JP5280832B2 - Pneumatic tire - Google Patents

Description

The present invention relates to a pneumatic tire.

When the rigidity of the sidewall portion of the pneumatic tire for passenger cars is increased, the steering stability (responsiveness when the rudder is turned off) is improved, but the riding comfort performance is deteriorated. On the other hand, when the rigidity is lowered, the riding comfort performance is improved, but the steering stability is lowered. For this reason, conventionally, by adjusting the thickness of the rubber in the sidewall portion, both steering stability and riding comfort performance have been achieved. However, in recent years, the fuel efficiency of tires has been reduced, and the thickness of the rubber in the sidewall portion has continued to decrease, making it difficult to achieve both steering stability and riding comfort performance.

Patent Document 1 discloses a tire having a bead apex that can improve steering stability and reduce rolling resistance by optimizing a vulcanization speed when preparing a bead apex rubber. However, it has not been studied in detail about the strip apex and the improvement of riding comfort performance by using it.

Patent Documents 2 and 3 disclose a pneumatic tire in which rolling resistance is reduced by disposing a short fiber reinforcing layer in the side wall portion region. Improvement of handling stability and riding comfort has not been studied.
JP 2008-38140 A JP-A-8-175119 JP-A-9-150610

An object of the present invention is to solve the above-mentioned problems and to provide a pneumatic tire provided with a strip apex that can achieve both steering stability and riding comfort performance even when the thickness of the sidewall portion is thin.

The present invention relates to a pair of beads having a bead core and a bead apex extending radially outward from the bead core, a first ply spanned between the two beads, and a second ply disposed on the outside thereof. A pneumatic tire having a strip apex extending along the carcass, wherein the first ply extends from the equator plane toward the bead core and the bead core. A first folded portion that is folded back and extends outward in the tire radial direction is integrally formed, and the second ply is folded back by the bead core and the second main portion that extends from the equator plane toward the bead core in the radial direction. A second folded portion that extends outward is integrally formed, and the strip apex extends in the tire radial direction along the outer side of the second main portion of the second ply. With extending, loss factor (tan [delta) of 0.20 or more, a pneumatic tire is a rubber hardness of 65 or more.

In the pneumatic tire, the strip apex is preferably disposed between the second main portion of the second ply and the bead apex.

According to the pneumatic tire of the present invention, the first main portion extending toward the bead core and the first first ply having the first folded portion that is folded and extends outward in the tire radial direction, and the outer side thereof. A strip having a loss factor (tan δ) of 0.20 or more and a rubber hardness of 65 or more along the outside of the second main part of the carcass comprising the second main part and the second ply having the second folded part. Since the apex is arranged, vibration absorption performance can be imparted and riding comfort performance can be improved. At the same time, the rigidity of the tire is increased, and the steering stability (particularly high-speed steering stability) can be improved.

Hereinafter, an example of a preferred embodiment of the pneumatic tire of the present invention will be described with reference to the drawings as appropriate.
FIG. 1 is a cross-sectional view showing a part of a pneumatic tire according to an embodiment of the present invention.
In FIG. 1, the vertical direction is the tire radial direction, the horizontal direction is the axial direction, and the direction perpendicular to the paper surface is the circumferential direction. The pneumatic tire 2 has a substantially bilaterally symmetric shape around the one-dot chain line CL in FIG. An alternate long and short dash line CL represents the equator plane of the pneumatic tire 2. The pneumatic tire 2 includes a tread portion 4, a sidewall portion 6, a bead 8, a carcass 10, a belt 12, an inner liner 14, a chafer 16, and a strip apex 18. The pneumatic tire 2 is preferably used as a tire to be attached to a tubeless type passenger car.

The tread portion 4 is made of a crosslinked rubber having excellent wear resistance. The tread portion 4 has a shape protruding outward in the tire radial direction. The tread portion 4 includes a tread surface 20. The tread surface 20 is in contact with the road surface. A groove 22 is carved in the tread surface 20. A tread pattern is formed by the groove 22 which is carved. In addition, the groove 22 may not be carved in the tread portion 4.

The sidewall portion 6 extends from the end of the tread portion 4 substantially inward in the tire radial direction. The sidewall 6a that forms the sidewall portion 6 is made of a crosslinked rubber. The sidewall portion 6 absorbs an impact from the road surface by bending. Further, the sidewall portion 6 prevents the carcass 10 from being damaged.

The bead 8 is located substantially inside the tire radial direction from the sidewall portion 6. The bead 8 includes a pair of a bead core 24 and a bead apex 26 extending from the bead core 24 outward in the tire radial direction. The bead core 24 has a ring shape. The bead core 24 includes a plurality of non-stretchable wires (typically steel wires). The bead apex 26 has a shape that tapers outward in the tire radial direction. The bead apex 26 is made of a highly hard crosslinked rubber.

The carcass 10 includes a first ply 28 and a second ply 30. The first ply 28 and the second ply 30 are bridged between the beads 8 on both sides, and extend along the inside of the tread portion 4 and the sidewall portion 6. A second ply 30 is disposed outside the first ply 28.

Although not shown, the first ply 28 and the second ply 30 are composed of 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 usually 70 ° to 90 °. In other words, the carcass 10 has a radial structure. The cord is usually made of organic fibers. Examples of preferable organic fibers include polyester fibers, nylon fibers, rayon fibers, polyethylene naphthalate fibers, and aramid fibers. A carcass 10 having a bias structure may be employed.

In the pneumatic tire 2 according to the present embodiment, the first ply 28 is folded around the bead core 24 from the inner side to the outer side in the axial direction. The first ply 28 integrally includes a first main portion 32 that extends from the equator plane toward the bead core 24 and a first folded portion 34 that is folded back by the bead core 24 and extends outward in the tire radial direction. ing. The first main portion 32 is located outside the inner liner 14. A portion of the first main portion 32 on the inner side in the tire radial direction is located on the inner side in the axial direction of the bead apex 26. The first folded portion 34 is located outside the first main portion 32 in the axial direction. The first folded portion 34 is located outside the bead apex 26 in the axial direction. An end 36 of the first folded portion 34 is an end of the first ply 28.

In the pneumatic tire 2 according to the present embodiment, the second ply 30 is folded around the bead core 24 from the inner side in the axial direction toward the outer side. The second ply 30 is formed by integrating a second main portion 38 extending from the equator plane toward the bead core 24 and a second folded portion 40 folded back by the bead core 24 and extending outward in the tire radial direction. Have. The second main portion 38 is located outside the first main portion 32. A portion on the inner side in the tire radial direction of the second main portion 38 is located on the inner side in the axial direction of the bead apex 26. This portion is located between the first main portion 32 and the bead apex 26. The second folded portion 40 is located outside the second main portion 38 in the axial direction. The second folded portion 40 is located on the outer side in the axial direction of the bead apex 26. The second folding part 40 is located between the bead apex 26 and the first folding part 34. An end 42 of the second folded portion 40 is an end of the second ply 30.

In the pneumatic tire 2 according to this embodiment, the end 42 of the second folded portion 40 is located on the inner side in the tire radial direction of the end 36 of the first folded portion 34. The end 42 of the second folded portion 40 may be located on the outer side in the tire radial direction of the end 36 of the first folded portion 34.

The belt 12 is located outside the carcass 10 in the tire radial direction. The belt 12 is laminated with the carcass 10. The belt 12 reinforces the carcass 10. The belt 12 includes an inner layer 44 and an outer layer 46. Although not shown, each of the inner layer 44 and the outer layer 46 is composed of a plurality of cords arranged in parallel and a topping rubber. Each cord is normally inclined with respect to the equator plane. The absolute value of the tilt angle is preferably 10 ° to 35 °. The cord inclination direction of the inner layer 44 is opposite to the cord inclination direction of the outer layer 46. The inner layer 44 and the outer layer 46 constitute a so-called cross-ply structure. A preferred material for the cord is steel. An organic fiber may be used for the cord.

The inner liner 14 is joined to the inner peripheral surface of the carcass 10. The inner liner 14 is made of a crosslinked rubber. The inner liner 14 is usually made of rubber having excellent air shielding properties. The inner liner 14 serves to maintain the internal pressure of the pneumatic tire 2.

The chafer 16 is located in the vicinity of the bead 8. When the pneumatic tire 2 is incorporated into the rim, the chafer 16 comes into contact with the rim. By this contact, the vicinity of the bead 8 is protected. The chafer 16 is usually made of a cloth and a rubber impregnated in the cloth. A chafer 16 made of a single rubber may be used.

The pneumatic tire 2 has a strip apex 18 located on the inner side in the axial direction of the sidewall portion 6. That is, the strip apex 18 extending along the carcass 10 is provided, and the strip apex 18 extends in the tire radial direction along the outside of the second main portion 38 of the second ply 30. For this reason, it is possible to achieve both steering stability (particularly high-speed steering stability) and riding comfort performance. In this pneumatic tire 2, the strip apex 18 (in FIG. 1, the radially inner portion of the strip apex 18) is between the second main portion 38 of the second ply 30 and the bead apex 26 (second main portion). 38 in the axially outer side).

In the pneumatic tire 2, the inner end 51 located on the inner side in the tire radial direction of the strip apex 18 is located on the inner side in the tire radial direction of the tip 61 of the bead apex, and the second main portion 38 of the second ply 30 and the bead. It is sandwiched between the apex 26 and is interrupted (positioned). The outer end 52 located on the outer side in the tire radial direction of the strip apex 18 is located on the outer side in the tire radial direction of the tip 61 of the bead apex, and the second main portion 38 of the second ply 30 and the side wall portion 6. It is sandwiched between the sidewalls 6a (disposed).

In the pneumatic tire 2, the end 36 of the first folded portion 34 is positioned on the outer side in the tire radial direction of the tip 61 of the bead apex. That is, the first folded portion 34 extends outward in the tire radial direction from the bead apex 26. For this reason, the tire radial center of the strip apex 18 of the pneumatic tire 2 is located between the second main portion 38 of the second ply 30 and the first folded portion 34 of the first ply 28 ( The center portion is in contact with the first folded portion 34. Further, as described above, in the pneumatic tire 2, the inner side in the tire radial direction of the strip apex 18 is positioned (sandwiched) between the second main portion 38 of the second ply 30 and the bead apex 26, and the tire radial direction. The outer side portion is located (sandwiched) between the second main portion 38 of the second ply 30 and the sidewall 6a of the sidewall portion 6.

FIG. 2 is an enlarged cross-sectional view illustrating a part of the pneumatic tire 2 of FIG. 1, that is, a part including the strip apex 18. In FIG. 2, a double arrow line TA represents the thickness of the strip apex 18. A double arrow line LA represents the length of the portion where the strip apex 18 and the bead apex 26 overlap.

In the tire 2, the thickness TA is preferably 0.5 mm or more, more preferably 0.8 mm or more. By setting the thickness TA to 0.5 mm or more, it is possible to effectively contribute to balance adjustment between the longitudinal rigidity and the lateral rigidity, and to achieve both steering stability and riding comfort performance. Moreover, thickness TA becomes like this. Preferably it is 3.0 mm or less, More preferably, it is 2.5 mm or less. By setting the thickness TA to 3.0 mm or less, the rigidity is not too high and the ride comfort is prevented from being impaired.

In the tire 2, the length LA is preferably 10 mm or more, and preferably 20 mm or more. By setting the length LA to 20 mm or more, the rigidity can be increased, and a decrease in riding comfort is also prevented. Moreover, length LA becomes like this. Preferably it is 50 mm or less, More preferably, it is 40 mm or less. By setting the length LA to be equal to or less than 50 mm, the rigidity is appropriately maintained, and the ride comfort and steering stability are suppressed from being impaired.

In FIG. 1, a double line BBL is a bead base line. The bead base line is a line that defines a rim diameter (see JATMA) of a rim on which the tire 2 is mounted. A double arrow line H0 represents the height in the radial direction from the bead base line to the equator plane. The radial height H0 is the tire 2 height. A double arrow line HA represents the height in the radial direction from the bead base line to the outer end 52 of the strip apex 18. A double arrow line H <b> 1 represents the height in the radial direction from the bead base line to the end 36 of the first folded portion 34. A double arrow line H <b> 2 represents the radial height from the bead base line to the end 42 of the second folded portion 40. A double arrow line H <b> 3 represents a radial height from the bead base line to the tip 61 of the bead apex 26.

From the viewpoint of steering stability and riding comfort performance, it is desirable that the outer end 52 of the strip apex 18 located on the outer side in the tire radial direction extends outward in the tire radial direction from the maximum tire width position AL. For this reason, in the tire 2, the ratio (HA / HO) of the radial height HA to the radial height H0 is preferably 0.50 or more, more preferably 0.60 or more, and further preferably 0.65 or more. is there. By setting it to 0.50 or more, the strip apex 18 effectively contributes to the balance adjustment between the longitudinal rigidity and the lateral rigidity of the tire 2, and it is possible to achieve both steering stability and riding comfort performance. HA / HO is preferably 0.85 or less, more preferably 0.80 or less, and still more preferably 0.75 or less. By setting it to 0.85 or less, the rigidity is not too high and the ride comfort is prevented from being impaired.

In the tire 2, the ratio (H1 / H0) of the radial height H1 to the radial height H0 is preferably 0.40 or more, more preferably 0.45 or more, and further preferably 0.50 or more. By setting it to 0.40 or more, the rigidity of the tire 2 is appropriately maintained, and excellent riding comfort and steering stability can be maintained. Further, H1 / H0 is preferably 0.75 or less, more preferably 0.65 or less, and still more preferably 0.60 or less. By being set to 0.75 or less, the rigidity is not too high and the ride comfort is prevented from being impaired. From the viewpoint of steering stability and riding comfort performance, it is desirable that the end 36 of the first folded portion 34 of the first ply 28 extends outward in the tire radial direction from the tire maximum width position AL.

In the tire 2, the ratio (H2 / H0) of the radial height H2 to the radial height H0 is preferably 0.05 or more, more preferably 0.10 or more, and 0.15 or more. By setting it to 0.05 or more, the rigidity of the tire 2 is appropriately maintained, and excellent riding comfort and steering stability can be maintained. Further, H2 / H0 is preferably 0.35 or less, more preferably 0.30 or less, and still more preferably 0.25 or less. By setting it to 0.35 or less, the rigidity is not too high and the ride comfort is prevented from being impaired.

In the tire 2, the ratio (H3 / H0) of the radial height H3 to the radial height H0 is preferably 0.20 or more, more preferably 0.25 or more, and further preferably 0.27 or more. By setting it to 0.20 or more, the rigidity of the tire 2 is appropriately maintained, and excellent riding comfort and steering stability can be maintained. Further, (H3 / H0) is preferably 0.48 or less, more preferably 0.43 or less, and still more preferably 0.40 or less. By setting it to 0.48 or less, the rigidity is not too high and the ride comfort is prevented from being impaired.

The pneumatic tire 2 can achieve both ride comfort and handling stability even if the sidewall portion is thin. The sidewall thickness W (see FIG. 2) at the maximum tire width position AL is the outer diameter of the tire. It is desirable that it is 0.01 to 0.06 times D. If it is less than 0.01 times, the steering stability is lowered, and if it exceeds 0.06 times, riding comfort tends to be impaired.

In the present invention, the dimension and angle of each member of the pneumatic tire 2 are measured in a state where the tire 2 is incorporated in a regular rim and the tire 2 is filled with air so as to have a regular internal pressure. 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 JATMA standard, “Design Rim” in TRA standard, and “Measuring Rim” in 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. The “maximum air pressure” in the JATMA standard, the “maximum value” published in the “TRAE LOAD LIMITS AT VARIOUS COLD INFLITI0N PRESSURES” in the TRA standard, and the “INFLATION PRESSURE” in the ETRTO standard are normal internal pressures. For convenience, the internal pressure of the passenger car tire 2 is set to 180 kPa.

The strip apex 18 (after vulcanization) of the pneumatic tire 2 has a loss coefficient (tan δ) of 0.20 or more, preferably 0.22 or more, more preferably 0.23 or more. If it is less than 0.20, the riding comfort performance may be sufficiently improved, and there is a possibility that the steering stability and the riding comfort performance cannot be compatible. The upper limit of tan δ is preferably 0.55 or less, more preferably 0.50 or less, and still more preferably 0.45 or less. If it exceeds 0.55, heat generation is likely to occur, and there is a risk of deterioration of rolling resistance and deterioration of durability.

Tan δ is a value measured using a viscoelastic spectrometer VES manufactured by Iwamoto Seisakusho under the conditions of a temperature of 70 ° C., an initial strain of 10%, a dynamic strain of 2%, and a frequency of 10 Hz. In this measurement, a test piece obtained by crosslinking (vulcanizing) the rubber composition constituting the strip apex 18 is used. The test piece is prepared by holding the rubber composition in a mold at a temperature of 160 ° C. for 10 minutes.

The strip apex 18 (after vulcanization) of the pneumatic tire 2 has a rubber hardness (Hs) of 65 or more, preferably 68 or more, more preferably 70 or more. If it is less than 65, the rigidity of the tire cannot be sufficiently increased, the steering stability cannot be sufficiently improved, and the steering stability and the riding comfort performance may not be compatible. The upper limit of the rubber hardness is preferably 80 or less, more preferably 77 or less, and even more preferably 75 or less. If the rubber hardness exceeds 80, the rigidity may be excessive.

The rubber hardness (Hs) is measured with a type A durometer according to JIS-K6253. Rubber hardness is measured at a temperature of 23 ° C. In this measurement, a test piece obtained by crosslinking (vulcanizing) the rubber composition constituting the strip apex 18 is used. The test piece is prepared by holding the rubber composition in a mold at a temperature of 160 ° C. for 10 minutes.

By using a rubber composition having characteristics of tan δ of 0.20 or more and rubber hardness of 65 or more as a strip apex 18 extending in the tire radial direction along the outside of the second main portion of the second ply. In addition to improving steering stability (particularly high-speed steering stability) by increasing rigidity, vibration absorption by energy absorption can be imparted to improve riding comfort performance. For this reason, even if the rubber thickness of the sidewall portion is thin, it is possible to satisfactorily achieve both steering stability and riding comfort performance.

The loss coefficient (tan δ) of the strip apex 18 (after vulcanization) is preferably larger than the loss coefficient (tan δ 2) of the bead apex 26 (after vulcanization). The difference (tan δ−tan δ2) between the loss coefficient (tan δ) of the strip apex 18 (after vulcanization) and the loss coefficient (tan δ 2) of the bead apex 26 (after vulcanization) is preferably 0.03 or more, 0 .05 or more is more preferable, and 0.10 or more is more preferable. If it is less than 0.03, there is a tendency that improvement in riding comfort performance cannot be expected. The difference (tan δ−tan δ2) is preferably 0.40 or less, and more preferably 0.35 or less. When it exceeds 0.40, there is a concern about a decrease in durability. The measurement of the loss coefficient (tan δ2) of the bead apex 26 (after vulcanization) is performed in the same manner as the measurement of the loss coefficient (tan δ) of the strip apex 18 (after vulcanization).

The difference (Hs2−Hs) between the rubber hardness (Hs) of the strip apex 18 (after vulcanization) and the rubber hardness (Hs2) of the bead apex 26 (after vulcanization) is preferably 5 or more, and 8 or more. More preferred. If it is less than 5, the rigidity may be excessive. The difference (Hs2−Hs) is preferably 25 or less, and more preferably 20 or less. If it exceeds 25, the rigidity of the tire cannot be sufficiently increased, and the maneuverability tends not to be improved.
The measurement of the rubber hardness (Hs2) of the bead apex 26 (after vulcanization) is performed in the same manner as the measurement of the rubber hardness (Hs) of the strip apex 18 (after vulcanization).

The strip apex 18 (vulcanized rubber composition) having the above tan δ and rubber hardness can be produced by appropriately adjusting the type and blending amount of the rubber component, carbon black, oil, etc. to be used. It can be produced by the methods (1) to (4).

(1) Use a large amount of styrene-butadiene rubber (SBR) as a rubber component and a large amount of carbon black.
(2) Use highly active carbon black.
(3) Use a resin (resin) as a tan δ improver.
(4) Use liquid polymer as oil.

In the method (1), examples of SBR that can be used include those obtained by a solution polymerization method and those obtained by an emulsion polymerization method, but are not particularly limited.

In the method (1), in the strip apex 18 (rubber composition), the content of SBR in 100% by mass of the rubber component is preferably 50% by mass or more, and more preferably 60% by mass or more. If it is less than 50% by mass, tan δ cannot be increased, and there is a possibility that a rubber composition having the above properties cannot be obtained. Further, the SBR content may be 100% by mass, but is preferably 80% by mass or less, and more preferably 70% by mass or less. If it exceeds 80% by mass, the low-temperature characteristics may be deteriorated, leading to a decrease in durability.

In the method (1), examples of rubber components that can be used with SBR include natural rubber (NR), butadiene rubber (BR), isoprene rubber (IR), butyl rubber (IIR), acrylonitrile butadiene rubber (NBR), and chloroprene. Examples thereof include rubber (CR), styrene isoprene butadiene rubber (SIBR), styrene isoprene rubber, and isoprene butadiene rubber diene rubber. Of these, NR and BR are preferable. These may be used alone or in combination of two or more.

The NR is not particularly limited, and for example, those commonly used in the tire industry such as SIR20, RSS # 3, TSR20, and the like can be used. The BR is not particularly limited, and for example, BR having a high cis content, BR containing a syndiotactic polybutadiene crystal, and the like can be used.

When NR is used in the method (1) above, the content of NR in 100% by mass of the rubber component in the strip apex 18 (rubber composition) is preferably 10% by mass or more, more preferably 20% by mass or more. preferable. If it is less than 10% by mass, it may not be possible to contribute to the improvement of low temperature characteristics. The NR content is preferably 40% by mass or less, and more preferably 35% by mass or less. If it exceeds 40% by mass, tan δ tends not to be increased unless a large amount of carbon black is blended.

When BR is used in the method of (1) above, in the strip apex 18 (rubber composition), the BR content in 100% by mass of the rubber component is preferably 10% by mass or more, more preferably 20% by mass or more. preferable. If it is less than 10% by mass, there is a possibility that it cannot contribute to the improvement of low temperature characteristics and bending fatigue resistance. The BR content is preferably 50% by mass or less, and more preferably 45% by mass or less. If it exceeds 50% by mass, tan δ tends not to be increased unless a large amount of carbon black is blended.

Examples of the carbon black that can be used in the method (1) include FEF, GPF, HAF, ISAF, SAF, and S-SAF. Among them, ISAF, SAF, and S-SAF are preferable because the high activity type is excellent in improving tan δ.

When carbon black is used, the iodine adsorption amount of carbon black is preferably 70 mg / g or more, more preferably 80 mg / g or more. When the iodine adsorption amount is less than 70 mg / g, the reinforcing property is insufficient and tan δ tends not to be improved. The iodine adsorption amount of carbon black is 160 mg / g or less, preferably 150 mg / g or less. If the iodine adsorption amount exceeds 160 mg / g, the processability may be deteriorated.
The iodine adsorption amount is measured in accordance with the sixth term of JIS K 6221.

Carbon black has a dibutyl phthalate oil absorption (DBP oil absorption) of preferably 80 ml / 100 g or more, preferably 90 ml / 100 g or more. When the DBP oil absorption is less than 80 ml / 100 g, there is a tendency that good steering stability cannot be obtained. The DBP oil absorption is preferably 180 ml / 100 g or less, more preferably 160 ml / 100 g or less. If the DBP oil absorption exceeds 180 ml / 100 g, the workability may be deteriorated.
In addition, DBP is calculated | required by the measuring method of JISK6217-4.

The content of carbon black is preferably 60 parts by mass or more, more preferably 70 parts by mass, and still more preferably 72 parts by mass or more with respect to 100 parts by mass of the rubber component. If it is less than 60 parts by mass, tan δ cannot be increased, so that there is a possibility that a rubber composition having the above properties cannot be obtained. The content of carbon black is preferably 150 parts by mass or less, more preferably 120 parts by mass or less, and still more preferably 100 parts by mass or less with respect to 100 parts by mass of the rubber component. When it exceeds 150 parts by mass, workability and mechanical strength tend to deteriorate.

In the method (1), oil may be used. Thereby, rubber hardness can be reduced and tan δ can be increased.
As the oil, for example, process oil, vegetable oil, or a mixture thereof can be used. Examples of the process oil include paraffinic process oil, naphthenic process oil, and aromatic process oil (aromatic process oil). As vegetable oils and fats, castor oil, cottonseed oil, sesame oil, rapeseed oil, soybean oil, palm oil, palm oil, peanut hot water, rosin, pine oil, pineapple, tall oil, corn oil, rice bran oil, beet flower oil, sesame oil, Examples include olive oil, sunflower oil, palm kernel oil, cocoon oil, jojoba oil, macadamia nut oil, safflower oil, and tung oil. Among these, from the viewpoint of compatibility with SBR, BR, and NR, aromatic process oil and paraffin process oil are preferably used.

When oil is used, the oil content is preferably 8 parts by mass or more, more preferably 15 parts by mass or more, and still more preferably 20 parts by mass or more with respect to 100 parts by mass of the rubber component. If it is less than 8 mass parts, workability will deteriorate and tan δ will tend not to be high. The oil content is preferably 45 parts by mass or less, more preferably 35 parts by mass or less. If it exceeds 45 parts by mass, the oil may move to the carcass and durability may be reduced.

For the strip apex 18 (rubber composition), in addition to the above components, compounding agents generally used in the manufacture of rubber compositions, for example, reinforcing fillers such as clay, zinc oxide, stearic acid, various anti-aging agents An agent, wax, vulcanizing agent, vulcanization accelerator and the like can be appropriately blended.

The pneumatic tire of the present invention is produced by a usual method using a rubber composition for each member such as a rubber composition for strip apex prepared by kneading each component with a Banbury mixer, a kneader, an open roll, or the like. The That is, each rubber composition such as a rubber composition for strip apex blended with the above-mentioned compounding agents as necessary is extruded in accordance with the shape of each member such as a strip apex at an unvulcanized stage. Together with the tire member, an unvulcanized tire is formed by molding by a normal method on a tire molding machine. The unvulcanized tire is heated and pressurized in a vulcanizer to obtain a passenger car pneumatic tire.
The pneumatic tire of the present invention can be suitably used for passenger cars.

The present invention will be specifically described based on examples, but the present invention is not limited to these examples.

(material)
Styrene butadiene rubber (SBR): SBR1502 manufactured by Sumitomo Chemical Co., Ltd.
Natural rubber (NR): TSR
Butadiene rubber (BR): BR150 manufactured by Ube Industries, Ltd.
Carbon black: N220 manufactured by Showa Cabot Co., Ltd. (Iodine adsorption amount: 119 mg / g, DBP oil absorption amount: 115 ml / 100 g)
Oil: Process oil NC300S manufactured by Japan Energy Co., Ltd.
Stearic acid: Zinc oxide manufactured by NOF Corporation: Zinc Hua No. 1 manufactured by Mitsui Mining & Smelting Co., Ltd. Sulfur: Powder sulfur vulcanization accelerator manufactured by Karuizawa Sulfur Co., Ltd .: Ouchi Shinsei Chemical Industry Co., Ltd. Noxeller CZ (N-cyclohexyl-2-benzothiazolylsulfenamide)

Examples 1-3 and Comparative Examples 1-2
[Preparation of rubber composition for strip apex]
(First kneading)
According to the formulation shown in Table 1, compounding agents other than the vulcanizing agent and the vulcanization accelerator were added, and after kneading with a 16 L Banbury mixer at a material temperature of 150 ° C., a sheet was formed with a 16-inch roll.
(Second kneading)
A sheet prepared by the first kneading, a vulcanizing agent and a vulcanization accelerator were charged, and after kneading with a 16 L Banbury mixer at a material temperature of 100 ° C., the sheet was formed with a 16-inch roll to prepare an unvulcanized rubber composition. .
Further, the obtained unvulcanized rubber composition was press vulcanized for 10 minutes under the condition of 160 ° C. to prepare a vulcanized rubber composition.
[Production of pneumatic tires for testing]
The unvulcanized rubber composition produced by the second kneading is processed in accordance with the shape of the strip apex, attached to the inside of the sidewall portion so as to have the basic configuration shown in FIG. An unvulcanized tire was formed by bonding and vulcanized at 170 ° C. for 20 minutes to prepare a test pneumatic tire (size: 225 / 50R17).
[Preparation of Vulcanized Rubber Test Pieces (Bead Apex)]
70 parts by mass of carbon black, 18 parts by mass of aroma oil with respect to 100 parts by mass of an unvulcanized rubber composition (rubber component (NR 70% by mass, SBR 30% by mass)) used as a bead apex for a pneumatic tire for testing, A mixture of 2 parts by mass of stearic acid, 3 parts by mass of zinc oxide, 3 parts by mass of sulfur, and 4 parts by mass of a vulcanization accelerator, kneaded with a 16 L Banbury mixer, and then sheeted with a 16 inch roll) at 160 ° C. Under pressure for 10 minutes, a vulcanized rubber specimen (bead apex) was produced.

The strip apex of the test pneumatic tire extends in the tire radial direction along the outside of the second main portion of the second ply. Further, the tire radial inner side portion is sandwiched between the second main portion of the second ply and the bead apex, and the center portion of the tire radial direction is the second main portion of the second ply and the first folded portion of the first ply. The tire radial direction outer side portion is sandwiched between the second main portion of the second ply and the sidewall. Further, Table 1 shows thickness TA, length LA, HA / H0, H1 / H0, H2 / H0, and H3 / H0. Table 1 also shows the thickness W (W / D) of the sidewall portion at the tire maximum width position AL with respect to the outer diameter D of the tire.

The following evaluation was performed about the produced vulcanized rubber composition and the test pneumatic tire. The evaluation results are shown in Table 1.

(Rubber hardness Hs)
Using the rubber hardness measurement method described above, the hardnesses of the vulcanized rubber test pieces and the vulcanized rubber test pieces (bead apex) of each Example and Comparative Example were measured.

(Viscoelasticity test)
Using the method for measuring the loss factor (tan δ) described above, tan δ of the vulcanized rubber test pieces and the vulcanized rubber test pieces (bead apex) of each Example and Comparative Example was measured.

(Tire evaluation (actual vehicle performance))
The produced pneumatic tire for test was mounted on a Corolla manufactured by Toyota Motor Corporation. The internal pressure of this tire was 210 kPa. The size of the wheel is 17 × 6.5J. This passenger car was tested on an asphalt road surface, and a driver's sensory evaluation was performed on high-speed steering stability, riding comfort performance, and noise. In addition, about high-speed steering stability, it implemented on the conditions of 140-200 km / h, and about riding comfort performance and noise, it implemented on the conditions of 60 km / h. Each standard is as follows.
(1) Stability of high-speed steering ◎: There is no wobbling when going straight, and you can feel a feeling of touching well ○: There is no wobbling when going straight, but a little touching feeling is felt △: There is some wobbling when going straight, and steering operation is always required (2 ) Riding comfort performance ◎: Damping is effective, there is almost no rugged feeling, there is a flat feeling ○: Some rugged feeling remains △: Strong rugged feeling, flat feeling is weak (3) Noise ○ : Not particularly concerned △: Slightly concerned

In Examples 1 to 3 in which the blending amounts of SBR and carbon black were large, tan δ of the vulcanized rubber was large and vibration absorption performance was excellent as compared with Comparative Examples 1 and 2. Therefore, it was excellent in all of high-speed steering stability, riding comfort performance and noise. In Comparative Examples 1 and 2 using a strip apex with a small tan δ, these performances were generally inferior (for example, in Comparative Example 1, although high-speed steering stability was excellent, riding comfort performance and noise) Was inferior).

1 is a cross-sectional view illustrating a part of a pneumatic tire according to an embodiment of the present invention. FIG. 2 is an enlarged cross-sectional view illustrating a part of the pneumatic tire of FIG. 1.

Explanation of symbols

2 Pneumatic tire 4 Tread 6 Side wall portion 6a Side wall 8 Bead 10 Carcass 12 Belt 14 Inner liner 16 Chafer 18 Strip apex 20 Tread surface 22 Groove 24 Bead core 26 Bead apex 28 First ply 30 Second ply 32 First One main portion 34 First folded portion 38 Second main portion 40 Second folded portion 44 Inner layer 46 Outer layer

Claims (8)

A pair of beads having a side wall, a bead core and a bead apex extending outward from the bead core in the radial direction of the tire, and spanned between the two beads. A pneumatic tire comprising a carcass composed of a first ply and a second ply arranged on the outside thereof, and a strip apex extending along the carcass,
The first ply integrally includes a first main portion extending from the equator plane toward the bead core and a first folded portion folded back at the bead core and extending outward in the tire radial direction. A second main portion extending from the equator plane toward the bead core and a second folded portion folded back at the bead core and extending outward in the radial direction are integrally formed,
Together with the strip apex extends in the tire radial direction along the outside of the second main portion of the second ply, the loss factor (tan [delta) of 0.20 or more state, and are rubber hardness of 65 or more,
In the strip apex, an inner portion in the tire radial direction is arranged between the second main portion and the bead apex of the second ply, and a central portion in the tire radial direction is the second main portion and the first ply of the second ply. A pneumatic tire that is disposed between the first folded portions of the tire and the tire radial direction outer portion is disposed between the second main portion and the sidewall of the second ply . The inner end of the strip apex located on the inner side in the tire radial direction is located on the inner side in the tire radial direction of the tip of the bead apex, and is interrupted by being sandwiched between the second main portion of the second ply and the bead apex. The outer end of the strip apex located on the outer side in the tire radial direction is located on the outer side in the tire radial direction of the tip of the bead apex and is sandwiched between the second main portion of the second ply and the side wall. and pneumatic tire according to claim 1, wherein are. The second folded portion is located between the bead apex and the first folded portion, the end of the second folded portion is located on the inner side in the tire radial direction of the end of the first folded portion, and the end of the first folded portion The pneumatic tire according to claim 1 or 2, wherein is located on the outer side in the tire radial direction at the tip of the bead apex. The pneumatic tire according to any one of claims 1 to 3, wherein the thickness of the strip apex is 0.5 to 3.0 mm. The pneumatic tire according to any one of claims 1 to 4, wherein a length of a portion where the strip apex and the bead apex overlap is 10 to 50 mm. The ratio (HA / HO) of the radial height HA from the bead base line to the outer edge of the strip apex and the radial height H0 from the bead base line to the equator plane is 0.50 to 0.85, the bead The ratio (H1 / H0) of the radial height H1 from the base line to the end of the first folded portion and the radial height H0 from the bead base line to the equator plane is 0.40 to 0.75, the bead base The ratio of the height H2 in the radial direction from the line to the end of the second folded portion and the height H0 in the radial direction from the bead base line to the equator plane (H2 / H0) is 0.05 to 0.35, and the bead base line The ratio (H3 / H0) between the radial height H3 from the bead apex to the tip of the bead apex and the radial height H0 from the bead base line to the equator plane is 0.20 to 0.48. Of 5 The pneumatic tire according to any deviation. The pneumatic tire according to any one of claims 1 to 6, wherein a ratio (W / D) between a thickness W of the sidewall portion at the tire maximum width position and an outer diameter D of the tire is 0.01 to 0.06. tire. The difference (tan δ-tan δ 2) between the loss coefficient (tan δ) of the strip apex and the loss coefficient (tan δ 2) of the bead apex is 0.03 to 0.40, the rubber hardness (Hs) of the strip apex, and the bead apex The pneumatic tire according to any one of claims 1 to 7, wherein a difference (Hs2-Hs) from the rubber hardness (Hs2) of the tire is 5 to 25.

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