JP2008001138A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of reducing both of low-frequency noise and high-frequency noise. <P>SOLUTION: The pneumatic tire comprises a pair of bead parts 1, at least two layers of carcass layer 5 reinforcing between the bead parts 1, side wall parts 2 respectively extended from the bead part 1 outward in the radial direction of the tire, a tread part 4 connecting both the peripheral side ends of each of the side wall parts 2 through each shoulder part 3, and a buffer pad 11 arranged near the shoulder part 3 between a ply P1 and a ply P2 structuring the carcass layer 5. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a pneumatic tire that can reduce both low-frequency road noise having a peak in the 160 Hz band and high-frequency road noise having a peak in the 315 Hz band.

  When a vehicle travels on a relatively rough road surface, the tire is vibrated by road surface unevenness, and the vibration propagates through a route such as a rim, an axle, and a vehicle body, and finally becomes noise called road noise in the passenger compartment. It has been known. Among road noises, those having a peak in the 160 Hz band (frequency range of about 100 to 200 Hz) are referred to as low frequency road noise, and those having a peak in the 315 Hz band (frequency range of about 250 to 400 Hz) are high frequency loads. This is called noise, and it is required to be reduced with the recent upgrade of automobiles.

  Tire vibration that generates low-frequency road noise is generally considered to be related to the circumferential primary mode. As a countermeasure, it is important to reduce the longitudinal eigenvalue of the tire and lower its primary eigenvalue. Has been. For example, in the tire described in Patent Document 1 below, the longitudinal rigidity is reduced by inclining the cord constituting the carcass layer at a predetermined angle at a specific portion, thereby reducing the primary eigenvalue.

  On the other hand, tire vibration that generates high-frequency road noise is generally considered to be related to the secondary mode of the cross section, and as a countermeasure, the rigidity of the portion that becomes the antinode of tire vibration, such as the buttress part near the shoulder part and the lower part of the side, is considered. It is important to increase For example, in the tire described in Patent Document 2 below, a film reinforcing layer is disposed in the buttress portion to increase rigidity, thereby reducing high-frequency road noise. Further, although not an example of countermeasures against road noise, in the tire described in Patent Document 3 below, a barrier rubber layer is provided in the buttress portion, and the suppression of vibration is achieved by utilizing the mass increase thereby.

As described above, reducing low-frequency road noise and reducing high-frequency road noise are contradictory design philosophies in terms of tire rigidity. For this reason, as a countermeasure against road noise, there is a fact that it must be biased to either low frequency road noise or high frequency road noise, and it has been very difficult to reduce both.
JP 2003-226118 A JP-A-6-32119 JP-A-7-266814

  Then, the objective of this invention is providing the pneumatic tire which can reduce both low frequency road noise and high frequency road noise.

  The above object can be achieved by the present invention as described below. That is, the pneumatic tire according to the present invention includes a pair of bead portions, at least two carcass layers that reinforce the space between the bead portions, a sidewall portion that extends outward in the tire radial direction from the bead portion, and the sidewalls. The tread part which connects each outer peripheral side edge of a part via a shoulder part, and the buffer pad distribute | arranged between the plies which comprise the said carcass layer in the said shoulder part vicinity are provided.

  In the pneumatic tire according to the present invention, since the cushion pad as the cushioning material is disposed in the vicinity of the shoulder portion, the primary eigenvalue of the tire can be shifted to the lower side by the cushioning effect, thereby reducing the low frequency. Road noise can be reduced. Further, the cushion pad is disposed between the plies constituting the carcass layer in the vicinity of the shoulder portion, so that the tension of the ply located on the outer peripheral side of the cushion pad can be increased, and the tire vibration that generates the secondary cross-section mode. High-frequency road noise can also be reduced by suppressing the amplitude of.

  Here, the reason why the tension of the ply located on the outer peripheral side of the buffer pad is increased is as follows. That is, in the tire molding process, the ply constituting the carcass layer is formed along the tire shape by bulging and deforming the central portion while rewinding the end portion from the cylindrical shape. If a buffer pad is disposed between the plies, the ply located on the outer peripheral side thereof bulges and deforms more on the outer peripheral side than usual, thereby increasing the tension. If the buffer pad is disposed not on the inner side of the carcass layer but between the plies, the rigidity at that portion is excessively increased, and low-frequency road noise cannot be sufficiently reduced.

  As described above, the present invention suppresses the amplitude by increasing the ply tension of the portion that becomes the antinode of vibration in the sectional secondary mode while lowering the primary eigenvalue using the buffering effect of the buffer pad. Thus, it is possible to achieve both low-frequency road noise reduction and high-frequency road noise reduction, both of which have been difficult in the past.

  In the above, it is preferable that the buffer pad is a rubber layer having a modulus lower than that of the rubber layer constituting the sidewall portion. As a result, the above-described buffer effect can be suitably obtained, and an effect of reducing the longitudinal rigidity of the tire can be obtained, and low-frequency road noise can be more appropriately reduced.

  In the above, it is preferable that the maximum thickness of the buffer pad is 5 mm or more, thereby effectively increasing the tension of the ply located on the outer peripheral side of the buffer pad and appropriately reducing high-frequency road noise. Can do.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a tire meridian cross-sectional view schematically showing an example of a pneumatic tire according to the present invention. As shown in FIG. 1, the pneumatic tire includes a pair of bead portions 1, a carcass layer 5 that reinforces the space between the bead portions 1, a sidewall portion 2 that extends outward from each bead portion 1 in the tire radial direction, The tread part 4 which connects each outer peripheral side edge of the wall part 2 via the shoulder part 3 is provided.

  The bead portion 1 is provided with an annular bead 1a formed by rubber-covering a converging body such as a steel wire, and a bead filler 1b made of hard rubber having a substantially triangular cross section disposed outside the bead 1a in the tire radial direction. It is installed. The carcass layer 5 is disposed so as to be bridged between the pair of bead portions 1, and the end portion thereof is wound around the bead 1 a to the outside to be locked.

  The carcass layer 5 has a two-layer structure in which two plies P1 and P2 are laminated. Each of the plies P1 and P2 is formed of a rubber-coated hook-shaped cord, and the cord is arranged at an angle of about 90 ° with respect to the tire equator line C. As the material of the cord, organic fibers such as polyester, rayon, nylon, and aramid, steel, and the like are preferably used.

  An inner liner layer 6 for maintaining air pressure is disposed on the inner periphery of the carcass layer 5. A rim strip rubber 8 is disposed on the outer periphery of the carcass layer 5 of the bead portion 1, and a sidewall rubber 9 is disposed on the outer periphery of the carcass layer 5 of the sidewall portion 2. Furthermore, a belt layer 7 for reinforcing reinforcement due to the effect of the shell is disposed on the outer periphery of the carcass layer 5 of the tread portion 4, and a tread rubber 10 is disposed on the outer periphery thereof.

  And between the ply P1 and the ply P2 in the vicinity of the shoulder portion 3, a buffer pad 11 as a buffer material is annularly arranged along the tire circumferential direction. Due to the buffering effect of the buffer pad 11, the primary eigenvalue of the tire can be shifted to a lower side, and low-frequency road noise can be reduced.

  The buffer pad 11 of the present embodiment is a rubber layer having a lower modulus than the sidewall rubber 9, thereby reducing the longitudinal rigidity of the tire while appropriately achieving the above-described buffer effect, and reducing low-frequency road noise. It can reduce more effectively. From the viewpoint of appropriately obtaining such a buffering effect, the buffer pad 11 preferably has a 100% elongation modulus (M100) measured in accordance with JISK6251 of 1.0 to 1.5 MPa, and preferably 1.0 to 1.1 MPa. It is more preferable that Moreover, it is preferable that the rubber | gum hardness measured according to the buffer pad 11 based on the durometer hardness test (A type) of JISK6253 is 40-50 degrees.

  In addition, since the buffer pad 11 is disposed between the ply P1 and the ply P2 in the vicinity of the shoulder portion 3, the tension of the ply P2 in the portion that becomes the antinode of vibration in the secondary cross-sectional mode is increased, and the amplitude thereof And high-frequency road noise can be reduced together with the low-frequency road noise described above. The reason why the tension of the ply P2 positioned on the outer peripheral side of the buffer pad 11 is increased is as described above.

  The maximum thickness of the buffer pad 11 is preferably 5 mm or more, more preferably more than 5 mm, and still more preferably 8 mm or more. Thereby, the tension of the ply P2 can be effectively increased and high-frequency road noise can be appropriately reduced. That is, when the maximum thickness is less than 5 mm, the bulging deformation of the ply P2 toward the outer peripheral side at the time of tire molding is relatively small, and the effect of increasing the tension tends to be small. The upper limit of the maximum thickness of the buffer pad 11 is preferably about 15 mm in consideration of the influence on other tire performances.

  The maximum thickness of the buffer pad 11 is a thickness measured at the tire meridian cross section, and is measured in a no-load state in which the tire is mounted on the specified rim and filled with the specified internal pressure. Here, the prescribed rim refers to a standard rim determined by JATMA corresponding to the tire size. The specified internal pressure is the maximum air pressure based on JATMA, but is 180 kPa when the tire is for a passenger car.

  The buffer pad 11 preferably has a substantially crescent-shaped cross section as in the present embodiment, and can be interposed between the plies appropriately along the shape of the carcass layer 5. The buffer pad 11 may have a substantially trapezoidal cross section or a substantially triangular cross section.

  The buffer pad 11 is disposed at the buttress portion in the vicinity of the shoulder portion 3 at the portion where the thickness is maximum, and the outer peripheral end is disposed 3 to 5 mm below the belt from the belt end, and the inner peripheral end is the maximum tire width. It is preferable to be disposed between the position TW and the upper end of the bead filler 1b. As a result, the tension of the ply P2 can be appropriately increased at the portion that becomes the antinode of vibration in the secondary cross-section mode, and high-frequency road noise can be effectively reduced.

  Further, the peripheral length of the portion circumscribing the buffer pad 11 of the ply P2 is preferably 2% or more, and more preferably 3% or more longer than the peripheral length of the portion inscribed to the buffer pad 11 of the ply P1. As a result, the tension of the ply P2 can be effectively increased to appropriately reduce the high-frequency road noise. This peripheral length is the length measured in the tire meridian cross section in the same state as when measuring the maximum thickness.

  Examples of the raw rubber such as the rubber layer described above include natural rubber, styrene butadiene rubber (SBR), butadiene rubber (BR), isoprene rubber (IR), butyl rubber (IIR), and the like. Used in combination with more than one species. These rubbers are reinforced with fillers such as carbon black and silica, and a vulcanizing agent, a vulcanization accelerator, a plasticizer, an anti-aging agent and the like are appropriately blended.

  Examples and the like specifically showing the configuration and effects of the present invention will be described below. The evaluation was performed as follows.

(1) Primary eigenvalue With a test tire pressure of 240 kPa and a load load of 4300 N, hammer vibration is applied to the center of the tread in the vertical direction, and the vertical response generated on the fixed shaft of the rim is the vibration transmission level. And displayed for each frequency. Of the plurality of natural vibration peaks generated at that time, the frequency at which the peak value is maximum is taken as the primary eigenvalue.

(2) Road noise level The test tire is mounted on a real car (domestic 2000cc class FF car), the front and rear have an air pressure of 200kPa, a microphone is attached to the ear of the driver's seat, 160km and 315Hz at a constant speed of 60km / h. The road noise level was measured.

  The test tires used for the evaluation were all size 205 / 60R16 92H, compared with the tire structure shown in FIG. 1 that does not have a buffer pad, Comparative Example 1, and the buffer pad disposed on the inner peripheral side of the carcass layer Example 2, Example 1 to 3 in which a buffer pad was arranged between plies. The modulus (M100) of the buffer pad was 1.5 MPa, and the modulus (M100) of the sidewall rubber was 1.9 MPa. The evaluation results are shown in Table 1.

  Comparative Example 1 does not have a structure capable of reducing road noise, and therefore the noise level is high for both low and high frequencies. Further, it can be seen from Table 1 that the low frequency road noise cannot be sufficiently reduced in Comparative Example 2. In contrast, in the first to third embodiments, the high frequency road noise can be reduced while reducing the low frequency road noise, and in particular, the excellent reduction effect is obtained in the first embodiment in which the buffer pad is relatively thick. .

Tire meridian cross-sectional view schematically showing an example of the pneumatic tire of the present invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Bead part 2 Side wall part 3 Shoulder part 4 Tread part 5 Carcass layer 9 Side wall rubber 11 Buffer pad TW Tire maximum width position P1 Ply P2 Ply

Claims (3)

  A pair of bead portions, at least two carcass layers that reinforce the space between the bead portions, sidewall portions that extend outward in the tire radial direction from the bead portions, and outer peripheral side ends of the sidewall portions are shoulders A pneumatic tire comprising a tread portion that is connected via a portion, and a buffer pad that is disposed between plies that constitute the carcass layer in the vicinity of the shoulder portion.   The pneumatic tire according to claim 1, wherein the buffer pad is a rubber layer having a modulus lower than that of the rubber layer constituting the sidewall portion.   The pneumatic tire according to claim 1 or 2, wherein the buffer pad has a maximum thickness of 5 mm or more.

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