Heavy duty tire
A tire 2 includes a tread 4 formed from a rubber composition containing: a rubber component including a styrene butadiene rubber; and a filler including silica. The tread 4 has a plurality of circumferential main grooves 10 . The plurality of circumferential main grooves 10 define a pair of crown land portion 20 in the tread 4 . Each crown land portion 20 has a crown narrow groove 24 . Each crown narrow land portion 34 defined by the crown narrow groove 24 has a crown sipe 40 . An amount CSB of the styrene butadiene rubber, an amount BS of the silica, a groove depth DGs of the crown sipe 40 , and a groove depth DGg of the crown narrow groove 24 satisfy the following relational expression. ( CSB + BS ) / ( DGg - DGs ) ≥ 5
1 . A heavy duty tire comprising a tread formed from a rubber composition comprising:
a rubber component including a styrene butadiene rubber; and
a filler including silica,
wherein the tread has a tread surface configured to come into contact with a road surface,
the tread has a plurality of circumferential main grooves extending continuously in a circumferential direction,
the plurality of circumferential main grooves include a crown circumferential main groove located on an equator plane and a pair of shoulder circumferential main grooves located on outermost sides in an axial direction,
the plurality of circumferential main grooves define a plurality of land portions in the tread,
the plurality of land portions include a pair of crown land portions closest to the equator plane and a pair of shoulder land portions including ends of the tread surface,
each of the crown land portions has a crown narrow groove extending continuously in the circumferential direction,
the crown narrow groove defines two crown narrow land portions in the crown land portion,
each of the crown narrow land portions has crown sipes traversing the crown narrow land portion,
the crown narrow groove includes a body portion main body and an enlarged width portion located radially inward of the body portion main body,
opposing wall surfaces of the body portion main body are brought into contact with each other by deformation of the tread,
a groove width of the enlarged width portion is wider than a groove width of the body portion main body,
the enlarged width portion includes an inflection portion and a bottom portion,
the bottom portion is located radially inward of the inflection portion,
a contour of the inflection portion is represented by an arc,
a contour of the bottom portion is represented by an arc,
a radius Rc of the arc representing the contour of the inflection portion is larger than a radius Rt of the arc representing the contour of the bottom portion,
a groove depth DGs of each crown sipe is shallower than a groove depth DGg of the crown narrow groove,
an amount CSB of the styrene butadiene rubber in 100 parts by mass of the rubber component is not less than 10 parts by mass,
an amount BS of the silica per 100 parts by mass of the rubber component is not less than 15 parts by mass, and
the amount CSB of the styrene butadiene rubber, the amount BS of the silica, the groove depth DGs (mm) of each crown sipe, and the groove depth DGg (mm) of the crown narrow groove satisfy the following relational expression:
(
CSB
+
BS
)
/
(
DGg
-
DGs
)
≥
5.
2 . The heavy duty tire according to claim 1 , wherein the rubber component further includes a natural rubber and a butadiene rubber, and
the amount CSB of the styrene butadiene rubber, an amount CN of the natural rubber, and an amount CB of the butadiene rubber in 100 parts by mass of the rubber component satisfy the following relational expression:
CN
≥
CSB
+
CB
.
3 . The heavy duty tire according to claim 1 , wherein an amount CS of the silica in 100 parts by mass of the filler is not less than 40 parts by mass.
4 . The heavy duty tire according to claim 1 , wherein the silica includes silica made from a biomass material.
5 . The heavy duty tire according to claim 1 , wherein the filler includes silica having an average primary particle diameter of not greater than 16 nm.
6 . The heavy duty tire according to claim 1 , wherein the filler further includes carbon black, and
the carbon black includes recycled carbon black.
7 . The heavy duty tire according to claim 1 , wherein the filler further includes carbon black, and
the carbon black includes carbon black having an average primary particle diameter of not greater than 19 nm.
8 . The heavy duty tire according to claim 1 , wherein the rubber composition further comprises a resin component.
9 . The heavy duty tire according to claim 1 , wherein a land ratio is not less than 80%, the land ratio being a ratio of a total area value of ground-contact surfaces of a plurality of land portions included in a ground-contact surface to an area value of an entirety of the ground-contact surface, the ground-contact surface being obtained by applying a load, which is 100% of a normal load, to the tire, which is fitted on a normal rim and whose internal pressure is adjusted to a normal internal pressure, with a camber angle as 0 degrees, and bringing the tire into contact with a flat road surface.
10 . The heavy duty tire according to claim 1 , wherein each crown sipe extends in a zigzag manner in a longitudinal direction and a depth direction thereof.
11 . The heavy duty tire according to claim 1 , wherein the crown narrow groove includes inner crown narrow grooves close to the equator plane, outer crown narrow grooves close to the end of the tread surface, and connection crown narrow grooves connecting the inner crown narrow grooves and the outer crown narrow grooves, and
the inner crown narrow grooves and the outer crown narrow grooves are arranged alternately in the circumferential direction.
12 . The heavy duty tire according to claim 1 , wherein a styrene content of the styrene butadiene rubber is not less than 5% by mass and not greater than 24% by mass.
13 . The heavy duty tire according to claim 1 , wherein a vinyl content of the styrene butadiene rubber is not less than 26% by mole.
14 . The heavy duty tire according to claim 1 , wherein the each crown sipe is deeper than a groove depth from a groove opening of the crown narrow groove to a boundary between the body portion main body and the enlarged width portion.
15 . The heavy duty tire according to claim 1 , wherein a groove bottom of each crown sipe is located radially outward of a maximum groove width position of the enlarged width portion.
16 . The heavy duty tire according to claim 1 , wherein the inflection portion is curved so as to be recessed inward from the outer side thereof, and
the bottom portion is curved so as to bulge outward from an inner side thereof.
17 . The heavy duty tire according to claim 1 , wherein the inflection portion is curved so as to be recessed inward from the outer side thereof,
the bottom portion is curved so as to bulge outward from an inner side thereof, and
a ratio Rc/Rt of the radius Rc of the arc representing the contour of the inflection portion to the radius Rt of the arc representing the contour of the bottom portion is not less than 1.5 and not greater than 20.
18 . The heavy duty tire according to claim 1 , wherein the bottom portion includes a maximum groove width position of the enlarged width portion.
19 . The heavy duty tire according to claim 1 , wherein the two crown narrow land portions are an inner crown narrow land portion closer to the equator plane and an outer crown narrow land portion closer to an end of the tread surface,
each of the inner crown narrow land portion and the outer crown narrow land portion has the crown sipes, and
the crown sipes of the inner crown narrow land portion and the crown sipes of the outer crown narrow land portion are discontinuous and staggered relative to one another.