Tire molding mold, tire manufacturing method using the same, and tire

Abstract

To provide a tire molding mold which makes it possible to prevent defects in appearance while ensuring exhaust properties during manufacturing, a tire manufacturing method using the same, and a tire.SOLUTION: A tire molding mold for molding a tire equipped with a display 9 on an outer surface of a sidewall part 2 depicting letters, figures, or symbols by means of a shape of a top of a protrusion 9' raised from the outer surface of the sidewall part 2 includes: a recess 30 for forming the protrusion 9; and an air vent slit 31 that is formed on an inner surface of the recess 30 so as to open thereto.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a tire molding mold for molding a tire having a marking depicting a letter, figure, or symbol on the outer surface of the sidewall portion, and a tire manufacturing method and tire using the same. [Background technology]

[0002] On the outer surface of the sidewall of a tire, a display for displaying a manufacturer name, a brand name, etc. may be formed. Such a display is mainly configured as a protrusion protruding from the outer surface of the sidewall, and a letter, figure, or symbol is depicted depending on the shape of the top surface of the protrusion (see, for example, Patent Document 1). A tire molding die for manufacturing such a tire is formed with a recess corresponding to the protrusion, and a vent hole (thin exhaust hole) may be provided in the recess to exhaust air accumulated in the recess to the outside of the die and obtain a protrusion of an appropriate shape. However, when exhausting air using a vent hole, there is a risk that rubber flows into the vent hole and spews, which are whisker-like protrusions, are generated on the surface of the protrusion. Such spews are cut off before shipping as a product tire, but even if the spews are cut off, there is a risk that traces (cut marks) of the spews being cut off remain on the surface of the protrusion. In other words, there is a possibility that the root part of the spews remains as a fine cylindrical protrusion. There is a problem that the presence of such cut marks deteriorates the appearance of the display composed of the protrusions. Therefore, there is a need for measures to prevent defects in appearance while ensuring the exhaust performance during manufacturing. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2018-114732 A Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present invention is to provide a tire molding mold that makes it possible to prevent defects in appearance while ensuring exhaust properties during manufacturing, and a tire manufacturing method and tire using the same. [Means for solving the problem]

[0005] In order to achieve the above object, the tire molding mold of the present invention is a tire molding mold for molding a tire having on the outer surface of a sidewall portion a display element depicting letters, figures or symbols by the shape of the top surface of a protrusion protruding from the outer surface of the sidewall portion, the tire molding mold being characterized by having a recess for forming the protrusion, and an air vent slit formed to open on the inner surface of the recess.

[0006] In order to achieve the above-mentioned object, the tire manufacturing method of the present invention is a tire manufacturing method using the above-mentioned tire molding mold, characterized in that a tire in an unvulcanized state is molded and the tire is vulcanized in the tire molding mold.

[0007] In addition, in order to achieve the above-mentioned object, the tire of the present invention is a tire having a marking on the outer surface of the sidewall portion, which depicts a letter, figure or symbol by the shape of the top surface of a protrusion protruding from the outer surface of the sidewall portion, and is characterized in that at least a part of the surface of the protrusion has traces of an air vent slit. Effect of the Invention

[0008] As described above, the tire molding mold of the present invention is for manufacturing a tire having a display on the outer surface of the sidewall portion, which displays characters, figures, or symbols by the shape of the top surface of the protrusion raised from the outer surface of the sidewall portion, and since slits are provided instead of conventional vent holes to exhaust air accumulated in the recesses for molding the protrusions to the outside of the mold, it is possible to prevent poor appearance while ensuring good exhaust properties. That is, with conventional vent holes, there is a risk that rubber will flow into the vent hole and cause a spew, and even if the spew is cut off, there is a possibility that a cut mark (the root part of the spew remaining as a fine cylindrical protrusion) will remain, but since the slit is a fine gap, rubber is unlikely to flow into it, and even if a mark of the slit remains due to the rubber that has flowed into the slit, only a fine linear mark will remain, so the appearance is not impaired and poor appearance can be prevented.

[0009] In addition, because the tire manufacturing method of the present invention uses the tire molding mold of the present invention described above, air remaining in the mold (particularly in the recesses) during vulcanization can be efficiently exhausted to the outside of the mold through the slits. At this time, since the slits are minute gaps as described above, rubber does not substantially flow into them, and even if traces of the slits remain due to the rubber that has flowed into the slits, only minute linear traces remain on the tire, so the appearance is not impaired and poor appearance can be prevented.

[0010] Furthermore, a tire manufactured using the tire molding mold of the present invention (tire of the present invention) does not leave any traces that impair the appearance or visibility of the indicia, as occurs in tires in which indicia are molded using a mold with conventional vent holes, and only has traces of the air-venting slits on at least a portion of the surface of the convex portion as described above. In other words, even if traces of the air-venting slits remain on a portion of the indicia (convex portion), the traces of the slits are fine linear traces as described above, and therefore the traces of the slits do not impair the appearance or visibility of the shape of the indicia (convex portion).

[0011] In the tire molding die of the present invention, the width of the slit is preferably 0.01 mm to 0.5 mm. Making the slit width sufficiently thin in this manner is advantageous in preventing defects in appearance. In the present invention, the "slit width" refers to the length measured along the short side direction of the slit.

[0012] In the tire molding die of the present invention, the total length of the slits is preferably 20% to 200% of the length of the contour line of the top surface of the convex portion. By ensuring an appropriate length of the slits relative to the convex portion in this manner, it is advantageous to prevent poor appearance while exhibiting good exhaust performance. In the present invention, the "length of the slit" is the length measured along the extension direction of the slit.

[0013] The tire molding mold of the present invention can also be designed to include a replacement piece having a slit formed therein and a fixing hole into which the replacement piece fits. In this design, cleaning of the inside of the slit becomes easier when cleaning the mold after vulcanization, thereby improving productivity.

[0014] In the tire manufacturing method of the present invention, it is preferable that the portion of the tire in an unvulcanized state corresponding to the marking is structured by laminating a different-colored rubber layer having a color different from the black rubber constituting the sidewall portion and a cover rubber layer made of black rubber covering the different-colored rubber layer, and then the marking is formed as a protrusion protruding from the surface of the sidewall portion, and at least the cover rubber layer on the surface of the protrusion is polished and removed to expose the different-colored rubber layer, thereby forming the marking made of the different-colored rubber. In such a tire marking (so-called "white letter"), if a conventional vent hole is used, excessive rubber may flow into the vent hole when air is released, and especially if the different-colored rubber flows in excessively, the intended shape of the marking cannot be formed or maintained, and the shape of the marking may become distorted. However, since a slit is used for air release in the present invention, excessive rubber does not flow in, which is advantageous for improving the appearance of the marking. In addition, when a conventional vent hole is used, it is necessary to cut off the spew before the process of polishing the cover rubber layer, but since a slit is used in the present invention, no spew occurs, and the process of cutting off the spew can be reduced. [Brief description of the drawings]

[0015] [Figure 1] FIG. 1 is an explanatory diagram showing an example of a tire vulcanizing apparatus. [Diagram 2] FIG. 2 is an explanatory diagram illustrating a recess of a tire vulcanizing mold according to an embodiment of the present invention. [Diagram 3] FIG. 4 is an explanatory view showing a schematic diagram of a recess of a tire vulcanization mold according to another embodiment of the present invention. [Figure 4] 1 is a meridian cross-sectional view showing an example of a tire according to an embodiment of the present invention. [Diagram 5] 1A to 1C are explanatory diagrams illustrating the states of an object before and after polishing. [Figure 6] FIG. 1 is an explanatory diagram showing an example of an indicia of a tire according to an embodiment of the present invention. [Figure 7] FIG. 4 is an explanatory view showing a schematic diagram of a recess of a tire vulcanization mold according to another embodiment of the present invention. [Figure 8]FIG. 4 is an explanatory view showing a schematic diagram of a recess of a tire vulcanization mold according to another embodiment 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] FIG. 1 shows an example of a tire vulcanizing apparatus including a tire vulcanizing mold (hereinafter, sometimes simply referred to as a "mold") of the present invention. The tire vulcanizing apparatus includes a mold 10 for molding the outer surface of a tire T, and a cylindrical bladder 20 inserted inside the tire T. The tire vulcanizing apparatus also includes a heating and pressurizing medium supplying means (not shown) for supplying a heating and pressurizing medium such as steam into the bladder 20, and a heating means (not shown) for heating the mold 10. Note that the present invention relates to a tire molding mold for molding a tire (described later) having a display depicting a character, figure, or symbol on the outer surface of the tire sidewall portion, and therefore the tire vulcanizing apparatus is not limited to the example shown in the figure as long as it has a molding surface for molding the tire sidewall portion and the display.

[0018] The mold 10 is composed of a pair of side plates 11 (lower side plate 11A and upper side plate 11B) for molding the sidewall portion of the tire T, a pair of bead rings 12 (lower bead ring 12A and upper bead ring 12B) for molding the bead portion of the tire T, and a plurality of sectors 13 for molding the tread portion of the tire T, and the tire T is vulcanized and molded inside the mold 10.

[0019] The heating and pressurizing medium supplying means (not shown) is adapted to supply steam adjusted to a predetermined temperature and pressure and nitrogen gas adjusted to a predetermined pressure as the heating and pressurizing medium at appropriate times. When such a heating and pressurizing medium is introduced into the bladder 20, the tire T is pressed from the inside toward the inner surface of the mold 10 based on the pressure. It is also possible to use only steam as the heating and pressurizing medium.

[0020] Heating means (not shown) is attached to the lower side plate 11, the upper side plate 12, and the sector 13 that constitute the mold 10, and the tire T is vulcanized by heating the mold 10 with the heating means.

[0021] In the tire vulcanizing apparatus thus configured, the tire molding die (mold 10) of the present invention, particularly at least one of the pair of side plates 11 (lower side plate 11A and upper side plate 11B) for molding the sidewall portion, is provided with a recess 30 for forming an indicia 9 (protrusion 9') in the tire, as shown in Fig. 2. The indicia 9, as described later, depicts a letter, figure, or symbol by the shape of the top surface of the protrusion 9' protruding from the outer surface of the sidewall portion 2.

[0022] In the tire molding die of the present invention, a slit 31 for venting air is provided in the recess 30 so as to open to the inner surface of the recess 30. As shown in Fig. 2, the slit 31 penetrates the die 10 (side plate 11) and reaches an exhaust mechanism (not shown) in the tire molding die or the outside of the tire molding die, and discharges air remaining in the die during tire molding. In the illustrated example, the slit 31 extends along the longitudinal direction of the recess 30. In this way, since the slit 31 is provided instead of a conventional vent hole (a thin cylindrical exhaust hole), it is possible to prevent poor appearance while maintaining good exhaust properties. That is, with conventional vent holes, there was a risk that rubber would flow into the vent hole and cause a spew, and even if the spew was removed, there was a possibility that a cut mark (the base of the spew remaining as a tiny cylindrical protrusion) would remain. However, because slits 31 are tiny gaps, almost no rubber flows into them, and even if a mark of slit 31 is formed due to rubber that has flowed into slit 31, only a very narrow linear mark remains, so the appearance is not marred and poor appearance can be prevented.

[0023] As described above, the slit 31 is a gap with a very small width at the opening, and the width w of the slit 31 is preferably 0.01 mm to 0.5 mm, more preferably 0.02 mm to 0.05 mm. When the width of the slit 31 is sufficiently small, the rubber does not substantially flow into the slit 31, and even if a trace of the slit remains due to the rubber that has flowed into the slit 31, only a very small linear trace remains, so that the appearance is not impaired and poor appearance can be prevented. If the width w of the slit 31 is smaller than 0.01 mm, it is difficult to ensure sufficient exhaust performance. In addition, since the slit 31 is too thin, it is difficult to manufacture the mold (machining the slit 31). If the width w of the slit 31 exceeds 0.5 mm, the rubber easily flows into the slit 31 and the trace of the slit 31 is easily left.

[0024] The slit 31 may be provided directly in the mold 10 (side plate 11), but as shown in FIG. 3, the mold 10 may be structured to include a mold body 10A and a replacement piece 10B in which the slit 31 is formed, and may be provided with a fixing hole for fitting the replacement piece 10B to the mold body 10A. The replacement piece 10B is a component that is detachably inserted into a fixing hole provided in the mold body 10A, and the molding surface of the mold 10 is formed by fitting the replacement piece 10B into the fixing hole. Note that FIG. 3 shows a state in which the replacement piece 10B is fitted into the fixing hole of the mold body 10A. In this specification, the slit 31 can be provided at any position of the replacement piece 10B, but it is preferable to form the slit 31 by recessing the surface of the replacement piece 10B that abuts against the side of the fixing hole against which it abuts when fitted, as in the example shown in the figure. With this configuration, cleaning inside the slit 31 becomes easier when cleaning the mold 10 after vulcanization, and productivity can be improved.

[0025] The slit 31 can be formed by any method (e.g., wire processing, laser processing, etc.) that can process a minute gap of the above-mentioned dimensions, whether it is formed directly in the mold 10 or using the replacement piece 10B as described above.

[0026] When a tire is manufactured using the above-mentioned tire molding die, a tire can be manufactured by a general method, that is, by molding an unvulcanized tire and vulcanizing the unvulcanized tire in the above-mentioned tire molding die. The tire manufactured in this way (the tire of the present invention) has a marking (protrusion) described later on the surface of the tire side portion (sidewall portion 2) as described later. At this time, air is removed from the recess 30 when the protrusion 9 is molded by the above-mentioned slit 31, and since the slit 31 is a fine gap, almost no rubber flows into it, so in the tire of the present invention, basically no trace due to air removal is formed on the surface of the protrusion 9. Even if a trace of the slit 31 is formed due to the rubber that has flowed into the slit 31, only a linear trace with a fine width remains on only a part of the protrusion 9. In addition, even if a trace of the slit 31 is formed, since the trace of the slit 31 is a linear trace with a fine width as described above, the shape of the protrusion 9 is not damaged by the trace of the slit 31, and the appearance and visibility of the marking can be improved.

[0027] FIG. 4 shows an example of a tire manufactured by the tire vulcanization mold of the present invention (hereinafter, referred to as "the tire of the present invention"). The tire of FIG. 4 is a pneumatic tire, and 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. 4, the symbol CL indicates the tire equator. Although not depicted in FIG. 4 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, and thus the toroidal basic structure of the pneumatic tire is constituted. The following explanation using FIG. 4 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.

[0028] In the tire of FIG. 4, 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 the folded back portion of the carcass layer 4. Meanwhile, a plurality of belt layers 7 (two layers in FIG. 4) 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. 4) 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.

[0029] In the present invention, as shown in Fig. 4, an indicia 9 is provided on the outer surface of at least one of the pair of sidewall portions 2. The indicia 9 depicts a letter, figure, or symbol by the shape of the top surface of a protrusion 9' protruding from the outer surface of the sidewall portion 2.

[0030] The indicia 9 of the present invention can also be designed so that at least a part of the top surface of the protrusion 9' constituting the indicia 9 has a different color from the outer surface of the sidewall portion by exposing a different color rubber layer (different color rubber G1) embedded in a part of the sidewall portion 2. Since the outer surface of the sidewall portion of a tire is generally black, it is preferable that the different color rubber G1 be white rubber from the viewpoints of visibility and decorativeness.

[0031] In more detail, the protrusion 9' constituting the display object 9 is formed as a protrusion 11 in which a different-colored rubber layer (different-colored rubber G1) embedded in the sidewall portion 2 and a cover rubber layer (cover rubber G2) covering the different-colored rubber layer are laminated as shown in FIG. 5(a), and then the surface of this protrusion 11 (cover rubber G2 and a part of different-colored rubber G1) is polished and removed to expose the different-colored rubber G1 as shown in FIG. 5(b), forming the display object 9 in which at least a part of the top surface of the display object 9 is made of the different-colored rubber G1. Note that FIG. 5(b) shows a state in which the upper part above the dashed line in FIG. 5(a) has been polished and removed. Since it is manufactured as described above, strictly speaking, the top surface of the protrusion 9' of the present invention is made of the different-colored rubber G1 in the region excluding the peripheral portion derived from the cover rubber G2.

[0032] The display object 9 shown in Fig. 6 depicts the letter "G". More specifically, the contour of the letter "G" is formed by the protruding portion 9' whose top surface is made of the different color rubber G1, and the letter "G" is depicted as a whole by this contour (protruding portion 9') and the portion surrounded by the contour (the surface of the sidewall portion 2). The dashed line in Fig. 6 depicts the bottom end of the protruding portion 9' (the portion that connects 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 surface of the protruding portion 9'.

[0033] In the above-mentioned specifications, at least the cover rubber G2 on the surface of the protruding portion 9' is polished and removed, so even if there are traces (such as spews when a conventional vent hole is used) on the surface of the protruding portion 9' before polishing, the traces due to air venting are removed by this polishing process, and in this respect, the appearance of the display 9 is good. However, even if a polishing process is performed to expose the different color rubber G1, there is a risk that polishing cannot be performed properly if there are spews, as in the case of using a conventional vent hole, so a preliminary process of removing the spews is required before the polishing process to expose the different color rubber G1, which is disadvantageous in terms of workability. In addition, while the conventional vent hole has good air venting efficiency, rubber is likely to flow into the vent hole when air is vented, and especially in the case of a structure using the above-mentioned different color rubber G1, if excessive rubber flows into the vent hole, the intended shape of the display 9 cannot be formed and maintained, and there is a risk that the shape of the display 9 (the shape of the different color rubber G1 exposed after the cover rubber G2 is polished and removed) will become distorted. In contrast, in the present invention, the above-mentioned slits 31 are used for air venting, so traces of the slits 31 are unlikely to be left, and even if traces of the slits 31 are left, they are fine linear traces, so a preliminary polishing step is unnecessary and workability is improved. Furthermore, the slits 31 make it difficult for rubber to flow in excessively, and it is possible to prevent poor appearance of the display object 9 due to the above-mentioned excessive inflow of rubber.

[0034] In the case of a tire not provided with the above-mentioned different-color rubber G1, since the step of polishing the surface of the convex portion 9' is not performed, if there are traces (such as spews when a conventional vent hole is used) on the surface of the convex portion 9' due to air venting, this will cause the appearance of the display object 9 to be poor. In contrast, in the present invention, air venting is performed by the slit 31 as described above, and since the slit 31 is a fine gap into which almost no rubber flows, in the tire of the present invention, basically no traces due to air venting are formed on the surface of the display object 9 (convex portion 9'). Even if a trace of the slit 31 is formed due to the rubber flowing into the slit 31, only a linear trace of a fine width remains on only a part of the convex portion 9'. In addition, even if a trace of the slit 31 is formed, since the trace of the slit 31 is a linear trace of a fine width as described above, the shape of the convex portion 9' is not damaged by the trace of the slit 31, and the appearance and visibility of the display object 9 can be improved.

[0035] The slit 31 of the present invention is preferably provided on the bottom surface of the recess 30 for forming the convex portion 9' (that is, the portion corresponding to the top surface of the convex portion 9' constituting the indicia 9) regardless of the form of the indicia 9 described above (so-called white letters having a different color rubber G1 or so-called black letters having no different color rubber G2). For example, the slit 31 can be provided at the center of the bottom surface of the recess 30 as shown in FIG. 7(a). Alternatively, the slit 31 can be provided on the edge portion of the bottom surface of the recess 30 (the portion corresponding to the edge portion of the top surface of the convex portion 9') as shown in FIG. 7(b). In any case, it is preferable to arrange the slit 31 on the bottom surface of the recess 30 so as to extend along the lines constituting the character, figure, or symbol depicted by the indicia 9. By providing the slit 31 in this way, the extension direction of the lines constituting the indicia 9 (character, figure, or symbol) and the trace (linear trace) of the slit 31 are aligned in the tire, so that the trace of the slit 31 is less noticeable, which is advantageous in preventing poor appearance.

[0036] The slits 31 may be provided over the entire length of the bottom surface of the recess 30 for forming the protrusion 9' (i.e., the portion corresponding to the top surface of the protrusion 9' constituting the display object 9), or may be provided locally in a portion where air is particularly likely to accumulate. For example, in the case of the illustrated letter "G," air is likely to accumulate where the lines constituting the letter bend, so it is advisable to provide the slits 31 at the bent portion as shown in FIG. 8. Note that the recess 30 shown in FIGS. 7(a)-(b) and FIG. 8 is for forming the display object 9 (the letter "G") in FIG. 6, and therefore has a shape that is an inverted version of the letter "G."

[0037] As shown in FIG. 6, when the display object 9 depicts a character, figure, or symbol by the entire contour line (the convex portion 9') and the portion surrounded by the contour line (the surface of the sidewall portion 2), the length of the slit 31 is preferably 20% to 200%, more preferably 20% to 100%, of the length of the contour line of the top surface of the convex portion 9' (the length of the solid line in the figure). If the length of the slit 31 is less than 20% of the length of the contour line of the top surface of the convex portion 9', the opening area of ​​the slit 31 cannot be sufficiently secured, making it difficult to exhibit good exhaust performance. If the length of the slit 31 exceeds 200% of the length of the contour line of the top surface of the convex portion 9', the total area of ​​the slit 31 becomes excessive even if the slit 31 is used, so the effect of preventing poor appearance is limited. In addition, when the display object 9 is a so-called white letter equipped with a different color rubber G1, a process of polishing the surface of the convex portion 9' is performed as described above, so the length of the slit 31 is more preferably 60% to 80% of the length of the contour line of the top surface of the convex portion 9'. Furthermore, when the display object 9 is a so-called black letter that does not have a different color rubber G1, unlike the case of a white letter, a process of polishing the surface of the convex portion 9' is not performed, so that traces of the slit 31 are less likely to remain, the length of the slit 31 is preferably 40% to 70% of the length of the contour line of the top surface of the convex portion 9'.

[0038] Unlike the example of FIG. 6, when the character, figure, or symbol depicted by the display object 9 is a raised convex portion 9' in its entirety, the length of the slit 31 is preferably 20% to 200%, more preferably 20% to 100%, of the length of the contour line of the top surface of the convex portion 9' (the length of the solid line in the figure). If the length of the slit 31 is less than 20% of the length of the contour line of the top surface of the convex portion 9', the opening area of ​​the slit 31 cannot be sufficiently secured, making it difficult to achieve good exhaust performance. If the length of the slit 31 exceeds 200% of the length of the contour line of the top surface of the convex portion 9', the total area of ​​the slit 31 becomes excessive even if the slit 31 is used, so that the effect of preventing poor appearance is limited. In addition, when the display object 9 is a so-called white letter equipped with a different color rubber G1, a process of polishing the surface of the convex portion 9' is performed as described above, so the length of the slit 31 is more preferably 60% to 80% of the length of the contour line of the top surface of the convex portion 9'. Furthermore, when the display object 9 is a so-called black letter that does not have a different color rubber G1, unlike the case of a white letter, a process of polishing the surface of the convex portion 9' is not performed, so that traces of the slit 31 are less likely to remain, the length of the slit 31 is preferably 40% to 70% of the length of the contour line of the top surface of the convex portion 9'.

[0039] The tire of the present invention may be a non-pneumatic tire as long as the indicia 9 (protrusion 9') is provided on the surface of the tire side portion 2 as described above. When the tire of the present invention is a pneumatic tire, the tire can be filled with air, an inert gas such as nitrogen, or other gases.

[0040] 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

[0041] In manufacturing a tire having a tire size of 165 / 50R16 75V and a structure as shown in Fig. 4, the method of exhausting air from the recesses, the width of the slit / vent hole, the length of the slit / vent hole, and the method of forming the slit / vent hole for the tire molding die were varied as shown in Tables 1 and 2 (Conventional Examples 1-2, Examples 1-7). Note that the markings for the tires manufactured in Table 1 (Conventional Example 1, Examples 1-3) are so-called white letters, and the markings for the tires manufactured in Table 2 (Conventional Example 2, Examples 4-7) are so-called black letters.

[0042] In Tables 1 and 2, the column "Exhaust method" indicates whether a vent hole or a slit was used as an exhaust hole for exhausting air in the recess. The column "Slit / vent hole width" indicates the width of the slit or vent hole. The width of the vent hole is essentially the diameter of the vent hole. The column "Slit / vent hole length" indicates the length of the slit or vent hole. The length of the vent hole is also essentially the diameter of the vent hole. In this column, if the exhaust mechanism is a vent hole, the actual dimension (unit: mm) is indicated, and if the exhaust mechanism is a slit, the ratio to the length of the outline of the protrusion constituting the display object is indicated. In the column "Slit / vent hole formation method", the case where a slit or vent hole is directly provided in the mold is indicated as "direct formation", and the case where a replacement piece with a slit or vent hole formed therein is used is indicated as "replacement piece".

[0043] These pneumatic tires were evaluated for prevention of molding defects, visibility and appearance, workability (buffing / vent cutting), and workability (mold cleaning) by the following evaluation methods, and the results are shown in Tables 1 and 2.

[0044] Prevents improper molding 100 tires were vulcanized using each tire molding mold, and the number of tires with molding defects caused by air pockets in the markings (protruding parts) of the resulting tires was counted to determine the incidence rate. The evaluation results are shown as an index using the reciprocal of the measured values, with the value of Conventional Example 1 being 100 in Table 1, and the value of Conventional Example 2 being 100 in Table 2. The higher the index value, the better the prevention of molding defects caused by air pockets.

[0045] Visibility and Appearance Testers visually inspected the sidewalls of test tires manufactured using each tire molding mold, and evaluated the visibility and appearance (appearance and beauty) of the markings. In particular, for Table 1 (white letters), the presence or absence of letter distortion due to rubber flow was confirmed, and for Table 2 (black letters), the presence or absence of traces (spew, etc.) due to the exhaust mechanism was confirmed. The evaluation results are shown as an index for Table 1, with the value of Conventional Example 1 set to 100, and for Table 2, with the value of Conventional Example 2 set to 100. The higher the index value, the better the decorativeness.

[0046] Workability (buffing / vent cutting) For test tires manufactured using each tire molding die, the time required for the buffing process (a polishing process to expose the white rubber) when the markings were white letters, or the time required for vent cutting (a process to remove spews and the like resulting from the exhaust mechanism) when the markings were black letters, was measured. The evaluation results were expressed as an index using the reciprocal of the measured value, with the value of Conventional Example 1 (when white letters) or Conventional Example 2 (when black letters) being set at 100. The higher the index value, the shorter the time required for each process and the better the workability.

[0047] Workability (mold cleaning) The time required to clean the mold (exhaust mechanism) after a tire was vulcanized using each tire molding mold was measured. The evaluation results are shown as an index using the reciprocal of the measured value, with the value of Conventional Example 1 being set to 100 for Table 1, and the value of Conventional Example 2 being set to 100 for Table 2. A higher index value means a shorter time required to clean the mold and better workability.

[0048] [Table 1]

[0049] [Table 2]

[0050] As is clear from Tables 1 and 2, the tires of Examples 1 to 7 had improved visibility and appearance while preventing poor molding compared to Conventional Example 1 and Conventional Example 2, and further improved workability (time required for buffing / vent cutting and mold cleaning).

[0051] The present disclosure includes the following inventions. Invention [1] A tire molding die 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, A tire molding die comprising: a recess for forming the protrusion; and an air vent slit formed so as to open on an inner surface of the recess. Invention [2] The tire molding mold according to invention [1], wherein the width of the slit is 0.01 mm to 0.5 mm. Invention [3] The tire molding mold according to invention [1] or [2], characterized in that the total length of the slits is 20% to 200% of the length of the contour line of the top surface of the convex portion. Invention [4] A tire molding mold according to any one of inventions [1] to [3], comprising a replacement piece having the slit formed therein, and a fixing hole into which the replacement piece fits. Invention [5] A method for manufacturing a tire using a tire molding mold according to any one of Inventions [1] to [4], comprising molding an unvulcanized tire and vulcanizing the tire in the tire molding mold. Invention [6] A method for manufacturing a tire as described in invention [5], characterized in that the portion of the unvulcanized tire corresponding to the indicia is formed by laminating a different color rubber layer having a color different from the black rubber constituting the sidewall portion and a cover rubber layer made of black rubber covering the different color rubber layer, and the indicia is formed as a convex portion protruding from the surface of the sidewall portion.After that, at least the cover rubber layer on the surface of the convex portion is polished and removed to expose the different color rubber layer, thereby forming the indicia made of different color rubber. Invention [7] A tire having markings on the outer surface of a sidewall portion which depict letters, figures or symbols by the shape of the top surface of a protrusion protruding from the outer surface of the sidewall portion, and characterized in that at least a part of the surface of the protrusion has traces of slits for venting air. [Explanation of symbols]

[0052] 1 Tread section 2 Sidewall 3 Bead section 4 Carcass layer 5 Bead Core 6 Bead Filler 7 Belt layer 8 Belt reinforcement layer 9 Display items 9' Convex 10. Mold 11 Side plate 12 Bead ring 13 Sectors 20 Bladder 30 Recess 31 Slit CL Tire Equator G1 Different Color Rubber G2 Cover Rubber

Claims

1. A tire molding die for molding a tire having a display on an outer surface of a sidewall portion, the display depicting a letter, figure, or symbol by the shape of a top surface of a protrusion protruding from the outer surface of the sidewall portion, A tire molding die comprising: a recess for forming the protrusion; and an air vent slit formed so as to open on an inner surface of the recess.

2. 2. The tire molding mold according to claim 1, wherein the width of the slit is 0.01 mm to 0.5 mm.

3. 3. The tire molding mold according to claim 1, wherein the total length of the slits is 20% to 200% of the length of the contour line of the top surface of the convex portion.

4. 3. The tire molding die according to claim 1, further comprising a replacement piece having the slit formed therein, and a fixing hole into which the replacement piece is fitted.

5. 3. A method for manufacturing a tire using the tire molding mold according to claim 1 or 2, comprising molding an unvulcanized tire and vulcanizing the tire in the tire molding mold.

6. 6. A tire manufacturing method as claimed in claim 5, characterized in that the portion of the unvulcanized tire corresponding to the indicia is formed by laminating a different color rubber layer having a color different from the black rubber constituting the sidewall portion and a cover rubber layer made of black rubber covering the different color rubber layer, and after forming the indicia as the convex portion protruding from the surface of the sidewall portion, at least the cover rubber layer on the surface of the convex portion is polished and removed to expose the different color rubber layer, thereby forming the indicia made of different color rubber.

7. 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, characterized in that at least a portion of the surface of the protrusion has a trace of an air vent slit.

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