Manufacturing method of precured tread and retreaded tire

Abstract

In precured tread according to the present invention, a tapered region, in which the thickness of the precured tread gradually decreases from an inner side in a width direction toward a tread end, is formed in a shoulder region. A manufacturing method of a retreaded tire according to the present invention is a manufacturing method of a retreaded tire using the above-described precured tread.

Description

Method for manufacturing a precure tread and a retread tire

[0001] The present invention relates to a method for manufacturing a precure tread and a retread tire.

[0002] As a general method for manufacturing a retread tire, a precure (cold retread) method and a mold cure (hot retread) method are known. Among these, in the precure method, first, after buffing a casing tire, a cushion rubber is attached to the casing tire. Then, a tread rubber (precure tread) having substantially the same thickness from the pre-vulcanized tire center portion to the shoulder portion is disposed on the cushion rubber, and vulcanization treatment is performed at a low temperature to bond the casing tire and the precure tread (see, for example, Patent Documents 1 and 2).

[0003] Since the precure method mainly performs vulcanization at a low temperature, it has little influence on the tire structure and can manufacture a retread tire with high tread dimensional accuracy.

[0004] Japanese Patent Application Laid-Open No. 2010-173614 Japanese Patent Application Laid-Open No. 2011-255563 Problems to be solved by the invention

[0005] However, in the above manufacturing method, since the thickness of the precure tread is uniform in the width direction, the ground contact pressure at the shoulder end of the retread tire becomes high. Further, such a retread tire has a structure in which a cushion rubber is disposed between the precure tread and the casing tire. In order to ensure the adhesiveness between the precure tread and the casing tire, a rubber having a relatively low hardness is usually used for the cushion rubber. Therefore, there is a possibility that cracks may occur in the cushion rubber between the shoulder end of the precure tread and the casing tire on the outer side of the vehicle mounting when the tire is mounted on the vehicle.

[0006] Therefore, an object of the present invention is to provide a method for manufacturing a precure tread and a retread tire that can suppress the occurrence of cracks in the cushion rubber in a retread tire manufactured by the precure method.

[0007] The gist of the present invention is as follows: (1) A pre-cure tread having one or more circumferential main grooves extending in the circumferential direction, characterized in that a tapered region is formed in the shoulder region, which is the tire width region located outside in the width direction of the circumferential main groove that is the outermost circumferential main groove in the width direction, in which the thickness of the pre-cure tread gradually decreases from the inside in the width direction toward the tread edge. Here, "circumferential main groove" means a groove that extends in the circumferential direction and has a groove width (opening width) of 2 mm or more.

[0008] (6) A method for manufacturing a retreaded tire, comprising the steps of: buffing a base tire; attaching cushion rubber to the buffed base tire; attaching the pre-cured tread to the cushion rubber; and performing cold vulcanization on the base tire to which the pre-cured tread has been attached.

[0009] According to the present invention, it is possible to provide a pre-cure tread, a retread tire, and a method for manufacturing a retread tire that can suppress the occurrence of cracks in the cushion rubber in a retread tire manufactured by a pre-cure method.

[0010] This is a cross-sectional view in the width direction showing a pre-cured tread according to one embodiment of the present invention.

[0011] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0012] <Pre-cure Tread> Figure 1 is a cross-sectional view in the width direction showing a pre-cure tread according to one embodiment of the present invention. This pre-cure tread 1 is used in the manufacture of retreaded tires by the pre-cure (cold retread) method and is pressed onto a base tire via a cushion rubber. Only one half in the width direction, with the center line CL corresponding to the tire equator as the boundary, is shown, but the other half has a similar configuration. On the other hand, in this disclosure, the configuration can be different between the width halves with the center line CL as the boundary.

[0013] As shown in Figure 1, this pre-cure tread 1 is provided with one or more circumferential main grooves 2 extending in the circumferential direction. In the illustrated example, one half in the width direction is provided with two circumferential main grooves 2a and 2b, but one half in the width direction may have one or three or more circumferential main grooves 2. Alternatively, if one half in the width direction has one or more circumferential main grooves 2, the other half in the width direction does not need to have circumferential main grooves 2 formed therein.

[0014] In the illustrated example, the pre-cured tread 1 has a trapezoidal shape. Specifically, this pre-cured tread 1 has an outer contour shape consisting of a tread surface (upper surface in the illustration) S1 which will become the tread surface of the retread tire after cold vulcanization, a base surface (lower surface in the illustration) S2 which will be pressed against the cushion rubber, and a side surface S3 which connects these.

[0015] The tread edge E is the widthwise edge of the tread surface of the retread tire after cold vulcanization, and is also the intersection of the tread surface S1 and the side surface S3. In the illustrated example, the tread surface S1 (excluding the tapered region 3 described later) and the base surface S2 extend straight without inclination in the width direction (straight in the left-right direction shown in the illustration), while the side surface S3 extends at an inclination angle θ with respect to the base surface S2. The inclination angle θ can be, for example, 50 to 80°.

[0016] Here, as shown in the figure, the tire widthwise region R is defined as the region outside the circumferential main groove 2a, which is the outermost circumferential main groove 2 in the widthwise direction among the one or more circumferential main grooves 2.

[0017] In this embodiment, the pre-cured tread 1 has a tapered region 3 in the shoulder region R where the thickness of the pre-cured tread 1 gradually decreases (continuously decreases) from the inside in the width direction toward the tread end E. The effects and advantages of the pre-cured tread 1 of this embodiment will be described below.

[0018] According to the pre-cure tread 1 of this embodiment, a retread tire can be manufactured by using the pre-cure tread 1 to buff a base tire, attaching a cushion rubber to the buffed base tire, attaching the pre-cure tread 1 of this embodiment to the cushion rubber, and performing cold vulcanization on the base tire with the pre-cure tread 1 attached. The retread tire manufactured in this manner uses the pre-cure tread 1 in which a tapered region 3 is formed in the shoulder region R, and therefore has a rounded shape at the shoulder end. As a result, the contact pressure at the shoulder end can be reduced when the tire makes contact with the ground, and the distortion of the cushion rubber in the portion corresponding to the shoulder end region can be reduced. As described above, according to the pre-cure tread 1 of this embodiment, it is possible to suppress the occurrence of cracks in the cushion rubber in a retread tire manufactured by the pre-cure method.

[0019] As shown in the figure, when the maximum width of the pre-cure tread 1 (width of the base surface S2) is 2L, it is preferable that the tapered region 3 is formed over a widthwise region, at least from the tread end E (starting point) to a position (ending point) spaced L / 3 inward in the widthwise direction from the tread end E. This is because it makes the effect of reducing the ground pressure at the shoulder end more reliable and more reliably suppresses the occurrence of cracks in the cushion rubber.

[0020] Furthermore, it is preferable that the tapered region 3 is formed over a widthwise region from the tread edge E (starting point) to the position (end) of the circumferential main groove 2a located at the outermost point in the widthwise direction. This is because it makes the effect of reducing the ground pressure at the shoulder edge described above more reliable and more reliably suppresses the occurrence of cracks in the cushion rubber. Note that, depending on the position of the circumferential main groove 2a located at the outermost point in the widthwise direction, it is possible that either the "position spaced L / 3 inward in the widthwise direction from the tread edge E" or the "position of the circumferential main groove 2a located at the outermost point in the widthwise direction" may be located further inward in the widthwise direction.

[0021] The tapered region 3 may also be formed in the widthwise region inward from the circumferential main groove 2a located at the outermost point in the widthwise direction.

[0022] The thickness of the pre-cure tread 1 at the tread edge E is preferably less than the maximum thickness of the pre-cure tread 1 in the shoulder region R by an amount of 5% to 30% of the groove depth (maximum depth) OTD of the circumferential main groove 2a located on the outermost side in the width direction. In other words, the drop height δt of the pre-cure tread 1 at the tread edge E is preferably less than the groove depth OTD by an amount of 5% to 30%. By setting it to 5% or more, the effect of reducing the contact pressure at the shoulder edge described above can be made more reliable, and the occurrence of cracks in the cushion rubber can be more reliably suppressed. On the other hand, by setting it to 30% or less, the contact shape can be not impaired, and the occurrence of uneven wear due to the progression of wear at the shoulder edge can be suppressed. For similar reasons, the thickness of the pre-cure tread 1 at the tread edge E is preferably less than the maximum thickness of the pre-cure tread 1 in the shoulder region R by an amount of 10% to 20% of the groove depth OTD of the circumferential main groove 2a located on the outermost side in the width direction.

[0023] The tapered shape of the tapered region 3 may be straight in the widthwise cross-section as shown in the figure, or it may be curved. Alternatively, the tapered shape of the tapered region 3 may be broken in the widthwise cross-section, or it may be a curve with an inflection point.

[0024] The maximum width 2L of the pre-cure tread 1 is not particularly limited, but can be, for example, 180 to 270 mm. The groove depth of the circumferential main groove 2a is not particularly limited, but can be, for example, 11 to 17 mm. In the illustrated example, the groove depth of the circumferential main groove 2a and the groove depth of the circumferential main groove 2b are the same, but if the pre-cure tread 1 has two or more circumferential main grooves 2, the groove depths may be the same or different. For example, if a specification with large center wear is expected when making a retreaded tire, it is preferable to make the groove depth of the circumferential main groove 2b greater than the groove depth of the circumferential main groove 2a.

[0025] <Method for Manufacturing Retread Tires> One example of a method for manufacturing a retread tire according to one embodiment of the present invention is a method using the pre-cure tread 1 of the above embodiment. The method of this embodiment includes the steps of buffing a base tire, attaching cushion rubber to the buffed base tire, attaching the pre-cure tread 1 of the above embodiment to the cushion rubber, and performing cold vulcanization on the base tire to which the pre-cure tread 1 is attached. According to the method of this embodiment, for the same reasons as described in the embodiment of pre-cure tread, it is possible to suppress the occurrence of cracks in the cushion rubber in retread tires manufactured by the pre-cure method.

[0026] <Retreaded Tires> A retreaded tire according to one embodiment of the present invention is, for example, manufactured by the method for manufacturing a retreaded tire of the above embodiment. According to the method of this embodiment, the occurrence of cracks in the cushion rubber can be suppressed for the same reasons as described in the pre-cure tread embodiment. The aspect ratio of such a tire is not particularly limited, but can be, for example, 45 to 80.

[0027] 1: Pre-cure tread, 2: Circumferential main groove, 3: Tapered region

Claims

1. A pre-cure tread having one or more circumferential main grooves extending in the circumferential direction, characterized in that a tapered region is formed in the shoulder region, which is the tire width region located wider than the circumferential main groove that is the outermost of the one or more circumferential main grooves in the width direction, in which the thickness of the pre-cure tread gradually decreases from the inside in the width direction toward the tread edge.

2. The pre-cure tread according to claim 1, wherein, when the maximum width of the pre-cure tread is 2L, the tapered region is formed over a widthwise region from at least the tread end to a position spaced L / 3 inward in the widthwise direction from the tread end.

3. The pre-cure tread according to claim 1 or 2, wherein the tapered region is formed over a widthwise region from the tread end to the position of the circumferential main groove located at the outermost edge in the widthwise direction.

4. The pre-cure tread according to any one of claims 1 to 3, wherein the tapered region is also formed in a widthwise region that is inward in the widthwise direction from the circumferential main groove located at the outermost part in the widthwise direction.

5. The pre-cure tread according to any one of claims 1 to 4, wherein the thickness of the pre-cure tread at the tread end is less than the maximum thickness of the pre-cure tread by an amount of 5% to 30% of the groove depth of the circumferential main groove located on the outermost side in the width direction.

6. A method for manufacturing a retreaded tire, comprising the steps of: buffing a base tire; attaching a cushion rubber to the buffed base tire; attaching a pre-cured tread according to any one of claims 1 to 5 to the cushion rubber; and performing cold vulcanization on the base tire to which the pre-cured tread has been attached.

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