JP7375440B2 - pneumatic tires - Google Patents

Description

The present invention relates to pneumatic tires.

Patent Document 1 listed below describes a pneumatic radial tire that includes a sound absorbing member on the inner cavity side of the tire. The sound absorbing member is provided, for example, at the center in the width direction of the tire.

JP2014-213837A

A pneumatic tire such as that disclosed in Patent Document 1 has a problem in that road noise, particularly medium frequency noise (sound pressure) level around 315 Hz, is high. In particular, in the case of narrow-width, large-diameter pneumatic tires that have been proposed in recent years as having excellent fuel efficiency, as the width of the belt layer becomes smaller, the cross-sectional secondary resonance frequency shifts to the lower frequency side, and the mid-frequency Getting worse. Moreover, this causes the problem that the cross-sectional secondary resonance frequency becomes close to that of the cavity resonance sound, which is especially worse in the 250 to 315 Hz range.

The present invention was devised in view of the above-mentioned circumstances, and its main purpose is to provide a pneumatic tire that can reduce medium frequency noise levels and improve noise performance.

The present invention provides a pneumatic tire, including a carcass extending between bead cores, a belt layer disposed on the outside of the carcass in the tire radial direction and inside a tread portion, and a belt layer disposed on the inner surface of the tread portion. a sound absorbing layer, the belt layer has belt ends in the tire axial direction on both outsides of the tire equator, and the sound absorbing layer has outer ends in the tire axial direction on both outsides of the tire equator. , on both sides of the tire equator, the outer end of the sound absorbing layer is located between the belt end and the tire maximum width position.

In the pneumatic tire according to the present invention, it is preferable that the outer end of the sound absorbing layer is located 3 mm or more outward from the belt end in the tire axial direction.

In the pneumatic tire according to the present invention, it is preferable that the outer end of the sound absorbing layer is located within 15 mm from the belt end in the tire axial direction.

In the pneumatic tire according to the present invention, the sound absorbing layer is composed of a pair separated in the tire axial direction, and the inner ends of the pair of sound absorbing layers in the tire axial direction are located inside the tire axial direction than the belt ends. It is desirable to be located.

In the pneumatic tire according to the present invention, it is preferable that the inner end of the sound absorbing layer is located 3 to 7 mm inward from the outer end of the belt in the axial direction of the tire.

In the pneumatic tire according to the present invention, it is desirable that the sound absorbing layer continuously extends between the outer ends.

In the pneumatic tire according to the present invention, it is desirable that the sound absorbing layer is a porous sound absorbing material.

In the pneumatic tire according to the present invention, the carcass has a carcass ply including a main body extending between the bead cores, and a folded part connected to the main body and folded back around the bead core from the inside to the outside in the tire axial direction. The tire preferably includes a first apex rubber disposed between the main body portion and the folded portion, and a second apex rubber disposed on the outside of the folded portion in the tire axial direction.

In the pneumatic tire according to the present invention, it is desirable that the complex modulus of elasticity E*b of the second apex rubber is larger than the complex modulus of elasticity E*a of the first apex rubber.

The pneumatic tire according to the present invention is characterized in that the maximum height of the second apex rubber in the tire radial direction is 2.5 to 4.0 times the maximum height of the first apex rubber in the tire radial direction. is desirable.

The pneumatic tire according to the present invention satisfies the following formulas (1) and (2), where the tire cross-sectional width is Wt (unit: mm) and the tire outer diameter is Dt (unit: mm). is desirable.
Dt≦59.078× ^Wt0.498 …(1)
Dt≧59.078× ^Wt0.460 …(2)

It is desirable that the pneumatic tire according to the present invention has an aspect ratio of 60% or less.

The pneumatic tire of the present invention includes a belt layer having belt ends in the tire axial direction on both sides of the tire equator, and a sound absorbing layer disposed on the inner cavity surface of the tread portion. The sound absorbing layer has outer ends in the tire axial direction on both sides of the tire equator. On both sides of the tire equator, the outer end of the sound absorbing layer is located between the belt end and the tire maximum width position. As a result of various experiments conducted by the inventors, the above-mentioned medium frequency noise level is largely influenced by the vibration of the belt end of the belt layer. The sound-absorbing layer of the present invention can absorb vibrations at the end of the belt, thereby reducing the medium-frequency noise level and improving noise performance.

FIG. 1 is a sectional view of a pneumatic tire of the present invention. FIG. 2 is an enlarged view of the tread portion of FIG. 1; This is a graph plotting the relationship between tire cross-sectional width and tire outer diameter in conventional tires listed by JATMA. FIG. 2 is a conceptual diagram illustrating the effect of increasing the diameter of a pneumatic tire. FIG. 2 is an enlarged view of the bead portion in FIG. 1; FIG. 2 is an enlarged view of the bead portion in FIG. 1; FIG. 2 is an enlarged view of the bead portion in FIG. 1; It is a sectional view of the pneumatic tire of other embodiments. 2 is a graph of noise levels in Comparative Example 1 and Example 1.

Hereinafter, one embodiment of the present invention will be described based on the drawings.
FIG. 1 is a tire meridian cross-sectional view including a tire rotation axis (not shown) of a pneumatic tire (hereinafter sometimes simply referred to as "tire") 1 of the present embodiment. FIG. 1 shows, for example, a tire 1 for a passenger car. However, the present invention may be applied to tires 1 for heavy loads, etc.

In this embodiment, the tire 1 includes a carcass 6, a belt layer 7, and a sound absorbing layer 8. The carcass 6 extends, for example, between bead cores 5 embedded in a pair of bead portions 4. The belt layer 7 is disposed, for example, outside the carcass 6 in the tire radial direction and inside the tread portion 2. The sound absorbing layer 8 is arranged, for example, on the inner cavity surface 2a of the tread portion 2.

The carcass 6 of this embodiment is formed from one carcass ply 6A in which carcass cords are arranged at an angle of, for example, 75 to 90 degrees with respect to the tire equator C. The carcass ply 6A includes, for example, a main body part 6a extending in a toroidal manner between each bead core 5, and a folded part 6b that is continuous with the main body part 6a and folded back around the bead core 5 from the inside to the outside in the tire axial direction. In this embodiment, the folded portion 6b is in contact with the main body portion 6a on the outer side of the bead core 5 in the tire radial direction.

In the tire 1 of this embodiment, an inner liner layer 10 made of air-impermeable rubber is disposed inside the main body 6a. The inner liner layer 10 has, for example, an outer end 10e in the tire axial direction inside the tire maximum width position M in the tire radial direction. In this embodiment, the inner surface of the inner liner layer 10 is formed as a lumen surface 2a. In this specification, the tire maximum width position M is the position that protrudes most outward in the tire axial direction on the virtual outer surface specified excluding protrusions such as letters and rim protectors provided on the outer surface 1a of the tire 1. It is.

The belt layer 7 is formed of, for example, two belt plies 7A and 7B in which belt cords are arranged at an angle of, for example, 10 to 35 degrees with respect to the tire equator C. The belt layer 7 has belt ends 7e in the tire axial direction on both sides of the tire equator C. For example, the belt layer 7 extends continuously between both belt ends 7e, 7e.

For example, the inner belt ply 7A is formed to have a wider width in the tire axial direction than the outer belt ply 7B. In other words, in this embodiment, the belt end 7e1 of the inner belt ply 7A is arranged on the outer side in the tire axial direction than the belt end 7e2 (shown in FIG. 2) of the outer belt ply 7B. The width Wa of the inner belt ply 7A in the tire axial direction is, for example, 70% to 80% of the tire cross-sectional width Wt. Further, the width Wb of the outer belt ply 7B in the tire axial direction is, for example, 85% to 95% of the width Wa of the inner belt ply 7A. In this specification, the tire cross-sectional width Wt is the tire axial distance at the tire maximum width position M. Note that the belt layer 7 is not limited to this embodiment.

In this specification, unless otherwise specified, the dimensions of each part of the tire 1 are the values specified when the bead portion 4 is held in accordance with the rim width specified by the tire size in a non-rim assembled state. .

FIG. 2 is an enlarged view of the tread portion 2 of the tire 1 shown in FIG. As shown in FIG. 2, the sound absorbing layer 8 of this embodiment has outer ends 8e in the tire axial direction on both sides of the tire equator C. On both sides of the tire equator C, the outer end 8e of the sound absorbing layer 8 is located between the belt end 7e and the tire maximum width position M (shown in FIG. 1). Such a sound absorbing layer 8 can absorb the vibrations of the belt end 7e, thereby reducing the medium frequency noise level and improving the noise performance. The outer end 8e of the sound absorbing layer 8 is specified at a position in contact with the lumen surface 2a.

The outer end 8e of the sound absorbing layer 8 is located, for example, 3 mm or more outward from the belt end 7e in the tire axial direction. Such a sound absorbing layer 8 can reliably suppress vibrations at the belt end 7e. In this case, as the belt end 7e, when two belt plies 7A and 7B are arranged as in this embodiment, the belt end 7e1 of the belt ply 7A having the larger width in the tire axial direction is adopted.

The outer end 8e of the sound absorbing layer 8 is preferably located at a distance La within 15 mm from the belt end 7e (7e1) in the tire axial direction. Such a sound absorbing layer 8 can further suppress vibrations at the belt end 7e. In addition, from the viewpoint of reducing the mass of the tire 1 and improving work performance (work efficiency) by reducing the length of the sound-absorbing layer 8 in the tire axial direction, the distance between the outer end 8e of the sound-absorbing layer 8 and the belt end 7e is La is more preferably located within 10 mm, and even more preferably within 7 mm.

In this embodiment, the sound absorbing layers 8 are formed as a pair separated in the tire axial direction. The inner ends 8i of the pair of sound absorbing layers 8A in the tire axial direction are located, for example, on the inner side of the belt end 7e in the tire axial direction. Such a sound absorbing layer 8 suppresses an increase in the mass of the tire 1. In this case, when two belt plies 7A and 7B are arranged as in this embodiment, the belt end 7e2 of the outer belt ply 7B having a smaller width in the tire axial direction is used as the belt end 7e.

The inner end 8i of the sound absorbing layer 8 is preferably located at a distance Lb from the belt end 7e (7e2) by 3 to 7 mm in the axial direction of the tire. Such a sound-absorbing layer 8 reduces the medium frequency noise level and improves noise performance, reduces the tire mass, improves fuel efficiency, and reduces cost.

In this embodiment, the sound absorbing layer 8 is formed by applying a porous sound absorbing material 9 to the inner cavity surface 2a. Note that the sound absorbing layer 8 may be formed, for example, by applying the porous sound absorbing material 9 to a sealant layer (not shown) having an adhesive property and having a known structure and arranged inside the inner liner layer 10 .

The porous sound absorbing material 9 is not particularly limited, and sponges, polyester nonwoven fabrics, polystyrene nonwoven fabrics, etc. can be used, and among them, sponges with known structures are preferred because they provide better effects.

The specific gravity of the porous sound absorbing material 9 is preferably 0.06 to 0.08. If the specific gravity is less than 0.06, there is a tendency that a sufficient sound absorption effect cannot be obtained. Furthermore, if the specific gravity exceeds 0.08, not only will the sound absorption effect reach a plateau, but there is also a risk that the sound absorption layer 8 will be destroyed by the stress of running, and the mass and cost of the tire 1 may increase.

Although not particularly limited, the thickness d1 of the sound absorbing layer 8 is preferably, for example, 10 mm or more and 20 mm or less.

As shown in FIG. 1, in this embodiment, the tire 1 is calculated by the following formulas (1) and (2), where the tire cross-sectional width Wt (unit: mm) and the tire outer diameter are set as Dt (unit: mm). It is formed as a so-called narrow and large diameter type that satisfies the following. In this specification, the tire outer diameter Dt is the outer diameter of the tire 1 measured on the tire equator C.
Dt≦59.078× ^Wt0.498 …(1)
Dt≧59.078× ^Wt0.460 …(2)

FIG. 3 is a graph plotting the results of an investigation into the relationship between the tire cross-sectional width Wt and the tire outer diameter Dt, which was conducted on conventional tires listed by JATMA. From the results of this investigation, the average relationship between the tire cross-sectional width Wt and the tire outer diameter Dt in conventional tires as shown by JATMA can be expressed by the following equation (A), as shown by the dashed line Ka in the figure. .
Dt= 59.078×Wt ^0.448 …(A)

On the other hand, the region Y1 that satisfies formulas (1) and (2) is located at a position where the average relationship Ka shown by formula (A) is shifted in parallel in the direction where the tire outer diameter Dt is large. . In this way, the tire 1 that satisfies formulas (1) and (2) is narrow and has a large tire outer diameter. Such a tire 1 has a reduced rolling resistance value and air resistance, and thus has excellent fuel efficiency. Further, such a tire 1 has a high medium frequency noise (sound pressure) level.

Furthermore, as conceptually shown in FIG. 4, the tire 1A with a relatively large tire outer diameter Dt has less bending deformation in the circumferential direction at the ground contact area than the tire 1B with a small tire outer diameter Dt. few. Therefore, the amount of energy loss is small and it is effective in reducing rolling resistance. Therefore, if it deviates from equation (2), it is no longer possible to reduce the rolling resistance by increasing the diameter of the tire 1. On the other hand, if it deviates from equation (1), it becomes necessary to set the operating internal pressure high to ensure the necessary load capacity, and the vertical spring increases, which has a negative impact on the noise performance resulting from medium frequency and cavity resonance sound. give. Cavity resonance is road noise with a frequency of around 250 Hz, and occurs in a frequency band close to medium frequency.

In this embodiment, on both sides of the tire equator C, the outer end 8e of the sound absorbing layer 8 is located between the belt end 7e and the tire maximum width position M. The noise level of frequency and cavity resonance sounds is more effectively reduced, demonstrating excellent noise performance.

FIG. 5 is an enlarged view of the bead portion 4 of the tire 1 shown in FIG. As shown in FIG. 5, the bead portion 4 of this embodiment includes a first apex rubber 13A disposed between the main body portion 6a and the folded portion 6b, and a first apex rubber 13A disposed on the outside of the folded portion 6b in the tire axial direction. A second apex rubber 13B is provided. In this embodiment, the complex modulus of elasticity E*b of the second apex rubber 13B is larger than the complex modulus of elasticity E*a of the first apex rubber 13A. Such first apex rubber 13A contributes to suppressing an increase in the vertical spring of the bead portion 4, thereby improving noise performance. Further, the second apex rubber 13B contributes to increasing the in-plane torsional rigidity of the bead portion 4, suppresses the decrease in rigidity of the bead portion 4 caused by the first apex rubber 13A, and maintains high steering stability performance.

In this specification, the complex elastic modulus E* is a value measured using a viscoelastic spectrometer manufactured by Iwamoto Seisakusho Co., Ltd. under the following conditions in accordance with the provisions of JIS-K6394.
Initial strain: 10%
Amplitude: ±2%
Frequency: 10Hz
Deformation mode: Tensile Temperature: 70℃

The difference (E*b−E*a) between the complex modulus of elasticity E*b of the second apex rubber 13B and the complex modulus of elasticity E*a of the first apex rubber 13A is preferably 15 to 35 MPa. If the difference (E*b-E*a) is less than 15 MPa, or if the difference (E*b-E*a) exceeds 35 MPa, the steering stability performance due to the increase in in-plane torsional rigidity of the bead portion 4, , there is a possibility that the noise performance cannot be improved in a well-balanced manner by suppressing the increase in the vertical spring.

The complex elastic modulus E*b of the second apex rubber 13B is preferably 60 to 70 MPa. If the complex elastic modulus E*b of the second apex rubber 13B is less than 60 MPa, there is a possibility that the in-plane torsional rigidity cannot be increased. When the complex elastic modulus E*b of the second apex rubber 13B exceeds 70 MPa, the vertical spring of the bead portion 4 becomes large, which may deteriorate the noise performance.

The first apex rubber 13A extends outward in the tire radial direction from the outer surface 5a of the bead core 5, for example. In this embodiment, the first apex rubber 13A is formed in a triangular shape that tapers outward in the tire radial direction. Such first apex rubber 13A suppresses excessive reduction in vertical spring and improves steering stability performance.

In this embodiment, the second apex rubber 13B is disposed adjacent to the outer side of the main body portion 6a and the folded portion 6b in the tire axial direction. The second apex rubber 13B prevents the main body portion 6a and the folded portion 6b from falling significantly inward in the axial direction of the tire, thereby maintaining even higher steering stability.

The outer end 16e of the second apex rubber 13B in the tire radial direction is located, for example, inside the tire maximum width position M in the tire radial direction. Such second apex rubber 13B suppresses an excessive increase in the in-plane torsional rigidity of the bead portion 4 and maintains high noise performance.

In this embodiment, the maximum thickness d3 of the second apex rubber 13B is the maximum height of the first apex rubber 13A in the tire radial direction from the outer end 15e of the first apex rubber 13A in the tire radial direction to the inside and outside of the tire radial direction. It is located within 10% of H1. Thereby, the rigidity of the vicinity of the outer end 15e of the first apex rubber 13A, where the vertical spring becomes excessively small, is reinforced, and the collapse of the main body portion 6a and the folded portion 6b is effectively suppressed.

Although not particularly limited, the maximum thickness d3 of the second apex rubber 13B is preferably 2.0 to 4.0 mm in order to effectively exhibit the above-mentioned effect.

The inner end 16i of the second apex rubber 13B in the tire radial direction is preferably located within 3 mm from the outer surface 5a of the bead core 5 in the tire radial direction. If the inner end 16i of the second apex rubber 13B is located more than 3 mm from the outer surface 5a to the outer skin in the radial direction of the tire, the effect of improving in-plane torsional rigidity may be reduced. If the inner end 16i of the second apex rubber 13B is located more than 3 mm inward from the outer surface 5a in the radial direction of the tire, there is a possibility that the in-plane torsional rigidity of the bead portion 4 will not improve and the tire mass may increase. .

The maximum height H2 of the second apex rubber 13B in the tire radial direction is desirably 2.5 times or more or 4.0 times or less the maximum height H1 of the first apex rubber 13A in the tire radial direction. If the maximum height H2 of the second apex rubber 13B is less than 2.5 times the maximum height H1 of the first apex rubber 13A, there is a possibility that the effect of suppressing the increase in vertical spring becomes excessively large. If the maximum height H2 of the second apex rubber 13B exceeds 4.0 times the maximum height H1 of the first apex rubber 13A, the in-plane torsional rigidity of the bead portion 4 may become excessively large. From this point of view, the maximum height H2 of the second apex rubber 13B in the tire radial direction is 3.0 times or more or 3.5 times or less the maximum height H1 of the first apex rubber 13A in the tire radial direction. It is even more desirable that

The maximum height H2 of the second apex rubber 13B is not particularly limited, but is preferably 25 to 40 mm, for example.

In the bead portion 4 of this embodiment, a clinch rubber 17 is provided on the outer side of the second apex rubber 13B in the tire axial direction.

The clinch rubber 17 is desirably formed with a complex modulus of elasticity E*2 smaller than the complex modulus of elasticity E*b of the second apex rubber 13B, for example. Such clinch rubber 17 suppresses excessive increase in in-plane torsional rigidity of bead portion 4 and maintains high noise performance. The difference (E*b-E*2) between the complex modulus of elasticity E*2 of the clinch rubber 17 and the complex modulus of elasticity E*b of the second apex rubber 13B is preferably, for example, 15 to 30 MPa.

The clinch rubber 17 is, for example, disposed adjacent to the outside of the second apex rubber 13B in the tire axial direction, and forms the outer surface 1a of the tire 1. Note that the clinch rubber 17 is not limited to this embodiment.

The outer end 17e of the clinch rubber 17 in the tire radial direction is located inside the tire radial direction than the outer end 16e of the second apex rubber 13B in the tire radial direction. Such a clinch rubber 17 suppresses an increase in the vertical spring of the bead portion 4 and increases in-plane torsional rigidity in a well-balanced manner. Although not particularly limited, the distance Lc in the tire radial direction between the outer end 17e of the clinch rubber 17 and the outer end 16e of the second apex rubber 13B is 20% of the maximum height H1 of the first apex rubber 13A. More than 50% is desirable, and 50% or less is desirable.

In this embodiment, the inner end 17i of the clinch rubber 17 in the tire radial direction is located inside the bead core 5 in the tire radial direction. Note that the inner end 17i of the clinch rubber 17 is not limited to this embodiment.

From the viewpoint of rolling resistance, the aspect ratio of the tire 1 is preferably 60% or less. When the aspect ratio exceeds 60, the proportion of the rubber member in the sidewall portion 3 increases, which tends to increase the amount of energy loss. If the aspect ratio becomes too small, the vertical spring of the sidewall portion 3 becomes large, which may deteriorate the noise performance. For this reason, it is preferable that the aspect ratio of the tire 1 is 40% or more.

FIG. 6 is an enlarged view of the bead portion 4 in FIG. 1. As shown in FIG. 6, the main body portion 6a of the carcass 6 of this embodiment is inclined at an angle θ1 of 50 to 60 degrees with respect to the tire axial direction on the inside of the tire maximum width position M in the tire radial direction. The first sloped portion 19 includes a first sloped portion 19 that has a first slope. Such a first inclined portion 19 can be effectively bent when a lateral force is applied to the tire 1 during a turn, and can increase the lateral spring of the bead portion 4 and improve steering stability. . In this specification, the angle θ1 is specified by the center line 6c of the carcass cord of the main body portion 6a. When the center line 6c extends in an arc, it is specified by a tangent to any point on the center line 6c.

In this embodiment, the first inclined portion 19 extends linearly. The first inclined portion 19 prevents the horizontal spring from becoming excessively high and maintains high ride comfort performance. In this specification, the term "linear" includes carcass cords in which the center line extends in a straight line as well as those in the form of an arc with a radius of curvature of 1000 mm or more.

In this embodiment, the first inclined portion 19 includes a first portion 19a adjacent to the inner side in the tire axial direction of the first apex rubber 13A, and a second portion 19b adjacent to the inner side in the tire axial direction of the second apex rubber 13B. Contains. The first inclined portion 19 cooperates with the first apex rubber 13A and the second apex rubber 13B to effectively improve steering stability.

The length L3 of the first inclined portion 19 in the tire radial direction is smaller than the maximum height H2 of the second apex rubber 13B. Further, the length L3 of the first inclined portion 19 in the tire radial direction is larger than the maximum height H1 of the first apex rubber 13A. The first inclined portion 19 prevents the lateral spring from becoming excessively large, and prevents the ride comfort performance from deteriorating.

In order to effectively exhibit the above-mentioned effect, it is desirable that the outer end 19e of the first inclined portion 19 in the tire radial direction be located inside the outer end 16e of the second apex rubber 13B in the tire radial direction. Further, it is desirable that the inner end 19i of the first inclined portion 19 in the tire radial direction is located on the outer side of the outer surface 5a of the bead core 5 in the tire radial direction. Further, the length L3 of the first inclined portion 19 is preferably 70% to 90% of the maximum height H2 of the second apex rubber 13B.

FIG. 7 is an enlarged view of the bead portion 4 in FIG. 1. As shown in FIG. 7, the main body portion 6a includes a first circular arc portion 20 that is continuous with the outside of the first slope portion 19 in the tire radial direction and is convex outward in the tire axial direction, and a first slope portion 20 that is convex outward in the tire axial direction. It includes a second arcuate portion 21 that is continuous inward in the tire radial direction and is convex inward in the tire axial direction. The first circular arc portion 20 and the second circular arc portion 21 are portions in which the radius of curvature specified by the center line 6c of the carcass cord is formed by a single circular arc, and is 25 mm or less. .

In this embodiment, the first arcuate portion 20 is located near the tire maximum width position M. The first arcuate portion 20 is located, for example, between the first inclined portion 19 and the tire maximum width position M. In this embodiment, the second circular arc portion 21 is provided adjacent to a corner portion 5c where the outer surface 5a and the inner surface 5b of the bead core 5 intersect. The second arcuate portion 21 extends, for example, inward and outward in the tire radial direction of the corner portion 5c. In this embodiment, the radius of curvature R1 of the first arcuate portion 20 is smaller than the radius of curvature R2 of the second arcuate portion 21. The first arcuate portion 20 serves to reduce the vertical spring of the sidewall portion 3 and improve ride comfort and noise performance. In addition, the second arcuate portion 21 suppresses looseness of the carcass ply 6A and helps maintain high steering stability.

FIG. 8 is a sectional view of a tire 1 according to another embodiment. Components that are the same as those of the tire 1 of this embodiment are given the same reference numerals and their descriptions will be omitted. As shown in FIG. 8, in the tire 1 of this embodiment, the sound absorbing layer 8 extends continuously between the outer ends 8e, 8e. Further, the outer end 8e of the sound absorbing layer 8 of this embodiment is located on the outer side in the tire axial direction of the belt end 7e1 of the inner belt ply 7A. Such a tire 1 exhibits excellent noise performance because the sound absorbing layer 8 effectively absorbs vibrations of the belt end 7e, particularly cavity resonance sound. In the tire axial direction, the distance La between the outer end 8e of the sound absorbing layer 8 and the belt end 7e1 of the inner belt ply 7A is preferably 3 mm or more, more preferably 5 mm or more, and preferably 10 mm or less, more preferably Preferably, the thickness is 7 mm or less.

Although particularly preferred embodiments of the present invention have been described in detail above, the present invention is not limited to the illustrated embodiments, and can be implemented in various forms.

A pneumatic tire for a passenger car of size 175/60R18 was prototyped based on the specifications shown in Table 1. Each test tire was then tested for noise performance and handling stability performance. The common specifications and test methods for each test tire are as follows.

<Noise performance/steering stability performance>
Each test tire was mounted on all wheels of a passenger car with a displacement of 1800 cc under the above conditions. Then, the test driver drove the test vehicle on a test course, which is a loop course on a dry asphalt road surface, and the noise performance was evaluated based on the noise level in the 100 to 350 Hz range measured inside the vehicle. Regarding steering stability performance, the test driver's sensual evaluations were made of the responsiveness, stiffness, grip, stability, and transient characteristics during driving. The results of noise performance are expressed as an index with the noise level (dB) of Comparative Example 1 as 100, and the smaller the value, the better. The results of the steering stability performance are expressed as a score with Comparative Example 1 being 100, and the larger the value, the better. Further, a graph of the noise level from 25 to 2000 Hz in Example 1 and Comparative Example 1 is shown in FIG.
Rim: 18 x 5.0J
Internal pressure: 260KPa
Speed: 40-100Km/h (However, the upper limit for maneuverability stability is 120Km/h.)
The test results are shown in Table 1. Note that the symbol "-" in the "La" column of Table 1 means that the belt is located inside the belt end in the tire axial direction.

As a result of the test, it is understood that the test tire of the example has improved noise performance compared to the test tire of the comparative example. Furthermore, as shown in FIG. 9, the tire of Example 1 has a particularly reduced noise level in the range of 200 to 315 Hz compared to the tire of Comparative Example 1.

1 Pneumatic tire 7 Belt layer 7e Belt end 8 Sound absorption layer 8e Outer end C Tire equator M Tire maximum width position

Claims (10)

A pneumatic tire,
a carcass extending between the bead cores;
a belt layer disposed on the outside of the carcass in the tire radial direction and inside the tread portion;
a sound absorbing layer disposed on the inner surface of the tread portion,
The belt layer has belt ends in the tire axial direction on both sides of the tire equator,
The belt layer includes an inner belt ply and an outer belt ply located outside the inner belt ply in the tire radial direction,
The belt end of the inner belt ply is arranged on the outer side in the tire axial direction than the belt end of the outer belt ply,
The sound absorption layer has outer ends in the tire axial direction on both sides of the tire equator,
On both sides of the tire equator, the outer end of the sound absorbing layer is located between the belt end and the tire maximum width position ,
The carcass is a carcass ply including a main body part extending between the bead cores, and a folded part connected to the main body part and folded back from the inside to the outside in the tire axial direction around the bead core,
a first apex rubber disposed between the main body portion and the folded portion; and a second apex rubber disposed on the outside of the folded portion in the tire axial direction;
The maximum height of the second apex rubber in the tire radial direction is 2.5 to 4.0 times the maximum height of the first apex rubber in the tire radial direction.
pneumatic tires. The pneumatic tire according to claim 1, wherein the outer end of the sound absorbing layer is located 3 mm or more outward from the belt end of the inner belt ply in the tire axial direction. The pneumatic tire according to claim 1 or 2, wherein the outer end of the sound absorbing layer is located within 15 mm from the belt end of the inner belt ply in the tire axial direction. The sound absorbing layer comprises a pair separated in the tire axial direction, and the inner ends of the pair of sound absorbing layers in the tire axial direction are located inside the belt end in the tire axial direction. A pneumatic tire as described in any of the above. The pneumatic tire according to claim 4, wherein the inner end of the sound absorbing layer is located 3 to 7 mm inward from the belt end of the outer belt ply in the tire axial direction. The pneumatic tire according to any one of claims 1 to 3, wherein the sound absorbing layer extends continuously between the outer ends. The pneumatic tire according to any one of claims 1 to 6, wherein the sound absorbing layer is a porous sound absorbing material. The pneumatic tire according to any one of claims 1 to 7, wherein a complex modulus of elasticity E*b of the second apex rubber is larger than a complex modulus of elasticity E*a of the first apex rubber. The tire according to any one of claims 1 to 8, which satisfies the following formulas (1) and (2), where the tire cross-sectional width is Wt (unit: mm) and the tire outer diameter is Dt (unit: mm). pneumatic tires.
Dt≦59.078×Wt0.498…(1)
Dt≧59.078×Wt0.460…(2) The pneumatic tire according to any one of claims 1 to 9, wherein the pneumatic tire has an aspect ratio of 60% or less.

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