JP3091264B2 - Manufacturing method for pneumatic tires - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION This invention relates to a method and apparatus for producing a pneumatic tire, in particular, relates to the production how of a pneumatic tire for reducing the protruding rubber after vulcanization.

[0002]

2. Description of the Related Art In general, in a method of manufacturing a pneumatic tire, a molded green tire is mounted on a vulcanizer, the inside of which is inflated with a bladder or the like and vulcanized at a high internal pressure and high temperature for a predetermined time. In this case, vulcanization is performed, but if air between the green tire and the tire mold is not released to the outside, a defect is generated on the tire surface due to air, resulting in a defective product. Particularly, in recent years, the production of high-performance tires and the like having complicated irregularities in the tread portion has been increasing. Therefore, the air is usually discharged to the outside of the mold by the following method.

A first method is to provide a mold with a vent hole communicating with the outside of the mold, and to discharge the air to the outside of the mold from the vent hole.

A second method is to use a sectional die or a small-segment die and discharge the air to the outside of the die from a joint between the two dies.

[0005] However, in the first method, tread rubber flows into the vent hole, leaving vent spew on the tire surface after vulcanization. In the second method, the tread rubber flows into a joint between the molds, and a flash remains on the tire surface after vulcanization. For this reason, as shown in FIG. 5, in order to make the tire 60 after vulcanization molding into a product tire, it was necessary to remove (trim) the vent spew 62 or the flash 64 remaining on the tire surface.
In particular, since the flash 64 has a low waist and is difficult to trim, the trimming operation is extremely complicated.

[0006] One method of improving this is to harden the rubber by increasing the filling amount of the carbon black in the rubber, thereby making it difficult for the rubber material to enter the vent hole or the joint between the molds. . However, in this method, the performance requirements of the tire may not be satisfied, and it may be difficult to knead the rubber, so that practical use is extremely difficult.

As another method, since the rubber is protruded due to the flow of the rubber near the vulcanization mold immediately after the start of the vulcanization, the rubber in contact with the mold must be made of a material having a high vulcanization rate. Methods such as changing the amount of sulfur and the type of vulcanization accelerator and increasing the amount are conceivable. In this case, during kneading or extrusion or rolling, the rubber is scorched, so-called burning phenomenon easily occurs, so Is extremely difficult.

Further, a method of using a curing agent as a compounding agent to harden the unvulcanized rubber and prevent the mold from breaking is conceivable. In this case, however, the burning phenomenon during kneading, extrusion or rolling is also considered. Is likely to occur, and practical application is extremely difficult from the viewpoint of tire performance.

Further, as shown in Japanese Patent Publication No. 56-11605, an electron beam (electron beam:
EB) A method in which an effective cross-linking reaction between carbon and rubber between rubber molecules is caused by radiation to form an EB irradiation layer on the tire surface layer. That is, a method of pre-vulcanizing a tire surface layer by electron beam radiation is known. In this method, the higher the voltage of the emitted electron beam, and the higher the radiation dose, the higher the transmission capability of the electron beam to the tread portion,
The thickness of the EB irradiation layer increases. For this reason, as shown in Table 1, it is effective to suppress bent spew and flush.

[0010]

[Table 1] However, in the method of pre-vulcanizing the tire surface layer by this electron beam radiation, as shown in FIG.
EB irradiation layer 6 of tread 66 formed by electron beam
8, the thickness M1 becomes extremely thick. Therefore, an extremely thick EB irradiation layer 68 remains on the tread surface portion 66A and the groove bottom 66B of the tread 66 after vulcanization molding. This EB irradiation layer 68
In addition to the fact that the wear resistance of the tread portion 66A of the tread 66 is reduced, the groove bottom 66B is cracked, which causes a so-called groove flux, and thus the durability of the product tire is reduced.

[0011]

SUMMARY OF THE INVENTION In consideration of the above facts, the present invention relates to a pneumatic tire which can suppress the protrusion of rubber during vulcanization molding without reducing the durability and wear resistance of the tire. it is an object to obtain a manufacturing how.

[0012]

According to a first aspect of the present invention, there is provided a method of manufacturing a pneumatic tire according to the present invention.
It is characterized in that the surface layer of the entire tread portion is pre-vulcanized by irradiating an electron beam under the condition of an irradiation dose of 1 to 10 MRAD at less than 0 kv.

[0013]

[0014]

FIG. 7 and Table 2 show the accelerating voltage of the electron beam due to the irradiation of the electron beam and the transmission capability of the electron beam in the material thickness direction. Further, it is said that when the relative dose in the curve shown in FIG. 7 is about 60% or more, the effective cross-linking between carbon atoms between rubber molecules is generated.

[0015]

[Table 2] Therefore, in the method of manufacturing a pneumatic tire of the present invention, the entire tread portion of the raw tire before the main vulcanization is irradiated with an electron beam under the conditions of an irradiation voltage of 1 to 10 MRAD at an acceleration voltage of less than 300 kv. 4 (A),
The thickness M2 of the EB irradiation layer 22 of the tread portion 20 formed by the electron beam was made thinner than the conventional example. Thereby, vent spew and flash can be suppressed, and as shown in FIG. 4 (B), during vulcanization molding in which a groove is formed by a vulcanizing mold in a flat green tire,
The EB irradiation layer 22 does not exist at all at the groove bottom 20A due to the flow of the rubber, or becomes extremely thin as shown in FIG. As a result, compared to the conventional example, the tread 20
The wear resistance of the tread portion of the tire is not reduced, and the occurrence of groove flux is less likely to occur, and the durability of the product tire is not reduced.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS.

As shown in FIG. 2, the pneumatic tire 10 of the present embodiment includes a tread portion 12, a pair of side wall portions 14, and a pair of bead portions 16. As shown in FIG. 3, the outer periphery in the radial direction of the carcass 18 is covered with a tread rubber or an elastomer material 20, and the outer side in the axial direction of the carcass 18 is covered with a rubber material 22.

The pneumatic tire 10 is a radial tire, for example, formed by vulcanization using a segment mold (not shown). This segment type is movable so as to approach or separate from each other in the tire axial direction, and is arranged between a segment forming a pair of side wall portions 14 of the tire 10 and a portion forming the pair of side wall portions 14. And an arc-shaped tread molding segment that moves radially inward of the tire to form a tread pattern.

As shown in FIG. 1, in the method of manufacturing a pneumatic tire according to the present embodiment, an electron beam vulcanizing apparatus 30 is used. The electron beam vulcanizing device 30 irradiates the entirety of the tread portion of the raw tire 42 with an electron beam before the main vulcanization is performed, and preliminarily vulcanizes the surface layer of the entire tread portion.

The electron beam vulcanizing apparatus 30 includes an operation section 32 and a DC power supply 34 connected to the operation section 32. An acceleration tube 36 is connected to the DC power supply 34 by a cable 37. The acceleration tube 36 is provided with a scanner 38 for scanning an electron beam in a predetermined direction, and a window 40 is provided on the electron beam irradiation side of the scanner 38. The window 40 is a slit-shaped opening from which an electron beam is emitted. The window 40 is provided with a beam shutter (not shown) so as to open and close the window 40.

A tire support 44 for supporting an unvulcanized green tire 42 is provided below the window 40 of the electron beam vulcanizing apparatus 30, that is, on the electron beam irradiation side.
The tire support portion 44 is connected to a motor (not shown) by a shaft 4.
6 and a rotatable drum 48. By fixing the raw tire 42 to the drum 48, the electron beam emitted from the window 40 is
The second tread portion 42A is irradiated at the center. In addition, a pair of driven rollers 50 is provided on the tire support portion 44, and the pair of driven rollers 50 is provided.
Are adapted to contact the treads of the tread portions 42A of the raw tires 42, respectively.

Next, a method of manufacturing the pneumatic tire of the present embodiment will be described. As shown in FIG. 1, the raw tire 42 is fixed to the tire support 44, and the tire support 44 is rotated by a motor. Next, the operation unit 32 of the electron beam vulcanizing apparatus 30 is operated to irradiate an electron beam from the acceleration tube 36, and this electron beam is transmitted to the window 40 by the scanner 38.
At the same time, the beam shutter of the window 40 is opened. As a result, the electron beam emitted from the window 40 is applied to the tread portion 42A of the raw tire 42.
, And is uniformly radiated in the tire circumferential direction.

In this case, the acceleration voltage of the electron beam is 200 kV or more and less than 300 kv, and the irradiation time is set to a necessary irradiation dose (1 to 10 MRAD) depending on the rotation speed and the number of rotations of the raw tire 42. When the irradiation dose of the electron beam becomes a predetermined value, that is, when the raw tire 42 rotates a predetermined amount, the beam shutter of the window 40 is closed, and the irradiation of the raw tire 42 with the electron beam is stopped. By operating the operation unit 32 of the electron beam irradiation device 30, the irradiation of the electron beam from the acceleration tube 36 is stopped.

Next, the tire which has been irradiated with an electron beam and pre-vulcanized as described above is set in a small-segment mold tire vulcanization molding machine (not shown) to complete the main vulcanization and complete the tire 10 (See FIG. 2).

As shown in FIG. 3, in the tire irradiated with the electron beam, the surface of the tire 10 irradiated with the electron beam is cured by effective cross-linking between carbon and rubber between rubber molecules and irradiated with EB. A layer is formed. Further, in this embodiment, since the electron dose is set to the irradiation dose of 1 to 10 MRAD at an acceleration voltage of less than 300 kv, the outer surface of the rubber is hardened to some extent, and the rubber flows into the joints between the segments of the mold or into the vent holes of the mold. And the flash 21 can be made smaller, and the rubber can be prevented from completely flowing into the matrix of the mold and forming a cavity in the tread pattern or the sidewall pattern. Further, in the pre-vulcanized tire irradiated with the electron beam, FIG.
As shown in FIG. 4A and FIG. 4B, since the thickness M2 of the EB layer 22 is thin, the tread surface and the groove bottom of the tread 20 are not excessively hardened, and the tread surface portion of the tread 20 has abrasion resistance. The wear resistance is not reduced, and the groove flux is hardly generated, and the durability of the product tire is not reduced.

In this embodiment, the electron beam vulcanizing device 30 is used.
Is a scanning type, but the electron beam vulcanizing apparatus 30 may be a non-scanning type. In this case, the apparatus can be downsized and the apparatus can be inexpensive. (Test Example) The tire of the present invention shown in FIG. 2 and the tire of the comparative example (the size of each tire is 205 / 65R15) were each pre-vulcanized under the conditions shown in Table 3, and then each tire was subjected to a small segment mold. After vulcanization molding, the flash height and flash thickness were measured at 20 to 30 points, respectively, and the respective comparative values are shown in Table 3. Table 3 shows the dynamic crack growth index and uneven wear index (Lambourn abrasion test, slip rate: 38.5%) of the tread rubber cut from the tire tread after vulcanization molding.

[0027]

[Table 3] From the experimental results shown in Table 3, the tire of the present invention suppresses the flash height as well as the tire of the comparative example, and is particularly excellent in the occurrence of groove cracks and uneven wear resistance as compared with the tire of the comparative example. Was revealed.

At an electron beam irradiation dose of more than 10 MRAD, dynamic crack growth and uneven wear resistance were unsatisfactory, although it was effective in suppressing flash.

[0029]

As has been described above, producing how the pneumatic tire of the present invention as set forth in claim 1, without reducing the durability and wear resistance of the tire, protruding rubber during vulcanizing Has an excellent effect that can be suppressed.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an apparatus for manufacturing a pneumatic tire according to an embodiment of the present invention.

FIG. 2 is a perspective view showing a pneumatic tire according to an embodiment of the present invention.

FIG. 3 is a sectional view taken along line 3-3 of FIG. 2;

FIGS. 4A and 4B are explanatory diagrams at the time of vulcanization molding of a pneumatic tire according to an embodiment of the present invention.

FIG. 5 is a sectional view corresponding to FIG. 3, showing a pneumatic tire according to a conventional example.

FIG. 6 is an explanatory diagram at the time of vulcanization molding of a pneumatic tire according to a conventional example.

FIG. 7 is a diagram (depth-dose curve) showing a relationship between a transmission depth of an electron beam and a relative dose.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Pneumatic tire 12 Tread part 30 Electron beam vulcanizer 32 Operation part 34 DC power supply 36 Accelerator tube 40 Window 42 Raw tire 44 Tire support part 48 Drum 50 Follower roller

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-57-4756 (JP, A) JP-A-57-84836 (JP, A) JP-A-63-109012 (JP, A) JP-A-1- 146929 (JP, A) JP-A-1-204803 (JP, A) JP-A-2-273226 (JP, A) JP-B-56-11605 (JP, B2) (58) Fields investigated (Int. Cl. ⁷ , DB name) B29C 33/02-33/04 B29C 35/08

Claims (1)

(57) [Claims] 1. An entire area of the tread portion of the green tire before the vulcanization is irradiated with an electron beam at an acceleration voltage of 200 kv or more and less than 300 kv under an irradiation dose of 1 to 10 MRAD to pre-vulcanize the surface layer of the entire tread portion. A method for producing a pneumatic tire, comprising vulcanizing.