JP2008285056A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of further surely restraining uneven wear. <P>SOLUTION: A shape of a plurality of block parts 20 formed on a tread surface 11 is formed small in a grounding width in the block parts 20 for lengthening in the length in the tire peripheral direction of the block parts 20. In other words, when the length is long in the tire peripheral direction of the block parts 20, the grounding width in the block parts 20 is reduced, and when the length is short in the tire peripheral direction of the block parts 20, the grounding width in the block parts 20 is increased. Thus, since a difference in the grounding area between mutual shoulder block parts 21 can be reduced, a difference in an abrasion quantity between the mutual shoulder block parts 21 can be reduced. As a result, the uneven wear can be further surely restrained. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a pneumatic tire. In particular, the present invention relates to a pneumatic tire having a tread pattern having a plurality of pitch variations.

  A conventional pneumatic tire has a plurality of main grooves extending in the tire circumferential direction and lug grooves extending in the tire width direction for the purpose of improving drainage performance in rainy weather. A block pattern which is a tread pattern having a plurality of partitioned block portions may be used. In the case of such a pneumatic tire having a block pattern, a tread portion is formed with a plurality of pitch variations in order to reduce pattern noise during vehicle travel.

  However, when the tread portion is formed with a plurality of pitch variations in this way, the plurality of block portions have different sizes for each pitch, and therefore the block portions are formed with different rigidity according to the size. . For this reason, when a vehicle equipped with a pneumatic tire having a block pattern is run, the block portion wears with different degrees of wear depending on the rigidity, and so-called uneven wear may occur. Therefore, some conventional pneumatic tires suppress the occurrence of uneven wear due to the formation of the tread portion with a plurality of pitch variations.

  For example, in the pneumatic tire described in Patent Document 1, the inclination angle of the side wall of the block portion is varied depending on the size of the block portion, and the side wall of the block portion having a small size is the side wall of the block portion having a large size. It is more inclined and has a shape that spreads toward the groove bottom of the groove section that divides the block section. Thereby, the uniformity of the rigidity of the block part from which a magnitude | size differs can be aimed at, and uneven wear can be suppressed.

JP-A-8-332808

  However, in a pneumatic tire having a block pattern having a plurality of pitch variations, when the difference in the length of the block portion in the tire circumferential direction increases, the difference in the contact area between the block portions also increases. This difference in ground contact area also occurs in the shoulder block portion, which is a block portion located at the end portion in the tire width direction, but since the contact width end is located in the shoulder block portion, uneven wear is more likely to occur.

  This invention is made | formed in view of the above, Comprising: It aims at providing the pneumatic tire which can suppress uneven wear more reliably.

  In order to solve the above-described problems and achieve the object, the pneumatic tire according to the present invention includes a main groove extending in the tire circumferential direction and a lug groove extending in the tire width direction on the tread surface which is the surface of the tread portion. A plurality of land portions defined by the main grooves and the lug grooves are formed, and a plurality of pattern elements having different pitch lengths in the tire circumferential direction are arranged in the tire circumferential direction. In the pneumatic tire in which a tread pattern having a plurality of pitch variations is formed, the plurality of land portions have a contact width in the land portion as the length of the land portions in the tire circumferential direction increases. Is smaller.

  In this invention, the ground contact width in the land portion is reduced as the length of the land portion in the tire circumferential direction increases. In other words, when the length of the land portion in the tire circumferential direction is long, the contact width in the land portion is reduced, and when the length of the land portion in the tire circumferential direction is short, the contact width in the land portion is increased. . Thereby, the difference in the contact area between land portions located on both sides in the tire width direction can be reduced. As a result, uneven wear can be more reliably suppressed.

  Further, in the pneumatic tire according to the present invention, the plurality of land portions is a maximum value of a shoulder land portion ground contact area which is a ground contact area of the land portion located at an end portion in the tire width direction among the plurality of land portions. Where Smax is Smax and the minimum value is Smin, Smax / Smin <1.1.

  In the present invention, since the ratio between the maximum value Smax and the minimum value Smin of the shoulder land contact area is within the range of Smax / Smin <1.1, the difference in the shoulder land contact area can be more reliably reduced. it can. As a result, uneven wear can be more reliably suppressed.

  Further, in the pneumatic tire according to the present invention, in the plurality of land portions, the land portion tire in which the shoulder portion has a radius of curvature of a shoulder portion located at an end portion in the tire width direction of the tread portion. It is characterized in that it increases as the length in the width direction increases.

  In the present invention, the radius of curvature of the shoulder portion is increased as the length in the tire width direction of the land portion where the shoulder portion is formed increases. In other words, when the length of the land portion in which the shoulder portion is formed is long in the tire width direction, the radius of curvature of the shoulder portion formed in the land portion is increased, and the land portion tire in which the shoulder portion is formed. When the length in the width direction is short, the curvature radius of the shoulder portion formed in the land portion is reduced.

  Thus, when the curvature radius of the shoulder portion is changed, the ground contact width in the land portion decreases as the curvature radius increases, and conversely, the ground contact width in the land portion increases as the curvature radius decreases. For this reason, by increasing the radius of curvature of the shoulder portion in the tire width direction of the land portion where the shoulder portion is formed, the ground contact width is increased as the length of the land portion in the tire width direction is increased. Can be reduced, and the ground contact area can be reduced. Thereby, the difference in the contact area between land portions located on both sides in the tire width direction can be reduced more reliably. As a result, uneven wear can be more reliably suppressed.

  The pneumatic tire according to the present invention has an effect that uneven wear can be more reliably suppressed.

  Hereinafter, an embodiment of a pneumatic tire according to the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments. In addition, constituent elements in the following embodiments include those that can be easily replaced by those skilled in the art or those that are substantially the same.

(Embodiment)
In the following description, the tire width direction means a direction parallel to the rotation axis of the pneumatic tire, and the outer side in the tire width direction means the direction opposite to the direction toward the tire equator line (tread center line) in the tire width direction. Say. Further, the tire radial direction refers to a direction orthogonal to the rotation axis, and the tire circumferential direction refers to a direction rotating around the rotation axis as a rotation center axis.

  FIG. 1 is a plan view showing a part of a tread portion of a pneumatic tire according to the present invention. In the pneumatic tire 1, a tread portion 5 made of a rubber material having elasticity is formed on the outermost side in the tire radial direction, and the surface of the tread portion 5, that is, a vehicle on which the pneumatic tire 1 is mounted. When the vehicle travels (not shown), the portion that contacts the road surface is formed as a tread surface 6. A plurality of main grooves 15 extending in the tire circumferential direction and a plurality of lug grooves 16 extending in the tire width direction are formed on the tread surface 6. The tread surface 6 is formed with a plurality of block portions 20 that are land portions defined by the plurality of main grooves 15 and lug grooves 16. Further, a shoulder portion 10 is located at an end portion of the tread portion 5 in the tire width direction, and among the plurality of block portions 20, the shoulder portion 10 is formed on both sides in the tire width direction. Is a shoulder block portion 21.

  These main grooves 15 and lug grooves 16 do not have to be formed accurately in the tire circumferential direction or in the tire width direction. The main groove 15 only needs to be formed so as to extend substantially in the tire circumferential direction, and may be formed obliquely in the tire width direction, or may be formed in a shape such as a curve or a zigzag shape. Similarly, the lug grooves 16 may be formed so as to extend substantially in the tire width direction, and may be formed in an oblique shape in the tire circumferential direction, or in a shape such as a curve or a zigzag shape.

  A tread pattern is formed on the tread surface 6 by arranging the main grooves 15, the lug grooves 16, and the block portions 20 in a predetermined pattern. This tread pattern has a plurality of pitch variations by arranging a plurality of pattern elements having different pitch lengths in the tire circumferential direction in the tire circumferential direction. That is, when a predetermined pattern including the main groove 15, the lug groove 16, and the block portion 20 is used as one pattern element, the tread pattern has a plurality of pattern elements having different pitch lengths in the tire circumferential direction. The plurality of pattern elements are formed by arranging them in the tire circumferential direction. For this reason, the plurality of pattern elements have a plurality of pitch lengths, and the tread pattern has a plurality of pitch variations.

  Further, since the tread pattern has a plurality of pitch variations in this way, the length of the block portion 20 in the tire circumferential direction is also a plurality of lengths. Further, in the block portion 20 having different lengths in the tire circumferential direction as described above, the ground contact width in the block portion 20 becomes smaller as the length of the block portion 20 in the tire circumferential direction becomes longer.

  For example, as shown in FIG. 1, the block length, which is the length of the block portion 20 in the tire circumferential direction, is Pa, Pb, Pc according to the length, and the block length 20 of the block portion 20 with the block length of Pa. Assume that the ground contact width is La, the ground contact width of the block unit 20 with the block length Pb is Lb, and the ground contact width of the block unit 20 with the block length Pc is Lc. Further, when the relationship between the block lengths is Pa> Pb> Pc, the relationship between the contact widths is La <Lb <Lc.

  Specifically, the block lengths Pa, Pb, and Pc are the lengths in the tire circumferential direction of the shoulder block portion 21, and the contact widths La, Lb, and Lc are the block lengths Pa, Pb, and Pc. Each of the shoulder block portions 21 has a ground contact width. Moreover, since the block length in this case represents the pitch length, the length including the width of one of the lug grooves 16 among the lug grooves 16 positioned on both sides of the shoulder block portion 21 in the tire circumferential direction It has become. That is, the block length is the distance between the end portions in the same direction in the tire circumferential direction between the shoulder block portions 21 adjacent in the tire circumferential direction.

  FIG. 2 is an explanatory diagram of the ground contact width. The contact width here is the shape of the portion where the tread surface 6 and the road surface come into contact when a load is applied with an air pressure of 200 kPa and a load load of 80% of the maximum load load specified by JATMA. This refers to the case where the distance between the ground contact end 31 which is the end portion in the tire width direction of the ground contact shape 30 and the tread center 35 which is the tire equator line and is the center in the tire width direction of the tread surface 6 is maximum. . Further, when the pneumatic tire 1 rotates, the ground contact shape 30 sequentially moves along the tire circumferential direction. The ground contact width in the block portion 20 is the contact end 31 of the ground contact shape 30 moving in this way. The ground contact width L in the case where it is located on the predetermined block portion 20 becomes the ground contact width L in the block portion 20.

  The plurality of shoulder block portions 21 have substantially the same size of the shoulder land portion ground contact area, ie, the shoulder block portion ground contact area, which is the ground contact area of the shoulder block portion 21 (FIG. 1). That is, Sa is the ground contact area of the shoulder block portion 21 where the block length is Pa, Sb is the ground contact area of the shoulder block portion 21 where the block length is Pb, and the ground contact area of the shoulder block portion 21 where the block length is Pc. Sa, Sb, and Sc are substantially the same size. Specifically, the shoulder block portion ground contact area is in the range of Smax / Smin <1.1 when the maximum value of the shoulder block portion ground contact area is Smax and the minimum value is Smin. That is, the maximum value Smax of the shoulder block contact area is less than 1.1 times the minimum value Smin of the shoulder block contact area.

  The shoulder block contact area here refers to the contact end position 25 which is the position of the contact end in the tire width direction of each shoulder block portion 21, the main groove 15 adjacent to the shoulder block portion 21 and two lugs. An area in a range surrounded by the grooves 16 is said.

  FIG. 3 is an explanatory diagram in which three cross-sections of the AA cross section, the BB cross section, and the CC cross section of FIG. 1 are overlapped. The shoulder portion 10 formed in the shoulder block portion 21 is formed in a curved shape that protrudes outward in the tire radial direction or outward in the tire width direction when the pneumatic tire 1 is viewed in a meridional section. ing. The shoulder portion 10 is formed in such a shape, but the curvature radius of the shoulder portion 10 increases as the length in the tire width direction of the shoulder block portion 21 where the shoulder portion 10 is formed increases.

  That is, the curvature radius of the shoulder portion 10 formed on the shoulder block portion 21 having a block length of Pa is Ra, the curvature radius of the shoulder portion 10 formed on the shoulder block portion 21 having a block length of Pb is Rb, When the curvature radius of the shoulder portion 10 formed in the shoulder block portion 21 having a block length of Pc is Rc, the relationship between the magnitudes of the curvature radius is Ra> Rb> Rc.

  When the pneumatic tire 1 is mounted on a vehicle and travels, the pneumatic tire 1 rotates while the tread surface 6 positioned below the tread surface 6 contacts the road surface. When the vehicle travels, the tread surface 6 contacts the road surface in this way, and therefore a load due to the weight of the vehicle acts on the tread surface 6. For this reason, the tread surface 6 is deformed, and the tread surface 6 is grounded with a predetermined grounding shape 30. Specifically, since the block portion 20 is formed on the tread surface 6, the block portion 20 is deformed when the tread surface 6 is grounded, and the block portion 20 is grounded with a grounding shape 30 corresponding to the load. The tread pattern formed on the surface 6 has a plurality of pitch variations. Thereby, the pattern noise during vehicle travel can be reduced.

  In addition, since the plurality of block portions 20 are formed with a plurality of block lengths, the length of the contact area in the tire circumferential direction for each block portion 20 varies depending on the block length. In this way, when the ground contact area for each block portion 20 differs due to the block length being different, the load acting on the block portion 20 also changes according to the size of the ground contact area, and the wear amount is also different for each block portion 20. May be different.

  In particular, since the ground contact end 31 of the ground contact shape 30 is located in the shoulder block portion 21, the difference in wear amount for each block portion 20 tends to be large in the shoulder block portion 21, but the pneumatic tire 1 according to the present invention. Then, the contact width in the block part 20 is made small as the length of the block part 20 in the tire circumferential direction of the block part 20 becomes long. In other words, when the length of the block portion 20 in the tire circumferential direction is long, the ground contact width at the block portion 20 is reduced, and when the length of the block portion 20 in the tire circumferential direction is short, the ground contact at the block portion 20 is reduced. The width is increased. Thereby, since the difference in the contact area between the shoulder block portions 21 can be reduced, the difference in the wear amount between the shoulder block portions 21 can be reduced. As a result, uneven wear can be more reliably suppressed.

  In addition, since the ratio between the maximum value Smax and the minimum value Smin of the shoulder block contact area is within the range of Smax / Smin <1.1, the difference in the shoulder block contact area can be more reliably reduced. . That is, when Smax / Smin, which is the ratio between the maximum value Smax and the minimum value Smin of the shoulder block contact area, is 1.1 or more, the difference between the shoulder block contact areas is not so small. There is a possibility that it is difficult to reduce the difference in wear amount between the portions 21. Therefore, by making it within the range of Smax / Smin <1.1, the difference in the shoulder block portion ground contact area can be reduced more reliably, and the difference in the amount of wear between the shoulder block portions 21 can be more reliably reduced. can do. As a result, uneven wear can be more reliably suppressed.

  Further, the radius of curvature of the shoulder portion 10 is increased as the length of the block portion 20 in which the shoulder portion 10 is formed in the tire width direction becomes longer. In other words, when the length of the block portion 20 in which the shoulder portion 10 is formed in the tire width direction is long, the radius of curvature of the shoulder portion 10 formed in the block portion 20 is increased, and the shoulder portion 10 is formed. When the length of the block portion 20 in the tire width direction is short, the radius of curvature of the shoulder portion 10 formed in the block portion 20 is reduced.

  As described above, when the radius of curvature of the shoulder portion 10 is changed, the shoulder portion 10 is less likely to be grounded as the radius of curvature is increased. Therefore, the ground contact width of the block portion 20 is decreased, and conversely as the radius of curvature is decreased. Since the shoulder portion 10 is easily grounded, the ground contact width in the block portion 20 is increased. For this reason, the length of the block portion 20 in the tire width direction is increased by increasing the radius of curvature of the shoulder portion 10 as the length of the block portion 20 in which the shoulder portion 10 is formed increases in the tire width direction. Accordingly, the grounding width can be reduced, and the grounding area can be reduced. Thereby, the difference in the ground contact area between the shoulder block portions 21 can be reduced more reliably, and the difference in the amount of wear between the shoulder block portions 21 can be more reliably reduced. As a result, uneven wear can be more reliably suppressed.

  In the pneumatic tire 1 described above, there are three types of pitch variations of the tread pattern, but the pitch variations may be other than three types. Even when the pitch variation is other than the three types, it is only necessary that the ground contact width in the block portion 20 becomes smaller as the block length becomes longer.

  In the pneumatic tire 1 described above, the tread pattern is a block pattern, but the tread pattern may be other than the block pattern. For example, if the block portion 20 is formed near the shoulder portion 10 such as a rib lug pattern and the ground contact end 31 in the tire width direction of the ground contact shape 30 is located in the block portion 20, the tread pattern is a block pattern. Other than that.

  Hereinafter, the performance evaluation test performed on the pneumatic tire 1 of the present invention and the conventional pneumatic tire 1 compared with the pneumatic tire 1 of the present invention will be described. The performance evaluation test was performed for uneven wear on the tread surface.

  The test method was as follows. A pneumatic tire 1 of 195 / 65R15 size was assembled on a 15 × 6J rim, and the pneumatic tire 1 was mounted on a vehicle (sedan) with a displacement of 1800 cc and a test run of 5000 km was performed. This was done by measuring the difference in the amount of wear in the block portion 21. The evaluation for uneven wear is indicated by an index with an evaluation of Conventional Example 1 described later as 100, and the larger the uneven wear index, the better the performance for uneven wear.

  In these tests, a conventional example which is an example of a conventional pneumatic tire 1 and the present inventions 1 and 2 which are pneumatic tires 1 according to the present invention are tested by the above-described methods. These pneumatic tires 1 have three types of pitch variations of the tread pattern, and the block lengths of the conventional example and all of the present inventions 1 and 2 are Pa = 32.0 mm, Pb = 28.5 mm. , Pc = 25.0 mm.

  Further, the pneumatic tire 1 to be tested has different ground contact widths with respect to the block length, the ground contact width of the block portion 20 having a block length of Pa is La, and the block portion 20 having a block length of Pb. When the ground contact width is Lb and the ground contact width of the block portion 20 where the block length is Pc is Lc, the conventional pneumatic tire 1 has La, Lb, and Lc all having the same width. On the other hand, La, Lb, and Lc are all different in the pneumatic tire 1 according to the first and second aspects of the invention.

  Moreover, since the ground contact width with respect to such a block length differs in the conventional example and the pneumatic tire 1 of this invention 1, 2, all the shoulder block part ground contact areas are also different. For this reason, the relationship between the maximum value Smax and the minimum value Smin of the shoulder block portion ground contact area is all different.

  These conventional examples and pneumatic tires 1 of the present invention 1 and 2 are subjected to an evaluation test by the above-described method, and the results obtained are shown in Table 1.

  As is clear from the above test results shown in Table 1, by forming the block portion 20 so that the contact width in the block portion 20 becomes smaller as the length of the block portion 20 in the tire circumferential direction becomes longer, The difference in the amount of wear between the shoulder block portions 21 can be reduced. Thereby, uneven wear can be more reliably suppressed (Inventions 1 and 2).

  Further, by making the relationship between the maximum value Smax and the minimum value Smin of the shoulder block portion ground contact area within the range of Smax / Smin <1.1, the difference in the shoulder block portion ground contact area is more reliably reduced. be able to. Thereby, since the difference in the amount of wear between the shoulder block portions 21 can be more reliably reduced, uneven wear can be more reliably suppressed (Invention 2).

  As described above, the pneumatic tire according to the present invention is useful for a pneumatic tire having a tread pattern having a plurality of pitch variations, and is particularly suitable for a pneumatic tire having a tread pattern formed in a block pattern. .

It is a top view which shows a part of tread part of the pneumatic tire which concerns on this invention. It is explanatory drawing about a contact width. It is explanatory drawing which accumulated the cross section of three places of the AA cross section of FIG. 1, a BB cross section, and CC cross section.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 5 Tread part 6 Tread surface 10 Shoulder part 15 Main groove 16 Lug groove 20 Block part 21 Shoulder block part 25 Grounding end position 30 Grounding shape 31 Grounding end 35 Tread center Pa, Pb, Pc Block length La, Lb , Lc Grounding width Sa, Sb, Sc Shoulder block grounding area Ra, Rb, Rc Curvature radius

Claims (3)

A plurality of main grooves extending in the tire circumferential direction and a plurality of lug grooves extending in the tire width direction are formed on the tread surface which is the surface of the tread portion, and a plurality of land portions defined by the main grooves and the lug grooves are provided. In the pneumatic tire in which a tread pattern having a plurality of pitch variations is formed by arranging a plurality of pattern elements having different pitch lengths in the tire circumferential direction in the tire circumferential direction.
The pneumatic tire according to claim 1, wherein the plurality of land portions have a ground contact width that decreases as the length of the land portions in the tire circumferential direction increases.   The plurality of land portions, when the maximum value of the shoulder land portion ground contact area, which is the contact surface area of the land portion located at the end in the tire width direction among the plurality of land portions, is Smax, and the minimum value is Smin The pneumatic tire according to claim 1, wherein Smax / Smin <1.1.   In the plurality of land portions, the radius of curvature of the shoulder portion located at the end portion of the tread portion in the tire width direction increases as the length of the land portion in which the shoulder portion is formed in the tire width direction increases. The pneumatic tire according to claim 1 or 2, wherein the pneumatic tire is provided.

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