JP2011148423A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce manufacturing cost, and to easily improve tire performance other than reduction of noise. <P>SOLUTION: A plurality of holes 14 and 15 are formed on a side of a width direction of a main groove 13 to be away in a peripheral direction and arranged closer to the main groove 13, and thereby rigidity of a land portion on the side of the main groove 13 is lowered by the plurality of holes 14 and 15, and column tube resonance sound is effectively reduced. Further, narrow grooves 16 and 17 communicated with all the holes 14 and 15 are formed, and thereby air in the holes 14 and 15 is not compressed and generation of high frequency noise (pumping sound) is prevented. Thus, the holes 14 and 15 and the narrow grooves 16 and 17 are just required to be formed in a tread surface 12, and thereby the manufacturing cost becomes inexpensive and a degree of freedom in designing a tread pattern is increased. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

    The present invention relates to a pneumatic tire in which a plurality of main grooves are formed on a tread surface.

    In recent years, as the proportion of tire noise in automobile noise has increased with the quietness of vehicles, reduction of tire noise has become a major issue. In particular, noise in the frequency band of 1000 to 2000 Hz that is generated from the tire due to air column resonance when the tire is running, so-called air column resonance, has a high peak and wide band, and is sensitive to human hearing. Because of this noise, immediate countermeasures are desired.

  Here, the air columnar resonance sound means that when a tire having a main groove extending continuously in the circumferential direction is grounded, a tube having the same length as the ground contact length is formed between the groove wall of the main groove and the ground contact surface. However, the groove wall of such a pipe (main groove) vibrates due to the input to the tire during running, and this vibration is a noise generated by repeatedly compressing and releasing the air in the pipe. The peak frequency depends on the length of the tube (contact length). Conventionally, as a technique for reducing noise based on such air column resonance, for example, a technique described in Patent Document 1 below is known.

JP 2008-155798 A

  This is provided with a number of Helmholtz resonators on the tread tread, each of which is composed of an air chamber that opens to the surface of the land portion at a position away from the main groove, and a narrow neck that communicates the air chamber and the main groove. By absorbing the energy in the vicinity of the resonance frequency of the air column resonance sound, the noise is effectively reduced.

    However, in such a conventional pneumatic tire, since a large number of resonators are disposed on the land surface, the tread pattern becomes a complicated shape, resulting in an increase in manufacturing cost. was there. In addition, when a large number of resonators are disposed on the land as described above, the degree of freedom is limited when designing a tread pattern, and tire performance other than noise reduction, such as wear durability performance, wet performance, etc. There is also a problem that it is difficult to improve the value to a sufficient value.

  An object of the present invention is to provide a pneumatic tire that is inexpensive to manufacture and that can easily improve tire performance other than noise reduction.

    In such a pneumatic tire in which a plurality of main grooves extending continuously in the circumferential direction is formed on the tread surface, the object is separated in the circumferential direction at least one side of the width direction of at least one main groove, This can be achieved by a pneumatic tire that forms a plurality of holes arranged close to the main groove, while communicating all the holes and forming a narrow groove extending continuously in the circumferential direction.

  In the present invention, since a plurality of holes are formed in the circumferential direction at least on one side in the width direction of the at least one main groove and are disposed close to the main groove, the land portion on the side of the main groove is formed. The rigidity is lowered by the plurality of holes, and as a result, vibration of the main groove groove wall due to input during tire traveling is suppressed, and air columnar resonance noise is effectively reduced. However, if a plurality of holes are formed apart in the circumferential direction as described above, when these holes enter the grounding area, the opening of the hole is closed by the road surface and the internal air is compressed, and then the grounding When the hole is removed from the area, the opening is opened and a part of the compressed air is exhausted at a stretch, generating high frequency noise (pumping sound) of 2000 Hz or more. As a result, it is difficult to reduce the noise as a whole. It becomes.

  However, in the present invention, since all the holes are communicated and the narrow groove extending continuously in the circumferential direction is formed, when the opening of the hole is closed and the internal air is compressed as described above, The air flows out of the ground contact area through the narrow groove, and as a result, the air in the hole is not compressed and the generation of the high frequency noise as described above is prevented. In addition, since it is only necessary to form the above-described holes and narrow grooves on the tread surface, the manufacturing cost is low, and the tread pattern design is more flexible and the tire performance other than noise reduction is easily improved. be able to.

  Moreover, if comprised as described in Claim 2, the rigidity of the land part in the side of a main groove can be reduced effectively. Furthermore, if constituted as in claim 3, air columnar resonance noise can be effectively reduced while suppressing uneven wear. Further, if configured as described in claim 4, it is possible to strongly reduce air columnar resonance noise, and further, if configured as described in claim 5, while suppressing uneven wear, The outflow of air from can be ensured. Further, if configured as described in claim 6, the vulcanization mold can be manufactured at a low cost, and further, if configured as described in claim 7, when the opening edge of the hole hits the road surface. The frequency of the generated hitting sound is dispersed, and the hitting sound can be made white noise.

It is a top view of the pneumatic tire which shows Embodiment 1 of this invention. It is the meridian sectional view. It is a top view of the main groove vicinity. FIG. 4 is a cross-sectional view taken along the line II of FIG. It is a graph which shows the spectrum of noise.

Embodiment 1 of the present invention will be described below with reference to the drawings.
In FIGS. 1, 2, 3, and 4, 11 is a pneumatic tire. The tread tread 12 of the pneumatic tire 11 extends continuously in the circumferential direction, that is, a plurality of tires that are not interrupted in the middle, here Four main grooves 13 are formed, and these main grooves 13 are arranged apart from each other in the width direction of the pneumatic tire 11. Here, the main groove 13 may extend linearly as in this embodiment, but may be bent in a zigzag shape, and the groove depth D is usually constant, but in the circumferential direction. It may change periodically or irregularly.

  Then, after mounting such a pneumatic tire 11 on the applicable rim and running on the road surface with the internal pressure filled, the contact length between the groove wall of the main groove 13 and the contact surface (the stepping end in the contact region) The length of the pipe is the same as that of the kicking end), but the groove wall of such a pipe (main groove) vibrates due to the input to the tire during running, and this vibration is Air is repeatedly compressed and released, generating noise (air column resonance).

  The tread tread 12 on the inner side in the width direction (the tire equator S side) and the outer side in the width direction (the tread end T side) of each main groove 13 extends in a plurality of radial directions separated by the same pitch (equal distance) in the circumferential direction. Bottom holes 14 and 15 are respectively formed, and these holes 14 and 15 are arranged on a straight line parallel to the main groove 13 at a position close to the corresponding main groove 13. The holes 14 and 15 have the same cross-sectional area and the same groove depth (here, the same as the groove depth D of the main groove 13). As described above, when the plurality of holes 14 and 15 which are disposed in the width direction side of the main groove 13 and close to the main groove 13 are formed in the circumferential direction, the rigidity of the land portion on the side of the main groove 13 is increased. As a result, the vibration of the groove wall of the main groove 13 due to input during tire traveling is suppressed, and air columnar resonance noise can be effectively reduced.

  However, if the holes 14 and 15 are formed apart in the circumferential direction as described above, when the holes 14 and 15 enter the grounding area, the openings of the holes 14 and 15 are closed by the road surface, and the holes When the air inside 14 and 15 is compressed, and then the holes 14 and 15 are removed from the ground contact area, the opening is opened and a part of the compressed air is exhausted at once, and high frequency noise of 2000 Hz or more (pumping sound) As a result, although air columnar resonance can be reduced, it is difficult to reduce noise as a whole.

  For this reason, in this embodiment, all the holes 14 communicate with each other, extend continuously in the circumferential direction, and are narrower than the main groove 13 (having a narrow cross-sectional area), in this case, one narrow groove 16. , And all the holes 15 communicate with each other and continuously extend in the circumferential direction. One or more narrow grooves 17 extending in a straight line shape in this case are formed in the width direction of the main groove 13. It was formed on the tread tread 12 on the side. As a result, when the openings of the holes 14 and 15 are closed as described above and the air inside is about to be compressed, the air flows out from the grounding region through the narrow grooves 16 and 17, and as a result, the holes 14 and 15 The inside air is not compressed, the generation of the high frequency noise as described above is prevented, and the noise can be reduced in a wide frequency band. Moreover, since it is only necessary to form the holes 14 and 15 and the narrow grooves 16 and 17 on the tread tread 12 as described above, the manufacturing cost is low, and the tread pattern design is more flexible and the noise is not reduced. Tire performance can be easily improved.

  In this embodiment, the holes 14 and 15 are formed on both sides of each main groove 13 in the width direction. However, in the present invention, either one of the main grooves 13 on one side in the width direction (inward in the width direction). Alternatively, a plurality of holes separated in the circumferential direction may be formed on the outer side in the width direction, and may be formed at least on one side in the width direction of at least one main groove 13. Here, if holes 14 and 15 are formed on both sides in the width direction of the main groove 13 as in this embodiment, the rigidity is reduced as compared with the case where holes are formed only on one side in the width direction of the main groove 13. Since the area of the land portion is increased, air columnar resonance can be further effectively reduced.

  And when forming a hole in the width direction side of some main grooves 13, since the main groove 13 adjacent to the tire equator S greatly contributes to generation | occurrence | production of air columnar resonance sound, tire equator S Preferably, it is formed on the side in the width direction of the main groove 13 disposed close to the main groove 13. Further, in the above-described embodiment, in order to reduce the manufacturing cost of the vulcanization mold, the holes 14 and 15 are arranged at the same pitch in the circumferential direction, but in the present invention, the openings of the holes 14 and 15 are arranged. In order to disperse the frequency of the hitting sound generated when the edge hits the road surface and make the hitting sound white noise, it may be arranged at different pitches in the circumferential direction. In this embodiment, the cross-sectional shape of the holes 14 and 15 on the plane orthogonal to the radial direction is circular. However, in the present invention, the cross-sectional shape may be a square, a rectangle, an ellipse, or the like.

  The hole 14 is formed between an opening edge 13a located on the hole 14 side of the main groove 13 and a position P separated from the opening edge 13a by the groove width W of the tread tread 12 inward in the width direction. The hole 15 is disposed between an opening edge 13b located on the hole 15 side of the main groove 13 and a position Q separated from the opening edge 13b by the groove width W of the tread tread 12 outward in the width direction. Is preferred. The reason is that when the holes 14 and 15 are arranged in the width direction inside and outside the positions P and Q, the rigidity of the holes 13 and 15 on the side of the main groove 13 may be insufficiently lowered. This is because, if it is disposed within the aforementioned range, the rigidity of the land portion on the side of the main groove 13 can be effectively reduced, and the air column resonance noise can be sufficiently reduced.

  Furthermore, when the distance from one circumferential end to the other circumferential end of the single hole is L, the volume of each hole 14, 15 is within the range of the distance L (the main groove 13 cut out at the distance L). It is preferable to be within the range of 0.2 to 0.5 times the volume of. The reason is that if the value is less than 0.2 times, the rigidity of the side of the main groove 13 due to the holes 14 and 15 is insufficiently lowered, and the air column resonance noise may not be effectively reduced. If it exceeds the double, the rigidity on the side of the main groove 13 is greatly reduced by the holes 14 and 15, and uneven wear may occur, but if it is within the above range, the air column resonance is suppressed while suppressing uneven wear. This is because the sound can be effectively reduced.

  The narrow grooves 16 and 17 pass through the center of the cross section of all the holes 14 and 15 in order to facilitate the outflow of air from the holes 14 and 15, and the narrow grooves 16 and 17 The meridian cross section is square in this embodiment, but may be rectangular, semicircular, or the like. The cross-sectional area of the narrow grooves 16 and 17 in the meridian section is preferably in the range of 0.02 to 0.10 times the cross-sectional area of the main groove 13. The reason is that if the value is less than 0.02 times, the compressed air outflow from the holes 14 and 15 is insufficient, and high-frequency noise is likely to occur.On the other hand, if the value exceeds 0.10 times, There is a risk that uneven wear may occur due to a significant decrease in rigidity in the land portion near the holes 14 and 15, but if it is within the above-mentioned range, the outflow of air from the hole is ensured while suppressing uneven wear. Because it can.

    Next, test examples will be described. In this test, in addition to the comparative tire 1 in which one main groove having a groove width W of 8 mm and a groove depth D of 8 mm is formed on the tread surface on the tire equator S, in addition to the main groove in the comparative tire 1, Comparative tire 2 in which a plurality of holes with a diameter of 4 mm are formed on both sides in the width direction of the main groove on a circumferential line 3 mm away from both opening edges and having a circular shape with a circular cross section separated by an equal pitch of 5 mm in the circumferential direction In addition to the main grooves and holes in the comparative tire 2, narrow grooves having a square cross section with a width of 1.5 mm and a depth of 1.5 mm are formed on circumferential lines located on both sides of the main groove in the width direction. An implementation tire was prepared. The reason why only one main groove extending linearly is formed on the tire equator S is that the effect can be easily confirmed.

  Here, the size of each tire was 195 / 65R15. Next, each of such tires is mounted on an applicable rim, filled with an internal pressure (gauge pressure) of 220 kPa, and pressed against the rotating drum of the indoor drum tester while applying a load of 4 kN, and 80 km / h. The noise at the side of the tire was measured under the conditions defined in JASO C606. From the measurement results, the partial overall value dB (A) in the 1000 to 2000 Hz band corresponding to the air column resonance was obtained. As a result, the comparative tire 1 was 82.0, but the comparative tire 2 was 81.1. In the case of the implemented tire, the partial overall value was 81.0 lower than that of the comparative tire 1 by 0.9 and 1.0, respectively, and the air column resonance noise was effectively reduced.

  However, the overall value dB (A) in all frequency bands was 85.2 in the comparative tire 1, but deteriorated by 85.4 and 0.2 in the comparative tire 2, but decreased by 84.7 and 0.5 in the actual tire. FIG. 5 shows the noise spectrum in the entire frequency band generated by each tire in the above-described test. Comparative tire 1 is a triangle (Δ), comparative tire 2 is a white circle (◯), Is represented by a cross (x). From FIG. 5, it can be understood that the sound pressure level of the comparative tire 2 is higher than that of the comparative tire 1 and the implementation tire in a high frequency range of 3000 Hz or more due to pumping.

  The present invention can be applied to the industrial field of pneumatic tires in which a plurality of main grooves are formed on the tread surface.

11 ... Pneumatic tire 12 ... Tread tread
13 ... Main groove 13a, 13b ... Open edge
14, 15 ... Hole 16, 17 ... Narrow groove W ... Groove width L ... Distance P, Q ... Position

Claims (7)

    In a pneumatic tire in which a plurality of main grooves extending continuously in the circumferential direction are formed on the tread surface, at least one side of the main groove is separated in the circumferential direction at least on one side in the width direction and is disposed close to the main groove. A pneumatic tire characterized in that, while forming a plurality of holes, all the holes are communicated and a narrow groove extending continuously in the circumferential direction is formed.     2. The pneumatic tire according to claim 1, wherein the hole is disposed between an opening edge on a hole side of the main groove and a position separated from the opening edge by a groove width of the main groove in the width direction side.     When the distance from one circumferential end to the other circumferential end of the single hole is L, the volume of each hole is in the range of 0.2 to 0.5 times the volume of the main groove within the distance L. Item 3. The pneumatic tire according to Item 1 or 2.     The pneumatic tire according to claim 1, wherein the hole and the narrow groove are formed on both sides in the width direction of the main groove.     The pneumatic tire according to any one of claims 1 to 4, wherein a cross-sectional area of the narrow groove is in a range of 0.02 to 0.10 times a cross-sectional area of the main groove.     The pneumatic tire according to claim 1, wherein the holes are arranged at the same pitch in the circumferential direction.     The pneumatic tire according to claim 1, wherein the holes are arranged at different pitches in the circumferential direction.

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