JP2015048023A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire improved in a drainage performance at a direct advancing time and at a cornering time.SOLUTION: A pneumatic tire 1a comprises a circumferential groove 20 and a width directional groove 30a communicating with the circumferential groove 20, and bottom-up parts 22a are formed at least partially at the groove bottom of the circumferential groove 20. The bottom-up parts 22a are formed alternately in a tire circumferential direction on each side of the tire width direction of the circumferential groove 20, and the bottom-up parts 22a adjoining in the tire circumferential direction have an identical tire circumferential direction region and adjoin in the tire width direction. The width directional groove 30a communicates with the region, in which the bottom-up part 22a of the circumferential groove 20 is not formed, over 70% or more of the groove width of the width directional groove 30a in the part communicating with the circumferential groove 20.

Description

  The present invention relates to a pneumatic tire having improved drainage performance during straight traveling and cornering.

  Conventionally, as disclosed in Patent Document 1, a pneumatic tire having a tread pattern including a circumferential groove and a lug groove branched from the circumferential groove is known. In the pneumatic tire disclosed in Patent Document 1, the drainage performance is improved by providing a plurality of protrusions on the wall surface of the circumferential groove opposite to the lug groove at the lug groove branching position.

Japanese Patent No. 3998573

  However, in the pneumatic tire disclosed in Patent Document 1, the circumferential groove buckling (buckling phenomenon) occurs during cornering, so that the volume of the circumferential groove decreases, and drainage performance during cornering may deteriorate. There is.

  Then, an object of this invention is to provide the pneumatic tire which improved the drainage performance at the time of going straight and cornering.

  In the first aspect of the present invention, in a pneumatic tire comprising a circumferential groove and a widthwise groove communicating with the circumferential groove, and a bottom raised portion is formed at least at a part of the groove bottom of the circumferential groove, Parts are alternately formed in the tire circumferential direction on each side in the tire width direction of the circumferential groove, and the bottom-up portions adjacent to each other in the tire circumferential direction have the same tire circumferential region and are continuous in the tire width direction, A pneumatic tire is provided in which the widthwise groove communicates with a region where the bottom-up portion of the circumferential groove is not formed over 70% or more of the width of the widthwise groove at the communication portion with the circumferential groove. Is done.

  In the second aspect of the present invention, in the plane parallel to the tire equator plane, the area As of the same tire circumferential direction region and the area Ar of the raised portion have a relationship of 0.1 ≦ As / Ar ≦ 0.4. Fulfill.

  In the third aspect of the present invention, the height Hr of the bottom raised portion and the depth D of the circumferential groove satisfy the relationship of 0.2 ≦ Hr / D ≦ 0.5.

  In the fourth aspect of the present invention, the width direction groove is inclined with respect to the tire circumferential direction on at least one side of the circumferential groove in the tire width direction.

  In the fifth aspect of the present invention, the tire rotation direction is specified, and the width direction groove is inclined from the circumferential groove toward the kick-out side on at least one side of the circumferential groove in the tire width direction. .

  ADVANTAGE OF THE INVENTION According to this invention, the pneumatic tire which improved the drainage performance at the time of linear advance and a cornering is provided by improving arrangement | positioning of the bottom raising part of a circumferential groove | channel, and a width direction groove | channel.

FIG. 1 is a plan development view showing a part of a tread surface of a pneumatic tire according to an embodiment of the present invention. FIG. 2 is a cross-sectional view of a circumferential groove in a plane parallel to the tire equatorial plane. FIG. 3 is a tire meridian cross-sectional view of a circumferential groove. FIG. 4 is a plan development view showing a part of a tread surface of a pneumatic tire in which a bottom raised portion of another arrangement is formed. 5 (a) and 5 (b) are plan development views showing a part of a tread surface of a pneumatic tire according to an additional embodiment of the present invention. 6 (a) and 6 (b) are each a plan development view showing a part of a tread surface of a pneumatic tire according to an additional embodiment of the present invention. FIG. 7 is a plan development view showing a part of a tread surface of a pneumatic tire according to an additional embodiment of the present invention.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention (the following basic modes and additional modes 1 to 4) will be described in detail with reference to the accompanying drawings. Note that these embodiments do not limit the present invention. In addition, constituent elements of the above embodiment include those that can be easily replaced by those skilled in the art and those that are substantially the same. Furthermore, various forms included in the above embodiment can be implemented in any combination.

  First, terms used in the description of the embodiments are defined as follows. The tire radial direction means a direction orthogonal to the rotation axis of the pneumatic tire. The inner side in the tire radial direction means the side toward the rotation axis in the tire radial direction. The outer side in the tire radial direction means the side away from the rotation axis in the tire radial direction. The tire circumferential direction means a direction around the rotation axis as a central axis. The tire width direction means a direction parallel to the rotation axis. The inner side in the tire width direction means the side toward the tire equatorial plane in the tire width direction. The outer side in the tire width direction means the side away from the tire equatorial plane in the tire width direction. The tire equatorial plane means a plane that is orthogonal to the rotational axis of the pneumatic tire and passes through the center of the tire width of the pneumatic tire.

[Basic form]
Hereinafter, the basic form of the pneumatic tire according to the present invention will be described. FIG. 1 is a plan development view showing a part of a tread surface of a pneumatic tire according to an embodiment of the present invention.

  The tread portion of the pneumatic tire 1a is made of a rubber material (tread rubber). The surface of the tread portion (tread surface 10a) located at the outermost portion in the tire radial direction comes into contact with the road surface when the vehicle travels. As shown in FIG. 1, a tread pattern having a predetermined pattern is engraved on the tread surface 10a.

  The tread surface 10 a of the pneumatic tire 1 a includes a circumferential groove 20 and a plurality of widthwise grooves 30 a communicating with the circumferential groove 20. A plurality of land portions 40a are defined by the circumferential grooves 20 and the plurality of width-direction grooves 30a.

  In the present specification, the circumferential groove means a groove extending over the entire circumference in the tire circumferential direction. The circumferential groove includes not only a linearly extending groove but also a groove extending in a zigzag shape or a wave shape, a groove having a bending point in at least one place in the tire circumferential direction, and the like. The circumferential groove 20 has a groove width of 3 mm or more and a groove depth of 6 mm or more and 10 mm or less. The groove width means the maximum groove dimension in a direction perpendicular to the direction in which the groove extends. The groove depth means the maximum dimension in the tire radial direction of the groove based on the tire tread profile line when there is no groove. The groove width and groove depth of the circumferential groove 20 do not have to be constant over the entire circumference in the tire circumferential direction as long as they are within the above ranges.

  Moreover, in this specification, the width direction groove | channel means the groove | channel extended in a tire width direction. Not only the groove extending in a straight line but also a groove extending in a zigzag shape or a wave shape are included in the width direction groove. Similarly to the circumferential groove, the width direction groove 22a has a groove width of 3 mm or more and a groove depth of 6 mm or more and 10 mm or less. The groove width and groove depth of the width direction groove 22a need not be constant over the entire circumference in the tire circumferential direction as long as they are within the above ranges.

  FIG. 2 is a cross-sectional view of a circumferential groove in a plane parallel to the tire equatorial plane. FIG. 3 is a tire meridian cross-sectional view of a circumferential groove. As shown in FIGS. 1 to 3, a bottom raised portion 22 a is formed at the groove bottom of the circumferential groove 20. In FIG. 1, the bottom raised portion 22a is indicated by hatching for the sake of clarity.

  As shown in FIG. 1, the raised bottom portions 22 a are alternately formed in the tire circumferential direction on each side of the circumferential groove 20 in the tire width direction. Moreover, the bottom raising part 22a adjacent to a tire circumferential direction has the same tire circumferential direction area | region, and is continued in the tire width direction. Thus, even if a load in the tire width direction is applied to the tread surface 10a during cornering, the raised portions 22a adjacent to each other in the tire circumferential direction can support each other via the same tire circumferential region. Therefore, in the pneumatic tire 1a, the buckling of the circumferential groove 20 during cornering is suppressed, and as a result, drainage performance during cornering is improved.

  The bottom raised portions 22a do not need to be alternately formed on each side in the tire width direction of the circumferential groove 20 over the entire circumference in the tire circumferential direction. In other words, the circumferential groove 20 may have a region where the bottom raised portion 22a is not formed at all in a part of the tire circumferential direction. In this region, for example, a wear indicator indicating the wear limit can be provided. In order to improve drainage performance and secure a region where a wear indicator or the like is provided, the bottom raised portion 22a is 90% or more of the tire circumferential direction dimension of the circumferential groove 20 on each side of the circumferential groove 20 in the tire width direction. % Are preferably alternately formed over a% or less.

  FIG. 4 is a plan development view showing a part of a tread surface of a pneumatic tire in which a bottom raised portion of another arrangement is formed. In FIG. 4, the same components as those in FIG. 1 are denoted by the same reference numerals. In the pneumatic tire 1b of FIG. 4, the bottom raised portions 22b adjacent in the tire circumferential direction have not only the same tire circumferential direction region but also the same tire width direction region. In the present specification, the fact that the bottom raised portion is continuous in the tire width direction means not only the case where the bottom raised portion 22a is adjacent in the tire width direction as shown in FIG. 1, but also the bottom raised portion 22b as shown in FIG. Including the same tire width direction region.

  In addition, when the bottom raised portions 22a and 22b rise vertically from the groove bottom, the flow of water through the circumferential groove 20 is significantly hindered by the bottom raised portions 22a and 22b. Therefore, it is preferable that the height of the raised portions 22a and 22b gradually increase from zero to the maximum value and gradually decrease from the maximum value to zero, as shown in FIG. 2, for example.

  As shown in FIG. 1 and FIG. 4, the widthwise groove 30 a has a raised portion 22 a of the circumferential groove 20 over 70% or more of the groove width W of the widthwise groove 30 a in the communication portion with the circumferential groove 20. , 22b is communicated with a region (in the example of FIGS. 1 and 4, the non-hatched region of the circumferential groove 20). The area | region where the bottom raising parts 22a and 22b of the circumferential groove | channel 20 are not formed has a larger groove volume than the area | region where the bottom raising parts 22a and 22b are formed. In this case, when the water on the road surface is drained through the circumferential groove 20, the pressure of the water in the region where the bottom raised portions 22a and 22b are not formed due to the venturi effect is that the bottom raised portions 22a and 22b are formed. It becomes larger than the water pressure in the area. Therefore, the widthwise groove 30a is formed in a region where the bottom raised portions 22a and 22b of the circumferential groove 20 are not formed over 70% or more of the groove width W of the widthwise groove 30a in the communication portion with the circumferential groove 20. By communicating, water on the road surface can be efficiently drained from the circumferential groove 20 to the widthwise groove 30a. As a result, in the pneumatic tires 1a and 1b, drainage performance during straight traveling and cornering is improved.

  In addition, although not shown in figure, the pneumatic tires 1a and 1b have the same meridional cross-sectional shape as the conventional pneumatic tire. Here, the meridional cross-sectional shape of the pneumatic tire refers to a cross-sectional shape of the pneumatic tire that appears on a plane perpendicular to the tire equatorial plane CL. The pneumatic tires 1a and 1b have a bead portion, a sidewall portion, a shoulder portion, and a tread portion from the inner side in the tire radial direction toward the outer side in a tire meridian cross-sectional view. Further, the pneumatic tires 1a and 1b have a carcass layer that extends from the tread portion to the bead portions on both sides and is wound around a pair of bead cores in the tire meridional cross section, and on the outer side in the tire radial direction of the carcass layer. A belt layer and a belt reinforcing layer are sequentially formed.

  The pneumatic tires 1a and 1b are obtained through normal manufacturing processes, that is, a tire material mixing process, a tire material processing process, a green tire molding process, a vulcanization process, and an inspection process after vulcanization. It is done. In the manufacturing process of the pneumatic tires 1a and 1b, in particular, concave portions and convex portions corresponding to the tread pattern shown in FIG. 1 or FIG. 4 are formed on the inner wall of the vulcanization mold, and vulcanization is performed using the molds. I do.

[Additional form]
Next, additional forms 1 to 4 that can be optionally implemented in the above-described basic form of the pneumatic tire according to the present invention will be described.

(Additional form 1)
In the basic configuration, in the plane parallel to the tire equator plane, the area As of the same tire circumferential direction region and the area Ar of the bottom raised portion 22a satisfy the relationship of 0.1 ≦ As / Ar ≦ 0.4. (Additional form 1) is preferred.

  Here, the area As of the same tire circumferential direction area means the area of the area where the raised portions adjacent to each other in the tire circumferential direction overlap in a plane parallel to the tire equator plane. In the example shown in FIG. And the area of each triangle surrounded by a solid line. Further, the area Ar of the raised portion means the cross-sectional area of the raised portion in a plane parallel to the tire equator plane, and in the example shown in FIG. 2, is the area of each trapezoid indicated by hatching.

  By setting As / Ar to be 0.1 or more, it is possible to sufficiently secure a region in the bottom raised portion 22a that supports the bottom raised portion 22a adjacent in the tire circumferential direction. Therefore, buckling of the circumferential groove 20 during cornering is further suppressed, and as a result, drainage performance during cornering is further improved. Further, by setting As / Ar to be 0.4 or less, it is possible to sufficiently ensure the water pressure difference in the tire width direction in the circumferential groove 20. Therefore, the water on the road surface can be efficiently drained from the circumferential groove 20 by the width direction groove 30a, and as a result, drainage performance during straight traveling and cornering is further improved.

(Additional form 2)
In the basic form or the like (the basic form or the form in which the additional form 1 is combined with the basic form), the height Hr of the bottom raised portion 22a and the depth D of the circumferential groove 20 are 0.2 ≦ Hr / D ≦ It is preferable to satisfy the relationship of 0.5 (additional form 2).

  Here, the height Hr of the raised bottom portion 22a means the maximum value in the tire radial direction dimension from the groove bottom of the circumferential groove 20 to the top surface of the raised bottom portion 22a, as shown in FIGS. . Further, as shown in FIGS. 2 and 3, the depth D of the circumferential groove 20 is the maximum tire radial dimension of the circumferential groove 20 with reference to the tire tread profile line when there is no groove. Mean value.

  By setting Hr / D to 0.2 or more, the rigidity of the bottom raised portion 22a can be sufficiently ensured. Therefore, buckling of the circumferential groove 20 during cornering is further suppressed, and as a result, drainage performance during cornering is further improved. Moreover, the volume of the circumferential groove | channel 20 can fully be ensured by setting Hr / D to 0.5 or less. Therefore, more water can be drained from the circumferential groove 20, and as a result, drainage performance during straight traveling and cornering is further improved.

(Additional form 3)
5, 6 and 7 are each a developed plan view showing a part of a tread surface of a pneumatic tire according to an additional embodiment of the present invention. 5, 6, and 7, the same components as those in FIG. 1 are denoted by the same reference numerals. In a basic form or the like (a form in which at least one of the additional forms 1 and 2 is combined with the basic form or the basic form), as in the pneumatic tires 1c and 1d shown in FIG. It is preferable that at least one side of the circumferential groove 20 in the tire width direction is inclined with respect to the tire circumferential direction (additional form 3). In the pneumatic tires 1c and 1d of FIG. 5, the width direction grooves 30b and 30c are formed only on one side of the circumferential groove 20 in the tire width direction and are inclined with respect to the tire circumferential direction.

  The width direction grooves 30b and 30c are inclined with respect to the tire circumferential direction on at least one side of the circumferential groove 20 in the tire width direction, so that water can be efficiently removed from the width direction grooves 30b and 30c even during high speed running. Can be drained automatically. As a result, drainage performance during straight traveling and cornering is further improved.

  In addition, like the pneumatic tires 1e, 1f, and 1g shown in FIG. 6 and FIG. 7, the width direction grooves 30d, 30e, and 30f are formed on both sides of the circumferential groove 20 in the tire width direction with respect to the tire circumferential direction. By tilting, the above effect can be achieved at a higher level. In the pneumatic tires 1e and 1f of FIG. 6, the widthwise grooves 30d and 30e are formed on both sides of the circumferential groove 20 in the tire width direction, and the tire circumferential direction differs from the circumferential groove 20 on each side in the tire width direction. Inclined in the direction. In the pneumatic tire 1g of FIG. 7, the widthwise grooves 30f are formed on both sides of the circumferential groove 20 in the tire width direction, and are inclined in the same direction in the tire circumferential direction from the circumferential groove 20 on each side in the tire width direction. doing.

(Additional form 4)
In the form in which the additional form 3 is combined with the basic form, the tire rotation direction is specified as in the pneumatic tires 1c to 1f shown in FIGS. 5 and 6, for example, and the width direction grooves 30b to 30e are provided. In addition, it is preferable that at least one side of the circumferential groove 20 in the tire width direction is inclined from the circumferential groove 20 toward the kick-out side (additional form 4). In the pneumatic tires 1c to 1f shown in FIGS. 5 and 6, the rotation direction (the tire rolling direction when the vehicle is moving forward) is designated. In the pneumatic tires 1c to 1f, when the vehicle moves forward, the stepping side in FIGS. 5 and 6 contacts the ground before the kicking side.

  The tire rotation direction is specified, and the widthwise grooves 30b to 30e are inclined toward the kicking side from the circumferential groove 20 on at least one side of the circumferential groove 20 in the tire width direction. Water can be efficiently drained from the width direction grooves 30b to 30e from the stepping side toward the kicking side. As a result, drainage performance during straight traveling and cornering is further improved.

  Note that, as in the pneumatic tire 1g shown in FIG. 7, the tire rotation direction is specified, and the width direction grooves 30f are on the sides of the circumferential grooves 20 in the tire width direction on the kicking side from the circumferential grooves 20 By inclining toward, the above effect can be achieved at a higher level.

  Pneumatic tires of Example 1 to Example 8 were produced by changing each condition shown in Table 1 (tread pattern, As / Ar, Hr / D, presence / absence of designation of rotation direction). Moreover, the pneumatic tire of the conventional example was produced so as to have the same conditions as the pneumatic tire of Example 1 except that the bottom raised portion was not formed in the circumferential groove. In all the pneumatic tires, the groove widths of the circumferential grooves and the width direction grooves were 8 mm, and the groove depths of the circumferential grooves and the width direction grooves were 8.8 mm.

  Regarding the tires (test tires) of the conventional example and Examples 1 to 8, the tire size was 245 / 40R18 93W, and each test tire was assembled into 18 × 8.5J rims at a pressure of 230 kPa, four by four. It was mounted on an FR vehicle with a displacement of 3500 CC. The tire of Example 6 is mounted so that the upper side of the tread pattern in FIG. 5 (a) is located on the kicking side and the lower side is located on the stepping side, unlike the rotational direction shown in FIG. 5 (a). It was. As shown in FIG. 5A, the tire of Example 7 was mounted such that the upper side of the tread pattern in FIG. 5A was located on the stepping side and the lower side was located on the kicking side. As shown in FIG. 7, the tire of Example 8 was mounted such that the upper side of the tread pattern in FIG. 7 was located on the stepping side and the lower side was located on the kicking side.

  With respect to all these test tires, drainage performance during straight traveling and drainage performance during cornering were evaluated as follows. These results are also shown in Table 1.

(Drainage performance when going straight)
The speed of the hydroplaning phenomenon was measured by a test driver while running in a straight pool with a water depth of 10 mm while changing the speed of the vehicle. And based on this measurement result, the index evaluation which made the conventional example the standard (100) was performed. This evaluation shows that the larger the value, the better the drainage performance when going straight.

(Drainage performance during cornering)
The speed of the hydroplaning phenomenon was measured by a test driver while running in a circular turning pool (radius 100 m) with a water depth of 10 mm while changing the speed of the vehicle. And based on this measurement result, the index evaluation which made the conventional example the standard (100) was performed. This evaluation shows that the larger the value, the better the drainage performance during cornering.

  According to Table 1, for the pneumatic tires of Examples 1 to 8 belonging to the technical scope of the present invention, all of the conventional pneumatic tires not belonging to the technical scope of the present invention, It can be seen that the drainage performance during straight running and cornering has been improved.

  The present invention includes the following aspects.

  (1) In a pneumatic tire that includes a circumferential groove and a widthwise groove that communicates with the circumferential groove, and a bottom raised portion is formed on at least a part of the groove bottom of the circumferential groove, the bottom raised portion has a circumferential direction. It is alternately formed in the tire circumferential direction on each side of the tire width direction of the groove, and the bottom raised portions adjacent to each other in the tire circumferential direction have the same tire circumferential direction region and are continuous in the tire width direction. A pneumatic tire that communicates with a region where the bottom-up portion of the circumferential groove is not formed over 70% or more of the groove width of the widthwise groove in the communication portion with the circumferential groove.

  (2) In the plane parallel to the tire equatorial plane, the area As of the same tire circumferential region and the area Ar of the raised portion satisfy the relationship of 0.1 ≦ As / Ar ≦ 0.4 (1) ) Pneumatic tires.

  (3) The air according to (1) or (2), wherein the height Hr of the bottom raised portion and the depth D of the circumferential groove satisfy a relationship of 0.2 ≦ Hr / D ≦ 0.5. tire.

  (4) The air according to any one of (1) to (3), wherein the width direction groove is inclined with respect to the tire circumferential direction on at least one side of the circumferential groove in the tire width direction. Enter tire.

  (5) The tire rotation direction is specified, and the width direction groove is inclined toward the kick-out side from the circumferential groove on at least one side of the circumferential groove in the tire width direction. Pneumatic tire described in 2.

1a, 1b, 1c, 1d, 1e, 1f, 1g Pneumatic tires 10a, 10b, 10c, 10d, 10e, 10f, 10g Tread surface 20 Circumferential grooves 22a, 22b Bottom raised portions 30a, 30b, 30c, 30d, 30e, 30f Width direction groove 40a, 40b, 40c, 40d, 40e, 40f Land part W Groove width As Area of the same tire circumferential direction area Ar Bottom raised part area Hr Bottom raised part height D Circumferential groove depth

Claims (5)

In a pneumatic tire comprising a circumferential groove and a widthwise groove communicating with the circumferential groove, and a bottom raised portion is formed at least at a part of the groove bottom of the circumferential groove,
The bottom raised portions are alternately formed in the tire circumferential direction on each side in the tire width direction of the circumferential groove,
The raised portions adjacent to each other in the tire circumferential direction have the same tire circumferential direction region and are continuous in the tire width direction,
The width direction groove communicates with a region where the bottom raised portion of the circumferential groove is not formed over 70% or more of the width of the width direction groove in the communication portion with the circumferential groove.
Pneumatic tire. In a plane parallel to the tire equatorial plane, the area As of the same tire circumferential region and the area Ar of the bottom raised portion are:
0.1 ≦ As / Ar ≦ 0.4
The pneumatic tire according to claim 1, satisfying the relationship: The height Hr of the bottom raised portion and the depth D of the circumferential groove are:
0.2 ≦ Hr / D ≦ 0.5
The pneumatic tire according to claim 1 or 2, satisfying the relationship:   The pneumatic tire according to any one of claims 1 to 3, wherein the widthwise groove is inclined with respect to the tire circumferential direction on at least one side of the circumferential groove in the tire width direction.   The tire rotation direction is specified, and the width direction groove is inclined toward the kick-out side from the circumferential groove on at least one side of the circumferential groove in the tire width direction. The described pneumatic tire.

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