JP2011251650A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire which more improves performance on ice in an initial time of use.SOLUTION: A thin groove 40 is provided on a tread surface 10. The thin groove 40 has a width W of 0.1 to 2.0 mm in an opening and a depth of 0.1 to 1.0 mm. The thin groove 40 includes a pair of side surfaces facing each other. One side surface is formed as a standing surface 4012 standing from a bottom of the thin groove 40 along a direction of the depth of the thin groove 40 orthogonal to the tread surface 10. The other side surface is formed as an inclined surface 4014 standing from the bottom at an inclination angle θ of 15° or larger and 60° or smaller with respect to the direction of the depth of the thin groove 40. Accordingly, in the thin groove 40, a sectional form cut on a plane orthogonal to an extending direction of the thin groove 40 is asymmetrical with respect to a central line L passing the center of the width of the opening of the thin groove 40.

Description

  The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire for icy and snowy roads that can sufficiently exhibit braking / driving performance on icy roads from the beginning of use.

In pneumatic tires for icy and snowy roads such as studless tires and snow tires, fine irregularities are formed on the tread surface by, for example, mixing a filler or air bubbles into the tread rubber. These irregularities exhibit gripping power by the effect of removing the water film on the icy road, and contribute to the improvement of the running performance on the icy road.
On the other hand, new pneumatic tires for icy and snowy roads required running-in because the grip force at the time of design was not exhibited from the initial use due to the influence of the release agent attached to the tread surface.
In view of this, various types of pneumatic tires for icy and snowy roads have been proposed in which a narrow groove is provided on the tread surface and the performance on ice is sufficiently exhibited from the beginning of use (Patent Document 1, Patent Document 2, and Patent Document 3).

JP 2006-151237 A JP 2004-34902 A JP 2002-67621 A

  It is an object of the present invention to provide a pneumatic tire with improved performance on ice at the initial stage of use.

  In order to achieve the above object, the present invention provides a pneumatic tire in which a narrow groove is provided on a tread surface, and the narrow groove has an opening width of 0.1 mm to 2.0 mm and a depth of 0.1 mm. The narrow groove extends in a direction intersecting the tire circumferential direction, and the narrow groove includes a bottom surface and a pair of side surfaces that are connected to both sides of the bottom surface and face each other. One side surface of the pair of side surfaces is formed as an upstanding surface rising from the bottom surface of the narrow groove along the depth direction of the narrow groove perpendicular to the tread surface. The other side surface is formed as an inclined surface rising from the bottom surface with an inclination angle of 15 degrees or more and 60 degrees or less with respect to the depth direction of the narrow groove.

  In the present invention, the rigidity of the block-shaped portion partitioned by the narrow groove on the tread surface is improved, and the block-shaped portion is not easily collapsed. Therefore, when receiving a force from the road surface during braking or cornering, a space in the narrow groove for taking in the water film can be secured, and deterioration of the water film removal performance can be prevented.

It is an expanded view which shows the tread pattern of the pneumatic tire of this Embodiment. It is AA sectional view taken on the line of FIG. (A), (B) is explanatory drawing of a narrow groove. It is the schematic explaining the effect | action of a narrow groove. It is explanatory drawing of a narrow groove. It is explanatory drawing of the test result of a narrow groove. It is explanatory drawing of the test result of a narrow groove.

Hereinafter, an embodiment in which the present invention is applied to a studless tire will be described with reference to the drawings.
As shown in FIG. 1, four circumferential grooves including two inner circumferential grooves 12 and two outer circumferential grooves 14 are provided on the tread surface 10 of the studless tire at intervals in the tire axial direction. Yes.
Due to these four circumferential grooves, the tread surface 10 includes a center rib 16 that includes the tire equator C and extends in the tire circumferential direction, and an inner block 18 and an outer block 20 that are arranged on both sides of the center rib 16 in the tire circumferential direction. The intermediate block row 22 is formed, and a shoulder block row 26 in which shoulder blocks 24 are arranged in the tire circumferential direction between the outer end E in the tire axial direction of the ground contact surface and the intermediate block row 22 is formed.
The intermediate block row 22 is formed with a first lateral groove 28 that extends from the inner circumferential groove 12 to the outer circumferential groove 14 while being displaced in the direction opposite to the tire rotation direction R, and is adjacent to the first circumferential groove 28 in the tire circumferential direction. A second horizontal groove 30 connecting the horizontal grooves 28 is provided, and the inner block 18 and the outer block 20 are partitioned by the horizontal grooves 28 and 30.
Further, the shoulder block row 26 is formed with a third lateral groove 32 that extends from the outer circumferential groove 14 to the tire shaft direction outer end E of the ground contact surface while being displaced in the direction opposite to the tire rotation direction R. The shoulder block 24 is partitioned by 32, and the shoulder block 24 is formed with a longitudinal groove 34 connecting the third lateral grooves 32 adjacent in the tire circumferential direction.
A sipe 36 is formed on the tread surface 10 of the center rib 16, the inner block 18, the outer block 20, and the shoulder block 24.

As shown in FIGS. 1, 2, 3 (A) and 3 (B), a plurality of narrow grooves 40 are formed on the tread surface 10 of the center rib 16, the inner block 18, the outer block 20 and the shoulder block 24 in addition to the sipes 36. Has been.
The narrow groove 40 extends in a direction intersecting the tire circumferential direction so that the edge effect is exhibited.
The width W of the opening 4002 of the narrow groove 40 is 0.1 mm to 2.0 mm.
When the width W of the opening 4002 of the narrow groove 40 is less than 0.1 mm, the amount of moisture that can be taken into the narrow groove 40 is reduced, and the water film removal performance is deteriorated. In addition, if the width W of the opening 4002 exceeds 2.0 mm, the area where the tread surface 10 of the tire contacts the ground decreases, and the braking / driving performance and cornering performance at the initial use of the tire deteriorate.
The depth D of the narrow groove 40 is 0.1 mm to 1.0 mm.
When the depth D of the narrow groove 40 is less than 0.1 mm, the cross-sectional area of the narrow groove 40 is extremely reduced, the water film removal performance is remarkably deteriorated, and the tread surface is greatly deformed under high internal pressure conditions. Further, the cross-sectional area of the narrow groove 40 is further reduced, and the water film removal performance is lowered. In addition, since the narrow groove 40 exhibits the performance on ice in the initial use of the tire, a depth D of 1.0 mm is sufficient.
As shown in FIGS. 4C and 4D, a band-like block-shaped portion 42 is formed on the tread surface 10 by such adjacent narrow grooves 40, and the width of the block-shaped portion 42 on the tread surface 10 is 0. .5 mm to 2.0 mm.

As shown in FIG. 3, the narrow groove 40 has a cross-sectional shape cut along a plane orthogonal to the extending direction of the narrow groove 40 with respect to a center line L passing through the center of the width W of the opening 4002 of the narrow groove 40. It is asymmetrical.
3A includes a pair of side surfaces facing each other and a bottom surface 4010 connecting the lower ends of the side surfaces.
One side surface is formed as an upstanding surface 4012 rising from the bottom surface 4010 of the narrow groove 40 along the depth direction of the narrow groove 40 orthogonal to the tread surface 10.
The other side surface has an inclined surface 4014 rising from the bottom surface 4010 side with an inclination angle θ with respect to the depth direction of the narrow groove 40, and extends from the lower end of the inclined surface 4014 along the depth direction of the narrow groove 40. And a lower side surface 4016 reaching the bottom surface 4010.
The narrow groove 40 shown in FIG. 3B has one side surface formed as an upstanding surface 4012 that rises from the bottom surface 4010 of the narrow groove 40 along the depth direction of the narrow groove 40 perpendicular to the toret surface 10. The side surface is formed as an inclined surface 4014 rising from the bottom surface 4010 with an inclination angle θ with respect to the depth direction of the narrow groove 40.
It should be noted that the standing surface 4012 is not limited to the inclination angle θ of 0 degrees with respect to the depth direction of the narrow groove 40, and may have a slight inclination angle θ.
Moreover, the intersection of the standing surface 4012 and the tread surface 10 and the intersection of the inclined surface 4014 and the tread surface 10 are formed as corners so that the edge effect is exhibited.

  By providing the tread surface 10 with the narrow groove 40 having such a width and depth and an asymmetrical cross section, the rigidity of the block-shaped portion 42 defined by the narrow groove 40 is improved and the block-shaped portion 42 is not easily collapsed. When receiving a force from the road surface during braking or cornering, it is possible to secure a space in the narrow groove 40 for taking in the water film, and to prevent a reduction in the water film removal performance. Furthermore, it is possible to moderate the change in tire performance in the initial use when the narrow groove 40 disappears due to tire wear.

This will be described in more detail with reference to FIG.
4A and 4B show the case where the conventional rectangular narrow groove 41 is formed on the tread surface 10, and FIGS. 4C and 4D show the conventional rectangular narrow groove 41 and FIG. The case where the narrow groove 40 of the present invention having the same opening width and depth is formed is shown.
As shown in FIGS. 4A and 4B, in the case where a force F acts on the tread surface 10, in the case of a conventional rectangular narrow groove 41, a block-shaped portion 43 partitioned by the narrow groove 41. Is easy to fall, and it is difficult for water to flow into the narrow groove 41.
On the other hand, as shown in FIGS. 4C and 4D, in the narrow groove 40 of the present invention, when a force F acts on the tread surface 10, one side surface of the narrow groove 40 is an inclined surface 4014. Since it is formed, the block-like portion 42 is unlikely to fall down, and water can easily flow into the narrow groove 40. When a force directed in the direction opposite to the arrow A direction is applied, it is the same as in the case of the conventional rectangular narrow groove 41.
Therefore, according to the narrow groove 40 of the present invention, the direction of the force F can improve the drivability as compared with the prior art while ensuring the drivability as in the conventional case, or ensure the drivability as in the conventional case. However, the braking performance can be improved as compared with the conventional one.

  The narrow groove 40 is preferably extended at an angle of 45 to 90 degrees with respect to the tire circumferential direction. Extending the narrow groove 40 in such a direction is advantageous in improving braking / driving performance due to an edge effect by the block-like portion 42 partitioned by the narrow groove 40.

3A and 3B, when the narrow groove 40 is formed by the standing surface 4012 and the inclined surface 4014, the depth direction of the narrow groove 40 perpendicular to the tread surface 10 is used. Is preferably 15 degrees or more and 60 degrees or less.
If the inclination angle θ is less than 15 degrees, it is a general groove wall angle range, and sufficient rigidity of the block-like portion 42 cannot be ensured, and if it exceeds 60 degrees, the ground contact area decreases. is there.

Further, the narrow groove 40 is formed so that a cross-sectional area cut along a plane orthogonal to the extending direction of the narrow groove 40 increases or decreases along the extending direction of the narrow groove 40 in at least a part of the extending direction. May be.
In the present embodiment, as shown in FIG. 1, the intermediate portion in the extending direction of the narrow groove 40 </ b> A that is open at both ends in the extending direction without interfering with the sipe 36 at the outer portion of the vertical groove 34 of the shoulder block 24. The cross-sectional area of the narrow groove 40A is gradually increased toward the open ends at both ends.
That is, the Y portion in FIG. 1 which is an intermediate portion in the extending direction of the narrow groove 40A is formed so that the cross-sectional area is the smallest between the standing surface 4012 and the inclined surface 4014 as shown in FIG. To do.
Further, the cross-sectional area of the narrow groove 40A is gradually increased from the position Y toward the outer circumferential groove 14 or the vertical groove 34 which is the open end of the narrow groove 40A. In this case, the narrow groove 40A is formed as X in FIG. In this place, as shown in FIG. 5 (X), a bottom surface 4010, a standing surface 4012, and an inclined surface 4014 are formed.
Further, the cross-sectional area of the narrow groove 40A gradually increases from the Y position toward the outer end in the tire axial direction of the ground contact surface that is the open end of the narrow groove 40A. In the place, as shown in FIG. 5 (Z), the bottom surface 4010, the standing surface 4012, and the inclined surface 4014 are formed.

By forming the narrow groove 40 in this way, the water taken into the narrow groove 40 can easily flow toward the open end. That is, the direction of drainage of the water taken into the narrow groove 40 can be controlled, which is advantageous in improving drainage efficiency.
Note that in this embodiment, the cross-sectional area is increased or decreased without changing the width and depth of the opening 4002, but the width of the opening 4002 is in the range of 0.1 mm to 2.0 mm and the depth. However, if it is in the range of 0.1 mm to 1.0 mm, the cross-sectional area may be increased or decreased while changing the width and depth of the opening 4002.

  Further, it is known that the driving performance is more contributed to the center side than the shoulder side of the tread surface 10 and the braking performance is more contributed to the shoulder side than the center side. Therefore, in the tire in which the rotation direction is specified, when the narrow groove 40 is provided from the center portion of the tread surface 10 to the shoulder portion as in the present embodiment, the narrow groove 40 provided on the center side, If the inclined surface 4014 is positioned behind the upright surface 4012 in the rotational direction, and the narrow groove 40 provided on the shoulder side is positioned ahead of the upright surface 4012 in the rotational direction, driving performance and braking This is advantageous in improving both the performance.

A conventional example in which a test tire having a tread pattern shown in FIG. 1 with a tire size of 225 / 65R17 is attached to an RV vehicle having a displacement of 2000 cc, and a narrow groove having a shape shown in the lower column of FIG. 1, 2 and 3 were tested for braking performance and driving performance.
In addition, the rectangular narrow groove 41 was formed in the conventional example, and in the first, second, and third embodiments, the narrow groove 40 was formed by positioning the inclined surface 4014 in front of the standing surface 4012 in the rotational direction.
The braking performance is measured by braking from the running condition of 40 km / h on ice, measuring the braking distance, and using the reciprocal of the braking distance as an index with the conventional example being 100. The larger the value, the better the braking performance. It means excellent.
In addition, the driving performance shows a driver's sensitivity evaluation when stopping on a slope, applying a side brake, starting while releasing the side brake, and climbing a hill. Means that.
As is apparent from the braking performance column and the driving performance column, in Examples 1, 2, and 3, it can be seen that the braking performance can be improved as compared with the conventional example while securing the driving performance in the same manner as the conventional example. In this case, the braking performance can be improved as the inclination angle θ of the inclined surface 4014 is increased.

Similarly to the above, the braking performance and driving performance of the conventional example in which the narrow groove having the shape shown in the lower column of FIG. 7 is processed on the tread surface 10 and Examples 1 and 2 are tested, and the braking performance and driving performance are evaluated. did.
In the conventional example, the rectangular narrow groove 41 is formed, and in the first embodiment, the narrow groove 40 is formed by positioning the inclined surface 4014 in front of the standing surface 4012 in the rotational direction.
In the second embodiment, the narrow groove 40 is formed on the center rib 16, the inner block 18, and the outer block 20 located on the center side of the tread surface 10 by positioning the inclined surface 4014 behind the upright surface 4012 in the rotational direction. The narrow groove 40 was formed in the shoulder block 24 that was formed and positioned on the shoulder side of the tread surface 10 with the inclined surface 4014 positioned in front of the standing surface 4012 in the rotational direction.
As is apparent from the braking performance column and the driving performance column, in the first embodiment, the braking performance can be improved while securing the driving performance as in the conventional example. In the second embodiment, both the braking performance and the driving performance are improved. It turns out that it can improve compared with a prior art example.

  The present invention is not limited to pneumatic tires for icy and snowy roads such as studless tires and snow tires, and can also be applied to all-season tires and summer tires.

  DESCRIPTION OF SYMBOLS 10 ... Tread surface, 36 ... Sipe, 40 ... Fine groove, 4010 ... Bottom surface, 4012 ... Standing surface, 4014 ... Inclined surface, 42 ... Block-shaped part.

Claims (5)

It is a pneumatic tire with a narrow groove on the tread surface,
The narrow groove has an opening width of 0.1 mm to 2.0 mm and a depth of 0.1 mm to 1.0 mm.
The narrow groove extends in a direction intersecting the tire circumferential direction,
The narrow groove includes a bottom surface and a pair of side surfaces connected to both sides of the bottom surface and facing each other,
One side surface of the pair of side surfaces is formed as an upstanding surface that rises from the bottom surface of the narrow groove along the depth direction of the narrow groove perpendicular to the tread surface.
The other side surface of the pair of side surfaces is formed as an inclined surface rising from the bottom surface with an inclination angle of 15 degrees or more and 60 degrees or less with respect to the depth direction of the narrow groove.
The pneumatic tire according to claim 1. The narrow groove is provided from the center portion of the tread surface to the shoulder portion,
In the narrow groove provided in the center portion, the standing surface is located in front of the inclined surface in the tire rotation direction,
As for the said narrow groove provided in the said shoulder part, the said standing surface is located in the back of the rotation direction of a tire rather than the said inclined surface,
The pneumatic tire according to claim 1. The narrow groove extends at an angle of 45 degrees or more and 90 degrees or less with respect to the tire circumferential direction.
The pneumatic tire according to claim 1 or 2, characterized in that. The narrow groove is formed so that a cross-sectional area cut along a plane perpendicular to the extending direction of the narrow groove increases or decreases along the extending direction of the narrow groove in at least a part of the extending direction. ,
The pneumatic tire according to any one of claims 1 to 3, characterized in that: The increase / decrease in the cross-sectional area is repeated along the extending direction of the narrow groove,
The pneumatic tire according to claim 4.

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