JP5533239B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire having a narrow groove on a tread surface.

Studless tires are provided with a large number of narrow grooves having a small width on the tread surface in order to enhance the edge effect.
In addition to the edge effect, the narrow groove also exhibits a drainage function for taking in water that could not be excluded by the wide groove.

JP2009-1176 JP2009-120055

On the other hand, when the width of the narrow groove is reduced, the tread rubber of the studless tire is softer than that of the summer tire, so that the opening of the narrow groove is likely to be blocked by a load load at the time of tire contact.
If the opening of the narrow groove is closed, it is difficult to take in water from the road surface, and it is difficult to discharge water taken into the groove, so there is room for improvement in improving the drainage function and improving wet performance. there were.
The present invention has been devised in view of the above circumstances, and an object of the present invention is to improve the wet performance even when the opening of the narrow groove is closed by devising the shape of the narrow groove. The purpose is to provide tires.

In order to achieve the above-mentioned object, the present invention provides a pneumatic system provided with a narrow groove formed on a tread surface so as to be opened through the opening portion, and the opening portion being closed by a load applied at the time of tire contact. In the tire, the narrow groove has a width of 3.0 mm or more and less than 5.0 mm, and the opening is closed on one or both of the parallel facing walls constituting the narrow groove. fine grooves opened recess on the tread surface that communicates with the portion of the bottom near the plurality et been at intervals in the extending direction of the narrow groove of the wall surface, the angle θ relative to the normal perpendicular to the tread surface Is −5 degrees ≦ θ ≦ + 5 degrees, more preferably 0 degrees ≦ when the inclination angle in the direction in which the lower ends of the wall surfaces approach each other is − (minus) and the inclination angle in the direction away from each other is + (plus). θ ≦ 3 degrees, The width of the groove is a, the dimension to the bottom of the recess in the direction farthest from the wall surface facing the recess is b, and the width of the recess along the extending direction of the narrow groove is c. When the dimension along the extending direction of the narrow groove on the wall surface where the concave portion is not formed between the concave portions is d, a to d are 0.3 ≦ a / b ≦ 0.9 (formula 1 ) And 0.3 ≦ c / d ≦ 0.9 (formula 2) .

  In the present invention, even when the opening is closed at the time of tire contact, water on the road surface can be easily taken into the narrow groove from the recessed portion, and the water taken into the groove can be easily discharged from the recessed portion. Can improve wet performance.

(A) is a plan view of a narrow groove in which an arc-shaped recess is formed, (B) is a plan view of a state where the opening of the narrow groove is closed by a load applied at the time of tire contact, and (C) is a triangular shape It is a top view of the narrow groove in which the recessed part was formed. 1E is a cross-sectional view taken along line EE in FIG. 1, FIG. 1F is a cross-sectional view taken along line FF in FIG. 1, FIG. 1G is a cross-sectional view taken along line GG in FIG. FIG. 1I is an explanatory diagram of a modified example of the recess. It is explanatory drawing of a narrow groove. It is a top view of the narrow groove in which the circular-arc-shaped recessed part was formed. It is a figure which shows an evaluation result. It is a figure which shows a tread pattern provided with a thin groove.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
As shown in FIG. 6, the tread portion 12 of the studless tire 10 is provided with a pair of longitudinal grooves 16A extending in the tire circumferential direction at a location near the shoulder portion 14 of the tread portion 12, and the longitudinal grooves 16A Crossing lateral grooves 16B are provided at intervals in the tire circumferential direction. Further, an inclined narrow groove 18 that connects between the inner ends of each lateral groove 16B is provided, and an inclined narrow groove 20 that connects between the intermediate portions of the lateral groove 16B is provided between the narrow groove 18 and the longitudinal groove 16A. It has been.
The tread portion 12 includes a center rib 12A extending on the tire equator C and blocks arranged in the circumferential direction on both sides of the center rib 12A by the longitudinal grooves 16A, the lateral grooves 16B, and the narrow grooves 18, 20. A land portion 24 composed of one block row 12B, a second block row 12C, and a third block row 12D is partitioned, and a sipe 26 is provided on a tread surface 1202 of the land portion 24.
In the present embodiment, the narrow groove that is the subject of the present invention is an inclined narrow groove 20 that connects between the intermediate portion of the transverse groove 16B between the narrow groove 18 and the longitudinal groove 16A.

The hardness of the rubber in the tread portion constituting the tread surface 1202 is 42 or more and 57 or less as measured by a JIS 6253 A type durometer in an atmosphere of 20 ° C.
This is because if the hardness of the rubber is less than 42, the edge effect of the fine groove 20 becomes insufficient, and if the hardness of the rubber exceeds 57, the fine groove 20 becomes difficult to collapse.

As shown in FIGS. 1A and 2E, the narrow groove 20 is formed by a wall surface 2002 facing each other and a bottom surface 2004 connecting the lower portions of the wall surface 2002, and an opening 2006 is formed in the tread surface 1202. Is open through.
The narrow groove 20 has a small width, and as shown in FIGS. 1 (B) and 2 (G), the block-shaped portion 1204 forming the wall surface 2002 is deformed by a load applied at the time of tire contact and the opening 2006 is closed. The
In the present invention, the narrow groove 20 which is a target preferably has a width of 1.0 mm to 5.0 mm. When the width of the narrow groove 20 is less than 1.0 mm, the drainage function is not sufficiently exhibited, and when the width exceeds 5.0 mm, the possibility that the opening 2006 is blocked when the tire contacts the ground is reduced. It is.
The narrow groove 20 may extend linearly, or may extend in a curved shape or a zigzag shape.

  Further, as shown in FIG. 3, the angle θ of the wall surface 2002 with respect to the normal line 22 perpendicular to the tread surface 1202 is − (minus) as the inclination angle in the direction in which the lower ends of the wall surface 2002 approach each other, When the angle is + (plus), −5 degrees ≦ θ ≦ + 5 degrees is preferable, and 0 degrees ≦ θ ≦ 3 degrees is more preferable. When the angle θ is −5 degrees or less, the groove volume when the opening 2006 is closed cannot be secured, which is disadvantageous in improving the wet performance. Further, if the angle θ exceeds 5 degrees, the removal from the mold after vulcanization of the tire becomes worse, and manufacturing problems such as chipping of the block occur. Therefore, if the angle θ with respect to the normal line 22 orthogonal to the tread surface 1202 is within the above-described range, the block-shaped portion 1204 forming the wall surface 2002 is deformed by a load load at the time of tire contact and the opening 2006 is closed. At this time, the groove volume in the narrow groove 20 can be secured, which is advantageous in improving the wet performance.

As shown in FIGS. 1 (A) and 2 (F), one or both of opposing wall surfaces 2002 constituting the narrow groove 20 are spaced apart in the extending direction of the narrow groove 20 and are opened to the tread surface 1202. A plurality of recesses 30 are provided.
As shown in FIGS. 1 (B) and 2 (G), the recessed portion 30 is in a state where the block portion 1204 forming the wall surface 2002 is deformed by a load load at the time of tire contact and the opening portion 2006 is closed. As shown in FIG. 2H, the narrow groove 20 communicates with a portion near the bottom surface 2004.
Thereby, even when the opening portion 2006 is closed, water on the road surface is easily taken into the narrow groove 20 from the concave portion 30, and water taken into the narrow groove 20 is easily discharged from the concave portion 30. Improves drainage function and improves wet performance.
As shown in FIG. 2 (F), the depth of the recess 30 may be the same as that of the narrow groove 20, and gradually increases as the distance from the narrow groove 20 increases as shown in FIG. 2 (I). May be reduced. When the recess 30 is formed to have the same depth as that of the narrow groove 20, the recess 30 is formed by a wall surface 3002 made of a cylindrical surface, for example, and as the depth of the recess 30 increases from the narrow groove 20. When the depth is gradually reduced, the recess 30 is formed by a wall surface 3002 made of a conical surface, for example.
In addition, the outline of the recessed part 30 cut | disconnected by the plane orthogonal to the depth direction of the narrow groove 20 is not limited to the circular arc shape shown to FIG. 1 (A), (B), The triangle shown to FIG. It may be a rectangle or the like.

When the concave portions 30 are provided on both of the opposing wall surfaces 2002, the concave portions 30 may be provided so as to face each other, or the phases may be shifted in the extending direction of the narrow grooves 20 so that the concave portions 30 do not interfere with each other. Also good.
In the present embodiment, the phase is shifted in the extending direction of the narrow groove 20 so that the concave portions 30 do not interfere with both of the opposing wall surfaces 2002.
When providing the recessed part 30 in both the wall surfaces 2002 which oppose, the location where the wall surfaces 2002 in which the recessed part 30 does not exist opposes is provided. The length L (see FIG. 1 (A)) along the extending direction of the narrow groove 20 at the location where the wall surfaces 2002 where the concave portion 30 does not exist is preferably 2 mm or more. When the length L is 2 mm or less, the block portions 1204 forming the wall surface 2002 cannot be supported by each other when the opening 2006 is closed, and the volume of the recess 30 is reduced.

Further, as shown in FIG. 4, the width of the narrow groove 20 is a, the dimension to the bottom of the concave portion 30 in the direction farthest from the wall surface 2002 where the concave portion 30 is opposed is b, and the narrow groove 20 extends in the extending direction. When the width of the concave portion 30 along the c is c and the dimension along the extending direction of the narrow groove 20 of the wall surface 2002 where the concave portion 30 is not formed between the adjacent concave portions 30 is d, the following formula 1 and formula 2 is preferably satisfied.
0.3 ≦ a / b ≦ 0.9 (Formula 1)
0.3 ≦ c / d ≦ 0.9 (Formula 2)
This is because when a / b> 0.9 and 0.3> c / d, the volume ratio of the recess 30 to the narrow groove 20 is small, so that the drainage function cannot be expected, and the WET performance is ensured. This is because it becomes difficult.
Further, when a / b <0.3, the block rigidity is reduced, and when 0.9 <c / d, there is a recess 30 that contacts when the opening 2006 is closed. The length L along the extending direction of the narrow groove 20 at the location where the non-walled surfaces 2002 face each other is shortened. For this reason, when the opening 2006 is closed, the amount of deformation of the block-shaped portion 1204 that forms the wall surface 2002 increases, the volume of the recess 30 itself decreases, and the drainage function cannot be expected.

A prototype studless tire with a tire size of 225 / 65R17 in which the tread pattern shown in FIG. 6 and the narrow groove 20 and the concave portion 30 (arc-shaped concave portion 30 shown in FIG. 1) having the specifications shown in FIG. Performance was evaluated.
The evaluation is performed on the WET turning test road, the water depth is 1 mm, the turning radius is 30 m, the turning speed is 5 laps at the highest speed within the grip travel range, and the maximum and minimum values are excluded from the speed for each lap. The average speed of minutes was calculated. The calculation result is displayed as an index with the conventional example being 100, and the larger the value, the better the WET turning performance.

From FIG. 5, it is clear that the WET turning performance can be improved by providing the recess 30 in the narrow groove 20 in which the opening 2006 is closed by a load applied at the time of tire contact.
Moreover, it is clear from Examples 2-5 that it is advantageous when improving said WET turning performance that said dimension ad satisfy | fills said Formula 1 and Formula 2.

  20... Fine groove, 2002... Wall surface, 2006.

Claims (3)

In a pneumatic tire provided with a narrow groove that is formed on a tread surface so as to be opened to the tread surface via an opening, and the opening is closed by a load load at the time of tire contact,
The narrow groove has a width of 3.0 mm or more and less than 5.0 mm,
On one or both of the walls facing each other in parallel with each other, the recessed portion opened to the tread surface communicating with the portion near the bottom of the narrow groove with the opening closed is formed on the narrow groove. plurality et been at intervals in the extending direction of the groove,
The angle θ of the wall surface with respect to the normal line orthogonal to the tread surface is −5 degrees when the inclination angle in the direction in which the lower ends of the wall surfaces approach each other is − (minus) and the inclination angle in the direction away from each other is + (plus). ≦ θ ≦ + 5 degrees, more preferably 0 degree ≦ θ ≦ 3 degrees,
The width of the narrow groove is a, the dimension to the bottom of the recess in the direction farthest from the wall facing the recess is b, the width of the recess along the extending direction of the narrow groove is c, When the dimension along the extending direction of the narrow groove on the wall surface where the concave portion is not formed between the adjacent concave portions is defined as d, a to d are 0.3 ≦ a / b ≦ 0.9 ( Satisfying Formula 1) and 0.3 ≦ c / d ≦ 0.9 (Formula 2),
A pneumatic tire characterized by that. The hardness of the rubber of the tread portion constituting the tread surface is 42 or more and 57 or less in hardness measured with an A type durometer of JIS 6253 in an atmosphere of 20 ° C.,
The pneumatic tire according to claim 1.   The length along the extending direction of the narrow groove at the location where the wall surfaces where the recess does not exist is 2 mm or more,
  The pneumatic tire according to claim 1 or 2, characterized in that.

Images