JP2021120242A - Tire and method of manufacturing tire - Google Patents

Abstract

To provide a tire 2 to which reduction of mass and rolling resistance is achieved while restraining influence on abrasion resistance and stability.SOLUTION: Ratio (W2/WC) of width W2 of a second reference layer 44 to maximum width WC of a carcass 12 is 72% or greater and 84% or less in reference condition which assembles a tire 2 to an applied rim including the narrowest rim width in the applied rim in JATMA standard and adjusts internal pressure of the tire 2 to 230 kPa and does not apply load to the tire 2. Ratio (D/MW) of camber amount D in end of a band 16 to reference ground width MW is 12% or greater and 14% or less.SELECTED DRAWING: Figure 1

Description

The present invention relates to a tire and a method for manufacturing the tire. In particular, the present invention relates to a tire mounted on a passenger car and a method for manufacturing the tire.

In consideration of the environment, tires mounted on vehicles are required to reduce mass and rolling resistance. In order to reduce the mass and rolling resistance, it is considered to reduce the number of elements constituting the tire, reduce the thickness of the elements, adopt a low heat generating material as the material constituting the elements, and the like (for example, the following). Patent Document 1).

Japanese Unexamined Patent Publication No. 2016-97778

For example, a tire belt contains a number of parallel steel cords. By narrowing the width of the belt, it is expected that the mass and rolling resistance can be reduced. However, if a narrow belt is used, the binding force at the end of the tread, that is, the shoulder, is weakened. Since the shoulder portion is easily deformed, there is a concern that wear is likely to proceed in the shoulder portion, for example. Since the ground contact condition of the tire with the road surface also changes, the performance such as steering stability may be impaired.

The present invention has been made in view of such an actual situation, and the present invention is to provide a tire in which reduction in mass and rolling resistance is achieved while suppressing the influence on wear resistance and steering stability.

A tire according to an aspect of the present invention includes a pair of beads, a carcass that bridges between one bead and the other bead, a belt located outside the carcass in the radial direction, and the above-mentioned tire in the radial direction. It includes a band located on the outside of the belt and a tread located on the outside of the band in the radial direction and in contact with the road surface. In this tire, the belt includes a first reference layer and a second reference layer that is laminated on the radial outer side of the first reference layer and has a width narrower than the width of the first reference layer. Among the applicable rims in the JATTA standard, the tire is assembled on the applicable rim having the narrowest rim width, the internal pressure of the tire is adjusted to 230 kPa, and no load is applied to the tire. The ratio of the width to the maximum width of the carcass is 72% or more and 84% or less. The ratio of the camber amount at the end of the band to the reference ground contact width is 12% or more and 14% or less. The ground contact width of the ground contact surface obtained by applying a normal load to the tire in the reference state and bringing the tire into contact with the road surface is the reference ground contact width.

Preferably, in this tire, when the position on the outer surface of the tread corresponding to the axial outer end of the ground contact surface is set as the ground contact reference position, the equatorial line of the tire and the ground contact reference position are connected in the reference state. The angle formed by the straight line with respect to the axial direction is 2 ° or more and 5 ° or less.

Preferably, in the tire, in the reference state, the contour of the outer surface of the tire has a center on a straight line extending in the axial direction through the maximum width position of the tire, and is radially inward from the maximum width position. The ratio of the radius of the lower arc to the cross-sectional height of the tire is 48% or less, including the lower arc which is an extending arc.

Preferably, in this tire, the end of the band is located outside the end of the first reference layer in the axial direction. The distance from the end of the second reference layer to the end of the first reference layer is longer than the distance from the end of the first reference layer to the end of the band, and from the end of the first reference layer. The distance to the end of the band is 4.0 mm or more and 6.0 mm or less.

Preferably, in this tire, the difference between the distance from the end of the second reference layer to the end of the first reference layer and the distance from the end of the first reference layer to the end of the band is , 1.0 mm or more and 3.0 mm or less.

Preferably, in this tire, the thickness of the outer portion of the carcass at a position on the outer surface of the tire whose height from the bead baseline corresponds to a height of 1.4 times the flange height of the applicable rim. The ratio of the thickness of the outer portion of the carcass to the maximum width position of the tire is 60% or less.

A method for manufacturing a tire according to one aspect of the present invention includes a pair of beads, a carcass that bridges between one bead and the other bead, a belt located outside the carcass in the radial direction, and a radial direction. A method for manufacturing a tire, comprising a band located on the outside of the belt and a tread located on the outside of the band in the radial direction. This manufacturing method
It includes (1) a step of preparing a raw tire in an unvulcanized state of the tire, and (2) a step of pressurizing and heating the raw tire in a mold. The mold comprises a cavity surface that shapes the outer surface of the tire into the raw tire. The cavity surface comprises a pair of flange molded surfaces that shape the outer surface of the bead portion, which is a portion of the tire that is fitted to the rim. The rim is an applicable rim having the narrowest rim width among the applicable rim widths in the JATTA standard. The difference between the clip width, which is the axial distance from one flange molding surface to the other flange molding surface, and the rim width of the rim is 0.6 inches or more and 1.2 inches or less.

Preferably, in this method of manufacturing the tire, the belt is laminated with the first reference layer on the radial outer side of the first reference layer, and has a width narrower than the width of the first reference layer. And. In a reference state in which the tire is assembled on the applicable rim, the internal pressure of the tire is adjusted to 230 kPa, and no load is applied to the tire, the ratio of the width of the second reference layer to the maximum width of the carcass is 72. % Or more and 84% or less. The ratio of the camber amount at the end of the band to the reference ground contact width is 12% or more and 14% or less. The ground contact width of the ground contact surface obtained by applying a normal load to the tire in the reference state and bringing the tire into contact with the road surface is the reference ground contact width.

In the tire of the present invention, reduction of mass and rolling resistance is achieved while suppressing the influence on wear resistance and steering stability.

FIG. 1 is a cross-sectional view showing an example of a tire according to an embodiment of the present invention. FIG. 2 is a schematic view showing the shape of the contact patch of the tire. FIG. 3 is a cross-sectional view showing a part of the tire. FIG. 4 is a diagram illustrating a method for manufacturing a tire.

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

In the present invention, a state in which a tire is incorporated in 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 invention, unless otherwise specified, the dimensions and angles of each part of the tire are measured in a normal state.

Regular rims are rims defined in the standards 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.

Regular internal pressure means the internal pressure defined in the standard on which the tire relies. The "maximum air pressure" in the JATMA 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. If the tires are for passenger cars, the normal internal pressure is 180 kPa unless otherwise noted.

Normal load means the load specified in the standard on which the tire relies. The "maximum load capacity" in the JATMA standard, the "maximum value" in the "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the TRA standard, and the "LOAD CAPACITY" in the ETRTO standard are normal loads. When the tire is for a passenger car, the normal load is a load corresponding to 88% of the load unless otherwise specified.

FIG. 1 shows an example of a tire 2 according to an embodiment of the present invention. The tire 2 is mounted on a passenger car. In FIG. 1, the tire 2 is assembled on the rim R. 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 complex. The tire-rim complex includes a rim R and a tire 2 assembled on the rim R.

In FIG. 1, the rim R on which the tire 2 is assembled is an applicable rim having the narrowest rim width among the applicable rims in the JATTA standard. A state in which the tire 2 is assembled on the rim R, the internal pressure of the tire 2 is adjusted to 230 kPa, and no load is applied to the tire 2 is referred to as a reference state.

The rim R includes a sheet S on which the inner peripheral surface of the bead portion, which will be described later, is placed, and a flange G on which the outer surface of the bead portion is pressed. In FIG. 1, the solid line BBL extending in the axial direction is the bead baseline. This bead baseline is a line that defines the rim diameter of the rim R (see JATTA and the like).

FIG. 1 shows a part of a cross section of the tire 2 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 represents the equatorial plane of the tire 2.

In FIG. 1, the reference numeral PW is the outer end in the axial direction of the tire 2. This outer end PW is specified based on the contour of the outer surface of the tire. When a decoration such as a pattern or a character is on the outer surface, the outer end PW is specified based on the contour of the virtual outer surface (two-dot chain line LV in FIG. 1) obtained assuming that the decoration is not present.

The axial distance from one outer end PW to the other outer end PW is the maximum width of the tire 2, that is, the cross-sectional width (see JATTA or the like). The outer end PW is a position where the tire 2 shows the maximum width (hereinafter, the maximum width position).

The tire 2 includes 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 as elements.

The tread 4 is made of crosslinked rubber. The tread 4 comes into contact with the road surface on its outer surface 22, that is, the tread surface 22. A groove 24 is carved in the tread 4. In the tire 2, a plurality of land portions 28 arranged in parallel in the axial direction are formed in the tread 4 by carving a groove extending in the circumferential direction (hereinafter referred to as a circumferential groove 26). The tread 4 is located outside the band 16 in the radial direction. The tread 4 has a base layer 30 and a cap layer 32.

The base layer 30 is located radially outward of the belt 14 and the band 16. The base layer 30 covers the entire band 16. The base layer 30 is made of a low heat-generating crosslinked rubber.

The cap layer 32 is located radially outside the base layer 30. The cap layer 32 covers the entire base layer 30. The outer surface of the cap layer 32 is the tread surface 22 described above. The cap layer 32 is made of crosslinked rubber in consideration of wear resistance and grip performance.

In FIG. 1, the reference numeral PC is the equator of the tire 2. This equatorial PC is represented by the intersection of the tread surface 22 and the equatorial surface. As shown in FIG. 1, when the groove 24 is located on the equatorial plane, the equatorial PC is specified based on the contour of the virtual tread plane obtained assuming that the groove 24 is not present.

In FIG. 1, the length represented by the double-headed arrow H is the cross-sectional height of the tire 2 (see JATTA and the like). This cross-sectional height H is represented by the radial distance from the bead baseline to the equatorial PC. The cross-sectional height H is measured in the tire 2 in the reference state.

Each sidewall 6 runs along the edge of the tread 4. The sidewall 6 is located radially inside the tread 4. The sidewall 6 extends from the edge of the tread 4 towards the clinch 8. The sidewall 6 is made of crosslinked rubber.

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

Each bead 10 is located axially inside the clinch 8. The bead 10 includes a core 34 and an apex 36. The core 34 includes a steel wire. The apex 36 is located radially outside the core 34. Apex 36 is made of crosslinked rubber having high rigidity.

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 38.

The carcass 12 of the tire 2 is composed of one carcass ply 38. The carcass ply 38 is folded around each core 34. The carcass ply 38 is a pair of a ply body 38a that bridges between one core 34 and the other core 34, and a pair that is connected to the ply body 38a and is folded back from the inside to the outside in the axial direction around each core 34. It has a folded-back portion 38b of. In the tire 2, the end of the folded-back portion 38b is located outside the maximum width position PW in the radial direction.

Although not shown, the carcass ply 38 includes a large number of parallel carcass cords. These carcass cords are covered with topping rubber. Each carcass code intersects the equatorial plane. In this tire 2, a cord made of organic fibers is used as a carcass cord. Examples of organic fibers include nylon fibers, rayon fibers, polyester fibers and aramid fibers.

The belt 14 is located outside the carcass 12 in the radial direction. The belt 14 is located inside the band 16 on the radial inside of the tread 4. The belt 14 is composed of at least two layers 40 laminated in the radial direction. In the tire 2, the layer 40 having the widest width among at least two layers 40 constituting the belt 14 is the first reference layer 42. The layer 40 laminated on the radial outer side of the first reference layer 42 is the second reference layer 44. The second reference layer 44 has a width narrower than the width of the first reference layer 42.

The belt 14 of the tire 2 is composed of two layers 40. The belt 14 includes a first reference layer 42 and a second reference layer 44. As shown in FIG. 1, in the axial direction, the end of the first reference layer 42 is located outside the end of the second reference layer 44.

Although not shown, the first reference layer 42 and the second reference layer 44 each include a large number of parallel belt cords. These belt cords are covered with topping rubber. Each belt cord inclines with respect to the equatorial plane. The material of the belt cord is steel.

The band 16 is located outside the belt 14 in the radial direction. The band 16 is located between the tread 4 and the belt 14 in the radial direction. As shown, the end of the band 16 is located outside the end of the first reference layer 42, which forms part of the belt 14, in the axial direction. The band 16 of the tire 2 is a full band that covers the entire belt 14. The band 16 may further include a pair of edge bands covering the ends of the full band. The band 16 may be composed of a pair of edge bands instead of a full band. In this case, the edge band covers the end of the belt 14.

Although not shown, band 16 includes a band cord. In the band 16, the band cord is spirally wound in the circumferential direction. The band cord is covered with topping rubber. A cord made of organic fibers is used as a band cord. Examples of organic fibers include nylon fibers, rayon fibers, polyester fibers and aramid fibers.

Each chafer 18 is located radially inside the bead 10. The chafer 18 comes into contact with the seat S of the rim R. In the tire 2, the chafer 18 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.

In the tire 2, the portion in contact with the road surface is also referred to as a tread portion 46. The portion fitted to the rim R is also referred to as a bead portion 48. The portion that bridges between the tread portion 46 and the bead portion 48 is also referred to as a side portion 50. The tire 2 includes a tread portion 46, a pair of bead portions 48, and a pair of side portions 50 as portions.

In this tire 2, the tread portion 46 includes a tread 4, a carcass 12, a belt 14, a band 16, and an inner liner 20. The bead portion 48 includes a clinch 8, a bead 10, a carcass 12, a chafer 18, and an inner liner 20. The side portion 50 includes a sidewall 6, a carcass 12, and an inner liner 20.

In FIG. 1, the length represented by the double-headed arrow W2 is the width of the second reference layer 44. This width W2 is represented by the axial distance from one end of the second reference layer 44 to the other end. Reference numeral PM is an axially outer end of the carcass 12, which is identified on the inner surface of the carcass 12. The double-headed arrow WC represents the axial distance from one outer end PM of the carcass 12 to the other outer end PM. In the tire 2, this distance WC is the maximum width of the carcass 12. The width W2 of the second reference layer 44 and the maximum width WC of the carcass 12 are measured in the tire 2 in the reference state.

In FIG. 1, the position on the outer surface of the tire 2 represented by the reference numeral PB is an intersection of a straight line extending in the radial direction through the end of the band 16 and the outer surface of the tire 2. In the tire 2, the position indicated by the intersection PB is a position on the outer surface of the tire 2 corresponding to the end of the band 16. The double-headed arrow D represents the radial distance from the equatorial PC to the intersection PB. In the tire 2, this distance D is the amount of camber at the end of the band 16. The camber amount D at the end of the band 16 is measured on the tire 2 in the reference state.

FIG. 2 schematically shows an example of the contact patch shape of the tire 2. FIG. 2 shows the outline of each land portion included in the ground plane. In FIG. 2, the left-right direction corresponds to the axial direction of the tire 2. The vertical direction corresponds to the circumferential direction of the tire 2.

The contact patch shape is obtained by applying a normal load to the tire 2 in the reference state using a tire contact patch shape measuring device (not shown) and bringing the tire 2 into contact with the road surface. It is obtained by tracing the contour of the part 28. In obtaining the ground contact surface, the tire 2 is arranged so that its axial direction is parallel to the road surface, and the above-mentioned load is applied to the tire 2 in a direction perpendicular to the road surface. In this measuring device, the road surface is composed of a flat surface. In this measurement of the ground contact surface, the tire 2 is pressed against a flat road surface with a camber angle of 0 °.

In FIG. 2, reference numeral PS is an axially outer end of the ground plane. In FIG. 1, the position on the outer surface of the tread 4 corresponding to the outer end PS is represented by the symbol PE. In the tire 2, the position PE on the outer surface of the tread 4 corresponding to the axial outer end PS of the ground contact surface is also referred to as the ground contact reference position. In FIG. 2, the double-headed arrow MW is the axial distance from one outer end PS of the ground plane to the other outer end PS. In the tire 2, this axial distance MW is the ground contact width of the ground contact surface. The ground contact width MW of the ground contact surface obtained by applying a normal load to the tire 2 in the reference state and bringing the tire 2 into contact with the road surface is the reference ground contact width.

In this tire 2, the ratio (W2 / WC) of the width W2 of the second reference layer 44 to the maximum width WC of the carcass 12 is 72% or more and 84% or less.

Since the ratio (W2 / WC) is 72% or more, the belt 14 contributes to ensuring the rigidity of the tread portion 46. With this tire 2, steering stability is improved. Since the second reference layer 44 close to the tread surface 22 contributes to the optimization of the shape of the ground contact surface, the leveling of the ground pressure distribution is promoted. In this tire 2, good wear resistance is maintained, and an increase in rolling resistance due to heat generation in the ground contact surface is suppressed. The tire 2 can improve steering stability while maintaining good wear resistance and low rolling resistance. From this point of view, this ratio (W2 / WC) is preferably 74% or more, more preferably 76% or more, still more preferably 78% or more.

Since the ratio (W2 / WC) is 84% or less, the belt 14 contributes to the reduction of the mass and rolling resistance of the tire 2. Since the end of the first reference layer 42 and the end of the second reference layer 42 are arranged at an appropriate distance, the concentration of strain on the end of the belt 14 can be suppressed. In this tire 2, damage is prevented from occurring at the end portion, and good wear resistance is maintained. From this point of view, this ratio (W2 / WC) is preferably 83% or less, more preferably 82% or less, still more preferably 81% or less.

In this tire 2, the ratio (D / MW) of the camber amount D at the end of the band 16 to the reference ground contact width MW is 12% or more and 14% or less.

Since the ratio (D / MW) is 12% or more, in this tire 2, the amount of deformation of the shoulder portion when the shoulder portion comes into contact with the road surface is larger than that of the conventional tire. Although the degree of displacement of the grounding end position of the grounding surface is small, the grounding end position fluctuates in the axial direction, so that a local increase in the grounding pressure near the grounding end can be suppressed. Although the tire 2 uses a belt 14 having a width narrower than that of the conventional tire, the contact pressure distribution can be leveled. In this tire 2, good wear resistance is maintained, and an increase in rolling resistance due to heat generation in the ground contact surface is suppressed.

Since the ratio (D / MW) is 14% or less, the degree of displacement of the ground contact end position of the ground contact surface is appropriately maintained. With this tire 2, a sufficient cornering force is secured, so that good steering stability can be obtained. Since heat generation due to deformation of the shoulder portion is suppressed, low rolling resistance is maintained. Since the length of the ground contact at the shoulder portion is suppressed from becoming long, good wear resistance is maintained.

In this tire 2, the mass and rolling resistance are reduced, and good wear resistance and steering stability can be obtained. In this tire 2, reduction in mass and rolling resistance is achieved while suppressing the influence on wear resistance and steering stability.

The contour of the outer surface of the tire 2 includes a plurality of arcs. Of the contours of the outer surface, the contours of the side surfaces include a lower arc which is an arc extending inward from the maximum width position PW and an upper arc which is an arc extending outward from the maximum width position PW in the radial direction. .. The maximum width position PW is the boundary between the lower arc and the upper arc, and the lower arc and the upper arc are in contact with each other at this maximum width position PW.

In the tire 2, the lower arc and the upper arc each have a center on a straight line extending in the axial direction through the maximum width position PW. In FIG. 1, the arrow UR is the radius of the lower arc, and the symbol PU is the center of the lower arc. The radius UR of this lower arc is measured on the tire 2 in the reference state. When decorations such as patterns and characters are on the outer surface, the contour configuration of the outer surface is specified in the above-mentioned virtual outer surface.

When the contour composition of the outer surface is not clear, for example, the cross-sectional image data of the tire 2 in the reference state taken by a computer tomography method using X-rays (hereinafter referred to as X-ray CT method), or a laser displacement meter. The contour configuration of the outer surface is specified based on the contour of the outer surface obtained by analyzing the shape data of the outer surface of the tire 2 in the reference state measured using a profile measuring device (not shown) having the above. .. In this case, the vertical bisector of the line segment connecting the maximum width position PW, the distance corresponding to 10% of the cross-sectional height H from the maximum width position PW, and the position separated from the inside, and the maximum width position PW. The radius UR of this lower arc can be obtained by finding the intersection with the straight line extending in the axial direction. This intersection is the center PU of the lower arc.

In the tire 2, the ratio (UR / H) of the radius UR of the lower arc to the cross-sectional height H of the tire 2 is preferably 48% or less. By setting this ratio (UR / H) to 48% or less, a local increase in the ground pressure near the ground end is suppressed. In this tire 2, although the narrow belt 14 is adopted, the contact pressure distribution can be leveled. Good wear resistance is maintained in the tire 2. From this point of view, this ratio (UR / H) is more preferably 47% or less, further preferably 46% or less.

In this tire 2, from the viewpoint of ensuring the rigidity of the portion from the side portion 50 to the bead portion 48, this ratio (UR / H) is preferably 40% or more, more preferably 42% or more, still more preferably 44% or more.

As described above, the tire 2 is assembled on the rim R. In FIG. 1, the length indicated by the double-headed arrow RW is the rim width of the rim R (see JATTA et al.). The rim width RW is represented by an axial distance from the inner surface of one flange G to the inner surface of the other flange G. The double-headed arrow RF represents the flange height of the rim R. The flange height RF is represented by the radial distance from the bead baseline to the radial outer edge of the flange G.

In FIG. 1, the position represented by the reference numeral PF is a specific position on the outer surface of the tire 2. The double-headed arrow HB is the radial distance from the bead baseline to this position PF, and this distance HB is 1.4 times the flange height RF. The position represented by the reference numeral PF is the position of the outer surface of the tire 2 whose height from the bead baseline corresponds to a height 1.4 times the flange height RF of the rim R.

In FIG. 1, the length represented by the double-headed arrow F is the thickness of the outer portion of the carcass 12 at the above-mentioned position PF. This thickness F is represented by the distance from the outer surface of the carcass 12 to the outer surface of the tire 2 measured along the normal of the outer surface of the carcass 12. In FIG. 1, the length represented by the double-headed arrow E is the thickness of the outer portion of the carcass 12 at the maximum width position PW. This thickness E is represented by the distance from the outer surface of the carcass 12 to the outer surface of the tire 2 measured along a straight line extending in the axial direction through the maximum width position PW. The thickness F and the thickness E are measured in the tire 2 in the reference state.

In this tire 2, the thickness of the outer portion of the carcass 12 at the position PF of the outer surface of the tire 2 whose height HB from the bead baseline corresponds to a height of 1.4 times the flange height RF of the rim R. The ratio (E / F) of the thickness E of the outer portion of the carcass 12 to F at the maximum width position PW of the tire 2 is preferably 60% or less. As a result, the weight of the tire 2 can be reduced. The weight reduction contributes to the reduction of rolling resistance. From this point of view, this ratio (E / F) is more preferably 55% or less, still more preferably 53% or less. From the viewpoint of ensuring the rigidity of the side portion 50, this ratio (E / F) is preferably 44% or more, more preferably 46% or more, still more preferably 48% or more.

In the tire 2, the thickness F contributes to ensuring the rigidity of the bead portion 48. From this viewpoint, the thickness F is preferably 4.0 mm or more. From the viewpoint of weight reduction, the tire 2 preferably has a thickness F of 5.0 mm or less.

FIG. 3 shows a part of the tire 2 shown in FIG. FIG. 3 shows the tread portion 46 of the tire 2. In FIG. 3, 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. 3 is the circumferential direction of the tire 2.

In FIG. 3, the straight line represented by the symbol LC is a straight line extending in the axial direction through the equator PC. The straight line represented by the symbol LE is a straight line passing through the equator PC and the ground reference position PE. The angle θ is an angle formed by the straight line LC and the straight line LE. This angle θ is the angle formed by the straight line LE connecting the equator PC of the tire 2 and the ground contact reference position PE with respect to the axial direction. This angle θ is measured on the tire 2 in the reference state.

In the tire 2, the angle θ formed by the straight line LE connecting the equator PC of the tire 2 and the ground contact reference position PE with respect to the axial direction is preferably 2 ° or more, and preferably 5 ° or less.

By setting the angle θ to 2 ° or more, a local increase in the ground pressure near the ground end can be suppressed. In this tire 2, although the narrow belt 14 is adopted, the contact pressure distribution can be leveled. Good wear resistance is maintained in the tire 2. From this point of view, the angle θ is more preferably 3 ° or more.

By setting the angle θ to 5 ° or less, a sufficient ground plane is secured. Good steering stability is maintained with this tire 2. From this point of view, the angle θ is more preferably 4 ° or less.

In FIG. 3, the double-headed arrow SV represents the shortest distance from the end of the second reference layer 44 to the end of the first reference layer 42. This distance SV is the length of the first reference layer 42 protruding from the second reference layer 44, and is also referred to as the first step amount. The double-headed arrow SB represents the shortest distance from the end of the first reference layer 42 to the end of the band 16. This distance SB is the length of the band 16 protruding from the first reference layer 42, and is also referred to as the second step amount.

As described above, in this tire 2, in the axial direction, the end of the first reference layer 42 is located outside the end of the second reference layer 44, and the end of the band 16 is located outside the end of the first reference layer 42. Located on the outside. In the tire 2, the end of the first reference layer 42, the end of the second reference layer 44, and the end of the band 16 are dispersedly arranged in the axial direction. In the tire 2, the first step amount SV is preferably longer than the second step amount SB, and the second step amount SB is 4.0 mm or more and 6.0 mm or less. This arrangement gently changes the binding force at the ends of the belt 14 and the band 16, so that the concentration of strain on the ends is suppressed. In this tire 2, the occurrence of damage at the end portion is prevented, and the wear resistance is also improved. From this viewpoint, the second step amount SB is more preferably 4.5 mm or more, and further preferably 4.8 mm or more. From the viewpoint of ensuring a sufficient distance from the end of the band 16 to the outer surface of the tire 2, the second step amount SB is more preferably 5.5 mm or less, further preferably 5.2 mm or less.

In the tire 2, the difference (SV-SB) between the first step amount SV and the second step amount SB is preferably 1.0 mm or more, and preferably 3.0 mm or less. By setting this difference (SV-SB) to 1.0 mm or more, the concentration of strain on the ends of the belt 14 and the band 16 can be effectively suppressed. From this point of view, this difference (SV-SB) is more preferably 1.5 mm or more, and further preferably 1.8 mm or more. By setting this difference (SV-SB) to 3.0 mm or less, the binding force of the belt 14 and the band 16 is secured. Good steering stability is maintained with this tire 2. From this point of view, this difference (SV-SB) is preferably 2.5 mm or less, and more preferably 2.2 mm or less.

In FIG. 3, the double-headed arrow WE represents the axial distance from one grounding reference position PE to the other grounding reference position PE. This distance WE is measured on a tire in reference condition.

In this tire 2, the ratio (WE / W2) of the axial distance WE from one grounding reference position PE to the other grounding reference position PE with respect to the width W2 of the second reference layer 44 is preferably 80% or more, and is 95. % Or less is preferable.

By setting the ratio (WE / W2) to 80% or more, a sufficient ground contact surface is secured. Good steering stability is maintained with this tire 2. From this point of view, this ratio (WE / W2) is more preferably 85% or more, and even more preferably 88% or more.

By setting the ratio (WE / W2) to 95% or less, a local increase in the ground pressure near the ground end is suppressed. In this tire 2, although the narrow belt 14 is adopted, the contact pressure distribution can be leveled. Good wear resistance is maintained in the tire 2. From this point of view, this ratio (WE / W2) is more preferably 93% or less, and further preferably 91% or less.

Next, the manufacture of the tire 2 will be described. Although not described in detail, in the manufacture of the tire 2, an unvulcanized rubber composition for the elements constituting the tire 2, such as the tread 4, the sidewall 6, and the bead 10, (hereinafter, also referred to as unvulcanized rubber). Is called.) Is prepared. The unvulcanized rubber is obtained by mixing the base rubber and chemicals using a kneader (not shown) such as a Banbury mixer.

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 components to which this rubber is applied.

In the manufacture of the tire 2, in a rubber molding machine (not shown) such as an extruder, the shape of the unvulcanized rubber is adjusted to prepare a preformed body of the tire component. In a tire molding machine (not shown), preformed bodies such as a tread 4, a bead 10, a carcass 12, a belt 14, and a band 16 are combined. As a result, the pair of beads 10, the carcass 12 that bridges between one bead 10 and the other bead 10, the belt 14 located outside the carcass 12 in the radial direction, and the belt 14 in the radial direction. An unvulcanized tire 2 (hereinafter, also referred to as a raw tire) including a band 16 located on the outside and a tread 4 located on the outside of the band 16 in the radial direction is prepared.

In the manufacture of the tire 2, the raw tire is put into a mold of a vulcanizer (not shown). The raw tire is pressurized and heated in the mold to obtain the tire 2. The tire 2 is a vulcanized molded product of a raw tire.

The method for manufacturing the tire 2 includes a step of preparing a raw tire, which is an unvulcanized state of the tire 2, and a step of pressurizing and heating the raw tire in a mold. 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. 4 shows a part of the vulcanizer 52 used in the manufacture of the tire 2. FIG. 4 shows a part of a cross section of the vulcanizer 52 along a plane including the rotation axis of the tire 2. In FIG. 4, 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. 4 is the circumferential direction of the tire 2. For convenience of explanation, the dimension of the vulcanizer 52 is represented by the dimension of the tire 2 below. In the vulcanizer 52, the raw tire 2r is vulcanized. The vulcanizer 52 includes a mold 54 and a bladder 56.

The mold 54 includes a cavity surface 58 on its inner surface. The cavity surface 58 abuts on the outer surface of the raw tire 2r and shapes the outer surface of the tire 2 into the raw tire 2r. Although not described in detail, this mold 54 is a split mold.

The cavity surface 58 includes a tread forming surface (not shown) forming the outer surface of the tread portion 46, a side forming surface 60 forming the side portion 50, and a bead forming surface 62 forming the bead portion 48. The bead forming surface 62 includes a sheet forming surface 64 and a flange forming surface 66. The sheet forming surface 64 forms the inner peripheral surface of the bead portion 48 mounted on the sheet S of the rim R. The flange forming surface 66 forms the outer surface of the bead portion 48 pressed against the flange G of the rim R.

The bladder 56 is located inside the mold 54. The bladder 56 is made of crosslinked rubber. The inside of the bladder 56 is filled with a heating medium such as steam. As a result, the bladder 56 expands. The bladder 56 shown in FIG. 4 is in a state of being filled with a heating medium and expanded. The bladder 56 abuts on the inner surface of the raw tire 2r and shapes the inner surface of the tire 2 into the raw tire 2r. In the manufacture of the tire 2, a metal rigid core (not shown) may be used instead of the bladder 56. The rigid core has a toroidal outer surface. The shape of the outer surface is similar to the shape of the inner surface of the tire 2 which is filled with air and the internal pressure is maintained at 5% of the normal internal pressure.

In the manufacture of the tire 2, the raw tire 2r is put into the mold 54 set to a predetermined temperature. After charging, the mold 54 is closed. The bladder 56 expanded by filling the heating medium presses the raw tire 2r against the cavity surface 58 from the inside. The raw tire 2r is pressurized and heated in the mold 54 for a predetermined time. As a result, the rubber composition of the raw tire 2r is crosslinked to obtain the tire 2.

In FIG. 4, the length represented by the double-headed arrow CW is the clip width of the mold 54. The clip width CW is represented by an axial distance from one flange forming surface 66 to the other flange forming surface 66. The rim R shown in FIG. 1 is an applicable rim having the narrowest rim width among the applicable rims in the JATTA standard. The rim width RW of this rim R is the narrowest rim width among the rim widths of the applicable rims in the JATTA standard to which the tire 2 is assembled.

In this method of manufacturing the tire 2, the difference (CW-RW) between the clip width CW and the rim width RW is 0.6 inches or more and 1.2 inches or less.

Since the difference (CW-RW) is 0.6 inches or more, the rigidity of the portion from the side portion 50 to the bead portion 48 is appropriately ensured in the tire 2 manufactured by this mold 54. Good steering stability is maintained with this tire 2. From this point of view, this difference (CW-RW) is preferably 0.7 inches or more.

Since the difference (CW-RW) is 1.2 inches or less, in the tire 2 manufactured by this mold 54, a local increase in the contact pressure near the contact end is suppressed. In this tire 2, although the narrow belt 14 is adopted, the contact pressure distribution can be leveled. Good wear resistance is maintained in the tire 2. From this point of view, this difference (CW-RW) is more preferably 1.1 inches or less, and even more preferably 1.0 inches or less.

As described above, according to the present invention, it is possible to obtain the tire 2 in which the mass and rolling resistance are reduced while suppressing the influence on the wear resistance and the steering stability. Among the tires for passenger cars, the tire 2 can be suitably used as a tire for a light vehicle.

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 (tire size = 175 / 55R15) for a passenger car having the basic configuration shown in FIG. 1 and the specifications shown in Table 1 below was obtained.

In the first embodiment, the ratio of the width W2 of the second reference layer to the maximum width WC of the carcass (W2 / WC), the axial distance WE from one ground reference position PE to the other ground reference position PE, is the first. (2) The ratio of the reference layer to the width W2 (WE / W2), the ratio of the camber amount D at the end of the band to the reference ground width MW (D / MW), and the straight line LE connecting the tire equatorial PC and the ground reference position PE. The angle θ formed in the axial direction, the ratio of the radius UR of the lower arc to the cross-sectional height H (UR / H), and the height HB from the bead baseline are 1. The ratio (E / F) of the thickness E of the outer part of the carcass at the maximum width position PW of the tire to the thickness F of the outer part of the carcass at the position PF of the outer surface of the tire corresponding to four times the height is , Set as shown in Table 1 below. Although not shown in Table 1, the first step amount SV was set to 7.0 mm and the second step amount SB was set to 5.0 mm.

In the mold used in the manufacture of this Example 1, the difference (CW-RW) was set to 0.8 inches.

[Comparative Example 1]
Comparative Example 1 is a conventional tire. The ratio (W2 / WC), ratio (WE / W2), ratio (D / MW), angle θ, ratio (UR / H) and ratio (E / F) of Comparative Example 1 are shown in Table 1 below. As you can see. Although not shown in Table 1, the first step amount SV was set to 7.0 mm and the second step amount SB was set to 5.0 mm as in Example 1.

In the mold used in the manufacture of Comparative Example 1, the difference (CW-RW) was 1.3 inches.

[mass]
The mass of the tire was measured. The results are shown exponentially in Table 1 below. The smaller the number, the lighter the tire.

[Rolling resistance (RRC)]
Using a rolling resistance tester, the rolling resistance coefficient (RRC) when the prototype tire traveled on the drum at a speed of 80 km / h under the following conditions was measured. The results are shown exponentially in Table 1 below. The smaller the number, the smaller the rolling resistance.
Rim: 15 x 5.0J
Internal pressure: 230 kPa
Vertical load: 2.83kN

[Maneuvering stability]
The prototype tire was incorporated into a rim (size = 15 x 5.0J) and filled with air to adjust the internal pressure of the tire to 250 kPa. The tires were mounted on a test vehicle (displacement 660 cc, front-wheel drive vehicle), and the test vehicle was run on a test course on a dry asphalt road surface. The driver was asked to evaluate the steering stability (sensory evaluation). The results are shown exponentially in Table 1 below. The higher the number, the better the steering stability of the tire.

[Abrasion resistance]
The prototype tire was incorporated into a rim (size = 15 x 5.0J) and filled with air to adjust the internal pressure of the tire to 250 kPa. The tires were mounted on a test vehicle (displacement 660 cc, front-wheel drive vehicle), and the test vehicle was run for 30,000 km on a test course on a dry asphalt road surface. After running, the estimated life of the tire was indexed from the remaining amount of the circumferential groove. The results are shown exponentially in Table 1 below. The higher the number, the better the wear resistance of the tire.

As shown in Table 1, in the examples, the mass and rolling resistance are reduced while suppressing the influence on the wear resistance and the steering stability. From this evaluation result, the superiority of the present invention is clear.

The technique described above for reducing mass and rolling resistance while suppressing the influence on wear resistance and steering stability can be applied to various tires.

2 ... Tires 2r ... Raw tires 4 ... Treads 6 ... Sidewalls 8 ... Clinch 10 ... Beads 12 ... Carcass 14 ... Belts 16 ... Bands 18 ...・ Chafer 20 ・ ・ ・ Inner liner 22 ・ ・ ・ Tread surface 26 ・ ・ ・ Circumferential groove 28 ・ ・ ・ Land 38 ・ ・ ・ Carcasply 42 ・ ・ ・ First reference layer 44 ・ ・ ・ Second reference layer 46 ... Tread part 48 ... Bead part 50 ... Side part 54 ... Mold 58 ... Cavity surface 62 ... Bead molding surface 64 ... Sheet molding surface 66 ... Flange molding surface

Claims (8)

A pair of beads, a carcass that bridges between one bead and the other bead, a belt that is located outside the carcass in the radial direction, a band that is located outside the belt in the radial direction, and a diameter. A tire that is located outside the band in the direction and has a tread that comes into contact with the road surface.
The belt includes a first reference layer and a second reference layer laminated on the radial outer side of the first reference layer and having a width narrower than the width of the first reference layer.
Among the applicable rims in the JATTA standard, the tire is assembled on the applicable rim having the narrowest rim width, the internal pressure of the tire is adjusted to 230 kPa, and no load is applied to the tire.
The ratio of the width of the second reference layer to the maximum width of the carcass is 72% or more and 84% or less.
The ratio of the camber amount at the end of the band to the reference ground contact width is 12% or more and 14% or less.
A tire in which the ground contact width of the ground contact surface obtained by applying a normal load to the tire in the reference state and bringing the tire into contact with the road surface is the reference ground contact width. When the position on the outer surface of the tread corresponding to the axial outer end of the ground contact surface is set as the ground contact reference position, in the reference state,
The tire according to claim 1, wherein the angle formed by the straight line connecting the equator of the tire and the ground contact reference position with respect to the axial direction is 2 ° or more and 5 ° or less. In the reference state,
The contour of the outer surface of the tire has a center on a straight line extending axially through the maximum width position of the tire, and includes a lower arc which is an arc extending inward in the radial direction from the maximum width position.
The tire according to claim 1 or 2, wherein the ratio of the radius of the lower arc to the cross-sectional height of the tire is 48% or less. In the axial direction, the end of the band is located outside the end of the first reference layer.
The distance from the end of the second reference layer to the end of the first reference layer is longer than the distance from the end of the first reference layer to the end of the band.
The tire according to any one of claims 1 to 3, wherein the distance from the end of the first reference layer to the end of the band is 4.0 mm or more and 6.0 mm or less. The difference between the distance from the end of the second reference layer to the end of the first reference layer and the distance from the end of the first reference layer to the end of the band is 1.0 mm or more. The tire according to claim 4, which is 0 mm or less. The maximum width of the tire relative to the thickness of the outer portion of the carcass at the position of the outer surface of the tire, where the height from the bead baseline corresponds to a height of 1.4 times the flange height of the applied rim. The tire according to any one of claims 1 to 5, wherein the ratio of the thickness of the outer portion of the carcass to the position is 60% or less. A pair of beads, a carcass that bridges between one bead and the other bead, a belt that is located outside the carcass in the radial direction, a band that is located outside the belt in the radial direction, and a diameter. A method of manufacturing a tire comprising a tread located outside the band in the direction.
The process of preparing a raw tire, which is in an unvulcanized state of the tire, and
Including the steps of pressurizing and heating the raw tire in the mold.
The mold comprises a cavity surface that shapes the outer surface of the tire on the raw tire.
The cavity surface comprises a pair of flange molded surfaces that shape the outer surface of the bead portion, which is the portion of the tire that is fitted to the rim.
The rim is an applicable rim having the narrowest rim width among the applicable rim widths in the JATTA standard.
A method for manufacturing a tire, wherein the difference between the clip width, which is the axial distance from one flange molding surface to the other flange molding surface, and the rim width of the rim is 0.6 inches or more and 1.2 inches or less. The belt includes a first reference layer and a second reference layer laminated on the radial outer side of the first reference layer and having a width narrower than the width of the first reference layer.
In a reference state in which the tire is assembled on the applicable rim, the internal pressure of the tire is adjusted to 230 kPa, and no load is applied to the tire.
The ratio of the width of the second reference layer to the maximum width of the carcass is 72% or more and 84% or less.
The ratio of the camber amount at the end of the band to the reference ground contact width is 12% or more and 14% or less.
The method for manufacturing a tire according to claim 7, wherein the ground contact width of the ground contact surface obtained by applying a normal load to the tire in the reference state and bringing the tire into contact with the road surface is the reference ground contact width.

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