JP4976214B2 - Pneumatic tire - Google Patents

Description

  The present invention includes a tread portion including at least one circumferential groove extending along the tire circumferential direction and a rib-like land portion adjacent to the groove, and the rib-shaped land portion has an opening in the circumferential groove. A plurality of resonators configured to reduce the noise caused by the circumferential groove, and the narrowed neck communicating with the circumferential groove through the narrowing neck and having a larger cross-sectional area than the narrowing neck And a pneumatic tire for which the direction to the vehicle is specified.

  The noise caused by the circumferential groove extending along the tire circumferential direction is a so-called air column resonance sound, which is in the pipe formed by the circumferential groove and the road surface in the contact area of the tread portion. It is generated by the resonance of air. The frequency of the air column resonance sound is often observed at about 800 to 1200 Hz in a general passenger car, and since the sound pressure level at the peak is high and the frequency band is wide, it occupies a large part of the noise generated by the tire. It will be.

  In addition, since human hearing is particularly sensitive in the above frequency band as shown by the A characteristic, for example, the reduction of the air column resonance is effective in improving the quietness in the feeling surface. It is.

Conventionally, as a method of reducing air column resonance sound, a so-called Helmholtz type resonator composed of a sipe (stenosis neck) opening in a circumferential groove and a resonance chamber (air chamber part) connected to the narrowing groove is used. A technique for absorbing energy in the vicinity of the resonance frequency of air column resonance has been proposed (see, for example, Patent Document 1).
Japanese Patent Laid-Open No. 5-338411

  However, in the tire as described in Patent Document 1, although the resonator has an effect of reducing the air column resonance sound caused by the circumferential groove, it has a space of a certain volume, so that the land portion of the tread portion. There is a problem that the rigidity is lowered and the steering stability and uneven wear resistance are lowered.

  An object of the present invention is to solve such problems of the prior art, and the object of the present invention is to effectively reduce the air column resonance sound by optimizing the arrangement pattern of the resonators. It is another object of the present invention to provide a pneumatic tire that can be reduced to a stable level and can ensure steering stability and uneven wear resistance.

  The present invention has been made to achieve the above object, and a pneumatic tire according to the present invention includes at least one circumferential groove extending along the tire circumferential direction in a tread portion, and a rib shape adjacent to the circumferential groove. A stenosis neck that opens into the circumferential groove in the rib-like land part, and an air chamber portion that communicates with the circumferential groove through the stenosis neck and has a larger cross-sectional area than the stenosis neck And a plurality of resonators that reduce noise caused by the circumferential groove are arranged, and the mounting direction to the vehicle is designated, that is, the direction to the outside and inside of the vehicle is designated. When the tread portion is partitioned into a vehicle outer half region and a vehicle inner half region with respect to the tire equator line, in the vehicle outer half region, the extending direction of the air chamber portion and the tire width direction The angle between and 0 degrees or more and less than 45 degrees The number of the width direction inclination resonators which are the resonators is such that the angle between the extending direction of the air chamber portion and the tire width direction is more than 45 degrees and not more than 90 degrees. More than the number, the number of the circumferential gradient resonators is greater than the number of the width gradient resonators in the vehicle inner half region. In such a configuration, the rigidity reduction of the land portion relative to the tire width direction due to the installation of the resonator is relatively within the rib-like land portion of the vehicle outer half region of the tread portion where the stress in the tire width direction is relatively concentrated during cornering. In the rib-like land portion in the vehicle inner half region of the tread portion where stress in the tire circumferential direction is relatively concentrated during driving and braking, the land with respect to the tire circumferential direction by installing the resonator is provided. By providing a large number of circumferentially inclined resonators with relatively small rigidity reduction, the rigidity of the rib-like land portion in the outer half of the vehicle is relatively increased with respect to the stress in the tire width direction. The rigidity of the rib-like land portion in the region is relatively increased with respect to the stress in the tire circumferential direction. Further, the deformation of the rib-like land portion with respect to the stress input during driving, braking and cornering is made uniform throughout the tread portion. Therefore, even if a resonator is installed, steering stability and uneven wear resistance are ensured.

  The “circumferential groove” referred to here includes not only a groove extending linearly along the tire circumferential direction, but also a so-called bent groove extending in the tire circumferential direction as a whole while bending in a wavy or zigzag manner, for example. Shall be included. Further, the “cross-sectional area” of the resonator means a cross-sectional area in each plane orthogonal to the virtual center line of each of the narrowed neck and the air chamber. Furthermore, the “extending direction” of the air chamber portion means a direction parallel to the longitudinal direction of the air chamber portion. Furthermore, “the angle formed by the extending direction of the air chamber portion and the tire width direction” means an angle when measured from the acute angle side.

  The angle formed by the extending direction of the air chamber portion of the widthwise tilt resonator and the tire width direction is 30 degrees or less, and the extending direction of the air chamber portion of the circumferential tilt resonator and the tire width direction Is preferably 60 degrees or more.

  In the vehicle outer half region, the number of the width direction tilt resonators is 50% or more than the number of the circumferential direction tilt resonators, and in the vehicle inner half region, the number of the circumferential direction tilt resonators is the width direction tilt resonator. The number is preferably 50% or more than the number of resonators.

  According to the present invention, the resonator having a relatively small influence on the rigidity of the rib-like land portion with respect to the direction of the stress is disposed at a place where the stress input during driving, braking and cornering becomes relatively large. Therefore, it is possible to ensure steering stability and uneven wear resistance while effectively reducing air column resonance noise.

  Next, embodiments of the present invention will be described with reference to the drawings. Here, FIG. 1 is a development view of a part of a tread portion of an entering tire (hereinafter referred to as “tire”) according to the present invention.

  The tire shown in FIG. 1 includes a tread portion 1 having a circumferential groove 2 extending along the tire circumferential direction and a rib-like land portion 3 adjacent thereto. The rib-like land portion 3 also includes a plurality of resonators 4 that reduce noise caused by the circumferential grooves 2. The resonator 4 further includes an air chamber portion 6 that opens to the tread portion 1 and the air chamber. A narrowing neck 8 is provided to communicate between the portion 6 and the circumferential groove 2. In addition, the cross-sectional area in the plane perpendicular to the virtual center line CL1 of the air chamber 6 is larger than the cross-sectional area in the plane perpendicular to the virtual center line CL2 of the narrowed neck 8.

  This tire is designated in the mounting direction to the vehicle (that is, the direction of the outside and the inside with respect to the vehicle). Here, when the tire is virtually divided into a half area outside the vehicle and a half area inside the vehicle around the tire equator line Le (in FIG. 1, the half area on the right side of the tire equator line Le is the vehicle outside half area, When the left half of the equator line Le is the vehicle inner half), in the vehicle outer half, the angle θout formed by the extending direction Lr of the air chamber 6 and the tire width direction Lw is 0 degree or more and less than 45 degrees. The number of the width direction inclined resonators 4a which are the resonators is a resonator in which the angle θin formed between the extending direction Lr of the air chamber 6 and the tire width direction Lw exceeds 45 degrees and is 90 degrees or less. On the other hand, the number of circumferentially inclined resonators 4b is larger than the number of laterally inclined resonators 4a in the vehicle inner half area. In general, in a tire, stress in the tire width direction is relatively concentrated in the vehicle outer half area of the tread portion 1 during cornering, and tire circumferential direction stress is relatively concentrated in the vehicle inner half area of the tread portion 1 during driving and braking. . Moreover, by installing the resonator in the rib-like land portion, the rigidity of the rib-like land portion is remarkably lowered, and not only the steering stability is impaired, but also uneven wear is likely to occur. In this invention, the width direction inclination resonator 4a which makes the rigidity fall of the land part 3 with respect to the tire width direction relatively small is provided in the vehicle outer half area, and the rigidity reduction of the land part 3 with respect to the tire circumferential direction is relatively set. By providing a large number of circumferentially inclined resonators 4b in the vehicle inner half area, the influence of the resonator 4 on the rigidity of the rib-like land portion 3 can be reduced, and the land portion 3 at the time of stress input can be reduced. Since deformation can be made uniform over the entire tread portion, steering stability and uneven wear resistance can be ensured while effectively reducing air column resonance.

  A more preferred embodiment related to the embodiment shown in FIG. 1 is shown in FIG. FIG. 2 is a diagram showing a pattern of a tread portion of a tire according to the present invention.

  By arranging the resonator 4 according to the present invention as described above, the influence of the resonator 4 on the rigidity of the rib-shaped land portion, that is, the decrease in rigidity can be reduced. In order to reduce this influence more effectively, it is necessary to make the extending direction Lr of the air chamber 6 of the resonator 4 close to parallel to the stress input direction. Therefore, the angle formed between the extending direction Lr of the air chamber portion 6 of the width direction inclination resonator 4a in the vehicle outer half region and the tire width direction Lw is set to 30 degrees or less, and the circumferential inclination resonator 4b in the vehicle inner half region is set to be 30 degrees or less. The angle formed by the extending direction Lr of the air chamber 6 and the tire width direction Lw is preferably 60 degrees or more. More preferably, the extending direction Lr of the air chamber portion 6 and the stress input direction are made completely parallel to each other, as shown in FIG. 2, in the vehicle outer half area (in FIG. 2, from the tire equator line Le). The angle formed by the extending direction Lr of the air chamber 6 of the width direction inclined resonator 4a in the right half region and the tire width direction Lw is 0 degree, and in the vehicle inner half region (in FIG. 2, from the tire equator line Le). The angle formed by the extending direction Lr of the air chamber 6 of the circumferentially inclined resonator 4b in the left half region and the tire width direction Lw is 90 degrees.

  Further, in order to more effectively reduce the influence of the resonator 4 on the rigidity of the rib-like land portion, in the vehicle outer half region, the number of the width direction tilt resonators 4a is the number of the circumferential direction tilt resonators 4b. It is preferable that the number of circumferentially inclined resonators 4b is 50% or more larger than the number of widthwise inclined resonators 4a in the vehicle inner half region. More preferably, as shown in FIG. 2, all of the resonators in the vehicle outer half region are configured by the width-direction inclined resonator 4a, and all the resonators in the vehicle inner half region are configured by the circumferential-direction inclined resonator 4b. is there.

  Various resonators 4 that can be used in the tire of the present invention will be described in detail with reference to the drawings. Here, FIG. 3 shows an example of a resonator applicable to the present invention. (A) is a schematic diagram of a Helmholtz type resonator, and (b) is a stepped tube type resonator. It is the schematic diagram shown in.

として表すことができるので、この共鳴周波数ｆは、周方向溝２の気柱共鳴周波数との関連の下で、狭窄ネック８の長さｌ_ｈ、狭窄ネック８の断面積Ｓ（半径ｒ）及び気室部６の容積Ｖの大きさを選択的に変えることによって、所要に応じて変化させることができる。 As described above, the resonator 4 constituted by the air chamber portion 6 and the constriction neck 8 is shown in FIG. 3A in a state where the rib opening of the air chamber portion 6 and the constriction neck 8 are both sealed by the road surface. The resonance frequency f of the resonator 4 is such that the length of the constriction neck 8 is l _h , the radius of the constriction neck 8 is r, and the constriction neck 8 is When the cross-sectional area is S, the volume of the air chamber 6 is V, and the sound speed is c,

This resonance frequency f can be expressed as: the length l _{h of} the constriction neck 8, the cross-sectional area S (radius r) of the constriction neck 8, and the relationship with the air column resonance frequency of the circumferential groove 2. By selectively changing the volume V of the air chamber 6, it can be changed as required.

  When the cross-sectional shape of the constriction neck 8 of the resonator 4 is not circular, the radius r in the above formula is obtained by calculating backward based on the cross-sectional area of the constriction neck 8. The coefficient “1.3” in the equation has a different value depending on the literature, but it can be generally obtained from an empirical equation and is used as one coefficient in the present invention.

  In addition, the air chamber 6 of the resonator 4 can be applied with the same cross-sectional area as the opening area over the entire depth direction, but the cross-sectional area gradually increases in the depth direction. Or you may apply what decreases gradually. Further, the bottom wall of the air chamber portion 6 may be a substantially flat surface, or may be a convex or concave curved surface toward the opening side.

  Furthermore, in the said embodiment, although the opening shape to the surface of the rib-like land part 3 of the air chamber part 6 of the resonator 4 is a rectangle, the air chamber part 6 should just have a longitudinal direction. The opening shape is not limited to this, and a polygon, an ellipse, another closed curve shape, an irregular closed shape, or the like can be applied.

  Alternatively, instead of the Helmholtz type resonator as described above, the air chamber 6 and the stenosis neck 8 are regarded as the first conduit 6 ′ and the second conduit 8 ′, respectively, as shown in FIG. A stepped tube type resonator comprising connecting pipes interconnecting them can also be applied. In this case, the resonance frequency f can be obtained as described below.

For the stepped tube type resonator, the acoustic impedance on the first pipeline 6 ′ side at the boundary is Z ₁₂ , the acoustic impedance on the second pipeline 8 ′ side in the boundary is Z ₂₁ , and the cross-sectional area of the first pipeline 6 ′. Is S ₁ , and the cross-sectional area of the second pipe line 8 ′ is S ₂ ,
Z ₂₁ = (S ₂ / S ₁ ) · Z ₁₂
The relationship is established.

'For the boundary condition, x = 0 at _V 2 _{= V} ⁰ e jwt, when at x = _{l 2} and _{P 2 / V 2 = Z 21} , the second conduit 8' second conduit 8 from the opening of the sound pressure _{P 2} at the position of distance x,
_{P 2 = Z c · {(} Z 21 cos (k (l 2 -x)) + jZ c sin (k (l 2 -x))) / (Z c cos (kl 2) + jZ 21 sin (kl 2)) } ・ V ₀ e ^jwt
It is expressed.
Where l ₂ is the length of the second conduit 8 ′, V ₂ is the particle velocity distribution of the second conduit 8 ′, V ₀ is the particle velocity at the input point, j is the imaginary unit, and Z _c Is ρc (ρ is the density of air, c is the speed of sound), and k is 2πf / c.

In addition, regarding the first pipeline 6 ′, when the boundary conditions are V ₁ = 0 when x = l ₁ and P ₂ = P ₁ when x = 0, the position of the distance x from the opening of the first pipeline 6 ′ The sound pressure P ₁ at
P ₁ = Z _c · [Z ₂₁ cos (k (l ₁ −x)) / (cos (kl ₁ ) · {Z _c cos (kl ₂ ) + jZ ₂₁ sin (kl ₂ )})] · e ^jwt
It is expressed.
Here, l ₁ is the length of the first pipeline 6 ′.

Here, since the resonance condition x = 0 and P ₂ = 0,
tan (kl ₁ ) tan (kl ₂ ) − (S ₂ / S ₁ ) = 0, and k, l ₁ , l ₂ , S ₂ , S ₁ , c are determined based on the conditional expression of this resonance. The resonance frequency f can be obtained.

  In the example shown in the figure, the stepped tube type resonator is a combination of pipes that are rectangular parallelepiped. However, to obtain the resonance frequency using the above conditional expression, the cross-sectional area and length of each pipe are determined. Therefore, the shape of the pipe line is not limited to a rectangular parallelepiped, and various shapes can be applied.

  In addition, it is indispensable that one end of the second pipe line 8 ′ is opened by the groove wall of the circumferential groove 2. The first pipe line 6 ′ and the second pipe line 8 ′ are provided on the tread tread surface. Since the closed space is formed by contact with the road surface, the upper end of the closed space can be opened at the surface of the rib, and this point is not limited.

  The above description shows only some of the embodiments of the present invention, and these configurations can be combined with each other or various modifications can be made without departing from the spirit of the present invention.

  Next, tires according to the present invention were prototyped and performance evaluations were performed, which will be described below.

  In the performance evaluation, the influence of the difference in the arrangement of the resonators on the steering stability and uneven wear resistance was investigated. The tire of Example 1 is a radial tire for passenger cars having a tire size of 225 / 55R17. As shown in FIG. 2, all the resonators in the vehicle outer half region are configured by width-direction inclined resonators, Have a tread pattern in which all the resonators are constituted by circumferentially inclined resonators. The circumferential groove has a width of 10 mm and a depth of 8 mm. In addition, the dimensions of the width direction tilt resonator and the circumferential direction tilt resonator are both 18 mm in the longitudinal length of the air chamber, 6 mm in the air chamber width, 7 mm in the air chamber depth, and the narrowed neck. The length of the stenosis neck is 1 mm, the depth of the stenosis neck is 2 mm, and the resonance frequency of the resonator is 1061 Hz. In addition, the dimensions of the circumferential groove, the width direction tilt resonator, and the circumferential direction tilt resonator of the tire used in this experiment are all in accordance with this.

  For comparison, although the tire size and the circumferential groove are the same as those in the first embodiment, as shown in FIG. 4, the resonators in the rib-like land portion located on both sides of the rib-like land portion including the tire equator line are arranged in the circumferential direction. As shown in FIG. 5, the tire of Comparative Example 1 having a tread pattern constituted by a tilt resonator and having resonators in rib-like land portions located on both sides thereof formed by a width-direction tilt resonator. Contrary to the tread pattern of Example 1, a comparison having a tread pattern in which the resonator in the outer half region of the vehicle is constituted by a circumferentially inclined resonator and the resonator in the inner half region of the vehicle is constituted by a widthwise inclined resonator. The tire of Example 2 was also prototyped.

  Each test tire is mounted on a rim of size 7.5J × 17, and after applying an air pressure of 220 kPa (relative pressure), the test tire is assembled in a passenger car for each test tire under the load load conditions equivalent to two passengers. The experiment and evaluation were performed.

(Silence)
Drive around a test track that has a long rounded section and a gently-curved handling evaluation road, etc. at a speed range from low speeds to around 100 km / h experienced by ordinary drivers on public roads. A professional driver evaluated the ease of hearing the column resonance sound and the ease of concern. The evaluation results are shown in Table 1. The larger this value, the greater the silencing effect by the resonator, that is, the quietness.

(Maneuvering stability)
Drive around a test track with a rounded road including a long straight section and a handling evaluation road with many gentle curves at a speed range from low speeds to around 100km / h experienced by ordinary drivers on public roads. A professional driver evaluated the feeling of handling on the road surface with a 10-point scale. The evaluation results are shown in Table 1. The larger this value, the greater the steering stability.

(Uneven wear resistance)
After traveling 10,000 km on a course including a general road, an expressway, and a mountain road, the level difference between the most worn portion and the least worn portion is measured in each rib-like land portion where the resonator is disposed. The average value of the steps is calculated and the results are shown in Table 1. The smaller the value, the better the uneven wear resistance.

  As is clear from the results shown in Table 1, the resonator in the outer half region of the vehicle is configured by a width direction tilt resonator, and the resonator in the inner half region of the vehicle is configured by a circumferential direction tilt resonator, thereby reducing silence. It was confirmed that steering stability and uneven wear resistance can be ensured while maintaining.

  As is apparent from the above description, according to the present invention, it is possible to provide a pneumatic tire that can achieve improved steering stability and uneven wear resistance while maintaining a reduction in air column resonance noise. .

FIG. 3 is a development view of a part of the tread portion of the pneumatic tire according to the present invention. It is a figure which shows the pattern of the tread part of the tire according to this invention. FIG. 1 shows an example of a resonator applicable to the present invention, in which (a) is a schematic diagram showing a Helmholtz resonator, and (b) is a schematic diagram showing a stepped tube resonator. . It is a figure which shows the tread pattern of the tire of the comparative example 1. It is a figure which shows the tread pattern of the tire of the comparative example 2.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tread part 2 Circumferential groove | channel 3 Rib-like land part 4 Resonator 4a Width direction inclination resonator 4b Circumferential direction inclination resonator 6 Air chamber part 6 '1st pipe line 8 Stenosis neck 8' 2nd pipe line

Claims (3)

The tread portion includes at least one circumferential groove extending along the tire circumferential direction, and a rib-shaped land portion adjacent to the circumferential groove, and a narrowed neck that opens into the circumferential groove in the rib-shaped land portion; A plurality of resonators configured to communicate with the circumferential groove through the stenosis neck and have an air chamber portion having a larger cross-sectional area than the stenosis neck and reduce noise caused by the circumferential groove. In a pneumatic tire with a specified mounting direction on the vehicle,
When the tread portion is partitioned into a half area outside the vehicle and a half area inside the vehicle from the tire equator line,
In the outer half of the vehicle, the number of width-direction inclined resonators, which are resonators in which the angle between the extending direction of the air chamber portion and the tire width direction is 0 ° or more and less than 45 °, is the extension of the air chamber portion. More than the number of circumferentially inclined resonators that are resonators in which the angle between the present direction and the tire width direction exceeds 45 degrees and is 90 degrees or less,
The pneumatic tire according to claim 1, wherein the number of the circumferential gradient resonators is greater than the number of the width gradient resonators in a vehicle inner half region. The angle formed between the extending direction of the air chamber portion of the width direction tilt resonator in the vehicle outer half region and the tire width direction is 30 degrees or less,
2. The pneumatic tire according to claim 1, wherein an angle formed between an extending direction of the air chamber portion of the circumferential gradient resonator in the vehicle inner half region and a tire width direction is 60 degrees or more. In the vehicle outer half region, the number of the width direction tilt resonators is 50% or more than the number of the circumferential direction tilt resonators,
The pneumatic tire according to claim 1 or 2, wherein the number of the circumferential gradient resonators is 50% or more greater than the number of the width gradient resonators in a vehicle inner half region.

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