JPH0867113A - Radial tire for heavy load of deep groove type - Google Patents

Abstract

PURPOSE: To improve a biased abrasion resistance while a drain function and a traction function, which are the natural functions of a block pattern, are maintained. CONSTITUTION: When it is assumed that the groove depth from the surface 1a of a block 1 to a groove bottom 2 is h, the thickness of a rubber layer from the groove bottom to the upper end of a belt is α, and the length of the surface 1a of the block 1 is A, the relation between the height of the block and the dimension of the block surface is expressed by 1.5(h+0.5α< A<2.0(h+0.5α). (Herein, the length of the block surface is expressed by A=ΣS/ W-ΣWG, assuming that ΣS is the surface area of a tread part for one pitch (one block in the circumferential direction) included in the distance W between both ground ends of a tread and ΣWG is a total of the widths in the lateral direction of the longitudinal grooves of a tire.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a deep groove type heavy load radial tire having a block-shaped pattern for all seasons or traction, and more particularly to improvement in uneven wear resistance and wear durability.

[0002]

2. Description of the Related Art Radial tires, particularly high pressure deep groove type heavy duty tires used in trucks, buses, etc.
The so-called heel and toe wear, which is a large difference in wear at both ends in the tire circumferential direction of the block, is likely to occur.

Conventionally, as a measure against such uneven wear, a bridge is provided between the blocks to make the groove shallow or the crown radius is increased to reduce the circumferential length difference of the tread surface, which is one of the exciting forces for causing uneven wear. Countermeasures have been taken such as reducing the shear force in the circumferential direction due to slippage.

[0004]

However, with these measures against uneven wear, the drainage function and the traction function originally intended by the block pattern are deteriorated, the steering stability during driving is deteriorated, and the blow caused by the heat generated during driving is reduced. Out is likely to occur, and further, the durability such as belt separation is deteriorated, which is a problem.

In view of the above facts, an object of the present invention is to provide a deep groove type heavy load radial tire having improved uneven wear resistance while maintaining the drainage function and the traction function which are the original functions of the block pattern. .

[0006]

As for the cause of uneven wear of the block, that is, heel and toe wear, this is due to the difference in slip energy applied to the front and rear portions of the block in the circumferential direction of the tire, and this slip The energy difference is caused by the difference in the shearing force of the block surface in the circumferential direction.

The slip energy is the size of the block, and in particular, as shown in FIGS. 1 and 2, the height (h + 0.5α) of the block 1 having a large influence on the vertical load and the deformability of the block 1 in the tire circumferential direction. Block 1
The width B and length A of Here, as shown in FIG.
Is the groove depth from the surface 1a of the block 1 to the groove bottom 2, and α is the thickness of the rubber layer 4 from the groove bottom 2 to the upper end of the belt layer 3, that is, non-skid depth. 1 and 2, 5 is a horizontal groove, 6 is a vertical groove, 7 is a carcass ply, T
C is a tire center line.

By the way, in the block of the running tire,
Both vertical and horizontal loads are applied from the road surface, but the pressure distribution in the vertical direction given to the block surface is 1 at the time of acceleration or braking, especially even if the average value is almost constant for each part in the ground contact surface. It is very different within one block.

FIG. 3 is a schematic sectional view showing the ground contact pressure distribution (SD) of the block during driving (acceleration), and FIG. 4 is the ground contact pressure distribution (S) of the block during braking or general coasting.
It is a schematic sectional drawing which shows D).

As shown in FIG. 3, during driving (acceleration),
By the action in the horizontal direction, the surface 1a of the block 1 and the base portion 1b of the block 1 relatively move in opposite directions in the circumferential direction, and at this time, the block 1 is subjected to the bending action and the front side of the inclination, that is, the circumferential force. On the upstream side UA of fc, the load center moves to the rear side, so the ground contact pressure on the road surface E becomes high, and on the back side of the slope, that is, on the downstream side DA of the circumferential force fc, the ground contact pressure is conversely small, and in some cases Since the part may float away from the road surface, a large difference may occur in the vertical (ground) pressure distribution at both circumferential ends of the block 1. At the time of braking or general coasting, as shown in FIG. 4, the surface 1a of the block 1 and the base 1b of the block 1 are the same in that they relatively move in opposite circumferential directions, but the block 1 is driven ( The center of the load moves to the front side under a bending action that is completely opposite to that at the time of acceleration), the back side of the inclination, the ground pressure is high at the upstream side UA of the circumferential force fc, the front side of the inclination,
That is, the ground contact pressure becomes smaller on the downstream side DA of the circumferential force fc.

It has been known that how these differences occur decreases as the length A of the block surface increases, the block height decreases, and the vertical load value increases. It is a factor that is already determined to give wear resistance determined by the application of the tire, and the vertical load is also limited by the vehicle and the tire size, so it is possible to change only the block dimensions (width and length). Therefore, this needs to have a different value depending on the block height already determined.

By the way, the fact that the difference in the ground pressure distribution SD is always large on the front side of the inclination makes it extremely inconvenient for uneven wear. That is, as shown in FIG. 3, the shear force distribution generated by the vertical load becomes larger on both sides in the circumferential direction on the block surface 1a, and the shear force fγ in the opposite direction is increased.
Is known to occur. And this shear force fγ
In addition, a circumferential force fc based on braking, truncation, circumferential difference, etc. is applied, and fc and fγ are added together in the upstream UA of this fc, and offset and reduced in the downstream DA.

However, the upstream side UA of the circumferential force fc is always on the front side of the inclination, and therefore the change Δf of the shearing force proportional to the pressure change Δp of the inclination is fc + on the front side of the inclination.
In addition to fγ, on the rear side of the inclination, Δf is further subtracted from the difference between fc and fγ, and before and after the inclination, that is, the upstream side UA of the circumferential force fc (front side of the inclination) and the downstream side DA of the circumferential force fc ( The difference in shearing force becomes larger on the back side of the inclination). The larger the shearing force, the easier it is to overcome the frictional force against slippage, and the larger the slippage, the greater the friction. Therefore, the difference in friction between the front and rear sides of the block increases and uneven wear occurs. The larger the size, the better). The amount of wear is large on the upstream side UA of the circumferential force fc (front side of the inclination) and small on the downstream side DA of the circumferential force fc (back side of the inclination). However, the block is sufficiently soft in the circumferential direction with respect to the circumferential force fc, and within the range where the tire is in contact with the ground, if the friction force is followed with a smaller value, slippage will disappear and uneven wear will disappear. Unlike the above, the smaller the block size, the better.

The present invention pays attention to the fact that the fact that these contradicting facts exist has an extreme value somewhere in the dimension, and by experiment and analysis, a certain block height (h
The maximum point of k _s × Δγ with respect to the circumferential dimension A, which is the most inconvenient for + 0.5α) (Δγ is the increase in shear strain due to the inclination of the block). k _s is the circumferential shear stiffness.
Further, the block length A in the present invention means A = ΣS / W−
ΣW _G , where ΣS is the total width of the tread per pitch length of the block, that is, the surface area of the tread included in the distance W (width of the tread) between the ground contact ends on both sides of the tread, and ΣW _G is the tire width of the vertical groove. It is the total width of the direction.

The shearing forces fγ and Δγ are installed in two holes of φ2 formed in the plane through which the rolling motion of the tire passes, with a sensor for detecting the pressure applied to the block surface on one side and a sensor for detecting the movement on the block surface on the other side. Using a tester (generally called PS plate) that rolls the tire on the device and measures the movement and pressure of a part of the block surface that has passed through the hole, the specified content (700 KP) , Specified cargo (2
6.72 KN) was given, and 80 points were measured in one block for calculation.

In FIG. 5, the solid line is A / (h + 0.5).
The dotted line shows the relationship between α) and k _s × Δγ, which is A / (h + 0.5).
It is a figure which shows the relationship between (alpha) and f (gamma).

From FIG. 5, the block length A is 1.35.
It was confirmed that there was an extreme value at (h + 0.5α).

Therefore, the block length A should be at least greater than 1.35 (h + 0.5α),
Substantially 1.35 (h + 0.5α) is the worst point, and at least 1.5 (h + 0.5α) is necessary to get the effect.
It turned out that it should be larger than α). On the other hand, since it is an extreme value, the length A of the block surface is 1.35 (h +
A range smaller than 0.5α) is acceptable, but A <
In the case of 1.35 (h + 0.5α), the width is narrow with respect to the block height, buckling often occurs due to vertical load, and complicated uneven wear, block chipping, unstable steering performance, etc. are practical. The dimensions will not be correct.

The shearing force, which is the maximum at the end of the block and is in the opposite direction, causes the block to bend due to vertical load, and the rubber volume determined by the product of the amount of bending and the area moves to the side surface of the block. It is generated against the frictional force with the road surface when it is attempted. Therefore, the shear force fγ is large at the center of the block and the moving rubber volume increases toward both ends. It becomes.

Uneven wear (toe & heel) is caused by this shearing force f.
The combined force of γ and the circumferential force fc is added in one direction from the center of the block and canceled in the other direction, and the values are greatly different, resulting in uneven wear, which causes uneven bias. In order to reduce wear, it is necessary to prevent the deviation of the load center and select a dimension that minimizes the shearing force fγ generated for the same load applied to the tire.

Under the same load per unit area (ground pressure), the block length A is set to the block height (h + 0.
As a function of 5α), the length of the block having the worst, that is, the largest shearing force fγ is found, as in the relationship between k _s × Δγ and the block height (h + 0.5α). The fact that A is A = 2.2 (h + 0.5α) was obtained.

As described above, the shearing force fγ is adjusted to fc even if there is no pressure fluctuation due to the inclination of the block, and the shearing force becomes different before and after the block, resulting in uneven wear.
2.2 (h + 0.5α) should be avoided at the worst point, but the length A of the block surface is A> 2.2 (h +
In the range of 0.5α), the block size becomes too large and the number of pitches becomes small, and the all-season property as a block pattern, that is, the drainage function and the traction property becomes poor and it becomes unpractical. That is, the smaller the length A of the block surface, the better in this case. In order to obtain the effect of reducing uneven wear, the length A of the block surface is A <2.0 × (h +
It was found to be 0.5α).

From these results, as described above, the smaller one has the relation of A> 1.5 (h + 0.5α) as described above, and the length A of the block surface is 1.5 (h + 0) after all. ．
The range of 5α) <A <2.0 (h + 0.5α) is required.

According to the present invention, a carcass containing a pressure gas therein and a reinforcing belt layer of at least three layers extending in the tire circumferential direction crossing the fiber direction of the carcass ply are provided on the outer side in the radial direction together with the rim wheel. In a radial tire for deep groove type heavy load in which a tread having blocks divided by vertical grooves and lateral grooves is arranged further on the outer side in the radial direction of this belt layer, the groove depth from the block surface to the groove bottom is h, from the groove bottom. Assuming that the thickness of the rubber layer up to the upper end of the belt is α and the length of the block surface is A, the relationship between the block height and the block surface dimension is 1.5 (h + 0.5α) <A <2.0 ( h + 0.5α) (However, the length A of the block surface is A = ΣS / W−ΣW
Represented by _G , ΣS is the total width of the tread per 1 block pitch length, that is, the step of 1 pitch (1 block in the circumferential direction) included in the distance W (width of the tread portion) between the tread ends on both sides of the tread. The surface area of the surface portion, ΣW _G, is the total width of the vertical grooves in the tire width direction. ) Is a deep groove type radial tire for heavy load.

The shape of the block is generally not a square or a circle, but a rectangle. At this time, the magnitude of the shearing force fγ is not the same on any side, and it is researched that it occurs largely on a long side. I was able to know the result. Therefore, in order to reduce the heel and toe, it is necessary to arrange the blocks such that the shorter side, that is, the block length A is along the tire circumferential direction, and the longer side, that is, the block width B is along the tire width direction. Yes becomes effective.

[0026]

According to the present invention, the relationship between the height of the block and the dimension of the block surface is 1.5 (h + 0.5α) <A <2.0 (h + 0.5α) (where the block surface length A is A = ΣS / W-ΣW
Represented by _G , ΣS is the total width of the tread per 1 block pitch length, that is, the step of 1 pitch (1 block in the circumferential direction) included in the distance W (width of the tread portion) between the tread ends on both sides of the tread. The surface area of the surface portion, ΣW _G, is the total width of the vertical grooves in the tire width direction. Since the deep groove radial tire for heavy load described in (4) is used, it is possible to improve uneven wear resistance while maintaining the drainage function and the traction function that the block pattern originally should have.

[0027]

[Examples] Under the design conditions shown in the following Table 1, a tire size of 11R24.5 14PR and a rim size of 8.25 × 2
A 4.5 tire was prototyped, mounted on the drive shaft of the vehicle, and after running about 60,000 miles on a road with a pavement ratio of 100%,
The uneven wear resistance was evaluated.

All the test tires have the tread pattern shown in FIG. 1, and the width W of the tire tread is 210 m.
m, the groove depth h of the lateral groove is 22.0 mm, the outer diameter of the tire is 11
It is 14 mm. In the table, L _p is the block pitch length.

As for the evaluation of the uneven wear state, as shown in FIG. 6, two blocks near the center of the tread among the four block rows shown in FIG. 1 are arranged with lateral grooves 5 in the tire circumferential direction. The step y between the toe portion T at the rear end of the front block 1A of one block 1 and the heel portion H at the front end of the rear block 1B was compared. Braking performance is 4 when a test tire is mounted on all axles in a wet road test that specifies the road surface condition and water depth.
We compared the braking distance when the vehicle was locked at 0 km / h. In all cases, the tire of Comparative Example 1 was set as 100 and displayed as an index. The smaller the value, the better.

[0030]

[Table 1]

From Table 1, as compared with the tire of Comparative Example 1 in which 2.0 (h + 0.5α) <A and Comparative Example 2 in which 1.5(h+0.5α)> A, 1.5 ( h + 0.5α) <
It is recognized that the tires of this example satisfying A <2.0 (h + 0.5α) have good uneven wear resistance. Also, 1.5 (h + 0.5α) <A <2.0 (h +
The tire of Comparative Example 3 satisfying 0.5α) but having B / A of more than 1 is poor in the effect of uneven wear resistance as compared with the embodiment having B / A of less than 1. On the other hand, B / A is 1
Since the tires of the examples exhibiting a remarkable effect of uneven wear resistance, the block has the longer side, that is, the block width B, and the shorter side in the tire width direction, that is, the block length. It is desirable to arrange A in the tire circumferential direction.

[0032]

As described above, according to the present invention, the relationship between the height of the block and the dimension of the block surface is 1.5 (h + 0.5α) <A <2.0 (h + 0.5α) The length is A = ΣS / W−ΣW _G
Where ΣS is the surface area of the tread portion for one pitch (one block in the circumferential direction) included in the distance W between the ground contact ends on both sides of the tread, and ΣW _G is the total width of the longitudinal grooves in the tire width direction. . Since the deep groove radial tire for heavy load described in (4) is used, it is possible to improve uneven wear resistance while maintaining the drainage function and the traction function that the block pattern originally should have.

[Brief description of drawings]

FIG. 1 is a schematic view showing a block-shaped tread pattern.

FIG. 2 is an enlarged cross-sectional view of the relevant part.

FIG. 3 is a schematic cross-sectional view showing a ground pressure distribution SD of a block during driving (acceleration).

FIG. 4 is a schematic sectional view showing a ground contact pressure distribution SD of a block during braking or general coasting.

FIG. 5 is a diagram showing a relationship between A / (h + 0.5α) and k _s × Δγ and a relationship between A / (h + 0.5α) and shear force fγ.

FIG. 6 is a schematic cross-sectional view showing an uneven wear state of a block.

[Explanation of symbols]

1 block 1a surface 1b base 2 a groove bottom 3 belt layer 4 rubber layer 5 lateral grooves 6 longitudinal grooves 7 carcass ply SD ground pressure distribution fc circumferential force fγ shear upstream DA circumferential force of UA circumferential force downstream k _s Circumferential shear rigidity Δγ Increase in shear strain due to inclination A Block length B Block width

Claims (2)

[Claims] 1. A carcass containing a pressure gas inside, together with a rim wheel, and at least three reinforcing belt layers extending radially outward of the carcass that extend in the tire circumferential direction and intersect the fiber direction of the carcass ply. In a deep groove type radial tire for heavy load in which a tread having blocks divided by vertical grooves and lateral grooves is arranged further on the outer side in the radial direction of the layer, the groove depth from the block surface to the groove bottom is h, and the groove bottom to the belt upper end. Where the thickness of the rubber layer up to and the length of the block surface are A, the relationship between the height of the block and the dimension of the block surface is 1.5 (h + 0.5α) <A <2.0 (h + 0. 5α) (However, the length of the block surface is A = ΣS / W−ΣW _G
Where ΣS is the surface area of the tread portion for one pitch (one block in the circumferential direction) included in the distance W between the ground contact ends on both sides of the tread, and ΣW _G is the total width of the longitudinal grooves in the tire width direction. . ) Is a deep groove type radial tire for heavy loads. 2. The deep groove type radial tire for heavy load according to claim 1, wherein when the width B of the block sandwiched by the longitudinal grooves is represented by S / A (S is the surface area of one block), B <A.