JP2006076076A - Manufacturing method of radial tire for building vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a radial tire for a building vehicle improving the quality of the radial tire by suppressing the outer peripheral growth of a secondary molded body shaped into a toroidal shape. <P>SOLUTION: When a green tire 104 is molded in the manufacturing method of the radial tire for the building vehicle constituted by arranging at least four belt layers 8, wherein reinforcing cords are obliquely arranged in the peripheral direction of the tire, on the outer peripheral side of the carcass layer 4 of a tread part 1, a cylindrical primary molded body 101 having an unvulcanized carcass layer 4' and at least two unvulcanized belt layers 8'A and 8'B are subsequently laminated on the unvulcanized carcass layer 4' of the primary molded body 101. Next, the primary molded body 102, on which the unvulcanized belt layers 8'A and 8'B are laminated, is molded into a secondary molded body 103 shaped into the toroidal shape and a remaining unvulcanized belt layer 8' is laminated on the unvulcanized belt layer 8'B of the secondary molded body 103 to mold the green tire 104. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing a radial tire for a construction vehicle, and more particularly, a method for manufacturing a radial tire for a construction vehicle capable of suppressing the outer peripheral growth of a secondary molded body shaped in a toroidal shape and improving the tire quality. About.

  Large radial tires for construction vehicles, called OR tires (Off the Road Tires), have a configuration in which four or more belt layers are arranged on the outer periphery of the carcass layer in the tread, with reinforcing cords inclined in the tire circumferential direction. is doing. Such a radial tire for construction vehicles is formed by forming a cylindrical primary molded body (so-called primary green tire) that forms a tire skeleton such as an unvulcanized carcass layer in a process of forming a green tire. A primary molded body is molded into a secondary molded body shaped in a toroidal shape (so-called secondary green tire), and an unvulcanized belt layer and a tread rubber layer are bonded to the secondary molded body to form a green tire. It is made to shape | mold (for example, refer patent document 1).

However, since the radial tire for construction vehicles is larger than a normal tire, the secondary molded body shaped in a toroidal shape naturally expands after shaping, and outer peripheral growth occurs. In particular, if the time until the belt layer is applied to the secondary molded body is long, the peripheral growth becomes remarkable, which is not preferable in terms of tire quality.
Japanese Patent Laid-Open No. 49-15776

  An object of the present invention is to provide a method for manufacturing a radial tire for a construction vehicle capable of suppressing the outer peripheral growth of a secondary molded body shaped in a toroidal shape and improving the tire quality.

  The present invention that achieves the above object is a method for manufacturing a radial tire for a construction vehicle in which four or more belt layers in which reinforcing cords are inclined and arranged in the tire circumferential direction are arranged on the outer circumferential side of a carcass layer of a tread, When forming a cylindrical primary molded body having an unvulcanized carcass layer, the four or more belt layers are formed on the unvulcanized carcass layer of the primary molded body. Secondary molding in which at least two unvulcanized belt layers that are a part of four or more unvulcanized belt layers are bonded together, and the primary molded body in which the unvulcanized belt layers are bonded together is shaped into a toroidal shape. A green tire is formed by forming a green tire by bonding the remaining unvulcanized belt layer onto the unvulcanized belt layer of the secondary molded body.

  In the present invention described above, a primary molded body in which a part of the unvulcanized belt layer is bonded is molded, and the secondary molded body is shaped into a toroidal shape and shaped into a secondary molded body. Since the outer periphery of the molded body is constrained by the unvulcanized belt layer, the change with time is small even if time passes, and the growth of the outer periphery can be suppressed. Therefore, tire quality can be improved.

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

  FIG. 1 shows an example of a radial tire for a construction vehicle, where 1 is a tread portion, 2 is a sidewall portion, 3 is a bead portion, and CL is a tire equatorial plane.

  A carcass layer 4 in which steel cords (not shown) extending in the tire width direction are arranged between the left and right bead portions 3 at predetermined intervals in the tire circumferential direction is extended inside the tire, and both end portions 4a thereof are beaded. A bead filler 6 is sandwiched around a bead core 5 embedded in the portion 3 so as to be folded back from the tire inner side to the outer side. The bead filler 6 includes a lower bead filler 6 </ b> A that contacts the outer peripheral side of the bead core 5 and an outer bead filler 6 </ b> B disposed on the outer peripheral side thereof.

  On the outer peripheral side of the carcass layer 4 of the tread portion 1, four or more layers (generally 4 to 4) in which reinforcing cords (not shown) made of steel cords are inclined and arranged in the tire circumferential direction at a predetermined interval via an interlayer rubber layer 7. The belt layer 8 is arranged in 8 layers (7 layers are illustrated in the figure). These belt layers 8 are laminated so that the reinforcing cords intersect with each other between the belt layers 8 adjacent to each other with the inclination direction with respect to the tire circumferential direction reversed.

  The inner two belt layers 8A and 8B adjacent to the carcass layer 4 are narrower than the remaining belt layers 8 and are located in the center region 1A of the tread portion 1. The remaining wide belt layer 8 extends to the shoulder region 1B side of the tread portion 1.

  On the inner side of the carcass layer 4, a non-breathable rubber inner liner layer 9 is attached. A tread rubber layer 12 including an under tread rubber layer 10 and a cap tread rubber layer 11 is disposed on the outer peripheral side of the belt layer 8, and a side rubber layer 13 and a rim cushion rubber layer 14 are disposed on the sidewall portion 2. ing.

  Hereinafter, the manufacturing method of the present invention will be described with reference to FIGS.

  2 to 4 show a process of forming a primary molded body (so-called primary green tire) with a primary molding machine. In the primary molding machine 100 shown in FIGS. 2 to 4, 21 is a headstock (main body), and 22 is a tailstock. A molding drum 25 is attached to the drive shaft 23 of the headstock 21, and the molding drum 25 is configured so that the size of the radius expands and contracts. A driven shaft 24 provided on the tail stock 22 rotates together with the drive shaft 23 and the forming drum 25. Further, the drive shaft 23 and the driven shaft 24 are provided with bead supply portions 26a and 26b, respectively, and these bead supply portions 26a and 26b reciprocate on the respective shafts to approach or separate from the forming drum 25. It is supposed to be.

  In the step of forming the primary molded body, first, a cylindrical band 27 molded in advance by a band molding machine (not shown) is attached to the molding drum 25 of the primary molding machine 100 as shown in FIG. In addition, a bead core assembly 28 in which a bead filler 6 'made of unvulcanized rubber is assembled to a bead supply unit 26a, 26b and a ring-shaped bead core 5 in which steel wires are converged. The cylindrical band 27 is configured by using an unvulcanized carcass layer 4 ′ as a base and lining an unvulcanized inner liner layer (not shown) on the inner peripheral surface of the carcass layer 4 ′.

  Next, both end portions 4′a of the carcass layer 4 ′ are bent radially inward as indicated by broken lines, and the bead supply portions 26a and 26b on which the bead core assemblies 28 are placed are moved to the end portions of the forming drum 25, respectively. The bead core assembly 28 is transferred to the end 4′a of the carcass layer 4 ′. Further, the end portions 4 ′ a of the carcass layer 4 ′ are folded back so as to wrap the bead core assembly 28, so that the state shown in FIG. 3 is obtained. Further, as shown in FIG. 4, the unvulcanized interlayer rubber layer 7 ′, the unvulcanized rim cushion rubber layer (not shown), and the unvulcanized so as to cover the end portion 4′a of the carcass layer 4 ′. The side rubber layer 13 ′ is wound to complete the primary molded body 101.

  After forming the primary molded body 101, as shown in FIG. 5, the inner 2 which is a part of four or more unvulcanized belt layers 8 ′ for forming four or more belt layers 8. The unvulcanized belt layers 8′A and 8′B of the layers are sequentially supplied from a belt supply unit (not shown), and the end portions are overlapped and bonded to the carcass layer 4 ′ to be bonded, and a part of the unvulcanized belt layers The primary molded body 102 in which the belt layers 8′A and 8′B are bonded together is molded. The two belt layers 8′A and 8′B intersect with each other with the reinforcing cords crossing each other with the inclination direction with respect to the tire circumferential direction reversed, and the width is narrower than the width of the remaining belt layer 8 ′. Located in region 1A.

  Next, the primary molded body 102 to which a part of the belt layer 8 ′ is bonded is removed from the molding drum 25 of the primary molding machine 100, and the removed primary molded body is removed as shown in FIGS. A vulcanization bladder unit 32 is mounted inside 102. The vulcanization bladder unit 32 is for inflating the inside of the finished green tire in a vulcanization process described later, and is detachably attached to the vulcanizer. The vulcanization bladder unit 32 includes a telescopic cylinder 33 composed of a pair of cylinders 33 a and 33 b that move relative to each other in the axial direction, and a bladder 34 that covers the outside of the cylinder 33.

  The operation of assembling the primary molded body 102 in which the belt layers 8′A and 8′B are bonded to the vulcanization bladder unit 32 is performed as shown in FIG. It is better to lift it with a crane through a forklift. Further, before the vulcanization bladder unit 32 is mounted on the primary molded body 102, a release material 36a is applied to the surface of the bladder 34 of the vulcanization bladder unit 32 by a spray nozzle 36 or the like to improve the releasability. It is preferable. Further, when the primary molded body 102 is mounted on the vulcanization bladder unit 32, as shown in FIG. 7, both bead rings 35 are attached so that the primary molded body 102 does not easily fall off.

  Next, as shown in FIG. 8, the cylindrical body 33 of the vulcanization bladder unit 32 is contracted in the axial direction to set the interval between the bead portions of the primary molded body 102 to a predetermined rim width, and the vulcanization bladder. Compressed air is supplied to the unit 32 to inflate the outer diameter until the belt is pasted, and the primary molded body 102 is molded into a secondary molded body 103 shaped in a toroidal shape.

  The secondary molded body 103 shaped in a toroidal shape so as to have a predetermined outer diameter and rim width is vertically oriented using a swivel device (not shown) with the vulcanization bladder unit 32 mounted. Change the posture so that it is level. Further, as shown in FIG. 9, it is mounted again on the drive shaft 23 of the primary molding machine 100 from which the molding drum 25 has been removed by being suspended by a crane 38 or transported by a forklift.

  Next, as shown in FIG. 10, the driven shaft 24 on the tail stock 22 side is assembled to the secondary compact 103 on the drive shaft 23 of the headstock 21, and the bladder of the vulcanization bladder unit 32 is further supplied from the air supply unit 39. Compressed air is supplied into 34 to maintain the secondary molded body 103 in a toroidal-inflated state. Then, after the remaining unvulcanized belt layer 8 ′ is bonded onto the belt layer 8′B of the secondary molded body 103, the unvulcanized tread rubber layer 11 ′ is wound around the outer periphery, and further not illustrated. Through the stitching (crimping) process, the green tire 104 is completed as shown in FIG.

  The completed green tire 104 obtained as described above is taken out from the primary molding machine 100 and conveyed into the vulcanization mold 42 with the vulcanization bladder unit 32 attached as shown in FIG. Then, the radial tire for a construction vehicle is completed by heating and curing in the vulcanization mold 42 while maintaining the inflated state of the completed green tire 104 by the vulcanization bladder unit 32.

  According to the present invention described above, the primary molded body 102 in which a part of the unvulcanized belt layers 8′A and 8′B is bonded is formed, and shaped into a toroidal shape to form the secondary molded body 103. Therefore, the outer periphery of the secondary molded body 103 shaped in a toroidal shape is restrained by the belt layers 8′A and 8′B, and the outer peripheral growth of the secondary molded body 103 can be suppressed. In particular, in the above-described method, since it takes time to re-attach to the primary molding machine 100 after shaping in a toroidal shape, the secondary molded body without the belt layers 8′A and 8′B has an outer periphery therebetween. Although it grows, the secondary molded body 103 provided with some belt layers 8′A and 8′B can effectively suppress such peripheral growth. Therefore, tire quality can be improved.

  In addition, it is possible to suppress deformation and crushing (particularly occurring in the center region 1A of the tread portion 1) due to its own weight before shaping into a toroidal shape, thereby reinforcing the carcass layer that is likely to occur in the vulcanization process. Code misalignment (code wave failure) can also be improved.

  Further, since the lift rate when shaping in a toroidal shape is large, if a belt layer extending to the shoulder region 1B of the tread portion 1 is bonded to the primary molded body 102, the belt layer positioned in the center region 1A In the portion, the reinforcing cords change at a predetermined angle, but in the portion on the end side of the belt layer located in the shoulder region 1B, the interval between the reinforcing cords is opened and does not change to the predetermined angle. In the present invention described above, the width of the belt layers 8′A and 8′B is set to a width in which the belt layers 8′A and 8′B are located in the center region 1A of the tread portion 1, so that the belt layers 8′A and 8′B are shaped in a toroidal shape. At this time, since the reinforcing cords of the belt layers 8'A and 8'B change at a predetermined angle, the functions of the belt layers 8A and 8B after vulcanization are not deteriorated.

  In the present invention, the inclination angle of the reinforcing cords of the belt layers 8'A and 8'B with respect to the tire circumferential direction is preferably in the range of 20 to 65 °. If the inclination angle is lower than 20 °, the reinforcing cord cannot change its angle following the inflation during shaping, and as a result, the first molded body 103 is restrained by the reinforcing cord and shaped to a predetermined size. I can't do that. On the other hand, when the angle exceeds 65 °, the restraining effect becomes too small, and it becomes difficult to suppress the outer peripheral growth of the secondary molded body 103 shaped in a toroidal shape. More preferably, it is 35 to 55 °.

  Further, as the reinforcing cords of the belt layers 8'A and 8'B, it is preferable to use reinforcing cords such as steel cords having a breaking strength per reinforcing cord of 2500 N or more. When the breaking strength is lower than 2500 N, it is difficult to effectively suppress the outer peripheral growth of the secondary molded body 103. The upper limit is preferably 8000 N or less (twisted diameter is 3 mm or less) from the viewpoint of heat generation of the belt layers 8A and 8B after vulcanization.

  The remaining unvulcanized belt layer 8 ′ can be of the same structure as the conventional one, and the reinforcing cord intersects with the belt layer 8 ′ adjacent to each other with the inclined direction with respect to the tire circumferential direction reversed. The inclination angle with respect to the tire circumferential direction can be in the range of 18 to 38 °. If the inclination angle is smaller than 18 °, the reinforcing cords bite into the inner peripheral layer at the time of lifting during vulcanization, which is not preferable. Conversely, if it exceeds 38 °, the hoop effect as the belt layer 8 cannot be fully exhibited.

  In addition, as described above, the number of the unvulcanized belt layers 8 ′ included in the first molded body 103 is effective in the inner two unvulcanized belt layers 8 ′ A and 8 ′ B. Although sufficient, it may be more than that, and at least two unvulcanized belt layers 8′A and 8′B may be used. Even when the number of layers is two or more, those belt layers are preferably configured in the same manner as the belt layers 8'A and 8'B.

  In the above embodiment, the green tire 104 is formed only by the primary molding machine 100 without using the secondary molding machine that performs the toroidal shopping. After forming the first molded body 103 described above at 100, the first molded body 103 is attached to a secondary molding machine and shaped in a toroidal shape, where the remaining unvulcanized belt layer 8 'and tread rubber layer The green tire 104 may be molded by attaching 11 ′.

  The tire size is the same for 2700R49, and the inner two unvulcanized belt layers are pasted by the method of the present invention as shown in FIGS. 2 to 8 (however, the steps shown in FIG. 6 are omitted). The molded body was shaped into a toroidal shape to form a secondary molded body. In addition, a primary molded body to which an unvulcanized belt layer was not attached was shaped in a toroidal shape in the same manner to form a secondary molded body.

  The circumference of the molding drum of the primary molding machine used when molding the primary molded body is 5267 mm. A steel cord having a structure of 7 × 7 × 0.22 is used for the reinforcing cord of the two unvulcanized belt layers, and its breaking strength is 4000N. The inclination angles of the reinforcing cords are both 50 °, the width of the inner belt layer of the two layers is 320 mm, the circumferential length at the time of bonding is 5319 mm, the width of the outer belt layer is 280 mm, and the circumference at the time of bonding is The length is 5330 mm. The internal pressure when shaping in a toroidal shape is 0.06 MPa.

  Each of the obtained secondary compacts was left as it was with an internal pressure applied, and the change over time in the peripheral growth was examined. The result shown in FIG. 13 was obtained. In FIG. 13, the solid line indicates the secondary molded body formed by the method of the present invention, and the dotted line indicates the secondary molded body obtained by shaping the primary molded body to which the unvulcanized belt layer is not attached in a toroidal shape.

  From FIG. 13, it can be seen that the secondary molded body molded by the method of the present invention has a small peripheral growth, and the present invention can suppress the peripheral growth of the secondary molded body shaped in a toroidal shape.

It is a tire meridian half sectional view showing an example of a radial tire for construction vehicles manufactured by a method of the present invention. It is explanatory drawing of the formation process of the primary molded object in the manufacturing method of the radial tire for construction vehicles of this invention. It is explanatory drawing which shows the formation process of the primary molded object following the process of FIG. It is explanatory drawing which shows the formation process of the primary molded object following the process of FIG. It is explanatory drawing which shows the formation process of the primary molded object which the unvulcanized belt layer stuck on following the process of FIG. It is explanatory drawing which shows the process of mounting | wearing the vulcanization bladder unit with the primary molded object obtained at the process of FIG. It is sectional drawing which shows the state after mounting | wearing a vulcanization bladder unit with a primary molded object. It is sectional drawing which shows the process of inflating the primary molded object of FIG. 7, and shape | molding a secondary molded object. It is explanatory drawing which shows the process of mounting | wearing a primary molding machine again with the secondary molded object obtained in FIG. It is explanatory drawing which shows the process of winding the remaining unvulcanized belt layers around the secondary molded body mounted on the primary molding machine in FIG. It is explanatory drawing which shows the process of winding a tread rubber layer and shape | molding a green tire next to the process of FIG. It is explanatory drawing which shows the process of vulcanizing the green tire obtained at the process of FIG. 11 with a vulcanization mold. It is a graph which shows the result of an Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tread part 1A Center area | region 1B Shoulder area | region 2 Side wall part 3 Bead part 4 Carcass layer 4 'Unvulcanized carcass layer 8, 8A, 8B Belt layer 8', 8'A, 8'B Unvulcanized belt layer 11 Tread Rubber layer 25 Molding drum 27 Band 28 Bead core assembly 32 Vulcanization mold 100 Primary molding machine 101, 102 Primary molded body 103 Secondary molded body 104 Green tire

Claims (8)

  A method of manufacturing a radial tire for a construction vehicle in which four or more belt layers in which reinforcing cords are inclined and arranged in the tire circumferential direction are arranged on the outer circumferential side of the tread portion of the carcass layer, and when unmolded when forming a green tire Four or more unvulcanized belt layers for molding a cylindrical primary molded body having a carcass layer and then molding the four or more belt layers on the unvulcanized carcass layer of the primary molded body At least two unvulcanized belt layers that are a part of the unvulcanized belt layer are bonded together, and the primary molded body bonded with the unvulcanized belt layer is molded into a toroidal shaped secondary molded body, and the secondary molding is performed. A method for manufacturing a radial tire for a construction vehicle, wherein a green tire is formed by bonding the remaining unvulcanized belt layer on an unvulcanized belt layer of a body.   The method for manufacturing a radial tire for a construction vehicle according to claim 1, wherein the reinforcing cords of the at least two unvulcanized belt layers intersect with each other with the inclination directions with respect to the tire circumferential direction being opposite to each other.   The method for manufacturing a radial tire for a construction vehicle according to claim 2, wherein an inclination angle of the reinforcing cord of the at least two unvulcanized belt layers with respect to a tire circumferential direction is 20 to 65 °.   The method for manufacturing a radial tire for a construction vehicle according to claim 1, wherein the width of the at least two unvulcanized belt layers is narrower than the width of the remaining unvulcanized belt layer.   The manufacturing method of the radial tire for construction vehicles of Claim 4 which has a width | variety in which the said at least 2 layer of unvulcanized belt layer is located in the center area | region of a tread part.   The method for manufacturing a radial tire for a construction vehicle according to any one of claims 1 to 5, wherein the breaking strength per reinforcing cord of the at least two unvulcanized belt layers is 2500 N or more.   The method for manufacturing a radial tire for a construction vehicle according to claim 1, wherein the at least two unvulcanized belt layers are two layers.   In the remaining unvulcanized belt layer, the inclination angle of the reinforcing cord with respect to the tire circumferential direction is 18 to 38 °, and the reinforcing cord has an inclination direction opposite to the tire circumferential direction between adjacent unvulcanized belt layers. The manufacturing method of the radial tire for construction vehicles of any one of Claim 1 thru | or 7 which cross | intersects.

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