JP5066453B2 - Pneumatic radial tire - Google Patents

Description

  This invention is a pneumatic radial tire, especially a pneumatic tire that becomes a block pattern, and when rolling on a load, the central area of the tread surface rises from the road surface, sufficiently suppressing the occurrence of the so-called buckling phenomenon on the snow. The present invention relates to a pneumatic radial tire that provides improved handling stability.

  A radial carcass having both ends fixed to each of the pair of bead portions and extending toroidally from one bead portion to the other bead portion, and a belt and a tread sequentially disposed on the outer peripheral side of the crown region of the radial carcass A plurality of block rows are defined on the tread surface by a plurality of circumferential grooves extending continuously in the tread circumferential direction and a plurality of widthwise grooves extending in the tread width direction intersecting the circumferential grooves. Pneumatic radial tires, especially in areas where high loads are applied, the tread's out-of-plane bending rigidity may be insufficient, and the tread tread's widthwise center area may buckle from the road surface. When such a buckling phenomenon occurs, the movement performance caused by the decrease in the contact area of the tread tread surface, Reduction of the dynamic performance occurs, not denied a reduction in steering stability.

  Therefore, for the occurrence of such a buckling phenomenon, by connecting the blocks facing each other across the circumferential groove by a groove bottom raised portion called a tie bar provided in the circumferential groove, It has been proposed to increase the out-of-plane bending rigidity of the tread, and it is also proposed to provide a sipe on the surface of the groove bottom raised portion in order to improve the performance on ice and snow.

  However, when a sipe is formed on the surface of the groove bottom raised portion provided in the circumferential groove, the performance on the snow of the tire can be improved by the sipe, but the bending rigidity of the groove bottom raised portion itself is increased by the sipe. Therefore, there is a problem that the buckling suppressing function by the groove bottom raised portion is insufficient, the grounding property of the tread surface is lowered, and the steering stability is lowered.

  The object of the present invention is to solve such problems of the prior art, and the object of the invention is to suppress buckling and improve steering stability on snow. The object is to provide a pneumatic radial tire that can achieve both high dimensions.

  The pneumatic radial tire according to the present invention has a plurality of circumferential grooves continuously extending in a linear shape, a zigzag shape, a crank shape, and the like in the tread circumferential direction, and extends in the tread width direction intersecting the circumferential grooves. A plurality of width direction grooves define a plurality of block rows on the tread surface, and at least a pair of circumferential grooves located closest to the respective tread side edges, with each circumferential groove being separated in the tread width direction Are provided with a plurality of groove bottom ridges for interconnecting all of the blocks facing each other, or every other one or more of the blocks facing each other. A set of at least one having only a sipe extending in the tread circumferential direction and having only a sipe extending in the tread width direction, and one having no sipe on the surface It is made to fit arrangement.

  Therefore, as a combination mode here, in addition to a combination of a surface having no sipes and a surface having only sipes extending in either the tread circumferential direction or the tread width direction, the surface There are combinations of those having no sipes, those having only sipes extending in the tread circumferential direction on the surface, and those having only sipes extending in the tread width direction on the surface.

  Here, the “widthwise groove extending in the tread width direction” refers to a groove whose extending component in the tread width direction is longer than the extending component in the tread circumferential direction. , Curved, zigzag, stepped and other required forms.

  By the way, in such a tire, more preferably, a groove bottom ridge is provided that interconnects all the blocks positioned opposite to each other in the tread width direction with a circumferential groove therebetween. The protruding height from the groove bottom is made lower than the similar protruding height of each block to which the groove bottom ridges are connected.

  Moreover, as arrangement | positioning aspects of the groove bottom bulge part of each form, the groove bottom bulge which has only the sipe extended in the tread width direction and the sipe extended only in the tread width direction on the surface At least one of the grooves and groove bottom ridges having no sipes on the surface alternately arranged in the tread circumferential direction, or groove bottom ridges having only sipes extending in the tread circumferential direction on the surface, and the surface It is preferable that each of the three types of raised portions of the groove bottom raised portion having only the sipe extending in the tread width direction and the groove bottom raised portion not having the sipe on the surface be alternately arranged in the tread circumferential direction. .

  And it is preferable to provide a groove bottom raised part in all the surrounding grooves.

  In addition, when extending a plurality of circumferential grooves on each side portion of the tire equator surface, the circumferential grooves that extend to each side portion to form a groove bottom raised portion are positioned adjacent to each other. It is preferable that the type of the groove bottom ridge, that is, the type of the surface form, is different in the tread width direction between the circumferential grooves to be formed. It is preferable to make each type of groove bottom raised portion provided in the groove a combination arrangement that is symmetrical with respect to the tire equator line.

  In the pneumatic radial tire according to the present invention, a portion of the plurality of groove bottom raised portions formed in the circumferential groove and interconnecting the opposing blocks is assumed to have no sipe on the surface, and the tire tread is out of the plane. By ensuring the bending rigidity and thereby suppressing the occurrence of the buckling phenomenon, it is possible to secure a sufficient contact area of the tread surface and realize excellent movement performance, in particular, steering stability.

  On the other hand, it is possible to provide excellent braking / driving performance and / or anti-skid performance on snow by having sipes on the surface of some of the plurality of groove bottom raised portions.

  In such a tire, when all the blocks facing the circumferential groove are interconnected by the groove bottom raised portion, it is possible to achieve both higher handling stability and improved performance on snow at a higher level, This is more effective when groove bottom bulges are provided in all the circumferential grooves.

  Note that when the protruding height of the groove bottom ridge from the circumferential groove bottom is lower than the similar protruding height of each block to which the groove bottom ridge is connected, the load rolling of the tire on the wet road surface is reduced. When moving, the drainage function of the circumferential groove can be sufficiently secured to effectively eliminate the possibility of occurrence of hydroplaning phenomenon.

  Further, here, at least one of the groove bottom raised portion having only the sipe extending in the tread circumferential direction and the groove bottom raised portion having only the sipe extending in the tread width direction on the surface, and the surface does not have the sipe. When the groove bottom ridges are alternately arranged in the tread circumferential direction, the functions of the respective groove bottom ridges can be balanced more effectively, and steering stability and performance on snow can be more effectively balanced. be able to.

  And this means that only the sipe that has a sipe extending in the tread circumferential direction on the surface, and a groove ridge that functions particularly effectively for the slip resistance on snow, and a sipe extending in the tread width direction on the surface. Groove bottom ridges that function particularly effectively for braking and driving performance on snow, and groove bottom ridges that do not have sipes on the surface and function particularly effectively to increase the out-of-plane bending stiffness of the tread This is particularly noticeable when the portions are alternately arranged in the tread circumferential direction.

  In the pneumatic radial tire as described above, the groove bottoms between the circumferential grooves located adjacent to each other of the circumferential grooves that extend to the respective sides of the tire equatorial plane to form the groove bottom raised portions. When the type of the raised portion is made different in the tread width direction, various functions as described above of the groove bottom raised portion can be effectively balanced in the tread width direction.

  In addition, when the groove bottom bulge portion of the groove bottom bulge portion is arranged symmetrically with respect to the tire equator line between the respective circumferential grooves, each function according to the type of the groove bottom bulge portion, As a result, the symmetry of each performance with respect to the tire equator line can be secured, the function of the groove bottom raised portion can be effectively balanced, and the handling stability on the snow and on the dry road surface can be improved.

FIG. 1 is a cross-sectional view of a main part in the tread width direction and a developed plan view of a tread surface, showing an embodiment of the present invention.
The internal reinforcement structure of the tire is the same as that of a general passenger car radial tire, and is not shown here.

  In the figure, two pairs of circumferential grooves 2 and 3 extending symmetrically with respect to the tire equator line E are formed on the tread tread 1 in a straight line, and each circumferential groove 2 is formed. , 3 and extending in a straight line shape in the tread width direction to form a plurality of width direction grooves 4 opened at the respective tread side edges, and the tread tread surface 1 is formed by these grooves 2, 3, 4 respectively. Are divided into five block rows 5, 6 and 7, and each circumferential groove 2 and 3 is opposed to each other in the tread width direction with the circumferential grooves 2 and 3 therebetween. By providing respective groove bottom ridges 8, 9 that interconnect all of the blocks 5a, 6a, 7a, these ridges 8, 9 result in increased out-of-plane bending stiffness of the tread 10, thereby Tread tread that contacts the road surface when tires are rolling Minute, the central region in the width direction is deformed in a direction floats from the tread surface, suppresses the occurrence of the buckling phenomenon.

  Further, here, with respect to such groove-bottom raised portions 8 and 9, in one circumferential groove 2 and 3, those having a sipe on the surface 8a and 9a, and those having no sipe on the surface 8b and 9b Arrange them in combination. In addition, although all of the groove bottom raised portions having sipes shown in the figure have only sipes extending in the tread width direction, in place of or in addition to those having sipes extending in the tread width direction, It is also possible to have only sipes extending in the tread circumferential direction.

  Here, preferably, the protruding height of the groove bottom raised portions 8 and 9 from the circumferential groove bottom is apparent from the position shown in FIG. 1A, and the groove bottom raised portions 8 and 9 are connected to each other. The blocks 5a, 6a, and 7a have the same protruding height to ensure smooth drainage by the circumferential grooves 2 and 3.

  Further, preferably, a groove bottom ridge having only a sipe extending in the tread circumferential direction on the surface, and a groove bottom ridge 8a having only a sipe extending in the tread width direction as shown in FIG. , 9a and groove bottom raised portions 8b, 9b having no sipes on the surface thereof are alternately arranged in the circumferential direction of the tread in one circumferential groove 2, 3.

  Also preferably, the tire equator line E, and thus the circumferential grooves 2, 3 extending on the respective sides of the tire equator plane and forming the groove bottom ridges 8, 9 are positioned adjacent to each other. As shown in FIG. 1B, the type of the groove bottom raised portion is made different in the tread width direction between the circumferential grooves 2 and 3 to be performed.

  Further, the groove bottom raised portions 8a, 8b, 9a, 9b provided in the respective circumferential grooves 2, 3 are symmetrical with respect to the tire equator line E as shown in FIG. It is preferable to adopt a combination arrangement.

  FIG. 2 is a view similar to FIG. 1 showing another embodiment, which is a groove bottom ridge 8 that interconnects the respective blocks 5a, 6a, and 7a of the five rows of blocks 5, 6, and 7. , 9, in particular, the raised portions 9 formed in the pair of circumferential grooves 3 positioned closest to the respective tread side edges have only the sipes extending in the tread width direction on the surface as described above. There are three types, one 9a, one 9b having no sipes on the surface, and one 9c having only sipes extending in the tread circumferential direction on the surface, and these three kinds of groove bottom raised portions 9a, 9b, 9c are The configuration shown in FIG. 1 is different from that shown in FIG. 1 in that they are alternately arranged in the tread circumferential direction.

  In addition, in the place shown in this figure, the groove bottom raised portions 8 formed in the pair of circumferential grooves 2 near the tire equator line E can also be of the same three types. The three types of raised portions are preferably arranged alternately in the tread circumferential direction.

  And here again, groove bottom ridges 8 and 9 that provide interconnection of the blocks 5a, 6a and 7a in all the circumferential grooves 2 and 3 of the blocks 5a, 6a and 7a facing each other with the circumferential grooves 2 and 3 therebetween. Is preferably provided.

  Preferably, as shown in FIG. 2 (a), the protruding height of the groove bottom ridges 8 and 9 from the circumferential groove bottom is set to the respective blocks 5a, 6a, Lower than the height of the similar protrusion of 7a.

  Further, also in the place shown in this figure, the circumferential grooves 2 and 3 which are extended to the respective side portions of the tire equatorial plane to form the groove bottom raised portions 8 and 9 are positioned adjacent to each other. The groove bottom ridges connected to the same blocks 5a and 6a are different in the tread width direction between the circumferential grooves 2 and 3, and the respective types of grooves provided in the respective circumferential grooves The bottom raised portions 8a, 8b, 9a, 9b, and 9c are preferably combined and arranged so as to be symmetric with respect to the tire equator line E.

1 and 2, the number of sipes on the surface of the groove bottom raised portions 8, 9 is three for sipes extending in the tread width direction and two for sipes extending in the tread circumferential direction. Of course, the number of sipes can be increased or decreased as needed.
Further, here, the volume of each groove bottom raised portion 8, 9 occupies 10% of each circumferential groove volume, and the ratio of the surface area of each groove bottom raised portion 8, 9 to each circumferential groove area is 50. However, these ratios can be appropriately changed as required.

  Example tire 1 and example tire 2 having a size of 225 / 50R17 and having the configuration shown in FIGS. 1 and 2, respectively, and comparative tire 1 having the same size and having the configuration shown in FIGS. 3 and 4 and comparison Example tire 2 was used as a test tire, and the steering stability on snow and dry road surfaces and the braking performance on dry and wet road surfaces were measured.

  The results are shown in Table 1 with index values. In addition, the index value in a table | surface shall have shown the result which was excellent, so that the comparative example tire 1 was large.

By the way, the driving stability on the snow and on the dry road surface is evaluated by measuring the time required for driving a vehicle equipped with each tire on a course with a circumference of 3 km and displaying the reciprocal number as an index,
The braking performance was evaluated by measuring the distance from the initial speed of 100 km / h to the stop and displaying the reciprocal number as an index.
The braking performance on the wet road surface was tested by forming a water film having a water depth of 2 mm on the road surface.

  According to Table 1, the tires 1 and 2 of the examples were both steered on the snow with little or no degradation in steering stability on the dry road surface due to the formation of sipes on the surface of the groove bottom ridge. It can be seen that the stability can be advantageously improved.

  However, in the comparative example tire 2 in which the sipe extending in the tread width direction is provided on the surface of all the groove bottom raised portions, the steering stability on the dry road surface is inevitably lowered due to the decrease in the out-of-plane bending rigidity of the tread. It is understood that it is done.

1 is a cross-sectional view of a main part in a tread width direction and a developed plan view of a tread surface showing an embodiment of the present invention. It is a figure similar to FIG. 1 which shows other embodiment of this invention. It is a figure similar to FIG. 1 which shows the comparative example tire 1. FIG. FIG. 2 is a view similar to FIG.

Explanation of symbols

1 tread surface 2, 3 circumferential groove 4 width direction groove 5, 6, 7 block row 5a, 6a, 7a block 8, 9 raised portion (8a, 8b, 9a, 9b, 9c raised portion)
10 tread

Claims (8)

A plurality of circumferential grooves extending continuously in the tread circumferential direction and a plurality of width directions extending in the tread width direction intersecting the circumferential grooves define a plurality of block rows on the tread surface, at least A pair of circumferential grooves located closest to the tread side edge of the tread is provided with a plurality of groove bottom ridges that interconnect the respective blocks facing each other in the tread width direction across the circumferential grooves. A radial tire,
A combination of at least one of those having only the sipe extending in the tread circumferential direction on the surface and those having only the sipe extending in the tread width direction, and those having no sipe on the surface. Pneumatic radial tire as an arrangement.   The pneumatic radial tire according to claim 1, further comprising a groove bottom raised portion that interconnects all the blocks facing each other in the tread width direction with a circumferential groove therebetween.   The pneumatic radial tire according to claim 1 or 2, wherein a protruding height of the groove bottom raised portion from the circumferential groove bottom is lower than a similar protruding height of each block connected to the groove bottom raised portion.   At least one of a groove bottom ridge having only a sipe extending in the tread circumferential direction on the surface, a groove bottom ridge having only a sipe extending in the tread width direction, and a groove bottom ridge having no sipe on the surface The pneumatic radial tire according to claim 1, wherein the tires are alternately arranged in a tread circumferential direction.   A groove bottom ridge having only a sipe extending in the tread circumferential direction on the surface, a groove bottom ridge having only a sipe extending in the tread width direction on the surface, and a groove bottom ridge having no sipe on the surface The pneumatic radial tire according to any one of claims 1 to 4, wherein the tires are alternately arranged in the tread circumferential direction.   The pneumatic radial tire according to any one of claims 1 to 5, wherein a groove bottom raised portion is provided in every circumferential groove.   The type of groove bottom bulge portion is made different in the tread width direction between the circumferential grooves located adjacent to each other of the circumferential grooves extending to each side portion of the tire equatorial plane. A pneumatic radial tire according to any one of the above.   The pneumatic radial tire according to any one of claims 1 to 7, wherein each type of groove bottom raised portion provided in each circumferential groove is combined and arranged symmetrically with respect to the tire equator line.

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