JPH03220007A - Pneumatic radial tire - Google Patents

Abstract

PURPOSE:To mitigate the concentration of stress at the intersection between a hard rubber section and a soft rubber section and improve durability by pinching a separation slant section and an outside slant section provided on the hard rubber section of a bead filler with the soft rubber section of the bead filler. CONSTITUTION:A reinforcing bead filler 60 constituted of a hard rubber section 61 and a soft rubber section 62 is arranged above a bead ring 50 between the carcass 30 and its winding section 31 of a tire. The hard rubber section 61 is constituted of a carcass fixed section 61A extended upward from the bead ring 50, a separation slant section 61B extended further upward from here, and an outside slant section 61C extended to the outside from here. The separa tion slant section 61B and the outside slant section 61C are pinched by the outside slant section 61C. The concentration of stress at the intersection between the hard rubber section 61 and the soft rubber section 62 is mitigated, and the occurrence of the breakage of the bead filler 60 is solved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to an improvement in the bead portion of a pneumatic radial tire.

(Prior Art) Generally, the bead portion of a pneumatic radial tire has the structure shown in FIG.

That is, in the bead structure shown in FIG. 3, a bead ring 2 is embedded at the tip of a pair of sidewalls extending approximately radially inward from both ends of a cylindrical tread portion (not shown). A carcass 3 consisting of at least one piece of braai with arranged corners is rolled up axially outward of the bead ring 2, and a carcass winding part 3' is formed at a relatively low position.

A bead filler 4 having a substantially triangular cross section with its base in contact with the bead ring 2 is arranged between the carcass 3 and the carcass winding part 3-.

If relatively hard hard rubber is used as the beat filler 4, it is possible to improve the steering stability, but
On the other hand, there was a problem that vibrations worsened the riding comfort.

Also, in order to improve the above problem, bead filler 4 and 1. When soft rubber is used, the steering stability tends to be inferior compared to when the above-mentioned hard rubber is used.

Therefore, recently, as shown in the figure, for example, hard rubber 4A made of relatively hard rubber with a Shore A hardness of 70 to 90 degrees has been developed.
Both steering stability and riding comfort are achieved by a composite bead filler in which a soft rubber 4B made of relatively soft rubber with abrasion resistance is arranged on the bead ring 2 side and above in contact with the outside in the axial direction. Measures are being taken to improve it.

(Problem to be Solved by the Invention) However, in the pneumatic radial tire using the conventional composite bead filler described above, when the difference in rigidity between the hard rubber 4A and the soft rubber 4B is increased to a certain extent, the point A shown in the drawings There was a problem in that stress was concentrated in this area, making it easy to break.

In other words, a normal radial tire for a passenger car costs between 40,000 and 100,000
Although it is said to have a durable life of 10,000 km, the strain caused by external force during driving is concentrated at the bead of the tire, especially at point A in the drawing, so the bead filler is likely to break in the cross-sectional direction of the tire from point A. The result is that the durability of the tire is significantly impaired.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the conventional pneumatic radial tires.

Therefore, an object of the present invention is to provide a pneumatic radial tire that is excellent in durability, handling stability, and riding comfort in a well-balanced manner.

[Structure of the Invention] (Means for Solving the Problems) In other words, the pneumatic radial tire of the present invention includes a cylindrical crown portion, each extending radially inward from both ends of the crown portion, A pair of sidewalls each having a bead ring embedded in the tip thereof are connected in a toroidal manner, and are reinforced with a radial carcass consisting of at least one ply of an organic fiber cord layer extending from one of the sidewalls to the crown part and the other sidewall. Both ends of the carcass ply are wound around the bead ring from the inside in the axial direction to the outside, and are located between the carcass and this rolled-up part, and extend from above the bead ring to the crown, tapering to the bead ring side. In a tire that includes a bead portion reinforced with a composite bead filler made of hard rubber and relatively soft rubber on the crown side, the hard rubber portion of the bead filler is attached to the carcass and extends upward from the axially inner upper end of the bead ring. a separating inclined part extending further upward away from the carcass from the upper end of the fixed part, and an outer inclined part extending from the upper end of the separating inclined part toward the outer side in the axial direction of the bead ring, facing the carcass winding part;
It is characterized by comprising a bead reinforcing portion formed by sandwiching the spaced apart inclined portion and the outer inclined portion of the hard rubber portion with the soft rubber portion.

(Function) In the pneumatic radial tire of the present invention, at the bead portion, the separating slope portion and the outer slope portion of the hard rubber portion are sandwiched between the soft rubber portions, so that stress is concentrated at the intersection of the hard rubber and the soft rubber. This eliminates the occurrence of breakage of the bead filler in the cross-sectional direction of the tire, and excellent durability can be expected.

Therefore, the pneumatic radial tire of the present invention exhibits excellent handling stability and ride comfort due to the bead filler that is a combination of hard rubber and soft rubber, as well as excellent durability.

(Embodiments) Hereinafter, embodiments 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, and FIG. 2 is an explanatory enlarged cross-sectional view of the bee F section.

That is, as shown in FIG. 1, the pneumatic radial tire of the present invention includes a pair of sidewalls 10 and a cylindrical crown portion 2 located at the radially outer ends of both sidewalls.
0 are connected in a toroidal manner, and a tread T to be engaged with the road surface is provided around the tread round part 20.

The crown part 20 includes a radial carcass (hereinafter referred to as a carcass) 30, which is a layer of organic fiber coat such as rayon or polyester arranged in a direction substantially perpendicular to the equatorial plane, and this force carcass 30. A heald layer 4 consisting of at least two plies of a layer in which non-extensible cords such as steel coats are arranged in an inclined manner above C1 and, if necessary, at least two plies of a heat-shrinkable material such as nylon.
The structure is reinforced by 0.

Further, the entire axially outer side of the sidewall 10 is covered with an outer covering rubber.

Note that in FIG. 1, the left half from the equatorial plane O is omitted, but in this embodiment, it is symmetrical with respect to the equatorial plane O.

As shown in FIG. 2, the bead portion of the pneumatic radial tire of the present invention is formed by winding both ends of the carcass 30 around the beet ring 50 from the inside in the axial direction to the outside. Winding part 31 of carcass 30
In this embodiment, the sidewall [O] remains at a relatively low position, that is, at a position slightly beyond the upper end of the rim flange when the tire is assembled on the rim.

And, between the carcass 30 and its winding part 31, a hard rubber part 6] which extends radially outward from the upper part of the bead ring 50 in a tapered manner without exceeding the tip of the carcass winding part 3]. The hard comb portion 61 is reinforced by a composite bead filler 60 having a substantially diagonal cross section and consisting of a soft rubber portion 62 that extends in a tapered manner beyond the tip of the force scrap winding portion 31 above the hard comb portion 61 (on the crown portion 20 side).

In this composite bead filler 60, for example, the hard rubber part 61 can have a Shore A hardness of 75 to 98 degrees, and the soft rubber part 62 can have a hardness of 60 to 85 degrees. Therefore, hard rubber is better within the above numerical range.

Here, the hard rubber part 61 is a carcass fixing part 6 extending upward from the axially inner upper end of the bead link 5 [ ].
1A, a separating inclined part 61B which extends further upward away from the carcass 30 from the upper end of the fixing part 61A, and the separating inclined part 6], and an axial tip of the bead ring 50 from the upper end of B to the carcass winding part 3]. Outer inclined portion 61 extending in the outward direction in the j direction. C, and the spaced apart sloped portion 61.8 and the outer sloped portion 61.8 of these hard rubber portions 61. C is the soft rubber part 62
It is important that it is held in place.

(7) The height of the crown part on the bead ring 50 is Ht.
, lf1 combined beat filler height (upper end of soft rubber part 62) height is Hf, height of hard rubber part 6 is h, height of the same spaced inclined part is h', hard rubber part 61 and soft rubber part When the axial width of the soft rubber portion 62 at the contact point of 62 is W, and the axial width of the separating inclined portion at the same point is W', the respective dimensions have the following relationship.

Hf/Ht + 0.25~屹65 h/Hf 屹25~0.65 h-/h: 屹05~屹2 w-7w: 0.15~0.5 That is, h-/h is 0.2 Beyond the soft rubber part 62
or hard rubber part 6], the carcass 30
The shearing force between the composite beet filler 60 and the composite beet filler 60 becomes large, and separation at the interface is likely to occur, which impairs durability, which is undesirable.

If w − / w exceeds 0.5 and the tip of the soft rubber 62 is biased toward the outside in the axial direction, the rigidity of the bead portion will be insufficient,
Exceeding a certain steering angle during driving causes a sudden change in the steering force, which is not desirable and should not give the operator a sense of uneasiness, as this will lead to deterioration of steering stability.

The height of the carcass winding part 31 is at least about 161 to about 60% of the height Ht, and the upper end position of the hard rubber part 61 is set within the height range of the carcass winding part 31.

The pneumatic radial tire of the present invention having the above-described structure has a hard rubber portion 6 in the composite bead filler 60.
1 is sandwiched between the soft rubber parts 62, the concentration of stress at the intersection of the hard rubber part 61 and the soft rubber part 62 can be alleviated, and the occurrence of cracks and destruction at this part can be effectively prevented. Eliminate.

Further, in the pneumatic radial tire of the present invention, the composite bead filler 60 can be integrally formed by simultaneously extruding the hard rubber part 61 and the soft rubber part 62 in the manufacturing process, thereby increasing productivity. can be significantly increased.

Next, the structure and effects of the pneumatic radial tire of the present invention will be further explained using test examples.

(Test Example) A tire A of the present invention was obtained by imparting the bead structure shown in FIG. 1 to a radial tire with a tire size of 185/70R14.

That is, the hard rubber part 61 is made of rubber with a Shore A hardness of 97 degrees, and the soft rubber part 62 is made of rubber with a hardness of near 6.
Using degree rubber, h: 30m + w, 63mm, w: 5m
A composite bead filler 60 was formed by combining m and w-+1.5+++n+ and extruding both at the same time.

For comparison, comparative tires B and C were obtained by changing h, h-w and W' as shown in the following table.

Further, h' and W- are each set to 0, and the same procedure is carried out except that the hard rubber part is not sandwiched between the soft rubber parts as shown in FIG.
Conventional tire D was obtained.

In addition, common to the above four types of tires, polyester cord 1500d/2xIP was used as the carcass 30, 2x steel belt was used as the belt layer, the height of the carcass winding part was 70m + W, Ht was 130 Dragon, Hf is 50
+nn+.

For these four types of radial tires, rims used: 5
1/2, tire internal pressure +2.5kg/c, load: 855
A drum running test was conducted under the condition of 1 kg, and the results of the following evaluations are shown in the table below.

"Durability" This is the observation result of failure parts when the tire was run on a steel drum with a smooth surface and a diameter of 1.7 m at a speed of 80 km/h for the distance shown in the following table.

"Actual Vehicle Feeling" Feeling evaluation in actual vehicle driving test ◎... Extremely good handling stability and ride comfort ○...
// Good ×...Poor steering performance (blank below) As is clear from the above table, the pneumatic radial tire of the present invention has excellent durability, and extremely good handling stability and ride comfort. .

[Effects of the Invention] As explained above in detail, the pneumatic radial tire of the present invention has the spaced-apart inclined part and the outer inclined part of the hard rubber part sandwiched between the soft rubber parts at the bead part, so that the hard rubber The concentration of stress at the intersection of the bead filler and the soft rubber is alleviated, and the occurrence of breakage of the bead filler in the cross-sectional direction of the tire is eliminated, making it possible to expect improved durability.

Therefore, the pneumatic radial tire of the present invention exhibits excellent handling stability and ride comfort due to the bead filler that is a combination of hard rubber and soft rubber, as well as excellent durability.

[Brief explanation of drawings]

FIG. 1 is an explanatory cross-sectional view of the pneumatic radial tire of the present invention, FIG. 2 is an explanatory enlarged cross-sectional view of the bead portion thereof, and FIG. 3 is an explanatory cross-sectional view of the bead portion of a conventional pneumatic radial tire. T... Tread part 10... Side wall 20... Crown part 30... Carcass 31... Carcass winding part 40. ...Belt layer 50...Bead ring 60...Composite bead filler 61...Hard rubber portion 61A...Carcass fixing portion 61B...Separating inclined portion 61C...Outside inclined part 62...Soft rubber part

Claims (1)

[Claims] A cylindrical crown part and a pair of sidewalls extending radially inward from both ends of the crown part and each having a bead ring embedded in the tip are connected in a toroidal manner, and from one sidewall to the crown part and the other side. The wall is reinforced with a radial carcass consisting of at least one ply of an organic fiber cord layer, and both ends of the carcass ply are wound up around a bead ring from the inside in the axial direction to the outside, and the carcass and this rolled up part are In a tire that includes a bead portion between the bead ring and reinforced with a composite bead filler that extends taperingly from above the bead ring toward the crown portion and is made of hard rubber on the bead ring side and relatively soft rubber on the crown side, the above-mentioned bead filler The hard rubber part includes a carcass fixing part extending upward from the axially inner upper end of the bead ring, a separating inclined part extending further upward away from the carcass from the upper end of the fixing part, and a separating inclined part extending upward from the upper end of the separating inclined part to the carcass. The bead reinforcing portion is provided with an outer inclined portion facing the winding portion and extending outward in the axial direction of the bead ring, and a bead reinforcing portion formed by sandwiching the spaced apart inclined portion and the outer inclined portion of the hard rubber portion with the soft rubber portion. Features pneumatic radial tires.