JP5216257B2 - Pneumatic tire - Google Patents

Description

  According to the present invention, the tread surface includes at least one circumferential groove extending substantially in the tire circumferential direction, and a resonator that reduces noise generated by resonance in the pipe formed by the circumferential groove and the road surface. The present invention relates to a pneumatic tire, and aims to reduce noise generated from 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 mainly generated by air column resonance. The air column resonance sound is noise generated by resonance of air in a pipe surrounded by a circumferential groove continuously extending in the circumferential direction of the tread portion tread surface and a road surface, and is 800 to 1200 Hz in a general passenger car. It is often observed to a certain extent, and since the peak sound pressure level is high and the frequency band is wide, it accounts for most of the noise generated from pneumatic tires.

  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.

  Therefore, in order to reduce the air column resonance noise, the number and the volume of the circumferential grooves are widely reduced, and as disclosed in Patent Document 1, only one circumferential groove is provided. It has been proposed to provide a long lateral groove that is open at the other end and terminates in the land portion at the other end, and to reduce air column resonance using anti-resonance in the lateral groove. However, in the pneumatic tire in which the groove volume of the circumferential groove is reduced, the groove volume of the circumferential groove is insufficient, and the drainage performance may be deteriorated. Further, in the pneumatic tire described in Patent Document 1, since it is essential to dispose long lateral grooves, the degree of freedom in designing the tread pattern is impaired, and the rigidity of the land portion is not sufficiently ensured. There is a possibility that the handling stability is lowered.

  As a solution to these problems, as described in Patent Documents 2 to 4, a technique for reducing air column resonance using anti-resonance by arranging Helmholtz type resonators has also been proposed. . 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 sufficiently securing the groove volume of the circumferential groove and ensuring the drainage performance.

International Publication No. 04/103737 Pamphlet Japanese Patent Laid-Open No. 5-338411 JP 2000-118207 A JP 2001-191734 A

  However, in the pneumatic tires described in Patent Documents 2 to 4, the resonator is arranged with the same shape and size on the tread surface, and the frequency band of the resonance frequency is constant. The frequency band of air column resonance that can be reduced may be limited. In order to change the resonance frequency of a Helmholtz type resonator, the cross-sectional area in the direction perpendicular to the longitudinal direction of the branch groove portion of the resonator opening in the circumferential groove, the distance in the longitudinal direction, and the branch groove portion are connected. It is necessary to change the cross-sectional area of the air chamber part of the resonator whose cross-sectional area in the direction perpendicular to the longitudinal direction is larger than that of the branch groove part, and the distance in the longitudinal direction thereof, but the resonator ensures predetermined performance In order to achieve this, it is necessary to make the size and shape of the air chamber part within a certain range, and it is generally difficult to change it. Therefore, it is generally effective to change the size and shape of the branch groove part. It has been supposed to be. However, if the distance in the longitudinal direction of the branch groove portion is excessively large, the resonator may not be disposed in the land portion region, and the desired resonance frequency may not be achieved.

  Accordingly, an object of the present invention is to provide a pneumatic tire in which the resonance frequency of the resonator can be set by expanding the frequency band in which the resonance frequency of the resonator can be set and the air column resonance sound is reduced by optimizing the shape of the resonator. It is in.

In order to achieve the above object, the tire according to the present invention is a noise generated by resonance in a pipe formed by at least one circumferential groove extending substantially in the tire circumferential direction on the tread portion tread surface, and the circumferential groove and the road surface. And a resonator that branches off from the circumferential groove and that has a cross-sectional area that is connected to the branch groove and orthogonal to the longitudinal direction is larger than that of the branch groove. comprises a section, branch grooves have at least one bent portion, the resonator of the branch grooves adjacent in the tire circumferential direction, have a different number of bends each other resonators adjacent the ground contact surface of the tread portion It is characterized by existing together .
In such a pneumatic tire, by bending the branch groove portion, the longitudinal distance of the branch groove portion can be increased compared to the case where the branch groove portion does not bend, so the frequency band of the settable resonance frequency is expanded. The tread pattern design can be performed by bending the branch groove part, so that the branch groove part can be effectively folded and the area where the resonator is disposed on the tread surface can be reduced. It is possible to secure the above degree of freedom. Here, “substantially tire circumferential direction” means not only a groove extending linearly in the tire circumferential direction, but also a groove extending in a zigzag shape or a wave shape and making one round in the tire circumferential direction as a whole tire. The “longitudinal direction” refers to the extending direction of the branch groove portion extending from the circumferential groove toward the air chamber portion. The “resonator adjacent in the tire circumferential direction” means a branch groove portion that opens in the same circumferential groove and is adjacent in the tire circumferential direction. "Is present together in the ground contact surface" means that two or more adjacent resonators are present at least partially simultaneously in the tread surface that is in contact with the road surface.

として表すことができる。このとき、Ｌの値は、文献によって相違するが、ここでは、枝溝部２の半径をｒ、長さをＬ_０としたとき、Ｌは１．３ｒとＬ_０との和とするものとする。従って、共鳴器１の共鳴周波数ｆ_０は、枝溝部２の断面積Ｓ、枝溝部２の長さと枝溝部２の開口端の補正長さとの和Ｌ、気室部３の容積Ｖ等を選択することで、必要に応じて変化させることができる。 In addition, although the kind of resonator is not limited, For example, it can be set as a Helmholtz type resonator. In this case, the resonance frequency f ₀ is generally expressed as a shape as shown in FIG. 1, and the sum of the distance between the length of the branch groove portion 2 and the corrected length of the opening end of the branch groove portion 2 is L, and the sectional area of the branch groove portion. Is S, the volume of the air chamber 3 is V, and the sound speed is c,

Can be expressed as At this time, the value of L differs depending on the literature, but here, when the radius of the branch groove portion 2 is r and the length is L ₀ , L is the sum of 1.3r and L _0. . Accordingly, the resonance frequency f ₀ of the resonator 1 selects the cross-sectional area S of the branch groove portion 2, the sum L of the length of the branch groove portion 2 and the corrected length of the opening end of the branch groove portion 2, the volume V of the air chamber portion 3, and the like. By doing so, it can be changed as necessary.

Further, as shown in FIG. 2, the air chamber portion 3 and the branch groove portion 2 of the resonator 1 are regarded as the first conduit 4 and the second conduit 5, respectively, and are connected to each other. It is also possible to use an attached type resonator, and the resonance frequency f _{0 in} this case can be obtained as follows.

For the stepped resonator, the cross-sectional area perpendicular to the extending direction of the first pipe is S ₁ , the cross-sectional area perpendicular to the extending direction of the second pipe is S ₂ , and the first pipe 4 side at the boundary If the acoustic impedance of the second pipe 5 at the boundary is Z ₁₂ and the acoustic impedance of the boundary is Z ₂₁ , the following expression is derived from the continuous condition.
Z ₂₁ = (S ₂ / S ₁ ) · Z ₁₂
The sound pressure _{P 2} at a point a distance x from an opening portion in the circumferential groove of the second conduit of the second conduit 5, the boundary conditions, and _V 2 _{= V} ^{0 e jwt} at x = 0, When x = L ₂ and P ₂ / V ₂ = Z ₂₁ , the following equation is derived.
P ₂ = Zc · [{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 (where k = 2πf ₀ / c)
At this time, V ₂ represents the particle velocity distribution of the second pipe 5, V ₀ represents the particle velocity at the input point, j represents the imaginary unit, and Zc represents ρc (ρ: density of air, c: sound velocity). ing.
The sound pressure P ₁ of the first pipeline 4 is derived by the following equation when the boundary conditions are x = L ₁ and V ₁ = 0, and x = 0 and P _{2 (X = L2)} = P _1. .
P ₁ = Zc · [Z ₂₁ cos (k (L ₁ −x)) / {cos (kL ₁ ) · Z _c cos (kL ₂ ) + jZ ₂₁ sin (kL ₂ )}] · V ₀ e ^jwt

Therefore, the conditional expression of the resonance frequency f ₀ is derived as the following expression when the resonance condition is x = 0 and P ₂ = 0. Based on this resonance conditional expression, k, L ₁ , L ₂ , S ₂ , S ₁ , and c can be determined to obtain the resonance frequency f ₀ .
tan (kL ₁ ) tan (kL ₂ ) − (S ₂ / S ₁ ) = 0

  Moreover, it is preferable that a branch groove part has a some bending part.

  Furthermore, it is preferable that the longitudinal distance between the bent portions in the same branch groove portion is uniform.

  In addition, the branch groove is preferably bent in a zigzag shape. Here, “bending in a zigzag shape” means bending in a sine wave shape, a rectangular wave shape, a triangular wave shape, a sawtooth wave shape, or the like.

  According to the present invention, by optimizing the shape of the resonator, it is possible to provide a pneumatic tire in which the frequency band in which the resonance frequency of the resonator can be set is expanded and the air column resonance noise is reduced. It becomes.

  Embodiments of the present invention will be described below with reference to the drawings. 3 and 4 are perspective views of a part of a tread portion of a typical pneumatic tire (hereinafter referred to as “tire”) according to the present invention.

  As shown in FIG. 3, the tire of the present invention generates noise generated by resonance in the pipe formed by the circumferential groove 7 extending substantially in the tire circumferential direction and the circumferential groove 7 and the road surface on the tread portion tread surface 6. A resonator 1 to be reduced. The resonator 1 includes a branch groove portion 2 that branches off from the circumferential groove 7 and an air chamber portion 3 that is connected to the branch groove portion 2 and has a larger cross-sectional area perpendicular to the longitudinal direction than the branch groove portion 2. The groove part 2 has at least one bent part 8. In such a pneumatic tire, the branch groove portion 2 of the resonator 1 is bent and the branch groove portion 2 is folded, so that the distance in the longitudinal direction of the branch groove portion 2 is larger than that of the resonator 1 where the branch groove portion 2 is not bent. Since the resonance frequency of the resonator 1 can be lowered and the frequency band of the air column resonance sound that can be reduced by the resonator 1 is expanded, the air column resonance sound can be secured. Since the tread portion region where the resonator 1 is disposed can be narrowed by folding the branch groove portion 2, the tread portion where the resonator 1 is not disposed can be reduced. It is possible to expand the area and increase the degree of freedom in designing the tread pattern. At this time, since the basic function of the resonator 1 is not affected, the resonator 1 opened in the circumferential groove 7 has a shape opened in the tread surface 6 as shown in FIG. However, as shown in FIG. 4, the shape which is not open to the tread part tread surface 6 may be sufficient.

  The branch groove portion 2 preferably has a plurality of bent portions 8. This is because a plurality of branch grooves 2 can be diffracted to increase the distance in the longitudinal direction of the branch grooves 2, so that the resonance frequency of the resonator 1 can be lowered and reduced by the resonator 1. This is because the frequency band of the air column resonance sound that can be generated is expanded, so that the air column resonance sound can be more effectively reduced. Moreover, since the tread part area | region where the resonator 1 is arrange | positioned can be narrowed by carrying out multiple diffraction folding of the branch groove part 2, the tread part area | region where the resonator 1 is not arrange | positioned is expanded, This is because the degree of freedom in design can be further increased.

Furthermore, it is preferable that the branch groove portions 2 of the resonators 1 adjacent to each other in the tire circumferential direction have different numbers of bent portions 8, and the adjacent resonators 1 are both present on the ground contact surface of the tread portion. This is because the branch groove portions 2 of the resonators 1 adjacent to each other in the tire circumferential direction have different numbers of bent portions 8 , so that the longitudinal distances of the branch groove portions 2 of the resonators 1 adjacent to each other in the tire circumferential direction are different. Accordingly, the resonance frequencies can be made different from each other and the resonators 1 having different resonance frequencies are simultaneously present in the ground surface of the tread portion, thereby resonating with the air column resonance sound. This is because the frequency band of the frequency is expanded, so that the air column resonance can be more effectively reduced.

  Furthermore, it is preferable that the longitudinal distance between the bent portions 8 in the same branch groove portion 2 is uniform. Because, since the distance in the longitudinal direction between the bent portions 8 is uniform, the total distance in the longitudinal direction of the branch groove portion 2 can be increased when the distance in the longitudinal direction between the bent portions 8 is increased. Since the resonance frequency of the resonator 1 can be lowered and the frequency band of the air column resonance sound that can be reduced by the resonator 1 is expanded, the air column resonance sound can be more effectively reduced. Because it can. Further, since the branch groove portion 2 is folded while being saved more spatially, the tread portion region where the resonator 1 is disposed is narrowed, and the tread portion region where the resonator 1 is not disposed is enlarged. This is because the design freedom of the tread pattern can be further increased.

  In addition, the branch groove portion 2 is preferably bent in a zigzag shape. Because the total distance in the longitudinal direction of the branch groove portion 2 can be increased by bending the branch groove portion 2 in a zigzag shape, the resonance frequency of the resonator 1 can be lowered. This is because the frequency column of the air column resonance sound that can be reduced is expanded, so that the air column resonance sound can be more effectively reduced. Further, since the branch groove portion 2 is folded while being saved more spatially, the tread portion region where the resonator 1 is disposed is narrowed, and the tread portion region where the resonator 1 is not disposed is enlarged. This is because the design freedom of the tread pattern can be further increased.

  The above description shows only a part of the embodiment of the present invention, and these configurations can be combined alternately or various changes can be made without departing from the gist of the present invention. For example, by making the dimensions and shapes of the plurality of resonators 1 arranged on the tread portion tread 6 all different, the resonance frequency is made different, and the frequency band of the anti-resonance resonance frequency is set to be wide. It is also possible.

Next, a conventional tire having a lateral groove extending from the circumferential groove in the tire width direction (conventional tire), a tire having a conventional resonator for comparison (comparative tire) , and a resonator according to the present invention Tires (Example tires 1) and reference tires (reference example tires 1 to 4) having a tire size of 195 / 65R15 as passenger car radial tires were prototyped and evaluated for performance. Since it went, it demonstrates below.

  The conventional example tire has a tread pattern shown in FIG. 5 (a), includes a plurality of circumferential grooves, extends between the circumferential grooves in an inclined manner, and includes lateral grooves that communicate between the circumferential grooves. The comparative example tire has a tread pattern shown in FIG. 5 (b), has a plurality of circumferential grooves, and has resonators so as to open in the circumferential grooves. Have.

Moreover, the reference example tires 1 and 2, the example tire 1 and the reference example tires 3 and 4 shown in FIGS. 5 (c) to 5 (g) respectively have a circumferential groove and a resonance opening in the circumferential groove. The reference tires 1 to 4 have 1, 3, 4, and 5 bent portions of the branch groove portions, respectively, and the tire 1 of the example has 1 bent portion. A resonator having three and three branch grooves is provided and has the specifications shown in Table 1.

Each of these test tires was attached to a rim of size 6JJ × 15 to form a tire wheel, applied with air pressure: 210 kPa (relative pressure), tire load load: 4.0 kN, on an indoor drum tester at 80 km / h. Measure the tire side sound when running with the conditions specified in the JASO C606 standard, calculate the partial overall value in the 1/3 octave center frequency 800-1000-1250Hz band, Evaluated . Real施例and resonators in reference example taken as resonator Helmholtz type, is obtained by calculating by the formula the resonant frequency conditions of the sound velocity c as 343.7m / s. Moreover, the evaluation of the air column resonance sound was performed by calculating the relative volume of the sound volume decreasing with respect to the sound volume of the noise generated from the conventional tire, and evaluating the effect of reducing the air column resonance sound. The results are shown in Table 2.

As is apparent from the results in Table 2, the column tire resonance noise is reduced in the example tire 1 and the reference example tires 1 to 4 compared to the comparative example tire. In Reference Example Tires 1 to 4 , air column resonance noise is reduced as the number of bent portions increases. Further, in the example tire 1 including two types of resonators having different numbers of bent portions of the branch groove portions and different resonance frequencies, air column resonance noise is most reduced.

  As is apparent from the above, by providing an appropriate shape of the resonator, the frequency band in which the resonance frequency of the resonator can be set is expanded to provide a pneumatic tire with reduced air column resonance noise. It became possible.

It is a figure which shows typically a Helmholtz type resonator. It is a figure which shows a stepped type resonator typically. 1 is a perspective view of a part of a tread portion of a typical tire according to the present invention. 1 is a perspective view of a part of a tread portion of a typical tire according to the present invention. (A)-(g) is a development view of a part of the tread portion of the tire corresponding to the conventional example tire, the comparative example tire, the reference example tires 1 and 2, the example tire 1, and the reference example tires 3 and 4 , respectively. is there.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Resonator 2 Branch groove part 3 Air chamber part 4 1st pipe line 5 2nd pipe line 6 Tread part tread 7 Circumferential groove 8 Bending part

Claims (4)

In a pneumatic tire having a tread portion tread surface including at least one circumferential groove extending substantially in the tire circumferential direction and a resonator for reducing noise generated by resonance in a pipe formed by the circumferential groove and a road surface. ,
The resonator includes a branch groove part extending from the circumferential groove and an air chamber part connected to the branch groove part and having an area of a cross section perpendicular to the longitudinal direction larger than that of the branch groove part,
The branches grooves have at least one bent portion,
The pneumatic tire according to claim 1, wherein the branch groove portions of the resonator adjacent to each other in the tire circumferential direction have different numbers of bent portions, and the adjacent resonators exist together in the ground contact surface of the tread portion .   The pneumatic tire according to claim 1, wherein the branch groove portion has a plurality of bent portions. The pneumatic tire according to claim 1 or 2 , wherein a distance in a longitudinal direction between the bent portions in the same branch groove portion is uniform. The pneumatic tire according to any one of claims 1 to 3 , wherein the branch groove portion is bent in a zigzag shape.

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