JP2002046421A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of increasing f wet performance related to a water drainage when a wear is advanced by holding superior dry steering stability performance and eccentric wear resistance of a shoulder part. SOLUTION: This pneumatic tire comprises one or more radial carcasses and belts, and one shoulder circumferential groove on both sides of a tread part. The tread part comprises a hollow-shaped lateral groove open from the positions on both sides of a tread near the end edge to a tread part side face toward a tire inner radial direction and extending through the inside of a shoulder rib formed of the groove from an opening position to the shoulder circumferential groove beyond a belt maximum width end in the tire outer radial direction.

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 a radial ply tire for use in a relatively small vehicle such as a passenger car or a small truck, and more particularly to a pneumatic tire for controlling the tread rubber at an early stage of wear. The present invention relates to a pneumatic tire that exhibits excellent performance in stable performance and uneven wear resistance, and exhibits excellent wet performance when wear is advanced.

[0002]

2. Description of the Related Art A conventional pneumatic tire 21 shown in FIG. 3 is a tread section 23 for securing traction / braking performance and steering stability on a wet road surface to a certain level or more. The tread surface 23t is provided with two or more circumferential grooves, in the illustrated example, two shoulder circumferential grooves 25,
On the side surface of the tread portion 23, there is provided a lug forming recess groove 26 short enough to recess the tread rubber 28.

[0003] However, the pneumatic tire 21 shown in FIG. 3 is assumed to have insufficient traction / braking performance and drainage performance. To improve this, another conventional pneumatic tire 21 shown in FIG. In the pneumatic tire 31 of the example, similarly to the tire 21, two shoulder circumferential grooves 35 are provided on the tread surface 33t of the tread portion 33, and further, a shoulder lug forming groove 36 extending from the side surface of the tread portion 33 to near the shoulder circumferential groove 35. Are provided on the tread rubber 38.

[0004]

However, as the tread rubbers 28, 38 wear with the running of the tire, the shoulder circumferential grooves 2 provided in the tread portions 23, 33 are not provided.
The groove widths of the grooves 35 and 35 and the shoulder lug forming groove 36 become narrower, and the groove having a relatively shallow depth disappears. The narrowing of the groove width and the disappearance of the groove, particularly when the tires 21 and 31 run on a wet road surface, significantly reduce the drainage performance and bring about a disadvantage that the running safety is impaired.

[0005] It is possible to solve this kind of inconvenience by increasing the number of grooves and the groove length, and further increasing the groove depth. However, these countermeasures all reduce the rigidity of the tread land portion, so that the steering stability on a dry road surface is reduced. In particular, in the case of the shoulder lug forming groove 36 shown in FIG.
Toe (hereinafter referred to as H & T) causes uneven wear called shoulder wear on the shoulder ribs.

Accordingly, the first to tenth aspects of the present invention are to completely solve the above-mentioned disadvantages. Specifically, the steering stability on a dry road surface and the uneven wear resistance of a shoulder portion are provided. It is an object of the present invention to provide a pneumatic tire that maintains wetness at an excellent level and improves wet performance related to drainage when abrasion of tread rubber progresses.

[0007]

According to a first aspect of the present invention, there is provided a radial carcass having at least one ply, and a belt for reinforcing a tread portion around the outer periphery of the radial carcass. In a pneumatic tire having one shoulder circumferential groove on each side of the tread portion, the tread portion opens on each side surface of the tread portion inward in the tire radial direction from a position near the edge on both sides of the tread, and the opening position A plurality of cave-shaped lateral grooves extending from the shoulder rib formed in the shoulder ribs and extending beyond the belt maximum width end outward in the tire radial direction inside the shoulder ribs formed by the grooves. .

[0008] The present invention described in claim 1 relates to claim 2.
As described above, the cave-shaped lateral groove has a shape in which the radial height of the tire increases from the groove bottom at the end where the cave-like groove extends to the opening position on the side surface of the tread portion.

According to the first and second aspects of the present invention, as in the third aspect of the present invention, the cave-shaped lateral groove has a chamfer having an arc-shaped cross section at an inner edge of the opening in the radial direction of the tire. Having.

According to the first to third aspects of the present invention, as in the fourth aspect of the present invention, the cave-shaped lateral groove is branched into two or more acute angles on the way from the groove bottom to the side surface of the tread portion. And each of the branch grooves has an opening on the side surface of the tread portion, and in relation to the invention described in claim 4, as in the invention described in claim 5, the tread portion side surface has a cave-like lateral direction. A rib sandwiched by the branch grooves adjacent to the groove is provided, and the rib is used as a reinforcing rubber member of the branch groove.

According to the first to fifth aspects of the present invention, as in the sixth aspect of the present invention, the distance from the tire radial line passing through the tread edge to the front end of the cave-like lateral groove is defined by the shoulder circumference. 0 of the distance from the outermost edge of the directional groove to the tread edge.
It shall be at least one time.

Further, according to the invention described in claims 1 to 6, as in the invention described in claim 7, the outermost layer of the belt passing through the center of the bottom of the tip groove of the cave-shaped lateral groove in the tire cross section. The distance from the center of the groove bottom, measured from the groove bottom center position, to a curve parallel to the tread surface passing through a half depth position of the groove depth of the shoulder circumferential groove is set to 0 mm or more, and described in claims 1 to 7. Regarding the invention, the minimum gauge from the tread width direction bottom of the cave-like lateral groove to the belt is set to 2.5 mm or more as in the invention described in claim 8.

Further, according to the invention as set forth in claims 1 to 8, as in the invention as set forth in claim 9, the cave-like lateral groove is provided between the center of the bottom of the leading groove and the edge of the tread. The lateral grooves have a ratio of height to width at the same location of 0.
It has a shape in the range of 5-1.5.

The tire according to the first to ninth aspects of the present invention is the same as the tenth aspect of the invention, except that the tread portion forming segment and the sidewall portion forming and the cave-like lateral groove forming are formed integrally. The surface to be engaged with the side mold is vulcanized using a split mold provided on the tread portion tread between the tread edge and the outermost edge of the shoulder circumferential groove.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. 1 and 2. FIG. FIG. 1 is a sectional view of the left half of the pneumatic tire of the present invention, and FIG.
FIG. 5 is a sectional view of a left half main part of another pneumatic tire according to the present invention.

In FIGS. 1 and 2, a pneumatic tire (hereinafter referred to as a tire) 1 has one ply or more.
It has a radial carcass 2 of a ply and a belt 4 for reinforcing the tread portion 3 around the outer periphery of the radial carcass 2. The tread portion 3 has one shoulder circumferential groove 5 extending in the circumferential direction on the tread surface 3t on each side thereof. The groove 5 may be zigzag or straight.

Here, the tread portion 3 has a plurality of cave-like lateral grooves which open on the side surface TS of the tread portion 3 inward from the vicinity of the edge Te on both sides of the tread surface 3t in the tire radial direction (hereinafter referred to as radial direction). 6. Cave-like lateral groove 6
Moves from the opening position to the shoulder circumferential groove 5, and the inside of the shoulder rib 7 formed by the circumferential groove 5
Extends beyond the maximum width end 4MWE radially outward. The cave-shaped lateral groove 6 does not show the shape of the lateral groove from a new tire to a predetermined wear amount of the tread rubber 8.

The tread surface 2 is used up to a predetermined amount of wear of the tread rubber 8.
By providing a cave-like lateral groove 6 that does not appear at t
(1) In the case of the thick gauge tread rubber 8 where dry steering stability is disadvantageous, the shoulder rib 7 retains excellent steering stability and the thin groove tread rubber 8 where steering stability is advantageous, and the lateral grooves 6 appear. The dry steering stability performance can be maintained at an excellent level throughout the entire wear period. (2) Since the cave-like lateral grooves 6 only open in the side surface TS of the tread portion 3, the tread rubber 8 has a thickness gauge. H of the shoulder rib 7 which has a property that is more likely to occur when
& T abrasion can be prevented. (3) As the wear of the tread rubber 8 progresses, in the conventional tire, when the wet performance related to drainage is reduced, the lateral groove 6 appears, and the cross-sectional area of the groove is greatly increased. As the amount increases, drainage is improved, and excellent wet performance can be exhibited, and traction and brake performance can also be improved.

The details of the cave-shaped lateral groove 6 will be described below. First, the cave-shaped lateral groove 6 has a shape in which the height in the radial direction increases in a tapered shape as it goes from the groove bottom 6b at the leading end to the opening position of the side surface TS of the tread portion 3. This contributes to increasing the drainage effect when the lateral grooves 6 appear. The tread pattern of the tire 1 is formed by a well-known pitch distribution, and it is suitable to provide one or more cave-shaped lateral grooves 6 per pitch.

Next, the cave-shaped lateral groove 6 has a chamfer having an arc-shaped cross section at the radially inner edge of the opening. This also contributes to increasing the drainage effect when the lateral grooves 6 appear as described above.

Next, the cave-like lateral groove 6 has a branch groove (not shown) which branches at two or more acute angles on the way from the groove bottom 6b at the leading end thereof to the side surface of the tread portion 3. Yes, each branch groove is opened on the side surface of the tread portion 3. Of course, cave-shaped lateral grooves 6 without branch grooves
Also exists. This further enhances the drainage effect of the lateral grooves 6 when appearing on the tread 2t.

In connection with this, the side surface of the tread portion 3
A rib (not shown) sandwiched between the adjacent branch grooves of the cave-shaped lateral groove 6 is provided. The rib serves as a reinforcing rubber member between the branch grooves.

Next, the tire 1 passing through the edge Te of the tread 3t
From the outermost edge 5e of the shoulder circumferential groove 5 to the tread 3
It is appropriate that the distance R be at least 0.1 times the distance R to the edge Te. If it is less than 0.1 times, the drainage performance of the lateral groove 6 becomes insufficient. Cave-like lateral groove 6 shown in FIG.
Is opened in the shoulder circumferential groove 5, and in this case, drainage when the groove 6 appears is further enhanced compared to the cave-like lateral groove 6 shown in FIG. Therefore, in the use condition in which the wet performance of the tread rubber 8 as viewed in the shoulder circumferential groove 5 is particularly important after the middle stage of wear, it is preferable to use the cave-like lateral groove 6 shown in FIG.

Next, in the cross section of the tire 1, a shoulder measured from the center position of the groove bottom 6b on the normal line L _{V of the} outermost layer of the belt 4 passing through the center position of the tip groove bottom 6b of the cave-shaped lateral groove 6 tread through the 1/2 depth position of the groove depth d ₅ of the circumferential groove 5 3t
The distance A to the curve L parallel to is set to 0 mm or more. If this value is less than 0 mm, that is, a negative value, the cave-like lateral grooves 6 appear on the tread surface 3t from the initial stage of wear of the tread rubber 8, resulting in a decrease in dry steering stability performance due to a decrease in rigidity and occurrence of uneven wear. This is unsuitable because the same adverse effects as those of the conventional tire are likely to occur.

Next, it is appropriate that the minimum gauge B from the tread surface 3t in the width direction of the cave-shaped groove 6 to the belt is set to 2.5 mm or more. Thereby, at the time of vulcanization molding of the tire 1, local deformation of the belt 4 due to the projection for forming the cave-like lateral groove 6 of the vulcanization mold can be eliminated.

Next, in FIG. 1, between the center position of the tip groove bottom 6b of the cave-like lateral groove 6 and the tread edge Te, the cave-like lateral groove 6 has a width of the same height. It is suitable that the value of the ratio to has a shape in the range of 0.5 to 1.5. This shape maintains the steering stability performance on dry road surfaces and the uneven wear resistance of the shoulder portion at an excellent level, and contributes to the improvement of the wet performance relating to drainage when the wear of the tread rubber 8 progresses.

Finally, the tire 1 is suitably formed by vulcanization using a split mold (not shown). At this time, the split mold includes a tread portion 3 forming segment, a sidewall portion 9 forming and a cave. In combination with the integral side mold for forming the lateral grooves 6, the engaging surfaces of these molds are formed on the tread portion 3t between the tread edge Te and the outermost edge 5e of the shoulder circumferential groove 5. Position. Thus, the tire 1 can be produced without any trouble. The engaging surface of the conventional split mold is located radially inward of the cave-like lateral groove 6.

[0028]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A radial ply tire for a light truck, having a size of 195 / 70R15 LT, was subjected to vulcanization molding using the split mold described above in accordance with the configuration shown in FIG. For the cave-shaped lateral groove 6, the value of the ratio D / R is 0.
5, the distance A was 3 mm, the minimum gauge B was 3 mm, and one tread pattern was provided for each pitch. This example tire could be vulcanized and formed without any trouble using the split mold of the type described above.

In order to evaluate the performance of the example tires, a conventional tire 1 having a recessed groove 26 shown in FIG. 3 and a conventional tire 2 having a shoulder lug forming groove 36 shown in FIG. 4 were prepared. Except for the grooves 26 and 36, all were adjusted to the example tires.

Using these tires as test tires, a comparison test was performed on the wet performance related to drainage between a new tire and a 50% wear, and the H & T step difference was measured at a 20% wear. The results of the wet performance comparison test are as follows.
The index is represented by an index of 00, and the larger the value, the better, and the average value of the H & T steps is shown in Table 1.

[0031]

[Table 1]

From Table 1, it can be seen that the tires of the example show the same wet performance as the conventional tire 1 when they are new, but are superior to the conventional tire 1 in the most problematic middle wear period, and the H & T uneven wear. When the wear is most likely to occur at 20% wear, the example tire exhibits uneven wear resistance remarkably superior to the conventional tire 2 and has uneven wear resistance close to that of the conventional tire 1 which only has the recessed groove 26. You can see that it is doing. In addition, with respect to the dry steering stability performance until the cave-shaped lateral groove 6 appeared, it was also verified that the example tire exhibited superior performance to the conventional tire 2 and exhibited the same performance as the conventional tire 1. I have.

[0033]

According to the first to tenth aspects of the present invention, by providing a cave-shaped lateral groove in the shoulder portion, the dry steering stability performance, which is a problem particularly when a new product is used, is maintained at an excellent level. In addition, it is possible to provide a pneumatic tire that suppresses uneven H & T wear, which is likely to occur at an early stage of wear, and improves wet performance, which becomes a problem after the middle stage of wear, without any trouble in manufacturing.

[Brief description of the drawings]

FIG. 1 is a sectional view of a left half of a pneumatic tire according to the present invention.

FIG. 2 is a cross-sectional view of a left half main part of another pneumatic tire according to the present invention.

FIG. 3 is a sectional view of a left main part of a conventional pneumatic tire.

FIG. 4 is a sectional view of a left half of a main part of another conventional pneumatic tire.

[Explanation of symbols]

 Reference Signs List 1 tire 2 carcass 3 tread portion 3t tread surface 4 belt 4 MWE belt maximum width end 5 shoulder circumferential groove 5e shoulder circumferential groove outermost edge 6 cave-like lateral groove 6b groove bottom 7 shoulder rib 8 tread rubber 9 sidewall portion Te tread end Edge TS Tread side

Claims (10)

[Claims] 1. A pneumatic tire having one or more plies of a radial carcass and a belt for reinforcing a tread portion on the outer periphery of the radial carcass, and having one shoulder circumferential groove on each side of the tread portion. Open from the position near the edge on both sides of the tread to the tread portion side surface going inward in the tire radial direction, and from the opening position to the shoulder circumferential groove, the inside of the shoulder rib formed by the groove passes through the belt maximum width end to the tire radial direction. A pneumatic tire having a plurality of cave-shaped lateral grooves extending outwardly. 2. The tire according to claim 1, wherein the cave-shaped lateral groove has a shape in which a height in a tire radial direction increases from a groove bottom at a tip end of the cave-like groove toward an opening position on a side surface of the tread portion. 3. The tire according to claim 1, wherein the cave-shaped lateral groove has a chamfer having an arc-shaped cross section at an inner edge in the tire radial direction of an opening thereof. 4. The cave-shaped lateral groove has two or more branch grooves branching at an acute angle on the way from the groove bottom to the tread side surface, and each branch groove is open to the tread side surface. The tire according to any one of Items 1 to 3. 5. The tire according to claim 4, wherein the side surface of the tread portion has a rib sandwiched between adjacent branch grooves of the cave-shaped lateral groove, and the rib serves as a reinforcing rubber member of the branch groove. 6. The distance from the tire radius line passing through the tread edge to the groove bottom tip of the cave-like lateral groove is 0.1 times or more the distance from the outermost edge of the shoulder circumferential groove to the tread edge. The tire according to any one of claims 1 to 5, comprising: 7. The groove depth of the shoulder circumferential groove measured from the groove bottom center position on the normal to the outermost layer of the belt passing through the center position of the tip groove bottom of the cave-like lateral groove in the cross section of the tire. / 2
The tire according to any one of claims 1 to 6, wherein a distance to a curve parallel to the tread surface passing through the depth position is set to 0 mm or more. 8. The tire according to claim 1, wherein a minimum gauge from the bottom of the cave-like lateral groove in the tread width direction to the belt is at least 2.5 mm. 9. Between the center of the bottom of the cave-like groove and the edge of the tread, the cave-like groove has a height-to-width value of 0.5 at the same position. The tire according to any one of claims 1 to 8, wherein the tire has a shape in a range from 1.5 to 1.5. 10. The engagement surface between the tread portion forming segment and the integral side mold for forming the sidewall portion and forming the cave-shaped lateral groove is formed between the tread edge and the outermost edge of the shoulder circumferential groove. The tire according to any one of claims 1 to 9, wherein the tire is formed by vulcanization molding using a split mold provided on the tread surface of the tread portion.