Note: Descriptions are shown in the official language in which they were submitted.
~12~243
The object of the present invention is an improved
wheel disk for automotive vehicles and especially for utility
vehicles. In particular it relates to the shape to be given
to a wheel disk in order to impart to it a minimum thickness
at each point and an optimum resistance to fatigue. The
invention makes it possible to decrease the weight of the disk
to the utmost while retarding the appearance of cracks in the
zone oE the disk closc to the hu~.
The known disks, which are of constant thickness,
have needless and expensive excess thicknesses in certain
regions; it has therefore been attempted to lighten them by
varying their thickness; this variation may reach 70~. However,
in order to avoid ruptures in the zone close to the hub, the
thickness of the disk is increased in said zone and, for reasons
of manufacture, in the other zones of the disk, although to a
lesser extent; this results in an increase in the weight to
the detriment of a saving of material and energy.
The invention applies to metal or other wheels whose
disk has a curved generating profile, the thickness of which
is variable by at least 20~.
In accordance with the broad concept of the present
invention, there is provided and claimed herein a wheel disk
with a generating curve profile, the thickness of which is
variable by at least 20~, having four successive zones; the
first zone being a substantially flat central hub attachment
zone having a standardized diameter of attachment D and termina-
ting at an outside diameter D ; the second zone being of concave
curvature and extending from said first zone and terminating at
an outside diameter D2; the third zone being of convex curvature
and extending from said second zone and terminating at an out-
side diameter D3; the fourth zone being a peripheral zone and
extending from said third zone and connectable to a rim with a
-- 1 -- ~
1~22~3
standardized nominal diameter D4. This wheel disk is
characterized by the fact that
(a) the value of the diameterD2 is less than a value
m which is a function of the diameter D and which is given by
the formula
m (D) = 103,710 U - 342,050 u6 + 444,880 U
- 290,390 U4 + 99,506 U3 - 16,712 u2
+ 1,279.2 U + 2~1.91
with U = (D-205)/220, in which D is expressed in millimeters;
and
(b) the axial length d of the second zone is at least
equal to 0.289 (D2 ~ Dl).
The accompanying drawing is a profile or meridian cross-
section of the upper half of a wheel disk made according to the
invention.
The meridian cross-section of this type of wheel
disk 1 is composed of four successive zones: a central attach-
; ment zone Zl~ substantially flat, extending away from the axis
X-X', intended to cooperate with the hub of the vehicle and
which stops at the point A; a zone Z2 whose average curvature
ls relatively high, referred to by definition as positive or
concave, this zone Z2 extending from the point A to the
point B; a zone Z3 of a negative or convex curvature which
- la -
1~22~3
stops at the point C; a peripheral zone Z4, which may or may
not be cylindrical and in which the connection to the rim 2
takes place. In order to determine the zone Z2' the point B
is defined as being the first point, starting from the axis,
where the curvature becomes negative.
The shape of this type of disk which forms the
object of the invention will be described with reference to
one of its faces, called the first face Sl: the second face
S2 is obtained from the first face Sl by the calculation of
the variable thickness of the disk at each point of a meridian
cross section. By definition, the first face Sl is that which
is on the side of the zone Z2 with respect t~ the median plane
of the zone Zl; it is this first face Sl whi~ch is generally
applied against the hub (not shown) by attachment elements
passing through holes 3, at least on the rear wheels of trucks
in the case of the mounting of twin wheels. In the drawing,
this first face Sl is on the left side.
Standards define the following diameters, measured
from the axis X-X' of the wheel :
- the standardized diameter of attachment D, which
is the diameter of the cylinder on which there are arranged
the geometrical axes of the mechanical elements for the
attachment of the wheel (IS0/DIS 4107; DIN 74361), and
- the standardized nominal diameter D4 of the rim 2
(TRA STANDARD).
In accordance with the present invention, a wheel
disk 1 with a curved generating profile, the thickness of which
is variable by at least 20 %, is characterized by the fact
that the value of the outside diameter D2 of the zone Z2
defined above isless than aval~e m which is a function of the
diameter D defined above and which is given by the formula :
Z2~3
m(D) = 103,710 U7 - 342,050 IJ6 + 444,880 U5
-- 290,390 U + 99, 506 J 16,712 U
+ 1,279.2 U + 281.91
with U = (D-205 ~/220, in which D is expressed in millimeters,
and by the fact that the axial length d of the zone Z2 ~ that
is to say the projection of its generating curve AB on the
axis X-X' of the wheel, is at least equal to 0.289 (D2-Dl )
in which Dl is the outside diameter of the zone Zl defined
above.
In a preferred variant of the invention, the improved
wheel disk 1 is characterized by the fact that the value of the
B outside diameter ~1 f the zone Zl is less than a value ~ ~
which is a function of the diameter D given by the formula :
(D) = 56,722 U7 - 181,150 U6 + 226,700 U5
- 141,660 U4 + 46,435 U3 -7,501.2 U2
+ 667.51 U + 264.97
with U = (D-205)/220, in which D is expressed in millimeters.
In another preferred variant of the invention, the
improved wheel disk is characterized by the fact that the
value of the outside diameter D3 of the zone Z3 defined above
being less than a value b which is a function of the diameter
D4 defined above given by the formula :
b (D4) = 17,549 X -- 63,951 X6 + 89,945 x5 -- 61,771 x4
+ 21,850 x3 - 3,955 X2 + 527.37 x 365.45
with x = (D4-419.1)/203.2, in which D4 is expressed in milli-
meters, the product of the average curvature of the zone Z3
times the diameter D is greater (in absolute value) than a
value g which is a function of the diameter D given by the
following formula, this average curvature being convex on the
side of the first face Sl defined above of the disk :
g (D) = - 5,319.7 U + 18,307 U6 - 25,047 U5 + 17,346 U4
il222~3
-6,361.8 U3 + ~,152.5 u2 - 77.16 U + 1.2352
with U = (D-205)/220, in which D is expressed in millimeters.
Finally, in a particular case, the zone Z2 could be
reduced to a straight line generating a cylinder or even
reduced to a point generatin~ a circle of the diameter Dl = D~;
in this latter case, the points A and B would then merge in
the drawing.
Two embodiments of the invention will now be describ-
ed, by way of illustration and not of limitation, with reference
to the accompanying drawing :
1st Example: A wheel having a diameter D of 335 mm
and a diameter D4 of 571. 5 mm (22, 5" ) has the following charac-
teristics :
- diameter Dl less than 397.2 mm, for instance 393 mm
- diameter D2 less than 427.0 mm, for instance 419 mm
- diameter D3 less than 514.5 mm, for instance 498 mm
- value of d greater than 7.5, for instance 13 mm
- radius of curvature R of the zone Z3 1~ss than
251.9 mm, for instance 70 mm.
2nd Example: A wheel having a diameter D of 225 rnm
and a diameter D4 of 444.5 mm (17.5") has the following
characteristics:
- diameter Dl less than 290.2 mm, for instanc~ 290 mm
- diameter D2 less than 317 .6 mm, for instance 317.5mm
- diameter D3 less than 399.7 mm, for instance ~99 mm
- value of d greater than 7.9 mm, for instance 11.2 mm.
On the wheel disks described above, the decrease of
the stresses in the attachment zone Zl makes it possible to
reduce considerably the thickness of the disk while retaining
the same fatigue strength measured in accordance with the known
tests run on a testing drum with cambered wheels and by tests
l~ZZ2~3
on vehicles.
In other words, an improved wheel disk in accordance
- with the present invention may have a thickness which is con-
siderably less than that of a known disk all other things
being equal, that is to say with the same loads, the same
material, the same vehicle, etc., therefore, the invention
results in a very great reduction in weight and cost.
Of c~ourse the symmetry of revolution of the disks
which was implicit in all of the foregoing ~ay be destroyed
in any known manner by holes or any machining intended for
aesthetic or technical purposes, without thereby going beyond
the scope of the present invention.
