JPH05112108A - Pneumatic tire - Google Patents

Abstract

PURPOSE:To prevent stone-biting effectively and also secure the drainage effect of a ditch and steering stability by forming a sipping extending along the ditch part on the sub-ditch wall on the tread surface. CONSTITUTION:In a sub-ditch 2 opening in relation to plural main ditches 1 formed in a tire circumferential direction on a tread T surface, a sipe 4 extending along a ditch part A1 is formed on both ditch walls 5, whose top end part 4a is inclined in a ditch bottom 2a direction side and formed in the more opening part 2b side than a half of the sub-ditch 2 depth. Accordingly, when the tire contacts to the road face, an upward step facing to the opening part 2b side is appeared while bordering this sipping 4. At this time, even if a stone 7 invades into the sub-ditch 2, its further invasion can be prevented by this step. When the tire is released from a road holding condition, outside by the rotation of a tire. Thereby, stone-biting can be prevented effectively even in the shallow part with a relatively small section.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire, and more particularly to improvement in prevention of stone trapping in grooves formed on the tread surface thereof.

[0002]

2. Description of the Related Art In tires, in particular, tires for trucks and buses, a large number of grooves formed on the tread surface may catch stones from the road surface during running. In this case, not only is it unsightly in appearance, but sometimes the bitten stones suddenly disengage from the groove due to the centrifugal force of tire rotation, which may damage the body or objects near the axle. Stones that do not come out of the groove will be pushed into the groove bottom by the rotation of the tire each time it touches the ground.As a result, the groove bottom will be damaged. In some cases, serious damage such as reaching the fiber layers of the tires, damaging them, allowing water to enter and accelerating the deterioration of the fibers, and causing a tire burst may occur.

In view of this point, various techniques have been proposed in the past for eliminating stones caught in the grooves on the tread surface. For example, as shown in FIG. 10, the groove bottom 15 has a stepped shelf 16
11, the groove bottom 17 is provided with a pedestal portion 18 that rises above the groove bottom, or the value of (groove width / groove depth) is set to be 1.0 or more, respectively. is suggesting.

[0004]

However, it can be said that it is preferable to form a shelf or a base on the bottom of the groove in order to effectively eliminate stones that enter the groove by the shelf or the base. ,
Since the shelves and pedestals generally have to be formed to be raised about 25 to 50% of the groove depth from the groove bottom,
There is no problem for a groove with a large (groove width / groove depth) value,
It is often structurally difficult to apply it to a sub-groove having a small value of (groove width / groove depth), and it is not always satisfactory in terms of measures against stone trapping. Further, when a shelf or a base is formed at the bottom of the groove, the shelf or the base appears on the surface of the tire as the wear of the tire progresses over time. At this time, since the groove width suddenly narrows, not only the drainage effect of the groove is substantially reduced, but also the steering stability is reduced, and further structural cracks are caused, which causes a problem in terms of durability. Occurs. Also, in order to fuel the driver's anxiety,
Not only will this hinder running on wet roads, it will also be uneconomical to prompt tire replacement. The object of the present invention is (groove width /
It is possible to effectively prevent stone trapping even in shallow groove portions with a relatively small cross-sectional area, such as sub-grooves with a small (depth of groove) value, drainage effect of the groove, steering stability, and durability. In terms of performance, there is no hindrance, and a pneumatic tire with good appearance is provided.

[0005]

[Means for Solving the Problems] The process of stone trapping will be examined as follows. For example, as shown in FIG. 7, a sub groove 1 having a relatively small cross-sectional area with respect to the main groove and having a shallow depth.
2 is a force F in the direction of the arrow, which is normally generated by a vertical load at the time of grounding, and changes from a position in a grounded state separated from the road surface G (shown by a chain double-dashed line) to a position in a grounded state shown by a solid line. In some cases, the groove wall 13 is bent and bulges toward the center of the sub groove 12 in a smooth curved line, and the groove width is narrowed to close the groove. However, if the timing of starting to bite the stone 7 precedes the closing of the groove wall 13, the bulge of the groove wall 13, that is, the bulge 14 is early in the vicinity of the central portion 12a of the auxiliary groove 12 and is delayed in the vicinity of the opening 12b, so that the auxiliary groove is formed. The closing of the opening 12b of 12 is delayed, and as shown in FIG. 8, the stone 7 spreads the sub groove 12 against the pressure of the bulge 14 and is pushed in by the ground pressure. After the ground contact is released, as shown in FIG. 9, the stone 7 is kept in the bitten state by the repulsive force f of the rubber pushed by the stone 7 more than in the free state.

In view of the above process of stone biting, the present invention divides the groove wall of the groove portion A into upper and lower parts by forming a sipe extending along the groove portion A in the groove wall of the groove portion A. ,
As a result, the spring constant for the vertical force at the time of contact with the ground is made as small as possible to increase the amount of flexure, and the shearing force acting inside the rubber is discontinuously changed by the sipe, resulting in different bulges intermittently present in the groove wall. The protrusion was formed to form a step inside the groove portion A due to the bulge difference, and the step prevents the stone from entering. That is, the present invention attempts to prevent the intrusion of stones by controlling the deformation of the groove wall due to the bulge by forming a sipe on the groove wall, and a large number of repeating patterns are formed on the tread surface by the groove and the convex portion. In a groove portion A having a relatively small cross-sectional area and a groove portion A having a relatively small cross-sectional area and a groove portion B having a large cross-sectional area and a large depth which are adjacent to each other and are continuous with each other, a sipe extending along the groove portion A is provided on the groove wall of the groove portion A. It is characterized by being formed.

Therefore, it is desirable to form the sipes on both groove walls of the groove portion A, but it is possible to form the sipes on one groove wall. It is also possible to form a plurality of groove walls on the same side. When forming multiple sipe on the groove wall, change the gap between the sipe on the opening side and the surface of the tire tread, and change the gap between the sipe on the opening side and the sipe on the groove bottom side. Is narrower, and it is desirable that the gap on the groove bottom side be wide. Regarding the depth of the sipes, it is desirable that the sipes have different depths between adjacent sipes so that the sipes are shallow on the opening side of the groove portion A and deep on the groove bottom side. In both cases, the spring constant is changed, and the amount of bulge is changed to prevent stones from entering.

The position where the sipe is formed is not particularly limited, but when it is formed closer to the opening side of the groove portion A than half the depth of the groove portion A, at the time of grounding, it is closer to the groove bottom side than the opening side. Since it expands, it becomes an upward step facing the opening side, and blocks invading stones as in the case where a shelf is provided inside the groove. When it is formed on the groove bottom side of the groove part A more than 1/2 of the depth of the groove part A, the step due to the bulge difference is a downward step facing the groove bottom side, and the bulge is closer to the opening side. Since it becomes large, the opening side becomes so-called lid-like, and a self-sealing effect is exerted against invading stones. In any case, it is possible to form a groove wall that eliminates stone trapping, but it is preferable to form the groove wall closer to the opening side of the groove portion A than half the depth of the groove portion A in terms of the stone scrub prevention effect.

Although the forming angle of the sipe is not particularly limited, the sipe forming blade to be attached to the tire molding die is one in which the tip end in the depth direction of the sipe is inclined toward the groove bottom direction side of the groove portion A. Therefore, it is preferable that the vulcanized tire can be easily removed from the mold.

Here, a groove portion A having a relatively small cross-sectional area and being adjacent to each other and having a relatively small cross-sectional area and a groove portion B having a large cross-sectional area and a deep cross-sectional area are not only related to a so-called sub-groove and a main groove but also branched. A groove portion having a wide cross-sectional width and a relatively different cross-sectional depth, such as a pair of sub-grooves, a branched portion and a sub-groove, a sub-groove and a slit, or a single groove having a continuous different groove width and depth. It includes all relationships between them. Therefore, for example, if the groove that can easily release the bitten stone is the main groove, not only the sub-groove that opens into the main groove but also the groove or slit that branches from this sub-groove to this sub-groove is the groove portion B. In the case of the relationship of the groove portion A with respect to the above, the sipe can be provided in all of these cases. The term “groove portion” means not only the entire groove but also a part of the groove, a branched portion, a groove connecting portion, or the like. In the case of a part of the groove, the vicinity of the opening of the groove portion A or the inner depth of the groove. This means that the sipe may be formed only on the part or the like. Further, the groove portion A can be applied not only when it is closed on one side, but also when the groove portion A is open on both sides to the groove portions B adjacent to both sides thereof.

[0011]

According to the present invention, in a pneumatic tire having a tread groove having a relatively small cross-sectional area and a shallow groove portion A opening to a deep groove portion B having a large cross-sectional area, at least one groove wall of the groove portion A is provided. Since the sipe extending along the groove portion A is formed, the spring constant with respect to the vertical force can be reduced and the amount of bending can be increased at the time of contact with the ground, and the shearing force acting inside the rubber is discontinuous to make the groove wall. Since different bulges that are intermittently exposed can be made to appear, a step due to the bulge difference can be formed inside the groove portion A, and this step can satisfactorily prevent stone intrusion.

In particular, the sipes described above are 1 / th of the depth of the groove portion A.
When it is formed on the opening end side on the tread surface side from 2, the groove bottom side swells more than the opening side at the time of grounding, so that there is an upward step facing the opening side and a shelf inside the groove. As with the case with the above, it is possible to block the invading stones. In addition, since the step occurs at the time of contact with the ground and is an upward step facing the opening side, unlike the conventional case where a shelf or a base is formed at the bottom of the groove, the drainage effect of the groove and the steering stability are improved. There is no problem in terms of durability and durability, and the appearance is good.

[0013]

1 is a partial schematic plan view of a tread surface showing an embodiment of a pneumatic tire according to the present invention, FIG.
FIG. 3 is an enlarged sectional view of the main part II-II line.

In the figure, 1 is a main groove formed on the surface of the tread T in the tire circumferential direction, and 2 is a sub-groove opening to both the main grooves 1 and 1. Reference numeral 3 is a groove formed in the shoulder direction from the main groove 1. The sub groove 2 is a groove having a relatively narrow groove width and a shallow groove depth with respect to the main groove 1. That is, the main groove 1 is a groove portion B having a relatively large cross-sectional area and a deep groove depth, while the sub groove 2 is a groove portion A having a relatively small cross-sectional area and a shallow groove depth. SH is the shoulder end and CL is the tire center line.

Reference numeral 4 denotes a groove portion AI on both groove walls 5 of the auxiliary groove 2.
As shown in FIG. 2, the sipe is formed so as to extend along the sipe. The tip portion 5a is inclined toward the groove bottom 2a direction side and is formed closer to the opening portion 2b than half the depth of the sub groove 2. ing.

Therefore, as shown in FIG. 3, when the road surface G is grounded, the groove wall 5b on the groove bottom side of the groove wall 5a on the opening 2b side is a spring against the vertical force with the sipe 4 as a boundary. Since the constant is small and the deflection is large, the groove wall 5 on the groove bottom 2a side
The b expands more greatly, and an upward step 6 facing the opening 2b side appears in the sipe 4. Therefore, as shown in FIG. 4, even if the stone 7 enters the sub-groove 2 and begins to bite the stone 7, it is possible to prevent further intrusion by the step 6, and as shown in FIG. Is released to the outside by the rotation of the tire when the grounded state is released.

FIG. 6 is an enlarged cross-sectional view of an essential part showing another embodiment of the present invention. Unlike the above embodiment, a plurality of sipes 9, 10 are formed in the groove wall 8. Sub groove 2 as shown
The sipe 9 formed on the opening 2b side has a shallower depth from the sipe 10 formed on the groove bottom 2a side to the tip of the sipe, and the sipe 9 on the opening 2b side and the tire The distance D ₁ between the surface 11 of the tread portion and the distance D ₂ between the sipe 9 on the side of the opening 2b and the sipe 10 on the side of the groove bottom 2a are made different so that the distance D ₁ on the side of the opening 2b is narrow and the side of the groove 2a is close. The interval D _{2 of} is wide. Therefore, the sipe 9 on the side of the opening 2b
The groove wall 8b extending from the sipe 9 on the opening 2b side to the sipe 10 on the groove bottom 2a side is further divided by the sipe 10 into a groove wall 8c on the groove bottom 2a side compared to the groove wall 8a part partitioned by. Since it may be in a divided state, the bulge difference at the time of contact with the ground becomes larger than that in the above-described embodiment, and a larger step can be revealed at the time of contact with the ground to prevent stone trapping.

The present invention is not limited to the above embodiment. For example, the groove width of the groove portion A, the groove depth, the groove width of the groove portion B, the groove depth, the width of the sipe, the depth of the sipe, the inclination angle of the sipe, the interval between the sipe formations, etc. can be arbitrarily set. There are various tread patterns other than the above. The sipe can be easily formed by attaching a blade to the tip of the groove forming protrusion of the tire mold, but the method is not particularly limited.

[0019]

As described above, since the present invention achieves the prevention of stone trapping by forming the sipes in the groove wall portion, it is possible to relatively prevent disconnection such as a sub-groove having a small groove width / groove depth value. It is possible to effectively prevent stone trapping even in a shallow groove portion having a small area, and there is no problem in terms of the drainage effect of the groove, steering stability, and durability. Further, even if the tread surface wears and the groove becomes shallower with use, the shelf formed at the groove bottom does not appear as in the conventional case, and the pneumatic tire has no apparent trouble.

[Brief description of drawings]

FIG. 1 is a partial schematic plan view of a tread surface showing an embodiment of a pneumatic tire according to the present invention.

FIG. 2 is an enlarged sectional view of the main part II-II line.

FIG. 3 is an enlarged cross-sectional view of a main part of the tire in a grounded state.

FIG. 4 is an enlarged sectional view of an essential part showing a state of stone trapping when the tire is in contact with the ground.

FIG. 5 is an enlarged cross-sectional view of a main part showing a state of stone trapping when the vehicle is separated from the road surface.

FIG. 6 is an enlarged sectional view of an essential part showing another embodiment according to the present invention.

FIG. 7 is an enlarged cross-sectional view of a main part in a grounded state showing an example of a conventional tire.

FIG. 8 is an enlarged sectional view of an essential part showing a state of stone trapping when the tire is in contact with the ground.

FIG. 9 is an enlarged sectional view of an essential part showing a state of stone trapping when the tire is separated from the road surface.

FIG. 10 is an enlarged cross-sectional view of an essential part showing another example of a conventional tire.

FIG. 11 is an enlarged cross-sectional view of an essential part showing another example of a conventional tire.

[Explanation of symbols]

 A groove part B groove part 5 groove wall 8 groove wall 4 sipes 10 sipes

Claims (2)

[Claims] 1. A groove portion A having a relatively small cross-sectional area and a relatively small cross-sectional area and a groove portion having a large cross-sectional area and being continuous and adjacent to each other in a pneumatic tire in which a large number of repeating patterns are formed by grooves and convex portions on a tread surface. In B, a sipe extending along the groove portion A is formed on at least one of the groove walls of the groove portion A. 2. The pneumatic tire according to claim 1, wherein the sipe according to claim 1 is formed closer to the end of the opening on the tread surface side than half the depth of the groove portion A. 2. The pneumatic tire described in 2.