JP7403303B2 - Tire vulcanization mold - Google Patents

Description

The present invention relates to a tire vulcanization mold.

Patent Document 1 discloses a tire vulcanization mold that includes a bead ring for molding a bead portion of a tire. A vent hole is formed in the bead ring to communicate the molding surface forming the cavity with the outside of the bead ring. During vulcanization, the tire vulcanization mold is placed in a negative pressure space, and by exhausting air between the green tire and the molding surface through vent holes, the occurrence of bare rubber defects due to residual air is suppressed. We are trying to

JP2017-209958A

The direction in which the rubber flows within the cavity differs depending on the individual green tire. In the tire vulcanization mold of Patent Document 1, all the vent holes are oriented in the same direction, so depending on the direction in which the rubber flows, all the vent holes may be clogged with rubber, causing bare rubber.

SUMMARY OF THE INVENTION An object of the present invention is to provide a tire vulcanization mold that can prevent rubber from clogging all the vent holes, thereby suppressing the occurrence of bare tires.

One aspect of the present invention includes an annular mold having a molding surface for molding a bead portion or a sidewall portion of a tire, and a plurality of vent holes formed in the mold and communicating the inside and outside of the mold, The molding surface includes an arc-shaped recess that is recessed outward, and the plurality of vent holes include a first vent hole that is formed based on a first reference line that is a normal line of the recess; a second vent hole formed based on a second reference line which is a normal line and is different from the first reference line , and the first reference line of the first vent hole is formed based on the second reference line of the first vent hole. On a first meridian cross section including the end on the molding surface side, the second reference line of the second vent hole is inclined with respect to the axis of the mold, and the second reference line of the second vent hole is located at the end of the second vent hole on the molding surface side. on a second meridian cross section including the section, the first vent hole is inclined at the same angle as the first reference line of the first vent hole with respect to the axis, and the inclination angle of the first vent hole with respect to the first reference line; The present invention provides a tire vulcanization mold in which the inclination angles of the second vent hole with respect to the second reference line are set to differ within an angle range of ±10° .

In this aspect, since the inclination angles of the first vent hole and the second vent hole with respect to the reference line are different, even if the inclination angle of one of them matches the direction of the flow of the rubber, the inclination angle of the other one is different from that of the rubber. It does not match the direction of the flow. Therefore, even if one of the first vent hole and the second vent hole is clogged with rubber, the other will not be clogged with rubber. Therefore, it is possible to prevent the occurrence of the problem that all the vent holes are clogged, and it is possible to ensure the exhaust performance inside the mold. As a result, the occurrence of bare air due to residual air between the green tire and the molding surface can be suppressed. Moreover, since the inclination angle of the first vent hole with respect to the first reference line and the inclination angle of the second vent hole with respect to the second reference line are both set within an angle range of ±10°, all vent holes can be reliably prevented from getting clogged by the rubber.

A spring vent is arranged in at least a portion of the plurality of vent holes at an end on the molding surface side.

This aspect is effective when forming a vent hole in a molding surface for molding a bead portion because no protruding whisker-like spews are formed that would be an obstacle when assembling a pneumatic tire to a rim.

The plurality of vent holes are provided at intervals in the circumferential direction of the mold, and the first vent hole and the second vent hole are arranged adjacent to each other in the circumferential direction. In this case, it is preferable that two or more ventholes having different inclination angles form one venthole group, and the venthole groups are provided at intervals in the circumferential direction of the mold.

In this aspect, rubber clogging that occurs unintentionally is dispersed without being concentrated in a part of the mold, so that exhaust performance can be ensured evenly. Therefore, the occurrence of bears can be effectively prevented.

In the tire vulcanization mold of the present invention, all the vent holes can be prevented from being clogged with rubber, thereby suppressing the occurrence of bare tires.

1 is a sectional view of a tire vulcanization mold according to an embodiment of the present invention. FIG. 6 is a cross-sectional view taken along the line AA in FIG. 5, which is a first meridian cross-section taken along the first vent hole. FIG. 6 is a cross-sectional view taken along the line BB in FIG. 5, which is a second meridian cross-section taken along the second vent hole. FIG. 6 is a cross-sectional view taken along the line CC in FIG. 5 taken along the third vent hole. FIG. 2B is a partially enlarged view of the bead molding surface as viewed from the X arrow in FIG. 2A. FIG. 4 is a sectional view taken along line AA in FIG. 3. FIG. 2B is a partially enlarged view of the bead molding surface as viewed from the Y arrow in FIG. 2A. FIG. 6 is a partially enlarged view of a bead molding surface of a bead ring according to another embodiment. FIG. 6 is a partially enlarged view of a bead molding surface of a bead ring according to another embodiment. FIG. 6 is a partially enlarged view of a bead molding surface of a bead ring according to another embodiment.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a tire vulcanization mold (hereinafter simply referred to as "mold") 10 according to an embodiment of the present invention. In FIG. 1, only a part of the mold 10 in the radial direction is illustrated together with the vulcanized pneumatic tire 1.

The pneumatic tire 1 includes a tread portion 2, a pair of sidewall portions 3, and a pair of bead portions 4. The sidewall portions 3 are continuous on both sides of the tread portion 2 in the tire width direction (vertical direction in FIG. 1). The bead portions 4 are provided at the inner ends of the sidewall portions 3 in the tire radial direction (left-right direction in FIG. 1).

The mold 10 includes a cylindrical sector mold 11 for molding the tread portion 2, and a pair of annular side molds 12 disposed above and below the inside of the sector mold 11. The sector mold 11 and the side mold 12 have coaxial axes A that extend in the vertical direction in FIG. 1 . The space defined by the sector mold 11 and the side mold 12 constitutes a cavity 13 in which a green tire, which is a pneumatic tire 1 before vulcanization, is set. The side molds 12 of this embodiment each include an annular side plate 16 for forming the sidewall portion 3 and an annular bead ring 18 for forming the bead portion 4.

The sector mold 11 is a cylindrical body centered on the axis A, and is composed of a plurality of sectors 14. The individual sectors 14 are movable in the radial direction (indicated by RD in FIG. 1) about the axis A, and are connected in a cylindrical shape by moving toward the inner diameter (to the right in FIG. 1). The inner surfaces of the plurality of continuous sectors 14 each constitute a tread forming surface 15 that forms the outer surface of the tread portion 2 .

The side plate 16 is an annular member disposed on the inner diameter side of the sector mold 11. The side plate 16 located on the lower side is fixed so as not to be movable. The upper side plate 16 is movable in the axial direction (indicated by AD in FIG. 1). The inner surfaces of the side plates 16 , 16 facing each other constitute sidewall molding surfaces 17 that mold the outer surface of the sidewall portion 3 .

The bead ring 18 is an annular member disposed on the inner diameter side of the side plate 16. The bead ring 18 located on the lower side is integrated with the side plate 16 and fixed immovably. The bead ring 18 located on the upper side is integrated with the side plate 16 and moves together with the side plate 16. A portion of the inner surfaces of the bead rings 18 , 18 facing each other constitute a bead forming surface 19 that forms the outer surface of the bead portion 4 .

As shown in FIG. 2A, the bead forming surface 19 includes a first curved section 19a, a second curved section 19b, a third curved section 19c, a flat section 19d, and a tapered section 19e. It continues from the side (upper side in FIG. 2A) to the inner side (lower side in FIG. 2A). The first curved portion 19a is an arc-shaped convex portion that bulges into the cavity 13 with a predetermined radius of curvature R1. The second curved portion 19b is an arc-shaped concave portion that is continuous with the first curved portion 19a and is depressed from the inside of the cavity 13 to the outside with a predetermined radius of curvature R2. The third curved portion 19c is an arc-shaped convex portion that is continuous with the second curved portion 19b and bulges into the cavity 13 with a predetermined radius of curvature R3. The flat portion 19d is continuous with the third curved portion 19c, and is inclined toward the axis A of the bead ring 18 as it goes from the outside to the inside in the axial direction AD.

In order to ensure exhaust performance between the green tire and the bead forming surface 19 during vulcanization, the bead ring 18 is provided with a plurality of saw cuts 21 and 22 and a plurality of vent holes 24. Similar to the bead ring 18, the side plate 16 is also provided with vent holes and saw cuts as necessary.

As shown in FIG. 3, the saw cuts 21 and 22 are grooves provided on the bead forming surface 19 so as to be recessed outward. The saw cut 21 extends in the circumferential direction CR of the bead ring 18. The saw cut 22 extends in the radial direction RD of the bead ring 18. The saw cut 21 extending in the circumferential direction is provided at the deepest part 19f, which is the most recessed position, of the second curved part 19b.

The vent hole 24 has one end opened at the bead molding surface 19 and the other end opened at the outer surface 18a of the bead ring 18 so as to communicate the inside (cavity 13) of the bead ring 18 with the outside. Among the individual vent holes 24, the inner end portion 24a located on the bead forming surface 19 side is located on the deepest portion 19f (saw cut 21), and a plurality of inner end portions 24a located on the bead forming surface 19 side are located on the deepest portion 19f (saw cut 21), and a plurality of vent holes are formed at equal intervals in the circumferential direction around the axis A of the bead ring 18. (for example, 18 locations). Among the plurality of vent holes 24, some of the vent holes 24 are located at the intersections of the saw cuts 21 extending in the circumferential direction and the saw cuts 22 extending in the radial direction RD.

A spring vent 25 is arranged in the vent hole 24 at an inner end 24a on the bead molding surface 19 side. The spring vents 25 may be arranged in all the vent holes 24, or may be arranged in only some of the vent holes 24 as needed. During vulcanization, the rubber constituting the green tire may flow into the vent hole 24, causing clogging. It is preferable to arrange the spring vent 25 at a portion where such inconvenience is desired to be avoided.

As shown in FIG. 4, the spring vent 25 includes a cylindrical housing 26, a stem 27 disposed within the housing 26, and a coil spring 28 that urges the stem 27 toward the inside of the cavity 13.

By press-fitting the housing 26 into the vent hole 24, the state of attachment to the bead ring 18 is maintained. The internal space of the housing 26 constitutes an exhaust passage 26a, the axis of which coincides with the axis of the vent hole 24. The exhaust passage 26a has an opening section 26b, a communication section 26c, a housing section 26d, and a tapered section 26e in this order from the outer surface 18a side (upper side in FIG. 4) toward the bead forming surface 19 side (lower side in FIG. 4). Separated. The inner diameter of the opening 26b is larger than the inner diameter of the communication portion 26c, and a step 26f is formed between them. The inner diameter of the accommodating portion 26d is larger than the inner diameter of the communication portion 26c, and a stepped portion 26g is formed between them. The tapered portion 26e has a conical shape whose inner diameter gradually increases as it approaches the bead forming surface 19 from the accommodating portion 26d.

The stem 27 includes a shaft portion 27a, a stopper 27b provided on the outer surface 18a side of the shaft portion 27a, and a valve body 27c provided on the bead forming surface 19 side of the shaft portion 27a. The shaft portion 27a is provided with a large diameter portion 27d having an increased outer diameter at an end located on the valve body 27c side. The stopper 27b has a generally conical shape whose outer diameter gradually increases as it approaches the bead forming surface 19, and the outer diameter of the largest portion is larger than the inner diameter of the communication portion 26c. The valve body 27c has a truncated conical shape whose outer diameter gradually increases as it approaches the bead forming surface 19. The outer circumferential surface of the valve body 27c extends parallel to the inner circumferential surface of the tapered portion 26e, and the two can come into surface contact.

The coil spring 28 is arranged around the shaft portion 27a, and is housed in the housing portion 26d of the housing 26 in a compressed state. One end of the coil spring 28 is in contact with the stepped portion 26g, and the other end of the coil spring 28 is in contact with the large diameter portion 27d. Thereby, the stem 27 is urged to protrude into the cavity 13, and is prevented from coming off by contact between the stopper 27b and the stepped portion 26f. A ventilation groove 27e extending in the axial direction is provided on the outer periphery of the stopper 27b of this embodiment, and gas can flow through this ventilation groove 27e.

In the mold 10 configured as described above, when vulcanizing a green tire, gas between the bead portion of the green tire and the bead molding surface 19 of the bead ring 18 flows through the spring vent 25 and the vent hole 24 into the metal mold. It is discharged to the outside of the mold 10. Specifically, in the spring vent 25, the stem 27 protrudes into the cavity 13 due to the biasing force of the coil spring 28, and a gap is secured between the valve body 27c and the tapered portion 26e. Thereby, the gas in the mold 10 enters into the accommodation part 26d through this gap, passes through the gap between the communication part 26c and the shaft part 27a, the gap (ventilation groove 27e) between the stopper 27b and the stepped part 26f, and passes through the vent hole. 24 and is discharged to the outside.

The spring vent 25 is formed at the deepest part 19f of the second curved part 19b, which is the most depressed part of the bead forming surface 19. The deepest part 19f including the saw cuts 21 and 22 is the place where gas that has nowhere to go is most likely to collect. By providing the spring vent 25 at this location, it is possible to prevent burning and voids from occurring due to residual gas.

When rubber flows onto the bead molding surface 19 due to vulcanization of the green tire, the pressure of this rubber causes the stem 27 to retreat into the housing 26 against the biasing force of the coil spring 28. As a result, the outer circumferential surface of the valve body 27c and the inner circumferential surface of the tapered portion 26e come into surface contact with each other, and communication between the inside and outside through the housing 26 is interrupted.

When the spring vent 25 is used in the vent hole 24, basically no rubber enters the housing 26. However, depending on the direction in which the rubber flows, there is a risk that the rubber may get stuck between the valve body 27c and the tapered portion 26e, resulting in clogging. Furthermore, if the spring vent 25 is not employed in the vent hole 24, there is a risk that rubber may enter the vent hole 24 and clog it. In these cases, evacuation of the clogged area becomes impossible during subsequent vulcanization.

In order to prevent rubber from clogging all the vent holes 24 including the spring vent 25, the bead ring 18 is provided with a plurality of types (three types in this embodiment) of vent holes 24 having different extending directions. . In the following description, vent holes 24A to 24C may be referred to for each type (inclination angle) as necessary.

The vent holes 24A to 24C are provided so as to have different inclination angles α and β with respect to the reference lines SL1 to SL3, respectively. Here, the inclination angles α and β of the vent holes 24A to 24C are defined as the angles formed by the axes AL1 to AL3 of the vent holes 24A to 24C and the reference lines SL1 to SL3. Further, the inclination angles α and β of the vent hole 24 include a posture in which the axes AL1 to AL3 and the reference lines SL1 to SL3 match.

Referring to FIG. 2A to FIG. 2C, the reference lines SL1 to SL3 are normal lines of the second curved portion 19b that pass through the deepest portion 19f and divide the second curved portion 19b into two axisymmetrically. The reference lines SL1 to SL3 pass through the centroids of the inner ends 24a of the vent holes 24A to 24C, respectively. Further, the reference lines SL1 to SL3 are inclined at the same angle θ0 with respect to the axis A of the bead ring 18 on a meridian cross section cut to include the inner ends 24a of the vent holes 24A to 24C. Referring to FIG. 5 viewed from the direction in which the axis A of the bead ring 18 extends, the reference lines SL1 to SL3 extend in the radial direction RD of the bead ring 18. More specifically, the reference lines SL1 to SL3 are inclined toward the outer surface 18a as they go from the outside (the left side in FIG. 2A) to the inside (the right side in FIG. 2A) in the radial direction RD of the bead ring 18. . The angle θ0 formed by the straight line ADL extending in the axial direction AD of the bead ring 18 through the deepest part 19f and the reference lines SL1 to SL3 is set to 20° or more and 65° or less (20°≦θ0≦65°). .

As shown in FIGS. 2A and 5, the inclination angles α and β of the vent holes 24A to 24C are set within an angular range of ±10°, preferably within an angular range of ±5°, with respect to the reference lines SL1 to SL3. There is. More specifically, the individual vent holes 24A to 24C differ in at least one of the axial inclination angle α with respect to the reference lines SL1 to SL3 and the circumferential direction inclination angle β with respect to the reference lines SL1 to SL3. . An example of each of the vent holes 24A to 24C will be specifically described below.

FIG. 2A is a first meridian cross-sectional view of the bead ring 18 taken to include the end of the vent hole 24A on the bead molding surface 19 side in FIG. As shown in FIGS. 2A and 5, the vent hole (first vent hole) 24A extends along the reference line SL1. That is, the axis AL1 of the vent hole 24A coincides with the reference line SL1.

FIG. 2B is a second meridian cross-sectional view of the bead ring 18 taken to include the end of the vent hole 24B on the bead molding surface 19 side in FIG. As shown in FIGS. 2B and 5, the vent hole (second vent hole) 24B is inclined in the axial direction with respect to the reference line SL2, but not in the circumferential direction. Specifically, referring to FIG. 2B, the axis AL2 of the vent hole 24B is inclined in the axial direction with respect to the reference line SL2 at an inclination angle α1 (for example, −5°). Further, the axis AL2 of the vent hole 24B is inclined such that the angle θ1 formed with the straight line ADL (axis line A) extending in the axial direction AD is smaller than the angle θ0 formed between the reference line SL2 and the straight line ADL. Referring to FIG. 5 viewed from the axial direction, the axis AL2 of the vent hole 24B coincides with the reference line SL2.

FIG. 2C is a cross-sectional view taken along the vent hole 24C in FIG. 5, and is slightly different from the third meridian cross-section taken to include the end of the vent hole 24C on the bead forming surface 19 side. As shown in FIGS. 2C and 5, the vent hole (third vent hole) 24C is inclined in the axial direction and the circumferential direction with respect to the reference line SL3. Specifically, referring to FIG. 2C, the axis AL3 of the vent hole 24C is inclined in the axial direction with respect to the reference line SL3 at an inclination angle α2 (for example, +5°). Further, the axis AL3 of the vent hole 24C is inclined so that the angle θ2 formed by the straight line ADL extending in the axial direction AD is larger than the angle θ0 formed by the reference line SL3 and the straight line ADL. Referring to FIG. 5 viewed from the axial direction, the axis AL3 of the vent hole 24C is inclined at an inclination angle β (for example, +5°) in the circumferential direction with respect to the reference line SL3.

In this embodiment, three types of ventholes 24A to 24C having different inclination angles α and β with respect to reference lines SL1 to SL3 are set as one venthole group, and this venthole group is arranged in plurality at intervals in the circumferential direction. It is provided. As a result, the inclination angles α and β with respect to the reference lines SL1 to SL3 are all different in the circumferentially adjacent vent holes 24A to 24C.

Specifically, in the example shown in FIG. 5, in each vent hole group, vent hole 24B, vent hole 24A, and vent hole 24C are provided in this order from left to right, and adjacent vent holes 24A to 24C are provided in this order from left to right. The inclination angles α and β of 24C are all different. In the adjacent vent hole groups, the vent hole 24B is located at the left end of the first vent hole group located on the right side, and the vent hole 24C is located at the right end of the second vent hole group located on the left side. The inclination angles α and β are different.

The mold 10 configured in this manner has the following features.

Vent holes 24A to 24C are provided with different inclination angles α and β with respect to reference lines SL1 to SL3. As a result, even if the inclination angle α, β of any one (1 type) of the vent holes 24A to 24C matches the direction of the rubber flow, the inclination angles α, β of the remaining two (2 types) β does not match the direction of rubber flow. Therefore, even if any of the vent holes 24A to 24C becomes clogged with rubber, the remaining vent holes will not become clogged. Therefore, it is possible to prevent the occurrence of the problem that all the vent holes 24A to 24C are clogged, and it is possible to ensure the exhaust performance inside the mold 10. As a result, the occurrence of bare gas due to residual gas between the green tire and the bead forming surface 19 can be suppressed.

A spring vent 25 is arranged at the end of at least part of the vent holes 24A to 24C on the bead forming surface 19 side. Therefore, in the vent holes 24A to 24C in which the spring vents 25 are arranged, no protruding whisker-like spews are formed that would hinder the assembly of the pneumatic tire 1 to the rim. Therefore, it is effective when forming the vent hole 24 on the bead forming surface 19 on which the bead portion 4 is formed.

The inclination angles α and β of the vent holes 24A to 24C are set within an angular range of ±10° with respect to the reference lines SL1 to SL3, respectively. Therefore, all the vent holes 24A to 24C can be reliably prevented from being clogged with rubber. Furthermore, if the vent hole 24B in FIG. 2B is tilted so that the axis AL2 approaches the axial direction AD (axis A), the overall length of the vent hole 24B can be shortened, thereby improving exhaust performance.

In the circumferentially adjacent vent holes 24A to 24C, the inclination angles α and β with respect to the reference lines SL1 to SL3 are different. Therefore, rubber clogging that occurs unintentionally is dispersed without concentrating on a part of the bead ring 18, so that uniform exhaust performance can be ensured. Therefore, the occurrence of bears can be effectively prevented.

The opening position of the vent hole 24 in the bead forming surface 19 is the deepest part 19f of the second curved part (recessed part) 19b that constitutes the bead forming surface 19. This area is where gas that has nowhere to go is most likely to collect, so gas can be efficiently discharged. Further, it is possible to prevent variations in exhaust performance from occurring depending on the circumferential portion of the bead ring 18, and to obtain a desired exhaust effect.

Note that the tire vulcanization mold 10 of the present invention is not limited to the configuration of the embodiment described above, and various changes can be made.

For example, the circumferential inclination angle β of the vent holes 24A to 24C with respect to the reference lines SL1 to SL3 may be as shown in FIGS. 6 to 8.

In the example of FIG. 6, the inclination angle of the vent hole 24A in the circumferential direction is made to coincide with the reference line SL1, and the vent hole 24B is made to incline in the circumferential direction with respect to the reference line SL2 at an inclination angle of β1 (for example, −5°). The hole 24C is inclined at an inclination angle β2 (for example, +5°) in the circumferential direction with respect to the reference line SL3. In this case, the axial inclination angles α of the vent holes 24A to 24C with respect to the reference lines SL1 to SL3 may all be the same.

In the example of FIG. 7, all the vent holes 24A to 24C are inclined at an inclination angle β (for example, +5°) in the circumferential direction with respect to the reference lines SL1 to SL3. In the example of FIG. 8, the inclination angles of all the vent holes 24A to 24C in the circumferential direction are made to coincide with the reference lines SL1 to SL3. In these cases, similarly to the embodiment shown in FIG. 2A, the axial inclination angles α of the vent holes 24A to 24C with respect to the reference lines SL1 to SL3 are preferably set to be different.

In the embodiment described above, the saw cut 21 and the vent hole 24 are provided at the deepest part 19f of the bead forming surface 19, but if the vent hole 24 is provided on the saw cut 21 extending in the circumferential direction, these formation positions will be located at the deepest part 19f. It doesn't have to be.

The number of types of vent holes 24 having different inclination angles α and β is not limited to three types, but two types may be provided alternately, or four or more types may be provided. However, the number of types of vent holes 24 is preferably a divisor of the total number of vent holes 24. Alternatively, only some of the plurality of vent holes 24 may have different inclination angles α and β.

Although an example has been described in which the vent hole 24 is formed in the bead ring 18, the vent hole 24 may be formed in the side plate 16. Even in this case, by providing a plurality of types of vent holes 24 so that the inclination angles α and β with respect to the inclined reference line on the meridian cross section are different, the same operation and effect as in the embodiment described above can be obtained.

In the above embodiment, a segmented mold was described as the mold 10, but even if it is a two-piece mold with upper and lower halves, the part where the bead part 4 or the sidewall part 3 is to be molded has an inclination with respect to the reference line SL. A similar effect can be obtained by employing vent holes 24 with different angles α and β.

1 Pneumatic tire 2 Tread portion 3 Sidewall portion 4 Bead portion 10 Mold 11 Sector mold 12 Side mold 13 Cavity 14 Sector 15 Tread molding surface 16 Side plate 17 Sidewall molding surface 18 Bead ring 18a Outer surface 19 Bead molding surface 19a No. 1 curved part 19b 2nd curved part (concave part)
19c Third curved part 19d Flat part 19e Tapered part 19f Deepest part 21 Saw cut 22 Saw cut 24, 24A to 24C Vent hole 24a Inner end part 25 Spring vent 26 Housing 26a Exhaust passage 26b Opening part 26c Communication part 26d Accommodation part 26e Tapered part 26f Step part 26g Step part 27 Stem 27a Shaft part 27b Stopper 27c Valve body 27d Large diameter part 27e Ventilation groove 28 Coil spring A Axis line of side mold AD Axial direction of side mold RD Radial direction of side mold (straight line extending in the radial direction)
SL 1 Reference line (1st reference line)
SL2 reference line (second reference line)
SL3 reference line (third reference line)
AL1 to AL3 Axis of the vent hole θ0 Angle between the axis and the reference line α Inclination angle in the axial direction with respect to the reference line β Inclination angle in the circumferential direction with respect to the reference line

Claims (3)

an annular mold having a molding surface for molding a bead portion or a sidewall portion of a tire;
a plurality of vent holes formed in the mold and communicating the inside and outside of the mold,
The molding surface includes an outwardly arcuate concave portion,
The plurality of vent holes are formed with a first vent hole formed based on a first reference line that is a normal line of the recess , and a second reference line that is different from the first reference line that is a normal line of the recess. a second vent hole formed as a reference ;
The first reference line of the first vent hole is inclined with respect to the axis of the mold on a first meridian cross section including the end of the first vent hole on the molding surface side,
The second reference line of the second vent hole is on a second meridian cross section including the end of the second vent hole on the molding surface side, and the second reference line of the first vent hole is relative to the axis. slope at the same angle as the line ,
The inclination angle of the first vent hole with respect to the first reference line and the inclination angle of the second vent hole with respect to the second reference line are both set to differ within an angular range of ±10°. , tire vulcanization mold. The tire vulcanization mold according to claim 1 , wherein a spring vent is arranged in at least some of the plurality of vent holes at an end on the molding surface side. The plurality of vent holes are provided at intervals in the circumferential direction of the mold,
The tire vulcanization mold according to claim 1 or 2 , wherein the first vent hole and the second vent hole are arranged adjacent to each other in the circumferential direction.

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