Abstract:
An exterior rear view mirror for a vehicle has a housing pivotally mounted on a base for angular movement about a first pivot axis and an electric motor for causing such movement. A controller operates the motor at either of two different speeds. The controller includes a counter for counting the number of revolutions of the output shaft of the motor so as to determining the angle through which the housing has been moved, thus enabling the housing to be restored to its original position by causing the motor to perform the same number of revolutions in the opposite direction.

Description:
FIELD 
   This invention relates to an exterior rear view mirror for a vehicle. 
   RELATED ART 
   EP-A-0209296 discloses an exterior mirror for a vehicle having a mirror comprising a base member for mounting on a vehicle body, a housing pivotally mounted on the base for angular movement about a first pivot axis, a reflective member pivotally mounted in the housing for angular movement relative thereto only about a second pivot axis and electrically operated drive means for causing angular movement of the housing about first pivot axis and angular movement of the reflective member relative to the housing about the second pivot axis. 
   EP-A-0881124 discloses an exterior mirror for a vehicle having a mirror head which can be moved from a deployed position for normal driving to a parked position in which it lies closely adjacent to the vehicle body and thus is less liable to damage when the vehicle is not in use. 
   SUMMARY OF THE INVENTION 
   It is an object of the present invention to provide an exterior vehicle mirror in which the same mechanism is used both to adjust the orientation of the mirror head about a first axis, in order to provide the driver with a required field of view, and to move the mirror head between a deployed position and a parked position. 
   According to the invention, an exterior rear view mirror for a vehicle comprises a base for mounting on a vehicle body, a housing pivotally mounted on the base for angular movement about a first pivot axis, a reflective member mounted in the housing, an electric motor having an output shaft arrange to cause angular movement of the housing about the first pivot axis, and a controller adapted to control the electric motor so as to selectively drive the housing about the first axis either at a first speed or at a second speed which is faster than the first speed. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a partially broken-away elevational view of a rear view mirror in accordance with the invention from the side of the housing on which the reflective member is exposed; 
       FIG. 2  is a cross-sectional view taken on the line  2 - 2  in  FIG. 1 ; and 
       FIG. 3  is a block diagram illustrating the control system for the mirror shown in  FIGS. 1 and 2 . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIGS. 1 and 2  illustrate a rear-view mirror having a base member  10  adapted to be mounted on the body of a vehicle. The base member  10  has a flat upper wall  12  which abuts against a flat lower wall of a mirror housing  16 . 
   Within the housing  16 , a reflective member  18  is secured to a mirror carrier  20  with integrally formed rearwardly extending brackets  22  and  24  which are journalled on a shaft  26 . The shaft  26  is mounted on ribs  28  and  30  which are formed integrally with the housing  16 . As can be seen from  FIG. 2 , the reflective member  18  comprises a prism oriented so that its upper edge is wider than its lower edge, the angle between its two faces preferably being between 1° and 3°. The prism  18  has a reflective layer on its surface abutting the mirror carrier  20 . At night, if the driver of a following car fails to dip his headlights, the mirror carrier  20  can be tilted through the angle between the faces of the prism (i.e. between 1° and 3°) so that a driver of the vehicle sees an image reflected from the front surface of the prism  18  which is dimmer than the image which would have been reflected by the reflective layer. 
   A mounting member  32  extends between the ribs  28  and  30  and has two electric motors  34  and  36  mounted thereon. A worm gear  38  is mounted on the output shaft  39  of the motor  34 . The worm gear  38  engages with a pinion  40  forming part of a screw jack drive  42  of the type described in EP-A-0549173. A jacking screw  44  projects through a flexible synthetic rubber boot  46  on one end of the screw jack drive  42 . A spherical formation  48  on the end of the jacking screw  44  engages in a complementary socket  49  on the inside surface of the mirror carrier  20 . Thus, rotation of the worm gear  38  causes adjustment of the orientation of the reflective member  18  about the shaft  26 . 
   The base member  10  has a flanged hollow spigot  50  secured by its flange to the flat upper wall  12  so as to project through an opening in the flat lower wall  14  of the housing  16 . A cylindrical wall  52 , formed integrally with the housing  16 , surrounds the spigot  50  so as to form a pivot bearing. A pinion  54  is journalled on the spigot  50  above the cylindrical wall  52 . The upper face of the pinion  54  carries detent formations  56  which are adapted to engage with complementary formations on a cap  58  which is rotationally fast with the spigot  50 . A compression spring  60  urges the detent formations  56  and the cap  58  into engagement with one another. The pinion  54  is engaged by a worm gear  62  secured to the output shaft  64  of the second motor  36 . Thus, rotation of the shaft  64  causes angular movement of the housing  16  relative to the base member  10 . 
   If the housing  16  is subject to impact from the front or rear, the detent formations  56  disengage from the complementary formations on the cap  58 , allowing the housing  16  to fold backwards or forwards against the side of a vehicle on which the mirror is mounted. 
     FIG. 3  is a block diagram of a control system for the motors  34  and  36 . The control system comprises a controller  70  which produces control signals to operate the motors  34  and  36 , each of which has associated therewith a respective counter  72 ,  74  for supplying a signal to the controller  70  indicating the number of revolutions made by the corresponding motor  34 ,  36 . 
   In order to adjust the mirror in the up/down direction, the controller  70  has an “Up” push button  76  and a “Down” push button  78 . The motor  34  rotates in the appropriate direction for as long as either of these push buttons is depressed so as to tilt the mirror carrier  20  at a rate of about 3° per second. Similarly, the controller  70  has “Left” and “Right” push buttons  80  and  82  for causing the controller to send appropriate signals to the motor  36  to cause angular movement of the housing  16  about the spigot  50 , once again at a rate of about 3° per second. This permits the orientation of the mirror carrier to be adjusted to provide the required field of view depending on the driver&#39;s seating position in the vehicle. 
   When it is desired to drive the mirror housing  16  to a parked position in which it is folded against the side of the vehicle, a “Park” button  84  on the controller is pressed. This causes the controller to drive the motor  36  at a speed such as to cause angular movement of the housing  16  about the spigot  50  at a rate of about 30° per second. At the same time, the controller counts the output produced by the counter  74  to determine the number of revolutions performed by the motor  36  to move the housing  16  until it abuts against a stop (not shown), thus causing the motor  36  to stall. The resulting rise in current is sensed by the controller which then disconnects the supply to the motor  36 . 
   When it is desired to restore the mirror from its parked position to its deployed position, a “Restore” push button  86  on the controller  70  is pressed. The controller then supplies electric current to the motor  36 , so as to cause it to rotate in the opposite direction until the counter  74  indicates that the same number of revolutions have been performed as was necessary to move the mirror head  16  from its deployed position to its parked position. 
   The controller  70  also receives an input from the gear selector  88  of the vehicle, indicating the engagement of reverse gear. This causes the controller  70  to supply current to the motor  34  to cause it to tilt the mirror carrier downwardly at a rate of about 30° per second until it abuts against a stop (not shown) located so that the field of view of the mirror includes the ground adjacent to the corresponding rear wheel of the vehicle. The counter  72  provides a signal to the controller  70  indicating the number of revolutions of the motor  34  necessary to perform this tilting movement. When the mirror carrier reaches this stop, the motor  34  stalls and the resulting increase in current is detected by the controller  70  which then disconnects the electrical supply to the motor  34 . When reverse gear is disengaged, the controller  70  causes the motor  34  to rotate in the opposite direction until the counter  72  indicates that the same number of revolutions have been performed as were necessary to move the mirror to its tilted position. 
   A comparator  90  is arranged to receive a signal from an ambient photocell  92  indicating the level of ambient light outside the vehicle. The comparator  90  also receives a signal from a rear photocell  94  indicating the level of light incident on the mirror from the rear of the vehicle. When the level of light indicated by the ambient photocell  92  indicates lack of daylight and the rear photocell  94  indicates a light level which exceeds that detected by the ambient photocell  92  by more than a predetermined amount e.g. because the driver of a following vehicle has failed to dip his headlights, the comparator  90  sends a signal to the controller  70 , causing the motor  34  to tilt the mirror carrier  20  downwardly until the counter  72  indicates that the number of revolutions performed is sufficient to tilt the mirror carrier  20  through an angle equal to the angle between the front and rear surfaces of the prism  18 . The driver now sees a dimmer image reflected from the front surface of the prism  18  rather than a bright image reflected from the reflective layer on the rear surface thereof. To avoid repeated rapid movement of the mirror between its tilted position and its normal position, the controller  70  causes the motor  34  to tilt the mirror carrier  20  back to its normal deployed position only when the difference in light levels between the two photocells  92  and  94  has been less than the above mentioned threshold for at least ten seconds. When this occurs, the motor  34  is run until the counter  72  indicates that the number of revolutions equivalent to the prism angle have been performed. 
   The controller  70  may include a memory adapted to store information identifying one or more desired deployed positions for the reflective member  18 .