Tire forming mold and tire manufacturing method

1. A tire forming mold comprising:

a pair of side mold portions forming an outer surface of a side wall portion of a tire;

an annular mold portion fitted to an outer side in a tire diametrical direction of the pair of side mold portions at a time of clamping the mold and forming an outer surface of a tread of the tire;

the annular mold portion being constructed by a combination of sectors which are divided in a tire circumferential direction; and

each of the sectors being capable of displacing in the tire diametrical direction,

wherein a fitting diameter of the annular mold portion is set to be equal to or more than a fitting diameter of the pair of side mold portions, an annular rubber introduction groove extending along the tire circumferential direction is provided in a fitting surface of the annular mold portion, and a groove portion whose shallowest depth position has a depth (d 2 ) of between 0.1 and 1.3 mm is formed in an introduction port of the rubber introduction groove,

wherein a back end surface of the rubber introduction groove is formed in such a manner as to come away from a fitting surface of the side mold portion incrementally in accordance with distance from the introduction port, and

wherein when a sector displaces to the outer side in the tire diametrical direction, the back end surface of the rubber introduction groove catches a leading end of a pinch formed by the rubber introduction groove.

2. The tire forming mold according to claim 1 , wherein a plurality of reinforcing groove portions formed by expanding the introduction port in such a manner as to thicken a root portion of the pinch formed by the rubber introduction groove are formed so as to be spaced in the tire circumferential direction.

3. The tire forming mold according to claim 1 , wherein a treatment facilitating a rubber peeling is applied to the fitting surface of the pair of side mold portions all over inner and outer sides of the rubber introduction groove.

4. The tire forming mold according to claim 1 , wherein the shallow groove portion has a first taper bottom surface in which the groove depth is gradually decreased from the introduction port of the rubber introduction groove toward the back end surface, and a second taper bottom surface in which the groove depth is gradually increased from the first taper bottom surface toward the back end surface.

5. A tire forming mold comprising:

a pair of side mold portions forming an outer surface of a side wall portion of a tire;

an annular mold portion fitted to an outer side in a tire diametrical direction of the pair of side mold portions at a time of clamping the mold and forming an outer surface of a tread of the tire;

the annular mold portion being constructed by a combination of sectors which are divided in a tire circumferential direction; and

each of the sectors being capable of displacing in the tire diametrical direction,

wherein a fitting diameter of the annular mold portion is set to be equal t o or more than a fitting diameter of the pair of side mold portions, an annular rubber introduction groove extending along the tire circumferential direction is provided at least in one of a fitting surface of the annular mold portion and a fitting surface of the pair of side mold portions, and a groove portion whose shallowest depth position has a depth (d 2 ) of between 0.1 and 1.3 mm is formed in an introduction port of the rubber introduction groove, and

wherein a treatment facilitating a rubber peeling is applied to the other of the fitting surface of the annular mold portion and the fitting surface of the pair of side mold portions all over inner and outer sides of the rubber introduction groove.

6. A tire manufacturing method comprising a step of vulcanization molding a tire while using a tire forming mold having a pair of side mold portions forming an outer surface of a side wall portion of a tire, and an annular mold portion fitted to an outer side in a tire diametrical direction of the pair of side mold portions at a time of clamping the mold and forming an outer surface of a tread of the tire, and structured such that the annular mold portion is constructed by a combination of sectors which are divided in a tire circumferential direction, and each of the sectors is capable of displacing in the tire diametrical direction,

wherein a fitting diameter of the annular mold portion is set to be equal to or more than a fitting diameter of the pair of side mold portions, an annular rubber introduction groove extending along the tire circumferential direction is provided in the fitting surface of the annular mold portion, and a groove portion whose shallowest depth position has a depth (d 2 ) of between 0.1 and 1.3 mm is formed in an introduction port of the rubber introduction groove,

wherein an unvulcanized tire is set to the tire forming mold so as to be clamped by the mold, and a rubber surplus of the unvulcanized tire is introduced to the rubber introduction groove at a time of the vulcanization molding,

wherein a back end surface of the rubber introduction groove is formed in such a manner as to come away from a fitting surface of the side mold portion incrementally in accordance with distance from the introduction port, and

wherein when a sector displaces to the outer side in the tire diametrical direction, the back end surface of the rubber introduction groove catches a leading end of a pinch of rubber from the rubber surplus formed by the rubber introduction groove.