JP4044367B2 - Heavy duty pneumatic tire - Google Patents

Description

【００３６】
【発明の効果】
上述したように、本発明の重荷重用空気入りタイヤは、タイヤの縦撓み量を減じて転がり抵抗を低減しうる。また内側補強ゴムの損失正接ｔａｎδを一定範囲に限定したので、より効果的に転がり抵抗の低減に役立つ。
【図面の簡単な説明】
【図１】本実施形態の重荷重用空気入りタイヤの断面図である。
【図２】その部分拡大図である。
【符号の説明】
１ 空気入りタイヤ
２ トレッド部
３ サイドウォール部
４ ビード部
５ ビードコア
６ カーカス
６Ａ カーカスプライ
６ａ カーカスプライの本体部
６ｂ カーカスプライの折返し部
７ ベルト層
９ クッションゴム
９ａ クッションゴムの内端
９ｂ クッションゴムの外端
１０ 内側補強ゴム
１０ａ 内側補強ゴムのトレッドショルダ部側の端部
１０ｂ 内側補強ゴムのタイヤ最大巾位置側の端部[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a heavy duty pneumatic tire capable of reducing rolling resistance.
[0002]
[Prior art and problems to be solved by the invention]
In recent years, from the viewpoint of protecting environmental resources, improving the fuel efficiency of vehicles has attracted attention as an important issue, and in particular, achieving high fuel efficiency in heavy-duty vehicles such as trucks and buses that consume a large amount of fuel It is effective. In view of such a situation, even in a heavy duty pneumatic tire used in a heavy duty vehicle, further reduction in rolling resistance is desired.
[0003]
As a method for reducing the rolling resistance, for example, it is known to use a low heat-generating rubber material for a tread rubber that comes in contact with the road surface. However, in general, in rubber materials, low heat generation performance and wear resistance performance are contradictory. For this reason, if a low heat-generating rubber material is used, the wear resistance and uneven wear resistance required for heavy-duty pneumatic tires cannot be sufficiently obtained, and it is not possible to meet market demands such as reducing the tire life.
[0004]
As another method, rolling resistance can be reduced by increasing the amount of vertical deflection of the tire by increasing the rubber thickness of the sidewall, increasing the diameter of the carcass cord, and increasing the number of driven carcass cords. Attempts to reduce this have also been proposed. However, with such a method, the weight of the tire is likely to increase significantly, and the rolling resistance increase margin due to the weight increase is larger than the rolling resistance reduction margin due to the reduction in the amount of longitudinal deflection, thereby reducing the rolling resistance. Does not contribute enough.
[0005]
The present invention has been devised in view of the above-described problems. The carcass is composed of a cushion rubber disposed between the carcass and the belt layer, and an inner reinforcing rubber disposed on the inner side of the carcass. The purpose is to provide a heavy-duty pneumatic tire that can reduce rolling resistance by reducing the amount of vertical deflection of the tire based on the use of a rubber material having the same viscoelastic properties as the cushion rubber for the inner reinforcing rubber. It is said.
[0006]
[Means for Solving the Problems]
The invention according to claim 1 is a heavy load comprising a carcass extending from a tread portion through a sidewall portion to a bead core of the bead portion, and a belt layer disposed outside the carcass and inside the tread portion. A heavy duty pneumatic tire,
A cushion rubber disposed between the outer end of the belt layer in the tire axial direction and the carcass and extending in a substantially triangular cross section;
An inner reinforcing rubber sandwiching the carcass with the cushion rubber by extending at least between the tread shoulder portion and the tire maximum width position inside the carcass,
The inner reinforcing rubber has a maximum thickness of 3.0 to 10 mm and substantially the same viscoelastic characteristics as the loss tangent tan δ and complex elastic modulus, and the loss tangent of the inner reinforcing rubber. It is characterized by being made of a rubber material having a tan δ of 0.035 to 0.065 .
[0007]
Incidentally, the “loss tangent tan δ” of the rubber material is obtained by cutting a strip-shaped sample 4 mm wide × 30 mm long × 1.5 mm thick and using a viscoelastic spectrometer manufactured by Iwamoto Seisakusho Co., Ltd. at a temperature of 70 It is a value measured under the conditions of ° C., frequency 10 Hz, and dynamic strain ± 2%.
[0008]
The invention according to claim 2 is the heavy duty pneumatic tire according to claim 1, wherein the cushion rubber 9 has a complex elastic modulus of 1.0 to 5.0 MPa .
[0009]
According to a third aspect of the present invention, the inner reinforcing rubber has an end on the tread shoulder portion side of the cushion rubber having a length L of 0.1 to 1. from the inner end in the tire axial direction. A distance A of 0 times is separated along the carcass to the tire equator side, and the end portion on the tire maximum width position side is 0.5 to 1.5 of the length L of the cushion rubber from the outer end of the cushion rubber. The heavy-duty pneumatic tire according to claim 1 or 2, wherein a double distance B is separated inward in the tire radial direction along the carcass.
[0010]
The invention according to claim 4 is characterized in that the cushion rubber has an overlap length in the tire axial direction overlapping the belt layer of 10 mm or more and less than a half width of the belt layer. The heavy-duty pneumatic tire described in 1.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view of a heavy-duty pneumatic tire (hereinafter sometimes simply referred to as “tire”) 1. In this example, a tubeless type heavy-duty radial tire used for trucks, buses, etc. is illustrated. ing.
[0012]
In the figure, a tire 1 is located at a tread portion 2, a pair of sidewall portions 3 extending inward in the tire radial direction from both ends thereof, and inner ends of the respective side wall portions 3 and seated on a rim (not shown). And a bead portion 4 to be provided. Further, the tire 1 includes a toroidal carcass extending from the tread portion 2 through the sidewall portion 3 to the bead core 5 of the bead portion 4 and a belt layer 7 positioned outside the carcass 6 and inside the tread portion 2. It is arranged.
[0013]
The carcass 6 includes a main body portion 6a extending from the tread portion 2 through the side wall portion 3 to the bead core 5 of the bead portion 4, and the bead core 5 connected to the main body portion 6a from the inner side in the tire axial direction in this example. The carcass ply 6A includes one or more (in this embodiment, one) carcass plies 6b having a folded portion 6b folded outward. As the carcass ply 6A, a sheet-like one in which a carcass cord is arranged in an angle range of 70 to 90 ° with respect to the tire equator C and both surfaces of a cord array body are covered with a topping rubber is used. In this example, a steel cord is used as the carcass cord. An inner liner rubber layer 12 is disposed between the bead portions 4 and 4 on the inner surface of the carcass 6. The inner liner rubber layer 12 is made of butyl rubber having excellent air permeation resistance and containing 50 parts by weight or more of halogenated butyl in the rubber, and prevents air leakage in the tire lumen.
[0014]
The belt layer 7 of the present embodiment includes an innermost belt ply 7A in which the belt cord is inclined with respect to the tire equator C at an angle of, for example, about 60 ± 10 °, and a small angle of 30 ° or less with respect to the tire equator C. The belt plies 7B, 7C, and 7D that are inclined in the above-described manner have a four-layer structure in which one or more portions where the belt cord intersects between the plies are provided and overlapped. In this example, the width of the second belt ply 7B from the inside is the largest, and this end portion forms the outer end 7e of the belt layer 7. Moreover, although the steel cord is employ | adopted as a belt cord in this example, highly elastic organic fiber cords, such as aromatic polyamide, can also be used as needed.
[0015]
The bead portion 4 is provided with a bead apex rubber 8 that tapers outwardly from the bead core 5 in the tire radial direction through the body portion 6a and the folded portion 6b. A reinforcement ply 15 is provided so as to wrap the bead core in a substantially U shape, and the bead portion 4 is appropriately reinforced.
[0016]
In the tire 1, a cushion rubber 9 extending in a substantially triangular shape is disposed between the outer end portion 7 </ b> E of the belt layer 7 in the tire axial direction and the carcass 6, and a tread shoulder portion is disposed inside the carcass 6. An inner reinforcing rubber 10 is disposed to sandwich the carcass 6 with the cushion rubber 9 by extending at least between the SH and the tire maximum width position M.
[0017]
The tire 1 of the present invention improves the longitudinal rigidity of the tire without changing the profile of the carcass 6 by sandwiching the carcass 6 near the buttress portion between the cushion rubber 9 and the inner reinforcing rubber 10 as described above. And the vertical deflection of the tire is reduced. As a result, the amount of deformation of the tire in the vicinity of the running buttress portion is reduced, and the rolling resistance at this portion can be reduced.
[0018]
As shown in FIG. 2, the cushion rubber 9 has a maximum thickness Ta in the vicinity of the outer end 7e of the belt layer 7, and from there toward the inner end 9a and the outer end 9b in the tire axial direction. Thus, the cross section has a substantially triangular shape with the thickness gradually reduced, and this cross-sectional shape is continuous in the tire circumferential direction. The maximum thickness Ta of the cushion rubber 9 is not particularly limited, but is preferably 5 to 15 mm, and particularly preferably 7 to 13 mm. If the maximum thickness Ta of the cushion rubber 9 is too small, the strain at the outer end 7e of the belt layer 7 tends to be reduced, the ability to absorb is likely to be reduced, and the effect of reinforcing the carcass 6 tends to be inferior. If it is too large, the shape of the outer end portion 7E of the belt layer 7 is impaired, and further, the profile of the carcass 6 tends to be distorted, which is not preferable.
[0019]
The cushion rubber 9 has an inner end 9a located at a separation portion J where the innermost belt ply 7A of the belt layer 7 and the carcass ply 6A begin to separate from each other, and the outer end 9b is an outer end of the belt layer 7. It extends in a tapered manner along the carcass 6 in the radial direction of the tire beyond 7e. Further, the length L of the cushion rubber 9 along the carcass 6 is not particularly limited, but is preferably 80 to 150 mm, particularly preferably 95 to 120 mm. The overlap length Wa in the tire axial direction in which the cushion rubber 9 and the belt layer 7 overlap is set to 10 mm or more and less than the half width bw of the belt layer 7, particularly preferably 25 mm or more and less than the half width bw of the belt layer. It is.
[0020]
Such a cushion rubber 9 fills a step formed between the outer end portion 7e of the flat belt layer 7 and the carcass 6 that is curved in an arc shape toward the side wall portion 3, and the tire along the carcass 6. By extending inward in the radial direction, it is useful for absorbing the distortion of the outer end portion 7E of the belt layer 7 that is easily deformed during load running and enhancing the durability.
[0021]
The cushion rubber 9 of this example is composed of a low heat generation rubber material having a loss tangent tan δ of 0.035 to 0.065, more preferably 0.04 to 0.06, and still more preferably 0.04 to 0.055. Is done. Such low heat-generating rubber suppresses energy loss due to deformation during load running and helps to reduce rolling resistance, and can also increase durability by reducing heat generation and preventing damage such as belt edge looseness. Further, since the cushion rubber 9 is not in direct contact with the road surface, the problem of deterioration of wear resistance that tends to occur in such a low heat-generating rubber material does not occur.
[0022]
If the loss tangent tan δ of the cushion rubber 9 is less than 0.035, the energy loss can be reduced, but there is a possibility that the reinforcing property is lowered and it is likely to be broken. There is a tendency that loss increases and rolling resistance is deteriorated and durability is lowered.
[0023]
As the viscoelastic characteristics of the cushion rubber 9, the complex elastic modulus is 1 . 0 to 5.0 MPa . The pressure is preferably 2.0 to 4.0 MPa, more preferably 2.5 to 3.5 MPa. Thereby, it helps to reduce the longitudinal deflection of the tire suitably.
[0024]
Further, the tire 1 is provided with an inner reinforcing rubber 10 that sandwiches the carcass 6 with the cushion rubber 9 by extending at least between the tread shoulder portion SH and the tire maximum width position M inside the carcass 6. The “tread shoulder portion” is a region having a distance of 25% of the tread ground contact width TW from the tread ground contact E. Further, the “tread contact width” TW is a distance in the tire axial direction between the tread contact ends when the tire is assembled on a normal rim and filled with a normal internal pressure, and a normal load is applied to contact with a flat surface.
[0025]
The “regular rim” is a rim determined for each tire in the standard system including the standard on which the tire is based. For example, a standard rim for JATMA, “Design Rim” for TRA, or ETRTO If so, use "Measuring Rim". In addition, “regular internal pressure” is the air pressure that each standard defines for each tire in the standard system including the standard on which the tire is based. It is the maximum air pressure for JATMA and the table “TIRE LOAD LIMITS” for TRA. The maximum value described in "AT VARIOUS COLD INFLATION PRESSURES". If ETRTO, "INFLATION PRESSURE". Furthermore, “regular load” is the load that each standard defines for each tire in the standard system including the standard on which the tire is based. The maximum load capacity is specified for JATMA, and the table “TIRE LOAD LIMITS” for TRA. The maximum value described in “AT VARIOUS COLD INFLATION PRESSURES”. If ETRTO, “LOAD CAPACITY”. In addition, the “maximum tire width position” is determined as a position protruding outside in the tire axial direction except for the marking on the sidewall portion, etc., when the tire is assembled on the regular rim and filled with the regular internal pressure.
[0026]
The end portion 10a on the tread shoulder portion SH side of the inner reinforcing rubber 10 may be positioned on the inner side of the inner end 9a of the cushion rubber. However, in the present embodiment, the end portion 10a is formed on the inner side of the cushion rubber 9. The distance A 0.1 to 1.0 times the length L of the cushion rubber is separated from the end 9a along the carcass 6 toward the tire equator side. In this way, the end portion 10a of the inner reinforcing rubber 10 is displaced from the inner end 9a of the cushion rubber 9, thereby preventing a large rigidity step from occurring in the vicinity of the end portion 10a. It is possible to suppress the deformation of the profile. Further, by extending the end portion 10 a of the inner reinforcing rubber 10 toward the tire equator C side from the inner end 9 a of the cushion rubber 9, it is useful to ensure a large length for sandwiching the carcass 6 with the cushion rubber 9. If the distance A is less than 0.1 times the length L of the cushion rubber 9, a rigidity step is likely to occur in the vicinity of the inner end of the cushion rubber 9. Conversely, if the distance A exceeds 1.0 times, the tire weight Increase easily.
[0027]
Further, the end portion 10b on the tire maximum width position M side of the inner reinforcing rubber portion 10 has a distance B that is 1.0 to 1.5 times the length L of the cushion rubber 9 from the outer end 9b of the cushion rubber 9. 6 is provided at a position separated inward in the tire radial direction along 6. Thereby, in this embodiment, the cushion rubber 9 and the inner reinforcing rubber 10 can sandwich the carcass 6 of the so-called buttress portion from the inside and the outside by the length L of the cushion rubber 9.
[0028]
The inner reinforcing rubber 10 has a maximum thickness Tb of 3.0 to 10 mm and is made of a rubber material having substantially the same viscoelastic characteristics as the cushion rubber 9. As described above, the inner reinforcing rubber 10 limits the maximum thickness Tb and the rubber material, thereby reducing the vertical deflection amount of the tire and preventing rolling resistance while preventing a significant increase in tire weight and a decrease in riding comfort. It can be reduced. Such a reinforcing structure of the carcass 6 hardly changes the carcass profile at the time of filling with the internal pressure. In other words, the carcass profile tends to approach a uniform arc due to expansion deformation due to the filling of the internal pressure, but when a reinforcing rubber layer is disposed on the outside of the carcass, the carcass enters the inside by the thickness of the rubber and is biased toward the carcass. The tension is applied. On the other hand, when the reinforcing rubber 10 is provided inside the carcass 6, there is no influence of such a rubber thickness. For this reason, it is possible to prevent the occurrence of a biased tension on the carcass cord and the deterioration of the durability of the tire.
[0029]
If the maximum thickness Tb of the inner reinforcing rubber 10 is less than 3.0 mm, the bending rigidity of the carcass 6 sandwiched between the cushion rubbers 9 cannot be increased, so that the effect of reducing the vertical deflection amount is reduced. On the contrary, if the maximum thickness Tb of the inner reinforcing rubber 10 exceeds 10.0 mm, it is not preferable because the tire weight is significantly increased. Particularly preferably, the maximum thickness Tb of the inner reinforcing rubber 10 is 4.0 to 10.0 mm, more preferably 5.0 to 8.0 mm. Note that the inner reinforcing rubber 10 of the present embodiment also has a cross-sectional shape in which the thickness gradually decreases toward both ends, similarly to the cushion rubber 9, and strain is concentrated at the ends 10a and 10b. Suppressed.
[0030]
The inner reinforcing rubber 10 desirably has substantially the same viscoelastic characteristics as the cushion rubber 9. For example, even in a run flat tire that can travel safely to a predetermined place even when punctured, such a reinforcing rubber layer is provided inside the carcass, but in such a run flat tire, the reinforcing rubber layer is a cushion rubber. A harder rubber material is used, which is completely different from the present invention. By making the viscoelastic characteristics of the cushion rubber 9 and the inner reinforcing rubber 10 substantially the same, it is possible to reduce the vertical deflection of the tire while preventing a significant deterioration in ride comfort. Moreover, the increase in the material of the compounded rubber can be prevented and the cost of the tire can be prevented from increasing. The “viscoelastic property” includes both tan δ and the complex elastic modulus, that is, substantially the same viscoelastic property as the loss tangent tan δ and the complex elastic modulus . The reason that “substantially the same” is used is that the same action and effect can be obtained, and a difference of about ± 3% can be allowed for each of tan δ and complex elastic modulus.
[0031]
【Example】
A heavy-duty pneumatic tire having a tire size of 11R22.5 14PR was prototyped based on the specifications in Table 1, and rolling resistance, longitudinal deflection, riding comfort, tire weight, and the like were measured. The test method and test results are as follows.
[0032]
a) Rolling resistance test load: 24.52 kN,
Air pressure: 700kPa
Room temperature: 25 ° C ± 2 ° C
Speed: 80km / H
Drum diameter: 1707.6 mm
Drum surface: Iron Note that the amount of vertical deflection is the value when a load is applied by bringing the tire into contact with the drum during a rolling resistance test from an unloaded state.
[0033]
b) Ride comfort The fixed tire weight of 10 tons (2-DD vehicle) is fitted with the test tires on all the wheels of the vehicle with the above rim and internal pressure, and the ride comfort when driving on a paved road depends on the driver. The five-point method was used for evaluation. The higher the number, the better.
[0034]
c) Running at a speed of 10km / H every 120 minutes using a drum tester under conditions of durable internal pressure (700kPa) and rim (22.5 × 7.50), until tire breakage occurs Travel time was measured. Evaluation is indicated by an index with the comparative example being 100, and the larger the value, the better.
[0035]
[Table 1]

[0036]
【The invention's effect】
As mentioned above, the heavy duty pneumatic tire of the present invention, Ru bovine reduce rolling resistance by subtracting the vertical deflection of the tire. Moreover, since the loss tangent tan δ of the inner reinforcing rubber is limited to a certain range, it helps to reduce the rolling resistance more effectively.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a heavy duty pneumatic tire of the present embodiment.
FIG. 2 is a partially enlarged view thereof.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Pneumatic tire 2 Tread part 3 Side wall part 4 Bead part 5 Bead core 6 Carcass 6A Carcass ply 6a Carcass ply main part 6b Carcass ply turn part 7 Belt layer 9 Cushion rubber 9a Cushion rubber inner end 9b Outside cushion rubber End 10 Inner reinforcing rubber 10a End portion 10b of inner reinforcing rubber on tread shoulder side End of inner reinforcing rubber on tire maximum width position side

Claims (4)

A heavy duty pneumatic tire comprising a carcass extending from a tread portion through a sidewall portion to a bead core of the bead portion and a belt layer disposed outside the carcass and inside the tread portion,
A cushion rubber disposed between the outer end of the belt layer in the tire axial direction and the carcass and extending in a substantially triangular cross section;
An inner reinforcing rubber sandwiching the carcass with the cushion rubber by extending at least between the tread shoulder portion and the tire maximum width position inside the carcass,
The inner reinforcing rubber has a maximum thickness of 3.0 to 10 mm and substantially the same viscoelastic characteristics as the loss tangent tan δ and complex elastic modulus, and the loss tangent of the inner reinforcing rubber. A heavy duty pneumatic tire comprising a rubber material having a tan δ of 0.035 to 0.065 . The heavy-duty pneumatic tire according to claim 1 , wherein the cushion rubber 9 has a complex elastic modulus of 1.0 to 5.0 MPa . The inner reinforcement rubber has an end on the tread shoulder portion side with a distance A 0.1 to 1.0 times the length L of the cushion rubber from the inner end of the cushion rubber in the tire axial direction. Along the tire equator side,
The end portion on the tire maximum width position side is separated from the outer end of the cushion rubber by a distance B that is 0.5 to 1.5 times the length L of the cushion rubber along the carcass inward in the tire radial direction. The heavy-duty pneumatic tire according to claim 1 or 2, characterized in that: 4. The heavy duty pneumatic tire according to claim 1, wherein the cushion rubber overlaps with the belt layer in the tire axial direction and is 10 mm or more and less than a half width of the belt layer. 5.

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