JP2018187995A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve weight saving while maintaining or improving steering stability.SOLUTION: On the outer surface 3S of a sidewall part 3 of a pneumatic tire 1 having a carcass 6 with a body part 6a and a folded part 6b, provided is a side reinforcement layer 11 composed of carbon fiber-reinforced plastic.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a pneumatic tire that can achieve weight reduction while maintaining or improving steering stability.

  In recent years, in order to improve the fuel efficiency of vehicles, there is a demand for weight reduction of pneumatic tires. The weight reduction of a pneumatic tire is performed mainly by reducing the thickness (thinning) of a rubber that forms the outer portion of the tire, for example, sidewall rubber. However, the weight reduction of such a tire can bring about a low fuel consumption, but there is a problem that the stability of the tire is deteriorated and the steering stability is deteriorated.

  In Patent Document 1 below, it is proposed that the sidewall rubber is formed of a hollow filler mixed rubber in which a hollow filler is mixed in a rubber base. However, it has not reached a level that is sufficiently satisfactory for weight reduction.

JP 07-2105018 A

  Accordingly, the present invention provides a pneumatic tire that can achieve weight reduction while maintaining or improving steering stability, on the basis of providing a side reinforcing layer made of carbon fiber reinforced plastic on the outer surface of the sidewall portion. It is an issue.

The present invention provides a carcass having a main body part that extends from a tread part to a bead core of a bead part through a sidewall part, and a folded part that is connected to the main body part and is folded from the inner side to the outer side in the tire axial direction around the bead core. A pneumatic tire,
A side reinforcing layer made of carbon fiber reinforced plastic is disposed on the outer surface of the sidewall portion.

In the pneumatic tire according to the present invention, in a grounded state in which a load that is 70% of the normal load is applied to the tire that is assembled to the normal rim and filled with the normal internal pressure,
The tire radial inner end of the side reinforcing layer has a tire radial height H1 from the bead base line of 45 to 55% of the tire radial height HT from the bead base line to the ground contact surface, and the side reinforcing layer The outer radial end of the tire preferably has a height H2 in the tire radial direction from the bead base line of 75 to 80% of the height HT.

  In the pneumatic tire according to the present invention, it is preferable that in the side reinforcing layer, the orientation direction of the carbon fibers is an angle of 60 degrees or less with respect to the tire radial direction.

  In the pneumatic tire according to the present invention, the thickness t from the outer end to the outer surface of the side reinforcing layer is 2.0 to 3.5 mm at the radially outer end of the turned-up portion of the carcass, and the side The thickness t1 of the reinforcing layer is preferably 0.5 to 1.5 mm.

  In the pneumatic tire according to the present invention, the carbon fiber reinforced plastic is preferably composed of a laminate of prepregs having a thickness of 0.08 to 0.12 mm, in which carbon fibers are impregnated with an epoxy resin.

  In the pneumatic tire according to the present invention, the carbon fiber reinforced plastic preferably has an epoxy resin impregnation amount of 30 to 50 wt%.

In the pneumatic tire according to the present invention, the carbon fiber reinforced plastic has a complex elastic modulus E ^* of 3.3 × 10 ^{10 to} 7.8 × 10 ¹⁰ Pa with respect to the fiber direction per thickness of 1.0 mm. preferable.

  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 means "Measuring Rim". The “regular internal pressure” is the air pressure defined by the standard for each tire. The maximum air pressure for JATMA, the maximum value described in the table “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” for ETRA, Means "INFLATION PRESSURE", but in the case of passenger car tires, it is 180 kPa. The “regular load” is the load specified by the standard for each tire. The maximum load capacity shown in the table “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” is the maximum load capacity for JATMA and TRA for TRA. If it is ETRTO, it is "LOAD CAPACITY".

The complex elastic modulus E ^* is measured in accordance with JIS K7244 “Plastics-Test method for dynamic mechanical properties”, and by dynamic strain control, strain (0.02%), frequency (10 Hz), deformation mode (tensile), measurement It is the value measured on condition of temperature (31 degreeC).

  In the present invention, as described above, a side reinforcing layer made of carbon fiber reinforced plastic is provided on the outer surface of the sidewall portion. This carbon fiber reinforced plastic exhibits very high tensile elastic properties in the fiber orientation direction.

  On the other hand, when a load is applied to the tire, on the outer surface of the sidewall portion, compressive strain is generated on the bead portion side, and tensile strain is generated on the tread side. Therefore, by providing the side reinforcing layer made of carbon fiber reinforced plastic in the region of the outer surface of the sidewall portion where tensile strain occurs, the amount of tire deflection can be effectively suppressed.

  As a result, it is possible to reduce the thickness of the sidewall rubber and achieve weight reduction while ensuring high tire rigidity and maintaining or improving steering stability.

It is sectional drawing which shows one Embodiment of the pneumatic tire of this invention. It is sectional drawing which expands and shows an inner reinforcement layer. It is sectional drawing which shows the grounding state of a pneumatic tire.

Hereinafter, embodiments of the present invention will be described in detail.
FIG. 1 is a meridional cross-sectional view of a tire in a normal internal pressure state Y0 in a no-load state in which a normal rim J is assembled with a rim and is filled with a normal internal pressure.

  As shown in FIG. 1, the pneumatic tire 1 of the present embodiment is a super flat tire having a flatness ratio of 55% or less, and reaches the bead core 5 of the bead portion 4 from the tread portion 2 through the sidewall portion 3. A carcass 6 and a belt layer 7 disposed outside the carcass 6 and inside the tread portion 2 are provided.

  The carcass 6 is formed of one or more, in this example, one carcass ply 6A in which carcass cords such as organic fiber cords are arranged at an angle of, for example, 70 to 90 degrees with respect to the tire equator C. The carcass 6 includes a main body portion 6a straddling between the bead cores 5 and 5, and a turn-back portion 6b connected to the main body portion 6a and folded back from the inner side in the tire axial direction around the bead core 5.

  In this example, the outer end 6E in the tire radial direction of the folded portion 6b terminates at a position beyond the carcass maximum width position M outward in the tire radial direction. The “carcass maximum width position M” is defined as a height position at which the main body portion 6a of the carcass 6 projects most outward in the tire axial direction in the normal internal pressure state Y0 (shown in FIG. 1).

  A bead apex rubber 8 for bead reinforcement extending in a tapered manner from the bead core 5 toward the outer side in the tire radial direction is disposed between the main body portion 6a and the folded portion 6b of the carcass 6.

  The belt layer 7 is formed of two or more belt plies 7A and 7B in this example in which belt cords such as steel cords are arranged at an angle of 10 to 35 degrees with respect to the tire equator C, for example. The belt cords cross each other between the belt plies 7A and 7B, whereby the belt rigidity is increased, and the tread portion 2 is strongly reinforced with a tagging effect.

  A band layer 9 is disposed on the outer side in the tire radial direction of the belt layer 7 for the purpose of improving high-speed durability and the like. The band layer 9 has a band cord wound spirally in the tire circumferential direction. As the band layer 9, a pair of left and right edge band plies that covers only the outer end portion in the tire axial direction of the belt layer 7 and a full band ply that covers substantially the entire width of the belt layer 7 can be appropriately employed. In this example, a case where the band layer 9 is composed of one full band ply 9A and an edge band ply 9B is exemplified.

  In this example, the rim protector 10 is formed at a position on the inner side in the tire radial direction from the carcass maximum width position M. The rim protector 10 protects the rim flange Jf in a super flat tire and prevents damage to the rim flange Jf due to contact with a curb or the like.

  The rim protector 10 has a top portion P that protrudes most outward in the tire axial direction, and extends continuously in the tire circumferential direction. The top portion P is located on the inner side in the tire radial direction with respect to the carcass maximum width position M, and protrudes on the outer side in the tire axial direction with respect to the rim flange Jf. An outer surface 3S (hereinafter sometimes referred to as “sidewall surface”) of the sidewall portion 3 is a convex circle that smoothly extends from the top portion P toward the tread contact end Te on the outer side in the tire radial direction from the top portion P. It is formed with an arcuate curve. Further, on the inner side and the outer side in the tire radial direction from the top part P, a concave arc-shaped curve extending smoothly from the top part P toward the outer side surface 4S of the bead part 4 is formed.

  Next, a side reinforcing layer 11 made of carbon fiber reinforced plastic (CFRP) is disposed on the sidewall surface 3S. The fiber orientation direction of the carbon fiber reinforced plastic is an angle of 60 degrees or less, preferably 45 degrees or less with respect to the tire radial direction. Such a side reinforcement layer 11 exhibits a very high tensile elastic characteristic with respect to the tire radial direction.

  FIG. 3 is a meridional cross-sectional view of the tire in the ground contact state Y1 in which a load of 70% of the normal load is applied to the tire 1 in the normal internal pressure state and grounded. As shown in FIG. 3, in the ground contact state Y1, compressive strain is generated on the bead side of the sidewall surface 3S, and tensile strain is generated on the tread side. This compressive strain and tensile strain are switched at position K. The tire radial height HK from the bead base line BL at the position K is generally in the range of 40 to 45% of the tire radial height HT from the bead base line BL to the contact surface GL. This position K is located in the vicinity of the carcass maximum width position M in the normal internal pressure state Y0.

  Therefore, by providing the side reinforcing layer 11 made of carbon fiber reinforced plastic in the region of the sidewall surface 3S where the tensile strain occurs, that is, the region outside the boundary position K in the tire radial direction, the amount of deflection of the tire is effectively reduced. Can be suppressed. As a result, it is possible to reduce the thickness of the sidewall rubber 3G and achieve weight reduction while ensuring high tire rigidity and maintaining or improving steering stability. The side reinforcing layer 11 is also useful for improving the cut resistance of the sidewall portion 3.

  Specifically, in the ground contact state Y1, the side reinforcing layer 11 preferably has a tire radial height H1 from the bead base line BL of the tire radial inner end E1 in a range of 45 to 55% of the height HT. . Moreover, the tire radial direction height H2 from the bead base line BL of the tire radial direction outer end E2 of the side reinforcing layer 11 is preferably in the range of 75 to 80% of the height HT. In this example, the outer end 6E of the folded portion 6b of the carcass 6 is located radially inward from the outer end E2 of the side reinforcing layer 11 and radially outward from the inner end E1.

  When the height H1 is less than 45% of the height HT, the inner end portion of the side reinforcing layer 11 is located in a region where tensile strain does not occur so much or a region where compressive strain occurs. Therefore, the inner end portion can not only contribute to the effect of suppressing the amount of deflection of the tire, but also causes an unnecessary increase in tire weight. When the height H1 exceeds 55% of the height HT, the radial width of the side reinforcing layer 11 itself is shortened, so that the effect of suppressing the amount of deflection of the tire is reduced, and the steering stability is disadvantageous.

  If the height H2 is less than 75% of the height HT, the width in the radial direction of the side reinforcing layer 11 itself is shortened, so that the effect of suppressing the amount of deflection of the tire is reduced, resulting in a disadvantage in steering stability. On the other hand, when the height H1 exceeds 80% of the height HT, the outer end portion of the side reinforcing layer 11 is located in a region where tensile strain is not so much generated. For this reason, the outer end portion not only contributes little to the effect of suppressing the amount of deflection of the tire, but also causes an unnecessary increase in tire weight.

  The difference (H2−H1) between the height H2 and the height H1 is preferably 22.5% or more, more preferably 25% or more of the height HT.

  Further, since the tire rigidity can be ensured by the side reinforcing layer 11, the thickness of the side wall rubber 3G can be reduced. As shown in an enlarged view in FIG. 2, the thickness t from the outer end 6E of the folded portion 6b of the carcass 6 to the outer surface of the side reinforcing layer 11 is preferably 2 to 3.5 mm. Of these, the thickness t1 of the side reinforcing layer 11 itself is preferably 0.5 to 1.5 mm. In particular, the difference in thickness (t−t1) is preferably 2.0 mm or less.

  If the thickness t1 is less than 0.5 mm, the effect of suppressing the amount of deflection of the tire becomes insufficient, and it is impossible to achieve both steering stability and weight reduction. On the other hand, if it exceeds 1.5 mm, the weight increases and it becomes difficult to achieve weight reduction, and the tire rigidity increases too much, leading to a decrease in steering stability, particularly riding comfort performance. From such a viewpoint, the lower limit value of the thickness t1 is preferably 0.8 mm or more, and the upper limit is preferably 1.2 mm or less.

  If the thickness t exceeds 3.5 mm or the difference (t−t1) exceeds 2.0 mm, it is difficult to achieve weight reduction. On the other hand, when the thickness t is less than 2.0 mm or the difference (t−t1) is less than 0.5 mm, the stress at the outer end 6E of the folded portion 6b of the carcass 6 is concentrated, and the outer end 6E is the starting point. Damage tends to occur.

  The carbon fiber reinforced plastic (side reinforcing layer 11) is preferably formed of a plurality of prepreg layers. A prepreg is a thin sheet-like composite material impregnated with a matrix resin in a state where carbon fibers are aligned in one direction. As the matrix resin, for example, a thermosetting resin such as an epoxy resin is employed. In particular, a flexible epoxy resin such as a polyalkylene ether-modified epoxy resin is suitable. Thereby, the bending rigidity of the side reinforcement layer 11 can be restrained low, and it is useful for the improvement of riding comfort performance.

  As the prepreg, those having an epoxy resin content of 30 to 50 wt% and a thickness of 0.08 to 0.12 mm can be suitably used, and the side reinforcing layer 11 is, for example, a laminate of 8 to 12 prepregs. Preferably formed. By using a thin prepreg having a thickness of 0.12 mm or less and setting the content of the epoxy resin to 30 wt% or more, flexibility can be imparted to the side reinforcing layer 11. In addition, when the content rate of an epoxy resin is less than 30 wt%, the side reinforcement layer 11 will become hard too much and it will be disadvantageous for riding comfort performance. On the other hand, if it exceeds 50%, the compounding amount of the carbon fiber is reduced, so that the effect of suppressing the amount of deflection of the tire cannot be exhibited sufficiently.

In the side reinforcing layer 11, it is preferable that the complex elastic modulus E ^* measured in the fiber orientation direction is 3.3 × 10 ^{10 to} 7.8 × 10 ¹⁰ Pa per 1.0 mm thickness of the carbon fiber reinforced plastic. . If the complex elastic modulus E ^* exceeds 7.8 × 10 ¹⁰ Pa, the side reinforcing layer 11 becomes too hard, which is disadvantageous for ride comfort performance. Conversely, if the complex elastic modulus E ^* is less than 3.3 × 10 ¹⁰ Pa, the effect of suppressing the amount of tire deflection cannot be sufficiently exhibited. The tangent loss tan δ per 1.0 mm thickness of the carbon fiber reinforced plastic is preferably 0.051 to 0.128.

  Such a pneumatic tire 1 can be formed by the following method. First, an uncured prepreg is sequentially attached to the sidewall surface 3S of a vulcanized pneumatic tire in a direction in which the fiber orientation direction is the tire radial direction, and a laminate of prepregs (uncured side reinforcing layer). 11).

  The side surface of the side wall for attaching the prepreg is a smooth surface without unevenness, and is cleaned with naphtha or the like. Further, the prepreg is cut in advance into a shape that matches the attachment position. Note that the prepreg can be laminated first, and this can be attached to the sidewall surface 3S.

  Then, the side reinforcing layer 11 can be integrated with the tire 1 by leaving the tire on which the prepreg laminate is attached, for example, in an oven at 170 ° C. for about 30 minutes.

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

A pneumatic tire (225 / 45R17) having the structure of FIG. 1 was prototyped based on the specifications in Table 1. The mass, lateral spring constant, and steering stability of each tire were tested and compared. The common specifications are as follows.
Carcass ply --- one sheet (polyester cord)
Belt ply --- two (steel cord: 1 × 4 / 0.27)
Band ply --- edge band ply + full band ply (nylon cord)

  Each of the side reinforcing layers was formed of a carbon fiber reinforced plastic using a prepreg having a thickness of 0.10 mm. The matrix resin is a flexible epoxy resin.

  In the conventional example, there is no side reinforcing layer and the sidewall rubber is thick, so that the lateral spring constant and the steering stability are ensured.

(1) Tire mass:
The mass per tire was measured. The results are displayed as an index with the conventional example being 100. Larger numbers are lighter.

(2) Lateral spring constant:
The lateral spring is calculated from the force when a lateral force (0.5 kN) is applied to the sample tire under the conditions of rim (17 x 7.5 JJ) and internal pressure (230 kPa) and the amount of movement at the tread center. In addition, the index of the conventional example is 100. The larger the value, the higher the lateral spring constant and the better.

(3) Steering stability:
The prototype tire was mounted on all wheels of a vehicle (2000 cc sedan car: 1 passenger) with a rim (17 × 7.5 JJ) and internal pressure (230 kPa) and ran on a dry asphalt road test course. Steering stability at that time was displayed as an index with the conventional example being 100 by sensory evaluation of the driver. The larger the value, the better the steering stability.

  As shown in the table, it can be confirmed that the tires of the examples achieve weight reduction while maintaining or improving steering stability.

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 2 Tread part 3 Side wall part 3S Outer surface 4 Bead part 5 Bead core 6 Carcass 6a Main part 6b Folding part 11 Side reinforcement layer

Claims (7)

A pneumatic body having a carcass having a main body part extending from the tread part through the sidewall part to the bead core of the bead part, and a folded part connected to the main body part and folded back from the inside in the tire axial direction around the bead core. Tire,
A pneumatic tire in which a side reinforcing layer made of carbon fiber reinforced plastic is arranged on an outer surface of the sidewall portion. In a grounding state where a load that is 70% of the normal load is applied to a tire that is assembled with a normal rim and filled with a normal internal pressure,
The tire radial inner end of the side reinforcing layer has a tire radial height H1 from the bead base line of 45 to 55% of the tire radial height HT from the bead base line to the ground contact surface, and the side reinforcing layer 2. The pneumatic tire according to claim 1, wherein the tire radial outer end has a tire radial height H2 from a bead base line of 75 to 80% of the height HT.   The pneumatic tire according to claim 1 or 2, wherein the side reinforcing layer has an orientation direction of carbon fibers of 60 degrees or less with respect to a tire radial direction.   At the radially outer end of the folded portion of the carcass, the thickness t from the outer end to the outer surface of the side reinforcing layer is 2.0 to 3.5 mm, and the thickness t1 of the side reinforcing layer is 0. The pneumatic tire according to any one of claims 1 to 3, wherein the pneumatic tire is 5 to 1.5 mm.   The pneumatic tire according to any one of claims 1 to 4, wherein the carbon fiber reinforced plastic is composed of a laminate of prepregs having a thickness of 0.08 to 0.12 mm in which carbon fiber is impregnated with an epoxy resin.   6. The pneumatic tire according to claim 5, wherein the carbon fiber reinforced plastic has an epoxy resin impregnation amount of 30 to 50 wt%. The carbon fiber reinforced plastic has a complex elastic modulus E ^* of 3.3 × 10 ^{10 to} 7.8 × 10 ¹⁰ Pa with respect to the fiber direction per thickness of 1.0 mm. Pneumatic tire.

Images