JP3913044B2 - Pneumatic tire - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire that reduces outside noise generated when the tire travels.
[0002]
[Prior art]
As the noise regulations become stricter, it is required to further reduce the outside noise generated when the tires are traveling. It is said that the noise caused by the block pattern is particularly large as the outside noise generated by the tire. The pattern noise due to the block pattern is noise generated mainly by an impact force in which blocks arranged in the tire circumferential direction are successively hit against the road surface. Therefore, conventionally, as a method of reducing this pattern noise, the pitch of the blocks arranged in the tire circumferential direction is randomly changed, and the impact sound generated by each block is dispersed to reduce the noise by white noise. The thing was the main.
[0003]
However, although the method using white noise reduces noise as a sense of sound, it has not been sufficient to reduce the absolute value of noise.
[0004]
[Problems to be solved by the invention]
An object of the present invention is to provide a pneumatic tire that reduces the absolute value of vehicle exterior noise generated by the tire.
[0005]
[Means for Solving the Problems]
The pneumatic tire of the present invention that achieves the above object is provided with three main grooves extending linearly in the tire circumferential direction on the tread surface, and the main grooves are spaced apart by a plurality of sub-grooves in the tire circumferential direction. In a pneumatic tire in which a block row is formed by communicating , both outer sides of the three main grooves are formed as ribs, the sub grooves are inclined obliquely with respect to the tire circumferential direction, and the sub grooves The groove area ratio in the total groove area is 5 to 30%, and the number of the sub-grooves distributed in the grounding region is 8 to 16.
[0006]
As described above, in the tire in which the block row partitioned by the sub grooves is formed between the three linear main grooves, the ratio of the groove area to the total groove area of the sub grooves, and the sub grooves are within the ground contact region. Since the number of distributed tires is in a specific range, when the tread surface is deformed when the tire contacts the ground, the block is prevented from slipping against the road surface by deforming so that the sub-groove is blocked by the block, and ground friction vibration Since the generation of air pumping sound due to the sub-groove space can be suppressed together with the sound, the absolute value of the noise is reduced.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings.
[0008]
FIG. 1 is a plan view illustrating a tread surface of a pneumatic tire according to the present invention.
[0009]
In FIG. 1, the tread surface is provided with three main grooves 1 extending linearly in the tire circumferential direction, and a plurality of sub-grooves 2 communicate with each other at intervals in the tire circumferential direction. A block 3 is formed. That is, two rows of block rows 4 extending in the tire circumferential direction are formed in the center portion in the tire width direction, and ribs 5 are formed on the outer sides of the main grooves 1 on both outer sides.
[0010]
In the two block rows 4, the arrangement pitch of the blocks 3 is changed, and the pattern noise is converted to white noise. The sub-groove 2 is inclined with respect to the tire circumferential direction so as to reduce the impact force when the block 3 collides with the road surface.
[0011]
The pneumatic tire of the present invention has a groove area ratio of 5 to 30%, preferably 5 to 25%, more preferably 5 to 20% in the tread pattern, and the sub groove 2 occupies the total groove area. There are always 8 to 16, preferably 10 to 12 sub-grooves 2 in the region. Since the tread pattern is configured as described above, when the tire is grounded and the tread surface is deformed, the block is deformed so that the sub-groove is blocked, thereby preventing slipping on the road surface and grounding. Generation of frictional vibration noise can be suppressed. In addition, since the sub-groove is blocked by the deformation of the block, it is possible to suppress the generation of air pumping noise derived from the sub-groove.
[0012]
Here, the contact area refers to an area where the tread surface contacts the ground when the tire contacts the flat road surface with JATMA maximum load load and maximum air pressure.
[0013]
In the pneumatic tire of the present invention, it is more preferable that both outer sides of the three main grooves are ribs. As a result, noise is not emitted from the outermost main groove to the outside of the tire, so that the effect of reducing outside noise is further increased.
[0014]
The shape of the sub-groove is not particularly limited, but a curve or a straight line having no inflection point is preferable, and a straight line is the best.
[0015]
FIG. 2 is a graph showing the relationship between the groove area ratio S occupied by the sub-grooves in the total groove area and the noise level N.
[0016]
This graph shows that the tire size is 185R14 8PR LT, the tread pattern is FIG. 1, the number of sub-grooves occupying the ground contact area is 10, the sub-groove angle with respect to the tire circumferential direction is 60 °, and the sub-groove depth is relative to the main groove depth. The point that the ratio is 60% and the ratio between the maximum value and the minimum value of the sub groove width (maximum value / minimum value) is 1.30 is common to each test tire, and the ratio of the sub groove to the total groove area is 5 Test results of vehicle exterior noise for 11 types of pneumatic tires with different values of 10%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 50%, 60%, and 70% It is.
[0017]
The noise level is measured by the following measurement method, and the result obtained is the reciprocal of the measurement result of the noise level. In FIG. 1, a rib-pattern tire without a sub-groove (except for the test tire except that no sub-groove is provided). The reciprocal of the noise level measured for (common conditions) was expressed as an index with 100 as the inverse. A larger numerical value indicates that the noise level is reduced.
[0018]
Noise level measurement method:
The vehicle was mounted on a small truck, which is a vehicle conforming to the test tire size, and the coasting noise was measured according to JIS D1015 “Automatic coasting test method”.
[0019]
From the graph shown in FIG. 2, it can be seen that when the groove area ratio of the sub grooves to the total groove area is 5 to 30%, the noise level of the outside noise is reduced as a whole.
[0020]
If the number is less than 5%, the area is too small. Therefore, when the number of sub grooves is constant, the width of the sub grooves is too small. Therefore, when the tire is grounded and the tread surface is deformed, stress from the road surface is further applied to the block 3 even after the sub-groove is blocked, and the block 3 cannot be further deformed. Slip occurs between the two and noise is generated, which is not preferable. If it exceeds 30%, the width of the sub-groove becomes too large when the number of sub-grooves is constant. Therefore, when the tire is grounded and the tread surface is deformed, a space formed by the sub-groove 2 and the road surface remains even after the block 3 is completely deformed, and an air pumping noise is generated, which is not preferable.
[0021]
FIG. 3 is a graph showing the relationship between the number of sub-grooves n distributed in the ground contact area and the noise level N.
[0022]
This graph shows the tire used as a test tire in the test of FIG. 2, the tire size, the sub-groove angle with respect to the tire circumferential direction, the ratio of the sub-groove depth to the main groove depth, and the maximum and minimum values of the sub-groove width. The ratio of the sub-grooves to the total groove area is 20%, and the number of sub-grooves in the grounding region is 4, 6, 8, 10, It is the result of having tested outside noise about nine kinds of pneumatic tires made to differ in each of 14, 14, 16, 18, and 20.
[0023]
The noise level was measured by the same method as in FIG. 2, and the noise level was also displayed as an index according to the same standard as in the test of FIG.
[0024]
It can be seen from the graph of FIG. 3 that an excellent noise level reduction effect is exhibited when the number of sub-grooves in the ground contact region is 8 to 16. If the number is less than 8, the deformation of the tread surface is not sufficiently absorbed by the sub-grooves, so that the tread surface and the road surface slip and a ground frictional vibration noise is generated, which is not preferable. When the number is more than 16, the width of the sub-groove is reduced, and further stress is applied from the road surface even after the sub-groove is closed, so that a ground frictional vibration noise is generated between the tread surface and the road surface. Absent. Moreover, since the rigidity of the block 3 will become small when there are many subgrooves, it is not preferable.
[0025]
4, 5, and 6, when the groove width of the sub groove changes (FIG. 4), when the groove depth of the sub groove changes (FIG. 5), the angle of the sub groove with respect to the tire circumferential direction changes. The result of investigating the influence on the outside noise is shown for each of the cases (FIG. 6).
[0026]
The tire used in each test has a tire size of 185R14 8PR LT, a tread pattern of FIG. 1, a groove area ratio occupying the total groove area of the sub grooves of 20%, and the number of sub grooves in the ground contact region is 10. The sub-groove angle with respect to the tire circumferential direction is 60 degrees, the ratio of the sub-groove depth to the main groove depth is 60%, and the maximum value of the sub-groove width The ratio to the minimum value (maximum value / minimum value) was 1.30 as a common condition.
[0027]
First, the graph of FIG. 4 shows the ratio W (maximum value / minimum value) of the maximum value and the minimum value of the groove widths of the sub-grooves under the above-mentioned common conditions as 1, 1.1, 1.2, 1.3. , 1.4, the noise level N was measured for five types of pneumatic tires.
[0028]
From FIG. 4, the noise level is good when the ratio W (maximum value / minimum value) of the maximum value and the minimum value of the groove width of the sub-groove is 1 to 1.4. You can see that If it is larger than 1.4, the distribution of the groove width of each sub-groove becomes wide, and air pumping noise derived from the sub-groove is likely to be generated.
[0029]
Next, FIG. 5 shows that the ratio D = 60% of the sub-groove depth to the main groove depth in the above common conditions is changed to 50%, 70%, 80%, 90%, and 100%, respectively. The noise level N was measured for six types of pneumatic tires.
[0030]
FIG. 5 shows that the noise level is good when the sub-groove depth is 50 to 100% of the main groove depth, and more preferably 60 to 100%. It can be seen that the closer to 100%, the more the noise level tends to be reduced. If it is less than 50%, the sub-groove cannot be sufficiently blocked even if lateral stress is applied to the block 3, so that slippage between the tread surface and the road surface is likely to occur, and the air pumping sound derived from the sub-groove Is likely to occur. If it exceeds 100%, the groove is deeper than the main groove 1 and may affect the inside of the tire.
[0031]
FIG. 6 shows the noise level of five types of pneumatic tires in which the angle A = 60 ° with respect to the tire circumferential direction of the sub-groove is changed to 50 °, 55 °, 65 °, and 70 °, respectively, under the above common conditions. N is measured.
[0032]
FIG. 6 shows that the noise level is good when the angle A with respect to the circumferential direction of the sub-groove is 50 to 70 °, and there is a peak near 60 °. If the angle is smaller than 50 °, the rigidity of the tire in the circumferential direction of the block becomes high and the block is difficult to deform, and it is easy to slip between the tread surface and the road surface. The air pumping sound derived from is likely to occur. If it is larger than 70 °, the pattern noise that occurs when the edge of the block contacts the ground tends to increase.
[0033]
【The invention's effect】
According to the pneumatic tire of the present invention as described above, in the tire forming a block row which is defined by the sub-grooves between three straight main grooves, the sub-grooves obliquely to the tire circumferential direction By tilting, the impact force when the block collides with the road surface is reduced , and the ratio of the groove area to the total groove area of the sub-groove and the number of sub-grooves distributed in the ground contact area are set to a specific range. When the tire is grounded and the tread surface is deformed, the block is deformed so that the sub-groove is blocked, so that the slip of the block against the road surface is suppressed, and the air pumping by the sub-groove space together with the ground friction vibration noise Since the generation of sound can be suppressed, the absolute value of noise is reduced. Further, by forming both outer sides of the three main grooves described above as ribs, noise is prevented from being emitted from the outermost main groove to the outside of the tire, and the effect of reducing outside noise is further increased.
[Brief description of the drawings]
FIG. 1 is a plan view illustrating a tread surface of a pneumatic tire according to the present invention.
FIG. 2 is a graph showing a relationship between a groove area ratio S in a total groove area of a sub groove and a noise level N;
FIG. 3 is a graph showing the relationship between the number of sub-grooves n in the ground contact area and the noise level N.
4 is a graph showing a relationship between a ratio (maximum value / minimum value) W of a maximum value and a minimum value of a groove width of a sub groove and a noise level N. FIG.
FIG. 5 is a graph showing a relationship between a ratio D of a sub groove depth to a main groove depth and a noise level N;
6 is a graph showing a relationship between an angle A with respect to a tire circumferential direction of a sub-groove and a noise level N. FIG.
[Explanation of symbols]
1 Main groove 2 Sub groove 3 Block 4 Block row 5 Rib

Claims (4)

In a pneumatic tire in which three main grooves extending linearly in the tire circumferential direction are provided on a tread surface, and a block row is formed by communicating the main grooves with a plurality of sub grooves spaced apart in the tire circumferential direction. ,
The outer sides of the three main grooves are formed as ribs, the sub grooves are inclined obliquely with respect to the tire circumferential direction, and the groove area ratio in the total groove area of the sub grooves is 5 to 30%. pneumatic tire to 8-16 present the number of the sub-grooves distributed in a ground area.   The pneumatic tire according to claim 1, wherein a ratio (maximum value / minimum value) between a maximum value and a minimum value of the groove width of the sub-groove is set to 1 to 1.4.   The pneumatic tire according to claim 1 or 2, wherein a ratio of a groove depth of the sub groove to a main groove depth is 50 to 100%.   The pneumatic tire according to any one of claims 1 to 3, wherein an angle of the sub groove with respect to a tire circumferential direction is set to 50 to 70 °.

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