JP3354483B2 - Pneumatic tire - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a pneumatic tire capable of improving wet performance without deteriorating noise performance.

[0002]

2. Description of the Related Art In a pneumatic tire in which a block is formed on a tread surface by a vertical groove and a horizontal groove intersecting the vertical groove, a block adjacent to the horizontal groove and one of the horizontal grooves in the tire circumferential direction. A pitch variation method is employed in which a plurality of types of pitch lengths, which are circumferential lengths of the pitch consisting of the following, are used and the arrangement is devised.

In such a pitch variation method, for example, when the pitch length is set to three types of L>M> S, the width of the lateral groove included in each pitch usually changes according to the pitch length. The L pitch is formed so as to be the largest, then the M pitch and the S pitch to be the smallest. Thereby, the groove volume of the lateral groove is changed, and the pitch noise of the tire is dispersed in a wide frequency band.

However, when such a pitch variation technique is used, for example, in the above-described example, the groove width of the lateral groove having the S pitch becomes small, so that the groove width becomes extremely narrow on the contact surface where a load is applied to the tire. There is also a problem that the groove may be closed depending on the situation, so that the drainage property on a wet road surface is reduced.

In order to solve such a problem, it is conceivable to make the groove width of each pitch the same. However, in this case, the groove volume ratio of the lateral groove to the pitch length is not constant at each pitch. There is a problem that the effect of noise dispersion due to variations cannot be sufficiently obtained.

The present inventors have devised in view of such a problem, and invented the inclination angles (θ1,...) Of the groove wall surfaces of the lateral grooves having pitches arranged in order from the large pitch length (L1,... Ln).
θn) is a tilt angle that increases in the above order,
Air that can improve wet performance without impairing noise performance based on making the pitch length ratio (L1:...: Ln) of the pitch and the groove area ratio (S1:. It is intended to provide tires containing the tire.

[0007]

According to the first aspect of the present invention, a block is formed by a vertical groove extending in a tire circumferential direction and a horizontal groove intersecting the vertical groove, and a block is formed in the horizontal groove and the horizontal groove. A pneumatic tire having a pattern portion of a pitch variation in which a plurality of types of pitch lengths, which are circumferential lengths of pitches formed of blocks adjacent to each other in the tire circumferential direction, are sequentially arranged from a large pitch length. The inclination angle (θ) of the groove wall surface with respect to the normal to the tread surface in the circumferential cross section of the lateral groove having the arranged pitch (P1,... Pn)
,... Θn) are the inclination angles that increase in the above order, the pitch length ratio (L1:...: Ln) of the pitches arranged in order from the larger pitch length, and the circumferential cross section of each lateral groove in this order. Are substantially the same as the groove area ratio (S1:...: Sn), which is the ratio of the groove area (S1,... Sn).

The invention according to claim 2 is the pneumatic tire according to claim 1, wherein all the lateral grooves have the same groove depth.

[0009]

An embodiment of the present invention will be described below with reference to the drawings. As shown in FIG. 1, the pneumatic tire of the present embodiment has a passenger car in which a plurality of blocks 5 are formed by a longitudinal groove 3 extending in a tire circumferential direction on a tread surface 2 and an extending lateral groove 4 intersecting the longitudinal groove 3. Are illustrated.

In the present embodiment, the longitudinal grooves 3 include inner longitudinal grooves 3a, 3a arranged on both sides of the tire equator CL, and outer longitudinal grooves 3b, 3b arranged on both sides. In each of the examples, a tire extending continuously in the tire circumferential direction and extending in a straight line is illustrated. In the present embodiment, the lateral groove 4 extends from the vicinity of the tire equator CL to the end of the tread.

The vertical ribs 3 and the horizontal grooves 4 allow the tread surface 2 to have a center rib 6 extending on the tire equator C.
Are formed, a first block 5A arranged on both sides thereof in the tire circumferential direction, and a second block 5B arranged on both sides thereof in the tire circumferential direction. The vertical groove 3 and the horizontal groove 4 have, for example, a groove width of 4 to 20 mm and a groove depth of 5 mm.
A size of about 15 mm can be preferably employed.

The pneumatic tire has a pitch length L1, which is a circumferential length of a pitch P1, P2 or P3 composed of the lateral groove 4 and, for example, a block 5B adjacent to the lateral groove 4 in the tire circumferential direction. It has a pattern portion of a pitch variation in which L2 and L3 are plural types. In the present embodiment, the blocks 5A and 5B each employ a pitch variation. Each pitch is composed of three types, P1, P2, and P3 in this example, and the pitch lengths L1, L2, and L3 are L1: L2: L3 = 120: 100: 80. Is illustrated as an example.

2 (A) to 2 (C) show X in the tire circumferential direction of each lateral groove 4 at each pitch P1, P2, P3 in FIG.
-X, YY and ZZ sectional drawing is shown. As described above, in the present invention, the inclination angle (θ) of the groove wall surface 4a with respect to the tread surface normal N in the circumferential cross section of the lateral groove 4 having the pitches (P1, P2, P3) arranged in order from the large pitch length
1, θ2, θ3) in the order described above.
<Θ2 <θ3). In addition, the said inclination angle is an angle of the direction which enlarges a groove width toward the tread surface 2 side.

As described above, the inclination angle (θ) of the groove wall surface 4a in the circumferential cross section of the lateral groove 4 with respect to the tread surface normal N.
1, θ2, θ3) is set to be the inclination angle that increases in the order of the pitch length, so that the pitch P3 having the smaller pitch length
, The inclination angle θ3 with respect to the tread surface normal N can be increased.

In the conventional tire, the inclination angle of the lateral groove 4 is the same at all pitches.
In the case of a pitch having a small pitch length, for example, P3, there was a problem that the groove width G3 of the lateral groove 4 became extremely narrow or the groove was closed when a load was applied to the tire. By providing the difference, it is possible to effectively prevent the block from falling down, and to prevent a decrease in wet performance.

The pitch P having the largest pitch length LI
In the present embodiment, the inclination angle θ1 of one lateral groove 4 is set to be larger than 0 ° and 10 ° or less. It is particularly preferable that θ3−θ2 and θ2−θ1 be 1 ° or more, more preferably 2 ° or more. The difference in the inclination angle of the lateral groove 4 between the pitches may be the same or different. Further, the groove wall surfaces 4a facing the lateral grooves 4 are formed symmetrically in this example.

Further, in the present invention, the pitch length ratio (L1: L2: L3) of the pitches (P1, P2, P3) arranged in order from the large pitch length, and the circumferential cross section of each lateral groove 4 in this order. The groove area ratio (S1: S2: S3), which is the ratio of the groove areas (S1, S2, S3), is substantially the same, and in this example, the setting is as follows. L1: L2: L3 = S1: S2: S3 = 120: 10
0:80

As described above, in the present invention, the groove area ratio and the pitch length ratio are made substantially equal to each other so that the inclination angle of the groove wall surface 4a of the lateral groove 4 having a small pitch length is increased while the groove volume is reduced. The noise performance can be improved by the pitch variation method while preventing the deterioration of the wet performance. In the present embodiment, all the lateral grooves 4 have groove depths d1 and d1.
2 and d3 are all formed with the same groove depth.

If the pitch length ratio is not substantially equal to the groove area ratio, the pitch variation effect is reduced. Especially when the groove area ratio is large relative to the pitch length ratio,
In the lateral groove 4 having a small pitch length (for example, the pitch P3), the groove volume tends to decrease, and improvement in wet performance cannot be expected. The expression that the ratios are substantially equal includes those having a difference within 3%.

The widths W1 to W3 of the lateral grooves 4 are as follows.
As long as the groove area ratio and the pitch length ratio can be made the same as described above, the pitch may be the same for all pitches, or may be changed according to the pitch length. Groove width W1 of lateral groove 4
When changing W3, it is preferable that the rate of change of the groove width be kept within 15% in the order of the pitch length. In order to enhance the effect of pitch variation, it is particularly preferable to set the total pitch number to about 60 to 70.

As described in detail above, the present invention only needs to provide a pattern portion having a pitch variation on a part of the tread surface 2, and can be suitably applied to a rib or a block pattern as shown in the example. The present invention can be suitably implemented also in the case of being formed only with blocks.

[0022]

EXAMPLES A pneumatic tire having a tire size of 205 / 60R15 and a pitch variation shown in Table 1 was prototyped (conventional examples, Examples 1 to 3, Comparative Examples 1 and 2), and wet performance and noise performance were also performed. And evaluated comparatively. The total number of pitches was 65, and the pitch length L2 of the pitch P2 was common to all tires. Except for Example 1, the groove depth was the same at each pitch. The test method is as follows.

<Wet Performance> (Lateral Hydroplaning Test) Tess value tires were mounted on a 100 m radius asphalt road surface on a course provided with a puddle having a depth of 10 mm and a length of 20 m while gradually increasing the speed. The vehicle was entered, the lateral acceleration (lateral G) was measured, and the average lateral G of the front wheels at a speed of 50 to 80 km / h was calculated. The results are indicated by an index with the conventional example as 100. The higher the value, the better.

<Noise Performance> The asphalt smooth road surface was run at a speed of 30 to 60 km / h, and the noise inside the vehicle centered on the pitch noise was evaluated by the driver's feeling. displayed. The higher the value, the lower the noise level and the better. Table 1 shows the test results.

[0025]

[Table 1]

As a result of the test, it was confirmed that the tires of the examples had improved wet performance without impairing noise performance.

[0027]

As described above, according to the first aspect of the present invention, the inclination angle of the wall surface of the lateral groove is increased as the pitch length becomes smaller, so that the blocks adjacent to the lateral groove can be effectively tilted. In a pitch of a small pitch length, when a load is applied to the tire, the width of the lateral groove becomes extremely narrow or the groove closes, thereby effectively suppressing a problem such as a decrease in wet performance.

Further, by making the pitch length ratio and the groove volume ratio of the lateral grooves substantially equal, it is possible to prevent the groove volume from being reduced while increasing the inclination angle of the groove wall surfaces of the lateral grooves having the small pitch length, and to prevent the wet performance from being lowered. Noise performance can be improved by the pitch variation method while preventing noise.

[Brief description of the drawings]

FIG. 1 is a developed view of a tread pattern of a pneumatic tire according to an embodiment of the present invention.

2A is a sectional view taken along line XX, FIG. 2B is a sectional view taken along YY, and FIG. 2C is a sectional view taken along ZZ.

[Explanation of symbols]

 2 Tread surface 3 Vertical groove 4 Horizontal groove 5 Block P1, P2, P3 Pitch L1, L2, L3 Pitch length S1, S2, S3 Groove area θ1, θ2, θ3 Slope angle of horizontal groove

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B60C 11/03-11/13

Claims (2)

(57) [Claims] 1. A block is formed by a vertical groove extending in the tire circumferential direction and a horizontal groove intersecting the vertical groove, and a circumferential direction having a pitch including the horizontal groove and a block adjacent to the horizontal groove in the tire circumferential direction. Pneumatic tire having a pattern portion of a pitch variation having a plurality of types of pitch lengths, the pitches being arranged in order from a large pitch length (P1,... P
The inclination angles (θ1,... θn) of the groove wall surface with respect to the tread surface normal in the circumferential cross section of the lateral groove of n) are set to the inclination angles increasing in the above order, and the pitch lengths of the pitches arranged in order from the large pitch length : Ln, and a groove area ratio (S1:...: Sn), which is a ratio of the groove area (S1,... Sn) in the circumferential cross section of each lateral groove in this order, is substantially the same. A pneumatic tire characterized by the following. 2. The pneumatic tire according to claim 1, wherein all the lateral grooves have the same groove depth.