JPH05162512A - Pneumatic tire - Google Patents

Abstract

PURPOSE:To provide a pneumatic tire, which can improve the noise performance without hindering the operation stability and the abrasion resistance. CONSTITUTION:The bottom of a depth alpha1 in a length beta1 of an end area of a cuff 8 is raised so as to satisfy that alpha1/alpha2<=0.5 with respect to a depth alpha2 of a cuff main frame. A length beta1 of the end area of the cuff 8 is set so as to satisfy that beta1/beta2<=0.4 and beta1>=2.0mm with respect to the full length beta2 of the cuff 8 within the tire grounding width W. Widths a1-a3, b1-b3, c1-c3 of the tire circumferential direction of small block components blocked by the cuff 8 are different from each other, and a ratio gamma of the maximum value thereof and the minimum value thereof is set so as to satisfy the condition that gamma<=1.65.

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 tread surface block provided with a kerf for reducing pattern noise.

[0002]

2. Description of the Related Art Conventionally, among the noises emitted by tires, there is a method of reducing block rigidity as a technique for reducing pattern noise. As one of the methods, there is a method of dividing a block on the tread surface with a kerf.

[0003]

However, in the conventional tire, since the blocks are divided by the kerf having a uniform depth, the rigidity of the block is remarkably reduced particularly at the edge portion where the kerf contacts the groove, and the steering stability is improved. There is a problem in that the resistance to uneven wear is reduced as well as the deterioration. As a countermeasure against this, it is conceivable to provide an independent kerf that does not join both ends of the kerf to the groove, but in this case, it is possible to suppress deterioration of block rigidity and maintain steering stability and uneven wear resistance. The pattern noise increases due to the air pumping phenomenon caused by the air pushed into the kerf.

Further, since the widths of the small block components separated by the kerf are uniform, the frequency dispersion effect due to the pitch variation cannot be obtained, and the noise performance reducing effect cannot be sufficiently enhanced. It was An object of the present invention is to provide a pneumatic tire capable of improving noise performance without impairing steering stability and uneven wear resistance.

[0005]

Means for Solving the Problems Pneumatic device according to the present invention
The ear is at least on the block formed on the tread surface.
Tire width by connecting one end to the groove adjacent to the block
In a pneumatic tire with a calf extending in the direction,
The length β of the end region where the kerf connects to the groove ₁Oke
Depth α₁Is raised shallowly and this depth α₁The power
Depth of the main body α₂Against α₁/ Α₂≦ 0.5,
Length of the end area β₁Β₁If ≧ 2.0 mm
Is the total length β of the calf within the tire ground contact width₂To
For β₁/ Β₂≤0.4 and separate into the calf
The width of the small block component in the tire circumferential direction varies irregularly.
Normalize, the maximum width of this small block component in the tire circumferential direction
It is characterized in that the ratio γ between the value and the minimum value is set to γ ≦ 1.65.
To do.

In the present invention, since the kerf provided for reducing the pattern noise has a structure in which at least one end is connected to the groove, no air pumping phenomenon is caused and the length β of the end portion where the kerf contacts the groove is β. with shallow raised the depth alpha ₁ in _1, this depth alpha ₁
By setting the above to the depth α ₂ of the kerf main body, it is possible to maintain steering stability and uneven wear resistance equivalent to those in the case of a block without a kerf.

The uneven wear resistance is impaired by irregularly varying the widths of the small block components separated by the kerfs in the tire circumferential direction and setting the ratio γ between the maximum value and the minimum value in the above range. It is possible to enhance the frequency dispersion effect due to the pitch variation and improve the noise performance. Hereinafter, the configuration of the present invention will be described with reference to the accompanying drawings.

In FIG. 1, the tread surface is provided with a main groove 1 and a sub groove 2 extending in the tire circumferential direction, and a lug groove 3 extending in the tread width direction. As a result, the blocks 4, 5, 6 and the rib 7 are formed separately on the tread surface. This block 4, 5,
Each of the ribs 6 and the ribs 7 is provided with a kerf 8 having at least one end connected to the groove. The kerf 8 is formed by a notch having a width of 1.5 mm or less, which is narrower than the sub groove 2 and the lug groove 3. W is the ground contact width of the tread surface, and this ground contact width W is the air pressure set by JATMA according to JATM.
It is the width when the load is 80% of the maximum load specified by A.

[0009] The present in invention, kerf 8 alpha ₁ / alpha ₂ ≦ depth alpha ₁ of the end section to be connected is the depth alpha ₂ of the calf body relative to the sub-grooves 2 in the tire circumferential direction 0. The bottom is raised to 5. And, the length β ₁ of this end region is β
_{In addition to 1} ≧ 2.0 mm, β ₁ / β ₂ ≦ 0.4 with respect to the total length β ₂ of the kerf 8 within the tire ground contact width W. By providing such a raised bottom portion of the kerf end, it is possible to maintain both steering stability and uneven wear resistance at substantially the same level as a tire made of a block without a kerf. However, α ₁ / α ₂ >
When it is 0.5, the block rigidity of the edge portion becomes low, so that it is not possible to sufficiently secure steering stability and uneven wear resistance. In addition, β ₁ / β ₂ ≦ 0.4 and β ₁ ≧ 2.0
However, if β ₁ / β ₂ > 0.4, the block rigidity is not sufficiently reduced and the noise reduction effect is weakened.
_{This is because if 1} <2.0 mm, the block rigidity cannot be ensured, and moreover, cracks may occur at the bottom raised portion. The lengths of β ₁ and β ₂ are the actual lengths along the kerf.

On the other hand, in the block 4, the block widths A, B and C are made different from each other so that the frequency dispersion effect due to the pitch variation is given. At this time, the widths a _{1 to} a ₃ , b _{1 to} b ₃ , c _{1 to} c ₃ in the tire circumferential direction of the small block components separated by the kerf 8 are irregularly different, and the maximum value and the minimum value thereof are different from each other. By setting the ratio (maximum value / minimum value) γ such that γ ≦ 1.65,
It is possible to enhance the frequency dispersion effect by the pitch variation and improve the noise performance without impairing the uneven wear resistance. However, the small block component widths a _{1 to} a ₁
The ratio γ between the maximum value and the minimum value of ₃ , b _{1 to} b ₃ and c _{1 to} c _3.
Is less than 1.40, the effect of improving the noise performance cannot be sufficiently obtained, and if it exceeds 1.60, uneven wear resistance may decrease, so 1.40 ≦ γ ≦ 1. 60
It is good to set. Here, the width of the small block component in the tire circumferential direction refers to the circumferential length L of each pitch at the midpoint position of the maximum length in the block width direction.

In the present invention, the above-mentioned raising of the kerf end portion does not necessarily have to be applied to all blocks and all ribs of the tread surface, and at least particularly to the shoulder side portion where pattern noise is likely to occur. I wish I had done it. The bottom of the kerf may be raised intermittently in the tire circumferential direction.

[0012]

EXAMPLES Tires of the present invention and comparative tires 1 to 3 having tire sizes of 205 / 65R15 and different kerf dimensions were manufactured as follows. Tire tire of the present invention Tread pattern: FIG. 1 (with kerf) Arrangement of kerfs: a ₁ ≠ a ₂ ≠ a ₃ , b ₁ ≠ b ₂ ≠ b ₃ , c
₁ ≠ c ₂ ≠ c ₃ α ₁ / α ₂ = 0.4, β ₁ / β ₂ = 0.25, γ = 1.
6

Comparative tire 1 tread pattern: FIG. 1 (without kerf) Comparative tire 2 tread pattern: FIG. 1 (with kerf) Calf arrangement: a ₁ = a ₂ = a ₃ , b ₁ = b ₂ = b ₃ , c
₁ = c ₂ = c ₃ α ₁ / α ₂ = 1.0, β ₁ / β ₂ = 0, γ = 1.0 Comparative tire 3 tread pattern: Fig. 1 (with kerf) Calf arrangement: a ₁ = a ₂ = A ₃ , b ₁ = b ₂ = b ₃ , c
₁ = c ₂ = c ₃ α ₁ / α ₂ = 0.4, β ₁ / β ₂ = 0.25, γ = 1.
0 For these tires of the present invention and comparative tires 1 to 3,
The noise performance, steering stability, and uneven wear resistance were examined by the following methods.

Noise performance: A test tire was mounted on a 2000 cc passenger car, vehicle interior noise data due to pattern noise during straight running was measured, and evaluated by the reciprocal of the measured value. Indicated. The larger the index value, the better the noise performance.

Steering stability: A test tire was mounted on a 2000 cc passenger car, and steering stability was evaluated by a feeling test by a panelist (test driver). The results are shown by an index with the evaluation value of comparative tire 1 being 100. The larger the index value, the better the steering stability.

Uneven wear resistance: A test tire was mounted on a 2000 cc passenger car, and the appearance of the tire after running 10,000 km was visually evaluated. As a result, the evaluation value of comparative tire 1 is 10
It is shown by an index of 0. The larger this index value, the better the uneven wear resistance.

[0017] As is clear from Table 1, the tires of the present invention were able to improve noise performance with almost no loss of steering stability and uneven wear resistance as compared with Comparative Tires 1 to 3.

Next, in the above-mentioned tire of the present invention, α ₁ /
α ₂ , β ₁ / β ₂ , and γ were changed respectively. Changes in uneven wear resistance or noise performance in this case are shown in FIGS. As a result, as shown in FIG. 3, α ₁ / α ₂ is 0.5
When it was below, the uneven wear resistance was excellent. Also, FIG.
As shown in, β ₁ / β ₂ is 0.4 or less (where β ₁ ≧
When it was 2.0 mm), the noise performance was excellent. Further, as shown in FIG. 5, when γ was 1.65 or less, the uneven wear resistance was excellent.

[0019]

As described above, according to the present invention, the depth α ₁ at the length β ₁ of the end region where the kerf connects to the groove is set.
And the depth α ₁ is set to α ₁ / α ₂ ≦ 0.5 with respect to the depth α ₂ of the kerf body, and the length β ₁ of the end region is set to β ₁ ≧ 2.0 mm. In addition, the total length β _{2 of the} kerf within the tire ground contact width is β ₁ /
β ₂ ≦ 0.4, and the width of the small block component divided in the kerf in the tire circumferential direction is irregularly varied, and the ratio between the maximum value and the minimum value of the tire circumferential width of the small block component Since γ is set to γ ≦ 1.65, the noise performance can be improved as compared with the conventional case without impairing the steering stability and the uneven wear resistance.

[Brief description of drawings]

FIG. 1 is a development view showing a tread surface of a pneumatic tire according to the present invention.

FIG. 2 is a partially enlarged cross-sectional view showing the kerf portion of FIG. 1 in an extracted manner.

FIG. 3 is a graph showing the relationship between α ₁ / α ₂ and uneven wear resistance.

FIG. 4 is a graph showing a relationship between β ₁ / β ₂ and noise performance.

FIG. 5 is a graph showing the relationship between γ and uneven wear resistance.

[Explanation of sign]

 1 Main groove 2 Sub groove 3 Lug groove 4, 5, 6 Block 7 Rib 8 Calf

Claims (1)

[Claims] 1. A pneumatic tire in which a block formed on a tread surface is provided with a kerf having at least one end connected to a groove adjacent to the block and extending in a tire width direction, an end region where the kerf is connected to the groove. Length of β ₁
And the depth α ₁ at
₁ for the depth of the calf body α ₂ α ₁ / α ₂ ≦ 0.5
And the length β ₁ of the end region is β ₁ ≧ 2.0 mm, and the total length β of the kerf within the tire ground contact width is
_{2 is set} to β ₁ / β ₂ ≦ 0.4, and the width of the small block component divided in the kerf in the tire circumferential direction is irregularly changed, and the maximum width of the small block component in the tire circumferential direction is increased. A pneumatic tire having a ratio γ between the value and the minimum value of γ ≦ 1.65.