JP2807915B2 - Pneumatic radial tire - Google Patents

Description

Description: BACKGROUND OF THE INVENTION (Industrial Application Field) The present invention relates generally to a tire mounted on a heavy-duty vehicle such as a heavy-duty truck, and more particularly, to a tire having one end opened at a side portion of a tire and having a tread tread portion. Prevents and controls group cracks that are likely to occur at the bottom of the lateral groove of a pneumatic radial tire that has elements on the tread tread that are divided into blocks or lugs sandwiched by lateral grooves formed in the area including the shoulder contact end. The present invention relates to a pneumatic radial tire.

(Prior art) As a large pneumatic radial tire mounted on heavy-duty vehicles such as conventional heavy trucks, it prevents slippage and cut-off on the tread surface, increases braking and driving force, and increases running power. As shown in FIG. 9, for example, as shown in FIG. 9, a shoulder region (1a) including shoulder tread portions (2) at both ends of the tire tread portion (1), in order to radiate heat and extend the life of the tire. In (1a), a number of lateral grooves (3) having one end opened to a side portion of the tire and extending substantially parallel to the tire rotation axis direction are arranged at substantially equal intervals in the tire circumferential direction, and the other tread (1) center. Five longitudinal grooves (4) extending in a zigzag manner in the circumferential direction of the tire, two ends of which are in communication with the lateral grooves (3), and a zigzag lateral groove (5) connecting the longitudinal grooves (4). And these grooves (3), (4), (5)
A four-row polygonal block (6) at the center of the tread (1) and a pentagonal shoulder block (7) on both sides thereof, and openings at the tire side portion and tread tread portion of the block (7). It has been practiced to arrange various basic patterns such as block patterns in which a large number of slits (10) having ends and being parallel to the horizontal groove (3) are formed at equal intervals. It is widely used on roads because of its excellent maneuverability and stability. However, in the tire as described above, each shoulder block (7) that touches the ground when traveling while receiving a large load and large braking, driving or traction,
(7) The groove bottoms of the lateral grooves (3) on both sides form a transmission path of force from the axle to the road surface or from the road surface to the axle, and are concentrated on the base end of the block (7) which is directly subjected to bending action and compression action. In particular, since the shape is susceptible to shock, particularly large distortion is generated, and the distortion changes and repeats with an irregular numerical value ranging from zero to a finite range every rotation of the tire. The groove bottom is provided with a radius to prevent the concentration of stress and strain. However, from the side wall of the block (7) to the bottom of the groove, the bending rigidity is also suddenly changed and the stress and strain are reduced.
Since the strain is repeatedly concentrated, the rubber material in this portion is fatigued, and in particular, the shoulder block (7) sandwiched between the lateral grooves (3) having one end opened on the tire side portion has a tread shoulder region (1a) during cornering. There is also a structural problem such as a particularly large load stress on the outer side of the mounting, and it is easy to reach the limit of fatigue, easily induce a group crack at the groove bottom, and water penetrates into the tire belt layer through the crack. There is also a problem that the intrusion may rapidly reduce the durability performance of the tire itself.

For this reason, recently, as an improved pneumatic radial tire for preventing the occurrence of group cracks at the bottom of the groove, for example, of the grooves constituting the block (7) as shown in FIG. ), A lateral groove (3) having a medium-narrow cross-sectional shape is provided in which the groove width is gradually reduced from the tread surface toward the groove bottom, and the groove width is gradually increased halfway, and a large number of side grooves are provided on the side wall of the lateral groove (3). There is a right angle cut in the book, that is, a sipe (10) is formed (Japanese Patent Laid-Open No. 1-16406), etc., to prevent the occurrence of group cracks due to stress concentration due to a vertical load, and to get stuck in the groove. One that promotes the falling of stones to prevent the occurrence of group cracks due to the bite of stones, and one in which a plurality of sipes extending in the radial direction are arranged at least in the lower part of the side wall of the lateral groove in the lateral direction (Japanese Patent Laid-Open JP-A-64-16406) Alternatively, a sipe extending in the groove direction is provided in a block between the groove center and the groove bottom having a groove depth of the side wall of the lateral groove (Japanese Patent Application Laid-Open No. 64-9009).
Further, various types of bridges or the like having a substantially shallow groove bottom have been proposed and are being put to practical use.

(Problems to be Solved by the Invention) In such a conventional pneumatic radial tire, the lateral groove (3) is formed to have a middle-narrow cross-sectional shape from the tread surface to the groove bottom, and the lateral groove (3) is formed. The number of sipes (10) cut at right angles to the side wall of ()) prevents the occurrence of group cracks at the bottom of the groove due to the prevention of stone bite. The stress relaxation effect corresponding to the main causes of the generation, the tension caused by the driving force and the shear stress caused by the large load, etc. is not sufficient. The same applies to a case where a plurality of sipes extending in the radial direction are arranged in at least the lower part of the side wall of the lateral groove in the groove direction.

Further, in the case where a sipe extending laterally from the middle of the side wall of the horizontal groove to the groove bottom is provided, since the sipe is parallel to the direction of the generated crack, when the crack moves to the sipe part near the groove bottom and occurs, Conceivable. In addition, a shallow groove with a bridge reduces the wear life of the groove, impedes drainage, reduces steering stability on wet roads, and implies its function as a groove without cracks. The problem remains.

The present invention has been made in view of such a situation, and an object of the present invention is to provide a block or lug sandwiched between lateral grooves provided on both shoulders of the tread in a tire near a bottom of the lateral groove in advance in the tire. Pressing and filling a solid material that imparts compressive strain to the rubber material of the portion to reduce tensile strain at the time of grounding, and is generated at the bottom of the lateral groove by limiting the range of the shape and filling position of the solid material Prevents easy group cracks,
It is to provide a pneumatic radial tire that suppresses.

(Means for Solving the Problems) The features of the pneumatic radial tire of the present invention for achieving the above object are as described in claims 1 to 4,
A vertical groove continuously extending in the tire circumferential direction, and a large number of lateral grooves provided at substantially equal intervals at an angle of not more than 45 ° with respect to the tire rotational axis direction, and at least a part of the lateral groove is a part of the tire. In a pneumatic radial tire with a tread pattern that forms a lug or a block in a shoulder region including a shoulder grounding end with one end opened to a side portion, solid inside the tire near a groove bottom of a lateral groove having one end opened to the side portion. The object is subjected to compressive strain in advance at the time of non-contact with the rubber part near the bottom including the bottom of the lateral groove, and
The solid is press-filled into a lateral hole having a smaller cross-sectional area than the cross-sectional area of the solid previously drilled from the side of the tire, based on a configuration in which press-fitting is performed so that tensile strain due to driving force is applied. Along with, the cross-sectional area of the solid material is in the range of 2 to 18 times the cross-sectional area of the horizontal hole, and the horizontal hole has a shape with a bulge inside, and the depth of the horizontal hole in the horizontal groove depth direction is also set. The bottom of the lateral groove is positioned at a depth of +10 to -15 mm from the groove bottom with respect to an arc extending in contact with the tire circumferential direction.

In addition, the cross-sectional area of the solid material is in the range of 2 to 18 times the cross-sectional area of the lateral hole, or the position at the side opening is from the groove bottom to the arc extending in contact with the lateral groove bottom in the tire circumferential direction. For each numerical range such as at +10 to -15 mm,
Although it has no critical significance, it is within the practical range.

(Operation) According to the first to fourth aspects of the present invention having the above-described configuration, at least a part of the lateral groove is opened at one end to the side portion of the tire and formed in a region including the shoulder contact end of the tread tread portion. When mounting or using pneumatic radial tires that form blocks or lugs on wheels of heavy-duty vehicles such as large trucks, use them inside the tire near the groove bottom of the lateral groove that has one end open at the tire side. The solid material is press-fitted beforehand to the rubber portion including the bottom of the lateral groove, including the bottom of the lateral groove, at the time of non-grounding, and is press-fitted so that tensile strain due to control and driving force is applied at the time of grounding. A part of the tensile strain applied to the bottom of the lateral groove through the block or lug is offset by the above-described compressive strain applied in advance, and the amplitude of the strain is extended to both sides in the compression and tension directions. Since the fatigue resistance of the rubber is improved by changing to the amplitude form that acts on the rubber, the occurrence of group cracks at the block or lug base end at the bottom of the lateral groove is suppressed and prevented.

This means that, as shown in FIG. 13, the fatigue life of the rubber is greatly reduced by the minimum strain with respect to the load amplitude, that is, the minimum strain value given to the rubber when the periodically fluctuating load is removed. It is a well-known fact that the worst case is obtained when the minimum distortion is 0, and the life is greatly extended within a certain finite range before and after the minimum distortion.

When the rubber material is only synthetic rubber or mainly composed of synthetic rubber, it may not be the same, but it is well known that the natural rubber alone or the substance mainly composed of natural rubber, such as tread rubber of a pneumatic radial tire for heavy load, matches well. .

In addition, the solid material is press-fitted into a small-diameter lateral hole whose cross-sectional area pre-drilled from the side of the tire is in the range of 1/2 to 1/18 of the solid material, or the lateral hole has a bulge inside. The one that has been drilled in the shape that it has is stably fixed in the side hole by the contraction force of the rubber on the side hole side and the repulsion force of the solid,
During the load, there is no sliding wear between the press-fit side and the press-fit solid, and a specific compressive strain is continuously applied to a portion near the groove bottom.

Further, the position of the side hole at the side opening is +10 to + from the groove bottom with respect to an arc extending while contacting the bottom of the lateral groove in the tire circumferential direction.
With the size of -15 mm, the compressive strain works efficiently up to the groove bottom surface, disperses and eliminates partial concentration of tensile strain generated at the time of load, and further suppresses and prevents the occurrence of group cracks at the horizontal groove bottom. is there.

(Example) Hereinafter, an example of the present invention is further described according to an accompanying drawing.

FIG. 1 is a partial plan view showing an embodiment of a pneumatic radial tire according to the present invention, FIG. 2 is a partial side view of FIG. 1, and FIG. 3 is a line AA of FIG. 4th in the sectional view
FIG. 5 is an enlarged view of a portion D in FIG. 3, FIG. 5 is an enlarged view of a portion C in FIG. 1, FIG. 6 is a sectional view taken along the line BB of FIG. FIG. 3 is a cross-sectional view showing a lateral hole portion having a different shape and a mode of press-fitting the fixed object.

In these figures, in FIGS. 1 to 4, the tire has one side opening from the shoulder regions (1a) and (1a) of the tread (1) to the side portion, and is substantially at an angle of 45 ° or less with respect to the rotation axis direction of the tire. A large number of deep lateral grooves (3) extending in the lateral direction are provided at substantially equal intervals in the tire circumferential direction.

In the center of the tread (1) of the tire, five vertical grooves (4) extending zigzag in the circumferential direction of the tire are provided at the same depth or the like as the lateral grooves (3), and two at both ends are respectively provided. And a sub-groove (5) connecting the vertical grooves (4) in a linear or zigzag manner is provided. , (4) and (5), a tread pattern of a block pattern having four rows of polygonal blocks (6) in the center of the tire tread (1) and blocks (7) of pentagonal shoulder regions on both sides thereof. As shown in FIGS. 1 to 5, four slits (1) are formed at the ridges of the side wall surfaces (2) located on the shoulders of the side surfaces of the tires of the block (7) in each shoulder region.
0) are formed at equal intervals in the horizontal direction.

Further, both ends of the lateral groove (3) adjacent to the base end of the block (7) in the shoulder region on the side closer to the groove bottom are provided with the first
As shown in FIGS. 6 to 6, the opening is provided at a position substantially equidistant from and horizontal to the bottom of the lateral groove (3) on both sides of the wall surface (2) of the tire side portion and is blocked in the tire width direction from the wall surface (2) of the side portion. A small-diameter cylindrical lateral hole (8) having a depth of about 2/3 of the depth of (7) is formed in parallel with the groove bottom of the lateral groove (3).

In each of the lateral holes (8), the rubber material in the lateral hole (8) portion has a cross-sectional area of 2 to 18 of the opening of the lateral hole (8).
Solids (9) each having a cross-sectional area twice as large and formed into a rod-like tip body or the like slightly shorter than the depth of the horizontal hole (8) are press-fitted and filled, respectively.

Also, lateral holes (8) opened in the wall surface (2) of the tire side portion and formed at both ends near the groove bottom of the adjacent lateral groove (3) at the base end of the block (7) in each shoulder region. As shown in FIG. 7 (a), for example, as shown in FIG. 7 (a), the opening is gradually expanded from the opening of the wall surface (2) toward the back to form a baseball bat-shaped cavity. ), A small-diameter cylindrical cavity having the same cross section from the opening to the back of the wall (2) can be considered. These are when the solid (9) is pressed into the inner back and filled. As shown in FIG. 7 (c), the opening of the lateral hole (8) provided longer than the solid material (9) at the back has a shape gently squeezed due to the elasticity of the rubber material. The solid (9) is stably held.

Further, as shown in FIG. 8 (a), the shape of the lateral hole (8) is larger than the diameter of the opening, and the inner diameter is made larger and the hole is pierced into a cylindrical cavity having a bulge inside. When the solid (9) is press-filled into the inner part, the opening is naturally squeezed as shown in FIG. 8 (b), and the solid (9) inside can be more stably held. It is suitable.

A lateral hole (8) having one end opened to the wall surface (2) of the tire side portion and being formed near the groove bottom of the lateral groove (3) in parallel with the groove bottom, and a rubber in the portion of the lateral hole (8) The index of the rolling speed of the tire, which leads to the occurrence of cracks at the groove bottom due to the change in the press-fitting ratio due to the cross-sectional area ratio with the solid material (9) molded from the same material and press-fitted into the lateral hole (8) ( The results of the experiment (N) are shown in the table of FIG. In the figure, D = outer diameter of the tire, L = mileage, When Nk = 1 is the total number of rotations of the tire that leads to the occurrence of cracks when k = 1, The numbers in the table indicate the positions of the side holes (8) at the side openings (of the central axis), that is, the positions from the bottom of the side grooves (3) shown in FIG. Indicates distance.

In addition, an experiment was conducted on the durability (crack resistance) of the tire in accordance with the change in the drilling position of the lateral hole (8), and the results shown in the table of FIG. 12 were obtained.

The tire size in this case is 10.000R20,
As shown in FIG. 6 (a), + and-at the position of the lateral hole (8) indicate + as the direction in which the groove depth becomes shallower and-as the direction in which the groove depth becomes deeper with respect to the bottom of the lateral groove (3). ing.

In addition, the gradient in FIG. 12 is the gradient of the straight line in FIG. 11, where + indicates durability improvement and-indicates reverse.

As is clear from the experimental results shown in the charts of FIGS. 11 and 12, the cross-sectional area ratio between the side hole (8) and the solid (9) is doubled in consideration of the stress relaxation due to rubber settling. Above this is necessary, below which tensile strain is eliminated by stress relaxation, while above 18 times the inner surface of the lateral hole (8) is too large and cracks are likely to occur from inside, and the opening of the lateral hole (8) at the time of filling Etc. are liable to be damaged by the maximum strain, and therefore it is necessary to set the range of 2 to 18 times.

If the position of the lateral hole (8) exceeds +10 mm (ie, in the direction to make the groove shallower), the tension is generated in the groove wall rather than compressing the groove bottom. If it exceeds 15 mm, the compression does not work efficiently on the groove bottom surface, and the belt end is too close to the belt end to cause another trouble. Therefore, it is necessary to set the position to +10 to -15 mm.

In the vulcanization molding of the tire, the lateral holes (8) are formed by previously projecting pins having shapes corresponding to the lateral holes (8) having a desired shape at predetermined positions in the molding mold. It is possible by putting.

Each small-diameter lateral hole (8) of the vulcanized tire is filled with a solid (9) having a larger diameter than the lateral hole (8) by post-processing. For example, using a known device for attaching a spike to a tire, the free end of the front end of the device is inserted into the lateral hole (8), and then widened to widen the lateral hole (8). The object (9) is pressed into the inner part of the lateral hole (8), after which only the free end of the apparatus is left, leaving the solid (9) behind.
It is possible by pulling it from inside.

The press-fitting and filling of the solid material (9) in the above-described embodiment is intended for the block (7) in the shoulder region, but like the block (7), one end is opened in the tire side wall surface (2). It goes without saying that the lug formed between 3) can be press-fitted and filled into the target.

The material of the solid (9) to be press-fitted is preferably the same as that of the tread rubber, but different materials such as rubber and plastic having different hardness can be used.

(Effect of the Invention) The present invention is a pneumatic radial tire configured as described above. When the tire is mounted on a wheel of a heavy-duty vehicle such as a large truck or the like, and is used, a lateral groove having one end opening in the tire side portion. The solid material is press-fitted into the tire near the groove bottom so as to apply a compressive strain to the rubber material in the vicinity including the bottom of the lateral groove at the time of non-contact, and to apply a tensile strain due to control and driving force at the time of contact with the ground. By that
The compressive strain preliminarily applied to the portion at the time of running or the like imparts the tensile strain applied to the bottom of the lateral groove to a large extent, and the generation of group cracks at the groove bottom caused by the tensile strain can be significantly suppressed or prevented.

Further, as described in claims 2 and 3, in a lateral hole pre-drilled from the side of the tire, a cross-sectional area press-filled with a solid material having a range of 2 to 18 times the lateral hole, or a lateral hole. The one with a bulging shape has a crack prevention function while the solid material is stably fixed without being pushed out from the side hole even under a heavy load due to the rubber contraction force of the side hole side and the large repulsion of the solid material. Can last.

Further, in the case where the position of the side hole at the side opening of the lateral hole is set to a depth range of +10 to -15 mm from the depth of the adjacent lateral groove, the compressive strain is efficiently increased up to the groove bottom surface. It has an extremely practical effect such as working and dispersing the tensile strain generated at the time of load to further prevent the occurrence of group cracks at the bottom of the lateral groove.

[Brief description of the drawings]

FIG. 1 is a partial plan view showing one embodiment of a pneumatic radial tire according to the present invention, FIG. 2 is a partial side view of FIG.
FIG. 3 is a sectional view taken along line AA of FIG. 1, and FIG.
FIG. 5 is an enlarged view of a portion D in FIG.
FIG. 6 is an enlarged view of a portion, FIG. 6 is a sectional view taken along line BB of FIG. 5,
7 and 8 are transverse cross-sectional views showing different shapes of lateral hole portions and the state of press-fitting solids, respectively. FIG. 9 is a partial plan view of a conventional tire, and FIG. 10 is a perspective view of another conventional tire. Figure, No.
FIGS. 11 and 12 show the experimental results of the index of the tire extension rotation speed leading to the occurrence of cracks at the bottom of the groove due to the change in the press-fit ratio between the side hole and the solid material, and the position of the side hole drilling position. 6 is a table showing experimental results of tire durability with changes. FIG. 13 is an explanatory diagram for explaining that the present invention exhibits effects. (1) ... tread tread, (1a) ... shoulder area, (2) ... shoulder contact end, (3) ... lateral groove, (4) ... vertical groove, (5) ... lateral groove, (6) ) Polygonal block, (7) Block of shoulder area, (8) Side hole, (9) Solid, (10) Slit.

Claims (4)

(57) [Claims] 1. A longitudinal groove continuously extending in a circumferential direction of a tire, and a large number of lateral grooves provided at substantially equal intervals at an angle of not more than 45 ° with respect to the tire rotational axis direction. A part of the pneumatic radial tire having a tread pattern formed by forming a lug or a block in a region including a shoulder contact end of a tread tread portion with one end opened in a sand portion of the tire, and one end opened in the side portion A solid material is press-fitted into the tire near the groove bottom of the lateral groove to apply a compressive strain to the rubber in the vicinity including the lateral groove bottom at the time of non-contact, and to apply tensile strain due to control and driving force at the time of contact. A pneumatic radial tire characterized by being filled. 2. The solid material is press-filled into a lateral hole having a cross-sectional area smaller than the cross-sectional area of the solid material, which is opened at one end from the side of the tire to the side portion and extends substantially in the width direction of the tire. 2. The cross-sectional area of the solid material is in the range of 2 to 18 times the cross-sectional area of the lateral hole.
The described pneumatic radial tire. 3. The pneumatic radial tire according to claim 1, wherein the lateral hole has a shape having a bulge inside. 4. The position of the lateral hole at the side opening is +10 from the groove bottom with respect to the arc extending in contact with the lateral groove bottom in the tire circumferential direction.
4. The pneumatic radial tire according to claim 2, wherein the pneumatic radial tire is located at a depth of about -15 mm.