JP6754186B2 - Pneumatic tires - Google Patents

Description

The present disclosure relates to a pneumatic tire having a closed groove in the land portion of the tread with at least one end closed.

As shown in Patent Document 1, for example, the pneumatic tire has a tread land portion defined by a main groove extending in the tire circumferential direction and a lateral groove intersecting in the circumferential direction.

Japanese Unexamined Patent Publication No. 2007-331412

As shown in FIG. 5, the land portion 50 of the tread may be formed with a closed groove 6 extending in the extending direction DD1 intersecting the circumferential direction PD and having one end closed. Since the rubber is incompressible, when a load is applied to the land portion 50 of the tread by grounding, the antinode of the wall surface of the closing groove 6 is pushed out as shown in the lower part of FIG. Since such deformation of the wall surface is an operation of closing the cross section of the groove, the air in the groove is compressed, which causes noise. For example, when the closed groove is a slit in which one end is closed and the other end is connected to the main groove, compressed air is pushed out into the main groove, and an air column resonance sound is invited. Further, for example, when the blocking groove is a dimple that closes both ends, compressed air is released at once when the land portion of the tread separates from the road surface, and noise is introduced.

The present disclosure has focused on such a problem, and an object of the present disclosure is to provide a pneumatic tire that reduces noise caused by deformation of a closed groove.

The present disclosure takes the following measures to achieve the above object.

The pneumatic tires of this disclosure are
An obstruction groove extending in the extending direction intersecting the circumferential direction and having at least one end closed is formed in the land part of the tread.
A sipe extends continuously or intermittently in the extending direction at the edge of at least one side wall of the peripheral wall of the closed groove.
The depth of the sipe has a depth of 60% or more of the depth of the closed groove.
The sipe is arranged within a range shorter than the sipe depth from the side wall.

As described above, at the edge of the side wall of the closed groove, a sipe having a depth of 60% or more of the depth of the closed groove extends continuously or intermittently in the extending direction of the closed groove, and the sipe depth is extended from the side wall. Since the sipe is arranged within a shorter range, when a force that deforms the land is applied, the sipe first collapses, and the force is difficult or not transmitted to the side wall of the closed groove, and the moment of the side wall of the closed groove. Since the deformation is suppressed, the air compression of the closed groove or the groove communicating with the closed groove is reduced. As a result, it is possible to reduce noise caused by air compression.

The tread view which shows typically the tread pattern of the pneumatic tire of this embodiment. Partially enlarged view of the tread pattern. FIG. 2A is a cross-sectional view taken along the line A1-A1 of FIG. 2A. The figure which shows the modification. The figure which shows the modification. The figure which shows the modification. The figure which shows the modification. The figure which shows the modification. The figure regarding the conventional tread pattern and its operation explanation.

Hereinafter, the pneumatic tire according to the embodiment of the present disclosure will be described with reference to the drawings.

As shown in FIG. 1, the tread of a pneumatic tire has a plurality of main grooves 51 and a plurality of lateral grooves 52, and the tread land portion 50 is divided by the main groove 51 and the lateral grooves 52. The land portion 50 of the tread is formed with a closed groove 6 also called a slit extending in the extending direction DD1 intersecting the circumferential direction PD. Note that FIG. 1 is an explanatory diagram and is abstracted, so the dimensions are not correct. In the example of FIG. 1, the tire width direction WD and the extension direction DD1 of the closing groove 6 coincide with each other.

As shown in FIG. 2A, one end of the closed groove 6 is closed and the other end communicates with the main groove 51. A sipe 7 continuously extends in the extending direction DD1 at the edge of both side walls 60 in the circumferential direction of the closing groove 6. In the present specification, the sipe means a groove having a width of 0.3 mm or more and 2.0 mm or less. In the present embodiment, the sipe 7 is linear in a plan view as shown in FIG. 2A, but may extend in a wavy or zigzag shape as shown in FIG. 3A. Further, as shown in FIG. 2A, the sipe 7 is in a continuously extended state, but as shown in FIG. 3B, the sipe 7 may be intermittently extended as shown by a broken line.

As shown in FIG. 2B, the sipe 7 extends along the tire radial direction RD perpendicular to the tread surface T. The depth d of the sipe 7 has a depth of 60% or more of the depth D of the closed groove 6. This is because when a load is applied, the deformation from the center of the closed groove 6 toward the road surface is large, and if the sipe 7 is shallower than less than 60%, the effect of suppressing the deformation of the side wall 60 of the closed groove 6 cannot be exhibited. The depth d of the sipe 7 is preferably 100% or less of the depth D of the closed groove 6.

The sipe 7 is arranged within a range shorter than the sipe depth d from the side wall 60. That is, the distance W between the sipe 7 and the side wall 60 is 1.5 mm or more and shorter than the sipe depth d. Expressed as an absolute numerical value, the distance W between the sipe 7 and the side wall 60 is preferably 1.5 mm or more and 6.0 mm or less. This is because if the distance W between the sipe 7 and the side wall 60 is large, the deformation of the land portion itself between the sipe 7 and the closed groove 6 cannot be ignored. This is because if the distance W between the sipe 7 and the side wall 60 is less than 1.5 mm, the land portion between the sipe 7 and the closed groove 6 remains without being worn.

In the present embodiment, the sipe 7 extends along the entire side wall 60 and is open to the end of the land portion (main groove 51). Of course, the sipe 7 may be terminated inside the land portion. Further, the sipe 7 is arranged along the closed end 61 of the closed groove 6 and surrounds the closed groove 6 in a U shape (U shape). Of course, the sipe 7 does not have to extend along the entire side wall 60. The total length L2 of the extension direction DD1 of the sipe 7 may be 70% or more of the length L1 of the extension direction DD1 of the side wall 60. The total length L2 of the extending direction DD1 of the sipe 7 is the total length of only the sipe 7 when the sipe 7 is intermittent as shown by the broken line, and is extended when the sipe 7 is wavy or zigzag. It is the projection length on the DD1 in the direction. In the present embodiment, since the length of the extension direction DD1 of the obstruction groove 6 is longer than the width of the obstruction groove 6, it is considered that the sipes 7 arranged at the edge of the side wall 60 dominates the noise reduction effect. ..

In the present embodiment, the sipe 7 is arranged along the closed end 61, but as shown in FIGS. 3A, 3B, 4A, and 4B, the sipe 7 is arranged along the closed end 61. It does not have to be. In the present embodiment, the sipe 7 is arranged along both side walls 60, but as shown in FIGS. 4B and 4C, the sipe 7 may be arranged along only one side wall 60. These have a reduced noise reducing effect as compared with the example of FIG. 2A, but at least have a noise reducing effect as compared with the case where the sipe 7 is formed.

The above configuration can also be applied to a closed groove in which both ends are closed in the tread land portion 50.

In order to concretely show the structure and effect of the present disclosure, the following evaluations were carried out for the following examples.

(1) Noise evaluation A test tire (tire size LT265 / 65R17) was tested on a stand-alone unit (JASO) with an air pressure of 193 kPa, a load of 8238 N, a rim used of 17 * 8-JJ, and a speed of 70 km / h, 80 km / h, and 90 km / h. C606-81) was performed. The sound pressure level was measured using a microphone installed at a height of 0.25 m at a distance of 1 m to the left of the center of the tire, and the average sound pressure level of the three speeds was obtained.

Example 1
As shown in FIGS. 1 and 2A, a U-shaped sipe 7 having a width of 0.8 mm and a depth of 8 mm was formed in a land portion 50 having a closed groove 6 having a width of 6 mm and a depth of 11 mm. .. The distance W between the sipe 7 and the side wall 60 is 2 mm. The U-shaped length of the sipe 7 with respect to the length of the side wall 60 of the closed groove 6 × 2 + the width of the closed groove 6 is 118%.

Example 2
As shown in FIG. 4C, the sipes 7 are arranged in an L shape surrounding about half of one side wall 60 and the closed end 61. The U-shaped length of the sipe 7 with respect to the length of the side wall 60 of the closed groove 6 × 2 + the width of the closed groove 6 is 58%. Other than that, it was the same as in Example 1.

Comparative Example 1
As shown in FIG. 5, the sipe 7 is not formed. Other than that, it was the same as in Example 1.

As described above, the pneumatic tire of this embodiment is
A closed groove 6 extending in the extending direction DD1 intersecting the circumferential direction PD and having at least one end closed is formed in the tread land portion 50.
A sipe 7 extends continuously or intermittently in the extending direction DD1 at the edge of at least one side wall 60 of the circumferential side wall 60 of the obstruction groove 6.
The depth d of the sipe 7 has a depth of 60% or more of the depth D of the closed groove 6.
The sipe 7 is arranged within a range shorter than the sipe depth d from the side wall 60.

In this way, at the edge of the side wall 60 of the closed groove 6, a sipe 7 having a depth d of 60% or more of the depth D of the closed groove 6 is continuously or intermittently in the extending direction DD1 of the closed groove 6. Since the sipe 7 extends from the side wall 60 and is arranged within a range shorter than the sipe depth d, when a force that deforms the land portion 50 acts, the sipe 7 is first crushed and the side wall of the closed groove 6 is crushed. Since the force is not easily transmitted to or not transmitted to the 60 and the momentary deformation of the side wall 60 of the closed groove 6 is suppressed, the air compression of the main groove 51 communicating with the closed groove 6 or the closed groove 6 is reduced. As a result, it is possible to reduce noise caused by air compression.

In the present embodiment, the total length L2 of the extension direction DD1 of the sipe 7 is 70% or more of the length L1 of the extension direction DD1 of the side wall 60. According to this configuration, since the side wall 60 covered by the sipe 7 is 70% or more, the momentary deformation of the side wall 60 of the closed groove 6 can be suppressed or prevented, and the noise reduction effect can be effectively exhibited. It becomes.

In the present embodiment, the distance between the sipe 7 and the side wall 60 is 1.5 mm or more and 6.0 mm or less. Problems caused by land between the sipe 7 and the side wall 60 can be suppressed. Problems include deformation of the wall surface of the closed groove 6 due to deformation of the land portion between the sipe 7 and the side wall 60, and that the land portion between the sipe 7 and the side wall 60 does not wear.

In this embodiment, the sipes 7 are arranged along both the circumferential wall 60s of the obstruction groove 6. According to this configuration, since the side wall 60 covered by the sipe 7 is increased, it is possible to improve the noise reduction effect as compared with the case where only one side is covered.

In the present embodiment, the sipe 7 is arranged along the closed end 61 of the closed groove 6 and surrounds the closed groove 6 in a U shape. According to this configuration, the deformation of the closed end 61 can also be suppressed or prevented, so that the noise reduction effect can be improved.

In the present embodiment, one end of the closed groove 6 is closed, and the other end communicates with the main groove 51 extending in the tire circumferential direction PD. According to this configuration, it is possible to effectively reduce the air column resonance sound caused by the compressed air being pushed out into the main groove 51.

In the present embodiment, both ends of the closed groove 6 are closed in the tread land portion 50. According to this configuration, it is possible to effectively reduce the noise caused by the compressed air being released at once when the tread land portion is separated from the road surface.

In the present embodiment, the length of the extension direction DD1 of the obstruction groove 6 is longer than the width of the obstruction groove 6, but both may be the same length.

It is possible to adopt the structure adopted in each of the above embodiments in any other embodiment.

50 ... Tread land part 6 ... Blocking groove 60 ... Side wall 61 ... Blocking end 7 ... Sipe PD ... Circumferential direction DD1 ... Extension direction

Claims (7)

An obstruction groove extending in the extending direction intersecting the circumferential direction and having at least one end closed is formed in the land part of the tread.
A sipe extends continuously or intermittently in the extending direction at the edge of at least one side wall of the peripheral wall of the closed groove.
The depth of the sipe has a depth of 60% or more of the depth of the closed groove.
Each part of the sipe is a pneumatic tire in which the distance from the side wall to each part is within a range shorter than the sipe depth at each part . The pneumatic tire according to claim 1, wherein the total length of the sipe in the extending direction is 70% or more of the length of the side wall in the extending direction. The pneumatic tire according to claim 1 or 2, wherein the distance between the sipe and the side wall is 1.5 mm or more and 6.0 mm or less. The pneumatic tire according to any one of claims 1 to 3, wherein the sipes are arranged along both the circumferential wall surfaces of the closed groove. The pneumatic tire according to claim 4, wherein the sipe is arranged along the closed end of the closed groove and surrounds the closed groove in a U shape. The pneumatic tire according to any one of claims 1 to 5, wherein the closed groove has one end closed and the other end communicating with a main groove extending in the tire circumferential direction. The pneumatic tire according to any one of claims 1 to 5, wherein both ends of the closed groove are closed in the land portion of the tread.

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