Patent Publication Number: US-2017371158-A1

Title: Compact pivot system for m1 mirror in head up display (hud) resulting in reduced friction and accurate mirror to mirror location

Description:
CROSS-REFERENCED TO RELATED APPLICATIONS 
     This application claims benefit of U.S. Provisional Application No. 62/354,607 filed on Jun. 24, 2016, which the disclosure of which is hereby incorporated by reference in its entirety for all purposes. 
    
    
     FIELD OF THE INVENTION 
     The disclosure relates to a head up display (HUD) in a motor vehicle. 
     BACKGROUND OF THE INVENTION 
     A head up display emits light that reflects from the front windshield to be seen by the driver. The light appears to come from a virtual image in front of the driver and in front of the windshield. 
     Conventional head op displays create the virtual image by first using a display to create an image. Next, the light from the image is reflected from one or more mirrors. Next, the light from the mirrors is reflected from the windshield. The mirrors are designed and positioned relative to the display so that the light seen by the driver, which is reflected from the windshield, appears to come from a virtual image that is outside of the vehicle. The mirrors and display are typically contained in a package that occupies a volume beneath the top surface of the dashboard. 
     The use of two free form mirrors in a HUD results in the smallest distance between the mirrors, and hence the smallest package size. However, accurate location of the mirrors with respect to each other is required to minimize distortion. This is achieved by having each mirror and its holder mounted directly to mounting features that are molded into the plastic lower housing. These molded features can be held accurately to each other since they are done in the same tool. Not having a separate M 1  mirror holder/mirror mounting bracket introduces additional tolerance stack-ups which results in mirror to mirror distance variation and introduces image distortions reducing virtual image quality. Existing designs use sub-assemblies or brackets which are not accurate. Accurate and consistent mirror locations are required when using two free form mirrors. 
     SUMMARY 
     The present invention may provide a mounting system for the main free form mirror (M 1 ) in a head up display utilizing two free form mirrors. The present invention also results in the smallest package width possible since there is no separate bracket and motor on the side of the bracket. 
     In one embodiment, the invention comprises a head up display mirror mounting arrangement for a motor vehicle, including a mirror positioned to reflect an image such that the image is again reflected by a windshield of the vehicle. A mirror holder includes two opposite ends each having a respective pivot. The pivots define an axis of rotation of the mirror. The mirror holder holds the mirror. A housing includes two opposite ends each having a respective bearing support. Two rotation mechanisms each pivotally couple a respective pivot to a respective bearing support. 
     In another embodiment, the invention comprises a head up display method for a motor vehicle, including emitting a light field based on image data. The light field is reflected with a mirror such that the light field further reflects off of a windshield of the motor vehicle and is visible to a driver of the vehicle as a virtual image. The mirror is held with a mirror holder having two opposite ends each having a respective pivot. The pivots define an axis of rotation of the mirror. A housing is provided including two opposite ends each having a respective bearing support. Each pivot is pivotably coupled to a respective bearing support. 
     In yet another embodiment, the invention comprises a head up display mirror mounting arrangement for a motor vehicle, including an image source emitting a light field. A mirror is positioned to reflect the light field such that the light field is again reflected by a windshield of the vehicle. A mirror holder assembly has two opposite ends each having a respective bearing. The bearings define an axis of rotation of the mirror. The mirror holder assembly holds the mirror. A housing includes two opposite ends each having a respective bearing support. Each bearing support is pivotably coupled to a respective bearing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A better understanding of the present invention will be had upon reference to the following description in conjunction with the accompanying drawings. 
         FIG. 1  is a perspective view of one example embodiment of a compact pivot system for a M 1  mirror in a HUD of the present invention. 
         FIG. 2  is an exploded, perspective view of the compact pivot system of  FIG. 1 . 
         FIG. 3  is an enlarged view of area A in  FIG. 2 . 
         FIG. 4  is a perspective view of another example embodiment of a compact pivot system for a M 1  mirror in a HUD of the present invention. 
         FIG. 5  is an exploded, perspective view of the compact pivot system of  FIG. 4 . 
         FIG. 6  is an enlarged view of area A in  FIG. 5 . 
         FIG. 7  is a flow chart of one embodiment of a head up display method of the present invention for a motor vehicle. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  illustrates one example embodiment of a compact pivot system  10  for a M 1  mirror  12  in a HUD of the present invention. Mirror  12  is mounted in a mirror holder  14  having two opposing integral pivots  16  ( FIG. 3 ). Pivots  16  define an axis of rotation  17  of mirror  12 . Mirror holder  14  is attached to a molded HUD lower housing  18  having two molded bearing supports  20  having internally threaded screw holes  22 . 
     Mirror holder  14  is coupled to housing  18  via two mirror holder rotation mechanisms  24 , each including a molded plastic hushing bearing  26  having an anti-rotation feature. Each bearing  26  is received in a respective bearing support  20 , and the anti-rotation features may limit the range of rotation of bearing  26  relative to bearing support  20  by abutting bearing support  20  at the ends of the rotation range. Two molded bearing caps  28  each secure a respective bearing  26  to a respective bearing support  20  via threaded screws  30  received through throughholes  32  in caps  28 , and received in screw holes  22 . 
     Two torsion springs  34 , each received on a respective pivot  16 , may preload mirror  12  and mirror holder rotation mechanism  24 . Using a torsion spring  34  at each pivot  16  to preload the M 1  mirror holder/mirror may make assembly easier because torsion spring  34  may be installed at the same time as mirror  12  and bushing bearing  26 . Mirror holder  14 , mirror holder rotation mechanisms  24 , and torsion springs  34  may be conjunctively referred to herein as a “mirror holder assembly.” 
     Bushing bearings  26  may be of the low friction variety in order to reduce friction between mirror holder pivots  16  and housing  18 . Housing  18  and mirror holder  14  may be made of glass filled materials which are abrasive and have high friction characteristics in order to inhibit jerky movement and vibration of mirror  12 . A metal bracket  14  could not be made to tight tolerances, and the mounting to housing  18  may add to the variability of the M 1  mirror holder/mirror location. 
       FIG. 4  illustrates another example embodiment of a compact pivot system  410  for a M 1  mirror  12  in a HUD of the present invention. Compact pivot system  410  is substantially similar to compact pivot system  10 , except that each molded bearing cap  428  ( FIG. 5 ) is retained with a female snap connector  436  ( FIG. 6 ), a male snap connector  438 , and a screw  30 , whereas compact pivot system  10  includes two screws  30  to retain each bearing cap  28 . 
       FIG. 7  illustrates one embodiment of a head up display method  700  of the present invention for a motor vehicle. In a first step  702 , a light field is emitted based on image data. For example, a head up display controller may control a light field emitted by a light projector, wherein the controlling is based upon image data corresponding to information to be presented (e.g., a current speed of the motor vehicle). 
     Next, in step  704 , the light field is reflected with a mirror such that the light field further reflects off of a windshield of the motor vehicle and is visible to a driver of the vehicle as a virtual image. For example, the light field may be reflected off of mirror  12  and further reflected off of the windshield of the vehicle such that the light field appears to the driver to be a virtual image disposed outside the windshield. 
     In a next step  706 , the mirror is held with a mirror holder having two opposite ends each having a respective pivot. The pivots define an axis of rotation of the mirror. For example, mirror  12  may be held by a mirror holder  14  having two opposing integral pivots  16 . Pivots  16  define an axis of rotation  17  of mirror  12 . 
     In step  708 , a housing is provided including two opposite ends each having a respective bearing support. For example, mirror holder  14  is attached to a molded HUD lower housing  18  having two molded bearing supports  20  at opposite ends. 
     In a final step  710 , each pivot is pivotably coupled to a respective bearing support. For example, each pivot  16  of a mirror holder  14  is coupled to housing  18  via two mirror holder rotation mechanisms  24 , each including a molded plastic bushing bearing  26 . Each bearing  26  is received in a respective bearing support  20 . 
     The foregoing description may refer to “motor vehicle”, “automobile”, “automotive”, or similar expressions. It is to be understood that these terms are not intended to limit the invention to any particular type of transportation vehicle. Rather, the invention may be applied to any type of transportation vehicle whether traveling by air, water, or ground, such as airplanes, boats, etc. 
     The foregoing detailed description is given primarily for clearness of understanding and no unnecessary limitations are to be understood therefrom for modifications can be made by those skilled in the art upon reading this disclosure and may be made without departing from the spirit of the invention.