Patent Description:
Tires are essential part of a vehicles for enabling movement of vehicle on different road surfaces. Tire is a circular and ring-like part of the vehicle which comes in direct contact with ground. The tires may be responsible for a plurality of functions, such as transfers weight of the vehicle, braking, to maintain steering, absorbing shock from the road surface, etc. In view of above stated function, tire design is essential for ensuring safe driving on different types of road surface conditions, such wet, dry and snowy.

In general, tires have a toroidal structure with an outer surface containing plurality of treads protruding from it. The treads are the main part of the tire which comes in direct contact with the road. The treads further contain tiny cuts along their surface called sipes which reduce slippering of vehicle in wet conditions by pumping water out from under the tire.

<CIT> discloses a pneumatic tire that includes plural blocks formed by plural grooves (circumferential grooves and lateral grooves) extending in a tire circumferential direction and in a tire width direction on a tread surface. The tire also has sipes narrower than the grooves, with each block containing sipes. Additionally, the tire has plural projections provided in the middle region (M) of each sipe, on one sidewall surface of the sipe, and having different projecting directions towards the other sidewall surface of the sipe.

<CIT> discloses a pneumatic tire furnished with a three dimensional type sipe on each of blocks constituting a block pattern formed on a tread part has a plurality of first projections provided on a plurality of first portions elongated in the same direction out of each of the portions of one side wall surface of the sipe and a plurality of second projections provided on a plurality of second portions elongated in the same direction out of each of the portions of the one side wall surface of the sipe, and the elongation direction of the first portions and the elongation direction of the second portions are different from each other.

Other known pneumatic tires known in the art are disclosed by publications <CIT>, <CIT>, <CIT>, <CIT> or <CIT>.

The same numbers are used throughout the drawings to reference like features and components.

Throughout the drawings, identical reference numbers designate similar, but not necessarily identical elements.

As described previously, vehicle tires have a tread pattern which extends circumferentially about the outer surface of the tire. The tread pattern is designed in such a manner that the plurality of tread blocks are formed, and these are spaced apart from each other by defining circumferentially and laterally extending grooves. These tread blocks provide the necessary grip or traction for driving, braking and cornering, and the tread block compound is specially formulated to provide a balance between wear, traction, handling and rolling resistance. The groove between the adjacent tread blocks provide free passage for expelling water backwards to provide better traction on wet surfaces and overcome adverse road phenomenon, such as hydroplaning. The pneumatic tire further includes a sipe along the circumferential outer surface. The sipe may be considered as thin slits molded into smooth tread block surface to improve traction of the tire in wet, snowy or icy road conditions. Such sipe essentially subdivide tread blocks into smaller elements to provide additional biting edges for foul-weather traction. Sipes also reduces the heat and its effects on tires by allowing it to cool when the air passes between these siping slices once they have opened after driving on them. Sipes also assist in channeling water away from underneath the tire, which helps build resistance to hydroplaning.

The sipes are formed in such a manner that these sipes may cut a single tread block in multiple portions. These sipes extend radially inward from top of the tread block to the bottom surface of the tread block up to a certain depth as compared to the height of the tread blocks. Improper location and design of sipes formed on the surface of the tread block may negatively affect the stiffness of the tread blocks. As may be understood, tread block stiffness plays an important role in proper functioning of tires in different road conditions. In an example, for increasing pattern stiffness of tire, there are several parameters are defined which may be varied to have a direct impact on the tread block stiffness. For example, tread width, block size, groove orientation, groove size, and many more may be varied to have a direct impact on the stiffness of the tire. However, on varying above mentioned parameters for optimizing pattern stiffness may negatively affect other tire performance parameters. For example, by increasing TW, the stiffness of the tread block increases but at the same time it may negatively impact on rolling resistance of the tire. So, to improve tread stiffness we may need to work on design of the sipes formed on surface of the tread such that instead of decreasing stiffness they may increase stiffness.

Conventionally, 2D sipes are available which may be used on tread block for enhancing wet traction of the tire. Such 2D sipes simply forms a cut along the surface of the tread block which helps in pumping out the water underneath the tire. However, conventional 2D sipe configuration had resulted in improving certain tire performance parameter but at the same time results in deterioration of other performance parameter. Therefore, considering above raised problems, there is a need for a 3D sipe configuration which increases connecting surface between the side walls of the sipe to enhance the stiffness of the tread block and still maintain other performance parameter in safety limit.

A pneumatic tire with a three-dimensional (3D) sipe for tread pattern, is described herein. A pneumatic tire as proposed in claim <NUM> is provided with a sipe configuration, which enhances performance parameters of the pneumatic tire. As may be understood, sipes are used to increase the stiffness to the adjacent tread blocks while rotating on a wet as well as on a dry road surface. The sipe, as described in the invention as claimed, may not only increase the wet performance and wear appearance of the pneumatic tire, but may also increase the stiffness of the tread block and also reduce breaking distance of the vehicle. Further, the sipe as disclosed in invention as claimed provides an interlocking feature between tread block pieces, which increases the tread pattern stiffness and the same time does not affect negatively other tire performances, i.e., tangential force, lateral force handling capability and principal stress and strain experience.

In one example, a pneumatic tire having toroidal shape with an outer surface includes plurality of tread block protruded and extended orthogonally from the outer surface of the pneumatic tire. The tread blocks are the component which make direct contact with the road surface and these are extruded on outer surface to impart wear resistance and traction to the tire. The material used for compounding tread block is such selected that it has long wear characteristics and good traction capability.

Continuing with the present example, the tread pattern on the outer surface of pneumatic tire is such that the plurality of tread blocks are spaced apart from each other to form a circumferentially and laterally extending grooves between the adjacent tread blocks amongst the plurality of tread blocks. Each tread block includes a sipe formed across the surface of the tread block. The sipe may be considered as thin slits molded into smooth tread block surface to improve traction of the tire in wet, snowy or icy road conditions. The sipe extends radially inward into the tread block up to a certain depth. Such sipe essentially subdivide tread blocks into smaller elements to provide additional biting edges for foul-weather traction. Sipes also reduces the heat and its effects on tires by allowing it cool when the air passes between these siping slices once they have opened after driving on them. Sipes also assist in channeling water away from underneath the tire, which helps build resistance to hydroplaning.

In an example, the sipe formed on the surface of the tread block may include a pair of walls facing each other. Both the walls have a periodically repeating corners and depressions extending along the lateral extension of the sipe. Such periodically repeating corners and depressions may also form a plurality of tapered sides of variant angles extending along the lateral extension of the sipe. In an example implementation, the pair of walls are arranged in such a manner that the corner of one wall may face corresponding depression of the other wall and these pair of walls are separated from each other by a distance to form a groove of certain width in between the walls.

The sipe further includes a sinusoidal connecting portion extending laterally along the length of the walls. For example, like sinusoidal wave has a positive and a negative peak upon its axis of extension, the sinusoidal connecting portion also include positive and negative peaks extending in the direction of length of the sipe. In an example, the sinusoidal connecting portion also extends along the width of the sipe. The sipe further includes a plurality of semicircular connecting portions. The semicircular connecting portions are positioned periodically above and below the sinusoidal connecting portion on adjacent tapered sides of the walls. In an example configuration, the semicircular connecting portions include an open end and a closed end. In one example, the semicircular connecting portion positioned on adjacent tapered sides are oppositely oriented, i.e., one has open end facing above and other has open end facing down, based on the type of peak of the sinusoidal connecting portion. In an example, both connecting portions, i.e., sinusoidal connecting portion and semicircular connecting portion makes a close contact with both walls by extending through the width of the sipe.

Thus, the invention as claimed provides enhanced wet condition performance and increased stiffness. The sipe configuration disclosed by the invention as claimed has a sinusoidal and a semicircular connecting portion, such that it increases the rate of flow of water through it for pumping water beneath the tire and also increases the tangential and lateral stiffness of the tire. Further, it improves maximum tangential forces and lateral forces for improving braking and cornering performance of the tire, respectively. Further, the sipe as disclosed by the invention as claimed, also improves wear appearance, shear stress and unidirectional bending of the tire.

These and other advantages of the invention as claimed would be described in greater detail in conjunction with the following figures, without limiting the scope of the invention. While configuration of the tie bar of the pneumatic tire may be implemented in any number of different configurations.

<FIG> illustrates schematics of a pneumatic tire <NUM> with a tread portion <NUM> for vehicles, such as utility vehicles (UVR), crossover utility vehicles (CUV), passenger buses, motor-bicycles, heavy equipment automobiles, aircrafts etc., in accordance with an implementation of the invention as claimed. The pneumatic tire <NUM> may further include a pair of shoulder portions <NUM> with the tread portion <NUM> placed between the pair of shoulder portions <NUM>. In an example, the tread portion <NUM> may be represented as a ring-shaped portion, located between the pair of shoulder portion <NUM>. In another example, the tread portion <NUM> may be considered as a circumferential outer surface of the pneumatic tire <NUM>. The circumferential outer surface may include the tread portion <NUM> which contacts directly with the surface of the road during rotation. Further, the shoulder portions <NUM> join the circumferential outer surface to the rim of the pneumatic tire <NUM>. The tread portion <NUM> as shown in <FIG> may be designed as per any possible pattern, without deviating from the scope of the invention, such that the designed pattern reliably provides wear resistance and traction with the road surface.

As may be understood, the tread portion <NUM> on the circumferential outer surface includes a plurality of tread blocks <NUM>-<NUM>, <NUM>, <NUM>,. N (collectively referred to as tread blocks <NUM>). The tread blocks <NUM> are to make close contact with the surface of the road while rotation. The pneumatic tire <NUM> (referred to as tire <NUM>) may further include a plurality of circumferentially extending grooves along the outer surface. The circumferentially extending grooves may be considered as a recess in between tread blocks <NUM> extending along the circumference of the tire <NUM>. The tread blocks <NUM> of tire <NUM> may further include sipes <NUM>-<NUM>, <NUM>, <NUM>,. N (collectively referred to as sipes <NUM> or sipe <NUM>) formed across the surface of the tread block. The sipe extending across the surface of the tread block may be result in a hollow channel extending laterally in the solid tread block of the tire along the width of tread block. Therefore, the sipes may be considered as the grooves defined in tread block having a defined width. Such sipes are formed by using a process called siping which cut thin slits across the surface of the tread blocks to improve traction for driving in snowy, wet or icy conditions. Siping also provides more gripping edges for the tire to appropriately grip the road in wet and snowy conditions.

Continuing with the present example, the sipe <NUM> includes a pair of walls (<NUM>, <NUM>) facing each other. In an example, pair of walls (<NUM>, <NUM>) have a periodically repeating corners and depressions extending along the lateral extension of the sipe <NUM>. Such periodically repeating corners and depressions may also form a plurality of tapered sides (<NUM>) of variant angle extending along the lateral extension of the sipe <NUM>. For example, such a configuration of walls forms a zig-zag looking sipe. In an example implementation, the pair of walls (<NUM>, <NUM>) are arranged in such a manner that the corner of one wall (<NUM>) may face corresponding depression of the other wall (<NUM>) and these pair of walls (<NUM>, <NUM>) are separated from each other by a distance to form a groove in between the walls having a certain width. In an example, not falling under the scope of the claims, instead of having corners and depressions, other structure may be formed to form the sipe <NUM>.

<FIG> further depicts an enlarged view of the tread block <NUM>, which illustrates the sipe <NUM> extending across the surface of the tread block <NUM>. In an example, only one sipe <NUM> is shown in the <FIG> for tread block, however, any possible number of sipes <NUM> may be formed on the surface of the tread block based on the requirement of the design. The sipe <NUM> includes pair of walls (<NUM>, <NUM>) having periodically repeating corners and depressions which may face each other to form a groove like structure in between them having a certain width. The periodically repeating corners and corresponding depressions form plurality of tapered sides <NUM> along the extension of sipe.

Returning to the present example, the sipe <NUM> may further include interlocking features, such as a sinusoidal connecting portion and a semicircular connecting portion. These and other portions of the sipe <NUM> may be described in detail in conjunction with <FIG>.

<FIG> illustrates an enlarged view of a tread block <NUM> with a three-dimensional (3D) sipe <NUM>, in accordance with an implementation of the invention as claimed. As shown in <FIG>, the tread block <NUM> is 'siped' through a siping process by forming a sipe, such as sipe <NUM>, across its surface. The sipe <NUM> extends along the surface of the tread block <NUM>. Further, the sipe <NUM> is formed radial inward direction into the tread block <NUM> up to a certain depth 'D' from the top surface of the tread block <NUM>. In an example, only one sipe <NUM> is shown as an example, multiple sipes <NUM> may be possible to increase the traction of the tread blocks <NUM> with the road surface. The sipe <NUM> includes a pair of walls, such as pair of walls (<NUM>, <NUM>). For clarity, only wall <NUM> is shown and wall <NUM> is not shown in <FIG>. As may be gathered from <FIG>, the wall <NUM> includes periodically repeating corners and depression. For example, firstly a depression is shown, thereafter, a corner then depression and so on. The periodically repeating corners and depression extends along the length of the sipe. Further, such periodically repeating corners and depressions forms multiple tapered sides <NUM>.

As may be understood, when the tread blocks <NUM> of tire <NUM> makes contact with road surface, they may experience a variety of loading conditions like braking, acceleration, and cornering. Such unexpected loading conditions may deform the structure of the tread blocks <NUM> and may decrease the tangential and lateral stiffness of the tread pattern. As a result, the tread blocks <NUM> lose their contact with the road surface and the vehicle slips, mainly in wed or snowy condition. The sipe <NUM> further includes a sinusoidal connecting portion <NUM> extending laterally along the length of the pair of walls (<NUM>, <NUM>). The sinusoidal connecting portion <NUM> is such that it may make close contact with both walls (<NUM>, <NUM>) and decreases deformation of tread blocks <NUM>. For depicting the 3D structure in 2D figures, the sinusoidal connecting portion <NUM> is shown as making contact only with wall <NUM>. However, it makes close contact with both walls (<NUM>, <NUM>). Such sinusoidal connecting portion <NUM> take care of the tangential stiffness of the tread pattern and improves tangential forces handling capacity.

The swipe <NUM> may further include a plurality of semicircular shaped connecting portions <NUM>. The semicircular connecting portions <NUM> are positioned periodically above and below the sinusoidal connecting portion <NUM> on adjacent tapered sides <NUM> of the pair of walls (<NUM>, <NUM>). In an example configuration, the semicircular connecting portions <NUM> include an open end <NUM> and a closed end <NUM>. In one example, the semicircular connecting portions <NUM> positioned on adjacent tapered sides <NUM> are oppositely oriented, i.e., one has open end <NUM> facing above and other has open end <NUM> facing down. The semicircular connecting portion <NUM> increases the lateral stiffness of the tread pattern and improves lateral force handling capacity. In an example, both connecting portions, i.e., sinusoidal connecting portion <NUM> and semicircular connecting portion <NUM> makes a close contact with both walls (<NUM>, <NUM>) by extending through the width of the sipe <NUM>.

In another implementation, the sinusoidal and semicircular connecting portions (<NUM>, <NUM>) are protruded or extended perpendicularly from one of the walls and the other wall include corresponding depression shapes to accommodate these protrusions. For example, wall <NUM> include protruded sinusoidal and semicircular connecting portions (<NUM>, <NUM>) and these are accommodated in corresponding depressions formed on another wall <NUM> facing the wall <NUM>.

In one example, not falling under the scope of the claims, the tapered sides <NUM> of the sipe <NUM> may further include a through hole <NUM> above the sinusoidal connecting portion <NUM>. The through hole <NUM> improves air passing capability in heating conditions. For example, these through holes <NUM> also reduces the heat and its effects on tires by allowing it cool when the air passes between these sipes <NUM>.

Returning to the present example, the proposed configuration of the sipe <NUM> results in an increase in the tangential and lateral stiffness of the tread pattern to avoid deformation of tires in loading conditions. Further, such structure of connecting portions does not interrupt the water flow from the sipe during wet conditions, as it improves wet traction of the tread pattern of tire. As may be understood, in conventional approaches, to improve stiffness of the tread pattern, other parameters like tread width, block size, groove orientation, groove size are changed, but these changes negatively impact the performance of the tire. However, the structure of sipe <NUM> as disclosed in invention as claimed provide improved stiffness and wet traction of the tire without changing any other parameters and improve other values of other tire performance as well. The comparison of the conventional sipe with the claimed sipe structure configuration based on the tire performance parameter is listed in the below table <NUM>.

Table <NUM> provides comparison of conventional 2D sipe with the claimed 3D sipe based on the tire performance parameters, such as tangential stiffness, lateral stiffness, maximum tangential force, maximum lateral force, maximum principal stress and maximum principal strain. For example, as mentioned in table <NUM>, in comparison to tangential stiffness offered by conventional 2D sipe design, e.g., <NUM>, the corresponding value of the tangential stiffness offered by proposed 3D sipe design is <NUM>, i.e., clear increase of <NUM>% in tangential stiffness, this is achieved due to the presence of the sinusoidal connecting portion <NUM>. Further, in comparison to the lateral stiffness offered by 2D sipe design, e.g., <NUM>, the corresponding value for the proposed 3D sipe is <NUM>, i.e., clear increase of <NUM>% in lateral stiffness, this is achieved due to the presence of the semicircular connecting portions <NUM>. Furthermore, as compared to 2D sipe design which may handle <NUM> max. tangential force, the 3D sipe proposed in the invention as claimed may handle <NUM> max. tangential force, i.e., <NUM>% increase in tangential force handling capability which may eventually improves the breaking performance of the tire, i.e., breaking distance is reduced.

Further, as compared to 2D sipe design which may handle <NUM> max. lateral force, the 3D sipe proposed in the invention as claimed may handle <NUM> max. lateral force, i.e., <NUM>% increase in lateral force handling capability which may eventually improves the cornering performance of the tire. Further, the maximum principle stress and strain experienced by the tire is also reduced by <NUM>% and <NUM>%, respectively. It may be noted that the values used in above table are exemplary and may change based on the condition and environment in which the vehicle is running.

Thus, based on various experimental results and data obtained from the tires, the 3D sipe with connecting portions provides improved wet performance and stiffness of the tire in loading conditions. Additionally, an improvement in tangential stiffness and lateral stiffness may result in decreased stress and strain experienced by the tire <NUM>.

<FIG> illustrates exemplary 2D view of sipe <NUM> showing dimensions of connecting portions. As shown in <FIG>, the sipe <NUM> include a sinusoidal connecting portion, such as sinusoidal connecting portion <NUM>, and a semicircular connecting portion, such as semicircular connecting portion, <NUM>. The thickness of the sinusoidal connecting portion <NUM> is depicted as 'A', diameter of semicircular connecting portions <NUM> is depicted as 'B' and thickness of semicircular connecting portion <NUM> is depicted as 'C'. The design permissible range and ranges used in present invention are depicted in below Table <NUM>:.

Table <NUM> provides design permissible ranges and range used in present invention for dimensions of the connecting portions. As mentioned in Table <NUM>, design permissible range of 'A', i.e., thickness of the sinusoidal connecting portion <NUM> is <NUM> to <NUM> and value used in present invention is <NUM>. Therefore, the sinusoidal connecting portion <NUM> utilizes minimum possible area of the sipe and allow maximum water to flow from it. Similarly, 'B', i.e., diameter of semicircular connecting portions <NUM> may have value in range of <NUM> to <NUM>. However, the value used in the present invention is <NUM>. Further, the value of 'C', i.e., thickness of semicircular connecting portion <NUM> is <NUM> which is well within the design permissible range of <NUM> to <NUM>.

Claim 1:
A pneumatic tire (<NUM>) having a tread block (<NUM>) protruding from an outer surface, wherein the tread block (<NUM>) comprises:
a sipe (<NUM>) formed across the surface of the tread block (<NUM>), wherein the sipe (<NUM>) comprises:
a pair of walls (<NUM>, <NUM>) facing each other having periodically repeating corners and depressions, wherein periodic corners and depression forms tapered sides (<NUM>) of variant angle along the lateral extension of sipe (<NUM>);
a sinusoidal connecting portion (<NUM>) extending laterally along the length of the walls, wherein the sinusoidal connecting portion (<NUM>) is in close contact with both walls (<NUM>, <NUM>) by extending through the thickness of the sipe (<NUM>);
characterized in that said sipe (<NUM>) further comprises:
a plurality of semicircular connecting portion (<NUM>) positioned periodically above and below the sinusoidal connecting portion (<NUM>) on adjacent tapered sides (<NUM>) of the walls.