JP7139943B2 - pneumatic tire - Google Patents

Description

The present invention relates to pneumatic tires.

When the vehicle runs, a large load is applied to the side portions of the tire. In order to withstand this load and achieve good steering stability and good transient characteristics when transitioning between straight running and cornering, the side portions are required to have sufficient rigidity.

On the other hand, due to the increasing demand for environmental performance of vehicles in recent years, there is a demand for lighter weight tires. For this reason, it is being studied to reduce the number of carcass plies as much as possible. However, reducing the number of carcass plies reduces the rigidity of the side portions. This may hinder realization of good steering stability and transient characteristics.

There is a method of providing a reinforcing layer on the side portion in order to realize weight reduction while maintaining sufficient rigidity of the side portion. In this method, the number of carcass plies is reduced by increasing the rigidity of the side portions with reinforcing layers. Japanese Patent Laid-Open No. 8-310206 and Japanese Patent Laid-Open No. 2015-63172 disclose studies on tires having reinforcing layers in the side portions.

JP-A-8-310206 Japanese Patent Application Laid-Open No. 2015-63172

While the reinforcing layer is provided at a predetermined portion of the side portion, the carcass extends from the bead portion of one side portion to the entire bead portion of the other side portion. The challenge is whether it is possible to achieve excellent durability when the number of carcass plies is reduced. There is a demand for a tire that achieves high rigidity and weight reduction in the side portion while realizing excellent durability of the tire.

SUMMARY OF THE INVENTION An object of the present invention is to provide a pneumatic tire that achieves excellent durability, high rigidity of the side portion, and weight reduction.

A pneumatic tire according to the present invention includes a carcass, a pair of clinches, and a pair of side reinforcing layers. Each side reinforcing layer is provided with cords and a topping rubber and is located axially outside the carcass. In the radial direction, the inner edge P of the side reinforcing layer is positioned inside the maximum width position of the tire and inside the outer edge of the clinch, and the outer edge Q of the side reinforcing layer is positioned outside the maximum width position. positioned. The ratio of the distance Lr between the inner edge P and the outer surface of the tire measured along the normal LV of the side reinforcing layer drawn from the inner edge P to the thickness T of the tire measured along the normal LV. (Lr/T) is 35% or more and 65% or less.

Preferably, the ratio (Lr/T) is 40% or more and 60% or less.

Preferably, the clinch comprises an outer layer and an inner layer located axially inward of the outer layer, the inner layer having a higher hardness than the outer layer.

Preferably, said clinch comprises an outer layer and an inner layer located axially inward of said outer layer, said inner edge P being located between said outer layer and said inner layer.

Preferably, the ratio (Hr/H) of the radial distance Hr between the inner end P and the outer end Q to the cross-sectional height H of the tire is 10% or more and 50% or less.

Preferably, the ratio (Hq/H) of the radial height Hq from the bead baseline to the outer edge Q to the cross-sectional height H of the tire is 70% or less.

The tire further comprises a pair of beads, the carcass comprising a carcass ply, the carcass ply being stretched between the beads on both sides and folded around the bead, whereby In the case where the carcass ply has a main portion and a turnup portion, the outer end Q is preferably positioned radially outside the end of the turnup portion.

In the pneumatic tire according to the present invention, in the radial direction, the inner end P of the side reinforcing layer is located inside the maximum width position and inside the outer end of the clinch, and the outer end Q of the side reinforcing layer is located inside the maximum width position. located outside. There is a side reinforcing layer from the widest point where the deflection is greater when a load is applied to the outer edge of the clinch. This side reinforcing layer contributes to the rigidity and durability of the side portion. Furthermore, in this tire, the ratio (Lr/T) is 35% or more and 65% or less. That is, the inner edge P, where stress tends to concentrate when a load is applied, is positioned near the center in the thickness direction of the tire, where there is little distortion. This effectively contributes to tire durability. Furthermore, since this side reinforcing layer effectively contributes to durability, it is possible to reduce the number of carcass plies while realizing excellent durability. This tire achieves high rigidity and weight reduction of the side portion while realizing excellent durability.

FIG. 1 is a cross-sectional view showing part of a pneumatic tire according to one embodiment of the present invention. 2 is an enlarged cross-sectional view showing a portion of the tire of FIG. 1; FIG.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail based on preferred embodiments with appropriate reference to the drawings.

FIG. 1 is a cross-sectional view showing a pneumatic tire 2 according to one embodiment of the invention. In FIG. 1 , the vertical direction is the radial direction of the tire 2 , the horizontal direction is the axial direction of the tire 2 , and the direction perpendicular to the paper surface is the circumferential direction of the tire 2 . In FIG. 1 , the dashed-dotted line CL represents the equatorial plane of the tire 2 . Solid line BBL represents the bead baseline. The bead baseline BBL corresponds to a line that defines the rim diameter of the rim (see JATMA). A bead baseline BBL extends axially. The shape of this tire 2 is symmetrical with respect to the equatorial plane CL, except for the tread pattern.

This tire 2 includes a tread 4, a pair of sidewalls 6, a pair of clinches 8, a pair of beads 10, a carcass 12, a belt 14, a band 16, an inner liner 18, a pair of chafers 20 and a pair of side reinforcing layers 22. I have. In this tire 2 , portions extending radially inward from the ends of the tread 4 are called side portions 24 . Side walls 6 , clinches 8 , beads 10 , chafers 20 and side reinforcing layers 22 are located on side portions 24 . A portion of the carcass 12 and innerliner 18 are also located on the side portions 24 . This tire 2 is of the tubeless type. This tire 2 is mounted on a passenger car.

The tread 4 has a shape that is convex radially outward. The tread 4 forms a tread surface 26 that contacts the road surface. Grooves 27 are cut in the tread 4 . The grooves 27 form a tread pattern. The tread 4 is made of a crosslinked rubber having excellent abrasion resistance, heat resistance and grip.

Each sidewall 6 extends radially generally inward from the edge of the tread 4 . The radially inner end of sidewall 6 is joined with clinch 8 . The sidewall 6 is made of crosslinked rubber having excellent cut resistance and weather resistance. This sidewall 6 prevents the carcass 12 from being damaged.

Each clinch 8 is positioned substantially radially inside the sidewall 6 . The clinch 8 is located outside the bead 10 and the carcass 12 in the axial direction. As shown in FIG. 1, clinch 8 comprises outer layer 28 and inner layer 30 . The outer surface of the outer layer 28 constitutes part of the outer surface of this tire 2 . The outer layer 28 is made of crosslinked rubber with excellent wear resistance. The outer layer 28 abuts the flange of the rim when the tire 2 is mounted on the rim. The inner layer 30 is located axially inward of the outer layer 28 . Outer edge 32 of inner layer 30 is radially outboard of outer edge 34 of outer layer 28 . In this embodiment, the radially outer edge 36 of the clinch 8 is the radially outer edge 32 of the inner layer 30 . In this clinch 8 , the hardness HDi of the inner layer 30 is higher than the hardness HDo of the outer layer 28 .

In the present invention, the hardness HDi and the hardness HDo are measured by a type A durometer according to "JIS K6253". This durometer is pressed against the cross-section shown in FIG. 1 and the hardness is measured. Measurements are made at a temperature of 23°C.

The clinch 8 may not have the inner layer 30 . Clinch 8 may be formed of outer layer 28 only. The radially outer edge 36 of the clinch 8 is then the radially outer edge 34 of the outer layer 28 .

Each bead 10 is located axially inside the clinch 8 . The bead 10 has a core 38 and an apex 40 extending radially outward from the core 38 . The core 38 is ring-shaped and includes a wound non-stretchable wire. A typical material for the wire is steel. Apex 40 tapers radially outward. The apex 40 is made of crosslinked rubber with high hardness.

The carcass 12 consists of carcass plies 42 . A carcass ply 42 spans between the beads 10 on both sides and runs along the tread 4 and the sidewalls 6 . A carcass ply 42 is folded around the core 38 . By this folding, the carcass ply 42 is formed with a main portion 44 and a folded portion 46 . The main portion 44 extends from the axially inner side of one bead 10 to the axially inner side of the other bead 10 . The main portion 44 is laminated to the outside of the inner liner 18 . The turnup 46 extends radially through the outer side of the apex 40 and the inner side of the inner layer 30 in the axial direction. As is clear from the drawing, the end 48 of the folded portion 46 is positioned near the maximum width position A of the tire 2, which will be described later. The carcass 12 of this tire 2 has a "high turn-up (HTU)" structure.

The carcass ply 42 consists of a large number of parallel cords and a topping rubber. The absolute value of the angle that each code forms with respect to the equatorial plane CL ranges from 75° to 90°. In other words, this carcass 12 has a radial structure. The cord consists of organic fibers. Preferred organic fibers include polyester fibers, nylon fibers, rayon fibers, polyethylene naphthalate fibers and aramid fibers. Carcass 12 may be formed from two or more carcass plies 42 .

The belt 14 is positioned radially inside the tread 4 . The belt 14 is laminated with the carcass 12 . Belt 14 reinforces carcass 12 . The belt 14 consists of a first layer 50 and a second layer 52 . Although not shown, each of the first layer 50 and the second layer 52 consists of a large number of parallel cords and a topping rubber. Each cord is inclined with respect to the equatorial plane CL. A general absolute value of the tilt angle is 10° or more and 35° or less. The direction of inclination of the cords of the first layer 50 with respect to the equatorial plane CL is opposite to the direction of inclination of the cords of the second layer 52 with respect to the equatorial plane CL. A preferred material for the cord is steel. Organic fibers may be used for the cord. Belt 14 may comprise three or more layers.

The band 16 is located radially outside the belt 14 . The width of the band 16 is greater than the width of the belt 14 in the axial direction. Although not shown, this band 16 consists of a cord and a topping rubber. The cord is spirally wound. This band 16 has a so-called jointless structure. The cord extends substantially circumferentially. The angle of the cords with respect to the circumferential direction is 5° or less, or even 2° or less. Since the belt 14 is constrained by this cord, lifting of the belt 14 is suppressed. The cord consists of organic fibers. Preferred organic fibers include nylon fibers, polyester fibers, rayon fibers, polyethylene naphthalate fibers and aramid fibers.

An inner liner 18 is positioned inside the carcass 12 . An inner liner 18 is joined to the inner surface of the carcass 12 . The inner liner 18 is made of crosslinked rubber with excellent air shielding properties. A typical base rubber for the inner liner 18 is butyl rubber or halogenated butyl rubber. The inner liner 18 retains the internal pressure of the tire 2 .

Each chafer 20 is positioned near the bead 10 . When the tire 2 is mounted on the rim, the chafer 20 contacts the rim. This abutment protects the vicinity of the bead 10 . In this embodiment, the chafer 20 consists of cloth and rubber impregnated in the cloth. A chafer 20 may be configured integrally with the clinch 8 . At this time, the material of the chafer 20 is the same as the material of the clinch 8 .

Each side reinforcing layer 22 is located inside the sidewall 6 in the axial direction. The side reinforcing layers 22 are located outside the carcass 12 in the axial direction. The side reinforcing layer 22 consists of a large number of parallel cords and a topping rubber. Each cord is inclined with respect to the circumferential direction. Typically, the absolute value of the tilt angle is 0° or more and 5° or less. The cord consists of organic fibers. Preferred organic fibers include polyester fibers, nylon fibers, rayon fibers, polyethylene naphthalate fibers and aramid fibers. The cord material is the same as the cord material of the carcass ply 42 . The cord material may be different from the cord material of the carcass ply 42 .

FIG. 2 shows an enlarged view of the vicinity of the side reinforcing layer 22 of FIG. In FIGS. 1 and 2, symbol A represents a position on the outer surface of this tire 2. As shown in FIG. At position A, the width of this tire 2 is maximum. Position A is the maximum width position. In FIG. 2, the symbol P represents the radially inner end of the side reinforcing layer 22. As shown in FIG. Symbol Q represents the radially outer end of the side reinforcing layer 22 .

As is clear from FIG. 2, the inner end P is located inside the maximum width position A in the radial direction. The inner end P is positioned inside the outer end 36 of the clinch 8 . Inner edge P is located between outer layer 28 and inner layer 30 . The outer end Q is located outside the maximum width position A in the radial direction.

In FIG. 2, a straight line LV is the normal line of this side reinforcing layer 22 at the inner end P. As shown in FIG. A double-headed arrow Lr represents the distance between the inner edge P and the intersection of the normal line LV and the outer surface of the tire 2, measured along the normal line LV. The distance Lr is measured from the midpoint of the inner end P of the side reinforcing layer 22 in the thickness direction. A double arrow T represents the thickness of the tire 2 measured along the normal line LV. The thickness T is the distance between the inner and outer surfaces of this tire 2 measured along the normal LV. In this tire 2, the ratio (Lr/T) of the distance Lr to the thickness T is 35% or more and 65% or less.

The effects of the present invention will be described below.

In the pneumatic tire 2 according to the present invention, the inner end P of the side reinforcing layer 22 is positioned inside the maximum width position A and inside the outer end 36 of the clinch 8 in the radial direction, and the outer end Q is positioned at the maximum width Located outside position A. The side reinforcing layer 22 is present from the maximum width position A, where the deflection increases when a load is applied, to the position of the outer edge 36 of the clinch 8 . This side reinforcement layer 22 effectively increases the stiffness from the maximum width position A to the position of the outer edge 36 of the clinch 8 . The side reinforcement layer 22 effectively increases the rigidity of the side portion 24 . This contributes to good durability and handling stability.

In this tire 2, the ratio (Lr/T) is 35% or more and 65% or less. When the side portion 24 of the tire 2 is bent so as to protrude outward, a compressive force is applied to the inner surface side of the side portion 24 and a tensile force is applied to the outer surface side. In the central portion of the inner and outer surfaces, both compressive and tensile forces applied are small. By setting the ratio (Lr/T) to 35% or more and 65% or less, it is possible to position the inner end P, where stress tends to concentrate, near the center in the thickness direction of the tire 2 (the center between the inner surface and the outer surface). . This effectively reduces the concentration of stress in the vicinity of the inner edge P. This tire 2 achieves excellent durability. From this point of view, the ratio (Lr/T) is more preferably 40% or more and 60% or less, and even more preferably 50%.

Since the side reinforcing layer 22 is provided at a predetermined position of the side portion 24, the influence on the mass of the tire 2 is small. Since the side reinforcing layers 22 contribute to durability as described above, the side reinforcing layers 22 can reduce the number of carcass plies 42 in addition to achieving excellent durability. For example, a tire that has conventionally been provided with two carcass plies for durability can be provided with one carcass ply 42 by providing the side reinforcing layer 22 . This side reinforcing layer 22 can reduce the weight of the tire 2 .

As mentioned above, the hardness HDi of the inner layer 30 of the clinch 8 is preferably higher than the hardness HDo of the outer layer 28 . The hardness of the outer layer 28 in contact with the rim is increased. In this tire 2, by positioning the inner layer 30, which is harder than the outer layer 28, inside the outer layer 28, distortion of the bead 10 is effectively suppressed without increasing the mass. . This tire 2 achieves excellent durability without increasing its mass.

The hardness HDi of the inner layer 30 is preferably 70 or more. By setting the hardness HDi to 70 or more, the inner layer 30 effectively suppresses distortion of the bead 10 portion. This tire 2 achieves excellent durability. The hardness HDi is preferably 90 or less. By setting the hardness HDi to 90 or less, the longitudinal spring constant of the tire 2 can be moderately suppressed. This tire 2 maintains excellent ride comfort.

The difference (HDi-HDo) between the hardness HDi of the inner layer 30 and the hardness HDo of the outer layer 28 is preferably 5 or more. By setting this difference to 5 or more, the inner layer 30 effectively suppresses the distortion of the bead 10 portion. This tire 2 achieves excellent durability. The difference (HDi-HDo) is preferably 15 or less. By setting this difference to 15 or less, distortion due to the difference in hardness at the boundary between the inner layer 30 and the outer layer 28 can be suppressed. This contributes to the durability of tire 2 . This tire 2 achieves excellent durability.

The inner edge P of the side reinforcement layer 22 is preferably located between the outer layer 28 and the inner layer 30 . By doing so, the inner layer 30 exists between the inner end P and the carcass 12 where stress tends to concentrate. This effectively relieves stress concentrations in the vicinity of the inner edge P. This tire 2 achieves excellent durability.

In FIG. 1 , a double arrow H represents the radial height from the bead baseline BBL to the radially outer edge of the tire 2 . Height H is the cross-sectional height of this tire 2 . In FIG. 2, a double arrow Hr represents the radial distance between the inner end P and the outer end Q. As shown in FIG.

The ratio (Hr/H) of the distance Hr to the height H is preferably 10% or more. By setting the ratio (Hr/H) to 10% or more, the side reinforcing layer 22 effectively contributes to the rigidity of the side portion 24 . This tire 2 achieves excellent durability and steering stability. From this point of view, the ratio (Hr/H) is more preferably 20% or more. The ratio (Hr/H) is preferably 50% or less. By setting the ratio (Hr/H) to 50% or more, the influence of the side reinforcing layer 22 on the mass of the tire 2 is suppressed. This tire 2 achieves good rolling resistance. From this point of view, the ratio (Hr/H) is more preferably 40% or less.

In FIG. 2, the double arrow Hq represents the radial height from the bead baseline BBL to the outer edge Q. The ratio of height Hq to height H (Hq/H) is preferably 70% or less. By setting the ratio (Hq/H) to 70% or less, the influence of the side reinforcing layer 22 on the mass of the tire 2 is suppressed. This tire 2 achieves good rolling resistance. From this point of view, the ratio (Hq/H) is more preferably 60% or less.

In FIG. 2, a double arrow Hc represents the height from the bead baseline BBL to the end 48 of the turnup portion 46 in the radial direction. As shown in the figure, the outer ends Q of the side reinforcing layers 22 are preferably located outside the ends 48 of the folded portions 46 in the radial direction. That is, the ratio of height Hq to height Hc (Hq/Hc) is preferably greater than 100%. Cracks are likely to occur near the end 48 of the folded portion 46 when a load is applied. By doing so, the side reinforcing layer 22 is positioned axially outside the end 48 of the folded portion 46 . This reduces strain near the end 48 of the folded portion 46 and effectively suppresses the occurrence of cracks. This tire 2 achieves excellent durability. From this point of view, the ratio (Hq/Hc) is more preferably 105% or more.

In the present invention, the dimensions and angles of each member of the tire 2 are measured with the tire 2 mounted on a regular rim and inflated to a regular internal pressure. No load is applied to the tire 2 during the measurement.

In the present specification, a regular rim means a rim defined in the standard on which the tire 2 relies. A "standard rim" in the JATMA standard, a "design rim" in the TRA standard, and a "measuring rim" in the ETRTO standard are regular rims. In this specification, the normal internal pressure means the internal pressure defined in the standard on which the tire 2 relies. The "maximum air pressure" in the JATMA standard, the "maximum value" in the "TIRE LOAD LIMITSAT VARIOUS COLD INFLATION PRESSURES" in the TRA standard, and the "INFLATION PRESSURE" in the ETRTO standard are regular internal pressures.

The effects of the present invention will be clarified by examples below, but the present invention should not be construed in a limited manner based on the description of these examples.

[Example 1]
A tire as shown in FIGS. 1-2 was constructed. The size of this tire is 205/70R15. Specifications of this tire are shown in Table 1. The number of carcass plies in this tire is one. In this tire, the inner end P of the side reinforcing layer is positioned radially inward from the maximum width position of the tire, and the outer end Q is positioned radially outward from the maximum width position of the tire. The tire clinch comprises an inner layer and an outer layer. This is indicated as "present" in the column "presence/absence of inner layer" in Table 1. The hardness of the inner layer was 80 and the hardness of the outer layer was 70. This tire had a ratio (Hq/H) of 70%. In this tire, the inner edge P of the side reinforcing layer is located between the inner layer and the outer layer. This is indicated as "Yes" in the column "Inner Layer to Outer Layer" in Table 1. This tire had a ratio (Hq/Hc) of 110%.

[Comparative Example 1]
The tire of Comparative Example 1 has two carcass plies without side reinforcing layers. The clinch of this tire does not have an inner layer. Others are the same as the first embodiment.

[Example 2]
A tire of Example 2 was obtained in the same manner as in Example 1, except that the position of the inner end P was changed so that the ratio (Hr/H) was as shown in Table 1. In this tire, the position of the inner end P is moved radially outward compared to Example 1, so the inner end P is not positioned between the inner layer and the outer layer. This is indicated as "No" in the column "Between inner layer and outer layer" in Table 1.

[Example 3-4]
Tires of Examples 3-4 were obtained in the same manner as in Example 1 except that the ratio (Lr/H) was as shown in Table 1.

[Example 5]
A tire of Example 5 was obtained in the same manner as Example 1, except that the clinch did not have an inner layer.

[durability]
The tire was mounted on a regular rim (15×6JJ), and the tire was inflated to an internal pressure of 290 kPa. This tire was mounted on a running test machine, and a vertical load of 10.27 kN was applied to the tire. This tire was run at a speed of 80 km/h on a drum having a radius of 1.7 m, and the running distance until damage to the tire was confirmed was confirmed. Regarding the tire of the example, the running distance until damage occurred near the inner end P of the side reinforcing layer and the running distance until damage occurred near the maximum width position were confirmed. These values are shown in Table 1 as "inner end durability" and "side portion durability", respectively, with the travel distance at which damage occurred near the maximum width position in the tire of Comparative Example 1 being set to 100. there is The higher the value, the better the durability. A higher value is preferred.

[mass]
Tire mass was measured. The results are shown in Table 1 below as indexes with Comparative Example 1 being 100. The smaller the numerical value, the better.

[Steering stability]
The tire was mounted on a regular rim (15×6JJ) and inflated to an internal pressure of 230 Pa. This tire was mounted on a passenger car. This passenger car was run on a test course made of asphalt, and a sensory evaluation was performed by a driver. The evaluation item is steering stability. The results are shown in Table 1 below as indexes with Comparative Example 1 being 100. A larger value is preferable.

As shown in Table 1, the tires of Examples are generally superior to the tires of Comparative Examples. From this evaluation result, the superiority of the present invention is clear.

The pneumatic tire described above can be used in various vehicles.

2 Tire 4 Tread 6 Sidewall 8 Clinch 10 Bead 12 Carcass 14 Belt 16 Band 18 Inner liner 20 Chafer 22 Side reinforcing layer 24 Side portion 26 Tread surface 28 Inner layer 30 Outer layer 36 Outer end of clinch 38 Core 40 Apex 42 Carcass ply 44 Main part 46 Folded part 48 Tip of folded part 50 First layer 52 Second layer

Claims (7)

comprising a carcass, a pair of clinches and a pair of side reinforcing layers,
Each side reinforcing layer is provided with cords and a topping rubber and is located axially outside the carcass,
In the radial direction, the inner edge P of the side reinforcing layer is positioned inside the maximum width position of the tire and inside the outer edge of the clinch, and the outer edge Q of the side reinforcing layer is positioned outside the maximum width position. is located
The ratio of the distance Lr between the inner edge P and the outer surface of the tire measured along the normal LV of the side reinforcing layer drawn from the inner edge P to the thickness T of the tire measured along the normal LV. A pneumatic tire in which (Lr/T) is 35% or more and 65% or less. The pneumatic tire according to claim 1, wherein the ratio (Lr/T) is 40% or more and 60% or less. The clinch comprises an outer layer and an inner layer located axially inward of the outer layer,
The pneumatic tire according to claim 1 or 2, wherein the hardness of the inner layer is higher than the hardness of the outer layer. The clinch comprises an outer layer and an inner layer located axially inward of the outer layer,
The pneumatic tire according to any one of claims 1 to 3, wherein the inner edge P is located between the outer layer and the inner layer. 5. Any one of claims 1 to 4, wherein a ratio (Hr/H) of the radial distance Hr between the inner end P and the outer end Q to the cross-sectional height H of the tire is 10% or more and 50% or less. Pneumatic tires as described. The ratio (Hq/H) of the radial height Hq from the bead base line to the outer edge Q to the cross-sectional height H of the tire is 70% or less. pneumatic tires. It also has a pair of beads,
The carcass comprises a carcass ply,
The carcass ply is stretched between the beads on both sides and folded back around the bead, and the carcass ply is folded back to form a main portion and a folded portion,
The pneumatic tire according to any one of claims 1 to 6, wherein the outer edge Q is located outside the edge of the folded portion in the radial direction.

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