JP2008155798A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire which enhances a suppression effect against columnar resonance of a peripheral groove by also disposing a Helmholtz resonator even in a shoulder part without sacrificing steering stability. <P>SOLUTION: When a tire peripheral direction extension length of an air chamber 6 of the resonator 5 is represented by L<SB>1</SB>, and the tire width direction extension length is represented by L<SB>2</SB>, L<SB>2</SB>is made ≤L<SB>1</SB>at least in the resonator 5 located in a land part except the shoulder part 4C. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a pneumatic tire having a Helmholtz resonator that suppresses air column resonance in a circumferential groove, and more particularly to a tire that can improve steering stability at a small steering angle.

  The air column resonance sound is noise generated by resonance of the air in the pipe surrounded by the circumferential groove extending continuously in the circumferential direction of the tread surface and the road surface in the tread surface area. The sound frequency is often observed at about 800 to 1200 Hz in a general passenger car, and since the peak sound pressure level is high and the frequency band is wide, it occupies a large part of the noise generated by the tire.

  In addition, since human hearing is particularly sensitive in the above frequency band, reduction of air column resonance is effective in improving the quietness of the feeling surface.

Therefore, as one of the methods for reducing air column resonance, a resonator is provided that opens in the circumferential groove and ends in the land portion. The resonator is provided with an air chamber that opens on the land surface, an air chamber, There has been proposed a technique of absorbing energy in the vicinity of the resonance frequency of the air column resonance sound by a so-called Helmholtz resonator constituted by a constricted neck that provides communication with the circumferential groove.
Japanese Patent Laid-Open No. 5-338411

  The air chamber of such a resonator also acts as a kind of groove, and when the resonator is provided on a rib that is separated by a circumferential groove and continuously extends in the circumferential direction, the rib is surrounded by the air chamber. As a result, the deformation accompanying the incompressible flow generated toward the outside in the circumferential direction of the rubber generated at the time of tire contact is divided and absorbed by the air chamber. The ground contact length will be shortened. As a result, when a resonator is arranged in the center in the tire width direction, such as the center rib and the second rib, when the steering is performed to generate a predetermined slip angle, the total amount of shear deformation of the rib is reduced and sufficient laterality is achieved. The force cannot be obtained, and this may cause a problem that the steering stability of the tire with respect to a small steering angle is lowered.

  The present invention has been made in view of such problems, and at least the center rib or the second rib is provided with a Helmholtz resonator without impairing the steering stability with respect to a small steering angle, and the circumferential groove An object of the present invention is to provide a pneumatic tire capable of enhancing the suppression effect on air column resonance.

<1> is a constriction that provides a circumferential groove continuously extending in the circumferential direction on the tread surface, opens an air chamber on the surface of the land portion at a position away from the circumferential groove, and communicates the air chamber with the circumferential groove. In the tire which arranged the resonator which consists of a neck at least in land parts other than a shoulder part,
The air chamber tire circumferential direction extending the length of the resonator and L _1, when the tire width direction extending length was L _2, at least in arranged resonator land portion other than the shoulder portion, L ₂ is a pneumatic tire characterized by being L ₁ or less.

<2> is the pneumatic tire according to <1>, wherein L ₂ is smaller than L ₁ and L ₂ is 0.5 times or less of L ₁ .

<3> is a resonator in which L ₂ is equal to or less than L ₁ in <1> or <2>, and connects the center line in the width direction of the air chamber to the midpoint in the width direction at each circumferential position of the air chamber. When defined as an elliptic line, an average gradient of the center line in the air chamber width direction is a range of 45 to 90 ° with respect to the tire width direction.

According to <1>, the tire circumferential direction extending a length L ₁ of the air chamber, since the tire width direction extending a length L ₂ or more, L ₁ is as compared with the case shorter than L _2, the resonance tone Although the suppression effect does not change, it is possible to increase the continuity of the rib by reducing the width direction component of the groove part that divides the rib, and to suppress the decrease in the total amount of shear deformation for a certain slip angle and to stabilize the steering to a small steering angle Can increase the sex.
Moreover, the steering stability at the time of minute steering depends on the in-plane shear stiffness at the position where the steel cord intersects, that is, the center side of the shoulder portion in the tire width direction, rather than the in-plane shear stiffness at the shoulder portion. And the ground contact length is longer at the center side than the shoulder portion, and the present invention is to arrange the resonator having L ₁ or more than L ₂ at least at the center side from the shoulder portion. Since it is an indispensable requirement, steering stability can be improved extremely effectively.

According to <3>, since L ₂ is 0.75 times or less of L ₁ , the continuity in the circumferential direction of the rib can be further increased, and the steering stability can be further effectively improved.

  According to <4>, since the center line in the air chamber width direction is inclined in the direction close to the circumferential direction, the steering stability can be further improved.

  FIG. 1 is a diagram schematically showing an embodiment of the present invention. In the figure, reference numeral 1 denotes a tread tread, in particular, a tire mounted on an applicable rim is filled with a prescribed air pressure, and the tire has a prescribed air pressure. A grounding surface 2 that contacts the road surface in a standard state in which a load corresponding to 80% of the mass is applied is shown. 3 extends continuously on the grounding surface 2 in the circumferential direction, for example, in a straight line. A circumferential groove having an annular shape is shown.

  In this case, “applicable rim” refers to the rim specified in the following standards according to the tire size, and “specified air pressure” refers to the air pressure specified in accordance with the maximum load capacity in the following standards. The maximum load capacity refers to the maximum mass allowed to be loaded on the tire according to the following standards. The “specified mass” refers to the above maximum load capacity. The air here can be replaced with an inert gas such as nitrogen gas or the like.

  The standard is determined by an industrial standard effective in the region where the tire is produced or used. For example, in the United States, it is "THE TIRE AND RIM ASSOCIATION INC. YEAR BOOK", and in Europe, the THE It is “STANDARDS MANUAL” of European Tire and Rim Technical Organization, and “JATMA YEAR BOOK” of Japan Automobile Tire Association in Japan.

  The land portion 4 separated by the circumferential groove 3 continuously extending in the circumferential direction has an air chamber 6 that opens on the surface of the land portion 4 at a position away from the circumferential groove, and the air chamber 6 communicates with the circumferential groove 3. A resonator 5 including a constricted neck 7 is disposed, and the resonator 5 is also disposed in the land portion 4B on the center side from the shoulder portion located on the outermost side of the tread surface.

  Here, the “shoulder portion” in the present specification refers to a land portion located on the outer side of the outermost circumferential groove in the tire width direction on the tread surface with respect to the standard state defined above. 4C will be referred to as “shoulder rib”. Further, as shown in FIG. 1, the land portion 4A located at the center in the tire width direction is referred to as “center rib”, and the land portion 4B adjacent to the center rib 4A with the circumferential groove 3 therebetween is referred to as “second rib”. To do.

When the length in the tire circumferential direction of the air chamber of the resonator 5 is L ₁ and the length in the tire width direction is L ₂ , the present invention is at least a land portion other than the shoulder portion (in FIG. 1). in resonator 5 disposed in second rib 4B), the tire circumferential direction extending a length L ₁ of the air chamber, characterized by a tire width direction extending a length L ₂ or more.

If the length L ₁ in the tire circumferential direction of the air chamber 6 arranged in the second rib 4B is shorter than the length L ₂ in the tire width direction, the second rib 4B is arranged in the tire width direction. It is divided in the circumferential direction by a long air chamber, and as a result, the tire ground contact length is shortened and the steering stability at a small steering angle is reduced. By setting L ₂ to L ₁ or less, the second rib 4B is circumferentially arranged. Without division, it is possible to increase the continuity of the rib in the circumferential direction, and to suppress noise caused by air column resonance without sacrificing steering stability at a minute steering angle.

The length L ₂ in the tire width direction of the air chamber 6 arranged in the shoulder rib 4C is preferably 0.5 times or less than the length L _{1 in} the tire circumferential direction, and the steering stability at a small steering angle is preferable. Can be more effectively suppressed.

Here, in this specification, when the cross-sectional shape of the air chamber 6 changes along the depth direction, the tire circumferential direction extending length L ₁ and the tire width direction extending length L ₂ are: It is set as the length in the opening part to the tire surface of the air chamber 6. FIG.

In the resonator 5 illustrated in FIG. 1, the opening of the air chamber 6 to the tire surface includes a side having a length L ₁ parallel to the tire circumferential direction and a tire as shown in FIG. parallel to the width direction, it is assumed that forms a more becomes rectangle with a side length L _2, the shape of the opening is not limited to a rectangle, also be elliptical other curved contour It can also be a quadrilateral or other polygonal shape, and when this is expressed as a general shape as shown in FIG. 2 (b), it extends in the tire circumferential direction of the air chamber 6 (the opening thereof). The length L ₁ is the projection length when the opening is projected onto a line parallel to the tire circumferential direction C, and the tire width direction extending length L ₂ of the air chamber 6 is parallel to the tire width direction D. It can be defined as the projection length when projected onto a line.

In general, in the case of a Helmholtz type resonator in which one constriction neck 7 is provided for one air chamber 6 as schematically shown in FIG. Under the condition that both the necks 7 are sealed by the road surface, the resonance frequency f ₀ is such that the radius of the constriction neck 7 is r, the length is l ₀ , the neck cross-sectional area is S, the air volume is V, and the sound velocity is When it is set as c, it can represent with Formula (1).

Accordingly, the resonance frequency (f ₀ ) of the resonator 5 can be changed as required by selecting the neck cross-sectional area (S), the air chamber volume (V), etc. For the purpose of suppressing air column resonance in a general frequency band that is generated, it is preferable that f ₀ be 700 to 1800 Hz as a resonance frequency to be provided in the resonator 5. It is more preferable that the frequency is set to ˜1400 Hz, and it is preferable to set various dimensions of the resonator in order to obtain frequencies in these ranges.

  In the equation (1), the coefficient 1.3 relating to r varies depending on the literature and is generally obtained from an empirical equation. In this specification, this coefficient is set to 1.3.

l₁、l₂はそれぞれ、狭窄ネックおよび気室の長さを表す。 In addition, when both the stenosis neck and the air chamber have constant cross-sectional areas S ₁ and S ₂ in the length direction, they can also be expressed using equation (2). When the length of the resonator is not sufficiently small with respect to the wavelength at the resonance frequency, the accuracy of the equation is lowered, whereas when equation (2) is used, the length of the resonator is reduced. The resonance frequency can be calculated with sufficient accuracy regardless of the dimensions.

l ₁ and l ₂ represent the stenosis neck and the length of the air chamber, respectively.

Here, the opening area of the air chamber 6 to the land surface under a no-load state on the tire is set to 50 to 600 mm ² , more preferably 100 to 360 mm ² .

  By the way, in this tire, since the air chamber 6 of the resonator 5 is formed by opening the surface of the land portion 4, the vulcanization molding for the raw tire is performed so that the mold portion enters the portion corresponding to the air chamber. Even if it is carried out, the extraction of the mold part from the air chamber 6 of the product tire is always smooth and reliable regardless of whether the cross-sectional area of the air chamber 6 changes somewhat in the depth direction. As a result, the tire can be manufactured in the same manner as a conventional tire without a resonator.

  Note that such an air chamber 6 that opens on the surface of the land portion 4 also defines a sealed space in the ground contact surface 2 of the tread tread 1 under the closed condition of the opening by the road surface. In addition, the function as a resonance chamber can be sufficiently exhibited.

  In addition, the cross-sectional area and the contour shape of the air chamber 6 in the cross section parallel to the land surface can be made the same as those of the land opening toward the bottom wall side of the air chamber 6. It can be gradually increased from the air chamber 6 of the molded tire to the extent that the extraction of the mold portion is not restricted, and conversely, it can be gradually decreased.

  In such a resonator 5, the constriction neck 7 can be a tunnel-like one embedded in the land portion 4 as illustrated in the perspective view of the main part in FIG. As shown in (b), it can also be opened to the surface of the block 4a. Here, when the open neck 7 like the latter is formed by, for example, pressing a blade of a vulcanization mold or the like, the constriction neck 7 can be easily formed in addition to the air chamber 6. .

  In this case, the narrowed neck 7 can also be formed by sipe. At this time, as illustrated in FIG. 4C, the shape of the sipe is a so-called flask-like shape having an enlarged space portion at the bottom. For example, portions other than the enlarged space portion have sipe walls in the ground plane. By making the narrow portion so as to be in contact with each other, the various dimensions of the narrowed neck 7A can be always constant as in the case shown in FIG.

  In such a resonator 5, more preferably, the maximum depth h of the air chamber 6 from the surface of the land portion is set to 20% or more of the maximum depth H of the groove defining the land portion 4, for example, the circumferential groove 3. Is 40 to 80%, and preferably, the maximum dimension d in the depth direction of the constriction neck 7 is 70% or less, particularly 50% or less of the maximum depth h of the air chamber 6.

  In the above description, the bottom wall of the air chamber 6 can be a flat surface or a curved surface that is convex or concave toward the opening side thereof. As shown in an enlarged cross-sectional view along the line Y-Y in FIG. 4A, the bottom wall is convex upward for the purpose of suppressing stone biting into the air chamber 6. One or more protrusions 6a are provided, and the resulting unevenness difference δ is 1.6 mm or more, more preferably 3.0 mm or more. However, the upper limit of the unevenness difference δ is smaller than the maximum depth of the air chamber, more preferably smaller than (maximum depth of the air chamber−2 mm) because the air chamber 6 needs to be resonated without being divided. Good.

  In this case, the protrusion 6a may be formed so as to protrude from the side wall of the air chamber and be independent from the bottom wall, in other words, separated from the bottom wall.

  The arrangement of the resonator 5 having such a configuration with respect to the circumferential groove 3 is such that at least one circumferential groove is formed in the ground plane 2 under the conditions described with reference to FIG. It is preferable that one or more resonators 5 provided in any one of the circumferential grooves 3 are always completely included. More preferably, one or more resonators 5 are provided for each of the plurality of circumferential grooves 3. Is always completely included in the ground plane 2.

  More preferably, a plurality of resonators 5 having different resonance frequencies are arranged in the circumferential grooves 3 in the ground plane 2 that are grounded under the same conditions as described above. Each is always open.

FIG. 6 is a conceptual diagram showing a ground contact surface in a state similar to that described with reference to FIG. 1 for a tire according to a modification of the embodiment of the present invention. This tire has a tire in the air chamber 6 in the second rib 4B. Although the circumferential direction extending a length L ₁ is about point to place the long resonator 5 from the tire width direction extending a length L ₂ are the same as those of the embodiments shown above, the other land portion, for example, the shoulder rib 4C, in which the tire width direction extending a length L ₂ is arranged a resonator 15 having a long air chamber 16 than the tire circumferential direction extending a length L _1.

  FIG. 7 is a conceptual diagram showing a ground contact surface in a state similar to that described with reference to FIG. 1 for a tire according to another modification of the embodiment of the present invention, and the resonator according to the embodiment shown in FIG. 5, the inclination angle θ of the air chamber width direction center line CL with respect to the tire width direction is 90 °. This is the same as the inclination angle θ of the air chamber 26 of the resonator 25 disposed on the land portion 4. The inclination angle θ is preferably an angle within a range of 45 to 90 °.

  Here, when the air chamber 6 forms a parallelogram, the average gradient θ of the air chamber width direction center line CL with respect to the tire width direction D is equal to two sides of the parallelogram, as shown in FIG. As described above, the shape of the air chamber 6 is not limited to a parallelogram. In this case, in this specification, the air chamber width direction with respect to the shape of any air chamber opening is used. As shown in FIG. 8A, the center line CL crosses the opening of the air chamber 6 and is innumerable line segment W parallel to the tire width direction D (only three lines are shown in FIG. 8A). Let the middle point M be a continuous line.

  A plurality of tires according to examples of the present invention and comparative example tires having different arrangements and specifications of resonators from each other were prototyped, and noises of these tires were measured and controlled by the following experiments 1 and 2. The stability was evaluated.

  The tires used in the experiment were all 195 / 65R15 in size, and these tires were mounted on a 6JJ rim and the air pressure was 210 kPa.

  As a noise measurement method, the tire was rolled with an indoor drum tester at a speed of 80 km / h under the action of a load of 4.47 kN, and the side sound of the tire at this time was in accordance with the conditions specified in JASO C606. Measured, and the overall value of the band of the center frequency 800-1000Hz-1250Hz in 1/3 octave band was obtained. And only the point without the resonator is expressed in decibel difference (dB) with respect to the conventional tire different from the tire of Example 1 described below.

  Steering stability was evaluated by driver's feeling evaluation. A conventional example in which the driver's evaluation of the vehicle's responsiveness when traveling on a test car at a speed of 100 mph and changing lanes is quantified, and only the point where there is no resonator is different from the tire of Example 1 described below. Expressed as the difference in scoring for tires. And in the scoring, when it was +1 point, it was judged that there was a significant effect, and when there was a difference of +3 points or more, it was judged that there was a big effect.

[Experiment 1]
A tire having the resonator 5 having the shape and arrangement shown in FIG. 1 is referred to as Example 1. As shown in FIG. 9, in all the resonators 15, the air chamber 16 has an opening size of the example. The tire 5 is the same as the air chamber 6 except that the direction of the tire is 90 ° different from that of the first embodiment. The second rib 4B has the same resonator 5 as the first embodiment, and the resonator 15 in the shoulder rib 4C has the same direction. In Example 2, the same tire as in Comparative Example 1 is used, and as shown in FIG. 10, the resonator 15 in the second rib 4B is the same as that in Comparative Example 1, and the resonator 5 in the shoulder rib 4C is the same as in Example 1. The same tire was used as Comparative Example 2, and noise measurement and steering stability evaluation were performed on these four types of tires by the method described above.

In the tire of the first embodiment, as shown in FIG. 1, three resonators 5 that open in each circumferential groove 3 are always arranged on each rib on the tread surface 1, and the resonator 5 is configured. chamber 6, the tire circumferential direction extending a length L ₁ is 18 mm, the tire width direction extending a length L ₂ is 6 mm, a depth a rectangular parallelepiped shape of 7 mm, so that its volume V is 756Mm ^3, narrowed neck 7 has a length l ₀ of 6 mm, a width w of 1 mm, and a depth h of 2 mm. The resonance frequency f ₀ in the Helmholtz resonator obtained by using the equation (1) for these dimensions is 1061 Hz. In the calculation, the sound velocity c was 343.7 m / s.

As is apparent from Table 1, although all the tires have substantially the same resonance noise suppressing effect, the tire circumferential direction extending length L _{1 of} the air chamber 6 arranged in the second rib is the tire width direction extending length. only if L ₂ is greater than, it is understood that the pass level (+1 or higher) in terms of steering stability.

[Experiment 2]
In addition to the tire of Example 2 and Comparative Example 1 used in Experiment 1, only the tire circumferential direction extending length L ₁ and the tire width direction extending length L _{2 of} the air chamber 6 are different from those of Example 2. Tires of Examples 3, 4, 5 and Comparative Example 3 were made as prototypes, and noise measurement and steering stability evaluation were also performed on these tires using the methods described above. Table 2 shows the measurement results of Examples 1, 3, 4, and 5 and Comparative Examples 1 and 3, and the opening size of the air chamber 6.

The tire circumferential direction extending length L ₁ and the tire width direction extending length L ₂ of each example shown in Table 2 have the same product, that is, the air chamber opening area, and therefore the air chamber. Note that all of these resonance frequencies f ₀ are 1061 Hz because the volumes are all set to be the same, and as a result, the depth of the air chambers is both 7 mm.

As can be seen from Table 2, if L ₂ / L ₁ is 1 or less, steering stability can be improved. Especially, if L ₂ / L ₁ is 0.5 or less, steering stability is more effective. Can be improved.

It is a figure showing typically the tread surface of the tire of the embodiment concerning the present invention. It is a top view which shows the opening part of an air chamber. It is a figure which shows typically a Helmholtz type resonator. It is a principal part perspective view which illustrates the formation aspect of a resonator. It is an expanded sectional view of the air chamber bottom wall which follows the YY line of Fig.4 (a). It is a figure showing typically the tread surface of the tire of the modification of an embodiment. It is a figure which shows typically the tread surface of the tire of the other modification of embodiment. It is a top view which shows the opening part of an air chamber. It is a figure which shows typically the tread surface of the tire of a comparative example. It is a figure which shows typically the tread surface of the tire of another comparative example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tread surface 2 Ground surface 3 Circumferential groove 4 Land part 4A Center rib 4A Second rib 4A Shoulder rib 5 Resonator 6 Air chamber 6a Protrusion 7 Stenosis neck 15 Resonator 16 Air chamber 17 Stenosis neck

Claims (3)

The tread surface is provided with a circumferential groove extending continuously in the circumferential direction, and an air chamber that opens to the land surface at a position away from the circumferential groove and a constriction neck that communicates the air chamber with the circumferential groove. In the tire disposed at least in the land portion other than the shoulder portion,
The air chamber tire circumferential direction extending the length of the resonator and L _1, when the tire width direction extending length was L _2, at least in arranged resonator land portion other than the shoulder portion, L ₂ is a pneumatic tire, wherein at L ₁ or less. _2. The pneumatic tire according to claim 1, wherein in at least the resonator located in the shoulder portion, a tire width direction extending length L ₂ is 0.5 times or less of a tire circumferential direction extending length L _1. . In the resonator in which L ₂ is L ₁ or less when the air chamber width direction center line is defined as a line connecting width direction midpoints in the circumferential positions of the air chamber, the air chamber width direction center line 3. The pneumatic tire according to claim 1, wherein an average slope of the tire is in a range of 45 to 90 ° with respect to a tire width direction.

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