Tire

Abstract

The present application provides a tire (2) capable of maintaining good wet performance and good durability, and achieving reduction in rolling resistance. The tire (2) has a tread (4) having a crown layer (38), an intermediate layer (40) having a tangent of loss angle at 30°C lower than that of the crown layer (38), and a base layer (42) having a tangent of loss angle at 30°C lower than that of the intermediate layer (40). In the radial direction, the intermediate layer (40) is located on the outer side of the base layer (42), and the crown layer (38) is located on the outer side of the intermediate layer (40). In the axial direction, the outer end PM of the intermediate layer (40) is located on the outer side of the outer end PB of the base layer (42), and the outer end (PC) of the crown layer (38) is located on the inner side of the outer end PM of the intermediate layer (40). The difference between the axial width (WC) of the crown layer (38) and the axial width (WB) of the base layer (42) is -10 mm or more and 10 mm or less.

Description

Technical Field

[0001] This invention relates to a tire. Background Technology

[0002] When low-heat-generating rubber is used in the tread, a tire with low rolling resistance can be obtained. However, low-heat-generating rubber has poorer grip than heat-generating rubber, which provides high grip. Therefore, when low-heat-generating rubber is used in the tread, braking performance (hereinafter also referred to as wet performance) is reduced, for example, on wet surfaces. It is difficult to achieve a good balance between rolling resistance and wet performance. Various studies have been conducted to reduce rolling resistance and improve wet performance (e.g., Patent Document 1 below).

[0003] Existing technical documents

[0004] Patent documents

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2018-2008 Summary of the Invention

[0006] The problem that the invention aims to solve

[0007] Considering the environmental impact, there is a need for further reductions in tire rolling resistance. As mentioned above, increasing the proportion of low-heat-generating rubber in the tread to reduce rolling resistance decreases wet performance. Low-heat-generating rubber is brittle, so increasing its proportion in the tread raises concerns about reduced durability. There is a need to establish a technology that can maintain good wet performance and good durability while achieving reduced rolling resistance.

[0008] The present invention was made in view of the following circumstances, and the object is to provide a tire that can maintain good wet performance and good durability, and achieve a reduction in rolling resistance.

[0009] Solution for solving the problem

[0010] One aspect of the present invention provides a tire having a tread that contacts the road surface. The tread comprises: a crown layer, an intermediate layer with a 30° loss tangent lower than that of the crown layer, and a base layer with a 30° loss tangent lower than that of the intermediate layer. Radially, the intermediate layer is located outside the base layer, and the crown layer is located outside the intermediate layer. Axially, the outer end of the intermediate layer is located outside the base layer, and the outer end of the crown layer is located inside the outer side of the intermediate layer. The difference between the axial width of the crown layer and the axial width of the base layer is -10 mm to 10 mm.

[0011] Preferably, in this tire, the difference between the axial width of the intermediate layer and the axial width of the crown layer is more than 10 mm and less than 30 mm.

[0012] Preferably, in this tire, the difference between the axial width of the base layer and the width of the tread is between -10 mm and 10 mm.

[0013] Preferably, in this tire, the tire is assembled onto a standard rim, the tire's internal pressure is adjusted to 230 kPa, and 70% of the standard load is applied to the tire as a longitudinal load. The contact surface formed by the tire contacting the road surface is designated as the reference contact surface, and the position on the tire surface corresponding to the axial outer end of the reference contact surface is designated as the reference ground contact end. Axially, the outer end of the tread layer is located outside the reference ground contact end.

[0014] Preferably, in this tire, the ratio of the 30° loss tangent of the crown layer to the 30° loss tangent of the intermediate layer is 110% or more and 250% or less.

[0015] Preferably, the tire has a belt layer located radially inside the tread and a crown layer located between the tread and the belt layer. The belt layer comprises a plurality of belt layer cords arranged side by side. The crown layer comprises crown layer cords wound in a spiral shape. The crown layer is wider than the belt layer. Axially, the outer end of the base layer is positioned at the same position as the outer end of the crown layer, or the outer end of the base layer is located outside the outer end of the crown layer.

[0016] Preferably, in this tire, the ratio of the axial width of the crown layer to the cross-sectional width of the tire is more than 70% and less than 90%.

[0017] Invention Effects

[0018] According to the present invention, a tire is obtained that can maintain good wet performance and good durability, and achieve a reduction in rolling resistance. Attached Figure Description

[0019] Figure 1 This is a cross-sectional view showing a portion of a tire according to one embodiment of the present invention.

[0020] Figure 2 It is used to represent Figure 1 An enlarged cross-sectional view of the tire shoulder section.

[0021] Figure 3 It is used to represent Figure 1 An enlarged cross-sectional view of a portion of a tire.

[0022] Figure 4 This is an enlarged cross-sectional view used to show a portion of the tire of Comparative Example 1.

[0023] Figure 5 This is an enlarged cross-sectional view used to show a portion of the tire of Comparative Example 2.

[0024] Figure 6 This is an enlarged cross-sectional view used to show a portion of the tire of Comparative Example 3.

[0025] Figure 7 This is an enlarged cross-sectional view used to show a portion of the tire of Comparative Example 4.

[0026] Marker description

[0027] 2. Tires

[0028] 4···Tread

[0029] 6··· Side of the tire

[0030] 12···Fetal body

[0031] 14··· Belt Layer

[0032] 16··· Crown layer

[0033] 34, 34a, 34b... curtain layers

[0034] 36, 36a, 36b... layers

[0035] 38···Tire crown layer

[0036] 42···Basic Layer Detailed Implementation

[0037] The present invention will now be described in detail with appropriate reference to the accompanying drawings and based on preferred embodiments.

[0038] In this disclosure, the state in which a tire is mounted on a standard rim, the tire pressure is adjusted to the standard pressure, and no load is applied to the tire is referred to as the standard state. The state in which a tire is mounted on a standard rim, the tire pressure is adjusted to 230 kPa, and no load is applied to the tire is referred to as the standard state.

[0039] In this disclosure, unless otherwise specified, the dimensions and angles of each part of the tire are measured under normal conditions. Dimensions and angles of each part in the radial section of the tire, which cannot be measured when the tire is mounted on a normal rim, are measured by taking a section of the tire obtained by cutting the tire along a plane including the axis of rotation, and ensuring that the distance between the left and right bead sections is consistent with the bead distance in a tire mounted on a normal rim.

[0040] A standard rim refers to the rim that the tire conforms to. Standard rims are defined in JATMA specifications ("Standard Rim"), TRA specifications ("Design Rim"), and ETRTO specifications ("Measuring Rim").

[0041] Standard tire pressure refers to the tire pressure specified in the tire's specifications. The standard tire pressure is defined as the "maximum pressure" in JATMA specifications, the "maximum value" listed in TRA specifications ("TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES"), and the "INFLATION PRESSURE" in ETRTO specifications.

[0042] Regular load refers to the load specified in the tire's specifications. The "maximum load capacity" in JATMA specifications, the "maximum value" recorded in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in TRA specifications, and "LOAD CAPACITY" in ETRTO specifications are all regular loads.

[0043] In this disclosure, crosslinked rubber refers to a molded body of a rubber composition obtained by pressurizing and heating a rubber composition. The rubber composition is a non-crosslinked rubber obtained by mixing a base rubber and a pharmaceutical material in a mixing mill such as a Banbury mixer. Crosslinked rubber is also called vulcanized rubber, and the rubber composition is also called unvulcanized rubber.

[0044] Examples of base rubbers include natural rubber (NR), butadiene rubber (BR), styrene-butadiene rubber (SBR), isoprene rubber (IR), ethylene-propylene rubber (EPDM), chloroprene rubber (CR), acrylonitrile-butadiene rubber (NBR), and butyl rubber (IIR). Examples of pharmaceuticals include reinforcing agents such as carbon black and silica, plasticizers such as aromatic oils, fillers such as zinc oxide, lubricants such as stearic acid, anti-aging agents, processing aids, sulfur, and vulcanization accelerators. The selection of base rubbers and pharmaceuticals, as well as the content of the selected pharmaceuticals, can be appropriately determined according to the specifications of various elements such as the tread and sidewall where the rubber composition is applied.

[0045] In this disclosure, the loss tangent (also known as tanδ) of the element constituting the rubber, formed from cross-linked rubber, at a temperature of 30°C, is measured using a viscoelastic spectrometer (VES manufactured by Iwamoto Manufacturing Co., Ltd.) under the following conditions, according to JIS K 6394: Initial deformation = 10%, Dynamic deformation = 2%, Frequency = 10Hz, Deformation mode = Tensile. In this determination, test pieces are taken from tires. When it is not possible to take test pieces from tires, the rubber composition used to form the element to be measured is pressurized and heated at 170°C for 12 minutes to obtain sheet-like cross-linked rubber (hereinafter also referred to as rubber sheet), from which test pieces are taken.

[0046] Figure 1 A portion of a tire 2 used to illustrate one embodiment of the present invention. The tire 2 is a passenger car tire. Figure 1 This represents a portion of a cross-section (hereinafter also referred to as a meridian section) of tire 2 along a plane including the axis of rotation of tire 2. Figure 1 In the diagram, the left-right direction is the axial direction of tire 2, and the up-down direction is the radial direction of tire 2. Figure 1 The direction perpendicular to the paper is the circumferential direction of tire 2.

[0047] exist Figure 1 In the diagram, the dotted line EL represents the equatorial plane of tire 2. Apart from the tread patterns, designs, and text engraved on its surface, tire 2 is symmetrical with respect to the equatorial plane.

[0048] exist Figure 1 In this configuration, tire 2 is mounted on rim R. Rim R is a standard rim. Tire 2 is filled with air to regulate its internal pressure. Tire 2 mounted on rim R is also called a tire-rim assembly. The tire-rim assembly consists of rim R and tire 2 mounted on rim R.

[0049] exist Figure 1 In the diagram, the symbol PW indicates the axial outer end of tire 2. When the pattern, text, or other devices are located on the surface, the outer end PW is determined based on an imaginary surface, which is obtained by assuming there is no decoration.

[0050] exist Figure 1 In the diagram, the length indicated by the symbol WA is the maximum width of tire 2, i.e., the section width (refer to JATMA et al.). The section width WA of tire 2 is the axial distance from the outer end PW on one side to the outer end PW on the other side. The outer end PW is the location indicating the maximum width of tire 2 (hereinafter referred to as the maximum width location). The section width WA is measured in tire 2 under standard conditions.

[0051] The tire 2 has a tread 4, a pair of sidewalls 6, a pair of bead 8, a pair of bead 10, a carcass 12, a belt layer 14, a crown layer 16, a pair of buffer layers 18, a pair of bead wraps 20, and an airtight layer 22.

[0052] The tread 4 contacts the road surface on its surface. The tread 4 is engraved with grooves 24, which together form the tread pattern.

[0053] At least three circumferentially extending grooves 26 are etched on the tread 4, forming at least four axially arranged land sections 28. In this tire 2, as... Figure 1 As shown, three circumferential grooves 26 are engraved on the tread 4, forming four land portions 28 on the tread 4. The circumferential grooves 26 form part of the grooves 24 that constitute the tread pattern. Of the four land portions 28, the land portion 28 located on the equatorial plane is the central land portion 28m, and the land portion 28 located outside the central land portion 28m is the shoulder land portion 28s.

[0054] exist Figure 1 In the diagram, the symbol PE indicates the equator of tire 2. Equator PE is the intersection of the tread surface 4 and the equatorial plane. For example... Figure 1 As shown, in the case of groove 24 on the equatorial surface, the equatorial PE is determined based on a hypothetical surface, which is obtained by assuming that the tread 4 does not have groove 24.

[0055] Each sidewall 6 is connected to the tread 4. The sidewall 6 is located radially inside the tread 4. The sidewall 6 extends from the edge of the tread 4 along the carcass 12 toward the bead 8. The sidewall 6 is formed of cross-linked rubber with cut resistance taken into account.

[0056] Each bead 8 is located radially inside the sidewall 6. The bead 8 contacts the rim R. The bead 8 is formed of cross-linked rubber with wear resistance taken into account.

[0057] Each bead 10 is located axially inside the bead 8. Each bead 10 has a bead core 30 and a triangular rubber strip 32. Although not illustrated, the bead core 30 includes steel wire.

[0058] The triangular rubber strip 32 is located radially outside the bead core 30. The triangular rubber strip 32 gradually tapers outwards. The triangular rubber strip 32 is formed of cross-linked rubber with high rigidity.

[0059] The tire body 12 is located inside the tread 4, a pair of sidewalls 6, and a pair of bead 8. The tire body 12 spans between one bead 10 and another bead 10. The tire body 12 has a radial structure.

[0060] The tire carcass 12 includes at least one ply 34. From the point of view of lightweighting, the tire carcass 12 of the tire 2 is composed of one ply 34.

[0061] Although not illustrated, the ply 34 comprises multiple carcass cords arranged side-by-side. These carcass cords are covered with top rubber. Each carcass cord crosses the equatorial plane. The carcass cords are cords formed of organic fibers. Examples of organic fibers include nylon, rayon, polyester, and aramid fibers.

[0062] The belt layer 14 is located radially inside the tread 4. The belt layer 14 accumulates radially from the tread side to the carcass 12. Figure 1 In this tire 2, the length indicated by the symbol WR is the axial width of the belt layer 14. The axial width WR is the axial distance from one end of the belt layer 14 to the other end. In this tire 2, the axial width WR of the belt layer 14 is more than 65% and less than 85% of the section width WA.

[0063] The belt layer 14 is composed of at least two layers 36 stacked radially. The belt layer 14 of the tire 2 is formed by two layers 36 stacked radially. Of the two layers 36, the inner layer 36 is called the inner layer 36a, and the outer layer 36 is called the outer layer 36b. Figure 1 As shown, the inner layer 36a is wider than the outer layer 36b. The length from the edge of the outer layer 36b to the edge of the inner layer 36a is more than 3 mm and less than 10 mm.

[0064] Although not illustrated, the inner layer 36a and outer layer 36b each comprise multiple parallel belt layer cords. These belt layer cords are covered with top rubber. Each belt layer cord is inclined relative to the equatorial plane. The belt layer cords are made of steel.

[0065] The crown layer 16 is located radially between the tread 4 and the belt layer 14. The crown layer 16 is stacked on the belt layer 14 on the inner side of the tread 4.

[0066] Although not illustrated, the crown layer 16 comprises crown layer cords wound in a spiral shape. The crown layer cords extend substantially circumferentially. Specifically, the angle between the crown layer cords and the circumferential direction is less than 5°. The crown layer 16 has a seamless structure. In this tire 2, cords formed of organic fibers are used as crown layer cords. Examples of organic fibers include nylon fibers, rayon fibers, polyester fibers, and aramid fibers.

[0067] The crown belt layer 16 of the tire 2 is formed by two full crown belt layers sandwiching equatorial PE at opposite ends. The crown belt layer 16 is wider than the belt layer 14. The length from the edge of the belt layer 14 to the edge of the crown belt layer 16 is more than 3 mm and less than 10 mm. The crown belt layer 16 covers the entire belt layer 14. The crown belt layers 16 are spaced apart in the axial direction and may include a pair of sidebands covering the edges of the full crown belt layer and the belt layer 14. The crown belt layer 16 may consist of only a pair of sidebands.

[0068] The various buffer layers 18 are spaced apart axially. The buffer layers 18 are located between the edges of the belt layer 14 and the crown belt layer 16 and the ply body 34a of the carcass 12. The buffer layers 18 are formed of cross-linked rubber with low rigidity. In this tire 2, the buffer layers 18 may not be provided.

[0069] Each bead wrap 20 is located radially inside the rim 10. The bead wrap 20 contacts the rim R. The bead wrap 20 of the tire 2 is formed of cloth and rubber impregnated with the cloth.

[0070] The airtight layer 22 is located inside the tire carcass 12. The airtight layer 22 forms the inner surface of the tire 2. The airtight layer 22 is formed of cross-linked rubber with a low gas permeability coefficient. The airtight layer 22 maintains the internal pressure of the tire 2.

[0071] exist Figure 1 In the diagram, the symbol PH indicates the position on the surface of the tread 4. Position PH corresponds to the outermost axial end of the contact patch between the tire 2 and the road surface.

[0072] The contact surface used to determine position PH is obtained using, for example, a contact surface shape measuring device (not shown). This contact surface is obtained as follows: in this device, with the camber angle of the tire 2 in its standard state set to 0°, 70% of the normal load is applied as a longitudinal load to the tire 2, causing the tire 2 to contact the road surface formed by the flat surface. In this tire 2, the contact surface thus obtained is the reference contact surface, and the position on the surface of the tread 4 corresponding to the axial outer end of this reference contact surface is the aforementioned position PH. In this tire 2, this position PH is the reference contact point.

[0073] Figure 2 Used to represent Figure 1 A portion of tire 2 shown. Figure 2 In the diagram, the left-right direction is the axial direction of tire 2, and the up-down direction is the radial direction of tire 2. Figure 2 The direction perpendicular to the paper is the circumferential direction of tire 2.

[0074] Figure 2 This shows the outline of the shoulder portion of tire 2 in the radial cross-section. Figure 2 The outline shown was obtained by measuring the surface shape of tire 2 under standard conditions using a displacement sensor.

[0075] In the meridian profile, the contour of the surface of tire 2 (hereinafter referred to as tire surface TS) is formed by connecting multiple contour lines formed by straight lines or circular arcs. In this disclosure, the contour lines formed by straight lines or circular arcs are simply referred to as contour lines. Contour lines formed by straight lines are called straight contour lines, and contour lines formed by circular arcs are called curved contour lines.

[0076] The tire surface TS has a tread surface T and a pair of sidewalls S connected to the edge of the tread surface T. In a radial section, the profile of the tread surface T includes multiple curved profiles with different radii. In this tire 2, among the multiple curved profiles included in the profile of the tread surface T, the curved profile with the smallest radius is located at the edge portion of the tread surface T and is connected to the sidewalls S.

[0077] In the radial profile, the profile of the tire surface TS includes a curved portion in the edge portion of the tread surface. This curved portion is formed by an arc with the smallest radius among the multiple curved profiles included in the tread surface profile and is connected to the sidewall. Figure 2 The curve is represented by the symbol RS.

[0078] In the profile of the tire surface TS, the curved portion RS contacts the innermost profile line (hereinafter referred to as the inner adjacent profile line NT) at the connection point CT. The curved portion RS contacts the outermost profile line (hereinafter referred to as the outer adjacent profile line NS) that forms the profile of the sidewall S at the connection point CS. The profile of the tire surface TS includes the inner adjacent profile line NT, which is located axially inside the curved portion RS and contacts it, and the outer adjacent profile line NS, which is located axially outside the curved portion RS and contacts it.

[0079] exist Figure 2 In the diagram, the solid line LT is the tangent to the curved portion RS at the connection point CT between the inner adjacent contour line NT and the curved portion RS. The solid line LS is the tangent to the curved portion RS at the connection point CS between the outer adjacent contour line NT and the curved portion RS. The symbol PT indicates the intersection of tangent lines LT and LS. In this tire 2, this intersection point PT is the imaginary tread end.

[0080] In the tread 4, the portion from one imaginary tread end PT to the other imaginary tread end PT is the area expected to contact the road surface under normal driving conditions of the tire 2 (hereinafter also referred to as the normal contact area). From the viewpoint of effectively reinforcing the portion of the tread 4 (hereinafter also referred to as the tread portion), the belt layer 14 and the crown belt layer 16 are disposed on this normal contact area.

[0081] exist Figure 1 In the diagram, the length indicated by the double arrow WT is the width of tread 4. The width of tread 4 is the axial distance from one imaginary tread end PT to the other imaginary tread end PT. The length indicated by the double arrow WH is the axial length of the reference ground plane. The axial width WH is the axial distance from one reference ground plane PH to the other reference ground plane PH.

[0082] In this tire 2, the ratio (WT / WA) of the tread width 4 to the section width WA is 70% to 90%. The imaginary tread end PT is located axially outside the reference contact end PH. In other words, the axial width WH of the reference contact area is narrower than the tread width WT. Specifically, the ratio (WH / WT) of the axial width WH to the tread width WT is 70% to 90%.

[0083] Figure 3 express Figure 1 Part of tire 2 shown. Figure 3 This refers to the tread portion of tire 2. Figure 3 In the diagram, the left-right direction is the axial direction of tire 2, and the up-down direction is the radial direction of tire 2. Figure 3 The direction perpendicular to the paper is the circumferential direction of tire 2.

[0084] The tire 2 has a tread 4 comprising a crown layer 38, an intermediate layer 40, and a base layer 42. Radially, the intermediate layer 40 is located outside the base layer 42, and the crown layer 38 is located outside the intermediate layer 40. Figure 3 As shown, the crown layer 38 is stacked on the intermediate layer 40, and the intermediate layer 40 is stacked on the base layer 42.

[0085] In this tire 2, at the center of the land portion 28 in the width direction, the ratio of the thickness of the crown layer 38 to the thickness of the tread 4 is preferably 10% to 40%. At the center of the land portion 28 in the width direction, the ratio of the thickness of the intermediate layer 40 to the thickness of the tread 4 is 30% to 70%.

[0086] exist Figure 3 In the diagram, the symbol PC indicates the outer end of the crown layer 38. The symbol WC indicates the axial width of the crown layer 38. The axial width WC is the axial distance from one outer end PC to the other. The symbol PM indicates the outer end of the intermediate layer 40. The symbol WM indicates the axial width of the intermediate layer 40. The axial width WM is the axial distance from one outer end PM to the other. The symbol PB indicates the outer end of the base layer 42. The symbol WB indicates the axial width of the base layer 42. The axial width WB is the axial distance from one outer end PB to the other.

[0087] exist Figure 3 In this tire 2, the symbol PS indicates the outer end of the tread 4 on the tire surface TS. In this tire 2, the outer end PS of the tread 4 is located axially outside the outer end PC of the crown layer 38. The portion of the tire surface TS from the outer end PC to the outer end PS is composed of an intermediate layer 40. In this tire 2, a portion of the intermediate layer 40 is exposed on the tire surface TS.

[0088] The crown layer 38, intermediate layer 40, and base layer 42 are each formed of cross-linked rubber with different thermal properties. In this tire 2, the crown layer 38 is most prone to thermal expansion, while the base layer 42 is least prone to thermal expansion. The intermediate layer 40 has thermal properties between those of the crown layer 38 and the base layer 42. In this tire 2, the 30°C loss tangent LTm of the intermediate layer 40 is lower than that of the crown layer 38 at 30°C. The 30°C loss tangent LTb of the base layer 42 is lower than that of the crown layer 40 at 30°C at 30°C.

[0089] The loss tangent LTb of the base layer 42 at 30°C is preferably 0.11 or less. This is because it effectively helps to reduce the rolling resistance of the base layer 42. From this point of view, the loss tangent LTb is more preferably 0.10 or less, and even more preferably 0.09 or less. The smaller the loss tangent LTb of the base layer 42, the better; therefore, no lower limit for preference is set.

[0090] The loss tangent LTm of the intermediate layer 40 at 30°C is preferably 0.15 or less. This is because it effectively contributes to reducing the rolling resistance of the intermediate layer 40. From this point of view, the loss tangent LTm is more preferably 0.14 or less, and even more preferably 0.13 or less. The loss tangent LTm of the intermediate layer 40 at 30°C is preferably 0.11 or more. This is because it ensures the required rigidity of the intermediate layer 40 and effectively contributes to improving wetland performance. From this point of view, the loss tangent LTm is preferably 0.12 or more.

[0091] The loss tangent LTc of the tread layer 38 at 30°C is preferably 0.15 or higher. This is because the tread layer 38 contributes to improved wet performance. From this viewpoint, the loss tangent LTc is more preferably 0.16 or higher, and even more preferably 0.17 or higher. The tread layer 38 is in contact with the road surface. From the viewpoint of improving wet performance, a higher loss tangent LTc is preferred. However, an excessively high loss tangent LTc leads to heat generation. It is concerning that the heated tread layer 38 may raise the temperature of the intermediate layer 40 above the expected level. From the viewpoint of stably maintaining the overall temperature of the tread 4 and thus maintaining low rolling resistance, the loss tangent LTc of the tread layer 38 at 30°C is preferably 0.30 or lower, more preferably 0.28 or lower, and even more preferably 0.27 or lower.

[0092] In this tire 2, axially, the outer end PM of the intermediate layer 40 is located outside the outer end PB of the base layer 42. The boundary between the intermediate layer 40 and the sidewall 6 spans the tire surface TS and the surface of the carcass 12. This boundary is axially located outside the base layer 42. In this tire 2, the intermediate layer 40 is located between the base layer 42 and the sidewall 6. The intermediate layer 40 covers the base layer 42 from both radially and axially outward.

[0093] When a vehicle is driven under severe conditions with large inertial forces, wear occurs at the boundary between the tread 4 and the sidewall 6 (hereinafter also referred to as the reinforcement). In this tire 2, a sufficiently thick intermediate layer 40 is located between the tire surface TS and the base layer 42, thus preventing the base layer 42 from being exposed even when the tire 2 is used under extreme driving conditions where the reinforcement may wear. In this tire 2, good durability is maintained.

[0094] In this tire 2, the outer end PC of the crown layer 38 is axially located inside the outer end PM of the intermediate layer 40. In other words, the crown layer 38 does not cover the entire intermediate layer 40, but only a portion of it. In this tire 2, compared to the tread 4 where the intermediate layer 40 is entirely covered by the crown layer 38, the volume of the crown layer 38, which increases rolling resistance, is smaller, while the volume of the intermediate layer 40, which contributes to reducing rolling resistance, is larger. The tread 4 contributes to the reduction of rolling resistance.

[0095] In this tire 2, the difference (WC-WB) between the axial width WC of the crown layer 38 and the axial width WB of the base layer 42 is -10 mm to 10 mm. The axial width WC of the crown layer 38 and the axial width WB of the base layer 42 are almost equal. As the overall heat generation and rigidity of the tread 4 are balanced, the crown layer 38 effectively contributes to improving wet performance, and the base layer 42 effectively contributes to reducing rolling resistance. From this perspective, the difference (WC-WB) is preferably -5 mm or more, and preferably less than 5 mm.

[0096] In this tire 2, axially, the outer end PM of the intermediate layer 40 is located outside the outer end PB of the base layer 42, and the outer end PC of the crown layer 38 is located inside the outer end PM of the intermediate layer 40. The difference (WC-WB) between the axial width WC of the crown layer 38 and the axial width WB of the base layer 42 is between -10mm and 10mm. This tire 2 maintains good wet performance and good durability while reducing rolling resistance.

[0097] In this tire 2, the portion of the tread 4 formed by the crown layer 38 and the intermediate layer 40 corresponds to the crown layer of a conventional tire tread formed by the crown layer and the base layer. In this tire 2, from the viewpoint that the tread 4 can effectively contribute to improved wet performance and reduced rolling resistance, the ratio (LTc / LTm) of the loss tangent LTc of the crown layer 38 at 30°C to the loss tangent LTm of the intermediate layer 40 at 30°C is preferably 110% or more and 250% or less. This ratio (LTc / LTm) is more preferably 130% or more, and even more preferably 150% or more. This ratio (LTc / LTm) is more preferably 240% or less, and even more preferably 230% or less.

[0098] In this tire 2, from the viewpoint that the tread layer 38 can effectively contribute to wet performance, the ratio (WC / WA) of the axial width WC of the tread layer 38 to the section width WA of the tire 2 is preferably 70% or more, more preferably 75% or more. From the viewpoint of effectively suppressing the influence of the tread layer 38 on rolling resistance, this ratio (WC / WA) is preferably 90% or less, more preferably 85% or less.

[0099] In this tire 2, from the viewpoint of reducing rolling resistance, the difference (WM-WC) between the axial width WM of the intermediate layer 40 and the axial width WC of the crown layer 38 is preferably 30 mm or less, more preferably 20 mm or less, and even more preferably 10 mm or less. From the viewpoint that the intermediate layer 40 can contribute to preventing the exposure of the base layer 42 during extreme driving, this difference (WM-WC) is preferably 10 mm or more. In this tire 2, from the viewpoint of preventing the exposure of the base layer 42 and effectively reducing rolling resistance, this difference (WM-WC) is particularly preferably 10 mm.

[0100] In this tire 2, the difference (WB-WT) between the axial width WB of the base layer 42 and the width WT of the tread 4 is preferably -10 mm to 10 mm. In other words, the axial width of the base layer 42 is preferably almost equal to the width WT of the tread 4. This effectively ensures the axial width WB of the base layer 42 and the distance from the tire surface TS to the base layer 42. In this tire 2, exposure of the base layer 42 during extreme driving is effectively prevented, and the rolling resistance reduction function provided by the base layer 42 is stably maintained. In this tire 2, good durability and low rolling resistance can be obtained. From this point of view, the difference (WB-WT) is more preferably -5 mm or more, and more preferably 5 mm or less.

[0101] As described above, in this tire 2, axially, the outer end PM of the intermediate layer 40 is located outside the outer end PB of the base layer 42. From the viewpoint of effectively preventing exposure of the base layer 42 during extreme driving and maintaining good durability, the difference (WM-WB) between the axial width WM of the intermediate layer 40 and the axial width WB of the base layer 42 is preferably 6 mm or more, more preferably 8 mm or more. From the viewpoint of ensuring the axial width WB of the base layer 42 and obtaining low rolling resistance, this difference (WM-WB) is preferably 14 mm or less, more preferably 12 mm or less.

[0102] During braking, a large load is applied to the tire. Consequently, the contact patch width of tire 2 tends to widen. In tire 2, the outer end PC of the tread layer 38 is axially located outside the reference contact patch PH. Even during braking, the tread layer 38 can maintain sufficient contact with the road surface. Good wet performance is achieved in this tire 2. From this perspective, it is preferable that the outer end PC of the tread layer 38 is axially located outside the reference contact patch PH.

[0103] In this tire 2, the difference (WC-WT) between the axial width WC of the crown layer 38 and the width WT of the tread 4 is preferably -10 mm to 10 mm. In other words, the axial width WC of the crown layer 38 is preferably almost equal to the width WT of the tread 4. Therefore, not only during straight-line driving, but also during braking under heavy loads, the crown layer 38 can maintain sufficient contact with the road surface. Good wet-weather performance is achieved in this tire 2. From this perspective, the difference (WC-WT) is preferably -5 mm or more, and more preferably less than 5 mm.

[0104] As described above, the area represented by the width WT of the tread 4 is the normal contact area, in which the belt layer 14 and crown layer 16 are arranged to effectively reinforce the tread. The base layer 42 contributes to the reduction of rolling resistance and, on the other hand, has lower rigidity than the crown layer 38 and the intermediate layer 40. In this tire 2, the base layer 42 is laminated on the crown layer 16, and the crown layer 16 is laminated on the belt layer 14. The belt layer 14 and the crown layer 16 effectively reinforce the base layer 42. The base layer 42 can effectively contribute to the reduction of rolling resistance. From this point of view, in the axial direction, it is preferable that the position of the outer end PB of the base layer 42 coincides with the position of the outer end of the crown layer 16, or that the outer end PB of the base layer 42 is located outside the outer end of the crown layer 16. In other words, it is preferable that the length from the outer end of the conductor 16 to the outer end PB of the base layer 42 is 0 mm or more. From the viewpoint of effectively reinforcing the base layer 42 and preventing its exposure, this length is preferably 4 mm or less, more preferably 2 mm or less. Furthermore, when the belt layer 14 is wider than the crown layer 16, from the viewpoint of reducing rolling resistance, the length from the outer end of the belt layer 14 to the outer end PB of the base layer 42 is preferably 0 mm or more. From the viewpoint of effectively reinforcing the base layer 42 and preventing its exposure, this length is preferably 4 mm or less, more preferably 2 mm or less.

[0105] As described above, according to the present invention, a tire is obtained that can maintain good wet performance and good durability, and achieve a reduction in rolling resistance.

[0106] Example

[0107] The present invention will be further described in detail below through embodiments, etc., but the present invention is not limited to these embodiments.

[0108] [Experiment 1]

[0109] We obtained pneumatic tires for passenger cars (tire size = 205 / 55R16), which have... Figure 1 The basic structure shown has the specifications shown in Table 1 below.

[0110] It uses a crown layer, intermediate layer and base layer, and has Figure 3 The diagram shows the tire tread configuration. The difference between the axial width WC of the crown layer and the axial width WB of the base layer (WC-WB) is 0 mm. The difference between the axial width WM of the intermediate layer and the axial width WC of the crown layer (WM-WC) is 10 mm. The difference between the axial width WM of the intermediate layer and the axial width of the base layer (WM-WB) is 10 mm. The difference between the axial width WM of the intermediate layer and the width WT of the tread (WM-WT) is 10 mm.

[0111] In this embodiment 1, the loss tangent LTc of the crown layer at 30°C is 0.27. The loss tangent LTm of the intermediate layer at 30°C is 0.12. The loss tangent LTb of the base layer at 30°C is 0.10.

[0112] [Comparative Example 1]

[0113] The tread structure is set as follows: Figure 4 The configuration shown was performed in the same manner as in Example 1, with the difference (WM-WC) and difference (WM-WB) set as shown in Table 1 below. The tire of Comparative Example 1 was obtained.

[0114] [Comparative Example 2]

[0115] The tread structure is set as follows: Figure 5 The configuration shown was performed in the same manner as in Example 1, with the difference (WC-WB) and difference (WM-WC) set as shown in Table 1 below. The tire of Comparative Example 2 was obtained.

[0116] [Comparative Example 3]

[0117] The tread structure is set as follows: Figure 6 The configuration shown was performed in the same manner as in Example 1, with the difference (WC-WB) and difference (WM-WC) set as shown in Table 1 below. The tire of Comparative Example 3 was obtained.

[0118] [Comparative Example 4]

[0119] The tread structure is set as follows: Figure 7 The configuration shown was performed in the same manner as in Example 1, with the difference (WC-WB) and difference (WM-WB) set as shown in Table 1 below. The tire of Comparative Example 4 was obtained.

[0120] Rolling resistance coefficient (RRC)

[0121] Using a rolling resistance testing machine, the sample tire was driven on a roller at a speed of 80 km / h under the following conditions, and the rolling resistance coefficient (RRC) was measured. The results are shown in Table 1 below. The smaller the value, the lower the rolling resistance of the tire. Rim: 16×6.5J, internal pressure: 210 kPa, longitudinal load: 4.82 kN

[0122] [Wetland Performance (WET)]

[0123] The sample tire was assembled onto a rim (size = 16 × 6.5 J), inflated with air, and the tire pressure was adjusted to 230 kPa. The tire was then mounted on a test vehicle (passenger car). The test vehicle was driven on a test route with a wet road surface (water film thickness = 1.4 mm). The test vehicle was braked at a speed of 100 km / h, and the distance traveled from the start of braking to a stop (braking distance) was measured. The results are shown in Table 1 below using indices. A higher value indicates a shorter braking distance and better wet performance of the tire.

[0124] [Extreme Performance]

[0125] The sample tire was assembled onto a rim (size = 16 × 6.5J), inflated, and the tire pressure was adjusted to 230 kPa. The tire was then mounted on a test vehicle (passenger car). The test vehicle was driven in an understeer state on a circular test track on a dry surface. The driving speed was set to 100 km / h. After 20 laps, the wear condition of the tire's reinforcing section was checked. The results are shown in Table 1 below. "NG" indicates that exposure of the base layer or tread separation was confirmed. "G" indicates that no exposure of the base layer or tread separation was confirmed.

[0126] Table 1

[0127]

[0128] As shown in Table 1, it was confirmed that in the embodiments, good wetland performance and good durability can be maintained, while rolling resistance is reduced. Based on these evaluation results, the superiority of the present invention is obvious.

[0129] [Industry Applicability]

[0130] The technologies described above, which enable the maintenance of good wet performance and durability while reducing rolling resistance, can also be applied to a wide variety of tires.

Claims

1. A tire having a tread that contacts the ground, characterized in that, The tread comprises: a crown layer, an intermediate layer with a loss tangent of 30°C lower than that of the crown layer, and a base layer with a loss tangent of 30°C lower than that of the intermediate layer. In the radial direction, the intermediate layer is located outside the base layer, and the crown layer is located outside the intermediate layer. In the axial direction, the outer end of the intermediate layer is located outside the outer end of the base layer, and the outer end of the crown layer is located inside the outer end of the intermediate layer. A portion of the intermediate layer is exposed to the tread surface. The difference between the axial width of the crown layer and the axial width of the base layer is between -10mm and 10mm, and the difference between the axial width of the intermediate layer and the axial width of the base layer is between 6mm and 14mm.

2. The tire according to claim 1, characterized in that, The difference between the axial width of the intermediate layer and the axial width of the crown layer is more than 10 mm and less than 30 mm.

3. The tire according to claim 1 or 2, characterized in that, The difference between the axial width of the base layer and the axial width of the tread is between -10mm and 10mm.

4. The tire according to claim 1 or 2, characterized in that, The process involves assembling the tire onto a standard rim, adjusting the tire's internal pressure to 230 kPa, and then applying 70% of the standard load as a longitudinal load to the tire. The contact surface formed by the tire contacting the road surface is designated as the reference contact surface, and the position on the tire surface corresponding to the axial outer end of the reference contact surface is designated as the reference grounding end. In the axial direction, the outer end of the crown layer is located outside the reference ground terminal.

5. The tire according to claim 1 or 2, characterized in that, The ratio of the loss tangent of the crown layer at 30°C to the loss tangent of the intermediate layer at 30°C is more than 110% and less than 250%.

6. The tire according to claim 1 or 2, characterized in that, It has a belt layer located radially inside the tread and a crown belt layer located between the tread and the belt layer. The belt layer comprises multiple belt layer cords arranged side by side. The coronal band layer comprises coronal band layer cords wound in a spiral shape. The crown band layer is wider than the band layer. In the axial direction, the outer end of the base layer is positioned at the same position as the outer end of the coronary band layer, or the outer end of the base layer is located outside the outer end of the coronary band layer.

7. The tire according to claim 1 or 2, characterized in that, The ratio of the axial width of the crown layer to the cross-sectional width of the tire is more than 70% and less than 90%.

Images