Abstract:
The invention relates to a thermal-expansion compensator for holding a light module in a housing of a headlamp for a motor vehicle, comprising a compensation pin extending along a pin axis with a stop element, wherein the compensation pin can be connected to the housing by means of a connecting means, a compensation element with a compensation body extending along a compensation axis and at least two stop receptacles that are each formed for holding the stop element of the compensation pin, and a holder that is arranged rigidly on the light module.

Description:
RELATED APPLICATIONS 
       [0001]    This application claims priority and benefit to German Patent Application No. 102011000735.0, filed on Feb. 15, 2011, all of which is incorporated herein by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a thermal-expansion compensator for compensating the thermal expansion of a headlamp unit of a light module. The present invention also relates to a corresponding light module. 
         [0004]    2. Related Art 
         [0005]    Light modules in headlamps are used for emitting light for illuminating the area in front of a vehicle, wherein the emitted light could be a low beam featuring a cut-off line. Here it is provided that the cut-off line of the low beam does not exceed a specified angle relative to the horizontal. However, the thermal behavior of the headlamp housing can lead to a not insignificant displacement of the cut-off line relative to the horizontal, because the receptacle element leaves its specified position due to the thermal expansion behavior of the housing, resulting in a tilting of the carrier frame and consequently a tilting of the light module, so that the cut-off line likewise leaves its specified angle or its specified height. 
         [0006]    FEM simulations can be performed for overcoming impermissible tilting of the light module in the housing of the headlamp. However, numerical modeling of the complex thermomechanical behavior of a headlamp is often inadequate. An advantageous, thermomechanically stable arrangement of the receptacle elements for holding the light module in the housing of the headlamp can indeed minimize tilting of the light module, but disadvantageous thermal relationships of the housing can nevertheless lead to undesired tilting of the light module. For example, superimposing the thermal effect of the housing of the headlamp by the ambient temperature and also radiant heat from the engine forms a complex temperature field, so that thermal effects also on parts of the housing are taken into account only to a limited extent. 
         [0007]    Thermal-expansion compensators for compensating the thermal expansion of a light module are generally known. They are used to compensate thermal expansions, that is, changes in geometry of a light module. When light modules are operating, they are subjected to different working temperatures. The temperatures and thermal-expansion coefficients of the materials being used produce different thermal expansions, that is, different geometrical dimensions for the headlamp unit. 
       SUMMARY OF THE INVENTION 
       [0008]    One goal in modern light modules is to produce the most exact light distribution possible on the street in front of a vehicle. In particular, a so-called horizontal cut-off line (hHDG), as well as a vertical cut-off line (vHDG), which separate an illuminated area from a non-illuminated area, can be generated in this way. The more precisely this cut-off line can be positioned, the more precisely these cut-off lines can increase the illuminated area, without the risk of blinding a driver possibly coming from the opposite direction. In other words, the illuminated area could be moved closer to an area that would blind a driver coming from the opposite direction. This method improves the illumination of the street and thus the viewing conditions at night. Such a control system, however, requires the most exact construction possible, that is, an especially low-play construction, and the lowest possible tolerances for the drive system, that is, the adjustment system of the headlamp unit, in particular, of a light source in the headlamp unit. 
         [0009]    Because the entire headlamp unit changes with respect to its geometrical dimensions due to thermal expansion when temperatures fluctuate, the geometric boundary conditions for regulating the respective cut-off line also change. In other words, the origin for the adjustment system shifts within the absolute coordinate system for the positioning of the respective cut-off line on the street. 
         [0010]    Taking into account the thermal changes for the control or the regulation with respect to the positioning of the cut-off line has the disadvantage that it requires, on one hand, particularly precise sensors, especially temperature sensors, and also particularly fine driving of the actuators of the headlamp unit. It has already been proposed to use mechanical compensators, that is, compensators that exhibit thermal expansion in a headlamp, with this thermal expansion being directed opposite the relevant thermal expansion when the light module is in use. In this way, when the temperature changes, a complementary thermal expansion of a thermal-expansion compensator can compensate the corresponding thermal expansion of the light module. 
         [0011]    In these known thermal-expansion compensators, it is disadvantageous that each of these must be developed specifically for the respective headlamp. Thus, for one, the respective geometric relationships in the headlamp must be taken into account and, second, the necessary compensating thermal expansion must be calculated exactly and incorporated in the material selection and geometry of the respective thermal-expansion compensator. In other words, each new development or each vehicle with specific headlamps requires a separate, newly designed thermal-expansion compensator. This increases, for one, the product diversity and thus the complexity of the headlamp system and, second, the development and production costs. 
         [0012]    Therefore the task of the present invention is to solve the disadvantages named above. In particular, the task of the present invention is to disclose a thermal-expansion compensator that can be used as universally as possible and allows large structural play for the light module due to the most compact construction possible. 
         [0013]    The preceding task is solved by a thermal-expansion compensator with the features of the independent claim  1  and also by a headlamp with the features of the independent claim  12 . Advantageous embodiments can be taken, among other things, from the subordinate claims following the independent claims. Additional features and details of the invention can be taken from the subordinate claims, the description, and the drawings. Here, features and details that are described in connection with the component according to the invention are obviously also applicable in connection with the method according to the invention and vice versa, so that, with respect to the disclosure, continuously alternating reference is made or could be made to the individual aspects of the invention. 
         [0014]    A thermal-expansion compensator according to the invention for holding a light module in a housing of a headlamp for a motor vehicle has a compensation pin extending along a pin axis with a stop element, wherein the compensation pin can be connected to the light module by means of a connecting means. Furthermore, a compensation element is provided with a compensation body extending along a compensation axis and at least two stop receptacles that are each constructed for holding the stop element of the compensation pin. A holder is also arranged rigidly on the light module. In a thermal-expansion compensator according to the invention, the compensation body of the compensation element is fixed with one of its two ends on the holder such that the compensation body of the compensation element can expand and/or contract freely in the holder along the compensation axis. Furthermore, the compensation pin extends into the compensation element and can be held selectively in one of the at least two stop receptacles of the compensation element for forming an effective expansion length. 
         [0015]    By providing at least two stop receptacles, when the thermal-expansion compensator is installed, its expansion length can be selected. When the headlamp is installed, it is also possible to adapt the expansion length of the thermal-expansion compensator to the specifications of the headlamp, without having to use another, specifically constructed thermal-expansion compensator. In other words, a thermal expansion compensator according to the invention can be used in this way more flexibly and, above all, more universally for a plurality of different headlamps. The expansion length is produced between the fixing of the compensation element on the holder and the position of the held stop element of the compensation pin. 
         [0016]    Obviously, a thermal-expansion compensator according to the invention could also be arranged in the reverse direction between the light module and the housing, so that the connecting means is formed for connecting to the light module and the holder for the rigid arrangement on the housing of the headlamp. 
         [0017]    In one embodiment of a thermal-expansion compensator according to the invention, the connecting means is formed as a spherical head for insertion into a spherical socket of the housing and the compensation pin has a pin body extending along the pin axis and the stop element. The stop element extends perpendicular to the pin axis and is spaced apart from the spherical head. In particular, the stop element can be formed integrally with the pin body. At a minimum, the stop element is arranged on the pin body. 
         [0018]    Furthermore, a thermal-expansion compensator of this embodiment according to the invention has the compensation element with a compensation body extending along the compensation axis and at least two stop receptacles. The stop receptacles are formed for holding the stop element. This means that the stop element of the compensation pin can be held in the stop receptacle of the compensation element. Here, “holding” means a geometric correspondence, at least in some regions, between the stop element on one hand and the stop receptacle on the other. The stop receptacle can be formed, for example, as a groove in which a projection in the form of the stop element can engage. 
         [0019]    In addition, in a thermal-expansion compensator of this embodiment according to the invention, the holder is provided that has a holder body extending along a holder axis and is provided with a module fastening means for fixing the holder on the light module and also a compensation-element fastening means for fixing the holder on the compensation element. The module fastening means and the compensation-element fastening means are here spaced apart from each other with respect to the holder axis. The holder is made, in particular, from sheet metal, because this has an especially low thermal-expansion coefficient. 
         [0020]    In one thermal-expansion compensator of this embodiment according to the invention, the stop element is held in one of the stop receptacles so that relative movement between the compensation element and the compensation pin along the pin axis and/or the compensation axis is prevented. In other words, such axial movement is not permitted, so that a transfer of forces is possible in this axial direction between the compensation element and the compensation pin. This can be realized, for example, through a positive fit at least in some regions between the stop element and the stop receptacle. In this way it is guaranteed that this relative movement is essentially prevented, in particular, it lies below the tolerances necessary for production. Preventing relative movement is thus to be understood technically and relative movements, that is, play in a specified tolerance range, are definitely permissible. Here, a relative movement in both directions along the defined axes is prevented, so that forces can also be transferred in both directions. 
         [0021]    The functioning of a thermal-expansion compensator according to the invention is to be described as follows using an example: 
         [0022]    The thermal-expansion compensator can be fixed on one side by means of its connecting means, for example, in a spherical receptacle, for example, in a receptacle element of a headlamp. On the opposite side, that is, the side of the holder on which, for example, a module fastening means can be provided as an interface, the thermal-expansion compensator is fixed on the light module. The intermediate section of the thermal-expansion compensator thus can compensate for thermal expansion in the light module due to a change in length along one of its axes, that is, the pin axis, the compensation axis, or the holder axis. 
         [0023]    In particular, the compensation element is responsible for the thermal compensation. Thus, when the temperature changes, the thermal-expansion coefficient of the material, in particular, of the compensation element, changes the axial extent of this compensation element. By changing the axial extent and also by fixing the connecting means, in particular, of the spherical head of the compensation pin, in the corresponding spherical receptacle in a headlamp, the change in length along the respective axis is transferred by means of the compensation element and the holder to the light module. According to the direction of the length variation, that is, as a function of whether the temperature increases or decreases, the holder, in particular, a module fastening means, is likewise shifted along the axis. In this way, it is possible to shift the linkage point, that is, the bearing point between the thermal-expansion compensator and the light module. Here, the bearing point is shifted opposite the shifting of the light module caused by its own thermal expansion due to the identical change in temperature. 
         [0024]    In other words, a change in temperature causes, on one hand, a thermal expansion of the light module and, on the other hand, a thermal expansion of the thermal-expansion compensator. The two thermal expansions are essentially complementary to each other, so that as a whole the two thermal expansions essentially cancel out and the headlamp unit remains at the desired predefined position. Due to this fact, the thermal expansion of the headlamp unit does not have to be taken into account, or only to a smaller degree, in the control/regulation of the position of the respective cut-off line, so that the necessary control logic can have a simpler construction and, in particular, temperature sensors can be eliminated. 
         [0025]    The fastening means of the holder of one embodiment of the present invention can involve, in particular, latching connections, for example, clamps. These could be formed such that they remain latched in the provided position after docking in this position, that is, after fixing the holder on the light module or on the compensation element, and can be removed only by destroying the holder or the respectively connected element. 
         [0026]    It can be advantageous if, in a thermal-expansion compensator according to the invention, the end of the compensation body of the compensation element facing the rigid arrangement of the holder on the light module is fixed on the holder. In other words, the linkage between the compensation element and the holder lies in the vicinity of the linkage of the holder to the light module. Alternatively, it is also possible that the end of the compensation body of the compensation element facing away from the rigid arrangement of the holder on the light module is fixed on the holder. According to the specific space requirements, a fitting thermal-expansion compensator can be created in this way. In particular, it is possible that the fixing of the compensation element on the holder can also be selected freely between these two alternatives when the thermal-expansion compensator is installed. Thus, in particular, the effective direction of the thermal-expansion compensator can be defined and the flexibility of a thermal-expansion compensator according to the invention can be further increased. 
         [0027]    It is also possible that the compensation element has an essentially multiple-shell, in particular, two-shell, construction, so that an especially simple installation is possible by putting the pieces together. This is the case especially when the compensation element involves two half-shells in whose interior the stop element of the compensation pin can be held. In such an embodiment, the stop receptacle is also formed in the interior of this respective shell of the compensation element. 
         [0028]    In the scope of the present invention, it is possible that the stop element and also the respective stop receptacle are provided partially or even completely in the circumferential direction around the compensation pin or the compensation element. It is also possible that the stop receptacle is essentially larger than the stop element of the compensation pin, but nevertheless sufficiently prevents relative movement between the compensation pin and the compensation element. 
         [0029]    It can be advantageous if, in a thermal-expansion compensator according to the invention, all of the axes, that is, the pin axis and/or the compensation axis and/or the holder axis, are parallel, in particular, coaxial, to each other. In particular, the coaxial arrangement of the axes named above has the advantage that the entire thermal-expansion compensator can have an even more compact construction. The three-part construction of the compensation pin, compensation element, and holder allows a nested construction of the thermal-expansion compensator that permits, in principle, an especially compact form for this compensator. Despite this compactness, the arrangement of the fastening means in corresponding embodiments in a state spaced apart from each other and the distance between the spherical head and the compensation stop produces a relatively large expansion length with respect to the thermal-expansion compensation. Thus, the necessary expansion length can be provided despite the compact construction, so that a large structural expansion space remains with respect to the necessary space requirements for a thermal-expansion compensator according to the invention in a headlamp. 
         [0030]    In a headlamp, a housing is advantageously provided in which, for example, one or more light sources are provided. These light sources can be influenced by means of actuators, for example, by means of different optical systems, such as reflectors, lenses, or mirror systems with respect to their beam path and in this way a control/regulation of the position of the cut-off line in front of the vehicle can be varied with such a headlamp unit. The light modules are advantageously provided in a stable holder frame that is provided for this purpose and is likewise part of the light module and is used as an interface to the housing of the vehicle. 
         [0031]    It can be advantageous if, in a thermal-expansion compensator according to the invention, at least two stop receptacles are present in the compensation body and these receptacles are spaced apart from each other with respect to the compensation axis. Providing at least two stop receptacles has the advantage that it further increases the variability of a thermal-expansion compensator according to the invention. Thus, different compensation pins with differently positioned stop elements can be used, in order to achieve different expansion lengths of the thermal-expansion compensation. Thus it is possible that the same construction of the thermal-expansion compensator can be used for a plurality of different headlamps. This allows at least identical holders and compensation elements to be provided for all variations of a wide range of different headlamps and the desired expansion length to be set when the headlamp is installed through the variable selection of the compensation pins that are also very similar to each other. This method increases the possible quantities for the thermal-expansion compensator and considerably reduces the parts costs. Thus, for each light module of a headlamp, the thermal-expansion compensator according to the invention is used and the expansion length desired for the specific case is provided for the thermal-expansion compensation through the selection of the compensation pin, in particular, with the specific position of the stop element. 
         [0032]    Likewise it is advantageous when, in a thermal-expansion compensator according to the invention, the compensation stop essentially completely surrounds the pin body radially with respect to the pin axis. Completely surrounding the pin has the advantage that a relatively small extent of the compensation stop is possible in the radial direction. Surrounding the pin body, especially in a pin body with a round cross section, thus has the advantage that despite a smaller radial extent and an associated particularly compact form, a sufficient force transfer area is provided, so that the relative movement between the compensation pin and component element can be prevented according to the invention. 
         [0033]    Furthermore, it can be advantageous if, in a thermal-expansion compensator according to the invention, the compensation pin has a profiled, in particular, cylindrical, pin body and a spherical head that is used as a connecting means to the light module. The construction of the connecting means as a spherical head has the advantage that this connection cannot transfer bending moments at least in large swiveling ranges. In this way, it is possible that no twisting due to relative movements between the light module and the housing of the headlamp can be produced during the thermal compensation. The longevity of the thermal compensator is significantly improved in this way. 
         [0034]    It is likewise advantageous if, in a thermal-expansion compensator according to the invention, the stop element is arranged inclined on the pin body, in particular, inclined by 90° relative to this pin body. This inclined arrangement allows an improved transfer of forces that are directed essentially along the pin axis and/or the compensation axis. 
         [0035]    It is also advantageous if, in a thermal-expansion compensator according to the invention, the materials of the compensation element and of the holder have different thermal-expansion coefficients. In particular, the compensation element has a thermal-expansion coefficient that is associated with relatively large thermal expansion. The holder itself is advantageously provided with a lower thermal-expansion coefficient and is made, for example, from sheet metal. The compensation element itself can be produced, for example, from plastic. 
         [0036]    It is likewise advantageous if, in a thermal-expansion compensator according to the invention, the compensation element has at least in some regions a cavity along the compensation axis, wherein at least the section of the pin body on which the stop element is arranged extends into this cavity. Furthermore, the at least one stop receptacle is arranged in this cavity. The internal arrangement of the section of the compensation pin has the advantage that this is particularly well protected. In addition, in this way the volume of the compensation element is used simultaneously for holding the pin, so that the dimension allows, especially in the radial direction, an even more compact form. The further increased compactness produces greater play and, associated with this greater play, greater structural freedom in the use of a thermal-expansion compensator according to the invention. 
         [0037]    It is also advantageous if, in a thermal-expansion compensator according to the invention, the module fastening means and the compensation-element fastening means are arranged on the two opposite end sections of the holder with respect to the holder axis. In this way, an especially large expansion length can be achieved with respect to the thermal expansion of the holder. In this way, the length of the compensation element is also increased with respect to the variation of the effective length of the compensation element, because essentially one end of the compensation element is fixed by the compensation-element fastening means, so that the rest of the compensation element is provided, with respect to its extent, along the compensation axis for the thermal-expansion compensation. Starting from this fixed point for the thermal expansion, when the thermal-expansion compensator is installed, the user can still select in which stop receptacle he or she will insert the stop element, so that, in this way, variability of the effective length of the thermal expansion of the compensation element can be achieved. 
         [0038]    It can also be advantageous if, in a thermal-expansion compensator according to the invention, the compensation pin is formed integrally and consists of a single material. In particular, the compensation pin has a monolithic construction. Thus, the compensation pin can be produced, for example, from metal and can be manufactured through metal-cutting processing, in particular, as a rotating and rotationally symmetric turned part. 
         [0039]    It can also be advantageous if, in a thermal-expansion compensator according to the invention, the compensation pin is formed rotationally symmetric with respect to the pin axis and/or the compensation element is formed rotationally symmetric with respect to the compensation axis and/or the holder is formed rotationally symmetric with respect to the holder axis. In addition to the simplified production, for example, through metal-cutting and turning work, the rotationally symmetric construction also produces a reduction of undesired shear stresses in the respective elements. In addition, the necessary use of materials and the costs associated with these materials decrease. The compactness of the entire thermal-expansion compensator can also be increased by such a construction. 
         [0040]    Another object of the present invention is a headlamp for a motor vehicle with a housing in which at least one light module is held in a predetermined position, wherein a thermal-expansion compensator of the present invention is arranged between the housing and the light module for supporting this light module in the housing. A corresponding headlamp is associated with the same advantages as explained in detail above through the use of a thermal-expansion compensator according to the invention. 
         [0041]    In a headlamp according to the invention, it can be advantageous if the light module is held in the headlamp by means of a carrier frame and if the thermal-expansion compensator is arranged between the carrier frame and the housing. In such a case, the carrier frame forms, as part of the light module, the interface to the thermal-expansion compensator. It is also advantageous if three receptacle elements are arranged between the carrier frame and the light module, in order to form a mounting plane for holding the light module. The three attachment points of the light module on the housing of the headlamp define the mounting plane that simultaneously also represents the coordinate system with respect to which the thermal compensation is realized. Another advantage is when two of the receptacle elements have a high stiffness and one of the receptacle elements is formed at least partially from the thermal-expansion compensator. In this way, thermal compensation that is able to compensate rotation about an axis of the reference coordinate system can be performed in a targeted way. 
         [0042]    Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0043]    The present invention will be explained in more detail with reference to the accompanying figures in the drawing. The terms “left,” “right,”, and “below” used here refer to the figures in the drawing being oriented so that the reference symbols can be read normally. Shown schematically are: 
           [0044]      FIG. 1  a first embodiment of a thermal compensator according to the invention, 
           [0045]      FIG. 2  the thermal compensator of  FIG. 1  with a different compensation pin, 
           [0046]      FIG. 3  the thermal compensator of  FIGS. 1 and 2  with a different compensation pin, 
           [0047]      FIG. 4  an embodiment of a holder frame, 
           [0048]      FIG. 5  an embodiment of a light module, and 
           [0049]      FIG. 6  in schematic cross section, the light module of  FIG. 5 , 
           [0050]      FIG. 7  a second embodiment of a thermal compensator according to the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0051]    In  FIG. 1 , a first embodiment of a thermal compensator  10  according to the invention is shown. This has a compensation pin  20  that has, on its left end, a connecting means  22  in the form of a spherical head in a spherical socket  122  of a housing  120 . Furthermore, the compensation pin  20  is provided with a pin body  24  that extends along the pin axis  28 . The compensation pin  20  involves an essentially rotationally symmetric component that is also provided with a stop element  26  spaced apart from the connecting means  22 . This stop element  26  is held in a stop receptacle  36  of a compensation element  30 , so that a relative movement between the compensation pin  20  and the compensation element  30  is essentially prevented. The pin body  24  here extends, in some sections, in a cavity  32  of the compensation element  30 . As is to be taken from  FIG. 1 , a plurality of stop receptacles  36 , namely five, is provided in the compensation element  30 , so that the stop receptacle position of the stop element  26  can vary, as still to be explained below with respect to  FIGS. 2 and 3 . 
         [0052]    In the embodiment of the thermal-expansion compensator  10  of  FIG. 1 , a holder  40  is provided that is fixed on one end E 1  of the compensation element  30  by means of a snap-on latching connection of a compensation-element fastening means  42   a  on one end section  40   a  of the holder  40 . On the essentially opposite end, namely the end section  40   b  of holder  40 , the holder  40  is fastened on a light module  110  by means of module fastening means  42   b  also as a snap-on latching connection. 
         [0053]      FIGS. 2 and 3  show alternative embodiments, wherein the compensation element  30  and the holder  40  are each identical in all three figures. Identical components are therefore also provided with identical reference symbols and their explanation will not be repeated. The respective compensation pins  20  in the embodiments of  FIGS. 1 to 3  are also very similar, and their difference can be recognized only in the different positions of the stop element  26 . According to where the stop element  26  of the compensation pin  20  is located, after the installation of the thermal-expansion compensator  10 , it also engages in a different stop receptacle  36  of the compensation element  30 . Different expansion lengths L 1 , L 2 , and L 3  of the compensation element  30  are predefined according to the position of this engagement. 
         [0054]    The function of a thermal-expansion compensator  10  according to the embodiments of  FIGS. 1 to 3  will be explained below. 
         [0055]    If the temperature changes, in particular, the material temperature of the individual components, for example, due to an increase in the outside temperature, then the respective geometric dimensions, in particular, the axial extent of the compensation element  30 , also change in the direction of the compensation axis  38 . Changing the axial extent of the compensation element  30  also changes, among other things, the distance between the position at which the compensation-element fastening means  42   a  of the holder  40  fixes this holder with the compensation element  30  and the position at which the stop element  26  is held in a stop receptacle  36 . 
         [0056]    If the temperature increases, then the length of the compensation element  30  increases and thus also the distance mentioned above, which is also designated as expansion length L 1 , L 2 , L 3 . The increase of this expansion length L 1 , L 2 , L 3 , that is, of the defined distance, has the result that stress appears in the material and this stress is relieved through movements to achieve force equilibrium. If the compensation pin  20  is now fixed in a spherical receptacle  122  as in the embodiment of  FIG. 1 , then the compensation pin  20  cannot move, so that an increase in the expansion length L 1 , L 2 , L 3  between the stop receptacle  36  in which the stop element  26  is held and the corresponding fastening point to the holder  40  results in that this fastening point of the compensation-element fastening means  42   a  shifts toward the left in  FIG. 1 . In other words, the opposite fastening point of the light module  110 , that is, the position of the module fastening means  42   b , is also moved toward the left in  FIG. 1 . Thus, the bearing point of the light module  110  is compensated toward the left in  FIG. 1 . 
         [0057]    An expansion of the light module  110 , however, results in a thermal expansion that moves the light module toward the right when the temperature increases. The complementary directions of the respective thermal expansions thus have the result that, in the sum of the two complementary thermal expansions, there is essentially no shift of the light module  110  itself, in particular, of the control device arranged therein for a light source. The thermal change and the thermal expansion associated with this change are thus compensated by a thermal-expansion compensator  10  according to the invention. 
         [0058]    In addition to the especially compact construction of a thermal compensator  10  according to the invention, the high flexibility with respect to insertion is easy to recognize in  FIGS. 1 to 3 . Thus, the desired effective length can be changed through slight changes, namely by just changing the position of the stop element  26  of the compensation pin  20 . 
         [0059]    Thus, in the use of a compensation pin  20  with a stop element  26  according to  FIG. 2 , an especially short expansion length L 1  is defined, while in the embodiment of the thermal-expansion compensator  10  in  FIG. 3 , the maximum expansion length L 3  can be used. As the expansion length L 1 , L 2 , L 3  becomes longer, the difference, that is, the linear expansion provided for thermal-expansion compensation when the temperature changes, also increases. Thus, the desired expansion length L 1 , L 2 , L 3  or the required calculated expansion length for the specific light module  110  can be provided through the corresponding selection of the position of the stop element  26 , that is, the selection of the receptacle in the respective stop receptacle  36  in the compensation element  30 . The same thermal-expansion compensator  10  can be produced in especially large quantities and used for a wide range of different headlamps  100 . According to the installation situation, in addition to the flexibility and the reduced production costs due to the increased quantities, it must also be taken into account that the installation is simplified to the extent that the installation steps always remain the same irrespective of the actual position of the compensation pin, that is, of the stop element  26  within a stop receptacle  36  of the compensation element  30 . The requirements for installation are thus significantly lower in comparison with known thermal-expansion compensators. 
         [0060]      FIGS. 4 to 6  show an embodiment of a headlamp  100  according to the invention and the method how this is mounted.  FIG. 4  shows the housing  120  of a headlamp  100  that has three receptacle elements  121 . In one of these three receptacle elements  121 , a spherical socket  122  is provided for holding a connecting means  22  in the shape of a spherical head of a compensation pin  20 . This spherical socket  122  holds a thermal-expansion compensator  10  according to the invention, for example, according to the embodiment in  FIGS. 1 to 3 . If a light module  110  is inserted into the housing  120 , then this light module  110  must be supported in the housing  120 . This is realized in the embodiment of  FIGS. 4 to 6  at three bearing points, namely in the receptacle elements  121 . As can be easily recognized schematically in  FIG. 6 , a thermal-expansion compensator  10  of the present invention, in particular, according to the embodiment of  FIGS. 1 to 3 , is inserted into one of the three receptacle elements  121 . This is provided between the receptacle elements  121  and the light module  110 , so that it can carry out thermal-expansion compensation in the way explained in detail above. 
         [0061]    If the geometric dimensions of the light module  110  now change due to thermal variation, for example, due to an increase in temperature, then the thermal-expansion compensator  10  will behave as explained above. The complementary direction of each change due to thermal expansion produces an essentially constant position of the light module  110 , in particular, of the light source components and the actuator mechanism for the light source contained in this light module. The thermal-expansion compensator  10  is thus used for greatly simplifying the position of a cut-off line generated by a light source in a light module  110 . In particular, a headlamp  100  according to the present invention requires no additional sensors monitoring the exact temperature of the headlamp  100 . Instead, an automatic thermal-expansion compensation takes place, which could also be called mechanical compensation and is associated with very low error susceptibility and very low control/regulation complexity. 
         [0062]    In  FIG. 7 , a second embodiment of a thermal compensator  10  according to the invention is shown. In this embodiment of the thermal-expansion compensator  10 , the holder  40  is fixed by means of a snap-on connection of the compensation-element fastening means  42   a  in the vicinity of the end E 2  of the compensation element  30 . On the same end E 2 , the holder  40  is fixed on the light module  110  by means of the module fastening means  42   b  also as a snap-on latching connection. In this embodiment of the thermal-expansion compensator  10  or the fixing of the compensation element  30  on the holder  40 , a maximum expansion length of the thermal-expansion compensator  10  can be used for thermal-expansion compensation. An expansion of the light module  110  here has the result that the compensation pin  20  is shifted to the left. This leads to an increase in the distance of the housing  120  to the light module  110 . 
         [0063]    As various modifications could be made to the exemplary embodiments, as described above with reference to the corresponding illustrations, without departing from the scope of the invention, it is intended that all matter contained in the foregoing description and shown in the accompanying drawings shall be interpreted as illustrative rather than limiting. Thus, the breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims appended hereto and their equivalents.