JP3537884B2 - Pneumatic tire - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire with reduced running noise.

[0002]

2. Description of the Related Art In recent years, noise has been taken up as a pollution problem caused by automobiles, and quietness has also been emphasized for drivers. The noise generated during running of the tire is mainly a sound accompanying air exhausted from a groove provided in the tread between the road surface and the tread of the tire. That is, in the case where gas is blown out or sucked into the atmosphere, if the strength is unsteady, the surrounding air undergoes compression and expansion vibrations. And part of it radiates as sound.

In order to reduce such noise generated by a tire, a pitch variation method based on a frequency modulation theory or the like is conventionally used, and a plurality of pitches having different lengths are used.
Usually, two or more types have been used to divide a land by dividing a groove by an appropriate pitch ratio and arrangement, thereby dispersing a specific frequency to make the sound unnoticeable.

On the other hand, in passenger car tires, high speed and high performance have been gradually improved, and particularly in terms of shape, tires having a wide tread having a tire cross-sectional ratio of 0.6 or less are becoming popular. In order to prevent a reduction in wet skid resistance, which is a problem in this case, four to six linear wide main grooves extending in the circumferential direction are provided in accordance with the width of the tread, and directions crossing these circumferential main grooves are provided. A tread having a block-shaped land portion formed by providing a large number of lug grooves in parallel is preferably used.

[0005]

In such a block-type tread, when an independent block steps on a ground contact surface during traveling, a vibration sound due to a forced input received by the tread due to unevenness of a road surface and a vibration caused by the forced input are generated. The air column resonance in the cavity formed by the circumferential main groove and the ground plane caused by the vibration causes a problem. They are pin back and forth 1KH _Z -
In order to reduce the noise level of the tread, it is necessary to reduce the noise caused by the vibrations caused by the above-mentioned blocks and the columnar resonances, although the pitch variation is applied in this case. is important. The present invention provides a pneumatic tire that solves the above-mentioned problems without impairing wet skid resistance, with respect to a tread having a plurality of linear circumferential main grooves and a block-shaped land portion row therebetween. Aim.

[0006]

SUMMARY OF THE INVENTION According to the present invention, at least four circumferentially extending linear main grooves extending from the both ends of a cylindrical tread and extending in the circumferential direction are provided on the tread, and a large number of these grooves intersect with the main grooves. In a tire having a central land portion separated by a lug groove, a shoulder-land portion facing both ends of the tread, and an intermediate land portion between both shoulder-land portions and the central land portion, the intermediate land portion of the tread has a central land portion. , And a shoulder-ground contact surface that is lower than the imaginary line connecting the contact surface, thereby assembling the tire into the use rim,
A pneumatic tire characterized in that the contact length of the intermediate land formed on the contact surface on the flat plate under the normal internal pressure and load specified in the JATMA standard is shorter than the contact length of the center and shoulder-land. is there.

[0007]

In order to investigate the cause of the noise affecting the block type tread, the inventor measured the vibration in the main groove in the circumferential direction of the straight. In order to reduce the vibration, it is necessary to suppress the vibration of the groove bottom, and for that purpose, the ground contact surface of the intermediate land should be lower than the surface level of the central land and the shoulder land located on both sides of the main groove. As a result, it was confirmed that the forced input amount due to the uneven road surface from the intermediate land portion was reduced, and the vibration of the groove bottoms connected on both sides at the base position of the intermediate land portion was reduced, and the noise was reduced.

The air column resonance is generated when the straight main groove becomes a Helmholtz resonance tube and the air vibrates. To lower the level, the shape of the groove is changed and the sound field characteristic sound field is generated. It is effective to reduce the transmission efficiency. In the present invention, since the contact surface of the intermediate land is one step lower and the contact length of the land is shorter than each contact length of the central land and the shoulder-land, the opening of both main grooves adjacent to the intermediate land is provided. The ends are widened, that is, the width of one open end of the main groove is functionally expanded to the width between the adjacent main grooves across the intermediate land portion, thereby reducing the noise accompanying the reduction in sound field transmission efficiency. Decreased levels were observed.

[0009] The distance between the surface of the intermediate land portion and an imaginary line connecting the center and the shoulder-land surface is preferably 0.5 to 2 mm. It is to effectively improve the sound field characteristics of the main groove,
This is a means to assemble the tire on the rim for convenience and to make the ground contact length of the middle land part on a flat plate under normal internal pressure and load specified by JATMA standard 80 to 90% of the ground contact length of the central land part . When the ratio is less than 80%, the effect of reducing air column resonance is improved, but the steering stability of the tire is reduced. When the ratio exceeds 90%, the effect of reducing air column resonance is too small, which is not preferable. . The above-mentioned distance to the surface of the intermediate land portion is also 0.5 to 2 for suppressing the forced input to the bottom of the main groove.
mm can be said to be a preferable range.

[0010]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. FIG. 1 is a partial sectional view of a tread showing one embodiment of the present invention, and FIG.
FIG. 4 is a view showing a tread contact shape on a flat plate.
In the present invention, the tire 1 has both ends E of the cylindrical tread 2.
Each of the side walls 3 is connected in a toroidal shape, and is divided into at least four circumferentially extending linear main grooves 4 extending in the circumferential direction on the tread 2 and a number of lug grooves (not shown) intersecting with the main grooves 4. a center land portion 5 _C that is, shoulder facing the tread ends E - land portion 5 _S, and both shoulders - a pair of middle land portions 5 _I located between the land portion 5 _S and the center land portion 5 _C
Is provided. And the middle land portion 5 _I is a ground surface lower than the imaginary line j connecting the ground surfaces 6 _C and 6 _S of the central and shoulder-land areas.
6 _I , whereby the contact length m _I of the intermediate land portion 5 _I ′ formed on the contact surface C (FIG. 2) during traveling is the contact length m _{C of} the central land portion 5 _C ′, and shoulder - shorter than the ground length m _S of the land portion 5 _S '. The distance between the imaginary line j and the ground surface 6 _{I in the} middle land
k is preferably in the range of 0.5 to 2 mm.

Although illustration of the reinforcement of the tire 1 is omitted, one or a plurality of plies in which a fiber code such as polyester or rayon is arranged in a direction substantially perpendicular to the equator O of the tire. (Usually two) are overlapped, and a radial arcus is arranged from one side wall 3 to the other side wall 3, and a full width of the tread 2 is provided between the carcass and the tread 2. A known structure reinforced by disposing a non-extensible belt layer (not shown) can be applied.

Referring to FIG. 2 showing the tire 1 as a tread 2 shown in FIG. 1 as a ground contact shape, the land portion 5 'is shown by ribs continuous in the circumferential direction divided by a straight main groove 4'. Although not arranged in the groove, at least the shoulder -, middle land portions 5 _S ', 5 _I' for tread end E
Between the main groove 4 'and the main groove 4', which correspond substantially to the main groove 4 ', are divided into independent blocks by a lug groove extending in a required direction and at an angle, and the central land portion _5C ' Similarly, a saw-tooth endless rib can be formed by dividing into independent blocks by lug grooves, or by partially providing lug grooves while leaving a part in the width direction.

FIGS. 1 and 2 show an example in which four main grooves 4 are used, but when five main grooves are used, if they are arranged at substantially equal intervals, a pair of left and right adjacent to the center main groove is used. The land portion is the central land portion, and the ground contact surface of the intermediate land portion between the central land portion and the shoulder land portion facing the tread edge E is formed to be lower by a distance k. Also, if six main grooves are used and they are similarly arranged at substantially equal intervals, two intermediate land portions are arranged between one central land portion and a shoulder land portion. In this case, Is the central land, or shoulder
Distance between any one of the intermediate land areas close to the land area
Lower by k. However, in this case, lowering the ground contact surface of the intermediate land portion close to the central land portion is more effective in light of the object of the present invention.

[0014] ground length m _I of the intermediate land portion in FIG. 2, the central land portion, and the shoulder - the ground contact length of the land portion m _C, less than m _S. Therefore, the width n of the main groove adjacent to the middle land portion side of the middle land portion 5 _I is, at the groove opening end position on the ground contact surface, a width q obtained by adding the width of the middle land portion and the width p of the adjacent main groove. Works enlarged,
The shoulder - the width p of the main groove adjacent to the land portion 5 _s side is enlarged in the width q at the open end position of the ground surface, whereby it is to contribute to a reduction in the sound field transmission efficiency.

[0015]

[Effect] To confirm the effect of the tire according to the present invention, 20
In the radial structure of 5 / 55R16 size, the tread shown in FIG. 1 (however, all land portions 5 are independent blocks) and the tires A and B of the embodiment having the ground contact shape shown in FIG. A noise test and a wet skid test were performed using the comparative example tire C shown in FIG. Tire of the comparative example the ground surface 16 _I of the intermediate land portion 15 _I, middle, and shoulder - provided Ryoriku portion 15 _C, 15 _S of the ground surface 16 _C, 16 connecting the _S on the virtual line j.

[0016] The test tire is set to 7J rim, the internal pressure and the 2.0Kgf / Cm ² filling, in a noise test bench noise measurement for the drum on, the load of 400Kgf addition to the tire, speed three levels (40, 50, Measure the noise at 60 km / h)
The average value was used as the evaluation value. In the wet skid test, the vehicle traveled straight through a water pool having a depth of 10 mm by a real vehicle, and a critical speed at which hydroplaning occurred was measured and evaluated. Table 1 shows details of the main part of the land portion of the test tire and the test results.

[0017]

[Table 1]

FIG. 3 shows a comparison graph of the bench tire noise spectrum at a speed of 50 km / H for the tire of Example 1 and the tire of the comparative example having a large reduction in noise shown in Table 1. Than 3, at a frequency range of 700～2KH _Z, it is understood that the sound pressure level of inter alia about 1 kH _Z is effectively reduced.

Thus, the intermediate land portion of the block-type tread having the linear circumferential main groove has a ground contact surface lower than an imaginary line connecting the center and the shoulder-land contact surface, thereby driving the vehicle. By making the contact length of the intermediate land part formed on the contact surface sometimes shorter than the contact length of the center and the shoulder-land part, it is possible to advantageously reduce noise during traveling while maintaining wet skid resistance. You can do it.

[Brief description of the drawings]

FIG. 1 is a partial sectional view of a tread of a tire according to an embodiment.

FIG. 2 is a diagram showing a contact shape of the tire according to the embodiment.

FIG. 3 is a comparison diagram of a bench tire noise spectrum.

FIG. 4 is a partial cross-sectional view of a tread of a tire of a comparative example.

FIG. 5 is a view showing a contact shape of a tire according to a comparative example.

[Description of Signs] 1 Tire 2 Tread 3 Sidewall 4 Circumferential main groove 5 _C Central land 5 _I Middle land 5 _S Shoulder land 6 _C Central land surface 6 _I Middle land surface 6 _S shoulder Land surface m _C Landing length of central land m _I Landing length of intermediate land m _S Shoulder-Landing length of land

Claims (2)

(57) [Claims] 1. A side wall extending from both ends of a cylindrical tread, and a central land divided by at least four circumferentially extending linear main grooves on the tread and a number of lug grooves intersecting the main grooves. Tire having a shoulder portion, a shoulder-land portion facing both ends of the tread, and an intermediate land portion between both shoulder-land portions and a central land portion, the intermediate land portion of the tread is connected to the center and the shoulder-land portion of the tread. has a lower ground surface than an imaginary line connecting the surface, thereby assembled tires to use a rim, a regular prescribed in JATMA standards
A pneumatic tire characterized in that the contact length of the intermediate land formed on the contact surface on the flat plate under the internal pressure and load is shorter than the contact length of the center and the shoulder-land. 2. The pneumatic tire according to claim 1, wherein a distance between the imaginary line and a ground contact surface of the intermediate land portion is in a range of 0.5 to 2 mm.