JPH11147405A - Precured tread - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve uniformity of a tire and to improve partial wear resistance of the tread. SOLUTION: A flat precured tread 1 is provided with a land portion 3 demarcated by a plurality of main grooves 2, and it is adhered to a base tire removed with tread rubber. The vicinity of a tread center side main groove 2 on the surface of the land portion 3 is made into a decreased height portion 5, within the cross section of the precured tread, so that the height thereof decreases toward the main groove in a curve. The radius of curvature R (mm) of the decreased height portion 5 is made to be in the range of R0 ±400 (mm) with respect to the radius of curvature R0 (mm) of the outer surface within the section of the base tire in its width direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a flat-shaped precured tread mainly used for a retreaded tire, and more particularly, to improving the uniformity of the tire and improving the uneven wear resistance. Things.

[0002]

2. Description of the Related Art As shown in a sectional view in the tire width direction in FIG. 5, for example, a buffed outer surface 23 of a base tire 21 from which tread rubber has been removed by a buffing process has a single radius of curvature R ₀ , and the outer radius of the buffed tire is set to a single radius of curvature R _0. In the rehabilitation of a precured tire, in which a precured tread 25 previously vulcanized and formed on the surface 23 is vulcanized and bonded via an unvulcanized rubber 27,
Generally, the cross-sectional shape of the flat precured tread 25 having a band shape as a whole is generally trapezoidal or rectangular as shown in the figure. Here, the precured tread 25 has, on its surface, a tread pattern according to its use.

[0003]

By the way, the tread pattern of the precured tread 25 is, in many cases, divided by a plurality of main grooves 29 extending continuously in the longitudinal direction thereof and the main grooves 29. Has a land portion 31,
Since the tread rigidity is low at the portion where the main groove 29 is formed, the precured tread 2 having a trapezoidal cross section is used.
5 is vulcanized and adhered to the buffed outer surface 23 of the base tire 21, the low rigid main groove portion of the tread 25 is greatly deformed particularly in the direction in which the groove width is widened. As shown in an enlarged manner in FIG. 6, the tread surface of the retreaded tire 33, in particular, the land portion located farthest from the tread center, in the vicinity of the tread center side main groove, has a cross section in the tire width direction. projections 35 occurs for the radius of curvature R ₁ of the given tread surface, the convex portion 35, result in deterioration of uniformity of the tire, such as radial force variation, also, a problem that results in uneven wear such as edge wear This was especially critical on the land located furthest from the tread center.

[0004] The present invention has been made as a result of studying to solve such problems of the prior art, and an object of the present invention is to increase the uniformity of the tire and to improve the uneven wear resistance. To provide a pre-cured tread that improves the quality of the product.

[0005]

The precured tread of the present invention has a substantially strip-like flat shape as a whole and includes a land portion defined by a plurality of main grooves extending in the length direction. At least a portion of the surface of the land located farthest from the tread center, at least a portion near the tread center side main groove, is precured tread. Through the highest point of the land within the cross section of
With respect to an imaginary line segment extending parallel to the bottom surface of the precured tread, a height-reduced portion whose height is reduced in a curved manner toward the main groove is defined as a radius of curvature R (mm) of a standard. The radius of curvature R ₀ (m) of the outer surface of the base tire assembled to the rim in the cross section in the width direction when the precured tread is stuck.
m) in the range of R ₀ ± 400 mm.

In a cross section in the width direction of a retread tire obtained by attaching a pre-cure tread to a base tire, generally, a land portion located farther from the tread center has a predetermined radius of curvature R _1.
The convexity of the tire tends to increase, which deteriorates the uniformity of the tire and reduces the ride comfort of the vehicle, and also causes uneven wear due to uneven distribution of the contact pressure, which limits the rejection limit of the tire. However, in the precured tread of the present invention, the land portion which is located farthest from the tread center and where the protrusion amount is likely to be the largest, at least on the surface, at least in the vicinity of the tread center side main groove. The part to an imaginary line passing through the highest point of the land,
By making the height decrease in a curved shape toward the main groove, the protrusion amount of the land portion with respect to a predetermined radius of curvature R ₁ (mm) can be effectively reduced. Is
The radius of curvature R (mm) of the reduced portion is calculated by the radius of curvature R of the base tire.
It becomes more remarkable by setting the range of R ₀ ± 400 (mm) with respect to ₀ (mm).

Therefore, in a retreaded tire using this pre-cure tread, the uniformity of the tire can be increased and the uneven wear resistance of the tread tread can be advantageously improved.

[0008] In this precured tread, more preferably, the reduced portion is provided on all land portions that do not overlap the tread center, and more preferably, the maximum distance of the reduced portion from the imaginary line segment is 0. .1 to 2.0
mm. According to these facts, in each land portion, the convex amount for the required radius of curvature R ₁ can be further reduced.

Here, when there is a land portion which overlaps with the tread center, it is preferable that both portions of the surface of the land portion near the respective main grooves be reduced portions. The amount of protrusion can be reduced more suitably.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a cross section of a flat-shaped precured tread 1 having a substantially band-like shape as a whole. This precured tread having a substantially trapezoidal cross-sectional shape is formed in a longitudinal direction, for example, in a linear or zigzag shape. Three main grooves 2 extending and their main grooves 2
And four land sections 3 partitioned by. Note that the land portion 3 here can be a block in addition to a rib.

Here, at least the land portion 3 located farthest from the tread center C, and more preferably all of the land portions 3, at least a portion of the land surface near the tread center side main groove 2 crosses the illustrated cross section. The imaginary line segment 4 extending parallel to the bottom surface of the pre-cured tread 1 and passing through the highest point of the land portion 3 in the plane, the height decreasing portion in which the height decreases in a curved shape toward the main groove 2 on the tread center side. 5, the radius of curvature R (mm) of the curved height-reducing portion 5 which is convex toward the main groove side is rim assembled to a standard rim 6 as shown in FIG. For example, a range of R ₀ ± 400 (mm) with respect to the radius of curvature R ₀ (mm) of the buffed outer surface 8 in the cross section in the width direction of the base tire 7 at the time of attaching.
More preferably, it is in the range of R ₀ ± 200 (mm).

Such a precured tread 1 is shown in FIG.
As shown by an imaginary line in FIG.
Can be contributed to the configuration of the retreaded tire 10 by being vulcanized and bonded via an unvulcanized rubber 9. As shown in FIG.
Because of the presence of the curved heightened portion 5, the amount of protrusion of the tread surface for a predetermined radius of curvature R ₁ (mm) is determined by the tread center C
In addition, it is possible to effectively reduce not only the land portion 3 close to the tire but also the land portion 3 farthest from the land portion 3, whereby the uniformity and uneven wear resistance of the tire can be sufficiently improved.

The reason why the reduced portion 5 is formed into a curved shape that is convex toward the main groove is to prevent an inflection point from occurring on the land portion. Radius R (mm)
With respect to the radius of curvature R ₀ (mm) of the outer surface 8 of the base tire.
₀ ± 400 (mm) is defined as R ₀ +400
If the value exceeds (mm), it may not be possible to contact the land portion, and the ground contact pressure distribution on land may not be uniform. On the other hand, if the value is smaller than R ₀ −400 (mm), the radius of curvature is too small, the ground contact pressure distribution on land is not uniform, and this becomes an uneven wear nucleus.

Further, in the above precured tread 1, more preferably, as shown in FIG.
The maximum distance from the virtual line segment 4 is in the range of 0.1 to 2.0 mm. That is, if it is out of the above range, it is difficult for the ground contact pressure distribution at the time of product to be uniform.

Meanwhile, in the retread tire 10 configured as described above, the radius of curvature R ₀ of the outer surface 8 of the base tire 7 is set.
(Mm), under the context of the oblateness etc. base tire 7, for a given tread curvature radius R ₁ a predetermined, specific land portion 3 or, in all of the land portion 3 of the surface, the tread center C If there is a possibility that the portion away from the side, in other words, the portion other than the height-reducing portion 5 may protrude relatively large outward in the radial direction, the surface of the land portion is in the vicinity of the tread end-side main groove or the tread end. Also in the part, the reduced part 5 mentioned above
A reduced portion similar to that described above can be provided, or the above-described nearby portion or the like can be a flat chamfered portion instead of the reduced portion.

FIG. 4 is a cross-sectional view showing another embodiment of the present invention, which shows an embodiment in which a three-land land portion 3 is partitioned as an example in which a land portion overlapping the tread center C exists. It is. Here, the two land portions 3 located at the end portions of the tread are provided with the same height reduction portions 5 as described above, and the main portions of the surface of the other land portions 3 which are located so as to overlap the tread center C are respectively provided. The portions near the grooves 2 are both convex to the main groove side, and are reduced portions 11 whose heights decrease in a curved shape toward the respective main grooves 2. The radius of curvature of each reduced portion 11 is also changed. The radius of curvature R ₀ (mm) of the outer surface 8 in the cross section of the base tire 7 in the width direction is R ₀ ± 200 (m).
m).

In the retreaded tire using the pre-cured tread 1 having the above-described structure, as is apparent from FIG. 4B, the entire surface of each land portion 3 is reduced by the respective height reduction. Under the action of the portions 5 and 11, the tread surface can be brought sufficiently close to a predetermined radius of curvature R ₁ (mm). Therefore, in this case as well, the uniformity of the tire can be increased, and the uneven wear resistance of the tread can be improved.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the precured tread 1 shown in FIG.
Is equal to the radius of curvature R ₀ (mm) of the outer surface of the base tire 6
A predetermined radius of curvature R ₁ (mm) of the tread surface when the maximum distance from the imaginary line segment 4 of each of the height reduction portions 5 and 11 is changed to 1.0 mm, 2.0 mm and 3.0 mm. Table 1 shows the results of measurement of the maximum convexity, the uniformity of the tire, and the uneven wear resistance of the tire.
It was as shown in.

Here, the maximum convexity is measured by measuring the convexity (using a laser shape measuring device) when the product is tied with a virtual uniform radius of curvature with respect to the product tread shape after filling the internal pressure. The tire uniformity was determined by indoor evaluation of radial force variation using a drum, and the uneven wear resistance was determined by field evaluation such as edge wear. By the way, the conventional tires in the table are retread tires using a precured tread having no height reduction portions 5 and 11. In addition, the uniformity in the table was determined to be better as the index value was smaller, and conversely, the uneven wear resistance was better as the index value was larger.

[0020]

[Table 1]

According to Table 1 above, there is an optimum value in the reduced portion, and in this case, the maximum distance of 1.0 mm is the best in both uniformity and uneven wear resistance.

[0022]

As described above, according to the present invention, based on the function of the height reduction portion provided on the land surface of the pre-cure tread,
The uniformity of the tire can be greatly increased to improve the ride comfort of the vehicle, and at the same time, the uneven wear resistance of the tread can be advantageously improved and the durability of the tire can be enhanced.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an embodiment of the present invention.

FIG. 2 is a cross-sectional view in the width direction of the base tire.

FIG. 3 is an enlarged sectional view of a main part showing a retreaded tire.

FIG. 4 is a cross-sectional view showing another embodiment.

FIG. 5 is a cross-sectional view showing a conventional technique together with a base tire.

FIG. 6 is a partially enlarged sectional view showing a conventional retreaded tire.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Precured tread 2 Main groove 3 Land part 4 Virtual line segment 5,11 Height reduction part 6 Standard rim 7 Tires 8 Outer surface 9 Unvulcanized rubber 10 Rehabilitated tire

Claims (4)

[Claims] 1. A land portion which is substantially band-shaped as a whole and is defined by a plurality of main grooves extending in a length direction.
A flat pre-cured tread to be attached to the platform tire from which the tread rubber has been removed, and at least a part of the surface of the land located farthest from the tread center, at least in the vicinity of the tread center side main groove, is pre-cured. In the cross section of the tread, passing through the highest point of the land portion, with respect to an imaginary line segment extending parallel to the bottom surface of the pre-cured tread, with a reduced portion in which the height decreases in a curve toward the main groove. , The radius of curvature R (m
m) is a range of R ₀ ± 400 (mm) with respect to the radius of curvature R ₀ (mm) of the outer surface in the cross section in the width direction of the base tire. 2. The pre-cured tread according to claim 1, wherein the reduced height portion is provided on all land portions that do not overlap the tread center. 3. The precured tread according to claim 1, wherein a maximum distance of the height-reducing portion from the virtual line segment is in a range of 0.1 to 2.0 mm. 4. The surface of a land portion overlapping a tread center,
The pre-cure tread according to any one of claims 1 to 3, wherein both portions near the respective main grooves serve as the balance portion.