JP2001191749A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire having improved durability at its bead portions. SOLUTION: A tire-rim assembly in a non-loaded condition, in which a radial carcass has wind-up portions around bead cores terminated at the outer peripheries of the bead cores and the tire assembled with a applicable rim is filled with the maximum air pressure, has the tire provided with recessed portions in a surface area ranging from a position apart from a flange of the rim, as a starting end, toward the end of a tread.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire, and more particularly, to a pneumatic radial tire for use in heavy vehicles such as trucks and buses, and more particularly to a pneumatic tire having improved bead portion durability. .

[0002]

BACKGROUND OF THE INVENTION Conventional pneumatic tires used in heavy vehicles of the type mentioned at the beginning roll under heavy loads,
Failure is likely to occur in a bead portion that directly supports a heavy load between the rim and the rim. In particular, a large strain is concentrated at the end of the radial carcass where the bead core is wound, so that a failure nucleus such as a crack is generated at the end of the turn, and the crack grows and a separation failure occurs at the turn. This is a typical example.

[0003] In order to improve the separation failure of the folded portion, it is customary to arrange a bead reinforcing layer extending beyond the folded portion along the outside of the folded portion.
The bead portion reinforcing layer is a rubber-coated steel cord layer generally called a wire chafer. This type of reinforcing layer is a layer in which the cords at the turn-back portions of the radial carcass extend substantially in the tire radial direction, but steel cords are inclined and arranged in the radial direction. As a result, the strain acting on the upper end of the steel cord of the reinforcing layer is smaller than the strain acting on the cord end of the folded portion, and has an advantage that it does not easily become a failure nucleus such as a crack.

However, recently, when the tendency of the tire to be flattened further increases, the input to the bead portion becomes more severe. As a result, even if the bead portion is reinforced by the wire chafer, the suppression of the separation failure from the end of the folded portion is insufficient. It became. Therefore, in order not to concentrate the strain on the end of the folded part,
A new structure has been proposed in which the entire end portion of the folded portion is located on the outer periphery of the bead core, and the winding portion of the bead core is rather than the folded portion. This new structure is, as shown in FIG. 4, a winding portion 16w of the radial carcass 16 from the main body 16b.

[0005]

By employing the structure of the winding portion 16w of the radial carcass 16, the distortion of the terminal 16we of the radial carcass 16 is greatly reduced, and the separation failure of the terminal 16we is eliminated. On the other hand, the failure nucleus is transferred to the wire chafer end 18e, which is indispensable for reinforcing the bead, to the extent that the bead durability is improved, and the bead durability problem has shifted to the separation failure at the wire chafer end 18e. .

However, until then, the wire chafer end 1
Since there is no example in which a failure such as separation occurs in 8e, this failure improvement means cannot be found. Therefore, today, there is an urgent need to crack the wire chafer end 18e and improve the separation failure due to the crack.

[0007] Therefore, the invention described in claims 1 to 3 of the present invention is to solve the above-mentioned problem of bead durability fundamentally, that is, to improve the durability of the radial carcass end portion, An object of the present invention is to provide a pneumatic tire capable of improving the separation resistance of a rubber-coated steel cord layer (wire chafer) as a reinforcing layer, thereby significantly improving the durability of a bead portion.

[0008]

According to a first aspect of the present invention, there is provided a tread portion having a pair of sidewall portions and a pair of bead portions connected to both sides of the tread portion. In a pneumatic tire provided with a one-ply radial carcass that reinforces these parts between bead cores embedded in a bead part, the radial carcass has a winding part that winds around the bead core from the inside of the tire to the outside through the outside of the tire. Then, the winding portion has a terminal end at an outer peripheral position of the bead core, and a tire and a rim assembly in a load-unloaded state and a rim in which the tire is assembled to the applicable rim and filled with the maximum air pressure are: A pneumatic tire having a concave portion in a surface region starting from a position at which the rim separates from the flange toward a tread portion end.

According to the first aspect of the present invention, preferably, as one aspect of the invention, as in the second aspect of the invention, the concave portion has a curved surface which is entirely convex toward the inside of the tire. Under a state where the tire of the assembly is loaded with any load selected from the range of 1.00 to 1.50 times the load corresponding to the maximum load capacity, the curved surface All have the same curved surface shape at the same position as the curved surface of the rim flange.

According to the first aspect of the present invention, preferably, as the second aspect, as in the third aspect of the present invention, the concave portion has a radially inward portion formed by a convex portion according to the second aspect. And the remaining radially outer portion has a curved surface shape that smoothly extends from the top of the convex curved surface toward the end of the tread portion.

[0011] In the first to third aspects of the present invention, the applicable rim, maximum air pressure and maximum load capacity are defined as JATMA YEAR.
According to the general information given in BOOK (1999), the actual applicable rim, the actual maximum air pressure and the maximum load capacity are
The type and value determined for each tire type in OOK shall be used. Overseas, TRA YEAR BOOK (1999) and ETRT
According to O STANDARDS MANUAL (1999).

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a left half sectional view of the pneumatic tire of the present invention, FIG. 2 is a left half sectional view of another pneumatic tire of the present invention, and FIG. It is a principal part expanded sectional view.

1 and 2, a pneumatic tire (hereinafter referred to as a tire) 1 is a typical example of a tubeless tire. The tire 1 has a tread portion 2 and a pair of sidewall portions (only one side) connected to both sides thereof. 3) and a pair of bead portions (only one side is shown) 4. The tire 1 has a one-ply radial carcass 6 extending between the bead cores 5 embedded in each bead portion 4.
Is provided. The radial carcass 6 is made of a ply of a rubber-coated steel cord, and reinforces the above-described parts 2 to 4. Further, the tire 1 includes a belt 7 for reinforcing the tread portion 2 at the outer periphery of the radial carcass 6 and one or more reinforcing layers 8 for reinforcing the bead portion 4.

The reinforcing layer 8 of the bead portion 4 comprises a rubber-coated steel cord layer or a rubber-coated organic fiber cord layer. The reinforcing layer 8 is disposed at least outside the tire 1, and in the illustrated example, the reinforcing layer 8 is disposed so as to extend to the inside of the main body 6 b of the radial carcass 6. In addition, the code | symbol 9 shown in FIG. 1 is a stiffener rubber, and the code | symbol E is the equatorial plane of the tire 1. FIG.

The radial carcass 6 has a winding portion 6w that winds around the bead core 5 from the inside to the outside of the tire 1 to the outer periphery. The winding portion 6w is located at the outer periphery of the bead core 5 and in the vicinity of the radial carcass body 6b. It has a termination 6we.

Here, the tire 1 shown in FIG. 1 and FIG.
It is assembled to the above-mentioned applicable rim 10 and shows the state of the assembly of the tire 1 and the rim 10 in a no-load state filled with the above-mentioned maximum air pressure. In this assembled state, the tire 1 has the concave portions 11 in the surface regions P to Q starting from the separation position P of the rim 10 from the flange 10F toward the end of the tread portion 2.

Here, in order to clarify the difference from the conventional tire and to clarify the separation position P, the outline of the cross section of the conventional tire is indicated by a two-dot chain line outside the recess 11 in FIG.
And FIG. Here, the separation position P is a position obtained by a conventional tire. The recess 11 is convex toward the inside of the tire 1.

The cause of impairing the bead durability in the conventional tire shown in FIG. 4 is as follows. That is, with reference to FIG. 3 in which the outline of the inside and outside of the main part cross section under rolling with the load of the tire is shown by a thin line, the region from the bead portion 14 to the sidewall portion 13 falls to the outside of the tire. As a result, the tire portion in contact with the flange 10F of the rim 10 is pushed up, and this pushing up causes a large strain in the bead portion 14, and a large amount of heat is generated in the bead portion 14 due to the repetitive action of this large strain. The temperature of the bead portion 14 becomes high, and the high temperature lowers the physical properties of the rubber, so that the separation failure easily occurs.

On the other hand, the recesses 11 are formed in the surface regions P to Q starting from the separation position P of the rim 10 from the flange 10F.
In the tire 1 provided with the tire, since the phenomenon of pushing up from the flange 10F is completely absent or slight, the calorific value of the bead portion 4 is significantly smaller than the calorific value of the conventional tire. The bead portion 4 of the tire 1 is kept at a low temperature, separation is prevented at least due to the high temperature, and the durability of the bead portion 4 is greatly improved in cooperation with the winding portion 6w of the radial carcass 6.

In practice, the shape of the recess 11 can be roughly classified into two types. As shown in FIGS. 1 and 3, one of the recesses 11 has a curved surface which is convex toward the inside of the tire 1 as a whole, and the tire of the assembly has its maximum load capacity (based on the above description). 1.00 to 1.50 of the load corresponding to
Under a state where an arbitrary load selected from a load within a double range is applied, all the curved surfaces have the same curved shape at the same position as the curved surface of the flange 10F of the rim 10. is there.

This will be described in detail with reference to FIG. 3. The end position Q of the concave portion 11 when there is no load moves in the direction of the arrow to a position S on the flange 10F under the above-mentioned load of the tire 1,
The curved shape from the start end position P to the end position Q of the concave portion 11 is the same as the curved surface of the flange 10F. The curved surface of the flange 10F is represented by an arc having one radius of curvature in the cross-sectional profile. In the case of the tubeless tire rim 10, the center of the radius of curvature of the arc of the curved surface exists on a straight line (hereinafter, referred to as a rim diameter line) parallel to the rotation axis passing through the rim diameter position.

As shown in FIG. 2, two of the concave portions 11
First, the radially inner portion of the tire 1 has a lower half curved shape from the top R of the convex curved surface of the concave portion 11 shown in FIGS. 1 and 3, and then the remaining radially outer portion has It has a curved surface shape that smoothly extends from the top R to the end position Q toward the end of the tread portion 2. Here, the top R indicates the position farthest from the contour in the cross section of the conventional tire indicated by the two-dot chain line.

Also in the second case of the recess 11, the top R of the recess 11 shown in FIG. 3 moves in the direction of the arrow to the position T on the flange 10F when the tire 1 is loaded with the load, and
The curved shape from the start position P to the top R of the
0F has the same shape as the curved surface, and the concave portion 1
1 means moving away from the flange 10F. The end position Q may be any position between the position shown in FIG. 1 and the end of the tread portion 2.

The recess 11 having the above-described structure is not limited to a tubeless tire, but is also applicable to a tire with a tube. The tire 1 is not limited to a truck and a bus, but is a so-called heavy load. Applies to all heavy duty pneumatic radial tires. At this time, FIG.
The recess 11 shown in FIG. 2 or the recess 11 shown in FIG. Any of the concave portions 11 has a remarkable effect of improving the durability of the bead portion 4.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A radial ply tire for trucks and buses having a size of 285 / 60R22.5. The configuration of the tire 1 of the first embodiment is in accordance with FIG. 1, and the configuration of the tire 1 of the second embodiment is in accordance with FIG. In the starting end position P, the height measured from the rim diameter line described above is 9 mm for both the first and second embodiments, and the top R
The height measured from the rim diameter line is 2 in both Examples 1 and 2.
1.5 mm. The depth of the top R from the conventional tire is 2 mm. A conventional tire shown in FIG. 4 was also prepared.

Each tire was used as a test tire, and the tires were mounted on standard rims 9.00 to 22.5 among applicable rims, and these were filled with a maximum air pressure of 900 kPa to form an assembly. A load equivalent to twice the maximum load capacity is applied to these assemblies, pressed against a drum rotating at 60 km / h, and the surface temperature and the internal temperature of the bead portion are measured. A temperature measurement test and
A durability test was performed.

As a result, the maximum temperature was 1
The tires of Example 1 were 96, and the tires of Example 2 were 94. The smaller the value, the better. From this result, it can be seen that the temperature of the bead portion 4 of the tires of Examples 1 and 2 significantly decreased.

The durability test is a measurement of the running distance until the running cannot be continued due to the occurrence of a failure in the bead portion. The running distance until the occurrence of a failure is represented by an index with the conventional tire being 100, and the larger the value, the better. The result is that the tire of Example 1 is 122 and the tire of Example 2 is 127 with respect to the conventional tire 100 because of the effect of lowering the temperature of the bead portion 4 of the tires of Examples 1 and 2. Was. The above results demonstrate that the tires of Examples 1 and 2 have significantly improved bead portion durability.

[0029]

According to the first to third aspects of the present invention, the bead portion is provided under the rolling load of the tire by providing the concave portion at the position away from the flange of the rim in the conventional tire. The temperature of the pneumatic tire can be significantly reduced, and as a result, the durability of the bead portion can be significantly improved.

[Brief description of the drawings]

FIG. 1 is a left half sectional view of a pneumatic tire of the present invention.

FIG. 2 is a left half sectional view of another pneumatic tire of the present invention.

FIG. 3 is a cross-sectional view of a main part of a tire for explaining the operation and effect of the present invention.

FIG. 4 is a left half sectional view of a conventional tire.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Pneumatic tire 2 Tread part 3 Side wall part 4 Bead part 5 Bead core 6 Radial carcass 6b Radial carcass body 6w Entrainment part 6we Entrainment part end 7 Belt 8 Bead part reinforcement layer 9 Stiffener rubber 10 Applicable rim 10F Flange 11 Concave E Tire equatorial plane P Start position of concave part Q End position of concave part R Top of concave part

Claims (3)

[Claims] 1. An air having a one-ply radial carcass having a tread portion, a pair of sidewall portions and a pair of bead portions connected to both sides thereof, and reinforcing these components between bead cores embedded in the bead portions. In a tire including a tire, the radial carcass has a winding portion that winds around the bead core from the inside to the outside of the tire to the outer periphery, the winding portion has an end at an outer circumferential position of the bead core, and the tire is assembled to the applicable rim. In an assembly of a tire and a rim in a no-load state in which a tire attached to the tire is filled with the maximum air pressure, the tire has a concave portion in a surface region toward a tread portion end from a position at which the rim separates from a flange as a start end. A pneumatic tire characterized by the following. 2. The concave portion has a curved surface which is convex toward the inside of the tire as a whole, and is applied to the tire of the assembly in a range of 1.00 to 1.50 times the load corresponding to its maximum load capacity. The tire according to claim 1, wherein all of the curved surfaces have the same curved shape at the same position as the curved surface of the flange of the rim under a state where an arbitrary load selected from among the loads is applied. . 3. The concave portion has an inner portion in the tire radial direction having a lower half curved shape from the top of the convex curved surface described in claim 2, and the remaining radially outer portion has the convex shape. 2. The tire according to claim 1, having a curved surface shape that smoothly extends from the top of the curved surface toward the end of the tread portion. 3.