JP6454197B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire that is useful for enhancing appearance and gripping power.

  The following Patent Document 1 proposes a pneumatic tire in which a plurality of inclined grooves and a vertically long land portion divided between the inclined grooves are provided in the tread portion. In the land portion, a dividing groove that completely crosses the land portion and a plurality of blocks divided by the dividing groove are formed.

JP-A-8-164712

  Generally, a vertically long block that is long in the tire circumferential direction may be provided with a shallow groove in order to adjust its rigidity. Conventionally, the shallow grooves are usually 2.0 mm or less in depth and width, and are provided so as to completely cross the vertically long block.

  The shallow groove is usually formed by a mold blade (convex portion). This blade prevents air between the tread of the vertically long block and the mold from moving along the tire circumferential direction during the vulcanization molding process. For this reason, in the mold for forming the vertically long block provided with the shallow grooves as described above, vent holes are formed in at least two, preferably all four corners of each block forming surface divided by the blade. Was provided.

  As is well known, after the air in the mold is discharged through the vent hole, a part of the plasticized unvulcanized rubber flows into the vent hole. FIG. 5 shows a perspective view of the block b provided with the shallow groove a as described above. As shown in FIG. 5, so-called spew c remains at the corners of the treads b1 and b1 divided into two by the shallow groove a. The spew c is usually cut off before shipping because it impairs the appearance of the tire. However, the spew marks obtained by excising the spew c usually protrude slightly from the tread surface of the block. For this reason, spew marks reduce the effective ground contact area of the tread surface of the block. In particular, in race tires and the like that require severe grip performance, a reduction in grip force that is damaged by spew marks is a major problem.

  The present invention has been made in view of the above circumstances, and has as its main object to provide a pneumatic tire that is useful for enhancing the appearance performance and gripping power on the basis of suppressing spew or spew marks. .

  The present invention provides a pneumatic tire in which a tread portion is provided with a plurality of main grooves extending continuously in a tire circumferential direction, and a plurality of lateral grooves for separating a plurality of blocks by connecting between the main grooves. The block includes a longitudinal block whose length in the tire circumferential direction is 1.5 times or more of the length in the tire axial direction, and the longitudinal block extends in the tire axial direction, and both end portions thereof are A shallow groove that terminates in the block without communicating with the main groove is provided.

  In the pneumatic tire according to the present invention, the vertically long block has a square tread surface, and a spew protruding from the tread surface or the spew only at each corner portion on one of the diagonal lines. It is desirable that a mark is formed.

  In the pneumatic tire according to the present invention, the shallow groove includes a groove bottom and an end wall surface extending from each end portion in the longitudinal direction of the groove bottom to the tread surface of the vertically long block, It is desirable that the tread is connected to the tread within a range of 2.0 mm from the ridgeline of the tread and the main groove.

  In the pneumatic tire according to the present invention, it is preferable that the end wall surface extends in a straight line shape or an arc shape between the groove bottom and the tread surface.

  In the pneumatic tire according to the present invention, it is preferable that the shallow groove has a groove depth in the range of 0.5 to 2.0 mm and a groove width in the range of 0.5 to 2.0 mm.

  The vertically long block of the pneumatic tire of the present invention is provided with shallow grooves extending in the tire axial direction and terminating in the block without both ends communicating with the main groove. Such a shallow groove moderately relaxes the rigidity of the vertically long block and improves the ground contact property of the tread. That is, when a large driving force or braking force in the tire circumferential direction is applied to the vertically long block, the vertically long block can flexibly follow the road surface starting from the shallow groove and suppress a large slip on the road surface. Thereby, the pneumatic tire of the present invention can exhibit high grip.

  Further, both ends of the shallow groove are terminated in the block without communicating with the main groove. That is, the shallow groove does not divide the ridge line between the tread surface of the block and the main groove. Accordingly, during the vulcanization molding of such a tire, the air between the tread of the block and the mold can move along the ridgeline, for example, a metal corresponding to any one of the four corners of the block tread. It can be discharged from a vent hole provided at a position on the mold side. In other words, in the pneumatic tire of the present invention, it is not necessary to provide a spew at the corner portion formed by the shallow groove and the main groove. Therefore, the pneumatic tire of the present invention can prevent an increase in spew formed on the tread surface of the block while reducing the rigidity of the block, and can improve the grip force without impairing the appearance of the tire.

It is an expanded view of the tread part of one Embodiment of this invention. It is an enlarged view of the block of FIG. It is AA sectional drawing of FIG. (A) is sectional drawing along the longitudinal direction of the shallow groove of another aspect, (b) is sectional drawing along the longitudinal direction of the shallow groove of another aspect. It is a perspective view of the conventional vertically long block.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 shows a development view of the tread portion 2 of the pneumatic tire of the present embodiment (hereinafter sometimes simply referred to as “tire”). The pneumatic tire of the present embodiment can be suitably used as a race suitable for running on a wet condition circuit.

  As shown in FIG. 1, the tread portion 2 is provided with a plurality of main grooves 3 extending continuously in the tire circumferential direction and a plurality of lateral grooves 4 connecting between the main grooves 3. Thereby, the tread portion 2 is divided into a plurality of blocks 5.

  The tread portion 2 of the present embodiment is provided with one main groove 3 on the tire equator C and three main grooves 3 on each side of the tire equator C. Each main groove 3 is preferably formed in a straight line, for example, in order to improve drainage performance in the tire circumferential direction.

  For example, the lateral grooves 4 are inclined with respect to the tire axial direction. In the present embodiment, the inclination angle of the lateral groove 4 positioned on the tire equator C side with respect to the tire axial direction is formed larger than the inclination angle of the lateral groove 4 positioned on the tread end Te side with respect to the tire axial direction.

  Further, the lateral grooves 4 of the present embodiment are arranged in a substantially V shape so as to be smoothly connected to each other via the main groove 3 from the tire equator C toward the tread end Te. Such a lateral groove 4 exhibits excellent drainage from the tire equator C side to the tread end Te side when the rotation direction of the tire is specified so that the tire equator C side of the lateral groove 4 is the first arrival side, for example. Is done. In order to improve such drainage, it is desirable that the lateral groove 4 be formed in a straight line, for example. In order to further improve the drainage, it is desirable that the lateral groove 4 closest to the tread end Te is terminated, for example, on the outer side in the tire axial direction than the tread end Te.

  In the present specification, the “tread end” is a position on the outermost side in the tire axial direction of the contact surface of the tread portion 2 when a normal tire is loaded with a normal load and brought into contact with a plane with a camber angle of 0 °. It is.

  The “normal state” is a no-load state in which a tire is assembled on a normal rim (not shown) and filled with a normal internal pressure. In the present specification and claims, unless otherwise specified, the dimensions of each part of the tire are values in a normal state.

  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, “Standard Rim” for JATMA, “Design Rim” for TRA, For ETRTO, "Measuring Rim".

  “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. For example, “maximum air pressure” for JATMA, “TIRE” for TRA The maximum value described in “LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES”, “INFLATION PRESSURE” in the case of ETRTO.

  “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. For example, “maximum load capacity” for JATMA, “table for TRA” The maximum value described in “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES”, or “LOAD CAPACITY” in the case of ETRTO.

  Race tires like this embodiment may not have applicable standards. In this case, the rim, air pressure, and load recommended by the manufacturer are applied to the “regular rim”, “regular internal pressure”, and “regular load”, respectively.

  FIG. 2 shows an enlarged view of the block 5 of FIG. The length of the block 5 in the tire circumferential direction (maximum length) Lb is 1.5 times or more, more preferably 2.0 times or more, more preferably 2.2 times or more of the length Wb in the tire axial direction. Block 6 is included. In the present embodiment, all the blocks 5 are formed as the vertically long blocks 6. Such a vertically long block 6 has high circumferential rigidity and can exhibit excellent traction during driving. From the viewpoint of drainability, it is desirable that the length Lb of the block 5 in the tire circumferential direction is 3.0 times or less the length Wb of the block 5 in the tire axial direction.

  Each of the vertically long blocks 6 has, for example, a tread surface 6S formed in a quadrangular shape, and is formed in a parallelogram shape in the present embodiment. In a more preferred aspect, it is desirable that a corner portion 9 forming an acute angle of the tread surface 6S is formed with a chamfered portion 12 formed of an inclined surface inclined inward in the tire radial direction from the tread surface 6S. The chamfered portion 12 prevents the stress from concentrating on the end portion in the tire circumferential direction when the vertically long block 6 is grounded, and helps prevent the occurrence of block chipping or the like there.

  Further, at least one of the vertically long blocks 6 (in this embodiment, all the vertically long blocks 6) is provided with a shallow groove 7 extending in the tire axial direction. The shallow groove 7 of the present embodiment is provided at the center of the longitudinal block 6 in the tire circumferential direction. In a preferred embodiment, the shallow groove 7 extends substantially parallel to the lateral groove 4. Such a shallow groove 7 moderately reduces the rigidity of the vertically long block 6 and improves the ground contact of the tread surface 6S. That is, when a large driving force or braking force in the tire circumferential direction is applied to the vertically long block 6, the vertically long block 6 flexibly follows the road surface starting from the shallow groove 7 and suppresses a large slip on the road surface. Grip power can be demonstrated.

  The shallow grooves 7 adjacent to each other in the tire axial direction through the main groove 3 are preferably formed so as to be continuous with each other in the tire axial direction. In the present embodiment, the shallow grooves 7 adjacent to each other in the tire axial direction via the main groove 3 are formed so as to be continuous with each other between the tire equator C and the tread end Te.

  Both ends of the shallow groove 7 terminate in the vertically long block 6 without communicating with the main groove 3. That is, the shallow groove 7 does not divide the ridgeline 8 between the tread surface 6S of the vertically long block 6 and the main groove 3.

  Since the ridge line 8 is not divided, the air between the tread surface 6S and the mold can move along the ridge line 8, for example, at the time of vulcanization molding of the tire. Accordingly, the air can be discharged from a vent hole provided at a mold side position corresponding to any of the four corners of the tread surface 6S, for example. In other words, in the tire according to the present embodiment, it is not necessary to form a vent hole or a spew at the corner portion 9a formed by the shallow groove 7 and the main groove 3.

  In the vertically long block 6 of this embodiment, a spew protruding from the tread surface 6S of the vertically long block 6 or a spew mark 11 from which the spew is removed is formed only at each corner portion 9 on one of the diagonal lines. In a preferred embodiment, in order to maintain the rigidity balance of the corner portion 9 on the acute angle side of the tread surface 6S, it is desirable that the spew or spew mark 11 is formed in the corner portion 9 on the obtuse angle side of the tread surface 6S. As described above, in the tire according to the present embodiment, it is possible to suppress the decrease in the effective ground contact area of the tread surface 6S of the vertically long block 6 due to the spew marks 11, and it is possible to further increase the grip force without deteriorating the appearance of the tire.

  FIG. 3 is a cross-sectional view taken along the line AA in FIG. As shown in FIG. 3, the shallow groove 7 includes, for example, a vertically long block 6 from a groove bottom 15, a side wall surface 16 extending along the longitudinal direction of the groove bottom 15, and an end 15 e in the longitudinal direction of the groove bottom 15. And an end wall surface 17 extending on the tread surface 6S.

  The depth D of the shallow groove 7 is formed in a range of 0.5 to 2.0 mm, for example. When the depth D is less than 0.5 mm, the follow-up deformation of the vertically long block 6 starting from the shallow groove 7 with respect to the road surface may be difficult. Conversely, when the depth D is greater than 2.0 mm, the rigidity of the vertically long block 6 may be excessively reduced. From the same viewpoint, it is desirable that the width W (shown in FIG. 2) of the shallow groove 7 is, for example, in the range of 0.5 to 2.0 mm.

  The end wall surface 17 preferably extends from the end 15e in the longitudinal direction of the groove bottom 15 and is connected to the tread surface 6S and the ridgeline 8 of the main groove 3, for example. Such an end wall surface 17 can further facilitate the follow-up deformation of the vertically long block 6 with respect to the road surface while sufficiently securing the groove volume of the shallow groove 7. In the present embodiment, the end wall surfaces 17 on both sides of the shallow groove 7 are connected to the ridge line 8.

  For example, the end wall surface 17 of the present embodiment extends linearly between the end 15 e of the groove bottom 15 and the ridgeline 8. Such an end wall surface 17 is useful for increasing the groove volume of the shallow groove 7 while maintaining the strength between the shallow groove 7 and the main groove 3.

  The end 15e of the groove bottom 15 of the present embodiment is desirably provided closer to the block center than the ridgeline 8. Thereby, the block intensity | strength in the vicinity of the ridgeline 8 is maintainable.

  FIG. 4A shows another embodiment of the shallow groove 7. In this embodiment, the end wall surface 17 is different in that it is away from the tread surface 6S and the ridgeline 8 of the main groove 3. Preferably, the shortest distance L between the end wall surface 17 and the ridge line 8 is preferably within 2.0 mm. The shallow groove 7 having such an aspect ensures, for example, movement along the ridge line 8 of air between the tread surface 6S and the mold at the time of vulcanization molding of the tire, and ensures an air pool in the vicinity of the shallow groove 7. Can be prevented.

  FIG. 4B shows another embodiment of the shallow groove 7. In this embodiment, the end wall surface 17 is different in that it extends between the groove bottom 15 and the tread surface 6S, for example, in an arc shape. The shallow groove 7 having such a configuration can enlarge the groove volume, and can further improve the followability of the vertically long block 6 to the road surface. In order to further expand the groove volume of the shallow groove 7, the arcuate end wall surface 17 may extend from the end 15 e of the groove bottom 15 and be connected to the ridge line 8, for example. In order to maintain the block strength while increasing the groove volume, the radius of curvature R of the arcuate end wall surface 17 is preferably in the range of 0.5 to 5.0 mm, for example.

  As mentioned above, although especially preferable embodiment of this invention was explained in full detail, this invention is not limited to these embodiment, It can deform | transform and implement in a various aspect.

Tires having the tread pattern of FIG. 1 (size: 280 / 655R18) were prototyped based on the specifications in Table 1 and their performance was tested. In the tire of the comparative example, as shown in FIG. 5, both ends of the shallow groove communicate with the main groove, a corner portion having an obtuse angle between the main groove and the lateral groove, and a corner having an obtuse angle between the main groove and the shallow groove. Spew marks are formed in each part. All the shallow grooves had a width and a depth of 2.0 mm.
The test method is as follows.

<Grip performance>
Each sample tire was mounted on all the wheels of the test vehicle, and the time required to travel 370m was measured on the asphalt road surface in rainy weather (rainfall 1mm). The evaluation is obtained by indexing the measured time, and is indicated by an index with the comparative example being 100. The larger the value, the better the grip performance.

<Steering stability performance>
In the above-mentioned vehicle, the test course on the asphalt road surface in the rainy weather was run by one professional test driver, and the characteristics related to steering wheel response, rigidity, grip, etc. during turning were evaluated based on the driver's sensuality. A result is a score which makes a comparative example 100, and it means that it is excellent in steering stability performance, so that a numerical value is large.

  As a result of the test, it can be confirmed that the tires of the examples have improved grip strength and steering stability performance as compared with the comparative examples.

2 Tread 3 Main groove 4 Horizontal groove 5 Block 6 Vertical block 7 Shallow groove

Claims (5)

A pneumatic tire provided with a plurality of main grooves extending continuously in the tire circumferential direction in the tread portion and a plurality of lateral grooves that divide a plurality of blocks by connecting between the main grooves,
The block includes a vertically long block whose length in the tire circumferential direction is 1.5 times or more of the length in the tire axial direction,
The vertically long block is provided with a shallow groove extending in the tire axial direction and terminating in the block without both ends communicating with the main groove .
The vertically long block is a pneumatic tire in which a tread has a quadrangular shape, and a spew protruding from the tread or a spew mark formed by removing the spew is formed only at each corner portion on one of the diagonal lines .
2. The pneumatic tire according to claim 1, wherein the tread portion includes a tread end that comes into contact with a normal load when a normal load is applied and contacted with a flat surface with a camber angle of 0 ° . The shallow groove includes a groove bottom and an end wall surface extending from each longitudinal end of the groove bottom to the tread of the vertically long block,
3. The pneumatic tire according to claim 1, wherein the end wall surface is connected to the tread within a range of 2.0 mm from a ridgeline of the tread and the main groove.   The pneumatic tire according to claim 3, wherein the end wall surface extends linearly or arcuately between the groove bottom and the tread surface.   The pneumatic tire according to any one of claims 1 to 4, wherein the shallow groove has a groove depth in a range of 0.5 to 2.0 mm and a groove width in a range of 0.5 to 2.0 mm.

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