JP2007137172A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent occurrence of a separation between a belt layer and a carcass layer and a cutoff of the carcass layer, thus improving durability of a pneumatic tire. <P>SOLUTION: A belt reinforcing layer 20, which is wider than the belt layer 10 and has a reinforcing element 25 embedded therein and extending in the circumference direction, is provided outward of the belt layer 10 composed of belt supplies 11 and 12 in the radial direction of the tire. A narrow reinforcing layer 30 is arranged between the belt layer 10 and the carcass layer 3 with crossing each edge portion of the belt layer 10. The reinforcing layer 30 is embedded with a plurality of reinforcing elements 15 in an abutting belt supply 12 and reinforcing elements 35, such as the one made of aromatic polyamide, slanting in the opposite direction to an equatorial plane S of the tire. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire in which a belt reinforcing layer in which a reinforcing element extending in the tire circumferential direction is embedded is superimposed on the belt layer.

  In general, a pneumatic tire is provided with a belt layer including one or more belt plies in which a stiff reinforcing element is embedded in the outer periphery of a carcass layer in a crown portion. This belt layer not only protects the carcass layer, but also serves to compress the pneumatic tire in the radial direction, and maintains the circumferential rigidity and exhibits the so-called effect. However, in a pneumatic tire having such a structure, during high-speed running at a high rotational speed, a large centrifugal force acts and the crown portion of the tire expands and deforms outward in the tire radial direction (hereinafter simply referred to as the radial direction). Maneuvering stability may be reduced.

  Therefore, conventionally, a pneumatic tire is known in which a belt reinforcing layer is disposed so as to overlap with a belt layer of a crown portion, and the crown portion is reinforced to suppress expansion deformation due to centrifugal force (see Patent Document 1).

FIG. 3 is a half cross-sectional view in the tire width direction showing an example of a pneumatic tire 91 provided with such a belt reinforcing layer 20, although not described in the patent literature.
As shown in the figure, this pneumatic tire 91 includes a carcass layer 3 composed of at least one carcass ply extending in a toroidal shape between a pair of bead cores 5 on the crown portion 2, and a tread 4 provided on the outer peripheral side thereof. A belt layer 10 composed of two belt plies 11 and 12 arranged in a radial direction between them, and a belt reinforcing layer composed of a single reinforcing ply arranged outside in the radial direction 20.

  The belt layer 10 is formed such that a radially inner belt ply 12 is wider than an outer belt ply 11, and the inside thereof is made of steel or the like extending in a reverse direction with respect to the tire equatorial plane S. A plurality of reinforcing elements are embedded. On the other hand, the belt reinforcing layer 20 is formed wider than the belt layer 10, covers both ends thereof, and is disposed up to the vicinity of the end portion of the crown portion 2. The belt reinforcing layer 20 has a reinforcing element embedded in the tire circumferential direction (hereinafter simply referred to as a circumferential direction) embedded in the belt reinforcing layer 20, and deformation in the circumferential direction is suppressed by the reinforcing element. Is very small.

  Therefore, in this conventional pneumatic tire 91, since the rigidity in the circumferential direction can be improved by the belt reinforcing layer 20, the above-described effect of pressing down the crown portion 2 is enhanced, and expansion deformation due to centrifugal force is suppressed. The handling stability, traction, and durability of the pneumatic tire 91 during high speed traveling can be greatly improved.

  Focusing on such effects, in recent years, the belt reinforcing layer 20 is similarly provided in various pneumatic tires other than those for passenger cars such as truck and bus tires and motorcycle tires. Yes. As a reinforcing element of the belt reinforcing layer 20, a cord made of organic fiber such as nylon or aromatic polyamide, steel, or the like is generally used. Among them, the aromatic polyamide or steel is difficult to stretch even at high temperatures, and the crown portion 2 In recent years, it has been attracting particular attention because it can effectively suppress the expansion and deformation.

  However, in the pneumatic tire 91 having such a structure, as described below, the belt layer 10 and the carcass layer 3 are caused by high rigidity against deformation in the circumferential direction of the belt reinforcing layer 20. There is a problem that cracks (separation) are likely to occur between them, and a reinforcing element such as a carcass cord constituting the carcass ply of the carcass layer 3 is easily cut.

  That is, the round crown portion 2 of the pneumatic tire 91 is deformed into a flat shape by undergoing deformation in the tire width direction (hereinafter simply referred to as the width direction) or the like in accordance with the road surface shape at the time of ground contact. At this time, the belt layer 10 and the belt reinforcing layer 20 are similarly deformed in the ground plane, but the belt layer 10 is covered from the outer side in the radial direction by the belt reinforcing layer 20 that is difficult to deform in the circumferential direction. It is pressed against the belt reinforcing layer 20 to suppress deformation, and the circumferential elongation at the time of grounding becomes very small.

  On the other hand, the carcass layer 3 is similarly restrained from being stretched in the circumferential direction on the inner side overlapping the belt reinforcing layer 20 with the outer end in the width direction of the belt reinforcing layer 20 as a boundary, but is not greatly restrained on the outer side. Will occur. In particular, in the carcass layer 3 having a radial structure in which the reinforcing element of the carcass ply extends 90 degrees with respect to the tire equatorial plane S, that is, in the width direction, the rubber between the reinforcing elements is easily deformed in the circumferential direction and stretched when grounded. The growth of becomes larger. In addition, this elongation is particularly large at the tire rotation direction front portion (stepping portion) and the tire rotation direction rear portion (kick-out portion) of the contact surface.

  Due to the difference in elongation between the belt layer 10 and the carcass layer 3, a large shear strain is repeatedly generated in the rubber therebetween. As a result, in the conventional pneumatic tire 91, the rubber between the layers 10 and 3 is easily separated and is durable. May be reduced. In particular, the shear strain generated in the interlayer rubber is maximized between both ends of the wide belt ply 12 and the carcass layer 3, and the possibility of occurrence of separation at the portion is greatest.

In addition, the pneumatic tire 91 has a problem in that the distance between the belt layer 10 and the carcass layer 3 is reduced in the vulcanization molding process, which is a part of the manufacturing process, and failure such as separation is likely to occur.
That is, in the vulcanization molding process, an unvulcanized green tire (raw tire) is inserted into a mold (mold), and then vulcanized and molded by applying heat and pressure from the inside of the green tire to obtain a predetermined shape. A product tire 91 is manufactured. With the pressure in the mold, the green tire is expanded outward by about 2% to 7% and pressed against the inner peripheral surface of the mold to be molded. At this time, the belt reinforcing layer 20 that hardly stretches in the circumferential direction hardly expands, whereas the belt layer 10 and the carcass layer 3 have reinforcing elements that are inclined with respect to the tire equatorial plane S. Expands in the circumferential direction.

  However, as described above, since the belt reinforcing layer 20 prevents the belt layer 10 from extending in the circumferential direction, that is, expansion, the belt layer 10 is pressed by the expanding carcass layer 3 to generate pressure on the unvulcanized rubber therebetween. Due to this pressure, the rubber between the layers is pushed and moved radially outward from between the reinforcing elements of the belt layer 10 and the belt reinforcing layer 20 or flows outward in the width direction along the inner periphery of the belt layer 10. Thus, it easily flows out from between the belt layer 10 and the carcass layer 3. This is a phenomenon that occurs because the heated unvulcanized rubber is a very soft fluid, whereas the belt layer 10 and the belt reinforcing layer 20 cannot flow due to the internal reinforcing elements. It occurs in the early vulcanization period.

  This outflow of rubber is likely to occur particularly in the vicinity of the end of the belt layer 10. Therefore, in the pneumatic tire 91, the distance between the carcass layer 3 and the belt layer 10, particularly the end thereof tends to approach. As a result, the circumferential shear strain generated in the above-described interlayer rubber is increased, and separation is more likely to occur. Further, the end portion of the belt layer 10 may move during rolling to come into contact with the carcass layer 3 and the reinforcing element may be cut. Further, when the reinforcing element of the belt layer 10 is made of a metal such as steel, the end of the belt layer 10 has a hard and highly rigid cutting surface, so that the extension and movement of the end are smaller. The interlayer rubber is likely to flow out, and the carcass layer 3 is pressed and the distance is further approached, and the end of the belt layer 10 may contact or bite into the carcass layer 3. Therefore, in this case, separation and carcass layer 3 are more likely to be cut.

  As one method for dealing with such a problem, a method of providing a rubber layer between both ends of the belt layer 10 and the carcass layer 3 and securing a distance between the layers 10 and 3 can be considered. Thereby, even if the difference in the elongation in the circumferential direction between the layers 10 and 3 is large, the shear strain generated in the interlayer rubber can be suppressed low, and the occurrence of separation can be suppressed. Further, it is possible to prevent the end of the belt layer 10 from coming into contact with the carcass layer 3 and to suppress the cutting of the carcass layer 3. However, even if a rubber layer is disposed between the belt layer 10 and the carcass layer 3 before vulcanization, it often flows out during vulcanization molding as described above. It is extremely difficult to manufacture.

JP 2000-203215 A

  The present invention has been made in view of the above-described conventional problems, and its object is to improve the durability of a pneumatic tire by suppressing the occurrence of separation between the belt layer and the carcass layer, the cutting of the carcass layer, and the like. It is.

The invention of claim 1 is a pneumatic tire comprising a pair of bead cores, a carcass layer extending in a toroidal shape between the bead cores, and a tread disposed on an outer peripheral side of a crown portion of the carcass layer, Between the carcass layer and the tread, a belt layer composed of a belt ply having a reinforcing element, and a belt layer disposed on the outer side in the tire radial direction of the belt layer so as to cover both ends of the belt layer and wider than the belt layer. A belt reinforcing layer composed of at least one reinforcing ply having a reinforcing element extending substantially in the tire circumferential direction, and the belt layer and the carcass layer are disposed across the end of the belt layer on the outer side in the tire width direction. And a narrow reinforcing layer having the reinforcing element formed.
According to a second aspect of the present invention, in the pneumatic tire according to the first aspect, the belt layer includes at least one belt ply having a metal reinforcing element.
According to a third aspect of the present invention, in the pneumatic tire according to the first or second aspect, the reinforcing element of the belt ply is inclined at an angle of 15 degrees to 70 degrees with respect to the tire equatorial plane. And
The invention according to claim 4 is the pneumatic tire according to any one of claims 1 to 3, wherein the reinforcing element of the narrow reinforcing layer is inclined at an angle of 20 degrees to 90 degrees with respect to the tire equatorial plane. It is characterized by that.
According to a fifth aspect of the present invention, in the pneumatic tire according to any one of the first to fourth aspects, the reinforcing element of the narrow reinforcing layer is connected to the reinforcing element of the adjacent belt ply and the tire equatorial plane. Inclined in the opposite direction.
A sixth aspect of the present invention is the pneumatic tire according to any one of the first to fifth aspects, wherein a width of the narrow reinforcing layer in a tire width direction is 20 mm to 70 mm.
A seventh aspect of the present invention is the pneumatic tire according to any one of the first to sixth aspects, wherein the reinforcing element of the narrow reinforcing layer is made of an organic fiber.
The invention according to claim 8 is the pneumatic tire according to claim 7, wherein the organic fiber is made of an aromatic polyamide.

(Function)
According to the present invention, the belt reinforcing layer having the reinforcing element that is wider than the belt layer and extends substantially in the circumferential direction is disposed on the outer side in the radial direction of the belt layer, and the belt layer is pressed from the outer peripheral side to perform high-speed rolling. Suppresses expansion and deformation of the crown portion caused by the centrifugal force and the belt layer from peeling off from the lower layer member. In addition, a narrow reinforcing layer having a reinforcing element is disposed between the belt layer and the carcass layer so as to straddle the end of the belt layer, ensuring a distance therebetween, and reducing the shear strain between the layers. It prevents the end of the layer from coming into contact with the carcass layer.

  According to the present invention, the separation of the belt layer and the carcass layer, the occurrence of cutting of the carcass layer, and the like can be suppressed, so that the durability of the pneumatic tire can be improved.

Hereinafter, an embodiment of a pneumatic tire of the present invention will be described with reference to the drawings.
FIG. 1 is a half-sectional view in the width direction of the pneumatic tire 1 of the present embodiment, and FIG. 2 is a partially broken plan development view schematically showing the structure of the crown portion 2 of the pneumatic tire 1.

  The pneumatic tire 1 is a pneumatic radial tire that is mounted on, for example, a passenger car or the like that requires high performance. As shown in FIG. 1, a pair of bead portions are located on the radially inner side (lower side in the figure). 6, a sidewall portion 7 extending from the bead portion 6 toward the outer side in the substantially radial direction (upper side in the drawing), and a substantially cylindrical crown portion 2 that connects the end portions on the outer side in the radial direction of both sidewall portions 7. With.

  Further, the pneumatic tire 1 is folded around a pair of bead cores 5 embedded in the vicinity of the radially inner end of the bead portion 6 and the bead core 5 in the same manner as the conventional pneumatic tire 91 shown in FIG. And a carcass layer 3 extending between the pair of bead cores 5 and a tread 4 provided on the outer peripheral side of the crown portion 2 and having a tread pattern formed of rib grooves 50 and the like. In addition, a belt layer composed of at least one (two in the figure) belt plies 11 and 12 disposed adjacent to the outer peripheral side of the carcass layer 3 between the carcass layer 3 and the tread 4 of the crown portion 2. 10 and a belt reinforcing layer 20 made of at least one (one in the drawing) reinforcing ply disposed radially outward of the belt layer 10. However, this pneumatic tire 1 is different from the conventional pneumatic tire 91 in that a narrow reinforcing layer 30 is provided between both ends of the carcass layer 3 and the belt layer 10 in the width direction.

  As shown in FIG. 1, the carcass layer 3 extends in a toroidal shape from the bead portion 6 through the sidewall portion 7 and the crown portion 2, and surrounds the bead core 5 so as to wrap around the bead core 5. It is arranged so as to be turned outward from the outside and wound up radially outward. The carcass layer 3 is composed of at least one carcass ply. As shown in FIG. 2, the carcass ply 3 extends in the carcass ply substantially in the radial direction, that is, in the width direction in which the angle with respect to the tire equatorial plane S is 90 degrees. A plurality of non-stretchable reinforcing elements 9 such as steel cords and nylon cords are embedded.

  As shown in FIG. 1, the belt layer 10 includes two belt plies 11 and 12 that extend from the tire equatorial plane S to both outer sides in the width direction over substantially the same length. In the belt plies 11 and 12, as shown in FIG. 2, a non-stretchable reinforcing element 15 extending at a predetermined angle with respect to the tire equatorial plane S, for example, a metal such as steel, an aromatic polyamide, or the like A plurality of cords made of organic fibers are embedded.

  As shown in FIG. 1, the belt layer 10 of the present embodiment is formed by superimposing a radially outer belt ply 11 and a wider inner belt ply 12 in the radial direction. Further, the belt plies 11 and 12 cross each other, that is, as shown in FIG. 2, the reinforcing elements 15 are inclined with respect to the tire equatorial plane S in opposite directions.

  Here, when the organic fiber cord having relatively low rigidity and flexibility is used as the reinforcing element 15, the belt layer 10 is filled with the internal pressure as compared with the case where the reinforcing element 15 made of metal having high rigidity is used. Since it can be deformed flexibly at the time of contact or at the time of grounding, it is less likely that an excessive tension or the like is applied to its end, and it can flexibly follow deformation in the circumferential direction. As a result, the circumferential shear strain generated in the rubber between the end of the belt layer 10 and the carcass layer 3 does not become excessive, and separation or the like is less likely to occur.

  However, since the reinforcing element 15 made of metal has higher rigidity against compression deformation than the organic fiber cord, the in-plane shear rigidity of the belt layer 10 is also increased, and the crown portion 2 is prevented from being excessively deformed at the time of ground contact. This has the advantage that the handling stability is higher. In the belt layer 10 of the present embodiment, the belt plies 11 and 12 are formed by reinforcing elements 15 made of metal such as a steel cord in consideration of this advantage.

  In addition, since the in-plane shear rigidity of the belt layer 10 can be sufficiently increased if one metal belt ply is used, the belt layer 10 composed of two or more belt plies, such as the belt layer 10, can be used. If one belt ply is formed of the metal reinforcing element 15, the other belt ply may be formed of the reinforcing element 15 made of organic fibers such as aromatic polyamide.

  As shown in FIG. 1, the belt reinforcing layer 20 is composed of a single reinforcing ply extending from the tire equatorial plane S to the outer sides in the width direction over substantially the same length. As shown, a reinforcing element 25 extending substantially in the circumferential direction, for example, a cord made of a metal such as steel or an organic fiber such as aromatic polyamide is embedded. The belt reinforcing layer 20 is formed wider than the wide belt ply 12 of the belt layer 10, and both end portions of the belt layer 10 are radially outward from the vicinity of the shoulder portions (shoulder portions) 8 at both ends of the crown portion 2. It is placed over.

  Here, the belt reinforcing layer 20 is formed by, for example, winding a strip-shaped member in which one or a plurality of parallel reinforcing elements 25 are covered with rubber around the outer periphery of the belt layer 10 in a spiral shape (spiral shape). Is done. Further, as shown in FIG. 2, the reinforcing element 25 may be arranged such that the linear reinforcing element 25 is substantially oriented in the circumferential direction, and in a plane parallel to the front and back surfaces of the belt reinforcing layer 20, For example, the reinforcing elements 25 bent in a waveform such as a square, a triangle, a sine waveform, or a zigzag shape may be arranged so as to have the same phase and the center line of the amplitude substantially in the circumferential direction. Therefore, in the substantially circumferential direction that is the extending direction of the reinforcing element 25, not only the circumferential direction but also the reinforcing element 25 when the belt reinforcing layer 20 is formed as described above, or the extension of the center line of the amplitude thereof. Including direction.

  As shown in FIG. 1, each reinforcing layer 30 has a width direction outer end between the belt layer 10 and the carcass layer 3, and a width direction more than a width direction outer end of the belt layer 10 (belt ply 12). The belt layer 10 is disposed so as to straddle the respective end portions of the belt layer 10 so that the inner end portion in the width direction is located outside the outer end portion in the width direction of the belt layer 10. Each reinforcing layer 30 is composed of a single reinforcing ply, and as shown in FIG. 2, a plurality of non-stretchable reinforcing elements 35 extending at a predetermined angle with respect to the tire equatorial plane S are embedded therein. ing. In the present embodiment, the reinforcing elements 35 are intertwined with each reinforcing element 15 of the adjacent belt ply 12 in an opposite direction with respect to the tire equatorial plane S.

  Here, as the reinforcing element 35 of the reinforcing layer 30, for example, a reinforcing element 35 made of a metal such as a steel cord having excellent tensile strength or the like may be used, but it is more preferable to use a reinforcing element 35 made of an organic fiber. In the case of the reinforcing element 35 made of an organic fiber, when the crown portion 2 is rolled to deform, the reinforcing element 15 in the adjacent belt layer 10 and the reinforcing element 9 in the carcass layer 3 are rubbed against each other with rubber interposed therebetween. Even if it matches, since the fiber itself is not hard, it is less likely to scrape the rubber between the layers, and there is an advantage that the separation can be more reliably suppressed. In particular, when the reinforcing element 35 is formed of an organic fiber made of an aromatic polyamide, it is excellent in heat resistance as compared with other organic fibers. Therefore, the reinforcing element 35 is disposed at the end of the belt layer 10 that becomes high temperature at high speed rolling. Even its function is not dissolved.

  Note that, as described above, during the vulcanization molding of the green tire, the reinforcing layer 30 is pressed by the expanding carcass layer 3 on the radially inner side to apply pressure toward the unexpanded belt layer 10 on the radially outer side. . However, since the reinforcing layer 30 has a plurality of reinforcing elements 35 inside, it is difficult to flow even by this pressure. As a result, the flow of the surrounding rubber is also suppressed, and even after the vulcanization molding, the layers 3 and 10 are separated. It remains in the same position while securing rubber.

The pneumatic tire 1 of this embodiment has various features described below.
First, since the reinforcing element 15 made of a metal having high rigidity against compression deformation is embedded in at least one of the belt plies 11 and 12 constituting the belt layer 10, the in-plane shear rigidity of the belt layer 10 can be increased, and at the time of grounding, etc. Further, it is possible to improve the steering stability by suppressing the crown portion 2 from being excessively deformed. At the same time, since the reinforcing element 15 is inclined with respect to the tire equatorial plane S, the rigidity is increased against bending deformation in the width direction and the steering stability can be maintained. Further, in this belt layer 10, since the reinforcing elements 15 extending in the opposite directions with respect to the tire equatorial plane S are embedded in the belt plies 11 and 12, the directions of the in-plane shear deformation are reversed. In addition, the deformation can be suppressed and the in-plane shear rigidity becomes high, and the steering stability can be further improved.

  Here, when the reinforcing elements 15 of the two belt plies 11 and 12 are inclined in the opposite directions as in the belt layer 10, the inclination angle of each reinforcing element 15 with respect to the tire equatorial plane S is 45 degrees. The in-plane shear rigidity of the belt layer 10 is maximized at 60 degrees, and the steering stability of the tire at the initial stage of steering is improved. However, when the belt reinforcing layer 20 having the reinforcing elements 25 extending in the circumferential direction is provided in addition to the belt layer 10 as in the pneumatic tire 1 of the present embodiment, the reinforcing elements 15 of the belt plies 11 and 12 Even if the range of the inclination angle is widened, a sufficiently large in-plane shear rigidity can be obtained.

  However, when the inclination angle of the reinforcing element 15 is less than 15 degrees, in addition to the angle difference between the reinforcing elements 15 in the two belt plies 11 and 12 being too small, the belt reinforcing layer 20 Since the angle difference with the reinforcing element 25 is too small, there is a possibility that sufficient in-plane shear rigidity of the belt layer 10 cannot be obtained. On the contrary, when the inclination angle of the reinforcing element 15 is large, for example, 90 degrees, the reinforcing elements 15 of the belt plies 11 and 12 are parallel to each other in the width direction. The shear rigidity is lowered, and the belt layer 10 is easily sheared in the width direction. Similarly, when the inclination angle is larger than 70 degrees, the angle difference between the two belt plies 11 and 12 is too small to obtain a sufficient in-plane shear rigidity, and the steering stability may be lowered. is there.

  Therefore, the inclination angle of the reinforcing element 15 of the belt layer 10 with respect to the tire equatorial plane S is preferably 15 degrees to 70 degrees. Within this range, the crossing angle with the reinforcing element 25 of the belt reinforcing layer 20 or the reinforcing element 15 of another belt ply becomes appropriate, and the in-plane shear rigidity of the belt layer 10 is increased to reduce the steering stability. Can be prevented.

  Further, since the belt reinforcing layer 20 is disposed radially outside covering both ends of the belt layer 10, the entire belt layer 10 that is about to be peeled off from the lower layer member by the centrifugal force during high-speed rolling is pressed and peeled off. And the separation can be effectively suppressed, and the effect of suppressing the expansion and deformation of the crown portion 2 is also increased. In addition, since the belt reinforcing layer 20 is formed wide and disposed near the shoulder portion 8 of the crown portion 2, the rigidity in the circumferential direction can be increased to the end portion of the crown portion 2, and the portion is expanded by centrifugal force. Deformation can be reliably suppressed. As a result, the contact pressure with the road surface of the entire crown portion 2 can be made uniform, heat generation due to the increase in contact pressure can be prevented, and the occurrence of failure due to heat of the crown portion 2 can be suppressed. As described above, the belt reinforcing layer 20 can improve the durability of the pneumatic tire 1 by suppressing the occurrence of a failure such as separation while maintaining steering stability and traction.

  Further, since the reinforcing layer 30 is disposed between the belt layer 10 and the carcass layer 3 so as to straddle the width direction outer side end portion of the belt layer 10, the distance between the layers 3 and 10 can be increased. The occurrence of separation can be suppressed by reducing the shear strain generated in the rubber between layers. At the same time, it is possible to prevent the end of the belt layer 10 from approaching, contacting or biting into the carcass layer 3 at the time of vulcanization molding or rolling. It is possible to suppress the (reinforcing element 9) from being cut.

  In addition to the above effects, the reinforcing element 35 of the reinforcing layer 30 and the reinforcing element 15 of the adjacent belt ply 12 are inclined in the opposite direction with respect to the tire equatorial plane S, so that the reinforcing elements 15 and 35 cross each other. It is possible to effectively prevent an increase in the number of locations where the end of the reinforcing element 15 of the belt ply 12 tries to bite into the reinforcing layer 30 by receiving it at more locations. As a result, the end of the belt ply 12 can be prevented from approaching or coming into contact with the carcass layer 3, and the effect of suppressing the occurrence of separation and the cutting of the carcass layer 3 can be improved. In addition, when the reinforcing layer 30 is formed by the reinforcing element 35 made of organic fibers, it is possible to more reliably suppress the occurrence of separation due to friction with the other reinforcing elements 9 and 15 as described above. When the fiber is made of an aromatic polyamide, it is possible to suppress the functional deterioration of the reinforcing layer 30 at the time of high-speed rolling in which the temperature rises.

  Here, when the rigidity in the circumferential direction of the reinforcing layer 30 is too high, a difference in elongation from the carcass layer 3 generated at the time of ground contact or the like and a shear strain become large, and separation may occur between them. . However, in this embodiment, since the reinforcing layer 30 is formed to be narrow, it can flexibly follow deformation stress received from other members, stress generated at the time of ground contact, and the like as compared with the wide belt layer 10 and the like. The rigidity in the direction does not become higher than necessary, and separation from the carcass layer 3 can be more reliably prevented.

  Although depending on the width of the belt reinforcing layer 20 and the belt layer 10 or the like, when the width of the reinforcing layer 30 is less than 20 mm, the width becomes too narrow, and the outflow of rubber during the vulcanization molding described above or the belt The effect of suppressing the biting of the end portion of the ply 12 is reduced, and conversely, when it is larger than 70 mm, the rigidity in the circumferential direction is increased, and there is a possibility that the shear strain with the carcass layer 3 is increased. Therefore, the width of the reinforcing layer 30 is preferably about 20 mm to 70 mm. Within this range, separation between the carcass layer 3 and cutting of the carcass layer 3 are less likely to occur.

  When the inclination angle of the reinforcing element 35 embedded in the reinforcing layer 30 with respect to the tire equatorial plane S is less than 20 degrees, the extending direction of the reinforcing element 35 is close to the circumferential direction, and the reinforcing layer 30 is circumferential. It becomes difficult to deform. As a result, the rigidity in the circumferential direction of the reinforcing layer 30 is increased, and there is a possibility that the shear strain between the reinforcing layer 30 and the carcass layer 3 is increased. Therefore, in order to more reliably suppress the occurrence of separation, it is more preferable that the inclination angle of the reinforcing element 35 with respect to the tire equatorial plane S is 20 degrees to 90 degrees. The upper limit of 90 degrees is the maximum angle at which the reinforcing element 35 can be inclined.

  As described above, in the pneumatic tire 1 of the present embodiment, the shear strain in the circumferential direction between the belt layer 10 and the carcass layer 3 is reduced, and between the layers 3 and 10, particularly in the vicinity of the end of the belt layer 10. Occurrence of separation can be suppressed. At the same time, the end of the belt layer 10 can be prevented from contacting the carcass layer 3 and the carcass layer 3 can be prevented from being cut. Therefore, it is possible to effectively suppress the occurrence of failure in the pneumatic tire 1 without impairing the steering stability, and it is possible to improve the durability, particularly the high speed durability.

(Tire test)
In order to confirm the effect of the pneumatic tire 1 of the present invention, the tires (hereinafter referred to as “implemented products”) of the four types of examples of the structure described above (see FIG. 1) and the structure obtained by removing the reinforcing layer 30 from the implemented products Using one type of comparative example tire (see FIG. 3) (hereinafter referred to as a comparative product), the durability of the tire was evaluated under the following conditions.

  The following implementation products and comparative products are all radial tires for passenger cars having a tire size 225 / 50R17 (tire outer diameter 658 mm) defined by JATMA YEAR BOOK (2004, Japan Automobile Tire Association Standard). The implemented product and the comparative product were all configured in the same manner except for the reinforcing layer 30. For example, the tread 4 was formed with the same tread pattern including a groove having a predetermined shape. In addition, the carcass layer 3 was formed by stacking two carcass plies in which a nylon cord having a diameter of 0.5 mm formed by twisting nylon fibers was embedded as the reinforcing element 9 so as to extend substantially in the radial direction.

  The belt layer 10 including the two belt plies 11 and 12 is disposed on the radially outer side of the carcass layer 3 in both the implemented product and the comparative product. In the belt plies 11 and 12, so-called 1 × 3 type cords in which three steel wires (diameter 0.2 mm) were twisted as the reinforcing elements 15 were embedded at a driving interval of 35/50 mm. The belt plies 11 and 12 are crossed with each other so that the reinforcing elements 15 in the belt plies 11 and 12 are inclined at an angle of 40 degrees with respect to the tire equatorial plane S and the inclination directions are opposite to each other. Thus, the belt layer 10 was formed. A belt reinforcing layer 20 made of one reinforcing ply is disposed on the outer side in the radial direction. For the reinforcing element 25 of the belt reinforcing layer 20, a twisted aromatic polyamide fiber cord having a diameter of 0.7 mm was used. The three cords were juxtaposed and covered with rubber to form a strip, and the belt reinforcing layer 20 was formed by winding the cord in a spiral shape in the circumferential direction so that the cord driving interval was 50/50 mm.

  The belt ply 12 on the inner side in the radial direction of the belt layer 10 was formed to have a width of 210 mm, the outer belt ply 11 was formed to have a width of 190 mm, and the belt reinforcing layer 20 was formed to have a width of 230 mm. Accordingly, the belt reinforcing layer 20 has the widest width, the end of the belt ply 12 is located at a position 10 mm from the end toward the inner side in the width direction, and the end of the belt ply 11 is further located 10 mm inside.

  In addition to the above, the reinforcing layer 30 was arrange | positioned between the belt layer 10 and the carcass layer 3 in four types of implementation goods. The reinforcing layer 30 is formed to have a width of 20 mm, and its outer end in the width direction is located between the end portions of the belt reinforcing layer 20 and the belt layer 10, that is, from the end of the wide belt ply 12 toward the outer side in the width direction. And 5 mm. In the reinforcing layer 30 of each embodiment, reinforcing elements 35 are embedded at an interval of 40/50 mm, and the material of the reinforcing elements 35 and the inclination angle and the inclination direction with respect to the tire equatorial plane S are changed. Various types of implementation products (hereinafter referred to as implementation products A, B, C, and D) were produced.

  In the reinforcing layer 30 of the product A, a twisted aromatic polyamide fiber cord having a diameter of 0.7 m is used as the reinforcing element 35, and the reinforcing element 35 is inclined at an angle of 60 degrees with respect to the tire equatorial plane S. And the reinforcing element 15 in the adjacent belt ply 12 and the tire equatorial plane S are arranged so as to be inclined in the same direction.

  The reinforcing layer 30 of the product B uses a twisted aromatic polyamide fiber cord having a diameter of 0.7 mm for the reinforcing element 35, and the reinforcing element 35 is inclined at an angle of 60 degrees with respect to the tire equatorial plane S. The reinforcing element 15 in the belt ply 12 and the tire equatorial plane S are disposed so as to be inclined in the opposite direction. That is, the inclination direction of the reinforcing element 35 is different from that of the implementation product A.

  For the reinforcing layer 30 of the product C, a twisted aromatic polyamide fiber cord having a diameter of 0.7 mm is used for the reinforcing element 35, and the reinforcing element 35 is 90 degrees with respect to the tire equatorial plane S, that is, in the width direction. It was arranged with facing. Therefore, the inclination angle of the reinforcing element 35 is different from the implementation products A and B.

  For the reinforcing layer 30 of the implementation product D, a twisted nylon fiber cord having a diameter of 0.7 mm is used as the reinforcing element 35, and the reinforcing element 35 is inclined at an angle of 60 degrees with respect to the tire equatorial plane S, and The reinforcing element 15 in the belt ply 12 and the tire equatorial plane S are disposed so as to be inclined in the opposite direction. That is, the material of the reinforcing element 35 is different from the implementation products A, B, and C, the inclination direction of the reinforcement element 35 is different from that of the implementation product A, and the inclination angle is different from that of the implementation product C.

Two kinds of durability tests and steering stability tests were performed using the above comparative products and the respective implementation products. The following tests were conducted using new tires.
The durability test was performed by pressing the tire on the outer periphery of a steel drum having a diameter of 3 m at a camber angle of 0 degrees and a slip angle of 0 degrees with two types of loads (6 kN and 9 kN) and rotating at high speed. At this time, the tire was mounted on a 7 J × 17 inch rim and then filled with an internal pressure of 180 kPa, which was lower than the specified internal pressure of 220 kPa. The reason for setting the tire internal pressure to be lower than the designated internal pressure is to increase the amount of deflection of the tire and promote the failure of the tire. Under the above conditions, after running continuously at a speed of 120 km / h for 200 hours, the tires were dissected to examine the presence or absence of cracks and the like, and the durability was compared.

  As a result, when the tire was pressed against the drum at 6 kN, a crack having a length of 2 mm occurred in the rubber between the end of the wide belt ply 12 of the comparative product and the carcass layer 3, whereas the product A, In B, C, and D, no cracks were confirmed. Therefore, it can be seen that, under this condition, the occurrence of separation can be suppressed in all the implemented products as compared with the comparative product.

  Further, in the test with a load of 9 kN that cannot occur during normal traveling, the products A, B, C, and D traveled for 200 hours, while the comparative product stripped the end of the belt layer 10 when traveling for 182 hours. Then a burst occurred. At this time, the carcass layer 3 was also cut in the comparative product. However, when each product was dissected, defects such as cracks were not confirmed in the products B and C, whereas defects were confirmed in the products A and D. Specifically, in the product A, a crack having a length of 2 mm occurred between the reinforcing layer 30 and the carcass layer 3, but no failure occurred in other portions. In the product D, the nylon cord of the reinforcing layer 30 was slightly frayed at a position adjacent to the end of the belt ply 12, and a crack of 1 mm in length occurred between the end of the belt ply 12 and the reinforcing layer 30. However, no failure occurred in other parts.

  Here, in the implementation product A, since the inclination directions of the reinforcement elements 15 and 35 of the belt ply 12 and the reinforcement layer 30 are the same, the end portion of the belt ply 12 is reinforced compared to the implementation product B in the opposite direction. It is considered that the layer 30 is easy to bite, the reinforcing layer 30 easily moves in the same manner as the end portion of the belt ply 12, the shear strain is slightly increased, and a slight crack is generated. In the product D, the reinforcing elements 15 and 35 of the belt ply 12 and the reinforcing layer 30 intersect with each other in opposite directions, but the reinforcing element 35 of the reinforcing layer 30 is made of nylon and softens during heat generation. Therefore, it is considered that the cord was deteriorated to cause some fraying and slight cracks. In contrast, in the products B and C, since the reinforcing element 35 intersects with the reinforcing element 15 of the belt ply 12, the distance between the end portion of the belt layer 10 and the carcass layer 3 is ensured and cracks are prevented. The occurrence is considered to be suppressed.

  As described above, under more severe conditions, although a failure occurred in a part of the product, the carcass layer 3 was not cut. In addition, it can be seen that the comparative product has a crack length of at least 20 mm or more, and compared with this, the failure level of each of the implemented products is extremely small, and the occurrence of separation and the cutting of the carcass layer 3 are effective. It can be seen that it can be suppressed.

  Next, each of the comparison product and the implementation products A, B, C, and D is attached to all four wheels of a rear-wheel drive sports type vehicle, and a test course run by an experienced driver is performed to compare the handling stability. did. As a result, no difference was found in the handling stability of the five tires.

  From the above results, it is proved that the present invention can effectively suppress the occurrence of failure and improve the durability of the pneumatic tire 1, particularly the high speed durability and the high load durability without impairing the steering stability. It was done.

It is a tire width direction half sectional view of the pneumatic tire of this embodiment. FIG. 3 is a partially broken plan development view schematically showing the structure of the crown portion of the pneumatic tire of the present embodiment. It is a tire width direction half sectional view of the conventional pneumatic tire.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Pneumatic tire, 2 ... Crown part, 3 ... Carcass layer, 4 ... Tread, 5 ... Bead core, 6 ... Bead part, 7 ... Side wall part, 8 ... Shoulder, 9 ... Reinforcing element, 10 ... Belt layer, 11 ... Belt ply, 12 ... Belt ply, 15 ... Reinforcing element, 20 ... Belt reinforcing layer, 25 ... Reinforcing element, 30 ... Reinforcing layer, 35 ... Reinforcing element, 50 ... Rib groove.

Claims (8)

A pneumatic tire comprising a pair of bead cores, a carcass layer extending in a toroidal shape between the bead cores, and a tread disposed on the outer peripheral side of the crown portion of the carcass layer,
Between the carcass layer and the tread,
A belt layer comprising a belt ply having a reinforcing element;
A belt reinforcement comprising at least one reinforcing ply having a reinforcing element that is wider than the belt layer and extends substantially in the tire circumferential direction, and is disposed outside the belt layer in the tire radial direction so as to cover both ends of the belt layer. Layers,
A narrow reinforcing layer having a reinforcing element disposed between the belt layer and the carcass layer across the end of the belt layer in the tire width direction; and
A pneumatic tire characterized by comprising: In the pneumatic tire according to claim 1,
The pneumatic tire according to claim 1, wherein the belt layer includes at least one belt ply having a metal reinforcing element. In the pneumatic tire according to claim 1 or 2,
The pneumatic tire according to claim 1, wherein the reinforcing element of the belt ply is inclined at an angle of 15 degrees to 70 degrees with respect to the tire equatorial plane. In the pneumatic tire according to any one of claims 1 to 3,
The pneumatic tire according to claim 1, wherein the reinforcing element of the narrow reinforcing layer is inclined at an angle of 20 to 90 degrees with respect to the tire equatorial plane. In the pneumatic tire according to any one of claims 1 to 4,
The pneumatic tire according to claim 1, wherein the reinforcing element of the narrow reinforcing layer is inclined in the opposite direction with respect to the reinforcing element of the adjacent belt ply and the tire equatorial plane. In the pneumatic tire according to any one of claims 1 to 5,
The pneumatic tire according to claim 1, wherein a width of the narrow reinforcing layer in a tire width direction is 20 mm to 70 mm. In the pneumatic tire according to any one of claims 1 to 6,
The pneumatic tire according to claim 1, wherein the reinforcing element of the narrow reinforcing layer is made of an organic fiber. In the pneumatic tire according to claim 7,
A pneumatic tire, wherein the organic fiber is made of an aromatic polyamide.

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