JPH11278016A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the generation of pattern noise and to prevent the occurrence of uneven wear. SOLUTION: A shoulder part is extended in a direction crossing the peripheral direction of a tire and lateral grooves 4 opened at a tread edge are formed at intervals in a peripheral direction, and a shoulder land part is formed between the lateral grooves (4), 4. In a so formed pneumatic tire, a tie bar 7 is formed to interconnect shoulder lands adjoining with each other in the peripheral direction of a tire and protrude from the groove bottom of the lateral groove 4 and have height (h) being 40-60% of the groove depth D of the lateral groove 4. The tie bar 7 is provided with a two-end non-opening fine groove 9 extending along the lateral groove 4 and having two ends terminating at the internal part of the tie bar 7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire having improved pattern noise and uneven wear without impairing the appearance during wear, and more particularly to a pneumatic radial tire for a passenger car.

[0002]

2. Description of the Related Art Conventionally, in order to ensure the drainage performance of a tire, a technique of expanding a groove volume is adopted. In order to increase the groove volume, the width or depth of a vertical main groove extending continuously in the tire circumferential direction or a horizontal groove extending in a direction intersecting with the vertical main groove is increased. However, such an increase in groove volume tends to cause a decrease in rigidity of a block or the like formed on the tread surface. In particular, if the rigidity of the block arranged on the shoulder side of the tread portion is insufficient, there is a problem that uneven wear such as shoulder wear easily occurs.

In order to solve such a problem, as shown in FIG. 4, a lateral groove g extending in the tire axial direction on the shoulder side s of the tread surface t is formed so as to protrude from the groove bottom and have a groove depth of the lateral groove g. It has been proposed, for example, in Japanese Patent Publication No. 57-9967 to provide a tie bar a having a raised height of 40 to 80% to prevent uneven wear of the shoulder-side blocks b1 and b2.

[0004]

SUMMARY OF THE INVENTION The aforementioned Japanese Patent Publication No. 57-99.
A tie bar a proposed in Japanese Patent Publication No. 67 (referred to as a buttress in this publication) has a narrow groove e extending along the horizontal groove g and both ends penetrating the tie bar a. Such a narrow groove e appears on the tread surface t at the same time as the tie bar a when the tread surface t is worn. Therefore, the tie bar a
Can be prevented to some extent from deterioration of the appearance of the tire at the time of abrasion, as compared with the case where appears alone.

[0005] As a result of various experiments by the present inventors, such a tie bar a has a rigidity of the tie bar itself in connection with increasing the circumferential rigidity of the blocks arranged in the front and rear direction of the tire. It has been found that by optimally adjusting, a tire noise reduction effect called pitch noise or pattern noise can be exerted.

However, when the tie bar a is provided with a narrow groove e penetrating both ends in the tire axial direction as disclosed in Japanese Patent Publication No. 57-9967, rigidity of the tie bar is insufficient for reducing pattern noise. It has been found that the tire noise reduction effect is small.

[0007] The present invention has been devised in view of such problems, and has as its object to provide a pneumatic tire capable of suppressing uneven wear and reducing pattern noise without impairing the appearance during wear. And

[0008]

According to the first aspect of the present invention, the shoulder portion extends in a direction intersecting the circumferential direction of the tire and a lateral groove which is opened at a tread edge is spaced apart in the circumferential direction of the tire. A pneumatic tire having a shoulder land portion formed between lateral grooves, wherein the lateral groove protrudes from a groove bottom of the lateral groove, connects the shoulder land portions adjacent to each other in the tire circumferential direction, and has a raised height h of the lateral groove. 40-60% of groove depth D
And a narrow groove extending along the lateral groove and having both ends non-opening at both ends is provided inside the tie bar.

In the invention according to claim 2, the narrow groove is
The groove width w is 0.5 to 1.5 mm, the groove depth d is 80 to 100% of the ridge height h, and the groove length GL is 40 to 80% of the tie bar length TL. The pneumatic tire according to claim 1, wherein:

According to a third aspect of the present invention, the shoulder land portion is formed between an outer longitudinal main groove disposed on the outermost side in the tire axial direction and the tread edge, and extends in the tire circumferential direction. The tie bar is formed between an outer shoulder block on the outer side in the tire axial direction divided by the sub-groove and an inner shoulder block disposed on the inner side in the tire axial direction, and between the inner shoulder blocks adjacent in the tire circumferential direction. The pneumatic tire according to claim 1 or 2, further comprising:

[0011]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows an example of a tread surface 2 of the radial tire for a passenger car according to the present embodiment. On the tread surface 2, there are formed grooves including a plurality of vertical main grooves 3 extending in the tire circumferential direction, and horizontal grooves 4 extending in a direction intersecting the shoulder SH with the tire circumferential direction and opening at the tread edge E. .

In the present embodiment, the vertical main groove 3 includes a central vertical main groove 3a extending continuously in the tire circumferential direction on the tire equator C,
A total of three grooves are arranged on both sides thereof, including outer vertical main grooves 3b, 3b extending continuously in the tire circumferential direction.
In the present embodiment, the lateral groove 4 extends from the tread edge E in a direction intersecting the shoulder SH with the circumferential direction of the tire, crosses the outer vertical main groove 3b inward in the tire axial direction, and forms a crown CR.
, And ends at the front end without reaching the central vertical main groove 3a.

In the present embodiment, each of the vertical main grooves 3a and 3b extends linearly in the tire circumferential direction. For example, the tread width TW is a groove width which is the distance between the tread edges E and E in the tire axial direction.
Is preferably about 2.5 to 7%, and in this example, 4%
Are exemplified. In addition, each vertical main groove 3a, 3b
For example, various shapes such as a zigzag groove or a mixture of a linear groove and a zigzag groove can be adopted.

Further, in the present embodiment, the lateral groove 4 is shown as an example in FIG.
The width of the lateral groove 4 is 1.5 to 6 of the tread width TW.
%, And in this example, the width is smaller than that of the vertical main groove 3 and about 3% of the tread width TW. The inclination of the lateral groove 4 is not limited to the example, but may be parallel to the tire axial direction, curved, or the like, or substantially V-shaped by being inclined in the opposite direction with respect to the tire equator C. Various forms such as eggplant can be adopted.

The tread surface 2 is formed by the vertical main grooves 3 and the horizontal grooves 4 so as to form the crown land portions 5, 5 between the central vertical main groove 3a and the outer vertical main groove 3b, and the outer vertical main groove. The shoulder land portions 6, 6 between 3b and the tread edge E are formed.

The crown land portion 5 is formed by a small groove 12 extending in the circumferential direction of the tire, the lateral groove 4 and an inclined small groove 13 having a small length extending from the central vertical groove 3a. It is divided into a crown block B1 and an outer crown block B2.

In the present embodiment, the shoulder land portion 6 is provided with an outer vertical main groove 3b disposed on the outermost side in the tire axial direction.
And an outer shoulder block 6A formed on the outer side in the tire axial direction and defined by a sub-groove 14 formed between the tread edge E and the circumferential direction of the tire, and an inner shoulder disposed on the inner side in the tire axial direction. FIG. 6 shows a block 6B. The sub-groove 14 has a small depth, about 15 to 40% of the groove depth D of the lateral groove 4 in this example.

These shoulder blocks 6A, 6B
Indicates that the center of gravity of the block is the tread width T
An example is shown that is included in the shoulder portion SH, which is a region on both sides when W is divided into three equal parts.

In this embodiment, FIGS. 1 and 2 (FIG. 1)
AA cross section of FIG. 3) and FIG. 3 (BB cross section of FIG. 1), each of the inner grooves adjacent to each lateral groove 4 in the tire circumferential direction by protruding from a groove bottom 4a of the lateral groove 4. Tie bars 7 each having a height of 40% to 60% of the groove depth D of the lateral groove 4 are formed one by one along the shoulder groove 6B. One end of the tie bar 7 is open and both ends are not open.
An example in which the narrow grooves 9 are provided is illustrated.

Such a tie bar 7 can increase the rigidity of the inner shoulder block 6B in the tire circumferential direction,
It is possible to effectively suppress the falling into the lateral groove side, and it is possible to suppress uneven wear such as heel and toe wear of the shoulder block. Also tie bar 7
Has a narrow groove 9 so that the narrow groove 9 can be made to appear on the tread surface 2 together with the tie bar 7 at the time of wear.
Deterioration of appearance can be prevented. The narrow groove provided in the tie bar 7 has a non-open end that terminates inside the tie bar 7, thereby preventing the stiffness of the tie bar 7 from lowering, reducing the pattern noise, and maintaining a relatively long period of time.
It can be left on the surface of the tie bar 7.

Further, in the present embodiment, an example is shown in which the outer shoulder block 6A is not provided with a tie bar. As a result, even when the tie bar 7 appears on the tread surface 2 due to the progress of wear, the drainage performance is enhanced by the vertical main groove 3b outside the tie bar 7 in the axial direction and the horizontal groove 4 outside the tie bar 7 in the axial direction. Can be secured. In particular, when the tie bar 7 is provided also on the outer shoulder block 6A, drainage tends to decrease.

Here, the raised height h of the tie bar 7 is
It is necessary to set the groove depth D of the lateral groove 4 to 40 to 60%. If the height h is less than 40% of the groove depth D of the lateral groove 4, the effect of reducing pattern noise and the effect of suppressing uneven wear are reduced. On the contrary, if the height h exceeds 60%, the appearance during wear is reduced. Tends to worsen.

The narrow groove 9 formed in the tie bar 7
For example, the groove width w is 0.5 to 1.5 mm, and the groove depth d is 60 to 80%, more preferably 80 to 100% of the height h of the tie bar 7, and the surface of the tie bar 7 The groove length GL measured in the step is 60 to 8 of the tie bar length TL.
It is preferably set to 0%.

If the groove width w of the narrow groove 9 is less than 0.5 mm, it is difficult to process such a groove, and the groove is too narrow, so that a decorative effect tends not to be expected when worn. When it exceeds 0.5 mm, the rigidity of the tie bar 7 is reduced, so that the effect of reducing the pattern noise cannot be expected, and the tie bar 7 tends to be worn out early.

The groove depth d of the narrow groove 9 (shown in FIG. 2)
However, if the height h of the tie bar 7 is less than 80%, the appearance at the time of wear tends to be deteriorated relatively early. Further, when the groove length GL is less than 40% of the tie bar length TL, the appearance at the time of wear tends to be deteriorated relatively early, and when it exceeds 80%, the rigidity of the tie bar is reduced and the pattern noise is reduced. Tends to decrease relatively.

[0026]

EXAMPLES A tire having a tire size of 165 / 65R14 and having a tread pattern shown in FIG. 1 was tested for noise performance and wear performance. The mounted rim was set at 5 J and the internal pressure was set at 200 kPa. The content of the test is as follows.

1) Noise performance (pattern noise) In accordance with the actual vehicle coasting test specified in JASO / C / 606, the vehicle is coasted on a straight test course (asphalt road surface) at a passing speed of 60 km / h for a distance of 50 m. At the same time, at the midpoint of the course, sideways from the running center line.
The maximum level of passing noise dB (A) was measured by a stationary microphone installed at a position of 5 m and 1.2 m from the road surface. The result is represented by an index with Conventional Example 1 being 100, and the larger the index, the smaller and better the passing noise.

2) Wear Performance Wear Appearance A sample tire was mounted on a 1000 cc displacement domestic car, and a 20 m / h speed 20 km / h circle on a 20 m radius circle was used.
Around 0 turns, the shoulder portion (the most abraded portion) of the tire outside the turning of the front tire was visually observed over several times until the vehicle completed, and the remaining condition of the narrow groove of the tie bar was evaluated on a 5-point scale. It was expressed by. The larger the numerical value, the longer the remaining state of the narrow groove and the better the appearance.

Uneven Wear Appearance After the above test, the heel-and-toe wear of the shoulder block was visually observed and expressed in five grades. The larger the value, the better the appearance. Table 1 shows the test results.

[0030]

[Table 1]

As a result of the test, it was confirmed that the tire of the example had reduced pattern noise and had a good appearance when worn. In the case of a tie bar provided with a narrow groove penetrating both ends in the tire axial direction (conventional example) and in the case of a tie bar provided with a narrow groove penetrating one end in the tire axial direction (comparative example), the effect of reducing the pattern noise is reduced Is small. In Example 4, the narrow groove of the tie bar remained even after traveling 200 times, which was very good.

[0032]

As described above, according to the first aspect of the present invention, a tie bar having a predetermined height is formed to protrude from the groove bottom of the lateral groove and to connect between adjacent shoulder land portions in the tire circumferential direction. This tie bar is provided with narrow grooves that extend along the lateral groove and are open at both ends that terminate inside the tie bar at both ends, so that even if the groove volume is large, the pattern noise is reduced and uneven wear of the shoulder land portion is reduced. Can be prevented. Also, with the progress of wear, on the tread surface, a narrow groove appeared along with the tie bar, and because the narrow groove was not open at both ends,
Fine grooves can be left over a long period of time, and the appearance during wear can be kept good.

According to the second aspect of the present invention, by limiting the groove width w, the groove depth d, and the groove length GL of the narrow groove, uneven wear of the shoulder land portion can be reduced more reliably while reducing pattern noise. Can be prevented.

According to the third aspect of the present invention, the shoulder land portion includes an outer shoulder block disposed on the outside in the tire axial direction and arranged along the tread edge, and an inner shoulder block disposed on the inner side in the tire axial direction. And by providing a tie bar between the inner shoulder blocks adjacent to each other in the tire circumferential direction, it is possible to prevent the drainage of the lateral groove between the outer shoulder blocks from being hindered, and to reduce the wet performance. Can be prevented.

[Brief description of the drawings]

FIG. 1 is a development view of a tread pattern showing an embodiment of the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a sectional view taken along line BB of FIG. 1;

FIG. 4 is a left half developed view of a tread pattern showing a conventional tie bar.

[Description of Signs] 2 Tread surface 3a Central vertical main groove 3b External vertical main groove 4 Lateral groove 5 Crown land 6 Shoulder land 6a Outer shoulder block 5b Shoulder block in 5b 7 Tie bar

Claims (3)

[Claims] 1. A pneumatic tire having a shoulder portion extending in a direction intersecting with a tire circumferential direction and a lateral groove opening at a tread edge being spaced in a tire circumferential direction to form a shoulder land portion between the lateral grooves. In the lateral groove, a tie bar that protrudes from the groove bottom of the lateral groove and connects the shoulder land portions adjacent in the tire circumferential direction and has a raised height h of 40 to 60% of the groove depth D of the lateral groove, The pneumatic tire according to claim 1, wherein said tie bar is provided with a narrow groove extending along said lateral groove and having both ends non-opening and terminating inside said tie bar. 2. The narrow groove has a groove width w of 0.5 to 1.5 mm and a groove depth d of 80% of the ridge height h.
~ 100%, and the groove length GL is 4 of the tie bar length TL
The pneumatic tire according to claim 1, wherein the content is 0 to 80%. 3. The tire according to claim 3, wherein the shoulder land portion is formed between an outer vertical main groove disposed on the outermost side in the tire axial direction and the tread edge, and is divided by a sub-groove extending in the tire circumferential direction. An outer shoulder block on the outside in the axial direction and an inner shoulder block arranged on the inner side in the tire axial direction, and the tie bar is provided between the inner shoulder blocks adjacent in the tire circumferential direction. The pneumatic tire according to claim 1 or 2, wherein: