JP2796194B2 - Radial tire - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radial tire capable of effectively suppressing uneven wear at a shoulder portion of a tire.

[0002]

2. Description of the Related Art In a pneumatic tire, the tire is inevitably worn as the vehicle runs. Particularly in recent years, in a radial tire that is frequently used, a belt layer made of a high-tensile cord such as a steel cord is arranged outside a carcass arranged in the radial direction, and a large tag effect is given. Pressure distribution tends to be non-uniform, and in particular, uneven wear, in which the shoulder portion of the tire is worn earlier than the crown portion, tends to occur. As such uneven wear, for example, in a radial tire for a passenger car, so-called heel and toe wear in which the front and rear of a tread portion sandwiching a lateral groove is worn early, or only a shoulder portion seen in a tire for heavy vehicles such as trucks and buses. There is shoulder wear, which wears out early.

[0003] Such uneven wear in the shoulder portion is caused by the fact that the tread surface has a substantially arc shape in a cross section including the tire axis of the tire, so that the circumferential length of the crown portion is smaller than the circumferential length of the shoulder portion. Therefore, when the tread surface is in contact with the ground, the crown portion forms the drag side, and the shoulder portion forms the drag side. It is considered that the uneven wear is promoted by the sliding friction generated in the above.

Heretofore, in order to prevent such uneven wear, the rigidity of the tread surface is increased by increasing the radius of curvature of the tread surface or by increasing the size of the shoulder block, and further, the rigidity of the belt layer is increased particularly in the shoulder portion. Proposals such as strengthening have been made.

[0005]

However, even with these proposals, the uneven wear described above has not been sufficiently solved, and when the rigidity of the block or belt layer at the shoulder portion is excessively increased, the tire noise is reduced. , Which tends to hinder ride performance.

In the present invention, various experiments were conducted to prevent uneven wear of the tire, particularly at the shoulder portion.
As a result, curvature at the end portion of which is the belt layer basic components of radial tires, i.e. focusing on the belt end camber quantity CH, same effective belt width BW, in association with the tire section width TW, the belt end camber quantity CH Is within a predetermined range to make the contact pressure distribution uniform,
They have found radial tires that can effectively suppress uneven wear and do not impair the performance of other tires.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a radial tire that can make the distribution of the contact pressure uniform and effectively suppress uneven wear of the shoulder portion. The radial tire can be used as a tire for various uses such as a tire for buses and trucks, as well as a tire for passenger cars.

[0008]

SUMMARY OF THE INVENTION The present invention relates to a radially or semi-radially arranged carcass which is folded from a tread portion to a side wall portion with a bead core at a bead portion, and to a radially outer side of the carcass and an inner side of the tread portion. And a belt layer including at least two belt plies using a belt cord, and at least two belt plies overlap in a standard state in which the rim is assembled to a regular rim and filled with a regular internal pressure. The ratio BW / TW of the effective belt width BW between the outer end points A, A in the tire axial direction of the belt effective area BE, which is the area of the overlapping area extending to the outermost side in the tire axial direction in the overlapping area, and the tire sectional width TW. The belt / tire width coefficient K defined as
The outer end point A of the effective belt area on the thickness middle line connecting the center of each of the belt cords of the two belt plies forming the E in the radial direction of the tire and the effective belt width BW from the outer end point A. A belt end camber amount CH which is a distance in the tire radial direction between the inner point B on the thickness intermediate line and a distance 0.2 times (0.2 BW) inward in the tire axial direction is expressed by the following relationship. Satisfies the above-mentioned thickness middle line
An inner area IP passing through the upper equatorial point C and the inner point B is:
An outer region OP between the outer end point A and the inner point B slides.
The radial tire is characterized by being connected by a smooth curved surface . 2.50K-1.25 <CH <13.3K-4.65

[0009] 2.50K-1.25 <CH <13.3K-4.65

[0010]

In the radial tire according to the present invention, the shape of the belt layer is set in a standard state in which the rim is assembled to the normal rim and the normal internal pressure is filled. Here, the regular rim is “JATMA Y” issued by the Japan Automobile Tire Association.
EAR BOOK "is the underlined rim of the applicable rim specified in the EAR BOOK.
It is defined as the maximum air pressure of each tire in the air pressure-load correspondence table of A. Radial tires can be applied as tires for trucks, buses, and small trucks, in addition to tires for passenger cars.

Further, in the radial tire of the present invention, a belt-tire width coefficient K defined as a ratio BW / TW of an effective belt width BW and a tire sectional width TW is expressed by the following equation with respect to a belt end camber amount CH. Satisfies the relationship. 2.50K-12.5 <CH <13.3K-4.65

For radial tires, steering stability,
In order to exhibit performance such as rolling characteristics and abrasion resistance, it is preferable to arrange a belt layer in a contact area where the contact is made under normal load conditions. Further, it is desirable that at least two belt plies are overlapped in the ground contact area, and a belt effective area BE including an overlap area where a sufficient hoop effect can be exhibited by the intersecting belt cords is provided. The belt effective area BE is an area of the overlap area having the maximum width extending to the outermost side in the tire axial direction in the overlap area. Excessively widening the belt layer in the tire axial direction may reduce ride comfort. Lower.

On the other hand, the belt layer has a curved surface having a smaller radius of curvature than the crown portion by bending toward the sidewall of the tire at the shoulder portion of the tread portion.

The present inventors have conducted various experiments in order to prevent uneven wear in the shoulder portion. As a result, while finding that the radius of curvature of the belt layer in the shoulder portion is related to uneven wear of the shoulder portion,
The following findings were obtained.

First, uneven wear at the shoulder portion correlates with the radius of curvature of the belt layer at the shoulder portion, and in particular, the belt effective region BE, which is the outermost overlap region in the tire axial direction where two belt plies overlap each other. Is related. Here, the belt effective area BE is an area of an overlap area extending to the outermost side in the tire axial direction in an overlap area where at least two belt plies overlap. Therefore, when two belt plies are used, the width of the narrow belt ply is the effective belt width BW, and when three or more belt plies are used, the width of the second widest belt ply is the belt effective area. BE.

Second, in the belt effective area BE,
The area that affects uneven wear and early wear is the outer end point A in the tire axial direction of the belt effective area BE, and the inner side that separates the effective belt width BW by 0.2 times the effective belt width BW from the outer end point A in the tire axial direction. What is affected by uneven wear and early wear in the region between the points B and B is the degree of curvature of the region. The effective belt width BW is the effective belt area B
E is defined as the length in the tire axial direction between the outer end points A of the tire axial direction A.

As the degree of curvature, a thickness center line L connecting equal distance points in the tire radial direction from the center of each of the belt cords of the two belt plies forming the effective belt area BE.
It is given by the belt end camber amount CH which is the distance in the tire radial direction between the outer end point A and the inner point B above.

Third, in order to prevent uneven wear and early wear, the belt-to-belt width is defined by defining the belt end camber amount CH as a ratio BW / TW between the effective belt width BW and the tire section width TW. That is, it is set within the range of the equation of linearly correlating with the coefficient K.

CH <13.3K−4.65

This is because various belt end camber amounts C are obtained by changing the number of belt plies, the flatness, and the type of tire.
Based on the results of FIG. 6 measured for tires of H and belt tire width coefficient K.

In FIG. 6, marks such as circles and squares indicate the tire sizes described in the figure, and black solid marks indicate cases where uneven wear and early wear occur. As is clear from FIG. 6, regardless of the flatness, the number of belt plies, and the type of tire, the belt
In the relationship between the tire width coefficient K and the belt end camber amount CH, a region where uneven wear and early wear do not occur is given by the above equation.

[0022] By setting the belt end camber quantity CH, the values obtained below from the equation, degree of curvature of the belt layer decreases in the shoulder portions, thereby to 5, in dashed line a belt layer before the ground, the belt layer deformation line X after the ground as indicated by the dashed line, the crown portion and shoulder portions belt layer over the shoulder portion from the crown portion during ground smoothly and continuously deformed radially, yet at the time of ground As a result, the difference in the amount of deformation of the belt layer in the tire radial direction between the tire and the tire is reduced, and the amount of deformation at the end of the belt layer is suppressed.
It is considered that the uneven wear and the early wear can be reduced by reducing the amount of slip between the shoulder portion and the road surface. In addition, the inner area IP between the equator point C and the inner point B at the middle line of the belt layer thickness is smoothly connected to the outer area OP to reduce the step in the ground pressure distribution and to achieve uniform wear. Can be.

A more preferable range of the belt end camber amount CH is as follows.

CH <10.0K-3.0 Fourth, when the belt end camber amount CH is excessively small, the contact pressure at the shoulder part rather increases,
In particular, when the vehicle turns, the wear in the shoulder portion becomes large. Therefore, the belt end camber amount CH is set to be larger than the value given by the following equation. A more preferred range is:

CH> 2.50K-12.5 CH> 6.67K-3.33 Accordingly, from the equation, the preferable range of the belt end camber amount CH is the above equation. 2.50K-1.25 <CH <13.3K-4.65 The deformation of the belt layer due to grounding can be measured by a CT scanner.

It should be noted that, with respect to the following equation, the effective belt area BE
However, when the width is set to be substantially the same as the contact surface of the tire, the belt-tire width coefficient K, which is the ratio between the effective belt width BW and the tire cross-sectional width TW, tends to increase as the tire flatness decreases. Therefore, a tire having a small flatness has a relatively large effective belt width BW, and can qualitatively argue that a relatively large belt end camber amount CH can be adopted.

[0027]

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a standard state in which the radial tire 1 is assembled on a regular rim R and filled with a regular internal pressure. Here, the regular rim is, as described above, a JATM
Among the applicable rims specified in AYEAR BOOK, these are the rims indicated by underlining, and the normal internal pressure is defined as the maximum air pressure of each tire in the air pressure-load correspondence table in the above specification. In the figure, a radial tire 1 has a tread portion 2, a side wall portion 3 extending radially inward from both ends thereof, and bead portions 4 provided at both ends thereof, and a tire around a bead core 5 of the bead portion 4. The carcass 6 includes a carcass 6 that is folded back from the inside to the outside and a belt layer 7 that is disposed radially outside the carcass 6. Further, in the present embodiment, a band layer 9 disposed radially outside the belt layer 7 is provided.

The carcass 6 includes an inner layer 6A surrounding the bead core 2 and an outer layer 6B disposed along the outer surface of the inner layer 6A.
The folded end 6A1 of the inner layer 6A is interrupted above the bead core 5, and the folded end 6B1 of the outer layer 6B.
Is interrupted near the maximum width position of the tire. Note that the carcass 6 may have another structure, and a reinforcing layer that prevents abrasion between the inner layer 6A and the bead core 5 that move with deformation due to grounding of the tire and enhances the rigidity of the bead portion,
A chafer (both not shown) or the like for preventing rim displacement may be provided. Note that the band layer 9 may be omitted. The bead portion 4 has a bead apex 10 made of a rubber material tapering radially outward from the bead core 5.
Is provided to improve lateral rigidity. The carcass 3 has a radial or semi-radial structure in which the carcass cords are arranged at 60 to 90 degrees with respect to the tire equatorial plane CO. As the carcass cords, in addition to steel cords, organic fibers such as nylon, rayon, and polyester are used. Code can be used.

In the present embodiment, the belt layer 7 is composed of a stack of two inner and outer belt plies 7A and 7B, and the width W7A of the inner belt ply 7A on the carcass 6 side is equal to the width of the outer belt ply 7B. The width is about 1.01 to 1.20 times wider than W7B, and the outer belt ply 7B is set to have a width substantially equal to the ground contact surface. By using the wide and narrow plies in this way, concentration of a rigidity step between the belt plies 7A and 7B and the surrounding rubber due to the axially outer edges of the belt plies 7A and 7B coinciding in the tire axial direction is prevented. ing.

Further, in the present embodiment, an overlapping area where the belt plies 7A and 7B overlap each other is formed in the width of the outer belt ply 7B, and in the present example where the two belt plies 7A and 7B are overlapped, this overlapping area is The belt effective area BE is configured.

The belt plies 7A and 7B use steel cords, and the steel cords are inclined at an angle of about 10 to 30 degrees with respect to the equator of the tire, and cross each other by the inner and outer belt plies 7A and 7B. This arrangement improves the uniformity of the tire. As shown in FIGS. 3 and 4, for example, three belt plies 7A,
7B and 7C can be used, and the outer belt ply 7 can be used.
B may be wider than the inner belt ply 7A.

Further, the inner belt ply 7A may be separated from the carcass 6 on the outer side in the tire axial direction. At this time, a breaker cushion rubber (not shown) is provided at the separated portion.
It is good to arrange.

The band layer 9 has a belt ply 7 inside.
A, starting from the outer end of A, covers the outer end of the outer belt ply 7B, and its width W9 is the width W of the belt ply 7A.
It is set to 15 to 40% of 7A. Further, the band layer 9 is made of a band ply using a band cord, and the band cord is made of relatively extensible organic fibers such as nylon, polyester, and rayon. Thereby, it is possible to follow the expansion and contraction of the belt layer 7 when the tire is deformed, thereby preventing peeling from the belt layer 7. The band cords are respectively substantially parallel to the tire equatorial plane CO, that is, in the range of 0 ° to 10 °, preferably 0 ° to 5 ° with respect to the tire equatorial plane C. Are arranged substantially in parallel. The band layer 9 can reduce the difference in rigidity at the end of the belt layer 7, make the contact pressure distribution uniform, improve the steering stability at high speed, and make the wear uniform. Radial tires can be used as tires for trucks, buses, light trucks, etc., in addition to tires for passenger cars.

Further, the radial tire 1 of the present invention has a ratio BW / TW between the effective belt width BW and the tire sectional width TW.
Satisfies the relationship with the belt end camber amount CH.

2.50K-1.25 <CH <13.3K-4.65

Here, the effective belt width BW is defined as a length in the tire axial direction between outer end points A, A in the tire axial direction of the belt effective area BE. The effective belt area BE is an area of an overlap area where at least two belt plies overlap and extends to the outermost side in the tire axial direction. Therefore, when the belt ply is composed of two belt plies 7A and 7B as in the present embodiment, as described above, the narrow belt ply 7
The width of B becomes the effective belt width BW. As shown in FIGS. 3 and 4, when three or more belt plies 7A, 7B, and 7C are used, the width of the second widest belt ply is the effective belt area BE.

Further, the tire section width TW is defined as the JAT
As defined in MA YEAR BOOK, it refers to the maximum width of the tire excluding the tire side pattern, characters, etc. from the total width of the tire. The belt end camber amount CH is defined as the outer end point A of the belt effective area BE and the outer end point A.
, An outer area OP between the inner point B that separates the effective belt width BW by 0.2 times (0.2 BW) inward in the tire axial direction.
The outer end point A and the inner point B are the belt cords D1 and B2 of the two belt plies 7A and 7B forming the effective belt area BE as shown in FIG.
It is located on the thickness center line L which is a curve connecting the equidistant points a, a in the tire radial direction from the centers D1C, D2C of D2. The above equation is based on the results of FIG. 6 measured using various types of tires while changing the belt end camber amount CH and the belt-tire width coefficient K as described above. In FIG. 6, black solid marks indicate cases where uneven wear and early wear have occurred. As apparent from FIG. 6, in relation to the belt / tire width coefficient K and the belt end camber amount CH,
The region where uneven wear does not occur has a linear correlation, and the belt end camber amount CH which does not cause uneven wear and early wear
Is represented by the following equation.

CH <13.3K−4.65

By setting the belt end camber amount CH to be equal to or less than the numerical value obtained by the following equation using the belt / tire width coefficient K, the belt layer deformation line X indicated by the dashed line in FIG. as shown the belt layer of the prior ground by a dashed line, the inner end B, the between B
The inner area IP on the thickness middle line smoothly contacts the outer area OP.
In conjunction with the connection , the belt layer smoothly continues in the tire radial direction from the crown portion to the shoulder portion at the time of contact with the ground, and the difference in the amount of deformation of the belt layer between the crown portion and the shoulder portion in the tire radial direction at the time of contact with the ground. It is considered that the uneven wear and the early wear can be reduced by reducing the amount of deformation at the end portion of the belt layer as a result of making the contact pressure uniform and reducing the amount of slip at the shoulder portion with the road surface. Note that
Thus, in the outer region OP between the outer end point A and the inner point B,
Is formed on a smooth curved surface on the thickness center line L.
You. Further, a more preferable range of the belt end camber amount CH is represented by the following equation.

CH <10.0K-3.0

On the other hand, when the camber amount CH of the belt end is too small, the contact pressure at the shoulder portion is increased at the time of contact with the ground, and particularly, the wear at the shoulder portion at the time of turning becomes large. Therefore, the belt end camber amount CH is set to be larger than the value given by the following equation. A more preferred range is: Therefore, from the above description, a preferable range of the belt end camber amount CH is represented by the following equation.

CH> 2.50K-1.25

CH> 667 K- 333

[Specific Example] A tire having a structure shown in FIG. 1 (without using a band layer) and having a tire size of 2 15 / 60R15 90H is shown in Table 1.
According to the specifications, prototypes were produced as Examples 1 to 3. Table 2
The prototypes shown in Comparative Examples 1 to 3 were also prototyped, and compared with the example product in terms of wear uniformity, cornering wear durability, and steering performance.

The durability was measured by a step speed test using ECE30, and the results are shown in Tables 1 and 2. Each tire was mounted on a 3000 CC rear-wheel-drive passenger car, and the results of steering performance measured by a feeling test were evaluated. This test was performed on a flat road surface at 80K / h.
It was measured by running on a curve at m / h.

The state of wear was tested by an actual vehicle test. After running the 3000Km rated load of the tire,
All tires were evaluated. In addition, cornering wear has a radius of 50
m was turned 500 times at a speed of 40 Km / h on the circumference of m to measure and evaluate the wear amount of the shoulder portion. All evaluations were performed using an index with Comparative Example 1 being 100, and Tables 1 and 2
Is shown in In each case, the larger the numerical value, the better.

[0048]

[Table 1]

[0049]

[Table 2]

All of the products of the examples exhibited uniform wear with no uneven wear as compared with the products of the comparative example.

[0051]

As described above, the radial tire contact pressure distribution of the present invention is made uniform, and uneven wear of the shoulder portion is prevented. Further, wear of the shoulder portion during turning can be effectively prevented.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is a cross-sectional view illustrating a thickness center line.

FIG. 3 is a sectional view showing another example of the belt ply.

FIG. 4 is a sectional view showing another example of the belt ply.

FIG. 5 is a cross-sectional view illustrating tire deformation.

FIG. 6 is a graph illustrating test results.

[Explanation of symbols]

 2 Tread part 3 Side wall part 4 Bead part 5 Bead core 6 Carcass 7 Belt layer

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Atsushi Yamahira 13-10-203 Kita-Showa-cho, Nishinomiya-shi, Hyogo (72) Inventor Hiroyuki Noma 3-163-3 Suzuran Taipei-cho, Kita-ku, Kobe (56) Reference Document JP-A-63-188502 (JP, A) JP-A-1-141104 (JP, A) JP-A-1-145202 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) B60C 9/18 F B60C 9/08 Z

Claims (1)

(57) [Claims] 1. A radially or semi-radially arranged carcass which is folded from a tread portion to a side wall portion by a bead core of a bead portion, and a belt cord which is arranged radially outside the carcass and inside a tread portion and uses a belt cord. A belt layer composed of at least two belt plies, and in a standard state in which the belt layer is assembled to a regular rim and filled with a regular internal pressure, in a tire axial direction within an overlapping area where at least two belt plies overlap. Outer end points A, A in the tire axial direction of the belt effective area BE, which is an overlapping area extending to the outermost side.
Ratio BW between the effective belt width BW between the tire and the cross-sectional width TW of the tire
/ TW is defined as the belt effective area on the median thickness line connecting the center of each of the belt cords of the two belt plies forming the effective area BE and the equidistant point in the tire radial direction. Of the effective belt width BW (0.2BW) from the outer end point A to the outer end point A
With satisfying the tire radial direction following the relationship in which the belt end camber quantity CH distance between the inner point B of the thick middle line that separates the axially inward of, the thickness of the intermediate line Pass through the equator point C and the inside point B
The inner area IP is located between the outer end point A and the inner point B.
It is connected to the outer area OP with a smooth curved surface.
Radial tire that. 2.50K-1.25 <CH <13.3K-4.65