JP4939969B2 - Pneumatic tire - Google Patents

Description

  According to the present invention, a circumferential groove extending substantially in the tire circumferential direction is provided on the tread portion tread surface, and a shoulder land portion is defined by the circumferential groove and the tread grounding end, and is opened to the circumferential groove. The present invention relates to a pneumatic tire including a resonator that reduces noise generated by resonance in a pipe formed by a directional groove and a road surface, and improves steering stability while reducing noise generated from the pneumatic tire. Plan.

  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. . Accordingly, the rigidity of the land portion can be increased 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 tire described in Patent Document 2, since the rigidity of the land portion around the air chamber portion of the resonator is reduced, there is a possibility that steering stability is not sufficiently ensured. Moreover, in the pneumatic tires described in Patent Documents 3 and 4, the Helmholtz type resonator is disposed so as not to contact the road surface during rolling of the tire load, while reducing air column resonance noise. Generation of pitch noise due to collision with the road surface of the resonator can be suppressed, and furthermore, the volume of the resonator that can be installed is limited to a small size. It is possible to ensure sufficient properties. However, since the shape and dimensions of the resonator are limited, the frequency band of the settable resonance frequency is also limited, and there is a possibility that the air column resonance sound cannot be sufficiently reduced.

  Accordingly, an object of the present invention is to provide a pneumatic tire with improved steering stability while reducing air column resonance noise during traveling by optimizing the tread pattern.

  In view of the above, in order to achieve the above-mentioned object, the present invention provides a circumferential groove extending substantially in the tire circumferential direction on the tread portion tread surface, and the shoulder land portion is formed by the circumferential groove and the tread grounding end. In a pneumatic tire having a resonator formed by partitioning and further having a resonator that opens to the circumferential groove and reduces noise generated by resonance in the pipe formed by the circumferential groove and the road surface. A pneumatic tire comprising at least one shoulder groove extending outward in the tire width direction and beyond a tread contact end. In such a pneumatic tire, by arranging the shoulder groove, the frequency of the air column resonance generated from the circumferential groove can be increased and the resonator can be downsized. While reducing the air column resonance noise, the rigidity of the land portion of the tread portion can be sufficiently ensured, and the steering stability can be improved. Here, “substantially tire circumferential direction” means not only a groove extending in a straight line in the tire circumferential direction but also a groove extending in a zigzag shape or a wave shape and making a round in the tire circumferential direction as a whole tire.

として表すことができる。なお、上記式中における枝溝部２端の補正は、通常は、実験によって求められるものであり、その値は、文献によって相違することになるも、ここでは、１．３ｒを用いるものとする。この場合、枝溝部２の断面が円形でないときは、枝溝部２の断面積から円形を仮定したｒを算出して使用するものとする。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、気室部３の容積Ｖ等を選択することで、所要に応じて変化させることができる。 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. The radius of the branch groove 2 is r, the length is l ₀ , the cross-sectional area of the branch groove is S, and the air chamber 3 When the volume is V and the sound velocity is c,

Can be expressed as Note that the correction of the end of the branch groove portion 2 in the above formula is usually obtained by experiments, and the value thereof varies depending on the literature, but 1.3r is used here. In this case, when the cross section of the branch groove portion 2 is not circular, r assuming the circular shape from the cross sectional area of the branch groove portion 2 is used. Therefore, the resonance frequency f ₀ of the resonator 1, by selecting the branch groove 2 cross-sectional area S, volume V and the like of the air chamber portion 3, can be changed if desired.

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,} is 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

  Further, it is preferable that a shoulder groove is disposed between adjacent resonators when viewed in the tire circumferential direction.

  Furthermore, it is preferable that the arrangement pitch of the shoulder grooves is smaller than the contact length of the circumferential grooves. The “circumferential groove contact length” is the road surface when the pneumatic tire is rolled by applying a load of 80% of the maximum load under the standard air pressure specified by JATMA. Tire circumferential direction length of the circumferential groove in the region of the tread portion tread surface that is in contact with the tire.

  Furthermore, it is preferable that the arrangement pitch of the resonators is smaller than the ground contact length of the circumferential groove.

  In addition, it is preferable that the resonator is disposed in the land portion on the inner side in the tire width direction of the circumferential groove.

  In addition, it is preferable that the shoulder groove is opened in the road contact area when the tire is loaded.

  Moreover, it is preferable to provide a circumferential groove, a resonator, and a shoulder groove in both tread half regions. Here, “both tread half regions” refer to two tread portions when the tread portion is virtually divided by the tire equatorial plane CL.

  Furthermore, the shoulder grooves are preferably arranged at a constant circumferential pitch. Here, the “constant circumferential pitch” means that they are all arranged at equal intervals when viewed in the tire circumferential direction.

  According to the present invention, by optimizing the tread pattern, it is possible to provide a pneumatic tire with improved steering stability while reducing air column resonance noise during traveling.

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

  In the tire according to the present invention, as shown in FIG. 3, the tread portion tread surface 6 is provided with a circumferential groove 7 extending substantially in the tire circumferential direction, and the shoulder land portion 9 is formed by the circumferential groove 7 and the tread grounding end 8. A resonator 1 is provided which is formed in a partition, opens into the circumferential groove 7 and reduces noise generated by resonance in the pipe formed by the circumferential groove 7 and a road surface. The shoulder land portion 9 includes at least one shoulder groove 10 extending from the circumferential groove 7 toward the outer side in the tire width direction and beyond the tread ground contact edge 8. In such a pneumatic tire, when the tire load rolls, the shoulder groove 10 opened in the circumferential groove 7 enters the ground contact surface, so that the air column is divided and shortened, and the air generated from the circumferential groove 7 is reduced. The frequency of the column resonance sound increases. At this time, the resonator 1 whose resonance frequency is increased by reducing the volume of the air chamber portion 3 enters the same ground plane as the shoulder groove 10, thereby reducing noise. Note that, even if the resonator 1 is the Helmholtz type resonator described above or the stepped type resonator 1, the resonator 1 is anti-resonant when a condition for reducing the volume of the air chamber portion 3 is applied. The resonance frequency increases. Further, since the volume of the air chamber portion 3 of the resonator 1 is reduced, the rigidity of the tread portion is increased, and the steering stability on the dry road surface is improved. Therefore, the volume of the air chamber portion 3 of the resonator 1 in the same ground plane is further reduced by increasing the number of the shoulder grooves 10 entering the ground plane and increasing the frequency of the air column resonance sound. Therefore, it is possible to increase the rigidity of the tread portion and improve the steering stability on the dry road surface while reducing the air column resonance sound. Moreover, since the edge component is increased by disposing the shoulder groove 10, the effect of cutting the water film on the wet road surface is improved, and the groove volume of the tread portion is increased, so that the water on the road surface enters the groove. Since the effect of sucking up is improved, the running performance on the wet road surface is comprehensively improved.

  At this time, since the basic function as the resonator 1 is not affected, the resonator 1 opened in the circumferential groove has a shape not opened in the tread portion tread surface 6 as shown in FIG. 4a. Alternatively, as shown in FIG. 4b, it may have a shape opened to the tread portion tread surface 6.

  Further, when viewed in the tire circumferential direction, shoulder grooves 10 are disposed between adjacent resonators 1, that is, disposed so that the resonators 1 and the shoulder grooves 10 are alternately grounded at the time of tire load rolling. It is preferable to do. This is because when the resonator 1 is continuously grounded or the shoulder groove 10 is continuously grounded, the frequency of the air column resonance generated from the circumferential groove 7 can be stably increased. This is because there is a possibility that the noise cannot be reduced sufficiently because variations occur in the reduction of the air column resonance due to the resonance frequency of the resonator 1.

  Furthermore, the arrangement pitch of the shoulder grooves 10 is preferably within the ground contact surface of the circumferential groove 7. This is because, when the pitch of the shoulder grooves 10 is larger than the contact length of the circumferential grooves 7 when rolling with a tire load, the shoulder grooves 10 are in contact with the road surface even if the resonator 1 is in contact with the road surface. Otherwise, a tube may not be formed between the shoulder groove 10 and the road surface during rolling of the tire load. As a result, the frequency of the air column resonance generated from the circumferential groove 7 does not increase, and the air chamber This is because there is a possibility that the air column resonance sound cannot be sufficiently reduced by the resonator 1 in which the volume of the portion 3 is reduced.

  In addition, it is preferable that the arrangement pitch of the resonators 1 is smaller than the ground contact length of the circumferential groove 7. This is because when the arrangement pitch of the resonator 1 is larger than the contact length of the circumferential groove 7 at the time of tire load rolling, the shoulder groove 10 contacts the road surface and the air column generated from the circumferential groove 7 This is because even if the frequency of the resonance sound is sufficiently high, the resonator 1 may not be grounded to the road surface, and the air column resonance sound may not be reduced.

  In addition, the resonator 1 is preferably disposed in the land portion 11 on the inner side in the tire width direction of the circumferential groove 7. This is because when the resonator 1 is disposed not on the land portion 11 inside the tire width direction but on the shoulder land portion 9, both the resonator 1 and the shoulder groove are disposed on the shoulder land portion 9. Therefore, the rigidity of the shoulder land portion 9 is lowered, and there is a possibility that the tread portion is destroyed due to uneven wear or baldness of the shoulder land portion 9.

  Moreover, it is preferable that the shoulder groove 10 is opened in the road surface contact area at the time of tire load rolling. This is because when the shoulder groove 10 is not opened in the road contact area during rolling of the tire load, the shoulder groove 10 is completely closed, and the air column resonance sound generated from the circumferential groove 7 by the shoulder groove 10 is reduced. This is because the frequency cannot be increased and the resonator 1 in which the volume of the air chamber 3 is reduced may not be able to effectively reduce the air column resonance.

  Furthermore, it is preferable to provide the circumferential groove 7, the resonator 1, and the shoulder groove 10 in both tread half regions. This is because when the circumferential groove 7 is disposed in both tread half areas, the resonator 1 and the shoulder groove 10 are disposed in both tread half areas, and the resonator 1 and the shoulder groove 10 are disposed only in one tread half area. This is because it is possible to further improve the steering stability while further reducing the air column resonance sound, rather than disposing the shoulder groove 10.

  Furthermore, the shoulder grooves 10 are preferably arranged at a constant tire circumferential pitch. This is because when the shoulder grooves 10 are arranged at a plurality of tire circumferential pitches, the rigidity of the tread portion is biased, which may cause variations in steering stability.

  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 disposed on the tread portion tread 6 different, it is also possible to set the frequency band of antiresonance widely by changing the resonance frequency. .

  Next, a conventional tire having a resonator (conventional tire) and a tire according to the present invention (example tires 1 and 2) were prototyped as radial tires for passenger cars having a tire size of 225 / 55R17, and performance evaluation was performed. Since it went, it demonstrates below.

  The conventional tire includes a circumferential groove and includes a resonator in a land portion on the inner side in the tire width direction of the circumferential groove so as to open to the circumferential groove, and has specifications shown in Table 1.

  In addition, Example tires 1 and 2 have a resonator in the land portion on the inner side in the tire width direction of the circumferential groove so as to open to the circumferential groove and the circumferential groove. Seen in direction, it is disposed between adjacent resonators and has the specifications shown in Table 1. The volume of the air chamber is indexed on the basis of the volume of the resonator per resonator of the conventional tire, and the smaller the value, the smaller the volume of the air chamber.

  Each of these test tires is attached to a rim of size 7.5J × 17.0 to make a tire wheel, and various tests are performed with the air pressure: 220 kPa (relative pressure) and tire load 5.0 kN applied to the passenger car. Performed and evaluated performance. Note that the resonance frequency of the resonator in the example is calculated by applying the conditional expression of the Helmholtz type resonator with the sound speed c being 343.7 m / s.

  In a test to evaluate quietness, a test vehicle is run at a speed ranging from a low speed to 100 km / h on a test course consisting of a circumference circuit including a long straight portion and a handling evaluation road with many gentle curves. A professional driver evaluated the ease of hearing of the air column resonance sound and the ease of being worried about it on a 10-point scale. In addition, it has shown that it is excellent in quietness, so that a score is large. The evaluation results of quietness are shown in Table 2.

  In tests to evaluate the stability of dry road maneuvering, a test vehicle is run on a test course consisting of a circumference circuit including a long straight section and a handling evaluation road with many gentle curves, and the speed ranges from low speed to 100 km / h. A professional driver evaluated the driving stability on a dry road surface with a maximum of 10 points. In addition, it shows that it is excellent in dry road surface steering stability, so that a score is large. The evaluation results of the dry road surface handling stability are shown in Table 2.

  In tests to evaluate wet road handling stability, the wet road surface of the test course consisting of handling evaluation roads with many up and down curves is run at the highest possible speed (limit speed), and wet performance such as grip performance and handling performance. A professional driver evaluated road handling stability on a 10-point scale. In addition, it has shown that it is excellent in wet road surface steering stability, so that a score is large. Table 2 shows the evaluation results of the wet road surface handling stability.

  As is clear from the results in Table 2, the example tires 1 and 2 have improved dry road surface handling stability while the air column resonance noise is similarly reduced as compared with the conventional tires. In addition, since Example Tire 2 has a larger number of shoulder grooves in the contact surface than Example Tire 1, the volume of the air chamber portion is small, and the dry road surface handling stability is further improved. In the example tires 1 and 2, the wet road surface handling stability is improved as compared with the conventional tires. At this time, since the example tire 2 has more shoulder grooves in the ground contact surface than the example tire 1, the wet road surface handling stability is further improved.

  As is clear from the above, while optimizing the tread pattern and optimizing the dimensions and location of the resonators disposed on the tread surface, the air column resonance noise during travel is reduced. It has become possible to provide a pneumatic tire with improved handling stability.

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 development 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. 1 is a perspective view of a part of a tread portion of a typical tire according to the present invention.

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 Tread grounding end 9 Shoulder land part 10 Shoulder groove 11 Land on the inner side in the tire width direction of the circumferential groove Part

Claims (8)

A circumferential groove extending substantially in the tire circumferential direction is disposed on the tread surface, and a shoulder land portion is defined by the circumferential groove and the tread grounding end, and the circumferential groove is opened to the circumferential groove. In a pneumatic tire including a resonator that reduces noise generated by resonance in a pipe formed by a groove and a road surface,
A pneumatic tire comprising at least one shoulder groove extending from the circumferential groove toward the outer side in the tire width direction and beyond the tread contact end.   The pneumatic tire according to claim 1, wherein a shoulder groove is disposed between adjacent resonators when viewed in the tire circumferential direction.   The pneumatic tire according to claim 1 or 2, wherein an arrangement pitch of the shoulder grooves is smaller than a contact length of the circumferential grooves.   The pneumatic tire according to any one of claims 1 to 3, wherein an arrangement pitch of the resonators is smaller than a contact length of the circumferential groove.   The pneumatic tire according to any one of claims 1 to 4, wherein the resonator is disposed in a land portion on the inner side in the tire width direction of the circumferential groove.   The pneumatic tire according to any one of claims 1 to 5, wherein the shoulder groove is open in a road contact area during rolling of a tire load.   The pneumatic tire according to any one of claims 1 to 6, comprising the circumferential groove, the resonator, and the shoulder groove in both tread half regions.   The pneumatic tire according to any one of claims 1 to 7, wherein the shoulder grooves are arranged at a constant circumferential pitch.

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