Patent Publication Number: US-7712934-B2

Title: Vehicle headlamp with daytime running light

Description:
This application is a continuation of U.S. patent application Ser. No. 11/361,555, filed Feb. 24, 2006. 

   FIELD 
   The present invention relates to vehicle headlamps, in particular a vehicle headlamp capable of varying the light distribution of a reflector assembly by adjusting the position of a movable shade in relation to a lamp. 
   BACKGROUND 
   Vehicles commonly have headlamps that provide low and high beam lighting for driving at night. High beam lighting provides a substantial amount of light aimed so as to enable the driver to see greater distances on dark roads, while low beam lighting provides a lesser amount of light aimed closer to the vehicle for driving on lighted streets or to prevent dazzling drivers of oncoming vehicles. Separate incandescent and/or halogen lamps may be utilized for low and high beam headlamps. Alternatively, a single lamp may have a plurality of selectable filaments for high and low beam operation, or a high beam lamp may be dimmed for low beam operation. 
   Vehicle designers are increasingly turning to high intensity discharge (“HID”) lamps for use in headlamp systems due to their high efficiency in comparison to incandescent and halogen lamps. A typical characteristic of HID lamps is that they must be operated at a generally fixed power level for proper operation. This inflexibility makes dimming of an HID high beam headlamp for low beam operation impractical. To avoid the complexity and expense of utilizing two HID systems to cover both high beam and low beam operation, vehicle designers have incorporated into headlamp assemblies various types of movable shades proximate a single HID lamp. The shades are typically moved to predetermined positions proximate the lamp for low beam operation, partially shielding and/or redirecting light emitted from the lamp. Accordingly, only a portion of the total amount of light emitted by the lamp reaches a reflector to be directed out of the headlamp. When high beam operation is desired, the shade is moved away from the HID lamp, allowing a greater portion of the light emitted by the lamp to reach the reflector and be directed out of the headlamp. 
   As a safety enhancement many vehicles now include daytime running lights (“DRL”) in addition to low and high beam headlamps. As the term implies, DRL are normally operated in substantially daylight conditions. A vehicle equipped with DRL is more likely to be noticed by other drivers, thereby reducing the probability of a collision with the vehicle. 
   Daytime running lights that use incandescent or halogen lamps as a light source are typically formed from the vehicle&#39;s low or high beam headlamps. For DRL operation with high beam headlamps, the headlamps are operated at a reduced intensity. Alternatively, low beam headlamps may be operated at either full or reduced power for DRL operation. Such systems are designed to automatically function as DRL when the vehicle is started and to be overridden when regular high or low beam headlamps are activated. 
   DRL presents a challenge for HID-based vehicle lighting systems, since HID lamps must be operated at a relatively fixed power level and are not easily dimmed, as discussed above. This limitation often drives the use of a separate DRL unit, adding cost and complexity to the vehicle. Thus, there is a need for a way to avoid the expense and complexity of a separate DRL system for vehicles having headlamps that use HID lamps as a light source. 
   SUMMARY 
   The present invention utilizes a movable shade that can be positioned at predetermined locations in relation to an HID lamp to control the lighting pattern and intensity of an HID headlamp for low beam and high beam operation. In addition, the movable shade can be positioned at a third predetermined location such that light emitted by the HID lamp meets vehicle requirements for DRL operation. Thus, the HID lamp can be operated a fixed power level while the light output of the headlamp can be electro-mechanically controlled to meet illumination needs for the vehicle for low beam, high beam and DRL operational modes. 
   An aspect of the present invention is a vehicle headlamp. The headlamp comprises a light source and a reflector to direct light received from the light source out of the headlamp. A movable shade is positionable to control the light received by the reflector. A shade driver is coupled to the movable shade to position the shade. A first shade position configures the headlamp for high beam lighting. A second shade position configures the headlamp for low beam lighting. A third shade position configures the headlamp for daytime running lights. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further features of the inventive embodiments will become apparent to those skilled in the art to which the embodiments relate from reading the specification and claims with reference to the accompanying drawings, in which: 
       FIG. 1  is a sectional side elevation of a vehicle headlamp according to an embodiment of the present invention; 
       FIG. 2A  depicts low and high beam positions of a movable shade in relation to a discharge lamp for a headlamp according to an embodiment of the present invention; 
       FIG. 2B  depicts low beam and DRL positions of the movable shade of  FIG. 2A  in relation to the discharge lamp; 
       FIG. 3A  illustrates example lighting patterns for light incident on a reflecting surface for low and high beams of a headlamp according to an embodiment of the present invention; 
       FIG. 3B  illustrates example lighting patterns for light incident on a reflecting surface for DRL and high beams of a headlamp according to an embodiment of the present invention; 
       FIG. 4  is a block diagram showing the general arrangement of a system to control the position of a movable shade of a vehicle headlamp, according to an embodiment of the present invention; 
       FIG. 5  is a block diagram showing the general arrangement of a system to control the position of a movable shade of a vehicle headlamp, according to an alternate embodiment of the present invention; 
       FIG. 6  is a block diagram depicting the general arrangement of a system to control the position of a movable shade of a vehicle headlamp, according to another alternate embodiment of the present invention; and 
       FIG. 7  is a block diagram showing an alternate arrangement of the system of  FIG. 6 , according to yet another alternate embodiment of the present invention. 
   

   DETAILED DESCRIPTION 
   In the discussion that follows, like reference numerals are used to indicate like elements and structures in the various figures. 
     FIG. 1  is a sectional side elevation of a vehicle headlamp  10  according to an embodiment of the present invention. The headlamp  10  according to this embodiment includes a reflector assembly  12  mounted in a lamp chamber  13  that is generally defined by a transparent cover  14  and a housing  16 . Reflector assembly  12  includes a discharge lamp  18 , a reflector  20 , a movable shade  22 , a shade driver  24  and a lamp support base  26 . 
   Cover  14  is generally transparent and serves to protect reflector assembly  12  from exposure to the elements. Cover  14  is a conventional cover made from any suitable conventional materials, such as glass and plastic. In some embodiments cover  14  may also include various grooves, fillets, contours and shapes optically designed to at least partially shape the distribution of light emitted from headlamp  10 . 
   Light distribution of headlamp  10  is primarily controlled by reflector assembly  12 . Reflector  20  has a reflecting surface  28  for directing light received from discharge lamp  18  in a generally forward direction “A” so that a beam is formed and emitted with a prescribed light distribution pattern that is shaped by diffusing and/or deflecting the light incident on the reflecting surface. Reflector  20  may be any conventional type of optical reflector, such as an elliptical or parabolic reflector. 
   Lamp  18  provides a light source for headlamp  10 . Lamp  18  may be any conventional type of discharge lamp including, as a non-limiting example, a high pressure metal vapor discharge lamp such as a metal halide HID lamp. 
   Lamp  18  is fixedly supported in relation to reflector  20  by lamp support base  26  so that a light-emitting portion  30  of the lamp is positioned generally at an optical focal point of reflector  20 . Lamp support base  26  may be made of any suitable material, such as metal, plastic and ceramic, and extends through an opening  32  of reflector  20 . 
   Movable shade  22  comprises a shade body  34  and a shade leg  36 . Shade body  34  is preferably opaque and generally cylindrical in shape with an open end oriented toward lamp  18  and an opposing, closed end. Shade body  34  may be made from any suitable material, such as metal, plastic, coated glass and ceramics. The material selected for shade body  34  is preferably capable of withstanding heat generated by lamp  18 , along with other environmental considerations for headlamp  10 . Shade body  34  may optionally have a polished, absorptive or reflective inner and/or outer surface. In various embodiments shade body  34  may be other geometric shapes, such as elliptical, hexagonal, octagonal and rectangular shapes. Cut-outs may also be added to shade body  34  as desired, to further shape the lighting pattern or control the lighting output of headlamp  10 . 
   Shade leg  36  extends between shade body  34  and shade driver  24 . Shade leg  36  may extend from the closed end of shade body  34  or from a sidewall of the shade body. Shade leg  36  may be a separate component that is attached to shade body  34 , or may be formed as an integral part of the shade body. The shape and dimensions of shade leg  36  are not critical and may vary as needed to accommodate the arrangement of other components of headlight  10 . 
   Shade driver  24  comprises a drive member  38  actuable by an electric motor  40 . Motor  40 , when powered, causes drive member  38  to move bidirectionally and generally linearly along an axis “B” such that shade body  34  shields more or less of the light emitted by lamp  18  from reaching reflective surface  28 . Motor  40  may be any conventional type of motor including, but not limited to, a permanent magnet motor, a brushless DC motor and a stepper motor. Motor  40  may optionally include a dynamic and/or mechanical brake  42  to stop the motor and/or keep its shaft  44  from rotating when the motor is not operating. Motor  40  may further include a gear reduction  46  to provide an output displacement, velocity and torque that is compatible with drive member  38  to move shade  22 . 
   Drive member  38  converts rotary motion from motor  40  to linear motion to move movable shade  22  toward or away from lamp  18  in accordance with the selected position for the shade, as detailed above. Drive member  38  may be any conventional type of rotary-to-linear motion converter including, without limitation, a ball screw, lead screw, belt drive, and a rack-and-pinion. In some embodiments drive member  38  may be a rotary-to-oscillatory converter, such as a four-bar linkage mechanism. In other embodiments motor  40  and drive member  38  may be replaced by a linear motor-actuator. Drive member  38  may further comprise gearing to reduce the speed of rotational motive force provided by motor  40  and/or amplify the amount of motive force delivered by the motor. 
   With reference now to  FIG. 2A , movable shade  22  can be positioned at a high-beam forming position, shown in outline at discrete position “C,” and a low-beam forming position, shown at discrete position “D.” Shade body  34  partially shields lamp  18  when it is positioned at the low-beam position “D,” thereby reducing the amount of light presented to reflecting surface  28 . Shade body  34  does not substantially shield lamp  18  when positioned at the high-beam position “C,” thereby allowing a greater amount of the light emitted by the lamp to reach reflecting surface  18 . 
   With reference to  FIG. 2B , movable shade  22  can be further moved to a third, discrete DRL position, shown in outline as position “E.” At position “E,” shade body  34  shields lamp  18  to an even greater degree than at low beam forming position “D,” thereby allowing a lesser amount of light sufficient for DRL operation to reach reflecting surface  28 . 
   The effect of the position of movable shade  22  upon light emitted by vehicle headlamp  10  is observed by additional reference to  FIG. 3A . In particular, when at the low beam forming position “D” shown in  FIG. 2A , movable shade  22  surroundably shields at least a portion of lamp  18  to obstruct a portion of light emitted from the lamp. Movable shade  22  accordingly prevents the obstructed light from reaching a peripheral region “G(H)” of the reflecting surface  28 , allowing the unobstructed portion of the light emitted by lamp  18  to be directly incident only on a central region “G(L)” thereof such that only a predetermined amount of light required to emit a low beam is incident on the reflecting surface  28 . Conversely, when at the high-beam forming position “C” of  FIG. 2A  movable shade  22  allows the light to be incident on substantially the entire region of reflecting surface  28  (i.e., both regions G(H) and G(L)) so as to ensure a sufficient amount of light to emit a high beam. 
   With reference to  FIG. 3B , when at the daytime running light position “E” of  FIG. 2B , movable shade  22  surroundably shields at least a portion of lamp  18  to obstruct a portion of the light emitted from the lamp and prevents the obstructed light from reaching the peripheral region G(P) of the reflecting surface  28 . The unobstructed portion of the light emitted by lamp  18  is directly incident only on a central region G(DRL) thereof such that only a predetermined amount of light required to emit a daytime running light is incident on reflecting surface  28 . 
   With reference now to  FIG. 4 , in accordance with an embodiment of the present invention movable shade  22  is selectively actuated to the aforementioned low beam, high beam and DRL positions by shade driver  24  in cooperation with a motor driver  46 , a controller  48 , a position feedback element  50  and a mode control  52 . 
   Motor driver  46  provides electrical power suitable for operating motor  40  and may be tailored to the requirements of the type of motor selected for a particular configuration of the present invention. For example, electromechanical and solid state relays and solid state devices such as bipolar and field effect transistors may be used to selectively supply power to motor  40  for either unidirectional or bidirectional rotation of an output shaft (not shown) of the motor. In addition, motor driver  46  may be configured to provide commutation to motors that require external commutation, such as brushless DC and stepper motors. Motor drivers and commutators for the various types and winding configurations of motors are well-known in the art. Accordingly, construction details of motor driver  46  are left to the artisan. 
   Controller  48  receives command information corresponding to a predetermined selected position (i.e., positions “C,” “D,” “E” of  FIGS. 2A and 2B ) for movable shade  22  from mode control  52  and determines the actual position of the movable shade from information provided by feedback element  50 . If the position of movable shade  22  does not match the position commanded by mode control  52 , controller  48  actuates motor driver  46  to operate motor  40  in a predetermined manner until feedback element  50  indicates to the controller that the movable shade has moved to the selected position. 
   Controller  48  may further monitor for various fault conditions and resolve them in a predetermined manner. For example, controller  48  may monitor for a locked motor rotor, over-temperature or short-circuit conditions in motor  40 , over-temperature and over-current conditions in motor driver  46 , illegal or invalid mode control  52  inputs, and invalid position information from feedback element  50 . Example fault resolution responses for controller  48  include, without limitation, selectably removing power from faulty components of headlight  10 , rerouting power among components of the headlight, calculating the current and/or commanded position of movable shade  22  from a last-known position, and switching from faulty components to alternate components. Controller  48  may further include fault resolution wherein movable shade  22  is positioned at a predetermined position under certain fault conditions, thus allowing the vehicle to be driven pending resolution of the fault. A secondary position sensing arrangement and/or a mechanical stop  54  ( FIG. 4 ) may optionally be included, thus allowing movable shade  22  to be positioned at the predetermined position even in the event of a failure of feedback element  50 . 
   Controller  48  may be implemented in any conventional form of analog or digital closed-loop servo controller having operational aspects including, but not limited to, force, velocity and directional controls for motor  40 . Controller  48  may further include a predetermined set of logical instructions, such as a computer program, to define the various operational aspects of the controller. 
   Position feedback element  50  provides information to controller  48  relating to the position of movable shade  22 . Feedback element  50  may be any conventional type of feedback element in the art that is compatible with the architecture chosen for controller  48 . For example, feedback element  50  may be an absolute or relative position encoder. In other embodiments feedback element  50  may be an arrangement of electromechanical or solid state limit switches or proximity-sensing elements located at predetermined positions relative to movable shade  22 . In some embodiments utilizing a stepper or brushless DC motor a limit switch or proximity sensor at a known or calibrated position of movable shade  22  may serve as an index point for a predetermined set of instructions used by controller  48  to count the number of commutation pulses required to reach a predetermined position of the movable shade. In addition to position information, feedback element  50  may provide controller  48  with information relating to the velocity of movable shade  22  when it is moving. The aforementioned encoders, switches and proximity-sensing elements for position feedback are well-known in the art. Accordingly, details of these devices are not further elaborated upon herein. 
   Mode control  52  provides controller  48  with information relating to the selected position of movable shade  22 , i.e. whether the shade is to be in high beam position “C” or low beam position “D” of  FIG. 2A , or the DRL position “E” of  FIG. 2B . In practice, mode control  52  may be incorporated as an element of a system that controls various operational aspects of the vehicle&#39;s headlamps. For example, mode control  52  commands may be generated variously by one or more of a driver&#39;s control, ambient lighting sensors and automatic headlamp dimming controls (not shown). 
   With reference now to  FIGS. 1-4  in combination, in operation of headlamp  10  the lamp  18  is powered at a predetermined optimum power level such that it emits substantially the same amount of light for low beam, high beam and DRL modes of the headlamp. If high beam operation of headlamp  10  is desired, mode control  52  provides a command signal to controller  48  representing high beam mode. In response, controller  48  uses information from feedback element  50  to determine whether movable shade  22  is in the predetermined position “C” for high beam operation. If movable shade  22  is in the prescribed position for high beam operation, controller  48  takes no further action. However, if movable shade is not in the prescribed position for high beam operation, controller  48  actuates motor driver  46 , which in turn supplies power to operate motor  40 . Motor  40  provides rotary motive power to drive member  38 , which in turn acts to generally linearly move movable shade  22  in the direction required to achieve the commanded mode. As movable shade  22  moves, controller  48  periodically or continuously monitors the position of the movable shade using information from feedback element  50 . When controller  48  determines that the predetermined position of movable shade  22  for high beam operation of headlamp  10  has been reached, the controller de-actuates motor driver  46 , causing power to be removed from motor  40  and causing the movable shade to come to rest at the predetermined position. Motor  40 , drive member  38 , motor driver  46 , controller  48 , feedback element  50  and mode control  52  all function in a likewise manner to position movable shade  22  for low beam and DRL modes of operation of headlamp  10  at positions “D” and “E,” respectively. 
     FIG. 5  depicts the general arrangement of a shade driver  124  comprising a drive member  138  and a pair of motors  140   a ,  140   b  (generally termed “motors  140 ”) to control the position of a movable shade  22  of a vehicle headlamp according to an alternate embodiment of the present invention. Movable shade  22  is actuated by motor  140   a  and/or  140   b , each motor being coupled to the shade by a common drive member  138 . Each motor  140   a ,  140   b  may be configured to operate such that a corresponding output shaft  142   a ,  142   b  respectively (generally termed “output shafts  142 ”), rotates between two predetermined limit positions or stops  154  ( FIG. 5 ). 
   In operation, one of motors  140  is actuated, causing its corresponding output shaft  142  to rotate clockwise or counter-clockwise to one of two limit positions, in turn causing drive member  138  to reposition shade  22  at a corresponding predetermined position, the displacement of the shade being determined by the angular rotation of the actuated motor&#39;s output shaft and the mechanical characteristics of drive member  138 . The output shaft  142  of the unactuated motor rotates freely, allowing the output shaft to be driven by common drive member  138 . A plurality of positions for shade  22  may be selected by mode control  52 , depending upon such factors as actuation of only one of motors  140 , actuation of one of motors  140  and then the other motor, the order of actuation of motors  140 , and the predetermined angular displacement limits for each of output shafts  142   a ,  142   b , among others. 
   Motors  140  may be any conventional type of motor including, but not limited to, a permanent magnet motor, a brushless DC motor, a linear actuator and a stepper motor. Motors  140  may optionally include a dynamic and/or mechanical brake to stop the motor and/or keep it from rotating when it is not actuated. Motors  140  may further include a gear reduction to provide an output shaft displacement, velocity and torque that is compatible with drive member  138  to move shade  22 . For example, motors  140  may be DC gearmotors having integral limit switches (not shown) such that output shafts  142  move to a counter-clockwise position when a voltage having a first polarity is applied to the motor. Conversely, output shafts  142  may move to a clockwise limit position when a voltage having opposite polarity is applied to motors  140 . In another example, motors  140  may be programmable stepper motors under directional and rotational control of a controller  148  wherein output shafts  142  rotate predetermined number of angular displacement steps with reference to an index or stop, providing for fixed limit positions in the clockwise and counter-clockwise directions of the output shafts. 
   Drive member  138  may be any conventional type of rotary-to-linear motion converter including, without limitation, a ball screw, lead screw, belt drive, and a rack-and-pinion. In some embodiments drive member  138  may be a rotary-to-oscillatory converter, such as a four-bar linkage mechanism. Drive member  138  may further comprise gearing to reduce the speed of rotational motive force provided by motors  140  and/or amplify the amount of motive force delivered by the motors. In other embodiments motors  140  and drive member  138  may be replaced by a linear motor-actuator. 
   In addition to having the previously-discussed aspects of controller  48 , controller  148  may include position-tracking capability. The position-tracking capability of controller  148  can be configured to store data relating to an initial known calibration or index position of shade  22  and also store data relating to subsequent actuations of each of motors  140 . This stored information can then be utilized by controller  148  to compute and track the current position of shade  22  to determine the required actuation of motors  140  to move shade  22  to a desired position in response to a command input received from mode control  52 . Alternatively, controller  148  may receive position information from a feedback element  50  (see  FIG. 4 ), as previously discussed, to move shade  22  to a desired position using one or both of motors  140 . 
     FIG. 6  shows the general arrangement of a shade driver  224  comprising a pair of drive members  238   a ,  238   b  (generally termed “drive members  238 ”) and a pair of motors  240   a ,  240   b  (generally termed “motors  240 ”) to control the position of a plurality of movable shades of a vehicle headlamp, according to another alternate embodiment of the present invention. A first movable shade  222   a  is actuated by a motor  240   a  through an intermediate drive member  238   a . A second movable shade  222   b  is likewise actuated by a motor  240   b  through an intermediate drive member  238   b . A shade body  234   b  is configured to movably fit within a shade body  234   a.    
   Motors  240  may be any type of motor suitable for use with headlight system  10 , such as those discussed above for motors  40  and  140 . Likewise, drive members  238  may be any type of drive mechanism suitable for use with headlight system  10 , such as those discussed above for drive members  38 ,  138 . Each motor  240  may optionally be configured to actuate a corresponding drive member  238  between two predetermined limit positions or stops  254  ( FIG. 6 ) in the manner previously described for motors  140 . 
   Shades  222   a ,  222   b  (generally termed “shades  222 ”) may be configured similarly to shade  22 , with shade body  234   b  being generally coaxial to fit within shade body  234   a . Shade body  234   b  is also independently positionable with respect to shade body  234   a . In one embodiment shade  222   a  may include a longitudinal slot  235  through which a shade leg  236   b  of drive member  238   b  extends, as shown in  FIG. 6 . Alternatively, an aperture  237  located at a closed end  239  of shade  222   a  can be provided to allow shade leg  236   b  and/or drive member  238   b  access to inner shade  222   b , as shown generally in  FIG. 7 . 
   With reference to  FIGS. 6 and 7 , controller  248  may include the features of either or both of controllers  48 ,  148  discussed above. The position-tracking capability of controller  248  can be configured to store data relating to an initial known calibration or index position of shades  222  and also store data relating to subsequent actuations of each of motors  240 . This stored information can then be utilized by controller  248  to compute the required actuation of motors  240  to satisfy a command input received from mode control  52  to move either or both of shades  222  to a desired position. Alternatively, controller  248  may receive position information from a feedback element  50  as previously discussed (see  FIG. 4 ), to move each of shades  222   a ,  222   b  to desired positions using corresponding drive members  238   a ,  238   b  and motors  240   a ,  240   b.    
   In operation, motor  240   a  may be actuated independently of motor  240   b , causing drive member  238   a  to move shade  222   a  to one of two predetermined limit positions, the displacement of the shade being determined by the angular rotation of the motor and the mechanical characteristics of drive member  238   a . Motor  240   b  may likewise be actuated independently of motor  240   b , causing drive member  238   b  to move shade  222   b  to one of two predetermined limit positions, the displacement of the shade being determined by the angular rotation of the motor and the mechanical characteristics of drive member  238   b . In this embodiment a plurality of shading levels for lamp  18  may be selected by mode control  52 , depending upon such factors as actuation of only one of motors  240 , actuation of one of motors  240  and then the other motor, the order of actuation of motors  240 , and the predetermined angular displacement of drive members  238 , among others. 
   While this invention has been shown and described with respect to several detailed embodiments thereof, it will be understood by those skilled in the art that changes in form and detail thereof may be made without departing from the scope of the claims of the invention.