Patent Application
20060254695
The present invention relates to a method of producing a pneumatic radial tire, and more particularly to a method of producing a pneumatic radial tire which does not trap air in a tire casing in a process of forming a tire casing.
A step of forming an unvulcanized tire in steps of producing a pneumatic radial tire generally includes: a step of forming a tire casing by winding a sheet material such as a carcass layer on a first shape-forming drum in a cylindrical shape, setting a bead core and a bead filler at both end portions of the outer periphery of the shape-forming drum, and winding a side rubber on both of the side parts (a first forming process); and a process of completing the unvulcanized tire by transferring the tire casing in the cylindrical shape to a second shape-forming drum, Furthermore expanding its diameter in the central part, and winding a belt layer and a tread rubber on the outer periphery (a second forming process).
Descriptions will be given of the above mentioned process of forming a tire casing (the first forming process) in further details. An inner liner is first wound on the shape-forming drum, and then a carcass layer is wound directly thereon, or the carcass layer is wound with a tie rubber layer interposed, the tie rubber layer playing a role of adhesiveness to the inner liner. However, when each sheet material is sequentially wound, the winding is performed by pressing each sheet with a pressing roller from the outside so as not to include air between the sheets. Nevertheless, if narrow adhesion sheets are inserted respectively on both end portions between the inner liner and the carcass layer or between the inner liner and the tie rubber layer for the purpose of, for example, reinforcing the left and right bead areas, the adhesion sheets cause level differences. Therefore, air tends to be included between the above mentioned sheet layers, especially in spots adjacent to the level differences when the sheet materials are pressed by the pressing roller as described above (see Patent Literature 1).
Patent Literature 1: Japanese patent application Kokai publication No. 8-25509.
An object of the present invention is to provide a method of producing a pneumatic radial tire to prevent air from being trapped in a tire casing in a process of forming a tire casing.
To achieve the above object, a method of producing a pneumatic radial tire according to the present invention includes a process of forming a tire casing in which at least an inner liner, a left and right pair of narrow adhesion sheets and a carcass layer are wound on an outer periphery of a shape-forming drum in a cylindrical shape sequentially from inside while being pressed by a pressing roller, and in which a bead core and a bead filler are set on both of the left and right end portions of the outermost periphery, wherein the method is characterized in that a shape-forming drum which has belt-like grooves formed in a circumferential direction in its outer periphery at positions corresponding to the positions of adhesion sheets is used as the shape-forming drum.
In this manner, according to the production method of the present invention, since the belt-like grooves are formed in the outer periphery of the shape-forming drum at positions corresponding to the positions of the adhesion sheets, the level differences of the adhesion sheets are eliminated from the surface of the shape-forming drum by making the adhesion sheets stuck and sink in the belt-like grooves when the sheet materials are wound on the shape-forming drum while being pressed by the pressing roller. Hence, it is made possible not to include air between the sheets.
Moreover, another method of producing a pneumatic radial tire to achieve the above object includes a process of forming a tire casing in which at least an inner liner, a left and right pair of narrow adhesion sheets and a carcass layer are wound on an outer periphery of a shape-forming drum in a cylindrical shape sequentially from inside while being pressed by a pressing roller, and in which a bead core and a bead filler are set on both of the left and right end portions of the outermost periphery, wherein the method is characterized in that a shape-forming drum having an elastic layer coated on its outer periphery is used as the shape-forming drum.
In this manner, since the elastic layer is coated on the outer periphery of the shape-forming drum, when the sheet materials are wound on the shape-forming drum while being pressed by the pressing roller, the level differences of the adhesion sheets are eliminated from the surface of the shape-forming drum by squeezing the adhesion sheets into the elastic layer. Thus, it is made possible not to include air between the sheets.
In the present invention, sheet materials used for forming a tire casing are at least an inner liner, a left and right pair of narrow adhesion sheets and a carcass layer. Furthermore, if needed, a tie rubber layer may be used in some cases.
Out of the above sheet materials, the carcass layer is a sheet material to form the frame of a pneumatic radial tire, and is configured by coating many carcass cords arranged in parallel to each other with an unvulcanized coat rubber. The carcass cord can be any of an organic fiber cord and a steel cord.
The inner liner is a sheet material to be provided in the innermost layer of a pneumatic tire as a seal layer, and an unvulcanized rubber sheet such as a butyl rubber, which has low air permeability, is used for the inner liner. In recent years, there are some cases where a film material made of thermoplastic resin or a thermoplastic resin/elastomer composition, which have air permeability resistance at the same level even if the film material is made thinner than a rubber material, is used for a sheet material for the inner liner for the purpose of the weight reduction of a tire. In terms of the thickness of the film material, a range from 0.02 to 1.1 mm is preferably used to balance weight reduction with a sealing ability. When this film material is used for the inner liner, a failure caused by trapped air tends to appear remarkably. Hence, the present invention can be applied most preferably.
The adhesion sheets are sheet materials which are inserted to reinforce mainly around bead areas. An unvulcanized rubber sheet or a sheet in which reinforcement fiber fabric is coated with an unvulcanized coat rubber is preferably used for the adhesion sheet.
The tie rubber layer is a sheet material used for adhesive reinforcement in a case where adhesiveness between the carcass layer and the inner liner is low. Therefore, an unvulcanized rubber sheet having excellent adhesiveness is used for the tie rubber layer. Especially, when a film material made of thermoplastic or a thermoplastic/elastomer composition is used for the inner liner, it is effective to use the tie rubber layer in order to reinforce adhesiveness to the carcass layer. Furthermore, an adhesive layer may be added to the foregoing film material to further increase adhesiveness.
In the present invention, as winding methods to form a cylinder-shaped tire casing on a shape-forming drum by using the above-mentioned sheet materials, there are the following types A to C in response to the winding order and combination of these sheet materials.
Here, “adhesion sheet+carcass layer” means to apply the left and right pair of adhesion sheets to the carcass layer in advance to integrate them before they are wound on a shape-forming drum. “Adhesion sheets+tie rubber layer” means to apply the left and right pair of adhesion sheets to the tie rubber layer in advance to integrate them before they are wound on the shape-forming drum. In addition, “adhesion sheets+tie rubber layer+carcass layer” means to apply the tie rubber layer to the carcass layer in advance to superimpose, and further apply the left and right pair of adhesion sheets to the tie rubber layer, thus integrating them. In this manner, the winding is performed on the shape-forming drum at the units (1) to (3) while the sheet materials are pressed by a pressing roller.
A drum where belt-like grooves are formed in the outer periphery at positions corresponding to the winding positions of the adhesion sheets is used as the shape-forming drum used in the present invention. In terms of the width of the belt-like groove, it is sufficient if the belt-like groove is wide enough to accommodate the adhesion sheet. In this manner, by forming belt-like grooves in the shape-forming drum, when the sheet materials are wound on the shape-forming drum in any one of the foregoing types A to C while being pressed by the pressing roller, the adhesion sheets are made to be fitted in the belt-like grooves. Hence, the level differences of the adhesion sheets are eliminated from the surface of the shape-forming drum. As a result, in the case of the winding method of the type A, it is made possible that air is not included between the inner liner and the carcass layer. Moreover, in the cases of the winding methods of the types B and C, it is made possible that air is not included between the inner liner and the tie rubber layer.
In terms of the depth of the above belt-like groove, it is preferable to be 0.3 to 1.5 times compared to the thickness of the adhesion sheet. Furthermore preferably, it is advantageous to be 0.7 to 1.3 times. If the depth of the belt-like groove is smaller than 0.3 times compared to the thickness of the adhesion sheet, it becomes harder to obtain the above-mentioned effect owing to the belt-like grooves. Moreover, if it is larger than 1.5 times, it is not preferable since level differences in depressed forms are created conversely.
In addition, a shape-forming drum having an elastic layer coated on its outer periphery may be used as the shape-forming drum used in the present invention. It is advantageous to use resin foam such as polyurethane for the elastic layer. In this manner, by coating the elastic layer on the outer periphery of the shape-forming drum, when the sheet materials are wound on the shape-forming drum while being pressed by the pressing roller, the adhesion sheets are squeezed into the elastic layer. Thus, the level differences of the adhesion sheets are eliminated from the surface of the shape-forming drum, and it is made possible not to include air between the sheets.
In terms of the thickness of the elastic layer, it is advantageous to be within a range from 0.5 to 5 times compared to the thickness of the adhesion sheet. If the thickness of the elastic layer is smaller than 0.5 times compared to the thickness of the adhesion sheet, it is difficult to eliminate the level differences of the adhesion sheets. In addition, if the thickness of the elastic layer becomes larger than 5 times compared to the thickness of the adhesion sheet, the winding of the sheet materials becomes unstable because of a decrease in rigidity of the surface of the shape-forming drum. Accordingly, it is not preferable.
The pressing roller to press the sheet materials to the shape-forming drum may be a straight-shaped roller having a flat and smooth outer surface. However, preferably, many hollow wheels are supported in parallel to each other on a supporting shaft, and also it is advantageous to use a roller in which each of these hollow wheels are configured to be displaceable independently in the radius direction of the supporting shaft. For example, it is possible to use rollers such as: a roller in which the many hollow wheels having heavy bobs are loosely fitted in parallel to be supported and each hollow wheel is configured to be displaceable independently in the diameter direction of the supporting shaft; or a roller where the many hollow wheels are loosely fitted in parallel in the axis direction to be supported on the bearing into which the supporting shaft fits and an elastic body such as a spring or resin foam including polyurethane are lain between the bearing and the hollow wheel to support the hollow wheel elastically.
In the pressing roller with the above configuration, a distance which the hollow wheels are displaceable in the radius direction in relation to the supporting shaft is not particularly limited. However, preferably, it is desired to make the distance 0.3 to 1.5 times compared to the thickness of the adhesion sheet. Moreover, it is advantageous for the hollow wheel to be made its width as small as 5 to 10 mm. In this manner, by making the width of the hollow wheel small, each hollow wheel presses the adhesion sheets in a small width unit. Hence, the adhesion sheets are made possible to be squeezed into the belt-like grooves and the elastic layer with high measurement precision. If the width of the hollow wheel is wider than 10 mm, it becomes difficult for the adhesion sheets to be uniformly squeezed into the belt-like grooves or the elastic layer. Furthermore, if the width of the hollow wheel is smaller than 5 mm, the local pressure applied by the hollow wheels becomes too large. Accordingly, the sheet materials may be deformed.
Hereinafter, with reference to embodiments shown in the drawings, descriptions will be given of the present invention.
A device for forming a tire casing includes a shape-forming drum 1 and a pressing roller 2. The forming of the tire casing is as follows: an assembled body of a bead core 6 and a bead filler 7 are made to stand by on both outer sides in the axis direction of the shape-forming drum 1. First, an inner liner 3 is wound on the outer periphery of the shape-forming drum 1 while being pressed by the pressing roller 2. Then, a carcass layer 4, to which a left and right pair of narrow adhesion sheets 5, 5 is applied beforehand on both inner end portions, is wound while being similarly pressed by the pressing roller 2.
The forming device used in the present invention is provided with belt-like grooves 8, 8 in the circumference direction of the shape-forming drum 1 along the circumference direction of the drum at positions corresponding to the positions where the above adhesion sheets 5 are wound. Consequently, when the carcass layer 4 is wound on the shape-forming drum 1 while being pressed by the pressing roller 2, the adhesion sheets 5 which are applied to the inner surface of the carcass layer 4 are fitted into the belt-like grooves 8. Level differences attributed to the adhesion sheets 5 are thus eliminated from the surface of the shape-forming drum 1. Therefore, the inner liner 3 and the carcass layer 4 are closely adhered to each other, thus removing air in a region G sandwiched by the adhesion sheets 5, 5 between both of the sheets. As a result, air will not be trapped.
As the pressing roller 2, it may be a straight-shaped roller with a flat and smooth surface shown in
The pressing roller 2 shown in
In this manner, the pressing roller 2 composed of the many hollow wheels 9 can have a structure shown in
In a method of producing a pneumatic radial tire in the present invention, when a process of winding all the sheet materials is completed in the process of forming the tire casing in
Next, the cylinder-shaped tire casing in which the assembled body of the bead core 6 and the bead filler 7 have been set as described above is separated by reducing the diameter of the shape-forming drum 1, and is transferred to a shape-forming drum of a publicly-known second forming process. In this second forming process, both end portions of the carcass layer 4 are turned up to wrap the assembled body of the bead core 6 and the bead filler 7 in accordance with a publicly-known forming method. Furthermore, sidewall rubbers are wound respectively on both side parts. Then, an unvulcanized tire 70 shown in
The unvulcanized tire 70 shown in
A shape-forming drum 1 used in this embodiment is formed in a manner that belt-like grooves 8 penetrate into the end portion of the drum. A carcass layer 4 and an adhesion sheet 5 are wound to protrude toward the side of the shape-forming drum 1. In this manner, the end portion of the carcass layer 4 and the adhesion sheets 5 protruded from the end portions of the shape-forming drum 1 are bent toward the inner diameter as shown with a dashed line, and an assembled body of a bead core 6 and a bead filler 7 is shifted in the directions indicated with arrows to be struck onto the surface of the protruding end portions which are bent. Next, the protruding end portions of the carcass layer 4 and the adhesion sheets 5 are tuned up to wrap the assembled body of the bead core 6 and the bead filler 7. Furthermore, a sidewall rubber is wound to complete the process of forming the tire casing.
After removed from the shape-forming drum, the tire casing formed in this manner is transferred to a publicly-known second process. Then, a belt layer, a tread rubber and the like are applied in accordance with a publicly-known forming method, and an unvulcanized tire is formed.
An elastic layer 15 is provided for a shape-forming drum 1 used in this embodiment to coat the drum instead of the belt-like grooves 8 provided in the outer periphery of the drum in
By using this forming device, when an inner liner 3, the left and right pair of narrow adhesion sheets 5, 5 and a carcass layer 4 are wound on the shape-forming drum 1 in a manner of the foregoing aspect A while being pressed by the pressing roller 2, the adhesion sheets 5 are squeezed into the elastic layer 15. Accordingly, the level differences of the adhesion sheets are eliminated from the surface of the shape-forming drum 1. Therefore, similarly to the case of
Any of the embodiments described respectively in
The common conditions were: the size of a tire was set to be 195/65R15; each sheet material of an inner liner, an adhesion sheet, and a carcass layer had the following specifications; and a device for forming a tire casing had the structure shown in
In addition, the same sheet material as above was used to form the tire casings by use of a conventional forming device of
Trapped air caused in the inner liners of the tires of above five kinds was examined with the following method. The number of faulty tires in which air was trapped was checked, and the result of table 1 was obtained.
Inner liner:
film made of a polyamide resin/elastomer composition (thickness: 0.1 mm)
Adhesion sheet:
rubber-covered sheet made of nylon fabric (width×thickness: 40 mm×2 mm)
Carcass layer:
rubber-covered sheet made of polyester carcass cords
[Examination Method for Trapped Air]
Used was a method to visually check projections which were trapped air in the inner liner to have developed into a state of projections on the surface of the inner liner owing to a thermal expansion after being vulcanized. When even a single projection of this kind is generated on the surface of the inner liner, the tire with the projection was counted as a faulty tire.
Two kinds of pneumatic radial tires were manufactured by a hundred. The two kinds were: a case where an elastic layer coating a shape-forming drum of the device for forming the tire casing was made of polyurethane foam with a thickness of 2 mm (Example 5); and a case where an elastic layer coating a shape-forming drum of the device for forming the tire casing was made of polyurethane foam with a thickness of 10 mm (Example 6). In both cases, a difference was only in a point of replacing the devices of forming the tire casings in FIGS. 1 to 4 with the device of forming the tire casing in
It was checked whether or not there was trapped air caused in the inner liner of the above two kinds. The number of faulty tires which have caused air to be trapped was then checked. Accordingly, the result of table 2 was obtained.
Except a point that the pressing roller was replaced with a flat and smooth straight-shaped roll in the device for forming the tire casing in the second example, a hundred pneumatic radial tires were manufactured on the same condition as the second example (Example 7).
Moreover, except a point that the pressing roller was replaced with a flat and smooth straight-shaped roll in the device for forming the tire casing of the Example 5, a hundred pneumatic radial tires were manufactured on the same condition as the fifth example (Example 8).
It was checked whether or not there was trapped air caused in the inner liner of the above two kinds. The number of faulty tires which have caused air to be trapped was then checked. Accordingly, the result of table 3 was obtained.
| Number | Date | Country | Kind |
|---|---|---|---|
| JP2003-142494 | May 2003 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP04/06642 | 5/18/2004 | WO | 8/30/2005 |
