JPH08230072A - Manufacture of retreaded tire for truck or bus - Google Patents

Abstract

PURPOSE: To enhance unbalanced abrasion resistance, heat generation resistance and durability in a tire retreading method by a mold system. CONSTITUTION: A buffing process buffing a used tire to form base tire 3 having a buff remaining rubber layer 9 between the tire and a belt layer 7, a retreading rubber molding process applying unvulcanized retreading rubber 4 to the base tire and a vulcanizing molding process vulcanizing the base tire and the retreading rubber in a vulcanizing mold to form a tread pattern to a tread surface 10 are contained. The buff remaining rubber layer is formed so that the thickness tc of a central region is 1.5-3.5mm, the thickness of a side region S is 1.0-3.0mm and made smaller than that of the central region and the total thickness of the tread rubber after molding and vulcanization is set so as to form the relation of Tc>=Ts>=(Tc-0.5)mm between the total thickness Tc of the central region and the total thickness Ts of the side region.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a retreaded tire for a truck or a bus, which is capable of providing a retreaded tire having improved wear resistance and heat resistance as a tire for a truck or a bus.

[0002]

2. Description of the Related Art For automobile tires, especially heavy duty tires for trucks, buses, etc., in order to reduce tire costs, replace the tires that have become worn due to the worn tread portion. So-called retreaded tires for reuse are increasing.

Conventionally, in order to rehabilitate a tire, as shown in the figure, a base tire a from which a worn or damaged tread portion is removed is pasted with a retret member b of substantially the same quality as a new tire, and then this base tire a. And a retret member b are vulcanized and molded using a vulcanization mold d, and both are adhered, and a remolding method by a remolding method is also performed in which the tread groove e is processed in the retret member b. Was used.

[0004]

However, in the molding method, as described above, since the unvulcanized retlet member b and the vulcanized base tire a are bonded and vulcanization molding is performed again, this vulcanization molding is performed. There is a problem that the tire shape is likely to be deformed such as the radius of curvature of the tread changing during vulcanization and molding, and the retreaded tire is inferior in wear resistance and heat resistance to a new tire.

There is a so-called pre-cure system in which a retret member is pre-patterned and vulcanized, and this retlet member is attached to a base tire to manufacture a retreaded tire. Is difficult to ensure the dimensional accuracy of the tire rehabilitated by such a pre-cure method, the wear resistance,
There is a problem of poor heat resistance.

The inventors of the present invention have paid attention to a buffing process in which a buffing surface is formed by randomly buffing the base tire and forming a buffing surface on the base tire. By making the thickness of the remaining rubber layer different between the central region and the side region, and by regulating the total tread rubber thickness between the tread surface after vulcanization molding and the belt layer in the central region and the side region as well. The present invention has been completed by finding that the above-mentioned problems can be solved even by a manufacturing method using a molding method.

It is an object of the present invention to provide a retreaded tire for trucks and buses, which can improve uneven wear resistance and heat resistance and can improve durability.

[0008]

DISCLOSURE OF THE INVENTION The present invention is a method of manufacturing a retread tire for a truck or a bus, which comprises a carcass of steel cords and a belt layer composed of a plurality of plies of steel cords. Buffing the tread portion of the tire, a buffing step of forming a buff residual rubber layer between the belt layer and the base tire by forming a tread buffing surface, an unvulcanized retret rubber on the tread buffing surface of the base tire. A reticle rubber molding step of adhering, and a vulcanization molding step of forming a tread pattern on the tread surface by vulcanizing the base tire and retret rubber in a vulcanizing mold, and the buff residual rubber layer, the tire equator. A central region C having a width 0.75 times the tread width TW as a center and side regions S on both sides of the central region C in the tire axial direction are provided. Te, the thickness tc of the central region C is 1.5
~ 3.5 mm, and the thickness ts of the side region S is 1.0 to 3.0.
mm and the thickness tc of the central region or less,
The total thickness of the tread rubber between the tread surface and the belt layer after the vulcanization molding step is such that the total thickness Ts of the side region S is equal to or less than the total thickness Tc of the central region C, and the total thickness of the central region C is the same. It is a method for manufacturing a retread tire for trucks and buses, wherein the thickness is equal to or more than a value obtained by subtracting 0.5 mm from the thickness Tc.

This manufacturing method can be suitably applied to truck and bus tires with tubes.

Further, in the die, it is preferable that the difference between the clip width GW and the rim width LW is 3 mm or less.

[0011]

The buff residual rubber layer has its thickness tc and ts regulated in the central region C and the side region S, respectively, and the total thickness of the tread rubber after vulcanization molding is controlled relative to the central region C and the side region S. The size difference is regulated. As a result, the tire axial direction cross section of the retreaded tire, particularly the shape of the tread surface, can be regulated with high accuracy, and the wear resistance and heat resistance can be enhanced to improve the durability of the retreaded truck or bus tire.

Further, when the grip width is set to have a dimensional difference of 3 mm or less with respect to the rim width, the shape of the tread surface can be maintained more accurately.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the manufacturing method of the present invention will be described below with reference to the drawings. The retreaded tire 1 for trucks and buses is a tread buffing surface obtained by removing the remaining tread portion of a pneumatic tire with a tube whose tread surface is worn out as shown in FIG. 1 by using a buff or the like. It is composed of a base tire 3 having 2 and a retret rubber 4 attached to the base tire 3.

The base tire 3 has sidewall portions 1 extending inward in the tire radial direction from both ends of the tread portion 5.
3 and 13 and the bead portion 14 located at the radially inner end of each sidewall portion 13, and each bead portion 1
Between 4 and 14, a toroidal carcass 6 is bridged from the tread portion 5 through the sidewall portion 13 and both ends of which are folded back around the bead core 15 of the bead portion 14 and is also radially outside thereof. And tread part 5
A tough belt layer 7 is wound inward in the circumferential direction to reinforce the tire and provide necessary rigidity.

In this example, the carcass 6 is composed of one carcass ply, and the carcass ply has a carcass cord made of steel cord with respect to the tire equator C.
It is formed as a radial or semi-radial array juxtaposed at an angle of ~ 90 °.

In this example, the belt layer 7 is composed of three belt plies 7A, 7B and 7C.
In 7B and 7C, belt cords in which steel cords are arranged in parallel with a space therebetween are arranged so that the belt plies intersect with each other.

The retret rubber 4 is made of a rubber composition having substantially the same quality as that of the tread portion 5 of the base tire 3, and is attached to the base tire 3 in an unvulcanized state. A retreaded tire is formed.

Next, the manufacturing method will be described in the order of steps. In this example, (1) buffing process, (2) retread rubber molding process, and (3) vulcanization molding process are performed in this order.

The buffing step is a step of obtaining a base tire 3 having a tread buffing surface 2 formed by buffing a tread portion of a used tire.

The tread buff hanging surface 2 is the belt layer 7
The buff remaining rubber layer 9 is formed between the outermost surface of the belt ply 7C and the outer surface of the belt ply 7C. The tread buff hanging surface 2 is formed on both sides of the tire equator CO with the same width as the widest belt ply 7B of the belt layer 7 or a width slightly larger than that, and from its end to the buttress surface 13A. Cut-off surface 1 that inclines radially inward
7 and 17 are formed.

The buff remaining rubber layer 9 includes a central region C having a width 0.75 times the tread width TW with the tire equator CO as the center, and two side regions adjacent to both sides of the central region C in the tire axial direction. In and, the thickness is different.

The buff residual rubber layer 9 has a thickness tc of 1.5 to 3.5 mm in the central region C, and a thickness ts of 1.0 to 3.0 mm in the side region S and has a thickness of the central region. The thickness is not more than tc.

In this way, the thickness tc of the buff remaining rubber layer 9
By regulating ts, the shape of the tread surface 10 after vulcanization molding can be stabilized.

The retret rubber 4 has an outer peripheral surface 19 forming a tread surface and an inner peripheral surface 20 facing the buffing surface 2 of the base tire 3, and the inner peripheral surface 20 is provided on both sides in the tire axial direction. It is a belt-shaped body in which a wing portion 21 that fits with the cut-off surface is raised, and is wound along the buffing surface 2 of the base tire 3 in an unvulcanized state and bonded to the base tire 3 using a rubber adhesive. By doing so, the retret rubber 4 is attached to the base tire 3.

The base tire 3 and the retret rubber 4 joined together through such a reticle rubber molding process are vulcanized and molded in a vulcanization mold K as shown in FIG. Is formed.

In the vulcanization molding step, a tread pattern including grooves 18 is formed on the tread surface 10 in addition to the vulcanization treatment.

As shown in FIG. 2, the vulcanization mold K is loaded with the base tire 3 and the retret rubber 4 in the mold cavity O thereof. The inward surface 23 of the vulcanizing mold K facing the mold cavity O is formed based on the contour of the completed retreaded tire, but in order to further improve the accuracy of the cross-sectional shape of the retreaded tire, The mold size is further regulated.

The difference between the grip width GW of the vulcanizing mold K and the rim width LW of the reference rim J on which the retreaded tire 1 is assembled is set to 3 mm or less.

Further, the mold size of the vulcanization mold K is set on the basis of the tire shape when a normal internal pressure is applied to the used tire before the base tire 3 is buffed, that is, the shape of an old tire. There is.

The groove bottom diameter KD of the vulcanizing mold K is in the range of -2 to +4 mm with respect to the groove bottom diameter GD of the old tire, and 0.48 to 0 with respect to the groove bottom diameter of the old tire. The maximum width BK of the vulcanization mold is ± ± with respect to the tire maximum width B located at a position of .52 times.
In the range of 2 mm, the groove bottom diameter of old tires is 0.
In the buttress 13 located at a position of 76 to 0.86 times, the vulcanization mold K is set within 3 mm with respect to that of an old tire.

Further, the radius of curvature KR in the meridional section of the tread surface of the vulcanization mold K is 40 mm or less with respect to the radius of curvature GR of the groove bottom radius line in the meridional section of the old tire.

By vulcanizing and molding the base tire 3 and the retret rubber 4 by using the vulcanizing mold K whose dimensions are controlled in this way, the space between the tread surface 10 and the belt layer 7 after the vulcanization molding process is The total thickness of the tread rubber is such that the total thickness Ts in the side region S is equal to or less than the total thickness Tc in the central region C,
Moreover, the retreaded tire 1 having a value equal to or larger than the value obtained by subtracting 0.5 mm from the total thickness Tc of the central region C is formed.

[0033]

SPECIFIC EXAMPLE A tubed tire having a tire size of 225/90 R17.5 was tested for its performance together with an example in which a tire having a specification shown in Table 1 was prototyped. A tire having a conventional retread (comparative example) was also tested to compare the performance. The test results are shown in Table 1.

[0034]

[Table 1]

As a result of the test, it was confirmed that the examples were superior in wear resistance and heat resistance to the comparative examples.

[0036]

As described above, the method for manufacturing a retreaded tire for trucks and buses according to the present invention has the thickness of the buff residual rubber layer in the central region and the side regions of the tread portion and after the molding vulcanization step as described above. As the gist is to control the total thickness of each tread rubber, the retreaded tire manufactured despite the molding method has improved uneven wear resistance, heat generation resistance and durability. By
It can be suitably used as a retreaded tire for trucks and buses.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an example of a retreaded tire manufactured according to the present invention.

FIG. 2 is a cross-sectional view showing an example of a vulcanizing mold used in the manufacturing method.

FIG. 3 is a sectional view schematically showing a conventional vulcanizing mold.

[Explanation of symbols]

 1 Rehabilitated tire 2 Buffing surface 3 Tire 4 Retlet rubber 5 Tread part 6 Carcass 7 Belt layer 10 Tread surface C Central area CO Tire equator GW Grip width K Vulcanization mold LW Rim width S side area TW Tread width

Claims (3)

[Claims] 1. A method of manufacturing a retreaded tire for a truck or a bus, which comprises a carcass of steel cords and a belt layer composed of a plurality of steel cord plies, wherein a tread portion of a used tire is buffed, A buffing step of forming a buff residual rubber layer between the belt layer and the base tire by forming a tread buffing surface, a retret rubber molding step of attaching unvulcanized retret rubber to the tread buffing surface of the base tire, and the base A vulcanization molding step of vulcanizing the tire and the retret rubber in a vulcanization mold to form a tread pattern on the tread surface, and the buff residual rubber layer has a tread width TW of 0.75 centered on the tire equator. In a central region C having a double width and side regions S on both sides of the central region C in the tire axial direction,
The thickness tc of the central region C is 1.5 to 3.5 mm, the thickness ts of the side region S is 1.0 to 3.0 mm, and the thickness tc of the central region is equal to or less than the thickness tc. The total thickness of the tread rubber between the rear tread surface and the belt layer is such that the total thickness Ts of the side region S is less than or equal to the total thickness Tc of the central region C, and the total thickness Tc of the central region C is 0 to 0. A method for producing a retreaded tire for a truck or bus, which is set to be not less than a value obtained by subtracting 0.5 mm. 2. The method for producing a retread tire for a truck bus according to claim 1, wherein the vulcanization mold has a grip width GW having a difference of 3 mm or less from a rim width LW. 3. The method for manufacturing a retread tire for a truck or bus according to claim 1, wherein the retread tire is a tire with a tube.