JP2008302898A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire for which a side branch type resonator for presenting a sufficient noise reducing effect to gas column resonant sounds having a wide-frequency band is arranged. <P>SOLUTION: At least on one contact surface 10 in a posture that a tire is incorporated in an applicable rim, filled with maximum air pressure, and at the same time, loaded with a mass equivalent to a maximum loading capacity, and has two or more of horizontal grooves 3a, 3b and 3c which open to at least a circumferential groove 1. At least two of those horizontal grooves 3a, 3b and 3c have groove lengths which are different from each other. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  According to the present invention, a circumferential groove continuously extending in the circumferential direction is disposed on the tread surface, and a lateral groove that opens in the circumferential groove and terminates at a position away from the circumferential groove without crossing the other groove. The present invention relates to a tire in which a side branch type resonator is constituted by the lateral groove, and particularly relates to a tire having a large effect of reducing air column resonance noise.

With the recent quietness of vehicles, since the ratio of tire noise to automobile noise has become relatively large, reduction of tire noise has become a major issue. Among them, tire noise around 1000 Hz, which is easily heard by humans, is a major factor of noise outside the vehicle, and this noise is expected to be promptly taken from the viewpoint of environmental problems.
By the way, the tire noise of about 800 to 1400 Hz may be generated by air column resonance caused by resonance of the air column defined by the circumferential groove and the road surface in the tire contact surface. In general, in order to suppress such air column resonance, the tread surface is provided with a circumferential groove extending continuously in the circumferential direction, and is opened in the circumferential groove and in a land portion away from the circumferential groove. There has been proposed a pneumatic tire in which a side branch type resonator composed of a lateral groove that terminates at a land portion is disposed in a land portion (see, for example, Patent Document 1). It can be reduced.

International Publication No. 04/103737 Pamphlet (2004)

  However, in the prior art described above, the plurality of horizontal grooves opening in the circumferential groove all have the same shape, and therefore, only the air column sound having a frequency determined by the shape of the horizontal groove has a sound reduction effect. However, since the actual air column resonance sound spreads over a wide frequency band, it cannot be reduced for all frequencies, and the effective sound reduction effect is not sufficient.

  The present invention has been made in view of such a problem, and is a pneumatic in which a side branch type resonator is provided that can obtain a sufficient sound reduction effect even for air column resonance sound having a wide frequency band. The object is to provide a tire.

According to the present invention, a circumferential groove continuously extending in the circumferential direction is disposed on the tread surface, and a lateral groove that opens in the circumferential groove and terminates at a position away from the circumferential groove without crossing the other groove. In the tire in which the side branch type resonator is configured by the lateral groove,
At least one circumferential groove is opened in at least one contact surface in rotation of the tire under a state in which the tire is assembled to the applicable rim, filled with the maximum air pressure, and loaded with a mass corresponding to the maximum load capacity. The pneumatic tire has two or more of the lateral grooves, and at least two of the lateral grooves have different groove lengths.

  According to the present invention, in at least one ground plane, at least one circumferential groove has a different length in at least two of the lateral grooves opened therein, and side branch resonators having different lengths have different frequencies. Depends on its length, it has a sound-reducing effect at at least two different frequencies, which makes it effective even for a wide-band air column resonance. Can be reduced.

  Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a plan view showing a tire ground contact surface in a state in which a pneumatic tire according to an embodiment of the present invention is assembled to an applicable rim, filled with a maximum air pressure and loaded with a mass corresponding to a maximum load capacity, This tire is provided with a circumferential groove 1 extending continuously in the circumferential direction on the tread surface and lateral grooves 3 a, 3 b, 3 c that open to the circumferential groove 1 and terminate in a land portion 2 separated from the circumferential groove 1. A side branch type resonator is disposed in the land portion 2.

  These lateral grooves 3a, 3b, 3c all have a shape in which a portion extending in the tire width direction and a portion extending in the tire circumferential direction are continuous, and the length of the portion extending in the tire width direction. Are the same, and only the length of the portion extending in the circumferential direction of the tire is different from a, b, and c, respectively, as shown in the figure. Therefore, they are mutually different from (b−a). , (B-c), and (ac) are different in length.

Here, the applicable rim refers to the rim specified in the following standards, the maximum air pressure refers to the air pressure defined in accordance with the maximum load capacity in the following standards, and the maximum load capacity refers to the following The maximum mass allowed to be loaded on a tire by standard.
The standard is determined by an industrial standard effective in the region where the tire is produced or used. For example, “THE TIRE AND RIM ASSOCIARION INC. YEAR BOOK” in the United States, “European Tire and Rim Technical Organization, Japan” .

  Also, the tread surface here means that the tire is mounted on the applicable rim, filled with the highest air pressure and placed vertically on the flat plate, and comes into contact with the flat plate when a mass corresponding to the maximum load capacity is loaded thereon. It shall mean the surface area of the tread rubber that will be different.

  The lateral groove refers to a groove branched from the circumferential groove, and there may be a portion that partially extends in the circumferential direction. Further, the length of the lateral groove refers to the length at the groove center line 11 that can connect the midpoints with respect to the width of the groove.

  In the present invention, at least one circumferential groove 1 (two in the center in the tire width direction in the case shown in FIG. 1) is provided on the ground contact surface with respect to at least one tire rotation position under the above-described state. There are two or more horizontal grooves 3a, 3b, 3c (4 to 5 in the case of illustration) that open to this, and at least two of these lateral grooves 3a, 3b, 3c (3 in the case of illustration). Is characterized in that the groove lengths are different from each other.

The air column resonance sound is generated by the air column partitioned by the circumferential groove and the road surface in the ground contact surface based on the vibration of each part of the tire during rolling. The frequency f ₀ of the air column resonance sound in this case is v, the sound speed is v, the circumferential contact length of the tread surface, in other words, If the length obtained by adding the opening end correction length to the circumferential groove length included in is L, it is expressed by the following equation (1).

f ₀ = v / 2L (1)

  In addition, such air column resonance is caused when a plurality of circumferential grooves continuously extending in the tread circumferential direction are communicated with each other by a lateral groove extending across the circumferential groove in the tread pattern of the tire. Only the air column resonance with a specific frequency is generated. Here, the width, depth, and number of the circumferential grooves greatly affect the sound pressure level of the resonance rather than the resonance frequency.

Here, when the horizontal groove is terminated in the middle of the land, when the length of the horizontal groove in the ground plane plus the opening end correction length is 1 and the sound speed is v, the following equation (2) It is clear that sound is absorbed at a frequency f represented by

f = (2n−1) × v / 4l (2)
Where n: vibration order (n = 1, 3, 5...)

Thus, the sound-absorption frequency f, when close to the columnar resonance frequency f ₀ of the circumferential groove, it is possible to reduce the resonance noise.

  It has also been found that the width, depth and number of transverse grooves also have a large influence on the sound absorption capacity rather than the sound absorption frequency.

  Here, the resonance frequency of the air column due to the circumferential groove is such that when the grounding surface changes, the circumferential groove length in the grounding surface changes, or the transverse groove that crosses the circumferential groove included in the grounding surface with respect to the rotation position of the tire. As a result, the actual air column resonance has a frequency distribution with a width centered on the frequency calculated by the equation (1).

  In the tire according to the present invention, the lateral groove has a plurality of sound absorption frequencies f expressed by the equation (2). Therefore, the vibration absorption frequency band can be widened, and a wide frequency band can be obtained. A sound absorbing effect can be effectively obtained by arranging resonators having a similar sound absorption frequency distribution by combining the lateral grooves 3a, 3b, and 3c having different lengths with respect to the column resonance sound.

  In addition, in such a tire, the formation of the lateral groove for the specific circumferential groove of interest can be performed only on one side of the circumferential groove, and can also be performed on both sides thereof. Even if it exists, the function as expected can fully be exhibited in the horizontal groove opened to a circumferential groove.

  Three types of tires having different tread patterns from each other were used as examples, comparative example 1 and comparative example 2, and these tires were prototyped.

  As shown in FIG. 1, the tire of the example has three kinds of lateral grooves 3 a, 3 b, 3 c that open in the two circumferential grooves 1 on the tread tread surface and terminate in the land portion 2 in the circumferential direction. The resonators are arranged in order. The primary resonance frequency calculated by the equation (2) is 800 Hz for the longest horizontal groove 3b, 1000Hz for the horizontal groove 3a having an intermediate length, and 1250Hz for the shortest horizontal groove 3c.

  As shown in FIG. 2, the tire of Comparative Example 1 has one type of lateral groove 3a that opens in each of the two circumferential grooves 1 on the center side in the width direction and terminates in the land portion 2A in the circumferential direction. The total number of these resonators is the same as that of the tire of Example 1, the shape thereof is the same as that of the lateral groove 3a in Example 1, and the resonance frequency is 1000 Hz.

  As shown in FIG. 3, the circumferential groove 1 of the tire of Comparative Example 2 does not have a lateral groove that terminates at the land portion 2 </ b> B. Instead, a lateral groove 4 that has both ends opened to the circumferential groove is provided. Yes, and therefore the tread surface of this tire means no resonator.

  As described above, the tires of the example, comparative example 1 and comparative example 2 are different from each other only in the shape of the lateral grooves, and all other configurations, for example, the dimensions, number, arrangement and the like of the circumferential grooves 1 are all provided. The same.

  Each of these tires was 195 / 65R15 in size, and these tires were mounted on a 6JJ rim and the noise was measured in a state where the air pressure was 210 kPa.

  As a method for measuring noise, the tire was rolled with an indoor drum tester at a speed of 80 km / h under the action of a load of 4.4 kN, and the side sound of the tire at this time was in accordance with the conditions specified in JASO C606. Measured, and the overall value of the band of the center frequency 800-1000Hz-1250Hz in 1/3 octave band was obtained. The evaluation results are shown in Table 1 as a decibel difference (dB) as a sound reduction effect of the example and the comparative example 1 with respect to the comparative example 2.

  Especially this invention can be used suitably for the tire for passenger cars.

1 is a plan view showing a ground contact surface of a tire according to an embodiment of the present invention. 5 is a plan view showing a ground contact surface of a tire of Comparative Example 1. FIG. 6 is a plan view showing a ground contact surface of a tire of Comparative Example 2. FIG. It is sectional drawing which shows the quarter part of the tire molding drum in a later operation state.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Circumferential groove 2, 2A, 2B Land part 3a, 3b, 3c Lateral groove 4 Lateral groove 10 Tire contact surface 11 Centerline

Claims (1)

A circumferential groove continuously extending in the circumferential direction is disposed on the tread surface, and a lateral groove that opens in the circumferential groove and terminates at a distance from the circumferential groove without intersecting the other grooves. In the tire that constitutes the side branch type resonator,
At least one circumferential groove is opened in at least one contact surface in rotation of the tire under a state in which the tire is assembled to the applicable rim, filled with the maximum air pressure, and loaded with a mass corresponding to the maximum load capacity. A pneumatic tire having two or more of the lateral grooves, wherein at least two of the lateral grooves have different groove lengths.

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