JP2003335111A - Radial tire for heavy load - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To eliminate a feeling of anxiety about low inner pressure, over- loading and the like by reducing apparent flexing of a sidewall part. <P>SOLUTION: An ornamental rib 10 extended in the tire circumferential direction, is mounted on a sidewall upper area 3U having a reference curve composed of an upper circular reference curve KU of an inner bulge extended from a tread end Pt, and a lower circular reference curve KL of an outer bulge intersecting with the upper circular reference curve KU at an inflection point Pa. The ornamental rib 10 is surrounded by an outer bilge line RA extended from an upper point Pb projecting from the inflection point Pa to the tire axial outward direction, to a lower point Pc in the radial inward direction in parallel with the lower circular reference curve KL, an upper connection line RB for connecting the upper point Pb and the upper circular reference curve KU, and a lower connection line RC connecting the lower point Pc and the lower circular reference curve KL. An inclination angle α of a straight line passing through the upper point Pb and the lower point Pc to the tire axial direction is 60-80°, and a radial distance Lbc between the upper point Pb and the lower point Pc is 0.15-0.40 times of a radial distance LO between the tire maximum width point Pm and the tread end Pt. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heavy-duty radial tire having a side wall portion provided with decorative ribs having a predetermined shape so as to reduce the slack of the sidewall portion.

[0002]

2. Description of the Related Art For example, in a radial tire for heavy loads such as trucks and buses, generally, as shown in FIG.
To the maximum width point Pm of the tire from the side wall area Y
u is a reference consisting of an upper arc reference curve KU of an inner bulge extending from the tread end Pt and a lower arc reference curve KL of an outer bulge that passes through the tire maximum width point and intersects the upper arc reference curve KU at an inflection point Pa. It is often formed along the curve K.

[0003]

However, in a tire having such a reference curve K, since the degree of outward bulging of the lower arc reference curve KL is exaggerated by the upper arc reference curve KU, the sidewall under a load is applied. The amount of deflection of the part feels larger than it actually is. As a result, for the driver,
The tire tends to give a false sense of anxiety such as a low internal pressure state or an overloaded state, which reduces reliability in tire performance and hinders the driver from performing an appropriate driving operation. Further, the tire tends to be used with an excessive internal pressure, which causes a problem that the original performance of the tire such as steering stability is not sufficiently exhibited.

In view of the above, the present invention is based on the fact that a decorative rib having a predetermined shape is provided in the region on the side wall, so that the slack feeling of the side wall can be reduced and the anxiety about low internal pressure and overloading can be eliminated. The purpose of the present invention is to provide a radial tire for heavy load that can ensure proper reliability of tire performance, allow the driver to perform appropriate driving operation, and can suppress the tire from being used with excessive internal pressure. There is.

[0005]

In order to achieve the above object, the invention according to claim 1 of the present application is such that, in a tire meridional section in a state in which a regular rim is assembled into a rim and a regular internal pressure is filled, the tire maximum from the tread end. The reference curve of the region on the sidewall reaching the width point is defined as an upper arc reference curve KU extending inward from the tread end and having a center outside the tire and an upper arc reference curve KU passing through the tire maximum width point. A radial tire for heavy load formed by a lower arc reference curve KL of an outer bulge that intersects at an inflection point Pa, the upper point Pb projecting outward in the tire axial direction from the inflection point Pa in the sidewall upper region. To a lower point Pc inward in the radial direction, an outer bulge line RA extending in parallel with the lower arc reference curve KL, an upper joint line RB connecting the upper point Pb and the upper arc reference curve KU, and the lower portion. Surrounded by the lower joint line RC splicing the Pc and lower arc reference curve KL and provided with a decorative rib extending in the tire circumferential direction, the upper point of the ornament rib P
The inclination angle α of the straight line passing through b and the lower point Pc in the tire axial direction with respect to the tire axial direction is 60 to 80 °, and the radial distance Lbc between the upper point Pb and the lower point Pc is
It is characterized in that the distance L0 in the radial direction between the tire maximum width point and the tread edge is 0.15 to 0.40 times.

According to the invention of claim 2, the upper point Pb is
It is characterized in that it is located on the tire axial direction line passing through the inflection point Pa, and the lower circular arc reference curve KL is an arc curve centered on the tire axial direction line passing through the tire maximum width point.

Further, in the invention of claim 3, the upper connection line RB is provided.
Is an arc curve of an inner bulge having a radius of curvature rb which is in contact with the upper arc reference curve KU and has a center outside the tire, and a lower joint line RC is in contact with the lower arc reference curve KL and outwardly of the tire. Has a center and a radius of curvature rc
Is formed by an arc curve of inward bulge having a radius of curvature smaller than the radius of curvature rb.

In the invention of claim 4, the distance Lab between the inflection point Pa and the upper point Pb in the tire axial direction is the radial distance L0 between the tire maximum width point and the tread end. It is characterized by being 0.02 to 0.12 times.

In this specification, the "regular rim" is used.
Is a rim defined by the standard in the standard system including the standard on which the tire is based. For example, the standard rim for JATMA, "Design Rim" for TRA, or "Measuring Rim" for ETRTO. means.
Further, the "regular internal pressure" is the air pressure that the standard defines for each tire, and if it is JATMA, the maximum air pressure,
If it's TRA, the table "TIRE LOAD LIMITS AT VARIOUS COLD
The maximum value described in "INFLATION PRESSURES" is "INFLATION PRESSURE" for ETRTO.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below.
This will be described together with the illustrated example. FIG. 1 is a tire meridian cross-sectional view of a heavy-load radial tire of the present invention in a state in which a rim is assembled to a regular rim and filled with regular internal pressure (may be referred to as regular internal pressure state), and FIG. 2 is a main part thereof. FIG.

In FIG. 1, a heavy duty radial tire 1
Is a carcass 6 extending from the tread portion 2 through the sidewall portion 3 to the bead core 5 of the bead portion 4, and the tread portion 2
Belt layer 7 disposed inside the carcass and outside the carcass 6
And with.

The carcass 6 is formed by one or more carcass plies 6A in which carcass cords are arranged at an angle of 70 to 90 degrees with respect to the tire circumferential direction, and in this example, one carcass ply 6A. The carcass ply 6A has the bead cores 5, 5
The bead cores 5 are provided on both sides of the ply body 6a extending in between.
Folding part 6b that is locked by folding back around the inside from the inside
Have. A bead apex rubber 8 extending radially outward from the bead core 5 is arranged between the ply body 6a and the folded-back portion 6b to reinforce the bead portion 4 to the sidewall portion 3.

The belt layer 7 is composed of three or more belt plies. In this example, the belt cords such as steel cords are arranged at an angle of, for example, 60 ± 15 ° with respect to the tire circumferential direction. The case where the first belt ply 7A and the second to fourth belt plies 7B, 7C, and 7D arranged at a small angle of 10 to 35 ° with respect to the tire circumferential direction have a four-sheet structure is illustrated. The belt layer 7 is provided with one or more places where the belt cords cross each other between the plies to enhance the belt rigidity, and the tread portion 2 is
The entire width is reinforced with a hoop effect.

Further, in the tire 1 of the present embodiment, in the tire meridional section under the normal internal pressure state, the sidewall upper region 3U from the tread end Pt to the tire maximum width point Pm is formed.
Has an upper arc reference curve KU that extends from the tread end Pt and has an inner bulge centered outside the tire.
The upper arc reference curve KU passing through the maximum tire width point Pm
Is formed along a reference curve K consisting of a lower arc reference curve KL of an outer bulge intersecting at the inflection point Pa.

The lower arc reference curve KL in this embodiment is an arc curve having its center on the tire axial direction line passing through the tire maximum width point Pm, and its radius of curvature r1 is equal to the maximum tire width point Pm and tread. It is larger than the radial distance L0 from the end Pt, and in this example, the radius of curvature r
1 illustrates the case where 1 is 1.1 to 1.2 times the distance L0. The radius of curvature r2 of the upper arc reference curve KU is larger than the radius of curvature r1 and preferably 1.5 times or more the radius of curvature r1.

In order to suppress the deterioration of the feeling of flexure in the sidewall portion, which is noticeable in the tire having the reference curve K as described above, in the present invention, the above-mentioned reference curve K is provided in the upper sidewall region 3U. A predetermined decorative rib 10 is formed which protrudes and extends continuously in the tire circumferential direction.

As shown in the enlarged view of FIG. 2, the decorative rib 10 has a lower circular arc reference from an upper point Pb protruding outward from the inflection point Pa to a lower point Pc radially inward of the tire. An outer bulge line RA extending in parallel with the curve KL (that is, forming a concentric circle with the lower arc reference curve KL), an upper joint line RB connecting the upper point Pb and the upper arc reference curve KU, and the lower point Pc and the lower arc. It is surrounded by a lower joint line RC that joins the reference curve KL. At this time, the upper point Pb is the inflection point P.
It is located on the tire axial line passing through a.

Here, what is important in the decorative rib 10 is that the inclination angle α of the straight line passing through the upper point Pb and the lower point Pc in the tire axial direction with respect to the tire axial direction is 60 to
80 °; and the radial distance L between the upper point Pb and the lower point Pc.
It is to set bc in the range of 0.15 to 0.40 times the distance L0.

Since the decoration rib 10 thus constructed covers the inflection point Pa, the degree of outward expansion of the lower arc reference curve KL is prevented from being exaggerated by the upper arc reference curve KU; Since the exposed area of the lower circular arc reference curve KL is limited from the decorative rib 10 to the tire maximum width point Pm,
The outer bulge amount of the lower arc reference curve KU is reduced and shown; ・ Since the inclination angle α is as large as 60 to 80 °, the outer bulge line RA is shown upright; and the like. It is possible to reduce the feeling of flexure in the sidewall portion 3, and it is possible to prevent the driver from having an erroneous sense of anxiety that the tire is in a low internal pressure state or in an overloaded state. As a result, the driver is relieved of such anxiety,
It is possible to perform an appropriate driving operation and prevent the tire from being used in an excessive internal pressure state.

When the inclination angle α is less than 60 ° and the distance Lbc is less than 0.15 × L0, the effect of reducing the sense of flexure cannot be sufficiently exerted, and the inclination angle α is less than 80 °. If it exceeds, the shape of the decorative rib 10 becomes distorted, and the appearance of the tire is impaired. If the distance Lbc exceeds 0.40 × L0, unnecessary increase in tire weight and material cost will be caused. From this perspective,
The inclination angle α is preferably 65 to 75 °, and the distance Lbc is preferably 0.2 to 0.3 times the distance L0.

Further, in order to reduce the feeling of flexure, the inflection point P
It is also preferable to set the distance Lab between the a and the upper point Pb in the tire axial direction within the range of 0.02 to 0.12 times the distance L0. If the distance is less than 0.02 times, the decorative rib 10 is too low. As a result, the effect of reducing the slackness becomes insufficient. Conversely, 0.12
If it exceeds twice, the rubber volume becomes too large, resulting in an unnecessary increase in tire weight and material cost, and an increase in heat storage amount, which adversely affects tire durability.

Further, in such a decorative rib 10, when the tire is loaded, the intersection between the upper joint line RB and the upper arc reference curve KU, and the lower joint line RC and the lower arc reference curve K.
Stress concentrates at the intersection with L, and crack damage such as cracks tends to occur. Therefore, in this example,
The upper joint line RB is in contact with the upper arc reference curve KU and has an inner bulging arc curve centered outside the tire, and the lower joint line RC is in contact with the lower arc reference curve KL and is centered outward of the tire. Is formed by an arc curve of an inner bulge having
The crack damage is suppressed. At this time, it is preferable to make the radius of curvature rb of the upper joint line RB larger than the radius of curvature rc of the lower joint line RC in order to reduce the feeling of flexure.

Although a particularly preferred embodiment of the present invention has been described above in detail, the present invention is not limited to the illustrated embodiment and can be modified in various modes.

[0024]

EXAMPLE Tire size 11R22.T having the structure of FIG.
A heavy load radial tire of No. 5 was prototyped based on the specifications of Table 1, and the bending feeling in the sidewall portion of each test tire was tested, and the results are shown in Table 1.

(1) Deflection: The sample tire was subjected to a load (24.52 kN) under the conditions of a rim (7.50 × 22.5) and an internal pressure (700 kPa), and the deflection of the tire at that time was Sensory evaluation was conducted by visual inspection by 10 examiners using a 10-point method with the conventional example being 5 points, and the average points were compared. The larger the score, the less the feeling of deflection and the better.

[0026]

[Table 1]

[0027]

As described above, according to the present invention, since the decorative ribs having a predetermined shape are provided in the region on the side wall, the side wall portion is less likely to sag, and the low internal pressure, overloading, etc. It is possible to ensure proper reliability in tire performance, to allow the driver to perform an appropriate driving operation, and to prevent the tire from being used with excessive internal pressure.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a heavy duty radial tire of the present invention.

FIG. 2 is a cross-sectional view showing an enlarged main part thereof.

FIG. 3 is a cross-sectional view showing a conventional tire.

[Explanation of symbols]

3U Sidewall area 10 decorative ribs K reference curve Pt tread edge Pm tire maximum width point

Claims (4)

[Claims] 1. In a tire meridional section in a state in which a regular rim is assembled into a rim and filled with a regular internal pressure, a reference curve of a region on a sidewall extending from a tread edge to a tire maximum width point extends from the tread edge. For a heavy load formed by an upper arc reference curve KU having an inner bulge having an outward center and a lower arc reference curve KL having an outer bulge passing through the tire maximum width point and intersecting the upper arc reference curve KU at an inflection point Pa. A radial tire, which extends in the upper region of the sidewall in parallel with the lower arc reference curve KL from an upper point Pb protruding outward from the inflection point Pa to a lower point Pc radially inward. It is surrounded by an outer bulge line RA, an upper joint line RB joining the upper point Pb and the upper arc reference curve KU, and a lower joint line RC joining the lower point Pc and the lower arc reference curve KL, and A decorative rib extending in the tire circumferential direction is provided, and a straight line passing through the upper point Pb and the lower point Pc of the decorative rib has an inclination angle α on the tire axial direction inner side with respect to the tire axial direction of 60 to 80 °, and Radial distance L between the point Pb and the lower point Pc
The radial tire for heavy loads, wherein bc is set to 0.15 to 0.40 times the radial distance L0 between the tire maximum width point and the tread edge. 2. The upper point Pb is located on the tire axial direction line passing through the inflection point Pa, and the lower arc reference curve KL.
The radial tire for heavy load according to claim 1, wherein the radial tire for heavy load comprises an arc curve having a center on an axial line of the tire passing through the maximum width point of the tire. 3. The upper joint line RB is in contact with the upper arc reference curve KU and has a radius of curvature rb centered outside the tire.
Is composed of an arc curve of the inner bulge, and the lower joint line RC is
The heavy load according to claim 1 or 2, which is in contact with the lower circular arc reference curve KL, has a center on the outside of the tire, and has an inwardly swelling circular arc whose curvature radius rc is smaller than the curvature radius rb. Heavy duty radial tire. 4. The tire axial distance Lab between the inflection point Pa and the upper point Pb is 0.02 to 0 of the radial distance L0 between the tire maximum width point and the tread end. .1
It is twice, The radial tire for heavy loads in any one of Claims 1-3 characterized by the above-mentioned.