JP2007283822A - Pneumatic radial tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic radial tire having at the tread part a plurality of main grooves stretching in the tire circumferential direction, which enhances the maneuvering stability by effectively increasing the side force of the tire. <P>SOLUTION: A thin groove 22 stretching in the tire circumferential direction is formed in a row 21 of shoulder lands arranged between the outermost main groove 8A across the tire width of the tread part 7 and the tread end TE, whereby the row 21 of shoulder lands is divided in the direction across the tire width. The edge of the land row 21 on its side with the main groove 8A and the outer side edge across the tire width of the thin groove 22 are chamfered 23 and 24. Provision of the thin groove 22 and the chamfers 23 and 24 decrease the shearing force in the counter-side force direction generated in the land row 21. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a pneumatic radial tire provided with a plurality of main grooves extending in the tire circumferential direction in a tread portion, and more particularly to a pneumatic radial tire in which side force is effectively generated to improve steering stability performance.

  For example, pneumatic radial tires such as tires for passenger cars have been required to have various performances such as steering stability performance and wear resistance performance when mounted on a vehicle. However, in recent years, particularly tires reflecting the social situation. The safety performance of has attracted attention. Accordingly, in recent years, there has been a tendency to increase so-called run-flat tires that can travel to some extent even in the event of a failure and have improved safety performance. Above all, a rubber reinforcement layer with a crescent cross section is provided on the tire side part to increase the rigidity of the side part, and when the internal pressure decreases due to puncture etc., the load on the tire is supported by the side part including the rubber reinforcement layer. Side-reinforced run-flat tires that run are the mainstream.

  On the other hand, with regard to the steering stability performance that has been conventionally required, in addition to the effect of suppressing tire deformation by increasing the rigidity of the side part, the rigidity in the ground contact surface of the tire ground contact part, the shearing force acting on the ground contact surface, and turning It is known that tire side forces (cornering forces) and the like that occur sometimes have a significant effect. Therefore, it is expected that the above-described run-flat tire having extremely high side portion rigidity has a high deformation suppressing effect, and the steering stability performance is higher than that of a normal tire. However, run-flat tires usually have the same rigidity in the ground contact surface of a ground contact part as a normal tire, and the ground contact performance of the tire as a whole may decrease due to the rigidity of the side part being too high. Compared to other tires, it is difficult to predict the handling stability at the time of design.

  In addition, as the rigidity of the side portion increases, the side force that also affects the steering stability performance generally increases.Therefore, in the run-flat tire, the side force and the steering stability performance are higher than those of a normal tire. Improvement can be expected. However, the actually generated side force is not greatly different between a run-flat tire and a normal tire. In this regard, the improvement effect of the steering stability performance of the run-flat tire is small. Here, the side force generated in the tire is a combined force of shear forces in the tire width direction (vehicle lateral direction) acting on the contact surface of the tire contact portion, and is generated by examining the shear force distribution on the contact surface. You can know the size of the side force.

FIG. 3A is a diagram illustrating an example of a distribution of shear force acting on the ground contact surface of the tire during turning, and FIG. 3B is a schematic diagram of a cross section in the tire width direction of the corresponding tire.
This shear force distribution diagram is an example of a side-reinforced run-flat tire having a plurality of main grooves extending in the tire circumferential direction in the tread portion, but the shear force distribution of a normal passenger car tire has a similar tendency. Indicates.

  As shown in FIG. 3B, the tire 90 includes a pair of bead portions 91, a side portion 92 that extends outward in the tire radial direction (downward in the drawing), and a crown portion 93 that connects both ends of the side portion 92. A radial carcass (not shown) extending in a toroidal shape across the pair of bead portions 91, and a rubber reinforcing layer 94 having a crescent-shaped cross section disposed along the inner peripheral surfaces of both side portions 92 of the carcass Prepare. The tire 90 includes a plurality of belt layers (not shown) and a tread portion 95 on the circumference of the crown portion 93 of the carcass, and the tread portion 95 includes a plurality (four in this case). A main groove 96 extending in the tire circumferential direction and a land portion (land portion row arranged in the tire circumferential direction) 97 partitioned by the main groove 96 and the like are arranged.

  In the tire 90 at the time of turning, the side portion 92 on the outer side of the turning (right side in the drawing) is compressed and deformed, and the side portion 92 on the inner side of the turning (left side in the drawing) is tensile-deformed by the force acting at that time. At the same time, each land portion 97 of the tread portion 95 comes into contact with the road surface and deforms due to a load or the like, thereby generating a shear strain on the ground contact surface of the tread portion 95 and applying a shearing force. At this time, the side force desired to be generated in the tire 90 is a force in a direction from the outside to the inside (hereinafter referred to as a side force direction) (in the direction of the arrow SF in the figure), the shear force in the same direction is large, and the reverse The smaller the shear force in the direction (hereinafter referred to as the anti-side force direction) (the arrow anti-SF direction in the figure), the larger the side force generated as a resultant force.

  In the shear force distribution diagram of FIG. 3A, the shear force generated in the tire 90 is shown with the side force direction upward and the anti-side force direction downward with reference to zero shear force. As described above, the shearing force in the ground plane is generated in different directions depending on the position of the tread portion 95. In particular, the shearing force is large at the edge (grounding end) of each land portion 97 following the groove wall of the main groove 96 and is generated in the opposite direction across the main groove 96. In particular, the shearing force at the outer edge of the turn across the main groove 96 acts greatly as a reaction force in the anti-side force direction, and it can be seen that the shear force in the vicinity greatly affects the side force of the tire.

  Here, the shear force increases at the edge of each land portion 97 because the land portion 97 is greatly deformed by the lateral force acting on the tire during turning, and the ground pressure is high because the pressure is concentrated on the edge portion. It is to become. In addition, when the land portion 97 comes into contact with the road surface, the land portion 97 is greatly bent due to the application of contact pressure, and the groove wall portion of the main groove 96 bulges toward the main groove 96 in parallel with the road surface, and also near the edge portion. Force in the same direction works. As the reaction force, a crushing force acts on the edge portion of the land portion 97, and the shearing force of the edge portion is further increased by applying the crushing force.

  In addition to the edge portion, the resultant shoulder land rows 97A and 97B disposed between the outer end in the tire width direction of the tread portion 95 and the main groove 96 on the outermost side in the tire width direction also have a large resultant force. Works. Especially, the shear force of the shoulder land part row | line | column 97B of the turning outer side acts as a reaction force of the anti-side force direction, and it turns out that the shear force of this part also has a great influence on the side force. It should be noted that the shear force of the shoulder land row 97B is generated due to a difference in shape between no load and a load, a price tear factor caused by deformation of the belt layer, and the like. It is known that the influence of the deformation is large.

  Therefore, in order to effectively generate the side force of the tire and improve the steering stability performance, in addition to the edge of the shoulder land portion row 97B on the main groove 96 side of the shoulder land portion row 97B located on the outer side of the turn, It is effective to reduce the shear force in the anti-side force direction. Of these, for the edge of the shoulder land portion row 97B on the side of the main groove 96, it is effective to suppress a rise in the contact pressure at the time of grounding, which generates a large shearing force in the anti-side force direction. As a method for that purpose, it has been proposed to form the edge in a chamfered shape (see Patent Document 1).

  That is, when the edge of the shoulder land portion row 97B on the side of the main groove 96 has a linear or curved chamfered shape, the concentration of pressure on the edge at the time of grounding is alleviated, and the contact pressure of the edge and An increase in crushing force can be suppressed. As a result, the shear force in the anti-side force direction (see FIG. 3A) in the vicinity of the edge portion can be reduced, so that the side force that is the resultant force of the shear force of the entire contact surface of the tread portion 95 can be increased.

However, with this chamfering method, the effect of reducing the shear force in the anti-side force direction acting on the other part of the shoulder land row 97B other than the vicinity of the edge portion is small. Not enough.
In the run-flat tire, the compression of the rubber reinforcing layer 94 in the side portion 92 generates a shear force in the anti-side force direction as a compression reaction force on the ground contact surface of the shoulder land portion row 97B. This compression reaction force has a large influence on the shear force of the entire shoulder land portion row 97B along with the deformation at the time of contact as described above. Therefore, in the run flat tire, the reaction force of the shoulder land portion row 97B is larger than that of a normal tire. The shear force in the side force direction tends to increase, and it is necessary to further reduce the shear force.

JP 2002-36826 A

  The present invention has been made in view of the above-described conventional problems, and its purpose is to effectively increase the side force of a pneumatic radial tire having a plurality of main grooves extending in the tire circumferential direction in the tread portion, The aim is to improve the steering stability performance.

The invention of claim 1 includes a belt layer and a tread portion on the periphery of the crown portion of the toroidal radial carcass, a plurality of main grooves extending in the tire circumferential direction in the tread portion, and a tire width direction of the tread portion. A pneumatic radial tire in which a shoulder land portion row is disposed between an outer end and the outermost main groove in the tire width direction, and a narrow groove extending in at least one of the shoulder land portion rows in the tire circumferential direction. And the outermost main groove side edge of the shoulder land portion row and the outer edge of the narrow groove in the tire width direction have a chamfered shape.
According to a second aspect of the present invention, in the pneumatic radial tire according to the first aspect, the narrow groove extends from the outermost main groove side end of the shoulder land portion row in the tire width direction of the shoulder land portion row. It arrange | positions in the position which separated the distance of 15 to 25% of the width, It is characterized by the above-mentioned.
According to a third aspect of the present invention, in the pneumatic radial tire according to the first or second aspect, the chamfered shape of the outermost main groove side edge is chamfered more than the chamfered shape of the fine groove side edge. Is large.
The invention according to claim 4 is the pneumatic radial tire according to any one of claims 1 to 3, wherein the outermost main groove side edge is chamfered or the narrow groove side edge is chamfered. The radial depth is 0.1 to 0.4 mm.
According to a fifth aspect of the present invention, in the pneumatic radial tire according to any one of the first to fourth aspects, a rubber reinforcing layer that shares and supports a tire load is provided on an inner peripheral surface side of the side portion of the carcass. And

(Function)
In the present invention, a narrow groove extending in the tire circumferential direction is provided in at least one shoulder land portion row arranged in the tread portion of the pneumatic radial tire, and the shoulder land portion row is divided in the tire width direction. Accordingly, the compression reaction force generated in the shoulder land portion row due to the compression of the tire side portion is released, and the compression reaction force is suppressed from acting on the shoulder land portion row on the inner side in the tire width direction from the narrow groove. Moreover, the shear force in the anti-side force direction generated in the shoulder land portion row is reduced by reducing the rigidity of the shoulder land portion row to facilitate deformation and reducing the shear force generated as the reaction force. In addition, the main groove side edge of the shoulder land row and the outer edge of the narrow groove in the tire width direction are chamfered to reduce the concentration of pressure on the edge at the time of ground contact and reduce the ground contact pressure and Increase in lashing force is suppressed, and shear force in the anti-side force direction near the edge is reduced.

  According to the present invention, the side force of a pneumatic radial tire having a plurality of main grooves extending in the tire circumferential direction at the tread portion can be effectively increased, and the steering stability performance can be improved.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a half cross-sectional view in the tire width direction showing an enlarged vicinity of a crown portion of a pneumatic radial tire (hereinafter referred to as a tire) of the present embodiment.
Similar to the conventional tire 90 shown in FIG. 3B, the tire 1 is a side-reinforced run-flat tire that can run even in the event of a failure. As shown in the figure, a pair of bead portions (not shown) (FIG. 3B) and a crown portion 3 that connects both ends of the side portion 2 to the outer side in the tire radial direction (upper side in the drawing).

  The tire 1 extends along a toroidal shape between a pair of bead portions, for example, a radial carcass 4 having a radial reinforcing element such as a steel cord, and the inner peripheral surface side of both side portions 2 of the carcass 4. For example, a rubber reinforcing layer 5 having a crescent-shaped cross section or a similar shape, and a plurality of belt layers 6 disposed adjacently on the circumference of the crown portion 3 of the carcass 4; And a tread portion 7 that forms a tire outer peripheral surface. Furthermore, the tread portion 7 has a plurality of main grooves 8 extending in the tire circumferential direction (here, a total of four each including two tire equator lines CL), and a tire partitioned by the main grooves 8 and the like. A land portion row 9 made up of ribs extending in the circumferential direction, or blocks arranged in the tire circumferential direction partitioned by main grooves 8 and lug grooves (not shown) extending in the tire width direction is arranged.

  In addition to the above, in the tire 1 of the present embodiment, the outer end TE (hereinafter referred to as the tread end) of the tread portion 7 and the outermost side in the tire width direction are reduced in order to reduce the shearing force in the anti-side force direction. The shoulder land portion row 21 disposed between the main groove 8A includes a narrow groove 22 extending in the tire circumferential direction, and the main groove 8A side edge of the shoulder land portion row 21 and the tire width direction of the narrow groove 22 are provided. Each of the outer edges has chamfered shapes 23, 24.

  The narrow grooves 22 are formed shallower and narrower than the respective main grooves 8, and are disposed between the main grooves 8A of the shoulder land portion row 21 and the tread end TE, and the shoulder land portion row 21 is disposed on the outer side in the tire width direction. It is divided into two parts inside. The narrow groove 22 may be formed in a shape extending in the tire circumferential direction while being bent in, for example, a zigzag shape or a sinusoidal shape, but in the present embodiment, the narrow groove 22 is formed in a linear shape in the tire circumferential direction. . Further, here, the narrow groove 22 is disposed at a position that is separated from the end of the shoulder land portion row 21 on the main groove 8A side by a distance of 15 to 25% of the width of the shoulder land portion row 21 in the tire width direction.

  The chamfered shapes 23 and 24 are formed by chamfering the edge of the shoulder land portion row 21 on the main groove 8A and narrow groove 22 side, that is, each groove 8A and 22 from the ground contact surface of the shoulder land portion row 21. The outer diameter of the tire is gradually reduced in a straight line shape or a curved shape (round shape) toward the groove wall. In the present embodiment, the chamfered shape of the chamfered shape 23 of the side edge of the main groove 8A in the tire radial direction is made deeper than that of the chamfered shape 24 of the side edge of the narrow groove 22; The chamfering amount of the shape 23 is set to be larger than the chamfering amount of the chamfering shape 24 at the side edge of the narrow groove 22. Further, the tire radial depth of each chamfered shape 23, 24, that is, the reduction amount of the tire outer diameter in the groove wall of each groove 8A, 22 of each chamfered shape 23, 24 is formed to 0.1 to 0.4 mm. ing.

  The tire 1 according to the present embodiment can improve the side force generated in the tire 1 during turning or the like by the narrow grooves 22 and the chamfered shapes 23 and 24. That is, as described above, the reaction force of the compression of the rubber reinforcing layer 5 provided on the side portion 2 acts on the shoulder land portion row 21 located on the outer side of the turn, and the shear force in the anti-side force direction (FIG. 3A). A large resultant force is generated. On the other hand, in the tire 1, since the shoulder land portion row 21 is provided with the narrow grooves 22 extending in the tire circumferential direction and the shoulder land portion row 21 is divided in the tire width direction, the compression reaction acting on the shoulder land portion row 21 is performed. You can escape power. At the same time, it is possible to suppress the compression reaction force from acting on the shoulder land portion row 21 on the inner side in the tire width direction than the narrow groove 22, and the rigidity of the shoulder land portion row 21 is lowered and easily deformed. The generated shear force can be reduced. As a result, the shear force in the anti-side force direction generated in the entire shoulder land portion row 21 can be reduced.

  In particular, in the side-reinforced run-flat tire 1, it is difficult to improve the shearing force by changing the structure and shape of the tire 1 including the rubber reinforcing layer 5 from the viewpoint of reinforcing the side portion 2. By forming the tread pattern of the tread portion 7 on the shoulder, the shearing force of the shoulder land portion row 21 can be effectively improved.

  Further, as described above, a large shear force in the anti-side force direction is generated at the edge of the main groove 8A side of the shoulder land row 21 due to the high ground pressure, the crushing force, etc. A large shearing force is also generated at the outer edge in the tire width direction of the narrow groove 22 of the shoulder land portion row 21. However, in the tire 1, since the respective edge portions are formed in the chamfered shapes 23 and 24, the concentration of pressure on each edge portion at the time of ground contact can be reduced, and the contact pressure and crushing force of each edge portion can be reduced. It is possible to suppress the rise and to reduce the shear force in the anti-side force direction in the vicinity of the edge.

  As described above, according to the tire 1 of this embodiment, since the shear force of the entire shoulder land portion row 21 in which a particularly large shear force in the anti-side force direction is generated can be reduced, The side force, which is the resultant force of the acting shear force, can be effectively increased, and the steering stability performance can be improved.

  Here, since the narrow groove 22 is not intended for drainage between the ground contact surface of the tread portion 7 and the road surface, the narrow groove 22 may be formed to a size that can exert the above-described effects, and is shallow. Even a narrow groove can provide a sufficient effect. Moreover, since the fine groove | channel 22 exhibits a high effect when it forms linearly along a tire peripheral direction, it is more preferable to form in such a shape. Further, if the position of the narrow groove 22 is too close to the main groove 8A or the tread end TE, the action of reducing the shear force in the anti-side force direction may be reduced. It is more preferable to arrange at a position 15 to 25% of the width in the tire width direction of the shoulder land portion row 21 from the main groove 8A side end.

  On the other hand, each of the chamfered shapes 23 and 24 preferably has a chamfered amount of the chamfered shape 23 on the side edge of the main groove 8A larger than a chamfered amount of the chamfered shape 24 on the side edge of the narrow groove 22. This is because the main groove 8A side edge portion tends to have a greater shearing force than the narrow groove 22 side edge portion, and the need to reduce the shearing force near the main groove 8A side edge portion is greater. It is. In addition, each chamfered shape 23, 24 is closer to the edge as the chamfering amount, that is, the difference in outer diameter (diameter difference) between the ground surface side of the tread portion 7 and the groove wall side of each groove 8A, 22 increases. Although the effect of suppressing an increase in the contact pressure or the like at the time becomes higher, if it is too large, the contact property of the tire 1 may be lowered. Accordingly, the depth in the tire radial direction of each of the chamfered shapes 23 and 24 is more preferably about 0.1 to 0.4 mm.

  Moreover, even when the narrow groove 22 and each chamfered shape 23, 24 are each provided alone in the shoulder land portion row 21, the effect of reducing the shear force in the anti-side force direction is exhibited. High effect can be obtained. As a result, even the run-flat tire 1 can be brought close to the level of shearing force similar to that of a normal tire, and the side force can be improved to the same extent.

  The narrow grooves 22 and the chamfered shapes 23 and 24 may be formed in both shoulder land rows 21 located at both ends of the tread portion 7 in the tire width direction, and a shear force in the anti-side force direction is generated. You may form in at least one shoulder land part row | line | column 21, such as providing only in the shoulder land part row | line | column 21 of the above-mentioned turning outer side. In this way, by making the tread pattern formed on the tread portion 7 asymmetrical, it is possible to control the design and performance in accordance with the use conditions of the tire 1.

  Moreover, in this embodiment, although the example of the side reinforcement type | mold run-flat tire with a larger shear force of a non-side force direction was shown, the narrow groove 22 and the chamfering shapes 23 and 24 are not restricted to this, A normal passenger car You may provide in the shoulder land part row | line | column 21 of other pneumatic radial tires, such as a tire. Also in this case, the compression reaction force generated by the compression of the side portion 2 can be reduced, and the shear force in the anti-side force direction can be reduced in the same manner as described above to improve the side force and steering stability performance.

(Tire test)
In order to confirm the effect of the present invention, the tires of the three types of embodiments (hereinafter referred to as “implemented products”) having the above-described structure, and the shoulder land portion row 21 do not have the narrow grooves 22 and the chamfered shapes 23 and 24 1. Various types of conventional tires (hereinafter referred to as conventional products) were prototyped and tested under the following conditions to measure the in-surface shear force distribution and side force of the tread portion 7.

  The following implementation products and conventional products are all side-reinforced pneumatic radial tires (run flat tires) of tire size 225 / 45R17 defined by ETRTO (European Tire and Rim Technical Organization) standards. Except for 23 and 24, the same structure (see FIG. 1) was formed.

FIG. 2 is a plan view showing a developed tread pattern formed on the tread portion 7 of the working products 1 and 2.
As shown in the figure, the working products 1 and 2 are provided with four main grooves 8 and 8A extending in the tire circumferential direction in the tread portion 7, and are divided by the main grooves 8 and 8A and the tread end TE. Five rows of land portion rows extending in the tire circumferential direction are formed. Further, the shoulder land portion rows 21 located at both ends in the tire width direction are provided with a plurality of lateral grooves 30 extending substantially in the tire width direction and arranged in parallel in the tire circumferential direction, and sub-grooves 31 extending continuously or discontinuously in the tire circumferential direction. The middle land portion row 9A adjacent to the inner side in the tire width direction of the shoulder land portion row 21 and the central land portion row 9B sandwiched between the middle land portion rows 9A are inclined or bent in the tire width direction. A plurality of lateral grooves 32 extending in the direction are formed.

  Further, the working products 1 and 2 include a narrow groove 22 that extends linearly in the tire circumferential direction in the shoulder land portion row 21 on the outer side of the turning (right side in the drawing), and the tire width of the main groove 8A side edge and the narrow groove 22. Chamfered shapes 23 and 24 were formed on each of the outer edges in the direction. The narrow grooves 22 are disposed at the inner ends in the tire width direction of the plurality of lateral grooves 30 and are formed narrower and shallower than the main grooves 8. In addition, each chamfered shape 23, 24 was formed by chamfering each edge in a curved shape. However, in the product 1, the chamfered shapes 23, 24 were both formed to have a tire radial depth of 0.2 mm. On the other hand, in the product 2, the depth of the chamfered shape 23 on the main groove 8A side was formed to 0.4 mm, and the chamfered shape 24 on the narrow groove 22 side was formed to 0.2 mm.

On the other hand, in the embodiment product 3, in addition to the above, the narrow groove 22 and the chamfered shapes 23 and 24 are also formed on the left and right shoulder land rows 21 on the other side (left side in the figure). The narrow grooves 22 of the shoulder land rows 21 of the implementation product 3 were formed in the same manner as the narrow grooves 22 of the implementation products 1 and 2, and the chamfered shapes 23 and 24 thereof were similarly formed in a curved shape. Further, the chamfered shape 23 at both edges on the main groove 8A side and the chamfered shape 24 at both edges on the outer side in the tire width direction of the narrow groove 22 were all formed to a depth of 0.2 mm.
A tread pattern similar to the above was formed on the tread portion 7 of the conventional product except for the narrow groove 22 and the chamfered shapes 23 and 24.

  The shear force distribution on the ground contact surface of each tire was measured by a field test in which each tire traveled on the road surface. The actual product and the conventional product are mounted on the standard rim defined by the ETRTO standard, the internal pressure is 88% of the maximum air pressure in the ETRTO standard, the load is 81% of the load in the ETRTO standard, the slip angle is 1 degree, The vehicle was run under the condition of adding a camber angle of 1 degree. The shear force of each part of the tread portion 7 was measured by a so-called three-component force sensor that measures forces in three directions within the ground contact surface embedded in the test road surface. The three-component force sensor has a diameter of about 3.0 mm, and the tread contact surface position in the tire width direction was brought into contact with the sensor to measure the shear force distribution. Further, the side force was obtained by adding the measured shear forces.

Table 1 shows the structural specifications, shear force, and side force of each tire.
The shear force in the table is the magnitude of the shear force in the anti-side force direction, and is represented by an index with the shear force of the conventional product as 100. The smaller this value, the smaller the shear force in the same direction and the better. . The side force is also expressed as an index with the conventional product being 100, and the larger the value, the better the side force.

  As shown in Table 1, the shear force index was 98 for the implementation product 1, 96 for the implementation product 2, and 96 for the implementation product 3 with respect to 100 of the conventional product. From this, it can be seen that the shear force in the anti-side force direction is reduced and the distribution of shear force on the ground contact surface is improved in all the implemented products as compared with the conventional product.

  Further, the side force index was 102 for the implementation product 1, 104 for the implementation product 2, and 103 for the implementation product 3, compared to 100 of the conventional product. From this, it can be seen that the side force is increased and improved in all the implemented products compared to the conventional products.

  From the above results, it was proved that the present invention can effectively increase the side force of the pneumatic radial tire and improve the steering stability performance.

FIG. 3 is a half cross-sectional view in the tire width direction showing an enlarged vicinity of a crown portion of the pneumatic radial tire of the present embodiment. It is a top view which expand | deploys and shows the tread pattern formed in the tread part of the implementation goods. FIG. 4 is a distribution diagram of shearing force acting on the ground contact surface of the tire during turning, and a schematic diagram of a cross section in the tire width direction of the corresponding tire.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Pneumatic radial tire, 2 ... Side part, 3 ... Crown part, 4 ... Carcass, 5 ... Rubber reinforcement layer, 6 ... Belt layer, 7 ... Tread part 8 ... main groove, 9 ... land portion row, 21 ... shoulder land portion row, 22 ... narrow groove, 23 ... chamfered shape, 24 ... chamfered shape, 30 ... Horizontal groove, 31 ... sub-groove, 32 ... horizontal groove, CL ... tire equator line, TE ... tread end.

Claims (5)

A belt layer and a tread portion are provided on the circumference of the crown portion of the toroidal radial carcass, and a plurality of main grooves extending in the tire circumferential direction, a tire width direction outer end of the tread portion and a tire width direction outermost end are formed in the tread portion. A pneumatic radial tire in which a shoulder land row is arranged between the main groove on the outside,
At least one of the shoulder land portion rows is provided with a narrow groove extending in the tire circumferential direction, and the outermost main groove side edge of the shoulder land portion row and the outer edge of the narrow groove in the tire width direction are chamfered. A pneumatic radial tire characterized by having a shape. In the pneumatic radial tire according to claim 1,
The narrow groove is disposed at a position that is separated from the outermost main groove side end of the shoulder land portion row by a distance of 15 to 25% of the width in the tire width direction of the shoulder land portion row. Pneumatic radial tire. In the pneumatic radial tire according to claim 1 or 2,
A pneumatic radial tire characterized in that a chamfering shape of the outermost main groove side edge portion is larger than a chamfering shape of the narrow groove side edge portion. In the pneumatic radial tire according to any one of claims 1 to 3,
A pneumatic radial tire characterized in that a chamfered shape of the outermost main groove side edge portion or a chamfered shape of the narrow groove side edge portion has a tire radial depth of 0.1 to 0.4 mm. In the pneumatic radial tire according to any one of claims 1 to 4,
A pneumatic radial tire comprising a rubber reinforcing layer for sharing and supporting a tire load on an inner peripheral surface side of the side portion of the carcass.

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