Method for manufacturing pneumatic tire

Abstract

To provide a method for manufacturing a pneumatic tire having high cornering power and low maximum cornering force.SOLUTION: A method for manufacturing a pneumatic tire is a method for manufacturing the pneumatic tire having a pair of beads, a pair of sidewalls extending radially outward from each of the pair of beads, a tread disposed between the pair of sidewalls, and a carcass ply spanning between the pair of beads. The method for manufacturing the pneumatic tire includes: a step of vulcanizing and molding a raw tire to obtain a vulcanized tire; and a step of cooling the vulcanized tire while inflating it at an internal pressure of 0.04 MPa or less.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a method for manufacturing a pneumatic tire. [Background technology]

[0002] Conventionally, a pneumatic tire has been known that includes a pair of beads, a pair of sidewalls extending radially outward from each of the pair of beads, a tread disposed between the pair of sidewalls, and a carcass ply spanning between the pair of beads (see, for example, Patent Document 1).

[0003] Patent Document 2 describes a method for manufacturing a pneumatic tire, which includes a vulcanization process in which an unvulcanized tire is vulcanized in a vulcanization mold while applying internal pressure to a bladder, followed by a post-cure inflation process in which the vulcanized tire is inflated and cooled. Here, when venting at the end of the vulcanization process, the internal pressure of the bladder is not lowered to atmospheric pressure but is maintained in the range of 0.05 to 1.0 MPa, and the process proceeds to the post-cure inflation process. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2023-69500 [Patent Document 2] JP 2009-18445 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the post-cure inflation process, tension is applied to the carcass cords constituting the carcass ply of the vulcanized tire, and the carcass cords are held in a stretched state, which reduces the lateral rigidity of the pneumatic tire. As a result, when the cornering power of the pneumatic tire increases, the maximum cornering force of the pneumatic tire also increases. Here, when the maximum cornering force of the pneumatic tire increases, the pneumatic tire may grip too much when the vehicle turns with a large steering angle, causing the vehicle to roll.

[0006] An object of the present invention is to provide a method for manufacturing a pneumatic tire having high cornering power and low maximum cornering force. [Means for solving the problem]

[0007] One aspect of the present invention is a method for manufacturing a pneumatic tire comprising a pair of beads, a pair of sidewalls extending radially outward from each of the pair of beads, a tread disposed between the pair of sidewalls, and a carcass ply spanning between the pair of beads, the method including the steps of vulcanizing a raw tire to obtain a vulcanized tire, and cooling the vulcanized tire while expanding it at an internal pressure of 0.04 MPa or less. Effect of the Invention

[0008] According to the present invention, it is possible to provide a manufacturing method for a pneumatic tire having high cornering power and low maximum cornering force. [Brief description of the drawings]

[0009] [Figure 1] 1 is a diagram showing a half cross section in the tire width direction of a pneumatic tire manufactured by a manufacturing method for a pneumatic tire according to one embodiment of the present invention. [Diagram 2] FIG. 1 is a diagram showing an example of a post-cure inflation device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0011] 1 shows a pneumatic tire (hereinafter referred to as tire 1) manufactured by a method for manufacturing a pneumatic tire according to one embodiment of the present invention. The tire 1 is a pneumatic tire for passenger cars, but may also be a pneumatic tire for various vehicles such as light trucks, trucks, and buses.

[0012] The basic structure of the tire 1 is symmetrical in a cross section in the tire width direction. Fig. 1 shows a half cross section of the right half of the tire 1, and the left half (not shown) has the same structure. In Fig. 1, the tire equatorial plane S1 is a plane perpendicular to the tire rotation axis (tire meridian) and is located at the center in the tire width direction.

[0013] FIG. 1 shows a tire 1 mounted on a standard rim and inflated to a standard internal pressure under no load. The standard rim refers to a standard rim determined by JATMA for a tire size. The standard internal pressure is also determined by JATMA. For example, the standard internal pressure for pneumatic tires for passenger cars is 180 kPa.

[0014] Here, the tire width direction is a direction parallel to the tire rotation axis, and is the left-right direction on the paper in Fig. 1. In Fig. 1, it is illustrated as the tire width direction X. The inner side in the tire width direction is a direction approaching the tire equatorial plane S1, and is the left side on the paper in Fig. 1. The outer side in the tire width direction is a direction away from the tire equatorial plane S1, and is the right side on the paper in Fig. 1.

[0015] The tire radial direction is a direction perpendicular to the tire rotation axis, and is the up-down direction on the paper in Fig. 1. In Fig. 1, this is illustrated as tire radial direction Y. The outer side in the tire radial direction is a direction away from the tire rotation axis, and is the upper side on the paper in Fig. 1. The inner side in the tire radial direction is a direction approaching the tire rotation axis, and is the lower side on the paper in Fig. 1.

[0016] 1, the tire 1 includes a pair of beads 10 provided on both sides in the tire width direction, a pair of sidewalls 20 extending radially outward from each of the pair of beads 10, a tread 30 disposed between the pair of sidewalls 20, a carcass ply 40 spanning between the pair of beads 10, and an inner liner 50 disposed on the tire cavity side of the carcass ply 40. Details of the structure of the tire 1 will be described later.

[0017] The manufacturing method of tire 1 includes a step of vulcanizing a raw tire to obtain a vulcanized tire, and a step of cooling the vulcanized tire while expanding it. At this time, the internal pressure at which the vulcanized tire is expanded is 0.04 MPa or less, preferably 0.01 MPa or more and 0.04 MPa or less, and more preferably 0.02 MPa or more and 0.04 MPa or less. If the internal pressure at which the vulcanized tire is expanded exceeds 0.04 MPa, the lateral rigidity of tire 1 decreases. As a result, if the cornering power (hereinafter referred to as CP) of tire 1 increases, the maximum cornering force (hereinafter referred to as CF max ) will also become more expensive.

[0018] When vulcanizing and molding a green tire, a known vulcanizing mold is used and heating and pressurization are performed under predetermined conditions.

[0019] When cooling a vulcanized tire while expanding it, for example, a post-cure inflation device (hereinafter referred to as a PCI device) 100 shown in Fig. 2 is used. In the PCI device 100, a pair of rims 102 on which the vulcanized tire T is mounted is disposed at a predetermined position of a support 101. The support 101 is also connected to an air supply pipe 103 and an air discharge pipe 104 that supply and discharge air to and from the inner cavity of the vulcanized tire T. Furthermore, an air valve 105 that adjusts the internal pressure of the vulcanized tire T is installed in the region of the support 101 where the pair of rims 102 are disposed.

[0020] Next, a method of cooling the vulcanized tire T while inflating it using the PCI device 100 will be described. First, the vulcanized tire T is mounted on the rim 102, and then air is supplied from the air supply pipe 103 to the inner cavity of the vulcanized tire T to inflate the vulcanized tire T. At this time, the internal pressure of the vulcanized tire T is adjusted by the air valve 105. In addition, the internal pressure of the vulcanized tire T is detected by a pressure sensor. Next, when a predetermined time has passed, that is, when cooling of the vulcanized tire T is completed, the air supplied to the inner cavity of the vulcanized tire T is discharged to the outside from the air discharge pipe 104, and the vulcanized tire T is removed from the rim 102.

[0021] In addition, since the PCI device 100 is equipped with two sets of rims 102, while the vulcanized tire T mounted on one rim 102 is being cooled, the vulcanized tire T can be removed from the other rim 102, and then the next vulcanized tire T to be cooled can be mounted.

[0022] As the PCI device, a known PCI device other than the PCI device 100 may be used.

[0023] The structure of the tire 1 will be described in detail below.

[0024] The bead 10 includes a bead core 11, a bead filler 12 extending radially outward from the bead core 11, a reinforcing layer 13 that reinforces the outer side of the bead filler 12 in the tire width direction, a chafer 14, and a rim protector 15. Note that the reinforcing layer 13 may be omitted if necessary.

[0025] The bead core 11 is an annular member in which a metal bead wire covered with rubber is wound multiple times in the tire circumferential direction, and is provided to fix the tire 1 to a rim.

[0026] The bead filler 12 is a member made of hard rubber, and since the rigidity of the periphery of the bead filler 12 of the tire 1 is high, the deflection of the tire 1 is small even when a high load is applied to the tire 1. The bead filler 12 has a shape that tapers toward the outside in the tire radial direction.

[0027] The ratio of the length of the bead filler 12 in the tire radial direction to the cross-sectional height L0 of the tire 1 (see FIG. 1) is preferably 25% or more and 45% or less, and more preferably 25% or more and 30% or less.

[0028] The cross-sectional height of a pneumatic tire means the distance between the surface of the tread at the center of the pneumatic tire and the measurement point of the rim diameter when the pneumatic tire is mounted on a specified rim, inflated to a specified internal pressure, and in an unloaded state.

[0029] The reinforcing layer 13 is a component in which multiple metal cords formed by twisting multiple metal fibers together are covered with topping rubber. Since the rigidity around the reinforcing layer 13 of the tire 1 is increased, the deflection of the tire 1 is reduced even when a high load is applied to the tire 1.

[0030] The multiple metal cords extend at an incline with respect to the radial direction of the tire 1, and are arranged at predetermined intervals in the tire circumferential direction. The intervals between the metal cords arranged in the tire circumferential direction increase toward the outside in the tire radial direction. The inclination angle between the radial direction of the tire 1 and the extending direction of the metal cords of the reinforcing layer 13 is preferably 10° or more and 40° or less.

[0031] The metal cord is not particularly limited, but may be, for example, a steel cord. The steel cord is made by twisting together several to several tens of wires made of high carbon steel with a diameter of about 0.1 mm to 0.5 mm, and may be plated as necessary to improve adhesion to rubber.

[0032] 2, the carcass ply 40 has a main body portion 40a and a folded-up portion 40b that is connected to the main body portion 40a and folded back along a part of the inner side in the tire radial direction of the bead core 11, while a part of the reinforcing layer 13 is sandwiched between a part of the outer side in the tire radial direction of the bead filler 12 and the folded-up portion 40b. Also, the remaining part of the reinforcing layer 13 is sandwiched between the main body portion 40a and the folded-up portion 40b.

[0033] The bead 10 does not have a reinforcing layer that reinforces the inner side of the bead filler 12 in the tire width direction.

[0034] The chafer 14 is provided along a part of the carcass ply 40 on the inner side in the radial direction of the tire.

[0035] The rim protector 15 is a member including a rim strip rubber 16, and is arranged on the outer side of the chafer 14 and the folded-back portion 40b in the tire width direction. The rim protector 15 has a peak 15a formed on its outer surface along the tire circumferential direction, and comes into contact with the inside of the rim on which the tire 1 is mounted. The rim protector 15 is continuous in an annular shape in the tire circumferential direction, and is provided to protect the rim.

[0036] The sidewall 20 is a member including a sidewall rubber 21, and is disposed on the outer side in the tire width direction of the carcass ply 40. The sidewall rubber 21 constitutes the outer wall surface of the tire 1, and is the portion that deflects the most when a load is applied to the tire 1.

[0037] The tread 30 includes an endless belt 31 , a cap ply 32 , and a tread rubber 33 .

[0038] The belt 31 is provided to reinforce the tread 30, and is disposed on the tire radial outer side of the carcass ply 40. The belt 31 is a laminated structure in which a first belt 311 and a second belt 312 are laminated. Here, the second belt 312 is disposed on the tire radial outer side of the first belt. The first belt 311 and the second belt 312 are members in which a plurality of steel cords are covered with rubber. The tire width direction outer end of the first belt 311 is located on the tire width direction outer side of the tire width direction outer end of the second belt 312. The belt 31 ensures the rigidity of the tire 1, and improves the contact of the tread 30 with the road surface.

[0039] The belt 31 may be a single-layer structure or a laminated structure of three or more layers.

[0040] The cap ply 32 is provided to reinforce the tread 30 together with the belt 31, and is disposed on the outer side of the belt 31 in the tire radial direction. The cap ply 32 is a member in which a plurality of insulating fiber cords (e.g., polyamide cords) are covered with rubber. The outer end of the cap ply 32 in the tire width direction is located on the outer side in the tire width direction than the outer end of the first belt 311 in the tire width direction. Therefore, the belt 31 is covered with the cap ply 32. The cap ply 32 improves the durability of the tire 1 and reduces road noise during running.

[0041] The tread rubber 33 is disposed on the outer side of the cap ply 32 in the tire radial direction. The tread rubber 33 is a member that constitutes the tread surface that comes into contact with the road surface during running. The tread surface of the tread rubber 33 is provided with a tread pattern that is composed of a plurality of grooves, for example.

[0042] The carcass ply 40 is embedded in the tire 1 in a manner that passes between a pair of beads 10 and on the tire cavity side of a pair of sidewalls 20 and the tread 30 .

[0043] The carcass ply 40 is a member in which a plurality of carcass cords (e.g., polyester cords, polyamide cords) that form the framework of the tire 1 are covered with rubber. The plurality of carcass cords extend along a plane along the tire width direction, and are arranged side by side in the tire circumferential direction. At this time, the carcass cords extend in the radial direction of the tire 1.

[0044] The carcass ply 40 is a laminated structure in which a first carcass ply 401 and a second carcass ply 402 are laminated. Here, the second carcass ply 402 is disposed on the outer side in the tire radial direction or the outer side in the tire width direction of the first carcass ply 401 in the main body portion 40a, and is disposed on the inner side in the tire radial direction or the inner side in the tire width direction of the first carcass ply in the folded-back portion.

[0045] The carcass ply 40 may be a single-layer structure or a laminated structure of three or more layers.

[0046] The inner liner 50 is a member made of air-permeable rubber and is provided to prevent air in the tire cavity from leaking to the outside. The inner liner 50 covers the inner surface of the first carcass ply 401 in the area of ​​the main body 40a that is not covered by the chafer 14. The inner liner 50 also covers the inner surface of the chafer 14 in the area of ​​the main body 40a that is covered by the chafer 14.

[0047] The inner liner 50 is a laminated structure in which a first inner liner 501 and a second inner liner 502 are laminated. Here, the second inner liner 502 is disposed on the outer side of the first inner liner 501 in the tire radial direction or the outer side in the tire width direction.

[0048] The inner liner 50 may be a single-layer structure or a laminated structure of three or more layers.

[0049] Although the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and the above embodiment may be modified as appropriate within the scope of the spirit of the present invention.

[0050] The configuration of the embodiment of the present invention is as follows.

[0051] (1) A method for manufacturing a pneumatic tire including a pair of beads, a pair of sidewalls extending radially outward from each of the pair of beads, a tread disposed between the pair of sidewalls, and a carcass ply spanning between the pair of beads, the method including the steps of: vulcanizing a raw tire to obtain a vulcanized tire; and cooling the vulcanized tire while inflating it at an internal pressure of 0.04 MPa or less.

[0052] (2) The method for manufacturing a pneumatic tire described in (1), wherein the bead comprises a bead core, a bead filler extending radially outward from the bead core, and a reinforcing layer reinforcing an outer side of the bead filler in the tire width direction.

[0053] (3) The method for manufacturing a pneumatic tire described in (2), wherein the carcass ply has a main body portion and a folded-back portion connected to the main body portion and folded back along at least a portion of the bead core, a portion of the reinforcing layer is sandwiched between a portion of the bead filler and the folded-back portion, and a remainder of the reinforcing layer is sandwiched between the main body portion and the folded-back portion. EXAMPLES

[0054] Examples of the present invention will be described below, but the present invention is not limited to these examples.

[0055] (Reference Example 1, Examples 1 to 3, Comparative Examples 1 to 4) The raw tire was vulcanized and molded using a vulcanizing mold to obtain a vulcanized tire. Next, the vulcanized tire was cooled while being inflated using a post-cure inflation device (see Figure 2) to obtain a pneumatic tire for passenger cars (see Figure 1). At this time, the internal pressure for inflating the vulcanized tire was adjusted to a predetermined value (see Table 1).

[0056] (lateral stiffness) After mounting the pneumatic tire on a specified rim, it was inflated to a specified internal pressure and a standard load was applied to the tire. When a lateral force was applied to the tire with the tire under this condition, the lateral force required to deflect the tire laterally by a unit length (1 mm) was measured, and an index was evaluated based on the lateral force of the pneumatic tire of Reference Example 1.

[0057] Here, the normal load is the "TIRE LOAD CAPACITY" in ETRTO, and in the case of a pneumatic tire for a passenger car, it is a load equivalent to 88% of the above load.

[0058] (CP) After mounting the pneumatic tire on a specified rim, a drum-type testing machine was used to measure the CF by setting the air pressure to 230 kPa and applying a load that was 70% of the maximum load of the load index. At this time, the CP was calculated from the CF at a slip angle of 1°, and an index evaluation was performed based on the CP of the pneumatic tire of Reference Example 1. Here, the target value of CP is 102 or more.

[0059] (CF max ) After mounting the pneumatic tire on the specified rim, a flat belt type tire testing machine is used, the air pressure is set to 230kPa, and the running speed is 80km / h. A load of 70% of the maximum load of the load index is applied, and the steering angle is gradually increased. The CF max The CF of the pneumatic tire of Reference Example 1 was measured. max The index was evaluated based on the following: CF max The target value is 96 or less.

[0060] Table 1 shows the evaluation results of the pneumatic tires.

[0061] [Table 1]

[0062] From Table 1, the pneumatic tires of Examples 1 and 2 have high lateral rigidity, so even if the CP is high, the CF max In contrast, in the pneumatic tires of Comparative Examples 1 and 2, the internal pressure for inflating the vulcanized tire is 0.1 to 0.2 MPa, so that the lateral rigidity is low and when the CP is high, the CF max will also be higher. [Explanation of symbols]

[0063] 1 Tire 10 Beads 11 Bead core 12 Bead filler 13 Reinforcement layer 20 Sidewall 30 Tread 33 Tread rubber 40 Carcass ply 40a Main body 40b Folded part 100 Post-cure inflation (PCI) device 102 Rims T Vulcanized tires

Claims

1. A method for manufacturing a pneumatic tire comprising: a pair of beads; a pair of sidewalls extending radially outward from each of the pair of beads; a tread disposed between the pair of sidewalls; and a carcass ply spanning between the pair of beads, the method comprising the steps of: A process of vulcanizing and molding the raw tire to obtain a vulcanized tire; and cooling the vulcanized tire while inflating it at an internal pressure of 0.04 MPa or less.

2. 2. The method for manufacturing a pneumatic tire according to claim 1, wherein the bead comprises a bead core, a bead filler extending outward in a tire radial direction from the bead core, and a reinforcing layer reinforcing an outer side of the bead filler in a tire width direction.

3. The carcass ply has a main body portion and a turn-up portion connected to the main body portion and turned up along at least a portion of the bead core, A portion of the reinforcing layer is sandwiched between a portion of the bead filler and the folded-back portion, The method for manufacturing a pneumatic tire according to claim 2 , wherein the remaining portion of the reinforcing layer is sandwiched between the main body portion and the folded-back portion.

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