Tire manufacturing apparatus, tire manufacturing method, and tire

Abstract

To effectively suppress occurrence of groove cracks.SOLUTION: A tire manufacturing apparatus has a paint transfer roller 60 comprising: a paint supply part 65 for supplying paint P; a transfer part 70 having a cylindrical shape, for receiving the paint P supplied from the paint supply part 65 on an outer circumferential surface 71 and transferring the paint P on the outer circumferential surface 71 to a surface on which the paint P is applied; a rotation part 80 having a cylindrical shape, and disposed integrally with the transfer part 70 at least on one side of the transfer part 70 in an axial direction of the transfer part 70; and a support part 90 for rotatably supporting the transfer part 70 and the rotation part 80 in a circumferential direction around an axis of the transfer part 70. A maximum radius RMaR [mm] of the rotation part 80 and a maximum radius RMaP [mm] of the transfer part 70 satisfy a relation of RMaR>RMaP.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a tire manufacturing apparatus, a tire manufacturing method, and a tire. [Background technology]

[0002] Some conventional pneumatic tires have a paint or resin layer on the surface of the tread. For example, in the pneumatic tire described in Patent Document 1, a colored rubber paint is transferred to the top surface of the tread rubber with a transfer roller, thereby providing a tire identification line on the tread surface that can identify the product number of the tread rubber. In addition, in the tire described in Patent Document 2, a urethane resin layer is provided that coats the surface of the rubber layer to form the tire outer surface, thereby improving the crack resistance of the tire surface. In addition, in the tire described in Patent Document 3, the outer surface of the tire body is coated with a thin layer made of rubber containing 5 to 70 phr of EPT or halogenated butyl, thereby preventing the occurrence of cracks on the tire outer surface. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 11-059125 [Patent Document 2] Japanese Patent Application Laid-Open No. 2017-105406 [Patent Document 3] Japanese Patent Application Publication No. 02-045202 Summary of the Invention [Problem to be solved by the invention]

[0004] One example of cracks that occur in tires is groove cracks, which are cracks that occur at the bottom of the main grooves. In addition to rubber degradation due to ozone and other factors, repeated stresses are likely to occur at the bottom of the main grooves when the vehicle is running, which makes groove cracks more likely to occur. One method for suppressing groove cracks is to apply a stress-relieving paint that can relieve stress to the bottom of the main grooves.

[0005] However, when groove cracks are suppressed by applying a stress relaxation paint to the groove bottoms of the main grooves, if there is a large variation in the coating thickness in the coating region, stress tends to concentrate in the thin film portion, and there is a risk that groove cracks may not be suppressed effectively even if the stress relaxation paint is applied. For this reason, there is room for improvement in the method of suppressing groove cracks by applying a stress relaxation paint to the groove bottoms of the main grooves of a tire, from the perspective of suppressing groove cracks more effectively.

[0006] The present invention has been made in view of the above, and has an object to provide a tire manufacturing apparatus, a tire manufacturing method, and a tire that can effectively suppress the occurrence of groove cracks. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems and achieve the object, a tire manufacturing apparatus according to the present invention has a paint transfer roller including: a paint supply unit that supplies paint; a transfer unit that is cylindrical in shape and receives the paint supplied from the paint supply unit on its outer peripheral surface and transfers the paint on the outer peripheral surface to a surface to be coated with the paint; a rotating unit that is cylindrical in shape and is disposed integrally with the transfer unit on at least one side of the transfer unit in the axial direction of the transfer unit; and a support unit that supports the transfer unit and the rotating unit so as to be rotatable in a circumferential direction around the axis of the transfer unit; MaR [mm] and the maximum radius R of the transfer part MaP [mm] is R MaR >R MaP The above relationship is satisfied.

[0008] In the tire manufacturing apparatus, the maximum radius R of the rotating portion MaR [mm] and the maximum radius R of the transfer part MaP The relationship with [mm] is 0.04≦R MaR -R MaP It is preferable that the ratio is in the range of ≦1.2.

[0009] In the tire building apparatus, the rotating part preferably has an uneven portion on its outer circumferential surface, in which unevenness is repeated in the circumferential direction of the rotating part.

[0010] In the tire manufacturing apparatus, the rotating portion has a radius at the position of the convex portion of the uneven portion that is equal to or smaller than the maximum radius R of the rotating portion. MaR [mm], and the radius at the position of the concave portion of the concave-convex portion is the minimum radius R of the rotating portion. MiR [mm], and the maximum radius R of the rotating part MaR [mm] and minimum radius R MiR [mm] and the maximum radius R of the transfer part MaP It is preferable that [mm] satisfies the following formula (1).

[0011]

number

[0012] In the tire building apparatus, the rotating units are preferably disposed on both sides of the transfer unit in the axial direction of the transfer unit.

[0013] In the tire building apparatus, the transfer unit is preferably provided with a paint straightening unit having an uneven outer peripheral surface.

[0014] In the tire manufacturing apparatus, the transfer unit is provided with a paint straightening unit having an uneven shape on its outer circumferential surface, and the convex portions of the paint straightening unit have a maximum radius R of the transfer unit. MaP [mm], and the concave portion in the paint straightening portion has the minimum radius R MiP [mm], and the maximum radius R of the transfer partMaP [mm] and minimum radius R MiP [mm] and the maximum radius R of the rotating part MaR [mm] and minimum radius R MiR It is preferable that [mm] satisfies the following formulas (2) and (3).

[0015]

number

[0016]

number

[0017] In the tire manufacturing apparatus, the total width W of the rotating part and the transfer part in the axial direction of the transfer part is S [mm] and the width W of the transfer part in the axial direction of the transfer part P [mm] and the relationship is 0.5≦W P / W S It is preferably in the range of ≦0.95.

[0018] In order to solve the above-mentioned problems and achieve the object, a tire manufacturing method according to the present invention includes a paint supply unit that supplies paint, a transfer unit that is cylindrical in shape and receives the paint supplied from the paint supply unit on its outer peripheral surface and transfers the paint on the outer peripheral surface onto a surface to be coated with the paint, a rotating unit that is cylindrical in shape and is disposed integrally with the transfer unit on at least one side of the transfer unit in the axial direction of the transfer unit, and a support unit that supports the transfer unit and the rotating unit so as to be rotatable in a circumferential direction around an axis of the transfer unit, and MaR [mm] and the maximum radius R of the transfer part MaP [mm] and R MaR >R MaPThe tire manufacturing method involves applying the paint to the surface of unvulcanized tread rubber by a paint transfer roller that satisfies the relationship above, and is characterized in that the paint is applied by bringing the rotating part into contact with the surface of the tread rubber and rotating the rotating part and the transfer part together, while transferring the paint received by the outer peripheral surface of the transfer part to the surface of the tread rubber.

[0019] In the tire manufacturing method, it is preferable that the temperature of the tread rubber in the step of transferring the paint using the paint transfer roller is within a range of 50° C. or more and 120° C. or less.

[0020] Furthermore, in the above-mentioned tire manufacturing method, it is preferable that the paint contains a diene or non-diene rubber material as a main component, as well as carbon, a vulcanizing agent, and a vulcanization accelerator, and that the rubber component is dissolved in an organic solvent containing a hydrocarbon as a main component at a concentration within the range of 5 wt% to 35 wt%.

[0021] In the tire manufacturing method, the viscosity of the paint in the paint supply section is preferably within a range of 500 [mPa·s] to 20,000 [mPa·s].

[0022] Furthermore, in the above-described tire manufacturing method, it is preferable that the paint transfer roller is disposed downstream of an extruder that extrudes the tread rubber in a moving direction of the tread rubber extruded from the extruder, and that the paint is applied by bringing the rotating part into contact with the surface of the tread rubber extruded from the extruder.

[0023] In order to solve the above-mentioned problems and achieve the object, a tire according to the present invention is a tire comprising main grooves formed in a tread surface, and a stress relaxation layer disposed at the bottom of the main groove, wherein the stress relaxation layer comprises: a paint supply portion that supplies paint; a transfer portion that is cylindrical in shape and receives the paint supplied from the paint supply portion on its outer peripheral surface and transfers the paint on the outer peripheral surface to a surface to be coated with the paint; a rotating portion that is cylindrical in shape and disposed integrally with the transfer portion on at least one side of the transfer portion in the axial direction of the transfer portion; and a support portion that supports the transfer portion and the rotating portion so as to be rotatable in a circumferential direction around the axis of the transfer portion; MaR [mm] and the maximum radius R of the transfer part MaP [mm] and R MaR >R MaP The paint is applied by contacting the rotating part of a paint transfer roller that satisfies the relationship above with the surface of unvulcanized tread rubber, rotating the rotating part and the transfer part together, and transferring the paint received on the outer peripheral surface of the transfer part to the surface of the tread rubber. [Effects of the Invention]

[0024] The tire building apparatus, tire building method, and tire according to the present invention have the effect of being able to effectively suppress the occurrence of groove cracks. [Brief explanation of the drawings]

[0025] [Figure 1] FIG. 1 is a tire meridian cross-sectional view showing a main part of a pneumatic tire according to a first embodiment. [Figure 2] FIG. 2 is a detailed view of part A in FIG. [Figure 3] FIG. 3 is a perspective view of a paint transfer roller provided in the tire building apparatus. [Figure 4] FIG. 4 is a perspective view of the paint transfer roller shown in FIG. 3 with the support portion omitted. [Figure 5] FIG. 5 is an explanatory diagram of the transfer unit and the rotating unit shown in FIG. 4 as viewed in the axial direction. [Figure 6]FIG. 6 is an explanatory diagram of the position of the paint transfer roller relative to the tread rubber extruder. [Figure 7] FIG. 7 is a view taken along the arrow CC in FIG. [Figure 8] FIG. 8 is an explanatory diagram showing the state in which paint is applied to the tread rubber by a paint transfer roller. [Figure 9] FIG. 9 is a cross-sectional view taken along line DD in FIG. [Figure 10] FIG. 10 is a perspective view of a paint transfer roller provided in the tire manufacturing apparatus according to the second embodiment. [Figure 11] FIG. 11 is an explanatory diagram of the transfer unit and the rotating unit shown in FIG. 10 as viewed in the axial direction. [Figure 12] FIG. 12 is a detailed view of part E in FIG. [Figure 13] FIG. 13 is a perspective view of a transfer unit and a rotating unit of a paint transfer roller provided in a tire manufacturing apparatus according to a third embodiment. [Figure 14] FIG. 14 is an explanatory diagram of the transfer unit and the rotating unit shown in FIG. 13 as viewed in the axial direction. [Figure 15] FIG. 15 is a detailed view of part F in FIG. [Figure 16] FIG. 16 is a plan view of a transfer portion formed in a wave shape, which is a modification of the first embodiment. [Figure 17] FIG. 17 is an explanatory diagram showing a modified example of the first embodiment, in which the rotating unit and the transfer unit are arranged on one side. [Figure 18] FIG. 18 is an explanatory diagram showing a modified example of the first embodiment, in which transfer units are arranged on both sides of a rotating unit. [Figure 19] FIG. 19 is an explanatory diagram showing a modified example of the second embodiment, in which triangular projections are arranged at intervals. [Figure 20] FIG. 20 is an explanatory diagram showing a modified example of the second embodiment, in which trapezoidal convex portions are arranged adjacent to each other. [Figure 21] FIG. 21 is an explanatory diagram showing a modified example of the second embodiment, in which trapezoidal convex portions are arranged at intervals. [Figure 22]FIG. 22 is a schematic diagram showing a modified example of the third embodiment, in which convex portions and concave portions extending while inclining in the circumferential direction with respect to the axial direction of the transfer portion are alternately arranged in a paint rectifying portion. [Figure 23] FIG. 23 is a schematic diagram showing a modified example of the third embodiment, in which the paint flow regulating portion is formed by bending the convex portion and the concave portion in the circumferential direction of the transfer portion. [Figure 24] FIG. 24 is a schematic diagram showing a modified example of the third embodiment, in which convex portions and concave portions are alternately arranged on both sides of the center in the axial direction of the transfer portion. [Figure 25] FIG. 25 is a schematic diagram showing a modified example of the third embodiment, in which the recessed portion is formed in a circular shape. [Figure 26] FIG. 26 is a schematic diagram showing a modified example of the third embodiment, in which a paint rectifying portion is formed with a recess extending in the circumferential direction of the transfer portion. [Figure 27] FIG. 27 is a schematic diagram showing a modified example of the third embodiment, in which convex portions and concave portions extending in the circumferential direction of the transfer portion are arranged alternately in the axial direction of the transfer portion. [Figure 28] FIG. 28 is a table showing the results of a performance evaluation test of pneumatic tires. DETAILED DESCRIPTION OF THE INVENTION

[0026] Hereinafter, embodiments of a tire manufacturing apparatus, a tire manufacturing method, and a tire according to the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to these embodiments. Furthermore, the components in the following embodiments include those that are replaceable and easily conceivable by a person skilled in the art, or those that are substantially the same.

[0027] [Embodiment 1] In the following description, a pneumatic tire 1 will be used as an example of a tire according to the present invention. The pneumatic tire 1, which is an example of a tire, can be filled with air, an inert gas such as nitrogen, or other gases.

[0028] In the following description, the tire radial direction refers to the direction perpendicular to the tire rotational axis (not shown), which is the rotational axis of the pneumatic tire 1, the tire radial inner side refers to the side toward the tire rotational axis in the tire radial direction, and the tire radial outer side refers to the side away from the tire rotational axis in the tire radial direction. The tire circumferential direction refers to the direction around the tire rotational axis as the central axis. The tire width direction refers to the direction parallel to the tire rotational axis, the tire width inner side refers to the side toward the tire equatorial plane (tire equator line) CL in the tire width direction, and the tire width outer side refers to the side away from the tire equatorial plane CL in the tire width direction. The tire equatorial plane CL is a plane that is perpendicular to the tire rotational axis and passes through the center of the tire width of the pneumatic tire 1, and the tire equatorial plane CL coincides in position in the tire width direction with the tire width centerline, which is the center position of the pneumatic tire 1 in the tire width direction. The tire width is the width in the tire width direction between the portions located outermost in the tire width direction, that is, the distance in the tire width direction between the portions farthest from the tire equatorial plane CL. The tire equator line refers to a line that is on the tire equatorial plane CL and extends along the tire circumferential direction of the pneumatic tire 1. In the following description, the tire meridian cross section refers to a cross section of the tire cut by a plane that includes the tire rotation axis.

[0029] [Pneumatic tires] FIG. 1 is a tire meridian cross-section showing a main portion of a pneumatic tire 1 according to a first embodiment. When viewed in a tire meridian cross-section, the pneumatic tire 1 according to the first embodiment has a tread portion 2 disposed on the outermost portion in the tire radial direction, and the tread portion 2 has tread rubber 4 made of a rubber composition. The surface of the tread portion 2, i.e., the portion that comes into contact with the road surface when a vehicle (not shown) equipped with the pneumatic tire 1 is traveling, is formed as a tread surface 3, and the tread surface 3 constitutes part of the contour of the pneumatic tire 1. The tread portion 2 has a plurality of main grooves 30 formed on the tread surface 3 extending in the tire circumferential direction, and in the first embodiment, four main grooves 30 are arranged side by side in the tire width direction. The surface of the tread portion 2 is partitioned by the plurality of main grooves 30 into a plurality of land portions 20 arranged side by side in the tire width direction.

[0030] The main grooves 30 referred to here are grooves that are required to display a wear indicator as defined by JATMA. The main grooves 30 have a groove width of 4.0 mm or more and a groove depth of 6.2 mm or more. The main grooves 30 may extend linearly along the tire circumferential direction, or may be formed in a zigzag pattern by repeatedly bending or curving in the tire width direction while extending in the tire circumferential direction. The number of main grooves 30 may be any number other than four.

[0031] In addition to the main grooves 30 extending in the tire circumferential direction, lug grooves (not shown) extending in the tire width direction are provided on the tread surface 3. The tread surface 3 may also be provided with circumferential narrow grooves (not shown) that extend in the tire circumferential direction with a groove width narrower than that of the main grooves 30, sipes (not shown) formed in the tread surface 3 in the form of cuts, and the like.

[0032] Shoulder portions 5 are located at both outer ends of the tread portion 2 in the tire width direction, and sidewall portions 8 are arranged on the tire radially inward sides of the shoulder portions 5. That is, the sidewall portions 8 are arranged on both sides of the tread portion 2 in the tire width direction. In other words, the sidewall portions 8 are arranged in two locations on both sides of the pneumatic tire 1 in the tire width direction, and form the outermost exposed portions of the pneumatic tire 1 in the tire width direction.

[0033] Bead portions 10 are located on the tire radially inward side of each sidewall portion 8 located on both sides in the tire width direction. Like the sidewall portions 8, the bead portions 10 are arranged in two locations on both sides of the tire equatorial plane CL; that is, a pair of bead portions 10 are arranged on both sides of the tire equatorial plane CL in the tire width direction. Each bead portion 10 is provided with a bead core 11, and a bead filler 12 is provided on the tire radially outer side of the bead core 11. The bead core 11 is an annular member formed by bundling bead wires, which are steel wires, into a circular shape, and the bead filler 12 is a rubber member located on the tire radially outer side of the bead core 11.

[0034] Further, a belt layer 14 is disposed in the tread portion 2. The belt layer 14 has a multi-layer structure in which a plurality of belts 141, 142 and a belt cover 143 are laminated, and in the first embodiment, two layers of belts 141, 142 are laminated. The belts 141, 142 constituting the belt layer 14 are formed by coating a plurality of belt cords made of steel or organic fiber material such as polyester, rayon, or nylon with coating rubber and rolling them, and the belt angle, defined as the inclination angle of the belt cords with respect to the tire circumferential direction, is within a predetermined range (for example, 20° to 55°). The two layers of belts 141, 142 have different belt angles. Therefore, the belt layer 14 has a so-called cross-ply structure in which the two layers of belts 141, 142 are laminated with the inclination directions of the belt cords crossing each other. That is, the two-layer belts 141 and 142 are provided as so-called cross belts in which the belt cords of the respective belts 141 and 142 are arranged in a direction that crosses each other.

[0035] The belt cover 143 is formed by covering a plurality of belt cover cords made of steel or organic fiber material such as polyester, rayon, or nylon with coating rubber and rolling the covered cords, and the belt angle, defined as the inclination angle of the belt cover cords with respect to the tire circumferential direction, is within a predetermined range (for example, 0° to 10°). The belt cover 143 is, for example, a strip material formed by covering one or more belt cover cords with coating rubber, and is formed by winding this strip material spirally around the tire rotation axis from the outer side in the tire radial direction of the two-layered belts 141 and 142.

[0036] A carcass layer 13 containing radial ply cords is provided continuously on the tire radially inward side of the belt layer 14 and on the tire equatorial plane CL side of the sidewall portion 8. Therefore, the pneumatic tire 1 according to the first embodiment is configured as a so-called radial tire. The carcass layer 13 has a single-layer structure consisting of one carcass ply or a multi-layer structure consisting of a plurality of carcass plies stacked together, and is toroidally spanned between a pair of bead portions 10 arranged on both sides in the tire width direction to form the framework of the tire.

[0037] Specifically, the carcass layer 13 is disposed from one of a pair of bead portions 10 located on both sides in the tire width direction to the other bead portion 10, and is wound back along the bead core 11 at the bead portion 10 toward the outside in the tire width direction so as to enclose the bead core 11 and the bead filler 12. The bead filler 12 is made of a rubber material that is disposed in a space formed on the outside in the tire radial direction of the bead core 11 by folding back the carcass layer 13 at the bead portion 10 in this manner. The belt layer 14 is disposed on the outside in the tire radial direction of the portion of the carcass layer 13 that is positioned in the tread portion 2 and that is stretched between the pair of bead portions 10 in this manner. The carcass ply of the carcass layer 13 is formed by covering a plurality of carcass cords made of steel or an organic fiber material such as aramid, nylon, polyester, or rayon with coating rubber and rolling the coated cords. The carcass cords constituting the carcass ply are arranged in parallel at a certain angle relative to the tire circumferential direction, along the tire meridian direction.

[0038] In the bead portion 10, a rim cushion rubber 17 that forms the contact surface of the bead portion 10 with the rim flange is disposed on the tire radially inner side and tire widthwise outer side of the bead core 11 and the turned-up portion of the carcass layer 13. Furthermore, an inner liner 16 is formed along the carcass layer 13 on the inner side of the carcass layer 13 or on the inner side of the carcass layer 13 in the pneumatic tire 1. The inner liner 16 forms a tire inner surface 18, which is the inner surface of the pneumatic tire 1.

[0039] [Stress relief layer] Fig. 2 is a detailed view of part A in Fig. 1. A stress relief layer 40 that suppresses groove cracks is disposed on the surface of the groove bottom 31 of the main grooves 30 formed on the tread surface 3. The stress relief layer 40 is disposed in each of the plurality of main grooves 30 formed on the tread surface 3.

[0040] The stress relief layer 40 is primarily composed of a diene rubber material and a non-diene rubber material, and contains carbon, a vulcanizing agent, and a vulcanization accelerator. The diene rubber is selected from the group consisting of diene polymers including natural rubber and synthetic diene rubber (isoprene rubber (IR), butadiene rubber (BR), styrene butadiene rubber (SBR), acrylonitrile butadiene rubber (NBR), chloroprene rubber (CR), etc.). The non-diene rubber is selected from the group consisting of non-diene polymers including synthetic non-diene rubber (butyl rubber (IIR), ethylene propylene rubber (EPDM, EPM), urethane rubber, silicone rubber, etc.). To ensure weather resistance, the stress relief layer 40 preferably does not contain a resin component.

[0041] It is also preferable that the stress relaxation layer 40 does not contain an antioxidant. This configuration is preferable in that in a configuration in which a paint P (see FIG. 8) for providing the stress relaxation layer 40 in the main groove 30, as described below, is applied to the unvulcanized tread rubber 4 and a vulcanization molding process is performed, transfer of the stress relaxation layer 40 to the mold is suppressed and coloring of the stress relaxation layer 40 is suppressed.

[0042] However, the present invention is not limited to this, and the stress relaxation layer 40 may contain an antioxidant. In this case, it is preferable to not use an amine-based antioxidant, but to compound another antioxidant (for example, a phenol-based, phosphorous-based, organic thioacid-based, or benzimidazole-based antioxidant) in an amount of 0.1 to 5 parts by weight per 100 parts by weight of the rubber component.

[0043] Furthermore, the modulus Mc of the stress relaxation layer 40 at 100°C and 100% elongation is in the range of 0.3 MPa≦Mc≦2.8 MPa, preferably 0.4 MPa≦Mc≦2.3 MPa, more preferably 0.5 MPa≦Mc≦1.8 MPa, and even more preferably 0.6 MPa≦Mc≦1.5 MPa. The lower limit prevents damage to the stress relaxation layer 40 due to foreign matter, such as pebbles, entering the main groove 30 during tire rolling, while the upper limit prevents uneven wear of the land portion 20 caused by an excessively large modulus Mc of the stress relaxation layer 40.

[0044] Furthermore, the modulus Mc of the stress relaxation layer 40 at 100°C and 100% elongation is in the range of 0.45≦Mc / Mt≦1.15, and preferably 0.50≦Mc / Mt≦1.10, relative to the modulus Mt of the tread rubber 4 at 100°C and 100% elongation. For example, in a summer tire, the ratio Mc / Mt is preferably in the range of 0.50≦Mc / Mt≦0.90, and in a winter tire, the ratio Mc / Mt is preferably in the range of 0.70≦Mc / Mt≦1.10.

[0045] The moduli Mc and Mt are measured by a tensile test using a dumbbell-shaped test piece at a temperature of 100°C in accordance with JIS K6251 (using a No. 3 dumbbell). The modulus Mt of the tread rubber 4 is measured as the modulus of the rubber material of the portion that comes into surface contact with the stress relaxation layer 40.

[0046] Furthermore, the rubber hardness Hc of the stress relaxation layer 40, relative to the rubber hardness Ht of the tread rubber 4, is in the range of 0≦Ht−Hc≦32, and preferably in the range of 2≦Ht−Hc≦27. The above lower limit ensures the rubber hardness Hc of the stress relaxation layer 40, and prevents damage to the stress relaxation layer 40 due to foreign matter, such as pebbles, entering the main groove 30 while the tire is rolling. The above upper limit also prevents uneven wear of the land portions 20 caused by the rubber hardness Hc of the stress relaxation layer 40 being too high.

[0047] The rubber hardnesses Hc and Ht are measured at a temperature of 20°C in accordance with JIS K6253. The rubber hardness Ht of the tread rubber 4 is measured as the rubber hardness of the rubber material that makes surface contact with the stress relaxation layer 40 among the rubber materials that make up the tread rubber 4.

[0048] Furthermore, the tensile strength TBc of the stress relaxation layer 40, relative to the tensile strength TBt of the tread rubber 4, is in the range of 0.30≦TBc / TBt≦0.90, and preferably 0.35≦TBc / TBt≦0.88. The above lower limit ensures the tensile strength TBc of the stress relaxation layer 40, thereby ensuring the fracture durability of the stress relaxation layer 40 against strain during tire rolling. The above upper limit prevents peeling of the stress relaxation layer 40 caused by an excessively high tensile strength TBc of the stress relaxation layer 40. It is also preferable that the tensile strength TBc of the stress relaxation layer 40, relative to the tensile strength TBt of the tread rubber 4, is in the range of 3 MPa≦TBt-TBc≦15 MPa.

[0049] The tensile strengths TBc and TBt are measured by a tensile test using a dumbbell-shaped test piece at room temperature (20°C) in accordance with JIS K6251 (using a No. 3 dumbbell). The tensile strength TBt of the tread rubber 4 is measured as the tensile strength of the rubber material at the portion that comes into surface contact with the stress relaxation layer 40.

[0050] The stress relaxation layer 40 extends continuously in the tire circumferential direction along the main groove 30. As shown in FIG. 2, the stress relaxation layer 40 extends not only to the groove bottom 31 of the main groove 30 but also to the groove wall 32 and groove opening of the main groove 30, covering the entire inner wall of the main groove 30. Furthermore, as shown in FIG. 2, in the tire meridian cross section, the stress relaxation layer 40 bends at the edge of the land portion 20 and extends to the tread of the land portion 20 to cover the edge of the land portion 20. In this case, the edge of the land portion 20 is the part where the tread of the land portion 20 and the groove wall 32 of the main groove 30 intersect. Furthermore, the stress relaxation layer 40 has an edge on the tread of the land portion 20, i.e., the ground contact area.

[0051] In this way, the stress relaxation layer 40 extends continuously from the groove bottom 31 of the main groove 30 to the tread surface of the land portion 20, covering the edge portion of the land portion 20, so that the adhesion area of ​​the stress relaxation layer 40 to the tread rubber 4 can be increased compared to when the stress relaxation layer 40 is formed only on the groove bottom 31 and groove wall 32. This makes it possible to suppress peeling of the stress relaxation layer 40 when the tire rolls.

[0052] Furthermore, the width Wc of the stress relaxation layer 40 at the tread surface of the land portion 20 is in the range of 0.06≦Wc / Hg, and preferably 0.10≦Wc / Hg, relative to the groove depth Hg of the main groove 30. The above lower limit ensures an appropriate width Wc of the stress relaxation layer 40 at the tread surface of the land portion 20, thereby appropriately suppressing peeling of the stress relaxation layer 40. That is, the deeper the main groove 30, the greater the amount of deformation of the main groove 30 during tire rolling, so the greater the groove depth Hg of the main groove 30, the greater the width Wc of the stress relaxation layer 40 is set. There is no particular upper limit to the ratio Wc / Hg, but it is subject to constraints depending on other conditions.

[0053] The width Wc of the stress relaxation layer 40 at the tread surface of the land portion 20 is measured as the distance in the tire width direction from the edge of the land portion 20 to the edge of the stress relaxation layer 40 in the tire meridian cross section. In addition, in a configuration in which the edge portion of the land portion 20 has a chamfered portion, the width Wc of the stress relaxation layer 40 is measured using the intersection of an extension line of the groove wall 32 of the main groove 30 and an extension line of the tread surface of the land portion 20 as an endpoint.

[0054] Furthermore, the total width ΣWc of the stress relaxation layer 40 on the tread surface of one land portion 20 is in the range of ΣWc / Wb≦0.70, and preferably in the range of ΣWc / Wb≦0.68, relative to the contact width Wb of the land portion 20. Therefore, the exposed width of the tread rubber 4 on the tread surface of the land portion 20 is ensured to be 30% or more of the contact width Wb of the land portion 20. The above upper limit ensures the exposed area of ​​the tread rubber 4 on the tread surface of the land portion 20, thereby ensuring the wet performance of the tire from a new tire until the stress relaxation layer 40 is worn away. There is no particular restriction on the lower limit of the ratio ΣWc / Wb, but it is subject to constraints depending on other conditions. As a result, compared to a configuration in which the stress relaxation layer 40 is installed only on the groove bottom 31 and groove wall 32 of the main groove 30, or a configuration in which the stress relaxation layer 40 is arranged to cover the entire tread surface of the land portion 20, it is possible to effectively achieve both peel resistance of the stress relaxation layer 40 and wet performance of the pneumatic tire 1.

[0055] The width Wc of the stress relaxation layer 40 at the tread surface of the land portion 20 is in the range of 2.0≦Wc / Gc1≦70, and preferably 2.3≦Wc / Gc1≦65, relative to the thickness Gc1 of the stress relaxation layer 40 at the groove bottom 31 of the main groove 30. The thickness Gc1 of the stress relaxation layer 40 at the groove bottom 31 of the main groove 30 is in the range of 0.030 mm≦Gc1≦0.400 mm, and preferably 0.040 mm≦Gc1≦0.380 mm. This optimizes the thickness Gc1 of the stress relaxation layer 40 at the groove bottom 31 of the main groove 30, and suppresses peeling of the stress relaxation layer 40 during tire rolling.

[0056] The thickness Gc1 of the stress relief layer 40 at the groove bottom 31 of the main groove 30 is measured on the groove center line (not shown) of the main groove 30.

[0057] Further, in the stress relaxation layer 40, the minimum value Gc2_min of the thickness Gc2 of the stress relaxation layer 40 in a predetermined region of the groove wall 32 of the main groove 30 is thinner than the thickness Gc1 of the stress relaxation layer 40 at the groove bottom 31 of the main groove 30 (Gc2_min < Gc1). With such a configuration, since the stress relaxation layer 40 has a thin portion on the groove wall 32 of the main groove 30, peeling of the stress relaxation layer 40 at the groove bottom 31 of the main groove 30 is suppressed. Further, for the stress relaxation layer 40, the ratio Gc2_min / Gc1 is in the range of Gc2_min / Gc1 ≤ 0.60, and preferably in the range of Gc2_min / Gc1 ≤ 0.40. Also, it is preferable that the minimum value Gc2_min of the thickness Gc2 of the stress relaxation layer 40 is 0.003 [mm] or more.

[0058] The thickness Gc2 of the stress relaxation layer 40 on the groove wall of the main groove 30 is measured in a region from 40 [%] to 60 [%] of the groove depth Hg from the groove bottom 31 of the main groove 30.

[0059] Further, in the stress relaxation layer 40, the minimum value Gc2_min of the thickness Gc2 of the stress relaxation layer 40 on the groove wall 32 of the main groove 30 is thinner than the thickness Gc3 of the stress relaxation layer 40 on the tread surface of the land portion 20 (Gc2_min < Gc3). With such a configuration, since the stress relaxation layer 40 has a thin portion on the groove wall 32 of the main groove 30, in the process of abrasion of the portion of the stress relaxation layer 40 exposed on the tread surface of the land portion 20 during wear progress, the situation where the entire stress relaxation layer 40 peels from the groove wall 32 to the groove bottom 31 of the main groove 30 is suppressed. Further, for the stress relaxation layer 40, the ratio Gc2_min / Gc3 is in the range of Gc2_min / Gc3 ≤ 0.60, and preferably in the range of Gc2_min / Gc3 ≤ 0.40.

[0060] Further, for the stress relaxation layer 40, the thickness Gc3 of the stress relaxation layer 40 on the tread surface of the land portion 20 is in the range of 0.030 [mm] ≤ Gc3 ≤ 0.400 [mm], and preferably in the range of 0.040 [mm] ≤ Gc3 ≤ 0.380 [mm]. Thereby, deterioration of the performance of the tread surface 3 due to grounding of the stress relaxation layer 40 is suppressed.

[0061] The thickness Gc3 of the stress relaxation layer 40 at the tread surface of the land portion 20 is measured as the maximum thickness of the portion of the stress relaxation layer 40 exposed at the tread surface of the land portion 20.

[0062] [Paint transfer roller] The stress relaxation layer 40 disposed in the main groove 30 of the pneumatic tire 1 as described above is provided by applying a paint that will become the base of the stress relaxation layer 40 to the tread rubber 4 before vulcanization molding during the manufacture of the pneumatic tire 1. The paint that will become the base of the stress relaxation layer 40 is applied by a paint transfer roller 60 provided in a tire manufacturing apparatus 50 used in the manufacture of the pneumatic tire 1. Next, the paint transfer roller 60 will be described.

[0063] Fig. 3 is a perspective view of the paint transfer roller 60 provided in the tire building apparatus 50. Fig. 4 is a perspective view of the paint transfer roller 60 shown in Fig. 3 with the support unit 90 omitted. The paint transfer roller 60 includes a paint supply unit 65, a transfer unit 70, a rotating unit 80, and a support unit 90. In the following description, the upper side of the paint transfer roller 60 in its normal usage state will also be referred to as the upper side of the paint transfer roller 60, and the lower side of the paint transfer roller 60 in its normal usage state will also be referred to as the lower side of the paint transfer roller 60.

[0064] The paint supply unit 65 supplies the paint P (see FIG. 8) to be transferred by the paint transfer roller 60 to the transfer unit 70. A paint storage unit 66 that stores the paint P therein is connected to the paint supply unit 65. The paint storage unit 66 is formed in a so-called bottle shape that stores a liquid therein, and is connected to the upper side of the paint supply unit 65 with the opening facing downwards. This allows the paint P stored inside the paint storage unit 66 to be supplied to the paint supply unit 65 by gravity. The paint supply unit 65 supplies the paint P supplied from the paint storage unit 66 to the transfer unit 70.

[0065] The paint storage unit 66 is detachably connected to the paint supply unit 65. Therefore, when the paint P inside the paint storage unit 66 runs out, the paint storage unit 66 connected to the paint supply unit 65 can be replaced with another paint storage unit 66 in which the paint P is stored.

[0066] The transfer unit 70 is formed in a substantially cylindrical shape. The transfer unit 70 is capable of receiving the paint P (see FIG. 8) supplied from the paint supply unit 65 on an outer peripheral surface 71 of the transfer unit 70, and is capable of transferring the paint P received on the outer peripheral surface 71 to a surface to which the paint P is to be applied.

[0067] The rotating unit 80 is formed in a substantially cylindrical shape. The rotating unit 80 is disposed integrally with the transfer unit 70 on at least one side of the transfer unit 70 in the axial direction of the cylindrical transfer unit 70. In other words, the rotating unit 80 is disposed on at least one side of the transfer unit 70 in the axial direction of the transfer unit 70, in a position and orientation where the axis of the rotating unit 80 coincides with the axis of the transfer unit 70. In the first embodiment, the rotating units 80 are disposed on both sides of the transfer unit 70 in the axial direction of the transfer unit 70, and are each provided integrally with the transfer unit 70. The two rotating units 80 disposed on both sides of the transfer unit 70 have the same maximum diameter.

[0068] The support unit 90 supports the transfer unit 70 and the rotating unit 80 so that they can rotate freely in the circumferential direction around the axis of the transfer unit 70. More specifically, a rotating shaft 95, which is a shaft-shaped member that passes through the axis of the transfer unit 70 and the rotating unit 80, is inserted into the transfer unit 70 and the rotating unit 80, and the transfer unit 70 and the rotating unit 80 are rotatable about the rotating shaft 95. That is, the transfer unit 70 and the rotating unit 80 each have an insertion hole (not shown) through which the rotating shaft 95 passes, formed at a position including the axis, and the rotating shaft 95 passes through the insertion hole of the transfer unit 70 and the rotating unit 80. This allows the transfer unit 70 and the rotating unit 80 to rotate integrally about the rotating shaft 95. The length of the rotating shaft 95 is longer than the combined width of the transfer unit 70 and the rotating unit 80 in the axial direction of the transfer unit 70. Therefore, the rotation shaft 95 protrudes near both ends in the longitudinal direction from the rotating units 80 arranged on both sides of the transfer unit 70.

[0069] The support unit 90 has a shaft support unit 91 that supports the rotation shaft 95 and a supply unit support unit 92 that supports the paint supply unit 65. The shaft support unit 91 supports the portion of the rotation shaft 95 that protrudes from the rotating units 80 that are arranged on both sides of the transfer unit 70. For this reason, the shaft support units 91 are arranged at two locations on both sides in the width direction of the two rotating units 80 and the transfer unit 70 combined. Each of the two shaft support units 91 is formed in a plate-like shape and is arranged with the thickness direction of the plate oriented in the extension direction of the rotation shaft 95. A support hole (not shown) through which the rotation shaft 95 passes and which supports the rotation shaft 95 is formed. The two shaft support units 91 support the portion of the rotation shaft 95 that protrudes from the rotation unit 80 by inserting the portion of the rotation shaft 95 that protrudes from the rotation unit 80 into the support hole of each of the shaft support units 91.

[0070] The supply unit support part 92 is disposed between the two shaft support parts 91 at a position outside the outer periphery of the transfer unit 70 or the rotation unit 80 in the radial direction of the transfer unit 70 or the rotation unit 80. In this way, the supply unit support part 92 connects the two shaft support parts 91. The paint supply unit 65 is attached to the supply unit support part 92 disposed between the two shaft support parts 91 in this way. Therefore, the paint supply unit 65 is disposed at a position facing the outer periphery 71 of the transfer unit 70.

[0071] The transfer unit 70 and the rotating unit 80, which are integrally and rotatably supported by the support unit 90, have a total width W S [mm] and the width W of the transfer unit 70 in the axial direction of the transfer unit 70 P [mm] and the relationship is 0.5≦W P / W S It is within the range of ≦0.95.

[0072] The total width W of the rotating part 80 and the transfer part 70 S [mm] and the width W of the transfer unit 70 in the axial direction of the transfer unit 70 P [mm] and the relationship is 0.6≦W P / W S It is preferable that the width W of the transfer part 70 in the axial direction of the transfer part 70 is in the range of ≦0.9. P [mm] is the width W of the sheet-like tread rubber 4 (see FIG. 7) to which the paint P is applied using the paint transfer roller 60. T In this case, the width W of the sheet-like tread rubber 4 T The relationship is 0.03≦W P / W T ≦0.12, and 0.04≦W P / W T It is more preferable that it is in the range of ≦0.1.

[0073] In addition, the total width W of the rotating part 80 and the transfer part 70 S [mm] is preferably in the range of 4 [mm] to 40 [mm], and the width W of the transfer section 70 PThe diameter of the rotating part 80 is preferably within a range of 2 mm to 36 mm. The diameter of the rotating part 80 is preferably within a range of 8 mm to 80 mm.

[0074] 5 is an explanatory diagram of the transfer unit 70 and the rotating unit 80 shown in FIG. 4 as viewed in the axial direction. The transfer unit 70 and the rotating unit 80 are each formed in a cylindrical shape, and the diameter of the rotating unit 80 is larger than the diameter of the transfer unit 70. In other words, the transfer unit 70 and the rotating unit 80 are formed such that the maximum radius R of the rotating unit 80 is larger than the maximum radius R of the rotating unit 80. MaR [mm] and the maximum radius R of the transfer part 70 MaP [mm] and R MaR >R MaP The transfer unit 70 and the rotating unit 80 have a maximum radius R MaR [mm] and the maximum radius R of the transfer part 70 MaP The relationship with [mm] is 0.04≦R MaR -R MaP The maximum radius R of the rotating part 80 is within the range of ≦1.2. MaR [mm] and the maximum radius R of the transfer part 70 MaP The relationship with [mm] is 0.06≦R MaR -R MaP It is preferably in the range of ≦1.0.

[0075] The paint transfer roller 60 has an outlet cross-sectional area S [mm 2 ] is the maximum radius R of the rotating part 80 MaR [mm] and the width W of the transfer section 70 P [mm] and the total width W of the rotating unit 80 and the transfer unit 70 S [mm] and (2πR MaR / 360)×W P ≦S≦(2πR MaR / 4)×W S Preferably, the size is in the range of

[0076] [Tire manufacturing method] Next, a method for manufacturing a tire using the tire manufacturing apparatus 50 equipped with the paint transfer roller 60 configured as described above will be described. When manufacturing a pneumatic tire 1, first, each of the components, such as the tread rubber 4 and the rubber constituting the sidewall portion 8, the inner liner 16, the rim cushion rubber 17, the carcass layer 13, the belt layer 14, the bead core 11, and the bead filler 12, is manufactured. After each of the components constituting the pneumatic tire 1 is manufactured, these are bonded together and assembled to manufacture a so-called green tire, which is the prototype of the pneumatic tire 1. Thereafter, the green tire is vulcanized and molded using a mold (not shown) and a bladder (not shown), thereby molding it into the shape of the pneumatic tire 1. As a result, each groove, such as the main groove 30, is formed in the tread surface 3 of the pneumatic tire 1 by the mold.

[0077] Here, the pneumatic tire 1 according to the first embodiment has a stress relaxation layer 40 disposed in the main groove 30. The stress relaxation layer 40 is disposed in the main groove 30 by applying a material to become the stress relaxation layer 40 as paint P (see FIG. 8 ) to the tread rubber 4 before it is bonded to other members, and then bonding the tread rubber 4 to other members and performing vulcanization molding.

[0078] FIG. 6 is an explanatory diagram of the position of the paint transfer roller 60 relative to the extruder 100 for the tread rubber 4. FIG. 7 is a view seen from the CC arrow in FIG. 6. FIG. 8 is an explanatory diagram showing the state in which the paint transfer roller 60 is applying paint P to the tread rubber 4. FIG. 9 is a cross-sectional view taken along the line DD in FIG. 8. When applying the material that will become the stress relaxation layer 40 as paint P to the tread rubber 4, the paint transfer roller 60 is used to apply the paint P to the sheet-like tread rubber 4 before it is laminated with other components. For this reason, the paint transfer roller 60 that applies the paint P is positioned downstream of the extruder 100 in the direction of movement of the tread rubber 4 extruded from the extruder 100 that extrudes the tread rubber 4. More preferably, the paint transfer roller 60 is positioned between the extrusion process and the cooling process of the tread rubber 4.

[0079] That is, the rubber material that constitutes the tread rubber 4 is formed into a sheet shape and extruded from the extruder 100, and the paint transfer roller 60 is positioned downstream of the extruder 100 in the movement direction of the tread rubber 4, thereby applying the paint P to the sheet-like tread rubber 4 formed by the extruder 100. The sheet-like tread rubber 4 is extruded from the extruder 100 with its thickness direction oriented vertically, and the paint transfer roller 60 is positioned on the upper surface side of the tread rubber 4, thereby applying the paint P to the upper surface of the tread rubber 4.

[0080] The paint P applied to the tread rubber 4 by the paint transfer roller 60 is mainly composed of a diene-based or non-diene-based rubber material and also contains carbon, a vulcanizing agent, and a vulcanization accelerator, and the rubber component is dissolved in an organic solvent mainly composed of hydrocarbons at a concentration within the range of 5 wt% to 35 wt%.

[0081] The viscosity of the paint P in the paint supply unit 65 of the paint transfer roller 60 is within the range of 500 mPa·s to 20,000 mPa·s. The viscosity of the paint P is measured, for example, by the viscosity measurement method using a single-cylindrical rotational viscometer in accordance with Chapter 9 of JIS Z 8803, "Method for measuring viscosity of liquids." The viscosity of the paint P can be adjusted, for example, by providing a heating mechanism in the paint supply unit 65, or by adjusting the compounding and dissolution concentration of the seed rubber, thickener, or diluent.

[0082] The paint transfer roller 60 is arranged on the upper surface side of the tread rubber 4, with the side where the paint supply unit 65 is located facing up and the side where the transfer unit 70 and the rotating unit 80 are located facing up. Furthermore, the paint transfer roller 60 is arranged so that the extension direction of the axis of the transfer unit 70 and the rotating unit 80, i.e., the extension direction of the rotating shaft 95, is parallel to the surface of the tread rubber 4 and perpendicular to the moving direction of the tread rubber 4 extruded from the extruder 100.

[0083] Furthermore, the paint transfer roller 60 is disposed at a position corresponding to the main groove 30 in which the stress relaxation layer 40 is to be disposed in the tread rubber 4. In other words, the paint transfer roller 60 is disposed at a position in the tread rubber 4 extruded from the extruder 100 where the main groove 30 is to be formed after vulcanization molding. Therefore, if the pneumatic tire 1 has a plurality of main grooves 30 in which the stress relaxation layer 40 is to be disposed, a plurality of paint transfer rollers 60 are disposed at positions corresponding to the respective main grooves 30 in which the stress relaxation layer 40 is to be disposed.

[0084] The maximum radius R of the rotating part 80 of the paint transfer roller 60 MaR [mm] is the maximum radius R of the transfer part 70 MaP [mm], the paint transfer roller 60 disposed on the upper surface side of the tread rubber 4 brings the rotating part 80 into contact with the surface of the tread rubber 4. When the rotating part 80 is in contact with the surface of the tread rubber 4, the maximum radius R MaP [mm] is the maximum radius R of the rotating part 80 MaR The transfer portion 70 having a diameter smaller than 1 / 4 [mm] is spaced apart from the surface of the tread rubber 4.

[0085] The extruder 100 sequentially extrudes the sheet-shaped tread rubber 4, and the sheet-shaped tread rubber 4 is sequentially delivered from the extruder 100. The paint transfer roller 60 brings the rotating part 80 into contact with the surface of the tread rubber 4 downstream of the extruder 100, causing the rotating part 80 to rotate about the rotation axis 95 due to the frictional force between the rotating part 80 and the tread rubber 4. As a result, the transfer part 70 also rotates integrally with the rotating part 80 about the rotation axis 95.

[0086] A paint supply unit 65 is disposed above the transfer unit 70, and the paint supply unit 65 is capable of supplying the paint P stored in the paint storage unit 66 to the outer peripheral surface 71 of the transfer unit 70. Therefore, the paint P supplied from the paint supply unit 65 at an upper position in the transfer unit 70 moves downward as the outer peripheral surface 71 of the transfer unit 70 rotates integrally with the rotating unit 80. In other words, the paint P received by the outer peripheral surface 71 of the transfer unit 70 from the paint supply unit 65 moves toward the side where the tread rubber 4 is located as the transfer unit 70 rotates.

[0087] As the transfer unit 70 rotates, the paint P moves toward the side where the tread rubber 4 is located, and when it reaches the position of the tread rubber 4, it adheres to the surface of the tread rubber 4. As a result, the paint P received by the outer peripheral surface 71 of the transfer unit 70 is transferred to the surface of the tread rubber 4 and applied to the surface of the tread rubber 4.

[0088] At this time, the transfer part 70 does not come into contact with the tread rubber 4, and the maximum radius R of the rotating part 80 MaR [mm] and the maximum radius R of the transfer part 70 MaP Due to the difference between the distance [mm] and the distance [mm], the paint P is transferred to the tread rubber 4 while the outer peripheral surface 71 of the transfer unit 70 is kept spaced apart from the surface of the tread rubber 4. As a result, the paint applied by being transferred to the tread rubber 4 is applied at a constant thickness.

[0089] As the sheet-like tread rubber 4 is sequentially extruded and sent out from the extruder 100, the paint transfer roller 60, whose rotating part 80 comes into contact with the surface of the tread rubber 4, continues to rotate both the rotating part 80 and the transfer part 70 as the tread rubber 4 moves. As a result, the paint P supplied from the paint supply part 65 to the transfer part 70 and received on the outer peripheral surface 71 is continuously transferred to the surface of the tread rubber 4 as the tread rubber 4 moves, and is continuously applied. In this way, by bringing the rotating part 80 into contact with the surface of the tread rubber 4 extruded from the extruder 100, the paint transfer roller 60 rotates the rotating part 80 and the transfer part 70 together as the tread rubber 4 moves, and continuously applies the paint P to the surface of the tread rubber 4.

[0090] In this way, in the process of extruding the tread rubber 4 from the extruder 100 and transferring the paint P using the paint transfer roller 60, the temperature of the tread rubber 4 when transferring the paint P is within a range of 50°C or higher and 120°C or lower. Furthermore, it is more preferable that the temperature of the tread rubber 4 when transferring the paint P is within a range of 65°C or higher and 110°C or lower.

[0091] The tread rubber 4 to which the paint P has been applied by the paint transfer roller 60 is then bonded to other components and then vulcanized. The paint P applied to the tread rubber 4 by the paint transfer roller 60 is applied to positions in the tread rubber 4 corresponding to positions where the main grooves 30 are formed, so when the tread rubber 4 is bonded to other components and vulcanized, the paint P covers the main grooves 30. Because the paint P is made of the material of the stress relaxation layer 40, the paint P covering the main grooves 30 becomes the stress relaxation layer 40 and is disposed in the main grooves 30.

[0092] [Effects of the First Embodiment] As described above, in the first embodiment, the paint transfer roller 60 for providing the stress relaxation layer 40 in the main groove 30 of the pneumatic tire 1 has the transfer portion 70 for transferring the paint P and the rotating portion 80 that rotates integrally with the transfer portion 70, and the maximum radius R of the rotating portion 80 is MaR [mm] and the maximum radius R of the transfer part 70 MaP [mm] is R MaR >R MaP The relationship between the paint P and the paint transfer roller 60 is satisfied. As a result, when the paint P is applied to the tread rubber 4 by the paint transfer roller 60, the rotating part 80 is brought into contact with the tread rubber 4, and the paint P supplied from the paint supply part 65 to the transfer part 70 can be applied to the tread rubber 4 while the rotating part 80 and the transfer part 70 rotate integrally, without the transfer part 70 coming into contact with the tread rubber 4. This makes it possible to keep the thickness of the paint P applied to the tread rubber 4 constant, and to prevent the paint P applied to the tread rubber 4 from causing thin portions in the stress relaxation layer 40 arranged in the main grooves 30. Therefore, groove cracks caused by stress concentration occurring in thin portions of the stress relaxation layer 40 can be prevented. As a result, the occurrence of groove cracks can be effectively prevented.

[0093] In addition, the maximum radius R of the rotating part 80 MaR [mm] and the maximum radius R of the transfer part 70 MaP The relationship with [mm] is 0.04≦R MaR -R MaP≦1.2, the thickness of the paint P applied to the tread rubber 4 can be made appropriate. MaR [mm] and the maximum radius R of the transfer part 70 MaP [mm] and R MaR -R MaP If the value is less than 0.04, the maximum radius R of the rotating portion 80 MaR [mm] and the maximum radius R of the transfer part 70 MaP Because the difference is too small, there is a risk that the distance between the outer peripheral surface 71 of the transfer portion 70 and the tread rubber 4 will become too small. In this case, it may be difficult to ensure the thickness of the paint P applied to the tread rubber 4, or the transfer portion 70 may be more likely to come into contact with the tread rubber 4.

[0094] In addition, the maximum radius R of the rotating part 80 MaR [mm] and the maximum radius R of the transfer part 70 MaP [mm] and R MaR -R MaP If it is >1.2, the maximum radius R of the rotating part 80 MaR [mm] and the maximum radius R of the transfer part 70 MaP [mm] is too large, there is a risk that the amount of paint P received by the outer peripheral surface 71 of the transfer unit 70 from the paint supply unit 65 will be too great. In this case, the paint P received by the outer peripheral surface 71 of the transfer unit 70 will drip due to the excessive amount of paint P while moving to the position of the tread rubber 4 due to the rotation of the transfer unit 70, and there is a risk that the thickness of the paint P applied to the tread rubber 4 will vary.

[0095] In contrast, the maximum radius R of the rotating portion 80 MaR [mm] and the maximum radius R of the transfer part 70 MaP The relationship with [mm] is 0.04≦R MaR -R MaPIf the ratio is within the range of ≦1.2, it is possible to ensure the thickness of the paint P applied to the tread rubber 4 while preventing dripping caused by an excessive amount of paint P received on the outer peripheral surface 71 of the transfer unit 70 from the paint supply unit 65. Therefore, it is possible to make the thickness of the stress relaxation layer 40 an appropriate and constant thickness, and it is possible to prevent groove cracks caused by stress concentration that occurs in thin portions of the stress relaxation layer 40. As a result, it is possible to effectively prevent the occurrence of groove cracks.

[0096] Furthermore, because the rotating units 80 are disposed on both sides of the transfer unit 70 in the axial direction of the transfer unit 70, the distance between the transfer unit 70 and the tread rubber 4 when applying the paint P can be kept constant along the axial direction of the transfer unit 70. This makes it possible to keep the thickness of the paint P applied to the tread rubber 4 constant, and therefore the thickness of the stress relaxation layer 40 constant, thereby suppressing groove cracks caused by stress concentration that occurs in thin portions of the stress relaxation layer 40. As a result, the occurrence of groove cracks can be effectively suppressed.

[0097] In addition, the total width W of the rotating part 80 and the transfer part 70 in the axial direction of the transfer part 70 is S [mm] and the width W of the transfer unit 70 in the axial direction of the transfer unit 70 P [mm] and the relationship is 0.5≦W P / W S ≦0.95, it is possible to suppress the occurrence of fluctuations in the thickness of the stress relaxation layer 40. In other words, the total width W S [mm] and width W of transfer section 70 P [mm] and W P / W S If it is <0.5, the width of the rotating portion 80 is too wide, and therefore, when applying the paint P to the tread rubber 4, there is a risk that too much of the tread rubber 4 will be pressed by the rotating portion 80 that comes into contact with the tread rubber 4. In this case, rubber flow will be induced around the main groove 30 during vulcanization molding, which will cause fluctuations in the thickness of the paint P and may make the thickness of the stress relaxation layer 40 more likely to fluctuate.

[0098] In addition, the total width W of the rotating part 80 and the transfer part 70 S [mm] and width W of transfer section 70 P [mm] and W P / W S If it is >0.95, the width of the rotating portion 80 is too narrow, which may make it difficult to ensure a sufficient contact area between the rotating portion 80 and the tread rubber 4. In this case, slippage occurs between the tread rubber 4 and the rotating portion 80, which rotates as the tread rubber 4 moves due to contact with the tread rubber 4, making it difficult for the rotation of the rotating portion 80 and the transfer portion 70 to follow the movement of the tread rubber 4, which may make it easier for variations to occur in the thickness of the paint P applied to the tread rubber 4.

[0099] In contrast, the total width W S [mm] and the width W of the transfer section 70 P [mm] and the relationship is 0.5≦W P / W S If the ratio is within the range of ≦0.95, the width of the rotating portion 80 can be set to an appropriate size, so that the thickness of the paint P applied to the tread rubber 4 can be made constant, and fluctuations in the thickness of the stress relaxation layer 40 can be suppressed. As a result, the occurrence of groove cracks can be effectively suppressed.

[0100] Furthermore, because the temperature of the tread rubber 4 in the process of transferring the paint P using the paint transfer roller 60 is within the range of 50°C or higher and 120°C or lower, the thickness of the paint P applied to the tread rubber 4 can be made constant. In other words, if the temperature of the tread rubber 4 in the process of transferring the paint P is less than 50°C, the temperature of the tread rubber 4 is too low, so the paint P applied to the tread rubber 4 takes a long time to dry, and there is a risk that the paint P will drip and cause variations in the thickness of the paint P. Furthermore, if the temperature of the tread rubber 4 in the process of transferring the paint P is higher than 120°C, the temperature of the tread rubber 4 is too high, so there is a risk that the solvent contained in the paint P will boil, and when the solvent boils, bubbles will form in the paint P, causing unevenness and resulting in variations in the thickness of the paint P applied to the tread rubber 4.

[0101] In contrast, if the temperature of the tread rubber 4 during the process of transferring the paint P is within the range of 50°C or higher and 120°C or lower, the paint P can be dried in a short time while suppressing boiling of the solvent contained in the paint P applied to the tread rubber 4. This prevents variations in the thickness of the paint P applied to the tread rubber 4 and makes it possible to keep the thickness of the paint P constant, thereby preventing variations in the thickness of the stress relaxation layer 40. As a result, the occurrence of groove cracks can be effectively suppressed.

[0102] Furthermore, by using a rubber material as the main component of the paint P, the stickiness of the paint P can promote transfer from the transfer portion 70 to the tread rubber 4, and also enable vulcanization adhesion between the paint P and the tread rubber 4. This reduces fluctuations in the thickness of the paint P during vulcanization molding, and suppresses fluctuations in the thickness of the stress relaxation layer 40.

[0103] Furthermore, since the concentration of the rubber component in the organic solvent of the paint P is within the range of 5 wt% to 35 wt%, the thickness of the paint P applied to the tread rubber 4 can be made constant. In other words, if the concentration of the rubber component in the organic solvent is less than 5 wt%, the concentration of the rubber component is too low, which may result in a large difference in the thickness of the paint P before and after drying, which may make the paint P more susceptible to thickness variations. Furthermore, if the concentration of the rubber component in the organic solvent is higher than 35 wt%, the concentration of the rubber component is too high, which may make the organic solvent and the rubber component more susceptible to dispersion, which may make the paint P more susceptible to thickness variations.

[0104] In contrast, when the concentration of the rubber component relative to the organic solvent is within the range of 5 wt% to 35 wt%, dispersion of the organic solvent and the rubber component is suppressed, and changes in the thickness of the paint P before and after drying can be suppressed. This suppresses variations in the thickness of the paint P applied to the tread rubber 4, and the thickness of the paint P can be kept constant, thereby suppressing variations in the thickness of the stress relaxation layer 40. As a result, the occurrence of groove cracks can be effectively suppressed.

[0105] Furthermore, because the viscosity of the paint P is within the range of 500 [mPa·s] to 20,000 [mPa·s], the thickness of the paint P can be made constant while ensuring the applicability of the paint P. In other words, if the viscosity of the paint P is less than 500 [mPa·s], the viscosity is too low, and there is a risk that the paint P will drip when or after application to the tread rubber 4, causing variations in the thickness of the paint P. Furthermore, if the viscosity of the paint P is higher than 20,000 [mPa·s], the viscosity is too high, and there is a risk that the paint P will clog the paint transfer roller 60, significantly reducing the applicability of the paint P.

[0106] In contrast, when the viscosity of the paint P is within the range of 500 [mPa·s] to 20,000 [mPa·s], clogging of the paint P on the paint transfer roller 60 can be suppressed while fluctuations in the thickness of the paint P due to dripping of the paint P can be suppressed. This ensures the applicability of the paint P while keeping the thickness of the paint P constant, thereby suppressing fluctuations in the thickness of the stress relaxation layer 40. As a result, the occurrence of groove cracks can be effectively suppressed.

[0107] Furthermore, because the paint transfer roller 60 is disposed downstream of the extruder 100 in the direction of movement of the tread rubber 4 extruded from the extruder 100, the paint P can be applied to the tread rubber 4 while it is at a high temperature, and the paint P can be applied without reheating the tread rubber 4. Furthermore, by disposing the paint transfer roller 60 downstream of the extruder 100, the paint P can be applied by bringing the rotating part 80 into contact with the surface of the tread rubber 4 extruded from the extruder 100, without providing a mechanism for moving the tread rubber 4 or the paint transfer roller 60 to apply the paint P to the tread rubber 4. As a result, a pneumatic tire 1 that is capable of suppressing the occurrence of groove cracks can be manufactured at low cost.

[0108] [Embodiment 2] The second embodiment has a configuration similar to that of the first embodiment, but is characterized in that an uneven portion 82 is provided on the rotating portion 80 of the paint transfer roller 60. Since the other configurations are the same as those of the first embodiment, the description thereof will be omitted and the same reference numerals will be used.

[0109] Fig. 10 is a perspective view of a paint transfer roller 60 provided in a tire building apparatus 50 according to embodiment 2. Fig. 11 is an explanatory view of the transfer unit 70 and the rotating unit 80 shown in Fig. 10 as viewed in the axial direction. In embodiment 2, the paint transfer roller 60 provided in the tire building apparatus 50 also includes a paint supply unit 65, the transfer unit 70, the rotating unit 80, and a support unit 90. In embodiment 2, the rotating unit 80 has an uneven portion 82 on its outer circumferential surface 81, where unevenness is repeated in the circumferential direction of the rotating unit 80.

[0110] The uneven portion 82 provided on the outer peripheral surface 81 of the rotating portion 80 is formed by alternately arranging convex portions 83 that protrude outward in the radial direction of the rotating portion 80 and concave portions 84 that are recessed toward the outside in the radial direction of the rotating portion 80 in the circumferential direction of the rotating portion 80. In the uneven portion 82, the pitch between adjacent convex portions 83 or the pitch between adjacent concave portions 84 is constant. The uneven portion 82 is formed by, for example, knurling.

[0111] In the second embodiment, when viewed in the axial direction of the rotating part 80, the convex part 83 is formed in a generally triangular shape with one corner pointing outward in the radial direction of the rotating part 80, and the concave-convex part 82 is formed by arranging a plurality of convex parts 83 of generally triangular shape adjacent to each other in the circumferential direction of the rotating part 80. Therefore, the concave part 84 of the concave-convex part 82 is located between adjacent convex parts 83 of generally triangular shape.

[0112] Fig. 12 is a detailed view of part E in Fig. 11. The rotating part 80 has an uneven part 82 on its outer circumferential surface 81. The radius at the position of the convex part 83 of the uneven part 82 is equal to the maximum radius R MaR The radius of the rotating part 80 at the position of the recessed part 84 of the uneven part 82 is the minimum radius R MiR In this way, the rotating part 80 having the uneven part 82 has a maximum radius R MaR [mm] and minimum radius R MiR [mm] and the maximum radius R of the transfer part 70 MaP [mm] satisfies the following formula (1).

[0113]

number

[0114] The maximum radius R of the rotating part 80 MaR [mm] and minimum radius R MiR [mm] and R MaR -R MiR The maximum radius R of the transfer part 70 is preferably in the range of 0.1 mm to 1.0 mm. MaP [mm] is the minimum radius R of the rotating part 80 MiR It is preferable that the thickness is smaller than [mm].

[0115] In addition, the pitch P of the uneven portion 82 of the rotating portion 80 R [mm / piece], for example, the pitch P between adjacent convex portions 83 R [mm / piece] is the number of convex portions 83 that one rotating portion 80 has, Z RWhen the number of the concave and convex portions 82 of the rotating portion 80 is [number of pieces], it is expressed by the following formula (4). R [mm / piece] is the value calculated by the following formula (4) when 0.1≦P R ≦10, and 0.2≦P R It is more preferable that it is in the range of ≦8.

[0116]

number

[0117] The uneven portion 82 of the rotating portion 80 has a maximum radius R MaR [mm] and minimum radius R MiR [mm] and R MaR -R MiR And Pitch P R [mm / piece] ratio is 1≦P R / (R MaR -R MiR )≦10.

[0118] In the second embodiment as well, when manufacturing the pneumatic tire 1, the paint transfer roller 60 is arranged downstream of the extruder 100 (see FIG. 6). The paint transfer roller 60 brings the rotating part 80 into contact with the surface of the tread rubber 4 extruded from the extruder 100, causing the rotating part 80 and the transfer part 70 to rotate integrally, and transfers the paint P received from the paint supply part 65 on the outer peripheral surface 71 of the transfer part 70 from the transfer part 70 to the surface of the tread rubber 4. In this way, the paint P is applied to the surface of the tread rubber 4.

[0119] At this time, since the rotating part 80 has an uneven portion 82 formed on its outer peripheral surface 81, the uneven portion 82 causes the rotating part 80 to come into contact with the surface of the tread rubber 4 with high friction. Therefore, when the rotating part 80 rotates in conjunction with the movement of the tread rubber 4 extruded from the extruder 100, the rotating part 80 can rotate in accordance with the movement of the tread rubber 4 without slippage occurring between the rotating part 80 and the tread rubber 4.

[0120] As a result, the transfer part 70, which rotates integrally with the rotating part 80, can also rotate following the movement of the tread rubber 4, so that the paint P transferred from the transfer part 70 to the surface of the tread rubber 4 is transferred at a constant thickness from the transfer part 70. Therefore, the paint P is applied to the surface of the tread rubber 4 at a constant thickness by the paint transfer roller 60.

[0121] [Effects of the second embodiment] As described above, in the second embodiment, the rotating portion 80 of the paint transfer roller 60 has the uneven portion 82 on the outer peripheral surface 81. This makes it possible to prevent slippage between the rotating portion 80 and the tread rubber 4 when the rotating portion 80 is rotated by contacting the surface of the tread rubber 4. This allows the rotating portion 80 to rotate in accordance with the movement of the tread rubber 4, and the transfer portion 70, which rotates integrally with the rotating portion 80, can also rotate in accordance with the movement of the tread rubber 4. This allows the thickness of the paint P transferred from the transfer portion 70 to the surface of the tread rubber 4 to be constant, and the paint P can be applied to the tread rubber 4 at a constant thickness, thereby preventing variations in the thickness of the stress relaxation layer 40 (see FIG. 2). As a result, groove cracks can be effectively prevented.

[0122] In addition, the maximum radius R of the rotating part 80 MaR [mm] and minimum radius R MiR [mm] and the maximum radius R of the transfer part 70 MaP [mm] is the maximum radius R of the rotating part 80 in the radial direction of the transfer part 70 to satisfy the above formula (1). MaR[mm] and the outer peripheral surface 71 of the transfer portion 70, the distance between these portions can be prevented from becoming too large. This prevents the outer peripheral surface 71 of the transfer portion 70 from coming into contact with the tread rubber 4 when the paint P is applied to the tread rubber 4, and also prevents the paint P from dripping. Therefore, it is possible to prevent variations in the thickness of the paint P applied to the surface of the tread rubber 4, and therefore it is possible to prevent variations in the thickness of the stress relaxation layer 40. As a result, it is possible to effectively prevent groove cracks from occurring.

[0123] Furthermore, the uneven portion 82 of the rotating portion 80 has a value calculated by the above formula (4) that is 0.1≦P R ≦10, the thickness of the paint P applied to the tread rubber 4 by the paint transfer roller 60 can be made constant. R If the pitch P of the uneven portion 82 is less than 0.1, R Because [mm / piece] is too small, even if the uneven portion 82 is provided on the rotating portion 80, it may be difficult to effectively increase the frictional force between the rotating portion 80 and the tread rubber 4. In this case, it may be difficult to effectively make the rotation of the rotating portion 80 and the transfer portion 70 follow the movement of the tread rubber 4, and even if the uneven portion 82 is provided on the rotating portion 80, it may be difficult to suppress fluctuations in the thickness of the paint P.

[0124] Also, P R If the pitch P of the uneven portion 82 is greater than 10, R Because [mm / piece] is too large, when the rotating portion 80 comes into contact with the surface of the tread rubber 4, the load is concentrated at the position of the convex portion 83 that comes into contact with the tread rubber 4, and there is a risk that the unevenness of the concave-convex portion 82 will be transferred to the tread rubber 4. In this case, rubber flow is induced during vulcanization molding, particularly in the uneven portions of the tread rubber 4, which causes fluctuations in the thickness of the paint P and may easily cause fluctuations in the thickness of the stress relaxation layer 40.

[0125] In contrast, with respect to the uneven portion 82 of the rotating portion 80, the value calculated by the above formula (4) is 0.1≦P RIf the ratio is within the range of ≦10, it is possible to ensure the frictional force between the rotating part 80 and the tread rubber 4 while suppressing the transfer of the unevenness of the uneven portion 82 to the tread rubber 4. This makes it possible to keep the thickness of the paint P applied to the tread rubber 4 by the paint transfer roller 60 constant, thereby suppressing fluctuations in the thickness of the stress relaxation layer 40. As a result, it is possible to effectively suppress the occurrence of groove cracks.

[0126] The uneven portion 82 of the rotating portion 80 has a maximum radius R MaR [mm] and minimum radius R MiR [mm] and R MaR -R MiR And Pitch P R [mm / piece] ratio is 1≦P R / (R MaR -R MiR )≦10, the thickness of the paint P applied to the tread rubber 4 by the paint transfer roller 60 can be made constant. R / (R MaR -R MiR )<1, the height of the convex portions 83 becomes greater relative to the width of the convex portions 83, which may cause the convex portions 83 to become too sharp, and when the rotating portion 80 comes into contact with the surface of the tread rubber 4, the unevenness of the uneven portion 82 may be easily transferred to the tread rubber 4. In this case, rubber flow is induced during vulcanization molding, particularly in the uneven portions of the tread rubber 4, which may cause fluctuations in the thickness of the paint P and may easily cause fluctuations in the thickness of the stress relaxation layer 40.

[0127] Also, P R / (R MaR -R MiR ) > 10, the height of the convex portions 83 becomes low relative to the width of the convex portions 83, which may cause the convex portions 83 to become too flat, and even if the uneven portions 82 are provided on the rotating portion 80, it may be difficult to effectively increase the frictional force between the rotating portion 80 and the tread rubber 4. In this case, it may be difficult to effectively make the rotation of the rotating portion 80 and the transfer portion 70 follow the movement of the tread rubber 4, and even if the uneven portions 82 are provided on the rotating portion 80, it may be difficult to suppress fluctuations in the thickness of the paint P.

[0128] On the other hand, the uneven portion 82 of the rotating portion 80 has a thickness of 1≦P R / (R MaR -R MiR )≦10, it is possible to ensure the frictional force between the rotating part 80 and the tread rubber 4 while suppressing the transfer of the unevenness of the uneven part 82 to the tread rubber 4. This makes it possible to keep the thickness of the paint P applied to the tread rubber 4 by the paint transfer roller 60 constant, thereby suppressing fluctuations in the thickness of the stress relaxation layer 40. As a result, it is possible to effectively suppress the occurrence of groove cracks.

[0129] [Embodiment 3] The third embodiment has a configuration similar to that of the second embodiment, but is characterized in that a paint straightening section 72 is provided in the transfer section 70 of the paint transfer roller 60. Since the other configurations are the same as those of the first embodiment, the description thereof will be omitted and the same reference numerals will be used.

[0130] FIG. 13 is a perspective view of the transfer unit 70 and the rotating unit 80 of the paint transfer roller 60 of the tire building apparatus 50 according to the third embodiment. FIG. 14 is an explanatory view of the transfer unit 70 and the rotating unit 80 shown in FIG. 13 as viewed in the axial direction. In the third embodiment, similar to the second embodiment, the rotating unit 80 has an uneven portion 82 on its outer peripheral surface 81. Also, in the third embodiment, the transfer unit 70 has a paint straightening unit 72 having an uneven shape on its outer peripheral surface 71. The paint straightening unit 72 is formed, for example, by arranging convex portions 73 and concave portions 74 extending in the axial direction of the transfer unit 70 alternately in the circumferential direction of the transfer unit 70. The convex portions 73 and concave portions 74 of the paint straightening unit 72 are preferably arranged alternately at equal intervals in the circumferential direction of the transfer unit 70.

[0131] Fig. 15 is a detailed view of part F in Fig. 14. The transfer part 70 has a paint straightening part 72 on its outer circumferential surface 71. The convex part 73 of the paint straightening part 72 has a maximum radius R MaP [mm], and the recess 74 in the paint straightening portion 72 is smaller than the minimum radius R MiPIn this way, the transfer portion 70 having the paint rectifying portion 72 has a maximum radius R MaP [mm] and minimum radius R MiP [mm] and the maximum radius R of the rotating part 80 MaR [mm] and minimum radius R MiR [mm] satisfies the following formulas (2) and (3).

[0132]

number

[0133]

number

[0134] In the third embodiment as well, when manufacturing the pneumatic tire 1, the paint transfer roller 60 is arranged downstream of the extruder 100 (see FIG. 6). The paint transfer roller 60 brings the rotating part 80 into contact with the surface of the tread rubber 4 extruded from the extruder 100, and rotates the rotating part 80 and the transfer part 70 together, while transferring the paint P received on the outer peripheral surface 71 of the transfer part 70 from a paint supply part 65 (see the figure) from the transfer part 70 to the surface of the tread rubber 4. In this way, the paint P is applied to the surface of the tread rubber 4.

[0135] At this time, because the transfer unit 70 is provided with a paint rectifying portion 72 on its outer peripheral surface 71, the transfer unit 70 can receive the paint P from the paint supply unit 65 while stirring it with the paint rectifying portion 72. Therefore, even if the viscosity of the paint P is high, the transfer unit 70 can receive the paint P while stirring it with the paint rectifying portion 72, thereby facilitating the supply of the paint P from the paint supply unit 65 and allowing the paint P to be received while preventing interruptions. As a result, when the paint P is applied to the tread rubber 4 by the paint transfer roller 60, preventing interruptions of the paint P can prevent the occurrence of thin portions of the paint P, and the paint P can be applied to the surface of the tread rubber 4 at a constant thickness.

[0136] [Effects of the Third Embodiment] As described above, in the third embodiment, the transfer portion 70 of the paint transfer roller 60 has the paint straightening portion 72 disposed on the outer peripheral surface 71, so that the paint P supplied from the paint supply portion 65 to the transfer portion 70 can be received while being stirred. This makes it possible to prevent the paint P from running out when applying the paint P to the tread rubber 4, and to apply the paint P to the surface of the tread rubber 4 at a constant thickness, thereby preventing variations in the thickness of the stress relaxation layer 40 (see FIG. 2). As a result, the occurrence of groove cracks can be effectively prevented.

[0137] In addition, the maximum radius R of the transfer part 70 MaP [mm] and minimum radius R MiP [mm] and the maximum radius R of the rotating part 80 MaR [mm] and minimum radius R MiR [mm] is the average of the unevenness of the paint straightening portion 72 to satisfy the above formula (2), and is the maximum radius R of the rotating portion 80 MaR [mm] and the maximum radius R of the transfer part 70 MaP This makes it possible to suppress variations in the thickness of the paint P applied to the tread rubber 4 when a paint straightening portion 72 having a convex portion 73 and a concave portion 74 is provided on the outer peripheral surface 71 of the transfer portion 70.

[0138] In addition, the maximum radius R of the transfer part 70 MaP [mm] and minimum radius R MiP [mm] and the maximum radius R of the rotating part 80 MaR [mm] and minimum radius R MiR The value [mm] satisfies the above formula (3), so that the size of the transfer part 70 having the paint straightening part 72 relative to the rotating part 80 can be made appropriate. This makes it possible to make the thickness of the paint P applied to the tread rubber 4 appropriate when the paint straightening part 72 having the convex parts 73 and concave parts 74 is provided on the outer peripheral surface 71 of the transfer part 70. Therefore, the stress relaxation layer 40 arranged in the main groove 30 can be arranged with an appropriate thickness while suppressing thickness fluctuations. As a result, the occurrence of groove cracks can be effectively suppressed.

[0139] [Variations] In the above-described first embodiment, the paint supply unit 65 is connected to the paint storage unit 66, and the paint supply unit 65 supplies the paint P stored in the paint storage unit 66 to the transfer unit 70, but the paint supply unit 65 may be connected to something other than the paint storage unit 66. For example, the paint supply unit 65 may be connected to a tube (not shown) that supplies the paint P to the paint supply unit 65, and the paint supply unit 65 may be configured to supply the paint P supplied from the tube to the transfer unit 70.

[0140] Furthermore, in the above-described first embodiment, the transfer portion 70 of the paint transfer roller 60 is formed linearly in the circumferential direction of the transfer portion 70, but the transfer portion 70 may be formed in a shape other than this. Fig. 16 is a plan view of a transfer portion 70 formed in a wave shape, which is a modification of the first embodiment. For example, as shown in Fig. 16, the transfer portion 70 may be formed in a wave shape in which the outer peripheral surface 71 extends in the circumferential direction of the transfer portion 70 and is repeatedly curved in the axial direction of the transfer portion 70. The transfer portion 70 has a total width W S [mm] and the width W of the transfer section 70 P [mm] and the relationship is 0.5≦W P / W S As long as it is within the range of ≦0.95, the form is not important.

[0141] Furthermore, in the above-described first embodiment, the rotating unit 80 of the paint transfer roller 60 has two rotating units 80 arranged on both sides of the transfer unit 70. However, the rotating unit 80 and the transfer unit 70 may be configured in other ways. FIG. 17 is an explanatory diagram showing a modified example of the first embodiment in which the rotating unit 80 and the transfer unit 70 are arranged on one side of the transfer unit 70. FIG. 18 is an explanatory diagram showing a modified example of the first embodiment in which the transfer units 70 are arranged on both sides of the rotating unit 80. For example, as shown in FIG. 17, one rotating unit 80 may be arranged on one side of the transfer unit 70 in the axial direction. Furthermore, one paint transfer roller 60 may have two transfer units 70. For example, as shown in FIG. 18, two transfer units 70 may be arranged on both sides of one rotating unit 80 in the axial direction.

[0142] Furthermore, in the above-described embodiment 2, the uneven portion 82 provided on the outer peripheral surface 81 of the rotating portion 80 is formed by a plurality of convex portions 83 formed in an approximately triangular shape being arranged adjacent to each other in the circumferential direction of the rotating portion 80, but the uneven portion 82 may be formed in any other shape.

[0143] FIG. 19 is an explanatory diagram showing a modified example of the second embodiment, illustrating a configuration of the uneven portion 82 in which triangular protrusions 83 are spaced apart. FIG. 20 is an explanatory diagram showing a modified example of the second embodiment, illustrating a configuration of the uneven portion 82 in which trapezoidal protrusions 83 are adjacently arranged. FIG. 21 is an explanatory diagram showing a modified example of the second embodiment, illustrating a configuration of the uneven portion 82 in which trapezoidal protrusions 83 are spaced apart. The uneven portion 82 of the rotating portion 80 may have, for example, a plurality of approximately triangular protrusions 83 spaced apart in the circumferential direction of the rotating portion 80, as shown in FIG. 19 . Alternatively, the uneven portion 82 may have, for example, a plurality of approximately trapezoidal protrusions 83 spaced apart in the circumferential direction of the rotating portion 80, as shown in FIG. 20 . Alternatively, the uneven portion 82 may have, for example, a plurality of approximately trapezoidal protrusions 83 spaced apart in the circumferential direction of the rotating portion 80, as shown in FIG. 21 .

[0144] Furthermore, in the above-described third embodiment, the paint straightening portion 72 provided on the outer peripheral surface 71 of the transfer portion 70 is formed by arranging convex portions 73 and concave portions 74 extending in the axial direction of the transfer portion 70 alternately in the circumferential direction of the transfer portion 70, but the paint straightening portion 72 may be formed in any other form.

[0145] FIG. 22 is a schematic diagram illustrating a modified example of the third embodiment of the paint rectifying portion 72, in which convex portions 73 and concave portions 74 extending at an angle in the circumferential direction of the transfer portion 70 are arranged alternately. FIG. 23 is a schematic diagram illustrating a modified example of the third embodiment of the paint rectifying portion 72, in which the convex portions 73 and concave portions 74 are bent in the circumferential direction of the transfer portion 70. For example, as shown in FIG. 22, the paint rectifying portion 72 may be configured such that the convex portions 73 and concave portions 74 extending at an angle in the circumferential direction of the transfer portion 70 with respect to the axial direction of the transfer portion 70 are arranged alternately in the circumferential direction of the transfer portion 70. Furthermore, as shown in FIG. 23, the paint rectifying portion 72 may be configured such that the convex portions 73 and concave portions 74 are all bent in the circumferential direction of the transfer portion 70 near the center of the transfer portion 70 in the axial direction, with all of the convex portions 73 and concave portions 74 projecting in the same direction in the circumferential direction of the transfer portion 70.

[0146] Fig. 24 is a schematic diagram showing a modified example of the third embodiment, in which convex portions 73 and concave portions 74 are alternately arranged on both sides of the center in the axial direction of the transfer unit 70. Fig. 25 is a schematic diagram showing a modified example of the third embodiment, in which the concave portions 74 are formed in a circular shape. Furthermore, the paint rectifying portion 72 may be, for example, as shown in Fig. 24, in which convex portions 73 and convex portions 73, and concave portions 74 and concave portions 74, are alternately arranged on both sides of the center in the axial direction of the transfer unit 70. Furthermore, the paint rectifying portion 72 may be, for example, formed by arranging a plurality of concave portions 74 each having a circular shape, as shown in Fig. 25.

[0147] FIG. 26 is a schematic diagram showing a modified example of the third embodiment of the paint rectifying portion 72 in which recesses 74 are formed extending in the circumferential direction of the transfer portion 70. FIG. 27 is a schematic diagram showing a modified example of the third embodiment of the paint rectifying portion 72 in which protrusions 73 and recesses 74 extending in the circumferential direction of the transfer portion 70 are arranged alternately in the axial direction of the transfer portion 70. Furthermore, the paint rectifying portion 72 may be formed by arranging a plurality of recesses 74 extending in the circumferential direction of the transfer portion 70, as shown in FIG. 26. Furthermore, the paint rectifying portion 72 may be formed by arranging a plurality of protrusions 73 and a plurality of recesses 74 extending in the circumferential direction of the transfer portion 70 alternately in the axial direction of the transfer portion 70, as shown in FIG. 27.

[0148] As described above, the paint rectifying portion 72 disposed on the outer peripheral surface 71 of the transfer portion 70 may have any shape as long as it has the convex portions 73 and the concave portions 74. The shape of the paint rectifying portion 72 may be, for example, a small knurled shape or a rounded uneven pattern.

[0149] Furthermore, in the above-described first to fourth embodiments, the paint transfer roller 60 is used to apply the paint P to the unvulcanized tread rubber 4 in order to arrange the stress relaxation layer 40 in the main groove 30 of the pneumatic tire 1, but the paint transfer roller 60 may also be used for other purposes. For example, the paint transfer roller 60 may be used when forming a dissolved rubber coating film on the tread rubber 4, and the type and purpose of the fluid applied by the paint transfer roller 60 are not important.

[0150] Furthermore, the above-described embodiments and modified examples may be combined as appropriate. Furthermore, in the above-described embodiments, the pneumatic tire 1 has been used as an example of a tire according to the present invention, but the tire according to the present invention may be a tire other than the pneumatic tire 1. The tire according to the present invention may be, for example, a so-called airless tire that can be used without being filled with gas.

[0151] [Example] 28 is a table showing the results of a performance evaluation test of pneumatic tires. The following describes performance evaluation tests conducted on the tire building apparatus 50 described above for a conventional pneumatic tire manufactured using a tire building apparatus having a commonly used paint transfer roller, and a pneumatic tire 1 manufactured using the tire building apparatus 50 according to the present invention. The performance evaluation test was conducted to test groove crack resistance.

[0152] The performance evaluation test was conducted using a test tire in which a stress relief layer 40 was placed in the main groove 30 by applying paint P for placing the stress relief layer 40 in the main groove 30 to the tread rubber 4 before vulcanization molding during the manufacture of a pneumatic tire 1 having a tire nominal size of 225 / 65R17 as specified by JATMA.

[0153] The groove crack resistance was evaluated using an indoor drum tester. Each test tire was inflated to the internal pressure specified by JATMA, and then subjected to 4,000 km of drum running under an ambient temperature of 30°C, an ozone concentration of 100 pphm, a load specified by JATMA, and a speed of 80 km / h. The length of cracks occurring in the main groove 30 was measured, the number of cracks counted, and the total crack length was calculated. The groove crack resistance was evaluated using an index based on the reciprocal of the calculated total crack length, with the conventional example (described below) being assigned an index of 100. The higher the index value, the fewer groove cracks occurred in the main groove 30, indicating better groove crack resistance.

[0154] The performance evaluation test was conducted on 14 types of pneumatic tires, including a conventional pneumatic tire and Examples 1 to 13, which are pneumatic tires 1 according to the present invention. Of these, the conventional pneumatic tire has a paint transfer roller that applies paint for disposing a stress relaxation layer in the main groove to unvulcanized tread rubber before vulcanization molding, but does not have a rotating part and a transfer part, and instead the paint is applied to the tread rubber by a single roller, resulting in the stress relaxation layer being disposed in the main groove.

[0155] In contrast, in Examples 1 to 13, which are examples of the pneumatic tire 1 according to the present invention, the maximum radius R MaR [mm] and the maximum radius R of the transfer part 70 MaP [mm] and R MaR >R MaP The paint P is applied to the tread rubber 4 by the paint transfer roller 60 that satisfies the relationship above, and thereby the stress relaxation layer 40 is disposed in the main groove 30. Furthermore, in the pneumatic tires 1 according to Examples 1 to 13, the maximum radius R of the rotation portion 80 of the paint transfer roller 60 that applies the paint P to the tread rubber 4 is MaR [mm] and the maximum radius R of the transfer part 70 MaP [mm] and difference R MaR -R MaP Whether the rotating part 80 has an uneven part 82 or not (R MaR -R MaP ) / (R MaR -R MiR ), the arrangement of the rotating unit 80 relative to the transfer unit 70, whether the transfer unit 70 has a paint straightening unit 72, {2R MiR -(R MaP +R MiP )} / R MaR , W P / W S However, each one is different.

[0156] These paint transfer rollers 60 were used to apply paint P to unvulcanized tread rubber 4, and then vulcanization molding was performed to conduct evaluation tests on pneumatic tires 1 in which stress relaxation layers 40 were arranged in the main grooves 30. As a result, it was found that the pneumatic tires 1 according to Examples 1 to 13 had improved groove crack resistance compared to the conventional tire, as shown in Fig. 28. In other words, the pneumatic tires 1 according to Examples 1 to 13 can effectively suppress the occurrence of groove cracks, and the tire manufacturing apparatus 50 used in manufacturing the pneumatic tires 1 according to Examples 1 to 13 and the manufacturing method for the pneumatic tires 1 according to Examples 1 to 13 can effectively suppress the occurrence of groove cracks.

[0157] The present disclosure encompasses the following inventions. Invention[1] a paint supply unit that supplies paint; a transfer section having a cylindrical shape, which receives the paint supplied from the paint supply section on an outer peripheral surface thereof and transfers the paint on the outer peripheral surface to a surface to be coated with the paint; a rotating part having a cylindrical shape and disposed integrally with the transfer part on at least one side of the transfer part in the axial direction of the transfer part; a support portion that supports the transfer portion and the rotating portion so as to be rotatable in a circumferential direction about an axis of the transfer portion; a paint transfer roller comprising: The maximum radius R of the rotating part MaR [mm] and the maximum radius R of the transfer part MaP [mm] is R MaR >R MaP A tire manufacturing apparatus characterized in that the following relationship is satisfied. Invention[2] The maximum radius R of the rotating part MaR [mm] and the maximum radius R of the transfer part MaP The relationship with [mm] is 0.04≦R MaR -R MaP The tire manufacturing apparatus according to the invention [1], wherein the range is ≦1.2. Invention[3] The tire manufacturing apparatus according to claim [1] or [2], wherein the rotating part has an uneven portion on its outer surface where unevenness is repeated in the circumferential direction of the rotating part. Invention[4] The rotating portion has a maximum radius R of the rotating portion at the position of the convex portion of the concave-convex portion. MaR [mm], and the radius at the position of the concave portion of the concave-convex portion is the minimum radius R of the rotating portion. MiR [mm], and the maximum radius R of the rotating part MaR [mm] and minimum radius R MiR [mm] and the maximum radius R of the transfer part MaP [mm] is the tire manufacturing apparatus according to invention [3] that satisfies the above formula (1). Invention[5] The tire manufacturing apparatus according to any one of the first to fourth aspects, wherein the rotating units are disposed on both sides of the transfer unit in the axial direction of the transfer unit. Invention[6] The tire manufacturing apparatus according to any one of the inventions [1] to [5], wherein the transfer unit has a paint straightening unit having an uneven shape on its outer peripheral surface. Invention[7] The transfer unit has a paint straightening unit having an uneven outer peripheral surface, The transfer portion has a maximum radius R MaP [mm], and the concave portion in the paint straightening portion has the minimum radius R MiP [mm], and the maximum radius R of the transfer part MaP [mm] and minimum radius R MiP [mm] and the maximum radius R of the rotating part MaR [mm] and minimum radius R MiR [mm] is the tire manufacturing apparatus according to invention [4] that satisfies the above formulas (2) and (3). Invention[8] The total width W of the rotating part and the transfer part in the axial direction of the transfer part S [mm] and the width W of the transfer part in the axial direction of the transfer part P [mm] and the relationship is 0.5≦W P / W SA tire manufacturing apparatus according to any one of Inventions [1] to [7], wherein the range is ≦0.95. Invention[9] a paint supply unit that supplies paint; a transfer section having a cylindrical shape, which receives the paint supplied from the paint supply section on an outer peripheral surface thereof and transfers the paint on the outer peripheral surface to a surface to be coated with the paint; a rotating part having a cylindrical shape and disposed integrally with the transfer part on at least one side of the transfer part in the axial direction of the transfer part; a support portion that supports the transfer portion and the rotating portion so as to be rotatable in a circumferential direction about an axis of the transfer portion; Equipped with The maximum radius R of the rotating part MaR [mm] and the maximum radius R of the transfer part MaP [mm] and R MaR >R MaP A tire manufacturing method in which the paint is applied to a surface of unvulcanized tread rubber by a paint transfer roller that satisfies the relationship: A tire manufacturing method characterized by applying the paint by bringing the rotating part into contact with the surface of the tread rubber and rotating the rotating part and the transfer part together, while transferring the paint received on the outer peripheral surface of the transfer part to the surface of the tread rubber. Invention

[10] A method for manufacturing a tire according to invention [9], wherein the temperature of the tread rubber during the process of transferring the paint using the paint transfer roller is within the range of 50°C or higher and 120°C or lower. Invention

[11] The method for manufacturing a tire according to invention [9] or invention

[10] , wherein the paint contains a diene or non-diene rubber material as a main component, carbon, a vulcanizing agent, and a vulcanization accelerator, and the rubber component is dissolved in an organic solvent mainly composed of hydrocarbons at a concentration within the range of 5 [wt%] to 35 [wt%]. Invention

[12] A tire manufacturing method according to any one of Inventions [9] to

[11] , wherein the viscosity of the paint in the paint supply section is in the range of 500 [mPa·s] or more and 20,000 [mPa·s] or less. Invention

[13] The method for manufacturing a tire according to any one of inventions [9] to

[12] , wherein the paint transfer roller is disposed downstream of the extruder in the direction of movement of the tread rubber extruded from the extruder, and the rotating part is brought into contact with the surface of the tread rubber extruded from the extruder to apply the paint. Invention

[14] A main groove formed on the tread surface; a stress relief layer disposed on the bottom of the main groove; A tire comprising: The stress relaxation layer is a paint supply unit that supplies paint; a transfer section having a cylindrical shape, which receives the paint supplied from the paint supply section on an outer peripheral surface thereof and transfers the paint on the outer peripheral surface to a surface to be coated with the paint; a rotating part having a cylindrical shape and disposed integrally with the transfer part on at least one side of the transfer part in the axial direction of the transfer part; a support portion that supports the transfer portion and the rotating portion so as to be rotatable in a circumferential direction about an axis of the transfer portion; Equipped with The maximum radius R of the rotating part MaR [mm] and the maximum radius R of the transfer part MaP [mm] and R MaR >R MaP a rotating part of a paint transfer roller that satisfies the relationship of (a) to (c) above, contacting the surface of unvulcanized tread rubber, and rotating the rotating part and the transfer part together, thereby transferring the paint received on the outer peripheral surface of the transfer part to the surface of the tread rubber. [Explanation of symbols]

[0158] 1 pneumatic tire 2 Tread section 3 Tread surface 4 Tread rubber 5 Shoulder section 8 Sidewall 10 Bead section 11 Bead core 12 Bead filler 13 Carcass layer 14 Belt Layer 141, 142 Belt 143 Belt cover 16 Inner liner 17 Rim cushion rubber 18 Tire inner surface 20 Land 30 Main groove 31 Groove bottom 32 Groove Wall 40 Stress relief layer 50 Tire manufacturing equipment 60 Paint transfer roller 65 Paint supply section 66 Paint storage section 70 Transfer unit 71 Outer surface 72 Paint rectifier 73 Convex 74 recess 80 Rotating part 81 Outer surface 82 Uneven part 83 Convex part 84 recess 90 Support part 95 Rotation axis 100 Extruder

Claims

1. a paint supply unit that supplies paint; a transfer section having a cylindrical shape, which receives the paint supplied from the paint supply section on an outer peripheral surface thereof and transfers the paint on the outer peripheral surface to a surface to be coated with the paint; a rotating part having a cylindrical shape and disposed integrally with the transfer part on at least one side of the transfer part in the axial direction of the transfer part; a support portion that supports the transfer portion and the rotating portion so as to be rotatable in a circumferential direction about an axis of the transfer portion; a paint transfer roller comprising: The maximum radius R of the rotating portion ＭａＲ [mm] and the maximum radius R of the transfer part ＭａＰ [mm] is R ＭａＲ >R ＭａＰ A tire manufacturing apparatus characterized in that the following relationship is satisfied.

2. The maximum radius R of the rotating portion ＭａＲ [mm] and the maximum radius R of the transfer part ＭａＰ The relationship between [mm] and R is 0.04≦R ＭａＲ -R ＭａＰ 2. The tire building apparatus according to claim 1, wherein the range is ≦1.

2.

3. The tire building apparatus according to claim 1 or 2, wherein the rotating part has an uneven portion on an outer circumferential surface, in which unevenness is repeated in the circumferential direction of the rotating part.

4. The rotating portion has a maximum radius R of the rotating portion at the position of the convex portion of the concave-convex portion. ＭａＲ [mm], and the radius at the position of the concave portion of the concave-convex portion is the minimum radius R of the rotating portion. ＭｉＲ [mm], and the maximum radius R of the rotating part ＭａＲ [mm] and minimum radius R ＭｉＲ [mm] and the maximum radius R of the transfer portion ＭａＰ The tire manufacturing apparatus according to claim 3, wherein [mm] satisfies the following formula (1): [Equation 1]

5. The tire building apparatus according to claim 1 or 2, wherein the rotating units are arranged on both sides of the transfer unit in the axial direction of the transfer unit.

6. The tire building apparatus according to claim 1 or 2, wherein the transfer unit is provided with a paint straightening unit having an uneven outer peripheral surface.

7. The transfer unit has a paint straightening unit having an uneven outer peripheral surface, The transfer portion has a maximum radius R ＭａＰ [mm], and the concave portion in the paint straightening portion has a minimum radius R ＭｉＰ [mm], and the maximum radius R of the transfer part ＭａＰ [mm] and minimum radius R ＭｉＰ [mm] and the maximum radius R of the rotating part ＭａＲ [mm] and minimum radius R ＭｉＲ The tire manufacturing apparatus according to claim 4, wherein [mm] satisfies the following formulas (2) and (3): [Equation 2] [Equation 3]

8. The total width W of the rotating part and the transfer part in the axial direction of the transfer part Ｓ [mm] and the width W of the transfer portion in the axial direction of the transfer portion Ｐ [mm] and the relationship is 0.5≦W Ｐ / W Ｓ 3. The tire building apparatus according to claim 1, wherein the ratio of the axial length of the tire to the axial length of the tire is in the range of ≦0.

95.

9. a paint supply unit that supplies paint; a transfer section having a cylindrical shape, which receives the paint supplied from the paint supply section on an outer peripheral surface thereof and transfers the paint on the outer peripheral surface to a surface to be coated with the paint; a rotating part having a cylindrical shape and disposed integrally with the transfer part on at least one side of the transfer part in the axial direction of the transfer part; a support portion that supports the transfer portion and the rotating portion so as to be rotatable in a circumferential direction about an axis of the transfer portion; Equipped with The maximum radius R of the rotating portion ＭａＲ [mm] and the maximum radius R of the transfer part ＭａＰ [mm] and R ＭａＲ >R ＭａＰ A tire manufacturing method in which the paint is applied to a surface of unvulcanized tread rubber by a paint transfer roller that satisfies the relationship: A tire manufacturing method characterized by applying the paint by bringing the rotating part into contact with the surface of the tread rubber and rotating the rotating part and the transfer part together, while transferring the paint received on the outer peripheral surface of the transfer part to the surface of the tread rubber.

10. The method for manufacturing a tire according to claim 9, wherein the temperature of the tread rubber in the step of transferring the paint using the paint transfer roller is within a range of 50°C or higher and 120°C or lower.

11. 11. The method for manufacturing a tire according to claim 9 or 10, wherein the paint contains a diene-based or non-diene-based rubber material as a main component, carbon, a vulcanizing agent, and a vulcanization accelerator, and the rubber component is dissolved in an organic solvent containing a hydrocarbon as a main component at a concentration within a range of 5 wt % to 35 wt %.

12. 11. The tire manufacturing method according to claim 9, wherein the viscosity of the paint in the paint supply section is in the range of 500 mPa·s to 20,000 mPa·s.

13. 11. The tire manufacturing method according to claim 9 or 10, wherein the paint transfer roller is disposed downstream of an extruder that extrudes the tread rubber in a moving direction of the tread rubber extruded from the extruder, and the paint is applied by bringing the rotating part into contact with a surface of the tread rubber extruded from the extruder.

14. A main groove formed on the tread surface; a stress relief layer disposed on the bottom of the main groove; A tire comprising: The stress relaxation layer is a paint supply unit that supplies paint; a transfer section having a cylindrical shape, which receives the paint supplied from the paint supply section on an outer peripheral surface thereof and transfers the paint on the outer peripheral surface to a surface to be coated with the paint; a rotating part having a cylindrical shape and disposed integrally with the transfer part on at least one side of the transfer part in the axial direction of the transfer part; a support portion that supports the transfer portion and the rotating portion so as to be rotatable in a circumferential direction about an axis of the transfer portion; Equipped with The maximum radius R of the rotating portion ＭａＲ [mm] and the maximum radius R of the transfer part ＭａＰ [mm] and R ＭａＲ >R ＭａＰ a rotating part of a paint transfer roller that satisfies the relationship of (a) to (c) above, contacting the surface of unvulcanized tread rubber, and rotating the rotating part and the transfer part together, thereby transferring the paint received on the outer peripheral surface of the transfer part to the surface of the tread rubber.

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