JP2014213617A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of ensuring a sufficient grip force even if a vehicle travels on a muddy land or the like.SOLUTION: A pneumatic tire according to this invention comprises blocks 6 defined by not less than two circumferential grooves 2 and width direction grooves 5, on a tread surface 1. A reference zone is specified by a tread circumferential direction range TCR corresponding to one pitch of the block 6 in a tread circumferential direction and a tread width direction range TWR between the two circumferential grooves 2 located on outermost sides in a tread width direction on both halves of a tread surface 1 in the tread width direction at tread width direction outermost positions out of the not less than two circumferential grooves 2. A negative rate of the reference zone on the tread surface 1 is gradually increased from a tread-in side to a kicking side in a portion at a length L1 exceeding 50% of a tread circumferential direction length of the reference zone.

Description

  In the present invention, the tread surface is divided into two or more circumferential grooves extending continuously in the tread circumferential direction and a widthwise groove opening to each of the two circumferential grooves adjacent to each other in the tread width direction. In particular, the present invention relates to a pneumatic tire suitable for use as a heavy duty pneumatic tire.

  Conventionally, as a heavy-duty pneumatic tire that may be used for a dump truck or the like, there is a tire described in Patent Document 1, for example, and this dump truck that can be used at a construction site, a mine or the like is hard after rain or snow. It may be used for traveling on a road surface in which a soft clay layer or snow layer of about several centimeters is formed on the ground.

JP-A-10-278513

  When traveling on the road surface on which the clay layer as described above (hereinafter, the same applies to the snow layer, only the case of the clay layer will be described), the tire mounted on the vehicle is the tread. Although the part will not be completely buried in the clay layer, the load rolling will occur with some tens of percent of the groove depth of the circumferential groove provided on the tread tread, but in this case the tread tread Due to the presence of a soft clay layer between the ground and the hard ground, sufficient ground contact of the tire cannot be secured, and therefore the grip force (friction force) of the tire is reduced, and the traction force and braking force are reduced to the road surface. It is difficult to efficiently transmit the data.

  In order to improve the ground contact of the tire, it is considered effective to increase the tread width direction component of the tread tread edge to exert a large scratching effect on the soft clay layer. If the width direction component of the edge is excessively increased by adding a width direction groove extending along the edge, the block is subdivided by the width direction groove and the block rigidity is lowered. Even if the ground contact property of the battery is improved, there is a problem that the grip force cannot be obtained as expected due to the decrease of the ground contact area.

  In general, the clay layer mud deposited on the hard ground is grounded from the stepped side of the tread tread block that touches the ground when the tire is rolling. It is pushed out to the kicking-out portion, and tends to accumulate between the kicking-out portion and the road surface. For this reason, if a sufficient groove area is not secured on the kick-out side, mud is sufficiently expelled on the kick-out side even if the block rigidity and the ground contact area are secured on the step-on side. Therefore, there is a problem in that sufficient contact with the road surface of the tire cannot be ensured, and sufficient grip force cannot be obtained for this reason.

  This invention makes it a subject to solve such a problem which the pneumatic tire which may be used for driving | running | working in a muddy area, and the place made into the object is to drive in a muddy place etc. Even if it is a case, it is providing the pneumatic tire which can acquire sufficient grip force.

  The pneumatic tire according to the present invention has two or more circumferential grooves continuously extending in the tread circumferential direction and two circumferential grooves adjacent to each other in the tread width direction on the tread surface. Tread circumferential direction range corresponding to one pitch in the tread circumferential direction of the block, and tread width direction in the tread width direction half of the tread tread surface among two or more circumferential grooves When the reference area is defined by the tread width direction range between the outermost positions in the tread width direction of the two outermost circumferential grooves, the negative rate of the reference area of the tread tread is calculated as the tread of the reference area. It is characterized in that it is gradually increased from the stepping-in side toward the kicking-out side over a portion that exceeds 50% of the circumferential length. According to the pneumatic tire of the present invention, it is possible to provide a pneumatic tire that can obtain a sufficient grip force even when traveling in a muddy ground.

  In addition, the “tread surface” referred to here comes into contact with the road surface when the tire that is assembled to the applicable rim and filled with the specified internal pressure is rolled with a load corresponding to the maximum load capacity applied. Means the outer peripheral surface of the entire circumference of the tire. The “tread end” refers to the outermost position of the tread surface in the tread width direction. Here, the “applicable rim” is a standard rim (“Design Rim” in YEAR BOOK of the following TRA, “Measuring Rim” in STANDARDDS MANUAL of the following ETRTO) defined in the following standards according to the tire size. The "specified internal pressure" means the air pressure specified in accordance with the maximum load capacity in the following standards, and the "maximum load capacity" is allowed to be applied to the tire according to the following standards. The maximum mass. The standard is determined by an industrial standard effective in the region where the tire is produced or used. For example, in the United States, “THE TIRE AND RIM ASSOCIATION INC. (TRA)” “YEAR BOOK” In Europe, it is “STANDARDS MANUAL” of “The European Tire and Rim Technical Organization (ETRTO)”, and in Japan it is “JATMA YEAR BOOK” of “Japan Automobile Tire Association (JATMA)”.

  The “negative rate” in the present invention is the sum of the areas of the grooves provided in a certain area of the tread tread at the opening position to the tread tread, in the opening position of the groove in the certain area. The ratio to the tread tread area including the area. In addition, “gradual increase” includes the case where the negative rate becomes constant or the rate of increase of the negative rate increases or decreases on the way from the stepping side to the kicking side, but the negative rate decreases Is not included. In addition, “tread width direction halves of the tread surface” refers to two portions of the tread surface that are located on one side and the other side in the tread width direction with the tire equator surface as a boundary.

  Here, in measuring the negative rate of the reference area of the tread surface, for example, the reference area is equally spaced in the tread circumferential direction (for example, an interval of 1/10 of the tread circumferential length of the reference area, or 5 mm). By dividing the tread circumferential direction by dividing a plurality of positions spaced apart from each other at intervals, etc., by defining a plurality of micro areas adjacent to each other in the tread circumferential direction, and determining the negative rate of each micro area The negative rate distribution within the reference area can be examined.

  The pneumatic tire according to the present invention has a lug groove extending from the tread end and opening to the circumferential groove, and a lug partitioned by the circumferential groove, and the circumferential groove is formed in both tread width direction halves of the tread surface. Each of the two circumferential grooves extends continuously in the circumferential direction of the tread in a zigzag shape, and each of the circumferential grooves extends in the tread width direction of the two circumferential grooves. At the bent part protruding inward, it opens in each of the two circumferential grooves and extends in a direction inclined with respect to the tread width direction, and the outer peripheral edge of the block is each of the two circumferential grooves. In the bent part which protrudes inside the tread width direction, you may have the recessed part dented inward from the outer periphery of the block. Thereby, while ensuring a big rigidity to a block, since the edge effect with respect to various directions can be exhibited, the grip force in the case of driving in a muddy place etc. can be improved further.

  In the pneumatic tire of the present invention, it is preferable to provide a groove in a block having the largest area among the blocks. As a result, the scratching effect on the muddy ground can be greatly improved without excessively reducing the rigidity of the block, and the grip strength can be further improved by further improving the mud repellency within the ground contact surface. Here, “the block having the largest area” means a block having the largest area on the outermost surface in the tire radial direction.

  In the pneumatic tire of the present invention, the block straddles the tire equatorial plane, and it is preferable to provide the block with a groove portion extending across the tire equatorial plane. This makes it possible to maximize the scratching effect on the muddy ground, especially in the vicinity of the tire equator where the ground pressure increases, and to further improve the grip power by further improving the mud repellency within the ground surface. it can.

  The negative rate as described above is measured along the tread surface as seen from the development view of the tread pattern in a no-load state in which the tire is assembled to the applicable rim and filled with the specified internal pressure. Also, other dimensions are measured under the same conditions unless otherwise specified.

  According to the pneumatic tire of the present invention, it is possible to provide a pneumatic tire that can obtain a sufficient grip force even when traveling in a muddy ground.

It is a partial development view of a tread pattern showing one embodiment of this invention. It is the partial expanded view of a tread pattern which shows the modification of one Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In FIG. 1, reference numeral 1 denotes a tread tread included in a pneumatic tire according to an embodiment of the present invention. In the present embodiment, two or more (two in the illustrated example) continuously extending along the tread circumferential direction are formed on the tread tread 1 in a form in which a plurality of inverted trapezoids are connected in the tread circumferential direction in the illustrated example. A circumferential groove 2 is provided. Further, the tread surface 1 has a plurality of widthwise grooves that open in each of two circumferential grooves 2 adjacent to each other in the tread width direction and extend in a linear form along the tread width direction in the illustrated example. 5 is provided. The circumferential grooves 2 and the width direction grooves 5 define a plurality of blocks 6 arranged in the circumferential direction of the tread, which are trapezoidal in the illustrated example.

  Furthermore, in the present embodiment, the tread circumferential direction range TCR corresponding to one pitch in the tread circumferential direction of the block 6 and the two circumferential grooves positioned on the outermost sides in the tread width direction at both halves of the tread tread surface 1 in the tread width direction. A tread width direction range TWR between the outermost positions P1 and P2 in the tread width direction 2 defines a reference area (region in the rectangle ABCD in FIG. 1). Here, when three or more circumferential grooves 2 are provided on the tread tread surface 1, the tread tread surface 1 is located at the outermost side in the tread width direction at both halves of the tread tread surface 1. A tread width direction range between the outer circumferential positions P1 and P2 of the two circumferential grooves 2 is defined as a tread width direction range TWR of the reference area. In this embodiment, the negative rate of the reference area of the tread tread 1 is set to a length exceeding 50% of the tread circumferential length of the reference area (in the example of the figure, 100% of the tread circumferential length of the reference area). In a portion extending over the length L1, it is gradually increased from the stepping side (lower side in FIG. 1) toward the kicking side (upper side in FIG. 1). Specifically, in the example of the figure, the groove width of the circumferential groove 2 gradually increases from the stepping side toward the kicking side in the portion extending over the entire length L1 in the tread circumferential direction of the reference area. The negative rate of the reference area of the tread surface 1 gradually increases from the stepping side to the kicking side.

  According to the above-described configuration, in the tread circumferential region extending over the length L1 in which the negative rate is gradually increased from the stepping side toward the kicking side, the ground contact surface is provided on the kicking side portion where the negative rate is relatively large. The mud repellency is greatly improved, so that the tread tread surface 1 can easily contact the road surface. Therefore, the tread surface is improved, and at the stepped side portion where the negative rate is relatively small, the rigidity of the block 6 and A sufficient ground contact area can be secured. Thereby, the rigidity of the block 6 and the ground contact area and the ground contact property can be achieved at a high level, and a sufficient grip force can be obtained. On the other hand, for example, as shown by a broken line in FIG. 1, the groove width of the circumferential groove 2 is constant along the extending direction, and therefore the negative rate of the reference area of the tread surface 1 is In the case where it increases only in the tread circumferential direction range over the length L2 which is less than 50% of the tread circumferential length of the reference area, which corresponds to the groove width of the groove 3, the block 6 is blocked at the stepping side portion of the reference area. Even if sufficient rigidity and ground contact area can be ensured, mud is accumulated without being expelled sufficiently at the kicking side portion of the reference area, so that sufficient grip strength can be obtained. Can not.

  Here, the “tread circumferential direction range TCR corresponding to one pitch in the tread circumferential direction of the block 6” is an arbitrary position on the block 6 (in the example of the figure, it is the most stepped side in the tread circumferential direction of the block 6). The position corresponding to the arbitrary position on the other block 6 adjacent to the block 6 in the tread circumferential direction from the position Q1) (in the example of the figure, the position Q2 closest to the stepping side in the other tread circumferential direction) The tread circumferential direction range.

  The tread surface 1 is further provided with a plurality of lug grooves 3 extending from the tread ends and opening in the circumferential grooves 2. A plurality of lugs 4 are defined by the circumferential grooves 2, lug grooves 3, and tread ends outside the circumferential grooves 2 in the tread width direction.

  Here, in the example shown in the figure, the groove portion 20 is provided in the block 6. As a result, the width direction component of the edge is increased to improve the scratching effect on muddy ground (in this specification, a road surface in which a soft clay layer or snow layer is formed on a hard ground after raining or after snowing). In addition, it is possible to improve the grip power by further improving the mud repellency within the ground contact surface. Here, from the viewpoint of increasing the above-described edge tread width direction component, it is preferable that the groove portion 20 extends along the tread width direction. Further, when the plurality of blocks 6 provided on the tread surface 1 are different in size from each other, it is preferable to provide the groove portion 20 in the block 6 having the largest area, thereby excessively reducing the rigidity of the block 6. In addition to greatly increasing the scratching effect on the muddy ground by greatly increasing the tread width direction component of the edge while further suppressing the mud, it is possible to further improve the ground contact characteristics by further improving the mud repellency in the ground contact surface it can. Furthermore, when the block 6 straddles the tire equator plane C as in the example of the figure, it is preferable to provide the block 6 with a groove portion 20 extending across the tire equator plane C. This makes it possible to maximize the scratching effect on the muddy ground, especially in the vicinity of the tire equatorial plane C where the contact pressure increases, and to further improve the grip power by further improving the mud repellency within the contact surface. be able to.

  As mentioned above, although this invention has been demonstrated based on the one embodiment, this invention is not limited to this embodiment, Various modifications are also included. For example, in the modification shown in FIG. 2, one circumferential groove 2 is provided in each half of the tread tread surface 1 in the tread width direction. The tread surface 1 is provided with two circumferential grooves 2 extending continuously in the circumferential direction of the tread in a zigzag form. Further, the tread tread 1 has a bent portion that protrudes inward in the tread width direction of each of the two circumferential grooves 2, and opens in each of the two circumferential grooves 2. A plurality of widthwise grooves 5 extending in the direction of inclination are provided. The circumferential grooves 2 and the width direction grooves 5 define a plurality of blocks 6 having a substantially parallelogram shape and arranged in a substantially tread circumferential direction. Further, the tread tread surface 1 has a plurality of lug grooves that are bent and extended from the tread end in the tread width direction and project outward in the tread width direction of the circumferential groove 2. 3 and a plurality of lugs 4 are defined by the circumferential groove 2, the lug groove 3, and the tread end on the outer side in the tread width direction from the circumferential groove 2. In addition, the outer peripheral edge of the block 6 has a pair of recesses 21 that are recessed inward from the outer peripheral edge of the block 6 at the bent portions of the two circumferential grooves 2 protruding inward in the tread width direction. According to such a configuration, the block 6 having a large area straddling the tire equatorial plane C can ensure a large rigidity in the block 6, and the sides of the block 6 and the lug 4 along various directions. The outer periphery of the polygonal shape can be used to exert edge effects in various directions, so that sufficient grip can be obtained even when traveling in muddy areas, especially for heavy duty tires. It can be suitable for use in a pneumatic tire.

  Also in this modified example, as in the embodiment of FIG. 1, the tread circumferential range TCR corresponding to one pitch in the tread circumferential direction of the block 6 and the tread width 1 half of the tread tread surface 1 are respectively in the tread width direction. A reference area (region in the rectangle ABCD in FIG. 2) is defined by the tread width direction range TWR between the tread width direction outermost positions P1 and P2 of the two circumferential grooves 2 positioned on the outermost side. Yes. Here, the tread width direction outermost positions P <b> 1 and P <b> 2 of the two circumferential grooves 2 are tread width direction outermost positions at bent portions protruding outward in the tread width direction of the circumferential grooves 2. When the tread width direction outermost positions P1 and P2 of the two circumferential grooves 2 are obtained, the circumferential direction of the outer peripheral edges of the pair of lugs 4 adjacent to each other in the tread circumferential direction with the lug groove 3 interposed therebetween The inner portions of the tread width direction along the groove wall of the groove 2 are connected by a virtual line (a chain line in FIG. 2), and the outermost position in the tread width direction of the virtual line is defined as the positions P1 and P2. Further, in this modification, the tread circumferential range TCR corresponding to one pitch in the tread circumferential direction of the block 6 is changed from the position Q1 closest to the tread circumferential direction of the block 6 to the block 6 in the tread circumferential direction. The tread circumferential range extends to a position Q2 which is the most stepped side in the tread circumferential direction of another adjacent block 6.

  Further, in this modification, the negative rate of the reference area of the tread tread 1 is set to a length exceeding 50% of the tread circumferential length of the reference area (specifically, 55% of the tread circumferential length of the reference area). In a portion extending over the length L1, it is gradually increased from the stepping side in the tread circumferential direction (lower side in FIG. 2) toward the kicking out side (upper side in FIG. 2). According to this configuration, as in the first embodiment, the negative rate is relatively increased in the tread circumferential region over the length L1 in which the negative rate is gradually increased from the stepping side to the kicking side. In the kick-out side part, the mud repellency in the ground contact surface is greatly improved to improve the ground contact property, and in the stepped side part where the negative rate is relatively small, sufficient rigidity and ground contact area of the block 6 are secured. can do. Therefore, the rigidity of the block 6 and the ground contact area and the ground contact property can be achieved at a high level, and a sufficient grip force can be obtained. On the other hand, for example, as shown by the broken line in FIG. 2, the groove widths of the circumferential groove 2 and the width direction groove 5 on the kicking side of the reference area are narrower than the present modification example shown by the solid line, and therefore the tread surface Only in the tread circumferential range over a length L2 where the negative rate of one reference zone is less than 50% of the tread circumferential length of the reference zone (eg 45% of the tread circumferential length of the reference zone). In the case of increase, even if the rigidity and the ground contact area of the block 6 can be sufficiently secured in the stepping side portion of the tread circumferential range, mud is sufficient in the kicking side portion of the tread circumferential range. Since it accumulates without being expelled, a sufficient tire grip force cannot be ensured.

  Further, in the modified example of FIG. 2, the groove 6 extending across the tire equatorial plane C is provided in the block 6 straddling the tire equatorial plane C as in the example of FIG. 1.

  In this modification, a region where the negative rate of the reference area of the tread surface 1 gradually increases from the stepping side to the kicking side extends over a length L1 of 55% of the tread circumferential length of the reference area. However, from the viewpoint of improving the grip force, it is preferable that this region is a portion extending over 70% or more of the tread circumferential length of the reference area. It is more preferable that the length is 100%, that is, a portion extending over the entire length.

1: tread surface, 2: circumferential groove, 3: lug groove, 4: lug, 5: width direction groove, 6: block, 20: groove portion, 21: recess, C: tire equatorial surface, L1, L2: tread surface TCR: Tread circumferential length corresponding to one pitch in the tread circumferential direction of the block, TWR: Tread located in the outermost direction in the tread width Tread width range between the outer circumferential positions of the two circumferential grooves

Claims (4)

A block defined on the tread surface by two or more circumferential grooves extending continuously in the tread circumferential direction and a widthwise groove opening to each of the two circumferential grooves adjacent to each other in the tread width direction. A pneumatic tire comprising:
The tread circumferential direction range corresponding to one pitch in the tread circumferential direction of the block, and the two circumferential grooves located on the outermost sides in the tread width direction on the tread width direction half of the tread tread surface are the outermost tread width direction. When the reference area is defined by the tread width direction range between the outer positions,
The negative rate of the reference area of the tread surface is gradually increased from the stepping side to the kicking side in a portion extending over 50% of the length of the reference area in the tread circumferential direction. Pneumatic tire to do. The tread tread further includes a lug groove extending from a tread end and opening to the circumferential groove, and a lug defined by the circumferential groove,
Each of the circumferential grooves is provided on each half of the tread tread in the tread width direction,
Each of the two circumferential grooves extends continuously in the tread circumferential direction in a zigzag shape,
The width direction groove is a bent portion that protrudes inward in the tread width direction of each of the two circumferential grooves, and opens in each of the two circumferential grooves and is inclined with respect to the tread width direction. Extending in the direction,
The outer peripheral edge of the block has a concave portion that is recessed from the outer peripheral edge of the block toward the inside of the block at a bent portion that protrudes inward in the tread width direction of each of the two circumferential grooves. Item 2. The pneumatic tire according to Item 1.   The pneumatic tire according to claim 1 or 2, wherein a groove is provided in a block having the largest area among the blocks. The block straddles the tire equator,
The pneumatic tire according to claim 1 or 2, wherein a groove portion that extends across the tire equatorial plane is provided in the block.

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