JP2009090824A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of reducing a pattern noise on the premise that an air core resonance can be reduced by a resonator. <P>SOLUTION: A pneumatic tire having at least one circumferential groove 3 extending along a circumferential direction of the tire is provided in a tread portion 1 and at least one row of rib-like land part 5 adjacent to it. The resonator 11, consisting of a branched groove 7 opening to the circumferential groove 3 and an air chamber part 9 for communicating with the circumferential groove 3 via the branched groove 7 of which section area is larger than that of the branched groove, for reducing noise caused by the circumferential groove 3 is provided in the rib-like land part 5. The resonator 11 has a first end part 13 and a second end part 15 for defining a length L in the circumferential direction of the tire of the air chamber part 9 and the branched groove 7 extends from the second end part 15 in a direction away from the first end part 13. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention includes a tread portion including at least one circumferential groove extending along the tire circumferential direction and at least one row of rib-shaped land portions adjacent to the tread portion, and the circumferential direction in the rib-shaped land portion. Resonance comprising a branch groove opening in the groove, and an air chamber portion communicating with the circumferential groove through the branch groove and having a larger cross-sectional area than the branch groove, and reducing noise caused by the circumferential groove. The present invention relates to a pneumatic tire provided with a vessel, and in particular, aims to reduce pattern noise of the pneumatic tire.

  In recent years, with the quietness of vehicles, the contribution to automobile noise resulting from load rolling of pneumatic tires has increased, and reduction thereof has been demanded. Among them, tire noise at a high frequency, particularly around 1000 Hz, is a main cause of noise outside the vehicle, and countermeasures for reducing the noise are also required in response to environmental problems.

  The tire noise around 1000 Hz is a so-called air column resonance sound generated by resonance of air in the pipe mainly formed by a circumferential groove extending along the tire circumferential direction and a road surface in a contact area of the tread portion. In general passenger cars, it is often observed at about 800 to 1200 Hz, and since the peak sound pressure level is high and the frequency band is wide, it occupies most of the noise generated from pneumatic tires. It becomes. In addition, since human hearing is particularly sensitive in the frequency band (A characteristic) around 1000 Hz, the reduction of such air column resonance sound is also effective in improving the quietness of the feeling during running. It is valid.

  In order to reduce such air column resonance noise, it is effective to reduce the number of circumferential grooves and the volume of the grooves, but in this case, the drainage performance is a result of insufficient groove volume of the circumferential grooves. May decrease. In order to reduce air column resonance without reducing the number of circumferential grooves and the volume of grooves, Patent Document 1 discloses that one end of the circumferential groove is opened in the rib-like land portion formed by the circumferential grooves. A pneumatic tire is disclosed in which a long horizontal groove (air column resonator) whose other end terminates in a land portion is provided, and air column resonance noise can be reduced by using anti-resonance in the horizontal groove. . However, in the pneumatic tire disclosed in Patent Document 1, since it is essential to dispose long lateral grooves corresponding to the air column resonance frequency, the degree of freedom in designing the tread pattern is impaired.

  As a solution to these problems, as disclosed in Patent Document 2, a so-called sipe (branch groove) that opens to a circumferential groove and a resonance chamber (air chamber part) that is connected to the branch groove is a so-called one. There has been proposed a technique for absorbing energy in the vicinity of the resonance frequency of air column resonance by disposing a Helmholtz resonator in the rib-like land portion. As a result, the degree of freedom in designing the tread pattern is improved as compared with the pneumatic tire described in Patent Document 1, while ensuring sufficient groove volume of the circumferential groove and ensuring drainage performance and the like. Is possible.

International Publication No. 04/103737 Pamphlet Japanese Patent Laid-Open No. 5-338411

  However, in the pneumatic tire described in Patent Document 2, the air column resonance noise is reduced by the resonator, but as shown in FIG. Since the air chamber portion 109, which is a hollow space having a large volume, is formed, the cross-sectional area in the tire width direction of the rib-like land portion 105 varies greatly as shown in FIG. . Thus, in the conventional pneumatic tire shown in FIG. 9A, the rib-like land portion 105 has a relatively high rigidity section X1, a section X2 having a rigidity lower than that of the section X1, and a rigidity higher than that of the section X2. A small section is formed, and as a result, during load rolling, the blocks formed around the resonator 111 are likely to fluctuate due to these rigidity differences, and the fluctuations cause the blocks around the resonator to collide with the road surface. There was a problem that the impact was increased and the pattern noise increased.

  Accordingly, it is an object of the present invention to solve these problems, and an object of the present invention is to optimize the arrangement of the resonators on the assumption that the air column resonance can be reduced by the resonators. It is an object of the present invention to provide a pneumatic tire capable of reducing pattern noise.

  In order to achieve the above object, the present invention comprises a tread portion having at least one circumferential groove extending along the tire circumferential direction and at least one row of rib-like land portions adjacent to the tread portion. A circumferential groove having a branch groove that opens into the circumferential groove and an air chamber that communicates with the circumferential groove through the branch groove and has a larger cross-sectional area than the branch groove. In the pneumatic tire provided with a resonator that reduces noise caused by the above, the resonator includes a first end portion and a second end portion that define a length of the air chamber portion in the tire circumferential direction. And the branch groove extends from the second end portion in a direction away from the first end portion. Here, the “circumferential groove” includes not only a groove extending linearly along the tire circumferential direction but also a groove extending in a zigzag shape or a wave shape and making a round in the circumferential direction as a whole tire. By adopting such a configuration, the rib is provided in a section where the rigidity is relatively large in the rib-shaped land portion, that is, in the case of the present invention, the section in which no air chamber portion is disposed in the tire width direction in the rib-shaped land portion. By arranging the branch grooves that reduce the rigidity of the land portion, the change in the cross-sectional area of the rib-shaped land portion in the tire width direction on the circumference is a section where the rigidity is relatively small in the rib-like land portion, that is, the rib shape Compared to the conventional case where the branch groove is arranged in the section where the air chamber part is arranged in the tire width direction in the land part, the rigidity on the circumference of the rib-like land part is made uniform. As described above, pattern noise is generated due to the fluctuation of rigidity formed on the rib-like land part over the circumference, and thus the rigidity on the circumference of the rib-like land part is made uniform in this way. By doing so, pattern noise can be reduced.

  The longitudinal direction of the air chamber is preferably along the tire circumferential direction. Here, “along the tire circumferential direction” means that the longitudinal direction of the air chamber portion extends from the acute angle side with respect to the tire circumferential direction in addition to the case where the longitudinal direction of the air chamber portion extends parallel to the tire circumferential direction. In addition, the case of tilting at 45 degrees or less is also included.

  The pneumatic tire includes a plurality of resonators in the rib-like land portion along the tire circumferential direction, and includes a first end portion of the resonator and other resonators adjacent to the resonator in the tire circumferential direction. The opening end where the branch groove opens in the circumferential groove is preferably located on the same line as viewed in the tire width direction.

  Alternatively, the pneumatic tire includes a plurality of resonators in the rib-shaped land portion along the tire circumferential direction, and includes a first end portion of the resonator and another resonator adjacent to the resonator in the tire circumferential direction. The second end portion is preferably located on the same line as viewed in the tire width direction.

  Further, the pneumatic tire includes a plurality of resonators in the rib-shaped land portion along the tire circumferential direction, and the cavity of the resonator is adjacent to the resonator in the tire circumferential direction when viewed in the tire width direction. Preferably, it overlaps at least partially with the branch of the resonator.

  Further, when viewed in the tire width direction, the air chamber portion of the resonator partially overlaps with the branch groove of another resonator adjacent to the resonator in the tire circumferential direction, and the cross section of the air chamber portion in the tire width direction. The cross-sectional area in the tire width direction in the section where both the air chamber portion and the branch groove are present is the tire cross-sectional area in the tire width direction in the section where only the air chamber portion exists in the cross section in the tire width direction. Is also preferably at least partially small.

  Furthermore, it is preferable that the cross-sectional area in the tire width direction of the air chamber portion gradually decreases as it goes toward the first end portion.

  In addition, as viewed in the tire width direction, it is preferable that the air chamber portion of the resonator completely overlaps with the branch grooves of other resonators adjacent to the resonator in the tire circumferential direction.

  According to the present invention, it is possible to provide a pneumatic tire capable of reducing pattern noise on the assumption that air column resonance can be reduced by a resonator.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an enlarged plan view showing an enlarged main portion of a tread portion of a pneumatic tire (hereinafter referred to as “tire”) according to the present invention, and an arrow C shown in the drawing is a tire circumferential direction. W is the tire width direction.

  The tire shown in FIG. 1 includes a tread portion 1 having a circumferential groove 3 extending along the tire circumferential direction and a rib-like land portion 5 adjacent thereto. Furthermore, this tire is comprised in the rib-like land part 5 by the branch groove 7 opened to the circumferential groove 3, and the air chamber part 9 communicating with the circumferential groove 3 through the branch groove 7, and in the circumferential direction. A resonator 11 is provided for reducing noise generated by resonance in the pipe formed by the groove 3 and the road surface. The air chamber portion 9 is formed so that a cross-sectional area in a plane orthogonal to the center line CL1 is larger than a cross-sectional area of the branch groove 7 in a plane orthogonal to the center line CL2.

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３の気柱共鳴周波数との関連の下で、枝溝７の長さにｌ_ｈ、枝溝７の断面積をＳ（半径ｒ）及び気室部９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。 The resonator 11 forms a Helmholtz resonator as schematically shown in FIG. 2 (a) under the condition that both the air chamber 9 and the branch groove 7 are sealed by the road surface. The resonance frequency f is expressed as follows: the length of the branch groove 7 is l _h , the radius of the branch groove 7 is r, the cross-sectional area of the branch groove 7 is S, the volume of the air chamber 9 is V, and the sound velocity is c.

This resonance frequency f can be expressed as follows: in relation to the air column resonance frequency of the circumferential groove 3, the length of the branch groove 7 is l _h , and the sectional area of the branch groove 7 is S (radius r ) And the volume V of the air chamber portion 9 can be selectively changed as required.

  In addition, when the cross-sectional shape of the branch groove 7 is not circular, the radius r in the above formula is obtained by calculating backward based on the cross-sectional area of the branch groove 7. 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.

  Further, the air chamber portion 9 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 or decreases in the depth direction. Things may apply. In addition, the bottom wall of the air chamber portion 9 may be a substantially flat surface, or may be a convex or concave curved surface toward the opening side.

  Furthermore, in the tire of the illustrated example, the opening shape of the air chamber portion 9 to the surface of the rib-like land portion 5 is a rectangle, but this opening shape is not limited to this, but a polygon, a circle, an ellipse, Other closed curve shapes, irregular closed shapes, etc. can be applied.

  The main feature of the present invention is that, as shown in FIG. 1, the resonator 11 includes a first end 13 and a second end that define a length L of the air chamber 9 in the tire circumferential direction. The branch groove 7 extends from the second end 15 in a direction away from the first end 13 (upward in FIG. 1).

  According to the tire of the embodiment shown in FIG. 1, a relatively stiff section in the rib-shaped land portion 5, that is, in the case of this illustrated example, the air chamber as viewed in the tire width direction in the rib-shaped land portion 5. By arranging the branch groove 7 that reduces the rigidity of the rib-like land portion 5 in the section A1 where the portion 9 is not provided, the change in the tire width direction cross-sectional area of the rib-like land portion 5 on the circumference is as follows. Conventionally, the branch groove 7 is arranged in a section where the rigidity becomes relatively small in the rib-like land portion 5, that is, in the section A2 where the air chamber portion 9 is arranged in the rib-like land portion 5 when viewed in the tire width direction. In this case, the rigidity on the circumference of the rib-like land portion 5 is made uniform. Since the pattern noise is generated due to the fluctuation of the rigidity formed on the rib-like land portion 5 over the circumference as described above, the rigidity on the circumference of the rib-like land portion 5 is thus reduced. By making it uniform, pattern noise can be reduced. Further, as shown in FIG. 1, when the longitudinal direction of the air chamber portion 9 is along the tire circumferential direction, the change in the tire width direction cross-sectional area of the rib-like land portion 5 on the circumference is made more uniform, and the pattern noise Can be further reduced.

  Next, another preferred embodiment according to the present invention will be described. Here, FIG. 3 is an enlarged plan view showing an enlarged main part of a tread portion of another tire according to the present invention, an arrow C shown in the drawing is a tire circumferential direction, and an arrow W is a tire width direction. is there. In addition, the same code | symbol is attached | subjected and demonstrated to the member similar to the tire of embodiment shown in FIG.

  The tire shown in FIG. 3 comprises a tread portion 1 having a circumferential groove 3 extending along the tire circumferential direction and a rib-like land portion 5 adjacent thereto. Furthermore, this tire is comprised in the rib-like land part 5 by the branch groove 7 opened to the circumferential groove 3, and the air chamber part 9 communicating with the circumferential groove 3 through the branch groove 7, and in the circumferential direction. A plurality of resonators 11 are provided along the tire circumferential direction to reduce noise generated by resonance in the pipe formed by the grooves 3 and the road surface. The air chamber portion 9 is formed so that a cross-sectional area in a plane orthogonal to the center line CL1 is larger than a cross-sectional area of the branch groove 7 in a plane orthogonal to the center line CL2.

  The resonator 11 in the illustrated example is a Helmholtz resonator similar to that of the tire of the previous embodiment, and the description thereof is omitted.

  And, as shown in FIG. 3, the main feature of the configuration of the present invention is that the resonator 11 includes a first end portion 13 and a second end portion that define the length of the air chamber portion 9 in the tire circumferential direction. 15, the branch groove 7 extends from the second end 15 in a direction away from the first end 13, and the first end 13 of the resonator 11 and the resonator 11 The branch grooves 7 of the other resonators 11 adjacent to the tire circumferential direction are located on the same line as viewed in the tire width direction.

  According to the tire of the embodiment shown in FIG. 3, a relatively stiff section in the rib-shaped land portion, that is, in the case of this illustrated example, the air chamber of one resonator 11 in the rib-shaped land portion 5. A branch groove 7 for reducing the rigidity of the rib-like land portion 5 is disposed in a section A3 between the portion 9 and the air chamber portion 9 of the other resonator 11, and the first end portion 13 of the resonator 11 and The branch groove 7 of another resonator 11 adjacent to the resonator 11 in the tire circumferential direction of the resonator 11 is positioned on the same line as the tire groove in the tire width direction so that the opening end 17 opened in the circumferential groove 3 is positioned on the same line. Thus, by eliminating the section where the branch groove 7 or the air chamber portion 9 of the resonator 11 does not exist in the rib-like land portion 5, the change in the cross-sectional area in the tire width direction on the circumference of the rib-like land portion 5 is further reduced. The rigidity on the circumference of the rib-like land portion 5 is further uniformized. As a result, pattern noise caused by a change in rigidity on the circumference of the rib-like land portion 5 is further reduced.

  Next, another preferred embodiment according to the present invention will be described. Here, FIG. 4 is an enlarged plan view showing an enlarged main part of a tread portion of another tire according to the present invention, an arrow C shown in the drawing is a tire circumferential direction, and an arrow W is a tire width direction. is there. In addition, the same code | symbol is attached | subjected and demonstrated to the member similar to the tire of embodiment described previously.

  The tire shown in FIG. 4 includes a tread portion 1 having a circumferential groove 3 extending along the tire circumferential direction and a rib-like land portion 5 adjacent thereto. Furthermore, this tire is comprised in the rib-like land part 5 by the branch groove 7 opened to the circumferential groove 3, and the air chamber part 9 communicating with the circumferential groove 3 through the branch groove 7, and in the circumferential direction. A plurality of resonators 11 are provided along the tire circumferential direction to reduce noise generated by resonance in the pipe formed by the grooves 3 and the road surface. The air chamber portion 9 is formed so that a cross-sectional area in a plane orthogonal to the center line CL1 is larger than a cross-sectional area of the branch groove 7 in a plane orthogonal to the center line CL2.

  The resonator 11 in the illustrated example is a Helmholtz resonator similar to that of the tire of the previous embodiment, and the description thereof is omitted.

  As shown in FIG. 4, the main feature of the configuration of the present invention is that the air chamber portion 9 of the resonator 11 is another resonance adjacent to the resonator 11 in the tire circumferential direction. When the air chamber portion 9 and the branch groove 7 are projected onto the tire equator plane, the extended range in the tire circumferential direction of each projection shape (not shown) is partially overlapped. It is to overlap.

  According to the tire of the embodiment shown in FIG. 4, a section having relatively high rigidity in the rib-like land portion 5, that is, in the case of this illustrated example, the one resonator 11 in the rib-like land portion 5. A branch groove 7 for reducing the rigidity of the rib-like land portion 9 is arranged in a section A4 between the air chamber portion 9 and the air chamber portion 9 of another resonator 11, and the resonator 11 is further viewed in the tire width direction. The air chamber portion 9 is partially overlapped with the branch groove 7 of another resonator 11 adjacent to the resonator 11 in the tire circumferential direction (section A5), and the inside of the rib-shaped land portion 5 is viewed in the tire width direction. By reducing the tire circumferential distance in the section A4 having only the branch groove 7 of the resonator 11 and having relatively high rigidity, the change in the cross-sectional area in the tire width direction on the circumference of the rib-like land portion 5 is changed. The influence on the rigidity on the circumference of the portion 5 is reduced. As a result, pattern noise caused by a change in rigidity on the circumference of the rib-like land portion 5 is further reduced.

  Furthermore, in the tire according to this embodiment, as shown in FIG. 5, as viewed in the tire width direction, the air chamber portion 9 of the resonator 11 and the branch groove of another resonator 11 adjacent to the resonator 11 in the tire circumferential direction. 7 is defined as a section A5 and a section where only the air chamber portion 9 exists is a section A6, the cross-sectional area in the tire width direction of the air chamber portion 9 in the section A5 It is preferable to make it at least partially smaller than the cross-sectional area in the tire width direction of the air chamber portion at A6. Thereby, the change of the cross-sectional area in the tire width direction on the circumference of the rib-like land portion 5 is further reduced, and the rigidity on the circumference of the rib-like land portion 5 is further uniformized. As a result, pattern noise caused by a change in rigidity on the circumference of the rib-like land portion is further reduced.

  Next, another preferred embodiment according to the present invention will be described. Here, FIG. 6 is an enlarged plan view showing an enlarged main part of a tread portion of another tire according to the present invention, an arrow C shown in the drawing is a tire circumferential direction, and an arrow W is a tire width direction. is there. In addition, the same code | symbol is attached | subjected and demonstrated to the member similar to the tire of embodiment described previously.

  The tire shown in FIG. 6 includes a tread portion 1 having a circumferential groove 3 extending along the tire circumferential direction and a rib-like land portion 5 adjacent thereto. Furthermore, this tire is comprised in the rib-like land part 5 by the branch groove 7 opened to the circumferential groove 3, and the air chamber part 9 communicating with the circumferential groove 3 through the branch groove 7, and in the circumferential direction. A plurality of resonators 11 are provided along the tire circumferential direction to reduce noise generated by resonance in the pipe formed by the grooves 3 and the road surface. The air chamber portion 9 is formed so that a cross-sectional area in a plane orthogonal to the center line CL1 is larger than a cross-sectional area of the branch groove 7 in a plane orthogonal to the center line CL2.

  The resonator 11 in the illustrated example is a Helmholtz resonator similar to that of the tire of the previous embodiment, and the description thereof is omitted.

  And, as shown in FIG. 6, the main feature of the configuration of the present invention is that the resonator 11 includes a first end portion 13 and a second end portion that define the length L of the air chamber portion 9 in the tire circumferential direction. The first end 13 of the resonator 11 and the second end 15 of another resonator 11 adjacent to the resonator 11 in the tire circumferential direction are the same when viewed in the tire width direction. Located on the line.

  According to the tire of the embodiment shown in FIG. 6, the rib-like land portion 5 is divided into a section A7 having only the air chamber portion 9 and a section A8 having the air chamber portion 9 and the branch groove 7 when viewed in the tire width direction. By configuring and eliminating the section having only the branch grooves 7 with relatively high rigidity, the change in the cross-sectional area in the tire width direction on the circumference of the rib-like land portion 5 is further reduced, and the circumference of the rib-like land portion 5 is increased. The rigidity at is further made uniform. As a result, pattern noise caused by a change in rigidity on the circumference of the rib-like land portion 5 is further reduced.

  Next, another preferred embodiment according to the present invention will be described. Here, FIG. 7 is an enlarged plan view showing an enlarged main part of a tread portion of another tire according to the present invention, an arrow C shown in the drawing is a tire circumferential direction, and an arrow W is a tire width direction. is there. In addition, the same code | symbol is attached | subjected and demonstrated to the member similar to the tire of embodiment described previously.

  The tire shown in FIG. 7 includes a tread portion 1 having a circumferential groove 3 extending along the tire circumferential direction and a rib-like land portion 5 adjacent thereto. Furthermore, this tire is comprised in the rib-like land part 5 by the branch groove 7 opened to the circumferential groove 3, and the air chamber part 9 communicating with the circumferential groove 3 through the branch groove 7, and in the circumferential direction. A plurality of resonators 11 are provided along the tire circumferential direction to reduce noise generated by resonance in the pipe formed by the grooves 3 and the road surface. The air chamber portion 9 is formed so that a cross-sectional area in a plane orthogonal to the center line CL1 is larger than a cross-sectional area of the branch groove 7 in a plane orthogonal to the center line CL2.

  The resonator 11 in the illustrated example is a Helmholtz resonator similar to that of the tire of the previous embodiment, and the description thereof is omitted.

  As shown in FIG. 7, the main feature of the configuration of the present invention is that the air chamber portion 9 of the resonator 11 is another resonance adjacent to the resonator 11 in the tire circumferential direction. When the air chamber portion 9 and the branch groove 7 are projected onto the tire equator plane, they extend in the tire circumferential direction in their respective projection shapes (not shown). Are in agreement with each other.

  According to the tire of the embodiment shown in FIG. 7, when viewed in the tire width direction, the air chamber portion 9 of the resonator 11 is mutually connected to the branch groove 7 of another resonator 11 adjacent to the resonator 11 in the tire circumferential direction. Since the rib-like land portion 5 is configured only by the section A9 having the air chamber portion 9 and the branch groove 7 in the tire width direction, the rib-like land portion 5 on the circumference of the rib-like land portion 5 is overlapped. The cross-sectional area in the tire width direction does not change, and the rigidity on the circumference of the rib-like land portion 5 is completely equalized. As a result, the pattern noise caused by the rigidity change on the circumference of the rib-like land portion 5 is further reduced.

  In the tire of the embodiment shown in FIGS. 1 to 7 (excluding FIG. 2), the cross-sectional area in the tire width direction of the air chamber portion 9 is directed toward the first end portion 13 as illustrated in FIG. It is preferable to gradually reduce it. Thereby, the rigidity of the rib-like land portion 5 can be increased smoothly toward the first end portion 13, that is, a sudden change in rigidity can be prevented. It becomes possible to further reduce the pattern noise caused by the change in rigidity.

  Note that the above description shows only a part of the embodiment of the present invention, and these configurations can be combined with each other or various modifications can be made without departing from the gist of the present invention. . For example, the resonator 11 may be configured by the branch groove 7 and the air chamber portion 9 that communicates with the circumferential groove 3 through the branch groove 7 and has a larger cross-sectional area than the branch groove 7. Instead of the Helmholtz type resonator 11, the air chamber 9 and the branch groove 7 are regarded as a first pipe line 9 'and a second pipe line 7' as shown in FIG. A stepped tube type resonator comprising the above-mentioned connecting pipelines 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 9 ′ side at the boundary is Z ₁₂ , the acoustic impedance on the second pipeline 7 ′ side in the boundary is Z ₂₁ , and the sectional area of the first pipeline 9 ′. Is S ₁ , and the cross-sectional area of the second pipeline 7 ′ 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 7' second conduit 7 from the opening of The sound pressure P _{2 at} the position of the distance x is 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. Here, l ₂ is the length of the second pipeline 7 ′, V ₂ is the particle velocity distribution of the second pipeline 7 ′, V ₀ is the particle velocity at the input point, j is the imaginary unit, 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 9 ′, 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 9 ′ Sound pressure P ₁
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 pipe line 9 ′.

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 7 ′ is opened by the groove wall of the circumferential groove 3. The first pipe line 9 ′ and the second pipe line 7 ′ are provided on the ground contact surface of the 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.

  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 shape and arrangement of the resonators on the pattern noise was investigated. Each of the tires of Examples 1 to 6 is a tire according to the present invention, and is a radial tire for a passenger car having a tire size of 225 / 45R17. As shown in FIG. And a rib-like land portion adjacent to the circumferential grooves. The circumferential groove has a width of 8 mm and a depth of 8 mm. Further, these tires have 60 resonators on the circumference as shown in FIG. 8 in each rib-like land portion, and the shape and arrangement of each resonator are shown in Table 1. In all of the resonators disposed in the tires of Examples 1 to 5, the volume of the air chamber is 1260 mm ³ , the length of the branch groove is 20 mm, the width of the branch groove is 1.5 mm, and the depth of the branch groove is 6 mm, the resonance frequency of the resonator is 980 Hz, and the resonator disposed in the tire of Example 6 has an air volume of 580 mm ³ , a branch groove length of 46 mm, and a branch groove width. The depth of the branch groove is 1.5 mm and the resonance frequency of the resonator is 980 Hz.

For comparison, the tire of Conventional Example 1 having the same configuration as the tire of Examples 1 to 6 except that no resonator is provided, and the shape and arrangement of the resonators of Examples 1 to 6 except for the resonator. A tire of Comparative Example 1 having the same configuration as the tire was also prototyped. Further, the tire of Comparative Example 1 has 60 resonators in the rib-like land portions on the circumference, and each resonator has the shape shown in FIG. 10 and has branch grooves when viewed in the tire width direction. The air chamber portion is disposed within the range of the tire circumferential direction, the air chamber volume is 1260 mm ³ , the branch groove length is 20 mm, the branch groove width is 1.5 mm, and the branch groove depth is 6 mm. The resonance frequency of the resonator is 970 Hz.

  For the measurement of air column resonance and pattern noise, the tire is mounted on a rim of size 7.5J, an air pressure of 230 kPa (relative pressure) is applied inside, and an indoor drum tester is used to measure these tires. The load rolling was performed at a speed of 60 km / h under the action of a load of 0.5 kN, and the side sound of the tire at this time was measured according to the conditions defined in JASO C606. The air column resonance sound of the tires of Comparative Example 1 and Examples 1 to 6 with respect to the tire of Conventional Example 1 having no resonator at the overall value of 1/3 octave band center frequency 800 Hz-1000 Hz-1250 Hz band. Each relative value was determined and evaluated. In this case, it is determined that the sound pressure is reduced by 1 dB or more, which can be improved by feeling evaluation of a professional driver by an actual vehicle test. Note that the resonators provided in these prototype tires correspond to the above-described formula (1), and the sound velocity c was 343.7 m / s. On the other hand, the pattern noise was evaluated by obtaining the relative values of the tires of Examples 1 to 6 with respect to the tire of Comparative Example 1 at the sound pressure in the primary pitch range. In this case, a sound pressure drop of 1 dB or more was judged to be effective. These results are shown in Table 2.

  As is clear from the results shown in Table 2, it was confirmed that air column resonance noise can be reduced by disposing a resonator in the rib-like land portion. Further, it was confirmed that the pattern noise can be reduced by extending the branch groove in the direction away from the second end portion with respect to the first end portion. Furthermore, it was confirmed that pattern noise can be further reduced by optimizing the arrangement of the resonators and uniformizing the cross-sectional area in the tire width direction on the circumference of the rib-like land portion.

  As is apparent from the above description, the present invention can provide a pneumatic tire capable of reducing pattern noise on the assumption that air column resonance can be reduced by a resonator.

FIG. 3 is an enlarged plan view showing an enlarged main part of a tread portion of a pneumatic tire according to the present invention. It is the figure which showed the resonator applicable to this invention typically, (a) is a Helmholtz type resonator, (b) is a stepped tube type resonator. It is an enlarged plan view which expands and shows the principal part of the tread part of the other pneumatic tire according to this invention. It is an enlarged plan view which expands and shows the principal part of the tread part of the other pneumatic tire according to this invention. It is an enlarged plan view which expands and shows the principal part of the tread part of the other pneumatic tire according to this invention. It is an enlarged plan view which expands and shows the principal part of the tread part of the other pneumatic tire according to this invention. It is an enlarged plan view which expands and shows the principal part of the tread part of the other pneumatic tire according to this invention. It is a figure which shows the tread pattern of the tire of the Example according to this invention. It is a figure for demonstrating the problem of a prior art, (a) is an enlarged plan view which expands and shows the principal part of the tread part of the pneumatic tire according to a prior art, (b) is FIG. 9 (a). It is a figure which shows the change of the tire width direction cross-sectional area over the circumference | surroundings of the rib-shaped land part of (). FIG. 3 is an enlarged plan view showing an enlarged main part of a tread portion of a pneumatic tire of Comparative Example 1.

Explanation of symbols

DESCRIPTION OF SYMBOLS 3 Circumferential groove | channel 5 Rib-like land part 7 Branch groove 9 Air chamber part 11 Resonator 13 1st edge part 15 2nd edge part 17 Open end

Claims (8)

The tread portion includes at least one circumferential groove extending along the tire circumferential direction and at least one row of rib-shaped land portions adjacent to the tread portion, and the rib-shaped land portion opens into the circumferential groove. A resonator configured to reduce the noise caused by the circumferential groove is formed by a branch groove and an air chamber portion communicating with the circumferential groove through the branch groove and having a larger cross-sectional area than the branch groove. In the pneumatic tire
The resonator has a first end and a second end that define a length in the tire circumferential direction of the air chamber,
The pneumatic tire according to claim 1, wherein the branch groove extends from the second end portion in a direction away from the first end portion.   The pneumatic tire according to claim 1, wherein a longitudinal direction of the air chamber portion is along a tire circumferential direction. The pneumatic tire includes a plurality of the resonators in the rib-shaped land portion along the tire circumferential direction,
The first end of the resonator and the open end where the branch groove of another resonator adjacent to the resonator in the tire circumferential direction opens in the circumferential groove are located on the same line as viewed in the tire width direction. The pneumatic tire according to claim 1 or 2. The pneumatic tire includes a plurality of the resonators in the rib-shaped land portion along the tire circumferential direction,
The first end of the resonator and the second end of another resonator adjacent to the resonator in the tire circumferential direction are located on the same line as viewed in the tire width direction. The pneumatic tire described in 1. The pneumatic tire includes a plurality of the resonators in the rib-shaped land portion along the tire circumferential direction,
The air chamber portion of the resonator is at least partially overlapped with a branch groove of another resonator adjacent in the tire circumferential direction of the resonator when viewed in the tire width direction. The pneumatic tire described in 1. When viewed in the tire width direction, the cavity portion of the resonator partially overlaps the branch groove of another resonator adjacent to the resonator in the tire circumferential direction,
The cross-sectional area in the tire width direction in the section of the air chamber portion where both the air chamber portion and the branch groove are present in the cross section in the tire width direction is only the air chamber portion in the cross section in the tire width direction of the air chamber portion. The pneumatic tire according to claim 5, wherein the pneumatic tire is at least partially smaller than a cross-sectional area in the tire width direction in an existing section.   The pneumatic tire according to any one of claims 1 to 6, wherein a cross-sectional area in the tire width direction of the air chamber portion gradually decreases toward the first end portion.   8. The air chamber portion of the resonator completely overlaps with a branch groove of another resonator adjacent to the resonator in the tire circumferential direction when viewed in the tire width direction. Pneumatic tire described in 2.

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