JP6900707B2 - Tire vulcanization mold, tire manufacturing method and pneumatic tire - Google Patents

Description

The present invention relates to a tire vulcanization molding die, a tire manufacturing method, and a pneumatic tire.

The tire molding mold used in the tire vulcanization process is called a vent hole in order to exhaust the air accumulated between the inner surface of the mold and the unvulcanized tire during tire vulcanization molding to the outside of the mold. A large number of narrow exhaust holes are formed. However, when a tire is vulcanized and molded by a mold having a large number of vent holes, rubber flows into the large number of vent holes, and a large number of whisker-shaped protrusions, spews, are generated on the surface of the product tire. For this reason, some conventional molds reduce the occurrence of spews. For example, in the tire molding die described in Patent Document 1, the hem portion is formed at the intersection of the surface of the mold and the strip-shaped convex portion formed on the surface of the mold toward the inside of the hem portion of the convex portion. A concave groove is formed so that the depth gradually increases from one end side to the other end side along the above, and a vent hole is formed in the deepest portion of the concave groove. As a result, the spew on the tire surface is reduced while ensuring the exhaust of air during tire vulcanization molding.

Japanese Patent No. 4236524

Here, in recent years, when manufacturing a pneumatic tire, a pureless mold is used in order to manufacture a pneumatic tire which has an excellent appearance and can reduce the occurrence of defective products during tire vulcanization molding. Sometimes. The pureless mold tire vulcanization mold is equipped with a slit vent consisting of minute gaps on the tread molding surface, and the slit vent is the outer surface of the green tire and the tire vulcanization mold in the tire vulcanization molding process. It serves as an air discharge path for residual air between the mold and residual gas generated by vulcanization. In the spureless mold, by providing the slit vent in the tire vulcanization molding mold in this way, it is possible to mold the pneumatic tire without forming a vent hole or a vent groove on the tread molding surface, and the pneumatic tire can be molded from the tread surface. It is possible to suppress molding defects of product tires caused by air while avoiding the generation of protruding spews.

However, in the pureless mold, it is difficult to adjust the interval when installing the slit vent. For example, if the distance between the slit vents is too narrow, the amount of air sucked per slit vent will be small, and the flow of air discharged from the slit vents will be poor, resulting in poor appearance of the vulcanized tire. There is a risk of On the other hand, if the interval between the slit vents is too wide, the amount of air sucked per slit vent becomes too large, and the rubber easily flows into the slit vent along with the flow of air discharged from the slit vent, resulting in overflow. May occur. Further, the slit vent in the pureless mold makes it difficult to add the slit vent after the mold is manufactured, as compared with the vent hole. For this reason, if a tire vulcanized by the pureless mold has a poor appearance, increase the thickness of the rubber on the cap tread of the tire to be vulcanized from the next time onward, and use a large amount of rubber to provide sufficient air. By extruding to, the appearance is prevented from being deteriorated.

However, thickening the cap tread increases the amount of rubber used, which increases manufacturing costs. In addition, thickening the cap tread also leads to an increase in rolling resistance when the tire rolls. For this reason, when vulcanizing a pneumatic tire using a pureless mold, it is very difficult to prevent the appearance from being deteriorated without increasing the manufacturing cost or deteriorating the rolling resistance. It was difficult.

The present invention has been made in view of the above, and an object of the present invention is to provide a tire vulcanization molding die, a tire manufacturing method, and a pneumatic tire capable of reducing rolling resistance and manufacturing cost.

In order to solve the above-mentioned problems and achieve the object, the tire brewing molding mold according to the present invention includes a plurality of circumferential main groove forming bones for forming the circumferential main groove of the pneumatic tire, and the pneumatic main groove forming bone. A plurality of lug groove-formed bones for forming the lug grooves of the tire and a plurality of lug-grooved bones adjacent to the circumferential main groove-formed bone and extending in the mold circumferential direction, which is a direction corresponding to the tire circumferential direction of the pneumatic tire, are described. In a tire brewing mold having a tread molding surface having a rib molding portion for molding a rib of a pneumatic tire and a slit vent arranged in the rib molding portion, the rib molding portion is used as the pneumatic tire. When the center of the rib molded portion in the mold width direction, which is the direction corresponding to the tire width direction of the above, is defined as a boundary, and the first belt region and the second belt region extending in the mold circumferential direction are divided into the first belt region and the second belt region, respectively. The volume of the rib-molded portion, which is the product of the width of the rib-molded portion in the mold width direction, the length in the mold circumferential direction, and the height of the circumferential main groove-molded bone adjacent to the rib-molded portion. The groove-molded bone volume ratio, which is the ratio to the volume of the lug-grooved bone adjacent to the rib-molded portion, differs between the first belt region and the second belt region, and is different between the first belt region and the second belt region. The slit vent arranged at least in the region having a larger groove-formed bone volume ratio than the belt region is characterized by having a widened portion in which the opening width of the opening to the rib-molded portion is widened. To do.

Further, in the tire vulcanization molding die, the groove-molded bone volume ratio of the first belt region is the first belt region of the lug-groove molded bone with respect to the volume of the first belt region in the rib-molded portion. It is the ratio of the volume of the portion located on the first belt region side of the boundary between the second belt region and the second belt region.
The groove-formed bone volume ratio of the second belt region is from the boundary between the first belt region and the second belt region of the lug-grooved bone with respect to the volume of the second belt region in the rib-molded portion. Is also preferably the ratio of the volume of the portion located on the second belt region side.

Further, in the tire vulcanization molding die, it is preferable that the slit vent has at least one widening portion extending over the circumference of the tread molding surface in the circumferential direction of the mold.

Further, in the tire vulcanization molding die, the widening portion has a semicircular cross-sectional shape in a direction orthogonal to the extending direction of the widening portion, and the width is within the range of 0.2 mm or more and 1.0 mm or less. The depth is preferably in the range of 0.1 mm or more and 0.5 mm or less.

Further, in order to solve the above-mentioned problems and achieve the object, the tire manufacturing method according to the present invention is characterized in that a tire vulcanization molding step is performed using the above-mentioned tire vulcanization molding die.

Further, in order to solve the above-mentioned problems and achieve the object, the pneumatic tire according to the present invention is manufactured by using a tire sulfide molding mold having a slit vent, and has a plurality of circumferential directions extending in the tire circumferential direction. A pneumatic tire including a main groove, a plurality of lug grooves extending in the tire width direction, and ribs extending in the tire width direction adjacent to the circumferential main groove, and the ribs correspond to the tire width direction. When the ribs are divided into a first belt region and a second belt region extending in the tire circumferential direction with the center of the rib in the tire circumferential direction as a boundary, the width of the rib in the tire width direction, the length in the tire circumferential direction, and the above. The groove volume ratio, which is the ratio of the volume of the rib, which is the product of the groove depth of the circumferential main groove adjacent to the rib, to the volume of the lug groove provided on the rib, is the ratio between the first belt region and the groove. Unlike the second belt region, a micro-convex portion extending in the tire circumferential direction is provided in at least the region having a larger groove volume ratio among the first belt region and the second belt region. A vent mark of the slit vent is located on the top of the micro-convex portion.

The tire vulcanization molding die, the tire manufacturing method, and the pneumatic tire according to the present invention have an effect that rolling resistance and manufacturing cost can be reduced.

FIG. 1 is a cross-sectional view of a meridian showing a main part of a pneumatic tire according to an embodiment. FIG. 2 is a plan view showing an example of the tread portion shown in FIG. FIG. 3 is an enlarged view of the first rib shown in FIG. FIG. 4 is a cross-sectional view of the first rib shown in FIG. 3, and is an explanatory view of the groove depths of the circumferential main groove and the lug groove. FIG. 5 is an enlarged view of the first lug groove shown in FIG. FIG. 6 is a cross-sectional view of the first lug groove shown in FIG. FIG. 7 is a cross-sectional view taken along the line BB of FIG. FIG. 8 is a detailed view of part D of FIG. FIG. 9 is a detailed view of part C of FIG. FIG. 10 is an explanatory view of a tire vulcanization molding die for manufacturing a pneumatic tire according to the embodiment. FIG. 11 is an explanatory diagram of a connected structure of a plurality of sectors constituting the tire vulcanization molding die shown in FIG. FIG. 12 is a plan view of the tread molding surface of the tire vulcanization molding die. FIG. 13 is an enlarged view of the first rib forming portion shown in FIG. FIG. 14 is a cross-sectional view taken along the line EE of FIG. 13, which is an explanatory view of values used for calculating the volume of the first rib molded portion. FIG. 15 is a cross-sectional view taken along the line FF of FIG. 13 and is an explanatory view of values used for calculating the volume of the first lug groove-formed bone. FIG. 16 is an enlarged view of the joint surface of the first lug groove formed bone shown in FIG. FIG. 17 is a cross-sectional view taken along the line EE of FIG. 13 and is an explanatory view of values used for calculating the volume of the first lug groove formed bone. FIG. 18 is an explanatory view showing a tire manufacturing method using the tire vulcanization molding die shown in FIG. FIG. 19 is an explanatory view showing a slit vent of a tire vulcanization molding die. FIG. 20 is a detailed view of the first rib molded portion of FIG. FIG. 21 is a detailed view of the G portion of FIG. 20. FIG. 22 is a view taken along the line PP of FIG. 20. FIG. 23 is a chart showing the results of performance tests of pneumatic tires.

Hereinafter, a tire vulcanization molding die, a tire manufacturing method, and an embodiment of a pneumatic tire according to the present invention will be described in detail with reference to the drawings. The present invention is not limited to this embodiment. In addition, the components in the following embodiments include those that can be easily conceived by those skilled in the art, or those that are substantially the same.

[Pneumatic tires]
FIG. 1 is a cross-sectional view taken along the meridian showing a main part of the pneumatic tire 1 according to the embodiment. FIG. 1 shows a meridional cross section of the pneumatic tire 1 according to the present embodiment passing through the rotation axis AX. The pneumatic tire 1 can rotate about the rotation shaft AX while being mounted on the rim wheel of the vehicle. The rotation axis AX of the pneumatic tire 1 is orthogonal to the tire equatorial plane CL indicating the center of the pneumatic tire 1 in the tire width direction.

In the following description, the direction parallel to the rotation axis AX is appropriately referred to as the tire width direction, and the radiation direction with respect to the rotation axis AX is appropriately referred to as the tire radial direction. The direction of rotation of the tire is appropriately referred to as the tire circumferential direction. Further, in the following description, the tire equatorial plane CL is appropriately referred to as a tire center CL.

In the present embodiment, the outer side in the tire width direction means a position far from or away from the tire center CL in the tire width direction. The inside in the tire width direction means a position close to or close to the tire center CL in the tire width direction. The outside in the tire radial direction means a position far from or away from the rotation axis AX in the tire radial direction. The inside in the tire radial direction means a position close to or close to the rotation axis AX in the tire radial direction. One side of the tire circumferential direction means a direction designated with respect to the tire circumferential direction. The other side of the tire circumferential direction means the direction opposite to the direction specified with respect to the tire circumferential direction.

The pneumatic tire 1 according to the present embodiment is a passenger car tire. Passenger car tires are tires specified in Chapter A of JATMA YEAR BOOK 2012 (Japan Automobile Tire Association Standards). The pneumatic tire 1 may be a tire for a light truck specified in Chapter B, or a tire for a truck or a bus specified in Chapter C.

The pneumatic tire 1 includes a carcass portion 2, a belt layer 3, a belt cover 4, a bead portion 5, a tread portion 10, and a side portion 7. The tread portion 10 is configured to have a tread rubber 6, and the side portion 7 is configured to have a side rubber 8.

Further, in the present embodiment, when the pneumatic tire 1 is mounted on the rim wheel of the vehicle, the right side of FIG. 1 is the vehicle side (inside the vehicle), and the left side of FIG. 1 is the side away from the vehicle (outside the vehicle). ).

Further, the rotation direction of the pneumatic tire 1 according to the present embodiment is specified in advance. When the vehicle is moving forward, the pneumatic tire 1 is mounted on the rim wheel of the vehicle so as to rotate in a designated rotation direction. A cerial symbol for designating the direction of rotation is provided on the surface of the side portion 7 of the pneumatic tire 1.

Each of the carcass portion 2, the belt layer 3, and the belt cover 4 included in the pneumatic tire 1 includes a cord. The cord is a reinforcing material. The cord may be referred to as a wire. A layer containing a reinforcing material such as the carcass portion 2, the belt layer 3, and the belt cover 4 may be referred to as a cord layer or a reinforcing material layer, respectively.

The carcass portion 2 is a strength member that forms the skeleton of the pneumatic tire 1. The carcass portion 2 includes a cord. The code of the carcass portion 2 may be referred to as a carcass code. The carcass portion 2 functions as a pressure vessel when the pneumatic tire 1 is filled with air. The carcass portion 2 is supported by the bead portion 5. The bead portion 5 is arranged on one side and the other side of the carcass portion 2 in the tire width direction. The carcass portion 2 is folded back at the bead portion 5. The carcass portion 2 includes an organic fiber carcass cord and rubber covering the carcass cord. The carcass portion 2 may include a polyester carcass cord, a nylon carcass cord, an aramid carcass cord, or a rayon carcass cord.

The belt layer 3 is a strength member that retains the shape of the pneumatic tire 1. The belt layer 3 contains a cord. The cord of the belt layer 3 may be referred to as a belt cord. The belt layer 3 is arranged between the carcass portion 2 and the tread rubber 6. The belt layer 3 includes a belt cord of a metal fiber such as steel and a rubber covering the belt cord. The belt layer 3 may include an organic fiber belt cord. In the present embodiment, the belt layer 3 includes a first belt ply 3A and a second belt ply 3B. The first belt ply 3A and the second belt ply 3B are laminated so that the cord of the first belt ply 3A and the cord of the second belt ply 3B intersect with each other.

The belt cover 4 is a strength member that protects and reinforces the belt layer 3. The belt cover 4 includes a cord. The cord of the belt cover 4 may be referred to as a cover cord. The belt cover 4 is arranged outside the belt layer 3 with respect to the rotation axis AX of the pneumatic tire 1. The belt cover 4 includes a cover cord of a metal fiber such as steel and a rubber covering the cover cord. The belt cover 4 may include a cover cord of an organic fiber.

The bead portion 5 is a strength member that fixes both ends of the carcass portion 2. The bead portion 5 fixes the pneumatic tire 1 to the rim of the rim wheel. The bead portion 5 has a bead core 5A, a bead filler 5B, an inner liner rubber 5C, and a rim cushion rubber 5D. The bead core 5A is a member in which a bead wire is wound in a ring shape. The bead wire is a steel wire. The bead filler 5B is a rubber material arranged in a space formed by folding back the end portion of the carcass portion 2 in the tire width direction at the position of the bead core 5A. The inner liner rubber 5C is provided inside the carcass portion 2 in the tire width direction and inside the carcass portion 2 in the tire radial direction. The rim cushion rubber 5D comes into contact with the rim on which the pneumatic tire 1 is mounted.

The tread rubber 6 protects the carcass portion 2. The tread portion 10 is formed on the tread rubber 6. The tread rubber 6 includes an outer layer tread rubber 6A provided on the outer side in the tire radial direction and an inner layer tread rubber 6B provided on the inner side in the tire radial direction with respect to the outer layer tread rubber 6A.

The side portions 7 are provided on one side and the other side of the tread portion 10 in the tire width direction. The side portion 7 is arranged outside the ground contact ends E1 and E2 of the tread portion 10 with respect to the tire center CL.

The ground contact ends E1 and E2 of the tread portion 10 are in a loaded state in which the pneumatic tire 1 is rim-assembled on a regular rim, filled with a regular internal pressure, placed vertically on a flat surface, and a regular load is applied. Sometimes refers to the end of the portion where the tread portion 10 touches the ground in the tire width direction.

A "regular rim" is a rim defined for each pneumatic tire 1 in a standard system including a standard based on the pneumatic tire 1, a standard rim for JATTA, and a "Design Rim" for TRA. If it is ETRTO, it is "Measuring Rim". However, when the pneumatic tire 1 is a tire mounted on a new car, a genuine wheel to which the pneumatic tire 1 is assembled is used.

The "regular internal pressure" is the air pressure defined for each pneumatic tire 1 in the standard system including the standard based on the pneumatic tire 1, the maximum air pressure for JATTA, and the table "TIRE" for TRA. The maximum value described in "LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES", and in the case of ETRTO, it is "INFRATION PRESSURE". However, when the pneumatic tire 1 is a tire mounted on a new vehicle, the air pressure displayed on the vehicle is used.

The "regular load" is the load defined for each pneumatic tire 1 in the standard system including the standard based on the pneumatic tire 1, and is the maximum load capacity for JATTA and the table "TRA" for TRA. The maximum value described in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES", and in the case of ETRTO, it is "LOAD CAPACITY". However, when the pneumatic tire 1 is a passenger car tire, the load corresponds to 88 [%] of the above load. When the pneumatic tire 1 is a tire mounted on a new vehicle, the wheel load is obtained by dividing the front and rear axle load described in the vehicle verification of the vehicle by the number of tires.

In the present embodiment, the ground contact end E1 is arranged inside the vehicle, and the ground contact end E2 is arranged outside the vehicle. Further, the distance between the ground contact end E1 of the tread portion 10 on one side of the tire center CL and the ground contact end E2 of the tread portion 10 on the other side in the tire width direction is the tread ground contact width TW. The tread ground contact width TW indicates the ground contact width of the tread portion 10, and the pneumatic tire 1 is rim-assembled on a regular rim, filled with a regular internal pressure, placed vertically on a flat surface, and a regular load is applied. The maximum value of the ground contact width in the tire width direction measured under load.

The side rubber 8 protects the carcass portion 2. The side rubbers 8 are arranged on one side and the other side of the tread rubber 6 in the tire width direction. A side portion 7 is formed on the side rubber 8.

FIG. 2 is a plan view showing an example of the tread portion 10 shown in FIG. As shown in FIG. 2, when the vehicle is moving forward, the pneumatic tire 1 rotates in the designated rotation direction R indicated by the arrow. In the following description, when the pneumatic tire 1 travels on the road surface while rotating in the designated rotation direction R about the rotation axis AX, the region of the tread portion 10 that first contacts the road surface is appropriately provided on the first-come-first-served side. Alternatively, it is referred to as a first-come-first-served portion, and a region that later contacts the road surface is appropriately referred to as a rear-arrival side or a rear-arrival portion. In FIG. 2, the lower side of the figure is the first-come-first-served side, and the upper side is the second-come-first-served side.

As shown in FIGS. 1 and 2, a plurality of tread portions 10 are provided in the tire width direction, and each of the tread portions 10 is partitioned by a circumferential main groove 30 extending in the tire circumferential direction and a plurality of circumferential main grooves 30. It has a rib 50 and a plurality of lug grooves 40 provided in the rib 50. The circumferential main groove 30 and the lug groove 40 are formed on the tread rubber 6. The rib 50 is a land portion of the tread rubber 6 partitioned by the circumferential main groove 30. The rib 50 has a ground contact surface (tread surface) 20 that can come into contact with the road surface.

The circumferential main groove 30 extends in the circumferential direction of the tire. The circumferential main groove 30 is substantially parallel to the tire equatorial line where the tire equatorial plane CL and the tread portion 10 intersect.

The circumferential main groove 30 means a vertical groove having a groove width of 1.0 mm or more, a groove depth of 4.0 mm or more, and at least a part extending in the tire circumferential direction. In general, the circumferential main groove 30 has a groove width of 6.0 mm or more and a groove depth of 7.0 mm or more. The circumferential main groove 30 has a tread wear indicator (slip sign) inside. The treadwear indicator indicates the end of wear.

At least a part of the lug groove 40 extends in the tire width direction. The lug groove 40 is provided in the rib 50 so as to intersect the circumferential main groove 30. In this case, the lug groove 40 does not have to be parallel to the tire width direction, and may be inclined in the tire circumferential direction while extending in the tire width direction. The lug groove 40 may be formed so as to extend at least in the tire width direction regardless of the inclination angle in the tire circumferential direction. Further, at least a part of the lug groove 40 is connected to the circumferential main groove 30.

The lug groove 40 means a lateral groove having a groove width of 2.0 mm or more, a groove depth of 3.0 mm or more, and at least a part extending in the tire width direction. The lug groove 40 may have an open structure that penetrates the rib 50 in the tire width direction, a semi-closed structure in which one end is terminated by the rib 50, or a closed structure in which both ends are terminated by the rib 50. Good.

At least three circumferential main grooves 30 are provided in the tire width direction. As shown in FIGS. 1 and 2, in the present embodiment, four circumferential main grooves 30 are provided. In the present embodiment, the circumferential main groove 30 includes a first circumferential main groove 31 provided most inside the vehicle, and a second circumferential main groove 32 provided inside the vehicle next to the first circumferential main groove 31. It includes a third circumferential main groove 33 provided on the inside of the vehicle next to the second circumferential main groove 32, and a fourth circumferential main groove 34 provided on the outermost side of the vehicle.

Further, in the present embodiment, the circumferential sub-groove 35 is provided outside the vehicle from the fourth circumferential main groove 34.

A plurality of ribs 50 are provided in the tire width direction. Each of the plurality of ribs 50 extends in the tire circumferential direction. The rib 50 is substantially parallel to the tire equatorial line where the tire equatorial plane CL and the tread portion 10 intersect.

At least two ribs 50 are provided in the tire width direction. As shown in FIGS. 1 and 2, in this embodiment, four ribs 50 are provided. In the present embodiment, the ribs 50 are the first rib 51 provided on the innermost side of the vehicle, the second rib 52 provided on the inner side of the vehicle following the first rib 51, and the second rib 50 provided on the inner side of the vehicle following the second rib 52. The three ribs 53 and the fourth rib 54 provided on the outermost side of the vehicle are included.

The first rib 51 is provided between the first circumferential main groove 31 and the second circumferential main groove 32, and is partitioned by the first circumferential main groove 31 and the second circumferential main groove 32. The second rib 52 is provided between the second circumferential main groove 32 and the third circumferential main groove 33, and is partitioned by the second circumferential main groove 32 and the third circumferential main groove 33. The third rib 53 is provided between the third circumferential main groove 33 and the fourth circumferential main groove 34, and is partitioned by the third circumferential main groove 33 and the fourth circumferential main groove 34. The fourth rib 54 is provided between the fourth circumferential main groove 34 and the circumferential sub-groove 35, and is partitioned by the fourth circumferential main groove 34 and the circumferential sub-groove 35.

In the present embodiment, the tire center CL is arranged on the second rib 52. The first circumferential direction main groove 31, the second circumferential direction main groove 32, and the first rib 51 are arranged inside the vehicle (ground contact end E1 side) with respect to the tire center CL. The third circumferential main groove 33, the fourth circumferential main groove 34, the circumferential sub-groove 35, the third rib 53, and the fourth rib 54 are arranged outside the vehicle (ground contact end E2 side) from the tire center CL. To.

The ground plane 20 of the rib 50 includes a first ground plane 21 which is a ground plane 20 of the first rib 51, a second ground plane 22 which is a ground surface 20 of the second rib 52, and a ground surface 20 of the third rib 53. The third ground contact surface 23 and the fourth ground contact surface 24, which is the ground contact surface 20 of the fourth rib 54, are included.

The lug groove 40 includes a first lug groove 41 provided in the first rib 51, a second lug groove 42 provided in the second rib 52, a third lug groove 43 provided in the third rib 53, and a fourth rib. Includes a fourth lug groove 44 provided in 54.

A plurality of first lug grooves 41 are provided in the first rib 51. The plurality of first lug grooves 41 are separated from each other in the tire circumferential direction. One end of the first lug groove 41 is connected to the first circumferential main groove 31, and the other end is not connected to both the first circumferential main groove 31 and the second circumferential main groove 32. The first lug groove 41 is directed from one end connected to the first circumferential main groove 31 to the other end not connected to both the first circumferential main groove 31 and the second circumferential main groove 32. Therefore, it is formed so as to extend in the rotation direction R of the pneumatic tire 1 after extending in the tire width direction.

A plurality of second lug grooves 42 are provided in the second rib 52. The plurality of second lug grooves 42 are separated from each other in the tire circumferential direction. One end of the second lug groove 42 is connected to the second circumferential main groove 32, and the other end is not connected to both the second circumferential main groove 32 and the third circumferential main groove 33. The second lug groove 42 is directed from one end connected to the second circumferential main groove 32 to the other end not connected to both the second circumferential main groove 32 and the third circumferential main groove 33. Therefore, it is formed so as to extend in the rotation direction R of the pneumatic tire 1 after extending in the tire width direction.

A plurality of third lug grooves 43 are provided in the third rib 53. The plurality of third lug grooves 43 are separated from each other in the tire circumferential direction. One end of the third lug groove 43 is connected to the third circumferential main groove 33, and the other end is not connected to both the third circumferential main groove 33 and the fourth circumferential main groove 34. The third lug groove 43 is directed from one end connected to the third circumferential main groove 33 to the other end not connected to both the third circumferential main groove 33 and the fourth circumferential main groove 34. Therefore, the pneumatic tire 1 is formed so as to be inclined in the direction opposite to the rotation direction R.

A plurality of fourth lug grooves 44 are provided in the fourth rib 54. The plurality of fourth lug grooves 44 are separated from each other in the tire circumferential direction. One end of the fourth lug groove 44 is connected to the fourth circumferential main groove 34, and the other end is not connected to both the fourth circumferential main groove 34 and the circumferential sub-groove 35. The fourth lug groove 44 extends from one end connected to the fourth circumferential main groove 34 toward the other end not connected to both the fourth circumferential main groove 34 and the circumferential sub-groove 35. The pneumatic tire 1 is formed so as to be inclined in the direction opposite to the rotation direction R.

[Belt area]
Next, the first belt region 61 and the second belt region 62 set on the rib 50 and the groove volume ratio of the rib 50 will be described. In the following description, the first belt region 61 and the second belt region 62 and the groove volume ratio of the first rib 51 will be described. The same applies to the second, third and fourth ribs 52, 53, 54.

FIG. 3 is an enlarged view of the first rib 51 shown in FIG. The first rib 51 is provided between the main groove 31 in the first circumferential direction and the main groove 32 in the second circumferential direction. The first circumferential direction main groove 31 and the second circumferential direction main groove 32 extend in the tire circumferential direction, respectively.

One end of the first rib 51 in the tire width direction is adjacent to the main groove 31 in the first circumferential direction with the open end K1 as a boundary. The opening end portion K1 is a boundary between the inner wall surface of the main groove 31 in the first circumferential direction and the ground contact surface 20. The other end of the first rib 51 in the tire width direction is adjacent to the main groove 32 in the second circumferential direction with the open end K2 as a boundary. The opening end portion K2 is a boundary between the inner wall surface of the main groove 32 in the second circumferential direction and the ground contact surface 20. The open end K1 and the open end K2 extend in the tire circumferential direction, respectively.

The rib width L indicating the dimension of the first rib 51 in the tire width direction is the first of the first rib 51 among the first circumferential main groove 31 and the second circumferential main groove 32 provided on both sides of the first rib 51. 1 This is the distance in the tire width direction between the opening end portion K1 and the opening end portion K2 arranged at the boundary with the ground contact surface 21. The open end portion K1 of the first circumferential direction main groove 31 refers to the apex of the corner portion formed by the inner wall surface of the first circumferential direction main groove 31 and the first ground contact surface 21 of the first rib 51. The open end K2 of the second circumferential main groove 32 refers to the apex of the corner formed by the inner wall surface of the second circumferential main groove 32 and the first contact patch 21 of the first rib 51. When the corner portion formed by the inner wall surface of the first circumferential direction main groove 31 and the first ground contact surface 21 of the first rib 51 is chamfered, the open end portion K1 of the first circumferential direction main groove 31 is , The intersection of the chamfered surface Cm and the first ground contact surface 21. Similarly, when the corner portion formed by the inner wall surface of the main groove 32 in the second circumferential direction and the first contact patch 21 of the first rib 51 is chamfered, the open end portion K2 of the main groove 32 in the second circumferential direction is chamfered. Refers to the intersection of the chamfered surface Cm and the first ground contact surface 21.

The rib peripheral length C indicating the dimension of the first rib 51 in the tire circumferential direction indicates the dimension of the first rib 51 in the tire circumferential direction. The rib peripheral length C is, for example, the dimension of the opening end portion K1 or the opening end portion K2 extending in the tire peripheral direction in the tire peripheral direction.

In the present embodiment, the opening end portion K1 and the opening end portion K2 are linear, respectively. The open end K1 and the open end K2 are substantially parallel. That is, the first rib 51 is a straight rib, and the rib width L of the first rib 51 is uniform (equal width) with respect to the tire circumferential direction.

The first rib 51 is provided with a plurality of first lug grooves 41. The plurality of first lug grooves 41 are separated from each other in the tire circumferential direction. One end of the first lug groove 41 is connected to the first circumferential main groove 31, and the other end of the first lug groove 41 is the first circumferential main groove 31 and the second circumferential main groove 32. Not connected to both. That is, the first lug groove 41 is a kind of non-penetrating lug groove, that is, a so-called semi-closed structure (one-sided non-penetrating lug groove).

Further, the first lug groove 41 is 2.0 mm or more in a no-load state in which the pneumatic tire 1 is rim-assembled on a regular rim, the regular internal pressure is applied, and no load is applied to the pneumatic tire 1. It has a groove width and a groove depth of 3.0 mm or more. The first lug groove 41 cannot be closed even when the first ground contact surface 21 is in contact with the ground.

The first lug groove 41 has an open end. The open end of the first lug groove 41 is a boundary between the inner wall surface of the first lug groove 41 and the first contact patch 21 arranged around the first lug groove 41. In the present embodiment, the shapes and dimensions of the plurality of first lug grooves 41 provided in the first rib 51 are the same. That is, the shapes and sizes of the open ends of the plurality of first lug grooves 41 are the same in the plane substantially parallel to the first ground plane 21. Further, in the meridional cross section passing through the rotation axis AX of the pneumatic tire 1, the cross-sectional shapes and groove depths of the plurality of first lug grooves 41 are the same.

In the present embodiment, the surface of the first rib 51 including the first contact patch 21 is divided into a first belt region 61 and a second belt region 62. The first belt region 61 and the second belt region 62 are separated by the center RL of the first rib 51 in the tire width direction as a boundary. The first belt region 61 and the second belt region 62 are regions extending in the tire circumferential direction, respectively. The width of the first belt region 61 in the tire width direction and the width of the second belt region 62 in the tire width direction are equal to each other.

The first belt region 61 is a region adjacent to the main groove 31 in the first circumferential direction and between the center RL and the open end K1. The second belt region 62 is an region adjacent to the main groove 32 in the second circumferential direction and between the center RL and the opening end K2.

[Groove volume ratio]
Next, the groove volume ratio will be described. The groove volume ratio described below is a value measured and calculated when the pneumatic tire 1 is rim-assembled on a regular rim, the regular internal pressure is applied, and no load is applied to the pneumatic tire 1. Is.

In the present embodiment, the lug groove 40 used for calculating the groove volume ratio is a groove having a groove width of 2.0 mm or more and a groove depth of 3.0 mm or more, and the lug groove 40 is It is a groove in which the opening of the lug groove 40 does not close even if the provided tread rubber 6 touches the ground. Therefore, a narrow groove whose opening closes when the tread rubber 6 touches the ground, such as a so-called sipe, is not used for calculating the groove volume ratio.

In the present embodiment, the groove volume ratio V is different between the first belt region 61 and the second belt region 62. The groove volume ratio V of the rib 50 is the ratio of the volume M of each rib 50 to the volume m of the lug groove 40 provided in the rib 50, and is represented by the following formula (1).
V = m / M ... (1)

For example, the groove volume ratio V of the first rib 51 can be expressed by the formula (1) using the volume M of the first rib 51 and the volume m of the first lug groove 41 provided in the first rib 51. it can. The volume M of the first rib 51 includes a rib width L indicating the dimension of the first rib 51 in the tire width direction, a rib circumference C indicating the dimension of the first rib 51 in the tire circumferential direction, and the first rib 51. It is the product of the adjacent circumferential main grooves 30 with the groove depth D. That is, the volume M of the first rib 51 is the volume of the tread rubber 6 of the first rib 51 when it is assumed that the first rib 51 is not provided with the first lug groove 41.

The volume m of the first lug groove 41 is the area q of the area surrounded by the open end of the first lug groove 41 in the plane substantially parallel to the first ground contact surface 21, and the first lug groove 41. It is the product of the groove depth d of the above and the number n of the first lug grooves 41 provided in the first rib 51. The area q of each first lug groove 41 is the product of the length l of the first lug groove 41 and the groove width w of the first lug groove 41. For the length l of the first lug groove 41, it is preferable to use the periphery length of the long side of the curved first lug groove 41, and the groove width w of the first lug groove 41 is that of the first lug groove 41. It is preferable to use the average groove width, and it is preferable to use the average groove depth d of the first lug groove 41 as the groove depth d of the first lug groove 41.

As described above, a plurality of first lug grooves 41 are provided in the tire circumferential direction, and the shapes and sizes of the open ends of the plurality of first lug grooves 41 are the same. Therefore, the areas q of the plurality of first lug grooves 41 are equal to each other. Further, the plurality of first lug grooves 41 are all formed to have the same cross-sectional shape when viewed in cross section passing through the opening and the groove bottom. Therefore, the groove depths d of the plurality of first lug grooves 41 are equal to each other.

The groove volume ratio V of the rib 50 defined as described above is different between the first belt region 61 and the second belt region 62. That is, the groove volume ratio V of the first belt region 61 is the first belt rather than the boundary between the first belt region 61 and the second belt region 62 in the lug groove 40 with respect to the volume M of the first belt region 61 in the rib 50. The ratio is the volume m of the lug groove 40 of the portion located on the region 61 side. Further, the groove volume ratio V of the second belt region 62 is a second belt from the boundary between the first belt region 61 and the second belt region 62 in the lug groove 40 with respect to the volume M of the second belt region 62 in the rib 50. It is the ratio of the volume m of the lug groove 40 of the portion located on the region 62 side. As for the groove volume ratio V of the rib 50, the groove volume ratio V of the first belt region 61 and the groove volume ratio V of the second belt region 62 are different from each other.

Further, the groove volume ratio V of the rib 50 is different for each rib 50. When the type of the rib 50 is x and the type of the belt region is y, the groove volume ratio V for each belt region in each rib 50 is represented by the following formula (2).

FIG. 4 is a cross-sectional view of the first rib 51 shown in FIG. 3, and is an explanatory view of the groove depths of the circumferential main groove 30 and the lug groove 40. The groove depth D of the circumferential main groove 30 in the formula (2) is the upper surface of the tread wear indicator 9 provided inside the circumferential main groove 30 adjacent to the rib 50 and the open end of the circumferential main groove 30. The effective groove depth D indicates the distance between the tire and the tire in the radial direction. Further, the groove depth d of the lug groove 40 in the formula (2) is the lug groove when the groove depth of the lug groove 40 changes depending on the position of the lug groove 40 in the length direction as shown in FIG. It is preferable to use an average groove depth of 40.

Further, in the present embodiment, the type x of the rib 50 in the formula (2) is x = 1 in the first rib 51, x = 2 in the second rib 52, and x = 3 in the third rib 53. In the fourth rib 54, x = 4. Further, in the present embodiment, the type y of the belt region is y = 1 in the first belt region 61 and y = 2 in the second belt region 62. In these cases, for example, the groove volume ratio V ₁₁ of the first belt region 61 of the first rib 51 can be expressed as the following equation (3).

_{The length l 11} of the first lug groove 41 in the formula (3) is the periphery length of the long side of the portion of the first lug groove 41 located in the first belt region 61. _{Further, the groove width w 11} of the first lug groove 41 in the formula (3) is the average groove width of the portion of the first lug groove 41 located in the first belt region 61. _{The periphery length l 11} of the long side of the portion located in the first belt region 61 in the first lug groove 41 and the average groove of the portion located in the first belt region 61 in the first lug groove 41. By multiplying the width w ₁₁ and the width w 11, the area q1 of the portion of the first lug groove 41 located in the first belt region 61 can be easily obtained. _{Further, the groove depth d 11} of the first lug groove 41 in the formula (3) is the average groove depth of the portion of the first lug groove 41 located in the first belt region 61.

The groove width w ₁₁ of the portion of the first lug groove 41 located in the first belt region 61 is simply the long side of the portion of the first lug groove 41 located in the first belt region 61. The groove width at the intermediate position may be used. Similarly, the groove depth d ₁₁ of the portion of the first lug groove 41 located in the first belt region 61 is also simply the length of the portion of the first lug groove 41 located in the first belt region 61. The groove depth at the intermediate position of the side may be used.

_{Further, the groove volume ratio V 12} of the second belt region 62 of the first rib 51 can be expressed by the following equation (4).

_{The length l 12} of the first lug groove 41 in the formula (4) is the periphery length of the long side of the portion of the first lug groove 41 located in the second belt region 62. _{Further, the groove width w 12} of the first lug groove 41 in the formula (4) is the average groove width of the portion of the first lug groove 41 located in the second belt region 62. The first lug grooves 41, the long side Periphery length l ₁₂ of the portion located in the second belt region 62, the first lug grooves 41, the average groove of the portion located in the second belt region 62 By multiplying the width w ₁₂ and the width w 12, the area q2 of the portion of the first lug groove 41 located in the second belt region 62 can be easily obtained. _{Further, the groove depth d 12} of the first lug groove 41 in the formula (4) is the average groove depth of the portion of the first lug groove 41 located in the second belt region 62.

The groove width w ₁₂ of the portion of the first lug groove 41 located in the second belt region 62 is simply the long side of the portion of the first lug groove 41 located in the second belt region 62. The groove width at the intermediate position may be used. Similarly, the groove depth d ₁₂ of the portion of the first lug groove 41 located in the second belt region 62 is also simply the length of the portion of the first lug groove 41 located in the second belt region 62. The groove depth at the intermediate position of the side may be used. _{In the present embodiment, the groove volume ratio V 11} of the first belt region 61 calculated by the formula (3) _{and the groove volume ratio V 12} of the second belt region 62 calculated by the formula (4) are different.

FIG. 5 is an enlarged view of the first lug groove 41 shown in FIG. FIG. 6 is a cross-sectional view of the first lug groove 41 shown in FIG. Explaining each value of the first lug groove 41 with reference to FIGS. 5 and 6, the length l ₁₁ of the first lug groove 41 is a portion of the first lug groove 41 located in the first belt region 61. The dimension of the longer opening end of the two opening ends Ka and Kb of the first lug groove 41 is shown. The length l ₁₂ of the first lug groove 41 is the longer opening of the two opening ends Ka and Kb of the first lug groove 41 of the portion of the first lug groove 41 located in the second belt region 62. Shows the dimensions of the end. The open ends Ka and Kb of the first lug groove 41 extend between one end and the other end of the first lug groove 41 in a plane substantially parallel to the first contact patch 21. To do. The dimensions of the open end portions Ka and Kb of the first lug groove 41 are the dimensions of one end portion and the other end portion of the open end portions Ka and Kb in a plane substantially parallel to the first ground contact surface 21. The dimension along the opening end Ka, Kb between them.

In the example shown in FIG. 5, of the two open end Ka and Kb of the first lug groove 41, the open end Kb is longer than the open end Ka. Therefore, in the example shown in FIG. 5, the length l ₁₁ of the first lug groove 41 is one end of the opening end Kb in the plane substantially parallel to the first ground plane 21 in the first belt region 61. It is a dimension along the open end Kb between the portion and the other end. The length l ₁₂ is the first lug grooves 41, between one end of the open end Kb of the first ground plane 21 and substantially parallel to the surface and the other end portion of the second belt region 62 It is a dimension along the opening end Kb of.

As shown in FIGS. 5 and 6, when the corners formed by the inner wall surfaces of the main grooves 31 and 32 in the first and second circumferential directions and the first contact patch 21 of the first rib 51 are chamfered. The dimension of the open end portion Kb of the first lug groove 41 is a dimension excluding the chamfered surface Cm. When the dimensions of the opening end Ka and the dimensions of the opening end Kb are equal, the lengths l ₁₁ and l ₁₂ of the first lug groove 41 are either the dimensions of the opening end Ka or the dimensions of the opening end Kb. Either one is adopted.

_{As the groove width w 11} of the first lug groove 41, basically, the average groove width of the portion of the first lug groove 41 located in the first belt region 61 is used. However, for simplicity, when the groove width of the portion located in the first belt region 61 of the first lug groove 41 at the intermediate position of the long side _{is used as the groove width w 11} of the first lug groove 41, the figure is shown in the figure. In the example shown in 5, the distance between the open end Kb and the open end Ka at the midpoint position of the portion located in the first belt region 61 of the open end Kb of the first lug groove 41 is set. 1 Used as the groove width w ₁₁ of the lug groove 41. _{As the groove width w 12} of the first lug groove 41, basically, the average groove width of the portion of the first lug groove 41 located in the second belt region 62 is used. However, when simply using the groove width at the intermediate position of the long side of the portion of the first lug groove 41 located in the second belt region 62 _{as the groove width w 12} of the first lug groove 41, FIG. In the example shown in 5, the distance between the open end Kb and the open end Ka at the position of the midpoint of the portion located in the second belt region 62 in the open end Kb of the first lug groove 41 is set. 1 Used as the groove width w ₁₂ of the lug groove 41.

_{As the groove depth d 11} of the first lug groove 41, basically, the average groove depth of the portion of the first lug groove 41 located in the first belt region 61 is used. However, for simplicity, when the groove depth of the portion located in the first belt region 61 of the first lug groove 41 at the intermediate position of the long side is used as _{the groove depth d 11 of the first lug groove 41.} In the examples shown in FIGS. 5 and 6, the bottom portion (bottom surface) of the first lug groove 41 at the midpoint position of the portion located in the first belt region 61 in the open end portion Kb of the first lug groove 41. The distance between the tire and the opening end Kb of the first lug groove 41 in the tire radial direction is used as _{the groove depth d 11 of the first lug groove 41. As the groove depth d 12} of the first lug groove 41, basically, the average groove depth of the portion of the first lug groove 41 located in the second belt region 62 is used. However, when simply using the groove width at the intermediate position of the long side of the portion of the first lug groove 41 located in the second belt region 62 as the groove depth d ₁₂ of the first lug groove 41, In the examples shown in FIGS. 5 and 6, the bottom portion (bottom surface) of the first lug groove 41 and the bottom portion (bottom surface) of the first lug groove 41 at the midpoint position of the portion located in the second belt region 62 in the open end portion Kb of the first lug groove 41 The distance in the tire radial direction from the opening end Kb of the first lug groove 41 is used as _{the groove depth d 12 of the first lug groove 41.}

[Micro convex part]
Next, the minute convex portion 70 will be described. A plurality of minute convex portions 70 are provided on the ground contact surface 20 of the tread portion 10. The minute convex portion 70 extends in the tire circumferential direction and is provided on each rib 50. Of these, some of the minute convex portions 70 extend around the rib 50 in the tire circumferential direction. Specifically, among the plurality of micro-convex portions 70, those that are not divided by the lug groove 40 all extend over one circumference in the tire circumferential direction. Further, the minute convex portion 70 divided by the lug groove 40 also extends in the tire circumferential direction except for the divided portion. It is preferable that the micro-convex portion 70 has at least one rib 50 extending over one circumference in the tire circumferential direction. In the present embodiment, the second rib 52 is provided with a minute convex portion 70 extending over one circumference in the tire circumferential direction.

The micro-convex portion 70 is provided at least in the region of the rib 50, whichever has the larger groove volume ratio, of the first belt region 61 and the second belt region 62. For example, at least the minute convex portion 70 is provided on the first ground contact surface 21 of the region having the larger groove volume ratio of the first belt region 61 and the second belt region 62 of the first rib 51. In the first belt region 61 of the first rib 51, each of the plurality of first lug grooves 41 is provided over both ends of the first belt region 61 in the tire width direction. Therefore, the minute convex portion 70 arranged in the first belt region 61 of the first rib 51 extends in the tire circumferential direction, and the portion intersecting with the first lug groove 41 is divided by the first lug groove 41. Has been done.

FIG. 7 is a cross-sectional view taken along the line BB of FIG. FIG. 8 is a detailed view of part D of FIG. Each micro-convex portion 70 has a small size and is formed so as to project from the ground contact surface 20, and the height from the ground contact surface 20 and the width of the micro-convex portion 70 in a plan view have a ratio of the height to the width of approximately 1. It is a pair of two. Specifically, the micro-convex portion 70 has a width Wc within a range of 0.2 mm or more and 1.0 mm or less, and a height Hc within a range of 0.1 mm or more and 0.5 mm or less. Further, the micro-convex portion 70 has a semicircular cross-sectional shape in a direction orthogonal to the extending direction of the micro-convex portion 70.

FIG. 9 is a detailed view of part C of FIG. The pneumatic tire 1 according to the present embodiment is manufactured by a tire vulcanization molding die 100 (see FIG. 11) having a slit vent T (see FIG. 10), which will be described later. Since the slit vent T is provided on the tread molding surface 135 (see FIG. 10) of the tire vulcanization molding die 100, the slit vent T of the tread molding surface 135 is provided on the ground contact surface 20 of the pneumatic tire 1. A vent mark 80, which is a mark of the slit vent T, is formed at a position corresponding to the position. The vent mark 80 is formed by the opening of the slit vent T of the tire vulcanization molding die 100 in the tire vulcanization molding step described later, and is provided on the ground plane 20 as a fine and linear convex portion. There is. The vent mark 80 appears on the ground plane 20 with a width of 0.005 mm or more and 0.008 mm or less, for example.

As described above, one or more vent marks 80 appearing on the ground contact surface 20 as traces of the slit vent T appear on the ground contact surface 20 of all the ribs 50 arranged in the tire width direction. The vent marks 80 of each rib 50 appear extending in the tire circumferential direction, and at the position where the lug groove 40 is arranged, they extend in the tire circumferential direction while being divided by the lug groove 40.

Of the vent marks 80 formed on the ground contact surface 20 of the rib 50, some of the vent marks 80 are formed on the minute convex portion 70. The vent mark 80 formed on the micro-convex 70 is formed at the top 71 of the micro-convex 70. That is, the vent mark 80 formed on the micro-convex portion 70 is formed at the top portion 71, which is the portion of the micro-convex portion 70 farthest from the ground plane 20, and extends along the micro-convex portion 70.

[Tire vulcanization molding mold]
Next, the tire vulcanization molding die 100 used for manufacturing the pneumatic tire 1 according to the embodiment will be described. FIG. 10 is an explanatory view of a tire vulcanization molding die 100 for manufacturing the pneumatic tire 1 according to the embodiment. FIG. 11 is an explanatory diagram of a connected structure of a plurality of sectors 101 constituting the tire vulcanization molding die 100 shown in FIG. As shown in FIG. 11, the tire vulcanization molding die 100 is configured as a so-called sector mold, which is a split type tire vulcanization molding die 100, and is an annular structure formed by connecting a plurality of sectors 101 to each other. It has a structure. Note that FIG. 11 illustrates the form of an eight-divided structure in which the tire vulcanization molding die 100 is composed of eight sectors 101, but the number of divisions of the tire vulcanization molding die 100 is not limited to this.

As shown in FIG. 10, one sector 101 includes a plurality of pieces 103 having uneven portions 102 corresponding to the tread profile of the pneumatic tire 1 to be a product, and a back on which these pieces 103 are mounted adjacent to each other. It includes a block 104. Note that FIG. 10 is an example of the sector 101, and has a tread molding surface 135 different from the tread pattern of the pneumatic tire 1 according to the above-described embodiment.

One piece 103 corresponds to a part of the tread pattern divided at a constant pitch or an arbitrary pitch, and has an uneven portion 102 on the tread forming surface 135 for forming the portion of the tread pattern. Further, a plurality of pieces 103 are assembled to form a tread forming surface 135 of one sector 101. For example, in the sector 101 shown in FIG. 10, the tread molding surface 135 of one sector 101 is divided into two in the tire axial direction corresponding to the width direction of the pneumatic tire 1 to be vulcanized by the tire vulcanization molding die 100. And, it is divided into four pieces in a direction corresponding to the tire circumferential direction of the pneumatic tire 1, and is divided into eight pieces 103.

Further, each piece 103 is composed of a first piece block 103a and a second piece block 103b, and the first piece block 103a and the second piece block 103b are laminated by die-casting in a plurality of shots. Manufactured.

Specifically, in each piece 103, first, in the first shot casting process, a metal material such as aluminum or an aluminum alloy is cast into the split mold for the first piece block 103a, and the first piece block 103a is cast. To cast. The first piece block 103a is formed with a part of the tread pattern portion assigned to one piece 103 and a region for laminating the second piece block 103b. Further, if necessary, the first piece block 103a after casting is machined. Next, in the second shot casting process, the first piece block 103a is placed in the split mold for the second piece block 103b, and a metal material of the same type as the first piece block 103a is cast into the first piece block. A laminate of 103a and the second piece block 103b is cast. At this time, the rest of the tread pattern portion is formed on the second piece block 103b. As a result, one piece 103 is cast. Further, if necessary, the piece 103 after casting is machined.

The back block 104 is composed of an arc-shaped member having a U-shaped cross section, and a plurality of pieces 103 are mounted and held in recesses having a U-shaped cross section in a predetermined arrangement. As a result, one sector 101 is configured.

The tire vulcanization molding die 100 is configured by using a plurality of sectors 101 configured as described above and connecting the plurality of sectors 101 in an annular shape (see FIG. 11). In the tire vulcanization molding die 100, the tread molding surfaces 135 of each sector 101 are assembled by connecting the plurality of sectors 101 in an annular shape in this way, and the tread molding surface 135 of the entire tread pattern is formed.

[Tread molding surface]
FIG. 12 is a plan view of the tread molding surface 135 of the tire vulcanization molding die 100. On the tread forming surface 135 formed by connecting the plurality of sectors 101, a plurality of circumferential main groove forming bones 120 for forming the circumferential main groove 30 of the pneumatic tire 1 and the circumference of the pneumatic tire 1 are formed. Circumferential auxiliary groove forming bone 125 for forming the directional auxiliary groove 35, a plurality of lug groove forming bones 130 for forming the lug groove 40 of the pneumatic tire 1, and a plurality of rib forming for forming the rib 50 of the pneumatic tire 1. A unit 140 is provided.

The circumferential main groove forming bone 120 and the circumferential auxiliary groove forming bone 125 project from the tread forming surface 135 and are provided on the piece 103 (see FIG. 11) of each sector 101 (see FIG. 11), and the plurality of sectors 101. By connecting the tires in an annular shape, the tires extend over the entire circumference of the tire vulcanization molding mold 100 in the mold circumferential direction, which is the direction corresponding to the tire circumferential direction of the pneumatic tire 1. The circumferential main groove formed bone 120 is provided corresponding to the circumferential main groove 30 of the pneumatic tire 1.

Therefore, the circumferential main groove formed bone 120 has a first circumferential main groove formed bone 121 corresponding to the first circumferential main groove 31 of the pneumatic tire 1 and a second main groove formed bone 121 corresponding to the second circumferential main groove 32. The circumferential main groove formed bone 122, the third circumferential main groove formed bone 123 corresponding to the third circumferential main groove 33, and the fourth circumferential main groove formed bone 124 corresponding to the fourth circumferential main groove 34. ,have. The first circumferential main groove formed bone 121, the second circumferential main groove formed bone 122, the third circumferential main groove formed bone 123, and the fourth circumferential main groove formed bone 124 are pneumatic tires. They are arranged side by side in the mold width direction, which is the direction corresponding to the tire width direction of 1. Further, the circumferential sub-groove forming bone 125 is in the fourth circumferential direction on the side opposite to the side where the third circumferential main groove forming bone 123 is located in the mold width direction with respect to the fourth circumferential main groove forming bone 124. They are arranged side by side with the main groove formed bone 124.

In the following description, the direction corresponding to the tire circumferential direction of the pneumatic tire 1 that is vulcanized and molded by the tire vulcanization mold 100 will be described as the mold circumferential direction of the tire vulcanization mold 100. The circumferential direction of the tire vulcanization mold 100 is an annular circumferential direction when a plurality of sectors 101 of the tire vulcanization mold 100 are connected in an annular shape. Further, in the following description, the direction corresponding to the tire width direction of the pneumatic tire 1 that is vulcanized and molded by the tire vulcanization mold 100 will be described as the mold width direction of the tire vulcanization mold 100. The mold width direction of the tire vulcanization molding die 100 is an annular axial direction when a plurality of sectors 101 of the tire vulcanization molding die 100 are connected in an annular shape.

The lug groove-formed bone 130 is arranged so as to project from the tread-formed surface 135 in the same manner as the circumferential main groove-formed bone 120, and extends in a direction along the shape of the target lug groove 40. That is, since the lug groove 40 is a groove extending mainly in the tire width direction, the lug groove forming bone 130 is mainly formed in a shape extending in the mold width direction of the tire vulcanization forming die 100. The lug groove formed bone 130 is provided corresponding to the lug groove 40 of the pneumatic tire 1. Therefore, the lug groove formed bone 130 includes a first lug groove formed bone 131 corresponding to the first lug groove 41 of the pneumatic tire 1, a second lug groove formed bone 132 corresponding to the second lug groove 42, and a second lug groove formed bone 132. It has a third lug groove-formed bone 133 corresponding to the three lug grooves 43 and a fourth lug groove-formed bone 134 corresponding to the fourth lug groove 44.

A plurality of first lug groove formed bones 131 are arranged between the first circumferential main groove formed bone 121 and the second circumferential main groove formed bone 122, and the plurality of first lug groove formed bones 131 are gold to each other. They are arranged apart from each other in the circumferential direction. A plurality of second lug groove-formed bones 132 are arranged between the second circumferential main groove-formed bone 122 and the third circumferential main groove-formed bone 123, and the plurality of second lug-groove-formed bones 132 are gold to each other. They are arranged apart from each other in the circumferential direction. A plurality of the third lug groove-formed bone 133s are arranged between the third circumferential main groove-formed bone 123 and the fourth circumferential main groove-formed bone 124, and the plurality of third lug-groove-formed bones 133 are gold to each other. They are arranged apart from each other in the circumferential direction. A plurality of fourth lug groove formed bones 134 are arranged between the fourth circumferential main groove formed bone 124 and the circumferential auxiliary groove formed bone 125, and the plurality of fourth lug groove formed bones 134 are formed around each other. They are arranged apart from each other in the direction.

The rib forming portion 140 extends in the circumferential direction of the mold adjacent to the main groove forming bone 120 in the circumferential direction. Further, unlike the circumferential main groove forming bone 120 and the lug groove forming bone 130, the rib forming portion 140 does not protrude from the tread forming surface 135, and is inside the tread forming surface 135 when the sectors 101 are connected in an annular shape. It constitutes the peripheral surface. That is, the rib forming portion 140 constitutes a reference surface in the tread forming surface 135, and forms the ground contact surface 20 of the rib 50 of the pneumatic tire 1. The rib forming portion 140 is provided corresponding to the rib 50 of the pneumatic tire 1.

Therefore, the rib forming portion 140 corresponds to the first rib forming portion 141 corresponding to the first rib 51 of the pneumatic tire 1, the second rib forming portion 142 corresponding to the second rib 52, and the third rib 53. It has a third rib forming portion 143 and a fourth rib forming portion 144 corresponding to the fourth rib 54. Of these, the first rib forming portion 141 is located between the first circumferential direction main groove forming bone 121 and the second circumferential direction main groove forming bone 122. The second rib forming portion 142 is located between the second circumferential main groove forming bone 122 and the third circumferential main groove forming bone 123. The third rib forming portion 143 is located between the third circumferential main groove forming bone 123 and the fourth circumferential main groove forming bone 124. The fourth rib forming portion 144 is located between the fourth circumferential main groove forming bone 124 and the circumferential auxiliary groove forming bone 125.

FIG. 13 is an enlarged view of the first rib forming portion 141 shown in FIG. In the rib forming portion 140, similarly to the rib 50 of the pneumatic tire 1, the groove forming bone volume ratio, which is the ratio between the volume of the rib forming portion 140 and the volume of the lug groove forming bone 130, is the first belt region 146. It is different from the second belt region 147. The volume of the rib forming portion 140 referred to here is the rib forming portion 140 and the circumferential main groove forming bone 120 and the circumferential auxiliary groove forming bone 125 provided on both sides of the rib forming portion 140 in the mold width direction. It is the volume of the space partitioned by. That is, the volume of the rib forming portion 140 is a volume calculated by the product of the surface area of the rib forming portion 140 and the heights of the circumferential main groove forming bone 120 and the circumferential auxiliary groove forming bone 125.

For example, to explain using the first rib forming portion 141, the first belt region 146 and the second belt region 147 of the first rib forming portion 141 refer to the center RL of the first rib forming portion 141 in the mold width direction. Divided as a boundary. In this case, the center RL of the first rib forming portion 141 is the center position of the width ML of the first rib forming portion 141 in the mold width direction. When the corner portion formed by the first rib forming portion 141 and the circumferential main groove forming bone 120 is chamfered, the width ML of the first rib forming portion 141 does not include the chamfered surface Cm. It has become. The first belt region 146 and the second belt region 147, which are separated by the central RL of the first rib forming portion 141 as a boundary, extend in the circumferential direction of the mold, respectively.

FIG. 14 is a cross-sectional view taken along the line EE of FIG. 13, which is an explanatory view of values used for calculating the volume of the first rib forming portion 141. Further, the volume of the first rib forming portion 141 is the width ML of the first rib forming portion 141 in the mold width direction, the length of the first rib forming portion 141 in the mold circumferential direction, and the first rib forming portion 141. It is the product of the height MD of the adjacent circumferential main groove formed bone 120.

In the first rib forming portion 141, the ratio of the volume of the first belt region 146 in the first rib forming portion 141 to the volume of the portion located in the first belt region 146 in the first lug groove forming bone 131, and the first The ratio of the volume of the second belt region 147 in the 1-rib forming portion 141 to the volume of the portion located in the second belt region 147 in the first lug groove forming bone 131 is different from each other.

As described using the first rib forming portion 141, the groove forming bone volume ratio MV of the rib forming portion 140 is different between the first belt region 146 and the second belt region 147. That is, the groove-formed bone volume ratio MV of the first belt region 146 is the boundary between the first belt region 146 and the second belt region 147 in the lug groove-formed bone 130 with respect to the volume of the first belt region 146 in the rib forming portion 140. It is the ratio of the volume of the lug groove formed bone 130 of the portion located on the side of the first belt region 146. Further, the groove-formed bone volume ratio MV of the second belt region 147 is the boundary between the first belt region 146 and the second belt region 147 in the lug groove-formed bone 130 with respect to the volume of the second belt region 147 in the rib forming portion 140. It is the ratio of the volume of the lug groove formed bone 130 of the portion located on the side of the second belt region 147. As for the groove-formed bone volume ratio MV of the rib forming portion 140, the groove-formed bone volume ratio MV of the first belt region 146 and the groove-formed bone volume ratio MV of the second belt region 147 are different from each other.

Further, the groove-formed bone volume ratio MV of the rib-molded portion 140 is different for each rib-molded portion 140. The length of the lug groove forming bone 130 is ml, the width of the lug groove forming bone 130 is mw, the height of the lug groove forming bone 130 is md, and the lug groove forming bone 130 provided in one rib forming portion 140 When the number is mn, the type of the rib forming portion 140 is x, and the type of the belt region is y, the groove forming bone volume ratio MV for each belt region in each rib forming portion 140 is expressed by the following formula (5). expressed.

FIG. 15 is a cross-sectional view taken along the line FF of FIG. 13, and is an explanatory view of values used for calculating the volume of the first lug groove-formed bone 131. The length ml and the width mw of the lug groove formed bone 130 are the length and width of the joint surface J with respect to the rib forming portion 140 in the lug groove formed bone 130, respectively. The joint surface J referred to here is a portion of the lug groove-formed bone 130 that is flush with the rib-molded portion 140, and the length ml and the width mw of the lug groove-formed bone 130 are at the positions of the joint surfaces J, respectively. The length is ml and the width is mw. Further, the height md of the lug groove forming bone 130 is the height of the lug groove forming bone 130 from the rib forming portion 140 in the protruding direction of the lug groove forming bone 130 from the rib forming portion 140.

Further, when the lug groove forming bone 130 is curved to form the curved lug groove 40, the length ml of the lug groove forming bone 130 in the formula (5) is the joining of the curved lug groove forming bone 130. It is preferable to use the periferary length of the long side of the surface J, and it is preferable to use the average width of the joint surface J of the lug groove-formed bone 130 as the width mw of the joint surface J of the lug groove-formed bone 130. Further, when the height md of the lug groove formed bone 130 changes depending on the position of the lug groove formed bone 130 in the length direction, the height md of the lug groove formed bone 130 is the average height of the lug groove formed bone 130. Is preferably used.

The type x of the rib forming portion 140 in the formula (5) is x = 1 in the first rib forming portion 141, x = 2 in the second rib forming portion 142, and x = 3 in the third rib forming portion 143. In the fourth rib forming portion 144, x = 4. The type y of the belt region is y = 1 in the first belt region 146 and y = 2 in the second belt region 147. In these cases, for example, the groove-formed bone volume ratio MV ₁₁ of the first belt region 146 of the first rib forming portion 141 can be expressed by the following formula (6).

_{The length ml 11} of the first lug groove formed bone 131 in the formula (6) is the periphery length of the long side of the portion of the joint surface J of the first lug groove formed bone 131 located in the first belt region 146. It has become. _{Further, the width mw 11} of the first lug groove formed bone 131 in the formula (6) is the average width of the portion of the joint surface J of the first lug groove formed bone 131 located in the first belt region 146. There is. _{Further, the height md 11} of the first lug groove formed bone 131 in the formula (6) is the average height of the portion of the first lug groove formed bone 131 located in the first belt region 146.

The width mw ₁₁ of the portion of the first lug groove formed bone 131 located in the first belt region 146 is simply located in the first belt region 146 at the joint surface J of the first lug groove formed bone 131. The width of the portion to be formed at the intermediate position of the long side may be used. _{Similarly, the height md 11} of the portion of the first lug groove formed bone 131 located in the first belt region 146 is simply in the first belt region 146 at the joint surface J of the first lug groove formed bone 131. The height of the portion located at the middle position of the long side may be used.

_{Further, the groove-formed bone volume ratio MV 12} of the second belt region 147 of the first rib forming portion 141 can be expressed as the following equation (7).

_{The length ml 12} of the first lug groove formed bone 131 in the formula (7) is the periphery length of the long side of the portion of the joint surface J of the first lug groove formed bone 131 located in the second belt region 147. It has become. _{Further, the width mw 12} of the first lug groove formed bone 131 in the formula (7) is the average width of the portion of the joint surface J of the first lug groove formed bone 131 located in the second belt region 147. There is. _{Further, the height md 12} of the first lug groove formed bone 131 in the formula (7) is the average height of the portion of the first lug groove formed bone 131 located in the second belt region 147.

The width mw ₁₂ of the portion of the first lug groove formed bone 131 located in the second belt region 147 is simply located in the second belt region 147 at the joint surface J of the first lug groove formed bone 131. The width of the portion to be formed at the intermediate position of the long side may be used. _{Similarly, the height md 12} of the portion of the first lug groove formed bone 131 located in the second belt region 147 is simply in the second belt region 147 at the joint surface J of the first lug groove formed bone 131. The height of the portion located at the middle position of the long side may be used. In the present embodiment, the groove-formed bone volume ratio MV _{11 of the first belt region 146 calculated by the formula (6) and the groove-formed bone volume ratio MV 12 of} the second belt region 147 calculated by the formula (7) are different. ing.

FIG. 16 is an enlarged view of the joint surface J of the first lug groove formed bone 131 shown in FIG. FIG. 17 is a cross-sectional view taken along the line EE of FIG. 13, which is an explanatory view of values used for calculating the volume of the first lug groove formed bone 131. FIG. 16 shows a joint surface J of the first lug groove forming bone 131 with respect to the first rib forming portion 141 by removing the first lug groove forming bone 131 protruding from the first rib forming portion 141. .. Explaining each value of the first lug groove formed bone 131 with reference to FIGS. 16 and 17, the length ml ₁₁ of the first lug groove formed bone 131 is the first lug groove formed bone 131 at the joint surface J. The dimension of the longer joint surface end portion of the two joint surface end portions Ea and Eb of the portion located in one belt region 146 is shown. The length ml ₁₂ of the first lug groove formed bone 131 is defined as one of the two joint surface end portions Ea and Eb of the portion of the joint surface J of the first lug groove formed bone 131 located in the second belt region 147. The dimensions of the end of the longer joint surface are shown. The joint surface ends Ea and Eb of the first lug groove formed bone 131 extend between one end and the other end in the length direction of the first lug groove formed bone 131. The length of the joint surface end portions Ea and Eb of the first lug groove formed bone 131 is defined as the joint surface end portions Ea and Eb between one end portion and the other end portion of the joint surface end portions Ea and Eb. The dimensions along.

In the example shown in FIG. 16, of the two joint surface end portions Ea and Eb of the first lug groove formed bone 131, the joint surface end portion Eb is longer than the joint surface end portion Ea. Therefore, in the example shown in FIG. 16, the length ml ₁₁ of the first lug groove formed bone 131 is the joint between one end and the other end of the joint surface end Eb in the first belt region 146. It is a dimension along the face end portion Eb. _{The length ml 12} of the first lug groove formed bone 131 is a dimension along the joint surface end Eb between one end and the other end of the joint surface end Eb in the second belt region 147. is there.

As shown in FIGS. 16 and 17, when the corner portion formed by the first and second circumferential main groove forming bones 121 and 122 and the first rib forming portion 141 is chamfered, the first lug is formed. The dimension of the joint surface end portion Eb of the groove-formed bone 131 is a dimension excluding the chamfered surface Cm. When the dimensions of the joint surface end Ea and the dimensions of the joint surface end Eb are equal, the lengths of the first lug groove formed bone 131 are set to ml ₁₁ and ml ₁₂ , and the dimensions of the joint surface end Ea and the joint surface end are set. One of the dimensions of part Eb is adopted.

_{As the width mw 11} of the first lug groove formed bone 131, basically, the average width of the portion of the joint surface J of the first lug groove formed bone 131 located in the first belt region 146 is used. However, simply, the width of the portion located in the first belt region 146 at the joint surface J of the first lug groove formed bone 131 at the intermediate position of the long side is the width mw _{11 of the first lug groove formed bone 131.} In the example shown in FIG. 16, the joint surface end portion Eb and the joint surface end portion Eb at the midpoint position of the portion located in the first belt region 146 in the joint surface end portion Eb of the first lug groove formed bone 131. The distance from the end portion Ea of the joint surface is used as _{the width mw 11 of the first lug groove formed bone 131. As the width mw 12} of the first lug groove formed bone 131, basically, the average width of the portion of the joint surface J of the first lug groove formed bone 131 located in the second belt region 147 is used. However, simply, the width of the portion located in the second belt region 147 on the joint surface J of the first lug groove formed bone 131 at the intermediate position of the long side is the width mw _{12 of the first lug groove formed bone 131.} In the example shown in FIG. 16, the joint surface end portion Eb and the joint surface end portion Eb at the midpoint position of the portion located in the second belt region 147 in the joint surface end portion Eb of the first lug groove formed bone 131. The distance from the end portion Ea of the joint surface is used as _{the width mw 12 of the first lug groove formed bone 131.}

_{As the height md 11} of the first lug groove formed bone 131, basically, the average height of the portion of the first lug groove formed bone 131 located in the first belt region 146 is used. However, simply, the height of the portion located in the first belt region 146 on the joint surface J of the first lug groove formed bone 131 at the intermediate position of the long side is the height of the first lug groove formed bone 131. When _{used as md 11} , in the examples shown in FIGS. 16 and 17, the first lug groove formed bone 131 has a position at the midpoint of a portion located in the first belt region 146 at the end portion Eb of the joint surface. The protruding height of the first lug groove forming bone 131 from the 1 rib forming portion 141 is used as _{the height md 11 of the first lug groove forming bone 131. As the height md 12} of the first lug groove formed bone 131, basically, the average height of the portion of the first lug groove formed bone 131 located in the second belt region 147 is used. However, simply, the height of the portion located in the second belt region 147 on the joint surface J of the first lug groove formed bone 131 at the intermediate position of the long side is the height of the first lug groove formed bone 131. When _{used as md 12} , in the examples shown in FIGS. 16 and 17, the first lug groove formed bone 131 has a position at the midpoint of a portion located in the second belt region 147 at the end portion Eb of the joint surface. The protruding height of the first lug groove formed bone 131 from the 1 rib forming portion 141 is used as _{the height md 12 of the first lug groove formed bone 131.}

[Tire manufacturing method]
Next, a method of manufacturing the pneumatic tire 1 according to the embodiment will be described. FIG. 18 is an explanatory view showing a tire manufacturing method using the tire vulcanization molding die 100 shown in FIG. FIG. 18 shows an axial cross-sectional view of a mold support device 105 including the tire vulcanization molding mold 100 shown in FIG. The pneumatic tire 1 according to the present embodiment is manufactured by the following manufacturing process.

First, the bead wire constituting the bead core 5A, the carcass ply constituting the carcass portion 2, the belt plies 3A and 3B constituting the belt layer 3, the tread rubber 6 constituting the tread portion 10, the side rubber 8 constituting the side portion 7, and the bead. Each member (see FIG. 1) such as the filler 5B, the inner liner rubber 5C, and the rim cushion rubber 5D is put on a molding machine to mold the green tire W. Next, the green tire W is mounted on the mold support device 105 (see FIG. 18).

In FIG. 18, the mold support device 105 includes a support plate 106, an outer ring 107, a segment 109, an upper plate 110 and a base plate 112, an upper mold side mold 111 and a lower mold side mold 113, and tire vulcanization molding. A mold 100 is provided. The support plate 106 has a disk shape and is arranged with the plane horizontal. The outer ring 107 is an annular structure having a tapered surface 108 on the inner side in the radial direction, and is suspended and installed at the lower part of the outer peripheral edge of the support plate 106. The segment 109 is a divisible annular structure corresponding to each sector 101 of the tire vulcanization mold 100, and is inserted into the outer ring 107 and slid axially with respect to the tapered surface 108 of the outer ring 107. Is placed in. The upper plate 110 is installed inside the outer ring 107 and between the segment 109 and the support plate 106 so as to be able to move up and down in the axial direction. The base plate 112 is arranged below the support plate 106 and at a position opposite to the support plate 106 in the axial direction.

The upper mold side mold 111 and the lower mold side mold 113 have side profile molding surfaces which are the shapes of both side surfaces of the pneumatic tire 1 in the tire width direction. Further, in the upper mold side mold 111 and the lower mold side mold 113, the upper mold side mold 111 is attached to the lower surface side of the upper plate 110, the lower mold side mold 113 is attached to the upper surface side of the base plate 112, and each of them. The molding surfaces are arranged so as to face each other. As described above, the tire vulcanization molding die 100 has a divisible annular structure (see FIG. 11) having a tread forming surface 135 capable of forming a tread profile. Further, in the tire vulcanization molding die 100, each sector 101 is attached to the inner peripheral surface of the corresponding segment 109, and the tread molding surface 135 is positioned on the molding surface of the upper mold side mold 111 and the lower mold side mold 113. It is placed toward the side to be vulcanized.

Next, the green tire W is mounted between the molding surface of the tire vulcanization molding die 100 and the molding surface of the upper mold side mold 111 and the lower mold side mold 113. At this time, as the support plate 106 moves downward in the axial direction, the outer ring 107 moves downward in the axial direction together with the support plate 106, and the tapered surface 108 of the outer ring 107 pushes the segment 109 inward in the radial direction. Then, the diameter of the tire vulcanization molding die 100 is reduced, the molding surfaces (see FIG. 10) of each sector 101 of the tire vulcanization molding die 100 are connected in an annular shape, and the tire vulcanization molding die 100 is connected. The entire molding surface and the molding surface of the lower mold side mold 113 are connected. Further, as the upper plate 110 moves downward in the axial direction, the upper mold side mold 111 is lowered, and the distance between the upper mold side mold 111 and the lower mold side mold 113 is narrowed. Then, the entire molding surface of the tire vulcanization molding die 100 and the molding surface of the upper mold side mold 111 are connected. As a result, the green tire W is surrounded and held by the molding surface of the tire vulcanization molding die 100, the molding surface of the upper mold side mold 111, and the molding surface of the lower mold side mold 113.

Next, the green tire W, which is a tire before vulcanization, is vulcanized and molded. Specifically, the tire vulcanization mold 100 is heated, and the green tire W is expanded outward in the radial direction by a pressurizing device (not shown) and pressed against the tread molding surface 135 of the tire vulcanization mold 100. Will be done. Then, when the green tire W is heated, the rubber molecules of the tread portion 10 and the sulfur molecules are combined to perform vulcanization. Then, the tread molding surface 135 of the tire vulcanization molding die 100 is transferred to the green tire W, and a tread pattern is formed on the tread portion 10.

After that, the tire after vulcanization molding is acquired as a product tire which is a pneumatic tire 1 to be a product. At this time, the support plate 106 and the upper plate 110 move upward in the axial direction, so that the tire vulcanization molding die 100, the upper die side mold 111, and the lower die side mold 113 are separated from each other, and the die support device 105 is moved. open. After that, the vulcanized and molded tire is taken out from the mold support device 105.

[Slit vent]
FIG. 19 is an explanatory view showing a slit vent T of the tire vulcanization molding die 100. FIG. 20 is a detailed view of the first rib forming portion 141 of FIG. FIG. 19 shows a radial cross-sectional view of the sector 101 shown in FIG. As shown in FIGS. 19 and 20, the tire vulcanization molding die 100 includes a plurality of slit vents T on the tread molding surface 135. The slit vent T is a fine linear exhaust port having an opening width Ws of 0.005 mm or more and 0.008 mm or less, and opens to the tread molding surface 135 of the tire vulcanization molding die 100. Further, the slit vent T communicates with the exhaust hole 114 formed inside the piece 103.

At the time of tire vulcanization molding, air such as residual gas generated between the outer surface of the green tire W and the tire vulcanization mold 100 is sucked into the exhaust hole 114 through the slit vent T to vulcanize the tire. It is discharged to the outside of the mold 100. As a result, molding defects of the product tire caused by air staying between the outer surface of the green tire W and the tire vulcanization molding die 100 are suppressed. At this time, vent marks 80 (see FIG. 9) of the plurality of slit vents T are formed on the ground contact surface 20 of the rib 50 of the product tire.

Such a fine slit vent T is formed, for example, by solidification shrinkage of a metal material. As a configuration for forming the slit vent T by solidification shrinkage of the metal material, the piece 103 of the tire vulcanization molding die 100 has a laminated structure including the first piece block 103a and the second piece block 103b (see FIG. 10). ). Further, in the piece 103, the first shot casting step of molding the first piece block 103a described above and the second shot casting step of molding the second piece block 103b on the first piece block 103a are sequentially performed, and the pieces are formed. A laminated structure of 103 is formed. Then, a fine opening width Ws of the slit vent T is formed by utilizing the solidification shrinkage of the metal material of the second piece block 103b in the second shot casting step. The process of forming the slit vent T formed in this manner is detailed in Japanese Patent No. 37332721 and the like. Further, the slit vent T may be formed by another method.

Each of the plurality of slit vents T is formed by extending the sector 101 in the circumferential direction of the mold, and penetrates the sector 101 connected in an annular shape in the circumferential direction of the mold. A plurality of slit vents T penetrating the sector 101 in the circumferential direction of the mold are arranged at predetermined intervals in the width direction of the mold, and one or more slit vents T are formed in all the rib forming portions 140 arranged in the width direction of the mold. (See FIG. 10).

Further, in the tire vulcanization mold 100 formed by connecting a plurality of sectors 101 in an annular shape, the slit vents T penetrating in the circumferential direction of the mold of each sector 101 communicate with each other, and the tire vulcanization mold 100 It extends over one circumference, that is, one circumference of the tread forming surface 135. At that time, in the slit vent T, at the position where the lug groove forming bone 130 is arranged in the direction in which the slit vent T extends, the slit vent T is divided by the lug groove forming bone 130, and the slit vent T is divided. It extends in the circumferential direction of the mold while being divided by the lug groove forming bone 130. On the other hand, the slit vent T in which the lug groove forming bone 130 is not arranged in the extending direction of the slit vent T extends all around the tread forming surface 135 without being divided by the lug groove forming bone 130. The slit vent T has at least one slit vent T extending around the tread molding surface 135 in the circumferential direction of the mold. By forming the slit vents T in this manner, a plurality of slit vents T are dispersedly arranged over the entire area of the tread forming surface 135.

[Wide part]
Next, the widening portion 150 of the slit vent T will be described. Of the plurality of slit vents T, at least a part of the slit vents T has a widened portion 150 in which the opening width of the opening to the rib forming portion 140 is widened. The widening portion 150 extends in the circumferential direction of the mold along the slit vent T extending in the circumferential direction of the mold, and is formed in at least one or more of the slit vents T of each rib forming portion 140. Similar to the slit vent T, the widening portion 150 extends in the circumferential direction of the mold while being divided by the lug groove forming bone 130 at the position where the lug groove forming bone 130 is arranged in the extending direction of the widening portion 150. To do. On the other hand, the widening portion 150 in which the lug groove forming bone 130 is not arranged in the extending direction of the widening portion 150 extends all around the tread forming surface 135 without being divided by the lug groove forming bone 130. Similar to the slit vent T, the widening portion 150 has at least one widening portion 150 extending over one circumference of the tread forming surface 135 in the circumferential direction of the mold. In the present embodiment, the second rib forming portion 142 is provided with a widening portion 150 extending over one circumference in the circumferential direction of the mold.

The widening portion 150 is formed at a position corresponding to the minute convex portion 70 of the pneumatic tire 1. In other words, the micro-convex portion 70 of the pneumatic tire 1 is formed by the widening portion 150 of the slit vent T provided in the tire vulcanization molding die 100. Similar to the micro-convex portion 70 of the pneumatic tire 1, the widening portion 150 is located in the region of the first belt region 146 and the second belt region 147 of the rib forming portion 140, whichever has the larger groove-formed bone volume ratio MV. It is formed at least in the slit vent T provided.

For example, the widening portion 150 is at least in the slit vent T arranged in the region of the first belt region 146 and the second belt region 147 of the first rib forming portion 141 where the groove forming bone volume ratio MV is larger. It is formed. In the first belt region 146 of the first rib forming portion 141, each of the plurality of first lug groove forming bones 131 is provided over both ends of the first belt region 146 in the mold width direction. Therefore, the slit vent T formed in the first belt region 146 of the first rib forming portion 141 extends in the circumferential direction of the mold, and the portion intersecting with the first lug groove forming bone 131 is the first lug groove. It is divided by the molded bone 131. Along with this, the widening portion 150 formed in the slit vent T also extends in the circumferential direction of the mold, and the portion intersecting with the first lug groove forming bone 131 is divided by the first lug groove forming bone 131. There is.

FIG. 21 is a detailed view of the G portion of FIG. 20. FIG. 22 is a view taken along the line PP of FIG. 20. Each widening portion 150 has a small size and is recessed from the tread molding surface 135, and the depth from the tread molding surface 135 and the width of each widening portion 150 in a plan view have a ratio of depth to width of approximately 1: 2. It has become. Specifically, the widening portion 150 has a width Wr within a range of 0.2 mm or more and 1.0 mm or less, and a depth Dr within a range of 0.1 mm or more and 0.5 mm or less. Further, the widening portion 150 has a semicircular cross-sectional shape in a direction orthogonal to the extending direction of the widening portion 150. That is, the widening portion 150 has substantially the same shape and size as the micro-convex portion 70 formed on the pneumatic tire 1, and is formed recessed from the tread forming surface 135.

The slit vent T having the widening portion 150 has an opening width Ws of a portion other than the widening portion 150 within a range of 0.005 mm or more and 0.008 mm or less. That is, the slit vent T having the widening portion 150 has the same shape as the slit vent T having no widening portion 150 except for the widening portion 150. In other words, in the slit vent T having the widening portion 150, the slit vent T is arranged at the bottom portion 151 of the widening portion 150 and is open to the bottom portion 151 of the widening portion 150. As described above, the slit vent T opens in the widening portion 150 at the bottom portion 151, which is the portion farthest from the tread forming surface 135 in the depth direction of the widening portion 150, and extends along the widening portion 150. Further, the opening width Wr of the widening portion 150 of the slit vent T preferably has a widening amount of 0.1 mm or more and 1.5 mm or less with respect to the opening width Ws of the slit vent T.

The pneumatic tire 1 according to the above-described embodiment is molded by performing a tire vulcanization molding step using a tire vulcanization molding die 100 configured as described above. At the time of tire vulcanization molding, air such as residual gas generated between the outer surface of the green tire W and the tire vulcanization mold 100 is sucked into the exhaust hole 114 through the slit vent T to vulcanize the tire. Vulcanization molding is performed while being discharged to the outside of the mold 100.

Here, when the tire vulcanization molding process is performed using the conventional tire vulcanization molding die, if the interval between the slit vents T is narrow with respect to the air to be discharged, the air is appropriately discharged from the slit vent T. Instead, it remains between the green tire W and the tire vulcanization molding die, and there is a possibility that an appearance defect such as a dent on the surface of the tire after vulcanization molding may occur. In this case, in the green tire W to be vulcanized from the next time onward, the thickness of the rubber of the cap tread part is increased so that air can be sufficiently pushed out by a large amount of rubber, so that the air can be added from the next time onward. Rework the tires to be vulcanized so that they do not look bad.

However, when the tire vulcanization molding process is performed using the conventional tire vulcanization molding mold to manufacture a pneumatic tire in this way, defective products may occur and the tread of the tread portion 10 is treaded. By increasing the thickness of the rubber 6, the manufactured pneumatic tire becomes heavier and the rolling resistance tends to increase. Further, increasing the thickness of the tread rubber 6 increases the amount of rubber used, which leads to an increase in manufacturing cost.

On the other hand, in the tire vulcanization mold 100 according to the present embodiment, at least the region having the larger groove-molded bone volume ratio MV of the first belt region 146 and the second belt region 147 of the rib molding portion 140. The slit vent T arranged in the above has a widening portion 150 in which the opening width of the opening to the rib forming portion 140 is widened. As a result, air can be appropriately discharged from between the green tire W and the tire vulcanization molding die 100. That is, at the time of vulcanization molding of the tire, the green tire W gradually comes into contact with the tread molding surface 135 from the portion of the tread molding surface 135 protruding from the tread molding surface 135 such as the circumferential main groove molding bone 120. The air between the green tire W and the tire vulcanization molding mold 100 is pushed out from the portion where the outer surface of the green tire W and the tread molding surface 135 are in contact with each other. In this case, the extruded air flows to the portion where the green tire W and the tread molding surface 135 are not in contact at that time.

During vulcanization molding of the tire, the outer surface of the green tire W is pressed against the tread molding surface 135 while the air moves to the portion where the green tire W and the tread molding surface 135 are not in contact with each other. The air moves to a portion where the green tire W and the tread molding surface 135 are difficult to contact. Examples of the portion where the green tire W and the tread forming surface 135 are difficult to contact include the root portion of the circumferential main groove forming bone 120 with respect to the rib forming portion 140 and the base portion of the lug groove forming bone 130 with respect to the rib forming portion 140. These parts are likely to collect air during vulcanization molding. Therefore, of the first belt region 146 and the second belt region 147 of the rib forming portion 140, the region having the larger groove forming bone volume ratio MV, that is, the ratio of the lug groove forming bone 130 to the rib forming portion 140 is By providing the widening portion 150 in the slit vent T which is often arranged in the region on the side where air tends to collect, the air collected near the base portion of the lug groove forming bone 130 can be easily sucked by the slit vent T. ..

That is, since the air during vulcanization molding flows to the portion where the green tire W and the tread molding surface 135 are not in contact with each other at that time, the air is formed by being recessed from the tread molding surface 135, so that the green tire W is formed. It is easy to flow to the widening portion 150 where the tread molding surface 135 and the tread molding surface 135 are difficult to contact. Therefore, of the first belt region 146 and the second belt region 147 of the rib forming portion 140, the air in the region on the side where the groove forming bone volume ratio MV is large and air is likely to collect is the slit vent T provided in the region. Since the air can flow to the widening portion 150 of the tire, the air near the base of the lug groove forming bone 130 can be efficiently sucked by the slit vent T and discharged to the outside of the tire vulcanization forming die 100. ..

In other words, the tire vulcanization mold 100 according to the present embodiment is located in at least the region having the larger groove-molded bone volume ratio MV of the first belt region 146 and the second belt region 147 of the rib molding portion 140. Since the widening portion 150 is provided in the arranged slit vent T, the slit vent T can be opened in a portion recessed one step from the other portion in the tread forming surface 135. As a result, the position of the slit vent T in the region on the side where air tends to accumulate during vulcanization due to the large ratio of the volume of the lug groove forming bone 130 to the volume of the rib forming portion 140. The slit vent T makes it possible to properly discharge the air. As a result, it is possible to suppress an appearance defect during vulcanization molding of the tire.

Further, by providing the widening portion 150 in the slit vent T, the green tire W needs rubber corresponding to the widening portion 150, but since the widening portion 150 is very small, the amount of rubber to be added is large. There are few. Therefore, even if the thickness of the tread rubber 6 in the green tire W is not made thicker than necessary, air can be efficiently discharged by locally increasing the amount of rubber, so that the tread rubber 6 can be discharged. It is possible to suppress an increase in rolling resistance and an increase in manufacturing cost due to the increase in thickness. That is, by providing the widening portion 150 in the slit vent T, air can be efficiently discharged while suppressing the amount of rubber added to the green tire W, and an increase in rolling resistance and an increase in manufacturing cost are suppressed. be able to. As a result, rolling resistance and manufacturing cost can be reduced.

Further, the widening portion 150 of the slit vent T is the ratio of the volume of the portion located on the first belt region 146 side of the lug groove molded bone 130 to the volume of the first belt region 146 in the rib forming portion 140 and the rib forming portion. The ratio of the volume of the portion located on the second belt region 147 side of the lug groove formed bone 130 to the volume of the second belt region 147 in 140 is compared, and it is provided at least in the region having the larger ratio, so that it is more reliable. The widening portion 150 can be provided in the region on the side where air is likely to collect. As a result, rolling resistance and manufacturing cost can be reduced more reliably.

Further, since the tire vulcanization molding die 100 has at least one slit vent T in which the widening portion 150 extends over one circumference of the tread molding surface 135 in the mold circumferential direction, the green tire W and the tread molding surface Air can be guided to the widening portion 150 over one round with 135. As a result, air can be guided to the widening portion 150 of the slit vent T over a wide range between the green tire W and the tread molding surface 135, and the air can be more reliably discharged from the slit vent T. .. As a result, rolling resistance and manufacturing cost can be reduced more reliably.

Further, since the widening portion 150 has a semicircular cross-sectional shape in the direction orthogonal to the extending direction of the widening portion 150, when the air between the green tire W and the tread forming surface 135 enters the widening portion 150. In addition, the air can be directed to the bottom portion 151 of the widening portion 150. As a result, the widening portion 150 can more reliably guide air to the slit vent T that opens to the bottom portion 151. As a result, rolling resistance and manufacturing cost can be reduced more reliably.

Further, since the widening portion 150 has a width Wr of 0.2 mm or more and 1.0 mm or less and a depth Dr of 0.1 mm or more and 0.5 mm or less, the amount of rubber to be added can be suppressed. , Air can be more reliably guided to the widening portion 150. That is, when the width Wr of the widening portion 150 is less than 0.2 mm or the depth Dr is less than 0.1 mm, the widening portion 150 is too small, so that the green tire W and the tread molded surface 135 are combined. There is a possibility that the ease of flow when the air between them flows to the widening portion 150 may be reduced. In this case, it may be difficult for the slit vent T to effectively discharge the air. Further, when the width Wr of the widening portion 150 exceeds 1.0 mm or the depth Dr exceeds 0.5 mm, the widening portion 150 is too large to satisfy the widening portion 150 during vulcanization molding. The amount of rubber required for the vulcanization may be too high. In this case, it may be difficult to effectively suppress an increase in rolling resistance and an increase in manufacturing cost.

On the other hand, when the width Wr of the widening portion 150 is within the range of 0.2 mm or more and 1.0 mm or less and the depth Dr is within the range of 0.1 mm or more and 0.5 mm or less, the widening portion during vulcanization molding. While suppressing the amount of rubber added to satisfy 150, air can be more reliably guided to the widening portion 150 and discharged from the slit vent T. As a result, rolling resistance and manufacturing cost can be reduced more reliably.

Further, the tire vulcanization molding die 100 is provided with a slit vent T having a widening portion 150, so that the appearance deterioration of the vulcanized tire can be suppressed, and the tire to be vulcanized from the next time onward. Since it is possible to eliminate the need for reworking as much as possible, the time spent on these tasks can be shortened. As a result, the tire development period can be shortened.

Further, the pneumatic tire 1 according to the above-described embodiment has a slit vent T at the top 71 in at least the region where the groove volume ratio V is larger among the first belt region 61 and the second belt region 62 of the rib 50. A micro-convex portion 70 is provided at which the vent mark 80 of the above is located. Therefore, during tire vulcanization molding, the air between the outer surface of the green tire W and the tread molding surface 135 in the region on the side where air tends to accumulate is applied to the portion where the minute convex portion 70 should be formed on the region side. Can be guided. As a result, it is possible to efficiently discharge the air in the region on the side where air tends to accumulate during tire vulcanization molding by the slit vent T, and it is possible to suppress appearance defects during tire vulcanization molding. Further, even if the thickness of the tread rubber 6 in the green tire W is not made thicker than necessary, air can be efficiently discharged by locally increasing the amount of rubber by the amount of the minute convex portion 70. , The increase in rolling resistance and the increase in manufacturing cost due to the increase in the thickness of the tread rubber 6 can be suppressed. As a result, rolling resistance and manufacturing cost can be reduced.

In the above-described embodiment, the widening portion 150 of the tire vulcanization molding die 100 is formed along the slit vent T with the same length as the slit vent T, but the widening portion 150 is the slit vent T. May be formed of different lengths. For example, the widening portion 150 may be formed longer than the slit vent T, and the slit vent T may be formed intermittently with respect to the widening portion 150.

Further, in the above-described embodiment, the slit vent T and the widening portion 150 of the tire vulcanization molding die 100 are continuously formed except for the portion divided by the lug groove molding bone 130, but the slit vent T is formed. The widening portion 150 may be divided into other portions as well. That is, the micro-convex portion 70 of the pneumatic tire 1 is continuously formed except for the portion divided by the lug groove 40, but the micro-convex portion 70 may be divided in other portions as well. .. The slit vent T, the widening portion 150, and the minute convex portion 70 may be formed intermittently depending on the balance with the tread pattern, the configuration of the piece 103 of the tire vulcanization molding die 100, and the like.

Further, in the above-described embodiment, the widening portion 150 of the slit vent T of the tire vulcanization molding die 100 and the minute convex portion 70 of the pneumatic tire 1 each have a semicircular cross-sectional shape in a direction orthogonal to the extending direction. Although it has a shape, the cross-sectional shape of the widening portion 150 and the minute convex portion 70 may be other than the semicircular shape. That is, as long as the widening portion 150 is formed so that the opening width to the rib forming portion 140 is larger than the opening width Ws of the slit vent T, the shape of the widening portion 150 or the minute convex portion 70 does not matter. For example, the widening portion 150 has a rectangular cross-sectional shape in a direction orthogonal to the extending direction, or one side is opened to the rib forming portion 140, and the diagonal thereof is the bottom portion 151, and the slit vent T is opened. It may be triangular in shape.

Further, in the above-described embodiment, the slit vent T of the tire vulcanization molding die 100, the widening portion 150, and the minute convex portion 70 of the pneumatic tire 1 are the first belt region 61, 146 and the second belt region 62, 147. However, a plurality of slit vents T, widening portions 150, and micro-convex portions 70 may be arranged in each region. Further, in the above-described embodiment, the region having the smaller groove-molded bone volume ratio MV is also included in the first belt region 146 and the second belt region 147 of the rib molding portion 140 of the tire vulcanization molding die 100. Although the slit vent T is provided, the slit vent T may not be provided in the region where the groove-formed bone volume ratio MV is smaller.

Further, the groove volume ratio V of the pneumatic tire 1 may be calculated using an equation other than the above equation (2). If it is possible to provide the minute convex portion 70 in at least the region where the groove volume ratio V is larger among the first belt region 61 and the second belt region 62 of the rib 50, the groove volume ratio V can be calculated. The formula of may be other than the formula used in the above-described embodiment. Similarly, the groove-molded bone volume ratio MV of the tire vulcanization molding die 100 may be calculated using a formula other than the above formula (5). The slit vent T arranged in at least the region having the larger groove-formed bone volume ratio MV of the first belt region 146 and the second belt region 147 of the rib forming portion 140 has a groove if it can have the widening portion 150. The formula for calculating the formed bone volume ratio MV may be other than the formula used in the above-described embodiment.

Further, the circumferential main groove 30 and the lug groove 40 of the pneumatic tire 1 may have a configuration other than the above-described embodiment, that is, the tread pattern of the pneumatic tire 1 may be a pattern other than the above-described embodiment. For example, the number, shape, and arrangement of the circumferential main groove 30 and the lug groove 40 may be any number, shape, and form other than those in the above-described embodiment.

[Example]
FIG. 23 is a chart showing the results of performance tests of pneumatic tires. Hereinafter, with respect to the above-mentioned pneumatic tire 1, the performance of the conventional pneumatic tire, the pneumatic tire 1 according to the present invention, and the pneumatic tire of the comparative example compared with the pneumatic tire 1 according to the present invention. The evaluation test of. The performance evaluation test was performed on the rolling resistance of the pneumatic tire 1 and the manufacturing cost at the time of manufacturing the pneumatic tire 1.

The performance evaluation test was carried out by vulcanizing and molding 200 pneumatic tires 1 having a tire designation of 195 / 70R14 size specified by JATTA. Regarding rolling resistance, each test tire is incorporated into a rim (size: 14 x 6J), filled with air pressure of 210 kPa, and an indoor drum tester (drum diameter: 1707 mm) is used, and the load is 4.82 kN in accordance with ISO28580. , The rolling resistance coefficient under the condition of a speed of 80 km / hour was calculated. The result is shown by an index in which the reciprocal of the rolling resistance coefficient of the conventional example described later is 100. The larger this index is, the lower the rolling resistance is. Regarding the manufacturing cost, the presence or absence of appearance defects and the degree of appearance defects during vulcanization molding, the time required for adjusting the amount of rubber of the green tire W due to the occurrence of appearance defects, and the appearance defects The evaluation was made based on the amount of rubber used so that The larger the index value, the less likely it is that the manufacturing cost will increase, indicating that the manufacturing cost is good.

The evaluation test compares the pneumatic tire of the conventional example, which is an example of the conventional pneumatic tire, the pneumatic tires 1 of the present invention, Examples 1 to 3, and the pneumatic tire 1 of the present invention. Five types of pneumatic tires were used with the comparative example of the tires. Of these, in the pneumatic tire of the conventional example, the rib 50 is not provided with the minute convex portion 70. Further, in the pneumatic tire of the comparative example, although the rib 50 is provided with the micro-convex portion 70, the micro-convex portion 70 is not provided in the region on the rib 50 on the side where the groove volume ratio V is large.

On the other hand, in Examples 1 to 3 which are examples of the pneumatic tire 1 according to the present invention, the rib 50 is provided with the micro-convex portion 70, and the micro-convex portion 70 has a groove volume ratio V in the rib 50. Is located in the larger area. Further, the pneumatic tires 1 according to Examples 1 to 3 differ in the presence or absence of the micro-convex portion 70 formed over the entire circumference and the size of the micro-convex portion 70.

As a result of conducting an evaluation test using these pneumatic tires 1, as shown in FIG. 23, the pneumatic tires 1 according to Examples 1 to 3 have reduced rolling resistance as compared with the conventional example and the comparative example. It has been found that tires can be used and manufacturing costs can be reduced. That is, the pneumatic tire 1 according to Examples 1 to 3, the tire vulcanization molding mold 100 used for these vulcanization moldings, and the tire manufacturing method using the tire vulcanization molding mold 100 have rolling resistance and rolling resistance. The manufacturing cost can be reduced.

1 Pneumatic tire 2 Carcass part 3 Belt layer 5 Bead part 6 Tread rubber 7 Side part 8 Side rubber 10 Tread part 20 Ground plane 30 Circumferential main groove 35 Circumferential auxiliary groove 40 Lug groove 50 Rib 61, 146 First belt area 62 147 Second belt area 70 Micro convex part 71 Top 80 Vent mark 100 Tire vulcanization molding die 101 Sector 103 Piece 120 Circumferential main groove forming bone 125 Circumferential secondary groove forming bone 130 Circumferential groove forming bone 135 Tread forming surface 140 Rib molding part 150 Widening part 151 Bottom

Claims (5)

A plurality of circumferential main groove forming bones for forming the circumferential main groove of the pneumatic tire, a plurality of lug groove forming bones for forming the lug groove of the pneumatic tire, and adjacent to the circumferential main groove forming bone. A rib forming portion extending in the circumferential direction of the mold, which is a direction corresponding to the tire circumferential direction of the pneumatic tire, and forming a rib of the pneumatic tire, and a slit vent arranged in the rib forming portion are provided. In a tire vulcanization molding die provided with a tread molding surface having a tread
The rib-molded portion is defined as a first belt region extending in the circumferential direction of the mold with the center of the rib-molded portion in the mold width direction, which is the direction corresponding to the tire width direction of the pneumatic tire, as a boundary. When dividing into the second belt area
The volume of the rib-molded portion, which is the product of the width of the rib-molded portion in the mold width direction, the length in the mold circumferential direction, and the height of the circumferential main groove-molded bone adjacent to the rib-molded portion. The groove-molded bone volume ratio, which is the ratio to the volume of the lug-grooved bone adjacent to the rib-molded portion, differs between the first belt region and the second belt region.
The groove-formed bone volume ratio of the first belt region is from the boundary between the first belt region and the second belt region of the lug-grooved bone with respect to the volume of the first belt region in the rib-molded portion. Is also the ratio of the volume of the portion located on the first belt region side.
The groove-formed bone volume ratio of the second belt region is from the boundary between the first belt region and the second belt region of the lug-grooved bone with respect to the volume of the second belt region in the rib-molded portion. Is also the ratio of the volume of the portion located on the second belt region side.
The slit vent arranged at least in the region of the first belt region and the second belt region in which the groove-molded bone volume ratio is larger has a widened opening width of the opening to the rib-molded portion. A tire vulcanization molding die characterized by having a widened portion. The tire vulcanization molding die according to claim 1, wherein the slit vent has at least one widening portion extending over one circumference of the mold circumferential direction of the tread molding surface. The widened portion has a semicircular cross-sectional shape in a direction orthogonal to the extending direction of the widened portion, has a width of 0.2 mm or more and 1.0 mm or less, and has a depth of 0.1 mm or more and 0. The tire vulcanization molding die according to claim 1 or 2 , which is within the range of 5 mm or less. A tire manufacturing method, characterized in that a tire vulcanization molding step is performed using the tire vulcanization molding die according to any one of claims 1 to 3. Manufactured using a tire vulcanization mold having a slit vent, a plurality of circumferential main grooves extending in the tire circumferential direction, a plurality of lug grooves extending in the tire width direction, and a tire adjacent to the circumferential main groove. A pneumatic tire with ribs extending in the width direction.
When the rib is divided into a first belt region and a second belt region extending in the tire circumferential direction with the center of the rib in the direction corresponding to the tire width direction as a boundary.
The volume of the rib, which is the product of the width of the rib in the tire width direction, the length in the tire circumferential direction, and the groove depth of the circumferential main groove adjacent to the rib, and the volume of the lug groove provided on the rib. The groove volume ratio, which is the ratio of, differs between the first belt region and the second belt region.
The groove volume ratio of the first belt region is the first belt region rather than the boundary between the first belt region and the second belt region in the lug groove with respect to the volume of the first belt region in the rib. It is the ratio of the volume of the part located on the side.
The groove volume ratio of the second belt region is the second belt region rather than the boundary between the first belt region and the second belt region in the lug groove with respect to the volume of the second belt region in the rib. It is the ratio of the volume of the part located on the side.
Of the first belt region and the second belt region, at least the region having the larger groove volume ratio is provided with a minute convex portion extending in the tire circumferential direction.
A pneumatic tire characterized in that a vent mark of the slit vent is located on the top of the micro-convex portion.

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