Hydrophobic tire tread patterns

Abstract

A tread for a pneumatic tire includes a plurality of grooves, the grooves including a groove surface (122) and a plurality of elements (410) spaced apart from one another in an arrangement on the groove surface (122). Each element (410) has a shape that defines a volume, the shape including a first cross-sectional shape (425) in a plane (420) parallel to the groove surface (122) and a second cross-sectional shape (435) in a plane (430) perpendicular to the groove surface (122). The arrangement includes a void volume in the space between the elements (410) and a porosity between 0.5 and 0.75, the porosity being defined as the ratio of the void volume to the total volume of the elements (410) in the arrangement.

Description

[Technical field]

[0001] The present invention relates to a hydrophobic pattern in the tread grooves of a tire, and thus to a tread with high drainage properties. [Background technology]

[0002] Part of the research in the field of pneumatic tires has been focused on obtaining treads with improved performance in terms of wet grip.

[0003] As known to those skilled in the art, the grip of a tread on a wet road surface is a function of the tread's own ability to eliminate the layer of water that forms between the road surface and the tread, which layer of water necessarily impedes the effective grip of the tread on the road surface.

[0004] To facilitate the removal of the layer of water, the tread is provided with grooves. In effect, the drainage process is carried out by the grooves in the tread.

[0005] In this regard, it is important to explain how the performance of a pneumatic tire in wet conditions results from a first drainage step, during which the layer of water between the tread and the road is removed from the tread, and a contact step, during which the blocks of the tread adhere to the road surface. The shorter the drainage step and the more water that is removed, the more efficient the wet grip will be.

[0006] As is known, a solution to shorten the water evacuation process and also increase the amount of water that is expelled is to increase the volume of the grooves in the tread. This solution succeeds in shortening the water evacuation process and making it more effective, but it reduces the contact surface between the tread and the road surface, which is detrimental to the contact process itself and thus to braking and steering behavior. Furthermore, it is known that an increase in the groove volume can have a negative effect on the wear resistance of the tread.

[0007] It is known in the tire industry that a particular structure of the tread grooves can favor a faster evacuation of water. Such a solution is highly advantageous since it only affects the groove surface and not the number and / or dimensions of the grooves, and therefore does not reduce the contact surface between the tread itself and the road surface.

[0008] There remains a need to improve tire tread groove surfaces to provide better hydrophobicity and enhanced water evacuation. Summary of the Invention

[0009] According to a first aspect of the present invention there is provided a tread for a pneumatic tire, the tread comprising: The grooves include: A groove surface; a plurality of elements spaced apart from one another in arrangement on the groove surface; Including, Each element has a shape that defines a volume, the shape being: a first cross-sectional shape in a plane parallel to the groove surface, the smallest dimension of the first cross-sectional shape defined at the groove surface defines a width w of the base of the element, where 0.1 mm≦w≦3 mm; a second cross-sectional shape in a plane perpendicular to the groove surface, the maximum dimension of the second cross-sectional shape from bottom to top at the groove surface defines a height h of the element, where 0.1 mm≦h≦3 mm; The aspect ratio, defined as the height h divided by the width w, must be at least 1 and at most 30. Including, The layout is Void volume in the space between the elements; and A porosity between 0.5 and 0.75, defined as the ratio of the void volume to the total volume of the elements in the arrangement; Includes.

[0010] The inventors have realized that by disposing elements at intervals in at least one surface of a groove in a tread of a pneumatic tire, it is possible to modify the physical properties of the groove surface. In particular, by incorporating elements into the groove surface, it is possible to change the hydrophobicity of the groove surface.

[0011] Within the meaning of the present invention, the hydrophobicity of a surface corresponds to the contact angle formed by a sessile drop of water when in contact with said surface. A contact angle greater than 90° thus corresponds to a surface having hydrophobic properties, whereas a contact angle less than 90° corresponds to a surface having hydrophilic properties.

[0012] It will be understood that the space between elements is defined by the three-dimensional space available between the elements in the arrangement, i.e., between the plane of the groove surface and the plane intersecting the top of the element (these two planes are separated by a height h). Elements may be considered as protrusions from the groove surface even if they are created by removing material from the initial groove surface, i.e., lowering the groove surface. The groove surface is the lowest surface in the groove when the tread is viewed from the outside. The void volume may therefore be considered as the negative of the total volume of the element. In other words, the void volume is defined as the total available area between the elements multiplied by their height h. The void volume may be defined regardless of whether the elements are formed by adding or removing material from the initial groove surface.

[0013] It will be understood that porosity is defined as the ratio of the total void volume to the total volume of the elements in the arrangement, e.g., the total void volume divided by the total element volume in any total volume of the arrangement at a groove surface. For example, if the porosity is 0.5, the volume of the elements is twice the void volume in the arrangement. As the porosity increases, the total void volume increases, and the space between adjacent elements increases, so that the contact angle provided by the elements is expected to increase, at least when the arrangement is newly formed.

[0014] However, it has been found to be beneficial to limit the porosity to 0.75 so that the relative volume of the elements remains greater than the void volume. The inventors have realized that the volume of the elements is important for their durability, and that increasing their volume provides resistance to aging, otherwise erosion of the elements over time tends to reduce the hydrophobicity of the groove surface. The porosity is therefore selected between 0.5 and 0.75, as this has been found to provide a balance between good hydrophobicity when the arrangement is freshly formed and resistance to aging over the life of the tread. In some preferred embodiments, the porosity is selected, for example, between 0.55 and 0.75, for example, between 0.6 and 0.75, for example, between 0.65 and 0.75, for example, between 0.7 and 0.75, for example, between 0.5 and 0.7, for example, between 0.5 and 0.65, for example, between 0.5 and 0.6, for example, between 0.5 and 0.55.

[0015] By the elements being disposed on the groove surface, it is meant that they are physically distinct from the groove surface, e.g., protruding from the surface or embossed into the surface. The elements present on the groove surface have the effect of modifying the hydrophobicity of the surface. In some embodiments, the elements are disposed on at least two, e.g., at least three, of the groove surfaces. In some embodiments, the elements are disposed on substantially all of the groove surfaces, e.g., the groove surfaces are completely covered with the elements. In a preferred embodiment, the elements protrude from the groove surface. Preferably, the elements are spaced apart from one another in the arrangement of the protruding elements on the groove surface.

[0016] It will be understood that the groove may have one or more groove surfaces. For example, the groove may have a bottom surface and two sidewall surfaces, and the groove has a substantially U-shaped cross-section in a plane perpendicular to the surface of the tire tread. However, it will be understood that the groove may have any suitable and / or desirable cross-section and thus include any suitable and / or desirable number of surfaces. In some embodiments, the groove may include only straight surfaces, e.g., having a polygonal cross-section. In some embodiments, the groove may include curved surfaces, e.g., a semicircular cross-section. In some embodiments, the groove may include any suitable and / or desirable combination of curved and / or straight surfaces, e.g., a bullet shape with straight sides and a curved (e.g., dome-shaped) bottom surface.

[0017] It will be appreciated that the hydrophobicity of a groove surface may be directly influenced by one or more of the element size (e.g., element volume), element shape (e.g., first and second cross-sectional shapes, aspect ratio), and the space between adjacent elements (e.g., void volume). Porosity may therefore be considered the primary parameter of interest as it links the volume of the elements with the void volume defined by the space between the elements.

[0018] In some embodiments, the second cross-sectional shape may be any suitable and / or desired shape. The overall shape of the element may be, for example, generally cylindrical, conical, cubic, rectangular, polygonal, pyramidal, parabolic, or hyperbolic. In one set of embodiments, the second cross-sectional shape is a square or rectangular. Thus, the overall shape of the element may be a cylinder or a triangular prism.

[0019] According to a second aspect of the present invention, there is provided a tread for a pneumatic tire, the tread comprising: The grooves include: A groove surface; a plurality of elements spaced apart from one another in arrangement on the groove surface; Including, Each element has the shape of a cylinder or a triangular prism that defines a volume; The layout is Void volume in the space between the elements; and A porosity between 0.5 and 0.75, defined as the ratio of the void volume to the total volume of the elements in the arrangement; Includes.

[0020] In an embodiment of this second aspect, the arrangement of the groove surface includes a plurality of cylindrical and / or triangular prism elements, which is confirmed to increase the contact angle between the water droplet and the surface to a point that ensures a shorter drainage process. Indeed, as known to those skilled in the art, the larger the contact angle between the water droplet and the surface, the more water tends to drain from the surface, thus shortening the drainage process.

[0021] At least some embodiments of this second aspect may include one or more of the features of the first aspect. In some embodiments of this second aspect, the cylindrical or triangular prism shape includes a first cross-sectional shape in a plane parallel to the groove surface, the smallest dimension of the first cross-sectional shape defined at the groove surface defines the width w of the element, where 0.1 mm≦w≦3 mm. In some embodiments of this second aspect, the cylindrical or triangular prism shape includes a second cross-sectional shape in a plane perpendicular to the groove surface, the largest dimension of the second cross-sectional shape from the groove surface defines the height h of the element, where 0.1 mm≦h≦3 mm. In some embodiments of this second aspect, the cylindrical or triangular prism shape includes an aspect ratio of the height h divided by the width w that is at least 1 and at most 30.

[0022] The inventors have found that, generally, as the volume of the elements increases, the surface area of ​​the tops of the elements increases, the contact angle (e.g., of the groove surface containing the elements) decreases, and the hydrophobicity of the apparent groove surface decreases when the elements are newly formed. Thus, minimizing the volume of the elements may be considered to increase the contact angle, which in turn increases the hydrophobicity of the tread. Reducing the volume of the elements also tends to increase the space between the elements, thereby increasing the porosity.

[0023] However, the inventors also realized that the hydrophobicity imparted by the elements to the groove surface may change as the elements erode with age of the tire tread, for example, due to use of the tire on the road. The inventors found that it is beneficial to limit the porosity so that the volume of the elements is not too small compared to the void volume. It was found that larger element volumes generally result in smaller changes in the contact angle over time.

[0024] Thus, the inventors have realized that the smaller the volume of the elements, the less resistant they are to aging, and therefore the more quickly they corrode, which can affect the hydrophobicity imparted by the elements. However, it is not straightforward to predict how aging will affect the geometry of the elements, and therefore the hydrophobicity of the groove surfaces. The inventors have realized that a compromise can be found between maximizing the volume of the elements, improving their resistance to aging, and minimizing the surface area of ​​the tops of the protrusions.

[0025] In some embodiments of the first aspect, the second cross-sectional shape may be any suitable and / or desirable shape. However, the inventors have surprisingly found that a compromise can be found by selecting the elements to have a second cross-sectional shape that is wider in a dimension at the bottom (e.g. adjacent the groove surface) than at the top (e.g. the surface that will come into contact with water). The inventors have found that by making the bottom of the element wider, e.g. by reducing the surface area at the top of the element, the element volume can be increased without negatively affecting the hydrophobicity of the surface. As a result, the inventors have surprisingly found that it is desirable to configure the elements to have a second cross-sectional shape that is not rectangular, such that the element is a non-columnar structure (e.g. rather than an element shape that has a constant width from the bottom to the top of the element). Such elements do not have a cylindrical or triangular prism shape.

[0026] Each element has a shape that may include more than one second cross-sectional shape in a plane perpendicular to the groove surface, for example when the first cross-sectional shape has both a width and a length. The second cross-sectional shape that has the most impact on the hydrophobicity of the groove surface is the second cross-sectional shape that includes the smallest dimension defined at the groove surface, i.e. the second cross-sectional shape that includes the width w of the element at its base. Thus, in a preferred embodiment, the second cross-sectional shape includes a width w and a height h, and the width w at the base of the second cross-sectional shape is greater than the corresponding width w' at the top of the second cross-sectional shape. In other words, the second cross-sectional shape tapers from its base (at the groove surface) to its top surface (furthest from the groove surface). Preferably, the second cross-sectional shape is selected to be not rectangular or square.

[0027] This is considered to be novel and original in itself. Thus viewed from a third aspect, the present invention provides a tread for a pneumatic tyre, the tread comprising: The grooves include: A groove surface; a plurality of elements spaced apart from one another in arrangement on the groove surface; Including, Each element is a first cross-sectional shape in a plane parallel to the groove surface, the smallest dimension of the first cross-sectional shape defined at the groove surface defining a width w of a base of the element; a second cross-sectional shape in a plane perpendicular to the groove surface, the maximum dimension of the second cross-sectional shape from bottom to top at the groove surface defining a height h of the element; and having a shape including The second cross-sectional shape includes a width w and a height h, where the width w at the base of the second cross-sectional shape is greater than a corresponding width w' at the top of the second cross-sectional shape.

[0028] By making the base of the elements wider, their volume can be increased without negatively affecting the hydrophobicity of the surface provided by the top of the second cross-sectional shape. The inventors have found that such elements improve resistance to ageing. The inventors have therefore advantageously found that the arrangement of elements having a second cross-sectional shape with a wide base achieves a good compromise between maximizing the volume of the elements, improving resistance to ageing, and minimizing the contact area between the elements and a static water drop. It will be understood that the corresponding width w' at the top of the second cross-sectional shape is measured in the same direction as the width w at the bottom.

[0029] At least some embodiments of this third aspect may include one or more of the features of the first aspect. In some embodiments of this third aspect, the shape of each element defines a volume, and the arrangement includes a void volume in the space between the elements and a porosity of 0.5 to 0.75, the porosity being defined as the ratio of the void volume to the total volume of the elements in the arrangement. In some embodiments of this third aspect, the width w of the elements is selected such that 0.1 mm≦w≦3 mm. In some embodiments of this third aspect, the height h of the elements is selected such that 0.1 mm≦h≦3 mm. In some embodiments of this third aspect, the shape includes an aspect ratio of the height h divided by the width w that is at least 1 and at most 30.

[0030] Furthermore, the inventors have found that the greater the degree of curvature at the top surface of the element (e.g., the surface in contact with the water drop), the greater the contact angle of the static water drop. Thus, for example, the inventors have found that the contact angle formed between a static water drop and a groove including an arrangement of columnar elements (e.g., including a rectangular second cross-sectional shape) is smaller (e.g., less hydrophobic) than the contact angle formed between a static water drop and an arrangement of elements including a second cross-sectional shape having a curved, filleted, rounded, or chamfered apex. This effect is further observed as the radius of curvature of the fillet (e.g., the degree of rounding of the apex) increases or the slope of the bevel (e.g., of a chamfered or curved surface) decreases (e.g., the greater the roundness or the smaller the slope slope, the greater the contact angle formed between the static water drop and the element, e.g., the greater the hydrophobicity).

[0031] In some embodiments, the second cross-sectional shape may have, for example, straight sides and generally taper from its base to its apex. For example, the second cross-sectional shape may be generally triangular, truncated triangular, or trapezoidal. However, the inventors have further found that it is beneficial to avoid corners between the sides and the apex of the second cross-sectional shape. As noted above, in some preferred embodiments, the second cross-sectional shape includes a curved, filleted, rounded, or chamfered apex. In at least some embodiments, the second cross-sectional shape tapers from its base to its apex and includes sides extending from the base to the apex and a curved or angled transition between the sides and the apex, and the apex is flat. The sides may extend from the base to the apex at an angle of about 90° (e.g., a column with a filleted or chamfered apex) or at an internal angle of 25° to 85° (e.g., a triangle with a truncated apex). The sides may be straight or curved.

[0032] In some preferred embodiments, the second cross-sectional shape may be generally semicircular, parabolic, hyperbolic, or semi-elliptical. In some embodiments, the second cross-sectional shape is generally parabolic or hyperbolic (e.g., the entire element is in the shape of a paraboloid or hyperboloid, e.g., a continuous curved structure truncated at the base).

[0033] In some embodiments, the second cross-sectional shape is a polygon, preferably with a flattened or rounded apex (e.g., to create a gradual change from the side to the top of the shape). In some embodiments, the second cross-sectional shape is a polygon with four sides, e.g., a square or rectangle with four interior angles greater than 90° and two interior angles less than or equal to 90° (e.g., preferably, the two angles less than or equal to 90° are at the bottom of the cross-section adjacent the groove surface), e.g., a trapezoid. In some embodiments, the second cross-sectional shape is a polygon with six sides, e.g., a square or rectangle with a chamfered edge on the top surface of the element. In some embodiments, the second cross-sectional shape includes a curved edge transitioning from the side to the top, e.g., a square or rectangle with a filleted apex, to create a gradual change from the side to the top surface of the element. In some embodiments, the second cross-sectional shape is truncated or flattened hyperbolic, e.g., the hyperbolic shape includes a truncated flat apex at its narrowest portion, such that the width of the base of the cross-section is greater than the width of the top of the cross-section. In some embodiments, the second cross-sectional shape is truncated or flattened parabolic, e.g., the parabolic shape includes a flat apex. In some embodiments, the second cross-sectional shape may include at least one straight edge and at least one curved edge.

[0034] Preferably, the apex of the second cross-sectional shape comprises a flat apex without sharp corners, e.g., the apex comprises curved sides or rounded edges, such that the three-dimensional element comprises a rounded shape that transitions from a flat element top surface to a side surface. For example, in some embodiments, the planar apex may transition to the base of the shape according to a sine or conic function, such that the width of the element base is greater than the element apex.

[0035] In some embodiments, the second cross-sectional shape lies in a plane perpendicular to the groove surface and perpendicular to the circumferential direction.In some embodiments, the second cross-sectional shape lies in a plane perpendicular to the groove surface and parallel to the circumferential direction.

[0036] In some embodiments, the height h is at least 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, or 0.9 mm. In some embodiments, the height h is at most 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, or 1 mm. In some embodiments, the height h is between 0.1 mm and 1 mm. In some other embodiments, the height h is at most 1.5 mm, 2 mm, 2.5 mm, or 3 mm.

[0037] In some embodiments, the aspect ratio of the elements is greater than 1, e.g., the second cross-sectional shape has a height, h, that is greater than the width, w, of the first cross-sectional shape. In preferred embodiments, the aspect ratio of the elements is substantially greater than 1, e.g., the ratio of height, h, to width, w, is at least 1.5, 2, 3, or 4.

[0038] Each element includes a first cross-sectional shape in a plane parallel to the groove surface. In some embodiments, the first cross-sectional shape may be any suitable and / or desirable geometric shape. For example, the first cross-sectional shape may be a square, a circle, an oval, a rectangle, a triangle, a polygon, a mathematical symbol, an algebraic symbol, an irregular polygon, e.g., a polyomino, e.g., a tetromino, e.g., a pentomino. It will be appreciated that the first cross-sectional shape may be selected or varied independently of the second cross-sectional shape, resulting in the elements being a variety of different three-dimensional shapes.

[0039] In some embodiments, the width w is at least 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, or 0.9 mm. In some embodiments, the width w is at most 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, or 1 mm. In some embodiments, the width w is between 0.1 mm and 1 mm. In some other embodiments, the width w is at most 1.5 mm, 2 mm, 2.5 mm, or 3 mm.

[0040] In some embodiments, the first cross-sectional shape has a generally constant width, e.g., a point-like element. In some other embodiments, the first cross-sectional shape may have a length l that is greater than the width w. For example, the first cross-sectional shape may be an elongated rectangle (optionally with a curved, filleted, rounded, or chamfered top). More generally, in some embodiments, the first cross-sectional shape is an elongated strip that defines a length l that is much greater than the width w. In some embodiments, the length l is at least 1 mm, 2 mm, 3 mm, 4 mm, or 5 mm. In some embodiments, the length l is at most 5 mm, 10 mm, 15 mm, or 20 mm. In some embodiments, the length l is at most 30 mm, 40 mm, 50 mm, 60 mm, 70 mm, 80 mm, 90 mm, or 100 mm. In some embodiments, the length l is between 1 mm and 100 mm.

[0041] In some embodiments, the elongated strip may extend partially or entirely along the circumferential direction of the groove. For example, in some embodiments, the first cross-sectional shape may be a stretched rectangle or strip that joins itself and forms a loop along the groove surface. In some embodiments, the strip may have an aspect ratio of length l to width w of 7:1 or more, such as 10:1 or more, such as 15:1 or more. In some embodiments, the stretched rectangle may have an aspect ratio of 7:1 to X:1, where X is equal to πd / w, d being the tread diameter and w being the groove width. This means that for a large tread with a diameter of about 1000 mm and an example groove width of 20 mm, X is 157. In some other embodiments, the elongate strips may extend at an angle other than 0 relative to the circumferential direction of the groove, for example at an angle of at least 30°, 40°, 45°, 50°, 60°, 70°, 80°, or at an angle of about 90° (i.e., perpendicular to the circumferential direction of the groove).

[0042] More generally, it will be understood that the first cross-sectional shape may have any suitable and / or desirable orientation relative to the groove surface. In some embodiments, the first cross-sectional shape may have a longitudinal axis oriented parallel to the tire circumference and the groove surface. For example, when the first cross-sectional shape is rectangular, the rectangle may be oriented to form a continuous line extending around the tire circumference. In some embodiments, the first cross-sectional shape may have a longitudinal axis aligned perpendicular to the groove wall, e.g., the first cross-sectional shape may extend across the width of the groove. In some embodiments, the first cross-sectional shape may extend diagonally across the groove, e.g., a line or elongated rectangle may extend diagonally across the groove surface.

[0043] To ensure that the elements are resistant to aging, preferably the element volume is about 0.1 mm 3 In some embodiments, the elements are greater than 0.2 mm. 3 Larger, e.g., 0.25 mm 3 Larger, e.g., 0.3 mm 3 Larger, e.g., 0.35 mm 3Larger, e.g. 0.4mm 3 Larger, e.g., 0.45 mm 3 Larger, e.g., 0.5 mm 3 Larger, e.g. 0.55mm 3 Larger, e.g. 0.6mm 3 The inventors have set the element volume to 0.1 mm 3 It was noted that larger volumes tend to maintain a relatively large contact angle even as the tire ages, but that the effect tends to plateau if the volume is too large. Large element volumes can affect the porosity of the pattern, as described below. Therefore, elements should be sized up to about 0.5 mm. 3 , for example, up to about 0.6 mm 3 , for example, up to about 0.7 mm 3 , for example, up to about 0.8 mm 3 , for example, up to about 0.9 mm 3 For example, up to about 1.0 mm 3 For example, up to about 1.1 mm 3 , for example, up to about 1.2 mm 3 , for example, up to about 1.3 mm 3 , for example, up to about 1.4 mm 3 , for example, up to about 1.5 mm 3 In some embodiments, the elements may have an element volume of 0.1 to 1.5 mm. 3 may have an element volume of

[0044] In some embodiments, as described above, the elements may not be point-like, but may instead extend like elongated strips having a length l much greater than their width w. For such elements, the element volume may be between 0.1 and 1.5 mm 3 The range is X times, where X is πd with respect to the tread diameter d.

[0045] It will be appreciated that the void volume depends on the arrangement via the spacing of the elements, i.e., the spacing between the elements. The spacing between adjacent elements in the arrangement may be defined by at least a first nearest neighbor spacing, s. In some embodiments, the arrangement may be further characterized by a second nearest neighbor spacing, s2, where the second nearest neighbor spacing is greater than the first nearest neighbor spacing. Such nearest neighbor spacing may be defined for either random or ordered arrangements.

[0046] In some embodiments, the arrangement of the plurality of elements is a random arrangement. In such an arrangement, the elements may be spaced apart from one another at a defined average interval, even though the arrangement is random. In some embodiments, the arrangement of the plurality of elements is a regular arrangement. The regular arrangement may occur alone or may be repeated, e.g., in a pattern. In some preferred embodiments, the arrangement of the plurality of elements is a regular pattern. It will be understood that the elements may be arranged in any suitable and / or desirable pattern. In some embodiments, the pattern may be an isotropic pattern, e.g., identical in all directions. In some embodiments, the pattern may be anisotropic, e.g., the pattern may have different nearest neighbor spacings in various directions.

[0047] In some embodiments, the pattern may be isotropic. For example, the pattern may be a cubic pattern, e.g., each element (e.g., a central element) is equally spaced from its four nearest neighbors, and the three nearest neighbors form either an angle of 90 degrees or an angle of 180 degrees, e.g., a repeating square pattern. In some embodiments, the pattern may be a repeating diamond pattern, e.g., each element (e.g., a central element) is equally spaced from its four nearest neighbors, and the three nearest neighbors form either an angle of less than 90 degrees or an angle of less than 180 degrees. In some embodiments, the pattern may be a repeating hexagonal pattern, e.g., each element is equally spaced from its six nearest neighbors.

[0048] In some embodiments, the pattern may be anisotropic. For example, the pattern may be a rectangular pattern, e.g., each element (e.g., a central element) has two nearest neighbors at 180 degrees to the central element and two second nearest neighbors at 180 degrees to the central element, and the first nearest neighbor interval is smaller than the second nearest neighbor interval. For example, the pattern may be a parallelogram pattern, e.g., each element (e.g., a central element) has two nearest neighbors at 180 degrees to the central element and two second nearest neighbors at 180 degrees to the central element, and the angle formed between any first nearest neighbor, the central element, and any second nearest neighbor is not 90 degrees.

[0049] It will be appreciated that the pattern may be defined relative to the location of the center of the first cross-sectional shape, such as by calculating the first closest spacing, s, from the center of the first cross-sectional area, and thus the pattern placement is completely independent of the first cross-sectional shape of the element.

[0050] In some embodiments, the elements are spaced apart from one another in the arrangement by a typical or average spacing of 50-500 μm, e.g., 100-500 μm, e.g., greater than 100 μm, e.g., greater than 200 μm, e.g., greater than 300 μm, e.g., greater than 400 μm, e.g., less than 500 μm, e.g., less than 400 μm, e.g., less than 300 μm, e.g., less than 200 μm, e.g., less than 100 μm. In some embodiments, the elements are spaced apart from one another in the arrangement by a typical or average spacing of 0.5 mm to 1.5 mm. In some other embodiments, the elements are spaced apart from one another in the arrangement by a typical or average spacing of up to 2 mm, 2.5 mm, or 3 mm. In various embodiments, the arrangement is an isotropic pattern and the spacing is the first nearest neighbor spacing.

[0051] It will be understood that the elements may be formed by any suitable and / or desirable method. For example, the elements may be formed on the groove surface by removing material from the groove surface, for example, by drilling, milling, ion milling, machining, electrical discharge machining, laser engraving, laser etching, plasma etching, chemical etching, photolithography, x-ray lithography, electron beam lithography, plasma, gas or liquid etching, probe microscopy, atomic force microscopy, nanoindentation microscopy, or evaporation. For example, the elements may be formed on the groove surface by replacing material at the groove surface, for example, by embossing, stamping, molding, forging. For example, the elements may be formed on the groove surface by depositing material on the groove surface, for example, by chemical vapor deposition, physical vapor deposition, electroplating, 3D metal printing, additive manufacturing, electrospinning.

[0052] In some embodiments, laser engraving techniques are used. The invention therefore extends to a method of making a tread according to any one of the embodiments disclosed herein, using laser engraving techniques.

[0053] In some embodiments, molding techniques are used. The invention therefore extends to a method of making a tread according to any one of the embodiments disclosed herein, using molding techniques. The invention further extends to a mold configured to make a tread according to any one of the embodiments disclosed herein.

[0054] In some embodiments, the elements may be formed on the groove surface using molding or casting techniques, and the mold includes a negative of the element pattern created by any suitable and / or desired technique. For example, the mold may be formed by one or more suitable techniques, such as drilling, milling, ion milling, machining, electrical discharge machining, electroplating, laser etching, 3D metal printing, additive manufacturing techniques, plasma etching, chemical etching, photolithography, x-ray lithography, electron beam lithography, embossing, stamping, molding, forging, etching with plasma, gas, or liquid, probe microscopy, atomic force microscopy, nanoindentation microscopy, chemical vapor deposition, physical vapor deposition, evaporation, electrospinning, etc.

[0055] In some embodiments, the arrangement of the elements is substantially the same across the groove surface. This can help ensure reliable hydrophobic performance. In some embodiments, multiple different arrangements can be present within a single groove. For example, the bottom surface of the groove (e.g., a groove surface substantially parallel to the outer surface of the pneumatic tire) can include a first arrangement of elements, and the walls of the groove (e.g., a groove surface substantially perpendicular to the surface of the pneumatic tire) can include a second arrangement of elements, the first arrangement and the second arrangement being different. In some embodiments, the first and second arrangements can include elements having the same first and / or second cross-sectional shapes and / or aspect ratios and / or volumes, but the elements can be spaced differently in the first and second arrangements. In some embodiments, the first and second arrangements can have the same element spacing, but the elements can have different first and / or second cross-sectional shapes and / or aspect ratios and / or volumes. It will be appreciated that these parameters can be related to each other by a range defined for porosity.

[0056] In some embodiments, a single groove surface may include multiple arrangements of elements. For example, a groove surface may include an array of arrangements. For example, a groove surface may include a first arrangement extending along the circumferential direction of the groove and a second arrangement extending parallel to the first arrangement, such that the groove surface includes two different arrangements extending along the circumferential direction of the groove (e.g., around the circumference of the tire). In some embodiments, the first arrangement is arranged to extend across the width of the groove and the second arrangement is arranged to extend across the width of the groove adjacent to the first arrangement, such that the arrangement includes alternating two different arrangements along the circumferential direction of the groove. In various embodiments, a groove surface may include any suitable and / or desirable number and configuration of arrangements, one, two or more arrangements.

[0057] In some embodiments, the grooves extend along the circumferential direction of the tread (e.g., summer tires), while in some embodiments, the grooves extend at an angle to the circumferential direction of the tread (e.g., winter tires), for example, grooves with a V-shaped layout.

[0058] In some embodiments, the grooves each have a width in the range of 0.2 to 20 mm. In some embodiments, the grooves each have a depth of at least 1 mm, preferably at least 1.6 mm, more preferably at least 2 mm. In some embodiments, the grooves each have a depth of 2 to 3 mm.

[0059] The disclosure herein relates to grooves formed in the tread of a pneumatic tire. The hydrophobicity of the groove surface is therefore considered in the context of the groove surface being made of a rubber material or a rubber-based polymer material. In some embodiments, the tread is made of a diene-based rubber compound. Diene-based rubbers, such as natural rubber, isoprene rubber, and butadiene rubber, contain repeat units derived from diolefins having conjugated carbon-carbon double bonds. The properties of synthetic diene-based rubbers can be specifically tailored by copolymerization of diolefin monomers with other monomers, and synthetic diene-based rubbers are used in a wide range of applications, including tire treads. Styrene butadiene rubber (referred to herein as "SBR") is an example of a butadiene rubber made by polymerization of styrene and butadiene. In some embodiments, the tread is made of a silica-containing diene-based rubber compound, such as an SBR-silica compound.

[0060] A typical SBR-silica rubber compound is made according to the following composition (where "phr" is weight per hundred weight rubber):

[0061] [Table 1]

[0062] S-SBR has a styrene content of 10-45% and a vinyl content of 20-70%, with a viscosity of 800-1500×10 3 and 500 to 900 x 10 3 It is a polymer obtained through a solution polymerization process with an average molecular weight of

[0063] BR is a polymer made of polybutadiene.

[0064] Silica is about 170m 2 / g and is sold under the name Ultrasil VN3 by the company EVONIK.

[0065] The carbon black is N134.

[0066] The silane bonding agent is sold by EVONIK under the name SI75.

[0067] TBBS is an abbreviation for N-tert-butyl-2-benzothiazylsulfenamide, a compound used as a vulcanization accelerator.

[0068] DPG is an abbreviation for diphenyl guanidine compound used as a vulcanization accelerator.

[0069] Some embodiments of the present invention are further described with the aid of the following non-limiting examples and the accompanying drawings. [Brief description of the drawings]

[0070] [Figure 1] FIG. 1 illustrates a tread of a pneumatic tire that includes a number of grooves. [Diagram 2] FIG. 2 is a detailed view of the tread shown in FIG. 1, the groove including multiple elements in an arrangement on the groove surface. [Figure 3A] FIG. 3 is a detailed view of the tread groove shown in FIGS. 1 and 2 taken along the AA distance. [Figure 3B] 3 is a cross-sectional view of a groove along the AA distance shown in FIG. 1 and FIG. 2, including three surfaces: two walls and a bottom. [Figure 4] 11A-11C show the shape of elements in placement on a groove surface in accordance with one embodiment of the present invention. [Diagram 5] FIG. 1 illustrates the relationship between the contact angle of a water droplet interacting with a surface and the volume of an element placed on the surface when the element is new. [Figure 6] FIG. 1 shows the relationship between the contact angle of a water droplet interacting with a surface and the volume of an element placed on the surface after the element has aged. [Figure 7] FIG. 7 is a diagram showing a combination of the data shown in FIGS. 5 and 6. [Figure 8] FIG. 1 illustrates the relationship between the real contact area of ​​an element and the contact angle formed between a water drop and a surface containing said element. [Figure 9]FIG. 2 illustrates an arrangement of elements in a first cross-sectional plane, according to one embodiment of the present invention. [Figure 10] A shows the corresponding void volume formed by the arrangement of elements shown in B, according to one embodiment of the present invention. [Figure 11] FIG. 1 illustrates the relationship between the contact angle of a water droplet interacting with a surface and the spacing parameters for the arrangement of elements on that surface. [Figure 12] FIG. 1 illustrates the relationship between the contact angle of a water droplet interacting with a surface and the porosity formed by an element placed on that surface. [Figure 13] FIG. 13 is a diagram showing a combination of the data shown in FIGS. 11 and 12. [Figure 14] 1A shows an element at a groove surface according to one embodiment of the present invention, B shows a first cross-sectional shape of the element, C shows a second cross-sectional shape of the element, and D shows a detailed view of the top of the second cross-sectional shape. [Figure 15] 1A shows an element at a groove surface according to one embodiment of the present invention, B shows a first cross-sectional shape of the element, C shows a second cross-sectional shape of the element, and D shows a detailed view of the top of the second cross-sectional shape. [Figure 16] 1A shows an element in a groove surface according to one embodiment of the present invention; B shows a first cross-sectional shape of the element; C shows a second cross-sectional shape of the element; and D shows a detailed view of a curved side of the second cross-sectional shape. [Figure 17] 1A shows an element at a groove surface according to one embodiment of the present invention, B shows a first cross-sectional shape of the element, C shows a second cross-sectional shape of the element, and D shows a detailed view of the side and transition to the top of the second cross-sectional shape. [Figure 18] 1A shows an element at a groove surface according to one embodiment of the present invention, B shows a first cross-sectional shape of the element, C shows a second cross-sectional shape of the element, and D shows a detailed view of the side and transition to the top of the second cross-sectional shape. [Figure 19]1A shows an element at a groove surface according to one embodiment of the present invention, B shows a first cross-sectional shape of the element, C shows a second cross-sectional shape of the element, and D shows a detailed view of the side and transition to the top of the second cross-sectional shape. [Figure 20] 1A shows an element at a groove surface according to one embodiment of the present invention, B shows a first cross-sectional shape of the element, C shows a second cross-sectional shape of the element, and D shows a detailed view of the side and transition to the top of the second cross-sectional shape. [Figure 21] 1A shows an element at a groove surface according to one embodiment of the present invention, B shows a first cross-sectional shape of the element, C shows a second cross-sectional shape of the element at one plane of the groove, and D shows a second cross-sectional shape of the element at a second plane of the groove. [Figure 22] 1A shows an element at a groove surface according to one embodiment of the present invention; B shows a first cross-sectional shape of the element; C shows a second cross-sectional shape of the element at one plane of the groove; D shows a second cross-sectional shape of the element at a second plane of the groove; and E shows an element at the second cross-sectional plane. [Figure 23] FIG. 23 shows a tire tread groove having the elements of FIG. 22 oriented with their longitudinal axes along the circumferential direction. [Figure 24] FIG. 23 shows a tire tread groove having the elements of FIG. 22 oriented with their longitudinal axes perpendicular to the circumferential direction. [Diagram 25] 1A-G are diagrams illustrating first cross-sectional shapes, second cross-sectional shapes, and 3D shapes of multiple elements according to various embodiments of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0071] FIG. 1 shows a tread 110 of a pneumatic tire 100 that includes a plurality of grooves 120 that extend around the circumference of the tread 110 parallel to a circumferential direction 130 .

[0072] FIG. 2 shows a detail of the tread 110 shown in FIG. 1, in which the groove 120 includes a number of elements disposed along the groove surface, shown as dots within the groove 120.

[0073] Figures 3A and 3B show details of groove 120 along the AA distance shown in Figures 1 and 2. Groove 120 has a U-shaped cross section at an axis perpendicular to the circumferential axis, such that groove 120 includes three groove surfaces 122: two walls 122b, 122c and a bottom 122a. Groove 120 has a width 124 perpendicular to the circumferential direction and a length 126 extending along the circumferential direction.

[0074] FIG. 4 illustrates one embodiment of elements 410 in an arrangement 400 on the groove surface 122. The elements 410 may be described in terms of their cross-sectional shapes in a first cross-sectional plane 420 and a second cross-sectional plane 430. The first cross-sectional plane 420 is a plane parallel to the groove surface, so that the first cross-sectional shape 425 of the elements 410 is essentially the area of ​​the element's grounded portion at the groove surface, thereby defining the width w of the element 410. The second cross-sectional plane 430 is a plane perpendicular to the groove surface and perpendicular to the circumferential axis, so that the second cross-sectional shape 435 of the elements 410 defines the height h of the elements 410. In this embodiment, the second cross-sectional shape 435 of the elements 410 is the same even if the second cross-sectional plane 430 is rotated 90 degrees. In other words, the elements 410 are point-like, rather than elongated.

[0075] 4, the first cross-sectional shape 425 is a square and the second cross-sectional shape 435 is a truncated hyperbola with smooth, continuously curved sides and two parallel top and bottom edges. This is provided by way of example, but the element 410 may have a variety of different shapes, as will be seen in the description below.

[0076] FIG. 5 illustrates the inverse relationship between element volume and the contact angle formed between a static drop of water and a groove containing a plurality of elements 410 when newly formed.

[0077] As can be seen from Figure 5, as the element volume increases, the contact angle formed between the element 410 and a static drop of water decreases, e.g., the surface becomes less and less hydrophobic. As can be seen from the trend shown in Figure 5, eventually the element volume reaches a volume where further increases in volume do not result in a significant decrease in the contact angle, e.g., the functional relationship plateaus at approximately 136 degrees for the data shown in Figure 5. This is believed to be because at very large volumes, the surface becomes essentially continuous when viewed from the element, and the contact angle approaches that which would have been observed if there were no elements present.

[0078] From the relationship shown in FIG. 5, to obtain a groove surface 122 exhibiting good hydrophobicity, elements 410 having a minimum element volume are desired, e.g., 0.1 mm 3 It is clear that the pores approach a needle-like structure having a volume less than 10 μm.

[0079] FIG. 6 shows the same relationships as shown in FIG. 5 (i.e., element volume vs. contact angle formed between a static water drop and elements), but for aged surfaces rather than new surfaces (as shown in FIG. 5). As can be seen from the data shown in FIG. 6, the element volume of 0.15 mm 3 Below this, the contact area formed between a static water droplet and the element 410 of the present invention decreases rapidly (eg, becomes less hydrophobic).

[0080] The data points shown in Figure 6 correspond directly to the data points shown in Figure 5. For example, data points A in Figure 5 and A' in Figure 6 indicate that element 410 is approximately 0.15 mm 3 When newly formed (FIG. 5), element 410 has a volume of approximately 0.03 mm and has aged, losing 75% of its material volume. 3 The contact angle is measured on the same element 410 at two different time periods: when the element has a volume of 0.1 mm (FIG. 6) and when the element has a volume of 0.1 mm (FIG. 7).

[0081] FIG. 7 shows the combined data from FIGS. 5 and 6 and illustrates how the relationship between element volume and the contact angle formed with a static water drop varies with element volume.

[0082] Figures 5, 6, and 7 thus show that elements 410 with smaller volumes when new have a greater effect of aging on their hydrophobicity, with the smaller element volumes (e.g., data points A / A', B / B', and C / C') initially being the most hydrophobic (Figure 5), but then decreasing in hydrophobicity more rapidly than the larger volumes. Thus, the effects of aging and the hydrophobicity of surface 122 when new place opposing demands on element volume.

[0083] On the other hand, the element volume is larger when new (e.g., 0.5 mm as shown by data points D and E). 3 4. The hydrophobicity of element 410 is approximately 100% (>100%), but the change in hydrophobicity after aging is small (as shown by data points D' and E') due to the small effect of aging. For example, Figure 6 shows that after aging, D' and E' of element 410 maintain approximately the same hydrophobicity (e.g., contact angle with water) even after losing approximately 75% of the element volume.

[0084] From Figure 7, 0.1 mm 3 It can be seen that elements 410 having a volume less than 0.1 mm experience a dramatic drop in contact angle after aging of the tread 110. Therefore, element volumes of 0.1 mm 3 Larger is better.

[0085] The inventors have realized that to improve aging resistance and maintain hydrophobicity as the tire tread ages, it is important to maximize the volume of the elements 410. An object of the present invention is therefore to provide an arrangement (e.g., pattern) for the groove surface 122 that maximizes element volume while minimizing the contact area (and thus the contact angle) between the elements 410 and a water droplet.

[0086] A solution envisioned by the present invention is to provide elements 410 with a shape having a wider base than top, for example including sloping sides and / or a curved or angled top surface (e.g., filleted sides, e.g., chamfered, e.g., beveled). The top surface of each element may be considered to represent its true contact area for a water droplet in contact with the groove.

[0087] 8 shows the relationship between the true contact area of ​​element 410, normalized to a pillar surface including a flat top, and the contact angle formed with a static water drop. It will therefore be understood that 100% surface area represents a pillar-shaped element configuration with straight edges and a flat top surface (including, for example, a rectangular or square second cross-sectional shape). The true contact area is therefore reduced by rounding the corners of the cross-sectional shape of the surface in contact with the water drop, gradually reducing the flat top.

[0088] Thus, as the corners of the second cross-sectional profile of the element become more rounded and the contact area decreases, the contact angle increases (eg, the top surface becomes increasingly hydrophobic).

[0089] The inventors have therefore realised that by rounding or angling the sides of the element shapes, a surface having desirable hydrophobic properties can be achieved while maintaining a large element volume which improves resistance to aging.

[0090] 9 shows a cross-section (in a first cross-sectional plane 420 parallel to the groove surface) of a pattern of elements according to one embodiment of the present invention. In the illustrated pattern (e.g., a cubic pattern), an element 411 is shown to have both a first nearest neighbor element 412 and a second nearest neighbor element 413, where the first nearest neighbor element has a spacing distance s that is shorter than the second nearest neighbor spacing s'. For the illustrated cubic pattern, the second nearest neighbor element 413 defines a square around the central element 411 (e.g., the central element 411 is located at the center of the square), and the first nearest neighbor element 412 is located along the midpoint of a side of the square defined by the second nearest neighbor element 413.

[0091] The nearest neighbor spacings s, s' are defined as the distance between the centers of the first cross-sectional shapes of the elements 411, e.g., the distance between the center of the first cross-sectional shape of the central element 411 and the center of the cross-sectional shapes of the first and / or second nearest neighbor elements.

[0092] FIG. 10B shows a three-dimensional representation of the groove surface 122 and (for example) a number of conical elements 410 in a projected arrangement on the groove surface 122. In this example, the arrangement comprises a cubic pattern. It can be seen that the total volume of the elements 410 in the arrangement is the sum of (1 / 3)Ah for all the conical elements 410, where A is the area of ​​the base at the groove surface 122 and h is the height of the conical elements 410. FIG. 10A shows a three-dimensional void volume 415 formed as the negative volume of the total element volume, e.g., the void volume is the volume formed by the spaces between the elements 410. As shown in FIG. 10A, the void volume 415 does not occupy the same volume or space as the total element volume, and the void volume 415 may be considered to fit around the elements 410 and form a real volume up to a height h across the groove surface 122. For example, the void volume and element volume have a key and lock fit. It will be appreciated that the void volume 415, in combination with the total element volume, may not completely fill the available volume of a groove (eg, a groove as shown in Figures 3A and 3B).

[0093] 11 illustrates the contact angle formed between a static water droplet and a plurality of elements 410 in accordance with one embodiment of the present invention as a function of the space between the elements 410 (in millimeters). As can be seen from the data presented, as the gap area decreases, for example, the spacing s between the elements 410 decreases, the contact angle between the static water droplet and the elements 410 decreases. Thus, the inventors have surprisingly realized that it is advantageous to increase the gap volume between the elements 410 in accordance with the present invention.

[0094] Figure 12 shows the contact angle formed between a static water droplet and a plurality of elements 410 according to one embodiment of the present invention as a function of the porosity of the pattern of elements disposed on a surface. As with Figure 11, it can be seen that as the porosity increases and the elements 410 become increasingly spaced apart, the contact angle increases and the surface becomes more hydrophobic.

[0095] From both Figures 11 and 12, it can be seen that the relationship between the contact angle and the one and three dimensional spacing between elements on the surface is sinusoidal, and therefore it can be seen that it is preferable to select the spacing between elements and the element volume that allows for optimal porosity.

[0096] FIG. 13 combines the data from FIG. 12 and FIG. 6 and illustrates how the optimum between porosity and element volume is determined. As can be seen from FIG. 13, the optimum range of porosity and element volume may be obtained by determining where the curve corresponding to the relationship between porosity and contact angle intersects with the curve corresponding to the relationship between element volume and contact angle. Thus, for the example shown in FIG. 13, the optimum range is between 50%-65% porosity and 0.2-0.6 mm 3 The pattern may be determined to include an element volume of

[0097] 14-22 show various embodiments of element shapes at various cross sections and angles according to some embodiments of the present invention. All elements depicted herein have, by way of example only, a height h of 0.6 mm.

[0098] FIG. 14A shows an element 410a in a groove surface 122 according to an embodiment of the present invention, with a first nearest neighbor spacing s of 1.2 mm. FIG. 14B shows a first cross-sectional shape 425a of the element 410a in a first cross-sectional plane 420, which is a square with a width w of 0.6 mm. FIG. 14C shows a second cross-sectional shape 435a of the element, which is an irregular hexagon with two sets of parallel sides and two chamfered corners, e.g., the second cross-sectional shape is substantially a square prism with a chamfered apex (i.e., two chamfered corners between the sides and the apex). FIG. 14C also shows that the width w at the base of the second cross-sectional shape 435a is greater than the corresponding width w' at the apex of the second cross-sectional shape. FIG. 14D shows a detail of one of the chamfered corners, where the corner is cut at an angle of 45° to the sides and top of the shape, and the chamfer depth is 0.15 mm.

[0099] 15A-D show element 410b at groove surface 122. The element shown in FIG. 15 is substantially identical to the element shown in FIG. 14, except that it has a rounded (e.g., filleted) top corner with a radius of curvature of 0.15 mm, rather than a chamfer (as shown in FIG. 14). However, because the radius of curvature is equal to the depth of the chamfer (e.g., 0.15 mm), the contact area of ​​the flat top surface is the same for both elements shown in FIG. 14 and FIG. 15. It can be seen that second cross-sectional shape 435b shown in FIG. 15C is cylindrical with a filleted top, and the width w at the base of second cross-sectional shape 435b is greater than the corresponding width w' at the top of second cross-sectional shape 435b.

[0100] FIG. 16 shows an element 410c in the groove surface 122 having a square first cross-sectional shape 425c with a first nearest neighbor distance of 1.2 mm and a width of 0.6 mm, similar to FIGS. 14 and 15. Unlike FIGS. 14 and 15, the element 410c has a second cross-sectional shape 435c that corresponds to a truncated hyperbola, for example, with two parallel edges connected by two non-parallel concave curved edges. FIG. 16C shows that the width w at the bottom of the second cross-sectional shape 435c is greater than the corresponding width w' at the top of the second cross-sectional shape 435c. FIG. 16D shows that the curved sides have a depth of 0.15 mm and the bottom of the element 410c has a width of 0.3 mm (for example, the area of ​​the top surface of the element 410c is one-quarter of the area of ​​the bottom).

[0101] Figure 17 shows element 410d in groove surface 122, which is a combination of the elements shown in Figures 14 and 16, for example, second cross-sectional shape 435d includes a truncated hyperbola with a chamfered top end, the chamfer depth is 0.15mm. First cross-sectional shape 425d is a square with a width of 0.9mm, and the width of the top surface (e.g., the square root of the surface area of ​​the element in contact with the water drop) is 0.3mm. Figure 17C shows that the width w at the bottom of second cross-sectional shape 435d is greater than the corresponding width w' at the top of second cross-sectional shape 435d.

[0102] Figure 18 shows an element 410e in the groove surface 122 that is a combination of the elements shown in Figures 15 and 16, for example, the second cross-sectional shape 435e includes a truncated hyperbola with a filleted upper end having a radius of curvature of 0.15 mm. The first cross-sectional shape 425e is a square with a width of 0.9 mm and the width of the upper surface (e.g., the square root of the surface area of ​​the element in contact with the water drop) is 0.3 mm. Figure 18C shows that the width w at the bottom of the second cross-sectional shape 435e is greater than the corresponding width w' at the top of the second cross-sectional shape 435e.

[0103] FIG. 19A shows an element 410f at the groove surface 122 according to an embodiment of the present invention, with a first nearest neighbor spacing s of 1.0 mm. FIG. 19B shows a first cross-sectional shape 425f of the element 410f at the first cross-sectional plane 420, which is a square with a width w of 0.6 mm. FIG. 19C shows a second cross-sectional shape 435f of the element that is flattened parabolic, e.g., a flattened-top parabolic cross-sectional shape having two parallel edges parallel to the groove surface 122 and two convex curved surfaces extending between the top and the sides with a depth of 0.15 mm. FIG. 19C shows that the width w at the base of the second cross-sectional shape 435f is greater than the corresponding width w′ at the top of the second cross-sectional shape 435f.

[0104] Figure 20 shows the same element 410g as shown in Figure 19, with the only difference between the two embodiments being that the first closest spacing s is 1.2 mm in Figure 20 (compared to 1.0 mm in Figure 19). Figure 20C shows that the width w at the bottom of the second cross-sectional shape 435g is greater than the corresponding width w' at the top of the second cross-sectional shape 435g.

[0105] 14 to 20 illustrate elements having a generally point-like shape, while in FIGS. 21 and 22 examples of elongated elements are seen.

[0106] Figure 21 shows an element 410h in a groove surface 122 according to one embodiment of the present invention having a first nearest neighbor spacing s (shown in Figure 21B) of 0.4 mm and a second nearest neighbor spacing s' of 2 mm. Figure 21B shows a first cross-sectional shape 425h of the element 410h in a first cross-sectional plane 420h, which is a rectangular elongated strip having a width w of 0.2 mm and a length l of 1.8 mm. It will be appreciated that the longitudinal axis of the element may be oriented in any suitable and / or desirable direction, for example parallel or perpendicular to the circumferential direction of the tread.

[0107] Figures 21C and 21D show different second cross-sectional shapes of element 410h in two planes perpendicular to groove surface 122. It will be appreciated that when element 410h is oriented with its longitudinal axis parallel to the circumferential direction, Figure 21D represents second cross-sectional shape 435h. On the other hand, when the element is oriented with its longitudinal axis perpendicular to the circumferential axis, Figure 21C represents second cross-sectional shape 435h. In Figure 21D, the second cross-sectional shape is a rectangle having an aspect ratio of about 5. Although not shown, the top of the rectangle may be rounded or chamfered as disclosed herein.

[0108] Figure 22 shows an element 410i in a groove surface 122 according to one embodiment of the present invention having a first nearest neighbor spacing s of 0.4 mm and a second nearest neighbor spacing s' of 2 mm. Figure 22B shows a first cross-sectional shape 425i of the element 410i in a first cross-sectional plane 420 which is a rectangular elongated strip having a width w of 0.2 mm and a length l of 1.8 mm. It will be appreciated that the longitudinal axis of the element may be oriented in any suitable and / or desirable direction, for example parallel or perpendicular to the circumferential direction of the tread.

[0109] FIG. 22C shows that the second cross-sectional shape of the element 410i in one of the planes perpendicular to the groove surface 122 is rectangular. FIG. 22D and E show that the second cross-sectional shape of the element 410i in another plane perpendicular to the groove surface 122 is trapezoidal. In FIG. 22D and E, the second cross-sectional shape is a trapezoid having an aspect ratio of about 4. Although not shown, the top of the trapezoid may be rounded or chamfered as disclosed herein. FIG. 22D and E also show that the width w at the base of the second cross-sectional shape 435i is greater than the corresponding width w′ at the top of the second cross-sectional shape 435i.

[0110] Figures 23 and 24 show two possible orientations of the elements shown in Figures 21 and 22 at the groove surface. For example, the elongated rectangular element may be oriented such that the longitudinal axis of the first cross-sectional shape is parallel to the tire circumference (Figure 23). Alternatively, the longitudinal axis of the first cross-sectional shape may be oriented perpendicular to the tire circumference, e.g., extending from groove wall to groove wall and / or from bottom to tread surface.

[0111] 25A-G show a first cross-sectional shape (left), a second cross-sectional shape (center), and a 3D shape (right) of a number of elements according to various embodiments of the present invention. All elements are shown with a width w defined for the first cross-sectional shape (left) and a height h defined for the second cross-sectional shape (center). It will thus be understood that the width w is defined as the smallest dimension of the first cross-sectional shape, and the height h is defined as the largest extended dimension of the second cross-sectional shape.

[0112] FIG. 25A shows an element having a square first cross-sectional shape and a flattened parabolic second cross-sectional shape (eg, an element similar in shape to the elements shown in FIGS. 19 and 20).

[0113] FIG. 25B shows an element having a rectangular first cross-sectional shape and a truncated or flattened Gaussian second cross-sectional shape, e.g., a Gaussian curve with a flat top, or two parallel surfaces of different widths and a sinusoidal shaped edge transitioning between the two.

[0114] FIG. 25C shows an element that resembles a rounded cone, having a first cross-sectional shape that is circular and a second cross-sectional shape that is parabolic (eg, truncated at the base).

[0115] FIG. 25D illustrates an element having a triangular first cross-sectional shape and a substantially triangular second cross-sectional shape with a rounded apex, such that the three-dimensional shape is that of a rounded triangular pyramid.

[0116] FIG. 25E shows an element having a first cross-sectional shape that is hexagonal and a second cross-sectional shape that is parabolic (eg, truncated at the base).

[0117] FIG. 25F shows an element having a circular first cross-sectional shape and a rectangular second cross-sectional shape such that the three-dimensional shape is a cylinder.

[0118] FIG. 25G shows an element having a triangular first cross-sectional shape and a rectangular second cross-sectional shape such that the three-dimensional element shape is a triangular prism.

Claims

1. A tread for a pneumatic tire, comprising: including a plurality of grooves; The groove is A groove surface; a plurality of elements spaced apart in arrangement on the groove surface; Including, The elements each have a shape that defines a volume, the shape comprising: a first cross-sectional shape in a plane parallel to the groove surface, the smallest dimension of the first cross-sectional shape defined at the groove surface defining a width w of a base of the element, where 0.1 mm≦w≦3 mm; a second cross-sectional shape in a plane perpendicular to the groove surface, the maximum dimension of the second cross-sectional shape from bottom to top at the groove surface defines a height h of the element, 0.1 mm≦h≦3 mm, the second cross-sectional shape being generally parabolic or hyperbolic; an aspect ratio of said height h divided by said width w, said aspect ratio being at least 1 and at most 30; Including, The arrangement is a void volume in the space between the elements; and a porosity of 0.5 to 0.75, defined as the ratio of the void volume to the total volume of the elements in the arrangement; Including the tread.

2. 2. The tread of claim 1, wherein said second cross-sectional shape includes said width w and said height h, said width w at said base of said second cross-sectional shape being greater than a corresponding width w' at said top of said second cross-sectional shape.

3. A tread for a pneumatic tire, comprising: including a plurality of grooves; The groove is A groove surface; a plurality of elements spaced apart in arrangement on the groove surface; Including, The elements each include: a first cross-sectional shape in a plane parallel to the groove surface, the smallest dimension of the first cross-sectional shape defined at the groove surface defining a width w of a base of the element; a second cross-sectional shape in a plane perpendicular to the groove surface, the maximum dimension of the second cross-sectional shape from the bottom to the top at the groove surface defining a height h of the element; and having a shape including the second cross-sectional shape includes the width w and the height h, the width w at the base of the second cross-sectional shape being greater than a corresponding width w' at the top of the second cross-sectional shape, the second cross-sectional shape being generally parabolic or hyperbolic.

4. The tread of any one of claims 1 to 3, wherein said second cross-sectional shape generally tapers from said base to said peak.

5. The tread according to any one of claims 1 to 4, wherein the second cross-sectional shape comprises a curved, filleted, rounded or chamfered peak.

6. The tread according to any one of the preceding claims, wherein the first cross-sectional shape has a length l that is greater than the width w.

7. A tread according to any one of the preceding claims, wherein said first cross-sectional shape is an elongate strip defining a length l that is much greater than said width w.

8. The elements are each about 0.1 mm ３ A tread according to any one of the preceding claims, having a shape that defines a larger volume.

9. The tread according to any one of the preceding claims, wherein the arrangement of the elements is in a regular pattern.

10. A tread according to any one of the preceding claims, wherein the elements are spaced apart from one another in said arrangement at a typical or average spacing of between 50 μm and 1.5 mm.

11. A method for making a tread according to any one of claims 1 to 10, using a moulding technique.

12. A mould configured to make a tread according to any one of claims 1 to 10.

13. A method for making a tread according to any one of claims 1 to 10, using laser engraving technology.

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