JP3213068B2 - Pneumatic tires that excel in 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 an improvement in uniformity, particularly in radial force variation, in an assembly of a pneumatic tire and a rim of a radial tire.

[0002]

2. Description of the Related Art As research on the riding comfort and noise of automobiles, especially passenger cars, has progressed, the importance of uniformity of pneumatic tires mounted thereon has become increasingly important. Here, to say that the tire is uniform means not only that it is a perfect circle on the shape, but also that the deflection against the same load is equal everywhere on the circumference, or that the tire rotates under a constant deflection. The force is required to be uniform. Uniformity in this sense is referred to as tire uniformity.

[0003] Among the uniformity evaluation measures, the runout of the outer periphery of the tire and the rim is called a radial runout (hereinafter abbreviated as RRO). When these radial runouts are large, the diameter at the time of rotation under a constant deflection is measured. It is known that uniformity is degraded due to an increase in directional reaction force variation, that is, radial force variation (hereinafter abbreviated as RFV). So this RF
By combining the primary peak position of the RFV of the conventional tire and the valley position of the primary component of the RRO at the bead seat of the rim so as to lower the V, the RFV as an assembly of the tire and the rim is improved. It has been. However, even in this case, there is a disadvantage that the peak-to-peak value of the tire is increased in some cases.

Therefore, as a countermeasure, Japanese Unexamined Patent Publication No. Hei 3-189201 discloses a tape-like rubber sheet between the rear surface of the bead and the rim flange corresponding to a large RRO in the shoulder portion of the pneumatic tire. Is interposed.

[0005] However, there is a disadvantage that the mounting state of the tire and the rim changes due to the application of a large external force during traveling, and correction is required again. For this reason, the rims, for which the machining accuracy has been sufficiently improved, are equipped with RROs as tires themselves.
When a good pneumatic tire was attached and its behavior was fundamentally investigated, even at this time, the RRO as the tire wheel may not be reduced. In Japanese Patent Application No.
In the specification of Japanese Patent No. 052610, an improvement of a bead of a tire that can be easily led concentrically when assembling a pneumatic tire to a rim has already been proposed.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to improve the RRO of a tire wheel due to eccentric mounting of the tire, to further improve the wheel uniformity, and to more effectively control the RFV of the tire wheel. It is assumed that.

[0007]

SUMMARY OF THE INVENTION A standard rim having a slanted beat sheet, a rounded concave fillet adjacent to the slanted beat sheet, or a rounded concave fillet, a projecting flange, and an outwardly curved curved flange. A bead portion to be tightly fitted to the inclined bead sheet,
The bead portion has a bulging heel that provides a tight bond around the entire periphery of the rim's rounded concave fillet prior to any contact between the rim flange and the facing bead outer surface; In a pneumatic tire that is assembled to the rim to form a wheel, the swelling heel portion has a JISA
A pneumatic tire having a soft rubber layer having a hardness of 60 ° or less and excelling in wheel uniformity, wherein the soft rubber layer preferably comprises a foam rubber.

In FIG. 1 (a), a pneumatic tire (two-dot chain line) having a bulging heel portion and a bead portion, which was previously proposed, is mounted on a rim (one-dot chain line), and then used at an internal pressure. Figure (b) shows the mounting condition (solid line) in which the bead fits the rim by filling in the section including the rotation axis of the tire / rim assembling wheel. The cross section is shown.

In the drawing, 1 is a bead portion, 2 is a bead core, 3 is a back surface of the bead portion, and 4 is a bulging heel portion.
In overall standard rim, the inclination bead seat in R _0, also showed rim flange respectively R _1, standard rim R
A rounded concave fillet and a curved flange curved outwardly or a rounded concave fillet and a protruding flange and an outwardly curved curved flange, which are successively arranged adjacent to the inclined bead sheet _R0 according to a custom. has, overhanging flange which may be interposed curved flange or these questions directly adjacent to Sumimaru凹fillets are both none other than the rim flange R ₁ on shown.

The inclined bead sheet R ₀ shown in FIG.
A straight line 1 extending the generatrix (consisting of conical surfaces) and a tangent m to the rim flange R ₁ orthogonal to the axis of the standard rim R
Is a fixed point that gives the nominal diameter D of the standard rim R, and the point Q shifted on the sectional view of the bead portion 1 in FIG. That is, the protrusion allowance α of the bulging heel portion 4 is defined by the vertical distance from the plane n perpendicular to the rotation axis of the tire including the point Q to the top surface of the bulging heel portion 4. Q is that the bead portion 1 is tightly fitted to the inclined bead sheet R ₀ by filling the internal pressure after the rim is assembled, so that the swelling heel portion 4 is strong against the rounded concave fillet of the standard rim R while approaching the intersection P endlessly. It is pressed into contact and a tight sealing joint is achieved.

[0011]

On the other hand, in the conventional assembly of the pneumatic tire and the rim, the fit between the bead portion 1 and the rim R when the internal pressure for use is filled is as shown in FIG. That is, backlash S occurs between the bead portions back 3 and the rim flange R ₁ inner surface, which tend divided into a wide part and a narrow part along the rim circumference, moreover in each bead portion 1 of the left and right The size of the back space S generated between the bead portion back surface 3 and the inner surface of the rim flange tends to be different from each other.

The reason why such a phenomenon occurs is that when the tire is mounted on the rim R, the tire is easily assembled such that the rotation axis of the tire does not coincide with the rotation axis of the rim. Thus, the above-mentioned uneven back gap S is one factor that generates RFV when the tire / rim assembly rotates.

In the invention of Japanese Patent Application No. 04-052610, when the rim is assembled to the conventional rim by the conventional rim assembling method, the back gap S caused by the rotation axis of the tire and the rim being inconsistent is determined. in narrow portion of, first pressed against the rim flange R ₁ by first filling the pressure bulging heel 4 is applied to the inner surface of the bead portion 1, whereby as correction of mismatch of the tire-rim rotation axis can be achieved The direction of the axis is changed, and the bead back 3 is a rim flange R
₁ over the entire circumference, and each left and right flange R ₁
We expect that both will come into contact evenly.

However, the above-mentioned uniform contact at the bulging heel portion 4 is affected by the interference of the fitting of the bead portion 1 with the inclined bead sheet R ₀ . When a contact occurs in a local area of the entire circumference of the area, the local contact may be particular and the proper fit may be hindered. This point is because the soft rubber layer is provided in the bulging heel portion 4 so that the soft rubber layer is deformed in the local contact area, and the inclined bead sheet R _{0 is formed.}
A proper fit under a strong interference of the bead part 1 can be achieved more easily. Here, the swelling heel portion 4 may be entirely made of soft rubber, and in this case, the soft rubber is preferably 60 ° (JISA) or less from the viewpoint of flexibility.

The bulged heel portion 4 may have a fixed composite ratio (1: 1) with the soft rubber layer 4-2 covered by the non-foamed rubber layer 4-1 as shown in a more preferred embodiment. Desirably, if the soft rubber layer 4-2 has a certain strength, the case where it is exposed from the cover and directly appears on the outer layer is not excluded.

The soft rubber layer 4-2 naturally includes foamed rubber and the like, and in this case, the foaming ratio is preferably in the range of 5 to 70%. It is preferable that the volume ratio occupying the inside of the bulging heel portion 4 is 50% or less. The foamed rubber preferably has closed cells as compared with open cells from the viewpoint of breaking strength.

The rubber composition of the foamed rubber layer 4-2 is, for example, 60 parts by weight of natural rubber, 40 parts by weight of polyethylene rubber, 70 parts by weight of carbon black, 30 parts by weight of process oil, 1.0 part by weight of wax, and 2.0 parts by weight of stearic acid. , Anti-aging agent
A composition of 1.5 parts by weight, 3.0 parts by weight of zinc white, 1.5 parts by weight of a vulcanizing agent, 1.5 parts by weight of sulfur, and 4.0% by weight of dinitrone / pentamethylene / tetraamine as a foaming agent is suitable.

The protrusion α of the bulging heel 4 is approximately 2.0 to
If it is 4.0 mm, it is not effective if it is less than 2.0 mm, and if it exceeds 4.0 mm, the required interference of the bead portion 1 with respect to the inclined bead portion _R0 may be too small.

[0019]

EXAMPLE For a test tire having a tire size of 175.times.65 R14, a foamed rubber layer having a foaming ratio of 40% occupying 50% of the volume of the bulging heel portion 4 by the non-foamed rubber layer 4-1 as shown in FIG. The tire according to the present invention, in which the protrusion margin of the bulging heel portion 4 is set to 3 mm so as to cover around 4-1,
Prepared with conventional tire shown in FIG. 2, was subjected to uni-follower Mi Teema Thin for these tires, tire radial runout 30 of the present invention the performance of the conventional tire by an index display to 100, 50 of the radial force burr mer Deployment Good results were obtained.

Here, the bead core 2 is formed by spirally winding a single rubber-coated wire a plurality of times around the circumference so that the cross-sectional profile becomes a quadrilateral or a hexagon. It is preferable that the number of parts is small and the rigidity on the periphery is also improved. Further, a cable bead having a round cross section and twisted with a wire, which is also referred to as a cable bead, is preferable from the viewpoint of uniformity on the periphery.

[0021]

According to the present invention, a bulging heel portion of a bead portion can be formed by using a normal rim which does not change the contour shape of the rim, without having to pay special attention to the rim assembling operation. The bead portion is more effectively guided to sit on the rim by the soft rubber employed in the above, and the RRO of the tire wheel assembled with the rim can be reduced, so that the RFV can be more effectively suppressed.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional view of a bead portion of a pneumatic tire having an inflated heel portion.

FIG. 2 is a partial sectional view of a bead portion of a conventional tire.

FIG. 3 is a partial sectional view of a bead portion according to the present invention.

[Explanation of symbols]

 1 bead part 2 bead core 3 bead part back 4 bulging heel part

Claims (2)

(57) [Claims] 1. A standard rim having an inclined bead sheet and a successively adjacent hollow circle fillet or a hollow round concave fillet, a projecting flange, and a curved flange curved outwardly, The bead portion has a bead portion which is tightly fitted to the inclined bead sheet, and the bead portion is formed on the rounded concave fillet of the rim before the contact between the rim flange and the outer surface of the bead portion facing the rim flange. In a pneumatic tire having a bulged heel portion for tightly joining the entire circumference and being assembled to the rim to form a wheel, the bulged heel portion has a JISA hardness of 60.
A pneumatic tire that excels in wheel uniformity, characterized by having a soft rubber layer of less than or equal to °. 2. The pneumatic tire according to claim 1, wherein the soft rubber layer contains foamed rubber.