JP2010105591A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire, in which eccentric wear resistance after a middle stage of wear of a land of a pneumatic tire provided with a rib for restraining eccentric wear in a peripheral groove, i.e., a so-called eccentric wear sacrifice protrusion. <P>SOLUTION: A plurality of peripheral grooves 2 extending in a tire peripheral direction are arranged on a tread 1, and a land is demarcated between two peripheral grooves adjacent to each other. A rib arranging groove 2 provided with a rib 4 having a step between it and a top face of the land is provided in at least one peripheral groove. A plurality of sipes 5 not opened to the top face of the land and extending in a tire radial direction are provided on at least one land side groove wall of the rib arranging groove 2. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a pneumatic tire, and more particularly to a heavy duty pneumatic tire having improved uneven wear resistance after the middle stage of wear.

  In pneumatic tires, uneven wear that tends to occur on the side edges of small-diameter land due to radial drag due to load rolling of the tire progresses relatively quickly over the entire width of the land. Such wear not only impairs the wear life of the tire, but also greatly affects steering stability.

  Therefore, in the circumferential groove, a step-down rib having a lower radial direction than the land portion defined by the circumferential groove, a so-called uneven wear sacrificial ridge is provided, and the diameter of the top surface of the land portion and the uneven wear sacrificial ridge are provided. Based on the difference in diameter from the top surface of the tire, the force in the drag direction during load rolling of the tire, in other words, the braking force, is concentrated on the uneven wear sacrificial ridge, and the ridge is brought into sliding contact with the road surface. By actively abrading the uneven wear sacrificial ridge, the uneven wear due to the component of the braking force of the land portion adjacent to the uneven wear sacrificial ridge is replaced by the uneven wear sacrificial ridge. Techniques for reducing uneven wear are widely used in practice.

  However, in this prior art, the uneven wear sacrificial ridge can effectively exhibit the uneven wear suppression function as described above from the initial stage to the middle stage of the tread surface. The height of the uneven wear sacrificial ridge is reduced and the land rigidity is increased, so that the contact length difference and the step are reduced, and the load of the braking force component of the ridge is reduced. The load of braking force increased in the land portion adjacent to the wear sacrificial ridge, and there was a risk of uneven wear developing in the land portion.

  Therefore, the present invention also effectively improves the uneven wear resistance of the land portion of a pneumatic tire in which ribs for suppressing uneven wear in the circumferential groove, so-called uneven wear sacrificial ridges, are disposed after the middle stage of wear. A pneumatic tire is provided.

  In the pneumatic tire according to the present invention, a plurality of circumferential grooves extending in the tire circumferential direction are arranged on the tread surface, and a land portion is defined between two circumferential grooves adjacent to each other, and at least one In the circumferential groove, it is provided with a rib disposition groove provided with a rib having a step with respect to the top surface of the land portion, and at least one land portion side groove wall of the rib disposition groove, A plurality of sipes extending in the tire radial direction that do not open on the top surface of the land portion are provided.

Here, the circumferential groove can be extended not only in a linear extension form but also in a zigzag form, a wave form, a crank form, or the like.
The cross-sectional shape of the sipe can be not only a quadrangle, but also a shape such as a triangle, a circle, and an ellipse, and the sipe cutting depth can be not only the same in the radial direction but also different.
The groove wall of the circumferential groove and the side wall of the land portion are the same region.

  More preferably, in such a tire, the sipe is formed in the land portion side groove walls on both sides of the rib installation groove.

  Preferably, the top surface of the rib in the rib disposition groove is located radially inward from the radially outer end of the sipe.

  Also preferably, the sipe is inclined with respect to the radial line segment.

  By the way, it is preferable that the total sum of the width dimensions in the tread circumferential direction of the sipe is in a range of 10 to 50% of the length in the tread circumferential direction as measured at the radially inner end position of the sipe.

In the pneumatic tire of the present invention, wear is started from the middle stage of wear by providing a plurality of sipes extending in the tire radial direction that do not open on the top surface of the land portion on at least one land portion side groove wall of the rib disposition groove. At the end, the sipe is exposed on the top surface of the land portion adjacent to the rib in the rib installation groove to reduce the circumferential rigidity of the land portion, and easily deform in the circumferential direction at the time of ground contact. By placing a large burden on the braking force component from the middle stage of wear to the last stage of wear, it is possible to guarantee the progress of wear more artificially than other areas, and after the wear progresses in that area, the braking force is applied by the ribs caused by the diameter difference. Burden.
As a result, the load of the braking force of the land portion adjacent to the circumferential groove provided with the rib is relatively reduced, and the uneven wear of the land portion can reduce the progress.

Hereinafter, the pneumatic tire of the present invention will be described in detail with reference to the drawings.
FIG. 1 is an enlarged perspective view of a circumferential groove area provided on a tread surface, showing one embodiment of the pneumatic tire of the present invention, and FIG. 2 is an enlarged view of a main part of the sipe of FIG.

In the figure, reference numeral 1 denotes a tread surface, and on this tread surface 1, a circumferential groove 2 extending along the tread circumferential direction is linearly extended, and between this circumferential groove 2 and the tread side edge. A land portion is defined by a rib-shaped shoulder land portion 3 and an adjacent circumferential groove (not shown).
The groove width of the illustrated circumferential groove 2 can be, for example, 11.5 to 19.0 mm, and the groove depth H can be in the range of 10.0 to 19.0 mm.

In such a circumferential groove, a rib 4 stepped down from the top surface of the land portion 3 is provided. For example, the step height of the rib top surface of the rib 4 from the top surface of the adjacent land portion is set to 0. Step down to a range of 5 to 5.0 mm.
In this case, the rib width of the rib 4 can be in the range of, for example, 3.5 to 11.5 mm.

  Further, in this tire, a plurality of sipes 5 cut in the tread width direction from at least one of the circumferential grooves (rib disposing grooves) 2 provided with the ribs 4, and both land-side groove walls in FIG. It is isolated from the top surface and extends in the tire radial direction.

  By providing such a sipe 5, the tread tread surface 1 is preferentially worn by the rib 4 due to the difference in diameter from the initial stage to the middle stage of wear, and further, from the middle stage of wear to the last stage of wear, FIG. As shown in FIG. 3, by exposing the sipe 5 to the top surface of the land portion, the circumferential rigidity of the land portion can be reduced, and thus, the region where the sipe 5 is provided in the circumferential direction can be reduced in the circumferential direction. By making it easy to deform, the braking force component can be greatly borne from the middle wear stage to the last wear stage. In addition, since the wear of the tread tread 1 has progressed after the middle stage of wear, even if the sipe 5 appears, the rigidity of the surrounding land area does not decrease, and uneven wear can be suppressed. .

  In such a tire, more preferably, the sipes 5 are formed in the land portion side groove walls on both sides of the rib disposition groove 2, whereby the circumferential rigidity of these land portions can be reduced uniformly.

  Preferably, the top surface of the rib 4 in the rib disposition groove is located radially inward from the radially outer end of the sipe 5.

And preferably, each sipe 5 is provided in the land part adjacent to the circumferential groove 2 located in the tire width direction outermost side.
With this configuration, it is possible to effectively suppress uneven wear that occurs in the land portion that becomes the small-diameter land portion due to the differential drag due to load rolling of the tire, and the uneven wear propagates to the adjacent land portion. Can be effectively suppressed.

Preferably, each sipe 5 has a height dimension d along the land-side groove wall larger than the width dimension b in the tread circumferential direction.
With this configuration, the rib 4 can bear the component of the braking force until the end of wear, and the occurrence and development of uneven wear can be suppressed.

  More preferably, the total sum of the width dimensions b of the sipe 5 in the tread circumferential direction is measured at the radially inner end position of the sipe 5 to be in the range of 10 to 50% of the length in the tread circumferential direction. Thus, the occurrence of uneven wear in the land can be further suppressed.

  That is, if it is less than 10%, the circumferential rigidity of the land portion cannot be sufficiently lowered. On the other hand, if it exceeds 50%, the braking force tends to be reduced.

  Preferably, the height dimension a along the land-side groove wall from the top surface of the land portion to the radially outer end of the sipe 5 is set to a range of ¼ to 3/5 of the depth of the circumferential groove 2. By setting the range, the sipe 5 is exposed from the middle stage to the end stage of wear, the rigidity of the land part is reduced, the component responsible for the braking force is improved, and the development of uneven wear of the land part is suppressed. it can.

  That is, if it is less than 1/4, the sipe 5 is exposed at the initial stage of wear, and a tear is generated due to a decrease in the rigidity of the land portion. On the other hand, if it exceeds 3/5, the exposure of the sipe 5 will be after the middle stage of wear, and therefore the effect of suppressing uneven wear in the entire tire tends to be insufficient.

By the way, the height dimension d along the land part side groove wall of the sipe 5 is in the range of 10% to 100% of the radial height dimension e of the sipe 5 from the radially outer end to the base end of the land part side groove wall. And the width dimension b in the tread circumferential direction of the sipe 5 is in the range of 0.5 to 2.5 mm, the cutting depth c in the tread width direction of the sipe 5 is 1.0 mm or more, and the sipe 5 Measured at the inner end position in the radial direction, the range is 1/3 or less of the width of the land portion provided with the sipe 5.
By setting it as this range, the circumferential direction rigidity of a land part can be reduced and generation | occurrence | production of uneven wear can further be suppressed.

  That is, if the height dimension d is less than 10% of the height dimension e, the circumferential rigidity of the land portion tends to be insufficiently reduced. On the other hand, if the height dimension d exceeds 100%, it is below the groove bottom of the circumferential groove 2. The sipe 5 is inserted, cracks are generated at the bottom of the sipe, and the durability of the land portion tends to decrease.

  When the width dimension b is less than 0.5 mm, the blade forming the sipe 5 is deformed. On the other hand, when the width dimension is more than 2.5 mm, the rib 4 is easily cracked when the tire is taken out from the vulcanization mold, and the manufacture becomes difficult. Tend.

  When the cutting depth c is less than 1.0 mm, there is a tendency that the circumferential rigidity of the land portion is not sufficiently lowered. On the other hand, when the cutting depth c exceeds 1/3 of the land portion width, the ratio of the cutting depth of the sipe 5 to the land portion width is increased, and is preferentially generated in the region where the sipe 5 of the land portion side groove wall is provided. Wear tends to be perceived as uneven wear that develops on land.

  Further, preferably, the arrangement pitch p of the sipe 5 is in a range of 0.5 to 10.0 mm, and by setting in this range, the generation of the tear at the sipe bottom due to a large input or the like is suppressed, and the effect after the middle stage of wear is also effective. In particular, the occurrence and progress of uneven wear due to the component of the braking force can be suppressed.

  That is, if it is less than 0.5 mm, the rigidity of the land portion is not sufficient with respect to a sudden input such as a large input, and there is a possibility that a tear occurs at the bottom of the sipe. On the other hand, if it exceeds 10.0 mm, the rigidity of the land portion becomes large, and the amount of wear becomes small because the rib deformation amount at the time of kicking is small. As a result, the step amount between the land portion and the rib 4 becomes small. No. 4 tends to reduce the load of the braking force component.

FIG. 4 is an enlarged view of a main part when the sipe of FIG. 1 is inclined.
By tilting the sipe 5 in a range of 0 to 45 ° with respect to the radial line segment, and making this range, the deformation amount of the land portion with respect to a certain input direction can be reduced, and the sipe bottom The occurrence of tear can be effectively suppressed.

  That is, if it exceeds 45 °, the mold may be damaged when it is taken out from the mold, and cracks may occur at the sipe bottom due to repeated grounding and non-grounding to the road surface during load rolling. There is.

  Next, Example tires 1 and 2 of a tire having a structure as shown in FIG. 1 and FIG. The tires 1 and 2 were made as prototypes, and as shown in Table 1, the specifications were changed to evaluate uneven wear resistance.

In this evaluation, each of Example Tires 1 and 2 and Comparative Example Tires 1 and 2 is mounted on a rim having a rim size of 8.25 × 22.5, an internal pressure is set to 690 kPa, and a load mass is 2800 kg. This was carried out by running 2574955.04 km (160000 miles) and measuring the uneven wear resistance of the land portion adjacent to the circumferential groove provided with the rib during running.
FIG. 4 shows uneven wear resistance depending on the travel distance. The uneven wear property was evaluated by I / W width (length in the width direction of the uneven wear generating portion) × depth × circumferential incidence.

  From the results of FIG. 5, the Example tires 1 and 2 were able to effectively suppress uneven wear not only from the initial stage of wear to the middle period but also from the middle stage of wear to the comparative tires 1 and 2.

1 is an enlarged perspective view of a circumferential groove area provided on a tread surface, showing an embodiment of a pneumatic tire of the present invention. It is a principal part enlarged view of the sipe of FIG. The state after the middle wear of a part of the tire shown in FIG. 1 is shown. It is a principal part enlarged view in case the sipe of FIG. 1 inclines. It is a figure which shows the result of having measured uneven wear property by the Example.

Explanation of symbols

1 tread surface 2 circumferential groove 3 shoulder land 4 rib 5 sipe

Claims (5)

A plurality of circumferential grooves extending in the tire circumferential direction are arranged on the tread surface, a land portion is defined between two circumferential grooves adjacent to each other, and at least one circumferential groove has In a pneumatic tire having a rib disposition groove provided with a rib having a step between the top surface,
A pneumatic tire comprising a plurality of sipes extending in a tire radial direction that do not open to a top surface of the land portion on at least one land portion side groove wall of the rib disposition groove.   The pneumatic tire according to claim 1, wherein the sipe is formed on land side groove walls on both sides of the rib arrangement groove.   The pneumatic tire according to claim 1 or 2, wherein a top surface of the rib in the rib disposition groove is located radially inward from the radially outer end of the sipe.   The pneumatic tire according to claim 1, wherein the sipe is inclined with respect to a radial line segment.   5. The total width dimension of the sipe in the tread circumferential direction is in a range of 10 to 50% of the length in the tread circumferential direction as measured at the radially inner end position of the sipe. Pneumatic tire.

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