JPS6259106A - Pneumatic tire - Google Patents

Abstract

PURPOSE:To suppress the eccentric abrasion by forming a recessed part which is departed from the shoulder edge and extends nearly in the circumferential direction of a tire onto the shoulder rib on the outermost side, in the captioned tire having a tread divided into a plurality of ribs by several main grooves extending in the circumferential direction. CONSTITUTION:The tread 1 of a radial tire has the ribs 3 and 4 divided by several wide main grooves 2 extending in zigzag form along the circumferential direction of the tire. In this case, a recessed part 7 extending nearly in the circumferential direction and departed in the direction of tire width from the shoulder edge 3a is formed on the shoulder rib 3 positioned on the both outermost sides of the tread. The recessed part 7 is formed so as to have the ridgelines 7a and 7b crossing with the surface 3a of the shoulder rib 3 and a recessed surface 7c formed with a single radius R7 of curvature between the ridgelines 7a and 7b, and the depth D7 is made 30% or less of the depth D2 of the contiguous main groove 2, and the width W7 is made 10-50% of the width W3 of the rib 3.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to pneumatic tires, and in particular to pneumatic tires used for high-speed driving on good roads, and also to tires of this type that are installed on trucks, buses, etc. This paper proposes an improvement in a tread pattern that is particularly suitable for use in heavy-duty pneumatic radial tires used in various applications.

(Prior art) As tread patterns for pneumatic tires that are mainly used for high-speed driving on good roads, in addition to the so-called completely piggyback trend pattern, rib/lug types, rib/block types, etc. are also used. However, in any case, the trend is divided in the axial direction of the tire by about 2 to 5 wide main grooves that extend roughly in the circumferential direction of the tire, and the trend is divided into multiple ridges (further circumferentially by the axial grooves). They have in common that they form ribs (hereinafter referred to as ribs), even when they are divided.

(Problem to be Solved by the Invention) One of the major drawbacks common to conventional pneumatic tires having the above-mentioned tread pattern is that each rib of the tread, especially the shoulder rib located at the outermost axial direction of the trend, There was a problem of noticeable uneven wear.

This uneven wear has various complicated aspects depending on the usage conditions and period of use of the tire, but as shown in Figures 10 and 11, in conventional pneumatic tires, the tread
Wear that begins at the outer end 103a of the first shoulder rib 103 progresses unevenly around the circumference of the tire to the inside of the tread. Eventually, the wear condition will develop as shown in the shaded area 105 in the figure (when the tire is viewed from the axial direction, the outer surface of the ribs has a wavy shape on the circumference, so the wavy A typical example is wear.

When such uneven wear occurs and expands, it not only makes the tire look extremely unsightly (it also causes vehicle vibration, etc.), it also significantly deteriorates the performance of the tire, and shortens the wear life of the tire. There is a problem in that it significantly reduces the

The present invention aims to advantageously solve the problem of uneven wear as described above without sacrificing reliability, and as a result, significantly improve the wear life of tires.

(Means for Solving the Problems) A pneumatic tire according to the present invention is a pneumatic tire in which a trend is divided into at least three ribs by at least two wide main grooves extending generally in the circumferential direction of the tire. The tire is characterized in that a concave portion is formed in the shoulder rib located at the outermost side of the tread among the ribs, the concave portion being spaced apart from the shoulder end and extending approximately in the circumferential direction of the tire.

Here, the term "outside" means the outside in the direction of the rotational axis of the tire. Furthermore, in this specification, "width" is measured in the direction of the rotation axis of the tire, and when the main groove has a zigzag shape, the width of the shoulder rib etc. is the outer edge of the zigzag ( A) shall be measured as the inside edge of the shoulder rib, etc.

(Function) The various types of uneven wear that occur on the shoulder ribs are caused by localized wear on the outer ends of the shoulder ribs due to the lateral force generated during cornering and the drag caused by the difference in diameter during straight running.
This becomes a nucleus and develops in the circumferential direction, axial direction, and depth direction, and progresses from edge drop wear to various types of uneven wear.

The present invention effectively suppresses the development of uneven wear and makes the tread wear uniform by forming a recess in the shoulder rib that is spaced apart from the shoulder end and extends substantially in the circumferential direction of the tire. In other words, the recess extends approximately in the tire circumferential direction and is lower than the outer surface of the rib end area of the shoulder rib in the cross section of the tire, which prevents local wear that has occurred from growing inside the shoulder rib. This recess allows for uniform blocking substantially in the circumferential direction.

Hereinafter, the present invention will be explained in more detail based on Examples.

(Embodiment) FIGS. 1 and 2 are diagrams showing a first embodiment, which is a typical example of a tread pattern of a pneumatic radial tire to which the present invention is applied, and FIG. 1 is a plan view thereof. As for the internal structure of the tire, it is very common for this type of tire to combine a radial carcass with a highly rigid belt placed around the crown and a trend that surrounds the outer circumferential surface of this belt. , the explanation will be omitted below.

The tread 1 has at least three (five in this embodiment) wide main grooves 2 with at least two (four in this embodiment) wide main grooves 2 extending in a zigzag shape generally along the circumferential direction of the tire.
The ribs are divided into 3.4 ribs, and among these ribs,
Shoulder rib 3 located on the outside of the trend rainfall,
A recess 7 is formed that is spaced apart from the shoulder end 3a in the tire width direction and extends approximately in the circumferential direction. It has a concave surface 7C formed by a radius of curvature R1. It is preferable that the ridgeline 7a of the recessed portion 7 on the shoulder end 3a side is provided linearly in the tire circumferential direction.

As shown in FIG. 2, in the cross section of the tire, the concave surface 7C of the concave portion 7 is positioned lower in the radial direction of the tire from the ridgeline 7a toward the tire equator. As described above, since the concave surface 7c of the concave portion 7 extending approximately in the circumferential direction is located low, local wear generated in the vicinity of the shoulder end 3a is effectively prevented from growing inside the tread, and uneven wear is less likely to occur.

Here, the cross-sectional shape of the recess 7 does not necessarily have to be arcuate.

The depth of the recess 7 in the tire radial direction (2 m in this example) is desirably 30% or less of the depth Dt of the adjacent main groove 2 (13 fi in this example), preferably 0.3 m.
~3 cranes and ink.

Further, as shown in FIG. 2, the axial width W of the recess 7 (that is, the width between 7a and 7b, 15 in this embodiment) is the width W of the shoulder rib 3! (i.e. A and 3
The width between a (in this example, 35 fins) is preferably 10 to 50%, more preferably 20 to 50%.

Further, the distance W311 (in this embodiment, 10
n) is desirably 10% or more of the width W of the shoulder rib 3, more preferably 20 to 40%.

FIG. 3 is an enlarged perspective sectional view showing a second embodiment of the pneumatic radial tire according to the present invention.

In the second embodiment, the concave portion 17 of the tread 11 divides the concave surface 17c between the ridge lines 17a and 17b at both ends in the tire rotation axis direction into three regions 13, 14 and 15 in the tire rotation axis direction, and has two types of curvature. Radius RI! , R.I.
4. Other than what has been mentioned above, this embodiment is the same as the first embodiment, and the explanation will be omitted.

Although this second embodiment shows a case where the recess 17 is formed with two types of radii of curvature, the present invention is not limited to this example. There may be.

FIG. 4 is an enlarged perspective sectional view showing a third embodiment of the pneumatic radial tire according to the present invention.

In the third embodiment, in the concave portion 27 of the tread 21, the ridge line 27b on the inner side in the tire rotation axis direction of the concave surface 27c is radially inward from the line A on the extension line 23 of the radius of curvature R1 forming the surface 3b of the shoulder rib 3. It is located in

The rest is the same as the first embodiment, and the explanation will be omitted.

FIG. 5 is an enlarged perspective sectional view showing a fourth embodiment of the pneumatic radial tire according to the present invention.

In the fourth embodiment, in the recessed portion 37 of the shoulder rib 3 of the tread 31, the inner ridgeline 37b of the recessed surface 37c in the tire rotation axis direction is a line A on the extension line 33 of the radius of curvature R1 forming the surface 3b of the shoulder rib 3. The team is set up to lose once and for all. Other than that, it is the same as the first embodiment,
The explanation will be omitted.

As described above in the first to fourth embodiments, in short, the recess formed in the shoulder rib 3 is spaced apart from the shoulder end 3a, and is provided so as to be located substantially in the tire circumferential direction and low in the radial direction. The cross-sectional shape of the recess 7 may be of any shape as long as it can prevent the local wear generated near the shoulder end 3a from growing inward.

FIG. 6 and FIG. 7 are diagrams showing a fifth embodiment of the pneumatic tire according to the present invention.

The fifth embodiment is a case in which the shoulder rib 3 in the first embodiment has an axial lug groove 45. The present invention also provides the shoulder rib 3 in such a tread 41.
A recessed portion 47 is formed spaced apart from the shoulder end 3a and extending substantially in the circumferential direction. A ridgeline 47a on the shoulder end 3a side of the recess 47 is provided in a straight line in the tire circumferential direction with the lug groove 45 interposed therebetween.

The second embodiment is the same as the first embodiment except for having the lug groove 45, and the explanation thereof will be omitted.

FIG. 8 and FIG. 9 are views showing a sixth embodiment of the pneumatic tire according to the present invention.

In the sixth embodiment, the shoulder rib 3 in the first embodiment is further divided in the circumferential direction by an axial groove 52, and a block 5
3 is formed. In the present invention, even in such a tread 51, a recess 57 is formed in the block 53, spaced apart from the outer end 53a of the block 53, and extending substantially in the circumferential direction. A ridgeline 57a on the outer end 53a side of the recess 57 is provided in a straight line in the tire circumferential direction with the groove 52 in between. The second embodiment is the same as the first embodiment except for having the groove 52, and the explanation thereof will be omitted.

(Effects of the Invention) Next, two types of test tires were prepared and the effects of the present invention were tested and will be described.

All tire sizes are 10.0OR20 (inner pressure 7.2
It is a pneumatic radial tire with a load capacity of 5 kg/cnl (JIS standard load), and its internal structure is conventional.

The test tires were manufactured in the same manner using the same construction materials, using the tire of the invention for the first example (FIG. 1) and the conventional tire for the comparative example (FIG. 10). In the test, the tire was attached to the front wheel axle (steering shaft) of a heavy-duty truck vehicle, traveled 50,000 km, and the uneven wear resistance performance was investigated.

The uneven wear resistance performance was evaluated by evaluating the uneven wear that occurred in the shoulder rib and reached the outermost main groove by the uneven wear step amount and the number of uneven wear occurrences, and is shown in the table below. In addition, other performances such as steering stability and braking performance were at a sufficient level.

In the table, the amount of uneven wear step is measured by measuring the amount of step in the radial direction of wear in one uneven wear area.
It is expressed as an index.

As shown in the table above, compared to conventional tires, the tires of the present invention have an extremely small number of occurrences of uneven wear, and the amount of uneven wear steps is also extremely small (and the uneven wear resistance has been greatly improved). There is.

As explained above, according to the present invention, both steering stability and braking performance are at a sufficient level, and uneven wear resistance can be significantly improved while maintaining these tire performances.

[Brief explanation of the drawing]

1 and 2 are diagrams showing a first embodiment of a pneumatic tire according to the present invention, FIG. 1 is a partial plan view thereof, and FIG. 2 is a cross section taken along the line ■-■ in FIG. 1. It is a diagram. FIG. 3 is a perspective sectional view of a main part showing a second embodiment of the pneumatic tire according to the present invention. FIG. 4 is a perspective sectional view of a main part showing a third embodiment of a pneumatic tire according to the present invention. FIG. 5 is a perspective sectional view of a main part showing a fourth embodiment of a pneumatic tire according to the present invention. 6 and 7 are views showing a fifth embodiment of the pneumatic tire according to the present invention, FIG. 6 is a partial plan view thereof,
FIG. 7 is a sectional view taken along the line ■-■ in FIG. 6. 8 and 9 are diagrams showing a sixth embodiment of the pneumatic tire according to the present invention, FIG. 8 is a partial plan view thereof, and FIG. 9 is a cross section taken along the line IX-IX in FIG. 8. It is a diagram. 10 and 11 are diagrams showing a conventional tire, with FIG. 10 being a partial plan view thereof, and FIG. 11 being a sectional view taken along the line XI-XI in FIG. 10. 1.11.21.31.41.51 Trend, 2 Main groove, 3 Shoulder rib, 7.17.27.37.47.57・Old... recess.

Claims (4)

[Claims] (1) In a pneumatic tire in which the tread is divided into at least three ribs by at least two wide main grooves extending generally in the circumferential direction of the tire, a shoulder rib located at the outermost side of the tread among the ribs has a shoulder A pneumatic tire characterized by forming a concave portion spaced apart from an end and extending substantially in the circumferential direction of the tire. (2) The pneumatic tire according to claim (1), wherein the depth of the recess is 30% or less of the depth of the adjacent main groove. (3) The width of the recess is 10 to 50 times the width of the shoulder rib.
% of the pneumatic tire according to claim (1). (4) The pneumatic tire according to claim (1), wherein the amount of separation from the shoulder end of the recess in the tire width direction is 10% or more of the width of the shoulder rib.