FORM 2
THE PATENTS ACT, 1970 (39 of 1970) & THE PATENTS RULES, 2003
COMPLETE SPECIFICATION (See section 10, rule 13)
1. Title of the invention: VEHICLE TIRE
2. Applicant(s)
NAME NATIONALITY ADDRESS
CEAT LIMITED Indian CEAT Ltd At: Get Muwala Po: Chandrapura Ta: Halol - 389 350 Dist: Panchmahal, Gujarat, India
3. Preamble to the description
COMPLETE SPECIFICATION
The following specification particularly describes the invention and the manner in which it
is to be performed.

TECHNICAL FIELD
[0001] The present subject matter relates to vehicle tires.
BACKGROUND
[0002] Tires support load of a vehicle and impact handling, drivability, and
safety of the vehicle. When it comes to measuring the property and performance of the tires of the vehicle (trucks, passenger cars, and the like), rolling resistance of the tires is considered one of the important performance measurement parameters. The rolling resistance may be understood as a force that the vehicle and its tires are required to overcome to move forward and make the tires roll on a given surface.
BRIEF DESCRIPTION OF DRAWINGS
[0003] The detailed description is described with reference to the
accompanying figures. In the figures, the left-most digit(s) of a reference
number identifies the figure in which the reference number first appears. The
same numbers are used throughout the drawings to reference like features
and components.
[0004] Figure 1 illustrates a conventional design of a tread region of a tire
depicting an arrangement of tread region of the tire.
[0005] Figure 2 illustrates a cross-sectional view of a tire taken in a
meridian direction showing an arrangement of tread radius of the tire, in
accordance with an implementation of the present subject matter.
[0006] Figure 3 illustrates a front view of a portion of the tire depicting an
arrangement of tread rows along a circumferential direction of the tire,
according to an example implementation of the present subject matter.
[0007] Figure 4 illustrates an arrangement of belt plies of the tire, according
to an example implementation of the present subject matter.

DETAILED DESCRIPTION
[0008] When a tire bearing the weight of a vehicle rotates, tread and
sidewall portions of the tire are subjected to flexing, bending, and shear forces. As the tire deforms during running, friction between molecules causes energy to be converted to heat. This is known as hysteresis loss. Such loss accounts for a majority of the rolling resistance in tires. High rolling resistance implies that to maintain forward momentum, more energy would be required in the form of fuel, leading to higher carbon dioxide emissions.
[0009] Hence, as is known, in the field of tire manufacturing, various
solutions are being worked upon that may be used to minimize the rolling resistance of tires as much as possible. Minimizing the rolling resistance enables vehicles to use less energy, thereby reducing fuel consumption by the vehicles and subsequently reducing carbon footprint.
[0010] One such conventional solution for reducing the rolling resistance of
the tires comprises diminishing internal friction loss caused by the deformation of the tire during running. A known approach for diminishing the internal friction loss is to use high-density rubber materials having a characteristic of a smaller internal friction loss in tire construction. However, this technique is also known to adversely impact other performance parameters of tires, such as braking performance, steering performance, comfort, wear-resistant properties, and so forth. For instance, diminishing the internal friction loss by use of high-density rubber materials may cause various unfavorable phenomena during high¬speed cruising on a wet road, such as an increase in braking distance, deterioration of the control stability, degraded comfortableness, and reduced wear resistance and so, on. These characteristics are certainly undesirable for a tire.

[0011] Another prior art solution proposes to change the design of the tire
to replace rubber material generally used in a tread portion of the tire with rubber material with a smaller loss tangent. However, the above method is also known to sacrifice other performance of tires such as wear resistance performance. Yet another prior art solution proposes reducing rolling resistance by regulating a shape of a section of the tire. While the proposed technique makes it possible to reduce rolling resistance, said technique is known to cause deterioration in the wear resistance of the tire.
[0012] Above suggests that various attempts have been made to meet the
requirement of reducing the rolling resistance, for example, by changing the materials or design parameters of the tire. However, there exists a conflicting trade-off in employing the conventionally known techniques for reducing the rolling resistance of a tire due to their limiting effects on both the performance characteristics and the extent of fuel efficiency of the vehicle.
[0013] To this end, the present subject matter provides a tire that exhibits
improved (reduced) rolling resistance with a resultant improvement in fuel economy for an associated vehicle.
[0014] In accordance with an embodiment of the present subject matter, a
tire having a tread region is disclosed. The tire includes a plurality of circumferential tread rows in the tread region. The tire further includes a plurality of tread blocks in each of the plurality of circumferential tread rows. Furthermore, one or more lateral grooves and at least one sipe are provided in each of the plurality of tread blocks. Also, in the tire, a first tread radius that spans across a central portion of the tread region is greater than a second tread radius spanned across a shoulder portion of the tread region, the shoulder portion being present on either side of the central portion. Furthermore, a length of the first tread radius of the tire is less than a tread width of the tire.

[0015] The tread radius combination disclosed by the present subject
matter provides a squarish footprint to the portion of the tire’s tread region that touches a road surface. The tread region of the tire with the squarish footprint ensures that under vertical loads, pressure on the tire is distributed evenly resulting in lower friction with the road surface. The lower friction enables a reduction in strain on belt package of the tire, thereby reducing the RRC of the tire.
[0016] Further, by introducing the lateral grooves and sipes in each of the
plurality of the tread blocks of the tire, it is ensured that the stiffness in all
directions is high so that, during loading and unloading cycle of the tire, high
stiffness causes less deformation, and less energy is required for the tire to
roll on the road surface. Hence, increasing the number of biting edges by
introducing more lateral grooves and sipes in the tread region and cross-linking
each other to form an individual tread block also helps in reducing the RRC in
the tire. Thus, the present subject matter provides a tire that delivers low
internal friction, thereby reducing the rolling resistance coefficient (RRC).
[0017] The above and other features, aspects, and advantages of the
subject matter will be better explained with regard to the following description and accompanying figures. It should be noted that the description and figures merely illustrate the principles of the present subject matter along with examples described herein and should not be construed as a limitation to the present subject matter. It is thus understood that various arrangements may be devised that, although not explicitly described or shown herein, embody the principles of the present disclosure. Moreover, all statements herein reciting principles, aspects, and examples thereof, are intended to encompass equivalents thereof. Further, for the sake of simplicity, and without limitation, the same numbers are used throughout the drawings to reference like features and components.

[0018] Figure 1 illustrates a conventional design of a tread region of a tire
depicting an arrangement of the tread region of the tire. A description of the conventional tire 100 in Figure 1 is provided in conjunction with a description of Figure 2 so as to provide a comparative explanation of the conventional tire 100 vis-a-vis a tire 200 designed in accordance with an implementation of the present subject matter.
[0019] Figure 2 illustrates a cross-sectional view of the tire 200 taken in a
meridian direction showing an arrangement of tread radius of the tire 200, in accordance with an implementation of the present subject matter. While Figure 3 illustrates a front view of a portion of the tire 200 depicting arrangement of tread rows along a circumferential direction of the tire 200, according to an example implementation of the present subject matter. For sake of ease of explanation, Figures 2 and 3 are explained together.
[0020] In an implementation of the present subject matter, the tire 200 has
a tread region 202, and the tread region 202 is distributed between a central
portion 204 and a shoulder portion 206. The should portion 206 is present on
either side of the center portion 204 of the tread region 102, as shown in Figure
1. More specifically, the tire 200 has two shoulder portions 206 with the central
portion 204 of the tread region 102 between the two shoulder portions 206.
[0021] As illustrated in Figure 2, the tire 200 has a first tread radius (TR1)
208 in the central portion 204 of the tread region 202. The shoulder portions 206 of the tread region 202, which are disposed on both sides of the central portion 204, have a second tread radius (TR2) 210. In an embodiment of the present subject matter, the TR1 208 of the tire 200 that spans across the central portion 204 of the tread region 202 is greater than the TR2 210 of the tire 200 that extends across shoulder portions 206 of the tread region 202 on either side of the central portion 204. Also, a length L1 of the TR1 208 is approximately 50 % of width W1 of the whole tread region 202 of the tire 200.

A footprint rectangle of the tire 200, which provides whether the footprint shape of the tire 200 is convex or concave along the tire 200 rolling direction, is in a range of 90-95%. A higher footprint rectangle ratio allows the tire 200 to remain in uniform contact with a road surface and affords a uniform pressure distribution that helps in maintaining a proper tire deformation, thereby reducing the rolling resistance coefficient (RRC).
[0022] Thus, in contrast to the conventional tire 100, as shown in prior art
Figure 1, which has a curved profile for tread region 106 due to a positive cavity profile for TR1 102 and negative cavity profile for TR2 104, and where TR1 102 length is approximately 30% of width W of the tread region 106, in the present invention, the TR1 208 and TR2 210 both are positive and length of the TR1 208 is 50% of the width W1 of the tread region 202. This provides a flatter curvature to the tread region 202 of the tire 200, thereby allowing forces and moments that are generated under vertical loads through deformations during rolling of the tire 200 to be distributed evenly across the whole tread region 202 resulting in the reduction of rolling resistance of the tire 200. The reduction in rolling resistance further reduces the amount of energy dissipation that happens during the process of overcoming the resistive force to move an associated vehicle on a road surface.
[0023] Further, as shown in Figure 3, the tread region 202 of the tire 200
includes a plurality of circumferential tread rows 302-1, 302-2,…..303-n. Each of the plurality of circumferential tread rows 302-1, 302-2,…..303-n include a plurality of tread blocks 304. Further, each of the plurality of tread blocks 304 includes one or more lateral grooves 306 and at least one sipe 308. Each of the one or more lateral grooves 306 of two consecutive tread blocks from amongst the plurality of tread blocks 304 in the at least one circumferential tread row are connected to each other through cross-linking of the at least one sipe 308 with at least two lateral grooves of the respective tread blocks.

[0024] Thus, by increasing the number of biting edges by introducing the
lateral grooves 306 and sipes 308, the stiffness on the tire 200 in all directions is equally distributed, thereby ensuring that during the loading and unloading cycle of the tire 200 high stiffness causes less deformation and less energy is required for the tire 200 to overcome the rolling resistance force. For example, as shown in the table below, during pattern stiffness simulation, the inventors of the present invention found that all the stiffnesses (tangential, lateral) and torque steer were high for the new tread pattern compared to the existing WinMile X3-R pattern. During the simulation, there was a 16.4% increase in the tangential stiffness and a 13.6% increase in lateral stiffness compared to the existing WinMile X3-R pattern.

Parameter Tread pattern described in the present invention Conventional
WINMILE X-3 R
Pattern
Tangential
Stiffness Kxx
(N/mm) 2722 2338
Lateral Stiffness Kxx (N/mm) 2586 2275
[0025] This reduces the RRC of the tire 200. For example, the inventors of
the present invention have found that after implementing the present solution, the RRC of the tire 200 has reduced below 5.
[0026] Figure 4 illustrates an arrangement of belt plies 402 of the tire 200,
according to an example implementation of the present subject matter. As
shown in Figure 4, the tire 200 comprises a plurality of belt plies 402. The
plurality of belt plies 402 include a second belt ply 403 and a third belt ply 404.
[0027] In conventional tires, such as the one shown in Figure 1, a distance
between a ground-facing surface of the tire 100 and a second belt ply is higher due to the presence of extra rubber material between the second belt ply 403 and the third belt ply 404. This causes fluctuation in belt plies of the tire 100 generating high strain energy density (SENER) in the belt plies area of the tire

100. Thus, to enhance the tire 100 endurance at the belt plies edges and to reduce the RRC, it is necessary that delta SENER, i.e., change between the strain energy density between loading and unloading conditions, is kept minimum.
[0028] To achieve the lower delta SENER, for example, in a range of 0.1-
0.2, in the present subject matter, the second belt ply 403, as shown in Figure 4, may be given a positive belt lift, i.e., the second belt ply 403 may be lifted upwards, by removing a certain amount of rubber material above the second belt ply 403. The positive belt lift is such that a distance between the second belt ply 403 and a ground facing surface of the tire 200 towards the shoulder portion 206 depends on a non-skid depth (NSD) of the tire 200, and in the present example, lies in a range of 22 to 26 mm, which is higher than the belt lift of the conventional tires, such as tire 100. Higher belt lift for the second belt ply 403 helps in achieving the squarish footprint for the tire 200 that lowers the strain on the belt plies 402 to equal pressure distribution over a contact surface of the tire 200, thereby ultimately facilitating the lowering of the rolling resistance of the tire 200.
[0029] Also, the positive belt lift makes the profile of the second belt ply 403
considerably straighter, thereby reducing the gap between the second belt ply 403 and the third belt ply 404. Due to a reduction in the gap and due to the removal of the unwanted rubber material, the fluctuation between the belt plies 402 is greatly controlled. Fewer fluctuation results in an onward reduction in the strain energy at the edges of the belt plies 402.
[0030] Although implementations of a tire are described, it is to be
understood that the present subject matter is not necessarily limited to the specific features of the systems described herein. Rather, the specific features are disclosed as implementations for the tire.

I/We Claim:
1. A tire (200) having a tread region (202) comprising:
a plurality of circumferential tread rows (302-1, 302-2,…..303-n) in the tread region (202);
a plurality of tread blocks (304) in each of the plurality of circumferential tread rows (302-1, 302-2,…..303-n); and
one or more lateral grooves (306) and at least one sipe (308) in each of the plurality of tread blocks (304),
wherein a first tread radius (208) of the tire (200) across central portion (204) of the tread region (202) is greater than a second tread radius (210) of the tire (200) across shoulder portion (206) of the tread region (202) on either side of the central portion (204), a length (L1) of the first tread radius (208) being different than a tread width (W1) of the tire (200).
2. The tire (200) as claimed in claim 1, wherein the length of the first tread radius (208) is approximately 50 % of the tread width (W1) of the tire (200).
3. The tire (200) as claimed in claim 1, wherein each of the one or more lateral grooves (306) of two consecutive tread blocks, from amongst the plurality of tread blocks (304) in the at least one circumferential tread row, are connected to each other through cross-linking of the at least one sipe (308) with at least two lateral grooves of the respective tread blocks.
4. The tire (200) as claimed in claim 1, a footprint rectangle ratio of the tread region (202) is in a range of 90-95%.
5. The tire (200) as claimed in claim 1, wherein a rolling resistance coefficient of the tire (200) lies in a range of 4-5.