JPH0811508A - Pneumatic tire - Google Patents

Abstract

PURPOSE:To reduce noise with wetting resistance maintained by positioning a lag groove which classifies a land part area in the land part area without an axial inside end reaching grooves in the peripheral direction, and forming at least one of the grooves in the peripheral direction by repeating an expanding width part and a contracting width part in the peripheral direction. CONSTITUTION:Treads 1 are partitioned in a land part area 3 by grooves in the peripheral direction and both ends E of treads, and the land part area 3 is classified in the peripheral direction by lag grooves 4. The lag grooves 4 are positioned in the land part area 3 without an inside end in the axial direction reaching a main groove 21 in the peripheral direction which partitions the land part area, and at least one of the grooves in the peripheral direction is formed by repeating an expanding width part 11 and a contracting width part 12 in the peripheral direction. It is thus possible to reduce noise with wet skid properties maintained.

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 reduced noise while maintaining wet skid resistance.

[0002]

2. Description of the Related Art In recent years, particularly in the field of passenger cars, the performance has been improved, and the tires used have a high running speed,
Also, due to the demand for steering stability, the tire cross section tends to be flattened in shape. When the tire cross section becomes flat, the tread width increases as the tire width increases,
It is known that the drainage property on the wet road is deteriorated and the hydroplaning phenomenon is likely to occur at a relatively low speed in a place where there is water depth.

In the case of a flat tire, in order to improve the drainage, four or more straight circumferential main grooves are arranged on the tread at intervals, and at the same time, a large number of crossing main circumferential grooves are extended. A structure in which an independent block is divided by providing an inclined lug groove is preferably used. Such a block type tread has a good drainage property in view of the negative ratio (the ratio of the groove portion to the entire ground contact surface). On the other hand, however, when the block is stepped on the ground contact surface during traveling, the noise caused by the hitting sound on the road surface due to the corner thereof often becomes a problem.

A tire aiming to achieve both the drainage property and the noise property, which have contradictory characteristics as described above, has been proposed in, for example, Japanese Patent Laid-Open No. 5-246214. In the tread of this tire, a plurality of straight circumferential main grooves are arranged on both sides of the tread, and a large number of inclined lug grooves extending from both ends of the tread and intersecting the circumferential main grooves converge at the center of the tread. By arranging like this, the blocks are divided in an arrow pattern,
The rotation direction of the tire is specified so that it touches the ground from the side where the inclined lug grooves converge.

[0005]

In the above-mentioned arrow-shaped tread, since the blocks are successively stepped into the ground contact surface between the blocks in the circumferential direction during traveling, the tapping sound at the corners of the blocks is dispersed. However, the tapping sound is still generated, and the noise level due to the tapping sound does not decrease. In addition to this, the deterioration of noise due to air column resonance in the straight circumferential main groove becomes a problem. Air columnar resonance is a stepping / kicking-out portion of the groove width during ground contact rolling, and high-frequency vibration occurs in the groove wall (or land wall) as it fluctuates rapidly due to the action of external force. Causes the air in the circumferential main groove on the ground contact surface, that is, the air in the pipe, to vibrate, and the acoustic resonance action based on this vibrates the noise. The present invention has been made in view of the above problems, and an object of the present invention is to provide a pneumatic tire having reduced noise while maintaining wet resistance.

[0006]

DISCLOSURE OF THE INVENTION The present invention is directed to sidewalls from both ends of a cylindrical crown portion inward in the radial direction.
Three continuous linear main grooves extending parallel to each other on the tread, and a land portion section defined by these main grooves and both ends of the tread. In a tire having a large number of lug grooves extending in a direction that divides the circumferential direction, the lug grooves remain in the land area without their axial inner ends reaching the circumferential main groove, and the circumferential main groove is also used. At least one of them is a pneumatic tire characterized in that a widened portion and a narrowed portion are repeatedly formed in the circumferential direction.

[0007]

In the tread of the tire according to the present invention, the lug groove extending in the land area defined by the circumferential main groove and both ends of the tread has the axially inner end not reaching the circumferential main groove in the land portion. Stays in. Therefore, when at least one land wall portion facing the main groove has a rib shape continuous in the circumferential direction, and the other land wall portion facing the circumferential main groove is divided into blocks by the lug groove. Also in the above, the rib-shaped portion is supported to prevent the node-shaped bending deformation at the lug groove position, and the hammering sound due to the acute angle portion of the block at the time of stepping on is advantageously suppressed.

Normally, when the air flowing into the main groove is suddenly discharged to the outside, noise called blowing noise is generated, which is a problem. In the present invention, however, there is a widened portion in the circumferential main groove. Since the narrowed width portion is repeatedly formed in the circumferential direction, the so-called silencer effect is obtained in the circumferential main groove having such a shape, thereby reducing noise.
In the tread of the tire according to the present invention, even if the number of circumferential main grooves is as small as three or less, it is possible to maintain the necessary drainage property by setting the groove width to be wide enough to correspond to the decrease in the number.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A description will be given below with reference to the drawings. FIG. 1 is a development view of a tread plane of a tire showing an embodiment of the present invention. In FIG. 1, treads 1 extend parallel to each other 3
The book includes a straight circumferential main groove 2 and a large number of lug grooves 4 extending in a direction that circumferentially divides the circumferential main groove 2 and a land area 3 defined by the tread ends E. In this embodiment, the center of the circumferential direction main groove - the main groove 2 ₁
It is located on the equatorial plane O, shoulder - the main grooves 2 _2, the equatorial plane
By pair also receives about 2/3 away point of the tread half width from O, a relatively wide middle land portion region 3 _1, shoulder narrowing - is defining the land portion area 3 _2. An intermediate lug groove 4 ₁ is formed in the intermediate land area 3 _{1 so} as to have a steep angle with respect to the axial direction on the outer side in the axial direction so that the angle gradually increases toward the equatorial plane O, and the tapered shape is formed. A large number are provided at intervals to divide the land part 5. Meanwhile, the shoulder-land area
3 _2, at a small angle relative to the axial direction from the tread end E, slightly mosquitoes - Bed with almost equal width of the shoulder - which divides the land portion 5 by lug grooves 4 provided ₂ as well. Although not shown in the drawings, in the present invention, the tire is provided with treads 1 on the crown portion, in which side walls are continuous inward in the radial direction from both ends of the cylindrical crown portion. A structure reinforced by arranging, for example, a radial arc, and a non-stretchable belt layer between the carcass and the tread, from one of the sidewalls through the crown portion to the other sidewall. Can be applied.

In the present invention, the lug groove 4 is to remain in the land area 3 without its axial inner end reaching the circumferential main groove that defines the land area. That is, the shoulder
Intermediate lug grooves 4 ₁ extending from the position of the circumferential main grooves 2 _2, center - stay in the circumferential main groove 2 ₁ in front, in this embodiment, center - relatively close to the circumferential main grooves 2 ₁ provided thin stress was - DOO circumferential auxiliary groove 6 an intermediate lug grooves 4 ₁ extended to the land portion 5 independent block-shaped by it and the auxiliary grooves 6,
The center - to form a rib 7 extending continuously in the circumferential direction between the circumferential main grooves 2 _1. Meanwhile shoulder - in the land portion region, shoulder extending from the tread end E - lug grooves 4 _2,
Leaving constricted portion 8 shoulder - stay in the circumferential main groove 2 _{and second} front, and thereby forming a land portion 5 of the comb-shaped.

In the present invention, at least one of the circumferential main grooves 2 has a widened portion 11 and a narrowed portion 12 which are repeatedly formed in the circumferential direction. Center 2 - To elaborate using an enlarged view of a portion of the circumferential main grooves, a center - the circumferential main grooves 2 ₁ The peak portion 9 which protrudes in the width direction at intervals in a circumferential direction, between them The groove 10 has a valley portion 10, and the widening portion 11 and the narrowing portion 12 are portions corresponding to the mountain portion 9 and the valley portion 11, respectively. In this embodiment, the left and right of the groove wall are provided with a phase difference of about 1/4 pitch in the circumferential direction, and the portions corresponding to the peaks of the left and right peaks are the widest, and the interval between them (about 1/4 pitch). According to this, a wide part is formed. The average groove width W _G is 4 to 8% of the tread width W _T , and the amount d of the peaks and valleys with respect to the reference line m of the average groove width is 5 to 30% of the average groove width W _G.
% Ranges are preferred respectively. In this embodiment, the shoulder - and the widened portion 11 and the reduced width portion 12 provided at a position corresponding to the ridges 9 and valleys 10 in the circumferential main grooves 2 _2. In FIG. 1, reference numeral 13 is a notch extending substantially along the direction of the lug groove, and reference numeral 14 is a notch extending in the same direction.

FIG. 3 is a partially enlarged view of the circumferential main groove showing the second embodiment of the present invention. The feature of this embodiment is that the crests 9 and the troughs 10 are laterally aligned in the circumferential direction, and therefore the widened portions 11
Is located between the ridges 9 on the left and right, and the reduced width portion 12 is also located between the valleys 10 that are aligned with each other. Tread 1 shown in Figure 1
Shows an example in which the left and right lug grooves 4 or the land portions 5 are arranged point-symmetrically around the equatorial plane O, but the left and right lug grooves can be plane-symmetrical with respect to the equatorial plane. That is, the block-shaped land portion 5 in the left and right middle land portion region 3 ₁ a herringbone-like arrangement, in which case the tire such that the portion forming the axially inner acute angle of the land portion is ground prior to the obtuse angle portion The direction of rotation is determined, and when traveling, it is supported by circumferential ribs that are located close to each other via a thin circumferential auxiliary groove, and the block acute angle portion helps suppress the tapping sound of the road surface.

[0013]

[Effect] To confirm the effect of the tire according to the present invention,
Using 235 / 60R16 size radial structure tires, the noise in the room and the wet skid test with an actual vehicle were tested and evaluated together with a comparative example. In the test, the tire of the example uses the tread shown in FIG. 1, while the tire of the comparative example basically uses the tread shown in FIG. 1, in which all the circumferential main grooves have a straight shape. ,
The intermediate land portion region 3 circumferential auxiliary groove 6 in the axial direction inside end of the intermediate lug grooves 4 ₁ omitted in _one center - the circumferential main grooves 2 ₁ to extend also shoulder - shoulder at land portion region 3 ₂ -
Lug grooves 4 ₂ axially inner end likewise shoulder - the circumferential main grooves
By extending to 2 ₂ , all land areas became independent blocks. However, the tires of Examples and Comparative Examples had the same tread negative ratio of 34%.

The test tire is assembled on the 16 × 7 1 / 2J rim,
After filling the internal pressure of 1.85 Kgf / Cm ² , the noise test was carried out by 570 Kg of the tire on a drum with a smooth surface in an anechoic chamber.
It was crimped with a load of f and rotated. Mike is on the drum 75
Cm was fixed at a position with an axial distance of 100 Cm from the tire. The test results are shown in Table 1.

[Table 1]

In the wet skid test, the tire internal pressure was adjusted to 1.95 Kgf / Cm ² , and a special paved road with a depth of 10 mm was drawn on a concrete paving road with an arc of a radius of 100 m. The vehicle was measured at various velocities at which the lateral acceleration was zero. The measurement result is
The example was 85 km / h, and the comparative example was 84 km / h.

As described above, in the present invention, the tread is
For a number of lug grooves extending in a direction that divides the land area defined by the linear circumferential grooves in the circumferential direction, the axial inner ends of the lug grooves remain in the land area without reaching the circumferential main groove, At least one of the circumferential main grooves
In the book, a widened portion and a narrowed portion are repeatedly formed in the circumferential direction. The tire provided with the tread thus formed has a high noise reduction effect, and has no inferior wet skid property.

[Brief description of drawings]

FIG. 1 is a development plan view of a tread according to a first embodiment.

FIG. 2 is an enlarged view of a circumferential main groove in FIG.

FIG. 3 is an enlarged view of a circumferential main groove in the second embodiment.

[Explanation of symbols]

 1 Tread 2 Circumferential main groove 3 Land area 4 Lug groove 11 Widened part 12 Reduced width part

Claims (1)

[Claims] 1. A cylindrical crown portion is provided with treads extending inward from both ends of the cylindrical crown portion toward the inner side in a radial direction, and the crown portion has a tread engaging with a road surface, and three or less extending parallel to each other on the tread. In a tire having a linear circumferential main groove and a large number of lug grooves extending in a direction that circumferentially separates a land portion area defined by these main grooves and tread ends, the lug groove has an axial inner end thereof. A pneumatic tire characterized by remaining in the land area without reaching the circumferential main groove, and at least one of the circumferential main grooves has a widened portion and a narrowed portion repeatedly formed in the circumferential direction. .