JP3247513B2 - Pneumatic radial tires with excellent wheel uniformity - 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 having excellent wheel uniformity.
In particular, the frequency components of the pattern noise are widely dispersed by the pitch variation, thereby improving the uniformity of the tire wheels.

[0002]

2. Description of the Related Art With respect to the pattern noise of the noise generated by a tire, the pitch of the tread pattern in the tire circumferential direction is made variable in order to prevent the sound of a specific frequency component from being heard particularly loudly. 2. Description of the Related Art It has been widely and generally practiced to widely disperse noise frequency components to make noise white noise.

[0003]

Therefore, according to such a conventional tire, even if the tread pattern is a block pattern, a rib pattern, a lug pattern, or the like, a change in weight of the tread portion in the tire circumferential direction is inevitable. As a result, the uniformity of tire wheels had to be reduced.

For the purpose of suppressing radial force variations (hereinafter abbreviated as "RFV") of tire wheels, a change in the RFV of the tire itself after vulcanization molding is measured, and the maximum value on the circumference of the tire is measured. Attachment of the tire to the rim has been performed so that the point and the minimum point of the RFV separately measured for the rim to which the tire is attached are matched. Significance has been practically lost, and in some cases the RFV of the tire itself, rather than the RF of the tire wheels,
V sometimes became larger.

[0005] The present invention has been made in view of such problems of the prior art, and it is inevitable that the variation of the RFV of the tire itself to some extent due to the adoption of the pitch variation, An object of the present invention is to provide a pneumatic radial tire excellent in wheel uniformity, in which wheel uniformity when viewed as a tire wheel is greatly improved as compared with the prior art.

[0006] That is, the present invention can be applied to a case where a pneumatic tire having a good radial run-out (hereinafter abbreviated as "RRO") is mounted on a standard rim having excellent machining accuracy, and the entire tire wheel is mounted. RRO as
Is not necessarily smaller, based on the finding that the cause is derived from the eccentric mounting of the tire when assembling the rim, it was made as a result of assembling the pneumatic radial tire to the rim By improving the tire bead portion so that the concentric mounting can be easily guided, a satisfactory wheel uniformity can be realized as a tire wheel in which a pneumatic radial tire is mounted on a standard rim, RRO is reduced, and RFV is reduced. Is effectively suppressed, thereby improving the wheel uniformity to a degree that can sufficiently compensate for the decrease due to the pitch variation.

[0007]

A pneumatic radial tire having excellent wheel uniformity according to the present invention is provided with a pair of sidewall portions connected to a tread portion.
A continuous bead portion is provided at the radially inner end of each sidewall portion, and usually, a radial carcass composed of at least one carcass ply, and a belt composed of at least two belt layers, each of which is embedded, In the tread portion, a tread pattern of a variable pitch is formed in the tire circumferential direction, and further, the bead portion closely fitted to the inclined bead sheet of the standard rim is positioned at the outermost side in the width direction of the standard rim. Prior to contact between the curved flange and the opposing bead outer surface,
A bulging heel is provided on the rounded concave portion adjacent to the outer side in the width direction of the inclined bead sheet so as to be in close contact with the whole circumference thereof. The hardness is 65 degrees or more.

Here, the standard rim is a split rim, 5
JA such as 15 ° deep rim, 15 ° deep rim, wide deep rim, etc.
A rim defined by TMA, TRA or the like shall be referred to as a rim. The standard rim includes an inclined bead sheet, a rounded concave portion successively extending outwardly in the width direction of the inclined bead sheet, and an outwardly curving rim. It may have a curved flange, and in some cases, an overhang flange between the curved flange and the corner recess. Here, the bulging amount of the bulging heel means a laterally protruding amount of the bulging heel when measured on the basis of a perpendicular to the tire center axis passing through the bead base point.

[0009]

In a pneumatic radial tire having excellent wheel uniformity, a pitch variation technique is employed to change a tread pattern provided on a tread portion into a block pattern, a rib pattern, a lug pattern, or two or more of them. Regardless of the combination pattern, by setting the variable pitch such as three pitches or five pitches in the circumferential direction of the tire, the frequency components of the pattern noise generated by the rolling of the tire are widely dispersed, so that it is unpleasant. The sound pressure level of the sound of the specific frequency component can be effectively reduced.

In order to compensate for the decrease in wheel uniformity resulting from the conversion of the pattern noise to white noise in this manner, and to provide an effective improvement in wheel uniformity, At the tire bead part, hit the rim of the tire,
Prior to the contact between the curved flange of the standard rim and the opposing outer surface of the bead portion, a protruding heel is provided in the rounded concave portion adjacent to the outer side in the width direction of the inclined bead sheet so as to be in close contact with the entire circumference.

According to this, when the rim assembly of the tire proceeds, the bulging heel first comes into close contact with the rounded concave portion of the standard rim, and then the bead outer surface is curved under the compressive deformation of the bulging heel. Because it will contact the flange,
By making the contact state between the bead outer surface and the curved flange etc. uniform over the entire circumference, the center axis of the tire can be aligned with the center axis of the standard rim with high accuracy,
Accordingly, the RRO, that is, the runout of the outer periphery of the tire wheel is reduced, and the fluctuation of the radial reaction force when the tire wheel is rotated under a constant deflection, that is, RFV, is effectively suppressed, and the wheel The uniformity is greatly improved, and therefore, the decrease in uniformity due to the pitch variation can be sufficiently compensated.

[0012] In addition, the improvement of the uniformity also makes the ground contact state at the time of rolling of the tire wheels sufficiently uniform over the entire circumference, and the force generated by the tire wheels is substantially constant at any position in the circumferential direction. Therefore, the running stability of the vehicle and, consequently, the steering stability can be effectively 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. In addition, the rubber hardness of the bulging heel is set to 65 degrees or more in JIS hardness, whereby the bulging heel can be firmly fitted and fixed to the rounded concave portion, and the bulged heel is fixed to the rounded concave portion. It can lead to uniform contact 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.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional perspective view showing an essential part of an embodiment of the present invention. In FIG.
Denotes a pair of left and right sidewalls continuous to each side of the tread portion 1, and 3 denotes a bead continuous to the radially inner end of each sidewall 2.

In this tire, a radial carcass 4 extending toroidally is formed by a single carcass ply made of, for example, a polyester cord extending at an angle of about 90 ° with respect to the tire circumferential direction.
Are wound from the inside to the outside around the bead core 5 embedded in the bead portion 3 and the outer peripheral side of the crown portion of the radial carcass 4 has a relatively small angle with respect to the tire circumferential direction. And a belt 6 composed of two belt layers 6a and 6b in which the cords intersect each other between the layers, and
On the outer peripheral side of the belt 6, there is provided a 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.

Here, the tread portion 1 is provided with a plurality of circumferential grooves 8 extending in the tire circumferential direction and a plurality of width direction grooves 9 extending in the tire width direction. Is formed by forming a block pattern composed of the blocks 10 of the above, and forming the block pattern into a variable pitch of, for example, three pitches or five pitches by selecting the arrangement pitch and the extension angle of the width direction grooves 9. The frequency components of the pattern noise are sufficiently dispersed.

Further, in this tire, the bead portion 3
In contact with the curved rim of the standard rim and the outer surface of the bead portion facing the rim portion of the tire, the bead heel portion is brought into close contact with the corner concave portion adjacent to the outer side in the width direction of the inclined bead seat over its entire circumference. A bulging heel 11 is provided. FIG. 2 illustrates this by bulging heel 1
1 is a cross-sectional view of a main part of a bead portion 3 provided with a tire 1 and a tire, in connection with a procedure for assembling the tire to a standard rim, in which 12 is a standard rim, 13 is an inclined bead seat thereof, 14
Indicates a rounded recess located adjacent to the widthwise outside of the inclined bead sheet 13, and 15 indicates a projecting flange projecting radially outward from the rounded recess 14, 16.
Shows curved flanges of the overhanging flange 15 that continuously and outwardly bend outward in the width direction and the radial direction, respectively. Note that the overhang flange 15 may be omitted depending on the type of the standard rim 12.

Here, the bulging heel 11 is defined as an imaginary straight line 1 in which the inclined bead sheet 13 is extended to the corner-recessed portion side in the cross section in the width direction of the standard rim 12 as shown in the figure, Overhang flange 15 , overhang franc
In a standard rim having no ridge, it is in contact with the curved flange 16 and is orthogonal to the center axis of the standard rim 12, which also corresponds to an intersection P with an imaginary straight line m, and a bead base point Q planned for tire design.
, The bead heel protruding from a perpendicular n drawn down from the tire center axis, and the bulging amount d of the bulging heel 11 is determined by an allowance from the perpendicular n.
Here, it is set to 2 mm or more.

Further, here, the rubber hardness of the bulging heel 11 is set to 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 13. Rubber 17, the hook-shaped toe tip rubber 17 in which the portion along the inclined bead sheet 13 is extended somewhat toward the rounded concave portion, has an elongation at break of 4 mm.
20 ± 50%, 300% modulus 200 ± 20
As Kgf / cm ² , the toe rubber 14 is given hardness and toughness.

In the tire bead portion 3 having the above-described structure, the intersection P between the straight line 1 and the straight line m is usually determined from the intersection P described above.
An appropriate interference is given to 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 12, and the tire having such a bead portion 3 is mounted on the standard rim. The arrangement is such that, for each bead portion 3, the bead portion 3 is partially and sequentially climbed over the outer periphery of the curved flange 16 of the standard rim 12, and both bead portions 3 are dropped into the drop or well of the standard rim 12 once. The subsequent assembly of the tire to the rim 12 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 beam sheet 13 until the outer surface thereof contacts the curved flange 16 as shown by the arrow in FIG.

Referring to the progress of such rim assembling with a conventional pneumatic tire having no bulging heel as shown in FIG. 3, as the bead portion 21 moves outward on the inclined bead seat, 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 14, the outer surface of the bead portion 21 comes into contact with the curved flange 16 of the rim 12, and the resistance to compressive deformation starting there causes the bead heel 22 to be rounded. It will approach the recess 14. However, in this case, the position and volume of the gap 23 that often occurs between the bead heel 22 and the rounded corner recess 14 often become uneven on the circumference of the standard rim 12, and such a state occurs once. Then, the air trapped in the gap restrains the further movement of the bead portion 21 along the inclined bead sheet 13 by the increase in the pressure, so that the rim assembling work is cut off as it is. Therefore, despite the fact that the pneumatic tire itself is vulcanized and formed with sufficient uniformity, the RR as a tire wheel
O increased, and as a result, RFV increased.

On the other hand, in the case of the inventive tire provided with the bulging heel 11, when the rim as described above is advanced,
First, the swelling heel 11 is the corner dent 1 of the standard rim 12
4, as shown in FIG. 2, and then, under compressive deformation of the swelling heel 11, the outer surface of the bead portion becomes curved flange 16.
And the rim assembling operation is completed in a state where moderate pressure is applied thereto, so that the above-described gap does not occur between the outer surface of the bead portion and the standard rim 12, The center axis of the tire will easily and accurately align with the center axis of the standard rim 12,
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 11
Is preferably 2 to 4 mm in a normal passenger car tire in order to improve wheel uniformity while preventing rim rubbing on the outer surface of the bead portion, and the JIS hardness of the bulging heel 11 is 65 mm. It is preferable that the angle be set to 80 degrees in order to improve the wheel uniformity while securing sufficient airtightness between the bulging heel 11 and the rounded concave portion 14.

In addition, in this example, by setting the elongation at break of the toe tip rubber 17 to 420 ± 50% and the 300% modulus to 200 ± 20 Kgf / cm ² , the bead portion 3 is effectively prevented from falling down. As a result, the steering stability is further improved, and the rim of the bead portion 3 is effectively prevented from being rubbed. Here, when the elongation at break is less than 370%, there is a high possibility that toe chipping occurs in the bead tow. On the other hand, when the value exceeds 470%, the bead portion is effectively prevented from falling down. Can not do this, it means that the 300% modulus is 220 kgf / cm ²
The same applies to the case where the value exceeds 180 kgf / cm ² and the case where the value exceeds 180 kgf / cm ² , respectively.

The swelling heel 11 is, for example,
If the swelling heel 11 is reinforced by a ring core which can be a non-stretchable endless band using steel cord, organic fiber cord, etc. The hardness of the bulging heel can be appropriately increased, and more excellent positioning accuracy can be obtained.

Thus, according to the pneumatic radial tire, the unpleasant sound can be effectively removed from the pattern noise by the variable pitch block pattern. On the other hand, the reduction in wheel uniformity due to the pitch variation is achieved. Can be sufficiently compensated for by improving the uniformity of a tire wheel having a tire mounted on a rim.

[Comparative Example 1] A comparative test on the wheel uniformity between the inventive tire and the comparative tire will be described below. ◎ Test tire A tire with a size of 205 / 65R15. This tire
It was mounted on a 5 × 6JJ rim and the filling pressure was set to 20 kgf / cm ² . ○ Inventive tire A tire having the configuration shown in FIG. 1, wherein the number of pitch types of the block pattern is five (7: 8: 9: 10: 11), the number of pitches on the circumference is 74, and the tire bulges. A heel with a bulge of 2 mm and a JIS hardness of 70 degrees. ○ Comparative tire 1 The same tire as the inventive tire except that the bulging heel was omitted. Comparative tire 2 The same tire as the inventive tire except that the type of pitch of the block pattern is one, the number of pitches on the circumference is 74, and the bulging heel is omitted.

試 験 Test Results RRO and RFV of each tire were measured, and the results are as shown in Table 1.

[Table 1] According to the results shown in Table 1, in the inventive tire, both RRO and RFV are smaller than those of the comparative tires 1 and 2, and it is clear that the wheel uniformity is greatly improved. [Comparative Example 2] Another comparative test of the wheel Uiformity will be described below.

◎ Test tire The tire size, the standard rim and the filling internal pressure were all the same as in Comparative Example 1. ○ Inventive tire The same tire as the inventive tire of Comparative Example 1 except that the pitch type of the block pattern was three (7: 9: 11) and the number of pitches was 66. ○ Comparative tire 1 The same tire as the above-described inventive tire except that the bulging heel was omitted. Comparative tire 2 The same tire as the above-described inventive tire except that the pitch type of the block pattern is one, the number of pitches on the circumference is 66, and the bulging heel is omitted.

試 験 Test Results The RRO and RFV of each tire were measured, and the results are as shown in Table 2.

[Table 2] It can also be seen from Table 2 that the wheel uniformity of the inventive tire is improved as compared with the comparative tire.

[0031]

As is apparent from the above description, according to the present invention, because of the presence of the bulging heel, the pattern noise is reduced to white noise by adopting the pitch variation, and the wheel uniformity is reduced. It can be improved effectively.

[Brief description of the drawings]

FIG. 1A is a cross-sectional perspective view showing an embodiment of the present invention with respect to main parts thereof. (b) is a diagram showing an embodiment of the present invention with respect to a pattern pitch variation.

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.

[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 reinforcing layer 8 Circumferential groove 9 Width groove 10 Block 11 Swelling heel 12 Standard rim 13 Inclined bead seat 14 Corner round Recess 15 Overhang flange 16 Curved flange 17 Toe rubber P Intersection point Q Bead base point D Rim diameter d Swell amount

Claims (1)

(57) [Claims] 1. A pneumatic radial tire comprising a tread portion, a pair of sidewall portions connected to the tread portion, and a bead portion continuing to a radially inner end of each sidewall portion, wherein the tread portion is provided. A variable pitch tread pattern is formed in the tire circumferential direction, and the bead portion tightly fitted to the inclined bead sheet of the standard rim, the standard rim has 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 bulging 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 over the entire circumference, and the bulging amount of the bulging heel is 2 mm or more. A pneumatic radial tire with excellent wheel uniformity, in which the bulge heel has a rubber hardness of 65 degrees or more in JIS hardness.