JP2001179848A - Method for manufacturing pneumatic tire and pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a pneumatic tire capable of molding the tire without lengthening a molding time by incorporating an easy regulation of a rubber thickness responsive to a rubber volume different according to the circumferential groove or the like of a tread pattern and good uniformity in the circumferential and radial directions of the tread. SOLUTION: When the tread 1 of an unvulcanized rubber is molded, a rubber sheet 10 having a width substantially corresponding to the tread is sequentially wound and laminated at the lower part 1a of the tread and the sheet 10 is wound and laminated in a separated state being partly cut out to match the necessary rubber volume of the upper part 1b of the tread or wound and molded while superposing tape-like rubber strips to match the necessary volume of the upper part 1b at the upper part 1b of the tread.

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, and more particularly to a method for manufacturing a tread and a pneumatic tire manufactured by the method.

[0002]

2. Description of the Related Art As is well known, a pneumatic tire is composed of an unvulcanized green tire in which many constituent members are joined to the same member or different members. To produce product tires,
The joint between the members is a major factor in causing non-uniformity of the tire due to its mass, dimensions and the like.

On the other hand, from the viewpoints of environmental problems and manufacturing costs,
The weight reduction of vehicles and tires is required. However, when the weight of a vehicle is reduced, the vibration problem generally increases, and the non-uniformity of the tires tends to affect the vibration. for that reason,
The demands on tire uniformity are becoming more stringent.

[0004] As a means of reducing the weight of a tire, it is generally practiced to reduce the thickness of the tire. However, when the thickness of the tire is reduced, the above-mentioned effect on the non-uniformity of the joined portion becomes large, and the There was a disadvantage that the uniformity was impaired.

In particular, the unevenness of the tread has a very large effect on the uniformity of the entire tire due to the direct contact with the road surface and the uneven centrifugal force caused by the rotation.

A major factor in the non-uniformity of the tread is the circumferential joint of the tread. Particularly, in the case of a conventional molding method in which both ends are joined by winding a tread rubber having a substantially trapezoidal cross section, the joint is used. The resulting non-uniformity is increased.

In order to avoid the above-mentioned problems, a so-called sheet build system (see, for example, Japanese Patent Application Laid-Open No. No. 47617), or a so-called strip build system in which a tape-shaped rubber strip of a predetermined thickness is wound from the shoulder portion to the center portion and the opposite shoulder portion while being overlapped little by little (for example, JP-A-9-29856). Has been implemented.

However, in the case of the sheet build system, there is no problem in the circumferential joining portion of the tread and the uniformity in the circumferential direction is good, but without considering the existence of the circumferential groove and the like of the tread pattern. Since the rubber sheet is simply wound around the tread in a substantially trapezoidal cross section and molded, the groove for the groove on the inner surface of the mold is pushed into the rubber during vulcanization to form the groove of the pattern. In some cases, the belt layer was deformed, the uniformity in the tread radial direction was impaired, and the tire performance was adversely affected.

That is, in the case of a tread simply having a substantially trapezoidal cross section, the rubber is strongly moved by the pressing of the groove projection on the inner surface of the mold at the time of vulcanization, and the force acting on the belt layer below the tread is also increased. The belt layer was easily deformed.

Also, in the case of the strip build method, there is no problem of the circumferential joining portion and the uniformity in the circumferential direction is well maintained. However, the whole of the tread upper part from the tread lower part is formed by a rubber strip. Then, the difference between the winding start and winding end shapes becomes large, and the larger the thickness or width of the rubber strip, the more difficult it is to make fine adjustment of the overlap, and the problem of uniformity in the tread radial direction remains. In addition, there is a problem that the molding time by winding becomes long. Therefore, it is not widely used except for large tires.

The present invention has been made in view of the above. In particular, in the tire molding process, it is easy to adjust the rubber thickness according to the rubber volume which varies depending on the circumferential groove of the tread pattern and the like. An object of the present invention is to provide a method of manufacturing a pneumatic tire having good uniformity in direction and capable of being molded without prolonging a molding time, and a pneumatic tire manufactured by the method.

[0012]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems, and a method of manufacturing a pneumatic tire according to the first invention is to provide a method for manufacturing a tread comprising an unvulcanized rubber in a tire molding process. In molding, the lower tread having a thickness of 25 to 75% of the tread thickness is sequentially wound and laminated with a wide band-like rubber sheet having a width substantially corresponding to the tread width, and the rubber sheet is attached to the upper tread with the rubber sheet. It is characterized in that it is sequentially wound in a partially cut-out state in the circumferential direction in accordance with the required rubber volume at the upper portion of the tread and laminated and molded.

In the above-mentioned manufacturing method, it is preferable that the wide band-shaped rubber sheet is cut out, divided and wound at a position corresponding to the circumferential groove of the tread pattern while adjusting an interval according to the groove width.

According to the manufacturing method of the first aspect of the invention, since no joint is formed in the circumferential direction of the tire, the uniformity in the circumferential direction is favorably maintained. In addition, the upper portion of the tread is partially cut out of the rubber sheet in accordance with a required rubber volume that differs depending on a circumferential groove or the like of the tread pattern, for example, a cutout state in which a position corresponding to the circumferential groove is cut out. And it is possible to easily adjust the necessary rubber thickness and rubber amount. In addition, a portion corresponding to the circumferential groove of the tread pattern can be formed into a corresponding concave shape. For this reason, excessive rubber flow does not occur due to the pressing of the groove projections on the inner surface of the mold at the time of vulcanization, and no excessive force acts on the belt layer below the tread, and the belt layer does not deform. Therefore, the uniformity in the tread radial direction is not impaired.

[0015] In the method for manufacturing a pneumatic tire according to the second invention, the lower portion of the tread is provided in the same manner as in the above invention.
A wide band-shaped rubber sheet having a width substantially corresponding to the tread width is sequentially wound and laminated, but for the upper part of the tread, particularly, a tape-shaped rubber strip is wound while being overlapped with the required rubber volume of the upper part of the tread. It is characterized by being molded.

In this case, as in the case of the first aspect, no joint is formed in the circumferential direction of the tire, and the uniformity in the circumferential direction is well maintained. In particular, since a rubber sheet is wound around the lower part of the tread and laminated, and only the remaining upper part of the tread is wound and molded with a rubber strip, the difference between the shape of the rubber strip at the beginning and the end of the winding is that the entire tread has a rubber strip. It is easy to adjust the amount of rubber according to the required rubber volume that differs depending on the circumferential groove of the tread pattern and the like, and it can be easily molded into a concave shape corresponding to the circumferential groove. Become. For this reason, the belt layer is not deformed due to the pressing of the groove projection on the inner surface of the mold during vulcanization, and the uniformity in the tread radial direction is not impaired. In addition, since the lower portion of the tread is formed by laminating a rubber sheet and the upper portion of the tread is formed by a rubber strip, the molding time is shorter than when the entire tread is formed by a rubber strip.

The rubber strip according to the second invention has a thickness of 0.30 to 3.0 mm and a width of 5.0 to 3 mm.
A tape having a narrow width of 0.0 mm is preferable.

That is, even if the thickness of the rubber strip is greater than the above or the width is greater than the above, it is difficult to finely adjust the rubber thickness according to the shape of the circumferential groove of the tread pattern. If it is thinner or has a smaller width, the molding time by winding becomes longer. Therefore, it is particularly preferable to use a tape-shaped rubber strip in the above range.

Further, the wide band-shaped rubber sheet in each of the above inventions has a thickness of 0.30 to 3.0 mm and a width of 70 to 100% of the tread width at the winding position. That is,
If the thickness of the rubber sheet is larger than the above, the step between the winding start and the winding end in the circumferential direction becomes large, and it is difficult to carry out the process with a normal rubber tire having a small rubber thickness.

Further, in the manufacturing method of each of the above-mentioned inventions, a wide band-shaped rubber sheet at the lower portion of the tread and a separated rubber sheet or rubber strip at the upper portion of the tread are wound and formed on the belt layer formed into an annular shape. be able to. Thereby, green tire molding can be performed efficiently.

Further, in the manufacturing method of each of the above-mentioned inventions, a first step of winding a wide band-like rubber sheet under a tread on a belt layer formed into an annular shape and temporarily stocking the rubber sheet, The second step of winding and molding a separated rubber sheet or rubber strip on the upper part of the tread on the lower part can be performed.

According to this method, the material of the rubber on the upper portion of the tread in the second step is changed by using the same molded body formed in the first step of winding the rubber sheet on the annular belt layer. In addition, it becomes possible to manufacture a plurality of types of tires having different tire characteristics, so that it is possible to reduce the number of steps required for the step change in the manufacture of different types of tires, and to increase the productivity.

The pneumatic tire of the present invention is manufactured by molding a tread by the manufacturing method of each of the above-mentioned inventions, and has good uniformity in the tire circumferential direction and the tread radial direction. is there.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described with reference to the embodiments shown in the drawings.

FIG. 1 is a schematic cross-sectional view of a tread molded state according to the first invention, FIG. 2 is an enlarged cross-sectional view of the same part, FIG. 3 is a schematic plan view showing a cutout state of a wide band-shaped rubber sheet, FIG. 4 is a schematic side view of the same.

In the embodiment of the present invention, when the tread (1) is formed from unvulcanized rubber in the tire molding process, the tread (1) is molded based on a sheet build system. A relatively wide band-shaped rubber sheet (10) is used. The thickness (t1) of the rubber sheet (10) is 0.30 to 3.0.
mm is preferably used. Such a rubber sheet can be obtained by a roller head system extruder having a roller head die at the tip. Of course, a rubber sheet manufactured by another method can be used.

Then, as shown in FIG. 4, on the forming drum (5), the tread extends from 25 to 75% of the total thickness of the tread (1) to the lower portion of the tread, particularly to the vicinity of the bottom of the tread pattern formed on the outer periphery of the tread. For the lower part (1a), the rubber sheet (10) is sequentially wound and laminated. At this time, since the rubber sheets (10) are laminated so as to form a substantially trapezoidal cross section, the width of the tread width at the winding position is, for example, 70 to 100% so as to substantially correspond to the tread width at the winding position. It is preferable to sequentially wind and laminate while adjusting the width (W1). The width may be adjusted by cutting the lugs at both ends while supplying the slightly wide rubber sheet (10) to the winding portion on the molding drum (5). Further, the rubber sheet (1)
By using a sheet cut so that both side edges form a tapered slope as 0), it can be further molded into a shape along the vulcanization mold.

Next, for the remaining tread upper part (1b), the rubber sheet (10) is continuously formed in a circumferential groove of a tread pattern on the outer periphery of the tire, mainly in a linear or zigzag shape in the circumferential direction of the tread. In accordance with the required rubber volume of the land portion (3) defined by the circumferential groove (2) as the main groove, in particular, a position substantially corresponding to the circumferential groove (2) is partially cut out in the circumferential direction. The wound portions are sequentially wound and laminated, and a portion corresponding to the circumferential groove (2) of the tread pattern is formed into a concave shape. (2a) shows the concave portion. (11) shows a cut-away portion of the rubber sheet (10), and (12) shows a cut sheet portion.

When the upper portion (1b) of the tread is molded, the rubber sheet (10) is cut off at a position corresponding to the circumferential groove (2) of the tread pattern according to the groove width (W2). It is good to wind while adjusting). That is, as shown by the chain line in FIG. 2, the circumferential grooves (2) such as the main grooves of the tread pattern are tapered on both sides so that the groove width (W2) becomes wider toward the opening side. The notch interval (S) is adjusted according to the groove width at the winding lamination position of the rubber sheet (10). It is preferable that the notch interval (S) is set to be slightly smaller than the groove width (W2) so as not to cause rubber shortage during vulcanization.

The cut-away position of the rubber sheet (10) is usually set at the center in the width direction of the circumferential groove (2). That is, when the circumferential groove (2) is linear in the circumferential direction, the circumferential groove (2) may be cut out and divided based on the center of the groove width (W2). In the case of the zigzag circumferential groove (2), Defines a center (C) by averaging the amount of displacement of the groove in the left-right direction as shown in FIG. 5, and the notch interval corresponding to the groove width (W2) as described above with reference to the center (C). In (S), the rubber sheet (10) is cut and cut at a plurality of locations.

As shown in FIGS. 3 and 4, this notch cutting means includes a wide band-shaped rubber in the middle of the supply to the winding portion on the forming drum (5), preferably at a position immediately before reaching the winding portion. The required position of the sheet (10) is determined by, for example, a pair of cutters (6a) (6
By cutting out according to a), it is cut into a notched state. The adjustment of the notch interval may be performed by adjusting the interval between the two cutters (6a) (6a) using a means such as a servomotor.

The width of the rubber sheet (10) and the distance between the cutout portions (11) can be adjusted by adjusting the thickness of the rubber sheet (10) around the sensor (7).
It is good to measure mainly for every layer. Since there is a distance from the cutters (6a) and (6a) to the winding and stacking position on the drum, it is preferable that this distance and the distance from the position of the sensor (7) to the winding and stacking position can be adjusted together. . Of course, it can be controlled by a computer. The cutter (6
a) If the cut by (6a) is tapered substantially corresponding to the side surface of the circumferential groove (2), it becomes easier to follow the mold during vulcanization.

In the above embodiment, as the rubber sheet (10) to be wound around the lower part (1a) and the upper part (1b) of the tread, a continuous rubber sheet is used by cutting a required portion from the middle and cutting it. Alternatively, different rubber sheets can be used for the tread lower part (1a) and the tread upper part (1b).

In the illustrated embodiment, the rubber sheet (1
The cut-off portion of 0) is only a portion corresponding to the circumferential groove (2) which is the main groove of the tread pattern, but in addition to this, at a position corresponding to the circumferential sub-groove narrower than the main groove. Can also be implemented by cutting out notches.

According to the manufacturing method of the first aspect of the present invention, circumferential uniformity is not formed in the tire circumferential direction unlike the related art, so that good uniformity in the circumferential direction is maintained. In addition, the upper part of the tread (1
Regarding b), a wide band-shaped rubber sheet (10) is inserted into the circumferential groove (2) in accordance with the required rubber volume of the land portion (3) defined by the circumferential groove (2) of the tread pattern. Since the layers are wound and laminated in a cut-off state in which the corresponding positions are notched, it is easy to adjust the rubber thickness and the rubber amount according to the required volume of the land portion (3) and the like.

Further, since the portion corresponding to the circumferential groove (2) can be formed into a corresponding concave shape, the rubber excessively flows even by pushing the groove convex portion on the inner surface of the mold during vulcanization. And no excessive force acts on the belt layer under the tread. Therefore, the belt layer is not deformed, and the uniformity in the tread radial direction is improved.

FIG. 6 is a schematic sectional view of a tread molded state according to the second invention, and FIG. 7 is an enlarged sectional view of a part of the tread.

In the case of the present invention, the thickness (t1) of the tread lower part (1a) of 25 to 75% of the total thickness of the tread (1) is 0.3 as in the case of the first invention described above.
0-3.0 mm, the width of which corresponds approximately to the tread width,
Preferably, the tread width (W1) at the winding position is 70
A 100% wide band-shaped rubber sheet (10) is sequentially wound and laminated.

The remaining tread upper part (1b) has a tape-like rubber strip, particularly preferably a thickness (t2) of 0.3 to 3.0 mm and a width (W3) of 5.
A rubber strip (20) in the form of a tape having a narrow width of 0 to 30.0 mm is formed on a necessary portion such as a land portion (3) defined by a circumferential groove (2) such as a main groove of the tread upper portion (1b). Wrap and mold while layering according to the rubber volume.

As a form of winding the tape-shaped rubber strip (20), for example, as shown in the figure, the winding is started from one shoulder portion, then the center portion is wound on the other shoulder portion, and according to the thickness. It is common to wind from the shoulder part on the other side to the center part and the original shoulder part on one side. Of course, not limited to this, it is also possible to wind up a plurality of tape-shaped rubber strips from one or both shoulder portions, and it is also possible to wind another rubber strip for each land portion excluding the circumferential groove. it can.

At the time of the winding, at a position corresponding to the circumferential groove (2) of the tread pattern, the rubber strip (20) is shifted obliquely to substantially correspond to the circumferential groove (2). It is superposed and wound so as to form a concave portion (2b). It is preferable that the concave portion (2b) is set to be slightly smaller than the circumferential groove (2) of the tread pattern so as to prevent rubber shortage during vulcanization. Also, with regard to the rubber strip (20), by cutting the side end in a tapered shape, the concave portion (2) is cut.
b) can be easily formed, and it is easy to follow the mold.

As a result, as in the case of the first aspect described above, no joint is formed in the circumferential direction, uniformity in the circumferential direction is maintained well, and particularly, only in the upper portion (1b) of the tread. Since the rubber strip (20) is wound and molded, the difference between the shape of the rubber strip (20) at the beginning and end of the winding is smaller than when the entire tread is molded by the rubber strip (20).

In addition, it is easy to adjust the amount of rubber according to the required rubber volume which varies depending on the circumferential groove (2) of the tread pattern, and it is not necessary to wind excessive rubber. For this reason, at the time of vulcanization, the groove projection on the inner surface of the mold has the concave portion (2).
Even if it is pushed into b), excessive rubber flow does not occur, and no deformation occurs in the belt layer under the tread, and the uniformity in the tread radial direction is well maintained. Further, in the case of the present invention, the lower portion of the tread (1a) is formed by laminating a rubber sheet (10), and only the upper portion of the tread (1b) is formed by winding a rubber strip (20). In comparison, the molding time is short.

In each of the first and second embodiments, the tread (1) is placed on a belt layer (not shown) formed in a ring shape on a forming drum (5). Wide rubber sheet (1) under the tread (1a)
0), and a rubber sheet (10) or a rubber strip (20) in a divided state at the upper portion (1b) of the tread can be wound and molded. Can also be molded by fitting onto a separately formed belt layer.

Further, in any of the above-mentioned inventions, a wide rubber sheet (10) at the lower portion of the tread (1a) is wound and laminated on the belt layer formed into an annular shape, and this is temporarily stocked. A first step, a rubber sheet (10) or a rubber strip (2) in which the tread upper part (1b) is divided on the tread lower part (1a);
0) can be molded separately from the second step of winding and molding.

According to this method, the upper portion of the tread (1b) in the second step is made common to the molded article formed in the first step of winding the rubber sheet (10) on the belt layer.
By changing the rubber material, it is possible to manufacture a plurality of types of tires having different tire characteristics, and it is possible to reduce the number of steps required to change the steps of manufacturing different types of tires.

That is, the change of the characteristics depending on the rubber material of the tire is mainly performed by changing the rubber at the upper portion of the tread, and the lower portion of the tread is generally made common. Therefore, by performing the molding in two stages as described above, the number of steps required for changing the stage can be reduced, the productivity can be improved, and the bulk can be reduced when stocking is performed.

Then, in the tire molding step, the tread (1) is molded as described above to form an unvulcanized green tire combined with a carcass and a belt layer, and this is subjected to predetermined vulcanization. Thus, in the case of the present invention, the pneumatic tire manufactured thereby has good uniformity in the circumferential and radial directions of the tread, and can maintain good tire characteristics, as described above. Becomes

[0049]

As described above, according to the present invention, in the manufacture of a tire, a tread is molded by a seat build method for a lower portion of a tread, and a tread is formed by an upper portion of a tread.
It is performed according to the required rubber volume, such as the land portion defined by the circumferential groove of the tread pattern, by using a sheet build method using a rubber sheet that has been partially cut and cut, or a strip build method using a tape-shaped rubber strip. Lamination or superimposition makes it possible to not only maintain good uniformity in the circumferential direction of the tread, but also to reduce the risk of deformation of the belt layer due to the indentation of the groove projections on the inner surface of the mold during vulcanization. The directional uniformity is also well maintained. In addition, in either case, the molding time is not so long, and the molding can be performed efficiently.

In particular, by separately performing the first step of molding the lower part of the tread and the second step of molding the upper part of the tread, the step change in changing the tire characteristics becomes easy, and the productivity can be increased. .

Further, the pneumatic tire obtained by the manufacturing method of the present invention has good uniformity in the tire circumferential direction and radial direction, can maintain characteristics such as tire uniformity in both schools, and can easily reduce tire weight. .

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a tire molding state according to an embodiment of the first invention.

FIG. 2 is an enlarged sectional view of a part of the above.

FIG. 3 is a schematic plan view showing a cut-away state of an upper portion of a tread of a rubber sheet in the same method.

FIG. 4 is a schematic side view of the same.

FIG. 5 is an explanatory view of a cut-away state of a zigzag circumferential groove.

FIG. 6 is a schematic sectional view showing a tread molding state according to an embodiment of the second invention.

FIG. 7 is an enlarged sectional view of a part of the above.

[Explanation of symbols]

(1) Unvulcanized rubber tread (1a) Tread lower part (1b) Tread upper part (2) Circumferential groove of tread pattern (2a) Concave part formed by cutout cut part of rubber sheet (2b) Formed by rubber strip (3) Land (5) Forming drum (6a) Cutter (7) Sensor (10) Rubber sheet (11) Notch (12) Divided sheet (20) Rubber strip (W1) Tread width (W2 ) Groove width (W3) Width of rubber strip (t1) Thickness of rubber sheet (t2) Thickness of rubber strip (S) Notch spacing of rubber sheet (C) Center

Claims (8)

[Claims] In a tire molding step, when a tread made of an unvulcanized rubber is molded, a thickness of the tread of 25 to 30 is used.
For a 75% tread lower part, a wide band-like rubber sheet having a width substantially corresponding to the tread width is sequentially wound and laminated, and for the tread upper part, the rubber sheet is
A method for manufacturing a pneumatic tire, comprising sequentially winding and laminating and molding in a divided state partially cut out in the circumferential direction in accordance with a required rubber volume of the upper portion of the tread. 2. The wide band-shaped rubber sheet is divided and wound at a position corresponding to a circumferential groove of a tread pattern while adjusting a notch interval according to the groove width. A method for manufacturing the pneumatic tire according to the above. 3. In the tire molding step, when molding a tread made of unvulcanized rubber, the thickness of the tread is 25 to 30%.
For the lower part of the tread of 75%, a wide band-like rubber sheet substantially corresponding to the tread width is sequentially wound and laminated, and for the upper part of the tread, a tape-shaped rubber strip is formed according to the required rubber volume of the upper part of the tread. A method for manufacturing a pneumatic tire, comprising winding and molding while overlapping. 4. The rubber strip according to claim 1, wherein said rubber strip has a thickness of 0.30 to 0.30.
The method for manufacturing a pneumatic tire according to claim 3, wherein the tape is in the form of a narrow tape having a width of 3.0 mm and a width of 5.0 to 30.0 mm. 5. The rubber sheet according to claim 1, wherein said rubber sheet has a thickness of 0.30 to 3.0.
mm, width is 70-100% of tread width at winding position
The method for manufacturing a pneumatic tire according to any one of claims 1 to 4, wherein 6. A wide belt-shaped rubber sheet at the lower part of the tread and a separated rubber sheet or rubber strip at the upper part of the tread are wound and formed on the belt layer formed into an annular shape. Any one of 5
13. The method for producing a pneumatic tire according to item 13. 7. A first step of winding a wide band-shaped rubber sheet under the tread on a belt layer formed into an annular shape and temporarily stocking the rubber sheet;
The method for manufacturing a pneumatic tire according to any one of claims 1 to 5, wherein the molding is divided into a second step of winding and molding a separated rubber sheet or rubber strip at an upper portion of the tread. 8. A pneumatic tire, wherein a tread is molded and manufactured by the method for manufacturing a pneumatic tire according to any one of claims 1 to 7.