JP2022096926A - Tire, and manufacturing method of tire - Google Patents

Abstract

To provide a tire 2 which can improve riding comfort without damaging high speed durability.SOLUTION: A tire 2 comprises: a tread 4; a pair of side walls 6; a pair of clinches 8; a pair of beads 10; a carcass 12; a belt 14; and a band 16. The band 16 consists of a full band 46. When a reference line ML is specified in the tire 2 at the standard state in which the reference line passes through the intermediate point between the radially outer edge PG of the wheel rim R and the maximum width position PW of the tire 2 and extends in an axial direction, an axial direction distance DA from the intersection PMt between an outer face of the tire 2 at the low pressure state and the reference line ML to the intersection PMh between an outer face of the tire 2 at the standard state and the reference line ML is 0.5 mm or more.SELECTED DRAWING: Figure 1

Description

The present invention relates to a tire and a method for manufacturing the tire.

Tires in which a band is provided between a tread and a belt are known (for example, Patent Document 1 below). The band contains a spirally wound band cord. The band contributes to improving the high speed durability of the tire.

Japanese Unexamined Patent Publication No. 2014-172582

Tire belts with a cross-sectional width of 225 mm or more are wide. A large centrifugal force acts on a tire whose speed symbol is V or higher. For tires with a cross-sectional width of 225 mm or more and a speed symbol of V or more, the full band that covers the belt and the end of the full band are covered to sufficiently restrain the end of the belt and ensure the required high-speed durability. Adoption of a band composed of a pair of edge bands is considered.

However, the aforementioned band increases the rigidity of the tread surface. Tires that use this band may reduce ride quality. Excluding the edge band from the band, in other words, if the band is composed only of the full band, the ride quality is expected to be improved. However, in this case, the high speed durability of the tire is reduced.

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 achieving an improvement in ride quality without impairing high-speed durability.

A tire according to one aspect of the present invention includes a tread that touches the road surface, a pair of sidewalls that are connected to the end of the tread and are located inside the tread in the radial direction, and are located inside the sidewall in the radial direction. Between a pair of clinches, a pair of beads located inside the clinches in the axial direction, a carcass located inside the tread, the sidewalls, and the clinches, and between the tread and the carcass in the radial direction. A belt located in the tread and a band laminated on the belt inside the tread. In this tire, the tread, the sidewall, and the surface layer portion including the clinch constitute the outer surface of the tire. The band consists of a full band whose ends face each other across the equator. The full band includes a spirally wound band cord. The standard state of the tire is a state in which the tire is assembled on the rim, the internal pressure of the tire is adjusted to 230 kPa, and no load is applied to the tire. A contact patch obtained by applying a load of 70% of the normal load to the tire in the standard state as a vertical load and bringing the tire into contact with a flat road surface is a reference contact patch, and the axis of the reference contact patch. The position on the outer surface of the tire corresponding to the outer end of the direction is the reference contact patch. The state in which the tire is assembled on the rim, the internal pressure of the tire is adjusted to 30 kPa, and no load is applied to the tire is the low pressure state of the tire. When the straight line extending in the axial direction through the midpoint between the radial outer end of the rim and the maximum width position of the tire, which is specified in the tire in the standard state, is used as a reference line, the tire in the low pressure state. The axial distance from the intersection of the outer surface of the tire and the reference line to the intersection of the outer surface of the tire in the standard state and the reference line is 0.5 mm or more.

Preferably, in this tire, the surface layer portion has a raised portion between the radial outer end of the rim and the maximum width position of the tire. The thickness of the surface layer portion at the top of the raised portion is 5.0 mm or more and 6.0 mm or less.

Preferably, in this tire, the ratio of the thickness of the surface layer portion at the reference ground contact end to the thickness of the surface layer portion at the equator is 0.50 or more and 0.80 or less.

Preferably, in this tire, the ratio of the radial height of the bead to the cross-sectional height of the tire is 0.35 or more and 0.45 or less.

Preferably, in this tire, the radial distance from the bead baseline indicates 0.77 times the cross-sectional height of the tire, the position on the outer surface of the tire is the buttress reference position, and the said in the buttress reference position. The surface layer portion has the same thickness as the thickness of the surface layer portion at the maximum width position of the tire.

Preferably, in this tire, the outer surface of the tread is divided into a plurality of regions parallel in the axial direction. The plurality of regions include a crown region including the equator, a pair of shoulder regions including the reference ground contact end, and a pair of middle regions located between the crown region and the shoulder region. The contours of the crown region, the middle region, and the shoulder region are each represented by an outwardly convex arc. The ratio of the radius of the arc representing the contour of the middle region to the radius of the arc representing the contour of the crown region is 0.50 or more and 0.54 or less. The ratio of the radius of the arc representing the contour of the shoulder region to the radius of the arc representing the contour of the crown region is 0.20 or more and 0.24 or less.

Preferably, in this tire, the tread comprises a plurality of land portions partitioned by circumferential grooves. Of the plurality of land parts, the land part located on the outer side in the axial direction is the shoulder land part. A horizontal groove is carved in the land portion of the shoulder. The lateral groove has an end within the shoulder land portion and extends from the end toward the end of the tread. The edges on both sides of the lateral groove are rounded.

The tire manufacturing method according to one aspect of the present invention is the tire manufacturing method described above. The method for manufacturing this tire includes a step of preparing a raw tire which is the unvulcanized tire, and a step of pressurizing and heating the raw tire in a mold. The mold comprises a cavity surface that forms the outer surface of the tire on the raw tire. The cavity surface comprises a pair of flange molded surfaces that shape the surface of the tire that contacts the flange of the rim. The difference between the axial distance from one flange forming surface to the other flange forming surface and the rim width of the rim is 1.0 inch or more.

According to the present invention, it is possible to obtain a tire capable of achieving an improvement in ride quality without impairing high-speed durability.

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 cross-sectional view illustrating the displacement of the outer surface of the tire when the state of the tire is changed from the low pressure state to the standard state. FIG. 3 is a developed view showing a part of the tread surface of the tire shown in FIG. FIG. 4 is an enlarged cross-sectional view showing a lateral groove carved in the land portion of the shoulder. FIG. 5 is a cross-sectional view illustrating the contour of the tread surface. FIG. 6 is a cross-sectional view showing a part of a mold used in the method for manufacturing a tire according to an 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. The state in which the tire is assembled on the regular rim, the internal pressure of the tire is adjusted to 230 kPa, and no load is applied to the tire is called the standard state. The state in which the tire is assembled on the regular rim, the internal pressure of the tire is adjusted to 30 kPa, and no load is applied to the tire is called a low pressure 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" in the JATMA standard, the "Design Rim" in the TRA standard, and the "Measuring Rim" in the ETRTO standard are regular rims.

Regular 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 speed symbol is a symbol specified in the JATTA standard, for example, and represents the maximum speed at which a tire can travel under a state in which the mass indicated by its road index is loaded under specified conditions. A tire having a speed symbol of V or more means a tire having a speed symbol of V, W, or Y.

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

In the present disclosure, among the elements constituting the tire, the loss tangent (also referred to as tan δ) of the element made of crosslinked rubber at a temperature of 30 ° C. or 0 ° C. conforms to the provisions of JIS K6394 and is a viscoelastic spectrometer. It is measured under the following conditions using (“VES” manufactured by Iwamoto Seisakusho Co., Ltd.).
Initial distortion = 10%
Dynamic distortion = 2%
Frequency = 10Hz
Deformation mode = tension In this measurement, the test piece is sampled from the tire. When the test piece cannot be sampled from the tire, a sheet-shaped crosslinked rubber (hereinafter referred to as a rubber sheet) obtained by pressurizing and heating the rubber composition used for forming the element to be measured at a temperature of 170 ° C. for 12 minutes is obtained. The test piece is sampled from).

In the present disclosure, the hardness of an element made of crosslinked rubber among the elements constituting the tire is measured by using a type A durometer under a temperature condition of 23 ° C. according to the provisions of JIS K6253. When the hardness of a tire cannot be measured, a test piece made of crosslinked rubber obtained by pressurizing and heating the rubber composition used for forming the element to be measured at a temperature of 170 ° C. for 12 minutes is used.

FIG. 1 shows a part of a tire 2 according to an embodiment of the present invention. The tire 2 is a passenger car tire. FIG. 1 shows a part of a cross section of a tire 2 (hereinafter, also referred to as a meridian cross section) along a plane including a rotation axis of the tire 2. In FIG. 1, 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 FIG. 1 is the circumferential direction of the tire 2. In FIG. 1, the alternate long and short dash line CL is the equatorial plane of the tire 2.

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

The rim R includes a seat T and a flange G. A radial inner portion of the tire 2 (hereinafter referred to as a bead portion B) is fitted to the rim R. In the tire 2 assembled on the rim R, the inner peripheral surface of the bead portion B is placed on the seat T, and the outer surface of the bead portion B is pressed against the flange G.

In FIG. 1, the distance indicated by the reference numeral RW is the rim width of the rim R (see JATTA and the like). The rim width RW is an axial distance from one flange G to the other flange G. In FIG. 1, the solid line BBL extending in the axial direction is a bead baseline. The bead baseline is a line that defines the rim diameter of the rim R (see JATTA and the like).

In FIG. 1, the position indicated by 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 standard 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.

In FIG. 1, the distance indicated by the reference numeral Wt is the maximum width of the tire 2, that is, the cross-sectional width (see JATTA and the like). The cross-sectional width Wt is an axial distance from one outer end PW to the other outer end PW. The cross-sectional width Wt is measured in the tire 2 in the standard state. The outer end PW is a position where the tire 2 shows the maximum width (hereinafter, the maximum width position).

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. A groove 24 is carved in the tread 4 of the tire 2.

In FIG. 1, the position indicated by the reference numeral PC is the equator of the tire 2. The equatorial PC is the intersection of the tread surface 22 and the equatorial surface. If there is a groove 24 on the equatorial plane, the equatorial PC is identified based on the virtual tread plane obtained assuming that there is no groove 24.

In FIG. 1, the distance indicated by the reference numeral HS is the cross-sectional height of the tire 2 (see JATTA and the like). The cross-sectional height HS is the radial distance from the bead baseline to the equatorial PC. The cross-sectional height HS is measured on the tire 2 in the standard state.

The tread 4 has a base layer 26 and a cap layer 28. The base layer 26 covers the belt 14 and the band 16. The base layer 26 is made of a low heat-generating crosslinked rubber. In this tire 2, the loss tangent LTb30 of the base layer 26 at 30 ° C. is 0.10 or less. Since the base layer 26 does not easily generate heat, damage due to the movement of the end of the belt 14 is unlikely to occur. The base layer 26 contributes to the improvement of high-speed durability.

The cap layer 28 is located outside the base layer 26 in the radial direction. The cap layer 28 covers the entire base layer 26. The outer surface of the cap layer 28 is the tread surface 22 described above. The cap layer 28 is made of crosslinked rubber in consideration of wear resistance and grip performance.

In this tire 2, the ratio (LTc30 / LTb30) of the loss tangent LTc30 of the cap layer 28 to the loss tangent LTb30 of the base layer 26 at 30 ° C. is 4 from the viewpoint of achieving a good balance between high-speed durability and steering stability. .2 or more is preferable.

From the viewpoint of ensuring grip performance on a wet road surface, the loss tangent LTb0 of the cap layer 28 at 0 ° C. is preferably 0.68 or more.

In this tire 2, the hardness of the cap layer 28 is preferably 65 or more, more preferably 66 or more, from the viewpoint of ensuring rigidity. From the viewpoint of obtaining a good ride quality, the hardness of the cap layer 28 is preferably 71 or less, more preferably 70 or less.

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 includes a core 30 and an apex 32. Although not shown, the core 30 includes a steel wire.

The apex 32 is located outside the core 30 in the radial direction. Apex 32 is made of crosslinked rubber having high rigidity. Apex 32 is tapered outward.

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 includes at least one carcass ply 34. The carcass 12 of the tire 2 is composed of two carcass plies 34. The carcass ply 34 located radially inside the tread 4 is the first carcass ply 36, and the carcass ply 34 located outside the first carcass ply 36 is the second carcass ply 38.

The first carcass ply 36 includes a first ply main body 36a and a pair of first folded portions 36b. The first ply body 36a bridges between one core 30 and the other core 30. Each first folded portion 36b is connected to the first ply main body 36a and is folded from the inside to the outside in the axial direction around each core 30. The end of the first folded portion 36b is located outside the maximum width position PW in the radial direction. The end of the first folded portion 36b is covered with the sidewall 6.

The second carcass ply 38 includes a second ply main body 38a and a pair of second folded portions 38b. The second ply body 38a bridges between one core 30 and the other core 30. Each second folded portion 38b is connected to the second ply main body 38a and is folded from the inside to the outside in the axial direction around each core 30. The end of the second folded portion 38b is located between the outer end of the apex 32 and the core 30 in the radial direction. In the axial direction, the end of the second folded portion 38b is located between the apex 32 and the first folded portion 36b.

Although not shown, the carcass ply 34 contains a large number of carcass cords in parallel. These carcass cords are covered with topping rubber. Each carcass code intersects the equatorial plane. The carcass cord is a cord made of organic fibers. Examples of the organic fiber include nylon fiber, rayon fiber, polyester fiber and aramid fiber.

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 belt 14 is composed of at least two layers 40 laminated in the radial direction. The belt 14 of the tire 2 is composed of two layers 40 laminated in the radial direction. Of the two layers 40, the inner layer 40 is the inner layer 42, and the outer layer 40 is the outer layer 44. As shown in FIG. 1, the inner layer 42 is wider than the outer layer 44. The distance from the end of the outer layer 44 to the end of the inner layer 42 is 3 mm or more and 10 mm or less.

Although not shown, the inner layer 42 and the outer layer 44 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.

In FIG. 1, the distance indicated by the reference numeral Bt is the axial width of the belt 14. The axial width Bt is the axial distance from one end of the belt 14 to the other end. In the tire 2, the axial width Bt of the belt 14 is represented by the axial width of the widest layer 40, that is, the inner layer 42 among the plurality of layers 40 constituting the belt 14. In the tire 2, the axial width Bt of the belt 14 is 75% or more and 85% or less of the cross-sectional width Wt of the tire 2. The axial width Bt of the belt 14 is the distance between the left and right beads 10 in the cross section obtained by cutting the tire 2 along a plane including the rotation axis of the tire 2, and the bead in the standard state tire 2. Measured in line with the distance between 10. The axial width Bt of the belt 14 may be measured in a cross-sectional image of the tire 2 in a standard state taken by a computer tomography method using X-rays (hereinafter referred to as an X-ray CT method).

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 inside the tread 4. The band 16 is wider than 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 46 whose both ends face each other across the equator. In this tire 2, the full band 46 includes a spirally wound band cord. The full band 46 covers the entire belt 14. The full band 46 restrains the entire belt 14.

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 made of crosslinked rubber and is integrated with the clinch 8. The material of the chafer 18 is the same as that of the clinch 8.

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 outer surface of the tire 2 includes the outer surface of the tread 4 (ie, the tread surface 22), the outer surface of the sidewall 6, and the outer surface of the clinch 8. In the tire 2, the tread 4, the sidewall 6, and the clinch 8 are included, and the elements constituting the outer surface of the tire 2 are referred to as the surface layer portion 48. In other words, the surface layer portion 48 including the tread 4, the sidewall 6, and the clinch 8 constitutes the outer surface of the tire 2. The surface layer portion 48 of the tire 2 includes a tread 4, a sidewall 6, and a clinch 8.

In FIG. 1, the position indicated by the reference numeral PH is a position on the outer surface (specifically, the tread surface 22) of the tire 2. The position PH corresponds to the outer end of the tire 2 in the axial direction of the contact patch with the road surface.

The ground plane for specifying the position PH can be obtained by using, for example, a ground plane shape measuring device (not shown). In this device, the ground contact surface is a flat road surface by applying a load of 70% of the normal load to the tire 2 as a vertical load in a state where the camber angle of the tire 2 in the standard state is 0 °. It is obtained by contacting the tire 2. In the tire 2, the ground contact surface thus obtained is the reference ground contact surface, and the position on the outer surface of the tire 2 corresponding to the axially outer end of the reference ground contact surface is the above-mentioned position PH. In this tire 2, this position PH is the reference ground contact end.

FIG. 2 shows the result of measuring the contour of the outer surface of the tire 2 with the displacement sensor. The contour of the outer surface shown in FIG. 2 is the contour of the outer surface in the meridian cross section of the tire 2. In FIG. 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 FIG. 2 is the circumferential direction of the tire 2.

FIG. 2 mainly shows the contour of the radial inner portion from the vicinity of the maximum width position PW. The solid line represents the contour of the outer surface of the tire 2 in the standard state. The two-dot chain line represents the contour of the outer surface of the tire 2 in a low pressure state. In FIG. 2, the contour of the outer surface of the tire 2 in the standard state and the contour of the outer surface of the tire 2 in the low pressure state are represented by matching the positions of the rims R on which the tire 2 is assembled.

In FIG. 2, the position indicated by the reference numeral PG is the radial outer end of the rim R. The solid line GL is a straight line extending in the axial direction through the radial outer end PG. The solid line WL is a straight line extending in the axial direction through the maximum width position PW. The solid line ML is a straight line extending in the axial direction through the midpoint between the radial outer end PG of the rim R and the maximum width position PW. In this tire 2, this straight line ML is a reference line. The reference numeral PMh is an intersection of the outer surface of the tire 2 in the standard state and the reference line ML. The symbol PMt is an intersection of the outer surface of the tire 2 in the low pressure state and the reference line ML. The double-headed arrow DA is the axial distance from the intersection PMt to the intersection PMh. This axial distance DA is the displacement distance of the outer surface of the tire 2 measured along the reference line ML when the state of the tire 2 is changed from the low pressure state to the standard state.

The distance DA in the conventional tire is about 0.4 mm. On the other hand, the distance DA of the tire 2 is 0.5 mm or more. In this tire 2, the carcass 12 located radially inside the maximum width position PW is more likely to move outward in the axial direction than the conventional tire.

When the tire inflates due to the filling of air, the end of the belt tends to rise. In this tire 2, since the carcass 12 located radially inside the maximum width position PW tends to move outward in the axial direction, the rising of the end of the belt 14 due to inflation is suppressed as compared with the conventional tire. Since the movement of the tread 4 is suppressed in the running state of the tire 2, the heat generation of the tread 4 is suppressed. Suppression of heat generation contributes to improvement of high-speed durability of the tire 2. With this tire 2, even if the band 16 is composed of only the full band 46, good high-speed durability can be obtained.

The band 16 of the tire 2 does not need a pair of edge bands that restrain the ends of the full band 46, unlike the bands of conventional tires, in order to ensure high-speed durability. Since the edge band can be removed from the band 16 of the tire 2, the ride quality can be improved. The tire 2 can achieve an improvement in ride quality without impairing high-speed durability.

As shown in FIG. 1, in this tire 2, the thickness of the surface layer portion 48 gradually increases and then gradually decreases from the maximum width position PW toward the radial inward direction. The surface layer portion 48 has a raised portion 50 between the radial outer end PG of the rim R and the maximum width position PW of the tire 2. The position indicated by the reference numeral PF is the apex of the raised portion 50. In the tire 2, the surface layer portion 48 exhibits the maximum thickness F at the top PF of the raised portion 50 between the radial outer end PG of the rim R and the maximum width position PW of the tire 2. This thickness F is measured along the normal of the outer surface of the carcass 12 through the apex PF.

In this tire 2, the surface layer portion 48 has a raised portion 50 between the radial outer end PG of the rim R and the maximum width position PW of the tire 2, and the surface layer portion 48 at the top PF of the raised portion 50. The thickness F is preferably 5.0 mm or more, and preferably 6.0 mm or less.

By setting the thickness F of the surface layer portion 48 at the top PF of the raised portion 50 to 5.0 mm or more, rigidity is ensured in the vicinity of the bead portion B of the tire 2. With this tire 2, good steering stability can be obtained. From this viewpoint, the thickness F of the surface layer portion 48 is more preferably 5.2 mm or more, further preferably 5.4 mm or more.

By setting the thickness F of the surface layer portion 48 at the top PF of the raised portion 50 to 6.0 mm or less, the above-mentioned displacement of the carcass 12 in the axial direction is promoted. In this tire 2, as described above, even if the band 16 is composed of only the full band 46, good high-speed durability can be obtained. Since the band 16 can be composed of only the full band 46, the ride quality is improved as compared with the conventional tire in which the band is composed of the full band and the pair of edge bands. From this viewpoint, the thickness F of the surface layer portion 48 is more preferably 5.8 mm or less, and further preferably 5.6 mm or less.

In FIG. 1, the distance indicated by reference numeral A is the thickness of the surface layer portion 48 in the equatorial PC. This thickness A is the thickness of the tread 4 in the equatorial PC. Thickness A is measured along the equatorial plane. The distance indicated by the reference numeral H is the thickness of the surface layer portion 48 at the reference grounding end PH. This thickness H is the thickness of the tread 4 at the reference grounding end PH. The thickness H is measured along the normal of the outer surface of the band 16 passing through the reference grounding edge PH.

In this tire 2, the ratio (H / A) of the thickness H of the surface layer portion 48 at the reference ground contact end PH to the thickness A of the surface layer portion 48 at the equatorial PC is preferably 0.50 or more, preferably 0.80 or less. ..

By setting the ratio (H / A) to 0.50 or more, the thickness of the surface layer portion 48 at the end portion of the belt 14, in other words, the thickness of the tread 4 is secured. The impact when the tread 4 touches the road surface is effectively mitigated in the tread 4. With this tire 2, a good ride quality is maintained. From this point of view, this ratio (H / A) is preferably 0.55 or more, more preferably 0.60 or more.

By setting the ratio (H / A) to 0.80 or less, the shape of the ground plane can be rounded. Since the increase in contact pressure at the end portion of the tread 4 is suppressed, the high-speed durability of the tire 2 is improved. From this point of view, this ratio (H / A) is more preferably 0.77 or less, and even more preferably 0.75 or less.

From the viewpoint of achieving a good balance between high-speed durability and ride quality, the thickness A of the tread 4 in the equatorial PC is preferably 10.0 mm or more, and preferably 10.5 mm or less.

In FIG. 1, the distance indicated by the reference numeral HB is the radial height of the bead 10. The radial height HB of the bead 10 is the radial distance from the bead baseline to the outer edge of the apex 32.

In the tire 2, the ratio (HB / HS) of the radial height HB of the bead 10 to the cross-sectional height HS of the tire 2 is preferably 0.35 or more, and preferably 0.45 or less.

By setting the ratio (HB / HS) to 0.35 or more, the rigidity of the bead portion B is ensured. Good steering stability is maintained with this tire 2. From this point of view, this ratio (HB / HS) is more preferably 0.36 or more, and even more preferably 0.37 or more.

By setting the ratio (HB / HS) to 0.45 or less, it is possible to prevent the rigidity of the bead portion B from being increased more than necessary. With this tire 2, the ride quality can be further improved. From this point of view, this ratio (HB / HS) is more preferably 0.42 or less, and even more preferably 0.40 or less.

In FIG. 1, reference numeral PD is a specific position on the outer surface of the tire 2. The distance indicated by the double-headed arrow HD is the radial distance from the bead baseline to the specific position PD. In this tire 2, the radial distance HD is set to 0.77 times the cross-sectional height HS. The specific position PD is a position on the outer surface of the tire 2 in which the radial distance HD from the bead baseline is 0.77 times the cross-sectional height HS. This specific position PD is a buttress reference position. The buttress reference position PD is specified by measuring the cross-sectional height HS and the radial distance HD in the mold described later. The buttress reference position PD may be specified by measuring the cross-sectional height HS and the radial distance HD in the tire 2 in the low pressure state.

In FIG. 1, the distance indicated by reference numeral D is the thickness of the surface layer portion 48 at the buttress reference position PD. The thickness D is the thickness of the boundary portion between the tread 4 and the sidewall 6 at the buttress reference position PD. The thickness D is measured along the normal of the outer surface of the carcass 12 through the buttress reference position PD. The distance indicated by reference numeral E is the thickness of the surface layer portion 48 at the maximum width position PW. The thickness E is the thickness of the sidewall 6 at the maximum width position PW. The thickness E is measured along a straight line extending in the axial direction through the maximum width position PW.

In the tire 2, the surface layer portion 48 at the buttress reference position PD preferably has the same thickness D as the thickness E of the surface layer portion 48 at the maximum width position PW of the tire 2. As a result, high-speed durability and ride quality are well-balanced while ensuring the required steering stability. In this case, the thickness E of the surface layer portion 48 at the maximum width position PW is preferably 5.0 mm or less from the viewpoint of further improving the riding comfort. From the viewpoint of maintaining good steering stability, the thickness E is preferably 2.5 mm or more.

In the present disclosure, the surface layer portion 48 at the buttress reference position PD has the same thickness D as the thickness E of the surface layer portion 48 at the maximum width position PW of the tire 2, and the thickness D of the surface layer portion 48 at the buttress reference position PD. This means that the ratio (D / E) of the surface layer portion 48 to the thickness E at the maximum width position PW of the tire 2 is 0.9 or more and 1.1 or less.

FIG. 3 shows a developed view of the tread surface 22. FIG. 3 shows a part of the tread surface 22. In FIG. 3, the left-right direction is the axial direction of the tire 2, and the vertical direction is the circumferential direction of the tire 2. The direction perpendicular to the paper surface of FIG. 3 is the radial direction of the tire 2.

In FIG. 3, the distance indicated by the double-headed arrow Wh is the ground contact width of the reference ground plane. This grounding width Wh is the axial distance from one reference grounding end PH to the other reference grounding end PH. The grounding width Wh is measured at the reference grounding surface for specifying the reference grounding end PH.

As described above, the tread 4 of the tire 2 is carved with a groove 24. This constitutes a tread pattern. Of the grooves 24 constituting this tread pattern, the grooves 24 having a groove width of 1.5 mm or less are referred to as sipes.

The tread 4 of the tire 2 is carved with a circumferential groove 52 extending in the circumferential direction as a groove 24 constituting the tread pattern. As a result, the tread 4 is configured with a plurality of land portions 54 partitioned by the circumferential groove 52. In the tire 2, four circumferential grooves 52 are carved in the tread 4, and five land portions 54 are formed in the tread 4.

In the tire 2, of the four circumferential grooves 52, the circumferential groove 52 located on the outer side in the axial direction is the shoulder circumferential groove 52s. The circumferential groove 52 located inside the shoulder circumferential groove 52s is the middle circumferential groove 52m.

In this tire 2, the ratio of the groove depth of the circumferential groove 52 to the thickness A of the surface layer portion 48 on the equatorial PC is 0.7 or more and 0.8 or less. The circumferential groove 52 has a groove width of at least 3.0 mm or more. The ratio of the total groove width of the four circumferential grooves 52 carved in the tread 4 to the ground contact width Wh is 20% or more and 25% or less. When the groove width of the circumferential groove 52 changes in the circumferential direction, the groove width of the circumferential groove 52 is represented by the average value of the maximum groove width and the minimum groove width.

In the tire 2, of the five land portions 54, the land portion 54 located on the outer side in the axial direction is the shoulder land portion 54s. The land portion 54 located inside the shoulder land portion 54s is the middle land portion 54m. The land portion 54 located inside the middle land portion 54m is the center land portion 54c. The center land portion 54c includes an equatorial PC. The shoulder land portion 54s includes the reference ground contact end PH.

A plurality of lateral grooves 56 are carved in the shoulder land portion 54s as grooves 24 constituting the tread pattern. These lateral grooves 56 extend in the substantially axial direction and are arranged at intervals in the circumferential direction. The lateral groove 56 has a groove width of at least 2.0 mm or more.

The lateral groove 56 has an end within the shoulder land portion 54s. The lateral groove 56 extends from this end toward the reference grounding end PH. The reference ground plane is formed in the tread plane 22. The lateral groove 56 further extends toward the boundary between the tread 4 and the sidewall 6 located outside the reference grounding end PH in the axial direction.

The lateral groove 56 includes an inclined portion 56a including an end and inclined with respect to the axial direction, and a straight portion 56b connected to the inclined portion 56a and extending in the axial direction. In this tire 2, the boundary between the inclined portion 56a and the straight portion 56b is located near the reference ground contact end PE.

In addition to the lateral groove 56, a plurality of dead-end sipes 58 (hereinafter, first dead-end sipes 58a) are engraved on the shoulder land portion 54s as grooves 24 constituting the tread pattern. The first dead end sipe 58a and the lateral groove 56 are alternately arranged in the circumferential direction. A part of the first dead end sipe 58a and a part of the lateral groove 56 overlap in the circumferential direction.

The first dead end sipe 58a is a sipe having a groove width of 1.5 mm or less. The plurality of first dead end sipes 58a are arranged at intervals in the circumferential direction. Each first dead end sipe 58a has an end within the shoulder land portion 54s. The first dead end sipe 58a extends from this end toward the shoulder circumferential groove 52s. The first dead end sipe 58a is inclined with respect to the axial direction. The direction of this inclination is the same as the direction of the inclination of the inclined portion 56a forming a part of the lateral groove 56.

A plurality of dead-end sipes 58 and a circumferential sipes 60 are carved in the middle land portion 54 m as grooves 24 constituting the tread pattern. At this middle land portion 54 m, the dead end sipe 58 and the circumferential sipe 60 do not intersect.

The circumferential sipe 60 is located near the center in the width direction of the middle land portion 54 m. The circumferential sipe 60 extends continuously in the circumferential direction. The circumferential sipe 60 is a sipe having a groove width of 1.5 mm or less. The plurality of dead-end sipes 58 includes a plurality of second dead-end sipes 58b carved in the outer portion of the middle land portion 54 m and a plurality of third dead-end sipes 58c carved in the inner portion of the middle land portion 54 m. The second dead-end sipe 58b and the third dead-end sipe 58c are sipes having a groove width of 1.5 mm or less. The circumferential sipe 60 is located between the second dead end sipe 58b and the third dead end sipe 58c.

The plurality of second dead-end sipes 58b are arranged at intervals in the circumferential direction. Each second dead end sipe 58b has an end within 54 m of middle land. The second dead end sipe 58b extends from this end toward the shoulder circumferential groove 52s. The second dead end sipe 58b is inclined with respect to the axial direction. The direction of inclination of the second dead end sipe 58b is the same as the direction of inclination of the first dead end sipe 58a carved in the shoulder land portion 54s. The second dead-end sipe 58b and the first dead-end sipe 58a are alternately arranged in the circumferential direction.

The plurality of third dead-end sipes 58c are arranged at intervals in the circumferential direction. Each third dead end sipe 58c has an end within 54 m of middle land. The third dead end sipe 58c extends from this end toward the middle circumferential groove 52m. The third dead end sipe 58c is tilted with respect to the axial direction. The direction of inclination of the third dead end sipe 58c is opposite to the direction of inclination of the second dead end sipe 58b.

A plurality of dead-end sipes 58 (hereinafter, fourth dead-end sipes 58d) are carved in the center land portion 54c as grooves 24 constituting the tread pattern. The fourth dead-end sipe 58d is a sipe having a groove width of 1.5 mm or less.

The plurality of fourth dead-end sipes 58d are arranged at intervals in the circumferential direction. Each fourth dead end sipe 58d has an end within the center land portion 54c. This end is located outside the equator in the axial direction. The fourth dead end sipe 58d extends from this end toward the middle circumferential groove 52m. The fourth dead end sipe 58d is tilted with respect to the axial direction. The direction of inclination of the fourth dead end sipe 58d is the same as the direction of inclination of the third dead end sipe 58c carved in the middle land area 54 m.

In this tire 2, a fourth dead end sipe 58d is carved on both side edges of the center land portion 54c. As shown in FIG. 3, the direction of inclination of the fourth dead end sipe 58d provided on one edge portion is the same as the direction of inclination of the fourth dead end sipe 58d provided on the other edge portion.

FIG. 4 shows a cross section of the tire 2 along a straight line representing the reference ground contact end PH of FIG. FIG. 4 shows a cross section of the lateral groove 56 provided in the shoulder land portion 54s.

The lateral groove 56 of the shoulder land portion 54s includes a groove bottom 62 and a pair of groove walls 64 extending from the groove bottom 62 toward the tread surface 22. The boundary between the groove wall 64 and the tread surface 22 is the edge 66 of the lateral groove 56. As shown in FIG. 5, the edges 66 on both sides of the lateral groove 56 are rounded.

As shown in FIG. 1, the lateral groove 56 extends in the substantially axial direction. The edge 66 of the lateral groove 56 also extends in the substantially axial direction. As described above, the edges 66 on both sides of the lateral groove 56, in other words, the edge 66 located on the first-come-first-served side and the edge 66 located on the second-arrival side in the running state of the tire 2 are rounded. The rounded edge 66 contributes to mitigating the impact when the tire 2 comes into contact with the road surface. In the tire 2, the deterioration of the ride quality due to the lateral groove 56 can be suppressed. The tire 2 can further improve the ride quality. From this point of view, in this tire 2, it is preferable that the edges 66 on both sides of the lateral groove 56 provided in the shoulder land portion 54s are rounded.

In FIG. 4, the arrow Ra is the rounding radius of one edge 66. The arrow Rb is the rounding radius of the other edge 66.

In this tire 2, from the viewpoint that the rounded edge 66 can effectively contribute to the reduction of noise, the rounding radius Ra of one edge 66 is preferably 0.5 mm or more, and preferably 1.5 mm or less. From the same viewpoint, the radius Rb of the rounding of the other edge 66 is preferably 0.5 mm or more, and preferably 1.5 mm or less.

As described above, in this tire 2, the circumferential sipe 60 is carved in the middle land portion 54 m. The circumferential sipe 60 slightly reduces the rigidity of the middle land portion 54 m, and adjusts the rigidity of the entire tread surface 22 in a well-balanced manner. In the tire 2, the cap layer 28 having a hardness of 65 or more and 71 or less improves the steering stability, and the circumferential sipe 60 improves the riding comfort.

In this tire 2, the depth of the circumferential sipe 60 is preferably 3.5 mm or more, and preferably 4.0 mm or less, from the viewpoint of maintaining a good balance between steering stability and ride quality. The width of the circumferential sipe 60 is preferably 0.5 mm or more, and preferably 1.0 mm or less.

FIG. 5 shows a part of the meridian cross section of the tire 2. FIG. 5 shows the tread surface 22. The tread surface 22 of the tire 2 is divided into a plurality of regions parallel in the axial direction in the meridian cross section. The plurality of regions include a crown region Cr, a pair of shoulder regions Sh, and a pair of middle regions Mi.

The crown region Cr is centrally located in the axial direction. The crown region Cr includes the equatorial PC. In the meridian cross section of the tire 2, the contour of the crown region Cr is represented by an outwardly convex arc. In the tire 2, the arc representing the contour of the crown region Cr is a crown arc. Although not shown, the center of the crown arc is located on the equatorial plane. In FIG. 6, the one-sided arrow indicated by the symbol Rc is the radius of the crown arc.

The shoulder region Sh is located outward in the axial direction. The shoulder region Sh includes the reference grounding end PH. In the meridian cross section of the tire 2, the contour of the shoulder region Sh is represented by an outwardly convex arc. In this tire 2, the arc representing the contour of the shoulder region Sh is a shoulder arc. In FIG. 6, the one-sided arrow indicated by the reference numeral Rs is the radius of the shoulder arc.

The middle region Mi is located between the crown region Cr and the shoulder region Sh in the axial direction. In the meridian cross section of the tire 2, the contour of the middle region Mi is represented by an outwardly convex arc. In this tire 2, the arc representing the contour of the middle region Mi is a middle arc. In FIG. 6, the one-sided arrow indicated by the symbol Rm is the radius of the middle arc.

In the present disclosure, the radius Rc of the crown arc, the radius Rm of the middle arc, and the radius Rs of the shoulder arc are specified in the mold described later. The radius Rc of the crown arc, the radius Rm of the middle arc, and the radius Rs of the shoulder arc may be specified in the tire 2 in the low pressure state. In this case, the radius Rc of the crown arc, the radius Rm of the middle arc, and the radius Rs of the shoulder arc are specified based on, for example, the contour of the tread surface 22 measured using a displacement sensor.

In FIG. 5, the position on the tread surface 22 represented by the reference numeral CM is the boundary between the crown region Cr and the middle region Mi. This boundary CM is the end of the crown region Cr and is also the inner end of the middle region Mi. The crown arc and the middle arc touch each other at this boundary CM.

In this tire 2, the boundary CM is located on the outer surface of the middle land portion 54 m. Specifically, the boundary CM is located between a position 5 mm away from the inner edge of the middle land portion 54 m and a position 10 mm away from this inner edge.

In FIG. 5, the position on the tread surface 22 represented by the reference numeral MS is the boundary between the middle region Mi and the shoulder region Sh. This boundary MS is the outer end of the middle region Mi and the inner end of the shoulder region Sh. The middle arc and the shoulder arc touch at this boundary MS.

In this tire 2, the boundary MS is located on the outer surface of the shoulder land portion 54s. Specifically, the boundary MS is located between a position 5 mm away from the edge of the shoulder land portion 54s and a position 10 mm away from this edge.

In FIG. 5, the position on the tread surface 22 represented by the reference numeral SE is the outer end of the shoulder region Sh. The outer end SE of the shoulder region Sh is located outside the reference grounding end PH in the axial direction.

In the tire 2, the contour of the tread surface 22 is represented by a plurality of arcs having different radii. The contour of the tread surface 22 is configured so that the radius Rc of the crown arc, the radius Rm of the middle arc, and the radius Rs of the shoulder arc are different. The tread surface 22 has a multi-radius contour shape. From the viewpoint that the crown arc, the middle arc, and the shoulder arc are smoothly connected, the radius Rc, the radius Rm, and the radius Rs preferably satisfy the following equation (1).
Rc>Rm> Rs (1)

Specifically, in this tire 2, the ratio (Rm / Rc) of the radius Rm of the middle arc to the radius Rc of the crown arc is preferably 0.50 or more, and preferably 0.54 or less.

By setting the ratio (Rm / Rc) to 0.50 or more, it is possible to prevent the contour of the tread surface 22 of the tire 2 assembled on the rim R from being excessively rounded. The contour of the tread surface 22 contributes to the suppression of the rising of the belt 14 end due to inflating. In this tire 2, not only the carcass 12 located radially inside the maximum width position PW tends to move outward in the axial direction, but also the contour of the tread surface 22 of the tire 2 assembled on the rim R is appropriately rounded. Since it is controlled, the rise of the belt 14 end due to inflatation is effectively suppressed. Since the movement of the tread 4 is suppressed in the running state of the tire 2, the heat generation of the tread 4 is sufficiently suppressed. With this tire 2, even if the band 16 is composed of only the full band 46, good high-speed durability can be obtained. From this point of view, this ratio (Rm / Rc) is more preferably 0.51 or more.

By setting the ratio (Rm / Rc) to 0.54 or less, an appropriately rounded ground plane shape can be obtained. The impact when the tread 4 touches the road surface is effectively mitigated in the tread 4. With this tire 2, a good ride quality is maintained. From this point of view, this ratio (Rm / Rc) is more preferably 0.53 or less.

In this tire 2, the ratio (Rs / Rc) of the radius Rs of the shoulder arc to the radius Rc of the crown arc is preferably 0.20 or more, and preferably 0.24 or less.

By setting the ratio (Rs / Rc) to 0.20 or more, it is possible to prevent the contour of the tread surface 22 of the tire 2 assembled on the rim R from being excessively rounded. The contour of the tread surface 22 contributes to the suppression of the rising of the belt 14 end due to inflating. In this tire 2, not only the carcass 12 located radially inside the maximum width position PW tends to move outward in the axial direction, but also the contour of the tread surface 22 of the tire 2 assembled on the rim R is appropriately rounded. Since it is controlled, the rise of the belt 14 end due to inflatation is effectively suppressed. Since the movement of the tread 4 is suppressed in the running state of the tire 2, the heat generation of the tread 4 is sufficiently suppressed. With this tire 2, even if the band 16 is composed of only the full band 46, good high-speed durability can be obtained. From this point of view, this ratio (Rs / Rc) is more preferably 0.21 or more.

By setting the ratio (Rs / Rc) to 0.24 or less, an appropriately rounded ground plane shape can be obtained. The impact when the tread 4 touches the road surface is effectively mitigated in the tread 4. With this tire 2, a good ride quality is maintained. From this point of view, this ratio (Rs / Rc) is more preferably 0.23 or less.

This tire 2 has a good balance between high-speed durability and ride quality.
It is more preferable that the ratio (Rm / Rc) is 0.50 or more and 0.54 or less, and the ratio (Rs / Rc) is 0.20 or more and 0.24 or less. In this case, the radius Rc of the crown arc is preferably 1100 mm or less, more preferably 1000 mm or less, still more preferably 900 mm or less, from the viewpoint that the contour of the tread surface 22 can effectively contribute to the improvement of high-speed durability. From the viewpoint that the contour of the tread surface 22 can effectively contribute to the improvement of the riding comfort, the radius Rc of the crown arc is preferably 600 mm or more, more preferably 700 mm or more, still more preferably 800 mm or more.

The tire 2 described above is manufactured as follows. The method for manufacturing the tire 2 includes a preparation step and a vulcanization step.

In the preparation step, a raw tire is prepared by combining elements constituting the tire 2, such as a tread 4, a sidewall 6, and a bead 10, in a molding machine (not shown). The raw tire is put into a mold described later.

In the present disclosure, the raw tire is a tire 2 in an unvulcanized state. In other words, the tire 2 is a vulcanized molded product of a raw tire.

In the vulcanization step, the raw tire is pressurized and heated in the mold for a predetermined time. As a result, the tire 2 is obtained. Although not described in detail, in the production of the tire 2, there are no particular restrictions on the vulcanization conditions such as temperature, pressure, and time, and general vulcanization conditions are adopted.

FIG. 6 shows an example of a mold 68 used for manufacturing a tire 2. FIG. 6 shows a portion of a cross section of the mold 68 along a plane including a central axis (not shown) corresponding to the axis of rotation of the tire 2. In FIG. 6, the vertical direction corresponds to the radial direction of the tire 2. The left-right direction corresponds to the axial direction of the tire 2. The direction perpendicular to the paper surface of FIG. 6 corresponds to the circumferential direction of the tire 2. For convenience of explanation, the dimension of the mold 68 is represented by the dimension of the tire 2. In FIG. 6, the alternate long and short dash line EL is the center line of the mold 68. This center line ML corresponds to the equatorial plane CL of the tire 2.

This mold 68 is a split mold. The mold 68 includes a tread ring 70, a pair of side plates 72, and a pair of bead rings 74. In FIG. 6, the mold 68 is in a state where the tread ring 70, a pair of side plates 72, and a pair of bead rings 74 are combined, that is, in a closed state.

The tread ring 70 constitutes a radial outer portion of the mold 68. The tread ring 70 is provided with a tread forming surface 76 on the inner surface thereof. The tread forming surface 76 forms the tread surface 22 of the tire 2. The tread ring 70 of the mold 68 is composed of a large number of segments 78. These segments 78 are arranged in a ring shape.

Each side plate 72 is located radially inside the tread ring 70. The side plate 72 connects to the end of the tread ring 70. The side plate 72 is provided with a sidewall forming surface 80 on the inner surface thereof. The sidewall molded surface 80 shapes the side surface of the tire 2.

Each bead ring 74 is located radially inside the side plate 72. The bead ring 74 is connected to the end of the side plate 72. The bead ring 74 is provided with a bead forming surface 82 on the inner surface thereof. The bead forming surface 82 forms the bead portion B. The bead forming surface 82 includes a sheet forming surface 84 and a flange forming surface 86. The sheet forming surface 84 forms the inner peripheral surface of the bead portion B in contact with the sheet T of the rim R. The flange forming surface 86 forms the outer surface of the bead portion B in contact with the flange G of the rim R.

In this mold 68, a large number of segments 78, a pair of side plates 72, and a pair of bead rings 74 are combined to form a cavity surface 88 forming the outer surface of the tire 2 on the outer surface of the raw tire 2r. The mold 68 comprises a cavity surface 88. The cavity surface 88 is composed of a tread forming surface 76, a pair of sidewall forming surfaces 80, and a pair of bead forming surfaces 82.

In the vulcanization step, the raw tire 2r is pressed against the cavity surface 88 of the mold 68 by the expanded bladder 90. As a result, the outer surface of the tire 2 is formed on the outer surface of the raw tire 2r. In this vulcanization step, a rigid core (not shown) may be used instead of the expanded bladder 90.

In FIG. 6, the distance indicated by the reference numeral CW is the clip width of the mold 68. The clip width CW is an axial distance from one flange forming surface 86 to the other flange forming surface 86. In this mold 68, of the flange molding surface 86, the surface extending in the radial direction is used as a reference surface for measuring the clip width CW.

In this manufacturing method, the clip width CW of the mold 68 is wider than the rim width RW of the rim R. Specifically, the difference between the clip width CW and the rim width RW is 1.0 inch or more.

In the tire 2 obtained by using the mold 68, the bead portion B is prevented from being pulled when the tire 2 is assembled to the rim R. In this tire 2, the tensile stress acting on the carcass 12 near the bead portion B can be reduced. The reduction in tensile stress facilitates the movement of the portion where the sidewall 6 and the clinch 8 are located, that is, the side portion S. In this tire 2, there is room for growth in the side portion S at the time of inflation as compared with the conventional tire.

In this manufacturing method, the tire 2 having a large axial displacement of the carcass 12 located radially inside the maximum width position PW can be obtained. In this tire 2, the carcass 12 located radially inside the maximum width position PW tends to move outward in the axial direction. Therefore, as described above, it is good even if the band 16 is composed of only the full band 46. High-speed durability is obtained. Since the band 16 can be composed of only the full band 46, the ride quality is improved as compared with the conventional tire in which the band is composed of the full band and the pair of edge bands. With this manufacturing method, a tire 2 that can achieve an improvement in ride quality without impairing high-speed durability can be obtained.

In this manufacturing method, the difference (CW-RW) between the clip width CW and the rim width RW is preferably 1.1 or more, and 1.2 inches or more, from the viewpoint of maintaining a good balance between high-speed durability and ride quality. More preferably, 1.4 inches or more is further preferable. From the viewpoint of easy incorporation of the tire 2 into the rim R, this difference (CW-RW) is preferably 1.7 inches or less, more preferably 1.6 inches or less, and even more preferably 1.5 inches or less.

As described above, according to the present invention, it is possible to obtain a tire 2 capable of achieving an improvement in ride quality without impairing high-speed durability. The present invention exerts a remarkable effect on the tire 2 having a cross-sectional width Wt of 225 mm or more and a speed symbol of V or more.

Hereinafter, the present invention will be described in more detail with reference to Examples and the like, but the present invention is not limited to such Examples.

[Example 1]
A pneumatic tire for a passenger car (tire size = 225 / 50R18 95V) having the basic configuration shown in FIG. 1 and having the specifications shown in Table 1 below was obtained.

In this Example 1, the band was composed of only a full band. This is represented by "1FB" in the band column of Table 1. The axial distance DA from the intersection PMt between the outer surface in the low pressure state and the reference line ML to the intersection PMh between the outer surface in the standard state and the reference line ML was 0.82 mm.

The ratio (H / A) of the thickness H of the surface layer portion at the reference grounding end PH to the thickness A of the surface layer portion at the equatorial PC was 0.72. The thickness F of the surface layer portion at the top PF of the raised portion was 5.6 mm. The ratio (HB / HS) of the radial height HB of the bead to the cross-sectional height HS of the tire was 0.39. The ratio (D / E) of the thickness D of the surface layer portion at the buttress reference position PD to the thickness E of the surface layer portion at the maximum width position PW of the tire was 1.0.

In this Example 1, the hardness of the cap layer was 66. The ratio of the loss tangent LTc30 of the cap layer at 30 ° C. to the loss tangent LTb30 of the base layer at 30 ° C. (LTc30 / LTb30) was 4.2. The loss tangent LTc0 of the cap layer at 0 ° C. was 0.68.

[Comparative Example 1]
Comparative Example 1 is a conventional tire. In Comparative Example 1, a band composed of a full band and a pair of edge bands was adopted. This is represented by "1FB + 1EB" in the band column of Table 1. The full band of Comparative Example 1 has the same specifications as the full band of Example 1.

The axial distance DA, ratio (H / A), thickness F, ratio (HB / HS), and ratio (D / E) of Comparative Example 1 were as shown in Table 1 below.

In Comparative Example 1, the hardness of the cap layer was 61. The ratio (LTc30 / LTb30) was 1.6. The loss tangent LTc0 of the cap layer at 0 ° C. was 0.66. Circumferential sipes are not engraved on the middle land.

[Comparative Example 2]
A tire of Comparative Example 2 was obtained in the same manner as in Comparative Example 1 except that the edge band was removed from the band of Comparative Example 1.

[Example 2]
The tires of Example 2 were obtained in the same manner as in Example 1 except that the ratio (H / A) was as shown in Table 1 below.

[Example 3]
The tires of Example 3 were obtained in the same manner as in Example 1 except that the ratio (D / E) was as shown in Table 1 below.

[Example 4-6]
The tires of Example 4-6 were obtained in the same manner as in Example 1 except that the thickness F was as shown in Table 1 below.

[High-speed durability]
The prototype tire was assembled on the rim (size = 18 × 7.0J) and filled with air to adjust the internal pressure of the tire to 300 kPa. The evaluation was carried out by the step speed method in accordance with the load / velocity performance test specified by ECE30 using a drum tester. In this evaluation, the running speed was increased sequentially, and the speed and time when the tire broke were measured. The results are shown exponentially in Table 1 below. The higher the number, the better the high-speed durability of the tire.

[Riding comfort and steering stability]
The prototype tire was assembled on the rim (size = 18 × 7.0J) and filled with air to adjust the internal pressure of the tire to 230 kPa. Tires were attached to the test vehicle (passenger car), and the test vehicle was run on a test course on a dry asphalt road surface. The driver was made to evaluate the ride comfort and steering stability (sensory evaluation). The results are shown exponentially in Table 1 below. The higher the number, the better the ride quality or steering stability of the tire.

As shown in Table 1, in the examples, the improvement of the ride quality is achieved without impairing the high speed durability. From this evaluation result, the superiority of the present invention is clear.

The technique described above that can achieve an improvement in ride quality without impairing high-speed durability can be applied to various tires.

2, 2r ... Tire 4 ... Tread 6 ... Sidewall 8 ... Clinch 10 ... Bead 12 ... Carcus 14 ... Belt 16 ... Band 22 ... Tread surface 26・ ・ ・ Base layer 28 ・ ・ ・ Cap layer 34 ・ ・ ・ Carcass ply 46 ・ ・ ・ Full band 48 ・ ・ ・ Surface layer 50 ・ ・ ・ Rising part 52, 52s, 52m ・ ・ ・ Circumferential groove 54, 54s, 54m, 54c ... Land 56 ... Horizontal groove 60 ... Circumferential sipe 66 ... Edge 68 ... Mold 82 ... Bead molding surface 86 ... Flange molding surface 88 ... Cavity surface

Claims (8)

A tread that touches the road surface, a pair of sidewalls that are connected to the end of the tread and are located inside the tread in the radial direction, a pair of clinches that are located inside the sidewall in the radial direction, and the above in the axial direction. A pair of beads located inside the clinch, a tread, a sidewall, and a carcass located inside the clinch, a belt located between the tread and the carcass in the radial direction, and the inside of the tread. A tire comprising a band laminated on the belt.
The surface layer including the tread, the sidewall, and the clinch constitutes the outer surface of the tire.
The band consists of a full band with both ends facing each other across the equator.
The full band contains a spirally wound band cord.
The standard state of the tire is that the tire is assembled on the rim, the internal pressure of the tire is adjusted to 230 kPa, and no load is applied to the tire.
The ground contact surface obtained by applying a load of 70% of the normal load to the tire in the standard state as a vertical load and bringing the tire into contact with the road surface made of a flat surface is the reference ground contact surface, and the axis of the reference ground contact surface. The position on the outer surface of the tire corresponding to the outer end of the direction is the reference contact patch.
The state in which the tire is assembled on the rim, the internal pressure of the tire is adjusted to 30 kPa, and no load is applied to the tire is the low pressure state of the tire.
When a straight line extending in the axial direction through the midpoint between the radial outer end of the rim and the maximum width position of the tire, which is specified in the tire in the standard state, is used as a reference line.
The axial distance from the intersection of the outer surface of the tire in the low pressure state and the reference line to the intersection of the outer surface of the tire in the standard state and the reference line is 0.5 mm or more.
tire. The surface layer portion has a raised portion between the radial outer end of the rim and the maximum width position of the tire.
The thickness of the surface layer portion at the top of the raised portion is 5.0 mm or more and 6.0 mm or less.
The tire according to claim 1. The ratio of the thickness of the surface layer portion at the reference grounding end to the thickness of the surface layer portion at the equator is 0.50 or more and 0.80 or less.
The tire according to claim 1 or 2. The ratio of the radial height of the bead to the cross-sectional height of the tire is 0.35 or more and 0.45 or less.
The tire according to any one of claims 1 to 3. The radial distance from the bead baseline indicates 0.77 times the cross-sectional height of the tire, and the position on the outer surface of the tire is the buttress reference position.
The surface layer portion at the buttress reference position has the same thickness as the surface layer portion at the maximum width position of the tire.
The tire according to any one of claims 1 to 4. The outer surface of the tread is divided into a plurality of regions parallel in the axial direction.
The plurality of regions include a crown region including the equator, a pair of shoulder regions including the reference ground contact end, and a pair of middle regions located between the crown region and the shoulder region.
The contours of the crown region, the middle region, and the shoulder region are each represented by an outwardly convex arc.
The ratio of the radius of the arc representing the contour of the middle region to the radius of the arc representing the contour of the crown region is 0.50 or more and 0.54 or less.
The ratio of the radius of the arc representing the contour of the shoulder region to the radius of the arc representing the contour of the crown region is 0.20 or more and 0.24 or less.
The tire according to any one of claims 1 to 5. The tread is composed of a plurality of land areas partitioned by a circumferential groove.
Of the plurality of land parts, the land part located on the outer side in the axial direction is the shoulder land part.
A horizontal groove is carved on the shoulder land part,
The lateral groove has an end within the shoulder land portion and extends from the end toward the end of the tread.
The edges on both sides of the lateral groove are rounded,
The tire according to any one of claims 1 to 6. The method for manufacturing a tire according to any one of claims 1 to 7.
The process of preparing the raw tire, which is the unvulcanized tire, and
Including the steps of pressurizing and heating the raw tire in the mold.
The mold comprises a cavity surface that forms the outer surface of the tire on the raw tire.
The cavity surface comprises a pair of flange forming surfaces that shape the surface of the tire that contacts the flange of the rim.
A method for manufacturing a tire, wherein the difference between the axial distance from one flange forming surface to the other flange forming surface and the rim width of the rim is 1.0 inch or more.

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