Patent Publication Number: US-2002012249-A1

Title: Headlamp for motor vehicles

Description:
[0001] This invention concerns a headlamp for a vehicle having holding part and a pivotal part pivotal about a vertical axis relative to the holding part, there being a light element in a central zone.  
       [0002] German Patent Publication DE 197 21 095 A1 discloses a headlamp for a vehicle, which is coupled to a horizontally driving worm via a vertically extending turn shaft and a worm wheel fixedly attached to the turn shaft. The worm is coupled to a motor, which is controlled by a control unit in such a manner that the headlamp experiences a desired horizontal alignment to achieve a curve illumination. It is disadvantageous in this known headlamp that the adjustment apparatus formed of the turn shaft, the worm wheel, the worm and the motor requires a relatively large amount of space. Because the entire headlamp must be pivoted, a relatively large amount of force is necessary. Further, it is disadvantageous that if the electronic control fails the headlamp stays fixed in its last assumed operational position.  
       [0003] Further, a headlamp for vehicles is disclosed in German patent document DE 198 02 023 A1, which can be provided with an adjustment apparatus which has a linear adjustment element coupled to a reflector of the headlamp by a ball joint so that a pivoting thereof about a vertical axis to achieve curve illumination is made possible. Indeed, by coupling the adjustment element only to the reflector, there is a decreased force requirement for pivoting. At the same time, tolerance errors can be caused by coupling the linear adjustment element with the reflector with a ball joint, which disadvantageously affects the exactness of predetermined pivot adjustments of the reflector. Also, a disadvantage of this known headlamp is that if the electronic control should fail, the reflector becomes fixed in its last assumed operational position.  
       [0004] It is an object of this invention to provide a headlamp for vehicles having a basic light function as well as additional light functions, for example curve light, city light etc., such that when there is a small mounting space a reliable adjustment of the illumination function is assured.  
       [0005] According to principles of this invention, a headlamp of the type set forth in the preamble of patent claim 1 is characterized by having an adjusting apparatus with an adjusting element attached to the holding part that operates on a coupling element of a pivotal part to adjust the pivotal part about a pivot axis, with a centering spring device being is provided so that the pivotal part is automatically returned to a predetermined position in a non-operational condition.  
       [0006] A particular benefit of this headlamp is that the adjusting apparatus as well as the centering spring device make possible a dependable and long-term stable adjustment to a predetermined curve-illumination operational position. In particular, the centering spring device causes the pivotal part to always return to a predetermined position, in particular to a zero position, in the case of disturbance or a current-less condition of the adjusting apparatus.  
       [0007] According to a preferred embodiment of the invention, the adjusting apparatus is structured as an electronic adjustment apparatus which is allocated to a holding part and which has an adjusting element that when operational is in engagement with a coupling element of the pivotal part. It is beneficial that each of the adjusting element and the coupling element has toothing so that a predetermined pivot angle can be positively and dependably set.  
       [0008] According to a particular beneficial embodiment of the invention, the adjusting apparatus has an electric drive motor that is coupled to the adjusting element by an electromagnetic coupling. In a non-operational condition, the coupling is released with the adjusting element being pivoted out of an engagement position, into a non-engagement position, with the coupling element. The coupling element is now free from the adjusting-element applied forces so that, in cooperation with the centering spring device, the coupling element and the pivotal part that is rigidly connected therewith are moved to the zero position. Thus, a certain and dependable zero-point positioning of the pivotal part can be beneficially achieved.  
       [0009] According to a further enhancement of the invention, the centering spring device is of two centering spring elements, which extend from opposite ends thereof substantially perpendicular to the pivot axis, between the holding part and the pivotal part. Because the centering spring device is mounted under pre-tension, the spring characteristic curve can be selected to be relatively flat so that upon an outward pivoting, or return pivoting, of the pivotal part a small return force change is developed. In a predetermined angle zone of for example +/−15° in a small bandwidth differential, a relatively high return force can be brought about.  
       [0010] A benefit of a further preferred embodiment of the headlamp is that the structure of a curved element rigidly connected with the reflector achieves a direct coupling with the adjusting apparatus, wherein the curved element can be directly coupled with a drive shaft of an electric motor of the adjusting apparatus. Because the reflector cooperates on the one hand directly with the drive shaft of the adjusting apparatus via the curved element and on the other hand rotationally with the holding element via the pre-tensioned centering spring element, a play-free adjustment of the reflector is made possible, with the high stiffness and relatively small number of movable parts of the headlamp favorably affecting lifetime stability. The pre-tensioned centering spring element has a double function. For one thing, it supports the adjustable mounting of the reflector relative to the holding part. For another thing, it makes possible the automatic pivoting of the reflector to a central default position in case of failure of an electrical supply to the adjustment apparatus.  
       [0011] According to a particular embodiment of the invention, the curved element extends sector-or fan-shaped from a central area in a light-exiting direction of the headlamp. Thereby, a curved edge of an end facing away from the pivot axis forms a toothing that has a constant radius to the pivot axis. The curved element is structured in the manner of a toothed-wheel segment and preferably extends into a lower front space of the headlamp so that the already-available and normally-not-used mounting space of the headlamp is filled out. Because of the relatively large spacing of the curved edge from the pivot axis, a relatively high gear reduction can be developed  
       [0012] According to a further enhancement of the invention, the centering spring element is structured as a leaf spring extending perpendicular to the pivot axis and extending between two vertically extending abutment lugs of the holding part. The leaf spring has a diminishing progression of the return moment relative to the deflection angle. The progression of the rotation moment is, up to a deflection angle of 20-30°, relatively steep so that simply a defined curve illumination operational position can be set. Further, upon a failure or a turning-off of the drive unit, a dependable return of the reflector to a central middle position is thereby assured.  
       [0013] According to a further enhancement of the invention, the drive unit has a step motor with a shaft, which engages directly with the toothing of the curved wheel of the curved element. It is beneficial in this regard that an uncomplicated control to intermediate positions of the curve-illumination function is produced. Abutment stops for the end positions of the curved element are not necessary.  
       [0014] According to a further enhancement of the invention, the light source is held on a light support part, which can be pivoted relative to the holding part about a horizontal axis. This horizontal axis is arranged orthogonal to the vertical pivot axis and forms together therewith a vertical plane. Thus, a cardanic mounting of the light support part is formed, so that a space-saving plurality of different light functions can be carried out by pivoting about two axes extending in a common plane.  
       [0015] According to a further enhancement of the invention, the light support part is coupled by a coupling element with an axially movable positioning pin of a second adjusting apparatus in such a manner that in two operational positions respective ends of the coupling element forms a vertical plane with the vertical pivot axis. In this manner, a decoupling of the curve-illumination-adjustment function on the one hand from two further light-function adjustments (low beam/high beam) on the other hand is achieved.  
       [0016] Preferably, by providing a pre-tensioned spring on the one hand, that is coupled to the light support part and a pivotal coupling of the coupling element with the positioning pin on the other hand, it is assured that the light support part is always in a predetermined end-position to produce a high beam or a low beam light function. Because the ends of the coupling element in the respective operational positions always find themselves in a plane with the vertical pivot axis, a holding force developed by the pre-tensioned spring is, independently of the adjustment of the curve light illumination, constant. By the pivotal mounting of the end of the coupling element facing the positioning pin, the adjustment angle remains constant during a curve-illumination function adjustment so that a set curve-illumination operational position is not changed during adjustment from the low beam to the high beam function or vise versa.  
       [0017] To positively engage the low-beam-and-high-beam function, the reflector support part and/or the light support part has abutment stops so that in the respective operational positions the support parts lie directly against one another. Thus, in connection with this linear operating adjustment apparatus a simple end-position operational adjustment can be achieved. 
     
    
    
     [0018] Embodiments of the invention are described below with reference to the drawings:  
     [0019]FIG. 1 is a perspective front view of a headlamp;  
     [0020]FIG. 2 is a schematic front view of the headlamp;  
     [0021]FIG. 3 is a schematic plan view of the headlamp;  
     [0022]FIG. 4 is a side view of the headlamp;  
     [0023]FIG. 5 a  is a schematic plan view of a coupling of a reflector support part to a holding part of the headlamp by a centering spring element in a central middle position of the reflector support part;  
     [0024]FIG. 5 b  is a schematic plan view of the coupling of the reflector support part to the holding part of the headlamp by the centering spring element in a 20-degree to the right pivoted position of the reflector support part;  
     [0025]FIG. 6 a  is a schematic representation of a coupling of a positioning pin to a pre-tensioned spring element of a light support part of the headlamp in a retracted (low-beam function);  
     [0026]FIG. 6 b  is a schematic representation of the coupling of the position pin to the pre-tensioned spring element of the light support part of the headlamp in a pushed-out position (high-beam function);  
     [0027]FIG. 7 is a perspective representation of a headlamp according to a second embodiment;  
     [0028]FIG. 8 is a perspective representation of a headlamp according to the second embodiment as seen from a back side;  
     [0029]FIG. 9 is a plan view of a headlamp according to the second embodiment;  
     [0030]FIG. 10 is a schematic representation of the coupling of a holding part and a pivotal part of the headlamp according to a further embodiment;  
     [0031]FIG. 11 is a plan view of a coupling element of the headlamp in engagement with an adjusting element of an adjusting apparatus that is rigidly coupled to the holding part;  
     [0032]FIG. 12 is a schematic representation of the adjusting element and the coupling element in a non-engaged position;  
     [0033]FIG. 13 is plan view of a centering spring device which is coupled with a holding part and a pivotal part of a headlamp; and  
     [0034]FIG. 14 is a spring characteristic curve of the centering spring device. 
    
    
     [0035]FIG. 1 shows a headlamp  1  for a vehicle, which basically including a reflector  2 , a light source  3  and an adjusting apparatus  4 .  
     [0036] The reflector has a reflector element  6  held on a pivotal part or reflector support part  7  whose reflecting interior surface is oriented in a beam direction  5 . The reflector support part  7  has a frame-like structure and has an opening for accommodating the light source  3  at a central zone thereof. A curved element  8  is rigidly attached to a side of the reflector support part  7  facing a cover pane (not shown) of the headlamp  1  that has a fan-like shape and has a rounded curved edge  9  with toothing  10 , which extends away from a central zone  11  in which the reflector support part  7  is arranged.  
     [0037] The curved edge  9  extends with a constant radius about a vertical pivot axis  12 , about which the reflector support part  7  is mounted to pivot relative to a frame-like holding part  13 . For this purpose, the reflector support part  7  is movably coupled with the holding part  13  in an upper space by a joint  14 . In a lower space the reflector support part  7  has a reflector projection  15  that is rotationally mounted to the holding part  13  by a pre-tensioned centering spring element  16 .  
     [0038] The centering spring element  16  is formed as a leaf spring extending perpendicular to the pivot axis  12 , with ends  17  thereof bent about support lugs  18  of the holding part  13 . As can be better seen in FIG. 5 a , the ends  17  lie directly on abutment stops  19  of the support lugs  18  in a central starting position of the reflector support part  7  and the reflector projection  15 .  
     [0039] For creating a curve-light function, the reflector is pivoted about the pivot axis  12  by the adjusting apparatus  4  to a desired operational position. For this purpose, a drive unit  20  of the adjusting apparatus  4  is in direct engagement with the curved edge  9  of the curved element  8 .  
     [0040] The drive unit  20  has an upright-standing step motor  21  with a drive shaft  22  that is oriented parallel to the pivot axis  12 . The drive shaft  22  engages the toothing  10  of the curved edge  9 .  
     [0041] By controlling the drive unit  20 , the curved element  8  is turned about the pivot axis  12  to a desired position, whereby simultaneously a pivoting of the reflector projection  15  occurs (see FIG. 5 b ). The reflector projection  15  has a central rounded portion  23  with a large radius between adjacent outer rounded portions  24 , each with a smaller radius. The central rounded portion  23  is oriented substantially coaxial to the pivot axis  12 . A rear contour of the reflector projection  15  assures that the reflector support part  7  is always safely held by pressure between the drive shaft  22  of the step motor  21  and the leaf spring  16  of the holding part  13 .  
     [0042] The drive unit  20  is fixedly located in a housing  25  of the adjusting apparatus  4  that is rigidly attached to the holding part  13 . The holding part  13  is mounted to be pivotal at a joint  26  about the horizontal axis  27  relative to a housing (not shown) of the headlamp  1  so that vertical inclination of the headlamp  1  can be adjusted by a distance-illumination adjustment device (not shown) arranged on a backside of the holding part  13 .  
     [0043] The horizontal axis  27  is positioned behind a further horizontal axis  28  about which a light support part  29  is mounted for rotation relative to the reflector support part  7 . The light support part  29  supports the light source  3 , which is structured as a gas discharge lamp and is attached on a backside of the discharge lamp  3 , along with an ignition module  30 . The light support part  29  is coupled to an axially movable positioning pin  32  of a second adjusting apparatus  33  by a coupling element  31 . The second adjusting apparatus  33  has an electric motor (not shown), which is coupled with the positioning pin  32  by a transmission. The thusly-structured second adjusting apparatus  33  can be mounted in the common housing  25  with the first adjusting apparatus  4 .  
     [0044] By manipulating the second adjusting apparatus  33  the light support part  29  is pivoted between two end positions, wherein in a first operational position according to FIG. 6 a  the headlamp assumes a low beam function, and in a second operational position according to FIG. 6 b  the headlamp assumes a high beam function. As can be seen from the low beam position according to FIG. 4, the light source  3  in the high beam operational position is arranged to be inclined downwardly about the horizontal axis  28 . The light support part  29  is coupled with the coupling element  31  by a pre-tensioned spring element  34 , with the spring element  34  being formed to be lamellar, and extending to be substantially bowed in the horizontal direction. In this regard, the spring element  34  is held in a receiver (not shown) of the coupling element  31  and touches it along a vertical line.  
     [0045] As can be seen in FIG. 6 a , the positioning pin  32  is in the low-beam operational position when it is in a retracted position with an end  35  of the coupling element  31  directed toward the spring element  34  extending in a common vertical plane with the vertical pivot axis  12 . In this manner, a bending of the spring element  34  is independent of the curve-light-function setting of the reflector  2 . Upon pivoting the reflector support part  7  about the vertical pivot axis  12 , the end  35  always remains in the same position.  
     [0046] Also, in the high-beam operational mode, according to FIG. 6 b , the headlamp  1  can assume a desired curve-light operational position without influencing the set high-beam operational position. In this regard, in the high-beam operational mode the positioning pin  32  is moved to such an outwardly driven position that an end  36  of the coupling element  31  directed toward the positioning pin  32  forms a common vertical plane with the vertical pivot axis  12 . To limit the retracted and outwardly-driven positions of the light support part  29 , abutment stops  37  are provided that come in contact with abutment stops of the reflector support part  7  in the respective operational positions.  
     [0047] Thus, the continually adjusted curve-light positions, on the one hand, and the low beam and high beam settings on the other hand are completely decoupled from one another. As can be seen in FIGS. 6 a  and  b,  the end  35  intersects the vertical pivot axis  12  in the low-beam position and the end  36  intersects the vertical pivot axis  12  in the high-beam position. The end  36  is coupled with the positioning pin  32  by a ball joint. Because the bend of the spring element  34  at the respective end positions is oriented differently, the adjustment path S 3  of the positioning pin  32  is larger than the adjustment path S 5  of the light support part  29  by an amount double the bowing of the spring element  34 . Upon the reflector support part being rotated about the pivot axis  12 , the coupling element  31  can follow the circular path of the spring element  34  about the pivot axis  12  in the manner of a pendulum support and thereby hold the bend constant. By providing a balljoint connection at the end  36  to the positioning pin  32 , a tensionfree spatial movement of the light support part  29  is made possible.  
     [0048] The light support part  29  is Cardanically arranged in the holding part  7 .  
     [0049] Alternatively, the headlamp  1  can also be structured according to a projection principle with the reflector support part being additionally coupled with a light shield (not shown) and a lens. The low beam/high beam function in this case is made possible by a second movable light shield. The light shield, in this case, includes a fixed shielding part and a movable shielding part, with the movable part preferably being structured to be pivotal about to the fixed shielding part between two end positions so that one can switch between the two light functions by manipulating the movable shielding part.  
     [0050] According to an alternative embodiment according to FIGS. 7 through 9, a headlamp is provided with a frame-like holding part  51  that is rigidly attached to a housing (not shown) of the headlamp. A pivotal part  53  is pivotally mounted on the holding part  51  to the pivotal about a pivot axis  52 . The pivotal part  53  has a cylindrically-shaped light-guide receiver  54  into which a light guide (not shown) can be extended from the rear. An end of the light guide directed away from the headlamp is preferably coupled with a light source and serves as a transmitting path for coupled light to the headlamp. Preferably, the light guide has a light-outcoupling element at an end directed in the light projection direction with a predetermined form that serves to create a symmetrical or asymmetrical light distribution. A spacer  55  in front of the holding part  51 , which is rigidly connected to the pivotal part  53 , aligns an optical element  56  to be coaxial to the light guide receiver  54  as well as the light-outcoupling element of the light guide.  
     [0051] So that the pivotal part  53 , along with the spacer  55  and the optical element  56 , can be pivoted about the pivot axis  52  relative to the holding part  51  for creating a curve illumination, an adjusting apparatus  57  is provided which generally comprises an electrical adjusting motor  58  and a plunger  59  as an adjusting element. The optical element  56  can be formed as a Fresnel lens, a free-surface lens, or a rotationally symmetrical convex-formed light-outcoupling element. Preferably, the light guide extends sufficiently far into the light-guide receiver from the backside that the light guide comes into direct contact with the optic element  56 . The plunger  59  is linked to a pivot arm  60  of the pivotal part  53  at a spacing from the pivot axis  52 . The pivot arm  60  serves as coupling element and is rigidly coupled with the pivotal part  53 . Operation of the adjusting motor  58  drives the plunger  59  in and out so that a corresponding pivoting of the pivotal part  53  takes place.  
     [0052] According to a further embodiment of the headlamp according to FIG. 10 and FIG. 11, contrary to the embodiments previously described, an adjusting apparatus  63  can be provided that instead of having a plunger has a worm  64  which can be rotated by an electric adjusting motor  65 . In the operational position of FIG. 11, the worm  64  is in engagement with a coupling element  66 , which is formed as a toothed segment. The toothed segment  66  is rigidly connected to the pivotal part  53 .  
     [0053] Additionally, a separating device  62  is provided for moving the worm  64  and the toothed segment away from each other with the separating device having an electric activation magnet (electromagnet)  67  and a plunger rod  68 . The electromagnet  67  is coupled with the toothed segment  66  by the plunger rod  68  so that in a non-operational condition, in which the electromagnet  67  is not energized by a current, a spring (not shown) coupled with the plunger rod  68  holds the plunger rod  68  in a return position in which the toothed segment  66  not engaged with the worm  64 . In an operational condition an electric current is applied to the electromagnet  67 , and the electromagnet  67  holds the plunger rod  68 , against the spring force, in a position in which the toothed segment  66  is in engagement with the worm  64 .  
     [0054] If the headlamp is in a non-operational condition, for example because of a defect in wiring or because of a controlled switching off, the electromagnet is also without current so that the plunger rod  68  moves in and thereby moves the toothed segment  66  about a rotational axis  69  that extends perpendicular to the pivot axis  52  into a non-engaging position with the worm  64 . The toothed segment  66 , and therefore the pivotal part  53 , is now force-free from the adjusting apparatus  63  and the toothed segment can therefore be transported under its own means into a centered, zeroed, position. Alternatively, the toothed segment  66  can be brought to a desired predetermined angular position.  
     [0055] Alternatively, also, the worm  64  can be brought into a non-engaging position. To achieve this, the electromagnet  67  coupled to the holding part  51  must be pivoted by an appropriate means opposite to the direction toward the toothed segment  66 .  
     [0056] According to a preferred embodiment, the separating device  62  has an electric adjusting motor rather than an electromagnet  67 , with the electric motor being coupled to the plunger rod  68  by an electromagnetic coupling. In dependence of the above on a current supply, a corresponding switch setup can be appropriately established. Alternatively, a friction clutch can be used.  
     [0057] To bias the headlamp of FIGS.  7 - 12  a centering spring device  70  according to FIG. 13 can be provided. The centering spring device  70  is of two identical centering spring elements  71  that are arranged to be substantially perpendicular to the pivot axis  52  and on oppositely positioned sides of the same. Ends of the centering spring elements  71  are respectively coupled, on the one hand, to a pivotal part  72  that, for example, can support a reflector, and, on the other hand, to a holding part  73 . As can be seen in FIG. 14, the centering spring elements  71  are pre-tensioned a predetermined spring force F. In this manner, the spring characteristic curve can be made to be relatively flat so that in a rotational angle zone from +/−15 degrees, only a spring force difference ΔF appears. Because of this, a relatively even return force can be created in the different pivot angle positions for the curve illumination. Because both centering spring elements  51  are pre-tensioned, only one centering spring element  71  is effective upon a deflection of the pivotal part  53 , while the other centering spring element  51  operates against the return force with a smaller, amount-wise, spring force, see the dashed characteristic line in FIG. 14. Upon each deflection of the pivotal part  53  around the zero position, a combined return force results which corresponds to the difference for the corresponding turn angle between bold characteristic line and the dashed characteristic line.  
     [0058] The centering spring elements  71  are arranged at the same spacing from the pivot axis  52  and each has a length that is greater than double the spacing of each centering spring element  71  from the pivot axis  52 . The centering spring elements can be structured as extension, compression or lever springs.