tire

Abstract

The present invention provides a tire (2) that suppresses the influence on conductivity and handling stability and achieves a reduction in rolling resistance. The tire (2) includes a tread (4), a pair of sidewalls (6), a pair of tire beads (10), a carcass (12), a belt layer (14), an inner liner (20), and a pair of insert layers (22) located between the carcass (12) and the inner liner (20). Each insert layer (22) is located between an end of the belt layer (14) and an end (PB) of the tire bead (10). The volume resistivity of the insert layer (22) is less than 10 8 Ω·cm. The complex elastic modulus of the insert layer (22) is equal to or higher than the complex elastic modulus of the inner liner (20). The thickness of the sidewall (6) at the maximum width position (PW) is 5.0 mm or less.

Description

Technical Field

[0001] The present invention relates to tires. In particular, the present invention relates to tires mounted on passenger vehicles. Background Art

[0002] For environmental reasons, tires with low rolling resistance are required. To reduce rolling resistance, for example, exothermic rubber is used. Since low exothermic rubber contains a large amount of silicon as a reinforcing agent, the conductivity of a tire using low exothermic rubber is reduced, and there is a concern about the accumulation of static electricity generated during driving. In order to ensure conductivity even when using low exothermic rubber, various studies have been conducted (for example, Patent Document 1).

[0003] [Prior art literature]

[0004] [Patent Literature]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2007-8269 Summary of the invention

[0006] [Problems to be solved by the invention]

[0007] Since the rubber forming part of the tire carcass is conductive, the carcass functions as a conductive path. The bonding rubber layer between the carcass and the inner liner is configured to span between one bead and the other bead like the carcass, with 10 8 Volume resistivity above Ω·cm does not function as a conductive path. If the bonding rubber layer is reduced to make the side of the tire thinner, rolling resistance is expected to be reduced. However, in the manufacture of tires, the uncured tire (hereinafter referred to as the green tire) thrown into the mold is pressed against the mold cavity surface by the inflated air bag, so the rubber cannot ensure sufficient thickness, and the tire body may not function as a conductive path. When a thinner side is used, there is also a possibility that the handling stability will be reduced.

[0008] The present invention has been made in view of such actual circumstances, and an object of the present invention is to provide a tire that reduces rolling resistance while suppressing influence on conductivity and steering stability.

[0009]

Methods to solve the problem

[0010] A tire according to one embodiment of the present invention comprises: a tread in contact with the ground; a pair of sidewalls connected to the ends of the tread and located radially inward of the tread; a pair of beads located radially inward of the sidewalls and having an annular core; a carcass spanning between one bead and another bead on the inner side of the tread and the sidewalls; a belt layer radially located between the tread and the carcass; an inner liner layer located on the inner side of the carcass; and a pair of insert layers located between the carcass and the inner liner layer. The carcass comprises a carcass cord having a cord body spanning between one core and another core, and a pair of folded portions connected to the cord body and folded back from the axial inside to the outside around each core. The insert layer is located between the end of the belt layer and the end of the bead, and the volume resistivity of the insert layer is less than 10 8 Ω·cm. The complex elastic modulus of the insert layer is equal to or higher than the complex elastic modulus of the inner liner layer. The thickness of the sidewall at the maximum width position is 5.0 mm or less.

[0011] Preferably, in the tire, a ratio of a complex elastic modulus of the insert layer to a complex elastic modulus of the inner liner layer is 4.9 or less.

[0012] Preferably, in the tire, the thickness of the insertion layer is not less than 0.2 mm and not more than 1.0 mm.

[0013] Preferably, in the tire, the complex elastic modulus of the insert layer is 4.0 MPa or more.

[0014] Preferably, in the tire, the outer end of the insert layer is located axially inward of the end of the belt layer, and the overlapping length between the insert layer and the belt layer is 20 mm or less.

[0015] Preferably, in the tire, an inner end of the insert layer is located radially inwardly of an end of the bead.

[0016] Preferably, in this tire, an end portion of the folded portion is located radially inward of the maximum width position.

[0017] Preferably, in the tire, the carcass cords include a plurality of parallel cords and a topping rubber covering the cords. The insert layer is made of the same material as the topping rubber.

[0018] Preferably, in the tire, the carcass is composed of one carcass cord. The tire bead includes an inner apex located radially outward of the core and an outer apex located radially outward of the inner apex. The folded portion is located between the outer apex and the inner apex, and the outer end of the outer apex is the end of the tire bead.

[0019] [Effects of the invention]

[0020] According to the present invention, it is possible to obtain a tire in which the influence on the electrical conductivity and the steering stability is suppressed and the rolling resistance is reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a cross-sectional view showing a part of a tire according to an embodiment of the present invention.

[0022] Figure 2 is along Figure 1 Cross-sectional view along line II-II.

[0023] Figure 3 Yes means Figure 1 An enlarged cross-sectional view of a portion of a tire.

[0024] Figure 4 This is a cross-sectional view showing a portion of a tire according to another embodiment of the present invention. DETAILED DESCRIPTION

[0025] Next, the present invention will be described in detail based on preferred embodiments with reference to the drawings as appropriate.

[0026] In the present disclosure, a tire is assembled on a standard rim, the internal pressure of the tire is adjusted to the standard internal pressure, and the state where no load is applied to the tire is referred to as a standard state. In the present disclosure, unless otherwise specified, the dimensions and angles of various parts of the tire are measured in the standard state.

[0027] The standard rim is a rim specified in the standard to which the tire is based. The "standard rim" in the JATMA standard, the "design rim" in the TRA standard, and the "measuring rim" in the ETRTO standard are standard rims.

[0028] The standard internal pressure refers to the internal pressure specified in the specifications to which the tire is based. The "maximum pressure" in the JATMA specifications, the "maximum value" in the "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the TRA specifications, and the "INFLATION PRESSURE" in the ETRTO specifications are standard internal pressures. The standard internal pressure of a passenger car tire is, for example, 180 kPa.

[0029] The standard load is the load specified in the specification to which the tire is based. The "maximum load capacity" in the JATMA specification, the "maximum value" in the "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the TRA specification, and the "LOAD CAPACITY" in the ETRTO specification are standard loads. The standard load of a passenger car tire is, for example, a load equivalent to 88% of the above load.

[0030] In the present disclosure, the side portion of the tire refers to a portion of the tire between a tread portion that comes into contact with the ground and a bead portion that fits around the rim R.

[0031] In the present invention, the complex elastic modulus of the element composed of the crosslinked rubber among the elements constituting the tire is measured under the following conditions using a viscoelasticity spectrometer in accordance with the provisions of JIS K6394.

[0032] Initial deformation = 10%

[0033] Amplitude = ±1%

[0034] Frequency = 10 Hz

[0035] Deformation Mode = Stretch

[0036] Measurement temperature = 70°C

[0037] In this measurement, a test piece sampled from a sheet-like crosslinked rubber (hereinafter also referred to as a rubber sheet) obtained by pressurizing and heating a rubber composition of various elements is used. In order to produce the rubber sheet, a commonly used press molding machine is used, and the heating temperature for producing the rubber sheet is set to 165° C. and the heating time is set to 10 minutes.

[0038] In the present disclosure, the volume resistivity of the element composed of crosslinked rubber among the elements constituting the tire is measured under constant temperature and humidity conditions of 23° C. and 55% relative humidity, with an applied voltage of 1000 V, in accordance with the provisions of JIS K 6271. The rubber sheet used for the measurement is produced in the same manner as the above-mentioned rubber sheet.

[0039] In the present disclosure, crosslinked rubber is a molded body of a rubber composition obtained by pressurizing and heating the rubber composition. The rubber composition is a rubber in an uncrosslinked state obtained by mixing a base rubber and a chemical in a mixer such as a Banbury mixer. Crosslinked rubber is also called vulcanized rubber, and a rubber composition is also called unvulcanized rubber.

[0040] Examples of base rubber 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 chemicals include reinforcing agents such as carbon black, 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. Although not described in detail, the selection of base rubber and chemicals, the content of the selected chemicals, etc. can be appropriately determined according to the specifications of the elements of the applicable rubber composition.

[0041] Figure 1 A portion of a tire 2 according to an embodiment of the present invention is shown. The tire 2 is mounted on a passenger car. Figure 1 In FIG. 1 , the tire 2 is assembled on the rim R (standard rim) and is in a standard state. The tire 2 is a pneumatic tire.

[0042] Figure 1 FIG. 2 shows a portion of a cross section of a tire 2 along a plane including the rotation axis of the tire 2. Figure 1 In the embodiment, the left-right direction is the axial direction of the tire 2, and the up-down direction is the radial direction of the tire 2. Figure 1 The direction perpendicular to the paper surface is the circumferential direction of the tire 2. Figure 1 In FIG. 2 , a dashed line CL indicates the equatorial plane of the tire 2 .

[0043] exist Figure 1 In FIG. 1 , a solid line BBL extending in the axial direction is a bead base line. The bead base line is a line that defines the rim diameter of the rim R (see JATMA, etc.).

[0044] exist Figure 1 In the figure, the symbol PW is the axial outer end of the tire 2. The axial distance from one outer end PW to the other outer end PW is the maximum width of the tire 2, that is, the cross-sectional width (refer to JATMA, etc.). The outer end PW is the position indicating the maximum width of the tire 2 (hereinafter referred to as the maximum width position). The outer end PW is determined based on the contour of the outer surface of the tire 2. When the outer surface is decorated with patterns, text, etc., the outer end PW is determined based on the contour of a virtual outer surface obtained by assuming that there is no such decoration.

[0045] Figure 2 Shown along Figure 1 The cross section of the tire 2 is shown on the II-II line. Figure 2 In the paper of FIG. 2 , the right side is the outer surface side of the tire 2 , and the left side is the inner surface side of the tire 2 .

[0046] The tire 2 includes a tread 4 , a pair of sidewalls 6 , a pair of heel rubbers 8 , a pair of beads 10 , a carcass 12 , a belt layer 14 , a reinforcing layer 16 , a pair of anti-friction fabrics 18 , an inner liner 20 and a pair of insert layers 22 .

[0047] The tread 4 contacts the ground at its outer surface, that is, the tread surface 24. Grooves 26 are engraved on the tread 4. The tread 4 is composed of a cross-linked rubber in consideration of wear resistance, grip performance, and the like.

[0048] exist Figure 1 , the reference numeral PC is the intersection of the tread surface 24 and the equatorial plane. The intersection PC is the equator of the tire 2. When the groove 26 is located on the equatorial plane, the equator PC is determined based on the profile of the virtual tread surface obtained assuming that there is no groove 26. The double arrow H is the radial distance from the bead base line to the equator PC. The radial distance H is the section height of the tire 2 (refer to JATMA, etc.).

[0049] exist Figure 1 In FIG. 4 , the double arrow tc is the thickness of the tread 4. The thickness tc is expressed by the distance from the inner surface of the tread to the equator PC measured along the equatorial plane.

[0050] In the tire 2, from the viewpoint of weight reduction, the thickness tc of the tread is preferably 8.5 mm or less, more preferably 8.0 mm or less, and further preferably 7.5 mm or less. From the viewpoint of being able to fully exert the function as a tread, the thickness tc is preferably 5.0 mm or more, more preferably 5.5 mm or more, and further preferably 6.0 mm or more.

[0051] Each sidewall 6 is connected to an end of the tread 4. The sidewall 6 is located radially inside the tread 4. The sidewall 6 extends from the end of the tread 4 toward the heel rubber 8. The sidewall 6 is composed of a cross-linked rubber in consideration of cut resistance.

[0052] Each heel rubber 8 is located radially inward of the sidewall 6. The heel rubber 8 contacts the rim R. The heel rubber 8 is made of a cross-linked rubber in consideration of wear resistance. The heel rubber 8 has a thickness of less than 10 8 The volume resistivity is Ω·cm. The butt rubber 8 functions as a conductive path.

[0053] Each bead 10 is located axially inside the bead heel rubber 8. As described above, the bead heel rubber 8 is located radially inside the sidewall 6. The bead 10 is located radially inside the sidewall 6. Figure 1 , reference numeral PB denotes an end portion of the bead 10 .

[0054] The tire bead 10 includes a core 28, an inner apex 30, and an outer apex 32. The core 28 is annular. The core 28 includes a steel wire. The inner apex 30 is made of a cross-linked rubber having high rigidity. The outer apex 32 is made of a cross-linked rubber having high rigidity. In the tire 2, the outer apex 32 may be made of the same material as the inner apex 30, or may be made of a material different from that of the inner apex 30.

[0055] The inner apex 30 is located radially outward of the core 28. The inner apex 30 tapers radially outward toward the front end. The height of the inner apex 30 is 5 mm or more and 20 mm or less. The height of the inner apex 30 is represented by the distance from the center of the boundary between the core 28 and the inner apex 30 to the end PU of the inner apex 30, which is represented by the symbol PM.

[0056] The outer apex 32 is located radially outward of the inner apex 30. The outer apex 32 is located between the carcass 12 and the bead rubber 8. The folded portion of the carcass cord fabric described later is located between the outer apex 32 and the inner apex 30. In the tire 2, the outer apex 32 is thick near the end PU of the inner apex 30, and becomes thinner from the thick portion radially inward toward the front end, and becomes thinner from the thick portion radially outward toward the front end.

[0057] In the tire 2, the inner end of the outer apex 32 is located near the boundary between the core 28 and the inner apex 30. The outer end of the outer apex 32 is located near the maximum width position PW in the radial direction. In the tire 2, the outer end of the outer apex 32 is the end PB of the bead 10.

[0058] exist Figure 1 In the figure, the length indicated by the double arrow HB represents the radial distance from the bead base line to the end PB of the bead 10. This distance HB is also called the bead height. In the tire 2, from the viewpoint of handling stability and ride comfort, the ratio of the bead height HB to the section height H (HB / H) is preferably 0.35 or more, more preferably 0.39 or more. The ratio (HB / H) is preferably 0.50 or less, more preferably 0.46 or less.

[0059] In the tire 2, the inner apex rubber 30 and the outer apex rubber 32 have a thickness of less than 10 8 The bead 10 of the tire 2 functions as a conductive path.

[0060] The carcass 12 is located inside the tread 4, the pair of sidewalls 6 and the pair of heel rubbers 8. The carcass 12 spans between one bead 10 and another bead 10. The carcass 12 has a radial structure. The carcass 12 includes at least one carcass cord 34.

[0061] The groove 12 of the tire 2 is formed by a carcass ply 34. The carcass ply 34 is folded back from the axial inner side to the outer side around each core 28. The carcass ply 34 includes a ply main body 36 spanning between one core 28 and another core 28, and a pair of folded back portions 38 connected to the ply main body 36 and folded back from the axial inner side to the outer side around each core 28.

[0062] In the tire 2, the end of the folded portion 38, that is, the end of the carcass cord 34 is located radially inward of the maximum width position PW. The carcass 12 has a low turn-up (LTU) structure. Figure 1 As shown, in this tire 2 , the end of the folded portion 38 is sandwiched between the outer apex 32 and the carcass main body 36 .

[0063] exist Figure 1 , the length indicated by the double arrow HF represents the radial distance from the bead base line to the end of the turn-back portion 38. This distance HF is also called the turn-back portion height. In the tire 2, from the viewpoint of handling stability and ride comfort, the ratio of the turn-back portion height HF to the section height H (HF / H) is preferably 0.18 or more, more preferably 0.20 or more. This ratio (HF / H) is preferably 0.25 or less, more preferably 0.23 or less.

[0064] The carcass ply 34 includes a plurality of parallel carcass cords 40. Although not shown, each carcass cord 40 crosses the equatorial plane. In the tire 2, cords made of organic fibers are used as the carcass cords 40. Examples of the organic fibers include nylon fibers, rayon fibers, polyester fibers, and aramid fibers.

[0065] like Figure 2 As shown, the carcass cord 40 is covered by a topping rubber 42. In the tire 2, the volume resistivity of the topping rubber 42 is less than 10 8 Ω·cm. The carcass 12 including the topping rubber 42 functions as a conductive path.

[0066] The belt layer 14 is located between the tread 4 and the carcass 12 in the radial direction. The belt layer 14 is stacked with the carcass 12 on the radial inner side of the tread 4. The belt layer 14 is composed of at least two layers 44 stacked in the radial direction. Among the layers 44 constituting the belt layer 14, the layer 44 having the largest width is the first layer 46, and the layer 44 located radially outside the first layer 46 and having a width less than the first layer 46 is the second layer 48.

[0067] The belt layer 14 of the tire 2 is composed of two layers 44. In the tire 2, the inner layer 44 of the two layers 44 is a first layer 46, and the outer layer 44 is a second layer 48. The belt layer 14 includes the first layer 46 and the second layer 48 located radially outward of the first layer 46. The width of the first layer 46 is wider than that of the second layer 48.

[0068] Although not shown, the first layer 46 and the second layer 48 each include a plurality of parallel belt layer cords. These belt layer cords are covered with rubber. Each belt layer cord is inclined relative to the equatorial plane. The material of the belt layer cord is steel. The rubber has a thickness of less than 10 8 The belt layer 14 functions as a conductive path.

[0069] exist Figure 1 In FIG. 1 , the length indicated by the double arrow EW represents the width of the belt layer 14. The width of the belt layer 14 is represented by the axial distance from the end of one belt layer 14 to the end of another belt layer 14. Figure 1 In the figure, the symbol PE indicates a position on the outer surface of the tread 4 corresponding to the axial outer end of the tire 2 contacting the ground (not shown) (hereinafter also referred to as the ground contact reference position). The ground contact reference position PE is determined based on the ground contact surface obtained by applying a standard load to the tire 2 in a standard state, setting the camber angle to 0°, and making the tire 2 contact a flat road surface. Figure 1 In the figure, the length indicated by the double arrow CW represents the axial distance from one ground contact reference position PE to another ground contact reference position PE. In the tire 2, this distance CW is called a reference ground contact width.

[0070] In the tire 2, from the viewpoint that the belt layer 14 helps to ensure the rigidity of the tread portion T, the ratio of the width EW of the belt layer 14 to the reference ground contact width CW (EW / CW) is preferably 1.10 or more, and more preferably 1.15 or more. From the viewpoint of suppressing the influence of the belt layer 14 on the mass and rolling resistance and preventing damage to the ends of the belt layer 14, the ratio (EW / CW) is preferably 1.30 or less, and more preferably 1.25 or less.

[0071] The reinforcing layer 16 is located radially inside the tread 4. The reinforcing layer 16 is located radially between the tread 4 and the belt layer 14. In the tire 2, in the axial direction, the end of the reinforcing layer 16 is further outward than the end of the belt layer 14. The reinforcing layer 16 is a full reinforcing layer covering the entire belt layer 14. The reinforcing layer 16 may also be provided with a pair of edge reinforcing layers covering the ends of the full reinforcing layer. The reinforcing layer 16 may also not be a full reinforcing layer, but may be composed of a pair of edge reinforcing layers. In this case, the edge reinforcing layer covers the ends of the belt layer 14.

[0072] Although not shown, the reinforcing layer 16 includes reinforcing layer cords. In the reinforcing layer 16, the reinforcing layer cords are spirally wound in the circumferential direction. The reinforcing layer cords are covered with a topping rubber. Cords composed of organic fibers are used as reinforcing layer cords. As organic fibers, nylon fibers, rayon fibers, polyester fibers, and aramid fibers are exemplified. The topping rubber has a thickness of less than 10 8 The volume resistivity is Ω·cm. The reinforcing layer 16 functions as a conductive path.

[0073] Each rubbing cloth 18 is located radially inside the bead 10. The rubbing cloth 18 is in contact with the rim R. In the tire 2, the rubbing cloth 18 is composed of cloth and rubber impregnated with the cloth.

[0074] The inner liner 20 is located inside the carcass 12. The inner liner 20 forms the inner surface of the tire 2. The inner liner 20 is made of a cross-linked rubber having a low gas permeability coefficient. The inner liner 20 maintains the internal pressure of the tire 2.

[0075] Each insert layer 22 is located between the carcass 12 and the inner liner 20. The insert layer 22 is located between the end of the belt layer 14 and the end PB of the bead 10. In the tire 2, the position of the outer end 50 of the insert layer 22 is consistent with the position of the end of the belt layer 14 in the axial direction, or the outer end 50 of the insert layer 22 is axially more inner than the end of the belt layer 14. The inner end 52 of the insert layer 22 is radially more inner than the end PB of the bead 10. The insert layer 22 is composed of a cross-linked rubber considering conductivity and rigidity.

[0076] In the tire 2, in the portion where the insert layer 22 is provided, the inner liner is bonded to the carcass via the insert layer 22. The inner liner 20 is directly bonded to the carcass 12 in the portion between the outer end 50 of one insert layer 22 and the outer end 50 of another insert layer 22, and in the portion where the insert side 22 is not provided like the inner side portion starting from the inner end 52 of the insert layer 22.

[0077] In the tire 2, the tread 4 is penetrated and has a thickness of less than 10 8 A conductive portion 54 having a volume resistivity of Ω·cm is provided on the tread 4. In the tire 2, a conductive path is constituted by the butt rubber 8, the bead 10, the carcass 12, the belt layer 14, the reinforcing layer 16, and the conductive portion 54. A vehicle equipped with the tire 2 is electrically connected to the ground through the conductive path.

[0078] Figure 3 Show Figure 1 A portion of a cross section of a tire 2 is shown. Figure 3 In the figure, the side S of the tire 2 is shown. Figure 3 In the figure, the left-right direction is the axial direction of the tire 2, and the up-down direction is the radial direction of the tire 2. Figure 3 The direction perpendicular to the paper surface is the circumferential direction of the tire 2 .

[0079] exist Figure 3 , the length indicated by the double arrow EA represents the thickness of the sidewall 6. The thickness EA is represented by the distance from the inner surface to the outer surface of the sidewall 6 measured along a straight line passing through the maximum width position PW and extending in the axial direction. The thickness EA is the thickness of the sidewall 6 at the maximum width position PW.

[0080] In the tire 2, the thickness EA of the sidewall 6 at the maximum width position PW is 5.0 mm or less. In the tire 2, the side portion S is thin. The thin side portion S helps to reduce the mass and rolling resistance of the tire. From this point of view, the thickness EA is preferably 4.9 mm or less, and more preferably 4.8 mm or less. From the viewpoint of preventing external damage to the side portion S, the thickness EA is preferably 1.0 mm or more, more preferably 1.1 mm or more, and further preferably 1.2 mm or more.

[0081] Although not shown, in conventional tires, the inner liner is bonded to the carcass via a bonding rubber layer. In contrast, in the tire 2, no bonding rubber layer is used, and the inner liner 20 is bonded to the carcass 12. The tire 2 is lighter than conventional tires having a bonding rubber layer. The rolling resistance of the tire 2 is lower than that of conventional tires.

[0082] In manufacturing the tire 2, an unvulcanized tire (hereinafter also referred to as a green tire) is prepared, which is a combination of elements such as the tread 4 in an unvulcanized state. The green tire is pressurized and heated in a mold (not shown).

[0083] Although not shown, in the manufacturing of the tire 2, in the pressurization and heating process (hereinafter also referred to as the vulcanization process), the green tire is pressed against the mold cavity surface of the mold by the inflated air bag. In the area from the end edge of the tread 4 to the maximum width position PW, the pressure of the air bag is strong, and the inner liner 20 may erode the rubber 42 which is a part of the carcass 12. At this time, the rubber 42 is crushed and the required thickness cannot be ensured, and the carcass 12 may not function as a conductive path.

[0084] However, as described above, in the tire 2, the insert layer 22 provided between the carcass 12 and the inner liner 20 is located between the end of the belt layer 14 and the end PB of the bead 10. The volume resistivity of the insert layer 22 is less than 10 8 Ω·cm, the complex elastic modulus E*s of the insert layer 22 is equal to the complex elastic modulus E*n of the lining layer 20, or is higher than the complex elastic modulus E*n of the lining layer 20.

[0085] Since the insert layer 22 of the tire 2 has a composite elastic modulus E*s that is equal to or greater than the composite elastic modulus E*n of the inner liner 20, the movement of the inner liner 20 caused by the pressure of the air bag is suppressed. In the tire 2, the inner liner 20 is prevented from eroding the rubber patch 42. Even in the above-mentioned area where the rubber patch 42 may be crushed, the carcass 12 functions as a conductive path because the thickness of the rubber patch 42 is guaranteed. The distance between the carcass cords 40 does not expand, but is appropriately maintained, so the occurrence of defects such as cord spread (poen thread) can also be suppressed. The insert layer 22 is made of conductive cross-linked rubber like the rubber patch 42, so even if the insert layer 22 erodes the rubber patch 42, the carcass 12 can still function as a conductive path.

[0086] Furthermore, since the insert layer 22 has a composite elastic modulus E*s equal to or greater than the composite elastic modulus E*n of the inner liner 20, the insert layer 22 also helps ensure the rigidity of the tire 2. In this tire 2, good steering stability can be obtained despite the thinner side portion S.

[0087] In the tire 2 , the rolling resistance is reduced while suppressing the influence on the electrical conductivity and the steering stability.

[0088] For example, Figure 2 As shown, the insert layer 22 is in contact with the topping rubber 42 of the carcass 12. From the viewpoint of forming a stable conductive path, the insert layer 22 is preferably made of the same material as that of the topping rubber 42.

[0089] exist Figure 2 In FIG. 1 , the length indicated by the double arrow ts represents the thickness of the insert layer 22. The length indicated by the double arrow ta represents the thickness of the portion composed of the insert layer 22 and the carcass 12. Figure 1 , the II-II line passes through the position where the thickness ta is the largest. The thickness ta represents the maximum thickness of the portion formed by the insert layer 22 and the carcass 12. In addition, the thickness ts of the insert layer 22 represents the thickness of the insert layer 22 at the position where the portion formed by the insert layer 22 and the carcass 12 has the maximum thickness.

[0090] In the tire 2, the thickness ts of the insert layer 22 is preferably 0.2 mm or more, more preferably 0.3 mm or more, and further preferably 0.4 mm, from the viewpoint that the insert layer 22 can ensure the thickness of the rubber 42 and help ensure the rigidity of the tire 2. From the viewpoint of effectively suppressing the influence of the insert layer 22 on the mass and rolling resistance of the tire 2, the thickness ts is preferably 1.0 mm or less, more preferably 0.9 mm or less, and further preferably 0.8 mm or less.

[0091] In the tire 2, from the viewpoint that the portion composed of the insert layer 22 and the carcass 12 can help ensure conductivity and handling stability, the thickness ta is preferably 0.8 mm or more, more preferably 0.9 mm or more, and further preferably 1.0 mm or more. From the viewpoint of effectively suppressing the influence of the portion composed of the insert layer 22 and the carcass 12 on the mass and rolling resistance of the tire 2, the thickness ta is preferably 2.0 mm or less, more preferably 1.9 mm or less, and further preferably 1.8 mm or less.

[0092] In the tire 2 , the ratio of the complex elastic modulus E*s of the insert layer 22 to the complex elastic modulus E*n of the inner liner layer 20 (E*s / E*n) is preferably 4.9 or less.

[0093] By setting the ratio (E*s / E*n) to 4.9 or less, the influence of the insert layer 22 on the riding comfort can be suppressed. From this viewpoint, the ratio (E*s / E*n) is preferably 3.5 or less, and more preferably 2.0 or less.

[0094] As described above, in the tire 2, the composite elastic modulus E*s of the insert layer 22 is equal to or greater than the composite elastic modulus E*n of the inner liner 20, and the insert layer 22 helps to ensure the conductivity and improve the steering stability of the tire 2. From this viewpoint, the ratio (E*s / E*n) is preferably 1.1 or greater, more preferably 1.3 or greater, and further preferably 1.5 or greater.

[0095] In the tire 2, the composite elastic modulus E*s of the insert layer 22 is preferably 4.0 MPa or more. Thus, the insert layer 22 can effectively contribute to ensuring the electrical conductivity of the tire 2 and improving the handling stability. From this point of view, the composite elastic modulus E*s of the insert layer 22 is more preferably 4.5 MPa or more, and further preferably 5.4 MPa or more. From the viewpoint of obtaining good ride comfort, the composite elastic modulus E*s of the insert layer 22 is preferably 7.0 MPa or less, more preferably 6.7 MPa or less, and further preferably 6.5 MPa or less.

[0096] exist Figure 3 In the figure, the position indicated by the reference numeral Pa is the intersection of a straight line passing through the end of the belt layer 14, extending in the radial direction, and the inner surface of the insert layer 22. The position Pa is a position on the inner surface corresponding to the end of the belt layer 14. The length indicated by the double arrow DS represents the distance from the position Pa to the outer end 50 of the insert layer 22. In the tire 2, the distance DS is the overlapping length of the insert layer 22 and the belt layer 14.

[0097] In the tire 2, the outer end 50 of the insert layer 22 is preferably located axially inwardly of the end of the belt layer 14, and the overlap length DS of the insert layer 22 and the belt layer 14 is less than 20 mm. Thus, the influence of the insert layer 22 on the mass and rolling resistance of the tire 2 is effectively suppressed. From this point of view, the overlap length DS is preferably less than 10 mm, more preferably less than 7 mm. From the point of view of ensuring the conductivity of the tire 2, the overlap length DS is preferably more than 1 mm, more preferably more than 2 mm, and further preferably more than 3 mm.

[0098] exist Figure 3 In the figure, the position indicated by the reference numeral Pb is the intersection of a straight line extending in the axial direction through the end PB of the bead 10 and the inner surface of the insert layer 22. The position Pb is a position on the inner surface corresponding to the end PB of the bead 10. The length indicated by the double arrow DU indicates the distance from the position Pb to the inner end 52 of the insert layer 22. In the tire 2, the distance DU is the overlapping length of the bead 10 and the insert layer 22.

[0099] In the tire 2, the overlap length DU between the bead 10 and the insert layer 22 is preferably 30 mm or less. Thus, the influence of the insert layer 22 on the mass and rolling resistance of the tire 2 is effectively suppressed. From this point of view, the overlap length DU is preferably 20 mm or less, and more preferably 15 mm or less. From the point of view of ensuring the conductivity and handling stability of the tire 2, the overlap length DS is preferably 1 mm or more, more preferably 3 mm or more, and further preferably 5 mm or more.

[0100] exist Figure 3 , the double arrow SV indicates the shortest distance from the end of the second layer 48 to the end of the first layer 46. This distance SV is the length of the first layer 46 protruding from the second layer 48, also referred to as the first step amount. The double arrow SB indicates the shortest distance from the end of the first layer 46 to the end of the reinforcing layer 16. This distance SB is the length of the reinforcing layer 16 protruding from the first layer 46, also referred to as the second step amount.

[0101] In the tire 2, in the axial direction, the end of the first layer 46 is further outward than the end of the second layer 48, and the end of the reinforcing layer 16 is further outward than the end of the first layer 46. In the tire 2, the end of the first layer 46, the end of the second layer 48, and the end of the reinforcing layer 16 are dispersedly arranged in the axial direction. Since this arrangement causes the restraining force of the ends of the belt layer 14 and the reinforcing layer 16 to change slowly, it is possible to suppress the deformation concentration to the ends. In the tire 2, the generation of end damage is prevented and the wear resistance is improved.

[0102] In the tire 2, from the viewpoint of preventing damage at the end, reducing rolling resistance and improving wear resistance, the first step feed SV is preferably 5.0 mm or more, more preferably 5.5 mm or more, and further preferably 6.0 mm or more. From the viewpoint of ensuring the restraining force of the belt layer 14 and obtaining good handling stability, the first step feed SV is preferably 9.0 mm or less, more preferably 8.5 mm or less, and further preferably 8.0 mm or less.

[0103] In the tire 2, from the viewpoint of preventing damage to the end and improving wear resistance, the second step amount SB is preferably 4.0 mm or more, more preferably 4.5 mm or more, and further preferably 4.8 mm or more. From the viewpoint of suppressing the influence of the reinforcing layer 16 on the quality and rolling resistance of the tire and sufficiently ensuring the distance from the end of the reinforcing layer 16 to the outer surface of the tire 2, the second step amount SB is preferably 6.0 mm or less, more preferably 5.5 mm or less, and further preferably 5.2 mm or less.

[0104] Figure 4 FIG. 6 shows a portion of a tire 62 according to another embodiment of the present invention. The tire 62 is mounted on a passenger car. Figure 4 In FIG. 6 , the tire 62 is assembled on the rim R (standard rim) and is in a standard state.

[0105] Figure 4 A portion of a cross section of the tire 62 is shown along a plane including the axis of rotation of the tire 62. Figure 4 In the embodiment, the left-right direction is the axial direction of the tire 62, and the up-down direction is the radial direction of the tire 62. Figure 4 The direction perpendicular to the paper surface is the circumferential direction of the tire 62 .

[0106] The tire 62 includes a tread 64, a pair of sidewalls 66, a pair of heel rubbers 68, a pair of beads 70, a carcass 72, a belt layer 74, a reinforcing layer 76, a pair of anti-friction cloths 78, an inner liner 80, and a pair of insert layers 82. In addition to the beads 70 and the carcass 72, the tire 62 has the same Figure 1 The structure of the tire 2 shown is identical to that of the tire 2 shown.

[0107] In the tire 62, the bead 70 is also located radially inward of the sidewall 66. Figure 4 , symbol PB represents the end portion of the bead 70 .

[0108] The bead 70 includes a core 84 and an apex 86. The core 84 is annular. The core 84 includes a steel wire. The apex 86 is made of a cross-linked rubber having high rigidity. In the tire 62, the apex 86 has a thickness of less than 10 8 The bead 70 functions as a conductive path.

[0109] The apex 86 is located radially outside the core 84. The apex 86 tapers radially outward toward the front end. The height of the apex 86 is 20 mm or more and 45 mm or less. The height of the apex 86 is represented by the distance from the center of the boundary between the core 84 and the apex 86 to the edge of the apex 86, which is represented by the symbol PM. The core 84 is represented by the symbol PM. In the tire 62, the bead 70 is composed of the core 84 and the apex 86. The end of the apex 86 is the end PB of the bead 70.

[0110] exist Figure 4 In the figure, the length indicated by the double arrow HB is the bead height. In the tire 62, from the viewpoint of handling stability and ride comfort, the ratio of the bead height HB to the section height H (HB / H) is preferably 0.20 or more, more preferably 0.25 or more. The ratio (HB / H) is preferably 0.35 or less, more preferably 0.30 or less.

[0111] The carcass 72 is located inside the tread 64, the pair of sidewalls 66 and the pair of heel rubbers 68. The carcass 72 spans between one bead 70 and another bead 70. The carcass 72 has a radial structure. The carcass 72 includes at least one carcass cord 88.

[0112] The carcass 72 of the tire 62 is composed of a carcass ply 88. The carcass ply 88 is folded back from the axial inner side to the outer side around each core 84. The carcass ply 88 includes a ply main body 90 spanning between one core 84 and another core 84, and a pair of folded back portions 92 connected to the ply main body 90 and folded back from the axial inner side to the outer side around each core 84.

[0113] like Figure 4 As shown, in the tire 62, the end of the folded portion 92, that is, the end of the carcass ply 88, is radially inward of the maximum width position PW. The carcass 72 has a low turn-up (LTU) structure. In the tire 62, the end of the folded portion 92 is radially outward of the end PB of the bead 70.

[0114] exist Figure 4 In the figure, the length indicated by the double arrow HF is the height of the turn-back portion. In the tire 62, from the viewpoint of handling stability and ride comfort, the ratio of the turn-back portion height HF to the cross-sectional height H (HF / H) is preferably 0.25 or more, more preferably 0.30 or more. The ratio (HF / H) is preferably 0.45 or less, more preferably 0.40 or less.

[0115] Although not shown, the carcass cord 88 includes a plurality of parallel carcass cords. Each carcass cord crosses the equatorial plane. In the tire 62, cords made of organic fibers are used as carcass cords. As organic fibers, nylon fibers, rayon fibers, polyester fibers, and aramid fibers are exemplified.

[0116] In the tire 62, the carcass cords are also covered with a topping rubber. The volume resistivity of the topping rubber is less than 10 8 The carcass 72 including the topping rubber functions as a conductive path.

[0117] In the tire 62, each insert layer 82 is also located between the carcass 72 and the inner liner 80. The insert layer 82 is located between the end of the belt layer 74 and the end PB of the bead 70. In the tire 62, the outer end 94 of the insert layer 82 is axially closer to the inner side than the end of the belt layer 74. The inner end 96 of the insert layer 82 is radially closer to the inner side than the end PB of the bead 70. The material of the insert layer 82 is also similar to Figure 1 The material of the insert layer 22 of the tire 2 shown is the same.

[0118] exist Figure 4 , the length indicated by the double arrow EA represents the thickness of the sidewall 66 at the maximum width position PW.

[0119] In this tire 62, the thickness EA of the sidewall 66 at the maximum width position PW is 5.0 mm or less. In this tire 62, the side portion S is thin. The thin side portion S contributes to reducing the mass and rolling resistance of the tire 62.

[0120] In the tire 62, the insert layer 82 provided between the carcass 72 and the inner liner 80 is located between the end of the belt layer 74 and the end PB of the bead 70. The volume resistivity of the insert layer 82 is less than 10 8 Ω·cm, the complex elastic modulus E*s of the insert layer 82 is equal to or greater than the complex elastic modulus E*n of the liner layer 80.

[0121] Since the insert layer 82 of the tire 62 has a composite elastic modulus E*s that is equal to or greater than the composite elastic modulus E*n of the inner liner 80, the insert layer 82 suppresses the movement of the inner liner 80 caused by the pressure of the air bag. In the tire 62, the inner liner 80 is prevented from eroding the rubber. Even in the area where the rubber may be crushed, the thickness of the rubber is ensured, so the carcass 72 can be used as a conductive path. Since the distance between the carcass cords is not expanded but maintained appropriately, the occurrence of defects such as open threads can also be suppressed. The insert layer 82 is made of conductive cross-linked rubber like the rubber, so even if the insert layer 82 erodes the rubber, the carcass 72 can function as a conductive path.

[0122] Furthermore, since the insert layer 82 has a complex elastic modulus E*s equal to or greater than the complex elastic modulus E*n of the inner liner 80, the insert layer 82 also helps ensure the rigidity of the tire 62. In this tire 62, good steering stability can be obtained despite the use of a thinner side portion S.

[0123] In the tire 62 , the rolling resistance is reduced while suppressing the influence on the electrical conductivity and the steering stability.

[0124] As described above, according to the present invention, it is possible to obtain a tire that reduces rolling resistance while suppressing the influence on conductivity and steering stability.

[0125] [Example]

[0126] Hereinafter, the present invention will be described in further detail with reference to Examples and the like, but the present invention is not limited to the Examples.

[0127] [Example 1]

[0128] Got the Figure 1 The basic structure shown is a tire for a passenger car having the specifications shown in the following Table 1 (tire size = 205 / 55R16).

[0129] In this Example 1, no tie rubber layer is provided. This is indicated by "N" in the tie rubber layer column of Table 1. The thickness EA of the sidewall at the maximum width position PW is 4.7 mm.

[0130] In this embodiment 1, an insertion layer is provided between the carcass and the inner liner. The insertion layer is arranged between the end of the belt layer and the end of the bead. The volume resistivity of the insertion layer is 10 4 Ω·cm, less than 10 8 Ω·cm. The repeat length DS of the belt layer and the insert layer is 5mm, and the repeat length DU of the tire bead and the insert layer is 10mm. The composite elastic modulus E*s of the insert layer is 4.0MPa, and the thickness ts of the insert layer is 0.5mm. The composite elastic modulus E*n of the inner liner layer is 3.5MPa, and the ratio of the composite elastic modulus E*s of the insert layer to the composite elastic modulus E*n (E*s / E*n) is 1.1. The first step feed SV is set to 7.0mm, and the second step feed SB is set to 5.0mm.

[0131] [Comparative Example 1]

[0132] Comparative Example 1 is a conventional tire. It has the same structure as Example 1 except that no insertion layer is provided between the carcass and the inner liner, but a bonding layer is provided to span between the two tire beads. The volume resistivity of the bonding layer is 10 4Ω·cm. The thickness EA of the sidewall at the maximum width position PW is 5.7 mm. The fact that a tie rubber layer is provided is indicated by "Y" in the tie rubber layer column of Table 1.

[0133] [Comparative Example 2]

[0134] A tire of Comparative Example 2 was obtained in the same manner as in Comparative Example 1 except that no tie rubber layer was provided and the thickness EA of the sidewall at the maximum width position PW was set to 4.5 mm.

[0135] [Example 2-3]

[0136] The tire of Example 2-3 was obtained in the same manner as Example 1 except that the repeat length DS was as shown in Table 1 below.

[0137] [Examples 4-6]

[0138] Tires of Examples 4 to 6 were obtained in the same manner as in Example 1 except that the complex elastic modulus E*s of the insert layer was changed so that the ratio (E*s / E*n) was as shown in Table 2 below.

[0139] [Example 7]

[0140] have Figure 4 With the basic structure shown, a passenger car tire (tire size = 205 / 55R16) having the specifications shown in Table 2 below was obtained.

[0141] No tie rubber layer was provided in Example 7. The thickness EA of the sidewall at the maximum width position PW was 4.7 mm.

[0142] In Example 7, an insertion layer is provided between the carcass and the inner liner. The insertion layer is disposed between the end of the belt layer and the end of the bead. The volume resistivity of the insertion layer is 10 4 Ω·cm, less than 10 8 Ω·cm. The repeat length DS of the belt layer and the insert layer is 5mm, and the repeat length DU of the tire bead and the insert layer is 10mm. The composite elastic modulus E*s of the insert layer is 4.0MPa, and the thickness ts of the insert layer is 0.5mm. The composite elastic modulus E*n of the inner liner layer is 3.5MPa, and the ratio of the composite elastic modulus E*s of the insert layer to the composite elastic modulus E*n (E*s / E*n) is 1.1. The first step feed SV is set to 7.0mm, and the second step feed SB is set to 5.0mm.

[0143] [Rolling resistance (RRC)]

[0144] The rolling resistance coefficient (RRC) of the test tire when running on a drum at a speed of 80 km / h was measured using a rolling resistance tester under the following conditions. The variation according to Comparative Example 1 was obtained based on Comparative Example 1. The results are shown in Table 1-2 below. The smaller the value, the lower the rolling resistance.

[0145] Rim: 16×6.5J

[0146] Internal pressure: 210kPa

[0147] Longitudinal load: 4.8kN

[0148] [Conductivity]

[0149] The tire was placed on a rim (size = 16 × 6.5J) and inflated to an internal pressure of 210 kPa. The rim was fixed to the fixed axis of the resistance measuring instrument and the tire was mounted on the resistance measuring instrument. In the resistance measuring instrument, the tire was placed on an insulating plate (resistance value = 10 12 Ω or more). After leaving it in this state for 2 hours, the tire was loaded with a longitudinal load of 5.3kN for 0.5 minutes. The load was temporarily released, and the tire was loaded with the same load for 0.5 minutes. The load was released again, and the tire was loaded with the same load for 2 minutes. After applying the test voltage (1000V) for 5 minutes, the resistance value between the fixed shaft and the metal plate was measured. The measurement was performed at 4 locations with an interval of 90° in the circumferential direction of the tire. As a result, when the resistance value at 4 locations was 10 8 The values ​​below Ω are set as 100, and are shown in Table 1-2 below. The larger the value, the stronger the conductivity. In addition, the measurement was performed under an environment of 25°C and 50% humidity. In the measurement, the tire was used in a fully dry state after the mold release agent and dirt on the surface were fully removed in advance.

[0150] [Defect resistance]

[0151] 50 trial tires were disassembled to confirm the occurrence of defects such as cord stretching and erosion of the inner liner to the rubber in the area from the end edge of the tread to the maximum width position. The defect resistance was evaluated based on the proportion of tires without defects to the total. The results are expressed as an index in Table 1-2 below. The larger the value, the stronger the defect resistance.

[0152] [Handling stability]

[0153] The test tire was installed in a rim (size = 16×6.5J), and the tire was filled with air to adjust the internal pressure of the tire to 230kPa. The tire was installed on all wheels of a rear-wheel drive vehicle (1 person) with a displacement of 2000cc as a test vehicle, and the vehicle was driven on a test route on a dry asphalt road. The driver was asked to evaluate the handling stability (sensory evaluation). The results are shown in the following Table 1-2 as indexes. The larger the value, the better the handling stability.

[0154]

Table 1

[0155]

[0156]

Table 2

[0157]

[0158] As shown in Table 1-2, in the examples, the influence on the conductivity and the steering stability was suppressed and the rolling resistance was reduced. The advantages of the present invention are obvious from the evaluation results.

[0159] [Possible industrial applications]

[0160] As described above, the technology for reducing rolling resistance while suppressing the influence on electrical conductivity and steering stability can be applied to various tires.

[0161]

Explanation of symbols

[0162] 2.62···Tire

[0163] 4, 64···tread

[0164] 6, 66···Sidewall

[0165] 10, 70···Bead

[0166] 12, 72···Carcass

[0167] 14, 74···Belt

[0168] 20, 80···Inner lining

[0169] 22, 82···Insertion layer

[0170] 28, 84···Core

[0171] 34, 88···Carcass cord

[0172] 36, 90···Cord body

[0173] 38, 92···Retraction

[0174] 40···Carcass cord

[0175] 42···Glue

[0176] 46···First floor

[0177] 48···Second floor

[0178] 50···Outer end of insertion layer 22

[0179] 52···Inner end of insertion layer 22

[0180] 94···Outer end of the insertion layer 82

[0181] 96···Inner end of the insertion layer 82

Claims

1. A tire, characterized in that: include: The tread that contacts the ground; A pair of sidewalls connected to the ends of the tread and located radially inward of the tread; A pair of beads having an annular core located radially inward of the sidewall; A carcass extending between one bead and another bead on the inner side of the tread and the sidewall; A belt layer located radially between the tread and the carcass; an inner liner layer located on the inner side of the carcass; as well as a pair of insert layers between the carcass and the inner liner, Wherein, the carcass comprises a carcass cord. The carcass cord has a cord main body spanning between one core and another core, and a pair of folded parts connected to the cord main body and folded back from the axial inside to the outside around each core. The insert layer is located between the end of the belt layer and the end of the tire bead, The volume resistivity of the insertion layer is less than 10 8 Ω·cm, The composite elastic modulus of the insert layer is equal to or higher than the composite elastic modulus of the inner lining layer. The thickness of the sidewall at the maximum width position is 5.0 mm or less.

2. The tire according to claim 1, characterized in that A ratio of a complex elastic modulus of the insert layer to a complex elastic modulus of the inner liner layer is 4.9 or less.

3. The tire according to claim 1 or 2, characterized in that: The thickness of the insertion layer is greater than or equal to 0.2 mm and less than or equal to 1.0 mm.

4. The tire according to any one of claims 1 to 3, characterized in that: The composite elastic modulus of the insertion layer is greater than 4.0 MPa.

5. The tire according to any one of claims 1 to 4, characterized in that: The outer end of the insert layer is located axially inwardly of the end of the belt layer. The overlapping length between the insert layer and the belt layer is 20 mm or less.

6. The tire according to any one of claims 1 to 5, characterized in that: In the radial direction, the inner end of the insert layer is located further inward than the end of the bead.

7. The tire according to any one of claims 1 to 6, characterized in that: In the radial direction, an end portion of the folded portion is located inside the maximum width position.

8. The tire according to any one of claims 1 to 7, characterized in that: The carcass cords include a plurality of parallel cords and a rubber covering the cords. The insert layer is made of the same material as the adhesive.

9. The tire according to any one of claims 1 to 8, characterized in that The carcass is composed of one carcass cord. The tire bead includes an inner apex located radially outward of the core, and an outer apex located radially outward of the inner apex. The folded portion is located between the outer apex and the inner apex. The outer end of the outer apex rubber is the end of the tire bead.

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