Manufacturing method for pneumatic tires

Abstract

To provide a pneumatic tire having a sealant layer formed on an inner surface of the tire, whose uniformity can be improved, and a manufacturing method for the same.SOLUTION: A manufacturing method for a pneumatic tire comprises: a static unbalance position measuring step; a light point grassing step of grasping light points K of a tire 1 on the basis of a static unbalance position; and a sealant layer forming step of forming a sealant layer 60 on an inner surface of the tire 1, by applying a plurality of belt-like sealant materials 61 to the inner surface while making the materials circle along a tire circumferential direction and while transferring a path of the circling to one direction side in a tire width direction at least for one circle and by arranging annular circling parts 62 of the plurality of sealant materials 61 extending in the tire circumferential direction, in the tire width direction. In the sealant layer forming step, winding-start points 61A and winding-end points 61B of the sealant materials 61 are arranged at positions in the tire circumferential direction corresponding to the light points K, and sealant material increase parts 62A1 and 62B1 are arranged at the winding-start points 61A and the winding-end points 61B respectively.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a pneumatic tire and a method for manufacturing the same.

Background Art

[0002] Conventionally, a pneumatic tire is known that has a puncture prevention function, in which a sealant layer provided on the inner surface of the tire automatically closes a hole formed in the tire at the time of a puncture. For example, Patent Document 1 describes a pneumatic tire in which a sealant layer is formed by applying a substantially string-shaped sealant material continuously in a spiral manner along the inner surface of the tire.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, good uniformity is generally required for tires. In the case of a pneumatic tire in which a sealant layer is disposed on the inner surface of the tire, the sealant layer may affect the uniformity.

[0005] An object of the present invention is to provide a pneumatic tire capable of improving the uniformity of a pneumatic tire provided with a sealant layer on the inner surface of the tire, and a method for manufacturing the same.

Means for Solving the Problems

[0006] The present invention provides a method for manufacturing a pneumatic tire, comprising: a static unbalance position measurement step for measuring the static unbalance position of the tire; a light point identification step for identifying the light point of the tire based on the measured static unbalance position; and a sealant layer formation step for forming a sealant layer on the inner surface of the tire by applying a strip-shaped sealant material in a circular motion along the circumferential direction of the tire, and shifting the circular path to one direction in the tire width direction at least every one rotation, thereby arranging annular circumferential portions of multiple sealant materials extending in the circumferential direction of the tire in parallel in the tire width direction, wherein in the sealant layer formation step, the starting end and ending end of the sealant material to be wrapped around the inner surface of the tire are positioned at circumferential positions of the tire corresponding to the light point, and sealant material increase portions are arranged at the starting end and ending end, respectively.

[0007] The pneumatic tire of the present invention comprises a tire having a light point and a sealant layer provided on the inner surface of the tire, wherein the sealant layer has a strip-shaped sealant material that circulates along the tire circumferential direction, and the circumferential path shifts to one side in the tire width direction at least every circumferential turn, so that a plurality of annular circumferential portions extending in the tire circumferential direction are arranged in parallel in the tire width direction, the circumferential portion located at the one end in the tire width direction of the plurality of circumferential portions has the starting end of the winding of the sealant material, and the circumferential portion located at the other end in the tire width direction has the ending end of the winding of the sealant material, the tire circumferential positions of the starting end and the winding ending correspond to the tire circumferential positions of the light point, and sealant material increase portions are provided at the starting end and the winding ending. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a pneumatic tire and a method for manufacturing the same that can improve the uniformity of a pneumatic tire having a sealant layer on the inner surface of the tire. [Brief explanation of the drawing]

[0009] [Figure 1]This is a side view of a tire according to an embodiment. [Figure 2] This is a cross-sectional view of the tire in the width direction shown above. [Figure 3] This is a flowchart showing the manufacturing method according to the embodiment. [Figure 4] This is an exploded view showing the inner surface of a tire according to an embodiment, and schematically shows the sealant layer. [Figure 5] This figure schematically illustrates an example of a method for applying a sealant material to the inner surface of a tire when manufacturing a tire according to the embodiment. [Modes for carrying out the invention]

[0010] The embodiments will now be described with reference to the drawings. Figure 1 is a side view of a tire 1 manufactured by the manufacturing method according to the embodiment. G in Figure 1 indicates the axis of rotation, which is the center of rotation of the tire 1 extending in the front-back direction of the paper in Figure 1. In Figure 1, the circumferential direction of the tire 1 is indicated by the arrow R. Figure 2 is a schematic diagram showing a cross-section of the tire 1 in the tire width direction. The tire 1 according to the embodiment is a pneumatic tire that is mounted on a rim (not shown) and has its internal cavity filled with internal pressure such as air. The tire 1 according to the embodiment is a tire for a passenger car. The tire manufacturing method according to the embodiment can also be applied to the manufacturing of tires for various vehicles such as light trucks, trucks, and buses.

[0011] Figure 2 briefly illustrates the internal structure of tire 1. Figure 2 shows a cross-section of tire 1, which has a symmetrical structure in the direction of the rotation axis G shown in Figure 1. The cross-sectional view in Figure 2 shows the state of tire 1 in an unloaded state, mounted on a specified rim (not shown) and filled with a specified internal pressure.

[0012] In Figure 2, the symbol S1 represents the tire equatorial plane perpendicular to the rotation axis G. In Figure 2, the tire width direction and tire diameter direction, as defined herein, are indicated by arrows X and Y, respectively. The tire width direction (arrow X direction) is the direction parallel to the rotation axis G, and corresponds to the left-right direction on the paper in the cross-sectional view of Figure 2. The inside of the tire width direction is the direction approaching the tire equatorial plane S1, and in Figure 2, it is the center side of the paper. The outside of the tire width direction is the direction away from the tire equatorial plane S1, and in Figure 2, it is the left and right sides of the paper. The tire diameter direction (arrow Y direction) is the direction perpendicular to the rotation axis G, and corresponds to the up-down direction on the paper in Figure 2. Figure 1 shows the tire diameter direction Y. The outside of the tire diameter direction is the direction away from the rotation axis G, and in Figure 2, it is the top side of the paper. The inside of the tire diameter direction is the direction approaching the rotation axis G, and in Figure 2, it is the bottom side of the paper.

[0013] The tire 1 comprises a pair of beads 10 provided on both sides in the tire width direction, a tread 20 that forms a contact surface with the road surface, and a pair of sidewalls 30 extending between the pair of beads 10 and the tread 20.

[0014] A pair of beads 10 constitute the inner portion of the tire 1 in the radial direction. To increase the rigidity of this portion, the beads 10 contain rubber with a high modulus. The beads 10 include an annular bead core 11 made of a metal bead wire that has been wound multiple times and covered with rubber. The bead core 11 serves to fix the tire 1 to the rim.

[0015] The tread 20 comprises a belt 21 and a tread rubber 25 positioned radially outward of the belt 21. The tread rubber 25 has a contact surface 25a that contacts the road surface. Multiple main grooves 26 extending in the circumferential direction are formed on the contact surface 25a.

[0016] The belt 21 is a member that reinforces the tread 20. The belt 21 in this embodiment has a two-layer structure comprising an inner belt 22 and an outer belt 23 positioned on the outer side of the inner belt 22 in the tire radial direction. Both the inner belt 22 and the outer belt 23 have a structure in which multiple belt cords, such as steel cords, are covered with rubber. The inner belt 22 has a longer length in the tire width direction than the outer belt 23. Therefore, each of the ends 21A on both sides of the belt 21 in the tire width direction is composed of the ends of the inner belt 22 in the tire width direction. The outer belt 23 may also have a longer length in the tire width direction than the inner belt 22. Furthermore, the belt 21 may have a single-layer structure or a structure with three or more layers.

[0017] The sidewall 30 includes sidewall rubber 31 that constitutes the outer sidewall surface of the tire 1. The sidewall rubber 31 is made of flexible rubber that flexes the most when the tire 1 is performing a cushioning action and is usually fatigue-resistant.

[0018] Although not shown in Figure 2, carcass plies, which constitute the framework of the tire 1, are embedded inside the tire 1. These carcass plies are embedded inside the tire 1 in such a manner that they pass between a pair of bead cores 11, through a pair of sidewalls 30 and tread 20. These carcass plies have a structure in which multiple ply cords made of insulating organic fiber cords such as polyester or polyamide are covered with rubber. The belt 21 is positioned on the radially outer side of these carcass plies. Also, although not shown in Figure 2, an inner liner, which is a rubber layer constituting the inner wall surface of the tire 1, is provided on the inner cavity side of the carcass plies, extending between a pair of beads. This inner liner is made of air-permeable rubber and prevents air inside the tire cavity from leaking to the outside.

[0019] As shown in Figure 2, the tire 1 according to the present embodiment further includes a sealant layer 60. The sealant layer 60 is disposed over the entire circumference in the tire circumferential direction in at least the region corresponding to the tread 20 on the tire inner cavity surface constituted by the inner liner. The length of the sealant layer 60 in the tire width direction is greater than the ground contact surface 25a of the tread 20, and both ends 60A of the sealant layer 60 in the tire width direction are preferably located further outward in the tire width direction than both ends of the ground contact surface 25a in the tire width direction. Further, the length of the sealant layer 60 in the tire width direction is smaller than the length of the belt 21 in the tire width direction, and each of the both ends 60A of the sealant layer 60 in the tire width direction is preferably located further inward in the tire width direction than both ends 21A of the belt 21 in the tire width direction. As will be described later, the sealant layer 60 is formed by winding a strip-shaped sealant material around the tire inner surface along the tire circumferential direction. As the sealant material, a material having adhesiveness is suitably used, and the sealant material is adhered to the tire inner cavity surface by its adhesiveness. The thickness of the sealant layer 60 is preferably 2 mm or more.

[0020] A tire manufacturing method according to an embodiment for manufacturing the tire 1 having the above configuration will be described below. The tire manufacturing method according to the embodiment relates to a method of forming the sealant layer 60 on the tire 1 obtained by vulcanizing a green tire, which is a prototype of the tire 1 molded to have the above configuration.

[0021] Here, the "static unbalance position", "static unbalance amount", "dynamic unbalance position" and "dynamic unbalance amount", which are requirements necessary for carrying out the tire manufacturing method according to the embodiment, will be described first. In general, for a pneumatic tire, the uniformity generated due to non-uniform mass of the tire is roughly classified into three types: static unbalance, couple unbalance, and dynamic unbalance. These uniformity values are measured, for example, in a product inspection step in the manufacturing process.

[0022] Static unbalance refers to the circumferential mass imbalance when the tire is not rolling. The heaviest point in the circumferential direction is called the static unbalance position, and its mass is called the static unbalance amount. Static unbalance can be caused by variations in the tire's constituent materials, or by deformation of materials during the molding or vulcanization of the green tire. Accidental unbalance refers to the mass imbalance between the front and back sides of the tire when it is not rolling. It can be caused by eccentricity of materials during tire molding, or eccentricity of the green tire or vulcanization mold. Dynamic unbalance is the mass imbalance when the tire is rolling. It occurs when static and accidental unbalances combine during rolling, and its mass is called the dynamic unbalance amount. The dynamic unbalance position and dynamic unbalance amount are measured on the front and back sides of the tire, respectively.

[0023] Figure 3 is a flowchart showing the manufacturing method according to the embodiment in order of steps. As shown in Figure 3, the manufacturing method of the tire according to the embodiment first involves a static unbalance position measurement step (step S1) to measure the static unbalance position. Next, a light point identification step is performed to identify the light point K of the tire 1 shown in Figure 1 based on the measured static unbalance position (step S2). The light point of the tire 1 is located 180° in the circumferential direction with respect to the static unbalance position, and is the lightest position in the circumferential direction 180° opposite to the heaviest static unbalance position. Therefore, when a weight of a predetermined mass that acts as a counter for the amount of static unbalance is placed at this light point K, the static unbalance is compensated and the weight balance in the circumferential direction of the tire is improved. Next, a dynamic unbalance position measurement step is performed to measure the dynamic unbalance position of the tire 1 (step S3). Next, a dynamic unbalance compensation position identification step is performed to identify the position where the dynamic unbalance of the tire 1 is compensated based on the measured dynamic unbalance position (step S4). Based on the above, the circumferential position within tire 1 that can compensate for static imbalance and the position that can compensate for dynamic imbalance are determined.

[0024] Next, a sealant layer 60 is formed on the inner surface of the tire by applying sealant material (step S5). Then, a dynamic unbalance compensation sealant material placement step is performed in which dynamic unbalance compensation sealant material 65 is placed at the identified dynamic unbalance compensation position (step S6).

[0025] Figure 4 is a diagram showing an example of how to specifically carry out step S5, and is an unfolded view showing a part of the circumferential direction of the inner surface of the tire where the sealant material 61 has been applied to form the sealant layer 60. In Figure 4, the circumferential direction of the tire is indicated by R, and the width direction of the tire is indicated by X. As shown in Figure 4, the sealant layer 60 is formed by a single strip of sealant material 61 that is applied to the inner surface of the tire while circumferentially extending along the circumferential direction of the tire. The sealant layer 60 has a plurality of annular circumferential portions 62 and a plurality of transition portions 63 formed by the sealant material 61.

[0026] The sealant layer 60 is formed by applying a strip of sealant material 61 to the entire circumference of the application area of ​​the sealant material 61 in the tire width direction on the inner surface of the tire, while circulating it along the tire circumferential direction and shifting the circumferential path to one direction in the tire width direction (to the right in Figure 4) with each rotation. As a result, annular circumferential portions 62 made of multiple sealant material 61 extending in the tire circumferential direction are arranged in parallel in the tire width direction. Note that the sealant material 61 may be applied to the inner surface of the tire while shifting in the tire width direction with each rotation, but it may also be applied in overlapping layers of two or more rotations at the same location in the tire width direction.

[0027] In Figure 4, reference numeral 61A indicates the starting end of the sealant material 61, and reference numeral 61B indicates the ending end of the sealant material 61. The sealant material 61 is applied continuously from one end in the tire width direction to the other end (left side to right side in Figure 4), as indicated by the arrow F, while circling around the tire from the starting end 61A to the ending end 61B. The circumferential positions of both the starting end 61A and the ending end 61B are set to correspond to the circumferential position of the light point K. That is, the circumferential position of the light point K is the same for both the starting end 61A and the ending end 61B.

[0028] The circumferential portion 62 is formed by attaching sealant material 61 to the inner surface of the tire parallel to the circumferential direction of the tire. Multiple circumferential portions 62 are arranged in parallel so as to be adjacent to each other in close proximity in the tire width direction. Multiple transition portions 63 are inclined at a predetermined angle with respect to the circumferential direction of the tire and are arranged in parallel so as to be adjacent to each other in close proximity.

[0029] The transition sections 63 are provided at predetermined positions in the circumferential direction of the tire. The transition sections 63 are the parts where the sealant material 61 is transferred to one side in the tire width direction (right side in Figure 4) after the sealant material 61 has been applied to the inner surface of the tire almost all the way around to form one circumferential section 62. The next circumferential section 62 is applied adjacent to the already applied circumferential section 62 on one side in the tire width direction via the transition sections 63. The next circumferential section 62 adjacent to one side in the tire width direction is repeatedly formed via the transition sections 63 to form the sealant layer 60. In this way, when applying the sealant material 61 to the inner surface of the tire, the method of sequentially arranging circumferential sections 62 parallel to the circumferential direction of the tire in the tire width direction via the transition sections 63 may be referred to as step application below.

[0030] As the sealant material 61, for example, a tacky sealing material can be used which is made by blending unvulcanized or semi-vulcanized butyl rubber with a plasticizer such as polyisobutylene or polybutene, a tackifier such as a thermoplastic olefin / diolefin copolymer, and a filler such as carbon black or silica. However, the sealant material 61 may be any other known sealing material that has been used conventionally, and is not limited thereto. Furthermore, it is preferable that the sealant material has low fluidity and does not flow easily even when driving at high speeds.

[0031] Figure 5 schematically shows an example of a method for applying sealant material 61 to the inner surface of a tire in a step-by-step manner. In Figure 5, the widthwise cross-section of the tire 1 is shown, along with the tire width direction X, tire diameter direction Y, and tire circumference direction R. To apply the sealant material 61 in a step-by-step manner, as shown in Figure 5, the tire 1 is rotated around the axis G, and the nozzle 100 is moved in the tire width direction while the sealant material 61 is discharged from the nozzle 100 and applied to the inner surface of the tire 1. The nozzle 100 is attached to the tip of an extruder (not shown) and inserted into the inside of the tire 1. The sealant material 61 extruded from the extruder is discharged from the tip of the nozzle 100 and applied to the inner surface of the tire 1.

[0032] While continuously discharging sealant material 61 from the nozzle 100 and continuously rotating the tire 1 around its axis, the tire 1 is rotated almost a full turn with movement in the tire width direction stopped, thereby coating one circumferential portion 62. Next, the nozzle 100 is moved to one side in the tire width direction by the width of the sealant material 61, and a transition portion 63 is coated in between. Then, movement in the tire width direction is stopped, and another circumferential portion 62 is coated next to the previously coated circumferential portion 62. By repeating the above operations, the sealant material 61 can be applied in steps to the area where the sealant layer 60 is formed. Once the entire area where the sealant layer 60 is formed has been coated and coated with sealant material 61, the discharge of sealant material 61 from the nozzle 100 is stopped. In this way, the sealant layer 60 is formed by the sealant material 61. When applying in steps, it is preferable to determine the starting end 61A so that the amount of coating does not change on the left and right sides of the center in the tire width direction.

[0033] As shown in Figure 5, the cross-sectional shape of the sealant material 61 discharged from the nozzle 100 and applied to the inner surface of the tire is preferably approximately rectangular. This allows for a uniform thickness of the sealant layer 60. In addition, adjacent circumferential portions 62 are in close contact with each other in the tire width direction, making it difficult for gaps to form between the circumferential portions 62.

[0034] When the sealant material 61 is applied in steps to the inner surface of the tire as described above, as shown in Figure 4, the first circumferential portion 62A, which is formed first at one end in the tire width direction (left side in Figure 4), has a first sealant material increase portion 62A1 that overlaps in the tire thickness direction with the transition portion 63 from the first circumferential portion 62A to the adjacent circumferential portion 62. The last circumferential portion 62B, which is formed last at the other end in the tire width direction (right side in Figure 4), has a second sealant material increase portion 62B1 that overlaps in the tire thickness direction with the transition portion 63 that transitions to the last circumferential portion 62B. The first sealant material increase portion 62A1 is a triangular portion where the transition portion 63 overlaps on the winding start end 61A. The second sealant material increase portion 62B1 is a triangular portion where the winding end end 61B overlaps on the transition portion 63.

[0035] As described above, both the winding start end 61A and the winding end 61B are positioned in the circumferential direction of the tire to correspond to the light point K. Therefore, the first sealant material increase section 62A1 and the second sealant material increase section 62B1 provided at these winding start end 61A and winding end end 61B are both positioned in the circumferential direction of the tire to correspond to the light point K. The first sealant material increase section 62A1 and the second sealant material increase section 62B1 are positioned at the light point K, which counteracts the heaviest static unbalance position in the circumferential direction of the tire. This compensates for the uneven weight balance of the tire 1 in the circumferential direction and improves the uniformity with respect to static unbalance.

[0036] In step S6, the dynamic unbalance compensation sealant placement step, as shown in Figure 4, the dynamic unbalance compensation sealant 65 is placed at the identified dynamic unbalance compensation position. The dynamic unbalance compensation sealant 65 can be made from a strip of sealant 61 cut to the required length. The dynamic unbalance compensation sealant 65 is attached to a position adjacent to one side in the tire width direction of the sealant layer 60 on the inner surface of the tire. This dynamic unbalance compensation sealant 65 makes it possible to improve the uniformity with respect to dynamic unbalance.

[0037] According to the tire 1 of this embodiment, if a hole is created in the tread 20 by, for example, a nail, reaching the sealant layer 60, the hole is automatically sealed by the sealant layer 60, preventing a puncture.

[0038] According to the above embodiment, the following effects are achieved.

[0039] (1) The method for manufacturing a pneumatic tire according to the embodiment includes: a static unbalance position measurement step for measuring the static unbalance position of the tire 1; a light point identification step for identifying the light point K of the tire 1 based on the measured static unbalance position; and a sealant layer formation step for forming a sealant layer 60 by applying a strip-shaped sealant material 61 to the inner surface of the tire 1 while circumferencing it along the tire's circumferential direction, and shifting the circumferential path to one side in the tire's width direction at least every circumferential turn, thereby arranging annular circumferential portions 62 of the sealant material 61 extending in the tire's circumferential direction in parallel in the tire's width direction. In the sealant layer formation step, the starting end 61A and ending end 61B of the sealant material 61 to be circumferred on the inner surface of the tire 1 are positioned at the circumferential position of the tire corresponding to the light point K, and sealant material increase portions 62A1 and 62B1 are positioned at the starting end 61A and ending end 61B, respectively.

[0040] This makes it possible to provide a method for manufacturing a pneumatic tire that can improve the uniformity with respect to static imbalance of a pneumatic tire having a sealant layer 60 on the inner surface of the tire.

[0041] (2) In the tire manufacturing method according to the embodiment, it is preferable that a static unbalance position measurement step is performed, along with a dynamic unbalance position measurement step to measure the dynamic unbalance position of the tire 1, and further, a dynamic unbalance compensation position determination step is performed to determine the position in which the dynamic unbalance of the tire 1 is compensated based on the measured dynamic unbalance position, and a dynamic unbalance compensation sealant material placement step is performed to partially place the sealant material 61 at the determined dynamic unbalance compensation position.

[0042] This makes it possible to provide a method for manufacturing a pneumatic tire that can improve the uniformity with respect to the dynamic imbalance of a pneumatic tire having a sealant layer 60 on the inner surface of the tire.

[0043] (3) The pneumatic tire according to the embodiment comprises a tire 1 having a light point K and a sealant layer 60 provided on the inner surface of the tire 1, wherein the sealant layer 60 has a strip-shaped sealant material 61 that circulates along the tire circumferential direction, and the circumferential path shifts to one side in the tire width direction at least every circumferential turn, so that a plurality of annular circumferential portions 62 extending in the tire circumferential direction are arranged in parallel in the tire width direction, and of the plurality of circumferential portions 62, the circumferential portion 62 located at the end furthest in the tire width direction has a winding start end 61A of the sealant material 61, and the circumferential portion 62 located at the other end furthest in the tire width direction has a winding end 61B of the sealant material 61, and the respective tire circumferential positions of the winding start end 61A and winding end 61B correspond to the tire circumferential position of the light point K, and sealant material increase portions 62A1 and 62B1 are arranged at the winding start end 61A and winding end 61B, respectively.

[0044] This makes it possible to provide a pneumatic tire that can improve the uniformity with respect to static imbalance of a pneumatic tire having a sealant layer 60 on the inner surface of the tire.

[0045] Although embodiments have been described above, the present invention is not limited to the embodiments described above, and modifications, improvements, etc., that can be made to the extent that the objectives of the present invention can be achieved are also included within the scope of the present invention. [Explanation of Symbols]

[0046] 1. Pneumatic tire 60 sealant layer 61. Sealant material 61A Starting end of winding 61B End of reel 62 Loop Section 62A1, 62B1 Sealant material increase section 65 Dynamic unbalance compensating sealant K light point

Claims

[Claim 1] A static unbalance position measurement process for measuring the static unbalance position of a tire, A light point identification step is performed to identify the light point of the tire based on the measured static unbalance position, The sealant layer forming step includes applying a strip-shaped sealant material to the inner surface of the tire while circumferentially moving it along the tire's circumferential direction, and shifting the circumferential path to one side in the tire's width direction at least every circumferential turn, thereby forming a sealant layer with multiple annular circumferential portions of sealant material extending in the tire's circumferential direction arranged in parallel in the tire's width direction, In the sealant layer formation process, the starting and ending ends of the sealant material to be wound around the inner surface of the tire are positioned at the circumferential tire position corresponding to the light point, and an increased sealant material portion is provided at each of the starting and ending ends. Along with the static unbalance position measurement step, a dynamic unbalance position measurement step is performed to measure the dynamic unbalance position of the tire. Furthermore, based on the measured dynamic unbalance position, a dynamic unbalance compensation position determination step is performed to determine the position where the dynamic unbalance of the tire is compensated. A method for manufacturing a pneumatic tire, comprising a dynamic imbalance compensation sealant placement step of partially placing sealant material at identified dynamic imbalance compensation positions.

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