JP2014037194A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve noise performance while maintaining drainage performance.SOLUTION: In a shoulder region 26 comparted by a main groove 22A extending in a tire circumferential direction A in a tread portion 14 is formed a lateral groove 28 passing through the main groove and extending to outside of a ground contact end. In the lateral groove 28, a portion ranging from the main groove 22A to a position corresponding to an end 20A1 in the width direction of a maximum width belt 20A is set as an effective lateral groove 30. On both ends in the longitudinal direction of the effective lateral groove are formed general grooves 32, and on the center in the longitudinal direction of the effective lateral groove is formed a recess 36 caved in the groove bottom of the general groove, as well as the recess 36 is formed overhanging the outside Wo in the groove width direction, so that an expansion portion 34 expanding the groove cross section area against the general groove is formed only under the groove bottom of the general groove.

Description

  The present invention relates to a pneumatic tire.

  In recent years, in pneumatic tires, it has been required to reduce noise generated during traveling, particularly noise outside the vehicle. Therefore, for example, Patent Document 1 below proposes providing a Helmholtz resonator at the groove bottom of the main groove in the tread portion. In the Helmholtz type resonator, an inflatable portion serving as an air chamber is provided through a narrow neck as an opening passage, and these are matched with the air column resonance frequency, thereby reducing a certain frequency. However, if such a thin neck resonator is provided, it is difficult to remove the mold from the mold during vulcanization, and therefore it is not easy to provide a resonator having the shape as designed.

  In the following Patent Document 2, the groove volume is increased while the apparent groove width is kept constant by providing a beveled portion in which the groove bottom side is recessed into the block in the side wall of the main groove or lateral groove of the tread. It is disclosed that the drainage performance is improved by this, thereby achieving both noise performance and drainage performance. However, in this case, even if the grooved portion provided at the bottom of the groove is considered to be an expansion-type silencer, such a grooved portion with only the groove bottom expands the groove cross-sectional area that is important for exhibiting the silencing effect. The rate is not enough. In addition, since the side wall of the general groove responsible for the drainage function is squeezed as it is, when considering the lateral groove in the shoulder region, when the water flow that flows from the main groove flows out of the grounding edge, the stagnation of the water flow occurs at the turning portion Therefore, there is a concern about the deterioration of drainage performance.

  In Patent Document 3 below, a groove width and a groove depth are included in a part of the groove in the longitudinal direction such as a lateral groove, for the purpose of improving the performance on snow without impairing the wear resistance and the like, for the purpose different from the noise performance. It is disclosed to provide a concave notch extending throughout. Since this notch can also change the groove cross-sectional area in the middle of the groove, it can be expected to act as a silencer, but as in Patent Document 2, since the concave portion is provided as it is on the side wall of the general groove portion, There is concern about deterioration of drainage performance due to stagnation of water flow.

  Patent Document 4 below discloses that a recess is formed at the bottom of the lateral groove in order to improve the overturning limit performance. However, the recess is grounded in order to reduce the rigidity of the land. It is provided outside the end in the tire width direction and does not contribute to the improvement of noise performance.

JP 2000-118207 A Japanese Patent Laid-Open No. 11-32238 JP 2002-264614 A JP 2006-347512 A

  An object of the present invention is to provide a pneumatic tire capable of improving noise performance while maintaining drainage performance.

  The pneumatic tire according to the present invention is a pneumatic tire in which a lateral groove extending from the main groove to the outside of the ground end is provided in a shoulder region defined by a main groove extending in the tire circumferential direction in the tread portion. The transverse groove has a portion from the main groove to a position corresponding to the end in the width direction of the maximum width belt as an effective transverse groove portion, and after providing general groove portions at both ends in the length direction of the effective transverse groove portion, the effective transverse groove portion In the central portion of the longitudinal direction, a recessed portion that is recessed with respect to the groove bottom of the general groove portion is provided, and the recessed portion is formed so as to protrude outward in the groove width direction, thereby enlarging the groove sectional area with respect to the general groove portion. The inflating part is provided limitedly below the groove bottom of the general groove part.

  As a preferred embodiment, the expanding portion may be provided within a range of 30 to 70% from the main groove with respect to the length of the effective lateral groove portion. As another aspect, the lateral groove may have an expansion coefficient of 150% or more, which is a ratio of a groove cross-sectional area at a portion where the expansion portion is provided to a groove cross-sectional area of the general groove portion. As another aspect, the inflating part may be provided by projecting and forming the concave part outward in the groove width direction on both sides of the lateral groove. In this case, the one overhanging portion and the other overhanging portion sandwiching the lateral groove may face each other by 60 to 100%. Further, the ratio of the amount of protrusion between the one overhanging portion and the other overhanging portion sandwiching the lateral groove may be in the range of 80 to 120%. Each of these aspects can be combined as appropriate.

  According to the present invention, in the lateral groove of the shoulder region, the expansion portion that expands the groove cross-sectional area is provided at the central portion in the length direction so as to be lower than the groove bottom of the general groove portion. Thus, the flow of water that has flowed into the lateral groove is not hindered in the expansion portion, and the deterioration of drainage performance can be prevented. On the other hand, when the sound generated in the main groove is radiated from the side through the lateral groove of the shoulder region, the expansion part becomes a silencer, and the radiated sound can be reduced, so that noise performance is improved. Can be improved.

1 is a half sectional view of a pneumatic tire according to a first embodiment. It is sectional drawing which expands and shows the shoulder area | region of this tire. It is a top view which expands and shows the shoulder area | region of this tire. (A) is the sectional view on the AA line of FIG. 3, (b) is sectional drawing on the BB line. It is a figure which shows the cross-sectional shape of the horizontal groove | channel which concerns on the example of a change. It is a top view which expands and shows a tire shoulder field concerning a 2nd embodiment. It is a top view which expands and shows the tire shoulder area | region which concerns on 3rd Embodiment. It is a top view expanding and showing a tire shoulder field concerning a 4th embodiment. It is a top view expanding and showing a tire shoulder field concerning a 5th embodiment. It is a top view which expands and shows the tire shoulder area | region which concerns on 6th Embodiment. It is a top view which expands and shows a tire shoulder field concerning a 7th embodiment. It is a top view which expands and shows a tire shoulder field concerning an 8th embodiment. It is a figure which shows the cross-sectional shape of the horizontal groove | channel which concerns on a comparative example.

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

(First embodiment)
As shown in FIG. 1, the pneumatic tire according to the embodiment includes a pair of left and right bead portions 10 that are assembled to a rim, a pair of left and right sidewall portions 12 that extend outward from the bead portion 10 in the tire radial direction, and the pair. The tread portion 14 is provided between the sidewall portions 12 and contacts the road surface. A ring-shaped bead core 16 is embedded in each of the pair of bead portions 10.

  A carcass ply 18 using an organic fiber cord is folded and locked around the bead core 16, and is provided in a toroidal manner between the left and right bead portions 10, and the tread portion 14 and the sidewall portion 12. Is reinforced.

  On the outer periphery side of the carcass ply 18 in the tread portion 14, a belt 20 composed of two or more cross belt plies using a rigid tire cord such as a steel cord or an aramid fiber is provided. The tread portion 14 is reinforced. In this example, the belt 20 has a two-layer structure of a first belt 20A disposed on the inner side in the tire radial direction and a second belt 20B disposed on the outer peripheral side thereof, and the first belt 20A has the widest width. It is a wide maximum width belt.

  A plurality of main grooves 22 extending in a straight shape in the tire circumferential direction A (see FIG. 3) are provided on the surface of the tread portion 14, and four in the tire width direction B are provided in this example. Of these, the tread portion 14 is partitioned into a central region 24 on the inner side in the width direction B and a shoulder region 26 on the outer side thereof by the main groove 22A on the ground contact end side.

  A plurality of lateral grooves 28 extending in a direction intersecting the main groove 22A are provided in the shoulder region 26 at a predetermined interval in the tire circumferential direction A. The lateral groove 28 is a groove that extends through the shoulder region 26 that is a land portion from the main groove 22A to the outside of the ground contact end, that is, does not terminate in the shoulder region 26 and opens outward in the width direction B. Is provided. In this example, the lateral groove 28 extends in a straight line parallel to the tire width direction B as shown in FIG. 3, but it may also be inclined with respect to the tire width direction B, or bend. However, it may extend.

  As shown in FIG. 2, the lateral groove 28 has a portion extending from the main groove 22 </ b> A to a position corresponding to the width direction end 20 </ b> A <b> 1 of the first belt 20 </ b> A (maximum width belt) as an effective lateral groove portion 30. After securing the general groove portions 32, 32 at both ends in the length direction, an inflating portion 34 that enlarges the groove cross-sectional area with respect to the general groove portion 32 is provided at the central portion in the length direction of the effective lateral groove portion 30.

  The effective lateral groove portion 30 is a portion that forms a tube in which the lateral groove 28 serves as an air escape path (passage) between the tire and the road surface. Since the ground contact end of the tire is usually located between the width direction end 20B1 of the second belt 20B and the width direction end 20A1 of the maximum width belt 20A, the maximum width is considered here in consideration of wear and the like. A position corresponding to the width direction end 20A1 of the belt 20A is defined as a virtual ground end E. Then, it can be considered that the lateral groove 28 forms a tube at the time of ground contact as a portion from the main groove 22A to the virtual ground end E, and this portion is defined as an effective lateral groove portion 30.

  In the present embodiment, an expansion portion 34 serving as a silencer is provided at the center in the length direction of the effective lateral groove portion 30. This is because the expansion silencer is provided at the center in the length direction of the path through which sound is radiated, so that its function is effectively exhibited. Therefore, both ends in the length direction of the effective lateral groove portion 30 are formed in the general groove portion 32 having no expansion portion. Here, the general groove portion 32 is a normal groove portion in which a groove portion or a concave portion serving as an expanding portion is not provided on the groove bottom or side wall, and in this example, as shown in FIG. The cross section perpendicular to the length direction is substantially rectangular.

  On the other hand, as shown in FIGS. 2 to 4, the inflating portion 34 is provided with a recessed portion 36 that is recessed with respect to the groove bottom of the general groove portion 32 in the central portion in the length direction of the effective lateral groove portion 30. It is formed by providing an overhanging portion 38 that protrudes outward in the groove width direction Wo. That is, the expansion part 34 is formed by rolling the groove bottom with respect to the general groove part 32 and also rolling the side wall at the rolled position.

  Thereby, the expansion part 34 is limitedly provided below the groove bottom of the general groove part 32, as is apparent from the comparison between FIG. 4A and FIG. 4B. In the portion corresponding to the side wall of the general groove portion 32 located on the upper side (that is, on the grounding surface side) from the bottom, there is not provided a bend portion that increases the groove cross-sectional area.

  Specifically, as shown in FIG. 4B, in this example, the inflating portion 34 forms a concave portion 36 by recessing the groove bottom of the general groove portion 32 over its entire width, The lateral groove 28 is provided by projecting on both sides of the stepping side and the kicking side of the lateral groove 28 (that is, both sides in the tire circumferential direction A across the lateral groove 28), respectively, on the outer side Wo in the groove width direction. On both sides of the side, projecting portions 38 projecting outward in the groove width direction Wo from the side wall of the general groove portion 32 are formed. Therefore, the expanding portion 34 is formed wider than the general groove portion 32.

  Further, as shown in FIG. 3, in this example, the inflating portion 34 is provided at a position where the protruding side protruding portion 38 </ b> A and the protruding side protruding portion 38 </ b> B coincide with each other in the length direction of the effective lateral groove portion 30. Therefore, the two overhanging portions 38A and 38B are opposed to each other by 100% (opposing ratio = 100%). Further, the overhang amount M of the stepped-out overhang portion 38A and the overhang amount N of the overhang side overhang portion 38B are set to the same value (M = N).

  Note that the cross-sectional shape of the inflatable portion 34 is not limited to the rectangular shape as shown in FIG. 4B, and for example, as shown in FIG. The formed track shape may be used, and as shown in FIG. 5B, the projecting portion 38 may be formed in a cross-sectional arc shape projecting outward in the groove width direction Wo toward the lower side. Thus, by making the projecting portion 38 of the expanding portion 34 have a round cross-sectional curved shape, it is possible to improve the demoldability from the mold after vulcanization.

  As described above, the inflatable portion 34 is provided in the central portion in the length direction of the effective lateral groove portion 30, but preferably in a range of 30 to 70% from the main groove 22 </ b> A with respect to the length J of the effective lateral groove portion 30 ( Hereinafter, it is preferable that this range is provided in the expansion portion arrangement region K). By providing the expansion portion 34 in the expansion portion arrangement region K, the function as the expansion silencer can be enhanced.

  The inflatable portion 34 can be provided in various lengths in the inflatable portion arrangement region K, but the length L of the inflatable portion 34 is 15 to 15 in relation to the inflatable portion arrangement region K in terms of noise reduction effect. It is preferably 100%, more preferably 60 to 90%. Therefore, the length L of the inflating part 34 is preferably 6 to 40%, more preferably 24 to 36%, with respect to the length J of the effective lateral groove part 30.

  Further, the expansion ratio of the groove cross-sectional area by the expansion portion 34 is preferably 150% or more, more preferably 200% or more, in order to enhance the noise reduction effect. Although the upper limit of an expansion coefficient is not specifically limited, Usually, it is 400% or less. Here, the expansion rate is the groove cross-sectional area at the portion where the expansion portion 34 shown in FIG. 4B is provided (that is, the expansion portion 34 is provided) with respect to the groove cross-sectional area of the general groove portion 32 shown in FIG. Ratio of the cross-sectional area of the lateral groove 28 at the same position. In addition, since the groove cross-sectional area of the general groove portion 32 may be gradually formed in the vicinity of the ground contact end portion, the position immediately before the inflating portion 34 is provided (that is, the nearest position inside the tire width direction with respect to the inflating portion 34) The cross-sectional area of the groove in FIG.

  In the pneumatic tire according to the present embodiment configured as described above, in the lateral groove 28 of the shoulder region 26, the groove cross-sectional area is enlarged at the central portion of the effective lateral groove portion 30 below the groove bottom of the general groove portion 32. Since the expanding portion 34 is provided, the water flow compressed in the main groove 22A and flowing into the lateral groove 28 when traveling on a wet road surface is not hindered in the expanding portion 34, and the drainage performance is reduced. Can be prevented. That is, the expansion portion 34 is not formed by squeezing the side wall of the general groove portion 32 as it is, but is provided limited to the lower side of the general groove portion 32, so that stagnation of water flow occurs in the expansion portion 34. It can be suppressed and drainage performance can be maintained.

  On the other hand, when the sound generated in the main groove 22A is radiated from the side via the lateral groove 28 of the shoulder region 26, the expansion portion 34 becomes a silencer, and the radiated sound can be reduced. Noise performance can be improved. In particular, since the expanding portion 34 is formed not only on the groove bottom but also on the outer side Wo in the groove width direction, the expansion coefficient, that is, the change in the groove cross-sectional area can be set large, and the change in the acoustic impedance is greatly increased. Thus, the radiated sound can be effectively reduced.

(Second Embodiment)
FIG. 6 shows the configuration of the lateral groove 28 in the second embodiment. The second embodiment differs from the first embodiment in that the amount of protrusion M of the overhanging portion 38A on the stepping side and the amount of protrusion N of the protruding portion 38B on the kicking side are set to different values.

  In this example, the overhang amount M on the stepping side is set larger than the overhang amount N on the kick side, but may be set in reverse. The ratio of the amount of protrusion M on the stepping side and the amount of protrusion N on the kicking side is not particularly limited, but is preferably 80 to 120% as a ratio N / M (× 100) of the protruding side with respect to the stepping side. About 2nd Embodiment, the other structure and effect are the same as that of 1st Embodiment, and description is abbreviate | omitted.

(Third embodiment)
FIG. 7 shows the configuration of the lateral groove 28 in the third embodiment. The third embodiment differs from the first embodiment in that instead of providing the overhang portions 38 on both the stepping side and the kicking side of the lateral groove 28, the overhang portions 38 are provided only on one side.

  As described above, the overhanging portions 38 do not need to be provided on both sides of the lateral groove 28. However, as in the first embodiment, providing the overhanging portions 38 secures release from the mold after vulcanization molding. However, it is preferable because the expansion rate in the expansion portion 34 can be easily set large. About 3rd Embodiment, the other structure and effect are the same as that of 1st Embodiment, and description is abbreviate | omitted.

(Fourth embodiment)
FIG. 8 shows the configuration of the lateral groove 28 in the fourth embodiment. The fourth embodiment differs from the first embodiment in that the step-side overhanging portion 38A and the kick-out overhanging portion 38B are provided without facing each other.

  In other words, in this example, the recess 36 is formed over the entire expansion portion arrangement region K, and the extension side 38A of the stepping side and the extension side 38B of the kicking side are not opposed to each other. It is provided at a position shifted in the vertical direction. Further, in FIG. 8, the overhanging portion 38A on the step-in side is provided on the side close to the main groove 22A, and the overhanging portion 38B on the kicking side is provided on the grounding end side, but may be set in reverse.

  As described above, it is not necessary that the stepped-out overhanging portion 38A and the kicking-out overhanging portion 38B are opposed to each other, but in terms of noise performance, it is preferable that they are opposed as in the first embodiment. Regarding the fourth embodiment, other configurations and operational effects are the same as those of the first embodiment, and a description thereof will be omitted.

(Fifth embodiment)
FIG. 9 shows the configuration of the lateral groove 28 in the fifth embodiment. 5th Embodiment differs in the shape of the recessed part 36 of the expansion part 34 from 4th Embodiment.

  That is, in this example, the recesses 36 are provided so as to correspond to the stepped-out protruding part 38A and the kicking-side protruding part 38B, respectively. Therefore, the recessed part 36 is 2 in the length direction of the effective lateral groove part 30. It is divided into two. In FIG. 9, the protruding portion 38 </ b> B on the kicking side is provided on the side close to the main groove 22 </ b> A, and the protruding portion 38 </ b> A on the stepping side is provided on the grounding end side. About 5th Embodiment, another structure and effect are the same as that of 4th Embodiment, and description is abbreviate | omitted.

(Sixth embodiment)
FIG. 10 shows the configuration of the lateral groove 28 in the sixth embodiment. The sixth embodiment is different from the first embodiment in that the step-side overhanging portion 38A and the kick-out overhanging portion 38B are partially opposed to each other.

  That is, in this example, the stepped-out overhanging portion 38A and the kicking-out overhanging portion 38B are not 100% opposite to each other as in the first embodiment, but are portions facing the central portion of the inflating portion arrangement region K. The two overhanging portions 38A and 38B are provided at positions shifted in the length direction of the effective lateral groove portion 30 while ensuring the above. The facing rate is preferably as large as possible from the viewpoint of noise performance, preferably 60 to 100%, and more preferably 90 to 100%. Here, the facing ratio is the ratio Q of the length Q of the facing portion to the length P of one of the overhanging portions 38 (the longer overhanging portion when the length of the overhanging portion on the stepping side and the kicking side is different). / P (× 100).

  In FIG. 10, the overhanging portion 38 </ b> A on the step-in side is provided on the side close to the main groove 22 </ b> A, and the overhanging portion 38 </ b> B on the kicking side is provided on the ground contact end side. Regarding the sixth embodiment, other configurations and operational effects are the same as those of the first embodiment, and a description thereof will be omitted.

(Seventh embodiment)
FIG. 11 shows the configuration of the lateral groove 28 in the seventh embodiment. The seventh embodiment differs from the sixth embodiment in the shape of the recess 36 of the inflating portion 34.

  That is, in this example, the concave portion 36 is not provided in the entire width of the general groove portion 32 over the entire length direction of the inflating portion 34, and is a facing portion between the stepped-side protruding portion 38A and the kicking-side protruding portion 38B. It is provided in the full width only within the range. Except for the facing portion, a recess 36 is formed in a half-width range adjacent to the overhang portions 38A and 38B. Thus, although the recessed part 36 does not necessarily need to be provided in the full width of the general groove part 32, it is preferable to provide in the full width in order to increase the expansion coefficient in the expanded part 34 and improve the noise performance. In the seventh embodiment, other configurations and operational effects are the same as those in the sixth embodiment, and a description thereof will be omitted.

(Eighth embodiment)
FIG. 12 shows the configuration of the lateral groove 28 in the eighth embodiment. The eighth embodiment is the same as the sixth embodiment in that the step-side overhanging portion 38A and the kick-out overhanging portion 38B are partially opposed to each other, but the form is different.

  That is, in this example, the overhanging portion 38A on the stepping side is provided in the entire length direction of the recess 36, but the overhanging portion 38B on the kicking side is provided close to the grounding end side in the length direction of the recess 36. It has been. Thus, after setting the extension part 38A on the stepping side and the extension part 38B on the kicking side to have different lengths, they may be provided so as to partially face each other. The stepping side and the kicking side may be set in reverse. In the eighth embodiment, other configurations and operational effects are the same as those in the sixth embodiment, and a description thereof will be omitted.

(Other embodiments)
In the above embodiment, the expanded portions 34 are provided in all the lateral grooves 28 provided in the shoulder region 26, but the expanded portions may not necessarily be formed in all the lateral grooves. Further, the number of belts 20 is not limited to two, and three or more belts may be used. Although not enumerated one by one, various modifications can be made without departing from the spirit of the present invention.

  As a conventional example of a pneumatic radial tire having a tire size of 195 / 65R15, a tire having a lateral groove in a shoulder region that is straight and extending in the tire width direction and not provided with an inflating portion is defined as a control tire. The noise performance and drainage performance were evaluated for the tires of Examples and Comparative Examples provided with various inflatable portions.

  Comparative Example 1 is an example in which, as shown in FIG. 13A, based on the disclosure of Patent Document 2, a curled portion 102 is provided as an inflating portion on both side walls in the central portion in the longitudinal direction of the lateral groove 100. . In Comparative Example 2, based on the disclosure of Patent Document 3, as shown in FIG. 13B, a concave notch 112 is formed as an inflating portion over the groove bottom and both side walls in the longitudinal center of the lateral groove 110. This is an example. Comparative Example 3 is an example in which the same expansion portion as that of the third embodiment shown in FIG. 7 is provided, but the arrangement is an end portion instead of the central portion of the effective lateral groove portion.

  Examples 1 to 3 correspond to the third embodiment shown in FIG. 7, Example 4 corresponds to the sixth embodiment shown in FIG. 10, and Examples 5 and 7 correspond to the first embodiment shown in FIG. Corresponding to the form, Example 6 corresponds to the second embodiment shown in FIG.

  The position of the expanding portion in Table 1 is the length from the main groove 22A with respect to the length J of the effective lateral groove portion 30, and the start and end positions of the expanding portion are indicated as "start end-end%".

  The performance evaluation was an actual vehicle evaluation, and was performed by the following method.

-Drainage performance (hydroplaning performance): The speed when hydroplaning phenomenon occurred was measured by running on a straight course having a wet road surface with a water depth of 8 mm. The evaluation is indicated by an index when the tire of the conventional example is 100, and the larger the value, the higher the speed and the better the drainage performance.

-Noise performance: The noise outside the vehicle evaluated by the ISO test method was measured as the tire noise performance. Specifically, the passing sound when traveling at a traveling speed of 80 km / hour on the dry road surface of the tire test site was measured, and the passing sound when using the tire of the conventional example was expressed as an index when the passing sound was set to 100. The larger the value, the smaller the passing sound and the better the noise performance.

  The results are as shown in Table 1. In Comparative Example 1, although the noise performance was improved by the expansion of the cross-sectional area of the lateral groove, the drainage performance was deteriorated as compared with the conventional example. In Comparative Example 2, the drainage performance was greatly deteriorated because the stagnation of the water flow occurred at the notch 112 of the lateral groove. In Comparative Example 3, since the expansion portion was provided not at the central portion but at the end portion of the effective lateral groove portion, the function as the expansion silencer was not exhibited, and noise performance was not obtained.

  On the other hand, according to the Example, the noise performance could be improved without impairing the drainage performance. From the comparison between Examples 1 to 3 and Examples 4 to 7, it can be seen that it is advantageous in terms of noise performance to provide the overhanging portion 38 of the inflating portion 34 on both the stepping side and the kicking side. Further, it can be seen from the comparison between Example 4 and Example 5 that the noise performance is superior when the facing ratio between the protruding portion and the protruding portion is increased. Further, it can be seen from the comparison between the fifth embodiment and the sixth embodiment that the noise performance is better as the protruding amounts on the stepping side and the kicking side are equal.

DESCRIPTION OF SYMBOLS 14 ... Tread part 20A ... Maximum width belt 22 ... Main groove 26 ... Shoulder area 28 ... Horizontal groove 30 ... Effective lateral groove part 32 ... General groove part 34 ... Expansion part 36 ... Recessed part 38 ... Overhang part A ... Tire circumferential direction Wo ... Groove width direction Outside J: Effective groove length

Claims (6)

In a pneumatic tire in which a lateral groove extending from the main groove to the outside of the ground contact end is provided in a shoulder region defined by a main groove extending in the tire circumferential direction in the tread portion,
The lateral groove has a portion from the main groove to a position corresponding to the end in the width direction of the maximum width belt as an effective lateral groove portion, and the effective lateral groove is provided with general groove portions at both ends in the length direction of the effective lateral groove portion. In addition to providing a recessed portion that is recessed with respect to the groove bottom of the general groove portion at the center in the length direction of the portion, and extending the recessed portion outward in the groove width direction, the groove cross-sectional area of the general groove portion is enlarged. The pneumatic tire is characterized in that the inflating portion to be provided is provided below the groove bottom of the general groove portion.   The pneumatic tire according to claim 1, wherein the inflatable portion is provided within a range of 30 to 70% from the main groove with respect to a length of the effective lateral groove portion.   The pneumatic groove according to claim 1 or 2, wherein the transverse groove has an expansion coefficient of 150% or more, which is a ratio of a groove cross-sectional area at a portion where the expansion portion is provided to a groove cross-sectional area in the general groove portion. tire.   The pneumatic tire according to any one of claims 1 to 3, wherein the inflatable portion is provided by projecting the concave portion outwardly in the groove width direction on both sides of the lateral groove. .   5. The pneumatic tire according to claim 4, wherein an overhang portion on one side and an overhang portion on the other side sandwiching the lateral groove are opposed to each other by 60 to 100%.   6. The pneumatic tire according to claim 4, wherein a ratio of the amount of overhang between the one overhanging portion and the other overhanging portion sandwiching the lateral groove is within a range of 80 to 120%.

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