JP2005297758A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire improving steering safety at the time of straight ahead traveling on snow and cornering by optimizing a wall surface shape of a wavy sipe. <P>SOLUTION: The tire 1 has a land part 6 arranged with the sipe 5 extending in a generally tire width direction in a shoulder area 4 when a tread portion 2 is sectioned into a center area 3 and the shoulder area 4. The sipe 5 has a wavelike extending shape alternately coupling a crest portion 7 and a trough portion 8 to keep a fixed wavelength. In the sipe 5 arranged on the land part 6, angles θ1 to θ7 made by a line segment connecting the maximum displacement points 10, 14 of the crest portion 7 on a tread surface 9 and a sipe bottom 12, a line segment connecting the maximum displacement points 11, 16 of the trough portion 8, and a normal raised on the tread are gradually increased from the inside to the outside in the tire width direction. The wall surface shape of the sipe 5 over full length is formed to gradually widen from the sipe bottom position toward an opening position of the tread surface 9. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  This invention has a land portion in which at least one sipe extending substantially along the tire width direction is disposed in a shoulder region when the tread portion is divided into a central region and a shoulder region, The present invention relates to a pneumatic tire having a wavy tread surface opening shape having a certain wavelength by alternately connecting valleys, and particularly to a studless tire, and to improve the handling stability of the tire during running on snow.

  Conventionally, in order to improve the steering stability of a studless tire when running on snow, a sipe extending approximately in the width direction of the tire is provided on the land, and a thin water film stretched on the road surface is cut by the sipe to grip the tire. Tires with an improved effect of so-called edge effects are known. As such sipe, in order to further increase the edge length, a sipe is generally used in which the edge effect is enhanced as a wavy tread opening shape in which peaks and valleys are alternately connected. In addition, the shape of the sipe is hardly changed in the depth direction in order to facilitate manufacture, and a line segment connecting the maximum displacement point of the peak portion on the tread surface and the maximum displacement point of the peak portion on the sipe bottom, and Both the line segment connecting the maximum displacement point of the valley on the tread surface and the maximum displacement point of the valley on the sipe bottom (hereinafter, the extending direction of these line segments is called the “depth direction” of the sipe) is the tread surface. In general, it is formed so as to substantially coincide with the normal line.

  As shown in FIG. 6 (a), the tire 100 exhibits an edge effect when the straight line travels while the angle between the line segment 101 located at the end of the tread and the tread contact surface 102 is substantially perpendicular. As shown in FIG. 6B, when cornering, the sipe collapses due to the action of the lateral force SF, the angle formed by the line segment 101 and the tread contact surface 102 becomes small, and a sufficient edge effect cannot be obtained.

In recent years, so-called three-dimensional sipe, in which the shape of the sipe is changed in the depth direction for the purpose of improving the edge effect, has attracted attention. For example, in Patent Document 1, a wavy sipe in which the length of the sipe in a surface parallel to the tread surface is extended from the tread surface toward the bottom of the sipe so that stable wet performance can be maintained even if worn. Entered tires are described. Further, in Patent Document 2, a wavy sipe whose wavelength is gradually increased from the tire surface side toward the deepest part of the sipe is arranged to improve the braking performance, uneven wear resistance performance and durability performance when traveling on ice. Entered tires are described. However, these tires are also considered only for improving the edge effect during straight traveling, and the above-described reduction in the edge effect during cornering is not considered.
Japanese Patent Laid-Open No. 11-208223 JP 2003-118322 A

  Accordingly, an object of the present invention is to provide a pneumatic tire that has improved steering stability both when traveling straight on snow and during cornering by optimizing the wall surface shape of the wavy sipe.

  In order to achieve the above object, the present invention has a land portion in which at least one sipe extending substantially along the tire width direction is disposed in a shoulder region when the tread portion is divided into a central region and a shoulder region. The sipe is a pneumatic tire having a wavy extending shape having a constant wavelength by alternately connecting peaks and valleys, and the sipe disposed at least on a land portion located in a shoulder region is a tread. A line connecting the maximum displacement point of the peak on the tread and the maximum displacement point of the peak on the sipe bottom, and a line connecting the maximum displacement point of the valley on the tread surface and the maximum displacement of the valley on the sipe bottom Are alternately positioned, the angle between the line segment and the normal line standing on the tread surface gradually increases from the inner side to the outer side in the tire width direction, and the sipe wall surface shape extends from the sipe bottom position to the tread surface. A pneumatic tire and forming so as to be flared toward the location.

  Here, the “central area” is a range of 0 to 50% of the tread width centering on the tire equator plane, and the “shoulder area” is an area on both sides of the central area. “Width direction” refers to a range of ± 20 ° in the tire width direction, preferably ± 10 ° in the tire width direction, and “wavelength” refers to the extension of the sipe between the maximum displacement points (mountains) of adjacent peaks. The distance measured along the direction or the distance measured along the extending direction of the sipe between the maximum displacement points (valleys) of adjacent valleys.

  Moreover, it is preferable that the wavelength in a tread tread is 1.1 to 2.0 times the wavelength in a sipe bottom at a sipe.

  Furthermore, it is preferable that the sipe has a divergence angle in a range of 10 to 30 °, which is an angle formed by a line segment located on the outermost side in the tire width direction and a normal line standing on the tread surface.

  Furthermore, when the distance measured along the direction perpendicular to the extending direction of the sipe between the maximum displacement point of the sipe peak and the maximum displacement point of the valley is taken as the height difference, the sipe is the height difference at the sipe bottom. Is preferably smaller than the height difference on the tread surface.

  In addition, the sipe preferably has a tread opening shape of a triangular wave, a trapezoidal wave, a square wave or a sine wave.

  According to the present invention, by optimizing the wall surface shape of the wavy sipe, it is possible to obtain an excellent edge effect both when traveling straight on snow and during cornering, and dramatically improve steering stability. it can.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a development view of a part of a tread portion of a typical pneumatic tire (hereinafter referred to as “tire”) according to the present invention, and FIG. 2 is a perspective view of a land portion of a shoulder region of the tire shown in FIG. FIG. 3 is a sipe extending direction sectional view of the shoulder region of the tire shown in FIG.

  In the tire 1, at least one sipe extending substantially along the tire width direction is disposed in the shoulder region 4 when the tread portion 2 is divided into the central region 3 and the shoulder region 4, and in FIG. 1, two sipes 5 are arranged. The land portion 6 is provided. The sipe 5 has a wavy extending shape having a constant wavelength by alternately connecting the crests 7 and the troughs 8.

The main structural features of the present invention are that the sipe 5 disposed at least in the land portion 6 located in the shoulder region 4 includes the maximum displacement point 10 of the ridge 7 on the tread surface 9 and the ridge on the sipe bottom 12. Lines l ₂ , l ₄ , and l ₆ connecting the 13 maximum displacement points 14, lines connecting the maximum displacement point 11 of the valley portion 8 in the tread tread 9 and the maximum displacement point 16 of the valley portion 15 in the sipe bottom 12. Minutes l ₁ , l ₃ , l ₅ , and l ₇ are alternately positioned, and angles θ _{1 to} θ ₇ formed by these line segments l _{1 to} l ₇ and normal lines n _{1 to} n ₇ standing on the tread tread 9. Are gradually increased from the inner side to the outer side in the tire width direction, that is, θ ₁ <θ ₂ <θ ₃ <θ ₄ <θ ₅ <θ ₆ <θ ₇ , and the wall shape of the sipe 5 over the entire length is As shown in FIG. 3, the opening position of the tread surface 9 from the sipe bottom position 12 It is to be formed so as to be widened toward the end.

Hereinafter, how the present invention has adopted the above configuration will be described together with the operation.
As described above, the line connecting the maximum displacement point of the sipe peak on the tread surface and the maximum displacement point of the sipe peak on the sipe bottom, and the maximum displacement point of the sipe valley on the tread surface and the sipe on the sipe bottom. In tires in which the line segments connecting the maximum displacement points of the valleys of the tires substantially coincide with the normals raised on the tread surface, as shown in FIG. There was a problem that the land part deformed and the sipe collapsed, and a sufficient edge effect could not be obtained. In order to obtain a sufficient edge effect even during such cornering, the sipe depth direction with respect to the top surface of the land portion is at a predetermined angle so that the sipe depth direction is substantially perpendicular to the tread surface when the land portion is deformed. It is conceivable that the sipe is arranged so that the sipe has a constant depth direction, but on the contrary, sufficient edge effect cannot be obtained during straight running, and the traction performance and braking performance are reduced. There is a problem of doing. The inventor has examined the deformation of the land portion of the shoulder region and the contact pressure during both straight running and cornering, and the ground pressure inside the land portion in the tire width direction has a relatively high contact pressure during straight running. Sometimes the deformation and the contact pressure are relatively small, while on the outer side of the land width in the tire width direction, the contact pressure is relatively low when traveling straight, the deformation and contact pressure is relatively large when cornering, and therefore the sipe tire width direction when traveling straight It was found that the inner part greatly contributed to the edge effect, and the outer part in the tire width direction of the sipe greatly contributed to the edge effect during cornering. Therefore, the inventor changes the sipe depth direction between the inside and the outside of the land width in the tire width direction according to the degree of deformation during cornering, that is, the sipe depth direction and the normal line standing on the tread surface. By making the corner relatively small on the inner side in the tire width direction and relatively large on the outer side in the tire width direction, the wall surface shape of the sipe over the entire length is formed so as to be divergent from the sipe bottom position toward the tread opening position. When traveling straight, as shown in FIG. 4 (a), the sipe 5 inclined to the outside in the tire width direction is subjected to the action of lateral force SF during cornering, and as shown in FIG. The inventors have found that it becomes substantially vertical and a sufficient edge effect can be obtained, and the present invention has been completed.

In the sipe 5, the wavelength λ _{1 at} the tread surface 9 is preferably 1.1 to 2.0 times the wavelength λ _{2 at} the sipe bottom 12. When the wavelength λ ₁ is less than 1.1 times the wavelength λ _2, the angle formed by the depth direction of the sipe 5 on the outer side in the tire width direction and the normal line standing on the tread tread surface 9, the normal line n _{7 in} FIG. When the angle θ ₇ formed by the angle is too small and exceeds 2.0 times, the angle θ ₇ becomes excessive, and in any case, the depth direction of the sipe 5 and the tread tread surface 9 are outside in the tire width direction during cornering. This is because they are not vertical and a sufficient edge effect cannot be obtained.

Further sipe 5 is spread angle theta ₇ is an angle between the normal line n ₇ stood in line l ₇ and the tread surface 9 of the outermost in the tire width direction of the line segment l ₁ to l ₇ 10 It is preferably in the range of -30 °. This is because when the divergence angle θ ₇ is less than 10 ° or exceeds 30 °, the sipe 5 and the tread surface 9 are not substantially vertical during cornering, and a sufficient edge effect cannot be obtained. The spread angle is more preferably set according to the crown shape.

Furthermore, the distance measured between the maximum displacement points 10 and 14 of the peak portions 7 and 13 of the sipe 5 and the maximum displacement points 11 and 16 of the valley portions 8 and 15 along the direction orthogonal to the extending direction of the sipe 5 is obtained. When making the height difference, the sipe 5 is preferably such that the height difference A _{2 at the} sipe bottom 12 is larger than the height difference A _{1 at the} tread surface 9. Since the wavelength lambda ₁ in the tread surface 9 is greater than the wavelength lambda ₂ in the sipe bottoms 12, the length of the sipe 5 tends to become shorter toward the sipe bottom 12, the height difference A ₂ in such a sipe bottom 12 by greater than height difference a ₁ in the tread surface 9, since it longer than maintain or the length of the sipe 5 exposed to the tread surface 9 with the progress of wear of the tread portion 2, the tire according to the deterioration of the tread rubber This is because the decrease in grip force can be compensated by improving the edge effect, and stable steering stability can be obtained over the service life of the tire.

  In addition to the triangular wave shown in FIG. 1, the sipe has a trapezoidal wave shown in FIG. 5 (a), a square wave shown in FIG. 5 (b), or an extended shape of a sine wave shown in FIG. 5 (c). You can also. In the case of having these extended shapes, the wavelength is a length obtained by measuring one period of the waveform along the extending direction of the sipe. In the case of a trapezoidal wave and a square wave, the midpoints of the peaks and valleys are the maximum displacement points.

  Such a sipe is formed as follows. That is, a blade having a predetermined shape, wavelength, and height difference is disposed in the mold. At this time, the height difference can be changed by moving one end of the blade toward the other end. When such a blade is implanted in the mold, the blade is attached so that an angle formed by the inner end of the blade in the tire width direction and a normal line standing on the tread surface of the mold is a predetermined angle. If a green tire is vulcanized using a mold in which such a blade is implanted, a tire having a sipe having a desired shape can be obtained.

  In addition, the place mentioned above only showed a part of embodiment of this invention, and can change a various change in a claim. For example, in FIG. 1, only the sipe disposed on the land portion of the shoulder region has been described, but the sipe in the central region also has a wall shape of the sipe extending from the sipe bottom position to the tread opening position according to the crown shape. It can also be formed so as to expand toward the end.

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

  The tires of Examples 1 to 4 are studless tires for passenger cars having a tire size of 205 / 55R16. The tires have the tread pattern shown in FIG. 1 and the specifications shown in Table 1.

  For comparison, although the tire size is the same as that of the tires of Examples 1 to 4 and has the tread pattern shown in FIG. 1, the angle formed by the sipe depth direction and the normal line standing on the tread surface is the tire width. A tire (conventional example) having zeros on the inside and outside in the direction and having the specifications shown in Table 1 was also prototyped.

  In the table, “depth direction angle” means the angle between the line connecting the maximum displacement point of the peak on the tread surface and the maximum displacement point of the peak on the sipe bottom and the normal on the tread surface. Or the angle between the line segment connecting the maximum displacement point of the valley on the tread surface and the maximum displacement point of the valley on the sipe bottom and the normal line standing on the tread surface.

  Each of the test tires is attached to a rim having a rim size of 61 / 2JJ to form a tire wheel, and the tire wheel is attached to four wheels of a test vehicle. The front wheel is 210 kPa (relative pressure) and the rear wheel is 230 kPa ( The following tests were performed under the conditions of a front tire load: 4.8 kN and a rear tire load: 2.8 kN. Each test was performed on both a new tire (when new) and a tire after running 10,000 km (when worn).

1. Steering stability during straight running The test course on a 50 m long snowy road was run straight, and the time required to run through this course was measured. From this measured value, the steering stability during straight running was evaluated. The evaluation results are shown in Table 1.

2. Steering stability during cornering Slalom running on a test course with a total of 6 pylons installed at intervals of 9 m on a 80 m long snowy road, and measuring the time required to run this course The steering stability during cornering was evaluated from the values. The evaluation results are shown in Table 1.

  From the evaluation results shown in Table 1, it can be seen that the tires of Examples 1 to 4 are superior in steering stability during cornering while having the same steering stability when traveling straight ahead as compared to the conventional tires. .

  According to the present invention, it is possible to provide a pneumatic tire with improved steering stability both when traveling straight on snow and during cornering.

1 is a development view of a part of a tread portion of a typical pneumatic tire according to the present invention. It is a perspective view of the land part of the shoulder region of the tire shown in FIG. It is a sipe extending direction sectional drawing of the shoulder region of the tire shown in FIG. It is a figure for demonstrating the deformation | transformation state at the time of the pneumatic tire according to this invention receiving lateral force, (a) shows the tire state at the time of straight running, (b) shows the tire state at the time of cornering traveling. (A)-(c) is a partial expanded view of the tread part of the other pneumatic tire according to this invention. It is a figure for demonstrating the deformation | transformation state at the time of the conventional pneumatic tire receiving a lateral force, (a) is a tire state at the time of straight running, (b) shows the tire state at the time of cornering driving | running | working.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tire 2 Tread part 3 Center area 4 Shoulder area 5 Sipe 6 Land part 7,13 Mountain part 8,15 Valley part 9 Tread tread 10,14 Mountain part maximum displacement point 11,16 Valley maximum displacement point 12 Sipe bottom

Claims (5)

The shoulder region when the tread portion is divided into a central region and a shoulder region has a land portion in which at least one sipe extending substantially along the tire width direction is disposed, and the sipe has a mountain portion and a valley portion. In a pneumatic tire having a wavy extended shape with a constant wavelength connected alternately,
The sipe placed on the land located at least in the shoulder area is the line connecting the maximum displacement point of the peak on the tread surface and the maximum displacement point of the peak on the bottom of the sipe, and the maximum displacement of the valley on the tread surface. The line and the line connecting the maximum displacement point of the valley at the sipe bottom are alternately positioned, and the angle between the line and the normal line standing on the tread surface gradually increases from the inside to the outside in the tire width direction. A pneumatic tire characterized in that the wall shape of the sipe extending over the entire length is formed so as to widen toward the tread opening position from the sipe bottom position.   2. The pneumatic tire according to claim 1, wherein the sipe has a wavelength at a tread surface of 1.1 to 2.0 times a wavelength at a sipe bottom.   The pneumatic sipe according to claim 1 or 2, wherein the sipe has an angle formed by a line segment located on the outermost side in the tire width direction of the line segment and a normal line standing on a tread surface in a range of 10 to 30 °. tire.   When the distance measured along the direction orthogonal to the extending direction of the sipe between the maximum displacement point of the peak portion of the sipe and the maximum displacement point of the valley portion is defined as a height difference, the sipe is a height difference at the bottom of the sipe. The pneumatic tire according to any one of claims 1 to 3, wherein is larger than a difference in height on a tread surface.   The pneumatic tire according to any one of claims 1 to 4, wherein the sipe has a tread opening shape of a triangular wave, a trapezoidal wave, a square wave, or a sine wave.

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