JP3358976B2 - 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 capable of improving vehicle flow while maintaining excellent dry steering stability and hydroplaning resistance.

[0002]

2. Description of the Related Art In recent years, high-performance flat radial tires having reduced flatness and improved tire rigidity and structural durability have been widely used. Also, in this kind of tire, in order to improve both dry steering stability and hydroplaning resistance,
Many tread patterns are provided with a vertical groove extending in the circumferential direction near the tire equator, and a horizontal main groove extending in the tire axially outward region while increasing the inclination angle with respect to the circumferential direction toward the tread edge side. Has been adopted.

[0003] In this type, the horizontal main groove extends close to the flowing water line, so that excellent drainage efficiency can be exhibited. In addition, the pattern rigidity in the circumferential direction on the equator side of the tire and the pattern rigidity in the lateral direction on the tread edge side are high. Since a large cornering force can be obtained such as being maintained, there is an advantage that dry steering stability can be improved.

[0004]

However, such a lateral main groove has a problem that, on the one hand, the residual lateral force in the tread pattern is increased, which adversely affects the vehicle flow.

As a mechanism for generating the residual lateral force based on the tread pattern, as shown schematically in FIG. 9, when the tire freely rolls, a top part p1 which first arrives at the time of contact with the ground in a block b1 arranged on the tire equator CO side. A force f1 in the traction direction, and a block b arranged on the tread edge side.
In No. 2, a force f2 in the braking direction is applied to the top portion p2 that arrives first, and a residual lateral force is generated by the torsional torque m of each of the blocks b1 and b2 generated thereby. If the torque is large, the vehicle flow is promoted, for example, a force is required for steering the steering wheel even in straight running. Note that the torque m
Becomes larger as the inclination of the horizontal main groove a is steeper, that is, as the inclination angle θ is smaller, and it is very disadvantageous particularly when the inclination is less than 50 degrees.

In view of the above, the present invention is based on the object of increasing the rigidity of a top portion of a substantially rhombic block formed by using a horizontal main groove extending at an angle θ on the tread edge side when the substantially rhombic block comes in contact with the ground when grounded. It is an object of the present invention to provide a pneumatic tire capable of suppressing the occurrence of torsional torque in a block and improving a vehicle flow caused by a residual lateral force while maintaining excellent dry steering stability and hydroplaning resistance.

[0007]

In order to achieve the above object, according to the first aspect of the present invention, there is provided a tire equator, which is 1/8 of a tread width TW and which extends circumferentially from the tire equator in a circumferential direction. In a region between the circumferential lines, a center groove is formed between the longitudinal grooves by providing longitudinal grooves each having a groove center extending in the circumferential direction, and the longitudinal grooves are formed in a region outside the longitudinal grooves in the tire axial direction. Includes a horizontal main groove extending from the groove to the 1/8 circumferential direction line at an angle θ of 10 to 50 degrees on the narrow angle side and extending to the tread edge side with the angle θ increasing, and a circumferential groove extending circumferentially. By providing an outer groove, a block is formed in the outer region, and the block has an oblique side in which one end in the tire axial direction and the other end are displaced in the circumferential direction on opposite sides in the circumferential direction. It includes a substantially rhombic blocks having a substantially rhombic by Moreover the substantially rhombic block, at an angle δ with respect to the tread surface normal of the groove wall surface constituting the hypotenuse, in oblique as the arrival side of the tire rotation
The angle δs of the groove wall on the first arrival side connected to the end on the first arrival side due to the positional deviation with respect to the normal to the tread surface is larger than the angle δe of the groove wall surface on the second arrival side connected to the end on the last arrival side. It is characterized by the following.

The pneumatic tire of the present invention can be suitably used as a tire having a non-directional pattern.

Preferably, the angle δ is continuously changed from the groove wall surface at the end of the first arrival side to the groove wall surface at the end of the rear arrival side from the viewpoint of uneven wear and drainage. It is preferable to form the groove as a zigzag groove in terms of grip force.

A sub-lateral groove having substantially the same inclination as the horizontal main groove is provided between the circumferential groove and the tread edge as one of the outer grooves, and an angle β between a circumferential line passing through the tread edge and the horizontal main groove is provided. 45
It is desirable that the angle be in the range of 90 ° to improve drainage while maintaining a high cornering force.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 1, a pneumatic tire 1 is a flat radial tire for a passenger car having a tire size of 195 / 65R15 in this example, and a tread portion 2.
A carcass 6 that is folded back around the bead core 5 of the bead portion 4 from the side wall portion 3 and is locked, and a belt layer 7 that is arranged radially outside of the carcass 6 and inside the tread portion 2. I can.

The carcass 6 is made of an organic fiber cord made of, for example, polyester or the like.
It is formed from one or more sheets arranged at a cord angle of 90 °, in this example, one carcass ply having a cord angle of 90 °.

The belt layer 7 is formed by arranging high elasticity belt cords such as steel cords at a cord angle of 10 ° to 30 ° with respect to the tire equator CO. Belt plies 7A, 7
B, and the belt cords are stacked in different directions so as to cross each other between the plies. Further, on the outer side of the belt layer 7, a reinforcing layer 9 that covers at least the outer end portion of the belt layer 7 and suppresses lifting due to high-speed running is formed by spirally winding an organic fiber cord such as nylon.

As shown in FIG. 2, a rib block type tread pattern is formed on the tread portion 2.

More specifically, the tread portion 2 is provided in each region between a 1/8 circumferential direction line X1 which circumferentially passes 1/8 of the tread width TW apart from the tire equator CO and the tire equator CO. Each of Yi and Yi has a vertical groove 10 whose groove center extends in the circumferential direction, and a center rib R that extends linearly and continuously is formed between the vertical grooves 10 and 10.

An outer area Y of the longitudinal groove 10 in the tire axial direction.
o is divided into a plurality of blocks B including a substantially rhombic block by the vertical groove 10 and the outer groove 11. The longitudinal groove 10 and the outer groove 11 arranged on one side of the tire equator CO
Are substantially point-symmetric with the longitudinal grooves 10 and the outer grooves 11 arranged on the other side of the tire equator CO, whereby the tread pattern is non-directional with respect to the direction of rotation.

The outer groove 11 includes at least a horizontal main groove 12 extending from the vertical groove 10 to the tread edge TE side and a peripheral groove 13 extending in the circumferential direction. Secondary lateral groove 1 extending between tread edge TE
It has five.

The horizontal main groove 12 is provided with the 1/8 circumferential direction line X1.
And at an angle θ of 10 to 50 degrees, and the tread edge TE
Is an inclined groove extending intermittently or continuously until the angle θ increases, and in this example, intersects with the circumferential line X2 passing through the tread edge TE at an angle β of 45 to 90 degrees. Note that the horizontal main groove 12 is formed in a bent line shape connecting a plurality of straight lines having different inclination angles, a curved line shape connecting a plurality of arcs having different curvatures, and further, a combination of the straight line and the arc. Can be.

The circumferential groove 13 is a zigzag groove which extends in the circumferential direction and intersects with the horizontal main groove 12. In the present embodiment, the horizontal main groove 12 is formed at an angle of 50 with respect to the circumferential direction.
It is divided into an inner groove portion 12i having a steep inclination of not more than a degree and an outer groove portion 12o having a gentle inclination whose angle with respect to the circumferential direction is larger than 50 degrees. The groove 12m between the inner groove 12i and the outer groove 12o overlaps the zigzag oblique piece 13A of the circumferential groove 13.

The sub-lateral grooves 15 have substantially the same inclination as the outer grooves 12o of the horizontal main grooves 12, are alternately arranged in the circumferential direction with the horizontal main grooves 12, and have a zigzag shape with the peripheral grooves 13. Connected at the outside corner.

As described above, the outer groove 11 is formed by
And the peripheral groove 13 and the sub-lateral groove 15, the outer region Yo in this example is a block row including an inner block Bi surrounded by the vertical groove 10, the horizontal main groove 12, and the peripheral groove 13, and It is formed in a block row composed of an outer block Bo surrounded by the horizontal main groove 12, the peripheral groove 13, and the tread edge TE.

Each of the inner and outer blocks Bi, Bo
Means that one end in the tire axial direction and the other end are
By having a hypotenuse that is misaligned on the opposite side in the circumferential direction
Substantially forming a rhombus, a countercurrent fit opposite sides substantially parallel rhombic block each other, for example, as shown enlarged in FIGS. 3 and 4,
In the inner and outer blocks Bi and Bo, the opposite sides 20a and 20b facing each other in the circumferential direction are the respective sides 20a and 20b.
One end E1 in the tire axial direction and the other end E2 form oblique sides 21a and 21b that are displaced in the circumferential direction.

[0023] Thus, in the figure, for example, when a substantially rhombic blocks are ground by the lower direction of the tire rotation K1, circumferential direction
The tire rotation of the oblique side 21a which is the first arrival side on the rotation direction side (downward side) of the oblique side which is the first arrival side among the opposite sides of the tire.
End E1a in the first-arrival side, the circumferential direction of the positional deviation <br/> other end E2a grounded become trailing end.

In the present application, as shown in FIGS. 5A to 5C, at an angle δ of the groove wall surface Sa forming the oblique side 21a with respect to the normal line N of the tread surface, the groove wall Sa is connected to the end portion E1a on the first arrival side. The angle δs of the groove wall surface S1a on the first arrival side is
The groove wall surface S2a on the back arrival side connected to the end portion E2a on the back arrival side
(Δs> δe). As a result, the rigidity of the vicinity of the end portion E1a on the first arrival side, that is, the top of the first arrival side of the substantially rhombic block can be increased, the torsional deformation and the generation of the torsional torque can be prevented, and the residual lateral force can be effectively suppressed. .

Here, the groove wall surface S1a on the first arrival side and the groove wall surface S2a on the rear arrival side are defined as groove wall surfaces within a distance of 0.3 times the length of the hypotenuse 21a from each of the ends E1a, E2a. In the region of Sa, the angle δs of the groove wall surface S1a on the first arrival side
In the present embodiment, the angle δe of the groove wall surface S2a on the rear arrival side is set to a range of 0 ° or more and less than 20 ° in this example.

The angles δs and δe are substantially constant within the groove wall surfaces S1a and S2a, and the groove wall surfaces S1a and S1b
Although the angle δ of the region between them may be substantially constant, as in this example, the entire angle δ may be continuously changed from the end E1a on the first arrival side to the end E2a on the rear arrival side. preferable. Thereby, it is possible to suppress the occurrence of uneven wear and a decrease in drainage due to the change in the inclination gradient of the groove wall surface Sa.

The difference between the minimum value of the angle δs and the maximum value of the angle δe is preferably at least 5 degrees, more preferably at least 10 degrees, and still more preferably at least 15 degrees. It is desirable in terms of the suppression effect. On the other hand, if the angle δs exceeds 40 degrees, the groove depth becomes too small or the groove width becomes too large, resulting in a decrease in dry steering stability or hydroplaning resistance. When the angle δs is less than 20 degrees and when the angle δe is less than 0 degrees, the rigidity of the block itself cannot be said to be sufficient, and when the angle δe exceeds 20 degrees, a necessary angle difference δs−δe Therefore, the effect of suppressing the residual lateral force is impaired.

On the other hand, when the tire rotation K2 is in the opposite direction due to a tire position change or the like, that is, in the upward direction in the figure, the rotational direction side (upward side) of the oblique side 21b that is the rotational direction side (upward side) End E1b is the first arrival side, and the other end E2b is the last arrival side, and is grounded. Therefore, the groove wall surface Sb that forms the hypotenuse 21b also has the groove wall surface Sa.
Similarly to the above, the angle δs of the groove wall S1b on the first arrival side connected to the first end E1b on the first arrival side is set to the end E2b on the second arrival side.
Greater than the angle δe of the groove wall surface S2b on the rear
s> δe).

As described above, the groove wall surfaces S on the opposite sides are formed.
In a and Sb, by changing the inclination gradient,
Not only can the effect of suppressing the residual lateral force be exerted without being affected by the rotation direction of the tire, but also the effect of suppressing the residual lateral force itself can be further improved.

In the present embodiment, in order to further enhance the effect of suppressing the residual lateral force, in the blocks Bi and Bo, the inclination gradients of the groove wall surfaces Sc and Sd forming the opposite sides 20c and 20d facing each other in the tire axial direction are also changed. I have.

That is, on the groove wall surface Sc, FIGS.
(C), the angle γ with respect to the tread surface normal N
, The angle γs of the groove wall surface S1c connected to the end E1a is changed to the angle γ of the groove wall surface S2c connected to the end E2b.
On the other hand, on the groove wall surface Sd, the angle γs of the groove wall surface S1d connected to the end E1b at the angle γ with respect to the tread surface normal N is set larger than the groove wall surface Sd (γs> γe). Larger than the angle γe of S2d (γs
> Γe). The angle γ is not particularly limited, but similarly to the angle δ, the angle γs is 20 to 40.
The angle and the angle γe should be 0 to 20 degrees, and the angle γs
Is preferably 5 degrees or more, more preferably 10 degrees or more, and still more preferably 15 degrees or more. The angle γ is preferably changed continuously over the entire length of the groove wall surfaces Sc and Sd.

In the present invention, the groove wall surfaces Sc and Sd can be formed at a constant angle without changing the angle γ, similarly to the conventional block wall surface.
3 may be formed as a straight groove. In addition, for all the substantially rhombic blocks, the angle δ of the groove wall surfaces Sa and Sb is set to δ
It is not necessary to set s> δe, but it is desirable to perform the processing for more substantially rhombic blocks.

The width and depth of the vertical groove 10, the horizontal main groove 12, the peripheral groove 13, and the auxiliary horizontal groove 15 are not particularly limited, but the same range as that of a general radial tire for a passenger car is used. For example, the groove depths are respectively 6.0 to 9.0.
mm is preferable, and the groove width is 3.0 to 1 respectively.
A range of 2.0 mm is preferred.

Further, sipes can be formed in the blocks Bi and Bo and the center rib R.

[0035]

[Example] The tire size is 195 / 65R15,
A pneumatic tire having the basic configuration of FIG. 1 was prototyped with the specifications shown in Table 1, and the dry steering stability of each sample tire was measured.
The hydroplaning resistance and the residual lateral force were measured, and the results are shown in Table 1. AA 'of each sample tire
Section, BB 'section, CC' section, DD 'section, E
Table 2 shows the values of the angles δ and γ of the groove wall surfaces in the E ′ section, the FF ′ section, the GG ′ section, and the HH ′ section. The test method is as follows.

(1) Dry steering stability test: A test tire was tested by applying a rim (15 × 6JJ) and an internal pressure (2.0 kgf / cm ² ).
On a dry asphalt road surface on a test course, the steering stability characteristics regarding steering wheel responsiveness, rigidity, grip, etc. were evaluated by a sensory evaluation of the driver using a five-point method with “3” as the average value. Scored. The larger the value, the better.

(2) Hydroplaning resistance test:
Using the vehicle equipped with test tires, on the asphalt road surface, on a straight course provided with a puddle of water depth 10mm,
Speed 3 levels (60km / h, 80km / h, 100km
/ H), the deceleration G when the vehicle enters and is braked (locked) is measured.
The speed at the time of G is indicated by an index with the value of Example 1 being 100, and the larger the value, the better.

(3) Residual lateral force test: Using a flat belt type testing machine, mounting rim (15 × 6JJ), internal pressure (2.
0 kgf / cm ² ) and an average of the measured values per 20 test tires measured under the standard conditions of a load (400 kgf). The residual lateral force is the lateral force when the self-aligning torque becomes zero. The residual lateral force to the right with respect to the traveling direction is positive (+).

[0039]

[Table 1]

[0040]

[Table 2]

As shown in Table 1, the tire of Example 1 has a high level of dryness which is substantially equal to that of Comparative Example 1 which has the same tread pattern and has a constant inclination angle δ of the groove wall surfaces Sa and Sb. It can be confirmed that the steering stability and the hydroplaning resistance can be exhibited.

The residual lateral force was +5.6 in Comparative Example 3 which was a slick tire having no tread pattern.
Indicates kgf. This means that the residual lateral force generated by the internal structure such as the cord arrangement of the belt layer is +5.6 kgf. Therefore, the residual lateral force due to the tread pattern is -6.8 kgf in Comparative Example 1, whereas it is -1.1 kgf in Example 1, which is extremely reduced in absolute value, and as a result, vehicle flow is improved. You can see that it was done. Also in the second embodiment, the generation of the residual lateral force of +1.6 kgf is suppressed. When the tire is destined for Japan, the residual lateral force has a road surface cant that is depressed to the left with respect to the traveling direction.

[0043]

Since the present invention is configured as described above,
Vehicle flow can be improved while maintaining excellent dry steering stability and hydroplaning resistance.

[Brief description of the drawings]

FIG. 1 is a sectional view of a tire according to an embodiment of the present invention.

FIG. 2 is a developed view showing the tread pattern.

FIG. 3 is an enlarged plan view showing an inner block.

FIG. 4 is an enlarged plan view showing an outer block.

FIGS. 5A to 5C are cross-sectional views illustrating an angle δ between groove wall surfaces Sa and Sb.

FIGS. 6A to 6C are cross-sectional views illustrating an angle γ between groove wall surfaces Sc and Sd.

FIG. 7 is a developed view showing a tread pattern of another example used in Table 1.

FIG. 8 is a developed view showing a tread pattern of a comparative example used in Table 1.

FIG. 9 is a schematic view illustrating a mechanism of generating a residual lateral force.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 Vertical groove 11 Outer groove 12 Horizontal main groove 13 Peripheral groove 15 Secondary horizontal groove 21a, 21b Oblique side CO Tire equator B, Bi, Bo Block E1, E2, E1a, E2a, E1b, E2b End of oblique side N Tread surface normal R Center ribs Sa, Sb Groove wall surfaces forming oblique sides S1a, S1b Groove wall surfaces on the first arrival side S2a, S2b Groove wall surfaces on the last arrival side TE Tread edge X1 1/8 Circumferential line X2 Circumferential line passing through tread edge Yi region Yo Outer region

Claims (6)

(57) [Claims] A longitudinal groove having a groove center extending in a circumferential direction in a region between a tire equator and a 1/8 circumferential line extending circumferentially from the tire equator by １ ／ of the tread width TW. By forming a center rib between the vertical grooves, an angle θ between the vertical groove and the ８ circumferential line starting from the vertical groove on the narrow angle side is formed in a region outside the vertical groove in the tire axial direction. 10-5
A block is formed in the outer region by providing an outer groove including a horizontal main groove extending at an angle θ on the tread edge side and a circumferential groove extending in a circumferential direction at a tread edge side, and the block includes a tire shaft. One end of the direction and the other end have a hypotenuse that is misaligned in the circumferential direction on the opposite side in the circumferential direction
A substantially rhombic block that forms a substantially rhombic shape, and the substantially rhombic block is capable of rotating the tire at an angle δ with respect to a normal to a tread surface of a groove wall surface forming the hypotenuse.
The angle δs of the groove wall surface on the first arrival side connected to the end on the first arrival side due to the displacement on the oblique side on the first arrival side with respect to the tread surface normal is determined by the second arrival on the second end on the second arrival side. A pneumatic tire characterized in that the angle is larger than the angle δe of the side groove wall surface. 2. The pneumatic tire according to claim 1, wherein the angle δ continuously changes from a groove wall surface at an end portion on a first arrival side to a groove wall surface at an end portion on a rear arrival side. 3. The vertical groove and the outer groove are formed in a circumferential direction as a point symmetry centered on the tire equator so as to have a non-rotational direction.
The pneumatic tire as described. 4. The pneumatic tire according to claim 1, wherein the peripheral groove is a zigzag groove. 5. The outer groove includes a sub-lateral groove extending between the peripheral groove and the tread edge and having substantially the same inclination as the horizontal main groove. Pneumatic tires. 6. The horizontal main groove according to claim 1, wherein an angle β intersecting with a circumferential line passing through a tread edge is 45 to 90 on a narrow angle side. Pneumatic tire.