Machine element or mechanism – Control lever and linkage systems – Elements
Reexamination Certificate
2002-02-08
2003-07-22
Joyce, William C (Department: 3682)
Machine element or mechanism
Control lever and linkage systems
Elements
C403S012000, C403S021000
Reexamination Certificate
active
06595083
ABSTRACT:
BACKGROUND OF THE INVENTION
A present invention relates to a steering wheel for vehicles.
Generally, a steering wheel includes an annular grip, spokes and a pad. The spokes extend from the grip towards the center of the steering wheel. The pad is located in the center of the grip ring. A metal grip core and a metal spoke core, which are made of magnesium alloy, are embedded in the grip and the spoke, respectively. A polyurethane layer covers the grip core and the spoke core. A boss including a boss body and a boss plate is connected to the spoke core below the pad by insert molding. The steering wheel is installed on the end of a steering shaft by engaging the boss with the steering shaft: The steering wheel is fixed by fastening a nut to threads on the end of the steering shaft.
In such steering wheels, when installing the steering wheel to the steering shaft, it is necessary to fasten the nut from above the boss. Accordingly, a pad that includes an airbag can not be attached on the cores in advance. The pad must be installed on the cores after the steering wheel is attached to the steering shaft.
On the other hand, it is known to employ a yoke-type boss, which is fixed to the steering shaft from the side by a bolt. The body of the yoke type boss includes a cylindrical portion with inner splines, which engage with outer splines on the steering shaft, and a C-shaped yoke portion, which is integrally formed with the cylindrical portion. Bolt holes are formed in facing parts of the yoke portion. At least one of the bolt holes has inner threads. A neck portion corresponding to the bolt holes is formed on the outer surface of the steering shaft.
After the boss is engaged with the steering shaft, a bolt is fastened in the bolt holes. Rotation of the steering wheel with respect to the steering shaft is prevented by engaging the splines of the boss with those of the steering shaft and by tightening the yoke portion with the bolt. The shaft of the bolt engages the neck portion, and axial movement of the steering wheel is also prevented.
When the yoke-type boss is used, a steering wheel assembly is installed on the steering shaft. The assembly includes the air bag device in the pad attached on the cores. Since the steering wheel is assembled before the installation, it can be transported as an assembly including the pad, which improves efficiency.
In the steering wheel assembly, the airbag device must be provided in the middle of the cores facing the driver. However, since the yoke-type boss is located in the center of the cores, supports for attaching the airbag device can not be formed in the center of the cores. This limits the formation of the airbag supports. It is necessary to make the airbag supports strong because, when the airbag is activated, a great load acts on the airbag supports. If the airbag supports are deformed when the airbag is activated, the air bag may not open in the proper direction.
Further, in the steering wheel assembly, fastening the bolt is troublesome. A worker must adjust the position of the bolt with one hand and tighten the bolt by a tool with another hand. Also, this work is done in a relatively small space, and the work takes time.
The weight of the steering wheel can be reduced by forming the cores by die casting using a light metal like magnesium. The light metal may also be aluminum or magnesium alloy. However, magnesium resists deformation. Thus, when a large load is applied to the steering wheel, the cores resist deformation. Deformation is desirable to absorb energy.
SUMMARY OF THE INVENTION
The boss will now be further described referring to FIG.
11
. The boss
51
includes a cylindrical portion
52
a,
a boss body
52
having yoke
52
b,
and a boss plate
53
. The boss plate
53
is welded to the cylindrical portion
52
a
of the boss body
52
. A step-like bend
53
a
is formed on the boss plate
52
. An insert portion
53
b
is on the rim of the boss plate
53
and is located toward the lower surface of the boss plate
53
. When a metal core
56
is molded on the insert portion
53
b
of the boss plate
53
using molds
54
,
55
, the metal core
56
does not project forward of the lower surface of the boss plate
53
.
Molten metal that flows in a cavity for molding the metal core
56
in the molds
54
,
55
is subjected to high pressure, and there is a concern that the molten metal in the cavity might leak toward the boss
51
, thus producing flash. Therefore, to prevent leakage of the molten metal, surfaces
55
a,
54
a
of the inner margins of the molds
54
,
55
contact the boss plate
53
. In other words, the molds
54
,
55
include anti-flash surfaces
54
a,
55
a.
However, since a bend
53
a
is formed on boss plate
53
, the width W
2
(as measured in the left to right direction of
FIG. 11
) of the anti-flash surfaces
54
a,
55
a
is too small. Therefore, flash, which extends from the inner edges of the molds
54
,
55
, is not prevented completely.
An installation structure of a prior art boss will now be described with reference to FIG.
14
. As shown in
FIG. 14
, a circular through hole
252
is formed on a boss plate
251
. A lower end of the cylindrical portion
253
a
of the boss body
253
occupies the through hole
252
. The boss plate
251
is welded to the cylindrical portion
253
a
of the boss body
253
. The projection amount P
2
of the boss body
253
rearward of the boss plate
251
(towards the airbag) is relatively large, and the boss body
253
thus interferes with the installation of an airbag device. The size of the steering wheel
11
also increases.
To solve this problem, it is possible for the boss body
253
to be further inserted forward in the through hole
252
of the boss plate
251
and then fixed by welding. In this way, the rearward projection amount of the boss body
253
from the boss plate
251
is reduced, and the size of the steering wheel is reduced. However, when the boss body
253
is further inserted in the through hole
252
of the boss plate
251
, a slit
253
c
of a yoke portion
253
b
overlaps the weld bead
254
. The part of boss body
253
with slit
253
c
is not uniformly deformed during welding, and strain is caused from welding. The length of the slit
253
c
may be shortened. However, if this were done, the axial length of the yoke portion would be shortened, and consequently the yoke portion
253
b
will not easily flex. Therefore, when a bolt is tightened in the bolt hole, the radius of the yoke portion
253
b
cannot be easily reduced. As a result, the steering wheel
11
may not be secured to the steering shaft
30
.
A first objective of the present invention is to provide a steering wheel that has a strengthened airbag supports on the cores.
A second objective of the present invention is to provide a steering wheel formed by die casting and that absorbs energy when a predetermined load is applied.
A third objective of the present invention is to provide a steering wheel that makes the work of installing the steering wheel to the steering shaft faster and easier.
To achieve the above objectives, the present invention provides a steering connected to a distal end of a steering shaft with a boss, the steering wheel having a grip for rotating the steering shaft, the steering wheel comprising: a metal grip core embedded in the grip; a plurality of spokes that extend from the grip; a metal spoke core embedded in each spoke, wherein the spoke core is integrally molded with the grip core by die casting; a layer of material covering the grip core and the spoke core; a pad, which is located over the boss in the center of the grip; a cylindrical portion, which is part of the boss, wherein the cylindrical portion receives the distal end of the steering shaft, wherein the cylindrical portion is a part of the boss; a fastening mechanism for fastening the boss to the steering shaft, wherein the fastening mechanism is integrally formed with the cylindrical portion; a boss plate fixed to the cylindrical portion of the boss, wherein the boss plate includes a rim which is embedded in
Hosoi Akio
Nagata Atsushi
Joyce William C
Posz & Bethards, PLC
Toyoda Gosei Co,., Ltd.
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