JP4969874B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire, and more particularly, to an improvement in a tread pattern for reducing tire passing noise without impairing steering stability.

As a tread pattern of a conventional pneumatic tire, for example, as shown in FIG. 3, the land portion 52 defined by a plurality of circumferential grooves 51 extending along the tire circumferential direction includes the circumferential groove 51. Various types of lug grooves 53 that form a block pattern penetrating the land portion 52, and rib patterns that open to the circumferential groove at one end and terminate in the land portion 51 while the other end terminates in the land portion 51. It is common that lug grooves 54-56 of the form are provided. (For example, refer to Patent Document 1).
By the way, it is known that a resonance sound (air column resonance sound) having a frequency corresponding to the contact length of the circumferential groove is generated and the passing noise level is deteriorated. This air column resonance sound is generated by the resonance phenomenon of the tubular cavity formed between the tire and the road surface when the circumferential groove contacts the ground, and the length of the air column, that is, the contact surface Resonance occurs at a wavelength twice that of the circumferential groove included in the groove. Therefore, in order to suppress the above air columnar resonance noise, conventionally, there are methods of reducing the number and volume of the circumferential grooves, or conversely increasing the circumferential groove width.
Further, the tread pattern is a pattern composed of one wide circumferential groove at the center and a lateral groove having one end terminating in the land portion, such as the second lug groove 54, and the sea / land ratio of the pattern is as follows. A method for reducing the air columnar resonance without impairing the wet characteristics by limiting the above has been proposed (for example, see Patent Documents 2 and 3).
JP-A-9-2025 Japanese Patent No. 2698739 JP-A-6-143932

However, when the number and volume of the circumferential grooves are reduced, the drainage function by the circumferential grooves is lowered, and thus the wet performance represented by the hydroplaning phenomenon is lowered. On the contrary, when the circumferential groove width is widened, the ground contact area is greatly reduced and a large step is generated in the width direction distribution of the contact pressure, so even if the sea / land ratio of the tread pattern is limited, There was a problem that steering stability on a dry road surface was lowered.
Further, even in a conventional tread pattern having a rib row provided with the lug grooves 54 to 56, the length of the lug grooves 54 to 56 is limited, so that the air column resonance sound can be effectively dispersed. Therefore, it has been difficult to sufficiently reduce the passing noise level.
Therefore, it is conceivable that the lug groove whose one end terminates in the land portion is bent in the circumferential direction to ensure the length of the lug groove and to disperse the air columnar resonance sound. When the depth of the groove is increased, the steering stability is deteriorated.

  The present invention has been made in view of the conventional problems, and provides a pneumatic tire capable of effectively reducing the passing noise level caused by air column resonance without impairing steering stability. With the goal.

Invention of Claim 1 of this application is the air provided with the several circumferential direction groove | channel extended in the tire circumferential direction provided in the tread surface, and the several land part row | line | column divided by the said circumferential direction groove | channel. a enters tire, to the rib rows are rib columns least one row of land portion rows are continuous in the tire circumferential direction, one end opening to the circumferential groove, the inclined groove portion that crosses the circumferential groove, the inclined A key-shaped groove having a longitudinal groove portion extending in a direction parallel to the tire circumferential direction from the end of the groove portion is provided , and the depth of the longitudinal groove portion is gradually increased from the communication portion communicating with the inclined groove portion toward the end portion. It is characterized by being formed so as to be shallow.
According to a second aspect of the present invention, in the pneumatic tire according to the first aspect, the longitudinal groove has a substantially triangular cross-sectional shape.
According to a third aspect of the present invention, in the pneumatic tire according to the first or second aspect, the groove width of the longitudinal groove portion is formed so as to gradually become narrower from the communicating portion communicating with the inclined groove portion toward the terminal portion. It is a thing.

According to the present invention, the rib row at least one row of zoned land row is rib successive rows in the tire circumferential direction by a plurality of circumferential grooves extending along a tire circumferential direction provided on the tread surface In addition, a key-shaped groove having one end opened in the circumferential groove, an inclined groove portion intersecting with the circumferential groove, and a vertical groove portion extending from the end of the inclined groove portion in a direction parallel to the tire circumferential direction is provided. Thus, since the air columnar resonance sound can be dispersed, the passing noise level can be sufficiently reduced. Moreover, since the depth of the vertical groove portion is formed so as to gradually decrease toward the end portion, the passing noise level can be reduced without impairing the steering stability.
At this time, or on Kitate groove sectional shape with a substantially triangular shape, from the communicating portion communicating with the inclined groove portion so as to gradually decrease toward the terminal end, since it is possible to further enhance the block rigidity, steering Stability can be improved.

Hereinafter, the best mode of the present invention will be described with reference to the drawings.
FIG. 1 is a development view of a tread pattern of a pneumatic tire according to the best mode of the present invention, in which 11a to 11d are circumferential grooves formed in the tire tread portion 10 along the tire circumferential direction. , 12 are formed in the land portion 13a defined by the circumferential grooves 11c and 11d, and communicated with the inclined groove portion 12a having one end opened in the circumferential groove 11c and the end of the gently inclined groove portion 12a, and in the tire circumferential direction. In this example, the key-shaped groove is composed of a longitudinal groove portion 12b extending in parallel. This key-shaped groove 12 disperses the air column resonance sound to reduce the passing noise level. 14 is a short lug groove provided in the same land portion 13a as the key-shaped groove, one end opening on the opposite side to the opening side of the key-shaped groove 12 and the other end terminating in the land portion 13a. , 15 and 16 are lug grooves provided on the land portions 13b and 13d, respectively, one end opening to the circumferential grooves 11b and 11c side and the other end terminating in the land portions 13b and 13c. 14 and lug grooves 15 and 16 are lug grooves that contribute to improving steering stability. In the figure, TW indicates the tread contact width.

In the key-shaped groove 12 according to the present invention, as shown in the schematic diagram of FIG. 2, the cross-sectional shape of the vertical groove portion 12b is substantially triangular, and the depth d thereof extends from the communication portion 12p communicating with the inclined groove portion 12a to the terminal portion 12q. The groove width w is formed so as to gradually become shallower toward the end, and the groove width w is formed to become gradually narrower toward the end portion 12q.
As a result, the length of the key-shaped groove 12 that is a lug groove can be secured to effectively disperse the air column resonance noise, and the vertical groove portion 12b receives road surface input at the narrow end portion 12q when depressed. As a result, the rigidity of the land portion 13a, which is a rib row, can be ensured, and the deterioration of steering stability can be suppressed to a minimum.
When the tire is worn, the groove length of the key-shaped groove 12 is shortened, so that the effect of reducing the air column resonance noise is reduced. However, as the tire is worn, the volume of the circumferential groove is reduced and the air column resonance noise is reduced. Therefore, there is no problem even if the groove depth of the vertical groove portion 12b is gradually reduced. Therefore, even when the tire is worn, it is possible to achieve both steering stability and reduction of the passing noise level.

  Thus, according to this best mode, the land portion 13a defined by the circumferential grooves 11c and 11d communicates with the inclined groove portion 12a whose one end opens in the circumferential groove 11c and the terminal end of the inclined groove portion 12a. The vertical groove portion 12b extends in parallel with the tire circumferential direction, and the cross-sectional shape of the vertical groove portion 12b is substantially triangular. The depth d and the groove width w are connected from the communicating portion 12p communicating with the inclined groove portion 12a to the terminal portion 12q. Since the key-shaped groove 12 formed so as to gradually become smaller toward the head is provided to disperse the air columnar resonance sound, the passing noise level can be effectively reduced without impairing the steering stability. Can do.

In the best mode described above, the key-shaped groove 12 is provided only in the land portion 13a, but may be provided in other land portions 13b and 13c. In this case, since the ground contact area of the tire decreases and the braking force decreases, it is necessary to appropriately select the number and depth of the key-shaped grooves 12 to be provided or the cross-sectional shape according to the specifications.
In the above example, the cross-sectional shape of the vertical groove portion 12b is substantially triangular. However, the shape is not limited to this and may be other shapes. At this time, as the cross-sectional shape, a cross-sectional shape in which the area becomes smaller as the position is deeper is preferable in consideration of steering stability.

表１から明らかなように、本発明のタイヤは、従来のタイヤに比較した各項目について優れた結果を示しており、本発明により、操縦安定性を損なうことなく、通過騒音レベルを低減することができることが確認された。
また、縦溝部の深さが一様な比較例のタイヤは、３０％磨耗時、６０％磨耗時の通過騒音レベルについては、本発明のタイヤよりも若干低いが、操縦安定性が従来のタイヤよりも悪化していることから、操縦安定性を確保するためには、縦溝部の深さをその終端部に向かうに従って徐々に浅くなるように形成することが必須であることが確認された。 The tire having the tread pattern provided with the key-shaped groove according to the present invention (the tire of the present invention) shown in FIG. 1 and the conventional tire (conventional tire) shown in FIG. The steering stability on the dry road and the passing noise level were evaluated. For reference, a tire (comparative example tire) having a tread pattern provided with a key-shaped groove having a uniform vertical groove portion depth was also prepared and subjected to the same evaluation.
The tire size was 245 / 40R18, which was incorporated into a rim of 7.5J-18, mounted on a European sedan, and the vehicle specified internal pressure was filled and evaluated under a load condition with 600N added to the driver's weight.
The longitudinal stability test was evaluated based on the feeling of a test driver when driving in various driving modes on a dry road surface.
As for passing noise, the passing noise level at the time of new article, 30% wear, and 60% wear was measured in accordance with the conditions in the European passing sound regulations.
The results are shown in Table 1 below. For these evaluation items, the steering stability value is assumed to be 100 for the conventional tire, and a larger value indicates better results. For passing noise, the value when the conventional tire is new is assumed to be 100. The smaller the value, the better the result.

As is clear from Table 1, the tire of the present invention shows excellent results for each item compared to the conventional tire, and the present invention reduces the passing noise level without impairing the steering stability. It was confirmed that
Moreover, the tire of the comparative example having a uniform depth of the longitudinal groove portion is slightly lower than the tire of the present invention in terms of passing noise level at the time of 30% wear and 60% wear, but the steering stability is a conventional tire. In order to ensure steering stability, it was confirmed that it is essential to form the depth of the longitudinal groove portion so as to gradually decrease toward the end portion.

  As described above, according to the present invention, it is possible to provide a pneumatic tire capable of reducing the passing noise level due to air column resonance without impairing the steering stability.

It is an expanded view of the tread pattern of the pneumatic tire which concerns on the best form of this invention. It is a schematic diagram which shows the outline | summary of the key type groove | channel by this invention. It is a development view of a conventional tread pattern.

Explanation of symbols

10 tire tread portion, 11a to 11d circumferential groove, 12 key groove,
12a inclined groove part, 12b vertical groove part, 13a-13c land part, 14 short lug groove,
15,16 Lug groove, TW tread contact width.

Claims (3)

And a plurality of circumferential grooves extending along a tire circumferential direction provided on the tread surface, a pneumatic tire and a plurality of land portion rows are partitioned by the circumferential groove,
The rib row in at least one row of the land row is rib successive rows in the tire circumferential direction,
One end opens to the circumferential groove, and the inclined groove portion intersects with the circumferential groove;
Extending from the end of the inclined groove in the direction parallel to the tire circumferential direction is provided a key-groove having a vertical groove terminating,
The pneumatic tire is characterized in that the depth of the vertical groove portion is formed so as to become gradually shallower from the communicating portion communicating with the inclined groove portion toward the terminal portion. The pneumatic tire according to claim 1, wherein a cross-sectional shape of the vertical groove portion is a substantially triangular shape. The pneumatic tire according to claim 1 or 2, wherein a groove width of the vertical groove portion is formed so as to gradually become narrower from a communication portion communicating with the inclined groove portion toward a terminal portion.

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