JPH03112703A - Pneumatic radial tire - Google Patents

Abstract

PURPOSE:To properly maintain a good ground contact area even at the time of braking by forming a ground contact slant surface having a higher circumferential forward end coming first in contact with the ground in travel on a block separated with the circumferential and lateral grooves of a tread. CONSTITUTION:A tire comprises a pair of side walls 10, and a cylindrical crown part 20 at the radial external end thereof toroidally continuous to each other, and a tread T in contact with a road around the crown part 20. The tread T has a plurality of blocks 60 formed with a plurality of circumferential grooves 30-32 along an equatorial surface 0, and a plurality of lateral grooves orthogonal therewith. In the aforesaid construction, the ground contact area 60A of the blocks 60 is made to have a higher circumferential forward end part 60B coming first in contact with a road during travel, and a lower circumferential rear end part 60C coming later in contact with the road. According to the aforesaid construction, a ground contact area is properly maintained with the ground contact slant surface, even when the blocks 60 are subjected to a strong braking force.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a pneumatic radial tire, particularly to an improvement in a radial tire for passenger cars, and more particularly to a pneumatic radial tire with improved braking performance. It is something.

(Prior Art) In recent years, as vehicles have increased in speed, increased horsepower, and diversified drive systems, the performance requirements for tires have also increased. Braking performance is particularly important for four-wheel drive (4WD) vehicles.

In other words, in a conventional two-wheel drive (2WD) vehicle, two wheels are driven and braking is performed by four wheels. On the other hand, in the case of a 4WD vehicle, braking is similarly performed on all four wheels, but while 2WD has superior dynamic characteristics such as acceleration ability, the braking performance is superior to that of 2WD.
The reality is that even higher braking performance is required from the standpoint of safety.

(Problem to be Solved by the Invention) On the other hand, the tread of a conventional tire usually has 4 to 8 circumferential grooves arranged at equal intervals approximately parallel to the axial direction, and grooves arranged in a direction that intersects with these circumferential grooves. A block pattern is formed consisting of a large number of lateral grooves that extend from the center of the tread to both ends of the tread or from one end of the tread to the other, and a large number of blocks that are divided by these circumferential grooves, lateral grooves, and tread ends. The height of each block was the same at any position.

However, when a tire brakes, a frictional force is generated between the road surface and the tire tread surface (contact surface), and this is how the braking force is obtained. When the action is applied, the independent blocks deform individually, some areas of the block are overly pressurized, and other areas are lifted off the road surface, and the rigidity of the block itself is not fully demonstrated. There was a problem with braking performance due to the frictional force of the block.

FIGS. 5(a) and 5(b) are diagrams explaining this point. That is, when the tire is being driven [FIG. 5(a)], the entire surface of the ground contact surface 60A of the block 60 is in contact with the road surface E. When a braking force is applied to the block 6o (Fig. 5 (b)), a pulling force acts on the block in the opposite direction to the traveling direction of the tire, the block deforms, and excessive ground pressure is applied to the part that touches the ground first. On the other hand, since the contact surface 60C on the side that makes contact with the ground later becomes lifted from the road surface E, the contact area is reduced, and as a result, block rigidity cannot be fully exerted, and braking performance is hindered.

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

Accordingly, an object of the present invention is to provide a pneumatic radial tire with improved braking performance.

[Configuration of the Invention (Means for Solving the Problems) That is, the pneumatic radial tire of the present invention has a pair of sidewalls and a cylindrical crown portion located at the radially outer ends of both sidewalls that are connected in a toroidal manner. , a tread that engages with the road surface is provided around the crown portion,
The tread includes a plurality of circumferential grooves that extend parallel to each other at predetermined intervals on both sides of the tire with the equatorial plane as the center, and a plurality of circumferential grooves that intersect with these circumferential grooves at an acute angle and that are arranged at predetermined intervals in the circumferential direction. A large number of lateral grooves extending in a herringbone shape from the center of the tread to both ends of the tread at intervals, and a large number of blocks separated by the circumferential grooves and the lateral grooves,
In a tire with a designated rotation direction, the block sandwiched between the two circumferential grooves of the tread has a circumferential leading edge that touches the ground first when running, and a circumferential trailing edge that touches the ground later. It is characterized by the formation of a high, sloping ground surface.

(Function) The pneumatic radial tire of the present invention has a ground contact surface of the block that is inclined so that the circumferential leading end that contacts the ground first during running is higher than the circumferential rear end that contacts the ground later. Because it is configured as a surface, even if the block is subjected to strong force during braking, the ground contact area is compensated by the above-mentioned inclined contact surface, and the ground contact area does not decrease, making it possible to secure the same ground contact area as when driving straight. can.

Therefore, according to the pneumatic radial tire of the present invention, since the block rigidity can be maximized during braking, the braking performance is excellent, and it has particularly ideal performance for 4WD vehicles. ing.

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

FIG. 1 is an explanatory cross-sectional view of the pneumatic radial tire of the present invention, FIG. 2 is a developed view of the tread in FIG. a)
4(b) is an explanatory cross-sectional view of the block during driving of the pneumatic tire of the present invention, and FIG. 4(b) is an explanatory cross-sectional view of the block during braking.

As shown in FIG. 1, the pneumatic radial tire of the present invention includes a pair of sidewalls 10 and a cylindrical crown portion 20 located at the radially outer ends of both sidewalls 10, which are connected in a toroidal manner. It has a structure including a tread T around the tread 20 that is to be engaged with the road surface.

The crown portion 20 includes a toroidal carcass (hereinafter simply referred to as a carcass) 21, which is a layer of organic fiber cords such as rayon or polyester arranged in a direction substantially perpendicular to the equatorial plane, and an upper part of the carcass 21. A belt layer 22 has at least two layers in which non-stretchable cords such as steel cords are arranged at an angle, and these cords overlap each other so that the cords intersect with each other. The structure is reinforced by an auxiliary belt layer 23 in which gender cords are arranged substantially parallel to the equatorial plane.

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

On the other hand, as shown in FIG. 2, the tread T includes a plurality of circumferential grooves 30, 31, and 32 extending parallel to each other at predetermined intervals on both sides of the tire with the equatorial plane O as the center. A large number of lateral grooves 50 intersect with the circumferential grooves at an acute angle and extend in a herringbone shape from the center of the tread T to both ends of the tread at predetermined intervals in the circumferential direction, and are divided by the circumferential grooves and the lateral grooves. The rotation direction is designated as the direction of the arrow.

That is, although the right half of the equatorial plane 0 is omitted in FIG. 2, it is symmetrical with respect to the equatorial plane 0 in this embodiment. In the drawing, the center ridge portion 41. A total of six intermediate land portions 42 and shoulder ridges 43 are formed in rows, three each on the left and right sides of the equatorial plane O, and these ridges extend from the center of the tread to both ends of the tread approximately in the axial direction of the tire. It is divided into a plurality of blocks 60 by a large number of lateral grooves 50 extending in parallel in a herringbone shape.

Here, the tread portion T is formed from ordinary hard rubber, but depending on the case, soft rubber or foamed rubber may be used for at least a portion thereof. Each circumferential main groove 3
0.31.32 may be in the shape of a straight line parallel to the circumferential direction as shown in the figure, but may also be in the form of a polygonal line (deformed flang shape), and the groove width and depth are the same in the groove group. It is the widest and deepest formed.

Further, the lateral groove 50 may be linear as shown in the figure, but may also be curved, and the groove width and depth are formed to be equal to or smaller than the circumferential main groove.

In the pneumatic radial tire of the present invention having the above configuration, the circumferential tip portion that touches the ground first when each block runs is
It is important to form an inclined ground contact surface that is higher than the circumferential rear end portion which contacts the ground later than this, and thereby the braking performance can be improved.

The third example is a detailed enlargement of this sloping ground plane.
It is a diagram. In FIG. 3, the inclined ground surface 60A of the block 60 is formed so that the circumferential front end 60B, which touches the ground first during running, is higher, and the circumferential rear end 60C, which touches the ground later, is lower. has been done.

Here, the height h of the circumferential tip portion 60B that touches the ground first and the circumferential rear tip portion that makes contact with the ground later with respect to the reference white S based on the average height H of the block 60 (substantially the height of the center of the block 60). The height h″ of the end portion 60C is 0.05 to 1, respectively.
It is preferable to select from a range of related areas.

Further, the inclined ground surface 60A of the block 60 may be a simple linear inclination, but it is preferably inclined in an S or Z shape as shown in FIG.

Next, the effects of the pneumatic tire of the present invention having the above-mentioned configuration will be explained with reference to FIGS. 4(a) and 4(b).

First, when the tires are driven, all of the contact surfaces 60A of the blocks 60 are substantially evenly in contact with the road surface E, as shown in FIG. 4(a).

On the other hand, when the brake force acts on the block, as shown in Figure 4 (
As shown in b), the block 60 is distorted by the strong force from the road surface E, and the rear end 60C in the circumferential direction that touches the ground later tries to lift up, but the floating portion is caused by the above-mentioned inclined ground surface. Since the same ground contact area as when driving is ensured, the rigidity of the block 60 is ideally demonstrated.
This allows excellent braking performance to be obtained.

Below, the structure and effects of the pneumatic radial tire of the present invention will be explained in more detail using test examples.

(Test example) Tire size: 205150ZR17, Rimnia used: JJX17, Air pressure used: 2. 55) Two types of tires, a tire of the present invention and a conventional tire, were manufactured by applying the conditions shown below and the contact surface conditions of the block shown in the table below to the tread of a cg/c radial tire, The braking performance of these tires was evaluated under the following conditions and the results are shown in the table below.

Note that the structures of the carcass, belt layer, auxiliary belt layer, and tread pattern are as follows, common to the tire of the present invention and the conventional tire.

Carcass cord type: Rayon cord 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: 17-1'Fli...1260/2 Nylon cord angle...approximately 0 degrees Number of plies...2 Tread pattern Tread width・Both sides 19811 m Full width in the center circumferential direction...4 reports Depth...7.6 mm Intermediate circumferential groove width...12 mm Depth...811 Shoulder circumferential groove width...11關〃 Depth...7.51 ■ Lateral full width...
・2 steps〃 Depth...7.6+am Braking performance evaluation method Using a trailer type tester with a friction coefficient of 11!1,
Peak friction coefficient (μ) at a slip rate of 9 to 11% and sliding friction coefficient (μ) at a slip rate of 100%
This is the index evaluation (high index is good) when the conventional tire is set as 100.

■) Block A...Professional Tsuku block of the center crest 41 B...Width of the pro Tsuku block of the side ridge 42
... Width in the axial direction Length of the block ... Length in the circumferential direction Note 2) The block surface had a curved shape as shown in FIG. 3 for the tire of the present invention.

From the above results, the pneumatic radial tire of the present invention has
It is clear that the braking performance is significantly improved.

[Effects of the Invention] As explained in detail above, in the pneumatic radial tire of the present invention, the circumferential tip of the block that touches the ground first during running is the same as the circumferential tip that makes contact with the ground later. Since it is configured as an inclined ground surface that is higher than the rear end of the block, even if the block receives a strong braking force during braking, the ground contact area is compensated by the inclined ground surface, and the ground contact area does not decrease, allowing straight running. It is possible to secure the same ground contact area as before.

Therefore, according to the pneumatic radial tire of the present invention, since the block rigidity can be maximized during braking, the braking performance is excellent, and it has particularly ideal performance for 4WD vehicles. ing.

[Brief explanation of drawings]

FIG. 1 is an explanatory cross-sectional view of the pneumatic radial tire of the present invention, FIG. 2 is a developed view of the tread in FIG. a)
is an explanatory cross-sectional view of the block when the pneumatic tire of the present invention is driven, FIG. 4(b) is an explanatory cross-sectional view of the block during braking, and FIG. 5(a) is a cross-sectional explanatory view of the block when the pneumatic tire of the present invention is driven. FIG. 5(b) is an explanatory cross-sectional view of the block during braking. 10... Side wall 11... Bead wire 12... Hard rubber filler 20... Crown portion 21... Carcass 22...・Belt layer 23...Auxiliary belt layer T...Tread portion 0...Equatorial plane 30...Central circumferential groove 31. ...Middle circumferential groove 32...Shoulder circumferential groove 41...Center ridge 42...Side ridge 50...Transverse groove 60...Block 60A...Slanted ground plane

Claims (1)

[Claims] A pair of sidewalls and a cylindrical crown located at the radially outer ends of both sidewalls are connected in a toroidal manner, and a tread that engages with the road surface is provided around the crown, and the tread extends along the equatorial plane of the tire. A plurality of circumferential grooves extending parallel to each other at predetermined intervals on both sides of the center, and grooves that intersect with these circumferential grooves at an acute angle and spaced at predetermined intervals from the center of the tread in the circumferential direction. In a tire that includes a large number of lateral grooves extending in a herringbone shape to both ends of the tread, and a large number of blocks separated by the circumferential grooves and the lateral grooves, and has a designated rotation direction, two circumferential grooves of the tread are provided. The blocks sandwiched in the air are characterized by forming an inclined ground surface in which the circumferential front end, which touches the ground first during running, is higher than the circumferential rear end, which touches the ground later. Includes radial tires.