JP4413590B2 - Pneumatic tire - Google Patents

Description

  According to the present invention, at least one central main groove located in the pattern center or in the vicinity thereof and extending along the tire circumferential direction in a half area obtained by dividing the tread portion into two half areas by the pattern center, At least one side main groove located between the tread ends and extending along the tire circumferential direction is disposed, and the central land portion is defined by the central main groove and the side main grooves adjacent thereto; The present invention relates to a pneumatic tire in which a side land portion is defined by a tread end and a side main groove adjacent to the tread end, and particularly an extension of a tread groove disposed in a tread portion of the tire, particularly a central land portion. By optimizing the shape and its cross-sectional shape, the shape of the land portion of the tread portion and its rigidity, the steering stability and drainage performance are satisfied at a high level and at the same time the noise is reduced.

  As a means for achieving both high drainage and excellent handling stability, for example, the tread part converges toward the pattern center from the circumferential groove extending along the tire circumferential direction and from both tread ends. It is useful to employ a so-called directional pattern in which a plurality of inclined grooves extending in a direction and opening in the circumferential groove are provided.

  Moreover, in order to further improve the drainage of such a tire, it is effective to make the inclined groove a steeply inclined groove that is inclined at a small angle with respect to the tire circumferential direction. The corner portion formed by the steeply inclined groove is inevitably sharpened, and the land portion rigidity is lowered, so that the steering stability is deteriorated.

  Furthermore, in order to improve drainage, it is effective to increase the negative rate by widening the groove width, etc., but the increase in the negative rate will lead to a decrease in the rigidity of the land and lower the steering stability. In addition, the noise level is increased, which is not preferable.

  In addition, in order to improve steering stability, it is effective that the inclined groove is a gently inclined groove that is inclined at a large angle with respect to the tire circumferential direction. Since the sound falls within the area, the hitting sound is increased, the pattern noise is deteriorated, and the drainage performance in the tread contact area, particularly in the central area, cannot be obtained sufficiently.

  As described above, it is difficult to satisfy all of the steering stability, drainage performance and noise level of the tire at a high level, and various studies have been made on this matter. For example, in Patent Document 1, a rib sandwiched between two circumferential grooves of a directional tread pattern composed of several circumferential grooves and a large number of inclined grooves is located on both sides of the ribs. By providing a large number of slit-shaped transverse grooves extending between the circumferential grooves, the width of the slit-like transverse grooves is narrowed on the side close to the tread surface and widened on the side close to the groove bottom, so that steering stability and drainage performance are achieved. Describes a tire in which the generation of pattern noise is suppressed at the same time. However, because this tire ensures drainage by increasing the number of circumferential grooves, a large amount of water is discharged in the traveling direction of the car. May interfere with visibility. Furthermore, since there are many circumferential grooves, pattern noise is reduced, but so-called air columnar resonance is generated, and it is difficult to obtain a total noise level reduction.

  In Patent Document 2, a plurality of inclined main grooves composed of a steeply inclined portion and a gently inclined portion are arranged on the tire circumference at substantially equal intervals, and two adjacent inclined main grooves are arranged. A gently inclined auxiliary groove that forms a plurality of land sections, has a steeply inclined auxiliary groove between two adjacent inclined main grooves, and further extends from the steeply inclined auxiliary groove to the pattern end or the tread grounding end. By providing these auxiliary grooves, the section land part is further divided into a center land part and a shoulder land part, so that both steering stability and drainage performance can be achieved at a high level and at the same time the generation of pattern noise is suppressed. Tires are described. In such a tire, an acute angle corner is formed in the land portion by the steeply inclined auxiliary groove, but because the land portion rigidity of this acute angle portion is low, there is little influence on the steering stability during cornering with a large rudder angle, When cornering with a small rudder angle, for example, when changing lanes, the reaction may be slow, resulting in poor overall steering stability.

JP 7-285303 A JP 9-328003 A

  Accordingly, the object of the present invention is to optimize the shape and the rigidity of the tread groove extending in the tread portion, particularly the central land portion, and the cross-sectional shape thereof, and the land portion of the tread portion and the rigidity thereof. An object of the present invention is to provide a pneumatic tire that satisfies a high level of stability and drainage and at the same time reduces noise.

In order to achieve the above object, the present invention provides at least one center extending along the tire circumferential direction, located in or near the pattern center, in a half area obtained by dividing the tread portion into two half areas at the pattern center. A main groove, and at least one side main groove located between the central main groove and the tread end and extending along the tire circumferential direction, the central main groove and the side main groove adjacent to the central main groove; In the pneumatic tire formed by dividing the central land portion by the tread end and the side main groove adjacent to the tread end, the side main land A plurality of transverse grooves extending substantially in the tire width direction toward the groove are disposed, whereby the side land portion is formed as a block row consisting of a number of substantially blocks, and the side main groove is formed in the central land portion. To the center main groove Extends against Shi inclined obliquely to the direction, terminate short of the center main groove, extending angle with respect to the tire circumferential direction, a first inclined groove gradually increasing toward the center main groove, the end of the first inclined groove A circumferential groove that extends substantially parallel to the tire circumferential direction and forms a first corner portion that forms an acute V shape with the first inclined groove, and a first circumferential portion of the circumferential groove from the end portion of the circumferential groove. A second inclined groove that extends at an angle larger than the extending angle of the inclined groove, opens into the side main groove, and forms a second corner portion that forms an obtuse angle V-shape together with the circumferential groove; A pneumatic tire characterized in that a large number of blocks are formed in the central land portion by arrangement.

Here, the “pattern center or the vicinity thereof” means a region in the range of 33% of the tread contact width with the pattern center as the center , and the “ substantially tire width direction” means ± 40 ° with the tire width direction as the center. The "substantially block" means that the transverse groove opens to the side main groove and the side land portion is formed as a block row made up of a number of blocks. It includes the case of so-called lug grooves that terminate in the side land portion without opening in the groove side main grooves, and “substantially parallel to the tire circumferential direction” means ± 20 ° centered on the tire circumferential direction. It shall mean the direction of the range.

  Moreover, it is preferable that the length measured along the tire width direction of the transverse groove is 30% or more of the width measured at the side land portion along the tire width direction.

  Furthermore, it is preferable that the 1st inclination groove has the extension angle with respect to the tire peripheral direction in the terminal part in the range of 20-70 degrees.

  Furthermore, it is preferable that the first inclined groove has an extended shape with a curvature that converges toward the side main groove.

  In addition, the circumferential groove preferably has an extension angle with respect to the tire circumferential direction in the range of −15 to + 15 °. Here, the extension angle of the circumferential groove with respect to the tire circumferential direction is positive when in the first quadrant or the third quadrant, and negative when in the second or fourth quadrant in the right half of the tread. In the left half area of the tread, the case in the first quadrant or the third quadrant is negative, and the case in the second quadrant or the fourth quadrant is positive.

  The circumferential groove preferably has a first chamfered portion inclined at a certain angle from the tread portion tread surface toward the groove bottom on the groove wall located on the outer side in the tire width direction. The upper surface of the chamfered portion has an extension angle of 95 to 155 ° with the tread portion tread surface, and the lower end position of the chamfered portion has a circumferential groove when measured along the tire radial direction from the tread portion tread surface. More preferably, the width of the first chamfered portion is substantially constant as measured along the tire width direction. Here, “the width is substantially constant” refers to a width including a change inevitable in manufacturing with respect to the target width.

  Further, the second inclined groove has an extension line of the imaginary center line passing through the inner end of the transverse groove in the tire width direction, the extending angle with respect to the tire circumferential direction is larger than that of the first inclined groove, and is substantially constant. It is preferable to have a groove width. More preferably, the extension angle with respect to the tire circumferential direction is 25 to 85 °.

  Furthermore, it is preferable that the second inclined groove extends through the end of the circumferential groove until it is further opened to the central main groove.

  The transverse groove preferably has a second chamfered portion inclined at a certain angle from the tread portion tread surface toward the groove bottom on the side wall that subsequently enters the contact area at the time of tire load rolling. The upper surface of the second chamfered portion has an extension angle with the tread portion tread surface in the range of 120 to 175 °, and the lower end position is a distance when measured along the tire radial direction from the tread portion tread surface. Is more preferably in the range of 10 to 100% of the groove depth of the transverse groove, and the width of the second chamfered portion measured along the tire circumferential direction is substantially constant.

  Moreover, it is preferable to provide the 3rd chamfering part which height reduces gradually toward the front-end | tip part in the 1st corner | angular part formed with a 1st inclination groove | channel and a circumferential direction groove | channel.

  Furthermore, it is preferable to provide the 4th chamfering part which height decreases gradually toward the front-end | tip in the 2nd corner | angular part formed with a 1st inclination groove | channel and a side main groove | channel.

  Furthermore, it is preferable that two central main grooves are disposed across the pattern center, and rib-shaped land portions extending continuously in the tire circumferential direction are partitioned by these central main grooves.

  In addition, the first inclined grooves located in both half areas of the tread portion are also arranged so as to sequentially enter the contact area from the pattern center side toward the tread end side during tire load rolling. A directional pattern is preferable.

  According to the present invention, the steering stability is improved by optimizing the extension shape and cross-sectional shape of the tread groove disposed in the tread portion, particularly the central land portion, and the shape and rigidity of the land portion of the tread portion. In addition, it is possible to provide a pneumatic tire that satisfies a high level of drainage and at the same time reduces noise.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a development of a part of a tread portion of a typical pneumatic tire (hereinafter referred to as “tire”) according to the present invention.

  The tire shown in FIG. 1 is located in the pattern center 2 or in the vicinity thereof in the half areas 3 and 4 in which the tread portion 1 is divided into two half areas 3 and 4 by the pattern center 2, and extends along the tire circumferential direction C. At least one central main groove, in FIG. 1, two central main grooves 5, 6 and at least one extending between the central main grooves 5, 6 and the tread ends 7, 8 along the tire circumferential direction C. One side main groove, in FIG. 1, one side main groove 9, 10 is provided. Further, the central land portions 11 and 12 are defined by the central main grooves 5 and 6 and the side main grooves 9 and 10 adjacent thereto. Further, the side land portions 13 and 14 are defined by the tread ends 7 and 8 and the side main grooves 9 and 10 adjacent thereto.

  The main structural features of the present invention are as follows. The lateral land portions 13 and 14 open to the tread ends 7 and 8 and extend in the tire width direction toward the lateral main grooves 9 and 10. Transverse grooves 15 and 16 are provided, whereby the side land portions 13 and 14 are formed as a block row consisting of a number of substantially blocks, and the central land portions 11 and 12 are formed in the side main grooves 9 and 10. The first inclined grooves 17 and 18 that open, extend toward the central main grooves 5 and 6 at a relatively small angle with respect to the tire circumferential direction C, and terminate before the central main grooves 5 and 6, A circumference that extends substantially parallel to the tire circumferential direction C from the end portions 19 and 20 of the first inclined grooves 17 and 18 and forms first corner portions 29 and 30 that form an acute angle V shape together with the first inclined grooves 17 and 18. Tire circumferential direction C from the directional grooves 21, 22 and the end portions 23, 24 of the circumferential grooves 21, 22 Second inclined grooves 25, 26 that extend at a relatively large angle, open to the side main grooves 9, 10, and form second corner portions 46, 47 that form an obtuse angle V shape with the circumferential grooves 21, 22. These blocks are arranged to form a large number of blocks 27 and 28 in the central land portions 11 and 12.

  When observing the flow of water in the tread area of a tire formed by partitioning the central land portion and the lateral land portion by a plurality of side main grooves extending along the tire circumferential direction, the water is generally It flows at a relatively large angle with respect to the tire circumferential direction in the land portion, and is discharged mainly to the side of the tire, and flows at a relatively small angle with respect to the tire circumferential direction in the central land portion, It can be seen that the tire is discharged in the longitudinal direction of the tire.

  Therefore, in the tire of the present invention, the lateral land portions 13 and 14 are provided with transverse grooves 15 and 16 extending in a direction substantially ± 30 ° around the tire width direction, preferably about the tire width direction. 11 and 12 are provided with first inclined grooves 17 and 18 extending at a relatively small angle with respect to the tire circumferential direction C, and the transverse grooves 15 and 16 and the first inclined grooves 17 and 18 are connected to the tread area. By substantially matching the flow (streamline) of the water in the inside, water existing in the tread area is quickly discharged out of the tread area to ensure good drainage.

  In addition, the first inclined grooves 17 and 18 are not opened in the central main grooves 5 and 6 but are terminated in the central land portions 11 and 12, so that the tires opened in the central main grooves 5 and 6 are compared. The rigidity of the central land portions 11 and 12 is increased, and the steering stability can be improved.

  Furthermore, by arranging the circumferential grooves 21, 22 and the second inclined grooves 25, 26 to form a plurality of blocks 27, 28 in the central land portions 11, 12, the central land portion 11, Accordingly, it is possible to optimize the rigidity of 12 and satisfy both excellent steering stability and low noise. In particular, by dividing the central land portions 11 and 12 into a large number of blocks 27 and 28, so-called heel and toe wear can be suppressed, so that generation of noise can be suppressed even when tire wear progresses. .

  Moreover, since the 1st inclination groove | channels 17 and 18 are terminated before the center main grooves 5 and 6 as mentioned above, compared with the case where it opens to the center main grooves 5 and 6 only by this, drainage property is inferior. However, by disposing the circumferential grooves 21 and 22, it becomes possible to assist the discharge of water that could not be completely discharged by the first inclined grooves 17 and 18, and the first inclined grooves 17 and 18 are the central main grooves. Equivalent or better drainage can be obtained than when the openings 5 and 6 are opened.

  In this way, by optimizing the shape of the tread groove, the shape of the land, and the rigidity thereof, the tire of the present invention achieves both a higher level of driving stability and drainage than the conventional tire. At the same time, noise can be further reduced.

Moreover, it is preferable that the length l measured along the tire width direction of the transverse grooves 15 and 16 is 30% or more of the width w ₁ measured along the tire width direction of the lateral land portions 13 and 14. . As shown in FIG. 1, the transverse grooves 15 and 16 do not necessarily need to open to the side main grooves 9 and 10, but the water present in the side land portions 13 and 14 is smoothly discharged to the tire side. In particular, it contributes to the prevention of the hydroplaning phenomenon during cornering, and if the length l is less than 30% of the width w ₁ of the lateral land portions 13 and 14, there is a concern that the drainage performance may deteriorate. is there.

  Furthermore, it is preferable that the 1st inclination grooves 17 and 18 have the extension angle with respect to the tire circumferential direction C in the terminal parts 19 and 20 in the range of 5-45 degrees. When the extension angle is less than 5 °, the rigidity of the first corner portions 29 and 30 formed by the first inclined grooves 17 and 18 and the circumferential grooves 21 and 22 is lowered, and the steering stability is deteriorated. This is because there is a concern about the occurrence of uneven wear, and when it exceeds 45 °, it becomes difficult to smoothly drain the water present in the central land portions 11 and 12, and as a result, the occurrence of the hydroplaning phenomenon is concerned. This is because that.

  Furthermore, it is preferable that the first inclined grooves 17 and 18 have an extended shape with such a curvature that they converge toward the side main grooves 9 and 10. This is because the water flowing in the first inclined grooves 17 and 18 is smoothly discharged into the side main grooves 9 and 10 by making the first inclined grooves 17 and 18 have such an extended shape. The extending shape of the first inclined grooves 17 and 18 may have a constant curvature, or may be a combination of curves having different curvatures.

  In addition, it is preferable that the first inclined grooves 17 and 18 gradually decrease in angle with respect to the tire circumferential direction C toward the side main grooves 9 and 10. By forming the first inclined grooves 17 and 18 into such extended shapes, the extension angles of the first inclined grooves 17 and 18 with respect to the tire circumferential direction on the central main grooves 5 and 6 side of the central land portions 11 and 12. As a result, the land portion rigidity is increased and the steering stability is further improved. On the side main grooves 9 and 10 side, the water in the first inclined grooves 17 and 18 is transferred to the side main grooves 9 and 10. This is because it can flow smoothly into the water and drainage performance is further improved.

  In addition, it is preferable that the circumferential grooves 21 and 22 have an extension angle with respect to the tire circumferential direction C in a range of −15 to + 15 °. From the viewpoint of ensuring drainage, the circumferential grooves 21 and 22 preferably extend outward in the tire width direction starting from the end portions 19 and 20 of the first inclined grooves 17 and 18. This is because if the extension angle with respect to the direction C is smaller than −15 °, the rigidity of the first corner portions 29 and 30 becomes insufficient and the steering stability may be lowered. Further, from the viewpoint of securing the rigidity of the land portion, the circumferential grooves 21 and 22 preferably extend inward in the tire width direction starting from the end portions 19 and 20 of the first inclined grooves 17 and 18. In addition, if the extending angle with respect to the tire circumferential direction C exceeds 15 °, the water in the circumferential grooves 21 and 22 cannot be smoothly drained, and there is a concern about deterioration of drainage.

  And it is preferable that the circumferential direction grooves 21 and 22 have the 1st chamfering parts 31 and 32 which incline at a fixed angle toward the groove bottom from a tread part tread surface in the groove wall located in the tire width direction outer side. By having such first chamfered portions 31 and 32, the rigidity of the central land portions 11 and 12 can be increased without impairing the drainage performance of the circumferential grooves 21 and 22, and the steering stability can be further improved. Because.

FIG. 2 shows a cross section on the line AA of FIG. The upper surface 33 of the first chamfered portion 31, 32 has an extension angle θ ₁ formed with the tread portion tread surface 34 in the range of 95 to 155 °, and its lower end position 35 extends from the tread portion tread surface 34 in the tire radial direction. it is preferred that the distance _{d 1} as measured along some 30 to 100% of the groove depth _{g 1} of the circumferential groove 21. It is because the angle theta ₁ is in the case of less than 95 ° insufficient reinforcing effect of the rigidity of the center land portion 11, 12 according to the first chamfered portions 31 and 32, steering stability is satisfied may become impossible to obtain If it exceeds 155 °, the ground contact surface area of the central land portions 11 and 12 will be too small, and the steering stability may be impaired, or the cross-sectional area of the circumferential grooves 21 and 22 may be excessively reduced and the drainage performance may be impaired. It is. The first chamfered portion 31 in the case of less than 30% of the groove depth g ₁ of the distance d ₁ from the tread surface 34 to the lower end position 35, measured along the tire radial direction is the circumferential groove 21 and 22, This is because the effect of reinforcing the rigidity of the central land portions 11 and 12 by 32 is insufficient, and satisfactory steering stability may not be obtained.

The first chamfered portions 31 and 32, it is further preferable that the width w _2, measured along the tire width direction is substantially constant. By thus setting the width w ₂ of the first chamfered portions 31 and 32 substantially constant, by keeping constant the cross-sectional area of the circumferential grooves 21, 22 on the circumferential, circumferential groove during tire rolling under load This is because the drainage function at 21 and 22 can be kept constant at a high level.

Further, the second inclined grooves 25, 26 are extended angles with respect to the tire circumferential direction C, with the extension lines I ₁ , I _{2 of} the imaginary center line passing through the inner ends 36, 37 of the transverse grooves 15, 16. Is larger than that of the first inclined grooves 17 and 18 and preferably has a substantially constant groove width. In this way, by arranging the transverse grooves 15 and 16 on the extension lines I ₁ and I ₂ of the virtual center line of the second inclined grooves 25 and 26, the water taken into the second inclined grooves 25 and 26 is transverse grooves. This is because the tire is smoothly discharged to the side of the tire via 15 and 16. Further, by making the extension angle of the second inclined grooves 25 and 26 with respect to the tire circumferential direction C larger than that of the first inclined grooves 17 and 18, the first inclined grooves 17 and 18 are provided for drainage during straight traveling. This is because the second inclined grooves 25 and 26 can be mainly contributed to drainage during cornering, and the overall drainage is further improved. Furthermore, the second inclined grooves 25 and 26 have a substantially constant groove width because the second inclined grooves 25 and 26 are narrower than other grooves. It is because it can make the most of it.

  Furthermore, it is preferable that the second inclined grooves 25, 26 extend through the end portions 23, 24 of the circumferential grooves 21, 22 until they are opened to the central main grooves 5, 6. By disposing the second inclined grooves 25 and 26 across the central land portions 11 and 12, water in the ground contact central area is smoothly discharged to the tire side via the second inclined grooves 25 and 26. This is because the drainage performance can be further improved, and the rigidity of the land portions of the central land portions 11 and 12 can be optimized to improve the steering stability. In addition, from the viewpoint of improving drainage, it is preferable that the groove width of the second inclined grooves 25 and 26 is large, but at the same time, deterioration of steering stability and increase of pattern noise due to a decrease in block rigidity are caused. The groove widths of the inclined grooves 25 and 26 are preferably set as appropriate so as to satisfy these performances in a well-balanced manner.

  FIG. 3 is a development of a part of the tread portion of another tire according to the present invention. As shown in FIG. 3, the transverse grooves 15, 16 are formed on the groove walls 38, 39 that subsequently enter the contact area, with the second chamfered portion 40 inclined at a certain angle from the tread portion tread surface toward the groove bottom. , 41 is preferable. By providing the second chamfered portions 40 and 41, the ground pressure of the side land portions 13 and 14 is reduced, and the hitting sound when the side land portions 13 and 14 collide with the road surface is reduced. The heel and toe wear can be suppressed even when the wear of the vehicle progresses, the noise after the wear can be reduced, and the rigidity of the side land portions 13 and 14 is increased, and the steering stability is improved. Further, on the tread portion tread surface, the opening width of the portion where the second chamfered portions 40 and 41 of the transverse grooves 15 and 16 are provided is the same as the opening width of the other portions of the transverse grooves 15 and 16. Therefore, the drainage performance is not impaired.

FIG. 4 shows a cross section taken along line BB in FIG. Upper surface 42 of the second chamfered portion 40 and 41 is in the range extending angle theta ₂ is one hundred and twenty to one hundred and seventy-five ° formed between tread surface 34, and its lower end position 43, the tread surface 34 in the tire radial direction it is preferred that the distance _{d 2} as measured along some 10 to 100% of the groove depth _{g 2} of the transverse grooves 15. If the extension angle is less than 120 °, the effect of reinforcing the rigidity of the side land portions 13 and 14 by the second chamfered portions 40 and 41 is insufficient, and there is a possibility that satisfactory steering stability may not be obtained. Yes, if it exceeds 175 °, the ground contact surface area of the side land portions 13 and 14 will be too small, and the steering stability may be impaired, or the cross-sectional area of the transverse grooves 15 and 16 may be too small and the drainage performance may be impaired. Because. Further, if the distance _{d 2} from the tread surface 34 to the lower end position 43, measured along the tire radial direction is less than 10% of a groove depth _{g 2} of the transverse grooves 15, 16 second chamfered portions 40 and 41 This is because the effect of reinforcing the rigidity of the side land portions 13 and 14 due to the shortage may be insufficient, and satisfactory steering stability may not be obtained.

The second chamfered portion 40 and 41, it is preferable that the width w _3, measured along the tire circumferential direction is substantially constant. By thus setting the width w ₃ of the second chamfered portion 40, 41 substantially constant, also it is possible to suppress the occurrence of heel and toe wear in advanced wear of the tread portion, the noise after abrasion This is because the generation can be reduced but further improved.

  Further, third chamfered portions 44 and 45 whose height gradually decreases toward the tip thereof are provided at the first corner portions 29 and 30 formed by the first inclined grooves 17 and 18 and the circumferential grooves 21 and 22. Is preferred. In addition to improving the block rigidity, water existing between the central land portions 11 and 12 and the road surface can be smoothly divided into the first inclined grooves 17 and 18 and the circumferential grooves 21 and 22, so This is because it is further improved.

  Furthermore, fourth chamfered portions 48 and 49 whose height gradually decreases toward the tip of the second corner portions 46 and 47 formed by the first inclined grooves 17 and 18 and the side main grooves 9 and 10 are provided. It is preferable to provide it. This is because the water flowing in the first inclined grooves 17 and 18 and the water flowing in the side main grooves 9 and 10 can be smoothly merged, and the drainage is further improved.

  In addition, two central main grooves 5 and 6 are arranged with the pattern center 2 interposed therebetween, and rib-shaped land portions 50 extending continuously in the tire circumferential direction are defined by the central main grooves 5 and 6. Is preferred. This is because by arranging the rib-like land portion 50 in the vicinity of the pattern center 2 of the tire, it is possible to further improve the handling stability, in particular, the responsiveness of the steering wheel.

  In addition, as shown in FIGS. 1 and 3, both the first inclined grooves 17 and 18 located in both the half areas 3 and 4 of the tread portion 1 are arranged so that the tread edge 7 and It is preferable to arrange so as to enter the contact area sequentially toward the 8 side. Thus, by making the tread pattern a so-called directional pattern, water in the tread portion tread is more smoothly discharged out of the tread portion tread, and drainage is further improved.

  The above description is merely an example of the embodiment of the present invention, and various modifications can be made within the scope of the claims. For example, FIGS. 1 and 3 show a symmetrical tread pattern across the tire equator plane, but the pattern center 2 may be somewhat shifted from the tire equator plane, or may be a laterally asymmetric tread pattern. In FIG. 1, the arrangement pitch of the transverse grooves 15, 16 is the same as the arrangement pitch of the second inclined grooves 25, 26, but may be different, and the size of the side land portions 9, 10 is optimized. From this point of view, as shown in FIG. 3, transverse auxiliary grooves 51, 52 may be disposed between the transverse grooves 15, 16.

  Next, tires according to the present invention were prototyped and performance evaluations were performed, which will be described below.

  The tires of Examples 1 and 2 have a tire size of 205 / 55R16 and have a tread pattern shown in FIG. 5 (Example 1) or FIG. 3 (Example 2). The width of the rib-like land portion is 17 mm, the width of the central land portion is 32.5 mm, the width of the lateral land portion is 26 mm, the groove width of the central main groove is 8.5 mm, and the groove width of the side main groove is 4. 5 mm, groove width of transverse groove 4 mm, groove width of first inclined groove 4 mm, extension angle of first inclined groove 45 ° on the end side, 10 ° on the opening side, groove width of circumferential groove Is 5 °, the extending angle of the circumferential groove is −5 °, the groove width of the second inclined groove is 0.5 mm, the extending angle is 50 °, and the groove depth is 8.3 mm for any tread groove. Furthermore, the tire of Example 2 is provided with first to fourth chamfered portions, and the first chamfered portion has an upper surface extending angle of 115 ° with respect to the tread portion tread surface along the tire radial direction from the tread portion tread surface. The distance to the lower end position when measured is 8.3 mm, the second chamfered portion has an upper surface extending angle of 135 ° with respect to the tread portion tread, and the lower end when measured from the tread portion tread along the tire radial direction. The distance to the position is 3 mm, the third chamfered portion has an upper surface extending angle of 45 ° with respect to the tread portion tread surface, and the fourth chamfered portion has an upper surface extending angle of 60 ° with respect to the tread portion tread surface.

  For comparison, tire size, rib-like land width, central land width, lateral land width, central main groove width, lateral main groove width, and transverse groove width are examples. Although it is the same as the tires 1 and 2, it has the tread pattern shown in FIG. 6, does not have the first inclined groove, the second inclined groove, and the circumferential groove, and has a central main groove in the central land portion. And a groove (groove width: 3 to 4 mm, extending angle: 10 to 50 °) opened to both the main groove and the side main groove, and a groove (groove) having one end opened to the side main groove and the other end terminated in the land portion. A tire (comparative example) provided with a width of 3 mm and an extension angle of 85 ° was also prototyped.

  Each of the above test tires is attached to a standard rim to form a tire wheel, and the first inclined groove is mounted on the test vehicle so that it gradually enters the contact area from the central area side to the side area when rolling the tire. The following tests were performed under conditions equivalent to tire pressure: 230 kPa (relative pressure), tire load: equivalent to two passengers.

1. Straight running drainage The vehicle traveled straight on a wet road surface with a water depth of 5 mm, the critical speed at which hydroplaning occurred was measured, and the straight running drainage was evaluated from this measured value. The evaluation results are shown in Table 1.

2. Drainability during cornering Driving on a wet road surface with a water depth of 5 mm and a radius of 80 m, the critical lateral G where hydroplaning phenomenon occurs was measured, and the drainage during cornering was evaluated from this measured value. The evaluation results are shown in Table 1.

3. Steering stability when dry The circuit course in the dry state was driven by sports in various driving modes and evaluated by the feeling of the test driver. The evaluation results are shown in Table 1.

4). Steering stability when wet
The wet circuit course was sported in various driving modes and evaluated by the feeling of the test driver. The evaluation results are shown in Table 1.

5). Noise Driving on a general road in a dry state in various driving modes, it was evaluated by the feeling of a test driver. The evaluation results are shown in 1.

  In addition, all the evaluation results in Table 1 are shown as index ratios when the evaluation result of the comparative example is 100, and the larger the value, the better.

  From the evaluation results shown in Table 1, the tires of Examples 1 and 2 are superior to the tires of the comparative examples in drainage when traveling straight, drainage when cornering, steering stability when dry, and steering stability when wet, It turns out that it is low noise.

  According to the present invention, it is possible to optimize steering stability and drainage by optimizing the shape and cross-sectional shape of the tread groove disposed in the tread portion, particularly the central land portion, and the shape and rigidity of the land portion of the tread portion. It has become possible to provide a pneumatic tire that satisfies a high level of performance while reducing noise.

1 is a development view of a part of a tread portion of a typical pneumatic tire according to the present invention. It is sectional drawing on the AA line of FIG. FIG. 6 is a development view of a part of a tread portion of another pneumatic tire according to the present invention. It is sectional drawing on the BB line of FIG. FIG. 3 is a development view of a part of the tread portion of the tire of Example 1; It is a development view of a part of the tread portion of a tire of a comparative example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tread part 2 Pattern center 3, 4 Half area 5, 6 Central main groove 7, 8 Tread end 9, 10 Side main groove 11, 12 Central land part 13, 14 Side land part 15, 16 Cross groove 17, 18 First inclined groove 19, 20 First inclined groove end portion 21, 22 Circumferential groove 23, 24 Circumferential groove end portion 25, 26 Second inclined groove 27, 28 Block 29, 30 First corner portion 31, 32 First chamfered portion 33 Upper surface of the first chamfered portion 34 Tread portion tread surface 35 Lower end position of the first chamfered portion 36, 37 Inner end portion of the transverse groove in the tire width direction 38, 39 Groove wall 40, 41 of the transverse groove Second chamfered portion 42 Upper surface of second chamfered portion 43 Lower end position of second chamfered portion 44, 45 Third chamfered portion 46, 47 Second corner portion 48, 49 Fourth chamfered portion 50 Rib-shaped land portion 51, 52 Crossing auxiliary groove

Claims (16)

At least one central main groove located in the pattern center or in the vicinity thereof and extending along the tire circumferential direction, and the central main groove and the tread end are arranged in a half area obtained by dividing the tread portion into two half areas by the pattern center. At least one side main groove located between and extending along the tire circumferential direction. The central main groove and the side main groove adjacent to the central main groove define a central land portion. In the pneumatic tire formed by dividing the side land portion by the side main groove adjacent to
In the side land portion, a plurality of transverse grooves that open to the tread end and extend in the tire width direction toward the side main groove are disposed, whereby the side land portion is substantially composed of a number of blocks. Formed as a block row,
The central land portion, opening to the side main groove, extends inclined obliquely Shi pairs in the circumferential direction of the tire toward the center main groove, and terminate short of the center main groove, which extending angle with respect to the tire circumferential direction, the central A first inclined groove that gradually increases toward the main groove, and a first corner that extends substantially parallel to the tire circumferential direction from the end portion of the first inclined groove and forms an acute V shape with the first inclined groove. A circumferential groove that extends from the terminal end of the circumferential groove at an angle greater than the extending angle of the first inclined groove with respect to the tire circumferential direction, opens into the side main groove, and forms an obtuse angle V-shape together with the circumferential groove. And a second inclined groove that forms a second corner portion, and a plurality of blocks are formed in the central land portion by these arrangements.   2. The pneumatic tire according to claim 1, wherein the transverse groove has a length measured along the tire width direction of 30% or more of a width measured at the side land portion along the tire width direction.   The pneumatic tire according to claim 1 or 2, wherein the first inclined groove has an extension angle with respect to a tire circumferential direction at a terminal portion in a range of 20 to 70 °. The pneumatic tire according to any one of claims 1 to 3 , wherein the circumferential groove has an extension angle with respect to the tire circumferential direction in a range of -15 to + 15 °. Circumferential groove, the groove wall which is located outside the tire widthwise direction, according to any one of claims 1 to 4 having a first chamfered portion inclined at an angle towards the groove bottom from the tread surface Pneumatic tire. The upper surface of the first chamfered portion has an extension angle of 95 to 155 ° with the tread portion tread surface, and the lower end position thereof is a distance when measured along the tire radial direction from the tread portion tread surface. The pneumatic tire according to claim 5 , which is in a range of 30 to 100% of a groove depth of the directional groove. The pneumatic tire according to claim 5 or 6 , wherein the first chamfered portion has a substantially constant width measured along the tire width direction. The second inclined groove has a substantially constant groove width in which the extension line of the virtual center line passes through the inner end of the transverse groove in the tire width direction, and the extension angle with respect to the tire circumferential direction is larger than that of the first inclined groove. The pneumatic tire according to any one of claims 1 to 7 , comprising: The pneumatic tire according to any one of claims 1 to 8 , wherein the second inclined groove extends until it passes through a terminal end of the circumferential groove and further opens to the central main groove. Transverse grooves, the side walls so as to follow at the time of tire rotation under load into the ground region, any one of the claims 1-9 having a second chamfered portion inclined toward the tread surface to the groove bottom at an angle The pneumatic tire according to item. The upper surface of the second chamfered portion has an extension angle of 120 to 175 ° with the tread portion tread surface, and the lower end position thereof is a distance when measured along the tire radial direction from the tread portion tread surface. the pneumatic tire according to claim 1 0 in 10 to 100% of the groove depth of the groove. The second chamfer pneumatic tire according to claim 1 0 or 1 1 width measured along the tire circumferential direction is substantially constant. The first corner portion formed by the first inclined groove and the circumferential groove, the air according to any one of claims 1 to 1 2 to provide a third chamfer gradually decreases in height toward its tip Enter tire. A second corner portion formed by the first inclined groove and the side main groove, according to any one of claims 1 to 1 3 to provide a fourth chamfered portion gradually decreasing in height toward its tip Pneumatic tire. Disposed central main grooves of the two sides of the pattern center, these central main grooves, in any one of claims 1 to 1 4 to define a rib-like land portion continuously extending in the tire circumferential direction The described pneumatic tire. Both first inclined groove located on both half area of the tread portion, of claim 1 to 1 5 made by arranging to enter from the pattern center side when the tire is rolling under load sequentially ground region toward the tread end side The pneumatic tire according to any one of the above.

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