JP3310558B2 - Method of manufacturing pneumatic tire and pneumatic tire manufactured by this method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a pneumatic tire which can reduce the vulcanization time and suppress over-vulcanization of the tire surface by utilizing preheating by induction heating. It relates to a manufactured pneumatic tire.

[0002]

2. Description of the Related Art In a heating method in a tire vulcanizing step, heat is generally transferred to a raw cover of a tire through a heating medium such as a hot plate or hot air.

[0003] However, such a method has a problem that, when heating a thick rubber or the like, it takes time to conduct heat to a central portion thereof, and the vulcanization time becomes longer.
If the center is to be vulcanized optimally, the tire surface tends to be over-vulcanized, which is not preferable.

For this reason, there is a method in which the raw cover of the tire is preheated in an oven and then vulcanized. However, it takes a long time to preheat, and the above problem has not been solved.

According to the present invention, after a rubber component using an induction heating rubber material in a raw cover is preheated by induction heating,
A method of manufacturing a pneumatic tire capable of shortening the vulcanization time and suppressing over-vulcanization of the tire surface based on heating and vulcanizing the entire raw cover, and air produced by the method. The aim is to provide tires with tires.

[0006]

In order to achieve the above object, a method of manufacturing a pneumatic tire according to the present invention is directed to a rubber using an induction heating rubber material in which a dielectric powder generating heat by induction heating is mixed with a rubber substrate. Forming a raw cover with components , or
One induction After preheating the rubber component by heating, with vulcanized by heating the whole of the raw cover, the rubber structure
The part is characterized by being located inside the raw cover .

As is well known, when a magnetic substance or a conductor is placed in a high-frequency magnetic field, heat is generated in a very short time by Joule heat due to hysteresis loss and eddy current generation. It is a method of heating metal, an adhesive containing magnetic powder, etc. by utilizing the so-called electromagnetic induction heating.

[0008] "Dielectric powder" refers to metals such as aluminum, iron,
A generic term for magnetic powder such as stainless steel.

[0009] Such induction heating does not occur in the usual rubber compounding for tires. However, the induction heating rubber material in which a rubber base material is mixed with a dielectric powder, that is, a magnetic powder such as a short metal fiber, has a dielectric powder. Heat is generated in a short time by generating heat by electromagnetic induction.

Therefore, by locating the rubber component using the induction heating rubber material inside the raw cover , the rubber component inside the tire can be instantaneously changed using the induction heating device immediately before vulcanizing the tire. If vulcanization is performed by a vulcanizer after heating, the temperature difference between the tire surface and the inside of the tire is reduced, and the tire can be vulcanized more efficiently and quickly.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In FIG. 2, a pneumatic tire 1
Are a pair of sidewall portions 3 extending radially inward from both ends of the tread portion 2, and a bead positioned at an inner end of each sidewall portion 3 and reinforced by an annular bead core 5. In this example, the tire is formed as a flat radial tire for a passenger car having a flatness ratio of 0.70 or less, for example, 0.65, which is a ratio of a tire sectional height to a tire maximum width.

The pneumatic tire 1 has a carcass 6 surrounding the tire cavity between the bead portions 4 and 4, and a tough outer portion of the carcass 6 in the tread portion 2. The belt layer 7 is arranged with a hoop effect.

Further, the bead portion 4 is provided with a bead apex 8 having a substantially triangular cross-section extending radially outwardly from the bead core 5 and extending from the bead core 5 to the side wall portion 3 for reinforcement.

The bead apex 8 has a JISA hardness of 80 to 95 degrees and a complex elastic modulus E * of 300 to 600 kg.
/ Cm ^2, a highly rigid rubber base material, and an induction heating rubber material 12 in which an induction powder that generates heat by induction heating, in this example, a short metal fiber made of iron, stainless steel, copper, aluminum or the like is mixed. I have.

Therefore, in this embodiment, the raw cover 13 which is to be vulcanized to be the pneumatic tire 1 has a rubber component portion 14 using the induction heating rubber material 12 located therein.

The short metal fibers have a diameter of 0.2 to 5 mm.
0 [mu] m, having an aspect ratio (length / diameter) of about 2 to 50, which is a ratio of length to diameter, is used. The proportion is 5 parts by weight or more and 50 parts by weight or less based on 100 parts by weight of the rubber base material. It is blended in.

If the compounding ratio of the short metal fibers is less than 5 parts by weight, the induction heating of the rubber material 12 by electromagnetic induction is prevented.
The heating efficiency becomes poor and the heating time is prolonged.
If the amount exceeds 0 parts by weight, the physical properties of the induction heating rubber material 12 are remarkably changed, which is not preferable.

Since the rubber base is reinforced by mixing the short metal fibers with the rubber base, when the bead apex 8 is formed by using the induction heating rubber material 12 as in this embodiment, The rigidity of the pneumatic tire 1 is increased, and various tire performances such as running performance can be improved.

As the dielectric powder, metal powder such as stainless steel atomized powder particles having a particle diameter of 5 μm or less can be used in addition to the short metal fiber.

The belt layer 7 is made of a highly elastic belt cord made of, for example, an aromatic polyamide fiber or the like.
The belt plies 7A and 7B are formed of a plurality of layers arranged at a small angle of 35 degrees or less with respect to O, in this example, two layers of the belt plies 7A and 7B. Distributed in the wrong direction.

The carcass 6 is formed of two inner and outer carcass plies 6A and 6B.
A and 6B are provided at both ends of the main body 6a extending from the tread portion 2 to the bead core 5 of the bead portion 4 through the sidewall portion 3;
A winding portion 6b that is wound around the bead core 5 by being turned from the inside to the outside in the tire axial direction is continuously provided.

The carcass plies 6A and 6B are formed from an array of carcass cords arranged at an angle of 70 to 90 degrees with respect to the tire equator CO. As the carcass cords, organic fibers such as polyester, rayon, nylon and the like are used. May be adopted.

A method for manufacturing a pneumatic tire for manufacturing such a pneumatic tire 1 is as follows. First, a dielectric powder which generates heat by induction heating, in this example, a metal short fiber is added to a rubber substrate in an amount of 5 to 50 parts by weight. A rubber component part 14 using an induction heating rubber material 12 mixed with this rubber base material in a ratio of parts by weight,
In this embodiment, a raw cover 13 having a bead apex 8 is formed, and thereafter, as shown schematically in FIG.
After preheating the raw cover 4, the whole raw cover 13 is heated and vulcanized.

The induction heating device 16 is provided with work coils 17, 1 located near the beads 4, 4 of the raw cover 13.
7, a motor 19 for rotating the work coils 17, 17 along the bead portions 4, 4, and a work coil 1
7, an induction heating device main body 20 connected to the work coils 17, 17 for generating high frequency from the work coils 17, 17.

The green cover 13 is induction heated immediately before vulcanization, during the vulcanization waiting time by the vulcanizer, whereby the rubber components 14, 14 located inside the green cover 13 are heated in a short time. .

The frequency of the induction heating is preferably not less than 50 kHz and not more than 1000 kHz. 50kHz
If it is lower than this, the heat generation efficiency due to the hysteresis loss of the dielectric powder becomes extremely poor. The higher the frequency, the better the heat generation efficiency. However, in general, the higher the oscillation frequency, the larger the whole device becomes, and the more expensive it becomes. In addition, electromagnetic interference generated by the electromagnetic wave generated from the induction heating device main body 20 and the work coil 17 causes a problem. Therefore, the upper limit of the frequency is set to 1000 kHz.

The shape of the work coil 17 may be any one of various shapes such as a single turn, a multi turn, a hairpin, and a pancake.

Thus, the raw cover 13 is heated by the induction heating.
Since the internal rubber component 14 is pre-heated, the temperature difference between the surface of the pneumatic tire during vulcanization and the inside of the tire is reduced, and the raw cover 13 of the pneumatic tire can be vulcanized efficiently and quickly, While the vulcanization time until the completion of the vulcanized product can be shortened, and the tire surface usually tends to be over-vulcanized in order to finish the inside of the tire with optimal vulcanization, the vulcanization time Due to the shortening, the supply of an excessive amount of heat to the tire surface portion can be suppressed, and an appropriate amount of heat is supplied to the inside and outside of the pneumatic tire, so that good rubber properties can be obtained.

It should be noted that the pneumatic tire manufactured by the manufacturing method of the present invention is not limited to the use for passenger cars, but also various kinds of pneumatic rubber tires for light trucks, heavy loads, motorcycles, aircrafts and the like. including.

The rubber component 14 can be used for various parts of the rubber inside the raw cover 13 such as a base tread rubber in addition to the bead apex 8.

[0031]

EXAMPLES In a raw cover of a pneumatic tire having a tire size of 215 / 65R15, Examples C, D, E, and C using rubber materials having the composition shown in Table 1 as bead apex.
A standard product A and a comparative example B were prototyped, and the area around the bead portion of the green cover was preheated by induction heating immediately before vulcanization, and then vulcanized by a vulcanizer.

[0032]

[Table 1]

The induction heating condition is a frequency of 400 kHz.
z, the output was 2.5 kW, and the test result of the induction heating efficiency of the bead apex is shown in the graph of FIG. From this graph, it can be seen that the compounding amount of the dielectric powder (short metal fiber) is
When the amount is less than 5 parts by weight with respect to 00 parts by weight, it is understood that the heating efficiency is extremely poor. In Table 1, the mark X in the column of induction heating efficiency indicates that the heating efficiency is poor, the mark O is acceptable, and the mark ◎ indicates good.

The bead apex of the raw cover of Example D was preheated by induction heating at a frequency of 900 kHz and an output of 2.5 kW for 120 seconds, and then the temperature and amount of vulcanization of the bead apex when vulcanized were determined. The change is shown in FIG. 4 together with the change in the temperature of the bead apex and the amount of vulcanization when the standard product A was vulcanized.

The vulcanization time was 8.5 minutes for Example D and 11 minutes for Standard A, and Example V was 2.5 minutes longer than Standard A.
Vulcanization time can be shortened, and the production efficiency was improved.

The vulcanization time of 8.5 minutes in Example D is the result of adjusting the amount of vulcanization at the most delayed part of vulcanization to that of the standard product A.

Table 2 shows the results of examining the final vulcanization amount between the tread surface of the tire obtained by vulcanizing Example D and the standard product A and the bead apex.

[0038]

[Table 2]

From Table 2, it can be seen that the standard product A is over-vulcanized on the tread surface, whereas in Example D, the vulcanization amount on the tread surface is almost the same as the vulcanization amount of the bead apex.
It can be seen that overvulcanization of the tire surface is suppressed and the tire is in a good vulcanized state.

[0040]

As described above, in the method of manufacturing a pneumatic tire according to the present invention, the rubber component using the induction-heatable rubber material of the raw cover is preheated by induction heating, and then the entire raw cover is heated and heated. For vulcanization, the vulcanization time can be shortened, and by positioning the rubber component inside the raw cover, over-vulcanization of the rubber material on the tire surface can be suppressed, and both the inside and outside of the tire can be supplied with appropriate heat quantity. Good rubber properties are obtained.

Further, the pneumatic tire obtained by such a manufacturing method has good rubber physical properties due to an appropriate amount of heat throughout the inside and outside of the tire, and thus can be useful for improving various performances of the tire such as running performance.

[Brief description of the drawings]

FIG. 1 is a perspective view schematically showing an example of an embodiment of a method for manufacturing a pneumatic tire according to the present invention.

FIG. 2 is a meridional sectional view of a tire right half molecule illustrating the pneumatic tire of the present invention.

FIG. 3 is a graph showing a test result of induction heating efficiency.

FIG. 4 is a graph showing test results of vulcanization time and vulcanization amount.

[Explanation of symbols]

 12 Induction heating rubber material 13 Raw cover 14 Rubber component

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B29C 35/02-35/14 B60C 1/00

Claims (5)

(57) [Claims] 1. A raw cover having a rubber component using an induction-heatable rubber material obtained by mixing a dielectric material that generates heat by induction heating with a rubber base material , and after preheating the rubber component by induction heating. , it is vulcanized by heating the whole of the raw cover
And the rubber component is located inside the raw cover.
A method for manufacturing a pneumatic tire, comprising: 2. The dielectric powder is a metal short fiber, and has a rubber base material 10
The method for producing a pneumatic tire according to claim 1, wherein 5 to 50 parts by weight is blended with respect to 0 parts by weight. 3. The bead apec according to claim 1, wherein the rubber component is a bead apec.
The method for producing a pneumatic tire according to claim 1 or 2, wherein the pneumatic tire is rubber or base tread rubber . 4. The induction heating is performed at a frequency of 50 kHz to 1000 kHz.
2. The method according to claim 1, wherein a high frequency of kHz is used.
4. The method for producing a pneumatic tire according to 2 or 3. 5. A pneumatic tire manufactured by the method according to claim 1.