JP2816143B2 - Pneumatic radial tire with excellent bead durability - 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, and more particularly to a heavy duty tire for trucks and buses, and more particularly to a pneumatic radial tire having excellent bead portion durability.

[0002]

2. Description of the Related Art The durability of a bead portion of a pneumatic radial tire is particularly strongly required of heavy duty pneumatic radial tires used for trucks, buses, and the like among such tires. This is because not only are the operating conditions severe, but also every time the tread rubber wears out, it is necessary to complete its life cycle as a base tire for recapping (rehabilitation).

[0003] The bead failure of this type of tire, which is detected by a pass / fail inspection as a base tire, is mainly caused by a large tensile strain in the vicinity of the winding end of the carcass ply, particularly in the radially outer side of the tire. There are many things that have led to rubber fatigue and eventually separation.

[0004] In order to improve the durability of the bead portion, the above-mentioned strain is alleviated, and the addition of a reinforcing material or a special member for suppressing the extension of a crack due to rubber fatigue has been taken as an example. Is detrimental to productivity and has disadvantages such as increased costs and heat generation.

[0005]

Generally, as described above, a heavy-duty pneumatic radial tire used for trucks and buses has a pair of beads and a pair of sidewalls, and a tread portion extending between the sidewalls. And a carcass comprising one or more plies of radially arranged cord plies reinforcing each of these parts between bead cores embedded in the bead parts, wherein the carcass is wound around at least one ply from the inside of the tire to the outside around the bead core. The basic structure is a turn-up structure, and the end of such a carcass has an effect on the durability of the bead, and the conventional measures taken directly therefor are, so to speak, paste-like. Poorly effective.

Accordingly, the inventions described in claims 1 to 8 of the present invention are intended for use in heavy vehicles, that is, for improving the durability of a bead portion so as to be adaptable as a base tire for renewing a wear life over and over by recapping. It is an object of the present invention to provide a pneumatic radial tire having excellent bead portion durability, which can be advantageously realized without using a special reinforcing material or a special member.

Here, the winding end of the carcass ply, which governs the durability of the bead portion, receives a force in the pulling-out direction due to the internal pressure of the tire acting on the carcass and also exerts a bending force from the sidewall portion of the tire to the bead portion. A large tensile strain acts on the rubber facing the winding end, which causes a failure of the bead portion. Therefore, a compressive stress for reducing the tensile strain is introduced into the rubber. Thus, the above-mentioned object is achieved from the viewpoint of reducing tensile strain, and thus, in fact, tensile stress remains.)

[0008]

That is, the invention described in claim 1 of the present invention comprises a pair of bead portions, a pair of sidewall portions, and a tread portion extending between both sidewall portions. A pneumatic radial tire having a carcass comprising a radially arranged cord ply reinforcing between bead cores embedded in a bead portion, wherein the carcass has a turn-up structure in which at least one ply is wound around the bead core from the inside to the outside of the tire. The ply measured from the rim diameter line RL on the carcass path line in the radial section of the tire in which the tire mounted on the rim is filled with a slight pressure of 5% of the standard internal pressure and the rim assembly in the unloaded state. On the inner side of the carcass near the height position corresponding to the height h of the winding end A wedge rubber having a convex lens-like cross-sectional shape is provided, and the arrangement of the wedge rubber causes the carcass path line in the cross-section of the tire in the assembly under the micro-pressure filling to be locally convex toward the ply winding end. Has a curvature change area v which detours to
Is formed by forming a local concave portion with respect to the carcass pass line of the adjacent region on both sides sandwiching it, as viewed from the tire inner surface, and under the standard internal pressure filling for the tire and the rim assembly, the ply is bent by bending deformation concentrated on the curvature change region v. A pneumatic radial tire having excellent bead portion durability, having a carcass path line for generating a compressive stress in rubber near a winding end portion.

Here, the radial cross section of the tire is a cross section of a plane including the rotation axis of the tire, and the carcass path line refers to a curve connecting the thickness center of the carcass ply, and is also referred to as a carcass line for short. The rim diameter line RL is not a nominal rim diameter of the applicable rim of the tire, but a straight line parallel to the tire rotation axis passing through the actual rim diameter dimension position.

In carrying out the first aspect of the present invention, as in the second aspect of the present invention, the curvature change area v of the carcass path line has a curvature smaller than the curvature of the adjacent curvature change area v. An adjacent area w formed by a curve smoothly continues, and the curve of the adjacent area w has a center of curvature inside the tire, or as in the invention described in claim 3, the curvature change area v of the carcass path line is: It is practically effective that the bead core is located farther than the curvature change region v and smoothly continues through an inflection point to an adjacent region w 'formed by a curve having a center of curvature outside the tire.

Regarding the preferred position and length of the curvature change area v, as in the invention described in claim 4, the curvature change area v of the carcass pass line is set such that the carcass pass line is at the maximum from the rim diameter line RL. A vertical distance g corresponding to 8% of the height H is located in a pass line area which is separated from above and below the winding end height h, and a curvature change area v has a distance l of 10 mm or less along the pass line in the area. It is suitable to extend between two points M and N.

Further, it can be understood that there is a preferable relationship between the inclination angles of the tangents passing through the two points M and N, and therefore, a point on the carcass path line as in the fifth aspect of the present invention. The intersection angle θ between the tangent (m, m ') and the tangent (n, n') at each of M and point N is 5 to 90.
It is useful to set the carcass pass line to be within the range of °.

In order to achieve the object of the present invention, it is effective to set the curvature of the adjacent region w on the radially outer side of the tire in the adjacent region w described above as small as possible.
As in the invention described in claim 6, the adjacent area w located farther from the bead core among the adjacent areas w connected to the curvature change area v of the carcass pass line has 12 to 24 of the maximum height H of the carcass pass line. Vertical distance j ~
A region having a curvature within 1/500 (mm ^-1 ) is provided between a point k on the pass line separating i from the height h of the winding end of the carcass ply. It is assumed that it is 12% or more of the maximum height H of the pass line.

[0014] Further, it is advantageous to specify the optimum arrangement position also for the adjacent region w 'different from the above, and therefore, as in the invention described in claim 7, a position farther than the curvature change region v with respect to the bead core is provided. Adjacent area w 'is defined by a vertical distance i corresponding to 24% of the maximum height H of the carcass path line.
Two points P located in the pass line second section reaching a point on the pass line separating the carcass ply winding end height h from
Preferably, the adjacent area w 'located farther than the curvature change area v with respect to the bead core corresponds to 12% of the maximum height H of the carcass pass line. Is provided between two points P and Q located in the second section of the pass line reaching a point on the pass line separated from the carcass ply winding end height h.

According to the present invention, the carcass ply is formed not by the folded portion itself of the carcass ply but by the unique shape of the toroidal carcass profile of the carcass pass line extending from one bead portion to the other bead portion of the radial ply of the cord. Under the new idea of reducing the tensile strain generated in the rubber near the folded end, it is not necessary to add a reinforcing member or a special member used for the conventional reinforcing measures to avoid the failure of the bead portion.

In order to remove the habit of measuring the carcass shape due to horizontal stacking or the like, it is allowed to stand for about 24 hours after filling with the normal internal pressure, and more preferably, is run under a load of about 1 hour at a speed of about 60 km / h empty. Should be measured after

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIGS. 1 to 9 illustrate carcass profiles of a pneumatic radial tire according to the present invention in a state in which a tire mounted on a rim is applied with a slight pressure of 5% of a standard internal pressure and a rim assembly under no load. .

In each figure, 1 is a bead portion, 2 is a side wall portion, 3 is a tread portion, 4 is a carcass, 5 is an inner liner, 6 is a bead core, 7 is a belt, 8 is a rim, and 9 is a convex lens-shaped cross section. Represents a shaped wedge rubber. In each of the figures, the radial cross section of the tire is shown in the left half or the main part thereof. Here, the carcass 4 is schematically illustrated by a thick solid line, and illustration of general bead reinforcing members such as bead chafers and stiffeners is omitted. A part of the inner liner 5 was omitted in some cases.

The radially arranged plies of cords used in the carcass 4 are wound around the bead core 6 from the inside to the outside of the tire, and the height measured from the bead base at the end of the winding, here the rim diameter line RL, is h, and Carcass 4
The maximum height of the carcass 4 is represented by H, and the inner surface of the carcass 4 near the height position on the pass line of the carcass 4 corresponding to the height h of the winding end with reference to FIGS. The wedge rubber 9 is arranged on the side.

With the arrangement of the wedge rubber 9, in the example shown in FIGS. 1 and 5, the first pass which extends a vertical distance g corresponding to 8% of the maximum height H over the top and bottom of the winding end height h. In the line area, a curvature change area v of the carcass pass line is formed between two points M and N at a distance l within 10 mm along the pass line, where the carcass 4 at the points M and N is formed. The tangents MM ′ and n− of the pass line
It is desirable n 'is the angle difference between the rim diameter line RL and the angle theta _M and theta _N is 5 to 90 °.

The curvature change region v is shown in FIGS. 1 and 5 for a self-standing tire with no load applied (see the solid line in FIG. 5) in which the tire and the rim assembly are filled with a slight pressure of 5% of the standard internal pressure. As shown in FIG. 5, when the tire is filled with the standard internal pressure indicated by a broken line in FIG. 5, the tire is inflated based on the internal pressure. The deformation concentrates the bending deformation in the curvature change region v and deforms so that the pass line of the carcass 4 is smoothly continuous. As a result, a compressive stress occurs in the rubber in the bead portion 1 near the winding end of the ply. Reduce tensile strain.

This compressive stress reduces the tensile strain in a state where no load is applied under the internal pressure, so that the tensile strain at the ply winding end of the bead portion is effectively reduced during running of the tire, and the failure of the bead portion is appropriately performed. Is avoided.

FIG. 6 shows a vertical distance j, i corresponding to 12 to 24% of the maximum height H of the carcass pass line in an adjacent area w of the curvature change area v farther from the bead core 6 (FIG. 1).
(See FIG. 3) has a curvature within 1/500 (mm ^-1 ) from the height K of the carcass ply winding end to the point K on the pass line. It is smaller than the curvature of v and smoothly connects to the curvature change area v. Also in this example, compressive stress is generated in the beat portion 1 and tensile strain is reduced as in the case of FIGS.

Next, in FIGS. 7 to 9, the adjacent area w 'of the curvature change area v which is farther from the beat core 6 also has a vertical distance j corresponding to 12% of the maximum height H of the carcass path line (see FIG. 1). Has a center of curvature outside the tire between points P and Q located in the second section of the pass line extending from the winding end height h to a point separated from the winding end height h, and smoothly passes through the curvature change area V and the inflection point. It is apparent from FIG. 9 that compressive stress is generated in the vicinity of the ply winding end of the bead portion 1 to reduce tensile strain, similarly to the case of FIGS. 1 and 5.

By adopting the technique of providing the curvature change area v in the carcass pass line, it is not necessary to newly change the structure of the tire, the members of the beat portion, and the like.
Since the durability of the bead portion can be improved while the conventional member using the tire structure is kept as it is, the merit in terms of tire quality and productivity is great.

In order to obtain the above-mentioned unique carcass profile, the wedge rubber 9 having a convex lens-shaped cross section is required.
It is most reliable and effective to arrange the rubber gauge, but it is also possible to control the distribution of the rubber gauge from the inner wall of the mold to the carcass ply on the inner side in the tire rotation axis direction at the time of molding and vulcanizing the tire. The following method is effective as a means for suppressing fluctuations and variations of the carcass line due to so-called "rubber flow" during vulcanization as much as possible.

That is, in the tire according to the conventional molding and vulcanization technique, the carcass ply extending between the bead cores is formed along the inner surface of the tire.
An inner liner 5 having locally formed portions 5 ′ having different thicknesses as shown in FIG. 11 may be used, or a vulcanizing bladder may be continuously formed on the periphery of the bladder at a position corresponding to a curvature change area v of a carcass pass line. By providing the projected ridge, the above-mentioned curvature change region v can be obtained in the pass line of the carcass (see FIG. 10).

[0028] As a result, variations and variations in the production of the carcass pass line according to the present invention can be appropriately suppressed.

According to the present invention, the carcass floe file in the radial direction cross section of the tire in which the tire mounted on the rim is applied with a slight pressure of 5% of the standard internal pressure and the rim assembly in the unloaded state is a wedge. Due to the arrangement of the rubber 9, when viewed from the tire inner surface, the carcass path line has a curvature change region v that exhibits a local concave portion. The local recesses cause the carcass and the accompanying rubber to bend and deform intensively in the local recess when the tire is filled with the standard internal pressure, thereby generating a large compressive stress and facing the winding of the carcass 4. The tensile strain generated in the rubber of the bead portion 1 is reduced in a canceling manner, and therefore, the durability of the bead portion is improved.

Here, in order to concentrate the bending deformation, the carcass pass line must have a significantly larger curvature in the above-mentioned local concave portion than the other portions, and the length along the carcass must be less than 10 mm. There must be a portion where the difference between the tangent lines MM ′ and nn ′ of the carcass pass line at the two points M and N with respect to the rim diameter line RL is 5 degrees or more.

In order to reduce the tensile strain generated at the ply end due to the effect of the bending deformation of the tire concentrated on the local recess, the local recess and the ply end must be sufficiently close to each other. That is, as shown in FIG.
Height in the range of ± 8% of the maximum height H of the carcass line from the ply end height h measured from, that is, from hg to h + g
Must be present on the carcass path line at the height of.

By the way, even if the curvature of the above-mentioned local concave portion is sufficiently large as compared with other portions, if this is spread over a wide range, the concentration of bending deformation as expected when the tire is filled with the standard internal pressure is obtained. I can't.

Therefore, it is necessary that a portion having a small curvature exists on the side of the tire rotation axis and the side of the tire tread from the local concave portion. However, since a reinforcing member such as a stiffener or a chafer is arranged on the side of the tire rotation axis from the local concave portion arranged near the winding end of the carcass ply, the rigidity is large, and the carcass profile at this position is a tire by standard internal pressure filling. It is not greatly affected by the bending deformation of. Therefore, as shown in FIG. 1 and FIG. 5, the carcass pass line extends over a sufficient length of 12 to 24% of the maximum height H of the carcass line at a portion close to the local concave portion of the carcass line at the side of the tire tread surface. Radius of curvature of
It is desirable that the curvature should be sufficiently small at 500 mm or more.

Even if the carcass ply has a convex portion when viewed from the tire inner surface instead of the small radius of curvature described above, the bending deformation of the tire due to the standard internal pressure filling is similarly concentrated on the local concave portion. By reducing the distortion of the end portion of the carcass ply, the durability of the bead portion can be improved.

That is, as shown in FIGS. 7 to 9, the maximum height H of the carcass line is located outside the local recess in the tire radial direction and closer to the tire tread surface than the carcass ply end height h measured from the rim diameter line RL. 24% of the height, 8% of H on the side of the tire axis, preferably 12% of H on the side of the tread.
It is also effective that the carcass ply 4 forms a convex portion when viewed from the tire inner surface at a height in the range of 8% of H on the side of the tire rotation axis.

In order to obtain the above-described carcass pass line of the present invention while suppressing production fluctuations and variations due to "rubber flow" during vulcanization, as shown in FIGS. It is optimal to dispose the wedge rubber 9 closer to the local concave portion on the inner side in the axial direction and to make the inner wall of the tire smooth or convex as viewed from the inner side of the tire rotation axis.

For the same purpose, in the conventional method, it is also recommended that the thickness of the inner liner 5, which is almost uniform, is locally changed near the local recess as shown by reference numeral 5 'in FIG. In order to sufficiently suppress the fluctuation of the case line, the average thickness of the inner liner is 1.7 to 8 times, preferably 2 to 8 times.
It is even more desirable to have a double to quadruple thickness near the local recess.

[0038]

EXAMPLE 1 As shown in FIG. 2, an example of the present invention is shown in a lug pattern tire (size 10.00 R20) having two nylon chafers and one wire chafer. Maximum carcass line height H = 233 m
m, ply end height h = 66.5 mm, and two points M with a length of 7 mm, which are located at heights of 72 mm (h + 0.024H) and 65.5 mm (h-0.004H) on the carcass path line. The angle difference between the tangent line of the carcass pass line and the rim diameter line RL at N is 6.0 °, and the carcass pass line is adjacent to a portion of the carcass ply forming a recess when viewed from the tire inner surface and closer to the tire tread surface than this portion. Is substantially linear over a length of 30 mm (0.129H), while a wedge rubber 9 with a convex lens-shaped cross-section with a width of 20 mm and a maximum thickness of 2 mm is placed between the carcass ply and the adjacent nylon chafer And a bead durability test in a drum running test showed that the running distance was increased by about 16% compared to the conventional tire with a naturally balanced carcass profile.

Example 2 As shown in FIG. 3, in a rib pattern tire (size 10.00R20) also having two nylon chafers and one wire chafer, the maximum height H of the carcass line from the rim diameter line RL is H = 241. mm, ply end height h = 67mm
65.7 mm (h-0.005 mm) above the carcass path line
H) and 59.2 mm (h−0.032H), the difference between the angles of the tangents of the carcass pass lines to the tire rotation axis at the two points M and N extending 7.8 mm is 14 °. As viewed from the inner surface of the ply, it is close to the portion where the recess is formed and has a height of 90 mm (h + 0.
099H), a tire having a wedge rubber 9 having a convex lens-shaped cross section having a width of 20 mm and a maximum thickness of 2.7 mm on the inner side in the tire axial direction of the inner liner was formed while the carcass ply viewed from the inner surface of the tire. When the durability of the bead portion was tested in the drum running test, the running distance was increased by about 15% as compared with the conventional natural equilibrium tire.

Example 3 As shown in FIG. 10, a rib pattern tire having two nylon chafers and one wire chafer (size 10.0
0R20), the maximum height of the carcass line from the rim diameter line RL is H = 241 mm, the ply end height is h = 67 mm, and the height on the carcass pass line is 68.3 mm (h + 0.005H).
62.8mm (h-0.017H)
The difference in angle between the tangent line of the carcass path line and the rim diameter line r at the points M and N is 6 °, and the carcass ply is close to the portion forming the local recess when viewed from the tire inner surface, and is closer to the tire tread surface than this portion. 95mm in height (h + 0.11
A prototype tire with a carcass ply up to 6H) forming a convex part when viewed from the tire inner surface was tested and the bead durability was tested in a drum running test. Mileage increased by about 18%.

Example 4 As shown in FIG. 4, a block pattern tire having two nylon chafers and one wire chafer (size
11 / 70R22.5), the maximum height of the carcass line from the rim diameter line RL H = 165.5 mm, and the ply end height h = 34
mm and a height of 46.3 mm (h + 0.07) on the carcass path line.
4H) and 42.1 mm (h + 0.049H), the angle difference between the tangent line of the carcass path line and the rim diameter line at two points M and N extending 5.2 mm in length is 8.5 °, and the tire of this carcass ply is The carcass pass line near the portion forming the recess when viewed from the inner surface and on the side of the tire tread from this portion is substantially linear over a length of 22 mm (0.133 H),
Prototype a tire in which a wedge rubber 9 having a cross section of a convex lens shape having a width of 20 mm and a maximum thickness of 2.5 mm is arranged between two chafers.
When the durability of the bead portion was tested in the drum running test, the running distance was increased by about 12% as compared with the conventional natural balanced tire.

[0042]

According to the invention as set forth in claims 1 to 8 of the present invention, pneumatic pneumatic tires exhibiting excellent bead portion durability required for extension of the regenerating life cycle due to repeated renewal of heavy duty radial tires. A radial tire can be provided.

[Brief description of the drawings]

FIG. 1 is a tire cross-sectional view illustrating a carcass pass line according to the present invention.

FIG. 2 is a tire cross-sectional view illustrating a wedge rubber and a carcass pass line according to the present invention.

FIG. 3 is a tire cross-sectional view illustrating a wedge rubber and a carcass pass line according to the present invention.

FIG. 4 is a tire cross-sectional view illustrating a wedge rubber and a carcass pass line according to the present invention.

FIG. 5 is a tire sectional view illustrating a carcass pass line according to the present invention.

FIG. 6 is a tire cross-sectional view illustrating a carcass pass line according to the present invention.

FIG. 7 is a tire sectional view illustrating a carcass pass line according to the present invention.

FIG. 8 is a tire sectional view illustrating a carcass pass line according to the present invention.

FIG. 9 is a tire sectional view illustrating a carcass pass line according to the present invention.

FIG. 10 is a sectional view of a tire according to an example.

FIG. 11 is a tire cross-sectional view of another specific example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Bead part 2 Side wall part 3 Tread part 4 Carcass 5, 5 'Inner liner 6 Bead core 7 Belt 8 Rim 9 Wedge rubber

Continuation of the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) B60C 15/00 B60C 15/06 B60C 9/08 B60C 9/06

Claims (8)

(57) [Claims] A pair of bead portions and a pair of side walls;
And a tread that spans between both sidewalls
Bead core with these parts embedded in the bead part
Radial cord plies that reinforce each other
A carcass comprising at least one plastic
I winds up around the bead core from the inside of the tire to the outside
Pneumatic radial tie consisting of curved turn-up structure
In the tires, apply 5% of the standard internal pressure to the tire mounted on the rim.
Tires and rim assemblies with no load
On the carcass path line in the radial section of the ear,
Height of ply winding end measured from rim diameter line (RL)
Carcass inner surface near the height position corresponding to (h)
Wedge rubber with a convex lens-shaped cross-section
For example, the arrangement of the wedge rubber, on top of the under the above-mentioned fine圧充heaven
Carcass path in the above section of the tire in the assembly
Inner detours locally at the ply winding end
A curvature change area (v), and the curvature change area (v)
Tires for the carcass pass line in the adjacent area on both sides
A local recess is formed when viewed from the inner surface, and a standard internal pressure filling for the tire and the rim assembly is performed.
The ply is bent by bending deformation concentrated in the curvature change area (v).
Carcass that generates compressive stress in rubber near the winding end
With bead durability characterized by having a pass line
Excellent pneumatic radial tire. 2. A curvature change area (v) of a carcass pass line.
Is smaller than the curvature of the adjacent curvature change area (v).
Smoothly connected to the adjacent area (w) consisting of the curvature curve,
The curve of the adjacent area (w) has a center of curvature inside the tire.
The tire according to claim 1, wherein: 3. A curvature change area (v) of a carcass pass line.
Is located farther than the curvature change area (v) with respect to the bead core.
Area consisting of a curve with a center of curvature outside the tire
2. The method according to claim 1, wherein the region (w ') is smoothly connected via the inflection point.
Tires described. 4. A curvature change area (v) of a carcass pass line.
Is the carcass pass line from the rim diameter line (RL)
The vertical distance (g) corresponding to 8% of the height (H) is rolled up.
Pass line area separated above and below the tip height (h)
And the curvature change area (v) is a path line in the area.
Points at a distance (l) of 10 mm or less along
4. Any of claims 1 to 3 extending between (M) and (N). 5.
The tire according to any one of the preceding claims. 5. A point (M) and a point on a carcass path line
(N) The tangents (m, m ') and (n,
n ′) is within the range of 5 to 90 °.
Item 7. The tire according to item 4. 6. A curvature change area (v) of a carcass pass line.
Is farther from the bead core in the adjacent area (w) connected to
Adjacent area (w)
A vertical distance (j to 12) corresponding to 12 to 24% of the height (H)
i) is separated from the height (h) of the carcass ply winding end
1/500 (mm ^-1 ) before reaching point k on the pass line
Has an area with a curvature within the range, and the path line length of the area
Is 12% or more of the carcass pass line maximum height (H)
The tire according to claim 2. 7. A method according to claim 1, wherein a curvature change range (v) is set for the bead core.
The adjacent area (w ') located far away is
Vertical distance (i) corresponding to 24% of the maximum height (H) of
Pass lay separated from carcass ply winding end height (h)
Points in the second area of the pass line leading to a point on the
4. The tie according to claim 3, which is provided between (P) and (Q).
Ya. 8. The curvature change region (v) for the bead core.
The adjacent area (w ') located far away is
Vertical distance (j) corresponding to 12% of the maximum height (H) of
Pass lay separated from carcass ply winding end height (h)
Points in the second area of the pass line leading to a point on the
4. The tie according to claim 3, which is provided between (P) and (Q).
Ya.