JPH07186630A - Pneumatic tire - Google Patents

Abstract

PURPOSE:To develop the sure heel and toe abrasion suppressing performance by forming the projection in the block circumferemtial direction continuously or discontinu ously in the vicinity of the end part on the pneumatic tire equator surface side and allowing the equator surface side at the stepping-on edge of the block to burden the grounded pressure in comparison with on the shoulder side. CONSTITUTION:As for the block 16 of a new product 16, the part which projects to the outside in the tire radial direction. Except the projection 20 on the tire equator surface side, is positioned at the center part in the tire circumferential direction of the block 16, and the max. grounded pressure position is the center part in the circumferential direction of the block 16 at the part excluding the projection 20 on the tire equator surface side. When a tire rolls, the stepping end side of the block 16 slides much for a road surface in comparison with the center part in the circumferential direction of the block 16. As for the rate (a) for the length in the tire circumferential direction which ranges from the A point to the B point, the heel and toe resistance performance after the initial stage of abrasion is developed by the projection formed in the block circumferential direction when the ratio between the height values. T1 and T2 at the A and B points at the end in the tread circumferential dire on the stepping-on side from the groove bottom is 1.0-0.5a.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire having a block pattern, and more particularly to a pneumatic tire having a high heel and toe wear suppressing effect.

[0002]

2. Description of the Related Art In a pneumatic tire having a block pattern, when the block surface has the same radius of curvature as the tire outer radius in a cross section perpendicular to the tire rotation axis, when the block is worn on the kick-out end side, However, the contact pressure between the stepped-in end and the kicked-out end, which has been the same until then, is imbalanced, and uneven wear called heel-and-toe wear occurs. When this heel-and-toe wear occurs, not only the appearance is deteriorated but also the grip ability of the tire is deteriorated.

In order to suppress the heel-and-toe wear, a proposal is made to make the step-end end side of the block slippery so as to promote the wear on the step-end end side and delay the occurrence of the heel-and-toe wear (actually, However, there is a problem that uneven wear further develops in some cases.

Regarding the progress of heel-and-toe wear, the amount of wear on the side of the leading edge is small and the amount of wear on the side of the kicking side is large. In order to suppress this heel-and-toe wear, it can be said that the wear at the kick-out end is less and the wear at the step-in end is more.

On the basis of this idea, the inventor has found that a pneumatic tire in which the outer contour of the block perpendicular to the tire rotation axis is formed in an arc shape having a smaller curvature than the outer diameter contour of the tire (Japanese Patent Application No. 91137) was proposed.

[0006] When this pneumatic tire rotates, the stepping end side of the block, which has a low height and a low ground contact pressure, slides a lot on the road surface. It is possible to delay the progress of heel and toe wear after the initial stage of wear.

Although the above-mentioned proposal has made it possible to delay the progress of heel-and-toe wear after the initial stage of wear, although it is effective depending on how the initial block shape is taken, it does not reach a sufficiently satisfactory level. There were cases.

[0008]

SUMMARY OF THE INVENTION In consideration of the above facts, the present invention ensures reliable heel resistance regardless of the initial block shape.
It is an object of the present invention to provide a pneumatic tire capable of exhibiting and-toe performance.

[0009]

According to various investigations and studies by the inventor, in a tire in which the effect of delaying the progress of heel-and-toe wear cannot be sufficiently exerted, the effect of promoting wear at the stepped end of the block is small. That is, it was found that the amount of slippage at the stepped end was small.

The present invention has been made in view of the above facts.
There are a plurality of main grooves extending in the tire circumferential direction and the main groove.
A plurality of blocks partitioned by intersecting lateral grooves
In preparation for red, the shoulder side end of the block is imaginary
The radius of curvature of the contour line of the tread circumferential direction is r, and the shoulder is
The tire circumferential length of the side end is L, and the tire outer radius is
R _T, The distance from the tire rotation axis to the groove bottom of the lateral groove is R
_BThe tire circumference on the step-in side at the shoulder side end
The direction end A and the block are projected most outward in the radial direction of the tire.
The tire circumferential length between the point B and the point B is aL (a is the above
When the tire circumferential length L of the shoulder end is set to 1
From the tire circumferential end A on the stepping side to the point B
Indicates a percentage. However, 0.5 ≦ a ≦ 1.0), tire rotation
The tread circumferential end A on the stepping side seen from the center and the
The angle sandwiching the point B is θ (= aL / R_T: Unit is radia
), The tray on the stepping side measured from the groove bottom of the lateral groove.
The height of the end A in the circumferential direction is T₁, Measured from the groove bottom of the lateral groove
The height of the point B₂And the tread on the stepping side
Height T of edge A in the circumferential direction₁And the height T of the point B₂Ratio T
₁/ T₂= When X is represented by the following formula 2, the value of X is
Circumferential direction of the tread on the stepping side when it becomes 1-0.5a
Virtual tread circumferential contour line passing through the end A and the point B
And the stepping when the value of X becomes 1-0.1a
Side virtual tread passing through the end A in the tread circumferential direction and the point B
In the area between the contour line in the circumferential direction and the shoulder side
The actual tread circumferential contour line at the end is set to the tire radial outside
For pneumatic tires formed with a smooth curve that is convex to
In the vicinity of the tire equatorial side end of the tread of the block
, A continuous or discontinuous projection is provided in the block circumferential direction.
It is characterized by.

[0011]

[Equation 2]

The above equation 2 is derived as follows. As shown in FIGS. 13 and 14, the straight line connecting the tire rotation axis O and the point B at which the block is convex most outward in the tire radial direction is the x-axis.

The virtual tread circumferential contour line (curvature r) is
Expressed by the formula (1) below, stepping on the tire rotation axis and block
The straight line passing through the end A in the circumferential direction of the side tread is the following formula (2).
, The intersection of the two, that is,
The position of the edge A in the circumferential direction is calculated from Equation (1) and Equation (2).
And then T₁And T₂, T₁And T ₂
And the ratio, that is, X is obtained.

{X- (R _T -r)} ² + y ² = r ² (1) y = xtan θ (2) Substituting the equation (2) into the equation (1), x ² (1 + tan ² θ) −2 ( _RT −r) x + ( _RT ²
-2R _T r) = 0

[0015]

[Equation 3]

[0016]

[Equation 4]

Here,

[0018]

[Equation 5]

Therefore,

[0020]

[Equation 6]

Since OA = R _B + T ₁ ,

[0022]

[Equation 7]

Since T ₂ = R _T −R _B ,

[0024]

[Equation 8]

[0025]

In the block of the pneumatic tire of the present invention, except for the end portion on the equatorial plane side of the tire, the position of the point B which is most outwardly convex in the radial direction of the tire is from the center portion in the tire circumferential direction of the block to the kicking end. Since it is located between the blocks, except for the protrusion on the equatorial plane side of the tire, the maximum position of the ground contact pressure from the time of new to the initial stage of wear is from the circumferential center of the block to the kick-out end.

Therefore, when the pneumatic tire rotates,
The stepped end side of the block, which has a low height and a low ground contact pressure, slides a lot on the road surface, which increases the speed of wear on the stepped end side of the block and increases the heel and・ The progress of toe wear can be delayed.

However, this effect is large or small depending on the convex shape of the block surface shape. Therefore, regardless of the convex shape, in order to always exert the effect of abrading a large amount of the stepped end, protrusions are provided continuously or discontinuously in the block circumferential direction in the vicinity of the end portion on the tire equatorial plane side. As a result, at the stepped end of the block, the tire equatorial side bears more ground contact pressure, but the contact pressure on the shoulder side becomes even lower, further promoting the progress of wear from the stepped end, and suppressing heel and toe wear. It is possible to obtain the effect more reliably.

[0028]

EXAMPLE An example of the pneumatic tire of the present invention will be described with reference to FIGS.

As shown in FIGS. 1 and 2, the tread 12 of the pneumatic tire 10 (tire size 11R22.5) of this embodiment is provided with four circumferential main grooves 13 in the circumferential direction at a predetermined pitch. A plurality of blocks 16 defined by the lateral grooves 14 are provided to form a so-called block pattern. The internal structure of the pneumatic tire 10 according to the present embodiment is a general structure, so details of the internal structure will be omitted.

On the tread of the block 16, the tire equatorial plane C
The protrusion 20 is formed at the end on the L side.

Explaining the overall shape of the block 16 excluding the protrusions 20 with reference to FIG. 1, the shape of the tread surface contour line of the block 16 in a cross section perpendicular to the tire rotation axis is convex in the tire radial direction. It is formed by a single arc, and the most convex portion is the central portion in the tire circumferential direction.

The block 16 has a length L in the tire circumferential direction of 50 mm, a width W in the tire axial direction of 35 mm, and a height T _{1 of the} end portion in the tire circumferential direction measured from the groove bottom of the lateral groove 14 (however, the projection 2
16.6 mm, and the height T ₂ (excluding the protrusion 20) of the most convex center portion of the tire in the circumferential direction of the tire is 1
It is 7.6 mm.

On the other hand, the projection 20 formed at the end of the block 16 on the tire equatorial plane CL side has a semi-cylindrical cross-section in the longitudinal direction and is continuous along the block end at a constant height. The protrusion 20 has a width w of 4 mm and a height h of 2 mm.

The top of the protrusion 20 does not have to be parallel to the surface of the block 16, but its width w and height h are the width W of the block 16 and the height T ₂ at the most convex portion. , 0.08 ≦ h / T ₂ ≦ 0.3 and 0.
It is necessary to satisfy 1 ≦ w / W ≦ 0.7.

Next, the operation of this embodiment will be described. As shown in FIG. 1, in the block 16 at the time of a new article of the present embodiment, except for the protrusion 20 on the tire equatorial plane CL side, the most convex portion in the radial direction of the tire is the central portion in the tire circumferential direction of the block 16. Since it is located, the maximum position of the ground contact pressure from the time of new article to the initial stage of wear is the central portion in the circumferential direction of the block 16 excluding the protrusion 20 on the tire equatorial plane side (see FIG. 3).

When the pneumatic tire 10 rotates, the stepped end side of the block 16, which is a portion having a low height and a low ground contact pressure, slides more on the road surface than at the central portion of the block 16 in the circumferential direction. The rate of progress of wear on the stepped end side of the block 16 is increased, and as shown in FIG. 4, the progress of heel-and-toe wear after the initial stage of wear can be delayed.

However, since the block 16 is provided with the protrusion 20 at the end portion on the tire equatorial plane CL side, looking at the ground pressure distribution in the tire width direction, the action of the protrusion 20 at the tread end A causes the equatorial plane to move. The CL side becomes higher and the anti-equatorial side becomes lower.

Since the stepping end wear for delaying the heel-and-toe wear progresses from the antiequatorial surface CL side of the stepping end A, lowering the ground contact pressure of this part means that the slippage of the part on the road surface is prevented. By increasing the size, the progress of wear from the stepped end can be further promoted, and the heel-and-toe wear suppressing effect can be increased.

In the dimensional relationship between the block 16 and the protrusion 20, if h / T ₂ is smaller than 0.08,
The ground contact pressure on the anti-equatorial surface side cannot be reduced sufficiently, and the desired heel-and-toe wear suppressing effect does not appear.

If h / T ₂ is larger than 0.3, the anti-equatorial surface side does not come into contact with the road surface, and the wear on the stepping end A side does not easily proceed. Therefore, the desired heel and toe wear is again obtained. The suppression effect cannot be obtained.

If w / W is smaller than 0.1, the ground contact pressure on the side opposite to the equatorial plane cannot be sufficiently reduced, and the desired heel-and-toe wear suppressing effect does not appear.

If w / W is larger than 0.7, the anti-equatorial surface side does not come into contact with the road surface, and it becomes difficult for the wear on the stepped end A side to proceed. Therefore, the desired heel-and-toe wear suppression is also achieved here. You can't get the effect.

Test Example 1 A pneumatic tire according to the present invention, a pneumatic tire according to a comparative example, and a pneumatic tire according to a conventional example were prototyped and tested for heel-and-toe wear resistance in an actual vehicle. .

The pneumatic tire according to the present invention is a tire having a block having the shape shown in FIG. 1 described above. As shown in FIG. 5, the pneumatic tire according to the comparative example includes a block 24 obtained by removing the protrusions from the block shown in FIG. Further, the pneumatic tire according to the conventional example is shown in FIG.
As shown in (1), the tire has a block 22 having a constant height T (17.6 mm). The blocks of each test tire had a tire circumferential length L of 50 mm and a width W.
Are all 35 mm.

The size of each test tire was 11
R22.5 and the internal pressure is 8.5 kg / cm ² .

The heel and toe abrasion resistance test was conducted as follows.
2000 with the test tire mounted on the front wheel of the actual vehicle (2D4)
After running for 0 km, the volume of rubber disappeared due to heel-and-toe wear after running (hatched portion S in FIG. 7) was measured.

The test results are shown in Table 1 below in the form of an index with the amount of lost rubber of the conventional pneumatic tire being 100. The smaller the value, the better the heel and toe wear resistance.

[0048]

[Table 1]

From the test results shown in Table 1 above, it is clear that the pneumatic tires of the examples to which the present invention is applied have a higher effect of suppressing heel-and-toe wear due to the action of the protrusions. .

In the above embodiment, the protrusion 2 having a constant height is used.
0 is continuously formed in the tire equatorial plane CL end portion of the block 16 in the circumferential direction, but the present invention is not limited to this, and the central portion may be removed as shown in FIG. It may be provided intermittently in the circumferential direction as long as it is possible to reduce the ground contact pressure on the tire equatorial plane side, and as shown in FIG. 10, a protrusion 20 is added to the intermediate portion in the tire axial direction of the block 16. Is also good.

Further, although the height of the protrusion 20 is constant in the above-described embodiment, the present invention is not limited to this, and it is possible to reduce the ground contact pressure on the side opposite to the equatorial plane of the tire on the stepping end A side. For example, as shown in FIG. 9, the central portion in the tire circumferential direction may be lowered. The block 1 is located at the center of the block 16 in the tire circumferential direction.
When there is a point B where 6 is the most outwardly convex in the radial direction of the tire, it is not necessary to consider the tire mounting direction and the tire rotation direction for the heel-and-toe wear suppressing effect.

If the pneumatic tire 10 does not have a directional pattern, the protrusion 20 may be provided at least on the stepping-in end portion A side, and need not necessarily be provided on the kicking-out end portion side. .

When the pneumatic tire has a directional pattern, as shown in FIG. 11, the point B at which the block 16 is most outwardly convex in the radial direction of the tire is kicked out C.
Heal and more effectively by shifting to the side
Toe wear can be suppressed, and the progress of wear of the block 16 is as shown in FIG.

Further, in the above-described embodiment, the outer contour of the block 16 in the cross section perpendicular to the axis of rotation is constituted by a single curvature, but the present invention is not limited to this, and it is smooth and convex outward in the tire radial direction. The shape of the curve does not matter as long as it is a curve.

Since heel-and-toe wear is likely to occur in the shoulder-side block, if the protrusion 20 is formed on the shoulder-side block 16, the heel-and-toe wear is suppressed when the tire as a whole is seen. The effect is sufficient, and it is not always necessary to form the protrusion 20 on all blocks.

[0056]

As described above, since the pneumatic tire of the present invention has the above-mentioned constitution, it has an excellent effect that it can surely exhibit heel and toe resistance regardless of the initial block shape. .

[Brief description of drawings]

FIG. 1 is a perspective view of a block of a pneumatic tire according to an embodiment of the present invention.

FIG. 2 is a cross-section taken along the axis of a tread of a pneumatic tire according to an embodiment of the present invention.

FIG. 3 is a graph showing a change in ground contact pressure of a block of a pneumatic tire according to an embodiment of the present invention.

4 is a cross-sectional view showing the progress of wear of the block shown in FIG. 1 at right angles to the tire axis.

FIG. 5 is a perspective view of a block of a comparative example.

FIG. 6 is a perspective view of a block having a constant height.

FIG. 7 is a cross-sectional view showing a block subjected to heel-and-toe wear.

FIG. 8 is a perspective view of a block according to another embodiment of the present invention.

FIG. 9 is a perspective view of a block according to still another embodiment of the present invention.

FIG. 10 is a perspective view of a block according to still another embodiment of the present invention.

FIG. 11 is a sectional view of a block according to another embodiment of the present invention, the cross section being perpendicular to the axis line.

12 is a cross-sectional view showing the progress of wear of the block shown in FIG. 11, which is perpendicular to the axis of the block.

FIG. 13 is a cross-sectional view perpendicular to the axis showing various dimensions of the block of the pneumatic tire of the present invention.

FIG. 14 is a cross-sectional view perpendicular to an axis showing various dimensions of the pneumatic tire of the present invention.

[Explanation of symbols]

 10 Pneumatic Tire 12 Tread 13 Circumferential Main Groove 14 Lateral Groove 16 Block 20 Protrusion

Claims (1)

[Claims] 1. A tread is provided with a plurality of blocks partitioned by a plurality of main grooves extending in a tire circumferential direction and lateral grooves intersecting with the main grooves, and a virtual tread circumferential direction contour line of a shoulder side end of the block is provided. The radius of curvature is r, the tire circumferential length of the shoulder side end is L, the tire outer radius is R _T , the distance from the tire rotation axis to the groove bottom of the lateral groove is R _B , and the shoulder side end is on the stepping side. The tire circumferential direction length A between the tire circumferential direction end A and the point B at which the block is convex most outward in the tire radial direction, where a is the tire circumferential direction length L of the shoulder side end portion and The ratio from the tire circumferential direction end A on the stepping side to the point B is shown below.
0.5 ≦ a ≦ 1.0), θ (= aL / _RT : unit is radian) between the tread circumferential end A on the stepping side and the point B viewed from the tire rotation center, and the lateral groove The height of the tread circumferential edge A on the stepping side measured from the groove bottom of T is T ₁ , the height of the point B measured from the groove bottom of the lateral groove is T _2, and the tread circumferential edge A on the tread side is Height T
_When the ratio T ₁ / T ₂ = X between ₁ and the height T ₂ of the point B is expressed by the following mathematical expression 1, the tread on the stepping side when the value of X is 1-0.5a A virtual tread circumferential contour line passing through the circumferential end A and the point B, and a virtual route passing through the tread circumferential end A on the stepping side and the point B when the value of X is 1-0.1a. In the region between the tread circumferential direction contour line and the area between the tread circumferential direction contour line, the actual tread circumferential direction contour line of the shoulder side end formed in a smooth curve that is convex outward in the tire radial direction, in the pneumatic tire, A pneumatic tire characterized in that a continuous or discontinuous projection is provided in the block circumferential direction in the vicinity of the tire equatorial side end portion of the tread surface. [Equation 1]