JP2000016032A - Pneumatic radial tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve ride comfortableness and improve anti-side crack performance while keeping side cut resistance favorable by improving a form of a protector as a pneumatic radial tire provided with the protector at a side part. SOLUTION: In a range of 80%-45% of a tire height from a bead heel part in a tire side part, a circular protector 10 only a little upheaved from a reference profile A of an outer surface of a side part 4 in a tire cross section is provided, plural lines of protruded ribs 12 in a tire circumferential direction are formed on an outer surface of a base part 11 of the protector 10, a rib width W and a rib interval P of the protruded ribs 12 are gradually reduced from a buttress part 9 in a side surface of a tread part toward the side part 4, and the whole thickness T of the protector 10 including the base part 11 and the protruded ribs 12 is gradually reduced from the buttress part 9 toward the side part 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic radial tire for a passenger car.

[0002]

2. Description of the Related Art Generally, a pneumatic radial tire for a passenger car has a bead portion (3) provided with bead cores (2) on both sides as shown in FIG. And a side portion (4) extending radially outward from the bead portion (3), and a tread portion (5) connecting the upper end thereof, and both ends along the inner periphery of the bead core (2). A carcass ply (1) having a radial code arrangement supported by being folded back, and a plurality of belt layers (6) arranged between the tread portion (5) and the carcass ply (1). ing. Outside the belt layer (6), a cord reinforcing layer (not shown) called a cap ply or an edge ply is often provided.

A tread rubber (51) is provided outside the belt layer (6) of the tread portion (5), and a sidewall rubber (4) is provided outside the carcass ply (1) of the side portion (4).
1) is attached to each.

[0004] In this type of tire, the side portion (4) is protected from crushed stones and the like during running on uneven terrain, cracks in the side portion are prevented, and ride comfort and durability are further improved. For this purpose, a protector comprising an annular raised portion extending in the circumferential direction of the tire is formed on the outer surface of a specific position of the side portion (4) of the tire, and a plurality of grooves extending in the circumferential direction of the tire are formed on the outer surface of the protector. And the depth of the groove is 3.0 m to avoid bending stress.
m or less and the depth is gradually reduced from the outside to the inside in the tire radial direction (JP-A-5-294115).

[0005] However, in the case of the proposed tire, the depth of the groove of the protector becomes shallower inward in the tire radial direction, but the overall thickness of the protector is set to be substantially the same. Therefore, the rubber thickness of the base portion of the protector below the line connecting the bottoms of the concave grooves of the protector is rather thick, and the rigidity is increased accordingly, and the riding comfort is not sufficiently satisfactory.

[0006] The present invention has been made in view of the above, and by improving the shape of the side protector,
An object of the present invention is to provide a pneumatic radial tire capable of improving ride comfort and side crack resistance while maintaining good side cut resistance.

[0007]

A pneumatic radial tire according to the present invention, which solves the above-mentioned problems, comprises a carcass ply having both ends folded and supported by a bead core, and a belt disposed outside the carcass ply in a tread portion. A tread rubber and a sidewall rubber are provided on the outer side of the tire, and the tire has a side portion in a range of 80% to 45% of a tire height from a bead heel portion in a tire side portion. An annular protector extending in the circumferential direction of the tire slightly raised from the reference profile of the outer surface is provided, and the protector includes a base portion and a plurality of convex ribs extending in the circumferential direction of the tire formed on the outer surface thereof. The rib width and the rib interval of this convex rib are gradually reduced from the buttress portion on the side surface of the tread portion to the side portion side. Form, the total thickness of the protector combined a base portion and a convex rib, and characterized by being gradually reduced form from the buttress portion to the side of the side portion.

According to this pneumatic radial tire, the convex ribs on the surface of the protector are formed thicker and coarser toward the buttress portion and the overall thickness of the protector is larger, so that the side cut resistance can be maintained better. Moreover, as the side portion is closer, the convex ribs are formed thinner and denser,
In addition, since the overall thickness of the protector is reduced, riding comfort and side crack resistance are improved.

In the above, if the upper end of the setting range of the protector exceeds 80%, the lug groove of the shoulder cannot be secured, and the traction performance is reduced. When the lower end of the set range is 45% or less, the rigidity of the side portion is increased, and the riding comfort is deteriorated. Therefore, it is preferable to set the above range.

Further, in order to set the total thickness of the protector as described above, the thickness of the base portion and / or the height of the convex rib of the protector are gradually reduced from the buttress portion to the side of the tire. can do.

It is preferable that the rib width of the convex rib is set in the range of 4 to 1.5 mm, the rib interval is set in the range of 7 to 3 mm, and the total thickness of the protector is set in the range of 4 to 1.7 mm. .

That is, when the maximum of the total thickness of the protector exceeds 4 mm, the riding comfort deteriorates, and when the minimum of the total thickness is less than 1.7 mm, the side cut resistance deteriorates. Even if the total thickness is within the above range, the ride comfort is deteriorated when the rib width of the convex rib is larger than the above range, and the side cut resistance is deteriorated when the rib width is smaller than the above range. Also, when the rib interval is reduced, the bend becomes easier and the riding comfort is improved, but the effect on side cracks is reduced. Also, if the rib spacing is increased, it is difficult to bend and the effect on side cracks is improved,
The effect of the ride is reduced. Therefore, it is preferable to set the above range.

Further, it is preferable that the protector is such that the thickness of the base portion is set in the range of 2 to 1 mm and the height of the convex rib is set in the range of 2 to 0.7 mm.

That is, even if the total thickness of the protector is within the above range, if the thickness of the base portion is 1 mm or less, the performance with respect to side cut is reduced, and if it is 2 mm or more, the riding comfort is reduced. .

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of the present invention will be described with reference to an embodiment shown in the drawings.

FIG. 1 is a half sectional view of a pneumatic radial tire according to an embodiment of the present invention, taken along a tire width direction. FIG. 2 is an enlarged sectional view of a part of the above.

The structure of the tire is as described in the description of the conventional art.
(2) shows a bead core, (3) shows a bead portion, (31) shows a bead filler, (4) shows a side portion, (5) shows a tread portion, and (6) shows a belt layer. (8) is a shoulder part.

The carcass ply (1) is composed of a cord arrangement layer in which cords are arranged at an angle of about 75 to 90 ° with respect to the center (equator) in the tire width direction, and the cords are made of fiber such as rayon, aramid, polyester or the like. Cord or steel cord is used. The carcass ply (1) generally has a winding ply whose both ends are wound up from the inside to the outside around the bead core (2). The belt layer (6) is composed of a cord layer in which steel cords or fiber cords having high tension are arranged at a relatively small angle with respect to the tire center. (41) indicates a side wall rubber, and (51) indicates a tread rubber, which is formed by being attached to the outside of the carcass ply (1) and the belt layer (6).

In the case of the present invention, the side portion (4) of the tire has a tire height (H) of 80 from the bead heel portion (7).
In the range of% to 45%, an annular protector (10) extending in the tire circumferential direction slightly raised from the reference profile (A) on the outer surface of the side portion (4) in the tire cross section is provided.

In the proptor (10), a plurality of rows of convex ribs (12) extending in the circumferential direction of the tire are formed on the outer surface of a base portion (11) and arranged at required intervals in the tire radial direction. The convex rib (12) has a substantially trapezoidal shape with a round cross section or a split circle.
The width of 2), for example, the rib width (W) represented by the diameter of the inscribed circle of the cross section and the rib interval (here, the distance between the top centers of the convex ribs) (P) are the buttresses on the side of the tread portion (5). From the portion (9) to the side of the side portion (4) (from the outer side to the inner side in the tire radial direction), it is formed smaller gradually.

Further, the base portion (11) and the convex rib (1)
The total thickness (T) obtained by combining 2) is also gradually reduced from the buttress portion (9) to the side portion (4). As this means, both the thickness (t1) of the base portion (11) of the protector (10) and the height (h1) of the convex rib (12) are changed from the buttress portion (9) to the side portion (4). In addition to the case where the base portion (11) is formed gradually smaller, the thickness (t1) of the base portion (11) and the convex rib (1
Only one of the height (h1) of the height (2) (same as the depth of the concave portion between the ribs) can be gradually reduced from the buttress portion (9) toward the side portion (4).

The dimensions of the components of the protector (10) and the degree of change thereof vary depending on the tire size and the like. For example, in the case of a tire that can be mounted on a light truck from a light vehicle CCV, the aforementioned convex rib ( 12), the rib width (W) is in the range of 4 to 1.5 mm, the rib interval (P) is in the range of 7 to 3 mm, and the protector (1)
The total thickness (T) of 0) is within the range of 4 to 1.7 mm,
As described above, each of them is gradually changed from the buttress portion (9) to the side portion (4). The thickness (t1) of the base portion (11) of the protector (10) is 2 to 1 mm, and the height (h1) of the convex rib (12) is 2 to 1 mm.
It shall be set in the range of 0.7 mm.

According to the pneumatic radial tire of the present invention having the above structure, the convex rib (12) on the surface of the protector (10) is thicker and coarser toward the buttress portion (9).
In addition, since the total thickness (T) of the protector (10) is large, the side cut resistance can be maintained satisfactorily, and the convex rib (12) is thinner and denser toward the side portion (4), and the protector (10) is smaller. Since the total thickness (T) of (10) is small, riding comfort and side crack resistance are improved.

Particularly, when the total thickness (T) of the protector (10) is gradually reduced from a maximum of 4 mm to a minimum of 1.7 mm, the ride comfort is maintained as compared with the case of the same thickness. While the performance against side cuts and side cracks can be improved, and when gradually reduced from a maximum of 3 mm to a minimum of 2 mm, the ride comfort and durability can be maintained while maintaining the performance against the side cuts as compared with those of the same thickness. Side cracking properties can be improved.

For example, as shown in FIG. 1 and FIG. 2, the side part (4) is provided with a protector (10) with a rib, and the tire size is 195R16C. T) and Example tires 1 to 4 of the present invention in which the rib shape was set as shown in Table 1 below.
For each tire of No. 4 and a comparative tire having the same protector thickness, rib shape, etc. of the same size tire, a comparative test was performed on the respective properties of side cut resistance, ride comfort and side crack resistance. However, the results are as shown in Table 1 below.

As a test method and an evaluation method, for side cut resistance, a 70 kg cylindrical steel having a hemispherical end with a diameter of 32 mm was mounted on a standard rim of an ETRTO standard (Europe tire, rim standard) at a standard air pressure. Drop the plunger made naturally from the upper end of the protector to a point 1/3 of the width of the protector, and drop height (H) at which the cord on the tire side cuts
From the weight (M) of the plunger and the breaking energy (W =
M × H × 9.8), and the index was expressed as an index, with the breaking energy of the comparative tire being 100.

Regarding the riding comfort, the light vehicle CCV (660
cc) and the sensory evaluation of the actual vehicle
It was indicated by an index as 00.

Regarding the side crack resistance, ETRT
It was mounted on a standard rim of the O standard under standard air pressure, and was run at a speed of 40 km / h with an ETRTO standard load on a 505 mm diameter steel drum installed outdoors. The distance at which cracks occurred on the tire side was measured. The crack occurrence distance of the comparative tire was set to 100 and indicated by an index. In each case, the larger the value, the better.

[0029]

[Table 1] As is clear from the above test results, each of the example tires of the present invention can maintain or improve the riding comfort and the performance against side cuts and side cracks better than the comparative example tires. I have. In particular, in Example tires 1 and 2 in which the total thickness (T) of the protector (10) was changed from a maximum of 4 mm to a minimum of 1.75 mm, the riding comfort was better maintained as compared with the comparative tire having the same thickness. In addition, the performance against side cuts and side cracks can be improved, and the total thickness (T) can be up to 3 mm or less.
With respect to the example tires 3 and 4 which are changed at a minimum of 2 mm, the ride comfort and the performance against side cracks can be improved while maintaining the performance against side cuts as compared with the comparative example tire having the same thickness.

[0030]

As described above, according to the pneumatic radial tire of the present invention, riding comfort and side crack resistance can be improved while maintaining good side cut resistance.

[Brief description of the drawings]

FIG. 1 is a half sectional view along a radial direction of a pneumatic radial tire of the present invention.

FIG. 2 is an enlarged sectional view of a part of the above.

FIG. 3 is a sectional view of a conventional tire.

[Explanation of symbols]

 (1) Carcass ply (2) Bead core (3) Bead part (4) Side part (5) Tread part (6) Belt layer (7) Bead heel part (8) Shoulder part (9) Buttress part (10) Protector (11) ) Base part (12) Convex rib (A) Reference profile of side part outer surface (W) Rib width (P) Rib interval (T) Total thickness of protector (t1) Base part thickness (h1) Rib height

Claims (4)

[Claims] 1. A carcass ply having both ends folded and supported by a bead core and a belt layer disposed outside the carcass ply in a tread portion, and a tread rubber and a sidewall rubber are attached to the outside of these. An annular protector extending in the circumferential direction of the tire slightly raised from the reference profile of the outer surface of the side portion in the cross section of the tire within a range of 80% to 45% of the tire height from the bead heel portion on the tire side portion. The protector comprises a base portion and a plurality of rows of convex ribs formed on the outer surface thereof and extending in the circumferential direction of the tire. The rib width and the rib interval of the convex rib are determined by a buttress portion on the side surface of the tread portion. From the side to the side part gradually formed,
A pneumatic radial tire, wherein a total thickness of a protector in which a thickness of a base portion is matched with a height of a rib is gradually reduced from the buttress portion to a side portion side. 2. The thickness of a base portion of the protector and / or
2. The pneumatic radial tire according to claim 1, wherein the height of the convex rib is set to be gradually smaller from the buttress portion toward the tire side portion. 3. 3. The protector according to claim 1, wherein the rib width is set in a range of 4 to 1.5 mm, the rib interval is set in a range of 7 to 3 mm, and the total thickness of the protector is set in a range of 4 to 1.7 mm. The pneumatic radial tire according to 1. 4. The pneumatic radial tire according to claim 2, wherein the thickness of the base portion is set in a range of 2 to 1 mm, and the height of the convex rib is set in a range of 2 to 0.7 mm.