Patent Grant
7188984
The present invention relates to a headlamp, and more particularly to an automotive headlamp using an LED light source array.
A modern vehicle headlamp assembly commonly includes sealed electrical connectors, sophisticated injection-molded lenses and molded, metal-coated reflectors which work in concert to collimate and distribute white light from an incandescent, halogen, or arc-discharge source (HID).
Many modern electric light sources are relatively inefficient, e.g., conventional tungsten incandescent lamps, or require high voltages to operate, e.g., fluorescent and arc-discharge lamps, and, therefore are not optimal for vehicular head lamp light sources where only limited power is available, only low voltage is available or where high voltage is unacceptable for safety reasons. Most conventional white-light headlamps rely upon incandescent, halogen or HID lamps as light sources. However, these lamps possess a number of shortcomings that must be taken into account when designing a headlamp assembly.
Incandescent lamps are fragile and have a short life even in stable environments and consequently must be replaced frequently at great inconvenience, hazard, and/or expense. In addition to their inherently short life, incandescent lamps are very susceptible to damage from mechanical shock and vibration. Automobiles experience severe shocks and significant vibration during driving conditions that can cause damage to incandescent lamps, particularly the filaments from which their light emissions originate.
Incandescent lights also exhibit certain electrical characteristics that make them inherently difficult to incorporate in vehicles, such as an automobile. For instance, when an incandescent light source is first energized by a voltage source, there is an initial surge of current that flows into the filament. This in-rush current, which is typically 12 to 20 times the normal operating current, limits the lifetime of the lamp, thus further amplifying the need for frequent replacement. Incandescent lamps also suffer from poor efficiency in converting electrical power into radiated visible white light. Most of the electrical energy they consume is wasted in the form of heat energy while less than 7% of the energy they consume is typically radiated as visible light.
Another problem associated with incandescent, halogen, and HID lamps is that they generate large amounts of heat for an equivalent amount of generated light. This results in very high bulb-wall temperatures and large heat accumulations which must be dissipated properly by radiation, convection, or conduction to prevent damage or destruction to the illuminator support members, enclosure, optics or to other nearby vehicle components. This high heat signature of common light sources in automotive headlamps has a particularly notable impact on the specialized reflector and lens designs and materials used to collimate and direct the light. Design efforts to dissipate the heat while retaining optical effectiveness further add requirements for space and weight to the illuminator assembly, a severe disadvantage for vehicular applications that are inherently sensitive to weight and space requirements.
Moreover, the illuminance of an incandescent light source depreciates over time. It is very common for a filament type light source used in headlamp applications to loose more than 25% of its output when compared to the initial output of the bulb. Very long life halogen bulbs may loose up to 50% of their output over their useful life.
HID lamps provide more light than that produced by halogen lamps and incandescent bulbs, and use less power than halogen, and thus, are more efficient. Moreover, since there is no filament to burn out, these bulbs are claimed to last for as much as 100,000 miles of driving time. However, although HID's last longer than halogen and incandescent light sources, they are very expensive and require the use of ballast. Moreover, a common complaint with HIDs is that they produce an excessive amount of glare. HID light sources (bulbs) typically have about two to three times the available light flux (volume) of halogen light sources and the HID beam pattern is more robust than that of halogen sources, providing more even and wider illumination and the potential for better visibility and comfort. This results in more light on the road surface and more of the roadway being illuminated. However, this additional light is not supposed to be projected upward from the lamp toward oncoming drivers' eyes. During inclement weather, when the road surface is wet, the additional volume of light can result in higher levels of light reflected off the road surface into other drivers' eyes.
More recently, great interest has been shown in the use of semi-conductor devices such as light emitting diodes (LEDs) as the light source for illuminator systems. Due to their strong coloration and relatively low luminous output as compared to incandescent lamps, early generations of LEDs found most of their utility as display devices, e.g., on/off and matrix-addressed indicators, etc. These uses still dominate the LED market today, however recent advances in LED materials, design and manufacturing have resulted in significant increases in LED luminous efficacy and, in their most recent commercial forms, exhibit a higher luminous efficacy than incandescent lights.
LEDs offer other many potential advantages as compared to other conventional low voltage light sources for vehicles. LEDs are highly shock resistant and therefore provide significant advantages over incandescent and fluorescent bulbs that can shatter when subjected to mechanical or thermal shock. LEDs possess operating lifetimes from 200,000 hours to 1,000,000 hours, as compared to the typical 1,000 to 2,000 hours for incandescent lamps, 1000 hours for halogen, and 5,000–10,000 hours for fluorescent bulbs. The heat generated by LED light sources is also significantly less than that generated by conventional vehicular headlamp light sources that use filaments. Since relatively little heat is generated by LED light sources, the volume inside the headlamp can be minimized, thereby minimizing package depth of the headlamp. Also, LED light sources have a very low level of light output degradation over time, i.e., less than ten percent over the life of the vehicle versus about twenty five percent of the life of the vehicle with conventional light sources.
Moreover, since conventional light sources generally utilize a single bulb or light source, headlamp design is generally limited. Use of an array of LED light source modules permit a range of possible headlamp design configurations. In addition, for customers who desire greater light output performance from the headlamp, more LED light source modules can be added. A further advantage of the use of an array of LED light source modules is the adjustability and adaptability of the headlamps utilizing such modules. By switching on or off certain LED modules within the headlamp, the beam pattern from the headlamp can be altered to meet road conditions or vehicle actions. For example, if some of the modules of the array are arranged to the right, when the vehicle enters a right turn, these modules can be selectively adjusted, either by switching them on or increasing their light output, to permit the driver of the vehicle greater visibility of the road and area into the right turn. Likewise, LED modules aimed to the left can be dimmed so as to minimize distraction to the driver. In addition, with an array of LED light source modules, failure of one or a couple of modules results only in a slight loss of light output as opposed to complete loss of light output resulting from the failure of conventional bulbs.
Finally, with LED headlamp arrays various individual lenses of the same or varying types can be associated with each individual LED to create different beam patterns and optimize those beam patterns depending on the desired use.
Thus, it is desirable to replace conventional bulbs with arrays of white light emitting diode light sources in headlamps used on vehicles. The present invention solves the above-identified problems associated with the use of conventional bulbs in vehicular headlamps.
The scope of the invention is determined solely by the appended claims and their equivalents and is not affected to any degree by the statements within this summary.
The present invention is directed to a vehicular headlamp assembly including an array of light emitting diode (LED) light source modules, each having dedicated optics. Specifically, the headlamp assembly of the present invention includes an array of LED light source modules in which each module includes its own LED light source, its own lens capable of both refracting and reflecting light from the light source, and its own reflector having a contoured inner reflective surface. In one embodiment, modules dedicated to a specific function, such as high beam or low beam function, are in electrical communication with a circuit board for control of that function. In another embodiment, each individual light source is selectively controlled. This can be accomplished by communication with the control module or through communication with vehicle electronics.
The file of this patent contains at least one drawing executed in color. Copies of this patent with color drawings will be provided by the Patent and Trademark Office upon request and payment of the necessary fee.
The present invention is directed to a vehicular headlamp assembly including an array of light emitting diode light source modules each having dedicated optics.
As shown in
Outer lens 16 may be adhered to housing 12 by any means known to one skilled in the art, such mechanical or adhesive means including, but not limited to, screws, bolts, adhesives, ultrasonic welding, tab in groove, and the like. Outer lens 16 may be permanently or removably attached to housing 12 depending on whether access to the interior of the housing is desired through front opening 14, and may be attached by any means known to one skilled in the art. Outer lens 16 may or may not include faceting or other light distribution means. In a preferred embodiment, outer lens 16 does not include faceting or light distribution means.
An array 18 of LED light source modules 20, as shown in
Module lens 26 may be generally and approximately elliptical or obround, as shown in
Light sources 22 may be operatively connected, either directly or indirectly, and in electrical communication with an electrical current control device with an optional logic control element. In one embodiment, array 18 may be in electrical communication with a logic control element, such as a control circuit board or microchip, that controls the functioning of the LED light source modules 20 of array 18. In another embodiment, each LED light source module 20 having a particular function, i.e. high beam or low beam, is associated with a control element having a logic control element dedicated to that function. In yet another embodiment, each individual LED light source module 20 is associated with its own logic control element for dedicated, individual control of light source module 20. In this way, each module 20 may be selectively and individually controlled so as to provide desirable amounts and patterns of light emitted from headlamp 10. In this way, modules in a single array may be selectively and differently operated and illuminated to achieve different lighting requirements. For example, to reduce or prevent glare to the vehicle driver, LED lights sources located in the driver's side headlamp may be selectively reduced in intensity or completely turned off. In another example, rather than having only two illumination intensities, as is common in most vehicle headlamps, a variety of intensities for varying driving conditions may be achieved.
Preferably, LED light source 22 is disposed within reflector 28, as shown
Preferably, the perimeter of lens 26 approximately conforms to the inner contour of reflective surface 48 of reflector 28 as seen from the focal point 49 of the LED light source 22. As shown in
Reflector 28 comprises a cup-shaped body having a generally parabolic internal reflecting surface 48, although other shapes, such ellipses, hyperbolas, hemispheres and cones are also contemplated. Reflecting surface 48 reflects light emitted from LED light source 22 that is not collected and distributed by lens 26. Preferably, reflector 28 is an axial reflector lens in which reflector 28 may be oriented in substantial registry with LED light source 22. Reflecting surface 48 preferably comprises at least two contiguous reflecting surfaces. More preferably, reflecting surface 48 comprises at least four and preferably six radially aligned contiguous reflecting surfaces. In the most preferred embodiment, reflecting surface 48 comprises eight contiguous facets 54 as shown in
Reflector 28 and lens 26 cooperate to overlap the illumination from the individual LED light source modules 22 to produce the beam patterns such as those shown in
Power for illumination of LED light source modules 20 may be provided by a low voltage power supply or 12 volt power supply which is conventionally available in vehicles.
Multiple LED modules for a desired function are arranged in an array so that LED modules dedicated to a particular function (such as high beam) are arranged to cooperate with adjacent like-function LED modules. Although any number of LED modules can be used for each function, a low-beam array preferably includes 5–25 LED modules with LED lights sources of at least 25 lumens each, preferably of at least 40 lumens and more preferably of at least 55 lumens each. An LED array dedicated to a low-beam function preferably includes about 10–18 individual LED modules. While Lumileds Luxeon LEDs are preferred, one of ordinary skill in the art would recognize that other types of LEDs may be available for use in the present invention. Although the LEDs may be any color, in the preferred embodiment the LEDs are white for use as vehicular high beam/low beam headlamps.
A preferred high-beam array includes from about 8 to about 30 LED light sources dedicated to that function of from about 25 lumens to about 100 lumens, and preferably at least 30 lumens each. Preferably, a high-beam LED module array includes from about 10 to about 18 modules. The number of LED modules dedicated to a high-beam function may be greater than, less than or equal to the number of modules dedicated to the low beam function.
Vehicular headlamps including LED arrays according to the present invention provide greater flexibility and diversity in the frontal configuration of the headlamp than conventional headlamps using halogen or HID bulbs as illustrated in
Of course, it should be understood that a wide range of changes and modifications can be made to the embodiments described above. It is therefore intended that the foregoing description illustrates rather than limits this invention, and that it is the following claims, including all equivalents, that define this invention.
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