Rotary shafts – gudgeons – housings – and flexible couplings for ro – Torque transmitted via flexible element – Element positioned between intermeshing teeth on driving and...
Reexamination Certificate
1999-12-07
2001-09-04
Browne, Lynne H. (Department: 3629)
Rotary shafts, gudgeons, housings, and flexible couplings for ro
Torque transmitted via flexible element
Element positioned between intermeshing teeth on driving and...
C074S492000, C464S075000, C464S083000, C464S158000
Reexamination Certificate
active
06283867
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an elastic shaft joint (hereafter referred to as a joint) that connects two coaxial shafts in a state having an elastic play in a rotation direction.
2. Description of the Related Art
Such a kind of joint is used, for example, in a steering mechanism of an automobile as shown in FIG.
9
. This joint shuts off vibration transmission from a wheel to a steering wheel and allows a steering wheel operation to have an elastic play by utilizing the torsion of a damper.
Referring to
FIG. 9
, a steering wheel
50
, a steering shaft
51
, an input shaft
52
of a steering gear device (power steering device), universal joints
53
,
54
, and a joint
55
are shown.
A conventional joint
55
is disclosed, for example, in Japanese Utility Model Publication No. 58-50105/1983, the contents of which will be hereafter explained with reference to
FIGS. 10 and 11
, wherein
FIG. 10
is a perspective view in an exploded state, and
FIG. 11
is a section view.
The joint
55
includes a tube shaft (pipe shaft)
56
being integral with a yoke (not illustrated), a solid shaft
57
inserted in the tube shaft
56
, and an elastic body
58
interposed therebetween.
Protrusions
56
a
to
56
c
outwardly protruding in the radial direction are disposed at three places on a circumference of the tube shaft
56
. Three projections
57
a
to
57
c
engaging with the inside of the three protrusions
56
a
to
56
c
of the tube shaft
56
with a gap in the rotation direction are disposed at the end of the shaft
57
. The elastic body
58
is bonded by vulcanization to both circumferential sides of the first and second projections
57
a
,
57
b
and to regions between the three projections
57
a
to
57
c.
The elastic bodies
58
on both sides of the first projection
57
a
are in contact with inner wall surfaces of the corresponding first protrusion
56
a
. However, the elastic bodies
58
on both sides of the second projection
57
b
are disposed to face the corresponding second protrusion
56
b
with slight gaps C
1
, C
1
. Further, large gaps C
2
, C
2
are disposed between the third projection
57
c
and the corresponding third protrusion
56
c.
Referring to
FIG. 12
, the characteristics of the torsion spring constant brought about by this structure are as follows. The joint has a low spring constant in a minute steering angle range from A to B due to elastic deformation of the elastic body
58
disposed between the first projection
57
a
and the protrusion
56
a
; the gap C
1
of
FIG. 11
disappears when the steering angle reaches B; and the joint has a high spring constant in a steering angle range from B to C due to elastic deformation also of the elastic body
58
between the second projection
57
b
and the protrusion
56
b
. When the steering angle reaches C, the gap C
2
of
FIG. 11
disappears and the torque is directly transmitted. In other words, as a sense of steering operation, when the rotation is started, a gradually increasing elastic reaction is felt in accordance with the increase in the rotation angle, and finally a rigid reaction is felt. This facilitates the steering operation.
The above-mentioned joint has a structure such that the transmitted torque is changed in three steps in accordance with the thickness and presence of the elastic body
58
between the projections
57
a
to
57
c
and the protrusions
56
a
to
56
c
at three places on the circumference. Therefore, the torque transmitted in each of the gaps between the projections
57
a
to
57
c
and the protrusions
56
a
to
56
c
is changed, so that an inclination of the tube shaft
56
or the shaft
57
in the rotation direction is liable to be generated. Due to this reason, it is sometimes difficult to obtain a spring constant as designed.
Moreover, since the tube shaft
56
and the shaft
57
have complex shapes, it requires labor in producing the joint
55
, and the production costs are high.
SUMMARY OF THE INVENTION
Accordingly, a principal object of the present invention is to provide a joint that can contribute to stability in steering by obtaining a spring constant as designed.
Another object of the present invention is to provide a joint that has a simple structure and can be produced with less labor and at low costs.
Other objects, features, and advantages of the present invention will be apparent from the following descriptions.
An elastic shaft joint according to the present invention comprises: a tube shaft; a shaft coaxially inserted in said tube shaft so that a predetermined axial region of said shaft overlaps with a predetermined axial region of said tube shaft; and a damper inserted between the predetermined axial region of said shaft and the predetermined axial region of said tube shaft for damping vibration and providing an elastic play in a rotation direction, wherein said damper includes: an inner tube fitted to an outside of the predetermined axial region of said shaft and having radially outwardly extending projections at a number of places in a circumferential direction of an outer circumferential surface thereof; an outer tube fitted to an inside of the predetermined axial region of said tube shaft so as to form a desired gap opposite to said inner tube, and having recesses engaging with the respective projections of said inner tube with a gap in the rotation direction; and an elastic body bonded to an inner surface of the recesses of said outer tube in a state of non-contact with at least said projections of said inner tube.
In short, in the present invention, the damper disposed between the tube shaft and the shaft can equalize the torque transmitted between the projections disposed at a number of places on the circumference of the inner tube and the recesses disposed at a number of places on the circumferences of the outer tube. This provides a good rotation balance and prevents the shaft and the tube shaft from being twisted in the rotation direction. In addition, unlike the conventional joint, the tube shaft and the shaft can be produced easily because the damper itself has a simple structure formed with the inner tube, the outer tube, and the elastic body.
Further, if a raised portion is disposed on the elastic body bonded to the inner surface of the recess, one can easily manage to keep constant the gap dimension between the projections and the elastic body bonded to the inner surface of the recesses.
REFERENCES:
patent: 5507203 (1996-04-01), Audibert et al.
patent: 5672111 (1997-09-01), Schremmer et al.
patent: 5916026 (1999-06-01), Sadakata
patent: 58-50105 (1983-11-01), None
patent: 988993 (1997-03-01), None
Aota Kenichi
Fujii Tooru
Muraosa Hiroyuki
Birch & Stewart Kolasch & Birch, LLP
Browne Lynne H.
Dunwoody Aaron
Koyo Seiko Co. Ltd.
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