JP7611687B2 - Pneumatic tires - Google Patents

Description

This disclosure relates to pneumatic tires.

The following Patent Document 1 discloses a pneumatic tire in which, for the purpose of achieving weight reduction while ensuring resistance to external damage, the rim strip rubber that forms the outer surface of the bead extends in the tire radial direction between the carcass and the sidewall rubber, and the tire radial outer end of the rim strip rubber is positioned outside the tread rubber in the tire width direction and terminates without reaching the outer peripheral surface of the tread rubber.

However, if the radially outer ends of the rim strip rubber on both sides of the tire width direction are positioned outside the tread rubber in the tire width direction, the tire's lateral rigidity increases and handling stability improves, but the tire's vertical rigidity becomes too high, deteriorating ride comfort.

JP 2018-108749 A

The objective of this disclosure is to provide a pneumatic tire that achieves both steering stability and ride comfort.

The pneumatic tire of the present disclosure includes a carcass extending from a tread through a sidewall to a bead, a sidewall rubber forming an outer surface of the sidewall, and a rim strip rubber forming an outer surface of the bead.
The rim strip rubber has an inner rim strip rubber located on the inner side when mounted on a vehicle, and an outer rim strip rubber located on the outer side when mounted on a vehicle,
The inner rim strip rubber extends in a tire radial direction between the carcass and the sidewall rubber,
The outer end of the inner rim strip rubber in the tire radial direction is located outer in the tire radial direction than the outer end of the outer rim strip rubber in the tire radial direction.

FIG. 1 is a cross-sectional view of a main portion of a pneumatic tire according to an embodiment of the present invention taken along a tire meridian plane. FIG. 2 is a partial enlarged view of the pneumatic tire shown in FIG. 1 . FIG. 11 is a cross-sectional view of a main portion of a pneumatic tire according to another embodiment taken along a tire meridian plane.

One embodiment of a pneumatic tire will be described below with reference to Figures 1 and 2. Note that in each figure, the dimensional ratios in the drawing do not necessarily match the actual dimensional ratios, and the dimensional ratios between the drawings do not necessarily match either.

In each figure, the first direction D1 is the tire width direction D1 that is parallel to the tire rotation axis that is the center of rotation of the pneumatic tire (hereinafter also simply referred to as "tire") 1, and the second direction D2 is the tire radial direction D2 that is the diameter direction of the tire 1. The direction perpendicular to the first direction D1 and the second direction D2 is the tire circumferential direction around the tire rotation axis.

In the tire width direction D1, the inner side is the side closer to the tire equatorial plane S1, and the outer side is the side farther from the tire equatorial plane S1. In the tire radial direction D2, the inner side is the side closer to the tire rotation axis, and the outer side is the side farther from the tire rotation axis.

The tire equatorial plane S1 is a plane perpendicular to the tire rotation axis and located at the center of the tire width direction D1 of the tire 1, and the tire meridian plane is a plane that includes the tire rotation axis and is perpendicular to the tire equatorial plane S1.

As shown in FIG. 1, the tire 1 according to this embodiment includes a pair of beads 1a, a pair of sidewalls 1b extending outward from each bead 1a in the tire radial direction D2, and a tread 1c connected to the outer ends of the pair of sidewalls 1b in the tire radial direction D2, the outer surface of which in the tire radial direction D2 comes into contact with the road surface. The bead 1a includes an annular bead core 11a and a bead filler 12a provided on the outer side of the bead core 11a in the tire radial direction D2. The bead core 11a is formed by rubber-coating a bundle such as a steel wire. The bead filler 12a is formed of hard rubber with a triangular cross section extending outward in the tire radial direction D2. In this embodiment, the tire 1 is a pneumatic tire 1 in which air is put, and is mounted on a rim (not shown).

The tire 1 further comprises a carcass 2 extending from the tread 1c through the sidewall 1b to the bead 1a, a tread rubber 3 forming the outer surface of the tread 1c, sidewall rubbers 4, 5 forming the outer surface of the sidewall 1b, and rim strip rubbers 6, 7 forming the outer surface of the bead 1a. The tread 1c comprises a belt layer 8 laminated on the outer side of the carcass 2 in the tire radial direction D2, and a belt reinforcing layer 9 laminated on the outer side of the belt layer 8 in the tire radial direction D2, which are covered with the tread rubber 3. Although not shown in the figure, a tread pattern is formed on the surface of the tread rubber 3 according to the required tire performance and usage conditions. The inner surface of the tire 1 is formed of an inner liner rubber 10.

The sidewall rubbers 4, 5 are made of rubber with excellent cut resistance and weather resistance. This tire 1 employs a so-called sidewall on tread (SWOT) structure in which the radially outer ends of the sidewall rubbers 4, 5 are placed on the sides of the tread rubber 3. In the tire meridian cross section, the sidewall rubbers 4, 5 extend radially inward from the buttress region, which is the radially outer region of the sidewall 1b, and reach the bead 1a via the tire maximum width position 1d.

The rim strip rubbers 6, 7 are made of rubber with excellent abrasion resistance. The rim strip rubbers 6, 7 are provided at the locations that come into contact with the rim (not shown) on which the tire 1 is mounted. The rubber hardness of the rim strip rubbers 6, 7 is higher than that of the sidewall rubbers 4, 5. The rubber hardness of the rim strip rubbers 6, 7 is lower than that of the bead filler 12a. The rubber hardness of the rim strip rubbers 6, 7 is, for example, 60 to 75 degrees. The rubber hardness of the sidewall rubbers 4, 5 is, for example, 45 to 60 degrees. The rubber hardness of the bead filler 12a is, for example, 85 to 100 degrees. In this specification, rubber hardness refers to a value (durometer hardness) measured using a type A durometer in an atmosphere of 23°C in accordance with JIS K6253.

The specific gravity of the rubber that makes up the rim strip rubbers 6, 7 is greater than the specific gravity of the rubber that makes up the sidewall rubbers 4, 6, but less than the specific gravity of the rubber that makes up the bead filler 12a.

The belt layer 8 is formed of a belt ply made of rubber-coated cords arranged in a direction inclined to the tire circumferential direction. As shown in FIG. 2, the belt layer 8 is made of a plurality of belt plies 81, 82 (two in this embodiment), and the cords are laminated so that they cross each other in opposite directions between the plies. Steel is preferably used as the material for the cords. The belt ply 81 is disposed inside the belt ply 82 in the tire radial direction D2. The width of the belt ply 81 in the tire width direction D1 is wider than the width of the belt ply 82 in the tire width direction D1.

The belt reinforcing layer 9 is formed of a reinforcing ply made of rubber-coated cords that extend substantially in the circumferential direction of the tire. Organic fibers are preferably used as the material for the cords. By reinforcing the belt layer 8 with the belt reinforcing layer 9, high-speed durability can be improved.

The tire 1 according to this embodiment has an asymmetric structure with respect to the tire equatorial plane S1. The tire 1 is a tire with a specified mounting orientation on a vehicle, and the left or right side of the tire 1 is specified to face the vehicle when mounted on a rim. The tread pattern formed on the outer surface of the tire, the tread 1c, may be symmetric or asymmetric with respect to the tire equatorial plane S1.

The orientation of the tire when mounted on the vehicle is indicated on the sidewall 1b. Specifically, the sidewall rubbers 4, 5 have an indication on their surface that indicates the orientation of the tire when mounted on the vehicle. In this embodiment, the sidewall 1b that is positioned on the inside (right side in FIG. 1) when mounted on the vehicle is indicated as being on the inside of the vehicle (e.g., "INSIDE"), and the other sidewall 1b that is positioned on the outside (left side in FIG. 1) when mounted on the vehicle is indicated as being on the outside of the vehicle (e.g., "OUTSIDE").

Of the tire width direction D1, the direction toward the inside when mounted on the vehicle is referred to as the vehicle inside direction D11, and the direction toward the outside when mounted on the vehicle is referred to as the vehicle outside direction D12. Of the pair of sidewall rubbers 4, 5, the sidewall rubber 4 that is positioned on the inside when mounted on the vehicle is referred to as the inner sidewall rubber 4, and the sidewall rubber 5 that is positioned on the outside when mounted on the vehicle is referred to as the outer sidewall rubber 5. Of the pair of rim strip rubbers 6, 7, the rim strip rubber 6 that is positioned on the inside when mounted on the vehicle is referred to as the inner rim strip rubber 6, and the rim strip rubber 7 that is positioned on the outside when mounted on the vehicle is referred to as the outer rim strip rubber 7.

The outer end 6a of the inner rim strip rubber 6 in the tire radial direction D2 is located outside the tire maximum width position 1d in the tire radial direction D2. On the other hand, the outer end 7a of the outer rim strip rubber 7 in the tire radial direction D2 is located inside the tire maximum width position 1d in the tire radial direction D2. That is, the outer end 6a of the inner rim strip rubber 6 in the tire radial direction D2 is located outside the tire radial direction D2 of the outer rim strip rubber 7 in the tire radial direction D2. In other words, the height H6 of the inner rim strip rubber 6 is higher than the height H7 of the outer rim strip rubber 7. Here, the height H6 of the inner rim strip rubber 6 is the height from the bead baseline BL to the outer end 6a of the inner rim strip rubber 6 in the tire radial direction D2, and the height H7 of the outer rim strip rubber 7 is the height from the bead baseline BL to the outer end 7a of the outer rim strip rubber 7 in the tire radial direction D2. Increasing the height H6 of the inner rim strip rubber 6 increases lateral rigidity, improving responsiveness and steering stability. In addition, decreasing the height H7 of the outer rim strip rubber 7 suppresses an increase in vertical rigidity and suppresses a deterioration in ride comfort. As a result, both steering stability and ride comfort can be achieved. The bead base line BL is a virtual straight line in the tire width direction D1 that defines the rim diameter of a standard rim.

The height H6 of the inner rim strip rubber 6 is preferably at least 30% higher than the height H7 of the outer rim strip rubber 7, and more preferably at least 50% higher. By making the height H6 of the inner rim strip rubber 6 at least 30% higher than the height H7 of the outer rim strip rubber 7, it is possible to appropriately achieve both steering stability and ride comfort.

In addition, the specific gravity of the rubber that makes up the rim strip rubbers 6, 7 is smaller than the specific gravity of the rubber that makes up the bead filler 12a, so when the heights of the rim strip rubbers 6, 7 located on the inside and outside when mounted on the vehicle are made different, the increase in tire weight can be suppressed compared to when the heights of the bead fillers 12a on the inside and outside when mounted on the vehicle are made different.

As shown in FIG. 2, the inner rim strip rubber 6 has a main body portion 61 located in the bead 1a, and an extension portion 62 extending from the main body portion 61 in the tire radial direction D2 and located between the carcass 2 and the inner sidewall rubber 4. The main body portion 61 contacts the inner end of the sidewall rubber 4 in the tire radial direction D2. The extension portion 62 extends from the main body portion 61 along the outer surface of the carcass 2 with a constant thickness, and reaches the outer surface of the tread rubber 3 in the tire width direction D1. The tip of the extension portion 62 is the outer end 6a of the inner rim strip rubber 6. The extension portion 62 tapers toward the tip.

The outer end 6a of the inner rim strip rubber 6 in the tire radial direction is preferably located inside the tire width direction end 81a of the belt ply 81, which is located the most inside in the tire radial direction D2 among the multiple belt plies 81, 82. If the outer end 6a of the inner rim strip rubber 6 is located near the tire width direction end 81a of the belt ply 81, the ground contact pressure near the tire width direction end 81a of the belt ply 81 increases, and there is a concern that separation will occur at the belt end. Therefore, by positioning the outer end 6a of the inner rim strip rubber 6 inside the tire width direction end 81a of the belt ply 81 in the tire radial direction D2, deterioration of durability can be prevented. The straight-line distance between the outer end 6a of the inner rim strip rubber 6 and the tire width direction end 81a of the belt ply 81 is preferably 10 mm or more. In addition, the straight-line distance between the outer end 6a of the inner rim strip rubber 6 and the tire width direction end 81a of the belt ply 81 is preferably 20 mm or less.

The thickness T62 of the extension 62 in the tire width direction D1 is 50% or less of the side rubber thickness Ti, and preferably 30% or less. Here, the side rubber thickness Ti is the thickness of the rubber arranged on the outer side of the carcass 2 in the tire width direction D1. Specifically, the side rubber thickness Ti in the sidewall 1b arranged on the inner side when mounted on the vehicle is the sum of the thicknesses of the extension 62 and the inner sidewall rubber 4 in the tire width direction D1. If the thickness T62 of the extension 62 is made larger than 50% of the side rubber thickness Ti, the vertical rigidity of the tire 1 becomes too large, adversely affecting the ride comfort performance. Note that the thickness T62 of the extension 62 and the side rubber thickness Ti are the thicknesses when viewed parallel to the tire width direction D1 at the tire maximum width position 1d (the same applies to the side rubber thickness To described later).

On the other hand, the outer rim strip rubber 7 has the shape of a typical rim strip rubber and is composed only of a main body portion 71 located in the bead 1a. The shapes of the main body portion 71 of the outer rim strip rubber 7 and the main body portion 61 of the inner rim strip rubber 6 are symmetrical with respect to the tire equatorial plane S1.

The side rubber thickness To (see FIG. 1) of the sidewall 1b that is disposed on the outside when mounted on a vehicle is the thickness of the outer sidewall rubber 5 in the tire width direction D1. The side rubber thickness To is the same as the side rubber thickness Ti at the same position in the tire radial direction D2.

Since the inner rim strip rubber 6 has an extension 62, the volume of the inner rim strip rubber 6 is larger than the volume of the outer rim strip rubber 7. Also, the total volume of the inner sidewall rubber 4 and the inner rim strip rubber 6 is the same as the total volume of the outer sidewall rubber 5 and the outer rim strip rubber 7 (including not only completely the same, but also approximately the same with a difference of ±3%).

The above-mentioned dimensional values, positional relationships, and magnitude relationships are measured when the pneumatic tire 1 is mounted on a standard rim, inflated to the standard internal pressure, and in a standard unloaded state. For example, the tire maximum width position 1d is the position in the tire radial direction D2 of the position where the dimension in the tire width direction D1, excluding structures such as patterns and letters protruding from the outer surface of the sidewall 1b, is maximum when the pneumatic tire 1 is mounted on a standard rim, inflated to the standard internal pressure, and in a unloaded state. A standard rim is a rim that is determined for each pneumatic tire 1 by the standard in the standard system that includes the standard on which the pneumatic tire 1 is based, and is, for example, a standard rim for JATMA, and a "Measuring Rim" for TRA and ETRTO.

The normal internal pressure is the air pressure set for each pneumatic tire 1 by each standard in the standard system including the standard on which the pneumatic tire 1 is based, and is the maximum air pressure in the case of JATMA, the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the case of TRA, and "INFLATION PRESSURE" in the case of ETRTO.

As described above, the pneumatic tire 1 according to this embodiment includes the carcass 2 extending from the tread 1c through the sidewall 1b to the bead 1a, the sidewall rubbers 4 and 5 forming the outer surface of the sidewall 1b, and the rim strip rubbers 6 and 7 forming the outer surface of the bead 1a.
The rim strip rubbers 6, 7 include an inner rim strip rubber 6 that is positioned on the inner side when mounted on a vehicle, and an outer rim strip rubber 7 that is positioned on the outer side when mounted on a vehicle,
The inner rim strip rubber 6 extends in the tire radial direction D2 between the carcass 2 and the sidewall rubber 4,
An outer end 6a of the inner rim strip rubber 6 in the tire radial direction D2 is located outer than an outer end 7a of the outer rim strip rubber 7 in the tire radial direction D2.

According to this configuration, by increasing the height H6 of the inner rim strip rubber 6, lateral rigidity is increased, responsiveness is improved, and steering stability is improved. In addition, by decreasing the height H7 of the outer rim strip rubber 7, an increase in vertical rigidity is suppressed, and a deterioration in ride comfort is suppressed. As a result, both steering stability and ride comfort can be achieved.

In addition, in the pneumatic tire 1 according to this embodiment, the height H6 from the bead baseline BL to the outer end 6a of the inner rim strip rubber 6 in the tire radial direction D2 is 30% or more higher than the height H7 from the bead baseline BL to the outer end 7a of the outer rim strip rubber 7 in the tire radial direction D2.

With this configuration, the height H6 of the inner rim strip rubber 6 can be made sufficiently higher than the height H7 of the outer rim strip rubber 7, allowing for an appropriate balance between steering stability and ride comfort.

In addition, in the pneumatic tire 1 according to this embodiment, the sidewall rubbers 4, 5 have an inner sidewall rubber 4 that is located on the inside when mounted on a vehicle, and an outer sidewall rubber 5 that is located on the outside when mounted on a vehicle, and the total volume of the inner sidewall rubber 4 and the inner rim strip rubber 6 is the same as the total volume of the outer sidewall rubber 5 and the outer rim strip rubber 7, and the volume of the inner rim strip rubber 6 is larger than the volume of the outer rim strip rubber 7.

With this configuration, the height H6 of the inner rim strip rubber 6 is made higher than the height H7 of the outer rim strip rubber 7, achieving both steering stability and ride comfort.

The pneumatic tire 1 according to this embodiment is also configured to include multiple belt plies 81, 82 laminated on the outer side of the carcass 2 in the tread 1c in the tire radial direction D2, and the outer end 6a of the inner rim strip rubber 6 in the tire radial direction D2 is located inward in the tire radial direction D2 of the tire width direction end 81a of the belt ply 81 that is located inward most in the tire radial direction D2 among the multiple belt plies 81, 82.

This configuration helps prevent separation from occurring due to increased ground pressure near the belt ends.

The pneumatic tire 1 is not limited to the configuration of the above-mentioned embodiment, nor is it limited to the above-mentioned effects. Furthermore, the pneumatic tire 1 can of course be modified in various ways without departing from the spirit of the present invention. For example, the configurations and methods of the above-mentioned embodiments may be arbitrarily adopted and combined, and further, one or more of the configurations and methods of the various modified examples described below may be arbitrarily selected and adopted in the configurations and methods of the above-mentioned embodiment.

(1) In the pneumatic tire 1 according to the above embodiment, the height H6 from the bead baseline BL to the outer end 6a of the inner rim strip rubber 6 in the tire radial direction D2 is 30% or more higher than the height H7 from the bead baseline BL to the outer end 7a of the outer rim strip rubber 7 in the tire radial direction D2. However, the pneumatic tire 1 is not limited to this configuration. For example, by making the height H6 of the inner rim strip rubber 6 25% or more higher than the height H7 of the outer rim strip rubber 7, it is possible to achieve both steering stability and ride comfort.

(2) In addition, in the pneumatic tire 1 according to the above embodiment, the sidewall rubbers 4, 5 have an inner sidewall rubber 4 that is located on the inside when mounted on a vehicle, and an outer sidewall rubber 5 that is located on the outside when mounted on a vehicle, and the total volume of the inner sidewall rubber 4 and the inner rim strip rubber 6 is the same as the total volume of the outer sidewall rubber 5 and the outer rim strip rubber 7, and the volume of the inner rim strip rubber 6 is larger than the volume of the outer rim strip rubber 7. However, the pneumatic tire 1 is not limited to such a configuration. For example, the total volume of the inner sidewall rubber 4 and the inner rim strip rubber 6 may be different from the total volume of the outer sidewall rubber 5 and the outer rim strip rubber 7.

(3) In addition, the pneumatic tire 1 according to the above embodiment includes a plurality of belt plies 81, 82 laminated on the outer side of the carcass 2 in the tread 1c in the tire radial direction D2, and the outer end 6a of the inner rim strip rubber 6 in the tire radial direction D2 is located on the inner side of the tire width direction end 81a of the belt ply 81 that is located on the inner side of the plurality of belt plies 81, 82 in the tire radial direction D2. However, the pneumatic tire 1 is not limited to such a configuration. For example, the outer end 6a of the inner rim strip rubber 6 in the tire radial direction D2 may be located at the same position in the tire radial direction D2 as the tire width direction end 81a of the belt ply 81.

(4) In addition, in the pneumatic tire 1 according to the above embodiment, the outer rim strip rubber 7 is configured to be composed only of the main body portion 71. However, the pneumatic tire 1 is not limited to this configuration. For example, the outer rim strip rubber 7 may have the main body portion 71 and an extension portion that extends from the main body portion 71 in the tire radial direction D2 and is positioned between the carcass 2 and the outer sidewall rubber 5. However, the outer end 7a of this extension portion in the tire radial direction D2 is configured to be positioned inside the tire maximum width position 1d in the tire radial direction D2.

(5) In addition, in the pneumatic tire 1 according to the above embodiment, the extension portion 62 of the inner rim strip rubber 6 extends from the main body portion 61 along the outer surface of the carcass 2 with a constant thickness and reaches the outer surface of the tread rubber 3 in the tire width direction D1. However, the pneumatic tire 1 is not limited to this configuration. The extension portion 62 does not necessarily need to reach the outer surface of the tread rubber 3 in the tire width direction D1.

(6) In addition, in the pneumatic tire 1 according to the above embodiment, the extension portion 62 of the inner rim strip rubber 6 extends from the main body portion 61 along the outer side surface of the carcass 2 with a constant thickness and reaches the outer side surface of the tread rubber 3 in the tire width direction D1. However, the pneumatic tire 1 is not limited to such a configuration. For example, as shown in FIG. 3, the extension portion 62 of the inner rim strip rubber 6 may be configured to extend from the main body portion 61 along the outer side surface of the carcass 2 with a constant thickness and reach the inner peripheral surface of the tread rubber 3 in the tire radial direction D2. In this case, too, it is preferable that the outer end 6a of the inner rim strip rubber 6 is located in the tire radial direction D2 more inward than the tire width direction end portion 81a of the belt ply 81 that is located in the innermost position in the tire radial direction D2 among the multiple belt plies 81, 82.

Reference Signs List 1...pneumatic tire, 1a...bead, 1b...sidewall, 1c...tread, 1d...maximum tire width position, 2...carcass, 3...tread rubber, 4...inner sidewall rubber, 5...outer sidewall rubber, 6...inner rim strip rubber, 6a...outer end of inner rim strip rubber in tire radial direction, 7...outer rim strip rubber, 7a...outer end of outer rim strip rubber in tire radial direction, 8...belt layer, 9...belt reinforcing layer, 10...inner liner rubber, 11a...bead core, 12a...bead filler, 61...main body portion, 62...extension portion, 81...belt ply, 81a...end of belt ply in tire width direction, BL...bead baseline, H6...height of inner rim strip rubber, H7...height of outer rim strip rubber, D1...tire width direction, D2...tire radial direction, S1...tire equatorial plane, D11...vehicle inner side, D12...vehicle outer side

Claims (3)

The tire comprises a carcass extending from a tread through a sidewall to a bead, a sidewall rubber forming an outer surface of the sidewall, and a rim strip rubber forming an outer surface of the bead,
The rim strip rubber has an inner rim strip rubber located on the inner side when mounted on a vehicle, and an outer rim strip rubber located on the outer side when mounted on a vehicle,
The inner rim strip rubber extends in a tire radial direction between the carcass and the sidewall rubber,
The tire radially outer end of the inner rim strip rubber is located radially outward of the tire radially outer end of the outer rim strip rubber ,
The sidewall rubber has an inner sidewall rubber located on the inner side when the tire is mounted on a vehicle, and an outer sidewall rubber located on the outer side when the tire is mounted on a vehicle,
A pneumatic tire, wherein a total volume of the inner sidewall rubber and the inner rim strip rubber is the same as a total volume of the outer sidewall rubber and the outer rim strip rubber, and a volume of the inner rim strip rubber is greater than a volume of the outer rim strip rubber . The pneumatic tire according to claim 1, wherein the height from the bead base line to the outer end of the inner rim strip rubber in the tire radial direction is 30% or more higher than the height from the bead base line to the outer end of the outer rim strip rubber in the tire radial direction. A plurality of belt plies are laminated on the outer side of the carcass in the tire radial direction in the tread,
3. The pneumatic tire according to claim 1, wherein an outer end of the inner rim strip rubber in the tire radial direction is located radially inward of an end of the inner rim strip rubber in the tire width direction of a belt ply that is disposed radially inwardly of the plurality of belt plies.

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