JP4138711B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire that can reduce road noise without impairing high-speed durability.

  One of the tire noises is so-called road noise that produces a “go” sound in the frequency range of about 50 to 400 Hz when traveling on the road surface. One of the main causes is the resonance of air generated in the tire lumen. Vibration (cavity resonance) is known. Therefore, for example, the applicant of the present application has proposed that a long band-shaped noise control body a made of a sponge material is stuck in the circumferential direction on the tire lumen surface under the tread (for example, as shown in FIG. 4). (See Patent Documents 1 and 2).

  Since the sound damper a has vibration-proofing properties and sound-absorbing properties, the resonance sound energy (vibration energy) generated in the tire cavity can be absorbed and relaxed, and the cavity resonance can be effectively suppressed. In addition, because it is fixed to the tire lumen surface under the tread, the rim assembly performance is not impaired, and the noise suppression body a moves during traveling, and the friction between the noise suppression bodies and the tire lumen surface, Since no collision occurs, there is an advantage that the durability of the sound control body a itself can be improved.

JP 2003-063208 A JP 2003-252003 A

  However, such a sound control body a is not particularly problematic for a normal tire whose maximum speed is lower than the H range (210 km / h), but for example, V, W, Y having a maximum speed of 240 km / h or more. It has been found that the high-speed durability of the tires for high-speed running in the ZR range is reduced.

  Here, the continued high speed running causes large distortion and internal heat generation in each part of the tire, and increases the temperature inside the tire as the running speed increases. When the internal temperature of the tire exceeds a certain critical temperature, thermal deterioration of the rubber is promoted, and damage such as so-called cord loose in which the carcass cord, the belt cord and the like peel from the rubber starts to occur. At this time, since the sponge material described above is a heat storage body that stores heat, if it is attached to the tread lumen surface, the temperature of the portion is greatly increased, and high speed durability due to damage such as cord loose is achieved. Cause a drop.

  In particular, the sound absorber a is preferably stuck on the tire equator C from the viewpoint of the weight balance of the tire. However, in the above-described tire for high-speed running, the tire equator is usually used for the purpose of improving the steering stability. A tread pattern in which circumferential ribs are formed on C is employed. Therefore, in the vicinity of the tire equator, the heat storage action by the circumferential rib itself and the heat generation action by the grounding are also large. Moreover, in the vicinity of the tire equator, due to the increase in weight due to the noise control body a, the centrifugal force received during high-speed driving increases, the heat generation becomes larger, for example, the contact pressure is increased unevenly, and the reduction in the high-speed durability is more remarkable Will be generated.

  Therefore, the present invention is based on the provision of a radial groove on the outer surface of the tread portion extending in the circumferential direction on the tire equator, and can dissipate the heat stored by the sound absorber, and also affects the centrifugal force during high-speed running. The purpose of the present invention is to provide a pneumatic tire that can effectively suppress the increase in contact pressure due to the noise and the accompanying heat generation, and maintain the high-speed durability while ensuring the road noise reduction effect by the noise control body. Yes.

In order to achieve the above-mentioned object, the invention of claim 1 of the present application is directed to a tire body having a carcass extending from a tread portion to a bead core of a bead portion through a sidewall portion, and bonded to the tire lumen surface on the tire equator. In addition to having a sound control body made of sponge material extending in the circumferential direction,
Wherein the tire body, the outer surface of the tread portion, extends over the tire equator in the circumferential direction and the braking sound body radiating heat to the heat storage, the groove depth d is formed over the radiation sources grooves 4.0 mm,
This radiation groove is characterized in that its cross-sectional area S satisfies the following formula (1) .
S ≧ (M1 + M2) / G · D · π −−−− (1)
(In the formula, M1 is the mass of the damping body, M2 is the mass of the adhesive, G is the specific gravity of the tread rubber, D is the tire outer diameter on the tire equator, and π is the circumference)

The invention according to claim 2 is characterized in that the ratio K determined by the following equation (2) is 1.5 or less in the radiation groove .
K = S / {(M1 + M2) / G · D · π} (2)

The invention of claim 3, wherein the radiation-groove, the groove depth d, is characterized in that not more than 2.5 times the groove width W.

  Since the present invention is configured as described above, it can dissipate the heat stored by the noise control body, and can effectively suppress the increase in ground pressure due to the centrifugal force during high-speed traveling and the accompanying heat generation. sell. As a result, it is possible to maintain high-speed durability while sufficiently ensuring the road noise reduction effect of the sound control body.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view showing a rim assembly state of the pneumatic tire of the present invention.

  In FIG. 1, a pneumatic tire 1 includes a tire body 10 that is a tubeless tire, and a sound damper 11 made of a sponge material that is bonded to the tire lumen surface 10S.

  In the present example, the tire body 10 is a tire for a high-speed passenger car having a speed symbol of the W range or higher, and includes a tread portion 2 that contacts the road surface and a pair of sides extending radially inward from both ends. The wall part 3 and the bead part 4 located in the radial direction inner end of each side wall part 3 are provided. The tire body 10 is provided with a carcass 6 spanned between the bead portions 4 and 4 and a belt layer 7 wound in the circumferential direction inside the tread portion 2 and radially outside the carcass 6. The

  The carcass 6 is formed of one or more, for example, one carcass ply 6A in which organic fiber carcass cords are arranged at an angle of, for example, 75 to 90 ° with respect to the tire circumferential direction. Includes a folded portion 6b that is folded and locked around the bead core 5 on both sides of the ply main body portion 6a that extends from the tread portion 2 through the sidewall portion 3 to the bead core 5 of the bead portion 4.

  The belt layer 7 is composed of, for example, two or more belt plies 7A and 7B in which steel belt plies are arranged at an angle of, for example, 10 to 35 ° with respect to the tire circumferential direction. By crossing between the plies, the belt rigidity is increased, and the tread portion 2 is strongly reinforced with a tagging effect. A band layer 8 in which a band cord of organic fibers is spirally wound in the tire circumferential direction can be disposed on the outer side of the belt layer 7 for the purpose of improving steering stability.

  Further, an inner liner rubber layer 9 made of a low air permeability rubber and forming the tire cavity surface 10S is attached inside the carcass ply 6A.

  Next, the noise control body 11 has a long band shape made of a sponge material, is bonded to the tire lumen surface 10S, and extends on the tire equator C in the circumferential direction.

  The sponge material is a sponge-like porous structure, for example, in addition to the so-called sponge itself having open cells in which rubber or synthetic resin is foamed, animal fibers, plant fibers or synthetic fibers are entangled and integrally connected. Includes web-like ones. The “porous structure” includes not only open cells but also closed cells. Preferably, a synthetic resin sponge such as an ether polyurethane sponge, an ester polyurethane sponge, or a polyethylene sponge, a rubber sponge such as a chloroprene rubber sponge (CR sponge), an ethylene propylene rubber sponge (EDPM sponge), or a nitrile rubber sponge (NBR sponge). Among them, a polyurethane or polyethylene-based sponge including an ether-based polyurethane sponge is particularly preferable from the viewpoints of sound damping property, light weight, foaming controllability, durability, and the like.

  Such a sponge material has high vibration proofing and sound absorbing properties, so it can effectively absorb and mitigate resonance sound energy (vibration energy) generated in the tire lumen and reduce road noise by suppressing cavity resonance. And can be controlled. Further, since the sponge material is easily deformed such as contraction and bending, it does not affect the rim assembly property and the steering stability.

  The sponge material preferably has a specific gravity of 0.005 to 0.060. When the sponge material is out of this range, the effect of suppressing cavity resonance tends to decrease in terms of the pore ratio. From such a viewpoint, the lower limit value of the specific gravity is more preferably 0.010 or more, more preferably 0.016 or more, and the upper limit value is preferably 0.050 or less, more preferably 0.035 or less. In addition, by making the specific gravity low in this way, adverse effects on the tire weight balance can be suppressed to a low level.

  The cross-sectional shape of the sound damper 11 is not particularly limited, but a rectangular shape as in this example or a trapezoidal shape with a narrow inner peripheral side in the radial direction is preferable from the viewpoint of posture stability at the time of bonding. However, a triangular shape with a sharp inner peripheral side in the radial direction is not preferable because it reduces the road noise reduction effect. Further, it is preferable that the sound control body 11 has a higher height ha from the viewpoint of road noise reduction effect. However, if the height is too high, the posture stability at the time of adhesion tends to be lost and it tends to fall down. A range of 30 to 160%, more preferably 50 to 120% of the width Wa is preferable.

  Here, the volume V2 of the sound control body 11 is in the range of 0.4 to 20% of the total volume V1 of the tire lumen surrounded by the pneumatic tire 1 and the rim, as in the case of Patent Document 1. It is preferable to set the ratio, and if the ratio V2 / V1 is less than 0.4%, the effect of suppressing the cavity resonance is not sufficiently exhibited. On the other hand, if the ratio V2 / V1 exceeds 20%, the effect of suppressing the cavity resonance reaches its peak, and an unnecessary increase in cost is caused.

The “volume V2” is an apparent volume determined from the outer shape of the sound control body 11, and includes the volume occupied by the internal bubbles. Further, “the total volume V1 of the tire lumen” is determined as a value V1 approximately obtained by the following equation (1) in a state where a normal internal pressure is filled in the tire assembled with the rim.
V1 = A × {(Di−Dr) / 2 + Dr} × π (1)
In the formula, “A” is the tire lumen area obtained by CT scanning of the tire lumen in the normal internal pressure filling state, “Di” is the maximum outer diameter of the tire lumen in the normal internal pressure filling state, and “Dr” is The rim diameter, “π”, is the circumference ratio. The “regular internal pressure” is the air pressure determined by each standard for each tire in the standard system including the standard on which the tire is based. The maximum air pressure is specified for JATMA, and the table “TIRE LOAD LIMITS” for TRA. The maximum value described in “AT VARIOUS COLD INFLATION PRESSURES” is “INFLATION PRESSURE” if it is ETRTO.

  The sound damper 11 has a substantially constant cross-sectional shape and extends in the tire circumferential direction. Since it is “substantially”, both end portions 11e in the circumferential direction of the sound damper 11 may be tapered as shown in FIG. The length of the sound damper 11 in the tire circumferential direction is also restricted by the cross-sectional shape, volume V2, and the like. When the circumferential length is represented by a circumferential angle α in the tire circumferential direction, the passenger car In the case of a tire for use, it is preferably 300 to 360 °, more preferably 350 to 360 °. In the case of 360 °, it is preferable to connect the both end portions 11e with an adhesive from the viewpoint of suppressing friction between the end portions.

  Further, the adhesive for adhering the sound damper 11 to the tire lumen surface 10S is not particularly restricted, and various synthetic rubber materials can be used, for example. A tape can be suitably employed.

However, when such a noise control body 11 is attached along the tire equator C, particularly in a passenger car tire for high-speed traveling with a speed symbol of the W range or higher, in the vicinity of the tire equator,
(A) Heat is stored by the sound control body 11; and (b) Due to the weight increase by the sound control body 11, the centrifugal force received during high speed travel increases, increasing the ground pressure and increasing heat generation;
Due to this phenomenon, the temperature rises remarkably, and there is a problem that the high-speed durability of the tire is lowered.

  Therefore, in the present invention, as shown in an enlarged view in FIG. 3, a radiation groove 20 extending in the circumferential direction on the tire equator C is formed on the outer surface of the tread portion 2.

  The radiation groove 20 can suppress a temperature rise near the tire equator due to a heat dissipation effect due to an increase in surface area. Further, since the rubber amount of the tread rubber corresponding to the groove volume is reduced, it can be offset with the weight of the sound control body 11, the increase of the centrifugal force can be suppressed, and the heat generated due to the increase of the ground pressure can be reduced. . And by these interactions, the temperature rise in the vicinity of the tire equator associated with the sound damper 11 can be suppressed, and excellent high-speed durability can be ensured. In addition, uneven wear resistance performance can be improved, such as suppressing uneven wear near the tire equator that occurs as the ground pressure increases.

Thus in order to sufficiently exhibit the can effects, Ru is satisfied the following equation (1) in the radiation-groove 20.
S ≧ (M1 + M2) / G · D · π −−−− (1)
(In the formula, S is the cross-sectional area S of the radiation groove 20, M1 is the mass of the sound control body 11, M2 is the mass of the adhesive, G is the specific gravity of the tread rubber, D is the tire outer diameter on the tire equator C, π is the circumference)

That is, the mass of the tread rubber that is removed by the formation of the radiation groove 20 is set to be larger than the mass that is increased by the adhesion of the noise control body 11. As a result, the heat dissipation effect and the effect of suppressing the increase in contact pressure due to the increase in centrifugal force can be sufficiently exerted, and the above-mentioned high-speed durability can be ensured and uneven wear resistance can be improved. If the cross-sectional area S of the radiation groove 20 is too large, other tire performance including steering stability may be reduced. Therefore, the ratio K determined by the following equation (2) is 1.5 or less, and further 1 .2 or less is preferable.
K = S / {(M1 + M2) / G · D · π} (2)

  Further, in the radiation groove 20, it is preferable to form the groove depth d as deep as 4.0 mm or more from the viewpoint of heat dissipation effect, and from the viewpoint of tire mold strength and mold cost, the groove width W It is preferably 2.5 times or less. That is, a range of 2.5 W ≧ d ≧ 4.0 mm is preferable. The groove width W is a value measured on the outer surface of the tread portion 2, and the groove width W is generally 20.0 mm or less from the viewpoint of steering stability.

  In the tire 1, the entire radiation groove 20 is preferably formed in the width region Y of the noise control body 11 from the viewpoint of heat dissipation effect and suppression of increase in centrifugal force. More preferably, the groove center and the width center of the sound control body 11 coincide. It should be noted that a part of the radiation groove 20 only needs to pass on the tire equator C, but the center of the groove preferably passes on the tire equator C, and a part of the sound absorber 11 also has the tire equator C. Although it is possible to pass above, it is preferable that the center of the width passes on the tire equator C. The radiation groove 20 is preferably a straight groove, but a zigzag groove can also be adopted. In such a case, the zigzag center is defined as the groove center.

  Further, in this example, the tire 1 has inner longitudinal main grooves 21 extending in the tire circumferential direction on both sides of the tire equator C, and the distance L between the center of the longitudinal main grooves 21 is set to In this case, the radiation groove 20 can exhibit a higher effect.

  As mentioned above, although especially preferable embodiment of this invention was explained in full detail, this invention is not limited to embodiment of illustration, It can deform | transform and implement in a various aspect.

  A radial tire for a passenger car having a tire size 215 / 45R17 having the structure shown in FIG. 1 was prototyped according to the specifications shown in Table 1, and the noise performance and high-speed durability of the sample tire were evaluated.

The sound control body 11 uses an ether polyurethane sponge having a specific gravity of 0.016 (Marubell Co., Ltd., product number E16), has a rectangular cross-sectional shape with a height ha of 24 mm, a width Wa of 60 mm, and both ends in the length direction. The part was sharply cut at an angle of 45 ° as shown in FIG. The length of the sound control body 11 is substantially 358 ° in terms of the circumferential angle α. In each example, the volume V2 of the sound control body 11 is the same (2635 cm ³ ). The total volume V1 of the tire lumen is 35320 cm ³ , and the ratio V2 / V1 is 10.4%. The sound control body 11 and the tire body 10 were bonded using a double-sided adhesive tape (5000 NS manufactured by Nitto Denko Corporation). The mass M1 of the noise control body 11 was 42.2 g, and the mass of the adhesive was 19.9 g.

(1) Noise performance:
A sample tire is mounted on all wheels of a vehicle (a domestic 2500cm ³ FR vehicle) under the conditions of a rim (17 × 7JJ) and internal pressure (200kPa), and a road noise measurement road (asphalt rough road) with one passenger. Ran at a speed of 60 km / h. The vehicle interior noise at that time was measured at the driver's seat window side ear position, and the sound pressure level of the peak value of the air column resonance sound in the vicinity of 240 Hz was shown as an increase / decrease value based on Comparative Example 1. A + (plus) display means an increase in road noise.

<High speed durability>
In accordance with the load / speed performance test defined by ECE30 using a drum tester, the test was performed by the step speed method. In the test, the running speed was sequentially increased, and the speed (km / H 2) and time (minutes) when the tire broke down were measured.

  As shown in the table, the tires of the examples improved the high-speed durability as compared with the tires of Comparative Example 1 that did not form a radiation groove on the tire equator while sufficiently exhibiting the road noise reduction effect by the sound absorber. Can be confirmed. In particular, in the tire of Example 1, it can be confirmed that the high-speed durability can be improved to the same level as that of a conventional tire without a sound-damping member.

It is sectional drawing which shows one Example of the pneumatic tire of this invention. It is a circumferential direction sectional view of a pneumatic tire. It is sectional drawing which expands and shows a radiation groove with a sound control body. It is sectional drawing of the tire explaining background art.

Explanation of symbols

2 Tread part 3 Side wall part 4 Bead part 5 Bead core 6 Carcass 10 Tire body 11 Sound control body 20 Radiation groove C Tire equator

Claims (3)

A tire body having a carcass extending from the tread portion through the sidewall portion to the bead core of the bead portion, and a sound absorber made of a sponge material bonded to the tire inner surface and extending in the circumferential direction on the tire equator ,
Wherein the tire body, the outer surface of the tread portion, extends over the tire equator in the circumferential direction and the braking sound body radiating heat to the heat storage, the groove depth d is formed over the radiation sources grooves 4.0 mm,
The pneumatic tire is characterized in that the cross-sectional area S satisfies the following expression (1) .
S ≧ (M1 + M2) / G · D · π −−−− (1)
(In the formula, M1 is the mass of the damping body, M2 is the mass of the adhesive, G is the specific gravity of the tread rubber, D is the tire outer diameter on the tire equator, and π is the circumference) The pneumatic tire according to claim 1 , wherein the radiation groove has a ratio K determined by the following expression (2) of 1.5 or less .
K = S / {(M1 + M2) / G · D · π} (2) The radiation-groove, pneumatic tire according to claim 1 or 2, characterized in that the groove depth d than 2.5 times the groove width W.

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