JP2018144656A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of ensuring excellent running performance on a wet road surface while maintaining excellent running performance on a dry road surface and achieving both of these performances. SOLUTION: A lug groove 30 extending along a tire width direction is formed in a shoulder land portion 21, and an inner end of the lug groove 30 in the tire width direction is terminated in the shoulder land portion 21 to form each lug groove 30. At least one vertical hole 40 is formed between the inner end in the tire width direction and the outermost main groove 11 and separated from the outermost main groove 11 and the lug groove 30, and a vertical hole is formed between the outermost main groove 11 and the lug groove 30. A sipe 51 extending across the 40 along the tire width direction and communicating with the outermost main groove 11 and the lug groove 30 is formed, and is wider than the sipe 51 at the bottom or the middle of the sipe 51 in the depth direction. A cavity H extending along the sipe 51 is provided. [Selection diagram] Fig. 2

Description

  The present invention relates to a pneumatic tire, and more specifically, air that ensures excellent driving performance on a wet road surface while maintaining excellent driving performance on a dry road surface, and makes it possible to achieve both of these performances. Related to tires.

  In the conventional pneumatic tire, in order to ensure the running performance (wet performance) on the road surface (wet road surface) wet by rain etc., the main groove extending in the tire circumferential direction on the surface of the tread part and the tire width direction An extending lug groove is provided to improve drainage performance. However, if there are many main grooves and lug grooves to increase drainage performance and the groove area increases, the ground contact area decreases and land rigidity decreases, resulting in driving performance on dry road surfaces (dry performance). ) May be adversely affected.

  For example, Patent Literature 1 and Patent Literature 2 propose a sipe in which drainage holes are combined. Such sipes ensure good groove performance by drainage holes and good wet performance, while suppressing the increase of groove area on the tread surface to ensure a ground contact area and good dry performance. Can do. However, even in such a sipe, there is an influence on the rigidity of the land because there is a hole for drainage, and the drainage performance by the sipe itself is not necessarily high. In order to improve the performance effectively, further measures are required for the shape and arrangement of the sipe and the combination with other grooves.

JP 2006-168462 A JP-A-62-241712

  An object of the present invention is to provide a pneumatic tire that maintains excellent driving performance on a dry road surface while ensuring excellent driving performance on a wet road surface and makes it possible to achieve both of these performances. is there.

  In order to achieve the above object, a pneumatic tire according to the present invention includes a tread portion that extends in the tire circumferential direction to form an annular shape, a pair of sidewall portions disposed on both sides of the tread portion, and the sidewall portions. A plurality of main grooves extending along the tire circumferential direction on the surface of the tread portion, and a plurality of rows of land portions partitioned by the main grooves. A pneumatic tire having a lug groove extending along a tire width direction on a shoulder land portion defined on an outer side of the outermost main groove located on the outermost side in the tire width direction of the main groove. An inner end in the tire width direction of the lug groove is terminated in the shoulder land portion, and the outermost outer groove is disposed between the inner end in the tire width direction of the lug groove and the outermost main groove. Main groove and lug At least one vertical hole opened in the tread tread and spaced in the tire radial direction and extending along the tire width direction across the vertical hole between the outermost main groove and the lug groove Then, a sipe is formed in which one end communicates with the outermost main groove and the other end communicates with the lug groove. It is characterized by comprising an extending cavity.

  In the present invention, as described above, the lug groove terminates in the land portion and is not in communication with the main groove, so that the rigidity of the shoulder land portion can be secured, and the dry performance can be maintained well. it can. On the other hand, since a vertical hole is provided between the main groove and the lug groove, it is necessary to ensure a groove area equivalent to the case where the lug groove communicates with the main groove while maintaining the land rigidity. Can do. At this time, since a sipe that connects the main groove and the lug groove across the vertical hole is provided, the water in the groove can flow between the main groove, the vertical hole, and the lug groove to improve drainage performance. Can do. In particular, as a sipe that connects the main groove, the vertical hole, and the lug groove, a sipe with a hollow portion and excellent drainage is adopted, so the drainage performance is about the same as when the lug groove reaches the main groove. Can be obtained. These synergies can effectively enhance wet performance while maintaining excellent dry performance.

In the present invention, it is _preferable that the maximum width W _{R on} the tread surface of the vertical hole satisfies the following formula (1) with respect to the groove width W _L of the lug groove at the ground contact end. By setting the dimensions in this way, the balance between the vertical hole and the lug groove width is improved, which is advantageous in achieving both dry performance and wet performance.
0.3 × W _L ≦ W _R ≦ 2.0 × W _L (1)

In the present invention, it is preferable that the sipe depth D _S satisfies the relationship of 0.9 × D _R ≦ D _S ≦ 1.0 × D _R with respect to the depth D _{R of the} vertical hole. By setting the dimensions in this way, the balance between the sipe and the depth of the vertical hole is improved, which is advantageous for achieving both dry performance and wet performance.

In the present invention, it is preferable that the maximum cross-sectional width W _A of the cavity satisfies the relationship of 2.0 × W _S ≦ W _A ≦ 4.0 × W _S with respect to the sipe width W _S of the sipe provided with the cavity. . By setting the dimensions in this way, the balance of the cavity with respect to the sipe is improved, which is advantageous for achieving both dry performance and wet performance.

In the present invention, it is _preferable that the maximum width W _{R on} the tread surface of the vertical hole and the maximum cross-sectional width W _A of the cavity satisfy the relationship of 1.0 × W _A ≦ W _R ≦ 3.0 × W _A. By setting the dimensions in this manner, the balance between the size of the vertical hole and the hollow portion becomes good, which is advantageous for achieving both dry performance and wet performance.

  In the present invention, the various dimensions are values measured when 80% of the normal load is applied by placing the tire on the normal rim and filling it with normal internal pressure and placing it vertically on a plane. Note that both ends of the grounding region formed in this state are “grounding ends”. The “regular rim” is a rim determined for each tire in the standard system including the standard on which the tire is based, for example, a standard rim for JATMA, “Design Rim” for TRA, or ETRTO. Then, “Measuring Rim” is set. “Regular internal pressure” is the air pressure that each standard defines for each tire in the standard system including the standard on which the tire is based. The maximum air pressure is JATMA, and the table “TIRE ROAD LIMITS AT VARIOUS” is TRA. The maximum value described in “COLD INFRATION PRESURES”, “INFLATION PRESURE” for ETRTO, but 180 kPa when the tire is a passenger car. “Regular load” is a load determined by each standard for each tire in the standard system including the standard on which the tire is based. The maximum load capacity is JATMA, and the table “TIRE ROAD LIMITS AT VARIOUS” is TRA. The maximum value described in “COLD INFORMATION PRESURES”, “LOAD CAPACITY” if it is ETRTO, but if the tire is for a passenger car, the load is equivalent to 88% of the load.

1 is a meridian cross-sectional view of a pneumatic tire according to an embodiment of the present invention. It is a front view which shows the tread surface of the pneumatic tire which consists of embodiment of this invention. It is explanatory drawing which expands and shows the structure of the sipe provided with the cavity part of this invention. It is a front view which shows the tread surface of the pneumatic tire which consists of another embodiment of this invention. It is a principal part enlarged view which expands and shows a part of tread part of FIG.

  Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings.

  As shown in FIG. 1, the pneumatic tire of the present invention includes a tread portion 1 that extends in the tire circumferential direction and has an annular shape, a pair of sidewall portions 2 that are disposed on both sides of the tread portion 1, And a pair of bead portions 3 disposed inside the wall portion 2 in the tire radial direction. In addition, in FIG. 1, the code | symbol CL shows a tire equator and the code | symbol E shows a grounding end.

  A carcass layer 4 is mounted between the pair of left and right bead portions 3. The carcass layer 4 includes a plurality of reinforcing cords extending in the tire radial direction, and is folded back around the bead core 5 disposed in each bead portion 3 from the vehicle inner side to the outer side. A bead filler 6 is disposed on the outer periphery of the bead core 5, and the bead filler 6 is wrapped by the main body portion and the folded portion of the carcass layer 4. On the other hand, a plurality of layers (two layers in FIG. 1) of belt layers 7 are embedded on the outer peripheral side of the carcass layer 4 in the tread portion 1. Each belt layer 7 includes a plurality of reinforcing cords that are inclined with respect to the tire circumferential direction, and is disposed so that the reinforcing cords cross each other between the layers. In these belt layers 7, the inclination angle of the reinforcing cord with respect to the tire circumferential direction is set in a range of 10 ° to 40 °, for example. Further, a belt reinforcement layer 8 (a pair of belt reinforcement layers 8 that respectively cover both ends of the belt layer 7 in the width direction) is provided on the outer peripheral side of the belt layer 7. The belt reinforcing layer 8 includes an organic fiber cord oriented in the tire circumferential direction. In the belt reinforcing layer 8, the organic fiber cord has an angle with respect to the tire circumferential direction set to, for example, 0 ° to 5 °.

  The present invention is applied to such a general pneumatic tire, but its cross-sectional structure is not limited to the basic structure described above.

  As shown in FIGS. 1 and 2, a plurality of main grooves 10 (three in FIGS. 1 and 2) extending in the tire circumferential direction are provided on the outer surface of the tread portion 1. The main groove 10 is a groove having the largest groove width and groove depth among the grooves formed in the tread portion 1 of the pneumatic tire of the present invention, and the groove width is 6.0 mm to 15.0 mm, for example. Is set to, for example, 5.0 mm to 15.0 mm. A plurality of rows (four rows in FIGS. 1 and 2) of land portions 20 are partitioned by the plurality of main grooves 10. Of these main grooves 10 and land portions 20, the main groove 10 located on the outermost side in the tire width direction is the outermost main groove 11, and the land portion 20 defined on the outer side in the tire width direction of the outermost main groove 11 is the shoulder. When the land portion 21 is used, the shoulder land portion 21 has a lug groove 30, a vertical hole 40, and a sipe 50 (specifically, a sipe that connects the outermost main groove 11, the lug groove 30, and the vertical hole 40). 51) is always provided. In the present invention, the “thin groove” is a groove having a groove width smaller than that of a main groove or a lug groove described later, and larger than that of a sipe described later, and “sipe” is a groove width. Is a fine groove of 1.5 mm or less. Further, the “land portion” in the present invention refers to a section defined by a main groove (or a lug groove described later), and the land portion is divided in the tire circumferential direction or the tire width direction by narrow grooves or sipes. Even so, the land portion is regarded as a substantially continuous land portion.

  In the present invention, the structure on the inner side in the tire width direction of the outermost main groove 11 is not particularly limited. For example, in the illustrated example, a land portion 20 (hereinafter referred to as a center) that is partitioned by an outermost main groove 11 and a center main groove 12 on both sides of a main groove 10 (hereinafter referred to as a center main groove 12) on the tire equator CL. Land section 22) is provided. In each center land portion 22, an inclined groove 60 extending in a direction inclined with respect to the tire width direction, one end communicating with the outermost main groove 11 and the other end terminating in the center land portion 22. Are provided at intervals in the tire circumferential direction. A center sipe 52 is provided that extends in a direction opposite to the inclined groove 60, has one end communicating with the inclined groove 60, and the other end terminating in the center land portion 22.

  The lug grooves 30 are grooves extending along the tire width direction in the shoulder land portion 21, and a plurality of lug grooves 30 are provided at intervals in the tire circumferential direction. The inner end in the tire width direction of the lug groove 30 does not communicate with the outermost main groove 11 but terminates in the shoulder land portion 21, and the outer end in the tire width direction of the lug groove 30 exceeds the ground contact E and extends in the tire width direction outside. It is extended to.

  The vertical hole 40 is a hole that opens in the tread tread and is formed in the tire radial direction, and is provided between the inner end in the tire width direction of each lug groove 30 and the outermost main groove 11. The vertical hole 40 is separated from the outermost main groove 11 and the lug groove 30 without intersecting or in contact with the outermost main groove 11 and the lug groove 30. At least one vertical hole 40 is disposed at an extended position of each lug groove 30. The plurality of vertical holes 40 thus provided are arranged over the entire circumference at intervals in the tire circumferential direction.

  The sipe 51 is a sipe provided between the outermost main groove 11 and the lug groove 30 and extending along the tire width direction across the vertical hole 40. The sipe 51 has one end communicating with the outermost main groove 11 and the other end communicating with the inner end in the tire width direction of the lug groove 30. One sipe 51 is provided for each lug groove 30. The sipe 51 is not a general sipe in which the sipe width is constant up to the groove bottom, but is wider than the other part of the sipe 51 and along the sipe 50 as shown in FIGS. 3 (a) and 3 (b). And a hollow portion H extending. The hollow portion H can be provided at an arbitrary position in the depth direction of the sipe 51. In FIG. 3A, the hollow portion H is provided at the bottom of the sipe 51, and in FIG. A hollow portion H is provided in the middle of the direction.

  Since the sipe 51 and the vertical hole 40 intersect as described above, the cavity H provided in the sipe 51 also intersects or is connected to the vertical hole 40. That is, in FIG. 3A, the vertical hole 40 extending to the bottom of the sipe 51 is connected to the middle part of the cavity H provided at the bottom of the sipe 51, and the vertical hole 40 and the cavity H are connected in a letter shape. 3B, the vertical hole 40 extending to the bottom of the sipe 51 intersects with the cavity H provided in the middle part of the sipe 51 in the depth direction, and the vertical hole 40 and the cavity H are formed in a cross shape. Connected.

  In the illustrated example, a shoulder sipe 53 that is not connected to the lug groove 30 or the vertical hole 40 is provided in addition to the sipe 51. However, the shoulder sipe 53 is an arbitrary element that is not necessarily provided in the present invention. . In the illustrated example, one shoulder sipe 53 is provided between the lug grooves 30 adjacent in the tire circumferential direction, each extends along the tire width direction, and one end communicates with the narrow groove 40. The other end extends beyond the ground contact E and extends outward in the tire width direction.

  Thus, in the shoulder land portion 21 of the pneumatic tire of the present invention, the lug groove 30 terminates in the shoulder land portion 21 and is not in communication with the outermost main groove 11, so that the rigidity of the shoulder land portion 21 is increased. Can be ensured, and the dry performance can be maintained well. On the other hand, since the vertical holes 40 that are not in communication with these grooves are provided between the outermost main groove 11 and the lug groove 30, the lug groove 30 is formed in the outermost main groove 11 while maintaining the rigidity of the land portion. It is possible to secure the same groove area as that in the case of communication. Although the vertical hole 40 is not an element having a length in the tire circumferential direction or the tire width direction like a groove, it can sufficiently take in water into the vertical hole 40 and functions sufficiently as an element for improving wet performance. To do. Since the sipe 51 which connects the outermost main groove 11 and the lug groove 30 across the vertical hole 40 is provided at this time, the water in the outermost main groove 11, the vertical hole 40, or the lug groove 30 passes between these. It becomes fluid and can improve drainage performance. In particular, as the sipe 51 that connects the outermost main groove 11, the vertical hole 40, and the lug groove 30, a sipe 51 having a hollow portion H and having excellent drainage is adopted, so that the lug groove 30 is the outermost main groove 11. The same level of drainage performance can be obtained. These synergies can effectively enhance wet performance while maintaining excellent dry performance.

  At this time, if the lug groove 30 divides the shoulder land portion 21, the rigidity of the shoulder land portion 21 is lowered and the dry performance cannot be maintained. If the vertical hole 40 is not formed, even if the sipe 51 connects the lug groove 30 and the outermost main groove 11, the groove area is insufficient and the wet performance cannot be improved. If the sipe 51 is not formed, the sipe 51 is not in communication with the outermost main groove 11 or the lug groove 30, or if the sipe 51 does not intersect the vertical hole 40, the outermost main groove 11, the vertical hole 40, and the lug groove 30 The fluidity of water during the period is insufficient and the wet performance cannot be improved. If a groove having a groove width larger than that of the sipe 51 is formed instead of the sipe 51, the land portion rigidity is insufficient and it is impossible to achieve both wet performance and dry performance. If the sipe 51 does not include the hollow portion H, sufficient drainage performance cannot be obtained and the wet performance cannot be improved.

  As described above, at least one vertical hole 40 is provided between the inner end in the tire width direction of each lug groove 30 and the outermost main groove 11. That is, the vertical holes 40 are provided in a one-to-one relationship with the lug grooves 30 as shown in FIG. In contrast, for example, as shown in FIG. 4, an additional vertical hole 41 is provided, and two or more vertical holes 40, 41 are provided between the inner end in the tire width direction of each lug groove 30 and the outermost main groove 11. You may be made to do. In this case, all the vertical holes 40 and 41 including the additional vertical hole 41 are arranged at intervals in the tire circumferential direction. At this time, the sipe 51 crosses the vertical hole 40 existing at the extended position of the lug groove 30, but does not cross or connect to the additional vertical hole 41. That is, the vertical hole 40 is connected to the outermost main groove 11 and the lug groove 30 via the sipe 51, but the additional vertical hole 41 is not connected to the outermost main groove 11 and the lug groove 30. Instead, an auxiliary sipe 54 connecting the vertical hole 40 and the additional vertical hole 41 can be provided as shown.

  In the aspect of FIG. 4, since the additional vertical hole 41 is provided, the groove area can be increased thereby, and the wet performance can be further enhanced. On the other hand, since the additional vertical hole 41 is connected to the vertical hole 40 only by the auxiliary sipe 54, the influence on the land part rigidity by providing the vertical hole 41 can be suppressed to the minimum. At this time, since the outermost main groove 11, the lug groove 30, and the vertical holes 40 and 41 are connected directly or indirectly by the sipe 51 or the auxiliary sipe 54, water can flow between them and good drainage performance. Can be obtained.

  In the present invention, at least the sipe 51 may be a sipe having a cavity H, but the auxiliary sipe 54 is preferably a sipe having a cavity H. Thereby, the fluidity | liquidity of the water between the vertical holes 40 and 41 arranged in the circumferential direction can be improved, and it becomes advantageous in improving wet performance. If the cavity H is provided to the shoulder sipe 53 that is optionally provided in the illustrated example, the rigidity of the land portion is significantly reduced. Therefore, the sipe provided with the cavity H is the sipe 51 (always provided). It is preferable to keep the auxiliary sipe 54 (which may be optionally provided).

  The hollow portion H can be provided at an arbitrary position in the depth direction of the sipe 50 (that is, the bottom portion or an intermediate portion in the depth direction). However, as the hollow portion H is provided at a position closer to the bottom portion of the sipe 50, the end of wear is reached. The hollow portion H remains, and excellent drainage performance can be exhibited until the end of wear. For this reason, the cavity H is preferably provided at a position separated from the tread surface by, for example, 50% or more of the depth of each sipe 50.

The opening shape of the vertical hole 40 is not particularly limited, and an arbitrary shape such as an elliptical shape or a polygonal shape can be employed in addition to the illustrated circular shape. Further, the maximum width W _R (the diameter in the case of the circular vertical hole 40 shown in the figure) of the tread surface of the vertical hole 40 is 0.3 × W _L ≦ the groove width W _L of the lug groove 30 at the ground contact E. It is preferable to set so as to satisfy the relationship of W _R ≦ 2.0 × W _L. By setting the size of the vertical hole 40 in this way, drainage performance can be ensured while maintaining land portion rigidity, which is advantageous in achieving both dry performance and wet performance. If the maximum width W _R of the vertical hole 40 is smaller than 0.3 times the groove width W _L , the drainage performance by the vertical hole 40 cannot be ensured sufficiently. If the maximum width W _R of the vertical hole 40 is larger than 2.0 times the groove width W _L , the rigidity of the land portion is lowered and it is difficult to maintain the dry performance.

Further, the maximum width W _R of the tread surface of the vertical hole 40 is 20% or more and 80% or less of the distance L in the tire width direction between the outermost main groove 11 and the inner end of the lug groove 30 in the tire width direction. preferable. In this way, by setting the vertical hole 40 to an appropriate size with respect to the region between the outermost main groove 11 and the inner end in the tire width direction of the lug groove 30, drainage performance is ensured while maintaining land rigidity. This is advantageous for achieving both dry performance and wet performance. If the maximum width W _R of the vertical hole 40 is smaller than 20% of the distance L, the drainage performance by the vertical hole 40 cannot be ensured sufficiently. If the maximum width W _R of the vertical hole 40 is greater than 80% of the distance L, the vertical hole 40 would substantially contact the outermost main grooves 11 and the lug grooves 30, maintaining the dry performance land portion rigidity is lowered It becomes difficult.

The depth D _R of the vertical hole 40 is preferably set to be approximately the same as the depth D _L of the lug groove 30. Specifically, it is preferable that the maximum groove depth D _L of the lug groove 30 and the depth D _{R of the} vertical hole 40 satisfy the relationship of 0.8 × D _L ≦ D _R ≦ 1.0 × D _L. As shown in FIG. 5, “the maximum groove depth D _{L of the} lug groove” means that the inner end point in the tire width direction of the lug groove 30 on the tread surface in the meridian section is A1, and the tread surface passes through this point A1. The distance from the point A1 to the point A2 when the intersection of the imaginary line perpendicular to the line and the extension line of the bottom of the lug groove 30 is A2. By setting the groove depth in this way, it is advantageous to ensure wet performance substantially equivalent to the case where the lug groove 30 communicates with the outermost main groove 11 while maintaining excellent dry performance. . In this case, the depth D _R of the vertical hole 40 is less than 0.8 times the maximum groove depth D _L of the lug grooves 30, to reduce the volume of the vertical hole 40, the effect limiting of improving the wet performance Become. If the depth D _R of the vertical hole 40 is greater than 1.0 times the maximum groove depth D _L of the lug grooves 30, that the land portion rigidity is sufficiently maintained dry performance dropped difficult.

Furthermore, it is preferable that the vertical hole 40 and the sipe 51 have the same depth. Specifically, it is preferable that the depth D _S of the sipe 51 satisfies the relationship of 0.9 × D _R ≦ D _S ≦ 1.0 × D _R with respect to the depth D _{R of the} vertical hole 40. Thereby, the depth relationship between the vertical hole 40 and the sipe 50 is optimized, and the drainage performance can be ensured while maintaining the rigidity of the land portion, which is advantageous in achieving both dry performance and wet performance. In this case, the depth D _S of the sipe 51 is less than 0.9 times the depth D _R of the vertical hole 40, the drainage performance of the sipe 51 is not expected sufficiently, the effect is limited to improve the wet performance . If the depth D _S of the sipe 51 is greater than 1.0 times the depth D _R of the vertical hole 40, it is difficult to sufficiently maintain the dry performance are affected land portion rigidity even sipe width is small. As shown in FIG. 3A, when the cavity H is provided at the bottom of the sipe 51, the depth of the sipe 51 extends from the opening (tread surface) of the sipe 51 to the bottom of the cavity H. _Let D _S.

The cross-sectional shape of the cavity H is not particularly limited, and an arbitrary shape such as an elliptical shape or a polygonal shape can be adopted in addition to the circular shape shown in the figure. Further, the maximum cross-sectional width W _A of the hollow portion is set so as to satisfy the relationship of 2.0 × W _S ≦ W _A ≦ 4.0 × W _S with respect to the sipe width W _S of the sipe having the hollow portion. It is preferable. By setting the size of the cavity H in this way, drainage performance can be ensured while maintaining the rigidity of the land portion, which is advantageous in achieving both dry performance and wet performance. If the maximum cross-sectional width W _A of the cavity H is less than 2.0 times the sipe width W _S, it is impossible to sufficiently ensure the drainage performance by cavity H. If the maximum cross-sectional width W _A of the hollow portion H is larger than 4.0 times the sipe width W _S , the rigidity of the land portion decreases and it becomes difficult to maintain the dry performance.

Although the vertical hole 40 and the hollow portion H have different extending directions, both are holes formed in the tread portion 1, so setting these magnitude relationships is effective in achieving both dry performance and wet performance. It is. That is, it is preferable that the maximum width W _{R on} the tread surface of the vertical hole 40 and the maximum cross-sectional width W _A of the cavity H satisfy the relationship of 1.0 × W _A ≦ W _R ≦ 3.0 × W _A. Thus, by making the size of the vertical hole 40 equal to or appropriately larger than the cavity H, drainage performance can be ensured while maintaining land rigidity, and dry performance and wet performance It is advantageous to achieve both. If the maximum width W _R of the vertical hole 40 is smaller than 1.0 times the maximum section width W _A of the cavity H, it is impossible to sufficiently ensure the drainage performance due to the vertical hole 40. If the maximum width W _R of the vertical hole 40 is larger than 3.0 times the maximum cross-sectional width W _A of the hollow portion H, the land portion rigidity is lowered and it is difficult to maintain the dry performance.

The tire size is 155 / 65R14 75S, has the basic structure illustrated in FIG. 1, and is based on the tread pattern of FIG. 2 or FIG. 4, and the shape of the lug groove, the presence / absence of a vertical hole, the presence / absence of a sipe, relationship, the relationship between the sipes and the vertical hole, the presence or absence of the cavity, the presence or absence of additional longitudinal hole, the presence or absence of the auxiliary sipe, a ratio W of the groove width W _L of the lug grooves in the maximum width W _R and the ground end in the longitudinal hole of the tread surface _R / W _L, the ratio D _S / D _R between the depth D _S and the vertical hole depth D _R of the sipe, the sipe having the hollow portion and the maximum section width W _a of the cavity of the sipe width W _S the ratio W _a / W _S, the maximum width W _R and the cavity portion of the maximum section width W conventional example were set as respective tables 1 to 3 the ratio W _R / W _a and _a 1 to 2 in the vertical hole of the tread surface, 24 types of pneumatic tires of Comparative Examples 1 to 4 and Examples 1 to 18 were produced.

  In the column of “Lug groove shape” in Tables 1 to 3, the case where the lug groove extends inward in the tire width direction and communicates with the outermost main groove is indicated as “communication”, and the lug groove terminates in the land portion. The case where the outermost main groove is not communicated is indicated as “non-communication”. In the column of “Relationship between sipe and groove” in Tables 1 to 3, the case where the sipe communicates with both the outermost main groove and the lug groove is indicated as “communication”. The case of not communicating with either or both was indicated as “non-communication”. In the column of “Relationship between sipe and vertical hole” in Tables 1 to 3, the case where the sipe crosses the vertical hole is indicated as “crossing”, and the sipe is positioned between the vertical holes adjacent to each other in the tire circumferential direction. The case where did not intersect was indicated as “non-intersection”. About the column of "the presence or absence of a cavity part" of Tables 1-3, whether the cavity part was provided in the bottom part of the sipe (displayed as "(bottom)"), or was planted also in the middle part of the sipe depth direction (" (In the middle) ").

  Conventional Example 1 is based on the tread pattern of FIG. 2, but the narrow groove, the first sipe and the second sipe are not formed, and the lug groove and the third sipe are specialized in wet performance communicating with the outermost main groove. This is an example having a tread pattern. Conventional example 2 is based on the tread pattern of FIG. 2, but the narrow groove, the first sipe, and the second sipe are not formed, and the lug groove and the third sipe do not reach the outermost main groove in the land portion. It is an example which has the tread pattern specialized in the dry performance which terminated. Example 3 is an example provided with both an additional vertical hole and an auxiliary sipe, and is an example based on the tread pattern of FIG.

  About these 24 types of pneumatic tires, dry performance and wet performance were evaluated by the following evaluation methods, and the results are also shown in Tables 1 to 3.

Dry performance Each test tire is assembled to a wheel with a rim size of 14 x 4.5 J and mounted on a light vehicle. The air pressure after warm-up is 240 kPa for the front tire and 240 kPa for the rear tire, and completely from the initial speed of 100 km / h on the dry road surface. The braking distance until stopping was measured. The evaluation results are shown as an index using the reciprocal of the measured value, with the value of Conventional Example 2 being 100. The larger the index value, the shorter the braking distance on the dry road surface, and the better the dry performance (driving performance on the dry road surface). If the index value is “98” or more, the same excellent dry performance as that of Conventional Example 2 is maintained.

Wet performance Each test tire is assembled to a wheel with a rim size of 14 x 4.5 J and mounted on a light vehicle. The air pressure after warm-up is 240 kPa for the front tire and 240 kPa for the rear tire, and completely from the initial speed of 100 km / h on the wet road surface. The braking distance until stopping was measured. The evaluation results are shown as an index using the reciprocal of the measured value, with the value of Conventional Example 1 being 100. The larger the index value, the shorter the braking distance on the wet road surface, and the better the wet performance (travel performance on the wet road surface). In addition, if the index value is “98” or more, excellent wet performance equivalent to that of Conventional Example 1 is maintained.

  As is clear from Tables 1 to 3, Examples 1 to 20 are all the same as Conventional Example 1 with excellent wet performance while maintaining the same level of dry performance as Conventional Example 2 with excellent dry performance. Exhibiting excellent wet performance above the level, we achieved both a good balance between wet performance and dry performance. On the other hand, in all of Comparative Examples 1 to 4, the lug groove is not in communication with the outermost main groove, and a vertical hole is formed between the outermost main groove and the lug groove. In Comparative Example 2, the sipe does not cross the vertical hole. In Comparative Example 3, the sipe does not communicate with the outermost main groove or the lug groove. In Comparative Example 4, the sipe does not have a hollow portion. The wet performance was worse than Example 1.

  In addition, in Example 3 based on the tread pattern of FIG. 4, compared with Example 1 based on the tread pattern of FIG. 2, there are no adverse effects due to the additional vertical holes and auxiliary sipes, and wet performance due to these. The effect on was added. Although not shown in Tables 1 to 3, when other items are changed as in Examples 4 to 18 based on FIG. 4 as in Example 3, Example 1 is compared with Example 3. The same results as in Examples 4 to 18 were obtained.

DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 3 Bead part 4 Carcass layer 5 Bead core 6 Bead filler 7 Belt layer 8 Belt reinforcement layer 10 Main groove 11 Outermost main groove 12 Center main groove 20 Land part 21 Shoulder land part 22 Center land part 30 Lug Groove 40 Vertical hole 50 (51, 52, 53, 54) Sipe H Cavity CL Tire equator E Grounding end

Claims (5)

An annular tread portion extending in the tire circumferential direction, a pair of sidewall portions disposed on both sides of the tread portion, and a pair of bead portions disposed on the inner side in the tire radial direction of the sidewall portions. A pneumatic tire having a plurality of main grooves extending along a tire circumferential direction on the surface of the tread portion and a plurality of rows of land portions partitioned by the main grooves;
Of the main grooves, the lug grooves extending along the tire width direction are spaced apart in the tire circumferential direction on the shoulder land portion of the outermost main groove located on the outermost side in the tire width direction. And the inner end of the lug groove in the tire width direction terminates in the shoulder land portion, and the outermost main groove and the lug groove between the inner end of the lug groove in the tire width direction and the outermost main groove. At least one vertical hole opened in the tread tread and spaced in the tire radial direction and extending along the tire width direction across the vertical hole between the outermost main groove and the lug groove Then, a sipe is formed in which one end communicates with the outermost main groove and the other end communicates with the lug groove. The sipe has a width wider than the sipe along the sipe at the bottom or in the middle of the depth direction. Pneumatic, characterized by having an extending cavity I hate. 2. The pneumatic tire according to claim 1, wherein the maximum width W _R of the tread surface of the vertical hole satisfies the following expression (1) with respect to the groove width W _{L of the} lug groove at the ground contact end.
0.3 × W _L ≦ W _R ≦ 2.0 × W _L (1) The depth _{S S of the} sipe satisfies a relationship of 0.9 × D _R ≦ D _S ≦ 1.0 × D _R with respect to the depth D _{R of the} vertical hole. Pneumatic tires. The maximum cross-sectional width W _A of the hollow portion satisfies a relationship of 2.0 × W _S ≦ W _A ≦ 4.0 × W _S with respect to the sipe width W _S of the sipe provided with the hollow portion. The pneumatic tire according to any one of claims 1 to 3. The maximum width W _{R on} the tread surface of the vertical hole and the maximum cross-sectional width W _A of the hollow portion satisfy a relationship of 1.0 × W _A ≦ W _R ≦ 3.0 × W _A. The pneumatic tire in any one of -4.

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