JP6501600B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire.

  Conventionally, there is known a tire in which uneven distribution of the tread shoulder portion is suppressed by regulating the tread surface shape such as the tread pattern and the radius of curvature of the tread outer surface to suppress uneven wear of the tread shoulder (for example, Patent Document 1).

JP-A-6-199105

  BACKGROUND ART In recent years, development of a tire having a thin gauge of sidewall rubber has been advanced in order to reduce the weight of the tire, as a means for coping with the low fuel consumption of the tire which is particularly desired from the viewpoint of environmental load reduction. Tires with thin gauges of sidewall rubber and tires for mini-vehicles have rigidity at the tire cross section along the tire width direction because the gauge of the tire measured along the carcass normal in the sidewall is thin Lower and hence the horizontal spring constant lowers. Then, as shown in FIG. 3, when a side force SF acts on the tire in the tire width direction when the vehicle is turning etc., the side portion acting on the side force sinks into the ground and the side opposite to the side force acting side The side portion on the side is largely deformed so as to be lifted from the ground, with the portion F 'where the gauge is thinned as a nodal point (fulcrum point) of bending. At this time, the contact length of the shoulder portion on the side sinking to the ground increases, and the force exerted by the shoulder portion increases, thereby promoting wear on the shoulder portion on the side sinking to the ground.

  In particular, in the case of a tire having a thin gauge of sidewall rubber, the rigidity of the sidewall is reduced and the periphery of the bead portion is likely to be largely deformed during turning, and in the tire for mini vehicles, the ratio of the rim width to the tread width is small. During turning, the bead portion is likely to be deformed significantly, and in either case, the contact length of the shoulder portion is significantly increased, and uneven wear is more pronounced. Therefore, in tires with thin gauge of sidewall rubber, and tires for mini vehicles, higher non-uniform wear resistance is required than that of conventional tires for passenger cars, which is obtained by regulating the shape of the tread surface. It is done.

  As a method of suppressing large deformation around the bead portion at the time of turning, there is a method of increasing the thickness of the bead portion or increasing the rigidity of the bead portion by making the material of the bead portion harder. However, in these methods, the weight of the tire is increased, and the weight saving of the tire may be impaired, and the ride comfort performance may be impaired.

  Therefore, the present invention provides a tire having a thin gauge of sidewall rubber, and a tire having a relatively small rim width for mini-vehicles, which can obtain high uneven wear resistance while maintaining the ride comfort performance. The purpose is to

The pneumatic tire according to the present invention is a pneumatic tire comprising a carcass comprising at least one layer of carcass ply straddling between a pair of bead cores and having a belt comprising a plurality of belt layers, wherein the tire is assembled to an application rim Of the carcass from the radially innermost end of the carcass in the tire radial direction outer end of the carcass in a cross section along the tire width direction in a rim assembly state in which the internal pressure is not filled substantially and unloaded. When the carcass height which is the radial direction height is h, in the rim assembled state, the tire width direction outermost end of the carcass is the tire radial direction innermost side of the carcass in the cross section along the tire width direction. The tire radial direction CWh from the end is in a tire radial direction region satisfying 0.47h <CWh <0.67h, and the carcass has 2 or more. The portion between the overlapping end position on the radial direction straight line parallel to the tire equatorial plane through the tire width direction outer end of the overlapping region where the belt layer of the tire overlaps in the tire radial direction and the tire width direction outermost end A first arc connecting a radial straight line and an axial straight line parallel to the tire rotation axis through the outermost end of the tire width direction, a first arc having a radius of curvature of 0.36 h, the radial straight line and the axial straight line And a second arc parallel to the first arc and located in an arc-like region sandwiched by a second arc having a radius of curvature of 0.42 h.
According to the present invention, even in a tire having a thin gauge of sidewall rubber or a tire having a relatively small rim width for mini-vehicles, a pneumatic tire having high uneven wear resistance while maintaining ride comfort performance. Can be provided.

The “application rim” is an industrial standard effective for the area where the tire is produced and used, and in Japan, JATMA (Japan Automobile Tire Association) JATMA YEAR BOOK, in Europe ETRTO (The European Tire and Rim STANDARDS MANUAL of Technical Organization, YEAR BOOK etc. of TRA (The Tire and Rim Association, Inc.) in the US, Standard rims in application size (Measuring Rim in STANDARDS MANUAL in ETRTO, Design in YEAR BOOK in TRA, Design in TRA) Refers to the Rim).
"Substantially no internal pressure is filled" means that the internal pressure of the tire is very low, for example, 30 to 50 kpa, which is the minimum required for the tire to support its own load and maintain its rim assembled shape. Points to the case.

The "outer end of the carcass in the tire width direction" is the outermost end of the ply in the tire radial direction when the carcass is composed of a plurality of plies. When the carcass has a main body portion and a folded back portion, it is the outermost end in the tire width direction of the main body portion. Furthermore, when the tire width direction outermost end of the carcass extends in the tire radial direction, it points to the center thereof.
When the carcass is composed of a plurality of plies, the “carcass innermost tire radial end” is the tire radial innermost end of the ply innermost in the tire radial direction. In addition, when the carcass extends in the tire width direction at the innermost end in the tire radial direction, it indicates the center thereof.
In addition, unless otherwise specified, the definition by the carcass in the case where the carcass has the main body portion and the folded back portion is based on the outer surface in the tire width direction of the main body portion of the carcass.

In the pneumatic tire according to the present invention, when the tire is assembled to the application rim and is in a rim assembly state in which the internal pressure is not substantially filled and unloaded, the rim assembly state in the cross section along the tire width direction An acute angle θ between a straight line parallel to the axis of rotation of the tire and an inclined straight line connecting the outermost end of the carcass in the tire width direction and the innermost end of the carcass in the tire radial direction in a cross section along the tire width direction. Is θ ≧ 63 °, and in the rim assembled state, the carcass has a portion between the outermost end in the tire width direction and the innermost end in the tire radial direction in a cross section along the tire width direction, It is preferable to exist in a virtual region sandwiched by two parallel straight lines having a distance of 0.045 h from the inclined straight line.
As a result, when the side force is applied to the tire, the change in the contact shape around the bead portion becomes small, and it is possible to further suppress the uneven wear of the shoulder portion.

  In the pneumatic tire according to the present invention, it is preferable that a value RW / TW obtained by dividing the rim width RW (mm) by the nominal cross section width TW (mm) of the tire is smaller than 0.78. The configuration of the present invention produces a remarkable effect in a tire whose value of RW / TW is smaller than 0.78, in which deformation around the bead portion at the time of turning is large.

Here, the “specified internal pressure” refers to the air pressure corresponding to the maximum load capacity in the application size prioritization described in the above-mentioned JATMA YEAR BOOK and the like.
"Rim width" refers to the nominal dimension of the rim width of the application rim.
"Nominal of section width of tire" is, for example, the nominal width of the section width of the tire for each tire size specified in JATMA Year Book, for example, when the expression of the tire size is "195 / 65R15" The width obtained by adding a unit millimeter to "195". In addition, when the area where the tire is produced or used is an area other than Japan, the nominal width refers to one that conforms to the industrial standard applied to the area.

  According to the present invention, even in a tire having a thin gauge of sidewall rubber or a tire having a relatively small rim width for mini-vehicles, a pneumatic tire having high uneven wear resistance while maintaining ride comfort performance. Can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS It is tire width direction sectional drawing which shows one Embodiment of the pneumatic tire of this invention. It is a figure which shows typically the example of the several belt layer which comprises a belt. It is a tire width direction sectional view for explaining modification at the time of side force operation of a pneumatic tire.

  Embodiments of the present invention will be illustrated and described below with reference to the drawings.

  FIG. 1 shows one embodiment of the pneumatic tire of the present invention (hereinafter sometimes referred to simply as "tire"). In the example of FIG. 1, the structure of the tire is symmetrical with respect to the tire equatorial plane C, but may be asymmetric with respect to the tire equatorial plane C.

  The tire shown in FIG. 1 is continuous from the tread portion 1, a pair of sidewall portions 2 extending inward in the tire radial direction from both end portions in the tire width direction of the tread portion 1 and the sidewall portions 2 respectively in the tire radial direction It consists of a pair of bead portions 3. This tire comprises a bead core 4a and a bead filler 4b embedded in the bead portion 3 and a carcass 5 including at least one layer (one layer in the example of the figure) extending in a toroidal manner between the bead cores 4a. , Equipped. The carcass ply is a radial carcass formed by rubber-coating a cord made of steel or organic fiber. In the example of the figure, the carcass 5 extends from both ends of the main body portion 5a extending in a toroidal shape between the bead cores 4a and both ends of the main body portion 5a, from the inner side in the tire width direction to the outer side in the tire width direction around the bead core 4a. And a pair of folded back portions 5b.

  In the tire according to the embodiment of the present invention shown in FIG. 1, the belt 6 and the tread rubber 7 consisting of a plurality of belt layers are sequentially disposed on the tread portion 1 outside the crown region of the carcass 5 in the tire radial direction. On the outer surface of the tread rubber 7, for example, a tread pattern including a plurality of (three in FIG. 1) circumferential grooves 1a extending in the tire circumferential direction is formed.

  In the following, the dimensions and the shape of the tire in a cross section along the tire width direction will be described in the unloaded state where the tire is assembled to the application rim and the internal pressure is not substantially filled.

The tire according to the embodiment of the present invention has a cross section taken along the tire width direction shown in FIG. When the carcass height which is the tire radial direction height from the tire radial direction innermost end of the carcass in the tire radial direction outer side end of the carcass in a cross section is h, the tire width direction outermost end CW of the carcass 5 However, it is necessary that the tire radial direction height CWh from the tire radial direction innermost end B of the carcass is within the tire radial direction region satisfying 0.47 h <CW h <0.67 h.
If the tire radial direction height CWh from the tire radial direction innermost end B of the carcass 5 at the tire lateral direction outermost end CW of the carcass 5 is 0.47 h or less, a side force at the time of turning is applied to the tire In addition, the carcass 5 tends to be shaped such that the portion of the main body portion 5a of the carcass 5 in the vicinity of the bead portion 3 falls to the ground, and deformation of the periphery of the bead portion 3 at the time of turning can not be sufficiently suppressed.
In addition, when the tire radial direction height CWh from the tire radial direction innermost end B of the carcass 5 at the tire lateral direction outermost end CW of the carcass 5 is 0.67 h or more, an increase in carcass tension becomes large, and beads Concerns about deterioration of durability may arise.
On the other hand, the tire width direction outermost end CW of the carcass 5 is in the tire radial direction region where the tire radial direction height CWh from the tire radial direction innermost end B of the carcass 5 satisfies 0.47h <CWh <0.67h In some cases, the curvature of the portion of the main body 5a of the carcass 5 in the sidewall portion 2 is increased as a whole, so that the local decrease in tension in the portion is suppressed, and thus the side force action It is possible to suppress the deformation of the tire at times.

  In the present invention, as in the embodiment shown in FIG. 1, when the tire is assembled to the application rim and in a rim assembly state in which the internal pressure is not substantially filled and no load is applied, the cross section along the tire width direction The carcass 5 passes through the tire width direction outer end ME of the overlapping region M where two or more belt layers overlap in the tire radial direction, and the overlapping end portion position CE on the radial direction straight line SL parallel to the tire equatorial plane C The portion between the tire width direction outermost end CW and the radial direction straight line SL and the axial direction straight line HL parallel to the tire rotation axis passing through the tire width direction outermost end CW, has a curvature radius of 0. And a second arc R2 having a radius of curvature of 0.42 h by connecting between the radial straight line SL and the axial straight line HL in parallel with the first arc R1. In the arc-shaped region T sandwiched by To, it is necessary.

Hereinafter, the operation and effect of the tire of the present embodiment will be described.
In the conventional tire in which the carcass 5 exists outside the region T, the carcass 5 is deformed to the inside of the tire by filling the internal pressure. In addition, since the shoulder portion grows in diameter due to the internal pressure, the belt tension of the shoulder portion is increased. Therefore, in the conventional tire, the bending rigidity of the shoulder portion due to the carcass 5 is reduced, so bending deformation due to side force is likely to occur, and the shoulder contact length tends to be large.
In the embodiment of the present invention, by disposing the main body portion 5a of the carcass 5 in the region T, the carcass 5 does not deform at the time of internal pressure filling, or deforms at the time of internal pressure to the tire outer side. Further, in the shoulder portion, since the diameter growth due to the internal pressure is suppressed, the belt tension of the shoulder portion is not increased, and the tension of the carcass 5 is increased. Therefore, in the embodiment of the present invention, the bending rigidity of the shoulder portion by the carcass increases and the buttress portion mainly bears the bending deformation due to the side force.
Therefore, even if deformation occurs due to a side force at the time of turning, the buttress portion can bear most of the bending deformation due to the side force, and the shoulder portion does not deform following the deformation of the buttress portion, so the turning At the same time, it is possible to suppress a change in the ground contact shape in which the shoulder portion is pushed inward in the tire width direction. Therefore, it can suppress that the contact length of the shoulder part at the time of turning becomes long, and can suppress the partial abrasion of a shoulder part.

  As described above, according to the tire of the present embodiment, high uneven wear resistance is maintained while maintaining the ride comfort performance even in a tire having a thin gauge of sidewall rubber and a tire having a relatively small rim width for mini-vehicles. Can be obtained.

  In order to further increase the difference in tension between the portion of the carcass 5 in the arc-shaped region T and the portion of the carcass 5 that is on the inner side in the tire width direction from the overlapping end position CE, a belt comprising a plurality of belt layers The tension of 6 may be weakened. By reducing the tension of the belt 6 composed of a plurality of belt layers, the tension of the portion of the carcass 5 in the region where the belt 6 exists is increased, and the tension difference between the buttress portion and the portion of the carcass 5 is further increased. Is possible.

The specific configuration of the plurality of belt layers of the belt 6 is, for example, as shown in FIG. 1 and FIG. 2A, formed of cords inclined with respect to the tire circumferential direction, and the cords intersect each other between layers In the configuration including two inclined belt layers having different dimensions in the tire width direction, at least the shoulder portion has a portion not covered by the circumferential cord layer, so in a conventional tire having a belt of these structures, the shoulder portion The contact length of the shoulders is likely to extend in the circumferential direction and the partial wear of the shoulders is likely to deteriorate. However, according to one embodiment of the present invention, even in a tire having a portion not covered by the circumferential cord layer in the shoulder portion, the uneven wear of the shoulder portion is sufficiently maintained while maintaining the lightness and ride comfort performance of the tire. Can be suppressed.
Also, as shown in FIG. 2B, a belt reinforcing layer (layer layer) comprising two inclined belt layers in which cords cross each other between layers and a circumferential cord covering only the end of the inclined belt layer And the like. In the structure as shown in FIG. 2 (b), since the number of circumferential members that bear the tension increases, the carcass tension in the shoulder portion decreases. In addition, since the diameter growth of the shoulder portion due to the internal pressure is suppressed by the layer layer, the contact length of the shoulder portion is hard to be large in the contact shape at the time of pressing and in the straight ahead state of the vehicle without side force input. However, as described above, since the carcass tension is lowered, when the side force is input, the bending rigidity by the carcass of the shoulder portion becomes small, so bending deformation easily occurs and the shoulder contact length tends to be large. Uneven wear is likely to deteriorate. However, according to one embodiment of the present invention, it is possible to sufficiently suppress uneven wear of the shoulder portion while maintaining the lightness and riding comfort performance of the tire.
In addition, it is commonly used for tires for passenger cars, from two inclined belt layers in which cords cross each other between layers, and a circumferential cord layer covering most of the inclined belt layers across the tire equatorial plane. It is a matter of course that the belt reinforcement layer can be provided (FIG. 2 (c)).

Further, when the belt 6 includes the inclined belt layer, the width of the maximum-width inclined belt layer of which the belt layer end is at the outer side in the tire width direction among the inclined belt layers of one or more layers 90% to 115% of the tread width which is the maximum width in the tire width direction of the contact surface when a prescribed internal pressure is applied and a maximum load load is applied, and more preferably 100% to 105% .
As cords for the belt layer, it is most common to use metal cords, in particular steel cords, but it is also possible to use organic fiber cords. The steel cord is mainly composed of steel and can contain various trace inclusions such as carbon, manganese, silicon, phosphorus, sulfur, copper, chromium and the like.
The cord may be a monofilament cord or a cord in which a plurality of filaments are twisted. Various designs can be adopted for the twist structure, and various cross-section structures, twist pitches, twist directions, and distances between adjacent filaments can be used. Furthermore, by adopting a cord in which filaments of different materials are wound together, the cross-sectional structure is not particularly limited, and various twist structures such as single twist, layer twist, and double twist can be taken.
The inclination angle of the cord is preferably 10 ° or more, and particularly preferably 30 ° or less with respect to the tire circumferential direction.
The number of implanted cords is generally in the range of 15 to 60/50 mm, but is not limited to this range.

Further, when the belt 6 comprising a plurality of belt layers is assembled to the applicable rim and is not loaded with the prescribed internal pressure and not filled with the specified internal pressure, the width of the maximum width inclined belt layer (the outer end of the inclined belt layer in the tire width direction Is preferably 90% to 115% of the tread width, and more preferably 100% to 105%.
Moreover, it is preferable that MW (mm) is 80%-100% of tread width about the width-of-tire direction dimension of the overlap area | region M.

  Furthermore, as in the embodiment shown in FIG. 1, one embodiment of the present invention is assembled to the application rim and filled with a prescribed internal pressure and unloaded, and the outermost end CW of the carcass 5 in the tire width direction and the carcass 5, an inclined straight line AL connecting the tire radial direction innermost end B and a straight line parallel to the tire rotation axis (in FIG. 1, shown by a straight line connecting the tire radial direction innermost ends B of the carcass 5 The acute angle θ with θ) is θ ≧ 63 °, and the main body portion 5a of the carcass 5 has a portion between the outermost end CW in the tire width direction and the innermost end B in the tire radial direction from the inclined straight line AL Preferably, it is within a region L surrounded by two parallel straight lines IL1 and IL2 having a distance of 0.045 h.

  When an acute angle θ between a slope straight line AL connecting the tire width direction outermost end CW of the carcass 5 and a tire radial direction innermost end B of the carcass 5 and a straight line parallel to the tire rotation axis becomes smaller than 63 °, The carcass 5 is likely to be shaped such that the portion of the main body portion 5a of the carcass 5 in the vicinity of the bead portion 3 falls to the ground, and deformation of the periphery of the bead portion 3 at the time of turning can not be sufficiently suppressed.

On the other hand, in the embodiment shown in FIG. 1 of the present invention, a slope straight line AL connecting the tire width direction outermost end CW of the carcass 5 and the tire radial direction innermost end B of the carcass 5 and a straight line parallel to the tire rotation axis Since the acute angle θ with that is θθ63 °, the portion of the main body portion 5a of the carcass 5 between the tire width direction outermost end CW of the carcass 5 and the tire radial direction innermost end B of the carcass 5 is In FIG. 1, a straight line connecting the tire radial direction innermost ends B of the carcass 5 is present in a more standing state.
Therefore, the deformation of the bead portion 3 when a side force is applied to the bead portion 3 at the time of turning can be made a deformation approximating a rigid body centered on the bead portion 3. Therefore, the main body portion 5a of the carcass 5 does not have a shape which falls down to the ground, and the moment applied to the bead portion 3 can be further reduced. Therefore, the rigidity of the entire bead portion 3 is secured. Can be sufficiently suppressed.

  In addition, if a portion existing outside region L between tire width direction outermost end CW of carcass 5 and tire radial direction innermost end B exists in main body portion 5 a of carcass 5, tire width direction outermost end CW The main body portion 5a of the carcass 5 between the tire and the tire radial direction inner end B can not be shaped so as to extend substantially along the inclined straight line AL, so that the tension is lowered, and the side force is exerted. The deformation of the bead portion 3 can not be sufficiently suppressed. In the case where the portion of the main body portion 5a of the carcass 5 between the outermost end CW in the tire width direction and the innermost end B in the tire radial direction exists outside the region L, particularly on the outer side in the tire width direction. The portion of the main body portion 5a of the carcass 5 in the vicinity of the bead portion 3 is likely to be shaped to fall to the ground, so that deformation around the bead portion 3 at the time of turning can not be sufficiently suppressed.

  On the other hand, in the embodiment shown in FIG. 1 of the present invention, the portion of the main body 5a of the carcass 5 between the tire width direction outermost end CW and the tire radial direction innermost end B has a distance of 0 from the inclined straight line AL. Since it exists in the area L surrounded by two parallel straight lines IL1 and IL2 which are parallel 045 h, the carcass 5 in the bead portion 3 is not largely bent and is closer to a straight line substantially along the inclined straight line AL. Since it becomes a shape, the tension | tensile_strength of the main-body part 5a of the carcass 5 in the bead part 3 can be maintained, and a deformation | transformation of the bead part 3 at the time of side-force effect | action can be fully suppressed.

  In the tire of the present invention, it is preferable that a value RW / TW obtained by dividing the rim width RW (mm) by the nominal cross section width of the tire TW (mm) is smaller than 0.78. In such a tire, since the ratio of the rim width to the tread width is generally smaller than that of the other tires, the deformation around the bead portion 3 at the time of turning is generally larger than that of the other tires. Therefore, the configuration of the present invention for suppressing the deformation around the bead portion 3 is remarkable in the pneumatic tire in which the value of RW / TW is smaller than 0.78 where the deformation around the bead portion 3 at the time of turning becomes large. Play an effect.

Further, in the present invention, in addition to the above-mentioned tire size regulations, when the tire is assembled to the applicable rim and filled with a prescribed internal pressure and in a no-load state, the tire cross section width No. TW (mm) The value TW / TR divided by the tire outer diameter TR (mm) has a remarkable effect on the uneven wear resistance of the shoulder portion in a pneumatic tire smaller than 0.31.
Here, the tire outer diameter TR can be obtained by “(tire side height) × 2 + rim width”. The “side height of tire” is a value obtained by multiplying the nominal cross section width of the tire by the nominal width ratio of the tire and dividing by 100.
In addition, "a nominal of flat ratio of tire" is, for example, a nominal width of flat ratio for each tire size specified in JATMA Year Book, and for example, when the expression of tire size is "195 / 65R15", "65 Is the value of
In a pneumatic tire whose value obtained by dividing the tire width TW (mm) by the tire outer diameter TR (mm) is smaller than 0.31, the difference in diameter between the center portion and the shoulder portion tends to be small when going straight on. Since the length tends to increase, uneven wear of the shoulder tends to be aggravated. Therefore, by applying the present invention to a tire in which the value obtained by dividing the tire width TW (mm) by the tire outer diameter TR (mm) is smaller than 0.31, the uneven wear both at the time of turning and at going straight is sufficiently made. It becomes possible to suppress.
In addition, as such a tire, a pneumatic radial tire for passenger cars is assumed, and in particular, a tire for light vehicles is assumed. Specific tire sizes are 165 / 50R15, 165 / 50R16, 155 / 55R14, 165 / 55R14, 185 / 55R14, 165 / 55R15, 175 / 55R15, 185 / 55R15, 185 / 55R16, 175 / 60R13, 185 / 60R13, 165 / 60R14, 175 / 60R14, 185 / 60R14, 155 / 60R15, 165 / 60R15, 175 / 60R15, 185 / 60R15, 175 / 60R16, 185 / 60R16, 155 / 65R12, 145 / 65R13, 155 / 65R13, 165 / 65R13, 145 / 65R14, 155 / 65R14, 165 / 65R14, 175 / 65R14, 185 / 65R14, 145 / 65R15, 165 / 65R15, 175 / 65R15, 185 / 65R15, 145 / 70R12, 155 / 70R12, 165 / 65R15 70R12, 175 / 70R12, 145 / 70R13, 155 / 70R13, 165 / 70R13, 175 / 70R13, 185 / 70R13, 165 / 70R14, 175 / 70R14, 185 / 70R14, 135 / 80R12, 145 / 80R12, 155 / 80R12, The sizes of 135/80 R13, 145/80 R13, 155/80 R13, 165/80 R13, 175/80 R13, 165/80 R14, 175/80 R14, 185/80 R14, 175/80 R15, 175/80 R16 can be exemplified.

  Furthermore, in the present invention, the dimension of the bead filler 4b in the tire radial direction is preferably 5% to 20%, and more preferably 5% to 10% of h. In the present invention, even if the shape, material, and the like of the bead filler 4b are not changed, the deformation of the bead portion 3 at the time of side force action can be sufficiently suppressed. Therefore, assuming that the size of the bead filler 4b in the tire radial direction is in such a range, the bead filler 4b has a dimension of 5% or more in the tire radial direction outer side than the vicinity of the rim flange. In addition, the bead filler 4b is miniaturized by making the size of the bead filler 4b in the tire radial direction not more than 20% and causing no bead filler 4 to be present on the tread side of the carcass maximum width height. A balance with weight reduction can be achieved. In the conventional tire, when the above-described small bead filler is used, the steering stability tends to decrease, and a reinforcing cord layer may be provided in the vicinity of the bead filler to compensate for the steering stability. However, in the present invention, steering stability can be compensated by the shape of the ply without requiring additional members such as a reinforcing cord layer, and compatibility with a small bead filler is possible.

  In the present invention, as in the embodiment shown in FIG. 1, the surface of the crown of the tread portion 1 in the cross section in the tire width direction does not have a flat crown shape parallel or substantially parallel to the rotation axis of the tire. It is possible to sufficiently suppress uneven wear of the shoulder portion. In this case, “substantially parallel” in this case indicates that, for example, the dimensional difference between the tire radius at the tread end and the tire radius at the equatorial plane (so-called drop width) is within 9% of the tread width. It is.

  In the present invention, as in the embodiment shown in FIG. 1, the plurality of belt layers of the belt 6 are not parallel or substantially parallel to the rotation axis of the tire in the tire radial cross section, for example, the width direction of the belt Since the end is inclined inward in the tire radial direction, the tire radial position of the belt at the tire width direction outer end ME of the overlapping region M is different from the tire radial position of the belt at the tire equatorial plane position Is preferred. In this way, the belt tension borne by the plurality of belt layers is reduced, so the tension of the ply at the tire width direction outer end ME of the overlapping area M becomes large, and the tension difference with the carcass 5 portion of the buttress portion The steering stability can be further improved. In this case, the tire width direction dimension of the overlapping area M is MW (mm), and the tire radial direction position of the belt at the tire width direction outer end ME and the tire radial direction position of the belt at the tire equatorial plane position When the dimensional difference (belt falling width in the tire radial direction) is ED (mm), ED / MW is preferably 5% or more and 10% or less.

  Furthermore, in the present invention, when the carcass 5 includes the folded portion 5 b, the folded portion 5 b is preferably in the region L. In this case, the entire carcass including the carcass folded-back portion 5b is present in a more standing state with respect to the straight line connecting the tire radial direction innermost ends B of the carcass in FIG. Can be further suppressed.

Hereinafter, examples of the present invention will be described. Example tires 1 to 4 and comparative example tires 1 to 2 were produced under the specifications shown in Table 1 to evaluate uneven wear resistance performance and ride comfort performance. The tires according to Examples 1 to 2 and Comparative Example 2 have a tire size of 195 / 65R15 and a rim of 6J. In the tires according to Examples 3 to 4 and Comparative Example 1, the tire size is 155/65 R14, and the rim is 4.5 J.
As shown in FIG. 1, each tire is composed of a carcass engaged with a bead core embedded in a pair of bead portions and a two-layer inclined belt layer provided on the tire radial direction outer side of the crown portion of the carcass. And a tread rubber 7.

(Uneven wear resistance)
The load was the same as when traveling on the cant road surface, and the wear drum test was performed to reproduce the worn state in the room. Specifically, the vehicle travels 5000 km at a constant speed of 70 km / h on a cant road surface having an inclination angle of 0.2 ° with respect to the horizontal direction from the road surface end toward the center of the road surface. Then, in each of the tire center area and the main groove in the shoulder area, the groove depth at the time of new article and the groove depth after wear are measured, and the wear life of each groove is calculated from this result. It evaluated by the ratio of the wear life of a shoulder area. The abrasion resistance value in Table 1 is the numerical value of the index of the abrasion life ratio of each tire to the value of the abrasion life ratio in Comparative Example 1 ((Abrasion life ratio of each tire / wear in Comparative Example 1 The ratio of life) × 100), and the smaller the value of this index, the more difficult it is for shoulder uneven wear, that is, better uneven wear resistance. The main groove in the tire center area referred to here is the circumferential main groove on the tire equatorial plane C of FIG. 1, and the groove in the shoulder area is the circumferential main groove on the outermost side in the tire width direction. is there.

(Comfortability)
The test driver travels on five types of road surfaces with different pavement roughness on the dry road course, and the test driver feels about the riding comfort of the running tire based on the vibration and sound transmitted to the vehicle interior. I made an evaluation. The ride comfort values in Table 1 are numerical values of the ratio of the ratio of vibration and sound transmitted to the passenger compartment of each tire to the ride comfort value in Comparative Example 1 (( Vibration and sound size / vibration and sound size in Comparative Example 1) × 100). The smaller the value of this index, the smaller the vibration and sound, which means that the ride comfort is better.

  As is clear from the results shown in Table 1, in all of the example tires 1 to 4, the uneven wear resistance is improved without lowering the ride comfort performance as compared with the comparative example tires 1 and 2. There is. From this, it was found that according to the pneumatic tire of the present invention, high uneven wear resistance can be obtained while maintaining the ride comfort performance.

1: Tread part, 1a: circumferential groove, 2: sidewall part, 3: bead part, 3a: bead heel, 4: bead, 4a: bead core, 4b: bead filler 5: carcass, 5a: main body part, 5b: folded part , 6: Belt, 7: Tread rubber, AL: inclined straight line, B: radial innermost end of carcass, C: tire equatorial plane, CE, overlapping end position, CW: outermost end of carcass in tire width direction, CWh: Height of the outermost end of the carcass in the tire width direction h: Carcass height, HL: Axial straight line, L: Virtual area, M: Overlapping area, ME: Tire width direction outer end, R1: First arc , R2: second arc, SF: side force, SL: radial straight line, T: arc-like area,

Claims (4)

A pneumatic tire comprising a carcass comprising at least one carcass ply straddling between a pair of bead cores and having a belt comprising a plurality of belt layers,
In a rim assembly state where the tire is assembled to the application rim and is not loaded with substantially no internal pressure, the tire radial direction of the carcass of the tire radial direction outer end of the carcass in a cross section along the tire width direction When the carcass height which is the tire radial direction height from the innermost end is h,
In the rim assembled state, in the cross section along the tire width direction, the tire width direction outermost end of the carcass has a tire radial direction height CWh from the tire radial direction innermost end of the carcass of 0.47h <CWh < In the tire radial direction area satisfying 0.67 h,
The carcass has an overlapping end position on a radial straight line parallel to the tire equatorial plane passing through the tire width direction outer end of an overlapping region where two or more belt layers overlap in the tire radial direction, and the tire width direction outermost end A first arc having a radius of curvature of 0.36 h and connecting the radial straight line and the axial straight line parallel to the tire rotation axis passing through the outermost end in the tire width direction; Between the straight line and the axial straight line, in parallel with the first arc, a circular arc-shaped region sandwiched by a second arc having a radius of curvature of 0.42 h ,
When the tire is assembled to the application rim and in a rim assembly state in which the inner pressure is not substantially filled and no load is applied, in a cross section along the tire width direction,
In the rim assembled state, in a cross section along the tire width direction, an inclined straight line connecting the outermost end in the tire width direction of the carcass and the innermost end in the tire radial direction of the carcass and a straight line parallel to the tire rotation axis The acute angle θ with that is θ ≧ 63 °,
In the rim assembled state, in the cross section along the tire width direction, the carcass has a portion between the outermost end in the tire width direction and the innermost end in the tire radial direction at a distance of 0. 0 from the inclined straight line. A pneumatic tire characterized by existing in a virtual region sandwiched by two parallel straight lines which are 045 h .   The pneumatic tire according to claim 1, wherein a value RW / TW obtained by dividing the rim width RW (mm) by the nominal cross section width of the tire TW (mm) is smaller than 0.78. Equipped with bead filler,
The pneumatic tire according to claim 1 or 2, wherein a dimension of the bead filler in a tire radial direction is 5% to 20% of the carcass height h. A tire width direction dimension of the overlapping area is MW (mm), and a tire radial position of the belt at the tire width direction outer end of the overlapping area and a tire radial position of the belt at a tire equatorial plane position The pneumatic tire according to any one of claims 1 to 3, wherein ED / MW is 5% or more and 10% or less when the dimensional difference in the radial direction is ED (mm).

Images