JP7238232B2 - pneumatic tire - Google Patents

Description

Embodiments of the present invention relate to pneumatic tires.

In general, pneumatic tires are prone to localized deflection in the radially outer region of the sidewall portion, ie, the so-called buttress portion, which is a factor in lowering steering stability. Therefore, it is known to improve the steering stability by extending the turn-up end of the carcass ply that is turned back at the bead portion through the sidewall portion until it reaches the belt layer embedded in the tread portion. Also, in order to increase the rigidity of a pneumatic tire, it is known to extend a hard rim strip disposed on the bead portion to the sidewall portion. Pneumatic tires having such a structure are disclosed in Patent Documents 1 to 3, for example.

However, extending the turn-up end of the carcass ply to the belt layer poses a problem that RFV (Radial Force Variation), which is one of tire uniformity performances, is impaired. This is for the following reasons. The carcass ply is formed by winding a sheet formed by rubber-coating a cord array in the tire circumferential direction and joining the ends of the sheet, and has the joint at one location in the tire circumferential direction. Therefore, in the tread portion, the joint portion of the main body portion of the carcass ply is originally present at one location on the circumference. It will be superimposed on the junction of the parts. This tends to make RFV even worse.

On the other hand, Patent Document 4 discloses extending the rim strip rubber to the buttress portion and providing the folded end of the carcass ply close to the upper end of the rim strip rubber. However, if the turn-up end of the carcass ply and the upper end of the rim strip rubber are provided close to each other, there is a problem that strain is concentrated and durability is impaired.

JP 2018-103931 A JP 2018-103956 A JP 2018-108751 A JP 2018-108749 A

An object of the present invention is to provide a pneumatic tire capable of achieving both steering stability and uniformity performance and improving durability.

A pneumatic tire according to an embodiment of the present invention includes a bead core embedded in a bead portion, a bead filler provided outside the bead core in the tire radial direction, and a bead core extending from a tread portion to a bead portion via a sidewall portion. a carcass ply folded back, a tread rubber forming the outer surface of the tread portion, a sidewall rubber forming the outer surface of the sidewall portion, and a rim strip rubber forming the outer surface of the bead portion. Here, a position that bisects the tire radial direction position of the tire axial end of the tread rubber and the tire maximum width position in the tire radial direction, and a tire radial position of the tire axial end of the tread rubber. The space between is the buttress part. The upper end of the turnup portion of the carcass ply is arranged radially outward of the upper end of the bead filler and radially inward of the buttress portion. The rim strip rubber extends radially outward of the tire between the carcass ply and the sidewall rubber, and the upper end of the rim strip rubber is arranged radially outward of the lower end of the buttress portion. there is

With the pneumatic tire according to the above embodiment, both steering stability and uniformity performance can be achieved, and durability can be improved.

Half sectional view of the pneumatic tire according to the first embodiment Enlarged cross-sectional view of the main part of FIG. Principal part cross-sectional view of a pneumatic tire according to a second embodiment Principal part cross-sectional view of a pneumatic tire according to a third embodiment

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[First embodiment]
A pneumatic tire 10 of the first embodiment shown in FIG. and a pair of left and right side wall portions 14 interposed between the bead portion 16. Note that FIG. 1 is a right half sectional view of the tire 10 cut along a meridional section including the tire rotation axis, and in this example, the tire 10 is bilaterally symmetrical.

In the figure, the symbol CL indicates the tire equatorial plane corresponding to the axial center of the tire. As used herein, the tire axial direction refers to a direction parallel to the tire rotation axis, and is indicated by symbol WD in FIG. The inner side in the tire axial direction WD is the direction toward the tire equatorial plane CL, and the outer side in the tire axial direction WD is the direction away from the tire equatorial plane CL. A tire radial direction means a direction perpendicular to the tire rotation axis, and is indicated by symbol RD in FIG. The inner side in the tire radial direction RD is the direction toward the tire rotation axis, and the outer side in the tire radial direction RD is the direction away from the tire rotation axis. The tire circumferential direction is the direction in which the tire rotates around the tire rotation axis.

An annular bead core 18 made of a bead wire is embedded in the bead portion 16 . A bead filler 20 is provided on the outer periphery of the bead core 18, that is, on the outer side in the tire radial direction RD. The bead filler 20 is a hard rubber member having a substantially triangular cross-section that narrows toward the tip. In this example, the upper end 20A of the bead filler 20 is located inside the tire radial direction RD from the tire maximum width position P2, which will be described later. 20 A of upper ends of the bead filler 20 point out the outer edge of the tire radial direction RD in the bead filler 20. As shown in FIG.

The tire 10 is provided with at least one (one in this example) carcass ply 22 that is toroidally bridged between the pair of bead portions 16 . The carcass ply 22 extends from the tread portion 12 through the sidewall portion 14 to the bead portion 16 and is folded back at the bead core 18 and locked. Specifically, both ends of the carcass ply 22 are folded back around the bead core 18 from the inner side to the outer side in the axial direction WD of the tire. Therefore, the carcass ply 22 includes a toroidal main body portion 22A extending between the pair of bead cores 18 and folded-back portions 22B folded around the bead cores 18 from both ends of the main body portion 22A. A bead core 18 and a bead filler 20 are arranged between the body portion 22A and the folded portion 22B.

The carcass ply 22 is formed by arranging in parallel a predetermined number of carcass cords as a reinforcing material and covering them with a topping rubber. That is, they are arranged in the radial direction. Examples of carcass cords include organic fiber cords such as polyester fibers, rayon fibers, aramid fibers and nylon fibers, and steel cords.

A belt layer 24 is embedded in the tread portion 12 on the outer periphery of the carcass ply 22 (that is, on the outer side in the tire radial direction RD). The belt layer 24 is provided over the outer periphery of the crown portion of the carcass ply 22, and is normally composed of at least two belt plies. In this example, the belt layer 24 is composed of two belts, a first belt 24A as a maximum width belt and a second belt 24B superimposed on the outer periphery thereof. The first and second belts 24A and 24B are belt cords such as steel cords that are inclined at a constant angle (for example, 10° to 35°) with respect to the tire circumferential direction and arranged at predetermined intervals in the tire axial direction WD. Become. Belt cords are arranged to cross each other between the two belts 24A and 24B.

A belt reinforcing layer 26 is provided outside the belt layer 24 in the tire radial direction RD. The belt reinforcing layer 26 is composed of a cap ply having cords extending substantially parallel to the tire circumferential direction.

A tread rubber 28 that forms the outer surface of the tread portion 12 is laminated on the outer circumference of the belt layer 24 , more specifically on the outer circumference of the belt reinforcing layer 26 . The tread rubber 28 is a rubber member forming a contact surface of the tire, and a tread pattern (not shown) is formed on the surface of the tread rubber 28 . The tread rubber 28 is provided so as to cover the entire width of the belt layer 24 and belt reinforcing layer 26 .

A sidewall rubber 30 forming the outer surface of the sidewall portion 14 is provided on the tire outer surface side of the carcass ply 22 in the sidewall portion 14 . In this example, the sidewall rubber 30 has an outer end 30A in the tire radial direction RD that covers an end 28A of the tread rubber 28 in the tire axial direction WD.

A rim strip rubber 32 is provided on the bead portion 16 . The rim strip rubber 32 is a rubber member that forms the outer surface of the bead portion 16 and contacts a rim (not shown) on which the tire 10 is mounted. The rim strip rubber 32 is made of rubber having a hardness higher than that of the sidewall rubber 30. - 特許庁For example, the sidewall rubber 30 may have a hardness of 50-60, while the rim strip rubber 32 may have a hardness of 62-77. The rim strip rubber 32 generally has a lower hardness than the bead filler 20 and a higher hardness than the tread rubber 28 .

Here, the hardness of rubber is JIS K6253-1-2012 3.2 durometer hardness, which is measured in an atmosphere of 23°C using a type A durometer for general rubber (medium hardness). be done.

As shown in FIG. 2, the rim strip rubber 32 is provided so as to cover the main body portion 22A and the folded portion 22B of the carcass ply 22 at the bead portion 16 from the inside in the tire radial direction RD. Therefore, the rim strip rubber 32 is composed of an outer rubber portion 34 arranged on the outer side of the folded portion 22B of the carcass ply 22 in the axial direction WD of the carcass and an inner rubber portion 34 arranged on the inner side of the main portion 22A of the carcass ply 22 in the axial direction WD of the tire. and a bottom rubber portion 38 connecting the lower ends of the outer rubber portion 34 and the inner rubber portion 36 to each other.

The bottom rubber portion 38 is a portion that forms the bottom surface of the bead portion 16 and contacts the bead seat of the rim (not shown).

The outer rubber portion 34 is a portion that forms the surface of the bead portion 16 on the tire outer surface side, and extends from the outer end of the bottom rubber portion 38 in the tire axial direction WD along the folded portion 22B of the carcass ply 22 to the outer side in the tire radial direction RD. extends to The outer rubber portion 34 is in contact with the sidewall rubber 30 , and the interface therebetween is exposed to the tire outer surface at the boundary position between the sidewall portion 14 and the bead portion 16 .

The inner rubber portion 36 extends outward in the tire radial direction RD from the inner end of the bottom rubber portion 38 in the tire axial direction WD along the main body portion 22A of the carcass ply 22 . In this example, the upper end of the inner rubber portion 36 (that is, the outer end in the tire radial direction R) terminates within the bead portion 16 . An inner liner rubber layer 40 made of air impermeable butyl rubber is provided on the tire inner surface (inner cavity surface). It is a rubber layer sandwiched between

Reference numeral 42 denotes a cushion rubber layer provided between the inner liner rubber layer 40 and the main body portion 22A of the carcass ply 22. As shown in FIG.

In the pneumatic tire 10 according to the present embodiment, a position P3 that bisects the tire radial direction position P1 of the tire axial end 28AE of the tread rubber 28 and the tire maximum width position P2 in the tire radial direction RD; A buttress portion 44 is defined between the tire axial end 28AE of the tread rubber 28 and the tire radial position P1. That is, the buttress portion 44 is a region between the positions P1 and P3 (including the positions P1 and P3) in the tire radial direction RD.

Here, the position P<b>1 is the position in the tire radial direction RD of the tire axial end 28 AE of the tread rubber 28 and corresponds to the upper end of the buttress portion 44 . Since the end portion 28A of the tread rubber 28 in the axial direction WD of the tread is curved so as to be located inward in the radial direction RD of the tire toward the outer side in the axial direction WD, the end portion 28AE in the axial direction of the tire is the tread rubber. It is also the inner end of 28 in the tire radial direction RD.

The tire maximum width position P2 is the position in the tire radial direction RD where the profile line of the outer surface of the pneumatic tire 10 in the sidewall portion 14 is the farthest from the tire equatorial plane CL in the tire axial direction WD. The profile line is the contour of the outer surface of the sidewall body excluding protrusions such as rim protectors, and generally has a tire meridian cross-sectional shape defined by smoothly connecting a plurality of circular arcs.

A position P3 is a position equidistant from the position P1 and the tire maximum width position P2 in the tire radial direction RD, and corresponds to the lower end of the buttress portion 44 .

As shown in FIG. 2 , the upper end 22BE of the turnup portion 22B of the carcass ply 22 (hereinafter referred to as the turnup end 22BE) is arranged outside the upper end 20A of the bead filler 20 in the tire radial direction RD. Here, the upper end 22BE of the folded portion 22B refers to the outer end of the folded portion 22B in the tire radial direction RD. Further, the folded end 22BE is arranged inside the buttress portion 44 in the tire radial direction RD, that is, positioned inside the position P3 in the tire radial direction RD.

More specifically, in this example, the turn-up end 22BE of the carcass ply 22 is arranged outside the tire maximum width position P2 in the tire radial direction RD. Therefore, the folded end 22BE is positioned within the region 46 between the positions P2 and P3.

The rim strip rubber 32 extends outward in the tire radial direction RD between the carcass ply 22 and the sidewall rubber 30 . Specifically, the outer rubber portion 34 extends outward in the tire radial direction RD from the bead portion 16 along the turned-up portion 22B of the carcass ply 22, beyond the turned-up end 22BE, and further to the main body portion of the carcass ply 22. It extends along 22A to buttress portion 44 .

An upper end 32AE of the rim strip rubber 32 (specifically, the outer rubber portion 34) is arranged outside the position P3, which is the lower end of the buttress portion 44, in the tire radial direction RD. The upper end 32AE of the rim strip rubber 32 refers to the outer end of the rim strip rubber 32 in the tire radial direction RD. A lower end of the buttress portion 44 refers to an inner end of the buttress portion 44 in the tire radial direction RD.

In this example, the upper end 32AE of the rim strip rubber 32 is located outside the position P1, which is the upper end of the buttress portion 44, in the tire radial direction RD. Therefore, the upper end 32A of the rim strip rubber 32 terminates with an overlap with the tread rubber 28, that is, overlaps the edge 28A of the tread rubber 28. As shown in FIG. Specifically, the upper end 32A of the rim strip rubber 32 is positioned laterally of the tread rubber 28 and overlaps the side surface 28B of the tread rubber 28. As shown in FIG. The upper end portion 32A of the rim strip rubber 32 is not exposed to the outer surface of the tire, and the outer end portion 30A of the sidewall rubber 30 in the tire radial direction RD covers the upper end portion 32A. The upper end portion 32A of the rim strip rubber 32 refers to the outer end portion of the rim strip rubber 32 in the tire radial direction RD, and the end thereof is the upper end 32AE.

The thickness of the rim strip 32 (that is, the thickness of the outer rubber portion 34) in the sidewall portion 14 is set as follows. The maximum thickness T1 of the rim strip rubber 32 at the buttress portion 44 is set larger than the thickness of the rim strip rubber 32 inside the buttress portion 44 in the tire radial direction RD. It is set larger than the thickness T2 of the strip rubber 32 . Here, the thickness of the rim strip rubber 32 is measured along the direction perpendicular to the carcass ply 22 .

Specifically, the rim strip rubber 32 extending outward in the tire radial direction RD between the carcass ply 22 and the sidewall rubber 30 is substantially constant from the lower side of the sidewall portion 14 to the tire maximum width position P2. is formed with a thickness T2. The buttress portion 44 has a portion where the thickness gradually increases after passing the tire maximum width position P2, and the buttress portion 44 is formed to have a thickness T1 larger than the thickness T2. Thus, the rim strip rubber 32 has a gradually increasing portion 32B between the tire maximum width position P2 and the position P3, which is the lower end of the buttress portion 44, and whose thickness gradually increases outward in the tire radial direction RD.

In the pneumatic tire 10 according to the present embodiment as described above, the turned-up end 22BE of the carcass ply 22 is arranged inside the buttress portion 44 in the tire radial direction RD and does not extend to the belt layer 24. , deterioration of RFV due to the presence of the joint portion of the turn-up portion 22B in the tread portion can be suppressed.

Further, by extending the rim strip rubber 32 beyond the turn-up end 22BE of the carcass ply 22 to the buttress portion 44 on the outer side in the tire radial direction RD, the buttress portion 44, which causes local deflection, is flexed and steered. Stability can be improved.

Further, by arranging the turn-up end 22BE of the carcass ply 22 and the upper end 32AE of the rim strip rubber 32 apart from each other, it is possible to suppress concentration of distortion and improve durability.

Therefore, with the pneumatic tire 10 according to the present embodiment, both steering stability and uniformity performance can be achieved, and durability can be improved.

In the present embodiment, since the turn-up end 22BE of the carcass ply 22 is arranged outside the tire maximum width position P2 in the tire radial direction RD, the rigidity at the tire maximum width position P2 is increased, and the steering stability is improved. can be improved.

In addition, by terminating the upper end portion 32A of the rim strip rubber 32 with overlap with the tread rubber 28, the entire buttress portion 44 is reinforced by the rim strip rubber 32, and the rigidity can be further increased, resulting in improved steering stability. It is excellent in the improvement effect of

In addition, since the thickness T1 of the rim strip rubber 32 at the buttress portion 44 is formed to be greater than the thickness T2 of the rim strip rubber 32 at the maximum tire width position P2, the buttress portion 44, in which local deflection occurs, further Flexibility can be effectively suppressed, and the effect of improving steering stability is excellent.

Also, by providing a gradually increasing portion 32B where the thickness of the rim strip rubber 32 gradually increases in the region 46 between the tire maximum width position P2 and the lower end P3 of the buttress portion 44, strain concentration is suppressed and durability is improved. can do. Particularly, in this example, the turn-up end 22BE of the carcass ply 22 is also present in the region 46 between the tire maximum width position P2 and the lower end P3 of the buttress portion 44 . Therefore, by eliminating abrupt changes in the thickness of the rim strip rubber 32 in the region 46, the effect of improving durability can be further enhanced.

[Second embodiment]
FIG. 3 is a cross-sectional view of essential parts of a pneumatic tire 10A according to the second embodiment. The second embodiment differs from the first embodiment in the position of the upper end 32AE of the rim strip rubber 32. As shown in FIG. In the second embodiment, the upper end 32A of the rim strip rubber 32 does not overlap the tread rubber 28 and terminates within the buttress portion 44. As shown in FIG.

Specifically, the upper end 32AE of the rim strip rubber 32 is arranged inside the position P1, which is the upper end of the buttress portion 44, in the tire radial direction RD, and terminates before reaching the position P1. The position of the upper end 32AE of the rim strip rubber 32 in the tire radial direction RD should be 50% or more of the height of the buttress portion 44 (the distance in the tire radial direction RD) from the position P3. Preferably, the height is 70% or more.

In the second embodiment, since the upper end 32AE of the rim strip rubber 32 is set lower than in the first embodiment, it is more disadvantageous in terms of steering stability than in the first embodiment, but the rigidity is lowered, resulting in ride comfort. It is advantageous in terms of sex. Other configurations and operational effects of the second embodiment are the same as those of the first embodiment, and description thereof will be omitted.

[Third Embodiment]
FIG. 4 is a cross-sectional view of essential parts of a pneumatic tire 10B according to the third embodiment. In the third embodiment, the position of the turn-up end 22BE of the carcass ply 22 is different from that in the second embodiment. In the third embodiment, the turn-back end 22BE of the carcass ply 22 is located inside the tire maximum width position P2 in the tire radial direction RD, and is located between the tire maximum width position P2 and the upper end 20A of the bead filler 20. are doing.

In the third embodiment, the turn-up end 22BE of the carcass ply 22 is set lower than that in the second embodiment, which is disadvantageous in terms of steering stability compared to the second embodiment. It is advantageous in terms of sex. Other configurations and effects of the third embodiment are the same as those of the second embodiment, and description thereof will be omitted.

In this specification, the dimensions of each part of the pneumatic tire, the tire maximum width position, etc. are values measured in an unloaded state in which the pneumatic tire is mounted on a regular rim and filled with regular internal pressure. A regular rim is a rim defined for each tire in a standard system that includes the standard on which the tire is based. Measuring Rim". The regular internal pressure is the air pressure determined for each tire by each standard in the standard system including the standard that the tire is based on. PRESSURES", or "INFLATION PRESSURE" for ETRTO. However, when the tire is for a passenger car, it is usually 180 kPa, but when the tire is labeled as Extra Load or Reinforced, it is 220 kPa.

Although several embodiments of the invention have been described above, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and modifications can be made without departing from the scope of the invention. These embodiments and their modifications are included in the scope and spirit of the invention, as well as the scope of the invention described in the claims and equivalents thereof.

DESCRIPTION OF SYMBOLS 10... Pneumatic tire 12... Tread part 14... Side wall part 16... Bead part 18... Bead core 20... Bead filler 20A... Upper end of bead filler 22... Carcass ply 22A... Body part 22B... Folded portion 22BE Upper end of folded portion 28 Tread rubber 28AE Tire axial end of tread rubber 32 Rim strip rubber 32A Upper end of rim strip rubber 32AE Upper end of rim strip rubber 32B Gradually increasing part 44... Buttress part P1... Tire radial position of the tire axial end of the tread rubber P2... Tire maximum width position P3... Position bisecting between position P1 and position P2 WD... Tire Axial direction, RD... Tire radial direction

Claims (3)

A bead core embedded in the bead portion, a bead filler provided outside the bead core in the tire radial direction, a carcass ply extending from the tread portion through the sidewall portion to the bead portion and folded back at the bead core, and the outside of the tread portion. A pneumatic tire comprising a tread rubber forming a surface, a sidewall rubber forming an outer surface of a sidewall portion, and a rim strip rubber forming an outer surface of a bead portion,
Between a position that bisects the tire radial direction position of the tire axial end of the tread rubber and the tire maximum width position in the tire radial direction and the tire radial position of the tire axial end of the tread rubber , as the buttress part,
The upper end of the folded portion of the carcass ply is arranged radially outside the upper end of the bead filler in the tire radial direction and inside the buttress portion in the tire radial direction,
The rim strip rubber extends radially outward of the tire between the carcass ply and the sidewall rubber, and the upper end of the rim strip rubber is arranged radially outward of the lower end of the buttress portion ,
the hardness of the rim strip rubber is higher than the hardness of the sidewall rubber;
The maximum thickness of the rim strip rubber at the buttress portion is greater than the thickness of the rim strip rubber at the maximum tire width position,
The rim strip rubber has a gradually increasing portion whose thickness gradually increases outward in the tire radial direction between the maximum width position of the tire and the lower end of the buttress portion.
pneumatic tires. The pneumatic tire according to claim 1, wherein the upper end of the folded portion of the carcass ply is arranged radially outward of the tire maximum width position. 3. The pneumatic tire according to claim 1 or 2, wherein an upper end of said rim strip rubber terminates with an overlap with said tread rubber.

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