JP2006130880A - Pneumatic tire and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To effectively shape a tread rubber by a strip winding method. <P>SOLUTION: The manufacturing method of a pneumatic tire includes a tread rubber forming process of making an unvulcanized tread rubber. The tread rubber forming process includes a stage of forming an inner layer portion 4 by spirally winding an unvulcanized ribbon-like rubbery strip 3 from the central portion 2C in the widthwise direction to the end portion 2E and a stage of forming an outer layer portion 5 on the radially outward side of the inner layer portion 4 by spirally winding the rubbery strip 3 from the end portion 2E to the central portion 2C without cutting the rubbery strip at the end portion 2E. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a pneumatic tire having a tread rubber formed by a so-called strip wind method and a manufacturing method thereof.

  In recent years, as shown in FIG. 8, a tread rubber c is obtained by winding a ribbon-like unvulcanized rubber strip b around a wound body a having a substantially cylindrical surface in a spiral manner with its side edges overlapped. A so-called strip wind method is proposed (Patent Documents 1 and 2 below). For example, a cylindrical forming former capable of expanding and contracting diameter may be used as the wound body a, and a raw cover base in which a belt layer is wound around a toroidal raw carcass may be used.

Japanese Patent No. 3477289 Japanese Patent No. 3352045

  However, in the conventional strip winding method, as shown in FIG. 8, many rubber strips b are spirally wound in one direction from one side to the other side in the width direction. The tread rubber c thus formed tends to have a very small helical winding pitch P of the rubber strip b in order to obtain a sufficient thickness. For this reason, in the cross-sectional shape at the time of winding, the rubber strip b is largely inclined and a large peripheral speed difference is generated between the outer end side f and the inner end side g of the rubber strip b in the tire radial direction. During winding, the rubber strip b tends to be drawn toward the outer end g where the peripheral speed is high, so that it is difficult to wind the rubber strip b at a predetermined position with high accuracy. Due to these factors, in the conventional method, it is very difficult to adjust the thickness (gauge) of each part of the tread rubber c, and the cross-sectional shape tends to vary.

  Further, in the tread rubber c described above, the winding start end S1 and the end S2 of the rubber strip are both positioned at the end of the tread rubber c in the tire axial direction. For this reason, the gauge at the end of the tread rubber c is not uniform in the tire circumferential direction. Since the tread rubber c has a cross-sectional shape in which the thickness gradually decreases toward the outer side in the tire axial direction, the nonuniformity of the gauge at the end of the tread rubber greatly affects the uniformity and the like. Specifically, when a portion having a thickness of 3 mm and a portion having a thickness of 2 mm are formed at the end portion of the tread rubber c having a small thickness, the variation in the gauge is 33%. However, even if a portion having a thickness of 10 mm and a portion having a thickness of 9 mm are generated in the central portion of the tread rubber c having a large thickness, the variation is 10%, and the influence on uniformity is relatively small.

  Thus, the nonuniformity of the gauge at the end portion of the tread rubber c is not preferable because the uniformity of the tire is more significantly deteriorated and the durability of the tire is lowered.

  The present invention has been devised in view of the above-described problems. A rubber strip is spirally wound from a central portion in the width direction toward an end portion to form an inner layer portion, and the rubber strip is formed at the end portion. By forming the outer layer part outside the inner layer part by winding it spirally from the end part toward the central part without cutting, the cross-sectional shape can be accurately improved while improving the productivity of the tread rubber. An object of the present invention is to provide a pneumatic tire useful for finishing and a manufacturing method thereof.

Invention of Claim 1 among this invention is a manufacturing method of the pneumatic tire containing the tread rubber formation process which forms unvulcanized tread rubber, Comprising: The said tread rubber formation process,
An unvulcanized and ribbon-like rubber strip is spirally wound from the center to the end in the width direction to form an inner layer portion, and the end is centered from the end without cutting the rubber strip. Forming an outer layer portion on the outer side in the tire radial direction of the inner layer portion by winding in a spiral shape toward the portion.

  According to a second aspect of the present invention, the inner layer portion is formed on the outer side of at least one base layer formed by spirally winding a rubber strip from one end portion side to the other end portion side. It is formed, The manufacturing method of the pneumatic tire of Claim 1 characterized by the above-mentioned.

  The invention according to claim 3 is the method for manufacturing a pneumatic tire according to claim 1 or 2, wherein the rubber strip has a winding start end and a winding end at the center.

  According to a fourth aspect of the present invention, there is provided a pneumatic tire in which a tread rubber is arranged in a tread portion, wherein the tread rubber is formed by a ribbon-like unvulcanized rubber strip spirally around a tire rotation axis. The tread rubber is formed using a wound tread rubber, and the tread rubber has an inner layer portion in which the rubber strip is spirally wound from a central portion to an end portion in the width direction, and the rubber strip is cut at the end portion. And an outer layer portion in which a rubber strip is spirally wound from the end portion toward the center portion.

  In the pneumatic tire manufacturing method of the present invention, in the tread rubber forming step, an unvulcanized and ribbon-shaped rubber strip is spirally wound from the center in the width direction toward the end to form the inner layer portion. And forming an outer layer portion on the outer side in the tire radial direction of the inner layer portion by spirally winding the rubber strip from the end portion toward the central portion without cutting the rubber strip at the end portion.

  As described above, since the tread rubber includes the inner layer portion and the outer layer portion, a sufficient tread rubber thickness can be ensured even if the spiral winding pitch (average pitch) of the rubber strip is increased. Therefore, a large peripheral speed difference of one strip during winding as has conventionally occurred can be reduced, and the rubber strip can be wound stably and accurately. Moreover, since the winding pitch of the rubber strip can be increased, the adjustment width is increased, and as a result, adjustment of the gauge of each part of the tread rubber can be facilitated.

  Further, the start and end of the winding of the rubber strip are not located at the end of the tread rubber. For this reason, the gauge at the end of the tread rubber can be made uniform in the circumferential direction. Therefore, it is possible to easily manufacture a pneumatic tire excellent in uniformity as compared with the conventional case.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
In the present invention, a pneumatic tire and a manufacturing method thereof are provided. The method for manufacturing a pneumatic tire includes a tread rubber forming step of forming an unvulcanized tread rubber, and the present invention is characterized by this step. Therefore, in this specification, it demonstrates focusing on this tread rubber formation process. About parts other than a tread rubber formation process, it can implement suitably according to a custom.

1 and 2 are schematic cross-sectional views illustrating a tread rubber forming process.
In the present embodiment, as indicated by phantom lines in FIG. 1, a tread rubber 2 having a substantially trapezoidal cross-sectional shape that is long in the width direction and gradually decreases in thickness toward the outer side in the tire axial direction at the end portion is formed. The

  The tread rubber 2 can be made using, for example, a cylindrical molding former F. Since the molding former F does not deform even when the rubber strip 3 is strongly wound, it is useful for forming the tread rubber 2 with high accuracy. The tread rubber 2 formed on the molding former F is appropriately removed therefrom and combined with other members to constitute a raw cover (not shown). A pneumatic tire is obtained by vulcanizing the green cover. However, the tread rubber 2 may be directly formed not on the molding former F but on the raw cover substrate described above.

  The tread rubber forming step includes a step of forming the inner layer portion 4 by winding the unvulcanized and ribbon-like rubber strip 3 spirally from the center portion 2C in the width direction of the tread rubber 2 toward the end portion 2E. .

FIG. 3 shows an example of the rubber strip 3. The rubber strip 3 of this embodiment is
A cross section having a width W larger than the thickness t is substantially rectangular. The rubber strip 3 is continuously supplied in an unvulcanized state from, for example, an extruder. As for rubber, “unvulcanized” means a state in which vulcanization is not completely completed. Therefore, those that have only been pre-vulcanized will be unvulcanized.

  The width W and the thickness t of the rubber strip 3 are not particularly limited, but preferably the width W is 15 to 35 mm and the thickness t is 0.5 to 1.5 mm. When the width W is less than 15 mm or the thickness t is less than 0.5 mm, when finishing a predetermined tread cross-sectional shape, a remarkably large number of windings are required, and the productivity tends to decrease. Conversely, when the width W exceeds 35 mm or the thickness t exceeds 1.5 mm, it tends to be difficult to make a fine tread rubber cross-sectional shape.

  Further, the central portion 2C in the width direction of the tread rubber 2 is a region in the vicinity of the width center TC of the tread rubber 2, and includes at least a range of 30% of the maximum tread rubber width TW around the width center TC. Shall be.

  In the tread rubber forming step of the present embodiment, two rubber strips 3 are used simultaneously. In FIG. 1 and FIG. 2, for easy understanding, one rubber strip 3 is lightly colored, but the rubber composition of both is the same. Each rubber strip 3, 3 is wound around a molding former F independently. This can be achieved by using two strip feeders (also called applicators) (not shown) that can move independently of each other.

  The winding start end S <b> 1 of each rubber strip 3 is provided at the central portion 2 </ b> C of the tread rubber 2. In this embodiment, the winding start end S1 is provided on both sides of the width center TC of the tread rubber 2, and the side edges of the rubber strips 3 are substantially in contact with the width center TC. Each rubber strip 3 is spirally wound from the starting end S1 toward the side edge 2E of the different tread rubber 2 to the end 2E.

  In addition, when the rubber strip 3 is spirally wound from the center portion 2C toward the end portion 2E, air between the molding former F and the rubber strip 3 is also preferable in that it is expelled to both outer sides in the width direction. The spiral winding of the rubber strip 3 can be realized, for example, by rotating the molding former F and moving the rubber strip 3 in the rotation axis direction.

  In this embodiment, the rubber strips 3 and 3 cross each other at the central portion 2C of the tread rubber 2, and are wound spirally toward the opposite ends 2E and 2E, respectively. This can be realized by winding the two rubber strips 3 around the molding former F at different positions on the circumference of the molding former F. By making the rubber strip 3 intersect at the width center TC, a gap can be eliminated in the central portion 2C of the tread rubber 2.

  Further, the inner layer portion 4 is wound while the side edges of the rubber strips 3 are overlapped with each other. In the present embodiment, the winding pitch P of the rubber strip 3 is gradually reduced from the central portion 2C toward the end portions 2E and 2E. Thereby, the gauge of the inner layer part 4 can be increased smoothly toward the end part 2E side. The winding pitch P is not particularly limited, but is preferably 3 to 10 mm, more preferably 5 to 7 mm.

  FIG. 1B shows a state in which the inner layer portion 4 of the tread rubber 2 is formed by winding the rubber strip 3 from the central portion 2C to the end portion 2E. In this state, the rubber strips S <b> 2 and S <b> 2 located on the outermost side in the tire axial direction are respectively located on the side edges 2 </ b> E on each side of the tread rubber 2. The inner layer portion 4 continues from one end 2E of the tread rubber 2 to the other side edge 2E, and forms the maximum width TW of the tread rubber 2.

  Further, as shown in FIGS. 2A and 2B, in the tread rubber forming process of the present embodiment, the rubber strip 3 (S2) wound up to the end 2E of the tread rubber 2 is cut. Instead, it is wound again spirally from the end 2E toward the center 2C. Thereby, the outer layer portion 5 is formed on the outer side in the tire radial direction of the inner layer portion 4. That is, the rubber strip 3 is wound in the reverse direction (U-turn) at the end 2E of the tread rubber 2. The rubber strip 3 whose direction of winding has been changed at the end portion 2E of the tread rubber 2 is wound up to the central portion 2C of the tread rubber 2, and is cut there in this embodiment.

As shown in FIG. 2B, the winding ends S3 and S3 of each rubber strip 3 are
In the present embodiment, the tread rubber 2 is positioned at the width center TC and overlapped with each other. Thereby, the outer layer part 5 also extends continuously from substantially one outer end 2E of the tread rubber 2 to the other outer end 2E. Further, the outer layer portion 5 gradually increases the winding pitch of the rubber strip 3 from the end portions 2E and 2E toward the central portion 2C. As a result, the gauge on the central part 2C side is made small. By forming such an outer layer portion 5 on the outer side of the inner layer portion 4, the tread rubber 2 having a substantially trapezoidal cross section in which the central portion 2C is slightly recessed can be formed with high accuracy.

  In the tread rubber 2 produced through the tread rubber forming step as described above, the thickness of each part can be adjusted by appropriately changing the winding pitch of the inner layer part 4 and / or the outer layer part 5. For this reason, adjustment of the gauge of each part of the tread rubber 2 can be facilitated, and it is useful for finishing the cross-sectional shape with high accuracy. In addition, at the end 2E of the tread rubber 2, the start end S1 and the end S3 of the winding of the rubber strip 3 are not located. For this reason, the gauge at the end 2E of the tread rubber 2 can be made uniform in the circumferential direction, and the uniformity can be improved.

  In the present embodiment, the two rubber strips 3 are wound around the molding former F at the same time, and the tread rubber 2 can be formed in a short time by winding the rubber strips 3 symmetrically with respect to the width center TC and synchronizing them. It also helps to improve sex. Further, the tread rubber 2 having a substantially line-symmetric cross-sectional shape with respect to the width center TC can be formed.

  Although the winding start end S1 and the termination end S3 are located in the central portion 2C of the tread rubber, the positions have relatively little influence on the uniformity as described above. 4A and 4B are schematic cross-sectional views taken along the lines XX and YY in FIG. As shown in FIG. 4A, it is desirable to position the winding end S3 in front of and in the vicinity of the winding start end S1 in one rubber strip 3 of the two rubber strips. 4B, in the other rubber strip 3, the winding end S3 is positioned in front of and in the vicinity of the winding start end S1, and the winding end S3 is placed on the one rubber strip 3. It is desirable to provide at a position β substantially 180 degrees apart from the position α of the winding end S3 in the tire circumferential direction. Thereby, the uniformity and weight balance of the rubber gauge can be further improved, and the uniformity of the tire can be further improved.

  5A to 5C show still another embodiment of the present invention. The tread rubber forming step of this embodiment is exemplified by one performed using one rubber strip 3. First, as shown in FIG. 5A, the rubber strip 3 has its winding start end S1 fixed to the central portion 2C of the tread rubber 2 and spirally toward the end portion 2E toward one end portion 2E. Wound around. Thereby, the inner layer part 4a which makes substantially the half width of the maximum width of the tread rubber 2 is formed.

  Next, the rubber strip 3 wound up to the end portion 2E of the tread rubber 2 is spirally wound from the end portion 2E toward the central portion 2C to the central portion 2C without being cut at the end portion 2E. . Thereby, the outer layer part 5a of substantially half width can be formed on the outer side in the tire radial direction of the inner layer part 4a of substantially half width (FIG. 5B).

  Further, the rubber strip 3 wound up to the central portion 2C is spirally wound up to the end portion 2E as it is toward the other end portion 2E. Thereby, the remaining substantially half-width inner layer portion 4b is formed. Then, the rubber strip 3 is spirally wound from the end 2E toward the center 2C to the center 2C without being cut at the end 2E. As a result, the remaining outer layer portion 5b having a substantially half width can be formed on the outer side in the tire radial direction of the inner layer portion 4b (FIG. 5C).

  In the tread rubber forming process of this embodiment, the tread rubber 2 similar to that shown in FIGS. 1 and 2 can be formed using one rubber strip 3, which is useful for simplifying the tread rubber forming equipment.

  Moreover, if the tread rubber formation process includes the step of forming the inner layer portion 4 and the outer layer portion 5 as described above, it can further include various other steps. For example, as shown in FIG. 6 (A) or (B), at least one layer formed by spirally winding the rubber strip 3 from the one end 2E side toward the other end 2E side. The base layer 7 can be formed in advance, and the inner layer portion 4 and the outer layer portion 5 can be formed outside thereof.

  The base layer 7 may be formed of one type of rubber strip 3 as shown in FIG. 6 (A), and further a two-layer structure in which the composition of the rubber strip 3 is different as shown in FIG. 6 (B). May be good. In addition, since the base layer 7 is bonded to the belt layer, it is preferable to use a rubber compound excellent in adhesion to the topping rubber of the belt layer for the rubber strip 3.

  Preferably, the winding start end S1 and the winding end S3 of the base layer 7 are also located on the inner side in the width direction than the ends 2E on both sides of the tread rubber 2. This helps to make the gauge at the end of the tread rubber 2 uniform.

  FIG. 7 shows a partially enlarged view of the pneumatic tire 1 made using the tread rubber 2 as described above. The pneumatic tire 1 includes a toroidal carcass 21 and a belt layer 22 disposed on the outside thereof, and a tread rubber 23 (vulcanized) is disposed on the outside of the belt layer 22.

  The tread rubber 23 is formed using the unvulcanized tread rubber 2 formed by the above-described method. In this embodiment, the base layer 7 arranged on the innermost radial direction, the inner layer part 4 arranged on the outer side and the rubber strip spirally wound from the center to the end in the width direction, and The outer layer portion 5 is formed on the outer side, and the rubber strip 3 is spirally wound from the end portion toward the central portion 2C. Such a tread rubber 23 has a winding start end S1 and a winding end S3 of the rubber strip on the inner side in the width direction than the tread end Te. Even after vulcanization, the boundary surface of the rubber strip 3 can be thinly observed in the cross section by cutting the tire with a sharp blade. Therefore, the position of each winding start end S1 and winding end S3 can be specified.

  As mentioned above, although embodiment of this invention was described, the pneumatic tire of this invention can be used for the pneumatic tire of various categories.

  Twenty heavy-duty pneumatic tires of size 11R22.5R were produced using the tread rubber shown in FIGS. 2 and 7 respectively. Except for the tread rubber, the tread pattern and the internal structure were the same. And about each test tire, the durability and durability of the tread rubber were evaluated. The evaluation method is as follows.

<Uniformity>
About each test tire, radial runout (RRO) was measured (average value of n = 20), and the RRO of the comparative example was displayed as an index of 100. The smaller the value, the better.

<Durability of tread rubber>
Each test tire was mounted on a 7.50 × 22.5 rim, and after running 50,000 km on a drum with a radius of 1.7 m at an air pressure of 700 kPa, a load of 50 kN, and a speed of 100 km / H, the tread rubber was visually observed. After the visual observation, the tread rubber was disassembled and the internal damage state was examined. Table 1 shows the test results.

  As a result of the test, it can be confirmed that the tire of the example has improved uniformity as compared with the comparative example. Considering the durability of the tread rubber, in the comparative example, since the rubber strip is terminated at the end of the tread rubber, it is considered that a crack originated from that position. Further, in the examples, since the end of the rubber strip is not located at the end of the tread rubber, it is considered that there is no gauge variation and no crack is generated.

(A) and (B) are the cross-sectional schematic diagrams explaining the formation procedure of a tread rubber. (A) and (B) are the cross-sectional schematic diagrams explaining the formation procedure of a tread rubber. It is a perspective view of a rubber strip. (A) is a schematic cross-sectional view at the XX position in FIG. 2, and (B) is a schematic cross-sectional view at the YY position in FIG. It is a section schematic diagram explaining the formation procedure of tread rubber of other embodiments. (A), (B) is sectional drawing explaining a base layer. It is a fragmentary sectional view of a pneumatic tire. It is sectional drawing of the conventional tread rubber.

Explanation of symbols

1 Pneumatic tire 2 Tread rubber (unvulcanized)
23 Tread rubber (vulcanized)
2C Tread rubber center 2E Tread rubber end 3 Rubber strip S1 Rubber strip winding start S3 Rubber strip winding start F Molding former

Claims (4)

A method for producing a pneumatic tire including a tread rubber forming step of forming an unvulcanized tread rubber,
The tread rubber forming step includes:
Winding an unvulcanized and ribbon-like rubber strip spirally from the center in the width direction toward the end, and forming an inner layer part;
Forming an outer layer portion on the outer side in the tire radial direction of the inner layer portion by spirally winding the rubber strip from the end portion toward the central portion without cutting the rubber strip at the end portion. A method for manufacturing a pneumatic tire.   The inner layer portion is formed on the outer side of at least one base layer formed by winding a rubber strip spirally from one end side toward the other end side. Item 2. A method for manufacturing a pneumatic tire according to Item 1.   The method for manufacturing a pneumatic tire according to claim 1, wherein the rubber strip has a winding start end and a winding end at the center portion. A pneumatic tire with tread rubber on the tread,
The tread rubber is formed by using a tread rubber in which a ribbon-like unvulcanized rubber strip is spirally wound around a tire rotation axis,
The tread rubber includes an inner layer portion in which the rubber strip is spirally wound from the central portion to the end in the width direction, and the end portion toward the central portion without cutting the rubber strip at the end portion. A pneumatic tire comprising an outer layer portion in which a rubber strip is spirally wound.

Images