JP2003300403A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of reducing an outdoor noise while ensuring a water-discharge property of the tire. <P>SOLUTION: A plurality of circumferential sipes 4 of the tire 10 are provided on one land part (rib) 3a surrounded by a plurality of grooves 2, 2. A plurality of sipes 4 of the land part 3a are formed such that a depth thereof becomes shallow as a distance from the groove 2 becomes far. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire capable of reducing vehicle exterior noise without reducing steering stability and wet performance of the vehicle.

[0002]

2. Description of the Related Art As one of tire patterns capable of ensuring drainage of a tire, a pattern in which grooves are formed in a tread of the tire is adopted. According to the tire in which the groove is formed on the tread of such a tire, drainage can be ensured while traveling on a wet road surface, a so-called aquaplane phenomenon can be prevented, and the vehicle can travel safely.

On the other hand, in recent years, in consideration of the surrounding environment, it is also desired to reduce the noise outside the vehicle while traveling.

[0004]

It is considered that the groove formed in the tread of the tire causes noise while the vehicle is running. That is, since the groove is formed to have a constant groove volume in order to secure drainage, vibration of air trapped between the groove of the tread of the tire rotating with respect to the road surface and the road surface occurs, and air column resonance occurs. It is believed to produce sound.

It is considered that the vibration of the center portion of the tread is particularly large due to the impact on the tread while the vehicle is running, and the air column resonance sound generated due to the groove is further increased to cause the noise outside the vehicle to be increased.

Therefore, it is an object of the present invention to provide a pneumatic tire capable of reducing the noise outside the vehicle while ensuring the drainage of the tire.

[0007]

In order to solve the above problems, the present invention provides a pneumatic tire including a tread having a plurality of circumferential grooves extending in the circumferential direction and a land portion divided by the circumferential grooves. In the tire, at least one land portion is provided with a plurality of sipes formed in the circumferential direction, and the plurality of sipes of the one land portion include those having different depths, and from the circumferential groove. The pneumatic tire is formed so that the depth becomes shallower as the distance of (1) increases (claim 1).

According to the tire of the present invention, by providing a plurality of sipes on the one land portion, it is possible to reduce the noise outside the vehicle caused by the tire during traveling. Moreover, since the depth of the sipe is reduced as the distance from the circumferential groove increases, the steering stability of the vehicle on which the tire is mounted is not reduced. And since it is not necessary to change the volume of the circumferential groove itself,
It does not reduce the drainage of the tire.

The pneumatic tire may have three or more sipes formed on the one land portion (claim 2).

Thus, according to the tire of the present invention,
Since three or more sipes are provided in the one land portion, noise generated by the tire during traveling can be reduced more reliably.

When three or more sipes are provided in the one land portion (claim 2), the number of sipes in the one land portion can be 5 or less (claim 3). According to the tire of the present invention, since the number of sipes in one land portion is 5 or less, steering stability is not deteriorated. And, in order to reduce noise more reliably, it is most preferable to provide five sipes in the one land portion.

Further, in the tire of the present invention, it is possible not to provide a sipe at the shoulder portion of the land portion at the end portion in the tire width direction (claim 4). As a result, the noise generated by the tire during traveling can be further reduced.

Further, in the tire according to the present invention, the tire pattern of the tread can be formed in a rib pattern in which the land portion is circumferentially connected with ribs (claim 5). Thereby, the noise can be reduced by the present invention for the tire in which the tread pattern is formed in the rib pattern.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described with reference to FIG. FIG. 1 is a diagram showing a tread portion of a tire 10 which is an embodiment of the present invention.
It is a partial cross section along the cross section perpendicular | vertical with respect to the circumferential direction in the arbitrary positions of 0 tread circumferential direction.

Reference numeral 1 is a tread portion of the tire. Inside the tread portion 1, a belt layer 6 including a plurality of belts is arranged in the tire circumferential direction. The belt constituting the belt layer 6 can be formed of a metal cord so as to increase rigidity and withstand a heavy load.

A carcass 7 is arranged on the inner layer side of the belt layer 6. The carcass 7 is formed by a reinforcing cord extending in the radial direction of the tire 10.

On the tread surface of the tread portion 1, as a tread pattern, a rib pattern composed of a main groove 2 corresponding to a circumferential groove and ribs 3a and 3b corresponding to a land portion is formed.

The main groove 2 is formed mainly along the circumferential direction of the tire. Each of the ribs 3a and 3b is formed by integrally connecting the ribs mainly along the circumferential direction.

Further, as shown in FIG. 1, the tire 10 has three main grooves 2 formed therein. And rib 3
Each of a and 3a is surrounded by two main grooves 2 adjacent to each other to form one land portion. The ribs 3b and 3b are located at the tire width direction ends of the tread portion 1 and correspond to shoulder portions.

Each of the ribs 3a, 3a is provided with a plurality of sipes 4 extending in the tire circumferential direction. In this tire 10, three sipes 4 are provided on one rib 3a.
Then, as shown in FIG. 1, the depths of the three sipes 4 provided on one rib 3a are different,
The portion closest to the main groove 2 is formed deepest, and the portion farthest from the main groove 2 and closest to the center of the rib 3a is formed shallowest.

The sipes 4 are preferably formed deeper in order to reduce noise. On the other hand, tire 10
It is preferable not to make the sipe 4 too deep so as not to reduce the steering stability of the vehicle in which the vehicle is mounted. In particular, in order not to reduce the steering stability, the rib 3
It is preferable not to deepen the sipe as it approaches the center of a.

Of the plurality of sipes 4 provided on one rib 3a, the depth of the one closest to the main groove 2 is approximately 80% to 10% of the depth of the main groove 2.
It is preferably about 0%. Further, the depth of the rib closest to the center of the rib 3a is preferably about 20% to 30% of the depth of the main groove 2. In addition, regarding the sipe provided between the sipe closest to the main groove 2 and the sipe closest to the center of the rib 3a,
It is preferably about 40% to 60% of the depth of the main groove 2.

According to this tire 10, one rib 3a is provided.
By providing a plurality of sipes 4 on the tire, the impact force when the rolling tire comes into contact with the road surface is mitigated, tread vibration can be suppressed, and air column resonance noise can be reduced, thus reducing tire noise. You can As a result, it is not necessary to change the volume of the main groove 2 in order to reduce the noise of the tire, so it is possible to reduce the noise while ensuring the drainage property of the tire.

According to the tire 10, the main groove 2
Since the sipe 4 is made shallower as it becomes farther from the vehicle, the steering stability of the vehicle on which the tire 10 is mounted is not reduced.

In the tire 10 described above, the sipe is not provided in the shoulder portion as shown in FIG. 1, but the sipe may be provided in the shoulder portion. However,
From the viewpoint of reducing noise, it is more preferable not to provide sipes on the shoulder portion.

Further, in the example of the tire 10 described above, the example in which the three ribs 3a are provided with three sipes 4 has been described, but the sipes may be provided with a plurality of two or more sipes. Also in the case of providing two sipes on one rib, the one closest to the main groove is deepened and the one near the center of the rib is shallowed.

Further, it is preferable that the number of sipes provided on one rib is 5 or less. This is because it is considered sufficient to provide five sipes on one rib to reduce noise. On the other hand, if six or more sipes are provided on one rib, steering stability may be reduced.

In addition, when five sipes are provided on one rib, the sipes closest to the center of the rib are made the shallowest, and two sipes are provided on each of the left and right sides of the shallowest sipe, and the main groove is formed. A closer sipes can be formed deeper.

In the above description, as the tire pattern formed on the tread portion, an example of the rib pattern formed by the circumferential groove 2 and the ribs 3a, 3b corresponding to the land portion has been described, but the present invention is not limited to this. Other tire patterns other than the above can be implemented.

That is, even when the tire pattern is, for example, a block pattern, the present invention is implemented by providing a plurality of sipes as described above in one land portion surrounded by the main groove and the sub groove. can do. Even in this case, noise generated by the tire can be reduced.

[0031]

EXAMPLES Examples of the present invention will be described below.
As examples of the present invention, four tires of Example 1 to Example 4 having different sipe conditions were prepared. In addition, in order to make a comparison with the example, a comparative example in which the sipe condition was different from that of the example was prepared. Then, a noise test and a steering stability test of these five tires were performed.

First, the conditions of the tested tire will be described. The tires that have undergone the above test are all 185
/ 70R14 size, speed 4
A noise test and a steering stability test were carried out at 0 to 100 km / h.

In each case, the tire pressure is set to 200
It was set to kPa. The vehicle used for the test was a sedan type middle class vehicle.

FIG. 2 is a view showing a tread pattern in which the outer surface of the tread of the tire used in the test without the sipe is viewed. The tire used in the test has three main grooves 2 formed in a tread 1 as shown in FIG. Also, ribs 3a and 3a are formed on both sides of the main groove 2 at the center of the tread, and ribs 3b and 3b at both ends form shoulder portions.

The main groove 2 at the center of the tread is formed so that its center substantially coincides with the center of the lateral width of the tread.
Further, the main grooves 2 on both sides are formed such that the centers thereof are located 40 mm laterally from the center of the main groove 2 at the center. The width of each of the three main grooves 2 is 10 m.
It is formed in m.

Next, the sipes provided on the tire will be described with reference to FIGS. FIG. 3 is a diagram showing a tread pattern of a tire of an example, (a) is a tread pattern of Example 1, (b) is a tread pattern of Example 2, and (c) is an example 3 Is a tread pattern of Example 4, and (d) is a tread pattern of Example 4. Further, FIG. 4 is a diagram showing a tread pattern of a tire of a comparative example.

The tire of Example 1 is shown in FIG.
, The ribs 3a, 3 on both sides of the central main groove 2 are
Three sipes were provided on each of a. And the rib 3a,
Each of the three sipes in 3a has a main groove 2 whose depth is in the center.
In order from 7.5 mm, 4 mm, and 2 mm. Further, the width of the sipe was set to 0.5 mm.

The tire of Example 2 is shown in FIG.
, The ribs 3a, 3 on both sides of the central main groove 2 are
Five sipes were provided on each of a. And the rib 3a,
Each of the 5 sipes in 3a has a depth equal to that of the main groove 2 in the center.
From the closest to 7.5mm, 4mm, 2mm, 4m
m, 7.5 mm.

That is, in the sipe of Example 2, the depth of the sipe formed at a position farther from the central main groove 2 is made shallower, and the depth of the sipe closest to the centers of the ribs 3a, 3a is 2 mm, which is the shallowest. The sipe is made deeper again as it approaches the adjacent main groove 2. Further, the width of the sipe was set to 0.5 mm.

The tire of Example 3 is shown in FIG.
, The ribs 3a, 3 on both sides of the central main groove 2 are
Five sipes were provided on each of a and one sipe was provided near the main groove 2 of the ribs 3b, 3b corresponding to the shoulder portion.

The five sipes on each of the ribs 3a, 3a are 7.5 mm, 4 mm, 2 mm, in order from the one whose depth is closer to the central main groove 2 as in the case of the second embodiment.
It was formed to 4 mm and 7.5 mm. The depth of the sipe of the rib 3b was 7.5 mm. The width of these sipes,
Both were 0.5 mm.

The tire of Example 4 is shown in FIG.
, The ribs 3a, 3 on both sides of the central main groove 2 are
Five sipes were provided on each of a. And the depth of these 5 sipes was 7.5 mm and made the same depth.

As for the tire of the comparative example, as shown in FIG. 4, the ribs 3a, 3a on both sides of the central main groove 2 are provided.
Only one sipe was provided in the vicinity of each of the main grooves 2. This sipe had a depth of 7.5 mm.

[Noise Test] A noise test was conducted on the above five tires. The noise test was carried out by the method specified in the standard of the tire noise test method for automobiles (JASO C 606-81). That is, as stipulated in JASO C 606-81, noise is detected by a microphone installed at a position at a predetermined distance and a predetermined ground height from the running center line on which the test vehicle is run, and the detected noise is measured according to JIS. It was measured by a sound level meter according to C 1505.

Further, when the test vehicle was run to measure the noise, the vehicle was coasted from a predetermined distance before the microphone in accordance with JASO C606-81. Regarding the vehicle speed at the time of noise measurement, the average vehicle speed obtained between predetermined positions with respect to the microphone was set as the vehicle speed at the time of noise detection.

And, 40 km / h, 60 km / h, 80
Noise was measured at three different vehicle speeds of km / h.
FIG. 5 is a bar graph showing the level difference in the vicinity of the frequency of 1 kHz of the noise measured for each of the comparative example and each example, and the vertical axis represents the unit in decibel (dB).

FIG. 5 shows the results of the comparative example and each example.
Different bar patterns are shown for each of the three speeds. In FIG. 5, (1) is the result of the comparative example,
(2) is the result of Example 1, (3) is the result of Example 2, (4) is the result of Example 3, and (5) is the result of Example 4.

As shown in FIG. 5, the noise level of each of Examples 1 to 4 is lower than that of Comparative Example.

Further, of the first to fourth embodiments, the fourth embodiment has the lowest noise level. Further, comparing Examples 2 to 4 in which one rib 3a is provided with five sipes, Example 2 and Example 4 have lower noise levels than Example 3. From this, in order to reduce noise,
It can be said that it is more preferable not to provide sipes on the shoulder portion.

[Steering Stability Test] A steering stability test was conducted on each of the tires of Examples 1 to 4 and Comparative Example. In carrying out this test, each tire was assembled on a rim of 5 × 5J at an air pressure of 200 kPa and mounted on a sedan type middle class vehicle.

Then, on this vehicle, an actual vehicle feeling test (straight ahead, lane change, handling stability) was carried out by a paneler on a dry test course. The results are shown in Table 1.

[0052]

[Table 1] The results shown in Table 1 are evaluations of the steering stability of Examples and Comparative Examples on a 10-point scale, and show that the larger the value, the better the steering stability. According to the results of Table 1, Example 1 and the comparative example with few sipes have the best steering stability, and Example 4 in which a deep sipe is provided even at a position far from the circumferential groove has the lowest steering stability. Is shown.

[0053]

As described above, according to the pneumatic tire of the present invention, by providing a plurality of sipes in one land portion surrounded by a plurality of grooves of the tire tread, the noise outside the vehicle caused by the tire is reduced. The effect that it can be made to be able to be exhibited. Further, since it is not necessary to reduce the volume of the groove, the noise can be reduced without lowering the drainage property of the tire.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view of a tire showing a structure of a tread portion.

FIG. 2 is a diagram showing an appearance of a rib pattern of a tread portion of a tire of an example.

FIG. 3 (a) is a diagram showing an appearance of a tread pattern of Example 1. FIG. 3B is a view showing the outer appearance of the tread pattern of the second embodiment. FIG. 3C is a view showing the outer appearance of the tread pattern of Example 3. Figure 3
(B) is a figure showing the appearance of the tread pattern of Example 4.

FIG. 4 is a diagram showing an appearance of a tread pattern of a tire of a comparative example.

FIG. 5 is a diagram showing results of noise tests of tires of Examples and Comparative Examples.

[Explanation of symbols]

1 tread section 2 main groove 3a rib 3b Rib (shoulder) 4 sipes 10 tires

Claims (5)

[Claims] 1. A pneumatic tire provided with a tread having a plurality of circumferential grooves extending in the circumferential direction and a land portion divided by the circumferential grooves, wherein the pneumatic tire is formed in at least one land portion in the circumferential direction. A plurality of sipes are provided, and the plurality of sipes of the one land portion include those having different depths, and are formed so that the depth becomes shallower as the distance from the circumferential groove increases. A pneumatic tire characterized in that 2. The sipe formed on the one land portion is 3
The pneumatic tire according to claim 1, wherein the pneumatic tire is equal to or more than a book. 3. The sipe formed on the one land portion is 5
The pneumatic tire according to claim 2, wherein the pneumatic tire is equal to or less than a book. 4. The pneumatic tire according to claim 1, wherein a sipe is not provided on a shoulder portion of an end portion in the tire width direction of the land portion. 5. The pneumatic tire according to claim 1, wherein the tire pattern of the tread is a rib pattern formed by connecting ribs in the circumferential direction in the land portion. .