JP3300494B2 - Pneumatic 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 tire having excellent wheel uniformity.
JATM of each type such as ° deep, 15 ° deep, wide deep, etc.
A rim specified by A, TRA, etc. (hereinafter simply referred to as a "standard rim"), particularly, a standard rim in which one side wall of the well is steeper than the other side wall. Achieving a satisfactory wheel uniformity as a tire wheel fitted with a radial runout (hereinafter referred to as "RR
It is an object of the present invention to provide a pneumatic tire that can reduce radial force variation (hereinafter, abbreviated as “RFV”) by reducing O ”).

[0002]

2. Description of the Related Art With the progress of research on measures against vibration, riding comfort, noise, and steering stability of automobiles, particularly passenger cars, the wheel uniformity of tire wheels has become increasingly important. Japanese Unexamined Patent Publication No. 3-189201 discloses that, with respect to the reduction of RFV of a tire wheel in which a pneumatic tire is mounted on a rim, RRO in a shoulder portion of the tire wheel is measured on the circumference, and a tire corresponding to a portion having a large value is measured. Is disclosed that a spacer is interposed between the bead portion of the rim and the flange of the rim. However, according to this, the operation of the rim assembly and the air injection requires repetition, and the workability of the rim assembly is significantly impaired.
V may change.

On the other hand, the RF of the tire itself after vulcanization molding has been completed.
The change in V is measured, and the rim assembly is performed so that the maximum peak position of the waveform representing the transition coincides with the minimum peak of the waveform indicating the fluctuation of the peripheral runout measured separately for the rim to which the tire is mounted. It is also known, however, that the improvement of the rim machining accuracy has practically lost its significance.

[0004]

With respect to the wheel uniformity, the tire wheels are not simply round in shape, but have equal deflection under the same load everywhere on the circumference. In this regard, it is important that the reaction force when rotating under a certain deflection is uniform.
That is, even if the RRO of the uniformity evaluation measure, that is, the runout of the outer circumference of the tire and the rim is small, the fluctuation of the radial reaction force when the tire wheel is rotated under a constant deflection, that is, the RFV is This is because it may become large.

[0005] The inventor has noticed that 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 RFV as a tire wheel does not always become small. It has been found that the cause is derived from eccentric mounting in rim assembly.

[0006] Based on this finding, the present invention has improved wheel uniformity and improved both RRO and RFV of the tire wheel by improving the bead portion of the tire that can be easily mounted concentrically when assembling the pneumatic tire to the rim. It is an object of the present invention to provide a pneumatic tire that can be effectively suppressed.

[0007]

The pneumatic tire according to the present invention, which is excellent in wheel uniformity, is located between each inclined bead seat and both inclined bead seats. A well that is eccentric to the outside, a rounded concave portion or a rounded concave portion and a protruding flange successively arranged outside in the width direction of the inclined bead sheet, and a curved flange that is bent outwardly are provided. A standard rim having a steep slope as compared with a side wall is provided with a bead portion closely fitted to each inclined bead seat, and is assembled to the standard rim to constitute a wheel, wherein a wheel is formed. The inner diameter of one bead portion fitted to the inclined bead sheet on the inclined side wall side, more specifically, based on the inner diameter of the bead portion at a position corresponding to the center of the bead core, the other of the steep side wall Similar internal diameter of the other bead portion to be fitted to the inclined bead seat 0.3 ～2.0Mm increased,
In addition, at least the bead portion fitted to the inclined bead seat on the steep side wall side, a curved flange of the standard rim,
Prior to contact with the outer surface of the bead part facing it, a bulging heel that closely adheres to the corner round recess over its entire circumference is provided,
The bulging amount of the bulging heel is 2 mm or more.

Here, the amount of bulging of the bulging heel means the amount of lateral bulging of the bulging heel with reference to a perpendicular to the tire center axis passing through the bead base point.

[0009]

Generally, each bead portion of a pneumatic tire is provided with an appropriate interference with respect to each inclined bead seat of a standard rim, and such a bead portion is assembled to the rim, After dropping both bead portions into the rim well, the pneumatic tire is filled with air pressure, so that each bead portion is bent along the inclined bead seat, and the outer surface of the bead portion is curved. This is done by pushing forward until it touches the flange.

In this case, in the conventional tire in which the inner diameters of the respective bead portions are equal to each other, first, one bead portion rides on the inclined bead sheet on the gentle side wall of the well and abuts on one curved flange, Thereafter, the other bead, under the action of high internal pressure, will momentarily reach the sloping bead seat over the steep side walls of the well.

[0011] In particular, regarding the other bead portion fitted to the inclined bead sheet on the steep side wall, the bead portion moves outward on the inclined bead sheet 21 as shown in FIG. As a result, the tightening allowance increases, and the degree of tightening fit can be increased. However, the frictional resistance of the bead portion 22 that hinders the movement is not necessarily uniform over the entire circumference, so that the frictional resistance is reduced. Before the bead heel 23 reaches the rounded concave portion 25 of the standard rim 24, the outer surface of the bead portion 22 comes into contact with the curved flange 26 of the rim 24, so that the resistance to the compressive deformation starting there is reduced. As a result, the bead heel 23 approaches the corner round recess 25. However, at this time, the bead heel 23
The position and volume of the gap 27 that often occurs between the corner rim 25 and the corner round recess 25 are often uneven on the circumference of the standard rim 24. Once such a state occurs, the gap 27 is sealed in the gap. Since the air limits further movement of the bead portion 22 along the inclined bead seat 21 by increasing its pressure, the rim assembling operation tends to be discontinued and the pneumatic tire itself is not sufficient. Despite being vulcanized and molded with a uniform uniformity, the RRO as a tire wheel has increased, and as a result, the RFV has increased.

On the other hand, in the tire of the present invention, based on the fact that the inner diameter of the bead portion on the side over the steep side wall of the well is larger than that of the opposing bead portion, The large-diameter bead portion can move over the steep side wall and move on the sloping bead seat much more smoothly than the conventional tire under a small frictional resistance. Easily adheres to the rounded corner recess over the entire circumference.

Therefore, in the tire according to the present invention, the possibility that a gap as in the conventional tire is generated between the bead heel and the rounded concave portion is reduced, and the center axis of the tire is easily and high relative to the center axis of the standard rim. By increasing the possibility of matching with accuracy, RRO as a tire wheel is reduced, RFV is sufficiently suppressed, and wheel uniformity is improved.

Here, the diameter difference between the inner diameter of the reference bead portion and that of the larger diameter bead portion is 0.3 m in order to move the bead portion on the inclined bead sheet sufficiently smoothly.
m or more, but if the difference is too large, it is not possible to secure a sufficient contact area between the outer surface of the bead portion including the bead heel and the rim, which may cause a decrease in airtightness. In extreme cases, the bead may come off the rim, so it is limited to 2.0 mm here.

Further, in the tire according to the present invention, at least the bead portion having the larger inner diameter is formed over the entire periphery of the rounded concave portion prior to contact with the curved flange of the standard rim and the opposing outer surface of the bead portion. By providing the bulging heel which is in close contact, during the progress of the rim assembly, the bulging heel firstly comes into close contact with the rounded concave portion, and then the bead outer surface contacts the curved flange under the compressive deformation of the bulging heel, Since the rim assembly work will be completed with moderate pressure applied to it,
Higher precision concentric mounting on the rim is more reliably achieved, and wheel uniformity is further 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, the rubber height of the bulging heel is preferably 65 degrees or more in JIS hardness. According to this, the bulging heel can be firmly fitted and fixed in the rounded concave portion, and the bulging heel can be fixed. The protruding heel can more effectively lead to uniform contact with the rounded concave part all around, but if the hardness is too hard, the sufficient amount of compressive deformation between the bulging heel and the rim is secured. It is not preferable to set the angle up to 80 degrees because it is not possible to perform the sealing and a problem may occur in the airtightness.

By the way, such improvement of the wheel uniformity can be achieved by sufficiently reducing fluctuations in the circumferential direction of the tire, such as the shape of the contact surface, the contact area, and the position of the contact surface in the width direction, when the tire is rolling. Since the force generated by the wheels is substantially constant at any position in the circumferential direction, the running stability of the vehicle and, consequently, the steering stability are also improved.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic cross-sectional view in the width direction illustrating a tire on which the present invention is based.
Denotes a pair of left and right sidewalls continuous to each side of the tread portion 1, and 3 denotes a bead portion continuous to the radially inner end of each sidewall 2.

Each bead portion 3 has a bead core 4
Is fixed to these bead cores 4 by winding up the side end portions of at least one carcass ply 5 extending toroidally from the inside to the outside in the width direction. Further, a belt 6 including at least two belt layers is disposed on the outer peripheral side of the clan portion of the carcass ply 5.

FIG. 2 is a cross-sectional view in the width direction of a standard rim on which such a tire is mounted. The standard rim 10 is located between each inclined bead seat 11 and the inclined bead seats. With respect to the well 12, which is located on one side with respect to the corner, the corner recess 13 adjacent to the widthwise outside of each inclined bead sheet 11, and a projecting flange 14 projecting radially outward from the corner recess 13. Of the overhang flange 14,
A curved flange 15 continuously and outwardly bent outwardly in each of the width direction and the radial direction;
Has a steeper slope than the other side wall 12b. Note that the overhang flange 14 may be omitted depending on the type of the standard rim 10.

In the tire shown in the figure, the steep side wall 12a is formed on the side of the gentle bead sheet 11 on the side of the gentle side wall 12b of the well 12 with reference to the inner diameter R1 of _one bead portion 3 fitted to the bead seat 11.
Of the inner diameter R ₂ of the other bead portion 3 to be fitted to the other inclined bead seat 11 side, from 0.3 to 2 with respect to the reference inner diameter R _1.
0 mm, more preferably 0.5 to 1.0 mm. Here, each of the inner diameters R ₁ and R ₂ of the bead portion 3 means an inner diameter at a position corresponding to the center of the bead core.

According to the tire configured as described above,
In the rim assembly, especially the large diameter side bead 3
However, as described above, since it is possible to smoothly climb over the steep side wall 12a of the well 12 and to move outwardly on the inclined bead seat sufficiently smoothly, the bead heel of the tire and the rounded recess 13 of the rim are formed. The tire is easily and concentrically mounted on the standard rim 10 with high precision, thereby effectively improving both the RRO and the RFV of the wheel and improving the wheel uniformity. Will be.

Further, according to the present invention, as shown in FIG. 3, the bead portion 3 fitted to the inclined bead sheet 11 on the side of the steep side wall 12a as shown in FIG. Prior to the contact between the curved flange 15 of the standard rim 10 and the outer surface of the bead portion facing the rim assembly, the rounded concave portion 13 is provided with a bulging heel 7 which is in close contact with the entire periphery thereof.

FIG. 3 shows that this bulging heel 7 is
FIG. 3 is a cross-sectional view of a main part shown in relation to an assembling procedure to a standard rim 10, and a bulging heel 7 of the standard rim 10 is formed by rounding an inclined bead sheet 11 in a widthwise cross section as shown in FIG. A virtual straight line 1 extending to the side, a projecting flange 14 continuing to the corner round recess 13, and a standard rim without a projecting flange, in contact with the curved flange 15 and orthogonal to the center axis of the standard rim 10, which is also a virtual straight line m. Passes through a bead base point Q corresponding to the intersection point P of the tire design and protrudes outward from a perpendicular line n down to the tire center axis from there. Here, the bulging amount d of the bulging heel 7 is determined by the protruding amount from the perpendicular line n, and is 2 mm or more here. The rubber hardness of the swelling heel 7 is preferably set to 65 degrees or more in JIS hardness.

According to such a bead portion 3, when the rim assembly of the tire proceeds, the bulging heel 7 first comes into close contact with the rounded concave portion 13, and then, under the compressive deformation of the bulging heel 7, Since the outer surface of the bead comes into contact with the curved flange 15, the contact state between the outer surface of the bead portion and the curved flange and the like is sufficiently uniform over the entire circumference, and the center axis of the tire is more accurately aligned with the center axis of the standard rim. Can be matched. Therefore, according to this, RRO and RFV of the tire wheel are more effectively suppressed, and further improvement of the wheel uniformity is realized. This becomes more remarkable when the bulging heels 7 are provided on both the bead portions 3.

On the other hand, such an improvement in the wheel uniformity, on the other hand, also leads to an improvement in the steering stability. However, from the viewpoint of the steering stability, the inclination bead seat 11 of each bead portion 3 has When the toe rubber 8 of the bead toe positioned at the inner end portion in the width direction along the bead toe, in the figure, the hook-shaped toe rubber 8 having a hook shape in which the portion along the inclined bead sheet 11 is extended somewhat toward the rounded concave side, The elongation of 420 ±
It is preferable that the toe tip rubber 15 is provided with hardness and toughness by setting the 50% and the 300% modulus to 200 ± 20 kgf / cm ² , thereby preventing the bead portion 3 from falling down and maneuvering. Stability can be further improved, and additionally, rim rubbing of the bead toe by the inclined bead sheet 11 can be prevented.

Here, the elongation at break of the toe tip rubber 15 is
If it is less than 370%, the possibility of toe chipping of the bead tow increases, while if it exceeds 470%, it is not possible to effectively prevent the bead from falling down. 300% modulus 220kgf / cm ²
The same applies to the case where the value is more than and the case where the value is less than 180 kgf / cm ² .

[Comparative Example] Hereinafter, comparative tests on the wheel uniformity of the inventive tire, the comparative tire, and the conventional tire will be described.

◎ Test tire A general radial tire having a size of 225/50 R16. The tire was assembled on a 16 × 8JJ standard rim, and the filling internal pressure was set to 2.5 kgf / cm ² .

The inner diameter of the bead portion on the large-diameter side of the comparative tire is set at 0.
7mm larger one. -Invented tire Same as the comparative tire except that each bead portion has a bulging heel with a bulging amount of 2.0 mm.・ Conventional tire A tire having no bulging heel in which the inner diameter of both bead portions is equal to the inner diameter of the bead portion on the reference side.

◎ Test method The wheel uniformity was determined by the RRO of each tire wheel.
And RFV were evaluated by actual measurement. Here, the supply internal pressure when both beads were fitted to the rim was also measured.

試 験 Test Results The average value of the measured values for each of the ten tires was determined, and the results are as shown in Table 1.

[0033]

[Table 1]

According to Table 1, it is clear that both the comparative tire and the inventive tire can be assembled on the rim with a small internal pressure, and the uniformity of the entire tire wheel can be greatly improved as compared with the conventional tire. However, these are particularly remarkable in the inventive tire.

[0035]

As is clear from the above comparative example, according to the present invention, in particular, the inner diameter of the bead fitted to the inclined bead sheet on the side of the steep side wall of the well is changed to that of the other bead. By providing a bulge of at least 2 mm in the bead portion fitted to the inclined bead sheet on the steep side wall of the well at least 0.3 to 2.0 mm, the airtightness is reduced and the rim is reduced. The wheel uniformity can be greatly improved without causing the possibility of disengagement.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view in the width direction showing a tire on which the present invention is based.

FIG. 2 is a cross-sectional view in the width direction illustrating a standard rim.

FIG. 3 is a fragmentary cross-sectional view showing a rim assembling point of an inventive tire provided with a bulging heel.

FIG. 4 is a cross-sectional view showing a rim assembly state of a conventional tire.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 tread portion 2 side wall portion 3 bead portion 4 bead core 7 bulging heel 10 standard rim 11 inclined bead seat 12 well 12 a steep side wall 12 b gentle slope side wall 13 corner round recess 14 overhang flange 15 curved flange R ₁ , R ₂ bead portion Inner diameter P Intersection point Q Bead base point D Rim diameter d Swelling amount

Claims (1)

(57) [Claims] 1. An inclined bead sheet, a well located between the inclined bead sheets, a rounded concavity or a rounded concavity and an overhanging flange that are sequentially connected to the widthwise outside of the slanted bead sheet; A curved rim with one side wall of the well being steeper relative to the other side wall, with a bead that is tightly fitted to each inclined bead seat. A pneumatic tire configured as a wheel by being assembled to a standard rim, wherein, based on the inner diameter of one bead portion fitted to the inclined bead seat on the gentle slope side wall of the well, the other slope on the steep side wall side While increasing the inner diameter of the other bead part fitted to the bead sheet by 0.3 to 2.0 mm, at least the curved part of the standard rim is fitted to the bead part fitted to the inclined bead sheet on the steep side wall. Prior to contact between the flange and the outer surface of the bead portion facing the flange, a bulging heel is provided in the rounded concave portion so as to be in close contact with the entire circumference thereof, and the bulging amount of the bulging heel is 2 mm or more. tire.