JPH089282B2 - Radial tires for heavy loads - Google Patents

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 capable of effectively suppressing uneven wear in the shoulder portion of the tire.

[0002]

2. Description of the Related Art A pneumatic tire is inevitably accompanied by wear of the tire as it travels. In particular, in radial tires that have been used a lot in recent years, a belt layer made of high-tensile cords such as steel cords is arranged outside the carcass arranged in the radial direction to give a large hoop effect. The pressure distribution is likely to be non-uniform, and in particular, the shoulder portion of the tire is more likely to be worn earlier than the crown portion, causing uneven wear. On the other hand, for example, so-called heel and toe wear, which is often found in radial tires for passenger cars, and only shoulder portions are stepped, as shown in FIG. Abnormal wear such as stepped wear M that wears may occur.

Due to such uneven wear in the shoulder portion, since the tread surface is substantially arcuate in a cross section including the tire shaft, the circumference length of the crown portion is larger than that of the shoulder portion. When the tread surface is relatively long, therefore, the crown portion forms the dragging side and the shoulder portion forms the dragging side when the tread surface touches the ground, and, for example, as shown in FIG. In particular, it is considered to be caused by sliding friction that occurs between the road surface and the protruding portion b.

[0004] In particular, when the tire is used for a front wheel on the non-driving side, the stepped wear M is caused by the fact that the attitude angle of the tire promotes the wear of the contact end portion. Grows with the mileage of the tire and eventually spreads over the full width of the outer ribs, reducing the life of the tire.

Conventionally, in order to prevent the uneven wear and the step wear, the radius of curvature of the tread surface is increased to reduce the circumferential difference between the crown portion and the shoulder portion, or the block of the shoulder portion is enlarged. Proposals have been made to increase its rigidity, and further to strengthen the rigidity of the belt layer especially in the shoulder portion.

[0006]

However, when the radius of curvature is increased and the difference in circumferential length is reduced carelessly, the ground contact pressure at the shoulder portion is increased, and heat is easily generated in this portion. Durability is rather reduced, such as rubber peeling at the edges.

As described above, there is a trade-off between uneven wear and heat generation, that is, durability. In addition, the increase in the rigidity of the block and the belt layer cannot sufficiently solve the wear, and when the rigidity of the block and the belt layer of the shoulder portion is excessively increased, the tire noise and the riding comfort performance tend to be impaired. Become.

As a result of various experiments conducted by the present inventors to prevent uneven wear and step wear in the shoulder portion of a heavy-duty radial tire, the inventors found a preferable range for the degree of curvature of the tread surface capable of preventing uneven wear. It was Further, as another example, it was also found that heat generation can be effectively reduced by setting the curvature of the tread surface within a predetermined range. Further, regarding the belt as the basic member, by setting the degree of curvature thereof within a predetermined range, it is possible to reduce the shear strain at the crown portion and the shoulder portion of the belt, particularly at the end portion, and control the movement of the tread rubber, and to reduce the stepped wear M. They also found that it can be effectively prevented.

Therefore, it is a first object of the present invention to provide a heavy load radial tire capable of effectively suppressing uneven wear that tends to occur in the shoulder portion.

[0010]

The present invention is directed to a carcass of a radial or semi-radial arrangement in which a tread portion goes from a tread portion to a side wall portion and is folded back at a bead core of a bead portion, and a carcass radially outward and inward of the tread portion. And a belt layer composed of at least three belt cords using belt cords which are arranged in an angle range of 5 to 70 ° with respect to the tire equator, and a belt ply which overlaps the inside and the outside, and is rim-assembled into a regular rim and regular. In the standard state of being filled with internal pressure, from the equatorial point T1 on the tread surface, the outer end point in the tire axial direction of the ground contact surface that contacts the ground when a normal load is applied to the tire is located on the tread surface when there is no load. T
The half-width of the ground contact SL, which is the distance in the tire axial direction to 0.
The tread equator-base point height Y1 which is the distance in the tire radial direction between the base point T2 that separates twice (0.2 SL) from the outside ground contact point T0 inward in the tire axial direction and the equator point T1 is A heavy load radial tire satisfying the following formula (1) with respect to the ground contact half width SL. 0.0901SL-3.67 ≦ Y1 ≦ 0.1060SL-4.32 (1)

[0011]

In the heavy-duty radial tire of the present invention, the curvature of the tread is set in a standard state in which the rim is assembled to the regular rim and the regular internal pressure is filled. Here, the regular rim is THE TIRE and RIM ASSOCIA.
TION INC. Issued by YEAR BOOK (T
RA) or THE EUROPEANTY
RE AND RIM TECHNICAL ORGA
STANDARDS MA issued by NIZATION
This is a standard rim defined by NUAL (commonly called ETRTO), and the normal internal pressure is defined as the maximum air pressure of each tire in TRA or ETRTO. The normal load means the maximum load.

Further, in the heavy duty radial tire of the present invention, the tread equator / base point height Y1 is satisfied by the following expression (1) with respect to the ground contact half width SL. 0.0901SL-3.67 ≦ Y1 ≦ 0.1060SL-4.32 (1)

Here, the height Y between the tread equator and the base point
As shown by the alternate long and short dash line in FIG. 1, the tire axial direction outer end point c of the tread surface from the equator point T1 on the tread surface to the ground when a normal load is applied to the tire is tread surface under no load. 0.2 times the ground contact half width SL, which is the distance in the tire axial direction to the outer ground contact point T0 located above (0.2S
L) is the distance in the tire radial direction between the equator point T1 and the base point T2 that is separated from the outside ground contact point T0 inward in the tire axial direction.

Here, in determining the base point T2,
The ground contact half width SL is used instead of the tread width TW in the actual vehicle test of the tire. The ground contact outer point T correlates with the outer end point c in the tire axial direction of the ground contact surface to be actually grounded.
It is related to the actual wear of the tread surface to obtain 0 as an origin, and 0.2 times (0.2 SL) of the ground contact half width SL from the contact outside point T0 is inwardly separated from the contact outside point T0. This is because it has been found that the height of the base point T2 has a great influence on uneven wear and the like in the shoulder portion at the time of contact with the ground. Therefore, the tread equator-base point height Y1 is set as the radial distance between the base point T2 and the equator point T1.

FIG. 2 shows tires having various ground contact widths SL.
The result was measured on uneven wear after the vehicle was mounted on each truck suitable for the tire size, and the general paved road was run at 50,000 km for 100% loading capacity.
Is plotted on the horizontal axis, and the height Y1 between the tread equator and the base point is plotted on the vertical axis.

In FIG. 2, the number attached to each mark is
As shown in FIG. 3, the uneven wear rate w is the uneven wear rate w, which is the amount of wear on the tread surfaces on both sides of the vertical groove A1 passing through the shoulder portion, and the longitudinal wear on the equatorial point T1 side. It is indicated by the ratio Sw / Cw with the crown wear amount Cw, which is the wear amount of the tread surface sandwiching the groove A2. Exponent is 1
When it is 00, it indicates that the crown portion and the shoulder portion are uniformly worn. When it exceeds 100, the wear is promoted at the shoulder portion, and when it is less than 100, the crown portion rather than the shoulder portion. It means that the wear is progressing. The preferable range is 80 to 120, which is indicated by a white circle. A more preferable range of wear is 110 to 90. It has been found that when in the above range, the desired wear life can be almost achieved.

The heavy duty radial tire of the present invention comprises:
By satisfying the right half of the formula (1), that is, the formula (A) of Y1 ≦ 0.1060SL-4.32 (A), it is possible to smoothly continue in the tire radial direction from the crown portion to the shoulder portion at the time of grounding. Deformation and further reduce the difference in deformation amount in the tire radial direction between the crown part and the shoulder part at the time of contact with the ground, and suppress the amount of deformation. As a result, the contact pressure is made uniform and the amount of slippage with the road surface at the shoulder part is reduced. Therefore, it is considered that the uneven wear can be reduced.

As shown in FIG. 2, the uneven wear rate w is 12
The range of 0 or less is substantially linearly correlated with the straight-line X between the ground contact half width SL and the tread equator / base point height Y1.
It can be seen that the following ranges can be displayed. This range
It is represented by the formula (A).

It has been found that the relation of the above formula (A) can be applied to a heavy load radial tire having a tread width TW of 150 to 250 mm. Here, the tread width TW means the distance in the tire axial direction between the intersection points d of the extension lines of the tread surface and the buttress surface.

Next, according to the equation (A), the ground contact half width S
The ratio Y1 between the reference tread height value S1 that is a value determined for each L and the actual tire tread equator / base point height Y1
FIG. 4 shows the result of measuring the heat generation of the tread shoulder portion with the reference height ratio K1 of / S1 as the horizontal axis.
This test is for the tire used in the test of FIG.
It was measured by a rotating drum tester in a measuring chamber. The load is a normal load, and the temperature value when the tire is rotated for 60 minutes at a speed corresponding to 80 km / h is indicated by an index.

As is clear from FIG. 4, when the reference height ratio K1 is smaller than 0.85, it is found that the temperature sharply increases.

The fact that the reference height ratio K1 is smaller than 1 means that the tread equator-base point height Y1 is smaller than the reference tread height value S1, that is, the camber amount is reduced, and the tread of the tire is reduced. It means that the surface is flattened. This is because the flatness increases the ground contact pressure at the shoulder portion, and the load bearing ratio at the tire maximum thickness portion sharply increases, thereby increasing heat generation. It is easy to cause rubber peeling at the edges, which adversely affects durability.

Therefore, as described in claim 2, the reference ratio K is set to 0.85 or more. That is, by combining with the above formula (A), the formula (1) of the constitution of the present application can be obtained. 0.0901SL-3.67 ≦ Y1 ≦ 0.1060SL-4.32 (1)

Further, in the test shown in FIG. 2, the inventors have found that the stepped wear M occurs in the range of the reference tread height value S1 or less even if the uneven wear rate w is 120 or less. Focused on the existence of things.

In order to investigate this cause, regarding the tire,
The range of the stepped wear in relation to the degree of curvature of the belt layer was examined. As a result of arranging data on the degree of curvature of the belt layer, as a degree of curvature of the belt, a belt base point B2 at which a radial line passing through the base point T2 intersects with the outer surface of the second belt ply second from the carcass side.
And a belt equator-base point height Y2, which is a radial distance between the tire equatorial plane and the belt equator point B1 where the outer surface of the second belt ply intersects, and the reference height. The height ratio K1 is plotted on the vertical axis, and the height Y between the belt equator and the base point is actually measured for each tire.
2 and the belt reference height ratio K2, which is the ratio Y2 / S1 of the reference tread height value S1, is plotted on the horizontal axis, as shown in FIG. 5, there is a linear correlation regarding the occurrence limit of the stepped wear. Found to have. This correlation equation is given by the following equation (2) as a function of the sum Y1 + Y2 of the tread equator / base point height Y1 and the belt equator / base point height Y2. Y1 + Y2 ≦ 1.85 (0.1060SL-4.32) (2)

With respect to the tread surface, the height between the tread equator and the base point Y1 is equal to or less than the expression (1), that is, the reference tread height value S1 or less. When Y2 is excessively large and the curvature of the shoulder portion of the belt layer is large, as shown in FIG. 6, shear strain occurs in the crown portion and the shoulder portion at the stepped-in portion a and the protruding portion b (see FIG. 6) (indicated by an arrow in FIG. 6), the movement of the rubber between the belt layer and the road surface becomes large, and the thickness of the rubber at the shoulder portion becomes large, so that the stepped wear is likely to occur. .

By satisfying the expression (2), as shown in FIG. 6, the stepped wear can be prevented and the uniform wear property can be further improved.

Therefore, the second aspect of the present invention is the above (2).
Requires an expression. Thus, the tire of the present invention,
The uneven wear can be reduced by the formula (1), heat generation in the shoulder portion can be prevented, and the durability of the tire can be improved. As still another example, a tire capable of preventing step wear more effectively can be obtained by satisfying the requirement of the expression (2).

Further, in the heavy duty radial tire of the present invention, in order to exert steering stability, rolling characteristics, wear resistance and the like performance, a belt layer is provided in the ground contact area where the tire is grounded under a normal load condition. It is good to arrange. Further, at least three belt plies overlap each other in the ground contact area, and the intersecting belt cords exert a sufficient hoop effect.

[0030]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a radial tire 1 for heavy loads having a regular rim R.
It shows a standard state in which the rim is assembled and the normal internal pressure is filled. Here, the regular rim R is the standard rim defined by TRA or ETRTO as described above, and the regular internal pressure is the maximum air pressure of each tire in the TRA or ETRTO, and the regular load is its maximum load. Define as.

The heavy duty radial tire 1 has a tread portion 2, sidewall portions 3 extending inward in the radial direction from both ends thereof, and bead portions 4 provided at both ends thereof.
Further, a carcass 6 which is folded around the bead core 5 of the bead portion 4 from the inside of the tire to the outside and is locked, and the carcass 6
And a belt layer 7 disposed radially outside of the belt.

In the present embodiment, the carcass 6 is composed of one ply having a radial structure in which the carcass cord is arranged at an angle of 90 ° with respect to the tire equatorial plane CO, and a steel cord is used as the carcass cord. There is. The carcass may have a radial or semi-radial structure in which carcass cords are arranged at 60 to 90 degrees. In addition to the steel cord, aramid, nylon,
It can be used by forming organic fiber cords such as rayon and polyester into a plurality of plies. In addition, the carcass turns back the bead core 2 and the turning end 6A.
Is interrupted above the bead core 5 and below the maximum width position of the tire. In addition, the bead portion 4 has a reinforcing layer which prevents friction between the carcass 6 and the bead core 5 that move due to deformation of the tire due to ground contact, etc. and enhances the rigidity of the bead portion.
In addition to chafers (both not shown) to prevent rim displacement,
Another reinforcing layer 8 or the like that covers the folded-back portion of the carcass 6 may be provided. Further, the tread portion 2 may be provided with a band layer (not shown) made of an organic fiber cord that covers an end portion of the belt layer 7 in the tire axial direction.

Further, a bead apex 10 made of a rubber material which is tapered outward from the bead core 5 in the radial direction is provided in the bead portion 4 to improve lateral rigidity.

Further, the belt layer 7 is a carcass 6 in this example.
A four-layer structure including a first belt ply 11, a second belt ply 12, a third belt ply 13, and a narrow fourth belt ply 14 arranged in this order from the side toward the tread portion 2 is formed. The ply width W2, which is the length between the outer edges of the second belt ply 12 in the tire axial direction, is larger than the ply width W1 of the first belt ply 11, and the ply width W1 of the third belt ply 13 is larger. The width W3 is substantially the same as the ply width W1. That is, the second belt ply 12 has the maximum width of the four belt plies, and the belt-tread width ratio BW that is the ratio of the maximum belt width BW that is the ply width W2 to the tread width TW. / TW is 0.85
By setting the above to 1.05 or less, the tread portion 6
Reinforce almost the entire width of it with a hoop effect. If the belt / tread width ratio BW / TW is less than 085, the rigidity at the tread shoulder portion is lowered, and the running performance is impaired.
Further, if the belt / tread width ratio BW / TW exceeds 1.05, the belt end and the outer surface of the buttress portion of the tire are too close to each other, and the external force from the buttress surface tends to cause a failure in separation of the belt end.

Further, the belt cord is inclined at an angle of 5 to 70 degrees with respect to the tire equator CO, and in this embodiment,
The first belt ply 11 inclines its belt cord at an angle of 50 to 70 degrees with respect to the tire equator CO, and the second belt ply 12 places the belt cord in the same direction as the first belt cord. The third belt ply 13 has an inclination angle of 14 to 22 degrees with respect to the equator CO.
The belt cord is disposed in the opposite direction to the second belt cord and at an inclination angle of 14 to 22 degrees with respect to the tire equator CO.

Therefore, in the belt layer 7, while the second and third belt cords intersect each other, the first and second belt cords are inclined in the same direction, so that the first and the first belt cords caused by the deformation of the tire during running. While the shear strain between the two belt plies 11 and 12 is relaxed, the belt cord angles of the plies 11 to 13 intersect to form a highly rigid triangle structure having a high restraining force over the ends of the belt layers. .

The cord angle of the first belt ply 11 is set to the cord angle of the carcass 7 and the cord angle of the second belt ply 12.
, The rigidity step between the carcass 7 and the belt 9 is reduced to prevent peeling damage. The fourth belt ply 14 is a ply 15 made of a steel cord narrower than the width of the third belt ply 13 by 45 to 10% and protects the first to third belt plies 11, 12 and 13 from external damage. .

Further, the first belt ply 11 is separated from the carcass 6 on the outer side in the tire axial direction, and the second belt ply 12 extends in the tire axial direction along the first belt ply and the third belt ply 12 The belt ply 13 of the above is separated from the second belt ply 12 at the end, and the cushion rubber 1 extending in the tire axial direction is provided at each separated portion.
By interposing 5 and 16, stress concentration at each end of each ply is relieved and separation is prevented.

As the belt cord, in addition to steel cords, organic fiber cords such as aramid, nylon, rayon and polyester can be used by forming a plurality of plies.

Further, in the heavy duty radial tire of the present invention, the height Y1 between the tread equator and the base point satisfies the following expression (A) with respect to the ground contact half width SL. Y1 ≦ 0.1060SL-4.32 (A)

Here, the height Y between the tread equator and the base point
1 means, from the equatorial point T1 on the tread surface, as shown by the one-dot chain line in FIG. 1, when the tire axially outer end point c of the grounding surface to be grounded when a normal load is applied to the tire is unloaded. 0.2 times the ground contact half width SL, which is the distance in the tire axial direction to the outer ground contact point T0 located above (0.2S
L) is the distance in the tire radial direction between the equator point T1 and the base point T2 that is separated from the outside ground contact point T0 inward in the tire axial direction.

As a result, as shown in FIG. 2, the uneven wear rate w can be set within the range of 120 or less. In addition,
As shown in FIG. 3, the uneven wear rate w is a shoulder wear amount Sw that is the wear amount of the tread surface on both sides of the vertical groove A1 passing through the shoulder portion and the wear of the tread surface that sandwiches the vertical groove A2 on the equator point T1 side. Ratio of crown wear amount Cw, which is the amount, Sw / C
It is displayed by w. When the index is 100, it indicates that the crown portion and the shoulder portion are evenly worn, and when the index exceeds 100, the wear is promoted at the shoulder portion, and when the index is less than 100, it is rather rather than the shoulder portion. It means that the wear is progressing in the crown portion. The more preferable wear mode is 11
0 to 90. Also, by this, the degree of curvature of the tread surface at the shoulder portion is made appropriate, the tire is smoothly deformed continuously in the tire radial direction from the crown portion to the shoulder portion at the time of grounding, and the tire radius at the crown portion and the shoulder portion at the time of grounding As a result of reducing the deformation amount difference in the direction and suppressing the deformation amount,
It is considered that the uneven wear can be reduced by making the contact pressure uniform and reducing the amount of slippage with the road surface at the shoulder portion.

Further, the height Y1 between the tread equator and the base point satisfies the following expression (B). 0.0901SL-3.67 ≦ Y1 (B)

As a result, heat generation at the tread shoulder portion is suppressed as shown in FIG. This expression (B) means preventing excessive flattening of the tread surface.
This is because the flattening increases the ground contact pressure at the shoulder portion and the load-bearing rate at the tire maximum thickness portion sharply increases, thereby increasing heat generation. It is easy to cause rubber peeling at the edges, which adversely affects durability.

Therefore, by combining the above formulas (A) and (B), it is possible to obtain the formula (1) which is 0.0901SL-3.67≤Y1≤0.1060SL-4.32 (1).

Further, the height between the tread equator and the base point Y1
And the belt equator / base point height Y2, the following expression (2) is satisfied. Y1 + Y2 ≦ 1.85 (0.1060SL-4.32) (2)

The height Y2 between the base points of the belt equator is
On the outer surface of the second belt ply second from the carcass side,
A belt base point B2 where a radial line passing through the base point T2 intersects,
It is the radial distance between the equatorial plane of the tire and the belt equatorial point B1 where the outer surface of the second belt ply intersects. this is,
It is focused on that the stepped wear M may occur even in the range of the expression (1). By satisfying the expression (2), the stepped wear is prevented as shown in FIG. Therefore, uniform wear can be improved. The reason for this is that when the expression (2) is not satisfied, the belt equator-base height Y2 of the belt is excessively large and the shoulder portion of the belt layer is largely bent, and as shown in FIG. Shear strain is generated in the crown portion and the shoulder portion at the protruding portion b (indicated by the arrow in FIG. 6), the movement of the rubber between the belt layer and the road surface becomes large, and the thickness of the rubber at the shoulder portion is large. Therefore, it is presumed that it becomes easy to increase the step wear.

As described above, in the tire of the present invention, uneven wear can be reduced and heat generation in the shoulder portion can be prevented and the durability of the tire can be improved by the formula (1). As still another example, a tire capable of further effectively preventing step wear by satisfying the requirement of the expression (2) is obtained.

[Specific Example] Tires having a tire size of 285 / 75R 24.5 having the tire structure shown in FIG. 1 were prototyped based on the specifications of Tables 1 and 2, and the uneven wear rate w and step wear of the prototype tires were tested. And the temperature rise of the tread shoulder were measured respectively. The results are shown in Table 3.
The ply widths W1, W2, W3, W4 and the belt equator / base point height Y2 shown in FIG. 1 were measured by an X-ray CT scanner.

[0050]

[Table 1]

[0051]

[Table 2]

[0052]

[Table 3]

As shown in Table 1, the tires of the examples of the present invention have better results than the comparative examples in terms of uneven wear rate w, presence or absence of step wear, and elevated temperature of the tread shoulder.

The temperature of the tread shoulder portion is the same as that of Comparative Example product 1
Is shown as an index, and the larger the number, the higher the heat generation.

As for the measuring method, the uneven wear rate w and the stepped wear were measured after traveling on a general pavement with a load of 100% by a truck for 50,000 km. The degree of temperature rise was measured by a rotating drum tester in the measuring room. The load indicates the temperature when a normal load is applied and the tire is rotated for 60 minutes at a speed corresponding to 80 km / H.

[0056]

As described above, the heavy duty radial tire of the present invention can prevent uneven wear of the shoulder portion.

[Brief description of drawings]

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

[Fig. 2] Tread equator-base height Y1 and ground contact half width S
It is a graph which illustrates the relationship with L.

FIG. 3 is a plan view illustrating a pattern.

FIG. 4 is a graph illustrating a relationship between a reference height ratio K1 and temperature.

FIG. 5 is a graph illustrating a relationship between a tread equator / base point height Y1 and a belt equator / base point height Y2.

FIG. 6 is a front view illustrating a grounding shape;

FIG. 7 is a cross-sectional view illustrating stepped wear.

[Explanation of symbols]

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

Claims (2)

[Claims] 1. A radially or semi-radially arranged carcass which is folded from a tread portion to a side wall portion with a bead core of a bead portion, and disposed outside the carcass in the radial direction and inside the tread portion and at the tire equator. 5-7
On a tread surface in a standard state in which a regular rim is assembled into a rim and is filled with a regular internal pressure, with at least three belt layers using belt cords inclined in an angle range of 0 ° Equator point T
From 1 to the contact point half-width SL, which is the distance in the tire axial direction from the outer end point in the tire axial direction of the contact surface that contacts the ground when a normal load is applied to the tire to the contact point outside the contact point T0 located on the tread surface when no load is applied. A base point T2 that separates 0.2 times (0.2 SL) inward in the tire axial direction from the outside ground contact point T0.
And the height Y1 between the tread equator and the base point, which is the distance in the tire radial direction between the equator point T1 and
On the other hand, a heavy-duty radial tire that satisfies the following formula (1). 0.0901SL-3.67 ≦ Y1 ≦ 0.1060SL-4.32 (1) 2. The second belt ply second from the carcass side of the belt ply has a belt base point B2 at which a radial line passing through the base point T2 intersects the outer surface of the second belt ply.
And the belt equator / base point height Y2, which is the radial distance between the tire equator plane and the belt equator point B1 where the outer surface of the second belt ply intersects, is the tread equator / base point height Y1. The radial tire for heavy loads according to claim 1, wherein the following expression (2) is satisfied in the sum (Y1 + Y2). Y1 + Y2 ≦ 1.85 (0.1060SL-4.32) (2)