Patent Publication Number: US-10775014-B2

Title: Vehicle headlight assembly and a corresponding lamp

Description:
TECHNICAL FIELD 
     The present invention relates to a headlight assembly for vehicles and a corresponding lamp, or particularly, the present invention relates to a vehicle headlight assembly and a corresponding lamp and reflector design. 
     BACKGROUND 
     A typical vehicle headlight assembly includes a reflector and a lamp placed with its light source at or near the focal point of the reflector. Currently, the majority of such lamps are of halogen type while some high end automobiles use High Intensity Discharge (HID) lamps and, in recent years, not only HID lamps, but also light-emitting diode (LED) retrofit bulbs have also been introduced to such assembly. The reflector commonly includes a poly-ellipsoid rear portion and flat wall sections between the rear portion and the front of the assembly. The front is usually covered with a transparent lens. Typically, the lens, the reflector, or a combination of both is designed to direct the light from the light source into a specified pattern. 
     Several prior art methods have been used to control the light emitted from the lamp in vehicle headlight assemblies. One common method is to mount a shuttle in front of the bulb, to make the bulb having a dual function—a high beam and a low beam function through setting down or raising the shuttle. However, such a method of controlling the light emitted by the lamp results in inefficiencies in the headlight assembly, particularly for the low beam function, because they prevent a large percentage of the light emitted by the lamp from being used by the headlight assembly for example through absorption by the raised shuttle. 
     SUMMARY OF THE INVENTION 
     Therefore, it is an object of the present invention to solve at least one of the above-mentioned problems. 
     According to one aspect of the invention, there is provided a lamp for a horizontal operating position within a vehicle headlight assembly. The lamp comprises, as seen with respect to the vehicle: a LED light source for emitting light mainly to one side, and a reflective member for shielding front and lower parts of the light emitted by the LED light source and reflecting them to desired directions. 
     According to another aspect of the invention, there is provided a vehicle headlight assembly. The headlight assembly comprises the above lamp, a reflector for shaping the light emitted by the LED light source into a beam, and a shuttle, adjustable between positions to shape the beam into a high beam or a low beam. 
     By scenarios or as a whole, the present invention will probably improve efficiencies of the vehicle headlight assembly or of the lamp integrated therein. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be described in detail by reference to the following drawings, in which: 
         FIG. 1  is a cross-sectional side view of a vehicle headlight assembly in accordance with the prior art; 
         FIG. 2  is a cross-sectional side view of a vehicle headlight assembly not claimed by the present invention; 
         FIG. 3  is a schematic view of a reflective member of a vehicle headlight assembly in accordance with an embodiment of the present invention; 
         FIG. 4  is a schematic view of a LED retrofit product with a reflective member mounted therein in accordance with an embodiment of the present invention; 
         FIG. 5  shows a simulation result of a vehicle headlight assembly with a traditional halogen bulb; and 
         FIG. 6  shows a simulation result of a vehicle headlight assembly in accordance with the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS 
     Embodiments of the present invention will be described more fully hereinafter with reference to the accompanying drawings. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth hereafter. 
       FIG. 1  is a cross-sectional side view of a vehicle headlight assembly  100  in accordance with the prior art. 
     As is shown in  FIG. 1 , a lamp  10  is mounted within a cavity  12  of a reflector  14 . The cavity  12  is closed by a transparent lens  16 , which may have light-directing elements. The reflector  14  has a shaped, light-directing interior surface  18  that is usually poly-ellipsoid in shape, but may be parabolic or may have other shapes. The reflector  14  is configured for shaping light emitted by a light source of the lamp  10  into a high beam and a low beam, in combination with the lens  16  or not in combination with the lens  16 . The poly-ellipsoid reflecting surface  18  has a central axis  20  and a focal point  22 . The reflector  14  also may include walls  24 , including a top wall, a bottom wall, and side walls which extend between light-directing surface  18  and lens  16 . The walls  24  may have any suitable shape and may have a reflective coating, but are typically not designed for reflecting light in a desired direction. 
     The headlight assembly further comprises a shuttle  26  mounted in the lower part in front of the lamp  10 , to make the lamp  10  having a dual function, high beam and low beam, through setting down or raising the shuttle  26 . The shuttle is at least adjustable between a position in which the light from the light source is blocked across a maximum cross section and an essentially transmissive position in which this light is substantially allowed to pass through, i.e., to pass through for the high beam and to be blocked for the low beam. The reflector further includes a heel portion for mounting of the lamp  10 . Typically, the heel portion is located on the axis  20  of reflecting surface  18 . The lamp  10  can be mounted in reflector  14  by any suitable mounting structure as known in the art, for example the lamp  10  can be supported by a lamp base and a mounting strap. The lamp base is provided with electrical conductors for connecting the contact pins of the lamp  10  to a source of electrical energy in conventional fashion. The lamp  10  can be any suitable lamp, but is typically a halogen type lamp, such as the one shown in  FIG. 1 , a LED retrofit lamp, a LED lamp, a laser lamp, or any new substitute. It is noted that a LED retrofit lamp refers to a lamp that is compatible with a mounting structure for a halogen type lamp and the lamp illuminates with light-emitting diodes. A LED lamp generally has a module of light-emitting diodes and is incompatible with a mounting structure for a halogen type lamp. A LED light source may be comprised in a LED lamp or a LED retrofit lamp. As the headlight assembly for vehicles evolves and LED technology develops, the LED lamp may be widely applied in the headlight assembly for vehicles. 
     The lamp  10  includes a hermetically sealed, light-transmissive lamp envelope  30  and a filament  32  sealed within the envelope  30 . The filament  32  functions as the light source. It is noted that a light source herein is referred to as a source for emitting light, i.e., does not include the envelope, and thus differs from a lamp e.g. in that a lamp may have an envelope. 
     The envelope  30  is preferably fabricated of a hard or quartz glass material such as borosilicate or aluminosilicate glass. It will be understood that the envelope and light source structure of the lamp  10  may have configurations other than that shown in  FIG. 1 . The lamp  10  is preferably mounted in reflector  14  such that the longitudinal axis of filament  32  coincides with the central axis  20  of poly-ellipsoid reflecting surface  18  and such that the center of filament  32  is located at or near the focal point  22  of poly-ellipsoid reflecting surface  18  and at or near the central axis of envelope  30 . This ensures that light emitted by filament  32  and incident on poly-ellipsoid reflecting surface  18  is reflected through lens  16  as a light beam approximately originating from a single point. 
     As is shown in  FIG. 1 , upward light such as light L 1  and L 2  is emitted out of the headlight assembly, while downward light such as light L 3  and L 4  is blocked by the shuttle  26  and thus light efficiencies are greatly reduced. 
     A vehicle headlight assembly  200  not claimed by the present invention is shown in  FIG. 2 . As is shown in  FIG. 2 , a lamp  10  is mounted within a cavity  12  of a reflector  14 . The cavity  12  is closed by a transparent lens  16 , which may have light-directing elements. The reflector  14  has a shaped, light-directing interior surface  18  that is usually poly-ellipsoid in shape, but may be parabolic or may have other shapes. The reflector  14  is configured for shaping light emitted by the light source into a high beam and a low beam, in combination with the lens  16  or not in combination with the lens  16 . The poly-ellipsoid reflecting surface  18  has a central axis  20  and a focal point  22 . The reflector  14  also may include walls  24 , including a top wall, a bottom wall, and side walls which extend between light-directing surface  18  and lens  16 . The walls  24  may have any suitable shape and may have a reflective coating, but are typically not designed for reflecting light in a desired direction. 
     The vehicle headlight assembly further comprises a shuttle  26  mounted in the lower part in front of the lamp  10 , to make the lamp  10  having a dual function, high beam and low beam functions, through setting down or raising the shuttle  26 . The shuttle is at least adjustable between a position in which the light from the light source is blocked across a maximum cross section and an essentially transmissive position in which this light is substantially allowed to pass through. In practice, the shuttle can be set down, but cannot completely disappear, therefore, still part of the light emitted by the light source is prevented from exiting from the headlight assembly and light inefficiency results. 
     The lamp  10  includes a hermetically sealed, light-transmissive lamp envelope  30  and a filament  32  sealed within the envelope  30 . The filament  32  functions as the light source. The envelope  30  is preferably fabricated of a hard or quartz glass material such as borosilicate or aluminosilicate glass. 
     Not claimed by the present invention, a reflective member  34  in front of and below the light source is provided. 
     Generally, the light source is located at or near the focal point  22  of the surface  18 , and preferably, the reflective member  34  is closely located to the light source, for example filament  32 , i.e., near the focal point  22  of the surface  18 , so that stray reflections and glare may be reduced. 
     The envelope  30  is formed as a cylinder in  FIGS. 1 and 2 , but actually it can be of any shape as appropriate. To ensure that as much as possible (i.e. substantially all) of the light emitted by filament  32  that will otherwise finally be blocked by the shuttle  26  is reflected by the reflective member  34  to the shaped, light-directing surface  18  of the reflector  14 , the reflective member  34  is mounted in front of and under the light source as is shown in  FIG. 2 , to reflect the light going forward and downward to the upper part of the reflector  14 . As is seen from the side view of  FIG. 2 , the reflective member  34  has an “L” shaped cross section for its reflecting part. As a result, the light is reflected by shaped, light-directing surface  18  in a desired direction, thereby increasing the useful output of the headlight assembly. 
     In a not claimed example, the reflective member  34  reflects light in a specular manner. Suitable specularly reflective materials include, but are not limited to, aluminum, silver, copper, chromium, nickel, gold, rhodium, palladium, platinum, and any combinations thereof. 
     As preferably the reflective member  34  is closely located to the light source, preferably the reflective member  34  is mounted inside the lamp envelope  30 . Therefore, the selected reflective material must be able to withstand operating conditions for the life of the lamp without melting, evaporating, subliming or oxidizing. Some materials which can survive these conditions without degradation in performance include gold, platinum, palladium and rhodium. 
     Another approach is to mount the reflective member  34  outside the lamp envelope but still as close to the light source as possible. 
     In case the lamp will be operated in air, one may also coat the outer surface of the reflective member  34  or make the reflective member  34  out of a more easily oxidized reflective material, such as aluminum or silver, and to overcoat the reflective areas with a protective film, such as silicon dioxide, to prevent these materials from degrading when the lamp is operated in air. 
     Alternatively, a more easily oxidized reflective material, such as silver or aluminum, may be used by mounting the lamp in a reflector assembly which is hermetically sealed and which is filled with an inert atmosphere, such as nitrogen. 
     The size of the reflective member  34  can be determined empirically or by the use of computer modeling or a CAD system. In a headlight assembly, it is desirable that all of the light which leaves the headlight is reflected from the poly-ellipsoid reflecting surface  18  of the reflector  14 , because the light is more controllable when it is reflected from the poly-ellipsoid surface. It is also desirable that the light be emitted from or near the focal point of the poly ellipsoid reflecting surface  18 , since this light is directed in a controlled and predictable manner. Preferably, design of the reflective member  34  should consider these aspects. 
     In a not claimed example, the reflective member  34  has an “L” shaped cross section for its reflecting part. In another not claimed example, the reflective member  34  has an arc shaped cross section for its reflecting part. 
     The size of the reflective member is preferably small to fit a light source of small size, for example, the width of the reflective member is 3 mm for a LED retrofit light source. 
     It is noted that the reflective member  34  is advantageous for both high beam and low beam scenarios, due to light blocking otherwise occurring both in high beam and low beam scenarios. 
     It is noted that the reflective member  34  is particularly advantageous for a LED light source. Compared with a halogen filament, a LED light source is less compact, which leads to a light beam not well focused behind the lens  16  and not contributing to a maximum intensity of the beam pattern. The reflective member  34 , which preferably is near the LED source, may help direct more light through the focus  22  behind the lens  16  and help get a higher maximum intensity. 
       FIG. 3  is a schematic view of a reflective member  312  usable for an embodiment of the present invention in a vehicle headlight assembly  200  very similar to that shown in  FIG. 2 , in which the inventive reflective member  312  replaces the not claimed reflective member  34  in  FIG. 2 . The reflective member  312  in  FIG. 3  has an “L” shaped cross section for the reflecting part, with one face  301  to reflect forward side light of the LED light source of an inventive lamp, and one face  302  to reflect down side light of the light source, as seen in the horizontal operating position of the lamp with respect to the vehicle. The reflective member  312  also has two parts  303  and  304  for it to be mounted in an inventive vehicle headlight assembly on the left and right sides of the “L” shape respectively, as seen in  FIG. 3 . Preferably, these two parts  303  and  304  will not further block desired light, or block it as little as possible to ensure high light efficiency. 
     A schematic illustration of an inventive lamp is shown in  FIG. 4  in form of a H7 LED retrofit product. 
     The “L” shaped reflective member  312  is mounted close to the light emitting chips forming the LED light source  311 , only a very small distance away as required out of manufacturing reasons, such as mechanical mounting spaces. The reflective member  312  is not limited to “L” shape, but rather can apply a series of shapes as long as it can reflect forward and downward light to desired directions, thus may have, for example, an arc shape. 
     It&#39;s vital for the invention that the LED light source  311  mainly emits its light to one side. I.e., as seen in the horizontal mounting position of the inventive lamp in an inventive vehicle headlight assembly, the LED light source  311  mainly emits to one side, i.e., the left or the right side of the vehicle, and not upwards or downwards. In the illustration of  FIG. 4 , such side direction is diagonal between the left and out of the drawing plane. In other words, on installing lamp  310 , in the orientation as shown in  FIG. 4 , in a vehicle headlight assembly, LED light source  311  mainly emits to the left side of the vehicle. 
     In a preferred embodiment of the invention, lamp  310  of  FIG. 4  has an other LED light source on the side of lamp  310  which cannot be seen in  FIG. 4 , i.e., an other LED light source having a mirrored configuration to the LED light source  311  visible in  FIG. 4 . This other LED light source then mainly emits light to the other side of the inventive lamp  310 , which, in the just discussed configuration of  FIG. 4 , means that this other LED light source mainly emits light to the diagonal between the right and behind the drawing plane of  FIG. 4 , i.e., to the right of the vehicle. 
     The mainly side emission of LED light source  311  allows direct utilization, i.e., without any intermediate redirection, of the main part of the emitted light by the side surfaces of reflector  14  in an inventive vehicle headlight assembly. Thus, by avoiding any intermediate redirections, e.g., by reflection at intermediate mirrors, any intermediate losses always connected with such redirections are avoided and the efficiency of lamp  310  is considerably increased. This allows for a compact LED light source with high luminance. 
     The latter is even further improved by using an other LED light source on the other side as explicated above. As all the LEDs of the two LED light sources can be placed very close to each other a very compact high luminance light source is obtained. 
     As said, the inventive concept of using mainly side emission avoids the necessity of redirecting the main part of the emitted light thus avoiding any loss mechanism for this part of the light. Furthermore, by using reflective member  312  in front of and below LED light source  311  further avoids loss of the otherwise unused part of the forward and downwards emitted light. 
     On using an other LED light source in mirrored configuration to LED light source  311 , in order to use its forward and downwards emitted light an other reflective member in mirrored configuration to reflective member  312  is used on the other side of lamp  310 . 
       FIG. 5  shows a simulation result of a prior art vehicle headlight assembly with a halogen bulb and  FIG. 6  shows a simulation result of an inventive vehicle headlight assembly integrated with a reflective member in accordance with the invention, respectively. The scenario for  FIG. 5  has a vehicle headlight assembly with a traditional halogen bulb, which was found to produce 1560 lumen at 13.2 volts and to consume 60 watts. The scenario for  FIG. 6  has a vehicle headlight assembly with an inventive retrofit LED product, which was found to produce 1350 lumen at 13.2 volts and to consume 16.6 watts.  FIG. 5  and  FIG. 6  are all results for low beam patterns on a standardized vertical screen in front of the vehicle. 
     Based on the simulation results, it can be seen that the flux out of the inventive headlight assembly in the scenario of  FIG. 6  is 529 lumen vs. 457 lumen for the prior art headlight assembly in the scenario of  FIG. 5 , which shows an improved light efficiency by more than 15% (529/457*100%=115.7%, despite using a lamp with lower light output, i.e., 1350 instead of 1560 lumen). 
     Such improvements can be obtained for headlight assemblies with H7, HIR2, H18 and similar retrofit products. 
     While the exemplary embodiments of the present invention have been illustrated and described, it will be understood by those skilled in the art that various changes and modifications may be made, and equivalents may be substituted for elements thereof without departing from the true scope of the present invention. In addition, many modifications may be made to adapt to a particular situation and to the teaching of the present invention without departing from its central scope. Therefore it is intended that the present invention is not limited to the particular embodiments disclosed as the best modes contemplated for carrying out the present invention, but that the present invention includes all embodiments falling within the scope of the appended claims. 
     The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises”, “comprising”, “includes” and/or “including” used herein, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. 
     Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms used herein should be interpreted as having a meaning that is consistent with their meaning in the context of this specification and the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein. 
     LIST OF REFERENCE NUMERALS 
     
         
           10  prior art lamp 
           12  reflector cavity 
           14  reflector 
           16  transparent lens 
           18  light-directing interior surface  18  of reflector  14   
           20  central axis of surface  18   
           22  focal point of surface  18   
           24  walls of reflector  1426  shuttle 
           30  envelope of lamp  10   
           32  filament of lamp  10   
           34  reflective member in front of and below the light source 
           100  prior art vehicle headlight assembly 
           200  not claimed vehicle headlight assembly 
           301  face of reflective member  34  for reflecting forward side light 
           302  face of reflective member  34  for reflecting downward side light 
           303 ,  304  parts for mounting reflective member  34   
         L 1 , L 2  upward directed light 
         L 3 , L 4  downward directed light