JP4428062B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire having a cavity, and more particularly, to a pneumatic tire that effectively reduces cavity resonance noise.

  In a pneumatic tire, one of the causes for generating noise is cavity resonance sound caused by vibration of air filled in the tire. This cavity resonance sound is generated when the tread portion vibrates due to road surface irregularities when the tire rolls, and the vibration of the tread portion vibrates the air inside the tire.

  As a technique for reducing noise due to such a cavity resonance phenomenon, the cross-sectional area of the closed space formed by the tire and the wheel is changed in the tire circumferential direction, thereby shortening the time for resonance at a single resonance frequency. Has been proposed (see, for example, Patent Document 1). More specifically, in order to change the cross-sectional area of the closed space, a bulkhead having a predetermined volume is attached to the tire inner surface or the rim outer peripheral surface.

However, in the above technique, if the change in the cross-sectional area of the closed space is increased in order to increase the effect of reducing the cavity resonance noise, the mass balance in the tire circumferential direction is deteriorated, and in some cases, the bulkhead interferes with the deformation of the tire. The rim assembly workability may be deteriorated. Therefore, the size of the bulkhead is limited, and it is difficult to enhance the effect of reducing the cavity resonance sound.
JP 2001-113902 A

  An object of the present invention is to provide a pneumatic tire capable of effectively reducing cavity resonance noise while maintaining a good mass balance in the tire circumferential direction.

In order to solve the above object, a pneumatic tire according to the present invention is a pneumatic tire having a cavity, and one end of the pneumatic tire is closed using a film coated on the surface of a porous material having a density of 5 to 70 kg / m ³ as a wall material. A plurality of tubes are formed so as to open into the cavity, and the circumferential length of these tubes is 55 to 110% (preferably 85%) of the reference length L ₀ corresponding to ¼ of the cavity resonance wavelength. ~ 105%), and the opening of the tube is arranged at two locations facing each other across the tire rotation axis, and a belt-like sound absorbing material is arranged at a portion on the tire circumference where the tube is not arranged It is characterized by that.

As a result of earnest research on the cavity resonance of a pneumatic tire, the present inventors, as a result, provided a pipe communicating with the cavity formed between the pneumatic tire and the rim, the vibration of the air in the pipe It has been found that the resonance frequency is split when the vibrations of the air in the cavity interfere with each other. In particular, an end-closed tube having a circumferential length of about ¼ of the cavity resonance wavelength causes a resonance frequency split while having a length shorter than the cavity resonance wavelength, and changes in resonance frequency due to rolling. It was found to express Therefore, by providing a tube with one end closed as described above, the cavity resonance noise can be effectively reduced as compared with the conventional case where the cavity resonance noise is reduced based on a change in the sectional area of the closed space. Is possible.

The cavity resonance wavelength (λ) is an average circumference of the cavity formed between the pneumatic tire and the rim. The reference length L ₀ (mm) corresponding to ¼ of the cavity resonance wavelength can be calculated from the tire size based on the following equation (1).
L ₀ = α · A · B + β · C (1)
Where A is the sectional width, B is the flatness ratio, C is the rim diameter, α (constant) is 8.33 × 10 ⁻³ , and β (constant) is 1.78 × 10 ¹ . is there.

For example, when the tire size is 215 / 60R16, A = 215, B = 60, C = 16, and L ₀ = 392 mm. That is, the above expression (1) is an expression for simply calculating the reference length L ₀ corresponding to ¼ of the cavity resonance wavelength from the tire size.

  In the present invention, by arranging the openings of a plurality of pipes at two locations facing each other across the tire rotation axis, the effect of reducing cavity resonance noise can be enhanced without deteriorating the mass balance in the tire circumferential direction. it can. At this time, it is preferable that the angle around the tire rotation axis that defines the range of each location where the opening of the tube is disposed is 35 ° or less. Thus, by defining the angular range of the location where the opening of the tube is disposed, the resonance frequency splits significantly.

  In addition, since the tube covered at one end is formed using the film coated on the surface of the low-density porous material as a wall material, an increase in the weight of the pneumatic tire can be minimized. As the film, a resin film is preferably used and the thickness is preferably 5 to 1000 μm. In addition, the cross-sectional area of the tube is preferably 3 to 20% of the cross-sectional area of the cavity.

  Furthermore, in the present invention, the band-shaped sound absorbing material is arranged on the tire circumference and the end-closed tube is not disposed, so that in addition to the resonance frequency dispersion effect by the one-end closed tube, the sound absorption by the band-shaped sound absorbing material Since the effect is obtained, the noise can be further reduced. Moreover, it becomes possible to maintain the mass balance of a pneumatic tire favorably by the combined use of the one-end-closed tube and the band-shaped sound absorbing material. In particular, when the pipe is opened in a direction orthogonal to the length direction and the pipe and the band-shaped sound absorbing material are arranged adjacent to each other in the tire circumferential direction, the mass balance in the tire circumferential direction becomes the best.

  In the present invention, the structure for mounting the pipe and the band-shaped sound absorbing material to the inner surface of the tire is not particularly limited. When it is mounted on the inner surface of the tread based on the elastic force, the installation work of the pipe and the band-shaped sound absorbing material is simple. In addition, the structure in which the tube and the band-shaped sound absorbing material are mounted on the inner surface of the tread using the elastic fixing band is lower in cost than the case where the tube and the band-shaped sound absorbing material are directly processed into a tire or a wheel, and the rim assembly property is also good. is there.

  Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 shows a pneumatic tire according to an embodiment of the present invention, FIG. 2 shows a noise reduction device composed of a tube, a band-shaped sound absorbing material, and an elastic fixing band, and FIG. 3 is composed of a porous material and a film. It shows a tube which is closed at one end. In FIG. 1, the pneumatic tire T includes a tread portion 1, a pair of left and right bead portions 2, and a sidewall portion 3 that connects the tread portion 1 and the bead portion 2 to each other.

  On the inner surface of the tread portion 1, a plurality of tubes 12 whose ends are closed and a plurality of strip-shaped sound absorbing materials 15 are attached by an annular elastic fixing band 11. These tubes 12 are arranged at equal intervals in the tire circumferential direction and are attached to the elastic fixing band 11. In FIG. 2, the opening part 12a of the pipe | tube 12 is a site | part shown with a broken line. On the other hand, the band-shaped sound absorbing material 15 is attached to the elastic fixing band 11 so as to be interposed between the tubes 12. And since these pipe | tube 12 and the strip | belt-shaped sound-absorbing material 15 are mounted | worn on the inner surface of the tread of the vulcanized pneumatic tire T based on the elastic force of the elastic fixing band 11, the installation operation | work is very easy.

  The elastic fixing band 11 may be an endless annular body, or may be formed by connecting both ends in the longitudinal direction of the band material to each other. In particular, when the elastic fixing band 11 is made of a band material, the circumference can be adjusted according to the tire size. As a constituent material of the elastic fixing band 11, a synthetic resin such as a polypropylene resin can be used. In particular, when polypropylene resin is used, the tensile elastic modulus according to the test method defined by ASTM test method D638 is preferably about 700 MPa. In addition to the synthetic resin, a metal material can be used, and stainless steel is preferable from the viewpoint of corrosion resistance.

The tube 12 that is closed at one end has a length L that approximates a reference length L ₀ corresponding to ¼ of the cavity resonance wavelength λ, and is formed by a pneumatic tire T and a rim (not shown). Is open. However, the rim mentioned here is a standard rim defined in the JATMA Yearbook (2003 edition). The pipe 12 opens in a direction (tire radial direction) orthogonal to the length direction. Therefore, even when the pipe 12 and the band-shaped sound absorbing material 15 are arranged so as to be adjacent to each other in the tire circumferential direction, the opening 12a of the pipe 12 can be secured. The openings 12a of these pipes 12 are arranged at two locations facing each other across the tire rotation axis.

  As shown in FIG. 3, each tube 12 is formed with a film 14 coated on the surface of a low-density porous material 13 as a wall material. By using the end-closed tube 12 having the above laminated structure, the weight increase of the pneumatic tire T can be minimized. The tube 12 may be one having only the film 14 as a wall material, or may be one using the tire inner surface as a wall material together with the film 14.

The porous material 13 has a density of 5 to 70 kg / m ³ . If the density is less than 5 kg / m ³ , the shape stability of the tube 12 is lowered. Conversely, if the density exceeds 70 kg / m ³ , it causes a weight increase, and further, the cavity resonance noise is reduced due to the interference action of the tube 12. The effect is also insufficient. As the material of the porous material 13, a resin foam can be used, and it is particularly preferable to use a foamed polyurethane foam.

  As a constituent material of the film 14, a synthetic resin such as an olefin resin, a polyester resin, or a polyurethane resin may be used. The film 14 made of these resins effectively functions as a wall material that blocks sound waves, and improves the durability (particularly, friction resistance) of the porous material 13. Here, the thickness of the resin film 14 is preferably 5 to 1000 μm. If the thickness of the film 14 is less than 5 μm, the effect of blocking sound waves is reduced. Conversely, if the thickness exceeds 1000 μm, the tube 12 becomes excessively hard and it is difficult to follow the deformation of the tire. In addition, in the film 14, about the part interposed between the porous material 13 and a tire inner surface, ie, the part which contact | connects a tire inner surface, in order to improve durability with respect to wear deterioration, the thickness shall be 100-1000 micrometers. Good.

  As a constituent material of the band-shaped sound absorbing material 15, a porous material such as a sponge having a high sound absorption rate can be selected. The plurality of band-shaped sound absorbing materials 15 may be composed of a single porous material, or a plurality of types of porous materials having different sound absorbing characteristics may be used in combination. By configuring the plurality of belt-shaped sound absorbing materials 15 from porous materials having different sound absorption characteristics, it is possible to obtain a noise reduction effect in a wide frequency range.

  In the pneumatic tire configured as described above, the vibration in the cavity 4 and the vibration in the tube 12 interfere with each other when assembled to the wheel, and the interference varies depending on the position of the opening of the tube 12. Therefore, as a result, three resonances shown in FIGS. 4A, 4B, and 4D exist at the time of rolling. However, “+” and “−” in the figure indicate a belly portion where the amplitude of the sound pressure is large, and the difference in sign indicates that the phases are opposite to each other. In FIG. 4B in which the opening of the tube 12 is at a position 90 ° from the grounding position, the opening in the position of the sound pressure change node of the cavity 4 has an opening, so Without being interfered, the resonance frequency is fb substantially the same as that without the tube 12. When the opening of the tube 12 is in the ground contact position and the opposite position in FIGS. 4A and 4D, the vibration in the cavity 4 and the vibration in the tube 12 interfere with each other, and the resonance frequency changes. In FIG. 4 (a), the vibration in the tube 12 is in phase with the vibration in the cavity 4 and acts to lower the resonance frequency, resulting in a resonance frequency fa lower than fb. In FIG. The resonance frequency fd is in the opposite phase to the vibration in the cavity 4 so as to increase the resonance frequency, and the resonance frequency fd is higher than fb. In other words, when the opening of the tube 12 is at the ground contact position and the opposite position, it has two resonances, fa and fd.

  Thus, when the opening position of the tube 12 changes with rolling, the resonance frequency is repeatedly changed from fb to fa and fd, and further to fb, so that the cavity resonance is not sustained and the cavity resonance sound is reduced. be able to. In particular, as shown in FIG. 5, since the resonance frequency is divided into three and the division width (difference between fa and fd) is increased, the noise level at each resonance frequency is reduced and the feeling is improved. The effect is increased.

Here, two pipes having the same length and the same cross-sectional area are provided on the inner surface of the tread of the pneumatic tire so as to open in the hollow portion, and the opening portions of these pipes are opposed to each other with the tire rotation axis therebetween ( The result of measuring the resonance frequency while changing the length L will be described. FIG. 6 shows the relationship between the resonance frequency and the tube length L. On the other hand, FIG. 7 shows the relationship between the absolute value of the difference in resonance frequency and the length L of the tube. However, the length L of the tube is indicated by an index with the reference length L ₀ (λ / 4) being 100.

As shown in FIGS. 6 and 7, it can be seen that when the tube length L is in the range of 55 to 110% of the reference length L ₀ , the absolute value of the difference between the split resonance frequencies is sufficiently large. . In particular, when the length L of the tube is in the range of 85 to 105% of the reference length L _0, it is found that there is a greater effect. In addition, when the opening part of a pipe | tube is obstruct | occluded, those pipe | tubes will be a factor which changes the cross-sectional area of a cavity part in a tire peripheral direction, but in FIG. 7, resonance frequency is distributed based on the cross-sectional area change by the obstructed pipe | tube. The measured value in the case of making it show was shown with the dashed-dotted line. From this result, it can be seen that the effect of reducing the cavity resonance sound based on the interference action of the tube is much greater than the effect of reducing the cavity resonance sound based on the cross-sectional area change.

  When providing a plurality of pipes, the openings of the pipes are arranged at two locations facing each other across the tire rotation axis. Here, two pipes having the same length and the same cross-sectional area are provided on the inner surface of the tread of the pneumatic tire so as to open in the cavity, and the resonance frequency is changed while changing the relative positions of the openings of the pipes. The results of measuring the division width will be described. FIG. 8 shows the relationship between the relative angle of the opening around the tire rotation axis and the split width of the resonance frequency. However, the split width of the resonance frequency is indicated by an index when the positions of the openings of the two tubes coincide with each other (0 °).

  As shown in FIG. 8, when the angle of the opening of the two pipes around the tire rotation axis is 0 ° or 180 °, the dispersion effect of the resonance frequency becomes the largest. In particular, the angle is 0 to 35 °. Alternatively, it can be seen that when it is in the range of 145 to 180 °, it is 80% or more of the maximum value of the resonance frequency dispersion width. Therefore, when the openings of a plurality of pipes are arranged at two locations facing each other across the tire rotation axis, the centers of the two locations are set at positions facing each other at an angle α of 180 ° as shown in FIG. The angle θ that defines the range of each location is preferably 35 ° or less. That is, the two locations where the opening of the tube is arranged are separated by an angle β of 145 ° or more. Thereby, cavity resonance can be effectively reduced without deteriorating the mass balance in the tire circumferential direction.

  In the present invention, it is effective to increase the cross-sectional area of the tube to enhance the dispersion effect of the resonance frequency. Here, the cross-sectional area of the pipe in the tire meridian section is preferably 3 to 20% of the cross-sectional area of the hollow section in the tire meridian section. If the cross-sectional area of the tube is less than 3% of the cross-sectional area of the cavity, the resonance frequency dispersion effect becomes insufficient. Conversely, if the cross-sectional area exceeds 20%, the tube becomes unnecessarily large. There is a risk of interfering with the deformation and worsening the rim assembly workability. When the tube opens in the length direction, the area of the opening of the tube is set in the range of 50 to 100% of the cross-sectional area of the tube, and when the tube opens in the direction perpendicular to the length direction, It is preferable to set the area of the opening to a range of 50 to 150% of the cross-sectional area of the tube.

1 is a perspective sectional view showing a pneumatic tire according to an embodiment of the present invention. It is a side view which shows the noise reduction apparatus comprised from the pipe | tube, the strip | belt-shaped sound absorption material, and the elastic fixed band. It is sectional drawing which shows the pipe | tube of the one end obstruction | occlusion comprised from the porous material and the film. (A), (b) and (d) are explanatory drawings showing the state of resonance in the present invention. It is a graph which shows the relationship between the noise level and frequency in this invention. It is a graph which shows the relationship between the resonant frequency in this invention, and the length L of a pipe | tube. It is a graph which shows the relationship between the absolute value of the difference of the resonant frequency in this invention, and the length L of a pipe | tube. It is a graph which shows the relationship between the relative angle around the tire rotating shaft of the opening part in this invention, and the split width of a resonant frequency. It is explanatory drawing which shows the arrangement | positioning location of the opening part of the pipe | tube in this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tread part 2 Bead part 3 Side wall part 4 Cavity part 11 Elastic fixing band 12 Pipe 12a Opening part 13 Porous material 14 Film 15 Band-shaped sound absorption material T Pneumatic tire

Claims (7)

In a pneumatic tire having a hollow portion, a film coated on the surface of a porous material having a density of 5 to 70 kg / m ³ is used as a wall material to form a plurality of tubes whose one ends are closed so as to open into the hollow portion. The circumferential lengths of these tubes are equivalent to ¼ of the cavity resonance wavelength, and are 55 to 110% of the reference length L ₀ calculated from the tire size based on the following equation (1). A pneumatic tire in which an opening portion of the pipe is disposed at two locations facing each other across a tire rotation axis, and a band-shaped sound absorbing material is disposed on a portion of the tire circumference where the pipe is not disposed.
L ₀ = α · A · B + β · C (1)
Where A is the sectional width, B is the flatness ratio, C is the rim diameter, α (constant) is 8.33 × 10 ⁻³ , and β (constant) is 1.78 × 10 ¹ . is there. The pneumatic tire according to claim 1, wherein the pipe is opened in a direction orthogonal to the length direction, and the pipe and the band-shaped sound absorbing material are arranged adjacent to each other in the tire circumferential direction. The pneumatic tire according to claim 1 or 2, wherein an angle around a tire rotation axis that defines a range of each portion where the opening of the pipe is disposed is 35 ° or less. The pneumatic tire according to claim 1, the circumferential length was 85 to 105% of the reference length L ₀ of the tube. The pneumatic tire according to any one of claims 1 to 4, wherein a cross-sectional area of the tube is 3 to 20% of a cross-sectional area of the hollow portion. The pneumatic tire according to claim 1, wherein the film is made of resin and has a thickness of 5 to 1000 μm. The pneumatic tire according to any one of claims 1 to 6, wherein the tube and the band-shaped sound absorbing material are attached to an annular elastic fixing band, and the tube and the band-shaped sound absorbing material are attached to the inner surface of the tread based on the elastic force of the elastic fixing band. .

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