Management method for unvulcanized tread rubber

Abstract

To provide a control method of an unvulcanized tread rubber capable of suppressing occurrence of manufacturing defects.SOLUTION: A first reference position is set for each first portion of an unvulcanized tread rubber that can be pressed against projections of a mold to form a main groove when a mold is pressed to the unvulcanized tread rubber, an odd number of second reference positions that equally divide an interval between the pair of first reference positions are set for a second portion of the unvulcanized tread rubber between the pair of first reference positions, a thickness of the unvulcanized tread rubber at each of the first reference positions and the second reference positions are measured. For a plurality of reference positions including the first reference positions and the second reference positions, it is determined that the molding of the unvulcanized tread rubber is appropriate when a thickness difference of the unvulcanized tread rubbers at reference positions adjacent to each other is equal to or less than a predetermined value, and it is determined that the molding of the unvulcanized tread rubber is defective when the thickness difference of the unvulcanized tread rubbers at the reference positions adjacent to each other exceeds the predetermined value.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present disclosure relates to a method for managing unvulcanized tread rubber for manufacturing pneumatic tires.

Background Art

[0002] Pneumatic tires are manufactured by heating and pressing an unvulcanized green tire in a mold. The green tire is formed by combining unvulcanized tread rubber that forms a tread and a case that constitutes a body. The unvulcanized tread rubber has different thickness shapes (profile shapes) depending on the thickness of the portion where the main grooves of the tire after vulcanization are located and the thickness of the tread. Although unevenness is required in the thickness shape of the unvulcanized tread rubber, if the unevenness changes abruptly, a lateral rubber flow against the vent piece having a valve body provided in the mold will cause rubber clogging of the vent piece. The rubber clogging of the vent piece may cause manufacturing defects such as bear (dents on the tire surface) due to poor air venting. Patent Documents 1 and 2 disclose technologies related to vent pieces.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] The present disclosure provides a method for managing unvulcanized tread rubber capable of suppressing the occurrence of manufacturing defects.

Means for Solving the Problems

[0005] The method for managing an unvulcanized tread rubber of the present disclosure is as follows. When applying a mold having recesses forming tread lands and protrusions forming main grooves adjacent to both axial sides of the tread lands in the tire axial direction to the unvulcanized tread rubber, first reference positions are respectively set at first portions of the unvulcanized tread rubber that can hit the protrusions. For a second portion between the pair of first reference positions of the unvulcanized tread rubber, an odd number of second reference positions that equally divide the space between the pair of first reference positions are set. The thickness of the unvulcanized tread rubber is measured for each of the first reference positions and the second reference positions. When the thickness difference of the unvulcanized tread rubber at the adjacent reference positions among the plurality of reference positions including the first reference positions and the second reference positions is equal to or less than a predetermined value, it is determined that the molding of the unvulcanized tread rubber is appropriate. When the thickness difference of the unvulcanized tread rubber at the adjacent reference positions exceeds the predetermined value, it is determined that the molding of the unvulcanized tread rubber is defective.

Brief Description of the Drawings

[0006]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0007] [First Embodiment] Hereinafter, the method for managing the unvulcanized tread rubber 3 according to the first embodiment of the present disclosure will be described with reference to the drawings. FIG. 1 is a schematic cross-sectional view showing a manufacturing apparatus (vulcanizer) for a pneumatic tire, and only the green tire T is hatched.

[0008] In the manufacturing process of a pneumatic tire, there is a vulcanization process in which the green tire T is heated and pressurized. In the vulcanization process, the vulcanizer shown in FIG. 1 is used. With the bladder 1 to which internal pressure is applied supporting the green tire T, the mold 2 is closed. The mold 2 has an upper mold unit 20, a lower mold unit 21, and a sector 22. The sector 22 has a molding surface for forming the tread, and on the molding surface for forming the tread, there are recesses 24 for forming the tread lands and protrusions 23 for forming the main grooves on both sides of the tread lands in the tire axial direction AD. Since a plurality of main grooves and tread lands are formed in the tread of the tire, a plurality of protrusions 23 and recesses 24 are formed.

[0009] In the recess 24 for forming the tread land partitioned by the protrusion 23, there are provided vent holes (not shown) for exhausting the air between the mold 2 (sector 22) and the green tire T and vent pieces (not shown) having a valve function for closing the vent holes (not shown). When rubber flows along the tire radial direction with respect to the vent piece, it is difficult for the rubber to enter the valve. However, when rubber flows in the lateral direction (the direction along the surface direction of the tread surface in contact with the road surface) intersecting the tire radial direction with respect to the vent piece, the rubber is likely to clog in the valve, the vent piece fails to function, and air remains, which causes the occurrence of burrs.

[0010] FIGS. 2 to 4 are cross-sectional views schematically showing the contact position relationship between the sector 22 and the unvulcanized tread rubber 3. As shown in FIG. 2, the unvulcanized tread rubber 3 constituting the tread of the green tire T has some unevenness in accordance with the rubber volume of the unevenness of the tread pattern of the completed tire. However, if the difference in local unevenness becomes large, rubber flow is likely to occur along the direction intersecting the axial direction of the valve of the vent hole (the direction along the surface direction of the tread surface in contact with the road surface). Therefore, in the present embodiment, the unvulcanized tread rubber 3 of the green tire T is managed as follows.

[0011] First, as shown in FIG. 2, among the molds 2 (sectors 22), identify a first recess 24a that forms a tread land having the smallest dimension in the tire axial direction AD, and first protrusions 23a adjacent to both sides of the first recess 24a in the tire axial direction AD.

[0012] Next, when the mold 2 is applied to the unvulcanized tread rubber 3, set first reference positions P1 at first portions 3a of the unvulcanized tread rubber 3 that can hit the first protrusions 23a, respectively. Since the center of the mold 2 and the center of the unvulcanized tread rubber 3 supported by the vulcanizer are aligned, the first portion 3a may be identified along a reference. Although centering is performed between the mold 2 and the unvulcanized tread rubber 3, there may be a slight misalignment. The first portion 3a may be a portion with a high possibility, and it does not have to be exact. For example, if the first reference position P1 is set at the center of the portion identified as the first portion 3a, the possibility that the first reference position P1 hits the first protrusion 23a can be increased.

[0013] Next, as shown in FIG. 3, identify a second portion 3b of the unvulcanized tread rubber 3 that is between a pair of the first reference positions P1. The second portion 3b is a portion that becomes a tread land and can contact the recess 24 (first recess 24a) of the mold 2. For the second portion 3b, set an odd number of second reference positions P2 that equally divide the space between the pair of first reference positions P1. In the example of FIG. 3, three second reference positions P2 are set, but if it is an odd number, it may be 1, 5, 7 or more. In this way, reference positions P1 and P2 are set for the portion corresponding to the protrusion 23 that forms the main groove and the portion corresponding to the recess 24 that forms the tread land. Therefore, the thickness differences at the reference positions P1 and P2 include the thickness difference between the portion that becomes the groove bottom and the portion that becomes the tread surface of the tread land. Thus, it becomes possible to accurately measure the portion where the unevenness is steep, and it becomes easier to suppress the occurrence of manufacturing defects.

[0014] Next, as shown in FIG. 4, for the portion of the unvulcanized tread rubber 3 other than the first portion 3a and the second portion 3b (referred to as the third portion 3c), a plurality of third reference positions P3 are set at intervals of the distance between the first reference position P1 and the second reference position P2. The separation distance in the tire axial direction AD of the reference positions P1, P2, P3 including the first reference position P1, the second reference position P2, and the third reference position P3 in the first embodiment is 12 mm, but it is not limited thereto.

[0015] Next, for the plurality of reference positions P1, P2, P3 including the first reference position P1, the second reference position P2, and the third reference position P3, the thickness of the unvulcanized tread rubber 3 at each reference position P1, P2, P3 is measured. The thickness means the thickness in the radial direction of the tire, which is the vertical direction in FIGS. 2 to 4. Next, the thickness difference of the unvulcanized tread rubber 3 at the mutually adjacent reference positions P1, P2, P3 is calculated. If all the thickness differences of the unvulcanized tread rubber 3 at the mutually adjacent reference positions P1, P2, P3 are below a predetermined value, it is determined that the molding of the unvulcanized tread rubber 3 is appropriate. Here, when there are five reference positions, there are four thickness differences, and if all four thickness differences are below the predetermined value, it is determined that the molding of the unvulcanized tread rubber 3 is appropriate. In the first embodiment, the predetermined value is 1.0 mm. If the thickness difference is 1.0 mm or less, it is determined that the molding is appropriate, and if the thickness difference exceeds 1.0 mm, it is determined that the molding is defective. However, the predetermined value can be changed as appropriate. On the other hand, if even one of the thickness differences of the unvulcanized tread rubber 3 at the mutually adjacent reference positions exceeds the predetermined value, it is determined that the molding of the unvulcanized tread rubber 3 is defective. When it is determined that the molding is defective, the die for discharging the rubber for extruding the unvulcanized tread rubber 3 may be modified. After modifying the die, the unvulcanized tread rubber 3 is discharged again, and the above management method is applied to the discharged unvulcanized tread rubber 3, and the modification of the die is repeated until the molding becomes appropriate. The management method of the unvulcanized tread rubber 3 of the first embodiment is a method for checking whether the molding of the unvulcanized tread rubber 3 by the die is appropriate. Once it is determined that the molding is appropriate, the confirmation can be omitted thereafter.

[0016] As described above, although not particularly limited, the method for controlling the unvulcanized tread rubber 3 of the first embodiment is as follows. When the mold 2 having the concave portions 24 forming the tread lands and the protrusions 23 forming the main grooves adjacent to both sides of the tread lands in the tire axis direction AD is applied to the unvulcanized tread rubber 3, first reference positions P1 are respectively set at the first portions 3a of the unvulcanized tread rubber 3 that can hit the protrusions 23. For the second portion 3b between the pair of first reference positions P1 of the unvulcanized tread rubber 3, an odd number of second reference positions P2 that equally divide the interval between the pair of first reference positions P1 are set. For each of the first reference position P1 and the second reference position P2, the thickness of the unvulcanized tread rubber 3 is measured. When the thickness difference of the unvulcanized tread rubber 3 at the adjacent reference positions P1 and P2 among the plurality of reference positions P1 and P2 including the first reference position P1 and the second reference position P2 is equal to or less than a predetermined value, it is determined that the molding of the unvulcanized tread rubber 3 is appropriate. When the thickness difference of the unvulcanized tread rubber 3 at the adjacent reference positions P1 and P2 exceeds the predetermined value, it may be determined that the molding of the unvulcanized tread rubber 3 is defective.

[0017] In this way, by setting an odd number of second reference positions P2 between the two first reference positions P1 set at the first portions 3a corresponding to the main grooves, one of the second reference positions P2 is set at the center of the tread land in the tire axis direction AD. By measuring the thickness of the unvulcanized tread rubber 3 at the reference positions P1 and P2 including the first reference position P1 and the second reference position P2 and suppressing the thickness difference of the unvulcanized tread rubber 3 at the adjacent reference positions P1 and P2 to be equal to or less than a predetermined value, the undulations of the rubber entering the concave portions 24 forming the tread lands can be suppressed. Therefore, it is possible to suppress the rubber entering the concave portions 24 forming the tread lands from flowing in the lateral direction (the direction orthogonal to the tire diameter direction and along the contact surface of the tread land with the road surface). As a result, it is possible to suppress the rubber clogging of the vent piece.

[0018] Although not particularly limited, as in the first embodiment, the mold 2 has a plurality of recesses 24 that form tread lands. Among the molds 2, a first recess 24a that forms a tread land with the smallest dimension in the tire axial direction AD is specified, and a pair of first protrusions 23a adjacent to both sides of the first recess 24a in the tire axial direction AD are specified. Among the unvulcanized tread rubber 3, a first reference position P1 is set at a first portion 3a that can hit the pair of first protrusions 23a, a second reference position P2 is set for a second portion 3b that can hit the first recess 24a, and for portions other than the first portion 3a and the second portion 3b of the unvulcanized tread rubber 3, a plurality of third reference positions P3 spaced apart by the interval between the first reference position P1 and the second reference position P2 may be set. In this way, if the reference positions P1, P2, and P3 are set at intervals corresponding to the tread land with the smallest dimension in the tire axial direction AD, the thickness difference between the portion that becomes the groove bottom and the portion that becomes the tread land can be accurately measured, and the rubber clogging of the vent piece can be further suppressed.

[0019] As described above, the embodiments of the present disclosure have been described based on the drawings. However, the specific configuration should be considered not to be limited to these embodiments. The scope of the present disclosure is shown not only by the description of the above embodiments but also by the claims, and further includes all changes within the meaning and scope equivalent to the claims.

[0020] It is possible to adopt the structure employed in each of the above embodiments in any other embodiment. The specific configuration of each part is not limited to only the above-described embodiments, and various modifications are possible without departing from the gist of the present disclosure.

[0021] It is possible to adopt the structure employed in each of the above embodiments in any other embodiment.

Explanation of Reference Numerals

[0022] 24... recess, 24a... first recess, 23... protrusion, 23a... first protrusion, 3... unvulcanized tread rubber, 3a... first part, 3b... second part, 3c... third part, P1... first reference position (reference position), P2... second reference position (reference position), P3... third reference position (reference position).

Claims

1. When applying a mold having recesses forming tread lands and protrusions forming main grooves adjacent to both sides of the tread lands in the tire axial direction to an unvulcanized tread rubber extruded by discharging rubber with a base, first reference positions are set respectively at first portions of the unvulcanized tread rubber that can hit the protrusions, For a second portion between the pair of first reference positions among the unvulcanized tread rubber, an odd number of second reference positions that equally divide the space between the pair of first reference positions are set, The thickness of the unvulcanized tread rubber is measured for each of the first reference positions and the second reference positions, When the thickness difference of the unvulcanized tread rubber at the adjacent reference positions among the plurality of reference positions including the first reference positions and the second reference positions is equal to or less than a predetermined value, it is determined that the molding of the unvulcanized tread rubber is appropriate, and when the thickness difference of the unvulcanized tread rubber at the adjacent reference positions exceeds the predetermined value, it is determined that the molding of the unvulcanized tread rubber is defective. A method for managing unvulcanized tread rubber.

2. The mold has a plurality of the recesses forming the tread lands, Among the molds, a first recess forming a tread land having the smallest dimension in the tire axial direction, A pair of first protrusions adjacent to both sides of the first recess in the tire axial direction are specified, Among the unvulcanized tread rubber, the first reference position is set at the first portion that can hit the pair of first protrusions, and the second reference position is set for the second portion that can hit the first recess, For portions other than the first portion and the second portion of the unvulcanized tread rubber, a plurality of third reference positions are set at intervals equal to the interval between the first reference position and the second reference position. The method for managing unvulcanized tread rubber according to Claim 1.

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