JPH08276707A - Pneumatic tire - Google Patents

Abstract

PURPOSE: To attain low noise and improve wet skid resistance in a tire provided with a tread having a plurality of lug grooves inlining and extending in a trapezoid, and land parts divided by the lug grooves, by devising the shape of the inclined rug grooves for pitch. CONSTITUTION: This tire, which is provided with a tread having a plurality of lug grooves 4 inclining and extending in a trapezoid and land parts divided by the lug grooves 4, employs at least three types P1 -P3 (P1 <P2 <P3 ) at regular pitches P which are intervals in the peripheral direction of the lug grooves 4. Through at least four pitch elements A, B where respective pitches P are equally-divided into two parts, pitch elements are combined so as to refract and extend in the increasing direction of inclining angle to a straight or the equatorial plane 0 at a boundary (k) between the pitches. The tread 6 is constituted of the land parts of identical shape to each other, so it is possible to maintain a low noise level.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a pneumatic tire having a figure-shaped lug groove and a directional tread having a pitch variation.

[0002]

2. Description of the Related Art In recent years, noise has come to be considered as a pollution problem caused by automobiles, and quietness has come to be emphasized even for a driver. The noise generated during running from the tire is mainly due to the landing sound of the land part divided by the lug component of the groove in the tread of the tire when striking the road surface and the land part generated when kicking. Friction noise with the road surface, and the intake of air into the lug groove,
It is the vibration sound of the air that accompanies the blowing.

In order to reduce such noise generated by a tire, a pitch variation method based on a frequency modulation theory has been conventionally used, and a land portion is formed by an appropriate pitch ratio and arrangement of a plurality of pitches having different lengths. Divide
It has been made to disperse specific frequencies and make them sound unpleasant.

On the other hand, in terms of tread structure, particularly in passenger car tires, from the viewpoint of noise resistance, the main groove is
When running on wet roads, it has a function of draining water in the circumferential direction as well as in the axial direction, and it has an inclined lug groove that extends in a smooth curve along a relatively long stroke from the center of the tread to both ends in a figure eight shape. A so-called directional tread, which is arranged in the direction and in which the land portion is substantially divided only by these lug grooves, is preferably used.

[0005]

However, a pitch varier is used in a tread having such an eight-shaped inclined lug groove.
Groove is formed by combining multiple pitch elements with different lengths, depending on how the pitch elements are combined, it bends and meanders at the boundary position of the pitch elements, resulting in a lug groove. It will affect the flow of water inside. The refraction of the lug groove has little influence in the axial direction, but if it is meandered in the direction of the equatorial plane, the flow of water toward the tread edge is obstructed. In view of the above problems, it is an object of the present invention to provide a pneumatic tire having both low noise and excellent wet skid resistance.

[0006]

DISCLOSURE OF THE INVENTION According to the present invention, a large number of lug grooves extending obliquely in an eight shape on the circumference of a crown portion extending between a pair of annular side walls, and divided by these lug grooves. Equipped with a tread having a land portion, at least three types P ₁ per pitch that is the circumferential interval of the lug groove,
P _2, P _3, where _{P 1 <P 2 <P 3} , using Pitchibarie - a tire having an array subjected to Deployment, tilt lug grooves of the tread, each A, B 2 equally divided pitch element the pitch Pneumatic tire characterized by being formed by combining at least four of the pitch elements so as to extend at a boundary of the pitch elements such that the pitch elements are bent and extend in the direction in which the inclination angle increases with respect to the equatorial plane of the straight tire or the tire. Is.

At least 4 types of 2 per pitch above
Pitch elements P _1A , P _1B , P _2A , P _2B , P _3A , P
_3B , P _4A , P _4B , where P _1A = P _1B <P _2A = P _2B <P _3A = P _3B <
P _4A = P _4B , and the pitch P _j located adjacent to any pitch P _i in the arrangement of pitch elements is _i −2 ≦
It is preferable that j ≤ i + 2, where j is a pitch number that i can take, and the relationship between adjacent pitch elements is.

In this case, when the maximum ratio of the ratio of the long pitch to the short pitch of the pitch elements adjacent to each other on the circumference is r _max , the intersection point between the center line of the inclined lug groove and the boundary of the pitch element is the axis. W _n ≧ w _n-1 from the inner point in the direction to the outer side in the same direction
It is more preferable that they are sequentially provided in the relationship of xr _max , where w is the axial distance between the intersections.

[0009]

The tire according to the present invention has at least three types of pitches P ₁ , P ₂ , P ₃ , but P _{1 for} each of the eight-shaped inclined lug grooves arranged on the tread and the land portion divided by these lug grooves. <P ₂ <P ₃ for pitch variability and arrangement.
, B and through at least four bisected pitch elements, a combination of pitch elements is formed at the boundary of the pitch elements so that the pitch elements bend and extend in the direction of increasing inclination angle with respect to the equatorial plane of the train or tire. What has been done is a feature of the configuration. Therefore, regarding noise resistance, unlike the one in which the tread is composed of a group of independent blocks divided by a plurality of circumferential grooves and lateral grooves, the tread is divided by an eight-shaped lug groove. Being configured, this type of tread is advantageous for the above tapping sound, and at the same time,
A low noise level is maintained by the applied pitch variation.

Regarding drainage during running on a wet road, the pitch angle of the pitch element at the boundary position of pitch elements existing in a long stroke, where the inclination angle with respect to the equatorial plane gradually increases from the central portion of the tread of the lug groove and smoothly connects to the tread end, Regardless of the combination, by avoiding the refraction toward the equatorial plane, it is possible to obtain a smooth water flow in the lug groove toward the tread end.

As for the axial refraction of the inclined lug groove, at least four types of pitch elements divided into the above-mentioned pitch are divided into two equal parts.
P _1A , P _1B , P _2A , P _2B , P _3A , P _3B , P _4A , P _4B , where P _1A = P _1B <P _2A = P _2B <P _3A = P _3B <P _4A = P _4B The pitch P _{j which} is arranged by using the pitch element and is located adjacent to an arbitrary pitch P _i of the arrangement of pitch elements is i-2 ≤ j ≤ i + 2, where j
By arranging the adjacent pitch elements such that i is a possible pitch number, it is possible to avoid undesired excessive refraction at the pitch element boundary position while maintaining a low noise level.

Furthermore, if the maximum ratio of the ratios of the long pitch to the short pitch of the pitch elements adjacent to each other on the circumference is r _max , the intersection of the center line of the inclined lug groove and the boundary of the pitch elements is in the axial direction. W _n ≧ w _n-1 × r in the same direction outward from the inner base point
_max , where w is the axial distance between the intersections, when sequentially provided, the smoothness of the water flow due to the geometrical smoothness of the octagonal inclined lug groove can be more effectively achieved. it can.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A description will be given below with reference to the drawings. FIG. 1 is a sectional profile view of a tire of an embodiment of the present invention, FIG. 2 is a tread plan view showing a tread structure of the tire, and FIG. 3 is a plan view of a tread showing a pitch arrangement state. Tire according to the present invention
1 indicates a large number of lug grooves 4 extending in a figure 8 on the circumference of the crown portion 3 straddling a pair of annular side walls 2.
And a tread 6 having a land portion 5 divided by these lug grooves, and at least three types of pitch intervals in the circumferential direction of the lug grooves, that is, pitches P ₁ , P ₂ , P ₃ , provided that P ₁ <P ₂ <P
_The pitch lag grooves 4 are arrayed by pitch variability using ₃ and the pitch lag groove 4 passes through at least four pitch elements that divide the pitch P into equal parts A and B, respectively, and is straight at the boundary k of those pitch elements. The pitch elements are formed by combining them so as to bend and extend in the direction in which the inclination angle increases with respect to the outer surface or the equatorial plane O 2.

FIGS. 1 to 3 show an example of a passenger car tire of 235 / 40ZR18 size. Tire 1 is not shown in the drawing, but it is reinforced by a radial cord between the left and right side walls 2 with a fiber cord. A non-stretchable belt layer having a width of about tread 6 is arranged around the crown portion of the carcass, which is the base portion of the tread 6, for reinforcement.

In this embodiment, the lug groove 4 is a tread.
6 From each position close to the equatorial plane O on the tread edge E _T
It extends in a figure eight shape. The shape of the lug groove 4 is such that the angle with respect to the equatorial plane O is extremely small at the inner end in the axial direction, the angle gradually increases from that position toward the outer side in the axial direction, and in the central region 7 of the stroke, it is parallel to the equatorial plane O. The average angle α with respect to the line m is 15 to 45 °, and is bent in the axial direction in the vicinity of the ground contact end E _C that contacts the ground during normal straight running and opens at the tread end E _T. The land part 5, which is divided by the lug groove 4 and is also continuous in an eight-shape, is apparently an independent block by a plurality of sipes 8 (width 0.7 mm) and narrow grooves 9 (width 3.5 mm).
It is subdivided into 10.

With respect to the pitch P, in this embodiment, for the sake of convenience, the intersection point 13 between the inclined portion 11 where the lug groove walls are continuous and the circumferentially extending portion 12 is used as a base point, and the pitch as the lug groove interval between the intersection points 13 is P. _{1, P 2, P 3,} P 4, P 5 and five types, their length ratio 7: 8: 9: 10: 11 is applied with a.
Further, these pitches P _{1 to} P ₅ are arranged on the circumference of the tread in the following manner, using pitch elements A 1 and B 2 which are divided into two equal parts, based on a random tone. In addition, when arranging,
Even though it is a random tone, the pitch elements A and B have different shapes, so they are arranged alternately.
The relationship of i−2 ≦ j ≦ i + 2, that is, the arrangement in which pitches having different pitch numbers of 3 or more and having different lengths are adjacent to each other is avoided. P _3A P _3B P _5A P _3B P _2A P _1B P _3A P _3B P _2A P _1B P _1A P _2B P _4A P _2B P _4A P _2B P _4A P _5B P _5A P _4B P _2A P _4B P _3A P _5B P _5A P _4B P _3A P _4B P _2A P _1B P _2A P _3B P _5A P _3B P _5A P _4B P _2A P _1B P _1A P _1B P _2A P _4B P _3A P _4B P _2A P _1B P _3A P _5B P _3A P _2B P _1A P _2B P _4A P _5B P _3A P _2B P _3A P _4B P _2A P _4B

FIG. 3 shows the 45th to 50th parts of the arrangement of the pitch elements having the largest change in length. The left half of the equatorial plane O (not shown) is The same arrangement as that on the right side of the drawing is provided with a phase difference in the circumferential direction of about 1/4 pitch as shown in FIG. In this embodiment, the lug groove 4 opens from the position close to the equatorial plane O 1 to the tread end E _T through the boundary k of the six pitch elements.

Lines d, e, f, g, h, i, j connecting the intersections of the center line 14 of the lug groove 4 and the boundary k of the pitch elements A, B.
Is parallel to the equatorial plane O and the widths w ₁ , w ₂ ,
w ₃ , w ₄ , w ₅ , and w ₆ are as follows. The maximum ratio of the long pitch to the short pitch of adjacent pitch elements on the circumference, r _max
Is 9/7, so first determine the width w ₁ from the line d as an origin,
The widths w ₂ to w ₆ on the outer side in the axial direction were determined according to the relationship of w _n ≧ w _n-1 × r _max . w ₁ : 7 mm w ₂ : 7 × 9/7 = 9… 9 mm w ₃ : 9 × 9/7 = 11.57… 11.6 mm w ₄ : 11.6 × 9/7 = 14.91… 15 mm w ₅ : 15 × 9 / 7 = 19.29… 19.3 mm w ₆ : 19.3 × 9/7 = 24.81… 24.9 mm

Pitch elements having different lengths P _{1A to} P _5A , P _1B
The lug groove 4 (FIG. 2) whose extension shape is substantially determined by .about.P _5B and the widths w _{1 to} w ₆ changes the pitch length as shown in FIG. 3 even if the pitch variation is performed in pitch element units. With the largest (r _max ) pitch elements next to each other P _1B and P _3A
At the boundary k of, the geometric smoothness of the lug groove centerline 14 is maintained. The axially inner end of the lug groove is stopped within the width w ₁ area before the line d, and the axially outer end is line i.
The groove width is narrowed by refracting in the axial direction within the area having a width w ₆ that is beyond.

[0020]

[Effect] To confirm the effect of the tire according to the present invention, 235 /
For the tire of the example described based on FIGS. 1 to 3 of 40ZR18 size, the widths w ₁ to w ₆ between the lines d to j are different only in the point that w _n <w _n-1 × r _max . Noise from the actual vehicle (pattern noise) and hydroplaning generation speed were measured and evaluated with the tires mixed.

The widths w _{1 to} w ₆ of the tire of the comparative example are as follows. w ₁ : 8.5 mm w ₂ : 8.5 × 9/7 = 10.92… 10 mm w ₃ : 10 × 9/7 = 12.86… 12.5 mm w ₄ : 12.5 × 9/7 = 16.07… 15 mm w ₅ : 15 × 9 / 7 = 19.29… 18.5 mm w ₆ : 18.5 × 9/7 = 23.9… 22.3 mm

As a test condition, the tire is assembled on an 18 × 8.5J rim, is filled with an internal pressure of 2.5 Kgf / Cm ² , and occurs in a noise test when traveling straight on a smooth asphalt pavement at a speed of 40 to 80 Km / H. Apply pattern noise to the driver
Evaluated by ring. In hydroplaning, the hydroplaning generation rate was measured when passing through a pool with a water depth of 5 mm provided on the road. The test results are shown in Table 1.

[0023]

[Table 1]

As described above, the land portion is divided by a large number of lug grooves extending obliquely in the shape of a figure of eight, and at least three types P are provided for the pitch which is the circumferential interval of the lug grooves.
₁ , P ₂ , P ₃ , where P ₁ <P ₂ <P ₃
A tread arranged in an array, and the inclined lug groove of the tread is passed through at least four pitch elements obtained by equally dividing the pitch by A and B 2, respectively, and at the boundary of the pitch elements, the straight line or the equatorial plane of the tire. On the other hand, the pneumatic tire according to the present invention, which is formed by combining pitch elements so as to extend by bending in a direction in which the inclination angle increases, has a low noise level while maintaining a low noise level. Since the water flow is smooth, the wet skid resistance and especially the hydroplaning generation rate can be advantageously increased.

[Brief description of drawings]

FIG. 1 is a sectional profile view of a tire according to an embodiment of the present invention.

FIG. 2 is a tread plan view showing a tread structure of the tire.

FIG. 3 is a tread plan view showing a pitch arrangement state of the tire.

[Explanation of symbols]

 1 Tire 2 Sidewall 3 Crown part 4 Lug groove 5 Land part 6 Tread P Pitch A Pitch element B Pitch element O Equatorial plane k Pitch element boundary

Claims (3)

[Claims] 1. A tread having a large number of lug grooves extending obliquely in an eight shape on the circumference of a crown portion extending between a pair of annular side walls and a land portion divided by these lug grooves. , At least three types per pitch that is the circumferential interval of the lug grooves P ₁ , P ₂ , P ₃ , where P ₁ <P ₂ <P ₃ , using the tires arranged with pitch variation, the tread of the The slanted lug groove has the above pitch
Through at least four pitch elements divided into A and B2,
A pneumatic tire formed by combining pitch elements so as to bend and extend in a direction in which an inclination angle increases with respect to a straight line or a equator plane of the tire at a boundary between the pitch elements. 2. At least four 2 per pitch
Pitch elements P _1A , P _1B , P _2A , P _2B , P _3A , P
_3B , P _4A , P _4B , where P _1A = P _1B <P _2A = P _2B <P _3A = P _3B <
P _4A = P _4B , and the pitch P _j located adjacent to any pitch P _i in the pitch element sequence is i-2.
≤j ≤i + 2, where j is a pitch number that i can take,
The pneumatic tire according to claim 1, wherein the pitch elements are adjacent to each other. 3. When the maximum ratio of the long pitch to the short pitch of adjacent pitch elements on the circumference is r _max , the intersection of the center line of the inclined lug groove and the boundary of the pitch element is axially inward. W _n ≥w _n-1 × r _max outward from the base point in the same direction, where w
The pneumatic tire according to claim 2, wherein are sequentially provided with a relationship of an axial distance between intersections.