JP2015120387A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of improving performance on uniformity on the condition that pitch variation is provided.SOLUTION: Wall surface grooves G11, G12, G13 and G14 having 1 mm or more in depth are provided on wall surfaces S1, S2, S3 and S4 of land parts B1, B2, B3 and B4, and the groove depths of the wall surface grooves G11, G12, G13 and G14 are different among the land parts B1, B2, B3 and B4 having different pitch lengths P1, P2, P3 and P4. If a land part volume in a region in a tire circumferential direction of the n-th (n is a number of 2 or more) largest pitch length is Vbn, and a wall surface groove volume in a region in the tire circumferential direction of the n-th largest pitch length is Vgn, then 1.02×Vg(n-1)/Vb(n-1)≤Vgn/Vbn is satisfied.

Description

  The present invention relates to a pneumatic tire with improved performance related to uniformity.

  In order to reduce pattern noise caused by a tread pattern, a pneumatic tire is known which is provided with a pitch variation in which a pitch length is changed as an index indicating a distribution state of land portions in the tire circumferential direction (see Patent Document 1). ).

JP 2013-18310 A

  However, in this type of pneumatic tire, the block rigidity on the tread surface changes in the tire circumferential direction, and therefore there is a possibility that the performance related to uniformity cannot be sufficiently exhibited.

  This invention is made | formed in view of the said situation, Comprising: Assuming that the pitch variation is provided, it aims at providing the pneumatic tire which improved the performance regarding uniformity.

In the pneumatic tire according to the present invention, a plurality of land portions are formed by a circumferential groove and an inclined groove inclined with respect to the circumferential groove, and a pitch in which two or more types of pitch lengths of the land portions in the tire circumferential direction exist. This is a pneumatic tire with variations. A plurality of wall grooves each having a depth of 1 mm or more are provided on at least one wall surface of the land portion, and the groove depths of the wall surface grooves are different between land portions having different pitch lengths. When the land portion volume in the tire circumferential direction region of the nth (n is a natural number of 2 or more) pitch length is Vbn, and the volume of the wall groove in the tire circumferential region of the nth largest pitch length is Vgn,
1.02 × Vg (n−1) / Vb (n−1) ≦ Vgn / Vbn
Meet.

  In the pneumatic tire according to the present invention, the relationship between the depth of the wall surface groove between the land portions, and the relationship between the ratio of the volume of the wall groove and the volume of the land portion between the land portions, Improvements are being made. As a result, according to the pneumatic tire according to the present invention, performance related to uniformity can be improved.

FIG. 1 is a perspective view showing a land portion partitioned in a tread portion of a pneumatic tire according to an embodiment of the present invention. FIG. 2 is a perspective view showing a modification of the wall surface groove shown in FIG. FIG. 3 is a perspective view showing a circled portion shown in FIG. FIG. 4 is a perspective view showing a modified example of the wall surface groove shown in FIG. FIG. 5 is a perspective view showing a modification of the wall surface groove shown in FIG.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of a pneumatic tire according to the present invention (basic forms and additional forms 1 to 5 shown below) will be described in detail with reference to the drawings. Note that these embodiments do not limit the present invention. In addition, the constituent elements of the above embodiment include those that can be easily replaced by those skilled in the art, or those that are substantially the same. Furthermore, various forms included in the above-described embodiment can be arbitrarily combined within a range obvious to those skilled in the art.

[Basic form]
Below, the basic form is demonstrated about the pneumatic tire which concerns on this invention. In the following description, the tire radial direction means a direction orthogonal to the rotational axis of the pneumatic tire, the tire radial inner side is the side toward the rotational axis in the tire radial direction, and the tire radial outer side is in the tire radial direction. The side away from the rotation axis. The tire circumferential direction refers to a circumferential direction with the rotation axis as a central axis. Furthermore, the tire width direction refers to a direction parallel to the rotation axis. In addition, the tire equatorial plane is a plane that is orthogonal to the rotational axis of the pneumatic tire and passes through the center of the tire width of the pneumatic tire.

  FIG. 1 is a perspective view showing a land portion partitioned in a tread portion of a pneumatic tire according to an embodiment of the present invention. The tread portion 2 shown in FIG. 2 includes two circumferential grooves 12 and 14 adjacent to each other in the tire width direction, and inclined grooves 16 that intersect these circumferential grooves 12 and 14 and extend in the tire width direction. 18, 20, 22, and 24 are provided, and land portions B 1, B 2, B 3, and B 4 are partitioned.

  Here, the circumferential groove in the present embodiment is not limited to a groove that extends in the tire circumferential direction and forms an annular shape as shown in FIG. The circumferential groove in the present embodiment includes an annular groove that extends in a zigzag manner in the tire circumferential direction, and extends at an angle of 45 ° or less with respect to the tire circumferential direction. Also included is a groove that terminates in. Further, the inclined grooves in the present embodiment refer to all grooves extending at an angle of more than 45 with respect to the tire circumferential direction, and also include grooves extending in the tire width direction. The 45 ° or less and the 45 ° or more refer to angles on each side in the tire width direction with respect to the tire circumferential direction.

  The tread portion 2 shown in FIG. 1 has a tread pattern in which units composed of land portions B1 to B4 and inclined grooves 18, 20, 22, 24 are regularly arranged in the tire circumferential direction. For this reason, the inclined groove 16 is a groove having the same shape as the inclined groove 24.

  That is, in the tread portion 2, in the tire circumferential direction, each region of the land portions B1 to B4 is defined by the sum of the half regions of the grooves located on both sides of the tire circumferential direction. There are four types of pitch lengths P1, P2, P3, and P4 shown in FIG. In the example shown in the figure, the relationship between the pitch lengths P1, P2, P3, and P4 is P1> P2> P3> P4.

  Under such a premise, in the pneumatic tire of the present embodiment, at least one wall surface in each of the land portions B1 to B4, wall surfaces S1, S2, S3 facing the circumferential groove 12 in the example shown in FIG. , S4 are provided with three wall surface grooves G11, G12, G13, and G14 each having a depth of 1 mm or more side by side in the tire radial direction. Here, the depth of the wall surface groove means the maximum dimension of the wall surface groove measured from the wall surface in the normal direction.

  And the groove depth of a wall surface groove | channel differs between land part B1 to B4 of different pitch length P1 to P4. Specifically, the groove depth of the wall surface groove G11 is the largest in the land portion B1 with the longest pitch length P1, and the wall surface grooves G11, G12 in the order of the land portions B1 to B4 of the pitch lengths P1 to P4. , G13, G14 are gradually reduced in groove depth, and the groove depth of the wall surface groove G14 is the smallest in the land portion B4 having the shortest pitch length P4.

  Here, the location of the wall surface groove in the land portion is not limited to the wall surface facing the circumferential groove as shown in FIG. The wall surface groove can also be provided on the wall surface facing the inclined grooves 18 to 24. Moreover, the arrangement | positioning location of the wall surface groove | channel in a land part can also be varied in each land part. For example, the wall surface groove may be provided on the wall surface facing the inclined groove in the land portion provided on the wall surface facing the circumferential groove and the land portion adjacent to the tire circumferential direction. Furthermore, about one land part, a wall surface groove | channel can also be formed not only in the wall surface which opposes a circumferential groove | channel, and the wall surface which opposes an inclination groove | channel, but in both of these. For example, in a land portion having four wall surfaces, wall grooves can be provided on four wall surfaces at the maximum.

  Further, the number of wall surface grooves provided in the tire radial direction and the shape of the wall surface grooves are not limited to the numbers and shapes shown in FIG. In the example shown in FIG. 1, each of the wall surface grooves G11 to G14 is composed of three riblets arranged in the tire radial direction (a linear groove having a shape appearing on the wall surface). A plurality of circular grooves) may be arranged in the tire circumferential direction and the tire radial direction.

  Furthermore, the relationship between adjacent land portions is not limited to the example shown in FIG. For example, the land portion B3 having the third longest pitch length P3 can be partitioned at positions adjacent to the tire circumferential direction of the land portion B1 having the longest pitch length P1. Further, the land portions B2 and B2 having the same pitch length P2 and P2 can be divided and formed adjacent to each other in the tire circumferential direction.

Next, in this embodiment, the land volume in the tire circumferential direction region of the nth (n = 2, 3, 4 in FIG. 1) having the largest pitch length is Vbn, and the tire having the nth largest pitch length. When the volume of the wall surface groove in the circumferential region is Vgn,
1.02 × Vg (n−1) / Vb (n−1) ≦ Vgn / Vbn
Meet.

(Action etc.)
In the pneumatic tire according to the present embodiment, as shown in FIG. 1, at least one wall surface of the land portion is provided with a plurality of wall grooves each having a depth of 1 mm or more, and the wall surface between the land portions having different pitch lengths is provided. The depth of the groove is different. In other words, in the example shown in FIG. 1, a groove having a certain depth (1 mm or more) is provided at least in a land portion having the largest volume to achieve uniform rigidity between land portions having different pitch lengths (operation). 1).

  Moreover, in the pneumatic tire according to the present embodiment, by satisfying the above inequality 1.02 × Vg (n−1) / Vb (n−1) ≦ Vgn / Vbn, between land portions having a close pitch length. Among them, for the land portion having a larger volume, the ratio of the volume of the wall surface groove to the land portion volume is increased to achieve uniform rigidity between the land portions having different pitch lengths (Operation 2).

  As described above, in the pneumatic tire according to the present embodiment, the relationship between the depth of the wall surface groove between the land portions and the volume of the wall surface groove and the volume of the land portion between the land portions. By improving the relationship of “ratio to”, it is possible to make the rigidity uniform between land portions having different pitch lengths (the above-described actions 1 and 2). As a result, according to the pneumatic tire according to the present invention, performance related to uniformity can be improved.

  In addition, although not shown in figure, the pneumatic tire which concerns on this Embodiment shown above has the same meridional cross-sectional shape as the conventional pneumatic tire. Here, the meridional cross-sectional shape of the pneumatic tire refers to a cross-sectional shape of the pneumatic tire that appears on a plane perpendicular to the tire equatorial plane. The pneumatic tire according to the present embodiment has a bead portion, a sidewall portion, a shoulder portion, and a tread portion from the inner side in the tire radial direction toward the outer side in a tire meridian cross-sectional view. The pneumatic tire includes, for example, a carcass layer extending from a tread portion to bead portions on both sides and wound around a pair of bead cores in a tire meridional section, and a tire radial outside of the carcass layer. The belt layer and the belt reinforcing layer are sequentially formed.

  In addition, the pneumatic tire of the present embodiment includes normal manufacturing processes, that is, a tire material mixing process, a tire material processing process, a green tire molding process, a vulcanization process, and an inspection process after vulcanization. It is obtained through the process. When manufacturing the pneumatic tire of the present embodiment, in particular, convex portions corresponding to, for example, the wall surface grooves G11 to G14 shown in FIG. 1 are formed on the inner wall of the vulcanizing mold, and this mold is used. Vulcanize.

[Additional form]
Next, additional embodiments 1 to 5 that can be optionally implemented with respect to the basic embodiment of the pneumatic tire according to the present invention will be described.

(Additional form 1)
In the basic form, as shown in FIG. 1, the depth d1 of the wall surface groove G11 provided in the wall surface S1 facing the circumferential groove 12 of the land portion (for example, B1), and the tire width direction dimension of the land portion B1. The ratio d1 / W1 to W1 is preferably 0.25 or less (additional form 1).

  In FIG. 1, by setting the ratio d1 / W1 to be 0.25 or less, it is possible to suppress a decrease in rigidity in the land portion B1. As a result, the deformation of the wall surface S1 facing the circumferential groove 12 can be suppressed, and in particular, when turning the vehicle, it is possible to suppress the deterioration of the steering stability performance and to prevent the land portion from baldness and the like. A decrease in performance can also be suppressed. In addition, this Embodiment is not restricted to the case where the range of the said ratio is applied only to land part B1 shown in FIG. 1, The range of the said ratio can also be applied about at least 2 land part shown in FIG.

(Additional form 2)
FIG. 2 is a perspective view showing a modification of the wall surface groove shown in FIG. The tread portion 4 shown in the figure is provided with the same grooves 12 to 24 as the tread portion 2 shown in FIG. 1, and the same land portions B1, B2, B3, and B4 are defined. In the example shown in FIG. 2, wall surface grooves G21, G22, G23, and G24 having a depth of 1 mm or more are formed on the wall surfaces S1 ′, S2 ′, S3 ′, and S4 ′ facing the inclined grooves 18 to 24 of the land portions B1 to B4. 1 is the same as the example shown in FIG. 1 except that three are provided side by side in the tire radial direction.

  In the basic form and the form in which the additional form 1 is added to the basic form, as shown in FIG. 2, a wall surface groove G21 provided on the wall surface S1 ′ facing the inclined groove 18 of the land part (for example, the land part B1). It is preferable that the ratio d2 / W2 between the depth d2 of the tire and the tire circumferential direction dimension W2 of the land portion B1 is 0.25 or less (additional form 2).

  In FIG. 2, by reducing the ratio d2 / W2 to 0.25 or less, it is possible to suppress a decrease in rigidity in the land portion B1. As a result, the deformation of the wall surface S1 ′ facing the inclined groove 18 can be suppressed, and in particular, when the vehicle is traveling straight, it is possible to suppress a decrease in steering stability performance and to prevent the land portion from being bald and durable. A decrease in performance can also be suppressed. In addition, this Embodiment is not restricted to the case where the said range of ratio is applied only to land part B1 shown in FIG. 2, The range of said ratio can also be applied about at least 2 land part shown in FIG.

(Additional form 3)
In the basic form and the form in which at least one of the additional forms 1 and 2 is added to the basic form, as shown in FIG. 3 (a perspective view showing a circled portion shown in FIG. 1), the tire tread surface X and the wall surface groove G11. Is preferably 30 ° or less (additional form 3).

  Here, the tire tread surface means a contact surface between a tire and a road surface under a condition that a normal rim is attached, a normal internal pressure is applied, and a normal load is applied. Here, the regular rim means “standard rim” defined in JATMA, “Design Rim” defined in TRA, or “Measuring Rim” defined in ETRTO. The normal internal pressure means “maximum air pressure” defined by JATMA, the maximum value described in “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” defined by TRA, or “INFLATION PRESSURES” defined by ETRTO. The regular load means “maximum load capacity” defined by JATMA, the maximum value described in “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” defined by TRA, or “LOAD CAPACITY” defined by ETRTO.

  Further, the angle θ formed between the tire tread surface X and the bottom surface Y of the wall surface groove G11 is, as shown in FIG. 3, the wall surface S1 facing the inclined groove 18 extending in the depth direction of the wall surface groove G11, that is, the tire width direction. It means an angle between the profile line LX of the tire tread surface X and the profile line LY of the bottom surface Y of the wall surface groove G11.

  By setting the angle θ between the tire tread surface X and the bottom surface Y of the wall surface groove G11 to be 30 ° or less, the wall surface S1 can be sufficiently deformed when the tire rolls, and as a result, the rigidity of the land portion B1 can be improved efficiently. To improve the performance related to uniformity.

  In addition, the said effect can be show | played by a higher level by making angle (theta) which the tire tread surface X and the bottom face Y of the wall surface groove | channel G11 make into 10 degrees or less.

(Additional form 4)
FIG. 4 is a perspective view showing a modified example of the wall surface groove shown in FIG. The tread portion 6 shown in the figure is provided with the same grooves 12 to 24 as the tread portion 2 shown in FIG. 1, and the same land portions B1, B2, B3, and B4 are partitioned. In the example shown in FIG. 4, wall surface grooves G31, G32, G33, and G34 having a depth of 1 mm or more are provided on the wall surfaces S1, S2, S3, and S4 facing the inclined grooves 18 to 24 of the land portions B1 to B4, respectively. It is the same as the example shown in FIG. 1 except that 8, 6, 4, and 2 are provided.

  In the basic form and the form obtained by adding at least one of the additional forms 1 to 3 to the basic form, different pitch lengths (pitch length P1> pitch length P2> pitch length P3> pitch length P4 in the example shown in FIG. 4). It is preferable that the area of one wall surface groove is the same and the number of wall surface grooves is different (additional form 4) between the tire circumferential direction regions. Here, the area of one wall surface groove means the area at the opening of each wall surface groove. Further, the number of types of pitch length is not limited to four as described above, and may be any number as long as it is plural.

  As described above, in the land portions B1 to B4 having different pitch lengths P1 to P4, when the wall surface grooves having the same area are provided, the pitch lengths are different by adjusting the number of the wall surface grooves according to the volume of the land portion. It is possible to make the rigidity uniform between the land portions. As a result, according to the present embodiment, performance related to uniformity can be improved.

  In the present embodiment, in particular, when the difference between the maximum pitch length and the minimum pitch length is large, that is, in the tire circumferential direction of the land portion having the maximum pitch length (hereinafter sometimes referred to as the “maximum land portion”). Useful when the dimensions are relatively large. Usually, the area of one wall groove is relative to the area of the wall surface of the minimum land portion so as not to cause a local rigidity difference in the land portion having the minimum pitch length (hereinafter sometimes referred to as “minimum land portion”). Therefore, it is important that the area be suitable. Moreover, when the tire circumferential direction dimension of the largest land part is comparatively large, the tire circumferential direction dimension of the wall surface facing the circumferential groove of the largest land part becomes excessively large with respect to the tire radial direction dimension. In that case, the wall surface facing the circumferential groove of the largest land part has more wall grooves of the same area as the wall groove provided on the wall surface of the smallest land part than the number provided on the wall surface of the smallest land part in the tire circumferential direction. It is preferable to provide it in order to make the rigidity between the land portions more uniform. As a result, the occurrence of cracks and the like can be prevented and the durability performance can be improved without causing a local difference in rigidity even in the maximum land portion.

(Additional form 5)
FIG. 5 is a perspective view showing a modification of the wall surface groove shown in FIG. The tread portion 8 shown in the figure is provided with the same grooves 12 to 24 as the tread portion 2 shown in FIG. 1, and the same land portions B1, B2, B3, and B4 are defined. In the example shown in FIG. 5, wall surface grooves G41, G42, G43 having a depth of 1 mm or more and different areas on the wall surfaces S1, S2, S3, S4 facing the inclined grooves 18 to 24 of the land portions B1 to B4, 1 is the same as the example illustrated in FIG. 1 except that four G44s are provided.

  In the basic form and the form obtained by adding at least one of the additional forms 1 to 3 to the basic form, different pitch lengths (pitch length P1> pitch length P2> pitch length P3> pitch length P4 in the example shown in FIG. 5). It is preferable that the area of one wall surface groove is different and the number of wall surface grooves is the same (additional form 5) between the tire circumferential direction regions. Here, the area of one wall surface groove means the area at the opening of each wall surface groove. Further, the number of types of pitch length is not limited to four as described above, and may be any number as long as it is plural.

  As described above, when the same number of wall surface grooves are provided in the land portions B1 to B4 having different pitch lengths P1 to P4, the pitch length can be adjusted by adjusting the area of one wall surface groove according to the volume of the land portion. It is possible to make the rigidity uniform between different land portions. As a result, according to the present embodiment, performance related to uniformity can be improved.

  The present embodiment is particularly useful when the difference between the maximum pitch length and the minimum pitch length is small, that is, when the tire circumferential dimension of the maximum land portion is relatively close to the tire circumferential dimension of the minimum land portion. It is. As described above, it is important that the area of one wall surface groove is a suitable area with respect to the area of the wall surface of the minimum land portion so as not to cause a local rigidity difference in the minimum land portion. Further, when the tire circumferential dimension of the largest land portion is relatively close to the tire circumferential dimension of the smallest land portion, the wall surface facing the circumferential groove of the largest land portion faces the circumferential groove of the smallest land portion. It has almost the same shape as the wall surface. In that case, on the wall facing the circumferential groove of the largest land part, the number of wall grooves which are similar to the wall groove provided on the wall surface of the smallest land part and have a larger area are provided on the wall surface of the smallest land part. It is preferable to provide the same number as in order to make the rigidity between the land portions more uniform. As a result, the occurrence of cracks and the like can be prevented and the durability performance can be improved without causing a local difference in rigidity even in the maximum land portion. Further, in the present embodiment, it is not necessary to excessively increase the number of wall surface grooves provided in the maximum land portion, which is advantageous in terms of tire manufacture.

  A tire having a tire size of 265 / 70R17 and an annular structure in which units including land portions B1 to B4 and inclined grooves 18, 20, 22, and 24 shown in FIG. 1 are regularly arranged in the tire circumferential direction on the tread surface. Pneumatic tires of Examples 1 to 7 including the width direction region were produced.

Here, the pneumatic tires of Examples 1 to 7 are tires having an n-th (n = 2, 3, 4) land portion volume in the tire circumferential direction region having the largest pitch length as Vbn and having the nth largest pitch length. When the volume of the wall surface groove in the circumferential region is Vgn,
1.02 × Vg (n−1) / Vb (n−1) ≦ Vgn / Vbn
Meet. In addition, other conditions regarding the pneumatic tires of Examples 1 to 7 are as shown in Table 1 below.

  On the other hand, the tire size was set to 265 / 70R17, and a conventional pneumatic tire was manufactured which was the same as the pneumatic tire of Example 1 except that the wall surface grooves G11 to G14 shown in FIG. 1 were not provided. .

  Each of the test tires of Examples 1 to 7 and the conventional example manufactured as described above was assembled on an 8J rim at an air pressure of 230 kPa, and performance related to uniformity was determined according to the method for testing uniformity of automobile tires defined in JIS D4233. Was evaluated.

  Specifically, using a uniformity testing machine, the magnitude of the variation in the force in the tire radial direction that occurs while a tire receiving an 8.8 kN load makes one revolution at a constant radius is measured. The index was evaluated based on the result as a standard example (100). This evaluation shows that the larger the index, the higher the performance with respect to uniformity.

  According to Table 1, it belongs to the technical scope of the present invention (the relationship between “the depth of the wall surface groove between each land portion” and “the volume of the wall surface groove and the volume of the land portion between each land portion”. Regarding the pneumatic tires of Example 1 to Example 7 in which the relationship of “ratio” has been improved, all are related to uniformity compared to the pneumatic tire of the conventional example, which does not belong to the technical scope of the present invention. It can be seen that the performance is high.

  The present invention includes the following aspects.

(1) Air provided with a pitch variation in which a plurality of land portions are formed by the circumferential grooves and the inclined grooves inclined with respect to the circumferential grooves, and there are two or more types of pitch lengths of the land portions in the tire circumferential direction. In the entering tire, at least one wall surface of the land portion is provided with a plurality of wall surface grooves having a depth of 1 mm or more, and the groove depth of the wall surface groove is different between land portions having different pitch lengths.
When the land portion volume in the tire circumferential direction region of the nth (n is a natural number of 2 or more) pitch length is Vbn, and the volume of the wall groove in the tire circumferential region of the nth largest pitch length is Vgn, A pneumatic tire characterized by satisfying 1.02 × Vg (n−1) / Vb (n−1) ≦ Vgn / Vbn.

(2) The ratio d1 / W1 between the depth d1 of the wall surface groove provided on the wall surface facing the circumferential groove of the land portion and the tire width direction dimension W1 of the land portion is 0.25 or less. The pneumatic tire according to (1) above.

(3) The ratio d2 / W2 between the depth d2 of the wall surface groove provided on the wall surface facing the inclined groove of the land portion and the tire circumferential direction dimension W2 of the land portion is 0.25 or less, The pneumatic tire according to (1) or (2).

(4) The pneumatic tire according to any one of (1) to (3), wherein an angle formed between the tire tread surface and the bottom surface of the wall surface groove is 30 ° or less.

(5) In any one of the above (1) to (4), the area of one wall surface groove is the same and the number of the wall surface grooves is different between tire circumferential regions of different pitch lengths. Pneumatic tires.

(6) In any one of the above (1) to (4), the area of one wall surface groove is different and the number of the wall surface grooves is the same between tire circumferential regions of different pitch lengths. Pneumatic tires.

2, 4, 6, 8 Tread portion 12, 14 Circumferential groove 16, 18, 20, 22, 24 Inclined groove B1, B2, B3, B4 Land portion d1 On the wall surface S1 facing the circumferential groove 12 of the land portion B1 Depth of wall surface groove G11 provided d2 Depth of wall surface groove G21 provided on wall surface S1 ′ facing inclined groove 18 of land portion B1 G11, G12, G13, G14, G21, G22, G23, G24, G31 G32, G33, G34, G41, G42, G43, G44 Wall surface groove LX Profile line of tire tread surface X Profile line of LY bottom surface Y P1, P2, P3, P4 Pitch length S1, S2, S3, S4, S1 ′, S2 ', S3', S4 'Wall surface W1 Tire width direction size of land portion B1 W2 Tire circumferential direction size of land portion B1 X Tire tread surface Y Bottom surface of wall surface groove G11

Claims (6)

In a pneumatic tire in which a plurality of land portions are formed by a circumferential groove and an inclined groove that is inclined with respect to the circumferential groove, and a pitch variation in which there are two or more types of pitch lengths of the land portion in the tire circumferential direction is provided. ,
A plurality of wall grooves each having a depth of 1 mm or more are provided on at least one wall surface of the land portion, and the groove depth of the wall surface groove is different between land portions having different pitch lengths.
When the land portion volume in the tire circumferential direction region of the nth (n is a natural number of 2 or more) pitch length is Vbn, and the volume of the wall groove in the tire circumferential region of the nth largest pitch length is Vgn,
1.02 × Vg (n−1) / Vb (n−1) ≦ Vgn / Vbn
A pneumatic tire characterized by satisfying   The ratio d1 / W1 between the depth d1 of the wall surface groove provided on the wall surface facing the circumferential groove of the land portion and the tire width direction dimension W1 of the land portion is 0.25 or less. Pneumatic tire described in 2.   The ratio d2 / W2 between the depth d2 of the wall surface groove provided on the wall surface facing the inclined groove of the land portion and the tire circumferential direction dimension W2 of the land portion is 0.25 or less, or 2. The pneumatic tire according to 2. The pneumatic tire according to any one of claims 1 to 3, wherein an angle formed by a tire tread surface and a bottom surface of the wall surface groove is 30 ° or less.   The pneumatic tire according to any one of claims 1 to 4, wherein the area of one wall surface groove is the same and the number of the wall surface grooves is different between tire circumferential regions having different pitch lengths.   The pneumatic tire according to any one of claims 1 to 4, wherein an area of one wall surface groove is different and the number of the wall surface grooves is the same between tire circumferential regions having different pitch lengths.

Images