Land vehicles: wheels and axles – Wheel – Compression wheel
Reexamination Certificate
1999-09-07
2001-12-25
Morano, S. Joseph (Department: 3617)
Land vehicles: wheels and axles
Wheel
Compression wheel
C301S065000
Reexamination Certificate
active
06332653
ABSTRACT:
BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
The present invention relates to a disc wheel for a passenger car.
Conventionally, the plate-like disc in a discs used wheel for motor vehicles such as passenger cars, motor trucks and the like are press formed. In such press formation, it is difficult to set the distribution of the thickness of the disc to a preferred level, and a description of the problems resulting follows.
Generally, in order to emit a breaking heat, the disc wheel for a motor vehicle is formed with a ventilation hole
103
in a portion outside a hat portion
102
of a disc
101
, as shown in
FIGS. 25A and 25B
. Accordingly, this ventilation hole portion
104
generally weakens in a rotational bending fatigue test and a crack
105
is generated in the ventilation hole portion
104
, as shown in
FIGS. 26A
,
26
B and
26
C. In order to strengthen this, it is necessary to increase the thickness of the portion
104
. Further, in some cross sectional shapes, a bolt hole
10
may weaken the hub mounting portion
106
and generate a crack
105
.
Accordingly, in the structure formed by a press molding as mentioned above, the ventilation hole portion
104
or the hub mounting portion
106
can only have adequate strength by being as thick as the whole of the disc, and must be at least as thick as the weakest portion. Accordingly, unless the strength of the ventilation hole portion
104
or the hub mounting portion
106
can be improved, a reduction of weight is limited.
Furthermore, when the thickness of the whole of the disc is increased, the stress in the welding portion between the disc and a rim generates a crack
105
′ in the rim drop portion of a welding portion WO, as shown in FIG.
26
A.
Moreover, in order to prevent interference with the brake portion
400
as shown in
FIGS. 4 and 10
and improve the design, the shape of the disc is frequently limited. Accordingly, an optimum shape is impossible to achieve and the stress balance deteriorates, so that in many cases, the fatigue life cannot be improved without increasing the thickness. As mentioned above, when partially increasing thickness, it is necessary to increase the thickness of the whole disc and the amount of weight that can be reduced is limited
Furthermore, in a double mounting type disc wheel used in a motor truck and a motor bus, the thickness of the joint welding portion
203
in the disc
202
with respect to a rim
201
is less than the thickness of a hub mounting portion
204
, and the thickness of the hat portion
205
is less than the thickness of the joint welding portion
203
, as shown in
FIG. 27
, which produces a disc wheel having uneven thickness. This type of disc wheel is, for example, disclosed in Japanese Patent Unexamined Publication No. 7-257101. This structure aims to prevent stress on the joint welding portion
203
in the disc, improve the fatigue strength and to reduce weight. However, if a disc wheel with uneven thickness is used in the hat portion, ventilation holes are formed in the thin hat portion
205
, so that the crack mentioned above is generated in the hat portion
205
Also, as shown in
FIG. 27
, the thickness of the flange portion corresponding to the joint welding portion
203
in the disc
202
is generally greater than the thickness of the hat portion
205
. Although, the flange portion
203
may have a low stress ratio and a reduced thickness but the rim can be made thinner than the disc, and a significant difference in thickness between the rim and the disc can cause stress that easily produces a crack in the rim side of the welding portion W
O
with respect to the wheel strength.
Accordingly, as mentioned above, when the flange portion in the disc
202
is thick, it is necessary to make the rim thick in order to secure fatigue strength and reduce the difference in thickness, so that it increases the weight of the wheel.
Furthermore, although a disc wheel with uneven thickness in a passenger car shown in
FIG. 28
, and disclosed in Japanese Patent Unexamined Publication No. 1-104423, contains a method of applying an excess metal
303
to a hat R portion
302
of a disc
301
so as to increase the thickness, the thickness of the ventilation hole portion
304
is not increased in the disc and the same crack mentioned above is easily generated in the ventilation hole portion
304
.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide a disc wheel for a passenger car, especially a disc wheel for a passenger car fitting the flange of the disc proportionate to a drop portion of a rim, which improves stress balance, improves the fatigue life in a rotational bending fatigue test, reduces weight, and prevents a crack in the ventilation hole portion.
In order to solve the problem mentioned above, in accordance with the present invention, there is provided a disc wheel for a passenger car comprising a plate-like rim, a plate-like disc, the disc having a hub mounting portion extending in a direction perpendicular to the axis thereof, a hat middle portion continuously extending from the hub mounting portion toward the outer side in a radial direction the outer side in an axial direction, a hat top portion continuously extending from the hat middle portion, a ventilation hole portion continuously extending from the top portion toward an inner peripheral surface of the rim and a flange portion continuously extending from the ventilation hole portion and fitted in the inner peripheral surface of the rim, and the rim inner peripheral surface and the disc flange being welded, wherein the thickness of the disc is varied in a diametrical direction at to either the hub mounting portion, the hat middle portion the hat top portion, the ventilation hole portion, or the flange portion.
In the first aspect of the present invention, the structure can be made such that the thickness of the hub mounting portion is equal to or less than the original thickness of the raw material, the thickness of the hat middle portion and the hat top portion is less than that of the hub mounting portion thickness of the ventilation hole portion is set to be original thickness of the raw material, and the thickness of the flange portion is less than thickness of any portion between the hub mounting portion and the ventilation hole portion.
Although the hat outer peripheral portion of the disc is inherently structured so that stress ratio is low thickness is small, the ventilation hole is formed in the hat outer peripheral portion such as the disc wheel for the passenger car and reduces the cross sectional area at this portion is reduced and a rigidity is lowered. Further, a stress is concentrated to the ventilation hole portion and a crack is easily generated
Therefore, according to the first aspect, it is possible to increase the rigidity and reduce the stress ratio of the ventilation hole portion by increasing the thickness of the ventilation hole portion.
Accordingly, it is possible to make the stress balance optimum by setting the thickness in each of the portions as in the present invention.
Also, in the first aspect mentioned above, the structure can be made so that when setting the thickness of the raw material of the disc to 1, the thickness of the hub mounting portion is between 0.8 and 1.0, the thicknesses of the hat middle portion and the hat top portion are between 0.75 and 0.90, the thickness of the ventilation hole portion extending from the hat top portion to the flange portion is the thickness of the flange portion is between 0.5 and 0.7, and a rounded portion connecting the respective portions can be a gradually changing rounded portion In this structure, the same operation as that of the first aspect can be obtained.
Furthermore, in the structure mentioned above, the thickness of the drop portion in the rim can be between 0.4 and 0.7 when setting the thickness of the raw material of the disc to 1.
In accordance with the first aspect, since the flange portion of the disc is made thin as mentioned above, it is possible to reduce the differen
Shimizu Kiichi
Takagi Shigemasa
Bellinger Jason R.
Central Motor Wheel Co., Ltd.
Connolly Bove Lodge & Hutz LLP.
Morano S. Joseph
LandOfFree
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