Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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The present invention relates to a tread design for a
pneumatic motor-vehicle tire having at least three relatively
wide and essentially straight peripheral grooves that divide
the tread into tread bands that run in the peripheral
direction, and having transverse grooves that are spaced
apart from each other in the peripheral directiron on each
tread half, said grooves dividing the tread bands at least
partially and which, when viewed across the width of the
tread, preferably run continuously or along an approximately
V-shaped curve.
Tires with treads of this particular kind are being designed
to an ever-increasing degree, particularly for high speeds.
Such high speed tires have a very small cross section ratio
and a relatively wide tread. Of primary importance in the
design of such tires is good wet-grip behaviour, above all at
high speeds, which is important in the centre region of the
ground contact area of the tire. In addition, the tires
should have good response behaviour both on wet and on dry
road surfaces. In addition to the effective removal of water
from the ground contact area, it is also extremely important
to keep noise generation as low as possible at high speeds.
Variations of a pneumatic motor vehicle tire of the type
described above are shown and described, for example, in EP-
A-0175829. Common to all of the embodiments shown in this
publication is the fact that along the centre peripheral line
of the running surface there is a continuous running surface
band that is separated from the laterally adjacent running
surface band by relatively narrow and straight peripheral
grooves. The configuration of the tread structure in the
middle range is such that optimal wet-grip behaviour cannot
be attained, particularly at high speeds.
` It is an object of the present invention to provide a tread
pattern for a pneumatic motor vehicle tire, particularly one
that is intended for high speed operation, such that
optimization of the chaxacteristics as set out above, which
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is to say good wet-grip behaviour, low noise development, and
high reaction capabilities in response to steering forces are
achieved even in the higher speed ranges.
According to the present invention there is provided a tread
pattern for a pneumatic motor-vehicle tire havi~g at least
three relatively wide, substantially straight peripheral
grooves that divide the tread into tread bands that run in a
peripheral direction, and having on each half of the tread
pattern transverse grooves that are spaced apart from each
other in the peripheral direction, said transverse grooves
dividing the tread bands at least in part, wherein within the
central area that accounts for approximately one-third of the
total area of the tread, there is at least one wide
peripheral groove into which no transverse grooves open, in
the central area the running surface portion is at least lO~
greater than in the two side areas, the transverse grooves
form blind grooves in the tread bands that are laterally
adjacent to the peripheral groove, and the end areas of said
blind grooves are crossed by a narrow, O.5 to 2 mm wide,
peripheral groove.
The measures according to the present invention create a
tread pattern that satisfies the demands that have been made,
even in the higher speed ranges. The rolling surface portion
provided in tbe central area, which is high relative to the
sid~ areas, causes a high level of profile tread stiffness in
this area. It has been shown that tires provided with the
tread pattern according to the present invention display very
good response behaviour around the null position in all speed
ranges. The narrow peripheral grooves that are additionally
provided in the central area also have a very good effect on
minimizing the noise of the tire.
It is preferred that in the central area the rolling surface
portion is greater than or equal to 70~, and in addition it
is also preferred that there be a single wide peripheral
groove along the centre line in this area
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In a further embodiment of the invention, in order to reduce
noise generation there is a narrow, 0.5 to 2 mm, wide
peripheral groove in each of the tread bands on the shoulders
of the tire.
The invention will now be described in more detail, by way of
example only, with reference to the accompanying drawings in
which:-
Figure 1 shows a plan view of a section of the tread of a
first embodiment of a pneumatic motor-vehicle tire; and
lo Figure 2 shows a plan view of a section of the tread of a
second embodiment o~ a pneumatic motor-vehicle tire.
The tread pattern shown in the Figures is intended in
particular for a high speed radial tire for passenger cars.
As used herein the term tread-width B should be understood to
mean the greatest axial width of the tread measured in the
ground contact area.
As figure 1 shows, along the centre line M-M the tread
pattern has a wide straight peripheral groove 1 and two
additional wide peripheral grooves 2 in the two tread halves
that are arranged symmetrically to the centre line M-M. The
three peripheral grooves 1, 2 divide the tread into tread
bands 3, 4, 5, and 6 that run in the peripheral direction.
In each of the two tread halves there is in each instance a
; plurality of transverse grooves 7 that are spaced apart from
each other in the peripheral direction and which divide the
tread bands 5 and 6 that are on the shoulders of the tire
into individual blocks 8 and which, in contrast to this, form
blind grooves 7a in the central tread bands 3 and 4, which do
not open out into the peripheral groove 1 that runs along the
centre line M-Mo An area of at least 15% of the tread-width
B that is free of transverse grooves is left in the central
~! area of the tread patternO
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'' ~iewed across the whole of the tread width B, the transverse
grooves follow an essentially shallow S-shape. The sections
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of the transverse grooves 7 that form the blind grooves 7a
subtend an angle alpha with the centre line ~-~ that is
between 50 and 70 on the one tread half, and which on the
other tread half, subtend an angle alpha' in the range
between 110 and 130. In the present embodiment, these
angles amount to approximately 60 or 120, res~ectively. In
the shoulder tread bands 5 and 6, the transverse grooves are
set at an angle beta of approximately 75 to 90 or an angle
beta' of 90 to 150 to the centre line M-M. As shown in the
present e~bodiment, preferred values are at approximately 83
or 97.
Both the sections of the transverse grooves 7 that for the
blind grooves 7a as well as the sections of these that are on
the outside of the tread are preferably so configured that
their width increases continuously towards both sides of the
tread, the extent of this widening being relatively small.
The width of the tread bands 3 and 4 that are arranged in the
centre of the tread lies in the range between 20 and 30% of
the tread width B, and preferably the width of these tread
bands 3 and 4 amounts to approximately 25%.
Running parallel to the centre line M-N, there is in each
tread band 3, 4, 5, 6, a narrow 0.5 to 2 mm and preferably
approximately ~ mm wide, straight peripheral groove 9. This
arrangement is symmetrical to the centre line M M. The depth
of the narrow peripheral grooves 9 amounts to at least 20% of
the other tread depths. The peripheral grooves 9 that are
arranged in the tread bands 3, 4 run at a distance from the
closed end areas o~ the blind grooves 7a and cross these.
This arrangement is particularly effective in combatting the
noise developed by this tread at high speeds.
If the tread is divided across its width B into three
approximately equally large peripheral areas, such that the
central area I is symmetrical to the centre line M-M and the
side areas II, III are each laterally adjacent thereto, then
the running surface in the central area is at least 10%
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greater than the running surface in the side areas II, III.
Here, the running surface is understood in each instanc~ to
be that portion of the total area of the individual areas I,
II, III, which come into co~tact with the ground when the
tire is in use. In the above embodiment, the running surface
in the side areas II, III amounts in each insta~ce to
approximately 60%, and in the central area I, to
approximately 72~. The high running surface portion in the
central area I increases the stiffness in this area and, in
lo conjunction with the peripheral groove 1 that runs along the
centre line M-M, has an extremely favourable effect on the
response behaviour o~ tires provided with this type of tread
pattern when such tires are operated at high speeds.
Figure 2 is an embodiment of a tread pattern for a
directional pneumatic motor-vehicle tire, wherein the sole
difference between this tread pattern and that shown in
figure 1 is that in figure 2, the two running surface halves
are mirror images of each other relative to the centre line
M-M. Accordingly, the angle alpha that the blind grooves 7a
subtend with the centre line M-M as well as the angle beta
that the sections of the transverse grooves 7a that run in
the area of the tread bands 5 and 6 subtend with the centre
line M-M are equally large in both halves of the tread. The
arrangement of the peripheral grooves 1 and 2, of the narrow
peripheral groove 9, as well as the division into three
individual peripheral areas I, II, and III is accordingly
similar to that in the first embodiment, so that no
repetition is required in this respect.
In another embodiment of the present invention~ not shown
separately herein, it is possible to have two grooves that
run on both sides of the mid-line in place of a peripheral
groove that runs along the mid-line, these two grooves then
being separated by a relatively narrow, continuous band that
runs along the mid-line.
