JP2012001075A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance uneven wearing resistance, while keeping high frequency component suppressing performance and drainage performance.SOLUTION: In a pneumatic tire, at least one peripheral directional main groove 3 extending in a tire peripheral direction is arranged in a tread face 21, the opening width Wt of the peripheral directional main groove 3 in the tread face 21 is made constant in the tire peripheral direction. While the opening width Wm thereof is made constant in the tire peripheral direction in the mid part 3b of the predetermined groove depth in the groove wall 3a of the peripheral directional main groove 3, the opening width Wm is periodically changed within the range of the opening width Wt in the tread face 21 of the peripheral directional groove 3 and within the range of the groove width Wd in the groove bottom 3d of the peripheral directional main groove 3. Also, the change amount of the mid part 3b in the tire width direction is made greater than the change amount of the opening 3c in the tire width direction in the tread face 21 of the peripheral directional main groove 3 and the change amount of the groove bottom 3d of the peripheral directional main groove 3 in the tire width direction.

Description

  The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire in which a circumferential main groove is meandered in the tire width direction to suppress a high frequency component.

  Conventionally, as a pneumatic tire aiming at suppressing a high frequency component (road noise) without impairing drainage, for example, a pneumatic tire (low noise pneumatic tire) described in Patent Document 1 is known. Yes. The pneumatic tire described in Patent Document 1 includes at least one circumferential main groove extending in the circumferential direction in a tread portion of the tire, and the groove bottom portion of the circumferential main groove is disposed on the circumferential main groove. While meandering within the tread surface opening width, the length along the groove bottom is made longer than the length along the tread surface opening.

JP-A-2-212203

  However, in the pneumatic tire described in Patent Document 1 described above, the groove bottom portion of the circumferential main groove is meandered. For this reason, since the base of the land portion defined by the circumferential main groove meanders, the rigidity of the land portion easily changes in the tire circumferential direction, and there is a possibility that uneven wear occurs on the tread surface.

  This invention is made | formed in view of the above, Comprising: It aims at providing the pneumatic tire which can improve uneven wear resistance, maintaining a high frequency component suppression performance and drainage performance.

  In order to solve the above-described problems and achieve the object, the pneumatic tire of the present invention has at least one circumferential main groove extending in the tire circumferential direction on the tread surface, and the circumferential main groove The opening width at the tread surface of the circumferential main groove is constant in the tire circumferential direction, and the opening width is constant in the tire circumferential direction in the middle of the predetermined groove depth in the groove wall of the circumferential main groove, while the circumferential main groove The amount of change in the tire width direction of the midway portion is periodically changed in the tire width direction within the range of the opening width on the tread surface and the groove width at the groove bottom portion of the circumferential main groove. The amount of change in the tire width direction of the opening in the tread surface of the circumferential main groove is larger than the amount of change in the tire width direction of the groove bottom portion of the circumferential main groove.

  According to this pneumatic tire, the meandering of the circumferential main groove is not caused by the opening width of the circumferential main groove or the vibration of the groove bottom in the tire width direction. The rigidity of the portion hardly changes in the tire circumferential direction, and uneven wear that occurs on the tread surface can be suppressed. In addition, since the opening width is constant in the tire circumferential direction, the change in the middle part does not impair the drainage performance, and the water between the road surface and the tread surface when running on a wet road surface. Hydroresistance that suppresses the hydroplaning phenomenon in which a film is formed can be maintained. Furthermore, by suppressing the air column resonance by a periodic change in the tire width direction in the middle part, the high-frequency component suppression performance can be obtained. As a result, uneven wear resistance can be improved while maintaining high-frequency component suppression performance and drainage performance.

  In the pneumatic tire of the present invention, the position in the tire width direction of the groove bottom portion of the circumferential main groove is constant in the tire circumferential direction.

  According to this pneumatic tire, since the groove bottom portion does not periodically change in the tire width direction, the rigidity change in the tire circumferential direction of the land portion is further reduced, and therefore, uneven wear resistance can be further improved.

  In the pneumatic tire of the present invention, the groove depth Dm from the tread surface of the midway part is in the range of 0.3 ≦ Dm / D ≦ 0.8 with respect to the groove depth D of the circumferential main groove. The groove width Wd of the groove bottom is set in a range of 0.5 ≦ Wd / Wt ≦ 0.9 with respect to the opening width Wt on the tread surface of the circumferential main groove. And

  When Dm / D is 0.3 or more and 0.8 or less and Wd / Wt is 0.5 or more and 0.9 or less, the change in the groove width in the groove depth direction of the circumferential main groove is abrupt. Is suppressed, and air column resonance in the circumferential main groove is disturbed. Therefore, according to this pneumatic tire, uneven wear resistance can be further improved while maintaining high-frequency component suppression performance and drainage performance.

  In the pneumatic tire of the present invention, the groove cross-sectional area of the circumferential main groove is constant in the tire circumferential direction.

  According to this pneumatic tire, since the groove cross-sectional area of the circumferential main groove does not change in the tire circumferential direction, the drainage performance can be maintained without impairing the high-frequency component suppression performance.

  In the pneumatic tire of the present invention, the midway portion is periodically changed along a sinusoidal curve in the tire circumferential direction.

  According to this pneumatic tire, the air column resonance in the circumferential main groove is effectively disturbed by the smooth and periodic change in the middle part, and excitation to the air column resonance is suppressed. Suppression of generation itself or sound pressure of air column resonance can be reduced, and high frequency component suppression performance can be improved.

  The pneumatic tire according to the present invention can improve uneven wear resistance while maintaining high-frequency component suppression performance and drainage performance.

FIG. 1 is a plan view of a pneumatic tire according to an embodiment of the present invention. FIG. 2 is an enlarged cross-sectional view of the circumferential main groove. FIG. 3 is a chart showing the results of the performance test of the pneumatic tire according to the example of the present invention.

  Embodiments of the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments. The constituent elements of this embodiment include those that can be easily replaced by those skilled in the art or those that are substantially the same. In addition, a plurality of modifications described in this embodiment can be arbitrarily combined within a range obvious to those skilled in the art.

  In the following description, the tire radial direction refers to a direction orthogonal to the rotation axis (not shown) of the pneumatic tire 1, and the tire radial direction inner side refers to the side toward the rotation axis in the tire radial direction, the tire radial direction outer side. The term “side away from the rotation axis” in the tire radial direction. The tire circumferential direction is a circumferential direction with the rotation axis as a central axis. The tire width direction refers to a direction parallel to the rotation axis, the inner side in the tire width direction is the side toward the tire equatorial plane CL in the tire width direction, and the outer side in the tire width direction is the tire equatorial plane in the tire width direction. The side away from CL. The tire equatorial plane CL is a plane that is orthogonal to the rotational axis of the pneumatic tire 1 and passes through the center of the tire width of the pneumatic tire 1.

  The pneumatic tire 1 of the present embodiment has a tread portion 2 as shown in FIG. The tread portion 2 is made of a rubber material, and is exposed at the outermost side in the tire radial direction of the pneumatic tire 1, and the surface (hereinafter referred to as a tread surface) 21 becomes the contour of the pneumatic tire 1. In the present embodiment, the tread surface 21 is a tread surface that comes into contact with the road surface when a vehicle (not shown) on which the pneumatic tire 1 is mounted travels.

  The tread surface 21 is provided with a plurality of circumferential main grooves 3 (in the present embodiment, four) extending along the tire circumferential direction in parallel in the tire width direction. Extending along the tire circumferential direction includes having an angle of ± 5 degrees or less (substantially 0 degrees) with respect to the tire circumferential direction. The tread surface 21 extends along the tire circumferential direction by the circumferential main groove 3, and a plurality of rib-like land portions 4 parallel to the tire equator surface CL are formed.

  Although not shown in the figure, the tread surface 21 is provided with a plurality of sub-grooves arranged in the tire circumferential direction so as to intersect (communicate with) the circumferential main groove 3 and have edge components in the tire circumferential direction. May be. The minor groove is provided parallel to the tire width direction or having a predetermined angle. Further, the sub-groove may be provided by being curved or bent. The tread surface 21 is provided in such a manner that the sub-grooves are provided so as to intersect (communicate with) the circumferential main grooves 3 adjacent to each other in the tire width direction. The land portion 4 is formed as a plurality of block-like land portions. In addition, when the sub-groove is provided so as to intersect (communicate with) only one of the circumferential main grooves 3 adjacent in the tire width direction, the rib-shaped land portion 4 is formed.

  2 (a) to 2 (c) are enlarged sectional views in which the circumferential main groove 3 is cut in the tire width direction, and FIG. 2 (a) is an AA enlarged sectional view in FIG. 2B is an enlarged cross-sectional view taken along the line BB in FIG. 1, and FIG. 2C is an enlarged cross-sectional view taken along the line CC in FIG.

  As shown in FIGS. 2 (a) to 2 (c), the circumferential main groove 3 described above has an opposing groove wall 3a divided into two stages in the tire radial direction, that is, in the middle of the groove depth direction. . And the middle part 3b which is a boundary of two steps makes the opening width Wm of the tire width direction constant in the tire circumferential direction, and periodically changes in the tire width direction as shown in FIG. That is, the midway part 3b is formed to meander in the tire width direction toward the tire circumferential direction. Further, in the circumferential main groove 3, the opening width Wt of the opening 3c opened at the tread surface 21 is constant in the tire circumferential direction, and the groove width Wd of the groove bottom 3d is constant in the tire circumferential direction.

  2A shows a form in which the midway part 3b has changed to the outermost side in the tire width direction, and FIG. 2C shows a form in which the midway part 3b has changed to the innermost side in the tire width direction. ) Shows an intermediate form in the change in the tire width direction of the midway part 3b.

  The form in which the midway part 3b is changed to the outermost side in the tire width direction is, as shown in FIG. 2A, the midway part 3b in the groove wall 3a on the outermost side in the tire width direction is the opening 3c of the circumferential main groove 3. The groove wall 3a is aligned with the outermost edge in the tire width direction in the tire radial direction, and the groove wall 3a on the opening 3c side of the midway portion 3b stands along the tire radial direction. Furthermore, the form in which the midway part 3b is changed to the outermost side in the tire width direction is, as shown in FIG. 2A, the groove wall 3a on the groove bottom part 3d side of the midway part 3b on the inner side in the tire width direction. It is the state which stands along. At this time, the distance in the tire width direction from the center position in the tire width direction of each of the midway portions 3b facing each other to the tire equatorial plane CL is defined as m1.

  Further, the form in which the midway part 3b is changed to the innermost side in the tire width direction means that the midway part 3b in the groove wall 3a on the innermost side in the tire width direction is an opening of the circumferential main groove 3 as shown in FIG. The groove wall 3a is aligned with the innermost edge in the tire width direction of the portion 3c in the tire radial direction, and the groove wall 3a on the opening 3c side of the midway portion 3b stands along the tire radial direction. Furthermore, the form in which the midway part 3b is changed to the innermost side in the tire width direction is, as shown in FIG. 2C, the groove wall 3a on the groove bottom part 3d side of the midway part 3b on the outer side in the tire width direction. It is the state which stands along. At this time, the distance in the tire width direction from the center position in the tire width direction of each of the midway portions 3b facing each other to the tire equatorial plane CL is defined as m2.

  That is, as shown in FIGS. 2 (a) and 2 (c), the midway part 3b has a constant opening width Wm in the tire circumferential direction, while the opening part 3c in the tread surface 21 of the circumferential main groove 3 remains constant. Within the range of the opening width Wt and within the range of the groove width Wd of the groove bottom portion 3d of the circumferential main groove 3, it periodically changes in the tire width direction.

  Moreover, as shown in FIG.2 (b), the intermediate form in the change of the middle part 3b in the tire width direction means that each groove wall 3a of the circumferential main groove 3 is in the tire width direction of the circumferential main groove 3. This is a state of being symmetric with respect to the center line SL as a reference.

  The distance m2 from the distance m1 to the tire equatorial plane CL in the form in which the midway part 3b is changed to the outermost side in the tire width direction to the tire equatorial plane CL in the form in which the midway part 3b is changed to the innermost side in the tire width direction. Is subtracted to obtain the amount of change Δm in the tire width direction of the midway portion 3b.

  Further, in the pneumatic tire 1 of the present embodiment, when the tire is new, the opening 3c or the groove bottom 3d periodically changes in the tire width direction and meanders in the tire width direction toward the tire circumferential direction. It may be formed. However, the distance t2 from the distance t1 to the tire equatorial plane CL in the form in which the opening 3c is changed to the outermost side in the tire width direction to the tire equatorial plane CL in the form in which the opening 3c is changed to the innermost side in the tire width direction. The amount of change Δm in the tire width direction of the midway portion 3b is larger than the amount of change Δt in the tire width direction of the opening 3c obtained by subtracting. Further, the distance d2 from the distance d1 to the tire equatorial plane CL in the form in which the groove bottom 3d is changed to the outermost side in the tire width direction to the tire equatorial plane CL in the form in which the groove bottom 3d is changed to the innermost side in the tire width direction. The amount of change Δm in the tire width direction of the midway portion 3b is larger than the amount of change Δd in the tire width direction of the groove bottom portion 3d obtained by subtracting. Further, in this case, the change amount Δd of the groove bottom portion 3d in the tire width direction is greater than or equal to the change amount Δt of the opening 3c in the tire width direction. That is, in the case where the opening 3c or the groove bottom 3d periodically changes in the tire width direction and is formed to meander in the tire width direction toward the tire circumferential direction, a relationship of Δm> Δd ≧ Δt is established. The Here, the amount of change Δt in the tire width direction of the opening 3c is preferably in the range of 0 ≦ Δt / Δm ≦ 0.1 with respect to the amount of change Δm in the tire width direction of the midway portion 3b. The change amount Δd in the tire width direction of the groove bottom portion 3d is preferably in the range of 0 ≦ Δd / Δm ≦ 0.1 with respect to the change amount Δm in the tire width direction of the midway portion 3b. Note that 0 = Δt / Δm is a case where 0 = Δt, and 0 = Δd / Δm is a case where 0 = Δd.

  In addition, the opening width Wm of the midway part 3b means the distance which the bending part or curved part used as the boundary which divides the groove wall 3a into two steps opposes in a tire width direction. The opening width Wt of the opening 3c of the circumferential main groove 3 is a distance between opening edges facing the tire width direction in which the circumferential main groove 3 opens in the tread surface 21. In addition, as shown in FIG. 2, when the opening edge of the opening part 3c is formed in circular arc shape, let the distance between the intersections of the extension line of the tread surface 21 and the extension line of each groove wall 3a be Wt. Further, the groove width Wd of the groove bottom 3d of the circumferential main groove 3 is a distance between the lower ends of the groove walls 3a facing the tire width direction at the bottom of the circumferential main groove 3. In addition, when the lower end of the groove wall 3a is formed in an arc shape as shown in FIG. 2, the distance between the intersections of the reference line in the tire width direction in contact with the groove bottom and the extended line of each groove wall 3a is expressed as Wd. And

  As described above, the pneumatic tire 1 of the present embodiment has at least one circumferential main groove 3 extending in the tire circumferential direction on the tread surface 21, and the tread surface 21 of the circumferential main groove 3. The opening width Wt of the opening 3c in the tire is made constant in the tire circumferential direction, and the opening width Wm in the tire width direction is made constant in the tire circumferential direction in the middle portion 3b of the predetermined groove depth in the groove wall 3a of the circumferential main groove 3. While periodically changing in the tire width direction within the range of the opening width Wt at the tread surface 21 of the circumferential main groove 3 and within the range of the groove width Wd at the groove bottom portion 3d of the circumferential main groove 3, Further, the amount of change Δm in the tire width direction of the midway portion 3b is the amount of change Δt in the tire width direction of the opening 3c in the tread surface 21 of the circumferential main groove 3 and the tire at the groove bottom 3d in the circumferential main groove 3 It is larger than the change amount Δd in the width direction.

  According to this pneumatic tire 1, the opening width Wt of the opening 3c of the circumferential main groove 3 is made constant in the tire circumferential direction, and a midway portion 3b of a predetermined groove depth in the groove wall 3a of the circumferential main groove 3 is a tire. It is periodically changed in the width direction. Moreover, the change in the midway part 3b is within the range of the opening width Wt in the tread surface 21 of the circumferential main groove 3 and the circumferential main groove 3 while keeping the opening width Wm in the tire width direction constant in the tire circumferential direction. The amount of change Δm in the tire width direction of the midway portion 3b that is within the range of the groove width Wd at the groove bottom portion 3d is the amount of change in the tire width direction of the opening 3c at the tread surface 21 of the circumferential main groove 3. Δt and the amount of change Δd in the tire width direction of the groove bottom 3d in the circumferential main groove 3 are made larger. For this reason, the meandering of the circumferential main groove 3 is not caused by the opening width Wt of the opening 3c of the circumferential main groove 3 or the wobbling of the groove bottom 3d in the tire width direction. It is difficult to change in the circumferential direction, and uneven wear that occurs on the tread surface 21 can be suppressed. Moreover, since the change in the midway portion 3b is such that the opening width Wm in the tire width direction is constant in the tire circumferential direction, the drainage performance is not impaired, and the road surface and the tread surface when traveling on a wet road surface. Thus, it is possible to maintain the hydro-resistance that suppresses the hydroplaning phenomenon in which a water film is formed between the first and second layers. Furthermore, by suppressing the air column resonance due to the periodic change in the tire width direction of the midway portion 3b, the high frequency component suppression performance can be obtained. As a result, according to the pneumatic tire 1 of the present embodiment, it is possible to improve uneven wear resistance while maintaining high-frequency component suppression performance and drainage performance.

  In the pneumatic tire 1 of the present embodiment, it is preferable that the position in the tire width direction of the groove bottom portion 3d of the circumferential main groove 3 is constant in the tire circumferential direction. That is, the groove bottom portion 3d is straight without periodically changing in the tire width direction, and only the midway portion 3b is formed meandering in the tire width direction toward the tire circumferential direction. Change amount Δd = 0.

  According to this pneumatic tire 1, since the groove bottom 3 d does not periodically change in the tire width direction, the rigidity change in the tire circumferential direction of the land portion 4 is further reduced, so that the uneven wear resistance is further improved. Is possible.

  Further, in the pneumatic tire 1 of the present embodiment, as shown in FIG. 2, the groove depth of the circumferential main groove 3 is D, the groove depth from the tread surface 21 of the midway portion 3b is Dm, and the remaining halfway When the groove depth from the portion 3b to the groove bottom portion 3d is Dd, the groove depth Dm from the tread surface 21 of the midway portion 3b is 0.3 ≦ Dm with respect to the groove depth D of the circumferential main groove 3 /D≦0.8 is preferably set. Moreover, it is preferable that the groove width Wd of the groove bottom portion 3d is set in a range of 0.5 ≦ Wd / Wt ≦ 0.9 with respect to the opening width Wt in the tread surface 21 of the circumferential main groove 3.

  When Dm / D is 0.3 or more and 0.8 or less and Wd / Wt is 0.5 or more and 0.9 or less, the circumferential main groove 3 has a tire depth direction in the groove depth direction. While suppressing a rapid change in the groove width, the air column resonance in the circumferential main groove 3 is disturbed. Therefore, according to the pneumatic tire 1, it is possible to further improve the uneven wear resistance while maintaining the high-frequency component suppression performance and the drainage performance.

  Moreover, in the pneumatic tire 1 of the present embodiment, it is preferable that the groove cross-sectional area of the circumferential main groove 3 is constant in the tire circumferential direction. That is, the opening width Wt of the opening 3c, the opening width Wm of the midway part 3b, and the groove width Wd of the groove bottom part 3d are constant in the tire circumferential direction.

  According to this pneumatic tire 1, since the groove cross-sectional area of the circumferential main groove 3 does not change in the tire circumferential direction, the drainage performance can be maintained without impairing the high-frequency component suppression performance.

  Moreover, in the pneumatic tire 1 of this Embodiment, it is preferable to change the middle part 3b periodically along a sine curve in the tire circumferential direction.

  According to the pneumatic tire 1, the smooth and periodic change of the midway part 3 b effectively disturbs the air column resonance in the circumferential main groove 3 and suppresses excitation to the air column resonance. It is possible to improve the high frequency component suppression performance by suppressing the occurrence of column resonance itself or reducing the sound pressure of air column resonance.

  In this example, performance tests on uneven wear resistance, which is DRY performance, hydro resistance, which is WET performance, and high-frequency component suppression performance, were performed on a plurality of types of pneumatic tires having different conditions (see FIG. 3). .

  In this performance test, a pneumatic tire with a tire size of 215 / 60R16 was assembled on a 16 × 6.5J rim, filled with air pressure (200 [kPa]), and mounted on a test vehicle (domestic 2.5-liter sedan). .

  In the evaluation method of uneven wear resistance, the test vehicle travels 8,000 [km] on a test course that is a dry road. And the partial wear which generate | occur | produced in the land part after driving | running | working is observed. Then, based on the observation result, index evaluation using the conventional example as a reference (100) is performed. This index evaluation is preferable as the numerical value increases.

  In the evaluation method for hydro-resistant performance, the hydro pool with a water depth of 10 mm travels straight through the test vehicle and gradually increases the vehicle speed, and the speed when the slip rate of the pneumatic tire reaches 10% is measured. . Then, based on the measurement result, index evaluation using the conventional example as a reference (100) is performed. This index evaluation indicates that the larger the value, the faster the speed when the slip ratio reaches 10%, and the faster the speed when the slip ratio reaches 10%, the less likely the hydroplaning phenomenon occurs. , Hydro-resistant performance is excellent. That is, the larger the index, the better the hydro-resistant performance.

  In the method for evaluating the high-frequency component suppression performance, the sound pressure level of high-frequency road noise (1 kHz band) is measured near the window on the driver's seat when traveling on a rough road surface at 60 km / h with the test vehicle. Then, based on the measurement result, index evaluation using the conventional example as a reference (100) is performed. This index evaluation indicates that the larger the numerical value, the smaller the sound pressure level and the better the high-frequency component suppression performance.

  In the conventional pneumatic tire, the groove bottom changes in the tire width direction.

  On the other hand, in the pneumatic tires of Examples 1 to 6, the opening width at the tread surface of the circumferential main groove is constant in the tire circumferential direction, and the predetermined groove depth in the groove wall of the circumferential main groove is halfway. In the tire width direction within the range of the opening width at the tread surface of the circumferential main groove and within the range of the groove width at the groove bottom portion of the circumferential main groove while keeping the opening width constant in the tire circumferential direction. The amount of change in the tire width direction at the midway portion is changed to the amount of change in the tire width direction of the opening in the tread surface of the circumferential main groove, and the tire width at the groove bottom portion in the circumferential main groove. It is larger than the amount of change in the direction. In the pneumatic tires of Examples 2 to 6, the groove bottom portion does not change in the tire width direction, and the position in the tire circumferential direction is constant. Further, in the pneumatic tires of Examples 3 to 6, the groove depth Dm of the midway portion with respect to the groove depth D of the circumferential main groove is defined, and the groove bottom portion with respect to the opening width Wt of the circumferential main groove The groove width Wd is defined. In the pneumatic tires of Example 5 and Example 6, the groove cross-sectional area of the circumferential main groove is constant in the tire circumferential direction. In the pneumatic tire of Example 6, the midway portion is periodically changed along the sinusoidal curve in the tire circumferential direction.

  As shown in the test results of FIG. 3, it can be seen that the pneumatic tires of Examples 1 to 6 have improved uneven wear resistance, hydroproof performance, and high-frequency component suppression performance, respectively.

  As described above, the pneumatic tire according to the present invention is suitable for improving uneven wear resistance while maintaining high-frequency component suppression performance and drainage performance.

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 2 Tread part 21 Tread surface 3 Circumferential main groove 3a Groove wall 3b Midway part 3c Opening part 3d Groove bottom part 4 Land part CL Tire equatorial plane SL Center line of circumferential main groove t1 Opening part of circumferential main groove T2 Distance from tire equatorial plane t2 Distance from circumferential main groove opening to tire equatorial plane m1 Distance from groove bottom to tire equatorial plane m2 Distance from groove bottom to tire equatorial plane d1 From midway to tire equatorial plane Distance d2 Distance from midway to tire equatorial plane Wt Opening width at tread surface of circumferential main groove Wm Opening width at midway part Wd Groove width at bottom of groove Δt Change amount of circumferential main groove in tire width direction Δm Groove Amount of change in the tire width direction at the bottom Δd Amount of change in the tire width direction in the middle

Claims (5)

The tread surface has at least one circumferential main groove extending in the tire circumferential direction,
The opening width at the tread surface of the circumferential main groove is constant in the tire circumferential direction,
In the middle of the predetermined groove depth in the groove wall of the circumferential main groove, the opening width is constant in the tire circumferential direction, within the range of the opening width on the tread surface of the circumferential main groove, and the circumferential direction Change periodically in the tire width direction within the range of the groove width at the groove bottom of the main groove,
And the amount of change in the tire width direction of the midway portion is the amount of change in the tire width direction of the opening in the tread surface of the circumferential main groove, and the change in the tire width direction of the groove bottom portion of the circumferential main groove. A pneumatic tire characterized by being larger than the amount.   The pneumatic tire according to claim 1, wherein a position in a tire width direction of a groove bottom portion of the circumferential main groove is constant in the tire circumferential direction.   The groove depth Dm from the midway tread surface is set in a range of 0.3 ≦ Dm / D ≦ 0.8 with respect to the groove depth D of the circumferential main groove, and the groove width of the groove bottom portion The Wd is set in a range of 0.5 ≦ Wd / Wt ≦ 0.9 with respect to the opening width Wt on the tread surface of the circumferential main groove. Pneumatic tire.   The pneumatic tire according to any one of claims 1 to 3, wherein a groove cross-sectional area of the circumferential main groove is constant in the tire circumferential direction.   The pneumatic tire according to any one of claims 1 to 4, wherein the midway portion is periodically changed along a sinusoidal curve in a tire circumferential direction.

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