Patent ID: 12187076

FIG.1shows a circumferential portion of a middle profile rib1of a tread, which has a directional profiling, of a vehicle tire, in particular of a utility vehicle tire, which is preferably a truck tire or a bus tire of radial type of construction. The profile rib1in the example runs in encircling fashion around the tread along the tire equator, has its mid-line M-M along the tire equator, and is divided into profile blocks3by transverse channels2. The tread has further profile ribs (not illustrated) to the side of the profile rib1, wherein a total of three to seven profile ribs are provided, which are separated from one another by circumferential channels running in the circumferential direction. Alternatively, the tread has one circumferential channel along the tire equator and two central profile ribs to the side of the circumferential channel.

In each case one sipe4is formed in the middle region in each profile block3of the middle profile rib1. The transverse channels2and the sipes4run substantially parallel to one another, and furthermore in an arc shape and symmetrically with respect to the mid-line M-M. Further channels that form the profiling, for example likewise transverse channels, in other provided profile ribs run such that, overall, a tread of directional design is provided, such that a pneumatic vehicle tire having such a tread must be installed on the vehicle such that, during forward travel, the transverse channels2and the sipes4enter the ground contact patch with their center of curvature first.

The central profile rib1may also be configured in some other way while maintaining the directionality, for example with transverse channels that are interrupted in the middle. The profile rib1may furthermore also be designed so as to have only sipes4and no transverse channels, and is therefore a profile rib of substantially closed design.

As will be described in detail below, each sipe4has a sipe base5which is rounded in cross section and which, in the axial extent of the sipe4, runs approximately in an arc shape, which is in particular approximately a circular arc with a radius of 28.0 mm to 35.0 mm. Each sipe4has two lateral portions4b, which are of identical design in a radial direction, and a central portion4asituated between these. Viewed along the correspondingly and substantially arc-shaped central line m of the sipe4, the central portion4aextends over 50% to 80% of the length of the line m, and each lateral portion4btherefore extends over 10% to 25%.

The special configuration of the sipe4in the central portion4aand in the lateral sections4bwill be discussed in more detail below with reference to a mold element4′ illustrated inFIG.3, the enlarged detail of the mold element4′ illustrated inFIG.4, and with reference toFIG.2. Only that part of the mold element4′ which forms the sipe4during the vulcanization of the pneumatic vehicle tire in a tire vulcanization mold is shown. As is generally known, mold elements are anchored by means of anchoring sections (not illustrated), for example are integrally cast, in those mold parts of the tire vulcanization mold which form the profiling of the tread during vulcanization. Correspondingly to the configuration of the sipe4, the mold element4′ has a central portion4′aand lateral portions4′band also an edge element5′ which forms the sipe base5and which runs substantially in an arc shape and which has a rounded, in particular circular, cross section. The edge element5′ has a diameter d2of 1.0 mm to 4.0 mm, in particular 1.5 mm to 3.5 mm, preferably 2.0 mm, and is at least 0.2 mm greater than the in particular constant thickness d1of 0.5 mm to 1.2 mm of the mold element4′ in its remaining region. That edge of the mold element4′ which is situated opposite the edge element5′ has an edge portion6′ which runs in the radial direction and which in this direction has a width b3′ of 1.5 mm to 2.5 mm.

The sipe4thus has a sipe width b1, corresponding to the thickness d1of the mold element4′, of likewise 0.5 mm to 1.2 mm, in particular 0.8 mm. The sipe base5of the sipe4, which is rounded in cross section, runs similarly to the central line m and has a width b2corresponding to the diameter d2of the edge element5′. At the tread periphery, the sipe4begins with an edge section6corresponding to the edge section6′ of the mold element4′.

The mold element4′ has, over at least 70% of the radial extent thereof, an undulation running in the radial direction. The two edge portions4′bof the mold element4′ are structured exclusively with this undulation. This undulation, which is in particular uniform, sinusoidal or similar to a sinusoidal shape, extends over at least 1.5 wavelengths A′, in particular two wavelengths A′, wherein one wavelength A′ corresponds to 20% to 50% of the greatest height of the mold element4′ in the radial direction and is for example 4.0 mm to 4.5 mm, in particular 4.25 mm. The undulation has an amplitude a1′ of 0.8 mm to 1.2 mm, in particular of 1.0 mm.

The sipe4thus runs, in the radial direction over at least 70% of its radial extent, with an undulation corresponding to the undulation of the mold element4′ and with a wavelength λ1of 20% to 50% of its greatest depth in the radial direction and with an amplitude a1of 0.8 mm to 1.2 mm.

In the central portion4′aof the mold element4′, the undulation present in the radial direction is overlapped by a zigzag undulation running in the direction of extent of the mold element4′, that is to say in the axial direction. A zigzag undulation differs from the already described undulation which is sinusoidal or similar to a sinusoidal shape in that its portions run in substantially straight fashion, and the undulation troughs and peaks are more sharply pointed. In the exemplary embodiment shown, a region which runs in a zigzag undulating shape and which is composed of at least one and a half wavelengths λ2′ is provided so as to begin in each case at one of the lateral sections4′b, wherein, between the two regions running in a zigzag undulating shape, a connecting portion7′ running in the axial direction is situated exactly in the middle of the mold element4′. The length1′ of the connecting portion7′ is 4.5 mm to 5.0 mm, and the wavelength λ2′ is 8.0 mm to 11.0 mm. The amplitude a2′ of the zigzag undulation is 0.8 mm to 1.2 mm, in particular 1.0 mm. A transition portion8′ to the edge element5′ is formed, in which both of the undulations disappear in a continuous manner.

In the central portion4aof the sipe4, correspondingly to the configuration of the mold element4′, the above-described undulation present in the radial direction is therefore overlapped by a zigzag undulation in the axial direction, corresponding to the zigzag undulation of the mold element4′. The amplitude a2and the wavelength λ2correspond in magnitude to the wavelength λ2′ and the amplitude a2′. In the middle of the sipe, there is situated a connecting portion7(FIG.1) which runs in the axial direction and in a straight manner in plan view. Also, in the sipe4, the zigzag undulation disappears in a transition portion8to the rounded sipe base5.

The sipes4are therefore provided with sipe walls which have surface elements which give rise to particularly advantageous mutual support under different loads; in particular, the stiffness of the profile rib or of the profile blocks of the rib is increased by way of such sipes. This is associated with reduced, and at the same time more uniform, wear of the tread. Above all, the mutual support of the sipe walls prevents the sipes from opening unfavorably widely in the circumferential direction, whereby the circumferential stiffness is increased. Since the mobility of the profile rib is restricted, the noise emissions otherwise associated with greater mobility are significantly suppressed. In the interior of the sipe close to the sipe base, the structures disappear, such that, with progressive wear of the tread, the already relatively high stiffness is compensated for. The rounded sipe base further reduces the risk of tears forming in this delicate region with respect thereto. Above all, the undulation present in the radial direction furthermore prevents an ingress of stones into the sipe.

LIST OF REFERENCE SIGNS

1. . . Profile rib2. . . Transverse channel3. . . Profile block4. . . Sipe4′ . . . Mold element4a,4′a. . . Central section4b,4′b. . . Lateral section5′ . . . Edge element5. . . Sipe base6,6′ . . . Edge portion7,7′ . . . Connecting portion8,8′ . . . Transition portiona1, a1′ . . . Amplitudea2, a2′ . . . Amplitudeλ1, λ1′ . . . Wavelengthλ2, λ2′ . . . Wavelengthb1, b2, b3. . . Widthd1. . . Thicknessd2. . . Diameterm . . . Central lineM-M . . . Mid-line