JP3247512B2 - Pneumatic radial tire - Google Patents

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 using a rayon fiber cord as a ply cord constituting a carcass ply, and more particularly to an improvement in uniformity as a tire wheel.

[0002] More specifically, rims of various types such as halves to be adapted to tires, such as 5 ° deep, 15 ° deep or wide deep, such as rims specified by JATMA, TRA, etc. The tires are mounted on the "standard rims" in this document to achieve a satisfactory wheel uniformity as a tire wheel, and radial runout (RRO)
The present invention intends to propose a pneumatic radial tire that can reduce the radial force variation (hereinafter, abbreviated as “RFV”) effectively by reducing the pneumatic radial tire.

[0003]

2. Description of the Related Art In a conventional pneumatic radial tire, a carcass ply of a radial carcass is formed by paying attention to rayon fiber having excellent dimensional stability against heat and other properties.
It is widely and generally used to form a structure using rayon fiber cords.

[0004]

By the way, since the rayon fiber cord generally has low strength, it is necessary to increase the thickness of the cord in order to give the carcass ply cord the necessary strength. Moreover, in the radial carcass, substantially 90 ° with respect to the tire circumferential direction.
Carcass ply made of rayon fiber cord
Since overlap joining is performed at one position in the tire circumferential direction, there is a disadvantage that the uniformity of the tire is impaired at the overlap joint.

Therefore, in order to suppress the RFV of the tire wheel as a whole, the change of the RFV of the product tire itself is measured, and the maximum point on the circumference thereof and the standard rim to which the tire is assembled are separately measured. Although the tire is assembled on the rim so that the minimum point of the RFV coincides with that of the rim, the significance of the rim has been practically lost due to the recent improvement in machining accuracy of the rim. In some cases, the RFV of the tire wheel was larger than the RFV of the tire itself.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art. The use of rayon fiber cords as the ply cords has reduced the uniformity of the tires themselves as tire wheels. It is an object of the present invention to provide a pneumatic radial tire that can be sufficiently compensated for by improving the wheel uniformity at the time.

That is, according to the present invention, even when a pneumatic tire having a good RRO with respect to the tire itself is mounted on a standard rim having excellent machining accuracy, the RRO as a whole tire wheel is not necessarily reduced. Based on the knowledge, it was made as a result of finding that the cause was caused by the eccentric mounting of the tire when assembling the rim, and concentric mounting was easily introduced when assembling the pneumatic radial tire to the rim. By improving the tire bead portion so that it can be removed, excellent wheel uniformity can be realized, thereby sufficiently compensating for the low uniformity of the tire itself and increasing the RRO of the entire tire wheel.
And a pneumatic radial tire capable of reducing both RFV and RFV sufficiently.

[0008]

A pneumatic radial tire according to the present invention includes a tread portion and a pair of sidewall portions connected to the tread portion, and a bead portion connected to a radially inner end of each sidewall portion. And a radial carcass made of at least one carcass ply, which extends toroidally between bead cores embedded in each bead portion, and is usually provided on the outer peripheral side of the crown portion of the radial carcass with at least two layers. In the place where the belt consisting of the belt layer is provided,
While the ply cord constituting the carcass ply is a rayon fiber cord, the bead portion tightly fitted to the inclined bead sheet of the standard rim, the standard rim, a curved flange located on the outermost side in the width direction, Prior to contact with the outer surface of the bead portion opposed thereto, a swelling heel is provided in the corner round recess adjacent to the outer side in the width direction of the inclined bead sheet so as to be in close contact with the entire periphery thereof, and the swelling amount of the swelling heel is 2 mm or more with a, the rubber hardness of the bulged heel, which was more than 65 degrees in JIS hardness, wherein more preferably, the thickness of the rayon fiber cord as a carcass ply cord those with 1500d / 2 or more
It is .

Here, the standard rim includes an inclined bead seat,
The slanted bead sheet includes a rounded concave portion and a curved flange that recurs outwardly, which are sequentially connected to the outside in the width direction of the inclined bead sheet. In some cases, a protruding flange is provided between the curved flange and the corner concave portion. Sometimes.

The bulging amount of the bulging heel means a lateral bulging amount of the bulging heel as measured on the basis of a perpendicular to the tire center axis passing through the bead base point. I do.

[0011]

In the pneumatic radial tire, the ply cord constituting the carcass ply is preferably 150 ply cord.
The use of rayon fiber cords having a thickness of 0d / 2 or more can provide excellent dimensional stability to heat under sufficient carcass strength as described in the prior art.

On the other hand, the uniformity of the product tire is reduced due to the use of the rayon fiber cord because the tire center axis and the rim center axis are always properly adjusted based on the improvement of the tire bead portion. By improving the uniformity of the tire wheels, the vehicle can be sufficiently covered.

That is, according to this tire, when the tire rim is assembled into the tire bead portion, the corner adjacent to the inclined bead seat of the rim is provided prior to the contact between the curved flange of the standard rim and the opposing outer surface of the bead portion. By providing a protruding heel that is in close contact with the round recess over the entire circumference, the bulging heel first comes into close contact with the corner round recess when the rim assembly proceeds, and then the bead is formed under the compression deformation of the protruding heel. The outer surface of the tire comes into contact with the curved flange, so that the contact state between the outer surface of the bead portion and the curved flange is sufficiently uniform over the entire circumference, and the center axis of the tire is aligned with the center axis of the standard rim with high accuracy. This reduces the RRO, i.e. the runout of the outer circumference of the tire wheel, and allows the tire wheel to rotate under a constant deflection. Variations in the radial reaction force when brought into,
That is, the RFV is effectively suppressed, and the uniformity of the wheels is greatly improved.

Therefore, in this case, by improving the uniformity of the tire wheels, it is possible to sufficiently compensate for the decrease in tire uniformity caused by using the rayon fiber cord as the ply cord.

By the way, such improvement of the wheel uniformity can be achieved by the following:
Variations in the circumferential direction of the wheel, such as the ground contact area and the position of the ground contact surface in the width direction, are sufficiently reduced, and the force generated by the tire wheel is almost constant at any position in the circumferential direction. Stability and, consequently, steering stability are also improved.

Here, the bulging amount of the bulging heel is 2 mm.
By the above, complete embedding of the rounded concave portion by the bulging heel can be ensured. However, if the bulging amount is too large, the movement of the outer surface of the bead portion with respect to the curved flange becomes large, and Since there is a possibility that rubbing may become severe, it is preferable to limit the thickness to 4 mm. Further, by setting the rubber hardness of the bulging heel to 65 degrees or more in JIS hardness, the bulging heel can be firmly fitted and fixed in the rounded concave portion, and the bulging heel has a rounded corner. It can lead to uniform contact with the recess all around, but if its hardness is too hard, it is not possible to secure a sufficient amount of compressive deformation between the bulge heel and the rim,
Since there is a possibility that a problem may occur in airtightness, it is preferable that the angle be up to 80 degrees. By the way, in this tire,
When the thickness of the rayon fiber cord as the carcass ply cord is 1500d / 2 or more, the strength of the carcass ply, and thus the radial carcass, can be sufficiently increased, and the strength as a tire can be increased. Since the step of the overlap portion becomes large and the wheel uniformity is significantly deteriorated, the effects of the present invention can be particularly effectively enjoyed.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view in the width direction showing an embodiment of the present invention, in which 1 is a tread portion, 2 is a pair of left and right sidewall portions continuous to respective side portions of the tread portion 1, and Reference numeral 3 denotes a bead portion that is continuous with the radially inner end of each sidewall portion 2.

In this example, a radial carcass 4 extending toroidally is formed by a single carcass ply made of rayon fiber cord extending at an angle of substantially 90 ° with respect to the tire circumferential direction, and each of the radial carcass 4 Around the bead core 5 buried in the bead portion 3 from the inside to the outside in the width direction of the tire, and is wound around the outer periphery of the crown portion of the radial carcass 4 with respect to the tire circumferential direction. A belt 6 made of a steel cord extending at a relatively small angle and composed of two belt layers 6a and 6b in which the cords intersect with each other is provided. A single belt reinforcing layer 7 made of an organic fiber cord extending substantially in the tire circumferential direction and covering the belt 6 over its entire width is provided. Here, a plurality of circumferential grooves 8 extending in the tire circumferential direction and a plurality of width grooves (not shown) extending in the tire width direction are formed in the tread portion.

Further, in this tire, prior to the contact between the curved flange of the standard rim and the outer surface of the bead portion facing the curved portion of the standard rim, the bead portion 3 is adjacent to the bead portion 3 at the outer side in the width direction of the inclined bead sheet. A protruding heel 9 is provided in the rounded concave portion so as to be in close contact with the entire periphery. FIG. 2 is a cross-sectional view of a main part showing this in connection with the procedure for assembling the bead portion 3 provided with the bulging heel 9 and, eventually, the tire to the standard rim.
Numeral 11 denotes an inclined bead sheet thereof, numeral 12 denotes a rounded concave portion located adjacent to the widthwise outer side of the inclined bead sheet 11, and numeral 13 denotes an overhang extending radially outward from the rounded concave portion 12. Reference numeral 14 denotes a curved flange which continuously and outwardly bends outwardly in the width direction and the radial direction, respectively, of the overhang flange 13. Note that the overhang flange 13 may be omitted depending on the type of the standard rim 10.

Here, the bulging heel 9 is defined as an imaginary straight line 1 in which the inclined bead sheet 11 is extended to the corner-recessed side in a cross section of the standard rim 10 in the width direction as shown, and a corner-recessed part 12. Overhang flange 13 , overhang flange
The standard rim without the rim contacts the curved flange 14 and is orthogonal to the center axis of the standard rim 10, which also corresponds to the intersection P with the virtual straight line m, passes through the bead base point Q planned for tire design, and A bead heel protruding from a perpendicular n dropped to the central axis, and the bulging amount d
Is determined by the allowance from the perpendicular line n, which is 2 mm or more here.

Further, here, the rubber hardness of the bulging heel 9 is 65 degrees or more in JIS hardness, and in addition, the toe tip of the bead toe located at the widthwise inner end of the bead portion 3 along the inclined bead sheet 11. The rubber 15, in the figure, has a hook-shaped toe tip rubber 15 in which the portion along the inclined bead sheet 11 is extended somewhat toward the rounded concave side, and the elongation at break is 42.
0 ± 50%, 300% modulus 200 ± 20kg
As f / cm ² , hardness and toughness are imparted to the toe tip rubber 15.

The tire bead portion 3 constructed as described above usually has a crossing point P between the straight line 1 and the straight line m described above.
An appropriate interference is provided for the rim diameter D defined by the diameter of a circle having a radius equal to the distance to the center axis of the standard rim 10, and the tire having such a bead portion 3 is arranged on the standard rim. For each bead portion 3, the bead portions 3 are partially and sequentially climbed over the outer periphery of the curved flange 14 of the standard rim 10, and are dropped into the drop or well of the standard rim 10 once. Performed, and the subsequent assembly of the tire to the rim 10 is performed by injecting air into the tire until a specified internal pressure is reached,
This is performed by pushing the bead portion 3 outward along the inclined bead sheet 11 until the outer surface thereof contacts the curved flange 14 as shown by the arrow in FIG.

Referring to the progress of such rim assembly in the case of a conventional pneumatic tire having no bulging heel as shown in FIG. 3, the bead portion 21 moves outward on the inclined bead seat as it moves outward. However, since the tightening allowance increases, the degree of tight fitting can be increased, but the frictional resistance of the bead portion 21 which hinders its movement is not always uniform over the entire circumference, so that the frictional resistance is reduced. In the larger part, before the bead heel 22 reaches the rounded corner recess 12, the outer surface of the bead portion 21 comes into contact with the curved flange 14 of the rim 10, and based on the resistance to compressive deformation starting there, the bead heel 22 It will approach the corner round recess 12. However, in this case, the position and volume of the gap 23 that often occurs between the bead heel 22 and the rounded concave portion 12 are different from those of the standard rim 1.
It is often uneven on the circumference of 0, and once such a condition occurs, the air trapped in the gap becomes
Since the further movement of the bead portion 21 along the inclined bead seat 11 is restrained by the increase in the pressure, the rim assembling work is easily cut off, and therefore, the pneumatic tire itself has sufficient uniformity. Despite being vulcanized, the RRO as a tire wheel increased, and as a result, the RFV increased.

On the other hand, in the invention tire provided with the bulging heel 9, when the rim as described above is advanced, first, the bulging heel 9 is turned into the corner round recess 12 of the standard rim 10.
As shown in FIG. 2, the outer surface of the bead portion comes into contact with the curved flange 14 under the compressive deformation of the swelling heel 9, and the rim assembling operation is completed in a state where an appropriate pressure is applied thereto. Therefore, the above-described gap does not occur between the outer surface of the bead portion and the standard rim 10, and the center axis of the tire is easily and accurately aligned with the center axis of the standard rim 10. Therefore, RRO as a tire wheel is reduced, RFV is sufficiently suppressed, and wheel uniformity is greatly improved.

Here, the bulging amount d of the bulging heel 9 is
In a normal passenger car tire, the thickness is preferably 2 to 4 mm in order to improve wheel uniformity while preventing rim rubbing on the outer surface of the bead, and the rubber hardness of the bulging heel 9 is 65 to JIS hardness. An angle of 80 degrees is preferable for improving the wheel uniformity while sufficiently securing the airtightness between the bulging heel and the rounded concave portion.

In addition, in this example, the elongation at break of the toe tip rubber 15 is 420 ± 50%, and the 300% modulus is 2%.
By setting it to 00 ± 20 kgf / cm ² , the bead portion is prevented from falling down and the steering stability is further improved.
In addition, the rim of the bead portion 3 is effectively prevented from being rubbed. Here, when the elongation at break of the toe tip rubber 15 is set to less than 370%, there is a high possibility that the toe chipping of the bead toe occurs.
Can not be effectively prevented falling of bead portions, these things, a 300% modulus when a value exceeding 220 kgf / cm ^2, and 180 kgf / cm ² less than the the versa the in each case is there.

By the way, the swelling heel 9 is, for example, shown in FIG.
As shown in the figure, the ring-shaped core 16 can be reinforced by being embedded therein, and can be a non-stretchable endless band using a steel cord, an organic fiber cord or the like. When the reinforcement 9 is reinforced, the hardness of the swelling heel 9 can be appropriately increased to provide better positioning accuracy.

Thus, according to the pneumatic radial tire, by forming the carcass ply with the rayon fiber cord, excellent dimensional stability against heat can be realized, but the use of the rayon fiber cord results. The decrease in tire uniformity can be sufficiently compensated for by improving the uniformity of a tire wheel in which a pneumatic tire is mounted on a rim.

Comparative Example 1 Size 205/65 R1
When the tubeless tire for passenger car No. 5 is mounted on a standard rim of 15 × 6JJ and filled with an internal pressure of 2.0 kgf / cm ² , the invention tire having the structure shown in FIG. When the RRO and RFV of the comparative tire were measured, the RRO and RFV of the inventive tire were 0.41 mm and 6.0 kgf, respectively, whereas those of the comparative tire were 0.60 mm, respectively.
mm and 8.5 kgf.

Here, the carcass ply cord is
Rayon fiber cords of 1650 d / 2 were used, and the angle of the cords with respect to the tire circumferential direction was 90 °, and the winding end of the carcass ply was positioned near the maximum width position of the tire. Here, the swelling heel of the inventive tire was 2 mm in swelling amount and 70 degrees in JIS hardness.

Comparative Example 2 As shown in FIG. 5, a radial carcass was formed by two carcass plies having an up-down structure, and a carcass ply cord was formed into a 1500 d / 2 rayon fiber cord. Of the code
For a tire having an angle of 90 ° with respect to the tire circumferential direction, RRO and RF were measured under the same conditions as in Comparative Example 1.
When the V was measured, the inventive tire having an inflated heel had an RRO of 0.42 mm and an RFV of 6.2 kgf, whereas the comparative tire having no inflated heel had RRO and RFV of 0.78 mm and 0.78 mmf, respectively. It was 8.8 kgf. Here, the bulging amount of the bulging heel was 2 mm and the JIS hardness was 70 degrees, and the winding end of one carcass ply was positioned near the maximum width position of the tire.

Comparative Example 3 As shown in FIG. 6, a radial carcass was composed of two carcass plies wound up from the inside to the outside around a bead core, and the cord of each carcass ply was 1500 d / 2. In addition to the rayon fiber cord, the angle of one ply cord with respect to the tire circumferential direction was 87 °, the same angle of the other ply cord was 93 °, and RRO and RFV was measured to be 0.45 mm and 6.5 kgf for the inventive tire, respectively, and 0.82 mm and 9.0 kg for the comparative tire having no bulging heel.
kgf. The bulging amount of the bulging heel of the inventive tire was 2 mm, the JIS hardness was 70 degrees, and the winding end of each carcass ply was located near the maximum width position of the tire.

[0033]

As is apparent from the above comparative examples, according to the present invention, the use of rayon fiber cords as the carcass ply cords provides the radial carcass, and hence the tire, with excellent dimensional stability against heat. It should be noted that the deterioration of the uniformity of the tire itself due to the use of the rayon fiber cord can be more than compensated for by improving the wheel uniformity.

[Brief description of the drawings]

FIG. 1 is a sectional view in the tire width direction showing an embodiment of the present invention.

FIG. 2 is a cross-sectional view illustrating a main part of the rim of the tire illustrated in FIG. 1;

FIG. 3 is a cross-sectional view of a main part showing a rim assembly procedure of a conventional tire.

FIG. 4 is a sectional view of a main part showing another embodiment of the present invention.

FIG. 5 is a sectional view of a main part showing a test tire.

FIG. 6 is a sectional view of a main part showing another test tire.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 3 Bead part 4 Radial carcass 5 Bead core 6 Belt 6a, 6b Belt layer 7 Belt reinforcement layer 8 Circumferential groove 9 Swelling heel 10 Standard rim 11 Inclined bead seat 12 Corner round recess 13 Extension flange 14 Curve Flange 15 Rubber toe point P Intersection point Q Bead base point D Rim diameter d Swelling amount

Claims (2)

(57) [Claims] A tread portion, a pair of sidewall portions connected to the tread portion, and a bead portion continuous to a radially inner end of each sidewall portion, and a bead core embedded in each bead portion. Extending toroidally,
A pneumatic radial tire comprising a radial carcass composed of at least one carcass ply, both when the ply cord constituting the carcass ply is rayon fiber cord, is closely fitted to the inclined bead seat of the standard rim Prior to contact with the curved outermost portion of the standard rim in the width direction of the standard rim and the outer surface of the bead portion facing the curved portion, the bead portion is provided with a rounded concave portion adjacent to the outer side in the width direction of the inclined bead sheet. A pneumatic radial tire having a swelling heel that adheres over the entire circumference, the swelling amount of the swelling heel is 2 mm or more, and the rubber hardness of the swelling heel is 65 degrees or more in JIS hardness. 2. The rayon fiber cord has a thickness of 150.
The pneumatic radial tire according to claim 1, wherein the tire is 0d / 2 or more.