JP2001039118A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the durability of a pneumatic tire by improving the partial wear resistant performance of a tread. SOLUTION: This tire is demarcated by four wide circumferential grooves 14 extending substantially along the circumferential direction of a tread 12, and the outer surface of the tread 12 is split into five rids 16, 18. A rib located on both outermost side ends in the axial direction of the tread 12 out of these five ribs 16, 18 in made the shoulder rib 18. A recessed part 20 which is recessed from a contour line L of the tread 12 to envelope the outer surface of the tread 12 and a part of which is opened in the circumferential groove 14 adjacent to the shoulder rib 18 is provided on a part close to the circumferential groove 14 closer to an inner end part 18B of the shoulder rib 18.

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 tread wear resistance, and more particularly to a pneumatic tire having a rib-based tread pattern.

[0002]

2. Description of the Related Art Conventionally, tread patterns of rib type, lug type, rib lug type, block type and the like have been known as tread patterns of pneumatic tires used for vehicles such as passenger cars, buses and trucks. Then, the outer surface of the tread is divided into a plurality in the axial direction by a wide circumferential groove extending in the circumferential direction of the tread, and a pneumatic tire such as a rib type in which a plurality of ribs as land portions are provided. , Is generally used for trucks.

[0003]

However, even a pneumatic tire having a rib-based tread pattern such as a rib type as described above cannot be used on a route track running on a mountain or a short distance on a general road. There was a lot of input of large side force, and uneven wear of the tire was inevitable. In particular, as shown in FIG. 10, the shoulder rib 118 located on the outer side of the tire mounted on the vehicle has a greater amount of wear at the outer end 118A of the shoulder rib 118 and the inner end 118B of the shoulder rib 118 Partially wear away so that it remains sharp.

[0004] Therefore, in order to improve uneven wear of a tire used for a track or the like having a large side force, for example, the outer surface of the tread is formed into a circular arc-shaped crown so that the outer end of the shoulder rib is grounded. The method of reducing the ground pressure at the outer end of the shoulder rib and reducing the amount of wear at the outer end of the shoulder rib by reducing the pressure or applying a large number of sipes to the outer end of the shoulder rib. Many have been devised.

However, when these methods are adopted, even if the amount of wear at the outer end of the shoulder rib can be reduced, it is not improved that the inner end of the shoulder rib remains sharply protruding after the wear. As a result, not only the appearance of the tire is deteriorated, but also the rubber forming the pattern inside the shoulder ribs is adversely affected, and the life of the tire is deteriorated. An object of the present invention is to provide a pneumatic tire which can improve the uneven wear resistance of a tread having a rib-based tread pattern and improve durability in consideration of the above fact.

[0006]

The pneumatic tire according to claim 1 is defined by a circumferential groove extending along the circumferential direction of the tread, and a shoulder rib is formed at an axial end of the tread. In a pneumatic tire having a simple tread pattern, a portion recessed from a contour line of the tread enveloping the outer surface of the tread is provided in a portion near the circumferential groove near the inner end of the shoulder rib. Features.

The operation of the pneumatic tire according to claim 1 will be described below. The pneumatic tire has a tread pattern in which an outer surface of the tread is defined by a circumferential groove extending along a circumferential direction of the tread so that a shoulder rib is formed at an axial end of the tread.
In addition, a concave portion is provided in a portion near the circumferential groove near the inner end portion of the shoulder rib so as to be depressed from a contour line of the tread enveloping the outer surface of the tread.

[0008] Therefore, since the concave portion is provided in the portion near the inner end of the shoulder rib, the inner end of the shoulder rib is separated from the outer end, and these portions are individually formed with respect to the road surface. As the shear strain is small, the inner edge of the shoulder rib starts to slide at an early timing. In other words, in the past, the shape began to slide from the outer end of the shoulder rib and gradually spread to the inner end, so the shear strain increased at the inner end of the shoulder rib and large bending deformation occurred at this inner end Was. As a result, the outer end of the shoulder rib is greatly worn, and the inner end of the shoulder rib is left so as to protrude sharply, thereby causing uneven wear.

On the other hand, by causing the inner ends of the shoulder ribs to start sliding independently as described above, the shear deformation at the time of slipping is reduced at both the inner ends and the outer ends of the shoulder ribs. it can. Therefore, each of the shoulder ribs will be abraded in a state where a small deformation that is preferable for both the inner end and the outer end is generated.

[0010] As described above, the inner end and the outer end of the shoulder rib are worn in a state where a small deformation is caused. Therefore, the input of the side force is used for a track having a relatively large input and the rib base is used. Even with the pneumatic tire having the tread pattern described above, the wear of the shoulder ribs can be advanced to the last stage while maintaining a good appearance, and the uneven wear resistance of the tread can be improved. As a result, the tire performance can be maintained for a long time, and the durability of the pneumatic tire can be increased.

The operation of the pneumatic tire according to claim 2 will be described below. In the present invention, the operation is the same as that of the first embodiment, but since a part of the concave portion is opened in the circumferential groove adjacent to the shoulder rib, the inner end portion of the shoulder rib is formed lower from the beginning. As a result, the inner ends of the shoulder ribs protruded sharply, and were more difficult to remain.

The operation of the pneumatic tire according to claim 3 will be described below. The present invention operates in the same manner as the first and second aspects, except that the contour of the tread extends through the outer surface of the outer end of the shoulder rib.
The recess is definitely lower than the outer end of the shoulder rib,
The functions of claims 1 and 2 are more reliably achieved.

The operation of the pneumatic tire according to claim 4 will be described below. The present invention operates in the same manner as claims 1 to 3, except that a sipe is provided at the outer end of the shoulder rib, so that the rigidity of the outer end of the shoulder rib is reduced and the ground pressure of this portion is reduced. And the start of slipping of the outer end of the shoulder rib can be further delayed.

The operation of the pneumatic tire according to claim 5 will be described below. The present invention operates in the same manner as in claims 1 to 4, except that the deepest position of the concave portion is not the end of the shoulder rib, but Wo / Wi which defines the deepest position of the concave portion is determined by test data. Since the concave portion is arranged at the center of the shoulder rib as a value in the range of 0.9 to 2.4, which is considered to be an appropriate range, the effect of suppressing uneven wear is further enhanced.

The operation of the pneumatic tire according to claims 6 to 8 will be described below. In claim 6, the same operation as in claims 1 to 5 is performed, but the depth of the concave portion, which is considered to be an appropriate range from the test data, is set to 1.0 to 2.7 m.
In claim 7, the same operation as in claims 1 to 6 is performed, but the depth of the recess, which is also considered to be an appropriate range from the test data, is set to 6% to 18% of the depth of the circumferential groove. %
In the eighth aspect, the depth is set within the range of
However, the depth of the sipe, which is also considered to be an appropriate range from the test data, was set to a depth in the range of 50% to 85% of the depth of the circumferential groove. For this reason, these claims further increase the effect of suppressing uneven wear as compared with claims 1 to 5 and above.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A pneumatic tire according to an embodiment of the present invention is shown in FIGS. 1 to 6 and will be described with reference to these drawings. FIG. 1 shows a pneumatic tire 1 according to the present embodiment.
It is a figure showing the typical example of 0 tread pattern. Here, the internal structure of the pneumatic tire 10 is a combination of a radial carcass, a highly rigid belt arranged to cover the crown of the radial carcass, and a tread 12 arranged on the outer peripheral surface of the belt. Since it is a very common type of pneumatic tire, its description is omitted in the following description.

Further, as shown in FIG. 1, the tread 12 constitutes an outer skin which comes into contact with the road surface of the pneumatic tire 10, and four wide circumferential grooves extending substantially along the circumferential direction of the tread 12. The pneumatic tire 10 has a tread pattern that is divided by 14 and the outer surface of the tread 12 is divided into five ribs 16 and 18. A rib defined by the circumferential grooves 14 of the five ribs 16 and 18 and located at both outermost ends in the axial direction of the tread 12 is a shoulder rib 18.

The outer surface of the tread 12 is shown in FIG.
As shown in (B), the shoulder rib 18 is formed in a crown shape, and a portion near the circumferential groove 14 near the inner end portion 18B of the shoulder rib 18 is a tread enveloping the outer surface of the tread 12. A concave portion 20 is provided which is depressed from the contour line L of 12 and partially opens in the circumferential groove 14 adjacent to the shoulder rib 18. The recess 20 is formed in an arc shape in the cross-sectional views shown in FIGS. 1B and 2 so as to extend along the circumferential direction of the tread 12. On the other hand, these five ribs 1
A contour line L of the tread 12 circumscribing the tires 6, 18 extends through the outer surface of the outer end 18A of the shoulder rib 18.

Further, as shown in FIG. 2, in Example 1 according to the present embodiment, the distance from the outer end of the shoulder rib 18 to the deepest part of the recess 20 is Wo, and the distance from the inner end of the shoulder rib 18 to the recess is The distance to the deepest part of 20 is Wi
And the depth d at the deepest portion of the concave portion 20 is 2.0 m
m, and the depth dimension d1 at the inner end portion 18B of the shoulder rib 18 is set to 1.0 mm. At this time, the width dimension W of the shoulder rib 18 is 35 mm,
4 has a depth H of 15 mm.

Next, a pneumatic tire according to a second embodiment of the present invention is shown in FIG. 3, and the present embodiment will be described with reference to FIG. As shown in FIG. 3, in the present embodiment, similarly to the first embodiment, the depth d at the deepest portion of the concave portion 20 is set to 2.0 mm, and the depth d1 at the inner end portion 18B of the shoulder rib 18 is set. Is set to 1.0 mm. However, in the present embodiment, a convex portion 22 projecting from the inner end portion 18B of the shoulder rib 18 into the circumferential groove 14 is formed, and this convex portion 22 starts sliding of the inner end portion 18B of the shoulder rib 18. And a sharply projecting abrasion residue at the inner end 18B of the shoulder rib 18 is prevented.

Next, a pneumatic tire according to a third embodiment of the present invention is shown in FIG. 4, and the present embodiment will be described with reference to FIG. As shown in FIG. 4, in the present embodiment, the deepest portion of the concave portion 20 is disposed at the inner end portion 18B of the shoulder rib 18, and the depth dimension d at the deepest portion of the concave portion 20 is 2.0 mm.
It has been.

Next, a pneumatic tire according to Example 4 of the present embodiment is shown in FIG. 5, and the present example will be described with reference to FIG. As shown in FIG. 5, the shoulder rib 18 of the present embodiment has the same shape as that of the first embodiment. Although the outer end 18A of the shoulder rib 18 of the present embodiment is also formed along the contour line L of the tread 12, a number of sipes 24 are formed at equal intervals along the outer end 18A of the shoulder rib 18. It is provided in. The depth h of the sipe 24 is set to 10.0 mm, and the width t of the sipe 24 is set to 0.5 mm.

Next, the operation of the pneumatic tire 10 according to the present embodiment will be described below. In the conventional tire, the slip starts from the outer end of the shoulder rib and gradually spreads to the inner end.Therefore, at the inner end of the shoulder rib, shear strain increases, and a large bending deformation occurs at the inner end. Had occurred. As a result, the outer end of the shoulder rib was greatly worn, and the inner end of the shoulder rib was left so as to protrude sharply.

That is, uneven wear at the outer end of the shoulder rib is caused not only by the fact that shear deformation of the outer end of the shoulder rib is increased by the input of the side force, but also at the outer end of the shoulder rib. It is considered that the contact pressure of the outer end is increased, and the outer end slips against the road surface while receiving a high frictional shearing force and wears rapidly. On the other hand, the reason why the inner end of the shoulder rib is left in a sharp shape is that shear strain increases due to input of side force from the outer end of the shoulder rib, and a large bending deformation occurs at this inner end. It is considered that the inner end of the shoulder rib is lifted, and as a result, the inner end of the shoulder rib forms a local land portion without being worn. And since the inner end part which became this local land part has low bending rigidity,
Bending deformation is apt to occur, and only the inner end remains in a sharp shape without being worn.

On the other hand, in the pneumatic tire 10 of the present embodiment, the outer surface of the tread 12 is defined by the circumferential groove 14 extending along the circumferential direction of the tread 12, so that the shaft of the tread 12 It has a tread pattern such that a shoulder rib 18 is formed at the end in the direction. A contour line L of the tread 12 is formed in a portion near the circumferential groove 14 near the inner end 18B of the shoulder rib 18.
A recess 20 that is more recessed is provided.

Therefore, the inner end 1 of the shoulder rib 18
Since the recess 20 is provided in the portion closer to 8B, the inner end 18B of the shoulder rib 18 is separated from the outer end 18A, and these portions individually slide on the road surface, Even when the shear strain is small, the inner end portion 18B of the shoulder rib 18 starts to slide at an early timing. Then, by causing the inner end 18B of the shoulder rib 18 to start sliding independently as described above, the shear deformation when slipping can be reduced at both the inner end 18B and the outer end 18A of the shoulder rib 18. . For this reason, the inner end 18B of the shoulder rib 18
And the outer ends 18A will wear, each with a small deformation that is desirable for both.

As described above, the inner end portion 18B and the outer end portion 18A of the shoulder rib 18 are worn in a state where a small deformation is caused, so that the side force is applied to a track having a relatively large input. Pneumatic tire 1 having a rib-based tread pattern
Even at 0, the wear of the shoulder ribs 18 can be advanced to the last stage while maintaining a good appearance, and the uneven wear resistance performance of the tread 12 can be improved. As a result, the tire performance can be maintained for a long time, and the durability of the pneumatic tire 10 can be increased.

On the other hand, since a part of the recess 20 is opened in the circumferential groove 14 adjacent to the shoulder rib 18, the inner end 18B of the shoulder rib 18 is
, The inner end 18B of the shoulder rib 18 is sharp and hardly remains.

Also, since the contour line L of the tread 12 extends through the outer surface of the outer end 18A of the shoulder rib 18, the recess 20 is reliably lower than the outer end 18A of the shoulder rib 18. The uneven wear resistance of the tread 12 can be more reliably improved. On the other hand, Example 2
In the above, since the bending rigidity around the inner end portion 18B is further increased due to the presence of the convex portion 22, bending deformation becomes difficult, and the convex portion 22 prevents the inner end portion 18B of the shoulder rib 18 from starting to slide as described above. The inner end portion 18B is quickly worn well, and a sharply protruding remaining portion of the inner end portion 18B is prevented. Further, in the fourth embodiment, since the sipes 24 are provided at the outer ends 18A of the shoulder ribs 18, the ground pressure at the outer ends 18A of the shoulder ribs 18 is reduced, and the outer ends 18A of the shoulder ribs 18 slide. It was possible to delay the start further.

Next, based on a running test on an actual vehicle, 100
The evaluation of uneven wear of the shoulder ribs 18 after traveling at 00 km, 20000 km, and 30000 km will be described below. First, in order to express the uneven wear shape of the shoulder rib 18, a cross-sectional view of a tire as shown in FIG. 6 was used. In this figure, the amount of wear at the outer end 18A of the shoulder rib 18 is D1, and the amount of wear at the inner end 18B of the shoulder rib 18 is D2. K = D1 / D2 Table 1 shows the results of the performance evaluation based on the values of. Here, the smaller the value of K shown in Table 1, the better the performance. In FIG. 6, the right side is the outside of the pneumatic tire 10 mounted on the vehicle, and the left side is the inside of the pneumatic tire 10 mounted on the vehicle. The performance was evaluated in parts.

[0031]

[Table 1]

That is, as the value of K becomes smaller and approaches 1 the better performance is obtained. From Table 1, it can be seen from Table 1 that all of Examples 1 to 4 have 3000 in the final evaluation.
The value is 1.42 to 1.7 when running at 0 km, and it can be understood that the performance is greatly improved as compared with 2.05 of the conventional product. The test conditions in Table 1 are as follows. Vehicle: 2-DD (front single-axle vehicle) Test tire mounting position: front (steering axis) Mileage at final evaluation: about 30,000 km (wear rate 40)
%) Features of the traveling route: traveling on a general road with a lot of curves

FIG. 7 is a graph showing the results of a test in which the position of the deepest portion of the recess 20 was changed. That is, as shown in the graph of FIG. 7, the value of Wo / Wi that defines the position of the deepest portion of the concave portion 20 is calculated from this test data by K
Is considered to be the smallest and appropriate range.
With the range of 4, it is expected that the effect of suppressing uneven wear is further enhanced.

Next, the result of a test in which the depth of the deepest portion of the concave portion 20 was changed is shown in the graph of FIG. That is, as shown in the graph of FIG. 8, the depth of the concave portion 20 is set to 1.0 to 2.7 mm from the test data, and the depth of the concave portion 20 is set to 6% to 18% of the depth of the circumferential groove 14. If the depth is within the range, it is considered that the value of K is small and the range is appropriate.
When the value of K is 1 or less, it is considered that the inner end portion 18B is excessively worn and becomes inappropriate.

FIG. 9 is a graph showing the result of a test in which the depth of the sipe 24 was changed with respect to the depth of the circumferential groove 14. That is, as shown in the graph of FIG. 9, if the depth of the sipe 24 is set to a depth in the range of 50% to 85% of the depth of the circumferential groove 14 based on the test data, the value of K is the smallest and the appropriate value is obtained. It is thought that it becomes a range. In the above-described embodiment, the number of the circumferential grooves 14 extending substantially along the circumferential direction of the tread 12 is four and the number of the ribs 16 and 18 is five. The number is not limited to a value and may be another number.

[0036]

Since the pneumatic tire of the present invention has the above-described structure, the tread having the rib-based tread pattern is improved in the uneven wear resistance and the durability of the pneumatic tire can be improved. Has an effect.

[Brief description of the drawings]

FIG. 1 is a diagram showing a pneumatic tire according to an embodiment of the present invention, wherein (A) is a plan view and (B) is (A).
1B-1B is a transverse cross-sectional view as seen from the arrow 1B-1B.

FIG. 2 is a perspective sectional view showing a pneumatic tire according to Example 1 of the present embodiment.

FIG. 3 is a perspective sectional view showing a pneumatic tire according to Example 2 of the present embodiment.

FIG. 4 is a perspective sectional view showing a pneumatic tire according to Example 3 of the present embodiment.

FIG. 5 is a perspective sectional view showing a pneumatic tire according to Example 4 of the present embodiment.

FIG. 6 is a cross-sectional view of the pneumatic tire according to the embodiment of the present invention after being worn.

FIG. 7 is a graph showing a result of a test in which the position of the deepest portion of the concave portion was changed in the pneumatic tire according to the embodiment of the present invention.

FIG. 8 is a graph showing a result of a test in which the depth of the deepest portion of the concave portion was changed in the pneumatic tire according to the embodiment of the present invention.

FIG. 9 is a graph showing a result of a test in which a sipe depth is changed in the pneumatic tire according to the embodiment of the present invention.

FIG. 10 is an enlarged sectional view of a main part of a pneumatic tire according to the related art after abrasion.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Pneumatic tire 12 Tread 14 Circumferential groove 18 Shoulder rib 20 Depression 24 Sipe

Claims (8)

[Claims] 1. A pneumatic tire having a tread pattern defined by a circumferential groove extending along a circumferential direction of a tread and having a shoulder rib formed at an axial end portion of the tread, wherein: A pneumatic tire, wherein a concave portion is provided in a portion near a circumferential groove near an end so as to be depressed from a contour line of a tread enveloping an outer surface of the tread. 2. The pneumatic tire according to claim 1, wherein a part of the recess is opened in a circumferential groove adjacent to the shoulder rib. 3. The pneumatic tire according to claim 1, wherein a contour line of the tread extends through an outer surface of an outer end portion of the shoulder rib. 4. The pneumatic tire according to claim 1, wherein a sipe is provided at an end of the shoulder rib. 5. When the distance from the outer end of the shoulder rib to the deepest portion of the recess is Wo, and the distance from the inner end of the shoulder rib to the deepest portion of the recess is Wi, Wo / W
The pneumatic tire according to any one of claims 1 to 4, wherein i takes a value in a range of 0.9 to 2.4. 6. The pneumatic tire according to claim 1, wherein a depth of the concave portion is 1.0 to 2.7 mm. 7. The depth of the recess is 6% to 1% of the depth of the circumferential groove.
The pneumatic tire according to any one of claims 1 to 6, wherein the depth is in a range of 8%. 8. The depth of the sipe is 50% of the depth of the circumferential groove.
The pneumatic tire according to any one of claims 4 to 7, wherein the depth is in the range of ~ 85%.