JP3182344B2 - Pneumatic tire - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire for a non-directional tire, in which the running performance in dry and wet conditions and the suppression of one-sided flow of the vehicle are improved in a well-balanced manner.

[0002]

2. Description of the Related Art In recent years, there has been a demand for improved driving stability at the time of high-speed running on a dry road surface as well as higher performance of a vehicle. In order to enhance steering stability on dry road surfaces, it is widely practiced to reduce the number of straight ribs extending in the circumferential direction and increase pattern rigidity on a tread surface.

[0003] However, by reducing the number of straight ribs, the grip force is insufficient, slipping is likely to occur on a wet road surface such as in rainy weather, and the hydro performance is reduced.

As described above, the dry running performance and the wet running performance are in a trade-off relationship, and in order to satisfy both performances, conventionally, for example, as shown in FIG. It is common to provide a lug groove that is inclined.

[0005] Such lug grooves are generally arranged symmetrically on both sides of the tire equator. However, when the lug grooves are arranged symmetrically, that is, in a C-shaped arrangement, the lug grooves of the tire are not provided. Directivity is generated in the rotation direction, and the mounting is troublesome.

For this reason, by arranging the lugs arranged on both sides in the axial direction of the tire so as to be symmetrical with respect to a point on the tire equator as shown in FIG. A non-directional tire could be formed. Further, the flow angle of the lug groove with respect to the tire equator is set to 40.
By setting it to less than the degree, the running performance in both wet and dry conditions can be stabilized.

[0007]

However, in the tire having the above-described structure, the flow angle is reduced, so that the effect of the pattern appears during traveling, and the value of the residual CF generated on the tread surface increases. A problem arises in that flow occurs.

[0008] The cause of such residual CF is as follows.
In a tire having a so-called conical ratio in which a radial difference occurs on both sides in the tire axial direction with respect to the tire equator as a center, when the tire freely rolls, a block arranged mainly in a shoulder region has a rotation direction of the tire in this shoulder region. Is applied in the braking direction due to the fact that the radius is smaller than the radius of the trad surface in the rotation direction, a torque M1 in the direction shown in FIG. 5A is generated. When the flow angle of the lug groove is small, FIG.
As shown in (B), the generation of torque also increases, and it is necessary to apply a force for steering the steering wheel even during straight running.

In order to solve one of these problems, Japanese Patent Application Laid-Open No. 2-147416 proposes changing the inclination angle of a lateral groove forming a block with respect to a tire axis between a central portion and a side portion of a tread portion. -193607
In Japanese Patent Application Laid-Open No. H11-163, a proposal has been made in which the inclination of the siping is different between the crown region and the shoulder region. However, none of the above proposals has solved the above problem completely, though the residual CF is slightly reduced.

The inventor of the present invention has adopted a pattern of rib lugs in which the circumferential groove is limited to the crown region and the lug groove has a steep flow gradient. It is an object of the present invention to provide a pneumatic tire capable of improving both wet and dry running performance and suppressing one-sided flow of a vehicle in a well-balanced manner based on different inclination angles of the groove walls.

[0011]

According to the present invention, a tread groove having a circumferential groove extending in a circumferential direction and a plurality of lug grooves extending from a tread edge is provided on a tread surface.
A non-directional pattern that is arranged point-symmetrically at the above points, and is mounted on a regular rim and applied with a regular internal pressure and a regular load. The circumferentially extending rib is sandwiched only in a central region between inner lines passing circumferentially through a 1/8 point that is axially separated from the tire equator C by a distance of 1/8 of the total contact width SW, which is a distance from the tire equator C. A block is formed on both sides of the tire equator C by providing at least one pair of the circumferential grooves and connecting an outer circumferential groove located closest to the tread edge to the lug groove, and the lug groove intersects the inner line. Intersection A
When, along with the line segment AB connecting the point of intersection B which lug grooves intersect is less and 40 degrees 10 degrees the flow angle θ of the lug groove formed between the tire equator C to the outside line through the ground end in the circumferential direction, wherein
In each of the groove walls on the kick-in side of the block, the groove wall of the ground contact portion that comes in contact with the tire before rolling becomes a radius line on a plane parallel to the tire equator C and has a groove wall angle α of 20 degrees or more on the first arrival side. The pneumatic tire has a groove wall angle β of less than 40 degrees and a groove wall angle β of the rear arrival side of not less than 0 degrees and less than 20 degrees, and furthermore, the groove wall of the first arrival side and the groove wall of the rear arrival side are smoothly continuous.

As described above, the circumferential grooves are provided only in the central region to increase the pattern rigidity and the pattern rigidity on a dry road surface.

Further, by setting the flow angle θ of the lug groove to a steep angle of 10 to 40 degrees as compared with the conventional tire, drainage is enhanced and wet grip performance is improved.

Further, in the block between the lug grooves, the inclination angle α of the groove wall on the first arrival side is set larger than the inclination angle β of the groove wall on the rear arrival side. By changing the inclination angle in this manner, a rotational moment caused by the difference in the inclination of the groove wall is generated, and the rotational moment generated by inclining the lug groove at a steep angle as described above is canceled, whereby the entire tire is produced. Can be brought close to 0,
Thereby, the one-sided flow of the vehicle is reduced, the straight running performance is enhanced, and the steering stability can be improved.

As described above, according to the present invention, even when the tire has an omnidirectional pattern, the running performance in both wet and dry running is achieved by organically combining and integrating the above-described components. And the suppression of the vehicle flow can be improved in a well-balanced manner.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings by taking a pneumatic tire for a passenger car having a tire size of 195 / 65R15 as an example.

1 to 4, a pneumatic tire 1 has one or two, three, in this example, two circumferential grooves 3, 3 extending circumferentially on a tread surface 2, and a large number extending from a tread edge E. The tread grooves 5 having the strip lugs 4... Are arranged in a point symmetrical manner at a point on the tire equator C and have a non-directional pattern.

The pneumatic tire 1 has a carcass 16 which rises from the tread portion 12 forming the tread surface 2 to the sidewall portion 13 and turns up around the bead core 15 of the bead portion 14, and the inside of the tread portion 2. And a belt layer 17 disposed radially outward of the carcass 16.

The carcass 16 includes one or more carcass plies having a radial or semi-radial configuration in which organic fiber cords such as nylon, rayon, and aromatic polyamide are arranged at an angle of 70 to 90 ° with respect to the tire equator C. It is formed by overlapping.

The belt layer 17 is composed of a plurality of belt plies 17A and 17B in this embodiment, and these belt plies 17A and 17B are made of nylon, polyester,
Organic fiber cords such as rayon and aromatic polyamide, or steel cords are arranged in a direction crossing each other between plies.

In a normal state in which the pneumatic tire 1 is mounted on a normal rim and a normal internal pressure and a normal load are applied, a ground contact which is a distance in the tire axial direction between the grounding ends F on which the tread surface 2 is grounded. The full width SW is formed.

In this embodiment, the central region M which passes the tread surface 2 in the circumferential direction through a 1/8 point P separating the tread surface 2 from the tire equator C by ８ times the total contact width SW on both sides in the tire axial direction.
And an outer region N between the ８ point P and the tread edge E,
N.

In only the central region M, the circumferential grooves 3, 3 are sandwiched by the ribs 6 extending in the circumferential direction in the central region M.
And the outer circumferential groove 3 </ b> A located closest to the tread edge E is connected to the lug groove 4.
Therefore, on the tread surface 2, a large number of blocks 7 are formed in the circumferential direction between the lug grooves 4 adjacent to each other between the tread edge E and the outer circumferential groove 3A.

In this embodiment, the block 7 extends from the tread edge E toward the tire equator C and the outer region N
Is provided at the middle position of the horizontal groove 19.

When the lug groove 4 intersects with the inner edge K at an intersection A, and when the lug groove 4 intersects with the outer line L passing through the grounding end F in the circumferential direction, the intersection A, , Intersection B
Is defined as the flow angle θ of the lug groove 4 between the line segment AB and the tire equator C. The flow angle θ is set to 10 degrees or more and 40 degrees or less. In this example, the block 7 is formed as a non-directional pattern by inclining rightward in FIG. 1 on both sides sandwiching the tire equator C.

The flow angle θ has a large effect on the steering stability on a wet road surface. When the flow angle θ exceeds 40 degrees, the induced drainage of rainwater becomes insufficient and the wet performance such as aquaplaning occurs. Causes a decrease in Conversely 1
If the angle is less than 0 degrees, a lack of grip force on a dry road surface is caused.

By restricting the flow angle θ in this manner, the block 7 has an oblique shape extending in an oblique direction with respect to the tire axis. In this case, not a uniform and simultaneous grounding, but a first-arrival portion and a second-arrival portion occur. FIG.
When the tire rotates in the direction of the solid arrow, the upper right end of the block 7 is the first arrival side Fr, and the lower left end is the rear arrival side Re.
Becomes When the tire rotates in the direction of the dashed arrow, the positions indicated by the dashed lines in FIG. Such non-uniformity of grounding can be prevented by the block 7
Causes a rotational moment M1 to cause the vehicle to flow in one direction.

Here, the principle of generation of the rotational moment M1 will be described. As shown in FIG. 5 (A), riser of the block
In the case where a time difference occurs between the first arrival side Fr and the second arrival side Re when the block 7 is grounded,
A braking force Br is generated in the block 7. This braking force Br causes an acting force to twist the block 7 in the direction indicated by the dashed line, and as a result, a rotational moment M1 is generated in the block 7.

As shown in FIG. 5 (B), the rotational moment M1 increases as the circumferential distance between the first arrival side Fr and the second arrival side Re increases, that is, as the flow angle θ of the lug groove 4 decreases. Become. Therefore, by making the flow angle θ small, both wet and dry running performances are satisfied, but the rotational moment M1 generated in the block 7 becomes large as described above, and the vehicle flows in one direction.

Therefore, as shown in FIG. 5 (C), the groove wall angle α of the first arrival side Fr which forms the radius line R on the plane parallel to the tire equator C of the block 7 is gently inclined to 20 degrees or more and less than 40 degrees. The groove wall 9 and the groove wall angle β of the rear arrival side Re under the same conditions are formed as a steeply inclined groove wall 9 of not less than 0 degree and less than 20 degrees, and the groove wall 9 of the first arrival side Fr and the rear arrival side Re are formed. And the groove wall 9 are smoothly continuous.

As described above, by making the groove wall angle α of the first arrival side Fr larger than the groove wall angle β of the rear arrival side, a difference in rigidity occurs in the block 7, so that the rotational moment M 1 caused by the flow angle θ is generated. Rotational moment in the opposite direction to-
M2 is generated, and the two moments M1 and -M2 cancel each other, thereby suppressing a one-sided flow in the vehicle.

If the groove wall angle α of the first arrival side Fr is less than 20 degrees or the groove wall angle β of the second arrival side Re becomes 20 degrees or more, the inclination of the groove wall 9 between the first arrival side Fr and the rear arrival side Re is reduced. The difference is so small that the rotational moment in the opposite direction with respect to the block 7-
M2 cannot be generated, and the one-sided flow of the vehicle cannot be suppressed. If the groove wall angle α of the first arrival side Fr becomes larger than 40 degrees, on the first arrival side Fr of the block 7,
As a result, the rigidity becomes locally excessive, so that the steering stability during dry operation is inferior and the grip force is insufficient. Further lug grooves 4
The groove bottom width cannot be secured, and the drainage performance is inferior, and the running performance when wet is reduced.

In the present invention, as shown in FIG. 6, the lug groove 4 may be inclined in the opposite direction to that of FIG. 1, that is, may be inclined leftward in FIG. 6, and the circumferential groove 3 is limited to the central area M. As long as it is arranged, the number of lines can be increased, and the present invention can be modified into various embodiments.

[0034]

[Example] The tire size is 195 / 65R15,
In addition, tires (Examples 1 and 2) having the patterns shown in FIGS.
Its performance was tested. A test was also performed on a tire other than the configuration of the present invention, and the performance was compared. The test conditions are as follows.

In each of the test tires, the belt layer 17 was reversely bonded, and was mounted on a 6JJ rim, and was set to 2.0 kgf / cm ^2.
Under an internal pressure of 400 kgf.

1) Driving stability on dry road surface The vehicle was mounted on all the wheels of a cc class passenger car, and the evaluation based on the driver's feeling on a general pavement road was evaluated by a five-point method. 3 is an average, and the larger the numerical value, the better.

2) Hydro Performance The same vehicle as in 1) was run on a road surface having a water film of 5 mm, and the speed at which hydroplaning occurs was represented by an index with the value of Example 1 being 100. The higher the value, the better.

3) Residual CF Measured using a flat belt type tire cornering tester. Table 1 shows the test results.

[0039]

[Table 1]

[0040]

[Table 2]

As a result of the test, the example of the present invention has both dry and wet running performance and residual CF compared to the comparative example.
It was confirmed that the values of and were improved in a well-balanced manner.

[0042]

As described above, the pneumatic tire of the present invention has the following features.
By providing the above configuration, it is possible to improve dry running performance including steering stability on a dry road surface, to improve wet running performance such as hydro performance on a wet road surface, and to reduce residual CF to zero to suppress one-way flow of a vehicle. Can be increased in a well-balanced manner.

[Brief description of the drawings]

FIG. 1 is a developed plan view showing a tread pattern of an example of a pneumatic tire according to an embodiment of the present invention.

FIG. 2 is an axial sectional view thereof.

FIG. 3 shows a cross section of a lug groove, wherein FIG.
(B) is a sectional view taken along the line bb 'and (C) is a sectional view taken along the line cc'.

FIG. 4 shows a cross section of a lug groove, where (A) is a dd ′ line,
(B) is a sectional view taken along the line ee ', and (C) is a sectional view taken along the line ff'.

FIGS. 5A, 5B, and 5C are plan views schematically showing the acting force generated in the block.

FIG. 6 is a plan view showing an embodiment of another tread pattern.

FIG. 7 is a plan view showing a conventional technique.

FIG. 8 is a plan view showing a conventional technique.

[Explanation of symbols]

 2 Tread surface 3 Circumferential groove 3A Outer circumferential groove 4 Lug groove 5 Tread groove part 6 Rib 7 Block 9 Groove wall A Intersection point A B Intersection point BC Tire equator F Grounding end K Inner line L Outer line M Central area P 1 / 8 points R radius line S ground plane SW total ground width α, β groove wall angle θ flow angle of lug groove

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-5-178026 (JP, A) JP-A-7-246806 (JP, A) JP-A-3-253409 (JP, A) JP-A-3- 186405 (JP, A) JP-A-8-183111 (JP, A) JP-A-5-178008 (JP, A) JP-A-6-2121006 (JP, A) JP-A-5-178026 (JP, A) JP-A-7-246806 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B60C 11/04-11/08 B60C 9/18

Claims (1)

(57) [Claims] 1. A non-directional pattern in which a circumferential groove extending in the circumferential direction and a plurality of lug grooves extending from the tread edge are arranged point-symmetrically at points on the tire equator C on the tread surface. In the normal condition where the tread surface is attached to the normal rim and the normal internal pressure and the normal load are applied, the total tread width SW, which is the distance in the tire axial direction between the tread surfaces where the tread surface contacts the tread surface, is 1/8 times. At least one pair of the circumferential grooves sandwiching a rib extending in the circumferential direction is provided only in a central region between inner lines passing circumferentially through a 点 point that separates the distance from the tire equator C on both sides in the axial direction,
A block is formed on both sides of the tire equator C by connecting the outer circumferential groove located closest to the tread edge side to the lug groove, and the outer side passing circumferentially through the intersection A where the lug groove intersects with the inner line and the grounding end. A line segment AB connecting the line to the intersection B where the lug groove intersects
The flow angle θ of the lug groove formed by the tire with the tire equator C is set to 10 degrees or more and 40 degrees or less, and the groove wall of the ground contact portion that contacts the ground before the tire rolls on each of the groove walls on the kick-in side of the block. The groove wall angle α on the first arrival side, which forms a radius line in a plane parallel to the tire equator C, is 20 degrees or more and less than 40 degrees, the groove wall angle β on the last arrival side is 0 degrees or more and less than 20 degrees, and the first arrival side The pneumatic tire is formed by smoothly connecting the groove wall of the rear side and the groove wall of the rear arrival side.