JP4400817B2 - Pneumatic radial tire - Google Patents

Description

  The present invention relates to a pneumatic radial tire in which a directional pattern mainly including an inclined main groove is provided on a tread surface.

  Hydroplaning performance is one of the most important performance items for pneumatic radial tires for passenger cars, especially high performance tires. A so-called V-shaped pattern in which a plurality of inclined main grooves that extend in the tire rotation direction while inclining from the center portion toward both outer sides is formed on the tread portion so as to form a substantially V shape at a predetermined pitch, (Patent Documents 1-3 below).

  FIG. 6 shows an example of a conventional V-shaped pattern. Inclined main grooves 52 and 52 extending in the tire rotation direction A from the central portion of the tread tread portion 51 and extending in the tire rotation direction A are formed in the shoulder area Sh. The inclination changes gradually so as to be laterally extended to the tread end. Further, sub-grooves 52a and 52a that branch from the inclined main grooves 52 and 52 and extend outward are formed approximately in the middle between the center area Ce and the shoulder area Sh.

  The V-shaped pattern exhibits excellent hydroplaning performance, but the inclination changes so that the inclined main grooves 52 and 52 constituting the V-shaped pattern become lateral in the shoulder area Sh. In this horizontal portion, pattern noise such as pitch noise is likely to occur. For this reason, it is difficult to achieve both pattern noise performance and hydroplaning performance.

  In addition, the V-shaped pattern as described above is a so-called toe that causes a step due to wear in land portions (blocks) in front and rear in the tire circumferential direction, mainly at the lateral portions of the inclined main grooves 52, 52 in the shoulder area Sh. And heel wear (T & H wear) is likely to occur, and pattern noise tends to be further deteriorated after the toe and heel wear occurs.

  As a solution to such a problem, the following Patent Document 4 (Japanese Patent Laid-Open No. 12-1106) has been proposed.

  In this proposal, the inclined main groove constituting the V-shaped pattern is not communicated with the design end (tread end), and the projected length (circumferential length) on the equator plane is larger than the contact length of the tire. Further, the lug groove formed in the shoulder area and communicating with the design end is shifted in the circumferential direction so as to overlap the inclined main groove, and the wrap length is set to 15 mm or more.

  However, the proposed pattern cannot sufficiently suppress the toe and heel wear mainly occurring in the shoulder area, and the amount of toe and heel wear is large, and is not sufficiently satisfactory as a solution to the above problem. .

The hydroplaning phenomenon occurs when water enters between the tread treads of the tire and the ground contact area decreases as the speed increases. However, hydroplaning occurs using a glass plate. As a result of testing, the drainage condition within the ground contact surface during hydroplaning was observed. The drainage performance and ground contact area of the center area are closely related to drainage performance, but the shoulder area is near the ground contact edge. It became clear that there was little effect on drainage.
JP-A-5-286212 JP-A-4-193608 Japanese Patent Laid-Open No. 11-227420 JP-A-2-001106

  The present invention has been made in view of the above, and air that has both a hydroplaning performance and a pattern noise performance while also having a V-shaped pattern in the center area and is effective in suppressing toe and heel wear. A radial tire is provided.

The present invention that solves the above problems is a tire whose rotation direction is specified, and a plurality of inclined main grooves that extend in the tire rotation direction while being inclined from the center portion toward both outer sides are provided on the tread tread surface portion. In the pneumatic radial tire thus formed , the tread tread surface portion has a center area centering on the center in the width direction within a range of 60 to 80% of the ground contact width in the tread tread surface portion , and a shoulder area outside the center area. The inclined main groove is in the center area and forms a substantially V-shaped pattern in the center area, and the shoulder area has a boundary portion with the center area. circumferential direction by leaving the rib structure portion continuous in a straight line in the ground plane, that the slit in the width direction is formed for each circumferential direction a predetermined distance It is an butterfly.

According to this pneumatic radial tire, in the center area of the tread tread portion, good drainage can be secured due to the V-shaped pattern by the inclined main groove, and in the shoulder area that does not affect drainage , The rib structure portion that continues linearly in the circumferential direction along the boundary portion is left in the ground plane, and the slits in the width direction are formed at predetermined intervals in the circumferential direction, thereby suppressing the occurrence of pattern noise. It occurs even suppression of the toe and heel wear reduction can also Ru suitably der to tire properties such as steering stability.

Further, the slit is preferably inclined in the direction opposite to the inclined main groove in the ground contact surface of the shoulder area, and a substantially M-shaped pattern is formed by combination with the inclined main groove. As a result, drainage when the vicinity of the shoulder area is separated from the ground contact surface and the behavior of the land portion between the slits are smooth, and generation of pattern noise and toe and heel wear can be effectively suppressed.

  In addition, a longitudinal groove extending in the tire circumferential direction is formed at a boundary portion between the center area and the shoulder area, and an outer end of the inclined main groove is continuously terminated to the longitudinal groove. It is preferable that a rib structure portion continuous in the direction is provided along the longitudinal groove. Thereby, the drainage property by the inclined main groove can be maintained well, and the effect of suppressing pattern noise and toe and heel wear can be further enhanced.

  The substantially V-shaped pattern formed by the inclined main groove is particularly preferable in that at least one inclined main groove is always in a penetrating state with respect to the ground contact surface shape of the tread surface.

In the above case, it is preferable that a penetration rate R obtained by the following expression of the inclined main groove with respect to the ground contact surface shape is larger than 2.5. Thereby, the effect of drainage improvement can be further enhanced. That is, when the penetration rate R is less than 2.5, the drainage effect may be reduced even if one of the inclined main grooves is in a penetrating state with respect to the ground plane shape. Therefore, it is better to set as described above.
R = TGL / AL (where TGL is the total length of the inclined main groove in the ground plane and AL is the average ground length)

  In the pneumatic radial tire, a narrow groove such as a notch or a sipe may be formed and disposed in the rib structure portion of the shoulder area at intervals in the circumferential direction. Thereby, the influence of the behavior of land portions such as blocks adjacent to the rib structure portion can be reduced, and toe-and-heel wear can be more effectively suppressed.

  It is preferable that the narrow groove is formed at a substantially intermediate position between the slits in the tire width direction formed in the shoulder area. Thereby, in the shoulder area, the balance of behavior of the land portion including the rib structure and defined by the slit is improved, and the effect of preventing toe and heel wear can be further enhanced.

  According to the pneumatic radial tire of the present invention, excellent hydroplaning is achieved by combining the V-shaped pattern with the inclined main groove in the center area of the tread tread portion and the rib structure of the land portion in the shoulder area that does not affect drainage. While ensuring the performance, the effect of suppressing the pattern noise can be enhanced and both performances can be achieved, and the effect of reducing toe and heel wear is excellent, and the durability can be enhanced.

  Next, embodiments of the present invention will be described based on examples shown in the drawings.

  FIG. 1 is a development view of a tread pattern of a first embodiment of the pneumatic radial tire of the present invention, FIG. 2 is a development view of a tread pattern of another embodiment of the tire of the present invention, and FIG. 3 is still another embodiment of the tire of the present invention. FIG. 4 and FIG. 5 are development views of a tread pattern of still another embodiment of the tire of the present invention. P1 in each figure indicates one repeat in the circumferential direction of the tread pattern.

  The tire according to the present invention is a pneumatic radial tire in which the rotational direction A is specified in a fixed direction, and the tread pattern has the following configuration.

  As a basic configuration of the present invention, as shown in the embodiments of the drawings, the tread tread surface portion 1 includes a plurality of inclined main grooves 2 extending in the tire rotation direction A while being inclined from the center portion toward both outer sides. 2 are formed on the left and right sides at a predetermined pitch in the circumferential direction, and are arranged so as to be substantially V-shaped in a front view or a plan view.

  In particular, the tread surface portion 1 is divided into a center area Ce in the width direction and shoulder areas Sh on both sides, and the inclined main grooves 2 and 2 are in the center area Ce and in the center area Ce. It is formed so as to constitute a substantially V-shaped pattern.

  The inclined main grooves 2 and 2 may be provided with one type of inclined main grooves on the left and right sides in a bilaterally symmetric shape, or in an asymmetrical shape with their positions shifted in the circumferential direction. Each of the inclined main grooves 2 and 2 on the left and right sides is alternately arranged with two types of long and short grooves, and is shifted in the left and right parts individually without intersecting in the vicinity of the center line CL in the tire width direction. It is formed independently. In addition, a straight main groove in the tire circumferential direction can be formed on or near the center line CL (not shown). In this case, the inclined main groove is made to be continuous with the straight main groove. You can also keep it. Further, the inclined main grooves 2 and 2 can be combined in three or more kinds.

  The inclination angle α of the inclined main grooves 2 and 2 is preferably in the range of about 10 ° to 45 ° with respect to the tire circumferential direction, but of course, the inclination angle α outside the range can also be set. As shown in the figure, the ground contact is formed in a substantially arc shape as a whole by changing from an angle of approximately 0 ° or close to 0 ° to the tire circumferential direction on the inner end side so as to gradually become a larger angle. From the viewpoint of securing the drainage effect and the circumferential length in relation to the shape.

  In any case, the inclined main grooves 2 and 2 in the substantially V-shaped pattern are usually formed in the shape of the contact surface when the vehicle of the tread tread portion 1 is stationary (two points in the figure) from the viewpoint of ensuring drainage. The arrangement pitch or length of the inclined main grooves 2 and 2 in the tire circumferential direction is always such that at least one of the inclined main grooves 2 and 2 on the left and right sides is always in a penetrating state with respect to the chain line B). Is set.

In particular, the arrangement pitch, the length, and the like are set so that the penetration rate R obtained by the following expression of the inclined main grooves 2 and 2 with respect to the ground plane shape B is larger than 2.5.
R = TGL / AL (where TGL is the total length of the inclined main groove in the ground plane and AL is the average ground length)

  The average contact length AL in the above is an average (CL + SL) / 2 of the contact length CL in the tire circumferential direction of the center area Ce and the contact length SL in the tire circumferential direction of the shoulder area Sh. The total length TGL of the inclined main grooves 2 and 2 in the ground contact surface is the sum of the lengths of the portions in the ground contact surface of all the inclined main grooves existing in the ground contact surface. And the lengths of the two types of long and short inclined main grooves are GL1 and GL2, respectively, and the average number of pitches in the ground plane: APN = AL / PL, the length of the inclined main grooves per pitch: GL = GL1 + GL2, It is obtained by the calculation formula TGL = GL × APN.

  The center area Ce of the tread tread portion 1 is in relation to the contact width W1 in the tread tread portion 1, that is, the maximum width in the tire width direction in the tire contact surface shape (two-dot chain line B in the figure) when the vehicle is stationary. The shoulder area Sh is an area outside the center area Ce. When the center area Ce is smaller than the above range, the drainage performance when traveling on a wet road surface is deteriorated, and the hydroplaning performance is deteriorated. When the center area Ce is larger than the above range, the pattern noise performance and the toe and heel wear performance are also lowered. Therefore, the center area Ce is preferably within the above range, and more preferably around 70% of the ground contact width W1.

In the case of the first embodiment of FIG. 1, the boundary portion between the center area Ce in the ground contact surface and the shoulder areas Sh on both sides is substantially linear in the tire circumferential direction as shown in the figure. Longitudinal grooves 4, 4 are formed as sub-grooves extending in an extended manner, and the outer ends of the inclined main grooves 2, 2 open to the longitudinal grooves 4, 4 and terminate. The vertical grooves 4 and 4 have the same depth as the inclined main groove, and the groove width is slightly narrower than the inclined main groove.

Also, the shoulder area Sh outside than the longitudinal grooves 4, 4, at least a portion of the land portions 5 and 5 other than the slits to be described later, the one first shape that is continuous with a straight line shape in the tire circumferential direction It has a rib structure. In the case of the present invention, as shown in the figure, the rib structure portions 5a, 5a that are continuous in the circumferential direction are provided in the ground plane along the longitudinal grooves 4, 4 at the boundary with the center area Ce. .

Then , in the shoulder areas Sh on both sides of the tread, the rib structure portions 5a and 5a that continue linearly in the circumferential direction along the boundary portion with the center area Ce as shown in the figure are left in the ground plane. In addition, slits 7 and 7 in the tire width direction different from the inclined main grooves 2 and 2 are formed and arranged at regular intervals in the tire circumferential direction.

  Although the width W2 of the rib structure portions 5a and 5a can be set as appropriate, it is usually preferable to set the width W1 ratio to about 2% to 15%. Reference numerals 5b and 5b in the figure denote the remaining land portions separated from the rib structure portions 5a and 5a. In the case of the figure, a pair of narrow grooves 6 and 6 are formed in the circumferential direction between the rib structure portion 5a and 5a and the remaining land portions 5b and 5b.

  Further, as shown in FIG. 1, the slits 7 and 7 are inclined in the same direction as the inclined main grooves 2 and 2 and correspond to the outer ends of the inclined main grooves 2 and 2. Two slits are formed for each pitch of the inclined main grooves 2, 2. In addition, three or four slits can be formed for each pitch of the inclined main grooves 2 and 2. Various implementations are possible for the shape of the slits 7, 7 and the direction and angle of inclination.

  In the first embodiment described above, the vertical grooves 4 and 4 are provided at the boundary between the center area Ce and the shoulder area Sh, but the vertical grooves 4 and 4 are omitted as shown in FIG. It is also possible to implement. Also in this case, the outer ends of the inclined main grooves 2 and 2 are terminated in the center area Ce, preferably at the boundary with the shoulder area Sh.

  The embodiment of FIG. 2 basically has the same configuration as that of the embodiment of FIG. 1 except for the longitudinal grooves 4 and 4. In this embodiment, the center area Ce has a V-shaped pattern with the inclined main grooves 2 and 2 and the land of the shoulder area Sh. In the portions 5 and 5, the rib structure portions 5a and 5a which are continuous in the circumferential direction are formed along the boundary portion between the center area Ce and the shoulder area Sh, and the slits 7 and 7 in the width direction are formed outside the rib structure portions 5a and 5a. It is formed and has a rib structure of one shape.

  In the case of the embodiment of FIG. 3, the slits 7 and 7 in the shoulder area Sh are inclined in the direction opposite to the inclined main grooves 2 and 2, and are approximately M in combination with the inclined main grooves 2 and 2. The case where it provided so that a character-shaped pattern may be formed is shown.

  In this embodiment, except for the points of the slits 7 and 7 in the inclination direction, the structure is basically the same as that of the embodiment of FIG. In the case of this embodiment, the rib area that is continuous in the circumferential direction in the land portions 5 and 5 of the shoulder area Sh is also formed in the center area Ce in the case of this embodiment. The portions 5a and 5a are formed along the longitudinal grooves 4 and 4 at the boundary portion between the center area Ce and the shoulder area Sh, and the slits 7 and 7 are inclined outwardly from the inclined main groove. Two or several of the inclined main grooves 2 and 2 are formed for each pitch, and each has a one-shaped rib structure.

  Although this M-shape is not shown in the case of a turn, as in the case of FIG. 2, the vertical grooves 4 and 4 at the boundary between the center area Ce and the shoulder area Sh can be omitted. . In either case, the effects of the pattern noise performance and the toe and heel wear performance can be enhanced as compared with the case of the first embodiment described above.

  Further, as in each of the above-described embodiments, at least a part of the land portions 5 and 5 of the shoulder area Sh has a rib structure continuous in the circumferential direction, and the rib structure portions 5a and 5a have notches or sipes or the like. Can be formed at every required interval in the tire circumferential direction.

  4 and FIG. 5 show such an example. In the rib structure portions 5a and 5a along the longitudinal grooves 4 and 4 in the circumferential direction, narrow grooves 8 formed by notches opened in the longitudinal grooves 4 and 4 are provided. Forming. As shown in FIGS. 4 and 5, the narrow grooves 8 such as notches and sipes are formed at substantially intermediate positions between the slits 7 and 7 formed at predetermined intervals in the circumferential direction. It is preferable in terms of balance.

  Thus, by forming the narrow grooves 8 such as notches and sipes in the rib structure portions 5a and 5a of the shoulder area Sh, it is possible to reduce the influence of the behavior of the land portion adjacent to the rib structure portions 5a and 5a. The toe and heel wear performance can be improved as compared with the embodiment of FIGS.

  For example, when two, three, or four slits 7 and 7 are arranged for each pitch of the inclined main grooves 2 and 2, affected by the behavior of the blocks and land portions between the inclined main grooves and the slits, Although wavy toe and heel wear may occur, by forming the narrow grooves 8 such as notches and sipes between the slits as described above, the influence of the behavior of the land portion can be reduced. The occurrence of toe-and-heel wear can be prevented.

  The notch and the narrow groove 8 such as a sipe are not necessarily formed into a notch shape that opens to the vertical groove 4 at a substantially intermediate position between the slits 7 and 7 as shown in the figure, but various other forms. Implementation is possible. For example, as shown in FIG. 2, the longitudinal groove 4 is omitted, and the rib structure portions 5a and 5a provided along the boundary portion between the center area Ce and the shoulder area Sh are also provided in the tire width direction including sipe. It can be carried out by forming a narrow groove 8 of a required length (not shown). Further, a plurality of narrow grooves such as notches and sipes can be set between the slits 7 and 7.

  Furthermore, the shape of the narrow groove 8 can be variously implemented such that the end has a tapered shape, or has an inclined or bent shape with the same groove width. For example, the slanting direction of the narrow groove 8 may be either slanted in the same direction as the slits 7 and 7 as shown in the figure, or slanted in the direction opposite to the slits 7 and 7 as shown in FIG. In this case, the slits 7 and 7 are inclined in the same direction with respect to the inclined main grooves 2 and 2 (V-shaped pattern) as shown in FIG. (M-shaped pattern) may be used.

  Although it is possible to carry out by omitting the slits 7 in the tire width direction in the shoulder area Sh, from the viewpoint of other tire performance such as steering stability, as in the illustrated embodiment, It is preferable to form slits 7 and 7 in advance.

  According to the pneumatic radial tire described above, in the center area Ce of the tread tread portion 1, the shoulder area that can ensure good drainage due to the V-shaped pattern by the inclined main grooves 2 and 2, and does not affect drainage. Since at least a part of Sh has a rib structure continuous in the circumferential direction, generation of pattern noise can be suppressed, and generation of toe and heel wear can also be suppressed and reduced. Such an effect is further enhanced in the case of the M-shaped pattern of FIG. 3 and when the narrow grooves 8 such as notches and sipes of FIG. 4 and FIG. 5 are set.

  Table 1 below shows the hydroplaning performance, the pattern noise performance, and the conventional tire (comparative example) of the tread pattern shown in FIG. 6 and the tread pattern tires (Examples 1 to 6) of each example according to the present invention. A comparison of toe and heel wear performance is shown.

  In Table 1, Example 1 is the tire of the tread pattern of FIG. 1, Example 2 is the tire of the example of FIG. 2, Example 3 is the tire of the example of FIG. 3, and Example 4 is basically the same as FIG. Tires (not shown) having the vertical grooves 4 in the same pattern, Example 5 shows a tread pattern tire shown in FIG. 4, and Example 6 shows a tread pattern tire shown in FIG.

  The test tires of the comparative example and Examples 1 to 6 are all 225 / 45ZR17 tires, and the test vehicle is an FR vehicle with a body weight of 1500 kg and a displacement of 2000 cc. Each performance in Table 1 was tested and evaluated as follows.

Hydroplaning performance The speed of hydroplaning phenomenon at a slip rate of 15% was measured by a straight running hydroplaning measurement test.

Pattern noise performance Both when new and after actual running, the sensory test was evaluated by running the vehicle at a speed of 60 km / h, and after running was evaluated after 9600 km.

Toe and heel wear performance 9600 km The amount of toe and heel wear after driving a vehicle was measured.

  The evaluation of each performance is basically displayed as an index with a comparative example as 100, but the evaluation of toe and heel wear performance is expressed as an index with the comparative example as 100 taking the inverse of each step amount. . For the evaluation of pattern noise performance after actual running, the pattern noise performance at the time of a new product of the comparative example was expressed as an index with 100 as the index. In all cases, higher numbers indicate better results.

  According to the above test results, the tires of Examples 1 to 6 of the present invention can ensure substantially the same performance as the conventional tire of the comparative example with respect to the hydroplaning performance, and the pattern noise performance and toe and heel wear performance. Also, it can be greatly improved compared to conventional tires. Further, when the slits 7 of the third and fourth embodiments are M-shaped patterns inclined in the opposite direction with respect to the inclined main groove 2, the rib structure portion 5a of the shoulder area of the fifth and sixth embodiments is further thinned such as notches and sipes. When the groove 8 is set, the effects of pattern noise performance and toe and heel wear performance are further enhanced. In particular, in the case of Example 6 in which the narrow groove 8 is formed in an M-shaped pattern, the above effect is the highest.

  INDUSTRIAL APPLICABILITY The present invention can be suitably used in a tire in which a directional pattern mainly including an inclined main groove is provided on a tread surface, particularly a high performance tire.

It is an expanded view of the tread pattern of the 1st Example of the tire of this invention. It is an expanded view of the tread pattern of the other Example of the tire of this invention. It is an expanded view of the tread pattern of the further another Example of the tire of this invention. It is an expanded view of the tread pattern of the further another Example of the tire of this invention. It is an expanded view of the tread pattern of the further another Example of the tire of this invention. It is an expanded view of the directional tread pattern of the conventional tire.

Explanation of symbols

A Rotation direction B Ground plane shape Ce Center area Sh Shoulder area CL Center line W1 Ground width W2 Rib structure width α Inclination angle 1 Tread tread section 2, 2 Inclined main groove 4, 4 Vertical groove 5, 5 Land in shoulder area Part 5a, 5a Rib structure part 5b, 5b Remaining land part 6, 6 Narrow groove 7, 7 Slit 8 Narrow groove such as notch and sipe

Claims (7)

In a pneumatic radial tire in which a rotation direction is specified, and a plurality of inclined main grooves extending in a tire rotation direction while being inclined toward both outer sides from a center portion are provided in a tread tread surface portion,
The tread tread portion is composed of a center area centered in the width direction center within a range of 60 to 80% of the ground contact width in the tread tread portion , and a shoulder area outside the center area ,
Said inclined main grooves, said constitutes a substantially V-shaped pattern in be in the center area and the center area, the shoulder area is straight in the circumferential direction along the boundary between the center area A pneumatic radial tire characterized in that a rib structure portion that is continuous in a shape is left in the contact surface, and slits in the width direction are formed at predetermined intervals in the circumferential direction . The slit is inclined in a direction opposite to the inclined main groove in a ground contact surface of a shoulder area, and a substantially M-shaped pattern is formed by a combination with the inclined main groove. the pneumatic radial tire according to 1. Continuous boundary portion of the center area and the shoulder area, are formed longitudinal grooves in the tire circumferential direction, and terminate the outer end of said inclined main grooves continuously in the longitudinal groove, in the circumferential direction of the tire shoulder area The pneumatic radial tire according to claim 1 or 2, wherein a rib structure portion is provided along the longitudinal groove.   The pneumatic according to any one of claims 1 to 3, wherein the substantially V-shaped pattern formed by the inclined main groove has at least one inclined main groove penetrating with respect to the ground contact surface shape of the tread surface portion. Radial tire. The pneumatic radial tire according to claim 4, wherein a penetration rate (R) obtained by the following formula of the inclined main groove with respect to the ground contact surface shape is greater than 2.5.
R = TGL / AL (where TGL is the total length of the inclined main groove in the ground plane and AL is the average ground length) The air according to any one of claims 1 to 5 , wherein a narrow groove such as a notch or a sipe is formed and arranged at intervals in the circumferential direction in the rib structure portion of the shoulder area. Entering radial tire. The pneumatic radial tire according to claim 6 , wherein the narrow groove is formed at a substantially intermediate position between the slits in the tire width direction formed in the shoulder area.

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