Vibration absorber for vehicle wiper devices

Details Vibration absorber for vehicle wiper devices Vibration absorber for vehicle wiper devices

2000-07-17

2002-03-12

Butler, Douglas C. (Department: 3613)

Spring devices

Vehicle

Lever and nontorsion spring

C267S293000, C267S141700

Reexamination Certificate

active

06354578

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to vibration absorbers preferably used for vehicle wiper devices, and, more particularly, to vibration absorbers arranged between wiper frames and vehicle body frames.
As shown in
FIG. 5
, a wiper device
2
is typically provided along a lower side of a windshield
1
of a vehicle. The wiper device
2
has a pair of wiper arms
5
,
6
. A pair of wiper blades
3
,
4
are secured to the distal ends, or ends spaced from a wiper frame
7
, of the associated wiper arms
5
,
6
. Each wiper blade
3
,
4
wipes a substantial area of an associated half of the windshield
1
with respect to the longitudinal middle of the windshield
1
. The proximal ends, or bases, of the wiper arms
5
,
6
are rotationally supported by associated shafts
8
,
9
. The shafts
8
,
9
are secured to the wiper frame
7
. A pair of movable levers
10
,
11
are rotationally supported by the associated shafts
8
,
9
at the bases, or proximal ends, of the levers
10
,
11
. In other words, the movable levers
10
,
11
are connected to the associated wiper arms
5
,
6
to rotate integrally with the wiper arms
5
,
6
with respect to the associated shafts
8
,
9
.
A worm
13
is coupled with the output shaft of a motor
12
and meshes with a worm wheel
14
. A base, or proximal end, of a drive lever
15
is secured to the center of the worm wheel
14
. The distal end of the drive lever
15
is connected to the distal ends of the movable levers
10
,
11
through associated link rods
16
,
17
.
When the motor
12
rotates the worm wheel
14
by means of the worm
13
, the drive lever
15
is rotated to extend and retract the link rods
15
,
16
. Accordingly, the movable levers
10
,
11
are rotated integrally with the associated wiper arms
5
,
6
within a predetermined range around the associated shafts
8
,
9
. Every rotation cycle of the worm wheel
14
corresponds to one movement cycle of each wiper arm
5
,
6
. The movement cycle of the wiper arms
5
,
6
is defined as proceeding from a lowermost position to an uppermost position and then returning to the lowermost position. While the wiper arms
5
,
6
repeat their movement cycles, the wiper blades
3
,
4
wipe corresponding portions of the windshield
1
, as indicated by the double-dotted chain lines in FIG.
5
.
When the link rods
16
,
17
are extended and retracted, force acts on the wiper frame
7
through the shafts
8
,
9
to vibrate the wiper frame
7
. To counter this, a rubber vibration absorber
18
is deployed between the wiper frame
7
and the vehicle body frame when installing the wiper frame
7
. The vibration absorber
18
prevents the vibration of the wiper frame
7
from being transmitted to the body frame. The vibration absorber
18
also absorbs vibration of the motor
12
. In the wiper device
2
of
FIG. 5
, for example, four vibration absorbers
18
are provided at corresponding ends of the wiper frame
7
.
FIG. 6
shows the structure of the vibration absorber
18
. Specifically, the vibration absorber
18
has a cylinder
18
b
and a pair of substantially annular flanges
18
c,
18
d.
The flanges
18
c,
18
d
extend from near opposite axial ends of the cylinder
18
b.
The recess of the cylinder
18
b
is defined as a through hole
18
a
in which a cylindrical collar
20
is fitted. A bolt
21
is inserted in the collar
20
. A washer
22
is fitted around the bolt
21
. One axial end of the collar
20
abuts the washer
22
. The other axial end of the collar
20
abuts a body frame
19
. The vibration absorber
18
is fitted in an opening
7
a
extending in the wiper frame
7
. The distal end of the bolt
21
is inserted in a hole
19
a
extending in the body frame
19
. A nut
23
is fastened to the distal end of the bolt
21
to fasten the wiper frame
7
to the body frame
19
.
One flange
18
c
is located between the wiper frame
7
and the washer
22
and has a pair of annular projections
18
e,
18
f.
The projections
18
e,
18
f
are located at a radial outer section of the flange
18
c
and project in opposite directions along the axis of the vibration absorber
18
. One projection
18
e
abuts against the washer
22
, and the other projection
18
f
abuts against the wiper frame
7
. The other flange
18
d
is located between the wiper frame
7
and the body frame
19
. The flange
18
d
is shaped as a mirror image of the flange
18
c
and has a pair of projections
18
h,
18
g.
One projection
18
g
abuts against the body frame
19
, and the other projection
18
h
abuts against the wiper frame
7
.
An annular projection
18
i
is projected from the axial middle of the cylinder
18
b
and abuts against the wall of the opening
7
a
of the wiper frame
7
. The projection
18
i
has a substantially semi-circular cross-sectional shape. A pair of annular projections
18
j,
18
k
project from the inner side of the cylinder
18
b
at positions substantially corresponding to the flanges
18
c,
18
d.
The projections
18
j,
18
k
have a substantially triangular cross-sectional shape. The projections
18
j,
18
k
abut against the collar
20
. The projections
18
j,
18
k
form a clearance A between the inner side of the cylinder
18
b
and the collar
20
. The clearance A enables a portion of the cylinder
18
b
corresponding to the annular projection
18
i
to elastically deform in a radially inward direction.
The vibration absorber
18
absorbs a vibration component acting along axis Y of the wiper frame
7
, or along the axis of the vibration absorber
18
, through elastic deformation of the projections
18
e
to
18
h.
The vibration absorber
18
also absorbs a vibration component acting along axis X of the wiper frame
7
, or in a radial direction of the vibration absorber
18
, through elastic deformation of the projections
18
i
to
18
k
and by means of the clearance A.
The annular projections
18
e
to
18
h
are located coaxially with one another and define a uniform diameter with respect to the axis of the vibration absorber
18
. In other words, the projections
18
e
to
18
h
are located along a line parallel to the axis of the vibration absorber
18
. In this state, the projections
18
e
to
18
h
abut against the washer
22
, the wiper frame
7
, or the body frame
19
at positions spaced radially from the axis of the vibration absorber
18
by a uniform distance. Accordingly, vibration of the wiper frame
7
along axis Y is readily transmitted to the body frame
19
through the projections
18
e
to
18
h.
As described above, the vibration absorber
18
absorbs the vibration of the wiper frame
7
along axis Y only through elastic deformation of the projections
18
e
to
18
h.
Accordingly, the vibration absorbing performance of the vibration absorber
18
depends greatly on the hardness of the rubber forming the vibration absorber
18
. However, it is difficult to optimize the vibration absorbing performance only by adjusting the rubber hardness of the vibration absorber
18
. Furthermore, if the rubber hardness is decreased to improve the vibration absorbing performance, the wiper frame
7
is not reliably secured to the body frame
19
.
The vibration absorbing performance of the vibration absorber
18
shown in
FIG. 6
will hereafter be explained with reference to FIGS.
7
(
a
) and
7
(
b
). FIGS.
7
(
a
) and
7
(
b
) are graphs showing a rate at which the vibration of the wiper frame
7
is transmitted to the body frame
19
in the vicinity of the wiper frame
7
. FIG.
7
(
a
) shows the vibration transmission rate along axis Y of the wiper frame
7
, and FIG.
7
(
b
) shows the vibration transmission rate along axis X of the wiper frame
7
. The natural frequency of the motor
12
shown in
FIG. 5
is approximately 500 Hz, and its harmonic component is 1 kHz. As shown in FIG.
7
(
a
), the vibration transmission rate is increased particularly for frequencies close to 1 kHz.
As shown in FIG.
7
(
b
), the vibration transmission rate along axis X is decreased as compared to the vibration transmission rate along a

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