JP4457735B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire, and more particularly, to a pneumatic tire in which noise performance is improved.

  One of the tire noise is air column resonance. This air column resonance sound is a sound generated by an air column resonance phenomenon in which a groove formed on the tread surface forms an air column tube at the time of ground contact, and resonance vibration occurs when air passes through the air column tube. The main groove extending in the tire circumferential direction in order to ensure the performance has a large groove volume, and thus greatly affects the air column resonance sound.

  Therefore, conventionally, in order to reduce the air column resonance noise, a technique has been proposed in which an elastically deformable fin portion is provided in the main groove so as to close the main groove. Protruding a fin in the main groove reduces the flow rate of air flowing through the main groove during ground contact and causes turbulence, thereby suppressing air column resonance and reducing air column resonance noise. On the other hand, when running on a wet road surface, the fin portion is elastically deformed by the hydrodynamic pressure of water flowing in the main groove, and the wet performance is ensured by preventing the main groove from being blocked (for example, Patent Document 1). reference).

By the way, in recent years, vehicle noise in the vicinity of highways is becoming a serious social problem, and further improvement in noise performance is demanded not only for the vehicle itself but also for tires attached to the vehicle.
JP-A-3-276802

  An object of the present invention is to provide a pneumatic tire capable of improving tire noise due to air column resonance while ensuring wet performance.

  The present invention that achieves the above object provides a tread surface with a main groove extending in the tire circumferential direction, a land portion is formed by dividing the main groove, and a sipe that opens to the main groove is formed on the tread surface of the land portion. In the pneumatic tire provided at a predetermined interval in the tire circumferential direction, a thin film extending adjacent to the opening of the sipe and extending along the opening is provided on the wall surface of the main groove.

  According to the present invention described above, when the tread surface contacts the road surface, the air flowing in the main groove blocked by the road surface is reduced in flow rate by the thin film and becomes turbulent. In addition to being able to reduce air column resonance noise, the thin film is a film-like body with low rigidity. Since the sound enters and is absorbed, air column resonance can be further reduced.

  On the other hand, when running on a wet road surface, the thin film is elastically deformed by the hydrodynamic pressure of water flowing in the main groove and sticks to the wall surface, so that the water flow in the main groove is not substantially inhibited, so that wet performance can be ensured. .

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 shows an embodiment of a pneumatic tire according to the present invention, in which a plurality of main grooves 2 extending straight along a tire circumferential direction T are provided on a tread surface 1, and ribs ( (Land part) 3 is divided and formed. The tread surface 3a of each rib 3 on both sides of the main groove 2 has end portions 3b of the rib 3 facing the main groove 2 and sipes 4 having one end opened in the main groove 2 along the tire circumferential direction T. It is provided at a position facing each other at a predetermined interval.

  As shown in detail in FIG. 2, both wall surfaces 2A and 2B of each main groove 2 are adjacent to only one side of the opening 4a of the sipe 4, and the groove bottom of the main groove 2 from the tread surface 3a along the opening 4a. A rubber thin film 5 extending to the side is integrally projected. The wall surface 4b on one side of the sipe 4 and the opening-side surface 5a of the thin film 5 are on the same plane and are flush with each other. The pneumatic tire having the thin film 5 projecting on one side of the opening 4a of the sipe 4 is mounted on the vehicle so as to be in the tire rotation direction R shown in FIG.

  In the above pneumatic tire, when the tread surface 1 contacts the road surface, the air flowing in the main groove 2 blocked by the road surface is reduced in flow rate by the thin film 5 and becomes turbulent. While suppressing the air column resonance noise, the thin film 5 is a film-like body having low rigidity, so that the thin film 5 itself can exhibit an effect as a sound absorbing material. Since air enters the sipe 4 and is absorbed, air column resonance can be further reduced.

  Further, when running on a wet road surface, the thin film 5 is elastically deformed by the hydrodynamic pressure of the water flowing in the main groove 2 and sticks to the wall surfaces 2A and 2B, so that the flow of water in the main groove 2 is not substantially hindered. Can be secured.

  Further, as shown in FIG. 3, the thin film 5 is provided with a slit 8 for forming a thin film at a portion of the main groove forming blade 6 adjacent to the base of the sipe forming blade 7 protruding from the main groove forming blade 6 of the mold. Thus, the rib 3 is integrally formed, but the one wall surface 4b of the sipe 4 and the opening-side surface 5a of the thin film 5 are flush with each other, so that the one surface 7a of the sipe molding blade 7 and the slit 8 are formed. The other wall surface 8a is flush. Therefore, the thin film 5 is easily removed when the mold is removed from the tire after vulcanization, and the thin film 5 can be prevented from being broken.

  FIG. 4 shows another embodiment of the pneumatic tire of the present invention. In the thin film 5 described above, the thin film 5B protruding from one wall surface 2B of the main groove 2 is provided only on one side of the opening 4a of the sipe 4. On the other hand, a thin film 5A protruding from the other wall surface 2A of the main groove 2 is provided only on the other side of the opening 4a of the sipe 4. In addition, the same component as the said embodiment attaches | subjects the same code | symbol, and abbreviate | omits description. The same applies to the embodiments shown in FIGS.

  Providing the thin film 5 in this way can also improve tire noise due to air column resonance while ensuring wet performance. The pneumatic tire can be mounted on the vehicle without specifying the tire rotation direction.

  FIG. 5 shows still another embodiment of the pneumatic tire of the present invention, in which the above-described thin film 5 is provided adjacent to both sides of the opening 4 a of the sipe 4. Providing the thin film 5 in this way can also improve tire noise due to air column resonance while ensuring wet performance.

  FIG. 6 shows still another embodiment of the pneumatic tire of the present invention. In the embodiment of FIG. 2, it is adjacent to one side of the opening 4a of the sipe 4 provided at a position shifted with respect to the tire circumferential direction T. Thus, a thin film 5 is projected. Thus, the sipe 4 in the shifted position may be used without facing the sipe 4 on both sides of the main groove 2. The embodiment shown in FIGS. 4 and 5 can be similarly performed.

  In the present invention, the thickness of the thin film 5 is preferably 0.1 to 2.0 mm. If the thickness is less than 0.1 mm, the mold cannot be easily removed and the thin film 5 is easily damaged. On the contrary, if the thickness exceeds 2.0 mm, the sound absorbing effect by the thin film itself cannot be exhibited, which is not preferable. The thickness is preferably 0.1 to 1.0 mm, more preferably 0.1 to 0.5 mm.

  The ratio of the cross-sectional area of the thin film 5 to the cross-sectional area of the main groove 2 can be 3 to 90%. When the thin film 5 is inclined with respect to the direction of the normal to the tread surface 3a, the cross-sectional area of the thin film 5 is an area obtained by projecting the thin film 5 from the tire circumferential direction T onto the cross section of the main groove 2. .

  If the ratio of the cross-sectional area of the thin film 5 is less than 3%, it is difficult to improve air column resonance. On the other hand, if it exceeds 90%, the flow of water in the main groove 2 is likely to be inhibited, and the wet performance is deteriorated. Preferably, it is 5 to 30%, more preferably 10 to 15%.

  2 and 5, in the tire circumferential direction T, in the case of the thin film 5 at the same position where both wall surfaces 2A and 2B of the main groove 2 face each other, the cross-sectional area of the thin film 5 is the wall surfaces 2A and 2B. The total cross sectional area of the two thin films 5. As shown in FIGS. 4 and 6, when the thin films 5 on both wall surfaces 2 </ b> A and 2 </ b> B are displaced in the tire circumferential direction T, the cross-sectional area of the thin film 5 is the cross-sectional area of each thin film 5.

  The sipe 4 is preferably provided at intervals of 5 to 10 mm along the tire circumferential direction in order to exhibit a high edge effect by the sipe 4. If the distance is less than 5 mm, the rigidity of the rib ends becomes too low, which is not preferable. Conversely, when it exceeds 10 mm, it becomes difficult to exhibit a high edge effect.

  As shown in the figure, the thin film 5 is preferably provided for each sipe 4 in order to achieve a high noise reduction effect. However, the thin film 5 may be provided randomly without being provided for each sipe 4, and the tread surface 1 is provided on the road surface. It is possible to provide at least one in each main groove 2 in the grounded ground plane.

  In the illustrated example, the sipe 4 extends from the tread surface 3a into the rib 3 along the normal direction with respect to the normal direction to the tread surface 3a where the sipe 4 is located. Further, it may be inclined in a range of 45 ° or less with respect to the normal direction. When the sipe 4 is inclined at an angle of more than 45 ° with respect to the normal direction, the detachment from the mold becomes worse, and the rib ends are easily damaged. Along with the inclination of the sipe 4, the thin film 5 formed along the opening 4a also has a range of 0 to 45 ° with respect to the normal direction.

  In the above embodiment, a pneumatic tire having a rib pattern in which the ribs 3 are formed on the tread surface 1 by the main grooves 2 is illustrated. However, the ribs 3 are formed on the land portion including blocks by the lateral grooves extending in the tire width direction. It may be a pneumatic tire having a block pattern, or may be a pneumatic tire having a tread pattern in which ribs and blocks are mixed.

  The present invention can be preferably used for a heavy-duty pneumatic tire used for buses, trucks, and the like that have particularly high tire noise, but is not limited thereto, and may be a pneumatic tire used for other applications. .

  A tire of the present invention having the structure shown in FIG. 4 having a tire size of 295 / 75R22.5 14PR and a tread pattern common to those of FIG. 1 and having a thin film and a comparative tire having no sipes were prepared.

  In each test tire, the thickness of the thin film is 0.2 mm, the ratio of the cross-sectional area of the thin film to the cross-sectional area of the main groove is 15%, and the sipe interval is 5 mm.

When each of these test tires was subjected to a noise performance evaluation test by the following test method, the results shown in Table 1 were obtained.
Noise performance Each test tire is mounted on a rim having a rim size of 22.5 × 8.25, and the air pressure is set to 760 kPa) and attached to a drum tester. Under conditions of a load of 27.47 kN and a speed of 80 km / h, JASO C606-81 It carried out in conformity with. The results are shown as index values with the comparative tire as 100. The smaller this value, the smaller the tire noise and the better the noise performance.

表１から、本発明タイヤは、騒音性能を改善できることがわかる。

Table 1 shows that the tire of the present invention can improve the noise performance.

It is a principal part expanded view of the tread surface which shows one Embodiment of the pneumatic tire of this invention. It is a principal part expansion perspective view of FIG. It is principal part sectional drawing of the metal mold | die explaining the effect of this invention. It is a principal part expansion perspective view in other embodiment of the pneumatic tire of this invention. It is a principal part expansion perspective view in further another embodiment of the pneumatic tire of this invention. It is a principal part expansion perspective view in further another embodiment of the pneumatic tire of this invention.

Explanation of symbols

1 tread surface 2 main groove 2A, 2B groove wall 3 rib (land)
3a tread surface 3b end portion 4 sipe 4a opening 4b wall surface 5, 5A, 5B thin film 5a opening side surface T tire circumferential direction

Claims (10)

  A main groove extending in the tire circumferential direction is provided on the tread surface, and a land portion is divided and formed by the main groove, and sipes that open to the main groove are provided at predetermined intervals in the tire circumferential direction on the tread surface of the land portion. A pneumatic tire according to claim 1, wherein a thin film extending adjacent to the opening of the sipe and extending along the opening is provided on a wall surface of the main groove.   The pneumatic tire according to claim 1, wherein a wall surface of the sipe and an opening side surface of the thin film are flush with each other.   The air according to claim 1 or 2, wherein the sipe is provided on land portions on both sides of the main groove, and thin films extending along the opening adjacent to the opening of the sipe are provided on both wall surfaces of the main groove. Enter tire.   The pneumatic tire according to claim 3, wherein thin films projecting from both wall surfaces of the main groove are provided only on one side of the opening of the sipe.   4. A thin film projecting on one wall surface of the main groove is provided only on one side of the opening of the sipe, and a thin film projecting on the other wall surface of the main groove is provided only on the other side of the opening of the sipe. Pneumatic tire described in 2.   The pneumatic tire according to claim 3, 4 or 5, wherein sipes provided on land portions on both sides of the main groove are provided at facing positions.   The pneumatic tire according to claim 3, 4 or 5, wherein sipes provided on land portions on both sides of the main groove are provided at positions shifted in the tire circumferential direction.   The pneumatic tire according to any one of claims 1 to 7, wherein the thin film has a thickness of 0.1 to 2.0 mm.   The pneumatic tire according to any one of claims 1 to 8, wherein a ratio of a cross-sectional area of the thin film to a cross-sectional area of the main groove is 3 to 90%. The pneumatic tire according to any one of claims 1 to 9, wherein the sipe extends from the tread surface into the land portion in a range of 0 to 45 ° with respect to a normal direction on a tread surface where the sipe is located.

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