JP2010167940A - Pneumatic tire for aircraft - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of suppressing falling deformation of the tire with high rigidity of a tire width direction and further suppressing damage to a ply body, even when a recessed thin part having a center of curvature at the outside of the tire from the viewpoint of a tire width direction cross section is provided in a side surface rubber part of the tire. <P>SOLUTION: A stiffener 40 includes a first rubber part 41 located just above a bead core 11, a second rubber part 42 located on the first rubber part 41 and at the tire width direction inside, and a third rubber part 43 located on the first rubber part 41 and at the tire width direction outside to constitute a tire radial direction outside part of the stiffener 40. The first rubber part 41 and the third rubber part 43 have higher elastic moduli than that of the second rubber part 42. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention mainly relates to a pneumatic tire for heavy-duty vehicles such as trucks and buses, and more particularly to a pneumatic tire in which a concave thin wall portion is provided on a side rubber to reduce the weight of the tire.

  In recent years, pneumatic tires have been required to have low fuel consumption from the viewpoint of environmental considerations and economy, and one of the countermeasures is to reduce rolling resistance. May reduce weight.

  In order to reduce the weight of the tire, there is a method to reduce the number of ply cords driven as a carcass material, but in this case, the overall rigidity of the tire is reduced, so that the tire performance, steering stability, etc. are reduced. Is concerned. In addition, a method of reducing the total thickness of the rubber in the sidewall portion and the bead portion of the tire is also conceivable, but since the rigidity of the sidewall portion and the bead portion is lowered, there is a concern that the steering stability performance and the like are similarly lowered. .

  In order to solve the above problem, for example, in Patent Document 1, a concave portion (thin wall portion) is formed in the outer rubber layer between the tire maximum width position and the position where the outer surface of the bead part is separated from the rim flange. The total thickness of the tire side portion in the recess is equal to or greater than the total thickness of the tire side portion in the maximum tire width position, and the maximum depth of the recess is 1.5 mm or more, thereby reducing the rubber weight and reducing the weight of the tire. And a pneumatic tire designed to suppress heat storage and prevent thermal degradation of the outer rubber layer.

  However, the pneumatic tire disclosed in Patent Document 1 has low rigidity in the tire width direction, and when it is loaded, it is directed to the portion where the concave portion is formed (thin wall portion) in the compressive strain directed radially inward in the tire radial direction and radially outward. As a result of repeated application of tensile strain, the rubber on the outer side in the tire radial direction collapses, resulting in a delay in response during driving and a problem that steering stability deteriorates.

  In order to suppress the decrease in rigidity in the tire width direction and the accompanying tire collapse deformation as described above, the air in which the rigidity in the tire width direction is improved by forming the stiffener located immediately above the bead core with hard rubber. Entered tires are considered.

  However, the pneumatic tire having the stiffener made of the hard rubber described above has high rigidity in the tire width direction of the thin portion and can suppress the tire collapse to some extent, but the stiffness of the stiffener is high. The rubber side protecting the ply located on the side may be damaged by contact with the stiffener.

JP 2000-158919 A

  The object of the present invention is to optimize the stiffener, even when a concave thin-walled portion having a center of curvature is provided on the outer side of the tire when viewed in a cross section in the tire width direction on the side rubber portion of the tire. An object of the present invention is to provide a pneumatic tire that has high rigidity in the tire width direction, can suppress the tire from falling down, and can suppress damage to the ply body.

  As a result of intensive studies to solve the above-mentioned problems, the present inventor, as for the stiffener of the present invention, the part positioned immediately above the bead core and the part constituting the tire radial direction outer part of the stiffener, In order to prevent damage due to contact with the rubber, a rubber having a high elastic modulus is used to increase rigidity in the tire width direction. On the other hand, for the portion in contact with the ply main body, damage to the rubber protecting the ply can be suppressed. It has been found that by using a rubber having a low hardness, a pneumatic tire having a high rigidity in the tire width direction and not damaging the rubber protecting the ply can be obtained.

The present invention has been made based on such findings, and the gist thereof is as follows.
(1) At least a bead core embedded in a pair of bead portions, a ply body portion that is locked between the bead cores and extends in a toroid shape, and a ply folding portion that is folded from the body portion around the bead core. In a pneumatic tire having a carcass consisting of a single ply, a concave shape having a center of curvature on the outer side of the tire when viewed in the tire width direction cross section in the tire side rubber portion in the tire radial direction inside the tire maximum width position And a stiffener is provided immediately above the bead core. The stiffener is a first rubber portion located immediately above the bead core, and a first rubber portion located on the inner side in the tire width direction on the first rubber portion. 2 rubber parts and a third rubber on the first rubber part and located on the outer side in the tire width direction and constituting the outer part in the tire radial direction of the stiffener It has a section, a pneumatic tire, wherein the first rubber portion and the third rubber portion is a high elastic modulus than the second rubber portion.

(2) at least a bead core embedded in each of the pair of bead portions, a ply main body portion that is locked between the bead cores and extends in a toroid shape, and a ply folding portion that is folded from the main body portion around the bead core. In a pneumatic tire having a carcass made of a single ply, a concave shape having a center of curvature on the outer side of the tire when viewed in the tire width direction cross section in the tire side rubber portion inside the tire radial direction from the tire maximum width position A thin rubber portion, and a stiffener is provided immediately above the bead core. The stiffener is located immediately above the bead core and located between the ply main body portion and the ply turn-up portion of the carcass, and the ply turn-up portion. A second rubber part located opposite to the first rubber part across the part, and located outside the second rubber part in the tire width direction, and A pneumatic tire having a third rubber portion constituting a tire radial direction outer portion of the Tiffner, wherein the first rubber portion and the third rubber portion have higher elastic modulus than the second rubber portion. .

(3) The pneumatic tire according to (1) or (2), wherein the third rubber portion has a higher elastic modulus than the first rubber portion.

(4) The third rubber portion has an upper end positioned in a range of 25 to 60% of a distance along the tire radial direction to the tire maximum width position as measured from a tire radial outer end position of the bead core. The pneumatic tire according to any one of (1) to (3) above.

(5) Any one of said (1)-(4) whose thickness of the said side rubber is the range of 2.5-4.5 mm in the position where the rubber thickness of a tire width direction is the thinnest in the said thin part. The pneumatic tire according to item.

(6) The thin-walled portion has a tire radial direction outer end position in a range of 65% or less of a distance along the tire radial direction to the tire maximum width position as measured from a rim flange height position. The pneumatic tire according to any one of (1) to (5).

  According to the present invention, even when the tire side rubber portion is provided with a concave thin wall portion having a center of curvature on the outer side of the tire when viewed in the tire width direction cross section, the rigidity in the tire width direction is high and the tire collapses. It has become possible to provide a pneumatic tire that can suppress deformation and further suppress damage to the ply body.

The width direction sectional view about the pneumatic tire according to the present invention is shown. It is width direction sectional drawing which expanded and showed the periphery of the bead part about each embodiment of the pneumatic tire according to this invention. It is width direction sectional drawing which expanded and showed the periphery of the bead part about the form of the conventional pneumatic tire.

Hereinafter, embodiments of the present invention will be described with reference to FIGS.
FIG. 1 is a view showing a cross section in the width direction of a half portion of a pneumatic tire according to the present invention, and FIGS. 2 (a) to 2 (c) show the bead portion of each embodiment of the pneumatic tire according to the present invention. It is the figure which expanded and showed the periphery. FIGS. 3A to 3C are enlarged views of the periphery of the bead portion of a conventional pneumatic tire.

  As shown in FIG. 1, the present invention includes a bead core 11 embedded in a pair of bead portions 10, a ply main body 21 a that is locked between the bead cores 11 and extends in a toroid shape, and the main body 21 a. A pneumatic tire 1 including a carcass 20 including at least one ply 21 having a ply folding portion 21 b folded around a bead core 11.

As shown in FIG. 1, the pneumatic tire 1 according to the first embodiment of the present invention has a tire side rubber 31 portion on the inner side in the tire radial direction from the tire maximum width position H, and the tire is viewed in the tire width direction cross section. A concave thin-walled portion 32 having a center of curvature is provided on the outer side, and a stiffener 40 is provided immediately above the bead core 11. As shown in FIG. 2A, the stiffener 40 is a first rubber part 41 located immediately above the bead core 11, and a second rubber part located on the first rubber part 41 and inside the tire width direction. The first rubber part includes a rubber part and a third rubber part 43 that is located on the outer side in the tire width direction on the first rubber part 41 and that constitutes an outer part in the tire radial direction of the stiffener 40. 41 and the third rubber part 43 have a higher elastic modulus than the second rubber part 42.
Since the first elastic portion 41 having a high elastic modulus is provided at a portion located immediately above the bead core, it is possible to prevent damage due to contact with the bead core 11, and the second rubber portion 42 having low hardness. Is provided at a portion in contact with the ply main body portion 21a, so that damage to the ply 21 can be suppressed. Further, the third rubber portion having a high elastic modulus is the outer portion in the tire width direction of the stiffener 40 and the tire. Since it is provided in the radially outer portion, it is possible to increase the rigidity in the tire width direction and suppress the collapse deformation of the stiffener 40 even when the thickness of the stiffener 40 is thin. It becomes. As a result, even when the weight of the tire is reduced, high steering stability can be realized.

Here, similarly to the pneumatic tire 1 of the present invention, a concave shape having a center of curvature on the outer side of the tire in the tire width direction cross section in the tire side rubber 31 portion inward in the tire radial direction from the tire maximum width position H. As compared with the conventional stiffener 50 (FIGS. 3B and 3C) of the pneumatic tire having the thin wall portion 32, the stiffener 50 shown in FIG. It consists of a first rubber 51 having a modulus of elasticity and a second rubber portion 52 having a low hardness directly above the first rubber portion 51, and hard rubber is provided on the outer portion in the tire width direction and the outer portion in the tire radial direction. Therefore, unlike the stiffener 40 of the present invention, the effect of increasing the rigidity in the tire width direction and the effect of suppressing the collapse of the tire cannot be achieved. Also, for the stiffener 50 shown in FIG. 3C, a high elastic modulus first rubber 51 located immediately above the bead core 11 and a high elastic modulus second rubber portion directly above the first rubber portion 51 are also provided. 52 and a low hardness third rubber portion 53 that is located on the outer side in the tire width direction on the second rubber portion 52 and that constitutes the outer portion in the tire radial direction of the stiffener 50, and the outer portion in the tire width direction. And hard rubber is not provided in the tire radial direction outer side part, and unlike the stiffener 40 of the present invention, the effect of increasing the rigidity in the tire width direction and the effect of suppressing the falling deformation of the tire cannot be achieved. .
FIG. 2 (a) shows a part of a conventional pneumatic tire that does not have the thin-walled portion 32. When the thin-walled portion is not present, the thickness of the stiffener 50 in the tire width direction is shown. Since the thickness can be increased, it is possible to suppress the tire from falling down and the like. However, since the weight of the tire is not sufficiently reduced, the outer rubber layer may be thermally deteriorated due to heat accumulation of the side rubber 31 of the tire.

  Further, the pneumatic tire 1 of the present invention is provided with the concave thin-walled portion 32 having a center of curvature on the outer side of the tire when viewed in the cross-section in the tire width direction, so that the tire can be reduced in weight and the rubber weight can be reduced. This is effective in reducing the weight of the tire by reducing the amount of heat and suppressing heat deterioration by suppressing heat storage. Here, the thin-walled portion 32 refers to a portion of the side rubber 31 that is thinned by cutting out a portion of the bead portion on the outer side in the tire width direction into a concave shape, which is a conventional portion shown in FIG. It can be seen that the shape and thickness of the side rubber 31 of the bead portion is different. In addition, the concave notch shape is not particularly limited, and in FIG. 1, the concave portion formed of one arc is formed, but the concave portion may be a combination of a plurality of arcs. Further, the radius of curvature R of the arc is not particularly limited, but the radius of curvature R is preferably in the range of 10 to 200 mm from the viewpoint of achieving both weight reduction of the tire and rigidity in the tire width direction. .

  The first, second, and third rubber portions 41, 42, and 43 are members made of rubber constituting the stiffener 40, and the first rubber portion 41 and the third rubber portion 43 are illustrated in FIG. As shown to (a), even if it is the rubber member united using the same rubber | gum, as shown in FIG.2 (b), it may be a rubber member each comprised from another rubber | gum. .

Further, in the second embodiment of the pneumatic tire 1 of the present invention, as shown in FIG. 1, a tire side rubber 31 portion located inward in the tire radial direction from the tire maximum width position H is seen in a tire width direction cross section. A concave thin-walled portion 32 having a center of curvature is provided outside the tire, and a stiffener 400 is provided immediately above the bead core 11. As shown in FIG. 2C, the stiffener 400 includes a first rubber portion 410 that is directly above the bead core 11 and located between the ply body portion 21a and the ply turn-up portion 21b of the carcass 21, and the ply A second rubber portion 420 that faces the first rubber portion 410 with the folded portion 21b interposed therebetween, and an outer portion in the tire radial direction of the stiffener 400 that is located on the outer side in the tire width direction of the second rubber portion 420 And the first rubber part 410 and the third rubber part 430 have a higher elastic modulus than the second rubber part 420.
Similarly to the first embodiment of the pneumatic tire 1 of the present invention, the first elastic rubber portion 41 having a high elastic modulus is provided in a portion located immediately above the bead core, so that damage due to contact with the bead core 11 is prevented. In addition, since the low hardness second rubber portion 42 is provided in a portion in contact with the ply turn-up portion 21b, it is possible to suppress damage to the ply 21, and further, a high elastic modulus. Since the third rubber portion is provided at the outer portion in the tire width direction and the outer portion in the tire radial direction of the stiffener 40, the rigidity in the tire width direction is obtained even when the thickness of the stiffener 40 is thin. It is possible to suppress the falling deformation of the stiffener 40. As a result, even when the weight of the tire is reduced, high steering stability can be realized.

  Furthermore, it is preferable that the third rubber parts 43 and 430 have a higher elastic modulus than the first rubber parts 41 and 410. In order to prevent the stiffener 40 from falling down, it is necessary to increase the rigidity of the outer portion in the tire width direction and the outer portion in the tire radial direction, and the third rubber portions 43 and 430 are the first rubber portions 21 and 410. This is because if the hardness is lower than the above, the above effects may not be achieved.

  Further, as shown in FIG. 1, the upper end 43a of the third rubber portion 43 is measured from the tire radial direction outer end position 11a of the bead core and extends along the tire radial direction up to the tire maximum width position H. It is preferably located in the range of 25 to 60% of the distance L1. If the distance L1 is less than 25%, the length of the third rubber portion 43 in the tire radial direction becomes small, and therefore there is a possibility that the collapse of the tire cannot be sufficiently suppressed. If it exceeds, the length of the third rubber portion 43 in the tire radial direction is too large, so that the tip of the stiffener with large deformation may cause separation.

  Further, as shown in FIG. 2A, the thickness d of the side rubber at the position where the rubber thickness in the tire width direction is the thinnest in the thin portion 32 is in the range of 2.5 to 4.5 mm. Is preferred. This is because when the thickness d is less than 2.5 mm, the thickness in the width direction of the stiffeners 40 and 400 is reduced accordingly, so that the rigidity in the tire width direction is lowered and steering stability may be deteriorated. If the thickness d exceeds 4.5 mm, the weight of the tire is not sufficient, and there is a possibility that the side rubber 31 is thermally deteriorated due to heat storage, and even without using the stiffeners 40 and 400 of the present invention to some extent. This is because the effect of the present invention is not remarkably exhibited because the rigidity in the tire width direction can be obtained.

  Furthermore, the thin-walled portion 32 has a tire radial direction outer end position 32a in a range of 65% or less of a distance L2 along the tire radial direction to the tire maximum width position as measured from the rim flange height position. Preferably there is. This is because when the outer end position 32a in the tire radial direction of the thin portion 32 exceeds 65% of L2, the durability when the tire is rubbed against a curb or the like during running is adversely affected.

  The above description is merely an example of the embodiment of the present invention, and various modifications can be made within the scope of the claims.

Next, an aircraft pneumatic tire according to the present invention was prototyped and its performance was evaluated, and will be described below.
(Example)
As examples, radial tires for trucks and buses (tire size: 11R22.5 14PR, applicable rim: 7.50), as shown in FIG. 1, bead cores 11 respectively embedded in a pair of bead portions 10; A carcass 20 comprising at least one ply 21 having a ply main body portion 21a that is locked between the bead cores 11 and extends in a toroidal shape, and a ply turn-back portion 21b that is folded from the main body portion 21a around the bead core 11a; And a concave thin portion 32 having a center of curvature on the outer side of the tire when viewed in a cross section in the tire width direction (at the position where the rubber is thinnest). Rubber thickness: 3.0 mm, 1.5 kg tire weight reduction), and further, as shown in FIG. 2 (a), the first rubber portion 41 (goose rubber) located immediately above the bead core 11. Elastic modulus: 13.3 MPa), the second rubber portion 42 (rubber elastic modulus: 3.5 MPa) located on the inner side in the tire width direction on the first rubber portion 41, and the first rubber portion 41. The third rubber part 43 (rubber elastic modulus: 13.3 MPa, the upper end position 43a is measured from the outer end position in the tire radial direction of the bead core and is located on the outer side in the tire width direction and constitutes the outer portion in the tire radial direction of the stiffener 40. The pneumatic tire 1 was manufactured in which a stiffener 40 composed of 32% of the distance along the tire radial direction to the tire maximum width position H was provided immediately above the bead core 11.

(Comparative Example 1)
Comparative Example 1 is a truck and bus radial tire (tire size: 11R22.5 14PR, applicable rim: 7.50), as shown in FIG. 1, and a bead core 11 embedded in a pair of bead portions 10. A carcass 20 comprising at least one ply 21 having a ply main body 21a that is locked between the bead cores 11 and extends in a toroidal shape, and a ply turn-back portion 21b that is folded from the main body 21a around the bead core 11a. The thin-walled portion 32 as in Example 1 is not provided (the tire is not reduced in weight), and further, as shown in FIG. 3 (a), ordinary air using a conventional stiffener 50 is used. An inset tire was produced.

(Comparative Example 2)
In Comparative Example 2, the rubber thickness of the thinnest portion 32 is 4.0 mm (0.8 kg weight reduction of the tire), and the stiffener provided immediately above the bead core 11 is shown in FIG. As shown in FIG. 4, the same pneumatic as in Example 1 except that the conventional stiffener 50 (the rubber elastic modulus of the first rubber part 51: 13.3 MPa, the rubber elastic modulus of the second rubber part 52: 3.5 MPa). A tire was produced.

(Comparative Example 3)
In Comparative Example 3, as shown in FIG. 3B, the stiffener provided immediately above the bead core 11 has a conventional stiffener 50 (the rubber elastic modulus of the first rubber part 51: 25.0 MPa, the second rubber part 52 A pneumatic tire was produced in the same manner as in Example 1 except that the rubber elastic modulus was 13.3 MPa).

(Evaluation)
The pneumatic tires of Examples and Comparative Examples 1 to 3 were evaluated by the following methods.

(1) Steering stability When each of the pneumatic tires of Examples and Comparative Examples 1 to 3 is actually attached to a car and travels at 80 km / h with the maximum loading weight of the vehicle, the vehicle travels straight. Based on the stability of the car body and the stability of the car body when the lane was changed, a feeling evaluation on the handling stability was performed. The evaluation results are shown as an index ratio when the steering stability of Comparative Example 1 is set to 100, and are shown in Table 1. In addition, the numerical value in Table 1 means that the greater the value is, the more stable the vehicle is when traveling straight and lane change, and the higher the steering stability.

(2) Weight reduction of tire About each pneumatic tire of an Example and Comparative Examples 1-3, each mass was measured and it evaluated about weight reduction of a tire. Evaluation shows how much weight reduction is achieved from the mass of Comparative Example 1 and is shown in Table 1.

(3) Damage to rubber protecting ply For each of the pneumatic tires of Examples and Comparative Examples 1 to 3, the state of each ply when running at 80 km / h with a load of 6430 kg was observed. And evaluated. The evaluation is expressed as an index ratio when the ply state of Comparative Example 1 is set to 100, and is shown in Table 1. In addition, the numerical value in Table 1 means that damage of a ply is so large that it is large.

  From the results shown in Table 1, the pneumatic tires of the examples show the steering stability of the pneumatic tire of Comparative Example 1 in which the weight of the tire is not reduced, and the tire of Comparative Example 2 in which the degree of weight reduction of the tire is small. There was no inferiority, and in addition, it was found that the steering stability was greatly improved as compared with the pneumatic tire of Comparative Example 3 in which the weight of the same tire was reduced. As a result, it can be seen that the pneumatic tire of the present invention achieves both reduction in weight of the tire and steering stability.

  According to the present invention, even when the tire side rubber portion is provided with a concave thin wall portion having a center of curvature on the outer side of the tire when viewed in the tire width direction cross section, the rigidity in the tire width direction is high and the tire collapses. It is possible to provide a pneumatic tire capable of suppressing deformation and further capable of suppressing damage to the ply body.

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 10 Bead part 11 Bead core 20 Carcass 21 Ply 21a Ply main-body part 21b Ply folding | turning part 30 Tread part 31 Side rubber 32 Thin part 40 Stiffener 41 1st rubber part 42 2nd rubber part 43 3rd rubber part 50 Stiffener 51 1st 1 rubber part 52 second rubber part 53 third rubber part

Claims (6)

At least one sheet having a bead core embedded in each of the pair of bead portions, a ply main body portion that is locked between the bead cores and extends in a toroid shape, and a ply folded portion that is folded from the main body portion around the bead core. In pneumatic tires with carcass made of ply,
A concave thin part having a center of curvature is provided on the outer side of the tire when viewed in the tire width direction cross section in the tire side rubber part inside the tire radial direction from the tire maximum width position, and a stiffener is provided immediately above the bead core. The stiffener includes a first rubber portion located immediately above the bead core, a second rubber portion located on the inner side in the tire width direction on the first rubber portion, and a tire on the first rubber portion. It has the 3rd rubber part which is located in the width direction outside, and constitutes the tire radial direction outside part of a stiffener, and the 1st rubber part and the 3rd rubber part are higher elastic modulus than the 2nd rubber part. A pneumatic tire characterized by that. At least one sheet having a bead core embedded in each of the pair of bead portions, a ply main body portion that is locked between the bead cores and extends in a toroid shape, and a ply folded portion that is folded from the main body portion around the bead core. In pneumatic tires with carcass made of ply,
A concave thin part having a center of curvature is provided on the outer side of the tire when viewed in the tire width direction cross section in the tire side rubber part inside the tire radial direction from the tire maximum width position, and a stiffener is provided immediately above the bead core. The stiffener is located immediately above the bead core and positioned between the ply body portion of the carcass and the ply turn-up portion, and a first rubber portion located opposite to the first rubber portion with the ply turn-up portion interposed therebetween. Two rubber parts, and a third rubber part that is located on the outer side in the tire width direction of the second rubber part and that constitutes an outer part in the tire radial direction of the stiffener, and the first rubber part and the third rubber part Has a higher elastic modulus than the second rubber part.   The pneumatic tire according to claim 1, wherein the third rubber portion has a higher elastic modulus than the first rubber portion.   The said 2nd rubber | gum part is located in the range of 25 to 60% of the distance along the tire radial direction to the tire maximum width position measured from the tire radial direction outer end position of a bead core. The pneumatic tire according to any one of claims.   The pneumatic tire according to any one of claims 1 to 4, wherein a thickness of the side rubber is in a range of 2.5 to 4.5 mm at a position where the rubber thickness in the tire width direction is the thinnest in the thin portion. .   The thin-walled portion has a tire radial direction outer end position in a range of 65% or less of a distance along the tire radial direction to the tire maximum width position, as measured from a rim flange height position. The pneumatic tire according to any one of 5.

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