JP5809655B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire with improved early wear performance of a shoulder portion without deteriorating noise performance.

  Pneumatic tires, particularly pneumatic tires for passenger cars, tend to be flattened by, for example, 70% or less with the recent increase in output and speed of vehicles. And, the tread contour shape X1 of such a low-flat tire, that is, the contour line X1 of the outer surface of the tread portion in the tire meridional section is conventionally, as shown in FIG. A plurality of arcs having different curvature radii r are connected and formed so as to be small (see, for example, Patent Documents 1 and 2).

  However, in the tire having such a tread contour shape X1, the tire radius Tr is greatly reduced on the tread contact edge Te side, and the slip amount with the road surface is increased. Therefore, there is a problem that the wear rate of the shoulder portion Sh becomes relatively fast, and the lateral groove arranged in the shoulder portion is worn away at an early stage.

  In order to delay the wear of the horizontal groove, it is conceivable to increase the groove depth of the horizontal groove. However, when the groove depth is increased, the noise performance is deteriorated and the block rigidity of the shoulder portion is reduced, so that the deformation amount is reduced. Increases the wear resistance.

JP-A-10-181309 Japanese Patent Laid-Open No. 10-287106

  Therefore, the present invention is based on the concept that the tread contour shape is formed by a single arc and the angle of the lateral groove provided in the shoulder portion with respect to the tire circumferential direction, the groove depth, the inner end position, and the like are basically controlled. An object of the present invention is to provide a pneumatic tire that can enhance wear performance and can suppress early wear of the lateral grooves without deteriorating noise performance.

The invention according to claim 1 of the present invention is a pneumatic tire having a tire flatness ratio of more than 55% and less than 70%, which is assembled to a normal rim and filled with an internal pressure of 5% of the normal internal pressure. In the tire meridional section in the 5% internal pressure state, the contour line of the surface of the tread portion forms an arc having a single radius of curvature R, and the radius of curvature R is a ground contact width that is the tire axial width between the tread ground contact edges. A circumferential main groove including a shoulder circumferential main groove that is 3.0 to 4.5 times the width TW1 and extends continuously in the tire circumferential direction and is arranged on the outermost side in the tire axial direction on the tread portion; Provided in a shoulder land portion disposed on the outer side in the tire axial direction of the shoulder circumferential main groove and extending from the outer side in the tire axial direction to the inner side in the tire axial direction of the tread contact edge, and the inner end in the tire axial direction is the shoulder A plurality of shoulder lateral grooves that are interrupted in the section, the shoulder lateral grooves having an angle α with respect to the tire circumferential direction in a range of 80 to 90 °, and a tire between an inner end in the tire axial direction and the shoulder circumferential main groove The axial distance Ds is in the range of 3.5 to 5.5 mm, the shoulder lateral groove has a deepest portion where the groove depth is maximum, and the groove depth of the deepest portion is the shoulder circumferential main. 70 to 90% of the groove depth of the groove, and the shoulder lateral groove includes a first inclined portion in which the groove depth gradually increases from the inner end in the tire axial direction toward the outer side in the tire axial direction, and the first inclined portion. And a constant depth portion extending at a constant groove depth, wherein the constant depth portion is the deepest portion, and the tire axial direction length of the first inclined portion is defined as a tire axis of the shoulder lateral groove. Tire axial direction from the inner edge of the direction to the tread contact edge And characterized in that 25 to 50% of the length.

  In the invention according to claim 2, the shoulder land portion includes a shoulder narrow groove extending in the tire circumferential direction through an inner end in the tire axial direction of the shoulder lateral groove and narrower than the shoulder main groove, The groove depth of the shoulder narrow groove is the same as the groove depth at the inner end in the tire axial direction of the shoulder lateral groove.

  The invention according to claim 3 is characterized in that a ratio TW1 / TW0 of a ground contact width TW1 which is a tire axial width between the tread ground edges and a tire cross-sectional width TW0 is 0.73 to 0.79. And

The invention according to claim 4 is characterized in that the shoulder narrow groove has a groove depth of 2 mm or less .

  In the invention according to claim 5, the shoulder lateral groove has a groove depth of 4.0 to 5.0 mm at a tread grounding edge.

  According to a sixth aspect of the present invention, the shoulder land portion includes an arc-shaped chamfered portion at a corner portion where a tread surface and a groove wall surface of the shoulder circumferential main groove intersect.

  Here, the tire shape in the “5% internal pressure state” is generally substantially the same as the tire shape in the vulcanization mold. By specifying the shape of the vulcanization mold, the 5% internal pressure state is determined. The tire shape can be controlled. In the present specification, unless otherwise specified, the dimensions and the like of each part of the tire are values specified in the 5% internal pressure state.

  The “regular rim” is a rim determined for each tire in the standard system including the standard on which the tire is based, for example, a standard rim for JATMA, “Design Rim” for TRA, or ETRTO means "Measuring Rim". The “regular internal pressure” is the air pressure defined by the standard for each tire. The maximum air pressure for JATMA, the maximum value described in the table “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” for TRA, If it is ETRTO, it means “INFLATION PRESSURE”, but in the case of a passenger car tire, it is 180 kPa.

  The tread grounding edge is the position of the outermost end in the tire axial direction of the tread grounding surface that comes into contact when a regular load is applied to a tire that is assembled with a regular rim and filled with a regular internal pressure. Is the load defined by the standard for each tire. If it is JATMA, it is the maximum load capacity. If it is TRA, it is the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES". If it is ETRTO, " LOAD CAPACITY ".

In the present invention, as described above, the contour line of the surface of the tread portion is formed by an arc having a single radius of curvature. Therefore, it is possible in the shoulder land portion, the ratio of the tire radius variation can be reduced, to reduce the difference in slip between the road surface with respect to differences in the positions in the tire axial direction relative.

  In addition, since the angle α of the shoulder lateral groove with respect to the tire circumferential direction is set to 80 to 90 ° and is close to the tire axial direction, for example, the corner portion sandwiched between the shoulder lateral groove and the shoulder circumferential main groove becomes a sword tip and the origin of wear Can be prevented. Moreover, since the inner end in the tire axial direction of the shoulder lateral groove is separated from the shoulder circumferential main groove, the rigidity of not only the corner portion but also the entire shoulder land portion can be increased. Therefore, even when the groove depth of the deepest part of the shoulder lateral groove is 70 to 90% of the groove depth of the shoulder circumferential main groove, which is deeper than before, the reduction in rigidity can be suppressed to a low level. Combined with the effect of reducing the amount of slip due to the single circular arc of the contour shape, the shoulder lateral groove can be deepened while improving the early wear performance, and early wear of the shoulder lateral groove can be suppressed.

  Further, the deterioration of noise performance due to the deepening of the shoulder lateral groove is suppressed by separating the inner end of the shoulder lateral groove from the shoulder circumferential main groove.

  In addition, the first inclined part can smoothly change the rigidity, such as the groove depth gradually changing over a wide range, ensuring a large groove depth at the deepest part and suppressing early wear of the shoulder lateral groove. However, it is possible to suppress the occurrence of uneven wear starting from the vicinity of the inner end in the tire axial direction. Further, the deepest portion can be formed in a wide range by the constant depth portion, and high drainage can be exhibited.

It is sectional drawing which shows one Example of the pneumatic tire of this invention. It is a diagram which shows a tread outline shape. It is an expanded view which expands and shows the tread pattern of the pneumatic tire on a plane. It is an expanded view which expands and shows a shoulder land part. It is an expanded view which expands and shows a middle land part. (A) is a sectional view taken along the line II of the shoulder lateral groove passing through the center of the groove width, and (B) is a sectional view taken along the line II-II passing through the center of the middle inclined groove. It is an expanded view which shows the other example of a tread pattern. It is sectional drawing which shows an example of the tread outline shape of the conventional tire.

  Hereinafter, embodiments of the present invention will be described in detail. FIG. 1 is a meridional section of a tire in a 5% internal pressure state in which the pneumatic tire 1 of the present invention is assembled to a normal rim 30 and is filled with an internal pressure of 5% of the normal internal pressure. In FIG. 1 includes a carcass 6 extending from the tread portion 2 through the sidewall portion 3 to the bead core 5 of the bead portion 4, and a belt layer 7 disposed on the inner side of the tread portion 2 and on the radially outer side of the carcass 6. Yeah.

  As the carcass 6 and the belt layer 7, those having the same structure as that of the conventional tire can be suitably employed. In this example, the carcass 6 has a carcass cord at an angle of 75 ° to 90 ° with respect to the tire circumferential direction. The case where it forms from one arranged carcass ply 6A is illustrated. The carcass ply 6A includes a series of ply turn-up portions 6b that are turned from the inner side to the outer side in the tire axial direction around the bead core 5 at both ends of the toroidal ply main body portion 6a straddling the bead cores 5 and 5. Between the ply body portion 6a and the ply turn-up portion 6b, a bead apex rubber 8 for bead reinforcement that extends from the bead core 5 outward in the tire radial direction is disposed.

  In the present example, the belt layer 7 is formed of, for example, two belt plies 7A and 7B in which the belt cord is arranged at, for example, about 10 to 35 ° with respect to the tire circumferential direction. By crossing the plies between each other, the belt rigidity is enhanced, and the substantially entire width of the tread portion 2 is strongly reinforced with a tagging effect. A band layer 9 having a known structure in which a band cord is spirally wound in the circumferential direction can be provided on the outer side in the radial direction of the belt layer 7 for the purpose of improving high-speed durability and the like.

  This pneumatic tire 1 is a flat tire having a tire flatness ratio of more than 55% and less than 70%, and in the meridional section of the tire in the 5% internal pressure state, as shown in FIG. An outline X of 2S (sometimes referred to as a tread surface 2S) is formed by an arc having a single radius of curvature R. In this way, the tread contour shape X of the flat tire having the flattening ratio in the above range is a single arc, so that the tire ground contact can be achieved as compared with the tread contour shape X1 (indicated by a one-dot chain line) of the conventional flat tire. The change ratio ΔTr of the tire radius on the end side can be kept small, and the difference in the slip amount from the road surface with respect to the difference in the position in the tire axial direction can be made relatively small. The ratio TW1 / TW0 between the contact width TW1 which is the tire axial width between the tread contact edges Te and Te and the tire cross-sectional width TW0 is in the range of 0.73 to 0.79, and the tire flatness ratio and ratio TW1 The tread contour shape of a flat tire having a range of / TW0 in the above range has conventionally been formed by a composite arc formed by connecting a plurality of arcs. The radius of curvature R is preferably in the range of 3.0 to 4.5 times the ground contact width TW1.

  Next, as shown in FIG. 3, in the tread portion 2, a circumferential main groove 10 including a shoulder circumferential main groove 10s extending continuously in the tire circumferential direction and disposed on the outermost side in the tire axial direction, It includes a plurality of shoulder lateral grooves 12 provided in a shoulder land portion 11s arranged on the outer side in the tire axial direction of the shoulder circumferential main groove 10s.

  Specifically, in this example, as the circumferential main groove 10, four of the shoulder circumferential main groove 10s and a crown circumferential main groove 10c disposed on both sides of the tire equator Co and the tire equator Co are formed. As a result, the tread portion 2 is divided into the crown land portion 11c between the crown circumferential main grooves 10c and 10c, the middle land portion 11m between the crown circumferential main groove 10c and the shoulder circumferential main groove 10s, and the shoulder land. It is divided into parts 11s.

  The crown circumferential main groove 10c and the shoulder circumferential main groove 10s are straight grooves extending linearly in the tire circumferential direction, and are arranged at line-symmetrical positions around the tire equator Co. As the groove width Wg and the groove depth Hg (shown in FIG. 6B) of the crown circumferential main groove 10c and the shoulder circumferential main groove 10s, the groove width and groove depth of the conventional circumferential main groove are shown. For example, in the case of a passenger car tire, the lower limit of the groove width Wg is preferably 3 mm or more, more preferably 5 mm or more, and the upper limit is 14 mm or less, more preferably 12 mm or less. Is preferred. The groove depth Hg has a lower limit of preferably 5 mm or more, more preferably 6 mm or more, and an upper limit of 12 mm or less, more preferably 10 mm or less. In this example, the crown circumferential main groove 10c has a groove width Wgc of 10.5 mm, a groove depth Hgc of 8.2 mm, the shoulder circumferential main groove 10s has a groove width Wgs of 8.2 mm, and a groove depth Hgs of 8 mm. .2 mm.

  The shoulder land portion 11s is provided with a plurality of shoulder lateral grooves 12 spaced in the tire circumferential direction. As shown in FIG. 4, the shoulder lateral groove 12 extends from the outer side in the tire axial direction of the tread grounding edge Te toward the inner side in the tire axial direction, and the inner end 12i in the tire axial direction is formed in the shoulder land portion 11s. It is interrupted. The angle α on the small side of the shoulder lateral groove with respect to the tire circumferential direction is in the range of 80 to 90 °, and the tire axial distance between the tire axial inner end 12i and the shoulder circumferential main groove 10s. Ds is in the range of 3.5 to 5.5 mm. Particularly in this example, the angle αi with respect to the tire circumferential direction at the tire axial direction inner end 12i of the shoulder lateral groove 12 is set to 84 to 90 °.

  In this way, the angle α is regulated and the shoulder lateral groove 12 is made closer to the tire axial direction, so that, for example, the corner portion Q sandwiched between the shoulder lateral groove 12 and the shoulder circumferential main groove 10s becomes a sword tip and wears. Can be prevented from starting. In addition, since the inner end 12i in the tire axial direction of the shoulder lateral groove 12 is separated from the shoulder circumferential main groove 10s, not only the corner portion Q but also the entire shoulder land portion 11s can have high rigidity.

  Therefore, as will be described later, even when the groove depth H12a of the deepest portion 15 of the shoulder lateral groove 12 is made deeper than before, a reduction in rigidity can be suppressed low, and the tread contour shape is a single arc. In combination with the effect of reducing the amount of slip, the shoulder lateral groove 12 can be deepened while improving the early wear performance, and the early wear of the shoulder lateral groove 12 can be suppressed.

  That is, as shown in FIG. 6A, a cross-section taken along line I-I along the center of the width of the shoulder lateral groove 12, the shoulder lateral groove 12 has a deepest portion 15 where the groove depth H12 is maximum, and The groove depth H12a of the deepest portion 15 is set to be 70 to 90% of the groove depth Hgs of the shoulder circumferential main groove 10s, which is deeper than conventional.

  Specifically, the shoulder lateral groove 12 is connected to the first inclined portion 12A in which the groove depth H12 gradually increases from the inner end 12i in the tire axial direction toward the outer side in the tire axial direction, and the first inclined portion 12A. A constant depth portion 12B having a constant groove depth is provided, and this constant depth portion 12B is connected to a second inclined portion 12C in which the groove depth gradually decreases toward the outer side in the tire axial direction. The first inclined portion 12A is inclined linearly, and the tire axial direction length La (shown in FIG. 4) of the first inclined portion 12A is the inner end of the shoulder lateral groove 12 in the tire axial direction. The tire axial length L12 from 12i to the tread grounding edge Te is set to 25 to 50%. Further, the shoulder lateral groove 12 forms the deepest portion 15 in the constant depth portion 12B, and in this example, the groove depth H12b in the tread grounding edge Te is set to 4.0 to 5.0 mm.

  As described above, the first inclined portion 12A can smoothly change the rigidity, for example, the groove depth H12 gradually changes over a wide range, and ensures a large groove depth H12a at the deepest portion 15. While suppressing the early wear of the shoulder lateral grooves 12, it is possible to suppress the occurrence of uneven wear starting from the vicinity of the inner end 12i in the tire axial direction. Moreover, the deepest part 15 can be formed in a wide range by the constant depth part 12B, and high drainage can be exhibited.

  Further, the deepening of the shoulder lateral groove 12 causes deterioration in noise performance. However, in this embodiment, since the inner end 12i of the shoulder lateral groove 12 is separated from the shoulder circumferential main groove 10s, the compressed air from the shoulder lateral groove 12 is generated. It can be suppressed that it flows into the shoulder circumferential main groove 10s and induces noise such as air column resonance. Further, since the shoulder lateral groove 12 opens outside the tread ground edge Te, deterioration of the pumping sound in the shoulder lateral groove 12 can be suppressed.

  Here, when the angle α of the shoulder lateral groove 12 is less than 80 °, particularly when the angle αi at the inner end 12i is less than 84 °, the corner portion Q becomes a sword tip and the rigidity is lowered. Reduces early wear, such as causing uneven wear as a starting point. Also, when the distance Ds is less than 3.5 mm, the corner portion Q has insufficient rigidity to reduce early wear, and conversely, when the distance Ds exceeds 5.5 mm, drainage Is insufficient. Further, if the groove depth H12a of the deepest portion 15 is less than 70% of the groove depth Hgs of the shoulder circumferential main groove 10s, although the early wear is suppressed, the early wear is suppressed because the groove depth H12a itself is small. Difficult to do. On the other hand, if it exceeds 90%, it is too deep and the rigidity of the shoulder land portion 11s is lowered, so that the early wear resistance is lowered. If the length La of the first inclined portion 12A in the tire axial direction is less than 25% of the length L12 of the shoulder lateral groove 12, the groove depth H12 changes abruptly, that is, the rigidity change becomes large and the shoulder changes. If uneven wear starts from the vicinity of the inner end 12i of the lateral groove 12 and exceeds 50%, the drainage and the early wear of the shoulder lateral groove 12 are disadvantageous. Similarly, even if the groove depth H12b of the shoulder lateral groove 12 at the tread grounding edge Te is less than 4.0 mm, it is disadvantageous for drainage and premature wear, and conversely if it exceeds 5.0 mm, the rigidity of the shoulder land portion 11s is reduced.

  In this example, the shoulder land portion 11s includes a shoulder narrow groove 16 extending in the tire circumferential direction through the inner end 12i of the shoulder lateral groove 12. The groove width W16 of the shoulder narrow groove 16 is sufficiently smaller than the groove width Wgs of the shoulder circumferential main groove 10s, and in this example, the groove width W16 is 3 mm or less, preferably 2 mm or less. . The groove depth H16 of the shoulder narrow groove 16 is also sufficiently smaller than the groove depth Hgs of the shoulder circumferential main groove 10s. In this example, the groove depth H16 is 3 mm or less, preferably 2 mm or less. Yes. In this example, the groove depth H16 of the shoulder narrow groove 16 is the same as the groove depth H12c at the inner end 12i of the shoulder lateral groove 12.

  The shoulder land portion 11s includes an arc-shaped chamfered portion 25 at a corner portion P where the tread surface 2S and the groove wall surface of the shoulder circumferential main groove 10s intersect, and in this example, the shoulder circumferential direction main groove 10s. A similar chamfered portion 25 is also formed at the corner portion P where the groove wall surface and the tread surface 2S of the middle land portion 11m intersect. The radius of curvature of the chamfered portion 25 is about 1.5 to 3.0 mm, and suppresses uneven wear starting from the corner portion P.

  In this example, a plurality of middle inclined grooves 17 are formed in the middle land portion 11m. As shown in FIG. 5, the middle inclined groove 17 extends steeply at a small angle β of 0 to 45 ° with respect to the tire circumferential direction from the shoulder circumferential main groove 10 s toward the inner side in the tire axial direction. At the same time, the inner end 17e in the tire axial direction is interrupted in the middle land portion 11m. The tire axial distance Dm between the tire axial inner end 17e and the crown circumferential main groove 10c is preferably in the range of 1.5 to 3.5 mm, and in this example is set to be smaller than the distance Ds. ing. In this example, the circumferential length Lm of the middle inclined groove 17 is set to 72 to 84% of the circumferential pitch Pm of the middle inclined groove 17, and the circumferential pitch Pm is equal to the shoulder lateral groove 10s. It is set in the range of 2.5 to 3.5 times the circumferential pitch Ps.

  Here, the middle inclined groove 17 includes a linear groove portion 17A extending linearly at an angle β1 of 20 ° or less with respect to the tire circumferential direction on the inner side in the tire axial direction. The term “straightly extending” refers to a case where two straight lines are bent at an angle of 170 ° to 180 ° in addition to the groove width center line 17i of the middle inclined groove 17 being a straight line. included.

  Specifically, the middle inclined groove 17 of the present example has the linear groove portion 17A extending from the tire axial direction inner end 17e, and the angle β from the linear groove portion 17A to the shoulder circumferential main groove 10s. The joint groove portion 17B extends while being curved in an arc shape and / or bent in a polygonal line so as to increase sequentially toward the outer side in the tire axial direction. In this example, the linear groove portion 17A has a groove inner edge 17Ae in the tire axial direction that forms a straight line, and the circumferential length Lm1 of the linear groove portion 17A is equal to the circumferential length Lm of the middle inclined groove 17. It is set to 40 to 70%.

  As described above, the middle inclined groove 17 has a circumferential length Lm and is steeply inclined, thereby improving drainage performance such as reducing drainage resistance. Further, the inner end 17e in the tire axial direction of the middle inclined groove 17 is interrupted at a distance Dm from the crown circumferential main groove 10c, so that the circumferential rigidity of the middle land portion 11m can be ensured high, and the drainage performance can be improved. Uneven wear resistance and steering stability can be improved while exhibiting. In particular, the drainage can be further improved by forming the linear groove portion 17A in the middle inclined groove 17. Moreover, since the distance from the crown circumferential main groove 10c is smoothly reduced by the linear groove portion 17A, formation of a large rigidity change point that becomes a starting point of uneven wear can be suppressed. In particular, by forming the groove inner edge 17Ae as a straight line, formation of a rigidity change point is further suppressed, which is advantageous in uneven wear resistance. If the angle β exceeds 45 °, it is difficult to ensure sufficient drainage. Further, when the angle β1 of the linear groove portion 17A exceeds 20 ° and the circumferential length Lm1 thereof is less than 40% of the circumferential length Lm of the middle inclined groove 17, the drainage by the linear groove portion 17A. And the effect of improving the uneven wear resistance by suppressing the occurrence of the starting point of uneven wear cannot be exhibited sufficiently. On the other hand, if the distance Dm is less than 1.5 mm, the rigidity of the middle land portion 11 m is reduced, resulting in a decrease in uneven wear resistance and steering stability. Conversely, if the distance Dm exceeds 3.5 mm, the drainage is insufficient.

  The joint groove portion 17B has an angle βj of 3.5 to 4.5 ° at the intersection portion Ja with the shoulder circumferential main groove 10s out of the angle β, and thereby drainage at the intersection portion Ja. And a decrease in lateral rigidity are suppressed. If the angle βj is out of the range, the drainage at the intersecting portion Ja is reduced and the lateral rigidity is lowered.

  The middle inclined groove 17 has a groove width W17 smaller than the groove width Wgs. Further, as shown in FIG. 6B, a sectional view taken along line II-II along the center of the groove width of the middle inclined groove 17, the groove depth (depth of the deepest portion) H17 of the middle inclined groove 17 is the groove depth. Hgs or less.

  Further, the middle land portion 11m has a first drainage extending from the shoulder circumferential main groove 10s toward the inner side in the tire axial direction through the middle inclined grooves 17 and 17 adjacent in the tire circumferential direction for drainage. Second middle sub-grooves 18 and 19 are arranged. The first and second middle sub-grooves 18 and 19 are inclined at an angle γ of 4.5 ° or less similarly to the middle inclined groove 17, and the tire axial direction inner ends 18e and 19e are both middle land portions. It is interrupted within 11m. The circumferential lengths L18 and L19 of the first and second middle sub-grooves 18 and 19 are 30% or less of the circumferential length Lm of the middle inclined groove 17, respectively. It is curved in an arc shape so that the angle γ decreases toward the inside in the tire axial direction. If the lengths L18 and L19 exceed 30% of the circumferential length Lm, the rigidity of the middle land portion 11m is excessively reduced, and the steering stability is adversely affected.

  The intersection of the shoulder circumferential main groove 10s and the middle inclined groove 17 is Ja, the intersection of the shoulder circumferential main groove 10s and the first middle subgroove 18 is Jb, and the shoulder circumferential main groove 10s and the second When the intersection with the middle sub-groove 19 is Jc, the circumferential distance Q1 between the intersections Ja and Jb adjacent in the circumferential direction, the circumferential distance Q2 between the intersections Jb and Jc, and between the intersections Jc and Ja The circumferential distance Q3 is in the range of 30 to 35% of the circumferential pitch Pm of the middle inclined groove 17, and the first and second middle subgrooves 18 and 19 are located between the middle inclined grooves 17 and 17, respectively. They are arranged at almost equal circumferential intervals.

  The crown land portion 11c is provided with a plurality of crown lateral grooves 20 that cross the crown land portion 11c and are spaced apart in the tire circumferential direction in this example. The crown lateral groove 20 is a narrow groove having a groove width W20 of 0.5 to 1.0 mm in this example, and extends at an angle δ with respect to the tire circumferential direction. In this example, the angle δ is set smaller than the maximum value of the angle α and larger than the minimum value of the angle β.

  FIG. 7 shows another embodiment of the tread pattern in the pneumatic tire 1. In this example, the case where the circumferential main groove 10 is formed by three of the shoulder circumferential main groove 10s and the crown circumferential main groove 10c arranged on the inner side and on the tire equator Co is shown. Therefore, the tread portion 2 of this example is divided into a middle land portion 11m between the crown circumferential direction main groove 10c and the shoulder circumferential direction main groove 10s, and four land portions of the shoulder land portion 11s. The land portion 11c is deleted. However, other than that, it is formed with substantially the same configuration.

  As mentioned above, although especially preferable embodiment of this invention was explained in full detail, this invention is not limited to embodiment of illustration, It can deform | transform and implement in a various aspect.

A radial tire for a passenger car having a tire size of 195 / 65R15 with the tread pattern of FIG. 1 as a basic pattern was manufactured based on the specifications in Table 1, and noise performance and early wear performance of each sample tire were tested. Each tire has substantially the same specifications except those listed in Table 1. The common specifications are as follows.
・ Crown circumferential main groove Groove width Wgc --- 10.5mm
Groove depth Hgc --- 8.2mm
・ Shoulder circumferential main groove Groove width Wgs ---- 8.2mm
Groove depth Hgs --- 8.2mm
・ Shoulder lateral groove Groove width W12 ---- 3.0mm
Groove depth (maximum value) H12a --- Table 1
・ Middle inclined groove Groove width W17 --4.5mm
Groove depth (maximum value) H17 --6.7 mm
・ Crown lateral groove Groove width W20 --- 0.8mm
Groove depth (maximum value) H20 --- 4.0 mm

<Noise performance>
The rim (15 × 6J) and internal pressure (200 kPa) were attached to all the wheels of the vehicle (displacement 2000 cc), and the noise level caused by the pattern noise when the vehicle passed through the dry paved road surface was measured. The evaluation results are shown as an index using Comparative Example 1 as 100, using the reciprocal of the measured value. The larger the index value, the smaller the pattern noise and the better.

<Early wear performance>
Using the above vehicle, the remaining amount of the shoulder lateral groove after running 8,000 km in MIX road wear mode (highway 50%, general road 35%, mountain road 15%) was measured. The index is evaluated. The measurement position was a position 10 mm away from the tread ground edge on the inner side in the tire axial direction.

  As shown in the table, it can be confirmed that the tires of the examples improve the early wear performance of the shoulder portion without deteriorating the noise performance.

2 tread portion 2S surface 10 circumferential main groove 10s shoulder circumferential main groove 11s shoulder land portion 12 shoulder lateral groove 12i tire axial direction inner end 12A first inclined portion 12B constant depth portion 15 deepest portion 16 shoulder narrow groove 25 chamfered portion 30 Regular rim P Corner radius R Curvature radius Te Tread grounding edge X Contour line

Claims (6)

A pneumatic tire having a tire flatness ratio of greater than 55% and less than 70%,
In a tire meridional section in a 5% internal pressure state in which a rim is assembled to a normal rim and filled with an internal pressure of 5% of the normal internal pressure, the contour line of the surface of the tread portion forms an arc having a single radius of curvature R, and the curvature The radius R is 3.0 to 4.5 times the ground contact width TW1, which is the tire axial width between the tread ground edges,
In the tread portion, a circumferential main groove including a shoulder circumferential main groove that extends continuously in the tire circumferential direction and is arranged on the outermost side in the tire axial direction;
The shoulder circumferential main axially inner end with provided in the shoulder land portions disposed in the tire axial direction outer side and the axially outer side of the tread grounding edge extending towards the inside of the tire axial direction of the groove is the shoulder land With a plurality of shoulder lateral grooves that break in the club,
The shoulder lateral groove has an angle α with respect to the tire circumferential direction in the range of 80 to 90 °, and a tire axial distance Ds between the inner end in the tire axial direction and the shoulder circumferential main groove is 3.5 to 5. In the range of 5 mm,
The shoulder lateral groove has a deepest portion where the groove depth is maximum, and the groove depth of the deepest portion is 70 to 90% of the groove depth of the shoulder circumferential main groove,
The shoulder lateral groove has a first inclined portion in which the groove depth gradually increases from the inner end in the tire axial direction toward the outer side in the tire axial direction, and a constant depth that is continuous with the first inclined portion and has a constant groove depth. And the constant depth portion is the deepest portion,
The pneumatic tire according to claim 1, wherein a tire axial direction length of the first inclined portion is 25 to 50% of a tire axial direction length from a tire axial inner end of the shoulder lateral groove to a tread contact edge. The shoulder land portion includes a shoulder narrow groove extending in the tire circumferential direction through an inner end in the tire axial direction of the shoulder lateral groove, and narrower than the shoulder main groove,
The pneumatic tire according to claim 1, wherein a groove depth of the shoulder narrow groove is the same as a groove depth at an inner end in the tire axial direction of the shoulder lateral groove.   The ratio TW1 / TW0 of the ground contact width TW1 which is the tire axial width between the tread ground edges and the tire cross-sectional width TW0 is 0.73 to 0.79. Pneumatic tire.   The pneumatic tire according to claim 2, wherein the shoulder narrow groove has a groove depth of 2 mm or less.   The pneumatic tire according to any one of claims 1 to 4, wherein the shoulder lateral groove has a groove depth of 4.0 to 5.0 mm at a tread ground contact edge. The said shoulder land part equips the corner part where the tread surface and the groove wall surface of the said shoulder circumferential direction main groove | channel cross | intersect, and comprises an arc-shaped chamfering part in any one of Claim 1-5 characterized by the above-mentioned. Pneumatic tire.

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