JPH06183213A - Pneumatic radial tire - Google Patents

Abstract

PURPOSE:To provide a pneumatic radial tire by which vehicle outside noise can be reduced without deteriorating wet performance. CONSTITUTION:Plural straight line shape main grooves 1 extending in a circumferential direction are arranged on a surface of a tread part T, and a center rib 2 partitioned by the straight line shape main grooves 1 is formed at least in the central part, and at least two belt layers 11 are arranged on the outer periphery of a carcass layer 13, and rib width WR is set in 0.15<=WR/W<=0.30 to tread ground contact width W, and groove width Wc of a narrow groove 7 extending in a circumferential direction is set in 0<=Wc/WR<=0.15 to WR, and the groove width sum total WG of the main grooves 1 is set in 0.18<WG/W<0.25, and at least three belt cover layers 12 are arranged respectively in both end parts of the belt layers 11, and total covering width to the belt layers 11 is set in 0.15<=a/Wb<=0.50 to the maximum width Wb of the belt layers 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic radial tire, and more particularly to a pneumatic radial tire suitable for passenger cars which reduces outside noise without deteriorating wet performance.

[0002]

2. Description of the Related Art In recent years, vehicle exterior noise regulations have become more and more strict in connection with environmental protection problems. Meanwhile, pneumatic radial tires for passenger cars are becoming flatter in response to higher performance of vehicles, and the tread is becoming wider accordingly. However, as is well known, widening the tire increases the sliding noise between the road surface and the tread surface and deteriorates the noise outside the vehicle. Therefore, it is very difficult to comply with the above noise regulation.

Further, in some pneumatic tires for passenger cars, a plurality of linear main grooves extending in the tire circumferential direction are provided on the tread surface in order to improve the drainability thereof. In a pneumatic tire having a tread pattern, air trapped between the main groove and the ground contact surface vibrates when the tire rotates, and air column resonance noise, which is a main cause of exterior noise, is generated. Although the sound pressure of the air column resonance sound can be reduced by narrowing the groove width of the main groove, the drainage characteristic which is the original characteristic of the main groove is deteriorated, resulting in deterioration of the wet cornering characteristics of the tire. become. Therefore, in the tire having the tread pattern in which the linear main grooves are arranged in the tire circumferential direction, the improvement of the exterior noise and the wet performance are in a mutually contradictory relationship, and a method of making them compatible has not been found. The current situation.

[0004]

DISCLOSURE OF THE INVENTION An object of the present invention is to reduce the original wet performance based on the main grooves in a tire in which a plurality of linear main grooves extending in the tire circumferential direction are arranged on the tread surface. The purpose of the present invention is to provide a pneumatic radial tire that can reduce the noise outside the vehicle.

[0005]

According to the present invention, which achieves the above object, a plurality of linear main grooves extending in the tire circumferential direction are arranged on the surface of a tread portion, and the linear main groove is provided at least at the center of the tread. Form a divided center rib,
In a pneumatic radial tire in which at least two belt layers are provided on the outer circumference of the carcass layer of the tread portion,
The rib width W _R of the center rib, 0.15 ≦ W _R /W≦0.30 the tread contact width is W, the groove width Wc of the thin groove extending in the tire circumferential direction provided in the center rib, the 0 ≤ Wc / W _R ≤ for the rib width W _R of the center rib
0.15, and the sum W _G of the groove width of the linear main grooves of the plurality of, the tread contact width W 0.18 <W _G /
With W <0.25, at least three belt cover layers are arranged at both ends of the belt layer, and the total coating width a of the belt cover layer with respect to the belt layer is the maximum width Wb of the belt layer. For 0.15 ≦ a / Wb ≦
It is characterized in that it is set to 0.50.

The present inventors have detailed air column resonance noise and slip noise generated when a tire having a plurality of linear main grooves formed on a tread surface and a center rib formed at the center of the tread makes a ground rotation. As for the air column resonance sound of the former, the noise generated in the main groove adjacent to the center rib is particularly large, and in particular, the sub-grooves in the tire width direction are arranged on both shoulders to form a block row. It was found that the main groove adjacent to the center rib becomes conspicuous in the case of doing so. Then, as a cause of this, it was found that the air column resonance sound was due to amplifying air vibration in the main groove by vibrating the center rib when the tire grounded.

On the other hand, it has been found that the latter slip noise tends to increase as the width of the tire becomes wider, such as that of a flat tire. Based on such knowledge, the present invention suppresses the vibration of the center rib during the tire ground contact rotation as much as possible within a range that does not sacrifice the drainage property of the main groove, and reduces the vibration amplification effect of the air in the main groove. To do so. for that reason,
The rib width W _R of the center rib is set to a relatively large value, and the rib width W _R set to this large value is set so that no narrow groove is provided in the rib, or more than that of a conventional tire. The rib rigidity is increased by reducing the amount to reduce the vibration, and at the same time, the total sum W _G of the main groove width is secured to maintain good drainage and suppress the deterioration of the wet performance. ing. Further, both ends of the belt layer are covered with three or more belt cover layers, and the total covering width a with respect to the belt layers is regulated to increase the rigidity of the tread shoulder portion and reduce the slip noise. .

In the present invention, the ribs are present between two linear main grooves extending in the tire circumferential direction, and connect two adjacent linear main grooves in the tire width direction. It refers to the land that does not have a secondary groove. However, even if this land portion has a linear groove extending in the tire circumferential direction, if the groove width is within 5 mm, it is 1 including this.
A book rib and its full width shall be interpreted as the rib width.

In the present invention, the main groove has a groove width of 5
The groove width is within 5 mm. The present invention will be described below with reference to the embodiments shown in the drawings. FIG. 1 is a tread pattern of a pneumatic radial tire showing an embodiment of the present invention, and FIG. 2 is a sectional view of a tread portion of the tire.

As shown in FIG. 1, four linear main grooves 1 having groove widths W _G1 , W _G2 , W _G3 , and W _G4 are provided on the tread surface along the tire circumferential direction. . Two straight main grooves 1 with groove widths W _G2 and W _{G3 in} the center of the tread
A center rib 2 having a rib width W _R is formed between the two.
A straight thin groove 7 having a groove width Wc is formed in the center portion of the center rib 2 in the width direction. Further, blocks 4 divided by the linear main groove 1 and the sub-groove 3 are formed on the shoulder portions on both the left and right sides to form two block rows. Each block 4 is provided with sipes 6.

Further, as shown in FIG. 2, a belt layer 11 made of two steel cords is arranged on the outer periphery of the carcass layer 13 of the tread portion T along the tire circumferential direction. The belt layer 11 has a cord angle in the range of 24 ° to 31 ° with respect to the tire circumferential direction and intersects between the layers. At both ends of these belt layers 11, belt cover layers 12 made of three nylon cords are arranged. The belt cover layer 12 is arranged such that the cord angle with respect to the tire circumferential direction is approximately 0 °, and the total covering width (actual overlapping width) of the left and right belt cover layers 12 with respect to the belt layer is a. .

In the tread pattern described above, the rib width W _R of the center rib 2 is 0.15 of the tread ground contact width W.
It is set to be more than twice and less than 0.30 times. Rib width W _R
By doing so, it is possible to increase the rigidity of the ribs and make it difficult for vibrations to occur during tire ground contact rotation.
Therefore, the air vibration in the main groove 1 is not amplified by the vibration of the center rib 2, so that the air column resonance noise can be reduced. However, the rib width W _R is the tread contact width W
If it exceeds 0.30 times, the drainage property in the central area of the ground will be deteriorated and the wet performance will be deteriorated.

The center rib 2 may be provided with a linear thin groove 7 to improve its drainage property. However, in order to maintain the rib rigidity that secures the effect of reducing the air column resonance noise, the linear narrow groove 7 has its groove width Wc less than or equal to 0.15 times the rib width W _R of the center rib 2. Also, the linear main grooves 1, in order to ensure the main grooves original drainage, their groove width W _G1, W _G2, the sum W _G of W _G3 and W _G4 of the tread contact width W 0.18 Be more than double. However, if the total width W _G of the main grooves is made too large, it becomes difficult to harmonize with the rib width W _R of the center rib 2, and the effect of reducing air column resonance noise decreases, so that the tread contact width W of 0 is reduced. .25
Less than double.

Further, the center rib 2 may be provided with a lug groove 5 for ensuring wet performance. However, if the number of lug grooves 5 is increased too much, the effect of reducing the air column resonance noise is deteriorated. Therefore, the total volume V _G of the lug grooves 5 is
The volume V _{R of the} center rib should be 0.04 times or less. Both shoulders of the tread portion T have increased rigidity because both end portions of the belt layer 11 are covered with three or more belt cover layers 12, and slip noise is reduced. In order to obtain such a slip noise reducing effect, the total covering width a of the belt cover layer with respect to the belt layer is set to 0.15 times or more the maximum width Wb of the belt layer. Further, even if the total covering width a is made too large, it does not contribute to the effect of reducing the slip noise, so that the maximum width Wb of the belt layer of 0.
50 times or less.

3 to 6 show the outside noise and wet performance of the pneumatic radial tire having the above-mentioned tread pattern and internal structure of the tread, the rib width W _{R of} the center rib, and the groove of the narrow groove provided in the center rib. The experimental results are shown in which the relationship between the width Wc, the total width W _G of the straight main grooves and the number of belt cover layers is investigated. In this experiment, the tire size is 225 / 55R16 94V, the tread pattern is shown in FIG. 1, the tread structure is shown in FIG.
The 176 mm, and the point where the total coating width a of the belt layer end portions of the belt cover layer 0.30 times the belt layer maximum width Wb in common, 3, 0.10 Wc / W _R, W _G / The results of evaluation of the vehicle exterior noise and the wet performance when W is 0.20 and the number of belt cover layers are fixed at 2 respectively, and only the rib width W _R / W of the center rib is changed are shown. Figure 4
Is set to W _R / W of 0.15, W _G / W of 0.20, and the number of belt cover layers is fixed to 2 respectively, and only the groove width Wc / W _{R of the} fine groove provided in the center rib is changed. shows the relationship between the exterior noise when, 5, 0.1 W _R / W
5, Wc / W _R 0.10, the number of the belt cover layer 2
The following shows the evaluation results of the vehicle exterior noise and the wet performance when the total width W _G / W of the main grooves is changed while keeping the same for each sheet. 6, W _R / W 0.15, 0 Wc / W _R.
10 and W _G / W are kept constant at 0.20, respectively, and the relationship with the vehicle exterior noise when only the number of belt cover layers is changed is shown.

In the above experiment, the noise outside the vehicle and the wet performance were evaluated by the following methods. Noise outside the vehicle : In accordance with the method specified in JASO C-606, the rim is assembled to a 16 x 7 1/2 JJ rim,
A test tire filled with air pressure of 226 kPa (2.30 kgf / cm ² ) was mounted on a vehicle with a displacement of 3000 cc, and the sound pressure level (dB) when passing a section of 10 km at a speed of 60 km / h was measured from the vehicle. It was measured by a microphone arranged at a height of 7.7 m and 1.2 m from the road surface.

The measurement results have the same tire size, tread pattern, and tread ground contact width W as in the above experiment.
_R / W, indicated by an index to _{Wc / W R, W G /} W and relative to the inverse of the conventional tire of the sound pressure level number were respectively set as follows in the belt cover layer (100). The larger this index is, the greater the effect of reducing the noise outside the vehicle is. _{W R /W=0.15, Wc / W R} = 0.10, W G /W=0.20, belt cover layer number = two wet performance: mounting the tire used in the test methods of the exterior noise The same vehicle was subjected to a steering stability performance test on an asphalt road surface sprayed to a water depth of about 1 mm, and the wet cornering performance was evaluated by a 10-point method. If the score of wet feeling is 6 or more, it is considered to be practically acceptable.

From FIGS. 3 and 5, the rib width W _R of the center rib is 0.15 to 0.30 times W, and the total width W of the main grooves is W.
It can be seen that by setting _G to be more than 0.18 times and less than 0.25 times W, the outside noise can be reduced as compared with the conventional tire while maintaining the wet performance. Also,
It can be seen from FIG. 4 that when the center rib is provided with a narrow groove, the effect of reducing the noise outside the vehicle due to the center rib can be maintained by setting the groove width Wc of the narrow groove to 0.15 times W _R or less. It can be seen from FIG. 6 that the noise outside the vehicle can be further reduced due to the effect of reducing the slip noise by setting the number of belt cover layers to three or more.

Next, for the tire having three belt cover layers in the experimental example of FIG. 6, the total coating width a with respect to the maximum width Wb of the belt layers of these three belt cover layers is shown in Table 1. Modified tires I, II, III of the present invention and comparative tires I, II, III, IV were manufactured. The vehicle exterior noise of these seven types of tires was evaluated by the method described above. When the noise outside the vehicle is improved by 1% or more compared to the conventional tire used as the standard of the above-mentioned measuring method, ○ is evaluated when it is less than 1%.
The results of the determination are shown in Table 1.

[0020] In Table 1, the first to third layers indicate the belt cover layer numbers when counted from the carcass layer side to the tread surface side.

From Table 1, as in the tires I, II, and III of the present invention, the total coating width a of the three belt cover layers is in the range of 0.15 to 0.50 times the maximum width Wb for all belt layers. When compared with the conventional tires, the effect of reducing the exterior noise by 1% or more can be obtained, while the comparative tires I, II, III
And IV, even one of the three belt cover layers covering both ends of the belt layer has the maximum width W of the belt layer.
It can be seen that the effect of reducing the noise outside the vehicle is lost when the total coating width a for b is out of the above range. The present invention is particularly effective when applied to flat radial tires, and is preferably applied to radial tires having a flatness ratio of 65 or less.

[0022]

EXAMPLE The tire size, tread pattern, and tread width W are the same as those of the tire of the above-described experimental example, the rib width W _R / W of the center rib, the groove width Wc / W _{R of the} narrow groove, and the groove width of the main groove. Of the present invention 1, 2 and 3, in which the total W _G / W and the number of belt cover layers are different as shown in Table 2.
3. Comparative tires 1 to 7 were manufactured.

The outside noise and the wet performance of each of these ten types of tires were evaluated by the above-mentioned methods. The results are shown in Table 2. For comparison, the values of the vehicle exterior noise and the wet performance of the conventional tire of the above experimental example are displayed together.

Table 2 It can be seen from Table 2 that the tires 1 to 3 of the present invention all have lower vehicle exterior noise than the conventional tires and have sufficient practical wet performance. On the other hand, it is understood that the comparative tires 1 to 7 do not satisfy one of the vehicle exterior noise and the wet performance.

[0025]

According to the present invention, a plurality of linear main grooves extending in the tire circumferential direction are arranged on the tread surface, a center rib is formed in the central portion of the tread, and the carcass layer on the outer periphery of the tread portion is formed. In a pneumatic radial tire provided with at least two belt layers, the rib width W _R of the center rib is increased in a specific range to increase the rigidity of the rib, and the groove width Wc of the narrow groove provided in this large rib is increased. It is possible to suppress the vibration of the center rib when the tire is in contact with the ground and to reduce the air column resonance noise by limiting the size to a specific size or not providing the size. Moreover, since the sum of the groove widths of the main grooves is ensured within a specific range, good drainage performance can be maintained and wet performance can be ensured. Further, by covering three or more belt cover layers at both ends of the belt layer by specifying the total coating width a for the belt layer, the rigidity of the shoulder portion can be increased and the slip noise can be reduced.

[Brief description of drawings]

FIG. 1 is a plan view showing a tread pattern of a pneumatic radial tire showing an embodiment of the present invention.

2 is a sectional view of a tread portion of the pneumatic radial tire of FIG.

FIG. 3 is a graph showing the relationship between the rib width W _R / W of the center rib and the vehicle exterior noise and wet performance.

4 is a graph showing the relationship between the groove width Wc / W _R and exterior noise of Hosomizomizo.

FIG. 5 is a graph showing the relationship between the total groove width W _G / W of the main grooves and the vehicle exterior noise and wet performance.

FIG. 6 is a graph showing the relationship between the number of belt cover layers and noise outside the vehicle.

[Explanation of symbols]

1 main groove 2 center rib 3 auxiliary groove 7 narrow groove 11 belt layer 12 belt cover layer W tire contact width W _R center rib rib width W _G1 , W _G2 , W _G3 , W _G4 main groove width Wc narrow groove Groove width Wb Maximum width of belt layer a Total coating width

Front page continued (72) Inventor Hirohisa Hazama Oiwake 2-1, Hiratsuka, Kanagawa Yokohama Rubber Co., Ltd. Hiratsuka Factory

Claims (1)

[Claims] 1. A plurality of linear main grooves extending in the tire circumferential direction are arranged on the surface of the tread portion, and a center rib divided by the linear main groove is formed at least in the central portion of the tread to form a center rib of the tread portion. In a pneumatic radial tire having at least two belt layers provided on the outer periphery of a carcass layer, the rib width W _R of the center rib is 0.15 ≦ W _R /W≦0.30 with respect to the tread ground contact width W. The groove width Wc of the narrow groove extending in the tire circumferential direction provided on the center rib is 0 ≦ Wc / W _R ≦ with respect to the rib width W _{R of the} center rib.
0.15, and the sum W _G of the groove width of the linear main grooves of the plurality of, the tread contact width W 0.18 <W _G /
With W <0.25, at least three belt cover layers are arranged at both ends of the belt layer, and the total coating width a of the belt cover layer with respect to the belt layer is the maximum width Wb of the belt layer. For 0.15 ≦ a / Wb ≦
Pneumatic radial tire with 0.50.