JP2006281689A - Tire mold and pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mold showing excellence in workability, working accuracy and durability in a case of making a vertical hole in a block land part of a tire having a block pattern, and to provide a tire having both a high stiffness of the land part and a drainability and showing a high dimensional accuracy. <P>SOLUTION: The tire shaping mold 1 comprises a groove forming protrusion 3 and vertical hole forming protrusions 4 on a tread portion forming surface 2. A connection part 5 connecting the vertical hole forming protrusions 4 is arranged between the vertical hole forming protrusions 4 each shaping the vertical hole in the same block land part of a product tire. The tire manufactured by this has a narrow groove 13 making the vertical holes 12 communicate with each other between the vertical holes 12 arranged in the same block land part 7. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention provides a mold for molding a tire having a groove forming projection for partitioning and molding a block land portion of a product tire and a vertical hole forming projection for forming the block land portion on a tread portion forming surface, and The present invention relates to a pneumatic tire molded using such a mold.

  In recent years, with increasing interest in safety and environmental performance, tires are also required to satisfy these performances under all use conditions. In particular, there is a high demand for improvement in basic motion performance such as bending and stopping as safety, and reduction in rolling resistance, improvement in wear resistance, and noise reduction as environmental performance. In a tire having a so-called block pattern in which a large number of block land portions are defined in the tread portion, in order to satisfy the required performance, it is indispensable to improve drainage while ensuring the rigidity of the block land portions. For the purpose of realizing this, generally, a narrow groove (so-called sipe) that closes at the time of tire contact is provided in the block land portion.

  Conventionally, sipes having various shapes have been proposed in order to achieve both the rigidity of the block land and the drainage at a higher level. For example, a so-called two-dimensional sipe in which the extending shape in the length direction of the sipe is wavy or zigzag, or a so-called three-dimensional sipe in which the extending shape in the depth direction of the sipe is also wavy or zigzag. It has been known. These sipes improve drainage by preventing the landslide part of the block land from coming into contact with each other and supporting each other when the block land part falls and deforms at the time of ground contact. While ensuring block rigidity. These sipes are formed by disposing a plate-like member processed corresponding to the sipe shape at a predetermined position in a tire molding die and vulcanizing and molding the raw tire using this die. However, these sipe shapes and arrangement patterns are naturally limited in terms of processing of the plate member, its mounting space, extraction of the plate member after vulcanization, etc. Therefore, the effect of the arrangement of these sipe is limited. In some cases, it was limited.

  In order to further enhance the rigidity and drainage of the block land without being restricted by the processing of the molding die, a plurality of vertical holes that open to the ground surface are formed in the block land instead of or together with the sipe. There has been proposed a tire molding die including a provided tire and a vertical hole forming protrusion for forming the vertical hole (see, for example, Patent Documents 1 to 3).

Japanese Patent Laid-Open No. 60-128005 Japanese Patent Laid-Open No. 3-189213 JP 2002-248906 A

  However, in such a molding die, it is necessary to attach pin-shaped vertical hole forming protrusions one by one inside and adjust the height and inclination angle one by one. Inferior workability. Also, since the pin-shaped protrusions are low in strength, they tend to bend due to external force during transportation and use, and it takes time to check and adjust this deformation. Must be remade, and there is a problem in terms of durability. Further, if the tire is vulcanized and molded in a deformed state, the dimensional accuracy of the product tire is lowered, and the expected performance may not be obtained.

  Therefore, the present invention aims to solve such problems of the prior art, the purpose of which, when forming a vertical hole in the block land portion of the tire having a block pattern, workability, The object is to provide a tire molding die excellent in processing accuracy and durability. Another object of the present invention is to provide a tire that can achieve both high land rigidity and drainage at a high level and has high dimensional accuracy.

  In order to achieve the above object, a tire molding die according to the present invention is provided with a groove forming projection for defining a block land portion of a product tire on a tread portion forming surface and a vertical hole forming a vertical hole in the block land portion. In a tire molding die having a projection for use, a connection for connecting these vertical hole forming projections to each other between at least two vertical hole forming projections forming a vertical hole in the same block land portion. A part is provided. According to this, since the plurality of vertical hole forming protrusions are connected by the connecting part and integrated as a unit, it is necessary to perform work one by one when attaching the vertical hole forming protrusions in the molding die. However, workability is greatly improved because it is only necessary to attach the unit as a unit. In addition, since the rigidity of the vertical hole forming protrusions connected by the connecting part can be increased, deformation with respect to an external force is reduced, and processing accuracy and durability are greatly improved.

  The term “vertical hole” as used herein means a hole extending in the tire radial direction as a whole, and includes a hole inclined, curved and / or bent with respect to the tire radial direction.

  Moreover, it is preferable that a connection part is a plate-shaped member, that height is constant, and that height changes along a longitudinal direction.

  Further, the height of the connecting portion is preferably greater than 0% but not more than 100% with respect to the height of the vertical hole forming projection.

  Furthermore, the width of the connecting portion is preferably larger than 0% but not larger than 40% with respect to the diameter of the vertical hole forming projection.

  In addition, it is preferable that the vertical hole forming protrusions extend while being inclined with respect to the tire radial direction.

  The pneumatic tire according to the present invention is the same in a pneumatic tire in which a plurality of block land portions are defined in the tread portion, and a plurality of vertical holes opened in the ground contact surface are provided in the block land portion. Between the at least 2 said vertical holes provided in a block land part, the narrow groove which connects these vertical holes mutually is provided. According to this, since the vertical hole absorbs the water in the ground plane and discharges the water absorbed by the centrifugal force, the drainage is improved, and there are few restrictions on the processing of the molding die, so the block land portion The vertical holes can be effectively arranged without impairing the rigidity of the. In addition, since the plurality of vertical holes communicate with each other, deformation of the member of the tire molding die can be suppressed, and a tire with high dimensional accuracy can be obtained.

  The “thin groove” here means a groove having a groove width smaller than the diameter of the vertical hole.

  The depth of the narrow groove is preferably larger than 0% but not larger than 100% with respect to the depth of the vertical hole.

  Further, the width of the narrow groove is preferably larger than 0% but not larger than 40% with respect to the diameter of the vertical hole.

  In addition, it is preferable that the vertical hole extends while being inclined with respect to the tire radial direction.

  According to this invention, when forming a vertical hole in a block land portion of a tire having a block pattern, it is possible to provide a tire molding die excellent in workability, processing accuracy, and durability. Further, according to the present invention, it is possible to provide a tire having both high land level rigidity and drainage performance and high dimensional accuracy.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a partially cutaway perspective view of a typical tire mold according to the present invention, and FIG. 2 is a plan view of a part of the mold shown in FIG.

  A tire molding die 1 shown in FIG. 1 includes a groove forming projection 3 for defining a block land portion of a product tire on a tread portion forming surface 2 and a vertical hole forming projection for forming a vertical hole in the block land portion of the product tire. Part 4.

The main structural features of the tire molding die according to the present invention are defined by a vertical hole forming protrusion that forms a vertical hole in the same block land portion, that is, a groove forming protrusion 3 in FIG. A connecting portion 5 for connecting the vertical hole forming protrusions 4 to each other is provided between at least two of the vertical hole forming protrusions 4 in the same space S ₁ and three in FIG. is there.

  Conventionally, the vertical hole forming protrusions are attached one by one in the mold, but there are several hundred or more vertical hole forming protrusions attached to one mold. It was a factor that greatly reduced productivity at the time. On the other hand, in the present invention, as shown in FIG. 3, the projection unit 6 in a state where the connecting portion 5 is provided between the vertical hole forming projections 4 and integrated is formed in advance, and this is formed into a mold. 1 tread portion forming surface 2 can be attached. Thereby, the number of times required for attachment can be reduced, and workability is greatly improved. Further, in general, the vertical hole forming projection has a large height compared to its diameter, and therefore has a low bending rigidity, and is easily deformed even when subjected to a relatively small external force during transportation or use. Then, since the connecting portion 5 also functions as a reinforcing member for the vertical hole forming projection 4, the conventional vertical hole forming projection is less likely to be deformed even if it receives a deformed external force. Processing accuracy and durability, and dimensional accuracy of a tire molded using the processing accuracy are improved.

  The cross-sectional shape of the projection 4 for forming the vertical hole is not particularly limited, and may be a triangular shape, a quadrangular shape, an elliptical shape, a cross shape, or the like, but the same bending rigidity is exhibited even with an external force from any direction. From the viewpoint, a circular shape as shown in the figure is preferable.

  Further, from the viewpoint of facilitating the processing of the mold, the connecting portion 5 is preferably a so-called plate-like member whose cross-sectional shape is a quadrangle. In particular, as shown in FIG. It is preferable that it is a continuous plate-shaped member. From this point of view, as shown in FIG. 4, the height h is constant, and it is also preferable to form a square shape in a side view. However, the height of the connecting portion 5 may be changed along the longitudinal direction L according to the performance required for the mold or the product tire. For example, if the connecting portion 5 is shaped as shown in FIG. 5 in a side view, the effect of reinforcing the vertical hole forming projection 4 is increased.

  Further, the height h of the connecting portion 5 is preferably in a relationship of 0 <h ≦ H with respect to the height H of the vertical hole forming projection 4. In addition, when the height of the connection part 5 changes along the longitudinal direction L as shown in FIG. 5, suppose that the height h measured in the maximum height position has the said relationship. The reason why the height h of the connecting portion 5 is set in such a range is that when the height h of the connecting portion 5 becomes zero, the connecting portion 5 does not exist and the above-described effect cannot be obtained. This is because if the height h of the connecting portion 5 is greater than the height H of the vertical hole forming projection 4, the land portion rigidity of the product tire may be reduced. From the viewpoint of facilitating handling of the protrusion unit 6 and sufficiently securing the effect of reinforcing the vertical hole forming protrusion 4 by the connecting part 5, the height h of the connecting part 5 is the height of the vertical hole forming protrusion 4. More preferably, it is in the range of 5 to 50% of H. When the height h of the connecting portion 5 is less than 5% of the height H of the vertical hole forming projection 4, the function as the reinforcing member of the connecting portion 5 is insufficient, and the vertical hole forming projection is particularly large due to a large external force. This is because the portion 4 may be deformed, and when it exceeds 50%, the land portion rigidity may be lowered particularly in a product tire in which many vertical holes are formed.

Furthermore, the width w ₁ of the connecting portion 5 is preferably in a relationship of 0 <w ₁ ≦ 0.4R ₁ with respect to the diameter R ₁ of the vertical hole forming projection 4. When the width w ₁ of the connecting portion 5 becomes zero, the connecting portion 5 does not exist and the above-described effect cannot be obtained. The width w ₁ of the connecting portion 5 is the diameter R _{1 of the} projection 4 for forming the vertical hole. This is because the land portion rigidity of the product tire may be lowered if the ratio exceeds 40%. From the viewpoint of facilitating handling of the protrusion unit 6 and sufficiently ensuring the reinforcing effect of the protrusion 4 for forming the vertical hole by the connecting part 5, the width w ₁ of the connecting part 5 is the diameter R of the protrusion 4 for forming the vertical hole. ₁ is more preferably 10% or more.

  In addition, as shown in FIGS. 6A to 6C, the vertical hole forming protrusion 4 may extend along the tire radial direction Z, but FIGS. 7A to 7C and FIG. As shown to (a)-(c), you may incline and extend with respect to the tire radial direction Z. This is because the rigidity of the block land portion of the product tire can be easily controlled by arranging the vertical hole forming projections 4 to be inclined with respect to the tire radial direction Z.

  Next, a pneumatic tire (hereinafter simply referred to as “tire”) molded using such a tire molding die will be described with reference to FIGS. 9 is a development view of a part of a tread portion of a typical tire according to the present invention, FIG. 10 is a cross-sectional perspective view of the tire shown in FIG. 9, taken along line II, and FIG. 11 is shown in FIG. It is sectional drawing on line I-I of a tire.

  In the tire shown in FIG. 9, a large number of grooves 8 and 9 are provided in the tread portion 7, and a large number of block land portions 11 are defined by the tread end 10. Further, the block land portion 11 is provided with a plurality of vertical holes 12 that open to the ground surface.

  The main structural features of the tire according to the present invention are such that these vertical holes 12 communicate with each other between at least two vertical holes provided in the same block land portion 11, and in FIG. 9, three vertical holes 12. In providing the narrow groove 13.

  When the block land portion 11 enters the ground plane, water existing in the ground plane is absorbed and stored in the vertical hole 12 due to capillary action in the vertical holes 12 and the narrow grooves 13, and the water film in the ground plane is removed. The When the block land portion 11 is separated from the ground contact surface by the rotation of the tire, the water in the vertical hole 12 and the narrow groove 13 is drained to the outside of the tire by the action of centrifugal force, and can be absorbed and stored before entering the ground contact surface again. Return to the correct state. By repeating such a cycle, the block land portion 11 provided with the vertical holes 12 and the narrow grooves 13 can obtain the same high drainage as the block land portion provided with the conventional sipe. Further, as described above, the vertical hole is less subject to the processing of the molding die than the two-dimensional and three-dimensional sipes, and can have a relatively free arrangement pattern. Thus, the vertical holes 12 can be effectively arranged without impairing the rigidity. Therefore, the tire according to the present invention can achieve both the land portion rigidity and drainage performance at a high level.

  Furthermore, since the plurality of vertical holes 12 are communicated with each other through the narrow grooves 13, vulcanization molding can be performed using the tire molding die as described above, and a tire with high dimensional accuracy can be obtained. It is.

The diameter R ₂ of the vertical hole 12, which may have various values depending on the number or the like of required performance and arranged, is preferably 3mm or less especially when the land portion rigidity is important, Particularly when drainage is important, it is preferably 1 mm or more.

Further, the depth d ₁ of the narrow groove 13 is preferably in a relationship of 0 <d ₁ ≦ d ₂ with respect to the depth d ₂ of the vertical hole 12. This is because when the depth d ₁ of the narrow groove 13 becomes zero, the narrow groove 13 does not exist. When the depth d ₁ of the narrow groove 13 becomes larger than the depth d _{2 of the} vertical hole 12, the rigidity of the land portion decreases. It is because there is a possibility of doing. The depth d ₁ of the narrow groove 13 is preferably constant as shown in FIG. 11 from the viewpoint of facilitating the processing of the mold for molding it, but as shown in FIG. Furthermore, it may change along the longitudinal direction. In this case, the depth of the narrow groove 13 means the depth measured at the maximum depth position. A more preferable range is 0.05d ₂ ≦ d ₁ ≦ 0.6d ₂ .

Furthermore, the width w _{2 of the} narrow groove 13 is preferably in a relationship of 0 <w ₂ ≦ 0.4R ₂ with respect to the diameter R _{2 of the} vertical hole 12. This is because if the width w ₂ of the narrow groove 13 becomes zero, the narrow groove 13 does not exist. If this is larger than 40% of the diameter R ₂ of the vertical hole 12, the rigidity of the land portion may be lowered. . A more preferable range is 0.1R ₂ ≦ w ₂ ≦ 0.3R ₂ .

  The vertical hole 12 may extend along the tire radial direction as shown in FIG. 10, but a mold as shown in FIGS. 7 (a) to (c) and FIGS. 8 (a) to (c) is used. Thus, a vertical hole extending obliquely with respect to the tire radial direction may be formed. This is because the land portion rigidity of the block land portion 11 can be easily controlled by arranging the vertical holes 12 so as to be inclined with respect to the tire radial direction.

  Note that the above description shows only a part of the embodiment of the present invention, and these configurations can be combined with each other or various modifications can be made without departing from the gist of the present invention. . For example, a description has been given by taking as an example a mold in which the vertical hole forming protrusions adjacent in the width direction of the mold are connected by a connecting portion and a tire molded by such a mold. FIG. As shown in FIG. 13, the vertical hole forming projections adjacent in the circumferential direction of the mold may be connected by a connecting portion, and particularly when high strength is required for the vertical hole forming projection, FIG. As shown to (b), you may connect the protrusion part for vertical hole formation adjacent to the width direction or the circumferential direction by a connection part. Furthermore, when high drainage is required particularly for a molded tire, as shown in FIG. 13B, the vertical hole forming protrusion and the groove forming protrusion may be connected by a connecting portion. Good. This is because in the tire molded with such a mold, the water stored in the vertical hole is drained into the groove through the narrow groove, so that the drainage is improved. Furthermore, the vertical hole forming projections connected by the connecting portion do not need to be aligned, and may be arranged shifted in the circumferential direction as shown in FIGS. 14 (a) to 14 (c). As shown to 15 (a)-(c), the inclination direction and inclination angle with respect to the tire radial direction may be different from each other.

  Next, a tire was prototyped using the tire molding die according to the present invention and performance evaluation was performed, which will be described below.

  The tires of Examples 1 to 5 are radial tires for passenger cars having a tire size of 195 / 65R15, the tread pattern is the pattern shown in FIG. 16, and have the specifications shown in Table 1. Moreover, the vertical hole of the tire of Examples 1-3 is formed with the metal mold | die which has the protrusion for vertical hole formation similar to what is shown in FIG. 6, and extends along a tire radial direction. The vertical hole of the tire of Example 4 is formed of a mold having a vertical hole forming projection similar to that shown in FIG. 7, and extends while being inclined in the tire circumferential direction with respect to the tire radial direction. The vertical hole of the tire of Example 5 is formed of a mold having a vertical hole forming projection similar to that shown in FIG. 8, and extends while being inclined in the tire width direction with respect to the tire radial direction.

  For comparison, the tire size is the same as in Examples 1 to 5, but the tread pattern is the pattern shown in FIG. 17 (Comparative Examples 1 to 5) or FIG. 21 (Conventional Example). A prototype was also made. The vertical holes of the tires of Comparative Examples 1 to 3 are formed of a mold having the vertical hole forming protrusions shown in FIG. 18 and extend along the tire radial direction. The vertical hole of the tire of Comparative Example 4 is formed of a mold having the vertical hole forming protrusions shown in FIG. 19 and extends in an inclined manner in the tire circumferential direction with respect to the tire radial direction. The vertical hole of the tire of Comparative Example 5 is formed of a mold having the vertical hole forming protrusions shown in FIG. 20 and extends while inclining in the tire width direction with respect to the tire radial direction. The sipe of the conventional tire is formed of a mold having a sipe forming blade shown in FIG. 22, and is bent and extended in a zigzag shape.

  Each of the test tires is mounted on a rim of size 6J to form a tire wheel, and an air pressure of 200 kPa (relative pressure) is applied to the tire wheel, and the road surface on snow, the road surface on ice, In each dry road surface condition (dry road surface) and asphalt road surface (wet road surface) with a water depth of 1 mm, a driving test is performed on a turntable type friction characteristic measurement tester to evaluate each driving performance. went. These evaluation results are shown in Table 1.

  Further, the time required to attach the vertical hole forming protrusion or the sipe forming blade to the mold for molding each test tire was measured, and the workability was evaluated based on the measurement result. Furthermore, the mounting error of the vertical hole forming projection was measured with a mold immediately after the vertical hole forming protrusion was mounted, and the processing accuracy of the mold was evaluated based on the average value of this error. Furthermore, the deformation of the vertical hole forming protrusions of the mold after vulcanization molding was examined, the generation ratio of the vertical hole forming protrusions deformed by 0.5 mm or more was determined, and the durability of the mold was evaluated based on this ratio. These evaluation results are shown in Table 1.

  In addition, the evaluation result in Table 1 is shown as an index ratio when the evaluation result of the conventional example is 100, and the larger the value, the better the performance.

  From the evaluation results shown in Table 1, Example 1 and Comparative Example 1, Example 2 and Comparative Example 2, Example 3 and Comparative Example 3, Example 4 and Comparative Example 4, Example 5 and Comparative Example 5, respectively. In comparison, it can be seen that the productivity of Examples 1 to 5 is significantly improved while the running performance is equal to or higher than that of Comparative Examples 1 to 5, respectively. In addition, when Examples 1 to 5 are compared with the conventional example, Examples 1 to 5 have improved productivity while the productivity is equal to or higher than that of the conventional example, and the land portion rigidity and drainage performance are improved. I understand that Furthermore, in Examples 1-5, there was an average mounting error of 0.1 mm or less, but in Comparative Examples 1-5, there was an average mounting error of 0.5 mm, and the processing accuracy of Examples 1-5 was high. I understood. In addition, the generation ratio of the vertical hole forming protrusions deformed by 0.5 mm or more after vulcanization molding was 0% in Examples 1 to 5, but 1% in Comparative Examples 1 to 5, and Example 1 It was found that the molds of ˜5 had high durability. Therefore, it turns out that the tire of Examples 1-5 is excellent in the comprehensive performance compared with the tire of Comparative Examples 1-5 and a prior art example.

  According to the present invention, when a vertical hole is formed in a block land portion of a tire having a block pattern, it is possible to provide a tire molding die excellent in workability, processing accuracy, and durability. In addition, it is possible to provide a tire that can achieve both high land rigidity and drainage at a high level and has high dimensional accuracy.

1 is a partially broken perspective view of a typical tire molding die according to the present invention. It is a top view of a part of metal mold | die shown in FIG. It is a perspective view of a projection unit. It is a front view of the projection part for vertical hole formation, and a connection part. It is a front view of the other projection part for vertical hole formation, and a connection part. The typical vertical hole formation projection part and connection part according to this invention are shown, (a) is a top view, (b) is a front view, (c) is a right view. The other vertical hole formation projection part and connection part according to this invention are shown, (a) is a top view, (b) is a front view, (c) is a right view. The other vertical hole formation projection part and connection part according to this invention are shown, (a) is a top view, (b) is a front view, (c) is a right view. 1 is a development view of a part of a tread portion of a typical pneumatic tire according to the present invention. It is a cross-sectional perspective view on line II of the tire shown in FIG. It is sectional drawing on line II of the tire shown in FIG. It is sectional drawing of the block land part of the other tire according to this invention. (A) And (b) is a partial expanded view of the tread part of the other pneumatic tire according to this invention. The other vertical hole formation projection part and connection part according to this invention are shown, (a) is a top view, (b) is a front view, (c) is a right view. The other vertical hole formation projection part and connection part according to this invention are shown, (a) is a top view, (b) is a front view, (c) is a right view. It is a top view which shows the tread pattern of the tire of Examples 1-5. It is a top view which shows the tread pattern of the tire of Comparative Examples 1-5. The protrusion part for vertical hole formation of the metal mold | die for shape | molding the tire of Comparative Examples 1-3 is shown, (a) is a top view, (b) is a front view, (c) is a right view. The protrusion part for the vertical hole formation of the metal mold | die for shape | molding the tire of the comparative example 4 is shown, (a) is a top view, (b) is a front view, (c) is a right view. The protrusion part for the vertical hole formation of the metal mold | die for shape | molding the tire of the comparative example 5 is shown, (a) is a top view, (b) is a front view, (c) is a right view. It is a top view which shows the tread pattern of the tire of a prior art example. The sipe formation braid | blade for shape | molding the tire of a prior art example is shown, (a) is a top view, (b) is a front view, (c) is a right view.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tire molding die 2 Tread part formation surface 3 Groove formation projection part 4 Vertical hole formation projection part 5 Connection part 6 Projection part unit 7 Tread part 8, 9 Groove 10 Tread edge 11 Block land part 12 Vertical hole 13 Narrow groove

Claims (11)

In a mold for molding a tire including a groove forming projection for partitioning and molding a block land portion of a product tire and a vertical hole forming projection for forming a vertical hole in the block land portion on a tread portion forming surface,
A mold for molding a tire, characterized in that a connecting portion for connecting the vertical hole forming projections to each other is provided between at least two vertical hole forming projections forming vertical holes in the same block land portion.   The tire molding die according to claim 1, wherein the connecting portion is a plate-like member.   The mold for tire molding according to claim 1 or 2, wherein the connecting portion has a constant height.   The mold for molding a tire according to claim 1 or 2, wherein the height of the connecting portion varies along the longitudinal direction.   The tire molding die according to any one of claims 1 to 4, wherein a height of the connecting portion is greater than 0% but not more than 100% with respect to a height of the vertical hole forming protrusion.   The tire molding die according to any one of claims 1 to 5, wherein a width of the connecting portion is larger than 0% but not larger than 40% with respect to a diameter of the vertical hole forming protrusion.   The tire molding die according to any one of claims 1 to 6, wherein the vertical hole forming protrusion extends while being inclined with respect to the tire radial direction. In a pneumatic tire in which a plurality of block land portions are defined in the tread portion, and a plurality of vertical holes opened in the ground contact surface are provided in the block land portions.
A pneumatic tire characterized in that a narrow groove is provided between at least two of the longitudinal holes provided in the same block land portion, and the longitudinal holes communicate with each other.   The pneumatic tire according to claim 8, wherein a depth of the narrow groove is greater than 0% but not greater than 100% with respect to the depth of the vertical hole.   The pneumatic tire according to claim 8 or 9, wherein a width of the narrow groove is greater than 0% but not greater than 40% with respect to the diameter of the vertical hole.   The pneumatic tire according to any one of claims 8 to 10, wherein the vertical hole extends while being inclined with respect to a tire radial direction.

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