JP4721770B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire excellent in high-speed performance, and particularly to a tire capable of improving steering stability.

A so-called high-performance radial tire excellent in high-speed performance is usually provided with at least two layers on the outer side in the radial direction of the carcass 92, as shown in FIG. In order to secure straight running stability at high speed and drainage, a tread 94 is formed with a circumferential groove 95 facing the circumferential direction (for example, , See Patent Document 1).
JP 2002-337509 A

  When a pneumatic tire having such a circumferential groove is filled with internal pressure and rolled on the road surface, the carcass and belt of the tread part must always have a groove as a crease, regardless of the amount of bending. Bending in the cross section, the carcass deforms closer to the road surface at the portion corresponding to the groove portion than at the portion corresponding to the land portion.

  FIG. 2 is a tire cross-sectional view schematically showing the deformation of the tread portion around the groove for explaining this, and the tread 94 that contacts the road surface is pushed from the inside in the radial direction by the filled internal pressure P. However, since the land portion 95 is supported on the road surface, the groove portion 96 does not directly contact the road surface, so there is nothing to support this from the back, so the carcass 92 and the belt 93 are The portion corresponding to the groove portion 96 is deformed closer to the road surface than the portion corresponding to 95.

  This bending varies depending on the size and structure of the tire, but in general, the wider the groove portion 96, the larger the bending, and the bending of the belt 93 generated in this way is on the outer side in the radial direction of the belt 93. The thickness of the land portion 95 that is originally formed with a uniform thickness is changed, that is, the amount of compression of the land portion 95 changes depending on the position in the cross section in the tire width direction. Provides uniform contact pressure distribution.

  In general, the more uniform the contact pressure distribution in the contact portion is, the better the steering stability is. Therefore, such bending of the belt causes a deterioration in the steering stability.

  The change in the contact pressure is greatly compressed in the portion of the land portion 95 adjacent to the groove portion 96, and the amount of compression decreases as the distance from the groove portion 96 increases. Therefore, uneven wear occurs in the end portion of the land portion 95. It can also be a cause.

  The present invention has been made in view of such problems, and improves steering stability and wear resistance by suppressing the occurrence of uneven contact pressure distribution caused by the presence of circumferential grooves. An object of the present invention is to provide a tire that can be used.

<1> is a tread having at least a groove extending in the circumferential direction, a carcass made of at least one carcass ply extending in a toroidal manner between a pair of bead cores, and a tread and a carcass. In pneumatic tires with belts installed,
A carcass inner reinforcement layer made of a steel cord having an inclination angle of 60 to 90 degrees with respect to the equator plane is provided in a width direction region corresponding to the tread width inside the carcass in the radial direction , and the carcass and the carcass inner reinforcement layer are provided . Is a pneumatic tire in which a buffer layer made of rubber is disposed between the two.

<2>, in <1>, as well as the thickness before Kigo beam buffer layer and 1 to 5 mm, a width direction end of the rubber buffer layers, the same side as the end with respect to the equatorial plane, the carcass inside from the widthwise end of the reinforcing layer is a pneumatic tire comprising by located in the region up to the end in the width direction region that corresponds to the tread width.

  <3> includes two belts, a first belt ply and a second belt ply, in which the belt is inclined to opposite sides with respect to the equator plane in <1> or <2>. The cord of the first belt ply is made of an organic fiber, the first belt ply is connected to the main body portion in the radial direction of the second belt ply, and both ends in the width direction of the second belt ply connected to the main body portion. It is a pneumatic tire comprised by each fold part folded back so that it may be located in the radial outside of a part.

  <4> is any one of <1> to <3>, and is provided with one or more circumferential reinforcing layers in which a cord is spirally arranged in the circumferential direction adjacent to the outer side or the inner side in the radial direction of the belt. A pneumatic tire according to any one of claims 1 and 3.

<5> is a pneumatic tire comprising constitute fraud and mitigating risk code of the circumferential reinforcing layer in the twisted cord of aramid fiber <4>.

<6> is a air-filled tire Oite, ing to the code of the circumferential reinforcement layer formed of a twisted cord of nylon fiber to <4>.

<7> is a pneumatic tire comprising forming by twisting fraud and mitigating risk code of the circumferential reinforcement layer and the aramid fiber and nylon fiber <4>.

  According to <1>, since the carcass inner reinforcing layer made of a steel cord having an inclination angle of 60 to 90 degrees with respect to the equator plane is provided in the width direction region corresponding to the tread width inside the carcass in the radial direction. As will be described in detail later, the amount of bending deformation in the tire cross section of the belt can be suppressed, which can equalize the contact pressure of the tread and thus improve the handling stability and wear resistance. it can.

  According to <2>, since the buffer layer made of rubber is disposed between the carcass inner reinforcing layer, the following manufacturing problems can be solved. In other words, the carcass ply tends to shrink in the width direction during the manufacturing process, and the angle of the carcass ply cord with respect to the equatorial plane is especially aimed at increasing the lateral rigidity of the tire with excellent high-speed running performance. In many cases, the angle is set to be smaller than 90 degrees, which further increases the shrinkage in the width direction. If such a carcass ply is directly adjacent to the carcass inner reinforcement layer, the carcass ply The steel cord of the carcass inner reinforcement layer is compressed and deformed by the contraction force of the carcass, resulting in deterioration of the cord wave and cord driving variation. However, the rubber buffer layer in the present invention can avoid such a problem. it can.

  In addition, although the thickness of the rubber buffer layer is 1 to 5 mm, when the thickness is less than 1 mm, it is not possible to obtain a sufficient buffering effect of the compression force for the above problem, and the rubber buffer When the thickness of the layer exceeds 5 mm, even if it is thicker than this, it is not possible to expect an increase in the buffering effect. Rather, the disadvantages due to the increase in the weight of the rubber surface.

Further, the widthwise end of the rubber buffer layers, the same side as the end with respect to the equatorial plane, the width-direction end of the carcass inner reinforcing layer, in the region up to the end in the width direction region that corresponds to the tread width However, if the end of the rubber cushioning layer in the width direction is positioned on the inner side of the end of the carcass inner reinforcement layer, the cushioning effect of the rubber cushioning layer is exerted over the entire width of the carcass inner reinforcement layer. can not be made to function, whereas, this when is positioned outside the edge of the width direction region that corresponds to the tread width, the buffering effect demerits appear due to the increased weight of the saturated rubber.

  According to <3>, the belt is composed of two sheets of a first belt ply and a second belt ply formed by inclining the cords on opposite sides with respect to the equator plane. It consists of organic fibers, and the first belt ply is located radially outside the second belt ply, and is connected to the body and located radially outward at both widthwise ends of the second belt ply. Since each of the folded portions is configured as described above, the high-speed durability can be improved by suppressing breakage from the belt end due to high-speed running, as will be described in detail later.

  According to <4>, since one or more circumferential reinforcing layers in which the cords are spirally arranged in the circumferential direction are provided adjacent to the radially outer side or the inner side of the belt, the carcass or belt Displacement of the end portion in the width direction to the outside in the radial direction can be suppressed, and high-speed durability can be further improved.

  According to <5>, since the cord of the circumferential reinforcing layer is an aramid fiber twisted cord, the tensile rigidity of the circumferential reinforcing layer can be effectively improved.

  According to <6>, since the cord of the circumferential reinforcing layer is a twisted cord of nylon fiber, resistance to compression can be secured while securing the tensile rigidity of the circumferential reinforcing layer.

  According to <7>, since the cord of the circumferential reinforcing layer is formed by twisting aramid fiber and nylon fiber, the tensile rigidity of the circumferential reinforcing layer is extremely high and the resistance to compression is also ensured. Can do.

  Embodiments of the present invention will be described with reference to the drawings. 3 is a cross-sectional view showing a pneumatic tire according to the present invention, FIG. 4 is a detailed view showing a portion “a” in FIG. 3, and FIG. 5 is an arrow view corresponding to the arrow AA in FIG. 6A is a plan view showing the belt, and FIG. 6B is a sectional view of the belt. The pneumatic tire 10 includes at least a tread 4 provided with a groove portion 6 extending in the circumferential direction, and at least one carcass ply (in the illustrated example, an inner carcass ply 2a) extending in a toroidal manner between the pair of bead cores 1. And the outer carcass ply 2 b), and a belt 3 disposed between the tread 4 and the carcass 2. A carcass inner reinforcing layer 8 in which steel cords are arranged is provided between the carcass 2 and the carcass 2 between the carcass 2 and the inner liner 7 that covers the inner peripheral surface of the tire 10.

  Here, in the case of a radial tire for a passenger car, the carcass plies 2a and 2b are configured by arranging organic fiber cords so as to face 90 degrees or an angle close to the equator plane. The belt 3 is composed of two belt plies 13 and 14 in which steel cords or organic fiber cords are arranged at a low angle with respect to the equator plane and inclined to opposite sides. The main body part 13a adjacent to the inner side in the radial direction of the two belt plies 14 and the respective ends folded to be positioned on the outer side in the radial direction of the both end parts in the width direction of the second belt ply 14 are connected to both ends in the width direction of the main body part 13a. It is preferable to constitute the fold portion 13b.

  Thus, by making the belt 3 a so-called fold structure in which both ends of the first belt ply 13 are folded back to form a fold portion 13b, the width direction of the belt 3 that has the highest stress and is likely to become the core of breakage during high-speed running. In addition to reinforcing both ends, it is possible to prevent the cord from sticking to the rubber, which is particularly likely to occur when the second belt ply 13 is made of a steel cord, thereby improving high-speed durability. it can.

  Further, it is preferable to provide the belt reinforcing layer 15 in which the cords are substantially oriented in the circumferential direction on the radially outer side or the inner side of the belt 3, and in particular, the belt reinforcing layer 15 is arranged in the width direction of the belt 3 as illustrated. More preferably, it is arranged so as to concentrate only on the radially outer side of the end portion, which suppresses the displacement of the end portion in the belt width direction to the radially outer side due to the centrifugal force during high-speed running, thereby increasing the speed. Durability can be improved. Such a belt reinforcing layer 15 can be formed by winding a cord covered with rubber spirally in the circumferential direction.

  The cord constituting the belt reinforcing layer 15 is preferably made of aramid fiber or nylon fiber, or preferably formed by twisting aramid fiber and nylon fiber, and thereby the tensile rigidity of the circumferential reinforcing layer The resistance to compression can be ensured.

In addition to the above configuration, preferably, a rubber buffer layer 9 is provided between the carcass 2 and the carcass inner reinforcing layer 8, and in this case, the thickness t of the rubber buffer layer 9 is 1 to 5 mm, The width direction end e ₁ of the rubber buffer layer 9 extends from the width direction end e ₂ of the carcass inner reinforcing layer 8 on the side corresponding to the end e ₁ to the width direction end e ₃ of the region corresponding to the tread width TW. Locate in the area.

  Here, the effect | action about arrange | positioning the carcass inner side reinforcement layer 8 in the radial direction inner side of the carcass 2 is demonstrated. FIG. 7 shows a conventional tire structure, a carcass 22 made up of two layers of carcass plies 22a, 22b in which nylon cords are arranged, a belt 23 made up of two layers of belt plies 23a, 23b in which steel cords are arranged, and a belt The internal pressure is applied to a tire for a passenger car having a structure including a pair of belt reinforcing layers (not shown) made of nylon cord arranged radially outward of the end portion in the width direction of 23 (the conventional tire shown in Table 1 for details). Is an image of the vicinity of the groove portion 36 taken by X-ray of a cross section immediately under the load of a tire rolled while applying a load of 500 kg.

  As can be seen from FIG. 7, the carcass 22 and the belt 23 corresponding to the groove portion show a behavior corresponding to a beam in a bending deformation state as shown in FIG. 8, and this was compared with the state before the deformation. However, the position of the belt ply 23a on the inner side in the radial direction corresponds to the neutral axis M of the beam in FIG. 8. Therefore, the carcass 22 arranged on the inner side in the radial direction from the belt ply 23a is compressed, and the radius is greater than that of the belt ply 23a. The outer belt ply 23b arranged on the outer side in the direction is pulled.

  Therefore, in order to suppress the amount of bending deformation, it is effective to provide a reinforcing layer having a high compressive strength in the pneumatic tire 10 at a position as far away as possible from the belt ply 13 serving as the neutral axis M inward in the radial direction. I know that there is. The present invention has been made based on this experiment, and a reinforcing layer made of a steel cord having a high compressive strength is provided in a portion located farthest from the belt ply 13 and located radially inward from the carcass 2. As a result, the amount of bending deformation of the belt 3 can be suppressed, and hence the ground pressure of the tread can be equalized.

  Here, the appropriate range of the carcass inner reinforcing layer 8 in the inclination direction of the steel cord 8a was also examined. FIG. 9 is a perspective view showing a test piece used in a bending experiment, in which FIG. 9A shows a state before bending deformation, and FIG. 9B shows a state after bending deformation. The test piece 31 has a rectangular parallelepiped shape with a thickness of 8 mm and a length and width of 100 mm, and a steel cord 33 inclined at an angle α with respect to the bending center line P is arranged on one surface of the rubber base 32 in the thickness direction. Formed. And the inclination angle (alpha) was changed and the relationship between angle (alpha) and bending strength with respect to it was graphed. FIG. 10 is a graph showing the results, and the vertical axis is expressed as an index with the bending strength being 100 when α is 90 degrees.

  In addition, three steel filaments having a diameter of 0.23 mm were twisted to form a steel cord 33, which was arranged at a pitch of 2 mm.

  As can be seen from FIG. 10, the greater the inclination angle α, the greater the flexural strength, but it can carry a large value as long as it does not dissipate 60 degrees. From this, the steel of the carcass inner reinforcing layer 8 is The appropriate range of the inclination direction of the cord 8a was set to 60 to 90 degrees.

  Two sheets of carcass ply with two layers of carcass ply with nylon cord arranged at 90 degrees to the equator plane E, and twisted cords of aramid fibers intersecting each other at an inclination angle of 25 degrees with the equator plane And a pair of left and right belt reinforcing layers formed by spirally winding a nylon cord in the circumferential direction on the outer side in the radial direction at both ends in the width direction of the belt. The four types of tires were prototyped.

  As shown in Table 1, these tires differ only in the presence / absence and thickness of the carcass inner reinforcing layer 8 and the presence / absence and hardness of the rubber buffer layer 9, and the other points are completely the same. It is a specification. The carcass inner reinforcing layer was formed by arranging steel cords in which three 0.23 mm filaments were twisted and arranged at intervals of 2 mm. The tire size was 215 / 55R15.

  And about each of these tires, the measurement of the amount of waviness in the tire cross section of the belt and the actual vehicle steering stability evaluation test were carried out. The results are shown in Table 1.

  “Measurement of the amount of waviness in the tire cross-section of the belt” refers to a tire filled with an internal pressure of 200 kPa, rolled slowly while rotating against the road surface with a load of 50 N applied, and then stationary with the load applied In this state, a belt cross section that can be placed directly under the load was photographed with X-rays, and the amount of undulation in the tire cross section of the belt was determined from the photographed image. Here, the swell amount is an amount defined as the difference between the maximum value and the minimum value of the distance from the ground contact surface of the belt portion straddling the groove portion as indicated by δ in FIG.

  In addition, in the actual vehicle steering stability evaluation test, four tires were prototyped for each type of tire, these were attached to each mounting position of the vehicle, this vehicle was driven on the circuit, and the vehicle was controlled by the driver's feeling at that time. The stability was evaluated. The results are shown in Table 1 as an index with Example 3 as 100. This index is superior in steering stability as the value increases. In addition, as a driver's comment on steering stability in a lane change from straight ahead, the tire of Example 4 in particular was evaluated to react quickly and move sharply, and Examples 1 and 2 were also conventional examples. It was evaluated to have a clearly improved handling stability compared to

  The present invention can be used as a tire for high-performance passenger cars or a tire for racing.

It is a cross-sectional view showing a conventional pneumatic tire. It is a schematic diagram which shows a deformation | transformation of the tread part around a groove part. 1 is a cross-sectional view showing a pneumatic tire according to the present invention. FIG. 4 is a detailed view showing a “a” portion in FIG. 3. It is an arrow view corresponding to the AA arrow view of FIG. It is the top view and sectional drawing which show a belt. It is a sample of an X-ray photograph of a conventional tire. It is a schematic diagram which shows the beam of a bending deformation state. The perspective view which shows the test piece used for the bending experiment of the steel cord test piece It is a graph which shows the relationship between cord angle (alpha) and bending strength with respect to it. It is a schematic diagram for defining the amount of undulations.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Bead core 2 Carcass 2a Inner carcass ply 2b Outer carcass ply 3 Belt 4 Tread 7 Inner liner 8 Carcass inner reinforcement layer 9 Rubber buffer layer 10 Pneumatic tire 13 First belt ply 13a Body part 13b Fold part 14 Second belt ply 15 Belt Reinforcing layer 16, 17 Cord 22 Carcass 22a, 22b Carcass ply 23 Belt 23a First belt ply 23b Second belt ply 31 Test piece 32 Rubber base 33 Steel cord 36 Groove

Claims (7)

A tread having at least a groove extending in the circumferential direction, a carcass made of at least one carcass ply extending in a toroidal manner between a pair of bead cores, and a belt disposed between the tread and the carcass. In pneumatic tires,
A carcass inner reinforcement layer made of a steel cord having an inclination angle of 60 to 90 degrees with respect to the equator plane is provided in a width direction region corresponding to the tread width inside the carcass in the radial direction , and the carcass and the carcass inner reinforcement layer are provided . A pneumatic tire in which a buffer layer made of rubber is disposed between the two . With the 1~5mm the thickness before Kigo beam buffer layer, a widthwise end of the rubber buffer layers, the same side as the end with respect to the equatorial plane, the width-direction end of the carcass inner reinforcing layer, the tread width the pneumatic tire according to claim 1 comprising by located in the region up to the end in the width direction region that corresponds to.   The belt is made up of two sheets, a first belt ply and a second belt ply, in which the cord is inclined opposite to the equator plane, and the cord of the first belt ply is made of an organic fiber. The first belt ply is folded back so as to be located on the radially inner side of the second belt ply, and on the radially outer side of both end portions in the width direction of the second belt ply connected to the body portion. The pneumatic tire according to claim 1 or 2, comprising a fold portion.   The pneumatic tire according to any one of claims 1 to 3, wherein one or more circumferential reinforcing layers in which cords are spirally arranged in the circumferential direction are provided adjacent to the outer side or inner side of the belt in the radial direction. The pneumatic tire according to claim 4, wherein the cord of the circumferential reinforcing layer is constituted by an aramid fiber twist cord. The pneumatic tire according to claim 4, wherein the cord of the circumferential reinforcing layer is formed of a twisted cord of nylon fiber. The pneumatic tire according to claim 4, wherein the cord of the circumferential reinforcing layer is formed by twisting aramid fibers and nylon fibers.

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