JP7015160B2 - Pneumatic tires and tire vulcanization dies - Google Patents

Description

The present invention relates to pneumatic tires and tire vulcanization dies.

The tire vulcanization die is provided with a plurality of vent holes for bleeding air existing between the raw tire and the die during vulcanization. The vent hole is mainly formed in the part of the mold where the tread is molded. When vulcanization is performed in the tire vulcanization mold, air is released from the vent hole, and then the rubber of the raw tire flows into the vent hole. Therefore, on the surface of the tire taken out from the mold after vulcanization, elongated protrusions called spews are formed by the rubber flowing into the vent holes.

Since spew not only impairs the appearance of the tire but also deteriorates the rolling resistance, trimming work for cutting the spew is indispensable in the post-process after vulcanization and molding of the tire, which causes a problem that workability and productivity are impaired. there were. Further, since the spew is an elongated columnar body made of rubber and is easily bent, even if the blade hits during trimming, the spew is pushed by the blade and bends, and the spew is liable to be left uncut. Such uncut parts of the spew impair the appearance and worsen the rolling resistance.

Patent Document 1 proposes to project a spew into a tread groove provided in a tread portion, but in such a case, the volume of the tread groove is reduced, so that the drainage performance is deteriorated.

Japanese Unexamined Patent Publication No. 9-2020

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an elongated protrusion that does not affect the tire characteristics such as appearance and rolling resistance without impairing the drainage performance of the groove provided in the tread portion. It is an object of the present invention to provide a pneumatic tire and a tire vulcanization mold that can be formed.

The pneumatic tire of the present invention is a pneumatic tire including a plurality of main grooves extending in the tire circumferential direction and a plurality of land portions partitioned by the main grooves in a tread portion, wherein the land portion is from a ground contact surface. It is provided with a small hole that sinks inward in the tire radial direction and a columnar portion that protrudes outward in the radial direction from the bottom surface of the small hole, and the small hole is deeper than the opening diameter .

In a preferred embodiment of the present invention, the top of the columnar portion may be located inward in the tire radial direction from the ground contact surface.

In another preferred embodiment of the present invention, the columnar portion may be a vent hole mark formed by a vent hole for bleeding air existing between the raw tire and the mold during vulcanization.

In another preferred embodiment of the present invention, the cross-sectional area of the small hole may be 10 times or less the cross-sectional area of the columnar portion.

The tire scouring die of the present invention is a tire scouring die provided with a tread molding die for molding a tread portion. A vent hole that penetrates the protrusion from the top surface and communicates between the inside of the mold and the outside of the mold, a ridge for forming a plurality of main grooves extending in the circumferential direction of the tire, and a plurality of lands partitioned by the main groove. It is provided with a land portion molding surface for molding a portion, and the protrusion protrudes from the land portion molding surface into the inside of the mold, and the protrusion height of the protrusion is larger than the diameter of the protrusion .

In another preferred embodiment of the present invention, the cross-sectional area of the protrusion may be 10 times or less the cross-sectional area of the vent hole.

According to the present invention, it is possible to form elongated protrusions that do not affect the tire characteristics such as appearance and rolling resistance without impairing the drainage performance of the groove provided in the tread portion.

A half cross-sectional view of a pneumatic tire according to an embodiment of the present invention. The plan view of the tread part of the pneumatic tire of FIG. FIG. 3 is a semi-cross-sectional view of a tire vulcanizing die for vulcanizing the pneumatic tire of FIG.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a right half cross-sectional view of a pneumatic tire T according to an embodiment cut along a meridian cross section including a tire shaft. Since the pneumatic tire T is a symmetrical tire, the left half is not shown.

The pneumatic tire T has a pair of left and right bead portions 1, a sidewall portion 2 extending from the bead portion 1 to the tire radial outer Ro, and a tread that is connected to the tire radial outer end of the sidewall portion 2 to form a tread. A unit 3 is provided.

An annular bead core 11 made of a convergent body obtained by laminating and winding rubber-coated bead wires is embedded in the bead portion 1, and a bead filler 12 is arranged on the outer Ro in the tire radial direction of the bead core 11.

The carcass ply 4 extends between the bead cores 11 arranged in the pair of bead portions 1, passes through the inner side surface of the bead filler 12 in the tire axial direction, and is wound around the bead core 11 from the inside to the outside. The carcass ply 4 is formed by covering a ply cord arranged in a direction substantially orthogonal to the tire circumferential direction with a topping rubber. As the ply cord, a steel cord or an organic fiber cord is preferably used.

In the sidewall portion 2, a sidewall rubber 6 constituting an outer wall surface of the pneumatic tire T is provided on the outside of the carcass ply 4. A rim strip rubber may be provided on the inner Ri in the tire radial direction of the sidewall rubber 6 at least at a portion in contact with the rim flange.

Inside the carcass ply 4, an inner liner member 5 constituting the inner peripheral surface of the pneumatic tire T is provided. That is, the inner liner member 5 is installed so as to cover the entire inner surface of the tire from the tread portion 3 to the bead portion 1 via the sidewall portions 2 on the left and right sides thereof.

In the tread portion 3, a belt 7 composed of two crossed belt plies using a tire cord such as a steel cord or an aramid fiber is provided on the outer peripheral side of the carcass ply 4. Further, a tread rubber 8 constituting a ground contact surface 35 is provided on the outer peripheral side of the belt 7.

A plurality of main grooves 31 extending along the tire circumferential direction are provided on the surface of the tread portion 3. Specifically, in the case of four grooves, the main grooves 31 are provided on the pair of center main grooves 31A arranged on both sides of the tire equatorial surface CL and the pair of center main grooves 31A on the outer side Wo in the tire width direction. It is composed of a pair of shoulder main grooves 31B. The outer Wo in the tire width direction means the side away from the tire equatorial plane CL in the tire width direction W.

Due to the above four main grooves 31, a central land portion 32 is formed between the two center main grooves 31A in the tread portion 3, and an intermediate land portion is formed between the center main groove 31A and the shoulder main groove 31B. 33 is formed, and the shoulder land portion 34 is formed on the outer Wo in the tire width direction of the two shoulder main grooves 31B.

In this example, the central land portion 32, the intermediate land portion 33, and the shoulder land portion 34 are composed of ribs continuous in the tire circumferential direction. The central land portion 32, the intermediate land portion 33, and the shoulder land portion 34 may be a block row divided in the tire circumferential direction by a lateral groove.

The central land portion 32, the intermediate land portion 33, and the shoulder land portion 34 are provided with a plurality of small holes 50 that are recessed from the ground contact surface 35 of the tread portion 3 toward the inward Ri in the tire radial direction.

The bottom surface 52 of the narrow hole 50 is provided with a columnar portion 54 projecting outward in the radial direction.

The small hole 50 has a circular cross-sectional shape and is deeply depressed as compared with the opening diameter M, that is, it is composed of elongated recesses in the depth direction (diametrical direction R) having a depth H larger than the opening diameter M.

The columnar portion 54 is a columnar elongated protrusion that protrudes in a direction parallel to the depth direction of the small hole 50 (that is, the radial direction R). The height h of the columnar portion 54 is set to be smaller than the depth H of the fine hole 50, and the top portion 55 of the columnar portion 54 is located inside the small hole 50 without protruding from the small hole 50. Such a columnar portion 54 may be a vent hole mark (spew) formed by a vent hole for allowing air inside the tire vulcanization die 100, which will be described later, to escape to the outside.

Here, to give an example of the dimensions of the fine hole 50 and the columnar portion 54, the opening diameter M of the fine hole 50 is 3 mm to 5 mm, the depth H of the fine hole 50 is 3 mm to 8 mm, and the diameter m of the columnar portion 54 is 0.3. The height h of the columnar portion 54 can be set to mm to 1.4 mm and the height h of the columnar portion 54 can be set to 2 mm to 7 mm.

At that time, the cross-sectional area of the fine hole 50 is preferably 10 times or less, more preferably 4 times or less, of the cross-sectional area of the columnar portion 54. When the cross-sectional shape of the fine hole 50 and the columnar portion 54 is circular as in the present embodiment, the opening diameter M of the fine hole 50 is preferably 3 times or less the diameter m of the columnar portion 54, and more preferably. It is less than twice. When the cross-sectional area of the fine hole 50 is 10 times or less the cross-sectional area of the columnar portion 54, it is possible to suppress a decrease in block rigidity without impairing the workability (manufacturing ease) of the vulcanization die for molding the tire. The effect becomes more remarkable when the cross-sectional area of the fine hole 50 is less than twice the cross-sectional area of the columnar portion 54.

Next, the tire vulcanization die 100 of this embodiment will be described. The tire vulcanization mold 100 is a mold for vulcanizing a green tire (raw tire) into a shape like the pneumatic tire T described above, and is attached to a vulcanizer via a container to be a tire vulcanizer. It constitutes.

The tire vulcanization die 100 includes a sector 102, an upper side plate 104, and a lower side plate 106, and forms a cavity 18 which is a molding space for a pneumatic tire.

The sector 102 is a mold for forming the tread portion 3 of the pneumatic tire T, and is divided into a plurality of (for example, 7) in the tire circumferential direction. The sectors 102 are provided so as to be expandable and displaceable in the tire radial direction (tire radial direction R), and in the mold closed state in which the sectors 102 are arranged at the mold closed positions, the sectors 102 gather together to form an annular shape. The sector 102 includes a plurality of ridges 108 for molding a plurality of main grooves 31 in the tread portion 3, and a land portion molding surface 110 partitioned by the plurality of main grooves 31. The land portion molding surface 110 molds the central land portion 32, the intermediate land portion 33, and the shoulder land portion 34 of the tread portion 3.

Further, the land molding surface 110 of the sector 102 is provided with a vent hole 112 for bleeding air that communicates with the outside of the tire vulcanization die 100. The vent hole 112 is provided on each land portion molding surface 110 that forms the central land portion 32, the intermediate land portion 33, and the shoulder land portion 34. The vent hole 112 penetrates a columnar protrusion 120 that protrudes from the land molding surface 110 into the mold. The protrusion 120 is a columnar protrusion that forms the fine hole 50 of the pneumatic tire T. The inner end of the mold of the vent hole 112 is open on the top surface 122 of the protrusion 120. The rubber of the green tire flows into the vent hole 112 together with the air inside the mold during vulcanization molding. As a result, the vent hole 112 forms a columnar portion 54 protruding from the bottom surface 52 of the narrow hole 50.

The protrusion height N at which the protrusion 120 protrudes from the land molding surface 110 is set to be larger than the height of the columnar portion 54 formed by the vent hole 112. The height of the columnar portion 54 formed by the vent hole 112 can be determined from the vulcanization time of the green tire and the vulcanization rate of the rubber arranged around the vent hole 112.

Here, to give an example of the dimensions of the protrusion 120 and the vent hole 112, the diameter Q of the protrusion 120 is 3.5 mm to 5.5 mm, the protrusion height N of the protrusion 120 is 4 to 9 mm, and the opening diameter q of the vent hole 112 is 0.4. It can be set to mm to 1.5 mm.

At that time, the cross-sectional area of the protrusion 120 is preferably 10 times or less, more preferably 4 times or less, of the cross-sectional area of the vent hole 112. When the cross-sectional shape of the protrusion 120 and the vent hole 112 is circular as in the present embodiment, the diameter Q of the protrusion 120 is preferably 3 times or less, more preferably 2 times or less the diameter q of the vent hole 112. Is.

In order to manufacture a pneumatic tire T using the tire vulcanization mold 100 as described above, an unvulcanized green tire is set in the tire vulcanization mold 100, the mold is closed, and then the tire T is placed inside. The unvulcanized tire is vulcanized by expanding the illustrated bladder, pressing the unvulcanized tire against the inner surface of the mold, and holding the tire in a heated state.

At that time, in the present embodiment, the air accumulated between the green tire and the inner surface of the mold is discharged to the outside of the mold through the vent hole 112, and the rubber of the green tire flows into the mold. As a result, the protrusion 120 forms a fine hole 50 in the central land portion 32, the intermediate land portion 33, and the shoulder land portion 34, and the vent hole 112 projects from the bottom surface 52 of the fine hole 50 toward the radial outward Ro. The columnar portion 54 is formed.

In the present embodiment, the radial outer Ro A columnar portion 54 projecting toward is provided. Therefore, without reducing the volume of the main groove 31, columnar protrusions can be provided in places that are not conspicuous in appearance, and the drainage performance of the groove is not impaired and the tire characteristics such as appearance and rolling resistance are not affected. Elongated protrusions can be formed on the pneumatic tire T.

Further, in the present embodiment, the top portion 55 of the columnar portion 54 is located inward Ri in the tire radial direction from the ground contact surface 35 of the central land portion 32, the intermediate land portion 33, and the shoulder land portion 34. However, the columnar portion 54 does not come into contact with the road surface, and it is possible to suppress deterioration of tire performance such as rolling resistance.

Further, in the present embodiment, since the columnar portion 54 is a vent hole mark formed by the vent hole 112 provided in the tire vulcanization die 100, the vent hole mark is made inconspicuous without trimming work. It is possible to prevent deterioration of tire characteristics such as appearance and rolling resistance.

The above embodiments are presented as examples and are not intended to limit the scope of the invention. This novel embodiment can be implemented in various other embodiments, and various omissions, replacements, and changes can be made without departing from the gist of the invention.

For example, in the above embodiment, the case where the cross-sectional shape of the fine hole 50 and the columnar portion 54 provided in the pneumatic tire T is circular has been described, but the cross-sectional shape of these is an arbitrary shape such as a polygonal shape such as a rectangle or an elliptical shape. It is possible to.

T ... tire, 1 ... bead part, 2 ... sidewall part, 3 ... tread part, 6 ... sidewall rubber, 8 ... tread rubber, 31 ... main groove, 31A ... center main groove, 31B ... shoulder main groove, 32 ... Central land part, 33 ... Intermediate land part, 34 ... Shoulder land part, 50 ... Fine hole, 52 ... Bottom surface, 54 ... Column part, 55 ... Top surface, 100 ... Tire vulcanization mold, 102 ... Sector, 104 ... Upper side Side plate, 106 ... lower side plate, 108 ... ridge, 110 ... land molded surface, 112 ... vent hole, 114 ... vent hole, 116 ... bead ring, 118 ... bead ring, 120 ... protrusion, 122 ... top surface

Claims (6)

In a pneumatic tire provided with a plurality of main grooves extending in the tire circumferential direction and a plurality of land portions partitioned by the main grooves in the tread portion.
The land portion includes a small hole that sinks inward in the radial direction from the ground contact surface, and a columnar portion that protrudes outward in the radial direction from the bottom surface of the small hole .
The small hole is a pneumatic tire that sinks deeper than the opening diameter . The pneumatic tire according to claim 1, wherein the top of the columnar portion is located inward in the tire radial direction from the ground contact surface. The pneumatic tire according to claim 1 or 2, wherein the columnar portion is a vent hole mark formed by a vent hole for removing air existing between the raw tire and the mold during vulcanization. The pneumatic tire according to any one of claims 1 to 3, wherein the cross-sectional area of the small hole is 10 times or less the cross-sectional area of the columnar portion. In a tire vulcanization die equipped with a tread molding die for molding a tread portion,
The tread molding mold has a columnar protrusion protruding into the mold, a vent hole penetrating the protrusion from the top surface of the protrusion and communicating the inside of the mold with the outside of the mold , and extending in the tire circumferential direction. It is provided with a ridge for molding a plurality of main grooves and a land portion molding surface for molding a plurality of land portions partitioned by the main grooves.
A tire vulcanization die in which the protrusions protrude from the land molding surface into the mold, and the protrusion height of the protrusions is larger than the diameter of the protrusions. The tire vulcanization die according to claim 5 , wherein the cross-sectional area of the protrusion is 10 times or less the cross-sectional area of the vent hole.

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