JP2004216943A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of effectively reducing void resonance noises without deteriorating a dynamic balance. <P>SOLUTION: In this pneumatic tire 2, a plurality of tubular bodies 4 having communication holes 5 are rollably accommodated in a tire void 3. Length H of the communication hole 5 is preferably set to one integer-th of a reference length R corresponding to a half of an effective void length L(L=C/f) of a tire found from a sound speed C and a void resonance frequency f of the tire. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a pneumatic tire having a cavity, and more particularly, to a pneumatic tire capable of effectively reducing cavity resonance sound without impairing dynamic balance.
[0002]
[Prior art]
In pneumatic tires for passenger cars, a vibration mode due to cavity resonance generally exists around 230 to 260 Hz. It has been known that this cavity resonance occurs when the tire is rotating (when the vehicle is running) and affects the characteristics of the vehicle during running (unsprung acceleration, road noise).
[0003]
Therefore, conventionally, in order to reduce the cavity resonance sound, a sound absorbing material is mounted on the inner surface of the tire or a partition plate is provided (for example, see Patent Documents 1 and 2). However, such a method has a problem that the dynamic balance of the tire is deteriorated, and the steering stability is impaired.
[0004]
[Patent Document 1]
JP 2001-47809 A [Patent Document 1]
JP-A-5-294102
[Problems to be solved by the invention]
An object of the present invention is to provide a pneumatic tire capable of effectively reducing cavity resonance sound without impairing dynamic balance.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, a pneumatic tire according to the present invention is characterized in that a plurality of tubular bodies having communication holes are rollably accommodated in a tire cavity.
[0007]
By accommodating a plurality of tubular bodies having communication holes in the tire cavity as described above, a sound absorbing effect on cavity resonance can be obtained. In addition, the tubular body is scattered in the tire cavity when the tire is rolling, thereby causing turbulence in the air in the tire cavity and suppressing the cavity resonance more effectively. In addition, even if the tubular body is small and light, the cavity resonance can be effectively reduced, so that the dynamic balance of the tire is not impaired.
[0008]
In the present invention, the length of the communication hole is an integral number of the reference length R corresponding to half of the effective cavity length L (L = C / f) of the tire obtained from the sound velocity C and the cavity resonance frequency f of the tire. It is preferably 1. That is, according to the research results of the present inventor, the effect of reducing the cavity resonance sound is further increased by setting the length of the communication hole to an integral number of the reference length R. The unit weight of the tubular body is preferably 1 g or less, and the total weight is preferably 50 g or more. As the material of the tubular body, it is preferable to use a non-breathable material. For example, a viscoelastic body or a sponge having closed cells can be used.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings.
[0010]
FIG. 1 shows a pneumatic tire according to an embodiment of the present invention, and FIGS. 2 and 3 each illustrate a tubular body accommodated in a tire cavity. In FIG. 1, a pneumatic tire 2 is fitted to a rim of a wheel 1. A tire cavity 3 is formed between the wheel 1 and the pneumatic tire 2. In the tire cavity 3, a plurality of tubular bodies 4 having communication holes are rotatably accommodated.
[0011]
The tubular body 4 shown in FIG. 2 has a communication hole 5 whose both ends are not closed, and has a spherical outer shape. On the other hand, a tubular body 4 shown in FIG. 3 has a communication hole 5 whose both ends are not closed, and has a cylindrical outer shape. That is, the tubular body 4 needs to have the communication holes 5 whose both ends are not closed, but the outer shape is not particularly limited. When a plurality of tubular bodies 4 having such communication holes 5 are accommodated in the tire cavity 3, the tubular bodies 4 are scattered in the tire cavity 3 when the tire rolls, causing turbulence in the air in the tire cavity 3. In addition, since the communication hole 5 exhibits a sound absorbing effect, cavity resonance can be effectively reduced. Further, since the tubular body 4 is lightweight, it is scattered moderately during rolling of the tire, and there is no adverse effect such as a decrease in steering stability due to a deterioration in dynamic balance.
[0012]
The length H (mm) of the communication hole 5 is defined as a half of the effective cavity length L (L = C / f) of the tire obtained from the sound velocity C and the cavity resonance frequency f of the pneumatic tire 2 as a reference length R (mm). ), It is preferable to satisfy the relationship of H = R / N for an arbitrary integer N. By setting the length H of the communication hole 5 to an integral fraction of the reference length R, the cavity resonance can be effectively reduced. Here, the length H of the communication hole 5 preferably coincides with the calculated value of R / N, but the calculated value of R / N may be obtained up to three significant digits. In determining the effective cavity length L, the sound speed C is the sound speed at 20 ° C. Further, the cavity resonance frequency f of the pneumatic tire 2 can be measured by a known hammering test. On the other hand, the diameter D of the communication hole 5 is preferably set to D / H ≦ 1.
[0013]
The unit weight of the tubular body 4 is preferably 1 g or less. If the unit weight exceeds 1 g, the dynamic balance of the tire may be reduced. For the same reason, the maximum dimension of the tubular body 4 is preferably set to 20 mm or less. The total weight of the tubular body 4 is desirably 50 g or more. If the total weight is less than 50 g, the effect of reducing the cavity resonance sound will be insufficient. However, the upper limit of the total weight of the tubular body 4 is preferably set to 300 g.
[0014]
As the material of the tubular body 4, a non-breathable material is preferably used. That is, the sound-absorbing effect of the communication hole 5 is insufficient with the breathable material. For example, a viscoelastic body such as rubber or a sponge having closed cells is most suitable as the material of the tubular body 4. When the tubular body 4 is made of such a material, the sound when the tubular body 4 contacts the inner surface of the tire or the outer peripheral surface of the rim can be minimized.
[0015]
【Example】
A pneumatic tire having a tire size of 215 / 45ZR17 was mounted on a wheel having a rim size of 17 × 71/2, and the air pressure was set to 230 kPa. At this time, a tire of Example 1 in which a large number of tubular bodies having communication holes were accommodated in a tire cavity, and a conventional tire in which a tubular body was not accommodated in a tire cavity were prepared. In Example 1, the tubular body shown in FIG. 2 (communication hole length 10 mm, communication hole diameter 6 mm, unit weight about 1 g) was housed in the tire cavity with a total weight of 300 g. Here, the effective cavity length L based on the experiment of the pneumatic tire is 1480 mm, and the reference length R is 790 mm. Therefore, the length of the communication hole of this tubular body is equal to 1 / integer of the reference length R, that is, 790 mm / 79 = 10 mm.
[0016]
With respect to these test tires, the vibration transmissibility (inertance) and the unsprung vibration level on various road surfaces were measured. The vibration transmissibility is the vibration transmissibility (inertance) of the tire axial acceleration in the radial direction with respect to the exciting force of the tread portion obtained by the impulse exciting method for the tire with the tire shaft fixed and no load. The result of the vibration transmissibility is shown in FIG. On the other hand, the unsprung vibration level is a result obtained by measuring the vertical axial acceleration of the right front wheel of the vehicle during steady running at a speed of 50 km / h and performing 1/3 octave analysis. As the test road surface, a road surface having a plurality of protrusions (projection road), a repaired road surface (repair road), a road surface having a large road noise (road noise road), and the like were used. FIG. 5 shows the results of the unsprung vibration level on the protruding road, FIG. 6 shows the results of the unsprung vibration level on the repair road, and FIG. 7 shows the results of the unsprung vibration level on the road noise road.
[0017]
As shown in FIGS. 4 to 7, the tire of Example 1 had a smaller vibration transmissibility at around 230 Hz and a lower unsprung vibration level at around 250 Hz than the conventional example.
[0018]
Next, a tire of Example 2 was prepared under the same conditions as in Example 1 except that the tubular bodies housed in the tire cavity were different. In Example 2, the tubular body shown in FIG. 3 (communication hole length 6 mm, communication hole diameter 5 mm, unit weight about 1 g) was housed in the tire cavity with a total weight of 300 g. The reference length R of the pneumatic tire is 790 mm. Therefore, the length of the communication hole of this tubular body slightly deviates from 1 / integer of the reference length R, that is, 790 mm / 131 = 6.03 mm.
[0019]
With respect to this test tire, the unsprung vibration level on various road surfaces was measured by the above-described measurement method. FIG. 8 shows the unsprung vibration levels in the frequency band centered on 250 Hz for the conventional example and Examples 1 and 2.
[0020]
As shown in FIG. 8, the tires of Examples 1 and 2 all show better results than the tire of the conventional example, but the tire of Example 1 is particularly better than the tire of Example 2. The results were shown.
[0021]
【The invention's effect】
As described above, according to the present invention, a plurality of tubular bodies having communication holes are rollably accommodated in the tire cavity, so that cavity resonance can be effectively reduced. In addition, even when the tubular body is small and light, the cavity resonance can be effectively reduced, so that the dynamic balance of the tire is not impaired and the steering stability due to the deterioration of the dynamic balance is reduced. Does not decrease.
[Brief description of the drawings]
FIG. 1 is a sectional view showing a pneumatic tire according to an embodiment of the present invention together with a wheel.
FIG. 2 is a perspective view showing an example of a tubular body used in the present invention.
FIG. 3 is a perspective view showing another example of the tubular body used in the present invention.
FIG. 4 is a graph showing a relationship between a vibration transmissibility and a frequency for a test tire.
FIG. 5 is a graph showing a relationship between an unsprung vibration level and a frequency on a protruding road for a test tire.
FIG. 6 is a graph showing a relationship between an unsprung vibration level and a frequency on a repair road for a test tire.
FIG. 7 is a graph showing the relationship between the unsprung vibration level and the frequency of a test tire on a road noise road.
FIG. 8 is a graph showing unsprung vibration levels of a test tire in a frequency band centered on 250 Hz.
[Explanation of symbols]
Reference Signs List 1 wheel 2 pneumatic tire 3 tire cavity 4 tubular body 5 communication hole

Claims (5)

A pneumatic tire in which a plurality of tubular bodies having communication holes are rollably accommodated in a tire cavity. The length of the communication hole is an integral part of the reference length R corresponding to half of the effective cavity length L (L = C / f) of the tire obtained from the sound velocity C and the cavity resonance frequency f of the tire. The pneumatic tire according to claim 1. The pneumatic tire according to claim 1 or 2, wherein the single body weight of the tubular body is 1 g or less, and the total weight is 50 g or more. The pneumatic tire according to any one of claims 1 to 3, wherein the material of the tubular body is a non-breathable material. The pneumatic tire according to any one of claims 1 to 4, wherein the material of the tubular body is a viscoelastic body or a sponge having closed cells.

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