JP3079039B2 - Pneumatic tire - Google Patents

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 a circumferential groove having a wide width, by preventing chipping of a groove ridge portion and breakage of a cord reinforcing layer located inward of the groove bottom, thereby improving the tread portion. The present invention relates to a pneumatic tire capable of improving durability.

[0002]

2. Description of the Related Art In a pneumatic tire, by providing a plurality of circumferential grooves in the circumferential direction of the tire, water on the tread surface during running on rainy weather is guided to the circumferential grooves to enhance wet grip. . However, it is known that providing such a circumferential groove causes tire noise.

In order to reduce tire noise while maintaining wet grip properties, for example, Japanese Patent Application Laid-Open No.
As disclosed in No. 32, the width of the circumferential groove is increased,
Also, proposals have been made to reduce the number.

[0004]

However, by increasing the width of the circumferential groove a, as shown in FIG. 7, the acting force is concentrated on the bottom of the groove, particularly on the corner p of the bottom of the groove. As a result, the corner p is greatly bent, so that the cord reinforcing layer b such as a belt layer located below the corner p is easily damaged. This tendency is remarkable especially in a heavy load tire on which a large load acts.

To solve one of the above problems, FIG.
As shown in FIG. 2, there is a zigzag circumferential groove d. However, by forming the zigzag shape, a rubber chip is generated at a corner e of a ridge line portion where the circumferential groove d intersects the tread surface.
This lack of rubber tends to occur when the tread rubber has a low rigidity, which deteriorates the appearance of the tire and significantly impairs the durability.

The inventor has found that the above problem can be solved by making the shape of the wide main groove different between the upper and lower portions, and has completed the present invention. The present invention can prevent chipping of a groove ridge portion and breakage of rubber and a reinforcing layer of a tread portion in a pneumatic tire provided with a wide main groove extending in a circumferential direction, and can solve the above problems. It aims to provide pneumatic tires.

[0007]

SUMMARY OF THE INVENTION The present invention is a pneumatic tire having at least one wide main groove extending circumferentially on a tread surface, the main groove having a groove wall intersecting with the tread surface. The initial groove width in the tire axial direction between the tread groove ridge lines is 32 to
60 mm, the main groove is located in a radially inner portion from the tread surface in the tire radial direction, and a groove line where a groove wall intersects a plane parallel to the tread surface is linear in a circumferential direction. A pneumatic tire characterized by comprising a zigzag lower region in which a groove line that is located radially inward of the region and in which the groove wall intersects a plane parallel to the tread surface is zigzag in the circumferential direction. .

By making the upper region of the main groove straight even in the case of a wide main groove, it is possible to prevent chipping of the groove ridge portion, especially when the rigidity of the tread rubber at the time of new article is low. The appearance can be improved and running stability can be maintained.

In addition, by forming the lower region in a zigzag shape, the position of the corner of the groove bottom in the tire axial direction changes in the tire circumferential direction, so that stress acting intensively at the corner can be dispersed. Damage such as peeling of the tread rubber and a cord reinforcing layer such as a belt layer disposed thereunder can be prevented.

Particularly, the present invention is effective for a heavy-duty tire used for a truck or a bus to which a heavy load is constantly applied. By adopting the above-described structure for a heavy-load tire, the durability can be remarkably improved.

[0011] Further, in the latter period of wear when the tread surface wears due to the running of the tire and the groove depth becomes shallow, a zigzag lower region appears on the tread surface, so that the ridge lines in the oblique direction increase, The stability of running can be secured by compensating for the decrease in grip performance.

Further, as set forth in claim 2, the linear region has a groove depth GH of 0.2 between the tread surface and the main groove.
The zigzag lower region is a range between the height separating the tread surface by five times and the groove bottom and the groove depth GH of the main groove.
And 0.7 times greater than 0.25 times the groove depth GH of the main groove between the straight-line region and the zigzag-lower region. The intermediate region in a range separating the smaller height from the tread surface includes a change range in which the groove line changes from a straight line to a zigzag, and the ratio JH between the circumferential pitch JP and the amplitude JH of the lower zigzag region. / JP is preferably 0.06 to 0.40.

By regulating such numerical values,
The chipping of the groove ridge portion and the damage of the cord reinforcing layer at the tread portion can be more effectively suppressed.

[0014] Further, the change range may be provided with a step-like flat portion parallel to the tread surface when the groove edge changes from a straight line to a zigzag.
By forming such a stepped flat portion, stones that have entered the main groove can be efficiently eliminated, and stone biting can be prevented.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings, taking as an example a case where a pneumatic tire is a heavy duty tire having a tire size of 11R22.5.

1 to 4, the pneumatic tire 1 is provided with one or more, in this embodiment, one wide main groove 3 extending in the circumferential direction on the tread surface 2.

As shown in FIG. 2, the pneumatic tire 1 has a carcass 16 that rises from the tread portion 12 to the sidewall portion 13 and turns up around the bead core 15 of the bead portion 14; A belt layer 17 disposed radially outward of the carcass 16.

The carcass 16 has a radial or semi-radial configuration in which organic fiber cords or steel cords such as nylon, rayon, and aromatic polyamide, in this example, steel cords are arranged at an angle of 70 to 90 ° with respect to the tire equator C. The carcass ply is formed of one or more sheets, in this example, one sheet.

The number of the belt layers 17 is two to four, in this example, four.
Belt plies, these belt plies are
An organic fiber cord such as nylon, polyester, rayon, or aromatic polyamide, or a steel cord, in this example, a steel cord, is formed so that the intersection angle with the tire equator C from the inside in the radial direction to the outside is 68 °, 18 °, 18 °. , 18
They are arranged at an angle in degrees and crossing each other between the plies. A band layer 19 (indicated by a dashed line in FIG. 2) in which band cords are arranged at an inclination of 0 to 5 ° with respect to the tire equator C can be provided outside the belt layer 17 in the radial direction.

In the present embodiment, the tread rubber 20 forming the tread portion 12 is slightly lower than the rubber hardness usually used, and is set in the range of 50 to 60 degrees in JISA hardness to reduce the force acting on the tread surface. Is being planned.

The main groove 3 orbits on the tire equator C and has a groove width 4 between tread groove ridges F where the groove wall 4 intersects the tread surface 2 in the tire axial direction,
That is, the initial groove width GW is set to 32 to 60 mm when the tire is mounted on a standard rim and a standard internal pressure is applied.

When the groove width GW is applied to a truck or bus tire defined in JIS D4202, the tread width E is 0.15 to 0.15 of the tread width TW which is the distance between the tread edges E of the tire in the tire axial direction. It is preferable to set the range to 0.30 times.

When the initial groove width GW is less than 32 mm, the effect of preventing air column resonance is poor and the wet grip tends to be insufficient. On the other hand, the noise reduction effect cannot be expected even if the distance exceeds 60 mm, and the dry grip performance and the steering stability performance will be reduced. Preferably, the initial groove width GW is in the range of 35 to 50 mm.

It is preferable that the groove depth GH of the main groove 3 is 0.15 to 0.35 times the initial groove width GW. 0.
If it is less than 15 times, the groove volume is reduced and the wet grip performance is reduced, and if it is larger than 0.35 times, the effect of preventing air column resonance is poor and noise cannot be suppressed.

On the tread surface 2, in this embodiment, in addition to the main groove 3, it circulates in a circumferential direction between the main groove 3 and the tread edge E and has a groove width of 1 to 5 mm and a groove width of 1 to 5 mm. There are provided narrow vertical grooves 21, 21 having a depth equal to the groove depth GH of the main groove 3, and a plurality of horizontal small grooves 22 connecting the narrow vertical grooves 21 and the main grooves. The width of the small horizontal groove is 1 to 3 mm, and the depth of the groove is 2 to 4 mm.

The main groove 3 is located radially inward from the tread surface 2 in the tire radial direction.
A linear region 5 in which a groove line MA intersecting with a plane LA parallel to the tire is a straight line in the circumferential direction, and a flat surface located radially inward of the linear region 5 in the tire radial direction and a groove wall 4B parallel to the tread surface 2. The groove line MB intersecting with the LB includes a zigzag lower region 6 which is zigzag in the circumferential direction.

In the present embodiment, the straight region 5 is set in a range separating the tread surface 2 from the tread surface 2 by 0.25 times the groove depth GH of the main groove 3 and the zigzag lower region. Reference numeral 6 designates a range between the groove bottom 8 and the height separating the tread surface 2 from 0.7 times the groove depth GH of the main groove 3.

Further, the straight line area 5 and the zigzag lower area 6
Between the tread surface 2 and the intermediate region 7 is set in a range that separates the height of the main groove 3 from the tread surface 2 by more than 0.25 times and less than 0.7 times the groove depth GH. 7 is a change range 9 in which the groove lines MA and MB change from straight lines to zigzag.
Contains.

In the present embodiment, the groove wall 4A in the linear region 5 is formed in a radially inward direction by 40 to 8 toward the groove center.
While being formed as an inclined groove wall inclined at an angle of 5 degrees,
At the radial inner end of the groove wall 4A, the groove wall 4A is connected to the groove wall 4B of the zigzag lower region 6 via a stepped flat portion 10 formed by a plane parallel to the tread surface 2.

In the linear region 5, the length range from the tread surface 2 is 0.25 of the groove depth GH of the main groove 3.
If it is smaller than twice, a zigzag groove is formed in the tread rubber 20.
Since the rigidity of the zigzag groove appears at an early stage of low wear, rubber chipping easily occurs at the top P of the zigzag groove. If the length range of the zigzag lower region 6 from the groove bottom 8 is less than 0.7 times the groove depth GH, at the time of middle wear of the tire,
There is a risk that the grip properties will be insufficient.

In the zigzag lower region 6, the pitch number of the zigzag groove is set in the range of 50 to 90 in this example. When the pitch number is less than 50, the ratio of the edge component is small and the wet grip performance is inferior. When the pitch number is more than 90, the pitch sound generated by collision with the road surface is in the practical speed range of 50-8.
500-200 with the highest human sensitivity at 0 km / h
The reason for this is that the noise is large in the 0 Hz band. Preferably, the range is 60 to 80. The groove width (JW) of the zigzag groove at the groove bottom 8 in the tire axial direction is set in a range of 0.4 to 0.7 times the initial groove width GW of the main groove 3.

Further, in the zigzag lower region 6, the zigzag top P and bottom Q of the zigzag groove are formed by arcs having a radius of 5 mm or more, so that cracks are formed at the top P and bottom Q.
Rubber chipping is prevented.

Further, in the lower zigzag region 6, the ratio JH / JP between the circumferential pitch JP of the zigzag and the amplitude JH is set in the range of 0.06 to 0.40. The ratio JH
If / JP is less than 0.06, the tread surface 2 wears out and the zigzag appears on the tread surface 2, and the wet grip performance is reduced. This is because there is a risk that rubber chipping may occur. More preferably, the ratio JH / JP is 0.1.
It is preferable that the ratio is JH / J.
P is preferably set to 0.25 or less.

The intermediate area 7 is located between the linear area 5 and the zigzag lower area 6. In this example, the intermediate area 7 is arranged in the intermediate area 7 and has a stepped flat surface 10 parallel to the tread surface 2.
The groove wall 4A that forms a straight line in the straight region 5 and the groove wall 4B that forms a zigzag in the zigzag lower region 6 are connected to each other.

As described above, the intermediate region 7 includes a change range in which the groove line of the main groove 3 changes from the straight groove line MA to the zigzag groove line MB.

Further, by providing the flat portion 10, foreign substances such as stones which are going to enter the main groove 3 during traveling can be pushed out by the flat portion 10 to prevent stone biting. 3 can be prevented from being damaged.
If the flat portion is not provided, foreign matter such as stones is pushed along the groove wall inclined to the groove bottom, and stones are likely to be bitten. In particular, when the main groove 3 is formed to have a wide width, the amount of foreign matter that enters the main groove 3 becomes large, and the main groove 3, mainly the bottom of the groove is easily damaged, so that the flat portion 10 functions effectively.

FIGS. 5 and 6 show another embodiment of the main groove 3A. In the present example, a linear upper region 5 and a zigzag lower region 6 formed substantially in the same manner as the main groove 3 shown in FIGS. 3 and 4 described above are provided, and between the linear upper region 5 and the zigzag lower region 6. In the intermediate region 7, the groove line is formed so as to gradually shift from the linear groove line MA. In this example, since a sharp change in shape such as a corner or a corner is removed from the groove wall 4, the concentration of stress is reduced, and the generation of a crack from the groove wall 4 can be prevented.

It is to be noted that a plurality of the main grooves may be provided in the ground area of the tread surface 2, and the present invention may be modified into various modes.

[0039]

EXAMPLE A tire having a tire size of 11R22.5 14PR and having a structure shown in FIGS.
The main groove 3 is prototyped with the configuration shown in Table 1 (Examples 1 to 3).
5) and its performance was tested. Note that a tire having a conventional configuration (conventional example) and a tire not having the configuration of the present application (Comparative Example 1,
A test was also conducted for 2), and the performance was compared.

At the time of the test, each tire was 7.50 × 2
It was mounted on a 2.5 rim, and the test was performed with an internal pressure of 7.0 kgf / cm ² applied. The test conditions are as follows.

1) Passing noise test A passing noise test was conducted by an actual vehicle coasting test specified in JASO C606. Each test tire was attached to all wheels of a 2-D / 4 (10-wheel vehicle), and passed on a straight test course. 6. With a speed of 50 km / H and coasting for a distance of 50 m, at the midpoint of the course 7.
The maximum passing noise was measured by a microphone installed at a height of 1.2 m from the test road surface at a distance of 5 m.

2) Braking test at 50% wear Each test tire is mounted on the above-mentioned vehicle under substantially the same conditions, loaded on the vehicle at 11 tons, and the vehicle is allowed to enter a wet road surface at a speed of 60 km / h. All the wheels were suddenly braked, and the distance slipped due to the sudden braking was measured. The higher the value, the better.

3) Endurance test Using a drum tester, each sample tire had an internal pressure of 7.0 kgf /
After a load of 5450 kgf was applied under cm ^{2 and} the vehicle was driven for 12000 km, it was disassembled and the state of damage was visually judged.

4) Rubber chipping test In a new tire and a 50% worn tire, using the same vehicle as in item 1), sudden braking was applied on a dry road at a speed of 60 km / h, and the presence or absence of rubber chipping in the tread portion was examined. did. Table 1 shows the test results.

[0045]

[Table 1]

As a result of the test, the passage noise was reduced by making the main groove wider (the relationship between Comparative Example 1 and Example 2), and the wet braking performance and durability were superior to the conventional example. Was confirmed. In addition, each embodiment is new, 50%
It was confirmed that the rubber chipping during wear was good.

[0047]

As described above, the pneumatic tire of the present invention has the following features.
The main groove extending in the circumferential direction has a wide width, and the main groove includes a region on a straight line extending above and extending straight, and a region below the zigzag that changes zigzag at a lower portion. Preventing chipping of the groove ridge of the main groove while maintaining the features of low noise by widening the groove and improving wet grip, preventing damage to the cord reinforcement layer arranged inside the tread part Can be compatible,
Since the durability of the tire can be improved, it can be suitably used especially for a heavy-duty tire on which a large load acts.

Further, the effect can be further enhanced by restricting the range between the region on the straight line and the region below the zigzag.

Further, by providing a flat portion parallel to the tread surface, stone biting can be prevented.

[Brief description of the drawings]

FIG. 1 is a developed plan view of a tread surface showing an embodiment of the present invention.

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

FIG. 3 is an enlarged perspective view showing a main groove.

FIG. 4 is an end view in the tire axial direction showing a main groove in an enlarged manner, (A) is an RR line, (B) is an SS line, and (C) is a T line.
The -T line is shown.

FIG. 5 is a developed plan view showing another form of the main groove.

6A and 6B are end views, in which FIG. 6A is an XX line, and FIG.
Indicates a YY line, and (C) indicates a ZZ line.

FIG. 7 is a sectional view showing a conventional main groove.

FIG. 8 is a plan view showing another conventional main groove.

FIGS. 9A, 9B, and 9C are cross-sectional views showing a conventional main groove.

[Explanation of symbols]

 2 Tread surface 3, 3A Main groove 4, 4A, 4B Groove wall 5 Linear region 6 Zigzag lower region 7 Intermediate region 8 Groove bottom 10 Flat surface F Tread groove ridgeline GH groove depth GW Initial groove width JH Zigzag amplitude JP Zigzag circumferential pitch LA, LB Plane parallel to tread surface MA, MA Groove line

Continuation of front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B60C 11 / 04,11 / 00,11 / 13

Claims (4)

(57) [Claims] 1. A pneumatic tire having at least one wide main groove extending circumferentially on a tread surface, wherein the main groove is formed in a tire axial direction between tread groove ridge lines where a groove wall intersects a tread surface. The main groove is located radially inward from the tread surface in the tire radial direction, and a groove line where a groove wall intersects a plane parallel to the tread surface is a straight line in the circumferential direction. An upper region and a zigzag lower region in which a groove line located inward in the tire radial direction from the linear upper region and whose groove wall intersects a plane parallel to the tread surface is zigzag in the circumferential direction. And pneumatic tires. 2. The linear region is a range between the tread surface and a height separating the groove depth GH of the main groove from the tread surface by 0.25 times the groove depth GH. It is a range between the height separating 0.7 times the groove depth GH of the main groove from the tread surface, and 0.25 times the groove depth GH of the main groove between the straight-line region and the zigzag-lower region. Greater and 0.
An intermediate region in a range separating the height smaller than 7 times from the tread surface includes a change range in which the groove line changes from a straight line to a zigzag, and furthermore, a circumferential pitch J of the lower zigzag region.
The pneumatic tire according to claim 1, wherein the ratio JH / JP between P and the amplitude JH is 0.06 to 0.4. 3. The pneumatic tire according to claim 2, wherein the change range has a stepped flat portion parallel to a tread surface. 4. The pneumatic tire according to claim 1, wherein the tire is a heavy duty tire, and the initial groove width is 0.15 to 0.30 times the tread width. .