JP6062775B2 - Tire vulcanizing mold, tire vulcanizing method and pneumatic tire - Google Patents

Description

  The present invention relates to a tire vulcanization mold, a tire vulcanization method using the tire vulcanization mold, and a pneumatic tire manufactured using the tire vulcanization method.

  Currently, in the field of pneumatic tires, pneumatic tires using foamed rubber in the tread (hereinafter also referred to as “foamed rubber tires”) are manufactured and marketed, and applied to studless tires specialized in performance on ice. (Patent Document 1).

  On the other hand, in recent years, there has been a strong demand for reducing the weight of tires in general in order to reduce the fuel consumption of automobiles.

  Therefore, in the manufacture of ordinary tires, it has been studied to reduce the weight of the tire by using foamed rubber in the tread portion as in the studless tire described above.

Japanese Patent Application Laid-Open No. 2012-3231

  However, when a normal pneumatic tire is manufactured using foamed rubber in the tread portion, the foaming ratio increases toward the center portion of the pattern block formed in the tread portion, so that the center portion of the pattern block is easily raised.

  When the central portion of the pattern block is raised, the ground contact shape and the contact pressure distribution of the pneumatic tire are not stable, and the steering stability and wear resistance may be reduced.

  Accordingly, the present invention provides a tire vulcanization mold and a tire vulcanization mold that can suppress the occurrence of bulge in the center portion of the pattern block when manufacturing a pneumatic tire reduced in weight by using foamed rubber in the tread portion. An object of the present invention is to provide a vulcanizing method and a pneumatic tire manufactured using the tire vulcanizing method.

The invention described in claim 1
A tire vulcanization mold provided with a recess for forming a pattern block in a tread portion of a pneumatic tire,
The bottom surface of the recess provided corresponding to the ground contact surface of the pattern block has a curved surface that curves convexly toward the center in the radial direction of the tire, and foam rubber is used for the tread portion. A tire vulcanization mold characterized in that it is used in a vulcanization process of a tire, and is configured to suppress the bulging of the center portion of the pattern block in the tire after vulcanization. .

The invention described in claim 2
2. The tire vulcanization mold according to claim 1, wherein a radius of curvature of the curved surface is 100 to 1500 mm.

The invention according to claim 3
A tire vulcanizing method comprising vulcanizing a pneumatic tire using foamed rubber in a tread portion using the tire vulcanizing mold according to claim 1.

The invention according to claim 4
The tire vulcanizing method according to claim 3, wherein the foamed rubber is a foamed rubber foamed with a foaming agent.

The invention described in claim 5
The foaming agent is at least one selected from the group consisting of azodicarbonamide, N, N′-dinitrosopentamethylenetetramine, 4,4′-oxobisbenzenesulfonylhydrazide, and sodium bicarbonate. The tire vulcanizing method according to claim 4.

The invention described in claim 6
The tire vulcanization method according to any one of claims 3 to 5, wherein the foaming ratio of the foamed rubber is 10 to 50%.

  According to the present invention, when manufacturing a pneumatic tire reduced in weight by using foamed rubber in the tread portion, a tire vulcanization mold and a tire vulcanization capable of suppressing the occurrence of swell in the center portion of the pattern block. While providing a vulcanization method, the pneumatic tire manufactured using the said tire vulcanization method can be provided.

It is a figure which shows typically the metal mold | die for tire vulcanization | cure which concerns on one embodiment of this invention. It is a figure which shows typically the cross-sectional shape of a part of tread segment of the tire vulcanization mold according to the embodiment of the present invention.

  Hereinafter, the present invention will be described based on embodiments with reference to the drawings.

1. Tire Vulcanization Mold First, a tire vulcanization mold according to an embodiment of the present invention will be described. FIG. 1 is a diagram schematically showing a tire vulcanization mold according to an embodiment of the present invention, and FIG. 2 schematically shows a partial cross-sectional shape of a tread segment of the tire vulcanization mold. FIG.

  As shown in FIG. 1, the tire vulcanizing mold 1 according to the present embodiment forms a pattern block on the tread portion of the tire T, similarly to the split mold conventionally used for vulcanizing tires. A tread segment 10 provided with a plurality of recesses, a pair of upper and lower molds 20 forming the side surface of the tire T, and a vulcanization bladder that presses the tire T held in the tire vulcanization mold 1 from the inside 30.

  As shown in FIG. 2, the bottom surface portion 11a of each recess 11 corresponds to the ground contact surface of the pattern block formed in the tread portion Ta. In the tire vulcanization mold 1 according to the present embodiment, unlike the conventional case, a curved surface that is convexly curved toward the center in the radial direction of the tire T is formed on the bottom surface portion 11a.

2. Tire vulcanization method Next, a tire vulcanization method using the tire vulcanization mold will be described.

  In the tire vulcanizing method according to the present embodiment, a foamed rubber composition is used as the tread rubber composition. This foamed rubber composition is manufactured by adding a foaming agent to a normal tire rubber composition, and kneading using a kneader such as a kneader or an open roll. After being molded into a tread shape, By being bonded to the tire member, it is produced as an unvulcanized tire.

  The above foaming agent can easily form appropriate closed cells by adjusting the addition amount.

  Examples of the foaming agent include azodicarbonamide, N, N′-dinitrosopentamethylenetetramine, 4,4′-oxobisbenzenesulfonylhydrazide, sodium hydrogen carbonate, and these foaming agents should be used appropriately. Thus, more uniform closed cells can be easily formed. In addition, although these foaming agents can be used independently, they can also be used in combination as appropriate.

  These foaming agents are preferably added so that the expansion ratio is 10 to 50%. By controlling the expansion ratio, it is possible to obtain a weight-reduced tire and to achieve desired driving stability. And sufficient wear resistance can be secured.

  When the produced unvulcanized tire T is vulcanized, it is first mounted on the tire vulcanization mold 1 in the open state, and then the tire vulcanization mold 1 is closed as shown in FIG. To do. Thereby, the tread portion Ta of the tire T comes into contact with the tread segment 10 and both side surfaces come into contact with the pair of upper and lower molds 20.

  Next, the vulcanization bladder 30 is expanded, the unvulcanized tire T is pressed against the tread segment 10 and the mold 20, and heated and pressurized. Thereby, the unvulcanized foamed rubber is vulcanized while being foamed, and a pattern block corresponding to the recess 11 of the tread segment 10 is formed in the tread portion Ta of the tire T. Conditions such as the degree of heating and pressurization and time are appropriately set in consideration of the tire size and the like.

  At this time, as described above, the bottom surface portion 11a is provided with a curved surface that curves in a convex shape toward the center in the radial direction of the tire T. The tire T is molded into a shape having a dent toward the center in the radial direction.

  After completion of the above vulcanization process, the vulcanized tire T is taken out from the tire vulcanization mold 1, but since the expansion of the foam rubber by the foaming agent continues thereafter, the center of the pattern block having a high expansion ratio The department tries to swell. However, in the present embodiment, since the concave pattern block is formed as described above, this bulge is suppressed, and the pattern block serving as the ground plane can be kept in a substantially flat shape.

  For this reason, although the foam rubber is used, a normal tire in which the contact shape and the contact pressure distribution are sufficiently stable and the desired handling stability and wear resistance are ensured can be manufactured. As a result, it is possible to provide a pneumatic tire excellent in handling stability and wear resistance while being reduced in weight.

  Further, the vulcanization method according to the present embodiment can be applied as appropriate to a studless tire or the like that conventionally uses a foam rubber tire for the tread portion.

  In addition, as a curvature radius of the curved surface formed in the bottom face part 11a, 100-1500 mm is preferable. If the radius of curvature is less than 100 mm, the size of the recess formed is too large, and the desired steering stability and wear resistance may not be ensured. On the other hand, if the thickness exceeds 1500 mm, the dents are not formed to a sufficient size, so that the expansion deformation (swell) caused by foaming at the center of the pattern block cannot be sufficiently suppressed, and desired steering stability and wear resistance are prevented. There is a risk that the sex cannot be secured. Since a dent is formed in a more suitable size as it is 150-1300 mm, it is more preferable.

  The material of the mold is not particularly limited, but is preferably made of a metal such as aluminum, stainless steel, or duralumin in view of durability, heat resistance, dimensional stability, and the like.

  Next, based on an Example, this invention is demonstrated more concretely.

1. Manufacture of a pneumatic tire A pneumatic tire having a tire size of 195 / 65R15 was manufactured as described below.

(1) Production of unvulcanized rubber composition A predetermined amount of the following materials was kneaded to produce a foamed rubber composition having an expansion ratio of 30%.

SBR: Nipol 1502 manufactured by Zeon Corporation (styrene content: 23.5% by mass)
BR: Hisys BR150B manufactured by Ube Industries
Carbon black: Show Black N220 manufactured by Cabot Japan (nitrogen adsorption specific surface area (N ₂ SA): 125 m ² / g)
Silica: Ultrasil VN3 manufactured by Degussa (nitrogen adsorption specific surface area (N ₂ SA): 175 m ² / g)
Silane coupling agent: Si69 (bis (3-triethoxysilylpropyl) tetrasulfide) manufactured by Degussa
Anti-aging agent: Nocrack 6C (N-1,3-dimethylbutyl-N′-phenyl-p-phenylenediamine) manufactured by Ouchi Shinsei Chemical Co., Ltd.
Stearic acid: Stearic acid manufactured by NOF Corporation Oil: Mineral oil PW-380 manufactured by Idemitsu Kosan Co., Ltd.
Zinc oxide: Zinc Hua No. 1 manufactured by Mitsui Mining & Smelting Co., Ltd. Wax: Sunnock wax manufactured by Ouchi Shinsei Chemical Co., Ltd. Sulfur: Powdered sulfur manufactured by Tsurumi Chemical Co., Ltd. Vulcanization accelerator: Noxeller manufactured by Ouchi New Chemical Co., Ltd. CZ (N-cyclohexyl-2-benzothiazolylsulfenamide)
Effervescent agent: Neocerbon N # 1000SW (4,4′-oxobisbenzenesulfonylhydrazide, average particle size 14 μm) manufactured by Eiwa Chemical Industries

(2) Production of Unvulcanized Foam Rubber Tire Next, the foam rubber having the above composition was formed into a tread shape, and then bonded to another tire member to produce an unvulcanized foam rubber tire.

(3) Vulcanization Using a vulcanization mold provided with curved surfaces with respective curvature radii shown in Table 1, an unvulcanized foamed rubber tire was vulcanized at 170 ° C. for 15 minutes, and Examples 1 to 3 A pneumatic foam rubber tire was manufactured. In addition, the comparative example 1 is a prior art example, and the convex curved surface is not provided in the bottom face part.

2. Test (1) Test method a. Measurement of curvature radius of tire block Each of the obtained pneumatic foam rubber tires was assembled on a 15x6 JJ aluminum wheel rim, filled with 210 kPa of internal pressure, and then subjected to profile measurement with a laser beam to obtain a pattern block ( The radius of curvature of the tire block) was determined. The results are shown in Table 1. In Table 1, those having a curved surface of the tire block in the direction opposite to the tire central portion (the tire block bulging) are negative, and those having the curved surface in the tire central portion direction (the tire block is recessed). Stuff) was written as positive.

b. Steering stability Each of the obtained pneumatic foamed rubber tires is assembled on a 15x6JJ aluminum wheel rim, filled with 210kPa internal pressure (same front and rear), and mounted on 4 wheels of a 2000cc domestic FF vehicle. Then, one driver got on the test course and sensuously evaluated. The evaluation was performed by a 100-point method with Example 1 as 100, and displayed as an index. The larger the value, the better the steering stability. The results are shown in Table 1.

c. Abrasion resistance Each of the resulting pneumatic foam rubber tires is assembled on a 15x6JJ aluminum wheel rim, filled with 210kPa internal pressure (same front and rear), and mounted on a 4-wheel taxi of a 2000cc domestic FF vehicle. The remaining groove after 6 months was measured. The evaluation was performed by a 100-point method with Example 1 as 100, and displayed as an index. It shows that abrasion resistance is so favorable that a numerical value is large. The results are shown in Table 1.

(2) Test results From Table 1, it can be seen that all of Examples 1 to 3 provided with a curved surface have improved steering stability and wear resistance compared to Comparative Example 1 provided with no curved surface. I understand.

  And also in Examples 1-3, Example 1 set to the curvature radius in the range of 150 mm or more and 1300 mm shows that steering stability and abrasion resistance are especially excellent.

  While the present invention has been described based on the embodiments, the present invention is not limited to the above-described embodiments. Various modifications can be made to the above-described embodiment within the same and equivalent scope as the present invention.

DESCRIPTION OF SYMBOLS 1 Tire vulcanization mold 10 Tread segment 11 Recess 11a Bottom face 20 Mold 30 Vulcanization bladder T Tire Ta tread

Claims (6)

A tire vulcanization mold provided with a recess for forming a pattern block in a tread portion of a pneumatic tire,
The bottom surface of the recess provided corresponding to the ground contact surface of the pattern block has a curved surface that curves convexly toward the center in the radial direction of the tire, and foam rubber is used for the tread portion. A tire vulcanization mold characterized in that it is used in a vulcanizing process of a tire, and is configured to suppress the bulging of the center portion of the pattern block in the tire after vulcanization .   The tire vulcanization mold according to claim 1, wherein a radius of curvature of the curved surface is 100 to 1500 mm.   A tire vulcanizing method comprising vulcanizing a pneumatic tire using foamed rubber in a tread portion using the tire vulcanizing mold according to claim 1.   The tire vulcanizing method according to claim 3, wherein the foamed rubber is a foamed rubber foamed using a foaming agent.   The foaming agent is at least one selected from the group consisting of azodicarbonamide, N, N′-dinitrosopentamethylenetetramine, 4,4′-oxobisbenzenesulfonylhydrazide, and sodium bicarbonate. The tire vulcanizing method according to claim 4.   The tire vulcanization method according to any one of claims 3 to 5, wherein the foaming ratio of the foamed rubber is 10 to 50%.

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