Reconditioned tires

Abstract

To provide retreaded tires that can improve durability. [Solution] The present invention relates to a retreaded tire 1 in which an annular tread ring 3 is mounted on the outer circumferential surface 2a of a base tire 2. The base tire 2 has a cord reinforcement layer 4 including a reinforcing outer surface 4a embedded inside the outer circumferential surface 2a. The tread ring 3 comprises a shoulder circumferential groove 5A and a shoulder land portion 6A. The contact surface 3a of the shoulder land portion 6A is defined as a first position P1, which is the innermost position in the tire axial direction, and a second position P2, which is separated from the first position P1 by a first distance L1 in the tire axial direction. The first thickness t1 in the tire radial direction of the tread ring 3 at the first position P1 is greater than the second thickness t2 in the tire radial direction of the tread ring 3 at the second position P2. The third thickness t3 from the reinforcing outer surface 4a to the outer circumferential surface 2a at the first position P1 is greater than the fourth thickness t4 from the reinforcing outer surface 4a to the outer circumferential surface 2a at the second position P2.

Description

Technical Field

[0001] The present invention relates to retread tires.

Background Art

[0002] Conventionally, a retread tire having an annular tread ring mounted on the outer peripheral surface of a casing tire is known. For example, the following Patent Document 1 proposes a retread tire manufactured by a manufacturing method including an integration step of integrating a precure tread body with a casing tire.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, there has recently been a strong demand for improving the durability performance of retread tires such as those in Patent Document 1.

[0005] The present invention has been devised in view of the above actual situation, and the main object thereof is to provide a retread tire capable of improving durability performance.

Means for Solving the Problems

[0006] The present invention relates to a retread tire having an annular tread ring mounted on the outer circumferential surface of a base tire, wherein the base tire has a cord reinforcement layer embedded in the inner side of the outer circumferential surface in the tire radial direction, the cord reinforcement layer includes the outermost reinforcing outer surface in the tire radial direction, the tread ring comprises a shoulder circumferential groove extending in the tire circumferential direction adjacent to the tread end, and a shoulder land portion separated by the shoulder circumferential groove and the tread end, the contact surface of the shoulder land portion has a first position furthest inward in the tire axial direction, and a second position separated from the first position outward in the tire axial direction by a first distance of 30% of the tire axial width of the shoulder land portion, the first thickness of the tread ring in the tire radial direction at the first position is greater than the second thickness of the tread ring in the tire radial direction at the second position, and the third thickness from the reinforcing outer surface to the outer circumferential surface at the first position is greater than the fourth thickness from the reinforcing outer surface to the outer circumferential surface at the second position. [Effects of the Invention]

[0007] The retreaded tire of the present invention can improve durability by having the above-described configuration. [Brief explanation of the drawing]

[0008] [Figure 1] This is a cross-sectional view showing one embodiment of the retreaded tire of the present invention. [Figure 2] This is an enlarged cross-sectional view of the shoulder area. [Modes for carrying out the invention]

[0009] Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings. Figure 1 is a meridian cross-sectional view of the retreaded tire 1 in the normal state according to this embodiment. Here, "normal state" refers to the unloaded state in which the retreaded tire 1 is mounted on a normal rim and adjusted to the normal internal pressure. Unless otherwise specified, the dimensions of each part of the retreaded tire 1 are values ​​measured in this normal state.

[0010] A "regular rim" is the rim specified for each tire by a standard system that includes the standard on which the retreaded tire 1 is based. For example, it is a "standard rim" for JATMA, a "design rim" for TRA, and a "measuring rim" for ETRTO. If there is no standard system that includes the standard on which the retreaded tire 1 is based, a "regular rim" is the rim with the smallest rim diameter and the smallest rim width among rims that can be mounted on a rim and do not cause air leaks.

[0011] "Regular internal pressure" refers to the air pressure specified for each tire by each standard, if there is a standard system on which the retreaded tire 1 is based. For example, it is the "maximum air pressure" for JATMA, the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" for TRA, and the "INFLATION PRESSURE" for ETRTO. If there is no standard system on which the retreaded tire 1 is based, "regular internal pressure" refers to the air pressure specified for each tire by the manufacturer, etc., in accordance with the above standards.

[0012] As shown in Figure 1, the retreaded tire 1 of this embodiment has an annular tread ring 3 mounted on the outer circumferential surface 2a of the base tire 2. Preferably, the base tire 2 has a cord reinforcement layer 4 embedded in the inner side of the outer circumferential surface 2a in the tire radial direction. The cord reinforcement layer 4 includes a plurality of reinforcing plies, for example, a first reinforcing ply 4A, a second reinforcing ply 4B, a third reinforcing ply 4C, and a fourth reinforcing ply 4D. Such a base tire 2 can exhibit excellent durability.

[0013] The cord reinforcement layer 4 includes the outermost reinforcement surface 4a in the tire radial direction. The reinforcement surface 4a is the outermost surface in the tire radial direction of the reinforcement ply located on the outermost side in the tire radial direction, in this embodiment, the outer surface of the fourth reinforcement ply 4D. In this case, the reinforcement surface 4a in the portion where the fourth reinforcement ply 4D is not present is defined as a virtual surface that is a virtual extension of the outer surface of the fourth reinforcement ply 4D in the tire radial direction.

[0014] The tread ring 3 preferably has an outer contact surface 3a in the radial direction of the tire and an inner circumferential surface 3b in the radial direction of the tire. In this embodiment, the retreaded tire 1 has the inner circumferential surface 3b of the tread ring 3 joined to the outer circumferential surface 2a of the base tire 2. Such a retreaded tire 1 can be reused by joining a new tread ring 3 even if the contact surface 3a wears down. The manufacturing method of the retreaded tire 1 can be any conventionally known method as appropriate.

[0015] The tread ring 3 of this embodiment has at least one circumferential groove 5 extending in the tire circumferential direction on the contact surface 3a, and a plurality of land areas 6 separated by the circumferential groove 5. Such a tread ring 3 can provide an appropriate tread pattern according to the various performance requirements of the retreaded tire 1.

[0016] The circumferential groove 5 of this embodiment includes a shoulder circumferential groove 5A that extends in the circumferential direction of the tire adjacent to the tread edge Te. The circumferential groove 5 may also include, for example, a crown circumferential groove 5B that extends in the circumferential direction of the tire between the shoulder circumferential groove 5A and the tire equator C. Such a circumferential groove 5 can exhibit excellent wet performance, straight-line stability, and the like.

[0017] Here, "tread edge Te" refers to the axial end of the contact surface 3a of the tire when a retreaded tire 1 in its normal state is subjected to 70% of its normal load and placed on a flat surface with a camber angle of 0°. Also, "tire equator C" is the midpoint of the pair of tread edges Te in the axial direction of the tire.

[0018] When there is a standard system including the standards on which the retread tire 1 is based, the "normal load" is the load defined for each tire by each standard. In the case of JATMA, it is the "maximum load capacity"; in the case of TRA, it is the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES"; and in the case of ETRTO, it is the "LOAD CAPACITY". When there is no standard system including the standards on which the retread tire 1 is based, the "normal load" refers to the maximum load applicable in using the retread tire 1 in accordance with the above-mentioned standards.

[0019] It is desirable that the land part 6 includes a shoulder land part 6A divided by the shoulder circumferential groove 5A and the tread edge Te, and a middle land part 6B divided by the shoulder circumferential groove 5A and the crown circumferential groove 5B. The land part 6 may include, for example, a crown land part 6C divided by the crown circumferential groove 5B. Such a land part 6 can exhibit excellent handling stability performance, wear resistance performance, etc.

[0020] FIG. 2 is an enlarged cross-sectional view of the shoulder land part 6A. As shown in FIG. 2, on the ground contact surface 3a of the shoulder land part 6A of the present embodiment, a first position P1 that is the innermost in the tire axial direction and a second position P2 that is separated from the first position P1 by a first distance L1 in the outer side in the tire axial direction are defined. Here, the first distance L1 is a distance of 30% of the width w1 of the shoulder land part 6A in the tire axial direction.

[0021] In the tire axial direction, it is desirable that the first thickness t1 in the tire radial direction from the ground contact surface 3a to the inner circumferential surface 3b of the tread ring 3 at the first position P1 is larger than the second thickness t2 in the tire radial direction to the inner circumferential surface 3b of the tread ring 3 at the second position P2. Such a tread ring 3 can suppress the ground contact pressure on the tread edge Te side of the shoulder land part 6A.

[0022] In the tire axial direction, the third thickness t3 from the reinforcing outer surface 4a to the outer peripheral surface 2a at the first position P1 is preferably greater than the fourth thickness t4 from the reinforcing outer surface 4a to the outer peripheral surface 2a at the second position P2. Such a retread tire 2 can suppress the ground contact pressure on the tread edge Te side of the shoulder land portion 6A.

[0023] In the retread tire 1 of the present embodiment, in both the tread ring 3 and the retread tire 2, since the thickness in the tire radial direction on the tread edge Te side is small, even when variations occur in the manufacturing process, the ground contact pressure on the tread edge Te side of the shoulder land portion 6A can be surely suppressed. In the retread tire 1 with a small aspect ratio, although there is a tendency for damage to occur from the tread edge Te side of the shoulder land portion 6A, by suppressing the ground contact pressure on the tread edge Te side, the durability performance of the retread tire 1 can be improved. Therefore, the retread tire 1 of the present embodiment can improve the durability performance.

[0024] As a more preferable aspect, the difference between the first thickness t1 at the first position P1 and the second thickness t2 at the second position P2 is 0.5 mm or more. By the difference between the first thickness t1 and the second thickness t2 being 0.5 mm or more, the ground contact pressure on the tread edge Te side of the shoulder land portion 6A can be surely suppressed.

[0025] The difference between the third thickness t3 at the first position P1 and the fourth thickness t4 at the second position P2 is preferably 0.5 mm or more. By the difference between the third thickness t3 and the fourth thickness t4 being 0.5 mm or more, the ground contact pressure on the tread edge Te side of the shoulder land portion 6A can be surely suppressed.

[0026] The second axial distance L2 from the tire equator C to the first position P1 is preferably 40% or more of the third axial distance L3 from the tire equator C to the tread edge Te. Having the second distance L2 be 40% or more of the third distance L3 suppresses heat buildup in the shoulder area 6A during travel, improving the durability of the retreaded tire 1. From this perspective, the second distance L2 from the tire equator C to the first position P1 is more preferably 45% or more of the third distance L3 from the tire equator C to the tread edge Te.

[0027] The second axial distance L2 from the tire equator C to the first position P1 is preferably 60% or less of the third axial distance L3 from the tire equator C to the tread edge Te. By making the second distance L2 60% or less of the third distance L3, the rigidity of the shoulder land portion 6A can be improved and uneven wear of the shoulder land portion 6A can be suppressed. From this viewpoint, the second distance L2 from the tire equator C to the first position P1 is more preferably 55% or less of the third distance L3 from the tire equator C to the tread edge Te.

[0028] Based on these considerations, the second axial distance L2 from the tire equator C to the first position P1 is preferably 40% to 60% of the third axial distance L3 from the tire equator C to the tread edge Te, and more preferably 45% to 55%. The combination of the upper and lower limits within these numerical ranges can be arbitrarily selected.

[0029] The base tire 2 is formed from a first rubber G1, for example, at least around the cord reinforcement layer 4. The tread ring 3 is preferably formed from a second rubber G2 having a different rubber component from the first rubber G1. Such a tread ring 3 is related to the durability performance of the retreaded tire 1.

[0030] The loss tangent tanδ2 of the second rubber G2 at 70°C is preferably 1.5 times or more the loss tangent tanδ1 of the first rubber G1 at 70°C. Having the loss tangent tanδ2 of the second rubber G2 be 1.5 times or more the loss tangent tanδ1 of the first rubber G1 allows for superior grip performance and improves the handling stability of the retreaded tire 1. From this viewpoint, the loss tangent tanδ2 of the second rubber G2 at 70°C is more preferably 2.0 times or more the loss tangent tanδ1 of the first rubber G1 at 70°C.

[0031] The loss tangent tanδ2 of the second rubber G2 at 70°C is preferably 3.0 times or less the loss tangent tanδ1 of the first rubber G1 at 70°C. By keeping the loss tangent tanδ2 of the second rubber G2 at 3.0 times or less the loss tangent tanδ1 of the first rubber G1, heat generation during driving can be suppressed, and the durability of the retreaded tire 1 can be improved. From this viewpoint, the loss tangent tanδ2 of the second rubber G2 at 70°C is more preferably 2.8 times or less the loss tangent tanδ1 of the first rubber G1 at 70°C.

[0032] Based on these considerations, the loss tangent tanδ2 of the second rubber G2 at 70°C is preferably 1.5 to 3.0 times, and more preferably 2.0 to 2.8 times, the loss tangent tanδ1 of the first rubber G1 at 70°C. The combination of the upper and lower limits within these numerical ranges can be arbitrarily selected.

[0033] Here, the loss tangent tanδ is measured using a viscoelastic spectrometer in accordance with the provisions of JIS-K6394, on a sample measuring 20 mm in length, 4 mm in width, and 1 mm in thickness, with the tire circumference being the longer side. Initial distortion: 5% Amplitude: ±1% Frequency: 10Hz Deformation mode: Tension Measurement temperature: 70℃

[0034] As shown in Figure 1, it is desirable that the base tire 2 has a pair of sidewall portions 7 extending inward in the tire radial direction from both sides of the outer circumferential surface 2a in the tire axial direction, and a bead portion 8 connected to the radially inward side of each sidewall portion 7. The bead portion 8 has, for example, an annular bead core 9 extending in the tire circumferential direction. Such a base tire 2 is suitable for improving the durability of the bead portion 8.

[0035] The base tire 2 preferably has a carcass 10 extending from the radially inner side of the cord reinforcement layer 4 to a pair of bead portions 8. The carcass 10 includes at least one, in this embodiment one, carcass ply 10A. Such a base tire 2 helps to achieve both durability and weight reduction.

[0036] The carcass ply 10A includes, for example, a main body portion 10a extending from the inner side of the outer peripheral surface 2a in the tire radial direction through the sidewall portion 7 to the bead portion 8, and a folded portion 10b connected to the main body portion 10a and folded back around the bead core 9 from the inner side in the tire axial direction to the outer side. Such a base tire 2 helps to improve the durability of the bead portion 8.

[0037] The tread ring 3 of this embodiment has a square shoulder with the tread edge Te extending in an edge shape. Such a tread ring 3 is suitable for supporting heavy loads such as those of small buses and low-floor electric vehicles.

[0038] The tread ring 3 in this embodiment includes an outer end 3c on the outer side in the tire axial direction. It is desirable that the outer end 3c of the tread ring 3 be located inward in the tire radial direction from the cord reinforcement layer 4. Such a tread ring 3 can increase the contact area with the base tire 2, thereby suppressing delamination and improving the durability of the retreaded tire 1.

[0039] The tread width TW of the contact surface 3a of the tread ring 3 in the tire axial direction is preferably 43% or more of the case length L4 of the carcass 10 between the pair of bead portions 8 in the tire meridional cross-section. Having a tread width TW of 43% or more of the case length L4 of the carcass 10 helps to increase the interior space of vehicles such as small buses and low-floor electric vehicles. From this viewpoint, the tread width TW of the tread ring 3 is more preferably 50% or more of the case length L4 of the carcass 10.

[0040] Here, the tread width TW is the distance in the tire axial direction between a pair of tread ends Te. Also, the case length L4 of the carcass 10 is the unfolded length in the tire axial direction of the main body portion 10a of the carcass ply 10A.

[0041] Although particularly preferred embodiments of the present invention have been described in detail above, the present invention is not limited to the embodiments described above and can be implemented in various modified forms. [Examples]

[0042] A retreaded tire having the basic structure shown in Figure 1 was prototyped based on the specifications in Table 1, and the durability performance of the prototype retreaded tire was tested. The test method was as follows:

[0043] <Durability> The prototype retreaded tire was mounted on a rim and the tire pressure was adjusted to 450 kPa. The retreaded tire with the adjusted tire pressure was placed in a drum testing machine, and the failure speed during high-speed driving was measured. The results are indexed with Comparative Example 1 set to 100, and a higher number indicates better durability.

[0044] The test results are shown in Table 1. [Table 1]

[0045] The test results confirmed that the retreaded tire in the example demonstrated superior durability compared to the comparative example.

[0046] [Note] The present invention is as follows:

[0047] [Invention 1] A retreaded tire having an annular tread ring attached to the outer surface of the base tire, The aforementioned base tire has a cord reinforcement layer embedded in the inner side of the outer surface in the radial direction of the tire, The aforementioned cord reinforcement layer includes the outermost reinforcing surface in the radial direction of the tire, The tread ring comprises a shoulder circumferential groove extending in the tire circumferential direction adjacent to the tread edge, and a shoulder land portion separated by the shoulder circumferential groove and the tread edge. The contact surface of the shoulder portion of the land is defined as having a first position, which is the innermost position in the tire axial direction, and a second position, which is located a distance of 30% of the tire axial width of the shoulder portion of the land, outward from the first position in the tire axial direction. The first thickness of the tread ring in the tire radial direction at the first position is greater than the second thickness of the tread ring in the tire radial direction at the second position. The third thickness from the reinforcing outer surface to the outer peripheral surface at the first position is greater than the fourth thickness from the reinforcing outer surface to the outer peripheral surface at the second position. Reconditioned tires.

[0048] [2nd Invention] The difference between the first thickness and the second thickness is 0.5 mm or more. The retreaded tire according to the present invention, wherein the difference between the third thickness and the fourth thickness is 0.5 mm or more.

[0049] [Invention 3] The aforementioned base tire has a carcass extending from the radially inner side of the cord reinforcement layer to a pair of bead portions, The retreaded tire according to invention 1 or 2, wherein the tread width of the tread ring in the tire axial direction is 43% or more of the case length of the carcass between the pair of bead portions in the tire meridional cross-section.

[0050] [4th Invention] The retreaded tire according to the present invention, wherein the tread width is 50% or more of the case length.

[0051] [5th ​​Invention] The aforementioned base tire is formed from first rubber, The tread ring is formed from the second rubber, A retreaded tire according to any one of inventions 1 to 4, wherein the loss tangent of the second rubber at 70°C is 1.5 to 3.0 times that of the first rubber at 70°C.

[0052] [Invention 6] The tread ring includes the outer end on the tire axial direction, The retreaded tire according to any one of inventions 1 to 5, wherein the outer end is located radially inward of the cord reinforcement layer.

[0053] [7th Invention] A retreaded tire according to any one of inventions 1 to 6, wherein the second distance in the tire axial direction from the tire equator to the first position is 40% to 60% of the third distance in the tire axial direction from the tire equator to the tread edge.

[0054] [8th Invention] The retreading tire according to any one of inventions 1 to 7, wherein the tread ring has a square shoulder with the tread end extending in an edge shape. [Explanation of symbols]

[0055] 1. Reconditioned tires 2 tires 2a Outer surface 3 Tread Rings 3a Ground plane 4. Code reinforcement layer 4a Reinforced outer surface 5A Shoulder circumferential groove 6A Shoulder Track and Field Club

Claims

1. A retreaded tire having an annular tread ring attached to the outer surface of the base tire, The aforementioned base tire has a cord reinforcement layer embedded in the inner side of the outer surface in the radial direction of the tire, The aforementioned cord reinforcement layer includes the outermost reinforcing surface in the radial direction of the tire, The tread ring comprises a shoulder circumferential groove extending in the tire circumferential direction adjacent to the tread edge, and a shoulder land portion separated by the shoulder circumferential groove and the tread edge. The contact surface of the shoulder portion of the land is defined as having a first position that is the innermost in the tire axial direction and a second position that is separated from the first position by a first distance of 30% of the tire axial width of the shoulder portion of the land, in the tire axial direction. The first thickness of the tread ring in the tire radial direction at the first position is greater than the second thickness of the tread ring in the tire radial direction at the second position. The third thickness from the reinforcing outer surface to the outer peripheral surface at the first position is greater than the fourth thickness from the reinforcing outer surface to the outer peripheral surface at the second position. Reconditioned tires.

2. The difference between the first thickness and the second thickness is 0.5 mm or more. The retreaded tire according to claim 1, wherein the difference between the third thickness and the fourth thickness is 0.5 mm or more.

3. The aforementioned base tire has a carcass extending from the radially inner side of the cord reinforcement layer to a pair of bead portions, The retreaded tire according to claim 2, wherein the tread width of the tread ring in the tire axial direction is 43% or more of the case length of the carcass between the pair of bead portions in the tire meridional cross-section.

4. The retreaded tire according to claim 3, wherein the tread width is 50% or more of the case length.

5. The aforementioned base tire is formed from first rubber, The tread ring is formed from the second rubber, The retreaded tire according to any one of claims 1 to 4, wherein the loss tangent of the second rubber at 70°C is 1.5 to 3.0 times the loss tangent of the first rubber at 70°C.

6. The tread ring includes the outer end on the outer side in the tire axial direction, The retreaded tire according to any one of claims 1 to 4, wherein the outer end is located radially inward of the cord reinforcement layer.

7. The retreaded tire according to any one of claims 1 to 4, wherein the second distance in the tire axial direction from the tire equator to the first position is 40% to 60% of the third distance in the tire axial direction from the tire equator to the tread edge.

8. The retreading tire according to any one of claims 1 to 4, wherein the tread ring has a square shoulder with the tread end extending in an edge shape.

Images