Manufacturing method for retreaded tires

Abstract

The present invention provides a method for manufacturing retreaded tires that can reduce the RRO (Recovery Cost) while suppressing the cost required for preparing the tread rubber and improving production efficiency. [Solution] A method for manufacturing a retreaded tire 1. The method includes: a first step S1 of preparing a base tire 1a; a second step S2 of preparing a first plurality of types of strip-shaped Precure tread rubber 2b, each having multiple convex edges 23 for forming the arc portion 12 of the block 11, and each having a different radius of curvature R of the convex edges 23; and a third step S3 of attaching one Precure tread rubber 2b selected from the first plurality of types of Precure tread rubber 2b according to the tire outer diameter D of the retreaded tire 1 to the base tire 1a. The number of the first plurality of types is less than the number of types of tire outer diameter D of the retreaded tire 1.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing retread tires.

Background Art

[0002] Retread tires are manufactured by replacing the worn tread rubber from used tires through running or the like. As one of such methods for manufacturing retread tires, the precure method is known. In this method, first, the tread rubber is removed from the used tire to form a casing tire. Next, a precured tread rubber band that has been vulcanized in advance is attached to the tread forming surface (the surface from which the tread rubber has been removed) of the casing tire via an unvulcanized rubber sheet for adhesion. After that, the casing tire, the unvulcanized rubber sheet, and the tread rubber band are heat-treated so that the casing tire and the tread rubber band are integrated.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] As described above, in the method for manufacturing retread tires by the precure method, first, a step of removing the tread rubber from the used tire to prepare a casing tire is performed. Next, a step of preparing a strip-shaped precured tread rubber (hereinafter referred to as "precure rubber") is performed, and further, a step of attaching the precure rubber to the casing tire is performed.

[0005] Furthermore, retreaded tires, like used tires (tires before retreading), may have blocks arranged in the circumferential direction of the tire and forming a contact surface in the tread area. In retreaded tires as well, it is desirable to minimize RRO (Radial Runout) and reduce tire vibration. For this reason, in a longitudinal section obtained by cutting the blocks along the circumferential direction of the tire, it is desirable that the contact surface of the blocks be an arc-shaped arc portion, and that the radius of curvature of the arc portion correlate with the outer diameter of the retreaded tire. In other words, it is desirable that the Precure rubber used to manufacture the retreaded tire has an arc-shaped convex edge portion for forming the arc portion, and that the radius of curvature of the convex edge portion correlate with the outer diameter of the retreaded tire.

[0006] Furthermore, retreaded tires come in multiple types with different outer diameters. Therefore, ideally, the Precure rubber should be prepared in multiple types, each with a different radius of curvature of the convex edge, corresponding to the outer diameter of the retreaded tire. However, such a method is costly and inefficient in terms of production.

[0007] This invention was devised in view of the above circumstances, and its main objective is to provide a method for manufacturing retreaded tires that minimizes the RRO (Return on Stock) while suppressing the cost required for the tread rubber (pre-cured rubber) to be prepared and improving production efficiency. [Means for solving the problem]

[0008] The present invention relates to a method for manufacturing a retreaded tire, wherein the tread portion includes at least one block row in which a plurality of blocks are arranged in the circumferential direction of the tire, and in a longitudinal section obtained by cutting the block row along the circumferential direction of the tire, the contact surface of the blocks includes an arc-shaped portion that is convex outward in the radial direction of the tire, comprising: a first step of preparing a base tire from which the tread rubber has been removed; a second step of preparing a first plurality of types of strip-shaped Precure tread rubber, each having a plurality of convex edges for forming the arc-shaped portion, and each having a different radius of curvature R of the convex edges, wherein the number of the first plurality of types is less than the number of types of tire outer diameters of the retreaded tire; and a third step of attaching one Precure tread rubber selected from the first plurality of types of Precure tread rubber according to the tire outer diameter of the retreaded tire to the base tire. [Effects of the Invention]

[0009] By adopting the above configuration, the method for manufacturing retreaded tires of the present invention can reduce the RRO (Recovery Cost of Use), suppress the cost required for preparing the tread rubber, and improve production efficiency. [Brief explanation of the drawing]

[0010] [Figure 1] This is a meridian cross-section of a retreaded tire. [Figure 2] This is a cross-sectional view along line AA in Figure 1. [Figure 3] This flowchart shows the procedure for the manufacturing method of this embodiment. [Figure 4] This is a perspective view of one embodiment of Precure rubber. [Figure 5] Figure 4 is a cross-sectional view along line BB. [Figure 6] This is a perspective view of an example of one of several types of Precure rubber bands. [Figure 7] (A) is a cross-sectional view of line CC in Figure 5, (B) is a cross-sectional view of line DD in Figure 5, and (C) is a cross-sectional view of line EE in Figure 5. [Figure 8](A) is a cross-sectional view along the FF line in Figure 4, (B) is a cross-sectional view along the GG line in Figure 4, and (C) is a cross-sectional view along the HH line in Figure 4. [Figure 9] This is a perspective view of the first group of Precure rubber. [Figure 10] This is a perspective view of the second group of Precure rubber. [Figure 11] This is a perspective view of the third group of Precure rubber. [Modes for carrying out the invention]

[0011] Hereinafter, one embodiment of the present invention will be described with reference to the drawings. The drawings may contain exaggerations or representations that differ from the actual dimensional ratios of the structure in order to aid in understanding the content of the present invention. Furthermore, the same or common elements are denoted by the same reference numerals throughout each embodiment, and redundant explanations may be omitted. Moreover, the specific configurations shown in the embodiments and drawings are for the purpose of understanding the content of the present invention. For this reason, the present invention is not limited to the specific configurations shown in the drawings.

[0012] Figure 1 is a meridian cross-sectional view of a retreaded tire 1 (hereinafter sometimes simply referred to as "tire 1") manufactured using the manufacturing method of the present invention. As shown in Figure 1, the tire 1 of this embodiment includes a base tire 1a obtained by removing tread rubber from a used tire, and retread rubber 2a. The tread rubber 2a is fixed to the base tire 1a. A portion of the base tire 1a is shown in Figure 1. Tires 1 manufactured using the manufacturing method of the present invention include, for example, pneumatic tires for small trucks, pneumatic tires for trucks and buses, and pneumatic tires for construction vehicles.

[0013] The base tire 1a has an adhesive surface 4 for attaching the Precure tread rubber 2b (shown in Figure 4), which will be described later. The width W of the adhesive surface 4 in the tire axial direction is correlated with the size of the base tire 1a (tire size (tire nominal size) of tire 1).

[0014] Figure 2 is a cross-sectional view taken along line A-A of Figure 1. Figure 2 shows a longitudinal section of the tire 1 cut in the tire circumferential direction. Figure 2 is, for example, a longitudinal sectional view on the tire equator C. As shown in Figures 1 and 2, the tire 1 has a tread portion 2 including at least one block row 10. The block row 10 includes a plurality of blocks 11 arranged in the tire circumferential direction. The block 11 includes a ground contact surface 12. The ground contact surface 12 is the portion that contacts the plane when a normal load is applied to the tire 1 in a normal state and the tire is grounded on the plane at a camber angle of 0°.

[0015] The "normal state" means that in the case of a pneumatic tire with various standards defined, the tire is rim-mounted on a normal rim and filled with a normal internal pressure, and moreover, it is in a non-loaded state. In this specification, unless otherwise specified, the dimensions and the like of each part of the tire are values measured in the normal state.

[0016] The "normal rim" is the rim defined for each tire in a standard system including the standards on which the tire is based. For example, in JATMA, it is the "standard rim", in TRA, it is the "Design Rim", and in ETRTO, it is the "Measuring Rim".

[0017] The "normal internal pressure" is the air pressure defined for each tire in a standard system including the standards on which the tire is based. In JATMA, it is the "maximum air pressure", in TRA, it is the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES", and in ETRTO, it is the "INFLATION PRESSURE".

[0018] The "normal load" is the load defined for each tire in a standard system including the standards on which the tire is based. In JATMA, it is the "maximum load capacity", in TRA, it is the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES", and in ETRTO, it is the "LOAD CAPACITY".

[0019] In the longitudinal section, the contact surface 12 includes a convex, arc-shaped portion 13 that extends outward in the radial direction of the tire. Such an arc-shaped portion 13 equalizes the contact pressure with the road surface, thereby reducing RRO (radial run-out).

[0020] Next, a method for manufacturing such a tire 1 will be described. Figure 3 is a flowchart showing the procedure of the manufacturing method of this embodiment. As shown in Figure 3, the manufacturing method includes a first step S1, a second step S2, and a third step S3. In the first step S1, a base tire 1a from which the tread rubber has been removed is prepared. In the second step S2, a strip of Precure tread rubber (hereinafter sometimes referred to as "Precure rubber") 2b (shown in Figure 4) is prepared. In the third step S3, the Precure rubber 2b is attached to the base tire 1a. The Precure rubber 2b is a vulcanized tread rubber that has been pre-vulcanized in a press mold. Note that the second step S2 may be performed after the first step S1, before the first step, or simultaneously with the first step S1.

[0021] Furthermore, between the second step S2 and the third step S3, there is an adhesion step in which an unvulcanized adhesive rubber (not shown) is attached between the Precure rubber 2b and the base tire 1a. The adhesive rubber promotes adhesion (fixation by vulcanization) between the Precure rubber 2b and the base tire 1a. After the third step S3, a vulcanization step is performed in which the Precure rubber 2b, the base tire 1a, and the adhesive rubber are vulcanized to form the tire 1. The first step S1, the adhesion step, and the vulcanization step employ well-known methods, so their explanation is omitted.

[0022] Figure 4 is a perspective view of one embodiment of the Precure rubber 2b, and Figure 5 is a cross-sectional view taken along line BB of Figure 4. Figure 5 is a cross-section at a position on the tire equator C when the Precure rubber 2b of Figure 4 is attached to the base tire 1a to form the tire 1 (hereinafter sometimes simply referred to as "when it forms the tire 1"). As shown in Figures 4 and 5, the Precure rubber 2b is formed, for example, as a rectangle in plan view. The Precure rubber 2b includes a back surface 24a that is attached to the adhesive surface 4 (shown in Figure 1) of the base tire 1a, and a front surface 24b that faces the opposite side of the back surface 24a. The Precure rubber 2b of this embodiment also includes block portions 21 for forming the blocks 11 of the tire 1. The Precure rubber 2b includes, for example, at least one row of block portions 20 in which the block portions 21 are arranged in the longitudinal direction X. Figure 4 shows the longitudinal direction X and the width direction Y perpendicular to the longitudinal direction X of the Precure rubber 2b.

[0023] The block portion 21 includes an outward-facing surface 22 that forms the contact surface 12 (shown in Figure 2) of the block 11. The outward-facing surface 22 is formed, for example, on the surface 24b. In this embodiment, the outward-facing surface 22 has a convex edge portion 23 for forming the arc portion 13 of the contact surface 12. In other words, the Precure rubber 2b has a plurality of convex edges 23 arranged in the longitudinal direction X in the block portion row 20. Each convex edge portion 23 is formed in the shape of an arc with the same radius of curvature R.

[0024] Then, in the second step S2, a first set of multiple types of Precure rubber 2b, each with a different radius of curvature R of the convex edge portion 23, are prepared. The number of these first sets of multiple types is less than the number of different tire outer diameters D of the tire 1. In the third step S3, one Precure rubber 2b selected from the first set of multiple types of Precure rubber 2b according to the tire outer diameter D of the tire 1 is attached. In this way, the manufacturing method of this embodiment eliminates the need to prepare all types of Precure rubber 2b having convex edge portions 23 with different radii of curvature R for each tire outer diameter D of the tire 1. As a result, the number of types of Precure rubber 2b to be prepared can be reduced, thus suppressing the cost required for the production of Precure rubber 2b. When it becomes tire 1, it is desirable that the radii of curvature R of at least multiple convex edge portions 23 located on the tire equator C of a single Precure rubber 2b are all the same size (length). Furthermore, when considered as tire 1, it is desirable that the radius of curvature R (not shown) of the multiple convex edge portions 23 located on each tire circumferential line (shown as tire circumferential line n in Figure 4) of the one Precure rubber 2b be the same size (length) for each tire circumferential line.

[0025] Furthermore, in the third step S3, the tire 1, to which the Precure rubber 2b is attached to the base tire 1a, includes an arc-shaped arc portion 13, thus keeping the RRO small. However, when the Precure rubber 2b with a straight convex edge portion 23 is used for the tire 1, the arc portion 13 is not formed on this tire 1, and in the longitudinal cross-section, a straight portion 16 (shown as a dashed line in Figure 2) is formed where the contact surface 12 extends in a straight line. Such a tire 1 will have a large RRO. RRO is an index of the runout of the tire's radial dimensions. RRO can also be used to evaluate the roundness of the tire. Furthermore, RRO is measured using a uniformity tester in accordance with the test conditions of JASO C607:2000 "Uniformity Test Method for Automobile Tires".

[0026] The configuration of this embodiment will be described in more detail below. Note that each configuration described below represents a specific aspect of this embodiment. Therefore, it goes without saying that the present invention can achieve the above-described effects even without the configurations described below. Furthermore, even if any one of the configurations described below is applied individually to the tire 1 of the present invention having the above-described features, an improvement in performance corresponding to each configuration can be expected. Moreover, if several of the configurations described below are applied in combination, a combined improvement in performance corresponding to each configuration can be expected.

[0027] The radius of curvature R is correlated with, for example, the outer diameter D of tire 1. The radius of curvature R is positively correlated with the outer diameter D of tire 1. In this embodiment, the radius of curvature R is positively correlated with 30% to 70% of the outer diameter D. The radius of curvature R may also be positively correlated with, for example, 40% to 60% of the outer diameter D, or with 45% to 55% of the outer diameter D. A convex edge portion 23 having such a radius of curvature R helps to further reduce RRO when it is made into tire 1.

[0028] The tire outer diameter D is the outer diameter of tire 1 calculated from the tire size indicated on the used tire. For example, if tire 1 has a tire size of "145 / 80R12", the tire outer diameter D is (145 × 0.8 × 2) + (12 × 25.4) = 536.8 (mm). The tire outer diameter D is substantially the same as the outer diameter d (shown in Figure 1) of tire 1 at the tire equator C measured in the normal state of tire 1. If recesses such as circumferential grooves, which will be described later, are provided on the tread portion 2, the outer diameter d of tire 1 is taken from the virtual contact surface 2s obtained by filling the recesses.

[0029] Then, in the third step S3, for example, the Precure rubber 2b is attached to a base tire 1a for manufacturing a tire 1 having an outer diameter D of 1.5 times or more and less than 2.5 times the radius of curvature R of the convex edge portion 23.

[0030] Figure 6 is a perspective view of an example of each of the first multiple types of Precure rubber 2b that are attached in the third step S3. In other words, Figure 6 shows an example of the first multiple types of Precure rubber 2b prepared in the second step S2. Figure 7(A) is a cross-sectional view of Figure 6 along line CC, Figure 7(B) is a cross-sectional view of Figure 6 along line DD, and Figure 7(C) is a cross-sectional view of Figure 6 along line EE. Each of Figures 7(A) to (C) is a longitudinal section at a position on the tire equator C when it is made into a tire 1. Figures 6 and 7 show the first Precure rubber 2b1, the second Precure rubber 2b2, and the third Precure rubber 2b3. The radius of curvature Ra of the convex edge 23 of the first Precure rubber 2b1 is smaller than, for example, the radius of curvature Rb of the convex edge 23 of the second Precure rubber 2b2. Furthermore, the radius of curvature Rb of the convex edge 23 of the second Precure rubber 2b2 is smaller than, for example, the radius of curvature Rc of the convex edge 23 of the third Precure rubber 2b3. Note that the first Precure rubber 2b1, the second Precure rubber 2b2, and the third Precure rubber 2b3 are each given the same length (shown in Figure 4) La and the same width w (shown in Figure 4), but they may also have different lengths La and different widths w. Length La is defined as the length in the longitudinal direction X of the back surface 24a. Width w is defined as the length in the width direction Y of the back surface 24a.

[0031] In this embodiment, the radius of curvature Ra of the first Precure rubber 2b1 is, for example, 350 mm. The radius of curvature Rb of the second Precure rubber 2b2 is, for example, 583 mm. Furthermore, the radius of curvature Rc of the third Precure rubber 2b3 is, for example, 972 mm. That is, in the third step S3, the first Precure rubber 2b1 is attached to a base tire 1a for manufacturing a tire 1 with an outer diameter D of 350 × 1.5 = 525 (mm) or more and less than 350 × 2.5 = 875 (mm). Similarly, the second Precure rubber 2b2 is attached to a base tire 1a for manufacturing a tire 1 with an outer diameter D of 583 × 1.5 = 874.5 mm or more and less than 583 × 2.5 = 1457.5 mm. Furthermore, the third Precure rubber 2b3 is attached to a base tire 1a for manufacturing a tire 1 with an outer diameter D of 972 × 1.5 = 1457.5 mm or more and less than 972 × 2.5 = 2430 mm. Tires 1 with an outer diameter D of less than 525 mm or 2430 mm or more are manufactured by attaching the similarly specified Precure rubber 2b to the base tire 1a. Thus, in this embodiment, the number of first multiple types of Precure rubber 2b prepared in the second step S2 can be reduced significantly compared to the number of types of tire outer diameter D. Note that the ratio of the radius of curvature R of the convex edge portion 23 to the outer diameter D of the tire is not limited to the numerical range described above.

[0032] As shown in Figure 1, the tire 1 includes a pair of sidewall portions 3 connected to both outer sides of the tread portion 2 in the tire axial direction, and a pair of bead portions (not shown) extending in the tire radial direction from the sidewall portions 3. For example, the tire size is stamped on the surface of the sidewall portions 3. The tire 1 also includes known components such as a carcass 6 and a tread reinforcement layer 7.

[0033] As shown in Figures 1 and 2, the tread portion 2 includes, for example, at least one circumferential groove 8 that extends continuously in the circumferential direction of the tire, and transverse grooves 9 that extend from the circumferential groove 8 in the axial direction of the tire. The circumferential groove 8 is provided, for example, one on each side of the tire equator C. The transverse grooves 9 include, for example, a plurality of first transverse grooves 9A that connect the circumferential grooves 8, and a plurality of second transverse grooves 9B that extend outward in the axial direction of the tire from each circumferential groove 8.

[0034] In this embodiment, block row 10 includes a first block row 10A located between the circumferential grooves 8, and a pair of second block rows 10B located further outward in the tire axial direction than the first block row 10A. The first block row 10A includes, for example, the tire equator C. The second block row 10B includes, for example, the tread edge Te. Block 11 also includes a plurality of first blocks 11A forming the first block row 10A, and a plurality of second blocks 11B forming the second block row 10B.

[0035] Furthermore, the block 11 includes a pair of side walls 14, 14 that connect to both sides of the contact surface 12 in the tire circumferential direction and extend inward in the tire radial direction. The side walls 14 are formed by transverse grooves 9. The side walls 14 are connected, for example, to one end 13e and the other end 13i of the arc portion 13 in the tire circumferential direction.

[0036] In this embodiment, the outer diameter d of tire 1 decreases from the tire equator C outward in the tire axial direction. Specifically, the outer diameter d2 of tire 1 in the first block row 10A on the circumferential groove 8 side of the tire equator C is smaller than the outer diameter d1 of tire 1 at the tire equator C. Furthermore, the outer diameter d3 of tire 1 on the circumferential groove 8 side of the second block row 10B is smaller than the outer diameter d2 of tire 1. Also, the outer diameter d4 of tire 1 at the tread edge Te of the second block row 10B is smaller than the outer diameter d3 of tire 1. The outer diameter d of tire 1 decreases continuously from the tire equator C to the tread edge Te. With such a tire 1, the contact pressure on the tread portion 2 is more evenly distributed.

[0037] As shown in Figure 4, in this embodiment, the block section row 20 of the Precure rubber 2b includes a first block section row 20A for forming the first block section row 10A and a second block section row 20B for forming the second block section row 10B. The second block section row 20B is arranged on both sides of the first block section row 20A.

[0038] When the Precure rubber 2b is used as tire 1, it includes a first region 26 that extends in the circumferential direction of the tire on the block row 10, and a second region 27 that is located outside the first region 26 in the tire axial direction and on the same block row 10.

[0039] Figure 8(A) is a cross-sectional view along the FF line of Figure 4. As shown in Figures 5 and 8(A), the convex edge portion 23 includes a first convex edge portion 28 formed in the first region 26 and a second convex edge portion 29 formed in the second region 27. The radius of curvature Rf of the first convex edge portion 28 is larger than the radius of curvature Rs of the second convex edge portion 29. As a result, when the Precure rubber 2b having such a first convex edge portion 28 and second convex edge portion 29 is used as a tire 1, the contact pressure is made uniform, and the RRO is kept small.

[0040] Furthermore, as shown in Figure 4, the first region 26 is divided into an inner first region 26A formed in the first block section row 20A and an outer first region 26B formed in the second block section row 20B. In addition, the second region 27 in this embodiment is divided into an inner second region 27A formed in the first block section row 20A and an outer second region 27B formed in the second block section row 20B.

[0041] Figure 8(B) is a cross-sectional view along the GG line in Figure 4, and Figure 8(C) is a cross-sectional view along the HH line in Figure 4. As shown in Figures 5 and 8, the first convex edge 28 includes an inner first convex edge 28A formed in the inner first region 26A and an outer first convex edge 28B formed in the outer first region 26B. Furthermore, the second convex edge 29 includes an inner second convex edge 29A formed in the inner second region 27A and an outer second convex edge 29B formed in the outer second region 27B. The radius of curvature Rf1 of the inner first convex edge 28A, the radius of curvature Rs1 of the inner second convex edge 29A, the radius of curvature Rf2 of the outer first convex edge 28B, and the radius of curvature Rs2 of the outer second convex edge 29B have the following relationship. Tires 1 manufactured with this type of Precure rubber 2b have the contact pressure on the tread portion 2 during driving further equalized, so the RRO can be reduced even further. Rf1>Rs1>Rf2>Rs2 Thus, it is desirable that the radius of curvature R of the convex edge 23 located on the outside of the width direction Y is smaller than the radius of curvature R of the convex edge 23 located on the center side in the width direction Y of the Precure rubber 2b.

[0042] Furthermore, in the third step S3, if the length La of the Precure rubber 2b (shown in Figure 4) is greater than the circumference Lb of the base tire 1a at the tire equator C (shown in Figure 2), the Precure rubber 2b may be cut at an appropriate position relative to the circumference Lb of the base tire 1a before being attached. Also, in the third step S3, if the length La of the Precure rubber 2b is smaller than the circumference Lb of the base tire 1a, the Precure rubber 2b and a part of another Precure rubber 2b may be attached to the base tire 1a. Moreover, when it becomes tire 1, it is desirable that the length La of the Precure rubber 2b with a small radius of curvature R of the convex edge portion 23 positioned on the tire equator C is smaller than the length La of the Precure rubber 2b with a large radius of curvature R of the convex edge portion 23 positioned on the tire equator C.

[0043] Furthermore, as shown in Figure 1, the base tire 1a has multiple types with different widths W of the adhesive surface 4. For this reason, in the second step S2, a second set of multiple types of Precure rubber 2b with different width dimensions (width w (shown in Figure 4)) may be prepared. Moreover, in the second step S2, it is desirable to prepare a second set of multiple types of Precure rubber 2b with widths w that are fewer than the number of types of widths W of the adhesive surface 4 of the base tire 1a (hereinafter sometimes referred to as "width W of the base tire 1a"). Then, in the third step S3, it is desirable that one Precure rubber 2b selected from the multiple types of Precure rubber 2b according to the width W of the base tire 1a is attached to the base tire 1a. This eliminates the need to prepare multiple types of Precure rubber 2b with different widths w for each width W of the base tire 1a. Therefore, the number of types of Precure rubber 2b to be prepared can be further reduced, thus further suppressing the cost required for the production of Precure rubber 2b.

[0044] In the second step S2 of this embodiment, for example, a first group Z1 (shown in Figure 9) of Precure rubber 2b, a second group Z2 (shown in Figure 10) of Precure rubber 2b, and a third group Z3 (shown in Figure 11) of Precure rubber 2b may be prepared. The first group Z1 is an aggregate of multiple Precure rubber 2b having a first width w1 and different radii of curvature R(Rx, Ry, Rz) of the convex edge portion 23. The second group Z2 is an aggregate of multiple Precure rubber 2b having a second width w2 which is greater than the first width w1 and different radii of curvature R(Rx, Ry, Rz) of the convex edge portion 23. The third group Z3 is an aggregate of multiple Precure rubber 2b having a third width w3 which is greater than the second width w2 and different radii of curvature R(Rx, Ry, Rz) of the convex edge portion 23. The Precure rubber 2b prepared in the second step S2 is not limited to this embodiment and may include, for example, a fourth group and groups from the fourth group onward (not shown). Furthermore, the matters described for the first group Z1 hereafter also apply to the fourth group and groups from the fourth group onward. It is desirable that each of the first group Z1 to the third group Z3 includes each of the first multiple types of Precure rubber 2b.

[0045] In the third step S3, it is desirable that the Precure rubber 2b of the first group Z1, the second group Z2, and the third group Z3 be attached to a base tire 1a having a width W (shown in Figure 1) that is 90% or more and less than 110% of the width w. If the width w of the Precure rubber 2b is less than 90% of the width W of the base tire 1a to which the Precure rubber 2b is attached, or if it is 110% or more of the width W of the base tire 1a, then in attaching the Precure rubber 2b in the third step S3, both the Precure rubber 2b and the base tire 1a will require significant processing, which may worsen workability. If the width w of the Precure rubber 2b is less than 90% to 95% of the width W of the base tire 1a to which the Precure rubber 2b is attached, or if it is 105% or more but less than 110% of the width W of the base tire 1a, then in the third step S3, processing of both the Precure rubber 2b and the base tire 1a is necessary, but the deterioration of workability is minimized. Furthermore, if the width w of the Precure rubber 2b is 95% or more but less than 97% of the width W of the base tire 1a to which the Precure rubber 2b is attached, or if it exceeds 103% but is less than 105% of the width W of the base tire 1a, then in the third step S3, only processing of either the Precure rubber 2b or the base tire 1a is required, thus minimizing workability issues. Furthermore, if the width w of the Precure rubber 2b is 97% to 103% of the width W of the base tire 1a to which the Precure rubber 2b is attached, then in the third step S3, neither the Precure rubber 2b nor the base tire 1a needs to be processed, and the Precure rubber 2b can be attached directly to the base tire 1a, resulting in improved workability. Note that the ratio of the width of the Precure rubber 2b to the width W of the base tire 1a is not limited to the numerical range described above. Also, the processing refers to cutting or adding to a part of the Precure rubber 2b and / or the base tire 1a.

[0046] From this perspective, for example, the first width w1 of each Precure rubber 2b in the first group Z1 is set to 163 mm, the second width w2 of each Precure rubber 2b in the second group Z2 is set to 200 mm, and the third width w3 of each Precure rubber 2b in the third group Z3 is set to 244 mm. In other words, each Precure rubber 2b in the first group Z1 is attached to a base tire 1a having a width W of 163 × 0.9 = 146.7 (mm) or more and less than 163 × 1.1 = 179.3 (mm). Also, each Precure rubber 2b in the second group Z2 is attached to a base tire 1a having a width W of 200 × 0.9 = 180 (mm) or more and less than 200 × 1.1 = 220 (mm). Furthermore, each Precure rubber 2b of the third group Z3 is attached to a base tire 1a having a width W of 244 × 0.9 = 219.6 (mm) or more and less than 244 × 1.1 = 268.4 (mm).

[0047] In this way, the second step S2 and third step S3 allow the Precure rubber 2b, which corresponds to the tire outer diameter D of the tire 1 and the width W of the base tire 1a, to be attached to the base tire 1a. This effectively reduces the RRO and suppresses the cost required for producing the Precure rubber 2b.

[0048] Although particularly preferred embodiments of the present invention have been described in detail above, the present invention is not limited to the embodiments described above and can be implemented in various modified forms.

[0049] [Note] The present invention includes the following embodiments.

[0050] [Invention 1] A method for manufacturing a retreaded tire, comprising: a tread portion including at least one block row in which a plurality of blocks are arranged in the circumferential direction of the tire; and a longitudinal section obtained by cutting the block row along the circumferential direction of the tire, wherein the contact surface of the block includes an arc-shaped portion that is convex outward in the radial direction of the tire, The first step is to prepare a rally tire from which the tread rubber has been removed. A second step of preparing a first plurality of types of strip-shaped Precure tread rubber, each having a plurality of convex edges for forming the arc portion, and each having a different radius of curvature R of the convex edges, wherein the number of the first plurality of types is less than the number of types of tire outer diameters of the retreaded tire, and The third step includes attaching one Precure tread rubber selected from the first plurality of Precure tread rubbers according to the tire outer diameter of the retreaded tire to the base tire, A method for manufacturing retreaded tires. [Invention 2] The method for manufacturing a retreaded tire according to the present invention, wherein the radius of curvature R is correlated with the outer diameter of the retreaded tire. [Invention 3] The method for manufacturing a retreaded tire according to the present invention, wherein in the third step, the Precure rubber is attached to the base tire of the retreaded tire having an outer diameter of 1.5 times or more and less than 2.5 times the radius of curvature R of the convex edge portion, as described in the second part of the present invention. [4th Invention] The Precure tread rubber, when attached to the base tire, includes a first region extending in the circumferential direction of the tire on the block row, and a second region located outside the first region in the axial direction of the tire and on the block row, extending in the circumferential direction of the tire. A method for manufacturing a retreaded tire according to any one of claims 1 to 3 of the present invention, wherein the radius of curvature R of the convex edge of the first region is greater than the radius of curvature R of the convex edge of the second region. [5th ​​Invention] The block row includes a first block row and a second block row located further outward in the tire axial direction than the first block row. The Precure tread rubber includes a plurality of first convex edges for forming the arc portion of the first block row, and a plurality of second convex edges for forming the arc portion of the second block row. A method for manufacturing a retreaded tire according to any one of claims 1 to 4 of the present invention, wherein the radius of curvature R of the first convex edge is greater than the radius of curvature R of the second convex edge. [Invention 6] The second step includes further preparing a second set of Precure tread rubbers with different width dimensions, A method for manufacturing a retreaded tire according to any one of inventions 1 to 5, wherein the number of the second type is less than the number of sizes of the base tire. [7th Invention] The method for manufacturing a retreaded tire according to the present invention, the third step of which is to select from among the second plurality of types of Precure tread rubber that can be attached according to the size of the base tire. [Explanation of symbols]

[0051] S1 Step 1 S2 Step 2 S3 Step 3 1. Reconditioned tires 1a Single tire 2b Precure tread rubber 11 blocks 12. Arc section 23 Convex edge D Tire outer diameter

Claims

1. A method for manufacturing a retreaded tire, comprising: a tread portion including at least one block row in which a plurality of blocks are arranged in the circumferential direction of the tire; and a longitudinal section obtained by cutting the block row along the circumferential direction of the tire, wherein the contact surface of the block includes an arc-shaped portion that is convex outward in the radial direction of the tire, The first step is to prepare a base tire from which the tread rubber has been removed. A second step of preparing a first plurality of types of strip-shaped Precure tread rubber having a plurality of convex edges for forming the arc portion, and having different radii of curvature R of the convex edges, wherein the number of the first plurality of types is less than the number of types of tire outer diameters of the retreaded tire, and The third step includes attaching one Precure tread rubber selected from the first plurality of Precure tread rubbers according to the tire outer diameter of the retread tire to the base tire, A method for manufacturing retreaded tires.

2. The method for manufacturing a retreaded tire according to claim 1, wherein the radius of curvature R is correlated with the outer diameter of the retreaded tire.

3. The method for manufacturing a retreaded tire according to claim 2, wherein in the third step, the Precure rubber is attached to the base tire of the retreaded tire having an outer diameter of 1.5 times or more and less than 2.5 times the radius of curvature R of the convex edge portion.

4. The Precure tread rubber, when attached to the base tire, includes a first region extending in the circumferential direction of the tire on the block row, and a second region located outside the first region in the axial direction of the tire and on the block row, extending in the circumferential direction of the tire. The method for manufacturing a retreaded tire according to claim 3, wherein the radius of curvature R of the convex edge of the first region is greater than the radius of curvature R of the convex edge of the second region.

5. The block row includes a first block row and a second block row located further outward in the tire axial direction than the first block row. The Precure tread rubber includes a plurality of first convex edges for forming the arc portion of the first block row, and a plurality of second convex edges for forming the arc portion of the second block row. The method for manufacturing a retreaded tire according to claim 3, wherein the radius of curvature R of the first convex edge is greater than the radius of curvature R of the second convex edge.

6. The second step includes further preparing a second set of Precure tread rubbers with different width dimensions, A method for manufacturing a retreaded tire according to any one of claims 1 to 5, wherein the number of the second multiple types is less than the number of sizes of the base tire.

7. The method for manufacturing a retreaded tire according to claim 6, wherein the third step includes selecting from the second plurality of types of Precure tread rubber that can be attached according to the size of the base tire.

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