Rear view mirror assembly for motor vehicle

A drive unit for adjusting the orientation of a reflective member of rear view mirror assembly for a motor vehicle is assembled within a drive housing. The drive housing contains an electric motor arranged to drive a jacking nut which is supported within the housing by first and second bearing surfaces formed on opposite walls of the housing. The drive housing is formed in two parts, each of which comprises a base portion and a peripheral side wall portion dimensioned so that, when the two parts are assembled together, part of the side wall portion of one part surrounds a corresponding part of the side wall portion of the other part. After assembly, glue is inserted between the side wall portions so as to hold the two parts together with their respective bearing surfaces spaced apart by a distance determined by the size of the jacking nut.

FIELD 
This invention relates to a rear view mirror assembly for a motor vehicle 
of the type in which a reflective member is mounted on a pivot mounting 
for angular movement within a mirror case and a drive housing is located 
within the mirror case and has a projecting jacking screw which is 
pivotally coupled to the rear surface of the reflective member at a 
location remote from said pivot mounting. 
RELATED ART 
Patent Specification No. EP-A-0272047 discloses a rear view mirror assembly 
of this type in which the drive housing containing an electric motor 
arranged to drive a jacking nut for effecting variation in the extent of 
protrusion of the jacking screw from the housing so as to adjust the 
orientation of the reflective member relative to the mirror case, the 
jacking nut being supported within the housing by a bearing surface formed 
on one wall of the housing and a bearing spring which engages with the 
opposite wall of the housing. The bearing spring serves to take up 
manufacturing tolerances affecting the size of the jacking nut and the 
distance between the two opposite walls of the housing. It is an object of 
the present invention to provide a rear view mirror assembly of this type 
in which the provision of a bearing spring is not necessary. 
Patent Specification No. GB-A-2032367 discloses a rear view mirror assembly 
in which the drive housing is formed in two parts, each of which comprises 
a base portion and a peripheral side wall portion, dimensioned so that, 
when the two parts are assembled together, part of the side wall portion 
of one part surrounds a corresponding part of the side wall portion of the 
other part and an edge of one of the side wall portions engages with a 
protrusion on the other side wall portion which limits the extent of 
overlap of the two side wall portions and thereby determines the distance 
between the base portions. 
SUMMARY OF THE INVENTION 
According to the invention in one aspect, a rear view mirror assembly for a 
motor vehicle comprises a reflective member mounted on a pivot mounting 
for angular movement within a mirror case and a drive housing located 
within the mirror case and formed in two parts, each of which comprises a 
base portion having a bearing surface formed on its inner surface and a 
peripheral side wall portion dimensioned so that part of the side wall 
portion of one part surrounds a corresponding part of the side wall 
portion of the other part when the two parts are assembled together, a 
jacking nut positioned between the bearing surfaces, glue inserted between 
the side wall portion of one part and the side wall portion of the other 
part so as to secure the two parts together with their respective bearing 
surfaces spaced apart by a distance determined by the size of the jacking 
nut, a jacking screw engaging in the jacking nut and having an end 
pivotally coupled to the rear surface of the reflective member at a 
location remote from said pivot mounting, and an electric motor located 
within the drive housing and arranged to drive the jacking nut for 
effecting variation in the extent of protrusion of the jacking screw from 
the drive housing so as to adjust the orientation of the reflective member 
relative to the mirror case. 
Another aspect of the invention provides a method of assembling a drive 
unit for a rearview mirror assembly for a motor vehicle comprising a 
reflective member mounted on a pivot mounting for angular movement within 
a mirror case, the method comprising: forming two parts of a drive 
housing, each part comprising a base portion and a peripheral side wall 
portion with a respective bearing surface on its base portion, the side 
wall portions being dimensioned so that, when the two parts are assembled 
together, part of the side wall portion of one part surrounds a 
corresponding part of the side wall portion of the other part; assembling 
an electric motor, a jacking nut and a jacking screw within the housing so 
that the jacking nut is supported within the housing by said bearing 
surfaces; and holding the two parts together with their respective bearing 
surfaces abutting the jacking nut while inserting glue between the side 
wall portions so as to secure the two parts together. 
By arranging for a predetermined force to hold the two parts together while 
the glue is applied, it can be ensured that the jacking nut is a precise 
sliding fit between the bearing surfaces, any variation in size due to 
manufacturing tolerance being taken up by variation in the degree of 
overlap of the side wall portions of the two parts. 
Preferably, the side wall portion of one of the parts of the drive housing 
is inclined relative to the side wall portion of the other part so as to 
provide a tapering gap to facilitate insertion of the glue.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to FIGS. 1 and 2, a rear view mirror assembly comprises a mirror 
case 10 containing a mounting plate 12 on which is mounted an adjustment 
mechanism housing which, in accordance with the invention, comprises an 
inner part 14 and an outer part 16. The outer part 16 is formed integrally 
with the mounting plate 12 and supports a ball element 18 which engages in 
a socket 20 formed in a mirror carrier 22 which has a reflective member 24 
on its outer surface. Projections 26 on the outer surface of the housing 
part 16 engage with flanges 28 on the back of the mirror carrier 22 to 
prevent relative angular movement of the mirror carrier 22 and the housing 
10 about an axis perpendicular to the plane of the mounting plate 12. 
A pair of jacking screws 30 and 32 project from the outer housing part 16 
and have ball formations on their outer ends which engage in respective 
sockets 34 and 35 in the back of the mirror carrier 22, for effecting 
angular movement of the mirror carrier 22 about two mutually orthogonal 
axes. As is shown in outline in FIG. 1, each jacking screw 30, 32 engages 
in a respective jacking nut, 36, 37, each of which has gear teeth on its 
periphery engaged by respective worms 38 and 40 on the output shafts of 
respective electric motors 42 and 44. 
As can be seen from FIG. 3, the jacking screw 30 has two limbs 46 which are 
splayed out by a U-shaped spring 48 and carry screw thread formations on 
the other surface of their ends which engage in an inner threaded surface 
50 in the jacking nut 36. The lower drive housing part 14 contains a 
part-spherical concave bearing surface 52 for engagement with the a 
complimentary spherical surface 54 on one end of the jacking nut 36. The 
upper part 16 has a hole 56, through which the jacking screw 30 projects, 
surrounded by a part-spherical concave bearing surface 58 which engages 
with a part-spherical surface 60 on the jacking nut opposite to the 
bearing surface 54. 
The two parts 14 and 16 of the drive housing are held together by glue 62 
between their overlapping side walls 64 and 66. The side wall 66 of the 
upper part 16 is inclined outwardly so as to provide a tapering gap with 
the side wall 64 of the lower part 14 so as to facilitate insertion of the 
glue 62. As the glue 62 is applied, the two parts 14 and 16 of the drive 
housing are held together by sufficient force to ensure that the jacking 
nut 36 is a rattle-free sliding fit between the bearing surfaces 54 and 
58. Too large a force would create excessive friction between the jacking 
nut 36 and the bearing surfaces 54 and 58.