pneumatic tires

Abstract

The present invention provides a pneumatic tire that can release static electricity accumulated in the vehicle onto the road surface without compromising FV (Functional Value). [Solution] The pneumatic tire 1 includes a tread portion 2 with a tread reinforcement layer 7 disposed inside and a conductive path 30. The conductive path 30 is formed to provide electrical conductivity from the tread reinforcement layer 7 to the rim R. The tread portion 2 has at least one circumferential groove 16 extending in the circumferential direction of the tire. The groove surface 16s, including a pair of groove edges 20 of the circumferential groove 16, is formed of conductive thin rubber 10. The thin rubber 10 is electrically conductive to the tread reinforcement layer 7 via at least one conductive thread 15.

Description

Technical Field

[0001] The present invention relates to pneumatic tires.

Background Art

[0002] Patent Document 1 below describes the tread rubber of a tire formed by a tread rubber forming device. The tread rubber includes a base layer, an intermediate layer located on the outer peripheral side of the base layer, a cap layer located on the outer peripheral side of the intermediate layer, and a conductive layer penetrating the base layer, the intermediate layer, and the cap layer in the thickness direction.

Prior Art Document

Patent Document

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] <000002SS>In a tire as described above, the static electricity of the vehicle is discharged from the conductive layer to the road surface. However, such a tire has a problem that force variation (FV) is likely to deteriorate.

[0005] The present invention has been devised in view of the above actual situation, and the main object is to provide a pneumatic tire capable of discharging the static electricity accumulated in the vehicle to the road surface without deteriorating FV.

Means for Solving the Problems

[0006] A pneumatic tire comprising a tread portion having a tread reinforcing layer disposed inside, a pair of sidewall portions, a pair of bead portions, and a conductive path, wherein the conductive path is formed to conduct electricity from the tread reinforcing layer to the rim when the tire is mounted on the rim, via at least one of the pair of sidewall portions and at least one of the pair of bead portions, the tread portion has at least one circumferential groove extending in the circumferential direction of the tire, the groove surface including a pair of groove edges of the circumferential groove is formed of conductive thin rubber, and the thin rubber conducts electricity to the tread reinforcing layer via at least one conductive thread. [Effects of the Invention]

[0007] By adopting the above configuration, the pneumatic tire of the present invention can release static electricity accumulated in the vehicle to the road surface without impairing FV (Functional Voltage). [Brief explanation of the drawing]

[0008] [Figure 1] This is a meridian cross-sectional view of a pneumatic tire according to one embodiment of the present invention. [Figure 2] This is an enlarged view of Figure 1. [Figure 3] This is a diagram showing the tread section. [Figure 4] This is a cross-sectional view of thin-walled rubber according to another embodiment. [Figure 5] This is a conceptual diagram to explain the first step. [Figure 6] (A) to (C) are conceptual diagrams to explain the second process. [Figure 7] This is a conceptual diagram to explain the fourth step. [Modes for carrying out the invention]

[0009] Hereinafter, one embodiment of the present invention will be described with reference to the drawings. The drawings contain exaggerations and representations that differ from the actual structural dimensional ratios in order to aid in understanding the present invention. Furthermore, where there are multiple embodiments, the same or common elements are denoted by the same reference numerals throughout the specification, and redundant descriptions are omitted.

[0010] Figure 1 is a meridional cross-sectional view of a pneumatic tire (hereinafter sometimes referred to as "tire") 1, including the tire rotation axis (not shown), which represents one embodiment of the present invention. In Figure 1, a passenger car tire is shown as a preferred embodiment. However, the present invention may also be applied to motorcycle tires, light truck tires, or heavy-duty tires. Figure 1 shows a tire 1 in its normal state.

[0011] The aforementioned "normal state" refers to the unloaded state in the case of pneumatic tires for which various standards are defined, where the tire is mounted on a standard rim (hereinafter sometimes referred to as "rim") R and adjusted to the standard internal pressure. In the case of tires for which various standards are not defined, the aforementioned normal state means the standard usage state according to the intended use of the tire, where it is not mounted on a vehicle and is unloaded. In this specification, unless otherwise specified, the dimensions of each part of the tire are values ​​measured in the aforementioned normal state. Furthermore, for components that cannot be measured in the aforementioned normal state (for example, the internal material of tire 1), the values ​​are measured with tire 1 in a state that approximates the aforementioned normal state as closely as possible.

[0012] A "standard rim" is the rim specified for each tire in the standards system that includes the standard on which the tire is based. For example, it is a "standard rim" for JATMA, a "design rim" for TRA, and a "measuring rim" for ETRTO.

[0013] "Regular internal pressure" refers to the air pressure specified for each tire by each standard within the standards system, including the standard on which the tire is based. For JATMA, it is the "maximum air pressure," for TRA, it is the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUSCOLD INFLATION PRESSURES," and for ETRTO, it is the "INFLATION PRESSURE."

[0014] The tire 1 includes a tread portion 2, a pair of sidewall portions 3 located on both sides of the tread portion 2 in the axial direction, and a pair of bead portions 4 located on the radially inward side of each sidewall portion 3. The tire 1 also includes a conductive path 30.

[0015] The tread portion 2 includes a tread reinforcing layer 7, a conductive thin rubber 10, and at least one circumferential groove 16A extending in the circumferential direction. The tread portion 2 also includes a tread rubber 2G adjacent to the radially outer side of the tread reinforcing layer 7 and a contact surface 2s that can come into contact with the road surface when the tire rolls. In this specification, "conductive" means 1.0 × 10 8 This refers to elements having a volumetric intrinsic electrical resistivity of less than Ω·cm. Furthermore, "non-conductive" in this specification means 1.0 × 10⁻⁶. 8 This refers to an element having a volumetric intrinsic electrical resistivity of Ω·cm or greater. Conductivity or non-conductivity is controlled by the type and content of carbon black.

[0016] The conductive path 30 is formed to provide electrical conductivity from the tread reinforcement layer 7 to the rim R, via at least one of the pair of sidewall portions 3 and at least one of the pair of bead portions 4. As a result, the tread reinforcement layer 7 is made conductive from the rim R through the conductive path 30. In this embodiment, the conductive path 30 is formed on both sides in the tire axial direction, with the tire equator C in between.

[0017] FIG. 2 is an enlarged view of the circumferential groove 16A in FIG. 1. As shown in FIG. 2, the circumferential groove 16A includes a groove surface 16s. The groove surface 16s includes a pair of groove edges 20. The groove surface 16s also includes, for example, a groove bottom 21 with the maximum groove depth, and a pair of groove walls 22 connecting the groove bottom 21 and each of the pair of groove edges 20. The groove edge 20 is the intersection of the ground contact surface 2s and the groove wall 22.

[0018] The thin rubber 10 forms the groove surface 16s. The thin rubber 10 forms the groove edge 20. The thin rubber 10 is electrically connected to the tread reinforcement layer 7 through at least one conductive thread (conductive thread) 15. Thereby, conductivity is ensured from the tread reinforcement layer 7 through the conductive thread 15 to the groove edge 20. Therefore, the static electricity of the vehicle is discharged to the road surface through the conductive path 30 from the rim R, the tread reinforcement layer 7, the conductive thread 15, and the thin rubber 10. Also, the thin rubber 10 is used for the groove surface 16s of the circumferential groove 16A. The conductive thread 15 is provided between the groove surface 16s and the tread reinforcement layer 7. Such thin rubber 10 and conductive thread 15 hardly have an adverse effect on FV (the contribution rate of FV is small) and do not impair FV. In particular, for example, compared with the case where a conductive rubber piece (not shown) extending from the ground contact surface 2s to the tread reinforcement layer 7 is arranged, the thin rubber 10 and the conductive thread 15 can enhance FV. Also, for example, when the tread rubber 2G including the rubber piece is extrusion-molded, shrinkage between the rubber piece and the tread rubber 2G is different, so FV tends to deteriorate. In this embodiment, the conductive thread 15 does not need to consider such deterioration of FV.

[0019] FIG. 3 is a developed view of the tread portion 2. As shown in FIG. 3, the circumferential groove 16A extends continuously in the tire circumferential direction. The circumferential groove 16A extends, for example, parallel to the tire circumferential direction. The circumferential groove 16A may extend, for example, in a wave shape or a zigzag shape.

[0020] As shown in Figures 1 and 3, the tread portion 2 is provided with a plurality of circumferential grooves 16. The plurality of circumferential grooves 16 include an outer circumferential groove 16a located on the outermost side in the tire axial direction, and an inner circumferential groove 16b located between the outer circumferential groove 16a and the tire equator C. The circumferential groove 16A, on which a thin rubber 10 is provided on the groove surface 16s, is, for example, the outer circumferential groove 16a. The circumferential groove 16A may also be the inner circumferential groove 16b.

[0021] The thin rubber 10 is continuous in the circumferential direction of the tire. In other words, the thin rubber 10 is formed continuously in the circumferential direction of the tire on the groove surface 16s of the circumferential groove 16A. Such a thin rubber 10 can constantly discharge static electricity from the vehicle to the road surface when the vehicle is in motion.

[0022] As shown in Figure 2, the thin-walled rubber 10 includes, for example, a first portion 10a and a second portion 10b connected to the first portion 10a. The first portion 10a in this embodiment extends from one groove edge 20 on the contact surface 2s in the opposite direction to the groove centerline 16c of the circumferential groove 16A. The second portion 10b in this embodiment extends to connect the first portion 10a and the conductive thread 15. The second portion 10b includes a groove bottom portion 17a formed along the groove bottom 21 and a groove wall portion 17b formed along the groove wall 22. The groove bottom portion 17a is connected to, for example, the conductive thread 15. The groove wall portion 17b is connected to, for example, the first portion 10a is located outside the circumferential groove 16A beyond the groove wall portion 17b. In cross-sectional view, the second portion 10b in this embodiment is formed in a J shape.

[0023] The thickness t1 of the thin-walled rubber 10 is preferably 0.1 mm or more, more preferably 0.2 mm or more, preferably 0.5 mm or less, and more preferably 0.4 mm or less. When the thickness t1 is 0.1 mm or more, static electricity from the vehicle can be smoothly discharged from the groove edge 20. When the thickness t1 is 0.5 mm or less, the effect of suppressing adverse effects on FV is enhanced, and the reduction in the volume of the tread rubber 2G is suppressed, allowing the characteristics of the tread rubber 2G to be fully exhibited.

[0024] The conductive thread 15 is connected, for example, to the groove bottom 21 of the circumferential groove 16A. Even if the groove depth decreases due to wear, such a conductive thread 15 can discharge static electricity from both groove edges 20.

[0025] In this embodiment, one conductive thread 15 is provided for each circumferential groove 16A. However, multiple conductive threads 15 may be provided for each circumferential groove 16A, specifically at equal pitches in the circumferential direction of the tire. The conductive thread 15 can be, for example, a synthetic fiber containing a highly conductive metal or carbon black, a fiber with a metal coating on its surface, or a metal fiber made from a metal such as stainless steel. The conductive thread 15 is 1.0 × 10 7 It is preferable that the yarn has a volumetric electrical resistivity of Ωcm or less.

[0026] The outer diameter d1 of the conductive thread is preferably 2 mm or less, and preferably 1.5 mm or less. Since the outer diameter d1 is 2 mm or less, the static electricity of the tread reinforcement layer 7 can be smoothly conducted to the thin rubber 10.

[0027] As shown in Figure 1 or Figure 2, the tread reinforcement layer 7 in this embodiment includes a breaker 12. The breaker 12 consists of at least one breaker ply, in this embodiment two breaker plies 12A and 12B, on which a plurality of breaker cords (not shown) are arranged. The breaker plies 12A and 12B are conductive. The breaker cords are arranged at an angle of 15 to 60 degrees with respect to the tire equator C.

[0028] The tread reinforcement layer 7 may also include a breaker 12 and a band (not shown) adjacent to the breaker 12 on the radially outer side of the tire. The band includes a plurality of band cords (not shown) arranged at an angle of 5 degrees or less with respect to the tire equator C. The band may be conductive or non-conductive.

[0029] The tread rubber 2G forms the contact surface 2s of the tread portion 2, except for the thin rubber 10. In this embodiment, the tread rubber 2G extends outward in the tire axial direction beyond the outer end 7e of the tread reinforcing layer 7 in the tire axial direction (as shown in Figure 1). The tread rubber 2G is non-conductive and contains silica. Such tread rubber 2G has excellent wear resistance and low heat generation. The tread rubber 2G may also contain carbon black as long as it is non-conductive and contains silica. Furthermore, the tread rubber 2G may be formed from multiple rubber layers stacked in the tire radial direction, as is customary (not shown).

[0030] As shown in Figure 1, the tire 1 includes a bead core 5 positioned in each bead portion 4 and a carcass 6 adjacent to the radially inner side of the tread reinforcement layer 7. The tire 1 further includes a bead apex rubber 8 adjacent to the radially outer side of the bead core 5 and an inner liner 9 positioned on the inner side of the carcass 6. Furthermore, the tire 1 includes a pair of sidewall rubbers 3G located on both sides of the tread rubber 2G in the tire axial direction and a clinch rubber 4G located radially inner of each sidewall rubber 3G.

[0031] The carcass 6 is composed of at least one carcass ply 6A, in this embodiment, in which parallel carcass cords are covered with topping rubber. The carcass ply 6A includes, for example, a main body portion 6a that extends in a toroidal shape between each bead core 5, and a pair of folded portions 6b that are connected to the main body portion 6a and folded back from the inside to the outside in the tire axial direction around the bead core 5. In this embodiment, the carcass ply 6A is conductive. The carcass cords are arranged at an angle of 70 to 90 degrees with respect to the tire equator C.

[0032] The clinch rubber 4G forms, for example, the outer surface of the tire bead portion 4. The clinch rubber 4G is in contact with the rim R. In this embodiment, the clinch rubber 4G is in contact with the carcass 6, for example, the folded portion 6b. In this embodiment, the clinch rubber 4G is conductive.

[0033] The sidewall rubber 3G forms, for example, the outer surface of the tire sidewall portion 3. The sidewall rubber 3G is in contact with the carcass 6. The sidewall rubber 3G is connected to the clinch rubber 4G and the tread rubber 2G. The radial outer end portion 3e of the sidewall rubber 3G is sandwiched between the tread reinforcement layer 7 and the main body portion 6a of the carcass 6. The sidewall rubber 3G may be conductive or non-conductive.

[0034] The bead core 5, bead apex rubber 8, and inner liner 9 are composed of a well-known structure.

[0035] In this embodiment, the conductive path 30 is formed of clinch rubber 4G and carcass 6. However, the conductive path 30 is not limited to this configuration. For example, the conductive path 30 may be formed of clinch rubber 4G and reinforcing rubber (not shown) connecting the clinch rubber 4G and the tread reinforcing layer 7, or it may be formed of clinch rubber 4G and conductive sidewall rubber 3G.

[0036] Figure 4 is a cross-sectional view of the thin-walled rubber 10 of another embodiment. As shown in Figure 4, the thin-walled rubber 10 of this embodiment also forms the groove surface 16s of the circumferential groove 16A. The thin-walled rubber 10 includes, for example, a pair of first portions 10a and a second portion 10b positioned between the pair of first portions 10a. The first portions 10a extend from each groove edge 20 on the contact surface 2s in the opposite direction to the groove centerline 16c of the circumferential groove 16A. The second portion 10b extends continuously from one groove edge 20 through the groove bottom 21 to the other groove edge 20. The second portion 10b includes a groove bottom portion 17a formed along the groove bottom 21 and a pair of groove wall portions 17b formed along each of the two groove walls 22. In cross-sectional view, the second portion 10b of this embodiment is formed in a U-shape.

[0037] Next, a method for manufacturing such a tire 1 will be described. Figures 5 to 7 are conceptual diagrams illustrating the manufacturing method of this embodiment. In this embodiment, the manufacturing method includes a first step S1 (shown in Figure 5), a second step S2 (shown in Figure 6), a third step, and a fourth step S3 (shown in Figure 7). In the first step S1, a cylindrical first cover 40 (shown in Figure 5) is formed. In the second step S2, a cylindrical second cover 41 (shown in Figure 6) is formed. In the third step, the toroidally inflated first cover 40 and the second cover 41 are bonded together to form a low cover 42 (shown in Figure 7). In the fourth step S3, the low cover 42 is vulcanized to form the tire 1. In this embodiment, the third step employs a well-known method according to convention, so a detailed explanation thereof is omitted.

[0038] Figure 5 is a conceptual diagram illustrating the first step S1. As shown in Figure 5, the first step S1 uses, for example, a first drum 35 of a well-known structure that is expandable and retractable and rotatable. Figure 5 shows a longitudinal section of the first drum 35. The first cover 40 includes, for example, an inner liner 9, a carcass 6, a pair of sidewall rubbers 3G, and a pair of clinch rubbers 4G. The first cover 40 also includes a bead core 5 and a bead apex rubber 8. The first cover 40 is formed by sequentially laminating the inner liner 9, carcass 6, etc., on the first drum 35.

[0039] Figure 6 is a conceptual diagram illustrating the second step S2. As shown in Figure 6, the second step S2 uses, for example, a second drum 36 of a well-known structure that is expandable and retractable and rotatable. Figure 6 shows a longitudinal section of the second drum 36. The second cover 41 comprises, for example, a tread reinforcement layer 7, tread rubber 2G, thin rubber 10, and conductive thread 15.

[0040] The second step S2 is carried out in the order shown in Figures 6(A) to (C). As shown in Figure 6(A), in the second step S2, first, the two breaker plies 12A and 12B of the tread reinforcement layer 7 are wrapped around the second drum 36. After that, the tread rubber 2G is wrapped around the outside of the tread reinforcement layer 7. The tread rubber 2G may be formed, for example, by a strip wind (not shown) in which a strip-shaped rubber strip is continuously wound in a spiral. Note that the formation of the tread rubber 2G is not limited to such a strip wind; it may also be formed by wrapping a sheet of extruded tread rubber 2G around the outside of the tread reinforcement layer 7 (not shown).

[0041] Next, as shown in Figure 6(B), in the second step S2, the conductive thread 15 is placed inside the tread rubber 2G. In this embodiment, the conductive thread 15 is inserted from the outer surface 2a of the tread rubber 2G toward the inside in the radial direction of the drum, at the position where the thin-walled rubber 10 (circumferential groove 16A (shown in Figure 7)) is placed. The conductive thread 15 is inserted into the interior of the tread rubber 2G by, for example, a needle (not shown). The conductive thread 15 may be inserted, for example, from the outer surface 2a to a position where it penetrates the tread reinforcement layer 7, or from the outer surface 2a to a position where it contacts the tread reinforcement layer 7. In this step, the second drum 36 is in an expanded diameter state. Therefore, a gap (not shown) is provided on the outer peripheral surface 36s of the second drum 36, spaced in the circumferential direction of the drum. Therefore, by passing the needle through this gap, the conductive thread 15 that penetrates the tread reinforcement layer 7 can be placed. The conductive thread 15 is inserted to a predetermined position and then cut.

[0042] Next, as shown in Figure 6(C), in the second step S2, the thin rubber 10 is wrapped around the outer surface 2a of the tread rubber 2G. The thin rubber 10 is positioned outside the conductive thread 15 (at the position where the circumferential groove 16A is formed). In addition, in the second step S2, the conductive thread 15 may be placed inside the tread rubber 2G after the thin rubber 10 has been wrapped around the outer surface 2a of the tread rubber 2G. Furthermore, the second step S2 may be performed simultaneously with the first step S1, or after the first step S1.

[0043] After the low cover 42 is formed in the third step, the fourth step S3 is performed. Figure 7 is a conceptual diagram illustrating the fourth step S3. As shown in Figure 7, a vulcanizing apparatus 50 is used in the fourth step S3. Figure 7 shows a cross-section of the vulcanizing apparatus 50. The vulcanizing apparatus 50 includes a bladder 51 and a vulcanizing mold 52. The bladder 51 is a rubber molded product that can be expanded by a heating medium. The vulcanizing mold 52 has an internal space into which the low cover 42 is placed. The vulcanizing mold 52 includes a tread ring 52a for forming the tread portion 2 (shown in Figure 1). The tread ring 52a includes a reference surface 53 and a plurality of protrusions 54 that rise from the reference surface 53 to form the contact surface 2s of the tread portion 2. Each protrusion 54 can form a circumferential groove 16 (shown in Figure 1) of the tread portion 2.

[0044] In the fourth step S3, first, the low cover 42 is placed into the internal section of the vulcanization mold 52. Then, when a heating medium is supplied, the bladder 51 presses the low cover 42 from its inner surface 42b side, pressing the outer surface 42a of the low cover 42 against the vulcanization mold 52. The protrusions 54 then form circumferential grooves 16A in which the thin rubber 10 is placed.

[0045] Although particularly preferred embodiments of the present invention have been described in detail above, the present invention is not limited to the illustrated embodiments and can be implemented in various modified forms.

[0046] [Note] The present invention includes the following embodiments.

[0047] [Invention 1] It is a pneumatic tire, The tread section has a tread reinforcement layer inside, A pair of sidewall sections, A pair of bead sections, Includes a conductive path, The conductive path is formed to provide electrical conductivity from the tread reinforcing layer to the rim when the tire is mounted on the rim, via at least one of the pair of sidewall portions and at least one of the pair of bead portions. The tread portion has at least one circumferential groove extending in the circumferential direction of the tire. The groove surface, including the pair of groove edges of the circumferential groove, is formed of conductive thin rubber. The thin rubber is electrically connected to the tread reinforcement layer via at least one conductive thread. Pneumatic tires. [Invention 2] The pneumatic tire according to the present invention 1, wherein the at least one conductive thread is electrically connected to the thin rubber extending from the bottom of the circumferential groove. [Invention 3] The aforementioned circumferential grooves extend continuously in the circumferential direction of the tire. The pneumatic tire according to the present invention 1 or 2, wherein the thin rubber is formed continuously in the circumferential direction of the tire. [4th Invention] The pneumatic tire according to any one of invention 1 to 3, wherein the thickness of the thin rubber is 0.1 to 0.5 mm. [5th ​​Invention] The pneumatic tire according to any one of inventions 1 to 4, wherein the outer diameter of the conductive thread is 2 mm or less. [Invention 6] The pneumatic tire according to any one of invention 1 to 5, wherein the contact surface of the tread portion is formed of a non-conductive rubber containing silica, except for the thin rubber portion. [Explanation of symbols]

[0048] 1. Pneumatic tire 2 Tread section 7. Tread reinforcement layer 10 Thin-walled rubber 15 Conductive thread 16 Circumferential groove 16s groove surface 20 groove edge 30 Conductive Path R Rim

Claims

1. It is a pneumatic tire, The tread section has a tread reinforcement layer inside, A pair of sidewall sections, A pair of bead sections, Includes a conductive path, The conductive path is formed to provide electrical conductivity from the tread reinforcing layer to the rim when the tire is mounted on the rim, via at least one of the pair of sidewall portions and at least one of the pair of bead portions. The tread portion has at least one circumferential groove extending in the circumferential direction of the tire. The groove surface, including the pair of groove edges of the circumferential groove, is formed of conductive thin rubber. The thin rubber is electrically connected to the tread reinforcement layer via at least one conductive thread. Pneumatic tires.

2. The pneumatic tire according to claim 1, wherein at least one conductive thread is electrically connected to the thin rubber extending at the bottom of the circumferential groove.

3. The aforementioned circumferential grooves extend continuously in the circumferential direction of the tire. The pneumatic tire according to claim 1 or 2, wherein the thin rubber is formed continuously in the circumferential direction of the tire.

4. The pneumatic tire according to claim 1 or 2, wherein the thickness of the thin rubber is 0.1 to 0.5 mm.

5. The pneumatic tire according to claim 1 or 2, wherein the outer diameter of the conductive thread is 2 mm or less.

6. The pneumatic tire according to claim 1 or 2, wherein the contact surface of the tread portion, excluding the thin rubber portion, is formed of a non-conductive rubber containing silica.

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