JP6081153B2 - Pneumatic tire manufacturing method and pneumatic tire - Google Patents

Description

  The present invention relates to a method for manufacturing a pneumatic tire and a pneumatic tire capable of preventing a rubber ribbon from being cut off by an ear.

  A so-called ribbon winding method is known in which a rubber ribbon wound body is formed by continuously supplying an unvulcanized rubber ribbon to a wound body such as a forming drum and winding the rubber ribbon in a spiral shape (for example, Patent Documents 1 to 3). According to the ribbon winding method, various cross-sectional shapes can be easily formed by appropriately adjusting the winding conditions. In addition, the rubber member formed of the rubber ribbon wound body does not have a joint portion that generates a large step, and is excellent in uniformity as compared with a rubber member formed by integral extrusion.

  By the way, when the rubber ribbon has a cross-sectional shape having a thickness smaller than the width, a process defect called “ear cutting” may occur when extrusion molding is performed. Ear cutting is a phenomenon in which corners formed at both ends of a rubber ribbon are undulated, which is inconvenient because it induces air entry when forming a rubber ribbon wound body. The inventor found that the flow resistance of the rubber in the mold is relatively large at the corner, and that the rubber at the corner tends to stay in the mold according to the flow rate difference between the corner and the other portion. We have obtained knowledge that ear loss occurs.

  On the other hand, if the cross-sectional shape is changed so as to increase the thickness at the corners such as both ends of the rubber ribbon, the occurrence of the ear break can be suppressed. However, this method is not practical because the thickness is locally increased at the overlapping portions of the rubber ribbons adjacent in the width direction, and the dimensional accuracy of the formed rubber ribbon wound body is deteriorated and air is easily generated. it is conceivable that.

JP 2007-8388 A JP 2007-176436 A JP 2012-111224 A

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a pneumatic tire manufacturing method and a pneumatic tire capable of preventing the pneumatic and rubber ribbon from being cut off in the ribbon winding method.

  The above object can be achieved by the present invention as described below. That is, in the method for manufacturing a pneumatic tire according to the present invention, a rubber ribbon winding body is formed by spirally winding a rubber ribbon around a wound body, and a pneumatic tire is formed using a rubber member made of the rubber ribbon winding body. In the method of manufacturing a pneumatic tire, the rubber ribbon wound around the wound body is a composite rubber ribbon obtained by co-extrusion of a plurality of types of rubber, and the composite rubber ribbon when cut along a plane perpendicular to the length direction The cross-section is a shape having a thickness smaller than the width, the thickness is gradually reduced toward both ends in the width direction, and corners are provided at a plurality of locations including both ends. The main body rubber that forms the main body of the rubber ribbon, and at least one of the corners, and the Mooney viscosity measured at 100 ° C. based on JISK6300 In which and a lower low-viscosity rubber than the main body rubber.

  In this method, the cross-section of the composite rubber ribbon used has a shape smaller than the width, and the thickness gradually decreases toward both ends in the width direction. The increase in thickness at the location is suppressed, and it is difficult for air to enter when forming the rubber ribbon winding body. In addition, since the corners of the composite rubber ribbon are made of low-viscosity rubber, the flow rate difference between the corners of the low-viscosity rubber and the other parts of the body rubber is reduced in the mold during extrusion. It can reduce and can prevent the rubber ribbon from being cut off.

  In the method for manufacturing a pneumatic tire according to the present invention, it is preferable that the corner portions at both ends of the composite rubber ribbon are respectively constituted by the low-viscosity rubber. As a result, it is possible to appropriately prevent the rubber ribbon from being cut off at both ends where the flow resistance of the rubber is particularly likely to increase.

  In the method for producing a pneumatic tire according to the present invention, it is preferable that the difference between the Mooney viscosity of the main rubber and the Mooney viscosity of the low-viscosity rubber is 2 to 10. By setting the Mooney viscosity difference to be 2 or more, the flow rate difference between the corner portion constituted by the low-viscosity rubber and the other portion constituted by the main rubber can be satisfactorily reduced in order to ensure the effect of preventing the ear-cut. Further, by setting the Mooney viscosity difference to 10 or less, the difference in rigidity between the corner portion and the other portion of the composite rubber ribbon does not become too large, and the practical handling is not hindered.

  The pneumatic tire according to the present invention is a pneumatic tire having a rubber member formed of a rubber ribbon wound body formed by spirally winding a rubber ribbon, wherein the rubber ribbon is a composite rubber ribbon formed by coextruding a plurality of types of rubber. The cross section of the composite rubber ribbon when cut along a plane perpendicular to the length direction is a shape having a thickness smaller than the width, and the thickness is gradually reduced toward both ends in the width direction. Mooney having a corner portion at a plurality of locations, wherein the composite rubber ribbon constitutes at least one of the main body rubber forming the main body of the composite rubber ribbon and the corner portion, and measured at 100 ° C. based on JISK6300 And a low-viscosity rubber having a viscosity lower than that of the main rubber.

  In this tire, the cross section of the rubber ribbon constituting the rubber ribbon winding body has a shape with a thickness smaller than the width, and the thickness gradually decreases toward both ends in the width direction. Entering is difficult to occur. In addition, since the corners of the composite rubber ribbon are made of low-viscosity rubber, the rubber ribbon is prevented from being cut off.

  In the pneumatic tire of the present invention, a rubber member made of the rubber ribbon wound body may be used at least in the tread portion. According to such a configuration, since the rubber member used for the tread portion is composed of the rubber ribbon winding body formed by winding the composite rubber ribbon in which the occurrence of the ear breakage is suppressed, the entry of air is prevented.

Tire meridian cross-sectional view showing an example of a pneumatic tire according to the present invention Sectional view schematically showing tread rubber Cross section of the tread rubber depicting the cross section of the rubber ribbon Cross section of composite rubber ribbon (but not included in the present invention) Diagram showing production equipment for wrapping rubber ribbon Sectional drawing of the composite rubber ribbon in another embodiment (however, the form of (c) is not included in this invention ) Sectional drawing of the composite rubber ribbon in another embodiment

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  A pneumatic tire T shown in FIG. 1 includes a pair of bead portions 1, sidewall portions 2 extending outward in the tire radial direction from each of the bead portions 1, and tire radial direction outer ends of the sidewall portions 2. And a tread portion 3 connected to the front. The bead portion 1 is provided with an annular bead core 1a formed by covering a converging body such as a steel wire with rubber and a bead filler 1b made of hard rubber. A toroidal carcass layer 7 is provided between the pair of bead portions 1, and an inner liner rubber 5 for holding air pressure is provided inside the carcass layer 7.

  The tire T includes a rim strip rubber 4 that is provided outside the carcass layer 7 at the bead portion 1 and can contact a rim (not shown), and a sidewall rubber provided outside the carcass layer 7 at the sidewall portion 2. 9 and a tread rubber 10 provided outside the carcass layer 7 in the tread portion 3. On the inner side of the tread rubber 10 in the tire radial direction, there are provided a belt layer 6 constituted by a plurality of belt plies and a belt reinforcing layer 8 formed by covering a cord extending substantially in the tire circumferential direction with a topping rubber. ing.

  As shown in FIG. 2, the tread rubber 10 includes a cap portion 12 that constitutes a ground contact surface, and a base portion 11 that is provided on the inner side in the tire radial direction of the cap portion 12. In the pneumatic tire T of the present embodiment, a rubber member made of a rubber ribbon winding body is used for the tread portion 3, and specifically, the cap portion 12 is configured by the rubber ribbon winding body as shown in FIG. Yes. This rubber ribbon winding body is formed by spirally winding the rubber ribbon 20 of FIG. 4 along the tire circumferential direction.

  Next, a method for manufacturing the pneumatic tire T will be described. Since the pneumatic tire T can be manufactured in the same manner as the conventional tire manufacturing process except for the point related to the tread rubber 10, the description will focus on the tread rubber molding process.

  The tread rubber 10 is formed by forming the base portion 11 and then forming the cap portion 12 by a ribbon winding method. The ribbon winding method is a method of forming a rubber member by winding a small, unvulcanized rubber ribbon spirally in the tire circumferential direction. Therefore, as described above, the cap portion 12 is formed of a rubber ribbon winding body formed by winding the rubber ribbon 20 in a spiral shape.

  Although not expressed in FIG. 3, the rubber ribbon 20 is a composite rubber ribbon formed by co-extruding a plurality of types (two types in the present embodiment) of rubber. As shown in FIG. 4, the cross section of the composite rubber ribbon 20 when cut along a plane perpendicular to the length direction has a shape with a thickness t smaller than the width w, and the thickness gradually decreases toward both ends in the width direction WD. In addition, corners are provided at a plurality of locations including both ends thereof. The composite rubber ribbon 20 of the present embodiment is formed in a triangular cross section, and has a corner 20c on the top in addition to the corners 20a and 20b at both ends. The width w is set to 14 to 36 mm, for example, and the thickness t is set to 1.0 to 3.6 mm, for example.

  The composite rubber ribbon 20 includes a main body rubber 21 constituting the main body of the composite rubber ribbon 20 and a low-viscosity rubber 22 that constitutes at least one of the corner portions 20 a to 20 c and has a Mooney viscosity lower than that of the main body rubber 21. In order to facilitate distinction on the drawing, the low-viscosity rubber 22 is colored lightly in FIG. In the present embodiment, since the corners 20a, 20b at both ends of the composite rubber ribbon 20 are each constituted by the low viscosity rubber 22, the main rubber 21 is not exposed at both ends.

  The Mooney viscosity is a Mooney viscosity measured at 100 ° C. based on JISK6300. Specifically, in accordance with JISK6300-1: 2001, a Toyo Seiki Co., Ltd. rotaryless Mooney measuring machine is used. This refers to Mooney unit (M) when the vulcanized rubber is preheated at 100 ° C. for 1 minute and the torque value after 4 minutes is measured.

  The molding and winding of the composite rubber ribbon 20 can be performed using equipment as illustrated in FIG. This equipment includes a rubber ribbon supply device 30 capable of forming a composite rubber ribbon 20 by co-extrusion of two kinds of rubber, and a rotary support 31 as a wound body around which the composite rubber ribbon 20 supplied from the rubber ribbon supply device 30 is wound. And a control device 32 for controlling the operation of the rubber ribbon supply device 30 and the rotary support 31. The rotary support 31 is configured to be capable of rotating in the R direction around the shaft 31a and moving in the axial direction.

  The extruder 33 includes a hopper 33a, a screw 33b, a barrel 33c, a drive device 33d for the screw 33b, and a head portion 33e incorporating a gear pump. Similarly, the extruder 34 includes a hopper 34a, a screw 34b, a barrel 34c, a driving device 34d, and a head portion 34e. At the front ends of the pair of extruders 33 and 34, a rubber unit 35 to which a base 36 is attached is provided. A rubber channel having a shape corresponding to the cross-sectional shape of the composite rubber ribbon 20 shown in FIG. 4 is formed in the base 36.

  When the rubber material to be the main rubber 21 is put into the hopper 33a and the rubber material to be the low viscosity rubber 22 is put into the hopper 34a, each rubber is fed forward while being kneaded by the screws 33b and 34b, and the head portions 33e and 34e. Then, they are united in a predetermined shape at the rubber uniting part 35 and extruded as a composite rubber ribbon 20 from the discharge port 36a. The molded composite rubber ribbon 20 is fed forward by a roll 37 and wound around a rotary support 31 while being pressed by a roller 38.

  When forming the tread rubber 10, first, the base portion 11 is formed on the outer peripheral surface of the rotary support 31 using an extrusion method or a ribbon winding method. The extrusion molding method is a method of extruding an unvulcanized belt-like rubber member having a predetermined cross-sectional shape, and joining the end portions to form an annular shape. Subsequently, the composite rubber ribbon 20 is wound around the outer periphery of the formed base portion 11 to form a rubber ribbon wound body, thereby forming the cap portion 12 as shown in FIG. In the present embodiment, the composite rubber ribbon 20 adjacent in the width direction is wound while being partially overlapped, but is not limited thereto.

  The cross section of the composite rubber ribbon 20 has a shape with a thickness t smaller than the width w, and the thickness is gradually reduced toward both ends in the width direction WD, so that the air can be entered when forming the rubber ribbon wound body. Hard to wake up. In addition, since the corner portions 20a and 20b of the composite rubber ribbon 20 are constituted by the low-viscosity rubber 22, the corner portions 20a and 20b that the low-viscosity rubber 22 constitutes in the mold (die 36) at the time of extrusion molding. It is possible to reduce the flow velocity difference between the main body rubber 21 and other parts. As a result, it is possible to prevent the rubber at the corners from staying in the mold (the base 36) and prevent the composite rubber ribbon 20 from being cut off.

  After the molding process of the tread rubber 10, the process proceeds to the molding process of the green tire, the tread rubber 10 is bonded to the outer peripheral surface of the carcass layer 7 molded in a toroid shape, and the green tire is combined with other tire constituent members. Mold. Thereafter, the process proceeds to a vulcanization process of the green tire, and the pneumatic tire T shown in FIG. 1 is manufactured by vulcanizing the green tire. The composite rubber ribbon 20 can be specified in the tire cross section after the vulcanization treatment, and can be determined by, for example, the property of the rubber interface observed thinly in the cross section by cutting the tire with a sharp blade.

  The cross-sectional area of the main rubber 21 occupies 97% or more, preferably 98% or more of the cross-sectional area of the composite rubber ribbon 20. In securing the rigidity of the composite rubber ribbon 20, the cross-sectional area of the low-viscosity rubber 22 is preferably 3% or less of the cross-sectional area of the composite rubber ribbon 20, and more preferably 2% or less. Further, the surface of the composite rubber ribbon 20 is formed by the main body rubber 21 and the low-viscosity rubber 22, and in order to ensure the rigidity of the composite rubber ribbon 20, the low-viscosity rubber 22 is 60% of the outer peripheral length in the cross section of the composite rubber ribbon 20. It is preferable to form the following surface.

  In the present embodiment, the low-viscosity rubber 22 has a thin portion extending in the width direction WD between both ends of the composite rubber ribbon 20, and the thickness ta is, for example, 0.04 to 0.2 mm. The low-viscosity rubber 22 constituting the corner portions 20a and 20b has a thickness larger than that of the thin portion and forms the entire thickness of both ends of the composite rubber ribbon 20. The thickness tb is, for example, 0.1 to 0.5 mm. . The width wb of the low-viscosity rubber 22 constituting the corner portions 20a, 20b is, for example, 5 to 50%, preferably 5 to 20%, of the width w of the composite rubber ribbon 20.

  In order to ensure the effect of preventing the ear-cut, the difference between the Mooney viscosity of the main rubber 21 and the Mooney viscosity of the low-viscosity rubber 22 is preferably 2 to 10, and more preferably 3 to 7. The Mooney viscosity of the main rubber 21 is 55 to 75, and the Mooney viscosity of the low viscosity rubber 22 is 53 to 65.

6 and 7 are sectional views of a composite rubber ribbon in another embodiment of the present invention (however, the form of FIG. 6C is not included in the present invention) . Since these are the same configurations as those in the embodiment of FIG. 4 except for the configurations described below, the common points are omitted, and the differences are mainly described. The same parts as those already described are denoted by the same reference numerals, and redundant description is omitted.

  FIG. 6A shows an example in which the low-viscosity rubber 22 is disposed only at the corners 20a and 20b at both ends. FIG. 6B shows an example in which the low-viscosity rubber 22 is disposed only at the top corner 20c instead of the corners 20a and 20b at both ends. FIG. 6C shows an example in which the low-viscosity rubber 22 is disposed on the entire circumference of the ribbon including all the corners 20a to 20c. Also in these composite rubber ribbons 20, the corner portions are constituted by the low-viscosity rubber 22, so that the effect of preventing the ear cut is obtained.

  The composite rubber ribbon 20 having a triangular cross section as described above is suitable for winding the composite rubber ribbon 20 adjacent in the width direction in a partially overlapping manner, and is advantageous in reducing air entry. However, the cross-sectional shape of the composite rubber ribbon 20 is not limited to this, and other shapes such as a trapezoidal shape or an elliptical shape illustrated in FIG. 7 may be used. FIGS. 7A and 7B are examples in which the corners 20 a and 20 b at both ends are each formed of a low-viscosity rubber 22.

  The rubber member formed of the rubber ribbon wound body is not limited to the cap portion 12 constituting the tread rubber 10 and may be another rubber member. Therefore, it is possible to form a tread rubber base, a rim strip rubber, a side wall rubber, and the like by winding the composite rubber ribbon as described above.

  The present invention is not limited to the embodiment described above, and various improvements and modifications can be made without departing from the spirit of the present invention.

DESCRIPTION OF SYMBOLS 1 Bead part 2 Side wall part 3 Tread part 10 Tread rubber 11 Base part 12 Cap part 20 Composite rubber ribbon 20a Corner part 20b Corner part 20c Corner part 21 Main body rubber 22 Low viscosity rubber

Claims (6)

In a pneumatic tire manufacturing method of forming a rubber ribbon winding body by spirally winding a rubber ribbon around a body to be wound, and manufacturing a pneumatic tire using a rubber member made of the rubber ribbon winding body,
The rubber ribbon wound around the wound body is a composite rubber ribbon formed by coextruding a plurality of types of rubber,
The cross-section of the composite rubber ribbon when cut along a plane perpendicular to the length direction is a shape having a thickness smaller than the width, and the thickness is gradually reduced toward both ends in the width direction, and a plurality of parts including the both ends are included. Has a corner in the place,
The composite rubber ribbon includes a main body rubber that is a main component of the composite rubber ribbon, and a low-viscosity rubber whose Mooney viscosity measured at 100 ° C. based on JIS K6300 is lower than the main body rubber ,
The method of manufacturing a pneumatic tire, wherein the composite rubber ribbon has a triangular cross section, and only a corner portion of the top is made of the low viscosity rubber . In a pneumatic tire manufacturing method of forming a rubber ribbon winding body by spirally winding a rubber ribbon around a body to be wound, and manufacturing a pneumatic tire using a rubber member made of the rubber ribbon winding body,
The rubber ribbon wound around the wound body is a composite rubber ribbon formed by coextruding a plurality of types of rubber,
The cross-section of the composite rubber ribbon when cut along a plane perpendicular to the length direction is a shape having a thickness smaller than the width, and the thickness is gradually reduced toward both ends in the width direction, and a plurality of parts including the both ends are included. Has a corner in the place,
The composite rubber ribbon includes a main body rubber that is a main component of the composite rubber ribbon, and a low-viscosity rubber whose Mooney viscosity measured at 100 ° C. based on JISK6300 is lower than the main body rubber,
The corners only at the ends of the composite rubber ribbon pneumatic tire manufacturing method which is characterized in that it is constituted by each of the low-viscosity rubber.   The method for producing a pneumatic tire according to claim 1 or 2, wherein a difference between the Mooney viscosity of the main rubber and the Mooney viscosity of the low-viscosity rubber is 2 to 10. In a pneumatic tire having a rubber member formed of a rubber ribbon wound body formed by spirally winding a rubber ribbon,
The rubber ribbon is a composite rubber ribbon obtained by coextruding a plurality of types of rubber,
The cross-section of the composite rubber ribbon when cut along a plane perpendicular to the length direction is a shape having a thickness smaller than the width, and the thickness is gradually reduced toward both ends in the width direction, and a plurality of parts including the both ends are included. Has a corner in the place,
The composite rubber ribbon includes a main body rubber that is a main component of the composite rubber ribbon, and a low-viscosity rubber whose Mooney viscosity measured at 100 ° C. based on JIS K6300 is lower than the main body rubber ,
A pneumatic tire characterized in that the composite rubber ribbon has a triangular cross-section, and only the top corner of the ribbon is made of the low-viscosity rubber . In a pneumatic tire having a rubber member formed of a rubber ribbon wound body formed by spirally winding a rubber ribbon,
The rubber ribbon is a composite rubber ribbon obtained by coextruding a plurality of types of rubber,
The cross-section of the composite rubber ribbon when cut along a plane perpendicular to the length direction is a shape having a thickness smaller than the width, and the thickness is gradually reduced toward both ends in the width direction, and a plurality of parts including the both ends are included. Has a corner in the place,
The composite rubber ribbon includes a main body rubber that is a main component of the composite rubber ribbon, and a low-viscosity rubber whose Mooney viscosity measured at 100 ° C. based on JISK6300 is lower than the main body rubber,
Only the corners at both ends of the composite rubber ribbon are each made of the low-viscosity rubber. The pneumatic tire according to claim 4 or 5 , wherein a rubber member made of the rubber ribbon winding body is used at least in a tread portion.

Images