Manufacturing methods for pre-cure treads and retread tires
The pre-cure tread with a tapered shoulder region reduces ground pressure and strain on the cushion rubber, addressing the cracking issue in retread tires by maintaining tire durability.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- BRIDGESTONE CORP
- Filing Date
- 2024-12-06
- Publication Date
- 2026-06-18
AI Technical Summary
Existing pre-cure tread manufacturing methods result in high ground pressure at the shoulder edge of retreaded tires, leading to a risk of cracking in the cushion rubber due to the use of low-hardness cushioning rubber for adhesion.
A pre-cure tread design with a tapered region in the shoulder area, where the thickness gradually decreases from the inner width towards the tread edge, reducing ground contact pressure and strain on the cushion rubber.
The tapered design effectively suppresses the occurrence of cracks in the cushion rubber, ensuring the durability and integrity of the retread tire.
Smart Images
Figure 2026099635000001_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to a method for manufacturing a precure tread and a retread tire.
Background Art
[0002] As general methods for manufacturing retread tires, 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 part to the shoulder part 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.
Prior Art Documents
Patent Documents
[0004]
Patent Document 1
Patent Document 2
Summary of the Invention
Problems to be Solved by the Invention
[0005] However, in the above manufacturing method, the thickness of the pre-cured tread is uniform across the width, resulting in high ground pressure at the shoulder edge of the retreaded tire. Furthermore, such retreaded tires have a structure in which a cushioning rubber is placed between the pre-cured tread and the base tire. To ensure adhesion between the pre-cured tread and the base tire, a rubber with relatively low hardness is usually used for the cushioning rubber. Therefore, when the tire is mounted on a vehicle, there was a risk of cracking occurring in the cushioning rubber between the shoulder edge of the pre-cured tread and the base tire on the outside of the vehicle.
[0006] Therefore, the present invention aims to provide a pre-cure tread 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 the pre-cure method. [Means for solving the problem]
[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, A pre-cure tread characterized in that a tapered region is formed in the shoulder region, which is the tire width region located wider than the outermost circumferential main groove among the one or more circumferential main grooves, 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" refers to a groove that extends in the circumferential direction and has a groove width (opening width) of 2 mm or more.
[0008] (2) The pre-cure tread according to (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.
[0009] (3) The pre-cure tread according to (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.
[0010] (4) The pre-cure tread according to any one of (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.
[0011] (5) The pre-cure tread according to any one of (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.
[0012] (6) The process of buffing the base tire, A step of attaching cushion rubber to the buffed base tire, A step of attaching the Precure Tread described in any one of (1) to (5) above to the cushion rubber, A method for manufacturing a retreaded tire, characterized by comprising the step of performing cold vulcanization on the base tire to which the pre-cured tread is attached. [Effects of the Invention]
[0013] 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. [Brief explanation of the drawing]
[0014] [Figure 1] This is a cross-sectional view in the width direction showing a pre-cured tread according to one embodiment of the present invention. [Modes for carrying out the invention]
[0015] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0016] <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.
[0017] 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.
[0018] 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.
[0019] 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°.
[0020] Here, as shown in the figure, a tire width direction region outside the width direction of the circumferential main groove 2a located on the outermost side in the width direction among one or more circumferential main grooves 2 is defined as a shoulder region R.
[0021] The precure tread 1 of the present embodiment forms a taper region 3 in the shoulder region R, where the thickness of the precure tread 1 gradually decreases (continuously decreases) from the inner side in the width direction toward the tread end E. Hereinafter, the operation and effect of the precure tread 1 of the present embodiment will be described.
[0022] According to the precure tread 1 of the present embodiment, using this precure tread 1, a casing tire is buffed, a cushion rubber is attached to the buffed casing tire, the precure tread 1 of the present embodiment is attached to the cushion rubber, and cold vulcanization is performed on the casing tire to which the precure tread 1 is attached, thereby manufacturing a retread tire. The retread tire thus manufactured uses the precure tread 1 in which the taper region 3 is formed in the shoulder region R, and thus has a shape in which the shoulder end is rounded. Thereby, the ground contact pressure at the shoulder end during grounding can be reduced, and the strain of the portion of the cushion rubber corresponding to the shoulder end region can be reduced. As described above, according to the precure tread 1 of the present embodiment, in a retread tire manufactured by the precure method, the occurrence of cracks in the cushion rubber can be suppressed.
[0023] As shown in the figure, when the maximum width (width of the base surface S2) of the precure tread 1 is 2L, it is preferable that the taper region 3 is formed over at least the width direction region from the tread end E (starting point) to the position (ending point) spaced apart by L / 3 in the width direction from the tread end E. This is because the effect of reducing the ground contact pressure at the shoulder end described above can be made more reliable, and the occurrence of cracks in the cushion rubber can be more reliably suppressed.
[0024] Furthermore, it is preferable that the tapered region 3 is formed over a widthwise region, at least from the tread edge E (starting point) to the position (end) of the circumferential main groove 2a located on the outermost side 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. Furthermore, depending on the position of the circumferential main groove 2a located on the outermost side in the width direction, it is possible that either "the position L / 3 inward in the width direction from the tread edge E" or "the position of the circumferential main groove 2a located on the outermost side in the width direction" may be located further inward in the width direction.
[0025] 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.
[0026] 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 5% to 30% of the groove depth OTD. 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, it is preferable that the thickness of the pre-cure tread 1 at the tread edge E is less than the maximum thickness of the pre-cure tread 1 in the shoulder region R by an amount of 10% to 20% less than the groove depth OTD of the circumferential main groove 2a located on the outermost side in the width direction.
[0027] 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.
[0028] The maximum width of Precure Tread 1 (2L) is not particularly limited, but can be, for example, 180-270mm. 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. However, 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 is expected in which there will be significant center wear when the tire is retreaded, 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.
[0029] <How to manufacture retreaded tires> A method for manufacturing a retreaded tire according to one embodiment of the present invention can, for example, be a method using the pre-cured 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-cured tread 1 of the above embodiment to the cushion rubber; and performing cold vulcanization on the base tire to which the pre-cured tread 1 is attached. According to the method of this embodiment, for the same reasons as described in the embodiment of pre-cure treads, it is possible to suppress the occurrence of cracks in the cushion rubber in retread tires manufactured by the pre-cure method.
[0030] <Retreaded tires> A retread tire according to one embodiment of the present invention is, for example, manufactured by the method for manufacturing a retread 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 embodiment of Precure Tread. The aspect ratio of such tires is not particularly limited, but it can be, for example, between 45 and 80.
[0031] [Contribution to the United Nations-led Sustainable Development Goals (SDGs)] The SDGs have been proposed to realize a sustainable society. One embodiment of this invention is considered to be a technology that can contribute to "No. 12: Responsible Consumption and Production" and "No. 13: Climate Action," among others. [Explanation of symbols]
[0032] 1: Precure Red, 2: Circumferential main groove, 3: Tapered area
Claims
1. A pre-cure tread having one or more circumferential main grooves extending in the circumferential direction, A pre-cure tread characterized in that a tapered region is formed in the shoulder region, which is the tire width region located wider than the outermost circumferential main groove among the one or more circumferential main grooves, 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 at least 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 claim 1 or 2, 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 claim 1 or 2, 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. The process of buffing the base tire, A step of attaching cushion rubber to the buffed base tire, The step of attaching the Precure Tread described in claim 1 or 2 to the cushion rubber, A method for manufacturing a retreaded tire, characterized by comprising the step of performing cold vulcanization on the base tire to which the pre-cured tread is attached.