has an opening toward the front side of the head lamp  1 . Herein, the opening of the hollow cylindrical shape of the whole shape of the upper reflective mirror  20  and the lower reflective mirror  30  will be called a “light developing hole  28 .” That is, the light emitted through the light developing hole  28  from the light source  12  and the light reflected by the upper reflective mirror  20  or the lower reflective mirror  30  are reflected toward the front of the head lamp  1 . Further, the light source  12  is inserted through another opening of the hollow cylindrical shape of the whole shape of the upper reflective mirror  20  and the lower reflective mirror  30 . Herein, the other opening of the hollow cylindrical shape will be called a “light source insertion hole  38 .” The light source insertion hole  38  is closed by the power supply  10 . 
     The upper shield  24  protrudes from the one end of the upper reflective mirror  20  toward an inner side of the head lamp  1  along a radial direction. In addition, the lower shield  34  extends from the one end of the lower reflective mirror  30  toward the inner side of the head lamp  1  to form a gradual curved shape along a radial direction. Further, the upper shield  24  and the lower shield  34  shield a part of the light reflected toward the front of the head lamp  1  from the light source  12 , the light reflected toward the front of the head lamp  1  by the upper reflective surface  22  of the upper reflective mirror  20 , and the light reflected toward the front of the head lamp  1  by the lower reflective surface  32  of the lower reflective mirror  30 . 
     The lower shield  34  forms a shield reflective surface  36  thereon for reflecting the light transmitted from the light source  12  toward the upper reflective surface  22  of the upper reflective mirror  20 . 
     The reflective mirror extended portion  26  extends from the one end of the upper reflective mirror  20  toward the front of the head lamp  1 . In addition, the reflective mirror extended portion  26  may have a ring shape which is concentrically disposed with the hollow cylindrical shape of the upper reflective mirror  20  and the lower reflective mirror  30 . 
     The lens  40  fits in and mounted to the ring shape of the reflective mirror extended portion  26 . In addition, the lens  40  is disposed to collect the light emitted from the light source  12  and emit the collected light emitted from the light source  12  toward the front of the head lamp  1 . That is, the light passing through the light developing hole  28  penetrates the lens  40  so as to be emitted toward the front of the head lamp  1 . In order to reduce a spherical aberration, the lens  40  may be an aspherical lens having a small number of surfaces. The aspherical lens is well-known to a person of an ordinary skill in the art such that a detailed description thereof will be omitted. 
     The figure shows an adjoint line L which passes through the center of the light source  12  and the center P 1  of the circle C of the hollow cylindrical shape formed by the upper reflective mirror  20  and the lower reflective mirror  30 . In addition, the center of the circle C P 1  is in the light source  12 . The figure further shows an ellipse E having a focal point at a center P 1  of the circle C along the center line of the light source  12  and a second focal point at a cross point P 2  where the adjoint line L intersects the light developing hole  28 . 
     In the ellipse E, the center P 1  of the circle C will be called the “first focal point P 1 ,” and the cross point P 2  will be called the “second focal point P 2 ”. 
     When the circle C extends 3-dimensionally so as to form a sphere C, the shield reflective surface  36  is formed and corresponds with a surface of the sphere C. In addition, when the ellipse E extends 3-dimensionally so as to form an ellipsoidal solid E. the upper reflective surface  22  and the lower reflective surface  32  are formed and correspond with a surface of the ellipsoidal solid E. The lower shield  34  which forms the shield reflective surface  36  extends from the one end of the lower reflective mirror  30 , such that, the shield reflective surface  36  is adjacent the second focal point P 2 . However, the shapes of the upper reflective surface  22 , the lower reflective surface  32 , and the shield reflective surface  36  are not limited thereto, and the shapes can be variously designed by a person of an ordinary skill in the art, such that, all light reflected by the upper reflective surface  22  and the lower reflective surface  32  are passed through the light developing hole  28 , and all light reflected by the shield reflective surface  36  are transmitted to the upper reflective surface  22 . 
     Hereinafter, development of light according to the shapes and the disposition of the upper reflective surface  22 , the lower reflective surface  32 , and the shield reflective surface  36  will be described in detail. 
     If a part of light emitted from the point P 1  in the light source  12  toward the front of the head lamp  1  reaches to the shield reflective surface  36 , the light reaching to the shield reflective surface  36  is reflected by the shield reflective surface  36 . In addition, if the light reflected by the shield reflective surface  36  reaches to the upper reflective surface  22  via the first focal point P 1  again, the light reaching to the upper reflective surface  22  is reflected by the upper reflective surface  22 . Further, the light reflected by the upper reflective surface  22  is developed via the second focal point P 2 , and simultaneously, passes through the light developing hole  28 . 
     Another part of the light emitted from the point P 1  in the light source  12  toward the front of the head lamp  1  directly passes through the light developing hole  28 . The other part of the light emitted from the point P 1  of the light source  12  toward the front of the head lamp  1  is shielded by the upper shield  24 . 
     The light directly transmitted from the point P 1  of the light source  12  to the upper reflective surface  22  and the light directly transmitted from the point P 1  to the lower reflective surface  32  are respectively reflected by the upper reflective surface  22  and the lower reflective surface  32 , and the light reflected by the upper reflective surface  22  and the lower reflective surface  32  is developed via the second focal point P 2 , and simultaneously, passes through the light developing hole  28 . 
     The light passing through the light developing hole  28  penetrates the lens  40  so as to be developed toward the front of the head lamp  1  and emitted to a front view of a vehicle. Particularly, as the light transmitted to the lower shield  34  is sequentially reflected by the shield reflective surface  36  and the upper reflective surface  22  and used as the low beam, efficiency of the light emitted from the light source  12  used for the low beam increases. 
     According to the exemplary embodiment of the present disclosure, efficiency of useful light emitted from the light source  12  can be increased by using light shielded by the shield  34 . In addition, performance of the low beam may be improved while minimizing production cost as the shield reflective surface  36  is formed at the lower shield  34 . Further, driving safety can be ensured since luminous efficiency of the low beam is improved. While this disclosure has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.