JP2897185B2 - Pneumatic radial tire - Google Patents

Description

The present invention relates to an improvement of a pneumatic radial tire, and more particularly to a pneumatic radial tire having improved steering stability, particularly cornering performance. is there.

(Prior Art) With the recent increase in speed and horsepower of vehicles, required performance for steering stability has been further increased.

In addition, the technology for controlling the suspension, engine power, etc. of a vehicle using a computer has been advanced, and it has become possible to maximize the characteristics of the tires. There is a demand for further improvement in performance.

As a means of improving the steering stability of the tire itself, various methods have been conventionally studied, but recently, the importance of the tread portion of the tire has been confirmed, and various block patterns have been formed by circumferential grooves and lateral grooves. The mainstream is the formed tread, particularly a tire having a directional pattern in which a rotation direction is designated or a tread having left and right asymmetric patterns.

(Problems to be Solved by the Invention) In the conventional block pattern, when the block is strongly subjected to a lateral force when the tire is turning (at the time of cornering), the block is deformed and an excessive contact pressure is applied to a part of the block. The other one minute tends to float off the road surface, and as a result, the rigidity of the entire block cannot be sufficiently exerted, resulting in a problem that steering stability at the time of cornering is poor.

That is, as shown in FIGS. 5 (a) and (b),
When the tire goes straight [Fig. 5 (a)], the block or rib
40, the entire surface of the ground contact surface 40A is in contact with the road surface E. However, at the time of cornering [FIG. 5 (b)], the blocks in the area outside the equatorial plane of the tire on the turning outer wheel are subject to external force. In particular, since the outer side of the contact surface is excessively pressed against the outer surface in the axial direction while the inner surface 40B rises from the road surface E and wins, the contact surface area is reduced, and the rigidity of the block cannot be sufficiently exhibited. Stability is impaired.

Therefore, an object of the present invention is to solve the problems of the conventional pneumatic radial tire described above.

Therefore, an object of the present invention is to provide a pneumatic radial tire with improved steering stability, particularly cornering performance.

[Means for Solving the Problems] That is, in the pneumatic radial tire of the present invention, a pair of sidewalls and a cylindrical crown portion located at a radially outer end of both sidewalls are connected in a toroidal manner. A tread to be engaged with a road surface around the crown portion, and the tread is divided by a plurality of circumferential grooves extending parallel to each other at predetermined intervals in both side regions centered on the equatorial surface of the tire. In the tire provided with a plurality of land portions, the land portion has a reference surface indicating an average height from the groove bottom, with respect to this reference surface, at the axially outer end of the land portion from 0.05 to
It is characterized by a ground slope that is 1 mm lower and 0.05-1 mm higher at the axially inner end of the land. Further, it is preferable that the ground inclined surface is formed in a curved shape composed of an S or Z-shaped curve.

(Operation) The pneumatic radial tire of the present invention has a contact surface of the land portion (block or rib) with respect to a reference surface indicating an average height from the groove bottom at an axially outer end portion of the land portion at 0.05 to 1mm lower and 0.05 to 1mm higher at the axially inner end of the land portion, and preferably a curved ground contact surface composed of an S or Z-shaped curve. Even if a strong force is received, the ground contact area is compensated for by the ground contact slope, and the ground contact area does not decrease, so that the same ground contact area as when traveling straight can be maintained.

Therefore, according to the pneumatic radial tire of the present invention, since the block rigidity of the land portion can be maximized, the steering stability particularly at cornering is excellent, and stable high-speed running can be realized. it can.

(Example) Hereinafter, an example of the pneumatic radial tire of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a cross-sectional explanatory view of a pneumatic radial tire of the present invention, FIG. 2 is a developed view of a tread in FIG. 1, FIG. 3 is an enlarged cross-sectional explanatory view taken along line AA in FIG. FIG. 4A is a cross-sectional explanatory view of a land portion of the pneumatic tire of the present invention when traveling straight, and FIG. 4B is a cross-sectional explanatory view of a land portion during cornering.

As shown in FIG. 1, the pneumatic radial tire of the present invention includes a pair of sidewalls 10 and both sidewalls.
A cylindrical crown portion 20 located at the radially outer end of 10 is connected to the toroidal shape, and has a structure provided with a tread T around the crown portion 20 to be engaged with a road surface.

The crown portion 20 has a toroidal carcass (hereinafter simply referred to as a carcass) 21 in which organic fiber cords such as rayon or polyester are arranged in a direction substantially perpendicular to the equatorial plane, and a portion above the carcass 21. A belt layer 22 in which at least two plies of a layer in which non-extensible cords such as steel cords are arranged in an inclined manner are overlapped so that the cords intersect with each other. It has a structure in which at least two plies of the sex cord are reinforced by an auxiliary belt layer 23 which is arranged substantially parallel to the equatorial plane.

Further, the carcass 21 is folded back by the pair of bead wires 11 to form a folded portion 21A, and a hard rubber filler 12 is provided between the carcass 21 and the folded portion 21A.
Is arranged.

On the other hand, the tread T is provided with a plurality of circumferential grooves extending in parallel with each other at predetermined intervals in both side areas centered on the central circumferential groove along the equatorial plane O of the tire. There are several land areas. That is, although the right half from the equatorial plane 0 is omitted in FIG. 2, it is symmetric with respect to the equatorial plane 0 in this embodiment.

In the drawing, the center land portion 41, the intermediate land portion 42, and the shoulder land portion 43 are formed by a total of five peripheral grooves along the equatorial plane O, that is, the central circumferential groove 30, the intermediate circumferential groove 31, and the shoulder circumferential groove 32. A total of six lines are formed on each side of the equatorial plane O, three lines each.

In this embodiment, the tread T has a number of lateral grooves extending substantially parallel to the axial direction of the tire from the center thereof to both ends of the tread as shown in FIG.
50 are formed, whereby each land portion 41, 42 is further divided into a plurality of blocks 60.

The land portions 41 and 42 in the present invention do not necessarily need to be divided into the blocks 60 by the lateral grooves 50 as shown in the figure, and may be land portions (ribs) substantially continuous in the circumferential direction. Including.

Therefore, the land portions 41 and 42 in the present invention mean both blocks and ribs.

Here, the tread portion T is formed of ordinary hard rubber, but in some cases, soft rubber or foamed rubber can be used for at least a part thereof.

Each of the circumferential main grooves 30, 31, 32 may be a linear shape parallel to the circumferential direction as shown, or may be a broken line shape (deformed clang shape), and the groove width and depth are It is formed the widest and deepest in the groove group.

The lateral groove 50 may be linear as shown, or may be curved, and the groove width and depth are formed to be equal to or less than the circumferential main groove.

As shown in FIG. 1, the pneumatic radial tire of the present invention having the above-described configuration has a contact surface of each of the land portions 41 and 42 with a contact inclined surface having a high axial inside and a low axial outside. The important point is that the steering stability can be improved.

FIG. 3 shows an enlarged view of this ground slope.

That is, in FIG.
Are formed such that the height h 'of the axially outer end 42B is 0.05 to 1 mm lower than the reference plane S, and the height h of the axially inner end 42C is 0.05 to 1 mm higher than the reference plane S. ing.

In FIG. 3, a reference plane S, which is a reference of the inclination angle of the ground inclined surface 42A, is based on the average height H of the land portion 42 (the height of the land portion 42 substantially at the center).

Here, when the groove depths of the left and right circumferential grooves 31 and 32 of the land portion 42 are equal, the reference plane S can be indicated by the distance from the groove bottom. The reference plane S can be determined by the distance from the outermost layer of the belt layer 22.

In addition, the ground inclined surface 42A of the land portion 42 may have a simple inclination, but is desirably inclined in an S or Z shape as shown in the figure.

Next, the operation and effect of the pneumatic tire of the present invention having the above configuration will be described with reference to FIGS. 4 (a) and 4 (b).

First, when the tire travels in the straight traveling direction, as shown in FIG. 4 (a), the entire contact surface 40A of the land portion 40 is in contact with the road surface E.

On the other hand, at the time of cornering, as shown in FIG. 4 (b), the land portion 40 receives a strong lateral force and is distorted, and the ground contact surface on the inner side in the axial direction tends to rise. Is compensated by the height of the axial end of the contacted inclined surface, and the same contact area as when traveling straight ahead is secured, so that the rigidity of the land part 40 is ideally exhibited and excellent steering stability is obtained. You can do it.

Hereinafter, the configuration and effect of the pneumatic radial tire of the present invention will be described in more detail with reference to test examples.

(Test example) Tire size: 205 / 50ZR17, rim used: 7JJ × 17, working air pressure: 2.55 kg / cm ^{2 For} the tread of a radial tire, the conditions shown below and the ground contact surface of the land shown in the following table Two types of tires of the present invention tire and the conventional tire were manufactured under given conditions, and the steering stability of these tires was evaluated under the following conditions. The results are shown in the following table.

The structures of the carcass, the belt layer, the auxiliary belt layer, and the tread pattern were as follows in common with the tire of the present invention and the conventional tire.

Carcass cord type ... rayon cord angle ... 90 degrees Number of plies ... 2 belt layer cord type ... 1 x 3 steel cord angle ... 25 degrees Ply number ... ... 2 auxiliary belt layer cord type ... 1260/2 nylon cord angle … Approximately 0 degrees Number of plies …… 2 Tread pattern Tread width… 198mm on both sides Central circumferential groove width… 4mm 〃 Depth… 7.6mm Intermediate circumferential groove width… 12mm… Depth… 8mm Shoulder circumferential groove width… 11mm 深 Depth Depth: 7.5mm Lateral groove width: 2mm 〃 Depth: 7.6mm Driving stability evaluation method Using flat belt type indoor drivability tester,
The cornering power and the maximum cornering force were measured.

Note 1) The surface of the block had a curved shape shown in FIG. 3 for the tire of the present invention.

Note 2) Both the tire of the present invention and the conventional tire are symmetrical with respect to the equatorial plane (see FIGS. 1 and 2).

From the above results, it is clear that the pneumatic radial tire of the present invention has extremely improved handling stability, particularly cornering performance.

[Effects of the Invention] As described above in detail, the pneumatic radial tire of the present invention is configured such that the ground contact surface of the land portion (block or rib) is moved with respect to the reference surface indicating the average height from the groove bottom. Constructed as a ground slope with 0.05-1 mm lower at the axially outer end of the land and 0.05-1 mm higher at the axial inner end of the land, preferably a curved grounded slope consisting of an S or Z-shaped curve Therefore, even when the land portion receives a strong lateral force, particularly at the time of cornering, the ground contact area is compensated by the above-described ground contact slope, the ground contact area does not decrease, and the same ground contact area as when traveling straight can be maintained. .

Therefore, according to the pneumatic radial tire of the present invention, since the block rigidity of the land portion can be maximized, the steering stability particularly at cornering is excellent, and stable high-speed running can be realized. it can.

[Brief description of the drawings]

FIG. 1 is an explanatory cross-sectional view of a pneumatic radial tire of the present invention, FIG. 2 is a developed view of a tread in FIG. 1, FIG. 3 is an enlarged cross-sectional explanatory view taken along line AA in FIG. a) is a cross-sectional explanatory view of a land portion of the pneumatic tire of the present invention when traveling straight, FIG. 4 (b) is a cross-sectional explanatory view of the land portion at the time of cornering, and FIG. 5 (a) is a conventional pneumatic tire. FIG. 5 (b) is an explanatory cross-sectional view of the land portion when the vehicle is traveling straight.
FIG. 5 is an explanatory cross-sectional view of a land portion at the time of cornering. 10 Side wall 11 Bead wire 12 Hard rubber filler 20 Crown part 21 Carcass 22 Belt layer 23 Auxiliary belt layer T Tread part O Equatorial plane 30 Central circumference Directional groove 31 Middle circumferential groove 32 Shoulder circumferential groove 41 Center land 42 Side land 50 Horizontal groove 60 Block

Continuation of the front page (56) References JP-A-2-185807 (JP, A) JP-A-57-41202 (JP, A) JP-A-1-289706 (JP, A) JP-A-61-92903 (JP, A) JP-A-63-17102 (JP, A) JP-A-62-241709 (JP, A) JP-A-61-229603 (JP, A) JP-A-63-6902 (JP, U) Patent 2573196 (JP, U) JP, B1) JP-B-57-33163 (JP, B2) JP-B-6-3682 (JP, Y2) JP-B-52-57524 (JP, Y2) (58) Fields surveyed (Int. Cl. ⁶ , (DB name) B60C 11/00-11/11

Claims (2)

(57) [Claims] 1. A pair of sidewalls, and a cylindrical crown portion located at a radially outer end of both sidewalls are toroidally connected, and a tread to be engaged with a road surface around the crown portion is provided. In a tire provided with a plurality of land portions divided by a plurality of circumferential grooves extending in parallel with each other at predetermined intervals in both side regions centered on the equatorial plane of the tire, the land portion is an average from the groove bottom. It has a reference surface indicating the height, and is lower than this reference surface by 0.05 to 1 mm at the axially outer end of the land, and 0.0 at the axially inner end of the land.
A pneumatic radial tire having a 5 to 1 mm higher contact slope. 2. The pneumatic radial tire according to claim 1, wherein the ground reference surface has a curved shape composed of an S or Z-shaped curve.