JPH07329512A - Pneumatic radial tire - Google Patents

Abstract

PURPOSE:To prevent jetting of water collected in a wide circular recess in a tread part ahead a vehicle in running on a place of a deep water depth by providing a wedge like protrusion directed in the circumferential direction at the bottom of the circular recess. CONSTITUTION:A tread part 3 comprises a circular recess 7 extended continuously in the circumferential direction, and treading parts 8 separated from it in the axial direction, the circular recess 7 is wide and deep, and a wedge-like protrusion directed in the circumferential direction is provided at a bottom 12 of the circular dent 7 in the tread part 3. This wedge-like protrusion has side walls 14 inclined at an acute angle to each other, and a forward end 15 at which both side surfaces 14 cross with each other is directed in a direction of an arrow A in a rotation direction. Water collected in the inside of the recess 7 is thus separated and discharged ahead in the right and left, thereby splash of discharged water to a vehicle running ahead can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radial tire having a plurality of treads whose treads are separated by wide annular recesses.

[0002]

2. Description of the Related Art In a tire having a radial structure, particularly for a passenger car, the cross-sectional height with respect to the width of the tire is required from the viewpoint of high speed and steering stability as the performance of vehicles has been improved in recent years. The ratio, that is, the flatness ratio tends to be small, and it is not uncommon for the flatness ratio to be around 50%, and even tires with an ultra-flat cross section of 30% have appeared. In the case of a tire having such a flat cross section, the tire width is wide, and accordingly, the tread width is wide, so that the wet skid resistance tends to decrease as the flatness decreases. This is because as the tread width becomes wider, it becomes more difficult to quickly drain the stepped water to the side. Grooves extending in various directions are engraved on the tread for drainage, but in order to arrange the grooves within a range that does not sacrifice important properties other than wet skid resistance, the shape and amount of grooves (number of There is a limit in terms of).

In order to solve such a problem, by providing a wide circumferential groove in the center of the tread portion, the tread portion is divided into left and right parts, and two small tires are arranged side by side. United Kingdom Published Patent No. 2,193,933
Proposed by A etc. Such a tread-shaped tire can effectively discharge the water in the left and right ground contact surfaces to the central part of the tread and to both sides when running on a road with shallow water, but the water depth becomes deeper and the tire If it becomes worn, the expected drainage effect cannot be obtained.

In response to the above-mentioned lack of drainage capacity and the same drop in drainage capacity, the tread portion is bent inward in the radial direction of the carcass and belt layers, and a wide and deep annular recess is provided in the central portion thereof, whereby left and right A tire having a divided tread portion was proposed by the applicant in Japanese Patent Laid-Open No. 4-243601.

[0005]

A tire having an annular recess in the center of the tread portion has good wet skid properties without impairing the drainage property pending until the end of wear. On the other hand, because of the good drainage, when driving in deep water, the skeleton such as the belt layer that bends inward in the radial direction of the annular recess protrudes when passing through the contact area and the bottom of the road surface and the recess. As a result, there is a problem that a large amount of water collected in the annular recess may be ejected in a large amount toward the front of the vehicle and may be splashed on the vehicle traveling ahead, as a result. The present invention aims to solve such problems.

[0006]

SUMMARY OF THE INVENTION According to the present invention, sidewalls are respectively radially inward from both ends of a cylindrical tread portion.
And a radial layer which extends from one of the side walls through the tread portion to the other side wall, and a belt layer is arranged between the carcass and the tread portion to reinforce the same. A tire having a tread portion including a wide annular recess and a tread portion including a plurality of land portions separated in the tire axial direction by the annular recess, wherein the bottom of the annular recess includes a plurality of wedge-shaped protrusions oriented in the circumferential direction. It is a pneumatic radial tire characterized by that.

[0007]

Since the tire of the present invention is provided with a wedge-shaped ridge facing in the circumferential direction at the bottom of the annular recess, when the sharp portion of the wedge-shaped ridge enters the ground contact area while traveling on a road with deep water, the annular recess is depressed. The water inside is dispersed and drained left and right by the sloping sides of the ridge. In order to obtain preferable dispersed drainage, it is appropriate to always arrange at least one wedge-shaped ridge in the ground contact surface at a circumferential interval during traveling, and the angle between both side faces of the ridge is preferably 20 to 90 °. .

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A description will be given below with reference to the drawings. FIG. 1 is a sectional view of a tire showing a first embodiment of the present invention, and FIG. 2 is a plan view of the tire. In FIG. 1, a tire 1 has a pair of side walls 2 and a tread portion 3 extending in a cylindrical shape across both side walls 2 in a toroidal shape and embedded in a tip portion of the side wall 2. A carcass 5 with its ends wound up around the dring 4 extends through the area of the side wall 2 and the tread part 3 and between the carcass 5 and the tread part 3 a tread part A belt layer 6 extending over the entire width W _{T of the} belt is arranged and reinforced. The carcass 5 is composed of at least one ply in which fiber cords typified by polyester and rayon are arranged at about 90 ° (radial) with respect to the equatorial plane O, and the belt layer 6 is composed of At least two plies in which non-extensible cords such as steel and / or aramid are inclined at an angle of 15 ° to 40 ° with respect to the equatorial plane O are arranged so that the cords intersect with each other. a trunk layer 6 ₁ superimposed, heat-shrinkable co-nylon or the like around - a plurality of de (rubberized ribbon-like body) was formed by turning substantially parallel to the helical winding and the equatorial plane O auxiliary layer 6 _A structure consisting of _two can be applied.
In FIG. 1, the right half of the equatorial plane O is symmetrical, although only the outer contour is shown and details are omitted.

The tread portion 3 comprises an annular recess 7 extending continuously in the circumferential direction, and a plurality of step portions 8 axially separated by the annular recess 7. In this example, the annular recess
7 is located at the center of the tread portion 3, and thus divides the pair of tread portions 8 symmetrically with respect to the equatorial plane O. Width of annular recess
W _D is 25% to 45% of the tread width W _T, the depth d is 190 to 200% of the thickness of the tread t (maximum rubber thickness of the step parts 8)
Remarkably wide and deep. In order to provide the annular recess having such a shape, the carcass 5 and the parts of the skeleton of the belt layer 6 are bent inward in the radial direction. By occupying the wide annular recess 7 in the central portion of the tread portion 3, the step width W _S is narrowed to 28 to 38% of the tread width W _T. It should be noted that the previously mentioned British published patent 2,193,
In the case of a conventional tire such as the tire shown in 933 A, the tread portion is axially separated by providing a wide circumferential groove in the center of the tread portion within the thickness range of the tread rubber.

Does the outer contour of the tread portion 8 be formed on an arc having a significantly large single radius of curvature R _T formed in the tread portion 3 like the tread portion of a normal tire having no annular recess 7? Alternatively, the step portion 8 can be formed to have a separate arc shape. The portion from the step portion 8 to the annular recess 7 smoothly connects with the annular recess with a small arc. As shown in FIG. 2, the left and right treads 8 have a straight circumferential groove 9 extending in the circumferential direction at substantially the center of this embodiment, and a tire axially outer end of the tread (or tread). From the annular recess 7 to the annular recess 7, the land portion 11 is divided by a large number of lug grooves 10 which are interrupted once in the vicinity of the circumferential groove 9 and curve in one direction in the circumferential direction so as to converge at the equatorial plane O. . In the tire having the tread portion in which the lug grooves are arranged in such a direction, the rotation direction of the tire is determined to be the direction indicated by arrow A so that the tire comes into contact with the ground from the side where the grooves converge.

In the present invention, the bottom 12 of the annular recess 7 in the tread portion is provided with a wedge-shaped ridge 13 oriented in the circumferential direction. That is, the wedge-shaped ridge 13 has side surfaces 14 and 14 inclined at an acute angle to each other.
And the tip 15 where both sides intersect shows the direction of rotation A
Facing in the direction of. The included angle α between the left and right side surfaces 14 is 20
The range of 90 ° is preferred. The maximum width w of the wedge-shaped ridge 13 (the position of the rear end in this embodiment) is substantially the upper limit of the width of the bottom 12 and is 5 to 40% with respect to the width W _{D of the} annular recess. The height h is preferably equal to or slightly lower than the vertical distance i between the extension line j at the upper end level of the belt layer 6 and the bottom 12 of the depression. The reason is that the upper surface of the wedge-shaped ridge does not substantially come into contact with the road surface even if the bottom portion of the bent depression overhangs to the outside at the time of ground contact throughout the life of the tire. The circumferential spacing D of the wedge-shaped ridges is preferably determined so that at least one wedge-shaped ridge 13 is always included in the ground contact surface during traveling, and, for example, about 16 wedge-shaped ridges can be provided at equal intervals D 1.

FIG. 3 is a plan view of a wedge-shaped ridge showing a second embodiment of the present invention. The feature of this embodiment is that it is applied to a tire in which the rotation direction B is in both directions due to the relationship of the lug grooves provided in the tread portion 8, and the wedge-shaped ridge 13 has the tips 15 ₁ , 15
_{It is in the} shape of a rhombus with ₂ on each side in the circumferential direction.
Along with this, side surfaces 14 ₁ and 14 ₂ inclined in different directions are provided to dissipate water in the annular recess 7.

FIG. 4 is a plan view of a wedge-shaped ridge showing a third embodiment of the present invention. The feature of this embodiment is that the wedge-shaped ridge
It is different from the case of the first embodiment in that a void 16 is provided in 13 and the shape is hook-shaped or barb-shaped as a whole.

FIG. 5 is a plan view of a wedge-shaped ridge showing a fourth embodiment of the present invention. The feature of this embodiment is that the wedge-shaped ridge
It differs from the case of the first embodiment in that it has a side surface 14 ′ that is a curved surface for 13 and a void space 16. The average included angle of the side surface 14 'is the same as the included angle α in the first embodiment.

[0015]

[Effect] To confirm the effect of the tire according to the present invention 235 /
Using tires for passenger cars of 45R17 size, tires of Examples having the structures shown in FIGS. 1 and 2 and tires of Comparative Examples in which no wedge-shaped ridge was applied were prepared, and wet skid test was conducted and evaluated. In preparing a test tire, the carcass has a radial structure with two 1500d / 2 polyester cord plies, and the belt layer has two 1x5 steel cord plies (code angle 24 °). Was applied. Regarding the specifications of the tread part, the tread width W _T , the annular recess width W _D and the depth d are 210 mm, 57 mm and 2 respectively.
It was set to 0 mm. The radius of curvature R _T of the step 8 is 2300
mm (the same value as the single radius of curvature of the tread portion, 7.6 times the tire radius). Then, for the tire of the example, 16 wedge-shaped ridges were provided in the annular recess at equal intervals on the circumference. Regarding the specifications of the wedge-shaped ridge, the included angle α on both sides was 45 °, the maximum width was 15 mm, and the height from the groove bottom was 5 mm.

The test tire was assembled on an 8J x 17 rim and
When the internal pressure of Kgf / Cm ² was filled, the water discharge state to the front of the vehicle was observed when the vehicle passed through a puddle with a water depth of 10 mm provided on an asphalt pavement at a speed of 70 Km / H. As a result, the tire of the comparative example, the water collected in the recess along the annular recess, was ejected in a considerable amount in front of the vehicle, whereas the tire of the example is the water collected in the recess. Dispersed and drained left and right.

[Brief description of drawings]

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

FIG. 2 is a plan view of the first embodiment.

FIG. 3 is a plan view of a wedge-shaped ridge according to the second embodiment.

FIG. 4 is a plan view of a wedge-shaped ridge according to the third embodiment.

FIG. 5 is a plan view of a wedge-shaped ridge according to a fourth embodiment.

[Explanation of symbols]

 1 tire 2 sidewall 3 tread 5 carcass 6 belt layer 7 annular recess 8 tread 13 wedge-shaped ridge

Claims (3)

[Claims] 1. Sidewalls are connected inward from both ends of a cylindrical tread portion toward the inside in the radial direction, and one sidewall passes through the tread portion and the other sidewall.
And a belt layer is disposed between the carcass and the tread portion for reinforcement, and the tread portion has a wide annular recess and is separated in the tire axial direction by the annular recess. A pneumatic radial tire comprising a plurality of stepped portions provided with a plurality of wedge-shaped ridges facing the circumferential direction at the bottom of the annular recess. 2. The pneumatic radial tire according to claim 1, wherein at least one wedge-shaped ridge is always included in a ground contact surface when the vehicle is running. 3. The point of the wedge-shaped ridge is 20 to 90.
The pneumatic radial tire according to claim 1, which is formed with an angle of °.