JP6514063B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire.

  In a tire having a main groove extending in the circumferential direction of the tire and a lateral groove opened in the main groove and extending in the tire width direction, the rigidity of the land portion of the tread is low in the vicinity of the intersection of the main groove and the lateral groove. It is easy to fall down. This causes deterioration of braking performance and generation of noise. In particular, in a tire having a lateral groove opened in a main groove at a shoulder land portion, deterioration of braking performance and generation of noise tend to be remarkable. Therefore, it is conceivable to increase the area of the land to increase the rigidity of the land as a countermeasure. However, this will reduce the area of the groove, which will reduce the performance of the tire on the WET road surface.

  By the way, there is known a tire provided with a projection so that a part of the groove bottom is high. For example, in the tire of Patent Document 1, a protrusion (raised bottom) is provided in the lateral groove. Moreover, in the tire of Patent Document 2, a protrusion (reinforcing block) is provided in a part of the main groove.

JP, 2011-143896, A JP 2012-140049

  However, even if the projections are provided only in the lateral grooves or only the main grooves, the rigidity of the land portion of the tread is low in the vicinity of the intersection between the main grooves and the lateral grooves.

  The present invention has been made in view of such circumstances, and it is an object of the present invention to provide a pneumatic tire having excellent braking performance and less generation of noise, in a pneumatic tire having a lateral groove opened in a main groove in a shoulder land portion. It will be an issue.

The pneumatic tire according to the embodiment is a pneumatic tire in which at least two main grooves extending in the tire circumferential direction are provided in the tread and at least three land portions aligned in the tire width direction are formed. A plurality of lateral grooves opening to the shoulder main groove are provided in a shoulder land portion on the tire width direction outer side from the shoulder main groove, and the opening of the lateral groove to the shoulder main groove of the lateral grooves is provided at all the lateral grooves. A protrusion extending over the entire width direction of each groove is formed on a portion within a certain distance from the end in the tire width direction outside and a portion within a certain distance from the open end to both sides in the tire circumferential direction of the shoulder main groove It is characterized by

  Although the pneumatic tire according to the embodiment has the lateral groove opened in the main groove in the shoulder land portion, it has excellent braking performance and hardly generates noise.

The tread pattern of this embodiment. The enlarged view of opening end 25 vicinity to the shoulder main groove 20 of the horizontal groove 22 of FIG. Sectional drawing in the AA in FIG. Sectional drawing in the BB line in FIG. The figure which looked at the protrusion 130 of the example of a change from the tire radial direction. The figure which looked at protrusion 230 of the example of a change from a tire radial direction.

  The pneumatic tire according to the embodiment has, on both sides in the tire width direction, bead portions including a bead core in which bundled steel wires are coated with rubber and a rubber bead filler provided on the tire radial direction outer side of the bead core. . The carcass wraps the bead portions on both sides in the tire width direction, and forms a skeleton of the pneumatic tire between the bead portions. A belt layer consisting of one or more belts in which steel cords are covered with rubber is provided on the tire radial direction outer side of the carcass, and a belt reinforcing layer is provided on the tire radial direction outer side. Further, a tread 10 is provided on the outer side in the tire radial direction. Further, sidewalls are provided on both sides of the carcass in the tire width direction. In addition, an inner liner is provided inside the carcass. In addition to these members, a plurality of members according to the functional needs of the tire are provided.

  The tread 10 is provided with at least two main grooves extending in the tire circumferential direction, and at least three land portions aligned in the tire width direction are formed by these main grooves. As shown in FIG. 1, in the case of the present embodiment, the number of main grooves is three, and two shoulder main grooves 20 on both sides in the tire width direction and one center main groove at the center in the tire width direction 21 are provided. Then, two shoulder land portions 11 outside the tire width direction from the shoulder main grooves 20 on both sides in the tire width direction, and two center land portions 12 sandwiched between the shoulder main groove 20 and the center main groove 21 are formed. .

  The shoulder land portion 11 is provided with a plurality of lateral grooves 22 at equal intervals in the tire circumferential direction. The lateral groove means a groove extending in the tire width direction, but those extending at an angle to the tire width direction and the tire circumferential direction are also included in the lateral groove. The lateral grooves may extend linearly or in a curved manner. The lateral groove 22 of the present embodiment extends in a curve so as to be convex on one side in the tire circumferential direction. The end of the lateral groove 22 on the inner side in the tire width direction is open to the shoulder main groove 20. Further, the end of the lateral groove 22 on the outer side in the tire width direction reaches the outer end in the tire width direction (tread pattern end 14) of the region where the tread pattern of the tread 10 is formed. Therefore, the shoulder land portion 11 is divided by the lateral groove 22 at a plurality of locations. The shoulder land portion 11 has a block row in which a plurality of shoulder blocks 13 surrounded by two lateral grooves 22 adjacent to each other in the tire circumferential direction, the shoulder main grooves 20 and the tread pattern end 14 are arranged in the tire circumferential direction. It has become. The shoulder land portion 11 may be provided with a groove 23 different from the lateral groove 22.

  The structure of the center land portion 12 is not limited. In the case of FIG. 1, the center land portion 12 is formed with a notch 24. The outer end of the notch 24 in the tire width direction opens to the shoulder main groove 20, and the inner end in the tire width direction closes in the center land portion 12. The opening to the shoulder main groove 20 of the notch 24 is offset in the tire circumferential direction with respect to the opening end 25 to the shoulder main groove 20 of the lateral groove 22. However, the center land portion 12 may also be a block row.

  As shown in FIGS. 1 to 4, in the vicinity of the opening end 25 to the shoulder main groove 20 of the lateral groove 22, a protrusion 30 is formed in the groove. The projection 30 is a portion of the lateral groove 22 within a certain distance from the open end 25 in the tire width direction outside, and a portion of the shoulder main groove 20 within a certain distance from the open end 25 to both sides of the tire circumferential direction. Is formed. The protrusions 30 are formed over the entire width direction of each groove (direction orthogonal to the extension direction of each groove). Therefore, the protrusion 30 is continuous from the corner 15 of the shoulder block 13 formed by the shoulder main groove 20 and the lateral groove 22. Then, the projections 30 connect the corner portions 15 of the two shoulder blocks 13 facing each other across the lateral groove 22 and the portion of the center land portion 12 facing the opening end 25.

  The length l (see FIG. 1) of the protrusion 30 in the tire width direction in the lateral groove 22 is the length m of the lateral groove 22 in the tire width direction (that is, the opening end 25 to the shoulder main groove 20 of the lateral groove 22 to the tread pattern end It is desirable that the length be 20% or more and 30% or less of the length in the tire width direction up to the portion 14. In addition, the position of the tire width direction corresponds with the opening end 25 and the tire width direction inner side edge part 35 of the contact surface of the shoulder land part 11. As shown in FIG. Further, the end portion q on one side in the tire circumferential direction in the shoulder main groove 20 of the protrusion 30 from the end portion p on one side in the tire circumferential direction of the opening end 25 to the shoulder main groove 20 of the lateral groove 22 (see FIG. 1) It is desirable that the length n in the tire circumferential direction up to the length is 5% or more and 10% or less of the pitch length o of the lateral grooves 22. Here, the pitch length o of the lateral groove 22 is the length from the opening end 25 to the shoulder main groove 20 of the lateral groove 22 to the opening end 25 to the shoulder main groove 20 of the lateral groove 22 adjacent to the tire circumferential direction. . Further, it is desirable that a portion of the protrusion 30 in the shoulder main groove 20 extends the same length on both sides in the tire circumferential direction centering on the open end 25.

  As shown in FIGS. 2 and 3, it is desirable that the portion of the protrusion 30 in the shoulder main groove 20 have a top 31 and a slope 32. The top portion 31 is a flat surface parallel to the ground contact surface, which is located inside the opening end 25 in the tire width direction. The inclined portion 32 is a slope which extends from the top portion 31 to both sides in the extension direction of the shoulder main groove 20 and continues to the groove bottom of the portion of the shoulder main groove 20 where the protrusion 30 is absent. A portion of the protrusion 30 in the shoulder main groove 20 has a top 31 and an inclined portion 32, so that the cross-sectional shape in the extension direction of the shoulder main groove 20 is trapezoidal. In this cross-sectional shape, the top 31 corresponds to the shorter base of the trapezoid and the two slopes 32 correspond to the two legs of the trapezoid. In addition, when the protrusion 30 has the bulging part 33 so that it may mention later, the cross-sectional shape of the extension direction of the shoulder main groove 20 which passes the bulging part 33 does not need to be trapezoid.

  The height of the projection 30 (height in the tire radial direction from the groove bottom of the portion without the projection 30 to the top of the projection 30) is preferably 10% to 30% of the depth of the groove . That is, in the shoulder main groove 20, it is desirable that the height s (see FIG. 3) of the protrusion 30 be 10% or more and 30% or less of the depth t of the shoulder main groove 20. In the lateral groove 22, the height u (see FIG. 4) of the projection 30 is preferably 10% or more and 30% or less of the depth v of the lateral groove 22.

  As shown in FIG. 4, the shoulder main groove 20 is deeper than the lateral groove 22 in the present embodiment. Therefore, the top portion 36 in the lateral groove 22 of the protrusion 30 is on the outer side in the tire radial direction than the top portion 31 in the shoulder main groove 20. Then, in the vicinity of the opening end 25 to the shoulder main groove 20 of the lateral groove 22, a step is generated in the protrusion 30.

  As shown in FIG. 4, in the present embodiment, the top 36 of the protrusion 30 in the lateral groove 22 is extended into the shoulder main groove 20, and the extension destination is connected to the portion of the step. And the said extension part and the said level | step-difference part form the bulging part 33. FIG. The extension portion is the top 34 of the bulging portion 33. The top portion 36 in the lateral groove 22 of the projection 30 and the top portion 34 of the bulging portion 33 are at the same position in the tire radial direction, and form one flat surface. The bulging portion 33 terminates at a predetermined position in the shoulder main groove 20. The length h (see FIG. 4) of the top 34 of the bulging portion 33 in the tire width direction is preferably 10% to 30% of the length i of the shoulder main groove 20 in the tire width direction. The length i of the shoulder main groove 20 in the tire width direction is from the tire width direction outer end portion of the contact surface of the center land portion 12 to the tire width direction inner end portion 35 of the contact surface of the shoulder land portion 11 It is the length in the tire width direction. Further, the end in the tire width direction outside of the top portion 34 of the bulging portion 33 and the tire width direction inward end portion 35 of the contact surface of the shoulder land portion 11 coincide with each other in the tire width direction.

  The length in the tire circumferential direction of the top portion 34 of the bulging portion 33 is not limited, and may be the same as the length in the tire circumferential direction of the opening end 25 to the shoulder main groove 20 of the lateral groove 22, for example It may be long.

  The relationship between the depth of the shoulder main groove 20 and the depth of the lateral groove 22 is not limited to the relationship in the present embodiment, and for example, the depth of the shoulder main groove 20 and the depth of the lateral groove 22 may be the same. Further, even when the shoulder main groove 20 is deeper than the lateral groove 22, the height of the protrusion 30 may be the same in the shoulder main groove 20 and in the lateral groove 22.

  In the tire having the above structure, the projection 30 is formed in the vicinity of the opening end 25 to the shoulder main groove 20 of the lateral groove 22. Therefore, the projection 30 can support the corner portion 15 of the shoulder block 13. Therefore, the vicinity of the corner 15 of the shoulder block 13 is unlikely to be deformed or fallen down, and the tire has excellent braking performance. Further, since the shoulder block 13 is supported by the projection 30, noise due to the vibration of the shoulder block 13 is unlikely to occur. In particular, the projections 30 connect the corner portions 15 of the two shoulder blocks 13 facing each other across the lateral groove 22 with the portion of the center land portion 12 facing the opening end 25, thereby forming the shoulder block 13. The vicinity of the corner portion 15 is more difficult to deform or the like, and each of the above effects is increased.

  In addition, when a general tire comes in contact with the ground, the main groove is deformed to change the volume of the space in the main groove, and air in the main groove repeats compression and expansion to generate air column tube resonance noise. Are known. However, in the tire having the above structure, the projections 30 continuously support the side walls in the width direction of the shoulder main groove 20 (the side walls on the shoulder land portion 11 and the center land portion 12 side of the shoulder main groove 20). The main groove 20 is difficult to deform. In addition, the projections 30 reduce the flow velocity of the air passing through the shoulder main groove 20. Therefore, air column resonance noise hardly occurs.

  In addition, if the length in the tire width direction of the portion in the lateral groove 22 of the protrusion 30 is 20% or more of the length in the tire width direction of the lateral groove 22, the corner portion 15 of the shoulder block 13 is formed by the protrusion 30. It is fully supported from the lateral groove 22 side. Further, if the length in the tire width direction of the portion in the lateral groove 22 of the protrusion 30 is 30% or less of the length in the tire width direction of the lateral groove 22, sufficient drainage property of the lateral groove 22 is ensured. Performance is secured.

  In addition, when the height of the protrusion 30 is too low, the drainage property is improved, but the effect of supporting the corner portion 15 of the shoulder block 13 may be reduced. In addition, when the height of the protrusion 30 is too high, the effect of supporting the corner portion 15 of the shoulder block 13 is increased, but there is a possibility that the drainage property may be inhibited. However, if the height of the projection 30 in each groove is 10% to 30% of the depth of the groove, the effect of supporting the corner portion 15 of the shoulder block 13 of the projection 30 and the drainage property by the groove It is compatible with the effect.

  In addition, if the length h in the tire width direction of the top portion 34 of the bulging portion 33 of the protrusion 30 is 10% or more of the length i in the tire width direction of the shoulder main groove 20, the shoulder main groove of the lateral groove 22 Since the opening end 25 to 20 and the step portion of the projection 30 are separated by a sufficient distance in the tire width direction, a large difference in rigidity is unlikely to occur near the opening end 25 of the tread 10. If the length h of the top portion 34 of the bulging portion 33 of the projection 30 in the tire width direction is 30% or less of the length i of the shoulder main groove 20 in the tire width direction, the bulging portion 33 is a shoulder main It is hard to inhibit the drainage property by the ditch 20.

  Further, if the portion of the protrusion 30 in the shoulder main groove 20 has the top portion 31 and the inclined portion 32 and the cross-sectional shape in the extension direction of the shoulder main groove 20 is trapezoidal, it enters the shoulder main groove 20 Water is easy to get over the protrusions 30. Therefore, the drainage property is secured despite the provision of the projections 30, and the WET performance is secured.

  As a modification of the above embodiment, a pneumatic tire having the projections of FIG. 5 and FIG. 6 can be mentioned.

  FIG. 5 shows the vicinity of the open end 25 to the shoulder main groove 20 of the lateral groove 22. The protrusion 130 of FIG. 5 has a top 131 and a slope 132 similarly to the protrusion 30 of the above embodiment. The top portion 131 is a flat surface parallel to the ground contact surface, which is located inward in the tire width direction of the opening end 25 to the shoulder main groove 20 of the lateral groove 22. The shape of the top portion 131 of this modification is a triangle having one side d at the opening end 25 and having a vertex e opposed to the one side on the side wall on the shoulder main groove 20 side of the center land portion 12. The height of the top portion 131 may be the same as or different from the height of the protrusion 130 in the lateral groove 22. The inclined portion 132 is an inclined surface extending from the top portion 131 to both sides in the extension direction of the shoulder main groove 20 and continuing to the groove bottom of the portion of the shoulder main groove 20 without the protrusion 130.

  Since the portion in the shoulder main groove 20 of the protrusion 130 has such a top 131 and the inclined portion 132, the cross-sectional shape in the extension direction of the shoulder main groove 20 is trapezoidal. In this cross-sectional shape, the top portion 131 corresponds to the shorter base of the trapezoid, and the two inclined portions 132 correspond to the two legs of the trapezoid.

  In such a protrusion 130, the area of the top portion 131 is narrow and the area of the inclined portion 132 is large, as compared with the protrusion 30 of the above embodiment. Therefore, the water which has entered the shoulder main groove 20 easily flows over the protrusion 130 and flows in the extension direction of the shoulder main groove 20 (the direction of the arrow in the drawing) than in the case of the above embodiment. Therefore, the drainage property of the tire is secured more than in the case of the above embodiment, and the WET performance is secured.

  FIG. 6 shows the vicinity of the open end 25 to the shoulder main groove 20 of the lateral groove 22. The protrusion 230 of FIG. 6 has the top part 231 and the inclined part 232 similarly to the protrusion 30 of the said embodiment. The top portion 231 is a flat surface parallel to the ground contact surface located near the inner side in the tire width direction of the opening end 25 to the shoulder main groove 20 of the lateral groove 22. The shape of the top 231 of this modification is a trapezoid having a shorter base f at the open end 25 and a longer base g on the side wall of the center land 12 on the shoulder main groove 20 side. In other words, the top portion 231 extends from the opening end 25 to the side wall of the center land portion 12 while gradually expanding in the extension direction of the shoulder main groove 20. Therefore, the length in the extension direction of the shoulder main groove 20 of the top portion 231 is shorter at the shoulder land portion 11 side and longer at the center land portion 12 side. The height of the top 231 may be the same as or different from the height of the protrusion 230 in the lateral groove 22.

  The inclined portion 232 is a slope which extends from the top portion 231 to both sides in the extension direction of the shoulder main groove 20 and continues to the groove bottom of the portion of the shoulder main groove 20 where the protrusion 230 is absent. The end in the extension direction of the shoulder main groove 20 of the inclined portion 232 shown by the solid line 232a in FIG. 6 is separated from the top portion 231 in the extension direction of the shoulder main groove 20 in the entire width direction of the shoulder main groove 20. ing. However, as shown by the phantom line (two-dot chain line) 232 b in FIG. 6, the position of the end in the extension direction of the shoulder main groove 20 of the inclined portion 232 is the end in the extension direction of the shoulder main groove 20 of the top 231. It may coincide with the position of the part. Since the top portion 231 is trapezoidal as described above, the boundary between the top portion 231 and the sloped portion 232 is farther from the opening end 25 in the extension direction of the shoulder main groove 20 on the center land portion 12 side. On the other hand, on the shoulder land portion 11 side, the boundary between the top portion 231 and the inclined portion 232 is close to the opening end 25 in the extension direction of the shoulder main groove 20. The end on the shoulder land portion 11 side of the inclined portion 232 reaches the end in the extension direction of the shoulder main groove 20 of the open end 25.

  Since the portion in the shoulder main groove 20 of the protrusion 230 has such a top portion 231 and the inclined portion 232, the cross-sectional shape in the extension direction of the shoulder main groove 20 is trapezoidal. In this cross-sectional shape, the top portion 231 corresponds to the shorter base of the trapezoid, and the two inclined portions 232 correspond to the two legs of the trapezoid.

  In such a protrusion 130, water flowing in the extension direction of the shoulder main groove 20 is guided to the lateral groove 22 by the inclined portion 232, as shown by the arrow in the figure. Then, the water passes through the inside of the lateral groove 22 and is discharged in the tire width direction. Therefore, the drainage property of the tire is secured, and the wet performance is secured.

  Also, although not shown, when the tread is provided with four main grooves, in addition to one center land portion and two shoulder land portions, two median lands of the center land portion and the shoulder land portion are provided. Land area is formed. In that case, the above-mentioned projection is provided in the main ditch between the shoulder land and the mediate land.

  In addition to the above, various modifications, substitutions, omissions, and the like can be made to the above embodiment without departing from the scope of the invention.

  The noise, braking performance, and steering stability on the WET road surface of the tires of the example and the comparative example were evaluated. The tire of the example is the tire of the above embodiment. The dimensions of the example tires are summarized in Table 1. On the other hand, the tire of the comparative example has the same tread pattern as that of the above embodiment, but has no protrusion 30 in the groove. A 195 / 65R15 tire was used in all evaluations. This tire was assembled on a regular rim and evaluated as a normal internal pressure. Here, the normal rim is a standard rim defined in standards such as JATMA, TRA, ETRTO, etc. The normal internal pressure is an internal pressure corresponding to the maximum load defined in the above standard.

  The evaluation method is as follows.

Noise: A drum test machine was run at 60 km / h to measure a noise level at a frequency of 1 kHz, and the measurement results were indexed. The larger the index, the smaller the noise.
Braking ability: Tires were attached to a domestic sedan car, braking was started from 60 km / hr, the distance to 0 km / hr was measured, and the measurement results were indexed. The larger the index, the better the braking performance.
Steering stability on the WET road surface: Tires were installed on a domestic sedan car, and the vehicle was driven on the WET road surface, and the driver gave a sensory evaluation using an index. The larger the index, the better the steering stability on the WET road surface.

  The results are as shown in Table 2. It was confirmed that the tire of the example is superior to the tire of the comparative example with respect to noise and braking performance, and is equivalent to the tire of the comparative example with respect to the steering stability on the WET road surface.

DESCRIPTION OF SYMBOLS 10 ... Tread, 11 ... Shoulder land part, 12 ... Center land part, 13 ... Shoulder block, 14 ... Tread pattern edge part, 15 ... Corner part, 20 ... Shoulder main groove, 21 ... Center main groove, 22 ... Horizontal groove, 23 ... groove ... 24 ... notch 25 ... opening end, 30 ... projection, 31 ... top, 32 ... inclined part, 33 ... bulging part, 34 ... top, 35 ... end, 36 ... top, 130 ... projection, 131 ... The top, 132, the slope, 230, the protrusion, the 231, the top, the 232, the slope

Claims (5)

In a pneumatic tire in which at least two main grooves extending in the tire circumferential direction are provided on a tread and at least three land portions aligned in the tire width direction are formed,
A plurality of lateral grooves opening to the shoulder main groove are provided in a shoulder land portion on the tire width direction outer side from the shoulder main grooves on both sides in the tire width direction,
At all the lateral groove positions, a portion of the lateral groove within a certain distance from the opening end of the lateral groove to the shoulder main groove in the tire width direction, and both sides of the shoulder main groove from the opening end in the tire circumferential direction In a pneumatic tire, projections are formed over the entire width direction of each groove at portions within a predetermined distance.   The pneumatic tire according to claim 1, wherein the length in the tire width direction of the portion in the lateral groove of the protrusion is 20% or more and 30% or less of the length in the tire width direction of the lateral groove.   A portion of the protrusion in the shoulder main groove has a top which is a plane parallel to the ground contact surface, and two slopes extending from the top to both sides in the extension direction of the shoulder main groove and continuing to the groove bottom. The air according to claim 1 or 2, wherein the cross-sectional shape in the extension direction of the shoulder main groove is a trapezoid in which the top portion on the cross section is a short base and the inclined portion on the cross section is two legs. Containing tire.   The shape of the top as a flat surface has one side at the open end of the lateral groove to the shoulder main groove, and an apex facing the one side on the side wall on the shoulder main groove side of the land adjacent to the shoulder land portion. The pneumatic tire according to claim 3, which is a triangle having a. The shape of the top as a flat surface has a shorter base at the open end of the lateral groove to the shoulder main groove, and a longer side wall on the side of the shoulder main groove on the land adjacent to the shoulder land portion. The pneumatic tire according to claim 3, which is a trapezoidal shape having a base.

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