JPH10305715A - Noise reducing device for pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a noise reducing device for a pneumatic tire whereby a noise can be effectively reduced without sacrificing the other performance of drive stability or the like. SOLUTION: In an internal peripheral surface of a tire 1, a piezoelectric film 5 is closely arranged, by controlling a strain motion of this piezoelectric film 5 by a control means, the tire 1 is damped or excited, so as to reduce a noise. In this way, the tire 1 is damped by the piezoelectric film 5, by suppressing a vibration component of resonance of an air pipe generated in the tire 1, magnifying of resonance sound of the air pipe can be suppressed. By exciting the tire 1 with a frequency canceling the resonance sound of the air pipe it can also be damped. In this way, the value Q of a air pipe resonance frequency of the tire 1 is decreased, the air pipe resonance sound can be reduced. Particularly, as the control means, if a resonance analog circuit 6 is provided in the tire 1 with the piezoelectric film 5, a power feed means from the outside can be eliminated to facilitate the mounting of the control means in the tire 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire noise reduction device.

[0002]

2. Description of the Related Art A pneumatic tire cannot avoid occurrence of air column resonance in a circular pipe due to its structure. The frequency of this air column resonance is uniquely determined by the length of the pipe, that is, the size of the tire. If the resonance frequency of the link system of the vehicle body, especially the suspension, matches that of the tire, it promotes running noise. It is said that it is preferable to design them so that they do not match. Conventionally,
By adjusting the weight, rigidity, and shape of the tread, carcass, belt, bead, and other components of the tire, or improving the material of the tread compound, the air column resonance of the tire itself is reduced. Was.

[0003]

However, the tire is
In addition to running noise, various factors must be balanced at a high level, from driving performance such as handling, riding comfort and fuel efficiency to wear resistance and design. For example, in order to reduce the rolling resistance of the tire, it is sufficient to increase the rigidity of the tread portion, but this has an adverse effect on reducing the air column resonance, and the above elements were temporarily optimally adjusted. However, a sufficiently satisfactory result is not always obtained in terms of noise reduction.

[0004]

SUMMARY OF THE INVENTION In order to solve such a problem, a noise reduction device for a pneumatic tire capable of effectively reducing noise without sacrificing other performances such as maneuverability is provided. In the present invention, a piezoelectric film is closely arranged on the inner peripheral surface of a tire, and the distortion motion of the piezoelectric film is controlled by a control means to control or excite the tire to reduce noise. And According to this, by suppressing the tire with the piezoelectric film and suppressing the vibration component of the air column resonance generated in the tire, amplification of the air column resonance sound can be suppressed. In addition, the air column resonance can be attenuated by vibrating the tire at a frequency that cancels the air column resonance. Thereby, the Q value of the air column resonance frequency of the tire can be reduced, and the air column resonance sound can be reduced. In addition, the air column resonance frequency of the tire varies depending on the size of the tire for a passenger car, but is generally 200 to 30.
By adjusting the frequency characteristic of the control means depending on the applied tire, which is between 0 Hz, further noise reduction can be contemplated.

In particular, it is preferable that a resonance analog circuit having a frequency characteristic corresponding to the air column resonance frequency of the tire is used as the control means, and the resonance analog circuit is provided on the tire together with the piezoelectric film. According to this, since it is not necessary to separately provide a power supply unit for the piezoelectric film, the configuration is simple, and the attachment to the tire is easy.

For the piezoelectric film, a high-polymer piezoelectric material having a high flexibility, for example, PVDF (polyvinylidene fluoride)
And P (VDF / TrFE) (vinylidene fluoride / trifluoroethylene copolymer) or the like is used.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure of the present invention will be described in detail below based on embodiments shown in the accompanying drawings.

FIG. 1 is an exploded view showing a tire to which the present invention is applied. A piezoelectric film 5 for reducing noise by damping or exciting the tire 1 is provided on the inner surface of the tread portion 2 and the left and right sidewall portions 3 and 4 of the tire 1.
And a plurality of sets of control circuits 6 for controlling the distortion motion of the piezoelectric film 5 are bonded at equal intervals over the entire circumference of the tire 1.

The piezoelectric film 5 is made of PVDF or P (VDF
/ TrFE), which generates a voltage in accordance with the strain and generates a strain in accordance with the applied voltage. As shown in detail, a conductive layer 7 is formed by applying a conductive paint or the like. The control circuit 6 is electrically connected to the front and back conductive layers 7 through a pair of lead wires 8.

The control circuit 6 is a resonance analog circuit having a frequency characteristic corresponding to the air column resonance frequency of the tire,
Specifically, as shown in FIG. 3, a resistor R is connected in series to a capacitor C and a coil L which are connected in parallel to each other, or a resistor R which is connected in series to each other as shown in FIG. And capacitor C for coil L
Are connected in parallel.

Next, the operation principle of the device of the present invention will be described.

When vibration occurs in the tire 1, a distortion is generated in the piezoelectric film 5 closely arranged on the outer peripheral surface of the tire 1 such that the direction is periodically inverted. Is input. When the tire 1 starts to resonate due to the air column resonance phenomenon, a control circuit 7 having a frequency characteristic corresponding to the resonance frequency acts to suppress the distortion of the piezoelectric film 5, and the tire 1
The damping force is applied to

For example, as shown in FIG. 5, when the tire 1 is going to be elastically deformed at the time of vibration, a compressive stress is generated in the piezoelectric film 5 as shown by an arrow, and the deformation of the tire 1 is suppressed. When the tire 1 is deformed in the opposite direction, a tensile stress opposite to the above is generated in the piezoelectric film 5 to suppress the deformation of the tire 1. In this way, the generation of the resonance frequency vibration in the tire 1 is suppressed, the resonance vibration component generated in the air column in the tire 1 is suppressed, and the amplification of the air column resonance sound is suppressed.

In the above embodiment, the passive control by the analog circuit has been described. However, the active control in which the vibration of the tire 1 is detected and the external power supply voltage is applied to the piezoelectric film 5 may be used. In this case, as shown in FIG. 6, a piezoelectric film as a vibration sensor 11 is provided separately from the piezoelectric film 5 as the above-described actuator, and the output of the vibration sensor 11 is processed by a control circuit 12 to control the tire. The vibration frequency and the vibration amplitude are obtained, and a voltage for generating an exciting force in a direction to cancel the vibration of the tire may be applied from the battery 13 to the piezoelectric film 5 via the amplifier 14.

As a result, it is possible to generate a larger vibration damping force or an exciting force on the piezoelectric film 5, and furthermore, the piezoelectric film 5 according to the vibration frequency of the tire 1.
By adjusting the frequency of the voltage applied to the power supply, noise in a wider range of frequencies can be reduced.
Further, the tread surface can be positively deformed by the piezoelectric film 5 provided on the tread portion 2 to make the envelope characteristics variable. Further, the overall shape of the tire 1 can be positively controlled by the piezoelectric films 5 provided on both the tread portion 2 and the sidewall portions 3 and 4.

In this embodiment, the piezoelectric film 5 is bonded to the inner surface of the tire 1, but the piezoelectric film 5 may be embedded in the tire 1. In this case, the polarization process of the piezoelectric film 5 may be performed in the vulcanization step or a subsequent step, and then the control circuit 6 may be bonded to the inner surface of the tire 1.

[0017]

As described above, according to the present invention, it is possible to reduce the air column resonance which has not been drastically improved. Therefore, the degree of design freedom for items that have conventionally had to be reduced in terms of compromise for improving air column resonance sound is increased. In particular, if the resonance analog circuit is provided on the tire together with the piezoelectric film, external power supply means is not required, and thus the tire can be easily mounted.

[Brief description of the drawings]

FIG. 1 is a cutaway perspective view showing a tire to which a noise reduction device according to the present invention is applied.

FIG. 2 is a sectional view of a principal part of the tire shown in FIG. 1;

FIG. 3 is a conceptual diagram showing a configuration example of a control circuit shown in FIG. 1;

FIG. 4 is a conceptual diagram showing another configuration example of the control circuit shown in FIG. 1;

FIG. 5 is a sectional view for explaining the principle of noise reduction by the piezoelectric film shown in FIG. 1;

FIG. 6 is a block diagram showing a configuration example of a control unit when an external voltage is applied.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Tire 2 Tread part 3.4 Side wall part 5 Piezoelectric film 6 Control circuit 7 Conductive layer 8 Lead wire 11 Vibration sensor 12 Control circuit 13 Battery 14 Amplifier

Claims (2)

[Claims] 1. A piezoelectric film having a high flexibility, which is disposed in close contact with an inner peripheral surface of a tire, and control means for controlling a distortion motion of the piezoelectric film. A noise reduction device for a pneumatic tire, characterized in that the noise is reduced by damping or applying vibration. 2. The tire according to claim 1, wherein the control means is a resonance analog circuit having a frequency characteristic corresponding to a resonance frequency of the tire, and is provided on an inner peripheral surface of the tire together with the piezoelectric film. The noise reduction device for a pneumatic tire according to claim 1.