JP5350874B2 - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of reducing the air column resonance, enhancing the quietness, and enhancing the braking performance, the water discharging performance and the steering stability on a wet road surface by appropriately shaping a land portion of a tread part. <P>SOLUTION: The pneumatic tire has circumferential grooves 7 extending in the tire circumferential direction, and a plurality of resonators 1 which are opened in the circumferential grooves 7 to reduce the noise generated by the resonance in tubes demarcated by the circumferential grooves 7 and the ground contact road surface. Further, at least one sipe 9 for communicating the resonators 1 with the circumferential grooves 7 is provided. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

In the tread portion tread, at least one circumferential groove extending in the tire circumferential direction, and a plurality of branch groove portions for reducing noise generated by resonance in the pipe defined by the circumferential groove and the grounding road surface and the air are provided. The present invention relates to a pneumatic tire including a Helmholtz type resonator having a chamber, which reduces noise generated from the pneumatic tire, improves quietness, and provides braking performance, drainage performance, and stable driving on a wet road surface. To improve performance.

  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 500 to 1800 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, there is a demand for improved drainage performance of pneumatic tires having a reduced groove volume in the circumferential groove. Further, in the pneumatic tire described in Patent Document 1, since it is essential to dispose a long lateral groove, the degree of freedom in designing the tread pattern is improved, and the rigidity of the land portion is ensured to ensure the handling stability. There is a desire to improve.

  As these measures, as described in Patent Document 2, a branch groove portion that branches off from the tire circumferential groove, and a cross-sectional area that is connected to the branch groove portion and orthogonal to the extending direction is larger than the branch groove portion. A technique has also been proposed in which a Helmholtz type resonator including an air chamber is disposed to reduce air column resonance using antiresonance by the resonator. By this, while ensuring sufficient groove volume of the circumferential groove and improving drainage performance, the degree of freedom in designing the tread pattern is improved as compared with the pneumatic tire described in Patent Document 1. Can do.

  As another technique for reducing air column resonance noise, Patent Document 3 discloses that a circumferential groove is divided into a plurality of sections by providing a fence portion extending in a direction crossing the circumferential groove in the circumferential groove. A pneumatic tire is disclosed. In such a pneumatic tire, since the circumferential groove is divided by the fence portion, the air flow through the circumferential groove is disturbed during tire load rolling, and turbulence is generated. As a result, the generation of air column resonance is suppressed by the turbulent flow, and the silence is improved.

International Publication No. 04/103737 Pamphlet Japanese Patent Laid-Open No. 5-338411 JP-A-3-276802

  The pneumatic tires described in Patent Documents 1 to 3 suppress the generation of air column resonance noise and improve the quietness during traveling, but in the background of tireless pursuit to improve comfort during traveling, There is a demand for further reducing air column resonance noise, improving quietness during traveling, and improving braking performance, drainage performance, and driving stability on wet road surfaces.

  Therefore, the object of the present invention is to optimize the land shape of the tread, thereby reducing air column resonance noise and improving quietness, as well as improving braking performance, drainage performance and driving stability on wet road surfaces. The object is to provide an improved pneumatic tire.

  In order to achieve the above object, a tire according to the present invention includes a circumferential groove extending in a tire circumferential direction on a tread portion tread surface, an opening in the circumferential groove, and a pipe defined by the circumferential groove and a grounding road surface. A plurality of resonators that reduce noise generated by resonance are provided, and at least one sipe that connects the resonator and the circumferential groove is provided. Here, the “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 wavy shape and making a round in the tire circumferential direction as a whole tire. Is the ground contact when rolling at a normal temperature (generally 20 ° C) under the standard air pressure specified by JATMA, ETRTO, TRA, etc., with the maximum load applied to the pneumatic tire. The area of the tread surface that is in contact with the road surface is meant, and “sipe” means a narrow groove whose cross-sectional area is reduced by 90% or more when touched.

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。 Although the type of the resonator is not limited, for example, in the case of a Helmholtz type resonator as shown in FIG. 1, the resonance frequency f ₀ is the correction length of the branch groove portion 2 and the opening end of the branch groove portion 2. L is the sum of the distances to S, the cross-sectional area of the branch groove part is S, the volume of the air chamber part 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 ₂ , the following equation is derived.
_{P 2 = Z s · {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 conduit 4, the boundary condition, and V ₁ = 0 at x = L _1, when the _P 2 _/ V 2 _{= Z 21} in x = _{L 2,} are guided by the following equation.
_{P 1 = Z s · [{} Z 21 cos (k (L 2 -x)) / cos (kL 1)} · {Z c co (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

として求めることができる。 Or as shown in FIG. 3, it can be set as the side branch type resonator 1 with which the air chamber part 3 is opening to the circumferential groove | channel. In this case, the resonance frequency f ₀ is such that the length of the air chamber is l ₃ and the speed of sound is c.

Can be obtained as

  Moreover, it is preferable that the arrangement pitch of the resonators is smaller than the ground contact length. Here, the “contact length” means the tire circumferential direction length on the contact road surface.

  According to the present invention, by providing a sipe in which the resonator and the circumferential groove are communicated with each other in the tread portion, the air column resonance noise is reduced, the quietness is improved, and the braking performance, drainage performance, and wetness are improved. It is possible to provide a pneumatic tire with improved steering stability on the road surface.

It is a figure which shows typically a Helmholtz type resonator. It is a figure which shows a stepped type resonator typically. It is a figure which shows a side branch type resonator typically. FIG. 3 is a development view of a part of the tread portion of the tire according to the present invention. FIG. 6 is a development view of a part of a tread portion of another tire according to the present invention. FIG. 6 is a development view of a part of a tread portion of another tire according to the present invention. FIG. 6 is a development view of a part of a tread portion of another tire according to the present invention. FIG. 6 is a development view of a part of a tread portion of a conventional tire. It is a graph which shows the evaluation result of the reduction effect of the air column resonance sound in Example tire 1.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 4 is a development view of a part of a tread portion of a pneumatic tire (hereinafter referred to as “tire”) according to the present invention. 5 and 6 are development views of a part of a tread portion of another tire according to the present invention.

As shown in FIG. 4, the tire of the present invention has noise generated by resonance in the pipe defined by the circumferential groove 7 extending in the tire circumferential direction, the circumferential groove 7 and the grounding road surface on the tread surface of the tread portion 6. And the resonator 1 opened in the road surface contact area 8. 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 that of the branch groove portion 2. . Further, a sipe 9 extending from the air chamber 3 of the resonator 1 to the circumferential groove 7 and communicating the circumferential groove 7 and the resonator 1 is provided. Thus, by providing the resonator 1, it is possible to reduce air column resonance and improve silence. Further, the inventor has found that when the resonator 1 comes in contact with the road surface, a pumping sound is generated as a result of the air in the resonator 1 being compressed and expanded. Therefore, as described above, by providing the sipe 9 in which the resonator 1 communicates with the circumferential groove 7, even if the resonator 1 contacts the road surface, the sipe 9 serves as an airway, Since air escapes, compression and expansion of air in the resonator 1 are suppressed. As a result, the generation of pumping noise is prevented, and the quietness can be further improved. Further, by providing the sipe 9, the negative rate in the tread portion 6 is increased, the drainage performance is improved, and the edge component is increased, so that the steering stability on the wet road surface is synergistically coupled with the improvement of the drainage performance. Improves. Furthermore, the inventor has found that, in a tire having only a conventional resonator, the rigidity of the land near the area where the resonator is disposed and the rigidity of the land near the land area where the resonator is not disposed. It has been found that pattern noise is generated during rolling of a tire load due to the fact that the difference is too large. Therefore, as described above, the sipe 9 is disposed in the land portion where the resonator 1 is not disposed (in the illustrated example, the land portion between the resonators 1 adjacent in the circumferential direction), and the resonator 1 is disposed. By reducing the rigidity of the land portion in the land region where no resonator is provided, the difference in rigidity between the land portion in the vicinity of the region where the resonator 1 is disposed and the land portion in the region where the resonator is not disposed is small. Thus, since the pattern noise is reduced, it is possible to further improve the quietness.
The arrangement position of the sipe 9 is not limited to the position shown in FIG. 4 and may be other arrangement positions. For example, as shown in FIG. It is also possible to communicate with the circumferential groove 7 on the opposite side of the circumferential groove 7 communicating with the resonator 1 shown in FIG. Alternatively, as shown in FIGS. 6 and 7, the resonator 1 and the circumferential groove 7 can be communicated with each other via a plurality of sipes.

  Although not shown, the resonators 1 are preferably arranged at a plurality of tire circumferential pitches, that is, at so-called variable pitches. This is because when the resonators 1 are all arranged at the same circumferential pitch, the pitch noises of the resonators 1 adjacent to each other in the tire circumferential direction resonate and amplify during tire load rolling. Because there is a possibility of becoming.

  Furthermore, it is preferable that the arrangement pitch of the resonators 1 is smaller than the ground contact length. This is because, when the arrangement pitch of the resonators 1 is larger than the contact length, the fence portion 9 contacts the road surface, and the frequency of the air column resonance generated from the circumferential groove 7 is sufficiently increased. This is because the resonator 1 may not be grounded to the road surface and the air column resonance noise may not be reduced.

  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.

  Next, a conventional tire having a resonator but not having a sipe (conventional tire), a tire having a sipe and a resonator according to the present invention (example tires 1 to 2), having a tire size of 225 / 45R17 Each of the radial tires for a passenger car was prototyped and evaluated for performance, and will be described below.

The conventional tire has a tread pattern shown in FIG. 8 and includes a circumferential groove and a resonator opening in the circumferential groove. Such a resonator is a stepped type resonator that includes an air chamber portion and a branch groove portion and reduces air column resonance sound of 980 Hz. Example tire 1 has a tread pattern shown in FIG. 6, a circumferential groove, a stepped resonator that opens to the circumferential groove, and reduces air column resonance noise of 980 Hz, and the resonator and the circumferential There are two sipes that communicate with the directional groove. Example tire 2 has a tread pattern shown in FIG. 7, and has a circumferential groove, a stepped resonator that opens in the circumferential groove, and reduces air column resonance noise of 980 Hz, and the resonator and the circumferential There are three sipes that communicate with the directional grooves. In addition, in the conventional example tire and the example tires 1-2, 30 step type resonators are provided on the circumference, the volume of the air chamber portion is 1260 m ² , the length of the branch groove portion is 20 mm, The width of the branch groove part is 1.5 mm, the depth of the branch groove part is 6.0 mm, and the volume of the branch groove part is 180 m ² . Moreover, the sipe of Example tires 1 and 2 has a sipe width of 0.5 mm and a depth of 4.0 mm. Further, the resonance frequency of the resonator is calculated by the above-described equation with the condition of the sound velocity c being 343.7 m / s.

  Each of these test tires is mounted on a rim of size 7.5J to form a tire wheel, air pressure: 230 kPa (relative pressure), tire load load: 4.5 kN, on an indoor drum tester at 80 km / h. Was measured under the conditions defined in the JASO C606 standard, and the partial overall value in the 1/3 octave center frequency 250-4000 Hz band was calculated to evaluate the air column resonance sound. . In addition, the evaluation of the air column resonance sound was performed by calculating the reduction effect of the air column resonance sound by calculating, as a relative value, the sound volume decreasing with respect to the sound volume of the noise generated from the conventional tire. The results are shown in Table 1. FIG. 9 shows a graph of relative values of the volume of the tire of Example 1 that is decreasing with respect to the volume of noise generated from the conventional tire.

  In addition, the driving stability on wet roads is evaluated by a professional driver with a feeling of driving stability when driving on wet road conditions with a water film of 2 mm on a test course laid with an iron plate with a maximum of 10 points. They were evaluated by comparing them. In addition, it shows that it is excellent in the steering stability in a wet road surface, so that a numerical value is large, and the result is shown in Table 1.

  As is clear from the results in Table 1, the column tire resonance noise is reduced in the example tires 1 and 2 as compared with the conventional tires. Specifically, as can be seen from FIG. 9, the volume in the frequency band near 630 Hz and 1000 Hz due to the effect of reducing the pattern noise is reduced, and the volume in the frequency band of 1250 Hz or more due to the effect of reducing the pumping sound. Reduced. Further, the example tires 1 and 2 have improved steering stability performance on the wet road surface as compared with the conventional tires.

  As is clear from the above, by providing a sipe that allows the resonator and the circumferential groove to communicate with each other, air column resonance noise is reduced, quietness is improved, and braking performance, drainage performance and wetness are improved. It has become possible to provide a pneumatic tire with improved handling stability on the road surface.

DESCRIPTION OF SYMBOLS 1 Resonator 2 Branch groove part 3 Air chamber part 4 1st pipe line 5 2nd pipe line 6 Tread part 7 Circumferential groove 8 Road contact area 9 Sipe

Claims (2)

A tread portion tread surface, a circumferential groove extending in the tire circumferential direction, and a plurality of branch groove portions that open to the circumferential groove and reduce noise generated by resonance in a pipe defined by the circumferential groove and the grounding road surface In a pneumatic tire comprising a Helmholtz resonator having an air chamber ,
A pneumatic tire comprising at least one sipe, which is a narrow groove whose cross-sectional area is reduced by 90% or more when the resonator is in communication with the circumferential groove.   The pneumatic tire according to claim 1, wherein an arrangement pitch of the resonators is smaller than a contact length.

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