JP2002087021A - Pneumatic radial tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic radial tire improved in driving performance and braking performance on a low-friction road surface in a balanced manner. SOLUTION: The pneumatic radial tire has a leading groove wall angle b of lug grooves 2 of -5 to 14 deg. in blocks situated in a middle region M ranging over at least 7.5% of a tread width W from a tire equator line E toward each of tread end 10 on the right and left, a trailing groove wall angle (a) of the lug grooves 2 relative to a normal of 0 to 15 deg. larger than b, an angle α of sipes 4 of more than 0 deg. to 15 deg. in the middle region M, a leading groove wall angle d of the lug grooves 2 to a normal of -5 to 14 deg. in blocks situated in both shoulder regions S ranging over at least 15% of the tread width W from the tread ends 10 toward the tire equator line E, a trailing groove wall angle c of the lug grooves 2 of 0 to 15 deg. smaller than d, and an angle β of sipes 4 of more than 0 to 25 deg. in both shoulder regions S.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic radial tire, and more particularly, to a pneumatic radial tire having a well-balanced driving performance and braking performance on a low friction road surface.

[0002]

2. Description of the Related Art Conventionally, in a tire having a directional block pattern on a tread surface, a block wall is formed by changing a groove wall angle with respect to a normal direction of a lug groove for partitioning the block between a kicking side and a stepping side of the block. There is known a method of utilizing the shearing force of the above to more effectively exert the driving performance or the braking performance. However, in this method, either one of the driving performance and the braking performance can be improved, but it is difficult to achieve both.

Accordingly, the present applicant has previously filed an application (Japanese Patent Application No. 9-259807) for a pneumatic tire in which driving performance and braking performance are well balanced.
That is, the groove wall angle with respect to the normal direction of the lug groove on the stepping side of the block in the center area of the tire tread surface is made smaller than the groove wall angle with respect to the normal direction of the lug groove on the kick-out side, and the block in the shoulder area. A pneumatic tire was proposed in which the angle of the groove wall with respect to the normal direction of the lug groove on the stepping side was larger than the angle of the groove wall with respect to the normal direction of the lug groove on the kick side.

However, there is a demand for improved driving performance and braking performance on slippery low friction road surfaces such as wet road surfaces, and further improvements are required.

[0005]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a pneumatic radial tire having a good balance of driving performance and braking performance on a low friction road surface.

[0006]

According to the present invention, a block is defined on a tread surface by a plurality of main grooves extending in a tire circumferential direction and a plurality of lug grooves extending in a tire width direction intersecting the main grooves. To form a block pattern
A pneumatic radial tire having a sipe in the block and a designated rotation direction, wherein at least 7.5% of the contact width from the tire equator line to the right and left contact ends.
The groove wall angle b with respect to the normal direction of the lug groove on the stepping side of the block located in the central area of the above range is −5 to 14 °,
The groove wall angle a with respect to the normal direction of the lug groove on the kick-out side is
0 to 15 °, a> b, and an angle α opposite to the tire rotation direction with respect to the normal of the sipe in the central region.
Is 0 ° <α ≦ 25 °, and a groove with respect to the normal direction of the lug groove on the stepping side of the block located in each of the shoulder regions within a range of 15% or more of the contact width from the contact edge toward the tire equator line. The wall angle d is -5 to 14 degrees, the groove wall angle c with respect to the normal direction of the lug groove on the kicking side is 0 to 15 degrees, c <d, and both shoulder areas are normal to the sipe normal. When the angle β on the tire rotation direction side is 0 <β ≦
A pneumatic radial tire that is 25 ° is provided.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a plan view showing an example of a tread pattern of a pneumatic radial tire of the present invention, FIG. 2 is a cross-sectional view showing a state in which a block is in contact with a road surface during rotation of a tire in a central region M, and FIG. It is sectional drawing which shows a mode that the block contacted the road surface at the time of tire rotation in S. In FIG. 1, the tread surface T
Has five main grooves 1a, 1b, 1 extending in the tire circumferential direction.
c, 1d, and 1e are provided, and a lug groove 2 inclined in a V-shape with respect to the tire rotation direction F is provided from one ground end 10 to the other ground end 10, and these main grooves are provided. A block pattern including a plurality of blocks 3 is formed by the lug grooves. The blocks 3 are provided with sipes 4 respectively. In the pneumatic radial tire of the present invention having the tread surface T, the rotation direction is designated as one direction F.

The angle of inclination of the lug groove 2 with respect to the tire circumferential direction is preferably set in a range of ± 45 to 90 °. Also,
In FIG. 1, the lug grooves 2 are continuous without interruption, but may be interrupted without being continuous near the tire equator line E (tire center line). As shown in FIG. 2, in the central region M of at least 7.5% or more, preferably 10% to 20% of the contact width W from the tire equator line E toward the left and right contact ends 10, as shown in FIG. The groove wall angle b with respect to the normal direction of the lug groove 2 on the stepping side and the groove wall angle a with respect to the normal direction of the lug groove 2 on the kick-out side are a> b and a = 0 to 15 °, b = −5 to 14 ° is set to be in the range. Here, "Stepping side of block 3"
Means the side of the block 3 that first comes into contact with the road surface when the tire rotates, and the “kick side of the block 3” means the side of the block 3 that comes into contact with the road surface later when the tire rotates. In the case of a tire for a passenger car, the contact width W is the maximum linear distance in the tire radial direction at a contact surface with a standard rim described in the 2000 JATMA Yearbook and a flat plate loaded with 88% of the maximum load capacity at an air pressure of 180 kPa. Say.

Also, each of the contact width W from the contact end 10 to the tire equator line E is 15% or more, preferably 20% of the contact width W.
As shown in FIG. 3, in both shoulder regions S, S in the range of ３０30%, the groove wall angle d with respect to the normal direction of the lug groove 2 on the stepping side of the block 3 and the normal line of the lug groove 2 on the kick-out side. The groove wall angle c with respect to the direction is c <d and d = 0 to 15 °,
It is set so that c = −14 °.

In a tire having a directional block pattern, frictional energy during braking / driving is relatively large in a block in a shoulder region during braking and relatively large in a block in a central region during driving. Therefore, with the above configuration, the groove wall angle b of the lug groove 2 on the stepping side of the block 3 is smaller in the central area M as shown in FIG. 2, and the groove wall angle is directed outward in the tire radial direction. Therefore, the driving performance is improved because the rotation direction is closer to the rotation direction F side. On the other hand, as shown in FIG. 3, in both shoulder regions S, S, the groove wall angle c of the lug groove 2 on the kick-out side of the block 3 is smaller, and the groove wall angle is smaller in the rotation direction F toward the tire radial outside. And the braking performance is improved. This makes it possible to improve the driving performance and the braking performance in a well-balanced manner.

By providing the sipe 4 in the block 3, the driving effect and the braking performance on a slippery low friction road surface such as a wet road surface can be improved by the edge effect. Further, the angle α on the side opposite to the tire rotation direction F with respect to the normal line of the sipe 4 in the central region M is 0 ° <α ≦ 25 °, preferably 5 ° ≦ α ≦ 15 °, and the sipe of both shoulder regions S, S The angle β on the tire rotation direction F side with respect to the normal to 4 is 0 <β ≦ 25 °, preferably 5 °
By setting ° ≦ β ≦ 15 °, as shown in FIG. 2, in the central region M, the sipe 4 tilts in the rotation direction F toward the tire radial outside, so that a greater edge effect is exhibited during driving. As shown in FIG. 3, the sipe 4 inclines outward in the tire radial direction in the opposite direction to the rotation direction F in the two shoulder regions S, S, so that a greater edge effect is exhibited during braking. The braking performance can be improved.

As described above, by setting the angle of the sipe of the central region M and the shoulder regions S, S in addition to the groove wall angles of the lug grooves of the central region M and the shoulder regions S, S, the low angle can be obtained. Driving performance and braking performance on a friction road surface can be improved extremely favorably.

Further, an appropriate interval may be provided between the central area M and the shoulder areas S, S. In the area of this interval, the groove wall angles a to d of the lug groove 2 and the angle α of the sipe 4 , Β need not be set as described above.

[0014]

EXAMPLES Hereinafter, the present invention will be further described with reference to Examples, but it goes without saying that the scope of the present invention is not limited to these Examples.

Tire size 205/55 R16 89
The block pattern shown in FIG. 1 is formed on a tread surface T of a pneumatic radial tire of V, and a central region M (contact width W =
The inclination angle a of the lug groove 2 of the block 3 located in the 168 mm range of 15% on one side and both shoulder regions S, S (each region is 25% of the contact width W, and each shoulder region has the same width). d, angles α and β of sipe 4
Were changed as shown in Table 1 to produce six types of tires (conventional examples 1-2, examples 1-2, comparative examples 1-2). Note that no sipes were provided in Conventional Examples 1 and 2.

With respect to these five types of tires, the air pressure 2
At 30 kPa, it was attached to the rim 16 × 6 1 / 2JJ, and the braking performance and the driving performance were evaluated by the following method.
The results are shown in Table 1. Braking Performance Using a domestically produced 3L-class passenger vehicle equipped with an ABS braking mechanism, the braking distance from 50 km / h per hour to the stop was measured on a smooth asphalt road surface sprayed, and the index was set to 100 with Conventional Example 1 as 100. The larger the value, the better the braking performance.

Driving Performance Using a special four-wheel drive vehicle, the same driving force is applied to three wheels and a different driving force is applied to the remaining one wheel mounted with test tires on a smooth asphalt road surface to which water is sprayed. The difference was determined by detecting the front-rear force of the test tire from the driving force and determining the difference as a driving force.
Class, measurement from 50 km / h). The higher the value, the better the drive performance.

[0018]

[Table 1]

As is clear from Table 1, the tires of the examples obtained excellent results that both the braking performance and the driving performance were improved as compared with the conventional example and the comparative example.

[0020]

According to the present invention, by setting both the groove wall angles of the lug grooves on the stepping side and the kicking side of the blocks located in the central region and the shoulder region and the angle of the sipe, the driving on the low friction road surface is achieved. A pneumatic radial tire having improved performance and braking performance in a well-balanced manner can be obtained.

[Brief description of the drawings]

FIG. 1 is a plan view showing an example of a tread pattern of a pneumatic radial tire of the present invention.

FIG. 2 is a cross-sectional view showing a state in which a block is in contact with a road surface during tire rotation in a central region.

FIG. 3 is a cross-sectional view showing a state in which a block contacts a road surface when a tire rotates in a shoulder region.

[Explanation of symbols]

1a to 1e Main groove 2 Lug groove 3 Block 4 Sipe 10 Ground end T Tread surface M Central area S Shoulder area F Rotation direction E Tire equator line W Ground width

Claims (2)

[Claims] 1. A block pattern is formed on a tread surface by dividing a block with a plurality of main grooves extending in a tire circumferential direction and a plurality of lug grooves extending in a tire width direction intersecting the main grooves. A pneumatic radial tire having a sipe in the block and a rotation direction specified,
The groove wall angle b with respect to the normal direction of the lug groove on the stepping side of the block located in the central region of at least 7.5% or more of the contact width from the tire equator line to the right and left contact ends is -5 to 14 respectively. °, the groove wall angle a with respect to the normal direction of the lug groove on the kick-out side is 0 to 15 °, a> b, and the angle opposite to the tire rotation direction with respect to the normal of the central sipe. α is 0 ° <α ≦ 25 °, and 15% of the contact width from the contact end to the tire equator line, respectively.
The groove wall angle d with respect to the normal direction of the lug groove on the stepping side of the block located in both shoulder regions in the above range is -5 to
14 °, the groove wall angle c with respect to the normal direction of the lug groove on the kick-out side is 0 to 15 °, c <d, and the angle β on the tire rotation direction side with respect to the normal of the sipe in both shoulder regions. Is a pneumatic radial tire in which 0 <β ≦ 25 °. 2. The tire according to claim 1, wherein the lug groove is located at ± 45 with respect to the tire circumferential direction.
The pneumatic radial tire according to claim 1, wherein the tire is inclined at 90 degrees.