JP6559497B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire.

  Conventionally, a tire in which a tread protrudes outward from a tire reference contour line has been proposed.

  For example, the tire of Patent Document 1 is intended to improve steering stability during cornering while maintaining speed, and the rib of the tread protrudes, and the position of the apex of the protrusion is the width direction of the rib. It is shifted inward from the center line when the vehicle is mounted. According to this tire, since a slanted inclined surface is attached to the outside of the rib when the vehicle is mounted, proper grounding is ensured during cornering while maintaining speed, and steering stability is ensured. The

  Further, the tire of Patent Document 2 is intended to improve the ground contact property in the entire tire width direction of the tread and improve the handling stability. The land portion of the tread protrudes, and the land portion at the top of the protrusion. The position in the width direction is a position where the contact length in the tire circumferential direction is shortened when there is no protrusion. In this tire, the maximum protrusion amount of the center land portion is larger than the maximum protrusion amount of the intermediate land portion. According to this tire, the ground contact property in the entire tire width direction is improved, and the steering stability is improved.

JP 2005-263180 A JP 2013-189121 A

  By the way, when a plurality of land portions having lateral grooves are arranged in the tire width direction, the void ratio is often different for each land portion. Since the land portion having a larger void ratio has a higher contact pressure, the contact pressure varies from land portion to land portion, and uneven wear may occur in the entire tread.

  Accordingly, an object of the present invention is to provide a pneumatic tire in which uneven wear is unlikely to occur even though the void ratio varies from land to land.

The pneumatic tire of the present embodiment is a pneumatic tire in which a plurality of land portions having lateral grooves are arranged in the tire width direction, and as the land portions, a center land portion in the center of the tire width direction and both sides of the tire width direction There are five land portions including a shoulder land portion and a mediate land portion between the center land portion and the shoulder land portion. In the entire tread, a land portion having a small void ratio is more than a land portion having a large void ratio. Also protrudes outward from the tire reference contour line.

  In the pneumatic tire of the present embodiment, uneven wear hardly occurs even though the void ratio is different for each rib.

Sectional drawing of the tire width direction of the pneumatic tire 10 of this embodiment The tread pattern of this embodiment. (A) The figure which looked at the land part 100 from the tire radial direction outer side. (B) The figure which looked at the land part 100 from the direction of arrow B of (a). (C) The figure which looked at the land part 100 from the direction of arrow C of (a).

  As shown in FIG. 1, a pneumatic tire 10 according to this embodiment includes a bead core 11 in which a bundled steel wire is covered with rubber, and a rubber bead provided outside the bead core 11 in the tire radial direction. A bead portion formed of the filler 12 is provided on both sides in the tire width direction. The carcass 13 wraps the bead portions on both sides in the tire width direction, and forms a skeleton of the pneumatic tire 10 between these bead portions.

  One or more belts are provided outside the carcass 13 in the tire radial direction. The belt is made of a plurality of steel cords covered with rubber. In the present embodiment, the first belt 14 on the inner side in the tire radial direction and the second belt 15 on the outer side in the tire radial direction are laminated. A belt reinforcing layer 16 is provided on the outer side in the tire radial direction of the second belt 15. The belt reinforcing layer 16 is formed by covering a plurality of cords made of organic fibers with rubber. The belt reinforcing layer 16 is longer in the tire width direction than the first belt 14 and the second belt 15 and covers them from the outside in the tire radial direction. A tread 20 is provided on the outer side of the belt reinforcing layer 16 in the tire radial direction. Further, sidewalls 17 are provided on both sides of the carcass 13 in the tire width direction, and inner liners 18 are provided on the inner side of the carcass 13, respectively. In addition to the above members, a plurality of members are provided according to the functional requirements of the tire.

  The tread 20 is provided with a plurality of main grooves 21 extending over the circumference of the tire in the tire circumferential direction. A plurality of land portions that are separated by these main grooves 21 and are arranged in the tire width direction are formed. The number of main grooves 21 and the number of land portions are not limited, but in the case of the present embodiment, four main grooves 21 are provided and five land portions are formed. The five land portions are, from one side to the other side in the tire width direction, the first shoulder land portion 23, the first mediate land portion 24, the center land portion 25, the second mediate land portion 26, and the second shoulder land portion. They are arranged in the order of 27.

  The positions on the outer side in the tire width direction of the first shoulder land portion 23 and the second shoulder land portion 27 are the ground contact ends 22 respectively. Here, the ground contact end 22 is the end portion in the tire width direction of the ground contact surface in a state where the pneumatic tire 10 is assembled on a regular rim and is subjected to a regular internal pressure and a regular load is applied. Here, the regular rim is a standard rim defined in standards such as JATMA, TRA, and ETRTO. The normal load is the maximum load defined in the standard. The normal internal pressure is an internal pressure corresponding to the maximum load.

  Each land is provided with a lateral groove. The lateral groove is a groove extending in a direction at a certain angle with respect to the extending direction of the main groove 21 and intersecting the main groove 21. The depth of the lateral groove of the present embodiment is, for example, less than 50% of the depth of the main groove 21. The lateral groove includes a width (so-called sipe) that is wide enough to close the open end at the time of grounding. The number of horizontal grooves provided in the land portion, and the width, depth, shape, and the like of the horizontal groove vary depending on the land portion. Therefore, the void ratio varies depending on the land. The void ratio means the sum x of the areas of the open ends of all grooves provided in the land portion to the ground contact surface, and the sum of the areas y of the ground contact portions of the land portion and the area x. X / (x + y) divided by. Referring to the example of FIG. 3, the area of the open end 102 to the ground contact surface of the groove 101 provided in the land portion 100 is x (the area of the portion x1 in FIG. 3), and all the grounded portions of the land portion 100 are grounded. Assuming that the sum of the areas of 103 is y (the sum of the areas of y1 and y2 in FIG. 3), the void ratio is a value x / (x + y) obtained by dividing x by the sum of x and y. is there.

  Below, based on FIG. 2, an example of the difference in the shape of a horizontal groove for every land part, and the difference in the void ratio for every land part is shown. First, in the center land portion 25, a plurality of center lateral grooves 35a that open to the main grooves 21 on both sides thereof are arranged in the tire circumferential direction. Therefore, the center land portion 25 is a block row in which a plurality of blocks sandwiched between two center lateral grooves 35a are arranged in the tire circumferential direction. In one block, one center narrow groove 35b that opens to the main groove 21 on both sides thereof is provided. The center narrow groove 35b is a kind of lateral groove, but is narrower than the center lateral groove 35a.

  Next, in the first mediate land portion 24, a plurality of first mediate lateral grooves 34a that open to the main groove 21 on the first shoulder land portion 23 side are arranged in the tire circumferential direction. Since the end of the first mediate lateral groove 34a on the inner side in the tire width direction terminates in the first mediate land portion 24, the first mediate land portion 24 is a rib continuous in the tire circumferential direction. The pitch of the first mediate lateral grooves 34a (the distance between the grooves in the tire circumferential direction) is the same as the pitch of the center lateral grooves 35a. Between the two first mediate lateral grooves 34a, two first mediate narrow grooves 34b that open to one main groove 21 are provided. The first mediate narrow groove 34b is a kind of lateral groove, but is narrower than the first mediate lateral groove 34a.

  In the second mediate land portion 26, a plurality of second mediate lateral grooves 36a that open to the main groove 21 on the second shoulder land portion 27 side are arranged in the tire circumferential direction. Since the end of the second mediate lateral groove 36a on the inner side in the tire width direction terminates in the second mediate land portion 26, the second mediate land portion 26 is a rib continuous in the tire circumferential direction. The pitch of the second mediate lateral groove 36a is the same as the pitch of the center lateral groove 35a and the first mediate lateral groove 34a. No narrow groove is provided between the two second mediate lateral grooves 36a.

  Next, in the first shoulder land portion 23, a plurality of first shoulder lateral grooves 33a that open outward in the tire width direction are arranged in the tire circumferential direction. Since the end portion on the inner side in the tire width direction of the first shoulder lateral groove 33a terminates in the first shoulder land portion 23, the first shoulder land portion 23 is a rib continuous in the tire circumferential direction. The pitch of the first shoulder lateral grooves 33a is the same as the pitch of the center lateral grooves 35a and the like. No narrow groove is provided between the two first shoulder lateral grooves 33a.

  In the second shoulder land portion 27, a plurality of second shoulder lateral grooves 37a that open outward in the tire width direction are arranged in the tire circumferential direction. Since the end of the second shoulder lateral groove 37a on the inner side in the tire width direction terminates in the second shoulder land portion 27, the second shoulder land portion 27 is a rib continuous in the tire circumferential direction. The pitch of the second shoulder lateral groove 37a is the same as the pitch of the center lateral groove 35a and the like. No narrow groove is provided between the two second shoulder lateral grooves 37a.

  As a result of the horizontal grooves as described above, the void ratio of the first mediate land portion 24 is the largest, and the void ratio of the center land portion 25 is the second largest. The void ratio of the 2nd mediate land part 26, the 1st shoulder land part 23, and the 2nd shoulder land part 27 is equal, and is the smallest in the void ratio of five land parts.

  Thus, when there are a plurality of land portions having different void ratios, the land portion having a small void ratio protrudes more outward than the tire reference contour L than the land portion having a large void ratio.

  The tire reference contour line L is a curve formed of one or a plurality of arcs that smoothly pass through the edges in the width direction of the land portions. When the open ends of all the main grooves 20 are on one arc, the arc is the tire reference contour L. When the open ends of all the main grooves 20 are not on one arc, the tire reference contour line L is determined as follows (see FIG. 1). First, in the center land portion 25, both edges d, e of the center land portion 25 and edges c, f of the mediate land portions 24, 26 facing these are obtained, and an arc passing through the edges c, d, e is obtained. Of the arcs passing through the edges d, e, and f, the arc having the larger radius of curvature is defined as the tire reference contour L. Further, in the first mediate land portion 24, both edges b and c in the width direction of the first mediate land portion 24 and an edge d on the first mediate land portion 24 side of the center land portion 25 are obtained, and the edge b , C, d is a tire reference contour L. In the second mediate land portion 26, both edges f and g in the width direction of the second mediate land portion 26 and the edge e on the second mediate land portion 26 side of the center land portion 25 are obtained, and the edge e , F, g is a tire reference contour L. Further, in the first shoulder land portion 23, the edge a on the first mediate land portion 24 side of the first shoulder land portion 23, the edge b on the first shoulder land portion 23 side of the first mediate land portion 24, The ground contact edge 22 is obtained, and an arc passing through the ground contact edge 22 and the edges a and b is defined as a tire reference contour line L. Further, in the second shoulder land portion 27, an edge h on the second mediate land portion 26 side of the second shoulder land portion 27, an edge g on the second shoulder land portion 27 side of the second mediate land portion 26, and The contact end 22 is obtained, and the arcs passing through the edges g and h and the contact end 22 are defined as the tire reference contour line L.

  In this embodiment, all the land portions protrude outward from the tire reference contour line L. The amount of protrusion (the amount of protrusion is the height (length) in the normal direction of the tire reference contour L from the reference contour L to the top of the protrusion, and the height of the protrusion is the highest. The land portion having the largest void ratio is the second mediate land portion 26, the first shoulder land portion 23, and the second shoulder land portion 27 having the smallest void ratio. The land portion having the second largest protrusion amount is the center land portion 25. The land portion having the smallest protrusion amount is the first mediate land portion 24 having the largest void ratio. It is desirable that the protruding amount of any land part is a length that is not less than 0.01 times and not more than 0.10 times the width of the land part. The widths of the first shoulder land portion 23 and the second shoulder land portion 27 are the lengths from the end portions of these land portions on the main groove 21 side to the ground contact end 22. Further, as shown in FIG. 1, in the first shoulder land portion 23 and the second shoulder land portion 27, it is desirable that the portion protruding outward from the tire reference contour line L is a portion on the inner side in the tire width direction from the ground contact end 22. .

  Here, in the land portion sandwiched between the two other land portions from both sides in the tire width direction, the position of the protruding vertex in the tire width direction is more than the other center position in the tire width direction of the land portion. It is desirable that the position is close to the land portion with the smaller void ratio among the two land portions. In that case, the position in the tire width direction of the top of the protrusion of the land portion is, for example, the land portion in the tire width direction (the void ratio of the land portion on one side of the land portion in the tire width direction): (the land It is the position which divides | segments by the ratio of the land part void ratio in the tire width direction other side of a part.

  In the present embodiment, the land portions sandwiched between the other two land portions from both sides in the tire width direction are the center land portion 25, the first mediate land portion 24, and the second mediate land portion 26. Looking at the center land portion 25 first, the land portions on both sides thereof are the first mediate land portion 24 and the second mediate land portion 26. The void ratio of the second mediate land portion 26 is smaller than the void ratio of the first mediate land portion 24. Therefore, the position in the tire width direction of the apex r of the protrusion of the center land portion 25 is closer to the second mediate land portion 26 side than the center position in the tire width direction of the center land portion 25. When (void ratio of the first mediate land portion 24) :( void ratio of the second mediate land portion 26) is 2: 1, the tire width direction of the apex r of the protrusion of the center land portion 25 is The position may be, for example, a position where the center land portion 25 is divided 2: 1 in the tire width direction.

  Next, looking at the first mediate land portion 24, the land portions on both sides thereof are the first shoulder land portion 23 and the center land portion 25. The void ratio of the first shoulder land portion 23 is smaller than the void ratio of the center land portion 25. Therefore, the position in the tire width direction of the apex q of the protrusion of the first mediate land portion 24 is closer to the first shoulder land portion 23 side than the center position in the tire width direction of the first mediate land portion 24. In addition, when (void ratio of the first shoulder land portion 23) :( void ratio of the center land portion 25) is 2: 3, the apex q of the protrusion of the first mediate land portion 24 in the tire width direction The position may be a position where the first mediate land portion 24 is divided 2: 3 in the tire width direction, for example.

  Next, regarding the second mediate land portion 26, the land portions on both sides thereof are the center land portion 25 and the second shoulder land portion 27. The void ratio of the second shoulder land portion 27 is smaller than the void ratio of the center land portion 25. Therefore, the position in the tire width direction of the apex s of the protrusion of the second mediate land portion 26 is closer to the second shoulder land portion 27 side than the center position in the tire width direction of the second mediate land portion 26. In addition, when (void ratio of the center land portion 25) :( void ratio of the second shoulder land portion 27) is 3: 2, in the tire width direction of the apex s of the protrusion of the second mediate land portion 26 For example, the position may be a position where the second mediate land portion 26 is divided 3: 2 in the tire width direction.

  Moreover, in the land part (the 1st shoulder land part 23 and the 2nd shoulder land part 27 in this embodiment) which has another land part only in the tire width direction one side, the position of the protrusion apexes p and t in the tire width direction Is preferably the center position of the land portion in the tire width direction.

  In the present embodiment, since the land portion with a small void ratio protrudes more outward than the tire reference contour L than the land portion with a large void ratio, the contact pressure of the land portion with a small void ratio depends on the amount of protrusion. It becomes higher and approaches the contact pressure of the land with a large void ratio. As a result, the variation in contact pressure between land portions is reduced, and uneven wear is less likely to occur in the entire tread.

  Here, when the depth of the lateral groove is shallower than that of the main groove, and particularly when the depth of the lateral groove is less than 50% of the depth of the main groove, the difference in ground pressure between the land portions is likely to be large. Prone to wear. However, in this embodiment, even if the depth of each lateral groove is less than 50% of the depth of the main groove 21, uneven wear is unlikely to occur because the difference in ground pressure between the land portions is small.

  Further, in the land portion sandwiched between the other two land portions from both sides in the tire width direction, the position of the protruding vertex in the tire width direction is the land portion having the smaller void ratio of the other two land portions. If it is closer to the side, the contact pressure of the entire tread becomes more uniform in the tire width direction, and uneven wear is less likely to occur.

  In addition, if the protruding amount of the land portion is 0.01 times or more and 0.10 times or less the width of the land portion, the protruding effect is obtained, and the protruding amount is too large and the ground contact state deteriorates instead. Can be prevented.

  Various changes, substitutions, omissions, and the like can be made to the above embodiments without departing from the scope of the invention.

  For example, in the above embodiment, all the land portions protrude outward from the tire reference contour line L, but some of the land portions may not protrude. Specifically, the land portion having the largest void ratio (the first mediate land portion 24 in the above embodiment) may not protrude. In addition, regarding a land portion having another land portion only on one side in the tire width direction (in the above embodiment, the first shoulder land portion 23 and the second shoulder land portion 27), the void ratio is the void of the adjacent mediate land portion. When it is larger than the ratio, it does not have to protrude.

  The contact pressure dispersion and uneven wear resistance of the tires of Comparative Examples and Examples in Tables 1 to 4 were evaluated. The tires of the comparative example and the example have four main grooves and five land portions as in the above embodiment. The five land portions are the first shoulder land portion, the first mediate land portion, the center land portion, the second mediate land portion, and the second shoulder land portion, as in the above embodiment. These land portions are arranged in this order from one side to the other side in the tire width direction. Each land is provided with a lateral groove. Each tire has a size of 205 / 60R16, a land width of 25 mm, a main groove depth of 7.5 mm, and a lateral groove depth of 3.5 mm.

  As described in Tables 1 to 4, the void ratio is different for each land portion. In addition, the void ratio of Table 1-Table 4 is represented by the index | exponent which makes the void ratio of a 1st mediate land part 100. The ratio between the land portions of this index is the same as the ratio between the land portions of the actual void ratio. That is, when the void ratio index of the first shoulder land portion is 50 and the void ratio index of the first mediate land portion is 100, the ratio of these indexes (the index of the void ratio of the first shoulder land portion): ( The void ratio index of the first mediate land portion is 1: 2, but the actual void ratio (the void ratio of the first shoulder land portion) :( the void ratio of the first mediate land portion) is also 1: 2. It is.

  Tables 1 to 4 show the amount of protrusion of each land portion and the position of the top of the protrusion in the comparative example and the example. In the tire of Comparative Example 1, none of the land portions protrudes. In the tire of Comparative Example 2, the land portion having a large void ratio protrudes more than the land portion having a small void ratio, and the position of the top of the protrusion is close to the land portion side having a large void ratio. On the other hand, in the tire of Example 1, the land part with a small void ratio protrudes more than the land part with a large void ratio, and the position of the top of the protrusion is at the center position in the tire width direction of the land part. In the tire of Example 2, the land portion having a small void ratio protrudes more than the land portion having a large void ratio, and the position of the top of the protrusion is close to the land portion side having a small void ratio. In the column of “displacement of the apex of the protrusion from the center position in the land portion width direction (mm)” in Tables 1 to 4, a positive value means that the apex is displaced toward the second shoulder land portion. A negative value means that the apex is displaced toward the first shoulder land portion.

The evaluation method is as follows.
Ground pressure dispersion: Tires are assembled on regular rims, filled with regular internal pressure, loaded with 70% of the maximum load described in JATMA and pressed against pressure sensitive paper, and the camber angle is 1 °. From the contact pressure measured by pressing against the pressure paper, the dispersion value of the contact pressure within the contact surface was calculated, and the amount of change was indexed. The larger the index, the less the change in contact pressure dispersion, and the better the contact stability when subjected to a load or lateral force.
Uneven wear resistance: After running a tire for 10,000 km on a drum testing machine, the amount of heel and toe wear was measured, and the measurement results were indexed. A larger index indicates less heel and toe wear.

  The results are shown in Table 5. It was confirmed that the tires of the examples were less susceptible to change in contact pressure dispersion than the tires of the comparative examples, had excellent contact stability, and had less heel and toe wear.

DESCRIPTION OF SYMBOLS 10 ... Pneumatic tire, 11 ... Bead core, 12 ... Bead filler, 13 ... Carcass, 14 ... 1st belt, 15 ... 2nd belt, 16 ... Belt reinforcement layer, 17 ... Side wall, 18 ... Inner liner, 20 ... Tread , 21 ... main groove, 22 ... ground contact edge, 23 ... first shoulder land, 24 ... first mediate land, 25 ... center land, 26 ... second mediate land, 27 ... second shoulder land 33a ... first shoulder transverse groove, 34a ... first mediate transverse groove, 34b ... first mediate narrow groove, 35a ... center transverse groove, 35b ... center narrow groove, 36a ... second mediate transverse groove, 37a ... second shoulder transverse groove , 100 ... land part, 101 ... groove, 102 ... open end, 103 ... part to be grounded

Claims (3)

In a pneumatic tire in which a plurality of land portions having lateral grooves are arranged in the tire width direction, as the land portion, a center land portion in the center of the tire width direction, a shoulder land portion on both sides in the tire width direction, the center land portion, and the There are five land portions with the mediate land portion between the shoulder land portion, and in the entire tread, the land portion with a small void ratio protrudes more outward than the tire reference contour line than the land portion with a large void ratio. Pneumatic tires.   In the land portion sandwiched between the other two land portions from both sides in the tire width direction, the position of the protrusion in the tire width direction is higher than the center position in the tire width direction of the land portion. The pneumatic tire according to claim 1, wherein the pneumatic tire is located at a position close to a land portion having a smaller void ratio among the portions. The pneumatic tire according to claim 1 or 2, wherein the depth of the lateral groove is less than 50% of the depth of the main groove extending in the tire circumferential direction.

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