Patent Publication Number: US-2021178713-A1

Title: Manufacturing device and manufacturing method for pneumatic tire

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority of Japanese Patent Application No.: 2019-225698 filed on Dec. 13 2019, the content of which is incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     Technical Field 
     The present invention relates to a manufacturing device and a manufacturing method for a pneumatic tire. 
     Related Art 
     A carcass ply of a pneumatic tire disclosed in Japanese Patent No. 5629356 includes a first ply that is continuous between a pair of bead portions and a discontinuous second ply that is disposed on the outer side in the tire radial direction of the first ply. The second ply includes a pair of ply pieces extending from a tread portion to one of a pair of the bead portions. In the center of the tread portion, a region where neither of the two ply pieces exists, that is, a hollow portion is provided. The hollow portion of the second ply is intended to have two contradictory types of performance. One type of performance is rigidity (which contributes to improving steering stability) and cut resistance, and the other type of performance is weight reduction and rolling resistance reduction by the weight reduction. 
     SUMMARY 
     The structure disclosed in Japanese Patent No. 5629356 can achieve the weight reduction and rolling resistance reduction by the weight reduction while ensuring rigidity and cut resistance. However, Japanese Patent No. 5629356 does not mention uniformity in the tire circumferential direction, and there is room for improvement regarding improvement in the uniformity in the tire circumferential direction. Further, when a pneumatic tire is manufactured, it is desired to manufacture the tire with excellent productivity. 
     An object of the present invention is to provide a manufacturing device and a manufacturing method for a pneumatic tire capable of manufacturing a pneumatic tire with excellent productivity while improving uniformity in the tire circumferential direction. 
     The present invention provides a manufacturing device for a pneumatic tire including a carcass ply stretching between a pair of bead cores disposed on both sides in a tire width direction, the carcass ply including a pair of ply pieces disposed separately on both sides in the tire width direction. The manufacturing device includes a molding drum, a drum drive device that rotationally drives the molding drum, a first supply device that supplies one ply piece of the pair of ply pieces to the molding drum, a second supply device that supplies the other ply piece of the pair of ply pieces to the molding drum, and a control device that controls operation of the drum drive device, the first supply device, and the second supply device so that the one and the other ply pieces are simultaneously supplied to the molding drum while the molding drum is rotationally driven, and two joint portions in which both end portions in a tire circumferential direction of the one and the other ply pieces are joined in a manner overlapping each other are provided at different positions in the tire circumferential direction. 
     By the present configuration, in the pneumatic tire, in a case where the carcass ply includes a pair of the ply pieces disposed separately on both sides in the tire width direction, the two joint portions of a pair of the ply pieces are provided at different positions in the tire circumferential direction. For this reason, as compared with the case where the two joint portions are provided at the same position in the tire circumferential direction, the joint portions are dispersed in the tire circumferential direction and uniformity in the tire circumferential direction of the pneumatic tire can be improved. 
     The joint portion of the ply piece has increased rigidity as compared with the non-joint portion of the ply piece. For this reason, the joint portion of the ply piece is less likely to bulge and deform than the non-joint portion when the tire is filled with internal pressure and bulged and deformed. Therefore, the joint portion of the ply piece may appear as a dent in the pneumatic tire. 
     By providing the two joint portions of a pair of the ply pieces at different positions in the tire circumferential direction, the dents caused by the two joint portions are dispersed in the tire circumferential direction and uniformity in the tire circumferential direction can be improved as compared with the case where the two joint portions are provided at the same position in the tire circumferential direction. 
     In the manufacturing of the pneumatic tire, the one and the other ply pieces are simultaneously supplied to the molding drum while the molding drum is rotationally driven, so that the supply time for supplying the one and the other ply pieces to the molding drum can be shortened and the manufacturing can be performed with excellent productivity, as compared with the case where the one and the other ply pieces are sequentially supplied to the molding drum. Therefore, the pneumatic tire can be manufactured with excellent productivity while the uniformity in the tire circumferential direction is improved. 
     The carcass ply includes the first ply including the central portion positioned on the inner side in the tire radial direction of the tread portion and a pair of the side portions extending to the inner side in the tire radial direction from both ends of the central portion, and the second ply having a pair of the ply pieces including the inner end portion disposed on the outer side in the tire radial direction with respect to the first ply and positioned in the tread portion and the side portion extending to the inner side in the tire radial direction from the inner end portion. The one and the other ply pieces of the second ply are supplied on the first ply wound around the molding drum. 
     The second ply on the first ply includes a pair of the ply pieces and is discontinuous. That is, between the inner end portions of a pair of the ply pieces, there is a hollow portion in which no ply exists. By employing the second ply having the hollow portion, the weight can be reduced as compared with the case where the second ply is one continuous ply. Further, rolling resistance can be reduced by weight reduction. 
     In the sidewall portion, two layers of plies, that is, the side portion of the first ply and the side portion of the ply piece of the second ply are disposed. By providing two layers of plies in the sidewall portion in this way, necessary cut resistance is ensured. Further, since plies are provided in two layers, necessary rigidity in the sidewall portion is ensured. 
     Therefore, it is possible to achieve weight reduction and reduction in rolling resistance due to the weight reduction while ensuring the rigidity and the steering stability due to the rigidity and the cut resistance, and, in addition, to manufacture the pneumatic tire with excellent productivity while achieving improvement in uniformity in the tire circumferential direction. 
     The first supply device preferably supplies the one ply piece to which a joining tape to be joined to the first ply is attached, and the second supply device preferably supplies the other ply piece to which a joining tape to be joined to the first ply is attached. 
     By the present configuration, the one and the other ply pieces of the second ply to which the joining tape is attached are supplied on the first ply, so that the first ply and the second ply can be joined strongly by the joining tape. 
     Further, the first supply device and the second supply device supply one and the other one of the ply pieces to the molding drum from the upper side and the lower side, respectively, and the control device controls operation of the drum drive device, the first supply device, and the second supply device so that the two joint portions of one and the other one of the ply pieces are provided at positions different by 180 degrees in the tire circumferential direction. 
     By the present configuration, one and the other one of the ply pieces are supplied to the molding drum from the upper side and the lower side, respectively, and the two joint portions are provided at positions different by 180 degrees in the tire circumferential direction, so that the two joint portions can be effectively dispersed in the tire circumferential, and the pneumatic tire can be manufactured with excellent productivity while the uniformity in the tire circumferential is improved. 
     The second supply device may include the holding portion that is disposed below the molding drum and holds the other one of the ply pieces, and the holding portion moving mechanism that moves the holding portion in the vertical direction. The holding portion holding the other one of the ply pieces may be moved to the upper side by the holding portion moving mechanism to supply the other one of the ply pieces to the molding drum. 
     By the present configuration, in a case where the other one of the ply pieces of the second ply is supplied to the molding drum from the lower side, the other one of the ply pieces is moved upward while being held by the holding portion and supplied to the molding drum. Accordingly, the other one of the ply pieces can be stably supplied to the molding drum. 
     The present invention also provides a manufacturing method for a pneumatic tire including a carcass ply stretching between a pair of bead cores disposed on both sides in a tire width direction, the carcass ply including a pair of ply pieces disposed separately on both sides in the tire width direction. The manufacturing method includes rotationally driving a molding drum, supplying one ply piece of the pair of ply pieces to the molding drum, and supplying the other ply piece of the pair of ply pieces to the molding drum, in which the one and the other ply pieces are simultaneously supplied to the molding drum while the molding drum is rotationally driven, so that two joint portions in which both end portions in a tire circumferential direction of the one and the other ply pieces are joined in a manner overlapping each other are provided at different positions in the tire circumferential direction. 
     By the present configuration, in the pneumatic tire, in a case where the carcass ply includes a pair of the ply pieces disposed separately on both sides in the tire width direction, the two joint portions of a pair of the ply pieces are provided at different positions in the tire circumferential direction. For this reason, as compared with the case where the two joint portions are provided at the same position in the tire circumferential direction, the joint portions are dispersed in the tire circumferential direction and uniformity in the tire circumferential direction of the pneumatic tire can be improved. 
     The joint portion of the ply piece has increased rigidity as compared with the non-joint portion of the ply piece. For this reason, the joint portion of the ply piece is less likely to bulge and deform than the non-joint portion when the tire is filled with internal pressure and bulged and deformed. Therefore, the joint portion of the ply piece may appear as a dent in the pneumatic tire. 
     By providing the two joint portions of a pair of the ply pieces at different positions in the tire circumferential direction, the dents caused by the two joint portions are dispersed in the tire circumferential direction and uniformity in the tire circumferential direction can be improved as compared with the case where the two joint portions are provided at the same position in the tire circumferential direction. 
     In the manufacturing of the pneumatic tire, the one and the other ply pieces are simultaneously supplied to the molding drum while the molding drum is rotationally driven, so that the supply time for supplying the one and the other ply pieces to the molding drum can be shortened and the manufacturing can be performed with excellent productivity, as compared with the case where the one and the other ply pieces are sequentially supplied to the molding drum. Therefore, the pneumatic tire can be manufactured with excellent productivity while the uniformity in the tire circumferential direction is improved. 
     According to the manufacturing device and the manufacturing method for a pneumatic tire according to the present invention, a pneumatic tire can be manufactured with excellent productivity while uniformity in the tire circumferential direction is improved. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing and the other features of the present invention will become apparent from the following description and drawings of an illustrative embodiment of the invention in which: 
         FIG. 1  is a meridian cross-sectional view of a pneumatic tire according to an embodiment of the present invention; 
         FIG. 2  is a meridian cross-sectional view of a tread portion of the pneumatic tire according to the embodiment of the present invention and its surroundings; 
         FIG. 3  is an enlarged view of Part III of  FIG. 1 ; 
         FIG. 4  is an enlarged view of Part IV of  FIG. 1 ; 
         FIG. 5  is a cross-sectional view of a first ply of a carcass ply along line V-V of  FIG. 2 ; 
         FIG. 6  is a cross-sectional view of a second ply of the carcass ply along lines VIa-VIa and VIb-VIb of  FIG. 2 ; 
         FIG. 7  is a schematic side view of a pneumatic tire for explaining a joint portion of the carcass ply; 
         FIG. 8  is an explanatory diagram for explaining a manufacturing method for a pneumatic tire; and 
         FIG. 9  is a schematic diagram of a manufacturing device for a pneumatic tire. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       FIGS. 1 to 4  show a pneumatic tire  1  made from rubber according to an embodiment of the present invention. 
     The pneumatic tire  1  includes a tread portion  2 , a pair of sidewall portions  3 , and a pair of ring-shaped bead portions  4 . 
     The tread portion  2  extends in the tire width direction (indicated by the reference numeral TW in  FIG. 1 ). A groove  2   a  is provided on the surface, that is, the tread surface of the tread portion  2 . 
     Each of a pair of the sidewall portions  3  extends from both ends in the tire width direction of the tread portion  2  to the inner side in the tire radial direction (reference numeral TR in  FIG. 1 ). 
     A pair of the bead portions  4  are disposed on both sides in the tire width direction and disposed in end portions on the inner side in the tire radial direction of a pair of the sidewall portions  3 . Each of the bead portions  4  includes a bead core  5  and a bead filler  6 . The bead core  5  includes a large number of steel wires bundled in a ring shape. The bead filler  6  has a ring shape and is made from rubber that is harder than rubber that constitutes the tread portion  2  and the sidewall portion  3 . The bead filler  6  includes a base end  6   a  disposed adjacent to the outer side in the tire radial direction of the bead core  5  and a tip end  6   b  on the side opposite to the base end  6   a,  and extends in a tapered shape from the base end  6   a  to the outer side in the tire radial direction toward the tip end  6   b.  Each of the bead portions  4  includes strip rubber  7  provided to wrap the bead core  5  and the bead filler  6 . 
     The pneumatic tire includes a carcass ply  10  stretching in a toroidal shape between the bead portions  4 . In the present embodiment, the carcass ply  10  includes a first carcass ply (hereinafter, referred to as “first ply”)  11  and a second carcass ply (hereinafter, referred to as “second ply”)  12 . The second ply  12  is a ply having a hollow portion  13   c,  while the first ply  11  is a normal ply having no hollow portion. The first and second plies  11  and  12  will be described in detail later. An inner liner  8  is provided on the inner side of the carcass ply  10 , that is, on the innermost peripheral surface of the pneumatic tire. 
     With reference to  FIGS. 2 and 3 , an endless belt layer  20  is provided on the tread portion  2 , more specifically, between the carcass ply  10  and the tread portion  2 . In the present embodiment, the belt layer  20  includes two belts  21  and  22 . The belt  21  is disposed adjacent to the outer side in the tire radial direction of the carcass ply  10 , and the belt  22  is disposed adjacent to the outer side in the tire radial direction of the belt  21 . Further, in the present embodiment, the dimension in the tire width direction of the belt  21  in the lower layer is larger than the dimension in the tire width direction of the belt  22  in the upper layer, and an end portion  21   a  of the belt  21  is positioned closer to the outer side in the tire width direction than an end portion  22   a  of the belt  22 . The belts  21  and  22  are formed by covering a belt cord made from steel or organic fiber with rubber. The belt layer  20  may be composed of one belt, or may include three or more belts. 
     An endless cap layer  30  is provided adjacent to the outer side in the tire radial direction of the belt layer  20 . The cap layer  30  of the present embodiment includes a pair of narrow edge plies  31  that directly cover either of the end portions  21   a  and  22   a  of the belts  21  and  22 . Further, the cap layer  30  of the present embodiment includes a wide cap ply  32 , which is disposed adjacent to the outer side in the tire radial direction of the edge ply  31 , as a single sheet that covers the entire belts  21  and  22  including the end portions  21   a  and  22   a.  The cap layer  30  may include one ply or three or more plies. Further, the cap layer  30  may be eliminated. 
     A pair of endless pads  40  made from rubber are disposed between both end portions on the outer side in the tire width direction of the belt layer  20  and the carcass ply  10 . The cross-sectional shape of the pad  40  is a flat triangular shape. The positions in the tire width direction of the end portions  21   a  and  22   a  of the belts  21  and  22 , the end portion  31   a  on the outer side in the tire width direction of the edge ply  31 , and an end portion  32   a  of the cap ply  32  are set in a region between an end portion  40   a  on the outer side in the tire width direction of the pad  40  and an end portion  40   b  on the inner side, that is, a region where the pad  40  exists. The pad  40  may be eliminated. 
     The first and second plies  11  and  12  constituting the carcass ply  10  will be described. 
     The first ply  11  is a single ply, whereas the second ply  12  is a discontinuous ply having the hollow portion  13   c  as described above, and is composed of a pair of ply pieces  13 . As will be described later, the first ply  11  and a pair of the ply pieces  13  are joined by a joining tape (joining member)  14 . All of the first ply  11  and the ply pieces  13  of the second ply  12  are a strip-shaped sheet in which a plurality of cords arranged in parallel at intervals are covered with rubber. 
     The first ply  11  and the ply pieces  13  of the second ply  12  may have the same modulus (stress generated when a constant strain is applied) or may have different moduli. Further, the first ply  11  and the ply pieces  13  of the second ply  12  may have the same breaking strength (tensile load at which breaking occurs) or may have different breaking strengths. 
     The first ply  11  includes a central portion  11   a  positioned on the inner side in the tire radial direction of the tread portion  2 , and a pair of side portions  11   b  extending from both ends in the tire width direction of the central portion  11   a  to the inner side in the tire radial direction. A pair of the side portions  11   b  are similarly configured. The side portion  11   b  is disposed in the sidewall portion  3 . The individual side portions  11   b  of the first ply  11  include an end portion  11   c  that terminates on the outer side in the tire radial direction of the bead core  5 . In other words, the first ply  11  is not wound up with respect to the bead core  5 . 
     In the present embodiment, the end portion  11   c  of the side portion  11   b  of the first ply  11  is positioned closer to the inner side in the tire radial direction than the tip end  6   b  of the bead filler  6  and closer to the outer side in the tire radial direction than the base end  6   a  of the bead filler  6 . That is, the side portion  11   b  of the first ply  11  overlaps the bead filler  6 . 
     The second ply  12  is disposed adjacent to the outer side in the tire radial direction of the first ply  11 , and is a discontinuous ply composed of a pair of the ply pieces  13  disposed separately on both sides in the tire width direction. A pair of the ply pieces  13  are configured similarly except for the positions of joint portions J 2  and J 3 , which will be described later. The ply piece  13  has the inner end portion  13   a  disposed between the belt layer  20  and the central portion  11   a  of the first ply  11 . The pad  40  is interposed between the inner end portion  13   a  and the belt layer  20 . The position in the tire width direction of the inner end portion  13   a  of the ply piece  13  is set in the region on the outer side in the tire width direction of the tread portion  2 , more specifically, in the region closer to the inner side in the tire width direction than both the end portions  21   a  and  22   a  of the belts  21  and  22  constituting the belt layer  20 . The hollow portion  13   c  is provided in the region at the center in the tire width direction of the tread portion  2 , more specifically, in the region between the inner end portions  13   a  of a pair of the ply pieces  13 . In the hollow portion  13   c,  the second ply  12  does not exist, and only the central portion  11   a  of the first ply  11  exists. 
     The ply piece  13  includes a side portion  13   b  extending to the inner side in the tire radial direction from the inner end portion  13   a.  The side portion  13   b  is disposed adjacent to the outer side in the tire width direction of the side portion  11   b  of the first ply  11 . 
     The ply piece  13  includes a wind-up portion  13   d  provided continuously with the side portion  13   b  and wound up from the inner side to the outer side in the tire width direction with respect to the bead core  5 . The wind-up portion  13   d  is terminated in the sidewall portion  3 . 
     The wind-up portion  13   d  of the ply piece  13  includes an inner portion  13   e  disposed closer to the inner side in the tire width direction than the bead portion  4 , that is, the bead core  5  and the bead filler  6 . Further, the wind-up portion  13   d  includes a winding portion  13   f  which is provided continuously with the inner portion  13   e  and is wound around the bead core  5 . Further, the wind-up portion  13   d  includes an outer portion  13   g  which is provided continuously with the winding portion  13   f  and is disposed closer to the outer side in the tire width direction than the bead portion  4 . The outer portion  13   g  is disposed so as to overlap the outer side in the tire radial direction of the side portion  13   b.  An end portion of the outer portion  13   g  constitutes an outer end portion  13   h  of the ply piece  13 . The outer end portion  13   h  is positioned closer to the outer side in the tire radial direction than the tip end  6   b  of the bead filler  6  and is positioned closer to the inner side in the tire radial direction than the tread portion  2 . 
     The pneumatic tire  1  includes a pair of joining tapes  14  that join either one of a pair of the side portions  11   b  of the first ply  11  to the wind-up portion  13   d  of either one of a pair of the ply pieces  13 , more specifically, the inner portion  13   e.  As most clearly shown in  FIG. 4 , the joining tape  14  joins a portion including the end portion  11   c  of the side portion  11   b  of the first ply  11  to the inner portion  13   e  of the wind-up portion  13   d  of the ply piece  13 . 
     The joining tape  14  is made from rubber and preferably has an adhesive strength of 500 gf or more in order to secure the joining strength of the first ply  11  to the second ply  12 . 
     An end portion  14   a  on the outer side in the tire radial direction of the joining tape  14  is positioned closer to the outer side in the tire radial direction than the tip end  6   b  of the bead filler  6 . The position in the tire radial direction of an end portion  14   b  on the inner side in the tire radial direction of the joining tape  14  is set between the base end  6   a  and the tip end  6   b  of the bead filler  6 . 
     The end portion  11   c  of the first ply  11  is positioned between the end portion  14   b  on the inner side and the end portion  14   b  on the outer side in the tire width direction of the joining tape  14 . 
     The pneumatic tire  1  according to the present embodiment will be further described with reference to  FIGS. 5 to 7 . 
       FIG. 5  shows a cross section of the first ply  11  of the carcass ply  10 . As shown in  FIG. 5 , the first ply  11  of the carcass ply  10  is wound in a cylindrical shape, and one end portion  11   d  and the other end portion  11   e  are joined in a manner overlapping each other. A joint portion J 1  in which the one end portion  11   d  and the other end portion  11   e , which are both end portions in the circumferential direction of the first ply  11 , are joined in a manner overlapping each other, is formed to be thicker than a non-joint portion  11   f  excluding the joint portion J 1  of the first ply  11 . 
     Each of a pair of the ply pieces  13  of the second ply  12  of the carcass ply  10  is also wound in a cylindrical shape in a similar manner to the first ply  11 , and one end portion and the other end portion are joined in a manner overlapping each other. A joint portion in which the one end portion and the other end portion, which are both end portions in the circumferential direction of the ply piece  13 , are joined in a manner overlapping each other, is formed to be thicker than a non-joint portion excluding the joint portion of the ply piece  13 . 
       FIG. 6  shows a cross section of the second ply  12  of the carcass ply  10 , and specifically shows a cross section of a pair of the ply pieces  13 . In  FIG. 6 , cross sections of one and the other one of the ply pieces  13  along lines VIa-VIa and VIb-VIb of  FIG. 2  are indicated by reference numerals  13 A and  13 B. 
     As shown in  FIG. 6 , the one ply piece  13 A is wound in a cylindrical shape, and one end portion  13   j  and the other end portion  13   k  are joined in a manner overlapping each other. The joint portion J 2  in which the one end portion  13   j  and the other end portion  13   k,  which are both end portions in the circumferential direction of the ply piece  13 A, are joined in a manner overlapping each other, is formed to be thicker than a non-joint portion  13   m  excluding the joint portion J 2  of the ply piece  13 A. 
     As shown in  FIG. 6 , the other ply piece  13 B is also wound in a cylindrical shape, and the one end portion  13   j  and the other end portion  13   k  are joined in a manner overlapping each other. The joint portion J 3  in which the one end portion  13   j  and the other end portion  13   k,  which are both end portions in the circumferential direction of the ply piece  13 B, are joined in a manner overlapping each other, is formed to be thicker than the non-joint portion  13   m  excluding the joint portion J 3  of the ply piece  13 B. 
     In  FIG. 7 , the joint portion of the first ply  11  is indicated by a broken line as J 1 , the joint portion of the one ply piece  13 A of the second ply  12  is indicated by a broken line as J 2 , and the joint portion of the other ply piece  13 B of the second ply  12  is shown by a broken line as J 3 . As shown in  FIG. 7 , the two joint portions J 2  and J 3  of a pair of the ply pieces  13  of the second ply  12  are provided at different positions in the tire circumferential direction TC, specifically, positions different by 180 degrees in the tire circumferential direction, which are on opposite sides in the tire circumferential direction. 
     The two joint portions J 2  and J 3  of the second ply  12  are provided at different positions in the tire circumferential direction from the joint portion J 1  of the first ply  11 . The two joint portions J 2  and J 3  of the second ply  12  are provided at positions different by 90 degrees in the tire circumferential direction from the joint portion J 1  of the first ply  11 . 
     As shown in  FIG. 7 , assuming that the position in the tire circumferential direction of the joint portion J 2  of one of the ply pieces  13  of the second ply  12  around the axial direction of the pneumatic tire  1  is at 0 degrees, the joint portion J 3  of the other one of the ply pieces  13  of the second ply  12  is provided so that a position θ 1  in the tire circumferential direction is at 180 degrees, and the joint portion J 1  of the first ply  11  is provided so that a position  92  in the tire circumferential direction is at 270 degrees. The first ply  11  and a pair of the ply pieces  13  of the second ply  12  are provided with the joint portions J 1 , J 2 , and J 3  dispersed in the tire circumferential direction. 
     As shown in  FIG. 5 , the position in the tire circumferential direction of the joint portion J 1  of the first ply  11  refers to an angular position of a center line L 1  extending in the tire radial direction of the joint portion J 1 , and the center line L 1  is a straight line that passes through the center of the tire and divides the joint portion J 1  into two equal parts in the tire circumferential direction. The positions in the tire circumferential direction of the two joint portions J 2  and J 3  of a pair of the ply pieces  13  of the second ply  12  are also set in a similar manner to the first ply  11 . 
     The joint portion J 1  of the first ply  11  is preferably at a predetermined angle, for example, within an angle within 2 degrees, on one side and the other side in the tire circumferential direction with respect to the center line L 1  of the joint portion J 1 . However, the configuration is not limited to this. The joint portions J 2  and J 3  of the second ply  12  are also preferably at a predetermined angle, for example, within an angle within 2 degrees, on one side and the other side in the tire circumferential direction with respect to center lines L 2  and L 3  of the joint portions J 2  and J 3 . However, the configuration is not limited to this. 
     The two joint portions J 2  and J 3  of the second ply  12 , which are provided at positions 180 degrees different from each other in the tire circumferential direction and are provided point-symmetrically in the tire circumferential direction, may be provided at different positions other than positions different by 180 degrees. Further, the two joint portions J 2  and J 3  of the second ply  12 , which are provided at positions 90 degrees different from the joint portion J 1  of the first ply  11  in the tire circumferential direction, may be provided at different positions other than positions different by 90 degrees. 
     Next, a manufacturing method of the pneumatic tire  1  configured in this way will be described. 
     When manufacturing the pneumatic tire  1 , first, tire components for molding a cylindrical tread band, such as the tread rubber  2   b  constituting the tread portion  2  and the belts  21  and  22 , are prepared. On the other hand, tire components for molding a cylindrical carcass band, such as the carcass ply  10  that includes the first ply  11  and the second ply  12  and is stretched between a pair of the bead cores  5  and the inner liner  8 , are prepared. 
     Then, tire components such as the inner liner  8  and the carcass ply  10  are wound around a molding drum to mold a cylindrical carcass band. In the molding of the carcass band, the first ply  11  is supplied to the molding drum and the first ply  11  is wound in a cylindrical shape, and the joint portion J 1  in which both the end portions  11   d  and  11   e  in the circumferential direction of the first ply  11  are joined in a manner overlapping each other is formed. 
     Next, one of the ply pieces  13  of the second ply  12  is supplied to the molding drum and wound in a cylindrical shape and the joint portion J 2  in which both end portions in the circumferential direction of the one of the ply pieces  13  are joined in a manner overlapping each other is formed, and the other one of the ply pieces  13  of the second ply  12  is supplied to the molding drum and wound in a cylindrical shape and the joint portion J 3  in which both end portions in the circumferential direction of the other one of the ply pieces  13  are joined in a manner overlapping each other is formed. One and the other one of the ply pieces  13  of the second ply  12  disposed separately in the tire width direction are simultaneously supplied and wound by using a manufacturing device  50  for a pneumatic tire described later. 
     As shown in  FIG. 8 , a molding drum  51  around which a pair of the ply pieces  13  of the second ply  12  are wound is rotationally driven, the one ply piece  13 A is supplied to the molding drum  51  from the upper side, and the other ply piece  13 B is supplied to the molding drum  51  from the lower side. The one and the other ply pieces  13 A and  138  are simultaneously supplied to the molding drum  51  and wound so that the two joint portions J 2  and J 3 , which are joined as both end portions in the tire circumferential direction overlap each other, are provided at different positions in the tire circumferential direction. 
     The one and the other ply pieces  13 A and  13 B are simultaneously supplied to and wound around the molding drum  51 , specifically the first ply  11  wound around the molding drum  51 . Although not shown, the joining tape  14  for joining to the first ply  11  is attached to each of the one and the other ply pieces  13 A and  138 . The one and the other ply pieces  13 A and  138  are simultaneously supplied to the molding drum  51  and wound with the joining tape  14  attached. 
     When the carcass band is molded, the carcass band is transferred to another molding drum, and, after that, the bead core  5  and bead filler  6  are assembled on both side portions of the carcass band, and the carcass band is folded back on both sides in the drum width direction around the bead core  5 , so that a cylindrical green case is molded. 
     On the other hand, tire components such as a belt and tread rubber are further wound around another molding drum to mold a cylindrical tread band. Then, after the tread band is transported to the outer side in the radial direction of the green case, the green case is bulged in a toroidal shape to the outer side in the radial direction, the outer surface of the green case is bonded to the inner surface of the tread band, and a carcass tread bond body is molded. 
     Next, a pair of sidewall rubbers  9  are wound around the carcass tread bond body to mold a green tire. The molded green tire is vulcanized and molded by a vulcanization molding machine (not shown) including a tire vulcanization mold, and the pneumatic tire  1  is manufactured. 
     A pair of the sidewall rubbers  9  are wound and molded after the carcass tread bond body is molded. However, it is also possible to wind and mold the sidewall rubber  9  when the carcass band is molded. 
     In the present embodiment, the second ply  12  includes the wind-up portion  13   d  wound up with respect to the bead core  5 , and, although the first ply  11  is not wound up with respect to the bead core  5 , the first ply  11  can include a wind-up portion that is wound up with respect to the bead core  5 . Further, both the first ply  11  and the second ply  12  may include a wind-up portion wound up with respect to the bead core  5 . 
     The manufacturing device for a pneumatic tire according to the present embodiment will be described with reference to  FIG. 9 . 
     As shown in  FIG. 9 , the manufacturing device  50  for a pneumatic tire for manufacturing a pneumatic tire molds a cylindrical carcass band by winding tire components such as the inner liner  8  and the carcass ply  10  sequentially, specifically, winds the second ply  12  of the carcass ply  10  around the first ply  11 . 
     The manufacturing device  50  includes the molding drum  51  around which a pair of the ply pieces  13  of the second ply  12  are wound, a drum drive device  52  for rotationally driving the molding drum  51 , a first supply device  60  that supplies one of the ply pieces  13  to the molding drum  51 , and a second supply device  70  that supplies the other one of the ply pieces  13  to the molding drum  51 . 
     Tire components such as the inner liner  8  and the first ply  11  of the carcass ply  10  disposed on the inner side in the tire radial direction of the second ply  12  are wound around the molding drum  51  before a pair of the ply pieces  13  of the second ply  12  are wound. 
     As the drum drive device  52 , a motor  52  that rotationally drives the molding drum  51  is used. As the drum drive device  52 , it is also possible to use another drum drive device that rotationally drives the molding drum  51  instead of the motor. 
     The first supply device  60  includes a servicer  61  that supplies the one ply piece  13 A to the molding drum  51  from the upper side, and a guide portion  62  that guides the one ply piece  13 A. The first supply device  60  has a configuration in which the one ply piece  13 A supplied from the servicer  61  is guided by the guide portion  62  and supplied to the molding drum  51  from the upper side. 
     The second supply device  70  includes a servicer  71  that supplies the other ply piece  13 B to the molding drum  51  from the lower side, and a guide portion  72  that guides the other ply piece  13 B. The second supply device  70  also includes a holding portion  75  that holds the other ply piece  13 B supplied from the servicer  71 , and a holding portion moving mechanism  76  that moves the holding portion  75  in the vertical direction. 
     As the holding portion moving mechanism  76 , a cylinder  76  configured to be able to move the holding portion  75  in the vertical direction is used. As the holding portion moving mechanism  76 , it is also possible to use another holding portion moving mechanism that moves the holding portion  75  in the vertical direction instead of the cylinder. 
     The second supply device  70  has a configuration, in which the other ply piece  13 B supplied from the servicer  71  is guided by the guide portion  72  and supplied to the upper surface of the holding portion  75  at the lower side position shown by the solid line in  FIG. 9 . The holding portion  75  holding the other ply piece  13 B is moved by the cylinder  76  to the upper side position shown by the alternate long and short dash line in  FIG. 9 , and the other ply piece  13 B is supplied to the molding drum  51  from the lower side. The joining tape  14  is attached to each of the one and the other ply pieces  13 . 
     The manufacturing device  50  includes a control device  80  that controls the operation of the drum drive device  52 , the first supply device  60 , the second supply device  70 , and the like. The control device  80  controls the operation of the motor  52  as the drum drive device  52 , the servicer  61  of the first supply device  60 , the servicer  71  of the second supply device  70 , the cylinder  76 , and the like. The control device  80  is configured with, for example, a microcomputer as a main part. 
     The control device  80  controls operation of the drum drive device  52 , the first supply device  60 , and the second supply device  70  so that the one and the other ply pieces  13 A and  13 B are supplied simultaneously to the molding drum  51  while the molding drum  51  is rotationally driven, and the two joint portions J 2  and J 3  where both end portions in the tire circumferential direction of the one and the other ply pieces  13 A and  13 B are joined in a manner overlapping each other are provided at different positions in the tire circumferential direction TC. 
     The control device  80  causes the first supply device  60  to supply the one ply piece  13 A from the upper side to the molding drum  51 , specifically, the molding drum  51  around which the first ply  11  is wound. The control device  80  also causes the second supply device  70  to supply the other ply piece  13 B from the lower side to the molding drum  51 , specifically, the molding drum  51  around which the first ply  11  is wound. A tip end portion of the one ply piece  13 A and a tip end portion of the other ply piece  13 B are supplied to positions separated from each other in the width direction and different by 180 degrees in the circumferential direction on the molding drum  51 . 
     Then, the control device  80  operates so that the one and the other ply pieces  13 A and  13 B are supplied to the molding drum  51  while causing the molding drum  51  to be rotationally driven in the direction indicated by the arrow in  FIG. 9 . The one and the other ply pieces  13 A and  13 B are wound around the molding drum  51  as shown by the alternate long and short dash line in  FIG. 9 , and the two joint portions J 2  and J 3  where both end portions in the tire circumferential direction of the one and the other ply pieces  13 A and  13 B are joined in a manner overlapping each other are provided to positions separated from each other in the tire width direction and different in the tire circumferential direction, specifically, at positions different by 180 degrees in the tire circumferential direction. 
     The first supply device  60  has a configuration, in which the servicer  61 , which supplies the one ply piece  13 A to the molding drum  51  from the upper side, cuts a strip-shaped ply piece sheet wound by the winding device to a predetermined length by a cutting device to supply the one ply piece  13 A. The servicer  61  can also be configured to supply the one ply piece  13 A previously cut to a predetermined length. 
     The second supply device  70  has a configuration, in which the servicer  71 , which supplies the other ply piece  13 B to the molding drum  51  from the lower side, cuts a strip-shaped ply piece sheet wound by the winding device to a predetermined length by a cutting device to supply the other ply piece  13 B. The servicer  71  can also be configured to supply the other ply piece  13 B previously cut to a predetermined length. 
     The second supply device  70  is configured to hold the other ply piece  13 B supplied from the servicer  71  in the holding portion  75  and then supply the other ply piece  13 B to the molding drum  51 . However, the second supply device  70  may be configured to supply the other ply piece  13 B supplied from the servicer  71  to the molding drum  51  from the lower side without holding the other ply piece  13 B in the holding portion. 
     Further, the manufacturing device  50  has a configuration in which the one and the other ply pieces  13  are supplied to the molding drum  51  at positions different by 180 degrees in the circumferential direction on the upper side and the lower side. However, it is also possible to supply the one and the other ply pieces  13  at different angle positions other than positions different by 180 degrees on the upper side and the lower side to the molding drum  51 . 
     As described above, in the manufacturing device  50 , when the second ply  12  is wound on the first ply  11  around the molding drum  51  and the carcass band is molded, the carcass band is transferred to another molding drum and a cylindrical green case is molded. Then, the green case is bulged outward in a toroidal shape to the outer side in the radial direction and bonded to the inner surface of a tread band so that a green tire is molded. The molded green tire is vulcanized and molded to produce the pneumatic tire  1 . 
     In the pneumatic tire  1 , the joining tape  14  for joining the first ply  11  and the second ply  12  is provided on the center side in the width direction of a pair of the ply pieces  13  of the second ply  12 . However, the joining tape  14  can be provided in other portions, such as the end portion side in the width direction of a pair of the ply pieces  13 . Further, it is also possible not to use the joining tape for joining the first ply  11  and the second ply  12 . 
     As described above, in the present embodiment, the manufacturing device  50  for a pneumatic tire in which the carcass ply  10  includes the pair of ply pieces  13  includes the molding drum  51 , the drum drive device  52 , the first supply device  60  for supplying one of the ply pieces  13  to the molding drum  51 , the second supply device  70  for supplying the other one of the ply pieces  13  to the molding drum  51 , and the control device  80  that controls operation of the drum drive device  52  and the first and second supply devices  60  and  70  so that the one and the other one of the ply pieces  13  are simultaneously supplied to the molding drum  51  while the molding drum is rotationally driven, and the two joint portions J 2  and J 3  of the one and the other ply pieces  13  are provided at different positions in the tire circumferential direction TC. 
     In this manner, in the pneumatic tire  1 , in a case where the carcass ply  10  includes a pair of the ply pieces  13  disposed separately on both sides in the tire width direction, the two joint portions J 2  and J 3  of a pair of the ply pieces  13  are provided at different positions in the tire circumferential direction TC. For this reason, as compared with the case where the two joint portions J 2  and J 3  are provided at the same position in the tire circumferential direction TC, the joint portions J 2  and J 3  are dispersed in the tire circumferential direction TC and uniformity in the tire circumferential direction TC of the pneumatic tire  1  can be improved. 
     The joint portions J 2  and J 3  of the ply piece  13  have increased rigidity as compared with the non-joint portion  13   m  of the ply piece  13 . For this reason, the joint portions J 2  and J 3  of the ply piece  13  are less likely to bulge and deform than the non-joint portion  13   m  when the tire is filled with internal pressure and bulged and deformed. Therefore, the joint portions J 2  and J 3  of the ply piece  13  may appear as dents in the pneumatic tire  1 . 
     By providing the two joint portions J 2  and J 3  of a pair of the ply pieces  13  at different positions in the tire circumferential direction TC, the dents caused by the joint portions J 2  and J 3  are dispersed in the tire circumferential direction TC and uniformity in the tire circumferential direction can be improved as compared with the case where the two joint portions J 2  and J 3  are provided at the same position in the tire circumferential direction TC. 
     In the manufacturing of the pneumatic tire  1 , the one and the other ply pieces  13  are simultaneously supplied to the molding drum  51  while the molding drum  51  is rotationally driven, so that the supply time for supplying the one and the other ply pieces  13  to the molding drum  51  can be shortened and the manufacturing can be performed with excellent productivity, as compared with the case where the one and the other ply pieces  13  are sequentially supplied to the molding drum  51 . Therefore, the pneumatic tire  1  can be manufactured with excellent productivity while the uniformity in the tire circumferential direction TO is improved. 
     Further, the carcass ply  10  includes the first ply  11  including the central portion  11   a  positioned on the inner side in the tire radial direction of the tread portion  2  and a pair of the side portions  11   b  extending to the inner side in the tire radial direction from both ends of the central portion  11   a,  and the second ply  12  having a pair of the ply pieces  13  including the inner end portion  13   a  disposed on the outer side in the tire radial direction with respect to the first ply  11  and positioned in the tread portion  2  and the side portion  13   b  extending to the inner side in the tire radial direction from the inner end portion  13   a.  The one and the other ply pieces  13  of the second ply  12  are supplied on the first ply  11  wound around the molding drum  51 . 
     The second ply  12  on the first ply  11  includes a pair of the ply pieces  13  and is discontinuous. That is, between the inner end portions  13   a  of a pair of the ply pieces  13 , there is the hollow portion  13   c  in which no ply exists. By employing the second ply  12  having the hollow portion  13   c,  the weight can be reduced as compared with the case where the second ply  12  is one continuous ply. Further, rolling resistance can be reduced by weight reduction. 
     In the sidewall portion  3 , two layers of plies, that is, the side portion  11   b  of the first ply  11  and the side portion  13   b  of the ply piece  13  of the second ply  12  are disposed. By providing two layers of plies in the sidewall portion  3  in this way, necessary cut resistance is ensured. Further, since plies are provided in two layers, necessary rigidity in the sidewall portion  3  is ensured. 
     Therefore, it is possible to achieve weight reduction and reduction in rolling resistance due to the weight reduction while ensuring the rigidity and the steering stability due to the rigidity and the cut resistance, and, in addition, to manufacture the pneumatic tire  1  with excellent productivity while achieving improvement in uniformity in the tire circumferential direction TC. 
     Further, the first supply device  60  supplies one of the ply pieces  13  to which the joining tape  14  to be joined to the first ply  11  is attached, and the second supply device  70  supplies the other one of the ply pieces  13  to which the joining tape  14  to be joined to the first ply  11  is attached. In this manner, the one and the other ply pieces  13  of the second ply  12  to which the joining tape  14  is attached are supplied on the first ply  11 , so that the first ply  11  and the second ply  12  can be joined strongly by the joining tape  14 . 
     Further, the first supply device  60  and the second supply device  70  supply one and the other one of the ply pieces  13  to the molding drum  51  from the upper side and the lower side, respectively, and the control device  80  controls operation of the drum drive device  52 , the first supply device  60 , and the second supply device  70  so that the two joint portions J 2  and J 3  of one and the other one of the ply pieces  13  are provided at positions different by 180 degrees in the tire circumferential direction TC. In this manner, one and the other one of the ply pieces  13  are supplied to the molding drum  51  from the upper side and the lower side, respectively, and the two joint portions J 2  and J 3  are provided at positions different by 180 degrees in the tire circumferential direction TC, so that the two joint portions J 2  and J 3  can be effectively dispersed in the tire circumferential direction TC, and the pneumatic tire  1  can be manufactured with excellent productivity while the uniformity in the tire circumferential direction TC is improved. 
     Further, the second supply device  70  includes the holding portion  75  that is disposed below the molding drum  51  and holds the other one of the ply pieces  13 , and the holding portion moving mechanism  76  that moves the holding portion  75  in the vertical direction. The holding portion  75  holding the other one of the ply pieces  13  is moved to the upper side by the holding portion moving mechanism  76  to supply the other one of the ply pieces  13  to the molding drum  51 . In this manner, in a case where the other one of the ply pieces  13  of the second ply  12  is supplied to the molding drum  51  from the lower side, the other one of the ply pieces  13  is moved upward while being held by the holding portion  75  and supplied to the molding drum  51 . Accordingly, the other one of the ply pieces  13  can be stably supplied to the molding drum  51 . 
     Further, in the present embodiment, in the manufacturing method for the pneumatic tire  1  in which the carcass ply  10  includes a pair of the ply pieces  13 , the molding drum  51  is rotationally driven, the one and the other one of the ply pieces  13  are supplied to the molding drum  51 , and the one and the other one of the ply pieces  13  are simultaneously supplied to the molding drum  51  while the molding drum  51  is rotationally driven so that the two joint portions J 2  and J 3  of the one and the other one of the ply pieces  13  are provided at different positions in the tire circumferential direction TC. 
     In this manner, in the pneumatic tire  1 , in a case where the carcass ply  10  includes a pair of the ply pieces  13  disposed separately on both sides in the tire width direction, the two joint portions J 2  and J 3  of a pair of the ply pieces  13  are provided at different positions in the tire circumferential direction TC. For this reason, as compared with the case where the two joint portions J 2  and J 3  are provided at the same position in the tire circumferential direction TC, the joint portions J 2  and J 3  are dispersed in the tire circumferential direction TC and uniformity in the tire circumferential direction TC of the pneumatic tire  1  can be improved. 
     The joint portions J 2  and J 3  of the ply piece  13  have increased rigidity as compared with the non-joint portion  13   m  of the ply piece  13 . For this reason, the joint portions J 2  and J 3  of the ply piece  13  are less likely to bulge and deform than the non-joint portion  13   m  when the tire is filled with internal pressure and bulged and deformed. Therefore, the joint portions J 2  and J 3  of the ply piece  13  may appear as dents in the pneumatic tire  1 . 
     By providing the two joint portions J 2  and J 3  of a pair of the ply pieces  13  at different positions in the tire circumferential direction TC, the dents caused by the joint portions J 2  and J 3  are dispersed in the tire circumferential direction TC and uniformity in the tire circumferential direction can be improved as compared with the case where the two joint portions J 2  and J 3  are provided at the same position in the tire circumferential direction TC. 
     In the manufacturing of the pneumatic tire  1 , the one and the other ply pieces  13  are simultaneously supplied to the molding drum  51  while the molding drum  51  is rotationally driven, so that the supply time for supplying the one and the other ply pieces  13  to the molding drum  51  can be shortened and the manufacturing can be performed with excellent productivity, as compared with the case where the one and the other ply pieces  13  are sequentially supplied to the molding drum  51 . Therefore, the pneumatic tire  1  can be manufactured with excellent productivity while the uniformity in the tire circumferential direction TC is improved. 
     The present invention is not limited to the illustrated embodiment, and various improvements and design changes can be made without departing from the gist of the present invention.