JP4921786B2 - 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, as shown in FIG. 6, the applicant of the present application has proposed that a long band-shaped sound absorber a made of a sponge material is stuck to the inner surface of the tread portion (hereinafter referred to as the inner surface of the tread) in the circumferential direction. (For example, see Patent Documents 1 and 2). Since the sound damper a has vibration-proofing properties and sound-absorbing properties, it can absorb and mitigate resonance sound energy (vibration energy) generated in the tire lumen, and effectively suppress the cavity resonance. In addition, because it is fixed to the inner surface of the tread, the performance of the rim assembly is not impaired, and the noise control body a moves during traveling, so that friction between the noise control bodies, friction with the tire cavity surface, and collision do not occur. There is also 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 noise control body a is not particularly problematic for normal tires having a maximum speed notation lower than the H range (210 km / h), but the maximum speed is 240 km / h or more, for example, V, W, It has been found that the tires for high speed running in the Y and ZR ranges tend to reduce the high speed durability. The continued high speed travel causes large distortion and internal heat generation in each part of the tire, and increases the temperature inside the tire as the travel 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 heat of that portion is not easily dissipated to the tire lumen side. As a result, it is considered that a rapid temperature rise occurs in the portion where the sponge material is provided, and the high-speed durability is lowered due to damage such as cord loose.

  On the other hand, in the above-mentioned sound control body a, it is preferable to stick on the tire equator C from the viewpoint of the weight balance of the tire. However, in the tire for high-speed running described above, the tire is usually used for the purpose of improving the steering stability. A tread pattern in which circumferential ribs are formed on the equator C is employed. Therefore, in the vicinity of the tire equator, the temperature is high due to the heat storage effect of the circumferential rib itself. Therefore, when the noise control body a is stuck on the tire equator of such a tire, the contact pressure on the circumferential rib is increased due to an increase in centrifugal force due to an increase in weight due to the sound control body a when traveling at high speed. Increases unevenly. As a result, the heat generation becomes larger, the deterioration of the high-speed durability is more remarkably generated, and uneven wear such as so-called center wear in which the circumferential rib itself wears out at an early stage is induced, so that the steering stability during high-speed running is stabilized. The problem of reducing the performance occurs.

  Therefore, the present invention forms a tire body with a double-sectioned cross section having a heat radiating recess opening toward the inside of the tire lumen and a crest disposed on both sides in the tire axial direction as a sound damper. On the outer surface of the tread, on the basis of providing a pair of circumferential grooves through which the groove width center line passes through each peak portion of the sound absorber, high-speed durability can be improved while ensuring a road noise reduction effect, and An object of the present invention is to provide a pneumatic tire capable of suppressing uneven wear such as so-called center wear and suppressing a decrease in steering stability during high speed running.

In order to achieve the object, the invention of claim 1 of the present application includes a tire body having a carcass extending from a tread portion to a bead core of a bead portion through a sidewall portion, and a fixing surface bonded to the inner surface of the tread portion. And a sound control body made of a sponge material extending in the circumferential direction on the tire equator,
The sound damping body has a heat radiating recess that opens toward the inside of the tire lumen and extends in the circumferential direction on the equator, and is disposed on both sides in the tire axial direction of the heat radiating recess and in the tire than the groove bottom of the heat radiating recess. Including a mountain that rises in the cavity and extends in the circumferential direction,
Said tire body, the outer surface and the tire equator both sides of the tread portion, the circumferential groove Ga extending as the tire circumferential direction of each crest of the groove width center line the noise damper, set the Gb,
The circumferential grooves Ga and Gb are characterized in that a ratio K determined by the following equation (1) is set to 1.2 or more and 3.2 or less.
K = (Sa + Sb) / {(M1 + M2) / (G × D × π)} --- (1)
(Where, Sa and Sb are the cross-sectional areas of the circumferential grooves Ga and Gb, M1 is the total mass of the sound control body, M2 is the total mass of the adhesive, G is the specific gravity of the tread rubber, and D is the tire equator. Tire outer diameter, π is the circumference ratio.)

In the invention of claim 2, the circumferential grooves Ga and Gb have groove depths da and db of 4.0 mm or more, respectively, and the ratio between the groove depths da and db and the groove widths Wa and Wb. It is characterized in that da / Wa and db / Wb are each 2.5 or less.

  As described above, the present invention includes, as a sound control body, a heat radiating recess that opens toward the inside of the tire lumen and extends in the circumferential direction on the tire equator, and peaks that are arranged on both sides in the tire axial direction. The cross section is formed in a double mountain shape. Therefore, the heat storage effect of the heat radiating recess can reduce heat storage of the sound damper itself.

  In addition, circumferential grooves are formed on the outer surface of the tread portion and on both sides of the tire equator so that the groove width center line passes through the peak portions of the sound absorber. This can be reduced by reducing the weight of the tread rubber by the groove. In other words, it is possible to reduce the influence of an increase in centrifugal force during high-speed running caused by the sound control body, and to suppress an increase in contact pressure near the tire equator. Therefore, the heat generation near the tire equator due to the increase in the contact pressure can be suppressed, and the high-speed durability can be improved in combination with the heat storage reducing effect of the sound control body itself by the heat radiating recess. Further, uneven wear (center wear) near the tire equator due to the increase in the contact pressure can be suppressed, and high steering stability during high speed running can be maintained.

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 sponge material that is bonded to an inner surface Si (hereinafter referred to as a tread inner surface Si) of a tread portion 2 and extends on the tire equator in the circumferential direction. And a sound control body 11.

  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. Further, the tire body 10 is provided with a carcass 6 spanned between the bead portions 4 and 4, and a belt layer 7 disposed inside the tread portion 2 and on the radially outer side of the carcass 6.

  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 sound absorber 11 is made of a long band-like sponge material extending in the tire circumferential direction, and is adhered and fixed to the inner surface Si of the tread so that the sound absorber 11 is in the tire lumen during traveling. In addition to hindering the free movement of the sound control body 11, the damage of the sound control body 11 is prevented, and the resonance suppression effect is stably exhibited.

  The sponge material constituting the sound control body 11 is a sponge-like porous structure. For example, in addition to a so-called sponge having open cells obtained by foaming rubber or synthetic resin, animal fibers, plant fibers, or synthetic fibers are used. Includes webs that are intertwined and connected together. 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). Polyurethane sponges, particularly ether-based polyurethane sponges, are particularly preferred from the viewpoints of sound damping, 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.

  The sponge material preferably has a specific gravity of 0.005 to 0.060. If 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 point of view, the lower limit of the specific gravity is 0.010 or more, more preferably 0.016 or more, and the upper limit is 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 kept low.

  The volume V2 of the sound control body 11 is preferably set in a range of 0.4 to 20% of the total volume V1 of the tire lumen. As described in the above-mentioned Patent Document 1, by securing 0.4% or more of the volume V2 of the sound control body 11 with respect to the total volume V1 of the tire lumen, a remarkable load of approximately 2 dB or more is obtained. A noise reduction effect can be expected. This noise reduction level can be said to be a value that can be clearly confirmed in the passenger compartment. From such a viewpoint, preferably, the volume V2 of the sound damper 11 is 1% or more, more preferably 2% or more, more preferably 4% or more of the total volume V1 of the tire lumen. On the other hand, if the volume V2 of the noise control body 11 exceeds 20% of the total volume V1 of the tire lumen, the effect of reducing road noise will reach its peak, and the cost may be increased or the tire weight balance may be deteriorated. . From this point of view, the volume V2 of the sound damper 11 is particularly preferably 15% or less, more preferably 10% or less of the total volume V1 of the tire lumen.

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. The “total tire lumen volume V1” is determined as a value V1 approximately obtained by the following equation (1) in a state in which a normal internal pressure is filled in a tire assembled with a rim.
V1 = A × {(Di−Dr) / 2 + Dr} × π (1)
In the formula, “A” is the tire lumen area obtained by CT scanning 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 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. “Substantially” means that, as shown in FIG. 2, the two outer end portions 11e in the circumferential direction of the sound damper 11 have a high cross-sectional height for the purpose of preventing adhesion peeling from the outer end portion 11e. This is because there is a case where a taper portion gradually decreasing is formed, and “substantially” allows such a shape change in the outer end portion 11e. The length of the sound damper 11 in the tire circumferential direction is also restricted by the volume V2 and the like, but when the circumferential length is represented by a circumferential angle α in the tire circumferential direction, In this case, the angle is preferably 300 to 360 °, more preferably 350 to 360 °. In the case of 360 °, it is preferable that the outer end portions 11e are connected to each other with an adhesive from the viewpoint of suppressing rubbing between the end portions.

  The adhesive for adhering the sound damper 11 to the inner surface Si of the tread is not particularly restricted. For example, various synthetic rubber-based adhesives can be used. A tape can be suitably employed.

  Next, as shown in FIG. 3, the cross-sectional shape of the sound damper 11 includes a fixed surface 11L bonded to the inner surface of the tread and an upper surface 11U facing inward of the tire lumen, and on the upper surface 11U side. A heat radiation recess 20 that opens toward the inside of the tire lumen and extends in the circumferential direction on the tire equator C, and is disposed on both sides in the tire axial direction of the heat radiation recess 20 and is closer to the tire than the groove bottom 20S of the heat radiation recess 20 It has a two-section cross section provided with ridges 21 and 21 that protrude inwardly in the lumen and extend in the circumferential direction.

  Such a sound damper 11 enhances the heat dissipation effect by increasing the surface area due to the heat radiating recess 20 and dividing the thick-walled portion to store heat to the left and right, and effectively suppresses the heat storage action of the sound damper 11. it can. At this time, the maximum value Tm of the thickness T from the fixed surface 11L of the mountain portion 21 is in the range of 20 to 50 mm, and the width W1 in the tire axial direction of the fixed surface 11L is greater than the maximum value Tm of the thickness. It is preferable to have a large flat horizontal shape, which stabilizes the posture of the sound damper 11 after bonding, and prevents the sound damper 11 from falling or being peeled off during traveling. The thickness Ti from the fixed surface 11L of the groove bottom 20S of the heat radiation recess 20 is preferably 1.0 mm or more and 50% or less of the maximum value Tm of the thickness, and if it is less than 1.0 mm, the strength is insufficient. The heat dissipation effect exceeding 50% is remarkably reduced, and heat storage cannot be sufficiently suppressed.

  Here, it is sufficient that the sound damping body 11 has the tire equator C passing through a part of the heat radiating recess 20, but preferably the tire equator C and the width center J of the heat radiating recess 20 are matched. The cross-sectional shape of the sound damper 11 is preferably formed in a bilaterally symmetric shape with the width center J as the center from the viewpoint of the weight balance of the tire. In this example, the upper surface 11U extends along a wavy curve 12 in which peaks and troughs are alternately repeated, and the upper surface 11U is formed by two pitches of the wavy curve 12. Thereby, the manufacturing efficiency of the sound control body 11 can be improved. The wavy curve 12 is more preferably a trapezoidal wave shape combining straight lines from the viewpoint of manufacturing efficiency, but may be a sine wave curve, for example.

  Next, when the noise control body 11 is bonded onto the tire equator C, particularly in a high-speed passenger car tire having a speed symbol of the W range or higher, the centrifugal force due to the weight of the sound control body 11 is increased during high-speed driving. The impact will increase. As a result, the contact pressure in the vicinity of the tire equator is increased, the amount of heat generation is increased and the high-speed durability is lowered, and at the same time, the center wear is caused and the steering stability is lowered.

  Therefore, in the present invention, circumferential grooves Ga and Gb for adjusting the centrifugal force extending in the tire circumferential direction are further formed on the outer surface So of the tread portion 2 and both sides of the tire equator C. The circumferential grooves Ga and Gb reduce the rubber amount of the tread rubber corresponding to the groove volume, so that they can be offset with the weight of the sound control body 11, suppressing an increase in centrifugal force and suppressing an increase in ground pressure. can do. Further, by forming the circumferential grooves Ga and Gb, the surface area is increased and the heat dissipation effect can be exhibited. For this purpose, it is necessary that the groove width center lines ia and ib of the circumferential grooves Ga and Gb pass through the peak portions 21 and 21 of the sound damping body 11, respectively.

In order to sufficiently exhibit such an effect, the ratio K determined by the following equation (1) is set to 1.2 or more.
K = (Sa + Sb) / {(M1 + M2) / (G × D × π)} ---- (1)
In the formula (1), Sa and Sb are the cross-sectional areas of the circumferential grooves Wa and Wb, M1 is the total mass of the sound damper, M2 is the total mass of the adhesive, G is the specific gravity of the tread rubber, and D is the tire. The tire outer diameter on the equator, π, means the circumference. That is, the mass of the tread rubber removed by forming the circumferential grooves Ga and Gb is set to be larger than 1.2 times the mass increased by the sound control body 11. Thereby, the heat dissipation effect by circumferential direction groove | channel Ga and Gb and the suppression effect of the ground-pressure rise resulting from the increase in centrifugal force can fully be exhibited. And by the synergistic effect of lowering the heat storage property of the sound absorber 11 itself forming the heat radiating recess 20 in the sound absorber 11, the temperature rise in the vicinity of the tire equator is suppressed and the high speed durability is improved. sell. Further, center wear can be suppressed, and a decrease in steering stability can also be suppressed.

In the circumferential grooves Ga and Gb, if the cross-sectional areas Sa and Sb are too large, other tire performances including steering stability may be reduced. Therefore, the ratio K determined by the above equation (1) is 3.2 or less. Set to.

Further, in the circumferential grooves Ga and Gb, it is preferable to form the groove depths da and db as deep as 4.0 mm or more from the viewpoint of the heat dissipation effect, and from the viewpoint of the mold strength of the tire and the mold cost. Therefore, the ratios da / Wa and db / Wb between the depths da and db and the groove widths Wa and Wb are preferably 2.5 or less, respectively. That is,
2.5 Wa ≧ da ≧ 4.0 mm,
2.5 Wb ≧ db ≧ 4.0 mm,
The range of is preferable. The groove widths Wa and Wb are values measured on the outer surface of the tread portion 2, and the groove widths Wa and WbW are preferably 20.0 mm or less from the viewpoint of steering stability.

  In the tire 1, the entire circumferential grooves Ga and Gb are formed between the radial lines n and n passing through both ends in the tire axial direction of the mountain portion 21, so that the heat dissipation effect and the increase in centrifugal force are suppressed. From the viewpoint of Further, as shown in FIG. 4D, the tire 1 may have an asymmetric pattern in which the distances of the groove width center lines ia and ib from the tire equator C are different from each other in the circumferential grooves Ga and Gb. 1 and 3, the groove width center lines ia and ib may be symmetrical patterns in which the distances from the tire equator C are equal to each other. Further, as shown in FIG. 4E, a circumferential groove Gc may be formed between the circumferential grooves Ga and Gb, preferably on the tire equator C. In such a case, the depth dc and the groove width Wc of the circumferential groove Gc are formed in a narrow groove shape that is smaller than the groove depths da and db and the groove widths Wa and Wb of the circumferential grooves Ga and Gb. It is preferable to do this.

  The circumferential grooves Ga and Gb are preferably linear grooves, but zigzag grooves can also be used. In such a case, zigzag centers are defined as groove width center lines ia and ib.

  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 high-speed durability of the sample tire was evaluated.

In addition, as shown in FIG. 4 (A), Comparative Example 1 has an A type sound absorber with a rectangular cross section adhered on the tire equator C, and circumferential grooves Ga, Gb on both outer sides of the sound absorber. Is forming. Further, in Comparative Example 2, as shown in FIG. 4 (B), a B-type noise control body having a double cross section is adhered on the tire equator C, and a circumferential groove Gc is formed only on the tire equator C. ing. In Example 1, as shown in FIG. 4C, the B-type sound absorber is bonded onto the tire equator C, and the circumferential groove Ga is formed at a symmetrical position on the mountain 21 and the tire equator. , Gb.
In Example 2, as shown in FIG. 4 (D), the B-type sound absorber is bonded onto the tire equator C, and the circumferential groove Ga is formed at the asymmetrical position on the mountain 21 and the tire equator. , Gb. In Example 3, as shown in FIG. 4 (E), the B-type sound absorber is bonded onto the tire equator C, the symmetrical position about the tire equator C and the tire equator, and the tire equator C. Circumferential grooves Ga, Gb, and Gc are formed thereon. In Examples 4 to 7, the groove volumes of the circumferential grooves Ga and Gb are changed in the aspect of Example 1.

  In addition, while using an ether polyurethane polyurethane sponge with a specific gravity of 0.039 made by INOAC (model number ESH2) as the sponge material of the sound control body, it was adhered to the inner surface of the tread using a double-sided adhesive tape made by Nitto Denko (model number 5000NS). . In addition, the A-type sound absorber has a cross-sectional dimension shown in FIG. 5A, and the B-type sound absorber has a cross-sectional dimension shown in FIG. 5B.

<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.

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 the circumferential groove | channel with a sound control body. (A)-(E) are the partial examples which show the comparative example of Table 1, and the tire of an Example. (A), B is sectional drawing which shows the cross-sectional dimension of the A type and B type noise control body used by the comparative example of Table 1, and an Example. 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 main body 11 Sound control body 20 Heat radiation recessed part C Tire equator

Claims (2)

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 sponge material having a fixing surface bonded to the inner surface of the tread portion and extending in the circumferential direction on the tire equator. With sound body,
The sound damping body has a heat radiating recess that opens toward the inside of the tire lumen and extends in the circumferential direction on the equator, and is disposed on both sides in the tire axial direction of the heat radiating recess and in the tire than the groove bottom of the heat radiating recess. Including a mountain that rises in the cavity and extends in the circumferential direction,
Said tire body, the outer surface and the tire equator both sides of the tread portion, the circumferential groove Ga extending as the tire circumferential direction of each crest of the groove width center line the noise damper, set the Gb,
In the circumferential grooves Ga and Gb, a pneumatic tire is characterized in that a ratio K determined by the following equation (1) is set to 1.2 or more and 3.2 or less.
K = (Sa + Sb) / {(M1 + M2) / (G × D × π)} --- (1)
(Where, Sa and Sb are the cross-sectional areas of the circumferential grooves Ga and Gb, M1 is the total mass of the sound control body, M2 is the total mass of the adhesive, G is the specific gravity of the tread rubber, and D is the tire equator. Tire outer diameter, π is the circumference ratio.) The circumferential grooves Ga and Gb have groove depths da and db of 4.0 mm or more, respectively, and ratios da / Wa and db / Wb between the groove depths da and db and the groove widths Wa and Wb are The pneumatic tire according to claim 1, wherein each is 2.5 or less .

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