JP2002120511A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively reduce level of a cavity resonance sound as a cause of uncomfortable interior noise without sacrificing the other performance. SOLUTION: This pneumatic tire comprises a carcass 6, a belt 11 formed of two or more belt layers 8 and 9 formed of cords on the outer peripheral side of a crown part 7 of the carcass, and an inner liner 14 disposed on the inner peripheral side of the carcass 6. At least one of circumferential grooves 12a to 12d extending in the circumferential direction of the tire is partitioned in a tire tread part of a tread part 2, a plurality of land part rows 13a to 13e are formed between both ends of the tire tread part of a tread part 2, at least one cord cutting region 16 is partitioned and formed in the circumferential direction of the tire in the width central region 15 of the carcass crown part 7, and tensile modulus in the tire width direction of the inner liner 14 is 1/5 or less of that of the carcass 6 in the cord extending direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an uncomfortable vehicle caused by a circumferential length of an annular tire inner space defined by assembling a toroidal tire on an applicable rim and filling a predetermined air pressure. The present invention relates to a pneumatic tire in which the level of cavity resonance that contributes to indoor noise is effectively reduced without sacrificing other performances.

[0002]

2. Description of the Related Art A pneumatic tire is an elastic body filled with pneumatic pressure. Due to its structure, when a vibrating force is applied from the outside, the vibrating force causes the tread portion and the sidewall portion of the tire, and furthermore, The air inside vibrates, but when the vibration of the air causes resonance (resonance), so-called cavity resonance sound is generated, which is transmitted to the vehicle interior through the axle and contributes to unpleasant vehicle interior noise. I have.

[0003] The frequency at which the cavity resonance sound is emitted (hereinafter referred to as "resonance frequency") is uniquely determined from the vibration propagation speed of air inside the tire and the circumferential length of the above-mentioned annular tire internal space. Therefore, the resonance frequency of the tire is constant unless the tire size is changed. For example, in the case of a normal passenger car tire, the resonance frequency is about 200 to 270 Hz from the circumference.

[0004] Cavity resonance is a phenomenon that is inevitably generated in pneumatic tires because the cause of the resonance is air resonance. Therefore, conventionally, even if the tire structure is improved, the cavity resonance is not generated. It was considered difficult to reduce the level.

For this reason, conventionally, for example, Japanese Patent Application Laid-open No. Sho 62-5002
No. 03, etc., the level of cavity resonance sound without improving the tire structure as in the method of improving the sound field inside the tire by inserting a sponge or other sound absorbing material inside the tire. Was reduced.

[0006]

However, when the level of cavity resonance is reduced by the method described in the above-mentioned publication, the sponge is mounted after the tire is manufactured as a product. However, there is a problem in that it takes time and effort to mount the device, and there is also a problem in terms of cost.

Therefore, the inventor of the present invention has proposed a novel method of reducing the level of cavity resonance sound by improving the tire structure itself instead of the time-consuming and costly method of attaching a sponge to a product tire. Various studies were conducted to develop new technologies.

First, the inventor conducted a detailed investigation on the relationship between the vibration mode of the tire and the level of the cavity resonance sound, and found that the vibration mode of the tire, when viewed in the tire width direction,
Initially, as shown in FIG. 4, the cross-section height uniformly changes in the tire width direction with both beads as fixed ends, and has two nodes when the tire (broken line) before vibration is used as a reference (standing wave). A vibration mode (hereinafter, referred to as a "two-node mode") is mainly used, and thereafter, as shown in FIG.
That. ), And further, sequentially to various vibration modes that are deformed to have six, eight, and-sections.

[0009] In the case of a tire for a passenger car, the frequency band of the two-bar mode is generally approximately as shown in FIG.
In the range of 30-300 Hz, and hence the resonance frequency (200-27
0Hz) is located in the frequency band of the two-bar mode, which was found to be the cause of increasing the level of cavity resonance.

Next, the inventor shifted the frequency band of each vibration mode and examined in detail the change of the level of the cavity resonance sound at this time, and found that the resonance frequency was located in the frequency band of the four-bar mode. In addition, they found that the level of the cavity resonance sound was low, and even when the resonance frequency was not located in the frequency band of the four-bar mode, it was relatively low.
It was also found that the level of the cavity resonance sound becomes relatively small when approaching the frequency band of the knot mode. Therefore, it became clear that it is preferable to shift the frequency bands of the respective vibration modes in the second and fourth sections to the lower frequency side.

[0011] Based on the above findings, the inventor has proposed 2
As a result of further research and analysis in order to achieve the shift of the frequency band of each vibration mode to the lower frequency side in Sections 4 and 4 by improving the tire structure, as a result,
From the mode of vibration of the nodes, it has been found that lowering the tensile modulus in the width direction of the tread portion of the tire effectively promotes the shift, and as a result, advantageously reduces the level of cavity resonance. .

SUMMARY OF THE INVENTION It is an object of the present invention to solve the problems of the prior art. It is an object of the present invention to shift the frequency band of the four-node mode to the lower frequency side and to increase the resonance frequency. Into or close to the frequency band of the four-bar mode, the level of the cavity resonance caused by the circumferential length of the annular inner space of the tire and contributing to the generation of unpleasant cabin noise can be reduced. An object of the present invention is to provide a pneumatic tire that is effectively reduced without sacrificing the performance of the tire.

[0013]

A pneumatic tire according to the present invention includes a tread portion, a sidewall portion, and a bead portion, and a rubber-coated cord is formed at 70 to 90 degrees with respect to the tire circumferential direction. At an angle of, the bead is disposed toroidally over the vicinity of the radially inner end of each bead portion, a carcass formed by one or more carcass plies, and disposed over the entire tread portion on the outer peripheral side of the crown portion of the carcass. With a belt formed by two or more belt layers made of cord and an inner liner arranged on the inner peripheral side of the carcass, on the tire tread portion of the tread portion,
By partitioning at least one circumferential groove extending in the tire circumferential direction, a plurality of land rows are formed between both ends of the tire tread portion of the tread portion. At least one cord cutout area is defined, and the tensile elastic modulus in the tire width direction of the inner liner is set to 1/5 or less of the tensile elastic modulus of the carcass in the cord extending direction.

First, a description will be given of an implementation means adopted by the applicant based on a mechanism for reducing the level of the cavity resonance sound. In the first place, the inventor of the tire 2
Based on the finding that it is effective to shift the frequency band of each of the vibration modes in Sections 4 and 4 to a lower frequency side by reducing the tensile modulus in the width direction of the tread portion of the tire, Various attempts have been made to reduce the tensile modulus in the width direction of the tread portion, but finally, this tensile modulus was cut at least at one location in the tire circumferential direction at the center of the width of the carcass crown portion. The formation of the area is performed for the following reason.

That is, among the components of the tire, it is generally the belt made of steel cord that is dominant in the air pressure holding function of the tread portion, and the carcass hardly contributes to the air pressure holding function. In view of the fact that the carcass is dominant in the tensile modulus for deformation of the central region of the tread portion and the carcass, if the carcass is cut off in the central region of the width of the crown portion, the air pressure holding function is sacrificed. Without lowering the tensile modulus of elasticity to the deformation of the central region of the tread portion, the frequency band of the four-bar mode can be shifted to the lower frequency side,
This is because the level of the cavity resonance that causes unpleasant cabin noise can be effectively reduced.

Here, the "central width region" of the crown portion of the carcass is, specifically, the belt located at the lowermost layer among at least two belt layers constituting the belt with the tire equatorial plane as the center. It refers to the area of 20 to 60% of the width of the layer.

Here, the cord cutting region is assumed to extend continuously or intermittently in a linear or band shape along the tire circumferential direction, and the cord cutting region is intermittent in the tire width direction. It can be provided at a plurality of positions.

Further, when the carcass is composed of two or more carcass plies, all the carcass plies are used in order to effectively reduce the tensile modulus in the width direction of the tread portion.
It is assumed that the cord cutting regions are provided so that the sections are formed at the same position.

On the premise of the above description, in this pneumatic tire, the tensile elastic modulus in the tire width direction of the inner liner is set to 1/5 or less of the tensile elastic modulus of the carcass in the cord extending direction. Thus, the tensile elastic modulus in the width direction of the tire tread portion can be more advantageously reduced, and therefore, the frequency band of each vibration mode of the second and fourth nodes of the tire can be significantly shifted to a lower frequency side. As a result, the level of the cavity resonance can be effectively reduced.

[0020] In such a pneumatic tire, more preferably, the inner liner is provided with 70 to 70 in the tire circumferential direction.
At least one fiber cord layer composed of fiber cords extending at 90 ° is included. According to this, by forming a cord cutting area in the carcass, the carcass formed into a tubular shape at the time of tire molding is expanded, and sufficient tensile strength of the carcass cannot be secured. By incorporating the fiber cord layer into the tire, the decrease in the tensile strength is compensated for by the increase in the tensile strength due to the fiber cord of the inner liner, and the tire can be molded while the carcass is partially discontinuous.

[0021] Preferably, the inner liner includes at least one short fiber layer composed of an aggregate of short fibers. According to such a pneumatic tire, as in the case of including the fiber cord layer in the inner liner, by including the short fiber layer, the decrease in the tensile strength caused by the carcass structure is increased by the increase in the tensile strength by the fiber cord of the inner liner. The tire can be molded while compensating for the minute and partially making the carcass discontinuous.

More preferably, the direction in which the short fibers constituting the short fiber layer extend is 70 to 90 ° with respect to the tire circumferential direction.
In one direction. According to this, the required tensile strength in the tire width direction can be secured while suppressing the total amount of the short fibers, which is more advantageous in terms of cost and weight.

[0023]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a typical cross section in the width direction of a pneumatic tire according to the present invention.
1 is a diagram showing a carcass cord arrangement state of the tire of FIG. 1, in which 1 is a pneumatic tire, 2 is a tread portion, 3 is a sidewall portion, 4 is a bead portion, 5 is a plane including a tire circumferential direction, 6 is the carcass, 7 is the carcass crown,
8 and 9 are belt layers, 10 is a cross belt layer, 11 is a belt, 12a to 12d are circumferential grooves, 13a to 13e are land rows, and 14 is an inner liner.

Here, as shown in FIG.
A cord extending at an angle of 70 to 90 ° with respect to a plane 5 including the tire circumferential direction (the tire equatorial plane in FIG. 1) is rubberized and wrapped around the bead core 4a from the inside to the outside in the tire width direction. A carcass 6 made of at least one carcass ply (one carcass ply in FIG. 1) and a belt layer made of a cord extending on the outer peripheral side of the crown portion 7 of the carcass 6 at a relatively small angle with respect to the plane 5. A belt formed by forming an intersecting belt layer 10 having at least two layers (two layers 8, 9 in FIG. 1), and the cords of the two layers 8, 9 intersect each other with the plane 5 interposed therebetween. 11
And at least one line extending parallel to the plane 5 (FIG. 1)
Tread portion 2 in which a plurality of land portions 13a to 13e are formed by arranging four circumferential grooves 12a to 12d, and an inner liner 14 which is located on the inner peripheral side of the carcass 6 and extends toroidally. The cord cutout area 16 is formed in at least one place (five places in FIG. 1) of the carcass 6 located in the width center region 15 of the crown portion 7.

The tensile elastic modulus of the inner liner 14 in the tire width direction is set to not more than 1/5 of the tensile elastic modulus of the carcass 6 in the cord extending direction. Incidentally, the tensile elastic modulus of the inner liner 14 in the tire width direction is 10 to 3
It is preferably set to 00 N / mm.

Here, the inner liner 14 includes at least one fiber cord layer made of a fiber cord extending at 70 to 90 ° with respect to the tire circumferential direction, or
The inner liner 14 includes at least one short fiber layer made of an aggregate of short fibers.

For example, the short fiber layer included in the inner liner 14 can be formed of a nonwoven fabric, and the diameter or the maximum diameter of the fibers constituting the nonwoven fabric is 0.0001.
When the length of the fibers is extremely short, the entanglement between the fibers becomes insufficient, and the strength of the inner liner 14 as a reinforcing layer is reduced. In view of the fact that it is not possible to sufficiently maintain the length of the short fibers,
It is preferable to use the above.

The thickness of the nonwoven fabric is set to 0.05 to 2.0.
mm, particularly preferably 0.1 to 0.5 mm. This is because if the thickness is less than 0.05 mm, it is difficult to maintain the uniformity as a nonwoven fabric, and if it exceeds 2.0 mm, when the fiber is combined with rubber, the gauge thickness increases. This is not preferable in that it leads to an increase in tire weight and the like.

It is preferable that the ratio of the fibers in the composite of the fibers and the rubber is 4 to 50 mass%. This is because if the fiber ratio is less than 4 mass%, the uniformity of the fiber cannot be maintained and the variation in tensile strength as a composite increases, and if it exceeds 50 mass%, the composite of the fiber and the rubber This is because the ratio of the continuous fiber layer of the body increases, and the durability of the composite decreases.

In addition, it is preferable that the basis weight of the composite of fiber and rubber is 0.1 to 3.0 N / m ² . This is because when the basis weight is less than 0.1 N / m ² , the uniformity of the fiber cannot be maintained, and the variation in tensile strength as a composite increases. When the basis weight exceeds 3.0 N / m ² , This is because rubber does not easily penetrate into the voids inside the nonwoven fabric, and the releasability of the composite decreases.

The fibers constituting the nonwoven fabric include natural polymer fibers such as cotton, rayon, and cellulose; synthetic polymer fibers such as aliphatic polyamide, polyester, polyvinyl alcohol, polyimide, and aromatic polyamide; and carbon. At least one kind of fiber appropriately selected from fibers, glass fibers, steel wires, and the like is included.

Further, the extending direction of the short fibers constituting the inner liner 14 is set at 70 to 90 ° with respect to the tire circumferential direction.
It is more preferable to set it in one direction. As a specific embodiment in this case, a plurality of organic fiber cords are arranged in parallel with each other, covered with rubber, and the cord diameter is set to 0.1 to 0.3.
mm and the number of shots is 20-70 / 50mm
And the organic fiber cord type can be, for example, nylon, polyester, rayon or vinylon.

[0033]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, a pneumatic tire according to the present invention was prototyped and its performance was evaluated. Example tires 1 to 9 have a tire size of 195 / 65R14, and are provided with four circumferential grooves (width: 8 mm, depth: 8 mm) extending along the tire circumferential direction in a tread portion, and a belt is provided. Is an intersecting belt in which two cord layers are stacked so that cords intersect (cord material: steel, cord arrangement angle: ± 24 °)
The carcass is a single carcass ply with rubberized cord (cord material: PET, cord angle: 90 °)
It consisted of. The specifications of the cord cutting area and the inner liner are as shown in Table 1, and the other tire structures are configured almost in the same manner as ordinary passenger car tires.

For comparison, a prototype tire 1 having the same structure as that of the tire 1 of the present invention except that the carcass ply does not have a cord cutout area was prototyped and its performance was evaluated.

(Evaluation of Performance) For each of the test tires described above,
An impact test using a hammer and a vehicle interior noise measurement test using an actual vehicle were performed, and will be described below. In the tire mode frequency, the test tires were assembled on a standard aluminum rim (14-6JJ), the tire wheel with an air pressure of 200 kPa was set on an impact tester, and a hammer was applied to the tread of the tire wheel. It was measured by applying vibration.

The vehicle interior noise was measured by mounting the above tire wheels on a 2000cc class passenger car (tire load: equivalent to two passengers).
The vehicle was run on a rougher asphalt road (test course) at a vehicle speed of 50 km / h. At this time, the measurement was performed by a measuring instrument installed at a position near the driver's ear.

Table 1 shows the results of these measurements. Table 1
The frequency of the middle tire mode is indicated by a reduction amount (Hz) with respect to the conventional example, and the vehicle interior noise is indicated by a noise level reduction amount (dB) with respect to the conventional example.

[0038]

[Table 1]

From the results shown in Table 1, it can be seen that all of the example tires 1 to 9 have lower noise levels than the comparative example tire 1.

Next, the effect of reducing the level of cavity resonance sound when the ratio of the tensile elastic modulus of the inner liner in the tire width direction to the tensile elastic modulus of the carcass in the cord extending direction is variously changed. Confirmation tests were performed on Example tires 10 to 12 and Comparative example tires 2 to 4. In addition, each tire structure of these example tires and comparative example tires has the specifications of the inner liner shown in Table 2, and the other structures are the same as those of the example tire 1. The result is shown in FIG.

[0041]

[Table 2] According to this, an excellent reduction effect of the level of the cavity resonance was confirmed when the above ratio was 1/5 or less, that is, 20% or less in FIG.

[0042]

As described above, according to the present invention, the toroidal tire is assembled to the applicable rim and filled with a predetermined air pressure, which is caused by the circumferential length of the annular inner space defined by the tire, which is uncomfortable. Thus, it is possible to provide a pneumatic tire in which the level of cavity resonance sound, which contributes to the generation of in-vehicle noise, is effectively reduced without sacrificing other performances.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view in the width direction of a pneumatic tire according to the present invention.

FIG. 2 is a view showing an arrangement state of cords of a carcass ply of the tire of FIG. 1;

FIG. 3 is a graph showing the effect of reducing cavity resonance sound when the ratio of the tensile elastic modulus in the tire width direction of the inner liner to the tensile elastic modulus in the carcass cord extending direction is variously changed. .

FIG. 4 is a diagram showing a deformed state of a tire in a two-node vibration mode.

FIG. 5 is a diagram showing a deformed state of a tire in a four-node vibration mode.

FIG. 6 is a diagram illustrating an example of plotting a force transmission rate with respect to a frequency.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 pneumatic tire 2 tread portion 3 sidewall portion 4 bead portion 4 a bead core 5 plane including tire circumferential direction 6 carcass 7 crown portion of carcass 3 8, 9 belt layer 10 crossed belt layer 11 belt 12 a to 21 d circumferential groove 13 a to 13 d 13e Land row 14 Inner liner 15 Central width of carcass crown 4 16 Code cutting area

Claims (4)

[Claims] 1. A tire comprising a tread portion, a side wall portion, and a bead portion, wherein a rubber-coated cord is provided at an angle of 70 to 90 ° with respect to a tire circumferential direction in a radial direction of each bead portion. A carcass formed by one or more carcass plies disposed toroidally over the vicinity of one end, and a belt layer comprising two or more layers of cords disposed over the entire tread portion on the outer peripheral side of the crown portion of the carcass. A belt and an inner liner disposed on the inner peripheral side of the carcass, and by defining at least one circumferential groove extending in the tire circumferential direction on the tire tread portion of the tread portion, the tire tread portion of the tread portion is provided. Pneumatic tire with a plurality of land rows between both ends of the carcass A pneumatic tire in which a cord cutout area is defined and formed so that the tensile elastic modulus of the inner liner in the tire width direction is 1/5 or less of the tensile elastic modulus of the carcass in the cord extending direction. 2. The pneumatic tire according to claim 1, wherein the inner liner includes at least one fiber cord layer made of a fiber cord extending at 70 to 90 ° with respect to the tire circumferential direction. 3. The pneumatic tire according to claim 1, wherein the inner liner includes at least one short fiber layer made of an aggregate of short fibers. 4. The pneumatic tire according to claim 3, wherein the direction in which the short fibers extend is one direction of 70 to 90 ° with respect to the tire circumferential direction.