Tires with improved snow performance

Abstract

The present invention relates to a tire (1) having an outer surface (10) with an innovative profile on the peripheral walls (2, 3, 4, 5) of the tread blocks (a, b) for improved snow performance, the peripheral walls exhibiting a three-dimensional void / ridge (9, 8) pattern configured to enhance snow-digging and snow-trapping effects.

Description

[Technical Field]

[0001] The present invention relates to a tire having an innovative 3D pattern profile in the outer peripheral wall of the land tread for improved snow performance in terms of snow digging and snow trapping effects. [Background technology]

[0002] Tire performance on snow is related to several mechanisms, mainly depending on the tread compound and pattern features (void ratio / distribution, edge geometry / number / distribution, tread block shape / stiffness).

[0003] In particular, the primary mechanisms responsible for this type of performance are the "snow digging" and "snow trapping" effects, the former relating to the penetration of the tread into the snowpack, and the latter relating to the ability of the tread voids to collect and compact snow.

[0004] In particular, snow digging relates to the ability of tread pattern elements (sipes, notches, edges) to penetrate snowpack and provide grip for traction / braking / cornering maneuvers.

[0005] Snow trapping, on the other hand, is the ability of the macrovoids (grooves, lugs, cranks, etc.) in the tread pattern to collect and compact snow in order to utilize the snow-on-snow friction mechanism as an additional contribution to snow grip.

[0006] With regard to the snow trapping effect, having flat surfaces as the longitudinal / lateral sidewalls of the tread blocks, even though common, is not a suitable solution to improve this mechanism.

[0007] One of the most common approaches adopted to improve snow performance is to implement Toledo blocks with simple polygonal chain-like contours (e.g., square wave, sawtooth, "zigzag", etc.) to increase the number of areas where snow can accumulate, thereby improving the trapping mechanism.

[0008] As an example, a first prior art solution is shown in Figures 1a-1c, where the cross-sectional profile of the tread block remains constant along the height of the block itself, and exhibits essentially "extruded" void pattern features (slashes, notches, "zigzag" lines) along the tire radial direction, i.e., along the block height z.

[0009] A second prior art solution, shown in Figures 2a-2c, is to have a tread block cross-sectional profile that varies along the height of the block itself (direction z) but is flat along the block width (direction x) and block length (direction y).

[0010] Figures 3a and 3b show the outer surface of a tread block peripheral wall of another prior art solution. The outer surface is provided with straight cuts achieved by extruding a "zigzag" profile (with some radii) along the block width. Each cut has a triangular profile.

[0011] In all of the above known solutions, the variable profile of the tread block walls is applied in one direction only, which can be width / length or height.

[0012] All such known embodiments have the limitation of not using the entire block wall to trap snow and improve snow performance. Summary of the Invention [Problem to be solved by the invention]

[0013] The technical problem posed and solved by the present invention is therefore to provide a tire that is able to overcome the drawbacks mentioned above with respect to the known technology. [Means for solving the problem]

[0014] This problem is solved by a tire according to claim 1. Preferred features of the invention are the subject matter of the dependent claims.

[0015] The objective of this concept is to provide a solution that enhances the "snow trapping" effect by introducing a series of additional three-dimensional (3D) shaped pattern elements (e.g., cuts, notches, wavy voids) into the peripheral wall surfaces of the tread land portions, particularly the peripheral wall surfaces of the tread blocks.

[0016] The 3D features (basically small patterned voids and / or protrusions) are shaped and distributed to trap and compress snow, which contributes significantly to snow grip. The problem solved is to improve snow performance by enhancing the overall snow trapping mechanism at the tread land level in addition to designing the tread compound properties.

[0017] To improve snow performance, the present invention provides a tire with an outer surface having an innovative 3D profile in the circumferential wall of the land tread, where the circumferential wall exhibits a 3D void (or recessed) and / or protruding pattern configured to enhance snow-digging and snow-trapping effects.

[0018] In this application, the terms "void" and "recess" are intended to be synonymous.

[0019] A first important aspect of the present invention is that voids (cuts, notches, grooves, etc.) and / or protruding elements are applied to the longitudinal walls (both forward and backward relative to the tire rolling direction) and / or lateral walls of the tread land portion, so as to allow a variable profile along both the height and / or width / length of the land portion simultaneously.

[0020] By applying variable profiles in both height and width / length, complex 3D patterns can be shaped, using the entire land wall to enhance the snow trapping mechanism and overall snow grip.

[0021] Because the entire tread land sidewall can be affected by this 3D pattern, the total surface area involved in such mechanisms can be much greater than that of prior art solutions, resulting in a higher number of voids that enhances snow trapping ability and therefore overall snow grip.

[0022] More specifically, a first technical advantage of the present invention is that it provides a higher edge density (which is very important for both snow trapping and digging effects).

[0023] Furthermore, by properly optimizing the land tread wall profile, snow trapping can be improved locally (at the land tread level) to trap more snow and at higher density.

[0024] Additionally, voids are introduced to ensure that land stiffness is not affected, especially not reduced, which is crucial for all other performance (i.e., dry and wet) that may actually be adversely affected by snow-first design objectives, such as reduced block stiffness.

[0025] It is important to note that the present invention provides a solution to enhance the snow trapping effect by introducing a series of small 3D "voids" (cuts or recesses) and / or protruding elements as additional pattern elements on the longitudinal / lateral sidewalls of the tread land portion, rather than on the inner surface. In other words, the 3D pattern is provided on the outer periphery of the tread land portion, which is designed to penetrate into the snow (or more generally into the ground). The small 3D voids, positioned in a specific layout, are shaped and distributed to trap and compress snow, thus contributing significantly to snow grip.

[0026] The solution according to the invention may be applied to all tires requiring improved overall snow performance (braking / traction / handling / slalom), but of course it is advantageous to apply it to all types of tires.

[0027] Other advantages, features and modes of use of the present invention will become apparent from the following detailed description of some embodiments, given by way of example and not of limitation.

[0028] Reference is made to the figures in the accompanying drawings. [Brief explanation of the drawings]

[0029] [Figure 1a] 1 shows a schematic perspective view of a first prior art embodiment of a tire; [Figure 1b] FIG. 1b shows a plan view of a first prior art tread block included in the embodiment of FIG. 1a. [Figure 1c] FIG. 1b shows a side view of a first prior art tread block included in the embodiment of FIG. 1a. [Figure 2a] 1 shows a schematic perspective view of a second prior art embodiment of a tire. [Figure 2b] 2b shows a plan view of a second prior art tread block included in the embodiment of FIG. 2a. [Figure 2c] FIG. 2b shows a side view of a prior art second tread block included in the embodiment of FIG. 2a. [Figure 3a] FIG. 1 shows a schematic perspective view of a third tread block of the prior art. [Figure 3b] FIG. 3b shows a cross-sectional side view of the third tread block of the prior art of FIG. 3a. [Figure 4a] 1 shows a schematic perspective view of a preferred embodiment of a tire according to the invention; [Figure 4b] 4b shows a plan view of a preferred embodiment of a tread block according to the present invention contained in the tire of FIG. 4a. [Figure 4c] 4b shows a side view of a preferred embodiment of a tread block according to the present invention contained in the tire of FIG. 4a. [Figure 5] 2 shows a side perspective view of a preferred embodiment of a tread block according to the present invention in greater detail. [Figure 6] FIG. 6 illustrates a side view of a preferred embodiment of the tread block shown in FIG. 5. [Figure 7] 6 illustrates a plan view of a preferred embodiment of the tread block shown in FIG. 5. [Figure 8] 5 shows the three-dimensional patterned outer surface of the tread block in FIG. 5 in further detail. [Figure 9] 1 shows the geometrical characteristics of a conductor D according to the invention. [Figure 10] 1 shows the geometry of a busbar G according to the invention. [Figure 11] 1 is a histogram showing potential indices of snow friction for prototypes of a first tread block of the prior art (Solution A), a second tread block of the prior art (Solution B), and a preferred embodiment of a tread block according to the present invention (Solution C). DETAILED DESCRIPTION OF THE INVENTION

[0030] It should be understood that the thicknesses and curvatures shown in the foregoing figures are for illustrative purposes only and are not necessarily drawn to scale. Additionally, the figures may omit some layers / components of the tire to more clearly illustrate aspects of the present invention.

[0031] In the following, some embodiments and variants of the invention will be described with reference to the aforementioned figures.

[0032] Furthermore, the different embodiments and variations described below may be used in combination where suitable.

[0033] With reference to FIG. 4a, a preferred embodiment of a tire 1 according to the invention is shown, which comprises an outer tread portion P comprising at least tread blocks a.

[0034] According to the present invention, the tread portion may refer to or include the central land portion, intermediate land portion, and / or shoulder land portion of the tread. Furthermore, according to the present invention, all of the features of the present invention that refer hereinafter to exemplary tread blocks having a prismatic shape also apply to tread blocks having different and even more complex shapes, for example, V-shaped ("palm") profiles, or tread lands more generally.

[0035] The tire 1 has a circumferential direction C, a radial direction R and a transverse direction T which is parallel to the tire's axis of rotation A. For greater clarity, the rolling direction of the tire 1 is indicated by an arrow.

[0036] In the exemplary illustration of FIG. 4a, the transverse direction T and the axis of rotation A are shown to coincide.

[0037] Furthermore, to facilitate the following description of the tread block geometry, Figure 4a illustrates a Cartesian coordinate system intended as a local frame of reference for the tread block defined by a longitudinal axis x, a transverse axis y, and a sagittal axis z. The longitudinal axis x is locally tangent to the circumferential direction C, the transverse axis y is parallel to the axis of rotation A, and the sagittal axis z is locally coincident with the radial direction R.

[0038] The tread portion P, or in particular according to this example the tread blocks a, comprise a plurality of outer peripheral surfaces or walls, which according to the invention are understood to be the outer walls of the blocks a, for example the outer walls facing the macrovoids or facing other blocks, but not the inner walls of the tread blocks facing the microvoids, such as the walls of the sipes. The peripheral walls are the walls which penetrate and engage snow, or more generally the ground, when the tire 1 is in use.

[0039] According to the invention, at least a portion of the outer surface of one of the peripheral walls has a three-dimensional (3D) pattern of recesses and / or protrusions.

[0040] Embodiments including 3D patterns of only recesses and 3D patterns of only protrusions are also contemplated by the present invention.

[0041] In other words, the 3D pattern comprises depressions and / or protrusions of the same outer surface that alternate according to at least two spatial directions, preferably perpendicular to each other. Preferably, the depressions and / or protrusions alternate according to two main directions that are perpendicular to each other and that define the extent of the corresponding outer surface in plan view. By way of example, with reference to the above Cartesian coordinate system, such two directions may be the transverse / longitudinal direction and the sagittal direction. The above 3D pattern is configured to enhance snow-digging and snow-trapping effects, since snow is trapped and compressed in the 3D depressions and / or between the 3D protrusions when the tire 1 is in use.

[0042] Preferably, each of said alternating recesses and / or protrusions is formed as a double-curved element, but according to preferred embodiments of the invention may also have a prismatic shape (embodiment of Figures 4b and 4c) or a pyramidal shape. Otherwise, various areas of the outer surface with different shapes of respective recesses and / or protrusions may be provided on the same block wall.

[0043] By way of example, Figures 4b and 4c show a plan view and a side view, respectively, of a preferred embodiment of a tread block a according to the present invention. The tread block a has a prismatic shape defined by four peripheral walls, namely, a first pair of longitudinal peripheral walls and a second pair of transverse peripheral walls. Preferably, the outer surfaces of all four peripheral walls have alternating recesses and / or protrusions in the prismatic shape, thereby forming a 3D pattern.

[0044] More generally, alternating recesses and / or protrusions provide a sort of 3D checkerboard pattern in the tread land area, particularly on the outer surfaces of the tread blocks.

[0045] According to other embodiments of the invention, the 3D pattern according to what has already been described may be provided on the outer surface of only one peripheral wall, or of two opposing peripheral walls (preferably a pair of lateral walls), or of course of all the peripheral walls of the tread block, as already mentioned. The 3D pattern may be provided on the entire outer surface of each peripheral wall, or only on a limited portion thereof.

[0046] Preferably, the distance between successive recesses and / or protrusions is constant when measured along a direction parallel to the outer surface of the peripheral wall on which the recesses and / or protrusions are provided.

[0047] Referring to Figure 5, another preferred embodiment of a tread portion P according to the present invention is shown. For greater clarity, the rolling direction of a tire including tread portion P is indicated by an arrow (the tire is not shown in Figure 5). Tread portion P includes, by way of example, two tread blocks, designated by the reference characters a and b, respectively, although the following description will refer only to tread block a. However, all following discussion of tread block a shall also extend to tread block b (or to any other tread block included in a tire according to the present invention).

[0048] As can be clearly seen in FIG. 5, the 3D patterns of the present invention are intended to be provided on the outer peripheral surfaces or walls that define the tread portion, or more particularly, the tread blocks, and these surfaces or walls do not include the inner walls that are provided within the tread block body, such as the walls that define the sipes 11.

[0049] The tread block a preferably has a prismatic shape and includes four peripheral walls, namely a first pair of peripheral walls 3, 5 and a second pair of peripheral walls 2, 4, generally substantially opposite each other. In particular, the tread block a includes two longitudinal peripheral walls 2, 4 extending in the circumferential direction C and the radial direction R, and two transverse peripheral walls 3, 5 extending in the transverse direction T and the radial direction R.

[0050] Preferably, the entire outer surface 10 of each of the first pair of two peripheral walls 3, 5 or the second pair of two peripheral walls 2, 4 is provided with a 3D pattern of alternating recesses 6 and / or protrusions 7.

[0051] That is, according to a preferred embodiment, the entire outer surface 10 of both of the two lateral peripheral walls 3, 5 has a 3D pattern of alternating recesses 6 and / or protrusions 7, as can also be seen in Figures 6 and 7. A close-up of the 3D patterned outer surface 10 is shown in Figure 8.

[0052] According to another preferred embodiment of the present invention, the entire outer surface 10 of two consecutive peripheral walls of a tread block a (with reference to Figures 6 and 7, the consecutive peripheral walls are designated by reference numerals 2, 3 or 3, 4 or 4, 5 or 5, 2) may also have a 3D pattern of alternating recesses and / or protrusions.

[0053] Alternatively, the entire outer surface 10 of the three peripheral walls of the tread block a may have a 3D pattern of alternating recesses and / or protrusions.

[0054] Preferably, the 3D pattern of alternating depressions and / or protrusions is achieved by a wavy generatrix G moved along the path of a wavy conductor D, with preferred embodiments of lines G and D shown in Figures 10 and 9, respectively. Both generatrix G and conductor D include peak points 8, which are the outermost points of each outer surface 10, and valley points 9, which are the innermost points of each outer surface 10.

[0055] It should be noted that for the purposes of the present invention, zigzag lines that exhibit non-zero bending radii at peaks and valleys are also considered to be wavy lines.

[0056] Referring to Figure 9, a conductor line D corresponding to the outer profile of the tread block 3D pattern surface according to the xz plane cross section is shown. Referring to Figure 10, a generatrix line G corresponding to the outer profile of the tread block 3D pattern surface according to the xy plane cross section is shown.

[0057] In particular, the 3D pattern is generated by the profile of the generatrix G (in the xy plane, as shown in FIG. 10) displaced along the profile of the conductor D (in the xz plane, as shown in FIG. 9).

[0058] According to a preferred embodiment of the invention, the distance between successive peaks 8 and valleys 9 measured along a longitudinal direction x, which is a direction parallel to said outer surface 10, is constant. Preferably, the height x of the peaks 8 relative to the outer surface 10 measured along a transverse direction y h out , x w outis constant. The depth x of the valley point 9 relative to the outer surface 10 h in , x w in can also be constant.

[0059] More specifically, the height x of the peak 8 relative to the outer surface 10 h out , x w out The depth x of the valley point 9 relative to the outer surface 10 can be 0 mm to 4 mm, preferably 0.5 mm to 3 mm. h in , x w in The thickness may be 0 mm to 4 mm, preferably 0.5 mm to 3 mm.

[0060] Preferably, the distance y between successive peaks 8 and valleys 9 measured along a transverse direction y parallel to said outer surface 10 is h 3.y w The distance 3 is 0.5 mm to 7.5 mm, preferably 0.5 mm to 5 mm. More preferably, the distance between each peak point 8 and each valley point 9 measured in the longitudinal direction x perpendicular to the outer surface 10 is 8 mm or less, preferably 0.5 mm to 6 mm.

[0061] In particular, the wavy generatrix G and / or the wavy conductor D present a bending radius equal to 0.2 mm at each of the peaks 8 and valleys 9 (not shown in Figures 9 and 10). According to other embodiments, the bending radius may be less than or equal to 2 mm, more preferably between 0.2 mm and 1.5 mm.

[0062] According to another embodiment of the invention, the 3D pattern of alternating depressions and / or protrusions is realized by a zigzag generatrix moved along a zigzag conductor wire (the zigzag generatrix and conductor wire having non-zero bending radii at their peaks and valleys), in such a case the generated depressions and / or protrusions have a pyramidal shape.

[0063] The purpose of introducing a complex 3D pattern is to maximize the number of grooves / notches / voids (of the correct shape and spacing) on ​​the walls of the tread land area (especially the tread blocks) to trap snow, compressing it and increasing the longitudinal shear force, further improving the overall grip effect.

[0064] The more the outer surface of the tread blocks is provided with a 3D pattern of recesses and / or protrusions according to the present invention, the better the snow performance will be. As will be appreciated by those skilled in the art, depending on the selection of the outer surface of the tread land portion that is provided with the 3D pattern, it is possible to improve snow traction and / or braking and / or cornering, or even all of the above characteristics simultaneously.

[0065] With reference to Figures 5, 9 and 10, the preferred dimensions of the busbar G and conductor D are as follows (a w and a h indicates the original height of the flat outer surface 10 without any recesses or protrusions).

[0066] [Table 1]

[0067] Experimental data An experimental campaign was conducted to demonstrate the extent of the improved snow performance of tires according to the present invention.

[0068] In the experimental campaign, three rubber block prototypes were slid down snow tracks under the same operating conditions, constant speed, temperature and applied pressure, and at controlled temperatures.

[0069] A first rubber block without a notch (Solution A), a second rubber block according to the prior art (Solution B), and a third rubber block according to the present invention (Solution C) were prepared.

[0070] Each of the rubber blocks in the experimental campaign has the same overall dimensions.

[0071] Referring to Figure 3b, the tread blocks of prior art solution B are provided with a pattern of recesses and protrusions with the following dimensions:

[0072] [Table 2]

[0073] Dimensions of the tested solution C according to the invention.

[0074] [Table 3]

[0075] The bending radius of Solution C is 0.2 mm.

[0076] The experimental results are shown in the histograms in Figure 11 for different potential indices of snow friction coefficient (snow friction coefficient is the ratio of longitudinal force Fx to normal force Fz), where, naturally, high friction was desired.

[0077] The snow friction potential index of solution C according to the invention is higher than solutions A and B tested.

[0078] The present invention has been described above with reference to preferred embodiments, and other embodiments are possible within the scope of the same central inventive concept, as defined by the protective scope of the appended claims.

Claims

1. A tire (1) having a circumferential direction (C), a radial direction (R), and a transverse direction (T), the tire (1) including an outer tread portion (P) including at least one tread block (a) having a plurality of outer peripheral walls (2, 3, 4, 5), At least a portion of the outer surface (10) of one of the outer peripheral walls (2, 3, 4, 5) has a three-dimensional pattern of recesses (6) and / or protrusions (7); the recesses (6) and / or protrusions (7) alternate according to at least two spatial directions (x, y) of the outer surface (10); The three-dimensional pattern of alternating recesses (6) and / or protrusions (7) is realized by a wavy generatrix (G) moved along a wavy conductor (D), and the generatrix (G) and the conductor (D) each include a peak point (8) that is the outermost point of each outer surface (10) and a valley point (9) that is the innermost point of each outer surface (10).

2. A tyre (1) according to claim 1, wherein said at least two spatial directions (x, y) are perpendicular to each other.

3. A tire (1) according to claim 1 or 2, in which the distance between successive recesses (6) and / or protrusions (7) measured according to a direction parallel to said outer surface (10) is constant.

4. A tire (1) according to any one of claims 1 to 3, wherein the entire outer surface (10) of one of the outer peripheral walls (2, 3, 4, 5) has a three-dimensional pattern of alternating recesses (6) and / or protrusions (7).

5. A tire (1) according to any one of claims 1 to 4, wherein the entire outer surface (10) of two opposing ones of the outer peripheral walls (2, 3, 4, 5) has a three-dimensional pattern of alternating recesses (6) and / or protrusions (7).

6. A tire (1) according to any one of claims 1 to 4, wherein the entire outer surface (10) of two consecutive of said outer peripheral walls (2, 3, 4, 5) has a three-dimensional pattern of alternating recesses (6) and / or protrusions (7).

7. A tire (1) according to any one of claims 1 to 4, wherein the entire outer surface (10) of three of the outer peripheral walls (2, 3, 4, 5) has a three-dimensional pattern of alternating recesses (6) and / or protrusions (7).

8. A tire (1) according to any one of claims 1 to 7, wherein the entire outer surface (10) of all said outer peripheral walls (2, 3, 4, 5) has a three-dimensional pattern of alternating said recesses (6) and / or protrusions (7).

9. In a tire (1) according to any one of claims 1 to 8, the distance (y y) between successive peaks (8) and valleys (9) measured according to a direction parallel to said outer surface (10) ｈ ３ , y ｗ ３ ) is constant.

10. In the tire (1) according to any one of claims 1 to 9, the height (x ｈ ｏｕｔ , x ｗ ｏｕｔ ) is constant.

11. A tire (1) according to any one of claims 1 to 10, wherein the depth (x ｈ ｉｎ , x ｗ ｉｎ ) is constant.

12. In the tire (1) according to any one of claims 1 to 11, the height (x) of the peak (8) relative to the outer surface (10) ｈ ｏｕｔ , x ｗ ｏｕｔ ) is a tire with a thickness of 0 mm to 4 mm.

13. The tire (1) according to any one of claims 1 to 11, wherein the heights (x h out , x w out ) of the peaks (8) relative to the outer surface (10) are 0.25 mm to 3 mm.

14. A tire (1) according to any one of claims 1 to 13, wherein the depth (x ｈ ｉｎ , x ｗ ｉｎ ) is a tire with a thickness of 0 mm to 4 mm.

15. The tire (1) according to any one of claims 1 to 13, wherein the depth (x h in , x w in ) of the valley points (9) relative to the outer surface (10) is 0.25 mm to 3 mm.

16. A tire (1) according to any one of claims 1 to 15, wherein the distance (y y) between successive peaks (8) and valleys (9) measured according to a direction parallel to said outer surface (10) ｈ ３ , y ｗ ３ ) is a tire that is 0.5 mm to 7.5 mm.

17. The tire (1) according to any one of claims 1 to 15, wherein the distances (y h3 , y w3 ) between successive peak points (8) and valley points (9) measured in a direction parallel to the outer surface (10) are between 0.5 mm and 5 mm.

18. Tyre (1) according to any one of the preceding claims, in which the height of the peaks (8) relative to the valleys (9), measured according to a direction perpendicular to the outer surface (10), is less than or equal to 8 mm.

19. A tire (1) as described in any one of claims 1 to 17, wherein the height of the peak points (8) relative to the valley points (9) measured in a direction perpendicular to the outer surface (10) is 0.5 mm to 6 mm.

20. Tyre (1) according to any one of the preceding claims, wherein said undulating generatrix (G) and / or said undulating conductor (D) presents a bending radius at each of said peak points (8) and valley points (9) equal to 0.2 mm.

21. Tyre (1) according to any one of the preceding claims, wherein said alternating recesses (6) and / or protrusions (7) present a prismatic or pyramidal shape.

22. Tyre (1) according to any one of claims 1 to 21, wherein the three-dimensional pattern of alternating recesses (6) and / or protrusions (7) is realised by a zigzag generatrix (G) displaced along a zigzag conductor (D).

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