JP3400005B2 - Pneumatic radial 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 having an annular recess in the center of the width of a tread, which can suppress the occurrence of hydroplaning phenomenon without sacrificing other performances.

[0002]

2. Description of the Related Art With the recent improvement in the performance of vehicles, it has been desired to flatten pneumatic tires. However, since the flattened pneumatic radial tire has a wide tread contact width, it is difficult to remove water that enters the tire ground contact center area when running on a wet road surface, and a hydroplaning phenomenon is likely to occur. For this reason, studies are being made to improve drainage by improving the tread pattern and the like.

As an example of the pneumatic tire, an annular recess is provided at the center of the width of the tread to enhance drainage and to supplement the rigidity of the thinned tread portion by the annular recess. A pneumatic tire provided with one or more belt reinforcing layers on the circumferential side is disclosed in JP-A-61-60.
No. 304 is disclosed. In this pneumatic tire, the width of the belt reinforcing layer is equal to or larger than the width of the annular recess, and the carcass and the belt are of ordinary shapes.

[0004]

However, although the pneumatic tire of the above publication can improve the drainage property in the tread ground contact central area, the carcass and the belt have a normal shape, that is, the crown portion is convex upward or flat. Since it has a cylindrical surface shape, the groove depth of the annular recess is limited by the thickness of the tread portion, and since the thickness of this tread portion has an unfavorable influence on the tread rigidity, tire weight, etc. It is practically difficult to significantly increase the groove volume of the annular recess as compared with a normal tread groove because the portion cannot be thickened. In addition, the belt reinforcing layer can suppress radial expansion particularly in the width center of the tire during high-speed running, but since the width of this belt reinforcing layer is equal to or larger than the width of the annular recess, the bending rigidity of the belt increases. The belt followability at a large slip angle is deteriorated and the side force is reduced. Therefore, the limit grip force when the vehicle is mounted is insufficient.

In view of the above, the present invention provides a pneumatic tire having an annular recess in the width center of the tread which can suppress the occurrence of the hydroplaning phenomenon without sacrificing other performances by optimizing the tire structure. The purpose is to develop.

[0006]

The present invention comprises a toroidal carcass, a belt in which cord rubberized layers are cross-laminated, and a tread portion reinforced by the belt, the tread portion having a width center thereof. In the radial radial tire having a double crown configuration by having an annular recessed portion along the tread circumference along with the carcass and the belt on the tire radial direction inner side, the cords are arranged in parallel on the tire radial direction inner side of the tread portion. At least one hoop reinforcement layer comprising a non-stretchable rubberized layer is provided, at least one of the hoop reinforcement layers having a tire mounted on an applicable rim, a specified air pressure, and a specified mass added in a stationary state. Under the conditions, the tread ground plane has a width equal to or less than the non-ground width corresponding to the annular recess, and the hoop reinforcing layer is formed in the annular recess. The negative ratio expressed by the percentage of the opening area of the non-grounded portion with respect to the total area of the contact area in the tread grounding state is 15 to 30% for each of the double crowns, and the annular concave portion is also for all the treads. Negative rate calculated by including is 40-60
%, Which is a pneumatic radial tire.

The depression depth of the annular recess is defined by a straight line connecting the maximum outer diameter positions of the double crowns in the tire width cross section, and a vertical line extending from this straight line to the deepest position of the annular recess. To 15 mm, the ratio of the volume of the groove opened in the tread portion to the volume of the depression of the annular recess in the tread ground contact state is in the range of 0.3 to 0.6, and the maximum depth of the annular recess The skid base gauge at the part position is in the range of 1.5 to 5.0 mm, the surface rubber of at least the annular recess of the tread portion has a breaking elongation of 300% or more at room temperature, and at least the surface rubber of the tread portion. Tan δ at 30 ° C is 0.3 or more, and at least one of the double crowns has a crown center with a plane including the circumference of the maximum outer diameter of the tire as a boundary. When divided into a part and a crown side part, the ratio of the radius of curvature of the crown side part to the radius of curvature of the crown center side part is in the range of 0.5 to 5.0, and the hoop reinforcing layer is More preferably, it is arranged at a position corresponding to the double crown.

FIG. 1 shows a width cross section of a typical pneumatic tire of the present invention, in which 1 is a pneumatic radial tire and 2 is a radial tire.
Is a carcass, 3 is a cord rubberized layer, 4 is a belt, 5 is a tread portion, 6 is an annular recessed portion, 7 is a hoop reinforcing layer, 8 is a crown central side portion, and 9 is a crown lateral side portion. A pneumatic radial tire 1 shown in FIG. 1 has a belt 4 in which a toroidal carcass 2 and a cord rubberized layer 3 are cross-laminated.
And a tread portion 5 reinforced by the belt 4, and the tread portion 5 has an annular recessed portion 6 which is recessed along the tread circumference along with the carcass 2 and the belt 4 in the tire radial direction inner side in the width center portion. However, the tread portion 5 has a double crown structure. This double crown is divided into a crown center side part 8 and a crown side part 9 with a plane S including the circumference of the maximum outer diameter of the tire as a boundary, and the center of curvature of the crown side part 9 is the center of the crown. The ratio of the side portion 8 to the radius of curvature is preferably in the range of 0.5 to 5.0. If it deviates from this range, a proper ground contact shape cannot be obtained. The crown shapes of the crown central side portion 8 and the crown lateral side portion 9 may be symmetrical or asymmetrical. The recess depth D of the annular recessed portion 6 is set to a length of a perpendicular line connecting the maximum outer diameter position of the double crown with a straight line l in the tire width cross section and dropping from this straight line l to the deepest position of the annular recessed portion 10. It is preferably in the range of ˜15 mm. If it is less than 10 mm, it is not much different from the groove volume of the circumferential groove normally arranged on the tread, and the expected drainage performance cannot be obtained. If it exceeds 15 mm, the shear strain between the cord rubberized layers becomes large. Belt separation may occur. The annular recess 6 has a skid base gauge t of 1.5 to 5.0 m at the deepest position.
It is preferably in the range of m. This is because if it is less than 1.5 mm, failure due to cutting is likely to occur, and if it exceeds 5.0 mm, the belt is likely to bend. Tread part 5
It is preferable that at least the surface layer rubber of the annular recess 6 has a percent elongation at break of 300% or more at room temperature in order to prevent cut.

Further, this pneumatic radial tire has one hoop reinforcing layer 7 consisting of a non-extensible rubberized layer in which cords are arranged in parallel inside the tread portion 5 in the tire radial direction.
Is equipped with. Although the hoop reinforcing layer 7 is arranged on the outer circumference of the belt 4 in FIG. 1, it may be arranged between the cord rubberized layer 3 or between the carcass 2 and the belt 4. At least one of the hoop reinforcing layers 7 is an annular concave portion 6 of the tread grounding surface under the condition where the tire is mounted on the applicable rim, the air pressure is set to a specified value, and the specified mass is added in a stationary state.
The width of the hoop reinforcing layer 7 having a width equal to or less than the non-grounding width corresponding to 1 is arranged corresponding to the annular recess 6. In order to prevent belt separation, the hoop reinforcing layer 7 may be provided not only at the position corresponding to the annular recess 6 but also at the position corresponding to each double crown.

Further, in the present invention, the negative ratio expressed as a percentage of the opening area of the non-grounded portion with respect to the entire contact area in the grounded state of the tread is 15 to 30% for each of the double crowns, and the annular recess 6 for all the treads. It is necessary that the negative rate calculated including the above is 40 to 60%. If the negative ratio is too large, the grip performance on a dry road surface deteriorates, and if it is too small, the drainage performance on a wet road surface deteriorates. The tread ground contacting state here means the tread grounding condition under the condition where the tire is mounted on the applicable rim, the tire is in a prescribed air pressure, and the tire is stationary and a prescribed mass is applied. Further, the ratio of the volume of the groove opened in the tread portion to the volume of the depression of the annular recess 6 in the tread ground contact state is 0.3 to 0.6.
It is preferable that it is within the range. If this range is too small, the drainage property during cornering will deteriorate, and if it is too large, the ground contact area will be small and the grip performance on a dry road surface will deteriorate. At least the surface rubber of the tread portion 5 is 30
It is preferable that tan δ at 0 ° C. is 0.3 or more in order to secure grip on a dry road surface. Furthermore, when higher drainage is desired, the lateral groove to be arranged in the double crown is preferably arranged in a so-called directional pattern. It is preferable to reinforce with a rubberized layer of an organic fiber cord represented by aramid. In order to prevent separation, the belt 4 preferably uses a pene cord as its cord.

Since the carcass shape is dented in the width center portion corresponding to the tread portion 5, the invention tire has a larger strain energy loss due to repeated bending applied to the carcass than a normal tire, and therefore the ply cord having a small loss It is preferable to use the organic fiber cord of, and polyester fiber is more preferable. The tire of the present invention may be used in combination with a so-called run-flat tire when importance is attached to safety when punctured. Further, when the tire is vulcanized, it is preferable to provide an air vent required for the tire mold corresponding to the annular recess.

[0012]

In the pneumatic radial tire 1 of the present invention, the tread portion 5 has an annular concave portion 6 recessed along the tread circumference inward in the tire radial direction at the width center, and the hoop corresponding to the annular concave portion 6. By disposing the reinforcing layer 7, it is possible to suppress the expansion of the tire diameter in the central portion of the tread during high-speed traveling,
By setting the width of the hoop reinforcing layer 7 to be equal to or less than the non-ground width corresponding to the annular recess 6, the belt rigidity can be appropriately maintained. Also, the carcass 2 and the belt 4
However, since the structure is such that it is recessed along the circumference of the tread at the annular recessed position, the restriction on the thickness of the tread rubber in the pneumatic tire disclosed in the above publication can be relaxed. Furthermore, by providing the annular recess 6, a very large hollow volume can be obtained, so that water entering the width center area of the tire ground contact surface when running on a wet road surface can be confined in the annular recess 6, and the tire and the ground can be prevented. Can be contacted without water intervention,
Also, since the tread will be a double crown, the actual ground contact area will not change much compared to normal tires, but the overall tread width will be wider, and non-ground contact with the total area of the contact area in the tread ground condition The negative ratio expressed as a percentage of the opening area of the part is 15 to 30% for each of the double crowns, and the negative ratio calculated for all treads including the annular recess 6 is 40 to 60% to obtain a dry road surface. Both grip performance on the road and drainage performance on a wet road surface can be improved.

[0013]

EXAMPLES Specific examples of the pneumatic tire according to the present invention will be described with reference to the drawings. Example The invention tire shown in FIG. 2 has a toroidal carcass 2,
A belt 4 formed by cross-laminating cord rubberized layers 3 and a tread portion 5 having a cap-and-base structure reinforced by the belt 4 are provided, and the tread portion 5 has a carcass 2 inwardly in a tire radial direction at a width central portion thereof. Further, the belt 4 and the belt 4 have an annular recess 6 recessed along the circumference of the tread, and the tread portion 5 has a double crown structure. This double crown is divided into a crown central side portion 8 and a crown lateral side portion 9 with a plane including the circumference of the maximum outer diameter of the tire as a boundary, and the crown shape of the crown central side portion 8 and the crown lateral side portion 9 is It was symmetric. The annular recess 6 has a recess depth D of 1
The thickness was 4.2 mm, and the skid base gauge t at the deepest position was 2.5 mm. The breaking elongation of the cap rubber of the tread portion 5 was 550% at room temperature. Further, on the outer periphery of the belt 4, a hoop reinforcing layer 7 having a width wider than that of the belt and a hoop reinforcing layer 7 having a narrow width at both ends thereof are provided. The hoop reinforcing layer 7 was provided so that its width was 50 mm with respect to the non-ground width (60 mm) corresponding to the annular recess 6 of the tread ground surface. Non-stretchable nylon cords were used for the cords of these hoop reinforcing layers, and the cords were arranged at 0 ° with respect to the tire equatorial plane. The negative rate in the tread contact state was 25% for one double crown, and the negative rate for all treads including the annular recess was 50%. The total groove volume of the non-grounded portion in the tread grounded state is 600 per 1 m including the annular recess 6 including the grounded length.
ml and the tread portion 5 with respect to the hollow volume of the annular recess 6
The ratio of the volume of the groove opened in the was 0.4%. Further, tan δ at 30 ° C. of at least the surface rubber of the tread portion 5 is set to 0.55. The belt 4 used a steel cord for the cord. Carcass 2 used a polyester fiber cord for its ply cord.

Comparative Example 1 The recess depth D of the annular recess 6 was 8.0 mm, and the volume of the groove opened in the tread portion including the recess volume was 350 ml per 1 m including the contact length, Except that the hoop reinforcing layer 7 corresponding to the concave portion 6 is not provided, and that the carcass 2 and the belt 4 are not depressed in the width center,
FIG. 3 having a structure substantially similar to the tire used in the example.
The tire shown in. Comparative Example 2 In the example except that the width of the hoop reinforcing layer 7 corresponding to the annular recess 6 was B × 1.2 mm with respect to the non-ground width (Bmm) corresponding to the annular recess 6 of the tread contact surface. The tire has a structure similar to that of the used tire.

The prior art example has a normal tread crown, carcass 2 and belt 4 shape without the annular recess 6 and the hoop reinforcing layer 7,
The tire shown in FIG. 4 has substantially the same structure as the tire used in the example except that the volume of the groove opened in the tread portion is 330 ml per 1 m including the ground contact length.

Test method The test was conducted on the following contents. (1) Measurement of side force and hydroplaning generation speed The side force is 8JJ × 16 for the tire rim size.
Was applied to a rim to which the tire was applied, and the tire was subjected to load rolling on a flat belt (safety walk) under the condition that a tire air pressure of 280 kPa and a mass of 660 kg were added, and measurement was performed.
Hydroplaning occurs at an air pressure of 250k
A tire of Pa is attached to the applicable rim, and the tire wheel is attached to a rear-wheel drive vehicle having a vehicle weight of 1.3 tons.
It was measured by running on a road surface having a water depth of 7 mm. The results of these tests are shown in Table 1. In addition, the value of the side force in Table 1 is shown by an index ratio, and the larger the value, the better.

[0017]

[Table 1]

From these results, in the example, the generation rate of hydroplaning was significantly increased as compared with the conventional example and the comparative example 1 without reducing the generation of side force.

(2) Relationship between Slip Angle and Side Force The relationship between slip angle and side force was examined by a flat belt tire characteristic tester. The test results are shown in Fig. 5.
Shown in.

From the test results, the slip angle increases and the side force tends to decrease in the comparative tire 2, but it does not decrease in the examples.

In addition to the above test, the following tests were conducted as auxiliary tests. (A) Relationship between skid base gauge and failure A tire was mounted on an actual vehicle, and after running on a bad road for 8000 km, the tire was visually inspected to check whether there were cut flaws in the tread or belt breakage, and the failure was comprehensively evaluated. The test results are shown in Table 2.

[0022]

[Table 2]

From the test results, the cut flaws of the tread were 1.
When it was 0 mm, it was recognized, and when it was 1.5 mm or more, there was no cut flaw. Further, belt breakage was not observed at 5 mm or less, but was observed at 5.5 mm. Therefore, the skid base gauge is 1.5 to 5.0 mm
There was no failure at that time.

(B) Relationship between elongation at break of cap rubber constituting tread portion and tire durability Four kinds of tires having different elongation at break were generated under the same test conditions as the above (a) after running for 4000 km. The tire durability was evaluated by examining the size and number of cut flaws of the tread. Table 3 shows the test results.

[0025]

[Table 3]

From the test results, the durability was greatly improved when the breaking elongation of the cap rubber was 300% or more.

(C) Measurement of tire radial expanded dimension at high speed when changing the tire radial position of the hoop reinforcing layer 7 arranged corresponding to the annular recess 6 The hoop reinforcing layer 7 of the belt 4 is The tires respectively arranged on the outer periphery (Example A), between the cord rubberized layer 3 (Example B), and between the belt 4 and the carcass 2 (Example C) were run at 200 km / h. The tire radial expansion dimension was measured. The test results are shown in Table 4.

[0028]

[Table 4]

From the test results, there is no great difference in arranging the hoop reinforcing layer 7 at any position, and there is an effect of suppressing expansion in the tire radial direction.

In the case of a tire in which at least one of the double crowns has asymmetrical radii of curvature between the crown central side portion 8 and the crown lateral side portion 9, the crown central side of the radius of curvature of this crown lateral side portion 9 When the ratio with respect to the proper ground contact shape was examined by changing the ratio of the portion 8 to the radius of curvature, when this ratio was less than 0.5, the wear on the width center side of the ground contact surface of the double crown was remarkable, and 5.
If it exceeds 0, wear on the shoulder side becomes remarkable. Therefore, the range of 0.5 to 5.0 became the proper grounding shape.

[0031]

According to the present invention, the tread portion 5 has the annular recessed portion 6 which is recessed inward in the tire radial direction along the tread circumference at the center of the width, and the hoop reinforcing layer 7 corresponding to the annular recessed portion 6. By arranging the above, since it is possible to suppress the radial expansion of the annular recessed portion 6 during high-speed traveling, sufficient drainage can be ensured, and there is an effect of suppressing the occurrence of the hydroplaning phenomenon. Further, by setting the width of the hoop reinforcing layer 7 to be equal to or less than the non-ground width corresponding to the annular recess 6, the belt rigidity can be appropriately maintained.
Further, since the carcass 2 and the belt 4 have a structure in which the carcass 2 and the belt 4 are depressed along the circumference of the tread at the annular recessed position, the restriction on the thickness of the tread rubber in the pneumatic tire disclosed in the above publication can be relaxed, and the tread rigidity and tread rigidity can be improved. It is advantageous in terms of tire weight. In addition, since the installation of the annular recessed portion 6 allows a very large hollow volume to be obtained, it is possible to confine in the annular recessed portion 6 water that enters the width center region of the tire ground contact surface during running on a wet road surface. Since the ground can contact without water intervention, it has the effect of suppressing the occurrence of the hydroplaning phenomenon. Also, since the tread crown will be a double crown, the actual ground contact area will not change much compared to normal tires, but the overall tread width will be wider, and non-ground contact with the total area of the contact area in the tread ground condition The negative ratio expressed as a percentage of the opening area of the part is 15 to 30% for each of the double crowns, and the negative ratio calculated for all treads including the annular recess 6 is 40 to 60% to obtain a dry road surface. Both grip performance on the road and drainage performance on wet road surface are improved.

[Brief description of drawings]

FIG. 1 is a width sectional view of a typical pneumatic radial tire according to the present invention.

FIG. 2 is a width sectional view of an inventive tire used in an example.

3 is a width sectional view of a comparative tire used in Comparative Example 1. FIG.

FIG. 4 is a width sectional view of a conventional tire used in a conventional example.

FIG. 5 is a diagram showing a relationship between a slip angle and a side force.

[Explanation of symbols]

1 Pneumatic radial tire 2 carcass 3 cord rubberized layer 4 belts 5 tread section 6 annular recess 7 hoop reinforcement layer 8 Crown center side 9 Crown lateral side L straight line t skid base gauge D Depth of annular recess S plane

Claims (8)

(57) [Claims] 1. A carcass having a toroidal shape, a belt in which cord rubberized layers are cross-laminated, and a tread portion reinforced by the belt, and the tread portion is a carcass radially inward at a width center portion thereof. And a pneumatic radial tire having a double crown structure by having an annular recess depressed along the circumference of the tread together with the belt, from the non-stretchable rubberized layer in which the cords are arranged in parallel on the tire radial inside of the tread portion. At least one of the hoop reinforcement layers, wherein at least one of the hoop reinforcement layers has a tread contact surface under a condition in which a tire is mounted on an applicable rim, a specified air pressure is applied, and a specified mass is added in a stationary state. , has the same or less width with respect to the non-contact width corresponding to the annular recess, the hoop reinforcement layer disposed in correspondence with the annular recess, and, DOO Against the contact region the total area of the head ground state
Negative expressed as a percentage of the open area of the ungrounded part
The rate is 15-30 for each of the double crowns
%, All treads were calculated including the annular recess.
A pneumatic radial tire having a gative ratio of 40 to 60% . 2. The recess depth of the annular recess is such that the maximum outer diameter position of the double crown is connected by a straight line in the tire width cross section,
The pneumatic radial tire according to claim 1, wherein a length of a perpendicular line drawn from the straight line to the deepest position of the annular recess is in a range of 10 to 15 mm. 3. The ratio of the volume of the groove opened in the tread portion to the volume of the depression of the annular recess in the tread grounded state is in the range of 0.3 to 0.6. 2. The pneumatic radial tire described in 2. 4. The pneumatic radial tire according to claim 1, 2 or 3, wherein the skid base gauge at the deepest position of the annular recess is in the range of 1.5 to 5.0 mm. 5. The pneumatic radial tire according to claim 1, wherein the surface rubber of at least the annular recess of the tread portion has a breaking elongation of 300% or more at room temperature. 6. At least the surface rubber of the tread portion is 3
Tan pneumatic at 0 degreeC is 0.3 or more, The pneumatic radial tire as described in any one of Claims 1-5 characterized by the above-mentioned. 7. The radius of curvature of the crown side portion when at least one of the double crowns is divided into a crown center side portion and a crown side portion with a plane including the circumference of the maximum outer diameter of the tire as a boundary. The radial radial tire according to any one of claims 1 to 6, wherein a ratio of the center of the crown to the radius of curvature of the crown is 0.5 to 5.0. 8. The pneumatic radial tire according to claim 1, wherein the hoop reinforcing layer is arranged at a position corresponding to the double crown.