JP5893375B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire having a tread pattern including a block, and is particularly useful as a studless tire.

  Conventionally, in a studless tire, a cut called a sipe is formed in a block on a tread surface, and an edge effect based on the sipe enhances running performance on an ice road surface having a low friction coefficient. Furthermore, a shallow groove having a depth smaller than that of a normal sipe may be formed, and an edge effect based on the shallow groove can improve running performance on an ice road surface in an initial stage of wear.

  In order to sufficiently exhibit the edge effect based on the shallow groove, it is necessary to set the shallow groove with an appropriate density with respect to the block. In particular, on an ice road surface with a low coefficient of friction, the contact pressure at the center of the block is higher than the contact pressure at the periphery, so it is effective to ensure the formation density of shallow grooves in the center of the block. Also, in the state where the strain is concentrated in the center due to such non-uniformity of the ground pressure, the grounding property of the block is deteriorated and the edge effect cannot be sufficiently exerted, so that the ground pressure in the block is made uniform. It is important.

  In the pneumatic tire described in Patent Document 1, polygonal narrow grooves are formed concentrically in order to improve the running performance on the ice road surface in the initial stage of wear. However, in such a structure, the formation density of the shallow grooves in the central portion of the block is low, and there is room for improvement. In addition, since the small blocks partitioned by the narrow grooves are concentrically arranged, the movement of the small blocks from the central part toward the peripheral part is regulated by the surrounding small blocks, and the distortion acting on the central part is appropriately dispersed. In other words, the contact pressure on the block is likely to be uneven.

  In the pneumatic tire described in Patent Literature 2, a plurality of V-shaped shallow grooves are arranged, and the shallow grooves are crossed at the center of the block. However, in such a structure, when the shallow groove intersects at an acute angle, the rigidity locally decreases at the intersection, so that the strain acting on the central portion is not properly distributed, and the ground pressure in the block tends to be uneven. . On the other hand, if the shallow groove is interrupted at the center of the block, the strain concentrates at the end of the block, resulting in nonuniform ground pressure.

JP 2007-216816 A JP 2010-137662 A

  The present invention has been made in view of the above circumstances, and the object thereof is to promote uniform ground pressure in the block, sufficiently exhibit the edge effect based on the shallow groove, and improve the running performance on the ice road surface. It is to provide a pneumatic tire.

  The above object can be achieved by the present invention as described below. That is, the pneumatic tire according to the present invention is a pneumatic tire provided with a tread pattern including a block, and the tip of the block is directed to the center of the block from the peripheral edge to the center of the block. The tip of the sword-shaped shallow groove extends flatly, the tip of the sword-shaped shallow groove, a pair of first bent portions bent at an obtuse angle at both ends of the tip portion, and the pair of first grooves A pair of second bent portions that are arranged closer to the edge of the block than one bent portion and bend at an obtuse angle; a connecting portion that connects the first bent portion and the second bent portion; A distal end portion extending from the second bent portion toward the edge of the block, and the tip-shaped shallow groove is formed with the tip portions facing each other from three or more directions with respect to one block. It is what.

  In this pneumatic tire, since a sword-shaped shallow groove extending from the peripheral part of the block to the central part and extending toward the tip part is formed at the central part of the block, not only the peripheral part of the block but also the shallow groove in the central part. The formation density of is ensured. In addition, the tip of the sword-shaped shallow groove is formed flat, and the first bent portion and the second bent portion are bent at an obtuse angle, so that the rigidity is not locally reduced at these locations. As a result, the ground contact pressure in the block can be made uniform, and the edge effect based on the shallow groove can be fully exerted to improve the running performance on the ice road surface.

  In the present invention, the sword-shaped shallow groove is arranged on each of the tire circumferential direction both sides and the tire width direction both sides of the block, and the sword-shaped shallow groove faces the tip from each other from four directions with respect to one block. Those formed together are preferred. As a result, the edge component in the front-rear direction and the lateral direction in the shallow sword-shaped shallow groove is increased, and both braking performance on the ice road surface (hereinafter referred to as ice braking performance) and turning performance (hereinafter referred to as ice turning performance) are balanced and effective. Can be enhanced.

  In the present invention, it is preferable that the first bent portion or the second bent portion is formed with a depth or groove width larger than that of the connecting portion or the end portion. Since the first bent portion and the second bent portion tend to be higher in rigidity than other portions, by setting these depths and groove widths to be large, the rigidity balance with other portions becomes good, and the block surface The edge effect based on the shallow groove can be enhanced without reducing the rigidity of the groove.

  In the present invention, it is preferable that the plurality of blade-shaped shallow grooves are arranged concentrically at intervals. As a result, the number of sword-shaped shallow grooves can be increased, and the edge effect based on the shallow grooves can be enhanced, thereby effectively improving the running performance on the ice road surface.

  In the present invention, it is preferable that a plurality of whisker-like shallow grooves that do not intersect the sword-like shallow grooves are arranged at intervals in the groove width direction at the peripheral edge of the block. Thereby, the formation density of a shallow groove can be increased, the edge effect based on a shallow groove can be improved, and the running performance on an ice road surface can be effectively improved thereby.

The expanded view which shows an example of the tread pattern with which the pneumatic tire which concerns on this invention is provided. A plan view showing the entire block (A) and a plan view showing the main part of (B). The figure for demonstrating area | region A1 and area | region A2. The figure for demonstrating area | region B1 and area | region B2. The top view which shows the principal part of the sword-shaped shallow groove in another embodiment of this invention (A) Plan view and (B) AA arrow sectional view showing the main part of the sword-shaped shallow groove The top view which shows the principal part of the sword-shaped shallow groove in another embodiment of this invention The top view which shows the shape of the shallow groove | channel which concerns on another embodiment of this invention. The top view of the block provided in the tire of the comparative example 1

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In this embodiment, a pneumatic tire provided with a tread pattern including a block 10 as shown in FIG. 1 is illustrated. The tread surface Tr is provided with a main groove 2 extending in the tire circumferential direction PD and a lateral groove 3 extending in the tire width direction WD, and the blocks 10 partitioned by them are arranged in five rows symmetrically with respect to the tire equator line CL. Has been.

  Each block 10 is formed with a cut sipe 4. However, in FIG. 1, the sipe 4 is drawn only in the upper right block 10, and the description of the sipe 4 is omitted in the other blocks 10. The sipe 4 extends in a wave shape, and both ends thereof are opened at the end sides of the block 10. The shape of the sipe formed in the block 10 is not limited to this, and it may extend linearly along the longitudinal direction, or one end or both ends of the sipe may be terminated inside the block 10.

  As shown in an enlarged view in FIG. 2, a sword-shaped shallow groove 1 is formed on the surface of the block 10 so as to extend from the peripheral portion of the block 10 to the central portion and toward the central portion of the block 10 with the tip portion 11 directed. Yes. The sword-shaped shallow groove 1 has four bent portions and extends in a polygonal line shape, and has a shape like a home base (home plate) used in baseball in a plan view, but its tip 11 is not pointed. It is flat. The blade-shaped shallow groove 1 contributes to the running performance on the ice road surface particularly in the initial stage of wear, and the depth thereof is set smaller than the depth of the sipe 4.

  The depth of the sipe 4 is set to 6.0 to 9.0 mm, for example, while the depth D1 (see FIG. 6) of the sword-shaped shallow groove 1 is set to 0.2 mm or more and less than 1.0 mm, for example. Is done. Further, the groove width W1 of the sword-shaped shallow groove 1 is set to, for example, 0.3 mm or more and less than 2.0 mm. The depth D1 and the groove width W1 are dimensions measured at the connecting portion 14 and the end portion 15 of the blade-shaped shallow groove 1, and as will be described later, the depth and groove width at the bent portions 12 and 13 are It is preferable to set the depth larger than the depth D1 and the groove width W1.

  The blade-shaped shallow groove 1 includes a tip portion 11 formed flat, a pair of bent portions 12 (corresponding to a first bent portion) bent at an obtuse angle at both ends of the tip portion 11, and the pair of bent portions 12. A pair of bent portions 13 (corresponding to the second bent portion) that are arranged near the end side of the block 10 and bend at an obtuse angle, and a connecting portion 14 that connects the bent portion 12 and the bent portion 13; And a terminal portion 15 extending from the bent portion 13 toward the end side of the block 10.

  The tip portion 11 is formed linearly between the pair of bent portions 12 and extends substantially parallel to the end side of the block 10 near the end portion 15 of the sword-shaped shallow groove 1. The length W11 of the distal end portion 11 is preferably 1.5 mm or more, and is set to 1.5 to 4.0 mm, for example. In the bent portion 12, the angle θ12 formed by the tip portion 11 and the connecting portion 14 is an obtuse angle, and the preferred angle θ12 is 100 to 160 °. In the bent portion 13, the angle θ13 formed by the connecting portion 14 and the end portion 15 is an obtuse angle, and the preferred angle θ13 is 100 to 160 °.

  The connecting portion 14 is formed linearly between the bent portion 12 and the bent portion 13, and an angle θ14 with respect to the tire circumferential direction PD is, for example, 45 ± 15 °. In the plurality of blade-shaped shallow grooves 1 formed in the block 10, the connecting portions 14 extend radially from the center portion of the block 10 toward the peripheral portion. The end portion 15 is linearly formed from the bent portion 13 toward the end side of the block 10, and an angle θ15 with respect to the end side is, for example, 90 ± 15 °.

  The sword-tip-shaped shallow groove 1 is formed with respect to one block 10 such that tip portions 11 face each other from three or more directions. In this embodiment, the sword-shaped shallow groove 1 is arranged on each of both sides of the tire circumferential direction PD of the block 10 and both sides of the tire width direction WD. The portions 11 are formed so as to face each other. The plurality of sword-shaped shallow grooves 1 formed in the block 10 do not intersect with each other, and a small block extending radially is defined by the distal end portion 11 and the connecting portion 14 via the bent portion 12.

  By forming such a sword-tip-shaped shallow groove 1, the formation density of the shallow groove is secured not only in the peripheral portion of the block 10 but also in the central portion. In addition, since the distal end portion 11 is flat and the bent portions 12 and 13 are bent at an obtuse angle, none of the local rigidity decreases. In addition, the sword-shaped shallow groove 1 extends continuously without being divided in the middle, and the terminal portion of the sword-shaped shallow groove 1 is not formed in the center of the block 10. As a result, the ground pressure in the block 10 can be made uniform, and the edge effect based on the shallow groove can be fully exhibited, thereby improving the running performance on the ice road surface.

  Of the running performance on the ice road surface, the contribution of the edge component in the front-rear direction is large for the ice braking performance, and the contribution of the edge component in the lateral direction is great for the ice turning performance. In this pneumatic tire, since the blade-shaped shallow groove 1 is formed from three or more directions, the edge component due to the shallow groove is set in each direction, and both ice braking performance and ice turning performance can be improved. In the present invention, it is preferable to form the blade-shaped shallow groove from four directions as in the present embodiment or from three directions as shown in FIG.

  Here, as shown in FIGS. 3 and 4, the length of the block 10 in the tire width direction is W, the reference line passing through the center thereof is WC, the length of the block 10 in the tire circumferential direction is L, and the reference line passing through the center is LC. And Further, in FIG. 3, a strip-like region having a width of 30% of the length W with the reference line WC as the center is A1, and a strip-like region having a width of 30% of the length L with the reference line LC in the center is A2. . The pair of bent portions 12 are preferably arranged in a region where the region A1 and the region A2 overlap each other, whereby the formation density of the shallow grooves in the central portion of the block 10 can be ensured satisfactorily.

  In FIG. 4, a band-like region having a width of 55% of the length W with the reference line WC as the center is B1, and a belt-like region having a width of 55% of the length L with the reference line LC in the center is B2. . The pair of bent portions 13 are preferably not arranged in a range where the region B1 and the region B2 overlap. Thereby, the range which the connection part 14 extends radially can be ensured moderately, and dispersion | distribution of the distortion which goes to the peripheral part from the center part of the block 10 along the longitudinal direction of the connection part 14 can be promoted.

  In the present embodiment, an example in which the distal end portion 15 of the sword-shaped shallow groove 1 is opened at the end side of the block 10 is shown, but the present invention is not limited to this, and the distal end portion 15 is the end of the block 10 as shown in FIG. It does not matter if it terminates inward from the side. In such a case, the distance D15 from the end side of the block 10 to the end portion 15 is preferably within 3 mm. As a result, an edge component due to the shallow groove can be secured, and a terminal portion where distortion tends to concentrate can be kept away from the central portion of the block 10.

  The sword-shaped shallow groove 1 may have a uniform depth, but the bent portion 12 or the bent portion 13 may have a depth larger than that of the connecting portion 14 or the end portion 15 as shown in FIG. Good. In this example, the depth is increased at both the bent portion 12 and the bent portion 13, but either one may be used. The depth D2 of the bent portions 12 and 13 is larger than the depth D1, and is set to 0.5 mm or more and 1.6 mm or less, for example. In order to promote equalization of the ground pressure in the block 10, it is effective to apply the depth D2 of the bent portion 12 to the tip portion 11 as in the present embodiment.

  In FIG. 2, the groove width of the blade-shaped shallow groove 1 is set uniformly. However, as shown in FIG. 7, the groove width is larger at the bent portion 12 or the bent portion 13 than at the connecting portion 14 or the end portion 15. May be. Such a groove width configuration can be used in place of or in combination with the depth configuration shown in FIG. The groove width W2 of the bent portions 12 and 13 is larger than the groove width W1, and is set to, for example, 0.7 mm or more and 2.0 mm or less. The bent portions 12 and 13 tend to increase in rigidity because the falling of the small block is supported from a plurality of directions. By increasing the depth and groove width in this way, the rigidity balance with other parts can be increased. It is possible to improve the edge effect.

  As shown in FIG. 2, in the present embodiment, a plurality of sword-shaped shallow grooves 1 are arranged concentrically at intervals. Thereby, the number of the sword-shaped shallow grooves 1 can be increased, the edge effect based on the shallow grooves can be enhanced, and the running performance on the ice road surface can be effectively improved. Between the blade-shaped shallow grooves 1 arranged in a nested manner, each of the tip portion 11, the connecting portion 14, and the end portion 15 extends in parallel with each other, and the interval H1 thereof is, for example, 0.7 to 2.0 mm. Is set.

  In the present embodiment, in order to increase the edge component due to the shallow groove, a plurality of whisker-like shallow grooves 5 that do not intersect the sword-shaped shallow groove 1 are arranged at intervals in the groove width direction at the peripheral edge of the block 10. The whisker-shaped shallow groove 5 is formed in a straight line in parallel with the end portion 15 of the sword-shaped shallow groove 1, and ends inward from the end side of the block 10 like the end portion 15 in FIG. 5. An interval between the whisker-like shallow grooves 5 and an interval H2 between the end portion 15 and the whisker-like shallow groove 5 are set to, for example, 0.7 to 2.0 mm.

  FIG. 8 shows the shape of a shallow groove according to another embodiment of the present invention. (A) is the example which increased the formation density of the shallow groove | channel by increasing the number of sword-shaped shallow grooves compared with embodiment mentioned above. (B) and (C) each illustrate other shapes related to the sword-shaped shallow groove. (D) is an example in which a sword-shaped shallow groove is formed from three directions, and the block is formed in a triangle by the auxiliary groove 20. The sub-groove 20 has a depth of about 50% with respect to the main groove, and the groove width W20 is set to 1.0 to 3.0 mm, for example.

  The tread pattern included in the pneumatic tire of the present invention is not particularly limited as long as it has a block, and a rib may be mixed therein. The shape of the block in which the sword-shaped shallow groove is formed is not limited to the rectangle as shown in the above-described embodiment, and other shapes such as a parallelogram or a hexagon can be adopted.

  The pneumatic tire of the present invention is the same as a normal pneumatic tire except that the blade-shaped shallow groove as described above is formed in the block, and any conventionally known material, shape, structure, etc. are adopted in the present invention. it can.

  Although the present invention can be applied to so-called summer tires, it is particularly useful as a studless tire (winter tire) because of its excellent running performance on an ice road surface.

  Examples and the like specifically showing the configuration and effects of the present invention will be described below. In addition, each performance evaluation of the tire was performed as follows.

(1) Ice braking performance A vehicle (1500 cc class 4WD middle sedan) was fitted with tires and traveled on an ice road surface, and the reciprocal of the braking distance when a braking force was applied at a speed of 40 km / h was evaluated. The result of Comparative Example 1 is shown as an index with the value 100, and the larger the value, the better the ice braking performance.

(2) Ice turning performance A vehicle (1500 cc class 4WD middle sedan) is fitted with tires to run on an ice road, and a steady circular turning is performed at a speed of 20 km / h, and the lateral force value generated on the front tire is evaluated. . The result of Comparative Example 1 is shown as an index with a value of 100, and the larger the value, the better the ice turning performance.

  In the pneumatic tire having the tread pattern of FIG. 1 (tire size: 195 / 65R15), those having various shallow grooves formed on the surface of the block were designated as Comparative Example 1 and Examples 1 to 3. Example 2 has the same configuration as Example 1 except that the depth is increased at the bent part as shown in FIG. 6, and the depth D1 of the connecting part and the terminal part is 0.3 mm, and the depth of the bent part. The length D2 is 1.0 mm. Further, the groove density in Table 1 is the ratio of the length of the shallow groove to the block area, and is indicated by an index with Comparative Example 1 being 100. The evaluation results are shown in Table 1.

  As shown in Table 1, in Examples 1 to 3, the ice braking performance and the ice turning performance are improved as compared with Comparative Example 1. Among them, although Examples 1 and 2 have a lower groove density than Comparative Example 1, the running performance on the ice road surface is improved. Further, in Example 2, although the groove density is the same as that in Example 1, a further improvement effect is obtained by increasing the depth at the bent portion.

DESCRIPTION OF SYMBOLS 1 Sword-shaped shallow groove 2 Main groove 3 Horizontal groove 4 Sipe 5 Whisker-shaped shallow groove 10 Block 11 Tip part 12 First bending part 13 Second bending part 14 Connection part 15 Terminal part

Claims (5)

In pneumatic tires with tread patterns including blocks,
On the surface of the block, a sword-shaped shallow groove extending from the peripheral part of the block to the center part and extending toward the tip part at the center part of the block is formed,
The block is formed with a cut-out sipe, the depth of the sword-shaped shallow groove is smaller than the depth of the sipe, and the depth of the sword-shaped shallow groove is 0.2 mm or more and less than 1.0 mm,
The sword-shaped shallow groove includes a flat tip portion, a pair of first bend portions bent at an obtuse angle at both ends of the tip portion, and an end side of the block more than the pair of first bend portions. And a pair of second bent portions that are bent at an obtuse angle, a connecting portion that connects the first bent portion and the second bent portion, and an edge of the block from the second bent portion And an end portion extending toward
The pneumatic tire according to claim 1, wherein the blade-shaped shallow groove is formed with the tip portions facing each other from three or more directions with respect to one block.
  The sword-shaped shallow grooves are arranged on both the tire circumferential direction side and the tire width direction both sides of the block, and the sword-shaped shallow grooves are formed so that the tip portions face each other from four directions with respect to one block. The pneumatic tire according to claim 1.   The pneumatic tire according to claim 1 or 2, wherein the first bent portion or the second bent portion is formed with a depth or groove width larger than that of the connecting portion or the end portion.   The pneumatic tire according to any one of claims 1 to 3, wherein the plurality of blade-shaped shallow grooves are arranged concentrically at intervals. The plurality of whisker-like shallow grooves that do not intersect with the sword-like shallow groove are arranged at intervals in the groove width direction of the whisker-like shallow groove on the peripheral edge of the block. The described pneumatic tire.

Images