JP2009090750A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire having improved quietness, controllability and stability, and uneven wear resistance while reducing columnar resonance during traveling by optimizing the shapes of a resonator and a rib-shaped land part. <P>SOLUTION: In the pneumatic tire, a tread surface of a tread part has at least two circumferential grooves extended to the tire circumferential direction and the rib-shaped land part defined and formed by the circumferential grooves. The rib-shaped land part has the resonator opened on a road surface grounding region to reduce noise generated by resonance inside columns formed by the circumferential grooves and the road surface. The resonator has a branch groove part branched and extended from the circumferential groove and an air chamber part connected to the branch groove part and having a cross section orthogonal to the extended direction larger than that of the branch groove part. The rib-shaped land part comprises a narrow width rib-shaped land part and a wide width rib-shaped land part having width wider than that of the narrow width rib-shaped land part, and the air chamber part of the resonator is arranged within the wide width rib-shaped land part. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention comprises, on the tread portion tread, at least two circumferential grooves extending in the tire circumferential direction, and rib-like land portions formed by partitioning with the circumferential grooves. In order to reduce noise generated by resonance in the pipe formed by the road surface, the resonator has a resonator opened in a road contact area, and the resonator is connected to a branch groove portion extending from a circumferential groove and a branch groove portion. In addition, the present invention relates to a pneumatic tire having an air chamber portion whose cross-sectional area perpendicular to the extending direction is larger than that of the branch groove portion, and is quiet while reducing air column resonance generated from such a pneumatic tire. To improve performance, steering stability and uneven wear resistance.

  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 measures to reduce it 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 Document 2 or 3, a technique for reducing air column resonance using anti-resonance by arranging a Helmholtz type resonator has 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

  However, in any pneumatic tire provided with a resonator, the rigidity of the rib-like land portion of the portion where the resonator is provided is lower than the rigidity of the other portion, and the ground pressure in the portion where the rigidity is reduced. Decreases. As a result, vibration due to fluctuations in contact pressure during rolling of tires and fluctuations in driving force and cornering force due to a decrease in rigidity occur, resulting in a decrease in quietness, steering stability and uneven wear resistance. There is a risk of doing.

  Accordingly, an object of the present invention is to optimize the shape of the resonator and the rib-like land portion, thereby reducing air column resonance noise during traveling, while improving steering stability and uneven wear resistance. The purpose is to provide tires.

  In order to achieve the above object, a pneumatic tire according to the present invention is provided with at least two circumferential grooves extending in the tire circumferential direction on a tread portion tread surface, and a rib-like land portion formed by a circumferential groove. The rib-like land portion has a resonator opened in the road contact area to reduce noise generated by resonance in the pipe formed by the circumferential groove and the road surface, and the resonator branches from the circumferential groove. The branch groove part extending to the branch groove part, and having an air space part whose cross-sectional area perpendicular to the extending direction is larger than that of the branch groove part, the rib-like land part is a narrow rib-like land part, A wide rib-shaped land portion having a width larger than that of the narrow-width rib-shaped land portion is provided, and an air chamber portion of the resonator is disposed in the wide-width rib-shaped land portion. In such a pneumatic tire, the width of the land portion of the rib-like land portion is large in the region where the resonator is disposed while reducing the air column resonance noise by the resonator during rolling of the tire load. As a result, it is possible to suppress the local decrease in the rigidity of the rib-shaped land part and to reduce the fluctuation of the ground pressure during tire load rolling. It is possible to improve the quietness, steering stability and uneven wear resistance by suppressing the fluctuations of the driving force and the cornering force due to the vibration and the rigidity fluctuation.

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。 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. 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 tire circumferential cross-sectional area of the first pipeline is S ₁ , the tire circumferential cross-sectional area of the second pipeline is S ₂ , and the acoustic impedance on the first pipeline 4 side at the boundary is Z _12. When the acoustic impedance of the second conduit 5 side at the boundary and Z _21, the following expression is derived from a continuous condition.
Z ₂₁ = (S ₂ / S ₁ ) · Z ₁₂
The sound pressure distribution P ₂ of the second conduit 5, a boundary condition, and the distance from an opening portion in the circumferential groove of the first conduit and x, V _{2 =} V ₀ at x = 0 e ^jwt 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
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 distribution 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 = l ₂ and P ₂ / V ₂ = Z _21. .
_{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 (where k = 2πf ₀ / c)

  Further, the width of the rib-shaped land portion is from the connecting position between the narrow rib-shaped land portion and the wide rib-shaped land portion toward the center position in the tire circumferential direction of the air chamber portion. It is preferable that the width gradually increases to a predetermined total width. Here, the “connection position” refers to the boundary position between the narrow rib-shaped land portion and the wide rib-shaped land portion.

  Furthermore, it is preferable that the width of the land portion of the rib-like land portion is constant. Specifically, the “width of the land portion of the rib-shaped land portion” specifically refers to the rib-shaped land portion along the tire width direction in the portion where the air chamber portion of the rib-shaped land portion is not disposed. In the portion where the air chamber portion is arranged, the width measured in the tire width direction is the width of the land portion excluding the air chamber portion.

  According to the present invention, by optimizing the shape of the resonator and the rib-like land portion, quietness, steering stability and uneven wear resistance are improved while reducing air column resonance noise during traveling. It becomes possible to provide a pneumatic tire.

  Hereinafter, embodiments of the present invention will be described 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. 4 and 5 are tread portions of other typical tires according to the present invention. FIG.

  As shown in FIG. 3, the pneumatic tire according to the present invention has two circumferential grooves 7 extending in the tire circumferential direction on the tread portion tread surface 6, and rib-shaped land portions formed by the circumferential grooves 7. The rib-shaped land portion 8 includes a resonator 1 opened in a road contact area in order to reduce noise generated by resonance in a pipe formed by the circumferential groove 7 and the road surface. Includes a branch groove portion 2 extending from the circumferential groove 7 and an air chamber portion 3 connected to the branch groove portion 2 and having a cross-sectional area perpendicular to the extending direction larger than that of the branch groove portion 2. With this configuration, air column resonance generated in the circumferential groove 7 on the side where the branch groove portion 2 communicates is anti-resonated using the resonator 1 and is effectively reduced. The rib-shaped land portion 8 includes a narrow rib-shaped land portion 9 and a wide rib-shaped land portion 10 having a width wider than that of the narrow-width rib-shaped land portion 9. An air chamber 3 of the resonator 1 is disposed. When the resonator 1 is disposed in the rib-like land portion 8 having a certain width as in the conventional tire, the width of the land portion of the rib-like land portion 8 is equal to the rigidity of the rib-like land portion 8. Since there is a correlation, the width of the land portion in the portion where the resonator 1 is disposed decreases, so that the rigidity of the rib-like land portion 8 is excessively lowered than the rigidity in the other portions, resulting in a rib-like shape. The difference in rigidity in the land portion 8 is increased. As a result, at the time of tire load rolling, the ground contact pressure of the rib-like land portion 8 greatly fluctuates, and vibrations due to such ground pressure fluctuations and fluctuations in driving force and cornering force due to stiffness fluctuations are generated. However, quietness, handling stability and uneven wear resistance are reduced. On the other hand, in the tire according to the present invention, the resonator 1 is disposed in the wide rib-shaped land portion 10, and the width of the land portion of the rib-shaped land portion 8 is increased to surround the resonator 1. Therefore, the rigidity of the rib-like land portion 8 where the resonator 1 is disposed does not significantly decrease compared to the rigidity of other portions. Therefore, the difference in rigidity is reduced over the tire circumference, and the fluctuation of the contact pressure at the time of tire load rolling can be reduced. Therefore, the vibration caused by the change in the contact pressure of the rib-like land portion 8 and the rigidity It is possible to suppress fluctuations in driving force and cornering force due to fluctuations, and to improve quietness, steering stability, and uneven wear resistance.

  Further, as shown in FIG. 4, the width of the rib-shaped land portion 8 is determined from the connecting position 11 of the narrow rib-shaped land portion 9 and the thick rib-shaped land portion 10 at the wide rib-shaped land portion 10. It is preferable that the air chamber part 3 gradually increases to a predetermined total width toward the center in the tire circumferential direction. This is because, by adopting such a configuration, the shape of the rib-like land portion 8 from the connecting position 11 to the center position in the tire circumferential direction of the air chamber portion 3 allows the water flowing in the circumferential groove 7 to smoothly flow when traveling on a wet road surface. Since it has a flowing shape, it resists the flow of water flowing in the circumferential groove 7 as shown in FIG. 3 and sufficiently secures the hydroplaning resistance without deteriorating the hydroplaning resistance. Because it can be done. The gradually increasing rib-shaped land portion 8 is a wide-width rib-shaped land portion 10.

  Furthermore, it is preferable that the width of the land portion of the rib-shaped land portion 8 is constant. As shown in FIG. 5, the width W1 of the land portion in the narrow rib-shaped land portion 9 and the wide-ribbed land portion That is, the sum of the widths W2 and W3 of the land portion at 10 is the same. Because, by making the width of the land portion of the rib-like land portion 8 constant, the rigidity of the rib-like land portion 8 can be made more uniform over the tire circumference even if the resonator 1 is disposed. Since the fluctuation of the contact pressure at the time of tire load rolling is further reduced, the vibration caused by the fluctuation of the contact pressure of the rib-like land portion 8 and the fluctuation of the driving force and the cornering force caused by the fluctuation of the rigidity are further suppressed. This is because silence, steering stability, and uneven wear resistance can be further improved.

  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, although not shown, the shape of the air chamber portion may be elliptical, and the width of the land portion of the rib-like land portion may be constant.

  Next, a conventional tire (conventional example tire) in which a resonator is disposed in a rib-shaped land portion as shown in FIG. 6, and a rib-shaped land portion is formed by a narrow rib-shaped land portion and a wide rib-shaped land portion. The tires of the present invention (example tires 1 to 6) configured and having resonators disposed in the wide rib-shaped land portion 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 four circumferential grooves and three rib-like land portions that are defined by the circumferential grooves and have a constant width over the circumference, and a resonator is provided on the rib-like land portions. It has the specifications shown in Table 1. In addition, Example tires 1 to 5 are divided into four circumferential grooves, and three ribs each formed by a narrow rib-shaped land portion and a wide rib-shaped land portion. Each of the thick rib-shaped land portions is provided with resonators and each has the specifications shown in Table 1. In addition, Example tire 1-5 has a shape where the width | variety of a wide rib-shaped land part becomes large suddenly in a connection position as shown in FIG. 3, and Example tire 6 is as shown in FIG. In addition, the rib-like land portion has a shape that gradually increases from the connecting position to the center position in the tire circumferential direction of the air chamber portion of the wide rib-like land portion. The “thick width rib-shaped land portion width” shown in Table 2 refers to the maximum width of the rib-shaped land portion in the portion where the air chamber portion is disposed.

  Each of these test tires was attached to a rim of size 7.5 × 17 to form a tire wheel, filled with air pressure: 220 kPa (relative pressure), and subjected to various tests.

  Reducing air column resonance noise is a condition defined by the JASO C606 standard when applying a load equivalent to two passengers and running tire wheels with an indoor drum tester at a speed of 80 km / h. The partial overall value in the 1/3 octave center frequency 800-1000-1200 Hz band was calculated, and the air column resonance was evaluated. The resonance frequency of the resonator in the embodiment is calculated as a Helmholtz type resonator with a sound speed c condition of 343.7 m / s.

  Silence is applied by applying a load equivalent to a two-seater ride, tire wheels are mounted on a Toyota model: Celsior (registered trademark), and a professional driver puts the vehicle on the circuit including a long straight road and a gentle curve. The vehicle was run from a low speed to about 100 km / h in a test course consisting of a lot of handling evaluation roads, etc., and the ease of hearing noise and ease of concern were evaluated by feeling on a full scale of 10 points. The evaluation results are shown in Table 2.

  Steering stability applies load equivalent to two passengers, tire wheels are mounted on Toyota's car model: Celsior, and professional drivers handle the above vehicles with a long circuit and a rounded circuit including a long straight road. The vehicle was run from a low speed to about 100 km / h in a test course consisting of an evaluation road and the like, and the steering stability on the dry road surface was evaluated to a maximum of 10 points by feeling. In addition, it shows that it is excellent in steering stability, so that a numerical value is large, and the evaluation result is shown in Table 2.

  Uneven wear resistance applies a load equivalent to two passengers, tire wheels are mounted on Toyota's model: Celsior, and a professional driver runs the above vehicle on a course including ordinary roads, highways, and mountain roads for 10,000 km. The difference in wear between the most worn and unworn parts in the block land was evaluated by comparing the average values. In addition, it is shown that it is excellent in uneven wear resistance that an abrasion difference is small, and the evaluation result is shown in Table 2.

  Hydroplaning resistance applies load equivalent to two passengers, tire wheels are mounted on Toyota's model: Celsior, and a professional driver runs the vehicle on a wet circuit road with a water depth of 10 mm. Evaluation was made by comparing the speed at which the slip ratio on the road surface of the tire reached 15%. At this time, the hydroplaning resistance of the conventional tire was converted to 100, and the other tires were relatively evaluated. In addition, it shows that it is excellent in hydroplaning resistance, so that a numerical value is large, and the evaluation result is shown in Table 2.

  As is apparent from the results in Table 2, all of the tires 1 to 6 were improved in quietness, steering stability, and uneven wear resistance as compared with the conventional tires. At this time, in Example tires 3 and 6, all of quietness, steering stability, and uneven wear resistance were improved in a well-balanced manner. In addition, in Example tires 1 and 6, the decrease in hydroplaning resistance was effectively suppressed, and the same hydroplaning resistance as in Example tires was ensured. From these, it was Example tire 6 that improved quietness, steering stability and uneven wear resistance in a well-balanced manner while ensuring hydroplaning resistance. Further, in the example tires 1 to 6, the air column resonance noise was reduced to the same extent as that of the conventional example tire.

  As is clear from the above, the present invention optimizes the shape of the resonator and the rib-like land portion to reduce air column resonance noise during traveling, while reducing silence, steering stability and It has become possible to provide a pneumatic tire with improved uneven wear resistance.

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. FIG. 5 is a development view of a part of a tread portion of another typical tire according to the present invention. FIG. 5 is a development view of a part of a tread portion of another typical tire according to the present invention. FIG. 6 is a development view of a part of a tread portion of a conventional tire.

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 Rib-like land part 9 Narrow rib-like land part 10 Thick-width rib-like land part 11 Connection position W1 Width of land portion of narrow rib-like land portion W2, W3 Width of land portion of wide rib-like land portion

Claims (3)

The tread portion tread includes at least two circumferential grooves extending in the tire circumferential direction, and rib-shaped land portions formed by partitioning the circumferential grooves. The rib-shaped land portions include the circumferential grooves and the road surface. In order to reduce noise generated by resonance in the pipe, and the resonator has an opening in a road contact area, the resonator branching from the circumferential groove, and the branching groove In a pneumatic tire having an air chamber portion that has a cross-sectional area perpendicular to the extending direction and larger than that of the branch groove portion,
The rib-shaped land portion includes a narrow rib-shaped land portion and a wide rib-shaped land portion having a width larger than that of the narrow rib-shaped land portion, and the air chamber of the resonator is disposed in the wide rib-shaped land portion. A tire characterized by comprising a portion.   The width of the rib-shaped land portion is the center position in the tire circumferential direction of the air chamber portion from the connection position of the narrow rib-shaped land portion and the wide rib-shaped land portion at the wide rib-shaped land portion. The pneumatic tire according to claim 1, which gradually increases to a predetermined total width.   The pneumatic tire according to claim 1 or 2, wherein a width of a land portion of the rib-like land portion is constant.

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