JP2022100772A - tire - Google Patents

Abstract

To provide a tire which can decrease rolling resistance, secure the required pinch-cut resistance, and achieve decrease in road noise.SOLUTION: A tire 2 comprises: a tread 4; a pair of side walls 6; a pair of beads 10; a carcass 12; a belt 14; and a thinner liner 20. The carcass 12 is constituted of a piece of carcass ply 34 which includes: a ply body 36; and a pair of folding parts 38 continuous to the ply body 36 and folded back around cores 28 of the respective beads 10. An end of the folding part 38 is positioned at an axial direction outer side in comparison with an axial direction outer side end of a shoulder peripheral direction groove and at an axial direction inner side in comparison with a ground contact end of the tread. The bead 10 includes an inside apex 30 positioned at the radial direction outer side of the core 28 and an outside apex 32 positioned at the radial direction outer side of the inside apex 30, and the folding part 38 is positioned between the outside apex 32 and the inside apex 30.SELECTED DRAWING: Figure 1

Description

The present invention relates to a tire.

Considering the impact on the environment, tires are required to contribute to the fuel efficiency of vehicles. Therefore, it is considered to reduce the number of parts for the purpose of weight reduction for reducing the rolling resistance of the tire. For example, it is being considered to reduce the number of carcass plies constituting the carcass from two to one. On the other hand, if the number of carcass plies is reduced to one, there is a concern that damage accompanying the cutting of the carcass cord contained in the carcass ply, that is, pinch cut may occur.

Therefore, there is also known a tire in which the number of carcass plies existing inside the sidewall is two while adopting a carcass composed of one carcass ply (for example, Patent Document 1).
The carcass included in the tire described in Patent Document 1 has a so-called Ultra High Turn Up structure (ultra high turn-up structure, hereinafter also referred to as UHTU structure). In a carcass with a UHTU structure, the end of the folded portion that is part of the carcass ply is located radially inside the tread.

Japanese Unexamined Patent Publication No. 2002-127712

In a tire using a carcass having a UHTU structure, road noise may increase due to the fact that the end of the carcass ply is located inside the radial direction of the tread.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a tire capable of ensuring necessary pinch cut resistance and achieving reduction of road noise while reducing rolling resistance. ..

The tire according to one aspect of the present invention comprises a tread that touches the road surface, a pair of sidewalls that are connected to the end of the tread and are located radially inside the tread, and a pair of sidewalls that are located radially inside the tread. A pair of beads having a ring-shaped core, a carcass that bridges between one bead and the other bead inside the tread and the sidewall, and radially between the tread and the carcass. It is equipped with a located belt and an inner liner located radially inside the carcass.
In the tread, a plurality of circumferential grooves are carved, and among the plurality of circumferential grooves, the circumferential groove located on the outermost side in the axial direction is the shoulder circumferential groove.
The carcass is composed of one carcass ply.
The carcass ply has a ply body that spans between one core and the other core, and a pair of folded portions that are connected to the ply body and are folded back from the inside to the outside in the axial direction around each core. Have and
The end of the folded portion is located on the outer side in the axial direction from the outer end in the axial direction of the peripheral groove of the shoulder, and on the inner side in the axial direction from the ground contact end of the tread.
The bead comprises an inner apex located radially outward of the core and an outer apex located radially outward of the inner apex, between the outer apex and the inner apex. The folded portion is located.

Preferably, in this tire, the length B from the axial outer end of the shoulder circumferential groove to the end of the folded portion with respect to the length A from the axial outer end of the shoulder circumferential groove to the ground contact end. The ratio is 40% or more and 60% or less.

Preferably, in this tire, the height HO of the outer apex is 3.5 times or more and 10.0 times or less the height HI of the inner apex.

Preferably, the tire is further provided with a band-shaped, sponge-based sound control body located inside the inner liner in the radial direction and extending in the circumferential direction of the tire.
In the axial direction, the ratio of the length D from the equatorial plane of the tire to the axially outer end of the sound control body to the length C from the equatorial plane of the tire to the end of the folded portion is 50% or more and 70% or less. Is.

According to the present invention, it is possible to obtain a tire capable of ensuring necessary pinch cut resistance and achieving reduction of road noise while reducing rolling resistance.

FIG. 1 is a cross-sectional view showing a part of a tire according to an embodiment of the present invention. FIG. 2 is a partially enlarged view of FIG. FIG. 3 is a cross-sectional view showing a part of a tire according to another embodiment of the present invention.

Hereinafter, the present invention will be described in detail based on a preferred embodiment with reference to the drawings as appropriate.

In the present disclosure, a state in which a tire is assembled on a normal rim, the internal pressure of the tire is adjusted to the normal internal pressure, and no load is applied to the tire is referred to as a normal state. In the present disclosure, unless otherwise specified, the dimensions and angles of each part of the tire are measured in normal condition.

Regular rim means the rim defined in the standard on which the tire relies. The "standard rim" included in the applicable rim in the JATTA standard, the "Design Rim" in the TRA standard, and the "Measuring Rim" in the ETRTO standard are regular rims.

The normal internal pressure means the internal pressure defined in the standard on which the tire relies. The "maximum air pressure" in the JATTA standard, the "maximum value" published in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the TRA standard, and the "INFLATION PRESSURE" in the ETRTO standard are normal internal pressures.

Normal load means the load specified in the standard on which the tire relies. The "maximum load capacity" in the JATTA standard, the "maximum value" published in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the TRA standard, and the "LOAD CAPACITY" in the ETRTO standard are normal loads.

In the present disclosure, the crosslinked rubber is a molded product of a rubber composition obtained by pressurizing and heating the rubber composition. The rubber composition is an uncrosslinked rubber obtained by mixing a base rubber and a chemical in a kneader such as a Banbury mixer. The crosslinked rubber is also referred to as vulcanized rubber, and the rubber composition is also referred to as unvulcanized rubber.

As the base rubber, natural rubber (NR), butadiene rubber (BR), styrene butadiene rubber (SBR), isoprene rubber (IR), ethylene propylene rubber (EPDM), chloroprene rubber (CR), acrylonitrile butadiene rubber (NBR) And butyl rubber (IIR) are exemplified. Chemicals include reinforcing agents such as carbon black and silica, plasticizers such as aromatic oils, fillers such as zinc oxide, lubricants such as stearic acid, antiaging agents, processing aids, sulfur and A vulcanization accelerator is exemplified. Although not described in detail, the selection of the base rubber and the chemicals, the content of the selected chemicals, and the like are appropriately determined according to the specifications of the elements to which the rubber composition is applied.

In the present disclosure, the tensile strength of a cord made of organic fibers is represented by "strength at cutting" measured in accordance with JIS L1017 "Chemical fiber tire cord".

[First Embodiment]
FIG. 1 shows a part of a tire 2 according to the first embodiment of the present invention. The tire 2 is a tire for a passenger car, for example, an SUV (sport utility vehicle). In FIG. 1, the tire 2 is assembled on the rim R. The rim R is a regular rim. The inside of the tire 2 is filled with air, and the internal pressure of the tire 2 is adjusted.
FIG. 2 is a partially enlarged view of FIG. FIG. 2 shows the vicinity of the bead 10 included in the tire 2.

The tire 2 assembled on the rim R is also referred to as a tire-rim complex. The tire-rim complex comprises a rim R and a tire 2 assembled on the rim R.

FIGS. 1 and 2 show a part of a cross section of the tire 2 (hereinafter, also referred to as a meridian cross section) along a plane including a rotation axis of the tire 2. In FIGS. 1 and 2, the left-right direction is the axial direction of the tire 2, and the vertical direction is the radial direction of the tire 2. The direction perpendicular to the paper surface of FIGS. 1 and 2 is the circumferential direction of the tire 2. In FIG. 1, the alternate long and short dash line CL represents the equatorial plane of the tire 2.

In FIGS. 1 and 2, the solid line BBL extending in the axial direction is a bead baseline. This bead baseline is a line that defines the rim diameter of the rim R (see JATTA and the like).

In FIGS. 1 and 2, the reference numeral PW is the outer end in the axial direction of the tire 2. The outer end PW is specified based on the contour of the outer surface of the tire 2 in the normal state. When decorations such as patterns and letters are on the outer surface, the outer edge PW is specified based on the contour of the virtual outer surface obtained assuming that there is no decoration.
The outer end PW is a position where the tire 2 shows the maximum width (hereinafter, the maximum width position).

In FIG. 1, the reference numeral PC is the equator of the tire 2. The equator PC is the radial outer end of the tire, which is identified based on the contour of the outer surface of the tire 2 in the normal state. If there is a groove on the equatorial plane, the equatorial PC is identified based on the contour of the virtual outer surface obtained assuming that there is no groove.

In FIG. 1, the reference numeral PE represents a position on the outer surface of the tread 4 (hereinafter, also referred to as a ground contact end) corresponding to the axial outer end of the contact patch (not shown) with the road surface of the tire 2. .. This ground contact end PE is assembled on the rim R, which is a regular rim, and a load of 80% of the load index (LI) is applied to the tire 2 having an internal pressure of 230 kPa, and the tire 2 is flattened with a camber angle of 0 °. It is the outer end in the axial direction of the ground contact surface obtained by contacting the road surface.

The load index (LI) is, for example, an index that expresses the maximum mass that can be loaded on a tire under specified conditions, that is, the maximum load capacity, as defined in the JATTA standard.

The 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, a pair of chafers 18, and an inner liner 20.

The tread 4 touches the road surface on its outer surface, that is, the tread surface 22. The tread 4 is located outside the band 16 in the radial direction. Four circumferential grooves 24 are carved in the tread 4 of the tire 2. These circumferential grooves 24 are arranged in parallel in the axial direction and continuously extend in the circumferential direction. Of the four circumferential grooves 24, the circumferential groove 24s located on the outermost side in the axial direction, that is, the circumferential groove 24 near the ground contact end PE of the tread surface 22, is the shoulder circumferential groove 24s.

Further, the tread 4 is provided with five land portions 26 partitioned by four circumferential grooves 24. Of the five land portions 26, the land portion 26 located on the outermost side in the axial direction is the shoulder land portion 26s.
The tread 4 is made of crosslinked rubber in consideration of wear resistance, grip performance and the like.

In the tire 2, the end portion of the tread 4 is also referred to as a tire shoulder portion S. The portion between one tire shoulder portion S and the other tire shoulder portion S is also referred to as a tire crown portion C. The axis center of the tire crown portion C coincides with the equatorial plane.

Each sidewall 6 runs on the edge of the tread 4. The sidewall 6 is located inside the tread 4 in the radial direction. The sidewall 6 extends along the carcass 12 from the edge of the tread 4 towards the clinch 8. The sidewall 6 is made of crosslinked rubber in consideration of cut resistance.

Each clinch 8 is located inside the sidewall 6 in the radial direction. The clinch 8 comes into contact with the rim R. The clinch 8 is made of crosslinked rubber in consideration of wear resistance.

Each bead 10 is located inside the clinch 8 in the axial direction. The bead 10 is located inside the sidewall 6 in the radial direction. In FIG. 1, the reference numeral PB represents the end of the bead 10.

The bead 10 includes a core 28, an inner apex 30, and an outer apex 32. The core 28 is ring-shaped. Although not shown, the core 28 includes a steel wire.
The inner apex 30 is made of crosslinked rubber having high rigidity. The outer apex 32 is made of crosslinked rubber having high rigidity. In the tire 2, the outer apex 32 may be made of the same material as the inner apex 30, or may be made of a material different from the material of the inner apex 30.

The inner apex 30 is located radially outward of the core 28. The inner apex 30 is radially outwardly tapered. The height of the inner apex 30 is preferably 5 mm or more and 15 mm or less. The height of the inner apex 30 is a radial length from the boundary center PM between the core 28 and the inner apex 30 to the end PU of the inner apex 30, and is represented by the reference numeral HI. The height HI of the inner apex 30 is more preferably 8 mm or more and 12 mm or less.

The outer apex 32 is located radially outside the inner apex 30. The outer apex 32 is located between the carcass 12 and the clinch 8. A folded portion 38 of the carcass ply, which will be described later, is located between the outer apex 32 and the inner apex 30. In this tire 2, the outer apex 32 is thick in the vicinity of the end PU of the inner apex 30, and is tapered inward in the radial direction from this thick portion, and is tapered in the outward direction in the radial direction from this thick portion.

The maximum thickness TM of the outer apex 32 is preferably 2 mm or more and 5 mm or less. If the maximum thickness TM is too thick, the ratio of the clinch 8 in the tire 2 becomes relatively small, the crimping force between the tire 2 and the rim R decreases, and rim misalignment occurs or the generated rim misalignment occurs. It becomes easy to grow up. On the other hand, if the maximum thickness TM is too thin, in the tire 2, the folded portion 38 of the carcass ply 12 easily passes through the region where the compression strain occurs in the tire 2, and as a result, the durability of the tire 2 is lowered. There is.

This maximum thickness TM is the thickness of the thickest portion of the outer apex 32 in the axial direction, and is represented by the reference numeral TM. The maximum thickness TM of the outer apex 32 is more preferably 3 mm or more and 4 mm or less.

In this tire 2, the inner end PF of the outer apex 32 is located near the boundary between the core 28 and the inner apex 30. The outer end PB of the outer apex 32 is located near the maximum width position PW in the radial direction. In this tire 2, the outer end of the outer apex 32 is the end of the bead 10. Therefore, the reference numeral PB is also the end of the bead 10.

In this tire 2, the height HO of the outer apex 32 is preferably 50 mm or more and 60 mm or less. The height of the outer apex 32 is a radial length from the bead baseline (BBL) to the outer end PB of the outer apex 32 and is represented by the reference numeral HO.

If the height of the outer apex 32 is too high, the crosslinked rubber constituting the outer apex 32 usually generates more heat than the crosslinked rubber constituting the sidewall 6, so that the tire 2 tends to generate heat. , The rolling resistance coefficient (RRC) may increase.
On the other hand, if the height of the outer apex 32 is too low, in the tire 2, the folded portion 38 of the carcass ply 12 easily passes through the region where the compression strain is generated in the tire 2, and as a result, the durability of the tire 2 is lowered. I have something to do.
The height HO of the outer apex 32 is more preferably 53 mm or more and 57 mm or less.

The carcass 12 is located inside the tread 4, the pair of sidewalls 6, and the pair of clinches 8. The carcass 12 bridges between one bead 10 and the other bead 10. The carcass 12 has a radial structure.

The carcass 12 is composed of one carcass ply 34. The carcass ply 34 is folded from the inside to the outside in the axial direction around each core 28. The carcass ply 34 has a ply body 36 that bridges between one core 28 and the other core 28, and is connected to the ply body 36 and is folded back from the inside to the outside in the axial direction around each core 28. It has a pair of folded portions 38.

The end PD of the folded portion 38 is located on the outward side in the axial direction from the outer end PA in the axial direction of the shoulder circumferential groove 24s and on the inner side in the axial direction from the ground contact end PE of the tread.
The tire 2 is a tire having a UHTU (Ultra High Turn Up) structure as the structure of the carcass 12.

The carcass ply 34 includes a large number of carcass codes arranged in parallel. Although not shown, each carcass code intersects the equatorial plane. The carcass cord is made of organic fibers such as nylon fiber, rayon fiber, polyester fiber and aramid fiber, for example. This carcass cord is covered with topping rubber (not shown). The angle formed by the carcass cord with respect to the equatorial plane (hereinafter, the inclination angle of the carcass cord) is 75 ° or more and 90 ° or less.

The carcass ply 34 including the carcass cord has a product of the tensile strength of the carcass cord and the ends ([tensile strength of the carcass cord] × [ends]) of 8000 N or more from the viewpoint of ensuring pinch cut resistance. preferable.
Here, [ends] means the number of cross sections of the carcass cord existing per 5 cm width in the cross section perpendicular to the extending direction of the carcass cord of the carcass ply 34.

The belt 14 is located between the band 16 located inside the tread 4 and the carcass 12 in the radial direction. The belt 14 is laminated on the carcass 12. The axial width of the belt 14 of the tire 2 is 70% or more and 85% or less of the cross-sectional width of the tire 2 (see JATTA or the like).

The belt 14 is composed of at least two layers 30 laminated in the radial direction. The belt 14 of the tire 2 is composed of two layers 30 laminated in the radial direction. Of the two layers 30, the inner layer 30 is the inner layer 30A, and the outer layer 30 is the outer layer 30B. As shown in FIG. 1, the inner layer 30A has a width wider than the width of the outer layer 30B. In the axial direction, the end of the inner layer 30A is located outside the end of the outer layer 30B. The distance from the end of the outer layer 30B to the end of the inner layer 30A is 3 mm or more and 10 mm or less.

Although not shown, the inner layer 30A and the outer layer 30B each include a large number of parallel belt cords. These belt cords are covered with topping rubber. Each belt cord tilts with respect to the equatorial plane. The material of the belt cord is steel.

The band 16 is located between the tread 4 and the belt 14 in the radial direction. The band 16 is laminated on the belt 14. In the axial direction, the end of the band 16 is located outside the end of the belt 14. The distance from the end of the belt 14 to the end of the band 16 is 3 mm or more and 7 mm or less.

Although not shown, the band 16 includes a spirally wound band cord. The band cord extends substantially in the circumferential direction. Specifically, the angle formed by the band cord with respect to the circumferential direction is 5 ° or less. The band 16 has a jointless structure. In this tire 2, a cord made of organic fibers is used as a band cord. Examples of the organic fiber include nylon fiber, rayon fiber, polyester fiber and aramid fiber.

The band 16 of the tire 2 is composed of a full band 36 whose both ends face each other across the equator surface. The full band 36 covers the entire belt 14. The full band 36 restrains the entire belt 14. Although not shown, the band 16 may include a pair of edge bands that are axially spaced apart and constrain the ends of the belt 14 and the ends of the full band 36. The band 16 may be composed of only a pair of edge bands.

Each chafer 18 is located radially inside the bead 10. The chafer 18 comes into contact with the rim R. The chafer 18 of the tire 2 is composed of a cloth and rubber impregnated in the cloth.

The inner liner 20 is located inside the carcass 12. The inner liner 20 constitutes the inner surface of the tire 2. The inner liner 20 is made of crosslinked rubber having a low gas permeability coefficient. The inner liner 20 holds the internal pressure of the tire 2.

The tire 2 according to the present embodiment is composed of a carcass ply 34 having one carcass 12. Therefore, compared to a tire having a carcass having a carcass ply on two tires, the number of parts is small, so that the tire is lightweight, heat is less likely to be generated, and the rolling resistance coefficient (RRC) is reduced.
On the other hand, if the number of carcass plies is reduced, pinch cuts are likely to occur. The position where the pinch cut occurs is usually the intersection of the imaginary straight line extending in the radial direction and the carcass, passing through the apex of the flange of the rim R (the radial outer end of the rim R). There are two intersections, one near the shoulder and the other near the bead, and the pinch cut occurs at either of them.

Therefore, in this embodiment, the UHTU structure is adopted as the structure of the carcass 12. By adopting the UHTU structure for the carcass structure, the number of carcass plies existing in both the vicinity of the shoulder and the vicinity of the bead can be reduced to two, whereby the occurrence of pinch cut can be suppressed.

In the tire 2, as described above, from the viewpoint of improving the pinch cut resistance while reducing the rolling resistance, the end PD of the folded portion 38 of the carcass ply 34 is axial from the axial outer end PA of the shoulder circumferential groove 24s. It is provided so as to be located on the outer side in the direction and on the inner side in the axial direction from the grounding end PE of the tread 4.

Here, the end PD of the folded portion 38 of the carcass ply 34 is folded back from the axial outer end PA of the shoulder circumferential groove 24s with respect to the length A from the axial outer end PA of the shoulder circumferential groove 24s to the grounding end PE. The ratio of the length B to the end PD of the portion ([B / A] × 100) is preferably 40% or more and 60% or less.

When the position of the end PD of the folded-back portion 38 is close to the shoulder circumferential groove 24s, the shoulder circumferential groove 24s is expanded in the axial direction when a force for pulling outward in the axial direction is applied to the folded-back portion 38 such as during inflating. There is a possibility that a groove bottom crack may occur in the shoulder circumferential groove 24s, or the generated groove bottom crack may grow. On the other hand, by setting the above ratio ([B / A] × 100) to 40% or more, it is possible to suppress the generation of the groove bottom crack and the growth of the groove bottom crack.
In addition, as the position of the end PD of the folded-back portion 38 approaches the shoulder circumferential groove 24s, the effect of reducing RRC by weight reduction becomes poor, but the above ratio ([B / A] × 100) is 40% or more. By doing so, it is possible to secure the effect of reducing RRC by reducing the number of carcass plies to one.
The above ratio ([B / A] × 100) is more preferably 44% or more, further preferably 48% or more.

Further, when the position of the end PD of the folded portion 38 is close to the grounding end PE, the end PD of the folded portion 38 is located near the end of the belt 14, and as a result, the end PD of the folded portion 38 and the belt 14 are located. Distortion tends to concentrate near the edge of the belt. Then, due to the concentration of this strain, peeling (belt edge loose, hereinafter also referred to as BEL) may occur at the end of the belt 14. On the other hand, by setting the above ratio ([B / A] × 100) to 60% or more, the occurrence of the above-mentioned BEL can be suppressed.
The above ratio ([B / A] × 100) is more preferably 56% or less, further preferably 52% or less.

As described above, in the tire 2, the carcass 12 has a UHTU structure, and the end PD of the folded portion 38 of the carcass ply 34 is provided so as to be located inward in the axial direction from the ground contact end PE of the tread 4. Therefore, the road noise tends to be larger than the case where the carcass having the LTU (low turn-up) structure is adopted.
Therefore, the tire 2 employs a bead 10 including a core 28, an inner apex 30, and an outer apex 32. In this way, the apex contained in the bead is composed of the inner apex 30 and the outer apex 32, and by providing the carcass 12 between the two, the apex is inside the folded portion 38 (on the tire lumen side). The volume of the apex can be reduced, and the vertical spring of the tire 2 can be reduced. Then, by reducing the vertical spring, it is possible to reduce the road noise. Therefore, the tire 2 can suppress an increase in road noise while making the structure of the carcass 12 a UHTU structure.

In this tire 2, the height HO of the outer apex is preferably 3.5 times or more and 10.0 times or less the height HI of the inner apex. In this case, it is more suitable for reducing the vertical spring, reducing the impact when the tread 4 comes into contact with the road surface, and reducing the road noise.
The height HO of the outer apex is more preferably 4.5 times or more and 7.0 times or less the height HI of the inner apex.

In FIG. 1, the double-headed arrow M is the thickness of the tread 4 on the equatorial plane. This thickness M is measured along the equatorial plane. The double-headed arrow N is the thickness of the tread 4 at the end of the belt 14. This thickness N is measured along the normal of the outer surface of the belt 14 passing through the end of the belt 14. The thickness M and the thickness N may be measured in the meridian cross section of the tire 2.

In this tire 2, from the viewpoint of ensuring grip performance and reducing rolling resistance, the thickness M of the tread 4 on the equatorial surface is preferably 5 mm or more, and preferably 15 mm or less. The thickness M is more preferably 6 mm or more, and more preferably 13 mm or less.
Further, in the tire 2, from the viewpoint of reducing rolling resistance, the ratio (N / M) of the thickness N of the tread 4 at the end of the belt 14 to the thickness M of the tread 4 on the equatorial plane is preferably 0.80 or less. , 0.75 or less is more preferable. From the viewpoint of ensuring grip performance, this ratio (N / M) is preferably 0.65 or more, more preferably 0.70 or more.

The tire 2 having the tread 4 having such a thickness is a tire having a relatively thin tread thickness, and is a tire suitable for reducing rolling resistance. On the other hand, tires with a thin tread tend to have a large road noise. Therefore, the tire 2 having the above-mentioned thick tread 4 is suitable as the tire according to the embodiment of the present invention, which has an excellent effect in reducing road noise.

[Second Embodiment]
FIG. 3 shows a part of the tire 52 according to the second embodiment of the present invention. The tire 52 is a tire for a passenger car, for example, an SUV (sport utility vehicle). In FIG. 3, the tire 52 is assembled on the rim R. FIG. 3 shows a part of a cross section of the tire along a plane including the axis of rotation of the tire 52. In FIG. 3, the left-right direction is the axial direction of the tire 52, and the vertical direction is the radial direction of the tire 52. The direction perpendicular to the paper surface in FIG. 3 is the circumferential direction of the tire 52.

The tire 52 according to the present embodiment has the same configuration as that of the tire 2 shown in FIG. 1, except that the tire 52 includes the sound control body 54. Therefore, in FIG. 3, the same components as those of the tire 2 of FIG. 1 are designated by the same reference numerals, and the description thereof will be omitted.
Similar to the tire 2 of the first embodiment, the tire 52 is a tire in which rolling resistance is reduced and necessary pinch cut resistance is ensured. Further, the tire 2 is provided with the sound control body 54, so that the road noise is reduced. The tire 52 has significantly reduced road noise as compared with the tire 2 of the first embodiment.

The sound control body 54 is provided at a position on the inner surface of the tread 4 in the radial direction of the inner surface of the tire 2 (inner surface of the inner liner 20).

The sound control body 54 is made of a sponge material. The sponge material is a sponge-like porous structure, and for example, in addition to the so-called sponge itself having open cells in which rubber or synthetic resin is foamed, animal fibers, plant fibers, synthetic fibers, etc. are entwined and integrally connected. It shall include web-like ones. Further, the above-mentioned "porous structure" includes not only open cells but also closed cells.

The above-mentioned sponge material reduces sound (air column resonance energy) and reduces road noise by converting the vibration energy of air vibrating on the surface or the internal porous portion into heat energy and consuming it. Further, since the sponge material is easily deformed by shrinkage, bending, etc., it does not substantially affect the deformation of the tire during traveling. Therefore, it is possible to prevent the steering stability from deteriorating. Moreover, since the sponge material has a very small specific gravity, it is possible to prevent deterioration of the weight balance of the tire.

Examples of the sponge material include ether-based polyurethane sponge, ester-based polyurethane sponge, synthetic resin sponge such as polyethylene sponge, chloroprene rubber sponge (CR sponge), ethylene propylene rubber sponge (EDPM sponge), and nitrile rubber sponge (NBR sponge). A rubber sponge or the like can be preferably used. Among these, a polyurethane-based sponge containing an ether-based polyurethane sponge or a polyethylene-based sponge is preferable from the viewpoints of sound control, lightness, controllability of foaming, durability, and the like.

The sound control body 54 has a long strip shape having a bottom surface 54A fixed to the inner surface of the inner liner 20, and extends in the circumferential direction of the tire 52. Both ends of the sound control body 54 in the tire circumferential direction are abutted against each other. As a result, it is formed as a continuous annular body in the tire circumferential direction.
In the sound control body, both ends of the sound control body may be separated from each other in the circumferential direction of the tire. Further, it may have a plurality of separated points and may be provided intermittently along the circumferential direction of the tire.

The sound control body 54 has substantially the same meridian cross-sectional shape at each position in the tire circumferential direction. As the cross-sectional shape, in order to prevent tilting and deformation during traveling, a flat and horizontally long shape having a small radial height with respect to the axial width is preferable. In particular, it is preferable that the sound control body 54 has a concave groove 56 extending continuously in the circumferential direction on the inner surface side in the radial direction. The concave groove 56 can increase the surface area of the sound control body 54, absorb more resonance energy, improve heat dissipation, and suppress the temperature rise of the sponge material.
Further, the shape of the sound control body 54 in the meridian cross section is preferably symmetrical with respect to the equatorial plane.

The sound control body 54 is the length from the equatorial surface of the tire to the axial outer end PF of the sound control body 54 with respect to the length C from the equatorial surface of the tire 2 to the end PD of the folded portion 38 of the carcass ply in the axial direction. The ratio of the D ([D / C] × 100) is preferably 50% or more and 70% or less. This makes it possible to further reduce road noise.
The axial outer end PF of the sound control body 54 means the outermost position of the bottom surface 54A of the sound control body 54 in the axial direction. Further, the length D from the equatorial plane of the tire to the outer end PG in the axial direction of the sound control body 54 may be constant in the entire tire circumferential direction, or changes continuously or intermittently along the tire circumferential direction. You can do it.

On the other hand, if the above ratio ([D / C] × 100) is less than 50%, the sound control body 54 may be small and sufficient sound absorption performance may not be ensured.
Further, when the above ratio ([D / C] × 100) exceeds 70%, the axial outer end PF of the sound control body 54 is close to the end PD of the folded portion 38 of the carcass ply, and the end PD of the folded portion 38. Strain caused by the presence of
The above ratio ([D / C] × 100) is more preferably 55% or more and 65% or less.

As described above, according to the present invention, it is possible to secure the necessary pinch cut resistance and achieve the reduction of road noise while reducing the rolling resistance.
The tire according to the embodiment of the present invention is suitable as, for example, a tire used for an electric vehicle that requires quietness.
Although the particularly preferred embodiments of the present invention have been described in detail above, the present invention is not limited to these embodiments and can be modified into various embodiments.

Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to such examples.

[Example 1]
A pneumatic tire for a passenger car (tire size = 235 / 55R19 101) having the basic configuration shown in FIG. 1 and having the specifications shown in Table 1 below was obtained.

The tire 2 obtained in the first embodiment has the following configuration.
The carcass 12 is composed of one carcass ply 34 and has a UHTU structure.
The carcass ply 34 has a product of the tensile strength of the carcass cord and the ends ([tensile strength of the carcass cord] × [ends]) of 10000 N.
The axial width of the belt 14 is 76% of the cross-sectional width of the tire 2.
The distance from the end of the outer layer 30B of the belt 14 to the end of the inner layer 30A is 7 mm.
The distance from the end of the belt 14 to the end of the band 16 is 5 mm.
The height HI of the inner apex 30 is 10 mm.
-The height HO of the outer apex 32 is 55 mm.
The maximum thickness TM of the outer apex 32 is 3.5 mm.
-The tread thickness M on the equatorial plane is 8.5 mm.
The tread thickness N at the end of the belt 14 is 6.1 mm.

[Comparative Example 1]
The tire of Comparative Example 1 is a conventional tire, and the tire size = 235 / 55R19 101. The carcass of this tire consists of two carcass plies. Further, the structure of the carcass is an LTU (low turn up) structure, and the position of the end of the folded portion of the carcass ply is inward from the outer end PW in the axial direction of the tire in the radial direction.
Further, the tire of Comparative Example 1 does not have an outer apex, and the bead is composed of a core including a steel wire and an inner apex having a height of 40 mm.
The tire of Comparative Example 1 has the same configuration as the tire of Example 1 except that it differs in the above-mentioned points.

[Comparative Example 2]
The tire of Comparative Example 2 is also a conventional tire, and the tire size = 235 / 55R19 101. The tire has no outer apex and the bead consists of a core containing steel wire and an inner apex 40 mm high.
The tire of Comparative Example 2 has the same configuration as the tire of Example 1 except that the tires of Comparative Example 2 differ in the above-mentioned points.

[Example 2]
The tire of Example 2 was obtained in the same manner as in Example 1 except that the position of the end of the folded portion was changed to the position where the B / A became 30%.

[Example 3]
The tire of Example 3 was obtained in the same manner as in Example 1 except that the position of the end of the folded portion was changed to the position where the B / A became 70%.

The rolling resistance coefficient (RRC), pinch cut resistance, road noise, presence / absence of groove bottom cracks, and durability of the tires obtained in Examples 1 to 3 and Comparative Examples 1 to 2 were measured and evaluated. The results are shown in Table 1. The above tires may be evaluated comprehensively based on the sum of the indexes of each evaluation result. The larger the sum of the indexes of each evaluation result, the better the tire can be judged.

[Rolling resistance coefficient (RRC)]
Using a rolling resistance tester, the rolling resistance coefficient (RRC) was measured when the prototype tire traveled on the drum at a speed of 80 km / h under the following conditions. The results are shown in Table 1 below as indices (relative to Comparative Example 1, the same for other evaluations). The larger the value, the lower the rolling resistance.
Rim: 19 x 7.5J
Internal pressure: 210 kPa
Vertical load: 6.47kN
CA (camber angle) = 0 °

[Pinch cut resistance]
A prototype tire was incorporated into a rim (19 x 7.5J), and the tire was filled with air so that the internal pressure was 260 kPa. I set this tire on the plunger test machine. A load corresponding to 80% of the road index (LI) was applied to this tire to crush the tire. The cord contained in the carcass was cut, and the energy (load-integral value of the deflection diagram) when this cut occurred was measured. The results are shown exponentially in Table 1 below. The larger the value, the better the pinch cut resistance of the tire.

[Road noise]
The test vehicle was an SUV type electric vehicle mounted on all wheels under the condition that the test tire mounted on the rim 19 x 7.5J had an internal pressure of 260 kPa. The above test vehicle was used on a dry asphalt road surface test course with one driver on board under the condition of a running speed of 100 km / h, and the sound pressure level of 0 to 1 kHz at the driver's seat window side ear position was O.D. The A value was measured. In this evaluation, the peak value of 160 Hz was used as the evaluation value of each Example and Comparative Example. The results are shown exponentially in Table 1 below. The higher the number, the smaller the road noise and the quieter the tire.

[Groove bottom crack]
A prototype tire was incorporated into a rim (19 x 7.5J), and the tire was filled with air so that the internal pressure was 260 kPa. A cut groove having a length of 8 mm and a depth of 2 mm was formed in the groove bottom of the shoulder circumferential groove of the pneumatic tire along the longitudinal direction, and then left for 24 hours. After that, the degree of growth of the cut groove was measured. Specifically, the maximum value of the opening width of the cut groove was measured and used as an evaluation value. The results are shown exponentially in Table 1 below. The larger the value, the less likely the tire will crack at the bottom of the groove.

[durability]
A prototype tire was incorporated into a rim (19 x 7.5J), and the tire was filled with air so that the internal pressure was 300 kPa. This pneumatic tire was mounted on a bench tester having a drive drum. The evaluation was carried out by the step speed method in accordance with the load / velocity performance test specified by ECE30. In this evaluation, the running speed was gradually increased and the running time until the tire broke was measured. The results are shown in Table 1 below as indices. The larger the value, the less likely it is that damage such as BEL will occur, indicating that the durability is excellent.

As shown in Table 1, in the tires of the examples, it is possible to secure the required pinch cut resistance and achieve the reduction of road noise while reducing the rolling resistance. From this evaluation result, the superiority of the present invention is clear.

The techniques described above that can reduce rolling resistance, secure the required pinch cut resistance, and achieve reduction of road noise can be applied to various tires.

2, 52 ... Tires 4 ... Treads 6 ... Sidewalls 10 ... Beads 12 ... Carcass 14 ... Belts 16 ... Bands 18 ... Chafer 28 ... Core 30・ ・ ・ Inner apex 32 ・ ・ ・ Outer apex 34 ・ ・ ・ Carcass ply 36 ・ ・ ・ Ply body 38 ・ ・ ・ Folded part 54 ・ ・ ・ Sound control body 56 ・ ・ ・ Recessed groove

Claims (4)

A tread that touches the road surface and
A pair of sidewalls connected to the end of the tread and located radially inside the tread,
A pair of beads located radially inside the sidewall and having a ring-shaped core.
A carcass that bridges between one bead and the other inside the tread and sidewalls.
A belt located between the tread and the carcass in the radial direction,
It is provided with an inner liner located inside the carcass in the radial direction.
In the tread, a plurality of circumferential grooves are carved, and the circumferential groove located on the outermost side in the axial direction among the plurality of circumferential grooves is a shoulder circumferential groove.
The carcass is composed of one carcass ply.
The carcass ply has a ply body that spans between one core and the other core, and a pair of folded portions that are connected to the ply body and are folded back from the inside to the outside in the axial direction around each core. Have and
The end of the folded portion is located axially outward from the axially outer end of the shoulder circumferential groove and axially inward from the ground contact end of the tread.
The bead comprises an inner apex located radially outward of the core and an outer apex located radially outward of the inner apex, between the outer apex and the inner apex. A tire in which the folded portion is located. The ratio of the length B from the axially outer end of the shoulder circumferential groove to the end of the folded portion to the length A from the axially outer end of the shoulder circumferential groove to the ground contact end is 40% or more 60. The tire according to claim 1, which is less than or equal to%. The tire according to claim 1 or 2, wherein the height HO of the outer apex is 3.5 times or more and 10.0 times or less the height HI of the inner apex. It is further provided with a band-shaped sound control body made of sponge material, which is located inside the inner liner in the radial direction and extends in the tire circumferential direction.
In the axial direction, the ratio of the length D from the equatorial plane of the tire to the axially outer end of the sound control body to the length C from the equatorial plane of the tire to the end of the folded portion is 50% or more and 70% or less. The tire according to any one of claims 1 to 3.

Images