Note: Descriptions are shown in the official language in which they were submitted.
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Description
Title of the Invention
Pneumatic vehicle tire
The invention relates to a pneumatic vehicle tire with a directional tread
strip with
two shoulder-side profile ribs, two middle profile ribs and one central
profile rib, the
profile ribs being separated by two shoulder-side circumferential grooves and
two
middle circumferential grooves, the shoulder-side profile ribs and the middle
profile
ribs being divided into profile blocks by way of transverse grooves which run
in a
V-shaped manner in plan view across the width of the tread strip, run parallel
to
one another within the profile ribs, open into the shoulder-side
circumferential
grooves and have a width from 3.5 mm to 6.5 mm, and the shoulder-side
circumferential grooves having groove sections which run inclined to the
circumferential direction in plan view, each divide a profile block of the
middle
profile ribs from a profile block of the shoulder-side profile ribs, and have
a leading
end, encountering the underlying surface first when the tire rolls during
forward
travel, and a trailing end.
Such a pneumatic vehicle tire, which is a winter tire provided with spikes in
the
tread strip, is known, for example, from DE 10 2015 221 118 Al. The tire has a
tread strip with a central profile rib, two middle profile ribs and two
shoulder-side
profile ribs. The central profile rib is traversed by sipe-like transverse
grooves
running parallel to one another in plan view. The transverse grooves formed in
the
shoulder-side profile ribs and in the middle profile ribs run in an arc shape
in plan
view. The shoulder-side circumferential grooves have groove sections running,
in
plan view, inclined to the circumferential direction and at the same time ¨
based on
the circumferential direction ¨ running inclined in the opposite direction to
the
transverse grooves, which each separate a profile block of the respective
middle
profile rib from a profile block of the adjacent shoulder-side profile rib.
Spikes are
anchored in the profile blocks of the middle profile ribs and the profile
blocks of the
shoulder-side profile ribs, which are surrounded by depressions formed in the
profile blocks and acting as ice reservoirs.
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Pneumatic vehicle tires of the type mentioned above are mainly used as winter
tires. The transverse grooves running in a V-shaped manner across the width of
the tread strip enable a high level of water drainage in the direction of the
tread
strip shoulder (good wet performance) on the one hand and a certain absorption
of
snow when driving on snow on the other, as a result of which ¨ via the effect
of
snow-snow friction ¨ advantages in terms of snow performance can be achieved.
Since winter tires are frequently also driven on dry roads, the dry
performance of
the tires should not be neglected.
The object of the invention is to improve the dry, wet and snow performance as
equally as possible in a pneumatic vehicle tire of the type mentioned at the
outset.
The stated object is achieved according to the invention in that the
transverse
grooves, which run in the middle profile ribs, end in front of the respective
middle
circumferential groove at a spacing determined in the axial direction, the
groove
sections of the shoulder-side circumferential grooves, seen in plan view,
being
inclined to the circumferential direction in such a way that the leading ends
of the
groove sections are closer to the tire equatorial plane in comparison with the
trailing ends of the groove sections.
The inventively inclined groove sections of the shoulder-side circumferential
grooves, in combination with the transverse grooves, bring about effective
drainage of the tread strip profile when driving on wet roads, in particular
improved
water drainage from the ground contact area, and thus improved wet
performance.
The middle profile ribs are increased in their rigidity due to the "blind
groove-like"
transverse grooves ending in front of the respective middle circumferential
groove,
which improves the power transmission from the tire to the ground and thus the
dry performance. In addition, snow accumulates well in the blind groove-like
transverse grooves when driving on a snow-covered road and is efficiently
compacted, thereby enhancing the effect of snow-snow friction and thus
achieving
advantages in terms of snow performance.
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According to one preferred embodiment, the spacing, at which the transverse
grooves running in the middle profile ribs end in front of the respective
middle
circumferential groove, is from 3.0 mm to 15.0 mm, in particular 5.0 mm to
10.0
mm. This design of the blind groove-like transverse grooves is particularly
favorable with regard to drying performance.
Furthermore, it is advantageous if the groove sections of the shoulder-side
circumferential grooves, in plan view, extend at an angle of 2 to 7 , in
particular of
at most 5 , with respect to the circumferential direction. Such inclined
groove
sections support water drainage in the direction of the lateral edges of the
ground
contact area, with a high water drainage capability in the circumferential
direction
being maintained in the shoulder-side circumferential grooves at the same
time.
The wet performance is thus further improved.
Another preferred embodiment is characterized in that connecting grooves run
between the ends of the transverse grooves on the inside of the tread strip,
which
run in the middle profile ribs, and the middle circumferential grooves, which
connecting grooves are of narrower and shallower design than the transverse
grooves and have a depth of preferably 2.0 mm to 5.0 mm and a width of
preferably 1.5 mm to 3.5 mm. The connecting grooves "decouple" the profile
blocks of the middle profile ribs from each other to a certain degree, which
contributes to the occurrence of an even wear pattern of the tread strip and
thus to
maintaining good dry performance. The preferred, correspondingly shallow
design
of the connecting grooves supports snow accumulation in the transverse grooves
when driving on snow.
The connecting grooves, in plan view, preferably run in the axial direction or
at an
angle of up to 5 with respect thereto.
According to a further preferred embodiment, the central profile rib is
traversed by
transverse grooves which run parallel to one another in plan view and which
each
consist of two groove sections which run toward one another in a V-shaped
manner and at an angle of at most 12 with respect to the axial direction, the
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inclination of the groove sections with respect to the axial direction being
in the
same direction as the inclination of the transverse grooves running in the
respective middle profile rib that is nearest, and the transverse grooves in
the
central profile rib having a width of preferably 1.8 mm to 3.5 mm and a
maximum
depth of preferably 70% to 100%, in particular 100%, of the profile depth. The
selected V-shape of the transverse grooves contributes to the drainage of the
central profile rib and therefore to an improvement in wet performance. If the
transverse grooves are designed according to the preferred depth and width,
the
central profile rib has a high level of rigidity, which is advantageous for
dry
performance.
According to a further preferred embodiment of the invention, the central
profile
rib, the middle profile ribs and the shoulder-side profile ribs each have a
maximum
width which is determined in the axial direction on the tread strip periphery,
the
maximum width of the middle profile ribs being greater than the maximum width
of
the central profile rib, and the maximum width of the shoulder-side profile
rib being
determined within the ground contact area and being greater than the maximum
width of the middle profile ribs. The transverse stiffness of the profile ribs
thus
increases from profile rib to profile rib in the direction of the tread strip
shoulder.
This is particularly beneficial for dry performance when cornering.
In this context, it is favorable if the maximum width of the central profile
rib is
13.5% to 14.7% of the width, determined in the axial direction, of the ground
contact area of the tread strip.
Furthermore, it is favorable in this context if the maximum width of the
middle
profile ribs is 15.8% to 17.3% of the width, determined in the axial
direction, of the
ground contact area of the tread strip, and preferably 108% to 123%, in
particular
110% to 120%, of the width of the central profile rib.
In addition, it is favorable in this context if the maximum width of the
shoulder-side
profile ribs is 19.0% to 21.0% of the width, determined in the axial
direction, of the
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ground contact area of the tread strip, and preferably 117% to 127% of the
width
of the middle profile ribs.
According to a further preferred embodiment, the profile blocks belonging to
the
5 middle profile ribs and to the shoulder-side profile ribs are each
traversed by a
number of sipes running parallel to the transverse grooves with a width of 0.4
mm
to 1.0 mm and a maximum depth of 75% to 100% of the profile depth. Because
they run parallel to the transverse grooves, the length of the sipes ¨ for
example in
comparison to sipes running at an angle with respect to the transverse grooves
when viewed from above ¨ supports good opening of the sipes, so that the sipes
absorb more snow when driving on snow and thus contribute to a further
improvement in the snow performance.
A further preferred embodiment is characterized in that the profile blocks
belonging to the middle profile ribs and to the shoulder-side profile ribs are
each
provided with a number of microgrooves running, in plan view, at angle of up
to
10 with respect to the circumferential direction, in particular perpendicular
to the
transverse grooves, with a width and a depth of 0.3 mm to 0.6 mm each.
A further preferred embodiment is characterized in that the central profile
rib is
provided with a number of microgrooves running in the circumferential
direction in
plan view and having a width and a depth of 0.3 mm to 0.6 mm each.
Such microgrooves help to improve the grip properties of new or less worn
tires.
Further preferred designs relate to the orientation of the transverse grooves,
these
designs primarily contributing to an improvement in wet performance.
The transverse grooves, which divide the middle profile ribs into profile
blocks,
viewed in plan view, preferably run at an angle of 30 to 45 with respect to
the
axial direction.
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The transverse grooves, which divide the shoulder-side profile ribs into
profile
blocks, viewed in plan view, preferably run at an angle of 0 to 25 , in
particular
from 5 to 20 with respect to the axial direction.
Further features, advantages and details of the invention will now be
described in
greater detail with reference to the single figure, fig. 1, which
diagrammatically
shows a plan view of a circumferential section of a tread strip of a pneumatic
vehicle tire with one design variant of the invention.
Pneumatic vehicle tires designed according to the invention are tires for
motor
vehicles, in particular for multi-track motor vehicles, and preferably radial
tires for
passenger cars, vans or light trucks, the tires being intended for use under
wintry
driving conditions.
Fig. 1 shows a plan view of a circumferential section of a tread strip of a
pneumatic
vehicle tire. The tire equatorial plane is indicated by dotted line A-A and
the lateral
edges of the tread ground contact area are indicated by dotted lines I. The
ground
contact area corresponds to the statically determined footprint according to
E.T.R.T.O. standards (load at 70% of the maximum load capacity with an
internal
pressure of 85% according to the E.T.R.T.O. standard) and has a width B in the
axial direction.
The tread strip is noise-optimized in a particularly known manner using a
method
of pitch length variation and has a directional profile, with the tire being
mounted
on the vehicle in such a way that it has the rolling direction indicated by
the arrow
R when driving forward. Furthermore, the tread strip has a central profile rib
1, two
adjacent middle profile ribs 2 and two shoulder-side profile ribs 3, and in
the
embodiment shown is symmetrical with respect to the tire equatorial plane
(line A-
A).
The middle profile ribs 2 are each separated from the middle profile rib 1 by
a
middle circumferential groove 4 running straight in plan view, for example,
and by
a shoulder-side circumferential groove 5 running sawtooth-shaped in plan view
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from the respective adjacent shoulder-side profile rib 3. The circumferential
grooves 4, 5 are designed for the respectively provided profile depth, which
is
usually 6.5 mm to 10.0 mm for the preferred type of tire, and have a width buR
determined perpendicular to their direction of extension from 6.0 mm to 13.0
mm.
The central profile rib 1 has a maximum width bi, which is constant in the
exemplary embodiment shown, on the tread strip periphery in the axial
direction of
13.5% to 14.7% of the width B of the ground contact area, is provided over its
circumference with a large number of sipe-like transverse grooves 6 running
parallel to one another in plan view, opening into the middle circumferential
grooves 4, and which, based on a line connecting the transverse groove ends in
plan view in the axial direction, have a width determined perpendicular to
their
extension of 1.8 mm to 3.5 mm and in the radial direction a maximum depth of
70% to 100%, preferably 100%, of the profile depth. In the exemplary
embodiment
shown, the transverse grooves 6, seen in plan view, are composed of two flat V-
shaped groove sections 6a, each straight and running at an angle a of at most
12
with respect to the axial direction, the ends of which lying on the tire
equatorial
plane (line A-A) encounter the underlying surface first when the tire rolls
during
forward travel (arrow R). Furthermore, the central profile rib 1 is traversed
by sipes
7 running parallel to the transverse grooves 6 and is narrower than the
transverse
grooves 6. In the areas between the sipes 7 and in the areas between the
marginal sipes 7 and the transverse grooves 6, two microgrooves 12 running in
the circumferential direction are formed, one microgroove 12 each on each side
of
the tire equatorial plane, which preferably open into a sipe 7 or into a
transverse
groove 6.
Each middle profile rib 2 is provided with middle transverse grooves 8 running
parallel to one another in plan view, and each shoulder-side profile rib 3 is
provided with shoulder-side transverse grooves 9 running parallel to one
another
in plan view, the transverse grooves 8, 9 being V-shaped across the tread
strip
width and therefore in each tread strip half run at least substantially in
continuation
of one another, and the middle transverse grooves 8 encountering the
underlying
surface first with their ends on the inside of the tread strip. In the radial
direction,
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the transverse grooves 8, 9 each have a maximum depth of 70% to 100% of the
profile depth and at the periphery of the tread strip each have a width baR
from
3.5mm to 6.5mm, determined perpendicularly with respect to its groove center
line
maR which follows the groove course in plan view.
Each middle profile rib 2 has a maximum width b2 at the tread strip periphery
in the
axial direction from 15.8% to 17.3% of the width B of the ground contact area,
with
the maximum width b2 preferably being 108% to 123%, in particular 110% to
120%, of the maximum width bi of the central profile rib 1. The transverse
grooves
8 open into the shoulder-side circumferential grooves 5, end within the middle
profile rib 2 at a spacing al determined at the tread strip periphery and in
the axial
direction from 3.0 mm to 15.0 mm, in particular from 5.0 mm to 10.0 mm, in
front of
the respective middle circumferential groove 4, run in a plan view in a
slightly
arcuate manner and - based on the groove center lines ma R - at an angle 13
with
respect to the axial direction of 30 to 45 , the angle 13 continuously
decreasing
over the extent of the transverse grooves 8 in the direction of the tread
strip
shoulder, in particular by up to 5 , and divide the middle profile rib 2 in
plan view
into essentially parallelogram-shaped middle profile blocks 2a. Between the
end of
each transverse groove 8 on the inside of the tread strip and the closest
middle
circumferential groove 4 in each case runs a short connecting groove 15, which
is
aligned in the axial direction in plan view and is narrower and shallower than
the
transverse groove 8 and has a width of preferably 1.5 mm to 3.5 mm and has a
depth of preferably 2.0 mm to 5.0 mm in the radial direction. The middle
profile
blocks 2a are each provided with a number of sipes 10 which, in plan view, are
parallel to the groove center lines ma R of the middle transverse grooves 8,
have an
axially extending peripheral sipe portion 10a opening into the corresponding
middle circumferential groove 4 and traverse the middle profile blocks 2a. In
the
areas between the sipes 10 and in the areas between the edge-side sipes 10 and
the transverse grooves 6, two microgrooves 13 are formed which run at least
for
the most part at an angle of in particular up to 10 with respect to the
circumferential direction in plan view and preferably open into a sipe 10 or
into a
transverse groove 8.
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Each shoulder-side profile rib 3 has a maximum width b3 in the axial direction
on
the tread strip periphery, determined within the ground contact area, from
19.0% to
21.0% of the width B of the ground contact area, with the maximum width b3
preferably being 117% to 127% of the maximum width b2 of the middle profile
rib
2. The shoulder-side transverse grooves 9 open into the shoulder-side
circumferential grooves 5, run beyond the respective lateral edge of the
ground
contact area (line I) and are slightly curved in plan view and - related to
the groove
center lines maR - at an angle y of 00 to 25 with respect to the axial
direction, in
particular from 50 to 20 , the angle y within the ground contact area
continuously
decreasing by up to 15 in particular over the extent of the transverse
grooves 9 in
the direction of the tread strip shoulder, and divide the shoulder-side
profile block
rows 3 into shoulder-side profile blocks 3a. The shoulder-side profile blocks
3a are
each provided with a number of sipes 11 extending parallel to the groove
center
lines maR of the transverse grooves 9 in plan view and traversing the profile
blocks
3a at least within the ground contact area. In the areas between the sipes 11
and
in the areas between the edge-side sipes 11 and the shoulder-side transverse
grooves 9, in particular four microgrooves 14 running along in plan view at an
angle of up to 10 with respect to the circumferential direction, in the
exemplary
embodiment perpendicular with respect to the groove center lines ma R of the
shoulder-side transverse grooves 9, which microgrooves 14 preferably open into
a
sipe 11 or into a transverse groove 9.
The mentioned maximum widths bi, b2 of the profile ribs 1, 2 are determined on
the tread strip periphery between the points of the respective profile rib 1,
2 that
are furthest apart from one another in the axial direction. The likewise
mentioned
maximum width b3 of the shoulder-side profile ribs 3 is determined between the
respective lateral edge of the ground contact area (line I) and the point of
the
profile rib 3 that is furthest away from this on the tread strip periphery in
the axial
direction. The likewise mentioned, correspondingly varying angles 13 and y of
the
transverse grooves 8, 9 are each determined relative to a tangent applied
locally
to the center line maR. All sipes 7 (central profile rib 1), 10 (middle
profile blocks
2a), 11 (shoulder-side profile blocks 3a) have a width of 0.4 mm to 1.0 mm, in
particular of at most 0.8 mm, and a maximum depth in the radial direction of
75%
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to 100%, in particular of 80% to 95%, of the profile depth. All microgrooves
12
(central profile rib 1), 13 (middle profile blocks 2a), 14 (shoulder-side
profile blocks
3a) have a width and depth of 0.3 mm to 0.6 mm, the width preferably being 0.4
mm and the depth preferably being 0.5 mm.
5
Due to the V-shaped course of the transverse grooves 8, 9, each shoulder-side
circumferential groove 5 has a multiplicity of groove sections 5a, which each
separate a shoulder-side profile block 3a from the adjacent middle profile
block 2a
and therefore reach the transverse grooves 8, 9. The groove sections 5a, in
plan
10 view, run straight and at an angle ö of 2 to 7 , in particular
at most 5 , with
respect to the circumferential direction, with all groove sections 5a of a
shoulder-
side circumferential groove 5 running parallel to one another in plan view.
Each
groove section 5a has a leading end 5a', which first encounters the ground
when
the tire rolls during forward travel, and a trailing end 5a", and is inclined
relative to
the circumferential direction in such a way that the leading end 5a' -
opposite the
trailing end 5a" - is located closer to the tire equatorial plane (line A-A).
The width
buR of the shoulder-side circumferential grooves 5 and the angle ö of the
groove
sections 5a are preferably matched to one another in such a way that the
shoulder-side circumferential grooves 5 have no or a reduced "lookthrough",
i.e.,
viewed in the axially aligned cross section, no or a reduced lookthrough
through
the shoulder-side circumferential grooves 5 is possible.
The invention is not restricted to the exemplary embodiment described. In
particular, the size of the maximum widths bi, b2, b3 of the profile ribs 1,
2, 3 can
deviate from the sizes mentioned. Furthermore, the sipes 7, 10, 11 and the
microgrooves 12, 13, 14 are optional. Moreover, the transverse grooves 6 in
the
middle profile rib 1 can be designed conventionally and the transverse grooves
8,
9 in the profile ribs 2, 3 can also run straight in plan view. The middle
profile rib 2
and the shoulder-side profile rib 3, which are located in one tread strip
half, can
have profile blocks 2a, 3a and transverse grooves 8, 9 configured offset in
the
circumferential direction compared to the middle profile rib 2 and the
shoulder-side
profile rib 3, which are located in the other tread half, with the result that
the tread
strip is non-symmetrical with respect to the tire equatorial plane (line A-A).
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List of reference signs
1 ...................... Central profile rib
2 ....................... Middle profile rib
2a ......... Middle profile block
3 ....................... Shoulder-side profile rib
3a ...................... Shoulder-side profile block
4 ....................... Middle circumferential groove
5 ....................... Shoulder-side circumferential groove
5a ......... Groove section
5a' ..................... Leading end
5a" ..................... Trailing end
6 ....................... Sipe-like transverse groove
6a ...................... Groove section
7 .................... Sipe
8 ....................... Middle transverse groove
9 ....................... Shoulder-side transverse groove
10 ...................... Sipe
10a ..................... Sipe section
11 ........ Sipe
12, 13, 14 ............. Microgroove
15 ...................... Connecting groove
al ...................... Spacing
A-A ..................... Line (tire equatorial plane)
B .................... Width
bi, b2, b3 .............. Maximum width
baR, buR ................ Width
I ...................... Line (lateral edge of the ground contact area)
MQR ..................... Groove center line
R .......... Arrow (rolling direction)
a, 13, y, ö ............. Angle
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