CA2994338C

CA2994338C - Pneumatic vehicle tires

Info

Publication number: CA2994338C
Application number: CA2994338A
Authority: CA
Inventors: Jurgen Brockmann; Matthias Seng; Michael Jackstadt
Original assignee: Continental Reifen Deutschland GmbH
Current assignee: Continental Reifen Deutschland GmbH
Priority date: 2015-08-11
Filing date: 2016-04-21
Publication date: 2019-07-02
Anticipated expiration: 2036-04-21
Also published as: EP3130481A1; RU2678783C1; EP3130481B1; CA2994338A1; PL3130481T3; WO2017025206A1; CN107921826A

Abstract

The invention relates to pneumatic vehicle tires having profile blocks, in which sipes (4) are formed each provided with two symmetrically running sipe walls (5), and which in a radial direction are composed of three adjoining portions (4a, 4b, 4c), having a radially outer portion (4a), which is substantially limited by wall portions (5a) running in a radial direction and extending up to a depth (ti) of 70% to 90% of the depth (t) of the sipe (4), a middle portion (4b) running between the radially outer portion (4a) and the radially inner portion (4c), and a radially inner portion (4c) that is provided with wall portions (5c), which in their cross-section extend from the central plane (E) in an outwardly rounded fashion.

Description

PNEUMATIC VEHICLE TIRES
Field The invention relates to a pneumatic vehicle tire, in particular for use in winter driving conditions, having a tread with profile positives, for example profile blocks, which are separated from one another by channels and in which sipes are formed, which sipes run substantially in an axial direction and extend in a radial direction in each case to a depth of 70% to 100% of the maximum profile depth, which sipes have in each case two sipe walls which run symmetrically with respect to the central plane of the sipe, and which sipes are made up, in a radial direction, of three sections adjoining one another, with a radially outer section which is delimited substantially by wall sections running in a radial direction and which extends to a depth of 70% to 90% of the depth of the sipe, with a middle section running between the radially outer section and the radially inner section, and with a radially inner section which has wall sections which, in cross section, run outward from the central plane in a rounded manner.
Background A tire as per the introduction is known from EP 2 072 286 B1 for example. The tread of the tire has profile blocks equipped with sipes. The sipes have an outer section of constant width running over the major part of their radial extent, and the radially innermost widened section runs in a circular-arc-shaped manner with an inner radius amounting to 0.5 mm to 5.0 mm.
A transition section between said sections has sipe walls which in a cross section are curved along an outer radius, which amounts to 0.5 mm to 8.0 mm. Furthermore, the outer and the inner radius have a specific relationship with respect to one another. A mold segment suitable for forming such sipes and having a lamella is known from EP 2 517 867 B1.
The pneumatic vehicle tire known from EP 1 920 951 B1 has a tread with profile blocks with an inner and an outer sipe pair. The inner sipe pair is arranged in the middle region of the profile block. Of the outer sipe pair, in each case one sipe is situated outside the inner sipe pair. Each sipe has a widened section at the sipe base, wherein the widened sections of the two sipe pairs have different curvatures.

2 During the use of tires in winter driving conditions, for example on roads covered with ice, the friction energy between the tread of the tire and the ice generates a meltwater film, a "liquid layer", which is for the most part wiped away by profile positive edges, in particular by the block edges in the case of transverse channels or sipes, such that it is also the case that a major part of the .. surface of the profile positives, for example of the profile blocks, comes into direct frictional contact with the underlying surface. The volume of the "liquid layer" to be wiped away is dependent on various factors, in particular the ambient temperatures, such as ice temperature, tire temperature and air temperature, and on the introduced friction energy, and is therefore at its greatest in the presence of temperatures around the freezing point. To ensure optimum frictional contact between the tread and the underlying surface, as much meltwater as possible should be received and discharged by the sipes, wherein, however, the size of the contact area of the profile positives or profile blocks with the underlying surface should remain as large as possible.
The hitherto known sipes provided in profile blocks with widened sections at the sipe base give rise to a stress profile in the profile block which has proven to be disadvantageous for the rolling resistance and wet grip. In particular, there is resulting non-uniform bending behavior of the block elements between the sipes, along with a disadvantageous excessive compression of the block elements under pressure loads.
Summary The invention is therefore based on the object of designing a tire of the type mentioned in the introduction such that the rolling resistance is reduced, and the wet grip performance is improved.
The stated object is achieved according to the invention in that the middle section running between the radially outer section and the radially inner section extends to a depth of 80 % to 95 % of the depth of the sipe and is delimited by wall sections which run in each case at an angle of 50 to 60 with respect to the radial direction, giving rise to a widening of the central section in the direction of the sipe base, wherein the curved profile of the wall sections in the radially inner section is based on radii, the associated circle central points of which lie along a line running perpendicular to the central plane of the sipe, wherein the central point of the circle belonging to the smallest radius lies on the central plane, and said radius runs to the lowest point of the sipe, wherein the largest radius runs in each case to the radially outer end point of each wall section, and the central point of the circle thereof is the central point situated furthest remote from the

3 central plane, and wherein, between the points, the radii increase continuously and the spacing of the central points of the associated circles to the central plane becomes larger.
Sipes designed according to the invention give rise to a considerable reduction of the rubber compression under pressure load and permit uniform bending and deformation behavior of the block elements of the profile blocks. In this way, the rolling resistance is reduced, and the wet grip performance is considerably improved. By means of the special design of the radially inner section, the form of the sipe at the sipe base, it is possible to obtain a considerable improvement in the bending behavior of the individual block elements, without the sipes being excessively widened in the region of the sipe base.
In a preferred embodiment, the spacing of the central point of the circle with the largest radius to the central plane amounts to 10 % to 50 % of the largest width of the radially inner section. In a further preferred embodiment, the smallest radius amounts to 40 % to 60 % of the largest width of the radially inner section, and the largest radius amounts to up to 2 times the smallest radius, in particular up to 1.5 times, particularly preferably up to 1.3 times. These measures provide a relatively large degree of design freedom with regard to the design of the radially inner section, wherein the effect of a considerable reduction of the rubber compression under pressure load is fully maintained.
Further special configurations of the sipes contribute to uniform bending and deformation behavior of the block elements of the profile blocks. Said configurations include the radially inner section having, at its widest point, a width of 150 % to 400 % of the width of the radially outer section, and the widest point of the radially inner section lying, in the radial direction, at a depth which amounts to 85% to 97% of the depth of the sipe.
The radially outer section, which has the greatest radial extent of all sections, preferably has a width of 0.30 mm to 0.80 mm, in particular of 0.40 mm to 0.60 mm.
Hence, according to a broad aspect, the invention provides a pneumatic vehicle tire for use in winter driving conditions, the tire having a tread with profile blocks, which are separated from one another by channels and in which sipes are formed, which sipes run substantially in an axial direction and extend in a radial direction in each case to a depth of 70% to 100% of a maximum

4 profile depth, which sipes have in each case two sipe walls which run symmetrically with respect to a central plane of the sipe, and which sipes are made up, in a radial direction, of three sections adjoining one another, with a radially outer section which is delimited substantially by wall sections running in the radial direction and which extends to a depth of 70% to 90% of the depth of the sipe, with a middle section running between the radially outer section and the radially inner section, and with a radially inner section which has wall sections which, in cross section, run outward from the central plane in a rounded manner, wherein the middle section running between the radially outer section and the radially inner section extends to a depth of 80 % to 95 % of the depth of the sipe and is delimited by wall sections which run in each case at an angle of 50 to 60 with respect to the radial direction, giving rise to a widening of the central section in the direction of the sipe base, wherein the curved profile of the wall sections in the radially inner section is based on radii, associated circle central points of which lie along a line running perpendicular to the central plane of the sipe, wherein the central point of the circle belonging to a smallest radius lies on the central plane, and the radius runs to a lowest point of the sipe, wherein a largest radius runs in each case to a radially outer end point of each wall section, and a central point of a circle thereof is a central point situated furthest remote from the central plane, and wherein, between the points, the radii increase continuously and the spacing of the central points of the associated circles to the central plane becomes larger.
Brief description of the drawings Further features, advantages and details of the invention will now be described in greater detail with reference to the drawing, which schematically illustrates one exemplary embodiment of the invention. In the drawing:
figure 1 shows a view of a detail of a tread of a pneumatic vehicle tire having a design variant according to the invention, and figure 2 shows a cross section through a sipe along the line II ¨ II in figure 1.

5 Detailed description of embodiments Variants, examples and preferred embodiments of the invention are described hereinbelow. In the following description, the curvature is to be understood to mean the reciprocal of the radius of the circle that best approximates to the curvature profile at every curved point.
Figure 1 illustrates four profile blocks 1 of a tread of a pneumatic vehicle tire of radial type of construction, in particular of a tire suitable for use in winter driving conditions, for passenger motor vehicles, vans or light trucks, wherein the circumferential direction of the tire is denoted by the double arrow U.
The profile blocks 1 belong to two profile block rows which each run in the circumferential direction U and which are separated from one another by a circumferential channel 2 which runs in a straight manner in the exemplary embodiment shown, wherein the profile block rows are preferably delimited by further circumferential channels that are not designated. The circumferential channel 2 has, in the radial direction, a depth T of 7.0 mm to 10.0 mm, in particular of up to 9.0 mm, wherein the depth T corresponds to the maximum profile depth provided for the respective pneumatic vehicle tire. Within the profile block rows, profile blocks 1 which are adjacent in the circumferential direction U are separated from one another in each case by a transverse channel 3, which preferably has a depth which at least substantially corresponds to the circumferential channel 2 or which is slightly shallower.
Each profile block 1 is equipped with a number of sipes 4, wherein, in the design variant shown, four correspondingly designed sipes 4 are provided per profile block 1. The sipes 4 extend at least substantially parallel to one another and at least substantially parallel to the transverse channels 3, and extend in each case all the way through the profile block 1. The spacings of the sipes 4 to one another within a profile block 1 at least substantially correspond, and are preferably substantially equal to the spacings between the respective sipe 4 situated furthest to the outside in the circumferential direction U and the profile block edge at the respective transverse channel 3.
As per figure 2, which shows a cross section through a sipe 4, each sipe 4 extends in a radial direction to a depth t which amounts to 70% to 100%, in particular 80% to 90%, of the depth T of the circumferential channel 2. Each sipe 4 is delimited by two sipe walls 5, which are of mirror-

6 symmetrical design with respect to one another in relation to a central plane E running through the sipe 4. As will be discussed below, the two sipe walls 5 provide the sipe 4 with a width which varies in a specific manner over the depth t of said sipe.
Each sipe 4 is made up of a radially outer section 4a, a middle section 4b and a radially inner section 4c, wherein the middle section 4b and the radially inner section 4c provide the sipe 4 with a pyriform design in cross section. The sipes 4a, 4b and 4c have wall sections 5a, 5b, 5c, wherein in each case two wall sections 5a, 5b, 5c are situated opposite one another. A
bend is situated in each case between the wall sections 5a and 5b, and the wall sections 5b and 5c adjoin one another without a bend.
The radially outer section 4a extends in a radial direction and to a depth ti, which amounts to 70%
to 90% of the depth t, and the wall sections 5a run in a radial direction. The radially outer section 4a therefore has a constant width B1, wherein the width B1 amounts to 0.30 mm to 0.80 mm, in particular 0.40 mm to 0.60 mm.
The middle section 4b directly adjoining the radially outer section 4a extends to a depth t2, which amounts to 80% to 95% of the depth t. The wall sections 5b delimiting the middle section 4b run at an angle a of 5 to 60 , preferably at most 45 , with respect to the radial direction, wherein the middle section 4b becomes continuously wider in the direction of the interior of the sipe.
The wall sections 5c in the radially inner section 4c are specially curved and adjoin one another without a bend (tangentially) at the lowest point of the sipe 4, at the depth t. The inner wall sections 5c have in each case a curvature which decreases continuously from their radially outer end to their radially inner end, such that their curvature is at its smallest at the depth t. The radially inner section 4c furthermore has, at a depth t3, its greatest width B2 of 150 % to 400 % of the width B1, wherein the depth t3 amounts to 85 % to 97 % of the depth t.
As shown in figure 2, the special curvature profile of the wall sections 5c is based on a continuous displacement of the circle central points belonging to radii, wherein the smallest radius r1 amounts to 40 % to 60 % of the largest width B2 of the radially inner section 4c. The central point of the circle belonging to said radius ri lies on the central plane E, and the radius ri runs to the deepest point P1 of the sipe 4. The largest radius r2 runs in each case to the radially outer end point P2 of that wall section 5c of which the central point of its circle is situated on a line Ii running

7 perpendicular to the central plane E of the sipe 4 and is the central point situated furthest remote from the central plane E. Between the points Pi, P2, the radius increases continuously, and the spacing of the central points, situated on the line 11, of the associated circles to the central plane E becomes larger. The circle central points on the line II thus move away from the respective wall section 5c on the opposite side of the central plane E. The spacing of the central point of the circle with the largest radius r2 to the central plane E amounts to 10 % to 50 % of the largest width B2 of the radially inner section 4c. The largest radius r2 amounts to up to 2 times the smallest radius in particular up to 1.5 times, particularly preferably up to 1.3 times.
In one design variant, a small transition rounding is provided in each case between the outer wall sections 5a and the middle wall section 5b, which transition rounding ensures, in the cross section, a bend-free transition of the wall sections 5a and the wall sections 5b.
Furthermore, the outer wall sections 5a may also, in the cross section, run at an angle of in particular up to 5 with respect to the radial direction, wherein the radially outer sections 4a becomes wider in the direction of the interior of the sipe.
Depending on the outer block shape, the sipes 4 may also run at an angle of up to 45 with respect to the transverse direction of the tire. Furthermore, the sipes 4 need not extend parallel to one another.
It is preferable for two to six sipes 4 to be provided per profile block 1, wherein the sipes 4 provided may also be of different designs, with preferably at least every second sipe being designed according to the invention.
List of reference numbers 1 ............. Profile block 2 ............. Circumferential channel 3 ............. Transverse channel 4 .......... Sipe 4a, 4b, 4c .... Section 5 ............. Sipe wall 5a, 5b, 5c .... Wall section

8 B1, B2 ...... Width E ............ Central plane T ............ Depth t, ti, t2, t3 .. Depth a ....... Angle

Claims

CLAIMS:

1. A pneumatic vehicle tire for use in winter driving conditions, the tire having a tread with profile blocks, which are separated from one another by channels and in which sipes are formed, which sipes run substantially in an axial direction and extend in a radial direction in each case to a depth of 70% to 100% of a maximum profile depth, which sipes have in each case two sipe walls which run symmetrically with respect to a central plane of the sipe, and which sipes are made up, in a radial direction, of three sections adjoining one another, with a radially outer section which is delimited substantially by wall sections running in the radial direction and which extends to a depth (t1) of 70% to 90% of the depth of the sipe, with a middle section running between the radially outer section and the radially inner section, and with a radially inner section which has wall sections which, in cross section, run outward from the central plane in a rounded manner, wherein the middle section running between the radially outer section and the radially inner section extends to a depth (t2) of 80 % to 95 % of the depth of the sipe and is delimited by wall sections which run in each case at an angle of 5° to 60° with respect to the radial direction, giving rise to a widening of the central section in the direction of the sipe base, wherein the curved profile of the wall sections in the radially inner section is based on radii, associated circle central points of which lie along a line running perpendicular to the central plane of the sipe, wherein the central point of the circle belonging to a smallest radius (r1) lies on the central plane, and the radius (r1) runs to a lowest point (P1) of the sipe, wherein a largest radius (r2) runs in each case to a radially outer end point (P2) of each wall section, and a central point of a circle thereof is a central point situated furthest remote from the central plane, and wherein, between the points (P1, P2), the radii increase continuously and the spacing of the central points of the associated circles to the central plane becomes larger.

2. The pneumatic vehicle tire as recited in claim 1, wherein a spacing of the central point of the circle with the largest radius (r2) to the central plane amounts to 10 %
to 50 % of a largest width of the radially inner section.

3. The pneumatic vehicle tire as recited in claim 1, wherein the smallest radius (r1) amounts to 40 % to 60 % of a largest width of the radially inner section.

4. The pneumatic vehicle tire as recited in any one of claims 1 to 3, wherein the largest radius (r2) amounts to up to 2 times, 1.5 times or 1.3 times the smallest radius (r1).

5. The pneumatic vehicle tire as recited in any one of claims 1 to 4, wherein a widest point of the radially inner section has a width of 150 % to 400 % of a width of the radially outer section.

6. The pneumatic vehicle tire as recited in any one of claims 1 to 4, wherein a widest point of the radially inner section lies, in the radial direction, at a depth (t3) which amounts to 85 % to 97 % of the depth (t) of the sipe.

7. The pneumatic vehicle tire as recited in any one of claims 1 to 6, wherein the radially outer section has a width of 0.30 mm to 0.80 mm.

8. The pneumatic vehicle tire as recited in any one of claims 1 to 6, wherein the radially outer section has a width of 0.40 mm to 0.60 rim.