Tire

Abstract

In this tire (1), the tire body layer (13) covers the bead core (11) and is rolled back to the outside in the tire width direction. Furthermore, the distance (GD) from the tire face profile at the position of the maximum width of the tire (D) to the inner surface of the tire, the distance (GE) from the tire face profile at the position of 30[%] of the tire section height (SH) to the inner surface of the tire, and the distance (GF) from the tire face profile at the self-contact start point (F) of the rolled back portion (312) of the tire body layer (13) to the inner surface of the tire satisfy the conditions of GE ≤ GF, 1.00 ≤ GE / GD ≤ 1.10, and 1.00 ≤ GF / GD ≤ 1.40.

Description

Technical Field

[0001] This invention relates to a tire, and more specifically, to a tire that improves the low rolling resistance and ride comfort of the tire. Background Technology

[0002] In recent years, tires have adopted a flat tread profile and ensure a wide contact patch width to reduce rolling resistance. Patent Document 1 describes a technique that is known as a conventional tire employing this structure.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2019-137327 Summary of the Invention

[0006] The problem the invention aims to solve

[0007] On the other hand, especially in passenger car tires, there is an issue of improving the ride comfort performance of tires.

[0008] Therefore, the present invention was made in view of the above-mentioned problems, and its object is to provide a tire that can improve the low rolling resistance performance and ride comfort performance of the tire.

[0009] Technical means to solve the problem

[0010] To achieve the above objectives, the tire of the present invention comprises: a pair of bead cores; a carcass layer disposed on the pair of bead cores; a belt layer disposed on the radially outer side of the carcass layer; a tread rubber disposed on the radially outer side of the belt layer; a pair of sidewall rubbers disposed on the outer side of the carcass layer in the tire width direction; and a rim cushioning rubber extending from the radially inner side of the pair of bead cores to the outer side in the tire width direction. The tire is characterized in that the carcass layer encloses the bead cores and rolls back outward in the tire width direction, and the distance GD from the tread profile at the maximum tire width position to the inner surface of the tire, the distance GE from the tread profile at a position of 30% of the tire section height to the inner surface of the tire, and the distance GF from the tread profile at the self-contact start point of the rolled-back portion of the carcass layer to the inner surface of the tire satisfy the conditions GE≤GF, 1.00≤GE / GD≤1.10, and 1.00≤GF / GD≤1.40.

[0011] Invention Effects

[0012] In the tire of the present invention, (1) the ratio of GE / GD and the ratio of GF / GD are within the above-mentioned range, thereby reducing the rubber volume from the position of the maximum tire width to the bead portion. This results in the advantage of reducing the longitudinal elastic coefficient of the tire and improving the tire's ride comfort performance. Furthermore, (2) by exceeding the above-mentioned upper limit of the ratio of GF / GD, it has the advantage of suppressing heat generation at the bead portion caused by excessive rubber volume at the bead portion and reducing the tire's rolling resistance. Attached Figure Description

[0013] Figure 1 This is a cross-sectional view of the tire along the radial direction according to an embodiment of the present invention.

[0014] Figure 2 It means Figure 1 An enlarged view of the radial outer region of the tire as described.

[0015] Figure 3 It means Figure 1 An enlarged view of the radial inner region of the tire as described.

[0016] Figure 4 It means Figure 1 An explanatory diagram of the tire improvement example described.

[0017] Figure 5 This is a graph showing the results of performance tests on tires according to embodiments of the present invention.

[0018] Figure 6 This is a graph showing the results of performance tests on tires according to embodiments of the present invention. Detailed Implementation

[0019] Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. It should be noted that the present invention is not limited to this embodiment. Furthermore, the constituent elements of this embodiment include elements that are replaceable while maintaining the identity of the invention, and the replacements are obvious. Moreover, the various improvements described in this embodiment can be arbitrarily combined within the scope that is obvious to those skilled in the art.

[0020] [tire]

[0021] Figure 1 This is a cross-sectional view of the tire along the radial direction according to an embodiment of the present invention. Figure 1 A cross-sectional view of a single-sided radial region of the tire is shown. In this embodiment, a pneumatic radial tire for passenger cars is described as an example of a tire.

[0022] exist Figure 1In this design, the tire's radial section is defined as the section cut along a plane including the tire's axis of rotation (not shown). Furthermore, the tire's equatorial plane CL is defined as a plane passing through the midpoint of the measurement point of the tire's section width as specified by JATMA and perpendicular to the tire's axis of rotation. Additionally, the tire width direction is defined as parallel to the tire's axis of rotation, and the tire radial direction is defined as perpendicular to the tire's axis of rotation. Furthermore, point T is the tire's contact patch end, and point D is the position of the tire's maximum width.

[0023] Tire 1 has a ring-shaped structure centered on the tire's axis of rotation, comprising: a pair of bead cores 11, 11; a pair of sidewall cores 12, 12; a carcass layer 13; a belt layer 14; tread rubber 15; a pair of sidewall rubbers 16, 16; and a pair of rim cushioning rubbers 17, 17 (see reference). Figure 1 ).

[0024] A pair of bead cores 11, 11 are formed by repeatedly winding one or more bead wires made of steel in a loop, and embedded in the bead portion to form the left and right bead portions. A pair of sidewall cores 12, 12 are respectively disposed on the radial outer periphery of the tire of the pair of bead cores 11, 11 to reinforce the bead portion. In addition, the rubber hardness of the sidewall cores is in the range of 65 or higher and 99 or lower.

[0025] The hardness Hs of rubber is determined according to JIS K6253.

[0026] The carcass layer 13 has a single-layer structure formed by a single layer of cord or a multi-layer structure formed by stacking multiple layers of cord, and is arranged in a ring between the left and right bead cores 11 to form the tire skeleton. Furthermore, the two ends of the carcass layer 13 are rolled back and secured to the outside in the tire width direction, wrapping around the bead core 11 and the sidewall core 12. Additionally, the cord layers of the carcass layer 13 are formed by coating multiple carcass cords made of steel or organic fiber materials (e.g., aramid, nylon, polyester, rayon, etc.) with coated rubber and then rolled, and have a cord angle of 80 degrees or more and 100 degrees or less (defined as the angle of inclination of the long dimension of the carcass cord relative to the tire circumference).

[0027] It should be noted that, in Figure 1 In its composition, the carcass layer 13 has a single-layer structure formed by a single ply. However, it is not limited to this, and the carcass layer 13 may also have a multi-layer structure formed by stacking multiple ply layers (illustration omitted).

[0028] The belt layer 14 is formed by stacking multiple belt ply layers 141 to 144 and is configured to surround the outer periphery of the carcass layer 13. The belt ply layers 141 to 144 include: a pair of cross belts 141 and 142, a belt cover layer 143 and a pair of belt edge cover layers 144.

[0029] A pair of cross belts 141 and 142 are constructed by rolling multiple belt cords made of steel or organic fiber material with coated rubber, and have a cord angle with an absolute value of 15 degrees or more and 55 degrees or less. Furthermore, the pair of cross belts 141 and 142 have cord angles of different signs (defined as the angle of inclination of the long dimension direction of the belt cord relative to the tire circumference), causing the long dimension directions of the belt cords to intersect and overlap (a so-called oblique cross configuration). Moreover, the pair of cross belts 141 and 142 are stacked and arranged on the radial outer side of the tire carcass layer 13.

[0030] The belt cover layer 143 and the belt edge cover layer 144 are constructed by coating belt cover cords made of steel or organic fiber material with coated rubber, and have a cord angle with an absolute value of 0 degrees or more and 10 degrees or less. Furthermore, the belt cover layer 143 and the belt edge cover layer 144 are, for example, a strip made by coating one or more belt cover cords with coated rubber, which is wound multiple times in a spiral along the tire circumference around the outer periphery of the cross belts 141 and 142. In addition, the belt cover layer 143 is configured to cover the entire area of ​​the cross belts 141 and 142, and the pair of belt edge cover layers 144 are configured to cover the left and right edges of the cross belts 141 and 142 from the radially outer side of the tire.

[0031] The tread rubber 15 is disposed on the radial outer periphery of the tire, comprising the carcass layer 13 and the belt layer 14, thus forming the tread portion of the tire. Furthermore, the tread rubber 15 is formed by stacking a crown and a base tread (reference numerals omitted in the figures). The crown is formed of a rubber material with excellent contact properties and weather resistance, extending across the entire contact area of ​​the tire and exposed on the tread surface, thus forming the outer surface of the tread portion. Furthermore, the rubber hardness of the crown is in the range of 60 to 80. The base tread is formed of a rubber material with superior heat resistance compared to the crown rubber, and is disposed between the crown and the belt layer, thus forming the base portion of the tread rubber. Furthermore, the rubber hardness of the base tread is in the range of 50 to 65.

[0032] A pair of sidewall rubbers 16, 16 are respectively disposed on the outer side of the tire carcass ply 13 in the tire width direction to form left and right sidewall portions. For example, in Figure 1 In this configuration, the radially outer end of the sidewall rubber 16 is disposed on the lower layer of the tread rubber 15 and sandwiched between the belt layer 14 and the carcass layer 13. However, it is not limited to this; the radially outer end of the sidewall rubber 16 may also be disposed on the outer layer of the tread rubber 15 and exposed at the tire shoulder reinforcement (illustration omitted). Furthermore, the rubber hardness of the sidewall rubber 16 is in the range of 40 or higher and 70 or lower. Additionally, the loss tangent tanδ of the sidewall rubber 16 is in the range of 0.20 or lower.

[0033] The loss tangent tanδ was measured using a viscoelastic spectrometer manufactured by Toyo Seiki Co., Ltd., under conditions of 60 °C, 10% shear strain, ±0.5% amplitude, and 20 Hz frequency.

[0034] A pair of rim cushioning rubbers 17, 17 extend radially inward from the left and right bead cores 11, 11 and the rolled-back portion of the carcass ply 13 towards the outer side in the tire width direction, forming the rim mating surface of the bead portion. For example, in Figure 1 In this configuration, the radially outer end of the rim buffer rubber 17 is inserted into the lower layer of the sidewall rubber 16 and sandwiched between the sidewall rubber 16 and the carcass layer 13. Furthermore, the rubber hardness of the rim buffer rubber 17 is in the range of 50 or higher and 80 or lower. Additionally, the elongation at break of the rim buffer rubber 17 is in the range of 150% or higher and 450% or lower.

[0035] In addition, Figure 1 In this configuration, the height HD of the tire's maximum width position D and the tire's section height SH have a relationship of 0.50 ≤ HD / SH ≤ 0.60, preferably 0.52 ≤ HD / SH ≤ 0.56. Therefore, the center of the point where the tire's maximum width position D is measured relative to the tire's section height SH is positioned on the outer radial side of the tire.

[0036] The maximum tire width position D is defined as the maximum width position of the tire section width SW as specified by JATMA.

[0037] The height HD at the maximum tire width position D is the radial distance from the point where the tire's inner diameter is measured to the maximum tire width position D. It is measured when the tire is mounted on a specified rim, a specified internal pressure is applied, and the tire is under no-load conditions.

[0038] The tire section width SW is measured as the straight-line distance (excluding patterns, text, etc. on the tire sidewalls) between the tire sidewalls when the tire is mounted on a specified rim, subjected to a specified internal pressure, and placed under no-load conditions. More specifically, the tire section width SW is measured using points on the tread profile of the tire sidewall portion as measurement points.

[0039] The specified rim refers to the "applicable rim" as specified by JATMA, the "design rim" as specified by TRA, or the "measuring rim" as specified by ETRTO. Furthermore, the specified internal pressure refers to the "maximum tire pressure" as specified by JATMA, the maximum value of the "tire load limits at various cold inflation pressures" as specified by TRA, or the "inflation pressure" as specified by ETRTO. Additionally, the specified load refers to the "maximum load capacity" as specified by JATMA, the maximum value of the "tire load limits at various cold inflation pressures" as specified by TRA, or the "load capacity" as specified by ETRTO. However, in JATMA, for passenger car tires, the specified internal pressure is 180 kPa, and the specified load is 88% of the maximum load capacity.

[0040] Furthermore, the tire section height SH and tire section width SW have a relationship of 0.55 ≤ SH / SW ≤ 0.65, preferably 0.58 ≤ SH / SW ≤ 0.60. Simultaneously, the tire contact patch width TW and tire section width SW have a relationship of 0.60 ≤ TW / SW ≤ 0.90, preferably 0.70 ≤ TW / SW ≤ 0.72. In this configuration, compared to an average passenger car tire, tire 1 has a high aspect ratio SH / SW and a high contact patch width ratio TW / SW, thereby reducing the rolling resistance of tire 1.

[0041] The tire section height SH is the distance of half the difference between the tire's outer diameter and the rim diameter. It is measured when the tire is mounted on a specified rim, given a specified internal pressure, and placed under no-load conditions.

[0042] Tire contact width (TW) is defined as the maximum straight-line distance in the tire axial direction at the contact surface between the tire and the flat plate when the tire is mounted on a specified rim, subjected to a specified internal pressure, and placed perpendicularly to the flat plate in a stationary state, and subjected to a load corresponding to a specified load.

[0043] Furthermore, the radius of the tread profile at the tire contact patch (dimension markings omitted in the figures) is in the range of 600 mm or more and 1700 mm or less, preferably in the range of 800 mm or more and 1500 mm or less. This lower limit ensures the contact patch area of ​​tire 1, and the upper limit ensures the contact characteristics of the central area of ​​the tread and the braking performance of the tire.

[0044] The contact patch of a tire is defined as the area between the contact patches T of the left and right tires.

[0045] Furthermore, the tire section width SW and the distance Wco between the pair of bead cores 11, 11 have a relationship of 1.20 ≤ SW / Wco ≤ 1.40, preferably 1.25 ≤ SW / Wco ≤ 1.35. Therefore, compared to average passenger car tires, the tire section width SW and the distance Wco between the bead cores 11, 11 are set narrower. In this configuration, the tire sidewall has a flat wall, thus reducing the tire's longitudinal elastic constant and improving ride comfort.

[0046] The distance Wco between a pair of bead cores 11, 11 is the distance between the centers of gravity of bead cores 11, 11 when viewed in cross-section along the radial direction of the tire. It is measured with the tire mounted on a specified rim, given a specified internal pressure, and set to an unloaded state.

[0047] Furthermore, the tire contact patch width TW and the distance Wco between the pair of bead cores 11, 11 have a relationship of 0.90 ≤ TW / Wco < 1.00, preferably 0.95 ≤ TW / Wco ≤ 0.98. Therefore, the tire contact patch end T is located closer to the tire equatorial plane CL than the center of gravity of the bead core 11. This lower limit ensures the tire contact patch width TW, thus ensuring tire performance. Furthermore, this upper limit suppresses the deterioration of tire ride comfort caused by an excessively large tire contact patch width TW.

[0048] The tire contact point T is defined as the position of the maximum axial width of the tire at the contact surface between the tire and the flat plate when the tire is mounted on a specified rim, given a specified internal pressure, and placed vertically relative to the flat plate in a stationary state, and a load corresponding to a specified load is applied.

[0049] In addition, Figure 1 In the pair of cross belts 141 and 142, the width Wbe of the wider cross belt 141 has a relationship of 1.05 ≤ Wbe / TW ≤ 1.30 with respect to the tire contact width TW, preferably 1.10 ≤ Wbe / TW ≤ 1.15. Therefore, the end of the wider cross belt 142 is located on the outer side of the tire width direction, which is further out than the tire contact width TW.

[0050] The width Wbe of the cross belts 141 and 142 is the distance in the tire width direction from the left and right endpoints B of the cross belts 141 and 142 (more specifically, the centroid of the outermost belt cord in the tire width direction), measured when the tire is mounted on a specified rim and a specified internal pressure is applied, and under no-load conditions.

[0051] [Tire radial outer region]

[0052] Figure 2 It means Figure 1 An enlarged view of the radial outer region of the tire as described.

[0053] exist Figure 2 In the cross-sectional view of the tire along its radial direction when the tire is mounted on a specified rim, given a specified internal pressure, and set to an unloaded state, the intersection point A of the tire equatorial plane CL and the tread profile, and the point C on the tread profile at a position of 70% of the tire section height SH from the point where the tire inner diameter is measured are defined.

[0054] The measurement point for the tire's inner diameter is consistent with the measurement point for the rim diameter specified by JATMA.

[0055] At this time, Figure 2 In this design, the distance GC from the tread profile at position C (70% of the tire section height SH) to the inner surface of the tire has a relationship of 1.00 ≤ GC / GD ≤ 1.20 with respect to the distance GD from the tread profile at position D (maximum tire width), and preferably, a relationship of 1.00 ≤ GC / GD ≤ 1.10. Therefore, the total thickness (distance GC) at position 70% of the tire section height SH is set to be approximately the same as the total thickness (distance GD) at position D (maximum tire width). This reduces the tire's longitudinal elastic coefficient, improving ride comfort. For example, in... Figure 2 In the configuration, the shoulder reinforcement of tire 1 has a thin-walled structure, thereby achieving the aforementioned GC / GD ratio. Furthermore, the distance GD is preferably in the range of 2.0 mm ≤ GD ≤ 5.0 mm, and more preferably in the range of 3.0 mm ≤ GD ≤ 4.0 mm.

[0056] The distance from the tread profile to the inner surface of the tire is measured as the length of a perpendicular line drawn from a point on the specified tread profile to the inner surface of the tire.

[0057] In addition, Figure 2In this design, the distance GT from the tread profile at the tire contact patch T to the inner surface of the tire and the distance GC from the tread profile at position C (70% of the tire section height SH) to the inner surface of the tire have a relationship of 3.00 ≤ GT / GC ≤ 4.00, preferably 3.10 ≤ GT / GC ≤ 3.50, and more preferably 3.15 ≤ GT / GC ≤ 3.25. This lower limit ensures sufficient rubber volume in the shoulder reinforcement, thus guaranteeing the tire's ride comfort. Furthermore, the upper limit suppresses overheating in the shoulder reinforcement caused by excessive rubber volume, reducing rolling resistance.

[0058] Furthermore, the distance GA from the tread profile at the tire equatorial plane CL to the tire inner surface and the distance GT from the tread profile at the tire contact patch T to the tire inner surface have a relationship of 1.00 ≤ GA / GT ≤ 1.10, preferably 1.00 ≤ GA / GT ≤ 1.10. Therefore, the total thickness (distance GA) at the tire equatorial plane CL and the total thickness (distance GT) at the tire contact patch T are set to be approximately the same. In this configuration, the total thickness at the tire contact patch area is uniform, thus suppressing heat generation during tire rotation and reducing tire rolling resistance. For example, in Figure 2 In its configuration, the shoulder of tire 1 is round, thereby achieving the aforementioned ratio GA / GT.

[0059] In addition, Figure 2 In this design, the thickness G1 of the tread rubber 15 at the tire equatorial plane CL has a relationship of 0.50 ≤ G1 / GA ≤ 0.70 with respect to the distance GA at the tire equatorial plane CL, preferably 0.60 ≤ G1 / GA ≤ 0.65. By using the aforementioned lower limit, the thickness G1 of the tread rubber 15 is ensured, thus guaranteeing the tire's ride comfort performance. Furthermore, by using the aforementioned upper limit, hysteresis losses caused by excessive tread rubber 15 thickness G1 are reduced, suppressing the deterioration of tire rolling resistance.

[0060] The thickness of the tread rubber 15 is measured as the length of a perpendicular line drawn from the tread profile to the outermost belt cord surface of the belt layer in a cross-sectional view along the tire's radial direction. The belt cord surface is defined as the surface formed by connecting the radially outer ends of the multiple belt cords constituting the belt ply.

[0061] In addition, Figure 2In this design, the distance GB from the end point B of the wide crossbelt 141 to the inner surface of the tire is related to the distance GT at the tire contact patch end T and the distance GC at position C (70% of the tire section height SH) with a relationship of GC ≤ GB ≤ GT. Furthermore, it is preferable that the total thickness of the shoulder reinforcement of the tire 1 decreases monotonically from position C (70% of the tire section height SH) towards the tire contact patch end T. This optimizes the distance GB at the end point B of the wide crossbelt 141, ensuring the tire's ride comfort performance.

[0062] In addition, Figure 2 In this design, the shoulder drop ΔT of the tread profile at the tire contact patch T has a relationship with the tire contact patch width TW where 0 < ΔT / (TW / 2) ≤ 0.06, and preferably, a relationship of 0.03 ≤ ΔT / (TW / 2) ≤ 0.04. This lower limit prevents the tread profile from becoming a so-called inverted R shape, ensuring the tire's contact patch characteristics. Furthermore, the upper limit ensures a flat shape in the tire contact patch area, appropriately reducing the tire's rolling resistance.

[0063] The shoulder drop ΔT of the tread profile is the radial distance from the intersection point A of the tire equatorial plane CL and the tread profile to the tire contact patch T, as observed in a cross-sectional view along the tire's radial direction. It is measured with the tire mounted on a specified rim, given a specified internal pressure, and set to an unloaded state.

[0064] Furthermore, the width WC of the tread profile at position C, which is 70% of the tire section height SH, has a relationship with the tire section width SW of 0.90 ≤ WC / SW ≤ 1.00, preferably 0.95 ≤ WC / SW ≤ 1.00. Therefore, position C, representing 70% of the tire section height SH, is located at approximately the same position in the tire width direction relative to the tire's maximum width position D. In this configuration, the tire sidewall has a flat (i.e., approximately parallel to the tire's radial direction) wall near the tire's maximum width position D, thus reducing the tire's longitudinal elastic constant and improving ride comfort.

[0065] The width of the tread profile is the width of the tread profile in the tire width direction at a specified position, and is measured by cross-sectional observation in the radial direction of the tire when the tire is mounted on a specified rim, given a specified internal pressure, and set to an unloaded state.

[0066] [Tire radial inner area]

[0067] Figure 3 It means Figure 1 An enlarged view of the radial inner region of the tire as described.

[0068] exist Figure 3In the cross-sectional view along the radial direction of the tire when the tire is mounted on a specified rim and given a specified internal pressure and is in an unloaded state, point E on the tread profile at a position defined as 30% of the tire section height SH, point F at the self-contact start point of the roll-back portion 132 of the carcass layer 13, and point U at the end position of the roll-back portion 132 of the carcass layer 13 are defined.

[0069] The main body 131 of the carcass layer 13 is defined as the portion of the carcass layer 13 extending inward from the bead core 11 in the tire width direction, and the roll-back portion 132 of the carcass layer 13 is defined as the portion of the carcass layer 13 extending outward from the bead core 11 in the tire width direction. Furthermore, the starting point F of the self-contact of the roll-back portion 132 of the carcass layer 13 is defined as the innermost point in the tire radial direction at the contact area between the main body 131 and the roll-back portion 132 of the carcass layer 13. Furthermore, the ending point U of the roll-back portion 132 of the carcass layer 13 is defined as the outermost point in the tire radial direction of the roll-back portion 132.

[0070] At this point, the distance GE from the tread profile at position E (30% of the tire profile height SH) to the inner surface of the tire and the distance GD from the tread profile at position D (maximum tire width) to the inner surface of the tire have a relationship of 1.00 ≤ GE / GD ≤ 1.10, preferably 1.00 ≤ GE / GD ≤ 1.05. Therefore, the total thickness (distance GE) at position E (30% of the tire profile height SH) and the total thickness (distance GD) at position D (maximum tire width) are set approximately the same. In this configuration, since GE / GD is within the above range, the rubber volume from position D (maximum tire width) to the bead portion is reduced. This reduces the longitudinal elastic modulus of the tire, improving the tire's ride comfort performance. For example, in Figure 2 In its construction, the sidewall rubber 16 has a thin-walled structure in the region from the tire's maximum width position D to the bead portion, thereby achieving the aforementioned GE / GD ratio.

[0071] In addition, Figure 3 In this context, the distance GF from the tread profile at the self-contact starting point F of the rollback portion 132 of the carcass layer 13 to the inner surface of the tire has a relationship of 1.00 ≤ GF / GD ≤ 1.40 with respect to the distance GD from the tread profile at the maximum tire width position D to the inner surface of the tire, preferably 1.10 ≤ GF / GD ≤ 1.30. Figure 3 In this configuration, the distance GF from the self-contact starting point F of the retraction portion 132 to the distance GE from the position E, which is 30% of the tire profile height SH, has a relationship of GE ≤ GF. By limiting the above-mentioned upper limit of GF / GD, the heating of the bead portion caused by excessive rubber volume in the bead portion is suppressed, thereby reducing the rolling resistance of the tire. For example, in Figure 2In its configuration, the total thickness of the tire sidewall increases monotonically from the tire's maximum width position D toward the tire's radial inward side, thereby achieving the aforementioned ratio GF / GD.

[0072] In addition, Figure 3 In the tire body layer 13, the height HU of the termination position U of the roll-back portion 132 of the tire body layer 13 has a relationship of 0.10≤HU / SH≤0.40 with respect to the tire section height SH, preferably 0.20≤HU / SH≤0.30.

[0073] The height HU of the end position U of the retraction section 132 is the radial distance from the measuring point of the inner diameter of the tire to the end position U of the retraction section 132 of the tire carcass ply 13. It is measured when the tire is mounted on a specified rim and a specified internal pressure is applied, and under no-load conditions.

[0074] In addition, Figure 3 In this tire carcass 13, the height HF of the contact start point F between the main body 131 and the roll-back portion 132, the height HU of the end position U of the roll-back portion 132, and the tire profile height SH have a relationship of 0.15 ≤ (HU-HF) / SH and HF / SH ≤ 0.30. Furthermore, it is preferable that the difference HU-HF is in the range of 15.0 [mm] ≤ HU-HF. This ensures the self-contact length (HU-HF) of the carcass 13 and the strength of the bead portion. Furthermore, by setting the height HF of the self-contact start point F of the carcass 13 relatively low, the flexibility area of ​​the tire sidewall portion is ensured. The lower limit of HF / SH is not particularly limited, but, for example, ... Figure 3 Thus, in the configuration with the sidewall core 12, the measurement point for the height HF is located near the radially outer end of the sidewall core 12. Furthermore, in a configuration where the sidewall core 12 is omitted (so-called fillerless configuration; see below for details). Figure 4 In the test, the measurement point for the height HF is located near the top surface of the radially outer side of the bead core 11.

[0075] In addition, Figure 3 In this configuration, the width WE of the tread profile at position E, representing 30% of the tire section height SH, has a relationship with the tire section width SW of 0.90 ≤ WE / SW ≤ 1.00, preferably 0.95 ≤ WE / SW ≤ 1.00. Therefore, position E, representing 30% of the tire section height SH, is located approximately at the same position in the tire width direction relative to the tire's maximum width position D. In this configuration, the tire sidewall has a flat (i.e., approximately parallel to the tire's radial direction) wall near the tire's maximum width position D, thus reducing the tire's longitudinal elastic constant and improving ride comfort.

[0076] [Improved Example]

[0077] Figure 4 It means Figure 1 An explanatory diagram of the tire improvement example described. Figure 4 An enlarged view of the bead portion of tire 1 is shown. Figure 4 In the middle, to and Figure 1 Components that are identical in the description are marked with the same reference numerals, and their descriptions are omitted.

[0078] exist Figure 1 In its composition, the tire 1 has a sidewall core 12, and the bead core 11 has a rectangular shape.

[0079] However, it is not limited to this, such as Figure 4 As shown, the sidewall core 12 can also be omitted. Alternatively, a very small sidewall core 12 can be configured (illustration omitted). This reduces the tire's weight. For example, in... Figure 4 In this configuration, the bead core 12 is omitted, and the roll-back portion 132 of the carcass layer 13 only wraps around the bead core 11 and rolls back, making self-contact with the main body portion 131. Therefore, the starting point F of the self-contact of the roll-back portion 132 of the carcass layer 13 is located near the bead core 11 and has a very small height HF.

[0080] In addition, Figure 4 In its construction, the bead core 11 has a wedge shape that protrudes radially outward from the tire. Specifically, in a radial cross-sectional view of the bead core 11, the layer with the largest number of bead wires (in...) Figure 4 In this context, the second layer from the innermost layer is defined as the maximum arrangement layer. At this point, the number of layers in the wire profile located radially outer of the tire than the maximum arrangement layer (in...) Figure 4 In the middle, the number of layers (three layers) is greater than the number of layers in the wire section located radially inside the tire than the maximum arrangement layer (in Figure 4 In the case of a single layer, the number of steel wire cross-sections in each layer radially outer from the maximum arrangement layer decreases monotonically from the maximum arrangement layer towards the radially outer side of the tire. Furthermore, it is preferable that the number of steel wire cross-section layers is in the range of 4 or more and 6 or less. Additionally, the number of steel wire cross-sections in the innermost layer radially outward of the tire in the steel wire arrangement structure is 3 or 4 (in...). Figure 4 In the case of 3), it is preferable that the number of wire arrangements in the maximum arrangement layer is the same as or less than the number of wire arrangements in the maximum arrangement layer. Furthermore, it is preferable that the number of wire arrangements in the maximum arrangement layer of the wire arrangement structure is 4 or 5 (in the case of 3). Figure 4 In the middle, it is 4), the number of arrangement of the outermost steel wire cross-section in the radial direction of the tire is 1 or 2 (in Figure 4 In the middle, it is 1).

[0081] Furthermore, preferably, the wire cross-sections are arranged in a densest filling configuration from the region on the radially outer side of the tire where the maximum arrangement layer is located. The densest filling configuration refers to a state where, in a cross-sectional view along the tire's radial direction, the centers of three adjacent wire cross-sections form an approximately equilateral triangle. In this densest filling configuration, compared to a grid arrangement where the wire cross-sections are arranged in orthogonal columns, the density of the wire cross-sections in the bead core 11 is increased, thus improving the bead core 11's resistance to core breakage. It should be noted that in this densest configuration, it is not necessary for all groups of adjacent wire cross-sections to contact each other; some groups can also be configured with small gaps between them (figures omitted).

[0082] It should be noted that in the manufacturing process of the bead core 11, for example, a core forming jig (not shown) is used to wind one or more bead wires 111 in a specified wire arrangement to form an uncured bead core 11. Then, the formed bead core 11 is pre-cured before the vulcanization molding process of the green tire.

[0083] [Effect]

[0084] As described above, the tire 1 includes: a pair of bead cores 11, 11; a carcass layer 13 mounted on the pair of bead cores 11, 11; a belt layer 14 disposed on the radially outer side of the carcass layer 13; a tread rubber 15 disposed on the radially outer side of the belt layer 14; a pair of sidewall rubbers 16, 16 disposed on the outer side of the carcass layer 13 in the tire width direction; and a rim cushioning rubber 17 extending from the radially inner side of the pair of bead cores 11, 11 towards the outer side in the tire width direction (see reference). Figure 1 Furthermore, the carcass layer 13 covers the bead core 11 and rolls back outward in the tire width direction. Additionally, the distance GD from the tread profile at the maximum tire width position D to the tire inner surface, the distance GE from the tread profile at a position of 30% of the tire section height SH to the tire inner surface, and the distance GF from the tread profile at the self-contact start point F of the rollback portion 312 of the carcass layer 13 to the tire inner surface satisfy the conditions GE≤GF, 1.00≤GE / GD≤1.10, and 1.00≤GF / GD≤1.40 (refer to...). Figure 3 ).

[0085] In this configuration, (1) the ratio of GE / GD and the ratio of GF / GD are within the aforementioned range, thereby reducing the rubber volume from the maximum tire width position D to the bead portion. This results in the advantage of reducing the tire's longitudinal elastic coefficient and improving the tire's ride comfort. Furthermore, (2) by exceeding the aforementioned upper limit of the ratio of GF / GD, it has the advantage of suppressing heat generation at the bead portion caused by excessive rubber volume and reducing the tire's rolling resistance.

[0086] Furthermore, in this tire 1, the height HU of the termination position U of the roll-back portion 132 of the carcass layer 13 has a relationship of 0.10 ≤ HU / SH ≤ 0.40 with respect to the tire profile height SH (refer to...). Figure 3 By setting the lower limit as described above, it is advantageous to ensure the roll-up height HU of the carcass layer 13 and to ensure the ability to maintain the tire shape achieved by the carcass layer 13. Furthermore, by setting the upper limit as described above, it is advantageous to suppress the increase in tire weight caused by an excessively large roll-back portion 132 of the carcass layer 13.

[0087] Furthermore, in this tire 1, the height HF of the contact start point F between the main body portion 131 of the carcass ply 13 and the roll-back portion 132, the height HU of the end position U of the roll-back portion 132 of the carcass ply 13, and the tire profile height SH have the relationships 0.15≤(HU-HF) / SH and HF / SH≤0.30 (refer to...). Figure 3 This ensures the self-contact length (HU-HF) of the carcass layer 13 and the strength of the bead portion. Furthermore, setting the height HF of the self-contact starting point F of the carcass layer 13 at a lower level has the advantage of ensuring the flexibility of the sidewall portion of the tire 1.

[0088] Furthermore, in this tire 1, the distance GC from the tread profile at position C (70% of the tire profile height SH) to the inner surface of the tire has a relationship of 1.00 ≤ GC / GD ≤ 1.10 with respect to the distance GD at the position D (maximum tire width). Figure 3 This configuration offers advantages such as reducing the rubber volume from the tire's maximum width position D to the shoulder reinforcement, reducing the tire's longitudinal elastic coefficient, and improving the tire's ride comfort.

[0089] Furthermore, in this tire 1, the distance GD at the maximum tire width position D is in the range of 2.0 [mm] ≤ GD ≤ 5.0 [mm] (refer to...). Figure 3 Therefore, it has the advantage of optimizing the total thickness at the maximum tire width position D.

[0090] Furthermore, in this tire 1, the width WE of the tread profile at position E, which is 30% of the tire section height SH, has a relationship with the tire section width SW of 0.90 ≤ WE / SW ≤ 1.00 (refer to...). Figure 3 In this configuration, the tire sidewall has a flat (i.e., approximately parallel to the tire radial direction) wall near the tire's maximum width position D, thus offering the advantages of reducing the tire's longitudinal elastic constant and improving the tire's ride comfort.

[0091] Furthermore, in this tire 1, the width WC of the tread profile at a position of 70% of the tire section height SH has a relationship of 0.90 ≤ WC / SW ≤ 1.00 with respect to the tire section width SW (refer to...). Figure 2In this configuration, the tire sidewall has a flat (i.e., approximately parallel to the tire radial direction) wall near the tire's maximum width position D, thus offering the advantages of reducing the tire's longitudinal elastic constant and improving the tire's ride comfort.

[0092] Furthermore, in this tire 1, the tire section width SW and the distance Wco between the pair of bead cores 11, 11 have a relationship of 1.20 ≤ SW / Wco ≤ 1.40 (refer to...). Figure 1 In this configuration, the tire sidewall has a flat wall, which has the advantages of reducing the tire's longitudinal elastic constant and improving the tire's ride comfort.

[0093] Furthermore, in this tire 1, the tire contact width TW and the distance Wco between the pair of bead cores 11, 11 have a relationship of 0.90≤TW / Wco≤1.00 (refer to...). Figure 1 By setting the lower limit mentioned above, it is advantageous to ensure the tire contact patch width (TW) and the tire's driving performance. Furthermore, by setting the upper limit mentioned above, it is advantageous to suppress the deterioration of tire ride comfort caused by an excessively large tire contact patch width (TW).

[0094] Furthermore, in this tire 1, the belt layer 14 has a pair of cross belts 141 and 142, and the width Wbe of the wider cross belt 141 among the pair of cross belts 141 and 142 has a relationship of 1.05 ≤ Wbe / TW ≤ 1.30 with respect to the tire contact width TW. By setting the lower limit as described above, it is advantageous to ensure the width Wbe of the wider cross belt 141, reduce hysteresis losses during tire rotation, and suppress the deterioration of tire rolling resistance. Furthermore, by setting the upper limit as described above, it is advantageous to suppress the increase in tire weight caused by an excessively large width Wbe of the cross belt 141 and suppress the deterioration of tire rolling resistance.

[0095] Furthermore, in this tire 1, the height HD at the maximum tire width position D and the tire section height SH have a relationship of 0.50 ≤ HD / SH ≤ 0.60 (refer to...). Figure 1 In this configuration, the maximum tire width position D is located at the center of the tire profile height SH on the radial outer side of the tire. Therefore, it has the advantages of reducing the longitudinal elastic constant of the tire and reducing the rolling resistance of the tire. In addition, it has the advantage of improving the ride comfort performance of the tire under a high inflation state compared with the specified internal pressure.

[0096] Furthermore, in this tire 1, the tire section height SH and tire contact width TW satisfy the conditions 0.55≤SH / SW≤0.65 and 0.60≤TW / SW≤0.90 (refer to...). Figure 1In this configuration, compared to an average passenger car tire, tire 1 has a high aspect ratio SH / SW and a high ground contact width ratio TW / SW, thereby having the advantage of reducing the rolling resistance of tire 1.

[0097] Example

[0098] Figure 5 and Figure 6 This is a graph showing the results of performance tests on tires according to embodiments of the present invention.

[0099] In this performance test, evaluations were conducted on (1) low rolling resistance performance and (2) ride comfort performance for various test tires. In addition, test tires with tire size 205 / 60R16 92V were assembled on rims with rim size 16×6.0J, and the test tires were subjected to an internal pressure of 250 [kPa] and a load equivalent to that of two people riding on the rim.

[0100] In the evaluation of (1) low rolling resistance performance, a drum testing machine with a drum diameter of 1707 [mm] was used, and the rolling resistance coefficient of the test tire was calculated according to ISO 28580 at a speed of 80 [km / h]. This evaluation was conducted by using an index evaluation based on previous examples (100), with a higher value being preferred.

[0101] In the evaluation of (2) ride comfort performance, the test vehicle, with test tires mounted on all wheels, was driven on a dry test track, and professional test drivers evaluated the ride comfort's stiffness and vibration damping. This evaluation was conducted using an index with previous examples as a baseline of 100, with higher values ​​indicating better performance.

[0102] The test tire in the embodiment has Figures 1-3 The tire profile is defined by the tire's tread width SW as 220 mm and its section height SH as 125 mm. Furthermore, the distance GD at the maximum tire width position D is 3.5 mm.

[0103] In the test tire of Example 1, the total thickness (distances GD, GE, GF) from the maximum width position D of the tire to the bead portion of the conventional test tire was set to be thicker.

[0104] As the test results show, the tires tested in the examples exhibit improved low rolling resistance and ride comfort.

[0105] Explanation of reference numerals in the attached figures

[0106] 1 tire

[0107] 11 tire bead core

[0108] 111 tire bead wire

[0109] 12 tire sidewall core

[0110] 13 fetal layers

[0111] 131 Main Body

[0112] Volume 132

[0113] 14-band layer

[0114] 141, 142 cross belts

[0115] 143 belt cover layer

[0116] 144 belt edge cover

[0117] 15 Tread Rubber

[0118] 16 sidewall rubber

[0119] 17-inch rim cushioning rubber

Claims

1. A tire provided with a pair of bead cores, a carcass layer erected on the pair of bead cores, a belt layer disposed on a tire radial direction outer side of the carcass layer, a tread rubber disposed on a tire radial direction outer side of the belt layer, a pair of sidewall rubbers disposed on a tire width direction outer side of the carcass layer, and a rim cushion rubber extending from a tire radial direction inner side of the pair of bead cores to a tire width direction outer side, characterized in that, the carcass layer covers the bead cores and is rolled back to a tire width direction outer side, a distance GD from a tread profile at a tire maximum width position to a tire inner surface, a distance GE from a tread profile at a position of 30[%] of a tire profile height to a tire inner surface, and a distance GF from a tread profile at a contact start point of the rolled back portion of the carcass layer to a tire inner surface satisfy conditions of GE < GF, 1.00 < GE / GD < 1.10, and 1.00 < GF / GD < 1.40, the distance GD is in a range of 2.0[mm] < GD < 5.0[mm], a distance GT from a tread profile at a tire ground contact end to a tire inner surface and a distance GC from a tread profile at a position of 70[%] of a tire profile height SH to a tire inner surface have a relationship of 3.00 < GT / GC < 4.

00.

2. The tire according to claim 1, wherein, a height HU of a termination position of the rolled back portion of the carcass layer and a tire profile height SH have a relationship of 0.10 < HU / SH < 0.

40.

3. The tire according to claim 2, wherein, a height HF of a contact start point of a main portion and a rolled back portion of the carcass layer and a height HU of a termination position of the rolled back portion of the carcass layer and a tire profile height SH have a relationship of 0.15 < (HU-HF) / SH and 0.15 < HF / SH < 0.

30.

4. The tire according to any one of claims 1 to 3, wherein, a distance GC from a tread profile at a position of 70[%] of a tire profile height to a tire inner surface and a distance GD at a tire maximum width position have a relationship of 1.00 < GC / GD < 1.

10.

5. The tire according to any one of claims 1 to 3, wherein, a width WE of a tread profile at a position of 30[%] of a tire profile height and a tire profile width SW have a relationship of 0.95 < WE / SW < 1.

00.

6. The tire according to any one of claims 1 to 3, wherein, a width WC of a tread profile at a position of 70[%] of a tire profile height and a tire profile width SW have a relationship of 0.90 < WC / SW < 1.

00.

7. The tire according to any one of claims 1 to 3, wherein, a tire profile width SW and a distance Wco of the pair of bead cores have a relationship of 1.20 < SW / Wco < 1.

40.

8. The tire according to any one of claims 1 to 3, wherein, ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ The tire ground contact width TW has a relationship of 0.90 ≤ TW / Wco ≤ 1.00 with the distance Wco of the pair of bead cores.

9. The tire according to any one of claims 1 to 3, wherein, The belt has a pair of cross belts, and a width Wbe of a wide cross belt of the pair of cross belts has a relationship of 1.05 ≤ Wbe / TW ≤ 1.30 with the tire ground contact width TW.

10. The tire according to any one of claims 1 to 3, wherein, The height HD of the tire maximum width position has a relationship of 0.50 ≤ HD / SH ≤ 0.60 with the tire profile height SH.

11. The tire according to any one of claims 1 to 3, wherein, The tire profile height SH and the tire ground contact width TW satisfy the conditions of 0.55 ≤ SH / SW ≤ 0.65 and 0.60 ≤ TW / SW ≤ 0.90 with the tire profile width SW.

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