JP3206837B2 - 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 that can improve braking performance on ice, wandering resistance, skid resistance and uneven wear resistance, and can be suitably used even in a flat tire.

[0002]

2. Description of the Related Art Conventionally, a spike tire in which a chain is attached to a tire or a spike is driven has been used for traveling on an icy road surface or a snowy road surface. However, in recent years, spiked tires and chains using hard spikes have become more self-restraining, as so-called studless tires without spikes have become widespread, as spiked road surfaces are damaged and dust is generated by scraping the road surface. It is getting.

[0003] Such studless tires are inferior in running performance such as grip performance and braking performance on icy and snowy road surfaces as compared with the spiked tires, and are particularly liable to cause side slip when turning on icy and snowy road surfaces. is there. Therefore, for heavy duty tires used for buses, trucks, etc., the flatness is reduced and the ground contact area is increased in order to ensure running performance on ice and snow, and in order to maintain a stable ground contact state, the tire is flattened and the radius of curvature of the tread surface To increase the rigidity of the tread.

[0004]

However, in the tire constructed as described above and having an aspect ratio of 55 to 75%, the tread surface is long in the tire axial direction and the radius of curvature of the tread surface is large. Therefore, it is not easy for the rut to escape, and the wandering resistance is reduced.

[0005] Further, it is difficult to maintain a stable shape of the ground contact surface, and uneven wear is likely to occur from a siping provided for improving grip.

In addition, in the conventional studless tire, a vertical sub-groove f is provided along the tread edge e as shown in FIGS. 5 to 7 to prevent side slip during turning. In the case where a curved surface S composed of a circular arc is provided at the tread edge e in order to get over the rut w, the open end of the vertical sub-groove f close to the tread edge e has the origin of uneven wear as shown in FIG. (Indicated by a chain line in the middle)).

However, braking performance on ice and anti-wandering performance are essential for vehicles running in snowy and icy areas, and durability is improved for heavy load tires such as buses and trucks. Therefore, it is essential to suppress uneven wear.

[0008] The inventor has conducted research and trial production on the cross-sectional shape of the tire and the configuration of the tread groove in order to improve these performances in a well-balanced manner. As a result, the inventor has restricted the contact area where the tread surface contacts the road surface, and The present invention was found to be able to be solved by regulating the shape of the buttress portion extending from the tread edge, the arrangement of the vertical sub-grooves along the tread edge, and the groove depth within certain ranges, respectively, and completed the present invention. .

The present invention can improve the braking performance on ice, wandering resistance, and uneven wear resistance of flat tires, and can be applied to heavy vehicles such as trucks and buses running in snowy areas and icy areas. It is another object of the present invention to provide a pneumatic tire that can be suitably employed.

[0010]

SUMMARY OF THE INVENTION The present invention is directed to a carcass which is folded from a tread portion through a sidewall portion and around a bead core of a bead portion, and a belt disposed inside the tread portion and radially outside the carcass in a tire radial direction. And a main groove comprising a vertical groove extending in the circumferential direction on the tread surface and a horizontal groove intersecting with the vertical groove and extending on the tread edge, wherein the flatness of the tire is 55% or more and 75% or less. A tread width, which is a distance in the tire axial direction between tread edges in a normal state in which a regular inner pressure and a regular maximum load are applied to a regular rim by applying a regular rim to a regular rim. Is equal to or greater than 80% of the maximum width of the tire, and in the normal state, the contact width, which is the length in the tire axial direction of the contact area where the tire contacts the road surface, is It has a small slope that is substantially the same length as the tread width, is inclined inward in the tire radial direction from the tread edge toward the tire axial direction outward, and extends substantially linearly and continues to the buttress surface. The inclination with respect to the tire equatorial plane is not less than 40 degrees and not more than 50 degrees, the surface length of the small slope portion in the tire axial direction is 5 to 10% of the tread width,
An outer point separating a distance of 0.015 times the tread width from the tread edge to the tire equator side from the small slope portion,
A small slope vertical sub-groove and a shoulder vertical sub-groove extending in the circumferential direction and opening in a lateral groove in a shoulder region between the tread edge and an inner point separating a distance of 0.05 times the tread width toward the tire equator side from the tread edge; And the small slope vertical sub-groove and the shoulder vertical sub-groove decrease in depth from the center toward the opening end of the pneumatic tire.

It is preferable that the belt width, which is the length of the belt layer in the tire axial direction, is larger than the contact width in the contact area.

[0012]

In a flat tire having an aspect ratio of 55% or more and 75% or less, the tread width in a normal state is made 80% or more of the maximum tire width, and the length of the ground contact area in the tire axial direction is substantially the same as the tread width. I am long. In such a configuration, the radius of curvature of the tread surface in the tire axial direction is formed with a large radius that is about six times or more the tire cross-sectional height.

Further, the contact width of the contact area is substantially equal to the tread width, that is, by contacting the ground substantially over the entire tread width,
Grip power is increased, and braking ability on ice and snowy road surfaces can be increased.

Further, a small slope portion extending linearly outward from the tread edge in the tire axial direction is formed, and the slope is inclined at an angle of 40 degrees or more and 55 degrees or less with respect to the tire equatorial plane. . In the case of conventional tires, they are formed by a small radius arc to get over the ruts.However, when formed in an arc, the contact position is not determined by the depth of the ruts, and the wandering resistance is poor. It was unstable. However, by making the small slope portion straight, the force for climbing the rut can be stabilized.

If the inclination of the small slope is less than 40 degrees, the camber thrust becomes small, and the climbing ability of the rut is reduced. On the other hand, if it exceeds 55 degrees, the small slope is repelled by the side wall of the rut and cannot be climbed over. There is danger.

When the surface length of the small slope is less than 5% of the tread width, the small slope is small and it is difficult to cross the rut. On the other hand, when it exceeds 10%, the maximum width of the tire increases, so that the tire weight increases. This increases the cost and increases the cost.

Further, a small slope vertical sub-groove and a shoulder vertical sub-groove extending in the circumferential direction are provided in the small slope portion and the shoulder region near the tread edge, respectively. By providing such a vertical sub-groove, the tread edge portion is formed with an edge in the tire circumferential direction, and the vertical sub-groove enhances grip performance against an axial force including a cornering force at the time of turning, In combination with the above configuration in which the contact area extends to the tread edge, it is possible to prevent the tire from skidding during turning. Moreover, since the vertical sub-groove is provided in both the small slope portion and the shoulder region, it is possible to more efficiently prevent the above-described side slip during turning.

Further, each of the vertical sub-grooves of the small slope portion and the shoulder is opened by a horizontal groove, and the depth of the groove gradually decreases from the center toward the opening end. Conventionally, such a vertical sub-groove has been formed with a substantially uniform groove depth at both the central portion and the opening end. However, by making the vertical sub-groove have a uniform depth, the opening end is formed as shown in FIG. Since the movement of the tread rubber is easier than in the central portion, uneven wear starting from the opening end tends to occur. Therefore, by reducing the depth of the vertical sub-groove near the opening end, the movement of the tread rubber near the opening end is suppressed, and the occurrence of uneven wear is prevented.

As described above, in the present invention, even if the tire is a flat tire, ice dynamic braking, anti-lateral skidding, anti-wandering and anti-wandering properties can be obtained by organically integrating the above-mentioned components. Both uneven wear properties can be improved, and even flat heavy load tires can safely and stably travel on icy and snowy roads.

[0020]

An embodiment of the present invention will be described below with reference to the drawings. 1 and 2, a pneumatic tire 1 includes a tread portion 2, a sidewall portion 3 extending inward in the tire radial direction from both ends thereof, and a bead portion 4 connected to an inner end of the sidewall portion 3 in the tire radial direction. And Further, the pneumatic tire 1 has a carcass 6 that is turned around a bead core 5 of the bead portion 4 from the inside in the tire axial direction to the outside thereof on a body portion 6a extending from the tread portion 2 through the sidewall portion 3 to the bead portion 4. And a belt layer 7 arranged inside the tread portion 2 and radially outside the carcass 6.

The pneumatic tire 1 has a tire height TH from the tire bead line BL with respect to the tire maximum width MW.
Is set in a range of 55% or more and 75% or less. By forming such a flat tire, the contact area S of the tire can be increased, and the grip performance can be easily improved.

In the tread portion 2, a tread width TW which is a distance between the tread edges E in the axial direction of the tire.
Is set to 80% or more of the maximum tire width MW.

The carcass 6 is composed of one or more carcass plies having a carcass cord having a radial or semi-radial arrangement inclined at an angle of 60 to 90 ° in the present embodiment with respect to the tire equator C, and in this embodiment, two carcass plies. As the carcass cord, cords of organic fibers such as nylon, rayon, polyester, and aromatic polyamide fibers are used.

The belt layer 7 is composed of a plurality of belt plies, three in this embodiment, and each belt ply is made of an organic fiber such as nylon, rayon, polyester, aromatic polyamide fiber or the like, similarly to the carcass ply. A belt cord made of an inorganic fiber such as a steel cord is arranged at an angle of 10 to 70 ° with respect to the tire equator C, and the adjacent belt cords are arranged to intersect with each other.

On the tread surface 2A, a plurality of, in the present embodiment, three longitudinal grooves 9 extending in the tire circumferential direction, and between the longitudinal grooves 9, 9 and between the longitudinal grooves 9 and the tread edge E are connected. A main groove 13 composed of a plurality of horizontal grooves 10 is provided, and a block pattern composed of a plurality of blocks 21 divided by the vertical grooves 9 and the horizontal grooves 10 is formed.

In this embodiment, the groove depth GH of the main groove 11 is in the range of 4 to 12% of the tread width TW, and the groove width GW is in the range of 6 to 12% of the tread width TW. Is set.

In a normal state in which the pneumatic tire 1 is rim-assembled on a regular rim J and a regular internal pressure and a regular maximum load defined for the tire 1 are applied, the tire 1 has a contact area S in contact with a road surface. Contact width W which is the length in the tire axial direction
Is substantially the same length as the tread width TW. That is, in the normal state, the grounding is performed in substantially the entire area of the tread width TW.

In the ground area S, the land ratio, which is the ratio of the total area occupied by the blocks 21 to the total area of the ground area S, is preferably 60% or more. This is because if the land ratio is less than 60%, the contact pressure acting on the surface of the block 21 becomes large, and the durability is reduced due to early wear.

A small-slope portion 1 having a small length inclined inward in the tire radial direction from the tread edge toward the tire axially outward.
2 is formed, and the inner end of the small slope 12 is continuous with the buttress surface 13 of the sidewall 3. In addition, in order to easily exceed the inclination θ of the small slope 12 with respect to the tire equatorial plane C, the surface length L in the tire axial direction along the surface of the small slope is 40 ° or more and 50 ° or less and the tread width. The range is 5 to 10% of TW.

The tread surface 2A has a tread edge E
, The outer point O separating the tread width TW by a distance of 0.015 times to the tire equator C side, and the tread edge E to the tire equator C side by 0.135 times the tread width TW as a starting point. Shoulder region S between inner point I
Set H.

The small slope portion 12 has a small slope vertical sub-groove 15 extending in the circumferential direction of the tire and opening at the lateral grooves 10 and 10 on both sides of the block 21. The shoulder region SH has the small slope vertical sub-groove 15. And a shoulder vertical sub-groove 16 formed substantially in the same manner as the above.

Small slope vertical sub-groove 15, shoulder vertical sub-groove 16
Are formed in such a manner as to be dug in a direction parallel to the tire equatorial plane, so that the center of the groove is deepest and the depth decreases toward the opening ends on both sides.

Each of the vertical sub-grooves 15 and 16 has a maximum groove depth gm at the center portion of the groove GH of the main groove 11.
4 times or more and 0.8 times or less, and each vertical sub-groove 1
The groove depth ge at the open ends opened by the horizontal grooves 10 and 10 is set to 0.25 times or more and 0.5 times or less the maximum groove depth gm of each vertical sub-groove. Here the vertical sub-grooves 15, 16
Is a depth in a direction parallel to the tire equatorial plane C.

The bottoms of the vertical sub-grooves 15 and 16 are formed in a V-shape as shown in FIG. 2 and a central portion as shown in FIG.
It is also possible to connect the two with a stepped portion by changing the groove depth of the open end portion.

The groove width gw of these vertical sub grooves 15 and 16 is preferably in the range of 1 to 3 mm. If the groove width gw is less than 1 mm, when a force is applied in the tire axial direction such as when turning,
This is because sideslip is likely to occur due to contact between the groove walls on both sides, and if it exceeds 3 mm, stone biting is likely to occur and the tread edge may be damaged.

The small slope sub-groove 15 and the shoulder vertical sub-groove 16 may be formed by inclining the groove direction at an angle α with the tire equatorial plane C, as shown in FIG. The groove depth gh is regulated by the depth parallel to the tire equatorial plane C.

The belt layer 7 has a belt width BW, which is the length in the tire axial direction, that is equal to the ground width W of the ground area S.
And greater than. As a result, the tread portion 2 is reinforced by the belt layer 7 over the entire region, the rigidity of the tread portion 2 is made uniform, and the occurrence of uneven wear in the shoulder region SH can be further suppressed.

[0038]

[Specific Example] A tire (Example 1) having a tire size of 195 / 70R17.5 and having the structure shown in FIG. 1 was prototyped and its performance was tested. For comparison, a tire having a conventional configuration (Comparative Example 1) and a tire having a configuration other than the configuration of the present invention were also tested and their performances were compared.

The test conditions are as follows. 1) Camber thrust The test tire was mounted on a 17.5 × 6.00 rim, an internal pressure of 6.0 kg / cm ² was applied, and the camber angle was set to 6 ° under the conditions of 1120 kg per tire. It was measured using a steering performance tester. The larger the value is, the more excellent the skid resistance is.

2) Anti-wandering performance The test tire was mounted on the front wheel of a 2D 2 ton truck, run at high speed under the same load conditions as in 1), and evaluated by a 5-point method based on the driver's feeling. The higher the value, the better.

3) Braking performance on ice A test track formed on an ice floe with an outside air temperature of -5 ° C.
While driving at a speed of km / H, braking was suddenly applied with the four-wheel lock and the braking distance until the car stopped was measured.
The reciprocal value of the distance was indicated by an index with Comparative Example 1 being 100. The higher the value, the better.

4) Uneven wear resistance The test tires were mounted on the front wheels of an actual vehicle under the same conditions as in item 2), and the vehicle was normally run on the right and left sides of the road every 20,000 km, and before and after the block having the building subgroove. , The uneven wear amounts m ₁ and m ₂ (shown in FIG. 7) were measured, and the average value M = (m ₁ + m ₂ ) / 2 was obtained. The uneven wear amount was averaged to obtain the uneven wear of the tire. The numerical values shown in Table 1 are represented by an index with Comparative Example 1 being 100, and the smaller the numerical value, the smaller the uneven wear amount. Table 1 shows the test results.

[0043]

[Table 1]

As a result of the test, it was confirmed that the camber thrust, the wandering performance, and the braking performance on ice were excellent in the example of the invention as compared with the comparative example.

[0045]

As described above, the pneumatic tire of the present invention has the following features.
A small slope that is inclined at a regulated angle with respect to the tire equatorial plane is formed outside the tread edge, so that it has excellent wandering resistance and a small slope vertical auxiliary extending in the circumferential direction near this small slope and the tread edge. Since the groove and the shoulder vertical sub-groove are formed, the cornering force can be increased, and a side slip at the time of turning, particularly at the time of turning on an icy and snowy road surface can be prevented. In addition, since these vertical sub-grooves are formed such that the depth of the groove decreases from the center toward the opening end, uneven wear starting from the opening end can be prevented and durability can be improved.

As described above, the present invention can eliminate a decrease in wandering resistance and uneven wear resistance, which are disadvantages of the conventional flat tire regardless of the flat tire, and can provide a studless tire that travels on an icy and snowy road surface. It can be suitably adopted.

[Brief description of the drawings]

FIG. 1 is a sectional view showing one embodiment of the present invention.

FIG. 2 is an enlarged perspective view showing a shoulder region of the tread portion.

FIG. 3 is a sectional view showing another example of the vertical sub groove.

FIG. 4 is a sectional view showing another example of the vertical sub groove.

FIG. 5 is a sectional view showing a conventional tire.

FIG. 6 is a cross-sectional view schematically showing a state of getting over a rut.

FIG. 7 is a perspective view schematically showing the state of occurrence of uneven wear.

[Explanation of symbols]

 2 Tread portion 2A Tread surface 3 Side wall portion 4 Bead portion 5 Bead core 6 Carcass 7 Belt layer 9 Vertical groove 10 Horizontal groove 11 Main groove 12 Small slope portion 13 Buttress surface 15 Small slope vertical sub groove 16 Shoulder vertical sub groove BW belt width C Tire equator E Tread edge GH Groove depth of main groove gm Maximum groove depth of vertical and auxiliary grooves gw Groove width I Inside point J Regular rim MW Tire maximum width O Outside point S Grounding area SH Shoulder area TW Tread width W Grounding width

Claims (3)

(57) [Claims] 1. A tire comprising: a carcass which is turned from a tread portion through a sidewall portion and around a bead core of a bead portion; and a belt layer disposed inside the tread portion and radially outside the carcass in a tire radial direction. A block pattern or rib block pattern having a flat groove having a flatness of 55% or more and 75% or less, and a main groove including a vertical groove extending in a circumferential direction on a tread surface and a horizontal groove crossing the vertical groove and extending on a tread edge. In a normal state in which a rim is assembled to a regular rim and a regular internal pressure and a regular maximum load are applied, the tread width, which is the distance between the tread edges in the tire axial direction, is 80% or more of the tire maximum width. In the normal state, the contact width, which is the length in the tire axial direction of the contact area where the tire contacts the road surface, is substantially the same as the tread width. The tire has a small inclined surface inclined inward in the tire radial direction from the tread edge toward the tire axial direction outward and extending substantially linearly and continuing to the buttress surface, and the inclination of the small inclined surface with respect to the tire equatorial plane is set to 40. Not less than 50 degrees and not more than 50 degrees, the surface length of the small slope portion in the tire axial direction is 5 to 10% of the tread width.
And an outer point separating a distance of 0.015 times the tread width from the tread edge to the tire equator side from the small slope portion,
A small slope vertical sub-groove and a shoulder vertical sub-groove extending in the circumferential direction and opening in the lateral groove in a shoulder region between the tread edge and an inner point which is separated from the tread edge by 0.05 times the tread width toward the tire equator side; And the small slope vertical sub-groove and the shoulder vertical sub-groove decrease in depth from the center toward the opening end. 2. The pneumatic tire according to claim 1, wherein the belt layer has a belt width, which is a length in the tire axial direction, larger than a contact width in the contact area. 3. The small-slope vertical sub-groove and the shoulder vertical sub-groove have a groove width of 1 to 3 mm and a maximum groove depth in a direction parallel to the tire equatorial plane of each of the vertical sub-grooves. The depth is not less than 0.4 times and not more than 0.8 times the depth, and the open end groove depth at the open end of each vertical sub-groove is not less than 0.25 times the maximum groove depth of each vertical sub-groove and not more than 0 times. The pneumatic tire according to claim 1, wherein the pneumatic tire is set to 0.5 times or less.