JP6542110B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire.

  As described in Patent Document 1, the pneumatic tire is provided with a plurality of main grooves extending in the tire circumferential direction, and a plurality of land portions separated by the main grooves are provided. Some of these lands extend from one end of the land in the tire width direction and end in the land, and extend from the other end of the land in the tire width direction and terminate in the land. There are two types of lateral grooves, one with lateral grooves. And although not described in patent document 1, a pneumatic tire is known in which the above-mentioned two types of lateral grooves overlap (overlap) in the tire circumferential direction near the widthwise center of the land portion. There is.

  In such an overlapping pneumatic tire, the contact pressure is high in the overlapping region (overlap region), particularly in the vicinity of the wall surface of the lateral groove in that region, and in the land portion provided with the overlap region. Contact pressure is uneven. And that causes the braking performance of the pneumatic tire not to be sufficiently improved.

  In the case where the lateral groove does not terminate in the land portion and opens on both sides in the tire width direction of the land portion, the contact pressure in the land portion is relatively uniform, and such a problem hardly occurs.

  By the way, as a general method to improve the braking performance, the method of changing the compounding of the rubber, the narrowing of the lateral grooves or the reduction of the number thereof reduces the area of the opening to the ground plane of the lateral grooves, Methods are included.

  In addition, as described in Patent Document 1, it is known that the ground contact surface is protruded to the outer side in the tire radial direction with respect to the reference contour of the tread rubber in order to improve the ground contact shape of the pneumatic tire.

JP, 2013-189121, A

  However, if the composition of the rubber is changed or the area of the opening to the contact surface of the lateral groove is reduced for the purpose of improving the braking performance, another problem may occur that the rolling resistance is deteriorated.

  Therefore, according to the present invention, a lateral groove extending from an end portion on one side in the tire width direction of the land portion and terminating in the land portion, and a lateral groove extending from the end portion on the other side in the tire width direction of the land portion and terminating in the land portion An object of the present invention is to provide a pneumatic tire that is overlapped in the circumferential direction of the tire in a land portion, in which extreme deterioration of rolling resistance is suppressed and braking performance is improved.

  In the pneumatic tire according to the present embodiment, a plurality of land portions extending in the circumferential direction of the tire are provided on a tread rubber forming a contact surface, and at least one of the land portions among them, an end portion on one side in the width direction And a second lateral groove extending from the other end in the width direction and terminating in the land portion, wherein the first lateral groove and the second lateral groove extend in the tire circumferential direction. A pneumatic tire provided with overlapping overlap regions, wherein the thickness of the tread rubber in the overlap region is thicker than the thickness of the tread rubber in regions on both sides of the overlap region in the same land portion. I assume.

  In the pneumatic tire according to the present embodiment, the extreme deterioration of the rolling resistance is suppressed, and the braking performance is improved.

BRIEF DESCRIPTION OF THE DRAWINGS The half cross section of the tire width direction of the pneumatic tire 10 of embodiment. 1 is a tread pattern of a pneumatic tire 10 according to an embodiment.

  FIG. 1 is a half sectional view of the pneumatic tire 10 of the present embodiment in the tire width direction. The structure of the pneumatic tire 10 of the present embodiment is symmetrical with respect to the tire equator E.

  The pneumatic tire 10 of the present embodiment includes a bead portion including a bead core 11 in which a bundled steel wire is coated with a rubber, and a rubber bead filler 12 provided on the outer side of the bead core 11 in the tire radial direction. Have on both sides in the width direction. The carcass ply 13 wraps the bead portion on both sides in the tire width direction, and forms a skeleton of the pneumatic tire 10 between the bead portions. Although two carcass plies 13 are provided in the present embodiment, there may be a case where only one carcass ply 13 is provided.

  One or more belts are provided on the radially outer side of the carcass ply 13 in the tire radial direction. The belt is a plurality of cords made of steel or the like coated 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 coating a plurality of cords made of organic fiber or the like 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 outer side in the tire radial direction.

  A tread rubber 20 that forms a ground contact surface is provided on the outer side in the tire radial direction of the belt reinforcing layer 16. Further, sidewall rubbers 17 are provided on both sides of the carcass ply 13 in the tire width direction. The tread rubber 20 is an end portion in the tire width direction of the second belt 15 which is the belt shorter in the tire width direction among the two belts (if the first belt 14 is shorter in the tire width direction than the second belt 15 It is thinner at the tire width direction outer side than the tire width direction end portion of the one belt 14, and the thinner portion overlaps the sidewall rubber 17. In the region where the tread rubber 20 and the sidewall rubber 17 overlap, either of the tread rubber 20 and the sidewall rubber 17 may be on the tire outer surface side.

  A rubber chafer 18 is provided on both sides in the tire width direction of the carcass ply 13 and at a position on the tire width direction outside of the bead filler 12. The upper portion of the rubber chafer 18 is in contact with the lower portion of the sidewall rubber 17. The rim is in contact with the surface of the rubber chafer 18.

  Further, an inner liner 19 is provided inside the carcass ply 13. In addition to the above members, a plurality of members are provided according to the functional needs of the tire.

  FIG. 2 shows a tread pattern formed on the tread rubber 20 of the pneumatic tire 10 of the embodiment. The tread rubber 20 is provided with a plurality of main grooves extending in the tire circumferential direction. In the case of the present embodiment, four main grooves 21 are provided. A central land portion 22 at the center in the tire width direction, a shoulder land portion 23 on both sides in the tire width direction, and a median land portion 24 between the center land portion 22 and the shoulder land portion 23 are separated by these main grooves 21. And are formed. In the present embodiment, these land portions are ribs that extend over the entire circumference of the tire.

  The end of the shoulder land portion 23 on the outer side in the tire width direction is a ground contact end R. The ground contact end R refers to the tire width direction end portion of the ground contact surface in a state where the pneumatic tire 10 is rim-assembled on a regular rim and has a regular internal pressure and a regular load. Here, the normal rim is a standard rim defined in standards such as JATMA, TRA, ETRTO, etc. The normal load is the maximum load defined in the above standard. The normal internal pressure is an internal pressure corresponding to the maximum load. In general, the ground contact end R is on the inner side in the tire width direction than the tire width direction end of the belt (second belt 15 in the case of this embodiment) which is the shortest in the tire width direction. However, when the pneumatic tire 10 is used under heavy load, the ground contact end R may be outside the tire width direction end of the second belt 15 in the tire width direction.

  Horizontal grooves are provided in the center land portion 22, the shoulder land portion 23, and the medium land portion 24, respectively. The lateral grooves mainly extend in the tire width direction, but may be inclined with respect to the tire width direction. The lateral groove has a slit with a certain length and width, a notch whose length is shorter than the slit and which opens only on one side in the width direction of the land, a sipe whose width is narrower than the slit or notch and closed at the time of grounding Etc. are included.

  The shoulder land portion 23 of the present embodiment is provided with a first lateral groove 31 which extends from an end portion on one side in the width direction (the inner side in the tire width direction) and terminates in the shoulder land portion 23. The first transverse groove 31 opens in the main groove 21. Further, the shoulder land portion 23 of the present embodiment is provided with a second horizontal groove 32 which extends from the end on the other side in the width direction (outside in the tire width direction) and terminates in the shoulder land portion 23. The second lateral groove 32 is opened outward from the ground contact end R in the tire width direction. The first lateral grooves 31 and the second lateral grooves 32 are alternately arranged in the tire circumferential direction. The first lateral groove 31 and the second lateral groove 32 overlap in the tire circumferential direction. An area where the first lateral groove 31 and the second lateral groove 32 overlap in the tire circumferential direction is referred to as an overlap area 30.

  In the shoulder land portion 23, the thickness of the tread rubber 20 in the overlap region 30 is thicker than the thickness of the tread rubber 20 in the region on both sides in the tire width direction of the overlap region 30 (referred to as non-overlap region 33). There is. Here, the thickness refers to the thickness in the normal direction of a member (in the case of this embodiment, the belt reinforcing layer 16) in contact with the tread rubber 20 on the inner side in the tire radial direction of the tread rubber 20.

  Specifically, the tread rubber 20 is thicker in the entire overlap area 30 than in the non-overlap area 33. That is, the thickness of the tread rubber 20 at any position of the overlap region 30 is thicker than the thickness of the tread rubber 20 at any position in the non-overlap region 33. Generally, the tread rubber is thickest at a position closest to the tire equator in the land portion, and at the shoulder land portion, the tread rubber is thickest at the inner end in the tire width direction. However, in the case of the present embodiment, the thickness of the tread rubber 20 at any position in the overlap region 30 is thicker than the thickness of the tread rubber 20 at the tire width direction inner end 25 of the shoulder land portion 23.

  However, it is desirable that the thickness of the tread rubber 20 in the overlap region 30 be 1.1 times or less the thickness of the tread rubber 20 at the tire width direction inner end 25 of the shoulder land portion 23. That is, assuming that the thickness of tread rubber 20 at any position in overlap region 30 is A, and the thickness of tread rubber 20 at tire width direction inner end 25 of shoulder land portion 23 is B, B <A ≦ 1.1. It is desirable that the relationship of × B be established.

  The thickness of the tread rubber 20 in the overlap region 30 is the thickest at a predetermined position in the tire width direction (referred to as the maximum thickness position 34), and becomes thinner as it is further away in the tire width direction. On the tire width direction cross section, the maximum thickness position 34 is preferably within the range of 60% of the tire width direction length of the overlap region 30 at the center of the overlap region 30 in the tire width direction. That is, from the end 35 on the inner side in the tire width direction of the overlap region 30 to the outer side in the tire width direction by 20-80% (including 20% and 80%) of the length in the tire width direction of the overlap region 30 Preferably, there is a maximum thickness location 34 at the location of. Further, assuming that the thickness of the tread rubber 20 at the maximum thickness position 34 is C, it is desirable that the relationship of B <C ≦ 1.1 × B is established.

  When viewed on the tire width direction cross section, the contact surface of the overlap region 30 draws a curve having the maximum thickness position 34 at the top. However, the ground contact surface of the overlap region 30 may be linear from the maximum thickness position 34 toward both sides in the width direction of the overlap region 30 on the tire width direction cross section.

  The form regarding the thickness of the tread rubber 20 as described above is the same at any position in the tire circumferential direction of the shoulder land portion 23. Further, as shown in FIG. 2, in the present embodiment, since the overlap region 30 is provided on both of the pair of (two) shoulder land portions 23, the thickness of the tread rubber 20 as described above is related. The form is common to the pair of shoulder lands 23.

  The thickness of the tread rubber 20 can be confirmed by the following method. First, a tire is cut parallel to the tire width direction and the tire radial direction to prepare a cut sample. If necessary, make the cut surface of the cut sample smooth by buffing or the like. Next, the bead portion of the cut sample is adjusted to the rim width of the normal rim, and the shape of the cut sample is adjusted to the shape when the tire is filled with normal internal pressure. In that state, the length from the boundary between the tread rubber 20 and the member in contact with it (the belt reinforcing layer 16 in the case of this embodiment) to the tire contact surface is the above-mentioned member (the belt reinforcing layer in the case of this embodiment) It measures in the normal direction of 16), and is taken as thickness of tread rubber 20. Here, the boundary between the tread rubber 20 and the belt reinforcing layer 16 in the cut surface of the cut sample can be represented by a curve connecting the end of the cord of the belt reinforcing layer 16 on the tire contact surface side.

  In the pneumatic tire 10 of the above embodiment, since the thickness of the tread rubber 20 in the overlap region 30 is thicker than the thickness of the tread rubber 20 in the non-overlap region 33, the contact area of the overlap region 30 corresponds to the thickness. is increasing. Therefore, the ground contact pressure of the overlap region 30 is lowered, and the ground contact pressure is uniformed in the entire shoulder land portion 23. Therefore, the braking performance is improved as compared with the conventional pneumatic tire provided with the overlap region. In addition, since the composition of the rubber is not changed or the area of the opening to the contact surface of the lateral groove is not reduced, the extreme deterioration of the rolling resistance is suppressed.

  In addition, the thickness A of the tread rubber 20 in the overlap region 30 and the thickness B of the tread rubber 20 at the tire width direction inner end 25 of the shoulder land portion 23 satisfy the relationship B <A ≦ 1.1 × B. For example, the thickness A of the tread rubber 20 in the overlap region 30 is not too large to significantly reduce the rolling resistance, and the thickness A of the tread rubber 20 in the overlap region 30 is too thin to improve the braking performance. Absent.

  Further, if the thickness of the tread rubber 20 is thickest at the maximum thickness position 34 of the overlap region 30 and thinner from there in the tire width direction, a large change in contact pressure of the shoulder land portion 23 The contact pressure of the entire shoulder land portion 23 is equalized.

  Further, if the maximum thickness position 34 is within 60% of the length of the overlap region 30 in the tire width direction at the center of the overlap region 30 in the tire width direction on the tire width direction cross section, When the maximum thickness position 34 is biased to one side in the tire width direction, the contact area of the non-overlap region 33 does not become wider than necessary, and the contact pressure of the entire shoulder land portion 23 is made uniform.

  Further, if the ground contact surface of the overlap region 30 draws a curve with the maximum thickness position 34 as the apex, no large change point occurs in the ground contact pressure of the shoulder land portion 23, and the ground contact pressure of the entire shoulder land portion 23 is It is uniformed.

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

  For example, in the above embodiment, the shoulder land portion 23 is provided with the overlap region 30 of the first lateral groove 31 and the second lateral groove 32, and the thickness of the tread rubber 20 in the overlap region 30 is thick. A similar overlap area may be provided in the land portion of the medium, and the thickness of the tread rubber may be increased as in the above embodiment in the overlap area.

  Also, in the case where an overlap area is provided on two or more land areas among the center land area, the shoulder land area, and the medium land area, at least one of the land areas provided with the overlap area is provided. The tread rubber in the overlap region may be thick as in the above embodiment. However, the effect becomes more remarkable if the tread rubber in the overlap region is thick as in the above embodiment in all the land portions provided with the overlap region.

  The rolling resistance coefficient (RRC) and the braking performance of the tires of the comparative example and the example were evaluated. The tires of the comparative example and the example have the same structure as the pneumatic tire 10 of the above embodiment except for the thickness of the tread rubber. That is, the tires of the comparative example and the example all have the center land portion, the median land portion, and the shoulder land portion. Then, in the shoulder land portion, a first lateral groove extending from the end portion on one side in the tire width direction and terminating in the shoulder land portion, and a second lateral groove extending from the end portion on the other side in the tire width direction and terminating in the shoulder land portion A lateral groove is provided, and the first lateral groove and the second lateral groove overlap in the tire circumferential direction. The size of each tire is 205 / 60R16.

  The characteristics of the thickness of the tread rubber of the pneumatic tire of the comparative example and the example are as shown in Table 1. In Table 1, "the tread rubber thickness A in the overlap region" is an average of the tread rubber thickness over the overlap region.

  The pneumatic tire of Comparative Example 1 is a conventionally known pneumatic tire in which the thickness of tread rubber decreases from the inside in the tire width direction of the shoulder land portion to the outside. Further, in the pneumatic tire of Comparative Example 2, the thickness of the tread rubber in the entire shoulder land portion is increased instead of increasing the thickness of the tread rubber only in the overlap region. The “thickness C of the tread rubber at the maximum thickness position” of Comparative Examples 1 and 2 and Example 3 in Table 1 is the thickness of the tread rubber at the same position in the tire width direction as the maximum thickness position of Examples 1 and 2. It is.

  The pneumatic tires of Examples 1 to 3 are all the pneumatic tires of the above-described embodiment, but “the thickness A of the tread rubber in the overlap region” is different. In the pneumatic tire of Example 3, the thickness of the tread rubber is constant in the overlap region.

  In the pneumatic tires of Examples 1 and 2, the length in the tire width direction of the overlap region is 23 mm, and the length in the tire width direction of the non-overlap region inside the tire width direction from the overlap region is 6 mm . And as shown in Table 1, "the length from the tire width direction inner end of the shoulder land portion to the maximum thickness position" is 17.5 mm. Therefore, the maximum thickness position of the pneumatic tire of Examples 1 and 2 corresponds to the center position in the tire width direction of the overlap region.

The evaluation method is as follows.
Rolling resistance coefficient: The rolling resistance test based on JIS D4234 was implemented, the rolling resistance coefficient was calculated | required, and it indexed. The smaller the index, the smaller the rolling resistance coefficient.
Braking performance: The tire was attached to a real vehicle, and the braking distance when the traveling speed was reduced from 100 km / h to 0 km / h was measured and indexed. The larger the index, the better the braking performance.

  The evaluation results are as shown in Table 1. Although the tires of Examples 1 to 3 were superior in braking performance as compared with the tires of Comparative Examples 1 and 2, it was confirmed that the rolling resistance coefficient was not extremely deteriorated.

E: tire equator, R: contact end,
DESCRIPTION OF SYMBOLS 10 ... Pneumatic tire, 11 ... Bead core, 12 ... Bead filler, 13 ... Carcass ply, 14 ... 1st belt, 15 ... 2nd belt, 16 ... Belt reinforcement layer, 17 ... Side wall rubber, 18 ... Rubber chafer, 19: Inner liner, 20: Tread rubber, 21: Main groove, 22: Center land, 23: Shoulder land, 24: Media land, 25: Tire width direction inner end of shoulder land 23, 30: ... Overlap area, 31: first lateral groove, 32: second lateral groove, 33: non-overlap area, 34: maximum thickness position, 35: inner widthwise end of overlap area 30

Claims (4)

A tread rubber forming a ground contact surface is provided with a plurality of land portions extending in the circumferential direction of the tire, and at least any one of them is extended from an end on one side in the width direction and terminates in the land Air provided with a lateral groove and a second lateral groove extending from an end on the other side in the width direction and terminating in the land portion, and an overlapping region in which the first lateral groove and the second lateral groove overlap in the tire circumferential direction In the tire containing
The pneumatic tire, wherein a thickness of the tread rubber in the overlap region is thicker than a thickness of the tread rubber in regions on both sides of the overlap region in the same land portion. Assuming that the thickness of the tread rubber in the overlap region is A, and the thickness of the tread rubber at the tire width direction inner end of the land portion provided with the overlap region is B,
B <A ≦ 1.1 × B
The pneumatic tire according to claim 1, wherein a relationship of   The air according to claim 1 or 2, wherein the tread rubber in the overlap area is thickest at the maximum thickness position set in the overlap area, and becomes thinner as it is separated from the maximum thickness position in the tire width direction. Containing tire.   4. The tire according to claim 3, wherein, on the tire width direction cross section, the maximum thickness position is within a range of 60% of the tire width direction length of the overlap region at the center of the overlap region in the tire width direction. The pneumatic tire according to.

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