tire

Abstract

To provide a tire that has a display object for depicting a character, a figure, or a symbol on the outer surface of the sidewall part, and that is manufactured through a step of polishing the surface of the display object, and capable of achieving an improved surface state of the display object.SOLUTION: In a tire having a display object on an outer surface of a sidewall part, in which at least a part of a top surface of a convex part constituting the display object exposes a different-colored rubber embedded in a part of the sidewall part and therefore has a color different from that of the outer surface of the sidewall part, when a part extending along a tire radial direction of the convex part constituting the display object is defined as a radial element, an angle θr formed by a side surface of the convex part and a normal direction to the outer surface of the sidewall part in a cross section orthogonal to the radial element is set to 15° to 30° inclusive, or a connection part of the side surface of the convex part that connects the outer surface of the sidewall part in the cross section orthogonal to the radial element is formed into an arc shape having a curvature radius Rr of 2.5 to 4.0 mm inclusive.SELECTED DRAWING: Figure 2

Description

[Technical field]

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

[0002] Indications 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 the indications, the indications are formed from a different-colored rubber (e.g., white rubber) that is a different color from the color of the sidewall (usually black) (so-called "white letters"). When manufacturing such tires, at least a part of the portion corresponding to the sidewall of a green tire (the portion corresponding to the indications) is structured by laminating 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, the indications are formed as convex portions protruding from the surface of the sidewall, and then the surface of the convex portions (cover rubber layer) is polished and removed to expose the white rubber layer, forming the indications made of different-colored rubber (see, for example, Patent Document 1).

[0003] In such tires, the process of polishing the surface of the markings (protruding parts) is performed by a dedicated polishing machine (buffing machine) or the like. This device rotates a polishing body (such as a grindstone) against the side of the tire that is mounted on a stand and rotates, and polishes the sidewall part (markings) of the tire in the thickness direction (the direction of the protruding height of the protruding parts) by an interval that is preset for each type of tire, so as to expose the embedded different color rubber on the tire surface (see, for example, Patent Document 2). When performing the polishing process (buffing process) with such a device, if the dimensions of the markings formed as the protruding parts are small, the rigidity of the markings (protruding parts) cannot be ensured, and problems such as the markings collapsing during polishing occur, which may cause the surface condition of the markings to deteriorate after polishing. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2018-114732 A [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 which has markings depicting letters, figures or symbols on the outer surface of the sidewall portion and is manufactured through a process of polishing the surface of the markings, and which makes it possible to improve the surface condition of the markings. [Means for solving the problem]

[0006] A first tire of the present invention for achieving the above object includes a tread portion extending in a circumferential direction of the tire to form an annular shape, and a pair of sidewall portions disposed on both sides of the tread portion, and an indicia depicting a letter, figure or symbol is formed on an outer surface of the sidewall portion by the shape of a top face of a protrusion protruding from the outer surface of the sidewall portion, and at least a part of the top face of the protrusion has a different color from the outer surface of the sidewall portion by exposing a different color rubber embedded in a part of the sidewall portion, and the tire has a different color from the outer surface ... by exposing a different color rubber embedded in a part of the sidewall portion. A portion of the protrusion constituting the indicia extending along the tire circumferential direction is defined as a circumferential element. When the radial direction element is perpendicular to the radial direction element, an angle θr between the side surface of the protrusion and the normal direction of the outer surface of the sidewall portion is 15° or more and 30° or less. and an angle θc between a side surface of the protrusion and a normal direction of an outer surface of the sidewall portion in a cross section perpendicular to the circumferential element is smaller than the angle θr. It is characterized by:

[0007] A second tire of the present invention for achieving the above object includes a tread portion extending in a circumferential direction of the tire to form an annular shape, and a pair of sidewall portions disposed on both sides of the tread portion, and an indicia depicting a letter, figure or symbol is formed on an outer surface of the sidewall portion by the shape of a top face of a protrusion protruding from the outer surface of the sidewall portion, and at least a part of the top face of the protrusion has a different color from the outer surface of the sidewall portion by exposing a different color rubber embedded in a part of the sidewall portion, and the tire has a different color from the outer surface ... by exposing a different color rubber embedded in a part of the sidewall portion. A portion of the protrusion constituting the indicia extending along the tire circumferential direction is defined as a circumferential element. When the radial direction element is in a cross section perpendicular to the radial direction element, a connecting portion of the side surface of the protrusion portion connected to the outer surface of the sidewall portion is arc-shaped, and a curvature radius Rr of the connecting portion is 2.5 mm or more and 4.0 mm or less. In a cross section perpendicular to the circumferential element, the side surface of the protrusion and the outer surface of the sidewall portion are smoothly connected via an arc-shaped connecting portion, and the curvature radius Rc of the connecting portion is smaller than the curvature radius Rr. It is characterized by: Effect of the Invention

[0008] The present inventors have conducted extensive research into the appearance defects of markings in tires manufactured through a process of polishing the surface of the convex parts that constitute the markings, and as a result have found that if the dimensions of the markings formed as the convex parts are small, when the polishing body rotates and comes into contact with the markings (convex parts), defects such as the markings (convex parts) collapsing in the rotation direction (polishing direction) of the polishing body occur, which causes the surface condition of the markings to deteriorate after polishing (the surface of the markings does not become smooth, and for example, scale-like irregularities occur).The present invention is based on this finding, and prevents the markings (convex parts) from collapsing by increasing the strength of the parts of the convex parts that are susceptible to load in the polishing direction (the parts extending in the direction perpendicular to the polishing direction, i.e., along the tire radial direction) that constitute the markings, thereby improving the surface condition of the markings after polishing. Specifically, in the first tire of the present invention, the angle θr between the wall surface of the radial element (the side surface of the convex portion in a cross section perpendicular to the radial element) and the normal direction of the outer surface of the sidewall portion is secured to be appropriately large, so that the rigidity of the radial element that is likely to receive a load in the polishing direction is secured, and the indicia (convex portion) can be prevented from collapsing. Similarly, in the second tire of the present invention, the radial element and the outer surface of the sidewall portion are connected via a connection portion that has a cross-sectional arc shape with an appropriately large curvature radius Rr, so that the rigidity of the radial element that is likely to receive a load in the polishing direction is secured, and the indicia (convex portion) can be prevented from collapsing. In either case, the indicia (convex portion) can be effectively prevented from collapsing, so that the appearance defects of the indicia caused by the collapse can be suppressed, and the surface of the indicia after polishing can be made smooth.

[0009] In the first tire of the present invention, when a portion of a protrusion constituting an indicia extending along the tire circumferential direction is defined as a circumferential element, an angle θc formed by a side surface of the protrusion and a normal direction of an outer surface of a sidewall portion in a cross section perpendicular to the circumferential element is smaller than the angle θr. stomach. In this way, by increasing the angle θr for the wall surfaces in areas (radial elements) where collapse is likely to occur and decreasing the angle θc for circumferential elements where the impact is less, the amount of rubber used in the display object can be reduced.

[0010] In the second tire of the present invention, when a portion of a protrusion constituting the indicia extending along the tire circumferential direction is defined as a circumferential element, in a cross section perpendicular to the circumferential element, a side surface of the indicia and an outer surface of the sidewall portion are smoothly connected via an arc-shaped connecting portion, and a curvature radius Rc of the connecting portion is smaller than a curvature radius Rr. stomach. In this way, by increasing the radius of curvature Rr for the wall surfaces in areas (radial elements) where collapse is likely to occur, and decreasing the radius of curvature Rc for circumferential elements where the impact is less, the amount of rubber used in the display object can be reduced.

[0011] In the second tire of the present invention, it is preferable that the angle θr formed by the side of the protrusion with the normal direction of the outer surface of the sidewall portion in a cross section perpendicular to the radial element is 15° or more and 30° or less. In addition, when the portion of the protrusion constituting the indicia extending along the tire circumferential direction is defined as the circumferential element, it is preferable that the angle θc formed by the side of the protrusion with the normal direction of the outer surface of the sidewall portion in a cross section perpendicular to the circumferential element is smaller than the angle θr. This makes it possible to reinforce the portion (radial element) where collapse is likely to occur not only by the radius of curvature of the connection portion but also by the angle of the side of the protrusion, thereby more effectively suppressing poor appearance of the indicia and smoothing the surface of the indicia after polishing.

[0012] In the present invention, it is preferable that the width W of the top surface of the convex portion and the protruding height H of the convex portion satisfy the relationship W / H≦1.0. If the protruding height H is large relative to the top surface width W, the display object (convex portion) is likely to collapse, so the effect of the present invention can be effectively achieved by applying the above-mentioned configuration of the present invention.

[0013] In the present invention, it is preferable that the angle that the radial element forms with respect to the tire radial direction is within a range of ±30°. By using a portion extending in the tire radial direction within such an angle range as the radial element, it is possible to effectively reinforce a portion that is likely to collapse when the surface of the display object is polished, which is advantageous for improving the surface condition of the display object.

[0014] In the present invention, it is preferable that the length L of the indicia in the tire radial direction is 25 mm or less. When the size of the indicia in the tire radial direction is small like this, the dimensions such as the width W of the top surface of the indicia are also small, and the indicia is likely to collapse when the surface is polished, so that the effect of the present invention can be more efficiently achieved by applying the present invention described above. [Brief description of the drawings]

[0015] [Figure 1] 1 is a meridian cross-sectional view of a pneumatic tire according to an embodiment of the present invention. [Diagram 2] FIG. 1 is an explanatory diagram showing an example of an indicia of a tire according to an embodiment of the present invention. [Diagram 3] 1A to 1C are explanatory diagrams illustrating the states of an object before and after polishing. [Figure 4] 1 is a cross-sectional view showing a display according to an embodiment of the present invention. [Diagram 5] FIG. 11 is a cross-sectional view showing a display according to another embodiment of the present invention. [Figure 6] FIG. 2 is an explanatory diagram showing radial portions of an indicia of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] The configuration of the present invention will be described in detail below with reference to the accompanying drawings.

[0017] When the tire of the present invention is a pneumatic tire as shown in FIG. 1, it includes 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 on the tire radial inner side of the sidewall portions 2. In FIG. 1, the symbol CL indicates the tire equator, and the symbol E indicates the ground contact edge. Although not depicted in FIG. 1 because it is a meridian cross section, the tread portion 1, the sidewall portions 2, and the bead portions 3 each extend in the tire circumferential direction to form an annular shape, thereby forming a toroidal basic structure of a pneumatic tire. The following explanation using FIG. 1 is basically based on the meridian cross section shown in the figure, but each tire component extends in the tire circumferential direction to form an annular shape.

[0018] 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 is folded back from the inner side to the outer side in the tire width direction around the bead cores 5 arranged in each bead portion 3. A bead filler 6 is arranged on the outer periphery of the bead cores 5, and the bead filler 6 is wrapped by the main body and folded back parts of the carcass layer 4. Meanwhile, a plurality of belt layers 7 (two layers in FIG. 1) are embedded on the outer periphery side 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 to, for example, a range of 10° to 40°. Furthermore, at least one belt reinforcing layer 8 (two layers in FIG. 1) is provided on the outer periphery side 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.

[0019] As described below, the present invention relates to indicia formed on the surface of the sidewall portion 2 of a tire, and therefore the basic structure (cross-sectional structure) of the tire is not limited to the general structure described above. In addition, 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 be applied to various tires, including non-pneumatic tires, as long as the tire is provided with indicia depicting letters, figures, or symbols on the outer surface of the sidewall portion and is manufactured through a process of polishing the surface of the indicia.

[0020] In the present invention, as shown in Figures 1 and 2, a display 10 is provided on the outer surface of at least one of the pair of sidewall portions 2. The display 10 depicts a letter, figure, or symbol by the shape of the top surface of a protrusion 11 protruding from the outer surface of the sidewall portion 2. The display 10 of the present invention has a color different from that of the outer surface of the sidewall portion by exposing a different color rubber 12 embedded in a part of the sidewall portion 2 at least in part of the top surface of the protrusion 11 constituting the display 10. Since the outer surface of the sidewall portion of a tire is generally black, it is preferable that the different color rubber be white rubber from the viewpoints of visibility and decorativeness.

[0021] In more detail, the protrusion 11 constituting the display 10 is formed as a protrusion 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 protrusion 11 (a part of the cover rubber 13 and the different color rubber 12) is polished and removed to expose the different color rubber 12 as shown in Fig. 3(b), forming the display 10 in which at least a part of the top surface of the display 10 is made of the different color rubber 12. Note that Fig. 3(b) shows the state in which the upper part above the dashed line in Fig. 3(a) has been polished and removed. Since it is manufactured as described above, strictly speaking, the top surface of the protrusion 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.

[0022] The example shown in FIG. 2 depicts the letter "N." More specifically, the contour of the letter "N" is formed by the convex portion 11 whose top surface is made of a different color rubber 12, and the letter "N" is depicted as a whole by this contour (the convex portion 11) and the portion surrounded by the contour (the surface of the sidewall portion 2). The dashed line in FIG. 2 depicts the lower end of the convex portion 11 (the portion connected to the outer surface of the sidewall portion 2), and the area between the dashed line and the solid line in FIG. 2 corresponds to the side of the convex portion 11. In the following description, of the convex portion 11 constituting such an indication 10, the portion extending along the tire radial direction (the up-down direction in the figure) is referred to as the radial element 11r, and the portion extending along the tire circumferential direction (the left-right direction in the figure) is referred to as the circumferential element 11c.

[0023] In the first embodiment of the present invention, in a cross section (cross section XX in FIG. 2) perpendicular to the radial element 11r shown in FIG. 4(a), when the angle between the side surface of the protrusion 11 and the normal direction of the outer surface of the sidewall portion 2 is defined as the wall angle θr, this wall angle θr is set to 15° to 30°, preferably 20° to 25°. The wall angle θr is measured based on an extension line of a part where the side surface of the protrusion 11 extends linearly in a cross section perpendicular to the radial element 11r. When the entire side surface of the protrusion 11 is arc-shaped, the structure is specified based on the radius of curvature Rr described later instead of the wall angle θr, as in the second embodiment described later.

[0024] In the first embodiment described above, the thickness of the protrusion 11 at the lower part (the part close to the surface of the sidewall part) of the protrusion 11 can be ensured, and the rigidity of the radial element 11r that is likely to receive a load in the polishing direction in the process of polishing the surface of the protrusion 11 constituting the display 10 can be ensured, so that the display 10 (protrusion 11) is prevented from collapsing, the appearance defect of the display 10 caused by the collapse is suppressed, and the surface of the display 10 after buffing can be made smooth. If the wall angle θr is less than 15° in the first embodiment, the thickness of the lower part of the protrusion 11 cannot be sufficiently ensured, and the collapse of the display 10 (protrusion 11) cannot be prevented. If the wall angle θr exceeds 30° in the first embodiment, the thickness of the lower part of the protrusion 11 becomes excessive, making it difficult to properly depict the intended characters, figures, or symbols by the display 10.

[0025] In the first embodiment, when the angle formed by the side surface of the protrusion 11 and the normal direction of the outer surface of the sidewall portion 2 in the cross section (YY cross section in FIG. 2) perpendicular to the circumferential element 11c shown in FIG. 4(b) is taken as the wall angle θc, this wall angle θc is preferably smaller than the wall angle θr described above. That is, in the radial element 11r, the thickness of the protrusion 11 on the lower side (part close to the surface of the sidewall portion) of the protrusion 11 is secured to be large, while in the circumferential element 11c, the thickness of the protrusion 11 on the lower side (part close to the surface of the sidewall portion) of the protrusion 11 is set to the conventional level. In this way, the wall angle θr is increased for the wall surface of the part (radial element 11r) where collapse is likely to occur, while the wall angle θc is reduced for the circumferential element 11c where the impact of collapse is small, thereby suppressing the amount of rubber used in the display object 10. The range of the wall angle θc is not particularly limited, but can be set to, for example, 5° or more and 15° or less. Moreover, the difference between the wall surface angle θr and the wall surface angle θc can be set to, for example, 5° to 20°. The wall surface angle θc is measured in the same manner as the wall surface angle θr described above.

[0026] 4(a) and (b) are for explaining the wall surface angles θr and θc, and therefore omit the distinction between the different color rubber 12 and the cover rubber 13. Even if the wall surface angles θr and θc are made different as described above, it is preferable that the width W of the top surface of the convex portion 11 (and the width of the different color rubber exposed at the top surface of the convex portion 11) is constant (especially when the top surface of the convex portion 11 forms the outline of the displayed object as in the illustrated example).

[0027] In a second aspect of the present invention, as shown in FIG. 5(a), in a cross section (cross section XX in FIG. 2) perpendicular to the radial element 11r, the connection portion 14 that connects to the outer surface of the sidewall portion 2 of the side of the convex portion 11 is arc-shaped, and the radius of curvature Rr of this connection portion 14 is set to 2.5 mm or more and 4.0 mm or less, preferably 3.0 mm or more and 3.5 mm or less.

[0028] In the second embodiment described above, the shape of the connecting portion 14 ensures the thickness of the protrusion 11 at the lower portion (the portion close to the surface of the sidewall portion) of the protrusion 11, and the rigidity of the radial element 11r that is likely to receive a load in the polishing direction in the process of polishing the surface of the protrusion 11 constituting the display 10 can be ensured. Therefore, the display 10 (protrusion 11) is prevented from collapsing, the appearance defect of the display 10 caused by the collapse is suppressed, and the surface of the display 10 after buffing can be made smooth. If the radius of curvature Rr is less than 2.5 mm in the second embodiment, the thickness of the lower portion of the protrusion 11 cannot be sufficiently ensured, and the collapse of the display 10 (protrusion 11) cannot be prevented. If the radius of curvature Rr exceeds 4.0 mm in the second embodiment, the thickness of the lower portion of the protrusion 11 becomes excessive, making it difficult to properly depict the intended characters, figures, or symbols by the display 10.

[0029] In the second embodiment, the side surface of the protrusion 11 and the outer surface of the sidewall portion 2 may be smoothly connected via the arc-shaped connecting portion 14 even in the cross section (YY cross section in FIG. 2) perpendicular to the circumferential element 11c shown in FIG. 5(b), and it is preferable that the radius of curvature Rc of the connecting portion 14 is smaller than the radius of curvature Rr. That is, in the radial element 11r, the thickness of the protrusion 11 on the lower side (the portion close to the surface of the sidewall portion) of the protrusion 11 is secured to be large, while in the circumferential element 11c, the thickness of the protrusion 11 on the lower side (the portion close to the surface of the sidewall portion) of the protrusion 11 is set to the conventional level. In this way, the radius of curvature Rr is increased for the wall surface of the portion (radial element 11r) where collapse is likely to occur, while the radius of curvature Rc is reduced for the circumferential element 11c where the effect of collapse is small, thereby suppressing the amount of rubber used in the display object 10. The range of the radius of curvature Rc is not particularly limited, but it can be set to, for example, 1.5 mm or more and 2.0 mm or less. Moreover, the difference between the radius of curvature Rr and the radius of curvature Rc can be set to, for example, 1.0 mm or more and 2.0 mm or less.

[0030] 5(a) and (b) are for explaining the radii of curvature Rr and Rc, and therefore do not distinguish between the different color rubber 12 and the cover rubber 13. Even if the radii of curvature Rr and Rc are made different as described above, it is preferable that the width W of the top surface of the convex portion 11 (the width of the different color rubber exposed at the top surface of the convex portion 11) is constant (especially when the top surface of the convex portion 11 forms the outline of the displayed object as in the illustrated example).

[0031] In both the first and second aspects, when the top surface of the protrusion 11 forms the contour line of the display object as in the illustrated example, the width W of the top surface of the protrusion 11 and the protruding height H of the protrusion 11 preferably satisfy the relationship W / H≦1.0, more preferably 0.5≦W / H≦0.8 in a cross section perpendicular to the radial element 11r. If the protruding height H is large relative to the top surface width W, the display object 10 (protrusion 11) is likely to collapse, so the effect of the present invention can be effectively achieved by applying the above-mentioned configuration of the present invention. If the ratio W / H of the width W to the protruding height H is in the relationship W / H>1.0, the protruding height H is small relative to the width W of the top surface of the protrusion 11, and the rigidity of the protrusion 11 is easily ensured, so the effect of applying the above-mentioned configuration of the present invention is limited. As mentioned above, it is preferable that the width W of the top face of the convex portion 11 and the protruding height H of the convex portion 11 are constant regardless of the part of the display object 10, so that even in a cross section perpendicular to the circumferential element 11c, the width W of the top face of the convex portion 11 and the protruding height H of the convex portion 11 preferably satisfy the relationship W / H≦1.0, and more preferably 0.5≦W / H≦0.8.

[0032] As described above, the radial element 11r refers to a portion of the protrusion 11 constituting the display object 10 that extends along the tire radial direction (the vertical direction in the figure), but it is particularly preferable that the angle α that the radial element 11r forms with respect to the tire radial direction is within the range of ±30°. For example, in the example of FIG. 6 (depicting the same alphabet "N" as in FIG. 2), the shaded portion corresponds to the radial element 11r, and the angle α that it forms with respect to the tire radial direction is all within the range of ±30°. By regarding the portion extending in the tire radial direction within such an angle range as the radial element 11r, it is possible to effectively reinforce the portion that is likely to collapse when the surface of the display object 10 is polished, which is advantageous for improving the surface condition of the display object 10. The angle α is measured based on the widthwise center of the top surface of the protrusion 11.

[0033] The tire indicia 10 to which the present invention is applied preferably has a length L along the tire radial direction of 25 mm or less. If the size of the indicia 10 in the tire radial direction is small, the dimensions such as the width W of the top surface of the indicia 10 are also small, and the indicia 10 is likely to collapse when its surface is polished, so that the effect of the present invention can be more efficiently achieved by applying the present invention described above. The length L of the indicia 10 along the tire radial direction is the size of each character, figure, or symbol contained in the indicia 10, and is measured as the length along the tire radial direction between the upper end and lower end of the indicia 10 in the tire radial direction, as shown in Figures 1 and 2.

[0034] The cross-sectional height SH of the tire to which the present invention is applied is preferably 150 mm or less, and more preferably 120 mm to 140 mm. In a tire having such a small cross-sectional height, the size of the indicia 10 provided on the sidewall portion 2 in the tire radial direction tends to be small, and the dimensions such as the width W of the top surface of the indicia 10 also become small, and the indicia 10 is likely to collapse when the surface is polished. Therefore, by applying the present invention described above, the effects of the present invention can be exhibited more efficiently.

[0035] As described above, the present invention is an invention intended to reinforce the portions (radial elements 11r) where collapse is likely to occur by increasing the wall angle θr of the protrusions 11 and the curvature radius Rr of the connection, and therefore it is not necessary to apply the above settings to all radial elements 11r depending on the shape of the characters, figures, or symbols depicted in the display object 10. In other words, in the portions where the protrusions 11 are close to each other and densely packed due to the shape of the depicted characters, figures, or symbols and the strength of the protrusions 11 can be ensured, the shape is already such that collapse is unlikely to occur and the force applied during polishing is distributed, so the above settings do not necessarily need to be applied.

[0036] The first tire feature (wall angle) and the second tire feature (curvature radius) of the present invention can be applied in combination. That is, in a cross section perpendicular to the radial element 11r, the connection portion 14 connecting the side surface of the protrusion 11 to the outer surface of the sidewall portion 2 is configured in an arc shape, and the curvature radius Rr of this connection portion 14 is set to 2.5 mm or more and 4.0 mm or less, preferably 3.0 mm or more and 3.5 mm or less, while the angle (wall angle θr) that the side surface of the protrusion 11 (the portion extending linearly between the top surface of the protrusion 11 and the connection portion 14) makes with the normal direction to the outer surface of the sidewall portion 2 is set to 15° or more and 30° or less, preferably 20° or more and 25° or less. In this case, it is further preferable to make the radius of curvature Rc of the connection portion 14 in the circumferential element 11c smaller than the radius of curvature Rr of the connection portion 14 in the radial element 11r, and to make the wall angle θc in the circumferential element 11c smaller than the wall angle θr in the radial element 11r. This makes it possible to reinforce the portion (radial element 11r) where collapse is likely to occur by increasing both the wall angle θr of the protruding portion 11 and the radius of curvature Rr of the connection portion, thereby making it possible to more effectively exert the effects of the present invention described above. Note that other features of the first and second aspects not described in detail in this paragraph can also be applied in appropriate combination.

[0037] The present invention will be further described below with reference to examples, but the scope of the present invention is not limited to these examples. EXAMPLES

[0038] Tires were produced as Conventional Examples 1-2, Comparative Examples 1-4, and Examples 1-8, with a tire size of 225 / 60R17 99T and a basic structure (cross-sectional structure) as illustrated in Fig. 1, with the structures of the display objects set as shown in Tables 1 and 2. Note that, as for the structures of the display objects, in Table 1, the wall angle θr in the radial element of the protrusion constituting the display object and the wall angle θc in the circumferential element, and the ratio W / H of the width W of the top face of the protrusion and the protruding height H of the protrusion were varied, and in Table 2, the radius of curvature Rr of the connecting portion in the radial element of the protrusion constituting the display object and the radius of curvature Rc of the connecting portion in the circumferential element, and the ratio W / H of the width W of the top face of the protrusion and the protruding height H of the protrusion were varied. (Note that Example 4, in which the wall angles θr and θc are the same value, and Example 8, in which the curvature radii Rr and Rc are the same value, are reference examples.) .

[0039] In all cases, the process of polishing the surface of the display object (convex portion) was carried out by mounting each tire on a wheel with a rim size of 17 x 6.5, inflating it to an internal pressure of 200 kPa, and then mounting it on a dedicated polishing machine (buffing machine).

[0040] The surface condition, character shape, and rubber amount of the markings on these pneumatic tires were evaluated using the following evaluation methods, and the results are shown in Tables 1 and 2.

[0041] Surface condition of the display The surface condition of the markings formed on each tire was visually inspected. The evaluation results were rated as "good" if the surface of the markings (the tops of the protrusions) was smooth, and "poor" if the surface of the markings was not smooth (having a hill in the middle or being worn down on one side) or had fine scale-like irregularities on the surface of the markings.

[0042] Character shape of the display The character shape of the markings formed on each tire (the appearance of the character, figure, or symbol that each marking is intended to depict) was visually confirmed. The evaluation results were rated "good" when the character shape of the markings was good, and "poor" when the appearance of the markings as characters, figures, or symbols was poor.

[0043] Amount of rubber used The amount (volume) of rubber used in the markings was calculated based on the measured dimensions of the markings formed on each tire. The evaluation results are shown as an index in Table 1, with Conventional Example 1 set to 100, and in Table 2, with Conventional Example 2 set to 100. The smaller the index value, the less rubber was used.

[0044] [Table 1]

[0045] [Table 2]

[0046] As is clear from Table 1, the tires of Examples 1 to 4 were able to improve the surface condition and character shape of the indicia while reducing the amount of rubber used, compared to Conventional Example 1. On the other hand, in Comparative Example 1, the width W of the indicia (protruding portion) was increased to ensure rigidity, so the surface condition and character shape of the indicia were good, but the amount of rubber used was increased. In Comparative Example 2, the wall angle θr was too large, so the balance between the radial element and the circumferential element was lost, and the character shape of the indicia (appearance as a character) was deteriorated.

[0047] Also, as is clear from Table 2, the tires of Examples 5 to 8 were able to improve the surface condition and character shape of the indicia while reducing the amount of rubber used, compared to Conventional Example 2. On the other hand, in Comparative Example 3, the width W of the indicia (protruding portion) was increased to ensure rigidity, so the surface condition and character shape of the indicia were good, but the amount of rubber used was increased. In Comparative Example 4, the radius of curvature Rr was too large, so the balance between the radial element and the circumferential element was lost, and the character shape of the indicia (appearance as a character) was deteriorated.

[0048] The present disclosure includes the following inventions. Invention [1] A tire comprising a tread portion extending in a circumferential direction of the tire to form an annular shape, and a pair of sidewall portions disposed on both sides of the tread portion, wherein the outer surface of the sidewall portion is formed with indicia depicting letters, figures or symbols formed by the shape of the top faces of protrusions protruding from the outer surface of the sidewall portion, and at least a part of the top faces of the protrusions exposes a different color rubber embedded in a part of the sidewall portion, thereby having a different color from the outer surface of the sidewall portion; When a portion of the protrusion constituting the indicia extending along the tire radial direction is defined as a radial element, an angle θr formed by a side surface of the protrusion and a normal direction to an outer surface of the sidewall portion in a cross section perpendicular to the radial element is 15° or more and 30° or less. Invention [2] A tire comprising a tread portion extending in a circumferential direction of the tire to form an annular shape, and a pair of sidewall portions disposed on both sides of the tread portion, wherein the outer surface of the sidewall portion is formed with indicia depicting letters, figures or symbols formed by the shape of the top faces of protrusions protruding from the outer surface of the sidewall portion, and at least a part of the top faces of the protrusions exposes a different color rubber embedded in a part of the sidewall portion, thereby having a different color from the outer surface of the sidewall portion; When a portion of the protruding portion constituting the indicia extending along the tire radial direction is defined as a radial element, a connection portion that connects the side surface of the protruding portion to the outer surface of the sidewall portion in a cross section perpendicular to the radial element is arc-shaped, and a radius of curvature Rr of the connection portion is 2.5 mm or more and 4.0 mm or less. Invention [3] The tire according to invention [1], characterized in that when the portion of the protrusion constituting the indicia extending along the tire circumferential direction is defined as a circumferential element, in a cross section perpendicular to the circumferential element, the angle θc that the side of the protrusion makes with the normal direction to the outer surface of the sidewall portion is smaller than the angle θr. Invention [4] The tire according to invention [2], characterized in that, when a portion of the protruding portion constituting the indicia extending in the tire circumferential direction is defined as a circumferential element, in a cross section perpendicular to the circumferential element, the side of the protruding portion and the outer surface of the sidewall portion are smoothly connected via an arc-shaped connecting portion, and the radius of curvature Rc of the connecting portion is smaller than the radius of curvature Rr. Invention [5] A tire as described in invention [2] or [4], characterized in that in a cross section perpendicular to the radial element, the angle θr between the side of the convex portion and the normal direction to the outer surface of the sidewall portion is 15° or more and 30° or less. Invention [6] The tire according to invention [5], characterized in that when the portion of the protrusion constituting the indicia extending along the tire circumferential direction is defined as a circumferential element, the angle θc that the side of the protrusion makes with the normal direction to the outer surface of the sidewall portion in a cross section perpendicular to the circumferential element is smaller than the angle θr. Invention [7] The tire according to any one of inventions [1] to [6], wherein a width W of a top face of the protrusion and a protruding height H of the protrusion satisfy the relationship W / H≦1.0. Invention [8] The tire according to any one of inventions [1] to [7], characterized in that the angle that the radial element forms with respect to the tire radial direction is within the range of ±30°. Invention [9] The tire according to any one of inventions [1] to [8], wherein the length L of the indicia along the tire radial direction is 25 mm or less. [Explanation of symbols]

[0049] 1 Tread section 2 Sidewall 3 Bead section 4 Carcass layer 5 Bead Core 6 Bead Filler 7 Belt layer 8 Belt reinforcement layer 10 Display items 11 Convex 11r radial element 11c Circumferential element 12 Different Rubber 13 Cover rubber 14 Connection CL Tire Equator E Ground end

Claims

1. A tire comprising a tread portion extending in a circumferential direction of the tire to form an annular shape, and a pair of sidewall portions disposed on both sides of the tread portion, wherein an indicia depicting a letter, figure or symbol is formed on an outer surface of the sidewall portion by the shape of a top surface of a protrusion protruding from the outer surface of the sidewall portion, and at least a part of the top surface of the protrusion has a different color from the outer surface of the sidewall portion by exposing a different color rubber embedded in a part of the sidewall portion, a tire characterized in that, when a portion of the protrusion constituting the display object extending along the tire radial direction is defined as a radial element, and a portion of the protrusion constituting the display object extending along the tire circumferential direction is defined as a circumferential element, an angle θr that the side of the protrusion forms with the normal direction to the outer surface of the sidewall portion in a cross section perpendicular to the radial element is 15° or more and 30° or less, and an angle θc that the side of the protrusion forms with the normal direction to the outer surface of the sidewall portion in a cross section perpendicular to the circumferential element is smaller than the angle θr.

2. A tire comprising a tread portion extending in a circumferential direction of the tire to form an annular shape, and a pair of sidewall portions disposed on both sides of the tread portion, wherein an indicia depicting a letter, figure or symbol is formed on an outer surface of the sidewall portion by the shape of a top surface of a protrusion protruding from the outer surface of the sidewall portion, and at least a part of the top surface of the protrusion has a different color from the outer surface of the sidewall portion by exposing a different color rubber embedded in a part of the sidewall portion, a tire in which, when a portion of the protrusion constituting the display object extending along the tire radial direction is defined as a radial element, and a portion of the protrusion constituting the display object extending along the tire circumferential direction is defined as a circumferential element, a connection portion that connects the side surface of the protrusion to the outer surface of the sidewall portion in a cross section perpendicular to the radial element is arc-shaped, a radius of curvature Rr of the connection portion is 2.5 mm or more and 4.0 mm or less, the side surface of the protrusion and the outer surface of the sidewall portion are smoothly connected via the arc-shaped connection portion in a cross section perpendicular to the circumferential element, and a radius of curvature Rc of the connection portion is smaller than the radius of curvature Rr.

3. The tire according to claim 2, wherein an angle θr between a side surface of the protrusion and a normal direction to an outer surface of the sidewall portion in a cross section perpendicular to the radial element is 15° or more and 30° or less.

4. The tire according to claim 3, characterized in that, when a portion of the protrusion constituting the indicia extending along the tire circumferential direction is defined as a circumferential element, an angle θc that a side surface of the protrusion makes with a normal direction to an outer surface of the sidewall portion in a cross section perpendicular to the circumferential element is smaller than the angle θr.

5. The tire according to any one of claims 1 to 4, characterized in that a width W of the top surface of each of the projections and a protruding height H of each of the projections satisfy the relationship W / H≦1.

0.

6. The tire according to any one of claims 1 to 4, characterized in that an angle formed by the radial element with respect to the tire radial direction is within a range of ±30°.

7. 5. The tire according to claim 1, wherein the length L of the indicia in the tire radial direction is 25 mm or less.

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