JP3184374B2 - Tire-rim assembly - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an assembly of a pneumatic radial tire and a rim provided with a wide annular groove in a central area of a tread portion for the purpose of suppressing the occurrence of a hydroplaning phenomenon. In particular, it increases the cornering power at a small steering angle.

[0002]

2. Description of the Related Art As a conventional technique for ensuring excellent wet drainage and suppressing the occurrence of the hydroplaning phenomenon, it is most common to provide a plurality of linear circumferential grooves in a tread tread portion. However, according to this, it is essential to increase the negative rate in order to secure a sufficiently large groove volume and to provide excellent wet performance, and the land portion rigidity naturally decreases, so that the wet performance and It is extremely difficult to achieve a high level of compatibility with steering stability on dry road surfaces.

In recent years, for example, Japanese Patent Application Laid-Open No. 61-60304 and Japanese Patent Application Laid-Open No.
As disclosed in Japanese Unexamined Patent Application Publication No. H10-163, by forming a circumferential groove having both a large width and a large depth in the central region of the tread portion, without significantly reducing the tread contact area,
It has been proposed to ensure a large groove volume.

[0004]

However, in the latter prior art, there is generally no land portion in the central area of the tread where the contact pressure is supposed to be the highest, especially due to the absence of a land portion. Insufficient cornering power at small steering angle was won. Accordingly, the present invention provides a circumferential groove having both a large width and a large depth in a central region of a tread portion, thereby securing a large groove volume without a significant decrease in a tread contact area, and further improving a tire bead portion. The present invention provides a tire-rim assembly capable of enhancing the uniformity of tire wheels and consequently sufficiently compensating for a lack of cornering power at a small steering angle.

That is, the present invention realizes a satisfactory wheel uniformity as a tire-rim assembly by improving a tire bead portion, reduces radial runout (hereinafter abbreviated as "RRO"), and reduces radial force. Variations (hereinafter abbreviated as "RFV")
Effectively suppresses 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, during rolling of the tire wheel, thereby reducing the force generated by the tire wheel. At any position in the circumferential direction, thereby effectively improving the cornering power.

[0006]

A tire-rim assembly according to the present invention has a pair of sidewall portions connected to a tread portion, a bead portion continuous with the radially inner end of each sidewall portion, and A radial carcass composed of at least one carcass ply and a belt composed of at least two belt layers are buried.
An assembly of a pneumatic radial tire and a rim formed with an annular groove having a width of 0 to 40%, wherein the bead portion tightly fitted to the inclined bead seat of the standard rim has the standard rim. Prior to the contact between the curved outermost flange located in the width direction and the outer surface of the bead portion facing the curved flange, a bulging heel is provided which is in close contact with the rounded concave portion adjacent to the widthwise outer side of the inclined bead sheet over its entire circumference, The amount of bulging of the bulging heel is 2 mm or more, and the rubber hardness of the bulging heel is 65 degrees or more in JIS hardness.
Here, preferably, a constricted portion is formed in each of the radial carcass, the belt, and the tread portion at a portion corresponding to the annular groove of the pneumatic radial tire.

Here, the standard rim refers to a rim specified by JATMA or TRA, such as a split rim, a 5 ° deep rim, a 15 ° deep rim, a wide deep rim, etc. This standard rim includes an inclined bead sheet, a rounded concave portion sequentially connected to the outer side in the width direction of the inclined bead sheet, and a curved flange that recurves outward,
In some cases, an overhanging flange may be provided between the curved flange and the rounded corner recess. Here, the amount of bulging of the bulging heel means the amount of lateral bulging of the bulging heel when measured on the basis of a perpendicular to the tire center axis passing through the bead base point.

[0008]

The tire of the tire-rim assembly according to the present invention has a tread contact width of 10 to 4 in the central area of the tread portion.
By providing an annular groove having a width of 0% and a depth sufficient to secure the required groove volume,
It can provide wet performance that can effectively suppress the occurrence of hydroplaning phenomena, and at the same time, avoids a significant decrease in tread contact area and rigidity of the tread land part, and provides excellent steering stability. Can also.

On the other hand, a decrease in cornering power at a small steering angle due to the fact that the center area of the tread cannot contribute to the load of the contact pressure due to the existence of the annular groove described above is caused by a decrease in tire bead. Due to the refinement of the part, the tire-rim assembly can be completely compensated for by always achieving proper alignment between the tire center axis and the rim center axis.

That is, according to the tire-rim assembly, when the tire rim is assembled to the tire bead portion,
Prior to contact between the curved flange of the standard rim and the outer surface of the bead portion facing the rim, a bulge heel is provided in the rounded concave portion adjacent to the inclined bead seat of the rim over the entire periphery thereof to advance the rim assembly. At this time, first, the bulging heel closely adheres to the rounded concave portion, and then, under compression deformation of the bulging heel, the outer surface of the bead portion comes into contact with the curved flange. The contact state can be made sufficiently uniform over the entire circumference so that the center axis of the tire can be aligned with the center axis of the standard rim with high accuracy, and therefore RRO, ie,
Les vibration of the outer circumference of the tire wheel is reduced, also, the variation of the radial reaction force when rotating the tire wheel under constant deflection, i.e., RFV is effectively suppressed, uniformity of the wheel greatly improved Will be done. And such improvement of the wheel uniformity makes the ground contact state of the tire wheel at the time of rolling, as described above, sufficiently uniform over the entire circumference, and the force generated by the tire wheel to any position in the circumferential direction. However, when the tire wheel is viewed as a whole, the variation in the generated cornering power due to the circumferential position is extremely small, and as a result, the above-described decrease in the cornering power is sufficiently compensated for. Can be.

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-rim assembly, when a constricted portion is formed in each of the radial carcass, the belt and the tread portion at a portion corresponding to the annular groove of the tire, the width and the depth of the annular groove are reduced. Each can be enlarged as desired with little effect on the other components. Moreover, here, the tread portion itself is completely worn due to the constriction of the tread portion itself, so that the groove depth of the circumferential groove or the width direction groove at least partially reaches 1.6 mm. Thus, the groove volume of the annular groove can be sufficiently ensured, and therefore, excellent wet performance can be ensured even after complete wear of the tread portion.

[0013] In addition, according to this, the radial carcass, the belt and the tread portion are made substantially cylindrical, and the volume of the tread portion is reduced as compared with the case where an annular groove having a required groove volume is formed therein. Tire-
It is possible to reduce the weight of the tread assembly and increase the rigidity of the tread portion.

[0014]

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 with respect to a pneumatic radial tire of a tire-rim assembly, where 1 is a tread portion, and 2 is a side portion of the tread portion 1. , A pair of left and right side wall portions, and 3 indicates a bead portion continuous to the radially inner end of each side wall portion 2.

In this example, the radial carcass 4 is formed by a single carcass ply made of, for example, a polyester cord extending at an angle of substantially 90 ° with respect to the tire circumferential direction, and each side of the radial carcass 4 is formed. The end portion is wound up from inside to outside around a bead core 5 embedded in the bead portion 3, and the radial carcass 4
A belt 6 made of a steel cord extending at a relatively small angle with respect to the tire circumferential direction and having two layers of belt layers 6a and 6b intersecting each other between the layers is disposed on the outer peripheral side of the belt. Further, on the outer peripheral side of the belt 6, 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, the radial carcass 4, the belt 6, the belt reinforcing layer 7, and the tread portion 1 are each provided with a ring-shaped constricted portion 8 depressed inward in the radial direction at a portion corresponding to the central area of the tread portion 1. And, at a position corresponding to the constricted portion 8, 10 to 40% of the tread contact width W.
And has a depth H required to secure a required groove volume. Note that, in addition to the annular groove 9, a circumferential groove 10 and a widthwise groove (not shown) can be formed in the tread portion 1 as necessary.

By the way, in this tire-rim assembly,
Prior to contact between the curved flange of the standard rim and the opposing outer surface of the bead portion, the bead heel portion of the bead portion 3 has a rounded concave portion adjacent to the outer side in the width direction of the inclined bead seat before contacting the curved flange of the standard rim and the outer surface of the bead portion. A swelling heel 11 is provided which is in close contact with the heel. FIG. 2 is a cross-sectional view of a main part showing this in relation to a procedure for assembling the bead part 3 provided with the bulging heel 11 and, eventually, the tire to the standard rim. Reference numeral 13 denotes an inclined bead sheet thereof, reference numeral 14 denotes a rounded concave portion located adjacent to an outer side in the width direction of the inclined bead sheet 13, and 15
Is a protruding flange that protrudes radially outward from the corner round recess 14, and 16 is a curved flange that recurves outward continuously in the width direction and the radial direction of the protruding flange 15. Shown 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 a virtual straight line 1 that extends the inclined bead sheet 13 toward the corner-recessed portion and a corner-recessed portion 14 in the cross section of the standard rim 12 in the width direction as shown. In contact with the continuous overhanging flange 15 or curved flange 16 and orthogonal to the center axis of the standard rim 12;
This also corresponds to the intersection point P with the virtual straight line m, and refers to a bead heel that passes through a bead base point Q planned for tire design and protrudes from a perpendicular line n down to the tire central axis from there. The quantity d is determined by the allowance from the perpendicular n, and is set to 2 mm or more here.

Further, here, the rubber hardness of the bulging heel 11 is 65 degrees or more in JIS hardness, and in addition, the toe rubber of the bead toe located at the inner end in the width direction along the inclined bead sheet 13 of the bead portion 3. 17, the elongation at break of the hook-shaped toe rubber 17 in which the portion along the inclined bead sheet 13 is extended slightly longer toward the rounded concave portion is 42.
0 ± 50%, 300% modulus 200 ± 20kg
As f / cm ² , hardness and toughness are imparted to the toe rubber 17.

Incidentally, the tire bead portion 3 usually has a rim diameter D defined by the diameter of a circle whose radius is the distance from the intersection P between the straight line 1 and the straight line m to the center axis of the standard rim 12. An appropriate interference is provided for the tire, and the tire having such a bead portion 3 is disposed on the standard rim. For each bead portion 3, the tire is provided on the outer periphery of the curved flange 16 of the standard rim 12. This is carried out by partially dropping both bead portions 3 into the drop or well of the standard rim 12 once, and then assembling the tire to the rim 12 in the tire. Fill with air until the internal pressure is reached,
2 is pushed outward along the inclined bead sheet 13 until its outer surface contacts the curved flange 16 as shown by the arrow in FIG.

Referring to the progress of the 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 beat 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 recess 14, the outer surface of the bead 21 comes into contact with the curved flange 16 of the rim 12, under the action of the resistance to compressive deformation starting there. Will approach the rounded concave portion 14. 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 14 are different from those of the standard rim 12.
When such a condition occurs once, the air trapped in the gap causes the bead portion 21 to move further along the inclined bead sheet 13 to prevent the air from being moved. Since the rim assembly operation is censored because it is restrained by the increase in pressure, the pneumatic tire itself is vulcanized and formed with sufficient uniformity.
The RO increased, and as a result, the RFV increased.

On the other hand, according to the tire-rim assembly in which the bulge heel 11 is provided on the tire, when the rim as described above is advanced, first, the bulge heel 11 As shown in FIG. 2, the rim assembling operation is completed in a state where the outer surface of the bead portion comes into contact with the curved flange 16 under the compressive deformation of the bulging heel 11 and a moderate pressure is applied thereto. Therefore, the above-described gap does not occur between the outer surface of the bead portion and the standard rim 12, and the center axis of the tire is easily aligned with the center axis of the standard rim 12 with high accuracy. Therefore, the RRO as a tire wheel is reduced, and the RFV is sufficiently suppressed.

Thus, in this tire-rim assembly,
In particular, according to the bead portion structure, based on such an improvement in the wheel uniformity, as described above, the forces generated by the tire wheels are made substantially uniform at any position in the circumferential direction, and the substantial cornering power is obtained. Can result in a significant increase.

In this assembly, the bulging amount d of the bulging heel 11 is set to 2 to 4 mm in a normal passenger car tire to improve wheel uniformity while preventing rim rubbing on the outer surface of the bead portion. The rubber hardness of the bulging heel 11 is 65 to 80 in JIS hardness.
It is preferable to set the degree to improve the wheel uniformity while sufficiently securing the airtightness between the bulging heel and the rounded concave portion.

In addition, here, the elongation at break of the toe tip rubber 17 is set to 420 ± 50% and the 300% modulus is set to 200 ± 20 kgf / cm ² , thereby preventing the bead portion from falling down and maneuvering. The 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 beet toe. On the other hand, when the value exceeds 470%, the bead portion is effectively prevented from falling down. it can not, in these things, the 300% modulus, which is also similar in each case was a and 180 kgf / cm less than ² when the value exceeding 220 kgf / cm ^2.

By the way, 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. By appropriately increasing the hardness of the bulging heel 11, it is possible to provide better positioning accuracy.

Therefore, according to the tire-rim assembly, in particular, the annular groove 9 formed in the central area of the tread portion and having a width of 10 to 40% of the tread contact width W provides a wet performance and a dry road surface. While the steering stability of the tire can be compatible with a high dimension, the lack of cornering power due to the presence of the annular groove 9 can be sufficiently compensated for by improving the uniformity of the tire wheels.

[Comparative Example] A comparative test on the wheel uniformity, wet performance and cornering power of the tire-rim assembly according to the present invention and the comparative assembly will be described below. ◎ Test assembly A tire having a size of 225 / 50R16 was used, and this was assembled to a 16 × 8JJ standard rim, and the filling internal pressure was set to 2.
It was 5 kgf / cm ² .

Inventive assembly 1 In addition to the parts described with reference to FIG. 1, as shown in FIG. 4 (a), a tire in which side reinforcing layers are further disposed so as to overlap the respective side end portions of the belt reinforcing layer. Was used. Here,
The width of the annular groove is set to 25% of the tread width, the depth is set to 14 mm, the volume of all circumferential grooves including the annular groove is 1160 cc over the entire circumference, the negative ratio is 30%, and the bulging heel is provided. The swelling amount was 2.5 mm, and the JIS hardness thereof was 70. Inventive assembly 2 Under the condition where each of the radial carcass, the belt, the belt reinforcing layer, and the tread portion is molded into a substantially cylindrical shape as shown in FIG. A tire having the same configuration as that of the preceding tire was used except that the thickness was set to 8.5 mm. Here, the width of the annular groove is set to 25% of the tread width, and the volume over the entire circumference of all the circumferential grooves including the annular groove is set to 72%.
0 cc and a negative rate of 30%.

Comparative Example 1 As shown in FIG. 4 (c), a tire having the same configuration as that shown in FIG. 4 (a) was used, except that the bulging heel was omitted. ○ Comparative assembly 2 As shown in FIG. 4 (d), radial carcass, belt,
A conventional general tire in which each of the belt reinforcing layer and the tread portion was molded into a substantially cylindrical shape and four linear circumferential grooves were formed instead of the annular grooves having a large width and depth. Here, the negative rate was 35%, and the groove volume of all the linear circumferential grooves was 500 cc.

Test method The wheel uniformity was determined by measuring each of RRO and RFV. The wet performance was determined by hydroplaning using a rear-wheel drive vehicle with a vehicle weight of 1.5 ton at a water depth of 3 mm. The vehicle speed at which the phenomenon occurs is detected and evaluated by index, and the cornering power is calculated as F /
It was determined by measuring with a B machine at a load of 450 kg.

Test Results Table 1 shows the results of the above tests. The larger the index value in the table, the better the result.

[Table 1] According to Table 1, in the tire-rim assembly according to the invention, the cornering power at the time of a small steering angle, while ensuring sufficient wet performance, in particular, anti-hydroplaning performance,
It is clear that this can be significantly increased for the comparison assembly 1 and even more so for the comparison assembly 2.

[0033]

Thus, according to the present invention, it is possible to achieve both wet performance and steering stability at a high level under the action of the annular groove of the tire. The resulting decrease in cornering power at a small steering angle can be more than compensated for based on the improvement of the wheel uniformity due to the improvement of the bead portion.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view in the width direction showing an embodiment of the present invention for a pneumatic radial tire of a tire-rim assembly.

FIG. 2 is a sectional view of a main part showing a rim assembling mode of the tire shown in FIG.

FIG. 3 is a view showing a rim assembling mode of a conventional tire.

FIG. 4 is a schematic cross-sectional view in the width direction showing a tire of a test assembly.

[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 Constricted part 9 Annular groove 10 Circumferential groove 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 Q Bead base point D Rim diameter d Swelling amount

Claims (2)

(57) [Claims] A radial portion comprising at least one carcass ply, comprising a tread portion, a pair of sidewall portions connected to the tread portion, and a bead portion connected to a radially inner end of each sidewall portion. A carcass and a belt comprising at least two belt layers , and a tread contact width of 10 to 4
The assembly of the pneumatic radial tire and rim ing with an annular groove having a 0% width, the bead portion which is closely fitted to the inclined bead seat of the standard rim, the standard rim, Prior to the contact between the curved outermost flange located in the width direction and the outer surface of the bead portion facing the curved flange, a bulging heel is provided which is in close contact with the rounded concave portion adjacent to the widthwise outer side of the inclined bead sheet over its entire circumference, A tire-rim assembly wherein the bulging heel has a bulging amount of 2 mm or more and the rubber hardness of the bulging heel is 65 degrees or more in JIS hardness. 2. The tire-rim assembly according to claim 1, wherein a constricted portion is formed in each of the radial carcass, the belt, and the tread portion at a portion corresponding to the annular groove of the pneumatic radial tire .