JP2011116319A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire which can more effectively suppress a shoulder abrasion or a step-down abrasion of a block located in a shoulder area. <P>SOLUTION: The pneumatic tire has a main groove formed in a tread part which extends along a circumferential direction of the tire. The pneumatic tire includes, in the shoulder area of the tread part, a first land part, a sipe extending along the circumferential direction of the tire, and a second land part having a plurality of circumferentially arranged blocks partitioned and formed by the sipe and sub-grooves extending beyond a tread ground end from the sipe, in order outward in the direction of width of the tire form the main groove. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a pneumatic tire in which a main groove extending along a tire circumferential direction is formed in a tread portion.

The tread portion of the tire is usually partitioned into a plurality of block land portions by a plurality of main grooves extending in the tire circumferential direction and a plurality of inclined grooves extending substantially in the tire width direction. Some of the plurality of block land portions are arranged in the shoulder region.
However, when the tread portion contacts the ground, the surface of the tread portion of the shoulder region is forcibly pressed against the flat road surface, so that the belt layer positioned on the radially inner side of the shoulder region is forcibly stretched. Further, when the tread part moves away from the road surface, the stretched shape tries to return to its original state. In this manner, the deformation of the shape is repeated in the shoulder region during tire rolling. It is known that due to the change in shape, shoulder block wear and step-down wear are likely to occur particularly in the block land portion located in the shoulder region among the blocks forming the tread portion.

In order to suppress shoulder drop wear and step-down wear in the block located in the shoulder region, for example, in Patent Document 1, a concave portion is formed outside the inclined groove wall surface and the tread grounding end of the block located in the shoulder region in the width direction. A configuration having
According to this configuration, since the concave portion is formed in the width direction outside the inclined groove wall surface of the block and the tread grounding end, the shoulder block is compressed and deformed when the shoulder region is grounded and the ground pressure is applied. . In this way, the force applied to the block in the shoulder region is reduced by reducing the force from the side transmitted to the inner side in the tire width direction at a point before the input to the inner side of the tread contact edge. Yes.

JP 2006-51927 A

  However, even if the force from the side is reduced by deforming the block on the outer side in the width direction from the tread ground end as in Patent Document 1, the force from the side is still in the land located in the shoulder region. Part (block referred to in Patent Document 1). Therefore, wear is still generated in the land portion of the shoulder region by repeating the contact and separation of the tread portion as described above. Furthermore, among these land parts, the land part wall surface facing the main groove receives the most force from the side and repeats contact with the road surface at the time of ground contact and takeoff, so the land part located in the shoulder region Among these, in particular, there is a problem that a portion adjacent to the main groove is most likely to be worn.

  In order to solve this problem, the inventor now applies a force on the outer side in the width direction (that is, a reaction force against the force input from the side) to the force on the inner side in the width direction applied to the land portion of the shoulder region. Thus, a novel idea completely different from the conventional configuration was obtained, in which the force from the side transmitted to the inner side in the width direction is canceled, and as a result, the force from the side is reduced. And if this push-back is performed from the wall surface on the main groove side of the land portion, it has been found that wear can be suppressed more effectively even in land portions adjacent to the main groove, which are particularly prone to wear. .

  Therefore, the present invention uses a novel idea that the force from the side (force from the outside in the width direction to the inside) applied to the land portion located in the shoulder region is canceled by the reaction force (from the inside in the width direction to the outside). Another object of the present invention is to provide a pneumatic tire that can more effectively suppress shoulder drop wear and step-down wear of a land portion located in a shoulder region.

In order to achieve the above object, the pneumatic tire of the present invention is
In the pneumatic tire in which the main groove extending along the tire circumferential direction is formed in the tread portion, in the shoulder region of the tread portion, in order from the main groove toward the outer side in the tire width direction,
The first land,
A sipe extending along the tire circumferential direction;
And a second land portion formed by arranging a plurality of blocks defined by the sub-groove extending from the sipe and beyond the tread grounding end in the circumferential direction.

  Here, the “shoulder region” means both regions outside the position corresponding to 50% of the tread contact width with the tire equatorial plane as the center.

  The “tread grounding end” is an industrial standard effective in an area where tires are produced or used, for example, The Tire and Rim Association Inc. in the United States. Assembling the tires to the standard rims of the standard sizes described in “Year Book” in Europe, “Standard Manual” of The European Tire and Rim Technical Organization in Japan, and “JATMA Year Book” of Japan Automobile Association in Japan, This tread contact width when the maximum load of the single wheel at the applicable size (maximum load capacity) and the air pressure corresponding to the maximum load is applied, and the maximum width of the surface where the tire surface contacts the ground is defined as the tread contact width. This means the outermost point in the tire width direction.

  In addition, “sipe” between the first land portion and the second land portion means that the rubber forming the first land portion is deformed by the ground compression from the road surface at the time of tread contact with the first land portion. It is the groove | channel which has the width | variety of the grade which contacts a 2nd land part. Specifically, it is a groove of 0 mm or more and less than 2 mm, and includes notches for rubber.

  In the pneumatic tire of the present invention, it is preferable that a contact width in the tire width direction of the second land portion is larger than a contact width in the tire width direction of the first land portion.

  In the pneumatic tire according to the present invention, a tire radial length from the groove bottom of the sipe to the tread surface of the first land portion is a tire from the groove bottom of the sipe to the tread surface of the second land portion. It is preferable that the length is not less than the radial length.

  In the pneumatic tire of the present invention, it is preferable that a ground contact width in the tire width direction of the first land portion is smaller than a width in the tire width direction in the innermost portion in the tire radial direction of the first land portion.

  Here, “the width in the tire width direction at the innermost portion in the tire radial direction of the first land portion” means the tire width direction of the first land portion at the same depth position as the groove bottom of the sipe forming the first land portion. Say the length.

  Furthermore, the pneumatic tire according to the present invention is preferably a side-reinforced run-flat tire provided with a reinforcing rubber at least on the inner surface side of the sidewall portion.

  According to the present invention, the force from the side (force from the outside in the width direction to the inside) applied to the land portion located in the shoulder region can be canceled by the force in the opposite direction (from the inside in the width direction to the outside). It is possible to provide a pneumatic tire that can more effectively suppress shoulder drop wear and step-down wear at land portions located in the shoulder region.

1 is a partial development view showing a tread pattern of an embodiment of a pneumatic tire according to the present invention. It is sectional drawing of the tire width direction of one Embodiment of the pneumatic tire by this invention. It is sectional drawing of the tire width direction of one Embodiment of the pneumatic tire by this invention. It is a figure which shows the shape deformation | transformation of the 1st land part at the time of the grounding of the pneumatic tire by this invention. It is sectional drawing of the tire width direction of other embodiment of the pneumatic tire by this invention. It is a figure which shows an example of the cross section of the tire width direction of the side reinforcement type | mold run flat tire by this invention. In the pneumatic tire according to the present invention, when various embodiments of the land portion in the shoulder region are used, the force received by the second land portion is compared with the case where the land portion by the conventional pneumatic tire is used. FIG. It is a figure which shows the various forms of the pneumatic tire by this invention used at the time of the measurement which shows a result in FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a partial development view showing a tread pattern of an embodiment of a pneumatic tire (hereinafter referred to as a tire) according to the present invention. In the drawing, the vertical direction indicates the tire circumferential direction (direction parallel to the equator plane C), and the left-right direction indicates the tire width direction (direction orthogonal to the equator plane C). FIG. 2 shows a cross section in the tire width direction of the pneumatic tire according to the present invention.

  As shown in FIG. 2, the tire of this embodiment includes a tread portion 20 that forms a tread surface of the tire, and a pair of sidewall portions that are connected to both ends in the width direction of the tread portion 20 via a shoulder region and a buttress region. 21, 21, and a carcass 23 extending in a toroid shape between a pair of left and right bead portions 22, 22 positioned on the side opposite to the shoulder region side of the pair of sidewall portions 21, 21, and the carcass 23 is a tire having a conventional tire structure, including a belt layer 24 disposed on the outer side in the tire radial direction of the crown portion of 23.

As shown in FIG. 1, the first land portion 12, the sipe 11, and the second land portion 13 are symmetrical with respect to the equator plane C in order from the circumferential main groove 2 of the tire 1 toward the outer side in the tire width direction. 2 are arranged. The second land portion 13 is disposed so as to straddle the ground contact end 3. The circumferential main groove 2 is a groove having such a width that adjacent blocks are not restrained from each other and can move individually, and has a groove width equal to or greater than the width of a sipe described later. Preferably, the groove width of the circumferential main groove 2 is 5 mm to 15 mm.
Further, as shown in FIG. 1, the first land portion 12 and the second land portion 13 may be partitioned and formed in a block shape in both land portions by sub-grooves 4 and 4 intersecting the circumferential main groove 2. However, the first land portion may be continuous in the circumferential direction without being partitioned by the sub-groove.

  Moreover, the 1st land part 12, the sipe 11, and the 2nd land part 13 should just exist in a shoulder area | region at least. Therefore, in FIG. 1, for the sake of simplicity, the form in which the tread portion in the central region between the shoulder regions is arranged as a rectangular parallelepiped block is illustrated. Ribs and rugs. Moreover, you may arrange | position the block similar to the block arrange | positioned in the shoulder area | region of FIG. 1 in the tread part inside a tire width direction.

  However, if such a land portion is simply formed in the tread portion, in particular, the land portion located in the shoulder region cannot withstand a shearing force due to a load received from the rim. As a result, there may be a problem that shoulder wear or step-down wear occurs.

  Here, a mechanism for receiving a force transmitted from the bead portion 22 when the tread portion 20 applies a load to the tire 1 (that is, a mechanism in which a land portion located in the shoulder region receives a force from the side) is shown in FIG. Will be described in detail.

First, in the tire having the structure shown in FIG. 2, when a load is applied to the tire 1 that is assembled to the rim 25 and filled with a predetermined air pressure, the side wall portion extends from the bead portion 22 perpendicular to the road surface at the time of ground contact. 21, a load is applied in the direction of the buttress area and the shoulder area (FIG. 2A). The vertical force is transmitted as stress to the tread portion 20 in the substantially tire width direction through the shoulder region. When this stress is transmitted, the tread portion 20 receives a force on the inner side in the width direction as shown in FIG. 2B, but the land portion near the road surface near the bead portion 22 has a force in the inner direction. Receive the most. That is, the land portion located in the shoulder region receives the most force in the inward direction, and shear deformation occurs as shown in FIG.
And when a tread part leaves | separates from a road surface, the force pressed with respect to the road surface with the load is relieve | moderated, and said deformation | transformation in a tread part tries to return to an original shape this time.

  Thus, since the land part located in a shoulder area repeats stepping and kicking by rolling, shear deformation due to force in the width direction is likely to occur.

  Furthermore, a force from the side is applied to the inner side in the width direction of the tread portion not only when a load is applied but also during cornering. Even in this case, a force is applied to the land portion of the shoulder region closest to the ground contact end 3 to cause shear deformation.

As described above, when the land portion is formed in the shoulder region, the land portion receives a force from the side applied from the outer side in the width direction to the inner side at the time of loading and cornering, so that shear deformation of the land portion occurs. Cheap.
Further, among the land portions of the shoulder region, particularly, the land portion adjacent to the circumferential main groove side is the portion that is most burdened by direct contact with the road surface, and thus wear is most likely to occur.
For these reasons, shoulder drop wear and step-down wear may occur due to repeated deformation of the land portion.

Accordingly, in the present invention, for the purpose of suppressing the occurrence of the above-mentioned wear, as shown in FIG. 1, in the shoulder region, in order from the circumferential main groove 2 toward the outer side in the tire width direction, the first land portion 12 and A sipe 11 extending along the tire circumferential direction and a second land portion 13 are formed.
The first land portion 12 is a land portion defined by the circumferential main groove 2 and the sipe 11 extending along the tire circumferential direction, out of the land portions located in the shoulder region. As shown in FIG. 1, when the first land portion is formed as a block, the block 12 defined by the circumferential main groove 2, the sipe 11, and the two sub-grooves 4, 4 is formed. That is. The second land portion 13 is a block defined by the sipe 11 and the sub-grooves 4 and 4 extending from the sipe 11 beyond the tread grounding end 3.

According to this characteristic configuration, the first land portion 12 can cancel the force from the side inward in the width direction transmitted by the above mechanism, and as a result, the first land portion 12 is input in the width direction inside. The force from the side can be reduced.
This is because the land portion has rubber elasticity, and when the land portion contacts the ground, the first land portion 12 is compressed from the road surface, and the land portion shape is deformed into a barrel shape as shown in FIG. That is, the center of the first land portion 12 swells. That is, the rubber compressed in the radial direction bulges and deforms in the width direction (both on the outer side and the inner side), and the width direction length of the land portion is displaced by the amount of the arrow shown in FIG. On the other hand, a force from the side acts on the second land portion 13 so as to push the rubber of the land portion inward in the tire width direction. Therefore, the first land portion 12 is displaced in the width direction distance due to the bulging deformation, and the second land portion 13 is pushed inward, so that both land portions come into contact with each other and press each other. . In this way, both forces can be canceled by the conflicting forces, and as a result, the force from the side transmitted from the second land portion 13 to the inner side in the width direction can be effectively reduced. Because.

  Thus, if the shape deformation due to the bulging of the first land portion 12 at the time of ground contact is used, the force from the side (force from the outside in the width direction to the inside) applied to the land portion located in the shoulder region is canceled out. Can do. According to the present invention based on this principle, it is possible to effectively reduce the force applied to the land portion of the shoulder region, and to suppress the shear deformation of the land portion as compared with the prior art.

  Below, the land part located in the shoulder region, which is a feature of the present invention, will be described in more detail based on various forms.

  FIG. 4 is a diagram showing an example of a cross section of a tire according to the present invention that includes the first land portion 12, the sipe 11, and the second land portion 13 in the shoulder region.

  In the present invention, a sipe 11 is formed on the inner side in the tire width direction from the ground contact end 3, and the first land portion 12 and the second land portion 13 are divided by the sipe 11. In the embodiment shown in FIG. 4, the sipe 11 is formed so that the wall surface of the sipe 11 is perpendicular to the tread surface, and the groove opening width of the sipe 11 and the groove bottom width are the same length.

  Here, the first land portion 12 is preferably located closer to the inner side in the width direction within the shoulder region. That is, it is preferable to form the sipe 11 and the second land portion 13 closer to the tread central portion as much as the first land portion 12 is formed closer to the tread central portion. The more the ground contact surface of the first land portion 12 is on the inner side in the width direction, the stronger the land portion can be grounded with respect to the road surface. By receiving the force from the road surface, the first land portion 12 is sufficiently To compressive deformation. As described above, the first land portion 12 bulges and deforms in the width direction by the amount of compression deformation in the radial direction as described above. As a result, the second land portion 13 is pushed inward from the outside in the width direction. This is because it can be countered more effectively. Moreover, since the 1st land part 12 is earth | grounding firmly, it is because it can fully oppose the force from the side which goes to the width direction inner side.

The ground contact width of the first land portion 12, i.e. circumference of the widthwise outermost point of the direction main groove 2 to the widthwise innermost point of the sipe 11 in length and W _in, ground contact width of the second land portion 13, That is, when the length from the outermost point in the width direction of the sipe 11 to the grounding end 3 is W _out , W _in <W _out is preferable.
This is because if W _in is long and W _in ≧ W _out , the length in the width direction of the first land portion 12 becomes too long relative to the length in the radial direction of the land portion. Even when the rubber is compressed, the rubber is difficult to bulge and deform in the width direction. That is, since the first land portion 12 is difficult to deform in the width direction, the second land portion 13 cannot be sufficiently blocked from being pushed in from the outside in the width direction.
_{However, W in} the not too short length of preferably has the above contact width 1.5 mm. This is because even if the land portion is compressed at the time of grounding, it is necessary to have a certain length so that the ground can be grounded without causing destruction or collapse. In addition, been an increase in the ground area it is long ground contact width W _in, it will also be increased force from the road surface to receive at the time of the grounding. Therefore, by making the ground contact width equal to or greater than a certain length, the first land portion 12 can be sufficiently compressed and deformed in the radial direction (ie, bulged and deformed in the width direction) to cancel the force applied from the outside in the width direction. Because it can.

In addition, when a surface passing through the deepest groove bottom of the sipe 11 and parallel to the tire width direction is A, the radial length from the surface A to the ground contact surface of the first land portion 12 is H _in , and the surface A the radial length to the ground surface of the second land portions 13 when the _{H out} from is _{preferably H in} ≧ _{H out.}
In order to push back the second land portion 13 that is pushed in from the outer side in the tire width direction, the first land portion 12 needs to be deformed in a barrel shape in the width direction when the tread surface is grounded. Therefore, at the time of ground contact, in order for the first land portion 12 to be deformed between the tire loaded with a load and the road surface, the ground surface of the first land portion 12 is changed to the ground surface of the second land portion 13 and It is preferable to be on the outer side in the tire radial direction than the other tread surfaces. With this configuration, when the load is applied and the tread portion contacts the road surface, the first land portion 12 is sufficiently compressed in the radial direction, so that the rubber of the land portion is deformed in a shape that swells in the width direction. Because it comes to do. However, when H _in is too long, even if the load is applied at the time of the ground, this time can not be other than the ground plane of the first land portion 12 is ground sufficiently, it becomes unstable ground. _Thus, the difference in length of the _{H in} the _{H out} is preferably about 0Mm～0.5Mm.

  Thus, the 1st land part 12 and the 2nd land part 13 which are formed in a shoulder area have the above relation between both about a contact width and radial direction length, and the 1st land part 12 Is bulged and deformed into a barrel shape, and the second land portion 13 that is pushed inward in the width direction is pushed back. As a result, the force from the side on the inner side in the width direction can be reduced.

That is, as push back the second land portion 13 outward in the width direction, since it is sufficient to deform the shape of the first land portion 12, for example, when ground contact width W _in the first land portion 12 is relatively long is the radial length H _in be formed sipe 11 to be relatively long, it can be rubber modified to easily occur. If contact width is relatively short in the opposite, radial length H _in also be made relatively short, it can be broken or the first land portion 12 collapses does not occur. A person skilled in the art can appropriately adjust the relationship between the ground contact width and the radial length in order to deform the shape of the first land portion 12.

Thus, since the 1st land part 12 should just compress-deform in radial direction at the time of earthing | grounding, the groove depth of the sipe 11 is not specifically limited, The deeper one is preferable. This is because the first land portion 12 is more easily deformed when the groove depth of the sipe 11 is deeper. However, the groove depth of the sipe 11 is not more than the circumferential main groove 2. If the groove depth of the sipe 11 becomes too deep, the wall surface of the first land portion 12 becomes difficult to bulge and deform outward in the width direction, and the groove forming the land portion becomes too deep, This is because the land is easily destroyed and becomes unstable.
Therefore, the depth is preferably the same as the depth of the circumferential main groove 2 as shown in FIG. That is, it is preferable that the groove bottom surface of the sipe 11 is on the same plane as the groove bottom surface of the circumferential main groove 2 in the width direction. If the groove depth of the sipe 11 is the same as the groove depth of the circumferential main groove 2, when the first land portion 12 is grounded, it is evenly distributed in the width direction (that is, like the first land portion 12 shown in FIG. 3). This is because the land shape can be changed symmetrically.

In addition, the width W _{shape of the} sipe 11 is preferably shorter because the first land portion 12 that deforms and the second land portion 13 that is pushed inward are in contact with each other at the time of ground contact. It may be a length that allows contact, and is preferably 0 mm or more and less than 2 mm. That is, the sum of the displacement of the first land portion 12 outward in the width direction and the displacement of the second land portion 13 inward in the width direction may be equal to or greater than the width W _{shape of the} sipe 11. And as described above, in accordance with the relationship between the radial length of the ground contact width W _in the sipe 11 of the first land portion 12, the deformation state of the first land portion 12 is deformed, when the deformation is large sipes The width W _shape of the sipe 11 may be relatively long. However, when the deformation is small, the width W _{shape of the} sipe 11 needs to be relatively short so that the land portions come into contact with each other.

FIG. 5 is a view showing a tire cross section of another embodiment of the pneumatic tire according to the present invention. In the first land portion 12 where ground contact width W _in is formed shorter than the land portion width W _bottom of the groove bottom and the coplanar position of the sipe. That is, when the tire is viewed in cross section, as shown in FIG. 5, the upper surface portion has a trapezoidal shape, and the groove opening width of the sipe 11 is wider than the groove bottom width. Other configurations are the same as those of the embodiment shown in FIG.

If the 1st land part 12 is made into such a shape, the land part width _Wbottom which exists in the same plane position as the groove bottom of a sipe becomes comparatively wide, and it can be set as a firm land part. Therefore, to reduce the contact area with a shorter contact width W _in, even when concentrating the force received from the road surface, while it is not the land portion to break, fully compressing the first land portion 12 It can be deformed.

  In this case, the trapezoidal shape is preferably a shape in which the side surface of the first land portion 12 on the outer side in the tire width direction is perpendicular to the ground contact surface. That is, the tire width direction length of the sipe 11 on the ground contact surface is preferably the same as the tire width direction length of the sipe 11 on the innermost side in the tire radial direction. If such a trapezoidal shape, the distance in the width direction between the first land portion 12 and the second land portion 13 is shortened, so when the first land portion 12 is grounded and the shape of the land portion is compressed and deformed, This is because the first land portion bulges more outward in the width direction and the second land portion 13 can be pushed back.

  As shown in the drawing, both the first land portion 12 and the second land portion 13 may be formed as a plurality of blocks by the circumferential main groove 2 and the sub-groove 3, but the first land portion 12 However, it may be formed as a land portion continuous in the circumferential direction without being divided into blocks. Similarly, the second land portion 13 may be formed as a land portion continuous in the circumferential direction without being divided into blocks by the sub-groove 3.

  Furthermore, in the pneumatic tire according to the present invention, a side reinforcing rubber layer having a crescent cross section is disposed inside the carcass of the side portion of the tire to improve the rigidity of the side portion, and the side portion is deformed and deformed when the internal pressure is reduced. A side-reinforced run-flat tire that can bear a load without being extremely increased may be used.

  In this run-flat tire, for example, as shown in FIG. 6, the body portion extending in a toroid shape between the bead cores 26 embedded in the pair of bead portions 22 and the bead core 26 from the inner side to the outer side in the tire width direction. A lucarcass 23 having a folded portion wound outward in the radial direction, a tread portion 20 disposed on the outer side in the tire radial direction of the crown portion of the carcass 23, and a pair of buttress regions located at both ends of the tread portion 20; A pair of side portions 21 that connect the buttress region and the bead portion 22, and a pair of crescent-shaped side reinforcing rubber layers 27 disposed inside the carcass 23 of the side portion 21. Tires can be used.

  As described above, in the run flat tire, the pair of crescent-shaped side reinforcing rubber layers 27 are arranged inside the carcass 23, so that the rigidity of the side portion 21 is increased. As a result, the force received by the rim when a load is applied is more directly applied from the rim to the shoulder region of the run flat tire. That is, the force for pushing the land portion (block) of the shoulder region from the outer side in the width direction to the inner side is applied as a stronger force than in the embodiment shown in FIG.

  And even if the pushing force from the side is strong like a run-flat tire, the first land portion is provided and the land portion bulges and deforms in the width direction, so that the second land portion is changed in the width direction. If this invention of pushing back from the inner side to the outer side is used, it is possible to cancel the force applied from the outer side in the width direction and suppress the shear deformation of the land portion of the shoulder region as compared with the conventional case. As a result, it is possible to more effectively suppress shoulder drop wear and step down wear than before.

  Note that the shapes of the first land portion and the second land portion, the shape and depth of the sipe are all examples for explaining the present invention, and are within the scope of the present invention. The shape can be changed as appropriate.

  FIGS. 7A to 7D show the results of measuring the force from the side applied to the second land portion using a tire including the first land portion, the sipe, and the second land portion in the shoulder region. FIG. For the measurement, a tire tread contact portion measuring device described in JP-A-7-63658 was used.

FIG. 8A is an example of a tire according to the present invention, which is the same as the tire cross section shown in FIG. 4 and has a first land portion 12, a sipe 11, and a second land portion 13. In this example, since the radial length H _in of the first land portion 12 and the radial length H _out of the second land portion 13 are the same, when the groove depth of the sipe 11 is H _shape , H _shape Is the same as the radial length H _in (or H _out ) of both land portions.
8B, the first land portion, the sipe, and the second land portion are located on the outer side in the tire width direction as compared with the case of FIG. 8A. Other land portions and sipe contact widths and radial lengths are the same as in FIG.
The FIG. 8 (c), ground contact width _{W in} the first land portion 12, (a trapezoidal shape) less than the land portion width _{W bottom} of the groove bottom and coplanar position of the sipe are _{formed, W bottom} 8 is the same as FIG.

And the force from the side concerning the 2nd land part 13 shown to these (a)-(c) of these is the standard value of the measured value of the force in the land part of the shoulder region where the sipe 11 is not formed. As a result, measurement was performed by comparing with this force. Specifically, five measurement points (i) to (v) were provided in the width direction between the circumferential groove of the second land portion 13 and the ground contact end, and measurement was performed for each point. The five points (i) to (v) are points obtained by dividing the land portion between the circumferential groove of each land portion and the ground contact end into five equal parts. At this time, the measurement was performed by changing the width W _{shape of} the sipe 11 and the groove depth H _shape of the sipe 11.

  The numerical values on the vertical axis shown in the results of FIGS. 7A to 7C are numerical values represented by an index based on 100 as the force applied to each point on the land portion of the conventional shoulder region where no sipes are formed. The smaller the value, the smaller the force applied to each point. Further, the horizontal axis indicates five measurement points (i) to (v) in each of the cases of FIGS.

<Measurement 1>
In the tire shown in FIG. 8A, the width of the sipe 11 is fixed at W _shape = 0.5 mm,
The groove depth H _shape was _changed to 8 mm (Example 1), 5.5 mm (Example 2), and 3 mm (Example 3). Ground contact width _{W in} the first land portion 12 is 3 mm, the groove bottom and the radial length of the width direction of the same plane to the ground plane of the first land portion 12 of the sipe 11 is fixed at _H in = 8 mm. The result is shown in FIG.

<Measurement 2>
In the tire shown in FIG. 8 (a), ground contact width W _in the 3 mm, the radial length from the same plane groove bottom and the width direction of the sipe 11 to the ground plane of the first land portion 12 of the first land portion 12 Was fixed at H _in = 8 mm, and this time, the groove depth H _shape of the sipe 11 was fixed at 8 mm, and the width W _shape was _changed to 1.5 mm (Example 4). The result of comparing this with Example 1 is shown in FIG.

<Measurement 3>
As shown in FIG. 8 (b), the inner end in the width direction of the circumferential main groove 2 is at the same position in the width direction as the inner end in the tire width direction of the second land portion 13 in FIG. 8 (a). The circumferential main groove 2 and the sipe 11 were formed (Example 5). Ground contact width _{W in} the first land portion 12 is 3 mm, the groove bottom and the radial length of the width direction of the same plane to the ground plane of the first land portion 12 of the sipe 11 is fixed to the _H in = 8 mm. Further, the sipe width and groove depth are the same as those in Example 1, and the sipe width W _shape = 0.5 mm and the sipe groove depth H _shape = 8 mm. The result of comparing this with Example 1 is shown in FIG.

<Measurement 4>
In the diagram shown in FIG. 8C, the ground contact width W _in = 3 mm of the first land portion 12 and the land width W _bottom = 4.5 mm at the same plane position as the groove bottom of the sipe (Example 6). The sipe groove bottom width is _defined as sipe width W _shape , and the sipe width and groove depth are sipe width W _shape = 0.5 mm and sipe groove depth H _shape = 8 mm, as in the first embodiment. The result of comparing this with Example 1 is shown in FIG.

  From the above measurement results, in any of the examples, the first land portion is provided and the land portion bulges and deforms, thereby pushing the second land portion back from the inner side in the width direction to the force from the side. It was found that the force applied to the land portion located in the shoulder region can be reduced.

  And it turned out that the reduction of the force burden to this land part is more remarkable when it is located near the circumferential main groove (in the examples, measurement points (i) to (iii)). .

At this time, the deeper the sipe groove depth, the smaller the force burden on the second land portion can be reduced (Measurement 1).
In addition, the shorter the groove width of the sipe to be formed, the second land portion can be pushed back strongly due to the bulging deformation of the first land portion, so that the force from the side input to the inner side in the width direction is canceled out. (Measurement 2).
Moreover, the direction which a 1st land part is located in the width direction inner side can reduce the force burden to a 2nd land part (measurement 3).
Furthermore, even when the shape of the first land portion is changed, it has been found that the force burden can be effectively reduced by compressing and deforming the first land portion and pushing back the second land portion. (Measurement 4).

  By this invention, the force from the side (force from the outside in the width direction to the inside) applied to the block located in the shoulder region can be pushed back by the reaction force (from the inside to the outside in the width direction), reducing the force from the side. In addition, it is possible to suppress wear at the block portion adjacent to the main groove side, which is particularly prone to wear. As a result, it has been possible to provide a pneumatic tire that can more effectively suppress the shoulder drop wear and step down wear of the block located in the shoulder region than before.

DESCRIPTION OF SYMBOLS 1 Tire 2 Circumferential direction main groove 3 Grounding end 4 Sub groove 11 Sipe 12 1st land part 13 2nd land part 20 Tread part 21 Side wall part 22 Bead part 23 Carcass 24 Belt layer 25 Rim 26 Bead core 27 Side reinforcement rubber layer

Claims (5)

In the pneumatic tire in which the main groove extending along the tire circumferential direction is formed in the tread portion, in the shoulder region of the tread portion, in order from the main groove toward the outer side in the tire width direction,
The first land,
A sipe extending along the tire circumferential direction;
A pneumatic tire comprising: the sipe; and a second land portion formed by arranging a plurality of blocks defined by a sub-groove extending from the sipe beyond the tread grounding end in the circumferential direction.   2. The pneumatic tire according to claim 1, wherein a contact width in a tire width direction of the second land portion is larger than a contact width in a tire width direction of the first land portion.   The length in the tire radial direction from the groove bottom of the sipe to the tread surface of the first land portion is not less than the length in the tire radial direction from the groove bottom of the sipe to the tread surface of the second land portion. The pneumatic tire according to claim 1 or 2.   The pneumatic contact according to claim 1, wherein a contact width in a tire width direction of the first land portion is smaller than a width in a tire width direction in an innermost tire radial direction of the first land portion. tire.   5. The pneumatic tire according to claim 1, wherein the pneumatic tire is a side-reinforced run-flat tire including a reinforcing rubber at least on an inner surface side of the sidewall portion.

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