JP7135832B2 - Method for manufacturing pneumatic tires - Google Patents

Description

The present invention relates to a method for manufacturing pneumatic tires. In particular, the present invention relates to a method of manufacturing a pneumatic tire whose sidewall has an inner layer and an outer layer.

In order to achieve low fuel consumption, there are tires in which sidewalls are provided with an inner layer and an outer layer. In this tire, the inner layer is made of low-heat-generating rubber to reduce rolling resistance and achieve low fuel consumption. The outer layer is made of rubber with excellent abrasion resistance and weather resistance to maintain excellent durability and appearance quality.

In manufacturing this tire, the sidewalls are formed by the stripwind method. In this method, a strip of unvulcanized rubber (first strip) for forming the outer layer and a strip of unvulcanized rubber (second strip) for forming the inner layer are prepared. The outer layer is formed, for example, by spirally winding a first strip on a drum. The inner layer is formed by spirally winding a second strip over the outer layer. This gives the sidewalls.

The sidewall is combined with other components of the tire to form a raw cover. The raw cover is placed in a mold and pressurized and heated during the vulcanization process. This heating causes the unvulcanized rubber to undergo a cross-linking reaction to obtain a tire. Japanese Patent Application Laid-Open No. 2002-127718 discloses a study on a manufacturing method of a tire having sidewalls with an inner layer and an outer layer.

Japanese Patent Application Laid-Open No. 2002-127718

In forming the sidewall, the outer layer is formed by winding the first strip, so its surface is not smooth. Since the second strip is wound on the outer layer to form the inner layer, air tends to remain between the outer layer and the inner layer. A mold for vulcanizing the raw cover is composed of a plurality of elements for loading the raw cover and taking out the obtained tire. For example, a typical mold includes a segment and a side plate located radially inward of and in contact with the segment. All of these come into contact with the outer surface of the sidewall. If air remains between the outer layer and the inner layer, the sidewall surface may expand at this portion. This expansion can cause the sidewall rubber to pinch (rubber bite) between those elements that contact the sidewall when the mold is closed. In the manufacture of tires, it is important to prevent rubber entrapment in sidewalls.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for manufacturing a tire in which rubber entrapment in sidewalls is prevented.

TECHNICAL FIELD The present invention relates to a method for manufacturing a pneumatic tire in which a sidewall has an outer layer forming the outer surface thereof and an inner layer positioned axially inside the outer layer. This manufacturing method is
(A) forming the outer layer by helically winding a first band-shaped strip and forming the inner layer by helically winding a second band-shaped strip to obtain the sidewalls;
(B) a step of combining the sidewall with other constituent members of the tire to obtain a low cover;
and (C) the raw cover comprises a first element in contact with the outer surface of the sidewall and a second element adjacent to the first element radially inward of the first element and in contact with the outer surface of the sidewall. It includes a step of applying pressure and heat with a provided mold. The inner layer is formed in step (A) so that the inner layer is located radially inward of the seam corresponding to the dividing line between the first element and the second element.

Preferably, the first element is a segment that contacts the tread surface of the raw cover and the outer surface of the sidewall, and the second element is a side plate that contacts the outer surface of the sidewall of the raw cover.

Preferably, in the radial direction, the distance between said seam and the outer edge of said inner layer is not less than 2 mm.

In the tire manufacturing method according to the present invention, a first element that contacts the outer surface of the sidewall, and a second element that is adjacent to the first element radially inside the first element and contacts the outer surface of the sidewall. is used. The inner layer of the sidewall is positioned radially inward from a position (seam) on the outer surface of the raw cover corresponding to the boundary (parting line) between the first element and the second element. Since there is no boundary between the inner layer and the outer layer at the position of the seam and its outside in the radial direction, residual air is suppressed in this region. In this region, expansion of the sidewall surface due to residual air is suppressed. This effectively prevents rubber jamming between the first and second elements. In this tire, rubber entrapment in the sidewall is prevented.

FIG. 1 is a cross-sectional view showing an example of a tire manufactured by the manufacturing method according to the present invention. 2 is a perspective view showing a strip used in the manufacturing method according to the invention; FIG. FIG. 3 is a front view showing the strip of FIG. 2 in the process of forming sidewalls on the drum; FIG. 4 is a cross-sectional view showing sidewalls formed on the drum by the method of FIG. FIG. 5 is a cross-sectional view in which a part of FIG. 4 is enlarged. FIG. 6 is a plan view showing a mold used in the manufacturing method according to the present invention. FIG. 7 is a cross-sectional view taken along line IIV--IV of FIG.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail based on preferred embodiments with appropriate reference to the drawings.

FIG. 1 shows an example of a pneumatic tire 2 manufactured by the manufacturing method according to the present invention. In FIG. 1 , the vertical direction is the radial direction of the tire 2 , the horizontal direction is the axial direction of the tire 2 , and the direction perpendicular to the paper surface is the circumferential direction of the tire 2 . A dashed-dotted line CL represents the equatorial plane of the tire 2 . The shape of this tire 2 is symmetrical with respect to the equatorial plane, except for the tread pattern.

This tire 2 comprises a tread 4 , sidewalls 6 , chafers 8 , beads 10 , carcass 12 , belt 14 , innerliner 16 and insulation 18 . This tire 2 is of the tubeless type. This tire 2 is mounted on a truck, a bus, or the like. This tire 2 is for heavy loads.

As shown in FIG. 1 , the sidewalls 6 extend radially generally inward from the edges of the tread 4 . The sidewall 6 of this tire 2 comprises an outer layer 20 and an inner layer 22 .

The outer surface of the outer layer 20 forms part of the outer surface of the tire 2 . The outer layer 20 is located axially outward of the inner layer 22 . A radially inner edge 24 of outer layer 20 abuts chafer 8 . The outer layer 20 is made of a crosslinked rubber that has excellent resistance to trauma and weather.

The inner layer 22 is located axially inward of the outer layer 20 . The inner layer 22 is in contact with the axial inner surface of the outer layer 20 . A radially inner end 26 of the inner layer 22 is located axially outward of the bead 10 . Outer edge 28 of inner layer 22 is radially inboard of outer edge 30 of outer layer 20 . Inner layer 22 does not extend to outer edge 30 of outer layer 20 . The inner layer 22 is made of a crosslinked rubber that generates less heat than the outer layer 20 .

The manufacturing method of this tire 2 includes:
(1) preparing a strip;
(2) obtaining sidewalls 6;
(3) obtaining a raw cover; and (4) pressurizing and heating the raw cover.

In step (1) above, a band-shaped strip used for forming the sidewall 6 is prepared. Specifically, a first strip formed from a rubber composition for the outer layer 20 and a second strip formed from a rubber composition for the inner layer 22 are provided. A first strip 32 is shown in FIG. The second strip 34 is shaped similarly to the first strip 32 . Accordingly, FIG. 2 is also a view of the second strip 34. FIG. The first strip 32 and the second strip 34 are formed by, for example, continuously extruding an unvulcanized rubber composition as a raw material with an extruder, passing it through a die, and molding it to a desired width and thickness. be. The thickness T of the first strip 32 and the second strip 34 is typically 0.5 mm or more and 2.0 mm or less, and their width W is typically 5.0 mm or more and 30.0 mm or less.

In step (2) above, the drum 36 shown in FIG. 3 is used. A first strip 32 is fed to this drum 36 . A leading edge 38 of the first strip 32 rests on the outer circumference of the drum 36 . As the drum 36 rotates, a head (not shown) feeding the first strip 32 is moved axially of the drum 36 (to the right in FIG. 3). This causes the first strip 32 to be helically wound around the outer circumference of the drum 36, as shown in FIG. The outer layer 20 is thus formed. This method is called the stripwind method. The outer layer 20 is formed by a strip winding method.

In step (2) above, the second strip 34 is further supplied to this drum 36 . The tip of the second strip 34 rests on the outer layer 20 . As the drum 36 rotates, the head feeding the second strip 34 moves axially of the drum 36 . Thereby, the second strip 34 is helically wound around the outer circumference of the outer layer 20 . This forms the inner layer 22 . The inner layer 22 is formed by a strip winding method. Sidewalls 6 are thus obtained.

FIG. 4 is a sectional view showing the sidewall 6 formed on the drum 36. As shown in FIG. FIG. 5 is a cross-sectional view in which the region indicated by symbol E in FIG. 4 is enlarged. As shown in FIG. 5, in this section the sections 40 of adjacent first strips 32 have an overlap. By adjusting the winding start position and the winding end position of the first strip 32 and the overlapping amount of the cross section 40 (that is, the feeding amount when winding the first strip 32), the outer layer 20 having a desired shape can be obtained. is formed. Similarly, cross-sections 42 of adjacent second strips 34 have an overlap. By adjusting the winding start position and the winding end position of the second strip 34 and the feeding amount when winding the second strip 34, the inner layer 22 having a desired shape is formed.

Note that the sidewalls 6 of FIGS. 4 and 5 are not the same as the sidewalls 6 of FIG. Sidewalls 6 of FIGS. 4 and 5 are bridged to become sidewalls 6 of FIG. 1, as described below. For purposes of clarity, both are referred to herein as "sidewalls 6". The same applies to other constituent materials of this tire 2 .

In step (3) above, the sidewall 6 is combined with other constituent members of the tire 2 . As shown in FIG. 4, this drum 36 is associated with the chafer 8 in this embodiment. In another drum, not shown, the innerliner 16, insulation 18, carcass 12 and bead 10 are combined and shaped into a toroidal shape. The sidewall 6 and the chafer 8 are laminated to this. Furthermore, the belt 14 and the tread 4 are laminated on the outer side in the radial direction to form a raw cover. A raw cover is obtained in this step.

In step (4) above, the mold 44 shown in FIG. 6 is used. This figure is a plan view of the mold 44 . In FIG. 6, the direction indicated by arrow X is radially inward, the direction perpendicular to the paper surface is the axial direction, and the direction indicated by double arrow A is the circumferential direction. FIG. 7 is a cross-sectional view along line VII-VII of FIG. In FIG. 7, the direction indicated by arrow X is radially inward, the direction indicated by arrow Y is the axial direction, and the direction perpendicular to the paper surface is the circumferential direction. FIG. 7 also shows the raw cover R obtained in step (3) above.

The mold 44 can be opened and closed for loading the raw cover R and taking out the obtained tire 2 . For this reason, the mold 44 is composed of a plurality of elements. The mold 44 includes a plurality of segments 46, a pair of side plates 48 and a pair of bead rings 50. As shown in FIG. As shown in FIG. 6, the planar shape of segment 46 is substantially arcuate. A plurality of segments 46 are arranged in a ring. Side plate 48 and bead ring 50 are substantially ring-shaped.

In step (4) above, the raw cover R is put into the mold 44 while the mold 44 is open. Segment 46 moves in the X direction in FIG. 6 and mold 44 is closed. FIG. 7 shows the mold 44 closed. In this condition, segment 46 contacts side plate 48, as shown in FIG. Side plate 48 abuts segment 46 radially inward of segment 46 .

In FIG. 7, reference numeral S indicates a position on the outer surface of the raw cover R corresponding to the boundary between the segment 46 and the side plate 48 (parting line between the segment 46 and the side plate 48). A position S on the outer surface of the raw cover R corresponding to the parting line is called a seam. The seam S is also shown in FIGS. 1 and 4-5. As shown in these figures, seam S is located on the outer surface of sidewall 6 . In other words, the segment 46 contacts the tread surface and the outer surface of the sidewall 6 and the side plate 48 contacts the outer surface of the sidewall 6 radially inward of the segment 46 .

The inner layer 22 of the sidewall 6 is located radially inward of the seam S, as shown in FIG. In the radial direction, the inner layer 22 is absent at the seam S and outside thereof. At and outside the seam S in the radial direction, the sidewall 6 consists of an outer layer 20 . In other words, as shown in FIG. 5, the inner layer 22 is formed radially inward of the seam S in the step (2).

In step (4) above, the raw cover R is pressurized and heated in the mold 44 . The rubber composition of the raw cover R flows inside the cavity due to the pressurization and heating. The heating causes the rubber to undergo a cross-linking reaction, and the tire 2 is formed. The mold 44 is opened and the tire 2 is removed from the mold 44 . Tire 2 is thus obtained.

The effects of the present invention will be described below.

Since the surface of the outer layer formed by winding the first strip is not smooth, when the second strip is wound on the outer layer to form the inner layer, there is no Air tends to remain. The sidewall surface of the raw cover R may expand due to the air between the outer layer and the inner layer. As shown in FIG. 6, after the raw cover R is put into the mold 44, the mold 44 is closed by moving the segment 46 in the X direction. Expansion of the sidewall surface can cause the sidewall rubber to become pinched between the segment 46 and the side plate 48 (rubber bite).

In the method of manufacturing the tire 2 according to the invention, the inner layer 22 of the sidewall 6 is positioned radially inward of the seam S corresponding to the dividing line between the segment 46 and the side plate 48 . There is no boundary between the inner layer 22 and the outer layer 20 at and outside the seam S in the radial direction. In this region, residual air is suppressed. In this region, expansion of the surface of the sidewall 6 is suppressed. This effectively prevents rubber jamming between segment 46 and side plate 48 . In this method, the side walls 6 are prevented from being caught by the rubber.

In the vicinity of the radially outer edge of the sidewall, structurally, air tends to remain between the outer layer and the inner layer, and between the inner layer and other components in contact with the inner surface of the inner layer. In the method for manufacturing the tire 2 according to the present invention, there is no boundary between the inner layer 22 and the outer layer 20 at the position of the seam S and its outer side in the radial direction. In this manufacturing method, residual air is suppressed between the outer layer 20 and the inner layer 22 in the vicinity of the radially outer end of the sidewall 6 . Furthermore, since the position of the seam S and the outside thereof are composed of the outer layer 20, the inner surface of the sidewall 6 in the axial direction is smoother than the sidewall in which this region is composed of the outer layer and the inner layer. be. This effectively contributes to preventing air from remaining between the inner surface of the sidewall 6 and other components that come into contact with this inner surface. In this manufacturing method, residual air on the inner surface side of the sidewall 6 is effectively suppressed in the vicinity of the radially outer end of the sidewall 6 .

In this manufacturing method, the location of the outer edge 30 of the outer layer 20 and the location of the outer edge 28 of the inner layer 22 are not aligned. These are far apart. In other words, the winding end position of the first strip 32 and the winding end position of the second strip 34 are separated. Therefore, the sidewalls 6 can be formed stably and accurately. This contributes to the uniformity of tire 2 . With this manufacturing method, a tire 2 with excellent uniformity can be manufactured.

In FIG. 1 the double arrow L represents the radial distance between the seam S and the outer edge 28 of the inner layer 22 . This distance L is measured while the tire 2 is in the mold 44 . The distance L is preferably 2 mm or more. By setting the distance L to 2 mm, the side walls 6 are effectively prevented from being caught by the rubber. From this point of view, the distance L is more preferably 2.5 mm or more. From the viewpoint of sufficiently exhibiting the effect of providing the inner layer 22 (reduction of rolling resistance in this embodiment), the distance L is preferably 5 mm or less.

A method for manufacturing a tire 2 according to another embodiment of the present invention includes:
(1a) preparing a strip;
(2a) obtaining an inner raw cover;
(3a) obtaining sidewalls 6;
(4a) obtaining a raw cover R; and (5a) pressurizing and heating the raw cover R.

The step (1a) above is the same as the step (1) described above. In this process, a first strip 32 formed from the rubber composition for the outer layer 20 and a second strip 34 formed from the rubber composition for the inner layer 22 are provided.

Although not shown, a drum is used in step (2a) above. In this drum the innerliner 16, the insulation 18 and the carcass 12 are laminated. Further, on this drum, beads 10 and chafers 8 are combined to obtain an inner raw cover.

Either the step (1a) or the step (2a) may be performed first. These steps should be completed before the next step (3a).

In step (3a) above, a second strip 34 is supplied to the drum. The leading edge of the second strip 34 rests on the inner raw cover. As the drum rotates, the head feeding the second strip 34 moves axially of the drum. As a result, the second strip 34 is spirally wound around the outer circumference of the inner row cover. This forms the inner layer 22 .

In step (3a) above, the first strip 32 is also supplied to this drum. The leading edge of the first strip 32 rests in place on the inner layer 22 or inner raw cover. As the drum rotates, the head feeding the first strip 32 moves axially of the drum. As a result, the first strip 32 is helically wound around the inner layer 22 and inner row cover. The outer layer 20 is thus formed. Sidewalls 6 are thus obtained.

In step (4a) above, the inner raw cover and sidewall 6 are combined with other constituent members of the tire 2 . In this process, the inner raw cover and the sidewall 6 are shaped into a toroidal shape, and the belt 14 and the tread 4 are laminated on the outer side in the radial direction to form the raw cover R. A raw cover R is obtained in this step.

The step (5a) is the same as the step (4) described above. In this step, the raw cover R is put into the mold 44. As shown in FIG. At this time, the seam S corresponding to the dividing line between the segment 46 and the side plate 48 is positioned on the outer surface of the sidewall 6 . The inner layer 22 of the sidewall 6 is located radially inward of the seam S. In other words, the inner layer 22 is formed radially inward of the seam S in the step (3a). The raw cover R is pressurized and heated in the mold 44 to obtain the tire 2 .

In this method of manufacturing the tire 2 , the inner layer 22 of the sidewall 6 is positioned radially inward of the seam S corresponding to the dividing line between the segment 46 and the side plate 48 . There is no boundary between the inner layer 22 and the outer layer 20 at and outside the seam S in the radial direction. In this region, residual air is suppressed. In this region, expansion of the surface of the sidewall 6 is suppressed. This effectively prevents rubber jamming between the segment 46 and the side plate 48 . In this method, the side walls 6 are prevented from being caught by the rubber.

Still another embodiment of the present invention includes a step of shaping the inner raw cover after the step (2a). The second strip 34 is wound around the shaped inner raw cover to form the inner layer 22 , and the first strip 32 is further wound to form the outer layer 20 . Sidewalls 6 are thus formed. At this time, the inner layer 22 is formed so as to be located radially inward of the seam S. In this embodiment, the raw cover R is obtained in the same manner as in (4a) above, and the tire 2 is obtained in the same manner as in (5a) above.

In the embodiments described above, mold 44 included segments 46 and side plates 48 . The configuration of the mold is not limited to this. Any mold comprising a first element in contact with the outer surface of the sidewall 6 and a second element adjacent to the first element radially inwardly of the first element and in contact with the outer surface of the sidewall 6 is a mold of the present invention. Be eligible. At this time, the inner layer 22 is formed so as to be positioned radially inward from the position of the seam corresponding to the boundary line between the first element and the second element.

The effects of the present invention will be clarified by examples below, but the present invention should not be construed in a limited manner based on the description of these examples.

[Example 1]
A tire was manufactured through the above steps (1) to (4). The inner layer is located radially inward of the seam. The distance L at this time was set to 3 mm.

[Comparative Example 1]
A tire was constructed as in Example 1, except that in the radial direction the inner layer extended beyond the seam to the outer edge of the outer layer.

[Remaining air]
For each of Example 1 and Comparative Example 1, 10,000 tires were manufactured. The presence or absence of residual air inside the sidewalls and between the inner side surfaces of the sidewalls and other components was inspected by X-rays. As a result, the rate of occurrence of residual air in Example 1 was 35% of the rate of occurrence of residual air in Comparative Example 1.

[Rubber biting on the sidewall]
The presence or absence of rubber entrapment in the sidewalls of the tires manufactured as described above was visually confirmed. As a result, the occurrence rate of rubber biting in Example 1 was 15% of the rate of occurrence of rubber biting in Comparative Example 1.

As shown by the results of the above examples, the production methods of the examples are evaluated higher than the production methods of the comparative examples. From this evaluation result, the superiority of the present invention is clear.

The methods described above can also be applied to the manufacture of various tires.

2 Tire 4 Tread 6 Sidewall 8 Chafer 10 Bead 12 Carcass 14 Belt 16 Inner liner 18 Insulation 20 Outer layer 22 Inner layer 24 Inner edge of outer layer 26 Inner edge of inner layer 28 Outer edge of inner layer 30 Outer edge of outer layer 32 First strip 34 Second strip 36 Drum 38 Tip of first strip 40 Section of first strip 42 Section of second strip 44 Mold 46 ..Segment 48..Side plate 50..Bead ring

Claims (3)

A method for manufacturing a pneumatic tire in which the sidewall comprises an outer layer forming the outer surface thereof and an inner layer positioned axially inside the outer layer,
(A) forming the outer layer by helically winding a first band-shaped strip and forming the inner layer by helically winding a second band-shaped strip to obtain the sidewalls;
(B) a step of combining the sidewall with other constituent members of the tire to obtain a low cover;
and (C) the raw cover comprises a first element in contact with the outer surface of the sidewall and a second element adjacent to the first element radially inward of the first element and in contact with the outer surface of the sidewall. including a step of applying pressure and heat with a mold comprising
A method for manufacturing a pneumatic tire, wherein the inner layer is formed in the step (A) so that the inner layer is positioned radially inward of the seam corresponding to the dividing line between the first element and the second element. . The pneumatic tire according to claim 1, wherein the first element is a segment that contacts the tread surface of the raw cover and the outer surface of the sidewall, and the second element is a side plate that contacts the outer surface of the sidewall of the raw cover. Production method. 3. The method of manufacturing a pneumatic tire according to claim 1, wherein the radial distance between the seam and the outer edge of the inner layer is 2 mm or more in the radial direction.

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