JP2021116044A - Pneumatic tire, pneumatic tire manufacturing method, and tire vulcanization die - Google Patents

Abstract

To suppress occurrence of abnormal wear and noise, and to improve low fuel consumption performance and driving stability while suppressing decrease in high speed durability.SOLUTION: A pneumatic tire T includes, in a tread 14, a pair of circumferential grooves 34 which are located at an interval in a tire width direction WD with a tire equator plane Cl interposed therebetween. In an unloaded state that the tire is rim-assembled to a normal rim and an internal pressure of 30kPa is charged therein, a concave shape part, which is recessed to tire radial direction inward with respect to a tire width direction outer side over the whole circumference in a tire circumferential direction, is formed in a tire width direction midship part. The concave shape part, which is formed in the tire width direction midship part in the unloaded state that the tire is rim-assembled to the normal rim and the internal pressure of 30kPa is charged therein, becomes a shape expanded to tire radial direction outward with respect to the tire width direction outer side in an unloaded state that the tire is rim-assembled to the normal rim and the internal pressure of 250kPa is charged therein. Tire width direction both ends 45 of the recess, which is formed in the tire width direction midship part of a contour line of the tread 14 in a tire width direction cross section in the unloaded state that the tire is rim-assembled to the normal rim and the internal pressure of 30kPa is charged therein, are positioned in the pair of circumferential grooves 34.SELECTED DRAWING: Figure 1

Description

The present invention relates to a pneumatic tire, a method for manufacturing a pneumatic tire, and a tire vulcanization mold for vulcanizing the pneumatic tire.

For pneumatic tires, the internal pressure of the tire is set high to suppress rolling resistance and improve fuel efficiency, and the belt cord that constitutes the belt is used to improve steering stability. The belt has a high angle so that it can be placed at a large angle with respect to the tire circumference.

As the internal pressure of the tire increases and the angle of the belt increases, the contact length in the circumferential direction at the center of the tire width direction becomes longer, and the amount of heat generated increases. Therefore, heat tends to be accumulated in the central portion in the tire width direction during high-speed running, and high-speed durability may decrease.

In Patent Document 1 below, a pneumatic tire in which the mold surface of the mold facing the tread of the tire is vulcanized and molded by a mold having a profile having a curve formed by a convex curve toward the cavity in its cross-sectional contour. It is disclosed. In the pneumatic tire disclosed in Patent Document 1, a concave portion corresponding to the convex curve of the cavity and convex portions bulging outward in the tire radial direction are formed on both sides of the concave portion in the tire width direction in the tread. Therefore, the ground contact pressure locally increases in the convex portion formed on the tread when the tire touches the ground, which may cause abnormal wear or noise in the vicinity of the convex portion.

Japanese Patent Application Laid-Open No. 10-157410

The present invention has been made in view of such circumstances, and is a pneumatic tire capable of improving fuel efficiency and steering stability while suppressing abnormal wear, noise generation, and deterioration of high-speed durability. It is an object of the present invention to provide a method for manufacturing a tire and a tire vulcanization mold for vulcanizing and molding the pneumatic tire.

The pneumatic tire of the present invention comprises a pair of beads, a pair of sidewalls extending outward in the tire radial direction from the pair of beads, a tread connecting the radial outer ends of the pair of sidewalls, and the tread. The tread is provided with a carcass ply locked by a bead through a sidewall and a belt arranged on the outer peripheral side of the carcass ply in the tread, and the treads are spaced apart in the tire width direction across the tire equatorial plane. In a pneumatic tire having a pair of circumferential grooves arranged in a tire, in a no-load state where the rim is assembled to a regular rim and an internal pressure of 30 kPa is filled, the tire width direction is centered on the outer side of the tire width direction over the entire circumference of the tire width direction. A concave portion that is recessed inward in the tire radial direction is formed, and in a no-load state in which the rim is assembled to the regular rim and the internal pressure of 30 kPa is filled, the concave portion formed in the central portion in the tire width direction becomes the regular rim. In the no-load state where the rim is assembled and the internal pressure of 250 kPa is filled, the shape bulges outward in the tire radial direction from the outside in the tire width direction. Both ends of the recess formed in the contour line of the tread in the cross section in the tire width direction are located in the pair of circumferential grooves.

According to the present invention, it is possible to improve fuel efficiency and steering stability while suppressing the generation of abnormal wear and noise and the deterioration of high-speed durability.

The figure which shows the cross section in the tire width direction of the pneumatic tire of one Embodiment of this invention. Semi-cross-sectional view of a tire vulcanization die for vulcanizing the pneumatic tire of FIG.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a right half cross-sectional view of a pneumatic tire T (hereinafter, also referred to as “tire T”) according to an embodiment cut in a tire width direction cross section including a tire shaft. Since the tire T is a symmetrical tire, the left half is not shown.

In the following description, the first state is a no-load state in which the normal rim is assembled with a rim, an internal pressure of 250 kPa is applied, and no load is applied to the tire T. The second state is a no-load state in which the rim is assembled on a regular rim, an internal pressure of 30 kPa is applied, and no load is applied to the tire T.

A regular rim is a rim defined for each tire in a standard system including a standard on which the tire is based. For example, JATMA is a standard rim, TRA is "Design Rim", and ETRTO is "Measuring Rim". The normal load is the maximum load defined in the above standard.

The tire T shown in FIG. 1 connects a pair of left and right bead 10s, a pair of left and right sidewalls 12 extending outward from the bead 10 in the tire radial direction, and the outer ends of the sidewall 12 in the tire radial direction to form a contact patch. It includes a tread 14 to be configured.

In the figure, reference numeral CL indicates a tire equatorial plane corresponding to the center in the tire width direction. Here, the tire radial direction is a direction perpendicular to the tire rotation axis, and is indicated by reference numeral RD in the figure. The inner side in the tire radial direction is a direction approaching the tire rotation axis, and the outer side in the tire radial direction is a direction away from the tire rotation axis. The tire width direction is a direction parallel to the tire rotation axis, and is indicated by reference numeral WD in the figure. The inside in the tire width direction is a direction approaching the tire equatorial plane CL, and the outside in the tire width direction is a direction away from the tire equatorial plane CL. The tire circumferential direction is a direction on the circumference centered on the tire rotation axis.

A ring-shaped bead core 16 is embedded in each of the pair of beads 10. A bead filler 18 made of hard rubber that tapers toward the outside in the tire radial direction is provided on the outer side of the bead core 16 in the tire radial direction.

The tire T includes a carcass layer 20 extending in a toroidal manner across a pair of beads 10. The carcass layer 20 reaches the bead 10 from the tread 14 via the sidewalls 12 on both sides, and is folded back around the bead core 16 from the inside to the outside in the tire width direction at the bead 10, so that both ends of the carcass layer 20 are locked. ing. The carcass layer 20 is composed of at least one carcass ply formed by arranging carcass cords made of organic fiber cords so as to be substantially perpendicular to the tire circumferential direction and coating them with rubber. In this example, two carcass layers are formed. It is composed of plies.

A belt 24 is provided between the carcass layer 20 and the tread rubber 22 on the outer peripheral side of the carcass layer 20 in the tread 14. The belt 24 is composed of at least two belt plies. In this example, the belt 24 is composed of two belt plies, a first belt ply 26 and a second belt ply 28 arranged on the outer periphery thereof.

Of these, the first belt ply 26 is the widest maximum width belt ply, and its outer end in the tire width direction corresponds to the belt end 24A which is the end in the tire width direction of the belt 24.

The belt plies 26 and 28 include a belt cord such as a steel cord and a coated rubber that covers the belt cord. The belt cords are arranged at an inclination angle of, for example, 10 ° or more and 40 ° or less, preferably 25 ° or more and 40 ° or less with respect to the tire circumferential direction, and are arranged at predetermined intervals in the tire width direction W. The two belt plies 26 and 28 are arranged so that the belt cords intersect with each other.

Further, a belt reinforcing layer 30 formed by spirally winding a cord in the tire circumferential direction is provided on the outer side of the belt 24 in the tire radial direction, that is, between the belt 24 and the tread rubber 22.
Specifically, in the belt reinforcing layer 30, a band-shaped member formed by rubber-coating one organic fiber cord or a plurality of organic fiber cords arranged in a row is spirally wound around the outer circumference of the belt 24 in the tire circumferential direction. It is formed by turning. Examples of the material of the organic fiber cord include nylon fiber, polyester fiber, aramid fiber and the like, and are not particularly limited.

The organic fiber cord constituting the belt reinforcing layer 30 is arranged so that the inclination angle with respect to the tire circumferential direction is 2 degrees or less in the central portion in the tire width direction, and is arranged so as to extend substantially parallel to the tire circumferential direction. There is. Further, the organic fiber cord is arranged so that the inclination angle with respect to the tire circumferential direction is 5 to 30 degrees on the outer side of the concave shape portion 42 provided on the tread 14 in the tire width direction. That is, in the belt reinforcing layer 30, the angle of the organic fiber cord with respect to the tire circumferential direction is larger on the outer side of the concave shape portion 42 in the tire width direction than on the inner side of the concave shape portion 42 in the tire width direction.

On the surface of the tread 14, four circumferential grooves extending in the tire circumferential direction are provided at intervals in the tire width direction WD. The four circumferential grooves are a pair of center main grooves 32 located on both sides of the tire equatorial plane CL and a pair of shoulder main grooves 34 located outside the tire width direction of each center main groove 32. The pair of center main grooves 32 and the pair of shoulder main grooves 34 are recessed inward in the tire radial direction in the first state of no load filled with an internal pressure of 250 kPa and the second state of no load filled with an internal pressure of 30 kPa. It has a groove shape.

The tread 14 has a center land portion 36 located at the center in the tire width direction, a pair of shoulder land portions 38 located at the end in the tire width direction of the tread 14, and a center by the four circumferential grooves 32 and 34. It is divided into a pair of mediated treads 40 located between the tread 36 and the shoulder tread 38.

The tread rubber 22 provided on the tread 14 preferably has a larger rubber thickness in the central portion in the tire width direction than on the outer side in the tire width direction. Specifically, it is preferable that the rubber thickness Tc at the tire equatorial plane CL is larger than the rubber thickness Ts at the shoulder land portion 38. The rubber thicknesses Tc and Ts are the rubber thicknesses in the normal line with respect to the contour lines of the tire equatorial plane CL and the shoulder land portion 38 in a no-load state where the tire internal pressure is 0 kPa and no load is applied to the tire. It is the length of the line segment from the tire surface to the belt reinforcing layer 30 in the normal line.

In the tire T of the present embodiment as described above, in the second state of no load filled with an internal pressure of 30 kPa, the central portion of the tread 14 in the tire width direction is within the tire radial direction from the outside in the tire width direction over the entire circumference in the tire circumferential direction. It has a dented shape.

That is, as shown by the solid line in FIG. 1, the tread 14 has a plurality of land portions (in the present embodiment, a center land portion 36, a pair of mediate land portions 40, and a pair of shoulder land portions) in the central portion in the tire width direction. One concave-shaped portion 42 that is recessed inward in the tire radial direction extending to the portion 38) is formed over the entire circumference in the tire circumferential direction.

The concave portion 42 is formed in the center portion in the width direction of the tread 14 in the second state of no load filled with an internal pressure of 30 kPa, but is outside in the tire width direction in the first state of no load filled with an internal pressure of 250 kPa. The shape bulges outward in the radial direction of the tire. Therefore, the concave portion 42 is clearly distinguished from the circumferential main grooves 32 and 34 having a shape recessed inward in the tire radial direction in the first state and the second state.

In the tire T of the present embodiment, in the second state as shown by the solid line in FIG. 1, a recess corresponding to the concave portion 42 is formed on the contour line of the tread 14 in the cross section in the tire width direction. The dent formed on the contour line of the tread 14 has a concave shape so as to move outward in the tire radial direction as the distance from the tire equatorial surface CL increases, and both ends 45 of the dent in the tire width direction are located in the shoulder main groove 34. ing.

The recessed tire width direction ends 45 formed on the contour line of the tread 14 are tires because the inclination of the contour line of the tire width direction cross section of the tread 14 is outward in the radial direction as it goes outward in the tire width direction. It is a position parallel to the width direction, or a position where the inclination changes inward in the radial direction toward the outside in the tire width direction. As shown in FIG. 1, when the outer side of the dent formed on the contour line of the tread 14 in the tire width direction 45 at both ends in the tire width direction is inclined inward in the tire radial direction toward the outer side in the tire width direction. Both ends 45 of the recess in the tire width direction are located most outward in the tire radial direction in the tread 14.

The contour line is complemented by the openings of the main grooves 32 and 34 so as to smoothly connect the ground contact surface (outer surface) of the tread 14 through the opening ends of the main grooves 32 and 34 in the cross section in the tire width direction. It is a curve that is formed, and is usually a curve in which a plurality of arcs are connected at a contact point having a common tangent line.

Further, from the second state of no load filled with an internal pressure of 30 kPa to the first state of no load filled with an internal pressure of 250 kPa, the tread 14 of the tire T bulges outward in the tire radial direction and is a two-dot chain line in FIG. The shape is as shown by. That is, in the first state, the concave portion 42 formed in the central portion in the width direction of the tread 14 in the second state disappears, and the contour line of the tread 14 of the tire T is shown by the chain double-dashed line in FIG. The closer to the tire equatorial plane CL from the sidewall 12, the more the tire becomes a convex shape that gently bulges outward in the radial direction of the tire.

In the tire T, the internal pressure of the tire at the time of use can be set to an arbitrary pressure, but the contour line of the tread 14 in the no-load state is from the sidewall 12 as shown by the alternate long and short dash line in FIG. It is preferable to set the tire internal pressure so that the tire has a convex shape that gently swells outward in the radial direction toward the tire equatorial plane CL, and it is preferable to fill the tire with an internal pressure of 250 kPa or more before use.

Next, the tire vulcanization die 100 of the present embodiment will be described with reference to FIG.

The tire vulcanization mold 100 is a mold for vulcanizing a green tire (unvulcanized tire) into a shape like the tire T described above, and is attached to a vulcanizer via a container to be a tire vulcanizer. It constitutes.

The tire vulcanization die 100 includes a sector 102, a pair of upper and lower side plates 104 for molding the sidewall 12, and a pair of upper and lower bead rings 106 for molding the bead 10. A cavity 108, which is a molding space for the tire T, is formed inside the sector 102, the pair of upper and lower side plates 104, and the pair of upper and lower bead rings 106.

The sector 102 is a mold having a molding surface forming the tread 14 of the tire T, and is divided into a plurality of (for example, 7) sectors in the tire circumferential direction. The sectors 102 are provided so as to be expandable and displaceable in the tire radial direction (tire radial direction R), and in the mold closed state in which the sectors 102 are arranged at the mold closing positions, they are gathered together to form an annular shape.

The molded surface provided in the sector 102 has a shape in which the central portion in the tire width direction is recessed inward in the tire radial direction over the entire circumference in the tire circumferential direction, and the outer side in the tire width direction is bulged outward in the tire radial direction from the central portion in the tire width direction. Is doing. Specifically, the molding surface provided in the sector 102 is a concave molding surface 110 for molding the concave portion 42 on the tread 14 and a convex molding for molding the outer portion of the concave portion 42 in the tire width direction. A surface 111 and a ridge 112 for molding the center main groove 32 and the shoulder main groove 34 are provided.

The concave molding surface 110 forms a concave contact patch that is recessed inward in the tire radial direction over the center land portion 36, the pair of mediat land portions 40, and the pair of shoulder land portions 38.

In order to manufacture the tire T using the vulcanization die 100 described above, the unvulcanized tire is set in the tire vulcanization die 100, the mold is closed, and then the bladder 114 arranged inside is expanded. By holding the tire at a predetermined internal pressure (for example, 1600 kPa), the green tire is pressed against the inner surface of the mold and held in a heated state. As a result, the green tire is vulcanized and molded, and the tire T as shown in FIG. 1 is obtained. The green tire can be molded by using a known method.

In the tire T of the present embodiment described above, the central portion of the tread 14 in the second state of no load, which is assembled on a regular rim and filled with an internal pressure of 30 kPa, is inward in the tire radial direction over the entire circumference in the tire circumferential direction. It has a dented shape. Therefore, as in the third state described above, it is possible to suppress an increase in the contact length in the central portion in the tire width direction when the tire T is further filled with the tire internal pressure from the second state. As a result, even if the tire internal pressure is set high or the belt cords constituting the belt plies 26 and 28 are greatly inclined with respect to the tire circumferential direction, the amount of heat generated in the central portion in the tire width direction is less likely to increase, resulting in high-speed durability. It is possible to improve fuel efficiency and steering stability while suppressing deterioration of performance.

Moreover, in the tire T of the present embodiment, both ends 45 of the recess formed in the contour line of the tread 14 in the tire width direction in the second state are located in the shoulder main groove 34. Therefore, both ends of the concave portion 42 in the tire width direction do not come into contact with the ground when the tire T is used, and abnormal wear of the concave portion 42 in the vicinity of both ends in the tire width direction can be suppressed and noise can be suppressed. can.

Further, in the present embodiment, the angle of the organic fiber cord forming the belt reinforcing layer 30 with respect to the tire circumferential direction is larger on the outer side of the concave shape portion 42 in the tire width direction than on the inner side of the concave shape portion 42 in the tire width direction. Therefore, it is possible to prevent the restraining force of the belt reinforcing layer 30 from becoming excessively large on the outer side in the tire width direction, and the ground contact length on the outer side in the tire width direction is not excessively shortened to maintain a good ground contact shape. Can be done.

Further, in the present embodiment, the rubber thickness Tc at the center of the tread 14 in the tire width direction is made larger than the rubber thickness Ts outside the tire width direction, and the maximum belt width Wb of the belt 24 is set to the maximum tire width Wc in the first state. The tire internal pressure during use should be 75% or more, the tire internal pressure during use should be 250 kPa or more, and the belt cords constituting the belt plies 26 and 28 should be arranged at an inclination angle of 25 ° or more and 40 ° or less with respect to the tire circumferential direction. Therefore, fuel efficiency and steering stability can be improved.

(Change example)
The above embodiments are presented as examples and are not intended to limit the scope of the invention. This novel embodiment can be implemented in various other embodiments, and various omissions, replacements, and changes can be made without departing from the gist of the invention.
For example, in the above-described embodiment, a pair of recesses formed in the contour line of the tread 14 corresponding to the concave portion 42 in the second state at both ends 45 in the tire width direction at positions farthest from the tire equatorial plane CL. The case where the tires are arranged in the shoulder main groove 34 of the tire is described. For example, both ends 45 of the recess in the tire width direction are arranged in the pair of center main grooves 32, or one center main groove 32 and the tire equatorial plane CL are arranged. Both ends 45 in the tire width direction of the recess may be arranged in the shoulder main groove 34 provided on the opposite side of the sandwich.

T ... tire, 10 ... bead, 12 ... sidewall, 14 ... tread, 16 ... bead core, 18 ... bead filler, 20 ... carcass layer, 22 ... tread rubber, 24 ... belt, 26 ... 1st belt ply, 28 ... first 2 belt ply, 30 ... belt reinforcement layer, 32 ... center main groove, 34 ... center main groove, 36 ... center land part, 38 ... shoulder land part, 40 ... mediate land part, 42 ... concave shape part, 45 ... dented Both ends in the tire width direction

Claims (6)

A pair of beads, a pair of sidewalls extending outward in the tire radial direction from the pair of beads, a tread connecting the radial outer ends of the pair of sidewalls, and a bead from the tread via the sidewall. A stopped carcass ply and a belt arranged on the outer peripheral side of the carcass ply in the tread are provided.
The tread is a pneumatic tire provided with a pair of circumferential grooves arranged at intervals in the tire width direction across the equator surface of the tire.
In a no-load state in which the rim is assembled to a regular rim and the internal pressure of 30 kPa is filled, a concave portion is formed in the central portion in the tire width direction, which is recessed inward in the tire radial direction from the outside in the tire width direction over the entire circumference in the tire circumferential direction.
In a no-load state in which the rim is assembled on a regular rim and filled with an internal pressure of 30 kPa, the concave portion formed in the central portion in the tire width direction is assembled on a regular rim and filled with an internal pressure of 250 kPa. The shape bulges outward from the outside in the width direction to the outside in the tire radial direction.
In a no-load state in which the rim is assembled on a regular rim and the internal pressure of 30 kPa is filled, both ends of the dent formed on the contour line of the tread in the tire width direction cross section are inflated in the pair of circumferential grooves. tire. The pneumatic tire according to claim 1, wherein both ends of the recess in the tire width direction are located in a circumferential groove located at a position farthest from the equatorial plane of the tire. A belt reinforcing layer having a fiber cord is provided on the outer side of the belt in the tire radial direction.
The pneumatic tire according to claim 1 or 2, wherein the angle of the fiber cord with respect to the tire circumferential direction is larger on the outer side in the tire width direction than on the inner side in the tire width direction of the concave portion. The pneumatic tire according to any one of claims 1 to 3, wherein the thickness of the central portion of the tread in the tire width direction is larger than the thickness of the outer side in the tire width direction. In the tire vulcanization die for vulcanizing and molding a pneumatic tire according to any one of claims 1 to 4.
A tire sulfide mold comprising a tread molding die for molding the tread, and the molding surface of the tread molding die is a tire sulfide mold in which the central portion in the tire width direction is recessed inward in the tire radial direction over the entire circumference in the tire circumferential direction. A method for manufacturing a pneumatic tire in which an unvulcanized tire is set in the mold according to claim 5 and the unvulcanized tire is vulcanized and molded.

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