Rear view mirror

A rear view mirror assembly comprising a bracket adapted to be mounted on a vehicle body, and a case, in which a reflective member is pivotally mounted. A lead screw is mounted in the bracket. A pair of arms projecting laterally from the reflective member beyond the periphery thereof and have ridge formations which engage with the lead screw so that rotation of the lead screw causes angular movement of the reflective member.

FIELD 
This invention relates to a rear view mirror assembly comprising a bracket 
adapted to be mounted on a vehicle body, a case, a reflective member 
mounted in the case for angular movement relative thereto about a 
predetermined range and a drive unit for effecting angular movement of the 
reflective member relative to the case. 
The invention is applicable both to rear view mirror assemblies of the type 
in which the case is rigidly mounted on the bracket and to mirror 
assemblies of the type in which the case is pivotally mounted on the 
bracket so as to be displaceable from its position of normal use, for 
example when subject to impact, for example as described in EP-A-0392721. 
RELATED ART 
In known mirror assemblies of this type, substantially all of the drive 
means is located within the case behind the reflective member (i.e. on the 
opposite side thereof from which the mirror is viewed by the user). For 
example, EP-A-0272047 discloses a mirror of this type in which two 
electric motors are mounted behind the reflective member and coupled 
thereto by respective screw jack drives. EP-A-0860323 discloses a similar 
mechanism in which a single motor and screw jack drive is used to vary the 
angular position of a reflective member about a single axis. In both 
cases, the motor or motors and their associated drives make a significant 
contribution to the weight of the mirror case and therefore increase the 
extent to which the mirror assembly is liable to vibrate. It is an object 
of the present invention to provide a mirror assembly of the type 
described above in which at least part of the drive mechanism is located 
in the mirror bracket so as to be closer to the location at which the 
mirror assembly is mounted on the vehicle body. 
SUMMARY OF THE INVENTION 
According to the invention, in a mirror assembly of the type described 
above, the drive unit comprises a lead screw mounted in the bracket with 
its axis oriented in a direction having a component perpendicular to the 
plane of the reflective member when said reflective member is in the 
middle of its range of movement, rotary drive means for causing rotation 
of the lead screw, an arm projecting laterally from the reflective member 
beyond the periphery thereof and a ridge formation on the arm arranged to 
engage with the lead screw so that rotation of the lead screw causes 
angular movement of the reflective member.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring to FIGS. 1 to 4, a rear view mirror has a case 10 mounted on a 
bracket 12 which has an inner face 14 adapted to abut a motor vehicle body 
(not shown). The case 10 is connected to the bracket 12 by a mechanism 
allowing relative angular movement in the fore and aft direction, as 
described in EP-A-0392721, the disclosure of which is hereby incorporated 
herein by reference. A reflective member 16, for example silvered glass, 
is mounted on a mirror carrier 18, which is coupled to a support member 24 
within the case 10 by hinges 20 and 22, both of which are shown in FIG. 4 
while only hinge 20 is visible in FIGS. 2, 5, 9 and 10. The hinges 20 and 
22 allow angular movement of the mirror carrier 18 about an inclined axis 
25 shown in FIG. 4, the orientation of which is determined in the manner 
described in EP-A-0860323. 
An electric motor 26 is mounted within the bracket 12 and has its output 
shaft coupled by a reduction gear 28 to a lead screw 30 which is mounted 
with its axis lying in the plane of separation between the case 10 and the 
bracket 12 when the former is pivoted forwardly or rearwardly, as 
described above. 
Referring to FIGS. 2 and 3, the mirror carrier 18 has a pair of mutually 
parallel arms 32 and 34 projecting rearwardly and laterally so that their 
ends embrace the lead screw 30 and are urged into contact therewith by a 
U-shaped spring 36. The confronting faces of ends of the arms 32 and 34 
have grooved regions 38 and 40 of the same pitch as the lead screw 30. 
Consequently, when the lead screw 30 is rotated by the motor 26, the arms 
32 and 34 are displaced longitudinally along the lead screw 30, causing 
the mirror carrier 18 to pivot about the axis 25 of the hinges 20 and 22 
shown in FIG. 4. The lead screw thread is of fine pitch and open angle 
form (for example 0.5 mm pitch and 45.degree. flank angle). Consequently, 
if the mirror carrier 18 is subject to a force tending to displace it 
about the axis 25, the grooved regions 38 and 40 of the arms 32 and 34 can 
jump over the thread of the lead screw 30 against the action of the spring 
34, thereby avoiding damage to the mechanism and allowing manual 
adjustment of the reflective member 16 in the event of motor drive 
failure. 
When the case 10 is subject to a force tending to displace it from its 
normal position, shown in FIG. 2, towards the rear of the vehicle, it 
pivots to the position shown in FIG. 5. The arms 32 and 34 have disengaged 
from the lead screw 30 and are urged into engagement with a stop bar 42 
(see FIGS. 3 and 6) on the case 10 which extends parallel and adjacent to 
the lead screw 30 when the case 10 is in its normal position. The stop bar 
42 has grooved formations of the same pitch as the lead screw on its 
surfaces facing the grooved regions 38 and 40 of the arms 32 and 34. As 
the grooved regions 38 and 40 disengage from the lead screw 30, they come 
into engagement with the groove formations on the stop bar 42 so as to 
hold the mirror carrier 18 in the orientation to which it had been set 
immediately prior to disengagement. As the case 10 is restored to its 
normal position, ramp surfaces 44 and 46 on the ends of the arms 32 and 34 
engage with lead screw 30 to force the arms 34 and 36 apart, against the 
action of the spring 36, so that the grooved regions 38 and 40 come into 
engagement with the thread of the lead screw 30 as they disengage from the 
groove formations on the stop bar 42. The bar 42 effectively forms a 
keeper to inhibit movement of the mirror relative to the case when the 
arms are disengaged from the screw. 
FIG. 7 shows the case 10 displaced forwardly from its normal position. The 
arms 32 and 34 disengage from the lead screw 30, and re-engage therewith 
when the case 10 is restored to its normal position, in the same manner as 
described with reference to FIGS. 5 and 6. 
FIG. 8 shows the mirror assembly with the case 10 in its normal position 
and the mirror carrier 18 driven by the lead screw 30 to its maximum 
outwardly directed orientation. FIG. 9 shows the mirror carrier 18 
displaced to its maximum inward facing orientation. 
FIG. 10 shows a second embodiment of the invention in which the separate 
mirror case 10 and bracket 12 are replaced by a single combined case 50 
which is rigidly fixed to the vehicle body. Since there is no displaceable 
case, the arms 32 and 34 do not disengage from the lead screw 30. 
Consequently, there is no stop bar equivalent to the stop bar 42 of the 
first embodiment. Otherwise, the mechanism is as described with reference 
to FIGS. 1-4, corresponding parts being denoted by the same reference 
numerals. 
FIGS. 11 to 14 show another rear view mirror having a case 60 mounted on a 
bracket 62 which has an inner face 64 adapted to abut a motor vehicle body 
(not shown). As with the embodiment of FIGS. 1 to 4, the case 60 is 
connected to the bracket 62 by a mechanism allowing relative angular 
movement in the fore and aft direction. A reflective member 66 is mounted 
on a mirror carrier 68 which differs from the mirror carrier of FIGS. 1 to 
4 in that it is coupled by a ball and socket joint 70 to a support member 
72 so as to allow angular movement of the mirror carrier 68 about both 
vertical and horizontal axes that may be referred to as first and second 
orthogonal axes. 
As can best be seen in FIG. 14, two electric motors 74 and 76 are mounted 
within the bracket 62, each having its output shaft coupled by a 
respective reduction gear 78, 80 to a respective upper and lower lead 
screw 82, 84. 
As can best be seen from FIG. 13, the mirror carrier 68 has an upper pair 
of mutually parallel arms 86, 88 and a lower pair of mutually parallel 
arms 90, 92 similar to the arms 32 and 34 shown in FIG. 3. The upper pair 
of arms 86, 88 have grooved regions for engagement with the upper lead 
screw 82 while the lower pair of arms has grooved regions for engagement 
with the lower lead screw 84. Each pair of arms has a respective U-shaped 
spring 94, 96 for urging the ends of the arms into engagement with the 
respective lead screws 82 and 84. 
Each of the lead screws operates in a similar manner to that described with 
reference to FIGS. 8 and 9. Rotation of both lead screws 82 and 84 in the 
same direction causes adjustment of the orientation of the mirror carrier 
68 about a generally vertical axis. Rotation of the two lead screws 82 and 
84 in opposite directions to one another causes variation in the 
orientation of the mirror carrier 68 about a generally horizontal axis. 
The case 60 has a pair of stop bars, one of which is visible at 98 in FIG. 
12 which engage between the respective pairs of arms 86, 88 and 90, 92 
when the case 60 is displaced forwardly or rearwardly in a similar manner 
to that described with reference to FIGS. 5 to 7. The vertical thickness 
of these stop bars is substantially less than the diameter of the lead 
screws 82 and 84 so as to avoid any risk of the grooved formations thereon 
coming into engagement with the grooved regions 38 and 40 of the arms 
88-92 during adjustment of the orientation of the mirror carrier 68 about 
said generally horizontal axis. 
With reference to FIG. 4, mirror carrier 18 has an outer periphery that 
includes top and bottom peripheral portions 120, 122, and opposite side 
peripheral portions 124, 126. These peripheral portions of carrier 18 also 
define corresponding peripheral portions of reflective member 16. In the 
embodiment of FIGS. 11 to 14, these peripheral portions of reflective 
member 66 and its carrier 68 are identified by numerals 220, 222, 224 and 
226. In the embodiment of FIGS. 11-14, reflective member 66 and its 
carrier 68 are capable of angular movement about both vertical and 
horizontal axes that are illustrated at 230, 232 in FIG. 13, and may be 
referred to as first and second orthogonal axes. 
Generally vertical axis 25 may be vertical, inclined within a vertical 
plane, and/or inclined out of a vertical plane. As previously mentioned, 
one way of determining a desirable angle of inclination for axis 25 is 
explained in EP-A-9272047. However, it will be recognised that other ways 
of determining a desirable angle can be used. 
Reflective member 16 and its carrier 18 rotate clockwise and 
counterclockwise about axis 25. The midpoint position of movement is 
illustrated in FIGS. 2 and 10, while the clockwise end limit position of 
movement is illustrated in FIG. 9. The opposite or counterclockwise end 
limit position of movement is counterclockwise from the midpoint position 
of FIGS. 2 and 10, and the end portions of arms 32, 34 would be located 
adjacent the opposite end portion of lead screw 30 as compared to the 
clockwise end limit position of FIG. 9. 
In the arrangement shown, side peripheral portion 124 of reflective member 
16 and its carrier 18 travel in an arcuate path adjacent to bracket or 
attaching portion 12. In the arrangement illustrated, the arcuate path is 
around 20.degree. which is around 10.degree. in each of opposite 
directions from the midpoint position of FIGS. 2 and 10. The arcuate path 
could extend anywhere from 10.degree. to 40.degree. which would be between 
5.degree. and 20.degree. in each of opposite directions from the midpoint 
position of FIGS. 2 and 10. 
Depending on the orientation of axis 25, a given point on side peripheral 
portion 124 may travel in an arcuate path that is within a horizontal 
plane or is inclined relative to a horizontal plane. Lead screw 30 extends 
in the general direction of movement of side peripheral portion 124 or in 
the general direction of the arcuate path. The arcuate path is closest to 
the screw in the midpoint position of the mirror and is further away from 
the screw in the end limit positions of the mirror. Considering a given 
point on side peripheral portion 124 that is horizontally aligned with the 
longitudinal axis of lead screw 30 in the midpoint position of FIGS. 2 and 
10, the axis of the lead screw is usually parallel to a line that is 
tangent to the arcuate path through which the given point travels. 
The longitudinal axis of lead screw 30 usually would be inclined at an 
included angle with the plane of bracket inner face 14 of 25.degree. to 
45.degree. and more preferably 30.degree. to 40.degree.. In the 
arrangement shown, the angle is about 35.degree.. Lead screw 30 may also 
be horizontal or inclined above or below a horizontal plane. When inclined 
to the horizontal the angle of inclination is within 20.degree. in each of 
opposite directions from the horizontal and more preferably within 
10.degree. either above or below the horizontal. 
Reflective member or mirror 16 is shown as having a curved outer surface at 
a very large radius but it could be flat. With the curvature flattened or 
removed, the mirror outer surface has a surface plane. Therefore, 
references to the mirror as having a surface plane does not necessarily 
mean that the mirror surface is flat or plane. 
In the midpoint position of the mirror and carrier shown in FIGS. 2 and 10, 
the longitudinal axis of lead screw 30 could extend perpendicular to the 
mirror plane or could be inclined relative thereto. When inclined, the 
angle of inclination preferably is not greater than 35.degree. in 
horizontal or vertical planes. Thus, the axis of lead screw 30 could be 
inclined up to 35.degree. in a horizontal plane in either of opposite 
directions from a line that is perpendicular to the mirror plane, and 
could be inclined up to 35.degree. in a horizontal plane in either of 
opposite directions from a line that is perpendicular to the mirror plane, 
and could be inclined up to 35.degree. in a vertical plane in either of 
opposite directions from a line that is perpendicular to the mirror plane. 
With the lead screw so inclined, the projected length of the lead screw 
that extends perpendicular to the mirror plane is equal to the length of 
the lead screw times the cosine of the angle between 0.degree. and 
35.degree.. The cosine of 35.degree. is 0.81915 so that approximately 82% 
of the length of the lead screw extends in a direction perpendicular to 
the mirror plane when the lead screw is inclined at 35.degree.. For 
purposes of this application, the length of the lead screw may be resolved 
into components that extend both parallel and perpendicular to the mirror 
plane in the midpoint position of the mirror. The parallel component is 
equal to the lead screw length times the sine of the inclination angle, 
and the perpendicular component is between 80% and 100% of the total lead 
screw length. 
The position, inclination or lack of inclination of the lead screw with 
respect to the mirror also may be considered with respect to the 
directional components. When the longitudinal axis of the lead screw 
extends in a direction that is perpendicular to the mirror plane in the 
midpoint position of the mirror between its opposite end limits of travel, 
the directional component of the axis that is perpendicular to the mirror 
plane is 100%. When the longitudinal axis of the screw is inclined to the 
surface plane of the mirror in its midpoint position in a direction that 
forms an included angle of 35.degree. with a line that is perpendicular to 
the surface plane of the mirror, the directional component that is 
perpendicular to the mirror plane is equal to the cosine of 35.degree. or 
about 82%. Thus, in the midpoint of the mirror between its opposite end 
limits of travel, the longitudinal axis of the lead screw is oriented in a 
direction such that its directional component that is perpendicular to the 
mirror plane is between 80 and 100% or greater than 80%. 
The principal directional component of the direction in which the shaft 
extends is one that extends perpendicular to the surface plane of the 
mirror. This principal directional component is at least 80% of the 
direction that is resolvable into components extending both parallel and 
perpendicular to the surface plane of the mirror. 
The arrangement described with ridges on the arms engaging the lead screw 
permits relative transverse movement between the arms and screw as the 
distance between the mirror axis 25 and the point of engagement between 
the screw and arms varies during movement of the arms along the screw. 
Lead screw or worm gear 30 may be considered an elongated rotatable shaft 
that co-operates with followers define by arms 32, 34 to convert rotary 
motion of the shaft to motion of the arms linearly along the shaft. Other 
motion conversion arrangements are possible such as a smooth shaft 
co-operable with skewed rollers attached to the follower arms, or a 
grooved shaft co-operable with small balls attached to the follower arms. 
In such arrangements, the rollers or balls would be on a part to which the 
arms are attached to import swinging motion of the arms as the part moves 
along the shaft while permitting relative movement between the part and 
the arms in a direction transversely of the shaft longitudinal axis.