Patent Application
20230271460
The present disclosure relates to a pneumatic tire.
Conventionally, a pneumatic tire provided with a carcass ply extending between a pair of bead cores is known. The carcass ply has a turn-up portion that is formed by turning the carcass ply up around the bead core from the inside to the outside in the tire width direction. Patent Literature (PTL) 1 and 2 disclose a pneumatic tire having a reinforcement layer, made of organic fibers, arranged outward in the tire width direction from the turn-up portion of the carcass ply.
PTL 1: JP 2012-46155 A
PTL 2: JP 2015-63172 A
During compression deformation of the pneumatic tire, such as when traveling on a road surface, the tire widthwise outer surface of the bead portion of the pneumatic tire is pressed by the rim flange of the rim to which it is assembled. As a result, the cover rubber on the outer side of the bead portion in the tire width direction is sandwiched between the turn-up portion of the carcass ply and the rim flange portion of the rim to be compressed and deformed, so that a portion thereof moves along the turn-up portion of the carcass ply. Therefore, shear strain along the turn-up portion is concentrated in the cover rubber near the turn-up portion. Provision of the reinforcement layer described in PTL 1 and 2 can suppress the concentration of shear strain along the turn-up portion in the cover rubber near the turn-up portion of the carcass ply. However, even when a reinforcement layer such as the one described in PTL 1 and 2 is provided, if the adhesiveness between the reinforcement layer itself and the surrounding cover rubber is weak, shear strain along the reinforcement layer may concentrate in the cover rubber near the reinforcement layer, which may in turn result in failure.
It is an aim of the present disclosure to provide a pneumatic tire capable of suppressing the concentration of shear strain along the reinforcement layer in the cover rubber near the reinforcement layer.
A pneumatic tire in a first aspect of the present disclosure includes a pair of bead cores, a carcass ply including a main body positioned between the bead cores and a turn-up portion connected to the main body and formed by turning up around each bead core from inside to outside in a tire width direction, a cover rubber covering the main body of the carcass ply and an outer side of the turn-up portion in the tire width direction and configuring a tire outer surface, and a reinforcement layer located inward from the tire outer surface of the cover rubber and covering an outer side, in the tire width direction, of at least a portion of the turn-up portion of the carcass ply, wherein the reinforcement layer is configured by a non-woven fabric including metal fibers or a rubber sheet material having metal fibers embedded therein.
According to the present disclosure, a pneumatic tire capable of suppressing the concentration of shear strain along the reinforcement layer in the cover rubber near the reinforcement layer can be provided.
In the accompanying drawings:
Embodiments of a pneumatic tire according to the present disclosure are described below with reference to the drawings. Configurations that are common across drawings are labeled with the same reference signs.
Hereafter, unless otherwise specified, the dimensions, length relationships, positional relationships, and the like of each element are assumed to be measured in a reference state in which the pneumatic tire is mounted on an applicable rim, filled to a prescribed internal pressure, and under no load.
The “applicable rim” refers to a standard rim designated in the following standards in accordance with tire size (“Design Rim” in the YEAR BOOK of the Tire and Rim Association, Inc. (TRA), and “Measuring Rim” in the STANDARDS MANUAL of the European Tyre and Rim Technological Organisation (ETRTO)). The standards are determined according to an effective industrial standard in areas where the tire is produced or used. Examples of the standards include the YEAR BOOK of the TRA in the USA, the STANDARDS MANUAL of the ETRTO in Europe, and the JATMA YEAR BOOK of the Japan Automobile Tyre Manufacturers Association (JATMA) in Japan.
The “applicable rim” includes sizes that could be included in the future in the aforementioned industrial standards, in addition to current sizes. Examples of the sizes that could be described in the future in the aforementioned industrial standards include the sizes described under FUTURE DEVELOPMENTS in the ETRTO 2013 edition. In the case of a size not listed in the aforementioned industrial standards, the “applicable rim” refers to a rim whose width corresponds to the bead width of the pneumatic tire.
The “prescribed internal pressure” refers to the air pressure (maximum air pressure) corresponding to the maximum load capability of a single wheel for the applicable size/ply rating in the aforementioned JATMA YEAR BOOK or the like. In the case of a size not described in the aforementioned industrial standards, the “prescribed internal pressure” refers to the air pressure (maximum air pressure) corresponding to the maximum load capability prescribed for each vehicle on which the tire is mounted. The “maximum load” described below refers to the tire maximum load capability specified in the aforementioned standards, such as JATMA, for tires of the applicable size, or in the case of sizes not specified in the aforementioned industrial standards, the “maximum load” refers to the load corresponding to the maximum load capability specified for each vehicle on which the tire is mounted.
<Applicable Rim 2>
B, and a rim flange portion 2b protruding outward in the tire radial direction B from both ends of the rim seat portion 2a in the tire width direction A. As illustrated in
<Tire 1>
As illustrated in
Furthermore, the outer surface of the tire includes the outer surface of the tread portion 1a, which is the surface on the outer side of the tread portion 1a in the tire radial direction B, the outer surface of the sidewall portion 1b, which is the surface on the outer side of the sidewall portion 1b in the tire width direction A, and the outer surface of the bead portion 1c, which is the surface on the outer side of the bead portion 1c in the tire width direction A. The tire outer surface is configured by a cover rubber 5 formed by tread rubber 10 and side rubber 11.
The tire 1 includes the bead cores 3, a carcass ply 4, four layers of belt plies 6 to 9, tread rubber 10 and side rubber 11 as cover rubber 5, an inner liner 12, and a reinforcement layer 21.
[Bead Core 3]
The bead core 3 is embedded in the bead portion 1c. The tire 1 may be further provided with a rubber bead filler located outward from the bead core 3 in the tire radial direction B. The bead core 3 includes a plurality of bead cords that are coated by rubber. The bead cords are formed by steel cords. The steel cords can, for example, be made of steel monofilaments or twisted wires.
[Carcass Ply 4]
The carcass ply 4 extends toroidally to straddle the pair of bead portions 1c, more specifically to straddle the pair of bead cores 3. The carcass ply 4 of the present embodiment has a radial structure.
Specifically, the carcass ply 4 extends toroidally across the pair of bead cores 3 and is folded from inside to outside in the tire width direction A around each bead core 3. The carcass ply 4 includes a plurality of ply cords arranged in parallel to each other and coating rubber that covers the plurality of ply cords. Instead of including the coating rubber, however, the carcass ply 4 may be configured by, for example, arranging a plurality of ply cords that are made of brass, or plated with a material including brass, in parallel and bonding adjacent ply cords. The tire 1 in the present embodiment includes one carcass ply 4 but may instead include two or more carcass plies 4. The plurality of ply cords of the carcass ply 4 are arranged at an angle of, for example, 75° to 90° with respect to the tire circumferential direction C. The ply cords of the carcass ply 4 can be metal cords, such as steel cords. The steel cords can be made of steel monofilaments or twisted wires with, for example, a brass coating on the surface. The ply cords may also be organic fiber cords, for example, with a brass coating on the surface.
More specifically, the carcass ply 4 has a main body 4a located between the pair of bead cores 3 and a turn-up portion 4b that is formed by being connected to the main body 4a and turned up from inside to outside in the tire width direction A around each bead core 3. As described above, the tire 1 may further include a bead filler extending while tapering toward the outer side of the bead core 3 in the tire radial direction B. In a case in which the tire 1 includes a bead filler, the bead filler is arranged between the main body 4a and the turn-up portion 4b of the carcass ply 4.
[Belt Plies 6 to 9]
The belt plies 6 to 9 are disposed in the tread portion 1a. Specifically, the belt plies 6 to 9 are disposed outside of the carcass ply 4 in the tire radial direction B relative to the crown of the carcass ply 4. The tire 1 in the present embodiment includes four layers of belt plies 6 to 9, but the number of layers is not particularly limited as long as at least one layer is provided. Each belt ply 6 to 9 includes a plurality of ply cords arranged in parallel to each other and coating rubber that covers the plurality of ply cords. Instead of including the coating rubber, however, each belt ply 6 to 9 may be configured by, for example, arranging a plurality of ply cords that are made of brass, or plated with a material including brass, in parallel and bonding adjacent ply cords. Each belt ply 6 to 9 forms a sloped belt layer in which the cord cut edges of the ply cords are exposed at both ends in the tire width direction A. The plurality of ply cords in each belt ply 6 to 9 extends at an angle with respect to the tire width direction A and the tire circumferential direction C. For example, the ply cords are arranged to be inclined at an angle of 10° to 60° with respect to the tire circumferential direction C. The ply cords in each belt ply 6 to 9 can be metal cords, such as steel cords. The steel cords can be made of steel monofilaments or twisted wires with, for example, a brass coating on the surface. The ply cords may also be organic fiber cords, for example, with a brass coating on the surface.
One or more of the four layers of belt plies 6 to 9 may be a circumferential belt layer that includes a plurality of ply cords extending along the tire circumferential direction C.
[Tread Rubber 10 and Side Rubber 11]
The tread rubber 10 covers the crown portion of the main body 4a of the carcass ply 4 and covers the outer side, in the tire radial direction B, of the four layers of belt plies 6 to 9. The outer surface of the tread portion 1a in the present embodiment is configured by the tread rubber 10. A tread pattern including circumferential grooves extending in the tire circumferential direction C, widthwise grooves extending in the tire width direction A, and the like is formed on the outer surface of the tread portion 1a.
The side rubber 11 covers the outside, in the tire width direction A, of the main body 4a and the turn-up portion 4b of the carcass ply 4. The outer surface of the sidewall portion 1b and the outer surface of the bead portion 1c in the present embodiment are configured by the side rubber 11. The outer end of the side rubber 11 in the tire radial direction B is connected to the end of the above-described tread rubber in the tire width direction A.
In this way, the tread rubber 10 and side rubber 11 in the present embodiment as a whole form the cover rubber 5 of the tire 1, which covers the carcass ply 4 and the belt plies 6 to 9 and configures the tire outer surface.
[Inner Liner 12]
The inner liner 12 covers the tire inner surface side of the main body 4a of the carcass ply 4 and configures the tire inner surface of the tire 1. The inner liner 12 is layered onto the tire inner surface side of the main body 4a of the carcass ply 4. The inner liner 12 may, for example, be formed from a butyl-based rubber having low air permeability. Butyl-based rubber refers to butyl rubber and butyl halide rubber, which is a derivative thereof.
[Belt Reinforcement Layer 21]
As illustrated in
As illustrated in
As illustrated in
As illustrated in
Furthermore, as illustrated in
Furthermore, in the reinforcement layer 21, the reinforcement main body 21a formed by being turned up around the bead core 3 from the outer side towards the inner side in the tire width direction A is more preferably wrapped up farther outward, in the tire radial direction B, than the outer edge 3b of the bead core 3 in the tire widthwise cross-sectional view (see
The reinforcement layer 21 configured by a non-woven fabric formed from metal fibers 22 can be manufactured by various methods, and the manufacturing method is not limited. For example, a needle punch can be used to entangle metal fibers 22, obtained by various cutting methods, into a felt-like shape. The diameter of the metal fibers 22 can be changed by changing the amount of cutting, for example. The thickness and density of the non-woven fabric formed from the metal fibers 22 can be changed by, for example, changing the amount of metal fibers 22 that are punched and changing the number of vertical movements per unit time during needle punching.
The reinforcement layer 21 in the present embodiment is configured by a non-woven fabric formed from metal fibers 22, but this configuration is not limiting. The reinforcement layer 21 may be configured by a rubber sheet material in which the metal fibers 22 are embedded. However, the reinforcement layer 21 is preferably configured by a non-woven fabric, as in the present embodiment. By the reinforcement layer 21 being a non-woven fabric, the edges of the metal fibers 22 tend not to be exposed on the outer surface of the reinforcement layer 21, and the occurrence of cracks in the surrounding rubber can be suppressed.
The density of the non-woven fabric configuring the reinforcement layer 21 is preferably 100 g/m2 to 900 g/m2 and in particular is preferably 200 g/m2 to 600 g/m2. When the density of the non-woven fabric configuring the reinforcement layer 21 is in the above range, the concentration of sheer stress at the cover rubber 5 near the reinforcement layer 21 can be further suppressed.
Consequently, the durability of the tire 1 can be further improved. Furthermore, when the density of the non-woven fabric configuring the reinforcement layer 21 is in the above range, an excessive increase in the weight of the tire 1 due to the reinforcement layer 21 can also be suppressed. The density of the non-woven fabric configuring the reinforcement layer 21 refers to the mass per unit area as measured in accordance with ISO 9073-1. Specifically, the density of the non-woven fabric configuring the reinforcement layer 21 can be calculated by removing the non-woven fabric from the tire 1, melting or incinerating the rubber to remove the rubber, and then weighing the non-woven fabric itself and calculating the density.
Furthermore, the diameter of the filament configuring the reinforcement layer 21 is preferably 10 μm to 75 μm and in particular is preferably 20 μm to 50 μm. In a case in which the cross-section is rectangular, the area may be replaced by the circular area. In this way, the durability of the tire 1 can be further enhanced, and an excessive increase in weight of the tire 1 can be also suppressed, for the same reasons as for the above-described density of the non-woven fabric.
As illustrated in
In the tire widthwise cross-sectional view (see
As illustrated in
As illustrated in
<Verification Test Using Test Pieces>
Next, an overview, along with the results, of a verification test conducted to verify the above-described effects of the reinforcement layer 21 are described. In this verification test, three test pieces in which a plurality of steel fibers were embedded in rubber were subjected to a load by repeatedly pressing cylindrical protrusions, with a tip radius of 10 mm and a width of 30 mm, from a vertical direction orthogonal to the extension direction of the steel fibers at a minimum load of −0.2 kN, a maximum load of −4 kN, and at an ambient temperature of 70° C. For each test piece, the lengths of cracks occurring in the steel fibers after 2×106 cycles of the aforementioned load were compared as an index, as illustrated in Table 1 below. The first test piece was a test piece in which nothing was disposed along the steel fibers (“Test piece X1” in Table 1 below). The second test piece was a test piece in which organic fibers were disposed along the steel fibers (“Test piece X2” in Table 1 below). The organic fibers used were nylon 6, with a mass of 470 dtex/1, and a number of embedded fibers equivalent to 78 fibers/5 cm. The third test piece was a test piece in which a brass non-woven fabric was disposed along the steel fibers (“Test piece X3” in Table 1 below). The brass used was C2680, the filament diameter of the non-woven fabric was 25 μm, and the density was 300 g/m2.
The pneumatic tire according to the present disclosure is not limited to the specific configurations described in the above embodiments. Various modifications and changes may be made without departing from the scope of the claims.
The present disclosure relates to a pneumatic tire.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2020-092586 | May 2020 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2021/000566 | 1/8/2021 | WO |
