JPH07276914A - Pneumatic tire - Google Patents

Abstract

PURPOSE:To suppress vibration and reduce noise of a tire by converting the vibrating energy of a belt layer generated during tire traveling into static electricity by piezoelectricity, converting the static electricity into heat, and then dissipating the heat. CONSTITUTION:A pneumatic tire is provided with a damping layer 9 which contains a piezoelectric material generating static electricity by the application of pressure between belt plies forming a belt layer 7 and an electric resistance material for converting the static electricity generated in the piezoelectric material into heat.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire in which static electricity is generated by vibration of a tire and the static electricity is converted into heat energy to suppress vibration and reduce passing noise.

[0002]

2. Description of the Related Art In recent years, as the noise outside the vehicle has become a major social problem, attention has been paid to tire noise, which is one factor of vehicle noise, and development of low-noise tires has been demanded.

As a source of noise generated from tires,
For example, it is known that air column resonance noise is generated when air passes through the air column formed by the tread groove and the ground when the tire touches the ground, and the tread pattern has been improved to reduce the air column resonance noise. .

However, there is a limit in suppressing the noise only by improving the tread pattern, and in order to further reduce the noise, it is necessary to take measures for the tire structure other than the tread pattern.

On the tire structure side, the vibration of the belt layer and the vibration of the side wall portion are considered as the factors of noise generation, and even if the vibration of the side wall portion is suppressed, the vibration of the belt layer is suppressed. It is known that this can be reduced.

In addition, the applicant of the present invention, in Japanese Patent Application No. 5-2405685, attaches a rubber sheet body having elasticity to a belt ply forming a belt layer so that the bending vibration energy of the breaker is converted into heat energy by the rubber sheet body. We have proposed to suppress the vibration by converting to.

[0007]

However, the above-mentioned proposal has a low heat exchange efficiency, cannot sufficiently change vibration energy into heat, and is insufficient in suppressing noise.

As a result of further research conducted by the inventor in order to further suppress the vibration of the tire, the belt ply constituting the belt layer is distorted by an external force to cause an electric polarization between the end portions and generate static electricity. By providing the damping material containing the piezoelectric material to be induced and the electrical resistance material to exchange heat with the piezoelectric material, vibration of the belt layer can be suppressed more efficiently, and as a result, the passing noise of the tire is reduced. That is why the present invention has been completed.

According to the present invention, a damping layer including a piezoelectric material capable of inducing static electricity due to deformation of a belt ply constituting the belt layer and an electric resistance material for thermally converting the static electricity of the rolled material is provided. Basically, it is an object of the present invention to provide a pneumatic tire capable of effectively suppressing vibration generated in a tread portion during tire running and reducing passing noise.

[0010]

SUMMARY OF THE INVENTION The present invention is directed to a carcass that folds from a tread portion through a sidewall portion and around a bead core of a bead portion, is disposed inside and outside the radius of the tread portion, and covers a metal cord with a topping rubber. A belt layer composed of a plurality of belt plies and a damping layer interposed between the belt plies, and the damping layer is electrically deformed between the end portions due to strain caused by deformation of the tread portion. A pneumatic tire including a piezoelectric material capable of inducing static electricity due to static polarization and an electric resistance material capable of thermally converting the static electricity generated in the piezoelectric material.

The thickness t of the damping layer is 0.02 times or more and 0.3 or less than the tread thickness T from the tread surface on the tire equatorial plane of the tread portion to the tire inner surface. Is preferred.

The damping layer may be formed by arranging a sheet-shaped piezoelectric material and a sheet-shaped electric resistance material side by side in the tire axial direction, or by stacking both materials in the tire radial direction. Good.

The piezoelectric material can also be formed as a composite piezoelectric body composed of a polymer resin material and piezoelectric particles made of a ferroelectric ceramic.

[0014]

The damping layer g is arranged between the belt plies forming the belt layer. As shown in FIGS. 10A and 10B,
A shear deformation acts on the damping layer g with respect to the bending vibration m of the belt ply b of the belt layer a, and a pressure due to the shear deformation causes a pressure to act on the piezoelectric material forming the damping layer g. Produces an electrical polarization. Therefore, when this damping layer is placed in the tread portion, the piezoelectric material follows the vibration of the belt layer,
It will be charged with static electricity having positive and negative poles above and below in the tire radial direction. Both electrodes of this static electricity are connected to the electric resistance material through the belt ply with the metal cord,
An electric circuit is formed in which static electricity passes through the electric resistance material only when pressure is applied to the piezoelectric material.

When the electric resistance material has a potential and a current flows through the electric resistance material, the electric resistance material generates heat. That is, the bending vibration of the tire can be converted into heat through electricity, the energy of vibration is converted into heat energy, and the heat energy is dissipated to the atmosphere.

Therefore, the vibration of the breaker, which has generated noise in the conventional tire, is dissipated to the outside of the tire as heat. As a result, passing noise is suppressed by the vibration generated during traveling, and the noise of the tire is reduced. It can be planned.

In order to reduce the passing noise, it is necessary to efficiently absorb the vibration energy especially in the sound vibration region.
When the electrostatic capacity of the piezoelectric material is C ₁ and the load resistance value of the electric resistance material is R ₂ , the following expression (1) is established between the piezoelectric material and the cutoff frequency fc. fc = 1 / 2πC ₁ R ₂ (1)

Here, the maximum frequency fc of the generated sound obtained by frequency-analyzing the passing noise of the tire is usually 5
000 Hz, and by substituting this value into the equation (1) and setting the range of the load resistance value R ₂ to exceed 10 Ω and 10 ⁸ Ω or less, the capacitance C ₁ of the piezoelectric material can be set. I can.

Regarding the regulation of the load resistance value R ₂ ,
If the resistance is 0 Ω or less, it is impossible to manufacture it with a rubber-like material having elasticity, and if it exceeds 10 ⁸ Ω, the leakage current flowing through other than the electric resistance material increases, so that the current circulating in the vibration damping material Since it becomes difficult to regulate the value and control to suppress the vibration frequency becomes difficult, it is preferable to set the load resistance value R ₂ in the above range.

The thickness t of the damping layer is the tread thickness T.
It is preferably 0.02 times or more and 0.3 times or less. If the rubber thickness t is less than 0.02 times the tread thickness T, the vibration of the belt layer cannot be suppressed, and if it exceeds 0.3 times and becomes thicker, the tire weight increases and the fuel efficiency decreases. In addition, it is inferior in durability.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. 1, 2 and 3, a pneumatic tire 1 includes a tread portion 2, a pair of sidewall portions 3 and 3 extending inward in the tire radial direction from both sides thereof, and a bead portion 4 extending inward of the sidewall portion 3. Have and.

Further, in the pneumatic tire 1, a main body portion 6 extending from the tread portion 2 to the side wall portion 3 to the bead portion 4 is formed.
The carcass 6 has a folded portion 6b which is formed by folding back around the bead core 5 from the inner side in the tire axial direction to the outer side, and a belt layer 7 arranged outside the carcass 6 and inside the tread portion.

The belt layer 7 is composed of a plurality of belt plies, and in this embodiment, an inner belt ply 7A arranged radially outside the carcass 6 and adjacent to the carcass 6.
The outer belt ply 7B is arranged outside the inner belt ply 7A.
Between A and 7B, these two belt plies 7A and 7B
A vibration damping layer 9 is provided so as to be sandwiched between.

In the present embodiment, the bead core 5 is radially outward and the carcass 6 has a body portion 6a and a folded portion 6b.
A bead apex 8 having a triangular cross section and made of hard rubber is erected between and.

In the present example, the carcass 6 is composed of two carcass plies 6A and 6B.
A and 6B are formed as a radial or semi-radial arrangement in which carcass cords made of organic fibers such as nylon, polyester, rayon, and aromatic polyamide are juxtaposed at an angle of 75 to 90 ° with respect to the tire equator CO. Further, the carcass cords are arranged so as to intersect with each other between the carcass plies 6A and 6B. In this example, the height of the tip of the folded-back portion 6b from the bead base line is formed as a high turn-up which is larger than the height of the tip of the bead apex.

The belt layer 7 is composed of the inner belt ply 7A and the outer belt ply 7B as described above. Each of the belt plies 7A and 7B is a cord made of metal, in this embodiment, the surface of a steel cord is plated with copper. The belt cord 15 having improved conductivity is applied to the tire equator CO in an amount of 10 to 10.
The belt plies 7A and 7B are inclined at an angle of 45 ° and are arranged so as to intersect each other. The belt cord 15 is covered with a topping rubber 16.

In the belt plies 7A and 7B, the minimum coating thickness δ of the topping rubber 16 that covers the belt cord 15 is set to be as thin as 0.15 to 0.25 m. As the comb used for the topping rubber 16, a highly conductive rubber, for example, a fluorocarbon rubber containing polyvinylidene fluoride, a natural rubber, a silicone rubber, or the like is used.

The belt ply 7A thus formed,
In 7B, the belt ply itself is one member of the electric circuit. That is, since the current from the power source can be guided to the metal belt cord 15 via the topping rubber, the belt ply itself functions as a conductor.

In this embodiment, the inner belt ply 7A is formed to be slightly wider than the outer belt ply 7B, and the ply width of the inner belt ply 7B is 0.8 to the tread width WT. It is formed as 0.95 times.

In this embodiment, the damping layer 9 is formed as shown in FIGS.
As shown in FIG.
2 is formed by arranging a plurality of vibration damping sheets 10 made of sheet bodies arranged on both sides of the piezoelectric material 11 in the tire axial direction side by side in the tire circumferential direction.

In the present embodiment, the piezoelectric material 11 is made of a polymer resin material as a polymer, and a granular ceramic material such as a ferroelectric ceramic powder based on titanate / lead zirconate (PZT) is used as the polymer. It is formed as a composite piezoelectric body formed by mixing dielectrics.

Examples of this dielectric include barium titanate based on titanic acid / lead silconate (PZT) based and zirconic acid / titanic acid / lead lanthanum based (PLZ).
T), lead titanate (PT), and lead zirconate (PZ) can be used as a basic component of a three-component system or a four-component system. The elements of the three-component system or the four-component system include Nb, Mg, Ni, Zn, Mn, Co, Sn and F.
e, Cd, Sb, Al, Yb, In, Sc, Y, Ta,
Bi, W, Te, Re and the like are preferably adopted.

Further, as the polymer resin material 12 used as a polymer, fluorine rubber containing polyvinylidene fluoride, natural rubber, and synthetic rubber such as silicone rubber can be used.

In order to form such a composite piezoelectric material, it is preferable to mix 100 parts by weight of the polymer resin material with 100 to 4000 parts by weight of the granular dielectric material having the above-mentioned structure.

In the piezoelectric material 11 thus formed, when the tire is running, the belt layer 7 is bent and deformed as shown in FIG. 10 (B), so that the piezoelectric material 11 is subjected to the pressure. It is polarized in the direction, that is, in the radial direction, upward and downward, and static electricity is induced. By releasing the bending deformation as shown in FIG. 10A, the polarization is released and the generation of static electricity is stopped.

When the amount of braking energy to be suppressed is determined from the viewpoint of tire structure and tire performance, and the required electrostatic capacitance C ₁ is determined accordingly, the surface area S (long length) of the piezoelectric material 11 used depends on the tire size. Lo ×
By setting the range of the width Wo) and the thickness t, the range of the relative permittivity Er, which is the material characteristic of the piezoelectric material 11, can be derived from the following equation (2), and the selection of the material configuration and type of the piezoelectric material 11 can be performed. Can be done easily.

The capacitance C ₁ of the piezoelectric body 11 is C ₁ = E × S / t E = Ev × Er E: Dielectric constant E: Dielectric constant in vacuum = 8.855PF / m Ev: Vacuum Dielectric constant = 8.855 pF / m Er: Relative dielectric constant S: Area of piezoelectric material = Length (Lo) x Width (Wo) t: Thickness of piezoelectric material Also, the dielectric constant of the piezoelectric material itself is that in vacuum Therefore, the relative permittivity Er is 1 <Er.

Here, the range of the length Lo is 0.001 ≦ Lo ≦ LT and the range of the width Wo is 0.001 ≦ Wo ≦ WT, where LT: the tire circumferential direction at the radial position where the piezoelectric material is arranged. Length, WT: Tire tread width

If the values of the length Lo and the width Wo are less than 0.001, they cannot contribute to the piezoelectric performance and L
It cannot be molded over T and WT. On the other hand, if the range of the thickness t is 0.02T ≦ t ≦ 0.3T with respect to the tread thickness T, the range in which the relative permittivity Er can be adopted is 2.26T × C ₁ × 10 ⁹ / (LT × WT) ≦ Er ≦ 3.39T × C ₁ × 10 ¹⁶ (2). However, 2.26H × C ₁ × 10 ⁹ / (LT × W
When the value of T) is smaller than 1, 1 <Er.

As the electric resistance material 12, for example, a conductive rubber having the composition shown in Examples 1 to 4 of Table 1 or a conductive resin capable of regulating the volume resistivity value, carbon metal, conductive ceramics or the like can be adopted. .

In the conductive rubber, the blending amount of carbon has a great influence on the volume resistivity value, and regarding the combination of a typical polymer and carbon black, the blending amount (Phr) and the volume of carbon black. FIG. 11 shows the relationship with the specific resistance value (Ω-cm), and Table 2 shows the structure of the polymer.

[0042]

[Table 2]

The electric resistance material 12 is for thermally converting the static electricity generated in the piezoelectric body 11 by the vibration of the belt layer 7, and according to the electrostatic capacitance C ₁ of the piezoelectric body 11 mentioned above, The load resistance value R ₂ is set as shown in the equation.

As for the passing noise of the tire, the maximum frequency of the generated sound is 5000 Hz as described above, but the frequency range of the noise that is particularly offensive to the ears is 2000 Hz or less.
If the cutoff frequency is set to 00 Hz or less, the above equation (1) can be transformed into R ₂ = 1 / (4 × π × C ₁ × 10 ³ ) (3).

The piezoelectric material 11 and the electric resistance material 12 are, as described above, the piezoelectric material 11 at the central portion in the tire axial direction including the tire equator C, and the electric resistance material 12 at both sides of the piezoelectric material 11 in the axial direction of the tire. The piezoelectric material 11 and the electric resistance materials 12, 12 form the vibration damping layer 9.

The thickness t of the damping layer 9 is 0.02 times or more and 0.3 times or less than the tread thickness T from the tread surface 2A on the tire equatorial plane CO of the tread portion 2 to the tire inner surface 2B. I am trying.

The damping layer 9 is composed of two belt plies 7A and 7A.
As shown in FIG. 4, the piezoelectric material 11 is sandwiched between B and
The static electricity generated by the polarization in and out of the tire radial direction is a closed circuit through which static electricity passes by electrically connecting the positive and negative terminals of the electric resistance material 12 with the belt plies 7A and 7B having good electric conductivity. It is formed.
Further, the static electricity flows through the electric resistance material 12 to cause the electric resistance material 12 to generate heat.

As described above, the vibration energy is converted into electric energy in the first step, the electric energy is converted into heat energy in the next step, and the generated heat is dissipated into the atmosphere, thereby vibrating the belt layer 7. It is possible to reduce the passing noise of the tire due to

The piezoelectric material 11 is polarized only in the acting direction of the pressure acting on the piezoelectric material 11 so that static electricity is generated. Therefore, the electric resistance material 12 is arranged adjacent to the tire circumferential direction and the tire axial direction. Both materials 11, even if
There is no leak between 12 points.

When the piezoelectric material 11 is arranged at the center portion of the damping layer 9 in the tire axial direction as in this embodiment, the piezoelectric material 11 is located at the position where the ground contact pressure is highest when the tire is grounded. By doing so, the pressure acting on the piezoelectric material 11 is increased, and static electricity can be efficiently generated,
The reduction of passing noise can be effectively achieved.

Further, when a plurality of vibration damping sheets 10 are arranged in the circumferential direction as in this embodiment, the number of the arranged vibration damping sheets 10 is adjusted to set the capacitance C ₁ of the piezoelectric material 11. Can be done easily and accurately. It is also possible to wind one damping sheet in the circumferential direction to form the damping layer.

5 to 9 show another mode of the damping layer 9. In FIG. 5, the outer end of the electric resistance material 12 in the axial direction of the tire is exposed to the buttress portion 3A of the sidewall portion 3 to enhance the heat dissipation efficiency of the electric resistance material 12. As a result, the electric resistance material 12 can be downsized and the piezoelectric material 11 can be made larger by that amount, so that the heat conversion efficiency can be further improved.

Further, as shown in FIG. 6, the damping layer 9 may be arranged with a gap provided between the piezoelectric material 11 and the electric resistance material 12. Further, as shown in FIG. 11 and 1
One electric resistance material 12 and two electric resistance materials 12 can be arranged and formed so as to face each other on both sides in the tire axial direction. 6 and 7,
The belt plies 7A and 7B arranged adjacent to the inside and outside of the damping layer 9 in the radial direction function as conductors for connecting the piezoelectric material 11 and the electric resistance material 12 for forming a circuit.

FIG. 8 shows another mode in which a plurality of piezoelectric materials 11A ... And a plurality of electric resistance materials 12A are laminated inside and outside of the tire radial direction to form a damping layer 9A. The electric circuit configuration when static electricity is generated by pressurization in this example is shown in FIG.
As shown in FIG. 5, a current is generated between the piezoelectric materials 11A and 11A disposed inside and outside of the electric resistance material 12A so that a closed circuit is formed using the two belt plies 7A and 7B as conductors. .

The piezoelectric material 11 can also be formed by using only a material having piezoelectric performance such as piezoelectric particles without using a polymer resin material. Furthermore, a polymer to which an electric resistance material is mixed is electrically conductive coated. The vibration damping layer may be formed as an integral sheet body by mixing the piezoelectric particles subjected to the above.

Further, the belt layer may be formed by laminating three or more belt plies, and the damping layer having the above-mentioned structure may be disposed between any two adjacent belt plies. The present invention can be modified into various aspects.

[0057]

【Concrete example】

(A) Test A Tires having tire sizes of 205 / 55R15 and having the configuration shown in FIG. 1 (Examples 1 to 4) were prototyped according to the specifications shown in Table 1, and their performances were compared. A tire having a configuration other than the configuration of the present application (Comparative Example 1) and a tire having a conventional configuration (Comparative Examples 2 and 3) were also tested and their performances were compared.

As the piezoelectric material shown in Table 1, a sheet-shaped composite piezoelectric material was formed by mixing a polyvinylidene fluoride polymer resin material with a ferroelectric ceramic powder such as titanic acid / lead zirconate. This piezoelectric material has a density of 5.59 g.
/ Cm ³ , the elastic modulus is 2.6 dyne / cm ^{3, and the} length / width / thickness is 0.023 to 0.1 / 0.003 m, the electrostatic capacitance C ₁ is 800 pF. The test conditions are as follows.

1) Passing noise A 2000cc class FF vehicle equipped with test tires was subjected to an actual vehicle coasting test stipulated in JASO C606, and a passing speed of 60km / H and a distance of 50m were coasted on a straight test course. At the same time, at the midpoint of the course, with a distance of 7.5 m from the running center line,
Moreover, the maximum passing noise was measured by the installed microphone installed at a height of 1.2 m from the test road surface.

2) Hashesiness performance The 2000 cc class FF vehicle equipped with the trial tire was used for 20 times.
The hashesiness performance when running at a speed of km / h was evaluated by the sensory of the driver, and 10
It is indicated by an index of 0. The larger the value, the better.

3) Road Noise The 2000 cc class FF vehicle equipped with the test tire was run at a speed of 60 km / H on a road surface made of rough asphalt and a microphone was installed at a position corresponding to the right ear of the driver for measurement. Table 1 shows the result at the overall level.

[0062]

[Table 1]

As a result of the test, it was confirmed that the embodiment example was able to reduce the passing noise and the road noise while maintaining the hashness performance as compared with the comparative example.

(B) Test B Furthermore, for a tire having the same structure as the test A, the size of the piezoelectric material portion of the vibration damping sheet was changed to obtain the total capacitance C ₁ generated by the piezoelectric material and its electrostatic capacity. The relationship between the highest frequencies that can be blocked by the capacitance C ₁ was investigated.
The test conditions are the same as in test A.

The test results are shown in Table 3. In addition, Example 5
Reference numeral 8 shows the configuration of the present application, Comparative example 4 shows the configuration outside the present application, and Comparative examples 5 and 6 show the conventional configuration.

[0066]

[Table 3]

[0067]

As described above, the pneumatic tire of the present invention is
A damping layer including a piezoelectric material that generates static electricity due to pressure acting between the belt plies forming the belt layer and an electric resistance material that converts the static electricity generated in the electrostatic material generated in the piezoelectric material into heat. Since it is provided, the vibration of the belt layer, which causes noise, is dissipated as heat, and the passing noise can be more effectively reduced by suppressing the vibration.

[Brief description of drawings]

FIG. 1 is a tire axial direction cross-sectional view showing an embodiment of the present invention.

FIG. 2 is a partial cross-sectional view showing the belt layer and the damping layer in an enlarged manner.

FIG. 3 is a plan view showing a damping layer.

FIG. 4 is an electric circuit diagram showing the damping function.

FIG. 5 is a schematic cross-sectional view showing another aspect of the damping layer.

FIG. 6 is a schematic cross-sectional view showing another aspect of the damping layer.

FIG. 7 is a schematic cross-sectional view showing another aspect of the damping layer.

FIG. 8 is a partial cross-sectional view schematically showing another aspect of the damping layer.

FIG. 9 is an electric circuit diagram thereof.

FIG. 10 is a cross-sectional view schematically showing a vibration state of a belt layer, (A) showing no vibration and (B) showing vibration.

FIG. 11 is a graph showing the relationship between the carbon blending amount of a polymer and electric resistance.

[Explanation of symbols]

 2 tread portion 2A tread surface 2B tire inner cavity surface 3 sidewall portion 4 bead portion 5 bead core 6 carcass 7 belt layer 7A, 7B belt ply 9, 9A damping layer 11, 11A piezoelectric material 12, 12A electric resistance material T tread thickness The thickness of the damping layer

Claims (5)

[Claims] 1. A carcass which folds from a tread portion to a sidewall portion around a bead core of a bead portion, and a plurality of belt plies which are arranged inside and outside the radius of the tread portion and whose metal cords are covered with a topping rubber. With a damping layer interposed between the belt layer and the belt ply, the damping layer, by the strain caused by the deformation of the tread portion, by causing electrical polarization between the ends,
A pneumatic tire comprising a piezoelectric material capable of inducing static electricity and an electric resistance material capable of thermally converting the static electricity generated in the piezoelectric material. 2. The damping layer has a thickness t of 0.02 times or more and 0.3 times or less of a tread thickness T from the tread surface on the tire equatorial plane of the tread portion to the tire bore surface. The pneumatic tire according to claim 1, wherein: 3. The pneumatic tire according to claim 1, wherein the damping layer comprises a sheet-shaped piezoelectric material and a sheet-shaped electric resistance material arranged side by side in the tire axial direction. 4. The pneumatic tire according to claim 1, wherein the damping layer is formed by stacking a sheet-shaped piezoelectric material and a sheet-shaped electric resistance material in a tire radial direction. 5. The pneumatic tire according to claim 1, wherein the piezoelectric material is a composite voltage body in which a polymer resin material is mixed with piezoelectric particles made of a ferroelectric ceramic.