Patent Application
20240123767
The present application claims priority to Japanese patent application JP 2022-165429, filed on Oct. 14, 2022, the entire contents of which is incorporated herein by reference in its entirety.
The present disclosure relates to a tire.
A tire comes into contact with a road surface at a tread thereof. The tread may wear. The wear of the tread influences the tire performance. Studies have been conducted to improve wear resistance (for example, Japanese Laid-Open Patent Publication No. 2018-199456).
The tread may include a cap portion which comes into contact with a road surface. The cap portion may be formed from a crosslinked rubber for which wear resistance and grip performance are taken into consideration. When a vehicle corners at a speed of 80 km/h or higher, for instance, wear tends to progress at an outer shoulder portion (portion including a land portion located on the outer side in the width direction of the vehicle when the tire is mounted to the vehicle) in the cap portion.
If the stiffness of the crosslinked rubber forming the cap portion is increased, the tire can suppress the progress of wear. The tire can have improved wear resistance. However, the sound of a road surface hitting the cap portion may become louder, and noise performance may decrease.
A tire according to the present disclosure includes a tread extending in a circumferential direction and having an outer circumferential surface that is a tread surface. The tread can have a plurality of circumferential grooves aligned in an axial direction and dividing the tread into a plurality of land portions. The plurality of circumferential grooves can include a first shoulder circumferential groove located on an outer side in a width direction of a vehicle when the tire is mounted to the vehicle, and a second shoulder circumferential groove located on an inner side in the width direction of the vehicle when the tire is mounted to the vehicle. The land portion located outward of the first shoulder circumferential groove in the axial direction can be a first shoulder land portion, and the land portion located outward of the second shoulder circumferential groove in the axial direction can be a second shoulder land portion. The tread can include a cap portion configured to come into contact with a road surface, and a base portion located radially inward of the cap portion and covered with the cap portion. The cap portion can include an outer cap portion located on the outer side in the width direction of the vehicle when the tire is mounted to the vehicle, and an inner cap portion located on the inner side in the width direction of the vehicle when the tire is mounted to the vehicle. A 300% modulus of the inner cap portion can be not less than 5.0 MPa. A 300% modulus of the outer cap portion can be higher than the 300% modulus of the inner cap portion, and can be not greater than 9.0 MPa. The first shoulder land portion can include a boundary between the outer cap portion and the inner cap portion.
The present disclosure has been made in view of such circumstances discussed in the Background section. An object of the present disclosure, among one or more objects, can be to provide a tire that can achieve improvement of wear resistance without decreasing noise performance.
According to the present disclosure, a tire that can achieve improvement of wear resistance without decreasing noise performance can be obtained.
Hereinafter, the present disclosure will be described in detail based on preferred embodiments with appropriate reference to the drawings.
A tire of the present disclosure can be fitted on a rim. The interior of the tire can be filled with air to adjust the internal pressure of the tire. The tire fitted on the rim may also be referred to as tire-rim assembly. The tire-rim assembly can include the rim and the tire fitted on the rim.
In the present disclosure, a state where a tire is fitted on a standardized rim, the internal pressure of the tire is adjusted to a standardized internal pressure, and no load is applied to the tire can be referred to as a standardized state.
In the present disclosure, unless otherwise specified, the dimensions and angles of each component of the tire are measured in the standardized state.
The dimensions and angles of each component in a meridian cross-section of the tire, which cannot be measured in a state where the tire is fitted on the standardized rim, can be measured in a cross-section of the tire obtained by cutting the tire along a plane including a rotation axis. In this measurement, the tire is set such that the distance between right and left beads can be equal to the distance between the beads in the tire that is fitted on the standardized rim.
The standardized rim can mean a rim specified in a standard on which the tire is based. The “standard rim” in the JATMA standard, the “Design Rim” in the IRA standard, and the “Measuring Rim” in the ETRTO standard are standardized rims.
The standardized internal pressure can mean an internal pressure specified in the standard on which the tire is based. The “highest air pressure” in the JATMA standard, the “maximum value” recited in “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” in the FRA standard, and the “INFLATION PRESSURE” in the ETRTO standard can be regarded as standardized internal pressures.
A standardized load can mean a load specified in the standard on which the tire is based. The “maximum load capacity” in the JATMA standard, the “maximum value” recited in the “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” in the TRA standard, and the “LOAD CAPACITY” in the ETRTO standard can be regarded as standardized loads.
In the present disclosure, a rubber composition can refer to a composition that is obtained by mixing a base rubber and chemicals in a kneading machine such as a Banbury mixer and that contains the uncrosslinked base rubber. A crosslinked rubber can refer to a crosslinked product, of the rubber composition, obtained by pressurizing and heating the rubber composition. The crosslinked rubber can contain a crosslinked product of the base rubber. The crosslinked rubber may also be referred to as vulcanized rubber, and the rubber composition may also be referred to as unvulcanized rubber.
Examples of the base rubber include natural rubber (NR), butadiene rubber (BR), styrene-butadiene rubber (SBR), isoprene rubber (IR), ethylene-propylene rubber (EPDM), chloroprene rubber (CR), acrylonitrile-butadiene rubber (NBR), and isobutylene-isoprene-rubber (IIR). Examples of the chemicals include reinforcing agents such as carbon black and silica, plasticizers such as aromatic oil, fillers such as zinc oxide, lubricants such as stearic acid, antioxidants, processing aids, sulfur, and vulcanization accelerators. Selection of a base rubber and chemicals, the amounts of the selected chemicals, etc., can be determined as appropriate according to the specifications of components, such as a tread and a sidewall, for which the rubber composition is used.
In the present disclosure, a 300% modulus of a component formed from a crosslinked rubber, of the components included in the tire, can mean the tensile stress at 300% elongation specified in JIS K6251. The 300% modulus can be measured according to the standards of JIS K6251, as an example. In this measurement, a test piece can be sampled from the tire such that the length direction thereof coincides with the circumferential direction of the tire. When a test piece cannot be sampled from the tire, a test piece can be sampled from a sheet-shaped crosslinked rubber (hereinafter, also referred to as rubber sheet) obtained by pressurizing and heating a rubber composition, which can be used for forming the component to be measured, at a temperature of 170° C. for 12 minutes.
In the present disclosure, the 300% modulus can be represented as a 300% modulus at 100° C.
In the present disclosure, a tread portion of the tire can be a portion of the tire that comes into contact with a road surface. A bead portion can be a portion of the tire that is fitted to a rim. A sidewall portion can bef a portion of the tire that extends between the tread portion and the bead portion. The tire can include a tread portion, a pair of bead portions, and a pair of sidewall portions as portions thereof.
A tire according to an aspect of the present disclosure can include a tread extending in a circumferential direction and having an outer circumferential surface that is a tread surface, wherein: the tread can have a plurality of circumferential grooves aligned in an axial direction and dividing the tread into a plurality of land portions; the plurality of circumferential grooves can include a first shoulder circumferential groove located on an outer side in a width direction of a vehicle when the tire is mounted to the vehicle, and a second shoulder circumferential groove located on an inner side in the width direction of the vehicle when the tire is mounted to the vehicle; the land portion located outward of the first shoulder circumferential groove in the axial direction can be a first shoulder land portion; the land portion located outward of the second shoulder circumferential groove in the axial direction can be a second shoulder land portion; the tread can include a cap portion configured to come into contact with a road surface, and a base portion located radially inward of the cap portion and covered with the cap portion; the cap portion can include an outer cap portion located on the outer side in the width direction of the vehicle when the tire is mounted to the vehicle, and an inner cap portion located on the inner side in the width direction of the vehicle when the tire is mounted to the vehicle; a 300% modulus of the inner cap portion may be not less than 5.0 MPa; a 300% modulus of the outer cap portion may be higher than the 300% modulus of the inner cap portion, and may not be greater than 9.0 MPa; and the first shoulder land portion can include a boundary between the outer cap portion and the inner cap portion.
By forming the tire as described above, an axially outer portion of the first shoulder land portion to which a large load is applied when the vehicle corners at a speed of 80 km/h or higher, for instance, can be composed of the outer cap portion having a higher stiffness. At the cap portion of the tire, wear during cornering at a high speed can be suppressed. Since a portion of the cap portion other than the axially outer portion of the first shoulder land portion can be composed of the inner cap portion having a lower stiffness, the sound of a road surface hitting the cap portion can be effectively reduced. The tire can maintain good noise performance.
The tire can achieve improvement of wear resistance without decreasing noise performance.
Preferably, in the tire described in [Configuration 1] above, an end, on the tread surface side, of the boundary between the outer cap portion and the inner cap portion can be a first boundary end, an end, on the base portion side, of the boundary can be a second boundary end, the first shoulder circumferential groove can include a groove bottom, an outer groove wall located on an outer side in the axial direction, and an inner groove wall located on an inner side in the axial direction, a boundary between the groove bottom and the outer groove wall can be a reference position of the first shoulder circumferential groove, a distance in the axial direction from the reference position of the first shoulder circumferential groove to the first boundary end can be not less than 3 mm, for instance, and a ratio of the distance in the axial direction to a ground-contact width of the first shoulder land portion can be not greater than 20%, for instance.
By forming the tire as described above, the tire can achieve improvement of wear resistance without decreasing noise performance.
Preferably, in the tire described in [Configuration 1] or [Configuration 2] above, in a meridian cross-section of the tire, a distance in the axial direction from an equator plane to the boundary between the outer cap portion and the inner cap portion can gradually increase from the first boundary end toward the second boundary end.
By forming the tire as described above, the stiffness difference in the first shoulder land portion can be gradually changed in the tire, so that occurrence of uneven wear at the first shoulder land portion can be effectively suppressed. The outer cap portion of the tire can sufficiently exhibit its function. The tire can achieve improvement of wear resistance without decreasing noise performance.
Preferably, in the tire described in [Configuration 2] or [Configuration 3] above, in the meridian cross-section of the tire, an angle formed between a straight line passing through the first boundary end and the second boundary end and a tangent line tangent to the tread surface at the first boundary end may be not less than 5 degrees and not greater than 80 degrees, for instance.
By forming the tire as described above, the outer cap portion can sufficiently exhibit its function. The tire can achieve improvement of wear resistance without decreasing noise performance.
The components other than the tread 4 can have a general configuration as a component of a tire. The detailed description of the components other than the tread 4 is omitted.
The tread 4 can be formed from a crosslinked rubber. The tread 4 can be located radially outward of the tire 2 and can extend in the circumferential direction. The outer circumferential surface of the tread 4 can be or have a tread surface 14. The tire 2 can come into contact with a road surface at the tread surface 14.
Grooves 16 can be formed on the tread 4. Accordingly, a tread pattern can be formed.
In
The tread 4 can include a cap portion 18 and a base portion 20.
The cap portion 18 can include the tread surface 14. The cap portion 18 can come into contact with a road surface. The cap portion 18 can be formed from a crosslinked rubber for which grip performance and wear resistance are taken into consideration. Although described later, the cap portion 18 can be formed using two crosslinked rubbers having different stiffnesses.
The base portion 20 can be located radially inward of the cap portion 18. According to one or more embodiments, the entirety of the base portion 20 can be covered with the cap portion 18. The base portion 20 can be formed from a crosslinked rubber for which low heat generation properties are taken into consideration.
Sidewalls 22 which can form the side surfaces of the tire 2 can be connected to the ends of the tread 4, respectively. Each sidewall 22 can be located radially inward of the tread 4. The sidewall 22 can be located axially outward of the carcass 10. The sidewall 22 can be formed from a crosslinked rubber for which cut resistance is taken into consideration.
A clinch which can come into contact with a rim can be provided radially inward of each sidewall 22. A bead can be provided axially inward of the clinch.
As shown in
The band 6 can be located between the tread 4 and the belt 8 in the radial direction. The band 6 can be stacked on the belt 8. Optionally, the band 6 of the tire 2 can be a full band. The band 6 may further include a pair of edge bands placed, for instance, so as to be spaced apart from each other in the axial direction. The band 6 may be composed of only a pair of edge bands, according to one or more embodiments of the present disclosure.
According to one or more embodiments, the band 6 can include a helically wound band cord. The band cord can extend substantially in the circumferential direction. A cord formed from an organic fiber can be used as the band cord. Examples of the organic fiber can include nylon fibers, rayon fibers, polyester fibers, and aramid fibers.
In the axial direction, each end of the band 6 can be located outward of an end of the belt 8. The length from the end of the band 6 to the end of the belt 8 may be not less than 3 mm and not greater than 7 mm, as an example.
According to one or more embodiments, the band 6 can have a jointless structure. The band 6 can hold the belt 8.
The belt 8 can be located between the band 6 and the carcass 10 in the radial direction. The belt 8 can be stacked on the carcass 10.
The belt 8 can include an inner layer 24 and an outer layer 26. The inner layer 24 can be stacked on the carcass 10. The outer layer 26 can be located radially outward of the inner layer 24, and can be stacked on the inner layer 24. Each end of the outer layer 26 can be located axially inward of an end of the inner layer 24. The length from the end of the outer layer 26 to the end of the inner layer 24 may be not less than 3 mm and not greater than 10 mm, as an example.
The tire 2 can have one or more layers provided between the inner layer 24 and the outer layer 26. From the viewpoint of mass reduction, the belt 8 can preferably be composed of two layers that are the inner layer 24 and the outer layer 26.
Each of the inner layer 24 and the outer layer 26 can include a large number of belt cords aligned with each other. Each belt cord can be tilted relative to the equator plane CL. The material of the belt cord can be steel, as one example.
In
In the tread portion, the carcass 10 can be located between the belt 8 and the inner liner 12. The carcass 10 can extend on and between a pair of the beads.
The carcass 10 can include at least one carcass ply 28. According to one or more embodiments, the carcass 10 of the tire 2 can includes two carcass plies 28. Each of the two carcass plies 28 can be turned up at the bead.
Each carcass ply 28 can include a large number of carcass cords aligned with each other. These carcass cords can intersect the equator plane CL. The carcass 10 of the tire 2 can have a radial structure. In the tire 2, a cord formed from an organic fiber can be used as each carcass cord. Examples of the organic fiber can include nylon fibers, rayon fibers, polyester fibers, and aramid fibers.
The inner liner 12 can be located inward of the carcass 10. The inner liner 12 can form an inner surface of the tire 2. According to one or more embodiments, the inner liner 12 can be formed from a crosslinked rubber that has an excellent air blocking property. The inner liner 12 can maintain the internal pressure of the tire 2.
In
The ground-contact surface for specifying the position PH can be obtained, for example, using a ground-contact surface shape measuring device. The ground-contact surface can be obtained by setting the camber angle of the tire 2 in the standardized state to 0°, applying a standardized load as a vertical load to the tire 2, and bringing the tire 2 into contact with a flat surface, on this device. The position, on the tread surface 14, corresponding to each axially outer end of the ground-contact surface obtained thus can be the above-described position PH. In the present disclosure, the position PH can be a ground-contact end.
In
In
The ratio (WH/WB) of the distance WH in the axial direction obtained in the tire 2 in the standardized state to the axial width WB of the belt 8 may be not less than 85% and not greater than 95%, as an example.
The tread pattern shown in
In
In
The tread pattern of the tire 2 can include a circumferential groove 30 continuously extending in the circumferential direction. The tread 4 of the tire 2 can have a plurality of such circumferential grooves 30 aligned in the axial direction. The plurality of circumferential grooves 30 can divide the tread 4 into a plurality of land portions 32. On the tread 4 of the tire 2, four circumferential grooves 30 can be formed, whereby five land portions 32 can be formed therein so as to be aligned in the axial direction.
Among the four circumferential grooves 30, the circumferential groove 30 located on each outermost side in the axial direction can be a shoulder circumferential groove 30s. The shoulder circumferential groove 30s located on the first ground-contact end PH1 side can be a first shoulder circumferential groove 30s1, and the shoulder circumferential groove 30s located on the second ground-contact end PH2 side can be a second shoulder circumferential groove 30s2.
The circumferential groove 30 located axially inward of each shoulder circumferential groove 30s can be a middle circumferential groove 30m. The middle circumferential groove 30m located between the first shoulder circumferential groove 30s1 and the equator plane CL can be a first middle circumferential groove 30m1, and the middle circumferential groove 30m located between the second shoulder circumferential groove 30s2 and the equator plane CL can be a second middle circumferential groove 30m2.
Among the five land portions 32, the land portion 32 located on each outermost side in the axial direction can be a shoulder land portion 32s. The land portion 32 located outward of the first shoulder circumferential groove 30s1 in the axial direction can be a first shoulder land portion 32s1, and the land portion 32 located outward of the second shoulder circumferential groove 30s2 in the axial direction can be a second shoulder land portion 32s2. The first shoulder land portion 32s1 can include the first ground-contact end PH1, and the second shoulder land portion 32s2 can include the second ground-contact end PH2.
Among the five land portions 32, the land portion 32 located axially inward of each shoulder land portion 32s can be a middle land portion 32m. The land portion 32 located between the first shoulder circumferential groove 30s1 and the first middle circumferential groove 30m1 can be a first middle land portion 32m1, and the land portion 32 located between the second shoulder circumferential groove 30s2 and the second middle circumferential groove 30m2 can be a second middle land portion 32m2.
Among the five land portions 32, the land portion 32 located axially inward of the middle land portions 32m can be a center land portion 32c. The center land portion 32c can be located between the first middle circumferential groove 30m1 and the second middle circumferential groove 30m2. The center land portion 32c of the tire 2 can be located on the equator plane CL.
On the first shoulder land portion 32s1, a first shoulder axial groove 34 can be formed as an axial groove. The first shoulder axial groove 34 can have a groove width of at least 2.0 mm or greater, for instance. The first shoulder axial groove 34 can extend between the first ground-contact end PH1 and the first shoulder circumferential groove 30s1. The first shoulder axial groove 34 can extend substantially in the axial direction.
A plurality of such first shoulder axial grooves 34 can be formed on the first shoulder land portion 32s1. These first shoulder axial grooves 34 can be arranged at intervals in the circumferential direction.
In the present disclosure, a groove extending substantially in the axial direction can mean that an angle of the groove with respect to the axial direction is not greater than 15 degrees, for instance.
On the first middle land portion 32m1, a first middle axial groove 36 can be formed as an axial groove. The first middle axial groove 36 can have a groove width of at least 2.0 mm or greater, for instance. The groove width of the first middle axial groove 36 can be smaller than the groove width of the first shoulder axial groove 34.
The first middle axial groove 36 can have an end (hereinafter, first end) in the first middle land portion 32m1. The first middle axial groove 36 can extend between the first end and the first shoulder circumferential groove 30s1. The first middle axial groove 36 can be connected at a second end thereof to the first shoulder circumferential groove 30s1. The first middle axial groove 36 can extend substantially in the axial direction.
A plurality of such first middle axial grooves 36 can be formed on the first middle land portion 32m1. These first middle axial grooves 36 can be arranged at intervals in the circumferential direction. According to one or more embodiments, each first middle axial groove 36 can be placed so as to oppose the first shoulder axial groove 34 across the first shoulder circumferential groove 30s1.
As shown in
On the center land portion 32c, a center axial groove 38 can be formed as an axial groove. The center axial groove 38 has a groove width of at least 2.0 mm or greater. The center axial groove 38 can have a groove width substantially equal to the groove width of the first middle axial groove 36.
The center axial groove 38 can have an end (hereinafter, first end) in the center land portion 32c. The center axial groove 38 can extend between the first end and the first middle circumferential groove 30m1. The center axial groove 38 can be connected at a second end thereof to the first middle circumferential groove 30m1.
The second end of the center axial groove 38 can be located axially outward of the equator plane CL. The center axial groove 38 can be located between the first middle circumferential groove 30m1 and the equator plane CL.
The center axial groove 38 can be tilted relative to the axial direction. The second end of the center axial groove 38 can be positioned closer to the above-described first middle axial groove 36a than the first end thereof is.
A plurality of such center axial grooves 38 can be formed on the center land portion 32c. These center axial grooves 38 can be arranged at intervals in the circumferential direction. Each center axial groove 38 can be located between two first middle axial grooves 36 adjacent to each other in the circumferential direction.
On the second middle land portion 32m2, a second middle axial groove 40 can be formed as an axial groove. The second middle axial groove 40 can have a groove width of at least 2.0 mm or greater. The second middle axial groove 40 can have a groove width substantially equal to the groove width of the center axial groove 38.
As shown in
Each of the inner middle axial groove 40a and the outer middle axial groove 40b can have an end (hereinafter, first end) in the second middle land portion 32m2. The inner middle axial groove 40a can extend between the first end and the second middle circumferential groove 30m2. The inner middle axial groove 40a can be connected at a second end thereof to the second middle circumferential groove 30m2. The outer middle axial groove 40b can extend between the first end and the second shoulder circumferential groove 30s2. The outer middle axial groove 40b can be connected at a second end thereof to the second shoulder circumferential groove 30s2.
The inner middle axial groove 40a and the outer middle axial groove 40b can be tilted relative to the axial direction. The direction of tilt of the inner middle axial groove 40a and the direction of tilt of the outer middle axial groove 40b may be the same, according to one or more embodiments of the present disclosure. The direction of tilt of the inner middle axial groove 40a and the outer middle axial groove 40b can be opposite to the direction of tilt of the center axial groove 38.
A plurality of such inner middle axial grooves 40a and a plurality of such outer middle axial grooves 40b can be formed on the second middle land portion 32m2. The inner middle axial grooves 40a and the outer middle axial grooves 40b can be alternately arranged in the circumferential direction. A pair of second middle axial grooves 40 composed of the inner middle axial groove 40a and the outer middle axial groove 40b can be located between two center axial grooves 38 adjacent to each other in the circumferential direction.
On the second shoulder land portion 32s2, a second shoulder axial groove 42 can be formed as an axial groove. The second shoulder axial groove 42 can have a groove width of at least 2.0 mm or greater. The second shoulder axial groove 42 can have a groove width substantially equal to the groove width of the first shoulder axial groove 34.
The second shoulder axial groove 42 can have an end (hereinafter, first end) in the second shoulder land portion 32s2. The second shoulder axial groove 42 can extend between the first end and the second ground-contact end PH2. According to one or more embodiments of the present disclosure, the second shoulder axial groove 42 may not be connected to the second shoulder circumferential groove 30s2.
The second shoulder axial groove 42 can extend substantially in the axial direction. A plurality of such second shoulder axial grooves 42 formed on the second shoulder land portion 32s2. These second shoulder axial grooves 42 can be arranged at intervals in the circumferential direction. Each second shoulder axial groove 42 can be located between two first shoulder axial grooves 34 adjacent to each other in the circumferential direction.
In
In
The ground-contact widths WS1, WM1, WC1, WC2, WM2, and WS2 can be specified using the above-described ground-contact surface for obtaining the ground-contact end PH.
In the tire 2, according to one or more embodiments of the present disclosure, the ground-contact width WS1 of the first shoulder land portion 32s1 can be larger than the ground-contact width WS2 of the second shoulder land portion 32s2. The ground-contact width WC1 of the outer portion of the center land portion 32c can be larger than the ground-contact width WC2 of the inner portion of the center land portion 32c. The first middle land portion 32m1 can have the ground-contact width WM1 substantially equal to the ground-contact width WM2 of the second middle land portion 32m2.
The fact that the ground-contact width WM1 and the ground-contact width WM2 may be substantially equal to each other can mean that the ratio (WM1/WM2) of the ground-contact width WM1 to the ground-contact width WM2 may be not less than 0.95 and not greater than 1.05, as an example.
According to one or more embodiments of the present disclosure, the opening width GS1 of the first shoulder circumferential groove 30s1 can be smaller than the opening width GS2 of the second shoulder circumferential groove 30s2. Additionally or alternatively, the opening width GM1 of the first middle circumferential groove 30m1 can be smaller than the opening width GM2 of the second middle circumferential groove 30m2. Among the circumferential grooves 30, the circumferential groove 30 having the largest opening width can be the second middle circumferential groove 30m2, and the circumferential groove 30 having the smallest opening width can be the first shoulder circumferential groove 30s1.
As described above, the cap portion 18 of the tire 2 can be formed using two crosslinked rubbers having different stiffnesses. The cap portion 18 can include an outer cap portion 44 and an inner cap portion 46. The outer cap portion 44 can have a stiffness higher than that of the inner cap portion 46. Specifically, a 300% modulus of the inner cap portion 46 may be not less than 5.0 MPa, and a 300% modulus of the outer cap portion 44 can be higher than the 300% modulus of the inner cap portion 46 and may be not greater than 9.0 MPa, as examples.
In
The boundary 48 can be the interface between the outer cap portion 44 and the inner cap portion 46. The cap portion 18 can be composed of two components that are the outer cap portion 44 and the inner cap portion 46. Optionally, the cap portion 18 can consist of the outer cap portion 44 and the inner cap portion 46.
The outer cap portion 44 can include the first ground-contact end PH1, and the inner cap portion 46 can include the equator PC and the second ground-contact end PH2. When the tire 2 is mounted to the vehicle, the outer cap portion 44 can be located on the outer side in the width direction of the vehicle, and the inner cap portion 46 can be located on the inner side in the width direction of the vehicle.
As shown in
In the tire 2, the axially outer portion of the first shoulder land portion 32s1 to which a large load is applied, for instance, when the vehicle corners at a speed of 80 km/h or higher, can be composed of the outer cap portion 44 having a higher stiffness. At the cap portion 18 of the tire 2, wear during cornering at a high speed can be suppressed.
Since the portion of the cap portion 18 other than the axially outer portion of the first shoulder land portion 32s1 can be composed of the inner cap portion 46 having a lower stiffness, the sound of a road surface hitting the cap portion 18 can be effectively reduced. The tire 2 can maintain good noise performance.
Moreover, since the 300% modulus of the inner cap portion 46 may be not less than 5.0 MPa, wear of the inner cap portion 46, to which a smaller load is applied during running than to the outer cap portion 44, can also be effectively suppressed.
Furthermore, since the 300% modulus of the outer cap portion 44 may be not greater than 9.0 MPa, the influence of the outer cap portion 44 on noise performance can also be effectively suppressed.
The tire 2 can achieve improvement of wear resistance without decreasing noise performance.
The outer cap portion 44 of the tire 2 can contribute to suppressing wear during cornering at a high speed. From the viewpoint of being able to achieve further improvement of wear resistance, the 300% modulus of the outer cap portion 44 can be preferably not less than 8.0 MPa, for instance.
The inner cap portion 46 of the tire 2 can contribute to reducing the sound of a road surface hitting the cap portion 18. From the viewpoint of being able to effectively maintain good noise performance, the 300% modulus of the inner cap portion 46 can be preferably not greater than 7.0 MPa, for instance.
As described above, the 300% modulus of the outer cap portion 44 can be higher than the 300% modulus of the inner cap portion 46. From the viewpoint of being able to well-balance noise performance and wear resistance, the ratio of the 300% modulus of the outer cap portion 44 to the 300% modulus of the inner cap portion 46 can be preferably not less than 1.1, more preferably not less than 1.2, and further preferably not less than 1.3. From the same viewpoint, this ratio can be preferably not greater than 1.8, more preferably not greater than 1.7, and further preferably not greater than 1.6.
The first shoulder circumferential groove 30s1 of the tire 2 can include a groove bottom 50 and a pair of groove walls 52 extending from the groove bottom 50 toward the tread surface 14 side. Of the pair of groove walls 52, the groove wall 52 located on the outer side in the axial direction can be an outer groove wall 52s, and the groove wall 52 located on the inner side in the axial direction can be an inner groove wall 52u. The first shoulder circumferential groove 30s1 can include the groove bottom 50, the outer groove wall 52s, and the inner groove wall 52u.
In
As shown in
In the tire 2, the ratio (L1/WS1) of the distance L1 in the axial direction from the reference position PB to the first boundary end PS, to the ground-contact width WS1 of the first shoulder land portion 32s1, may be preferably not greater than 20%, as an example. Accordingly, in the tire 2, the stiffness difference between the outer side and the inner side in the first shoulder land portion 32s1 to which a large load is applied during cornering at a high speed can be reduced. In the tire 2, wear of the inner portion, of the first shoulder land portion 32s1, composed of the inner cap portion 46 can be effectively suppressed. From this viewpoint, the ratio (L1/WS1) can be more preferably not greater than 15%, for instance.
In the tire 2, from the viewpoint of being able to achieve improvement of wear resistance without decreasing noise performance, more preferably, the distance L1 in the axial direction may be not less than 3 mm, and the ratio (L1/WS1) may be not greater than 20%, as examples.
As shown in
The boundary 48 may be formed such that the position of the second boundary end PU coincide with the position of the first boundary end PS in the axial direction.
In the first shoulder land portion 32s1, the boundary 48 can be a change of stiffness. Therefore, by forming the first shoulder land portion 32s1 such that the boundary 48 is tilted as shown in
In
In the tire 2, the tilt angle θ of the boundary 48 can be preferably not less than 5 degrees and not greater than 80 degrees, for instance.
When the tilt angle θ is set to be not less than 5 degrees, the first shoulder land portion 32s1 can be formed such that the outer cap portion 44 has a required volume. The tire 2 can effectively suppress wear, and can appropriately control the exposure amount of the inner cap portion 46. In the tire 2, the outer cap portion 44 can sufficiently exhibit its function. From this viewpoint, the tilt angle θ can be more preferably not less than 15 degrees and further preferably not less than 25 degrees.
When the tilt angle θ is set so as to be not greater than 80 degrees, the stiffness difference in the first shoulder land portion 32s1 can be gradually changed in the tire 2, so that occurrence of uneven wear at the first shoulder land portion 32s1 can be effectively suppressed. In this case as well, the outer cap portion 44 can sufficiently exhibit its function. From this viewpoint, the tilt angle θ can be more preferably not greater than 70 degrees and further preferably not greater than 60 degrees, for instance.
As described above, in the tire 2, the outer cap portion 44 can be provided in the first shoulder land portion 32s1. The portion of the cap portion 18 other than the outer cap portion 44 can be composed of the inner cap portion 46.
From the viewpoint that the tire 2 is able to achieve improvement of wear resistance without decreasing noise performance, the ratio (WS1/WA) of the ground-contact width WS1 of the first shoulder land portion 32s1 to the ground-contact width WA can be preferably not less than 15% and not greater than 20%, for instance.
As described above, in the tire 2, the ground-contact width WS1 of the first shoulder land portion 32s1 can be larger than the ground-contact width WS2 of the second shoulder land portion 32s2. In the tire 2, the outer cap portion 44, which forms a part of the first shoulder land portion 32s1, can sufficiently exhibit its function. From this viewpoint, the ratio (WS1/WS2) of the ground-contact width WS1 of the first shoulder land portion 32s1 to the ground-contact width WS2 of the second shoulder land portion 32s2 can be preferably not less than 120% and not greater than 130%, for instance.
The center land portion 32c of the tire 2 can be formed such that the ground-contact width WC1 of the outer portion thereof is larger than the ground-contact width WC2 of the inner portion thereof. The center land portion 32c can contribute to improvement of wear resistance without decreasing noise performance. From this viewpoint, the ratio (WC1/WC2) of the ground-contact width WC1 of the outer portion to the ground-contact width WC2 of the inner portion can be preferably not less than 170% and not greater than 180%.
As shown in
As described above, in the tire 2, among the circumferential grooves 30, the circumferential groove 30 having the largest opening width can be the second middle circumferential groove 30m2. The second middle circumferential groove 30m2 can be formed on the inner cap portion 46. From the viewpoint that the inner cap portion 46 can contribute to maintaining good noise performance, the ratio (GM2/WA) of the opening width GM2 of the second middle circumferential groove 30m2 to the ground-contact width WA can be preferably not less than 5% and not greater than 10%, for instance.
As described above, in the tire 2, the circumferential groove 30 having the smallest opening width can be the first shoulder circumferential groove 30s1. The first shoulder land portion 32s1 in which the outer cap portion 44 is provided can be located axially outward of the first shoulder circumferential groove 30s1. The first shoulder circumferential groove 30s1 having the small opening width GS1 can contribute to exhibition of the function of the outer cap portion 44. From this viewpoint, the ratio (GS1/GM2) of the opening width GS1 of the first shoulder circumferential groove 30s1 to the opening width GM2 of the second middle circumferential groove 30m2 can be preferably not less than 30% and not greater than 40%, for instance.
As is obvious from the above description, according to one or more embodiments of the present disclosure, the tire 2 that can achieve improvement of wear resistance without decreasing noise performance, is obtained.
Hereinafter, the present disclosure will be described in further detail by means of examples, etc., but the present disclosure is not limited to these examples.
A pneumatic tire for a passenger car (tire designation=235/35ZR19) having the basic structure shown in
A 300% modulus Mu of the inner cap portion, a 300% modulus Ms of the outer cap portion, the ratio (L1/WS1), and the tilt angle θ of the boundary were set as shown in Table 1 below.
A tire of Comparative Example 1 is a conventional tire. In Comparative Example 1, the cap portion was formed from a single crosslinked rubber. As described in the cell for “Ms” in Table 1, the 300% modulus of the cap portion was 8.0 MPa.
Tires of Examples 2 and 3 and Comparative Examples 2 and 3 were obtained in the same manner as Example 1, except that the 300% modulus Mu of the inner cap portion, the 300% modulus Ms of the outer cap portion, the ratio (L1/WS1), and the tilt angle θ of the boundary were set as shown in Table 1 below.
[Noise Performance]
Test tires were each fitted onto a rim (size=19×8.0J) and inflated with air to adjust the internal pressure thereof to 240 kPa. The tires were mounted to a test vehicle (passenger car). The noise in the vehicle interior was measured when the test vehicle was driven at a speed of 100 km/h on a test course having a dry asphalt surface. The results are shown in Table 1 below as indexes with the result of Comparative Example 1 being regarded as 100. The higher the value is, the better the noise performance is.
[Wear Resistance]
Test tires were each fitted onto a rim (size=19×8.0J) and inflated with air to adjust the internal pressure thereof to 240 kPa. The tires were mounted to a test vehicle (passenger car). The test vehicle was driven on a test course having a dry asphalt surface. After driving, a groove depth Cr of the second middle circumferential groove and a groove depth Sh of the first shoulder axial groove were measured and the ratio (Sh/Cr) was obtained. The results are shown in Table 1 below as indexes with the result of Comparative Example 1 being regarded as 100. The higher the value is, the better the wear resistance is.
As shown in Table 1, it is confirmed that, in each Example, improvement of wear resistance is achieved without decreasing noise performance. From the evaluation results, advantages of the present disclosure are clear.
The above-described technology capable of achieving improvement of wear resistance without decreasing noise performance can also be applied to various tires.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2022-165429 | Oct 2022 | JP | national |
