JP5041466B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire having a partial wear sacrificial protrusion (BCR, Braking-Force Control Rib) in a main groove extending in the tire circumferential direction of the tread portion, and in particular, improved wet performance and quietness. Related to pneumatic tires.

  Conventionally, as a typical tread pattern formed in a tread portion of a pneumatic tire, a rib pattern in which a plurality of land portions are divided by a plurality of main grooves extending in the tire circumferential direction, and the land portions are divided into main grooves. There is known a block pattern that is divided into a plurality of horizontal grooves extending in a direction intersecting with each other. Since these have high drainage performance and excellent steering stability performance, they are widely used in pneumatic tires such as heavy duty tires such as trucks and buses and passenger car tires.

  However, in a pneumatic tire provided with such a tread pattern, wear progresses from the vicinity of the edge portion along the main groove of each land portion, and each end portion wears locally (selectively). Uneven wear may occur at the end of the main groove. This uneven wear is mainly due to the fact that the braking force (braking force) that occurs when rolling tires under load is concentrated near the edge of the land, resulting in an increase in the load near that, It occurs due to wear at an early stage, and tends to occur particularly in the shoulder land portion on the outermost side in the tire width direction (shoulder portion side).

  Therefore, conventionally, protrusions (ribs) for uneven wear that sacrifice sacrificial wear are provided in the main groove of the pneumatic tire, and the uneven wear that occurs around the main groove is provided to the land portion. Suppressing side uneven wear is widely performed (see Patent Document 1).

FIG. 5 is a cross-sectional view in the tire width direction schematically showing the main part of the conventional pneumatic tire.
As shown in the figure, the pneumatic tire 100 has a plurality of main grooves 102 and 103 (two on both sides of the tire equatorial plane CL in the figure) that extend in the tire circumferential direction in the tread portion 101, and are partitioned by them. The plurality of land portions 110, 111, 112, and the outermost main groove 103 arranged in the tire width direction, project from the groove bottom toward the outer side in the tire radial direction, and along the main groove 103 in the tire circumferential direction And a protrusion 105 extending in the direction. In this pneumatic tire 100, the ridge 105 in the main groove 103 has its apex (outer peripheral surface) on the outer side in the tire radial direction positioned on the inner side in the tire radial direction with respect to the treads of the adjacent land portions 111 and 112, In addition, it is formed so as to come into contact with the road surface when the tire is loaded with a load, and is used as the above-mentioned uneven wear sacrifice protrusion.

  That is, the protrusion 105 contacts the road surface with a contact pressure lower than the tread surface of the adjacent land portions 111 and 112 when the load is rolled, so that the outer peripheral surface is slidingly contacted while being dragged by the road surface within the contact surface. . As a result, a large force (braking force) in the direction opposite to the traveling direction of the vehicle is generated on the protrusion 105, and accordingly, the braking force generated in the vicinity of the edge portions of the surrounding land portions 111 and 112 is reduced. Thus, the braking force generated around the main groove 103 is concentrated on the protrusion 105. In this way, the ridge 105 is worn while bearing much of the braking force in place of the vicinity of the edge portions of the land portions 111 and 112, while the load near the edge portions of the land portions 111 and 112 is reduced. Its wear is reduced.

  As described above, the pneumatic tire 100 wears the protrusion 105 (protrusion for uneven wear sacrifice) as a sacrifice for suppressing uneven wear of the adjacent land portions 111 and 112, thereby the land portion 111. , 112 prevents the wear from progressing, and prevents the wear life and tire performance from deteriorating.

  However, in this conventional pneumatic tire 100, since the volume of the air gap (cavity) in the main groove 103 decreases with the formation of the protrusion 105, the drainage performance is lowered, and the tire performance on a wet road surface or the like is reduced. Some wet performance may be degraded. On the other hand, in order to cope with this, the distance in the tire radial direction between the top of the ridge 105 and the treads of the adjacent land portions 111 and 112 is increased as much as possible, or the ridge with respect to the groove width of the main groove 103. When the width of 105 is reduced, the volume of the cavity in the main groove 103 is increased and drainage performance is improved. However, tire noise generated from the cavity is increased, and the quietness of the pneumatic tire 100 is improved. May fall.

  This tire noise is mainly caused by a resonance phenomenon in a tubular cavity (air column tube) in the main groove 103 formed between the main groove 103 and the road surface when the main groove 103 portion of the tread portion 101 is grounded. The main groove 103 in which the uneven wear sacrificial protrusion (projection 105) is formed tends to increase as the cavity in the main groove 103 increases. Therefore, in this conventional pneumatic tire 100, it is difficult to achieve both improvement of drainage performance and reduction of air column resonance noise, and it is difficult to ensure both high wet performance and sufficient silence.

Japanese Patent Laid-Open No. 10-6715

  The present invention has been made in view of the above-described conventional problems, and an object of the present invention is to improve the wet performance of a pneumatic tire having a partial wear sacrificial protrusion in a main groove extending in the tire circumferential direction. It is to suppress the increase in the columnar resonance sound and ensure sufficient silence.

The invention of claim 1 includes a tread portion including a plurality of main grooves extending in the tire circumferential direction and a plurality of land portions defined by the main grooves, and the main grooves are provided in at least one of the main grooves. A pneumatic tire having a protrusion for sacrificial wear that protrudes from a groove bottom of the groove and has a projecting end located on the inner side in the tire radial direction with respect to the tread surface of the adjacent land portion, wherein the protrusion for sacrificial wear Is composed of a plurality of protrusions that are in sliding contact with the road surface when the tire is loaded and rolled, and a non-contact portion that does not contact the road surface when the load is applied between the protrusions and continuously along the main groove. ridge der extending is, the plurality of protrusions, at least one that exists disposed in said protrusion, said a radially outer side of the top of the protrusion on the load rolling under load when in the ground plane The distance in the tire radial direction between the adjacent treads of the land is 1. A ～3.5Mm, and wherein the tire radial distance is 4.0~10.0mm der Rukoto between tread land portions the adjacent radially outer side of the top portion of the non-contact portion To do .
請 Motomeko 2 of the invention is the pneumatic tire according to claim 1, characterized in that it has the protrusion in the main groove in the tire width direction outermost side.

  According to the present invention, it is possible to improve the wet performance of a pneumatic tire having a protrusion for sacrificing uneven wear in a main groove extending in the tire circumferential direction, while suppressing the increase in air columnar resonance noise and providing sufficient silence. Sex can be secured.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
The pneumatic tire of the present embodiment is a pneumatic tire such as a heavy load tire or a passenger car tire, for example, a bead core disposed in a pair of tire bead portions, and at least one carcass layer extending in a toroidal shape therebetween. It has a known pneumatic tire structure including a belt layer disposed on the outer peripheral side of the carcass layer of the tread portion and a tread rubber formed with a predetermined tread pattern.

FIG. 1 is a plan view showing a developed tread pattern of the pneumatic tire 1 of the present embodiment, and schematically shows a part of the tire circumferential direction.
As shown in the figure, the pneumatic tire 1 has a plurality of tires extending in a tread portion 2 extending in a tire circumferential direction (vertical direction in the figure), for example, in a straight line, or in a zigzag shape or a wave shape (here, zigzag shape). (Here, four) main grooves 10, 11 and a plurality of (here, five rows) land portions 20, 21, 22 extending in the tire circumferential direction partitioned by them. Further, the pneumatic tire 1 includes lateral grooves 12, 13, 14 extending in a direction intersecting the main grooves 10, 11, 12, and a connecting groove 15 and a narrow groove 16 extending in a direction close to the tire circumferential direction, respectively. A plurality of them are provided, and thereby, the land portions 20, 21, and 22 are divided into blocks in the tire circumferential direction, the tire width direction (left-right direction in the drawing), and the like.

  The main grooves 10 and 11 are provided between the two center side main grooves 10 disposed with the tire equatorial plane CL interposed therebetween, and the center side main groove 10 and the outer end (tread end) TE of the tread portion 2 in the tire width direction. The two outer main grooves 11 are arranged at predetermined and substantially symmetrical positions in the tire width direction across the tire equatorial plane CL. Each of the main grooves 10 and 11 is, for example, a tire that is bent in a predetermined shape including substantially linear or curved portions that are alternately inclined in the opposite direction with respect to the tire circumferential direction in accordance with the required tire performance and the like. Although it is formed in a zigzag shape extending in the circumferential direction, here it is formed in a zigzag shape consisting of a substantially linear portion. In addition, the main grooves 10 and 11 are formed so that the outer main grooves 11 are slightly wider, but the depth in the tire radial direction, the width of the zigzag (amplitude), the pitch, and the like are substantially the same or similar. The phase (zigzag apex position) is shifted from each other by a predetermined distance in the tire circumferential direction.

  The land portions 20, 21, 22 are between the center land portion 20 located on the tire equator plane CL disposed between the two center side main grooves 10, and between the center side main groove 10 and the outer main groove 11. Two rows of intermediate land portions 21 arranged, and two rows of shoulder land portions 22 located between the outer main groove 11 and the tread end TE and located on the outermost side in the tire width direction (shoulder portion side), Become. Each of the land portions 20, 21 and 22 has an edge portion and a groove wall in the tire width direction bent in the tire width direction in a zigzag shape corresponding to the shapes of the main grooves 10 and 11 and the like. The center land portion 20 and the intermediate land portion 21 are formed on both sides in the tire width direction (each main groove 10, 11 side), and the shoulder land portion 22 is on the inner side in the tire width direction (outside main portion). Only the groove 11 side) is formed in a zigzag shape. Further, each of the land portions 20, 21, and 22 has a maximum width in the tire width direction (a width between the convex portions protruding in the main groove 10, 11 direction, or a width between the convex portion and the tread end TE). The portion 21, the shoulder land portion 22, and the center land portion 20 become wider in this order.

  In the center land portion 20, a plurality of transverse grooves 12, connection grooves 15, and narrow grooves 16 extending in a substantially straight line are sequentially and repeatedly arranged in the tire circumferential direction. The lateral groove 12 extends in a tire width direction from one end opening in one central side main groove 10, and does not cross to the other central side main groove 10, and the other end is a tire in the center land portion 20. It terminates at a position beyond the equatorial plane CL. The plurality of lateral grooves 12 are alternately arranged at substantially equal intervals in the center land portion 20 alternately along the tire circumferential direction on both central side main grooves 10 side. Further, each of the plurality of lateral grooves 12 is open to each central side main groove 10 at the recesses of both tire width direction edge portions of the center land portion 20, and extends in substantially the same direction relatively close to the tire width direction therefrom. Is formed. The connecting grooves 15 and the narrow grooves 16 are alternately arranged in the tire circumferential direction in the vicinity of the tire equatorial plane CL, and open to each end portion side of the adjacent lateral grooves 12 to connect the lateral grooves 12 to each other. Inclined and extending in the direction. In addition, the connecting groove 15 and the narrow groove 16 extend in substantially the same direction that is relatively close to the tire circumferential direction, the connecting groove 15 has the same groove width as the lateral groove 12, and the narrow groove 16 is larger than the grooves 12 and 15. Each has a narrow groove width.

  These grooves 12, 15, and 16 communicate with each other as a whole to divide the center land portion 20 in the tire width direction, and further divide each of the divided portions in the tire circumferential direction so that the center land portion 20 is viewed in plan view. It is partitioned into a plurality of block-like portions (hereinafter referred to as blocks) 20B having substantially the same shape. The plurality of blocks 20B are arranged in the tire circumferential direction on both sides of the tire equatorial plane CL in the center land portion 20, corresponding to the arrangement of the grooves 12, 15, and 16, and The rows are alternately arranged along the tire circumferential direction.

  On the other hand, a plurality of one type of lateral grooves 13 that are inclined in the tire width direction and extend substantially linearly are formed in the intermediate land portion 21 at predetermined intervals in the tire circumferential direction. The lateral groove 13 is formed at an angle relatively close to the tire width direction, and both end portions open to the central main groove 10 and the outer main groove 11 sandwiching the intermediate land portion 21, respectively. Has crossed. Further, the lateral grooves 13 open to the respective concave portions of both the tire width direction edge portions of the intermediate land portion 21, and connect the concave portions facing substantially in the tire width direction, thereby connecting the intermediate land portion 21 in the tire circumferential direction. It is divided into a plurality of blocks 21B arranged in the tire circumferential direction having substantially the same shape in plan view.

  Similarly, the shoulder land portion 22 is formed with a plurality of one type of lateral grooves 14 extending substantially linearly in the tire width direction at predetermined intervals in the tire circumferential direction. Both ends of the lateral groove 14 open to the outer main groove 11 and the tread end TE sandwiching the shoulder land portion 22, respectively, and cross the shoulder land portion 22 in the tire width direction. The lateral groove 14 is formed such that the groove width on one end portion side on the tread end TE side gradually widens toward the tread end TE, and the other end portion on the outer main groove 11 side is the shoulder land portion 22. Opening in each recess, the shoulder land portion 22 is divided in the tire circumferential direction, and is partitioned into a plurality of blocks 22B arranged in the tire circumferential direction having substantially the same shape in plan view.

  In the pneumatic tire 1 of the present embodiment, one or a plurality of sipes 19 that terminate in the main grooves 10 and 11 side and the tread end TE side of the respective blocks 20B, 21B, and 22B are terminated inside. For example, it arrange | positions in predetermined positions, such as the front-end | tip of the convex part which protrudes in the main grooves 10 and 11 direction.

  In addition, the pneumatic tire 1 has the above-described uneven wear sacrifice protrusions independent of the land portions 20, 21, and 22 in at least one main groove 10, 11, but in the present embodiment, the tire A protrusion 30 that functions as a partial wear sacrificial protrusion is formed in the outer main groove 11 that divides the outermost shoulder land portions 22 in the width direction. The ridge 30 continuously extends along the outer main groove 11 and bends in a zigzag shape according to the shape, and extends in the tire circumferential direction independently from the land portions 21 and 22 on both sides in the tire width direction. Is formed. Hereinafter, the protrusion 30 (protrusion part for uneven wear sacrifice) will be described in more detail.

2 is a perspective view schematically showing the protrusion 30 and the like by enlarging the X region of FIG. 1, and FIG. 3 is a side view of the protrusion 30 and the like seen from the Y direction of FIG.
As shown in the figure, the protrusion 30 protrudes from the substantially central portion of the groove bottom 11M of the outer main groove 11 toward the outer side in the tire radial direction (upper side in the figure), and the protruding end thereof is adjacent to the intermediate land portion 21 and the shoulder. It is formed at a height located on the inner side in the tire radial direction (see FIG. 3) with respect to the tread surfaces (outer peripheral surfaces) 21T and 22T of the land portion 22. Further, the protrusion 30 has a top portion (outer peripheral surface) (see FIG. 2) on the outer side in the tire radial direction in a planar shape substantially parallel to the tread surfaces 21T and 22T of the land portions 21 and 22, and both side surfaces are opposed to each other. The outer main groove 11 is formed substantially parallel to both groove walls with a predetermined distance therebetween, and the cross-sectional shape perpendicular to the longitudinal direction is formed in a substantially rectangular shape.

  Further, the protrusions 30 have protrusions 35 protruding partially at a predetermined height toward the outer side in the tire radial direction (H in FIG. 3) on the outer peripheral surface at predetermined intervals (here, substantially omitted). A plurality are provided at equal intervals. The protrusion 35 has a substantially trapezoidal shape in which the length gradually decreases toward the outer side in the tire radial direction, and the outer surface in the radial direction of the tire is dragged to the road surface when the tire is loaded with a load and is in sliding contact. It is formed to do. The ridge 30 is in the tire radial direction between the top portion (hereinafter referred to as the top portion) of the projection portion 31 in which the projection 35 is formed in the tire radial direction, and the treads 21T and 22T of the adjacent land portions 21 and 22. The distance (S in FIG. 3) is formed to a predetermined value that allows sliding contact with the road surface, and the portion other than the protrusion 31 is a non-contact portion 32 that does not contact the road surface during load loading rolling.

  That is, the non-contact portion 32 of the ridge 30 is such that the distance in the tire radial direction (F in FIG. 3) between the top portion and the tread surface 21T, 22T is larger than the distance S of the protrusion 31. A predetermined step H is formed on the inner side in the tire radial direction with respect to the top of the protrusion 31. Accordingly, the ridge 30 is composed of a plurality of protrusions 31 that are in sliding contact with the road surface when the load is rolled, and a non-contact portion 32 that is positioned between the protrusions 31 and is not in contact with the road surface when the load is loaded. Are alternately arranged with a predetermined length in the longitudinal direction (tire circumferential direction).

  In the pneumatic tire 1, the plurality of protrusions 31 are provided on the protrusions 30 at predetermined substantially equal intervals in the tire circumferential direction so that at least one protrusion 31 is present in the ground contact surface at the time of rolling load of the tire. It is arranged. Further, the distances S and F of the protrusions 31 of the ridges 30 and the tops of the non-contact parts 32 with respect to the treads 21T and 22T of the land parts 21 and 22 are 1.5 to 3.5 mm and 4 respectively. 0.0 to 10.0 mm.

  In the pneumatic tire 1 of the present embodiment described above, the protrusion 31 of the ridge 30 disposed in the outer main groove 11 is brought into sliding contact with the road surface during load load rolling as the above-described uneven wear sacrifice protrusion. The protrusion 31 is made to bear the wear which should be made to function and should generate | occur | produce in the edge part vicinity of the adjacent land parts 21 and 22. FIG. As a result, with the use of the pneumatic tire 1, the projection 31 wears at the expense, but uneven wear near the edge portions of the land portions 21 and 22 can be reduced. Uneven wear can be improved, and the progress of wear on the land portions 21 and 22 side can be suppressed to prevent the tire performance and the wear life from deteriorating.

  Moreover, in this pneumatic tire 1, the portion other than the protrusion 31 of the ridge 30 is a non-contact portion 32 that does not contact the road surface, and a relatively large volume void (cavity) is secured in the outer main groove 11. The drainage performance can be increased and the wet performance can be enhanced. At the same time, since the air column tube formed in the outer main groove 11 at the time of tire contact is divided in the tire circumferential direction by the respective protrusions 31, it is possible to prevent the resonance phenomenon from occurring inside, as described above. Air columnar resonance can be reduced. As a result, tire noise generated from the outer main groove 11 portion is reduced, so that the quietness of the pneumatic tire 1 can be improved.

  Therefore, according to this pneumatic tire 1, it is possible to achieve both the improvement of drainage performance and the reduction of air column resonance noise, and the wet performance of the pneumatic tire 1 having the uneven wear sacrificial protrusions can be achieved. While improving, it can suppress that an air column resonance sound becomes large, and can ensure sufficient silence. Further, in this pneumatic tire 1, the ridge 30 is formed in the outer main groove 11 on the outermost side in the tire width direction, and the ridge 30 is arranged along the edge portion of the shoulder land portion 22 where uneven wear is particularly likely to occur. The uneven wear resistance of the pneumatic tire 1 can be effectively increased.

  Here, in the pneumatic tire 1 of the present embodiment, since the protrusions 31 that are in sliding contact with the road surface are intermittently disposed on the ridges 30, they are in sliding contact with the road surface as a whole from the start of use of the tire to the beginning of wear. Compared to the uneven wear sacrificial projection, the area that is in sliding contact with the road surface is reduced, and the effect of suppressing uneven wear is accordingly reduced. However, even in this case, the occurrence of uneven wear at the edge portions of the land portions 21 and 22 can be sufficiently suppressed, and when the protrusion 31 (protrusion 35) wears due to the progress of the wear of the tread portion 2, the protrusions. The entirety of 30 comes into contact with the road surface, and the original uneven wear suppression effect as the uneven wear sacrifice protrusion is exhibited.

  In addition, when the protrusions 31 are arranged on each protrusion 30 so that at least one of the protrusions 31 exists in the contact surface during rolling under load, the air column tube in the outer main groove 11 during contact is surely Since the effect of reducing the air columnar resonance sound is exerted by being divided, it is desirable to arrange the protrusions 31 of the ridges 30 as such.

  Further, the protrusion 30 has the above-described distances S and F (see FIG. 3) of the tops of the protrusion 31 and the non-contact part 32 with respect to the treads 21T and 22T of the adjacent land parts 21 and 22, respectively. It is more desirable to form in a thickness of 0.5 to 3.5 mm and 4.0 to 10.0 mm. First, the distance S of the protrusion 31 is set to a range of 1.5 to 3.5 mm. If the distance S is less than 1.5 mm, the top of the protrusion 31 is not in sliding contact with the road surface. If it exceeds 3.5 mm, the top of the protrusion 31 may not be grounded to the road surface when it is new. This is because, if it is 3.5 mm, the air column tube dividing function is exhibited in order to make sure that it is grounded even if it is slightly new. On the other hand, the distance F of the non-contact portion 32 is set to a range of 4.0 to 10.0 mm if the distance F is 4.0 mm or more and the top of the non-contact portion 32 is not grounded even when new. The function as the groove is surely exhibited, and the reason why it is set to 10.0 mm or less is that the above-described protrusion 30 that is exhibited as a result of the top portion being grounded is the original function as a whole. This is because the wear-inhibiting effect is exhibited before the middle stage of wear.

  In addition, the protrusion 30 (protrusion part for uneven wear sacrifice) is, for example, in the central main groove 10, in all the main grooves 10, 11, or the main groove 10 on one side across the tire equatorial plane CL, 11 may be formed, or may be formed in any one of the main grooves 10 and 11. Even if it does in this way, each above-mentioned effect can be acquired, for example, the uneven wear of the circumference can be controlled.

  Further, in the pneumatic tire 1, a plurality of protrusions 35 having a substantially trapezoidal shape in side view (see FIG. 3) are formed on the ridge 30, but each protrusion 35 is formed in, for example, a substantially rectangular shape in side view, or The boundary portion with the non-contact portion 32 may be formed in another shape such as a curved shape such as an arc shape when viewed from the side. Furthermore, although this embodiment took and demonstrated the pneumatic tire 1 which has the zigzag-shaped main grooves 10 and 11 and each other groove | channels 12-16 as an example, for example, the main groove extended in a straight line or a wave shape in the tire peripheral direction Similar protrusions 30 corresponding to the shape may be formed in the main groove of a tire having another tread pattern, such as a tire having a tire or a tire having no lateral groove.

(Tire test)
In order to confirm the effect of the present invention, without providing the protrusion 35 on the pneumatic tire 1 of the embodiment (hereinafter referred to as an implementation product) having the tread pattern (see FIG. 1) described above, A conventional pneumatic tire (hereinafter referred to as a conventional product) formed in the shape of a conventional uneven wear sacrifice protrusion and a comparative example of a pneumatic tire (hereinafter referred to as a comparative product) were prototyped and subjected to the following conditions: We performed wet performance test and noise test. All of these tires were radial ply tires for trucks and buses having a tire size of 11R22.5 as defined by JATMA YEAR BOOK (2006, Japan Automobile Tire Association Standard).

FIG. 4 is a cross-sectional view in a direction perpendicular to the longitudinal direction schematically showing the vicinity of the protrusions 30 of the conventional product and the comparative product.
In the conventional product and the comparative product, as shown in the drawing, each protrusion 30 is formed at a substantially constant predetermined height along the longitudinal direction without forming a step on its top (outer peripheral surface). The protrusion 30 of the conventional product (see FIG. 4A) has a tire radial direction distance D1 of 2.5 mm between the top and the treads 21T, 22T of the adjacent land portions 21, 22, and is a comparative product (FIG. 4). 4B), the tire radial distance D2 between the top and the treads 21T and 22T was set to a larger 6.0 mm.

  On the other hand, with respect to the treads 21T and 22T, the protrusion 30 of the embodiment product has the distance F (see FIG. 3) of the top of the non-contact part 32 set to 6.0 mm and the distance S of the top of the protrusion 31 is set to 2 The height H of the protrusion 35 (step between the tops) was 3.5 mm. In the product, twelve protrusions 35 are arranged on the protrusion 30 at substantially equal intervals in the tire circumferential direction.

  In the wet performance test, each tire was mounted on a 7.50 × 22.5 rim at an internal pressure of 900 kPa, and 2-D · 4 (the front wheel had two axles, the rear wheels had two driving wheels and two driving wheels). (2 axes). In the test, the starting acceleration on the wet road surface was measured so that the load on each tire was constant, and the wet performance was evaluated by comparing the measurement results based on the measured values of the conventional products.

  The noise test was performed by attaching each tire to a 7.50 × 22.5 test rim at an internal pressure of 900 kPa and rotating the tire on the drum of the indoor drum test device under conditions of a load of 2500 kg and a speed of 60 km / h. It was. In the test, a noise level of 630 to 800 Hz during rotation of each tire was measured, and the measurement result was compared with a conventional product as a reference to evaluate noise (silence).

  Table 1 shows the results of each test. The wet road surface acceleration is expressed as an index with the acceleration of the conventional product taken as 100, and the larger the value, the larger the acceleration and the better the wet performance. The noise level is expressed as a noise level dB (A) (decibel A) with respect to the standard of the conventional product, and the larger the value, the higher the noise level and the lower the silence.

  As a result of the test, as shown in Table 1, the starting acceleration on the wet road surface is larger with both the comparison product 115 and the execution product 113 compared to the conventional product 100, and in these, the wet performance is large. It turned out that it improved. On the other hand, the noise level was +2 dB (A) in the implementation product compared to +6 dB (A) in the comparison product, and the noise level in the implementation product could be kept low.

  From the above results, according to the present invention, it is possible to improve the wet performance of the pneumatic tire having the uneven wear sacrificial protrusion in the main groove extending in the tire circumferential direction, and to suppress the increase of the air column resonance noise. It has been proved that sufficient silence can be secured.

It is a top view which expands and shows the tread pattern of the pneumatic tire of this embodiment. FIG. 2 is a perspective view schematically showing an X region in FIG. 1 in an enlarged manner. It is the side view seen from the Y direction of FIG. It is sectional drawing of the direction orthogonal to the longitudinal direction which shows each protrusion vicinity of a conventional product and a comparison product typically. It is sectional drawing of the tire width direction which shows typically the principal part of the conventional pneumatic tire.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Pneumatic tire, 2 ... Tread part, 10 ... Central side main groove, 11 ... Outer side main groove, 11M ... Groove bottom, 12 ... Horizontal groove, 13 ... Horizontal groove , 14 ... transverse groove, 15 ... connecting groove, 16 ... narrow groove, 19 ... sipe, 20 ... center land part, 20B ... block, 21 ... intermediate land part, 21B ... Block, 21T ... Tread, 22 ... Shoulder land, 22B ... Block, 22T ... Tread, 30 ... Projection, 31 ... Projection, 32 ... Non Contact part, 35 ... projection, CL ... tire equatorial plane, TE ... tread end.

Claims (2)

The tread portion includes a plurality of main grooves extending in the tire circumferential direction, and a plurality of land portions partitioned by the main grooves, and protrudes from the groove bottom of the main grooves into at least one of the main grooves, A pneumatic tire having a protruding part for sacrificial uneven wear located on the inner side in the tire radial direction with respect to the tread of the land part adjacent to the protruding end,
The protrusion for sacrificial uneven wear is composed of a plurality of protrusions that are in sliding contact with a road surface when the tire is loaded with rolling load, and a non-contact portion that is not in contact with the road surface when the load is loaded between the protrusions. Ri ridge der extending continuously along the groove,
The plurality of protrusions are disposed on the protrusions so that at least one of the protrusions is present in the ground contact surface at the time of the load load rolling,
The distance in the tire radial direction between the apex on the outer side in the tire radial direction of the protrusion and the tread surface of the adjacent land portion is 1.5 to 3.5 mm,
A pneumatic tire distance in the tire radial direction between the tread land portions the adjacent radially outer side of the top portion of the non-contact portion is characterized 4.0~10.0mm der Rukoto. In the pneumatic tire according to claim 1,
A pneumatic tire according to claim Rukoto that having a said projection in the tire width direction outermost side of the main groove.

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