JPH04306104A - Pneumatic tire - Google Patents

Abstract

PURPOSE:To reduce noise level at the time of grounding without sacrificing a function at the time of wet condition. CONSTITUTION:On a tread part 12 of a pneumatic tire 10, a rubber material 22 (e.g. the one with 20% modulus value of 8X10<8>dyn/cm<2>) which is softer than a rubber material 21 (e.g. the one with 20% modulus value of 13X10<8>dyn/cm<2>) that forms a tread hill part 20, is provided on the entire part of the inner circumference of a main groove 14, while a ratio D of the 20% modulus value of the rubber material 22 that forms the inner circumferential part of the main groove 14, to the 20% modulus value of the rubber material 21 that forms the tread hill part 20 is 0.1<=D<=0.9, or 0.62 for example. The thickness of the rubber material 22 is not less than 0.2mm and not more than 0. 5mm, or 1mm for example.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a pneumatic tire.
In particular, the present invention relates to a pneumatic tire having a plurality of main grooves along the circumferential direction of the tire in the tread portion.

0002

[Prior Art] Conventionally, in order to improve the wet performance of tires, especially the anti-hydroplaning performance, a plurality of main grooves were formed in the tread along the circumferential direction of the tire, and the main grooves were used to prevent water from entering the ground contact surface. Pneumatic tires designed to quickly drain water are known. In particular, in recent high-performance pneumatic tires, hydroplaning is extremely likely to occur as the tires become flatter. For this reason, the width of the main groove is set to be quite large.

However, when the width of the main groove of the tread portion is set large, the air column formed by the road surface and the main groove becomes thick. For this reason, there has been a problem in that the noise level at the time of ground contact, which is caused by the resonance phenomenon of these air columns, becomes high.

0004

SUMMARY OF THE INVENTION In view of the above facts, it is an object of the present invention to provide a pneumatic tire that can reduce the noise level upon contact with the ground without deteriorating wet performance.

[0005]

[Means for Solving the Problems] In order to achieve the above object, the present invention as set forth in claim 1 provides a main groove formed along the circumferential direction of the tire in the tire tread surface of the tread portion, and a section defined by the main groove. A pneumatic tire is provided with a tread land portion, and is characterized in that a rubber material having a hardness different from that of the rubber material constituting the tread land portion is provided at the inner peripheral portion of the main groove.

[0006] In addition, the present invention as set forth in claim 2 is characterized in that the ratio of the 20% modulus value of the rubber material of the inner peripheral portion of the main groove to the 20% modulus value of the rubber material constituting the tread land portion is 0.1 or more. It is characterized by being set to 0.9 or less.

[0007] Further, in the present invention as set forth in claim 3, the ratio of the 20% modulus value of the rubber material of the inner peripheral portion of the main groove to the 20% modulus value of the rubber material constituting the tread land portion is 1.2 or more. It is characterized by being set to 3.0 or less.

[0008] The present invention as set forth in claim 4 is characterized in that the thickness of the rubber material at the inner peripheral portion of the main groove is set to 0.2 mm or more and 0.5 mm or less.

[0009]

[Operation] When a pneumatic tire runs on a dry road surface, the air flowing in the air column formed by the road surface and the main groove vibrates, generating air column resonance sound in the groove. The main source of this intra-groove air column resonance sound is high-frequency vibrations generated in the wall of the main groove. For this reason, when the high-frequency vibration frequency generated in the wall of the main groove deviates from the air columnar resonance frequency, air columnar resonance becomes less likely to occur, and the air columnar resonance sound becomes smaller. Furthermore, when the tread rubber is made softer, the high frequency vibration frequency generated on the walls of the main groove becomes smaller, and when the tread rubber is made harder, the high frequency vibration frequency generated on the walls of the main groove becomes larger.

On the other hand, if the tread rubber is made softer for the purpose of lowering the high-frequency vibration frequency generated in the wall portion of the main groove, the tread portion becomes more prone to wear and wear resistance decreases. Furthermore, when the tread rubber is made harder for the purpose of increasing the high-frequency vibration frequency generated in the walls of the main groove, grip performance, riding comfort, etc. deteriorate.

Therefore, in the pneumatic tire of the present invention as set forth in claim 1, a rubber material different from that constituting the tread land portion is formed on the inner circumferential portion of the main groove formed along the circumferential direction of the tire on the tire tread surface of the tread portion. A hard rubber material is provided so that the high frequency vibration frequency generated on the wall of the main groove deviates from the resonance frequency of the air column tube. For this reason, air columnar resonance becomes less likely to occur, and air columnar resonance sound becomes smaller. Further, since a rubber material having a hardness different from that of the rubber material constituting the tread land portion is provided only on the inner peripheral portion of the main groove, the wear resistance, grip performance, riding comfort, etc. of the tread portion will not deteriorate.

[0012] In addition, when the hardness of the rubber material at the inner circumference of the main groove is made softer than the hardness of the rubber material constituting the tread land section, the hardness within the main groove relative to the 20% modulus value of the rubber material constituting the tread land section is It is preferable that the ratio of the 20% modulus values of the rubber material in the peripheral part is 0.1 or more and 0.9 or less, and if the ratio is larger than 0.9, there is almost no effect of reducing the noise level.
Moreover, if the ratio is smaller than 0.1, peeling is likely to occur between the rubber material constituting the tread land portion and the rubber material of the inner peripheral portion of the main groove. In addition, when the hardness of the rubber material at the inner peripheral part of the main groove is made harder than the hardness of the rubber material constituting the tread land part, It is preferable that the ratio of the 20% modulus values of the rubber material is 1.2 or more and 3.0 or less; if the ratio is less than 1.2, there is almost no effect of reducing the noise level, and if the ratio is 3.0
If it is larger, the hard rubber material of the inner peripheral portion of the main groove will be extremely difficult to wear against the rubber material forming the tread land portion, and uneven wear will easily occur. Also, the thickness of the rubber material at the inner circumference of the main groove is 0.
．． It is preferable to set it to 2 mm or more and 0.5 mm or less, and 0
．． If it is less than 2 mm, there is almost no effect in reducing the noise level. Moreover, if it exceeds 0.5 mm, the load on the boundary between the hard and soft rubber will increase, making peeling more likely.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

As shown in FIG. 2, a pneumatic tire 10
Three main grooves 14 are formed in the tread portion 12 of the tire along the tire circumferential direction (vertical direction in FIG. 2) at predetermined intervals in the tire width direction (horizontal direction in FIG. 2). A plurality of tread land portions 20 are formed which are partitioned by main grooves 14 .

As shown in FIG. 1, a pneumatic tire 10
In the tread portion 12, the rubber material 21 (for example, 2
0% modulus value is 13 x 108 dyn/cm2) softer rubber material 22 (for example, 20% modulus value is 8
×108dyn/cm2), and the main groove 14
The ratio D of the 20% modulus value of the rubber material 22 constituting the inner peripheral portion of the rubber material 21 to the 20% modulus value of the rubber material 21 constituting the tread land portion 20 is 0.1≦D≦0.9 (for example,
0.62). Furthermore, the thickness of the rubber material 22 is 0.
．． It is set to be 2 mm or more (for example, 1 mm).

Next, the operation of this embodiment will be explained.

When the pneumatic tire 10 of this embodiment runs on a dry road surface, the air flowing in the air column formed by the road surface and the main groove 14 vibrates, generating groove air column resonance sound. . In this case, the pneumatic tire 1 of this embodiment
0, since the rubber material 22 that is softer than the rubber material 21 constituting the tread land portion 20 is provided on the entire inner circumference of the main groove 14, the high frequency vibration frequency generated in the wall portion 14A of the main groove 14 is transmitted to the air column. It deviates from the tube resonance frequency. For this reason, air columnar resonance becomes less likely to occur, and air columnar resonance sound becomes smaller. Furthermore, since the rubber material 22, which is softer than the rubber material 21 constituting the tread land portion 20, is provided only on the inner peripheral portion of the main groove 14, the wear resistance of the tread portion does not deteriorate.

[0018] The ratio D of the 20% modulus value of the rubber material 22 at the inner peripheral portion of the main groove 14 to the 20% modulus value of the rubber material 21 constituting the tread land portion 20 is 0.1 or more.
．． It is preferable that the ratio D be 9 or less; if the ratio D is larger than 0.9, there will be almost no effect of reducing the noise level;
If it is smaller than 1, the rubber material 2 constituting the tread land portion 20
1 and the rubber material 22 on the inner circumference of the main groove 14 is likely to separate. Further, it is preferable that the thickness of the rubber material 22 at the inner peripheral portion of the main groove 14 is 0.2 mm or more, and if it is less than 0.2 mm, there is almost no effect of reducing the noise level. Also, main groove 1
If the thickness of the rubber material 22 at the inner circumferential portion of No. 4 exceeds 0.5 mm, the burden on the boundary between the hard and soft rubber will increase, and peeling will easily occur.

A second embodiment of the present invention will be described with reference to FIG. Note that the same members as those in the first embodiment are given the same reference numerals and their explanations will be omitted.

As shown in FIG. 3, a pneumatic tire 24
In the tread portion 12, a rubber material 22 having a thickness of 1 mm, which is softer than the rubber material 21 constituting the tread land portion 20, is provided on the inner circumferential portion of the main groove 14. The ratio D of the 20% modulus value of the rubber material 22 to the 20% modulus value of the rubber material 21 constituting the tread land portion 20 is 0.62. Further, a rubber material 22 is also provided on the tread surface 20A of each tread land portion 20, which improves productivity compared to the case where a soft rubber material 22 is provided only on the inner peripheral portion of the main groove 14. . Further, the thickness of the rubber material 22 of the tread surface 20A of the tread land portion 20 is 0.5 mm, so that it wears out quickly.

Therefore, also in the pneumatic tire 24 of this embodiment, the high-frequency vibration frequency generated in the wall portion 14A of the main groove 14 deviates from the air column resonance frequency, making it difficult for air column resonance to occur, resulting in air column resonance sound. becomes smaller. In addition, since the rubber material 22 of the tread surface 20A of the tread land portion 20 wears out quickly,
The wear resistance of the tread portion 12 does not decrease significantly.

A third embodiment of the present invention will be described with reference to FIG. Note that the same members as those in the first embodiment are given the same reference numerals and their explanations will be omitted.

As shown in FIG. 4, a pneumatic tire 26
In the tread portion 12 of the main groove 14, approximately at the center in the depth direction where air columnar resonance is most likely to occur within the wall portion 14A of the main groove 14,
A rubber material 22 that is softer than the rubber material 21 constituting the tread land portion 20 is provided, and the tread land portion 2 has a modulus value of 20% of the rubber material 22 constituting the inner peripheral portion of the main groove 14.
The ratio D to the 20% modulus value of the rubber material 21 constituting 0 is 0.62.

Therefore, also in the pneumatic tire 24 of this embodiment, the high-frequency vibration frequency generated in the wall portion 14A of the main groove 14 deviates from the air columnar resonance frequency, making it difficult for air columnar resonance to occur, resulting in air columnar resonance noise. becomes smaller. Furthermore, the amount of rubber material 22 used can be reduced.

A fourth embodiment of the present invention will be described with reference to FIG. Note that the same members as those in the first embodiment are given the same reference numerals and their explanations will be omitted.

As shown in FIG. 5, a pneumatic tire 28
In the tread portion 12, the tread land portion 2 is located near the tread surface 20A of the tread land portion 20 of the wall portion 14A of the main groove 14.
A rubber material 22 that is softer than the rubber material 21 that makes up the tread land portion 20 is provided, and has a modulus of 20% of the rubber material 22 that makes up the inner peripheral portion of the main groove 14. The ratio D to the % modulus value is 0.62
It becomes.

Therefore, also in the pneumatic tire 24 of this embodiment, the high-frequency vibration frequency generated in the wall portion 14A of the main groove 14 deviates from the air column resonance frequency, making it difficult for air column resonance to occur, resulting in air column resonance sound. becomes smaller. Furthermore, when the tread land portion 20 wears out and the rubber material 22 wears out, the depth of the main groove 14 becomes shallower and the air column becomes thinner.
Air column resonance sound becomes smaller.

In each of the above embodiments, the rubber material 22 is softer than the rubber material 21 constituting the tread land portion 20.
was provided on the inner peripheral part of the main groove, but instead of this, the tread land part 2
A rubber material harder than the rubber material 21 constituting the main groove may be provided at the inner peripheral portion of the main groove. In this case, the ratio D of the 20% modulus value of the rubber material of the inner peripheral portion of the main groove to the 20% modulus value of the rubber material constituting the tread land portion is set to 1.2 or more and 3.0 or less. This means that if the ratio D of the 20% modulus value of the rubber material at the inner circumferential portion of the main groove 14 to the 20% modulus value of the rubber material constituting the tread land portion 20 is smaller than 1.2, the effect of reducing the noise level will be reduced. If the ratio D is more than 3.0, the rubber material on the inner circumference of the hard main groove 14 is extremely difficult to wear against the rubber material forming the tread land area, and uneven wear is likely to occur. It is. (Experimental example) In the pneumatic tire 10 of the first embodiment (tire size 11R22.5), the 20% modulus of the rubber material 22 at the inner circumferential portion of the main groove relative to the 20% modulus value of the rubber material 21 constituting the tread land portion By changing the value ratio D,
The sound pressure level (S.P..L) is the same as that of a conventional pneumatic tire whose entire tread portion is made of the same rubber material. P. L
is shown in FIG. 6 as 0.

According to FIG. 6, 0.1≦D≦0.9, 1.2
The preferred tire of this example with ≦D≦3.0 has S. P. It became clear that L was superior.

[0030]

As described above, the present invention has the excellent effect of reducing the noise level during ground contact without deteriorating wet performance.

[Brief explanation of drawings]

FIG. 1 is a sectional view taken along line 1-1 in FIG. 2;

FIG. 2 is a plan view showing the tread portion of the pneumatic tire according to the first embodiment of the present invention.

FIG. 3 is a sectional view corresponding to FIG. 1 showing a tread portion of a pneumatic tire according to a second embodiment of the present invention.

FIG. 4 is a sectional view corresponding to FIG. 1 showing a tread portion of a pneumatic tire according to a third embodiment of the present invention.

FIG. 5 is a sectional view corresponding to FIG. 1 showing a tread portion of a pneumatic tire according to a fourth embodiment of the present invention.

FIG. 6 shows the ratio D and S. of the 20% modulus value of the rubber material of the inner circumferential portion of the main groove to the 20% modulus value of the rubber material constituting the tread land portion. P. It is a graph showing the relationship with L.

[Explanation of symbols]

10 Pneumatic tires 12 Tread part 14 Main groove 14A Wall section 20 Tread land section 21 Rubber material 22 Rubber material 24 Pneumatic tires 26 Pneumatic tires 28 Pneumatic tires

Claims (4)

[Claims] 1. A pneumatic tire comprising a main groove formed along the circumferential direction of the tire in the tire tread surface of a tread portion, and a tread land section defined by the main groove, wherein A pneumatic tire characterized in that a rubber material having a hardness different from that of the rubber material constituting the tread land portion is provided around the periphery. 2. A ratio of a 20% modulus value of the rubber material of the inner peripheral portion of the main groove to a 20% modulus value of the rubber material constituting the tread land portion is set to 0.1 or more and 0.9 or less. The pneumatic tire according to claim 1. 3. The ratio of the 20% modulus value of the rubber material of the inner peripheral portion of the main groove to the 20% modulus value of the rubber material constituting the tread land portion is set to 1.2 or more and 3.0 or less. The pneumatic tire according to claim 1. 4. The thickness of the rubber material at the inner peripheral portion of the main groove is 0.
The pneumatic tire according to claim 1, wherein the pneumatic tire is set to 2 mm or more and 0.5 mm or less.