JPH08268006A - Pneumatic tire - Google Patents

Abstract

PURPOSE: To reduce passage sounds in traveling by providing a sound isolation sheet consisting of a thin layer of foamed rubber having a predetermined % or more of the rate of foam occupied area and a predetermined range of the thickness in at least a groove part of a cap tread surface. CONSTITUTION: A sound isolation sheet consisting of a thin layer of foamed rubber having 20% or more of the rate of foam occupied area and 0.1-2mm of the thickness is provided at least in a groove part of a cap tread surface. Also, a sound isolation sheet consisting of a thin layer 1 having tanδ at least 10% higher than tanδ of the cap tread rubber and 0.1-2mm of the thickness is formed at least in the grove part of the cap tread part. Here, the rate of foam occupied area refers to the rate of foam occupied area to a unit area of the foamed rubber. The foamed rubber forming the thin layer 1 is foamed by combining rubber like styrene.butadiene copolymer rubber with a reinforcing filler and foaming agent for vulcanization and can be prepared by obtaining a predetermined rate of foam occupied area.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire in which passing noise (noise) during running is reduced while maintaining various characteristics required for a pneumatic tire.

[0002]

The tread portion of a pneumatic tire is generally composed of an outer layer side cap tread and an inner layer side undertread portion. Such pneumatic tires are required to have various performances, but when the vehicle is traveling, passing noise or noise is generated inside or outside the vehicle due to vibration or air pumping that occurs when the tire tread surface and the road surface come into contact with each other. Therefore, there is a proposal to prevent such passing noise (noise) from various viewpoints. For example, JP-A-63
JP-A-154410 and JP-A-1-254411 disclose that a layer of a foamed rubber composition having a foaming rate of 150% or more is provided inside the tire to reduce the noise of a pneumatic tire without impairing tire characteristics. Is proposed. However, such a proposal has not been sufficient to obtain a practically acceptable noise reduction effect.

On the other hand, JP-A-5-320423 proposes that a high modulus rubber is used for the tread to reduce road noise and passing noise without impairing steering stability. However, with this method,
There is a problem that the 0% modulus is too high and the grip performance is not sufficient. Further, in JP-A-1-269601, a thin layer of a rubber composition containing an ethylene / propylene / diene rubber and a halogenated butyl rubber is provided on the tire tread surface to form an ozone crack in the groove portion formed on the tread surface, particularly in the groove bottom portion. Although it has been proposed to prevent the occurrence of the above, the sound absorbing effect is insufficient with this.

[0004]

SUMMARY OF THE INVENTION Therefore, according to the present invention, while maintaining various characteristics required for a pneumatic tire (for example, steering stability, wet braking, wear resistance, rolling resistance, etc.), An object of the present invention is to provide a pneumatic tire with reduced passing sound (noise).

[0005]

According to the present invention, a soundproof sheet made of a thin layer of foamed rubber having a bubble occupation area ratio of 20% or more and a thickness of 0.1 to 2 mm is provided on at least the groove portion of the cap tread surface. A pneumatic tire provided is provided.

According to the invention, tan δ (-10
A pneumatic tire having a soundproof sheet made of a thin rubber layer having a thickness of 0.1 to 2 mm, which is 10% or more higher than tan δ (-10 ° C.) of a cap tread rubber, in at least a groove portion of a cap tread surface. Provided.

The present invention will be described in more detail below. According to the first aspect of the present invention, the bubble occupation area ratio is 2
0% or more, preferably 20 to 100% with a thickness of 0.1
A soundproof sheet made of a thin layer of foamed rubber having a thickness of 2 mm, preferably 1 to 2 mm is provided at least in the groove portion of the cap tread surface of the pneumatic tire. Here, the bubble occupied area ratio means an area ratio of bubbles occupied per unit area of the foamed rubber.

The foamed rubber constituting the thin layer in the first embodiment of the present invention is, for example, styrene / butadiene copolymer rubber (SBR), natural rubber (NR), polybutadiene rubber (BR), polyisoprene rubber (IR). , Ethylene-propylene copolymer rubber (EPDM) and other rubbers with reinforcing fillers (carbon, silica, etc.), and other general-purpose compounding agents with general blowing agents (eg, organic blowing agents such as benzenesulfonyl hydrazide, di- Incorporating nitrosopentamethylenetetramine, azodicarbonamide, etc., inorganic foaming agents such as sodium bicarbonate, ammonium carbonate, ammonium nitrite) and general foaming aids (eg urea, organic acids (salicylic acid, phthalic acid, etc.)) Then, vulcanization is performed by a normal tire manufacturing method to foam and obtain the above-mentioned bubble occupied area ratio. It can be prepared by. If the bubble occupying area ratio of the foamed rubber is less than 20%, the desired noise absorbing effect cannot be obtained, which is not preferable.

The layer thickness of the sound absorbing thin layer according to the present invention is 0.1.
It is ~ 2 mm, but if this layer thickness is less than 0.1 mm, the desired noise absorption effect cannot be obtained, which is not preferable. On the contrary, if it exceeds 2 mm, it is affected by the thin layer rubber, dry, wet,
It is not preferable because the wear resistance decreases. In the first aspect of the present invention, the air in the tread groove in the ground contact surface of the tire receives the pumping action of compression / release and the air column resonance sound is generated, so that the highly foamed rubber layer of the groove portion can directly absorb it. However, noise can be reduced, and other tire performances are hardly adversely affected. If there is a thin layer on the tread contact surface, it will be affected in the early stage of running, but this thin layer will be worn during the initial running and the cap will be exposed, so there is no practical problem.

According to the second aspect of the present invention, tan δ
(-10 ° C) is tan δ (-1 of cap tread rubber)
0%), 10% or more, preferably 10 to 50% higher,
A soundproof sheet made of a thin rubber layer having a thickness of 0.1 to 2 mm, preferably 1 to 2 mm is provided at least in the groove portion of the cap tread surface of the pneumatic tire. Here, tan δ is temperature −10 ° C., initial strain 10%, dynamic strain ± 2% and frequency 20.
The value measured under the condition of Hz.

The rubber constituting the sound absorbing sheet in the second aspect of the present invention is, for example, styrene / butadiene copolymer rubber (SBR), natural rubber (NR), polybutadiene rubber (BR), polyisoprene rubber (IR), It can be obtained by compounding a rubber such as ethylene / propylene copolymer rubber (EPDM) with a reinforcing filler (carbon black, silica, etc.) and other general compounding agents according to a conventional method and vulcanizing.

The layer thickness of the sound absorbing thin layer according to the present invention is 0.1.
Although it is ~ 2 mm, if this layer thickness is less than 0.1 mm, the desired noise absorption effect cannot be obtained, which is not preferable, and conversely, if it exceeds 2 mm, it is affected by the thin layer rubber, and wear resistance or rolling resistance. Is reduced, which is not preferable. In the second aspect of the present invention, the noise energy is absorbed by the thin layer rubber having a higher tan δ than the cap rubber, and the same effect as that of the foamed rubber can be obtained.

The thin rubber layer 1 constituting the sound absorbing sheet according to the present invention is attached to the surface layer of an unvulcanized rubber tread extrudate (cap rubber 2 and under rubber 3) as shown in FIG. The tire can be placed on the cap tread surface by subjecting it to tire molding by the method described above and performing vulcanization (or vulcanization foaming). When this is seen in the cross section in the tread width direction, as shown in FIG. 2, the thin rubber layer 1 is the cap rubber layer 2.
Place along the surface of. In the following examples, the tire was preliminarily run, the thin rubber layer 4 on the tread contact surface was abraded, and the cap rubber 2 was exposed for evaluation (the residual grooves were unified).

In addition to the above essential components, the thin rubber composition constituting the soundproof sheet for a pneumatic tire of the present invention contains, in addition to the above essential components, sulfur, a vulcanization accelerator, an antiaging agent, a filler, a softening agent, a plasticizer and the like. Various additives that are generally blended for tires can be blended, and such blends can be vulcanized by a general method to produce a soundproof sheet. The compounding amount of these additives may be a general amount. For example,
The content of sulfur is preferably 0.5 parts by weight or more, more preferably 0.5 to 3.0 parts by weight, based on 100 parts by weight of rubber. Carbon black can also be used in a general amount, and when silica is used as the reinforcing filler, a silane coupling agent can be used according to a conventional method.

There is no particular limitation on the cap tread material on which the soundproof sheet according to the present invention is laminated, and any rubber material conventionally used as a rubber material for tires can be used. Examples of such rubbers include diene rubbers such as NR, IR, BR, SBR, halogenated butyl rubbers, ethylene-propylene copolymer rubbers, styrene elastomers, etc., and carbon black, process oils, vulcanizing agents, etc. Although a rubber composition containing an agent can be used, it is preferable to use a low hardness rubber in order to reduce road noise. A preferred rubber has a hardness Hs (20 ° C.) of 70 or less, preferably 65
-50 are more preferable.

[0016]

The present invention will be described in more detail below with reference to Examples and Comparative Examples, but it goes without saying that the technical scope of the present invention is not limited to these Examples.

Examples 1 and 2 and Comparative Example Each component was blended according to the blending content (parts by weight) shown in Table I, and a vulcanization accelerator and a raw rubber excluding sulfur and a blending agent were prepared as follows.
After mixing for 5 minutes with a 7 liter Banbury mixer,
A vulcanization accelerator and sulfur were kneaded with this mixture for 4 minutes with an 8-inch test kneading roll machine to obtain a rubber composition. These rubber compositions were placed on an unvulcanized cap rubber as shown in FIGS.
The test pieces were placed in the same manner as shown in Table 1 and press-vulcanized at 160 ° C. for 20 minutes, and various tests were conducted and evaluated. The results obtained are shown in Table I. The compounding agents used and the evaluation methods are as shown below. As the cap rubber, the rubber compounded in Comparative Example 1 was used.

[0018]

[Table 1]

Regarding the compounding agents in Comparative Examples and Examples SBR-1 ... "Nipol 1" manufactured by Nippon Zeon Co., Ltd.
712 "(37.5 phr oil extension) (Styrene content: 23.5%, vinyl content: 15%) SBR-2 ..." Nipol 9 "manufactured by Nippon Zeon Co., Ltd.
520 "(37.5 phr oil extension) (Styrene content: 38%, Vinyl content: 14%) Carbon black ... Mitsubishi Kasei Co., Ltd." Dia Black A "foaming agent ... Dinitrosopentamethylene tetramine (Neiwa Chemical Industry Co., Ltd.)""CellularD" manufactured by Urea-based auxiliary agent ... Urea compound ("Cell Paste K5" manufactured by Eiwa Chemical Industry Co., Ltd.) Silica ... "Nipseal AQ" silane coupling agent manufactured by Nihon Silica Co., Ltd. "Si69" manufactured by Degussa Agent ... Diethylene glycol aromatic oil ... Kyo Oil Co., Ltd. “Process Oil X-140” Zinc flower… Shodo Kagaku Co., Ltd. “Zinc flower No. 3” Stearic acid… Kao Soap Co., Ltd. “Lunac Y
A "anti-aging agent ... N-phenyl-N '-(1,3-
dimethyl) -p-phenylenediam
ine (Sumitomo Chemical Co., Ltd. "Antigen 6C") Wax ... Ouchi Shinko Chemical Co., Ltd. "Sunnock" Sulfur ... N-tert-butyl-2-benz
otiazolyl-sulfenamido ("Nox Cellar NS-F" manufactured by Ouchi Shinko Chemical Co., Ltd.)

Performance evaluation method (1) Image occupancy rate was measured using NEXUS 6400 (manufactured by Kashiwagi Laboratory) at 165 times, and the average value of 10 samples was shown (unit:%). The larger the value, the higher the foam rubber. (2) tan δ (−10 ° C.) Value measured using a viscoelasticity spectrometer (manufactured by Toyo Seiki Co., Ltd.) under conditions of temperature −10 ° C., initial strain 10%, dynamic strain ± 2%, and frequency 20 Hz. Is.

The following tests are based on tire size 195/60
Performed at R14. (3) Passing noise performance It was carried out based on the acceleration noise test method defined in ISO 362. The evaluation result was shown by the difference (dB) from the reference value, using the measurement value in Comparative Example 1 as the reference value. (4) Dry steering stability Feeling of each tire by a test driver was scored on a dry road surface, and Comparative Example 1 was set to 100 and indicated as an index.
The larger the numerical value, the better the steering stability. (5) Wet braking performance Running on a sprinkled asphalt road at an initial speed of 40 km / h,
The braking distance when braking was measured, and the comparative example 1 was set to 100 and displayed as an index. The larger the value, the better the braking performance.

As is clear from the results in Table I, Comparative Example 1
Shows an example of a conventional tire, and in Examples 1 and 2, high foam rubber is used for the groove portion thin layer rubber, and an effect of improving passing sound is recognized while maintaining dry and wet performance.

Examples 3 to 5 and Comparative Examples Examples 3 to 5 shown in Table II in the same manner as Examples 1 to 2 above.
Evaluation was performed in the same manner as in Examples 1 and 2 using the thin layer rubber having the composition of. Comparative Example 1 is the same as that described above, and all were used as the compounding of Comparative Example 1 and as the cap rubber. The compounding results are shown in Table II.

[0024]

[Table 2]

As is apparent from the results in Table II, Example 3
It was confirmed that the same effects as in Examples 1 and 2 were obtained by using high tan δ rubber as the groove thin layer rubber in the formulations of 4 and 4. In addition, in Example 5, it was confirmed that the foamed rubber and the high tan δ rubber were used in combination with the groove thin layer rubber, and that the effect was further improved as compared with Example 4. If the rubbers of these examples are used as cap rubbers as they are, in the case of a highly foamed rubber, a decrease in dry and wet properties, especially a significant decrease in wear resistance is expected, and a high tan δ rubber is also expected. In this case, a decrease in wear resistance or rolling resistance is measured, which is not consistent with the gist of the present invention.

[0026]

As described above, according to the present invention,
It is possible to reduce passing noise (noise) during traveling of the pneumatic tire while maintaining various characteristics required for the pneumatic tire.

[Brief description of drawings]

FIG. 1 is a drawing (cross-section of extrudate) showing a state in which a thin rubber layer is attached to a surface layer of an unvulcanized rubber tread extrudate of a pneumatic tire according to the present invention.

FIG. 2 is a drawing showing a cross section of a tire tread of a pneumatic tire according to the present invention.

FIG. 3 is a drawing showing a state of a tread contact surface at the time of evaluation in an example of a pneumatic tire according to the present invention.

[Explanation of symbols]

 1 ... Thin rubber 2 ... Cap rubber 3 ... Under rubber 4 ... Thin rubber worn during preliminary running

Continuation of the front page (72) Inventor Shiji Fujita, Oiwake 2-1, Hiratsuka, Kanagawa Yokohama Rubber Co., Ltd. Hiratsuka Factory

Claims (3)

[Claims] 1. A pneumatic tire having a soundproof sheet made of a thin layer of foamed rubber having a bubble occupying area ratio of 20% or more and a thickness of 0.1 to 2 mm, provided in at least a groove portion of a cap tread surface. 2. A soundproof sheet comprising a thin rubber layer having a thickness of 0.1 to 2 mm and having a tan δ (-10 ° C.) higher than tan δ (-10 ° C.) of a cap tread rubber by 10% or more. A pneumatic tire provided at least in the groove. 3. The pneumatic tire according to claim 1, wherein the hardness Hs (room temperature) of the cap tread rubber is 70 ° C. or lower.