JP4933349B2 - Pneumatic tire - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a pneumatic tire having a radial structure or a bias structure, and more particularly to a pneumatic tire for winter. The present invention proposes a technique that enables a spike pin to be driven and effectively prevents an unexpected drop of the spike pin once it has been driven.

  In winter tires used for applications that require spike pin driving, the surface side portion of the tread rubber, which is located outside the tire radial direction, is relatively soft to ensure performance on ice and snow. The tread rubber is generally formed of a relatively hard base rubber layer in order to enhance the pulling out restraint force against the spike pin that has been driven. In manufacturing a pneumatic tire having such a tread rubber having a so-called cap-and-base structure, a tread rubber member composed of a cap rubber layer material and a base rubber layer material is usually formed into a two-layer structure. After extruding through a die, the tread rubber member is stuck on a green case to form a raw tire.

  However, when extruding a tread rubber member in this way, the thickness of each rubber layer material may vary depending on the shape of the die and the properties of each rubber layer material. As a result, in the product tire, the desired thickness may not be imparted to the relatively hard base rubber layer.

  And when the thickness of the base rubber layer of the product tire is insufficient, for example, when the spike pin driving hole 31 having a predetermined depth is formed in the block as the tread land portion as illustrated in FIG. Further, since the penetration depth of the driving hole 31 into the base rubber layer 32 becomes shallow, the spike pin is driven into the driving hole 31 to the bottom of the hole, and the holding force of the spike pin by the base rubber layer 32 is further reduced. As a result, the spike pin may be accidentally dropped out.

  In the case of driving a spike pin, the thickness of the base rubber layer 32 in the driven portion is usually determined by the specifications of the spike pin (body diameter, overall length, flange diameter, etc.), and is usually a tread rubber. The total thickness is preferably about 50%.

  The present invention has been made with the object of solving such problems of the prior art, and the object of the invention is in the extrusion molding of the tread rubber member as described above, respectively. Even if there are variations in the thickness of the rubber layer material, the base rubber layer thickness should be as expected at the portion where the spike pin driving hole is formed in the tread land portion of the product tire. As a result, it is an object of the present invention to provide a pneumatic tire that can sufficiently eliminate the risk of dropping of a spike pin that has been driven in.

  In the pneumatic radial or bias tire according to the present invention, the tread rubber disposed on the outer peripheral side of the belt at the tread portion of the tire has at least a base rubber layer and a cap rubber layer positioned inside and outside in the radial direction. Two layers, sometimes composed of three or more rubber layers including an intermediate layer, etc., reaching the innermost base rubber layer, which is harder than the outermost cap rubber layer, on the surface of the tread land part. Are provided on the surface of the tread land portion around each driving hole with an equal interval around the driving hole, for example, an angular interval, an arc-shaped or linear distance interval, and the like. A plurality of bent spew cutting marks are provided.

  Here, preferably, the vent spew cutting traces are provided at two positions opposite to each other in the linear direction of the driving hole, and preferably, two pairs of vent spew cutting traces are arranged at two positions perpendicular to each other through the center of the driving hole. The pent spew cut marks are positioned around the driving hole at an angular interval of 45 °.

    In the tire according to the present invention, in particular, a plurality of bent spew cutting traces are provided around the spike pin driving hole, in other words, corresponding to the occurrence position of the bend spew in the vulcanization molding of the raw tire. At each vulcanization mold part, each vent hole is forcibly sucked into the vulcanization mold, the gas generated there, etc. through the vent hole, for example, by negatively suctioning it and exhausting it out of the mold. In the part, since the base rubber layer material of the raw tire is sucked up to the molding surface side of the vulcanization mold, it becomes possible to always give a sufficient thickness to the base rubber layer material around the driving hole, This means that when extruding a tread rubber member, the cap rubber layer material and the base rubber layer material each have a variation with respect to the expected thickness. It should be noted that the same occurred.

  Therefore, in the product tire formed by vulcanizing the raw tire, the position where the bent spew cut mark is generated around the spike pin driving hole, and the thickness of the hard base rubber layer in the formation part of the driving hole is stable. As a result, for the spike pin driven into the spike pin insertion hole, the base rubber layer should exert a high retaining restraint force with sufficient penetration depth of the spike pin. Can do.

  Here, a plurality of vent spew cutting marks are provided around the spike pin driving hole at equal intervals, for example, based on the suction of the base rubber layer material by negative pressure suction as described above. The increase in the thickness of the base rubber layer can be made uniform in the implantation hole portion and the peripheral portion thereof, and the holding force of the spike pin can be made uniform.

  In other words, if the bent spew cut marks are irregularly arranged around the driving hole, the thickness of the base rubber layer in the driving hole portion and the peripheral portion of the product tire will be uneven. The holding force with respect to the spike pin driven in becomes uneven.

  It should be noted that the vent spew cutting traces are provided at two locations opposed to the diameter direction of the driving hole, or two pairs of vent spew cutting traces are formed on two straight lines orthogonal to each other through the center of the driving hole. In order to prevent unevenness in the thickness of the base rubber layer of the product tire and to provide sufficient strength to the vulcanization mold, it is preferable to provide the same at a position that is equidistant from the center.

  FIG. 1 is a cross-sectional view in the tire width direction showing an embodiment of a tire according to the present invention with respect to a half portion thereof. In the figure, 1 is a tread portion, and 2 is continuous to each side portion of the tread portion 1. A pair of side wall portions extending inward in the radial direction, and 3 indicates a bead portion continuous on the inner peripheral side of each side wall portion 2.

  Here, between a pair of bead cores 4 arranged in each bead portion 3, a carcass ply of, for example, a radial structure made of one or more carcass plies is extended toroidal, and a side portion of the carcass 5 is Around the bead core 4, the belt 6 is rolled back from the inner side to the outer side in the tire width direction, and a belt 6 and a tread rubber 7 made of one or more belt layers are sequentially provided on the outer peripheral side of the crown region of such a carcass 5. The tread rubber 7 is composed of two layers of a base rubber layer 8 having a high rubber hardness on the inner peripheral side and a cap rubber layer 9 having a lower hardness than the base rubber layer 8 on the outer peripheral side.

  Note that the tread rubber 7 may have a laminated structure of three or more layers in which one or more intermediate rubber layers are interposed between the base rubber layer 8 and the cap rubber layer 9.

  By the way, as shown in the figure, the interface between the base rubber layer 8 of the tread rubber 7 and the cap rubber layer 9 is a circumferential groove 10 and a lateral groove (not shown) to the tread surface when the raw tire is vulcanized. Based on the escape deformation from the ridge of the base rubber layer material by pushing the vulcanization mold ridge into the tread rubber member, etc. for forming, the inter-groove portions of the circumferential groove 10 and the lateral groove Thus, they are located radially outward from the groove bottom positions of these grooves.

  Under such a situation of the tread rubber 7, the surface of the tread land portion, for example, the surface of the block 11 reaches the base rubber layer 8 having a hardness higher than that of the cap rubber layer 9 by a projection or the like provided on the vulcanization mold. When the spike pin driving hole 12 is formed, in the prior art, the interface between the base rubber layer 8 and the cap rubber layer 9 is located radially outward at the groove portion as shown in the figure. In addition, due to the extrusion molding error of the tread rubber member as described above, the driving hole 12 formed at a certain depth cannot enter the base rubber layer 8 over the intended depth. In contrast, in the present invention, as schematically illustrated in FIG. 2A, the block surface around the driving hole 12 is positioned sufficiently close to the driving hole 12 and the driving hole 12. By providing a plurality of, in the figure, four bent spew cutting marks, which are located at equal intervals around the circumference, the thickness of the base rubber layer 8 in the portion where the driving hole 12 is formed and its peripheral portion can be varied without any variation. In addition, the depth of penetration of the formed driving hole 12 into the base rubber layer 8 can be set as expected, which is always sufficient without unevenness.

  That is, the vent spew cut mark 13 referred to in the present invention, when vulcanizing and molding a raw tire with a vulcanization mold, through a vent hole provided in the vulcanization mold, residual air in the mold, generated gas, etc. The spew formed by the rubber part of the tire that has flowed into the vent hole is cut and removed afterwards when the exhaust is forced out of the mold or by natural flow. The portion where the pure cut mark 13 is present is a portion where more aggressive exhaust has been performed under the action of the vent hole of the vulcanization mold. In such a portion, the base rubber layer material of the raw tire is sucked up. Therefore, the thickness of the base rubber layer 8 in the portion corresponding to the portion where the bent spew cut mark 13 exists is shown in FIG. As illustrated in FIG., It is by inevitably thick.

  Therefore, in this tire, for example, when the spike pin is driven into the driving hole 12 formed between the bent spew cutting marks 13, the base rubber layer 8 causes a sufficient holding force to act on the spike pin. The spike pin can be effectively prevented from coming off.

  Moreover, in this tire, a plurality of the bend spout cut marks 13 are provided in the vicinity of the driving hole 13 at equal angular intervals around the driving hole 13, thereby forming the base rubber layer 8 at the portion where the driving hole 12 is formed and the peripheral portion thereof. Can be made sufficiently uniform.

  In addition, the vent spew cutting trace 13 is equidistant from the center of the driving hole 12 when it is provided at two positions opposed to the diameter direction of the driving hole 12 and as illustrated in FIG. In the case where it is provided at each position, it is possible to advantageously eliminate the possibility of a decrease in mold strength caused by forming a plurality of vent holes while preventing the occurrence of uneven thickness in the base rubber layer 8. it can.

In FIG. 2A, reference numeral 14 denotes a sipe having a zigzag extending form formed on the surface of the block 11 and extending in the tread width direction.
Here, it is needless to say that the extending direction, the extending form, and the like of the sipe 14 can be appropriately changed as necessary in relation to the sipe forming position and the like.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. It is a figure which illustrates the plane and cross section of a block. It is the top view and sectional drawing of a block which illustrate a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 3 Bead part 4 Bead core 5 Carcass 6 Belt 7 Tread rubber 8 Base rubber layer 9 Cap rubber layer 10 Circumferential groove 11 Block 12 Driving hole 13 Vent spew cutting trace

Claims (3)

The tread rubber arranged on the outer periphery of the belt in the tire tread part is composed of at least two layers of a base rubber layer and a cap rubber layer located inside and outside in the radial direction, and the cap is placed on the surface of the tread land part. A pneumatic tire having spike pin driving holes reaching a base rubber layer having a higher hardness than the rubber layer,
A pneumatic tire in which a plurality of vent spew cutting marks are provided on the surface of a tread land portion around each driving hole at an equal interval around the driving hole.   The pneumatic tire according to claim 1, wherein vent spew cut marks are provided at two locations facing each other in the diameter direction of the driving hole.   2. The pneumatic tire according to claim 1, wherein two pairs of vent spew cut marks are provided at positions that are equidistant from the center on two straight lines that are orthogonal to each other through the center of the driving hole.

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