JP2009061985A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire suppressing uneven wear of a land portion of a tread surface of the tire, more particularly, uneven wear of the land portion on a tire equator or adjacent to the tire equator, while maintaining steering stability of a vehicle. <P>SOLUTION: In this tire, the center land portion arranged on the equator or adjacent to the equator to be sectioned by a plurality of peripheral direction grooves extending along the tire equator is provided on the tread surface of the tire, and the center land portion is divided into a plurality of block-shaped land portion pieces by a plurality of sipes extending in a direction crossing the equator. At least either one side of end parts of the block-shaped land portion pieces adjacent to the sipes is chamfered. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a pneumatic tire that suppresses uneven wear on the surface of a tread without reducing the steering stability of the vehicle.

  Conventionally, in order to ensure the steering stability of a vehicle, a land portion that is partitioned by a plurality of circumferential grooves provided along the equator of the tire and extends in the circumferential direction on or adjacent to the equator of the tire is provided. It was. Furthermore, in order to improve the drainage of the tire, a lateral groove extending in the tread width direction is usually provided in the above-described land portion.

  In such a tire, in addition to ensuring steering stability and drainage, it is desired to suppress uneven wear in the land.

For example, Patent Document 1 proposes a technique for improving steering stability and uneven wear resistance by chamfering almost the entire circumference of a land portion.
In Patent Document 2, at least a part of the end portion of the land portion made into a block shape is chamfered, and the ground contact pressure that locally increases is made uniform, thereby improving steering stability and uneven wear resistance. Improvement techniques have been proposed.
JP-A-2-179508 Japanese Patent Laid-Open No. 2002-36826

  However, in Patent Document 1 and Patent Document 2, since the above-described land portion is provided with a wide groove, the contact between the end of the land portion in contact with the lateral groove and the road surface at the time of stepping on and kicking out the road surface Since the frequency increases, not only noise and vibration are easily generated, but it is difficult to obtain a sufficient effect for suppressing uneven wear.

Therefore, in Patent Document 3, a circumferential groove extending along the equator of the tire and a sipe that is partitioned by the circumferential groove and is narrower than the width of the lateral groove in the central land portion provided on the equator of the tire. Proposes a technology that suppresses uneven wear in the central land and improves vehicle handling stability by arranging narrow grooves, called, at intervals in the circumferential direction of the central land. .
JP 2007-15596 A

  That is, in Patent Document 3, the central land portion is arranged on the equator of the tire, thereby improving the steering stability of the vehicle, and by dividing the central land portion in the circumferential direction by a plurality of sipes, the road surface There has been proposed a pneumatic tire that suppresses the circumferential shear force applied to the central land portion when stepping on and kicking out the tire, and as a result, suppresses uneven wear.

  However, even with the technique of Patent Document 3, it is difficult to say that a sufficient effect is obtained with respect to the suppression of uneven wear, and therefore, even better steering stability and a more excellent uneven wear suppression effect. Is desired.

  Therefore, the present invention provides a pneumatic tire that suppresses uneven wear of the land portion of the tread surface, particularly uneven wear of the land portion on or adjacent to the equator of the tread surface, while maintaining the steering stability of the vehicle. With the goal.

Now, as a result of intensive studies to achieve the above-mentioned object, the inventors have made a block-shaped land piece segmented in the circumferential direction by a sipe provided on the equator of the tire or on a land part adjacent to the equator. It has been found that uneven wear can be further suppressed by devising the shape of and distributing the ground pressure of the block-like land piece.
The present invention is based on the above findings.

That is, the gist of the present invention is as follows.
(1) A tread surface of the tire has a central land portion that is arranged on or adjacent to the equator and that is partitioned by a plurality of circumferential grooves extending along the equator of the tire. A pneumatic tire divided into a plurality of block-like land pieces by a plurality of sipes extending in a direction crossing the sipe, wherein at least one side of the end of the block-like land piece adjacent to the sipe is chamfered. A featured pneumatic tire.

(2) The interval at the tread surface between adjacent block-like land pieces gradually increases from one end to the other end in the width direction of the block-like land pieces via the chamfered portion. The pneumatic tire according to (1) above, which is characterized.

(3) The pneumatic tire according to (2), wherein the end in the width direction on the side where the interval between the block-like land pieces is narrow is not chamfered.

(4) The above-mentioned (2), wherein the chamfering depth at the end in the width direction on the side where the interval between the block-like land pieces is wide is 20 to 50% of the height of the block-like land pieces. Or a pneumatic tire according to (3).

(5) Any of the above (1) to (4), wherein the angle of the ridge line of the chamfered portion on the one surface of the block-shaped land portion is smaller than the angle of the sipe with respect to the circumferential groove. Pneumatic tire described in 2.

(6) The tread surface has a peripheral land portion adjacent to a central land portion via the circumferential groove, the peripheral land portion including a plurality of horizontal grooves extending in a direction crossing the tire equator, The pneumatic tire according to any one of (1) to (5) above, wherein the shape of the chamfered portion and the shape of the lateral groove are continuous in a direction radiating from the equator of the tire.

(7) When the central land portion is disposed on the equator of the tire, the center line in the width direction of the central land portion is disposed on the vehicle inner side when the vehicle is mounted than the equator. The pneumatic tire according to any one of (1) to (6) above.

(8) The distance between the center line in the width direction of the central land portion and the equator is in the range of 1/6 to 1/2 of the width of the central land portion. Pneumatic tire

(9) In the cross section of the pneumatic tire in the width direction, the length of the perpendicular line from the maximum width position of the area outside the vehicle when the vehicle is mounted to the tire rotation axis at the tire equator plane is SWHout, and the vehicle is mounted (1) or (1) or (2), where SWHin is a length of a perpendicular line from the maximum width position of the tire in the region inside the vehicle to the tire rotation axis, and SWHout> SWHin. The pneumatic tire according to 8).

(10) The pneumatic tire according to any one of (9), wherein the SWHout is 1.1 to 2.0 times the SWHin.

  According to the present invention, the central land portion provided on the equator of the tire and the portion adjacent to the equator is divided into block-shaped land portion pieces by a plurality of sipes extending in a direction crossing the equator. By chamfering at least one side of the end portion of the piece, not only the steering stability of the vehicle but also uneven wear of the tread surface can be suppressed.

The present invention will be specifically described below.
FIG. 1 shows a representative example of a tread pattern of a tire according to the present invention, and FIG. 2 shows an enlarged view of a part of the tread pattern in a perspective view.
In FIG. 1, reference numeral 1 is a tread surface, 2a to 2d are circumferential grooves extending along the equator of the tire, 3 is a central land portion 3a defined by the circumferential grooves 2b and 2c and disposed on the tire equator, 3a -3b is a peripheral land portion that is divided by circumferential grooves 2a to 2d and is adjacent to the central land portion 3, and 3c to 3d are divided by the tread edge and the circumferential grooves 2a and 2d, The surrounding land part arrange | positioned adjacent to the parts 3a and 3b is shown. Incidentally, illustrated tread end in T, the equator of the tire in _CL, the centerline of the tread _{T CL.}

  Reference numeral 4 denotes a sipe extending in a direction crossing the equator of the tire. Reference numeral 5 denotes a block-shaped land portion piece obtained by dividing the central land portion 3 by the sipe 4, and a chamfered portion in which the end portion of the block-shaped land portion piece is chamfered at 6. Indicates. 7a and 7b are transverse grooves that open from the peripheral land portion 3a to the circumferential grooves 2a and 2b, 7c is a transverse groove that includes sipes and branched grooves, and opens to the circumferential groove 2c, and 7d is open to the circumferential groove 2a. A transverse groove 7e including a sipe is a transverse groove opening in the circumferential groove 2d, and 7f is a transverse groove including a sipe opening in the circumferential groove 2d.

  Here, when the contact shape of the tire is observed in order to maintain the steering stability of the vehicle, the contact length in the circumferential direction of the tire is almost the maximum on the tire equator, and the center of gravity of the tire contact area is also approximately on the tire equator. In order to generate the most efficient steering force (lateral force) and improve the driver's responsiveness to the steering wheel operation, a highly rigid land is placed at that position. However, it is important to increase the efficiency of force transmission from the tire to the road surface. Therefore, also in the present invention, since the central land portion 3 is disposed on the equator of the tire, the steering stability of the vehicle can be maintained.

  In addition, by arranging the central land portion 3 adjacent to the tire equator instead of on the tire equator, the steering stability of the vehicle can be similarly maintained.

Now, in FIG. 1, regarding the chamfered portion 6, the case where the interval on the tread surface between adjacent block-like land pieces 5 is gradually increased from one end to the other end of the block-like land pieces 5 is shown. However, in the present invention, it is sufficient that at least one of the end portions of the block-shaped land portion piece 5 is chamfered regardless of the shape. Therefore, from one end of the block-shaped land portion piece 5 to the other end. The case where it chamfers so that it may become the same space | interval is also included.
In particular, as shown in FIG. 1, the interval on the tread surface 1 between adjacent block-like land pieces 5 is gradually increased from one end to the other end in the width direction of the block-like land pieces 5. By chamfering, it is possible to further increase the effect of suppressing the uneven wear described below.

  That is, if the chamfering as shown in FIG. 1 is performed, the ground pressure of the block-like land piece 5 can be effectively dispersed when stepping on and kicking out the road surface. The force can be made smaller. As a result, uneven wear of the block-like land portion 5 is further suppressed.

The chamfering described above can provide an advantageous effect even if it is applied to either one side or both sides of the end of the block-like land piece 5 adjacent to the sipe 4. When chamfering is performed on both sides of the end of the block-like land piece 5, the shearing force to the end of the block-like land piece 5 can be reduced, and uneven wear of the block-like land piece 5 can be reduced. An advantageous effect that can be further suppressed can be obtained.
Here, when chamfering is performed on both sides of the end of the block-shaped land piece 5, in addition to uneven wear resistance, in consideration of noise and vibration characteristics generated when stepping on and kicking off the road surface, FIG. As shown in a), chamfering that increases the interval between adjacent block-like land pieces 5 is performed so as to be opposite to each other from one end to the other end in the width direction of the block-like land pieces 5. Is effective.
Similarly, when chamfering is performed on both sides of the end portion of the block-shaped land portion piece 5, in consideration of the rigidity of the central land portion 3 in addition to the uneven wear resistance, as shown in FIG. It is recommended that the chamfering in which the interval between the adjacent block-like land pieces 5 gradually increases is performed so that both ends of the block-like land piece 5 are in the same direction from one end to the other end in the width direction.

  Moreover, since the space | interval on the tread surface between the block-like land part pieces 5 increases gradually in the width direction, the space | interval between the adjacent block-like land part pieces 5 becomes wide gradually, Therefore The amount of drainage can be increased. As a result, the drainage of the pneumatic tire can be improved.

  In addition, since the distance between adjacent block-like land pieces 5 is gradually increased, the contact pressure generated when stepping on and kicking off the road surface can be effectively dispersed, so that the effect of reducing noise and vibration can be reduced. Can be improved.

  Next, it is preferable that the end in the width direction on the side where the interval between the block-shaped land pieces 5 is narrow is not chamfered. Thus, when the block-like land part piece 5 is in the ground contact state immediately under the load in the tread contact area by providing a portion which is not chamfered between the block-like land part pieces 5, it is adjacent. The space between the block-like land pieces 5 is closed, and a state like the central land portion 3 in which the adjacent block-like land pieces 5 are continuous is obtained. As a result, it is possible to suppress uneven wear and improve drainage without reducing the rigidity of the block-shaped land piece 5.

  Here, in the central land portion 3, the portion that requires the most rigidity is a portion that becomes the inside of the vehicle when the pneumatic tire is mounted on the vehicle. It is preferable that the part which is not chamfered is a part which becomes the inner side of the vehicle of the block-shaped land part piece 5. FIG.

  Moreover, the rigidity of the land part 3 is ensured by the block-shaped land part piece 5 continuing in the circumferential direction in the part where the space | interval direction edge part of the side with a narrow space | interval between the block-like land piece pieces 5 is not chamfered. And as a range which drainage improves effectively, it is preferred that it is within 20% of the width of a block-like land piece from the end of block-like land piece 5.

  And as shown in FIG. 2, the chamfering depth d in the width direction edge part by the side where the space | interval of the block-like land part piece 5 is wide is 20 to 50% of the height H of the block-like land part piece 5. Is preferred. This is because when the height H of the block-shaped land piece 5 is less than 20%, the block-shaped land piece 5 is almost in the same state as when the block-shaped land piece 5 is not chamfered. The effect of suppressing wear cannot be sufficiently obtained. On the other hand, when the height H of the block-shaped land portion piece 5 exceeds 50%, the chamfered portion 6 of the block-shaped land portion piece 5 is inclined in the depth direction. Since the angle is close to the angle in the depth direction of the block-shaped land piece 5 that is not chamfered, there is a disadvantage that the effect of reducing noise and vibration cannot be sufficiently obtained.

  And it is preferable that the angle (alpha) with respect to the circumferential groove | channel of the ridgeline of the chamfer 6 in the surface of the block-shaped land part piece 5 is smaller than the angle (beta) with respect to the circumferential groove | channel of the sipe 4. Here, as shown in FIG. 1, when the pneumatic tire having the block-like land piece 5 is mounted on the vehicle, the angle α and the angle β are such that the wide side between the block-like land pieces 5 When facing the outside, it is an angle with respect to the circumferential groove 2c, and when the wide side between the block-like land pieces 5 is facing the inside of the vehicle, it means an angle with respect to the circumferential groove 2b.

That is, since the angle α is smaller than the angle β, the ground pressure of the block-shaped land piece 5 can be effectively dispersed when stepping on and kicking out the road surface, so that the effect of reducing noise and vibration can be sufficiently achieved. Obtainable. On the other hand, if the angle α is larger than the angle β, the input angle of the block-shaped land piece 5 is close to a right angle with respect to the road surface when stepping on and kicking out the road surface, so that the effect of reducing noise and vibration is sufficient. Cause disadvantages that cannot be obtained.
In addition, when the angle β is 90 to 45 °, the angle α is preferably 75 to 30 °.

  And it is preferable that the shape of the chamfered portion 6, the shape of the lateral groove 7b, and the shape of a part of the lateral groove 7c are continuous in the direction radiating from the equator of the tire. Here, being connected in a direction radiating from the equator of the tire means that the shape of the chamfered portion 6 and the shape of the lateral groove 7b extend from the equator of the tire, for example, from one arbitrary point in a direction crossing the equator. . That is, when the vehicle is running, when the tire drains in a direction crossing the equator, the shape of the chamfered portion 6 and the shape of the lateral groove 7b are continuous in the radiating direction, so that each shape is not continuous in the radiating direction. Compared with the tread pattern, drainage can be effectively secured.

  Here, the shape of the chamfered portion 6 is not limited to the shape as shown in FIG. 2, for example, as shown in FIG. A shape in which one arbitrary point of the direction end is connected by a curve so as to be recessed inside the block-shaped land piece 5, or a part of the four corners of the block-shaped land piece 5 as shown in FIG. Even if it is the shape rounded and chamfered, the advantageous effect of this invention can be acquired.

When the central land portion is disposed on the tire equator, it is preferable that the center line _{TCL in} the width direction of the central land portion is disposed on the vehicle inner side when the vehicle is mounted than the tire equator. This is because the road surface unevenness input to the tire can be substantially biased toward the vehicle mounting inner side.

  Here, the largest external factor that reduces the steering stability of the vehicle is the unevenness of the road surface that gives vibration to the traveling vehicle regardless of the vertical or horizontal direction of the vehicle. When this unevenness collides with the outer part of the vehicle when the vehicle is mounted on the equator of the tire, and when it collides with the inner part, if the unevenness of the road surface is the same, In most vehicles, the vehicle mounting support portion (the wheel hub surface) is offset, and the vehicle-mounted outer portion with a larger load share causes more vibration. For this reason, suppressing vibration input at the vehicle-mounted outer portion is effective in suppressing a decrease in steering stability.

  Therefore, if the input of the road surface unevenness can be substantially biased toward the vehicle mounting inner side, the vibration input at the vehicle mounting outer portion is suppressed, and as a result, a decrease in steering stability can be suppressed.

Then, the distance between the widthwise center line T _CL and the equator of the central land portion is preferably 1 / 6-1 / 2 of the range of the width t of the central land portion. This is because if the width of the central land portion is less than 1/6 of the width t, the effect of causing the tire input due to road surface unevenness to be substantially unevenly distributed inside the vehicle is not sufficiently obtained.

  On the other hand, if it exceeds 1/2 of the width t of the central land portion, the central land portion becomes a tread pattern disposed in a portion adjacent to the equator of the tire, and the advantageous effects of the present invention can be obtained. Compared to a tread pattern with a central land on the tire equator, there is no land on the equator, which is the center of gravity of the tire ground contact area, so the driver's responsiveness to steering wheel operation cannot be obtained sufficiently It is.

  Also, considering the coexistence of the effect of unevenly distributing the input to the tire due to the unevenness of the road surface by placing it near the center (center of gravity) of the tire ground contact surface and offsetting it inside when mounting the vehicle, the offset amount is It is considered that it is optimal to be about 1/4 of the width t of the central land portion.

  Here, in the cross-section in the width direction of the pneumatic tire shown in FIG. 5, the length of the perpendicular drawn from the maximum width position Pout of the region outside the vehicle when the vehicle is mounted to the tire rotation axis L from the tire equator is SWHout. When the length of the perpendicular line extending from the maximum width position Pin of the region on the vehicle inner side to the tire rotation axis L when the vehicle is mounted is SWHin, it is preferable that both satisfy the relationship of SWHout> SWHin. Here, in the cross section of the tire shown in FIG. 5, reference numeral 8 is a bead core, 9 is a carcass, 10 is a belt, and 11 is a tread.

  That is, when the maximum width position Pout of the tire is brought close to the tread portion, the curvature of the curved portion from the tread portion having the thinnest thickness in the tire cross section to the sidewall portion becomes small, and the rigidity against bending deformation of the portion is reduced. It can be further lowered. Therefore, such an action is applied to the cross-sectional structure of the region that is outside the vehicle when the vehicle is mounted. In other words, SWHout is lengthened. Then, it becomes easy to absorb the vibration applied to the tread portion from the road surface.

  On the contrary, when the maximum width position Pin of the tire is moved away from the tread portion, the curvature of the curved portion from the tread portion to the sidewall portion in the tire cross section increases, and the rigidity against bending deformation of the portion can be increased. Therefore, such an action is applied to the cross-sectional structure of the region that is inside the vehicle when the vehicle is mounted. In other words, SWHin is shortened. Then, transmission of the steering force intended by the driver to the road surface can be easily achieved.

  Here, the fact that the length SWHout of the vertical line is 1, 1 to 2.0 times the length of the vertical line SWHin separates the function of the outside and the inside when the vehicle is mounted, and in particular the vibration attenuation at the outside It is preferable in order to fully exhibit the effect. This is because, if SWHout is less than 1.1 times SWHin, the same effect is exhibited, but the amount of the effect is small, and it is difficult for a general driver assumed by the present invention to recognize it, and it is not profitable. On the other hand, if it exceeds 2.0 times, there will be a significant difference in rigidity between the outside and inside sidewalls, and the behavior of the vehicle may become suddenly unstable.

  Pneumatic radial tires for passenger cars of 205 / 55R16, in which the various dimensions shown in Table 1 were applied to the treads shown in FIGS. Here, the tread pattern shown in FIG. 6 is a tread pattern of a conventional example, and reference numerals 1 to 7e are the same as those in FIG. In addition, the code | symbol 6a shows the chamfer part of a block front-end | tip part.

  Then, the prototype tire is incorporated into a rim of size 16 × 6.5 JJ, adjusted to an internal pressure of 220 kPa, mounted on a passenger car, and two passengers are on the passenger car, and dry maneuvering stability, Noise, vibration, uneven wear and drainage were investigated. The results are shown in Table 2. The evaluation results shown in Table 2 are all indexed with the result of the conventional example taken as 100. Larger numbers indicate better results.

  Here, dry maneuvering stability has been experienced by ordinary drivers on public roads from low speeds to around 100 km / h in a test course consisting of a circumference circuit including a long straight part and a handling evaluation road with many gentle curves. The vehicle was run at a speed range and was investigated by the feeling of the dry par.

  In addition, noise and vibration travel on a circumference circuit including a long straight portion, a vehicle interior sound evaluation road surface, and a special road for noise testing in a speed range experienced by a general driver on a public road from low speed to about 100 km / h. Investigated by

  And the uneven wear was investigated by evaluating the results when traveling on courses including ordinary roads, highways and mountain roads using the same tires and vehicles.

In addition, the drainage was investigated by evaluating the driver's feeling on the wet road surface in the test course, assuming a rainy day on a general road.

    As shown in Table 2, according to the present invention, the chamfered chamfered end portion of the block-shaped land portion improves the uneven wear without reducing the steering stability compared to the conventional example without chamfering. is doing.

It is a figure which shows the tread pattern according to this invention. It is a perspective view which shows a part of chamfering part according to this invention. It is a figure which shows the chamfering given to the both sides of the block-shaped land part piece according to this invention. It is a figure which shows the other shape of the chamfering part according to this invention. It is a figure which shows the cross section of the width direction of the pneumatic tire according to this invention. It is a figure which shows the tread pattern of a prior art example. It is a figure which shows an example of the tread pattern according to this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tread surface 2a-2d Circumferential groove | channel 3 Central land part 3a-3d Peripheral land part 4 Sipe 5 Block-shaped land part piece 6 Chamfer part 6a Chamfer part 7a-7e Lateral groove 8 Bead core 9 Carcass 10 Belt 11 Tread

Claims (10)

  The tread surface of the tire has a central land portion located on or adjacent to the equator, which is partitioned by a plurality of circumferential grooves extending along the equator of the tire, and the central land portion is oriented across the equator. A pneumatic tire divided into a plurality of block-shaped land pieces by a plurality of sipes extending in the shape of the block, wherein at least one side of one end of the block-shaped land pieces adjacent to the sipe is chamfered. Pneumatic tire.   The interval at the tread surface between adjacent block-like land pieces via the chamfered portion is gradually increased from one end to the other end in the width direction of the block-like land pieces. The pneumatic tire according to claim 1.   The pneumatic tire according to claim 2, wherein the end in the width direction on the side where the interval between the block-like land pieces is narrow is not chamfered.   The depth of the chamfered portion at the width direction end on the side where the interval between the block-like land pieces is wide is 20 to 50% of the height of the block-like land pieces. Pneumatic tire described in 2.   5. The pneumatic tire according to claim 1, wherein an angle of the ridge line of the chamfered portion on the one surface of the block-shaped land portion is smaller than an angle of the sipe with respect to the circumferential groove. .   The tread surface has a peripheral land portion adjacent to the central land portion via the circumferential groove, and the peripheral land portion includes a plurality of horizontal grooves extending in a direction crossing the equator of the tire. The pneumatic tire according to any one of claims 1 to 5, wherein the shape and the shape of the lateral groove are continuous in a direction radiating from the equator of the tire.   When the central land portion is disposed on the equator of the tire, the center line in the width direction of the central land portion is disposed on the vehicle inner side when the vehicle is mounted than the equator. The pneumatic tire according to claim 1.   The pneumatic tire according to claim 7, wherein an interval between the center line in the width direction of the central land portion and the equator is in a range of 1/6 to 1/2 of the width of the central land portion.   In the cross section in the width direction of the pneumatic tire, SWHout is the length of the perpendicular line from the maximum width position of the area outside the vehicle when the vehicle is mounted to the tire rotation axis, and the inside of the vehicle when the vehicle is mounted. 9. When SWHin is a length of a perpendicular line extending from the maximum width position of the tire in the region to the tire rotation axis, both satisfy a relationship of SWHout> SWHin. The described pneumatic tire.   The pneumatic tire according to claim 9, wherein the SWHout is 1.1 to 2.0 times the SWHin.

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