JP6350002B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire that employs a pitch variation in a tread pattern, and more particularly to a pneumatic tire that can effectively improve steering stability and rolling resistance on a dry road surface.

  Various pneumatic tires that employ pitch variations in the tread pattern have been proposed (see, for example, Patent Documents 1 to 5). More specifically, a plurality of repeating elements including lateral grooves in the tread portion are repeatedly formed along the tire circumferential direction, and a plurality of types of pitches are set for these repeating elements. When such a pitch variation is employed, the noise performance of the pneumatic tire can be improved by dispersing the frequency of pattern noise generated during traveling.

  However, when the pitch variation is adopted, there is a problem that the steering stability and the rolling resistance on the dry road surface are deteriorated because the rigidity of the plurality of repeating elements including the lateral grooves becomes nonuniform on the tire circumference. Therefore, it is extremely difficult to improve the handling stability and rolling resistance on the dry road surface in the framework of pitch variation.

JP 2012-56464 A JP 2010-76561 A JP 2007-168572 A Japanese Patent Application Laid-Open No. 2004-299652 JP 2004-210133 A

  An object of the present invention is to provide a pneumatic tire that can effectively improve steering stability and rolling resistance on a dry road surface when adopting pitch variations in a tread pattern.

In order to achieve the above object, a pneumatic tire according to the present invention includes a tread portion that extends in the tire circumferential direction to form an annular shape, a pair of sidewall portions disposed on both sides of the tread portion, and the sidewall portions. In a pneumatic tire provided with a pair of bead portions arranged on the inner side in the tire radial direction of
The tread portion is provided with at least two main grooves extending in the tire circumferential direction and a plurality of lateral grooves extending in the tire width direction, and a pair of outermost main grooves positioned on the outermost side in the tire width direction among the main grooves. A center region on the inner side in the tire width direction from the center line of the tire, and a shoulder region from the center line of the outermost main groove to the ground contact end of the tread portion, the center region and the shoulder region include a plurality of the lateral grooves. The repeating elements are repeatedly formed along the tire circumferential direction, and the repeating elements are constituted by pitch variations including at least three types of pitches, the number of pitch variations being N, and the grooves of the repeating elements in the center region. When the area ratio is Sc (1), Sc (2),..., Sc (N-1), Sc (N) in order from the longer pitch. , Sc (2) -Sc (1 ) <Sc (3) -Sc (2) <··· <Sc (N) -Sc (N-1), and, Sc (1)> Sc ( 2)> · ..> Sc (N-1)> Sc (N) is satisfied, and the groove area ratio of each repeating element in the shoulder region is set to Ss (1), Ss (2), in order from the longer pitch. ..., Ss (N-1), Ss (N), Ss (2) -Ss (1) <Ss (3) -Ss (2) <... <Ss (N) -Ss ( N-1) and Ss (1)> Ss (2)>...> Ss (N-1)> Ss (N) .

  In the present invention, based on the above relational expression, the groove area ratio of the repeating elements in the center region and the shoulder region is decreased from the longest pitch toward the shortest pitch, and the groove area ratio of the repeating elements having a relatively small pitch is relatively By making it small, the rigidity of the repeating element can be made uniform on the tire circumference and the rolling resistance can be improved. Further, by reducing the amount of change in the groove area ratio as the repetitive element has a relatively small pitch, the rigidity of the repetitive element can be made uniform and the steering stability on the dry road surface can be improved. As a result, it is possible to effectively improve steering stability and rolling resistance on a dry road surface in the framework of pitch variation. In addition, according to such a method, the desired effect can be obtained by specifying the groove area ratio of the repetitive elements, so that the center region and the shoulder region can be improved in order to improve steering stability and rolling resistance on a dry road surface. Therefore, there is no need to adopt different pitch numbers and arrangements, and as a result, it is possible to reduce the time required for the pitch design and to avoid the complexity of the mold manufacturing process.

  Here, the groove area ratio of each repeating element is the ratio (%) of the area of the negative element to the sum of the area of the negative element and the area of the positive element included in the repeating element. The negative element means the groove part, and the positive element means the land part.

  From the difference [Sc (N) −Sc (1)] between the groove area ratio Sc (N) of the repeating element having the shortest pitch in the center region and the groove area ratio Sc (1) of the repeating element having the longest pitch in the center region. The maximum difference in the groove area ratio in the obtained center region is preferably -1% to -4%. Thereby, the steering stability and the rolling resistance on the dry road surface can be effectively improved without deteriorating the steering stability on the wet road surface.

  Further, the difference between the groove area ratio Ss (N) of the repeating element having the shortest pitch in the shoulder region and the groove area ratio Ss (1) of the repeating element having the longest pitch in the shoulder region [Ss (N) −Ss (1). ], The maximum difference in the groove area ratio in the shoulder region is preferably -1% to -4%. Thereby, the steering stability and the rolling resistance on the dry road surface can be effectively improved without deteriorating the steering stability on the wet road surface.

  In particular, when Sc (N) -Sc (1)> Ss (N) -Ss (1), the maximum difference in the groove area ratio is relatively large in the center region, which has a great influence on the steering stability on the dry road surface. Smaller, more uniform rigidity is promoted, driving stability on dry road surface is improved, and the maximum difference in groove area ratio is relatively large in the shoulder area, which has a large influence on passing sound, and the frequency of pattern noise Since dispersibility is improved, noise performance is improved and passing sound is reduced. Further, when Sc (N) −Sc (1) <Ss (N) −Ss (1), the maximum difference in the groove area ratio is relatively small in the shoulder region having a large influence on the uneven wear, and the rigidity of Uniformity is promoted and uneven wear resistance is improved.

  On the tire circumference, the number of repeating elements having the longest pitch is preferably smaller than the number of repeating elements having the shortest pitch. In the present invention, in order to adjust the groove area ratio of repeating elements having a relatively small pitch, when the above-described configuration is applied in an arrangement in which the number of repeating elements having the shortest pitch is larger than the number of repeating elements having the longest pitch. A remarkable effect is obtained.

  The repeating elements are preferably arranged so that the pitch length periodically increases and decreases along the tire circumferential direction. In such a periodic array, repetitive elements having a relatively small pitch are locally gathered, so that a remarkable effect can be obtained when the above-described configuration is applied to the periodic array.

  In the present invention, the contact area of the tread portion is the contact width in the tire axial direction measured when a normal load is applied by placing the tire on a regular rim and filling the regular internal pressure vertically on a plane. Specified based on. The ground contact edge is the outermost position in the tire axial direction of the ground contact region. 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. Then, “Measuring Rim” is set. “Regular internal pressure” is the air pressure that each standard defines for each tire in the standard system including the standard on which the tire is based. The maximum air pressure is JATMA, and the table “TIRE ROAD LIMITS AT VARIOUS” is TRA. The maximum value described in “COLD INFRATION PRESURES”, “INFLATION PRESURE” for ETRTO, but 180 kPa when the tire is a passenger car. “Regular load” is a load determined by each standard for each tire in the standard system including the standard on which the tire is based. The maximum load capacity is JATMA, and the table “TIRE ROAD LIMITS AT VARIOUS” is TRA. The maximum value described in “COLD INFORATION PRESSURES” is “LOAD CAPACITY” if it is ETRTO, but if the tire is a passenger car, the load is equivalent to 88% of the load.

It is meridian sectional drawing which shows the pneumatic tire which consists of embodiment of this invention. FIG. 2 is a development view showing a tread pattern of the pneumatic tire of FIG. 1. It is a top view which shows the center area | region of a tread part. It is a top view which shows the shoulder area | region of a tread part.

  Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings. 1 to 4 show a pneumatic tire according to an embodiment of the present invention.

  As shown in FIG. 1, the pneumatic tire of the present embodiment includes a tread portion 1 that extends in the tire circumferential direction and has an annular shape, and a pair of sidewall portions 2, 2 disposed on both sides of the tread portion 1. And a pair of bead portions 3 and 3 disposed inside the sidewall portion 2 in the tire radial direction.

  A carcass layer 4 is mounted between the pair of bead portions 3 and 3. The carcass layer 4 includes a plurality of reinforcing cords extending in the tire radial direction, and is folded from the inside of the tire to the outside around the bead core 5 disposed in each bead portion 3. A bead filler 6 made of a rubber composition having a triangular cross-section is disposed on the outer periphery of the bead core 5.

  On the other hand, a plurality of belt layers 7 are embedded on the outer peripheral side of the carcass layer 4 in the tread portion 1. These belt layers 7 include a plurality of reinforcing cords inclined with respect to the tire circumferential direction, and are arranged so that the reinforcing cords cross each other between the layers. In the belt layer 7, the inclination angle of the reinforcing cord with respect to the tire circumferential direction is set in a range of, for example, 10 ° to 40 °. A steel cord is preferably used as the reinforcing cord of the belt layer 7. For the purpose of improving high-speed durability, at least one belt cover layer 8 in which reinforcing cords are arranged at an angle of, for example, 5 ° or less with respect to the tire circumferential direction is disposed on the outer peripheral side of the belt layer 7. Yes. As the reinforcing cord of the belt cover layer 8, an organic fiber cord such as nylon or aramid is preferably used.

  In addition, although the tire internal structure mentioned above shows the typical example in a pneumatic tire, it is not limited to this.

  As shown in FIG. 2, four main grooves 11 extending in the tire circumferential direction are formed in the tread portion 1. The main groove 11 includes a pair of inner main grooves 11A, 11A located on both sides of the tire equator CL and a pair of outermost main grooves 11B, 11B located on the outermost side in the tire width direction. By these four main grooves 11, the tread portion 1 has a center land portion 20 located on the tire equator CL, a pair of intermediate land portions 30 located on the outer side in the tire width direction of the center land portion 20, A pair of shoulder land portions 40 located on the outer side in the tire width direction of the intermediate land portion 30 are partitioned.

  The center land portion 20 has a plurality of lateral grooves 21 extending in the tire width direction and having one end communicating with the inner main groove 11A and the other end closed in the center land portion 20 at intervals in the tire circumferential direction. Is formed. The center land portion 20 includes a plurality of sipes 25 extending in the tire width direction and having one end communicating with the inner main groove 11A and the other end closed in the center land portion 20; A plurality of sipes 26 for connecting the lateral grooves 21 and 21 formed at both edges are formed. The lateral grooves 21 and the sipes 25 are alternately arranged along the tire circumferential direction.

  The intermediate land portion 30 is extended in the tire width direction, one end communicates with the inner main groove 11A, and the other end is closed in the intermediate land portion 30 and is extended in the tire width direction. One end communicates with the outermost main groove 11B, while the other end closes within the intermediate land portion 30 and a plurality of lateral grooves 32, and one end communicates with the outermost main groove 11B while extending in the tire width direction. A plurality of lateral grooves 33 whose ends are closed in the intermediate land portion 30 are formed at intervals in the tire circumferential direction. The lateral grooves 32 and the lateral grooves 33 are alternately arranged along the tire circumferential direction, and the lateral grooves 33 are longer than the lateral grooves 32. The intermediate land portion 30 includes a plurality of sipes 35 extending in the tire width direction and having one end communicating with the inner main groove 11A and the other end closed in the intermediate land portion 30; A plurality of sipes 36 extending in the tire width direction and a plurality of sipes 37 extending in the tire width direction from the distal end portion of the lateral groove 32 are formed. The lateral grooves 31 and the sipes 35 are alternately arranged along the tire circumferential direction.

  The shoulder land portion 40 is formed with a circumferential auxiliary groove 48 extending in the tire circumferential direction and narrower than the outermost main groove 11B. Further, the shoulder land portion 40 extends in the tire width direction so as to cross the ground contact edge E, and extends in the tire width direction so as to cross the ground contact edge E, and a plurality of lateral grooves 41 communicating with the circumferential auxiliary groove 48. Thus, a plurality of lateral grooves 42 that are not in communication with the circumferential auxiliary grooves 48 are formed at intervals in the tire circumferential direction. The lateral grooves 41 and the lateral grooves 42 are alternately arranged along the tire circumferential direction. The shoulder land portion 40 includes a plurality of sipes 45 that connect the outermost main groove 11B and the circumferential auxiliary groove 48, and a plurality of sipes 46 that connect the circumferential auxiliary groove 48 and the lateral groove 42. Is formed.

  When the center region Ce is the center in the tire width direction from the center line of the pair of outermost main grooves 11B and the shoulder region Sh is from the center line of the outermost main groove 11B to the ground contact edge E of the tread portion 1, the center region Ce. The center land portion 20 and the intermediate land portion 30 are arranged in the shoulder region, and the shoulder land portion 40 is arranged in the shoulder region Sh. The center line of the outermost main groove 11B is a straight line passing through the center position of the groove width at the narrowest portion of the outermost main groove 11B.

  As shown in FIG. 3, a plurality of repetitive elements Rc including the lateral grooves 21, 31, 32, 33 are formed in the center region Ce. Here, each repetitive element Rc is composed of a negative element composed of the lateral grooves 21, 31, 32, 33, the sipes 25, 26, 35, 36, 37 and the main grooves 11A, 11B and a positive element composed of other land portions. It is configured. These repeating elements Rc are composed of pitch variations including at least three types of pitches Pc (1) to Pc (N). That is, the number of pitch variations of the repeating element Rc is N. The pitches Pc (1) to Pc (N) satisfy the relationship Pc (1)> Pc (2)>...> Pc (N). Note that the pitches Pc (1) to Pc (N) are measured with reference to the same position in the tire circumferential direction in each repeating element Rc. In FIG. 3, the pitches Pc (1) to Pc (N) are specified based on the specific position of the lateral groove 21 of the center land portion 20, but the reference position can be arbitrarily determined.

  When the groove area ratio of each repeating element Rc in the center region Ce is Sc (1), Sc (2),..., Sc (N-1), Sc (N) in order from the longer pitch, Sc (2) -Sc (1) ≤Sc (3) -Sc (2) ≤ ... ≤Sc (N) -Sc (N-1) and Sc (1)> Sc (N) Is pleased. More preferably, Sc (2) -Sc (1) <Sc (3) -Sc (2) <... <Sc (N) -Sc (N-1) and Sc (1)> Sc (2 ) >>...> Sc (N-1)> Sc (N).

  As shown in FIG. 4, a plurality of repeating elements Rs including the lateral grooves 41 and 42 are formed in the shoulder region Sh. Here, each repetitive element Rs is composed of a negative element composed of lateral grooves 41, 42, sipes 45, 46, a circumferential auxiliary groove 48, and a main groove 11B, and a positive element composed of other land portions. These repeating elements Rs are composed of pitch variations including at least three types of pitches Ps (1) to Ps (N). That is, the number of pitch variations of the repeating element Rs is N. The pitches Ps (1) to Ps (N) satisfy the relationship Ps (1)> Ps (2)>...> Ps (N). Note that the pitches Ps (1) to Ps (N) are measured with reference to the same position in the tire circumferential direction in each repeating element Rs. In FIG. 4, the pitches Ps (1) to Ps (N) are specified based on the specific position of the lateral groove 41 of the shoulder land portion 40, but the reference position can be arbitrarily determined.

  When the groove area ratio of each repeating element Rs in the shoulder region Sh is set to Ss (1), Ss (2),..., Ss (N-1), Ss (N) in order from the longer pitch, Ss (2) −Ss (1) ≦ Ss (3) −Ss (2) ≦ ・ ・ ・ ≦ Ss (N) −Ss (N−1) and Ss (1)> Ss (N) Is pleased. More preferably, Ss (2) −Ss (1) <Ss (3) −Ss (2) <... <Ss (N) −Ss (N−1) and Ss (1)> Ss (2 ) >>...> Ss (N-1)> Ss (N).

  Table 1 shows specific examples of the pitches and groove area ratios of the repeating elements Rc and Rs in the center region Ce and the shoulder region Sh.

  In the pneumatic tire described above, the groove area ratio of the repetitive elements Rc and Rs in the center region Ce and the shoulder region Sh is changed from the longest pitch Pc (1), Ps (1) to the shortest pitch Pc (N) based on the above relational expression. , Ps (N), and the groove area ratio [for example, Sc (N), Ss (N)] of the repetitive elements Rc, Rs having a relatively small pitch is made relatively small. The rigidity of Rc and Rs can be made uniform on the tire circumference, and the rolling resistance can be improved. Further, as the repetitive elements Rc and Rs have a relatively small pitch, the change amount of the groove area ratio [for example, the absolute value of Sc (N) −Sc (N−1), Ss (N) −Ss (N−1) By making the [absolute value] small, the rigidity of the repetitive elements Rc and Rs can be made uniform, and the steering stability on the dry road surface can be improved. As a result, it is possible to effectively improve steering stability and rolling resistance on a dry road surface in the framework of pitch variation.

  In the pneumatic tire, the difference between the groove area ratio Sc (N) of the repeating element Rc having the shortest pitch in the center region Ce and the groove area ratio Sc (1) of the repeating element Rc having the longest pitch in the center region Ce [Sc. The maximum difference in the groove area ratio in the center region Ce obtained from (N) −Sc (1)] is preferably −1% to −4%. Thereby, the steering stability and the rolling resistance on the dry road surface can be effectively improved without deteriorating the steering stability on the wet road surface. Here, if the maximum difference in the groove area ratio in the center region Ce is more than -1%, the effect of improving the rolling resistance and the driving stability on the dry road surface is lowered, and conversely, if it is less than -4%, the pitch is reduced. Since the groove area of the relatively small repeating element Rc is insufficient, the drainage performance is deteriorated, and the steering stability on the wet road surface is deteriorated.

  Further, the difference between the groove area ratio Ss (N) of the repeating element Rs having the shortest pitch in the shoulder region Sh and the groove area ratio Ss (1) of the repeating element Rs having the longest pitch in the shoulder region Sh [Ss (N) − The maximum difference in the groove area ratio in the shoulder region Sh obtained from Ss (1)] is preferably −1% to −4%. Thereby, the steering stability and the rolling resistance on the dry road surface can be effectively improved without deteriorating the steering stability on the wet road surface. Here, if the maximum difference in the groove area ratio in the shoulder region Sh is more than -1%, the effect of improving the rolling resistance and the driving stability on the dry road surface is lowered, and conversely if it is less than -4%, the pitch is reduced. Since the groove area of the relatively small repeating element Rs is insufficient, the drainage performance is deteriorated, and the steering stability on the wet road surface is deteriorated.

  The maximum difference in the groove area ratio between the center region Ce and the shoulder region Sh can be Sc (N) −Sc (1) = Ss (N) −Ss (1), but Sc (N) It is also possible to make the value of −Sc (1) and the value of Ss (N) −Ss (1) different from each other.

When Sc (N) −Sc (1)> Ss (N) −Ss (1), in the center region Ce, the maximum difference in the groove area ratio of the repeating element Rc [absolute value of Sc (N) −Sc (1) ] Is relatively small, and uniform rigidity is promoted, so that the steering stability on the dry road surface is improved. In the shoulder region Sh, the maximum difference in the groove area ratio of the repeating element Rs [Ss (N) −Ss ( The absolute value of 1)] becomes relatively large and the frequency dispersibility of the pattern noise is improved, so that the noise performance is improved.

  Table 2 shows specific examples of pitches and groove area ratios of the repeating elements Rc and Rs in the center region Ce and the shoulder region Sh when Sc (N) -Sc (1)> Ss (N) -Ss (1). Indicates.

  Further, when Sc (N) −Sc (1) <Ss (N) −Ss (1), in the shoulder region Sh, the maximum difference in the groove area ratio of the repetitive element Rs [Ss (N) −Ss (1) [Absolute value] becomes relatively small, and uniform rigidity is promoted, so that uneven wear resistance is improved.

  Table 3 shows specific examples of pitches and groove area ratios of the repeating elements Rc and Rs in the center region Ce and the shoulder region Sh when Sc (N) −Sc (1) <Ss (N) −Ss (1). Indicates.

  In the pneumatic tire, the number of repeating elements Rc, Rs having the longest pitch [ie, Pc (1), Ps (1)] on the tire circumference is the shortest pitch [ie, Pc (N), Ps (N). It is desirable that the number is less than the number of repeating elements Rc and Rs having That is, by adjusting the groove area ratio of the repetitive elements Rc and Rs having a relatively small pitch, the effect of improving the rolling resistance and the driving stability on the dry road surface is obtained, so that the repetitive elements Rc, A remarkable effect is obtained when the above-described configuration is applied to an arrangement in which the number of Rs is larger than the number of repeating elements Rc and Rs having the longest pitch.

  The repeating elements Rc and Rs are preferably arranged so that the pitch length periodically increases and decreases along the tire circumferential direction. For example, an arrangement in which the lengths of the pitches Pc (1) to Pc (N) and Ps (1) to Ps (N) repeat increasing and decreasing 3 to 5 times on the tire circumference is preferable. At that time, it is not always required that the pitch length be uniformly increased or decreased along the tire circumferential direction, and a case where pitches of the same length are arranged may be included. In such a periodic array, repetitive elements having a relatively small pitch are locally gathered, so that a remarkable effect can be obtained when the above-described configuration is applied to the periodic array.

  In the pneumatic tire described above, the groove area ratio of each of the repetitive elements Rc, Rs in the center region Ce and the shoulder region Sh is not particularly limited, but is, for example, in the range of 20% to 40%, more preferably 25. It is desirable to set in the range of% -35%. Thereby, the rolling resistance and the effect of improving the steering stability on the dry road surface can be sufficiently ensured without impairing the steering stability on the wet road surface.

  In the pneumatic tire described above, the value of the pitch Pc (1) to Pc (N) of the repeating element Rc in the center region Ce and the value of the pitch Ps (1) to Ps (N) of the repeating element Rs in the shoulder region Sh. Are identical to each other and have the same sequence. However, the arrangement of the repeating elements Rc and Rs is different in the center region Ce and the shoulder region Sh, or the pitches Pc (1) to Pc (N) of the center region Ce and the pitches Ps (1) to Ps of the shoulder region Sh are different. It is possible to vary the value of (N). In any case, Pc (1) / Pc (N) and Ps (1) / Ps (N) are in the range of 1.2 to 2.0, more preferably in the range of 1.3 to 1.6. It is desirable to set.

  In a pneumatic tire having a tread portion, a pair of sidewall portions, and a pair of bead portions with a tire size of 215 / 45R17, the tread portion has four main grooves extending in the tire circumferential direction, and extends in the tire width direction. A plurality of transverse grooves are provided, and a plurality of repeating elements including the transverse grooves in the center region and the shoulder region are repeatedly formed along the tire circumferential direction, and these repeating elements are configured with pitch variations including five types of pitches, The groove area ratio of each repeating element in the center region is Sc (1), Sc (2), Sc (3), Sc (4), Sc (5) in order from the longer pitch, and each repetition in the shoulder region When the groove area ratio of the elements is set to Ss (1), Ss (2), Ss (3), Ss (4), Ss (5) in order from the longer pitch Sc (1) ~Sc (5) and Ss (1) Conventional Example was set as relationship tables 4 ~Ss (5), was fabricated tire of Comparative Example and Examples 1-7.

  For the shortest / longest number of pitches, “shortest> longest” indicates that the number of repeating elements having the longest pitch is less than the number of repeating elements having the shortest pitch, and the number of repeating elements having the longest pitch is the shortest pitch. A case where the number of repeating elements is greater than the number of repeating elements is indicated by “shortest <longest”. In addition, regarding the arrangement, the case where the repeating elements are arranged so that the pitch length periodically increases and decreases along the tire circumferential direction is indicated by “period”, and the repeating elements are indicated by the pitch length along the tire circumferential direction. The case where the arrangement is made to increase or decrease randomly is indicated by “random”.

  These test tires were evaluated for rolling resistance and handling stability on a dry road surface by the following test methods, and the results are also shown in Table 4.

Rolling resistance:
Each test tire was assembled on a wheel having a rim size of 17 × 7 J, and rolling resistance was measured in accordance with ISO regulations. The evaluation results are shown as an index with the conventional example being 100, using the reciprocal of the measured value. It means that rolling resistance is so small that this index value is large.

Steering stability on dry roads:
Each test tire is mounted on a wheel with a rim size of 17 × 7J and mounted on a front-wheel drive vehicle with a displacement of 1800 cc. Evaluation was performed. The evaluation results are shown as an index with the conventional example being 100. The larger the index value, the better the steering stability on the dry road surface.

  As can be seen from Table 4, in the tires of Examples 1 to 7, steering stability and rolling resistance on the dry road surface were effectively improved. On the other hand, in the comparative example, since the amount of change in the groove area ratio of the repeating elements is uniform in the center region and the shoulder region, the steering stability on the dry road surface and the effect of improving the rolling resistance are not always sufficient.

DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 3 Bead part 11 Main groove 21, 31, 32, 33, 41, 42 Cross groove Ce Center area | region Sh Shoulder area | region Rc Repeat element of center area | region Rs Repeat element of shoulder area | region

Claims (5)

An annular tread portion extending in the tire circumferential direction, a pair of sidewall portions disposed on both sides of the tread portion, and a pair of bead portions disposed on the inner side in the tire radial direction of the sidewall portions. In the provided pneumatic tire,
The tread portion is provided with at least two main grooves extending in the tire circumferential direction and a plurality of lateral grooves extending in the tire width direction, and a pair of outermost main grooves positioned on the outermost side in the tire width direction among the main grooves. A center region on the inner side in the tire width direction from the center line of the tire, and a shoulder region from the center line of the outermost main groove to the ground contact end of the tread portion, the center region and the shoulder region include a plurality of the lateral grooves. The repeating elements are repeatedly formed along the tire circumferential direction, and the repeating elements are constituted by pitch variations including at least three types of pitches, the number of pitch variations being N, and the grooves of the repeating elements in the center region. When the area ratio is Sc (1), Sc (2),..., Sc (N-1), Sc (N) in order from the longer pitch. , Sc (2) -Sc (1 ) <Sc (3) -Sc (2) <··· <Sc (N) -Sc (N-1), and, Sc (1)> Sc ( 2)> · ..> Sc (N-1)> Sc (N) is satisfied, and the groove area ratio of each repeating element in the shoulder region is set to Ss (1), Ss (2), in order from the longer pitch. ..., Ss (N-1), Ss (N), Ss (2) -Ss (1) <Ss (3) -Ss (2) <... <Ss (N) -Ss ( N-1) and satisfying the relationship of Ss (1)> Ss (2)>...> Ss (N-1)> Ss (N) .   Difference between the groove area ratio Sc (N) of the repeating element having the shortest pitch in the center region and the groove area ratio Sc (1) of the repeating element having the longest pitch in the center region [Sc (N) -Sc (1) 2. The pneumatic tire according to claim 1, wherein the maximum difference in the groove area ratio in the center region determined from the above is −1% to −4%.   Difference between the groove area ratio Ss (N) of the repeating element having the shortest pitch in the shoulder region and the groove area ratio Ss (1) of the repeating element having the longest pitch in the shoulder region [Ss (N) −Ss (1) 3. The pneumatic tire according to claim 1, wherein the maximum difference in the groove area ratio in the shoulder region determined from the above is −1% to −4%.   The pneumatic tire according to claim 1, wherein the number of repeating elements having the longest pitch is smaller than the number of repeating elements having the shortest pitch on the tire circumference.   The pneumatic tire according to any one of claims 1 to 4, wherein the repeating elements are arranged so that a pitch length periodically increases and decreases along a tire circumferential direction.

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