JP4353822B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire having a block pattern on a tread.

  Conventionally, in a pneumatic tire having a block pattern, if the block surface has a curvature with the same radius as the tire outer peripheral radius in a cross section perpendicular to the tire rotation axis, if wear occurs at the kick-out side end of the block, it is the same as before As a result, an imbalance of the contact pressure occurs between the kicking side end and the stepping side end of the block, and uneven wear called heel and toe wear occurs. When heel-and-toe wear occurs, not only the appearance deteriorates but also the gripping ability of the tire decreases.

As a technique for suppressing the heel and toe wear, a method of changing the surface shape of the block has been proposed. Specifically, a technique for forming the outer contour of a cross section perpendicular to the tire rotation axis into an arc shape having a smaller radius of curvature than the tire outer contour is disclosed (for example, Patent Document 1).
JP-A-6-166304

  However, with the conventional technology, it has been difficult to sufficiently suppress the heel and toe wear on the entire surface of the tread. That is, by changing the surface shape of the block, if the heel and toe wear can be effectively suppressed for the outermost block row arranged at both ends of the tread, it is difficult to suppress in other rows. In addition, if the heel and toe wear can be effectively suppressed for block rows other than the outermost block row, it is difficult to suppress the outermost block row.

  In view of the above problems, an object of the present invention is to provide a pneumatic tire capable of effectively suppressing heel and toe wear on the entire tread surface.

  In order to solve the above-described problems, a feature of the present invention is that a pneumatic tire includes a tread having a plurality of block rows partitioned by a circumferential main groove extending in the tire circumferential direction and a lateral groove intersecting the circumferential main groove. The blocks arranged at both ends of the tread gradually reduce the block height from the point where the block height becomes maximum toward the kicking-out side end and the stepping-side end in a cross section perpendicular to the tire rotation axis. The contour line connecting the point where the block height is maximum and the kicking side end or the stepping side end includes at least one arc having a center of curvature inside the tire and smaller than the curvature of the tire outer periphery, except at both ends of the tread In the cross section perpendicular to the tire rotation axis, the block height gradually decreases from the point where the block height is maximum toward the kicking-out side edge and the stepping-side edge. Click on the height contour line connecting the side end or leading side trailing edge and the point of maximum, and summarized in that at least 1 pneumatic tire comprising one arc having a center of curvature outside the tire.

  The blocks arranged at both ends of the tread are made up of circular arcs with the center of curvature inside the tire, so the length of the block surface is different from that of a conventional block that has the same radius of curvature as the tire outer periphery. Can take longer. Further, since the center of curvature is inside the tire, rubber is pushed out in the traveling direction at the time of grounding, and the distance between the stepping side end and the kicking side end at the time of grounding can be made longer than that at the time of non-grounding. For this reason, the bending deformation of the block kicking-out side end can be reduced, and as a result, wear of the kicking-out side end can be suppressed.

  On the other hand, the blocks arranged at both ends of the tread have a center of curvature on the outside of the tire, so the tread surface shrinks in the circumferential direction at the time of ground contact, and the distance between the stepping side end and the kicking side end at the time of ground contact is not grounded Can be shorter than time. For this reason, the bending deformation of the block kicking-out side end can be reduced, and as a result, wear of the kicking-out side end can be suppressed.

  Therefore, according to the pneumatic tire according to the feature of the present invention, heel and toe wear can be effectively suppressed over the entire tread surface.

  Further, in the pneumatic tire according to the feature of the present invention, the point where the block height of the block arranged at both ends of the tread and the block arranged at other than the both ends of the tread is maximum is located at the center in the tire circumferential direction of the block. The contour line connecting the point where the block height is maximum and the kicking side end and the contour line connecting the point where the block height is maximum and the stepping side end are symmetrical at the center in the tire circumferential direction. Good.

  According to this pneumatic tire, in the cross section perpendicular to the tire rotation axis, the contour of the block surface is symmetric in the rotation direction and the opposite direction, so that the heel and toe can be applied to the entire tread regardless of the rotation direction of the tire. Abrasion can be effectively suppressed.

  Further, in the pneumatic tire according to the present invention, the block height of the blocks arranged at both ends of the tread is maximized in that the tire circumferential direction length is 1/4 of the tire circumferential direction length from the tire circumferential center of the block. The point where the block height of the block located within the range of the tread and other than both ends of the tread is maximum is 1 / of the tire circumferential direction length from the tire circumferential direction center of the block in the direction opposite to the tire rotation direction. It may be located within a range of 4 or less.

  As will be described in detail later, since the expansion and contraction action of the tread surface is different between the outermost block arranged at both ends of the tread and the other blocks, in order to generate this better, the point where the block height is the largest In the outermost block, the rotation direction is preferable, and in the other blocks, the rotation direction is preferably opposite to the rotation direction. However, the point where the block height is maximum is the outermost block, from the center in the tire circumferential direction of the block to the rotational direction side from the position of 1/4 of the tire circumferential direction length, and in the other blocks, the tire circumference of the block If the center of the direction is set to the opposite side of the rotation direction from the position of 1/4 of the tire circumferential length, the rigidity distribution in the block becomes non-uniform and the pattern noise becomes worse, which is not preferable.

  According to the present invention, it is possible to provide a pneumatic tire capable of effectively suppressing heel and toe wear on the entire tread surface.

  Next, embodiments of the present invention will be described with reference to the drawings. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, it should be noted that the drawings are schematic and ratios of dimensions and the like are different from actual ones. Accordingly, specific dimensions and the like should be determined in consideration of the following description. Moreover, it is a matter of course that portions having different dimensional relationships and ratios are included between the drawings.

(First embodiment)
As shown in FIG. 1, the pneumatic tire 10 according to the first embodiment includes a tread 12, a circumferential main groove 14 that extends in the tire circumferential direction (arrow A direction), and a lateral groove that intersects the circumferential main groove. A plurality of block rows 17 and 18 divided by 16 are provided. The length in the tire circumferential direction of the blocks 17 arranged at both ends of the tread 12 is OL, and the width in the tire width direction is OW. The length in the tire circumferential direction of the blocks 18 arranged at both ends of the tread 12 is CL, and the width in the tire width direction is CW.

  FIG. 1 shows, for example, tires for trucks and buses having a tire size of 295 / 75R22.5. About the internal structure of a pneumatic tire, since it is a structure of a general radial tire, the detail about an internal structure is abbreviate | omitted.

  2A and 2B show cross sections perpendicular to the tire rotation axis of the block 17 disposed at both ends of the tread 12 and the block 18 disposed at both ends of the tread 12, respectively. The tire rotates in the direction indicated by arrow C. In the sectional view, the maximum block height is OH1, CH1, the block height at the kick-out side end is OH2, CH2, and the block height at the step-in end is OH3, CH3.

  As shown in FIG. 2 (a), the blocks 17 arranged at both ends of the tread 12 have a kick-out side end 17a and a step-in side end from a point OM at which the block height is maximum in a cross section perpendicular to the tire rotation axis. The block height gradually decreases toward 17b. That is, the height gradually decreases from the maximum block height OH1 to the kick-out side end block height OH2, and the height gradually decreases from the maximum block height OH1 to the step-in side end block height OH3. Further, at least one arc OR having a center of curvature on the inner side of the tire and smaller than the curvature of the outer periphery of the tire is formed on the contour line connecting the point OM at which the block height becomes maximum and the kicking side end 17a or the stepping side end 17b. Including. At this time, the arc may be composed of a plurality, and may have a straight portion instead of the arc.

  In the first embodiment, the point OM at which the block height is maximum is located at the center in the tire circumferential direction of the block (the position OL / 2 from the kick-out side end 17a or the tread side end 17b), and the block height. The contour line connecting the point OM where the maximum value and the kick-out side end 17a and the contour line connecting the point OM where the block height becomes the maximum and the stepping side end 17b are symmetrical at the center in the tire circumferential direction.

  Further, as shown in FIG. 2 (b), the blocks 18 arranged at both ends of the tread 12 have a kick-out side end 18a and a side edge 18a, which are at the maximum height in the cross section perpendicular to the tire rotation axis. The block height gradually decreases toward the stepping side end 18b. That is, the height gradually decreases from the maximum block height CH1 to the kick-out side end block height CH2, and the height gradually decreases from the maximum block height CH1 to the step-in side end block height CH3. Further, at least one arc CR having a center of curvature on the outer side of the tire is included in the contour line connecting the point CM at which the block height is maximum and the kicking side end 18a or the stepping side end 18b. At this time, the arc may be composed of a plurality, and may have a straight portion instead of the arc.

  In the first embodiment, the point CM at which the block height is maximum is located at the center in the tire circumferential direction of the block (at a position CL / 2 from the kick-out side end 18a or the tread side end 18b), and the block height. The contour line connecting the point CM at which the maximum value and the kick-out side end 18a and the contour line connecting the point CM at which the block height is maximum and the stepping-side end 18b are symmetrical at the center in the tire circumferential length. Become.

(Second Embodiment)
Since the tread plan view of the pneumatic tire 10 according to the second embodiment is the same as FIG. 1, the description thereof is omitted here.

  Sections perpendicular to the tire rotation axis of the block 17 disposed at both ends of the tread 12 and the block 18 disposed at both ends of the tread 12 of the pneumatic tire 10 according to the second embodiment are shown in FIG. ) And (b). The tire rotates in the direction indicated by arrow C. In the sectional view, the maximum block height is OH1, CH1, the block height at the kick-out side end is OH2, CH2, and the block height at the step-in end is OH3, CH3.

  As shown in FIG. 3 (a), the blocks 17 arranged at both ends of the tread 12 have a kick-out side end 17a and a tread side end from a point OM at which the block height is maximum in a cross section perpendicular to the tire rotation axis. The block height gradually decreases toward 17b. That is, the height gradually decreases from the maximum block height OH1 to the kick-out side end block height OH2, and the height gradually decreases from the maximum block height OH1 to the step-in side end block height OH3. Further, at least one arc OR having a center of curvature on the inner side of the tire and smaller than the curvature of the outer periphery of the tire is formed on the contour line connecting the point OM at which the block height becomes maximum and the kicking side end 17a or the stepping side end 17b. Including. At this time, the arc is composed of two arcs OR1, OR2, or more, and may have a straight portion instead of the arc.

  In the second embodiment, the point OM at which the block height is maximum is the tire circumferential direction from the center in the tire circumferential direction of the block (the position OL / 2 from the kick-out side end 17a or the tread side end 17b). It is located in a range within 1/4 of the direction length OL.

  Further, as shown in FIG. 3 (b), the blocks 18 arranged at both ends other than the both ends of the tread 12 have a kick-out side end 18a and a side edge 18a which are at the maximum height in the cross section perpendicular to the tire rotation axis. The block height gradually decreases toward the stepping side end 18b. That is, the height gradually decreases from the maximum block height CH1 to the kick-out side end block height CH2, and the height gradually decreases from the maximum block height CH1 to the step-in side end block height CH3. Further, at least one arc CR having a center of curvature on the outer side of the tire is included in the contour line connecting the point CM at which the block height is maximum and the kicking side end 18a or the stepping side end 18b. At this time, the arc is composed of two arcs R1, CR2, or more, and may have a straight portion instead of the arc.

  In the second embodiment, the point CM at which the block height is maximum is opposite to the tire rotation direction from the center in the tire circumferential direction of the block (the position OL / 2 from the kick-out side end 17a or the stepping-side end 17b). It is located in a range within 1/4 of the tire circumferential length CL in the direction.

(Operation and effect of the pneumatic tire according to the present embodiment)
As for the heel-and-toe wear of the block, as a result of intensive researches by the present inventor regarding the wear form and the reason for the occurrence by the tread width direction position, the outermost block row located at both ends of the tread and other block rows Then, the reason for the occurrence is different, and it has been found that this is the reason why the heel-and-toe wear on the entire tread surface cannot be suppressed in the prior art.

  Specifically, in the outermost block row, as shown in FIG. 4 (a), the kick-out side end 17a extends to cause a slip in the same direction as the tire rotation direction. The amount of wear of 17a was larger than the amount of wear of the stepped side end 17b.

  Further, in the other block rows, as shown in FIG. 4B, the kick-out side end 18a contracts to cause a slip in the direction opposite to the tire rotation direction. The amount was larger than the wear amount of the stepping side end 18b.

  Furthermore, as a result of studying the cause, this difference in block deformation is due to the fact that the tire crown is designed in a convex shape, resulting in a difference in the circumference between the center and the shoulder, which is the tread deformation when kicking out. It turns out that it makes a difference.

  However, in order to prevent unevenness in contact pressure and contact length distribution due to the rigidity of the tire side portion and adverse effects on steering stability performance, etc., it is necessary to design the crown shape to be convex. . Therefore, in order to suppress the heel and toe wear on the entire tread surface, it is necessary to improve the block deformation by a method other than changing the tire crown.

  In light of such a background, the outermost block 17 of the pneumatic tire 10 according to the present embodiment has the kick-out side end 17a and the stepping-in side from the point OM at which the block height is maximum in the cross section perpendicular to the tire rotation axis. The contour line connecting the point OM where the block height gradually decreases toward the end 17b and the block height becomes maximum and the kick-out side end 17a or the tread side end 17b has a center of curvature inside the tire, The other block 18 includes at least one arc OR smaller than the curvature of the above-mentioned, and the other block 18 is directed from the point CM at which the block height is maximum in the cross section perpendicular to the tire rotation axis toward the kicking side end 18a and the stepping side end 18b. The contour line connecting the point CM at which the block height gradually decreases and the block height becomes maximum and the kicking side end 18a or the stepping side end 18b An arc CR with rates center was to contain at least one.

  Since the outermost block 17 is formed by an arc OR having a curvature center on the inner side of the tire, the outermost block 17 has a longer block surface length than the conventional block having the same curvature radius as the tire outer periphery. Can do. Further, since the center of curvature is inside the tire, the rubber is pushed out in the traveling direction at the time of grounding, and the distance between the stepping side end 17b and the kicking side end 17a at the time of grounding can be made longer than that at the time of non-grounding. For this reason, the bending deformation of the block kick-out side end 17a can be reduced, and as a result, wear of the kick-out side end 17a can be suppressed.

  On the other hand, since the other block 18 has a center of curvature on the outer side of the tire, the tread surface contracts in the circumferential direction at the time of grounding, and the distance between the stepping side end 18b and the kicking side end 18a at the time of grounding is shorter than that at the time of non-grounding. can do. For this reason, the bending deformation of the block kick-out side end 18a can be reduced, and as a result, wear of the kick-out side end 18a can be suppressed.

  According to the pneumatic tire 10 according to the present embodiment, heel and toe wear can be effectively suppressed over the entire tread surface.

  Further, in the pneumatic tire 10 according to the first embodiment, the points OM and CM at which the block heights of the outermost block 17 and the other blocks 18 are maximized are located at the center in the tire circumferential direction of the block. Contour lines connecting the points OM and CM where the height is maximum and the kick-out side ends 17a and 18a, and contour lines connecting the points OM and CM where the block height is maximum and the stepping-side ends 17b and 18b. In addition, the tire is symmetrical at the center in the tire circumferential direction.

  According to the pneumatic tire according to the first embodiment, in the cross section perpendicular to the tire rotation axis, the contour of the block surface is symmetric in the rotation direction and the opposite direction, so that the entire tread surface regardless of the rotation direction of the tire. , Heel and toe wear can be effectively suppressed.

  Further, in the pneumatic tire 10 according to the second embodiment, the point OM at which the block height of the outermost block 17 is maximum is 1 in the tire circumferential length from the tire circumferential center of the block in the tire rotating direction. The point CM where the block height of the other block 18 is maximum within the range of / 4 is within ¼ of the tire circumferential length in the direction opposite to the tire rotation direction from the center of the tire circumferential direction of the block. Located in the range.

  Since the expansion and contraction action of the tread surface is different between the outermost block 17 disposed at both ends of the tread and the other blocks 18, in order to generate this better, the outermost block 17 has the largest block height. It is preferable that the point OM is arranged on the rotation direction side, and in the other blocks 18, the point CM having the largest block height is arranged on the direction opposite to the rotation direction. This is because the expansion action at the outermost block 17 is due to the rubber being pushed out in the rotation direction at the time of ground contact, so it is effective to increase the length of the arc portion on the opposite side to the rotation direction. This is because the contracting action at the block 18 is due to the crushing of the portion of the rubber that comes into contact first at the time of ground contact, so it is effective to increase the length of the arc portion on the rotational direction side.

  However, the points OM and CM at which the block height is maximum are changed from the center in the tire circumferential direction of the block to the rotational direction side from the center in the tire circumferential direction of the block, and in the other blocks 18. If the rotation direction is opposite to the 1/4 position of the tire circumferential length from the tire circumferential center of the block, the rigidity distribution in the block becomes non-uniform and the pattern noise deteriorates. Absent.

  According to the pneumatic tire according to the second embodiment, the outermost block 17 rotates the point OM having the largest block height toward the rotation direction, and the other blocks 18 rotate the point CM having the largest block height. By disposing on the direction opposite to the direction, heel and toe wear can be effectively suppressed over the entire tread surface.

  Examples of the pneumatic tire according to the embodiment of the present invention will be described in detail below. In order to confirm the effect of the present invention, heel and toe wear evaluation was performed on two types of tires of the examples to which the present invention was applied, two types of tires of comparative examples, and one type of conventional tire.

  In all of the examples, comparative examples, and conventional examples, the tire size was 295 / 75R22.5, and the internal pressure was 650 kPa. Tire and rim diameters shall conform to JATMA. Further, the radius of curvature of the tire outer periphery was 516 mm.

  The block shape of Example 1 is the shape shown in FIG. 2 described in the first embodiment, and the block shape of Example 2 is the shape shown in FIG. 3 described in the second embodiment. .

  Moreover, the block shape of the comparative example 1 makes all the outermost block 17 and the other blocks 18 the shape shown in FIG. 2A, and the block shape of the comparative example 2 makes all the outermost block 17 and the other blocks 18 all the same. The shape shown in FIG.

  Further, as shown in FIG. 5, the block shape of the conventional example is a shape having a constant height H from the kicking side end to the stepping side end.

The blocks of Examples 1 and 2, Comparative Examples 1 and 2 and the conventional example all had a circumferential length L of 50 mm and a tire width direction width W of 32 mm. Other conditions are shown in Table 1.

  In addition, the block height in Table 1 is a height in a cross section perpendicular to the tire rotation axis. In both the outermost block and other blocks, the block height is the value listed in Table 1. Also, the inside of () written after the radius of curvature indicates whether the center of curvature is inside the tire or outside the tire.

  In the heel-and-toe wear evaluation test, each pneumatic tire was mounted on a driving wheel of a 2D4 actual vehicle, and the vehicle was run at 20000 km, and the volume of rubber lost due to heel-and-toe wear after running was measured. The test results are shown as an index when the rubber loss of the conventional example is set to 100, and the smaller the value, the more the heel and toe wear resistance is suppressed.

(result)
The results are shown in Table 2.

  It was found that Examples 1 and 2 suppressed heel and toe wear in the outermost row and other rows as compared with the conventional example. Therefore, it was found that by setting the block shapes of the outermost row and other rows to the design values shown in Table 1, heel and toe wear can be effectively suppressed over the entire tread surface.

  In addition, it was found that Examples 1 and 2 suppressed heel and toe wear in the outermost row and other rows as compared with Comparative Examples 1 and 2. In Comparative Examples 1 and 2, the unevenness of the heel and toe wear performance when the entire surface of the tread was made the same surface shape was remarkable, but by making the outermost block and the other blocks different shapes, the tread It was found that heel and toe wear can be effectively suppressed over the entire surface.

It is a top view of the tread of the pneumatic tire concerning the embodiment of the present invention. (A) is sectional drawing orthogonal to the tire rotating shaft of the outermost block which concerns on 1st Embodiment, (b) is right-angled to the tire rotating shaft of the other block which concerns on 1st Embodiment. FIG. (A) is sectional drawing orthogonal to the tire rotating shaft of the outermost block which concerns on 2nd Embodiment, (b) is right-angled to the tire rotating shaft of the other block which concerns on 2nd Embodiment. FIG. (A) is a figure explaining the modification of an outermost block, (b) is a figure explaining the modification of other blocks. It is sectional drawing orthogonal to the tire rotating shaft of the conventional block.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Pneumatic tire 12 ... Tread 14 ... Circumferential main groove 16 ... Horizontal groove 17 ... Outermost row block 17a ... Kicking side end 17b ... Depressing side end 18 ... Blocks other than outermost row 18a ... Kicking side end 18b ... Depression side end A ... Tire circumferential direction B ... Tire width direction C ... Tire rotation direction

Claims (3)

A pneumatic tire including a plurality of block rows partitioned by a circumferential main groove extending in the tire circumferential direction and a lateral groove intersecting the circumferential main groove on the tread,
The blocks arranged at both ends of the tread are such that the block height gradually decreases from the point at which the block height is maximized toward the kick-out side end and the tread side end in the cross section perpendicular to the tire rotation axis. Including at least one arc having a center of curvature on the inner side of the tire and smaller than the curvature of the outer circumference of the tire, on the contour line connecting the point where the maximum value is reached and the kicking side end or the stepping side end.
The blocks disposed at both ends of the tread have a block height that gradually decreases from the point at which the block height is maximized toward the kick-out side end and the tread side end in a cross section perpendicular to the tire rotation axis. A pneumatic tire characterized by including at least one arc having a center of curvature on the outer side of a tire on a contour line connecting a point having the maximum length and a kicking side end or a stepping side end.   The point where the block height of the block disposed at both ends of the tread and the block disposed at both ends of the tread is maximized is located at the center in the tire circumferential direction of the block, and the block height is maximized. The contour line connecting the point and the kicking side end and the contour line connecting the point where the block height is maximum and the stepping side end are symmetric in the center in the tire circumferential direction. The pneumatic tire according to 1. The point where the block height of the blocks arranged at both ends of the tread is maximum is located in a range within 1/4 of the tire circumferential direction length from the tire circumferential center of the block in the tire rotating direction,
The point where the block height of the block arranged at both ends of the tread is maximum is within a range of 1/4 of the tire circumferential length from the center in the tire circumferential direction to the direction opposite to the tire rotation direction. The pneumatic tire according to claim 1, wherein the pneumatic tire is positioned.

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