JP2878358B2 - Pneumatic radial tire - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a pneumatic radial tire with improved cornering characteristics.

[Conventional technology]

In recent years, with the increase in speed and performance of vehicles, high handling stability, especially straight running stability at high speeds, road surface grip during turning, and controllability of breakaway, etc. have also been improved for tires. It is desired for both a road surface and a wet road surface. Therefore, a double crown radius has conventionally been adopted as a contour shape of a tread surface.

[Problems to be solved by the invention]

However, with conventional double crown radius tires, although the steering wheel responsiveness and road surface grip during straight running or early turning are improved to some extent, the marginal performance at cornering, such as breakaway controllability, is not enough. Not improved.

Note that breakaway is a phenomenon in which the cornering force generated on the ground contact surface due to the slip angle during cornering becomes insufficient compared to the centrifugal force, causing the entire tire to skid and deviating from the cornering track. Is the eighth
As shown in the figure, it is considered that the cornering force CF, which increased substantially in proportion to the slip angle α in the range where the slip angle α is small, gradually decreases the increase rate in the range where the slip angle α is large.

The present invention is based on the fact that the intersection of the first arc and the second arc forms a wide main groove passing through the opening, thereby improving the marginal performance at cornering, and particularly improving the steering stability at high speed running. It aims to provide a pneumatic radial tire that can be used.

[Means for solving the problem]

In order to achieve the above object, the present invention provides a carcass having a radial structure in which a bead portion of a bead portion is turned around from a tread portion to a sidewall portion, and is disposed radially outward of the carcass and inside the tread portion. The tread surface on the outer surface of the tread portion has a center at the tire equatorial plane, a radius of curvature R1 and a first arc passing through the tire equatorial point, and a center at the tire equatorial plane. A radius of curvature R2 smaller than the radius of curvature R1 and a second arc intersecting the first arc at a position separating the tire width SW by 0.2 to 0.25 times the equatorial plane of the tire. The intersection of the arcs forms a main groove passing through the opening, and this main groove has a groove width equal to the tire width.
It is not less than 0.06 times and not more than 0.10 times SW and extends linearly and circumferentially, and extends in the direction intersecting the tire circumferential direction on the crown portion between the main flutes and the shoulder portion outside the main flutes. Thus, the pneumatic radial tire is provided with a large number of transverse grooves having a small groove width and dividing a crown portion and a shoulder portion into blocks.

[Action]

The tread surface is formed as a double crown radius having a first arc and a second arc. Accordingly, the shape of the ground contact surface is improved, and in addition to the straight running stability particularly during high-speed running, the controllability of the breakway during cornering is enhanced, and the turning stability is improved.

Further, the degree of freedom in selecting the first arc and the second arc is increased, and the radius of curvature can be optimized, which can be used to improve the running performance of the tire, and the die can be easily manufactured.

Since the intersection of the first and second arcs passes through the opening and has a wide and linear main groove that is 0.06 times or more and 0.10 times or less the tire width, ground disturbance that tends to occur at the intersection of the arcs It improves drainage and grounding while improving cornering force and improves wet brake performance. In addition, the crown portion and the shoulder portion are formed in a block shape by the lateral grooves, so that a gripping force with a road surface is increased and traveling performance is improved.

〔Example〕

 An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of the present invention in a standard internal pressure state mounted on a standard rim 8 and filled with a standard internal pressure.

The pneumatic radial tire 1 has a flat portion including a bead portion 3 through which a bead core 2 passes, a sidewall portion 4 connected to the bead portion 3 and extending outward in the tire radial direction, and a tread portion 5 connecting between outer ends thereof. In the case of the tire shown in FIG. 1, the flatness ratio H / SW, which is the ratio of the tire section height H to the tire width SW, is set to 0.62.

Between the bead portions 3, a carcass 7 whose both ends are bent from the inside to the outside around the bead core 2 at both ends of the main body portion 7A passing through the tread portion 5 and the sidewall portion 4, and the carcass 7 A belt layer 9 is wound outside and inside the tread portion 5.

The carcass 7 is formed by applying an organic fiber cord such as nylon, polyester, or aromatic polyamide to the tire equator CO.
In this example arranged at an angle of 75 to 90 °, the carcass plies are formed from two carcass plies 7a and 7b, and the folded end 7a1 of the inner carcass ply 7a covers the folded end 7b1 of the outer carcass ply 7b at a standard internal pressure state. End near the maximum tire width position.
Further, a bead apex 10 made of hard rubber, for example, having a JISA hardness of 65 ° to 90 ° and extending in a tire radial direction from the bead core 2 is provided between the main body portion 7A and the folded portion 7B of the carcass 7, In cooperation with the high turn-up structure of the carcass 7, the lateral rigidity of the tire is increased.

The bead portion 3 has a well-known or known reinforcing structure such as a bead filler for reinforcing the bead apex 10 together with the bead core 2 and a chafer for preventing rim displacement.

In this example, the belt layer 9 has a two-layer structure including an inner belt ply 9a adjacent to the outside of the carcass 7 and an outer belt ply 9b, and a belt width exceeding the tire contact width TW along the carcass 7. By having the BW, the tread portion 5 is reinforced over substantially the entire width thereof with a tag effect. Here, the tire contact width TW is a contact outer edge point E, which is a point of a tire axial direction outer edge of the tread contact surface TS in a standard load state in which a normal load is applied to a tire mounted on the standard rim 8 and filled with a standard internal pressure, Is the straight line length between E,
The belt width BW is a linear length between the outer edges U and U of the belt layer, which is the outer edge of the region where at least two belt plies overlap, in the standard internal pressure state.

And the belt width BW is 0.7 times or more of the tire width SW and
It is preferably 0.85 times or less. When the thickness is less than 0.7 times, the restraining force on the carcass 7, particularly the restraining force on the overhang portion of the carcass 7 protruding outward from the bead portion 3 in the tire axial direction due to the flattening, is lacking. This lack of binding force
The outer diameter of the shoulder portion grows in the tire radial direction due to centrifugal force, tire internal pressure, and the like accompanying high-speed rotation, and the contact pressure at this portion becomes uneven.

If it exceeds 0.85 times, the tire rigidity is excessively increased, and the ride comfort is reduced. Therefore, the belt width BW is more preferably not less than 0.75 times and not more than 0.85 times the tire width SW.

The belt plies 9a and 9b are each formed by a belt cord inclined at an angle of 10 ° to 30 ° with respect to the tire circumferential direction, and the belt cord has an initial tensile elastic modulus of 2500.
kg / cm ² or higher high modulus cord,
For example, organic fiber cords such as aromatic polyamide fibers and carbon fibers, and inorganic fiber cords such as metal fibers and glass fibers are used. Although a steel cord is used in this example, different kinds of material codes may be used for the respective belt plies 9a and 9b as required. Or belt layer 9
A soft breaker cushion 13 is interposed between the end of the carcass 7 and the carcass 7 to alleviate the stress.

On the outer side of the belt layer 9, in this example, a nylon cord or the like is used.
A reinforcing band 15 made of an organic fiber cord having relatively high strength and low mass is provided to suppress lifting of the belt layer 9 due to centrifugal force or the like. The reinforcing band 15 covers the outer end of the belt ply 9b, and the first band ply 15a for preventing the separation from the outer end and the entire width of the belt layer 9 together with the band ply 15a and the in-plane rigidity. And a second band ply 15b that uniformly increases the

The tread surface S on the outer surface of the tread portion 5 has a pair of main grooves 16 for dividing the tread surface S into a crown portion S1 including the tire equator CO and a shoulder portion S2 outside the crown portion S1. The first arc P1 and the second arc P2 forming the reference curved surface P
Are arranged linearly and in the tire circumferential direction with the intersection H of the inside located in the opening.

As shown in FIG. 4, the reference curved surface P has a center on the tire equatorial plane and a first arc P1 having a radius of curvature R1 passing through the tire equatorial point A, and has a center on the tire equatorial plane and the tire has the center. A second arc P2 having a radius of curvature R2 intersecting the first arc P1 at the intersection H separating 0.2 to 0.25 times the width SW from the tire equatorial plane.
, And a third arc surface outside the third arc P3. The third arc P3 forms a tread surface S at the outer peripheral point E on the ground.
A belt intermediate point having a center on a normal line n and a tire axial direction line L extending parallel to the tire axis through the belt layer outer edge U and the thickness center of the belt layer 9 and intersecting the tread surface S. F and an arc having a radius of curvature R3 passing through the ground outer edge point E, wherein the second arc P2 is a correction coupling line P2a
Connected through. In this specification, the tire outer surface between the belt intermediate points F, F is referred to as a tread surface S.

The main groove 16 is the first groove as shown in FIG.
The intersection point H of the arc P1 and the second arc P2 is located within the opening and extends in the tire circumferential direction, and the crown S1 between the main grooves 16 and the shoulder S2 outside the main groove 16 have the tire circumference. By crossing the main groove 16 in a direction intersecting with the direction, a small transverse groove 19 having a bent groove width 19W is partitioned in the circumferential direction so as to be divided into a large number of blocks. In this example, a sub-groove 20 extending in the tire circumferential direction substantially parallel to the main groove 16 is formed in the crown portion S1. The sub groove 20 is a shoulder
It may be provided on S2, or may be provided on shoulder S2 together with crown S1.

The main groove 16 and the sub-groove 20 are linear grooves in this example, and the groove width 16W of the main groove 16 is formed to be 0.06 times or more and 0.10 times or less the tire width SW. This can enhance the drainage effect while reducing the decrease in the cornering force. Groove width 16
If W is less than 0.06 times the tire width SW, the wet brake performance is insufficient, and if it exceeds 0.10 times, uneven wear such as rail wear near the groove edge is promoted.

The phrase that the intersection point H passes through the opening of the main groove 16 may be a range where the intersection point H is separated from the center by a length equal to or less than 1/2 of the main groove width 16W.

The sub-groove 20 enhances grip performance during cornering and maintains steering stability, and also reduces the impact noise of the road surface of the block and reduces pattern noise.
Are formed 0.1 times or more and 0.3 times or less of the groove width 16W of the main groove 16, respectively. If the ratio is less than 0.1 times, the drainage becomes insufficient. If the ratio exceeds 0.3 times, the pattern rigidity in the width direction is reduced, and the handle responsiveness and the controllability of the breakaway are reduced.

The number of sub-grooves is preferably one or more and four or less, and the tread pattern can be variously deformed by providing sipes and lug grooves in addition to the main groove 16, the lateral groove 19, and the sub-groove 20.

Further, for the curvature radii R1 and R2, the flatness H / SW is 0.
In this example, which is 62, the radius of curvature R of the reference curved surface P
1, the radius ratio R1 / R2 of R2 and R3 is 1.6 or more and 2.6 or less, and the radius ratio R2 / R3 is 4 or more and 12 or less.

This reference curved surface P is an ideal curved surface capable of improving the steering stability from the viewpoint of the shape of the contact surface, and the contact surface shapes d1 and d2 in a normal load state with a sliding angle of 0 degree are shown in FIGS. 5 (a) and 5 (b).
As shown in FIG. 5, the contact surface TS having a substantially horizontal rectangular shape with the front and rear edges e1 and e2 substantially parallel to the tire axis can be obtained. As a result, a uniform contact pressure distribution and a high cornering force can be obtained, and the responsiveness and grip of the steering wheel during straight running or at the beginning of turning can be improved.

When the radius ratio R1 / R2 is less than 1.6, as shown in FIG. 5 (c), the contact length of the crown S1 is longer than the contact length of S2 of the shoulder and the front and rear edges e1, e2 are curved. It becomes a deformed substantially butterfly-shaped grounding surface shape d3, and is inferior in grounding performance. Radius ratio R1
When / R2 exceeds 2.6, as shown in FIGS. 5 (d) to 5 (e), the contact length of the crown portion S1 becomes a very long and irregular rhombic contact surface shape d4, d5, and the contact inconsistency of the contact property becomes uneven. And the cornering force is reduced. (Note that FIGS. 5A to 5E show that the tire flatness is 0.62 and the radius ratio R1 / R.
2 is 3.1, 4.0, 1.7, 5.2, and 8.5, respectively. The reference curved surface P has a radius ratio R2 / R between the intermediate arc P2 and the outer arc P3.
3 is restricted to 4 to 12, so when turning, the outer edge E
The outer arc P3 on the outside can be newly grounded, and as shown in FIG. 6, the reduction of the grounding width and the increase of the grounding length are suppressed as compared with the conventional grounding surface shape d6 during turning, and the cornering force is reduced. Can be optimized.

7 (a) and 7 (b) show the relationship between the radius ratio R2 / R3 and the reduction in the contact width and the controllability of the breakaway. As shown in FIG. 7, the radius ratio R2 / R3 is in the range of 12 or less, particularly 10 or less. In the range, the decrease in the contact width can be suppressed, and the cornering force can be increased, thereby improving the controllability of the breakaway. However, the radius ratio R2
If / R3 is less than 4, the uneven wear resistance is reduced, so that the radius ratio R2 / R3 is in the range of 4 or more and 12 or less, more preferably 6 or more and 10 or less. FIG. 7A shows the measured values when the slip angle is 5 degrees, and the broken line indicates the conventional level. FIG. 7 (b) shows the result of evaluating the breakaway controllability by an actual vehicle feeling test, and the broken line shows the case of a conventional tire.

In order to effectively exhibit the characteristics of the reference curved surface P, as shown in FIG.
A range Q1 having a length of 30% of the tire width SW around the center, a range Q2 separating a tire ground width TW of 37.5% or more and 45% or less from the tire equator CO, and the ground outer edge point E and the belt layer intermediate point F. It is necessary to make the tread surface S along the reference curved surface P in the range Q3. In this example, the range Q1
The main groove 16 is arranged between the area Q2 and the area Q2, and is connected by a substantially smooth curved surface including the area between the area Q2 and the area Q3. As a result, a tread surface S having a high steering stability performance substantially equal to the reference curved surface P is obtained. In addition, the area other than the ranges Q1, Q2, and Q3 may be formed along the reference curved surface P, or the entire tread surface may be formed along the reference curved surface P.

Also, in the relationship between the flattening ratio H / SW and the ratio R1 / R2, when the flattening ratio H / SW is set to 0.55 or less, the ratio R1 / R2 is set to 2.6 times or more and 4.6 or less, and the flattening ratio H / SW is larger than 0.55 and When the ratio is less than 0.70, the ratio R1 / R2 is 1.6 or more and 2.6 or less, and when the flattening ratio H / SW is 0.7 or more, the ratio R1 / R2 is 1.2 or more and less than 1.6. It has been found that the shape of the ground contact surface can be optimized as in FIGS. 5 (a) and 5 (b).

This is because the larger the flatness ratio H / SW, that is, the larger the tire section height H, the larger the amount of deflection when the tire is in contact with the ground. By approaching the radius R1, it is considered that a horizontally long substantially rectangular contact surface shape with the front and rear edges substantially parallel to the tire axis can be obtained.

〔Concrete example〕

A tire having the tire structure shown in FIG. 1 and having a tire size of 225 / 50R16 based on the specifications in Table 1 was prototyped, and the steering stability performance of the tire was measured on a dry road surface and a wet road surface by an actual vehicle running test. The ring was evaluated. In addition, the evaluation results are shown in Table 1 by a five-point method, and the larger the score, the better.

〔The invention's effect〕

As described above, the pneumatic radial tire of the present invention can enhance the marginal performance such as cornering.

[Brief description of the drawings]

1 is a sectional view showing an embodiment of the present invention, FIG. 2 is a partial plan view showing a tread groove, FIG. 3 is a diagram showing a contour shape of a tread surface, and FIG. 4 is a line showing a reference curved surface. FIGS. 5 (a) to 5 (e) are schematic diagrams showing the shape of the ground contact surface, FIG. 6 is a schematic diagram showing the shape of the contact surface during turning, and FIG. 7 (a) is a radius ratio R2 / R.
FIG. 7B is a diagram showing the relationship between 3 and the contact width, and FIG.
FIG. 8 is a diagram showing a relationship between 2 / R3 and breakaway controllability, and FIG. 8 is a diagram showing a relationship between a cornering force and a slip angle. 2 ... bead core, 3 ... bead part, 4 ... side wall part, 5 ... tread part, 7 ... carcass, 9 ... belt layer, 16 ... main groove, 19 ... horizontal groove, 20 ... auxiliary Groove, A ...
Tire equator point, CO ... Tire equator, E ...
F: belt intermediate point, H: intersection point, L: tire axis direction line, P: reference curved surface, P1: first arc, P2 ... second arc, P3 ... third arc, S ... Tread surface, S1 ... crown part, S2 ... shoulder part.

Continuation of the front page (56) References JP-A-55-22534 (JP, A) JP-A-60-60404 (JP, A) JP-A-59-124406 (JP, A) JP-A-63-184505 (JP) JP-A-60-148702 (JP, A) JP-A-52-111104 (JP, A) JP-A-63-240403 (JP, A) JP-A-61-146606 (JP, A) 58-147803 (JP, U) JP-A 63-6902 (JP, U) Utility model registration 2524780 (JP, Y2) JP 7-64165 (JP, B2) JP 2 6644 (JP, B2) JP-B-47-17643 (JP, B1) (58) Field surveyed (Int. Cl. ⁶ , DB name) B60C 3/00 B60C 11/00-11/06

Claims (3)

(57) [Claims] 1. A belt comprising a radially structured carcass folded back around a bead core of a bead portion from a tread portion to a sidewall portion, and a belt ply disposed radially outward of the carcass and inward of the tread portion. A first arc passing through the tire equatorial point and having a center at the tire equatorial plane, and a radius of curvature R1 having a center at the tire equatorial plane. A radius of curvature R2 smaller than 0.2 and 0.2 to 0.25 times the tire width SW and a second arc intersecting the first arc at a position separated from the tire equatorial plane, and the intersection of the first arc and the second arc is within the opening. A main groove passing through the tire width SW.
Not less than 0.06 times and not more than 0.10 times that of the tire, extending linearly and circumferentially, and extending in a direction intersecting the tire circumferential direction on the crown portion between the main flutes and the shoulder portion outside the main flutes. A pneumatic radial tire provided with a large number of lateral grooves having a small groove width that divide a crown portion and a shoulder portion into blocks in the form of a block. 2. The method according to claim 1, wherein the crown portion or the shoulder portion has a sub-groove having a groove width of 0.1 to 0.3 times the groove width of the main groove and extending linearly in the circumferential direction of the tire. The pneumatic radial tire according to claim 1. 3. The tread surface has at least two belt plies overlapping with the first arc, the second arc, and the outer peripheral contact point in the tire axial direction of the contact surface when a normal load is applied. The tire axial line passing through the intermediate height position of the outer edge of the belt layer, which is the outer edge of the region, includes a third arc of a radius of curvature R3 passing through a belt intermediate point intersecting the tread surface, and the third of the radius of curvature R2, R3 The ratio R2 / R3 is 4 or more and 12 or less, the belt width which is the distance between the outer edges of the belt layer is larger than the contact width which is the distance between the contact outer edge points, and the ratio R1 of the radii of curvature R1 and R2. / R2, when the flatness H / SW, which is the ratio of the tire section height H to the tire width SW, is 0.55 or less, and the curvature radius ratio
R1 / R2 is not less than 2.6 and not more than 4.6, and the ratio R1 / R2 when the aspect ratio H / SW is larger than 0.55 and smaller than 0.70 is 1.6 or more and 2.6.
2. The pneumatic radial tire according to claim 1, wherein the ratio R1 / R2 is 1.2 or more and 1.6 or less when the aspect ratio H / SW is 0.70 or more.