JP7082513B2 - Tire manufacturing method and tire vulcanization mold - Google Patents

Description

The present disclosure relates to a tire manufacturing method and a tire vulcanization die.

Conventionally, a tire vulcanization die (hereinafter, may be simply referred to as a “mold”) in which an exhaust hole is provided on a molded surface in which the outer surface of the tire is in close contact has been used. The exhaust hole is a hole for removing air from the mold. When an unvulcanized tire is vulcanized with a mold provided with an exhaust hole, a spew is formed on the outer surface of the tire. Spews are rubber protrusions that extend from the surface of a pneumatic tire. The spew is formed by the rubber on the outer surface of the unvulcanized tire flowing into the exhaust holes.

When the mold is opened and the vulcanized tire is taken out from the mold, the spew may be cut in the exhaust hole and the exhaust hole may be clogged. Spew breaks are particularly likely to occur with rubbers with low tear strength (eg, rubbers containing silica). Clogged exhaust holes can result in poor appearance of pneumatic tires, called bares. The bear is a defect caused by deterioration of exhaust performance and accompanying insufficient filling of rubber in the mold.

Japanese Unexamined Patent Publication No. 2004-98815

Patent Document 1 discloses a mold provided with an exhaust hole 18 as shown in FIG. 9 in order to prevent spewing out. The exhaust hole 18 has a tapered portion 181 extending from an opening 180 provided in a molded surface 170 in contact with the outer surface of the unvulcanized tire while continuously reducing the diameter, and a tapered portion 181 from the back side of the tapered portion 181. It has a smaller diameter portion 182 that is thinner and extends with a constant diameter. The minimum diameter of the tapered portion 181 is larger than the diameter of the small diameter portion 182. The length L181 of the tapered portion in the tapered portion 181 is set to about 7 mm. The exhaust hole 18 has an abutting wall 197 at the innermost part of the tapered portion 181. The end wall 197 is provided so as to be orthogonal to the length direction d18 of the exhaust hole 18.

However, when vulcanization is performed using such a mold, the rubber that has flowed into the exhaust hole 18 reaches the end wall 197 as shown in FIG. 9, and the rubber also enters the small diameter portion 182. Therefore, when the mold is opened and the vulcanized tire is taken out, the tip of the rubber that has entered the exhaust hole 18, that is, the tip of the spew 191 causes friction between the side wall 199 of the small diameter portion and the abutting wall 197. There is a risk that the spew 191 will be cut off in the exhaust hole 18 due to the pull-out resistance.

Further, in such a method, by repeatedly vulcanizing, rubber is likely to be deposited on the end wall 197 of the exhaust hole 18 at an early stage, and the deposited rubber blocks the entrance of the small diameter portion 182, and the exhaust hole is exhausted. 18 may be clogged. The reason why the rubber is deposited on the end wall 197 at an early stage is that the rubber is likely to be accumulated in the corner formed by the end wall 197 and the side wall 198 of the tapered portion 181. It is considered that the rubber is deposited in this corner because the rubber that has flowed into the exhaust hole 18 tends to remain in the corner and the flow of rubber is small in this corner. The rubber remaining in the corners promotes the deposition of new rubber. That is, the rubber remaining in this corner serves as a starting point for promoting the deposition of new rubber (hereinafter referred to as "deposition starting point"). This is because the affinity between the rubber remaining in the corner and the new rubber is higher than the affinity between the new rubber and the mold.

An object of the present disclosure is to provide a method for manufacturing a pneumatic tire capable of suppressing clogging of an exhaust hole. Another object of the present disclosure is to provide a tire vulcanization die capable of suppressing clogging of exhaust holes.

In the method for manufacturing a pneumatic tire in the present disclosure, an unvulcanized tire is set in a tire vulcanization mold, and the outer surface of the tire is brought into close contact with the molded surface of the tire vulcanization mold to perform vulcanization. Includes vulcanization process. The molded surface is provided with an exhaust hole having a tapered portion extending continuously from an opening provided in the molded surface while gradually reducing the diameter. In the vulcanization step, the exhaust hole is provided with an outside of the tire. The method for manufacturing a pneumatic tire according to the present disclosure is characterized in that a rubber on the surface is allowed to flow in and the rubber is used to form a spew having a tip in the middle of the tapered portion.

It is sectional drawing of the tire vulcanization die in this embodiment. It is sectional drawing which enlarges and shows the vicinity of the tapering part of the tire vulcanization die in this embodiment. It is a cross-sectional view which enlarges and shows the vicinity of the tapering part after spew formation of the tire vulcanization die in this embodiment. It is a cross-sectional view which enlarged and shows the vicinity of the tapering part after the spew formation of the tire vulcanization die in the modification 1. It is a cross-sectional view which enlarged and shows the vicinity of the tapering part after spew formation of the tire vulcanization die in the modification 2. It is a cross-sectional view which enlarged and shows the vicinity of the tapered part after spew formation of the tire vulcanization die of the 1st example in the modification 3. It is a cross-sectional view which enlarged and shows the vicinity of the tapered part after spew formation of the tire vulcanization die of the 2nd example in the modification 3. It is a cross-sectional view which enlarged and shows the vicinity of the tapering part after the spew formation of the tire vulcanization die in the modification 4. It is sectional drawing which shows the exhaust hole of the tire vulcanization die described in Patent Document 1. FIG.

Hereinafter, embodiments of the present disclosure (hereinafter referred to as “the present embodiment”) will be described with reference to the drawings. In each drawing, the dimensional ratio of the drawings and the actual dimensional ratio do not always match, and the dimensional ratios between the drawings do not necessarily match.

First, the three directions of the tire reference (tire width direction, tire circumferential direction, and tire radial direction) appearing in the present embodiment will be described. The tire width direction is a direction parallel to the tire rotation axis. The tire circumferential direction is the direction around the tire rotation axis. The tire radial direction is the tire radial direction.

Next, the two surfaces (tire equatorial plane and tire meridional plane) appearing in the present embodiment will be described. The tire equatorial plane is a plane orthogonal to the tire rotation axis and located at the center in the tire width direction. The tire meridional plane is a plane including the axis of rotation of the tire and orthogonal to the equatorial plane of the tire.

As shown in FIG. 1, an unvulcanized tire T whose outline is shown by a broken line is set in the tire vulcanizing die 7 of the present embodiment with the tire shaft up and down. Therefore, in FIG. 1, the vertical direction is the tire width direction, and the left-right direction is the tire radial direction. The tire vulcanization die 7 is a so-called segmented mold.

The tire vulcanizing die 7 includes a molded surface 70 in contact with the outer surface of the unvulcanized tire T set in the cavity 79. The molding surface 70 includes a tread molding surface 701 for molding the tread portion of the pneumatic tire and a side molding surface 702 for molding the sidewall portion of the pneumatic tire.

The tire vulcanization die 7 includes a tread ring 71 composed of a plurality of sectors and side plates 72 and 73. The tread ring 71 plays a role of forming the tread portion of the pneumatic tire. The side plates 72 and 73 play a role of forming the sidewall portion of the pneumatic tire. At the time of mold clamping, a plurality of sectors are connected in the tire circumferential direction to form an annular tread ring 71. On the other hand, at the time of mold opening, the tread ring 71 and the side plate 73 rise, and the sectors are displaced outward in the tire radial direction so as to spread radially.

Each sector constituting the tread ring 71 includes a tread forming surface 701. The tread forming surface 701 is provided with an uneven pattern (not shown) corresponding to the tread pattern. More specifically, the tread forming surface 701 is provided with a convex portion and a concave portion. The convex portion plays a role of forming a groove in the tread portion of the pneumatic tire. On the other hand, the concave portion plays a role of forming a land portion in the tread portion of the pneumatic tire.

As shown in FIG. 2, the tire vulcanization die 7 is provided with an exhaust hole 8 having an opening 80 in the tread molding surface 701. In FIG. 2, the vertical direction is the tire radial direction, and the upward direction is the tire radial direction outside. This is the same for FIGS. 3 and later. The exhaust hole 8 extends in the length direction d8. The length direction d8 is the direction of the length in the exhaust hole 8. In the example shown in FIG. 2, the length direction d8 coincides with the tire radial direction. In the present embodiment, the length direction d8 is a cross section in which the exhaust hole 8 is cut along the tire meridional surface, and coincides with the normal line of the tread forming surface 701, but is not limited to this. In the present embodiment, the length direction d8 is a cross section obtained by cutting the exhaust hole 8 along the equatorial plane of the tire, and coincides with the normal line of the tread molded surface 701, but is not limited to this. The air between the outer surface of the unvulcanized tire T and the tread molding surface 701 is discharged through the exhaust hole 8 during vulcanization molding, whereby the generation of bares can be prevented. A plurality of exhaust holes 8 are provided in each sector. More specifically, at least one exhaust hole 8 is provided in the recess of the tread forming surface 701 of each sector.

The exhaust hole 8 has a tapered portion 81 extending from an opening 80 provided in the tread forming surface 701 while continuously reducing the diameter. The diameter of the tapered portion 81 is measured in a direction orthogonal to the length direction d8. The tapered portion 81 extends straight from the opening 80 while being continuously tapered. The tapered portion 81 extends in a tapered shape from the opening 80. Specifically, the tapered portion 81 extends from the opening 80 in a truncated cone shape. Therefore, the wall 810 forming the tapered portion 81 has a linear cross section obtained by cutting the tapered portion 81 on the surface including the axis of the tapered portion 81. The axis of the tapered portion 81 is a straight line extending in the length direction d8 through the midpoint of the diameter of the tapered portion 81. In this way, the tapered portion 81 extends from the opening 80 while being tapered to a certain degree. That is, the tapered portion 81 has no portion extending in the length direction d8 with a constant diameter.

The taper angle θ81 of the tapered portion 81 is preferably 0.5 degrees to 3.2 degrees. The taper angle θ81 is a cross section obtained by cutting the tapered portion 81 on a surface including the axis of the tapered portion 81, and is an angle formed by the wall 810 forming the tapered portion 81 and the length direction d8.

The maximum diameter LD81 of the tapered portion 81 is preferably 1.5 mm or more, more preferably 1.8 mm or more, in the sense that the spew 91 is prevented from collapsing when trimming the spew 91 (see FIG. 3). The maximum diameter LD81 is preferably 3.0 mm or less, more preferably 2.3 mm or less.

The exhaust hole 8 has a connecting portion 82 that is connected to the tapered portion 81. The connecting portion 82 is located on the back side (direction away from the cavity 79) of the tapered portion 81 with respect to the tread forming surface 701. The connecting portion 82 extends straight from the tapered portion 81 in the length direction d8. The connecting portion 82 extends with a constant diameter. That is, the connecting portion 82 extends in a columnar shape. Specifically, the connecting portion 82 extends in a straight columnar shape. The diameter D82 of the connecting portion 82 is the same as the minimum diameter SD81 of the tapered portion 81. However, the shape of the connecting portion 82 is not limited to such a shape, and may extend into an oblique columnar shape, for example.

In such a method of manufacturing a pneumatic tire using the tire vulcanization mold 7, an unvulcanized tire T is set in the tire vulcanization mold 7, and the outer surface of the tire T is set on the tire vulcanization mold 7. It includes a vulcanization step in which vulcanization is performed in close contact with the molding surface 70. Further, if necessary, a cutting step of cutting the spew 91 of the tire after vulcanization may be included.

In the vulcanization step, the unvulcanized tire T is set in the tire vulcanization mold 7, the tire vulcanization mold 7 is closed, and the bladder is expanded to press the outer surface of the tire T against the molded surface 70. , Heat the tire T.

As shown in FIG. 3, in the vulcanization step, rubber on the outer surface of the tire T is allowed to flow into the exhaust hole 8, and the rubber forms a spew 91 having a tip in the middle of the tapered portion 81. The tip of the rubber that has flowed into the tapered portion 81 of the exhaust hole 8 does not reach the innermost part of the tapered portion 81, but stops in the middle of the tapered portion 81. That is, the tip of the rubber that has flowed into the tapered portion 81 is reached halfway through the tapered portion 81. This rubber is vulcanized by the heat applied in the vulcanization step, and becomes a spew 91 having a tip in the middle position of the tapered portion 81. By forming the spew 91 having a tip in the middle position of the tapered portion 81, the pull-out resistance when the spew 91 is pulled out from the exhaust hole 8 can be eliminated or effectively reduced.

The length L81 of the tapered portion 81 is preferably 15 mm or more, and more preferably 20 mm or more, because the spew 91 having a tip at an intermediate position of the tapered portion 81 can be appropriately formed. Since the length of a general spew is less than 15 mm, when the length L81 of the tapered portion 81 is 15 mm or more, the spew 91 having a tip in the middle position of the tapered portion 81 can be appropriately formed. However, the length L81 of the tapered portion 81 may be less than 15 mm. On the other hand, the upper limit of the length L81 of the tapered portion 81 is preferably 25 mm. It is preferable that the spew 91 is 25 mm or less because the degree of inclination (taper angle θ81) that can eliminate or effectively reduce the pull-out resistance when the spew 91 is pulled out from the exhaust hole 8 can be set. The length L81 of the tapered portion 81 is preferably 5 to 14 times the maximum diameter LD81 of the tapered portion 81.

The maximum diameter LD81 of the tapered portion 81 is tapered because the degree of inclination (taper angle θ81) that can eliminate or effectively reduce the pull-out resistance when the spew 91 is pulled out from the exhaust hole 8 can be set. It is preferably 1.3 times or more the minimum diameter SD81 of the portion 81. On the other hand, the maximum diameter LD81 of the tapered portion 81 is preferably 2.3 times or less the minimum diameter SD81 of the tapered portion 81.

The length L91 of the spew 91 is, for example, 8 mm or more and less than 15 mm. The length L91 of the spew 91 is shorter than the length L81 of the tapered portion 81. The length L91 of the spew 91 is, for example, 50% to 80% when the length L81 of the tapered portion 81 is 100%.

After the vulcanization is completed, the mold is opened and the vulcanized tire is taken out from the tire vulcanization mold 7. The spew 91 has a tapered shape.

The method for manufacturing a pneumatic tire in the present embodiment can include a cutting step of cutting the spew 91 of the tire after vulcanization. The spew 91 can be cut with a cutter while rotating the tire. The cutter is preferably placed at the base of the Spew 91. As another method, for example, there is a method of cutting the spew 91 by rotating the cutter along the tire circumferential direction of the tire without rotating the tire. In this way, the spew 91 can be trimmed.

Up to this point, it has been described that the exhaust hole 8 is a hole provided in the tread forming surface 701 and is a so-called vent hole. However, the present disclosure is not limited to this, and the exhaust hole 8 may be formed of a vent piece fitted in a perforation provided in the tread forming surface 701. The vent piece is a member having a cylindrical shape.

Further, although the exhaust hole 8 of the tread molding surface 701 has been described so far, the exhaust hole (not shown) provided on the side molding surface 702 also has the configuration (shape) described in the exhaust hole 8 of the tread molding surface 701.・ Size etc.) can be adopted as appropriate.

Although the tire vulcanization die 7 of the present embodiment is a segmented mold, it may be a so-called two-piece mold which is divided into upper and lower parts at the center of the tread portion.

As described above, in the method for manufacturing a pneumatic tire of the present embodiment, the unvulcanized tire T is set in the tire vulcanization mold 7, and the outer surface of the tire T is formed by molding the tire vulcanization mold 7. It includes a vulcanization step of performing vulcanization in close contact with the surface 70.

The molding surface 70 is provided with an exhaust hole 8 having a tapered portion 81 extending from an opening 80 provided in the molding surface 70 while continuously reducing the diameter. In the vulcanization step, the tire T is provided in the exhaust hole 8. The rubber on the outer surface of the tire is poured, and the rubber forms a spew 91 having a tip in the middle position of the tapered portion 81.

The method for manufacturing a pneumatic tire according to the present embodiment can suppress clogging of the exhaust hole 8. The reason why the clogging of the exhaust hole 8 can be suppressed is that the method for manufacturing the pneumatic tire of the present embodiment can suppress the spew breakage, so that the clogging of the exhaust hole 8 due to the spew 91 can be suppressed and the generation of the accumulation starting point can be suppressed. Since it can be prevented, clogging of the exhaust hole 8 due to the accumulation of rubber can be suppressed.

Since the method for manufacturing a pneumatic tire of the present embodiment can suppress spew breakage, clogging of the exhaust hole 8 due to spew can be suppressed. In the method for manufacturing a pneumatic tire of the present embodiment, it is possible to suppress the spew breakage, although the friction between the spew 91 and the wall 810 of the exhaust hole 8 acts only in the initial stage of demolding, after that, This is because the entire side surface of the spew 91 is separated from the wall 810, so that friction does not act and the pull-out resistance that causes the spew break does not occur.

Since the method for manufacturing a pneumatic tire of the present embodiment can prevent the generation of a deposit starting point, it is possible to suppress the clogging of the exhaust hole 8 due to the deposition of rubber. In the method for manufacturing a pneumatic tire of the present embodiment, the generation of a deposit starting point can be prevented because a spew 91 having a tip is formed at an intermediate position of the tapered portion 81, so that rubber tends to remain and the flow of rubber is small. (For example, the corner formed by the end wall 197 and the side wall 198 as shown in FIG. 9) is not reached by the rubber. Therefore, the method for manufacturing a pneumatic tire according to the present embodiment can prevent the generation of a deposit starting point and suppress the clogging of the exhaust hole 8 due to the deposition of rubber.

Further, the method for manufacturing a pneumatic tire according to the present embodiment can suppress the uncut portion of the spew 91 when trimming the spew 91. This is because the tapered spew 91 is formed, so that the rigidity of the base of the spew 91 can be ensured, and thereby the spew 91 can be suppressed from collapsing at the time of trimming.

The length L81 of the tapered portion 81 is preferably 15 mm or more. Since the tapered portion 81 has a length sufficiently larger than the length of a general spew, the spew 91 having a tip in the middle position of the tapered portion 81 can be appropriately formed.

The tapered portion 81 preferably extends in a tapered shape from the opening 80. The tapered shape is preferable because the pull-out resistance when the spew 91 is pulled out from the exhaust hole 8 can be eliminated or effectively reduced.

On the other hand, the tire vulcanization die 7 of the present embodiment includes a molding surface 70 in contact with the outer surface of the unvulcanized tire T and an exhaust hole 8 provided in the molding surface 70, and the exhaust hole 8 is molded. It has a tapered portion 81 extending from an opening 80 provided in the surface 70 with a length of 15 mm or more while continuously reducing the diameter.

According to the tire vulcanization die of the present embodiment, clogging of the exhaust hole 8 can be suppressed. This is because the length L81 of the tapered portion 81 is longer than the length of a general spew, so that it is possible to suppress the spew breakage, thereby suppressing the clogging of the exhaust hole 8 due to the spew 91. Secondly, it is possible to prevent the occurrence of a deposit starting point, thereby suppressing clogging of the exhaust hole 8 due to the deposition of rubber.

Both the method for manufacturing a pneumatic tire of the present invention and the tire vulcanization die of the present invention are not limited to the configuration of the above-described embodiment, and are limited to the above-mentioned action and effect. It's not a thing. Of course, various changes can be made to both of them without departing from the gist of the present invention. For example, it is of course possible to arbitrarily select one or a plurality of configurations and methods according to various modifications described later and adopt them in the configurations and methods according to the above-described embodiment.

From here, some modifications of the present embodiment described above will be described.

As shown in FIG. 4, in the first modification of the present embodiment, the tire vulcanization die 7 provided with the exhaust hole 8 having the counterbore hole portion 811 (hereinafter referred to as “first hole portion 811”) is inflated. Manufacture tires. Specifically, the tapered portion 81 includes a first hole portion 811 and a second hole portion 812 extending from the inner side of the first hole portion 811.

As described above, in the tire vulcanization die 7 of the modification 1, the tapered portion 81 includes the first hole portion 811. The first hole portion 811 has an opening 80 in the tread forming surface 701. The first hole portion 811 extends in a tapered shape from the opening 80. Specifically, the first hole 811 extends from the opening 80 in a truncated cone shape.

In the first modification, the taper angle θ811 of the first hole portion 811 is larger than the taper angle θ812 of the second hole portion 812. By making the taper angle θ811 of the first hole portion 811 larger than that of the second hole portion 812, it is possible to suppress the uncut portion of the spew 91 when trimming the spew 91. This is because it is possible to secure the rigidity of the base of the spew 91, so that it is possible to suppress the fall of the spew 91 at the time of trimming.

In the first modification, the length L811 of the first hole portion 811 is, for example, 1.5 mm to 3.5 mm. The length L811 of the first hole portion 811 is, for example, 10% to 25% when the length L81 of the tapered portion 81 is 100%.

The maximum diameter LD81 of the tapered portion 81 in the first modification can be set larger than that of the present embodiment described above (see FIG. 3), and is, for example, 2 mm to 3.5 mm. On the other hand, when the maximum diameter LD81 is 100%, the minimum diameter SD811 of the first hole 811 is, for example, 50% to 80%.

The second hole portion 812 extends in a tapered shape from the inner side of the first hole portion 811. Specifically, the second hole portion 812 extends in a truncated cone shape from the inner side of the first hole portion 811. The preferred numerical range of the taper angle θ812 of the second hole portion 812 is the same as that of the taper angle θ81 (see FIG. 2) in the present embodiment. The length L812 of the second hole portion 812 is longer than the length L811 of the first hole portion 811. The maximum diameter of the second hole portion 812 is the same as the minimum diameter SD811 of the first hole portion 811.

In the first modification, in the vulcanization step, rubber on the outer surface of the tire T is made to flow into the exhaust hole 8, and the rubber forms a spew 91 having a tip in the middle position of the second hole portion 812. That is, the tip of the rubber that has flowed into the second hole portion 812 does not reach the innermost part of the tapered portion 81, and stops in the middle of the second hole portion 812. In this way, the spew 91 is formed.

However, in the first modification, the shape of the first hole portion 811 does not have to be tapered. In this regard, for example, the wall forming the first hole portion 811 may be curved in a cross section obtained by cutting the first hole portion 811 at the surface including the axis of the tapered portion 81. Here, the wall forming the first hole portion 811 refers to a portion of the wall 810 forming the tapered portion 81 that forms the first hole portion 811.

In the first modification, the shape of the second hole portion 812 does not have to be tapered. In this regard, for example, the wall forming the second hole portion 812 may be curved in a cross section obtained by cutting the second hole portion 812 at the surface including the axis of the tapered portion 81. Here, the wall forming the second hole portion 812 refers to the portion of the wall 810 forming the tapered portion 81 that forms the second hole portion 812.

As shown in FIG. 5, in an example in which the modified example 1 of the present embodiment is further modified (hereinafter referred to as “modified example 2”), the first hole portion 811 and the second hole portion 812 are interposed between the first hole portion 811 and the second hole portion 812. A pneumatic tire is manufactured with a tire vulcanization die 7 provided with an exhaust hole 8 having a third hole portion 813. The third hole portion 813 extends in a tapered shape from the inner side of the first hole portion 811. Specifically, the third hole portion 813 extends from the back side of the first hole portion 811 in a truncated cone shape.

In the second modification, the taper angle θ813 of the third hole 813 is smaller than the taper angle θ811 of the first hole 811 and larger than the taper angle θ812 of the second hole 812. However, the taper angle θ813 of the third hole portion 813 is not limited to this, and may be larger than the taper angle θ811 of the first hole portion 811 and larger than the taper angle θ812 of the second hole portion 812, for example.

In the second modification, the length L813 of the third hole portion 813 is shorter than the length L812 of the second hole portion 812. However, the length L813 of the third hole portion 813 may be longer than the length L812 of the second hole portion 812. On the other hand, the length L813 of the third hole portion 813 may be the same as the length L811 of the first hole portion 811, may be longer than that, or may be shorter than that.

In the second modification, in the vulcanization step, rubber on the outer surface of the tire T is made to flow into the exhaust hole 8, and the rubber forms a spew 91 having a tip in the middle position of the second hole portion 812. That is, the tip of the rubber that has flowed into the second hole portion 812 does not reach the innermost part of the tapered portion 81, and stops in the middle of the second hole portion 812. In this way, the spew 91 is formed. However, the formation of the spew 91 is not limited to this, and for example, the spew 91 having a tip in the middle position of the third hole 813 may be formed.

However, in the second modification, the shape of the third hole portion 813 does not have to be tapered. In this regard, for example, the wall forming the third hole portion 813 may be curved in a cross section obtained by cutting the third hole portion 813 at the surface including the axis of the tapered portion 81. Here, the wall forming the third hole portion 813 refers to the portion of the wall 810 forming the tapered portion 81 that forms the third hole portion 813.

As shown in FIG. 6, in the modified example 3 in the present embodiment, the wall 810 forming the tapered portion 81 is a cross section obtained by cutting the tapered portion 81 at a surface including the axis of the tapered portion 81, and is formed on the axis of the tapered portion 81. It forms a curved shape that bulges toward it. This is the first example of the modified example 3.

As shown in FIG. 7, in the modified example 3, the wall 810 forming the tapered portion 81 is a cross section obtained by cutting the tapered portion 81 at a surface including the axis of the tapered portion 81, and faces outward in the diameter direction of the tapered portion 81. It may have a curved shape that is curved so as to bulge. This is the second example of the modified example 3.

However, in the modified example 3, the wall 810 forming the tapered portion 81 is not limited to the curved shape shown in FIGS. 6 and 7, and for example, the first curved portion and the second curved portion curved in opposite directions are connected to each other. It may be curved (not shown). This is the third example of the modified example 3.

As shown in FIG. 8, in the modified example 4 of the present embodiment, the pneumatic tire is manufactured by the tire vulcanization die 7 provided with the exhaust hole 8 having the abutting wall 800. The end wall 800 is formed at the innermost part of the tapered portion 81 so as to be orthogonal to the length direction d8. As described above, the abutting wall 800 is a cross section obtained by cutting the tapered portion 81 on the surface including the axis of the tapered portion 81, orthogonal to the length direction d8, and forms a straight line. However, the end wall 800 is not limited to such a cross-sectional shape, and may have a curved shape in the cross-sectional shape, for example.

In the modified example 4, the tip of the rubber that has flowed into the tapered portion 81 in the vulcanization step does not reach the end wall 800 and stops in the middle of the tapered portion 81. Therefore, the tip of the formed spew 91 does not come into contact with the abutting wall 800.

7 ... Tire vulture mold, 79 ... Cavity, 70 ... Molded surface, 71 ... Tread ring, 72.73 ... Side plate, 80 ... Opening, 8 ... Exhaust hole, d8 ... Length direction, 81 ... Tapered part, 810 ... wall, L81 ... length of tapered part, LD81 ... maximum diameter of tapered part, SD81 ... minimum diameter of tapered part, 82 ... articulated part, D82 ... diameter of articulated part, 91 ... spew, L91 ... length of spew, 811 ... 1st hole, L811 ... length of 1st hole, SD811 ... minimum diameter of 1st hole 811, 812 ... 2nd hole, L812 ... length of 2nd hole, 813 ... 3rd hole Part, L813 ... Length of third hole, 800 ... End wall

Claims (2)

In a method for manufacturing a pneumatic tire including a vulcanization step in which an unvulcanized tire is set in a tire vulcanization mold and the outer surface of the tire is brought into close contact with the molding surface of the tire vulcanization mold to perform vulcanization. ,
The molded surface is provided with an exhaust hole having a tapered portion extending from an opening provided in the molded surface while continuously reducing the diameter.
In the vulcanization step, rubber on the outer surface of the tire is allowed to flow into the exhaust hole, and the rubber forms a spew having a tip in the middle of the tapered portion.
The length of the tapered portion is 15 mm or more, and the tapering portion has a length of 15 mm or more.
The exhaust hole further has a small diameter portion extending from the inner side of the tapered portion with a constant diameter, and the tapered portion extends from the opening with a certain degree of tapering over the entire area.
Method for manufacturing a pneumatic tire (However, except for the first case, in the first case, the tire vulcanization mold includes a tread ring composed of a plurality of sectors, and each sector is tread-molded. The tread-molded surface of each sector having a surface is provided with a plurality of exhaust holes extending outward from the tread-molded surface, and the extending directions of the plurality of exhaust holes in the tread ring are for each sector. And the direction is such that the sector is separated from the tread surface at the time of mold release). In a tire vulcanizing die provided with a molded surface in contact with the outer surface of an unvulcanized tire and an exhaust hole provided on the molded surface.
The exhaust hole has a tapered portion extending from an opening provided in the molding surface to a length of 15 mm or more while continuously reducing the diameter.
The exhaust hole further has a small diameter portion extending from the inner side of the tapered portion with a constant diameter, and the tapered portion extends from the opening with a certain degree of tapering over the entire area.
Tire vulcanization mold (However, except for the first case, in the first case, the tire vulcanization mold includes a tread ring composed of a plurality of sectors, and each sector is a tread forming surface. The tread molding surface of each sector is provided with a plurality of exhaust holes extending outward from the tread molding surface, and the extending directions of the plurality of exhaust holes in the tread ring are for each sector. It is parallel and the direction is such that the sector is separated from the tread surface at the time of mold release).

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