Tire manufacturing method

Abstract

To provide a tire manufacturing method including a step of providing a plurality of markings on an outer surface of a sidewall part and polishing surfaces of the markings, which makes it possible to improve the appearance of the markings after polishing.SOLUTION: A molding of a tire having a marking 10 on an outer surface of a sidewall 2, the marking 10 depicting letters, figures, or symbols by a shape of a top surface of a protrusion 11 raised from the outer surface of the sidewall 2, includes a step of removing at least a cover rubber layer 13 on the surface of the protrusion 11 by applying an abrasive to the sidewall 2 while rotating the vulcanized tire, thereby exposing a different-color rubber layer 12. When a specific character 10' is defined as the marking 10 that is surrounded by the protrusion 11 and includes a concave part 20 that is independent of the surroundings, a chamfered part 21 is formed on an edge adjacent to the concave part 20 on the top surface of the protrusion 11 that constitutes the specific character 10' before polishing.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a tire having indicia depicting letters, figures, or symbols on the outer surface of the sidewall portion. [Background technology]

[0002] Indicia for displaying the manufacturer's name, brand name, etc., may be formed on the outer surface of the sidewall of a tire. In particular, in order to improve the visibility and decorativeness of these indicators, they are formed using a different-colored rubber (e.g., white rubber) that is a different color from the color of the sidewall (generally black) (so-called "white letters"). When manufacturing such tires, at least a portion of the portion corresponding to the sidewall of a green tire (the portion corresponding to the indicator) is formed into a laminated structure of a different-colored rubber layer (white rubber layer) and a cover rubber layer (black rubber layer) that covers the different-colored rubber layer, the green tire is vulcanized, and the indicators are formed as protrusions protruding from the surface of the sidewall. The surface of the protrusions (cover rubber layer) is then polished and removed to expose the white rubber layer, thereby forming the indicators made of different-colored rubber (see, for example, Patent Document 1).

[0003] In such tires, the process of polishing the surface of the indicia (protrusions) is carried out using a dedicated polishing machine (buffing machine) or the like. This machine rotates a polishing body (such as a grindstone) against the side of the tire, which is mounted on a stand and rotates, and polishes the tire sidewall (indicia) in the thickness direction (the direction of the protrusion height of the protrusions) at intervals preset for each type of tire, polishing the embedded rubber of a different color to expose it on the tire surface (see, for example, Patent Document 2). When the polishing process (buffing process) is carried out using such a machine, indicia of certain shapes tend to have a hard time achieving a smooth surface after polishing, which could result in a deterioration in the appearance of the indicia (character strings) after polishing. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2018-114732 [Patent Document 2] Japanese Patent Application Publication No. 05-277925 Summary of the Invention [Problem to be solved by the invention]

[0005] The object of the present invention is to provide a tire manufacturing method that provides a plurality of markings depicting letters, figures, or symbols on the outer surface of the sidewall portion and includes a step of polishing the surfaces of these markings, which method makes it possible to improve the appearance of the markings after polishing. [Means for solving the problem]

[0006] The tire manufacturing method of the present invention for achieving the above-mentioned object is a manufacturing method for molding a tire with indicia that depict letters, figures, or symbols on the outer surface of a sidewall portion by the shape of the top surfaces of convexities that protrude from the outer surface of the sidewall portion, the method comprising the steps of: molding a green tire in which a different colored rubber layer that has a color different from black rubber and a cover rubber layer made of black rubber that covers the different colored rubber layer are laminated in the portion corresponding to the indicia; vulcanizing the green tire in a mold to form the convexities that correspond to the indicia; and rotating the vulcanized tire while applying a polishing body to the sidewall portion to remove at least the cover rubber layer on the surface of the convexities to expose the different colored rubber layer.When a specific character is defined as a character among the indicia that includes a concave portion that is surrounded by the convex portions and is independent from its surroundings, a chamfered portion is formed on the edge adjacent to the concave portion on the top surface of the convexity that constitutes the specific character before polishing. [Effects of the Invention]

[0007] The inventors of the present invention have conducted extensive research into the poor appearance of markings in tires manufactured through a process of polishing the surfaces of convex portions that make up the markings, and have found that when polishing certain characters (referred to as "specific characters" in this invention) that are surrounded by convex portions and include a concave portion that is independent of the surrounding area, the edges of the convex portions adjacent to the concave portions tend to curl up, resulting in an uneven surface after polishing and a poor appearance.The present invention is based on this finding, and by forming chamfered portions on the edges adjacent to the concave portions on the top surfaces of the convex portions that make up the specific characters before polishing, the load of the polishing body on the affected area can be distributed, preventing the aforementioned curl up, and smoothing the surface of the marking after polishing, thereby improving its appearance.

[0008] In this invention, for the sake of convenience, a display object that includes a recess surrounded by a convex portion and is independent of its surroundings is defined as a "specific character." However, display objects also include objects depicting figures or symbols in addition to letters, and even figures or symbols other than letters that include a recess surrounded by a convex portion and is independent of its surroundings are all considered to be "specific characters."

[0009] The above-mentioned turning-up becomes more pronounced when the rotation direction of the vulcanized tire and the rotation direction of the polishing body are opposite in the process of exposing the different-colored rubber layer. Therefore, when the rotation directions of the tire and the polishing body are different, the use of the present invention is particularly effective in preventing the above-mentioned turning-up.

[0010] In the present invention, the chamfered portion is provided at least on the rear side in the direction of rotation of the tire after vulcanization, and when the length along the tire radial direction of the recessed portion at the top surface of the convex portion constituting the specific character before polishing is L and the length along the tire radial direction of the chamfered portion is L1, it is preferable that these lengths L and L1 satisfy the relationship 0.2≦L1 / L. This allows the chamfered portion to be provided sufficiently in areas where the aforementioned curling-up is likely to occur, which is advantageous for preventing the aforementioned curling-up, smoothing the surface of the display object after polishing, and improving its appearance.

[0011] In the present invention, it is preferable that, at the tire radial center position of the indicia, the chamfer width Wa of the chamfered portion satisfies the relationship 0.01≦Wa / W≦0.7 with respect to the length W of the portion of the convex portion where the chamfered portion is formed along the tire circumferential direction, and the chamfer depth Da of the chamfered portion satisfies the relationship 0.2≦Da / D≦0.7 with respect to the protrusion height D of the indicia before polishing. This is advantageous for preventing the above-mentioned lifting up, smoothing the surface of the indicia after polishing, and improving its appearance.

[0012] In the present invention, it is preferable that the chamfered portion is a rounded chamfer with a chamfer radius R satisfying the relationship 1.0 mm≦R≦5.0 mm. This is advantageous for preventing the above-mentioned peeling up, smoothing the surface of the display after polishing, and improving its appearance.

[0013] In the present invention, when the difference between the protrusion height D of the display before polishing and the protrusion height D' after polishing is defined as the polishing amount Db, it is preferable that the polishing amount Db and the chamfer depth Da of the chamfered portion satisfy the relationship 0.1≦Db / Da≦0.8. This is advantageous for preventing the above-mentioned peeling up, smoothing the surface of the display after polishing, and improving its appearance. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a meridian cross-sectional view of a pneumatic tire according to an embodiment of the present invention. [Figure 2] FIG. 2 is an explanatory diagram schematically showing a step of polishing a vulcanized tire. [Figure 3] 1A and 1B are explanatory diagrams schematically showing the state of a display object before and after polishing. [Figure 4] 1 is an explanatory diagram schematically illustrating an example of a display object (specific characters) according to an embodiment of the present invention. [Figure 5] 10 is an explanatory diagram schematically illustrating another example of a display object (specific characters) according to an embodiment of the present invention. FIG. [Figure 6] 10A and 10B are explanatory diagrams showing the state of the vicinity of the chamfered portion of the indicia (specific characters) before and after polishing. DETAILED DESCRIPTION OF THE INVENTION

[0015] The configuration of the present invention will be described in detail below with reference to the accompanying drawings.

[0016] When a tire manufactured according to the present invention is a pneumatic tire as shown in FIG. 1, it comprises a tread portion 1 that contacts the road surface, a pair of sidewall portions 2 arranged on both sides of the tread portion 1, and a pair of bead portions 3 arranged radially inward of the sidewall portions 2. In FIG. 1, the symbol CL denotes the tire equator, and the symbol E denotes the ground-contact edge. Although not depicted in FIG. 1 because it is a meridian cross-section, the tread portion 1, sidewall portions 2, and bead portions 3 each extend circumferentially in the tire direction and form an annular shape, thereby constituting the basic toroidal structure of a pneumatic tire. The following explanation using FIG. 1 will be based essentially on the meridian cross-section shown, but each tire component also extends circumferentially in the tire direction and forms an annular shape.

[0017] A carcass layer 4 is installed between a pair of left and right bead portions 3. The carcass layer 4 includes a plurality of reinforcing cords extending in the tire radial direction and folded back from the inner side to the outer side in the tire width direction around a bead core 5 arranged in each bead portion 3. A bead filler 6 is arranged on the outer periphery of the bead core 5, and this bead filler 6 is wrapped by the main portion and folded back portion of the carcass layer 4. Meanwhile, a plurality of belt layers 7 (two layers in FIG. 1 ) are embedded on the outer periphery of the carcass layer 4 in the tread portion 1. Each belt layer 7 includes a plurality of reinforcing cords inclined with respect to the tire circumferential direction, and the reinforcing cords are arranged so as to cross each other between the layers. In these belt layers 7, the inclination angle of the reinforcing cords with respect to the tire circumferential direction is set, for example, in the range of 10° to 40°. Furthermore, at least one belt reinforcing layer 8 (two layers in FIG. 1 ) is provided on the outer periphery of the belt layer 7. The belt reinforcing layer 8 includes organic fiber cords oriented in the tire circumferential direction. In the belt reinforcing layer 8, the organic fiber cords are set at an angle of, for example, 0° to 5° with respect to the tire circumferential direction.

[0018] As shown in Figure 1, a tire manufactured according to the present invention has a display element 10 provided on the outer surface of at least one of a pair of sidewall portions 2. The display element 10 depicts letters, figures, or symbols using the shape of the top surfaces of protrusions 11 that protrude from the outer surfaces of the sidewall portions 2. The display element 10 of the present invention has a different color from the outer surfaces of the sidewall portions by exposing different-colored rubber 12 embedded in part of the sidewall portions 2 at least in part of the top surfaces of the protrusions 11 that make up the display element 10. Since the outer surfaces of tire sidewall portions are generally black, it is preferable that the different-colored rubber be white rubber from the standpoints of visibility and decorativeness.

[0019] The present invention is primarily directed to a method for manufacturing the indicia 10 described above, and therefore the basic structure (internal structure) of a tire manufactured by the present invention is not limited to the general structure described above. The following description will be based on a pneumatic tire (a tire filled with air, an inert gas such as nitrogen, or other gases) as shown in Fig. 1, etc., but the present invention can also be applied to the manufacture of various types of tires, including non-pneumatic tires, as long as it is a method for manufacturing a tire provided with indicia depicting letters, figures, or symbols on the outer surface of the sidewall portion and includes a step of polishing the surface of the indicia.

[0020] The tire manufacturing method of the present invention includes a first step of molding a green tire in which a different color rubber layer (different color rubber 12) and a cover rubber layer (cover rubber 13) are laminated in a portion corresponding to the above-mentioned display object 10; a second step of vulcanizing this green tire in a mold to form a convex portion 11 corresponding to the display object 10; and a third step of applying a polishing body B to the sidewall portion 2 while rotating the vulcanized tire T as shown in Figure 2, thereby removing at least the cover rubber layer (cover rubber 13) on the surface of the convex portion 11 and exposing the different color rubber layer (different color rubber 12) as shown in Figure 3. To explain in detail the third step (buffing step) particularly relevant to the present invention, the convex portion 11 constituting the marking 10 is formed as a convex portion 11 in which a different color rubber 12 embedded in the sidewall portion 2 and a cover rubber 13 covering the different color rubber 12 are laminated, as shown in FIG. 3(a), and then the surface of this convex portion 11 (the cover rubber 13 and a part of the different color rubber 12) is polished and removed to expose the different color rubber 12 as shown in FIG. 3(b), thereby forming a marking 10 in which at least a part of the top surface of the marking 10 is made of the different color rubber 12. Note that FIG. 3(b) shows the state in which the portion above the dashed line in FIG. 3(a) has been polished and removed. Because it is manufactured as described above, strictly speaking, the top surface of the convex portion 11 of the present invention is made of the different color rubber 12 in the region excluding the peripheral portion derived from the cover rubber 13.

[0021] In the present invention, among the indicia 10, those that include a recess 20 that is surrounded by a protrusion 11 and is independent of the surroundings are referred to as specific characters 10'. Examples of specific characters include the alphabets "A," "B," "D," "O," "P," "Q," "R," "a," "b," "d," "e," "o," "p," and "q," as well as the numbers "0," "6," "8," and "9." These are all characters that include a portion surrounded by a line, and when depicted as an indicia 10 for a tire, they include a recess 20 that is surrounded by a protrusion 11 and is independent of the surroundings. Not limited to the above-mentioned characters, various shapes and symbols that include a recess 20 that is surrounded by a protrusion 11 and is independent of the surroundings are also considered specific characters 10'.

[0022] As shown in FIGS. 4 and 5, the present invention forms a chamfered portion 21 on the edge adjacent to the recess 20 on the top surface of the protrusion 11 constituting the specific character 10′ (the letter "O" in the illustrated example) before polishing. Each of FIGS. 3 and 4 shows the specific character 10′ in a combination of a top view and a cross-sectional view taken along the arrow XX. In the top view, the chamfered portion 21 is shown as a shaded portion to make the position of the chamfered portion 21 easier to understand. Furthermore, in the cross-sectional views taken along the arrow XX in FIGS. 4 and 5, the different-colored rubber 12 and cover rubber 13 are omitted. Conventional specific characters 10′ tend to curl up on the edge adjacent to the recess 20, resulting in poor appearance. Therefore, by forming a chamfered portion 21 on the edge adjacent to the recess 20 on the top surface of the protrusion 11 constituting the specific character 10′ before polishing, the load of the polishing body on the relevant area is distributed, preventing the aforementioned curling up, and smoothing the surface of the display object 10 after polishing, thereby improving its appearance.

[0023] The above-mentioned turning-up becomes more pronounced when the rotation direction of the vulcanized tire T and the rotation direction of the polishing body B are opposite in the process of exposing the different-colored rubber 12. Therefore, it is preferable to employ the present invention when the rotation directions of the vulcanized tire T and the polishing body B are different. Note that, as shown in FIG. 2, "the rotation direction of the vulcanized tire T and the rotation direction of the polishing body B are opposite in the movement direction of the polished surface of the rotating vulcanized tire T (see the arrow in the figure)." In this case, it is preferable to provide the chamfered portion 21 at least on the rear side of the rotation direction of the vulcanized tire. This effectively suppresses the above-mentioned turning-up.

[0024] As shown in Figures 4 and 5, when the length of the recess 20 along the tire radial direction at the top surface of the protrusion 11 constituting the specific character 10' before polishing is L and the length of the chamfered portion 21 along the tire radial direction is L1, these lengths L and L1 preferably satisfy the relationship 0.2 ≦ L1 / L, and more preferably 0.4 ≦ L1 / L ≦ 1. This allows the chamfered portion 21 to be sufficiently provided in the area prone to the aforementioned peeling-up, which is advantageous for preventing the aforementioned peeling-up, smoothing the surface of the display object after polishing, and improving its appearance. If the ratio L1 / L is less than 0.2, the area prone to the aforementioned peeling-up cannot be sufficiently chamfered, and the effect of preventing peeling-up is limited.

[0025] As shown in Figures 4 and 5, when the chamfer width of the chamfered portion 21 is Wa and the length of the portion of the protrusion 11 where the chamfered portion 21 is formed along the tire circumferential direction at the tire radial center position of the display element 10 at the tire radial center position, these width Wa and length W preferably satisfy the relationship 0.01 ≦ Wa / W ≦ 0.7, more preferably 0.01 ≦ Wa / W ≦ 0.6. Furthermore, when the chamfer depth of the chamfered portion 21 is Da and the protrusion height of the display element 10 before polishing is D, these chamfer depth Da and protrusion height D preferably satisfy the relationship 0.2 ≦ Da / D ≦ 0.7, more preferably 0.3 ≦ Da / D ≦ 0.6. This is advantageous for preventing the aforementioned peeling-up, smoothing the surface of the display element after polishing, and improving its appearance. If the ratio Wa / W is less than 0.01, the chamfering is small, and the effect of preventing peeling-up is limited. If the ratio Wa / W exceeds 0.7, the chamfering will be excessive, which may deteriorate the appearance of the display 10 itself (the shape of the characters, symbols, or figures to be depicted). If the ratio Da / D is less than 0.2, the chamfering will be small, which may limit the effect of preventing peeling. If the ratio Da / D exceeds 0.7, the lower part of the chamfered portion 21 may remain even after the upper part of the convex portion 11 is polished and removed, which may deteriorate the appearance of the display 10 itself (the shape of the characters, symbols, or figures to be depicted).

[0026] The shape of the chamfered portion 21 may be an inclined chamfer as shown in Fig. 4 (the edge of the convex portion 11 is chamfered linearly in cross section) or a rounded chamfer as shown in Fig. 5 (the edge of the convex portion 11 is chamfered in an arcuate shape in cross section). In the case of the inclined chamfer of Fig. 4, the chamfer width Wa and chamfer depth Da are measured starting from the point where the top or side surface of the convex portion 11 connects with the surface of the chamfered portion 21 in cross section. In the case of the rounded chamfer of Fig. 5, the measurement is started from the point where the arc of the chamfered portion 21 begins in cross section.

[0027] When the shape of the chamfered portion 21 is a rounded chamfer as shown in Figure 5, the chamfer radius R preferably satisfies the relationship 1.0 mm ≤ R ≤ 5.0 mm, more preferably 2.0 mm ≤ R ≤ 4.0 mm. This optimizes the chamfering amount of the chamfered portion 21, preventing peeling, smoothing the surface of the display object after polishing, and improving its appearance. If the chamfer radius R is less than 1.0 mm, the chamfer is small, and the effect of preventing peeling is limited. If the chamfer radius R exceeds 5.0 mm, it becomes difficult to form a mold with such a large chamfered portion 21.

[0028] As shown in FIG. 6, when the difference between the protrusion height D of the indicia 10 before polishing and the protrusion height after polishing is defined as the polishing amount Db, the polishing amount Db preferably satisfies the relationship 0.1≦Db / Da≦0.8 and more preferably the relationship 0.2≦Db / Da≦0.7 relative to the chamfer depth Da of the chamfered portion 21. Note that in FIG. 6, the top surface of the indicia 10 before polishing is indicated by a dashed line. This is advantageous for preventing the aforementioned lifting, smoothing the surface of the indicia after polishing, and improving its appearance. If the ratio Db / Da is less than 0.1, the lower portion of the chamfered portion 21 may remain even after the upper portion of the protrusion 11 is polished and removed, potentially deteriorating the appearance of the indicia 10 itself (the shape of the characters, symbols, or figures to be depicted). If the ratio Db / Da exceeds 0.8, polishing will continue even after most of the chamfered portion 21 has been removed (i.e., after the effect of the chamfered portion 21 has decreased), making it difficult to adequately prevent peeling.

[0029] The present invention will be further explained below with reference to examples, but the scope of the present invention is not limited to these examples. [Example]

[0030] In manufacturing a tire having a tire size of 195 / 80R15 107 / 105L and having the basic structure (internal structure) illustrated in FIG. 1 and a character string (indication object) including five specific characters on the sidewall portion, tires of Conventional Example 1 and Examples 1 to 11 were produced with the following settings for the structure of the convex portion corresponding to the indication object (specific characters): presence or absence of a chamfer; the ratio L1 / L of the length L of the recessed portion along the tire radial direction at the top surface of the convex portion before polishing to the length L1 of the chamfered portion along the tire radial direction; the ratio Wa / W of the chamfered width Wa of the chamfered portion to the length W of the indication object along the tire circumferential direction at the center position of the indication object in the tire radial direction; the ratio Da / D of the chamfered depth Da of the chamfered portion to the raised height D of the indication object before polishing; the chamfer radius R; and the ratio Db / Da of the difference in raised height before and after polishing of the indication object (polishing amount Db) to the chamfer depth Da, as shown in Tables 1 and 2. In the column "Whether or not there is a chamfered portion," if there is a chamfered portion, the drawing number is also listed, along with whether the beveled chamfer shown in Figure 4 or the rounded chamfer shown in Figure 5 was used.

[0031] In each example, the process of polishing the surface of the markings (protrusions) was carried out by mounting each tire on a wheel with a rim size of 15 x 6.5, inflating the wheel to an internal pressure of 200 kPa, and then mounting the tire on a dedicated polishing machine (buffing machine). In each example, the rotation direction of the vulcanized tire and the rotation direction of the polishing body were opposite to each other.

[0032] The surface condition of the markings on these tires was evaluated by the following evaluation method, and the results are shown in Tables 1 and 2.

[0033] Surface condition of the display The surface condition of the markings (specified characters) formed on each tire was visually inspected. The evaluation results were rated as "poor" if two to five of the five specified characters in the character string had curled-up edges adjacent to the recess, resulting in poor appearance; "fair" if only one character had curled-up and the character string as a whole had almost no poor appearance; and "good" if none of the specified characters had curled-up, the surface of the markings was smooth, and no poor appearance occurred.

[0034] [Table 1]

[0035] [Table 2]

[0036] As is clear from Tables 1 and 2, the tires of Examples 1 to 11 were able to prevent the edges adjacent to the recesses of the specific characters from curling up, making the surface of the display smooth and preventing poor appearance.

[0037] The present disclosure includes the following inventions. Invention [1] A manufacturing method for molding a tire having a marking on the outer surface of a sidewall portion, the marking depicting a letter, figure, or symbol by the shape of the top surface of a protrusion protruding from the outer surface of the sidewall portion, comprising: a step of molding a green tire in which a different color rubber layer having a color different from that of the black rubber and a cover rubber layer made of black rubber covering the different color rubber layer are laminated in a portion corresponding to the indicia; a step of vulcanizing the green tire in a mold to form the protrusion corresponding to the indicia; and applying an abrasive body to the sidewall portion while rotating the vulcanized tire, thereby removing at least the cover rubber layer on the surface of the convex portion and exposing the different-color rubber layer, When a specific character is defined as an indicia that includes a recess surrounded by a convex portion and independent from its surroundings, a chamfered portion is formed on the edge adjacent to the recess on the top surface of the convex portion that constitutes the specific character before polishing. Invention [2] The method for manufacturing a tire according to invention [1], characterized in that in the step of exposing the different color rubber layer, the rotation direction of the vulcanized tire and the rotation direction of the polishing body are opposite to each other. Invention [3] The method for manufacturing a tire according to Invention [2], characterized in that the chamfered portion is provided at least on the rear side in the rotational direction of the vulcanized tire, and when the length along the tire radial direction of the recessed portion at the top surface of the convex portion constituting the specific character before polishing is L and the length along the tire radial direction of the chamfered portion is L1, these lengths L and L1 satisfy the relationship 0.2≦L1 / L. Invention [4] A method for manufacturing a tire according to any one of inventions [1] to [3], characterized in that, at the tire radial center position of the marker, the chamfer width Wa of the chamfered portion satisfies the relationship of 0.01≦Wa / W≦0.7 with respect to the length W of the part of the convex portion where the chamfered portion is formed along the tire circumferential direction, and the chamfer depth Da of the chamfered portion satisfies the relationship of 0.2≦Da / D≦0.7 with respect to the protrusion height D of the marker before polishing. Invention [5] The method for manufacturing a tire according to inventions [1] to [4], wherein the chamfered portion is a rounded chamfer and the chamfer radius R satisfies the relationship 1.0 mm≦R≦5.0 mm. Invention [6] A method for manufacturing a tire according to any one of inventions [1] to [5], characterized in that when the difference between the protrusion height D of the marking object before grinding and the protrusion height D' after grinding is defined as the grinding amount Db, the grinding amount Db satisfies the relationship 0.1≦Db / Da≦0.8 with respect to the chamfer depth Da of the chamfered portion. [Explanation of symbols]

[0038] 1 Tread section 2 Sidewall 3 Bead section 4 carcass layers 5 bead core 6 Bead filler 7 Belt Layer 8 Belt reinforcement layer 10 Display items 10' Specific characters 11 Convex part 12 Unique Rubber 13 Cover rubber 20 recess 21 Chamfered part CL Tire Equator E Ground end

Claims

1. A manufacturing method for molding a tire having indicia on an outer surface of a sidewall portion, the indicia depicting letters, figures, or symbols by the shape of a top surface of a protrusion protruding from the outer surface of the sidewall portion, comprising: a step of molding a green tire in which a different color rubber layer having a color different from that of the black rubber and a cover rubber layer made of black rubber covering the different color rubber layer are laminated in a portion corresponding to the indicia; a step of vulcanizing the green tire in a mold to form the protrusion corresponding to the indicia; and applying an abrasive body to the sidewall portion while rotating the vulcanized tire, thereby removing at least the cover rubber layer on the surface of the convex portion and exposing the different-color rubber layer, When a specific character is defined as an indicia that includes a recess surrounded by a convex portion and independent from its surroundings, a chamfered portion is formed on the edge adjacent to the recess on the top surface of the convex portion that constitutes the specific character before polishing.

2. 2. The method for manufacturing a tire according to claim 1, wherein the rotation direction of the vulcanized tire and the rotation direction of the polishing body are opposite to each other in the step of exposing the different color rubber layer.

3. 3. The tire manufacturing method according to claim 2, wherein the chamfered portion is provided at least on the rear side in the rotational direction of the vulcanized tire, and when a length along the tire radial direction of the recessed portion on a top surface of the convex portion constituting the specific character before polishing is L and a length along the tire radial direction of the chamfered portion is L1, these lengths L and L1 satisfy the relationship 0.2≦L1 / L.

4. 3. The tire manufacturing method according to claim 1, wherein, at the tire radial center position of the marker, a chamfer width Wa of the chamfered portion satisfies a relationship of 0.01≦Wa / W≦0.7 with respect to a length W of the portion of the convex portion where the chamfered portion is formed along the tire circumferential direction, and a chamfer depth Da of the chamfered portion satisfies a relationship of 0.2≦Da / D≦0.7 with respect to a protrusion height D of the marker before polishing.

5. 3. The tire manufacturing method according to claim 1, wherein the chamfered portion is a rounded chamfer, and the chamfer radius R satisfies the relationship 1.0 mm≦R≦5.0 mm.

6. 3. The tire manufacturing method according to claim 1, wherein when a difference between a protrusion height D of the marking object before polishing and a protrusion height D' after polishing is defined as a polishing amount Db, the polishing amount Db satisfies the relationship of 0.1≦Db / Da≦0.8 with respect to a chamfer depth Da of the chamfered portion.

Images