Land vehicles – Wheeled – Running gear
Reexamination Certificate
1999-04-05
2003-03-11
Zeender, F. (Department: 3627)
Land vehicles
Wheeled
Running gear
C074S492000, C188S371000
Reexamination Certificate
active
06530599
ABSTRACT:
This application claims the benefit of Japanese Application No. 10-115197 which is hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to improvements in a shock absorbing type steering shaft of an automobile which is utilized to transmit the movement of a steering wheel to a steering gear, and to regulate a load required for contracting the total length of the steering shaft during a collision accident to protect the driver.
2. Related Background Art
In a steering apparatus for an automobile, a steering mechanism as shown in
FIG. 6
is used to transmit the movement of a steering wheel to a steering gear. The first steering shaft
2
having a steering wheel
1
fixed to the upper end portion thereof is rotatably inserted in a steering column
3
. This steering column
3
is fixed to the lower surface of an instrument panel
6
by upper and lower brackets
4
,
5
. The upper end portion of a second steering shaft
8
is connected through a first universal joint
7
to a lower end portion of the first steering shaft
2
which protrudes from the lower end opening of the steering column
3
. Further, the lower end portion of this second steering shaft is connected through a second universal joint
9
to a third steering shaft
10
leading to a steering gear (not shown), In the steering mechanism thus constructed, the movement of the steering wheel
1
is transmitted to the steering gear through the first steering shaft
2
inserted through the steering column
3
, the first universal joint
7
, the second steering shaft
8
, the second universal joint
9
, and the third steering shaft
10
to give a steering angle to wheels.
In the steering mechanism thus constructed, the steering column
3
and the steering shafts
2
,
8
are usually made into a shock absorbing type in which the total length shortens due to a shock in order to protect a driver during collision. The structure described in U.S. Pat. No. 5,623,756 is known as such a shock absorbing type steering shaft.
FIGS. 7
to
13
show the shock absorbing type steering shaft described in this the United States patent, while
FIGS. 14
to
18
a method of manufacturing the shock absorbing type steering shaft which is also described in this United States patent, respectively.
This shock absorbing type steering shaft
11
is constructed such that an outer shaft
12
and an inner shaft
13
are combined for relative displacement in an axial direction (the left to right direction as viewed in FIG.
7
), whereby the total length of the shaft shortens when an impact force in the axial direction is applied. The outer shaft
12
as a whole is of a tubular shape and one end portion (the left end portion of the steering shaft
11
as viewed in
FIG. 7
) thereof is subjected to drawing, whereby a small-diametered portion
14
is formed in this end portion. A female serration
15
is formed on the inner peripheral surface of this small-diametered portion
14
. The inner shaft
13
as a whole is also of a tubular shape and one end portion (the right end portion as viewed in
FIGS. 7 and 8
) thereof is widened to thereby form a large-diametered portion
16
. A male serration
17
is formed on the outer peripheral surface of this large-diametered portion
16
to be engaged with the female serration
15
.
Also, the fore end portion (the right end portion as viewed in
FIGS. 7 and 8
) of the large-diametered portion
16
is squeezed a little in the diametral direction thereof, whereby a first deformed portion
18
of an elliptical cross-sectional shape is formed over a length L. The major axis d
1
of this first deformed portion
18
is larger than the diameter d
0
of the body portion of the large-diametered portion
16
, and the minor axis d
2
of the first deformed portion is smaller than this diameter d
0
(d
1
>d
0
>d
2
). Note that the diameters of the large-diametered portion
16
on which the male serration
17
is formed are all represented by the diameter (pcd) of that portion of the serration which corresponds to a pitch circle.
On the other hand, the fore end portion (the left end portion as viewed in
FIGS. 7 and 11
) of the small-diametered portion
14
is also squeezed a little in the diametral direction thereof, whereby a second deformed portion
19
of an elliptical cross-sectional shape is formed over the length L. The major axis D
1
of this first deformed portion
19
is larger than the diameter D
0
of the body portion of the small-diametered portion
14
, and the minor axis D
2
of the second deformed portion
19
is smaller than this diameter D
0
(D
1
>D
0
>D
2
). The diameters of the small-diametered portion
14
on which the female serration
15
is formed are also all represented by the diameter (pcd) of that portion of the serration which corresponds to a pitch circle.
The diameter D
0
of the small-diametered portion
14
is made slightly larger than the diameter d
0
of the large-diametered portion
16
(D
0
>d
0
) so that the female serration
15
and the male serration
17
may be brought into loose engagement with each other in portions other than the first and second deformed portions
18
and
19
. However, the major axis d
1
of the first deformed portion
18
is made slightly larger than the diameter D
0
of the body portion of the small-diametered portion
14
(d
1
>D
0
) and the minor axis D
2
of the second deformed portion
19
is made slightly smaller than the diameter d
0
of the body portion of the large-diametered portion
16
(D
2
<d
0
).
The outer shaft
12
and the inner shaft
13
having such shapes as described above are combined together as shown in
FIG. 7
to thereby provide the shock absorbing type steering shaft
11
. More specifically, the large-diametered portion
16
formed on one end portion of the inner shaft
13
is located inside the small-diametered portion
14
formed on one end portion of the outer shaft
12
, and the female serration
15
on the inner peripheral surface of the small-diametered portion
14
and the male serration
17
on the outer peripheral surface of the large-diametered portion
16
are brought into engagement with each other. In this state, the first deformed portion
18
formed on the fore end portion of the large-diametered portion
16
is pushed into a base end portion (the right end portion as viewed in
FIGS. 7 and 11
) of the small-diametered portion
14
while being elastically deformed (or plastically deformed). Also, the second deformed portion
19
formed on the fore end portion of the small-diametered portion
14
is pushed into a base end portion (the left end portion as viewed in
FIGS. 7 and 8
) of the large-diametered portion
16
while also being elastically deformed (or plastically deformed).
Accordingly, in the state in which the outer shaft
12
and the inner shaft
13
are combined together as shown in
FIG. 7
, the outer peripheral surface of the first deformed portion
18
is frictionally engaged with the inner peripheral portion of the base end portion of the small-diametered portion
14
, and the inner peripheral surface of the second deformed portion
19
is frictionally engaged with the outer peripheral portion of the base end portion of the large-diametered portion
16
, respectively. As a result, the outer shaft
12
and the inner shaft
13
are coupled together for the transmission of a rotational force between the two shafts
12
and
13
, but against relative displacement in the axial direction so long as a strong force is not applied.
As described, the coupling between the outer shaft
12
and the inner shaft
13
is effected by bringing the first and second deformed portions
18
and
19
formed on the metallic outer shaft
12
and the inner shaft
13
into pressure-fitting to partner members and therefore, the heat resisting property of the coupling portion becomes sufficient and it never happens that the supporting force of the coupling portion becomes deficient depending on use conditions. Also, the first and second deformed portions
1
Miles & Stockbridge P.C.
NSK Ltd.
Zeender F.
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