JP4397090B2 - Pneumatic tire manufacturing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for manufacturing a pneumatic tire, and more particularly, to a method for manufacturing an unvulcanized tire for a pneumatic radial tire in which a steel cord is applied to a carcass ply. The present invention relates to a method for manufacturing a pneumatic tire that can rewind a material for a bead core member with high accuracy and stably.
[0002]
[Prior art]
Among pneumatic radial tires, a so-called heavy duty pneumatic radial tire used for heavy vehicles such as trucks and buses generally uses a rubber-coated ply of a steel cord for a carcass. In addition, since this type of tire is filled with a high internal pressure, a structure is employed in which the carcass is folded around the bead core from the inside of the tire to the outside and the carcass is locked to the pair of bead cores.
[0003]
However, since the carcass folding is located in the radial direction in the rubber of the bead part and has a cut-off end, a large strain concentrates on the carcass folding end under the rolling load of the tire, and the carcass folding takes place. A separation failure tends to occur from the end. Therefore, in order to avoid strain concentration at the folded end, as shown in the cross section of the bead portion 30 in FIG. 13, a winding in which the end portion 31E of the carcass 31 wraps around the circumferential surface of the bead core 32 instead of the folded structure thus far. Including structures have been proposed.
[0004]
However, the winding end portion 31E remains in the winding deformation within the elastic region of a large number of steel cords embedded in the ply of the carcass 31, and the steel cord of the carcass 31 is in a radial arrangement and has a rebound resilience. Since the force is large, the bead core 32 is moved away from the tire during the manufacturing process. As a result, it becomes difficult to realize a desired bead core winding state, eventually, concentrated strain acts on the winding end 31Ee in the rubber, and a failure from crack generation to burst is likely to occur, as expected. The bead portion durability cannot be improved. In addition, unreasonable wrapping also causes the inconvenience of damaging the steel cord and creating a poorly bonded portion with rubber.
[0005]
In view of this, the present applicant has already disclosed a pneumatic tire in the specification according to Japanese Patent Application No. 11-19847 in which one or more plastically deformed portions are provided in a bead core winding portion of a carcass ply that becomes a rubber coating of a steel cord. is suggesting. The bead 3 core entrainment part that undergoes plastic deformation is shown in the bead part cross-sectional view of FIG. In the bead portion 20 shown in FIG. 12, the carcass 21 has a winding portion 21R of a bead core 22, and the bead core 22 has a substantially hexagonal cross section, and the winding portion 21R has plastic deformation locations p ₁ , p ₂ , p. _{Has 3} .
[0006]
By providing plastic deformation points p ₁ , p ₂ , and p ₃ in the winding portion 21R, the winding portion 21R is located along the peripheral surface of the bead core 22, so that the strain acting on the winding end 21Re is significantly reduced. It has been confirmed that the separation resistance of the winding end 21Re is greatly improved, and the durability of the bead portion 20 is significantly improved. When the winding end 21Re is positioned closer to the bead core 22, the plastic deformation portion near the winding end 21Re plays a particularly important role.
[0007]
[Problems to be solved by the invention]
However, it has been found that the following problems exist when manufacturing a tire in which the plastic deformation portions p ₁ , p ₂ , and p ₃ are provided in the entrained portion 21R.
That is, in FIG. 11 showing a cross section of a cylindrical band 10A in which a carcass ply material 10A having plastic deformation points p ₁ , p ₂ , and p ₃ is wound around an end portion 10AE on a forming drum 2B, a pair of bead core members 15 is shown. Is applied to the plastic deformation locations p ₁ , p ₂ , and p ₃ on each side, first, the pair of bead setters 4 holding the bead core members 15 once pass through the plastic deformation locations p ₁ , p ₂ , and p ₃ . Must.
[0008]
Then, as shown in FIG. 11, to set a predetermined position of each bead core members 15 to the band 10A, Bidosetta 4, the plastic deformation of the end 10AE of the band 10A p ₁ ~p ₂ ~p ₃ the two points It is necessary to forcibly deform from the position indicated by the chain line to the position indicated by the solid line. In this state, the bead core member 15 is locked and fixed to the band 10A by expanding the bead core member 15 in the arrow direction of the locking means 16.
[0009]
However, once passing through the plastic deformation portions p _{1 to} p _{2 to} p ₃ of the bead setter 4 and forced deformation, a large reaction force is exerted on the bead setter 4. Since this reaction force is a heavy burden on the bead setter 4, it takes time for forced deformation, eventually increasing the molding cycle time and lowering the molding productivity. Further, in order to face this large reaction force, it is necessary to strengthen the output system of the molding machine. On the other hand, serious problems such as insufficient durability of the molding machine due to the reaction force occur. In addition, there is a problem that molding accuracy is impaired, such as inconvenience in accurate positioning of the bead core member 15.
[0010]
Accordingly, the object of the present invention described in claims 1 to 4 is to completely solve the above-mentioned remaining problems. More specifically, the reaction force of the bead core member to the bead setter is greatly reduced. Accordingly, an object of the present invention is to provide a pneumatic tire manufacturing method that can maintain high durability and high productivity while maintaining the conventional molding machine and can perform high-precision molding.
[0011]
In order to achieve the above object, the invention described in claim 1 of the present invention is used for molding an unvulcanized tire,
The radial carcass ply material, in which a large number of parallel arrangement steel cords are coated with unvulcanized rubber, is subjected to two or more upwards in advance on both side ends where the bead core is wound along the circumferential direction of the carcass of the tire, After that, cuts are made at a predetermined pitch in the covered rubber parts on both side ends with the crease part, and a material having a plurality of cuts on both sides is supplied to the molding drum and joined in a cylindrical shape,
A pair of bead core members are supplied to and positioned at both end portions of the cylindrical material having the crease portion, and each bead core member at this position is locked and fixed from the inside through the material. Bulging and deforming into a toroidal shape, each squeezed portion of the bulging and deforming material is wound around the bead core member and closely adhered,
Then, the manufacturing method of the pneumatic tire characterized by sticking an unvulcanized belt and an unvulcanized tread rubber on the outer peripheral side of a toroid-like material.
[0012]
With respect to the invention described in claim 1, as in the invention described in claim 2, the predetermined pitch to be cut is set to 150 mm or less, and the invention described in claims 1 and 2, the cut from the edge of each side end portion It is preferable that the length is within a range of 3/12 to 9/12 times the circumferential length of the bead core member.
[0013]
And as for the invention described in claims 1-3, as in the invention described in claim 4, the steel cord ends sandwiching the incision positions from both sides when the squeezed portions are wound around and closely contacted around the bead core member. The respective parts are inclined in opposite directions with respect to the cut position.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to FIGS.
FIG. 1 is a schematic plan view of a molding machine used in the present invention.
FIG. 2 is a plan view of a radial carcass ply material immediately before feeding a molding drum according to the present invention,
FIG. 3 is a right half sectional view of the radial carcass ply material shown in FIG.
FIG. 4 is a partial cross-sectional view of a radial carcass ply material according to the present invention after being wound around a molding drum,
FIG. 5 is a cross-sectional view of the material staking end and the bead setter when the bead core member is positioned;
FIG. 6 is a schematic cross-sectional view of the whole when the material shown in FIG. 5 is bulged and deformed, and the squeezed end portion is wound around and closely adhered to the bead core member.
FIG. 7 is a diagram showing the relationship between the inclination angle on the molding drum and the tensile strength retention rate of the steel cord with respect to the brazing end,
FIG. 8 is a diagram showing the relationship between the cutting pitch and the reaction force against the bead setter.
FIG. 9 is a partial perspective view of the bracing end and the bead core member shown in FIG. 6 according to the present invention.
FIG. 10 is a side view of the steel cord and the bead core member at the butt end shown in FIG. 6 according to the present invention.
[0015]
In FIG. 1, a molding machine includes a housing 1 incorporating a motor for driving each rotating part, a molding drum 2 mounted on a shaft extending from the housing 1, and a radial carcass ply material (hereinafter referred to as a carcass material) described later on the molding drum 2. A pair of bead core members for transporting the pair of bead core members to the molding drum 2 and fixing them to a predetermined position, and a carcass material on the molding drum 2 for closely contacting the bead core members. And a pair of stitcher rolls 5. The molding drum 2 includes an expandable bladder 2B at the center.
[0016]
The molding machine also includes a belt tread band drum (BT drum) 7 in which an unvulcanized belt and an unvulcanized tread rubber supplied from another servicer 6 are laminated in a cylindrical shape, and a belt tread laminated on the BT drum 7. And an O-ring 8 for conveying the band onto the molding drum 2.
[0017]
2 and 3, the carcass material 10 is formed by applying unvulcanized rubber 12 to a large number of parallel-arranged steel cords 11 substantially orthogonal to the circumferential direction of the tire carcass 21 (around the tire axis). It is a coated member. In FIG. 2, the steel cord 11 is indicated by a broken line. Reference numeral C denotes a width center line of the carcass material 10.
[0018]
As shown in each figure, the carcass material 10 has two or more portions on each side end portion 10E corresponding to both side end portions 21R where the bead core 22 is wound back along the circumferential direction of the carcass 21 of the tire. The carcass material 10 is supplied from the servicer 3 to the molding drum 2 by applying an upward crease.
[0019]
This caulking refers to a state in which the steel cord 11 is plastically deformed. As shown in FIG. 3, when the carcass material 10 is supplied to the molding drum 2, the tacking portions p ₁ , p ₂ , and p ₃ that cause plastic deformation are set upward. Imprint unit p _1, p _2, p ₃ corresponds to the imprint of the each side region 21R p _1, p _2, p ₃ of the carcass 21 of the tire.
[0020]
Here, before being supplied to the molding drum 2, incisions 13 are made at a predetermined pitch P in the covering rubber 12 portions of the side end portions 10E having the crease portions p ₁ , p ₂ , and p ₃ of the carcass material 10 in advance. And However, for each turn of the carcass material 10 wound around the molding drum 2, a plurality of cuts 13 are provided at both end portions 10E. Further, it is preferable that the cut 13 is cut from the edge 10Ee of the side end portion 10E. The carcass material 10 having the plurality of cuts 13 is jointed on the bladder 2B of the molding drum 2 in a cylindrical shape. The state of the cylindrical carcass material 10 at this time is shown in the sectional view of FIG. Reference numeral X denotes a rotation axis of the molding drum 2.
[0021]
Thereafter, the pair of bead core members 15 held by the pair of bead setters 4 are transported toward the molding drum 2, and as shown in FIG. 5, both sides of the cylindrical carcass material 10 having the interposing portions p ₁ , p ₂ , and p _3. Each bead core member 15 is positioned at the end 10E. At this position, each bead core member 15 held by each bead setter 4 is locked and fixed to the bladder 2B from the inside via the carcass material 10. In this locking method, for example, a pair of locking means 16 that can be enlarged and reduced in diameter are provided in the molding drum 2 immediately below the bead core member 15 to be positioned with respect to the molding drum 2.
[0022]
Thereafter, each bead setter 4 is released from holding each bead core member 15 and is retracted from the molding drum 2. Then, as shown in FIG. 6, in a state where the lock of each bead core member 15 is held, for example, pressurized gas is supplied to the inside of the bladder 2B and, at the same time, the mutual distance between the pair of lock means 16 is narrowed, so that the carcass material 10 is bulged and deformed into a toroidal shape.
[0023]
At the same time as the bulging deformation, the stitcher roll 5 is moved in the direction of the arrow, and by rotating and pressing around the axis of the stitcher roll 5, each squeezed end portion 10E of the bulged and deformed carcass material 10 is moved to the bead core member. Tighten it around and bring it into close contact. At this time, the crease portions p ₁ , p ₂ , and p ₃ are adjusted to the respective refraction angle portions of the bead core member 15.
[0024]
Thereafter, a band (not shown) of an unvulcanized belt and an unvulcanized tread rubber previously laminated on the BT drum 7 is conveyed to a predetermined position of the molding drum 2 by the O-ring 8, and this band is a toroidal carcass material. Then, the molding of the unvulcanized tire is completed. Thereafter, the unvulcanized tire is vulcanized and molded to complete the pneumatic tire having the bead portion 20 shown in FIG.
[0025]
The effects of the pneumatic tire described above will be described below.
That is, in FIGS. 2 to 4, the portion of the carcass material 10 before being supplied to the molding drum 2 excluding the squeezing end portion 10 </ b> E has a planar shape, and the squeezing parts p ₁ to p ₂ with respect to this plane. In the cylindrical carcass material 10 on the molding drum 2, the inclination angle α changes to an inclination angle β with respect to the axis X direction of the molding drum 2.
[0026]
When the carcass material 10 is changed from a planar shape to a cylindrical shape, both end portions try to increase the circumferential length. At this time, the heeled end portion of the conventional carcass material is deformed outward, and the inclination angle β tends to be smaller than the inclination angle α.
[0027]
On the other hand, the carcass material 10 having a plurality of cuts 13 at the squeezing end portions 10E on both sides opens to both sides in the circumferential direction with the cuts 13 as a boundary. Therefore, as shown in FIG. The end 10E is inclined outward, so that the inclination angle β is larger than the inclination angle α. According to the experimental results, when the circumferential length of the inner circumferential surface of the cylindrical carcass material 10 is 1654 mm, α = 53 ° is β = 60 °, and when 1800 mm, α = 50 ° is β = 60 °. Change.
[0028]
In short, the change in which the inclination angle increases is the same as that shown in the diagram of FIG. 7, in which the relationship between the inclination angle β and the tensile strength retention rate (%) of the steel cord 11 at the crimped end 10E is shown by a diagram. When viewed at the inclination angle β, the embodiment indicated by the solid line exhibits the effect of having a larger retention rate (%) than the conventional case indicated by the broken line. Further, since the crease part p ₁ causes the steel cord 11 to undergo plastic deformation, the inclination angle β returns to the inclination angle α when the bead core member 15 is locked.
[0029]
Since the notch 13 exists, the reaction force against the bead setter 4 when passing through the squeezing end 10E and the reaction force of the squeezing end 10E against the bead setter 4 when positioning the bead core member 15 at a predetermined position. Is greatly reduced. This eliminates the need for modification of the conventional molding machine, guarantees sufficient durability of the conventional bead setter 4, and can maintain a high level of productivity in the molding process. Molding becomes possible.
[0030]
Here, the cutting pitch P is preferably 150 mm or less. This is because, as is clear from the diagram showing the relationship between the cutting pitch P (mm) and the reaction force (MPa) against the bead setter 4 in FIG. 8, the reaction force saturates when the cutting pitch P exceeds 150 mm. It is.
[0031]
The bead core member 15 shown in each drawing is a so-called hexagonal bead core having a hexagonal cross section. Alternatively, the bead core member 15 may be a polygon having a quadrangular shape or more, or a round shape. In relation to the bead core member 15 to be applied, the cut length of the cut 13 from the edge 10Ee of each crease end 10E is within a range of 3/12 to 9/12 times the circumferential length of the bead core member 15. It is suitable to do.
[0032]
Further, as shown in FIG. 9, when each squeezed end portion 10E is wound around and closely adhered to the bead core member 15, both sides of the notch 13 are fan-shaped from the end of the notch 13 toward the edge 10Ee of the squeezed end portion 10E. As a first opening, it is wound around the bead core member 15 and closely attached.
[0033]
At this time, as shown in FIG. 10, the ends of the steel cord 11 that sandwich the plane 13 extending from both sides of the cut 13 position, that is, the original cut 13 and extending in the radial direction from the axis X to the plane Q with the plane Q as a boundary. In contrast, they are inclined in opposite directions with an inclination angle θ. Thereby, even if a crack occurs at the end of the steel cord 11 located at the winding end 21Re of a certain part of the carcass 21 in the tire, the gap between the winding ends 21Re on both sides sandwiching the plane Q is circumferential. Therefore, it is possible to prevent the progress of cracks in the circumferential direction and eventually obtain the effect of improving the durability of the bead portion 20.
[0034]
【Example】
A radial ply tire for trucks and buses having a size of 435 / 45R22.5, a carcass material having a bead core member 15 having a hexagonal bead core and an internal angle of plastic deformation at the squeezed portions p ₁ , p ₂ , and p ₃ of 120 ° 10 was used. The cross-sectional circumferential length of the hexagonal bead core 15 was 56 mm, the cutting pitch P was 30 mm, and the length of the cutting 13 was 40 mm.
[0035]
The carcass material 10 is wound around the molding drum 2 into a cylindrical shape, the bead setter 4 holding the hexagonal bead core 15 is transported to a predetermined position, and the reaction force acting on the bead setter 4 when passing through the tacking end portion 10E. The reaction force acting on the bead setter 4 when the hexagonal bead core 15 is positioned at the lock position was measured and compared between the example and the conventional example.
[0036]
When the measurement result is expressed by an index in which the two reaction forces in the conventional example are 100, respectively, the reaction force in the embodiment is 86 and 82 in the lock positioning. From these results, the effectiveness of the examples can be demonstrated.
[0037]
【The invention's effect】
According to the first to fourth aspects of the present invention, the reaction force accompanying the passing of the bead core member holding bead setter with respect to the both side squeezed end portions of the carcass material and the reaction force of the bead setter when the bead core member is locked are determined. Providing a pneumatic tire manufacturing method that can maintain a sufficient durability and high productivity while maintaining the conventional molding machine, and can perform high-precision molding. Can do.
[Brief description of the drawings]
FIG. 1 is a schematic plan view of a molding machine used in the present invention.
FIG. 2 is a plan view of a carcass material immediately before supplying a molding drum according to the present invention.
FIG. 3 is a right half sectional view of the carcass material shown in FIG. 2;
FIG. 4 is a partial cross-sectional view of a carcass material according to the present invention after being wound around a molding drum.
FIG. 5 is a cross-sectional view of an end portion and a bead setter when positioning a bead core member according to the present invention.
6 is a schematic cross-sectional view of the whole when the carcass material shown in FIG. 5 is bulged and deformed, and the crimped end portion is wound around the bead core member and brought into close contact therewith.
FIG. 7 is a diagram showing the relationship between the inclination angle on the molding drum and the tensile strength retention rate of the steel cord with respect to the brazed end portion.
FIG. 8 is a diagram showing a relationship between a cutting pitch and a bead setter reaction force.
9 is a partial perspective view of the squeezed end portion and the bead core member shown in FIG. 6. FIG.
FIG. 10 is a side view of the steel cord and the bead core member at the crease end shown in FIG. 6;
FIG. 11 is a cross-sectional view of an end portion and a bead setter when positioning a conventional bead core member.
FIG. 12 is a cross-sectional view of a bead portion of a tire using a carcass material according to the present invention.
FIG. 13 is a cross-sectional view of a bead portion of a conventional tire having no crease portion.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Housing 2 Molding drum 2B Bladder 3 Carcass material servicer 4 Bead setter 5 Stitcher roll 6 Servicer 7 BT drum 8 O-ring 10 Carcass material 10E Both side edge part 10Ee which has a crushed part 11 Steel cord 12 Cover rubber 13 Notch 15 Bead core member 16 Locking means p ₁ , p ₂ , p ₃ Inclined portion α, β Inclined angle P of incised portions p _{1 to} p ₂ Cutting pitch X Forming drum axis Q Plane including cutting θ Plane steel cord for plane Q Inclination angle

Claims (4)

When molding unvulcanized tires,
The radial carcass ply material, in which a large number of parallel arrangement steel cords are coated with unvulcanized rubber, is subjected to two or more upwards in advance on both side ends where the bead core is wound along the circumferential direction of the carcass of the tire, After that, cuts are made at a predetermined pitch in the covered rubber parts on both side ends with the crease part, and a material having a plurality of cuts on both sides is supplied to the molding drum and joined in a cylindrical shape,
A pair of bead core members are supplied to and positioned at both end portions of the cylindrical material having the crease portion, and each bead core member at this position is locked and fixed from the inside through the material. Bulging and deforming into a toroidal shape, each squeezed portion of the bulging and deforming material is wound around the bead core member and closely adhered,
Then, the manufacturing method of the pneumatic tire characterized by sticking an unvulcanized belt and an unvulcanized tread rubber on the outer peripheral side of a toroid-like material. The manufacturing method according to claim 1, wherein the predetermined pitch for cutting is 150 mm or less. The manufacturing method according to claim 1 or 2, wherein a cut length from an edge of each side end portion is in a range of 3/12 to 9/12 times the cross-sectional circumferential length of the bead core member. The steel cord end portions sandwiching the cut positions from both sides are inclined in opposite directions to each other with the cut positions as boundaries when each of the crease portions is wound around the bead core member and brought into close contact therewith. The manufacturing method described in the item.

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