JP2017113994A - Pneumatic tire manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress generation of air reservoirs in interfaces between inner layers and outer layers in a ribbon winding process for a tread rubber.SOLUTION: In a step for forming an unvulcanized tread rubber 34 by winding a ribbon rubber 40 around a tire rotation shaft, inner layers 42 to be arranged inside in a tire radial direction are formed and outer layers 44 to be laminated outside in the tire radial direction are formed. When forming the outer layers 44, the ribbon rubber 40 is wound around the shaft so that boundaries 46 between ribbon rubbers adjacent in a tire width direction in the inner layers 42 and boundaries 48 between ribbon rubbers adjacent in the tire width direction in the outer layers 44 do not correspond to each other in interfaces 50 between the inner layers and the outer layers.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a method for manufacturing a pneumatic tire.

  In general, a pneumatic tire is manufactured by molding a green tire on a molding drum and then setting the green tire in a mold and vulcanization molding. As a method for forming such a green tire, there is known a ribbon winding method for forming a tread rubber by winding a belt-like ribbon rubber spirally along the tire circumferential direction (see, for example, Patent Documents 1 to 3).

  When forming a tread rubber by a ribbon winding method, the tread rubber is formed by laminating a tread rubber in a structure of at least two layers of an inner layer on the inner side in the tire radial direction and an outer layer laminated on the outer side in the tire radial direction. There is.

JP 2010-264959 A JP 2006-062518 A JP 2001-179848 A

  As described above, when the tread rubber is formed in a laminated structure of two or more layers by the ribbon winding method, air accumulation may occur at the interface between the inner layer and the outer layer. It has been found that such air pockets are likely to occur where the boundary between the ribbon rubbers in the inner layer and the boundary between the ribbon rubbers in the outer layer coincide with each other at the interface between them. That is, when laminating the outer layer by wrapping the ribbon rubber around the outer surface of the inner layer formed by wrapping the ribbon rubber, if the boundary between the two coincides, a minute gap or recess in the boundary between the ribbon rubber in the inner layer Therefore, a minute gap or a recess at the boundary between the ribbon rubber of the outer layer laminated on the outside overlaps with each other, and an air pocket is easily generated.

  In view of the above points, an embodiment of the present invention provides a method for manufacturing a pneumatic tire that can suppress the occurrence of air accumulation at the interface between an inner layer and an outer layer in a tread rubber ribbon winding method. Objective.

  A method for manufacturing a pneumatic tire according to an embodiment of the present invention includes a tread rubber forming step of forming an unvulcanized tread rubber by winding a ribbon rubber around a tire rotation axis, and the tread rubber forming step includes a tire diameter. A step of forming an inner layer disposed on the inner side of the tire and a step of forming an outer layer stacked on the outer side of the tire in the radial direction of the inner layer. The ribbon rubber is wound so that the boundary between the ribbon rubbers adjacent in the width direction and the boundary between the ribbon rubbers adjacent in the tire width direction in the outer layer do not coincide with each other at the interface between the inner layer and the outer layer.

  According to the present embodiment, when the tread rubber is formed by the ribbon winding method, the boundary between the ribbon rubbers of the inner layer and the boundary between the ribbon rubbers of the outer layer are not matched at the interface between the inner layers. The occurrence of air accumulation at the interface between the outer layer and the outer layer can be suppressed.

Half sectional view of a pneumatic tire according to an embodiment Sectional drawing which shows the process of forming the 1st inner layer of the unvulcanized tread rubber in the embodiment Sectional drawing which shows the process of forming the 1st outer side layer of the tread rubber Sectional drawing which shows the process of forming the 2nd inner layer of the tread rubber Sectional view showing the tread rubber The figure which shows the manufacturing apparatus used in the formation process of the tread rubber Plan view showing the winding process of the ribbon rubber in the same embodiment

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a half sectional view of a pneumatic tire 10 according to an embodiment. The tire 10 includes a pair of left and right bead portions 12, a pair of left and right sidewall portions 14 that extend outward from the bead portion 12 in the tire radial direction, and a tread portion 16 that connects the outer peripheral ends of the sidewall portions 14. In the present embodiment, since the tire 10 is bilaterally symmetric, only the right half is shown in the figure. In the figure, CL indicates the tire equator. In the present specification, the tire width direction is a direction parallel to the tire rotation axis, and is indicated by a symbol W in the drawing. Further, the tire radial direction is a direction perpendicular to the tire rotation axis, and is indicated by a symbol R in the figure. The tire circumferential direction is a circumferential direction around the tire rotation axis.

  In the bead portion 12, an annular bead core 18 made of a bead wire and a bead filler 20 made of hard rubber joined and integrated on the outer peripheral surface of the bead core 18 are embedded.

  The pneumatic tire 10 has a toroidal carcass ply 22 embedded between a pair of bead portions 12. The carcass ply 22 extends from the tread portion 16 through the side wall portions 14 on both sides to the bead portion 12, and is wound up and locked around the bead core 18 in the bead portion 12. The carcass ply 22 is formed by rubber covering a carcass cord disposed so as to be substantially perpendicular to the tire circumferential direction. An inner liner 24 is provided on the tire inner surface side of the carcass ply 22.

  A rim strip rubber 26 is provided on the tire outer surface side of the carcass ply 22 in the bead portion 12. Further, a sidewall rubber 28 is provided on the tire outer surface side of the carcass ply 22 in the sidewall portion 14.

  A belt 30 is disposed on the outer peripheral side of the carcass ply 22 in the tread portion 16. The belt 30 is composed of one or a plurality of belt plies formed by covering a belt cord inclined at a constant angle with respect to the tire circumferential direction, and in this example, the belt cords are crossed in opposite directions between the plies. It consists of two belt plies. A belt reinforcing layer 32 made of an organic fiber cord extending in the tire circumferential direction is provided on the outer peripheral side of the belt 30.

  On the outer peripheral side of the belt 30 in the tread portion 16 (more specifically, on the outer peripheral side of the belt reinforcing layer 32), a tread rubber 34 constituting a ground contact surface is provided. One or a plurality of circumferential grooves (main grooves) 36 extending in the tire circumferential direction are provided on the surface of the tread rubber 34 (that is, the ground contact surface). In this example, there are provided three circumferential grooves 36, one center main groove 36 </ b> A extending on the tire equator CL, and a pair of left and right shoulder main grooves 36 </ b> B arranged on both sides in the tire width direction. . The surface of the tread rubber 30 is partitioned into a plurality of land portions 38 by circumferential grooves 36. In this example, a pair of left and right center land portions 38A formed between the center main groove 36A and the shoulder main grooves 36B. And a pair of left and right shoulder land portions 38B formed on the outer side Wo in the tire width direction of the left and right shoulder main grooves 36B.

  Next, a method for manufacturing the pneumatic tire 10 will be described. Since the pneumatic tire 10 can be manufactured in the same manner as the conventional tire manufacturing process except for the point related to the tread rubber 34, the process of forming the tread rubber 34 (tread rubber forming process) will be mainly described.

  In the present embodiment, the tread rubber 34 is formed by a so-called ribbon winding method. That is, the unvulcanized tread rubber 34 having a desired cross-sectional shape is formed by winding the ribbon rubber 40, which is an unvulcanized belt-shaped rubber, along the tire circumferential direction C, that is, around the tire rotation axis. .

  For example, using the manufacturing apparatus 70 shown in FIG. 6, the ribbon rubber 40 is supplied from the ribbon rubber supply unit 74 to the rotary support 72 while the rotary support 72 is rotated, and the ribbon rubber 40 is wound around the rotary support 72. The ribbon rubber supply unit 74 is configured to be able to extrude the ribbon rubber 40 into a predetermined shape. The rotation support 72 is configured to be capable of rotating in the rotation direction K around the axis (same as the tire rotation axis) 72A and moving in the axial direction (same as the tire width direction W). In addition, as long as the rotation support body 72 and the ribbon rubber supply part 74 can move relatively in the axial direction, the ribbon rubber supply part 74 may be configured to be movable instead of the rotation support body 72. Reference numeral 76 denotes a control device that controls the operation of the rotary support 72 and the ribbon rubber supply unit 74. Reference numeral 78 denotes a pressing roll that presses the ribbon rubber 40 supplied from the ribbon rubber supply unit 74 onto the rotary support 72 so as to follow the shape of the attaching position.

  The cross-sectional shape of the ribbon rubber 40 is not particularly limited, and various shapes having a flat cross-sectional shape such as a trapezoidal shape, a crescent shape, and a triangular shape can be employed. In this example, a triangular cross section is used (see the ribbon rubber shape of the winding start end 40A in FIG. 2). The dimensions of the ribbon rubber 40 are not particularly limited. For example, the width may be 15 to 40 mm, and the thickness (thickness at the maximum thickness portion) may be 0.5 to 3.0 mm.

  In the present embodiment, the tread rubber forming step includes, as shown in FIGS. 2 to 5, a step of forming an inner layer 42 disposed on the tire radial inner side Ri and an outer layer laminated on the tire radial outer side Ro. Forming 44. In this example, the first inner layer 42A and the second inner layer 42B are formed as the inner layer 42, and the first outer layer 44A and the second outer layer 44B are formed as the outer layer 44. That is, the first inner layer 42A is formed by winding from the winding start end 40A located at the center in the tire width direction toward one side W1 in the tire width direction (see FIG. 2), and then folded back at the end on the one side. The first outer layer 44A is formed by winding up to the center in the width direction (see FIG. 3), and the second inner layer 42B is formed by winding toward the other side W2 in the tire width direction (see FIG. 4). The second outer layer 44B is formed by folding back to the center of the tire and winding it to the center in the tire width direction (see FIG. 5).

  Specifically, first, as shown in FIG. 2, the first inner layer 42 </ b> A is formed on the outer peripheral surface of the rotary support 72. Although not shown, a belt 30 and a belt reinforcing layer 32 (see FIG. 1) are provided in advance on the outer peripheral surface of the rotary support 72. Further, when the tread rubber is composed of a cap rubber constituting the ground contact surface and a base rubber provided on the inner side in the tire radial direction, the base rubber may be provided on the outer peripheral surfaces of the belt 30 and the belt reinforcing layer 32 in advance. Good. The tread rubber 34 according to the present embodiment is formed on these.

  The first inner layer 42A is formed by setting the winding start end 40A on the tire equator CL and winding the ribbon rubber 40 around the tire rotation axis while moving in the tire width direction W therefrom. The winding pitch p1 of the ribbon rubber 40 is smaller than the width (ribbon rubber width) wr of the ribbon rubber 40. Therefore, the ribbon rubber 40 is wound with an overlapping portion between adjacent ribbon rubbers in the tire width direction W. Here, the winding pitch refers to the distance in the tire width direction between the centers in the tire width direction of the ribbon rubber adjacent to the tire width direction W, and is equal to the moving distance in the tire width direction W for each turn during winding.

  After forming the first inner layer 42A in this manner, as shown in FIG. 3, the ribbon rubber 40 is folded back without cutting at the tread end E1 on the one side W1 in the tire width direction, toward the other side W2 in the tire width direction. By winding the ribbon rubber 40, the first outer layer 44A is formed. The first outer layer 44A is a rubber layer laminated on the outer peripheral surface of the first inner layer 42A, and the tire rotates while moving in the tire width direction W from the tread end E1 on the one side W1 to the tire equator CL. It is formed by winding the ribbon rubber 40 around the axis. The winding pitch p2 of the ribbon rubber 40 in the first outer layer 44A is also smaller than the ribbon rubber width wr. Therefore, the ribbon rubber 40 is wound with an overlapping portion between adjacent ribbon rubbers in the tire width direction W.

  After forming the first outer layer 44A, as shown in FIG. 4, the ribbon rubber 40 is wound as it is toward the other side W2 in the tire width direction from the tire equator CL to the tread end E2 on the other side W2 in the tire width direction. Thus, the second inner layer 42B is formed. Similar to the first inner layer 42A, the second inner layer 42B is a rubber layer that is laminated on the belt 30 and the belt reinforcing layer 32 (base rubber in some cases) and rotates the tire while moving in the tire width direction W. It is formed by winding the ribbon rubber 40 around the axis. The winding pitch p1 of the ribbon rubber 40 in the second inner layer 42B is set similarly to the first inner layer 42A.

  After forming the second inner layer 42B, as shown in FIG. 5, the ribbon rubber 40 is folded back at the tread end E2 on the other side W2 in the tire width direction without being cut, and the ribbon rubber 40 is wound toward the one side W1 in the tire width direction. Thus, the second outer layer 44B is formed. The second outer layer 44B is a rubber layer laminated on the outer peripheral surface of the second inner layer 42B. The tire rotates while moving in the tire width direction W from the tread end E2 on the other side W2 to the tire equator CL. It is formed by winding the ribbon rubber 40 around the axis. The winding with the ribbon rubber 40 is terminated at the tire equator CL. The winding pitch p2 of the ribbon rubber 40 in the second outer layer 44B is set similarly to the first outer layer 44A.

  In addition, as a winding method of the ribbon rubber 40, although it can also wind spirally, as shown in FIG. 7, it is preferable to wind by winding pitch at every round. Here, the spiral winding is performed by continuously changing the winding position of the ribbon rubber in the tire width direction along with the rotation of the rotary support. On the other hand, as shown in FIG. 7, the pitch feed winding is performed every time the rotary support 72 is rotated once while the ribbon rubber 40 is wound in parallel (that is, wound in parallel with the tire circumferential direction C). This is done by shifting the winding position in the tire width direction W by one pitch at a predetermined location.

  In the above tread rubber forming step, in the present embodiment, when forming the outer layer 44, the boundary 46 between the ribbon rubbers adjacent to the tire width direction W of the inner layer 42 and the tire width direction W of the outer layer 44 are adjacent. The ribbon rubber 40 is wound so that the boundary 48 between the ribbon rubbers does not coincide with the interface 50 between the inner layer 42 and the outer layer 44. That is, as shown in FIG. 5, each boundary 46 (see FIG. 2) between the ribbon rubbers on the upper surface (outer peripheral surface) 42X of the inner layer 42 and each boundary between the ribbon rubbers on the lower surface (inner peripheral surface) 44Y of the outer layer 44. 48 (see FIG. 3) does not match. Therefore, the edges 40E of the respective ribbon rubbers 40 on the lower surface 44Y of the outer layer 44 are all in contact with the side surfaces of the ribbon rubber 40 that are not the boundary 46 between the ribbon rubbers on the upper surface 42X of the inner layer 42.

  In such a configuration, when the ribbon rubber 40 of the outer layer 44 is wound, the boundary 48 between the ribbon rubbers does not coincide with the boundary 46 between the ribbon rubbers of the inner layer 42 at the interface 50 between the outer layer 44 and the inner layer 42. Further, this can be realized by setting the winding pitch p2.

  In this embodiment, as shown in FIGS. 2 and 4, in the step of forming the inner layer 42, the ribbon rubber 40 is wound at a constant winding pitch p <b> 1, thereby gently rolling the inner layer 42 without undulations. It is formed in a simple shape. On the other hand, as shown in FIGS. 3 and 5, in the step of forming the outer layer 44, the winding pitch p2 (p2 <p1) smaller than the winding pitch p1 of the inner layer 42 and in the tire width direction W. The ribbon rubber 40 is wound by changing the winding pitch p2, thereby forming the outer layer 44 in a undulating shape.

  As a preferred example, the winding pitch p1 in the inner layer 42 may be set to ½ of the ribbon rubber width wr. On the other hand, the winding pitch p2 of the outer layer 44 may be set within a range of 1/12 to 5/12 of the ribbon rubber width wr.

  Thus, by setting the winding pitch p2 of the outer layer 44 to be smaller than the winding pitch p1 of the inner layer 42, the lower surface 44Y of the outer layer 44 is placed on the side surface of the ribbon rubber 40 in each turn on the upper surface 42X of the inner layer 42. At least two edges 40E of the ribbon rubber 40 are in contact with each other. However, the ribbon rubber 40B at both ends in the tire width direction W of the inner layer 42 (in this example, ribbon rubber for two rounds at both ends as shown in FIG. 5) and the ribbon rubber 40A at the winding start end are zero or one. This is also the case with the other inner layer 42 since only the abutment may be in contact.

  In the present embodiment, as shown in FIG. 5, in the step of forming the outer layer 44, the winding pitch p <b> 2 of the ribbon rubber 40 according to the circumferential groove 36 and the land portion 38 (see FIG. 1) of the tread rubber 34. To change. That is, the winding pitch p2a at the position corresponding to the circumferential groove 36 of the tread rubber 34 is made larger than the winding pitch p2b at the position corresponding to the land portion 38 of the tread rubber 34 (p2a> p2b), and the ribbon rubber 40 Wrap. Thus, a concave groove 52 is formed on the outer peripheral surface of the unvulcanized tread rubber 34 at a position corresponding to the circumferential groove 36. In FIG. 5, reference numeral 80 indicates a mold shape in a tread portion when a pneumatic tire is vulcanized, and reference numeral 82 indicates a ridge for forming the circumferential groove 38.

  As a preferred example, the winding pitch p2a at the portion corresponding to the land portion 38 is set within a range of 1/4 to 1/12 of the ribbon rubber width wr, and the winding pitch p2b at the position corresponding to the circumferential groove 36 is set. The ribbon rubber width wr may be set within a range of 1/6 to 5/12.

  Thereby, the unvulcanized tread rubber 34 is formed on the outer periphery of the belt 30 and the belt reinforcing layer 32, and a tread ring used for tire manufacture is formed.

  When manufacturing a pneumatic tire using such a tread ring, for example, an inner liner and a carcass ply are formed in a cylindrical shape on the outer peripheral surface of the molding drum, and after bead cores are extrapolated on both sides in the width direction, the bead cores are The end portion of the carcass ply is folded back so as to wrap, thereby producing a cylindrical case body. And in the state where the above-mentioned tread ring is arranged on the outer peripheral side of this cylindrical case main body, the case main body is inflated and deformed in a toroidal shape in the tire radial direction using, for example, a bladder, and the outer peripheral surface is Adhere to the inner surface of the tread ring. Then, a green tire (unvulcanized tire) is formed by attaching a sidewall rubber. The sidewall rubber may be formed before the case body is expanded and deformed. The green tire formed in this manner is set in a mold that is a vulcanization mold and vulcanized and molded according to a conventional method to obtain a pneumatic tire.

  According to this embodiment, when the tread rubber 34 is formed by the ribbon winding method, the boundary 46 between the ribbon rubbers of the inner layer 42 and the boundary 48 between the ribbon rubbers of the outer layer 44 do not coincide with each other at the interface 50 between them. To do. As a result, the minute gap or recess of the boundary 46 between the ribbon rubbers in the inner layer 42 and the minute gap or recess of the boundary 48 between the ribbon rubbers of the outer layer 44 laminated on the outer side are not overlapped. The occurrence of air pockets at the interface 50 between the inner layer 42 and the outer layer 44 can be suppressed.

  The inner layer 42 is wound with the ribbon rubber 40 at a substantially constant winding pitch p1, and the outer layer 44 is wound with a winding pitch p2 smaller than the winding pitch p1 of the inner layer 42 and in the tire width direction W. By winding the ribbon rubber 40 while changing the winding pitch p2, the following operational effects are achieved.

  That is, since the inner layer 42 has a gentle shape, when the ribbon rubber 40 for the outer layer 44 is wound around the outer peripheral surface thereof, air entrapment is suppressed and the occurrence of air pockets is more effectively suppressed. Can do. At the same time, in the outer layer 44, the tread rubber 34 can be formed with a rubber volume corresponding to the cross-sectional shape of the tread by winding the ribbon rubber 40 with a finer winding pitch p2 and changing the winding pitch p2. In addition, it is easy to set a winding configuration in which the boundary 46 between the ribbon rubbers of the inner layer 42 and the boundary 48 between the ribbon rubbers of the outer layer 44 do not coincide with each other. When the inner layer 42 is referred to as a substantially constant winding pitch, it is sufficient that the thickness of the inner layer 42 is substantially constant over substantially the entire width thereof, not necessarily the constant winding pitch over the entire width of the inner layer 42. For example, as shown in FIGS. 2 and 4, the folded portions at both ends in the tire width direction W (for example, ribbon rubber for one or two turns at both ends in the tire width direction) may be used for thickness adjustment, etc. The winding pitch may be changed, and such a case is also included in the concept.

  Further, according to the present embodiment, in the step of forming the outer layer 44, the winding pitch p2a at the position corresponding to the circumferential groove 36 is made larger than the winding pitch p2b at the position corresponding to the land portion 38. By winding the ribbon rubber 40, the following effects are exhibited. That is, as shown in FIG. 5, in the portion corresponding to the circumferential groove 36, the winding pitch p2a is wide and the rubber volume is small (that is, thinned), and in the portion corresponding to the land portion 38, the winding pitch p2b is Narrow and the rubber volume is large (ie thick). Therefore, it is possible to secure a necessary rubber volume in each of the groove portion and the land portion while suppressing the occurrence of air accumulation.

  In the above embodiment, the first inner layer 42A and the second inner layer 42B are provided as the inner layer 42, and the first outer layer 44A and the second outer layer 44B are provided as the outer layer 44. After forming the inner layer by winding toward one side over the entire width in the tire width direction, the tread rubber is formed by folding back without cutting and winding toward the other side over the entire width in the tire width direction. It may be formed. In the above embodiment, the ribbon rubber 40 is continuously wound without being cut to form the inner layer 42 and the outer layer 44. However, the inner layer and the outer layer may be formed of different ribbon rubbers. Moreover, in the said embodiment, although it was set as the 2 layer structure of the inner side layer 42 and the outer side layer 44, it is good also as a structure of three or more layers.

  The above embodiment is presented as an example and is not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention.

10 ... Pneumatic tire, 34 ... Tread rubber, 36 ... Circumferential groove, 38 ... Land part,
40 ... Ribbon rubber, 42 ... Inner layer, 44 ... Outer layer,
46 ... Boundary between the ribbon rubbers in the inner layer, 48 ... Boundary between the ribbon rubbers in the outer layer 50 ... Interfaces between the inner layer and the outer layer, p1 ... Wounding pitch of the ribbon rubber in the inner layer p2 ... Wounding of the ribbon rubber in the outer layer Pitch p2a: Winding pitch at a position corresponding to the circumferential groove,
p2b: Winding pitch W at a position corresponding to a land portion ... Tire width direction, R ... Tire radial direction

Claims (3)

Including a tread rubber forming step of forming an unvulcanized tread rubber by winding a ribbon rubber around the tire rotation axis;
The tread rubber forming step includes a step of forming an inner layer disposed on the inner side in the tire radial direction, and a step of forming an outer layer laminated on the outer side in the tire radial direction of the inner layer,
In the step of forming the outer layer, the boundary between the ribbon rubbers adjacent in the tire width direction in the inner layer and the boundary between the ribbon rubbers adjacent in the tire width direction in the outer layer are at the interface between the inner layer and the outer layer. Wrap the ribbon rubber so that it does not match,
A method of manufacturing a pneumatic tire.   In the step of forming the inner layer, the ribbon rubber is wound at a substantially constant winding pitch, and in the step of forming the outer layer, the winding pitch is smaller than the winding pitch of the inner layer, and in the tire width direction. The method for manufacturing a pneumatic tire according to claim 1, wherein the ribbon rubber is wound by changing a winding pitch.   In the step of forming the outer layer, the ribbon rubber is wound by setting a winding pitch at a position corresponding to a circumferential groove of the tread rubber to be larger than a winding pitch at a position corresponding to a land portion of the tread rubber. Item 3. A method for manufacturing a pneumatic tire according to Item 1 or 2.

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