JP6291367B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire.

  In recent years, the required performance for vibration and noise of vehicles has been increasing. Correspondingly, low vibration and low noise are also required for pneumatic tires.

  Japanese Patent Laying-Open No. 2008-24048 discloses a pneumatic tire in which road noise generated in a vehicle is reduced. In this tire, a hard rubber portion is provided in a shoulder land portion defined by a main groove. This hard rubber part reduces the shock received from the small protrusion of a road surface. By providing this hard rubber portion, road noise is reduced.

JP 2008-24048 A

  From the viewpoint of reducing noise, tires are also required to reduce outside noise when a vehicle passes. One of the main causes of this outside noise is air column resonance. This air column resonance sound is a sound having a frequency of 800 Hz to 1000 Hz, and is also called a shear sound. This air column resonance is generated in the main groove.

  The tire disclosed in Japanese Patent Application Laid-Open No. 2008-24048 cannot sufficiently reduce the air column resonance sound. As a method for reducing the air column resonance noise, for example, it is conceivable to reduce the groove volume of the main groove of the tire. However, reducing the groove volume of the main groove hinders drainage performance. This tire tends to be inferior in hydroplaning performance. It is not easy to reduce the air column resonance sound of the main groove without impairing the drainage performance.

  An object of the present invention is to provide a tire that reduces air column resonance noise of the main groove without impairing drainage performance.

The pneumatic tire according to the present invention includes a tread whose outer surface forms a tread surface, a pair of sidewalls that extend substantially inward in the radial direction from the end of the tread, and a pair that is positioned radially inward of the sidewalls. Bead, a carcass stretched between one bead and the other bead along the inside of the tread and the sidewall, a belt laminated with the carcass on the radially inner side of the tread, and a radially outer side of the belt And a reinforced rubber member located at the position. A main groove extending in the circumferential direction is formed on the tread surface. The main groove has a bottom surface facing radially outward. The reinforcing rubber member is located on the radially inner side of the bottom surface of the main groove and on the radially outer side of the belt. This reinforcing rubber member extends in the circumferential direction. The outer end width Wc in the radial direction of the reinforcing rubber member is smaller than the bottom width Wb in the axial direction of the main groove. The axial width of the reinforcing rubber member is increased from the radial inner end width Wd toward the radial outer end width Wc. The complex elastic modulus E ^* _r of the reinforced rubber member is larger than the complex elastic modulus E ^* _t of the tread.

  Preferably, the reinforcing rubber member constitutes a part of the bottom surface of the main groove.

  Preferably, the ratio Wc / Wd between the radial outer end width Wc and the radial inner end width Wd of the reinforcing rubber member is set to 1.4 or less.

  Preferably, the ratio Ws / Wb between the axial displacement Ws between the reinforcing rubber member and the main groove and the bottom width Wb of the main groove is 0.2 or less.

Preferably, a ratio E ^* _r / E ^* _t between the complex elastic modulus E ^* _{r of the} reinforcing rubber member and the complex elastic modulus E ^* _t of the tread is set to 1.3 or less.

  Preferably, the ratio Wb / Wa between the opening width Wa of the main groove and the bottom width Wb of the main groove is 0.1 or more and 1.0 or less.

  Preferably, the ratio Wc / Wb between the radial outer end width Wc of the reinforcing rubber and the bottom width Wb of the main groove is 0.05 or more and 0.4 or less.

  Preferably, the ratio Wa / Wt between the opening width Wa of the main groove and the tread width Wt is 0.05 or more and 0.2 or less.

  In the tire according to the present invention, the vibration of the bottom of the main groove is suppressed by the reinforcing rubber member. Thereby, generation | occurrence | production of the air column resonance sound of a main groove is suppressed. By providing this reinforcing rubber member, the generation of air column resonance is suppressed without reducing the volume of the main groove. Thereby, generation | occurrence | production of the air column resonance sound of a main groove is suppressed, maintaining drainage performance.

FIG. 1 is a cross-sectional view showing a part of a pneumatic tire according to an embodiment of the present invention. FIG. 2 is a partially enlarged view indicated by an arrow II in FIG.

  Hereinafter, the present invention will be described in detail based on preferred embodiments with appropriate reference to the drawings.

  FIG. 1 shows a pneumatic tire 2. In FIG. 1, the vertical direction is the radial direction of the tire 2, the horizontal direction is the axial direction of the tire 2, and the direction perpendicular to the paper surface is the circumferential direction of the tire 2. In FIG. 1, an alternate long and short dash line CL represents the equator plane of the tire 2. The shape of the tire 2 is symmetric with respect to the equator plane CL except for the tread pattern.

  The tire 2 includes a tread 4, a sidewall 6, a clinch 8, a bead 10, a carcass 12, a belt 14, a band 16, an inner liner 18 and a reinforcing rubber member 20. The tire 2 is a tubeless type. The tire 2 is mounted on a passenger car.

  The tread 4 has a shape protruding outward in the radial direction. The tread 4 forms a tread surface 22 that contacts the road surface. A main groove 24 is carved in the tread 4. The main groove 24 extends in the circumferential direction of the tire 2. The main groove 24 goes around the tread surface 22 in the circumferential direction. The main groove 24 includes a bottom surface 24a and a pair of wall surfaces 24b. The bottom surface 24a faces outward in the radial direction. The pair of wall surfaces 24b face each other and extend from the bottom surface 24a to the tread surface 22. Although not shown, the tread 4 is further formed with other grooves. A plurality of blocks 25 are formed in the tread 4 by the main groove 24 and other grooves. The tread surface 22 formed by the outer peripheral surfaces of the plurality of blocks 25 contacts the road surface. The main groove 24 and other grooves form a tread pattern. The tread 4 is made of a crosslinked rubber.

  The sidewall 6 extends substantially inward in the radial direction from the end of the tread 4. A radially outer end of the sidewall 6 is joined to the tread 4. The radially inner end of the sidewall 6 is joined to the clinch 8. This sidewall 6 is made of a crosslinked rubber having excellent cut resistance and weather resistance. This sidewall 6 prevents the carcass 12 from being damaged.

  The clinch 8 is located substantially inside the sidewall 6 in the radial direction. The clinch 8 is located outside the beads 10 and the carcass 12 in the axial direction. The clinch 8 is made of a crosslinked rubber having excellent wear resistance. When the tire 2 is assembled to the rim, the clinch 8 comes into contact with the flange of the rim.

  The bead 10 is located inside the clinch 8 in the axial direction. The bead 10 includes a core 26 and an apex 28 that extends radially outward from the core 26. The core 26 has a ring shape and includes a wound non-stretchable wire. A typical material for the wire is steel. The apex 28 is tapered outward in the radial direction. The apex 28 is made of a highly hard crosslinked rubber.

  The carcass 12 includes a carcass ply 30. The carcass ply 30 is stretched between the beads 10 on both sides, and extends along the tread 4 and the sidewall 6. The carcass ply 30 is folded around the core 26 from the inner side toward the outer side in the axial direction. As a result of the folding, a main portion 30a and a folded portion 30b are formed in the carcass ply 30.

  The carcass ply 30 includes a large number of cords arranged in parallel and a topping rubber. The absolute value of the angle formed by each cord with respect to the equator plane is 75 ° to 90 °. In other words, the carcass 30 has a radial structure. The cord is made of organic fiber. Examples of preferable organic fibers include polyester fibers, nylon fibers, rayon fibers, polyethylene naphthalate fibers, and aramid fibers. The carcass 12 may be formed from two or more carcass plies.

  The belt 14 is located on the inner side in the radial direction of the tread 4. The belt 14 is laminated on the outer side in the radial direction of the carcass 12. The belt 14 reinforces the carcass 12. The belt 14 includes an inner layer 32 and an outer layer 34. Although not shown, each of the inner layer 32 and the outer layer 34 is composed of a large number of cords arranged in parallel and a topping rubber. Each cord is inclined with respect to the equator plane CL. The general absolute value of the tilt angle is 10 ° or more and 35 ° or less. The inclination direction of the cord of the inner layer 32 with respect to the equator plane CL is opposite to the inclination direction of the cord of the outer layer 34 with respect to the equator plane CL. A preferred material for the cord is steel. An organic fiber may be used for the cord. The axial width of the belt 14 is preferably 0.7 times or more the maximum width of the tire 2. The belt 14 may include three or more layers.

  The band 16 is located on the radially outer side of the belt 14. In the axial direction, the width of the band 16 is larger than the width of the belt 14. The belt 14 and the band 16 constitute a reinforcing layer 36. The reinforcing layer 36 may be configured only from the belt 14.

  The inner liner 18 is located inside the carcass 12. In the vicinity of the equator plane CL, the inner liner 18 is joined to the inner surface of the carcass 12. The inner liner 18 is made of a crosslinked rubber. For the inner liner 18, rubber having excellent air shielding properties is used. A typical base rubber of the inner liner 18 is butyl rubber or halogenated butyl rubber. The inner liner 18 maintains the internal pressure of the tire 2.

  The reinforcing rubber member 20 is disposed on the radially inner side of the main groove 24. The reinforcing rubber member 20 extends in the circumferential direction along the bottom surface 24 a of the main groove 24. The reinforcing rubber member 20 is located on the inner side between one end and the other end of the bottom surface 20a of the main groove in the axial direction. The reinforcing rubber member 20 is not disposed on the radially inner side of the tread surface 22 and on the radially inner side of the pair of wall surfaces 24b. The reinforcing rubber member 20 is located on the outer side in the radial direction of the belt 14. In other words, the reinforcing rubber member 20 is disposed between the main groove 24 and the belt 14 in the radial direction. In the tire 2, the radially outer end of the reinforcing rubber member 20 constitutes a part of the bottom surface 24 a of the main groove 24. The reinforcing rubber member 20 is disposed on the outer side in the radial direction from the band 16.

The reinforcing rubber member 20 is made of a highly hard crosslinked rubber. The hardness of the crosslinked rubber of the reinforcing rubber member 20 is greater than that of the crosslinked rubber of the tread 4. The reinforcing rubber member 20 is joined to the tread 4 in the axial direction. The complex elastic modulus E ^* _r of the reinforced rubber member 20 is larger than the complex elastic modulus E ^* _t of the tread 4.

  As shown in FIG. 2, the band 16 includes a cord 38 and a topping rubber 40. The cord 38 is spirally wound in the circumferential direction. The band 16 has a so-called jointless structure. The cord 38 extends substantially in the circumferential direction. The angle of the cord 38 with respect to the circumferential direction is 5 ° or less, and further 2 ° or less. Since the belt 14 is restrained by the cord 38, the lifting of the belt 14 is suppressed. The cord 38 is made of an organic fiber. Examples of preferable organic fibers include nylon fibers, polyester fibers, rayon fibers, polyethylene naphthalate fibers, and aramid fibers.

  A double arrow Wt in FIG. 1 indicates a tread width. The tread width Wt is a distance from one tread end to the other tread end. The tread width Wt is measured along the tread surface 22. The tread width Wt is measured in a cross section cut out from the tire 2 as shown in FIG.

  A double arrow T in FIG. 2 indicates the thickness of the tread 4. A double arrow Hg indicates the depth of the main groove 24. The depth Hg is measured as a radial distance from the bottom surface 24a to the tread surface 22. A double-headed arrow Ht indicates the thickness from the bottom surface 24a to the inner circumferential surface in the radial direction of the tread 4, that is, the thickness of the tread 4 on the bottom surface 24a. The thickness T, depth Hg, and thickness Ht are measured as a linear distance in the radial direction. The thickness T, depth Hg, and thickness Ht are measured in a cross section cut out from the tire 2 as shown in FIGS.

  A double arrow Wa in FIG. 2 indicates the opening width of the main groove 24. The opening width Wa is measured as the distance between the intersection of the extension line of the tread surface 22 and the extension line of one wall surface 24b and the intersection of the extension line of the tread surface 22 and the extension line of the other wall surface 24b. A double-headed arrow Wb indicates the bottom width of the main groove 24. The bottom surface width Wb is measured as the distance between the intersection of the extension line of the bottom surface 24a and the extension line of one wall surface 24b and the intersection of the extension line of the bottom surface 24a and the extension line of the other wall surface 24b. A double-headed arrow Wc indicates the axial width of the radially outer end of the reinforcing rubber member 20. A double-headed arrow Wd indicates the axial width of the radially inner end of the reinforcing rubber member 20. The opening width Wa, the bottom surface width Wb, the width Wc, and the width Wd are measured as linear distances in the axial direction. The opening width Wa, the bottom surface width Wb, the width Wc, and the width Wd are measured in a cross section cut out from the tire 2 as shown in FIGS. 1 and 2.

  A one-dot chain line Lr in FIG. 2 indicates the center line of the reinforcing rubber member 20. The center line Lr is a straight line extending in the radial direction through the center in the axial direction of the reinforcing rubber member 20. The reinforcing rubber member 20 has a symmetrical shape with respect to the center line Lr. An alternate long and short dash line Lg indicates the center line of the main groove 24. The center line Lg is a straight line extending in the radial direction through the center of the main groove 24 in the axial direction. The main groove 24 is formed symmetrically with respect to the center line Lg. The bottom surface 24a is formed symmetrically with respect to the center line Lg. A double arrow Ws indicates an axial distance between the center line Lr and the center line Lg. This distance Ws indicates the positional deviation in the axial direction between the reinforcing rubber member 20 and the main groove 24. This positional deviation Ws is measured in a cross section cut out from the tire 2 as shown in FIGS.

  When the vehicle travels, the tire 2 rolls on the road surface. The ground contact surface of the tread surface 22 moves in the circumferential direction. In the tread 4, one rotation of the tire 2 is set as one cycle, and the compression deformation portion moves in the circumferential direction. The tread 4 repeats this periodic deformation.

  Due to the periodic deformation of the tread 4, the belt 14 vibrates. In the tire 2, the bottom surface 24a faces outward in the radial direction. When the tire 2 rolls, the bottom surface 24a of the main groove 24 is not grounded. This bottom surface 24a is not restrained by the ground. For this reason, the bottom surface 24 a is likely to vibrate due to the vibration of the belt 14. The vibration of the bottom surface 24a generates air column resonance sound.

In the tire 2, the reinforcing rubber member 20 is located inside the bottom surface 24 a of the main groove 24. The reinforcing rubber member 20 extends in the circumferential direction along the bottom surface 24a. The reinforcing rubber member 20 is located between the bottom surface 24a and the belt 14 in the radial direction. The complex elastic modulus E ^* _r of the reinforcing rubber member 20 is larger than the complex elastic modulus E ^* _t of the tread. The reinforcing rubber member 20 suppresses vibration from being transmitted from the belt 14 to the bottom surface 24a. The reinforcing rubber member 20 suppresses vibration of the bottom surface 24a of the main groove 24. Thereby, generation | occurrence | production of air column resonance is suppressed.

  The radially outer end width Wc of the reinforcing rubber member 24 is smaller than the bottom surface width Wb of the main groove 24. The reinforcing rubber member 24 is not located on the radially inner side between the tread surface 22 and the wall surface 24b of the main groove 24. The reinforcing rubber member 24 does not hinder the deformation of the block 25. In the tire 2, various performances such as steering stability are suppressed from being impaired along with suppression of generation of air column resonance sound.

  The bottom surface 24a of the main groove 24 vibrates mainly in the radial direction between one end and the other end in the axial direction. At this time, in the bottom surface 24a, the amplitude tends to increase at the center in the axial direction of the bottom surface 24a. In the tire 2, since the reinforcing rubber member 20 is positioned at the center in the axial direction of the bottom surface 24a, the amplitude at the center in the axial direction of the bottom surface 24a is reduced.

  From this viewpoint, it is preferable that the axial positional deviation Ws between the reinforcing rubber member 20 and the main groove 24 is small. The ratio Ws / Wb between the positional deviation Ws and the bottom surface width Wb is preferably 0.2 or less, and more preferably 0.1 or less.

  Further, the axial width of the reinforcing rubber member 20 is increased from the radial inner end width Wd toward the radial outer end width Wc. By increasing the outer end width Wc, the distance between the axial end of the bottom surface 24a and the outer end of the reinforcing rubber member 24 is reduced. Similarly, the distance between the other axial end of the bottom surface 24a and the outer end of the reinforcing rubber member 24 is reduced. Thereby, the vibration of the bottom surface 24a is suppressed. Moreover, since the radial inner end width Wd of the reinforcing rubber member 20 is made small, the volume of the reinforcing rubber member 20 is small. Since the volume of the reinforced rubber member 20 is small, the deformation of the tread 4 is suppressed from being inhibited. In the tire 2, it is suppressed that various performances such as steering stability are impaired as generation of air column resonance noise is suppressed. From these viewpoints, the ratio Wc / Wd between the outer end width Wc and the inner end width Wd is set to be larger than 1.0, and preferably set to 1.05 or more.

  In the tire 2 having the large outer end width Wc, the reinforcing rubber member 20 tends to hinder the deformation of the block 25. When the outer end width Wc is increased, steering stability and riding comfort are easily hindered. From this viewpoint, the ratio Wc / Wd is preferably 1.4 or less, more preferably 1.3 or less, and particularly preferably 1.2 or less.

  In the tire 2, the outer end of the reinforcing rubber member 20 is exposed in the main groove 24. In other words, the outer end of the reinforcing rubber member 20 constitutes a part of the bottom surface 24 a of the main groove 24. In the tire 2, the reinforcing rubber member 20 is positioned in the center in the axial direction of the bottom surface 24 a, so that the cross-linked rubber of the tread constituting the bottom surface 24 a is divided by the reinforcing rubber member 20. It is suppressed that the bottom surface 24a vibrates integrally. The amplitude at the center in the axial direction of the bottom surface 24a is reduced.

  In the tire 2, the opening width Wa of the main groove 24 is made larger than the bottom surface width Wb. The reinforcing rubber member 20 is sufficiently separated from the tread surface 22 in the axial direction. By interposing this reinforcing rubber member 20, changes in various performances of the tire 2 are suppressed. From this viewpoint, the ratio Wb / Wa is preferably 1.0 or less, more preferably 0.9 or less, and particularly preferably 0.8 or less.

  The tire 2 having a large bottom width Wb of the main groove 24 can increase the groove volume of the main groove 24. The tire 2 having a large groove volume of the main groove 24 is excellent in drainage performance. Since the tire 2 includes the reinforcing rubber member 20, even if the bottom surface width Wb is increased, generation of air column resonance noise is suppressed. From the viewpoint of drainage performance, the ratio Wb / Wa is preferably 0.1 or more, more preferably 0.3 or more, and particularly preferably 0.5 or more.

  Further, in the tire 2, the outer end width Wc of the reinforcing rubber member 20 is sufficiently smaller than the bottom surface width Wb. Since the width Wc is small, the reinforcing rubber member 20 does not hinder the deformation of the block 25. The reinforcement rubber member 20 suppresses the deterioration of the riding comfort of the tire 2. From this viewpoint, the ratio Wc / Wb is preferably 0.4 or less, more preferably 0.3 or less, and particularly preferably 0.2 or less. On the other hand, from the viewpoint of suppressing the vibration of the bottom surface 24a, the ratio Wc / Wb is preferably 0.05 or more, and more preferably 0.1 or more.

The complex elastic modulus E ^* _r of the reinforced rubber member 20 is larger than the complex elastic modulus E ^* _t of the tread 4. The reinforcing rubber member 20 suppresses vibration of the bottom surface 24a of the main groove 24. From this viewpoint, the ratio E ^* _r / E ^* _t of the complex elastic modulus E ^* _{r of the} reinforced rubber member 20 and the complex elastic modulus E ^* _t of the red 4 is preferably 1.02 or more, more preferably 1.05 or more. On the other hand, the reinforced rubber member 20 having a small complex elastic modulus E ^* _r suppresses changes in various performances of the tire 2. From this viewpoint, the ratio E ^* _r / E ^* _t is preferably 1.3 or less, more preferably 1.2 or less, and particularly preferably 1.1 or less.

  In the tire 2, the reinforcing rubber member 20 and the band 16 are in contact with each other in the radial direction. The reinforcing rubber member 20 is in contact with the reinforcing layer 36. The tire 2 may not include the band 16 and the reinforcing rubber member 20 may be in contact with the belt 14. The crosslinked rubber of the tread 4 is divided by the reinforcing rubber member 20 on the bottom surface 24a of the main groove 24. By providing the reinforced rubber member 20, the bottom surface 24a is prevented from vibrating as a unit.

  In the tire 2, by providing the reinforcing rubber member 20, generation of air column resonance noise is suppressed. Since the generation of air column resonance is suppressed, the thickness T of the tread 4 can be increased and the depth Hg of the main groove 24 can be increased. The depth Hg of the main groove 24 can be increased to improve drainage performance.

  In the tire 2, since the generation of air column resonance noise is suppressed, the opening width Wa of the main groove 24 can be increased. The drainage performance can be improved by increasing the opening width Wa. From this viewpoint, the ratio Wa / Wt between the opening width Wa of the main groove 24 and the tread width Wt is preferably 0.05 or more, and more preferably 0.1 or more. On the other hand, when the opening width Wa becomes too large, the ground contact area of the tread surface 22 becomes small. From this viewpoint, the ratio Wa / Wt is preferably 0.2 or less, and more preferably 0.15 or less.

The complex elastic modulus E ^* of the present invention is measured in accordance with the rules of “JIS K 6394”. A rubber slab sheet of cross-linked rubber whose complex elastic modulus E ^* is measured is produced. A measurement specimen is cut out from the rubber slab sheet. This loss complex elastic modulus E ^* is measured under the following conditions using this measurement specimen.
Measuring device: Viscoelastic spectrometer "VES / F-3 type" (manufactured by Iwamoto Seisakusho)
Initial distortion: 10%
Dynamic distortion: 2%
Frequency: 10Hz
Deformation mode: Tensile Measurement temperature: 30 ° C

  In the present invention, the size and angle of each member of the tire 2 are measured in a state where the tire 2 is incorporated in a regular rim and filled with air so as to have a regular internal pressure unless otherwise specified. At the time of measurement, no load is applied to the tire 2. In the present specification, the normal rim means a rim defined in a standard on which the tire 2 depends. “Standard rim” in the JATMA standard, “Design Rim” in the TRA standard, and “Measuring Rim” in the ETRTO standard are regular rims. In the present specification, the normal internal pressure means an internal pressure defined in a standard on which the tire 2 relies. “Maximum air pressure” in JATMA standard, “Maximum value” published in “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” in TRA standard, and “INFLATION PRESSURE” in ETRTO standard are normal internal pressures.

  Hereinafter, the effects of the present invention will be clarified by examples. However, the present invention should not be construed in a limited manner based on the description of the examples.

[Example 1]
A pneumatic tire having the basic structure shown in FIGS. 1 and 2 was obtained. The ratio Wa / Wt between the opening width Wa of the main groove and the tread width Wt, the ratio E ^* _r / E ^* _t of the complex elastic modulus E ^* _{r of} the reinforcing rubber member and the complex elastic modulus E ^* _t of the tread, and reinforcement The ratio Ws / Wb between the axial displacement Ws between the rubber member and the main groove and the bottom surface width Wb of the main groove, and the ratio Wc / between the radial outer end width Wc and the radial inner end width Wd of the reinforcing rubber member. Table 1 shows the ratio Wa / Wt of Wd and the opening width Wa of the main groove and the tread width Wt.

[Comparative Example 1]
A tire having the same structure as Example 1 was obtained except that the ratio Wa / Wt, the ratio E ^* _r / E ^* _t , the ratio Ws / Wb, and the ratio Wc / Wd were set as shown in Table 1. .

[Example 2 and Comparative Example 3 ]
A tire was obtained in the same manner as in Example 1 except that the ratio Wc / Wd was set as shown in Table 1.

[ Example 3 and Comparative Example 2]
A tire was obtained in the same manner as in Example 1 except that the ratio Ws / Wb was set as shown in Table 2.

[ Example 4-5 ]
A tire was obtained in the same manner as in Example 1 except that the ratio Wa / Wt and the ratio E ^* _r / E ^* _t were set as shown in Table 2.

[ Example 6-7 ]
A tire was obtained in the same manner as in Example 1 except that the ratio Wb / Wa was set as shown in Table 2.

  These tires were incorporated into regular rims. These tires were evaluated for drainage performance and outside noise.

<Drainage performance>
Using a test vehicle with all four wheels mounted, the lateral acceleration (lateral G) of the front wheels during the following test course is measured, and the average lateral G when the speed of the test vehicle is 50 to 80 km / h is calculated. (Lateral Hydroplaning Test). A result is shown by the index | exponent which sets the comparative example 1 to 100, and it is so favorable that a numerical value is large. The test conditions are as follows.
Internal pressure: 230 kPa
Test vehicle: Hybrid FF passenger car, displacement 1500cm ³ (cc)
Test course: Asphalt road surface with a radius of 100m with a puddle with a depth of 5mm and a length of 20m

[Vehicle noise]
Passage noise during actual coasting was measured. This measurement was carried out on an ISO road surface test course defined by ISO 10844 based on JASO C606. This evaluation was obtained by comparing sound pressure values at a frequency of 800 Hz. The evaluation results are shown in Tables 1 to 5. In this evaluation result, the evaluation result of the tire of Comparative Example 1 is indicated as 100, and the evaluation results of other tires are indicated as indexes. The evaluation result is preferably as the numerical value is larger.

  As shown in Tables 1 and 2, the tire of the example has a higher evaluation than the tire of the comparative example. From these evaluation results, the superiority of the present invention is clear.

  The invention described above can be widely applied to various tires having a main groove.

2 ... tyre 4 ... tread 6 ... side wall 8 ... clinch 10 ... bead 12 ... carcass 14 ... belt 16 ... band 18 ... inner liner 20 ... -Reinforcing rubber member 22 ... Tread surface 24 ... Main groove 25 ... Block 26 ... Core 28 ... Apex 30 ... Carcass ply 32 ... Inner layer 34 ... Outer layer 36 ... Reinforcing layer 38 ... Cord 40 ... Topping rubber

Claims (8)

A tread whose outer surface forms a tread surface, a pair of sidewalls each extending substantially inward in the radial direction from the end of the tread, a pair of beads each positioned radially inward of the sidewalls, and a tread and sidewalls A carcass extending between one bead and the other bead along the inner side, a belt laminated with the carcass on the inner side in the radial direction of the tread, and a reinforcing rubber member positioned on the outer side in the radial direction of the belt And
A main groove extending in the circumferential direction is formed on the tread surface,
The main groove has a bottom surface facing radially outward,
This reinforcing rubber member is located on the radially inner side of the bottom surface of the main groove and on the radially outer side of the belt, and extends in the circumferential direction, and has one end and the other end of the bottom surface of the main groove in the axial direction. Located between the inside and
The radial outer end width Wc of the reinforcing rubber member is smaller than the bottom width Wb in the axial direction of the main groove,
The axial width of the reinforcing rubber member is increased from the radially inner end width Wd toward the radially outer end width Wc.
A pneumatic tire in which the complex elastic modulus E ^* _{r of the} reinforcing rubber member is larger than the complex elastic modulus E ^* _{t of the} tread.   The pneumatic tire according to claim 1, wherein the reinforcing rubber member constitutes a part of the bottom surface of the main groove.   The tire according to claim 1 or 2, wherein a ratio Wc / Wd between a radial outer end width Wc and a radial inner end width Wd of the reinforcing rubber member is set to 1.4 or less. The ratio Ws / Wb between the axial displacement Ws between the center line Lr of the reinforcing rubber member and the center line Lg of the main groove and the bottom width Wb of the main groove is 0.2 or less. The tire according to any one of the above. The ratio E ^* _r / E ^* _t between the complex elastic modulus E ^* _{r of the} reinforcing rubber member and the complex elastic modulus E ^* _t of the tread is set to 1.3 or less. The described tire.   The tire according to any one of claims 1 to 5, wherein a ratio Wb / Wa between the opening width Wa of the main groove and the bottom width Wb of the main groove is 0.1 or more and 1.0 or less.   The tire according to any one of claims 1 to 6, wherein a ratio Wc / Wb between a radial outer end width Wc of the reinforcing rubber and a bottom surface width Wb of the main groove is 0.05 or more and 0.4 or less.   The tire according to any one of claims 1 to 7, wherein a ratio Wa / Wt between the opening width Wa of the main groove and the tread width Wt is 0.05 or more and 0.2 or less.

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