Tire

Abstract

To provide a tire 12 which can attain improvement in rim-off efficacy.SOLUTION: The tire 12 comprises a tread 14, a pair of side walls 16, a pair of beads 20, a carcass 22, a belt 28 and a band 30. A difference between a half of an outer diameter of the tire 12 and an L dimension described in JIS D4230 is equal to 20 mm or less. The beads 20 comprise cores 34 extending in a circumferential direction. Flexural rigidity in a width direction of the cores 34 is equal to 7.80×106 N.mm2 or more.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a tire.

Background Art

[0002] A tire is used by being mounted on a rim. A tire is required to be easily mountable on a rim. In a tire mounted on a rim, it is required that the tire is less likely to shift with respect to the rim and is less likely to come off the rim. For example, in Patent Document 1 below, studies have been conducted aiming at improving the resistance to coming off the rim, that is, the rim-off resistance, without impairing the ease of mounting on the rim.

[0003] As a method for evaluating the resistance to coming off the rim, for example, a bead unseating test is known. According to "6.1 Bead Unseating Test" in JIS D4230 "Automobile Tires", the test apparatus 2 shown in FIG. 8 is used. This test apparatus 2 includes a support base 4 for setting the tire T mounted on the rim R, a load block 6 for pressing the side surface of the tire T, and a load arm 8 for supporting this load block 6.

[0004] In this test, the tire T is mounted on the rim R. Air is filled inside the tire T to adjust the internal pressure of the tire T. The inner peripheral surface of the bead portion of the tire T contacts the seat of the rim R, and the outer surface contacts the flange of the rim R. The tire T is set on the support base 4, and the position of the load block 6 is adjusted. The load block 6 is pressed against the side surface of the tire T at a predetermined speed, and the force immediately before the bead portion comes off the seat of the rim R is measured as the rim-off resistance. The higher the rim-off resistance, the less likely the tire T is to come off the rim R.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] In the bead unseating test, the position of the load block 6 conforms to the L dimension described in Table 4 of JIS D4230. The L dimension is determined by the nominal rim diameter. According to JIS D4230, for example, when the nominal rim diameter is 15 inches, the L dimension is 279 mm. The difference between half of the outer diameter of the tire T and the L dimension corresponds to the radial distance from the equator of the tire T to the position where the load block 6 contacts the tire T.

[0007] In a tire with a tire size of 195 / 65R15, the load block 6 contacts at a position approximately 39 mm radially away from the equator. In a tire with a tire size of 165 / 65R15, the load block 6 contacts at a position approximately 19 mm radially away from the equator. When the nominal aspect ratio and the nominal rim diameter are the same, in a tire having a smaller nominal section width, the load block 6 contacts the tire at a position closer to the tread than in a tire having a larger nominal section width.

[0008] In a tire where the load block 6 contacts at a position closer to the tread, there is a tendency for the rim dismounting resistance to be low, and an improvement in the rim dismounting effectiveness is required.

[0009] The present invention has been made in view of such circumstances, and an object thereof is to provide a tire capable of achieving an improvement in rim dismounting effectiveness.

Means for Solving the Problems

[0010] A tire according to one aspect of the present invention includes a tread that contacts the road surface, a pair of sidewalls that are continuous with an end of the tread and are located inside the tread in the radial direction, a pair of beads that are located inside the sidewalls in the radial direction, a carcass that is located inside the tread and the pair of sidewalls and bridges between one bead and the other bead, a belt that is located outside the carcass in the radial direction, and a band that is located between the tread and the belt in the radial direction. The difference between half of the outer diameter of the tire and the L dimension described in JIS D4230 is 20 mm or less. The bead includes a core that extends in the circumferential direction. The bending rigidity of the core in the width direction is 7.80×10 6 N·mm 2 or more.

[0011] Preferably, in this tire, the core includes a steel wire. The wire has an elliptical wire cross-section. In the cross-section of the core, a plurality of units in which a plurality of the wire cross-sections are arranged in the width direction of the core are formed, and the plurality of units are arranged in the height direction of the core. In the unit, the major axis of the wire cross-section faces the width direction of the core. The ratio of the minor axis length of the wire cross-section to the major axis length of the wire cross-section is 0.60 or more and 0.90 or less.

[0012] Preferably, in this tire, among the tire, the portion that contacts the rim on which the tire is mounted is the bead portion. The outer surface of the bead portion includes a seat surface that contacts the seat of the rim, a flange surface that contacts the flange of the rim, and a heel surface that is located between the seat surface and the flange surface and is formed of a curved surface. In the meridian cross-section of the tire, the contour of the heel surface is represented by an arc. The radius of the arc is 6.0 mm or more and 11.0 mm or less.

[0013] Preferably, in this tire, the belt includes two radially laminated layers. Each layer includes a number of parallel belt cords. Each belt cord is a steel cord. The steel cord is a stranded wire composed of 4 or more and 8 or less strands, and each strand has an outer diameter of 0.20 mm or more and 0.30 mm or less and a tensile strength of 3000 MPa or more. The cord density of the layer is 20 ends or more and 50 ends or less.

[0014] Preferably, in this tire, the band includes a full band that covers the entire belt. The full band includes a full band cord wound in a spiral. The full band cord is an aramid cord made of aramid fibers or a hybrid cord made of nylon fibers and aramid fibers.

[0015] Preferably, in this tire, the band includes a pair of edge bands that are arranged axially spaced apart and cover the ends of the full band. Each edge band includes an edge band cord wound in a spiral. The edge band cord is an aramid cord made of aramid fibers or a hybrid cord made of nylon fibers and aramid fibers.

Advantages of the Invention

[0016] According to the present invention, a tire can be obtained that achieves an improvement in the rim detachment effect.

Brief Description of the Drawings

[0017]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, the present invention will be described in detail based on preferred embodiments with appropriate reference to the drawings.

[0019] In the present disclosure, a state in which a tire is mounted on a standard rim, the internal pressure of the tire is adjusted to the standard internal pressure, and no load is applied to this tire is referred to as a standard state.

[0020] In the present disclosure, unless otherwise specified, the dimensions and angles of each part of the tire are measured in the standard state. Dimensions and angles that cannot be measured in a state where the tire is mounted on the standard rim are measured by cutting the tire along a plane including the rotation axis so that the distance between the left and right beads in the cross section of the tire coincides with the distance between the beads in the tire mounted on the standard rim.

[0021] The standard rim means a rim defined in the standard to which the tire conforms. 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.

[0022] The standard internal pressure means the internal pressure defined in the standard to which the tire conforms. The "maximum air pressure" in the JATMA standard, the "maximum value" published in the "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the TRA standard, and the "INFLATION PRESSURE" in the ETRTO standard are standard internal pressures.

[0023] The normal load means the load defined in the standard on which the tire depends. The "maximum load capacity" in the JATMA standard, the "maximum value" published in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the TRA standard, and the "LOAD CAPACITY" in the ETRTO standard are the normal loads.

[0024] In the present disclosure, the "nominal section width", "nominal aspect ratio", and "nominal rim diameter" are the "nominal section width", "nominal aspect ratio", and "nominal rim diameter" included in the "tire designation" defined in JIS D4202 "Automobile Tires - Designation and Dimensions".

[0025] In the present disclosure, the outer diameter OD (mm) of the tire is calculated based on the following formula when the nominal section width is NW (mm), the nominal aspect ratio is NA (%), and the nominal rim diameter is NR (inch). OD = NW × NA / 50 + 25.4 × NR

[0026] In the present disclosure, the load index (LI) is, for example, an index defined in the JATMA standard and representing the maximum mass, that is, the maximum load capacity, that is allowed to be loaded on the tire under specified conditions.

[0027] In the present disclosure, the tread portion of the tire is the portion of the tire that contacts the road surface. The bead portion is the portion of the tire that contacts the rim. The sidewall portion is the portion of the tire that bridges between the tread portion and the bead portion. The tire includes, as parts, a tread portion, a pair of bead portions, and a pair of sidewall portions. The rim includes a seat and a flange. When the tire is assembled to the rim, the inner peripheral surface of the bead portion contacts the seat. The outer surface of the bead portion contacts the flange.

[0028] In the present disclosure, among the elements constituting the tire, the hardness of the element made of crosslinked rubber is measured using a Type A durometer under the temperature condition of 23°C in accordance with the provisions of JIS K6253. When the hardness cannot be measured in the tire, a test piece made of crosslinked rubber obtained by pressurizing and heating the rubber composition used for forming the element to be measured at a temperature of 170°C for 12 minutes is used.

[0029] In the present disclosure, the number of cords included per 5 cm width of an element of the tire, which includes parallel cords, is expressed as the cord density (unit: ends) of the element. For example, if the number of cords included per 5 cm width of an element of the tire is 30, the cord density of this element is expressed as 30 ends. Unless otherwise specified, the cord density is obtained in the cross-section of the element obtained by cutting in a plane perpendicular to the length direction of the cord.

[0030] FIG. 1 shows a part of a tire 12 according to an embodiment of the present invention. This tire 12 is a passenger car tire. In FIG. 1, the tire 12 is mounted on a rim R. The rim R is a standard rim. The inside of the tire 12 is filled with air, and the internal pressure of the tire 12 is adjusted.

[0031] The tire 12 mounted on the rim R is also referred to as a tire-rim assembly. The tire-rim assembly includes the rim R and the tire 12 mounted on this rim R.

[0032] FIG. 1 shows a part of the cross-section (hereinafter also referred to as the meridian cross-section) of the tire 12 along a plane including the rotation axis (not shown) of the tire 12. In FIG. 1, the left-right direction is the axial direction of the tire 12, and the up-down direction is the radial direction of the tire 12. The direction perpendicular to the plane of FIG. 1 is the circumferential direction of the tire 12. In FIG. 1, the dashed-dotted line CL represents the equatorial plane of the tire 12.

[0033] In FIG. 1, the position indicated by the reference symbol PW is the axially outer end of the tire 12. When there are decorations such as patterns or letters on the outer surface, the outer end PW is specified based on the virtual outer surface obtained assuming there is no decoration. The axial distance from one outer end PW to the other outer end PW is the maximum width of the tire 12, that is, the section width (refer to JATMA, etc.). The outer end PW is the position where the tire 12 exhibits its maximum width (hereinafter, the maximum width position).

[0034] This tire 12 includes a tread 14, a pair of sidewalls 16, a pair of beads 18, a pair of beads 20, a carcass 22, an inner liner 24, a pair of chafers 26, a belt 28, and a band 30.

[0035] The tread 14 contacts the road surface on its outer surface. Grooves 32 are engraved in the tread 14. Thereby, a tread pattern is formed.

[0036] Although not shown in the figure, the tread 14 has a cap layer and a base layer. The cap layer constitutes the outer surface of the tread 14. The cap layer is made of crosslinked rubber in which wear resistance and grip performance are considered. The base layer is located radially inside the cap layer. The base layer is made of crosslinked rubber with low heat generation.

[0037] In FIG. 1, the position indicated by the reference symbol PC is the equator of the tire 12. The equator PC is the intersection of the outer surface of the tread 14 and the equatorial plane. When a groove 32 is located on the equatorial plane, the equator PC is specified based on the virtual outer surface obtained assuming there is no such groove 32.

[0038] In FIG. 1, the position indicated by the reference symbol PH is a position on the outer surface of the tread 14. The position PH corresponds to the axially outer end of the contact surface of the tire 12 with the road surface.

[0039] The ground contact surface for specifying the position PH is obtained, for example, using a ground contact surface shape measuring device (not shown). In this device, with the tire 12 assembled to a standard rim and the camber angle of the tire 12 adjusted to 0° with an internal pressure of 240 kPa, a load of 80% of the load represented by the load index is applied as a vertical load to the tire 12, and the tire 12 is brought into contact with a road surface composed of a flat plane to obtain it. In the present disclosure, the ground contact surface thus obtained is the reference ground contact surface, and the position on the outer surface of the tread 14 corresponding to the axial outer end of the reference ground contact surface is the aforementioned position PH. In this tire 12, this position PH is the reference ground contact end.

[0040] FIG. 2 shows an image of the reference ground contact surface. In FIG. 2, the vertical direction corresponds to the circumferential direction of the tire 12, the horizontal direction corresponds to the axial direction of the tire 12, and the direction perpendicular to the plane of FIG. 2 corresponds to the radial direction of the tire 12.

[0041] In FIG. 2, the length indicated by the symbol CW is the ground contact width of the reference ground contact surface. The ground contact width CW is the axial distance from one reference ground contact end PH to the other reference ground contact end PH. The ground contact width CW is represented by the maximum width of the reference ground contact surface.

[0042] Each sidewall 16 is continuous with the end of the tread 14. The sidewall 16 is located inside the tread 14 in the radial direction. The sidewall 16 extends along the carcass 22 from the end of the tread 14 toward the clinch 18. The sidewall 16 is made of crosslinked rubber considering cut resistance.

[0043] Each clinch 18 is located inside the sidewall 16 in the radial direction. The clinch 18 contacts the flange F of the rim R. The clinch 18 is made of crosslinked rubber considering wear resistance.

[0044] Each bead 20 is located inside the clinch 18 in the axial direction. The bead 20 is located inside the sidewall 16 in the radial direction. The bead 20 includes a core 34 and an apex 36.

[0045] The core 34 extends in the circumferential direction. The core 34 is ring-shaped. As shown in FIG. 1, the cross-section of the core 34 is substantially square. The core 34 has a predetermined width in the axial direction and a predetermined height in the radial direction. The core 34 includes a steel wire.

[0046] Although not shown, the core 34 is formed by winding a wire coated with rubber. The portion of the core 34 other than the wire is filled with cross-linked rubber. In this tire 12, the portion made of cross-linked rubber of the core 34 is referred to as cover rubber. In this tire 12, the hardness of the cover rubber is 81 or more and 84 or less.

[0047] The apex 36 is located outside the core 34 in the radial direction. The apex 36 is tapered outward. The apex 36 is made of cross-linked rubber having high rigidity. In the radial direction, the outer end of the apex 36 is located inside the maximum width position PW. The length of the apex 36 is appropriately set within the range of 20 mm to 40 mm.

[0048] The carcass 22 is located inside the tread 14, a pair of sidewalls 16, and a pair of beads 18. The carcass 22 spans between one bead 20 and the other bead 20. The carcass 22 has a radial structure.

[0049] The carcass 22 includes at least one carcass ply 38. The carcass 22 of this tire 12 consists of one carcass ply 38.

[0050] The carcass ply 38 includes a ply body 38a that spans between one bead 20 and the other bead 20, and a pair of folded-back portions 38b that are connected to the ply body 38a and are folded back from the inner side to the outer side around each bead 20 in the axial direction. In the radial direction, the ends of the folded-back portions 38b are located outside the maximum width position PW.

[0051] Although not shown, the carcass ply 38 includes a number of parallel carcass cords. Each carcass cord intersects the equatorial plane. The carcass cord is a cord made of organic fibers. Examples of the organic fibers include nylon fibers, rayon fibers, polyester fibers, and aramid fibers.

[0052] The inner liner 24 is located inside the carcass 22. The inner liner 24 constitutes the inner surface of the tire 12. The inner liner 24 is made of a crosslinked rubber having a low gas permeability coefficient. The inner liner 24 retains the internal pressure of the tire 12.

[0053] Each chafer 26 is located radially inside the bead 20. The chafer 26 contacts the seat S of the rim R. The chafer 26 of this tire 12 is composed of a fabric and rubber impregnated in the fabric.

[0054] The belt 28 is located radially outside the carcass 22. The belt 28 is laminated on the carcass 22 from the radially outer side.

[0055] The belt 28 is composed of at least two layers 40 laminated in the radial direction. The belt 28 of this tire 12 is composed of two layers 40 laminated in the radial direction. Of the two layers 40, the layer 40 located on the inner side is the inner layer 40a, and the layer 40 located on the outer side is the outer layer 40b. As shown in FIG. 1, the inner layer 40a is wider than the outer layer 40b. The length from the end of the outer layer 40b to the end of the inner layer 40a is 3 mm or more and 10 mm or less.

[0056] The band 30 is located radially between the tread 14 and the belt 28. The band 30 is laminated on the belt 28 inside the tread 14. The band 30 includes a full band 42. The full band 42 covers the entire belt 28. This band 30 is composed of the full band 42 that covers the entire belt 28. The full band 42 is wider than the belt 28. The length from the end of the belt 28 to the end of the full band 42 is 3 mm or more and 7 mm or less.

[0057] In FIG. 1, the length indicated by the symbol OD is the outer diameter of this tire 12. In this tire 12, the difference (OD / 2 - L) between half of the outer diameter OD and the L dimension described in JIS D4230 is 20 mm or less. In this tire 12, in the bead unseating test described in JIS D4230, the load block 6 contacts at the boundary between the tread 14 and the sidewall 16 (hereinafter referred to as the buttress portion), or radially outside of this buttress portion. In this tire 12, the load block 6 is pressed against the portion near the tread 14. As a result, the vicinity of the buttress portion is moved inward in the axial direction. By this movement, the carcass 22 is pulled, and a force acts on the bead portion B to separate the bead portion B from the rim R.

[0058] In this tire 12, the nominal aspect ratio NA and the nominal rim diameter NR are the same, and the distance from the position where the load block 6 contacts to the bead portion B is shorter than that of a tire in which the difference (OD / 2 - L) exceeds 20 mm. Therefore, the force acting on the tire 12 when the load block 6 presses the tire 12 is likely to be transmitted to the bead portion B. For this reason, there is a concern that this tire 12 exhibits a low rim dismounting resistance.

[0059] The inventors of the present invention have intensively studied aiming at improving the rim dismounting resistance, and found that if the bending rigidity in the width direction of the core 34 included in the bead portion B is 7.80×10 6 N·mm 2 or more, the deformation of the bead portion B caused by the load block 6 pressing the tire 12 can be suppressed, and thus the present invention has been completed.

[0060] In the present disclosure, the bending rigidity Gc (N·mm 2 ) in the width direction of the core 34 is calculated based on the following formula, where Ew (kgf / mm 2 ) is the elastic modulus of the wire and Mi (mm 4 ) is the second moment of area in the width direction of the core 34. For the elastic modulus Ew of the wire, the elastic modulus of steel (21000 kgf / mm 2 ) is used. Gc = Ew × 9.8 × Mi The secondary moment of inertia Mi of the cross-section is calculated based on the following formula, where Wa is the apparent width and Ha is the apparent height of the core 34. Mi = Ha × (Wa 3 ) / 12 The apparent width Wa and apparent height Ha of the core 34 are calculated in consideration of the outer diameter of the wire and the configuration of the core 34 described below. For example, when the configuration of the core 34 is represented as "4 + 4 + 4", if the outer diameter of the wire with a circular cross-section is d, the apparent width Wa is represented as 4 times the outer diameter d, and the apparent height Ha is represented as 3 times the outer diameter d.

[0061] In this tire 12, the bending rigidity in the width direction of the core 34 is 7.80 × 10 6 N·mm 2 or more. When the load block 6 presses against the tire 12, a force acts on the bead portion B, but in this tire 12, the deformation of the core 34 is suppressed. Despite the short distance from the contact position of the load block 6 to the bead portion B, the bead portion B of this tire 12 is difficult to move relative to the rim R. In the bead unseating test, a large force needs to be applied to the bead portion B to remove this tire 12 from the rim R. In other words, this tire 12 has a high rim unseating resistance. When the tire size of this tire 12 is, for example, 165 / 65R15, the rim unseating resistance of this tire 12 is 9567 N or more. In this tire 12, an improvement in rim unseating resistance is achieved. From this perspective, the bending rigidity in the width direction of the core 34 is preferably 13.3 × 10 6 N·mm 2 or more. From the perspective of improving the rim unseating resistance, the higher the bending rigidity in the width direction of the core 34, the more preferable it is. Therefore, in this regard, the upper limit of the bending rigidity is not set.

[0062] FIG. 3 shows a part of the cross-section of the tire 12 shown in FIG. 1. In this FIG. 3, the cross-section of the bead portion B is shown. In FIG. 3, the left-right direction is the axial direction of the tire 12, and the up-down direction is the radial direction of the tire 12. The direction perpendicular to the plane of FIG. 3 is the circumferential direction of the tire 12.

[0063] As described above, the core 34 is formed by winding a wire 44 coated with rubber. The cross-section of the core 34 includes cross-sections of a plurality of wires 44 (hereinafter referred to as wire cross-sections 44cs). As shown in FIG. 3, in its cross-section, the core 34 is configured such that a plurality of units 46 in which a plurality of wire cross-sections 44cs are arranged in the width direction of the core 34 are formed, and the plurality of units 46 are arranged in the height direction of the core 34. In the bead portion B shown in FIG. 3, three units 46 in which five wire cross-sections 44cs are arranged in the width direction of the core 34 are formed, and the core 34 is configured such that these units 46 are arranged in the height direction of the core 34.

[0064] In the present disclosure, the configuration of the core 34 is represented by using the number of wire cross-sections 44cs included in each unit 46. The configuration of the core 34 shown in FIG. 3 is represented as "5 + 5 + 5". In this notation, the right side represents the number of wire cross-sections 44cs of the unit 46 located on the outer side in the radial direction. Although not shown, for example, if the core 34 includes four units 46 arranged in the height direction, and the number of wire cross-sections 44cs of the unit 46 located most on the outer side in the radial direction of the tire 12 is 3, and the number of wire cross-sections 44cs included in each of the remaining units 46 is 4, the configuration of this core 34 is represented as "4 + 4 + 4 + 3".

[0065] The shape of the wire cross-section 44cs included in the cross-section of the core 34 is usually circular. As shown in FIG. 3, the shape of the wire cross-section 44cs may be elliptical instead of circular. By having the wire 44 included in the core 34 have an elliptical wire cross-section 44cs, the bending rigidity of the core 34 can be effectively increased while considering the influence on the mass. In this case, in the tire 12, in the unit 46 constituting the core 34, it is preferable that the wire cross-section 44cs is arranged such that the major axis of the wire cross-section 44cs faces the width direction of the core 34. This arrangement of the wire cross-section 44cs can contribute to an increase in the bending rigidity in the width direction of the core 34.

[0066] In FIG. 3, the length indicated by the double arrow La is the length of the major axis of the wire cross-section 44cs. The length indicated by the double arrow Sa is the length of the minor axis of this wire cross-section 44cs. As described above, for calculating the bending rigidity in the width direction of the core 34, the apparent width Wa and the apparent height Ha of the core 34 are used. In the present disclosure, when the shape of the wire cross-section 44cs is an ellipse, the major axis length La is used for calculating the apparent width Wa, and the minor axis length Sa is used for calculating the apparent height Ha.

[0067] In this tire 12, in the unit 46 constituting the core 34, when the wire cross-section 44cs is arranged such that the major axis of this wire cross-section 44cs faces the width direction of the core 34, from the viewpoint of effectively increasing the bending rigidity in the width direction of the core 34 while suppressing the influence on the mass, the ratio (Sa / La) of the minor axis length Sa of the wire cross-section 44cs to the major axis length La of this wire cross-section 44cs is preferably 0.90 or less, and more preferably 0.85 or less.

[0068] In the tire 12 mounted on the rim R, it is required not only to be difficult to come off from the rim R but also to be difficult to shift with respect to the rim R. From the viewpoint that the bead portion B can sufficiently clamp the rim R, the ratio (Sa / La) is preferably 0.60 or more, more preferably 0.70 or more, and even more preferably 0.75 or more.

[0069] In this tire 12, when the ratio (Sa / La) is set in the range of 0.60 or more and 0.90 or less, from the viewpoint of effectively increasing the bending rigidity in the width direction of the core 34 while suppressing the influence on the mass, the major axis length La is preferably set in the range of 1.0 mm or more and 1.5 mm or less.

[0070] In FIG. 3, the length indicated by the symbol W is the width of the core 34. The length indicated by the symbol H is the height of the core 34. The width W and the height H of the core 34 are obtained in the cross-section of the tire 12. The width W and the height H of the core 34 are the net width and height considering not only the wire 44 but also the cover rubber filled in the core 34.

[0071] In this tire 12, from the viewpoint that the core 34 can contribute to improving the rim detachment resistance, the ratio (H / W) of the height H of the core 34 to the width W of the core 34 is preferably 0.55 or less, and more preferably 0.50 or less. From the viewpoint that the core 34 can contribute to improving the force with which the bead portion B clamps the rim R, i.e., the clamping force, this ratio (H / W) is preferably 0.35 or more, and more preferably 0.40 or more.

[0072] In this tire 12, from the viewpoint of improving the rim detachment resistance while ensuring the necessary clamping force, the width W of the core 34 is preferably 4.5 mm or more and 9.0 mm or less.

[0073] The bead portion B of this tire 12 contacts the rim R. The outer surface 48 of this bead portion B includes a seat surface 50 that contacts the seat S of the rim R, a flange surface 52 that contacts the flange F of the rim R, and a heel surface 54 that is located between the seat surface 50 and the flange surface 52 and consists of a curved surface. In this tire 12, in its meridian cross-section, the contour of the heel surface 54 is represented by an arc. In FIG. 3, the arrow indicated by the symbol Rh is the radius of the arc representing the contour of this heel surface 54.

[0074] When the tire 12 is assembled to the rim R, the bead portion B is dropped into a well (not shown) of the rim R. When air is filled inside the tire 12, the bead portion B moves toward the flange F. The bead portion B gets over a hump (not shown) of the rim R, is placed on the seat S, and contacts the flange F. Thereby, the setting of the tire 12 to the rim R is completed, and a tire-rim assembly is obtained.

[0075] In this tire 12, the radius Rh of the arc representing the contour of the heel surface 54 is preferably 6.0 mm or more and 11.0 mm or less.

[0076] By setting the radius Rh to 6.0 mm or more, when the bead portion B crosses over the hump of the rim R, it is possible to suppress the bead portion B from getting caught on the hump. Since the bead portion B is less likely to get caught on the hump, the tire 12 can achieve a reduction in fitting pressure. From this perspective, the radius Rh is more preferably 8.0 mm or more, and even more preferably 10.0 mm or more.

[0077] By setting the radius Rh to 11.0 mm or less, the bead portion B adheres sufficiently to the rim R. Since it is possible to prevent a gap from being formed between the bead portion B and the rim R, good air leakage resistance performance is maintained in this tire 12.

[0078] FIG. 4 shows the configuration of the belt 28 and the band 30 of this tire 12. In FIG. 4, the left - right direction is the axial direction of the tire 12, the up - down direction is the circumferential direction of the tire 12, and the direction perpendicular to the plane of FIG. 4 is the radial direction of the tire 12. The front side of the plane of FIG. 3 is the radially outer side, and the back side of the plane of FIG. 4 is the radially inner side.

[0079] As described above, the belt 28 of this tire 12 includes an inner layer 40a and an outer layer 40b. As shown in FIG. 4, the inner layer 40a and the outer layer 40b each include a large number of belt cords 56 arranged in parallel. In FIG. 4, for convenience of explanation, the belt cords 56 are represented by solid lines, but the belt cords 56 are covered with topping rubber 58.

[0080] In each of the inner layer 40a and the outer layer 40b, the belt cords 56 are inclined with respect to the equatorial plane. The direction of inclination of the belt cords 56 included in the inner layer 40a (hereinafter, the inclination direction of the first belt cord 56A) is opposite to the direction of inclination of the belt cords 56 included in the outer layer 40b (hereinafter, the inclination direction of the second belt cord 56B).

[0081] In FIG. 4, the angle θa is the angle formed by the first belt cord 56A with respect to the equatorial plane (hereinafter referred to as the first inclination angle θa). The angle θb is the angle formed by the second belt cord 56B with respect to the equatorial plane (hereinafter referred to as the second inclination angle θb). In this tire 12, the first inclination angle θa is 15 degrees or more and 35 degrees or less. The second inclination angle θb is 15 degrees or more and 35 degrees or less.

[0082] In this tire 12, from the viewpoint of improving the rim dismounting resistance, preferably, a steel cord formed by twisting a plurality of strands is used as the belt cord 56. In other words, the belt cord 56 is a steel cord, and the steel cord is preferably a stranded wire composed of a plurality of strands. The number of strands constituting the steel cord is 4 or more and 8 or less, the outer diameter of the strand is 0.20 mm or more and 0.30 mm or less, and the tensile strength of the strand is preferably 3000 MPa or more. Specifically, this belt cord 56 is preferably a steel cord formed by twisting a plurality of strands having an outer diameter of 0.20 mm or more and 0.30 mm or less and a tensile strength of 3000 MPa or more. Examples of such a steel cord include a steel cord having a structure represented by 1×4×0.27 and a steel cord having a structure represented by 1×8×0.23. From the viewpoint of effectively contributing to the improvement of the rim dismounting resistance, the belt cord 56 is more preferably a steel cord having a structure represented by 1×8×0.23.

[0083] As described above, the inner layer 40a and the outer layer 40b include a large number of belt cords 56 arranged in parallel. The larger the number of belt cords 56 included in each layer, the more the belt 28 can contribute to improving the rim dismounting resistance. If the number of belt cords 56 is too large, the mass of the tire 12 increases. From the viewpoint of contributing to the improvement of the rim dismounting resistance without increasing the mass, it is preferable that the cord density of the inner layer 40a is 20 ends or more and 50 ends or less, and the cord density of the outer layer is 20 ends or more and 50 ends or less. From the viewpoint that the belt 28 can effectively contribute to the improvement of the rim dismounting resistance, the belt cords 56 included in the inner layer and the outer layer are steel cords, the steel cords are stranded wires composed of a plurality of strands, and each strand has an outer diameter of 0.20 mm or more and 0.30 mm or less and a tensile strength of 3000 MPa or more. It is more preferable that the cord density of the inner layer and the outer layer is 20 ends or more and 50 ends or less. When a steel cord having a structure represented by 1×4×0.27 is used as the belt cord 56, it is further preferable that the cord density of the inner layer and the outer layer is 30 ends or more and 50 ends or less. When a steel cord having a structure represented by 1×8×0.23 is used as the belt cord 56, it is further preferable that the cord density of the inner layer and the outer layer is 20 ends or more and 30 ends or less.

[0084] As described above, the band 30 of this tire 12 includes a full band 42 that covers the entire belt 28. As shown in FIG. 4, this full band 42 includes a full band cord 60 wound in a spiral shape. In FIG. 4, for convenience of explanation, the full band cord 60 is represented by a solid line, but this full band cord 60 is covered with topping rubber 62.

[0085] In the full band 42, the full band cord 60 extends substantially in the circumferential direction. Specifically, the angle formed by the full band cord 60 with respect to the circumferential direction is 5° or less. This full band 42 has a jointless structure.

[0086] In this tire 12, the density of the full band code 60 in the full band 42 is 40 ends or more and 60 ends or less. This density of the full band code 60 is represented by the number of cross-sections of the full band code 60 included per 5 cm width of the full band 42 in the cross-section of the full band 42 included in the meridian cross-section.

[0087] In this tire 12, a code made of organic fiber (hereinafter referred to as organic fiber code) is used for the full band code 60. Examples of this organic fiber code include a code made of nylon fiber, a code made of polyester fiber, a code made of rayon fiber, a code made of aramid fiber, and a hybrid code made of nylon fiber and aramid fiber. From the viewpoint that the full band 42 can contribute to the improvement of rim detachment resistance, this full band code 60 is preferably a code made of aramid fiber or a hybrid code made of nylon fiber and aramid fiber. From the viewpoint that the full band 42 can effectively contribute to the improvement of rim detachment resistance, the full band code 60 is more preferably a code made of aramid fiber.

[0088] In FIG. 1, the length indicated by the symbol WB is the width of the belt 28. This width of the belt 28 is the axial distance from one end of the belt 28 to the other end. The length indicated by the symbol WF is the width of the full band 42. This width of the full band 42 is the axial distance from one end of the full band 42 to the other end. Since the band 30 of this tire 12 is made of the full band 42, the width of this full band 42 is also the width of the band 30.

[0089] In this tire 12, from the viewpoint that the belt 28 can contribute to the improvement of rim detachment resistance, the ratio (WB / CW) of the width WB of the belt to the contact width CW is preferably 100% or more, more preferably 110% or more. From the viewpoint of suppressing the influence on the mass by the belt 28, this ratio (WB / CW) is preferably 120% or less.

[0090] In this tire 12, from the viewpoint that the full band 42 can contribute to the improvement of the rim detachment resistance, the ratio (WF / CW) of the width WF of the full band 42 to the contact width CW is preferably 110% or more, and more preferably 115% or more. From the viewpoint of suppressing the influence on the mass by the full band 42, this ratio (WF / CW) is preferably 130% or less, and more preferably 125% or less.

[0091] FIG. 5 shows a part of a tire 72 according to another embodiment of the present invention. This tire 72 is a passenger car tire. Also in FIG. 5, as in FIG. 1, a part of the meridian cross-section of this tire 72 is shown. In FIG. 5, the left-right direction is the axial direction of the tire 72, and the up-down direction is the radial direction of the tire 72. The direction perpendicular to the plane of FIG. 5 is the circumferential direction of the tire 72.

[0092] In this tire 72, except for the band 74, it has the same configuration as the configuration of the tire 12 shown in FIG. 1. Therefore, in this FIG. 4, the same components as the components of the tire 12 in FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted.

[0093] The band 74 of this tire 72 includes a full band 76 and a pair of edge bands 78. The full band 76 covers the entire belt 28. The pair of edge bands 78 are arranged axially spaced apart with the equatorial plane interposed therebetween. The edge band 78 covers the end of the full band 76 from the outside in the radial direction. As shown in FIG. 5, the position of the outer end of the edge band 78 coincides with the position of the end of the full band 76 in the axial direction. The outer end of this edge band 78 may be located outside the end of the full band 76 in the axial direction, or the outer end of this edge band 78 may be located inside the end of the full band 76 in the axial direction.

[0094] FIG. 6 shows the configuration of the band 74 of this tire 72 together with the configuration of the belt 28. In FIG. 6, the left-right direction is the axial direction of the tire 72, and the up-down direction is the circumferential direction of the tire 72. The direction perpendicular to the plane of FIG. 6 is the radial direction of the tire 72. The front side of the plane of FIG. 6 is the outside in the radial direction. The back side of the plane of FIG. 6 is the inside in the radial direction.

[0095] As shown in FIG. 6, the full band 76 includes a full band cord 80 wound in a spiral shape. In this FIG. 6, for convenience of explanation, the full band cord 80 is represented by a solid line, but this full band cord 80 is covered with topping rubber 82. The full band 76 of this tire 72 has a configuration equivalent to that of the full band 42 of the tire 12 shown in FIG. 1.

[0096] As shown in FIG. 6, each edge band 78 includes an edge band cord 84 wound in a spiral shape. In this FIG. 6, for convenience of explanation, the edge band cord 84 is represented by a solid line, but this edge band cord 84 is covered with topping rubber 86.

[0097] In the edge band 78, the edge band cord 84 extends substantially in the circumferential direction. Specifically, the angle formed by the edge band cord 84 with respect to the circumferential direction is 5° or less. This edge band 78 has a jointless structure.

[0098] In this tire 72, the density of the edge band cord 84 in the edge band 78 is 40 ends or more and 60 or less. The density of this edge band cord 84 is represented by the number of cross-sections of the edge band cord 84 included per 5 cm width of the edge band 78 in the cross-section of the edge band 78 included in the meridian cross-section.

[0099] In this tire 72, an organic fiber cord is used for the edge band cord 84. Examples of such organic fiber cords include cords made of nylon fibers, cords made of polyester fibers, cords made of rayon fibers, cords made of aramid fibers, and hybrid cords made of nylon fibers and aramid fibers. From the viewpoint that the edge band 78 can contribute to improving the rim dismounting resistance, this edge band cord 84 is preferably a cord made of aramid fibers or a hybrid cord made of nylon fibers and aramid fibers. From the viewpoint that the edge band 78 can effectively contribute to improving the rim dismounting resistance, it is more preferable that the edge band cord 84 is a cord made of aramid fibers.

[0100] In FIG. 5, the length indicated by the double arrow WE is the width of the edge band 78. This width WE is the axial distance from the outer end to the inner end of the edge band 78.

[0101] In this tire 72, from the viewpoint that the edge band 78 can contribute to improving the rim dismounting resistance, the ratio (WE / CW) of the width WE of the edge band 78 to the contact width CW is preferably 10% or more, more preferably 15% or more. From the viewpoint of suppressing the influence of the edge band 78 on the mass of the tire 72, this ratio (WE / CW) is preferably 30% or less, more preferably 25% or less.

[0102] As described above, according to the present invention, a tire can be obtained that achieves an improvement in rim dismounting effectiveness.

Example

[0103] Hereinafter, the present invention will be described in more detail by way of examples and the like, but the present invention is not limited to such examples only.

[0104] [Example 1] A passenger car tire (tire size = 165 / 55R15) having the basic configuration shown in FIG. 1 and the specifications shown in Table 1 below was obtained. In Example 1, the difference (OD / 2 - L) between half of the outer diameter OD of the tire and the L dimension described in JIS D4230 was 19 mm. A core having the configuration shown in FIG. 3 was used as the bead core. This is shown as "5 + 5 + 5" in the column of "Core Configuration" in Table 1. The bending rigidity in the width direction of the core was 13.78×10 6 N·mm 2 . The cross-sectional shape of the wire included in the core was an ellipse, and the ratio (Sa / La) of the minor axis length Sa to the major axis length La was 0.75. The radius Rh of the arc representing the contour of the heel surface of the bead portion was 10.0 mm. The major axis length La was 1.30 mm. In this Example 1, a belt and a band having the configuration shown in FIG. 4 were adopted. This is shown in the column of "Belt and Band Configuration" in Table 1. The band of Example 1 was composed only of a full band. For the belt cord, a steel cord having a structure of 1×4×0.27 was adopted. The number of strands included in the belt cord was 4, and the outer diameter of the strand was 0.27 mm. The cord density of the inner layer and the outer layer was 40 ends. For the full band cord, a cord made of nylon fiber was adopted. This is represented by "N" in the column of "Full Band Cord Type" in Table 1. The configuration of this cord was 1400 dtex / 2. This is represented by "1400 / 2" in the column of "Full Band Cord Configuration" in Table 1.

[0105] [Comparative Example 1] A tire of Comparative Example 1 was obtained in the same manner as in Example 1, except that a core having the configuration shown in FIG. 7 ("4 + 4 + 4") was adopted for the bead core and the radius Rh was as shown in Table 1 below. In this Comparative Example 1, the bending rigidity in the width direction of the core was 6.83×10 6 N·mm 2 . The cross-sectional shape of the wire included in the core was a circle. Therefore, the ratio (Sa / La) was 1.00. The outer diameter of this wire was 1.20 mm. This is shown in the column of La in Table 1.

[0106] [Example 2] The tire of Example 2 was obtained in the same manner as in Comparative Example 1, except that the core structure was changed so that the bending rigidity in the width direction of the core was as shown in Table 1 below.

[0107] [Example 3] The tire of Example 3 was obtained in the same manner as in Example 1, except that the radius Rh was as shown in Table 1 below.

[0108] [Reference Example] The tire size of the reference example was 195 / 55R15. The difference (OD / 2 - L) between half of the outer diameter OD of the tire and the L dimension described in JIS D4230 was 39 mm. The core structure of the bead was the same as that of Comparative Example 1. For the belt and band, the belt and band having the configuration shown in FIG. 4, which was the same as that of Example 1, were adopted. For the belt cord, a steel cord having a structure of 1×2×0.295 was adopted, and the cord density of the inner layer and the outer layer was set to 36 ends. For the full band cord, a cord made of nylon fiber (configuration = 1100 dtex / 2) was used.

[0109] [Example 4] The tire of Example 4 was obtained in the same manner as in Example 1, except that a steel cord having a structure of 1×8×0.23 was adopted for the belt cord and the cord density of the inner layer and the outer layer was set to 24 ends.

[0110] [Example 5] The tire of Example 5 was obtained in the same manner as in Example 4, except that a cord made of aramid fiber (configuration = 1670 dtex / 2) was used for the full band cord. The fact that the full band cord is a cord made of aramid fiber is represented by "A" in the column of the type of the full band cord in Table 2.

[0111] [Example 6] The tire of Example 6 was obtained in the same manner as in Example 1, except that the band having the configuration shown in FIG. 6 was adopted. For the edge band cord, a cord made of nylon fiber (configuration = 1400 dtex / 2) was used.

[0112] [Example 7] A steel cord having a structure of 1×8×0.23 was adopted for the belt cord, and the tire of Example 7 was obtained in the same manner as in Example 6 except that the cord density of the inner layer and the outer layer was 24 ends.

[0113] [Example 8] The tire of Example 8 was obtained in the same manner as in Example 7 except that a cord made of aramid fiber (configuration = 1670 dtex / 2) was used for the full-band cord.

[0114] [Example 9] The tire of Example 9 was obtained in the same manner as in Example 8 except that a cord made of aramid fiber (configuration = 1670 dtex / 2) was used for the edge-band cord.

[0115] [Example 10] The tire of Example 10 was obtained in the same manner as in Example 1 except that the wire used for forming the core of Comparative Example 1 was used to change the bending rigidity.

[0116] [Examples 11 - 12] The tires of Examples 11 - 12 were obtained in the same manner as in Example 1 except that the short-axis length Sa was changed so that the ratio (Sa / La) was as shown in Table 3 below.

[0117] [Rim disengagement resistance] The prototype tire was assembled on a rim (size = 15×5J), filled with air, and the internal pressure of the tire was adjusted to 180 kPa. For the reference example, the tire was assembled on a rim (size = 15×6J), filled with air, and the internal pressure of the tire was adjusted to 180 kPa. Using the test apparatus shown in Fig. 8, the bead unseating test described in JIS D4230 was carried out to obtain the rim disengagement resistance. The results are shown in Tables 1 and 2 below with the reference example taken as 100. The higher the numerical value, the higher the rim disengagement resistance. In this evaluation, if the index is 80 or more, the rim disengagement resistance is considered to meet the standard value and is acceptable.

[0118] [Durability] A prototype tire was mounted on a rim (size = 15×5J), filled with air, and the internal pressure of the tire was adjusted to 250 kPa. Using a drum tester, a durability test was carried out by the step speed method in accordance with the load / speed performance test specified by ECE30. The running distance until the tire broke was measured. The results are shown in Tables 1 and 2 below with the index of Example 2 being set to 100. The larger the numerical value, the better the durability of the tire.

[0119] [Handling Stability] A prototype tire was mounted on a rim (size = 15×5J), filled with air, and the internal pressure of the tire was adjusted to 240 kPa. The tire was mounted on a test vehicle (a passenger car with a displacement of 660 cc). The test vehicle was driven on a dry road test course, and the driver was asked to evaluate the handling performance (sensory evaluation). The results are shown in Tables 1 and 2 below with the index of Example 2 being set to 100. The larger the numerical value, the better the handling stability of the tire.

[0120] [Rim Displacement] A prototype tire was mounted on a rim (size = 15×5J), filled with air, and the internal pressure of the tire was adjusted to 240 kPa. The tire was mounted on a test vehicle (a passenger car with a displacement of 660 cc). The test vehicle was driven on a dry road test course. Braking suddenly from a speed of 50 km / h to stop the vehicle was repeated 20 times, and the displacement of the tire with respect to the rim was measured. The results are shown in Tables 1 and 2 below with the index of Example 2 being set to 100. The larger the numerical value, the smaller the displacement of the tire with respect to the rim.

[0121] [Rim Mounting] After fitting a prototype tire onto a rim (size = 15×5J), the tire was filled with air (supply pressure = 600 kPa), and the pressure (fitting pressure) when the bead part passed over the hump of the rim was measured. The results are shown in Tables 1 and 2 below with the index of Example 2 being set to 100. The larger the numerical value, the lower the fitting pressure, and the easier it is to mount the tire on the rim. In this evaluation, if the index is 90 or more, it is considered that the criteria for ease of mounting on the rim are met and is allowed.

[0122]

Table 1

[0123]

Table 2

[0124]

Table 3

[0125] As shown in Tables 1 - 3, in the examples, it has been confirmed that the improvement of the rim detachment effect can be achieved. From this evaluation result, the superiority of the present invention is obvious.

Industrial Applicability

[0126] The technology for achieving the improvement of the rim detachment effect described above can also be applied to various tires.

Explanation of Signs

[0127] 2 ··· Test device 4 ··· Support stand 6 ··· Load block 8 ··· Load arm 12, 72 ··· Tires 14 ··· Tread 16 ··· Sidewall 20 ··· Bead 22 ··· Carcass 28 ··· Belt 30, 74 ··· Band 34 ··· Core 38 ··· Carcass ply 40, 40a, 40b ··· Layers 42, 76 ··· Full band 44 ··· Wire 44cs ··· Wire cross - section 46 ··· Unit 48 ··· Outer surface of bead part B 50 ··· Sheet surface 52 ··· Flange surface 54 ··· Heel surface 56, 56A, 56B ··· Belt code 60, 80 ··· Full band code 78 ··· Edge band 84 ··· Edge band code

Claims

1. A tire comprising a tread that contacts the road surface, a pair of sidewalls that are continuous with the ends of the tread and are located inside the tread in the radial direction, a pair of beads that are located inside the sidewalls in the radial direction, a carcass that is located inside the tread and the pair of sidewalls and bridges between one bead and the other bead, a belt that is located outside the carcass in the radial direction, and a band that is located between the tread and the belt in the radial direction, wherein the difference between half of the outer diameter of the tire and the L dimension described in JIS D4230 is 20 mm or less, the bead includes a core that extends in the circumferential direction, the core includes a wire made of steel, in the cross-section of the core, a plurality of units in which a plurality of wire cross-sections are arranged in the width direction of the core are formed, and the plurality of units are arranged in the height direction of the core, the configuration of the core represented by the number of wire cross-sections included in each of the units is 4 + 4 + 4 + 3 or 5 + 5 + 5, The bending rigidity in the width direction of the core is 7.80×10 ６ N·mm ２ or more. a tire.

2. the wire has an elliptical wire cross-section, in the unit, the major axis of the wire cross-section faces the width direction of the core, the ratio of the minor axis length of the wire cross-section to the major axis length of the wire cross-section is 0.60 or more and 0.90 or less, the tire according to Claim 1.

3. in the tire, the portion that contacts the rim on which the tire is mounted is the bead portion, the outer surface of the bead portion includes a seat surface that contacts the seat of the rim, a flange surface that contacts the flange of the rim, and a heel surface that is located between the seat surface and the flange surface and consists of a curved surface, in the meridian cross-section of the tire, the contour of the heel surface is represented by an arc, the radius of the arc is 6.0 mm or more and 11.0 mm or less, the tire according to Claim 1 or 2.

4. the belt includes two layers laminated in the radial direction, each layer includes a number of belt cords arranged in parallel, each belt cord is a steel cord, the steel cord is a stranded wire composed of 4 or more and 8 or less strands, each strand has an outer diameter of 0.20 mm or more and 0.30 mm or less and a tensile strength of 3000 MPa or more, the cord density of the layer is 20 ends or more and 50 ends or less, the tire according to any one of Claims 1 to 3. Claim 5: The belt cord is a steel cord having a structure represented by 1×4×0.27 or a steel cord having a structure represented by 1×8×0.23, When the steel cord having a structure represented by 1×4×0.27 is used as the belt cord, the cord density of the layer is 30 ends or more and 50 ends or less, When the steel cord having a structure represented by 1×8×0.23 is used as the belt cord, the cord density of the layer is 20 ends or more and 30 ends or less, The tire according to claim 4.

6. The band includes a full band that covers the entire belt, The full band includes a full band cord wound in a spiral, The full band cord is an aramid cord made of aramid fiber or a hybrid cord made of nylon fiber and aramid fiber, The tire according to any one of claims 1 to 5.

7. The band includes a pair of edge bands that are arranged to be spaced apart in the axial direction and cover the ends of the full band, Each edge band includes an edge band cord wound in a spiral, The edge band cord is an aramid cord made of aramid fiber or a hybrid cord made of nylon fiber and aramid fiber, The tire according to claim 6.

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