Abstract:
A position sensing device for a mirror assembly displaced by an electric motor for a mirror assembly having a memory unit which relies upon position information. The position sensing device connects directly between the housing reinforcement member and the mirror glass. The position sensing device also includes inherent damping capabilities. A dampening assembly provides additional damping capabilities, thereby further limiting vibration of the mirror due to road and wind vibration.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to vehicle mirror systems which may be adjusted by electrically controlled motors and, more particularly, to a potentiometer for measuring the position of the mirror glass which includes dampening properties to minimize vibrations affecting the mirror glass. 
     2. Discussion 
     In order to facilitate use of exterior mirror assemblies on vehicles, many mirror assemblies come equipped with a pair of electrical motors which may be operated within the vehicle. Electrical signals sent to the motors by an internal vehicle switch causes displacement of the motors which in turn causes displacement of the mirror glass. This facilitates adjusting the position of the mirror glass so that driver can obtain an optimum view with minimum effort. To further facilitate the use of motorized mirror assemblies for operation by the driver, some motorized mirror assemblies include a memory so that vehicle mirror or mirrors can be set to a predetermined position and the position can be memorized. The mirror or mirrors can later be automatically returned to the predetermined position for a particular vehicle operator. One or more vehicle operators can be accommodated by providing corresponding memory settings for each driver. 
     Mirror assembly systems having memory capabilities include one or a pair of motors to displace the mirror glass about a pivot point for the mirror glass. The motors typically include a position sensor which measures displacement of the motor to determine the position of the mirror glass. In such systems, the position sensor attaches to the motor housing at one end and to the gear train at the other end in order to measure displacement of the gear train. By arranging the position sensor in this manner, the position sensor will have inherent inaccuracies due to the play or slop in the gear train, commonly known as backlash. Such systems effectively measure the position of the motor, rather than the position of the mirror glass. 
     Existing systems utilize a position sensor which has no damping capability. Because exterior mirrors are subject to road vibration transmitted through the vehicle and wind vibration, such position sensing devices output a signal adversely affected by the vibration experienced by the mirror glass. The varying signal introduces inherent inaccuracy when attempting to position the mirror when the vehicle is in operation. Although the position signal output by the position sensor can be filtered, this adds, to the cost of the electrical control system for the mirror assembly. 
     It is an object of the present invention to provide a mirror assembly having a position sensor which measures the actual position of the mirror glass. 
     It is a further object of the present invention to provide a mirror assembly having a position sensor for the mirror glass which is detached from the motor mechanism. 
     It is yet a further object of the present invention to provide a position sensor for the mirror glass which is unaffected by backlash in the motorized gear train. 
     It is yet a further object of the present invention to provide a position sensor having dampening properties to compensate for noise and vibration experienced by the mirror assembly. 
     SUMMARY OF THE INVENTION 
     The invention is directed to a mirror assembly for a vehicle. The mirror assembly includes a mirror housing and a reflective element. A backing assembly supports the reflective element and includes a pivot point about which the backing assembly and the reflective element pivot. An electric motor is mounted to the mirror housing and is responsive to an electrical input to displace the backing assembly and supported reflective element about the pivot point. A position sensor detects displacement of the backing assembly, and the position sensor includes a dampener to dampen movement of the position sensor. 
     These and other advantages and features of the present invention will become readily apparent from the following detailed description, claims and drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The drawings, which form an integral part of the specification, are to be read in conjunction therewith, and like reference numerals are employed to designate identical components in the various views: 
     FIG. 1 is a front perspective view of the mirror assembly mounted to a vehicle arranged in accordance with the principles of the present invention; 
     FIG. 2 is a rear perspective view of the mirror assembly of FIG. 1; 
     FIG. 3 is a horizontal cross-section of the mirror assembly showing the position sensor arranged in accordance with the principles of the present invention; 
     FIG. 4 is an exploded view of the position sensor assembly; 
     FIG. 5 is a top view of the combined sensor and dampener element; 
     FIG. 6 is a side cross-sectional view of the combined dampener and position sensor along Section  5 — 5  of FIG. 5; 
     FIG. 6 a  is a perspective view showing the friction spring and wiping members; 
     FIG. 7 is a further side cross-sectional view of the combined dampener and position sensor along Section  7 — 7  of FIG. 5; 
     FIG. 8 is a sectional view of an alternate embodiment of a combined sensor and dampener element; and 
     FIG. 9 is a second sectional view of an alternate embodiment of the combined sensor and dampener element of FIG.  8 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention will be described with respect to FIGS. 1-4. Mirror assembly  10  attaches to a vehicle  12  in proximity to the A-pillar  14 . In the embodiment shown, mirror assembly  10  is a left side mirror assembly, as would be used for a driver side and rear view exterior mirror. Mirror assembly  10  attaches to the front portion of a vehicle door  16  or to A-pillar  14  via a bracket  18 . Bracket  18  attaches to housing  20 . Preferably, housing  20  pivots with respect to bracket  18  so that housing  20  may be displaced in response to an applied force in order to prevent housing  20  from breaking off from bracket  18 . 
     Mirror glass  22  is supported within housing  20 . Housing  20  includes a housing reinforcement member  24  which is mounted to bosses or supports  26 . Bosses or supports  26  may be integrally formed with housing  20 , such as through an injection molding process, or may be attached to housing  20  through a separate process. Housing reinforcement member  24  fastens to bosses  26  using a threaded fastener, rivet, heat staking process, or other suitable fasteners. Housing reinforcement member  24  supports a backing plate  28  which attaches to and supports mirror glass  22 . Backing plate  28  preferably pivots with respect to housing reinforcement member  24  about a center point  30 . 
     Pivotal movement of backing plate  28  and attached mirror glass  22  is accomplished through electronic adjustment means. In particular, a motor  32  such as a direct current (DC) operated motor includes a shaft  34  which moves in an axial direction upon actuation of motor  32 . Shaft  34  includes a head  36  which connects to backing plate  28 . Displacement of motor  32  causes backing plate  28  and mirror glass  22  to rotate about center point  30 . In the sectional view of FIG. 3, this displacement occurs about a vertical axis in proximity to center point  30 , thereby varying the distance away from the vehicle which the operator may view through mirror glass  22 . 
     Opposite center point  30  of motor  32 , a position sensor assembly  38  is mounted to housing reinforcement number  28 . Position sensor assembly  38  will be described herein as a dampened potentiometer which has a varying resistance in accordance of displacement of a wiper or shaft. Position sensor assembly  38  includes a potentiometer  40 . Potentiometer  40  includes a wiper or shaft  42 . Shaft  42  may be displaced into and out of potentiometer housing  44 . The opposite end of shaft  42  includes a head  46 . Potentiometer  40  includes a trio of electrical leads  48  and operates as is well known in the art. Briefly, displacement of wiper or shaft  42  into and out of potentiometer housing  44  varies the resistance between a predetermined pair of electrical leads  48 . By determining the variation in resistance in accordance with displacement and storing the same in memory or generating a function correlating the tow, displacement of shaft  42  can be determined in accordance with vibration across the two predetermined two electrical leads  48 . 
     In a preferred embodiment, potentiometer housing  44  includes a viscous fluid which dampens movement of shaft  42  into and out of potentiometer housing  44 , thereby dampening vibrational-type movement of mirror glass  22 . In order to maintain a seal of potentiometer housing  40 , an o-ring  50  is disposed around shaft  42  passes into potentiometer housing  44 . 
     In addition to the dampening properties described above, mirror assembly  10  is also shown with a dampening assembly  52 . Dampening assembly  52  connects to housing reinforcement member  24  at one end and to backing plate  28  at another end. Dampening assembly  52  includes a friction pin  54  having a head  56  and a shank  58 . Friction pin  54  includes flange  60  arranged between head  56  and shank  58 . Flange  60  includes a socket  62  which receives head  46  of potentiometer  40 . Engagement between friction pin  54  and potentiometer  40  enables friction pin  54  to dampen movement of potentiometer  40 . The shank  58  of friction pin  54  passes through a dampening spring  64  which exerts a clamping force upon shank  58  to thereby dampen movement of friction pin  54 . A pair of symmetric retaining lips  66  hold dampening spring in position to housing reinforcement number  24 . Retaining spring  64  constricts movement of friction pin  54  to induce drag on the pin as it moves in and out. 
     As shown in FIG. 4, one of the retaining lips  66  is formed integral with potentiometer case  68 . Potentiometer case  68  may be formed integral with housing reinforcement member  24  or may be mounted independently to housing reinforcement member  24 . Potentiometer case  68  receives potentiometer  40  and has a pair of protrusions  70  which engage dimples formed in potentiometer housing  44 . Mounting of potentiometer housing  44  within potentiometer case  68  as described herein enables potentiometer  42  to rotate about the interconnection between protrusions  70  and dimples  72 . This compensates for slight arcuate movement of friction pin head  56 . 
     In operation, potentiometer case  68 , retaining lips  66 , and dampening spring  64  are attached to housing reinforcement member  24 . Alternatively, retaining lips  66  and potentiometer case  68  may be formed integral with housing reinforcement member  24 , and dampening spring  64  may be installed thereafter. Friction pin head  56  attaches to backing plate  28  at a socket  74  and translates with displacement of backing plate  28  and attached mirror glass  22 . As backing plate  28  and mirror glass  22  experience vibration transmitted through the vehicle and from wind, the interaction between shank  58  and dampening spring  64  dampens axial movement of friction pin  54 , thereby dampening axial movement of wiper or shaft  42  of potentiometer  40 . As described above, adjustment of backing plate  28  and mirror glass  22  by motor  32  causes slight arcuate movement of head  56  and shank  58  about dampening spring  64 , thereby causing corresponding arcuate movement of head  46  and shaft  42  of potentiometer  40 . This slight tendency for arcuate movement of potentiometer  40  is compensated by enabling rotation of potentiometer  30  about the interconnection between protrusions  70  and dimples  72 . 
     In view of the foregoing, one can see that the subject invention provides an improved position sensing assembly for a motorized mirror. In particular, direct attachment between the position sensor assembly and the backing plate provides more accurate positional information, as it eliminates inaccuracies introduced by gear backlash. Further, the position sensor is located opposite the pivot point about which the backing plate pivots when displaced by the electric motor. Further yet, a dampening device may be included integral to the potentiometer or an additional dampening device may provide more stability to the mirror glass and a more stable output signal from the position sensor assembly. Further yet, the position sensor assembly is embodied as a free standing assembly which may be retrofit onto existing systems and may be separated from the motorized unit. 
     Referring now to FIGS. 5-7, FIG. 5 depicts a plan view of the top of a combined dampener and position sensor  140  showing the four sided outline of the recess within which the carrier shaft moves longitudinally in this depiction in and out of the page. 
     The carrier shaft  142  is shown in more detail in FIGS. 6 and 7, which show two cross-sections of the combined dampener and position sensor  140 . FIG. 6 depicts a section  5 — 5  of FIG. 5, showing, in side profile, the recess housing  144  and attached to the base of carrier shaft  142  is a two pronged friction spring  146 . The U-shaped spring is attached to the base of the carrier shaft  142  by the press fit of an aperture in the base of the spring over a slightly oversized pin so as to become frictionally engaged with the end of the carrier shaft. The two substantially planar spring portions  143  and  143   a  are biased against opposed inner walls of the cavity  144   a  of the housing  144 . This is merely a preferable arrangement since there may be other arrangements of springs such as for example two or more surfaces of the sides of the spring arranged to be slidably biased against the inner walls of the cavity. 
     The use of a U-shaped spring is merely preferable since many other arrangements of springs, resilient surfaces and friction applying elements could be provided on the movable carrier shaft  142 . 
     A preferred position sensing arrangement is depicted in side profile in FIG. 7, comprising an outwardly biased wiper contact element  148  of conductive material which is attached to the base of the longitudinally movable carrier shaft  142  and arranged to wipingly contact the surface of a resistive track or tracks  149  located on a printed circuit board  49   a  positioned along a wall of the recess  144   a . There are in FIGS. 5-7, three wires  150 ,  152  and  154  connecting the position sensor printed circuit board with remote electronics used to interpret the signal provided by the position sensor arrangement. 
     An additional dampening and position sensor located in recess  120  would provide additional dampening as well as a position sensing means for measuring the relative position of the mirror with respect to the mirror housing along at least the axis controlled by discrete drive assembly  124 . 
     The top of the carrier shaft  142  has a bulbous shaped end  156  which is shaped to provide a pivotal engagement with the rear of the rear view mirror. The carrier shaft  142  moves longitudinally in and out of the recess  144  as a result of the motor controlled movement of the mirror. As the discrete drive assembly  122  moves the mirror away from the mirror housing, the mirror pivots about ball joint pivot  138  and the carrier shaft reciprocally moves inwards of the cavity  144   a , resisted by the friction applied on the opposed inner walls of the recess  144   a  by spring  146  and at the same time the wiper contact  148  slides across the resistive tracks  149  and provides a means to interpret the relative position of the mirror (in that particular axis) with respect to the mirror housing. Electrical contacts generally shown at  150  provide electrical connection for securing the position of the potentiometer and dampener. 
     When two dampener and position sensors are used, any position of the mirror can be detected and hence any mirror position can be replicated by moving the mirror until the same relative signals from the position sensors are achieved. 
     Clearly it is advantageous to keep the wiper contact clean so as to provide consistent electrical conductivity and thus repeatable position sensing as well as maintaining substantially constant friction characteristics so that the electric motors will be able to provide sufficient motive force to overcome that resistance. Thus, the aperture about the carrier shaft at the opening of the recess  144   a  is preferably sealed against the ingress of dust and particulate matter as well as moisture all of which could adversely effect the conductive characteristics of the position sensor and the friction characteristics of the dampener. A sealing grommet  158  is provided which preferably not only seals the aperture about the carrier shaft, but also covers the terminals of the electric wiring  150 ,  152  and  154  entry point to the assembly. 
     Furthermore, the combined dampener and position sensor is manufactured so that it can be engaged with both the rear of the rear view mirror and the mirror housing in a typically pre-existing recess. FIG. 6 depicts cooperating tabs  160  and grooves  162  which allow the combined dampener and position sensor to snap into place. This allows for the retrofitting of the dampener and position sensor into mirror assemblies which may previously have only housed a dampener. 
     Referring now to FIGS. 8 and 9, there is shown a combined dampener and position sensor  240 . In this embodiment, an outer housing  244  includes a cavity  244   a . In the embodiment of the combined dampener and position sensor  240  shown in FIGS. 8 and 9, the dampening method is different than that shown in FIGS. 5-7. The friction member  246  includes a pair of flexible legs  248  and  250  which are pressed against the sidewall cavity  244   a  by way of a compressed spring  252 . The shaft includes a thinned, bendable web  254  for controlled bending of the shaft portion facilitating controlled friction of the friction member  248 . Additionally, friction member  248  includes raised protrusions  256  and  258  which also facilitate the controlled friction motion of the friction member  246 . A printed circuit board  260  is provided and cooperates with the wiper contact  262  to provide the positional inputs of the potentiometer. A cap member  264  seals the unit and a boot generally shown at  266  seals the cavity  244   a . The cap member  264  also includes electrical contacts for the printed circuit board. 
     While specific embodiments have been shown and described in detail to illustrate the principles of the present invention, it will be understood that the invention may be embodied otherwise without departing from such principles. For example, one skilled in the art will readily recognize from such discussion and from the accompanying drawings and claims that various changes, modifications and variations can be made therein without departing from the spirit and scope of the invention as described in the following claims.